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Barometric pressure variations  

Energy Technology Data Exchange (ETDEWEB)

This report presents Hanford Site barometric data that can be used to determine the breathing rate of Hanford Site tanks and details the derivation of the data. The barometric pressure data recorded at the Hanford Weather Station were used for this analysis. Data for 1988, 1989, 1990, and 1991 were used.

Crippen, M.D.

1993-06-01

2

Measuring barometric pressure with a manifold pressure sensor in a microprocessor based engine control system  

Energy Technology Data Exchange (ETDEWEB)

A microprocessor based electronic engine control system is described for an internal combustion engine, a method for updating the stored ambient pressure signal by measuring the ambient barometric pressure during engine operation using a manifold pressure sensor. The method consists of: generating timing signals indicating the rotational position of an engine member and including a signal indicating a predetermined rotational position in the rotation of the engine member; generating a pressure signal from the manifold pressure sensor representing the pressure surrounding the sensor in response to the predetermined rotational position; reading the value of ambient barometric pressure stored in the memory of the microprocessor; comparing the value of the barometric pressure stored in the memory of the microprocessor and the value of the pressure signal; increasing the value of the barometric pressure by one unit to generate a new barometric pressure value when the value of the pressure signal is greater than the value of the barometric pressure; comparing the new barometric pressure value with a predetermined fixed constant representing the maximum barometric pressure; and storing in the memory of the microprocessor either the new barometric pressure value if equal to or less than the fixed constant or the value of the maximum barometric pressure if the new barometric pressure value is greater than the fixed constant.

Pauwels, M.A.; Wright, D.O.

1986-07-15

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

Barometric pressure, emergency psychiatric visits, and violent acts.  

UK PubMed Central (United Kingdom)

BACKGROUND: Associations between human behaviour and psychiatric decompensation and weather variables have been inconsistent. OBJECTIVES: We studied the association of certain weather variables (specifically, humidity, wind speed, and barometric pressure) with emergent psychiatric presentations, psychiatric admissions, incidence of violent crimes, and suicides in a metropolitan area. METHOD: We performed a retrospective study for the year 1999 in a mid-sized city. We included all documented emergent psychiatric visits to the city's psychiatric emergency room. We obtained violence data from the city police department and suicide data from the country medical examiner. RESULTS: The data suggest that total numbers of acts of violence and emergency psychiatry visits are significantly associated with low barometric pressure. Psychiatric inpatient admissions and suicides are not associated with any of the weather variables investigated. CONCLUSIONS: While alternate conclusions can be drawn, we propose that the data support the interpretation that low barometric pressure is associated with an increase in impulsive behaviours. Additional investigation is warranted.

Schory TJ; Piecznski N; Nair S; el-Mallakh RS

2003-10-01

5

Lowering barometric pressure aggravates depression-like behavior in rats.  

UK PubMed Central (United Kingdom)

Weather change has been known to influence the condition of patients with mood disorder. However, no animal studies have tested the influence of climatic factor on emotional impairment. In this study, we examined the effect of lowering barometric pressure (LP) in a climate-controlled room on immobility time in the forced swim test in rats, which is considered to be an index of behavioral despair (helplessness). When the rats were exposed to daily repeated forced swim, the immobility time gradually increased. This increment was inhibited by repeated administration of the antidepressant imipramine, suggesting that the immobility is an anxiety/depression-like behavior. LP exposure (20 hPa below the natural atmospheric pressure) further increased immobility time in rats submitted to repeated forced swim. In another series of experiments, we examined the effect of daily repeated LP exposure on the maintenance of immobility after withdrawal from 6-day repeated forced swim. When the rats were challenged with forced swim under natural atmospheric pressure on day 14 after the withdrawal, immobility time was significantly longer than in non-conditioned rats. These findings demonstrated that LP in the range of natural weather change augmented the depression-like behavior in rats.

Mizoguchi H; Fukaya K; Mori R; Itoh M; Funakubo M; Sato J

2011-03-01

6

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

Energy Technology Data Exchange (ETDEWEB)

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.

Hanson, J.M.

1985-12-01

7

Time series analysis of barometric pressure data  

International Nuclear Information System (INIS)

Time series of atmospheric pressure data, collected over a period of several years, were analysed to provide undergraduate students with educational examples of application of simple statistical methods of analysis. In addition to basic methods for the analysis of periodicities, a comparison of two forecast models, one based on autoregression algorithms, and the other making use of an artificial neural network, was made. Results show that the application of artificial neural networks may give slightly better results compared to traditional methods.

2010-01-01

8

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

9

Environment, behavior and physiology: do birds use barometric pressure to predict storms?  

UK PubMed Central (United Kingdom)

Severe storms can pose a grave challenge to the temperature and energy homeostasis of small endothermic vertebrates. Storms are accompanied by lower temperatures and wind, increasing metabolic expenditure, and can inhibit foraging, thereby limiting energy intake. To avoid these potential problems, most endotherms have mechanisms for offsetting the energetic risks posed by storms. One possibility is to use cues to predict oncoming storms and to alter physiology and behavior in ways that make survival more likely. Barometric pressure declines predictably before inclement weather, and several lines of evidence indicate that animals alter behavior based on changes in ambient pressure. Here we examined the effects of declining barometric pressure on physiology and behavior in the white-crowned sparrow, Zonotrichia leucophrys. Using field data from a long-term study, we first evaluated the relationship between barometric pressure, storms and stress physiology in free-living white-crowned sparrows. We then manipulated barometric pressure experimentally in the laboratory and determined how it affects activity, food intake, metabolic rates and stress physiology. The field data showed declining barometric pressure in the 12-24 h preceding snowstorms, but we found no relationship between barometric pressure and stress physiology. The laboratory study showed that declining barometric pressure stimulated food intake, but had no effect on metabolic rate or stress physiology. These data suggest that white-crowned sparrows can sense and respond to declining barometric pressure, and we propose that such an ability may be common in wild vertebrates, especially small ones for whom individual storms can be life-threatening events.

Breuner CW; Sprague RS; Patterson SH; Woods HA

2013-06-01

10

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

1984-01-01

11

Estimating large-scale fracture permeability of unsaturatedrockusing barometric pressure data  

Energy Technology Data Exchange (ETDEWEB)

We present a three-dimensional modeling study of gas flow inthe unsaturated fractured rock of Yucca Mountain. Our objective is toestimate large-scale fracture permeability, using the changes insubsurface pneumatic pressure in response to barometric pressure changesat the land surface. We incorporate the field-measured pneumatic datainto a multiphase flow model for describing the coupled processes ofliquid and gas flow under ambient geothermal conditions. Comparison offield-measured pneumatic data with model-predicted gas pressures is foundto be a powerful technique for estimating the fracture permeability ofthe unsaturated fractured rock, which is otherwise extremely difficult todetermine on the large scales of interest. In addition, this studydemonstrates that the multi-dimensional-flow effect on estimatedpermeability values is significant and should be included whendetermining fracture permeability in heterogeneous fracturedmedia.

Wu, Yu-Shu; Zhang, Keni; Liu, Hui-Hai

2005-05-17

12

A barometric pressure sensor based on the air-gap scale effect in a cantilever  

Science.gov (United States)

The most common structure for a conventional barometric pressure sensor consists of a vacuum-sealed cavity and a diaphragm. However, we hypothesize that a simple structure with an unsealed cavity and an ultra-thin cantilever can provide more sensitive measurements. We produced a 300-nm-thick cantilever with a small spring constant, which made the cantilever sensitive to low pressures. We demonstrated that miniaturizing the air-gap of the cantilever enables the sensor to measure barometric pressure changes at a low pressure change rate with a high resolution, which was 1 Pa at 0.05 Hz, and for a gap size of 1.7 ?m.

Minh-Dung, Nguyen; Takahashi, Hidetoshi; Uchiyama, Takeshi; Matsumoto, Kiyoshi; Shimoyama, Isao

2013-09-01

13

Cerebrospinal fluid levels of monoamine compounds and cholecystokinin peptides after exposure to standardized barometric pressure.  

UK PubMed Central (United Kingdom)

BACKGROUND: Connections between mood changes and weather have been described throughout the ages, and in more recent years, there have been reports on a relationship between atmospheric pressure and neurotransmitter levels in cerebrospinal fluid. METHODS: To further investigate this issue under strictly standardized conditions, we have lumbar-punctured 8 healthy males under low (963 hPa) and high (1064 hPa) barometric pressure, using a pressure chamber. RESULTS: Under high pressure, the tyrosine concentrations in the cerebrospinal fluid (CSF) were lower, while the cholecystokinin tetrapeptide (CCK-4) levels were higher. No differences between low and high pressure were found for tryptophan, 5-hydroxyindolacetic acid (5-HIAA), dopamine (DA), and sulphated cholecystokinin octapeptide (CCK-8S). The serum level of CCK-8S was higher under high pressure. On comparing concentration ratios between the second and the first CSF fraction, we found significantly increased ratios for homovanillic acid (HVA) and 4-hydroxy-3-methoxyphenylglycol (HMPG), but a decreased ratio for tyrosine under high pressure. The difference in the concentration ratios of HVA between low and high pressure correlated negatively with age. Intraspinal pressure correlated negatively with tapping time at low pressure. CONCLUSION: Our results are in line with the hypothesis that atmospheric pressure influences CSF levels of monoamine compounds and cholecystokinin peptides.

Eklundh T; Gunnarsson T; Ornhagen H; Nordin C

2000-11-01

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Barometric pressure influences host-orientation behavior in the larva of a dipteran ectoparasitoid.  

UK PubMed Central (United Kingdom)

Rain and temperature have been awarded as the most important weather factors that influence insect behavior. Barometric pressure studies have been relegated to a secondary place mainly because most studies deal with adult insects where temperature and water availability are the main environmental factors that influence behavior. We studied the influence of barometric pressure on the host orientation behavior in Mallophora ruficauda, an ectoparasitoid with an active host-seeking larval stage. Our results show that a steeper decrease in barometric pressure than expected by regular variation reduced orientation to host chemical cues. This study is the first to show a correlation between changes in the barometric pressure and the seeking behavior of parasitoid soil-dwelling larvae. Our results show that in this kind of insects, ambient factors other than temperature, water availability and light, can influence and have a profound impact on the process of parasitism. We discuss the influence of this behavior on a task so important for parasitoids as host location, and highlight the importance of including such information in parasitoid foraging ecology and climatic change studies.

Crespo JE; Castelo MK

2012-12-01

15

Inhibitors of ex vivo aggregation of human platelets induced by decompression, during reduced barometric pressure.  

UK PubMed Central (United Kingdom)

It has been shown experimentally ex vivo that human platelet aggregation is induced by decompression (reduced pressure) produced by various means, i.e., reduced barometric pressure, reduced hydrostatic pressure, and reduced hydrodynamic pressure due to Bernoulli's principle. We report here that the spontaneous platelet aggregation induced by reduced barometric pressure (253 torr for three hours) is inhibited by 1:10(7) diluted Japanese herbal plant oil (JHP) and also by two of its major constituents, menthone and menthol with the median inhibitory concentration (IC50) in the millimolar range. These drugs gave essentially similar results when collagen and ADP were used as aggregating agents. Inhibitor concentrations were determined by microscopic examination of platelets in wet preparations when the aggregating stimulus was reduced pressure and by optical aggregometry when collagen and ADP were the aggregating agents. Potential usefulness of these compounds in the prevention of decompression syndrome (DCS) and acute mountain sickness (AMS) are discussed.

Murayama M; Kumaroo KK

1986-05-01

16

The effects of temperature, humidity, and barometric pressure on short-sprint race times  

Science.gov (United States)

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 degrees C 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 overall effects of these factors on sprint times can be considered a ``second order'' adjustment to previous methods that rely strictly on a venue's physical elevation, but can become important in extreme conditions.

Mureika, J. R.

2006-04-01

17

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

18

Effect of reduced barometric pressure on water availability related to microbial growth.  

UK PubMed Central (United Kingdom)

Data obtained from Mariner IV indicate that the barometric pressure on Mars is considerably lower than previously estimated. Current estimates from Mariner IV indicate a range from 4 to 7 mb and by near infrared spectroscopy 33-56 mb. Inasmuch as the pressure has a marked influence on availability of water, this should affect the existence of Martian life. At the maximum temperatures recorded on Mars, namely 25 degrees C, a barometric pressure of 30 mb is required for the retention of free water. The lower pressure, 4 mb, would suggest that the moisture is present as a vapor above the freezing point and consequently it is not available for utilizing by living cells. The lower estimates of barometric pressure also inversely affect the carbon dioxide concentration in the Martian atmosphere. Our previous studies have demonstrated that spores of Bacillus cereus survive, germinate and grow in a simulated Martian environment (2.4% CO2, 98 mb) supplemented with moisture. The studies described in this paper were designed to determine the effect of low barometric pressures (10 to 98 mb Hg) and high concentrations of carbon dioxide (37 to 100%) in the simulated Martian environment on survival and growth of B cereus. The organism was inoculated into a felsite-limonite soil at 8% moisture level. The temperature cycles used were 8 hr at -65 degrees C and 16 hr at 25 degrees C, or 20 hr at -65 degrees C and 4 hr at 25 degrees C. The data suggest that the organism after achieving maximum growth in the simulated Martian environment (2.4% CO2, 98 mb) immediately enters into the growth phase upon reinoculation into fresh soil. These data reflect upon the possibility of contamination through air movements. Based upon currently available Martian environmental data, the probability of contamination of Mars by terrestrial micro-organisms will be discussed.

Hawrylewicz EJ; Hagen C; Tolkacz V; Ehrlich R

1967-01-01

19

[Behavior of the impedance of the middle ear and of the stapedius reflex under static conditions of barometric depression  

UK PubMed Central (United Kingdom)

The authors present the preliminary results of a range of their aero-space medicine studies, carried out in hypobaric chamber, in simulated flight and at different atmospheric pressures, to asses the tubal function in normal hearing people. The tympanometric determination through a Z072 Madsen inpendenzometer in static and dynamic conditions of barometric depression gave a clear and exact indications about the impedence variation capacity of the middle ear in similated flight, giving homogenous data which allow the use of this method in flying recruitment aptitude test routine.

De Benedetto M; Cesareo G

1977-12-01

20

Torricelli and the ocean of air: the first measurement of barometric pressure.  

UK PubMed Central (United Kingdom)

The recognition of barometric pressure was a critical step in the development of environmental physiology. In 1644, Evangelista Torricelli described the first mercury barometer in a remarkable letter that contained the phrase, "We live submerged at the bottom of an ocean of the element air, which by unquestioned experiments is known to have weight." This extraordinary insight seems to have come right out of the blue. Less than 10 years before, the great Galileo had given an erroneous explanation for the related problem of pumping water from a deep well. Previously, Gasparo Berti had filled a very long lead vertical tube with water and showed that a vacuum formed at the top. However, Torricelli was the first to make a mercury barometer and understand that the mercury was supported by the pressure of the air. Aristotle stated that the air has weight, although this was controversial for some time. Galileo described a method of measuring the weight of the air in detail, but for reasons that are not clear his result was in error by a factor of about two. Torricelli surmised that the pressure of the air might be less on mountains, but the first demonstration of this was by Blaise Pascal. The first air pump was built by Otto von Guericke, and this influenced Robert Boyle to carry out his classical experiments of the physiological effects of reduced barometric pressure. These were turning points in the early history of high-altitude physiology.

West JB

2013-03-01

 
 
 
 
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Torricelli and the ocean of air: the first measurement of barometric pressure.  

Science.gov (United States)

The recognition of barometric pressure was a critical step in the development of environmental physiology. In 1644, Evangelista Torricelli described the first mercury barometer in a remarkable letter that contained the phrase, "We live submerged at the bottom of an ocean of the element air, which by unquestioned experiments is known to have weight." This extraordinary insight seems to have come right out of the blue. Less than 10 years before, the great Galileo had given an erroneous explanation for the related problem of pumping water from a deep well. Previously, Gasparo Berti had filled a very long lead vertical tube with water and showed that a vacuum formed at the top. However, Torricelli was the first to make a mercury barometer and understand that the mercury was supported by the pressure of the air. Aristotle stated that the air has weight, although this was controversial for some time. Galileo described a method of measuring the weight of the air in detail, but for reasons that are not clear his result was in error by a factor of about two. Torricelli surmised that the pressure of the air might be less on mountains, but the first demonstration of this was by Blaise Pascal. The first air pump was built by Otto von Guericke, and this influenced Robert Boyle to carry out his classical experiments of the physiological effects of reduced barometric pressure. These were turning points in the early history of high-altitude physiology. PMID:23455767

West, John B

2013-03-01

22

On reduction of long-period horizontal seismic noise using local barometric pressure  

Science.gov (United States)

Tilt from atmospheric loading has long been known to be the major source of long-period horizontal seismic noise. We try to quantify these effects for seismic data from the Black Forest Observatory (BFO), which is known to be a very quiet station. Experimental transfer functions between local barometric pressure and horizontal seismic noise are estimated for two long time-series by standard methods. Two simple analytical physical models are developed: the local deformation model (LDM) and the acoustic-gravity wave model (TWM). Subsequently these models, with only two free parameters are fit using least squares to the observed seismic noise for time-series of widely differing lengths. The results are variable, sometimes rather dramatic variance reductions are obtained and sometimes the reduction is hardly significant. The method produces the best results when barometrically induced noise is high. The resulting admittances for the LDM are compared to finite element calculations. Since the methods are simple and can result in conspicuous reductions in noise we provide one more reason for installing barometers at even the best broad-band seismic stations.

Zürn, W.; Exß, J.; Steffen, H.; Kroner, C.; Jahr, T.; Westerhaus, M.

2007-11-01

23

Simulated effects of barometric pressure and ozone content upon the estimate of marine phytoplankton from space  

Energy Technology Data Exchange (ETDEWEB)

Barometric pressure and total ozone content may significantly depart from their mean climatology values; these values, however, are used when processing the visible sensing (VRS) data with the aim of estimating the phytoplanktonic pigments concentration (chlorophyll a + phaeophytin a, in milligrams per cubic meter) with the upper ocean. The effect of ignoring such departures upon the retrieved concentration has been simulated for the broad oceanic range (0.015-20 mg/m{sup 3}). The simulation is effected for typical VRS situations (geometry, aerosol) when information about the variable aerosol is not available when entering the processing (as is the case with the Coastal Zone Color Scanner (CZCS) data) or, conversely, when such information has been separately obtained (simulation of future sensors with dedicated near-IR channels). The result is that in both these cases the use of up to 2 in many common VRS situations, and above 2 for very low or high actual pigment content. After the results are discussed, the conclusion is that the actual values of the barometric pressure and of the ozone content will have to be introduced in the processing of future visible sensor data in order to preserve the expected accuracy. With regard to the exploitation of the CZCS archive, this requirement is not so essential, insofar as the pressure and ozone effects on the pigment concentration retrieval remain of the same order as the noise due to the limited radiometric accuracy of this sensor. However, at the scale of a CZCS scene, neglecting the strong structures in the pressure and ozone content fields may bias the phytoplankton concentration mapping. The use of the actual values is therefore recommended.

