WorldWideScience
1

Influence of Barometric Pressure Changes on Ventilation Conditions in Deep Mines  

Science.gov (United States)

Barometric air pressure and its changes have a critical impact on ventilation conditions in the underground workings of deep mines. Changes in pressure are particularly important because they are responsible for the transient states of ventilation conditions, therefore, assessing the scale of pressure change is essential. Unfortunately, previously for many years in the Polish mining industry barometric pressure was recorded only on tapes of mechanical barographs by the ventilation department on the surface and therefore such dependencies of methane concentration due to barometric pressure changes have not been properly documented. Today, after the implementation in mines of instruments enabling the monitoring of absolute pressure in the workings of mines (Wasilewski, 2009) the conditions have been created to study the influence of pressure changes on changes of air parameters in the mine workings. Barometric pressure changes were observed and recorded over a course of approximately two years using monitoring system that utilized high accuracy pressure sensors on the surface and in selected workings of an underground mine. This paper presents a statistical analysis of the data that we generated from assessing pressure changes on the surface and at selected underground points in the mine. In the article, which presents the results of the first part of the study, some examples of when significant changes in pressure prior to the tragic events, which were not accompanied by changes in the methane concentration in mine workings, will also be shown. Interestingly, we found that the relationship between methane ignitions and explosions in longwall gob mined via the cave-in method is associated with changes in the barometric pressure. Several instances of methane ignitions and explosions in the gob of cave-in longwalls in recent years were compared with background barometric pressure changes. Research carried out in within the strategic project "Improving work safety in the mines" allowed to record air parameters changes inside the gob of longwalls and show the influence of pressure changes on changes in methane and oxygen concentration in the gob, which will be shown in the second part of the article to be published in the near future.

Wasilewski, Stanis?aw

2014-10-01

2

Continuous monitoring of barometric pressure in deep mines  

Energy Technology Data Exchange (ETDEWEB)

Barometric pressure and its variation in deep underground workings have a considerable effect on ventilation conditions. Pressure changes which create transient states of air flow and air parameters in workings are especially significant. Experiments have shown that pressure changes have a remarkable effect on air parameters at mine workings. Continuous monitoring of the barometric pressure on the surface of mines allows for the detection of changes in pressure which influence alternations of pressure in the underground areas of mines. Important factors are the internal disturbances of pressure within a mine ventilation system due to variable conditions of fan operation and the operation of a winding machine where a mine cage moving in a shaft causes piston like disturbances. Local transient disturbances caused by temporary opening/closing of air stoppings due to personnel or underground transport traffic are of importance. The results of over two years of observations of barometric pressure and its influence on pressure variation in underground mine workings are presented. The observations were possible through the installation of pressure sensors at selected points of the downcast shaft in a mine. Of interest are the observations of the transient states of pressure and other air parameters caused by emergency fan stoppage, movement of a mine cage and changes due to the opening of air stoppings. Data acquired during experiments of opening and closing air stoppings were used for the validation of a flow model in a long working. 13 refs., 15 figs.

Trutwin, W.; Mironowicz, W.; Wasilewski, S.; Krawczyk, J. [Research and Development Centre for Electrical Engineering and Automation in Mining EMAG, Katowice (Poland)

2005-07-01

3

Impact of Changes in Barometric Pressure on Landfill Methane Emission  

Science.gov (United States)

Landfill methane emissions were measured continuously using the eddy covariance method from June to December 2010. The study site was located at the Bluff Road Landfill in Lincoln, Nebraska USA. Methane emissions strongly depended on changes in barometric pressure; rising barometric pressure suppressed the emission, while falling barometric pressure enhanced the emission. Emission rates were systematically higher in December than during the summer period. Higher methane emission rates were associated with changes in barometric pressure that were larger in magnitude and longer in duration in winter than in summer, and with lower mean temperatures, which appeared to reduce methane oxidation rates. Sharp changes in barometric pressure caused up to 35-fold variation in day-to-day methane emissions. Power spectrum and ogive analysis showed that continuous measurements over a period of at least 10 days were needed in order to capture 90% of total variance in the methane emission time series at our site. Our results suggest that point-in-time methane emission rate measurements taken at monthly or even longer time intervals using techniques such as the tracer plume method, the mass balance method, or the closed-chamber method may be subject to large variations because of the strong dependence of methane emissions on changes in barometric pressure. Estimates of long-term integrated methane emissions from landfills based on such measurements will inevitably yield large uncertainties. Our results demonstrate the value of continuous measurements for quantifying total annual methane emission from a landfill.

McDermitt, Dayle; Xu, Liukang; Lin, Xiaomao; Amen, Jim; Welding, Karla

2013-04-01

4

Impact of changes in barometric pressure on landfill methane emission  

Science.gov (United States)

Landfill methane emissions were measured continuously using the eddy covariance method from June to December 2010. The study site was located at the Bluff Road Landfill in Lincoln, Nebraska, USA. Our results show that landfill methane emissions strongly depended on changes in barometric pressure; rising barometric pressure suppressed the emission, while falling barometric pressure enhanced the emission, a phenomenon called barometric pumping. There was up to a 35-fold variation in day-to-day methane emissions due to changes in barometric pressure. Wavelet coherence analysis revealed a strong spectral coherency between variations of barometric pressure and methane emission at periodicities ranging from 1 day to 8 days. Power spectrum and ogive analysis showed that at least 10 days of continuous measurements was needed in order to capture 90% of the total variance in the methane emission time series at our landfill site. From our results, it is clear that point-in-time measurements taken at monthly or longer time intervals using techniques such as the trace plume method, the mass balance method, or the closed-chamber method will be subject to large variations in measured emission rates because of the barometric pumping phenomenon. Estimates of long-term integrated methane emissions from landfills based on such measurements could yield uncertainties, ranging from 28.8% underestimation to 32.3% overestimation. Our results demonstrate a need for continuous measurements to quantify annual total landfill emissions. This conclusion may apply to the study of methane emissions from wetlands, peatlands, lakes, and other environmental contexts where emissions are from porous media or ebullition. Other implications from the present study for hazard gas monitoring programs are also discussed.

Xu, Liukang; Lin, Xiaomao; Amen, Jim; Welding, Karla; McDermitt, Dayle

2014-07-01

5

The relationship of headache occurrence to barometric pressure  

Science.gov (United States)

A total of 75 people residing in the metropolitan Boston area who had frequently recurring headaches kept a headache diary for one month beginning March 1975. Data were also collected about barometric pressure during this time. We found that the probability of headache severity on any day was independent of the effects of time. An inference of this, supported by other findings in this study, is that headache occurrence is minimally affected by time-related phenomena such as barometric pressure readings or changes..

Schulman, Jane; Leviton, A.; Slack, W.; Porter, D.; Graham, J. R.

1980-09-01

6

Barometric pressure transient testing applications at the Nevada Test Site. Nuclear chimney analysis. Final report  

International Nuclear Information System (INIS)

Investigations of barometric pressure testing of NTS nuclear chimneys were reviewed. This review includes the models used in the interpretation, methods of analysis, and results. Analytic and semi-analytic models were presented and applied to both historical data and new data taken for this current project. An interpretation technique based on non-linear least squares methods was used to analyze this data in terms of historic and more recent chimney models. Finally, a detailed discussion of radioactive gas transport due to surface barometric pressure fluctuations was presented. This mechanism of transport, referred to as ''barometric pumping,'' is presented in terms of conditions likely to be encountered at the NTS. The report concludes with a discussion of the current understanding of gas flow properties in the alluvial and volcanic areas of the NTS, and suggestions for future efforts directed toward increasing this understanding are presented

7

Flip-chip packaging of piezoresistive barometric pressure sensors  

Science.gov (United States)

To miniaturize piezoresistive barometric pressure sensors we have developed a package using flip-chip bonding. However, in a standard flip-chip package the different coefficients of thermal expansion (CTE) of chip and substrate and strong mechanical coupling by the solder bumps would lead to stress in the sensor chip which is not acceptable for piezoresistive pressure sensors. To overcome this problem we have developed a new ultra low stress flip-chip packaging technology. In this new packaging technology for pressure sensors first an under bump metallization (UBM) is patterned on the sensor wafer. As the next step solder bumps are deposited. After wafer-dicing the chips are flip-chip bonded on copper springs within a ceramic cavity. As sources of residual stress we identified the copper springs, the UBM and the solder bumps on the sensor chip. Different CTEs of the silicon chip and the UBM/solder lead to creep strain in the aluminum metallization between UBM and chip. As a consequence a temperature hysteresis can be measured.

Waber, T.; Pahl, W.; Schmidt, M.; Feiertag, G.; Stufler, S.; Dudek, R.; Leidl, A.

2013-05-01

8

Barometric pressure transient testing applications at the Nevada Test Site: formation permeability analysis. Final report  

Energy Technology Data Exchange (ETDEWEB)

The report evaluates previous investigations of the gas permeability of the rock surrounding emplacement holes at the Nevada Test Site. The discussion sets the framework from which the present uncertainty in gas permeability can be overcome. The usefulness of the barometric pressure testing method has been established. Flow models were used to evaluate barometric pressure transients taken at NTS holes U2fe, U19ac and U20ai. 31 refs., 103 figs., 18 tabs. (ACR)

Hanson, J.M.

1984-12-01

9

Barometric pressure transient testing applications at the Nevada Test Site: formation permeability analysis. Final report  

International Nuclear Information System (INIS)

The report evaluates previous investigations of the gas permeability of the rock surrounding emplacement holes at the Nevada Test Site. The discussion sets the framework from which the present uncertainty in gas permeability can be overcome. The usefulness of the barometric pressure testing method has been established. Flow models were used to evaluate barometric pressure transients taken at NTS holes U2fe, U19ac and U20ai. 31 refs., 103 figs., 18 tabs

10

Insights into aquifer vulnerability and potential recharge zones from the borehole response to barometric pressure changes  

Science.gov (United States)

Borehole water levels fluctuate in response to deformation of the surrounding aquifer caused by surface loading due to barometric pressure or strain caused by Earth and ocean tides. The magnitude and nature of this response mainly depend on the hydraulic properties of the aquifer and overlying units and borehole design. Thus water level responses reflect the effectiveness of a confining unit as a protective layer against aquifer contamination (and therefore groundwater vulnerability) and to potential aquifer recharge/discharge zones. In this study, time series of borehole water levels and barometric pressure are being investigated using time series analysis and signal processing techniques with the aim of developing a methodology for assessing recharge/discharge distribution and groundwater vulnerability in the confined/semi-confined part of the Chalk aquifer in East Yorkshire, UK. The chalk aquifer in East Yorkshire is an important source for industrial and domestic water supply. The aquifer water quality is threatened by surface pollution particularly by nitrates from agricultural fertilizers. The confined/semi-confined part of this aquifer is covered by various types of superficial deposits resulting in a wide range of the aquifer's degree of confinement. A number of boreholes have been selected for monitoring to cover all these various types of confining units. Automatic pressure transducers are installed to record water levels and barometric pressure measurements at each borehole on 15 minutes recording intervals. In strictly confined aquifers, borehole water level response to barometric pressure is an un-drained instantaneous response and is a constant fraction of the barometric pressure changes. This static confined constant is called the barometric efficiency which can be estimated simply by the slope of a regression plot of water levels versus barometric pressure. However, in the semi confined aquifer case this response is lagged due to water movement between the aquifer and the confining layer. In this case the static constant barometric efficiency is not applicable and the response is represented by a barometric response function which reflects the timing and frequency of the barometric pressure loading. In this study, the barometric response function is estimated using de-convolution techniques both in the time domain (least squares regression de-convolution) and in the frequency domain (discrete Fourier transform de-convolution). In order to estimate the barometric response function, borehole water level fluctuations due to factors other than barometric pressure should be removed (de-trended) as otherwise they will mask the response relation of interest. It is shown from the collected borehole data records that the main four factors other than barometric pressure contribute to borehole water level fluctuations. These are the rainfall recharge, Earth tides, sea tides and pumping activities close to the borehole location. Due to the highly variable nature of the UK weather, rainfall recharge shows a wide variation throughout the winter and summer seasons. This gives a complicated recharge signal over a wide range of frequencies which must be de-trended from the borehole water level data in order to estimate the barometric response function. Methods for removing this recharge signal are developed and discussed. Earth tides are calculated theoretically at each borehole location taking into account oceanic loading effects. Ocean tide effects on water levels fluctuations are clear for the boreholes located close to the coast. A Matlab code has been designed to calculate and de-trend the periodic fluctuations in borehole water levels due to Earth and ocean tides using the least squares regression technique based on a sum of sine and cosine fitting model functions. The program results have been confirmed using spectral analysis techniques.

El Araby, Mahmoud; Odling, Noelle; Clark, Roger; West, Jared

2010-05-01

11

The Effects of Temperature, Humidity and Barometric Pressure on Short Sprint Race Times  

CERN Document Server

A numerical model of 100 m and 200 m world class sprinting performances is modified using standard hydrodynamic principles to include effects of air temperature, pressure, and humidity levels on aerodynamic drag. The magnitude of the effects are found to be dependent on wind speed. This implies that differing atmospheric conditions can yield slightly different corrections for the same wind gauge reading. In the absence of wind, temperature is found to induce the largest variation in times (0.01 s per $10\\dc$ increment in the 100 m), while relative humidity contributes the least (under 0.01 s for all realistic conditions for 100 m). Barometric pressure variations at a particular venue can also introduce fluctuations in performance times on the order of a 0.01 s for this race. The combination of all three variables is essentially additive, and is more important for head-wind conditions that for tail-winds. As expected, calculated corrections in the 200 m are magnified due to the longer duration of the race. The...

Mureika, J R

2006-01-01

12

Barometric pressure, dry bulb temperature and vapor pressure at the lowest terrestrial site on earth, Dead Sea basin, Neve Zohar, Israel  

Science.gov (United States)

The Dead Sea basin is located at the lowest terrestrial site on the earth and, thereby, has the tallest atmospheric air column above its surface. Consequently, the Dead Sea basin is expected, a priori, to have the highest terrestrial barometric pressure and, thereby, the highest molecular oxygen density on the earth. The barometric pressure and dry bulb temperature have been monitored continuously at Neve Zohar, located on the western shore of the Dead Sea, since January 1995. The monthly average daily barometric pressure values exceed normal atmospheric pressure by a maximum of 4.83 hPa (4.77%) and a minimum of 33.1 hPa (3.26%) for December and July, respectively. This increase in barometric pressure can serve as a simple way to improve arterial oxygenation in hypoxemic patients. As a result, a number of research projects have been initiated on the treatment of patients suffering from pulmonary and cardiac diseases at the Dead Sea basin. The hourly barometric pressure data with regard to both its diurnal and monthly variation and the correlation between barometric pressure and dry bulb temperature will be analyzed.

Kudish, A. I.; Evseev, E. G.

2006-03-01

13

Energy expenditure estimation during normal ambulation using triaxial accelerometry and barometric pressure.  

Science.gov (United States)

Energy expenditure (EE) is an important parameter in the assessment of physical activity. Most reliable techniques for EE estimation are too impractical for deployment in unsupervised free-living environments; those which do prove practical for unsupervised use often poorly estimate EE when the subject is working to change their altitude by walking up or down stairs or inclines. This study evaluates the augmentation of a standard triaxial accelerometry waist-worn wearable sensor with a barometric pressure sensor (as a surrogate measure for altitude) to improve EE estimates, particularly when the subject is ascending or descending stairs. Using a number of features extracted from the accelerometry and barometric pressure signals, a state space model is trained for EE estimation. An activity classification algorithm is also presented, and this activity classification output is also investigated as a model input parameter when estimating EE. This EE estimation model is compared against a similar model which solely utilizes accelerometry-derived features. A protocol (comprising lying, sitting, standing, walking, walking up stairs, walking down stairs and transitioning between activities) was performed by 13 healthy volunteers (8 males and 5 females; age: 23.8 ± 3.7 years; weight: 70.5 ± 14.9 kg), whose instantaneous oxygen uptake was measured by means of an indirect calorimetry system (K4b(2), COSMED, Italy). Activity classification improves from 81.65% to 90.91% when including barometric pressure information; when analyzing walking activities alone the accuracy increases from 70.23% to 98.54%. Using features derived from both accelerometry and barometry signals, combined with features relating to the activity classification in a state space model, resulted in a VO(2) estimation bias of -0.00 095 and precision (1.96SD) of 3.54 ml min(-1) kg(-1). Using only accelerometry features gives a relatively worse performance, with a bias of -0.09 and precision (1.96SD) of 5.99 ml min(-1) kg(-1), with the largest errors due to an underestimation of VO(2) when walking up stairs. PMID:23110944

Wang, Jingjing; Redmond, Stephen J; Voleno, Matteo; Narayanan, Michael R; Wang, Ning; Cerutti, Sergio; Lovell, Nigel H

2012-11-01

14

Long-term stability and zero drift of digital barometric pressure gauges  

Science.gov (United States)

Several digital pressure gauges at the National Metrology Institute of Japan (NMIJ) have been calibrated in the barometric pressure range on a regular basis for over ten years. The long-term stability of the zero and span readings for these pressure gauges was evaluated using their historical calibration data. The evaluation showed that most of the gauges have quite good long-term stabilities for the span readings, but some have large zero drifts with rates of about (10 to 50) Pa?yr?1. This paper discusses the causes for this drift: it can be explained by the combination of a small leak and gas emissions from the sensor volume, which are estimated from the typical drift rates. The zero drift of a particular gauge is well-approximated by an exponential function of time; the fitting function may give a good estimation of the zero drift in the future. This indicates that continuous characterization of a pressure gauge may enable appropriate correction of the indication and provide users more reliable data with less calibration work.

Kojima, M.; Kobata, T.; Fujii, K.

2015-04-01

15

Microblower assisted barometric valve  

Science.gov (United States)

A gas exchange apparatus is provided which provides for both passive fluid flow and blower associated fluid flow through a barometric valve. A battery powered blower is provided which allows for operation of the barometric valve during times when the barometric valve would otherwise be closed, and provides for enhanced volume of gas exchange.

Rossabi, Joseph; Hyde, Warren K.; Riha, Brian D.; Jackson, Dennis G.; Sappington, Frank

2005-12-06

16

The Influence od Air Temperature and Barometric Pressure on Radon and Carbon Dioxide Levels in Air of a Karst Cave  

International Nuclear Information System (INIS)

Radioactive noble gas radon (222Rn) is created in minerals by radioactive transformation of 226Ra within the 238U natural decay chain. It migrates through the ground, accumulates in underground rooms (e. g., karst caves) and eventually enters the atmosphere. It is always present in our living and working environment. Because of its harmful health effect, it presents a serious social concern but is, on the other hand, a useful tool in several scientific disciplines. It is thus used as a tracer in exploring movement of air masses and an indicator of tectonic faults. Another minor constituent of air is carbon dioxide. Similar as radon, it is dangerous at high levels, but its presence in air of karst caves is indispensable for their life, because it governs speleogenetic processes. In the cave air, its concentration is determined by the inflow of outside air, biogenic activity of soil, degradation of organic matter and carbonate, degassing from water, and human activity. Therefore, ventilation of the cave is crucial for its conservation. Based on temporal variations of radon and carbon dioxide levels, ventilation regime in the cave can be estimated. Radon has been surveyed in all the twenty show caves and in thirty other caves in Slovenia, with emphasis on the Postojna Cave. In the present study, in addition to radon, monitoring of carbon dioxide was introduced for the first time. The Kostanjevica Cave, situated in southern Slovenia in an isolated island of karst, was selected because it is crossed by a tectonic fault at which measurements of three-dimensional micro displacements are underway. Because of the fault, high levels of radon and carbon dioxide were expected. In this paper, measurements are described and both the spatial and time variations of radon and carbon dioxide levels are presented and commented on. Continuous radon monitoring was carried out with the RadonScout devices (Sarad, Germany) from April to December 2009, with several interruptions because of the instrument failures. At several points along the guided tourist route, instantaneous concentrations of radon and carbon dioxide were measured monthly from August 2009 to March 2010. Outdoor air temperature and barometric pressure for the nearby meteorological station were obtained from the Office of Meteorology of the Environmental Agency of the Republic of Slovenia. Change of ventilation regime in the cave is reflected in seasonal variation of radon concentration. It is high in summer (1800 - 2200 Bq m-3) and substantially reduced in winter (20 - 500 Bq m-3), when temperature in the cave is higher than outside and radon is diluted by the inflow of outside air, caused by natural air draught. This draught is minimal or reversed in summer. Concentrations of both gases, radon and CO2, are well correlated. (author)

17

No More Snow Pits? Potential to Retrieve Bulk Snow Pack Structure from Transient Barometric Pressure Waves measured from a Prototype Embedded Wireless Sensor Network  

Science.gov (United States)

Networked micro-sensors have the capacity to enable improvements in ground-based data collection at resolutions that are currently unresolved. Crossbow® Environmental Motes (MEP410 Models) were embedded in an accumulated snow pack in a meadow at Niwot Ridge Long-Term Ecological Research (LTER) C1 site. Motes were mounted to a custom designed deployment structure that constitutes an adaptive sensor "tower" at a maximum height of 142 with sensors deployed at depths of 122cm, 71cm, and 17cm from the ground. Barometric pressures measured from this embedded wireless network indicate low frequency fluctuations over the study period with higher frequency components varying as a function of depth. Mean pressure measured over the analysis period were 707.82 mb (122cm), 702.48 mb (71cm), and 704.09mb (17cm). Results indicate filtering of high frequency components of pressure measured at depth with reduced amplitude and time-lag (phase shift) modulated by changes in snow pack permeability related to density changes.

Lampkin, D. J.

2007-12-01

18

Effects of Barometric Fluctuations on Well Water-Level Measurements and Aquifer Test Data  

Energy Technology Data Exchange (ETDEWEB)

The Pacific Northwest National Laboratory, as part of the Hanford Groundwater Monitoring Project, examines the potential for offsite migration of contamination within underlying aquifer systems. Well water-level elevation measurements from selected wells within these aquifer systems commonly form the basis for delineating groundwater-flow patterns (i.e., flow direction and hydraulic gradient). In addition, the analysis of water-level responses obtained in wells during hydrologic tests provides estimates of hydraulic properties that are important for evaluating groundwater-flow velocity and transport characteristics. Barometric pressure fluctuations, however, can have a discernible impact on well water-level measurements. These barometric effects may lead to erroneous indications of hydraulic head within the aquifer. Total hydraulic head (i.e., sum of the water-table elevation and the atmospheric pressure at the water-table surface) within the aquifer, not well water-level elevation, is the hydrologic parameter for determining groundwater-flow direction and hydraulic gradient conditions. Temporal variations in barometric pressure may also adversely affect well water-level responses obtained during hydrologic tests. If significant, adjustments or removal of these barometric effects from the test-response record may be required for quantitative hydraulic property determination. This report examines the effects of barometric fluctuations on well water-level measurements and evaluates adjustment and removal methods for determining areal aquifer head conditions and aquifer test analysis. Two examples of Hanford Site unconfined aquifer tests are examined that demonstrate barometric response analysis and illustrate the predictive/removal capabilities of various methods for well water-level and aquifer total head values. Good predictive/removal characteristics were demonstrated with best corrective results provided by multiple-regression deconvolution methods.

FA Spane, Jr.

1999-12-16

19

Mapping of multi-floor buildings: A barometric approach  

DEFF Research Database (Denmark)

This paper presents a new method for mapping multi5floor buildings. The method combines laser range sensor for metric mapping and barometric pressure sensor for detecting floor transitions and map segmentation. We exploit the fact that the barometric pressure is a function of the elevation, and it varies between different floors. The method is tested with a real robot in a typical indoor environment, and the results show that physically consistent multi5floor representations are achievable.

Özkil, Ali Gürcan; Fan, Zhun

2011-01-01

20

Variations in cosmic radiation intensity associated with the barometric effect  

Directory of Open Access Journals (Sweden)

Full Text Available The barometric effect for the Mexico City neutron monitor is obtained from cosmic ray intensity data obtained during the years 1990-1997, more than half a solar cycle, by correlation between the neutron intensity and the atmospheric pressure. In order to eliminate other factors of solar or geomagnetic origin we use only geomagnetically quiet days (kp<20°. The evolution of the barometric coefficient from maximum (1990 to minimum (1997 solar activity is discussed.

José Fco. Valdés-Galicia

2000-05-01

21

16 CFR 1203.8 - Conditioning environments.  

Science.gov (United States)

...2010-01-01 2010-01-01 false Conditioning environments. 1203.8 Section...HELMETS The Standard § 1203.8 Conditioning environments. Helmets shall...13. The barometric pressure in all conditioning environments shall be 75 to...

2010-01-01

22

BETCO: A Computer Program for the Removal of Barometric and Earth Tide Effects From Water Levels  

Science.gov (United States)

Barometric pressure effects in long-term water level measurements can mask drawdown responses to well tests and natural stimuli. Noise caused by barometric pressure and earth tide effects complicates analysis of pressure response data using diagnostic pressure derivative plots. A computer program has been developed to remove fluctuations in groundwater levels induced by changes in barometric pressure and earth tides. The program implements a regression deconvolution method to obtain a barometric response function and remove the barometric pressure and earth tide effects from the groundwater level data. Using the barometric response function yields a better residual or corrected head than using a constant barometric efficiency. The graphical response function can be used to diagnose aquifer type and well skin effects. A modification of the regression deconvolution has been implemented to simultaneously remove earth tide effects as well as barometric effects on water levels. The removal of the earth tide effects is provided as a beta feature. The software has been applied to 13 water level data sets at the Waste Isolation Pilot Plant in Carlsbad, NM. The results are compared to a constant barometric efficiency correction method. The freeware software is available as an install wizard for Windows XP and 2000. As of submission, all results output from BETCO are considered preliminary, please do not cite. The code is under continued development and will be qualified per the Sandia National Laboratories WIPP Software QA Plan requirements. This research is funded by WIPP programs administered by the Office of Environmental Management (EM) of the U.S. Department of Energy. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Toll, N.; Rasmussen, T. C.

2005-12-01

23

Critical conditions of pressurized pipes.  

Czech Academy of Sciences Publication Activity Database

Ro?. 20, ?. 5 (2013), s. 401-412. ISSN 1802-1484 R&D Projects: GA ?R(CZ) GAP105/10/2052 Institutional support: RVO:68378297 Keywords : pressurized pipe * J-integral * C factor * critical conditions Subject RIV: JL - Materials Fatigue, Friction Mechanics http://www.engineeringmechanics.cz/obsahy.html?R=20&C=5

Gajdoš, Lubomír; Šperl, Martin

2013-01-01

24

Determination of Barometric Altimeter Errors for the Orion Exploration Flight Test-1 Entry  

Science.gov (United States)

The Exploration Flight Test 1 (EFT-1) mission is the unmanned flight test for the upcoming Multi-Purpose Crew Vehicle (MPCV). During entry, the EFT-1 vehicle will trigger several Landing and Recovery System (LRS) events, such as parachute deployment, based on on-board altitude information. The primary altitude source is the filtered navigation solution updated with GPS measurement data. The vehicle also has three barometric altimeters that will be used to measure atmospheric pressure during entry. In the event that GPS data is not available during entry, the altitude derived from the barometric altimeter pressure will be used to trigger chute deployment for the drogues and main parachutes. Therefore it is important to understand the impact of error sources on the pressure measured by the barometric altimeters and on the altitude derived from that pressure. The error sources for the barometric altimeters are not independent, and many error sources result in bias in a specific direction. Therefore conventional error budget methods could not be applied. Instead, high fidelity Monte-Carlo simulation was performed and error bounds were determined based on the results of this analysis. Aerodynamic errors were the largest single contributor to the error budget for the barometric altimeters. The large errors drove a change to the altitude trigger setpoint for FBC jettison deploy.

Brown, Denise L.; Bunoz, Jean-Philippe; Gay, Robert

2012-01-01

25

Field measurements of tracer gas transport by barometric pumping  

International Nuclear Information System (INIS)

Vertical gas motions induced by barometric pressure variations can carry radioactive gases out of the rubblized region produced by an underground nuclear explosion, through overburden rock, into the atmosphere. To better quantify transit time and amount of transport, field experiments were conducted at two sites on Pahute Mesa, Kapelli and Tierra, where radioactive gases had been earlier detected in surface cracks. At each site, two tracer gases were injected into the rubblized chimney 300-400 m beneath the surface and their arrival was monitored by concentration measurements in gas samples extracted from shallow collection holes. The first ''active'' tracer was driven by a large quantity of injected air; the second ''passive'' tracer was introduced with minimal gas drive to observe the natural transport by barometric pumping. Kapelli was injected in the fall of 1990, followed by Tierra in the fall of 1991. Data was collected at both sites through the summer of 1993. At both sites, no surface arrival of tracer was observed during the active phase of the experiment despite the injection of several million cubic feet of air, suggesting that cavity pressurization is likely to induce horizontal transport along high permeability layers rather than vertical transport to the surface. In contrast, the vertical pressure gradients associated with barometric pumping brought both tracers to the surface in comparable concentrations within three months at Kapelli, whereas 15 months elapsed before surface arrival at Tierra. At Kapelli, a quasisteady pumping regime was established, with tracer concentrations in effluent gases 1000 times smaller than concentrations thought to exist in the chimney. Tracer concentrations observed at Tierra were typically an order of magnitude smaller. Comparisons with theoretical calculations suggest that the gases are traveling through ?1 millimeter vertical fractures spaced 2 to 4 meters apart. 6 refs., 18 figs., 3 tabs

26

A Graphical Method for Estimation of Barometric Efficiency from Continuous Data - Concepts and Application to a Site in the Piedmont, Air Force Plant 6, Marietta, Georgia  

Science.gov (United States)

A graphical method that uses continuous water-level and barometric-pressure data was developed to estimate barometric efficiency. A plot of nearly continuous water level (on the y-axis), as a function of nearly continuous barometric pressure (on the x-axis), will plot as a line curved into a series of connected elliptical loops. Each loop represents a barometric-pressure fluctuation. The negative of the slope of the major axis of an elliptical loop will be the ratio of water-level change to barometric-pressure change, which is the sum of the barometric efficiency plus the error. The negative of the slope of the preferred orientation of many elliptical loops is an estimate of the barometric efficiency. The slope of the preferred orientation of many elliptical loops is approximately the median of the slopes of the major axes of the elliptical loops. If water-level change that is not caused by barometric-pressure change does not correlate with barometric-pressure change, the probability that the error will be greater than zero will be the same as the probability that it will be less than zero. As a result, the negative of the median of the slopes for many loops will be close to the barometric efficiency. The graphical method provided a rapid assessment of whether a well was affected by barometric-pressure change and also provided a rapid estimate of barometric efficiency. The graphical method was used to assess which wells at Air Force Plant 6, Marietta, Georgia, had water levels affected by barometric-pressure changes during a 2003 constant-discharge aquifer test. The graphical method was also used to estimate barometric efficiency. Barometric-efficiency estimates from the graphical method were compared to those of four other methods: average of ratios, median of ratios, Clark, and slope. The two methods (the graphical and median-of-ratios methods) that used the median values of water-level change divided by barometric-pressure change appeared to be most resistant to error caused by barometric-pressure-independent water-level change. The graphical method was particularly resistant to large amounts of barometric-pressure-independent water-level change, having an average and standard deviation of error for control wells that was less than one-quarter that of the other four methods. When using the graphical method, it is advisable that more than one person select the slope or that the same person fits the same data several times to minimize the effect of subjectivity. Also, a long study period should be used (at least 60 days) to ensure that loops affected by large amounts of barometric-pressure-independent water-level change do not significantly contribute to error in the barometric-efficiency estimate.

Gonthier, Gerard J.

2007-01-01

27

Barometric pumping of a fractured porous medium  

Science.gov (United States)

Fluctuations in the ambient atmospheric pressure result in motion of air in porous and fractured media. This mechanism, known as barometric (or atmospheric) pumping, efficiently transports gaseous species through the vadose zone to the atmosphere. This is of interest in many environmental and engineering fields, such as transport of trace gases from soil to atmosphere, environmental remediation of contaminated sites, radon in buildings and last but not least detection of nuclear explosions or leakage from carbon sequestration sites. The physical situation has been addressed in the following way. The fractures are modeled as polygonal plane surfaces with a given transmissivity embedded in a porous medium with a given permeability. The fluid is slightly compressible and is assumed to obey Darcy's law in the fractures and the porous medium with exchanges between them. The solute obeys convection-diffusion equations in both media again with exchanges between them. The fractures and the porous medium located in between them are meshed by triangles and tetrahedra. The equations are discretized by the finite volume method. In order to improve numerical precision, a Flux Limiting Scheme is applied to the transport equations ; moreover, special care is devoted to the description of the solute transfer between the fractures and the porous medium. The resulting equations are solved by conjugate gradient algorithms. This model is applied to the Roselend Natural Laboratory. At a 55 m depth, a sealed cavity allows for gas release experiments across fractured porous rocks in the unsaturated zone. The fractures are hexagons with a radius of 5m; their density is larger than 2.4 10-3 m-3; the aperture is of the order of 0.5 mm. The pressure fluctuations are sinusoidal, of amplitude 0.01 bar and period 1 week. The solute concentration is supposed to be equal to 1 at the bottom of the site. Systematic results will be presented. First, the precision of the calculations is assessed. Second, the pressure fluctuations and the solute concentration in the fractured porous medium is displayed and discussed. Third, the influence of the major parameters (fracture density and aperture, porosity, diffusion coefficient,…) is illustrated and discussed. These results are discussed in terms of the amplification of solute transfer to the ground surface by the pressure fluctuations. Finally, it should be emphasized that the codes can be easily modified to address time dependent thermal transfers in fractured porous media.

Adler, Pierre; Varloteaux, Clément; Mourzenko, Valeri; François Thovert, Jean; Guillon, Sophie; Pili, Eric

2014-05-01

28

Correlation between seismicity and barometric tidal exalting  

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Full Text Available Changes of barometric pressure in the area of Thessaloniki in Northern Greece were studied by analyzing a sample of 31 years of hourly measurements. The results of this analysis on the periodicities of tidal components are expressed in terms of amplitude and phases variability. An earlier investigation revealed a detectable correlation between the exalting of the amplitude parameters of the tidal waves with strong seismic events. A problem of this work was that we had compared the tidal parameters resulting from the analysis of data covering the period of one year with instantaneous seismic events, although the earthquake is the final result of a tectonic process of the upper lithosphere. Consequently, in order to increase the resolution of our method we had analyzed our data in groups of 3-months extent and the resulted amplitudes were compared with seismicity index for corresponding time periods. A stronger correlation was found in the last case. However, the estimation of tidal parameters in this case was restricted to short period (from one day down to eight hours constituents. Therefore, a new analysis was performed, retaining the one-year length of each data block but shifting the one year window by steps of three months from the beginning to the end of the 31 years period. This way, we are able to estimate again tidal parameters ranging from periods of one year (Sa down to eight hours (M3. The resulting correlation between these tidal parameters with a cumulative seismicity index for corresponding time intervals was remarkably increased.

D. N. Arabelos

2008-10-01

29

Effect of fluctuation of surface sea water temperature and ambient pressure on evaporation rate of evaporator in barometric type OC OTEC system; Barometorikku gata opun saikuru kaiyo ondosa hatsuden system no johatsuki ni okeru ondo, atsuryoku henka ni yoru johatsuryo eno eikyo  

Energy Technology Data Exchange (ETDEWEB)

The ocean thermal energy conversion (OTEC) is the system to generate electric power using a temperature gradient between the surface sea water which has been warmed up by the sun and the deep sea water as the energy source. This system is divided into two cycles, namely the closed cycle and the open cycle. In case of the latter, since the pressure inside the system is lower than the atmospheric pressure, the system is under the pressure of one atmospheric pressure from the outside, hence the surface sea water is supplied to an evaporator without an intake pump by installing the whole system at a height of about 10m which shows the waterhead pressure equivalent to one atmospheric pressure. This system requiring only the power for a discharge pump is the barometric type open cycle OTEC system. In this paper, aiming at studying the performance of the system at its evaporator, in order to obtain the stable power generation output against the fluctuations of temperature and pressure in the evaporator as well as the atmospheric pressure, a thermodynamical analysis has been made taking a perfectly heat insulated evaporator as a model. As a result, it has been found that as the temperature inside the evaporator is higher, the fluctuation of the amount of evaporation against inflowing sea water temperature, etc. is smaller. 6 refs., 5 figs.

Amano, M.; Takazawa, H.; Tanaka, T. [Electrotechnical Lab., Tsukuba, Ibaraki (Japan)

1994-09-20

30

Detecting the vulnerability of groundwater in semi-confined aquifers using barometric response functions  

Science.gov (United States)

The use of barometric response functions (BRFs) for detecting the presence of fully penetrating, highly conductive bodies within aquifer confining layers that present potential pathways for contaminants is explored. BRFs are determined from borehole water level (WL) and barometric pressure (Bp) records. Past studies have shown that confining layer properties can be estimated from BRFs, providing a potential link between BRFs and the concept of groundwater vulnerability. Existing analytical models that predict the BRF from system properties assume homogeneity within the aquifer and its confining layer, conditions which are seldom satisfied in nature. The impact of partially and fully penetrating, high diffusivity heterogeneities within a confining layer (representing potential high flow pathways for contaminants) on the BRF is investigated through a suite of three-dimensional, transient numerical simulations of the confining layer-aquifer system. The results are interpreted through comparison with a modified pre-existing analytical model for the BRF. Comparison of numerically and analytically calculated BRFs reveals that the key effect of a localised, fully penetrating, high diffusivity heterogeneity within a low diffusivity confining layer is to reduce the BRF gain with only minor changes to the phase. This impact on the BRF decreases with increasing distance from the heterogeneity. The importance of heterogeneity size is secondary to distance from the borehole and partially penetrating heterogeneities affect the BRF to only a minor extent. Data from a study of the Chalk Aquifer (E. Yorkshire, England) which is semi-confined by heterogeneous glacial sediments display variations in BRFs which are qualitatively similar to those shown by the numerical results. It is suggested that the variation in BRFs estimated from borehole records across a semi-confined aquifer could be used to assess the degree of spatial continuity of low diffusivity lithologies within the confining layer which protect the aquifer against surface sourced contamination, and thus provide a tool to improve groundwater vulnerability assessment.

Odling, N. E.; Perulero Serrano, R.; Hussein, M. E. A.; Riva, M.; Guadagnini, A.

2015-01-01

31

A Stochastic Approach to Noise Modeling for Barometric Altimeters  

OpenAIRE

The question whether barometric altimeters can be applied to accurately track human motions is still debated, since their measurement performance are rather poor due to either coarse resolution or drifting behavior problems. As a step toward accurate short-time tracking of changes in height (up to few minutes), we develop a stochastic model that attempts to capture some statistical properties of the barometric altimeter noise. The barometric altimeter noise is decomposed in three components w...

Angelo Maria Sabatini; Vincenzo Genovese

2013-01-01

32

Effects of Weather and Heliophysical Conditions on Emergency Ambulance Calls for Elevated Arterial Blood Pressure  

Directory of Open Access Journals (Sweden)

Full Text Available We hypothesized that weather and space weather conditions were associated with the exacerbation of essential hypertension. The study was conducted during 2009–2010 in the city of Kaunas, Lithuania. We analyzed 13,475 cards from emergency ambulance calls (EACs, in which the conditions for the emergency calls were made coded I.10–I.15. The Kaunas Weather Station provided daily records of air temperature (T, wind speed (WS, relative humidity, and barometric pressure (BP. We evaluated the associations between daily weather variables and daily number of EACs by applying a multivariate Poisson regression. Unfavorable heliophysical conditions (two days after the active-stormy geomagnetic field or the days with solar WS > 600 km/s increased the daily number of elevated arterial blood pressure (EABP by 12% (RR = 1.12; 95% confidence interval (CI 1.04–1.21; and WS ? 3.5 knots during days of T < 1.5 °C and T ? 12.5 °C by 8% (RR = 1.08; CI 1.04–1.12. An increase of T by 10 °C and an elevation of BP two days after by 10 hPa were associated with a decrease in RR by 3%. An additional effect of T was detected during days of T ? 17.5 °C only in females. Women and patients with grade III arterial hypertension at the time of the ambulance call were more sensitive to weather conditions. These results may help in the understanding of the population’s sensitivity to different weather conditions.

Jone Vencloviene

2015-02-01

33

Effects of weather and heliophysical conditions on emergency ambulance calls for elevated arterial blood pressure.  

Science.gov (United States)

We hypothesized that weather and space weather conditions were associated with the exacerbation of essential hypertension. The study was conducted during 2009-2010 in the city of Kaunas, Lithuania. We analyzed 13,475 cards from emergency ambulance calls (EACs), in which the conditions for the emergency calls were made coded I.10-I.15. The Kaunas Weather Station provided daily records of air temperature (T), wind speed (WS), relative humidity, and barometric pressure (BP). We evaluated the associations between daily weather variables and daily number of EACs by applying a multivariate Poisson regression. Unfavorable heliophysical conditions (two days after the active-stormy geomagnetic field or the days with solar WS > 600 km/s) increased the daily number of elevated arterial blood pressure (EABP) by 12% (RR = 1.12; 95% confidence interval (CI) 1.04-1.21); and WS ? 3.5 knots during days of T < 1.5 °C and T ? 12.5 °C by 8% (RR = 1.08; CI 1.04-1.12). An increase of T by 10 °C and an elevation of BP two days after by 10 hPa were associated with a decrease in RR by 3%. An additional effect of T was detected during days of T ? 17.5 °C only in females. Women and patients with grade III arterial hypertension at the time of the ambulance call were more sensitive to weather conditions. These results may help in the understanding of the population's sensitivity to different weather conditions. PMID:25734792

Vencloviene, Jone; Babarskiene, Ruta M; Dobozinskas, Paulius; Sakalyte, Gintare; Lopatiene, Kristina; Mikelionis, Nerijus

2015-01-01

34

Barometric response functions from borehole water level records and quantification of aquifer vulnerability  

Science.gov (United States)

In confined and semi-confined aquifers, borehole water levels respond to fluctuations in barometric pressure and this response can be used to estimate the properties of aquifer confining layers. We use this response as indicator of groundwater vulnerability for the semi-confined Chalk aquifer in East Yorkshire, UK. Time series data of borehole water levels are corrected for Earth tides and recharge, and barometric response functions (BRFs) estimated using cross-spectral deconvolution-averaging techniques. The resulting BRFs are fitted using a theoretical model of the BRF gain and phase for a semi-confined aquifer (Rojstaczer, 1988) to obtain confining layer properties. For all of the boreholes, non-zero hydraulic diffusivities for the confining layer were found indicating that the aquifer is semi-confined. A ';characteristic time scale' based on the hydraulic and pneumatic diffusivities of the confining layer is introduced as a measure of the degree of aquifer confinement and therefore groundwater vulnerability. The analytical model assumes that the confining layer and aquifer are homogeneous. However, in nature, confining layers are heterogeneous and groundwater vulnerability dominated by the presence of high diffusivity, high flow pathways through the confining layer to the aquifer. A transient numerical model (MODFLOW) was constructed to test the impact of such heterogeneities on the BRF. In the model, an observed barometric pressure time series is used as a boundary condition applied to the upper surface of the top unit of the model (representing the confining layer) and BRFs determined from the time series of model heads in the bottom unit (representing the aquifer). The results from a numerical model with a homogeneous confining layer were found to accurately reproduce the BRFs from a modified version of the analytical model. The introduction of a localized, high diffusive block in the confining layer was found to modify the BRF, reducing the gain amplitude while having limited impact on the phase. It was found that the BRF reflects the presence of a fully penetrating, high diffusivity heterogeneity up to several hundred meters distant from the observation borehole, and shows little sensitivity to the heterogeneity's horizontal dimension. Heterogeneities that are 50% partially penetrating do not significantly impact on the BRF and 90% penetrating heterogeneities can only be detected when large and close to the observation borehole. These results show that BRF gain may be particularly useful in detecting the presence of fully penetrating heterogeneities of high diffusivity within confining layers that potentially enhance groundwater vulnerability. This research has been funded in part through the EU ITN ';IMVUL' (PITN-GA-2008-212298). Reference: Rojstaczer, S. (1988) Determination of fluid-flow properties from the response of water levels in wells to atmospheric loading, Water Resources Research, 24(11), 1927-1938.

Odling, N. E.; Serrano, R. P.; Hussein, M.; Guadagnini, A.; Riva, M.

2013-12-01

35

Using Multiple Barometers to Detect the Floor Location of Smart Phones with Built-in Barometric Sensors for Indoor Positioning  

Directory of Open Access Journals (Sweden)

Full Text Available Following the popularity of smart phones and the development of mobile Internet, the demands for accurate indoor positioning have grown rapidly in recent years. Previous indoor positioning methods focused on plane locations on a floor and did not provide accurate floor positioning. In this paper, we propose a method that uses multiple barometers as references for the floor positioning of smart phones with built-in barometric sensors. Some related studies used barometric formula to investigate the altitude of mobile devices and compared the altitude with the height of the floors in a building to obtain the floor number. These studies assume that the accurate height of each floor is known, which is not always the case. They also did not consider the difference in the barometric-pressure pattern at different floors, which may lead to errors in the altitude computation. Our method does not require knowledge of the accurate heights of buildings and stories. It is robust and less sensitive to factors such as temperature and humidity and considers the difference in the barometric-pressure change trends at different floors. We performed a series of experiments to validate the effectiveness of this method. The results are encouraging.

Hao Xia

2015-03-01

36

Using Multiple Barometers to Detect the Floor Location of Smart Phones with Built-in Barometric Sensors for Indoor Positioning.  

Science.gov (United States)

Following the popularity of smart phones and the development of mobile Internet, the demands for accurate indoor positioning have grown rapidly in recent years. Previous indoor positioning methods focused on plane locations on a floor and did not provide accurate floor positioning. In this paper, we propose a method that uses multiple barometers as references for the floor positioning of smart phones with built-in barometric sensors. Some related studies used barometric formula to investigate the altitude of mobile devices and compared the altitude with the height of the floors in a building to obtain the floor number. These studies assume that the accurate height of each floor is known, which is not always the case. They also did not consider the difference in the barometric-pressure pattern at different floors, which may lead to errors in the altitude computation. Our method does not require knowledge of the accurate heights of buildings and stories. It is robust and less sensitive to factors such as temperature and humidity and considers the difference in the barometric-pressure change trends at different floors. We performed a series of experiments to validate the effectiveness of this method. The results are encouraging. PMID:25835189

Xia, Hao; Wang, Xiaogang; Qiao, Yanyou; Jian, Jun; Chang, Yuanfei

2015-01-01

37

Practical conditions in the neutron diffraction under high pressure  

International Nuclear Information System (INIS)

Practical analysis is made on some conditions in utilizing neutrons for the study of atomistic structure of materials under high pressure. Investigation is made on the geometrical conditions; size of the specimen, width of slits, and the rate of extra-scattering. Experiments are performed on the effects of absorption by high pressure cell and the disturbance due to an overlapping of diffraction peaks. An observation is presented on the pressure-induced transformation in RbBr. (author)

38

A Sensor Fusion Method for Tracking Vertical Velocity and Height Based on Inertial and Barometric Altimeter Measurements  

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Full Text Available A sensor fusion method was developed for vertical channel stabilization by fusing inertial measurements from an Inertial Measurement Unit (IMU and pressure altitude measurements from a barometric altimeter integrated in the same device (baro-IMU. An Extended Kalman Filter (EKF estimated the quaternion from the sensor frame to the navigation frame; the sensed specific force was rotated into the navigation frame and compensated for gravity, yielding the vertical linear acceleration; finally, a complementary filter driven by the vertical linear acceleration and the measured pressure altitude produced estimates of height and vertical velocity. A method was also developed to condition the measured pressure altitude using a whitening filter, which helped to remove the short-term correlation due to environment-dependent pressure changes from raw pressure altitude. The sensor fusion method was implemented to work on-line using data from a wireless baro-IMU and tested for the capability of tracking low-frequency small-amplitude vertical human-like motions that can be critical for stand-alone inertial sensor measurements. Validation tests were performed in different experimental conditions, namely no motion, free-fall motion, forced circular motion and squatting. Accurate on-line tracking of height and vertical velocity was achieved, giving confidence to the use of the sensor fusion method for tracking typical vertical human motions: velocity Root Mean Square Error (RMSE was in the range 0.04–0.24 m/s; height RMSE was in the range 5–68 cm, with statistically significant performance gains when the whitening filter was used by the sensor fusion method to track relatively high-frequency vertical motions.

Angelo Maria Sabatini

2014-07-01

39

A sensor fusion method for tracking vertical velocity and height based on inertial and barometric altimeter measurements.  

Science.gov (United States)

A sensor fusion method was developed for vertical channel stabilization by fusing inertial measurements from an Inertial Measurement Unit (IMU) and pressure altitude measurements from a barometric altimeter integrated in the same device (baro-IMU). An Extended Kalman Filter (EKF) estimated the quaternion from the sensor frame to the navigation frame; the sensed specific force was rotated into the navigation frame and compensated for gravity, yielding the vertical linear acceleration; finally, a complementary filter driven by the vertical linear acceleration and the measured pressure altitude produced estimates of height and vertical velocity. A method was also developed to condition the measured pressure altitude using a whitening filter, which helped to remove the short-term correlation due to environment-dependent pressure changes from raw pressure altitude. The sensor fusion method was implemented to work on-line using data from a wireless baro-IMU and tested for the capability of tracking low-frequency small-amplitude vertical human-like motions that can be critical for stand-alone inertial sensor measurements. Validation tests were performed in different experimental conditions, namely no motion, free-fall motion, forced circular motion and squatting. Accurate on-line tracking of height and vertical velocity was achieved, giving confidence to the use of the sensor fusion method for tracking typical vertical human motions: velocity Root Mean Square Error (RMSE) was in the range 0.04-0.24 m/s; height RMSE was in the range 5-68 cm, with statistically significant performance gains when the whitening filter was used by the sensor fusion method to track relatively high-frequency vertical motions. PMID:25061835

Sabatini, Angelo Maria; Genovese, Vincenzo

2014-01-01

40

A Sensor Fusion Method for Tracking Vertical Velocity and Height Based on Inertial and Barometric Altimeter Measurements  

OpenAIRE

A sensor fusion method was developed for vertical channel stabilization by fusing inertial measurements from an Inertial Measurement Unit (IMU) and pressure altitude measurements from a barometric altimeter integrated in the same device (baro-IMU). An Extended Kalman Filter (EKF) estimated the quaternion from the sensor frame to the navigation frame; the sensed specific force was rotated into the navigation frame and compensated for gravity, yielding the vertical linear acceleration; finally,...

Angelo Maria Sabatini; Vincenzo Genovese

2014-01-01

41

Pyrolysis and gasification behavior of black liquor under pressurized conditions  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this study has been to enhance the understanding of the processes involved in pressurized black liquor gasification. Gasification is known to occur in three stages: drying, pyrolysis and char gasification. The work presented here focuses on the pyrolysis and gasification stages. Experiments were carried out primarily in two laboratory-scale reactors. A pressurized grid heater was used to study black liquor pyrolysis under pressurized conditions. Char yields and the fate of elements in the liquor, as well as the degree of liquor swelling, were measured in this device. A pressurized thermogravimetric reactor was used to measure the rate of the char gasification process under different temperatures and pressures and in various gas atmospheres. Pyrolysis experiments were also carried out in this device, and data on swelling behavior, char yields and component release were obtained 317 refs.

Whitty, K.

1997-11-01

42

Bulging of pressure tubes at hot spots under LOCA conditions  

International Nuclear Information System (INIS)

During certain postulated loss-of-coolant accidents (LOCA) in a CANDU reactor, some fuel channels can become highly voided within a very short time. Although the pressure tubes are heated mainly by convection and thermal radiation during the LOCA transient, additional heat flow occurs through the bearing pads that are in contact with the pressure tribe. This contact can lead to local hot spots and associated thermal stresses in the pressure tube wall. The two factors that affects the behavior of the pressure tubes during LOCA conditions are the internal pressure and the local heating. Although the effect of internal pressure and of axially uniform temperature has been studied elsewhere, the effect of the local heating on the pressure tube behavior has not been modelled before. This paper shows that the bulging of a pressure tube at a hot spot is the result of the thermal stresses that are developed in a pressure tube during a LOCA transient. To isolate the local heating effect from the internal pressure, a series of single-effect experiments was performed. In these experiments, sections of a CANDU pressure tube were subjected to local heating only. The thermal profile and the local deformation were measured function of time. To quantify the effect of the thermal stresses on the bulging of pressure tubes at hot spots and to develop numerical tools that can predict such bulging, finite element analyses were performed rising the ABAQUS finite element computer code. Use oABAQUS finite element computer code. Use of the measured thermal profiles in the ABAQUS finite element analysis, resulted in very good agreement between the predicted and measured displacements. (author)

43

Barometric tides from ECMWF operational analyses  

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Full Text Available The solar diurnal and semidiurnal tidal oscillations in surface pressure are extracted from the operational analysis product of the European Centre for Medium Range Weather Forecasting (ECMWF. For the semidiurnal tide this involves a special temporal interpolation, following Van den Dool et al. (1997. The resulting tides are compared with a "ground truth" tide data set, a compilation of well-determined tide estimates deduced from many long time series of station barometer measurements. These comparisons show that the ECMWF (analysis tides are significantly more accurate than the tides deduced from two other widely available reanalysis products. Spectral analysis of ECMWF pressure series shows that the tides consist of sharp central peaks with modulating sidelines at integer multiples of 1 cycle/year, superimposed on a broad cusp of stochastic energy. The integrated energy in the cusp dominates that of the side-lines. This complicates the development of a simple empirical model that can characterize the full temporal variability of the tides.

Key words. Meteorology and atmospheric dynamics (waves and tides

R. D. Ray

44

Rotating incompressible flow with a pressure Neumann condition  

Science.gov (United States)

This work considers the internal flow of an incompressible viscous fluid contained in a rectangular duct subject to a rotation. A direct velocity-pressure algorithm in primitive variables with a Neumann condition for the pressure is employed. The spatial discretization is made with finite central differences on a staggered grid. The pressure and velocity fields are directly updated without any iteration. Numerical simulations with several Reynolds numbers and rotation rates were performed for ducts of aspect ratios 2:1 and 8:1.

Claeyssen, Julio R.; Bravo Asenjo, Elba; Rubio, Obidio

2006-01-01

45

A stochastic approach to noise modeling for barometric altimeters.  

Science.gov (United States)

The question whether barometric altimeters can be applied to accurately track human motions is still debated, since their measurement performance are rather poor due to either coarse resolution or drifting behavior problems. As a step toward accurate short-time tracking of changes in height (up to few minutes), we develop a stochastic model that attempts to capture some statistical properties of the barometric altimeter noise. The barometric altimeter noise is decomposed in three components with different physical origin and properties: a deterministic time-varying mean, mainly correlated with global environment changes, and a first-order Gauss-Markov (GM) random process, mainly accounting for short-term, local environment changes, the effects of which are prominent, respectively, for long-time and short-time motion tracking; an uncorrelated random process, mainly due to wideband electronic noise, including quantization noise. Autoregressive-moving average (ARMA) system identification techniques are used to capture the correlation structure of the piecewise stationary GM component, and to estimate its standard deviation, together with the standard deviation of the uncorrelated component. M-point moving average filters used alone or in combination with whitening filters learnt from ARMA model parameters are further tested in few dynamic motion experiments and discussed for their capability of short-time tracking small-amplitude, low-frequency motions. PMID:24253189

Sabatini, Angelo Maria; Genovese, Vincenzo

2013-01-01

46

A Stochastic Approach to Noise Modeling for Barometric Altimeters  

Directory of Open Access Journals (Sweden)

Full Text Available The question whether barometric altimeters can be applied to accurately track human motions is still debated, since their measurement performance are rather poor due to either coarse resolution or drifting behavior problems. As a step toward accurate short-time tracking of changes in height (up to few minutes, we develop a stochastic model that attempts to capture some statistical properties of the barometric altimeter noise. The barometric altimeter noise is decomposed in three components with different physical origin and properties: a deterministic time-varying mean, mainly correlated with global environment changes, and a first-order Gauss-Markov (GM random process, mainly accounting for short-term, local environment changes, the effects of which are prominent, respectively, for long-time and short-time motion tracking; an uncorrelated random process, mainly due to wideband electronic noise, including quantization noise. Autoregressive-moving average (ARMA system identification techniques are used to capture the correlation structure of the piecewise stationary GM component, and to estimate its standard deviation, together with the standard deviation of the uncorrelated component. M-point moving average filters used alone or in combination with whitening filters learnt from ARMA model parameters are further tested in few dynamic motion experiments and discussed for their capability of short-time tracking small-amplitude, low-frequency motions.

Angelo Maria Sabatini

2013-11-01

47

Pohorje eclogites revisited: Evidence for ultrahigh-pressure metamorphic conditions  

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Full Text Available Kyanite eclogites from the Pohorje Mountains, Slovenia, are providing the first evidence of ultrahigh-pressureEo-Alpine metamorphism in the Eastern Alps. Polycrystalline quartz inclusions in garnet, omphacite and kyaniteare surrounded by radial fractures and exhibit microtextures diagnostic for the recovery after coesite breakdown.The non-stoichiometric supersilicic omphacites found in Pohorje eclogites contain up to 5 mol % of Ca-Eskola molecule.Such clinopyroxenes are known to be stable exclusively at high-pressure conditions exceeding 3 GPa. Theirbreakdown during decompression resulted in exolution of quartz rods and needles that are oriented parallel toomphacite c-axis. The absence of coesite is a consequence of near-isothermal decompression during the first stagesof exhumation.Pressure and temperature conditions for the formation of the peak metamorphic mineral assemblages have beenassessed through a consideration of a Fe2+-Mg partitioning between garnet and omphacite pairs, based on differentcalibrations; b the equilibrium between garnet + clinopyroxene + phengite ± kyanite ± quartz/coesite assemblage.Estimated peak pressure and temperature conditions of 3.0-3.1 GPa and 750-783 °C are well within the coesite, i.e.the ultrahigh-pressure stability field.