Andre, J.M.; Morel, A. (Univ. Pierre et Marie Curie, Villefranche-sur-Mer (France))

1989-01-15

24

Direction sensitive fall detection using a triaxial accelerometer and a barometric pressure sensor.  

UK PubMed Central (United Kingdom)

Falling is one of the leading causes of serious health decline or injury-related deaths in the elderly. For survivors of a fall, the resulting health expenses can be a devastating burden, largely because of the long recovery time and potential comorbidities that ensue. The detection of a fall is, therefore, important in care of the elderly for decreasing the reaction time by the care-givers especially for those in care who are particularly frail or living alone. Recent advances in motion-sensor technology have enabled wearable sensors to be used efficiently for pervasive care of the elderly. In addition to fall detection, it is also important to determine the direction of a fall, which could help in the location of joint weakness or post-fall fracture. This work uses a waist-worn sensor, encompassing a 3D accelerometer and a barometric pressure sensor, for reliable fall detection and the determination of the direction of a fall. Also assessed is an efficient analysis framework suitable for on-node implementation using a low-power micro-controller that involves both feature extraction and fall detection. A detailed laboratory analysis is presented validating the practical application of the system.

Tolkiehn M; Atallah L; Lo B; Yang GZ

2011-01-01

25

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)

[en] 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)

2011-01-01

26

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

27

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.

Rogelio Caballero López; José Fco. Valdés-Galicia

2000-01-01

28

An online application for the barometric coefficient calculation of NMDB stations  

International Nuclear Information System (INIS)

[en] One of the most important data corrections related to the primary data processing of the neutron monitors is the pressure correction due to the barometric effect. This effect induces considerable variation in the counting rate of a cosmic ray detector which is not related to the real variation of the cosmic rays flux but only to the local atmospheric pressure of the station. In order to provide the worldwide neutron monitor network with good quality data, a correction has to be made that requires the calculation of the barometric coefficient. A new method that effectively calculates the barometric coefficient for a station using data of a reference station in order to subtract the primary variations of cosmic rays is presented in this work. Moreover, this method is the prototype of an online tool that uses data of the NMDB stations and calculates the barometric coefficient for any available station. This tool is also presented.

2013-02-01

29

Barometric pumping with a twist: VOC containment and remediation without boreholes  

Energy Technology Data Exchange (ETDEWEB)

A large national cost is incurred in remediating near-surface contamination such as surface spills, leaking buried pipelines, and underground storage tank sites. Many of these sites can be contained and remediated using enhanced natural venting, capitalizing on barometric pumping. Barometric pumping is the cyclic movement experienced by soil gas due to oscillations in atmospheric pressure. Daily variations of 5 millibars are typical, while changes of 25 to 50 millibars can occur due to major weather front passage. The fluctuations can cause bulk vertical movement in soil gas ranging from centimeters to meters, depending on the amplitude of the pressure oscillation, soil gas permeability, and depth to an impermeable boundary such as the water table. Since the bulk gas movement is cyclic, under natural conditions no net advective vertical movement occurs over time. Science and Engineering Associates, Inc., is developing an engineered system to capitalize on the oscillatory flow for soil contaminant remediation and containment. By design, the system allows normal upward movement of soil gas but restricts the downward movement during barometric highs. The earth`s surface is modified with a sealant and vent valve such that the soil gas flow is literally {open_quotes}ratcheted{close_quotes} to cause a net upward flow over time. A key feature of the design is that it does not require boreholes, resulting in a very low cost remediation effort and reduced personnel exposure risk. In the current phase (Phase I) the system`s performance is being evaluated. Static and transient analysis results are presented which illustrate the relative magnitude of this advective movement compared to downward contaminant diffusion rates. Calculations also indicate the depth of influence for various surface and soil configurations. The system design will be presented, as well as a cost assessment compared to conventional techniques.

Lowry, W.; Dunn, S.D.; Walsh, R. [Science and Engineering Associates, Inc., Santa Fe, NM (United States)] [and others

1995-10-01

30

Barometric pumping with a twist: VOC containment and remediation without boreholes  

International Nuclear Information System (INIS)

A large national cost is incurred in remediating near-surface contamination such as surface spills, leaking buried pipelines, and underground storage tank sites. Many of these sites can be contained and remediated using enhanced natural venting, capitalizing on barometric pumping. Barometric pumping is the cyclic movement experienced by soil gas due to oscillations in atmospheric pressure. Daily variations of 5 millibars are typical, while changes of 25 to 50 millibars can occur due to major weather front passage. The fluctuations can cause bulk vertical movement in soil gas ranging from centimeters to meters, depending on the amplitude of the pressure oscillation, soil gas permeability, and depth to an impermeable boundary such as the water table. Since the bulk gas movement is cyclic, under natural conditions no net advective vertical movement occurs over time. Science and Engineering Associates, Inc., is developing an engineered system to capitalize on the oscillatory flow for soil contaminant remediation and containment. By design, the system allows normal upward movement of soil gas but restricts the downward movement during barometric highs. The earth's surface is modified with a sealant and vent valve such that the soil gas flow is literally open-quotes ratchetedclose quotes to cause a net upward flow over time. A key feature of the design is that it does not require boreholes, resulting in a very low cost remediation effort and reduced personnel exposure risk. In the current phase (Phase I) the system's performance is being evaluated. Static and transient analysis results are presented which illustrate the relative magnitude of this advective movement compared to downward contaminant diffusion rates. Calculations also indicate the depth of influence for various surface and soil configurations. The system design will be presented, as well as a cost assessment compared to conventional techniques.

1995-01-01

31

Barometric pumping with a twist: VOC containment and remediation without boreholes  

International Nuclear Information System (INIS)

[en] A large national cost is incurred in remediating near-surface contamination such as surface spills, leaking buried pipelines, and underground storage tank sites. Many of these sites can be contained and remediated using enhanced natural venting, capitalizing on barometric pumping. Barometric pumping is the cyclic movement experienced by soil gas due to oscillations in atmospheric pressure. Daily variations of 5 millibars are typical, while changes of 25 to 50 millibars can occur due to major weather front passage. The fluctuations can cause bulk vertical movement in soil gas ranging from centimeters to meters, depending on the amplitude of the pressure oscillation, soil gas permeability, and depth to an impermeable boundary such as the water table. Since the bulk gas movement is cyclic, under natural conditions no net advective vertical movement occurs over time. Science and Engineering Associates, Inc., is developing an engineered system to capitalize on the oscillatory flow for soil contaminant remediation and containment. By design, the system allows normal upward movement of soil gas but restricts the downward movement during barometric highs. The earth's surface is modified with a sealant and vent valve such that the soil gas flow is literally open-quotes ratchetedclose quotes to cause a net upward flow over time. A key feature of the design is that it does not require boreholes, resulting in a very low cost remediation effort and reduced personnel exposure risk. In the current phase (Phase I) the system's performance is being evaluated. Static and transient analysis results are presented which illustrate the relative magnitude of this advective movement compared to downward contaminant diffusion rates. Calculations also indicate the depth of influence for various surface and soil configurations. The system design will be presented, as well as a cost assessment compared to conventional techniques

1995-01-01

32

Passive remediation of chlorinated volatile organic compounds using barometric pumping  

International Nuclear Information System (INIS)

The purpose of the Savannah River Integrated Demonstration Program, sponsored by the Department of Energy, is to demonstrate new subsurface characterization, monitoring, and remediation technologies. The interbedded clay and sand layers at the Integrated Demonstration Site (IDS) are contaminated with chlorinated volatile organic compounds (CVOCs). Characterization studies show that the bulk of the contamination is located in the approximately 40 m thick vadose zone. The most successful strategy for removing contaminants of this type from this environment is vapor extraction alone or in combination with other methods such as air sparging or enhanced bioremediation. Preliminary work at the IDS has indicated that natural pressure differences between surface and subsurface air caused by surface barometric fluctuations can produce enough gas flow to make barometric pumping a viable method for subsurface remediation. Air flow and pressure were measured in wells that are across three stratigraphic intervals in the vadose zone' The subsurface pressures were correlated to surface pressure fluctuations but were damped and lagging in phase corresponding to depth and stratum permeability. Piezometer wells screened at lower elevations exhibited a greater phase lag and damping than wells screened at higher elevations where the pressure wave from barometric fluctuations passes through a smaller number of low permeable layers. The phase lag between surface and subsurface pressures results in significant fluxes through these wells. The resultant air flows through the subsurface impacts CVOC fate and transport. With the appropriate controls (e.g. solenoid valves) a naturally driven vapor extraction system can be implemented requiring negligible operating costs yet capable of a large CVOC removal rate (as much as 1--2 kg/day in each well at the IDS)

1993-01-01

33

An Educational Study of the Barometric Effect of Cosmic Rays with a Geiger Counter  

Science.gov (United States)

An educational study of the barometric effect of cosmic rays was carried out using an inexpensive experimental set-up that allowed for long-term monitoring of atmospheric pressure and cosmic ray flux as measured in a Geiger counter. The investigation was intended as a pilot study in view of ongoing involvements of high-school teams operating…

Famoso, Barbara; La Rocca, Paola; Riggi, Francesco

2005-01-01

34

Pressure capability of BWR containment vessel under severe accident conditions  

International Nuclear Information System (INIS)

In the case of a severe accident of a LWR, excessive internal pressure loading beyond design pressure is possible to act on a containment vessel statically or dynamically. In the present paper, three kinds of limit pressures are calculated from finite element analyses in order to determine the pressure capability of a Mark II type BWR containment vessel under a severe accident condition. Three kinds of limit pressures calculated are as follows: (1) the limit pressure for the global collapse of a containment vessel, (2) the limit pressure for the bifurcation buckling of a torispherical head of a containment vessel under statically applied internal pressure, and (3) the limit pressure for the bifurcation buckling of a torispherical head of a containment vessel under dynamically applied internal pressure. The safety margin of a containment vessel is discussed by comparing the calculated limit pressures with the design pressure. (author)

1993-01-01

35

Pressure control system in air-conditioning equipment (Part 2)  

Energy Technology Data Exchange (ETDEWEB)

Pressure control in air-conditioning equipment has two types: environment pressure control and barrier pressure control. A number of examples, environmental requirements, equipment specifications, operation flow, etc. are introduced in this paper. The example of environment pressure control are a constant-pressure room (carburetor flow rate testing room), a high-altitude simulator (engine intake and exhaust pressure controller), and an air dome. The examples of barrier pressure control are an industrial clean room (semiconductor plant), an animal breeding and testing room), and a chemical laboratory. (29 figs, 11 tabs)

1986-12-10

36

Operant Conditioning of Increases in Blood Pressure.  

Science.gov (United States)

Four monkeys were presented with 10 sec tones which terminated with shocks. The tones were immediately terminated without shock if the animal's diastolic blood pressure rose above a criterion level and remained high for 1 sec. Termination of the tone was ...

L. A. Plumlee

1969-01-01

37

Sealing of rotary drums for operation under pressurized conditions  

International Nuclear Information System (INIS)

[en] In practice, rotary drums are always designed for operation under vacuum conditions. In this paper, a novel technique is proposed for sealing the rotary drums under pressurized conditions. The proposed system is based on applying a secondary pressurized volume around the leaking gap of the drum. By controlling the pressure of this volume above the pressure of the drum, it will be possible to prevent from any leakage of gases to the ambient. The objective of a controller in this system is that the pressure of secondary volume be kept above the pressure of the drum in spite of the disturbances which may be exerted on the system by the wind outside the drum. The control system is also required to trace the variations in the drum pressure with the least fluctuations in the pressure difference among the drum and the volume

2006-01-01

38

Electrochemical noise measurements under pressurized water reactor conditions  

International Nuclear Information System (INIS)

Electrochemical potential noise measurements on sensitized stainless steel pressure tubes under pressurized water reactor (PWR) conditions were performed for the first time. Very short potential spikes, believed to be associated to crack initiation events, were detected when stressing the sample above the yield strength and increased in magnitude until the sample broke. Sudden increases of plastic deformation, as induced by an increased tube pressure, resulted in slower, high-amplitude potential transients, often accompanied by a reduction in noise level

2000-01-01

39

Performance characteristics of conditioned blood pressure elevations in the baboon.  

UK PubMed Central (United Kingdom)

Operant conditioning of diastolic blood pressure elevation was accomplished in six baboons (Papio sp.) by a procedure using food delivery when diastolic pressure was maintained above a prespecified level, and shock delivery when diastolic pressure remained below that level. Data from steady-state performance indicated a rise in diastolic pressure by a median 22 mm Hg when the daily session was begun. Elevated levels of diastolic blood pressure and low shock frequencies were maintained throughout the 12-hour session. The frequency and duration of shifts in diastolic pressure to below criterion level were found to be variable during the first 1-2 hours but were stable throughout the remainder of the session. Heart rate had a phasic temporal pattern over the 12-hour session, characterized for most subjects by a rate increase at session onset followed by a rate decrease. Analysis of individual performance records showed that the blood pressure increases could occur without concomitant elevations in heart rate.

Harris AH; Turkkan JS

1981-03-01

40

Bridge Pressure Flow Scour for Clear Water Conditions.  

Science.gov (United States)

The equilibrium scour at a bridge caused by pressure flow with critical approach velocity in clear-water simulation conditions was studied both analytically and experimentally. The flume experiments revealed that (1) the measured equilibrium scour profile...

J. Guo J. E. Pagan-Ortiz K. Kerenyi

2009-01-01

 
 
 
 
41

Variation of the barometric coefficient during a solarcycle NM64 Utrecht, 1969-1978; cut-off rigidity 2.7 GV  

International Nuclear Information System (INIS)

More reliable estimates for the barometric coefficient are obtained by applying a moving average model to 12 hourly sums of intensity and pressure data with a statistically optimal period length of 2 months. Plotting coefficients against corrected intensities large hysteresis loops show up. Clockwise or anti-clockwise directions seem to be connected to the polarity of the Solar Polar Fields

1981-07-25

42

Analysis of pressure drops under reversing flow conditions  

Energy Technology Data Exchange (ETDEWEB)

This paper examines pressure-drop data from the Reversing Flow Test Facility (RFTF) at Argonne National Laboratory (ANL). The data comprise part of an initial series of measurements conducted with pressurized helium gas under reversing flow conditions. The characteristics of fluid pressure drops in compressible, reversing flows are discussed in the paper and compared with pressure-drop measurements for steady, incompressible flows. The methodology used to calculate instantaneous mass flows in the test section of the RFTF is summarized. The measured pressure drops are analyzed in terms of their frictional and inertial components. Pressure-drop data are presented for both tubes and wire mesh regenerators over a range of flow reversal frequencies. The results are discussed with reference to other experimental data and analytical models available in the literature. 10 refs., 6 figs., 2 tabs.

Krazinski, J.L.; Holtz, R.E.; Uherka, K.L.; Lottes, P.A.

1986-01-01

43

A correlation for critical pressure with subcooled upstream conditions  

International Nuclear Information System (INIS)

A simple correlation for critical pressure has been developed by examining 283 critical flow data for subcooled inlet conditions. Present correlation predicts critical pressure at the critical location in the channel with the geometry of converging rounded inlet followed by sufficiently long constant diameter pipe and then gradually diverging diffuser. The flow directions are horizontal and vertical upflow. Major assumptions used are (1) the critical pressure resembles the nucleation pressure and (2) the main parameters that affect the critical pressure are the inlet temperature and the degree of subcooling. Present work is an extension of the static flashing undershoot correlation to broader upstream ranges of data from the previous critical flow experiments. The ranges of variables covered for stagnation pressure is from 94 to 12000 KPa, inlet temperatures from 69 to 324 .deg. C, and inlet subcooling from 0.1 to 115.1 .deg. C (or stagnation quality from -0.0002 to -0.15). The present correlation predicts total 283 critical pressure data with mean relative error of 0.3 %, RMS relative error of 3.94 % and standard deviation of 3.93 %. The present correlation can be applied directly to simple homogeneous nonequilibrium critical flow models for subcooled upstream conditions where the critical pressure should be known a priori

1990-01-01

44

Effects of the imposed pressure differential conditions on duoplasmatron performance  

International Nuclear Information System (INIS)

The duoplasmatron plasma source (D.P.T.) was modified to allow access to the arc discharge (to measure the discharge properties) and to vary independently the pressures in different volumes of the arc with the aim of seeing if this freedom would help in optimising the output. The duoplasmatron plasma source was operated under normal running condition (N.R.C.), positive imposed pressure differential condition (P.I.P.D.C.) and negative imposed pressure differential condition (N.I.P.D.C.) and the corresponding properties of the plasma output were measured. Running the duoplasmatron under P.I.P.D. condition did not seem to improve the output as compared to that under N.R.C. However, running the duoplasmatron under N.I.P.D. condition seemed to be advantageous as the output increased by about 30%. It was observed that the back pressure was critical in maintaining the arc and the gap pressure could be lowered much below the normal minimum (while the arc was on) if back pressure was kept above a critical value. The results showed that the effects of varying the dimensions of the intermediate electrode nozzle on the output could be understood in terms of the effect of changes in these dimensions on the relative pressures. An empirical expression for the effect of the pressure ratio was developed from the observations and compared with the experimental results. The reasons for various results can be related to the plasma emission mechanism. (author). 8 refs, 6 figs, 1 tab.

1987-06-19

45

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

46

Sources of corrosive conditions in low pressure steam turbines  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this paper is to provide a brief review of those aspects of power plant circuit chemistry that can lead to the formation of corrosive conditions in low-pressure steam turbines. The topic has received considerable attention in the recent past, and there has been a major review of turbine steam path damage from EPRI.

Bignold, G.J. [National Power, London (United Kingdom)

2000-09-01

47

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

48

A NEW METHOD FOR PRESSURE SENSOR EQUILLIBRATION AND CONDITIONING  

Directory of Open Access Journals (Sweden)

Full Text Available PAPAIOANNOU, G.; PROTOPAPPAS, V.C.; TSOPELAS, P.; MITROGIANNIS, C.; NIANIOS, G.; TASHMAN, S. A New Method for Pressure Sensor Equillibration and Conditioning. Brazilian Journal of Biomotricity, v. 2, n. 3, p. 176-195, 2008. Assessing pressure and contact stress distributions between two adjacent surfaces is a well established research area in biomechanics. Typical applications of measuring the interface pressure include human-machine interfaces in ergonomics, joint congruency studies in orthopaedics, in-vitro cadaveric experimentation and the design of Orthotic-Prosthetic devices. Tekscan pressure sensors are widely used in both in-vivo and in-vitro experiments. An all-round efficient equilibration and calibration approach of the Tekscan sensor system is yet to be clearly defined in the literature and is attempted here for one type of Tekscan sensors. The response of individual sensels from two 5315 Tekscan sensors for quasi-static, repeated constant and dynamic loading was investigated with the use of two methods, namely the “Bladder Method” and the “Pin Method”. In the first method, uniform pressure was applied by a bladder-equilibrator, whereas in the second loads were applied in a sensel-by-sensel approach by means of a pin attached to a frame installed on a material testing machine. The “Pin Method”, although far more laborious, is a better method for equilibration and calibration of sensors, particularly when saturation is prevalent. The pin-method also provides a better characterization of the sensor drift. It was shown that when test conditions resulted in some of the sensels being saturating due to high pressure, the loss of load data from the sensor mat could be estimated using the individual sensel output.

George Papaioannou; Vasilios.C. Protopappas; Tsopelas Panagiotis; Christos Mitrogiannis; George Nianios; Scott Tashman

2008-01-01

49

Solid biomass barometer; Le barometre biomasse solide  

Energy Technology Data Exchange (ETDEWEB)

Primary energy production from solid biomass increased more slowly in the 27 member European Union in 2007. First available estimations evaluate production in the region of 66,4 Mtoe, i-e only 0,7 Mtoe more than in 2006. While the exceptional climatic conditions of 2007 explain this slowdown, evolutions remain contrasted between the different EU countries and do not reflect the same realities. Many statistical data on biomass production, heat and electricity production and manufacturers are provided and analyzed.

Anon

2008-11-15

50

Material dynamics under extreme conditions of pressure and strain rate  

Energy Technology Data Exchange (ETDEWEB)

Solid state experiments at extreme pressures (10-100 GPa) and strain rates ({approx}10{sup 6}-10{sup 8}s{sup -1}) are being developed on high-energy laser facilities, and offer the possibility for exploring new regimes of materials science. These extreme solid-state conditions can be accessed with either shock loading or with a quasi-isentropic ramped pressure drive. Velocity interferometer measurements establish the high pressure conditions. Constitutive models for solid-state strength under these conditions are tested by comparing 2D continuum simulations with experiments measuring perturbation growth due to the Rayleigh-Taylor instability in solid-state samples. Lattice compression, phase, and temperature are deduced from extended x-ray absorption fine structure (EXAFS) measurements, from which the shock-induced {alpha}-{omega} phase transition in Ti and the {alpha}-{var_epsilon} phase transition in Fe are inferred to occur on sub-nanosec time scales. Time resolved lattice response and phase can also be measured with dynamic x-ray diffraction measurements, where the elastic-plastic (1D-3D) lattice relaxation in shocked Cu is shown to occur promptly (< 1 ns). Subsequent large-scale molecular dynamics (MD) simulations elucidate the microscopic dynamics that underlie the 3D lattice relaxation. Deformation mechanisms are identified by examining the residual microstructure in recovered samples. The slip-twinning threshold in single-crystal Cu shocked along the [001] direction is shown to occur at shock strengths of {approx}20 GPa, whereas the corresponding transition for Cu shocked along the [134] direction occurs at higher shock strengths. This slip-twinning threshold also depends on the stacking fault energy (SFE), being lower for low SFE materials. Designs have been developed for achieving much higher pressures, P > 1000 GPa, in the solid state on the National Ignition Facility (NIF) laser.

Remington, B A; Allen, P; Bringa, E; Hawreliak, J; Ho, D; Lorenz, K T; Lorenzana, H; Meyers, M A; Pollaine, S W; Rosolankova, K; Sadik, B; Schneider, M S; Swift, D; Wark, J; Yaakobi, B

2005-09-06

51

A multigrid fluid pressure solver handling separating solid boundary conditions.  

UK PubMed Central (United Kingdom)

We present a multigrid method for solving the linear complementarity problem (LCP) resulting from discretizing the Poisson equation subject to separating solid boundary conditions in an Eulerian liquid simulation’s pressure projection step. The method requires only a few small changes to a multigrid solver for linear systems. Our generalized solver is fast enough to handle 3D liquid simulations with separating boundary conditions in practical domain sizes. Previous methods could only handle relatively small 2D domains in reasonable time, because they used expensive quadratic programming (QP) solvers. We demonstrate our technique in several practical scenarios, including nonaxis-aligned containers and moving solids in which the omission of separating boundary conditions results in disturbing artifacts of liquid sticking to solids. Our measurements show, that the convergence rate of our LCP solver is close to that of a standard multigrid solver.

Chentanez N; Müller-Fischer M

2012-08-01

52

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

53

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

54

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

55

Weather forecasting by insects: modified sexual behaviour in response to atmospheric pressure changes.  

UK PubMed Central (United Kingdom)

Prevailing abiotic conditions may positively or negatively impact insects at both the individual and population levels. For example while moderate rainfall and wind velocity may provide conditions that favour development, as well as movement within and between habitats, high winds and heavy rains can significantly decrease life expectancy. There is some evidence that insects adjust their behaviours associated with flight, mating and foraging in response to changes in barometric pressure. We studied changes in different mating behaviours of three taxonomically unrelated insects, the curcurbit beetle, Diabrotica speciosa (Coleoptera), the true armyworm moth, Pseudaletia unipuncta (Lepidoptera) and the potato aphid, Macrosiphum euphorbiae (Hemiptera), when subjected to natural or experimentally manipulated changes in atmospheric pressure. In response to decreasing barometric pressure, male beetles exhibited decreased locomotory activity in a Y-tube olfactometer with female pheromone extracts. However, when placed in close proximity to females, they exhibited reduced courtship sequences and the precopulatory period. Under the same situations, females of the true armyworm and the potato aphid exhibited significantly reduced calling behaviour. Neither the movement of male beetles nor the calling of armyworm females differed between stable and increasing atmospheric pressure conditions. However, in the case of the armyworm there was a significant decrease in the incidence of mating under rising atmospheric conditions, suggesting an effect on male behaviour. When atmospheric pressure rose, very few M. euphorbiae oviparae called. This was similar to the situation observed under decreasing conditions, and consequently very little mating was observed in this species except under stable conditions. All species exhibited behavioural modifications, but there were interspecific differences related to size-related flight ability and the diel periodicity of mating activity. We postulate that the observed behavioral modifications, especially under decreasing barometric pressure would reduce the probability of injury or death under adverse weather conditions.

Pellegrino AC; Peñaflor MF; Nardi C; Bezner-Kerr W; Guglielmo CG; Bento JM; McNeil JN

2013-01-01

56

Weather forecasting by insects: modified sexual behaviour in response to atmospheric pressure changes.  

Science.gov (United States)

Prevailing abiotic conditions may positively or negatively impact insects at both the individual and population levels. For example while moderate rainfall and wind velocity may provide conditions that favour development, as well as movement within and between habitats, high winds and heavy rains can significantly decrease life expectancy. There is some evidence that insects adjust their behaviours associated with flight, mating and foraging in response to changes in barometric pressure. We studied changes in different mating behaviours of three taxonomically unrelated insects, the curcurbit beetle, Diabrotica speciosa (Coleoptera), the true armyworm moth, Pseudaletia unipuncta (Lepidoptera) and the potato aphid, Macrosiphum euphorbiae (Hemiptera), when subjected to natural or experimentally manipulated changes in atmospheric pressure. In response to decreasing barometric pressure, male beetles exhibited decreased locomotory activity in a Y-tube olfactometer with female pheromone extracts. However, when placed in close proximity to females, they exhibited reduced courtship sequences and the precopulatory period. Under the same situations, females of the true armyworm and the potato aphid exhibited significantly reduced calling behaviour. Neither the movement of male beetles nor the calling of armyworm females differed between stable and increasing atmospheric pressure conditions. However, in the case of the armyworm there was a significant decrease in the incidence of mating under rising atmospheric conditions, suggesting an effect on male behaviour. When atmospheric pressure rose, very few M. euphorbiae oviparae called. This was similar to the situation observed under decreasing conditions, and consequently very little mating was observed in this species except under stable conditions. All species exhibited behavioural modifications, but there were interspecific differences related to size-related flight ability and the diel periodicity of mating activity. We postulate that the observed behavioral modifications, especially under decreasing barometric pressure would reduce the probability of injury or death under adverse weather conditions. PMID:24098362

Pellegrino, Ana Cristina; Peñaflor, Maria Fernanda Gomes Villalba; Nardi, Cristiane; Bezner-Kerr, Wayne; Guglielmo, Christopher G; Bento, José Maurício Simões; McNeil, Jeremy N

2013-10-02

57

Weather Forecasting by Insects: Modified Sexual Behaviour in Response to Atmospheric Pressure Changes  

Science.gov (United States)

Prevailing abiotic conditions may positively or negatively impact insects at both the individual and population levels. For example while moderate rainfall and wind velocity may provide conditions that favour development, as well as movement within and between habitats, high winds and heavy rains can significantly decrease life expectancy. There is some evidence that insects adjust their behaviours associated with flight, mating and foraging in response to changes in barometric pressure. We studied changes in different mating behaviours of three taxonomically unrelated insects, the curcurbit beetle, Diabrotica speciosa (Coleoptera), the true armyworm moth, Pseudaletia unipuncta (Lepidoptera) and the potato aphid, Macrosiphum euphorbiae (Hemiptera), when subjected to natural or experimentally manipulated changes in atmospheric pressure. In response to decreasing barometric pressure, male beetles exhibited decreased locomotory activity in a Y-tube olfactometer with female pheromone extracts. However, when placed in close proximity to females, they exhibited reduced courtship sequences and the precopulatory period. Under the same situations, females of the true armyworm and the potato aphid exhibited significantly reduced calling behaviour. Neither the movement of male beetles nor the calling of armyworm females differed between stable and increasing atmospheric pressure conditions. However, in the case of the armyworm there was a significant decrease in the incidence of mating under rising atmospheric conditions, suggesting an effect on male behaviour. When atmospheric pressure rose, very few M. euphorbiae oviparae called. This was similar to the situation observed under decreasing conditions, and consequently very little mating was observed in this species except under stable conditions. All species exhibited behavioural modifications, but there were interspecific differences related to size-related flight ability and the diel periodicity of mating activity. We postulate that the observed behavioral modifications, especially under decreasing barometric pressure would reduce the probability of injury or death under adverse weather conditions.

Pellegrino, Ana Cristina; Penaflor, Maria Fernanda Gomes Villalba; Nardi, Cristiane; Bezner-Kerr, Wayne; Guglielmo, Christopher G.; Bento, Jose Mauricio Simoes; McNeil, Jeremy N.

2013-01-01

58

Comparing temporal and spatial change of pore water pressure and slope stability between wet soil condition and unsaturated soil condition  

Science.gov (United States)

Intense rainfall event during short duration is the most significant reason of landslide in South Korea. Typically, it increases pore water pressure in soil and reduces soil effective stress, which cause landslide. In rainfall-induced landslide, saturation rate of soil at initial condition can affect whether landslide occurs. The objective of this study is to compare temporal and spatial pore water pressure and slope stability between in wet soil and in unsaturated soil under same rainfall condition. Two different infiltration models of TRIGRS 2 (Fortran Program for Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability Analysis) were employed to analyze difference of pore water pressure and soil stability under different soil initial conditions. The study site was two small watersheds of Mt. Umyeon in South Korea, where several landslides occurred under an extreme rainfall event on July 27, 2011. Topographical data were generated based on 1 m x 1 m-LiDAR data, and parameters of soil and water characteristics were measured in-situ for TRIGRS 2 simulation. In addition, soil water characteristic curve of the site for the unsaturated soil condition was estimated by the pressure plate method and the filter paper method. The simulation results showed that pore water pressure differently responded between the different water conditions of soil. Ground water table rise appeared relatively faster and higher in the wet soil condition than in the unsaturated soil condition. Moreover, in the wet soil condition, pore water pressure increased with depth while in the unsaturated soil condition, vertical distribution of pore water pressure varied in time. In terms of slope stability, lower factor of safety (FS) were estimated in the wet soil condition than in the unsaturated soil condition. Comparing with landslide initiation positions in reality, FS were calculated more reasonably in the wet soil condition while FS were under-estimated in the unsaturated soil condition. These results indicate that estimating accurate initial water condition of landslide site is important for assessing landslide susceptibility.

Kim, Dongyeob; Im, Sangjun; Lee, Eun Jai; Ahn, Byungkyu

2013-04-01

59

High Blood Pressure Reading in Kids Linked to Triple Risk for Condition as Adults  

Science.gov (United States)

High blood pressure reading in kids linked to triple risk for condition as adults American Heart Association Meeting Report: September 12, 2013 Study ... Kids with at least one high blood pressure reading were about three times more likely to develop ...

60

Barometric pumping with a twist: VOC containment and remediation without boreholes. Phase I  

Energy Technology Data Exchange (ETDEWEB)

The majority of the planned remediation sites within the DOE complex are contaminated with volatile organic compounds (VOCs). In many instances the contamination has not reached the water table, does not pose an immediate threat, and is not considered a high priority problem. These sites will ultimately require remediation of some type, either by active vapor extraction, bioremediation, or excavation and ex-situ soil treatment. The cost of remediating these sites can range from $50 K to more than $150 K, depending on site characteristics, contaminants, and remediation method. Additionally, for many remediated sites, residual contamination exists which could not practically be removed by the applied remediation technology. These circumstances result in modest sites with contamination of limited risk, but by regulation they must still be controlled. A remediation solution being developed by Science and Engineering Associates, Inc. (SEA) for the Department of Energy serves as an in-situ containment and extraction methodology for sites where most or all of the contamination resides in the vadose zone soil. The approach capitalizes on the advective soil gas movement resulting from barometric pressure oscillations.

NONE

1996-08-01

 
 
 
 
61

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

62

Particle behavior and char burnout mechanisms under pressurized combustion conditions  

Energy Technology Data Exchange (ETDEWEB)

Combined cycle systems with coal-fired gas turbines promise highest cycle efficiencies for this fuel. Pressurized pulverized coal combustion, in particular, yields high cycle efficiencies due to the high flue gas temperatures possible. The main problem, however, is to ensure a flue gas clean enough to meet the high gas turbine standards with a dirty fuel like coal. On the one hand, a profound knowledge of the basic chemical and physical processes during fuel conversion under elevated pressures is required whereas on the other hand suitable hot gas cleaning systems need to be developed. The objective of this work was to provide experimental data to enable a detailed description of pressurized coal combustion processes. A series of experiments were performed with two German hvb coals, Ensdorf and Goettelborn, and one German brown coal, Garzweiler, using a semi-technical scale pressurized entrained flow reactor. The parameters varied in the experiments were pressure, gas temperature and bulk gas oxygen concentration. A two-color pyrometer was used for in-situ determination of particle surface temperatures and particle sizes. Flue gas composition was measured and solid residue samples taken and subsequently analyzed. The char burnout reaction rates were determinated varying the parameters pressure, gas temperature and initial oxygen concentration. Variation of residence time was achieved by taking the samples at different points along the reaction zone. The most influential parameters on char burnout reaction rates were found to be oxygen partial pressure and fuel volatile content. With increasing pressure the burn-out reactions are accelerated and are mostly controlled by product desorption and pore diffusion being the limiting processes. The char burnout process is enhanced by a higher fuel volatile content.

Bauer, C.M.; Spliethoff, H.; Hein, K.R.G.

1999-07-01

63

Intelligent fiber optic pressure sensor for measurements in extreme conditions  

International Nuclear Information System (INIS)

[en] 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)

2009-01-01

64

A Correlation Study of Cardiopulmonary Arrests, Cholesterol and Pressures  

Directory of Open Access Journals (Sweden)

Full Text Available 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, age, cholesterol, temperature and each of these dependent variables vs the independent variable, barometric pressure are depicted. Small value of the correlation coefficient in each case indicates no significant linear correlation between sudden changes in barometric pressure, cholesterol level and cardiopulmonary arrests.

S.E. Rider; S.M. Taher

2003-01-01

65

Ionospheric Plasma Outflow Under High Solar Wind Dynamic Pressure Conditions  

Science.gov (United States)

The polar cusp is well-known to be one of the most intense source regions of iono- spheric outflow. Since this region is of direct access for solar wind plasma, changes in the interplanetary magnetic field and solar wind dynamic pressure are expected to influence the ion outflow. We report combined observations from the Interball- Auroral in the high-altitude range (10,000-20,000km) and the FAST satellite in the mid-altitude range (4000 km) revealing enhanced ion outflows in association with the passage of an interplanetary shock and CME. Several case studies based on the anal- ysis of ion data recorded from several orbits before and after the pressure impulse are made to investigate how the dynamic pressure affects the amount of outflowing ions. We found a clear relationship between the ion outflow variations and the dy- namic pressure changes when choosing average ion flux and average ion energy flux, inferred from global conservation laws, as parameters to characterize the ion outflow.

Malingre, M.; Bouhram, M.; Dubouloz, N.; Sauvaud, J. A.; Berthomier, M.; Carlson, C. W.

66

Discussion of the CO2 corrosion mechanism between low partial pressure and supercritical condition  

International Nuclear Information System (INIS)

Highlights: ? CO2 corrosion behaviour of X65 steel at low partial pressure. ? CO2 corrosion behaviour of X65 steel under supercritical condition. ? CO2 corrosion mechanism under low pressure and supercritical condition. - Abstract: The corrosion behaviour of X65 pipeline steel at various temperatures for different immersion time under low CO2 partial pressure and supercritical CO2 condition were investigated by weight loss measurements and surface analysis techniques. By comparing the characteristics of CO2 corrosion product scale formed under experimental conditions and the variation rule of corrosion rate with temperature, the CO2 corrosion mechanism under low partial pressure and supercritical condition was studied. To explain the big difference of corrosion rate between low CO2 partial pressure and supercritical CO2 condition, thermodynamic calculation of the solubility of CO2 in H2O were discussed.