Mirijam Vrabec

2010-06-01

48

Oxide ceramics under extreme pressure and radiation conditions  

International Nuclear Information System (INIS)

This experimental study tackles the question how oxide ceramics (ZrO2 and HfO2) respond to the simultaneous exposure to two extreme conditions, pressures up to several ten GPa and irradiation with highly energetic (MeV-GeV) heavy ion projectiles. The combination of these two extreme conditions influences the materials in ways none of those two conditions alone could. In both materials, the exposure to high-fluence irradiations at ambient pressure result in a crystalline-to-crystalline phase transformation from the monoclinic into the first high temperature tetragonal phase. For heavy ions such as Xe, Au, Pb, and U this structural change requires a double impact process. For light ions such as Ni and Cr, the transferred energy does not suffice to induce any transformation indicating an energy loss threshold in ZrO2 as well as in HfO2. If the irradiation is performed under high pressure, the monoclinic-to-tetragonal transformation occurs already at a fluence that is more than one order of magnitude lower, suggesting a single-hit process. Although the ZrO2 and HfO2 behave much alike as no two other compound materials, their response to the combination of pressure and ion irradiation differs. X-ray diffraction analysis of the irradiated, pressurized samples and Raman and TEM measurements at ambient conditions revealed that the monoclinic-to-tetragonal transformation in ZrO2 around 10 GPa is not direct but includes a detour into the cubic high-temperature phase, before the tetragonal structure becomes stable under decompression. For HfO2, high fluence irradiation at 10 GPa results in the intensification of the first high pressure phase which is afterwards stabilized to ambient conditions. At higher pressures, additional ion irradiation forces both ceramics to perform a transition into their second high pressure phase (orthorhombic-II) far away from its stability field. This study demonstrates that the combination of ion irradiation and high pressure can serve as a trigger for transitions into different phases and as stabilization mechanism of usually unstable structures.

49

Investigations on pressure suppression system loads at accident conditions  

International Nuclear Information System (INIS)

For simulation of the integral behavior of pressure suppresion systems at accident conditions a mathematical model was developed which simulates a wide range of the loads occurring during a loss-of coolant accident. The multi-zone point model DRASYS serves for mathematical simulation of quasistatic (pressure and temperature build-up in the dry well and the suppression chamber) as well as dynamic loads (free-blowing process, water throw-up and condensing oscillations) in the course of a loss-of-coolant accident. For determination of the state variations with time in the individual pressure sections thermodynamic equilibrium is assumed between steam and water phases. Thermal non-equilibrium states are taken into account if phase separation interfaces between water and steam/air mixture exist. The flows between the individual pressure sections are treated as homogeneous, nonsteady, incompressible flows. For verification of the mathematical model recalculations were made of experiments performed at various test stands. Teh recalculations showed that the mathematical model has got a wide range of application and is suited for design and assessment of pressure suppression systems at accident conditions. (orig.)

50

Modelling of radionuclide migration after underground nuclear explosions by barometric pumping  

International Nuclear Information System (INIS)

During and shortly after a nuclear explosion several noble gas isotopes (131mXe, 133mXe, 133Xe and 135Xe) besides many other fission products are produced. If the explosion is emplaced underground for clandestine test purposes these isotopes, all other fission and activation products are injected into the surrounding rocks. Only the noble gases are able to migrate upwards to the surface through suitable pathways in a fractured permeable medium due to cyclical changes in barometric surface pressure. Possible pathways are cracks, faults or high-permability layers. Times of arrival are much shorter than is expected by diffusion-process alone and may be of orders of magnitude more significant to allow verifying the Comprehensive Nuclear Test Ban Treaty (CTBT). This work calculates time of arrival and shifts in abundance of the radioxenons due to its different molecular diffusion lengths

51

Drying kinetics of RDX under atmospheric pressure and vacuum conditions  

International Nuclear Information System (INIS)

Highlights: • In this study, RDX is dried in the ranges of 60–90 °C under atmospheric pressure and vacuum conditions. • Ten models are used to describe the drying of RDX. • The Midilli–Kucuk model is determined as the most suitable model. • Effective moisture diffusivity and activation energy for drying process are determined. - Abstract: The drying characteristics of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) are investigated in the ranges of 60–90 °C of drying temperature under atmospheric pressure and vacuum conditions in a laboratory scale dryer. The effect of drying temperature and absolute pressure on the drying characteristics is determined. In order to estimate and select the suitable form of RDX drying curves, the curves are fitted to ten different semi-theoretical and/or empirical thin-layer drying models and coefficients are evaluated by non-linear regression analysis. The models are compared based on their coefficient of determination, such as mean bias error, root mean square error, reduced chi-square and modeling efficiency between experimental and predicted moisture ratios. It is deduced that Midilli–Kucuk model has shown a better fit to the experimental drying data as compared to other models. A diffusion model is used to describe the moisture transfer and the effective diffusivity for RDX drying is also determined at each temperature. Beside, the activation energy is also expressed using Arrhenius-type relationship under atmospheric pressure and vacuum conditions

52

Touch mode micromachined capacitive pressure sensor with signal conditioning electronics  

DEFF Research Database (Denmark)

In the last decades, pressure sensors have been one of the greatest successes of the MEMS industry. Many companies are using them in a variety of applications from the automotive to the environmental field. Currently piezoresistive pressure sensors are the most developed, and a well established technology to design and fabricate these sensors has been implemented. Capacitive pressure sensing, on the other hand, is still an open and really promising field. Results Capacitive microsensors were designed and fabricated (Fig. 1) and an analytical model for touch mode regime, which fitted accurately the measurements done on the devices, was investigated. Fabrication was carried on at Danchip cleanrooms where fusion bonding was used in order to obtain a thin silicon plate on top of a sealed vacuum cavity (Fig. 2). A viable signal conditioning scheme for capacitive pressure sensing was simulated and implemented. A measurement setup was arranged and tested for accuracy and reliability with respect to hysteresis. Finally, designs with different radii of the top plate were characterized by a capacitance versus pressure curve at different frequencies and temperatures (Fig. 3). Industrial possibilities Energy saving systems is one of the key challenges nowadays. In this context, house heating is a priority for environmental issues. For this reason, the possibilities of using a low power consumption technique, such as capacitive pressure sensing, in harsh environments is a concrete market opportunity. Our aim is therefore to develop new technologies based on capacitive sensing to be able to fulfil future requirements in this field.

Fragiacomo, Giulio; Eriksen, Gert F.

2010-01-01

53

Ash formation under pressurized pulverized coal combustion conditions  

Science.gov (United States)

Coal combustion is a source of inorganic particulate matter (ash), which can deposit in boilers and also be emitted into the atmosphere becoming part of ambient fine particulate matter (PM 2.5). In order to decrease coal combustion emissions per unit of power produced, higher efficiency systems have been proposed, including systems operating at elevated pressures. These new operating conditions will affect pollutant formation mechanisms, particularly those associated with the conversion of mineral matter to ash. Ash particle formation mechanisms are particularly sensitive to changes in pressure as they are related to the structure of coal char particles at early stages of combustion. To assess the importance of pressure on ash particle formation, pyrolyzed chars and ash particles from pressurized pulverized combustion of two bituminous and one subbituminous U.S. coals at operating pressures up to 30 atm were studied. Pressure changes the distribution of char particle types, changing the spatial distribution of the minerals during the combustion process and therefore affecting particle formation mechanisms. Chars were examined by Scanning Electron Microscopy (SEM) and classified into two different types (cenospheric and solid) depending on porosity and wall thickness. A correlation for estimating the amount of these cenospheric char particles was then proposed for bituminous coals based on the operating conditions and coal maceral analysis. The ash particle size distribution of the coals combusted at different operating pressures was measured using Computer Controlled Scanning Electron Microscopy (CCSEM). The results of the char characterization and ash particle size distribution measurements were then incorporated into an ash particle formation algorithm that was proposed and implemented. The model predicts ash particle size and composition distributions at elevated pressures under conditions of complete char burnout. Ash predictions were calculated by first developing char structure distribution functions based on coal characteristics. To obtain an ash particle size distribution, carbon is then allowed to react away while following coalescence, fragmentation and other transformation processes as combustion proceeds. Particle size distributions calculated with this model showed qualitative agreement with the trends identified in the experimental portion of this research.

Davila Latorre, Aura Cecilia

54

Materials Science under Extreme Conditions of Pressure and Strain Rate  

Energy Technology Data Exchange (ETDEWEB)

Solid state dynamics experiments at very high pressures (P >> 10 GPa) and strain rates ({var_epsilon} >> 10{sup 5} s{sup -1}) have been demonstrated on high energy laser facilities, albeit over brief intervals of time and small spatial scales. We have developed two methods for driving samples to high pressures (10-100 GPa) at high strain rate (10{sup 6}-10{sup 8} s{sup -1}) in the solid state. One method uses a shockless compression technique, and the other uses multiple staged shocks. These drives are calibrated with VISAR measurements of the resulting compression wave. Deformation mechanisms are inferred under these conditions by characterizing recovered samples. Material strength at high pressures and strain rates is deduced by measuring the reduced growth of material perturbations at a hydrodynamically unstable interface. Microscopic lattice response is determined by time-resolved Bragg diffraction and x-ray absorption spectroscopy (EXAFS). Large-scale simulations, both at the continuum level using constitutive models and at the lattice level using molecular dynamics simulation, are used to interpret these integral experiments. We will review our progress in this new area of laser-based materials science research, then present a vision for carrying these solid-state experiments to much higher pressures, P > 1000 GPa, on the National Ignition Facility (NIF) laser facility.

Remington, B A; Bazan, G; Bringa, E; Caturla, M; Edwards, M J; Glendinning, S G; Kad, B; Kalantar, D H; Kumar, M; Lasinski, B F; Lorenz, K T; McNaney, J; Meyerhofer, D; Meyers, M A; Pollaine, S M; Reisman, D B; Rowley, D; Schneider, M; Stolken, J; Wark, J; Yaakobi, B

2003-03-27

55

Photoelectron Spectroscopy under Ambient Pressure and Temperature Conditions  

Energy Technology Data Exchange (ETDEWEB)

We describe the development and applications of novel instrumentation for photoemission spectroscopy of solid or liquid surfaces in the presence of gases under ambient conditions or pressure and temperature. The new instrument overcomes the strong scattering of electrons in gases by the use of an aperture close to the surface followed by a differentially-pumped electrostatic lens system. In addition to the scattering problem, experiments in the presence of condensed water or other liquids require the development of special sample holders to provide localized cooling. We discuss the first two generations of Ambient Pressure PhotoEmission Spectroscopy (APPES) instruments developed at synchrotron light sources (ALS in Berkeley and BESSY in Berlin), with special focus on the Berkeley instruments. Applications to environmental science and catalytic chemical research are illustrated in two examples.

Ogletree, D. Frank; Bluhm, Hendrik; Hebenstreit, Eleonore B.; Salmeron, Miquel

2009-02-27

56

Continuous positive airway pressure setups evaluated at simulated exercise conditions  

Scientific Electronic Library Online (English)

Full Text Available INTRODUCTION: Studies have shown increases in airway opening pressure (Pao) swings and work of breathing (WOB) by different continuous positive airway pressure (CPAP) devices at rest, but few address this issue during exercise. The aim of the present work was to analyze the imposed WOB (WOBi), the a [...] pparent resistance (Rapp) and swings of Pao (deltaP) of 3 CPAP assemblies at simulated exercise conditions. METHODS: The CPAP measures were obtained from: a commercial CPAP (Assembly 1), a high flow CPAP (Assembly 2) and the parallel association of these devices (Assembly 3). In each assembly the spring-loaded positive end-expiratory pressure (PEEP) valve was set to fully opened (mode A) or at the same CPAP pressure (mode B). The exercise protocol simulation, performed manually by a calibrated syringe and a metronome, employed a respiratory frequency of 30 bpm, tidal volume of 2.7 L and inspiratory-to-expiratory ratio of 1. The setups were evaluated at CPAP settings of 5, 10 and 15 cmH2O. RESULTS: The lowest deltaP as well as Rapp and WOBi were obtained with Assembly 3 in mode A with an adjusted CPAP of 10 cmH2O (deltaP=8.1 (0.5) cmH2O, WOBi=1.4 (0.14) cmH2O/L/s, Rapp= 1.3 (0.07) J/s) showed as median (interquartile range). CONCLUSION: For the conditions studied, the best CPAP setup was obtained with mode A.

Marcelo Vieira Leão, Nunes; Antonio, Giannella-Neto; Frederico Caetano Jandre de Assis, Tavares.

2014-06-01

57

On equilibrium conditions of the sunspot total pressure and the pressure of the environmental photosphere  

International Nuclear Information System (INIS)

For different sunspots (with magnetic field strength H=2000-4000 Gs) using transparent and opaqUe models, the values of vertical gradients of magnetic field ?H/?h are selected to fit the equilibrium condition Psub(t)* (h)=PsUb(g)(h) at optical depths 10-45, where Psub(t)*(h) is the total pressure in a sunspot and Psub(g)(h) is the pressure in the environmental photosphere. In transparent models the equilibrium is realized at ?H/?h=3-5 Gs/km. The increase of sunspot magnetic field strength leads to the increase of vertical gradients ?h/?h, but the spots become more transparent. The values ?H/?h<3 Gs/ km might be obtained both for transparent and opaque models if the gradient of gaseous pressure is decreasing with height. The values of vertical gradients of magnetic field, obtained earlier are found to be in good agreement with values ?H/?h satisfying eqUilibrium conditions for small gradients of gaseous pressure in a sunspot

58

Pressurized thermal shock. Thermo-hydraulic conditions in the CNA-I reactor pressure vessel  

International Nuclear Information System (INIS)

In this paper we analyze several reports issued by the Utility (Nucleo Electrica S.A.) and related to Reactor Pressure Vessel (RPV) phenomena in the CNA-I Nuclear Power Plant. These analyses are aimed at obtaining conclusions and establishing criteria ensuring the RPV integrity. Special attention was given to the effects ECCS cold-water injection at the RPV down-comer leading to pressurized thermal shock scenarios. The results deal with hypothetical primary system pipe breaks of different sizes, the inadvertent opening of the pressurizer safety valve, the double guillotine break of a live steam line in the containment and the inadvertent actuation pressurizer heaters. Modeling conditions were setup to represent experiments performed at the UPTF, under the hypothesis that they are representative of those that, hypothetically, may occur at the CNA-I. No system scaling analysis was performed, so this assertion and the inferred conclusions are no fully justified, at least in principle. The above mentioned studies, indicate that the RPV internal wall surface temperature will be nearly 40 degree. It was concluded that they allowed a better approximation of PTS phenomena in the RPV of the CNA-I. Special emphasis was made on the influence of the ECCS systems on the attained RPV wall temperature, particularly the low-pressure TJ water injection system. Some conservative hypothesis made, are discussed in this report. (author)

59

Micromachined capacitive pressure sensor with signal conditioning electronics  

DEFF Research Database (Denmark)

Micromachined capacitive pressure sensors for harsh environment together with interfacing electronic circuits have been studied in this project. Micro-electromechanical systems (MEMS) have been proposed as substitutes for macro scale sensor’s systems in many different fields and are the only possible solution in many cases where, for example, the dimensions of the sensing element is the limiting factor. Furthermore, MEMS can significantly reduce costs and power consumption being the best candidate for consumer electronics such as mobile phones and cameras, or for the automotive industry where a great deal of sensors are used. Pressure sensors are among the most successful MEMS and are used in a huge variety of applications. In this project an absolute capacitive pressure sensor has been developed with the aim to integrate it in pump control systems to improve the efficiency of the pump. The developed MEMS consist of hermetically sealed vacuum cavities surrounded by two heavily doped silicon layers which constitute the plates of a capacitor. The top plate is also the sensing element being a thin diaphragm that deflects when pressure is applied, thus increasing the capacitance (i.e. the output signal) of the device. Fusion bonding of two wafers has been used in order to obtain the cavities, this is also the only non-standard cleanroom process involved in the fabrication of the transducers. The device developed can measure absolute pressures from 0 to 10 bar with sensitivity up to 80 pF/bar. As a part of the project a suitable interfacing circuit has been developed. Different solutions have been studied in order to optimize size, costs, sensitivity and stability. A comparative analysis between them has been carried out and suggestion for the final product has been proposed. Both the electronic conditioning circuits and the MEMS have been fully described with mathematical models and simulated with electrical networks software for the circuit part and finite element for the sensor part. A good matching between analytical models and simulations results has been achieved. Furthermore, the experimental results are in good agreement with the models proposed. Finally a demonstrator has been fabricated under the constraints of a previously designed case in order to contain costs; modification or re-design of the packaging is in fact one of the major costs for the MEMS industry. This demonstrator has been characterized and presented at Grundfos Direct Sensors A/S and constitute the preliminary work for a new product which is intended target the low power or wireless pressure sensor for harsh environment market.

Fragiacomo, Giulio

2012-01-01

60

Evaluating road surface conditions using dynamic tire pressure sensor  

Science.gov (United States)

In order to best prioritize road maintenance, the level of deterioration must be known for all roads in a city's network. Pavement Condition Index (PCI) and International Roughness Index (IRI) are two standard methods for obtaining this information. However, IRI is substantially easier to measure. Significant time and money could be saved if a method were developed to estimate PCI from IRI. This research introduces a new method to estimate IRI and correlate IRI with PCI. A vehicle-mounted dynamic tire pressure sensor (DTPS) system is used. The DTPS measures the signals generated from the tire/road interaction while driving. The tire/road interaction excites surface waves that travel through the road. DTPS, which is mounted on the tire's valve stem, measures tire/road interaction by analyzing the pressure change inside the tire due to the road vibration, road geometry and tire wall vibration. The road conditions are sensible to sensors in a similar way to human beings in a car. When driving on a smooth road, tire pressure stays almost constant and there are minimal changes in the DTPS data. When driving on a rough road, DTPS data changes drastically. IRI is estimated from the reconstructed road profile using DTPS data. In order to correlate IRI with PCI, field tests were conducted on roads with known PCI values in the city of Brockton, MA. Results show a high correlation between the estimated IRI values and the known PCI values, which suggests that DTPS-based IRI can provide accurate predictions of PCI.

Zhao, Yubo; Wu, H. Felix; McDaniel, J. Gregory; Wang, Ming L.

2014-03-01

61

Summary on the depressurization from supercritical pressure conditions  

Energy Technology Data Exchange (ETDEWEB)

When a fluid discharges from a high pressure and temperature system, a 'choking' or critical condition occurs, and the flow rate becomes independent of the downstream pressure. During a postulated loss of coolant accident (LOCA) of a water reactor the break flow will be subject to this condition. An accurate estimation of the critical flow rate is important for the evaluation of the reactor safety, because this flow rate controls the loss of coolant inventory and energy from the system, and thus has a significant effect on the accident consequences[1]. In the design of safety systems for a super critical water reactor (SCWR), postulated LOCA transients are particularly important due to the lower coolant inventory compared to a typical PWR for the same power output. This lower coolant inventory would result in a faster transient response of the SCWR, and hence accurate prediction of the critical discharge is mandatory. Under potential two-phase conditions critical flow is dominated by the vapor content or quality of the vapor, which is closely related with the onset of vaporization and the interfacial interaction between phases [2]. This presents a major challenge for the estimation of the flow rate due to the lack of the knowledge of those processes, especially under the conditions of interest for the SCWR. According to the limited data of supercritical fluids, the critical flows at conditions above the pseudo-critical point seem to be fairly stable and consistent with the subcritical homogeneous equilibrium model (HEM) model predictions, while having a lower flow rate than those in the two-phase region. Thus the major difficulty in the prediction of the depressurization flow rates remains in the region where two phases co-exist at the top of the vapor dome. In this region, the flow rate is strongly affected by the nozzle geometry and tends to be unstable. Various models for this region have been developed with different assumptions, e.g. the HEM and Moody model [3], and the Henry-Fauske non-equilibrium model [4], and are currently used in subcritical pressure reactor safety design[5]. It appears that some of these models could be reasonably extended to above the thermodynamic pseudo-critical point. The more stable and lower discharge flow rates observed in conditions above the pseudo-critical point suggests that even though SCWR's have a smaller coolant inventory, the safety implications of a LOCA and the subsequent depressurization may not be as severe as expected, this however needs to be confirmed by a rigorous evaluation of the particular event and further evaluation of the critical flow rate. This paper will summarize activities on critical flow models, experimental data and numerical modeling during blowdown from supercritical pressure conditions under the International Atomic Energy Agency (IAEA) Coordinated Research Project (CRP) on 'Heat Transfer Behaviour and Thermo-hydraulics Code testing for SCWRs'. (authors)

Anderson, M. [Univ. of Wisconsin Madison, 1500 Engineering Dr., Madison, WI 53706 (United States); Chen, Y. [Dept. of Reactor Engineering, Research and Design, Reactor Thermal-Hydraulic Lab., China Inst. of Atomic Energy, P.O.Box 275 59, 102413 Beijing (China); Ammirable, L. [JRC/Inst. for Energy and Transport (Netherlands); Novog, D. [Dept. of Engineering Physics, McMaster Univ., 1280 Main Street, ON (Canada); Yamada, K. [International Atomic Energy Agency, Vienna International Centre, P.O. Box 100, 1400 Vienna (Austria)

2012-07-01

62

Origins of life and biochemistry under high-pressure conditions.  

Science.gov (United States)

Life on Earth can be traced back to as far as 3.8 billion years (Ga) ago. The catastrophic meteoritic bombardment ended between 4.2 and 3.9 Ga ago. Therefore, if life emerged, and we know it did, it must have emerged from nothingness in less than 400 million years. The most recent scenarios of Earth accretion predict some very unstable physico-chemical conditions at the surface of Earth, which, in such a short time period, would impede the emergence of life from a proto-biotic soup. A possible alternative would be that life originated in the depth of the proto-ocean of the Hadean Earth, under high hydrostatic pressure. The large body of water would filter harmful radiation and buffer physico-chemical variations, and therefore would provide a more stable radiation-free environment for pre-biotic chemistry. After a short introduction to Earth history, the current tutorial review presents biological and physico-chemical arguments in support of high-pressure origin for life on Earth. PMID:17003893

Daniel, Isabelle; Oger, Philippe; Winter, Roland

2006-10-01

63

PRESSURE INTEGRITY OF 3013 CONTAINER UNDER POSTULATED ACCIDENT CONDITIONS  

Energy Technology Data Exchange (ETDEWEB)

A series of tests was carried out to determine the threshold for deflagration-to-detonation transition (DDT), structural loading, and structural response of the Department of Energy 3013 storage systems for the case of an accidental explosion of evolved gas within the storage containers. Three experimental fixtures were used to examine the various issues and three mixtures consisting of either stoichiometric hydrogen-oxygen, stoichiometric hydrogen-oxygen with added nitrogen, or stoichiometric hydrogen-oxygen with an added nitrogen-helium mixture were tested. Tests were carried out as a function of initial pressure from 1 to 3.5 bar and initial temperature from room temperature to 150 C. The elevated temperature tests resulted in a slight increase in the threshold pressure for DDT. The elevated temperature tests were performed to ensure the test results were bounding. Because the change was not significant the elevated temperature data are not presented in the paper. The explosions were initiated with either a small spark or a hot surface. Based on the results of these tests under the conditions investigated, it can be concluded that DDT of a stoichiometric hydrogen-oxygen mixture (and mixtures diluted with nitrogen and helium) within the 3013 containment system does not pose a threat to the structural integrity of the outer container.

Rawls, G.

2010-02-01

64

Behaviour of concrete containment under over-pressure conditions  

International Nuclear Information System (INIS)

The Atomic Energy Control Board of Canada initiated June, 1975, a major study of the behaviour of concrete containment under over-pressure conditions. Although extensive theoretical and experimental work has been carried out for thick-walled Prestressed Concrete Reactor Vessels (PCRV's), there is a want of information on the non-linear response of thin-walled structures typical of the CANDU, 600 MW(e) cylindrical/spherical, post-tensioned containment shells. The purpose of this paper is to provide an overview of the total program, to present the reasons behind the research contract, and the specification and implementation of the work. The results of the theoretical and experimental work and their implications with respect to Canadian Concrete Containment practice are discussed. This study is unique, and, as far as is known, has no world-wide precedence. (orig.)

65

Characterization of contaminant transport by gravity, capillarity and barometric pumping in heterogeneous vadose regimes. 1998 annual progress report  

International Nuclear Information System (INIS)

'The intent of this research program is to obtain an improved understanding of vadose zone transport processes and to develop field and modeling techniques required to characterize contaminant transport in the unsaturated zone at DOE sites. For surface spills and near-surface leaks of chemicals, the vadose zone may well become a long-term source of contamination for the underlying water table. Transport of contaminants can occur in both the liquid and gas phases of the unsaturated zone. This transport occurs naturally as a result of diffusion, buoyancy forces (gravity), capillarity and barometric pressure variations. In some cases transport can be enhanced by anisotropies present in hydrologic regimes. This is particularly true for gas-phase transport which may be subject to vertical pumping resulting from atmospheric pressure changes. For liquid-phase flows, heterogeneity may enhance the downward transport of contaminants to the water table depending on soil properties and the scale of the surface spill or near-surface leak. Characterization techniques based upon the dynamics of transport processes are likely to yield a better understanding of the potential for contaminant transport at a specific site than methods depending solely on hydrologic properties derived from a borehole. Such dynamic-characterization techniques can be useful for evaluating sites where contamination presently exists as well as for providing an objective basis to evaluate the efficacy of proposed as well as implemented clean-up technologies. The real-time monitoring of processes that may occur during clean-up of tank waste and the mobility of contaminants beneath the Hanford storage tanks during sluicing operations is one example of how techniques developed in this effort can be applied to current remediation problems. In the future, such dynamic-characterization methods might also be used as part of the site-characterization process for determining suitable locations of new DOE facilities that have the potential of introducing contamination into the vadose zone. This report summarizes work and accomplishments at the midpoint of the 3-year project. The authors have pursued the concept of a vadose-zone observatory (VZO) to provide the field laboratory necessary for carrying out the experiments required to achieve the goals of this research. The approach has been: (1) to carry out plume release experiments at a VZO allowing the acquisition of several different kinds of raw data that, (2) are analyzed and evaluated with the aid of highly detailed, diagnostic numerical models. Because the soil properties of a single VZO are unlikely to cover the full range of conditions encountered at all DOE facilities, the authors anticipate studying at least two and possibly three sites spanning a wide range of hydrologic and geologic properties.'

66

Determination of barometric efficiency and effective porosity, boreholes UE-25 cNo.1, UE-25 cNo.2, UE-25 cNo.3, Yucca Mountain, Nye County, Nevada  

International Nuclear Information System (INIS)

Simultaneous records of water-level altitudes in boreholes UE-25 cNo.1, UE-25 cNo.2, and UE-25 cNo.3 (the C-holes) and atmospheric pressure at and near the C-holes were obtained from July 15 to September 8, 1993, to determine the barometric efficiency of the entire uncased section of each of the C-holes, for the purpose of analyzing pumping tests. Each of the C-holes is 3,000 feet deep. About 1,600 feet of each borehole is open in Miocene tuffaceous rocks. Water-level altitudes in the C-holes fluctuate in response to Earth tides and changes in atmospheric pressure, which are characteristics of wells completed in an elastic, confined aquifer. The barometric efficiency of the C-holes in this study was analyzed by filtering simultaneously collected water-level-altitude and atmospheric-pressure data to remove the influences of Earth tides and semi-diurnal heating and cooling and then regressing filtered water-level-altitude changes as a function of filtered changes in atmospheric pressure. The average barometric efficiency of the uncased sections of boreholes UE-25 cNo.1 and UE-25 cNo.3 was determined to be 0.94. Malfunctioning equipment prevented determining the barometric efficiency of bore-hole UE-25 cNo.2. An average effective porosity of 0.36 was calculated from barometric efficiency values determined in this study and a specific storage value of 0.497 x 10-6 per foot that was determined previously from geophysical logs of the C-holes. A porosity of 0.36 i logs of the C-holes. A porosity of 0.36 is consistent with values determined from geophysical logs and core analyses for the Calico Hills Formation

67

Phase stability limit of c-BN under hydrostatic and non-hydrostatic pressure conditions.  

Science.gov (United States)

Phase stability limit of cubic boron nitride (c-BN) has been investigated by the crystal structure search technique. It indicated that this limit is ?1000 GPa at hydrostatic pressure condition. Above this pressure, c-BN turns into a metastable phase with respect to rocksalt type boron nitride (rs-BN). However, rs-BN cannot be retained at 0 GPa owing to its instability at pressure below 250 GPa. For non-hydrostatic pressure conditions, the phase stability limit of c-BN is substantially lower than that under hydrostatic pressure conditions and it is also dramatically different for other pressure mode. PMID:24784296

Xiao, Jianwei; Du, Jinglian; Wen, Bin; Melnik, Roderick; Kawazoe, Yoshiyuki; Zhang, Xiangyi

2014-04-28

68

Phase stability limit of c-BN under hydrostatic and non-hydrostatic pressure conditions  

Energy Technology Data Exchange (ETDEWEB)

Phase stability limit of cubic boron nitride (c-BN) has been investigated by the crystal structure search technique. It indicated that this limit is ?1000 GPa at hydrostatic pressure condition. Above this pressure, c-BN turns into a metastable phase with respect to rocksalt type boron nitride (rs-BN). However, rs-BN cannot be retained at 0 GPa owing to its instability at pressure below 250 GPa. For non-hydrostatic pressure conditions, the phase stability limit of c-BN is substantially lower than that under hydrostatic pressure conditions and it is also dramatically different for other pressure mode.

Xiao, Jianwei; Du, Jinglian; Wen, Bin, E-mail: wenbin@ysu.edu.cn; Zhang, Xiangyi [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Melnik, Roderick [M2NeT Lab, Wilfrid Laurier University, Waterloo25, 75 University Ave. West, Ontario, Canada N2L 3C5 (Canada); Kawazoe, Yoshiyuki [New Industry Creation Hatchery Center, Tohoku University, 6-6-4 Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8579, Japan and Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, 1, Lavyrentyev Avenue, Novosibirsk 630090 (Russian Federation)

2014-04-28

69

An alternative method to Mariotte reservoir system for maintaining constant hydraulic pressure  

International Nuclear Information System (INIS)

Some studies being done to evaluate the suitability of the Yucca Mountain area as a potential radioactive waste repository require the application of a constant water pressure as a boundary condition to study water flow through porous media. The Mariotte reservoir system is commonly used to supply such a boundary condition. Several problems with the Mariotte reservoir system were discovered when it was used to apply a constant water pressure as a boundary condition for a prolonged period. The constant-pressure boundary condition is required for some lab. experiments to study water flow through porous media. The observed problems were caused by temperature and barometric-pressure fluctuations while the flow rates were very small and caused erroneous water flow-rate measurements. An alternative method was developed and used where the water pressure is controlled by regulating its level by using water-level sensing electrodes. The new method eliminated the effects of temperature and barometric-pressure fluctuations and maintained an acceptable accuracy of the estimated water flow rate without compromising the advantage of the Mariotte reservoir

70

Barometric process separation: New method for quantifying nitrification, denitrification, and nitrous oxide sources in soils  

Energy Technology Data Exchange (ETDEWEB)

A method, Barometric Process Separation (BaPS), was developed for the quantification of gross nitrification rates and denitrification rates in oxic soil using intact soil cores incubated in an isothermal gas tight system. Gross nitrification rates and denitrification rates are derived from measurements of changes (i) in air pressure within the closed system, which are primarily the result of the activities of nitrification, denitrification, and respiration, and (2) of O{sub 2} and CO{sub 2} concentrations in the system. Besides these biological processes, the contribution of physicochemical dissolution of produced CO{sub 2} in soil water to the pressure changes observed is to be considered. The method allows collection of additional information about the contribution of nitrification and denitrification to N{sub 2}O emission from soil, provided simultaneous measurements of N{sub 2}O emission are performed. Furthermore, BaPS can be used to quantify the percentage of N{sub 2}O lost from nitrification. The advantage of BaPS is that disturbance of the soil system is minimized compared with other methods such as the use of gaseous inhibitors (e.g., acetylene) or application of {sup 15}N compounds to the soil. The authors present the theoretical considerations of BaPS, results for nitrification rates, denitrification rates, and identification of soil N{sub 2}O sources in a well-aerated coniferous forest soil using BaPS. The suitability of BaPS as a method for determination of gross nitrification is demonstrated by validation experiments using the {sup 15}N-pool dilution technique.

Ingwersen, J.; Butterbach-Bahl, K.; Gasche, R.; Papen, H. [Fraunhofer Inst. for Atmospheric Environmental Research, Garmisch-Partenkirchen (Germany); Richter, O. [Technischen Universitaet Braunschweig (Germany). Inst. fuer Geographie und Geooekologie

1999-01-01

71

Single particle studies of black liquor gasification under pressurized conditions  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this project is to provide experimental data relevant to pressurized black liquor gasification concepts. Specifically, the following two goals will be achieved: Data on swelling, char yields and component release during pressurized pyrolysis of small samples of black liquor will be obtained. The reactivity and physical behavior of single black liquor droplets during simultaneous pyrolysis and gasification will be investigated. The structure and composition of black liquor char during formation and conversion will be studied. (orig.)

Whitty, K.; Backman, R.; Hupa, M.; Backman, P.; Ek, P.; Hulden, S.T.; Kullberg, M.; Sorvari, V.

1997-10-01

72

Intelligent fiber optic pressure sensor for measurements in extreme conditions  

International Nuclear Information System (INIS)

Application of a fiber optic Fabry-Perot interferometer (FFPI) for measurements of pressure and speed of pressure variation in water reactors of nuclear power plants contributes to improving their safety and long-term metrological stability, which demands for intelligent sensors. It is shown that the manufacturing of a FFPI sensitive element based on a molecular layering nano-technology provides for substantial enhancement of the quality of the gauge. The algorithm of self-calibration of the pressure sensor based on the fact that the length of the FFPI cavity depends on the pressure at a constant spectrum of an optical source is considered. By means of fast tuning of the spectrum of an optical source it is possible to make self-calibration in the course of continuous work of the pressure gauge. It is also shown that the intelligent FFPI pressure sensor maintains metrological characteristics when the total dose of high-neutron/ gamma radiation is over 2 MGy. (authors)

73

Intelligent fiber optic pressure sensor for measurements in extreme conditions  

Energy Technology Data Exchange (ETDEWEB)

Application of a fiber optic Fabry-Perot interferometer (FFPI) for measurements of pressure and speed of pressure variation in water reactors of nuclear power plants contributes to improving their safety and long-term metrological stability, which demands for intelligent sensors. It is shown that the manufacturing of a FFPI sensitive element based on a molecular layering nano-technology provides for substantial enhancement of the quality of the gauge. The algorithm of self-calibration of the pressure sensor based on the fact that the length of the FFPI cavity depends on the pressure at a constant spectrum of an optical source is considered. By means of fast tuning of the spectrum of an optical source it is possible to make self-calibration in the course of continuous work of the pressure gauge. It is also shown that the intelligent FFPI pressure sensor maintains metrological characteristics when the total dose of high-neutron/ gamma radiation is over 2 MGy. (authors)

Buimistriuc, G. Y. [Instruments Plant Vibrator, 194294, Saint-Petersburg (Russian Federation); Rogov, A. M. [Saint-Petersburg State Technological University, 190013 (Russian Federation)

2009-07-01

74

Beat Pressure and Comparing it with Ascending Aorta Pressure in Normal and Abnormal Conditions  

CERN Document Server

Lumped method (Electrical analogy) is a quick and easy way to model human cardiovascular system. In this paper Lumped method is used for simulating a complete model. It describes a 36-vessel model and cardiac system of human body with details that could show hydrodynamic parameters of cardiovascular system. Also this paper includes modeling of pulmonary, atrium, left and right ventricles with their equivalent circuits. Exact modeling of right and left ventricles pressure with division of ascending aorta into 27 segments increases the accuracy of our simulation. In this paper we show that a calculated pressure for aorta from our complex circuit is near to measured pressure by using advanced medical instruments. Also it is shown that pressure graph from brachial is so near to aortic pressure because of this its pressure signal is usable instead of aortic pressure. Furthermore, obstruction in ascending aorta, brachial and its effects has been showed in different figures.

Ghasemalizadeh, Omid; Firoozabadi, Bahar; Sajadi, Behrang; Zolfonoon, Ali

2014-01-01

75

Tribological performance of ashless antiwear additives under extreme pressure conditions  

Science.gov (United States)

Zinc diakyl dithiophosphate (ZDDP) has been used in engine oil for several decades as an antiwear additive. However, ZDDP is the primary source of P, S and Zn in the exhaust, which results in frequent maintenance or replacement of exhaust gas treatment systems. The use of ashless additives is more desirable because of recent environmental regulations. The main goal of this research was to develop a fundamental understanding of how ashless compounds protect the tribological surface in comparison to ZDDP. X-ray absorption near edge structure spectroscopy (XANES) has been performed on tribo and thermal films in order to investigate the chemical properties of films generated from ashless antiwear additives like chemical structure as well as chemical composition. In order to achieve this objective, three approaches were used. First, the relationships between ashless thiophosphates and wear properties under extreme pressure were examined. Ashless antiwear additives properly form their tribofilms on the sliding steel surface, reacting with iron (Fe) which is originated from the substrate. The tribofilms consist of iron phosphates, iron sulfides, and iron sulfates that have lower reduced modulus and hardness compared to tribofilms from ZDDP. However, they are still sufficiently stiff to prevent asperity contact and provide antiwear behavior. In addition, the thickness of protective tribofilms formed with ashless thiophosphates was found to be thicker than the ones formed when ZDDP was used under identical tribological conditions. Secondly, in order to understand the mechanism of tribofilm generation of metal free additives, a fundamental understanding of thermal decomposition of ashless antiwear chemistries and their influence on thermal film formation was derived. The decomposed P- and S- containing products of ZDDP reacted with the metal surface and their own metal cations forming thermal films. In case of metal free dithiophosphates, sulfur species initially formed on the surface very fast, and then, phosphate species formed and diffused into the thermal film. It was one of the reasons why DDP-2 had better antiwear protection. While, DDP-1 with low thermal stability suffered from the oxidation and hydrolysis of thermal film and oil, which was related with poor wear performance. The amine phosphate showed the cross-link of phosphates and the oxidation of thermal film (iron nitrate or nitrite), resulting in its stick-slip behavior and big wear volume. The distinction of wear performance of different chemistries could be interpreted by these different mechanisms of formation of thermal films. Thirdly we examined how ashless fluorinated compounds may influence the formation and the characteristics of tribofilms and in proxy the wear properties. While the general form of the tribofilms were essentially the same with and without the presence of PTFE, an important distinction was the presence of a layer of PTFE on the surface of the tribofilm that prevented its oxidation of the tribofilm and yielded better wear performance.

Kim, Bohoon

76

Probes for bulk superconductivity in iron pnictide systems under hydrostatic pressure conditions  

International Nuclear Information System (INIS)

We discuss the sensitivity of iron based superconductors to the hydrostaticity of pressure conditions, which results in discrepancies between different studies. To clarify the situation we present the phase diagram of several systems obtained on single crystals, using the highly hydrostatic pressure conditions of argon in a diamond anvil cell, and an ac susceptibility method to detect superconductivity.

77

Systems and methods of monitoring acoustic pressure to detect a flame condition in a gas turbine  

Science.gov (United States)

A method may detect a flashback condition in a fuel nozzle of a combustor. The method may include obtaining a current acoustic pressure signal from the combustor, analyzing the current acoustic pressure signal to determine current operating frequency information for the combustor, and indicating that the flashback condition exists based at least in part on the current operating frequency information.

Ziminsky, Willy Steve (Simpsonville, SC); Krull, Anthony Wayne (Anderson, SC); Healy, Timothy Andrew (Simpsonville, SC), Yilmaz, Ertan (Glenville, NY)

2011-05-17

78

Intra-oral compartment pressures: a biofunctional model and experimental measurements under different conditions of posture  

OpenAIRE

Oral posture is considered to have a major influence on the development and reoccurrence of malocclusion. A biofunctional model was tested with the null hypotheses that (1) there are no significant differences between pressures during different oral functions and (2) between pressure measurements in different oral compartments in order to substantiate various postural conditions at rest by intra-oral pressure dynamics. Atmospheric pressure monitoring was simultaneously carried out with a digi...

Engelke, Wilfried; Jung, Klaus; Kno?sel, Michael

2010-01-01

79

A Correlation Study of Cardiopulmonary Arrests, Cholesterol and Pressures  

OpenAIRE

This study consisted of cardiopulmonary arrests occurring between January 1990 and December 1991 in a Midwestern City in Kansas, U.S.A., with a population of 300,000. Admission cholesterol levels and hourly barometric pressures were obtained to show if there exists a relationship between cardiopulmonary arrests, cholesterol levels and barometric pressures. Statistical analysis was performed using Pearson-Moment Correlation Coefficient. Scattergrams amongst the dependent variables such as time...

Rider, S. E.; Taher, S. M.

2003-01-01

80

Estimation of partial pressure during graphite conditioning by matrix method  

International Nuclear Information System (INIS)

Plasma Facing Components (PFC) of SST-1 tokamak are designed to be compatible for UHV as it is kept in the main vacuum vessel. Graphite is the most widely used plasma facing material in present day tokamaks. High thermal shock resistance and low atomic number carbon are the most important properties of graphite for this application. However, graphite is porous and absorbs gases, which may be released during plasma operation. Graphite tiles are baked at high temperature of about 1000 deg. C in high vacuum (10-5 Torr) for several hours before installing them in the tokamak to remove the impurities (mainly water vapour and metal impurities), which may have been deposited during machining of the tiles. The measurements of the released gas (such as H2, H2O, CO, CO2, Hydrocarbons, etc.) from graphite tiles during baking are accomplished with the help of a Quadrupole Mass Analyzer (QMA). Since, the output of this measurement is a mass spectrum and not the partial pressures of the residual gases, one needs to adopt some procedure to convert the spectrum to obtain the partial pressures. The conventional method of analysis is tedious and time consuming. We propose a new approach based on constructing a set of linear equations and solving them using matrix operations. This is a simple method compared to the conventional one and also eliminates the limitations of the conventional method. A Fortran program has been developed which identian program has been developed which identifies the likely gases present in the vacuum system and calculates their partial pressures from the data of the residual gas analyzers. Application of this method of calculating partial pressures from mass spectra data will be discussed in detail in this paper

81

The impact of hepatic pressurization on liver shear wave speed estimates in constrained versus unconstrained conditions  

International Nuclear Information System (INIS)

Increased hepatic venous pressure can be observed in patients with advanced liver disease and congestive heart failure. This elevated portal pressure also leads to variation in acoustic radiation-force-derived shear wave-based liver stiffness estimates. These changes in stiffness metrics with hepatic interstitial pressure may confound stiffness-based predictions of liver fibrosis stage. The underlying mechanism for this observed stiffening behavior with pressurization is not well understood and is not explained with commonly used linear elastic mechanical models. An experiment was designed to determine whether the stiffness increase exhibited with hepatic pressurization results from a strain-dependent hyperelastic behavior. Six excised canine livers were subjected to variations in interstitial pressure through cannulation of the portal vein and closure of the hepatic artery and hepatic vein under constrained conditions (in which the liver was not free to expand) and unconstrained conditions. Radiation-force-derived shear wave speed estimates were obtained and correlated with pressure. Estimates of hepatic shear stiffness increased with changes in interstitial pressure over a physiologically relevant range of pressures (0–35 mmHg) from 1.5 to 3.5 m s?1. These increases were observed only under conditions in which the liver was free to expand while pressurized. This behavior is consistent with hyperelastic nonlinear material models that could be used in taterial models that could be used in the future to explore methods for estimating hepatic interstitial pressure noninvasively. (paper)

82

The impact of hepatic pressurization on liver shear wave speed estimates in constrained versus unconstrained conditions  

Science.gov (United States)

Increased hepatic venous pressure can be observed in patients with advanced liver disease and congestive heart failure. This elevated portal pressure also leads to variation in acoustic radiation-force-derived shear wave-based liver stiffness estimates. These changes in stiffness metrics with hepatic interstitial pressure may confound stiffness-based predictions of liver fibrosis stage. The underlying mechanism for this observed stiffening behavior with pressurization is not well understood and is not explained with commonly used linear elastic mechanical models. An experiment was designed to determine whether the stiffness increase exhibited with hepatic pressurization results from a strain-dependent hyperelastic behavior. Six excised canine livers were subjected to variations in interstitial pressure through cannulation of the portal vein and closure of the hepatic artery and hepatic vein under constrained conditions (in which the liver was not free to expand) and unconstrained conditions. Radiation-force-derived shear wave speed estimates were obtained and correlated with pressure. Estimates of hepatic shear stiffness increased with changes in interstitial pressure over a physiologically relevant range of pressures (0-35 mmHg) from 1.5 to 3.5 m s-1. These increases were observed only under conditions in which the liver was free to expand while pressurized. This behavior is consistent with hyperelastic nonlinear material models that could be used in the future to explore methods for estimating hepatic interstitial pressure noninvasively.

Rotemberg, V.; Palmeri, M.; Nightingale, R.; Rouze, N.; Nightingale, K.

2012-01-01

83

Pressurized water reactor iodine spiking behavior under power transient conditions  

International Nuclear Information System (INIS)

The most accepted theory explaining the cause of pressurized water reactor iodine spiking is steam formation and condensation in damaged fuel rods. The phase transformation of the primary coolant from water to steam and back again is believed to cause the iodine spiking phenomenon. But due to the complex nature of the phenomenon, a comprehensive model of the behavior has not yet been successfully developed. This paper presents a new model based on an empirical approach, which gives a first-order estimation of the peak iodine spiking magnitude. Based on the proposed iodine spiking model, it is apparent that it is feasible to derive a correlation using the plant operating data base to monitor and control the peak iodine spiking magnitude

84

A study on the manufacturing conditions of metal matrix composites by low pressure infiltration process  

Energy Technology Data Exchange (ETDEWEB)

Metal fiber preform reinforced aluminum alloy composite as made by the infiltration of molten metal under low pressure casting process. The infiltration behavior of filling pattern and the velocity profile with low-pressure casting process was investigated. The thermocouple was inserted into the preform in order to observe the infiltration behavior. The infiltration of applied pressure time, 1, 2 and 5 s under constant pressure of 0.4 MPa was completely filled during 0.4 s. In these conditions, molten aluminum alloy has successfully infiltrated to FeCrSi metal fiber preform by low-pressure casting process. It was observed the porosity of composites for reliability of composites. The automobile piston was developed with FeCrSi reinforced aluminum alloy that is 0% porosity by the optimal applied pressure and applied pressure time.

Park, Won Jo; Hessian, Md Anowar; Park, Sung Ho [Gyeongsang National University, Tongyoung (Korea, Republic of); Huh, Sun Chul [Gyeongsang National University, JinJu (Korea, Republic of)

2007-10-15

85

A study on the manufacturing conditions of metal matrix composites by low pressure infiltration process  

International Nuclear Information System (INIS)

Metal fiber preform reinforced aluminum alloy composite as made by the infiltration of molten metal under low pressure casting process. The infiltration behavior of filling pattern and the velocity profile with low-pressure casting process was investigated. The thermocouple was inserted into the preform in order to observe the infiltration behavior. The infiltration of applied pressure time, 1, 2 and 5 s under constant pressure of 0.4 MPa was completely filled during 0.4 s. In these conditions, molten aluminum alloy has successfully infiltrated to FeCrSi metal fiber preform by low-pressure casting process. It was observed the porosity of composites for reliability of composites. The automobile piston was developed with FeCrSi reinforced aluminum alloy that is 0% porosity by the optimal applied pressure and applied pressure time

86

Jump conditions for pressure anisotrophy and comparison with the Earth's bow shock  

Science.gov (United States)

Taking into account the pressure anisotropy in the solar wind, we study the magnetic field and plasma parameters downstream of a fast shock, as functions of upstream parameters and downstream pressure anisotropy. In our theoretical approach, we model two cases: a) the perpendicular shock and b) the oblique shock. We use two threshold conditions of plasma instabilities as additional equations to bound the range of pressure anisotropy. The criterion of the mirror instability is used for pressure anisotropy p perp /pallel > 1. Analogously, the criterion of the fire-hose instability is taken into account for pressure anisotropy p perp /pallel < 1. We found that the variations of the parallel pressure, the parallel temperature, and the tangential component of the velocity are most sensitive to the pressure anisotropy downstream of the shock. Finally, we compare our theory with plasma and magnetic field parameters measured by the WIND spacecraft.

Vogl, D. F.; Biernat, H. K.; Erkaev, N. V.; Farrugia, C. J.; Mühlbachler, S.

87

Jump conditions for pressure anisotropy and comparison with the Earth's bow shock  

Directory of Open Access Journals (Sweden)

Full Text Available Taking into account the pressure anisotropy in the solar wind, we study the magnetic field and plasma parameters downstream of a fast shock, as functions of upstream parameters and downstream pressure anisotropy. In our theoretical approach, we model two cases: a the perpendicular shock and b the oblique shock. We use two threshold conditions of plasma instabilities as additional equations to bound the range of pressure anisotropy. The criterion of the mirror instability is used for pressure anisotropy p perp /pparrallel > 1. Analogously, the criterion of the fire-hose instability is taken into account for pressure anisotropy p perp /pparrallel < 1. We found that the variations of the parallel pressure, the parallel temperature, and the tangential component of the velocity are most sensitive to the pressure anisotropy downstream of the shock. Finally, we compare our theory with plasma and magnetic field parameters measured by the WIND spacecraft.

D. F. Vogl

2001-01-01

88

Mechanical pressure gages under difficult conditions; Mechanische Druckmessgeraete unter schwierigen Einsatzbedingungen  

Energy Technology Data Exchange (ETDEWEB)

In spite of electronic solutions, mechanical pressure meters still find their place in reliable in-situ process pressure monitoring without external influences. Planners and users often have difficulties selecting the optimum meter for a given application, especially where difficult operating conditions are concerned. The contribution presents a neutral and practical guide. (orig.)

Nieswandt, T. [Wika Alexander Wiegand GmbH und Co. KG, Klingenberg (Germany)

2008-05-15

89

PRESBC: pressure boundary conditions for the K-FIX code. Supplement III  

Energy Technology Data Exchange (ETDEWEB)

Recommended pressure boundary condition modifications are described for the computer code K-FIX, which has been published in the report LA-NUREG-6623 and released to the National Energy Software Center in April 1977.

Travis, J.R.; Rivard, W.C.

1980-07-01

90

Individual Pressure Vessel (PV) and Common Pressure Vessel (CPV) Nickel-Hydrogen Battery Performance Under LEO Cycling Conditions  

Science.gov (United States)

LEO life cycle testing of Individual Pressure Vessel (PV) and Common Pressure Vessel (CPV) nickel-hydrogen cell packs have been sponsored by the NASA Aerospace Flight Battery Program. The cell packs have cycled under both 35% and 60% depth-of- discharge and temperature conditions of -5 C and +lO C. The packs have been on test since as early as 1992 and have generated a substantial database. This report will provide insight into performance trends as a function of the specific cell configuration and manufacturer for eight separate nickel-hydrogen battery cell packs.

Miller, Thomas B.; Lewis, Harlan L.

2004-01-01

91

Blind source separation for groundwater pressure analysis based on nonnegative matrix factorization  

Science.gov (United States)

The identification of the physical sources causing spatial and temporal fluctuations of aquifer water levels is a challenging, yet a very important hydrogeological task. The fluctuations can be caused by variations in natural and anthropogenic sources such as pumping, recharge, barometric pressures, etc. The source identification can be crucial for conceptualization of the hydrogeological conditions and characterization of aquifer properties. We propose a new computational framework for model-free inverse analysis of pressure transients based on Nonnegative Matrix Factorization (NMF) method for Blind Source Separation (BSS) coupled with k-means clustering algorithm, which we call NMFk. NMFk is capable of identifying a set of unique sources from a set of experimentally measured mixed signals, without any information about the sources, their transients, and the physical mechanisms and properties controlling the signal propagation through the subsurface flow medium. Our analysis only requires information about pressure transients at a number of observation points, m, where m?r, and r is the number of unknown unique sources causing the observed fluctuations. We apply this new analysis on a data set from the Los Alamos National Laboratory site. We demonstrate that the sources identified by NMFk have real physical origins: barometric pressure and water-supply pumping effects. We also estimate the barometric pressure efficiency of the monitoring wells. The possible applications of the NMFk algorithm are not limited to hydrogeology problems; NMFk can be applied to any problem where temporal system behavior is observed at multiple locations and an unknown number of physical sources are causing these fluctuations.

Alexandrov, Boian S.; Vesselinov, Velimir V.

2014-09-01

92

Biogenic amines in pressurized vacuum-packaged cooked sliced ham under different chilled storage conditions.  

Science.gov (United States)

This work was undertaken to study how storage conditions (at constant temperatures of 2±1 and 12±1°C and temperature fluctuations at 7±5°C) affect microbial development and the production of biogenic amines in vacuum-packaged cooked sliced ham subjected to high pressure (400MPa/10min/30°C). Initially, the product exhibited low levels of contamination. Microbiological changes during storage depend on the processing (non-pressure and pressure treatment) and the chilled storage conditions. Generally, microbial growth in pressurized samples was similar to that in the non-pressurized samples, although the total viable count and lactic flora were lower and growth was delayed. Processing and storage conditions affected the formation of each amine differently. The most important changes were in tyramine, which formed more quickly in non-pressurized products stored at 12°C and with temperature fluctuations. The formation of biogenic amines in these products can be prevented not only by ensuring good manufacturing practices and applying high pressure but also by ensuring the right chilled storage conditions. PMID:22063795

Ruiz-Capillas, C; Carballo, J; Jiménez Colmenero, F

2007-03-01

93

Deformation behaviour of Zr-2.5 wt percent Nb pressure tubes under internal pressurization and ramp temperature conditions  

International Nuclear Information System (INIS)

The deformation behaviour of 0.6 m long Zr-2.5 wt percent Nb pressure tube specimens deformed under internal pressurization and ramp temperature conditions has been studied. Both inert gas and steam have been used as the pressurizing medium. Controlled heating rates in the range 1-25 K/s and internal pressures in the range 0-12 MPa have been investigated. It was observed that, except at the very high test pressures, the samples deformed to circumferential strains well in excess of the nominal 'contact' strain of 0.18 before possible rupture. Over the time scale of the biaxial tests carried out, the effect of steam on deformation behaviour appeared to be minimal. It was also found that the major features of the biaxial deformation behaviour can be investigated, at least qualitatively, by carrying out uniaxial tensile tests. However, detailed analysis of uniaxial and biaxial data showed that there were several major differences between the two types of data. These differences are discussed in considerable detail in the present report

94

A fórmula barométrica como instrumento de ensino em Química / The barometric formula as resource for teaching Chemistry  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese [...] Abstract in english The barometric equation is revisited. Restrictions imposed for its derivation are investigated. Results are discussed and related to simple themes of ordinary life. The theoretical models fit to experimental data. Correction for temperature effect improves the fitting in comparison to the barometric [...] formula. The scope for application of the model is discussed.

Otávio Luiz, Bottecchia.

1965-19-01

95

First-principles study of 6H-AlN under various pressure conditions  

International Nuclear Information System (INIS)

We calculated the electronic and lattice properties of 6H-AlN under various pressure conditions. The pressure conditions are hydrostatic, biaxial, and uniaxial compression and expansion. The 6H polytype has two structures. One is ABCBCB (ABC notation) and the other is ABCACB. 6H-AlN(ABCBCB) is energetically more favorable than 6H-AlN(ABCACB). Symmetry and hexagonality (H[%]) of 6H-AlN(ABCBCB) are P3m1 and 67 %, respectively. The electronic band structures of 6H-AlN polytypes under the ambient pressure show indirect band gaps. The band gap of 6H-AlN(ABCBCB) is closer to direct than that of 6H-AlN(ABCACB). The lattice properties of 6H-AlN(ABCBCB) under the various pressure conditions were optimized automatically by the first-principles molecular dynamics (FPMD) method. We also calculated the electronic band structures, the band gap values, the valence band maximum (VBM), and conduction band minimum (CBM) of 6H-AlN(ABCBCB) under the various pressure conditions. Their electronic band structures are non-metallic and band gaps are indirect with the exception of a few cases. The indirect band gap transforms to direct under expansion conditions.

96

Simulation of subcooled boiling at low pressure conditions with RELAP5-3D computer program  

International Nuclear Information System (INIS)

Simulation of subcooled boiling was carried out using RELAP5 thermal hydraulic computer programs. Both 1D and 3D analyses were carried out with RELAP5/MOD3.2 and RELAP5-3D code. Experimental data from the subcooled boiling experiment at low pressure conditions of Bartel, and Zeitoun and Shoukri were simulated. The RELAP5/MOD3.2 was executed to determine the axial void faction distribution. The predictions of void fraction distributions at low-pressure conditions were underestimated. The same model was used to simulate high pressure subcooled boiling data. High pressure subcooled boiling experiments of Bartolomey and Sabotinov were simulated. The axial void fraction distribution results of RELAP5/MOD3.2 were in a good agreement with the experimental data. (author)

97

Analysis of Pressure Fluctuations in a Natural Gas Engine Under Lean Burn Conditions  

OpenAIRE

Abstract We have investigated the cycle-to-cycle pressure fluctuations in a natural gas engine under lean burn conditions. In particular, we have examined the dynamics of the indicated mean effective pressure (IMEP) variations for four different values of the equivalence ratio. For each equivalence ratio, we used a continuous wavelet transform to identify the dominant spectral modes and the number of cycles over which these modes may persist. Our results reveal that when the mixtur...

Sen, A. K.; Litak, G.; Yao, B. -f; Li, G. -x

2009-01-01

98

Determination of optimal conditions for pressure oxidative leaching of Sarcheshmeh Molybdenite concentrate using Taguchi method  

OpenAIRE

The present research work is based on finding the optimum conditions for pressure oxidative leaching of the molybdenite concentrate to produce technical-grade molybdic oxide (MoO3) with high recovery through further treatment of the filtrate solution. The Taguchi method was used to design and minimize the number of experiments. By using Taguchi orthogonal (L25) array, five parameters (time, temperature, oxygen pressure, pulp density and acid concentration) at five levels were selected f...

Khoshnevisana A.; Yoozbashizadeha H.

2012-01-01

99

Charge Accumulation in LDPE and XLPE Conditioned at 80oC under Reduced Pressure  

DEFF Research Database (Denmark)

The effects of thermal conditioning, under reduced pressure, on space accumulation in planar LDPE and XLPE samples under DC stress, have been investigated. The samples were conditioned prior to voltage application by being held at 80oC for 2-3 days in short circuit at rotary pump pressure. Some were then cooled to room temperature over a period of at least 6hr, still under rotary pump pressure and in short circuit, while others were cooled to room temperature in less than 1.5hr in the laboratory air. DC fields of 18kV/mm were then applied at room temperature, and space charge accumulation was monitored as a function of time using the PEA (Denmark) and LIPP (Australia) techniques. Conditioning did not prevent space charge accumulation in either the LDPE or XLPE samples.