2012-01-01

67

Analysis of air-conditioning and drying processes using spreadsheet add-in for psychrometric data  

Directory of Open Access Journals (Sweden)

Full Text Available A spreadsheet add-in for the psychrometric data at any barometric pressure and in the air-conditioning and drying temperatureranges was developed using appropriate correlations. It was then used to simulate and analyse air-conditioning and dryingprocesses in the Microsoft Excel environment by exploiting its spreadsheet and graphic potentials. The package allowsone to determine the properties of humid air at any desired state, and to simulate and analyse air-conditioning as well asdrying processes. This, as a teaching tool, evokes the intellectual curiosity of students and enhances their interest and abilityin the thermodynamics of humid-air processes.

C.O.C. Oko; E.O. Diemuodeke

2010-01-01

68

Cylinder Pressures and Vibration in Internal Combustion Engine Condition Monitoring  

UK PubMed Central (United Kingdom)

: We focus on the detection of incipient faults in an internal combustion engine using a minimumnumber of sensory information. Inducing several faults in a 4 stroke diesel engine, cylinder pressure (P) andvibration (V) data are acquired. Two sets of artificial neural nets (ANN) are trained separately, using featuresfrom the pressure and vibration data. Both sets of nets show very good fault detection capabilities, thusdemonstrating an alternative to the multi-sensory approach commonly adopted in fault diagnosis. In aseparate study, P and V are fused together at the signal level and then used to train another set of ANNs whichis shown to exhibit better reliability than either system. In the final study, the outputs of the 3 systems (P, Vand fused P and V), are combined together in a majority voting system which outperforms all of itsconstituents in its diagnostic abilities, successfully identifying 2854 out of 3000 test cases with a confidencelevel of 90%.Keywords: cylinder p...

G O Ch; A J C Sharkey; N E Sharkey

69

A cylinder pressure based proportional controller for fuel injected engines at idle conditions  

Energy Technology Data Exchange (ETDEWEB)

An investigation into the use of cylinder pressure as a control system feedback variable was conducted using computer simulation techniques. A control algorithm was developed to apply closed-loop control to the warmup phase of engine operation. The control algorithm used a correlation between effective equivalence ratio and cylinder pressure. The cylinder pressure was characterized by the difference in cylinder pressure between the pressure at top dead center on the compression stroke and the maximum cylinder pressure. This differential pressure provided the minimum number of points to describe the cylinder pressure curve. Testing of the control strategy was done with the use of a spark ignition engine cycle model. The control system was able to respond to changes in engine conditions during warmup to re-establish the desired effective equivalence ratio within three engine cycles. These favorable results demonstrated the potential of this method for further development. 69 refs., 48 figs., 3 tabs.

Wilson, D.A.C.

1990-06-01

70

Simulation of ATWS conditions in pressurized water reactors  

International Nuclear Information System (INIS)

Safety analyses of nuclear power plants use ATWS (Anticipated Transients without Scram) as a term covering also events involving assumed failure of the reactor scram system. In this type of failure of the reactor scram system, power development in the reactor core is determined only by neutron kinetics feedback via the fuel temperature, moderator temperature and moderator density. If borated coolant is supplied, there is the additional feedback from the boron concentration. For nuclear power plants, coupled code complexes are developed and used which are made up of a thermohydraulic plant code and a 3D neutron kinetics model of the reactor core. These lend themselves to the use in analyses of ATWS states. The work presented here about the ATWS problem was performed in the interest of a consistent application of the DYN3D 3D neutron kinetics code in combination with the ATHLET thermohydraulic system code, and the quantification of differences resulting from variations of initial and boundary conditions. The DYN3D/ATHLET coupled code complex was validated by recalculation of various operating transients and by solving benchmark problems. The article contains results computed taking into account the influence of systems engineering and neutron kinetics boundary conditions. The calculations shown are methodological studies in no way demonstrating proof. (orig.)

2009-01-01

71

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

2007-01-01

72

Unsteady Pressure Measurements around Rotor of an Axial Flow Fan under Stable and Unstable Operating Conditions  

Science.gov (United States)

This study presents some measurement results on the unsteady pressure fields around rotor under stable and unstable operating conditions of an axial flow fan. The unsteady static pressure of rotor passage was measured by using high frequency pressure transducers mounted on the casing wall. The measurements on the unsteady total pressure at rotor inlet and outlet were also conducted with specially designed high frequency total pressure probe. Double Phase-Locked Ensemble Averaging Technique was used for analysis of pressure fluctuations around the rotor at rotating stall onset point. From the results, the unsteady pressure fields during stable and unstable operations of the axial fan were investigated and compared with each other. Particularly one period of rotating stall could be divided into two regions, stalled flow and unstalled flow region respectively. Furthermore the former could be also classified into two zones, bubbled and disturbed region by their features. The flow characteristics for each zone were described in detail and the static and total pressure fields were also analyzed in terms of the pressure distribution along pressure side and suction side on the blade tip profile.

Shin, You Hwan; Kim, Kwang Ho; Kang, Chang Sik

73

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

1984-01-01

74

Accessing High Pressure States Relevant to Core Conditions in the Giant Planets  

Energy Technology Data Exchange (ETDEWEB)

We have designed an experimental technique to use on the National Ignition Facility (NIF) laser to achieve very high pressure (P{sub max} > 10 Mbar = 1000 GPa), dense states of matter at moderate temperatures (kT < 0.5 eV = 6000 K), relevant to the core conditions of the giant planets. A discussion of the conditions in the interiors of the giant planets is given, and an experimental design that can approach those conditions is described.

Remington, B A; Cavallo, R M; Edwards, M J; Ho, D D; Lorenz, K T; Lorenzana, H E; Lasinski, B F; McNaney, J M; Pollaine, S M; Smith, R F

2004-04-15

75

A Variable Condition Calculation Method for Thermal Power Units Sliding Pressure Operation  

Directory of Open Access Journals (Sweden)

Full Text Available This paper first analyzes how thermodynamic system state parameters are affected when main steam’s pressure changes under sliding pressure operation .Then a new state distribution equation of sliding pressure operation based on thermo-economy equation of state of thermal power unit is given .With the help of this equation, a new algorithm is proposed to determine the state parameters distribution for variable working condition under sliding pressure operation. Experiment of one supercritical unit is provided to validate the effectiveness of our approach under sliding pressure operation. Simulation results show that this algorithm is beneficial for analyzing the security and economy of thermal power unit with deep fast variable loads. It also has vital important significance for thermal power unit to develop its peak shaving ability.

Wei Liu; Jizhen Liu; Wei Wang; Deliang Zeng; Taihua Chang

2013-01-01

76

Directly measured cabin pressure conditions during Boeing 747-400 commercial aircraft flights.  

UK PubMed Central (United Kingdom)

BACKGROUND AND OBJECTIVES: In the low pressure environment of commercial aircraft, hypoxaemia may be common and accentuated in patients with lung or heart disease. Regulations specify a cabin pressure not lower than 750 hPa but it is not known whether this standard is met. This knowledge is important in determining the hazards of commercial flight for patients and the validity of current flight simulation tests. METHODS: Using a wrist-watch recording altimeter, cabin pressure was recorded at 60 s intervals on 45 flights in Boeing 747-400 aircraft with three airlines. A log was kept of aircraft altitude using the in-flight display. Change in cabin pressure during flight, relationship between aircraft altitude and cabin pressure and proportion of flight time with cabin pressure approaching the minimum specified by regulation were determined. RESULTS: Flight duration averaged 10 h. Average cabin pressure during flight was 846 hPa. There was a linear fall in cabin pressure as the aircraft cruising altitude increased. At 10,300 m (34,000 ft) cabin pressure was 843 hPa and changed 8 hPa for every 300 m (1000 ft) change in aircraft altitude (r(2) = 0.993; P < 0.001). Lowest cabin pressure was 792 hPa at 12 200 m (40,000 ft) but during only 2% of flight time was cabin pressure less than 800 hPa. CONCLUSIONS: Cabin pressure is determined only by the engineering of the aircraft and its altitude and in the present study was always higher than required by regulation. Current fitness-to-fly evaluations simulate cabin conditions that passengers will not experience on these aircraft. There may be increased risks to patients should new or older aircraft operate nearer to the present minimum standard.

Kelly PT; Seccombe LM; Rogers PG; Peters MJ

2007-07-01

77

Resistivity Variation due to CO2 Migration in Different Temperature and Pressure Conditions  

Science.gov (United States)

CO2 geological sequestration is one of the effective approaches solving the global warming problem. Captured CO2 is injected to the deep aquifers or depleted oil and gas fields. Injected CO2 migrates thorough the reservoir rock, however, the details behavior of injected CO2 under the ground at super critical phase is not yet fully understood. Migration of injected CO2 will change by the condition of the injected reservoir such as the temperature and pressure. Also density and permeability of the rock may be changed due to temperature or pressure variations. These changes control the migration behavior of injected CO2. In this study, experiments of resistivity measurements were conducted to detect the migration difference of CO2 in different temperature and pressure conditions by using sandstone core samples. Core sample was taken from Berea sandstone and processed to 5cm diameter and 12cm length. For the resistivity measurement, impression electrode was set on the both end and the measurement electrode of ring condition was set on the side of the rock sample. We stetted the core sample in the pressure vessel and recreated the condition of underground reservoir which is high pressure and high temperature. We injected supercritical CO2 in different pressure and temperature for each experiment. Pressure was changed in range of 8 to 11MPa and temperature was changed in range of 35° to 45°. This means that all the experiments were conducted in supercritical phase. From the measured resistivity variation, we verified the migration of CO2 and compared the migration behavior of CO2 in different conditions.

Nakatsuka, Y.; Onishi, K.; Yamada, Y.; Matsuoka, T.; Xue, Z.

2007-12-01

78

Cutting and conditioning of the reactor pressure vessel in the NPP Wuergassen  

International Nuclear Information System (INIS)

NPP Wuergassen was shutdown in 1995 after 23 years of operation. Since 1997 the nuclear power plant is being dismantled. The cutting of the reactor pressure vessel internals was performed between 2003 and 2008. After decontamination the cylindrical parts of the reactor pressure vessel were dissected, the process was finalized in 2010. AREVA has now a 30 years-experience concerning repair, replacement and dismantling of reactor components. In the contribution the authors describe the process planning, manufacture and testing of appropriate remote handled tools, decontamination, dissection of the pressure vessel (320 t), conditioning, packaging and transport of the radioactive waste including radiation protection monitoring.

2011-01-01

79

Influence of different boundary conditions on modulating inlet pressure and velocity of regenerator  

Science.gov (United States)

In present paper, a model driven by double loudspeakers is proposed, which can widely modulate acoustic pressure and oscillating velocity at the inlet boundary of regenerator. For the sake of contrastive analysis, other two models driven by single loudspeaker are built up. Based on linear thermoacoustic theory, the governing equations concerning different boundary conditions in three models are setup and discussed. The modulating ranges of inlet pressure and velocity in three models are compared. It verifies that the model driven by double loudspeakers is preferable than other two models for modulating acoustic pressure and oscillating velocity.

Zhou, Lihua; Xie, Xiujuan; Li, Qing

2012-05-01

80

LHe Flow Regime/Pressure Drop for D0 Solenoid at Steady State Conditions  

Energy Technology Data Exchange (ETDEWEB)

This paper describes in a note taking format what was learned from several sources on two phase liquid helium flow regimes and pressure drops as applied to the D-Zero solenoid upgrade project. Calculations to estimate the steady state conditions for the D-Zero solenoid at 5, 10 and 15 g/s are also presented. For the lower flow rates a stratified type regime can be expected with a pressure drop less than 0.5 psi. For the higher flow rate a more homogeneous flow regime can be expected with a pressure drop between 0.4 to 1.5 psi.

Rucinski, R.; /Fermilab

1993-03-03

 
 
 
 
81

Separating expansion from contraction: generalized TOV condition, LTB models with pressure and $\\Lambda$CDM  

CERN Document Server

We discuss the existence of a dividing shell separating expanding and collapsing regions in spherically symmetric solutions with pressure. We obtain gauge invariant conditions relating not only the intrinsic spatial curvature of the shells to the ADM mass, but also a function of the pressure which we introduce that generalises the Tolman-Oppenheimer-Volkoff equilibrium condition, in the framework of a 3+1 spacetime splitting. We consider the particular case of a Lema\\^itre-Tolman-Bondi dust models with a cosmological constant (a $\\Lambda$-CDM model) as an example of our results.

Delliou, Morgan Le; Mimoso, José Pedro

2009-01-01

82

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)

2008-01-01

83

Frictional property of fault gouges in high-velocity and high-fluid pressure condition  

Science.gov (United States)

Fluid in fault zones will influence on fault dynamics and cause water-rock interaction in the fault zone during earthquakes. Frictional heating during friction can increase pore pressure in a fault zone due to the thermal expansion of fluid, and that will reduce the effective normal stress on the fault. This pore pressure rise is also induced by an increase of fluid volume that associates with a dehydration of hydrous minerals or decarbonation of carbonate minerals. Recently laboratory friction experiments demonstrated that high velocity friction can cause remarkable fault weakening and chemical-reaction which is induced by rapid heating during friction. However, a correlation of fluid and pore fluid pressure with friction property and chemical-reaction had not been well investigated. Therefore, we carried out the high velocity friction tests by controlling fluid pressure under high pore pressure condition. We used shale in the fracture zone from the Taiwan Chelungpu Fault Drilling Project (TCDP Hole B, 1090.88 m depth) as simulated gouge materials for friction tests. Shale (Chinshui Shale) is mainly made up by quartz, feldspar, and clay minerals. We made powders with less than 0.125 mm grain size from shale by crushing and sieving. Frictional experiments were performed (1) under constant normal pressure and pore fluid pressure, and (2) under constant normal pressure without controlling pore fluid pressure. Pore pressure was applied from 2 to 5 MPa, and normal stress was from 2 to 12 MPa. We also controlled slip velocity by keeping constant from 0.1 to 0.5 m/s. Total slip displacements were reached to 15 m or 30 m at the end of sliding. In all friction tests, shear strength was decreased with sliding, and then reached to steady state values over ~10 m displacement. For friction tests without controlling pore pressure, pore pressure was gradually increased with sliding. Even though the effective normal stress was decreased by the pore pressure increase, friction coefficient was not changed much. Peak friction was lager for the pore pressure control tests than that for the test without controlling pore pressure. Steady state shear stress was proportional to effective normal stress, and 0.2 of friction coefficient was evaluated for both tests. Temperatures around the slip surface were increased up to 400 degrees Celsius. Lithium concentration in the gouge was decreased after friction tests, and high temperature water-rock interaction at more than 300 degrees Celsius for 60 seconds can explain the anomaly of Lithium concentration. This result agrees with the observation of surface temperature. However, the chemical anomaly we detected was generally small, therefore much higher slip velocity is necessary to occur the water-rock interaction effectively.

Tanikawa, Wataru; Ishikawa, Tsuyoshi; Hirono, Tetsuro; Honda, Go

2013-04-01

84

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.; Yoozbashizadeha H.

2012-01-01

85

Whole body barometric plethysmography: a screening method to investigate airway reactivity and acute lung injuries in freely moving pigs.  

Science.gov (United States)

The aim of this work was to investigate whether the Penh index, measured using whole body barometric plethysmography, can be used as a screening parameter to evaluate the airway reactivity and the intensity of the pulmonary response to endotoxins. Penh was firstly recorded in non-sedated freely moving piglets exposed (1) to a nebulized acetylcholine (Ach) pre-treated or not with clenbuterol, or (2) to endotoxin challenge. To measure Penh simultaneously with total pulmonary resistance (R(L)), dynamic compliance (C(dyn)) and intrapleural pressure changes (Max Delta Ppl), an oesophageal balloon catheter technique was used and the piglets were anaesthetised. The recordings were performed during (1) an intravenous metacholine (Mch) challenge and (2) in endotoxin-exposed animals. In freely moving animals, Ach induced a significant dose-dependent increase in Penh, which was significantly blocked by clenbuterol. Endotoxin instillation also resulted in a significant rise in Penh while the corresponding response measured under anaesthesia was significantly and positively correlated with R(L) and Max Delta Ppl. Similar results were obtained during Mch challenge but the Penh was negatively correlated with C(dyn). We conclude that Penh could be used in freely moving piglets as a screening index for airway reactivity and pulmonary functional changes in cholinergic and endotoxin challenges. PMID:15501145

Halloy, David J; Kirschvink, Nathalie A; Vincke, Grégoire L; Hamoir, Julien N; Delvaux, François H; Gustin, Pascal G

2004-11-01

86

Analysis of the DHLW cask under normal and hypothetical accident-condition loads with initial pressure  

International Nuclear Information System (INIS)

[en] The paper describes analyses performed for the Defense High-Level Waste (DHLW) cask design that establish an upper limit of 700 lbf/in2 (1 lbf/in2(g) = 6.895x103 Pa) for the cask maximum normal operating pressure (MNOP). Analyses of the cask with this MNOP as an initial condition show that for both normal and hypothetical accident conditions of transport, the stresses are within allowable values. (author)

1987-01-01

87

A non-invasive probe for online-monitoring of turgor pressure changes under field conditions.  

UK PubMed Central (United Kingdom)

An advanced non-invasive, field-suitable and inexpensive leaf patch clamp pressure probe for online-monitoring of the water relations of intact leaves is described. The probe measures the attenuated output patch clamp pressure, P(p), of a clamped leaf in response to an externally applied input pressure, P(clamp). P(clamp) is generated magnetically. P(p) is sensed by a pressure sensor integrated into the magnetic clamp. The magnitude of P(p) depends on the transfer function, T(f), of the leaf cells. T(f) consists of a turgor pressure-independent (related to the compression of the cuticle, cell walls and other structural elements) and a turgor pressure-dependent term. T(f) is dimensionless and assumes values between 0 and 1. Theory shows that T(f) is a power function of cell turgor pressure P(c). Concomitant P(p) and P(c) measurements on grapevines confirmed the relationship between T(f) and P(c). P(p) peaked if P(c) approached zero and assumed low values if P(c) reached maximum values. The novel probe was successfully tested on leaves of irrigated and non-irrigated grapevines under field conditions. Data show that slight changes in the microclimate and/or water supply (by irrigation or rain) are reflected very sensitively in P(p).

Westhoff M; Reuss R; Zimmermann D; Netzer Y; Gessner A; Gessner P; Zimmermann G; Wegner LH; Bamberg E; Schwartz A; Zimmermann U

2009-09-01

88

A non-invasive probe for online-monitoring of turgor pressure changes under field conditions.  