Fleming, Robert J.; Henriksen, Mogens

1997-01-01

100

The Rheological Properties of Oil-Based Mud under High Pressure and High Temperature Conditions  

OpenAIRE

Designing a proper drilling fluid that can function properly under the conditions of High-Pressure, High-Temperature (HP/HT) operations is very challenging. Among these challenges is the alteration of the rheological properties of drilling fluid due to the high temperature and high pressure (Ibeh et. al, 2007). This work investigates the rheological behavior of oil-based drilling fluids with different properties at Ultra-HP/HT conditions using a state-of-the-art viscomet...

Mahmood Amani

2012-01-01

101

Effect of Specific Operating Conditions on the Properties of LPPS Plasma Jets Expanding at Low Pressure  

International Nuclear Information System (INIS)

The LPPS processes, which use DG plasma jets expanding at low pressure, are widely used for the deposition of various kinds of layers. The supersonic expansion of the plasma jet in a low-pressure environment requires special care in the operating conditions in order to obtain the desired properties of the flow, regarding powder injection and transport and plasma jet-surface interaction. This paper presents measurements of the plasma jet properties for different chamber pressures. The torch is operated both in the over-expanded and under-expanded regimes, according to pressure measurements at the exit of the nozzle as a function of the backpressure. The topology of the expansion-compression zones of the plasma jet for the different operating pressures is inferred from imaging of the plasma jet. In addition, a modified enthalpy probe system is used to measure the specific enthalpy and the stagnation pressure profiles throughout the jet. De- termination of the local free-stream jet parameters, such as the temperature and velocity, for the case of supersonic flow is made assuming an isentropic frozen stagnation process at the probe tip. For these calculations the pressure dependence of the equilibrium thermodynamic and transport properties is accounted for. Discussion on expanded jet rarefaction is made for chamber pressure below 20 mbar, in the light of plasma jet imaging and nozzle exit pres- sure measurements. (author)

102

Embedded optical probes for simultaneous pressure and temperature measurement of materials in extreme conditions  

Science.gov (United States)

We present recent efforts at Los Alamos National Laboratory (LANL) to develop sensors for simultaneous, in situ pressure and temperature measurements under dynamic conditions by using an all-optical fiber-based approach. While similar tests have been done previously in deflagration-to-detonation tests (DDT), where pressure and temperature were measured to 82 kbar and 400°C simultaneously, here we demonstrate the use of embedded fiber grating sensors to obtain high temporal resolution, in situ pressure measurements in inert materials. We present two experimental demonstrations of pressure measurements: (1) under precise shock loading from a gas-gun driven plate impact and (2) under high explosive driven shock in a water filled vessel. The system capitalizes on existing telecom components and fast transient digitizing recording technology. It operates as a relatively inexpensive embedded probe (single-mode 1550 nm fiber-based Bragg grating) that provides a continuous fast pressure record during shock and/or detonation. By applying well-controlled shock wave pressure profiles to these inert materials, we study the dynamic pressure response of embedded fiber Bragg gratings to extract pressure amplitude of the shock wave and compare our results with particle velocity wave profiles measured simultaneously.

Sandberg, R. L.; Rodriguez, G.; Gibson, L. L.; Dattelbaum, D. M.; Stevens, G. D.; Grover, M.; Lalone, B. M.; Udd, E.

2014-05-01

103

Boiling heat transfer and dryout in helically coiled tubes under different pressure conditions  

International Nuclear Information System (INIS)

Highlights: • Heat transfer characteristics and dryout for helically coiled tube are performed. • A boiling heat transfer tends to increase with a pressure increase. • Dryout occurs at high quality test conditions investigated. • Steiner–Taborek’s correlation is predicted well based on the experimental results. - Abstract: A helically coiled once-through steam generator has been used widely during the past several decades for small nuclear power reactors. The heat transfer characteristics and dryout conditions are important to optimal design a helically coiled steam generator. Various experiments with the helically coiled tubes are performed to investigate the heat transfer characteristics and occurrence condition of a dryout. For the investigated experimental conditions, Steiner–Taborek’s correlation is predicted reasonably based on the experimental results. The pressure effect is important for the boiling heat transfer correlation. A boiling heat transfer tends to increase with a pressure increase. However, it is not affected by the pressure change at a low power and low mass flow rate. Dryout occurs at high quality test conditions investigated because a liquid film on the wall exists owing to a centrifugal force of the helical coil

104

Effects of pressure condition for LOCA acceleration test profile on equipment integrity  

International Nuclear Information System (INIS)

All equipment related to safety in nuclear power plants must perform their safety functions under defined condition, including postulated DBA condition as well as normal environmental condition. LOCA (Loss of Coolant Accident) of the DBA is the severest condition of high temperature, high pressure and sprayed chemicals during approximately 6 months. Since the perfect qualification of equipment in such LOCA test requires a long time and highly reliable test facility, the realistic LOCA simulation test for equipment qualification is performed with modified shortened test profile enveloping temperature and pressure condition of specific NPP. The detailed process for modification of this LOCA test profile are proposed by Park et al. (2006), based on the Arrhenius equation. However, the shortened test profile may cause quite unfavorable effects on equipment integrity during and after LOCA test. In this paper, we have found that failure possibility of limit switch during LOCA test may be greatly increased due to elevated test pressure in the modified test profile. Therefore, we suggest the refined modification method of LOCA test profile, which is applicable for pressure-vulnerable equipment. (author)

105

Influence of reaction conditions on the enantioselectivity of biocatalyzed C-C bond formations under high pressure conditions.  

Science.gov (United States)

Benzoylformate decarboxylase (BFD, EC 4.1.1.7) is a homotetrameric thiamine diphosphate (ThDP)-dependent enzyme which catalyzes the synthesis of chiral 2-hydroxyketones accepting a broad range of aldehydes as substrates. In this study the synthesis of 2-hydroxypropiophenone (2-HPP) from benzaldehyde and acetaldehyde was catalyzed by three BFD variants namely BFD F464I, BFD A460I and BFD A460I-F464I. This paper reports the effect of hydrostatic pressure up to 290 MPa when the reactions were carried out at different benzaldehyde concentrations (5-40 mM) as well as at different pH values (7.0-8.5). Acetaldehyde concentration was fixed at 400 mM in all biotransformations. Reactions performed at high benzaldehyde concentrations and at high hydrostatic pressures showed an increase in (R)-2-HPP formation catalyzed by all BFD variants. For BFD A460I-F464I we observed an increase in the ee of (R)-2-HPP up to 80%, whereas at atmospheric conditions this variant synthesizes (R)-2-HPP with an ee of only 50%. Alkaline conditions (up to pH 8.5) and high hydrostatic pressures resulted in an increase of (R)-2-HPP synthesis, especially in the case of BFD A460I and BFD F464I. PMID:21295624

Kara, Selin; Long, Wei Sing; Berheide, Marco; Peper, Stephanie; Niemeyer, Bernd; Liese, Andreas

2011-03-20

106

Determination of optimal conditions for pressure oxidative leaching of Sarcheshmeh Molybdenite concentrate using Taguchi method  

Directory of Open Access Journals (Sweden)

Full Text Available The present research work is based on finding the optimum conditions for pressure oxidative leaching of the molybdenite concentrate to produce technical-grade molybdic oxide (MoO3 with high recovery through further treatment of the filtrate solution. The Taguchi method was used to design and minimize the number of experiments. By using Taguchi orthogonal (L25 array, five parameters (time, temperature, oxygen pressure, pulp density and acid concentration at five levels were selected for 25 experiments. The experiments were designed and carried out in a high-pressure reactor in the presence of nitric acid as solvent and oxidizing agent for the molybdenite concentrate and its ReS2 content. The optimum conditions for pressure leaching of molybdenite were obtained through using Signal to Noise analysis and modified by using Minitab software prediction tool. Furthermore, the optimum condition for an economical pressure leaching of rhenium sulfide (ReS2 was achieved with the same process. Analysis of variance (ANOVA showed that the pulp density is of paramount importance in this process.

Khoshnevisana A.

2012-01-01

107

Temperature regime of heated channels under supercritical pressure in nonstationary conditions  

International Nuclear Information System (INIS)

Model for calculating temperature regime of supercritical pressure heated channel based on the conditioned solution of hydrodynamics and heat conductivity nonstationary equations, is suggested. Temperature regime of shield tubes of power faciliti with high residual heat release at feed pump shutdown is investigated numerically. The effect of heat removal nonuniformity along the channel length and perimeter is investigated. It is found out, that values of temperature field by stationary solutions manifest essential errors. Coolant mass flowrate affects essentially temperature regime under emergency conditions

108

Phase transformation of cadmium sulfide under high temperature and high pressure conditions.  

Science.gov (United States)

Cadmium sulfide (CdS) is one of the most significant wide band gap semiconductors, and knowledge of the phase transformation of CdS under high temperature and pressure is especially important for its applications. The pressure-temperature phase diagram and the phase transformation pathways of CdS have been investigated by using density functional theory combined with quasiharmonic approximation. Our results indicated that under ambient conditions, wz-CdS is a stable phase, while under high temperature and pressure, rs-CdS becomes the stable phase. It is also found that zb-CdS is an intermediate phase in transforming from rs-CdS to wz-CdS. Therefore, although there are no zb-CdS phase regions in the CdS pressure-temperature phase diagram, zb-CdS can be found in some prepared experiments. PMID:24930763

Xiao, Jianwei; Wen, Bin; Melnik, Roderick; Kawazoe, Yoshiyuki; Zhang, Xiangyi

2014-07-28

109

Power X-ray diffraction under extreme conditions of pressure and temperature  

International Nuclear Information System (INIS)

An important work has been carried out in the field of X-ray diffraction in obtaining accurate structure information from materials at extreme conditions of pressure and temperature. An experimental set-up combining a diamond-anvil high-pressure cell and a laser-heating technique has been installed at the high-pressure beamline ID30 at the ESRF (Grenoble) to study two major constituents of the Earth's deep interior: MgSiO3 perovskite and iron. Experiments carried out on MgSiO3 perovskite up to 86 GPa and over 2000 K yielded detailed structural information on this compound under these conditions and thus important constraints for the lower mantle mineralogical model, favouring a mixture of perovskite and magnesiowuestite. X-ray diffraction patterns recorded on imaging plates with micro-focused monochromatic radiation revealed a new high-temperature structure of iron above 40 GPa. (au)

110

Hydrate dissociation conditions at high pressure : experimental equilibrium data and thermodynamic modelling  

Energy Technology Data Exchange (ETDEWEB)

Gas hydrates are crystalline compounds that are created when water or ice and certain molecules come together under favourable conditions, normally at low temperatures and elevated pressures. Gas hydrates could form in numerous hydrocarbon production and processing operations, causing serious operational and safety concerns, therefore making it essential to gain a better understanding of the behaviour of gas hydrate. Most of the existing experimental gas hydrate data for real reservoir fluids are limited to low to medium pressure conditions. However, production from deeper water reservoirs, and the need for long tie backs, requires hydrate prevention at high pressure conditions. Therefore, this study investigated the hydrate dissociation point measurements for simple nitrogen, ethane and propane hydrates from medium to high pressure. Existing experimental gas hydrate data were used in the development and validation of the presented predictive techniques. The Valderrama modification of the Patel-Teja equation-of-state, combined with non-density-dependent mixing rules, was used to model the fluid phases with previously reported binary interaction parameters. The hydrate-forming conditions were modelled by the solid solution theory of van der Waals and Platteeuw. Langmuir constants were calculated by both Kihara potential as well as direct techniques. Model predictions were then validated against independent experimental data. It was concluded that there was a good agreement between predictions and experimental data, supporting the reliability of the developed model. 33 refs., 5 tabs., 2 figs.

Haghighi, H.; Burgess, R.; Chapoy, A.; Tohidi, B. [Heriot-Watt Univ., Centre for Gas Research, Edinburgh (United Kingdom). Inst. of Petroleum Engineering

2008-07-01

111

Multiple uncontrolled conditions and blood pressure medication intensification: an observational study  

OpenAIRE

Abstract Background Multiple uncontrolled medical conditions may act as competing demands for clinical decision making. We hypothesized that multiple uncontrolled cardiovascular risk factors would decrease blood pressure (BP) medication intensification among uncontrolled hypertensive patients. Methods We observed 946 encounters at two VA primary care clinics from May through August 2006. After each encounter, clinicians recorded BP medication intensification (BP medication was added or titrat...

Halanych Jewell H; Allison Jeroan J; Agee Bonita S; Funkhouser Ellen; Salanitro Amanda H; Houston Thomas K; Litaker Mark S; Levine Deborah A; Safford Monika M

2010-01-01

112

Effect of Low Pressure End Conditions on Steam Power Plant Performance  

Directory of Open Access Journals (Sweden)

Full Text Available Most of the electricity produced throughout the world today is from steam power plants and improving the performance of power plants is crucial to minimize the greenhouse gas emissions and fuel consumption. Energy efficiency of a thermal power plant strongly depends on its boiler-condenser operating conditions. The low pressure end conditions of a condenser have influence on the power output, steam consumption and efficiency of a plant. Hence, the objective this paper is to study the effect of the low pressure end conditions on a steam power plant performance. For the study each component was modelled thermodynamically. Simulation was done and the results showed that performance of the condenser is highly a function of its pressure which in turn depends on the flow rate and temperature of the cooling water. Furthermore, when the condenser pressure increases both net power output and plant efficiency decrease whereas the steam consumption increases. The results can be used to run a steam power cycle at optimum conditions.

Ali Syed Haider

2014-07-01

113

Experimental study of the APR+ reactor core flow and pressure distributions under 4-pump running conditions  

Energy Technology Data Exchange (ETDEWEB)

Highlights: • Experimental facility with a 1/5 scale was designed to perform various hydraulic tests of an APR+ reactor. • Two kinds of experiments, balanced and unbalanced flows under 4-pump running conditions were carried out. • The core inlet flow rates and exit pressure distributions were measured and analyzed at 257 discrete points. • The coolant mixing characteristics were investigated with the sectional pressure loss coefficients. - Abstract: The core inlet flow rates and exit pressure distributions of an APR+ (Advanced Power Reactor Plus) reactor were evaluated experimentally with the ACOP (APR+ Core Flow and Pressure) test facility. The ACOP test facility was constructed with a linear reduced scale of 1/5 referring to the APR+ reactor. The major flow path from the clod leg to hot leg was preserved with a principle of similarity. The core region was simulated using 257 core simulators, which are representative of the real HIPER fuel assemblies that APR+ reactor adopted. The core inlet flow rates and pressure distributions along the main flow path, which are significant information as an input data to evaluate the core thermal margin and reactor safety, were obtained by differential pressures measured at core simulators representing 257 fuel assemblies, and the static or differential pressures at 584 points, respectively. Two kinds of experiments, 4-pump balanced and unbalanced flow conditions, were conducted to examine the hydraulic characteristics of the reactor coolant flow. The mass balance and overall pressure drop were carefully examined to check the reliability of the obtained values. The inlet flow rates of the two test results showed similar distributions, which met the hydraulic performance requirement. The details of these experiments, the facility, and a data analysis are also described in this paper.

Kim, Kihwan, E-mail: kihwankim@kaeri.re.kr; Euh, Dong-Jin; Chu, In-Cheol; Youn, Young-Jung; Choi, Hae-Seob; Kwon, Tae-Soon, E-mail: tskwon@kaeri.re.kr

2013-12-15

114

Experimental study of the APR+ reactor core flow and pressure distributions under 4-pump running conditions  

International Nuclear Information System (INIS)

Highlights: • Experimental facility with a 1/5 scale was designed to perform various hydraulic tests of an APR+ reactor. • Two kinds of experiments, balanced and unbalanced flows under 4-pump running conditions were carried out. • The core inlet flow rates and exit pressure distributions were measured and analyzed at 257 discrete points. • The coolant mixing characteristics were investigated with the sectional pressure loss coefficients. - Abstract: The core inlet flow rates and exit pressure distributions of an APR+ (Advanced Power Reactor Plus) reactor were evaluated experimentally with the ACOP (APR+ Core Flow and Pressure) test facility. The ACOP test facility was constructed with a linear reduced scale of 1/5 referring to the APR+ reactor. The major flow path from the clod leg to hot leg was preserved with a principle of similarity. The core region was simulated using 257 core simulators, which are representative of the real HIPER fuel assemblies that APR+ reactor adopted. The core inlet flow rates and pressure distributions along the main flow path, which are significant information as an input data to evaluate the core thermal margin and reactor safety, were obtained by differential pressures measured at core simulators representing 257 fuel assemblies, and the static or differential pressures at 584 points, respectively. Two kinds of experiments, 4-pump balanced and unbalanced flow conditions, were conducted to examine the hydraulic characteristics of the reactor coolant flow. The mass balance and overall pressure drop were carefully examined to check the reliability of the obtained values. The inlet flow rates of the two test results showed similar distributions, which met the hydraulic performance requirement. The details of these experiments, the facility, and a data analysis are also described in this paper

115

Experimental study of the pressure fluctuations in a pump turbine at large partial flow conditions  

Science.gov (United States)

Frequent shifts of output and operating mode require a pump turbine with excellent stability. Current researches show that large partial flow conditions in pump mode experience positive-slope phenomena with a large head drop. The pressure fluctuation at the positive slope is crucial to the pump turbine unit safety. The operating instabilities at large partial flow conditions for a pump turbine are analyzed. The hydraulic performance of a model pump turbine is tested with the pressure fluctuations measured at unstable operating points near a positive slope in the performance curve. The hydraulic performance tests show that there are two separated positive-slope regions for the pump turbine, with the flow discharge for the first positive slope from 0.85 to 0.91 times that at the maximum efficiency point. The amplitudes of the pressure fluctuations at these unstable large partial flow conditions near the first positive slope are much larger than those at stable operating condtions. A dominant frequency is measured at 0.2 times the impeller rotational frequency in the flow passage near the impeller exit, which is believed to be induced by the rotating stall in the flow passage of the wicket gates. The test results also show hysteresis with pressure fluctuations when the pump turbine is operated near the first positive slope. The hysteresis creates different pressure fluctuations for those operation points even though their flow rates and heads are similar respectively. The pressure fluctuation characteristics at large partial flow conditions obtained by the present study will be helpful for the safe operation of pumped storage units.

Ran, Hongjuan; Luo, Xianwu; Zhu, Lei; Zhang, Yao; Wang, Xin; Xu, Hongyuan

2012-11-01

116

Quantitative analysis of water dispersion conditions and pressure transmission characteristics of a wet kneaded mass.  

Science.gov (United States)

In our previous paper [Watano S. et al., J. Powder Technology Japan, 37, 362-370 (2000)], a novel compaction tester was developed to quantitatively evaluate the water dispersion condition of a wet kneaded mass prepared by a paddle type kneader. It has been demonstrated that the physical properties of pellets prepared by extrusion granulation after the kneading can be well predicted by the pressure transmission obtained through the compaction tester. This paper describes a more detailed investigation of the water dispersion, its mechanism and pressure transmission characteristics of wet kneaded masses prepared under various operating conditions. First, kneading by a paddle type kneader was conducted to prepare wet masses under various binder contents using different additional methods and different starting materials. Secondly, water dispersion and pressure transmission characteristics of wet masses were investigated. After the wet kneading, the wet kneaded masses were extruded through a dome type extruder and were dried by a fluidized bed to prepare dry pellets. The relationship between water dispersion and pressure transmission can be expressed by a single line, regardless of binder content or methods of addition. This implies that these parameters have no effect on the water dispersion condition of the wet kneaded mass prepared by a high shear paddle type kneader. Different water dispersion characteristics and the mechanism obtained by different starting materials can also be evaluated by the pressure transmission data. Properties of dry pellets can also be predicted by the pressure transmission. It can be concluded that the developed compaction tester can quantitatively evaluate the water dispersion condition of a wet kneaded mass and also predict properties of the final extruded products. PMID:11201227

Watano, S; Furukawa, J; Osako, Y; Yasutomo, T

2001-01-01

117

Earth tidal and barometric responses observed in the Callovo-Oxfordian formation at ANDRA Meuse/Haute-Marne underground research laboratory  

International Nuclear Information System (INIS)

Document available in extended abstract form only. Fluid pressure or hydraulic head measured in wells in geological formations can respond to Earth tidal forces and atmospheric pressure variations. At Andra Meuse/Haute-Marne underground research laboratory located in Bure (France), water level and fluid pressure are measured in several boreholes in the Callovo-Oxfordian clay formation (COX) and in overlying geological formations. One of these boreholes (EST207) is equipped with a multi-packer system monitoring 11 intervals, including 8 in the COX. The recorded fluid pressures in EST207 were analyzed to determine possible Earth tidal responses. In this borehole, the fluid pressure and atmospheric pressure variations data are recorded every fifteen minutes and 6.5 years of such data from 2004/06/02 to 2010/12/31 were analyzed. Various perturbed data, gaps, drift and abnormal data were corrected through a data preprocessing process. Data interpolation and filtering processes were performed to have data available every 15 minutes at 0, 15, 30 and 45 minutes on the hour. A spectral analysis (Fast Fourier Transform) of each pressure data series shows amplitude peaks at frequencies corresponding to various Earth tidal frequencies: diurnal and semi diurnal waves can be identified. Spectral analyses were also performed on the atmospheric pressure data. The solar semi diurnal wave (S2) was identified. The 'Earth Tides ETERNA package' was used to separate the waves according to s used to separate the waves according to the frequencies bands. The analyses performed using ETERNA are indicated as 'Earth Tidal Analyses' (ETAN). Tidal parameters are estimated from ETAN: amplitudes A and its standard deviation ?(A)[hPa], phase ? for the main waves in diurnal and semi diurnal frequencies bands before and after atmospheric pressure variations correction. The barometric efficiency (BE) and its standard deviation ? (BE) as regression coefficient is calculated. The atmospheric pressure data are also analyzed with ETERNA; the wave S2 amplitude and phase values usually taken into account as references are in good agreement with values calculated at others sites. This result validates the atmospheric pressure data sets. Having high quality data and multi-year data sets, it was possible to separate several main tidal waves in the diurnal band and in the semi diurnal band. K1, O1, P1, S1 and M2, N2, S2, K2 bands were first taken into account in each series to determine whether they were significant or not. The ETAN results are in good agreement with the spectral analyses results and with these results it can be concluded that the 11 monitoring intervals in borehole EST207 respond to Earth Tidal forces and to atmospheric pressure variations. The ETERNA software allows identifying more tidal waves with more accuracy. In all the intervals, the best identified significant waves are O1, K1, M2 and S2. While the M2 amplitude is not or only slightly perturbed by atmospheric pressure variations and the M2 phase is not, the S2 wave amplitude and phase are very sensitive to atmospheric pressure. After barometric correction, the amplitudes through the borehole are generally decreasing from the bottom to the top. In a preliminary hydrogeological interpretation, the detailed intercomparison of tidal analyses results according to the barometric correction effect, the BE values and the waves identification quality provide a classification of the barometric and tidal responses as a function of the various intervals. These responses were classified into four groups depending on the monitoring intervals in the Dogger, the lower COX, the upper COX and the base of Oxfordian. The BE values show that the greater the clay content of the formation is, the greater the BE values are. The BE values in the Dogger are similar to the values estimated in the Oxfordian. In 2003, Andra investigated earth tides and barometric responses in the Oxfordian of two boreholes, EST203 and EST104. The hydrogeological interpretation in these two boreholes provided estimates of transmissi

118

Detectability and significance of 12 hr barometric tide in radon-222 signal, drip water flow rate, air temperature and carbon dioxide concentration in an underground tunnel  

International Nuclear Information System (INIS)

Searching for small periodic signals, such as the 12 hr (S2) barometric tide, and monitoring their amplitude as a function of time, can provide important clues on the complex processes affecting fluid transport in unsaturated fractured media under multiple influences. Here, first, we show that a modified spectrogram analysis (MSA) is more efficient than simple Fourier transform to reveal weak periodic signals. Secondly, we show how transient periodic signals can be monitored as a function of time using spectrograms. These methods are applied to time-series of radon and carbon dioxide concentration, drip water flow rates and air temperature measured during several years in the Roselend dead-end tunnel, located in the French Alps near an artificial lake. A weak S2 line is evidenced in radon concentration, with enhanced amplitude during transient radon bursts. Similarly, the S2 line is observed using MSA in drip water flow rates which sample mainly fracture flow, as suggested by a hydrochemical analysis, while it is not seen in drip water flow rates sampling matrix flow. In the absence of a strong 24 hr line, the presence of a S2 line suggests sensitivity to barometric pressure, and thus a significant advective contribution in radon and some drip water transport. No S2 line is observed in the carbon dioxide time-series. The temporal structure of the S2 component, however, is not similar in the radon concenowever, is not similar in the radon concentration and the drip water flow rates, suggesting, in particular, that drip water does not play a significant role in the generation of radon bursts. Temperature time-series exhibit a significant S2 contribution, induced by atmospheric pressure, spatially organised in the tunnel, decreasing vertically upwards. A remarkable transient temperature inversion during radon bursts suggests that the additional advective air contributions responsible for the radon bursts occur from the non-saturated rocks below the tunnel. (authors)

119

Detectability and significance of 12 hr barometric tide in radon-222 signal, dripwater flow rate, air temperature and carbon dioxide concentration in an underground tunnel  

Science.gov (United States)

Searching for small periodic signals, such as the 12 hr (S2) barometric tide, and monitoring their amplitude as a function of time, can provide important clues on the complex processes affecting fluid transport in unsaturated fractured media under multiple influences. Here, first, we show that a modified spectrogram analysis (MSA) is more efficient than simple Fourier transform to reveal weak periodic signals. Secondly, we show how transient periodic signals can be monitored as a function of time using spectrograms. These methods are applied to time-series of radon and carbon dioxide concentration, dripwater flow rates and air temperature measured during several years in the Roselend dead-end tunnel, located in the French Alps near an artificial lake. A weak S2 line is evidenced in radon concentration, with enhanced amplitude during transient radon bursts. Similarly, the S2 line is observed using MSA in dripwater flow rates which sample mainly fracture flow, as suggested by a hydrochemical analysis, while it is not seen in dripwater flow rates sampling matrix flow. In the absence of a strong 24 hr line, the presence of a S2 line suggests sensitivity to barometric pressure, and thus a significant advective contribution in radon and some dripwater transport. No S2 line is observed in the carbon dioxide time-series. The temporal structure of the S2 component, however, is not similar in the radon concentration and the dripwater flow rates, suggesting, in particular, that dripwater does not play a significant role in the generation of radon bursts. Temperature time-series exhibit a significant S2 contribution, induced by atmospheric pressure, spatially organised in the tunnel, decreasing vertically upwards. A remarkable transient temperature inversion during radon bursts suggests that the additional advective air contributions responsible for the radon bursts occur from the non-saturated rocks below the tunnel.

Richon, Patrick; Perrier, Frédéric; Pili, Eric; Sabroux, Jean-Christophe

2009-03-01

120

Experimental study of the pressure fluctuations on propeller turbine runner blades: part 2, transient conditions  

Science.gov (United States)

Transient conditions such as load rejection will often lead to high amplitude pressure fluctuations that will affect a turbine residual-life. If Computational Fluid Dynamic offers a promising tool to study the flow dynamic under transient regime, focused validation data on the runner are still lacking to assess the accuracy of different simulation strategies. Hence within the framework of the AxialT project of the International Consortium on Hydraulic Machines, exploratory measurements of the pressure field on the runner blades of a propeller turbine model were performed in transient conditions. The model was setup on the test stand of the LAMH of Laval University. The test stand control procedures were adapted to mimic transient condition such as load rejection or the transition from a normal operating condition to a speed-no-load condition. The pressure on the runner blades were measured using miniature piezo-resistive transducer linked to a high frequency telemetric system. Using specifically adapted data processing routines, it was possible to characterize the variations of the energy content during the transient runs. Specifically, the main fluctuations appear to occur in the sub-synchronous range in both cases.

Houde, S.; Fraser, R.; Ciocan, G.; Deschênes, C.

2012-11-01

121

Flare-out condition of Morris-Thorne wormhole and finiteness of pressure  

CERN Document Server

Wormhole is defined as the topological structure with the throat connecting two asymptotically flat spaces. In order to have and maintain the structure of the wormhole, there needs the geometrical flare-out condition, i.e., the minimal size at throat. In the case of Morris-Thorne type wormhole, the condition is given by the huge surface tension compared to the energy density times the square of the light speed. In this paper, we re-considered the flare-out condition for the wormhole with the Einstein equation, checked the finiteness of the pressure, and investigated its physical meaning.

Kim, Sung-Won

2013-01-01

122

Numerical simulation of pressure fluctuation in 1000MW Francis turbine under small opening condition  

International Nuclear Information System (INIS)

In order to study the cause of abnormal vibration in large Francis turbine under small opening condition, CFD method was adopted to analyze the flow filed and pressure fluctuation. Numerical simulation was performed on the commercial CFD code Ansys FLUENT 12, using DES method. After an effective validation of the computation result, the flow behaviour of internal flow field under small opening condition is analyzed. Pressure fluctuation in different working mode is obtained by unsteady CFD simulation, and results is compared to study its change. Radial force fluctuation is also analyzed. The result shows that the unstable flow under small opening condition leads to an increase of turbine instability in reverse pump mode, and is one possible reason of the abnormal oscillation.

123

Impact of Mental and Physical Stress on Blood Pressure and Pulse Pressure under Normobaric versus Hypoxic Conditions  

Science.gov (United States)

Objective Hypobaric hypoxia, physical and psychosocial stress may influence key cardiovascular parameters including blood pressure (BP) and pulse pressure (PP). We investigated the effects of mild hypobaric hypoxia exposure on BP and PP reactivity to mental and physical stress and to passive elevation by cable car. Methods 36 healthy volunteers participated in a defined test procedure consisting of a period of rest 1, mental stress task (KLT-R), period of rest 2, combined mental (KLT-R) and physical task (bicycle ergometry) and a last period of rest both at Graz, Austria (353 m asl) and at the top station Dachstein (2700 m asl). Beat-to-beat heart rate and BP were analysed both during the test procedures at Graz and at Dachstein and during passive 1000 m elevation by cable car (from 1702 m to 2700 m). Results A significant interaction of kind of stress (mental vs. combined mental and physical) and study location (Graz vs. Dachstein) was found in the systolic BP (p?=?.007) and PP (p?=?.002) changes indicating that during the combined mental and physical stress task sBP was significantly higher under hypoxic conditions whereas sBP and PP were similar during mental stress both under normobaric normoxia (Graz) and under hypobaric hypoxia (Dachstein). During the passive ascent in cable car less trivialization (psychological coping strategy) was associated with an increase in PP (p?=?.004). Conclusion Our data show that combined mental and physical stress causes a significant higher raise in sBP and PP under hypoxic conditions whereas isolated mental stress did not affect sBP and PP under hypoxic conditions. PP-reaction to ascent in healthy subjects is not uniform. BP reactions to ascent that represents an accumulation of physical (mild hypobaric hypoxia) and psychological stressors depend on predetermined psychological traits (stress coping strategies). Thus divergent cardiovascular reactions can be explained by applying the multidimensional aspects of the biopsychosocial concept. PMID:24817135

Trapp, Michael; Trapp, Eva-Maria; Egger, Josef W.; Domej, Wolfgang; Schillaci, Giuseppe; Avian, Alexander; Rohrer, Peter M.; Hörlesberger, Nina; Magometschnigg, Dieter; Cervar-Zivkovic, Mila; Komericki, Peter; Velik, Rosemarie; Baulmann, Johannes

2014-01-01

124

Interfacial tension measurement between CO2 and brines under high temperature and elevated pressure conditions  

Science.gov (United States)

We have investigated the dependence of interfacial tension of (CO2 + brine) on temperature, pressure and salinity (including both salt type and molality) over the range of conditions applicable to CO2 storage in saline aquifers. The study covered a wide range of measurements of the interfacial tensions between carbon dioxide and (NaCl + KCl)(aq), CaCl2(aq), MgCl2(aq), Na2SO4(aq), KHCO3(aq), NaHCO3(aq) and two laboratory constructed brines with molality ranging from (0.3 to 5.0) mol·kg-1. The measurements were made at temperatures between (298 and 448) K at various pressures up to 50 MPa, using the pendant drop method in a high-pressure view cell filled with water-saturated CO2. The drop to be imaged was created by injecting brine from a high-pressure syringe pump into a capillary sealed through the top of the cell. The expanded uncertainties of the experimental state variables at 95 % confidence are +0.05 K in temperature and +70 kPa in pressure. For the interfacial tension, the overall expanded relative uncertainty at 95 % confidence was +1.6%. The experimental results show that interfacial tension for all the systems increases linearly with molality, indicating that relatively few measurements and simple interpolation procedures are adequate for describing this property accurately over wide ranges of conditions.

Li, X.; Boek, E. S.; Maitland, G. C.; Trusler, J. P. M.

2012-04-01

125

Flash-type barometric desalination plant powered by waste heat from electricity power stations in Cyprus  

International Nuclear Information System (INIS)

This paper describes and evaluates the results of a study into the problems of freshwater production and shortages on the island of Cyprus. The use of a novel barometric flash-type desalinator, driven by otherwise waste-heat from the island's power-stations, is proposed as a means of increasing freshwater supplies. Mathematical models are described and used to investigate the thermodynamic performance and economic viability of the proposed system. Although water and electricity-supply data for the island of Cyprus were used for the purposes of this investigation, the overall findings are thought to have a wider applicability

126

Improvement of the RELAP5 subcooled boiling model for low pressure conditions  

International Nuclear Information System (INIS)

The RELAP5/MOD3.2.2 Gamma code was assessed against low pressure subcooled boiling experiments performed by Zeitoun and Shoukri [1] in a vertical annulus. The predictions of subcooled boiling bubbly flow showed that the present version of the RELAP5 code underestimates the void fraction growth along the tube. To improve the void fraction prediction at low pressure conditions a set of model changes is proposed, which includes modifications of bubbly-slug transition criterion, drift-flux model, interphase heat transfer coefficient and wall evaporation modeling. The improved experiment predictions with the modified RELAP5 code are presented and analysed. (author)

127

Valve inlet fluid conditions for pressurizer safety and relief valves in combustion engineering-designed plants. Final report  

International Nuclear Information System (INIS)

The purpose of this study is to assemble documented information for C-E designed plants concerning pressurizer safety and power operated relief valve (PROV) inlet fluid conditions during actuation as calculated by conventional licensing analyses. This information is to be used to assist in the justification of the valve inlet fluid conditions selected for the testing of safety valves and PORVs in the EPRI/PWR Safety/Relief Valve Test Program. Available FSAR/Reload analyses and certain low temperature overpressurization analyses were reviewed to identify the pressurization transients which would actuate the valves, and the corresponding valve inlet fluid conditions. In addition, consideration was given to the Extended High Pressure Liquid Injection event. A general description of each pressurization transient is provided. The specific fluid conditions identified and tabulated for each C-E designed plant for each transient are peak pressurizer pressure, pressure ramp rate at actuation, temperature and fluid state

128

Pressure Gradient Influence on MHD Flow for Generalized Burgers’ Fluid with Slip Condition  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a research for magnetohydrodynamic (MHD flow of an incompressible generalized Burgers' fluid including by an accelerating plate and flowing under the action of pressure gradient. Where the no – slip assumption between the wall and the fluid is no longer valid. The fractional calculus approach is introduced to establish the constitutive relationship of the generalized Burgers' fluid. By using the discrete Laplace transform of the sequential fractional derivatives, a closed form solutions for the velocity and shear stress are obtained in terms of Fox H- function for the following two problems: (i flow due to a constant pressure gradient, and (ii flow due to due to a sinusoidal pressure gradient. The solutions for no – slip condition and no magnetic field, can be derived as special cases of our solutions. Furthermore, the effects of various parameters on the velocity distribution characteristics are analyzed and discussed in detail. Comparison between the two cases is also made.

Ghada H. Ibraheem,

2014-07-01

129

Optimal heat rejection pressure in transcritical carbon dioxide air conditioning and heat pump systems  

DEFF Research Database (Denmark)

Due to the urgent need for environmentally benign refrigerants, the use of the natural substance carbon dioxide in refrigeration systems has gained more and more attention. In systems such as automobile air-conditioners and heat pumps, owing to the relatively high heat rejection temperatures, the cycles using carbon dioxide as refrigerant will have to operate in the transcritical area. In a transcritical carbon dioxide system, there is an optimal heat rejection pressure that gives a maximum COP. In this paper, it is shown that the value of this optimal heat rejection pressure mainly depends on the outlet temperature of the gas cooler, the evaporation temperature and the efficiency of the compressor. General correlations for this optimal heat rejection pressure were derived based on cycle simulations. The correlations presented in this paper provide a basisfor designing transcritical carbon dioxide air conditioning or heat pump systems and for intelligent controlling such systems.

Liao, Shengming; Jakobsen, Arne

1998-01-01

130

Assessment of Fuel Behaviour under Large Break LOCA Condition for Indian Pressurized Heavy Water Reactor  

International Nuclear Information System (INIS)

Pressurized heavy water reactor (PHWR) consists of a large number of coolant channel assemblies. Each channel assembly is loaded with number of short length fuel bundles. A fuel element consists of sintered cylindrical UO2 pellets contained in a thin collapsible Zircaloy-4 cladding. Large break loss of coolant accident (LBLOCA) in PHWR results in insertion of positive reactivity due to core voiding leading to increase in reactor power. For large breaks, there is an early increase in neutron power and the event leads to reactor trip occurring from neutronic signals besides various other process trips. PHT system depressurizes rapidly and heat transfer from fuel rods decreases sharply which results in rapid rise in clad temperature. With this rise in clad temperature, the exothermic zirconium-metal water reaction would also start contributing toward energy generation and hence results in rapid rise in fuel clad temperature. The fuel clad temperature in the core is estimated during large break LOCA accident and fuel failures in this case are calculated. Under the postulated accident conditions, fuel shall remain in position and not suffer distortion to an extent that would render post- accident core cooling ineffective. The criteria for accident conditions for predicting fuel failure are: (1) The maximum oxygen concentration in the least affected half thickness of clad shall not exceed 0.7 per cent by weight. (2) Stress in the cladding shall not exceed burst stress. (3) adding shall not exceed burst stress. (3) The total energy in fuel element including radial average enthalpy shall be less than 200 cal.g-1 in the over power transient. In an accident transient fuel clad will be subjected to high temperature and high pressure difference across the clad. The coolant pressure goes down in case of large break LOCA. The fission gas pressure is estimated in transient considering fuel temperature and deformation of clad. The fuel element failure is considered if the fuel clad local stress equal or exceeds the burst stresses. The burst stress is calculated considering, clad temperature, differential pressure between clad and coolant and oxidation of the Zircaloy-4 during the transient. In the over power transient initiated by reactivity initiated accident or LOCA, cumulative energy deposition in the fuel is estimated. In this paper, assessment of fuel damage under LBLOCA condition for Indian PHWRs is performed for identified limiting governing break sizes. Analysis demonstrates that under governing LOCA condition with high pressure ECCS available, adequate coolant pressure at the time of peak clad temperature on collapsible clad prevents the gross fuel failure and fuel clad failure is limited to low value of full core in the entire spectrum of break sizes and locations. (author)

131

The Rheological Properties of Oil-Based Mud under High Pressure and High Temperature Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available

Designing a proper drilling fluid that can function properly under the conditions of High-Pressure, High-Temperature (HP/HT operations is very challenging. Among these challenges is the alteration of the rheological properties of drilling fluid due to the high temperature and high pressure (Ibeh et. al, 2007. This work investigates the rheological behavior of oil-based drilling fluids with different properties at Ultra-HP/HT conditions using a state-of-the-art viscometer capable of measuring drilling fluids properties up to 600°F and 40,000 psi. For this purpose, two actual oil based mud samples used by industry with the same mud weight (12.5 ppg were chosen to carry out a matrix of experiments. The results of this study led to concluding that the viscosity, yield point and gel strength decrease with increasing temperature (until the mud sample fails, for oil-based mud with regular formulation. This behavior is the result of the thermal degradation of the solid, polymers, and other components of the mud samples and the expansion of the molecular distances which will lower the resistance of the fluid to flow and, hence, its viscosity, yield point, and gel strength. Moreover, it is concluded that the viscosity and yield point increase as the pressure increases. Pressure’s effect on these parameters, however, is more apparent at low temperature (below failure point, for oil-based mud with regular formulation.

Key words: High pressure high temperature; Oil-based mud; Rheology; Rheological properties

Mahmood Amani

2012-07-01

132

Freezing and melting of 3D complex plasma structures under microgravity conditions driven by neutral gas pressure manipulation  

OpenAIRE

Freezing and melting of large three-dimensional complex plasmas under microgravity conditions is investigated. The neutral gas pressure is used as a control parameter to trigger the phase changes: Complex plasma freezes (melts) by decreasing (increasing) the pressure. Evolution of complex plasma structural properties upon pressure variation is studied. Theoretical estimates allow us to identify main factors responsible for the observed behavior.

Khrapak, S. A.; Klumov, B. A.; Huber, P.; Molotkov, V. I.; Lipaev, A. M.; Naumkin, V. N.; Thomas, H. M.; Ivlev, A. V.; Morfill, G. E.; Petrov, O. F.; Fortov, V. E.; Malentschenko, Yu; Volkov, S.

2011-01-01

133

A modified resistance equation for modeling underwater spark discharge with salinity and high pressure conditions  

Science.gov (United States)

This work investigates the performance of underwater spark discharge relating to bubble growth and decay under high pressure and with salinity conditions by introducing a modified form of the resistance equation. Here, we study salinity influence on circuit parameters by fitting the experimental data for which gap resistance is much larger in conductive water than in dielectric water. Accordingly, the resistance equation is modified by considering the influence of both plasma and its surrounding liquid. Thermal radiation effect of the bubble is also studied by comparing two different radiation models. Numerical results predict a larger bubble pressure for saline water but a reduced size and a smaller bubble cycle at a greater water depth. Such study may be useful in many saltwater applications, including that for deep sea conditions.

Zhao, Pengfei; Roy, Subrata

2014-05-01

134

A modified resistance equation for modeling underwater spark discharge with salinity and high pressure conditions  

International Nuclear Information System (INIS)

This work investigates the performance of underwater spark discharge relating to bubble growth and decay under high pressure and with salinity conditions by introducing a modified form of the resistance equation. Here, we study salinity influence on circuit parameters by fitting the experimental data for which gap resistance is much larger in conductive water than in dielectric water. Accordingly, the resistance equation is modified by considering the influence of both plasma and its surrounding liquid. Thermal radiation effect of the bubble is also studied by comparing two different radiation models. Numerical results predict a larger bubble pressure for saline water but a reduced size and a smaller bubble cycle at a greater water depth. Such study may be useful in many saltwater applications, including that for deep sea conditions

135

The effect of pressure on the electrical conductivity of olivine under the hydrogen-rich conditions  

Science.gov (United States)

The influence of pressure on the hydrogen-assisted electrical conductivity in olivine has been studied under conditions of 4-10 GPa and 873-1273 K. Synthetic polycrystalline olivine samples with the water content of 160 ppm wt (Paterson calibration) were used and the electrical conductivity was determined from the results of the impedance spectroscopy. We found that the pressure reduces the hydrogen-assisted electrical conductivity, but its magnitude is small: between 4 and 10 GPa, the difference is a factor of ?2.5 for the same water content and temperature. The pressure dependence is characterized by a negative activation volume and the negative dependence of the pre-exponential factor on pressure. Such anomalous behavior is explained by a model where hydrogen-related defect is considered as a weak inclusion in a strong matrix. We use these new data to calculate the electrical conductivity contrast at the 410-km discontinuity. We found that if the water content of the mantle does not change with depth, there should be a large (a factor of ?10) drop in conductivity from above to below the 410-km discontinuity. In contrast, geophysically inferred electrical conductivity increases at 410-km suggesting the increase in water content from above to below the 410-km discontinuity. The present results are used to compare several previous results obtained at different pressures. It was shown that our results agree well with most of previous studies but not with (Yoshino et al., 2009). Possible causes for this discrepancy are discussed.

Dai, Lidong; Karato, Shun-ichiro

2014-07-01

136

Nonlinear Analysis of Onset of Nucleate Boiling in Natural Circulation under Different Pressure Conditions  

OpenAIRE

In this study, we obtain the flow signals before and after the ONB through natural circulation experiments under pressure conditions of 0.15MPa and 0.3MPa. Researches were conducted by applying nonlinear analysis techniques. Results revealed that the power spectrum of volume flow data declined exponentially over time in semi logarithmic coordinates, the autocorrelation coefficient declined gradually and the phase diagram exerted the subtle structures of chaotic movement, which might prove the...

Cheng Sheng; Tao Zhou; Lei Zhang; Zhongyun Ju

2013-01-01

137

Microstructure and spectroscopy studies on cubic boron nitride synthesized under high-pressure conditions.  

OpenAIRE

High-resolution electron microscopy (HREM) studies of the microstructure and specific defects in hexagonal boron nitride (h-BN) precursors and cubic boron nitride (c-BN) crystals made under high-pressure high-temperature conditions revealed the presence of half-nanotubes at the edges of the h-BN particles. Their sp 3 bonding tendency could strongly influence the nucleation rates of c-BN. The atomic resolution at extended dislocations was insufficient to allow us to determin...

Manfredotti, Claudio; Vittone, Ettore

2002-01-01

138

Natural Circulation Characteristics at Low-Pressure Conditions through PANDA Experiments and ATHLET Simulations  

OpenAIRE

Natural circulation characteristics at low pressure/low power have been studied by performing experimental investigations and numerical simulations. The PANDA large-scale facility was used to provide valuable, high quality data on natural circulation characteristics as a function of several parameters and for a wide range of operating conditions. The new experimental data allow for testing and improving the capabilities of the thermal-hydraulic computer codes to be used for treating natural c...

Domenico Paladino; Max Huggenberger; Frank Schäfer

2008-01-01

139

Durability of polydicyclopentadiene under high temperature, high pressure and seawater (offshore oil production conditions)  

OpenAIRE

In the offshore industry polymer coatings are widely used to ensure thermal insulation of steel pipes, and to avoid over-cooling of the hot oil inside. Because of very severe service conditions (i.e. high temperature, high pressure and presence of seawater) and an expected life time of 20 years, durability of these coatings is a major issue for this industry. Polypropylene and polyurethane are often used for this application, nevertheless these polymers have some limitations in terms of proce...

Le Gac, Pierre-yves; Choqueuse, Dominique; Paris, Marc; Recher, G.; Zimmer, Celine; Melot, D.

2013-01-01

140

Modeling and Investigation of Electromechanical Valve Train Actuator at simulated Pressure conditions  

DEFF Research Database (Denmark)

In an electromechanical valve actuated engine, the valves are driven by solenoid-type actuators and cam-shaft is eliminated. Control of each valve provides flexibility in valve timings over all engine conditions and achieves the benefits of variable valve timing(VVT). This paper is about investigation of Electro-mechanical actuator at simulated pressure conditions for a single cylinder engine. For this purpose, a scaled down actuator with reduced armature lift and high stiffness springs are being used. Experiments are conducted to measure valve release timings, transition times and contact velocities. Furthermore, discussion about the spring, magnetic, exhausts gas forces and their ability to actuate the system as desired.

Habib, Tufail

2012-01-01

141

Seismic-safe conditions of blasting near pressure pipe-lines during power installation construction  

International Nuclear Information System (INIS)

Seismic-safe conditions for performing drill-blasting operations in the vicinity of underground gas pipelines when constructing thermal- or nuclear power plants are discussed. It is shown that, for the determination of seismic-safe parameters, of drill-blasting operations, the maximum permissible level of seismic loads should be specified taking into account the mechanical properties of the pipeline.metal, structural parameters of the gas pipeline and the pressure of the medium transported. Besides, the seismic effect of the blast should be considered with regard to particular conditions of blasting and rock properties. The equations and diagrams used in the calculation are given

142

High-pressure behavior of cristobalite under quasi-hydrostatic conditions  

Science.gov (United States)

Cristobalite is a high-temperature, low-pressure polymorph of SiO2. It is comprised of a framework of SiO4 tetrahedra, like many other low-pressure silica polymorphs, e.g. quartz tridymite, or coesite. Its cubic form known as ?-cristobalite crystallizes above 1470 ° C and at atmospheric pressure. The tetragonal ?-phase is a metastable polymorph which appears upon cooling of the cubic ?-cristobalite to ambient temperature and it can be found in natural acidic volcanic rocks. High-pressure behavior of ?-cristobalite is of interest form the geological standpoint because it was experimentally observed that under elevated pressures and at ambient temperature this polymorph with 4-fold coordinated silicon can transform to seifertite - a lower mantle phase with octahedrally coordinated Si. The transformational sequence is as follows. The tetragonal ?-cristobalite transforms to a monoclinic cristobalite II near ~1.5 GPa upon hydrostatic compression. The structure of this higher-pressure polymorph was recently solved. Above ~10 GPa cristobalite II is found to transforms to cristobalite X-I. Apart from the recent determination of the unit cell parameters, the structure of the cristobalite X-I still remains unknown. Further compression of cristobalite X-I above pressures exceeding ~35 GPa leads to formation of cristobalite X-II, which is the polymorph reported to have the structure of seifertite. However, there is a large discrepancy among various experimental observations regarding the pressure at which this transition takes place. Motivated by the recent studies, we aim at understanding how the structure of this "bridging phase", cristobalite X-I, is evolving under pressure and how it transforms to the seifertite phase. We performed in-situ single crystal Raman spectroscopy and X-ray diffraction up to 82 GPa in steps of 3-5 GPa. We used diamond-anvil cells with 250 ?m diamond culet size and neon as the pressure-transmitting medium. In-situ Raman spectra indicated the phase transition to cristobalite II near 1.5 GPa and the formation of the X-I phase above 10 GPa, in agreement with previous studies. This high-pressure phase persists up the highest pressures achieved and it is not quenchable - upon decompression it retransforms into a phase with Raman spectra very similar to that of the starting ?-cristabolate. Single crystal X-ray diffraction data were collected at Extreme Conditions Beamline P02.2 at Petra III. We confirmed the phase transition to cristobalite II and further above 10 GPa to the phase X-I. Indexing of the diffraction patterns of the phase X-I collected at 17 GPa yields a primitive monoclinic unit cell with a = 6.5899(9) Å, b = 4.0493(6) Å, c = 6.841(8) Å, ? = 98.15(3)° and the most likely space groups P21/c or P21/n. A preliminary structure analysis reveals that all Si atoms are octahedrally coordinated at this pressure. Single-crystal X-ray diffraction data from experiments at higher pressures are currently being analyzed.

Cernok, Ana; Bykova, Elena; Liermann, Hanns-Peter; Dubrovinsky, Leonid

2014-05-01

143

Measurements of mixtures with carbon dioxide under supercritical conditions using commercial high pressure equipment  

Energy Technology Data Exchange (ETDEWEB)

There is a growing interest in studying physical properties of binary and multicomponent fluid mixtures with supercritical carbon dioxide (CO{sub 2}) over an extended range of temperature and pressure. The estimation of properties such as density, viscosity, saturation pressure, compressibility, solubility and surface tension of mixtures is important in design, operation and control as well as optimization of chemical processes especially in extractions, separations, catalytic and enzymatic reactions. The phase behaviour of binary and multicomponent mixtures with supercritical CO{sub 2} is also important in the production and refining of petroleum where mixtures of paraffin, naphthene and aromatics with supercritical fluids are often encountered. Petroleum fluids can present a complex phase behaviour in the presence of CO{sub 2}, where two-phase (VLE and LLE) and three phase regions (VLLE) might occur within ranges of supercritical conditions of temperature and pressure. The objective of this study is to develop an experimental methodology for measuring the phase behaviour of mixtures containing CO{sub 2} in supercritical regions, using commercial high-pressure equipment. (author)

Andrade, Luciana L.P.R. de; Rutledge, Luis Augusto Medeiros; Moreno, Eesteban L.; Hovell, Ian; Rajagopal, Krishnaswamy [Universidade Federal do Rio de Janeiro (LATCA-EQ-UFRJ), RJ (Brazil). Escola de Quimica. Lab. de Termodinamica e Cinetica Aplicada

2012-07-01

144

Condition health monitoring of composite wound pressure vessels using fiber Bragg gratings  

Science.gov (United States)

Structure health monitoring refers to a real time and in situ monitoring system. It can diagnose the condition status of composite structure in time and effectively estimate the safety, increasing the reliability, extending the service life, at the same time, reducing the maintenance cost. In this paper, the sensing technology based on FBG sensors is employed to monitor the health of composite wound pressure vessel in service. Strain monitoring of the vessel in fatigue tests is carried out with the surface mounted FBG sensors. The experiment result shows that FBG sensors have several excellent performances: it has anti-fatigue capability to accurately measure the cycle strain; it is linear with the inner pressure and can be used as pressure sensor; the wavelength is diverged in the high stress gradient field, so the FBG can be used to measure the non-homogeneous strain field. Based on the fatigue damage mechanism of composite laminates and stiffness degradation model, the variation regularity of cycle strain of composite pressure vessel is studied and the residual stiffness during damage is obtained.

Zhang, Xiaojing; Zhang, Boming; Wu, Zhanjun

2007-07-01

145

Core void fraction distribution under high-temperature high-pressure boil-off conditions  

International Nuclear Information System (INIS)

The prediction of void fraction distributions in a core under boil-off conditions is important for analyzing the core cooling performance during reactor accidents. In this work, boil-off experiments were conducted under high-temperature high-pressure conditions using PWR-type and tight-lattice type (p/d = 1.11) simulated fuel assembly test sections of the Two-Phase flow Test Facility (TPTF). Several existing void fraction correlations and models were assessed against the experimental data. As a result, it has become clear that: 1) while the Chexal-Lellouche model predicts best the present experimental data, the model has a tendency to underestimate void fraction at higher pressures; 2) no significant problems are found in the applicability of the tested correlations and models to the tight-lattice geometry; and 3) void fractions measured by single-beam gamma densitometers tend to be larger than those measured by differential pressure transducers due to the radial void fraction distribution. (author)

146

Cryogenic Tunnel Pressure Measurements on a Supercritical Airfoil for Several Shock Buffet Conditions  

Science.gov (United States)

Steady and unsteady experimental data are presented for several fixed geometry conditions from a test in the NASA Langley 0.3-Meter Transonic Cryogenic Tunnel. The purpose of this test was to obtain unsteady data for transonic conditions on a fixed and pitching supercritical airfoil at high Reynolds numbers. Data and brief analyses for several of the fixed geometry test conditions will be presented here. These are at Reynolds numbers from 6 x 10(exp 6) to 35 x 10(exp 6) bases on chord length, and span a limited range of Mach numbers and angles of attack just below and at the onset of shock buffet. Reynolds scaling effects appear in both the steady pressure data and in the onset of shock buffet at Reynolds numbers of 15 x 10(exp 6) and 3O x 10(exp 6) per chord length.

Bartels, Robert E.; Edwards, John W.

1997-01-01

147

Structural integrity assessment of the reactor pressure vessel under the external reactor vessel cooling condition  

Energy Technology Data Exchange (ETDEWEB)

Since the suggestion of External Reactor Vessel Cooling (ERVC), the effects of malting and cooling on the response of structural integrity of the Reactor Pressure Vessel (RPV) under core melting accident conditions have been investigated. This paper describes the vessel response according to the ERVC condition and analysis method. The steady state and transient analysis for the temperature and stress field were performed using ABAQUS. Especially, transient analyses were studied for the variable boundary conditions. To obtain an analogy with real phenomena, the material properties were determined by combining and modifying the existing results considering phase transformation and temperature dependency. The results show that the vessel can be melted if there is no external cooling. Finally, the potential for vessel damage is discussed using the Larson-Miller curve and damage rule. (author)

Kim, Jong-Sung; Jin, Tae-Eun [Korea Power Engineering Company, Inc. (Korea, Republic of)

1998-12-31

148

Outflow boundary conditions for 3D simulations of non-periodic blood flow and pressure fields in deformable arteries.  

OpenAIRE

The simulation of blood flow and pressure in arteries requires outflow boundary conditions that incorporate models of downstream domains. We previously described a coupled multidomain method to couple analytical models of the downstream domains with 3D numerical models of the upstream vasculature. This prior work either included pure resistance boundary conditions or impedance boundary conditions based on assumed periodicity of the solution. However, flow and pressure in art...

Vignon-clementel, Irene; Figueroa, C. A.; Jansen, K. E.; Taylor, C. A.

2010-01-01

149

Toward measurements of volatile behavior at realistic pressure and temperature conditions in planetary deep interiors. (Invited)  

Science.gov (United States)

Laboratory studies of volatiles at high pressure are constantly challenged to achieve conditions directly relevant to planets. While dynamic compression experiments are confined to adiabatic pathways that frequently exceed relevant temperatures due to the low densities and bulk moduli of volatile samples, static compression experiments are often complicated by sample reactivity and mobility before reaching relevant temperatures. By combining the speed of dynamic compression with the flexibility of experimental path afforded by static compression, optical spectroscopy measurements in volatiles such as H, N, and Ar have been demonstrated at previously-unexplored planetary temperature (up to 11,000 K) and pressure (up to 150 GPa). These optical data characterize the electronic properties of extreme states and have implications for bonding, transport, and mixing behavior in volatiles within planets. This work was conducted in collaboration with D.A. Dalton and A.F. Goncharov (Carnegie Institution of Washington) and M.F. Mahmood (Howard University).

McWilliams, R. S.