Science.gov (United States)

An advanced non-invasive, field-suitable and inexpensive leaf patch clamp pressure probe for online-monitoring of the water relations of intact leaves is described. The probe measures the attenuated output patch clamp pressure, P(p), of a clamped leaf in response to an externally applied input pressure, P(clamp). P(clamp) is generated magnetically. P(p) is sensed by a pressure sensor integrated into the magnetic clamp. The magnitude of P(p) depends on the transfer function, T(f), of the leaf cells. T(f) consists of a turgor pressure-independent (related to the compression of the cuticle, cell walls and other structural elements) and a turgor pressure-dependent term. T(f) is dimensionless and assumes values between 0 and 1. Theory shows that T(f) is a power function of cell turgor pressure P(c). Concomitant P(p) and P(c) measurements on grapevines confirmed the relationship between T(f) and P(c). P(p) peaked if P(c) approached zero and assumed low values if P(c) reached maximum values. The novel probe was successfully tested on leaves of irrigated and non-irrigated grapevines under field conditions. Data show that slight changes in the microclimate and/or water supply (by irrigation or rain) are reflected very sensitively in P(p). PMID:19689778

Westhoff, M; Reuss, R; Zimmermann, D; Netzer, Y; Gessner, A; Gessner, P; Zimmermann, G; Wegner, L H; Bamberg, E; Schwartz, A; Zimmermann, U

2009-09-01

89

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

90

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 mi...

Khoshnevisana A.; Yoozbashizadeha H.

91

Effect of Antecedent Conditions on Prediction of Pore-Water Pressure using Artificial Neural Networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The effect of antecedent conditions on the prediction of soil pore-water pressure (PWP) using Artificial Neural Network (ANN) was evaluated using a multilayer feed forward (MLFF) type ANN model. The Scaled Conjugate Gradient (SCG) training algorithm was used for training the ANN. Time series data of...

Muhammad Raza Ul Mustafa; Rezaur Rahman Bhuiyan; Mohamed Hasnain Isa; Saied Saiedi; Harianto Rahardjo

92

Kinetics of CaO-H{sub 2}S reaction at high temperature under pressurized conditions  

Energy Technology Data Exchange (ETDEWEB)

Kinetic study of H{sub 2} absorption with calcined limestone was performed under pressurized conditions (up to 20 atm) by means of a self-made pressurized thermobalance mainly consisting of a quartz spring balance and a pressure vessel. The adsorption of 200--4,200 ppm (mainly 1000 ppm) of H{sub 2}S was carried out with calcined limestone (710--1,000 {micro}m) at 1,023--1,223 K and 1--20 atm. The effect of pressure on the kinetics of H{sub 2}S adsorption was investigated. The film resistance of mass transfer was negligible when the total gas velocity was 0.53 m/s (10 SLM). The rate of H{sub 2}S adsorption decreased with increasing total pressure (H{sub 2}S pressure was kept at 0.004 atm). The level of conversion of CaO to CaS was 87% at 1 atm and 38% at 20 atm after 5 h of reaction. The used limestone samples were characterized with SEM and EDAX. Based on the SEM and EDAX observations on the cross section of limestone particles, a CaS layer was clearly developed from the surface to the interior in the progress of sulfidation in all cases. Although the authors applied the conventional shrinking-core models with different rate-determining steps for analyzing the H{sub 2}S adsorption kinetics, these SCM models failed to explain the sulfidation behavior in the early stage of sulfidation at higher pressures. Thus, they developed empirical equations to express the sulfidation behavior in the wide ranges of the solid conversion and the total pressure. Equations developed in this study can predict the sulfidation kinetics at higher pressure well.

Matsukata, M.; Ando, H.; Ueyama, K.; Hosoda, S.

1999-07-01

93

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

Science.gov (United States)

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.

Gong, R. Z.; Wang, H. G.; Yao, Y.; Shu, L. F.; Huang, Y. J.

2012-11-01

94

Stability of amino acids and their oligomerization under high-pressure conditions: implications for prebiotic chemistry.  

UK PubMed Central (United Kingdom)

The polymerization of amino acids leading to the formation of peptides and proteins is a significant problem for the origin of life. This problem stems from the instability of amino acids and the difficulty of their oligomerization in aqueous environments, such as seafloor hydrothermal systems. We investigated the stability of amino acids and their oligomerization reactions under high-temperature (180-400°C) and high-pressure (1.0-5.5?GPa) conditions, based on the hypothesis that the polymerization of amino acids occurred in marine sediments during diagenesis and metamorphism, at convergent margins on early Earth. Our results show that the amino acids glycine and alanine are stabilized by high pressure. Oligomers up to pentamers were formed, which has never been reported for alanine in the absence of a catalyst. The yields of peptides at a given temperature and reaction time were higher under higher-pressure conditions. Elemental, infrared, and isotopic analyses of the reaction products indicated that deamination is a key degradation process for amino acids and peptides under high-pressure conditions. A possible NH(3)-rich environment in marine sediments on early Earth may have further stabilized amino acids and peptides by inhibiting their deamination.

Otake T; Taniguchi T; Furukawa Y; Kawamura F; Nakazawa H; Kakegawa T

2011-10-01

95

Study of chemically induced pressure generation of hydrogels under isochoric conditions using a microfabricated device  

Science.gov (United States)

A method is proposed to study the behavior of stimulus-sensitive hydrogels under isochoric conditions. Freedom of swell movement of such a hydrogel was restricted in all directions by enclosing the hydrogel between a micropressure sensor and a porous cover. Water and external stimuli can be applied to the hydrogel through the pores of the cover to provoke swelling, which results in pressure generation measured by the pressure sensor. The method was put to the proof by examining the response of a pH-sensitive hydrogel to changes in pH, ionic strength, and buffer concentrations of the surrounding solution. Both equilibrium and dynamic pressure generation were observed. The results show that higher pressures are obtained by incorporating more ionizable groups into the hydrogel network or by lowering the ionic strength of the external solution. Furthermore it was proven that pressures reach equilibrium faster when less titratable groups are incorporated or at the presence of higher buffer concentrations in the surrounding solution. By using microfabrication techniques the dimensions of the hydrogel could be kept small with the advantage that responses are fast. A DMAEMA-co-HEMA hydrogel with 2.5% protonable groups and a thickness of 15 ?m generated a ?pressure of 0.67×105 Pa in 12 min when a pH step from 9 to 6 was applied. The presented method is a simple and fast manner to characterize the static and dynamic stimulus-dependent behavior of hydrogels.

Herber, S.; Eijkel, J.; Olthuis, W.; Bergveld, P.; van den Berg, A.

2004-08-01

96

Modeling mass transfer during osmotic dehydration of strawberries under high hydrostatic pressure conditions  

UK PubMed Central (United Kingdom)

Simultaneous application of high hydrostatic pressure (200-400MPa) during osmotic dehydration of strawberries was studied in this investigation. The high hydrostatic pressure treatment improved the diffusion coefficients of water and soluble solids compared to atmospheric pressure operation. Effects of process pressure on diffusion coefficients were achieved through an Arrhenius-type equation. Mathematical modeling of mass transfer was performed applying Newton, Henderson-Pabis, Page and Weibull models. Based on statistical results, the Weibull model gave the best goodness of fit on the experimental data under the studies' operative conditions. Industrial relevance: This article deals with the mathematical modeling of mass transfer during simultaneous high hydrostatic pressure treatment and osmotic dehydration of strawberries. Transfer of water and soluble solids during this combined process were satisfactorily simulated with the Weibull model. Results indicated that application of this innovative technology improved strawberries dehydration rates compared to atmospheric pressure operation resulting in a dried fruit with intermediate moisture content ready to be used as input material of further processes.

Nuñez-Mancilla Y; Perez-Won M; Vega-Gálvez A; Arias V; Tabilo-Munizaga G; Briones-Labarca V; Lemus-Mondaca R; Di Scala K

2011-07-01

97

Series of metal hydride high pressure hydrogen compressors  

Energy Technology Data Exchange (ETDEWEB)

The institute for Problems in Machinery of the National Academy of Sciences of the Ukraine has developed an experimental batch of the single-stage metal hydride thermosorption compressors (TSCs) with different gas deliveries: TSC-70, TSC-80, TSC-150 and TSC-300. These have delivery pressure from 7.0 to 30.0 MPa at the initial pressure of 0.3-1.0 MPa. These devices can work in continuous mode or in periodic mode. They are characterized with the original design properties, caused by severe barometric working conditions. The technical parameters of these compressors as well as the results of their long-term operation in the different energy-technological systems are presented in the report. The prospective fields of their application are shown. (orig.)

Solovey, V.V. [National Ukrainian Acad. of Sci., Kharkov (Ukraine). Inst. for Problems in Machinery]|[Ukrainian Academy of Science for National Progress, Kiev (Ukraine). Inst. for Hydrogen and Solar Energy; Ivanovsky, A.I. [National Ukrainian Acad. of Sci., Kharkov (Ukraine). Inst. for Problems in Machinery; Kolosov, V.I. [National Ukrainian Acad. of Sci., Kharkov (Ukraine). Inst. for Problems in Machinery; Shmal`ko, Yu.F. [National Ukrainian Acad. of Sci., Kharkov (Ukraine). Inst. for Problems in Machinery]|[Ukrainian Academy of Science for National Progress, Kiev (Ukraine). Inst. for Hydrogen and Solar Energy

1995-12-15

98

Necessary conditions for the homogeneous formation of pulsed avalanche discharges at high gas pressures  

Science.gov (United States)

The preionization level and other initial conditions necessary for the formation of spatially homogeneous pulsed avalanche discharges at high gas pressures are examined. Assuming properly shaped electrodes with no strong edge effects, the minimum preionization level required for homogeneous discharge initiation is found to depend on the voltage rise time across the electrodes as well as on the total pressure and various electrochemical properties of the gas mixture which govern the net rate of change of the first Townsend coefficient with respect to the local electric field strength. Our predictive results are found to be consistent with experimental observations.

Levatter, Jeffrey I.; Lin, Shao-Chi

1980-01-01

99

Heterogeneous Catalysis under pressure - In-situ neutron diffraction under industrial conditions  

International Nuclear Information System (INIS)

The present work describes the application of a tubular reactor that allows in-situ neutron diffraction on working catalysts at high pressures. The designed reactor enables the application to a sample of industrially-relevant reaction conditions, i.e., in a temperature range up to 330° C and 60 bar pressure, coupled with online gas-analysis. Application of the cell is demonstrated by ammonia synthesis over a commercial catalyst with diffraction data obtained from the high-resolution powder diffractometer, Echidna, at the Australian Nuclear Science and Technology Organisation, ANSTO.

2012-02-08

100

Virial coefficients and osmotic pressure in polymer solutions in good-solvent conditions  

CERN Document Server

We determine the second, third, and fourth virial coefficients appearing in the density expansion of the osmotic pressure of a monodisperse polymer solution in good-solvent conditions. Using the expected large-concentration behavior, we extrapolate the low-density expansion outside the dilute regime, obtaining the osmotic pressure for any concentration in the semidilute region. Comparison with field-theoretical predictions and experimental data shows that the obtained expression is quite accurate. The error is approximately 1-2% below the overlap concentration and rises at most to 5-10% in the limit of very large polymer concentrations.

Caracciolo, S; Pelissetto, A; Caracciolo, Sergio; Mognetti, Bortolo Matteo; Pelissetto, Andrea

2006-01-01

 
 
 
 
101

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 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 transmissivity and storage coefficient consistent wi

2012-01-01

102

Pressure indicating analysis on a common rail DI diesel engine in transient operating conditions  

Energy Technology Data Exchange (ETDEWEB)

For a long time noise remained the fundamental obstacle to the application of DI Diesel engines to passenger cars, despite the important advantages in terms of fuel consumption. Since 1997, the industrial availability of the Common Rail Fuel Injection System (FIS) allowed to achieve a significant reduction of the overall engine noise level and quality, while demonstrating good potential in terms of engine performance and emission optimisation. The main characteristics which distinguishes the Common Rail FIS from the others is the extreme freedom with regard to the management of injection parameters such as injection pressure, injection timing and injection quantity of both pilot and main. These parameters may furthermore be controlled under transient conditions, stroke to stroke, as function of the relevant engine parameters. In the first part of the paper the effect of C.R. FIS control parameters on cylinder pressure, combustion noise and emissions is analysed under steady state conditions. In the second part, the differences in terms of noise between steady state and transient operating conditions are highlighted, underlining the necessity of specific transient control strategies based on the flexibility of the Common Rail technology coupled with electronic engine management. It turns out that an accurate measurement and analysis of the cylinder pressure time histories under transient engine conditions, requiring last generation high-tech instrumentation, is therefore become indispensable in order to optimise the engine sound level within the limits imposed by exhaust emission, smoke, fuel consumption and performance requirements. (orig.)

Borrione, S.M.; Vaccarino, P.D. [Centro Richerce Fiat, Orbassano (Italy)

2000-07-01

103

Simple Molecular Systems Under Simultaneous Conditions of High Pressure and Temperature  

Science.gov (United States)

Knowledge of the elastic, optical and vibrational properties of materials under extreme conditions of high pressure and temperature is crucial for interpreting the results of seismological and planetary observations, for materials science, and for improving our understanding of fundamental physics and chemistry under such conditions. Here, I will present the results of Raman and optical spectroscopy (in pulsed and continuous modes), and also x-ray diffraction measurements of simple molecular materials under conditions of high static pressure and temperature in the diamond anvil cell. High temperatures were generated mainly by laser heating (including a pulsed laser heating), but also using internal and external resistive heating. The behavior of hydrogen, deuterium, nitrogen, oxygen and water under simultaneous conditions of high temperature and high static pressure up to 120 GPa and 4000 K will be reported. The results reveal unexpected routes of transformation to nonmolecular materials and establish the behavior of interatomic interactions in molecular materials. I thank the following individuals for contributing to this work: J. Crowhurst, N. Goldman, L. Fried, C. Mundy, J. Zaug, R. J. Hemley, V. V. Struzhkin, P. Beck, C.-S. Zha, E. Gregoryanz, C. Sanloup, M. Somayazulu, Y. Meng, N. Guignot, M. Mezouar. I acknowledge support by DOE/BES, DOE/NNSA (CDAC), NSF, and the W. M. Keck Foundation.

Goncharov, A.

2007-12-01

104

Local conditions separating expansion from collapse in spherically symmetric models with anisotropic pressures  

Science.gov (United States)

We investigate spherically symmetric spacetimes with an anisotropic fluid and discuss the existence and stability of a separating shell dividing expanding and collapsing regions. We resort to a 3+1 splitting and obtain gauge invariant conditions relating intrinsic spacetime quantities to properties of the matter source. We find that the separating shell is defined by a generalization of the Tolman-Oppenheimer-Volkoff equilibrium condition. The latter establishes a balance between the pressure gradients, both isotropic and anisotropic, and the strength of the fields induced by the Misner-Sharp mass inside the separating shell and by the pressure fluxes. This defines a local equilibrium condition, but conveys also a nonlocal character given the definition of the Misner-Sharp mass. By the same token, it is also a generalized thermodynamical equation of state as usually interpreted for the perfect fluid case, which now has the novel feature of involving both the isotropic and the anisotropic stresses. We have cast the governing equations in terms of local, gauge invariant quantities that are revealing of the role played by the anisotropic pressures and inhomogeneous electric part of the Weyl tensor. We analyze a particular solution with dust and radiation that provides an illustration of our conditions. In addition, our gauge invariant formalism not only encompasses the cracking process from Herrera and co-workers but also reveals transparently the interplay and importance of the shear and of the anisotropic stresses.

Mimoso, José P.; Le Delliou, Morgan; Mena, Filipe C.

2013-08-01

105

Analysis of brittle fracture conditions in WWER reactor pressure vessel under thermal shock  

International Nuclear Information System (INIS)

[en] The principal steps are shown of computer assessment of the resistance of the WWER pressure vessels to brittle fracture during transients due to thermal shocks in emergency cooling. A pipe with inner diameter of 20 mm was used to show that a typical WWER-440 pressure vessel is always free from brittle fracture. Calculations were made of temperature and stress fields during emergency cooling. An analysis of brittle fracture conditions was performed in accordance with the INTERATOMEHNERGO, an international corporation for cooperation in the nuclear field, standard. Graphs are presented of the typical temperature distribution along the pressure vessel perimeter, of temperature and stress field distribution through vessel thickness, of stress intensity factor dependence on crack depth for different time intervals during pipe failure, and the time and temperature dependence of the stress intensity factor for different crack depths. (J.B.). 7 figs

1987-01-01

106

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

107

Ion current based pressure peak detection under different air humidity conditions  

Energy Technology Data Exchange (ETDEWEB)

A model based soft sensor that estimates the location of the in-cylinder pressure peak from the ion current is described. The soft sensor uses a neural network algorithm and has been implemented in a SAAB 9000 low-pressure turbo production car. It estimates the pressure peak location, in real time, during normal highway driving with an error of 2-3 crank angle degrees. The soft sensor has been tested during normal Scandinavian weather conditions, with a relative air humidity of about 50%, as well as when water is sprayed into the intake manifold, resulting in approximately 100% relative humidity. The neural network based soft sensor is significantly better than that of another method, based on nonlinear Gaussian curve fits, for the same task. The neural network has a low computational load, is deterministic, and could easily be implemented in either an engine control unit or a stand-alone integrated circuit. (orig.)

Hellring, M.; Roegnvaldsson, T.; Wickstroem, N. [CCA, Halmstad Univ. (Sweden); Larsson, M. [Mecel AB, Amal (Sweden)

2000-07-01

108

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

2012-01-01

109

A SiC high-temperature Pressure Sensor Operating in Severe Condition  

Directory of Open Access Journals (Sweden)

Full Text Available The tranditional MEMS pressure sensor based on Silicon (Si) material has not been suitable for operating in severe condition such as high-temperature (>500°C). However, as an alternative material, Silicon Carbide (SiC) can be used in hash environment due to its unique properties. Hence this paper presents a touch mode capacitive pressure sensor with double-notches structure, which employs a special SiC-AlN-SiC sandwich structure to achieve high-accuracy pressure measurement in high-temperature environment. In order to get the relation of capacitance and external pressure, the large deflection theory is applied in simulation analysis of the diaphragm deformation. At the same time, the sandwich structure and technical process of the sensor are studied in the paper. The results showed that the sensor has excellent high-temperature performance due to application of SiC and AlN materials, and the sensor has higher sensitivity and longer linear range than traditional single-cavity structure. Consequently, the sensor can be applied to accuracy pressure measuremet in high-temperature and harsh environment.