2013-12-01

150

Sulphation of oil shale ash under atmospheric and pressurized combustion conditions  

International Nuclear Information System (INIS)

One of the main problems in conventional combustion boilers firing pulverized oil shale is the corrosion and fouling of heating surfaces, which is caused by sulphur compounds. Another major problem, from the environmental point of view, are the high SO2 emissions. Consequently, the amount of sulphur in flue gases must be reduced. One alternative to lower the SO2, concentration is the use of new technologies, such as pressurized fluidized bed combustion (PFBC). In FBC processes, the sulphur components are usually removed by the addition of limestone (CaCO3) or dolomite (CaCO3 x MgCO3) into the bed. The calcium in these absorbents react with SO2, producing solid CaSO4. However, when burning oil shale, there would be no need to add limestone or dolomite into the bed, due to the initially high limestone content in the fuel (molar ratio Ca/S =10). The capture of sulphur by oil shale ashes has been studied using a pressurized thermogravimetric apparatus (PTGA). The chosen experimental conditions were typical for atmospheric and pressurized fluidized bed combustion. Four different materials were tested - one cyclone ash from an Estonian oil shale boiler, two size fractions of Estonian oil shale and, one fraction of Israeli oil shale. The cyclone ash was found to be the poorest sulphur absorbent. In general, the results from the sulphur capture experiments under both atmospheric and pressurized fluidized bed conditions showed that the oil shale can capture not only its own sulphur but also significant amounts of additional sulphur from another fuel if the fuels are mixed together. (author)

151

Microstructural Changes in SA508 Gr.4N Pressure Vessel Steel with Heat Treatment Conditions  

International Nuclear Information System (INIS)

Low carbon low alloy steels, are used for nuclear reactor pressure vessels, which determine the safety and the life span of nuclear power plant. In addition, they are utilized for long period under very severe conditions such as high pressure, high temperature, and neutron irradiation and corrosion, so that they are requested high strength and toughness, weldability, neutron irradiation resistance. These mechanical properties can be affected by grain size and carbide precipitation behavior that depend on chemical composition and heat treatment condition. It is well known that SA508 Gr.4N steel with higher Ni and Cr contents has excellent mechanical properties due to its enhanced hardenability. However more verification is needed, in order to use for the nuclear plant. This study was initiated to evaluate the effects of metallurgical variables on mechanical properties of SA508 Gr.4N steel as a candidate for the advanced RPV materials. In order to control grain size and carbide morphology, austenitizing and tempering condition were changed. Also SA508 Gr.3 steel was used to compare microstructure and mechanical properties to those of SA508 Gr.4N steel

152

Windsock memory conditioned RAM (Co-Ram) pressure effect: forced reconnection in the Earth's magnetotail  

CERN Document Server

Magnetic reconnection (MR) is a key physical concept explaining the addition of magnetic flux to the magnetotail and closed flux lines back-motion to the dayside magnetosphere. This scenario elaborated by \\citet{dung63}, can explain many aspects of solar wind-magnetosphere interaction processes, including substorms. However, neither the Dungey model nor its numerous modifications were able to explain fully the onset conditions for MR in the tail. In this paper, we introduce new onset conditions for forced MR in the tail. We call our scenario the "windsock memory conditioned ram pressure effect". Our non-flux-transfer associated forcing is introduced by a combination of large-scale windsock motions exhibiting memory effects and solar wind dynamic pressure actions on the nightside magnetopause during northward oriented IMF. Using global MHD GUMICS-4 simulation results, upstream data from WIND, magnetosheath data from Cluster-1 and distant-tail data from the two-probe ARTEMIS mission, we show that the simultaneo...

Vörös, Z; Khodachenko, M; Honkonen, I; Janhunen, P; Palmroth, M

2014-01-01

153

High-pressure behavior of iron carbide (Fe7C3) at inner core conditions  

Science.gov (United States)

Carbon is a plausible light element candidate in the Earth's core owing to its cosmic abundance and its chemical affinity for iron. Recent experimental studies on Fe-C phase relations at high pressures have demonstrated that Fe7C3 iron carbide is a likely candidate for the Earth's inner core. Using electronic structure calculations, we determine the equation of state, the full elastic constant tensor, and the sound wave velocities for Fe7C3, up to inner core pressures. We find that Fe7C3 is ferromagnetic (fm) at low pressure, and that its compression behavior is well represented by a third-order Birch Murnaghan finite strain expression with V0fm = 9.1 Å3/atom, K0fm = 231 GPa, and K'0fm = 4.4. Under compression the magnetic moments of the Fe atoms gradually decrease, and at ˜67 GPa the magnetic moment is lost. The high-pressure nonmagnetic phase (nm) has distinct finite strain parameters with V0nm = 8.8 Å3/atom, K0nm = 291 GPa, and K'0nm = 4.5. Calculated elastic constants show softening associated with the loss of magnetization. In addition, we have conducted nuclear resonant inelastic X-ray scattering experiments on 57Fe enriched Fe7C3 at 1 bar and 300 K. On the basis of our nuclear resonant inelastic X-ray scattering spectra we have derived a Debye sound velocity of 3.18 km/s. The experimentally determined value is in good agreement with the computational predictions, based on athermal single elastic constants. The static P wave velocity at inner core pressures agrees well with seismological constraints, whereas the S wave velocity is greater by 30%. On the basis of the density of Fe7C3 at inner core conditions, we predict that the maximum possible carbon content of the inner core is around 1.5 wt %.

Mookherjee, Mainak; Nakajima, Yoichi; Steinle-Neumann, Gerd; Glazyrin, Konstantin; Wu, Xiang; Dubrovinsky, Leonid; McCammon, Catherine; Chumakov, Aleksandr

2011-04-01

154

Windsock memory COnditioned RAM (CO-RAM) pressure effect: Forced reconnection in the Earth's magnetotail  

Science.gov (United States)

Magnetic reconnection (MR) is a key physical concept explaining the addition of magnetic flux to the magnetotail and closed flux lines back-motion to the dayside magnetosphere. This scenario elaborated by Dungey (1963) can explain many aspects of solar wind-magnetosphere interaction processes, including substorms. However, neither the Dungey model nor its numerous modifications were able to explain fully the onset conditions for MR in the tail. In this paper, we introduce new onset conditions for forced MR in the tail. We call our scenario the "windsock memory conditioned ram pressure effect." Our nonflux transfer-associated forcing is introduced by a combination of the large-scale windsock motions exhibiting memory effects and solar wind dynamic pressure actions on the nightside magnetopause during northward oriented interplanetary magnetic field (IMF). Using global MHD Grand Unified Magnetosphere Ionosphere Coupling Simulation version 4 simulation results, upstream data from Wind, magnetosheath data from Cluster 1 and distant tail data from the two-probe Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun mission, we show that the simultaneous occurrence of vertical windsock motions of the magnetotail and enhanced solar wind dynamic pressure introduces strong nightside disturbances, including enhanced electric fields and persistent vertical cross-tail shear flows. These perturbations, associated with a stream interaction region in the solar wind, drive MR in the tail during episodes of northward oriented interplanetary magnetic field (IMF). We detect MR indirectly, observing plasmoids in the tail and ground-based signatures of earthward moving fast flows. We also consider the application to solar system planets and close-in exoplanets, where the proposed scenario can elucidate some new aspects of solar/stellar wind-magnetosphere interactions.

Vörös, Z.; Facskó, G.; Khodachenko, M.; Honkonen, I.; Janhunen, P.; Palmroth, M.

2014-08-01

155

Predicting CO2-water interfacial tension under pressure and temperature conditions of geologic CO2 storage  

Science.gov (United States)

Storage in subsurface geologic formations, principally saline aquifers, is currently under development as a major approach to counter anthropogenic CO2 emissions. To ensure the stability and long-term viability of geologic carbon storage, injected CO2 must be kept in place by an overlying cap rock of very low permeability. Capillary forces in the cap rock act to prevent upward migration and escape of the stored supercritical fluid, with interfacial tension (IFT) between the aqueous brine phase and the CO2 phase being the primary control. However, published experimental CO2-water IFT data vary widely, mainly because of inadequate experimental protocols or inappropriate use of bulk-fluid properties in computing IFT from experimental observations. Only two published data sets were found to meet all criteria of merit for an accurate measurement of IFT over the entire range of pressure (5-45 MPa) and temperature (298-383 K) pertinent to geologic carbon storage. In such circumstances, molecular simulations can enhance the utility of limited data when used to validate assumptions made in their interpretation, resolve discrepancies among data, and fill gaps where data are lacking. Simulations may also be used to provide insight into the relationship between IFT and fundamental properties, such as the strength of the CO2-H2O interaction. Through molecular dynamics simulations, we compared the quality of three CO2 models and two H2O models (SPC/E and TIP4P2005) in predicting IFT under the pressure and temperature conditions relevant to geologic CO2 sequestration. Interfacial tension at fixed temperature simulated via molecular dynamics decreased strongly with increasing pressure below the critical CO2 pressure of 7 MPa, then leveled off, in agreement with experiment, whereas increasing temperature from 300 to 383 K at fixed pressure had little effect on IFT, which is also consistent with experimental data. Our results demonstrated that the strength of the short-range portion of the CO2-H2O interaction exerts a major influence on IFT. The CO2 model that best represented the attractive part of this interaction for randomly-oriented water molecules also best captures the experimental pressure dependence of IFT when combined with either water model. When combined with the SPC/E water model, this CO2 model underestimated IFT by ˜10 mN/m, which approximately equals the amount by which the SPC/E water model underestimates the surface tension of pure water. When combined with the TIP4P2005 water model, this model accurately captured the pressure dependence of the CO2-H2O IFT at 383 K over the entire pressure range examined. These pressure variations will have the dominant effect on IFT—especially at pressures lower than the CO2 critical pressure (˜7 MPa)—and, therefore, on the CO2 storage capacity and sealing integrity of a subsurface reservoir.

Nielsen, Laura C.; Bourg, Ian C.; Sposito, Garrison

2012-03-01

156

The Influence of Collar on Surge Pressure Caused by the Drill String Inertia Force Under Closed Pipe Condition  

Directory of Open Access Journals (Sweden)

Full Text Available The study of surge pressure is of significant importance for the safety of drilling process. However, the existing surge pressure models rarely take the impact of the collar into consideration and thus will inevitably affect the precision of the surge pressure calculation. In this paper, based on closed pipe condition, a steady-state calculation model for surge pressure caused by drill string inertia force is developed considering the presence of collar. In the end a case study is presented to demonstrate the importance of collar during the calculation of surge pressure.

Jun Li

2013-04-01

157

Structural and mechanical properties of dolomite rock under high pressure conditions: A first-principles study  

Energy Technology Data Exchange (ETDEWEB)

The structural behaviour of carbonate minerals under lower mantle pressures, experimentally investigated by means of X-ray diffraction and infrared spectra measurements can be interpreted and difficulties surmounted by first principles quantum mechanical simulations based on density functional theory (DFT). This work is devoted to structural and mechanical properties of CaMg(CO{sub 3}){sub 2}-dolomite mineral. From Birch-Murnaghan equation of state (BM-EoS) applied to the energy-volume data of the dolomite polymorph, we obtain a bulk modulus of 93.7 GPa with a pressure derivative of 4.7, which show suitable agreement with experimental data. Under hydrostatic pressure the mineral system shows an anisotropic compression behaviour and is found to be more compressible in the z direction. The investigation of dolomite mineral structural phase stability under hydrostatic pressure has confirmed previously range-determined but still debated values of structural phase transition. Two phases transitions were encountered when increasing pressure. The first one occurring from dolomite to the orthorhombic calcite-III-like structure was predicted at {proportional_to}34 GPa; and the second one between the calcite III and the aragonite II at {proportional_to}52.5 GPa. This approach overestimates the transition pressure value when confronted to experimental findings. On the other hand the mechanical behaviour of this mineral under ambient and high pressure conditions was studied. To this end we used a stress-strain ab initio based model to calculate the elastic constants of CaMg(CO{sub 3}){sub 2}-dolomite. Based on the trigonal symmetry (space group R3) we found 196.6, 64.4, 54.7, 22.4, 110 and 41.6 GPa for C{sub 11}, C{sub 12}, C{sub 13}, C{sub 14}, C{sub 33} and C{sub 44}, respectively. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Bakri, Z.; Zaoui, A. [Universite Lille Nord de France, LGCgE (EA 4515), Lille 1, Polytech' Lille, Cite Scientifique, Avenue Paul Langevin, 59655 Villeneuve d' Ascq (France)

2011-08-15

158

Using weather data from the internet to study how atmospheric pressure varies with altitude  

Science.gov (United States)

This article presents a simple and motivating activity for schools and colleges that is based on active learning and the use of new technologies to study the variation in atmospheric pressure with height at the lowest altitudes. Students can learn how barometric pressure decreases with height by plotting the atmospheric pressure versus altitude using data obtained from the internet. Using similar methods to those of scientific researchers, the students can learn a practical rule to correct barometric pressure data with altitude, something that is usually expressed at sea level in weather maps.

Moya, A. A.

2014-11-01

159

Mechanical behavior of irradiated fuel-pin cladding evaluated under transient heating and pressure conditions  

International Nuclear Information System (INIS)

Fast breeder fuel-pin cladding has been tested under experimental conditions simulating the temperature and pressure history characteristic of anticipated transient events. Irradiation induces severe reductions in both strength and ductility. Ductility losses are independent of the rate of temperature increase and saturate by a fluence of approx. 2 x 1022 n/cm2 (E > 0.1 MeV). Losses in strength are dependent on the rate of temperature increase but saturate at a fluence of approx.5 x 1022 n/cm2. Evidence is presented to show that fission products are probably responsible for the degradation in mechanical properties

160

Estimation of pressure-, temperature- and frictional heating-related effects on proteins' retention under ultra-high-pressure liquid chromatographic conditions.  

Science.gov (United States)

The goal of this work was to evaluate the changes in retention induced by frictional heating, pressure and temperature under ultra high pressure liquid chromatography (UHPLC) conditions, for four model proteins (i.e. lysozyme, myoglobin, fligrastim and interferon alpha-2A) possessing molecular weights between 14 and 20kDa. First of all, because the decrease of the molar volume upon adsorption onto a hydrophobic surface was more pronounced for large molecules such as proteins, the impact of pressure appears to overcome the frictional heating effects. Nevertheless, we have also demonstrated that the retention decrease due to frictional heating was not negligible with such large biomolecules in the variable inlet pressure mode. Secondly, it is clearly shown that the modification of retention under various pressure and temperature conditions cannot be explained solely by the frictional heating and pressure effects. Indeed, some very uncommon van't Hoff plots (concave plots with a maximum) were recorded for our model/therapeutic proteins. These maximum retention factors values on the van't Hoff plots indicate a probable change of secondary structure/conformation with pressure and temperature. Based on these observations, it seems that the combination of pressure and temperature causes the protein denaturation and this folding-unfolding procedure is clearly protein dependent. PMID:25823888

Fekete, Szabolcs; Guillarme, Davy

2015-05-01

161

Meshfree finite differences for vector Poisson and pressure Poisson equations with electric boundary conditions  

CERN Document Server

We demonstrate how meshfree finite difference methods can be applied to solve vector Poisson problems with electric boundary conditions. In these, the tangential velocity and the incompressibility of the vector field are prescribed at the boundary. Even on irregular domains with only convex corners, canonical nodal-based finite elements may converge to the wrong solution due to a version of the Babuska paradox. In turn, straightforward meshfree finite differences converge to the true solution, and even high-order accuracy can be achieved in a simple fashion. The methodology is then extended to a specific pressure Poisson equation reformulation of the Navier-Stokes equations that possesses the same type of boundary conditions. The resulting numerical approach is second order accurate and allows for a simple switching between an explicit and implicit treatment of the viscosity terms.

Zhou, Dong; Shirokoff, David; Chidyagwai, Prince; Rosales, Rodolfo Ruben

2013-01-01

162

Electrical conductivity measurement of granulite under mid- to lower crustal pressure-temperature conditions  

Science.gov (United States)

We have developed a technique to measure electrical conductivity of crustal rocks with relatively low conductivity and complicated mineral components in order to compare with results given by magneto-telluric (MT) measurements. A granulite from Hidaka metamorphic belt (HMB) in Hokkaido, Japan at high temperature and pressure conditions was obtained. The granulite sample was ground and sintered under the conditions similar to those of mid- to lower crust. We have observed smooth and reversible change of conductivity with temperature up to about 900 K at 1 GPa. The results were consistent with the electrical conductivity structures suggested by the MT data analysis. Considering pore fluid conduction mechanism or the role of accessory minerals in the rock, the mechanisms of electrical conductivity paths in dry or basic rocks should be reconsidered.

Fuji-ta, K.; Katsura, T.; Tainosho, Y.

2004-04-01

163

The osmotic pressure of highly concentrated monoclonal antibody solutions: effect of solution conditions.  

Science.gov (United States)

The behavior of monoclonal antibodies at high concentrations is important in downstream processing, drug formulation, and drug delivery. The objective of this study was to evaluate the osmotic pressure of a highly purified monoclonal antibody at concentrations up to 250 g/L over a range of pH and ionic strength, and in the presence of specific excipients, using membrane osmometry. Independent measurements of the second virial coefficient were obtained using self-interaction chromatography, and the net protein charge was evaluated using electrophoretic light scattering. The osmotic pressure at pH 5 and low ionic strength was >50 kPa for antibody concentrations above 200 g/L. The second virial coefficients determined from the oncotic pressure (after subtracting the Donnan contribution) were in good qualitative agreement with those determined by self-interaction chromatography. The second virial coefficient decreased with increasing ionic strength and increasing pH due to the reduction in intermolecular electrostatic repulsion. The third virial coefficient was negative under all conditions, suggesting that multi-body interactions in this system are attractive. The virial coefficients were essentially unaffected by addition of sucrose or proline. These results have important implications for the analysis of protein-protein interactions in downstream processing at high protein concentrations. PMID:23996891

Binabaji, Elaheh; Rao, Suma; Zydney, Andrew L

2014-03-01

164

Liquid Fuel Emulsion Jet-in-Crossflow Penetration and Dispersion Under High Pressure Conditions  

Science.gov (United States)

The current work focuses on the jet-in-crossflow penetration and dispersion behavior of water-in-oil emulsions in a high pressure environment. Both fuel injection strategies of using a water-in-oil emulsion and a jet-in-crossflow have demonstrated unique benefits in improving gas turbine performance from an emissions and efficiency standpoint. A jet-in-crossflow is very practical for use in gas turbine engines, rocket propulsion, and aircraft engines since it utilizes already available crossflow air to atomize fuel. Injecting water into a combustion chamber in the form of a water-in-oil emulsion allows for pollutant emissions reduction while reducing efficiency loses that may result from using a separate water or steam injection circuit. Dispersion effects on oil droplets are expected, therefore investigating the distribution of both oil and water droplets in the crossflow is an objective in this work. Understanding the synchronization and injection behavior of the two strategies is of key interest due to their combined benefits. A water-to-oil ratio and an ambient pressure parameter are developed for emulsion jet-in-crossflow trajectories. To this end, a total of 24 emulsion jet-in-crossflow tests were performed with varying ambient pressures of 2-8 atm and momentum flux ratios of 50, 85, and 120. Sobel edge filtering was applied to each averaged image obtained from a high speed video of each test case. Averaged and filtered images were used to resolve top and bottom edges of the trajectory in addition to the overall peak intensity up to 40 mm downstream of the injection point. An optimized correlation was established and found to differ from literature based correlations obtained under atmospheric pressure conditions. Overall it was found that additional parameters were not necessary for the top edge and peak intensity correlations, but a need for a unique emulsion bottom edge and width trajectory correlation was recognized. In addition to investigating emulsion jet-in-crossflow trajectory correlations, a unique Dual Planar Laser Induced Fluorescence (Dual-PLIF) method was applied for the first time on emulsions at elevated pressure conditions. From the Dual-PLIF results, qualitative observations provided insight into the unique dispersion of oil and water concentrations within a cross-sectional plane down stream of the jet-in-crossflow injection.

Gomez, Guillermo Andres

165

The relation between intraocular pressure change and plasma natriuretic peptide under simulated hypobaric conditions  

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Full Text Available Purpose: To ascertain whether the changes in intraocular pressure (IOP that occur during hypobaric hypoxic exposure are related to plasma N-terminal pro-brain natriuretic peptide (BNP levels. Materials and Methods: The study group comprised 26 healthy participants (all male, mean age 23.1 years. IOP was measured at local ground level, (792 m above sea level, then while in a chamber providing hypobaric hypoxic conditions (the subjects were exposed to a pressure equivalent to 9144 m for 1-3 min, and again after exit from the chamber. In each condition, the mean of three consecutive measurements of IOP was calculated for each eye. For BNP measurements, blood samples were drawn before the participants entered the chamber and just after they left the chamber. Results: IOP during hypobaric hypoxic exposure (18.00 ± 3.70 mmHg was significantly greater than that before (15.66 ± 2.10 mmHg, P < 0.001 or after (16.10 ± 2.63 mmHg, P = 0.001 the exposure. IOP levels before and after the exposure were not significantly different (P = 0.136. Plasma BNP levels measured before and after exposure to hypobaric hypoxic conditions were not significantly different (P = 0.462. Conclusion: Plasma BNP levels did not change after short-term hypobaric hypoxic exposure, while the IOP increased. This increase may have been caused by some other systemic factors. As the hypobaric hypoxic conditions were reversed, IOP decreased to normal levels.

Karadag Remzi

2010-01-01

166

Surveillance of prestressed concrete pressure vessels under commissioning and operational conditions at Hunterston 'B' Power Station  

International Nuclear Information System (INIS)

Monitoring procedures were established to satisfy the Statutory requirements set by the Licensing Authority (The Nuclear Installations Inspectorate), and to demonstrate the continuing safety of the Prestressed Concrete Pressure Vessels (P.C.P.V.) under operational conditions to the Purchaser and Operator (South of Scotland Electricity Board), and the N.I.I. For the long term, 80 vibrating wire strain gauges have been selected as indicating the general behaviour of each vessel under commissioning and operational conditions. A programme of tendon check loading has been set up, allowing an estimate of the prestress obtaining in the vessel to be made. Also, strands are withdrawn for visual and metallurgical examination. Regular temperature scans are carried out using the thermocouples installed in the vessel concrete and on the liner and penetrations. The results of these and other monitoring procedures are discussed. It is concluded that the Prestressed Concrete Pressure Vessels at Hunterston 'B' Power Station are performing in a predictable and satisfactory manner. (orig.)

167

CFD simulation of pressure and discharge surge in Francis turbine at off-design conditions  

International Nuclear Information System (INIS)

A hybrid 1D-3D CFD model is developed for the numerical simulation of pressure and discharge surge in hydraulic power plants. The most essential part – the turbine itself – is simulated directly using 3D unsteady equations of turbulent motion of fluid-vapor mixture, while the rest of the hydraulic system is simulated in frames of 1D hydro-acoustic model. Thus the model accounts for the main factors responsible for excitation and propagation of pressure and discharge waves in hydraulic power plant. Boundary conditions at penstock inlet and draft tube outlet are discussed in detail. Then simulations of dynamic behavior at part load and full load operating points are performed. It is shown that the numerical model is able to capture self-excited oscillations in full load conditions. The influence of penstock length and flow structure behind the runner are investigated. The presented approach seems to be a promising tool for prediction and investigation the dynamic behavior in hydraulic power plants.

168

Polymerization Experiment Of Amino Acids Under High Pressure And Temperature Conditions Simulating The Deep Lithosphere  

Science.gov (United States)

Chemical evolution in deep sea or deep lithosphere is one of the popular hypotheses for the origin of life on the early Earth. In such hypothesis, effects of pressure and temperature on polymerization (and/or stability) of amino acids needed to be evaluated. In this study, high temperature and pressure experiments were performed using of a test-tube-type autoclave for polymerization of amino acids. Approximately 100 mg of Glycine powder were placed into sterilized gold capsule. Multiple experiments were done at 150 degrees for 1 to 8 days at variable pressures (25MPa, 50MPa, 75MPa and 100MPa). Glycine peptides were identified and quantified by high performance liquid chromatography (HPLC). Each capsule was opened carefully and 1 ml of mobile phase was added to release the amino acids and oligopeptide from the solid phase. Liquid phases were separated by the cetrifugal method. Peptides were identified by retention times of authentic reference substances. The reaction yields were determined as percentage of the reactant converted to the reaction product. Pligopeptides more than hexamer were additionally identified by the detection of the molecular ion by liquid chromatography mass spectrometry (LC / MS). A HPLC chromatogram of the products indicated at least seven oligomers: diketopiperazine (cyc(Gly)2), di-glycine (Gly2), tri-glycine (Gly3), tetra-glycine (Gly4), penta-glycine (Gly5) and hexa-glycine (Gly6). We also identified hepta-glycine (Gly7), octa-glycine (Gly8) and nona-glycine (Gly9) with LC/MS. This is the first report that up to nona-glycine was synthesized under high temperature and pressure conditions. In addition, our experiments indicate that polymerization occurs wide range of pressure from 25 to 100 MPa. On the other hand, yields of total amounts of peptide did not change with pressure, suggesting that an unknown process in the autoclave is limiting the yield. We speculate the activity of water vapor, generated by peptide formation reaction, controlled the yield in the autoclave. The results from this study support the theory that chemical evolution could happen in deep Earth environments, such as inside of lithosphere.

Ohara, S.; Kakegawa, T.; Nakazawa, H.

2005-12-01

169

Freezing and Melting of 3D Complex Plasma Structures under Microgravity Conditions Driven by Neutral Gas Pressure Manipulation  

International Nuclear Information System (INIS)

Freezing and melting of large three-dimensional complex plasmas under microgravity conditions is investigated. The neutral gas pressure is used as a control parameter to trigger the phase changes: Complex plasma freezes (melts) by decreasing (increasing) the pressure. The evolution of complex plasma structural properties upon pressure variation is studied. Theoretical estimates allow us to identify the main factors responsible for the observed behavior.

170

The Influence of Collar on Surge Pressure Caused by the Drilling Fluid Viscous Force under Pumping Condition  

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Full Text Available The study of surge pressure is of significant importance for the safety of drilling process because field practice shows that the surge pressure caused by fluid viscous force can cause a great damage to the drilling operation. The accurate calculation of surge pressure is directly related to the safety of the drilling process. However, the existing surge pressure models rarely take the impact of the collar into consideration and thus will inevitably affect the precision of the surge pressure calculation. In this study, based on the pumping condition, a steady-state calculation model for surge pressure caused by drilling fluid viscous force is developed considering the presence of collar. In the end a case study is presented to demonstrate the importance of collar during the calculation of surge pressure.

Jun Li

2013-02-01

171

The investigation of argon diffusion in phlogopite under high pressure conditions  

Science.gov (United States)

The present study deals with assessment of pressure effect on the mechanism of bleeding an argon from mica at high temperatures and pressures. The influence of pressure on the diffusion of argon in crustal conditions is not significant (Harrison et al., 2009), while in the mantle conditions, should be significant. The authors suggest that the findings will help to better understand the behavior of K/Ar isotopic system in mica under the lower crust and mantle, including xenoliths transport by kimberlite melt. The experiment was made by using high-pressure spacer "split-sphere" (BARS - 300). Phlogopite from veins cutting metamorphic rocks from the Sludyanka number 2 quarry was used as a testing material. Inclusions of other minerals were not found in the original phlogopite crystal. Chemical composition of phlogopite is homogeneous. 8 experiments was made at a constant pressure of 30 kbar and different temperature and duration: 20 degrees Celsius, 20 minutes; 700 degrees Celsius, 20 minutes; 800 degrees Celsius, 10 minutes; 800 degrees Celsius, 20 minutes; 800 degrees Celsius, 30 minutes; 900 degrees Celsius, 20 minutes; 1000 degrees Celsius, 20 minutes; 1100 degrees Celsius, 20 minutes. According the results of SEM-observation, there is no signs of recrystallization and solid state transformations and melting of phlogopite. It's chemical composition is identical to that of the original phlogopite. Diffractograms of phlogopites after the experiments are similar to the diffractograms of the original phlogopites. Research results of IR spectroscopy, together with the results of SEM and microprobe analysis suggest that phlogopite dehydroxylation in the temperature range T = 700-900 degrees Celsius was negligible. Numerical simulation of the behavior of radiogenic argon in phlogopite at high temperatures and pressure was performed using «Diffarg» software finite differences algorithm, based on the mechanism of bulk thermally activated diffusion (Wheeler, 1996). The size of the effective diffusion domain of mica was considered to be 100-150 microns, when modeling (Baxter, 2010). Comparison of results of simulations and experiments suggests that the mobility of argon isotopes in phlogopite at high temperatures and pressure is well described by the mechanism of thermally activated volume diffusion. Stepwise release of argon in a vacuum experiment was also conducted. The activation energy of 207,714 J/mol was calculated from the slope of the line on the Arrhenius chart. This value is consistent with data obtained by other authors in hydrothermal experiments (Baxter, 2010). The work was supported by the grant of the President of Russia MK-3240.2014.5. Baxter E.F. Diffusion of Noble Gases in Minerals // Reviews in Mineralogy & Geochemistry. 2010. V.72. P.509-557. Harrison T.M., Celerier J., Aikman A.B., Hermann J., Heizler M.T. Diffusion of 40Ar in muscovite // Geochim Cosmochim Acta. 2009. V.73. P.1039-1051. Wheeler J. Diffarg: A program for simulating argon diffusion profiles in minerals // Computers & Geosciences. 1996. V. 22(8). P. 919-929.

Yudin, Denis; Korzhova, Sophia; Travin, Alexey; Zhimulev, Egor; Murzintsev, Nikolay; Moroz, Tatiana

2014-05-01

172

Heat transfer on natural convection from a horizontal cylinder to CO2 under supercritical pressure in conditions of cooling  

International Nuclear Information System (INIS)

Heat transfer is studied on natural convection from a horizontal cylinder to a desiccated condensate of CO2 of supercritical pressure under cooling conditions. The experiments are conducted at pressures of 70, 80, 90, and 100 kgf/cm2 and at CO2 temperatures of 40-80 deg C. The treatment of the experimental data in the criterial form shows a considerable deviation from the available calculation recommendations obtained under heating conditions

173

Analysis of pressure locking and thermal binding conditions on shutdown cooling system suction isolation valves  

International Nuclear Information System (INIS)

Shutdown Cooling System (SCS) suction isolation valves for Yonggwang Nuclear Units 5 and 6 (YGN 5 and 6) had been selected as the valves susceptible to pressure locking and thermal binding (PLTB) phenomena considering valves' allowable internal leakage and various operating conditions. To prevent the anticipated PLTB phenomena, the isolation valve type was changed from the flexible-wedge gate valve to the double-disk gate valve with the drilled hole on the upstream disk. During plant pre-operational hydrostatic tests, however, the technical issue regarding the valve type change was raised due to the inherent difficulty in pressurizing the valve downstream piping, which was caused by the drilled hole. In order to resolve this technical issue, the technical adequacy of the valve type change was justified through the identification of the PLTB conditions on the SCS isolation valves using brief hand calculations and FLUENT code simulations. From these calculations and simulations, it was found that the upstream fluid temperatures of the second and third valves were almost the same as the ambient temperature for the case of no leakage in the isolation valves. However, if there were leakage through each isolation valve up to the maximum allowable leakage in the plant Technical Specification, the upstream fluid temperature of the farthest third isolation valve even increased enough to cause the PLTB phenomena. In these analyses, the valve leakage and turbulent penetration duvalve leakage and turbulent penetration due to high-velocity flow in the RCS hot leg were identified as dominant factors which cause the PLTB conditions such as a valve bonnet overpressurization and a thermal difference between both ends of the valve disk. (author)

174

Direct ion flux measurements at high-pressure-depletion conditions for microcrystalline silicon deposition  

International Nuclear Information System (INIS)

The contribution of ions to the growth of microcrystalline silicon thin films has been investigated in the well-known high-pressure-depletion (HPD) regime by coupling thin-film analysis with plasma studies. The ion flux, measured by means of a capacitive probe, has been studied in two regimes, i.e., the amorphous-to-microcrystalline transition regime and a low-to-high power regime; the latter regime had been investigated to evaluate the impact of the plasma power on the ion flux in collisional plasmas. The ion flux was found not to change considerably under the conditions where the deposited material undergoes a transition from the amorphous to the microcrystalline silicon phase; for solar-grade material, an ion-to-Si deposition flux of ?0.30 has been determined. As an upper-estimation of the ion energy, a mean ion energy of ?19 eV has been measured under low-pressure conditions (4 to an H2 plasma resulted in an increase of the ion flux by about 30% for higher power values, whereas the electron density, deduced from optical emission spectroscopy analysis, decreased. The electron temperature, also deduced from optical emission spectroscopy analysis, reveals a slight decrease with power. Although the dominant ion in the HPD regime is SiH3+, i.e., a change from H3+ in pure hydrogen HPD conditions, the measured larger ion loss can be explained by assuming steeper electron density profiles. These results, therefore, confirm the results reported so far: the ion-to-Si deposition flux is relatively large but has neither influence on the microcrystalline silicon film properties nor on the phase transition. Possible explanations are the reported high atomic hydrogen to deposition flux ratio, mitigating the detrimental effects of an excessive ion flux

175

The development of an auto-sealing system using an electrically shrinkable tube under a low-pressure condition  

Energy Technology Data Exchange (ETDEWEB)

This article describes the development of a system to create high quality, automatic sealing of field joints of polyethylene coated pipelines. The system uses a combination of an electrically heated shrinkable tube and a low-pressure chamber. The self-heating shrinkable tube includes electric heater wires that heat when connected to electricity. A method was developed to eliminate air trapped between the tube and the steel pipe by shrinking the tube under a low-pressure condition. The low-pressure condition was automatic and easily attained by using a vacuum chamber. It was verified that the system produced high quality sealing of the field joints.

Okano, Yoshihiro; Kitagawa, Takao [NKK Corp, Tsu, Mie (Japan); Shoji, Norio [NKK Corp., Yokohama (Japan); Namioka, Toshiyuki [Nippon Kokan Koji Corp., Yokohama (Japan). Research and Development Dept.; Komura, Minoru [Nitto Denko Corp., Fukaya, Saitama (Japan)

1997-04-01

176

QUAVER - A programme to evaluate monopole and dipole boundary conditions in pressure tube reactor lattices  

International Nuclear Information System (INIS)

In order to apply source-sink theory to pressure tube reactor lattices it is necessary to calculate boundary conditions at the fuel channel/moderator interfaces to be satisfied by the neutron flux. A method is described for evaluating the necessary coefficients using multi-group diffusion theory in a cylindricalised lattice cell for both monopole and dipole components of flux. Provision is made for in or out leakage of neutrons in each group at the cell boundary so that allowance can be made for effects of cell environment on the channel boundary conditions. The programme QUAVER (written in EGTRAN) is described for use on the English Electric KDF9 Computer. QUAVER outputs the boundary condition matrices on cards for use in source-sink core calculations, and includes a facility for the condensation of the primary group output to a secondary group structure. The numerical method and the data input specification are described together with full details of a sample calculation. (author)

177

Bench-Scale Trace Contaminant Testing of SA9T at Ambient and Reduced Pressure Conditions  

Science.gov (United States)

A principal concern for air revitalization technology in a closed loop system is the capability to control carbon dioxide (CO2) and humidity (H2O). An amine based sorbent technology, SA9T, has been evaluated for use in this application and several programs are evaluating it for use in both cabin and space suit applications. While the CO2 and H2O performance of the sorbent has been tested extensively, the question of how trace contaminants impact performance requires further evaluation. This paper presents experimental results of bench-scale SA9T testing that was performed under a variety of test conditions and with several different trace contaminants. Tests were conducted to determine if the capacity of the SA9T media to sufficiently remove CO2 and H2O is compromised after exposure to a fully saturated trace contaminant at ambient conditions. Tests also were conducted to evaluate the performance of SA9T at ambient conditions in a continuous 30-day test with a mixed trace contaminant stream. In addition, testing also evaluated the impact of CO2 and H2O removal performance at suit loop pressures (29.6 KPa/4.3 psia) during cyclic operation with a constant inlet contaminant load.

Broerman, Craig; Sweterlitsch, Jeff

2011-01-01

178

Small Scale Trace Contaminant Testing of SA9T at Ambient and Reduced Pressure Conditions  

Science.gov (United States)

A principle concern for air revitalization technology in a closed loop system is the capability to control carbon dioxide (CO2) and humidity (H2O). An amine based sorbent technology, SA9T, has long been evaluated for use in this application and several programs are evaluating it for use in both a cabin as well as space suit applications. While the CO2 and H2O performance of the sorbent has been tested extensively, the question of how trace contaminants impact performance requires further evaluation. This paper presents experimental results of small scale SA9T testing that was performed over a variety of test conditions and with a variety of trace contaminants. Testing evaluated the ability of SA9T media to sufficiently remove CO2 and H2O after exposure to a fully saturated trace contaminant at ambient conditions. Testing also evaluated the impact of CO2 and H2O removal performance at suit loop pressures during cyclic operation with a constant inlet contaminant load. In addition, testing evaluated the performance of SA9T at ambient conditions in a continuous 30-day test with a mixed trace contaminant stream.

Broerman, Craig; Sweterlitsch, Jeffrey

2011-01-01

179

Micromechanical Cohesion Force between Gas Hydrate Particles Measured under High Pressure and Low Temperature Conditions.  

Science.gov (United States)

To prevent hydrate plugging conditions in the transportation of oil/gas in multiphase flowlines, one of the key processes to control is the agglomeration/deposition of hydrate particles, which are determined by the cohesive/adhesive forces. Previous studies reporting measurements of the cohesive/adhesive force between hydrate particles used cyclopentane hydrate particles in a low-pressure micromechanical force apparatus. In this study, we report the cohesive forces of particles measured in a new high-pressure micromechanical force (MMF) apparatus for ice particles, mixed (methane/ethane, 74.7:25.3) hydrate particles (Structure II), and carbon dioxide hydrate particles (Structure I). The cohesive forces are measured as a function of the contact time, contact force, temperature, and pressure, and determined from pull-off measurements. For the measurements performed of the gas hydrate particles in the gas phase, the determined cohesive force is about 30-35 mN/m, about 8 times higher than the cohesive force of CyC5 hydrates in the liquid CyC5, which is about 4.3 mN/m. We show from our results that the hydrate structure (sI with CO2 hydrates and sII with CH4/C2H6 hydrates) has no influence on the cohesive force. These results are important in the deposition of a gas-dominated system, where the hydrate particles formed in the liquid phase can then stick to the hydrate deposited in the wall exposed to the gas phase. PMID:25785915

Lee, Bo Ram; Sum, Amadeu K

2015-04-01

180

Shock-induced incongruent crystallization from forsterite melt at extreme pressure and temperature conditions  

Science.gov (United States)

We have measured the Hugoniot of forsterite melt under laser-driven shock compression at pressures of 300-1000 GPa and sample temperatures of 6000-9000 K under shock at 300-400 GPa. We employed VISAR and SOP methods that become poluar in the laser-shock community recently, to monitor velocity and temperature simultaneously. The shock velocity-particle velocity relation displays a kink around 350-400 GPa. The slope increase beyond the kink is associated with heating and volume expansion. This has been discussed in the Huginot of antigorite which also displays a similar change. This can be explained as an exothermic reaction by incongruent crystallization of MgO and the residual melt composition becomes MgSiO3. The MgO will be a B2 structure based on the current proposed phase diagram of MgO. Further increasing of shock pressure follows complete melting above ~400 GPa. Laser-driven shock continues to decay with time but the measured temperature profile has indicated an abrupt increase around 250 GPa with decaying pressure. This state is on a linear extension of the phase transition of liquid-liquid on MgSiO3 that was reported recently. Shock-induced incongruent crystallization at extreme conditions has been recognized for the first time in this study, and it plays an important role in the process of planetary formation and giant impacts to change the melt composition abruptly. This research was performed at ILE as collaboration work.

Sekine, T.; Ozaki, N.; Asami, Y.; Miyanishi, K.; Uranishi, H.; Kodama, R.; Sano, T.; Sawaka, Y.

2012-12-01

181

Nonlinear Analysis of Onset of Nucleate Boiling in Natural Circulation under Different Pressure Conditions  

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Full Text Available In this study, we obtain the flow signals before and after the ONB through natural circulation experiments under pressure conditions of 0.15MPa and 0.3MPa. Researches were conducted by applying nonlinear analysis techniques. Results revealed that the power spectrum of volume flow data declined exponentially over time in semi logarithmic coordinates, the autocorrelation coefficient declined gradually and the phase diagram exerted the subtle structures of chaotic movement, which might prove the existence of chaos in natural circulation system. The natural convection of single phase appeared before the occurrence of ONB belonged to a non equilibrium process which showed remarkable random features. The occurrence of ONB was a process containing the beginning of chaotic motion and the continuing occurrence of bubbles at ONB and the tendency of phase change to become nucleation boiling would achieve certain states, which embodied the characteristics of chaos. In addition, the intense density difference environment of natural circulation could accelerate the occurrences of both chaotic motion and ONB. While the density difference of heated liquid decreased with the increase of pressure, which could delay the occurrence of ONB.

Cheng Sheng

2013-04-01

182

Advanced development and operating experience with a canned motor pump under pressurized water reactor conditions  

International Nuclear Information System (INIS)

At the research reactor FRG-2, Geesthacht, an irradiation device is in operation for testing defective light-water-reactor (LWR) test fuel rods under pressurized water reactor conditions (3200C, 160 bar). The requirements to the canned motor pump for cooling water circulation: medium: Demineralized water, operating temperature 3200C, operating pressure 155 bar, radiation field of the reactor, integration in the irradiation capsule, helium leak rate -6mbar.dm3.s-1, minimum working life 3000 hours, were high and caused difficulties in the acquisition of this component. First test runs with supplied pumps showed that the desired working life could not be achieved. The results of the development steps, the test runs, and the performance in service show that for our range of applications, the best combination of materials for the radial bearings is silicon-infiltrated SiC (8% free Si) against the same material. These bearings allowed a good working life for the pump to be achieved. (orig./GL)

183

Irradiation of collectrons under the physical conditions of a pressurized-water reactor core  

International Nuclear Information System (INIS)

Collectrons are radiation detectors that work without external polarization. They are used to measure neutron flux in reactors. To test their reliability, two devices each containing about 20 collectrons were irradiated in the core of Osiris, where the physical conditions (medium, temperature, pressure) of a pressurized-water reactor core were reproduced. The sensitive parts were made of cobalt and platinum for the fast-response collectrons and of rhodium, silver and vanadium for the delayed-response collectrons. One of the devices was a loop in which light water circulated. This experiment was stopped in June 1977, after 8.8x1021ncm-2 had been integrated. Out of 21 samples two were taken out of use during the experiment. The other device was a capsule containing a non-circulating neutral gas. After the integration of over 5x1021ncm-2 the loss rate was about 50%. Post-irradiation tests are being conducted at Saclay. Various parameters have been studied: nature of cladding and insulation, contribution of cables to signal, and sensitivity of platinum. (author)

184

Molecular dynamics study of the dielectric constant of water under high pressure and temperature conditions  

International Nuclear Information System (INIS)

The static dielectric constant of a water model (extended simple point charges, SPC/E) was evaluated by molecular dynamics simulations in the (N, V, E) ensemble for temperatures ranging from T=324 K to 1278 K and densities from 0.257 g/cm3 to 1.1108 g/cm3. The dielectric constants calculated from fluctuations of the total dipole moment of the simulation box in the absence of an external field, and those obtained from the polarization response to an applied field were demonstrated to be consistent. Simulations within the pressure-temperature range (up to 500 MPa and 823 K) of available experimental data yield dielectric constant in very good agreement with experiment. It appears therefore that the SPC/E potential model can be used for the simulation of the dielectric properties of supercritical water and of aqueous solutions under supercritical conditions. (orig.)

185

Natural Circulation Characteristics at Low-Pressure Conditions through PANDA Experiments and ATHLET Simulations  

Directory of Open Access Journals (Sweden)

Full Text Available Natural circulation characteristics at low pressure/low power have been studied by performing experimental investigations and numerical simulations. The PANDA large-scale facility was used to provide valuable, high quality data on natural circulation characteristics as a function of several parameters and for a wide range of operating conditions. The new experimental data allow for testing and improving the capabilities of the thermal-hydraulic computer codes to be used for treating natural circulation loops in a range with increased attention. This paper presents a synthesis of a part of the results obtained within the EU-Project NACUSP “natural circulation and stability performance of boiling water reactors.” It does so by using the experimental results produced in PANDA and by showing some examples of numerical simulations performed with the thermal-hydraulic code ATHLET.

Frank Schäfer

2008-04-01

186

High Pressure Compression-Molding of ?-Cellulose and Effects of Operating Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available Commercial ?-cellulose was compression-molded to produce 1A dog-bone specimens under various operating conditions without any additive. The resulting agromaterials exhibited a smooth, plastic-like surface, and constituted a suitable target as replacement for plastic materials. Tensile and three-points bending tests were conducted according to ISO standards related to the evaluation of plastic materials. The specimens had strengths comparable to classical petroleum-based thermoplastics. They also exhibited high moduli, which is characteristic of brittle materials. A higher temperature and higher pressure rate produced specimens with higher mechanical properties while low moisture content produced weaker specimens. Generally, the strong specimen had higher specific gravity and lower moisture content. However, some parameters did not follow the general trend e.g., thinner specimen showed much higher Young’s Modulus, although their specific gravity and moisture content remained similar to control, revealing a marked skin-effect which was confirmed by SEM observations.

Antoine Rouilly

2013-05-01

187

Characterization of transient discharges under atmospheric pressure conditions applying nitrogen photoemission and current measurements  

CERN Document Server

Plasma parameters of three transient discharges (filamentary and homogeneous dielectric barrier discharges in air, and the spark discharge of an argon plasma coagulator) operated at atmospheric pressure conditions are determined applying a combination of diagnostics methods, namely numerical simulation, current measurement, and optical emission spectroscopy. These diagnostic methods supplement each other and resolve problems, which arise when these methods are used separately. Nitrogen is used as sensor gas and is admixed to argon for studying the argon plasma coagulator. The Boltzmann equation is solved in 'local' approximation to determine electron velocity distribution function. Drift velocity, electron-impact excitation rate constants for nitrogen molecular emission, electric current density, and emission spectrum of nitrogen molecule are calculated. Plasma parameters (electron velocity distribution function and electron density) are determined applying calculated as far as measured electric current, and ...

Keller, Sandra; Bibinov, Nikita; Awakowicz, Peter

2011-01-01

188

Investigation of LPP combustors under elevated pressure conditions; Untersuchungen zu LPP-Flugtriebwerksbrennkammern unter erhoehtem Druck  

Energy Technology Data Exchange (ETDEWEB)

The development of new combustor concepts for aero engines to meet future emissions regulations in based on a detailed knowledge of the combustion process and the velocity field. In the presented thesis, non intrusive measurements were performed in a model combustion chamber under almost realistic pressure and temperature conditions. The species OH, NO, unburned hydrocarbons and fuel droplets were detected in 2 dimensions with the Laser Induced Fluorescence (LIF). The velocity field was measured with the Particle Image Velocimetry technique (PIV). [German] Die Weiterentwicklung neuer Brennkammerkonzepte zur Erfuellung zukuenftiger Schadstoffemissionsrichtlinien erfordert genaue Kenntnisse der ablaufenden Verbrennungs- und Stroemungsvorgaenge in der Brennkammer. Bei den in der Arbeit vorgestellten Untersuchungen wurden in einer LPP-Modellbrennkammer unter annaehernd realistischen Eintrittsbedingungen die Spezies OH, NO, unverbrannte Kohlenwasserstoffe sowie noch fluessiger Brennstoff zweidimensional anhand der Laserinduzierten Fluoreszenz (LIF) nachgewiesen. Das Stroemungsfeld wurde mit Hilfe der Particle Image Velocimetry (PIV) gemessen.

Fink, R.

2001-05-01

189

Effect of Nb additions on the microstructure, thermal stability and mechanical behavior of high pressure Zr phases under ambient conditions  

Energy Technology Data Exchange (ETDEWEB)

Research highlights: {yields} We analyze the influence of Nb additions on the shear-induced {alpha} {yields} {omega} {yields} {beta} phase transformations in pure Zr by high pressure torsion (HPT). {yields} Nb reduces the transition pressures and increases the transformation kinetics. {yields} High pressure phases are retained under ambient conditions due to the presence of an internal stress. {yields} Post-HPT annealing allows to fabricate bimodal/biphase nanostructures with enhanced mechanical behavior. - Abstract: This paper analyzes the influence of Nb on the shear-induced {alpha} {yields} {omega} {yields} {beta} transformation taking place when processing Zr by high pressure torsion (HPT) under suitable conditions of pressure and shear. With that purpose, pure Zr and Zr-2.5%Nb were processed by HPT at room temperature and at pressures ranging from 0.25 to 6 GPa using 5 anvil turns. Nb causes a further reduction of the transition pressures, which are already lower when applying shear besides pressure. Thus, the transition pressure to the {beta} phase is reduced at least 100 times in the Zr-Nb alloy. Alloying with Nb decreases the grain size of the transformed phases, significantly enhances their thermal stability and increases their UTS and elongation to failure. Selected post-HPT annealing treatments lead to the development of very tough, multiphase Zr and Zr-Nb with bimodal grain size distributions. The retention of the high pressure phases under ambient conditions is explained by the development of a high internal stress during processing. This stress is measured by synchrotron radiation diffraction at HZB-BESSY II. It is proposed that the presence of Nb reduces the internal stress level required for the retention of the high pressure phases.

Zhilyaev, A.P. [Centro Nacional de Investigaciones Metalurgicas (CENIM), CSIC, 28040 Madrid (Spain); Institute for Metals Superplasticity Problems, RAS, 450001 Ufa (Russian Federation); Sabirov, I. [Madrid Institute for Advanced Studies of Materials (IMDEA-Materials Institute) C/Profesor Aranguren s/n, 28040 Madrid (Spain); Gonzalez-Doncel, G. [Centro Nacional de Investigaciones Metalurgicas (CENIM), CSIC, 28040 Madrid (Spain); Molina-Aldareguia, J.; Srinivasarao, B. [Madrid Institute for Advanced Studies of Materials (IMDEA-Materials Institute) C/Profesor Aranguren s/n, 28040 Madrid (Spain); Perez-Prado, M.T., E-mail: teresa.perez.prado@imdea.org [Madrid Institute for Advanced Studies of Materials (IMDEA-Materials Institute) C/Profesor Aranguren s/n, 28040 Madrid (Spain)

2011-04-15

190

Research on dynamic behaviors in remote pressure-regulating pipeline under the condition of controllable maximum stiffness coefficient  

International Nuclear Information System (INIS)

Aiming at remote pressure-regulating system controlled by pilot overflow valve and based on dynamic-characteristics fundamental equation of distributed-parameter model in hydraulic pipelines, the mathematical model of remote-pressure-regulating hydraulic pipelines is deduced. Discussing the controllability of the remote pressure-regulating system shows that the controllability depends on the controllable maximum stiffness coefficient, which mainly includes the length and the inner radius of remote pressure-regulating pipeline, the spring stiffness coefficient of overflow valve, and the properties of hydraulic oil. And if a remote pressure-regulating system wants to work normally and avoid resonance, the conditions of controllable maximum stiffness coefficient must be derived. The concept, controllable maximum stiffness coefficient, and the mathematical models provide theoretical and practical instruction in study of hydraulic remote pressure-regulating system.

191

An experimental study on sub-cooled flow boiling CHF of R134a at low pressure condition with Atmospheric Pressure (AP) Plasma assisted surface modification  

Energy Technology Data Exchange (ETDEWEB)

In this study, sub-cooled flow boiling critical heat flux tests at low pressure were conducted in a rectangular flow channel with one uniformly heated surface, using simulant fluid R-134a as coolant. The experiments were conducted under the following conditions: (1) inlet pressure (P) of 400 ~ 800 kPa, (2) mass flux (G) of 124 ~ 248 kg/m2·s, (3) inlet sub-cooling enthalpy (??!) of 12~ 26 kJ/kg. Parametric trends of macroscopic system parameters (G, P, ??!) were examined by changing inlet conditions. Those trends were found to be generally consistent with previous understandings of CHF behavior at low pressure condition (i.e. reduced pressure less than 0.2). A fluid-to-fluid scaling model was utilized to convert the test data obtained with the simulant fluid (R-134a) into the prototypical fluid (water). The comparison between the converted CHF of equivalent water and CHF look-up table with same operation conditions were conducted, which showed good agreement. Furthermore, the effect of surface wettability on CHF was also investigated by applying atmospheric pressure plasma (AP-Plasma) treatment to modify the surface characteristic. With AP-Plasma treatment, the change of microscopic surface characteristic was measured in terms of static contact angle. The static contact angle was reduced from 80° on original non-treated surface to 15° on treated surface. An enhancement of 18% on CHF values under flow boiling conditions were observed on AP-Plasma treated surfaces compared to those on non-treated heating surfaces.

Seung-Jun Kim; Ling Zou; Barclay G. Jones

2015-02-01

192

Sufficient conditions for globally asymptotic self-stability of pressurized water reactors  

International Nuclear Information System (INIS)

Highlights: • Self-stability analysis of the PWR is presented through the shifted-ectropy based approach. • Sufficient conditions for the globally asymptotic self-stability are established. • The correctness of the theoretic results are finally verified through numerical simulation. - Abstract: After the Fukushima accident, safe, stable and efficient operation of reactors is very necessary for the development of nuclear power industry. Since pressurized water reactor (PWR) is the mostly widely used fission reactor, the improvement of its operation performance is quite meaningful. Self-stability is the most important dynamic feature of any reactors, and analyzing the self-stability can give the approach of improving the operation performance. With this in mind, the self-stability analysis of the PWR is presented through the shifted-ectropy based approach, and sufficient conditions for the globally asymptotic self-stability in cases of negative, zero and positive coolant temperature feedback coefficient are all established. The correctness of the theoretical results are finally verified through numerical simulation. The results of this paper give the way to not only guaranteeing self-stability through physical and thermal-hydraulic reactor design but also strengthening closed-loop stability and robustness by the means of feedback control

193

Theoretical and numerical investigations of TAP experiments: new approaches for variable pressure conditions  

Science.gov (United States)

Temporal analysis of products ("TAP", see Gleaves et al. in Catal Rev Sci Eng 30:49, 1988) is a valuable tool for characterisation of porous catalytic structures. Established TAP-modelling requires a spatially constant diffusion coefficient and neglect convective flows, which is only valid in Knudsen diffusion regime. A new theoretical model is developed for estimating the number of molecules per pulse to stay in Knudsen diffusion regime under any conditions and at any time. Moreover a new methodology for generating a full three-dimensional geometrical representation of beds is presented and used for numerical simulations. In computational fluid dynamics software (ANSYS CFX® version 14) a transient diffusive transport equation with time-dependent inlet boundary conditions is solved. Three different pellet diameters were investigated with 1E+18 molecules per pulse, which is higher than the limit from the theoretical calculation (about 1E+15). From this results, the distance from inlet can be calculated where the theoretical pressure limit ( Kn = 2) is obtained, i.e., from this point to the end of reactor, Knudsen regime can be assumed.

Breitkopf, Cornelia; Sénéchal, Ulf

2014-03-01

194

Appropriate welding conditions of temper bead weld repair for SQV2A pressure vessel steel  

International Nuclear Information System (INIS)

Temper bead welding technique is one of the most important repair welding methods for large structures for which it is difficult to perform the specified post weld heat treatment. In this study, appropriate temper bead welding conditions to improve the characteristics of heat affected zone (HAZ) are studied using pressure vessel steel SQV2A corresponding to ASTM A533 Type B Class 1. Thermal/mechanical simulator is employed to give specimens welding thermal cycles from single to quadruple cycle. Charpy absorbed energy and hardness of simulated CGHAZ by first cycle were degraded as compared with base metal. Improvability of these degradations by subsequent cycles is discussed and appropriate temper bead thermal cycles are clarified. When the peak temperature lower than Ac1 and near Ac1 in the second thermal cycle is applied to CGAHZ by first thermal cycle, the characteristics of CGHAZ improve enough. When the other peak temperatures (that is, higher than Ac1) in the second thermal cycle are applied to the CGHAZ, third or more thermal cycle temper bead process should be applied to improve the properties. Appropriate weld condition ranges are selected based on the above results. The validity of the selected ranges is verified by the temper bead welding test. (orig.)

195

Appropriate welding conditions of temper bead weld repair for SQV2A pressure vessel steel  

Energy Technology Data Exchange (ETDEWEB)

Temper bead welding technique is one of the most important repair welding methods for large structures for which it is difficult to perform the specified post weld heat treatment. In this study, appropriate temper bead welding conditions to improve the characteristics of heat affected zone (HAZ) are studied using pressure vessel steel SQV2A corresponding to ASTM A533 Type B Class 1. Thermal/mechanical simulator is employed to give specimens welding thermal cycles from single to quadruple cycle. Charpy absorbed energy and hardness of simulated CGHAZ by first cycle were degraded as compared with base metal. Improvability of these degradations by subsequent cycles is discussed and appropriate temper bead thermal cycles are clarified. When the peak temperature lower than Ac1 and near Ac1 in the second thermal cycle is applied to CGAHZ by first thermal cycle, the characteristics of CGHAZ improve enough. When the other peak temperatures (that is, higher than Ac1) in the second thermal cycle are applied to the CGHAZ, third or more thermal cycle temper bead process should be applied to improve the properties. Appropriate weld condition ranges are selected based on the above results. The validity of the selected ranges is verified by the temper bead welding test. (orig.)

Mizuno, R.; Matsuda, F. [NDE Center, Japan Power Engineering and Inspection Corp. (Japan); Brziak, P. [Welding Research Inst. - Industrial Inst. of Slovak Republic (Slovakia); Lomozik, M. [Inst. of Welding (Poland)

2004-07-01

196

Coolant recirculation in a pressurized water reactor core under loss-of-coolant accident conditions  

International Nuclear Information System (INIS)

A model has been developed to predict the thermal hydraulics in the uncovered part of a pressurized water reactor core. The core is considered to be a heterogeneous porous medium with different permeabilities and effective thermal conductivities in the radial and axial directions. The flow in the core is modeled by the Brinkman-Forchheimer extended Darcy equations. The dependence of the thermophysical properties of the coolant (steam-hydrogen mixture) and the fuel rods with temperature is accounted for. Oxidation of the Zircaloy is also modeled, and transport of the generated hydrogen in the uncovered portion of the reactor core is considered. The effects of the thermal boundary condition at the outlet of the core (i.e., at the upper tie plate) are studied and reported. Partial blockage of the core due to the mechanical failure and/or melting of some of the fuel rods is also modeled, and its effects on the thermal hydraulics of the core are studied and discussed. Numerical simulations are reported for the Three Mile Island Unit 2 reactor conditions. The results show that the flow field in the core is affected by exothermic heat release as well as by a decrease of the coolant density due to the Zircaloy cladding oxidation. In addition, the results show that there is entrainment of the coolant from the upper plenum in the core. The partial blockage of the core was found to have a profound influence on the heatup of the core

197

Performance of pressurized metered-dose inhalers at extreme temperature conditions.  

Science.gov (United States)

The performance of pressurized metered-dose inhalers (pMDIs) under a variety of temperature conditions was investigated. The effects of both inhaler temperature and ambient temperature were considered. The inhaler temperature ranged from -13.0°C to 41.7°C and the ambient temperature ranged from -12.0°C to 41.7°C. The in vitro lung dose was measured for four widely available pMDIs: Airomir(TM) , QVAR(TM) , Symbicort(®) , and Ventolin(®) . The in vitro lung dose through an Alberta Idealized Throat was measured by gravimetric assay, which was verified by UV spectroscopic assay. A decrease in the in vitro lung dose was observed for all evaluated pMDIs when ambient temperature and device temperature were simultaneously reduced, decreasing on average by 70% at the coldest temperatures, whereas increasing on average by 25% at the elevated temperature condition. In vitro lung dose is strongly dependent on both inhaler temperature and ambient temperature with the tested pMDIs. PMID:25252183

Morin, Chelsea M D; Ivey, James W; Titosky, Jordan T F; Suderman, Jonathan D; Olfert, Jason S; Vehring, Reinhard; Finlay, Warren H

2014-11-01

198

Electrical Conductivity Measurement of Granulite Under Mid to Lower Crustal Pressure-Temperature Conditions  

Science.gov (United States)

We have developed a technique to measure electrical conductivity of crustal rocks with relatively low conductivity and complicated mineral components in order to compare with results given by Magneto-Telluric (MT) measurements. A granulite from Hidaka Metamorphic Belt (HMB) in Hokkaido, Japan at high temperature and pressure conditions was obtained. The granulite sample was ground and sintered under the conditions similar to those of mid to lower crust. We have observed smooth and reversible change of conductivity with temperature up to about 900 K at 1 GPa. Through the qualitative and quantitative evaluations using Electron Probe Micro Analysis (EPMA), microstructures of the sintered sample were inspected. This inspection is essential to confirm the sample was not affected by chemical interaction of minerals. We also examined the role of accessory minerals in the rock, and the mechanisms of electrical conductivity paths in _gdry_h or _gbasic_h rocks should be reconsidered. Finally, results from electrical conductivity measurements were consistent with the electrical conductivity structures suggested by the former MT data analysis.

Fuji-Ta, K.; Katsura, T.; Tainosho, Y.

2003-12-01

199

Modelling of laminar spray flames in high-pressure conditions; Modellierung laminarer Sprayflammen unter Hochdruckbedingungen  

Energy Technology Data Exchange (ETDEWEB)

The structure of laminar spray diffusion flames is investigated in counterflow configuration using numerical methods in a spray of liquid oxygen with hydrogen as carrier gas. The model considers detailed chemistry and detailed transport. The conditions selected require an extension of the model to consider the transport properties at cryogenic inlet temperatures as well as changed phase equilibria of binary mixtures at high pressure. The parametric dependence of the flame structure on the elongation velocity and the global equivalence ratio is presented and discussed. The model enables calculation of quenching conditions which are a fundamental parameter in simulating turbulent spray diffusion flames by means of a flamelet approach. [German] Die Struktur laminarer Spraydiffusionsflammen wird in der Gegenstromkonfiguration mittels numerischen Methoden untersucht. Ein Spray aus fluessigem Sauerstoff mit Traegergas Wasserstoff wird gegen Wasserstoff bei hohem subkritischen Druck und mit kryogener Eintrittstemperatur eingeduest. In dem Modell werden detaillierte Chemie und detaillierter Transport beruecksichtigt. Die gewaehlten Bedingungen erfordern die Modellerweiterung bezueglich der Transporteigenschaften bei kryogenen Eintrittstemperaturen sowie die Beruecksichtigung veraenderter Phasengleichgewichte binaerer Mischungen bei Hochdruck. Parametrische Abhaengigkeiten der Flammenstruktur von der Streckungsgeschwindigkeit und dem globalen Aequivalenzverhaeltnis werden dargestellt und diskutiert. Das Modell ermoeglicht die Bestimmung von Verloeschbedingungen, die fuer die Simulation turbulenter Spraydiffusionsflammen mittels eines Flamelet-Ansatzes grundlegend sind. (orig.)

Schlotz, D.; Gutheil, E.

1999-07-01

200

Direct ion flux measurements at high-pressure-depletion conditions for microcrystalline silicon deposition  

Energy Technology Data Exchange (ETDEWEB)

The contribution of ions to the growth of microcrystalline silicon thin films has been investigated in the well-known high-pressure-depletion (HPD) regime by coupling thin-film analysis with plasma studies. The ion flux, measured by means of a capacitive probe, has been studied in two regimes, i.e., the amorphous-to-microcrystalline transition regime and a low-to-high power regime; the latter regime had been investigated to evaluate the impact of the plasma power on the ion flux in collisional plasmas. The ion flux was found not to change considerably under the conditions where the deposited material undergoes a transition from the amorphous to the microcrystalline silicon phase; for solar-grade material, an ion-to-Si deposition flux of ?0.30 has been determined. As an upper-estimation of the ion energy, a mean ion energy of ?19 eV has been measured under low-pressure conditions (<1 mbar) by means of a retarding field energy analyzer. Combining this upper-estimate with an ion per deposited Si atom ratio of ?0.30, it is concluded that less than 6 eV is available per deposited Si atom. The addition of a small amount of SiH{sub 4} to an H{sub 2} plasma resulted in an increase of the ion flux by about 30% for higher power values, whereas the electron density, deduced from optical emission spectroscopy analysis, decreased. The electron temperature, also deduced from optical emission spectroscopy analysis, reveals a slight decrease with power. Although the dominant ion in the HPD regime is SiH{sub 3}{sup +}, i.e., a change from H{sub 3}{sup +} in pure hydrogen HPD conditions, the measured larger ion loss can be explained by assuming steeper electron density profiles. These results, therefore, confirm the results reported so far: the ion-to-Si deposition flux is relatively large but has neither influence on the microcrystalline silicon film properties nor on the phase transition. Possible explanations are the reported high atomic hydrogen to deposition flux ratio, mitigating the detrimental effects of an excessive ion flux.

Bronneberg, A. C.; Kang, X.; Palmans, J.; Janssen, P. H. J.; Lorne, T. [Applied Physics Department, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven (Netherlands); Creatore, M. [Applied Physics Department, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven (Netherlands); Solliance Solar Research, High Tech Campus 5, 5656AE Eindhoven (Netherlands); Sanden, M. C. M. van de [Applied Physics Department, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven (Netherlands); Dutch Institute for Fundamental Energy Research (DIFFER), P.O. Box 1207, 3430BE Nieuwegein (Netherlands)

2013-08-14

201

The kinetics of dolomite reaction rim growth under isostatic and non-isostatic pressure conditions  

Science.gov (United States)

During burial and exhumation, rocks are simultaneously exposed to metamorphic reactions and tectonic stresses. Therefore, the reaction rate of newly formed minerals may depend on chemical and mechanical driving forces. Here, we investigate the reaction kinetics of dolomite (CaMg[CO3]2) rim growth by solid-state reactions experiments on oriented calcite (CaCO3) and magnesite (MgCO3) single crystals under isostatic and non-isostatic pressure conditions. Cylindrical samples of 3-5 mm length and 7 mm diameter were drilled and polished perpendicular to the rhombohedral cleavage planes of natural clear crystals. The tests were performed using a Paterson-type deformation apparatus at P = 400 MPa confining pressure, temperatures, T, between 750 and 850°C, and reaction durations, t, of 2 - 146 h to calculate the kinetic parameters of dolomite rim growth under isostatic stress conditions. For non-isostatic reaction experiments we applied in addition differential stresses, ?, up to 40 MPa perpendicular to the contact interface at T = 750°C for 4 - 171 h duration, initiating minor inelastic deformation of calcite. The thickness of the resulting dolomite reaction rims increases linearly with the square root of time, indicating a diffusion-controlled reaction. The rims consist of two different textural domains. Granular dolomite grains (? 2 -5 ?m grain size) form next to calcite and elongated palisade-shaped grains (1-6 ?m diameter) grow perpendicular to the magnesite interface. Texture measurements with the electron backscatter diffraction technique indicate that the orientations of dolomite grains are mainly influenced by the orientation of the calcite educt crystal, in particular in the granular rim. To some extent, the texture of dolomite palisades is also influenced by the orientation of magnesite. The thickness of the two individual layers increases with temperature. At 400 MPa isostatic pressure, T = 750°C and t = 29 hours, a 5 ?m thick granular dolomite layer and a 7 ?m thick palisade-shaped layer evolve. At similar conditions and a differential stress of 30 MPa, the rim thickness remains similar; consequently the effect of non-isostatic stress on dolomite rim growth is negligible. Platinum markers show that the initial calcite-magnesite interface is located between granular and palisade-forming dolomite, indicating that rim growth occurs by counter diffusion of MgO and CaO. Diffusion of MgO across the dolomite reaction rim into calcite forms additionally magnesio-calcite grains with diameters of ? 13 - 46 ?m, depending on the experimental conditions and increasing with increasing distance to the dolomite boundary. At T = 750°C, t = 29 hours, the thickness of the magnesio-calcite layer is 32 ?m (isostatic) - 35 ?m (? = 30 MPa). The experiments indicate that solid-state reaction rim growth of dolomite between calcite and magnesite is primarily controlled by diffusion of MgO and CaO, forming layers with different microstructures during growth into the educt phases. The kinetics of the reaction in the carbonate system are not significantly changed by differential stresses up to 40 MPa. We suggest that volume diffusion is the dominant transport mechanism, which is presumably less affected by non-isostatic stresses than grain boundary diffusion.

Helpa, V.; Rybacki, E.; Morales, L. G.; Abart, R.; Dresen, G. H.

2013-12-01

202

Porcine liver decellularization under oscillating pressure conditions: a technical refinement to improve the homogeneity of the decellularization process.  

Science.gov (United States)

Decellularization and recellularization of parenchymal organs may facilitate the generation of autologous functional liver organoids by repopulation of decellularized porcine liver matrices with induced liver cells. We present an accelerated (7?h overall perfusion time) and effective protocol for human-scale liver decellularization by pressure-controlled perfusion with 1% Triton X-100 and 1% sodium dodecyl sulfate via the hepatic artery (120?mmHg) and portal vein (60?mmHg). In addition, we analyzed the effect of oscillating pressure conditions on pig liver decellularization (n=19). The proprietary perfusion device used to generate these pressure conditions mimics intra-abdominal conditions during respiration to optimize microperfusion within livers and thus optimize the homogeneity of the decellularization process. The efficiency of perfusion decellularization was analyzed by macroscopic observation, histological staining (hematoxylin and eosin [H&E], Sirius red, and alcian blue), immunohistochemical staining (collagen IV, laminin, and fibronectin), and biochemical assessment (DNA, collagen, and glycosaminoglycans) of decellularized liver matrices. The integrity of the extracellular matrix (ECM) postdecellularization was visualized by corrosion casting and three-dimensional computed tomography scanning. We found that livers perfused under oscillating pressure conditions (P(+)) showed a more homogenous course of decellularization and contained less DNA compared with livers perfused without oscillating pressure conditions (P(-)). Microscopically, livers from the (P(-)) group showed remnant cell clusters, while no cells were found in livers from the (P(+)) group. The grade of disruption of the ECM was higher in livers from the (P(-)) group, although the perfusion rates and pressure did not significantly differ. Immunohistochemical staining revealed that important matrix components were still present after decellularization. Corrosion casting showed an intact vascular (portal vein and hepatic artery) and biliary framework. In summary, the presented protocol for pig liver decellularization is quick (7?h) and effective. The application of oscillating pressure conditions improves the homogeneity of perfusion and thus the outcome of the decellularization process. PMID:25164028

Struecker, Benjamin; Hillebrandt, Karl Herbert; Voitl, Robert; Butter, Antje; Schmuck, Rosa B; Reutzel-Selke, Anja; Geisel, Dominik; Joehrens, Korinna; Pickerodt, Philipp A; Raschzok, Nathanael; Puhl, Gero; Neuhaus, Peter; Pratschke, Johann; Sauer, Igor M

2015-03-01

203

Bottom nozzle failure mechanism of water reactor pressure vessel under severe accident conditions  

International Nuclear Information System (INIS)

Most of past studies devoted to the creep rupture of a nuclear reactor pressure vessel (RPV) lower head under severe accident conditions, have focused on global deformation and rupture modes. Limited efforts were made on local failure modes associated with penetration nozzles as a part of TMI-2 vessel investigation project (TMI-2 VIP) in 1990s. However, it was based on an excessively simplified shear deformation model. In the present study, the mode of nozzle failure has been investigated using data and nozzle materials from Sandia National Laboratory's lower head failure experiment (SNL-LHF). Crack-like separations were revealed at the nozzle weld metal to RPV interfaces indicating the importance of normal stress component rather than the shear stress in the creep rupture. Creep rupture tests were conducted for nozzle and weld metal materials, respectively, at various temperature and stress levels. Stress distribution in the nozzle region is calculated using elastic-viscoplastic finite element analysis (FEA) using the measured properties. Calculation results are compared with earlier results based on the pure shear model of TMI-2 VIP. It is concluded from both LHF-4 nozzle examination and FEA that normal stress at the nozzle/lower head interface is the dominant driving force for the local failure. From the FEA for the nozzle weld attached in RPV, it is shown that nozzle welds failure occur by displacement controlled fracture of nozzle hole not by load controlled fracof nozzle hole not by load controlled fracture of internal pressure. Considering these characteristics of nozzle weld failure, new concept of nozzle failure time prediction is proposed

204

Methods for quantifying the influences of pressure and temperature variation on metal hydride reaction rates measured under isochoric conditions  

Science.gov (United States)

Analysis techniques for determining gas-solid reaction rates from gas sorption measurements obtained under non-constant pressure and temperature conditions often neglect temporal variations in these quantities. Depending on the materials in question, this can lead to significant variations in the measured reaction rates. In this work, we present two new analysis techniques for comparison between various kinetic models and isochoric gas measurement data obtained under varying temperature and pressure conditions in a high pressure Sievert system. We introduce the integral pressure dependence method and the temperature dependence factor as means of correcting for experimental variations, improving model-measurement fidelity, and quantifying the effect that such variations can have on measured reaction rates. We use measurements of hydrogen absorption in LaNi5 and TiCrMn to demonstrate the effect of each of these methods and show that their use can provide quantitative improvements in interpretation of kinetics measurements.

Voskuilen, Tyler G.; Pourpoint, Timothée L.

2013-11-01

205

HEADCO: a program for converting observed water levels and pressure measurements to formation pressure and standard hydraulic head  

International Nuclear Information System (INIS)

Static water-level and fluid pressure measurements are commonly converted in hydrologic studies to formation pressure and hydraulic head, which are used to determine groundwater flow characteristics of aquifer systems. While the direct use of field measurements is usually adequate for determining formation pressure and hydraulic head for shallow flow systems (i.e., <1000 ft), corrections and conversion parameters must be used to properly account for fluid-column density effects, which commonly occur with deep systems. This report presents a program, HEADCO, for converting static water-level and pressure measurements to formation pressure and standard hydraulic head. The HEADCO program corrects field measurements for the effects of fluid-density variation and selected external stresses. Factors that affect density of the fluid column, in which field measurements are made, include temperature, pressure, salinity, suspended solids, and multiphase conditions. External stresses examined in HEADCO include barometric and earth tide fluctuations, and gravitational acceleration variation. A program description and procedures for converting field measurements obtained using field test arrangements commonly employed in the Basalt Waste Isolation Project field program are provided in this report. The report includes user instructions and an illustrative test example. Results of a field example comparison are also provided. This comparison examines observed and HEADCO-calculated p examines observed and HEADCO-calculated pressures for 30 pressure probes recently calibrated in a laboratory and tested under field conditions at borehole DC-8. The test case and field example comparisons indicate that HEADCO provides accurate estimates of formation pressure and standard hydraulic head that are well within the accuracy range of downhole pressure-measuring instrumentation. 44 refs., 14 figs., 8 tabs

206

EXAFS and Raman studies of mechanical alloyed Ni25Se75 mixture under high-pressure conditions  

International Nuclear Information System (INIS)

Extended X-ray Absorption Fine Structure and Raman studies were performed to follow the structural and vibrational behavior of a mechanical alloyed Ni25Se75 mixture, containing nanocrystalline pyrite NiSe2 phase, when exposed to high-pressure conditions. An increase in the local structural order of the nanocrystalline phase with pressure increasing was observed by means of Debye-Waller factor analysis. The relative Ni nearest-neighbors distances were determined as a function of pressure, which were used to determine the inverse linear compressibility of the nanocrystalline pyrite NiSe2 alloy as well as its derivate by means of Murnaghan's equation. The Raman results showed tentative NiSe2 phonons dispersion with pressure that becomes a difficult task since the existence/photo-induced nucleation of an important amount of nanocrystalline Se, detected due to the observation of its pressure-induced phase transitions

207

Measurement of subcooled boiling pressure drop and local heat transfer coefficient in horizontal tube under LPLF conditions  

International Nuclear Information System (INIS)

Highlights: ? Measured subcooled boiling pressure drop and local heat transfer coefficient in horizontal tubes. ? Infra-red thermal imaging is used for wall temperature measurement. ? Developed correlations for pressure drop and local heat transfer coefficient. -- Abstract: Horizontal flow is commonly encountered in boiler tubes, refrigerating equipments and nuclear reactor fuel channels of pressurized heavy water reactors (PHWR). Study of horizontal flow under low pressure and low flow (LPLF) conditions is important in understanding the nuclear core behavior during situations like LOCA (loss of coolant accidents). In the present work, local heat transfer coefficient and pressure drop are measured in a horizontal tube under LPLF conditions of subcooled boiling. Geometrical parameters covered in this study are diameter (5.5 mm, 7.5 mm and 9.5 mm) and length (550 mm, 750 mm and 1000 mm). The operating parameters varied are mass flux (450–935 kg/m2 s) and inlet subcooling (29 °C, 50 °C and 70 °C). Infra-red thermography is used for the measurement of local wall temperature to estimate the heat transfer coefficient in single phase and two phase flows with water as the working medium at atmospheric pressure. Correlation for single phase diabatic pressure drop ratio (diabatic to adiabatic) as a function of viscosity ratio (wall temperature to fluid temperature) is presented. Correlation for pressure drop under subcooled boiling conditions as a function of Boiling number (Bo) and Jakob number (Ja) is obtained. Correlation for single phase heat transfer coefficient in the thermal developing region is presented as a function of Reynolds number (Re), Prandtl number (Pr) and z/d (ratio of axial length of the test section to diameter). Correlation for two phase heat transfer coefficient under subcooled boiling condition is developed as a function of boiling number (Bo), Jakob number (Ja) and Prandtl number (Pr)

208

An Inexpensive Arterial Pressure Wave Sensor and its application in different physiological condition  

OpenAIRE

Arterial Blood Pressure wave monitoring is considered to be important in assessment of cardiovascular system. We developed a novel pulse wave detection system using low frequency specific piezoelectric material as pressure wave sensor. The transducer detects the periodic change in the arterial wall diameter produced by pressure wave and the amplified signal after integration represents the pressure wave. The signal before integration is proportional to the rate of change of ...

Sur, Shantanu; Ghatak, S. K.

2005-01-01

209

Effectiveness of Sealed Double-Ring Infiltrometers trademark and effects of changes in atmospheric pressure on hydraulic conductivity  

International Nuclear Information System (INIS)

The Savannah River Site is currently evaluating some 40 hazardous and radioactive-waste sites for remediation. Among the remedial alternatives considered is closure using a kaolin clay cap. The hydraulic conductivity suggested by the US Environmental Protection Agency is 1.0 x 10-7 cm/sec. One instrument to measure this value is the Sealed Double-Ring Infiltrometer trademark (SDRI). Six SDRI were recently installed on a kaolin test cap. Test results demonstrated uniform performance of these instruments. However, the test data showed as much as an order of magnitude of variation over time. This variation is attributed to both internal structural heterogeneity and variable external boundary conditions. The internal heterogeneity is caused by construction variability within a specified range of moisture and density. The external influences considered are temperature and barometric pressure. Temperature was discharged as a source of heterogeneity because of a lack of correlation with test data and a negligible impact from the range of variability. However, a direct correlation was found between changes in barometric pressure and hydraulic conductivity. This correlation is most pronounced when pressure changes occur over a short period of time. Additionally, this correlation is related to a single soil layer. When the wetting front passes into a more porous foundation layer, the correlation with pressure changes disappears. Conclusions are that the SDRI performsrs. Conclusions are that the SDRI performs adequately, with good repeatability of results. The duration of test is critical to assure a statistically valid data set. Data spikes resulting from pressure changes should be identified, and professional judgment used to determine the representative hydraulic conductivity. Further evaluation is recommended to determine the impact of pressure change on the actual hydraulic conductivity

210

On the Physics of Flow Separation Along a Low Pressure Turbine Blade Under Unsteady Flow Conditions  

Science.gov (United States)

The present study, which is the first of a series of investigations dealing with specific issues of low pressure turbine (LPT) boundary layer aerodynamics, is aimed at providing detailed unsteady boundary flow information to understand the underlying physics of the inception, onset, and extent of the separation zone. A detailed experimental study on the behavior of the separation zone on the suction surface of a highly loaded LPT-blade under periodic unsteady wake flow is presented. Experimental investigations were performed at Texas A&M Turbomachinery Performance and Flow Research Laboratory using a large-scale unsteady turbine cascade research facility with an integrated wake generator and test section unit. To account for a high flow deflection of LPT-cascades at design and off-design operating points, the entire wake generator and test section unit including the traversing system is designed to allow a precise angle adjustment of the cascade relative to the incoming flow. This is done by a hydraulic platform, which simultaneously lifts and rotates the wake generator and test section unit. The unit is then attached to the tunnel exit nozzle with an angular accuracy of better than 0.05 , which is measured electronically. Utilizing a Reynolds number of 110,000 based on the blade suction surface length and the exit velocity, one steady and two different unsteady inlet flow conditions with the corresponding passing frequencies, wake velocities and turbulence intensities are investigated using hot-wire anemometry. In addition to the unsteady boundary layer measurements, blade surface pressure measurements were performed at Re=50,000, 75,000, 100,000, and 125,000 at one steady and two periodic unsteady inlet flow conditions. Detailed unsteady boundary layer measurement identifies the onset and extent of the separation zone as well as its behavior under unsteady wake flow. The results presented in ensemble-averaged and contour plot forms contribute to understanding the physics of the separation phenomenon under periodic unsteady wake flow. Several physical mechanisms are discussed.

Schobeiri, Meinhard T.; Ozturk, Burak; Ashpis, David E.

2005-01-01

211

X-ray spectroscopy at in-situ high-pressure conditions. X-ray Raman scattering on silicate glasses  

International Nuclear Information System (INIS)

Nonresonant inelastic X-ray scattering investigates electronic excitation using hard X-ray, and is therefore applicable to materials under extreme conditions, e.g. high pressure. Excitations of inner-shell electrons measured by so-called X-ray Raman scattering give information on unoccupied electronic structures. In this article, we discuss applications of X-ray Raman scattering to high pressure studies from technical points of view, and then introduce examples of investigations on the pressure variations on local structures of silicate glasses discussed from the electronic structures. (author)

212

Numerical simulation of pressure fluctuation of a pump-turbine with MGV at no-load condition  

International Nuclear Information System (INIS)

In order to analyse the pressure fluctuation caused by misaligned guide vanes (MGV) during starting period at no-load condition, 3-D (three dimensional), unsteady flows in a pump-turbine were numerically studied. Pressure fluctuations of different points at no-load condition are obtained. Fast Fourier Transform(FFT) was used to analyse the frequency spectrum of pressure fluctuations. The amplitude and dominant frequency of pressure fluctuation at vaneless space between the runner and guide vane, as well as the inlet of draft tube, was investigated. The amplitude of pressure fluctuation of the pump-turbine with MGV device is twice that of synchronous vanes. This might be caused by the non-uniform flow in the pump-turbine due to the pre-opened guide vanes. The pump-turbine with synchronous vanes has a low frequency which is 0.33fn, while the low frequency changes into 0.63fn when the MGV device is used. The vortex rope in the draft tube is large than that of synchronize vanes. Resultsof pressure fluctuations with synchronous vanes agree with each other between computational and testing results. The numerical study of pressure fluctuations with MGV can provide a basic understanding for the improvement of the instability of a pump-turbine.

213

Numerical simulation of pressure fluctuation of a pump-turbine with MGV at no-load condition  

Science.gov (United States)

In order to analyse the pressure fluctuation caused by misaligned guide vanes (MGV) during starting period at no-load condition, 3-D (three dimensional), unsteady flows in a pump-turbine were numerically studied. Pressure fluctuations of different points at no-load condition are obtained. Fast Fourier Transform(FFT) was used to analyse the frequency spectrum of pressure fluctuations. The amplitude and dominant frequency of pressure fluctuation at vaneless space between the runner and guide vane, as well as the inlet of draft tube, was investigated. The amplitude of pressure fluctuation of the pump-turbine with MGV device is twice that of synchronous vanes. This might be caused by the non-uniform flow in the pump-turbine due to the pre-opened guide vanes. The pump-turbine with synchronous vanes has a low frequency which is 0.33fn, while the low frequency changes into 0.63fn when the MGV device is used. The vortex rope in the draft tube is large than that of synchronize vanes. Resultsof pressure fluctuations with synchronous vanes agree with each other between computational and testing results. The numerical study of pressure fluctuations with MGV can provide a basic understanding for the improvement of the instability of a pump-turbine.

Liu, J. T.; Liu, S. H.; Sun, Y. K.; Wu, Y. L.; Wang, L. Q.

2012-11-01

214

Artificial maintenance of the relative ocular tissue pressure during eye surgery.  

OpenAIRE

We describe an operating table in which the whole patient, apart from the eye undergoing surgery, is enclosed in a caisson within which the barometric pressure can be lowered at any time during surgery. This increases the effect of atmospheric pressure on the eye, enabling 'open sky' surgery to be carried out on patients of any age.

Maggi, C.; Maggi, R.

1990-01-01

215

Novel open-framework europium silicates prepared under high-temperature and high-pressure conditions.  

Science.gov (United States)

Two new europium silicates, Na15Eu3Si12O36 (denoted as 1) and K2EuSi4O10F (denoted as 2), were successfully synthesized under high-temperature and high-pressure conditions, and structurally characterized by single-crystal and powder X-ray diffraction (XRD). The single-crystal XRD analysis of 1 reveals that its structure is based on [Si6O18]n(12n-) cyclosilicate anions that are built from six SiO4 tetrahedra sharing two of their four O corners with each other. Such [Si6O18]n(12n-) cyclosilicate anions are linked via EuO6 octahedra to form a three-dimensional (3D) framework containing 6-membered ring channels delimited by the SiO4 tetrahedra and EuO6 octahedra along the [010] direction. The structure of 2 consists of infinite tubular chains of corner-sharing SiO4 tetrahedra, which are further linked together via corner sharing O atoms by infinite chains of EuO4F2 octahedra forming a 3-D framework that contains 8-ring and 6-ring channels along the [010] direction. The photoluminescence properties of 1 and 2 were also investigated. PMID:25111041

Liu, Wei; Ji, Ying; Bao, Xinjian; Wang, Ying; Li, Benxian; Wang, Xiaofeng; Zhao, Xudong; Liu, Xiaoyang; Feng, Shouhua

2014-10-01

216

Nozzle failure mechanism of a water reactor pressure vessel under severe accident conditions  

International Nuclear Information System (INIS)

Most of past studies for the creep rupture of a nuclear reactor pressure vessel (RPV) lower head under severe accident conditions, have focused on global deformation and rupture modes. Limited efforts were made on local failure modes associated with penetration nozzles as a part of TMI-2 Vessel Investigation Project (TMI-2 VIP) in 1990's. However, it was based on an excessively simplified shear deformation model. In the present study, the mode of nozzle failures has been investigated using data and nozzle materials from Sandia National Laboratory's Lower Head Failure Experiment (SNL-LHF). Crack-like separations were revealed at the nozzle weld metal to RPV interfaces indicating the importance of normal stress component rather than the shear stress in the creep rupture. Creep rupture tests were conducted for nozzle and weld metal materials, respectively, at various temperature and stress levels. Stress distribution in the nozzle region is calculated using elastic-viscoplastic finite element analysis (FEA) using the measured properties. Calculation results are compared with earlier results based on the pure shear model of TMI-2 VIP. It has been concluded from both LHF-4 nozzle examination and FEA that normal stress at the nozzle/lower head interface is the dominant driving force for the local failure with its likelihood significantly greater than previously assumed. (authors)

217

Local failure characteristics of a nuclear reactor pressure vessel nozzle under severe accident conditions  

International Nuclear Information System (INIS)

Most past studies for the creep rupture of a nuclear reactor pressure vessel (RPV) lower head under severe accident conditions, have focused on global deformation and rupture modes. Limited efforts were made on local failure modes associated with penetration nozzles as a part of TMI-2 Vessel Investigation Project (TMI-2 VIP) in 1990's. However, it was based on an excessively simplified shear deformation model. In the present study, the mode of nozzle failures is investigated using data and nozzle materials from Sandia National Laboratory's Lower Head Failure Experiment (SNL-LHF). Crack-like separations were revealed at the nozzle weld metal to RPV interfaces indicating the importance of normal stress component rather than the shear stress in the creep rupture. Creep rupture tests were conducted for nozzle and weld metal materials, respectively, at various temperature and stress levels. Stress distribution in the nozzle region is calculated using elastic-viscoplastic finite element analysis (FEA) using the measured properties. Calculation results are compared with earlier results based on the pure shear model of TMI-2 VIP. It has been concluded from both LHF-4 nozzle examination and FEA that normal stress at the nozzle/lower head interface is the dominant driving force for the local failure with its likelihood significantly greater than previously assumed

218

Microstructure and spectroscopy studies on cubic boron nitride synthesized under high-pressure conditions  

International Nuclear Information System (INIS)

High-resolution electron microscopy (HREM) studies of the microstructure and specific defects in hexagonal boron nitride (h-BN) precursors and cubic boron nitride (c-BN) crystals made under high-pressure high-temperature conditions revealed the presence of half-nanotubes at the edges of the h-BN particles. Their sp3 bonding tendency could strongly influence the nucleation rates of c-BN. The atomic resolution at extended dislocations was insufficient to allow us to determine the stacking fault energy in the c-BN crystals. Its mean value of 191 pm, 15 mJ m-2 is of the same order of magnitude as that of diamond. High-frequency (94 GHz) electron paramagnetic resonance studies on c-BN single crystals have produced new data on the D1 centres associated with the boron species. Ion-beam-induced luminescence measurements have indicated that c-BN is a very interesting luminescent material, which is characterized by four luminescence bands and exhibits a better resistance to ionizing radiation than CVD diamond

219

Microstructure and spectroscopy studies on cubic boron nitride synthesized under high-pressure conditions  

CERN Document Server

High-resolution electron microscopy (HREM) studies of the microstructure and specific defects in hexagonal boron nitride (h-BN) precursors and cubic boron nitride (c-BN) crystals made under high-pressure high-temperature conditions revealed the presence of half-nanotubes at the edges of the h-BN particles. Their sp sup 3 bonding tendency could strongly influence the nucleation rates of c-BN. The atomic resolution at extended dislocations was insufficient to allow us to determine the stacking fault energy in the c-BN crystals. Its mean value of 191 pm, 15 mJ m sup - sup 2 is of the same order of magnitude as that of diamond. High-frequency (94 GHz) electron paramagnetic resonance studies on c-BN single crystals have produced new data on the D1 centres associated with the boron species. Ion-beam-induced luminescence measurements have indicated that c-BN is a very interesting luminescent material, which is characterized by four luminescence bands and exhibits a better resistance to ionizing radiation than CVD di...

Nistor, L C; Dinca, G; Georgeoni, P; Landuyt, J V; Manfredotti, C; Vittone, E

2002-01-01

220

Using conditional tree forests and life history traits to assess specific risks of stream degradation under multiple pressure scenario.  

Science.gov (United States)

The full accomplishment of the European Water Framework Directive objectives has required from EU members three successive steps: (i) the evaluation of their water body ecological status, (ii) the risk assessment of different anthropogenic pressure categories and (iii) the implementation of appropriate management and restoration programs. We aimed at designing an innovative retrospective ecological risk assessment (ERA) tool working for most of the French wadeable rivers in a context of multiple anthropogenic pressures (step ii). This tool, including conditional tree forest (CTF) models, was built on combinations of benthic macroinvertebrate trait-based metrics for each of sixteen anthropogenic pressure categories. For eleven pressure categories, CTF models have given good impairment risk assessment (i.e. AUC?0.70), even at moderate risk level and in a multi-pressure context. The four other models have provided poorer but promising results (AUC=0.67±0.02). Identifying the potential weight of individual anthropogenic pressures that lead to biotic assemblage impairment in streams under multiple pressure scenario, is a key step for managers to implement appropriate stream restoration programs. Simultaneously considering the whole complexity of bio-ecological adaptations within biotic assemblages subjected to human pressures provides a functional diagnostic tool both (i) ecologically relevant and (ii) efficient for ERA. PMID:23774251

Mondy, Cédric P; Usseglio-Polatera, Philippe

2013-09-01

221

Sulphate chemistry under pressurized oxidizing, reducing and fluctuating conditions; Sulfatkemi under trycksatta oxiderande, reducerande och fluktuerande foerhaallanden  

Energy Technology Data Exchange (ETDEWEB)

In the literature it has been reported that sulfur capture with limestone (CaCO{sub 3}) under atmospheric fluidized bed combustion conditions reaches a maximum at about 850 deg C. Previously, the maximum has been attributed to the sintering of sorbent particles which decreases the reactive surface area. Lately, also another explanation has been reported. In this case the sulfur capture decrease at higher temperatures was concluded to be due to fluctuating oxidizing/reducing conditions in the atmospheric combustor. In this work the influence of alternating oxidizing/reducing conditions on SO{sub 2} capture at atmospheric and elevated pressure (15 bar) has been studied. In the pressurized case, the CO{sub 2} partial pressure was kept high enough to prevent CaCO{sub 3} from calcining and therefore the CaSO{sub 4} would not form CaO but CaCO{sub 3} under reducing conditions. The experiments were done with a pressurized TGA by periodically changing the gas environment between oxidizing (O{sub 2}. SO{sub 2}, CO{sub 2} and N{sub 2}) and slightly reducing (CO, SO{sub 2}, CO{sub 2} and N{sub 2}) gas mixtures at different temperatures. The results from the experiments showed that under normal pressure and slightly reducing conditions CaO formation from CaSO{sub 4} increased with temperature as expected. However, no significant amounts of CaCO{sub 3} were formed from CaSO{sub 4} at elevated pressure. It was also concluded that since the formation of CaO from CaSO{sub 4} was relatively slow it could not explain the sharp sulfur capture maximum at about 850 deg C. Therefore, it was assumed that the strongly reducing zones, where CaS thermodynamically is the stable compound, play a more important role concerning the sulfur capture in fluidized bed combustors. (orig.)

Hupa, M.; Yrjas, P.; Backman, P. [Aabo Akademi, Turku (Finland). Combustion Chemistry Research Group

1997-10-01

222

Numerical prediction of the pressure fluctuations on small discharge condition of a pump-turbine at pump mode  

Science.gov (United States)

The operational stability of the pump turbine at the pump mode will be greatly influenced by large pressure fluctuations when operated in the small-discharge conditions. Therefore, it is significant to analyse the flow characteristic under the small discharge operating conditions deeply. Study of the internal flow in the small discharge condition has been investigate in great detail combined with model experiments in this paper. The SST k-? turbulence model is adopted to perform three-dimensional numerical simulation of the entire pump-turbine flow passage at optimal guide vanes opening. The numerical simulation results match well with experimental data. Then internal flow under the small discharge condition is analysed. The results show that the dominant frequency inside the flow passage is a relative low frequency. In addition, there are obvious complex flow phenomena inside the draft tube, runner and diffuser domains, such as secondary flow, backflow and even vortex, leading to strong unsteady flow and significant pressure fluctuation.

Yao, Y. Y.; Xiao, Y. X.; Zhu, W.; An, S. H.; Wang, Z. W.

2015-01-01

223

Determination of safe operating conditions for gasketed flange joint under combined internal pressure and temperature: A finite element approach  

Energy Technology Data Exchange (ETDEWEB)

Performance of a flange joint is characterised mainly by its 'strength' and 'sealing capability'. A number of analytical and experimental studies have been conducted to study these characteristics under internal pressure loading. However, with the advent of new technological trends for high temperature and pressure applications, an increased demand for analysis is recognized. The effect of steady-state thermal loading makes the problem more complex as it leads to combined application of internal pressure and temperature. The present design codes do not address the effects of temperature on the structural integrity and sealing ability. In addition, the available design solutions do not solve problems of failure of a gasketed flange joint even under bolt up and internal pressure loading conditions. To investigate joint strength and sealing capability under combined internal pressure and different steady-state thermal loading, a 3D nonlinear finite element analysis (FEA) of a gasketed flange joint is carried out and its behaviour is discussed. To determine the safe operating conditions or the actual joint load capacity, the joint is further analyzed for different internal pressures keeping the temperature constant.

Abid, Muhammad [Faculty of Mechanical Engineering, Ghulam Ishaq Khan Institute of Engineering Sciences and Technology, Topi-23460, NWFP (Pakistan)]. E-mail: abid@giki.edu.pk

2006-06-15

224

Determination of safe operating conditions for gasketed flange joint under combined internal pressure and temperature: A finite element approach  

International Nuclear Information System (INIS)

Performance of a flange joint is characterised mainly by its 'strength' and 'sealing capability'. A number of analytical and experimental studies have been conducted to study these characteristics under internal pressure loading. However, with the advent of new technological trends for high temperature and pressure applications, an increased demand for analysis is recognized. The effect of steady-state thermal loading makes the problem more complex as it leads to combined application of internal pressure and temperature. The present design codes do not address the effects of temperature on the structural integrity and sealing ability. In addition, the available design solutions do not solve problems of failure of a gasketed flange joint even under bolt up and internal pressure loading conditions. To investigate joint strength and sealing capability under combined internal pressure and different steady-state thermal loading, a 3D nonlinear finite element analysis (FEA) of a gasketed flange joint is carried out and its behaviour is discussed. To determine the safe operating conditions or the actual joint load capacity, the joint is further analyzed for different internal pressures keeping the temperature constant

225

Pressure-stability of phospholipid bicelles: Measurement of residual dipolar couplings under extreme conditions  

Energy Technology Data Exchange (ETDEWEB)

High-pressure NMR of proteins in solutions currently gains increasing interest. 3D structure determination of proteins under high pressure is, however, so far impossible due to the lack of NOE information. Residual dipolar couplings induced by the addition of magnetically orienting media are known to be capable of replacing NOE information to a very high extent. In the present contribution we study the pressure-wstability of dimyristoylphosphatidylcholine (DMPC)/ dihexanoylphosphatidylcholine (DHPC) bicelles and demonstrate the feasibility of measuring residual dipolar couplings in proteins under high pressure.

Brunner, E.; Arnold, M.R.; Kremer, W.; Kalbitzer, H.R. [University of Regensburg, Institute of Biophysics and Physical Biochemistry (Germany)

2001-10-15

226

Pressure-stability of phospholipid bicelles: Measurement of residual dipolar couplings under extreme conditions  

International Nuclear Information System (INIS)

High-pressure NMR of proteins in solutions currently gains increasing interest. 3D structure determination of proteins under high pressure is, however, so far impossible due to the lack of NOE information. Residual dipolar couplings induced by the addition of magnetically orienting media are known to be capable of replacing NOE information to a very high extent. In the present contribution we study the pressure-wstability of dimyristoylphosphatidylcholine (DMPC)/ dihexanoylphosphatidylcholine (DHPC) bicelles and demonstrate the feasibility of measuring residual dipolar couplings in proteins under high pressure

227

Leakage rate through a non-cracked concrete wall, comparison between two situations: Air pressure test and accident conditions  

International Nuclear Information System (INIS)

This experimental research investigated the behaviour of a concrete wall, with a local zone very permeable to air, subjected to accident conditions. The high level of permeability in the concrete was obtained for one specimen with a porous concrete having connected pores (intrinsic permeability of 10-16 m2). The aim of this work was to study comparatively, in the laboratory, the permeability of a non-cracked concrete wall under two conditions. A cylindrical specimen 1.3 m thick was used. No appreciable stresses were applied on the concrete. The first condition was at ambient temperature, under an increasing pressure (up to 0.42 MPa) of the air applied on one face of the specimen, the other one being at atmospheric pressure. The second condition was an accident scenario with simultaneous effects of temperature and gas (a mix of air and steam) pressure applied on one face, the other one remaining at atmospheric pressure and temperature. During the test, the lateral face of the cylindrical specimen was thermally isolated and made leak tight. So, a uni-dimensional experimental analysis was performed. The accident conditions consisted of a rise from ambient conditions to a temperature of 141 deg C and a relative pressure of 0.42 MPa (steam pressure of 0.377 MPa and air pressure of 0.043 MPa) for 3 h, the maximum values remaining constant for several days. Thermocouples, pressure taps and moisture gauges were implanted in the specimens at the moment ofmplanted in the specimens at the moment of casting, to provide local information about the inner wall under the simultaneous effects of temperature and steam pressure. Outside the specimen, the chamber enclosed a condenser with a humidity meter and thermocouple, so it was possible to quantify separately the saturated airflow with a flow-metre and the condensed water. During the permeability test at ambient temperature, the field of pressure was affected by the variation of local permeability of the concrete. Furthermore, some movement of interstitial water inside the specimen induced an increase of the predicted outflow, no liquid phase appeared. For the natural porous concrete, during accident testing, the field of pressure advanced slowly, the outflow progressively increased to obtain a maximum at 70 h, after this time on the one hand the airflow rate decreased and became equal to zero; on the other hand, the liquid flow rate was constant, at the end of the test, about 30 cm of the specimen was water saturated. A uni-dimensional numerical analysis was performed. The Tham model (non-saturated porous media thermo-hydro-mechanic) included in CodeAster[reg] was used. Two fluid phases can be considered in the material: a liquid phase (water) and a gas phase (dry air plus vapour) with the liquid/vapour phase changes. The thermodynamic aspects dealt with open systems framework, with temperature, capillary pressure and gas total pressure as variables. Observing the considered conditions (progressive saturation of the wall), the shape of sorption isotherm and permeabilities had an important influence on the results. The numerical results were in good agreement with experimental results, on the phenomenology and on flow rate through the wall. This study gave some indicators about the relations between airflow during a permeability test and gas (air + steam) flows during accident testing

228

Experimental determination of heat transfer critical conditions in water forced convection at low pressure in a circular channel  

International Nuclear Information System (INIS)

An experimental determination was made of heat transfer critical conditions in a circular channel, uniformly heated, and internally cooled by water in ascending forced convection, under a pressure slightly above atmospheric pressure. Measurements were made of water flow, pressure, electric power temperature and heating, and a systematic analysis was made of the system's parameters. The values obtained for the heat critical flux are circa 50% lower than those predicted by Becker and Biasi and this is accounted to flowing instabilities of thermo-hydrodynamic nature. It is suggested that the flowing channels of circuits aiming at the study of the boiling crisis phenomenon be expanded in its upper extremity, and that the coolant circulation be kept through a pump with a pressure X flow characteristic as vertical as possible

229

Multiple uncontrolled conditions and blood pressure medication intensification: an observational study  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Multiple uncontrolled medical conditions may act as competing demands for clinical decision making. We hypothesized that multiple uncontrolled cardiovascular risk factors would decrease blood pressure (BP medication intensification among uncontrolled hypertensive patients. Methods We observed 946 encounters at two VA primary care clinics from May through August 2006. After each encounter, clinicians recorded BP medication intensification (BP medication was added or titrated. Demographic, clinical, and laboratory information were collected from the medical record. We examined BP medication intensification by presence and control of diabetes and/or hyperlipidemia. 'Uncontrolled' was defined as hemoglobin A1c ? for diabetes, BP ? 140/90 mmHg (? 130/80 mmHg if diabetes present for hypertension, and low density lipoprotein cholesterol (LDL-c ? 130 mg/dl (? 100 mg/dl if diabetes present for hyperlipidemia. Hierarchical regression models accounted for patient clustering and adjusted medication intensification for age, systolic BP, and number of medications. Results Among 387 patients with uncontrolled hypertension, 51.4% had diabetes (25.3% were uncontrolled and 73.4% had hyperlipidemia (22.7% were uncontrolled. The BP medication intensification rate was 34.9% overall, but higher in individuals with uncontrolled diabetes and uncontrolled hyperlipidemia: 52.8% overall and 70.6% if systolic BP ? 10 mmHg above goal. Intensification rates were lowest if diabetes or hyperlipidemia were controlled, lower than if diabetes or hyperlipidemia were not present. Multivariable adjustment yielded similar results. Conclusions The presence of uncontrolled diabetes and hyperlipidemia was associated with more guideline-concordant hypertension care, particularly if BP was far from goal. Efforts to understand and improve BP medication intensification in patients with controlled diabetes and/or hyperlipidemia are warranted.

Halanych Jewell H

2010-07-01

230

Flow Control Under Low-Pressure Turbine Conditions Using Pulsed Jets  

Science.gov (United States)

This publication is the final report of research performed under an NRA/Cooperative Interagency Agreement, and includes a supplemental CD-ROM with detailed data. It is complemented by NASA/CR-2012-217416 and NASA/CR-2012-217417 which include a Ph.D. Dissertation and an M.S. thesis respectively, performed under this contract. In this study the effects of unsteady wakes and flow control using vortex generator jets (VGJs) were studied experimentally and computationally on the flow over the L1A low pressure turbine (LPT) airfoil. The experimental facility was a six passage linear cascade in a low speed wind tunnel at the U.S. Naval Academy. In parallel, computational work using the commercial code FLUENT (ANSYS, Inc.) was performed at Cleveland State University, using Unsteady Reynolds Averaged Navier Stokes (URANS) and Large Eddy Simulations (LES) methods. In the first phase of the work, the baseline flow was documented under steady inflow conditions without flow control. URANS calculations were done using a variety of turbulence models. In the second phase of the work, flow control was added using steady and pulsed vortex generator jets. The VGJs successfully suppressed separation and reduced aerodynamic losses. Pulsed operation was more effective and mass flow requirements are very low. Numerical simulations of the VGJs cases showed that URANS failed to capture the effect of the jets. LES results were generally better. In the third phase, effects of unsteady wakes were studied. Computations with URANS and LES captured the wake effect and generally predicted separation and reattachment to match the experiments. Quantitatively the results were mixed. In the final phase of the study, wakes and VGJs were combined and synchronized using various timing schemes. The timing of the jets with respect to the wakes had some effect, but in general once the disturbance frequency was high enough to control separation, the timing was not very important.

Volino, Ralph J.; Ibrahim, Mounir B.

2012-01-01

231

Photochemical modelling of the Barcelona area under weak pressure synoptic summer conditions  

International Nuclear Information System (INIS)

This city of Barcelona and its surrounding area, located in the western Mediterranean basin, can reach high levels of O3 in summertime under weak pressure synoptic conditions. To study the origin of this photochemical pollution, the episode that took place between the 3 and 5 August 1990 was chosen. The main meteorological mesoscale flows that take place in the region, such as sea and land breeze, convection cells and topographic injections, were reproduced with the meteorological non-hydrostatic mesoscale model MEMO for 5 August 1990. Industrial and commercial activity on 5 August 1990 was very low because it was a Sunday in the summer holiday period. Therefore, the emissions inventory calculated for this day in an area of 80x80 km2 around Barcelona showed that the main sources of VOC were traffic (51%) and vegetation (34%), while NOx were mostly emitted by traffic (88%). Photochemical simulation with the MARS model has shown that the combination of mesoscale circulations and local emissions is crucial in the production of O3. For instance, NOx inland transport towards regions where biogenic VOC are emitted causes the formation of O3, while topographic injections cause the formation of elevated O3 air layers. The synoptic wind, coming from the northeast in this case, also played an important role in advecting the air masses with local generated O3 away from their precursor emissio>3 away from their precursor emission sources. Evaluation of the model simulations is also performed and discussed by means of comparison of meteorological measurements in 9 surface stations and concentration measurements in 5 surface stations. (Author)

232

Optimization of hydrostatic pressure at varied sonication conditions - power density, intensity, very low frequency - for isothermal ultrasonic sludge treatment.  

Science.gov (United States)

This work aims at investigating for the first time the key sonication (US) parameters: power density (DUS), intensity (IUS), and frequency (FS) - down to audible range, under varied hydrostatic pressure (Ph) and low temperature isothermal conditions (to avoid any thermal effect). The selected application was activated sludge disintegration, a major industrial US process. For a rational approach all comparisons were made at same specific energy input (ES, US energy per solid weight) which is also the relevant economic criterion. The decoupling of power density and intensity was obtained by either changing the sludge volume or most often by changing probe diameter, all other characteristics being unchanged. Comprehensive results were obtained by varying the hydrostatic pressure at given power density and intensity. In all cases marked maxima of sludge disintegration appeared at optimum pressures, which values increased at increasing power intensity and density. Such optimum was expected due to opposite effects of increasing hydrostatic pressure: higher cavitation threshold then smaller and fewer bubbles, but higher temperature and pressure at the end of collapse. In addition the first attempt to lower US frequency down to audible range was very successful: at any operation condition (DUS, IUS, Ph, sludge concentration and type) higher sludge disintegration was obtained at 12kHz than at 20kHz. The same values of optimum pressure were observed at 12 and 20kHz. At same energy consumption the best conditions - obtained at 12kHz, maximum power density 720W/L and 3.25bar - provided about 100% improvement with respect to usual conditions (1bar, 20kHz). Important energy savings and equipment size reduction may then be expected. PMID:25199444

Delmas, Henri; Le, Ngoc Tuan; Barthe, Laurie; Julcour-Lebigue, Carine

2015-07-01

233

Navier-Stokes equations with periodic boundary conditions and pressure loss  

OpenAIRE

We present in this note the existence and uniqueness results for the Stokes and Navier-Stokes equations which model the laminar flow of an incompressible fluid inside a two-dimensional channel of periodic sections. The data of the pressure loss coefficient enables us to establish a relation on the pressure and to thus formulate an equivalent problem.

Amrouche, Che?rif; Batchi, Macaire; Batina, Jean

2007-01-01

234

Local charge transport properties of hydrazine reduced monolayer graphene oxide sheets prepared under pressure condition  

International Nuclear Information System (INIS)

Charge transport properties of chemically reduced graphene oxide (RGO) sheets prepared by treatment with hydrazine were examined using conductive atomic force microscopy. The current-voltage (I-V) characteristics of monolayer RGO sheets prepared under atmospheric pressure followed an exponentially increase due to 2D variable-range hopping conduction through small graphene domains in an RGO sheet containing defect regions of residual sp3 carbon clusters bonded to oxygen groups, whereas RGO sheets prepared in a closed container under moderate pressure showed linear I-V characteristics with a conductivity of 267.2?537.5?S/m. It was found that the chemical reduction under pressure results in larger graphene domains (sp2 networks) in the RGO sheets when compared to that prepared under atmospheric pressure, indicating that the present reduction of GO sheets under the pressure is one of the effective methods to make well-reduced GO sheets.

235

Local charge transport properties of hydrazine reduced monolayer graphene oxide sheets prepared under pressure condition  

DEFF Research Database (Denmark)

Charge transport properties of chemically reduced graphene oxide (RGO) sheets prepared by treatment with hydrazine were examined using conductive atomic force microscopy. The current-voltage (I-V) characteristics of monolayer RGO sheets prepared under atmospheric pressure followed an exponentially increase due to 2D variable-range hopping conduction through small graphene domains in an RGO sheet containing defect regions of residual sp3carbon clusters bonded to oxygen groups, whereas RGO sheets prepared in a closed container under moderate pressure showed linear I-V characteristics with a conductivity of 267.2-537.5S/m. It was found that the chemical reduction under pressure results in larger graphene domains (sp2networks) in the RGO sheets when compared to that prepared under atmospheric pressure, indicating that the present reduction of GO sheets under the pressure is one of the effective methods to make well-reduced GO sheets.

Ryuzaki, Sou; Meyer, Jakob Abild Stengaard

2014-01-01

236

Local charge transport properties of hydrazine reduced monolayer graphene oxide sheets prepared under pressure condition  

Science.gov (United States)

Charge transport properties of chemically reduced graphene oxide (RGO) sheets prepared by treatment with hydrazine were examined using conductive atomic force microscopy. The current-voltage (I-V) characteristics of monolayer RGO sheets prepared under atmospheric pressure followed an exponentially increase due to 2D variable-range hopping conduction through small graphene domains in an RGO sheet containing defect regions of residual sp3 carbon clusters bonded to oxygen groups, whereas RGO sheets prepared in a closed container under moderate pressure showed linear I-V characteristics with a conductivity of 267.2-537.5 S/m. It was found that the chemical reduction under pressure results in larger graphene domains (sp2 networks) in the RGO sheets when compared to that prepared under atmospheric pressure, indicating that the present reduction of GO sheets under the pressure is one of the effective methods to make well-reduced GO sheets.

Ryuzaki, Sou; Meyer, Jakob A. S.; Petersen, Søren; Nørgaard, Kasper; Hassenkam, Tue; Laursen, Bo W.

2014-09-01

237

Local charge transport properties of hydrazine reduced monolayer graphene oxide sheets prepared under pressure condition  

Energy Technology Data Exchange (ETDEWEB)

Charge transport properties of chemically reduced graphene oxide (RGO) sheets prepared by treatment with hydrazine were examined using conductive atomic force microscopy. The current-voltage (I-V) characteristics of monolayer RGO sheets prepared under atmospheric pressure followed an exponentially increase due to 2D variable-range hopping conduction through small graphene domains in an RGO sheet containing defect regions of residual sp{sup 3} carbon clusters bonded to oxygen groups, whereas RGO sheets prepared in a closed container under moderate pressure showed linear I-V characteristics with a conductivity of 267.2?537.5?S/m. It was found that the chemical reduction under pressure results in larger graphene domains (sp{sup 2} networks) in the RGO sheets when compared to that prepared under atmospheric pressure, indicating that the present reduction of GO sheets under the pressure is one of the effective methods to make well-reduced GO sheets.

Ryuzaki, Sou, E-mail: ryuzaki.soh.341@m.kyushu-u.ac.jp; Meyer, Jakob A. S.; Petersen, Søren; Nørgaard, Kasper; Hassenkam, Tue; Laursen, Bo W. [Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetparken 5, 2100 Københaven Ø (Denmark)

2014-09-01

238

Volume based vs. time based chromatograms: reproducibility of data for gradient separations under high and low pressure conditions.  

Science.gov (United States)

A critical aspect in fast gradient separations carried out under constant pressure, in the very high pressure liquid chromatography (VHPLC) mode is that time-based chromatograms may not yield highly reproducible separations. A proposed solution to improve the reproducibility of these separations involves plotting the chromatograms as functions of the volume eluted vs. UV absorbance instead of time vs. UV. To study the consequences of using the volume-based rather than the time-based chromatograms, separations were first performed under low pressures that do not generate significant amounts of heat and for which the variations of the eluent density along the columns are negligible. Secondly, they were performed under very high pressures that do generate heat and measurable variations of the local retention factor and eluent density along the column. Comparison of the results provides estimates of the improvements obtained when volume based chromatograms are used in gradient analyses. Using a column packed with fully porous particles, four different types of methods and several sets for each method were used to perform the gradient elution runs: two sets of constant flow rate operations, four sets of constant pressure operations, two sets of constant pressure operations with programmed flow rate, and one set using the constant heat loss approach. The differences between time-based and volume-based chromatograms are demonstrated by using eight replicates of early, middle, and last eluting peaks. The results show that volume-based chromatograms improve the retention time reproducibility of the four constant pressure methods by a factor of 3.7 on average. If the column is not thermally conditioned prior to performing a long series of separations, flow controlled methods (constant flow rate, programmed constant pressure, and constant wall heat approaches) are more precise. If one gradient run is used to bring the column to a relatively stable temperature, constant pressure separations have a factor of 3 times better reproducibility of retention times with respect to constant flow rate gradient separations. PMID:24717849

Stankovich, Joseph J; Gritti, Fabrice; Stevenson, Paul G; Vajda, Péter; Beaver, Lois Ann; Guiochon, Georges

2014-05-23

239

The Effects of Temperature, Pressure, and Humidity Variations on 100 Meter Sprint Performances  

CERN Document Server

It is well known that ``equivalent'' sprint race times run with different accompanying wind speeds or at different altitudes are anything but equivalent races. The drag force acting on a sprinter is a function of air density and the relative wind speed, where the former has traditionally been calculated using the race venue's elevation above sea level. However, air density variation is dependent on more than just altitude. This work will quantify how changes in air temperature, barometric pressure, and humidity levels influence 100 m sprint performances. When these effects are considered in combination, the corrections to performances can be very large. The results suggest that a non-negligible difference in race times can be expected for ``equivalent'' performances run with the same wind speed at the same venue or physical altitude, but under different atmospheric conditions.

Mureika, J R

2005-01-01

240

Transient behavior of pressure and wall temperature in water flow in a tube under flow reduction conditions  

International Nuclear Information System (INIS)

Flow reduction transient boiling phenomena have been studied in vertical up-flow of water in a tube under an atmospheric pressure to provide information on the transient thermal-hydraulic behavior of a LWR core during Power Cooling Mismatch (PCM) conditions. The electrically heated test section was stainless steel tube 8 mm in diameter and 800 mm long. Experiment was conducted under the conditions; inlet water temperature = 30 -- 800C heat flux = 0.54 -- 1.1 x 106 kcal/hm2, initial mass velocity=3.6 -- 8.4 x 106 kg/hm2, and flow reduction time = 0.05 -- 62 sec. According to the observed behavior of the pressure and wall temperature, the flow reduction transient boiling phenomena are similar to those in the steady-state boiling at flow reduction rates below about 10cm/sec/sec under the ranges of experimental conditions. (auth.)