Haojie Lv; Huiyong Yu; Guoqing Hu

2012-01-01

110

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

111

BWR In-Core Monitor Housing Replacement Under Dry Condition of Reactor Pressure Vessel  

International Nuclear Information System (INIS)

A new method of In-Core Monitor Housing replacement has been successfully applied to Tokai Unit 2 (BWR with 1100 MWe) in April of 2001. It was designed to replace a housing under dry condition of reactor pressure vessel (RPV): this enabled the elimination of water filled-up and drained processes during the replacement procedure resulting in the reduction of implementation schedule. To realize the dry condition, the radiation shields were placed in the RPV and the hollow guide pipe (GP) was adopted to transfer the apparatuses from the top to the bottom work area. (authors)

2002-01-01

112

Consideration of loading conditions initiated by thermal transients in PWR pressure vessels  

International Nuclear Information System (INIS)

This report describes the present state of PWR-plants in the Federal Republic of Germany with respect to - the design of the primary pressure boundary - the analysis of thermal transients and resulting loads - the material conditions and neutron fluence - the requirements for protection against fast fracture. The experimental and analytical research and development programs are delineated together with some foreign R and D programs. It is shown that the parameters investigated (loading condition, crack shape and orientation etc.) cover a broad range. Extensive analytical investigations are emphasized. (orig./RW)

1983-01-01

113

A test facility for heat transfer, pressure drop and stability studies under supercritical conditions  

International Nuclear Information System (INIS)

Supercritical water (SCW) exhibits excellent heat transfer characteristics and high volumetric expansion coefficient (hence high mass flow rates in natural circulation systems) near pseudo-critical temperature. SCW is being considered as a coolant in some advanced nuclear reactor designs on account of its potential to offer high thermal efficiency, compact size, elimination of steam generator, separator and dryer, making it economically competitive. The elimination of phase change results in elimination of the Critical Heat Flux (CHF) phenomenon. Cooling a reactor at full power with natural instead of forced circulation is generally considered as enhancement of passive safety. In view of this, it is essential to study natural circulation, heat transfer and pressure drop characteristics of supercritical fluids. Carbon-dioxide can be considered to be a good simulant of water for natural circulation at supercritical conditions since the density and viscosity variation of carbon-dioxide follows a parallel curve as that of water at supercritical conditions. Hence, a supercritical pressure natural circulation loop (SPNCL) has been set up in Hall-7, BARC to investigate the heat transfer, pressure drop and stability characteristics of supercritical carbon-dioxide under natural circulation conditions. The details of the experimental facility are presented in this report. (author)

2013-01-01

114

Spherically symmetric models: generalised local conditions separating expansion from collapse in models with anisotropic pressures  

CERN Document Server

We investigate spherically symmetric spacetimes with an anisotropic ?uid and discuss the exis- tence and stability of a dividing shell separating expanding and collapsing regions. We resort to a 3 + 1 splitting and obtain gauge invariant conditions relating intrinsic spacetimes quantities to characteristics of the matter source. We ?nd that the dividing shell is de?ned by a generalization of the Tolman-Oppenheimer-Volko? equilibrium condition. The latter establishes a balance between the pressure gradients, both isotropic and anisotropic, and the strength of the ?elds induced by the Misner-Sharp mass inside the separating shell and by the pressure ?uxes. This de?nes a local equi- librium condition, but conveys also a non-local character given the de?nition of the Misner-Sharp mass. By the same token it is also a generalized thermodynamical equation of state as usually interpreted for the perfect ?uid case, which now has the novel feature of involving both the isotropic pressure P and the anisotropic stress. W...

Mimoso, José P; Mena, Filipe C

2013-01-01

115

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

2007-01-01

116

Characterization of Contaminant Transport by Gravity, Capillarity and Barometric Pumping in Heterogeneous Vadose Zones  

Energy Technology Data Exchange (ETDEWEB)

This final report summarizes the work and accomplishments of our three-year project. We 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. Our 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. The key feature of the VZO constructed at Lawrence Livermore National Laboratory (LLNL) is the variety of plume-tracking techniques that can be used at a single location. Electric resistance tomography (ERT) uses vertical arrays of electrodes across the vadose zone that can monitor electrical resistance changes in the soil as a plume moves downward to the water table. These resistance changes can be used to provide ''snapshots'' of the progress of the plume. Additionally, monitoring wells have been completed at multiple levels in the vicinity of a central infiltration site. Sensors emplaced at different levels include electrically conducting gypsum blocks for detecting saturation changes, thermistors for monitoring temperature changes and pressure transducers for observing barometric changes at different levels in the vadose regime. The data from these sensors are providing important information about the state of the gas- and liquid-phase dynamics of the infiltration process. Similarly, access ports at different levels have been used to supply gas-phase samples while lysimeters yield liquid-phase samples. Studies involving gas-phase tracers were carried out at LLNL and at an Orange County Water District site in southern California to evaluate the time-dependent chemical signature of a plume that was spiked with an array of dissolved noble-gas tracers. Our work also correlate chemical signatures with those of the above-mentioned sensors that track the physical changes in the vadose zone. From the VZO at the LLNL site and from 3-D diagnostic simulations of our very first tracer-spiked plume infiltration event, we produced a much better understanding of the implications of soil heterogeneity for unsaturated zone contaminant transport at DOE sites. Even though the LLNL VZO site is considered to be hydrologically ''tight'' owing to the low permeability of the clays and silts that dominate the soil formations there, we find that saturation increases resulting from a near-surface ''leak'' reach the water table across the 20-meter-thick vadose zone in only tens of hours. This rapid transport at the site cannot be accurately simulated by layered models that derive their hydrologic properties from borehole-soil samples. In the LLNL vadose zone, layered infiltration models clearly underpredict of the rate of contaminant infiltration to the water table. Chemical transport simulations based on layered models of the Hanford vadose zone also appear to drastically underpredict contaminant migration. Furthermore, only simulations assuming a heterogeneous regime ''threaded'' by extremely high-permeability pathways can explain the rapid increase in saturation observed with ERT near the water table. Three-dimensional predictive models of a hypothetical tritiated water leak that are based on the above mentioned VZO infiltration-experiment diagnostic models were run. Tritiated water is an excellent conservative tracer and the infiltration simulations predict, in very good agreement with VZO experiments, that a continuous hypothetical tritium release (2-3 liters/rein) would be expected to reach the water table at significant concentrations within days. The numerical model suggests that this arrival time is determined by the amount of time required, infiltrating liquid at a given rate, to flush one pore volume in the soil between the infiltration point and the water table. Another infiltration event monitored by ERT demonstrated that infiltration could occur even more

Carrigan, C R; Martins, S A; Ramirez, A L; Daily, W D; Hudson, G B; Ralsont, D; Ekwurzel, B

2001-02-27

117

Equation of state for solids with high accuracy and satisfying the limitation condition at high pressure  

Energy Technology Data Exchange (ETDEWEB)

An equation of state (EOS) with high accuracy is proposed to strictly satisfy the Fermi gas limitation condition at high pressure. The EOS (SJX EOS) is a modification of the effective Rydberg (ER2) EOS. Instead of Holzapfel's method to directly modify the ER2 EOS, one modifying term is added to the ER2 EOS to make it not only satisfy the high pressure limitation condition, but also to avoid the disadvantages occurring in the Holzapfel and 'adapted polynomial expansion of the order 3' (AP3) EOSs. The two-parameter ER2, Holzapfel, and three-parameter SJX, AP3, Kumari and Dass (KD) EOSs are applied to 50 materials to fit all experimental compression data available. The five EOSs also are applied to 37 of the 50 materials to fit experimental compression data at low-pressure ranges. The results show that for all pressure ranges the AP3 EOS gives the best fitting results; the SJX, ER2, Holzapfel and KD EOSs sequentially give inferior results. Otherwise, it is shown that the values of B{sub 0}, B{sub 0}{sup '} and B{sub 0}{sup '}' are different for different EOSs and also, within one EOS, for high and low-pressure ranges. The SJX EOS gives the best consistency between the values obtained by fitting all experimental data available, and the experimental data at low-pressure ranges, respectively. The AP3 EOS gives the worst results. The differences of the values of B{sub 0}, B{sub 0}{sup '} and B{sub 0}{sup '}' obtained for the ER2, Holzapfel and KD EOSs with those obtained for the SJX EOS are large at high-pressure ranges, but decrease at low-pressure ranges. At present, the newest experimental compression data, within the widest compression range, are available for solid n-H{sub 2}. The values of B{sub 0}, B{sub 0}{sup '} and B{sub 0}{sup '}' fitted by using the SJX EOS are almost in agreement with these experimental data. The ER2 EOS gives inferior values, and other EOSs give fairly bad results. For the predicted compression curves and the cohesive energy, the SJX EOS gives the best results; the AP3 EOS gives the worst results, even for many solids the AP3 EOS cannot give physically correct results for the cohesive energy. The analysis shows that for such solids, the variation of pressure and energy versus compression ratio calculated by using the AP3 EOS would oscillate, physically incorrectly. Although the AP3 EOS has the best fitting ability to the pressures, it has the worst predicting ability, and fails to be a universal EOS. The SJX EOS is recommended and can be taken as a candidate of universal EOSs to predict compression curves of solids in a wide pressure range only using the values of B{sub 0}, B{sub 0}{sup '} and B{sub 0}{sup '}' obtained from low-pressure data.

Sun Jiuxun [Department of Applied Physics, University of Electronic, Science and Technology, Chengdu 610054 (China)]. E-mail: sjx@uestc.edu.cn; Wu Qiang [Laboratory for Shock Wave and Detonation Physics Research, Southwest Institute of Fluid Physics, Mianyang 621900 (China); Cai Lingcang [Laboratory for Shock Wave and Detonation Physics Research, Southwest Institute of Fluid Physics, Mianyang 621900 (China); Jing Fuqian [Laboratory for Shock Wave and Detonation Physics Research, Southwest Institute of Fluid Physics, Mianyang 621900 (China)

2006-01-31

118

Experimental investigation of symmetric and asymmetric heating of pressure tube under accident conditions for Indian PHWR  

International Nuclear Information System (INIS)

Highlights: ? Circumferential temperature gradient for asymmetric heat-up was 400 °C. ? At same pressure ballooning initiates at lower temperature in asymmetrical heat-up. ? At 1 MPa ballooning initiated at 408 °C and with expansion rate of 0.005 mm/s. ? At 2 MPa ballooning initiation at 330 °C and with expansion rate of 0.0056 mm/s. ? For symmetrical heat-up strain rate was 10 times faster than asymmetric heat-up. - Abstract: In pressurized heavy water reactor (PHWR), under postulated scenario of small break Loss of Coolant Accident (LOCA) coincident with the failure of Emergency Core Cooling System (ECCS), a situation may arise under which reduction in mass flow rate of coolant through individual reactor channel can lead to stratified flow. Such stratified flow condition creates partial uncover of fuel bundle, which creates a circumferential temperature gradient over PT. The present investigation has been carried out to study thermo-mechanical behaviour of PT under asymmetric heating conditions for a 220 MWe PHWR. A 19-pin fuel simulator has been developed in which preferential heating of elements could be done by supplying power to the selected pins. The asymmetric heating of PT has been carried out at pressure 2 MPa and 1 MPa, respectively, by supplying power to upper region heating elements thus creating an half filled stratified flow conditions. The temperature difference up to 425 °C has been observed along top to bottom periphery of PT. A comparison is made between thermo-mechanical behaviour of PT under asymmetrical and symmetrical heat-up, expected from a large break LOCA condition. The radial expansion rate during symmetrical heating is found to be much faster as compared to that for asymmetric ballooning of PT at the same internal pressure. Integrity of PT is found to be maintained under both loading conditions. Heat sink around of test section, simulating moderator is found to be helpful in arresting the rise in temperature for both fuel pins and PT, thus establishing moderator as an effective heat sink under accident conditions.

2013-01-01

119

Circadian modulation of sequence learning under high and low sleep pressure conditions.  

UK PubMed Central (United Kingdom)

Humans are able to learn complex sequences even without conscious awareness. We have studied the repercussions of circadian phase and sleep pressure on the ability to learn structured sequences using a serial reaction time task (SRT). Sixteen young healthy volunteers were studied in a 40-h "constant posture protocol" under high sleep pressure (i.e. sleep deprivation) and low sleep pressure conditions (i.e. sleep satiation attained by multiple naps). Here we show that learning of different sequence structures improved after multiple naps, in particular after naps that followed the circadian peak of rapid-eye-movement (REM) sleep. This situation following sleep contrasted with the lack of learning without sleep. We have evidenced that the observed amelioration of learning new sequences came about by memorizing short sub-fragments ("chunks") of the sequence train. However, SRT performance did not deteriorate under high sleep pressure, despite the high level of sleepiness. Our data indicate that sequence learning is modulated by circadian phase, and the neurophysiological medium required for this type of learning is related to sleep.

Cajochen C; Knoblauch V; Wirz-Justice A; Kräuchi K; Graw P; Wallach D

2004-05-01

120

SAG behaviour of the CANDU pressure tubes under reactor operating conditions  

International Nuclear Information System (INIS)

[en] In the past few years significant advances in the mathematical modelling of the fuel channel behaviour have been made. This is particularly important for a proper prediction of the pressure tube structural integrity during their service life in the reactor. The present paper describe a computational technique of the stress and strain distribution in the pressure tube, in order to simulate the response of the fuel channel assemblies to different operating conditions. Numerical analysis of deformations and stresses are performed using TPSAG code, specialized in thermo-mechanical calculations by the finite element method.The developed computational technique is based on the equivalence of the pressure tube and calandria tube with rods having the same length; this permits to transform the problem of the stress-strain fields calculation in a two-dimensional problem. The Von Misses criterion was used for calculation of the effective stresses and strains and, also, the small deformation approximation was applied in the first order. The thermo-mechanical analysis on the fuel channel assemblies (pressure tube/ garter spring/calandria tube) permits the prediction of the time dependencies of both axial deformation and vertical deflection of the fuel channels. The calculated values are in good agreement with the measured data reported for various channels in different Candu reactors. (author)

1995-12-02

 
 
 
 
121

Effect of Antecedent Conditions on Prediction of Pore-Water Pressure using Artificial Neural Networks  

Directory of Open Access Journals (Sweden)

Full Text Available The effect of antecedent conditions on the prediction of soil pore-water pressure (PWP) using Artificial Neural Network (ANN) was evaluated using a multilayer feed forward (MLFF) type ANN model. The Scaled Conjugate Gradient (SCG) training algorithm was used for training the ANN. Time series data of rainfall and PWP was used for training and testing the ANN model. In the training stage, time series of rainfall was used as input data and corresponding time series of PWP was used as the target output. In the testing stage, data from a different time period was used as input and the corresponding time series of pore-water pressure was predicted. The performance of the model was evaluated using statistical measures of root mean square error and coefficient of determination. The results of the model prediction revealed that when antecedent conditions (past rainfall and past pore-water pressures) are included in the model input data, the prediction accuracy improves significantly.

Muhammad Raza Ul Mustafa; Rezaur Rahman Bhuiyan; Mohamed Hasnain Isa; Saied Saiedi; Harianto Rahardjo

2012-01-01

122

Photoelectron spectroscopic study of CO and NO adsorption on Pd(100) surface under ambient pressure conditions  

Science.gov (United States)

We report molecular CO and NO adsorption structures on Pd(100) single crystal surfaces under sub-Torr pressure conditions at room temperature. A combination of ambient pressure X-ray photoelectron spectroscopy and density functional theory based calculations indicates that CO molecules adsorb at 2-fold bridge sites with (2?2 × ?2)R45°, (3?2 × ?2)R45° and (4?2 × ?2)R45° structures under the CO gas pressures at room temperature. Furthermore a higher-density adsorption structure is reversibly formed at 0.5 Torr CO, where all the CO molecules keep sitting on the bridge sites. In case of NO adsorption, at 10? 7 Torr, a (2?2 × ?2)R45° structure with occupying bridge sites is formed, which is the same as the case of CO. However, subsequent gas introduction up to 0.5 Torr causes additional site occupation of on-top sites. Furthermore NO molecules partially dissociate into atomic N and O species but they disappear from the surface due to further reaction with NO under ambient conditions.

Toyoshima, Ryo; Yoshida, Masaaki; Monya, Yuji; Suzuki, Kazuma; Amemiya, Kenta; Mase, Kazuhiko; Mun, Bongjin Simon; Kondoh, Hiroshi

2013-09-01

123

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)

1993-01-01

124

Critical heat flux of water in vertical round tubes at low pressure and low flow conditions  

International Nuclear Information System (INIS)

[en] An experimental study on critical heat flux (CHF) has been performed for water flow in vertical round tubes under low pressure and low flow (LPLF) conditions to provide a systematic data base and to investigate parametric trends. Totally 513 experimental data have been obtained with Inconel-625 tube test sections in the following conditions: diameter of 6, 8, 10 and 12 mm; heated length of 0.3?1.77 m; pressure of 106?951 kPa; mass flux of 20?277 kg m-2 s-1; and inlet subcooling of 50?654 kJ kg-1, thermodynamic equilibrium critical quality of 0.323?1.251 and CHF of 108?1598 kW m-2. Flow regime analysis based on Mishima and Ishii's flow regime map indicates that most of the CHF occurred due to liquid film dryout in annular-mist and annular flow regimes. Parametric trends are examined from two different points of view: fixed inlet conditions and fixed exit conditions. The parametric trends are generally consistent with previous understandings except for the complex effects of system pressure and tube diameter. Finally, several prediction models are assessed with the measured data; the typical mechanistic liquid film dryout model and empirical correlations of (Shah, M.M., 1987. Heat Fluid Flow 8 (4), 326-335; Baek, W.P., Kim, H.G., Chang, S.H., 1997. KAIST critical heat flux correlation for water flow in vertical round tubes, NUTHOS-5, Paper No. AA5) show good predictions. The measured CHF data are listed in Appendix B for future reference. (orig.)

2000-01-01

125

Entropy Generation in Pressure Gradient Assisted Couette Flow with Different Thermal Boundary Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available The present paper is concerned with an analytical study of entropy generation in viscous, incompressible Couette flow between a stationary plate and a moving plate. The flow induced by the moving plate is assisted by a constant pressure gradient along the flow direction. Four different combinations of thermal boundary conditions are investigated: (a) plates at different temperatures, (b) stationary plate at a fixed temperature and moving plate subjected to a constant heat flux, (c) stationary plate at a fixed temperature and convection at the moving plate, and (d) convection at both plates. Besides the velocity and temperature profiles, dimensionless results are presented for the entropy generated due to heat transfer, the entropy generated due to viscous dissipation, and the total entropy generation. These results illustrate the effect of pressure gradient, temperature asymmetry, heat flux, convection Biot numbers, and ambient temperatures. For certain combinations of thermal variables, the total entropy generated is minimized.