241

Effect of Normal Operating Condition Analysis Method for Weld Residual Stress of CD-ROM Nozzle in Reactor Pressure Vessel  

International Nuclear Information System (INIS)

In pressurized water nuclear reactors (PWRs), the reactor pressure vessel (RSV) upper head contains penetration nozzles that use a control rod drive mechanism (CD-ROM). The penetration nozzle uses J-groove weld geometry. Recently, the occurrence of cracking in alloy 600 CD-ROM penetration nozzle has increased. This is attributable to primary water stress corrosion cracking (PWSCC). PWSCC is known to be susceptible to the welding residual stress and operational stress. Generally, the tensile residual stress is the main factor contributing to crack growth. Therefore, this study investigates the effect on weld residual stress through different analysis methods for normal operating conditions using finite element analysis. In addition, this study also considers the effect of repeated normal operating condition cycles on the weld residual stress. Based on the analysis result, this paper presents a normal operating condition analysis method

242

Effect of Normal Operating Condition Analysis Method for Weld Residual Stress of CD-ROM Nozzle in Reactor Pressure Vessel  

Energy Technology Data Exchange (ETDEWEB)

In pressurized water nuclear reactors (PWRs), the reactor pressure vessel (RSV) upper head contains penetration nozzles that use a control rod drive mechanism (CD-ROM). The penetration nozzle uses J-groove weld geometry. Recently, the occurrence of cracking in alloy 600 CD-ROM penetration nozzle has increased. This is attributable to primary water stress corrosion cracking (PWSCC). PWSCC is known to be susceptible to the welding residual stress and operational stress. Generally, the tensile residual stress is the main factor contributing to crack growth. Therefore, this study investigates the effect on weld residual stress through different analysis methods for normal operating conditions using finite element analysis. In addition, this study also considers the effect of repeated normal operating condition cycles on the weld residual stress. Based on the analysis result, this paper presents a normal operating condition analysis method.

Nam, Hyun Suk; Bae, Hong Yeol; Oh, Chang Young; Kim, Ji Soo; Kim, Yun Jae [Korea Univ., Seoul (Korea, Republic of)

2013-09-15

243

Real-Time Optical Monitoring of Flow Kinetics and Gas Phase Reactions Under High-Pressure OMCVD Conditions  

Science.gov (United States)

This contribution addresses the real-time optical characterization of gas flow and gas phase reactions as they play a crucial role for chemical vapor phase depositions utilizing elevated and high pressure chemical vapor deposition (HPCVD) conditions. The objectives of these experiments are to validate on the basis of results on real-time optical diagnostics process models simulation codes, and provide input parameter sets needed for analysis and control of chemical vapor deposition at elevated pressures. Access to microgravity is required to retain high pressure conditions of laminar flow, which is essential for successful acquisition and interpretation of the optical data. In this contribution, we describe the design and construction of the HPCVD system, which include access ports for various optical methods of real-time process monitoring and to analyze the initial stages of heteroepitaxy and steady-state growth in the different pressure ranges. To analyze the onset of turbulence, provisions are made for implementation of experimental methods for in-situ characterization of the nature of flow. This knowledge will be the basis for the design definition of experiments under microgravity, where gas flow conditions, gas phase and surface chemistry, might be analyzed by remote controlled real-time diagnostics tools, developed in this research project.

Dietz, N.; McCall, S.; Bachmann, K. J.

2001-01-01

244

Effects of surface conditions on transient pool boiling CHF in various liquids with different mechanisms depending on pressure and subcooling  

International Nuclear Information System (INIS)

Many aspects of saturated and subcooled pool boiling CHF have been investigated by many researchers for pressure, subcooling, test heater configurations, surface conditions, thermal properties, etc., assuming a CHF model mainly based on a kind of hydrodynamic instability at CHF. Recently the saturated and subcooled pool boiling CHF for a horizontal cylinder in water and wetting liquids such as liquid nitrogen, liquid helium etc. were measured for comparatively wide ranges of pressure and subcooling. It was clarified that the CHFs measured were mainly divided into two mechanisms for lower and higher subcooling at a pressure as a typical case. It was assumed that the former and latter CHFs occur due to hydrodynamic instability (HI) and explosive-like heterogeneous spontaneous nucleation (HSN) on the cylinder surface respectively though the CHFs for subcooling occur only due to the HI or only due to the HSN depending on subcooling, pressure and liquid. In this paper, it was clarified that the trend of CHF for the short periods is significantly affected by the test cylinder surface conditions in a pool of water, ethanol and FC-72. This paper suggests that more study on the effect of the cylinder surface condition on the transient CHF is necessary. (authors)

245

A flow and pressure distribution of APR+ reactor under 4-pump running conditions with a balanced flow rate  

International Nuclear Information System (INIS)

In order to quantify the flow distribution characteristics of APR+ reactor, a test was performed on a test facility, ACOP (APR+ Core Flow and Pressure Test Facility), having a length scale of 1/5 referring to the prototype plant. The major parameters are core inlet flow and outlet pressure distribution and sectional pressure drops along the major flow path inside reactor vessel. To preserve the flow characteristics of prototype plant, the test facility was designed based on a preservation of major flow path geometry. An Euler number is considered as primary dimensionless parameter, which is conserved with a 1/40.9 of Reynolds number scaling ratio. ACOP simplifies each fuel assembly into a hydraulic simulator having the same axial flow resistance and lateral cross flow characteristics. In order to supply boundary condition to estimate thermal margins of the reactor, the distribution of inlet core flow and core exit pressure were measured in each of 257 fuel assembly simulators. In total, 584 points of static pressure and differential pressures were measured with a limited number of differential pressure transmitters by developing a sequential operation system of valves. In the current study, reactor flow characteristics under the balanced four cold leg flow conditions at each of the cold legs were quantified, which is a part of the test matrix composing the APR+ flow distribution test program. The final identification of the reactor flow distribution was obtained by enactor flow distribution was obtained by ensemble averaging 15 independent test data. The details of the design of the test facility, experiment, and data analysis are included in the current paper.

246

EXAFS measurements under high pressure conditions using a combination of a diamond anvil cell and synchrotron radiation  

International Nuclear Information System (INIS)

EXAFS spectra for Fe, Co, Ni K-edges were successfully measured under high pressure conditions using a combination of a set of normal 1/8 carat diamond anvils, synchrotron radiation and a scintillation counter. A newly developed motor controlled goniometer stage was used for adjusting the position of a miniature diamond anvil cell. On the measurement of Cr and Mn spectra, specially designed thinner diamond anvil was necessary. EXAFS analysis of bis(dimethylglyoximato)nickel(II) at pressures from 1 atm to 5.6 GPa was made. (author)

247

Osmosis-induced water uptake by Eurobitum bituminized radioactive waste and pressure development in constant volume conditions  

Energy Technology Data Exchange (ETDEWEB)

Highlights: Black-Right-Pointing-Pointer The water uptake by Eurobitum is studied to judge the safety of geological disposal. Black-Right-Pointing-Pointer High pressures of up to 20 MPa are measured in constant volume water uptake tests. Black-Right-Pointing-Pointer The morphology of leached Eurobitum samples is studied with {mu}CT and ESEM. Black-Right-Pointing-Pointer The observations are reproduced by an existing CHM formulation for Eurobitum. - Abstract: The chemo-hydro-mechanical (CHM) interaction between swelling Eurobitum radioactive bituminized waste (BW) and Boom Clay is investigated to assess the feasibility of geological disposal for the long-term management of this waste. These so-called compatibility studies include laboratory water uptake tests at Belgian Nuclear Research Center SCK-CEN, and the development of a coupled CHM formulation for Eurobitum by the International Center for Numerical Methods and Engineering (CIMNE, Polytechnical University of Cataluna, Spain). In the water uptake tests, the osmosis-induced swelling, pressure increase and NaNO{sub 3} leaching of small cylindrical BW samples (diameter 38 mm, height 10 mm) is studied under constant total stress conditions and nearly constant volume conditions; the actual geological disposal conditions should be intermediate between these extremes. Two nearly constant volume tests were stopped after 1036 and 1555 days to characterize the morphology of the hydrated BW samples and to visualize the hydrated part with microfocus X-ray Computer Tomography ({mu}CT) and Environmental Scanning Electron Microscopy (ESEM). In parallel, a coupled CHM formulation is developed that describes chemically and hydraulically coupled flow processes in porous materials with salt crystals, and that incorporates a porosity dependent membrane efficiency, permeability and diffusivity. When Eurobitum BW is hydrated in (nearly) constant volume conditions, the osmosis-induced water uptake results in an increasing pressure to values that can be (in theory) as high as 42.8 MPa, being the osmotic pressure of a saturated NaNO{sub 3} solution. After about four years of hydration in nearly constant volume water uptake tests, pressures up to 20 MPa are measured. During this hydration period only the outer layers with a thickness of 1-2 mm were hydrated (as derived from {mu}CT and ESEM analyses), and only about 10-20% of the initial NaNO{sub 3} content was released by the samples. In the studied test conditions, the rates of water uptake and NaNO{sub 3} leaching are low because of the low porosity, and thus low permeability, of the hydrated BW samples in combination with a highly efficient semi-permeable bitumen membrane. In contrast to the hydration in free swelling conditions, the increase in porosity is limited by the high pressures in the nearly constant volume tests. Furthermore, at the interface with the stainless steel filters, a low permeable re-compressed bitumen layer is formed, as observed on the ESEM images. The experimental results of pressure increase and NaNO{sub 3} leaching, as well as observations on {mu}CT and ESEM images (e.g. compression of leached layers, high dissolved NaNO{sub 3} concentration in hydrated BW after about four years), were reproduced rather successfully by the coupled CHM formulation for Eurobitum BW. A long-term model prediction of the evolution of the osmosis-induced pressure in the nearly constant volume tests shows that the pressure would reach a maximal value of about 20 MPa after about 5.5 years, after which the pressure would start to decrease. After 10,000 days ({approx}27 years) the pressure would have decreased to a value of {approx}2 MPa.

Marieen, A., E-mail: amarien@sckcen.be [Waste and Disposal Expert Group, Belgian Nuclear Research Centre (SCK-CEN), Boeretang 200, 2400 Mol (Belgium); Mokni, N., E-mail: Nadia.mokni@upc.edu [Department of Geotechnical Engineering and Geosciences, Universidad Politecnica de Catalunya (UPC), Calle Gran Capitan, s/n, Edificio C-1, 08034 Barcelona (Spain); Valcke, E. [Waste and Disposal Expert Group, Belgian Nuclear Research Centre (SCK-CEN), Boeretang 200, 2400 Mol (Belgium); Olivella, S. [Department of Geotechnical Engineering and Geosciences, Universidad Politecnica de Catalunya (UPC), Calle Gran Capitan, s/n, Edificio C-1, 08034 Barcelona (Spain); Smets, S. [Waste and Disposal Expert Group, Belgian Nuclear Research Centre (SCK-CEN), Boeretang 200, 2400 Mol (Belgium); Li, X., E-mail: xli@sckcen.be [EIG EURIDICE, Boeretang 200, 2400 Mol (Belgium)

2013-01-15

248

Osmosis-induced water uptake by Eurobitum bituminized radioactive waste and pressure development in constant volume conditions  

International Nuclear Information System (INIS)

Highlights: ? The water uptake by Eurobitum is studied to judge the safety of geological disposal. ? High pressures of up to 20 MPa are measured in constant volume water uptake tests. ? The morphology of leached Eurobitum samples is studied with ?CT and ESEM. ? The observations are reproduced by an existing CHM formulation for Eurobitum. - Abstract: The chemo-hydro-mechanical (CHM) interaction between swelling Eurobitum radioactive bituminized waste (BW) and Boom Clay is investigated to assess the feasibility of geological disposal for the long-term management of this waste. These so-called compatibility studies include laboratory water uptake tests at Belgian Nuclear Research Center SCK-CEN, and the development of a coupled CHM formulation for Eurobitum by the International Center for Numerical Methods and Engineering (CIMNE, Polytechnical University of Cataluña, Spain). In the water uptake tests, the osmosis-induced swelling, pressure increase and NaNO3 leaching of small cylindrical BW samples (diameter 38 mm, height 10 mm) is studied under constant total stress conditions and nearly constant volume conditions; the actual geological disposal conditions should be intermediate between these extremes. Two nearly constant volume tests were stopped after 1036 and 1555 days to characterize the morphology of the hydrated BW samples and to visualize the hydrated part with microfocus X-ray Computer Tomography (?CT) and Environmental Scanning Electron Miironmental Scanning Electron Microscopy (ESEM). In parallel, a coupled CHM formulation is developed that describes chemically and hydraulically coupled flow processes in porous materials with salt crystals, and that incorporates a porosity dependent membrane efficiency, permeability and diffusivity. When Eurobitum BW is hydrated in (nearly) constant volume conditions, the osmosis-induced water uptake results in an increasing pressure to values that can be (in theory) as high as 42.8 MPa, being the osmotic pressure of a saturated NaNO3 solution. After about four years of hydration in nearly constant volume water uptake tests, pressures up to 20 MPa are measured. During this hydration period only the outer layers with a thickness of 1–2 mm were hydrated (as derived from ?CT and ESEM analyses), and only about 10–20% of the initial NaNO3 content was released by the samples. In the studied test conditions, the rates of water uptake and NaNO3 leaching are low because of the low porosity, and thus low permeability, of the hydrated BW samples in combination with a highly efficient semi-permeable bitumen membrane. In contrast to the hydration in free swelling conditions, the increase in porosity is limited by the high pressures in the nearly constant volume tests. Furthermore, at the interface with the stainless steel filters, a low permeable re-compressed bitumen layer is formed, as observed on the ESEM images. The experimental results of pressure increase and NaNO3 leaching, as well as observations on ?CT and ESEM images (e.g. compression of leached layers, high dissolved NaNO3 concentration in hydrated BW after about four years), were reproduced rather successfully by the coupled CHM formulation for Eurobitum BW. A long-term model prediction of the evolution of the osmosis-induced pressure in the nearly constant volume tests shows that the pressure would reach a maximal value of about 20 MPa after about 5.5 years, after which the pressure would start to decrease. After 10,000 days (?27 years) the pressure would have decreased to a value of ?2 MPa.

249

A pressure correction scheme for generalized form of energy-stable open boundary conditions for incompressible flows  

CERN Document Server

We present a generalized form of open boundary conditions, and an associated numerical algorithm, for simulating incompressible flows involving open or outflow boundaries. The generalized form represents a family of open boundary conditions, which all ensure the energy stability of the system, even in situations where strong vortices or backflows occur at the open/outflow boundaries. Our numerical algorithm for treating these open boundary conditions is based on a rotational pressure correction-type strategy, with a formulation suitable for $C^0$ spectral-element spatial discretizations. We have introduced a discrete equation and associated boundary conditions for an auxiliary variable. The algorithm contains constructions that prevent a numerical locking at the open/outflow boundary. In addition, we have also developed a scheme with a provable unconditional stability for a sub-class of the open boundary conditions. Extensive numerical experiments have been presented to demonstrate the performance of our meth...

Dong, Suchuan

2014-01-01

250

Evaluation of environmentally-assisted cracking in the simulated PWR primary water conditions for pressure vessel and piping materials  

International Nuclear Information System (INIS)

Two pressure vessel steels (A533 Gr.B, cl.1 and A508 cl.3) and high strength cast and forged stainless steels (CF8A and 316LN) which have been expected as the promising piping materials for PWR primary piping systems were evaluated concerning the reliability in the simulated PWR primary water conditions. Metallurgical and mechanical properties of these new materials lied completely within the specifications. Corrosion fatigue tests for the reactor pressure vessel steels and stress corrosion cracking tests for stainless steels were performed in simulated PWR high temperature water environment. The results are sammarized as follows: (1) Reactor Pressure Vessel Steels (A533B cl.1 and A508 cl.3). Both under air and high temperature water conditions, no significant difference of the fatigue crack growth rate was found in these steels. In comparison with the ASME reference curves in air, a little acceleration effect on crack growth rate in the water condition was observed in a certain stress intensity factor range (low ?K). This environmentally assisted crack growth rate could be negligible. (2) SCC Resistance of cast and forged Stainless Steels (CF8A and 316LN). Following three kinds of SCC tests, constant extention rate test, cyclic tensile test and constant load test were conducted. Even in the heavily sensitized stainless steels, no SCC was observed. These results indicate that CF8A and 316LN stainless steels have enough resistance against SCC in the PWR primary water nce against SCC in the PWR primary water condition. (author)

251

Re-investigation of the crystal structure of enstatite under high-pressure conditions  

DEFF Research Database (Denmark)

A synthetic single crystal of pure orthoenstatite (MgSiO3, space group Pbca) has been investigated at high pressure for structural determinations by in situ single-crystal X?ray diffraction using a diamond-anvil cell. Ten complete intensity data collections were performed up to 9.36 GPa. This study significantly improved the accuracy of structural parameters in comparison to a previous high-pressure structural study, allowing a more detailed examination of structural behavior of orthoenstatite at high pressures and a comparison to other more recent structural studies performed on orthopyroxenes with different compositions. The structural evolution determined in this work confirms the high-pressure evolution found previously for other orthopyroxenes and removes some ambiguities originating from the less accurate published data on the MgSiO3 structure at high pressure. The structural compression is mostly governed by significant volume decrease of the Mg1 and Mg2 octahedra, affecting in turn the kink of the tetrahedral chains, especially the TB chain of larger SiO4 tetrahedra. The Mg2 polyhedron undergoes the largest volume variation, 8.7%, due especially to the strong contraction of the longest bond distance (Mg2-O3B), whereas Mg1 polyhedral volume decreases by about 7.4%. The compressional behavior of the tetrahedral sites is quite different from previously published data. The TA and TB tetrahedral volumes decrease by about 2.8 and 1.8%, respectively, and no discontinuities can be observed in the pressure range investigated. Using the data on the pure orthoenstatite as reference, we can confirm the basic influences of element substitutions on the evolution of the crystal structure with pressure.

Periotto, Benedetta; Balic Zunic, Tonci

2012-01-01

252

Synthesis of novel Ru2C under high pressure-high temperature conditions  

International Nuclear Information System (INIS)

We report here, for the first time, synthesis of the Fe2N type hexagonal phase of ruthenium carbide by a high pressure-high temperature technique using a laser heated diamond anvil cell (LHDAC). The synthesis is carried out by laser heating a mixture of pure elements, Ru and C, at very low ‘pressure’ of 5 GPa and T ? 2000 K. The structure of the temperature quenched high pressure phase is characterized by in situ high pressure x-ray diffraction (HPXRD) and is corroborated by ex situ TEM imaging and diffraction, carried out for the first time on the retrieved sample synthesized by LHDAC. The lattice parameters of Ru2C at ambient pressure are found to be a = 2.534 ? and c = 4.147 ?. In situ HPXRD studies up to 14.2 GPa yield a bulk modulus of 178(4) GPa. Electronic structure calculations reveal the system to be metallic in nature with a degree of covalence along the Ru-C bond. As ruthenium is isoelectronic to osmium, this result for Ru2C has significant implications in the synthesis and study of osmium carbides.

253

Osmosis-induced water uptake by Eurobitum bituminized radioactive waste and pressure development in constant volume conditions  

Science.gov (United States)

The chemo-hydro-mechanical (CHM) interaction between swelling Eurobitum radioactive bituminized waste (BW) and Boom Clay is investigated to assess the feasibility of geological disposal for the long-term management of this waste. These so-called compatibility studies include laboratory water uptake tests at the Belgian Nuclear Research Center SCK•CEN, and the development of a coupled CHM formulation for Eurobitum by the International Center for Numerical Methods and Engineering (CIMNE, Polytechnical University of Cataluña, Spain). In the water uptake tests, the osmosis-induced swelling, pressure increase and NaNO3 leaching of small cylindrical BW samples (diameter 38 mm, height 10 mm) is studied under constant total stress conditions and nearly constant volume conditions; the actual geological disposal conditions should be intermediate between these extremes. Two nearly constant volume tests were stopped after 1036 and 1555 days to characterize the morphology of the hydrated BW samples and to visualize the hydrated part with microfocus X-ray Computer Tomography (?CT) and Environmental Scanning Electron Microscopy (ESEM). In parallel, a coupled CHM formulation is developed that describes chemically and hydraulically coupled flow processes in porous materials with salt crystals, and that incorporates a porosity dependent membrane efficiency, permeability and diffusivity. When Eurobitum BW is hydrated in (nearly) constant volume conditions, the osmosis-induced water uptake results in an increasing pressure to values that can be (in theory) as high as 42.8 MPa, being the osmotic pressure of a saturated NaNO3 solution. After about four years of hydration in nearly constant volume water uptake tests, pressures up to 20 MPa are measured. During this hydration period only the outer layers with a thickness of 1-2 mm were hydrated (as derived from ?CT and ESEM analyses), and only about 10-20% of the initial NaNO3 content was released by the samples. In the studied test conditions, the rates of water uptake and NaNO3 leaching are low because of the low porosity, and thus low permeability, of the hydrated BW samples in combination with a highly efficient semi-permeable bitumen membrane. In contrast to the hydration in free swelling conditions, the increase in porosity is limited by the high pressures in the nearly constant volume tests. Furthermore, at the interface with the stainless steel filters, a low permeable re-compressed bitumen layer is formed, as observed on the ESEM images. The experimental results of pressure increase and NaNO3 leaching, as well as observations on ?CT and ESEM images (e.g. compression of leached layers, high dissolved NaNO3 concentration in hydrated BW after about four years), were reproduced rather successfully by the coupled CHM formulation for Eurobitum BW. A long-term model prediction of the evolution of the osmosis-induced pressure in the nearly constant volume tests shows that the pressure would reach a maximal value of about 20 MPa after about 5.5 years, after which the pressure would start to decrease. After 10,000 days (˜27 years) the pressure would have decreased to a value of ˜2 MPa.

Mariën, A.; Mokni, N.; Valcke, E.; Olivella, S.; Smets, S.; Li, X.

2013-01-01

254

Volatilization of silicon dioxide under low-pressure electrical-discharge conditions  

Energy Technology Data Exchange (ETDEWEB)

This communication is concerned with certain questions associated with the heating and volatilization of SDO in a low-pressure electrical discharge, such as the time required for total volatilization of the material particles and the length of volatilizer/reactor needed for total volatilization of particles of a given size. It has been established that the factors determining the power balance during the volatilization of silicon dioxide in a low-pressure electrical discharge are the power supplied to the particles by electrons and ions from the discharge and the power removed by radiation. The possibility is shown of calculating the total time for volatilizing the particles by taking into account the effective (useful) power supplied to the particles from the low-pressure electrical discharge.

Gusev, A.V.; Eliseev, A.V.; Kalinkin, I.P.

1986-08-20

255

Linear and Nonlinear Viscoelastic Modeling of Aorta and Carotid Pressure-Area Dynamics under in vivo and ex vivo Conditions  

Science.gov (United States)

A better understanding of the biomechanical properties of the arterial wall provides important insight into arterial vascular biology under normal (healthy) and pathological conditions. This insight has potential to improve tracking of disease progression and to aid in vascular graft design and implementation. In this study, we use linear and nonlinear viscoelastic models to predict biomechanical properties of the thoracic descending aorta and the carotid artery under ex vivo and in vivo conditions in ovine and human arteries. Models analyzed include a four-parameter (linear) Kelvin viscoelastic model and two five-parameter nonlinear viscoelastic models (an arctangent and a sigmoid model) that relate changes in arterial blood pressure to the vessel cross-sectional area (via estimation of vessel strain). These models were developed using the framework of Quasilinear Viscoelasticity (QLV) theory and were validated using measurements from the thoracic descending aorta and the carotid artery obtained from human and ovine arteries. In vivo measurements were obtained from ten ovine aortas and ten human carotid arteries. Ex vivo measurements (from both locations) were made in eleven male Merino sheep. Biomechanical properties were obtained through constrained estimation of model parameters. To further investigate the parameter estimates we computed standard errors and confidence intervals and we used analysis of variance to compare results within and between groups. Overall, our results indicate that optimal model selection depends on the arterial type. Results showed that for the thoracic descending aorta (under both experimental conditions) the best predictions were obtained with the nonlinear sigmoid model, while under healthy physiological pressure loading the carotid arteries nonlinear stiffening with increasing pressure is negligible, and consequently, the linear (Kelvin) viscoelastic model better describes the pressure-area dynamics in this vessel. Results comparing biomechanical properties show that the Kelvin and sigmoid models were able to predict the zero-pressure vessel radius; that under ex vivo conditions vessels are more rigid, and comparatively, that the carotid artery is stiffer than the thoracic descending aorta; and that the viscoelastic gain and relaxation parameters do not differ significantly between vessels or experimental conditions. In conclusion, our study demonstrates that the proposed models can predict pressure-area dynamics and that model parameters can be extracted for further interpretation of biomechanical properties. PMID:21203846

Valdez-Jasso, Daniela; Bia, Daniel; Zócalo, Yanina; Armentano, Ricardo L.; Haider, Mansoor A.; Olufsen, Mette S.

2013-01-01

256

Multiphase Binary Mixture Flows in Porous Media in a Wide Pressure and Temperature Range Including Critical Conditions  

Science.gov (United States)

Multiphase flows in porous media with a transition between sub- and supercritical thermodynamic conditions occur in many natural and technological processes (e.g. in deep regions of geothermal reservoirs where temperature reaches critical point of water or in gas-condensate fields where subject to critical conditions retrograde condensation occurs and even in underground carbon dioxide sequestration processes at high formation pressure). Simulation of these processes is complicated due to degeneration of conservation laws under critical conditions and requires non-classical mathematical models and methods. A new mathematical model is proposed for efficient simulation of binary mixture flows in a wide range of pressures and temperatures that includes critical conditions. The distinctive feature of the model lies in the methodology for mixture properties determination. Transport equations and Darcy law are solved together with calculation of the entropy maximum that is reached in thermodynamic equilibrium and determines mixture composition. To define and solve the problem only one function - mixture thermodynamic potential - is required. Such approach allows determination not only single-phase states and two-phase states of liquid-gas type as in classical models but also two-phase states of liquid-liquid type and three-phase states. The proposed mixture model was implemented in MUFITS (Multiphase Filtration Transport Simulator) code for hydrodynamic simulations. As opposed to classical approaches pressure, enthalpy and composition variables together with fully implicit method and cascade procedure are used. The code is capable of unstructured grids, heterogeneous porous media, relative permeability and capillary pressure dependence on temperature and pressure, multiphase diffusion, optional number of sink and sources, etc. There is an additional module for mixture properties specification. The starting point for the simulation is a cubic equation of state that is used for mixture thermodynamic potential - entropy - calculation in pressure, enthalpy and composition variables. A polynomial spline is implemented to save the potential for subsequent hydrodynamic simulations. At this stage the majority of complicated thermodynamic procedures are performed prior to hydrodynamic that results in sufficient acceleration of calculations. The code was used for analysis of multiphase water-carbon dioxide mixture flows in porous media. Using the developed methodology the mixture phase diagram was calculated both below and above critical point of water. A zone of three-phase state conditions was detected where the mixture splits in three phases: liquid water and liquefied and gaseous carbon dioxide. The mixture flows subjected to formation of the three-phase flow region were investigated. The work is supported by Grant of the President of the Russian Federation (575.2010.1, 4810.2010.1).

Afanasyev, A.

2011-12-01

257

Conditional knockout of smooth muscle sodium calcium exchanger type-1 lowers blood pressure and attenuates Angiotensin II-salt hypertension.  

Science.gov (United States)

The functions of smooth muscle sodium calcium exchanger (NCX) in the vasculature are controversial and poorly understood. To determine the possible roles of NCX in the vascular phenotype and function, we developed a novel mouse model (SM-NCX1 KO) in which the smooth muscle-specific NCX type-1 (NCX1) was conditionally knocked out using tamoxifen-inducible Cre-loxP recombination technique. SM-NCX1 KO mice exhibit significantly lower blood pressure and attenuated angiotensin II (Ang II)-salt-induced hypertension (measured by radio telemetry and intra-arterial catheterization). Isolated, pressurized mesenteric small resistance arteries from SM-NCX1 KO mice, compared to control arteries, were characterized by the following: (1) ~90% reduced NCX1 protein expression; (2) impaired functional responses to (i) acute NCX inhibition by SEA0400 or SN-6, (ii) NCX activation by low [Na(+)]o, and (iii) Na(+) pump inhibition by ouabain; (3) attenuated myogenic reactivity; and (4) attenuated vasoconstrictor response to phenylephrine but not Ang II. These results provided direct evidence that arterial NCX1 normally mediates net Ca(2+) influx that helps maintain basal vascular tone in small resistance arteries and blood pressure under physiological conditions. Importantly, NCX1 contributes to blood pressure elevation in Ang II-salt hypertension, possibly by regulating ?-adrenergic receptor activation. PMID:25626872

Wang, Youhua; Chen, Ling; Li, Meng; Cha, Helen; Iwamoto, Takahiro; Zhang, Jin

2015-01-01

258

A Computational Fluid Dynamics Study of Transitional Flows in Low-Pressure Turbines under a Wide Range of Operating Conditions  

Science.gov (United States)

A transport equation for the intermittency factor is employed to predict the transitional flows in low-pressure turbines. The intermittent behavior of the transitional flows is taken into account and incorporated into computations by modifying the eddy viscosity, mu(sub p) with the intermittency factor, gamma. Turbulent quantities are predicted using Menter's two-equation turbulence model (SST). The intermittency factor is obtained from a transport equation model which can produce both the experimentally observed streamwise variation of intermittency and a realistic profile in the cross stream direction. The model had been previously validated against low-pressure turbine experiments with success. In this paper, the model is applied to predictions of three sets of recent low-pressure turbine experiments on the Pack B blade to further validate its predicting capabilities under various flow conditions. Comparisons of computational results with experimental data are provided. Overall, good agreement between the experimental data and computational results is obtained. The new model has been shown to have the capability of accurately predicting transitional flows under a wide range of low-pressure turbine conditions.

Suzen, Y. B.; Huang, P. G.; Ashpis, D. E.; Volino, R. J.; Corke, T. C.; Thomas, F. O.; Huang, J.; Lake, J. P.; King, P. I.

2007-01-01

259

Conditions of pressure scanning of a Fabry-Perot interferometer over a wide spectrum range.  

Science.gov (United States)

The association of a Michelson interferometer and a Fabry-Perot etalon enables the control of the displacement of the peaks of Fabry-Perot transmittance by pressure scanning through Michelson fringes counting. Assuming the variations of the refractive index of gas as a function of wavenumber, pressure, and temperature are known, we show that it is perfectly possible to compute the number of fringes to shift in order to position a chosen peak of Fabry-Perot transmittance for any point in the spectrum. These possibilities enable us to build a real spectrometer whose accuracy is better than 0.05 cm(-1) in the whole visible range. PMID:20168884

Helbert, J M; Laforie, P; Miche, P

1977-08-01

260

Pressure effect on nitrogen boiling heat transfer in conditions of natural convection in an annular channel  

International Nuclear Information System (INIS)

The study is made of boiling heat transfer at natural convection of nitrogen in a vertical annular channel with the gap from 0.14 to 3.5 mm at pressures from 1.25x104 to 9x105 Pa. The data are obtained of the pressure effect on the boiling crisis characteristics and heat transfer coefficients. The relationship is established between the gap boundary value complying with the onset of the 'enhanced' heat transfer and the value of the bubble departure diameter for boiling of various liquids, such as nitrogen, helium, water, ethanol and freon

261

Crack growth morphology in real pressure vessel and in small scale specimen under LWR condition  

International Nuclear Information System (INIS)

Thermal shock experiments are conducted in the full scale pressure vessel of the decommissioned HDR plant in the FRG. Cyclic crack growth calculations done were based on the application of the ASME Section XI curve so far. To confirm results of theoretical analysis cyclic crack growth studies have been carried out in simulated autoclave environment. In this paper fractography and crack growth results obtained by CT-specimens in autoclaves are presented and comparisons to the crack growth morphology in the HDR reactor pressure vessel are made and discussed. (orig.)

262

Feasibility of laser-induced plasma spectroscopy for measurements of equivalence ratio in high-pressure conditions  

Energy Technology Data Exchange (ETDEWEB)

In this paper, experimental results obtained with laser-induced plasma spectroscopy to retrieve local compositions are presented for an ambient pressure up to 5.0 MPa in a still cell. Well-controlled mixtures of gases are introduced and plasma is obtained with the fundamental emission of a pulsed Nd:YAG laser. Simultaneously, plasma shape and spectrally resolved data are taken with a temporal resolution down to 2 ns. First, the temporal evolutions of a high-pressure nitrogen plasma are analyzed as function of spark energy. It is shown that plasma changes orientation from an elongated shape parallel to the laser line to a perpendicular one in a very short time. Results are reported for both spatial and spectral variations. Afterward, the effects of increased carbon concentration are discussed in both shape and spectra. It is seen that strong intensity due to the atomic carbon emissions appear for the high-pressure case. From those experiments, calibration strategies are proposed to get equivalence ratio under high-pressure conditions with a ratio of carbon versus nitrogen and oxygen. The delay between plasma and measurements is set to 2,000 ns and the signal is integrated for 5,000 ns, so as to yield a good signal to noise ratio and a good sensitivity of the technique to changes in mixture fraction. Calibration curves are reported for equivalence ratio up to 1.00 and for pressure from 1.0 to 5.0 MPa. It is shown that typical uncertainties are limited to 7.5% regardless the equivalence ratio in a single shot approach using a spectral fit procedure, whereas it accounts to two times more in a more classical peak ratio approach. Increasing the pressure tends to increase the precision as lower pressure had higher uncertainties. (orig.)

Zimmer, Laurent [CNRS, UPR 288 Laboratoire d' Energetique Moleculaire et Macroscopique, Combustion (EM2C) Grande Voie des Vignes, Chatenay-Malabry (France); Ecole Centrale Paris, Grande Voie des Vignes, Chatenay-Malabry (France); Yoshida, Seiji [Japan Aerospace Exploration Agency, Chofu (Japan)

2012-04-15

263

Crack growth behaviour of low-alloy steels for pressure boundary components under transient light water reactor operating conditions - CASTOC, Part I: BWR/NWC conditions  

Energy Technology Data Exchange (ETDEWEB)

One of the ageing phenomena of pressure boundary components of light water reactors (LWR) is environmentally-assisted cracking (EAC). The project CASTOC (5. Framework Programme of the EU) was launched September 2000 with six European partners and terminated August 2003. It was focused in particular on the EAC behaviour of low-alloy steels (LAS) and to some extent to weld metal, heat affected zone and the influence of an austenitic cladding. The main objective was directed to the clarification of EAC crack growth behaviour/mechanism of LAS in high-temperature water under steady-state power operation (constant load) and transient operating conditions (e.g., start-up/shut-down, transients in water chemistry and load). Autoclave tests were performed with Western and Russian type reactor pressure vessel steels under simulated boiling water reactor (BWR)/normal water chemistry (NWC) and pressurised water reactor (VVER) conditions. The investigations were performed with fracture mechanics specimens of different sizes and geometries. The applied loading comprised cyclic loads, static loads and load spectra where the static load was periodically interrupted by partial unloading. With regard to water chemistry, the oxygen content (VVER) and impurities of sulphate and chlorides (BWR) were varied beyond allowable limits for continuous operation. The current paper summarises the most important crack growth results obtained under simulated BWR/NWC conditions. The results are discussed in the context of the current crack growth rate curves in the corresponding nuclear codes. (authors)

Ritter, S.; Seifert, H.P. [Paul Scherrer Institute, PSI, Villigen (Switzerland); Devrient, B.; Roth, A. [Framatome ANP GmbH, Erlangen (Germany); Ehrnsten, U. [VTT Industrial Systems, Espoo (Finland); Ernestova, M.; Zamboch, M. [Nuclear Research Institute, NRI, Rez (Czech Republic); Foehl, J.; Weissenberg, T. [Staatliche Materialpruefungsanstalt, MPA, Stuttgart (Germany); Gomez-Briceno, D.; Lapena, J. [Centro de Investigaciones Energeticas Medioambientales y Tecnologicas, CIEMAT, Madrid (Spain)

2004-07-01

264

Crack growth behaviour of low-alloy steels for pressure boundary components under transient light water reactor operating conditions - CASTOC, Part I: BWR/NWC conditions  

International Nuclear Information System (INIS)

One of the ageing phenomena of pressure boundary components of light water reactors (LWR) is environmentally-assisted cracking (EAC). The project CASTOC (5. Framework Programme of the EU) was launched September 2000 with six European partners and terminated August 2003. It was focused in particular on the EAC behaviour of low-alloy steels (LAS) and to some extent to weld metal, heat affected zone and the influence of an austenitic cladding. The main objective was directed to the clarification of EAC crack growth behaviour/mechanism of LAS in high-temperature water under steady-state power operation (constant load) and transient operating conditions (e.g., start-up/shut-down, transients in water chemistry and load). Autoclave tests were performed with Western and Russian type reactor pressure vessel steels under simulated boiling water reactor (BWR)/normal water chemistry (NWC) and pressurised water reactor (VVER) conditions. The investigations were performed with fracture mechanics specimens of different sizes and geometries. The applied loading comprised cyclic loads, static loads and load spectra where the static load was periodically interrupted by partial unloading. With regard to water chemistry, the oxygen content (VVER) and impurities of sulphate and chlorides (BWR) were varied beyond allowable limits for continuous operation. The current paper summarises the most important crack growth results obtained under simulated BWR/NWC conditions. The results are discussed in the context of the current crack growth rate curves in the corresponding nuclear codes. (authors)

265

On the mechanism of phase transition in BN during its reaction with Al under high pressure and temperature conditions  

International Nuclear Information System (INIS)

Solid phase AlN is formed under the conditions of high pressures and temperatures in the contact melted Al-BN; this phase acts as a catalytist in the process of ?-BN ? ?-BN phase transformation; AlN and ?-BN are texturated in the contact region; they have general axis of texture, which coincides with crystallographic direction (001) AlN and (111) ?-BN. Mechanism of ?-BN formation in the Al-?-BN contact is suggested

266

Aluminum oxide films deposited in low pressure conditions by reactive pulsed dc magnetron sputtering  

International Nuclear Information System (INIS)

The reactive pulsed dc sputtering technique is widely used for the deposition of oxide films. The operating pressure for sputtering is commonly above 0.13 Pa. In this study, however, aluminum oxide (alumina) films were deposited at operating pressures from 0.06 to 0.4 Pa using a sputtering system equipped with a scanning magnetron cathode and a pulsed dc power supply. The pulsed dc power was found to be useful not only to reduce arcing, but also to sustain the discharge at low pressure. The electrical breakdown field, intrinsic stress, O/Al ratio, refractive index, and surface roughness were investigated. Both a low intrinsic stress and an O/Al ratio around the stoichiometry were required to get the film having a high breakdown field. A low operating pressure of 0.1 Pa was found to provide the necessary stress and O/Al ratio targets. A 50-nm-thick alumina film having a maximum breakdown field of 7.4 MV/cm was obtained

267

CO2/water interfacial tensions under pressure and temperature conditions of CO2 geological storage  

International Nuclear Information System (INIS)

CO2 storage in aquifers and depleted hydrocarbon reservoirs is one of the most promising options for reducing CO2 atmospheric concentration. However, its implementation in a given reservoir requires demonstration that CO2 leakage through the reservoir seal (caprock) is extremely limited. One possible cause of rapid leakage is capillary failure of the caprock, which is to a large extent controlled by the CO2/water interfacial tension (IFT). This paper presents pendant drop measurements of IFTs between water and CO2 in a range of temperatures (308-383 K) and pressures (5-45 MPa) relevant to CO2 storage in deep geological formations. Phase densities were measured simultaneously, allowing precise IFT determinations. Increasing the pressure along a given isotherm, IFTs were observed to decrease sharply, then to level off and reach, for pressures above 20 MPa, a pseudo-plateau that decreases slightly with temperature, from around 30 mN/m at 308 K to 23 mN/m at 383 K. The presence of salt (20 g/l NaCl) in the water phase has a negligible effect on the IFT. An important conclusion for CO2 storage is that CO2/brine IFTs have low but reasonable values (higher than 20 mN/m) even at the highest pressures and temperatures examined, and that, neglecting all other possible effects, CO2 storage can, therefore, be considered even in deep geological formationsal formations

268

Aluminum oxide films deposited in low pressure conditions by reactive pulsed dc magnetron sputtering  

CERN Document Server

The reactive pulsed dc sputtering technique is widely used for the deposition of oxide films. The operating pressure for sputtering is commonly above 0.13 Pa. In this study, however, aluminum oxide (alumina) films were deposited at operating pressures from 0.06 to 0.4 Pa using a sputtering system equipped with a scanning magnetron cathode and a pulsed dc power supply. The pulsed dc power was found to be useful not only to reduce arcing, but also to sustain the discharge at low pressure. The electrical breakdown field, intrinsic stress, O/Al ratio, refractive index, and surface roughness were investigated. Both a low intrinsic stress and an O/Al ratio around the stoichiometry were required to get the film having a high breakdown field. A low operating pressure of 0.1 Pa was found to provide the necessary stress and O/Al ratio targets. A 50-nm-thick alumina film having a maximum breakdown field of 7.4 MV/cm was obtained.

Seino, T

2002-01-01

269

RCS pressure under reduced inventory conditions following a loss of residual heat removal  

International Nuclear Information System (INIS)

The thermal-hydraulic response of a closed-reactor coolant system to loss of residual heat removal (RHR) cooling is investigated. The processes examined include: core coolant boiling and steam generator reflux condensation, pressure increase on the primary side, heat transfer mechanisms on the steam generator primary and secondary sides, and effects of noncondensible gas on heat transfer processes

270

Experimental investigations of BWR pressure suppression pool behavior under loss of coolant accident conditions  

International Nuclear Information System (INIS)

The experiments discussed in this paper look into different processes which may occur during a loss-of-coolant accident in the pressure suppression pool of a Boiling Water Reactor (BWR). These processes include: a) development of a thermal stratification, b) bubble dynamics and related water flow during continuous release of air and c) air blowdown and associated water slug phenomenon in the water pool. The experiments have been performed in the THAI test facility, which is a cylindrical vessel of 9.2 m height, 3.2 m diameter and with a gas volume of 60 m3. The variation in the investigated test parameters included, steam and air mass flux, initial water pool temperature, blowdown pressures, downcomer submergence, etc. A systematic variation of the test parameters allowed better understanding of the phenomena. Experiments discussed in this paper were performed with a vertical downcomer of 0.1 m diameter and 2 m submergence depth in the water pool. For the blowdown experiments, a separate interconnecting vessel of 1 m3 volume was used to inject air at pressures between 3 bar and 10 bar. A high speed camera (1000 fps) was installed to visualize the formation and propagation of air bubbles in the suppression pool and the resulting pool swelling phenomena. Customized instrumentation applied during the tests included grids of densely spaced thermocouples and of pressure transducers at various locations in order to capture the temperature distribution r to capture the temperature distribution in the pool and the water slug induced pressure loadings, respectively. The present paper discusses the main outcome of the selected experiments. On the whole the experimental data may be very useful for code validation. (authors)

271

Seasonal variation in the incidence of preeclampsia and eclampsia in tropical climatic conditions  

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Full Text Available Abstract Background Observational studies have demonstrated various correlations between hypertensive disorders of pregnancy and different weather parameters. We aim to study if a correlation exists between the incidence of eclampsia and pre-eclampsia and various weather parameters in the tropical coastal city of Mumbai which has the distinction of having relatively uniform meteorological variables all throughout the year, except for the monsoon season. Methods We retrospectively analysed data from a large maternity centre in Mumbai, India over a period of 36 months from March 1993 to February 1996, recording the incidence of preeclampsia and eclampsia. Meteorological data was acquired from the regional meteorological centre recording the monthly average temperature, humidity, barometric pressure and rainfall during the study period. Study period was then divided into two climate conditions: monsoon season (June to August and dry season September to May. The incidence of preeclampsia and eclampsia and the meteorological differences between the two seasons were compared. Results Over a 36-month period, a total of 29562 deliveries were recorded, of which 1238 patients developed preeclampsia (4.18% and 34 developed eclampsia (0.11%. The incidence of preeclampsia did not differ between the monsoon and the dry season (4.3% vs. 4.15%, p = 0.5. The incidence of eclampsia was significantly higher in the monsoon (0.2% vs. 0.08%, p = 0.01. The monsoon was significantly cooler (median maximum temperature 30.7°C vs. 32.3°C, p = 0.01, more humid (median relative humidity 85% vs. 70%, p = 0.0008, and received higher rainfall (median 504.9 mm vs. 0.3 mm, p = 0.0002 than the rest of the year. The median barometric pressure (1005 mb during the monsoon season was significantly lower than the rest of the year (1012 mb, p Conclusion In the tropical climate of Mumbai, the incidence of eclampsia is significantly higher in monsoon, when the weather is cooler and humid with a lower barometric pressure than the rest of the year. This effect is not seen with preeclampsia. This strengthens the association of low temperature and high humidity with triggering of eclampsia.

Subramaniam Vidya

2007-10-01

272

Border control! Capillary pressure / saturation relationships in a diphasic flow in a random medium: Influence of the boundary conditions  

Science.gov (United States)

Solving problems involving biphasic flows in porous media, at a scale larger than the pore one, normally requires the use of relationships between pressure and saturation. These allow the closure of generalized Darcy flow models for two phases, commonly used in hydrology or large scale problems of diphasic flow in porous media. There are mathematical models which approximate experimental records with curve-fitting equations. The two most common models are the Brooks-Corey and van Genüchten ones, they are used to complete a system of generalized Darcy equations. The purpose of the current study is the influence of the boundary conditions on the relationship between pressure and saturation. We perform numerical simulations of drainage experiments. Water is the wetting fluid and air is the non wetting fluid. The results highlight the fact that a filter which allows only water to flow at the exit face of the system modifies both the shape of the curve and the value of the residual saturation. The pressure of the models that are commonly used does not match with the pressure of real flows since there is no filter to cross, to flow from an elementary volume to another. Experiments performed in transparent Hele-Shaw cells exhibit the same features, showing the influence of the semi permeable boundary conditions on the pressure-saturation measures obtained. This effect corresponding to the formation of localized plugging clusters at the boundaries, is obtained in slow flow conditions, and is independent of any dynamic fingering, also known to affect such relations (1,2,3). Modeling flows in open media thus would require to use the central part of the curves pressure saturation where the effect of the boundaries is the least important, or to modify properly these relationships to extract the behavior unaffected by boundaries. References: (1) Two-phase flow: structure, upscaling, and consequences for macroscopic transport properties Renaud Toussaint ; Knut Jørgen Måløy; Yves Méheust; Grunde Løvoll; Mihailo Jankov; Gerhard Schäfer; Jean Schmittbuhl Vadose Zone Journal, 2012, 11 (3), pp. vzj2011.0123 (2) Løvoll, G., M. Jankov, K.J. Måløy, R. Toussaint, J. Schmittbuhl, G. Schaefer and Y. Méheust, Influence of viscous fingering on dynamic saturation-pressure curves in porous media, Transport in Porous Media, 86, 1, 305-324, 2010 (3) Toussaint, R., G. Løvoll, Y. Méheust, K.J. Måløy and J. Schmittbuhl, Influence of pore-scale disorder on viscous fingering during drainage, Europhys. Lett., 71, 583 (2005).

Fiorentino, Eve-Agnès; Toussaint, Renaud; Moura, Marcel; Jankov, Mihailo; Schäfer, Gerhard; Jørgen Måløy, Knut

2013-04-01

273

Boundary-Layer Separation Control under Low-Pressure Turbine Airfoil Conditions using Glow-Discharge Plasma Actuators  

Science.gov (United States)

Modem low-pressure turbines, in general, utilize highly loaded airfoils in an effort to improve efficiency and to lower the number of airfoils needed. Typically, the airfoil boundary layers are turbulent and fully attached at takeoff conditions, whereas a substantial fraction of the boundary layers on the airfoils may be transitional at cruise conditions due to the change of density with altitude. The strong adverse pressure gradients on the suction side of these airfoils can lead to boundary-layer separation at the latter low Reynolds number conditions. Large separation bubbles, particularly those which fail to reattach, cause a significant degradation of engine efficiency. A component efficiency drop of the order 2% may occur between takeoff and cruise conditions for large commercial transport engines and could be as large as 7% for smaller engines at higher altitude. An efficient means of of separation elimination/reduction is, therefore, crucial to improved turbine design. Because the large change in the Reynolds number from takeoff to cruise leads to a distinct change in the airfoil flow physics, a separation control strategy intended for cruise conditions will need to be carefully constructed so as to incur minimum impact/penalty at takeoff. A complicating factor, but also a potential advantage in the quest for an efficient strategy, is the intricate interplay between separation and transition for the situation at hand. Volino gives a comprehensive discussion of several recent studies on transition and separation under low-pressure-turbine conditions, among them one in the present facility. Transition may begin before or after separation, depending on the Reynolds number and other flow conditions. If the transition occurs early in the boundary layer then separation may be reduced or completely eliminated. Transition in the shear layer of a separation bubble can lead to rapid reattachment. This suggests using control mechanisms to trigger and enhance early transition. Gad-el-Hak provides a review of various techniques for flow control in general and Volino discusses recent studies on separation control under low-pressure-turbine conditions utilizing passive as well as active devices. As pointed out by Volino, passive devices optimized for separation control at low Reynolds numbers tend to increase losses at high Reynolds numbers, Active devices have the attractive feature that they can be utilized only in operational regimes where they are needed and when turned off would not affect the flow. The focus in the present paper is an experimental Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions represent flow over the suction surface of a modem low-pressure-turbine airfoil ('Pak-B'). The Reynolds number, based on wetted plate length and nominal exit velocity, is varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low (0.2%) and high (2.5%) Gee-stream turbulence intensities are set using passive grids. A spanwise-oriented phased-plasma-array actuator, fabricated on a printed circuit board, is surface- flush-mounted upstream of the separation point and can provide forcing in a wide frequency range. Static surface pressure measurements and hot-wire anemometry of the base and controlled flows are performed and indicate that the glow-discharge plasma actuator is an effective device for separation control. of active separation control using glow discharge plasma actuators.

Hultgren, Lennart S.; Ashpis, David E.

2003-01-01

274

Study of ballooning of a completely voided pressure tube of Indian PHWR under heat up condition  

Energy Technology Data Exchange (ETDEWEB)

Highlights: Black-Right-Pointing-Pointer Simulating of LOCA at 4 and 6 MPa internal pressures for IPHWR was carried out at IIT Roorkee, India. Black-Right-Pointing-Pointer The sagging of PT takes place at 500 Degree-Sign C before the commencement of ballooning. Maximum sagging is less than 2 mm. Black-Right-Pointing-Pointer Once PT touches the CT, there is no further rise in PT temperature. Black-Right-Pointing-Pointer The maximum PT temperature was below 700 Degree-Sign C. Black-Right-Pointing-Pointer The transverse creep correlation for CANDU material also holds good for Indian PT material for the temperature range expected during LOCA. - Abstract: In a nuclear reactor, loss of coolant accident (LOCA) considers wide range of postulated damage or rupture of pipe in the heat transport piping system. In case of LOCA with/without failure of emergency core cooling system in a Pressurized Heavy Water Reactor, the pressure tube (PT) temperature can rise significantly due to fuel heat up and gross mismatch of heat generation and heat removal in the affected channel. The extent and nature of deformation is important from reactor safety point of view. Experimental set-ups have been designed and fabricated to simulate ballooning (radial deformation) of PT for 220 MWe IPHWRs. Experiments have been conducted using voided PTs at 4 and 6 MPa internal pressure at different heating rates. It is observed that at 4 MPa and 6 MPa internal pressure, the PT sagged at about 500 Degree-Sign C before the ballooning initiation. The ballooning initiates at a temperature around 625 Degree-Sign C and contact between PT and Calandria Tube (CT) occurs at around 680 Degree-Sign C, respectively, for 4 MPa and the same was at 550 Degree-Sign C and 640 Degree-Sign C for 6 MPa. The structural integrity of PT is retained (no breach) for all the experiments. The PT heat up is found to be arrested after the contact between PT and CT, thus establishing the moderator acting as an efficient heat sink for IPHWRs. A thermal creep model 'PTCREEP' has been developed to predict creep behaviour of the PT of IPHWR. It is found that the contact time predicted by PTCREEP is very close to the experimental result. Hence, PTCREEP can be used for the prediction of the ballooning behaviour of the PT for IPHWR in case of LOCA for the operating temperature and pressure range.

Nandan, Gopal [Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee (India); Majumdar, P. [Reactor Safety Division, Bhabha Atomic Research Centre, Trombay, Mumbai (India); Sahoo, P.K., E-mail: sahoofme@iitr.ernet.in [Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee (India); Kumar, Ravi [Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee (India); Chatterjee, B.; Mukhopadhyay, D.; Lele, H.G. [Reactor Safety Division, Bhabha Atomic Research Centre, Trombay, Mumbai (India)

2012-02-15

275

Reduced herbivore pressure under rainy ENSO conditions could facilitate dryland reforestation  

OpenAIRE

Most semi-arid and arid regions around the world have lost a major part of their original vegetation. Restoration of once shrublands and woodlands is often challenged by low seedling establishment success due to water stress and herbivory. In some regions, increased rainfall during El Niño Southern Oscillation (ENSO) events can significantly stimulate plant recruitment. However, recruitment seems to be strongly modulated by herbivore pressure. Also, seedling establishment in arid ecosystems ...

Gutierrez, J. R.; Holmgren, M.; Manrique, R.; Squeo, F. A.

2007-01-01

276

Microstructural studies on steam oxidised Zr-2.5%Nb pressure tube under simulated LOCA condition  

International Nuclear Information System (INIS)

Study of the microstructural evolution of Zr-2.5%Nb pressure tube material of Indian Pressurized Heavy Water Reactors (PHWRs) due to steam oxidation at high temperature (in the range 500-1050°C) was carried out on pressure tube coupons. Hydrogen pick up was less than 55 ppm in the samples oxidized at temperatures up to 850°C but high (250-400 ppm) in the samples oxidized in the ? phase region (900°C and above). The microstructure of the samples oxidized above the ?-Zr/?-Zr transition temperature showed from the surface inwards sequentially the presence of an oxide layer, an underlying oxygen stabilized ?-Zr layer and a prior ?-Zr phase containing hydride precipitates. An increase in the hardness was observed near the oxide-metal interface in the coupons oxidized above 900°C, due to formation of oxygen stabilized ?-Zr layer. Higher hardness was also observed in the base metal in the samples oxidized at 1000 and 1050°C (author)

277

Turbulence sets the initial conditions for star formation in high-pressure environments  

CERN Document Server

Despite the simplicity of theoretical models of supersonically turbulent, isothermal media, their predictions successfully match the observed gas structure and star formation activity within low-pressure (P/k 10^7 K cm^-3) environments, like those in the Galaxy's inner 200 pc Central Molecular Zone (CMZ) and in the early Universe. Here we present ALMA 3mm dust continuum emission within a cloud, G0.253+0.016, which is immersed in the high-pressure environment of the CMZ. While the log-normal shape and dispersion of its column density PDF is strikingly similar to those of solar neighbourhood clouds, there is one important quantitative difference: its mean column density is 1--2 orders of magnitude higher. Both the similarity and difference in the PDF compared to those derived from solar neighbourhood clouds match predictions of turbulent cloud models given the high-pressure environment of the CMZ. The PDF shows a small deviation from log-normal at high column densities confirming the youth of G0.253+0.016. Its...

Rathborne, J M; Jackson, J M; Kruijssen, J M D; Alves, J F; Bally, J; Bastian, N; Contreras, Y; Foster, J B; Garay, G; Testi, L; Walsh, A J

2014-01-01

278

''Iodine delivery rate'' with catheterangiography under pressure conditions of hand injection  

International Nuclear Information System (INIS)

Purpose: The aim of this study was to record the flow-rate and to calculate the 'iodine delivery rate' (IDR) of contrast media of various viscosities when the contrast media are injected by hand. Methods: Five different catheters for coronary angiography were tested with the injection system Medral Mark V Plus. Injections were performed with pressures of 100, 200 and 400 PSI. The contrast media examined were Imeron 350, Imeron 400, Omnipaque 350 and Ultravist 370. The IDR was calculated on the basis of the measured flow rate and the Iodine content of the contrast medium. Results: As was expected, the IDR was higher as the pressure increased. In addition to the iodine content the viscosity of the contrast medium is a very important factor for the IDR. At both 100 PSI and 200 PSI the increase of the IDR was higher with Imeron 350 than with Imeron 400. The comparison of contrast media with identical iodine contents but differing viscosities (Imeron 350, Omnipaque 350) clearly showed that the IDR depended on viscosity. Conclusion: The 'iodine delivery rate' is a decisive factor in the opacification of arterial vessels. Both iodine content and viscosity of a contrast medium are important for the IDR. Because of the low pressure at manual injection, contrast media with low viscosities should be used. A further possibility to increase the IDR is warming-up the contrast medium to body temperature. (orig.)

279

Critical heat flux under conditions of high subcooling and high velocity at atmospheric pressure  

International Nuclear Information System (INIS)

A quantitative analysis of critical heat flux (CHF) under high mass flux with high subcooling at atmospheric pressure was successfully carried out by applying a new transition region model for a macro-water-sublayer on heated walls to the existing model of a vapor blanket over the macro-water-sublayer. The CHF correlation proposed in this study could predict well the existing experimental data obtained for water mass flux of 940 to 20 300 kg/m2s using circular tubes of 2 to 4 mm in diameter and 30 to 100 mm in length with inlet subcooling of 30 to 90degC and rectangular channels heated from one side with gap of 3 to 20 mm, length of 50 to 305 mm and inlet subcooling of 30 to 77degC and revealed a unique feature of CHF that the effects of wall friction of subcooled boiling flow and the velocity of the steam blanket above the macro-water-sublayer at atmospheric pressure become the dominant factors while those were not dominant at higher pressures. (author)

280

Pressure measurements and high speed visualizations of the cavitation phenomena at deep part load condition in a Francis turbine  

Science.gov (United States)

In a hydraulic power plant, it is essential to provide a reliable, sustainable and flexible energy supply. In recent years, in order to cover the variations of the renewable electricity production, hydraulic power plants are demanded to operate with more extended operating range. Under these off-design conditions, a hydraulic turbine is subject to cavitating swirl flow at the runner outlet. It is well-known that the helically/symmetrically shaped cavitation develops at the runner outlet in part load/full load condition, and it gives severe damage to the hydraulic systems under certain conditions. Although there have been many studies about partial and full load conditions, contributions reporting the deep part load condition are limited, and the cavitation behaviour at this condition is not yet understood. This study aims to unveil the cavitation phenomena at deep part load condition by high speed visualizations focusing on the draft tube cone as well as the runner blade channel, and pressure fluctuations associated with the phenomena were also investigated.

Yamamoto, K.; Müller, A.; Favrel, A.; Landry, C.; Avellan, F.

2014-12-01

281

Flare-out condition of Morris-Thorne wormhole and finiteness of pressure  

OpenAIRE

Wormhole is defined as the topological structure with the throat connecting two asymptotically flat spaces. In order to have and maintain the structure of the wormhole, there needs the geometrical flare-out condition, i.e., the minimal size at throat. In the case of Morris-Thorne type wormhole, the condition is given by the huge surface tension compared to the energy density times the square of the light speed. In this paper, we re-considered the flare-out condition for the ...

Kim, Sung-won

2013-01-01

282

Effects of FeNi-phosphorus-carbon system on crystal growth of diamond under high pressure and high temperature conditions  

Science.gov (United States)

This paper reports the crystal growth of diamond from the FeNi–Carbon system with additive phosphorus at high pressures and high temperatures of 5.4–5.8 GPa and 1280–1360 °C. Attributed to the presence of additive phosphorus, the pressure and temperature condition, morphology, and color of diamond crystals change obviously. The pressure and temperature condition of diamond growth increases evidently with the increase of additive phosphorus content and results in the moving up of the V-shape region. The surfaces of the diamonds also become coarse as the additive phosphorus added in the growth system. Raman spectra indicate that diamonds grown from the FeNi-phosphorus-carbon system have more crystal defects and impurities. This work provides a new way to enrich the doping of diamond and improve the experimental exploration for future material applications. Project supported by the Doctoral Fund of Henan Polytechnic University, China (Grant Nos. B2013-013 and B2013-044) and the Research Projects of Science and Technology of the Education Department of Henan Province, China (Grant Nos. 14B430026 and 12A430010).

Hu, Mei-Hua; Bi, Ning; Li, Shang-Sheng; Su, Tai-Chao; Zhou, Ai-Guo; Hu, Qiang; Jia, Xiao-Peng; Ma, Hong-An

2015-03-01

283

Effects of dobutamine on cardiac index and arterial blood pressure in isoflurane-anaesthetized horses under clinical conditions.  

Science.gov (United States)

Volatile agent-induced hypotension may contribute to anaesthetic-related morbidity and mortality in horses. Dobutamine is commonly used to support arterial blood pressure (ABP) but little is known about its cardiovascular effects under clinical conditions. The aim of this clinical study was to elucidate the relationship between cardiovascular function and dobutamine infusion in isoflurane-anaesthetized horses. Forty-four horses anaesthetized for a variety of surgical procedures were studied. Premedication with acepromazine, methadone and detomidine was followed by induction of anaesthesia with ketamine and midazolam. Anaesthesia was maintained with isoflurane vaporized in oxygen. Routine anaesthetic monitoring was applied and cardiac output was measured by lithium dilution. Dobutamine was infused to maintain mean ABP above 70 mmHg. The relationship between dobutamine infusion rate, heart rate (HR), ABP and cardiac index was investigated immediately prior to (T(0)) and 15 min (T(1)) after dobutamine infusion started, followed at 30 min intervals (T(2), etc.). Arterial blood pressure increased significantly after dobutamine infusion started, HR and cardiac index increased significantly only with dobutamine infusion in combination with surgical stimulus. Although isoflurane decreases blood pressure mainly by vasodilation, dobutamine is an effective treatment for hypotension under clinical conditions in isoflurane-anaesthetized horses. The effect of dobutamine is not directly proportional to dose and surgical stimulus probably contributes to the cardiovascular improvement. PMID:19614840

de Vries, A; Brearley, J C; Taylor, P M

2009-08-01

284

Numerical study of the pressure drop in a plain fin-and-circular tube heat exchanger under frost condition  

International Nuclear Information System (INIS)

Full text: Three-dimensional computational fluid dynamics (CFD) simulations are carried out to study the pressure drop behavior in a plain fin-and-four staggered layout and circular tube rows for different fin pitches under frost conditions using FLUENT 6.3 CFD code. Models geometry is created and meshed using GAMBIT 2.3. Fluid flow and heat transfer are simulated and results calculated using (Transitional SST k-omega) turbulence model, with steady-state solver. Model validation is carried out by comparing the pressure drop of a simulated case with experimental results from the literature. It was found that Fluent 6.3 software has been sufficient for simulating the flow characteristics in tube-fin heat exchangers. (author)

285

Experimental investigation of supersonic low pressure air plasma flows obtained with different arc-jet operating conditions  

International Nuclear Information System (INIS)

A stationary arc-jet plasma flow at low pressure is used to simulate some properties of the gas flow surrounding a vehicle during its entry into celestial body's atmospheres. This paper presents an experimental study concerning plasmas simulating a re-entry into our planet. Optical measurements have been carried out for several operating plasma conditions in the free stream, and in the shock layer formed in front of a flat cylindrical plate, placed in the plasma jet. The analysis of the spectral radiation enabled the identification of the emitting species, the determination of the rotational and vibrational temperatures in the free-stream and in the shock layer and the determination of the distance of the shock to the flat plate face. Some plasma fluid parameters like, stagnation pressure, specific enthalpy and heat flux have been determined experimentally along the plasma-jet axis.

286

The response of the magnetosphere-ionosphere system to a sudden dynamic pressure enhancement under southward IMF conditions  

Directory of Open Access Journals (Sweden)

Full Text Available The magnetospheric response to step-like solar wind dynamic pressure increases under southward IMF conditions is studied using the University of Michigan MHD code. A two phased response in the ionosphere is observed, similar to what is observed when the IMF is northward by looking into the residual potential and field-aligned current (FAC patterns in the ionosphere. The first phase response right after the high pressure enhancement hits the magnetopause is associated with a pair of FACs downward in the postnoon and upward in the prenoon region. These FACs are caused by dusk-to-dawn electric fields inside the dayside magnetopause launched by a fast mode compressional wave. The second phase response shows another pair of potential cells as well as FACs in opposite polarity, which originates from magnetospheric vortices on the equatorial plane. The vortices appear to be formed by the recovery of the system from the fast mode wave.

Y Yu

2009-12-01

287

Post-dryout heat transfer and entrained droplet sizes at low pressure and low flow conditions  

International Nuclear Information System (INIS)

The entrainment mechanisms and the entrained droplet sizes with relation to the flow regimes are investigated. Through the analysis of many experimental post-dryout data, it is shown that the most probable flow regime near dryout or quench front is not annular flow but churn-turbulent flow when the mass flux is low. A correlation describing the initial droplet size just after the CHF position at low mass flux is suggested through regression analysis. The history-dependent post-dryout model of Varone and Rohsenow replaced by the Webb-Chen model for wall-vapor heat transfer is used as a reference model in the analysis. In the post-dryout region at low pressure and low flow, it is found that the suggested one-dimensional mechanistic model is not applicable when the vapor superficial velocity is very low. This is explained by the change of main entrainment mechanism with the change of flow regime. In bubbly or slug flow a number of tiny droplets generated from bubble burst become important in the heat transfer after dryout. Therefore, the suggested correlation is valid only in the churn-turbulent flow regime (jg* = 0.5?4.5). It is also suggested that the droplet size generated from the churn-turbulent surface is dependent not only on the pressure but also on the vapor velocity. It turns out that the present model can predict the measured cladding and vapor temperatures within 20% and 25%, respectively

288

Barometric effects on tabular iceberg drift in the Ross Sea, Antarctica  

Science.gov (United States)

The Inverse Barometer Effect (IBE) was observed in the nineteenth century by Sir James Clark Ross (Ross, 1854a), as deviations in sea-surface elevation in response to deviations in atmospheric pressure. This effect embodies the inverse relationship between sea-surface height (relative to long-term mean sea level) and atmospheric surface pressure. This thesis addresses the hypothesis that icebergs in the Ross Sea region of Antarctica are influenced by the same forces that create the IBE. This hypothesis is motivated by studies of icebergs in the Ross Sea, where drift data suggest that icebergs are drawn into temporary holding zones, or "Iceberg Parking Lots" situated where the surface pressure tends to display persistent, annual average low pressure. A physical explanation for the IBE's influence on icebergs is that they are often able to travel up the sea-surface slope induced by the IBE below atmospheric lows against the gravitational pull because of the pressure gradient force of the atmosphere acting on the iceberg's freeboard (the part of the iceberg that is above the waterline). Here, I evaluate the validity of the hypothesized IBE-iceberg relationship using a combined approach of data analysis and modeling. I have examined atmospheric surface pressure and wind records taken directly from the surfaces of four Ross Sea icebergs---B15A, B15K, C16, and B15J, and I have also built, and experimented with, models that predict iceberg drift response to atmospheric surface pressure and surface winds, using observed pressures and winds from B15A and B15J as model forcing. I additionally performed various experiments on a large, idealized tabular iceberg's physical sensitivity to the IBE using a model that treats atmospheric pressure and winds in an idealized, theoretical manner. I discovered that the IBE is indeed a significant influence on iceberg drift in and around Lewis Bay, just to the north of Ross Island, which will further our understanding of these icebergs' trajectories. While I do not believe that the IBE-iceberg relationship is universally so pronounced as it is in Lewis Bay, and may not necessarily be responsible for all other places where icebergs tend to collect for long periods, it should be considered in any iceberg drift models that deal with regions having strong and persistent pressure gradients. In the Ross Sea, the pressure gradient toward Ross Island can be the overwhelming force on icebergs drifting just to the north of it, until another force such as the ocean current is able to exert itself more strongly.

Turnbull, Ian D.

289

Electrical safety equipment for pressurized water reactor power stations: insulation losses under accident conditions  

International Nuclear Information System (INIS)

Thermodynamic conditions prevailing during the accidents examined often cause high insulation losses in K1 safety equipment located in the containment building. This article analyses the physical phenomena involved, gives examples of calculation of minimal insulation resistances which are necessary for the system operation and maximum insulation resistance required, indicates some rules for defining threshold values required in equipment qualification tests

290

Experimental study on DNB heat flux of plate-type fuel in pressurized condition  

International Nuclear Information System (INIS)

Experimental study was carried out in order to determine the DNB correlation for the safety analysis of the JMTR low enrichment fuel core. Since it is essential to examine applicability and safety margin of the correlation for the safety analysis, DNB heat fluxes were measured with the test section of rectangular flow channel simulating JMTR fuel element subchannel in the pressure range of 1 ? 13 kg/cm2 abs and the velocity range of 0 ? 4.4 m/s. Reviewing existed DNB correlations based on the experimental data, Sudo correlations scheme was selected for the JMTR safety analysis with minor modification for the high flow rate region. Comparing the correlations scheme with experimental data, allowable limit of the minimum DNBR was determined to be 1.5. (author)

291

Iron under Earth's core conditions Liquid-state thermodynamics and high-pressure melting curve  

CERN Document Server

{\\em Ab initio} techniques based on density functional theory in the projector-augmented-wave implementation are used to calculate the free energy and a range of other thermodynamic properties of liquid iron at high pressures and temperatures relevant to the Earth's core. The {\\em ab initio} free energy is obtained by using thermodynamic integration to calculate the change of free energy on going from a simple reference system to the {\\em ab initio} system, with thermal averages computed by {\\em ab initio} molecular dynamics simulation. The reference system consists of the inverse-power pair-potential model used in previous work. The liquid-state free energy is combined with the free energy of hexagonal close packed Fe calculated earlier using identical {\\em ab initio} techniques to obtain the melting curve and volume and entropy of melting. Comparisons of the calculated melting properties with experimental measurement and with other recent {\\em ab initio} predictions are presented. Experiment-theory comparis...

Alfe`, D; Gillan, M J

2001-01-01

292

Characteristic study of atmospheric pressure microplasma jets with various operating conditions  

Energy Technology Data Exchange (ETDEWEB)

Non-thermal microplasma jets generated under atmospheric pressure by means of radio-frequency of 13.56 MHz and low-frequency of several tens of kilohertz are characterized. They show several distinct discharge characteristics. Two operation modes of the plasma are observed when the single pin electrode is utilized and separated by the remote ground, and where plasma is sustained between the pin electrode and the ground ring electrode. The electrical characteristic of discharges and various effects of the ground ring electrode are presented. We observe that the emission spectra are dominated by the presence of excited nitrogen, helium, and nitrogen ions. Highly reactive radicals such as hydroxyl (OH) and atomic oxygen are also detected. With the addition of a ground ring electrode, the discharge current and optical emission intensities from the plasma plume are enhanced significantly indicating that the generated plasma is near the glow discharge mode.

Kim, S.J. [Department of Physics, Dong-A University, 840 Hadan-dong, Saha-gu, Busan 604-714 (Korea, Republic of); Chung, T.H., E-mail: thchung@dau.ac.k [Department of Physics, Dong-A University, 840 Hadan-dong, Saha-gu, Busan 604-714 (Korea, Republic of); Bae, S.H. [Department of Physics, Dong-A University, 840 Hadan-dong, Saha-gu, Busan 604-714 (Korea, Republic of)

2009-05-29

293

Integrity criteria of the mockup of the RBMK fuel channel pressure tube in case of emergency heating conditions  

International Nuclear Information System (INIS)

Multi-parameter standards of wholeness/damage of Zr-2.5% Nb channel tubes in mockups during conditions of disturb output at the RBMK type reactor (LOCA, ATWR accidents) are suggested. Standards allow for conducting estimation and prediction of state of the RBMK channel tube mockup under emergency heating on the basis of actual values of pressure inside the channel, velocity and properties of heating. Thermomechanical behaviour of the channel tube mockup was evaluated by ATM-TK code. Comparison analysis of calculating results with experimental data demonstrated their satisfactory fit

294

In situ X-ray diffraction of natural chromium-bearing spinel under high pressure and high temperature conditions  

International Nuclear Information System (INIS)

Energy dispersive X-ray powder diffraction (EDXD) of natural chromium-bearing spinel collected from Damapin using synchrotron radiation has been in situ measured under high pressure (0-12.82 GPa) and high temperature (300-603 K) conditions. Based on Murnaghan equation, the state equation of natural chromium-bearing spinel was deduced, the bulk modulus KT(0)=369 Gpa and compression coefficient K=2.713x10-3/Gpa were obtained. In addition, the thermal expansion of spinel was discussed, and a thermal expansion coefficient of ?=1.004 x 10-5/K was calculated. (authors)

295

Influence of dc Pulsed Atmospheric Pressure Plasma Jet Processing Conditions on Polymer Activation  

OpenAIRE

Plasma treatments are widely used to activate polymer surfaces prior to adhesive bonding. This study investigates the influence of plasma treatment conditions on the surface activation of a range of polymers using the PlasmaTreat (Open Air) system. In this study the effect of dc pulse plasma cycle time, compressed air flow rate and the plasma jet nozzle to substrate distance on the plasma discharge was examined. The influence that the dc pulse plasma cycle time parameter has on the activation...

Dowling, Denis P.; O Neill, Feidhlim T.; Langlais, Simon J.; Law, Victor J.

2011-01-01

296

Working conditions under economic pressure: The case of the German cleaning industry  

OpenAIRE

This paper investigates changes in collective bargaining policy in the German cleaning industry in recent years. It uses the Socio-economic Panel (GSOEP) to survey employees on employment conditions and expert interviews with key members of the industry to look at possible new paths of development in the industry as well as the range of attitudes of the players involved. The socio-demography of the employees in the industry was given close attention and, with regard to collective labour agree...

Schramm, Florian; Schlese, Michael

2005-01-01

297

Morphological variations in AuxSiy nanostructures under variable pressure and annealing conditions  

Science.gov (United States)

Well-ordered, substrate symmetry-driven, AuxSiy structures of average size ~25 nm were formed under ultra-high vacuum (UHV) conditions using molecular beam epitaxy method. Post-annealing was done at 500 °C in three different vacuum conditions: (1) low vacuum (LV) (10-2 mbar), (2) high vacuum (HV) (10-5 mbar) and (3) UHV (10-10 mbar) (MBE chamber). For both HV and LV cases, the AuxSiy nanostructures were found to have their corners rounded unlike in UHV case where the structures have sharp edges. In all the above three cases, samples were exposed to air before annealing. In situ annealing inside UHV chamber without exposing to air resulted in well-aligned rectangles with sharp corners, while sharp but irregular island structures were found for air exposed and UHV annealing system. The role of residual gases present in LV and HV annealing environment and inhibition of lateral surface diffusion due to the presence of surface oxide (through air exposure) would be discussed. Annealing at various conditions yielded variation in the coverage and correspondingly, the average area of nanostructures varied from a ~329 nm2 (as deposited) to ~2,578 nm2 (at high temperature). High-resolution transmission electron microscopy (planar and cross section) has been utilized to study the morphological variations.

Rath, A.; Dash, J. K.; Juluri, R. R.; Satyam, P. V.

2015-03-01

298

A reactor water level and pressure prediction method under small loss-of-coolant-accident conditions in boiling water reactors  

International Nuclear Information System (INIS)

An on-line method of predicting reactor water level and pressure under small loss-of-coolant-accident (LOCA) conditions has been proposed. The method features initialization of a simplified reactor model in transient conditions. This is done by using plant data in time series and estimating unknown parameters, such as break area, by a nonlinear optimization method. Off-line simulations were performed for small LOCAs (break area: about100 cm2) using the results of a reference LOCA analysis code for plant data. These showed that the difference from the reference calculation during a 10-min period was within 10%, normalized by the value at the initialization time, and the estimation error for break area was below 11%. The overall CPU time required for the prediction was below 10 s in a general purpose computer of 10 million instructions per second

299

Verification of effects of fuel management schemes on the condition of pressure vessels and their support structures  

International Nuclear Information System (INIS)

A number of potential methods exist for assuring the adequacy of fracture control of reactor pressure vessel (PV) beltlines under normal and accident loads. One of these methods, involving the use of fuel management schemes for reducing the rate of neutron damage accumulation at points of high neutron exposure, shows considerable promise. Practices for assessing and controlling the condition of PV beltlines and their support structures follow the recommendations in the US Code of Federal Regulations 10CFR50 (App. G and H) and 10CFR21, respectively, as well as those of the ASME Boiler and Pressure Vessel Code, Sec. III ad XI. In summary fashion, this paper reviews the methods for fracture behavior assessment and control and the interfaces with physics-dosimetry-metallurgy. It then reviews the calculated effects of new fuel management schemes on derived exposure parameter values for a representative PWR power plant. This is followed by a review of recent results of LWR Pressure Vessel Surveillance Dosimetry Improvement Program (LWR-PV-SDIP) interlaboratory efforts. Also provided is an updated set of references to the literature that is most relevant to the LWR-PV-SDIP work through September, 1982

300

Experimental study on the transfer while helium turbulent convection at supercritical pressure in conditions of strong nonisothermality  

International Nuclear Information System (INIS)

Experimental study of heat transfer to helium of supercritical pressure in the range of quasi-stabilized heat transfer and in the initial part of a heated tube is carried out. The experiments are conducted in the range of regime parameters: pressure P=(0.24-0.68)x106 Pa (P/Psub(cr)=1.05-3.1); flow rate (0.037-0.2)x10sup(-3) kg/s (Re9x103-6.5x104); heat flux density 900-6000 W/m2; Tsub(in)4.41-7.1 K. Experimental model presents a horizontally placed stainless steel of inner diameter d=1.4 mm, heated part length 545 mm. The temperature of the wall was controlled at the distances x/d=(11-239) from the heated part end. The dependence of heat transfer intensity on the input temperature, pressure, distance from the input and heat flux density during liquid heating is studied. A formula, taking into account the peculiriarities of heat exchange variation in the range of pseudocritical temperatures in the flow under conditions of a strong nonisothermicity and effect of the initial section, is suggested

301

A model for calculation of RCS pressure during reflux boiling under reduced inventory conditions and its assessment against PKL data  

International Nuclear Information System (INIS)

There has been recent interest in the United States concerning the loss of residual heat removal system (RHRS) under reduced coolant inventory conditions for pressurized water reactors. This issue is also of interest in the Federal Republic of Germany and an experiment was performed in the integral PKL-HI experimental facility at Siemens-KWU to supply applicable data. Recently, an NRC-sponsored effort has been undertaken at the Idaho-National Engineering Laboratory to identify and analyze the important thermal-hydraulic phenomena in pressurized water reactors following the long term loss-of-RHRS during reduced inventory operation. The thermal-hydraulic response of a closed reactor coolant system during such a transient is investigated in this report. Some of the specific processes investigated include: reflux condensation in the steam generators, the corresponding pressure increase in the reactor coolant system, and void fraction distributions on the primary side of the system. Mathematical models of these and other physical processes Experiment B4.5

302

A model for calculation of RCS pressure during reflux boiling under reduced inventory conditions and its assessment against PKL data  

Energy Technology Data Exchange (ETDEWEB)

There has been recent interest in the United States concerning the loss of residual heat removal system (RHRS) under reduced coolant inventory conditions for pressurized water reactors. This issue is also of interest in the Federal Republic of Germany and an experiment was performed in the integral PKL-HI experimental facility at Siemens-KWU to supply applicable data. Recently, an NRC-sponsored effort has been undertaken at the Idaho-National Engineering Laboratory to identify and analyze the important thermal-hydraulic phenomena in pressurized water reactors following the long term loss-of-RHRS during reduced inventory operation. The thermal-hydraulic response of a closed reactor coolant system during such a transient is investigated in this report. Some of the specific processes investigated include: reflux condensation in the steam generators, the corresponding pressure increase in the reactor coolant system, and void fraction distributions on the primary side of the system. Mathematical models of these and other physical processes Experiment B4.5.

Palmrose, D.E. [EG and G Idaho, Inc., Idaho Falls, ID (United States); Mandl, R.M. [Siemens AG, Berlin (Germany)

1991-12-31

303

Effect of chelating agent concentration in alkaline Cu CMP process under the condition of different applied pressures  

Science.gov (United States)

We propose the action mechanism of Cu chemical mechanical planarization (CMP) in an alkaline solution. Meanwhile, the effect of abrasive mass fraction on the copper removal rate and within wafer non-uniformity (WIWNU) have been researched. In addition, we have also investigated the synergistic effect between the applied pressure and the FA/O chelating agent on the copper removal rate and WIWNU in the CMP process. Based on the experimental results, we chose several concentrations of the FA/O chelating agent, which added in the slurry can obtain a relatively high removal rate and a low WIWNU after polishing, to investigate the planarization performance of the copper slurry under different applied pressure conditions. The results demonstrate that the copper removal rate can reach 6125 Å/min when the abrasive concentration is 3 wt.%. From the planarization experimental results, we can see that the residual step height is 562 Å after excessive copper of the wafer surface is eliminated. It denotes that a good polishing result is acquired when the FA/O chelating agent concentration and applied pressure are fixed at 3 vol% and 1 psi, respectively. All the results set forth here are very valuable for the research and development of alkaline slurry.

Haobo, Yuan; Yuling, Liu; Mengting, Jiang; Weijuan, Liu; Guodong, Chen

2014-11-01

304

A model for calculation of RCS pressure during reflux boiling under reduced inventory conditions and its assessment against PKL data  

International Nuclear Information System (INIS)

There has been recent interest in the United States concerning the loss of residual heat removal system (RHRS) under reduced coolant inventory conditions for pressurized water reactors. This issue is also of interest in the Federal Republic of Germany and an experiment was performed in the integral PKL-III experimental facility at Siemens-KWU to supply applicable data. Recently, an NRC-sponsored effort has been undertaken at the Idaho National Engineering Laboratory to identify and analyze the important thermal-hydraulic phenomena in pressurized water reactors following the long term loss-of-RHRS during reduced inventory operation. The thermal-hydraulic response of a closed reactor coolant system during such a transient is investigated in this report. Some of the specific processes investigated include: reflux condensation in the steam generators, the corresponding pressure increase in the reactor coolant system, and void fraction distributions on the primary side of the system. Mathematical models of these and other physical processes were developed and assessed against the experimental data from the PKL III Experiment B4.5

305

Study and Optimization on graft polymerization under normal pressure and air atmospheric conditions, and its application to metal adsorbent  

International Nuclear Information System (INIS)

Radiation-induced graft polymerization of glycidyl methacrylate (GMA) onto non-woven polyethylene (NWPE) fabric was achieved under normal pressure and air atmospheric conditions, without using unique apparatus such as glass ampoules or vacuum lines. To attain graft polymerization under normal pressure and air atmospheric conditions, the effects of the pre-irradiation dose, pre-irradiation atmosphere, pre-irradiation temperature, de-aeration of GMA-emulsion, grafting atmosphere in a reactor, and dissolved oxygen (DO) concentration in GMA-emulsion on the degree of grafting (Dg) were investigated in detail. It was found that the DO concentration had the strongest influence, the pre-irradiation dose, de-aeration of emulsion and grafting atmosphere had a relatively strong impact, and the pre-irradiation atmosphere and pre-irradiation temperature had the least effect on Dg. The optimum DO concentration before grafting was 2.0 mg/L or less. When a polyethylene bottle was used as a reactor instead of a glass ampoule, graft polymerization under normal pressure and air atmospheric conditions could be achieved under the following conditions; the pre-irradiation dose was more than 50 kGy, the volume ratio of GMA-emulsion to air was 50:1 or less, and the DO concentration in GMA-emulsion during grafting was below 2.0 mg/L. Under these grafting conditions, Dg was controlled within a range of up to 362%. The prepared GMA–grafted NWPE (GMA–g-NWPE) fabric was modified with a phosphWPE) fabric was modified with a phosphoric acid to obtain an adsorbent for heavy metal ions. In the column-mode adsorption tests of Pb(II), the adsorption performance of the produced phosphorylated GMA–g-NWPE fabric (fibrous metal adsorbent) was not essentially dependent on the flow rate of the feed. The breakthrough points of 200, 500, and 1000 h?1 in space velocity were 483, 477 and 462 bed volumes, and the breakthrough capacities of the three flow rates were 1.16, 1.15 and 1.16 mmol-Pb(II)/g-adsorbent.

306

Study and Optimization on graft polymerization under normal pressure and air atmospheric conditions, and its application to metal adsorbent  

Science.gov (United States)

Radiation-induced graft polymerization of glycidyl methacrylate (GMA) onto non-woven polyethylene (NWPE) fabric was achieved under normal pressure and air atmospheric conditions, without using unique apparatus such as glass ampoules or vacuum lines. To attain graft polymerization under normal pressure and air atmospheric conditions, the effects of the pre-irradiation dose, pre-irradiation atmosphere, pre-irradiation temperature, de-aeration of GMA-emulsion, grafting atmosphere in a reactor, and dissolved oxygen (DO) concentration in GMA-emulsion on the degree of grafting (Dg) were investigated in detail. It was found that the DO concentration had the strongest influence, the pre-irradiation dose, de-aeration of emulsion and grafting atmosphere had a relatively strong impact, and the pre-irradiation atmosphere and pre-irradiation temperature had the least effect on Dg. The optimum DO concentration before grafting was 2.0 mg/L or less. When a polyethylene bottle was used as a reactor instead of a glass ampoule, graft polymerization under normal pressure and air atmospheric conditions could be achieved under the following conditions; the pre-irradiation dose was more than 50 kGy, the volume ratio of GMA-emulsion to air was 50:1 or less, and the DO concentration in GMA-emulsion during grafting was below 2.0 mg/L. Under these grafting conditions, Dg was controlled within a range of up to 362%. The prepared GMA-grafted NWPE (GMA-g-NWPE) fabric was modified with a phosphoric acid to obtain an adsorbent for heavy metal ions. In the column-mode adsorption tests of Pb(II), the adsorption performance of the produced phosphorylated GMA-g-NWPE fabric (fibrous metal adsorbent) was not essentially dependent on the flow rate of the feed. The breakthrough points of 200, 500, and 1000 h-1 in space velocity were 483, 477 and 462 bed volumes, and the breakthrough capacities of the three flow rates were 1.16, 1.15 and 1.16 mmol-Pb(II)/g-adsorbent.

Ueki, Yuji; Chandra Dafader, Nirmal; Hoshina, Hiroyuki; Seko, Noriaki; Tamada, Masao

2012-07-01

307

Advances in Thin Film Thermocouple Durability Under High Temperature and Pressure Testing Conditions  

Science.gov (United States)

Thin film thermocouples for measuring material surface temperature have been previously demonstrated on several material systems and in various hostile test environments. A well-developed thin film fabrication procedure utilizing shadow masking for patterning the sensors elements had produced thin films with sufficient durability for applications in high temperature and pressure environments that exist in air-breathing and hydrogen-fueled burner rig and engine test facilities. However, while shadow masking had been a reliable method for specimens with flat and gently curved surfaces, it had not been consistently reliable for use on test components with sharp contours. This work reports on the feasibility of utilizing photolithography processing for patterning thin film thermocouples. Because this patterning process required changes in the thin film deposition process from that developed for shadow masking, the effect of these changes on thin film adherence during burner rig testing was evaluated. In addition to the results of changing the patterning method, the effects on thin film adherence of other processes used in the thin film fabrication procedure is also presented.

Martin, Lisa C.; Fralick, Gustave C.; Taylor, Keith F.

1999-01-01

308

Impact of in-sewer transformation on 43 pharmaceuticals in a pressurized sewer under anaerobic conditions.  

Science.gov (United States)

The occurrence of 43 pharmaceuticals and 2 metabolites of ibuprofen was evaluated at the inlet and the outlet of a pressure sewer pipe in order to asses if in-sewer processes affect the pharmaceutical concentrations during their pass through the pipe. The target compounds were detected at concentrations ranging from low ng/L to a few ?g/L, which are in the range commonly found in municipal wastewater of the studied area. The changes in concentrations between two sampling points were negligible for most compounds, i.e. from -10 to 10%. A higher decrease in concentrations (25-60 %) during the pass through the pipe was observed for diltiazem, citalopram, clarithromycin, bezafibrate and amlodipine. Negative removal was calculated for sulfamethoxazole (-66 ± 15%) and irbesartan (-58 ± 25%), which may be due to the conversion of conjugates back to their parent compounds in the sewer. The results show that microbial transformation of pharmaceuticals begins in sewer, albeit to different extents for different compounds. Therefore, the in-sewer transformation of pharmaceuticals should be assessed especially when their concentrations are used to estimate and refine the estimation of their per capita consumption in a catchment of interest in the sewage epidemiology approach. PMID:25462720

Jelic, Aleksandra; Rodriguez-Mozaz, Sara; Barceló, Damia; Gutierrez, Oriol

2015-01-01

309

Farmers Under Pressure : Analysis of the Social Conditions of Cases of Animal Neglect  

DEFF Research Database (Denmark)

In this paper we analyse how risk factors in highly industrialised agriculture are connected to animal neglect. With Danish agriculture as a case study, we use two types of data. First, we use register data from Statistics Denmark to map how risk factors such as farmers’ financial and social troubles are connected to convictions of neglect. Second, we analyse narratives where interviewed farmers, involved in cases of neglect, describe how they themselves experienced the incidents. We find that while livestock farmers in general have a low risk of animal neglect problems, a small percentage of them face severe financial difficulties, divorce and psychiatric problems, which are connected to an increased risk of being convicted for the neglect of farm animals. The narratives bring forward themes of pressure related to financial trouble, technological break down, family problems, stress and a growing concern among the farmers towards the governmental control in farm animal production. We discuss how these factorscan be used to identify and help farmers with a high risk of being convicted of livestock neglect.

Andrade, Stefan Bastholm; Anneberg, Inger

2014-01-01

310

The ReactorSTM: Atomically resolved scanning tunneling microscopy under high-pressure, high-temperature catalytic reaction conditions  

Science.gov (United States)

To enable atomic-scale observations of model catalysts under conditions approaching those used by the chemical industry, we have developed a second generation, high-pressure, high-temperature scanning tunneling microscope (STM): the ReactorSTM. It consists of a compact STM scanner, of which the tip extends into a 0.5 ml reactor flow-cell, that is housed in a ultra-high vacuum (UHV) system. The STM can be operated from UHV to 6 bars and from room temperature up to 600 K. A gas mixing and analysis system optimized for fast response times allows us to directly correlate the surface structure observed by STM with reactivity measurements from a mass spectrometer. The in situ STM experiments can be combined with ex situ UHV sample preparation and analysis techniques, including ion bombardment, thin film deposition, low-energy electron diffraction and x-ray photoelectron spectroscopy. The performance of the instrument is demonstrated by atomically resolved images of Au(111) and atom-row resolution on Pt(110), both under high-pressure and high-temperature conditions.

Herbschleb, C. T.; van der Tuijn, P. C.; Roobol, S. B.; Navarro, V.; Bakker, J. W.; Liu, Q.; Stoltz, D.; Cañas-Ventura, M. E.; Verdoes, G.; van Spronsen, M. A.; Bergman, M.; Crama, L.; Taminiau, I.; Ofitserov, A.; van Baarle, G. J. C.; Frenken, J. W. M.

2014-08-01

311

The ReactorSTM: Atomically resolved scanning tunneling microscopy under high-pressure, high-temperature catalytic reaction conditions  

International Nuclear Information System (INIS)

To enable atomic-scale observations of model catalysts under conditions approaching those used by the chemical industry, we have developed a second generation, high-pressure, high-temperature scanning tunneling microscope (STM): the ReactorSTM. It consists of a compact STM scanner, of which the tip extends into a 0.5 ml reactor flow-cell, that is housed in a ultra-high vacuum (UHV) system. The STM can be operated from UHV to 6 bars and from room temperature up to 600 K. A gas mixing and analysis system optimized for fast response times allows us to directly correlate the surface structure observed by STM with reactivity measurements from a mass spectrometer. The in situ STM experiments can be combined with ex situ UHV sample preparation and analysis techniques, including ion bombardment, thin film deposition, low-energy electron diffraction and x-ray photoelectron spectroscopy. The performance of the instrument is demonstrated by atomically resolved images of Au(111) and atom-row resolution on Pt(110), both under high-pressure and high-temperature conditions

312

Phenomenology during the loss of residual heat removal system at midloop conditions with pressurizer PORVs open: Associated boron dilution  

International Nuclear Information System (INIS)

The loss of residual heat removal system (RHRS) at midloop operation is an important risk contributor at low power and shutdown conditions. In this kind of transient the reflux-condensation can play an important role during the sequence to avoid the core damage. Several simulations concerning the loss of the RHRS in a PWR-W with the pressurizer PORVs open have been carried out with TRACE code considering the availability of steam generators. The present study aims to analyze, firstly, the thermal-hydraulic behavior after the loss of RHRS at midloop conditions throughout different configurations with reflux-condensation as the sole cooling mechanism available, and secondly, the issue related to the boron dilution that takes place during this kind of transient. The simulation results show that in the open RCS configuration, an equilibrium pressure is obtained in all cases and the reflux-condensation removes an important part of the decay heat. Moreover, in some configurations, this mechanism may cause the formation of an unborated water slug in the crossover leg that can lead to a boron dilution sequence

313

The ReactorSTM: Atomically resolved scanning tunneling microscopy under high-pressure, high-temperature catalytic reaction conditions  

Energy Technology Data Exchange (ETDEWEB)

To enable atomic-scale observations of model catalysts under conditions approaching those used by the chemical industry, we have developed a second generation, high-pressure, high-temperature scanning tunneling microscope (STM): the ReactorSTM. It consists of a compact STM scanner, of which the tip extends into a 0.5 ml reactor flow-cell, that is housed in a ultra-high vacuum (UHV) system. The STM can be operated from UHV to 6 bars and from room temperature up to 600 K. A gas mixing and analysis system optimized for fast response times allows us to directly correlate the surface structure observed by STM with reactivity measurements from a mass spectrometer. The in situ STM experiments can be combined with ex situ UHV sample preparation and analysis techniques, including ion bombardment, thin film deposition, low-energy electron diffraction and x-ray photoelectron spectroscopy. The performance of the instrument is demonstrated by atomically resolved images of Au(111) and atom-row resolution on Pt(110), both under high-pressure and high-temperature conditions.

Herbschleb, C. T.; Tuijn, P. C. van der; Roobol, S. B.; Navarro, V.; Bakker, J. W.; Liu, Q.; Stoltz, D.; Cañas-Ventura, M. E.; Verdoes, G.; Spronsen, M. A. van; Bergman, M.; Crama, L.; Taminiau, I.; Frenken, J. W. M., E-mail: frenken@physics.leidenuniv.nl [Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. box 9504, 2300 RA Leiden (Netherlands); Ofitserov, A.; Baarle, G. J. C. van [Leiden Probe Microscopy B.V., J.H. Oortweg 21, 2333 CH Leiden (Netherlands)

2014-08-15

314

Preliminary Testing of a Pressurized Space Suit and Candidate Fabrics Under Simulated Mars Dust Storm and Dust Devil Conditions  

Science.gov (United States)

In August 2009 YAP Films (Toronto) received permission from all entities involved to create a documentary film illustrating what it might be like to be on the surface of Mars in a space suit during a dust storm or in a dust devil. The science consultants on this project utilized this opportunity to collect data which could be helpful to assess the durability of current space suit construction to the Martian environment. The NDX-1 prototype planetary space suit developed at the University of North Dakota was used in this study. The suit features a hard upper torso garment, and a soft lower torso and boots assembly. On top of that, a nylon-cotton outer layer is used to protect the suit from dust. Unmanned tests were carried out in the Martian Surface Wind Tunnel (MARSWIT) at the NASA Ames Research Center, with the suit pressurized to 10 kPa gauge. These tests blasted the space suit upper torso and helmet, and a collection of nine candidate outer layer fabrics, with wind-borne simulant for five different 10 min tests under both terrestrial and Martian surface pressures. The infiltration of the dust through the outer fabric of the space suit was photographically documented. The nine fabric samples were analyzed under light and electron microscopes for abrasion damage. Manned tests were carried out at Showbiz Studios (Van Nuys, California) with the pressure maintained at 20 2 kPa gauge. A large fan-created vortex lifted Martian dust simulant (Fullers Earth or JSC Mars-1) off of the floor, and one of the authors (Lee) wearing the NDX-1 space suit walked through it to judge both subjectively and objectively how the suit performed under these conditions. Both the procedures to scale the tests to Martian conditions and the results of the infiltration and abrasion studies will be discussed.

Gaier, James R.; deLeon, Pablo G.; Lee, Pascal; McCue, Terry R.; Hodgson, Edward W.; Thrasher, Jeff

2010-01-01

315

Geochemistry of ultrahigh-pressure anatexis: fractionation of elements in the Kokchetav gneisses during melting at diamond-facies conditions  

Science.gov (United States)

The Kokchetav complex in Kazakhstan contains garnet-bearing gneisses that formed by partial melting of metasedimentary rocks at ultrahigh-pressure (UHP) conditions. Partial melting and melt extraction from these rocks is documented by a decrease in K2O and an increase in FeO + MgO in the restites. The most characteristic trace element feature of the Kokchetav UHP restites is a strong depletion in light rare earth elements (LREE), Th and U. This is attributed to complete dissolution of monazite/allanite in the melt and variable degree of melt extraction. In contrast, Zr concentrations remain approximately constant in all gneisses. Using experimentally determined solubilities of LREE and Zr in high-pressure melts, these data constrain the temperature of melting to ~1,000 °C. Large ion lithophile elements (LILE) are only moderately depleted in the samples that have the lowest U, Th and LREE contents, indicating that phengite retains some LILE in the residue. Some restites display an increase in Nb/Ta with respect to the protolith. This further suggests the presence of phengite, which, in contrast to rutile, preferentially incorporates Nb over Ta. The trace element fractionation observed during UHP anatexis in the Kokchetav gneisses is significantly different from depletions reported in low-pressure restites, where generally no LREE and Th depletion occurs. Melting at UHP conditions resulted in an increase in the Sm/Nd ratio and a decoupling of the Sm-Nd and Lu-Hf systems in the restite. Further subduction of such restites and mixing with mantle rocks might thus lead to a distinct isotopic reservoir different from the bulk continental crust.

Stepanov, Aleksandr S.; Hermann, Joerg; Korsakov, Andrey V.; Rubatto, Daniela

2014-05-01

316

Re-embrittlement of annealed pressure vessel, IAI1-material condition of a Loviisa irradiated weld  

International Nuclear Information System (INIS)

The re-irradiated (IAI1) material condition data of a VVER-440 weld, which is part of the contribution of Fortum Nuclear Services Ltd. to the IAEA research programme, are given in summary. The data were created with the lower half of the Loviisa NPP re-irradiation chain 12K3 using specimen reconstitution. The second re-irradiation fluence will be created with the upper half of the same chain later on. The tests include tensile tests, ISO Charpy-V impact tests, Charpy-V impact tests of 5 mm x5 mm and 3 mm x 4 mm cross-sectional specimens and fracture toughness tests of 10 mm x10 mm and 5 mm x 5 mm cross-sectional specimens. The baseline, I and IA-condition data have been reported earlier. The joint analyses of the test results including earlier Loviisa data as well as a short comparison to an irradiation in Halden are given. (orig.)

317

A Barometric Survey of Dust-Devil Vortices on a Desert Playa  

Science.gov (United States)

Dust devils, and other columnar vortices, are associated with local surface pressure drops that can be observed in time-series data on both Earth and Mars. High cadence measurements are needed to resolve these small structures, and we report a month-long survey (June/July 2012) on a Nevada desert playa using microbarographs sampled multiple times per second. Candidate dust-devil signatures are classified, with detections being robust at about one per day for pressure drops exceeding 0.3 hPa (roughly a 5:1 signal-to-noise threshold, where the observed noise level corresponds reasonably well with the dynamic pressure associated with the estimate convective velocity scale). The vortex population is evaluated and compared with those observed on Mars: a broken power law or a more convex distribution describes the terrestrial data. A single station observes about three events per week (for normalized pressure drops of 0.06 %), about three times fewer than Mars observations for the same normalized drop. We find evidence for clustering of vortex events in a pseudo-periodic manner with a 20-min period, consistent with the size of boundary-layer convection cells.

Lorenz, Ralph D.; Lanagan, Peter D.

2014-12-01

318

Electrochemical promotion of catalytic ethylene oxidation on Pt/YSZ catalyst under low pressure conditions  

Energy Technology Data Exchange (ETDEWEB)

The catalytic oxidation of C{sub 2}H{sub 4} on Pt catalyst film interfaced with the oxygen-ion conducting yttria-stabilized zirconia solid electrolyte (YSZ) has been studied in the 10{sup -5} and 10{sup -4} mbar range. Photoemission electron microscopy (PEEM) was used as spatially resolving method. Under open circuit conditions (VWR=0 V) the CO{sub 2} production increases by rising p(C{sub 2}H{sub 4}) and then at a critical point decreases sharply, showing a pronounced hysteresis. The hysteresis and the abrupt rate decrease are attributed to the build-up of a carbonaceous CH{sub x} layer inhibiting O{sub 2} adsorption and hence poisoning the catalyst. Applying an anodic potential of +1V leads to trigger a transition from the unreactive branch of the reaction to an active branch. The huge non-Faradayicity reported in the literature for this reaction system is explained as an ignition effect caused by the partial removal of the inhibiting carbonaceaous layer. The electrode has been characterized by SEM, XRD and a profilometer.

Toghan, Arafat; Roesken, Liz Michaela; Imbihl, Ronald [Institut fuer Physikalische Chemie und Elektrochemie, Universitaet Hannover, Callinstrasse 3-3a, D-30167 Hannover (Germany)

2010-07-01

319

Ethanol preference, metabolism, blood pressure, and conditioned taste aversion in experimental cholestasis.  

Science.gov (United States)

The effect of a ligation of the common bile duct (BDL) on the chronic free-selection intake of ethanol was investigated. Rats were given a choice between water and a solution of either 6% (v/v) ethanol, 0.06% (w/v) sodium saccharin, or a mixture of both ethanol and saccharin. In different experiments, solutions were first presented either 3 weeks before surgery, about the time of surgery, or 2 weeks after surgery. Reductions in ethanol or saccharin intake were observed in BDL rats whenever the solutions were first presented either 3 weeks before or shortly after the surgery. No differences attributable to BDL were seen when ethanol solutions were first presented 2 weeks after surgery. The contingent nature of the effect suggests that the reduction results from a conditioned taste aversion rather than from differences in ethanol metabolism, sensitivity, or neurohormones such as angiotensin. The findings urge caution in the monitoring of the dietary habits of patients with a rapidly developing biliary obstruction. PMID:9259003

Lane, J R; Starbuck, E M; Fitts, D A

1997-08-01

320

Analytical investigation of multicavity prestressed concrete pressure vessels for elastic loading conditions  

International Nuclear Information System (INIS)

A three-dimensional finite-element analysis of a commercial high-temperature gas-cooled reactor (HTGR) was made using the finite-element code STATIC-SAP. Four loading conditions were analyzed elastically to evaluate the behavior of the concentric core prestressed concrete reactor vessel (PCRV) of the HTGR. The results of the analysis were evaluated in accordance with Section III, Division 2, of the ASME Code for Reactor Vessels and Containments. The calculated maximum stresses were found to be well within the Code-allowable values. The analysis was preceded by an evaluation of candidate computer codes using comparisons of experimental data with analytical results for the Ohbayashi-Gumi multicavity PCRV model. This vessel was chosen as a basis for comparison because of its geometrical similarity to the large multicavity PCRV and the anticipated availability of a complete set of the original experimental data. The three-dimensional finite-element codes NONSAP and STATIC-SAP were used for the analysis of the Ohbayashi-Gumi vessel

321

In situ Evidence of Breaking the Ion Frozen-in Condition via the Non-gyrotropic Pressure Effect in Magnetic Reconnection  

CERN Document Server

For magnetic reconnection to proceed, the frozen-in condition for both ion fluid and electron fluid in a localized diffusion region must be violated by inertial effects, thermal pressure effects, or inter-species collisions. It has been unclear which underlying effects unfreeze ion fluid in the diffusion region. By analyzing in-situ THEMIS spacecraft measurements at the dayside magnetopause, we present clear evidence that the off-diagonal components of the ion pressure tensor is mainly responsible for breaking the ion frozen-in condition in reconnection. The off-diagonal pressure tensor, which corresponds to a nongyrotropic pressure effect, is a fluid manifestation of ion demagnetization in the diffusion region. From the perspective of the ion momentum equation, the reported non-gyrotropic ion pressure tensor is a fundamental aspect in specifying the reconnection electric field that controls how quickly reconnection proceeds.

Dai, Lei; Angelopoulos, Vassilis; Glassmeier, Karl-Heinz

2015-01-01

322

Field-emitting Townsend regime of surface dielectric barrier discharges emerging at high pressure up to supercritical conditions  

Science.gov (United States)

Surface dielectric barrier discharges (DBDs) in CO2 from atmospheric pressure up to supercritical conditions generated using 10 kHz ac excitation are investigated experimentally. Using current–voltage and charge–voltage measurements, imaging, optical emission spectroscopy, and spontaneous Raman spectroscopy, we identify and characterize a field-emitting Townsend discharge regime that emerges above 0.7 MPa. An electrical model enables the calculation of the discharge-induced capacitances of the plasma and the dielectric, as well as the space-averaged values of the surface potential and the potential drop across the discharge. The space-averaged Laplacian field is accounted for in the circuit model by including the capacitance due to the fringe electric field from the electrode edge. The electrical characteristics are demonstrated to fit the description of atmospheric-pressure Townsend DBDs (Naudé et al 2005 J. Phys. D: Appl. Phys. 38 530–8), i.e. self-sustained DBDs with minimal space-charge effects. The purely continuum emission spectrum is due to electron–neutral bremsstrahlung corresponding to an average electron temperature of 2600 K. Raman spectra of CO2 near the critical point demonstrate that the average gas temperature increases by less than 1 K.

Pai, David Z.; Stauss, Sven; Terashima, Kazuo

2015-04-01

323

Numerical simulation on the "S" characteristics and pressure fluctuation of reduced pump-turbine at start-up condition  

Science.gov (United States)

The performance of a reversible pump turbine with S-shaped characteristics is of great importance to the transition processes such as start-up and load rejection. In order to improve the "S" characteristics of reduced pump-turbine, several MGV (misaligned guide vane) schemes are calculated. The SST (shear stress turbulence) model is added to the N-S (Navier-strokes) governing equation. In order to predict the S-shaped curve accurately and develop a reliable tool for design improvement, the "S" characteristic is investigated in a whole pump-turbine including spiral casing, stay vanes, guide vanes, runner and draft tube. To validate the scheme reasonable, the mesh independent is tested. Comparison of unit discharge and unit speed performance showed that good correspondence is obtained between experimental data and calculated results. The "S shape" of reduced pump-turbine is eliminated with MGV schemes. Based on this, internal flow analysis is carried out adopting six typical MGV schemes at the same working condition. Through the calculation, we find that, first the pressure fluctuation is different between the guide vane and runner among the five MGV schemes, second the pressure fluctuation amplitude of MGV schemes D (4*35° and 16*6° average installed) is smallest, third the main frequency is the blade passing frequency and guide vane passing frequency at vane-less space and head cover, respectively. The conclusion is the "S shape" of pump-turbine can be improved with the average installed scheme.

Liu, D. M.; Zheng, J. S.; Wen, G. Z.; Zhao, Y. Z.; Shi, Q. H.

2012-11-01

324

Experimental determination of stability conditions of methane hydrate in aqueous calcium chloride solutions using high pressure differential scanning calorimetry  

International Nuclear Information System (INIS)

The validity of differential scanning calorimetry (d.s.c.) as an alternate method of determination of thermodynamic conditions of stability of gas hydrates in aqueous media was asserted by comparison to literature data, in the case of methane hydrate in pure water and in sodium chloride solutions. Requirements for thermodynamic validity of the equilibrium temperatures measured by this technique were investigated and are discussed in details. New equilibrium data of (methane hydrate + water + methane) in aqueous calcium chloride solutions, in the concentration range from x=8.47·10-3 to x=53.27·10-3, were determined using the same method, in the pressure range 5 MPa to 11 MPa. Experimental results were compared to data computed using a model that is presented, showing very good agreement over a wide range of salt concentration. These results confirm the interesting perspectives of application of this technique in the field of gas hydrate thermodynamics

325

Influence of deposition conditions on mechanical properties of low-pressure chemical vapor deposited low-stress silicon nitride films  

International Nuclear Information System (INIS)

The effect of deposition temperature, deposition pressure, or input gas ratio (SiH2Cl2:NH3) on film stress was determined for low-pressure chemical vapor deposited silicon nitride films. Wafer curvature measurements were performed for films deposited on single crystal silicon and amorphous silica wafer substrates to determine film stress ?dep, biaxial modulus Ef+, and coefficient of thermal expansion ?f. Apparent plane strain film modulus E-barf' and hardness H were measured using depth-sensing indentation. Ellipsometry was used to measure film thickness tf and refractive index n. Infrared spectroscopy, x-ray photoelectron spectroscopy (XPS), forward recoil energy spectroscopy (FReS), and Rutherford backscattering spectroscopy (RBS) experiments were performed to determine film composition. Although film deposition stress varied from -135 MPa (compressive) to 235 MPa (tensile) Ef+, E-barf', H, and ?f remained nearly constant. Infrared spectroscopy resolved only Si-N species for all films, and results from FReS on three films confirmed that the hydrogen content was negligible. RBS and XPS indicated that Si/N increased with increased compressive ?dep. Ellipsometry and RBS indicated that all films were silicon-rich, to a greater extent with increased compressive ?dep. As RBS indicatesive ?dep. As RBS indicated that atomic density decreased with increased compressive deposition stress, it was concluded that the deposition conditions changed both thermal and intrinsic deposition stress for all films. In particular, intrinsic stress was tensile, and became increasingly tensile for increased Si/N and decreased atomic density. Assuming thermal stress was similar for all films examined here, the intrinsic stress must have varied from changes dependent on the deposition conditions

326

Density and formation of high coordinated Si in v-MgSiO3 recovered from high pressure conditions  

Science.gov (United States)

The density and structure of decompressed vitreous MgSiO&3 were measured using the Archimedean method and ^{29}Si MAS-NMR spectroscopy. Glasses were compressed in the 6/8 multianvil apparatus to 10.0 ± 0.5 GPa at room temperature, and some were heated to 773 K for four hours, quenched, and decompressed at rates of 10.4 GPa/min and 0.08 GPa/min. Recovered samples from 10 GPa and room temperature are permanently densified by ~ 3.0% relative to the glass as-made. Heating samples to 773 K at the same pressure condition results in ~ 7.4% of permanent densification at slow decompression rates and ~11.0% for rapid decompression rates. ^{29}Si MAS-NMR spectra were obtained from these recovered glasses. At ambient pressure the ^{29}Si spectrum has one dominant peak with an isotropic chemical shift (?-iso) of 82.3 ppm and full width half maximum (FWHM) of 24 ppm. This peak corresponds to tetrahedrally coordinated Si (^{[4]}Si) with two bridging oxygens (Q2 species). The Q2 peak for high-pressure samples is more symmetric and shifted to -81.6 ppm with a FWHM of 21 ppm. The pressure-quenched samples also possess peaks at 180 ppm and, in the case of the rapidly quench glass, an additional peak at 124 ppm. The 180 ppm peak is assigned to octahedrally coordinated Si (^{[6]}Si), based on the ?-iso measured for ^{[6]}Si species by Stebbins and Kanzaki (1991). We assign the peak at 124 ppm to 5-fold coordinated Si (^{[5]}Si), based on its intermediate position between the ^{[4]}Si and ^{[6]}Si and the results of ab initio calculations. These calculations predict a chemical shift of -120 ppm for ^{[5]}Si with three bridging oxygens (Q^{3*} species). It is noteworthy that the high-pressure samples exhibit a -0.7 ppm shift and 3 ppm reduction in the FWHM for the Q2 peak. We attribute these features to a permanent reduction in inter-tetrahedral (Si-O-Si) bond angles. The measured density differences in pressure-quenched samples and the preservation of ^{[5]}Si in the rapidly decompressed sample demonstrates the importance of quench rate on the kinetics of back-reaction to ^{[4]}Si. We conclude that densification of v-MgSiO3 at 10.0 GPa and 773 K is largely accommodated by the twisting of network chains to form ^{[5]}Si and eventually stabilization of ^{[6]}Si with significant contribution from Si-O-Si bond angle compression. These observations of structural changes accommodating densification of v-MgSiO3 aid in understanding of the properties of refractory silicate melts in the Earth's deep interior.

Gaudio, S. J.; Sen, S.; Yu, P.; Lesher, C. E.

2006-12-01

327

Stability of supercritical water-cooled reactor during steady-state and sliding pressure start-up conditions  

International Nuclear Information System (INIS)

Full text of publication follows: The drastic change of fluid density in the reactor core of a supercritical water-cooled reactor (SCWR) gives rise to the concern of density wave stability. Using a single channel thermal-hydraulic model, the stability boundary maps of the U.S. reference SCWR design have been constructed for both the steady state and the sliding pressure start-up conditions. For the steady state, the supercritical water in the reactor core has been simulated using a three-region model - (1) a 'heavy fluid' with constant density, (2) a mixture of 'heavy fluid' and 'light fluid' similar to homogeneous-equilibrium two-phase mixture, and finally (3) a 'light fluid' which behaves like an ideal gas or superheated steam. The governing non-dimensional groups have been determined from a non-dimensional analysis of the conservation equations for this three-region supercritical water model. Two important non-dimensional groups, namely, Pseudo-Subcooling number (Npsub) and Expansion number (Nexp), which are similar to the Subcooling number (Nsub) and Phase Change number (Npch) commonly used in the analysis of the subcritical two-phase flow, have been identified for the supercritical region. The stability map in the supercritical region has been plotted in the Pseudo-Subcooling number versus Expansion number plane. It has been found that the U. S. reference SCWR design operates in the stable region with a big margin. Sens the stable region with a big margin. Sensitivity studies have been performed with respect to the inlet orifice coefficient, system pressure and the inlet coolant velocity. It has been found that the stability boundary in the Npsub - Nexp plane is not sensitive to the system pressure and the inlet coolant velocity, but it is sensitive to the inlet orifice coefficient. This is consistent with the findings of the earlier research done for the subcritical two-phase flow. During the sliding pressure start-up operation of the SCWR, two-phase steam-water mixture at subcritical pressure will appear in the reactor core. A non-homogeneous (e. g., drift-flux) nonequilibrium two-phase flow model was applied. An exponential vapor generation rate for subcooled boiling was assumed along with a simplified but recent correlation for vapor drift velocity. The characteristic equation was numerically integrated, and the stability boundary map was plotted on the traditional Subcooling number versus Phase Change number plane. The effects of different two-phase flow models on the stability boundary have also been investigated. Thus, stability boundary maps have been constructed using four different models, namely, the Homogenous-Equilibrium model, the Homogenous-Nonequilibrium model, the Non-homogenous-Equilibrium model and the Non-homogenous-Non-Equilibrium model. It has been found that the Homogenous-Nonequilibrium model predicts the most conservative stability boundary at high Subcooling numbers, while the Homogenous-Equilibrium model yields the most conservative boundary at low Subcooling numbers. These maps are being used to develop the sliding pressure start-up strategies of the SCWR. Work is underway to expand the single channel model to a multi-channel model with neutronic feedback to study the local flow instabilities in a SCWR. (authors)

328

Environmentally-Assisted Cracking of Low-Alloy Reactor Pressure Vessel Steels under Boiling Water Reactor Conditions  

International Nuclear Information System (INIS)

The present report summarizes the experimental work performed by PSI on the environmentally-assisted cracking (EAC) of low-alloy steels (LAS) in the frame of the RIKORR-project during the period from January 2000 to August 2001. Within this project, the EAC crack growth behaviour of different low-alloy reactor pressure vessel (RPV) steels, weld filler and weld heat-affected zone materials is investigated under simulated transient and steady-state BWR/NWC power operation conditions. The EAC crack growth behaviour of different low-alloy RPV steels was characterized by slow rising load (SRL) / low-frequency corrosion fatigue (LFCF) and constant load tests with pre-cracked fracture mechanics specimens in oxygenated high-temperature water at temperatures of either 288, 250, 200 or 150 C. These tests revealed the following important interim results: Under low-flow and highly oxidizing (ECP >= 100 mV SHE) conditions, the ASME XI 'wet' reference fatigue crack growth curve could be significantly exceeded by cyclic fatigue loading at low frequencies (<0.001 Hz), at high and low load-ratios R, and by ripple loading near to DKth fatigue thresholds. The BWR VIP 60 SCC disposition lines may be significantly or slightly exceeded (even in steels with a low sulphur content) in the case of small load fluctuations at high load ratios (ripple loading) or at intermediate temperatures (200 -250 C) in RPV materials, which show a distinct susceptibility to dynamic strain ageing (DSA). (author)

329

Shape-controlled synthesis of diamond crystal by epitaxial growth under high pressure and high temperature conditions  

Science.gov (United States)

In this paper, the diamond epitaxial growth mechanism has been studied in detail by employing several types of diamond as a seed in a catalyst—graphite system under high pressure and high temperature (HPHT) conditions. We find that the diamond nucleation, growth rate, crystal orientation, and morphology are significantly influenced by the original seeds. The smooth surfaces of seeds are beneficial for the fabrication of high-quality diamond. Our results reveal that the diamond morphology is mainly determined by the original shape of seeds in the early growth stage, but it has an adjustment process during the growth and leads to well symmetry. Additionally, we have also established the growth model for the twinned diamond grown on several seeds, and proposed the possible growth processes by tracking the particular shapes of seeds before and after treatment under HPHT conditions. These results suggest that the shape-controlled synthesis of diamond with well morphology can be realized by employing certain suitable diamond seeds. This work is expected to play an important role in the preparation of trustworthy diamond-based electronic and photonic devices.