Abdul Aziz

2006-01-01

126

Dynamic response of berea sandstone shock-loaded under dry, wet and water-pressurized conditions  

Energy Technology Data Exchange (ETDEWEB)

A single-stage light-gas gun was used to perform shock-recovery experiments on Berea sandstone under dry, wet and hydrostatically water-pressurized conditions. The samples were impacted by flyer-plates to achieve stress levels in the range 1.3 to 9.8 GPa. The microstructure of the shocked samples was analyzed using scanning electron microscopy (SEM), laser particle analysis and X-ray computed microtomography (XCMT). The dry samples show strongly fragmented and irregularly fractured quartz grains with a considerably reduced porosity, whereas the wet and water-pressurized specimens show less grain damage and less porosity reduction. During shock compression the water in the pores distributes the stresses and therefore the contact force between the grains is reduced. The interaction between the grains during the shock process was modeled by explicitly treating the grain-pore structure using Smooth Particle Hydrodynamics (SPH) and the Discrete Element Method (DEM).

Carney, T C; Hagelberg, C R; Hilt, M; Nellis, W J; Swift, R P

1999-09-03

127

Dynamic response of berea sandstone shock-loaded under dry, wet and water-pressurized conditions  

International Nuclear Information System (INIS)

[en] A single-stage light-gas gun was used to perform shock-recovery experiments on Berea sandstone under dry, wet and hydrostatically water-pressurized conditions. The samples were impacted by flyer-plates to achieve stress levels in the range 1.3 to 9.8 GPa. The microstructure of the shocked samples was analyzed using scanning electron microscopy (SEM), laser particle analysis and X-ray computed microtomography (XCMT). The dry samples show strongly fragmented and irregularly fractured quartz grains with a considerably reduced porosity, whereas the wet and water-pressurized specimens show less grain damage and less porosity reduction. During shock compression the water in the pores distributes the stresses and therefore the contact force between the grains is reduced. The interaction between the grains during the shock process was modeled by explicitly treating the grain-pore structure using Smooth Particle Hydrodynamics (SPH) and the Discrete Element Method (DEM)

1999-01-01

128

Fracturing fluid leakoff under dynamic conditions Part II: Effect of shear rate, permeability, and pressure  

Energy Technology Data Exchange (ETDEWEB)

This paper discusses the results of an industry consortium established to understand and allow modeling of the fluid leakoff process in hydraulic fracturing applications. Over 1,000 laboratory experiments structured to study the effects of shear rate, permeability, differential pressure, temperature, gel concentration, fluid-loss additives, and fluid type have been conducted. Fluid-loss data was measured with a state-of-the-art experimental setup that included fluid preconditioning loops for high shear and low shear regimes and a novel cell design that minimized flow irregularities. Part 2 presents the results of experiments involving linear hydroxypropyl guar (HPG) gel, HPG/borate systems, and HPG/titanate systems at shear rates between 0 and 200 sec{sup -1}, pressures between 500 to 10,000 psi, a temperature of 180{degrees}F, and core permeabilities between 0.1 md and 1000 md. This study found that fluid loss under dynamic conditions can be significantly higher than under static conditions. Significant differences in fluid-loss behavior were observed between linear gels, transition-metal crosslinked gels, and borate-crosslinked systems. The behavior of linear gels was sensitive to permeability and pressure, but insensitive to shear rate. The behavior of crosslinked gels was more sensitive to shear rate, but less sensitive to permeability and pressure. The fluid loss of all fluids tested could be modeled though the mechanisms of non-Newtonian viscous invasion, classical filter-cake deposition, and filter-cake resuspension. This paper presents guidelines for fluid-loss prediction for these systems with appropriate fluid-loss mechanisms.

Vitthal, S.; McGowen, J.M.

1996-12-31

129

Performance of a monolithic silica column in a capillary under pressure-driven and electrodriven conditions  

UK PubMed Central (United Kingdom)

A continuous macroporous silica gel network was prepared in a fused-silica capillary and evaluated in reversed-phase liquid chromatography. Under pressure-driven conditions, the monolithic silica column derivatized to C18 phase (100 microns in diameter, 25 cm in length, silica skeleton size of approximately 2.2 microns) produced plate heights of about 23 and 81 microns at 0.5 mm/s with a pressure drop of 0.4 kg/cm2, and at 4.0 mm/s with 3.6 kg/cm2, respectively, in 90% acetonitrile for hexylbenzene with a k value of 0.7. The separation impedance, E, calculated for the present monolithic silica column was much smaller at a low flow rate than those for particle-packed columns, although higher E values were obtained at a higher flow rate. Considerable dependence of column efficiency on the linear velocity of the mobile phase was observed despite the small size of the silica skeletons. A major source of band broadening in the HPLC mode was found in the A term of the van Deemter equation. The performance of the continuous silica capillary column in the electrodriven mode was much better than that in the pressure-driven mode. Plate heights of 7-8 microns were obtained for alkylbenzenes at 0.7-1.3 mm/s, although the electroosmotic flow was slow. In HPLC and CEC mode, the dependency of plate height on k values of the solutes was observed as seen in open tube chromatography presumably due to the contribution of the large through-pores. Since monolithic silica capillary columns can provide high permeability, the pressure-driven operation at a very low pressure can afford a separation speed similar to CEC at a high electric field.

Ishizuka N; Minakuchi H; Nakanishi K; Soga N; Nagayama H; Hosoya K; Tanaka N

2000-03-01

130

High pressure gas pipeline in Artic conditions; Hochdruck-Gaspipeline in arktischen Gebieten  

Energy Technology Data Exchange (ETDEWEB)

More than 2000 km north of moscow, in the timan-pechora region, the kharyaga oil field is located. Gas is transported through a 9.5 km long 6{sup ''} pipeline with an operating pressure of up to 356 bar to a field injection well and is reinjected into the reservoir. The installations are erected in Artic conditions, with ambient temperatures of down to -56 C. The pipeline is laid above ground on piled supports, heat insulated in permafrost conditions. Due to environmental conditions the construction of pipelines is carried out during winter season. A particular difficulty for the design was the fact that Russian as well as western norms and standards for design and material selection had to be fulfilled. In October 2003 the pipeline has been successfully pressure tested with a pressure of 534 bar and put in operation. (orig.) [German] Mehr als 2000 km noerdlich von Moskau, in der Region Timan-Pechora, liegt das Kharjaga Oelfeld. Durch eine 9,5 km lange 6{sup ''} Pipeline mit einem Betriebsdruck von bis zu 356 bar wird Gas zu einer Sondenstation transportiert und wieder in die Lagerstaette eingepresst. Die Anlage wird unter arktischen Bedingungen errichtet und betrieben, mit Temperaturen bis -56 C. In dieser Gegend gibt es durchgaengig Permafrostboden. Deshalb ist die Leitung oberirdisch auf Pfaehlen installiert. Auf Grund der Umweltbedingungen kann der Bau nur im Winter erfolgen. Eine besondere Schwierigkeit fuer die Planung war die Tatsache, dass sowohl westliche als auch russische Normen beruecksichtigt werden mussten. Im Oktober 2003 wurde die Wasserdruckpruefung mit einem Druck von 534 bar erfolgreich durchgefuehrt und die Leitung in Betrieb genommen. (orig.)

Heinz, C. [ILF Beratende Ingenieure GmbH, Muenchen (Germany)

2004-03-01

131

PULMONARY HYPERTENSION IN RATS LIVING UNDER COMPRESSED AIR CONDITIONS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

1. Pulmonary arterial hypertension was demonstrated in a series of rats that had been kept for 24–31 days in an environment of compressed air, having a barometric pressure of 3040 mm. Hg. The partial pressure of oxygen was 635 mm. Hg, which is equivalent to an 83.6 per cent oxygen mixture at normal...

Bennett, Granville A.; Smith, F. J. C.

132

Conditioning of waste from the dismantling of reactor pressure vessel components and of core components  

Energy Technology Data Exchange (ETDEWEB)

When power reactors are shut down, the treatment of the core components and of the reactor pressure vessel components constitutes a particular task. Due to its special radiological characteristics, this waste must basically be handled using remote-control equipment with regard to the treatment. For its conditioning in a manner appropriate for the final storage, the waste must be dried and packed into suitable packing drums. The solution implemented by GNS and DSD in order to treat this waste from the Wuergassen nuclear power plant is described in the present contribution. (orig.)

Cleve, R.; Oldiges, O.; Splittler, U.

2001-07-01

133

Interaction in AlN-BN system under conditions of high pressures and temperatures  

International Nuclear Information System (INIS)

[en] Interaction of AlN with different modifications of BN is studied at high temperatures and pressures to specify the mechanism of cubic boron nitride formation in the system. It is ascertained that under the conditions at any ratios of components no formation of new individual substances occurs. When turbostrate form of BN is used in the initial mixture formation of solid solution with it in AlN-BNsolid system takes place much more actively. Catalytic effect of AlN on ???-phase transition in BN is considered

1989-01-01

134

SMD/12R305C, Steady state critical flow in nozzles, medium to high pressure conditions  

International Nuclear Information System (INIS)

1 - Description of test facility: The Super Moby Dick experiment is devoted to study steady state critical flow in nozzles at medium to high pressure and for various thermal hydraulic conditions. 2 - Description of test: Three test sections are available. The test 12B305C corresponds to the 'long nozzle test section'. It consists of a shaped or conical convergent nozzle 66.7 mm inlet diameter and 100 mm long, connected to a straight pipe 20.13 mm inner diameter and 363 mm long which is surmounted by a conical 7 deg. divergent section

1988-01-01

135

Finite Element Simulation of Photoacoustic Pressure in a Resonant Photoacoustic Cell Using Lossy Boundary Conditions  

DEFF Research Database (Denmark)

The finite-element method (FEM) is used to simulate the photoacoustic signal in a cylindrical resonant photoacoustic cell. Simulations include loss effects near the cell walls that appear in the boundary conditions for the inhomogeneous Helmholtz equation governing the acoustic pressure. Reasonably good agreement is obtained between theoretical results and experimental data. However, it was anticipated that loss mechanisms other than viscous and thermal boundary losses occur and should be included. Nevertheless, the feasibility to use FEM together with the derived boundary conditions to simulate the photoacoustic signal was demonstrated and good agreement with experiments for the actual resonance frequency and the quality factor of the cell was obtained despite its complicated geometry.

Duggen, Lars; Lopes, Natasha

2011-01-01

136

Spherically symmetric models with pressure: separating expansion from contraction and generalizing TOV condition  

CERN Document Server

We investigate spherically symmetric perfect fluid spacetimes and discuss the existence and stability of a dividing shell separating expanding and collapsing regions. We perform a 3+1 splitting and obtain gauge invariant conditions relating the intrinsic spatial curvature of the shells to the ADM mass and to a function of the pressure which we introduce and that generalises the Tolman-Oppenheimer-Volkoff equilibrium condition. We analyse the particular cases of the Lema\\^itre-Tolman-Bondi dust models with a cosmological constant as an example of a $\\Lambda$-CDM model and its generalization to contain a central perfect fluid core. These models provide simple, but physically interesting illustrations of our results.

Mimoso, José Pedro; Mena, Filipe C

2009-01-01

137

An assessment of the Tongonan geothermal reservoir, Philippines, at high-pressure operating conditions  

Energy Technology Data Exchange (ETDEWEB)

An evaluation of the Tongonan geothermal reservoir was conducted to improve the power recovery through reservoir and process optimization. The performance of the existing production wells was reviewed and the response of the field based on the anticipated production levels was simulated at various operating conditions. The results indicate that the Tongonan geothermal reservoir can be exploited at a high pressure operating condition with substantial improvement in the field capacity. The authors calculate that the Upper Mahiao and the Malitbog sectors of the Tongonan field are capable of generating 395 MWe at 1.0 MPa abs., on top of the existing 112.5 MWe plant, compared with 275 MWe if the field is operated at 0.6 MPa abs. The total capacity for the proposed Leyte A 640 MWe expansion can be generated from these sectors with the additional power to be tapped from Mahanagdong and Alto Peak sectors.

Sarmiento, Z.F.; Aquino, B.G.; Aunzo, Z.P.; Rodis, N.O.; Saw, V.S. [PNOC-Energy Development Corp., Fort Bonifacio (Philippines)

1993-10-01

138

Pressure retarded osmosis for energy production: membrane materials and operating conditions.  

UK PubMed Central (United Kingdom)

Pressure retarded osmosis (PRO) is a novel membrane process to produce energy. PRO has the potential to convert the osmotic pressure difference between fresh water (i.e. river water) and seawater to electricity. Moreover, it can recover energy from highly concentrated brine in seawater desalination. Nevertheless, relatively little research has been undertaken for fundamental understanding of the PRO process. In this study, the characteristics of the PRO process were examined using a proof-of-concept device. Forward osmosis (FO), reverse osmosis (RO), and nanofiltration (NF) membranes were compared in terms of flux rate and concentration polarization ratio. The results indicated that the theoretical energy production by PRO depends on the membrane type as well as operating conditions (i.e. back pressure). The FO membrane had the highest energy efficiency while the NF membrane had the lowest efficiency. However, the energy production rate was low due to high internal concentration polarization (ICP) in the PRO membrane. This finding suggests that the control of the ICP is essential for practical application of PRO for energy production.

Kim H; Choi JS; Lee S

2012-01-01

139

Tongue pressure and oral conditions affect volatile release from liquid systems in a model mouth.  

Science.gov (United States)

The release of volatile organic compounds (VOCs) into the mouth cavity is an integral part of the way flavor is perceived. An in vitro model mouth with an artificial tongue was developed to measure the dynamic release of VOCs from liquid model systems [e.g., aqueous solution, oil, and oil-in-water (O/W) emulsions] under oral conditions. The release of seven selected VOCs was affected by the different polarity and vapor pressure of the compounds and their affinity to the liquid system media. Different tongue pressure patterns were applied to the liquid systems, and the release of VOCs was monitored in real time using proton transfer reaction-mass spectrometry. The release was significantly more intense for longer tongue pressure duration and was influenced by the tongue altering the sample surface area and the distribution of the VOCs. The role of saliva (artificial versus human) and the sample temperature had a significant effect on VOC release. Saliva containing mucin and a higher sample temperature enhanced the release. PMID:22957471

Benjamin, O; Silcock, P; Beauchamp, J; Buettner, A; Everett, D W

2012-09-20

140

Tongue pressure and oral conditions affect volatile release from liquid systems in a model mouth.  

UK PubMed Central (United Kingdom)

The release of volatile organic compounds (VOCs) into the mouth cavity is an integral part of the way flavor is perceived. An in vitro model mouth with an artificial tongue was developed to measure the dynamic release of VOCs from liquid model systems [e.g., aqueous solution, oil, and oil-in-water (O/W) emulsions] under oral conditions. The release of seven selected VOCs was affected by the different polarity and vapor pressure of the compounds and their affinity to the liquid system media. Different tongue pressure patterns were applied to the liquid systems, and the release of VOCs was monitored in real time using proton transfer reaction-mass spectrometry. The release was significantly more intense for longer tongue pressure duration and was influenced by the tongue altering the sample surface area and the distribution of the VOCs. The role of saliva (artificial versus human) and the sample temperature had a significant effect on VOC release. Saliva containing mucin and a higher sample temperature enhanced the release.

Benjamin O; Silcock P; Beauchamp J; Buettner A; Everett DW

2012-10-01

 
 
 
 
141

Intraocular pressure vs intracranial pressure in disease conditions: A prospective cohort study (Beijing iCOP study)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background The correlation between intracranial pressure (ICP) and intraocular pressure (IOP) is still controversial in literature and hence whether IOP can be used as a non-invasive surrogate of ICP remains unknown. The aim of the current study was to further clarify the p...

Li Zhen; Yang Yingxin; Lu Yan; Liu Dachuan; Xu Erhe; Jia Jianping; Yang Diya; Zhang Xiaojun; Yang Huiqing; Ma Daqing; Wang Ningli

142

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

Science.gov (United States)

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.

Chirkov, D.; Avdyushenko, A.; Panov, L.; Bannikov, D.; Cherny, S.; Skorospelov, V.; Pylev, I.

2012-11-01

143

Comparison of three mineral candidates in middle and low-pressure condition. Experimental study  

Energy Technology Data Exchange (ETDEWEB)

''Greenhouse Effect'', which is scientifically proven to be main caused by the increasing concentration of CO{sub 2}, has become a topic of national and international concern. Mineral carbonation, such as carbonation of alkaline silicate Ca/Mg minerals, analogous to natural weathering processes, is a potentially attractive route to mitigate possible global warming on the basis of industrial imitation of natural weathering processes. In this paper, three typical natural mineral candidates in China, serpentine, olivine and wollastonite, were selected as carbonation raw materials for direct mineral carbonation experiments under middle and low-pressure. A series number of experiments were carried out to investigate the factors that influence the conversion of carbonation reaction, such as reaction temperature, reaction pressure, particle size, solution composition and pretreatment. The solid products from carbonation experiments were filtered, collected, dried and analyzed by X-ray diffraction (XRD) and field scanning electron microscopy equipped with energy dispersive X-ray analysis (FSEM-EDX) to identify the reaction of mineral carbonation. And the method of mass equilibrium after heat decomposition was used to calculate the mineral carbonation conversion. All the XRD and FSEM analysis validate that carbonation reaction was occurred during the experiments and mineral carbonation is one of the potential techniques for carbon dioxide sequestration. The data of mass equilibrium after heat decomposition was collected and then the conversion formula was used to calculate the carbonation conversion of all the three mineral candidates. The mass equilibrium results show that, for all of the three mineral materials, the carbonation conversion increases with the increasing of reaction temperature. But once the temperature increases above 150 C, the conversion of serpentine decreases a little. Reaction pressure is also an important factor to mineral carbonation process. For all of the three mineral materials, the carbonation conversion increases with the increasing of reaction pressure. Decrease of mineral particle sizes and use of heat treatment before carbonation experiments can effectively improve the carbonation conversion of mineral carbonation. And the addition of NaHCO{sub 3}, which had a buffering effect that kept the solution pH in a certain range, can also improve the carbonation conversion. In this paper, a highest carbonation conversion of 89.5% was obtained under the condition of T = 150 C, P{sub CO{sub 2}} = 4.0 MPa, particle sizes <37 {mu}m in 1 h using wollastonite as the raw material. Compared with serpentine and olivine, wollastonite is the most promising material for carbon dioxide mineral carbonation under middle and low-pressure.