Liu, Xiao-Bing; Jia, Xiao-Peng; Zhang, Zhuang-Fei; Huang, Hai-Liang; Zhou, Zhen-Xiang; Ma, Hong-An

2011-12-01

330

Environmentally-Assisted Cracking of Low-Alloy Reactor Pressure Vessel Steels under Boiling Water Reactor Conditions  

Energy Technology Data Exchange (ETDEWEB)

The present report summarizes the experimental work performed by PSI on the environmentally-assisted cracking (EAC) of low-alloy steels (LAS) in the frame of the RIKORR-project during the period from January 2000 to August 2001. Within this project, the EAC crack growth behaviour of different low-alloy reactor pressure vessel (RPV) steels, weld filler and weld heat-affected zone materials is investigated under simulated transient and steady-state BWR/NWC power operation conditions. The EAC crack growth behaviour of different low-alloy RPV steels was characterized by slow rising load (SRL) / low-frequency corrosion fatigue (LFCF) and constant load tests with pre-cracked fracture mechanics specimens in oxygenated high-temperature water at temperatures of either 288, 250, 200 or 150 C. These tests revealed the following important interim results: Under low-flow and highly oxidizing (ECP >= 100 mV SHE) conditions, the ASME XI 'wet' reference fatigue crack growth curve could be significantly exceeded by cyclic fatigue loading at low frequencies (<0.001 Hz), at high and low load-ratios R, and by ripple loading near to DKth fatigue thresholds. The BWR VIP 60 SCC disposition lines may be significantly or slightly exceeded (even in steels with a low sulphur content) in the case of small load fluctuations at high load ratios (ripple loading) or at intermediate temperatures (200 -250 C) in RPV materials, which show a distinct susceptibility to dynamic strain ageing (DSA). (author)

Seifert, H.P.; Ritter, S

2002-02-01

331

Study of hydride blisters grown on Zr-2.5Nb pressure tube spool piece under simulated condition of in-reactor pressure and temperature  

International Nuclear Information System (INIS)

Indian Pressurised Heavy Water Reactor (PHWR) have pressure tubes, made from zirconium alloy. These pressure tubes undergo corrosion with the high temperature (300 deg C) heavy water coolant under the reactor environment and pick up a part of hydrogen generated as result of this corrosion reaction. This hydrogen affects the integrity of pressure tubes in many ways; nucleation and growth of hydride blisters being one of them. The present study has been carried out to understand the mechanisms of nucleation and growth of hydride blisters and their effect on the serviceability of the component in the reactor environment. (author)

332

Numerical simulation on the 'S' characteristics and pressure fluctuation of reduced pump-turbine at start-up condition  

International Nuclear Information System (INIS)

The performance of a reversible pump turbine with S-shaped characteristics is of great importance to the transition processes such as start-up and load rejection. In order to improve the 'S' characteristics of reduced pump-turbine, several MGV (misaligned guide vane) schemes are calculated. The SST (shear stress turbulence) model is added to the N-S (Navier-strokes) governing equation. In order to predict the S-shaped curve accurately and develop a reliable tool for design improvement, the 'S' characteristic is investigated in a whole pump-turbine including spiral casing, stay vanes, guide vanes, runner and draft tube. To validate the scheme reasonable, the mesh independent is tested. Comparison of unit discharge and unit speed performance showed that good correspondence is obtained between experimental data and calculated results. The 'S shape' of reduced pump-turbine is eliminated with MGV schemes. Based on this, internal flow analysis is carried out adopting six typical MGV schemes at the same working condition. Through the calculation, we find that, first the pressure fluctuation is different between the guide vane and runner among the five MGV schemes, second the pressure fluctuation amplitude of MGV schemes D (4*35° and 16*6° average installed) is smallest, third the main frequency is the blade passing frequency and guide vane passing frequency at vane-less space and head cover, respectively. The conclusion is the 'S shape' of pump-turbine can be improved withpe' of pump-turbine can be improved with the average installed scheme.

333

Crack growth behaviour of low alloy steels for pressure boundary components under transient light water reactor operating conditions (CASTOC)  

International Nuclear Information System (INIS)

The CASTOC project addresses environmentally assisted cracking (EAC) phenomena in low alloy steels used for pressure boundary components in both Western type boiling water reactors (BWR) and Russian type pressurised water reactors (VVER). It comprises the four work packages (WP): inter-laboratory comparison test (WP1); EAC behaviour under static load (WP2), EAC behaviour under cyclic load and load transients (WP3); evaluation of the results with regard to their relevance for components in practice (WP4). The use of sophisticated test facilities and measurement techniques for the on-line detection of crack advances have provided a more detailed understanding of the mechanisms of environmentally assisted cracking and provided quantitative data of crack growth rates as a function of loading events and time, respectively. The effect of several major parameters controlling EAC was investigated with particular emphasis on the transferability of the results to components in service. The obtained crack growth rate data were reflected on literature data and on commonly applied prediction curves as presented in the appropriate Code. At relevant stress intensity factors it could be shown that immediate cessation of growing cracks occurs after changing from cyclic to static load in high purity oxygenated BWR water and oxygen-free VVER water corresponding to steady state operation conditions. Susceptibility to environmentally assisted cracking under static load was observed for a heat affected zone material in oxygenated high purity water and also in base materials during a chloride transient representing BWR water condition below Action Level 1 of the EPRI Water Chemistry Guidelines according to the lectrical conductivity of the water but in the range of Action Level 2 according to the content of chlorides. Time based crack growth was also observed in one Russian type base material in oxygenated VVER water and in one Western type base material in oxygenated high purity BWR water at stress intensity factors above the limit for linear elastic fracture mechanics. There is evidence that the prediction curves of the ASME Boiler and Pressure Vessel Code Section XI, Appendix A are not conservative for some relevant cases with regard to crack growth rates under cyclic load even in oxygenated high purity BWR water. The CASTOC results have provided an important contribution to the understanding of crack growth behavior on the one hand as a function of time and on the other hand as a consequence of the number and height of loading events. This is an important key for the evaluation of transient events, which may occur in a plant during service. (orig.)

334

Crack growth behaviour of low alloy steels for pressure boundary components under transient light water reactor operating conditions (CASTOC)  

Energy Technology Data Exchange (ETDEWEB)

The CASTOC project addresses environmentally assisted cracking (EAC) phenomena in low alloy steels used for pressure boundary components in both Western type boiling water reactors (BWR) and Russian type pressurised water reactors (VVER). It comprises the four work packages (WP): inter-laboratory comparison test (WP1); EAC behaviour under static load (WP2), EAC behaviour under cyclic load and load transients (WP3); evaluation of the results with regard to their relevance for components in practice (WP4). The use of sophisticated test facilities and measurement techniques for the on-line detection of crack advances have provided a more detailed understanding of the mechanisms of environmentally assisted cracking and provided quantitative data of crack growth rates as a function of loading events and time, respectively. The effect of several major parameters controlling EAC was investigated with particular emphasis on the transferability of the results to components in service. The obtained crack growth rate data were reflected on literature data and on commonly applied prediction curves as presented in the appropriate Code. At relevant stress intensity factors it could be shown that immediate cessation of growing cracks occurs after changing from cyclic to static load in high purity oxygenated BWR water and oxygen-free VVER water corresponding to steady state operation conditions. Susceptibility to environmentally assisted cracking under static load was observed for a heat affected zone material in oxygenated high purity water and also in base materials during a chloride transient representing BWR water condition below Action Level 1 of the EPRI Water Chemistry Guidelines according to the lectrical conductivity of the water but in the range of Action Level 2 according to the content of chlorides. Time based crack growth was also observed in one Russian type base material in oxygenated VVER water and in one Western type base material in oxygenated high purity BWR water at stress intensity factors above the limit for linear elastic fracture mechanics. There is evidence that the prediction curves of the ASME Boiler and Pressure Vessel Code Section XI, Appendix A are not conservative for some relevant cases with regard to crack growth rates under cyclic load even in oxygenated high purity BWR water. The CASTOC results have provided an important contribution to the understanding of crack growth behavior on the one hand as a function of time and on the other hand as a consequence of the number and height of loading events. This is an important key for the evaluation of transient events, which may occur in a plant during service. (orig.)

Foehl, J.; Weissenberg, T. [Materialpruefungsanstalt, Univ. Stuttgart (Germany); Gomez-Briceno, D.; Lapena, J. [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT) (Spain); Ernestova, M.; Zamboch, M. [Nuclear Research Inst. (NRI) (Czech Republic); Seifert, H.P.; Ritter, S. [Paul Scherrer Inst. (PSI) (Switzerland); Roth, A.; Devrient, B. [Framatome ANP GmbH (F ANP) (Germany); Ehrnsten, U. [Technical Research Centre of Finland (VTT) (Finland)

2004-07-01

335

Detectability and significance of the 12h barometric tide in the radon-222 signal, dripwater flow rate, carbon dioxide concentration and air temperature of an underground laboratory.  

Science.gov (United States)

Radon concentration has been measured since 1995 in the Roselend dead-end tunnel, in the French Alps, together with other geophysical and geochemical parameters. Bursts of radon concentration, reaching 65,600 Bq m-3 and up to several weeks duration, are observed over a background level of ca. 800 Bq m-3. These bursts appear to be related to the bedrock deformation or to the hydrogeological processes associated with the yearly cycle of water level in the nearby artificial Roselend Lake. In order to work out a generation mechanism, for these bursts, we developed tools to characterize the transport properties in the host rocks. Here, we concentrate on the 12h (S2) barometric tide. We first show, using real radon time series integrating synthetic signals, that a modified spectrogram method is more efficient than simple FFT to evidence weak periodic signals in such a context. Then, we apply this method to the radon concentration in the tunnel atmosphere measured by two different sensors: the AlphaGUARDTM sensor based on volumetric detection in an ionizing chamber, and the BarasolTM sensor, based on surface detection. Using the time series recorded by the AlphaGUARDTM, the S2 line, difficult to see with a simple FFT method, emerges clearly with our spectrogram method. This S2 line is not seen using the BarasolTM time series, illustrating the superior sensitivity of the AlphaGUARDTM for this particular purpose. Using a regular spectrogram analysis, we further show that the amplitude of the S2 line in the AlphaGUARDTM data depends on time, and appears particularly strong during the radon bursts. The presence of the S2 line reveals a high sensitivity of radon exhalation flux from the tunnel wall to changes of atmospheric pressure, and thus supports the advective transport mechanism for the radon bursts. A small but clear S2 component is also evidenced using our spectrogram method in a dripwater flow rate time series, representing a flow averaged over a 6 m2 area of the tunnel ceiling, while it is not observed in the flow rate of a more localized dripping. This suggests that some water drippings can also be affected by atmospheric pressure variations. The temporal structures of the S2 component in the flow rate and in the radon concentration, however, are not similar, indicating that water dripping from the ceiling cannot be the dominant source mechanism for the radon bursts. No S2 component is observed in the time series of carbon dioxide, but an interesting pattern is revealed by the S2 component of a temperature profile in the atmosphere. This study illustrates how a refined analysis to extract the S2 component in various geophysical time series can provide interesting clues on the complex processes affecting transport of fluids in unsaturated fractured media under multiple influences.

Richon, P.; Perrier, F.; Pili, E.; Boudon, G.; Villemant, B.; Sabroux, J.

2007-12-01

336

Numerical investigation of the spray-mesh-turbulence interactions for high-pressure, evaporating sprays at engine conditions  

International Nuclear Information System (INIS)

This work presents a numerical methodology to simulate evaporating, high pressure Diesel sprays using the Eulerian-Lagrangian approach. Specific sub-models were developed to describe the liquid spray injection and breakup, and the influence of the liquid jet on the turbulence viscosity in the vicinity of the nozzle. To reduce the computational time and easily solve the problem of the grid dependency, the possibility to dynamically refine the grid where the fuel-air mixing process takes place was also included. The validity of the proposed approach was firstly verified simulating an evaporating spray in a constant-volume vessel at non-reacting conditions. The availability of a large quantity of experimental data allowed us to investigate in detail the effects of grid size, ambient diffusivity and used spray sub-models. In this way, different guidelines were derived for a successful simulation of the fuel-air mixture formation process. Finally, fuel injection and evaporation were simulated in an optical engine geometry and computed mixture fraction distributions were compared with experimental data.

337

Influence of neutron exposure, chemical composition and metallurgical condition, on the irradiation shift of reactor pressure vessel steels  

International Nuclear Information System (INIS)

The work described in this paper is part of a continuing program to produce well-characterized data for use in the development of models for the prediction of irradiation shift in pressurized water reactor steels. Results are presented for around 50 batches of Charpy specimens, irradiated either in the DIDO or PLUTO heavy water, or in the HERALD light water, research reactors, to doses up to 35 mdpa (approx. 2 x 1019) n/cm2, E > 1 MeV). The materials include A533B plate, weld, and heat affected zones. The results are compatible with a log/log relationship between dose and shift with an exponent of 0.5 for all materials. They also show that irradiation response is dependent on heat treatment condition. If it is assumed that the Varsik and Byrne Chemistry Relationship, or a similar expression, is an appropriate parameter to characterize the effect of chemical composition on irradiation sensitivity, the results also demonstrate a difference between plate and weld irradiation sensitivity. An empirical model of the data has been developed and assessed, and this is compared with the Odette physically-based irradiation damage model

338

Surface charging patterns of stainless alloys – Effect of ageing in conditions of primary cooling circuit of pressurized water reactors  

International Nuclear Information System (INIS)

The predominance of electrostatic interactions in the mechanism of particle deposition onto solid surfaces is well documented. Therefore, an electrostatic approach has been used to predict the behavior of activated corrosion products in the primary cooling circuit of a pressurized water reactor (PWR). Only few results have been published on the potential at the interface of metallic alloys and aqueous solutions, even at room temperature. In this study, we present results about the characterization of representative materials such as Inconel 690, stainless steel 304 and Zircaloy 4 at room temperature, for pristine polished samples as well as after an 80-day ageing step in physico-chemical conditions similar to those of a primary circuit (360 °C, boron 1 g L?1 (as H3BO3), lithium 2 mg L?1 (as LiOH), hydrogen 30 cm3 kg?1). The surface potentials of these alloys have been determined using a streaming current method for pH from 3 to 7. Isoelectric points between 4.1 and 4.6 have been found for all samples and there is no effect of the ageing step. These values have been confirmed by adhesion studies of grafted latex particles either positively charged (amidine surface groups) or negatively charged (carboxylate groups) at pH 3.3 and pH 5.5. The results show that particles deposition is favored only when they carry a charge opposite to the substrate surfaces.

339

Simulated thin pericardial bioprosthetic valve leaflet deformation under static pressure-only loading conditions: implications for percutaneous valves.  

Science.gov (United States)

Percutaneous aortic valve (PAV) replacement is currently being investigated as an endovascular alternative to conventional open-chest valve surgery for patients with severe aortic stenosis. The results of multi-center clinical trials of PAV devices have been encouraging. However, there are serious adverse events associated with this procedure. Furthermore, long-term durability and safety of PAV need to be studied carefully. In this study, we developed a thin pericardial bioprosthetic valve model, which has similar design features of PAV. We utilized this model to investigate PAV deformation under static, pressure-only loading conditions using Finite Element method. Mechanical properties of PAV leaflet were obtained from planar biaxial testing of glutaraldehyde treated thin bovine pericardium (BP) and porcine pericardium (PP), and characterized by the Fung-elastic model. Simulations were performed to examine the effects of tissue thickness and anisotropy on the valve deformation and stress distribution. The results indicated peak stress and strain occurred in the vicinity of commissures. The peak maximum principal stresses (MPS) were reduced with the increase of leaflet tissue thickness, by 36% and 59% from the mean thickness to 0.35 mm for BP and PP, respectively. The PAV with BP leaflet had a lower peak MPS than that with PP leaflet. Moreover, leaflet material orientation had a significant influence on the peak MPS of PAV. PMID:20336372

Li, Kewei; Sun, Wei

2010-08-01

340

Evaluation of Low Pressure Fogging System for Improving Crop Yield of Tomato (Lycopersicon esculentum Mill.: Grown under Heat Stress Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available In Mediterranean regions, many tomato plants are grown throughout the hot summer period (May–September in sheltered cultivation, mainly for plant protection reasons. Most of the shelters that are used are low cost net houses covered with 50 mesh insect proof net. In most cases these net houses have a flat roof and no ventilation or climate control measures. This insufficient ventilation during the hot summer leads to above optimal air temperatures and causes moderate heat stress inside the shelters, which leads to yield reduction. The aim of this study was to evaluate the ability of a simple and inexpensive low pressure fogging system installed in a naturally ventilated net house to lower temperatures and improve the yield during the summer. The study showed that in areas where relative air humidity (RH during the daytime is less than 60%, tomato plants improved their performance when grown through the summer in net houses under moderate heat stress. Under fogging conditions pollen grain viability and fruit set were significantly improved. This improvement influenced the yield picked during September (104–136 DAP. However, total seasonal yield was not affected by the fogging treatment.

Kobi Shilo

2013-06-01

341

Stability of Hydrogen-Bonded Supramolecular Architecture under High Pressure Conditions: Pressure-Induced Amorphization in Melamine-Boric Acid Adduct  

International Nuclear Information System (INIS)

The effects of high pressure on the structural stability of the melamine-boric acid adduct (C3N6H6 2H3BO3, M 2B), a three-dimensional hydrogen-bonded supramolecular architecture, were studied by in situ synchrotron X-ray diffraction (XRD) and Raman spectroscopy. M 2B exhibited a high compressibility and a strong anisotropic compression, which can be explained by the layerlike crystal packing. Furthermore, evolution of XRD patterns and Raman spectra indicated that the M 2B crystal undergoes a reversible pressure-induced amorphization (PIA) at 18 GPa. The mechanism for the PIA was attributed to the competition between close packing and long-range order. Ab initio calculations were also performed to account for the behavior of hydrogen bonding under high pressure.

342

Experimental Study of Abiotic Organic Synthesis at High Temperature and Pressure Conditions: Carbon Isotope and Mineral Surface Characterizations  

Science.gov (United States)

Abiotic organic synthesis processes have been proposed as potential mechanisms for methane generation in subseafloor hydrothermal systems on Earth, and on other planets. To better understand the detailed reaction pathways and carbon isotope fractionations in this process under a wide range of physical and chemical conditions, hydrothermal experiments at high temperature (750 °C) and pressure (0.55 GPa) were performed using piston cylinder apparatus. Formic acid was used as the source of CO2 and H2, and magnetite was the mineral catalyst. The chemical and carbon isotopic compositions of dissolved organic products were determined by GC-C-MS-IRMS, while organic intermediaries on the mineral catalyst were characterized by Pyrolysis-GC-MS. Among experimental products, dissolved CO2 was the dominant carbon species with a relative abundance of 88 mol%. Dissolved CH4 and C2H6 were also identified with a mole ratio of CH4 over C2H6 of 15:1. No dissolved CO was detected in the experiment, which might be attributable to the loss of H2 through the Au capsule used in the experiments at high temperature and pressure conditions and corresponding conversion of CO to CO2 by the water-gas shift reaction. Carbon isotope results showed that the ?13C values of CH4 and C2H6 were -50.3‰ and -39.3‰ (V-PDB), respectively. CO2 derived from decarboxylation of formic acid had a ?13C value of -19.2‰, which was 3.2‰ heavier than its source, formic acid. The ?13C difference between CO2 and CH4 was 31.1‰, which was higher than the value of 9.4‰ calculated from theoretical isotopic equilibrium predictions at experimental conditions, suggesting the presence of a kinetic isotope effect. This number was also higher than the values (4.6 to 27.1‰) observed in similar experiments previously performed at 400 °C and 50 MPa with longer reaction times. CH4 is 11.0‰ less enriched in 13C than C2H6. Alcohols were observed as carbon compounds on magnetite surfaces by Pyrolysis-GC-MS, which confirms the hypothesis regarding the reaction pathways of hydrothermal abiotic organic synthesis proposed by Fu et al. (2007, 2008). In this proposed pathway, hydroxymethylene (-CHOH) groups serve as organic intermediaries on mineral surfaces while dissolved H2 serves as a chain terminator/breaker to generate short chain hydrocarbons and oxygenated compounds. This pathway is different from the carbide polymerization theory of Fischer-Tropsch-type (FTT) synthesis in a gas phase. The observed increase of ?13C values of C1 and C2 alkanes with carbon number in our hydrothermal experiments can be readily interpreted by hydroxymethylene pathway, and might be used to differentiate between hydroxymethylene and carbide polymerization pathways. Carbon isotope analysis of alcohols on mineral catalyst surfaces is under way to provide further constraints on formation of organic compounds by FTT in hydrothermal systems.

Fu, Q.; Socki, R. A.; Niles, P. B.

2010-12-01

343

RELAP5 Capability to Predict Pressure Wave Propagation Phenomena in Single- and Two-Phase Flow Conditions  

OpenAIRE

Correct evaluation of the hydrodynamic loads induced by large and rapid pressure waves propagating with the speed of sound along the reactor piping systems and Reactor Pressure Vessel (RPV) is an important and difficult issue of nuclear power plant safety. The pressure shock transients and resulting hydrodynamic loads on the pipes and RPV structures are commonly calculated with one-dimensional thermo-hydraulic system codes such as RELAP5, TRACE, DRAKO and ROLAST. In Sweden, the most widely us...

Lukasz Sokolowski; Zbigniew Koszela

2012-01-01

344

Measuring unsteady pressure on rotating compressor blades. [with semiconductor strain gages under gas turbine engine operating conditions  

Science.gov (United States)

The capability for accurate measurement of unsteady pressure on the surface of compressor and fan blades during engine operation was established. Tests were run on miniature semiconductor strain gage pressure transducers mounted in several arrangements. Both surface mountings and recessed flush mountings were tested. Test parameters included mounting arrangement, blade material, temperature, local strain in the blade, acceleration normal to the transducer diaphragm, centripetal acceleration, and pressure. Test results showed no failures of transducers or mountings and indicated an uncertainty of unsteady pressure measurement of approximately + or - 6%, plus 0.1 kPa for a typical application.

Englund, D. R.; Grant, H. P.; Lanati, G. A.

1979-01-01

345

Fuel pellets from biomass: The importance of the pelletizing pressure and its dependency on the processing conditions  

DEFF Research Database (Denmark)

The aim of the present study was to identify the key factors affecting the pelletizing pressure in biomass pelletization processes. The impact of raw material type, pellet length, temperature, moisture content and particle size on the pressure build up in the press channel of a pellet mill was studied using a single pellet press unit. It was shown that the pelletizing pressure increased exponentially with the pellet length. The rate of increase was dependent on biomass species, temperature, moisture content and particle size. A mathematical model, predicting the pelletizing pressure, was in good accordance with experimental data. It was shown that increasing the temperature resulted in a decrease of the pelletizing pressure. Infrared spectra taken from the pellets surface, indicated hydrophobic extractives on the pellet surface, for pellets produced at higher temperatures. The extractives act as lubricants, lowering the friction between the biomass and the press channel walls. The effect of moisture content on the pelletizing pressure was dependent on the raw material species. Different particle size fractions, from below 0.5 mm up to 2.8 mm diameter, were tested, and it was shown that the pelletizing pressure increased with decreasing particle size. The impact of pelletizing pressure on pellet density was determined, and it was shown that a pelletizing pressure above 200 MPa resulted only in minor increase in pellet density. 2011 Published by Elsevier Ltd.

Stelte, Wolfgang; Holm, Jens K.

2011-01-01

346

An evaluation of the quantitative effects on radon gas from the modification of a home heating and air conditioning system  

International Nuclear Information System (INIS)

The quantitative effects associated with the design, construction, operation, environmental and meteorological conditions on radon gas levels in a typical residential dwelling with a basement, having a measured radon level of approximately 20 pico-curies/liter (pCi/L), are evaluated. After several mechanical and electrical modifications are made on the dwelling's heating system, two different furnace breathing modes are studied. The effect on radon levels in the dwelling are observed as the furnace receives all of its combustion, draft and ventilation air - as the experiment alternates, on a bi-weekly basis - from inside and then outside the dwelling. Radon, barometric pressure, outside temperature, relative humidity, wind-speed and direction are monitored continuously; special household activity in the dwelling is also observed. A novel differential air pressure technique is used to measure inside versus outside house air pressure variations, twice each day, resulting from meteorological conditions, dwelling activity, and the furnace breathing mode. A rigorous statistical analysis is employed that includes sequential linear regression of time-series data, trend corrections to remove variations that contribute to the variance in the data without addition useful information. A novel approach using an electrical analog, to screen out unwanted variations is applied, by utilizing a computer routine to simulate the effect of an electronic RC filter, to achieve the desired ctronic RC filter, to achieve the desired analytical discrimination

347

Effect of aviation fuel type and fuel injection conditions on the spray characteristics of pressure swirl and hybrid air blast fuel injectors  

Science.gov (United States)

Feddema, Rick T. M.S.M.E., Purdue University, December 2013. Effect of Aviation Fuel Type and Fuel Injection Conditions on the Spray Characteristics of Pressure Swirl and Hybrid Air Blast Fuel Injectors. Major Professor: Dr. Paul E. Sojka, School of Mechanical Engineering Spray performance of pressure swirl and hybrid air blast fuel injectors are central to combustion stability, combustor heat management, and pollutant formation in aviation gas turbine engines. Next generation aviation gas turbine engines will optimize spray atomization characteristics of the fuel injector in order to achieve engine efficiency and emissions requirements. Fuel injector spray atomization performance is affected by the type of fuel injector, fuel liquid properties, fuel injection pressure, fuel injection temperature, and ambient pressure. Performance of pressure swirl atomizer and hybrid air blast nozzle type fuel injectors are compared in this study. Aviation jet fuels, JP-8, Jet A, JP-5, and JP-10 and their effect on fuel injector performance is investigated. Fuel injector set conditions involving fuel injector pressure, fuel temperature and ambient pressure are varied in order to compare each fuel type. One objective of this thesis is to contribute spray patternation measurements to the body of existing drop size data in the literature. Fuel droplet size tends to increase with decreasing fuel injection pressure, decreasing fuel injection temperature and increasing ambient injection pressure. The differences between fuel types at particular set conditions occur due to differences in liquid properties between fuels. Liquid viscosity and surface tension are identified to be fuel-specific properties that affect the drop size of the fuel. An open aspect of current research that this paper addresses is how much the type of aviation jet fuel affects spray atomization characteristics. Conventional aviation fuel specifications are becoming more important with new interest in alternative fuels. Optical patternation data and line of sight laser diffraction data show that there is significant difference between jet fuels. Particularly at low fuel injection pressures (0.345 MPa) and cold temperatures (-40 C), the patternation data shows that the total surface area in the spray at 38.1 mm from the pressure swirl injector for the JP-10 fuel type is one-sixth the amount of the JP-8. Finally, this study compares the atomizer performance of a pressure swirl nozzle to a hybrid air blast nozzle. The total surface area for both the hybrid air blast nozzle and the pressure swirl nozzle show a similar decline in atomization performance at low fuel injection pressures and cold temperatures. However, the optical patternator radial profile data and the line of sight laser diffraction data show that the droplet size and spray distribution data are less affected by injection conditions and fuel type in the hybrid air blast nozzle, than they are in the pressure swirl nozzle. One explanation is that the aerodynamic forces associated with the swirler on the hybrid air blast nozzle control the distribution droplets in the spray. This is in contrast to the pressure swirl nozzle droplet distribution that is controlled by internal geometry and droplet ballistics.

Feddema, Rick

348

Constraining the Depth of a Martian Magma Ocean through Metal-Silicate Partitioning Experiments: The Role of Different Datasets and the Range of Pressure and Temperature Conditions  

Science.gov (United States)

Mars accretion is known to be fast compared to Earth. Basaltic samples provide a probe into the interior and allow reconstruction of siderophile element contents of the mantle. These estimates can be used to estimate conditions of core formation, as for Earth. Although many assume that Mars went through a magma ocean stage, and possibly even complete melting, the siderophile element content of Mars mantle is consistent with relatively low pressure and temperature (PT) conditions, implying only shallow melting, near 7 GPa and 2073 K. This is a pressure range where some have proposed a change in siderophile element partitioning behavior. We will examine the databases used for parameterization and split them into a low and higher pressure regime to see if the methods used to reach this conclusion agree for the two sets of data.

Righter, K.; Chabot, N.L.

2009-01-01

349

Desaturation of a clay-stone around a ventilated gallery: numerical modelling of pressures and water contents under various conditions  

International Nuclear Information System (INIS)

Document available in extended abstract form only. We present simulation tests focusing on the drying process around a gallery in an initially saturated (water-filled) porous clay rock, in the framework of a research on the isolation properties and hydro-mechanical behaviour of a clayey geologic repository for radioactive waste. The saturated/unsaturated hydrodynamic parameters used in these tests correspond to a hypothetical clay-stone, similar to the 130 m thick Callovo-Oxfordian formation located between depths 400 m and 600 m at the Meuse / Haute-Marne (MHM) Underground Research Laboratory (URL), operated by ANDRA (Bure, France). The simulations tests were designed according to 3 'types' of computational geometries. The drying period was extended to very long time scales in some cases. The clay rock was taken homogeneous in many tests, but the damaged zone was represented in some (Type III) tests. Type (I) tests are conducted in a simplified non circular geometry. Assuming a square cross-section for the drift, the drying process is obtained by imposing a fixed suction on a flat piece of wall at the roof. The bottom of the porous domain coincides with the roof of the drift. The imposed suction at the roof affects the near field pressure both horizontally and vertically. Type (II) tests reproduce the circular cylindrical geometry of a partially or perfectly filled gallery, with drying conditions imposed at both ends of the drift. Finally, Type (III) tests consider trift. Finally, Type (III) tests consider the case of an empty ventilated cylindrical drift with circular cross-section. In this case the drying is imposed on the curved walls of the drift via a transmission mechanism thanks the 'macro-porous immersion' method. In all cases, the drying of the porous clay rock is modeled by imposing a suction condition (?), obtained from relative air humidity (HR) via Kelvin's law (?). Briefly, the macro-porous immersion method consists in the following interrelated procedures. First, the volumetric excavation (cylindrical drift) is discretized and internalized as a 3D 'macro-porous' body within the computational porous domain. Secondly, the properties of this internal macro-porous body are adjusted in such a way that it will transmit properly the imposed suction (or pressure, or flux, as the case may be) from external to internal boundaries. Here, the suction is imposed on the entry face of the gallery (external boundary), and it is transmitted to the clay/gallery interface (internal boundary). The macro-porous body has a porosity of 100%, a large Darcy permeability compared to the clay-stone, and other special nonlinear and non-isotropic unsaturated properties. Briefly, numerical modelling was conducted with BIGFLOW 3D, an implicit finite volume solver of the saturated/unsaturated Richards equation in mixed form (moisture content '?', pressure head 'h'). We used the nonlinear Van Genuchten / Mualem conductivity and water retention curves (K(h); ?(h)) in the unsaturated zone. A specific elastic storativity (SS) was added in the saturated zone to take into account slight deformation mechanisms in a simplified way (the storativity model does not deal with total stress; it assumes ??EFF ? ?p, where p is pore pressure, and ?EFF is Terzaghi's effective stress taken positive when extensional). Finally, the BIGFLOW code can also handle 3D heterogeneity and nonlinear diagonal anisotropy, that is: [Kii(h,x,y,z); ?(h,x,y,z)]. We used these additional capabilities of the code in some of the tests. Figs.1 and 2 show the evolution of desaturation for a 'Type I' test, i.e., with suction imposed on a flat horizontal piece of wall located at the roof of the drift. The drift 'radius' (half-side) is R=2 m. The case shown here is only 'moderately dry': the prescribed suction is ?=3000 m (?30 MPa), corresponding to HR=80.74% at TAIR=25 C and PATM=1 bar (according to Kelvin's law). The imposed desaturation of the porous medium at the drift wall is significant (more than 50% drop of the degree of saturation). The steady state is atta

350

Pressure ulcers  

OpenAIRE

Unrelieved pressure or friction of the skin, particularly over bony prominences, can lead to pressure ulcers, which affect up to one third of people in hospitals or community care, and one fifth of nursing home residents. Pressure ulcers are more likely in people with reduced mobility and poor skin condition, such as older people or those with vascular disease.

Grey, Joseph E.; Harding, Keith G.; Enoch, Stuart

2006-01-01

351

Hydrogen transfer hydrocracking of C. procera latex under ambient pressure conditions to get value added chemicals and fuels  

Energy Technology Data Exchange (ETDEWEB)

Biomass is renewable source of energy while the reserves of petroleum are being depleted. The latex of a potential petrocrop, Calotropis procera, a laticifer, arid-plant which is rich in hydrocarbon type triterpene compounds etc. was found to be a better feed stock for thermal hydrocracking as compared to whole plant biomass in terms of liquid product yield. Studies of chemical reaction dynamics of the thermal cracking of latex at 200-400[degree]C showed that the process should be termed as hydrogen-transfer (H-T) hydrocracking of latex under ambient pressure conditions. The hydrogen rich cracked triterpenoids act as the H-donors in this process, where nascent hydrogen atoms and free radicals chemically plug the cracked moieties to stabilise these. Latex was also coagulated and the H-T hydrocracking of the feedstock coagulum gave a higher yield of cracked oil in comparison to that from the dried latex. The temperature for hydrocracking of latex has been optimized to 350[degree]C and molecular sieve was found to catalyse the H-T hydrocracking process to yield more liquid product. The distillation range of cracked latex oil (CLO) obtained from H-T hydrocracking of C. procera latex indicated that it can be used as fuel oil or substitute for diesel fuel. Moreover, CLO resembled diesel fuels and was predominantly paraffinic in nature as characterised by NMR and FTIR spectral analysis. A process has been recommended for getting value added fuels and chemicals from C. procera latex. 29 refs., 5 figs., 3 tabs.

Sharma, D.K.; Behera, B.K.; Arora, M. (Indian Institute of Technology, New Delhi (India). Fuels and Biofuels Engineering Lab.)

1994-01-01

352

Surface charging patterns of stainless alloys - Effect of ageing in conditions of primary cooling circuit of pressurized water reactors  

Energy Technology Data Exchange (ETDEWEB)

The predominance of electrostatic interactions in the mechanism of particle deposition onto solid surfaces is well documented. Therefore, an electrostatic approach has been used to predict the behavior of activated corrosion products in the primary cooling circuit of a pressurized water reactor (PWR). Only few results have been published on the potential at the interface of metallic alloys and aqueous solutions, even at room temperature. In this study, we present results about the characterization of representative materials such as Inconel 690, stainless steel 304 and Zircaloy 4 at room temperature, for pristine polished samples as well as after an 80-day ageing step in physico-chemical conditions similar to those of a primary circuit (360 Degree-Sign C, boron 1 g L{sup -1} (as H{sub 3}BO{sub 3}), lithium 2 mg L{sup -1} (as LiOH), hydrogen 30 cm{sup 3} kg{sup -1}). The surface potentials of these alloys have been determined using a streaming current method for pH from 3 to 7. Isoelectric points between 4.1 and 4.6 have been found for all samples and there is no effect of the ageing step. These values have been confirmed by adhesion studies of grafted latex particles either positively charged (amidine surface groups) or negatively charged (carboxylate groups) at pH 3.3 and pH 5.5. The results show that particles deposition is favored only when they carry a charge opposite to the substrate surfaces.

Martin Cabanas, B. [EDF R and D Les Renardieres, Departement MMC, Avenue de Sens, Ecuelles, 77818 Moret/Loing Cedex (France); Luetzenkirchen, J. [Institute for Nuclear Waste Disposal (INE), Karlsruhe Institute for Technology (KIT), P.O. Box 3640, 76021 Karlsruhe (Germany); Leclercq, S. [EDF R and D Les Renardieres, Departement MMC, Avenue de Sens, Ecuelles, 77818 Moret/Loing Cedex (France); Barboux, P. [Chimie ParisTech, UMR 7574 LCMCP, 11 rue Pierre et Marie Curie, 75005 Paris (France); Lefevre, G., E-mail: gregory-lefevre@chimie-paristech.fr [Chimie ParisTech, UMR 7575 LECIME, 11 rue Pierre et Marie Curie, 75005 Paris (France)

2012-11-15

353

Modelling of crud growth mechanisms under local boiling conditions in pressurized water reactors fuel clads leading to important volumes activities  

International Nuclear Information System (INIS)

The Pressurized Water Reactors (PWRs) primary circuit materials are subject to general corrosion leading to soluble metallic element (mainly Fe, Ni, Cr, Mn, Co) transfer and subsequent ion precipitation processes on the primary circuit surfaces. When deposited on fuel rods, these species are activated by neutron flux. Thus, crud erosion and dissolution processes induce to primary coolant activity. During a normal operating cycle in a EDF PWR, the volume activity in the coolant is relatively stable (usually about 10-20 MBq.m-3 in 58Co). In some cycles (depending on fuel management), significant increases in 58Co and 51Cr volume activities are observed (10 to 100 times the ordinary volume activities). These increases of volume activities are due to local sub-cooled nucleate boiling on the 'hot' parts of fuel assemblies. As presented in this thesis, boiling at the top of some fuel assemblies may lead to much higher amount of metallic elements than usual (some micrometers). Indeed, boiling that can locally occurs under PWR conditions concentrates species and to increase significantly the quantity of deposited and precipitated material. Erosion flux is higher in these regions due to thicker crud thickness, involving a greater mass transfer of activated isotopes to the primary coolant. The OSCAR calculation code, developed by the 'Laboratoire de Modelisation des interactions et Transferts en Reacteur' in CEA, with these new mass transfer models can now well estimate the amount of deposit and the volume activities in the primary coolant in case of boiling in accordance with french PWR measurements. (author)

354

Influence of experimental conditions on the extraction of phenolic compounds from parsley (Petroselinum crispum) flakes using a pressurized liquid extractor  

Science.gov (United States)

The influence of six pressurized liquid extraction parameters (temperature, pressure, particle size, flush volume, static time, and solid to-solvent ratio) on extraction of phenolic compounds from parsley flakes was examined. Parsley extracts were analyzed for their phenolic content by high performa...

355

Potential application of a flash-type barometric desalination plant powered by waste heat from electric-power stations in Cyprus  

International Nuclear Information System (INIS)

This paper describes and evaluates the results of a study into the problems of freshwater production and shortages on the island of Cyprus. The use of a novel barometric flash-type desalinator, driven by otherwise waste-heat from the island's power-stations, is proposed as a means of increasing freshwater supplies. Mathematical models are described and used to investigate the thermodynamic performance and economic viability of the proposed system. Although water and electricity supply data for the island of Cyprus were used for the purposes of this investigation, the overall findings are thought have a wider applicability

356

Effects of Partial O2 Pressure, Partial CO2 Pressure, and Agitation on Growth Kinetics of Azospirillum lipoferum under Fermentor Conditions  

OpenAIRE

Azospirillum lipoferum crt1 was grown in batch cultures under standard conditions at 85% saturation of dissolved oxygen (DO) and 30-g/liter glucose concentrations. Kinetic studies revealed nutritional limitations of growth and the presence of an initial lag phase prior to consumption of glucose. The influences of various gaseous environments and shear stress on growth, i.e., various conditions of agitation-aeration, were characterized. Faster growth in the first stages of the culture and shor...

Paul, Etienne; Mulard, Daniel; Blanc, Philippe; Fages, Jacques; Goma, Gerard; Pareilleux, Alain

1990-01-01

357

Experimental investigation of the influence of boundary conditions on the stability of cylindrical shells made of fiberglass-reinforced plastic subjected to external pressure  

International Nuclear Information System (INIS)

The influence of attachment conditions on the stability of cylindrical shells subjected to external pressure has been studied in detail in a number of works. These works mainly focused on single-layer, isotropic shells. In the present article results are presented from an experimental investigation of the stability of cylindrical shells made of fiberglass-reinforced plastic subjected to the load of a uniform (confining) external pressure. Experiments are performed for different types of boundary conditions. The influence of boundary conditions on the stability of cylindrical shells has been studied using shells manufactured by pouring and wounding mutually orthogonal, longitudinally transverse strips of fiberglass-reinforced plastic in a 1:2 ratio. In these experiments all the shells had a length of 260±1 mm, radius of 94 mm, and total thickness of the walls 0.66±0.01 mm

358

Biogas barometer; barometre biogaz  

Energy Technology Data Exchange (ETDEWEB)

The biogas sector has never before aroused so much attention as it does today. Elected officers and investors' interest has been fired by the gradual introduction of regulatory restrictions on the treatment of organic waste and the renewable energy commitments recently made by the European Union Member States. The biogas sector is gradually deserting its core activities of waste cleanup and treatment and getting involved in energy production, with so much enthusiasm that in some countries its scope of action has extended to using energy crops. Across the European Union, the sector's progress is as clear as daylight, as in 2009, primary energy growth leapt by a further 4.3 per cent. (author)

Anon.

2010-11-15

359

Influence of arterial wall compliance on the pressure drop across coronary artery stenoses under hyperemic flow condition.  

Science.gov (United States)

Hemodynamic endpoints such as flow and pressure drop are often measured during angioplasty procedures to determine the functional severity of a coronary artery stenosis. There is a lack of knowledge regarding the influence of compliance of the arterial wall-stenosis on the pressure drop under hyperemic flows across coronary lesions. This study evaluates the influence in flow and pressure drop caused by variation in arterial-stenosis compliance for a wide range of stenosis severities. The flow and pressure drop were evaluated for three different severities of stenosis and tested for limiting scenarios of compliant models. The Mooney-Rivlin model defined the non-linear material properties of the arterial wall and the plaque regions. The non-Newtonian Carreau model was used to model the blood flow viscosity. The fluid (blood)-structure (arterial wall) interaction equations were solved numerically using the finite element method. Irrespective of the stenosis severity, the compliant models produced a lower pressure drop than the rigid artery due to compliance of the plaque region. A wide variation in the pressure drop was observed between different compliant models for significant (90% area occlusion) stenosis with 41.0, 32.1, and 29.8 mmHg for the rigid artery, compliant artery with calcified plaque, and compliant artery with smooth muscle cell proliferation, respectively. When compared with the rigid artery for significant stenosis the pressure drop decreased by 27.7% and 37.6% for the calcified plaque and for the smooth muscle cell proliferation case, respectively. These significant variations in pressure drop for the higher stenosis may lead to misinterpretation and misdiagnosis of the stenosis severity. PMID:21391325

Konala, Bhaskar Chandra; Das, Ashish; Banerjee, Rupak K

2011-03-01

360

Iron reduction by the deep-sea bacterium Shewanella profunda LT13a under subsurface pressure and temperature conditions  

Science.gov (United States)

Microorganisms influence biogeochemical cycles from the surface down to the depths of the continental rocks and oceanic basaltic crust. Due to the poor recovery of microbial isolates from the deep subsurface, the influence of physical environmental parameters, such as pressure and temperature, on the physiology and metabolic potential of subsurface inhabitants is not well constrained. We evaluated Fe(III) reduction rates (FeRRs) and viability, measured as colony-forming ability, of the deep-sea piezophilic bacterium Shewanella profunda LT13a over a range of pressures (0–125 MPa) and temperatures (4–37?C) that included the in situ habitat of the bacterium isolated from deep-sea sediments at 4500 m depth below sea level. S. profunda LT13a was active at all temperatures investigated and at pressures up to 120 MPa at 30?C, suggesting that it is well adapted to deep-sea and deep sedimentary environments. Average initial cellular FeRRs only slightly decreased with increasing pressure until activity stopped, suggesting that the respiratory chain was not immediately affected upon the application of pressure. We hypothesize that, as pressure increases, the increased energy demand for cell maintenance is not fulfilled, thus leading to a decrease in viability. This study opens up perspectives about energy requirements of cells in the deep subsurface. PMID:25653646

Picard, Aude; Testemale, Denis; Wagenknecht, Laura; Hazael, Rachael; Daniel, Isabelle

2015-01-01

361

Heat transfer parameters for glass-peened calandria tube in pressure tube and calandria tube contact conditions  

Energy Technology Data Exchange (ETDEWEB)

During a postulated event of large LOCA in CANDU reactors, the pressure tube may balloon to contact with its surrounding calandria tube to transfer heat to the moderator. To confirm the integrity of the fuel channel after the contact with a given moderator subcooling, many experiments have been performed in the last three decades by applying different pressure tube heatup rates, different pressure tube pressures and different moderator subcoolings for calandria tubes with smooth outer surface and glass-peened surface. A concept of Equivalent Moderator Subcooling (EMS) has been put forward to determine integrity of fuel channel upon pressure tube/calandria tube contact based on the existing experiment results. This concept has been presented in another work. In this work, the contact thermal conductance between pressure tube and calandria tube, critical heat flux, minimum film boiling temperature, empirical methods for nucleate boiling and film boiling heat transfer coefficient on the glass-peened calandria tube surface are discussed and estimated based on some experimental results and the EMS concept. These parameters are confirmed by simulating the existing experiments using a computer code. The estimated results may help detailed analyses on fuel channel integrity upon PT/CT contact if necessary. (author)

Sun, L.; Willemsen, B. [Point Lepreau Generating Station, Lepreau, New Brunswick (Canada)

2010-07-01

362

CHF experiments of tight pitch lattice rod bundles under PWR pressure condition for development of reduced moderation water reactor  

Energy Technology Data Exchange (ETDEWEB)

In order to improve plutonium utilization, design studies of reduced moderation water reactors which have hard neutron energy spectrum have been carried out at Division of Energy System Research of Japan Atomic Energy Research Institute (JAERI). At present, triangle, tight pitch lattice cores with about 1 mm gap width between fuel rods have been focused in the neutronic core design. Since a degradation of the heat removal from the fuel rods is worried, an evaluation of heat removal capability i.e. critical heat flux becomes one of important evaluation items in the feasibility study. However, any of published data base, which can be applicable to the evaluation on such narrow gap width cores, does not exist. Therefore, in the present study, in order to accumulate applicable data and to confirm applicability of an evaluation methodology of critical heat flux, basic experiments on the critical heat flux were performed using the test sections consisted of 7 heater rods bundles with the gap widths of 1.5, 1.0 and 0.6 mm under the PWR pressure conditions. The present report describes the experimental apparatus, experimental conditions and accumulated data. Analysis results of the data and the applicability of the evaluation methodology used for the design work are also discussed in this report. As the results of the experiment, it was found that the critical heat flux increased as the mass flux and the inlet subcooling increased. In the region of the mass flux less than about 2,000 kg/m{sup 2}/s, the critical heat flux decreased as the gap width decreased. In the larger mass flux region, obvious trend of effects of the gap width on critical heat flux were not observed due to data scatterings. The flow-area-averaged thermal-equilibrium quality at the CHF position was in the higher ranges from 0.3 to 0.8 in the cases of gap widths of 1.0 and 0.6 mm, and 0.1 to 0.3 in the 1.5 mm case. Based on the experimental results such that the CHFs occurred in the higher quality range and in the comparably lower axial heat flux region of the heater rod, it was implied that the film dryout type CHFs might be occurred in the experiments. The experiment analysis with the evaluation methodology of critical heat flux i.e. the subchannel analysis code COBRA-IV-I incorporated the KfK CHF correlation showed that the calculated critical heat fluxes were 10 to 60% smaller than the experimental values. Based on the calculated results, it can be said that the present evaluation methodology can evaluate the critical heat flux with enough margin for the core configurations with narrow gap widths treated in the present study. (author)

Araya, Fumimasa; Nakatsuka, Toru; Yoritsune, Tsutomu [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment] [and others

2002-10-01

363

RELAP5 Capability to Predict Pressure Wave Propagation Phenomena in Single- and Two-Phase Flow Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available Correct evaluation of the hydrodynamic loads induced by large and rapid pressure waves propagating with the speed of sound along the reactor piping systems and Reactor Pressure Vessel (RPV is an important and difficult issue of nuclear power plant safety. The pressure shock transients and resulting hydrodynamic loads on the pipes and RPV structures are commonly calculated with one-dimensional thermo-hydraulic system codes such as RELAP5, TRACE, DRAKO and ROLAST. In Sweden, the most widely used computer code for this purpose is RELAP5. This code needs, therefore, to be assessed for its capability to predict pressure wave behavior. The conducted assessment involves simulations of single- and two-phase shock-tube problems and two-phase blowdown as well as water hammer experiments. The performed numerical experiments clearly show that RELAP5, with the proper time step and spatial mesh size, is capable of predicting the complex dynamics of single- and two-phase pressure wave phenomena with good to reasonable accuracy.

Lukasz Sokolowski

2012-01-01

364

Predicting crystal structures and properties of matter under extreme conditions via quantum mechanics: the pressure is on.  

Science.gov (United States)

Experimental studies of compressed matter are now routinely conducted at pressures exceeding 1 mln atm (100 GPa) and occasionally at pressures greater than 10 mln atm (1 TPa). The structure and properties of solids that have been so significantly squeezed differ considerably from those of solids at ambient pressure (1 atm), often leading to new and unexpected physics. Chemical reactivity is also substantially altered in the extreme pressure regime. In this feature paper we describe how synergy between theory and experiment can pave the road towards new experimental discoveries. Because chemical rules-of-thumb established at 1 atm often fail to predict the structures of solids under high pressure, automated crystal structure prediction (CSP) methods are increasingly employed. After outlining the most important CSP techniques, we showcase a few examples from the recent literature that exemplify just how useful theory can be as an aid in the interpretation of experimental data, describe exciting theoretical predictions that are guiding experiment, and discuss when the computational methods that are currently routinely employed fail. Finally, we forecast important problems that will be targeted by theory as theoretical methods undergo rapid development, along with the simultaneous increase of computational power. PMID:25427780

Zurek, Eva; Grochala, Wojciech

2015-02-01

365

Meteorological conditions are associated with physical activities performed in open-air settings  

Science.gov (United States)

Meteorological conditions (MC) are believed to modify physical activity. However, studies in this area are limited and none have looked at the associations between MC and physical activity in open-air settings. Therefore, we examined the relationships between MC and physical activities performed on sidewalks/streets and outdoor oval tracks. Observation techniques were used to count individuals walking to school, exercising on oval tracks and walking/jogging/biking on sidewalks/streets. Meteorological conditions were obtained from an Automated Surface Observing System located at a nearby airport for the same time periods physical activities were observed. On weekdays, fewer children were seen walking to school and more bicyclists were observed on sidewalks/streets as wind speed increased ( p physical activities observed on weekends. Multiple linear regression analyses showed that apparent temperature (+), barometric pressure (-) and dew point (-) accounted for 58.0% of the variance in the number of walkers on the track. A significant proportion of the variance (>30%) in the number of joggers and the length of time they jogged was accounted for by apparent temperature (+) and dew point (-). We found that meteorological conditions are related to physical activity in open-air settings. The results embellish the context in which environmental-physical activity relationships should be interpreted and provide important information for researchers applying the observation method in open-air settings.

Suminski, Richard R.; Poston, Walker C.; Market, Patrick; Hyder, Melissa; Sara, Pyle A.

2008-01-01

366

Self-overcoming of the boiling condition by pressure increment in a water target irradiated by proton beam  

International Nuclear Information System (INIS)

An experiment was conducted to examine and visualize the boiling phenomena inside a water target by irradiating it with a proton beam from MC-50 cyclotron. The boiling phenomena were recorded with a CMOS camera. While an increase of the fraction of the water vapor volume is generally considered to be normal when water is boiled by a proton beam, our experiment showed the opposite result. The volume expansion of the liquid water exceeded the compressibility of the initial air volume. A grid structure in front of the entrance window foil held the target volume constant. Therefore, the phenomena inside the target underwent an isochoric process, and the pressure inside the target was increased rapidly beyond the pressure at the boiling point. Consequently, there was no more bulk boiling in the Bragg-peak region in the target water. Our results show that the boiling of the water can be controlled by controlling the equilibrium pressure of the water target

367

Some observations of the pressure distribution in a tube bank for conditions of self generated acoustic resonance  

International Nuclear Information System (INIS)

The results for mean and fluctuating pressure distributions around tubes in an in-line tube bank are presented for both non-resonant and self-excited acoustic standing wave resonant flow regimes. It is readily deduced that the nature of the flow in the bank is dramatically altered with the onset of acoustic resonance. The velocity gradients which appear across the bank with the onset of resonance would suggest regions of flow recirculation in the bank although no evidence of this was found. The spectra of fluctuating pressure on the duct roof in the bank and on tubes deep in the bank exhibited coherent peaks only during resonance. (author)

368

Method for calculating coolant resonance frequencies under normal and accident conditions in nuclear power plants with WWER-type pressurized water reactors  

International Nuclear Information System (INIS)

Mathematical models are proposed for calculating acoustic oscillation resonance frequencies in the coolant in various components of the WWER type primary circuit (core, steam generator, pressurizer, piping). Due to the correspondence between model calculations and experimental results obtained in operating nuclear power plants the developed models can be used for practical calculations. The possibility of calculating the eigenfrequencies of the coolant oscillation under different operating conditions leads to the interpretation of operational data, to the analysis of operational conditions, to the detection of coolant boiling in the reactor, and to design changes in order to prevent resonance oscillations with the coolant. (author)

369

Method for calculating coolant resonance frequencies under normal and accident conditions in nuclear power plants with WWER-type pressurized water reactors  

Energy Technology Data Exchange (ETDEWEB)

Mathematical models are proposed for calculating acoustic oscillation resonance frequencies in the coolant in various components of the WWER type primary circuit (core, steam generator, pressurizer, piping). Due to the correspondence between model calculations and experimental results obtained in operating nuclear power plants, the developed models can be used for practical calculations. The possibility of calculating the eigenfrequencies of the coolant oscillation under different operating conditions leads to the interpretation of operational data, to the analysis of operational conditions, to the detection of coolant boiling in the reactor, and to design changes in order to prevent resonance oscillations within the coolant.

Proskuryakov, K.N. (Moskovskij Ehnergeticheskij Inst. (USSR))

1983-03-01

370

High-pressure behavior and crystal–fluid interaction under extreme conditions in paulingite [PAU-topology].  

Czech Academy of Sciences Publication Activity Database

Ro?. 206, April (2015), s. 34-41. ISSN 1387-1811 Institutional support: RVO:67985831 Keywords : paulingite * high pressure * X-ray diffraction * compressibility * crystal–fluid interaction Subject RIV: DB - Geology ; Mineralogy Impact factor: 3.209, year: 2013

Gatta, G. D.; Scheidl, K. S.; Pippinger, T.; Skála, Roman; Lee, J.; Miletich, R.

2015-01-01

371

Desulfurization under Conditions of Substoichiometric Pressurized Fluidized Bed Combustion of Coal - Comparison with TG-Tests and Equilibrium Limits.  

Czech Academy of Sciences Publication Activity Database

Ro?. 11, ?. 120 (2001), s. 39-53. ISSN 1211-1929 R&D Projects: GA AV ?R IAA4072801; GA MŠk OK 349 Institutional research plan: CEZ:AV0Z4072921 Keywords : desulfurization * sub-stoichiometric * pressurized fluidized bed combustion Subject RIV: CI - Industrial Chemistry, Chemical Engineering

Svoboda, Karel; Hartman, Miloslav; ?ermák, Ji?í; Poho?elý, Michael

2001-01-01

372

High-pressure crystal structure of elastically isotropic CaTiO3 perovskite under hydrostatic and non-hydrostatic conditions  

Science.gov (United States)

The structural evolution of orthorhombic CaTiO3 perovskite has been studied using high-pressure single-crystal x-ray diffraction under hydrostatic conditions up to 8.1 GPa and under a non-hydrostatic stress field formed in a diamond anvil cell (DAC) up to 4.7 GPa. Under hydrostatic conditions, the TiO6 octahedra become more tilted and distorted with increasing pressure, similar to other 2:4 perovskites. Under non-hydrostatic conditions, the experiments do not show any apparent difference in the internal structural variation from hydrostatic conditions and no additional tilts and distortions in the TiO6 octahedra are observed, even though the lattice itself becomes distorted due to the non-hydrostatic stress. The similarity between the hydrostatic and non-hydrostatic cases can be ascribed to the fact that CaTiO3 perovskite is nearly elastically isotropic and, as a consequence, its deviatoric unit-cell volume strain produced by the non-hydrostatic stress is very small; in other words, the additional octahedral tilts relevant to the extra unit-cell volume associated with the deviatoric unit-cell volume strain may be totally neglected. This study further addresses the role that three factors—the elastic properties, the crystal orientation and the pressure medium—have on the structural evolution of an orthorhombic perovskite loaded in a DAC under non-hydrostatic conditions. The influence of these factors can be clearly visualized by plotting the three-dimensional distribution of the deviatoric unit-cell volume strain in relation to the cylindrical axis of the DAC and indicates that, if the elasticity of a perovskite is nearly isotropic as it is for CaTiO3, the other two factors become relatively insignificant.

Zhao, Jing; Ross, Nancy L.; Wang, Di; Angel, Ross J.

2011-11-01

373

Probabilistic structural integrity assessment of reactor coolant pressure boundary piping. 1. The scatter of welding conditions and welding residual stress  

International Nuclear Information System (INIS)

Residual stress by welding would be one of the most significant factors in evaluating failure probabilities of PLR piping since the SCC growth behavior is strongly affected by residual stress distribution. The residual stress di