Yan, Heng; Zhang, Jun-ying; Zhao, Yong-chun; Wang, Zhi-lang; Pan, Xia; Xu, Jun; Zheng, Chu-guang [Huazhong Univ. of Science and Technology, Wuhan (China). State Key Lab. of Coal Combustion

2013-07-01

144

AMPTRACT: an algebraic model for computing pressure tube circumferential and steam temperature transients under stratified channel coolant conditions  

International Nuclear Information System (INIS)

In a number of postulated accident scenarios in a CANDU reactor, some of the horizontal fuel channels are predicted to experience periods of stratified channel coolant condition which can lead to a circumferential temperature gradient around the pressure tube. To study pressure tube strain and integrity under stratified flow channel conditions, it is, necessary to determine the pressure tube circumferential temperature distribution. This paper presents an algebraic model, called AMPTRACT (Algebraic Model for Pressure Tube TRAnsient Circumferential Temperature), developed to give the transient temperature distribution in a closed form. AMPTRACT models the following modes of heat transfer: radiation from the outermost elements to the pressure tube and from the pressure to calandria tube, convection between the fuel elements and the pressure tube and superheated steam, and circumferential conduction from the exposed to submerged part of the pressure tube. An iterative procedure is used to solve the mass and energy equations in closed form for axial steam and fuel-sheath transient temperature distributions. The one-dimensional conduction equation is then solved to obtain the pressure tube circumferential transient temperature distribution in a cosine series expansion. In the limit of large times and in the absence of convection and radiation to the calandria tube, the predicted pressure tube temperature distribution reduces identically to a parabolic profile. In this limit, however, radiation cannot be ignored because the temperatures are generally high. Convection and radiation tend to flatten the parabolic distribution

1986-01-01

145

High-pressure refrigeration system with CO2 in automobile air-conditioning  

Energy Technology Data Exchange (ETDEWEB)

Due to high consumer acceptance of automobile air conditioning systems, the discussion of the effects of refrigerants on global warming is becoming more important to an environmentally-aware public. The consumption of fossil fuels to operate air conditioning systems, combined with refrigerant emissions, contribute to the greenhouse effect. Substitution of conventional refrigerants with CO2 reduces the load on heat-adsorbing gases in our atmosphere by providing an environment-friendly alternative. Because the amount of engine power devoted to air conditioning systems is limited, carbon dioxide makes an attractive substitute for HFC refrigerants in vehicle applications. In this paper, TEWI-figures for a vehicle with A/C System are considered, and the reduction potential due to CO2 as refrigerant as a motive for phasing out current technology is shown. This includes a comparison of COP`s between a conventional cold vapor cycle and the transcritical refrigerant cycle using CO2 to evaluate benefits and disadvantages. The high pressure refrigerant cycle has to be seen in the light of the requirement profile for introduced MACS. Furthermore, assorted results from the European RACE (Refrigeration and Automotive Climate systems under Environmental aspects) project are presented. The theory of the refrigerant cycle, tests results, packaging in a vehicle, and first experiences of component development are discussed, as well as difficulties in adapting this `Green Technology` to a car. 7 refs.

Wertenbach, J.; Kauf, F. [Daimler-Benz, Stuttgart (Germany)

1998-12-31

146

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

Directory of Open Access Journals (Sweden)

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; Tao Zhou; Lei Zhang; Zhongyun Ju

2013-01-01

147

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

148

MCCI study for Pressurized Heavy Water Reactor under hypothetical accident condition  

International Nuclear Information System (INIS)

In case of severe core damage accident in Pressurized Heavy Water Reactor (PHWR), large amount of molten corium is expected to come out into the calandria vault due to failure of calandria vessel. Molten corium at high temperature is sufficient to decompose and ablate concrete. Such attack could fail CV by basement penetration. Since containment is ultimate barrier for activity release. The Molten Core Concrete Interaction (MCCI) of the resulting pool of debris with the concrete has been identified as an important part of the accident sequence. MCCI Analysis has been carried out for PHWR for a hypothetical accident condition where total core material is considered to be relocated in calandria vault. Concrete ablation rate in vertical and radial direction is evaluated for rectangular geometry using MEDICIS module of ASTEC Code. Amount of gases released during MCCI is also evaluated. (author)

2011-01-01

149

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

CERN Multimedia

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

150

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.

Thibaud Pintiaux; David Viet; Virginie Vandenbossche; Luc Rigal; Antoine Rouilly

2013-01-01

151

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.

Domenico Paladino; Max Huggenberger; Frank Schäfer

2008-01-01

152

Theoretical and numerical investigations of TAP experiments. New approaches for variable pressure conditions  

Energy Technology Data Exchange (ETDEWEB)

Temporal analysis of products (TAP) is a valuable tool for characterization of porous catalytic structures. Established TAP-modeling requires a spatially constant diffusion coefficient and neglect convective flows, which is only valid in Knudsen diffusion regime. Therefore in experiments, the number of molecules per pulse must be chosen accordingly. New approaches for variable process conditions are highly required. Thus, a new theoretical model is developed for estimating the number of molecules per pulse to meet these requirements under any conditions and at any time. The void volume is calculated as the biggest sphere fitting between three pellets. The total number of pulsed molecules is assumed to fill the first void volume at the inlet immediately. Molecule numbers from these calculations can be understood as maximum possible molecules at any time in the reactor to be in Knudsen diffusion regime, i.e., above the Knudsen number of 2. Moreover, a new methodology for generating a full three-dimensional geometrical representation of beds is presented and used for numerical simulations to investigate spatial effects. Based on a freely available open-source game physics engine library (BULLET), beds of arbitrary-sized pellets can be generated and transformed to CFD-usable geometry. In CFD-software (ANSYS CFX registered) a transient diffusive transport equation with time-dependent inlet boundary conditions is solved. Three different pellet diameters were investigated with 1e18 molecules per pulse, which is higher than the limit from the theoretical calculation. Spatial and temporal distributions of transported species show regions inside the reactor, where non-Knudsen conditions exist. From this results, the distance from inlet can be calculated where the theoretical pressure limit (Knudsen number equals 2) is obtained, i.e., from this point to the end of the reactor Knudsen regime can be assumed. Due to linear dependency of pressure and concentration (assuming ideal gas thermodynamics), the results from one numerical simulation can be converted to any number of molecules per pulse. With this procedure, the distance from inlet from which on Knudsen regime can be assumed for different molecules per pulse can be calculated easily. The new model will be applied to enhance the description of industrially relevant conversions, as for instance alkane conversions on transition metal oxides. (orig.)

Senechal, U.; Breitkopf, C. [Technische Univ. Dresden (Germany). Inst. fuer Energietechnik

2011-07-01

153

Intraocular pressure vs intracranial pressure in disease conditions: A prospective cohort study (Beijing iCOP study)  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background The correlation between intracranial pressure (ICP) and intraocular pressure (IOP) is still controversial in literature and hence whether IOP can be used as a non-invasive surrogate of ICP remains unknown. The aim of the current study was to further clarify the potential correlation between ICP and IOP. Methods The IOP measured with Goldmann applanation tonometer was carried out on 130 patients whose ICP was determined via lumber puncture. The Pearson correlation coefficient between ICP and IOP was calculated, the fisher line discriminated analysis to evaluate the effectivity of using IOP to predict the ICP level. Results A significant correlation between ICP and IOP was found. ICP was correlated significantly with IOP of the right eyes (p? Conclusion Our data suggested that although a significant correlation exists between ICP and IOP, caution needs to be taken when using IOP readings by Goldmann applanation tonometer as a surrogate for direct cerebrospinal fluid pressure measurement of ICP.

Li Zhen; Yang Yingxin; Lu Yan; Liu Dachuan; Xu Erhe; Jia Jianping; Yang Diya; Zhang Xiaojun; Yang Huiqing; Ma Daqing; Wang Ningli

2012-01-01

154

Online monitoring of steel-lined pressure shafts by using pressure transient signals under normal operation conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The local deterioration of the mechanical properties of steel-lined pressure shafts and tunnels induces a decrease of the celerity and an increase of the energy attenuation of water hammer waves. This deterioration may arise from the weakening of the backfill concrete and the surrounding rock mass, ...

Hachem, Fadi; Schleiss, Anton

155

Crack tip conditions related to environmentally assisted cracking in pressure vessel steels: Effect of temperature  

International Nuclear Information System (INIS)

[en] The effect of temperature on the anodic dissolution and film repair on pressure vessel steel in deaerated environments was measured by using CERT under controlled potential. The effect of dissolved sulfide was taken into account in this study. The results show that temperature has little effect on the kinetics of anodic processes between 80 and 290 degrees C except that the amount of sulfide required to trigger high dissolution rates decreases when the temperature decreases. In the range 200-290 degrees C, these results are consistent with the current model which assumes that corrosion fatigue crack growth rates on low alloy steel in PWR water are controlled by the film repair kinetics at the crack tip. The agreement is questionable at lower temperatures. The CERT under controlled potential also suggested that plastic deformation cannot account for the effect of sulfur on the anodic processes at crack tip in EAC conditions. Thus, besides anodic dissolution, mechanical decohesion is assumed to contribute to crack advance in EAC conditions

1992-01-01

156

Pressurizer  

International Nuclear Information System (INIS)

[en] A thin walled tube is welded on to the coupling of the overpressure protection in the lid of the pressurizer. The tube opening is located above the highest possible water level in the pressurizer occurring at different regimes of the nuclear power plant. The advantage of the configuration is that an elastic steam cushion is always preserved in the pressurizer during an accident. (Ha)

1980-01-14

157

Magnetite reactivity in representative conditions of the secondary circuit of pressurized water reactors  

International Nuclear Information System (INIS)

In the secondary circuit of Pressurized Water Reactors (PWR), magnetite deposits lead to steam generators (SG) fouling, which decreases thermal performances and enhances stress corrosion cracking (SCC). The aim of this study is to improve the understanding of magnetite particles behaviour and their reactivity in the secondary circuit conditions. Experimental tests investigated the fast thermal decomposition of hydrazine, injected in the secondary circuit to eliminate oxygen. Temperature, pH, and catalytic properties of materials surfaces have an influence on the kinetics of hydrazine decomposition. A predictive model was proposed. Growing, transport and deposits of iron oxides, essentially formed with magnetite, responsible of the steam generator fouling, were studied in the experimental loop FORTRAND, Formation and Transport of Deposits. Surface characterizations show that magnetite is the corrosion product formed on carbon steel and stainless steel at 220 C, and goethite is formed at room temperature on stainless steel. Results indicate also that the effect of different amines, used in the secondary circuit, on the soluble iron is principally due to their effect on the pH. Performed tests highlight transport and deposition of magnetite particles in the loop. Deposits formed in the SG could promote SCC of tubes by sorption and reduction of sulfates. To reproduce secondary circuit conditions, studies of sorption were made in reducing medium imposed by hydrazine. At 275 C, the presence of hydrazine has an effect on the speciation of sulfates in solution but does not seem to influence the sorption nor to lead to H2S(g) emission predicted by thermodynamic calculations. These experimental results are used to predict sulfur and iron species behaviour in the secondary circuit. Low pH conditioning enhances soluble iron concentration, consequently iron transport in the SG. Sulfides are the most probable sulfur species in flow-restricted areas of SG, harmful for stress corrosion cracking. (author)

2010-01-01

158

Stress corrosion cracking of ferritic reactor pressure vessel steels under boiling water reactor conditions  

International Nuclear Information System (INIS)

The stress corrosion cracking (SCC) behaviour of low-alloy reactor pressure vessel (RPV) steels in oxygenated high-temperature water and its relevance to boiling water reactor (BWR) power operation, in particular its possible effect on both, RPV structural integrity and safety, has been a subject of controversial discussions for many years. The SCC crack growth behaviour of different RPV steels under simulated BWR/NWC conditions was therefore characterized by constant load and ripple load tests with pre-cracked fracture mechanics specimens in oxygenated high-temperature water at temperatures of either 288, 250, 200 or 150 C. Modern high-temperature water loops, online crack growth monitoring (DCPD) and fractographical analysis by scanning electron microscopy were used to quantify the cracking response. It is concluded that there is no susceptibility to sustained SCC crack growth at temperatures around 288 C under purely static loading, as long as small-scale-yielding conditions prevail at the crack tip and the water chemistry is maintained within current BWR/NWC operational practice (EPRI water chemistry guidelines). However, sustained, fast SCC (with respect to operational time scales) cannot be excluded for faulted water chemistry conditions (EPRI Action Level 3) and/or for highly stressed specimens, either loaded near to KIJ or with a high degree of plasticity in the remaining ligament. The conservative character of the 'BWR VIP 60 Disposition Lines 1 and 2' for SCC crack growth in low-alloy steels has been confirmed by this study for 288 C and RPV base material. Preliminary results indicate, that these disposition lines may be significantly or slightly exceeded (even in steels with 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). (orig.)

2001-01-01

159

Relative effects of negative versus positive pressure ventilation depend on applied conditions.  

UK PubMed Central (United Kingdom)

PURPOSE: Comparisons of negative versus positive pressure ventilation have imperfectly matched the pressure-time profile or the lung volume history, or have incompletely applied in vivo negative pressure to include the complete thoracic wall and abdomen. HYPOTHESIS: Negative pressure exerts the same pattern of lung distension as positive pressure when the pressure-time and volume history profiles are identical and the application of negative pressure is over the whole lung. METHODS: (1) In isolated (ex vivo) and (2) intact (in vivo) mouse lungs (n = 4/group) (sealed chamber enclosing either the whole lung or whole mouse except for external airway opening), identical and inverse-tidal, square-wave pressure-time profiles were obtained with positive and negative pressure ventilation. (3) Following an identical volume history, surfactant-depleted rabbits (n = 7) were randomly assigned to sustained, static equivalent positive versus negative pressures. (4) Surfactant-depleted anesthetized rabbits (n = 10) with identical volume histories were randomized to positive versus negative ventilation with identical pressure-time characteristics. RESULTS: Matched positive and negative pressure time profiles in ex vivo and in vivo mice resulted in identical tidal volumes. Identical (negative vs. positive) sustained static pressures resulted in similar PaO(2) and end expiratory lung volumes. Positive and negative ventilation with identical volume histories and pressure time characteristics showed no difference in oxygenation or lung volumes. Historical comparisons suggested better oxygenation with negative pressure when the volume history was not identical. CONCLUSIONS: These data do not support major biological differences between negative and positive pressure ventilation when waveforms and lung volume history are matched.

Engelberts D; Malhotra A; Butler JP; Topulos GP; Loring SH; Kavanagh BP

2012-05-01

160

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

2005-01-01

 
 
 
 
161

Cutting and conditioning of the reactor pressure vessel in the NPP Wuergassen; Zerlegung und Konditionierung des Reaktordruckgefaesses im Kernkraftwerk Wuergassen  

Energy Technology Data Exchange (ETDEWEB)

NPP Wuergassen was shutdown in 1995 after 23 years of operation. Since 1997 the nuclear power plant is being dismantled. The cutting of the reactor pressure vessel internals was performed between 2003 and 2008. After decontamination the cylindrical parts of the reactor pressure vessel were dissected, the process was finalized in 2010. AREVA has now a 30 years-experience concerning repair, replacement and dismantling of reactor components. In the contribution the authors describe the process planning, manufacture and testing of appropriate remote handled tools, decontamination, dissection of the pressure vessel (320 t), conditioning, packaging and transport of the radioactive waste including radiation protection monitoring.

Kraps, Uwe [AREVA NP GmbH, Erlangen (Germany); Duwe, Peter [E.ON Kernkraft GmbH, Bewerungen (Germany)

2011-07-01

162

Effect of Shear Deformation and Relaxation of Support Conditions on Buckling of Pressurized Pipelines containing Expansion Bellows  

CERN Document Server

Mechanical stability of pressurized expansion bellows and tube-bellows-tube interconnects is considered.Effect of shear deformation on buckling pressure of bellows is shown y using Engesser's model. A generalized equivalent column concept is developed in order to study the effect of relaxation of support conditions on stability of interconnects containing expansion bellows. Two general modes of buckling are discussed: column instability of well-supported bellows (I) and buckling of tube-bellows--tube interconnect if the support-bellows distances are large enough (II). A dramatic drop of critical pressure in the transition region from mode I to mode II is shown.

Skoczen, Blazej

1998-01-01

163

Influence of detonator strength in the behavior of cap sensitive explosives under dynamic pressure conditions  

Energy Technology Data Exchange (ETDEWEB)

The desensitization of an explosives column by the transmitted effects of the earlier detonations in nearby explosive charges is of vital concern to the explosives and blasting industries. Stress waves from detonations of borehole charges have the capacity to desensitize adjacent delayed borehole charges. This desensitization can be of a transient or a permanent nature. The dead pressing, or shock desensitization, phenomenon has been identified as one of the contributing to underperformance of explosive charges. Practical research was carried out to determine how the use of different initiation energies affected the behavior of various water based explosives under dynamic pressure conditions. It is generally accepted that stronger stimulation improves the performance of an explosive charge suffering from the dead-pressing or shock desensitization effect. This is even more important for the new generation of water based explosives, which have reduced sensitivity characteristics to achieve increased safety. This paper describes a series of experiments wherein the propagation of detonation in various types of water based cartridged explosives were studied. Two detonator strengths were used to provide for a stronger and weaker priming of the explosive charges under dynamic stress.

Huidobro, J. [Union Espanola de Explosivos, Madrid (Spain); Hall, M. [Dantex Explosives Pty Ltd, Florida (South Africa)

1994-12-31

164

High Knudsen Number Fluid Flow at Near-Standard Temperature and Pressure Conditions using Precision Nanochannels  

Science.gov (United States)

Gas flows over a wide range of Knudsen numbers (˜0.5-10) are studied using silicon nanochannel arrays with slit-shaped pores that range from micrometer to sub-10nm scales. The flows are generated under conditions of room temperature and near-atmospheric pressure (˜22^oC and ˜101-115 kPa) and span the continuum flow, continuum-slip flow, transition flow and free-molecular flow regimes. The measured flow rates of helium, argon and carbon dioxide are in good agreement with the Unified Slip Model(USM) proposed by Beskok and Karniadakis (Beskok A., Karniadakis G.E., Nanoscale and Microscale Thermophysical Engineering 3 (1999), no. 1, 43-77). The measured volumetric gas flow rates agree well with calculations based on the USM up to a Knudsen number of about Kn ˜ 4, well into the transition regime; above this value the agreement for much of the data is qualitative and at very large Knudsen numbers the data is in the free molecular regime as expected.

Datta, Subhra; Conlisk, A. T.; Fissell, William H.; Roy, Shuvo; Majestrelli, Jeff

2010-11-01

165

Effects interaction of ion beams with electrolyte surface at atmospheric pressure glow discharge conditions  

International Nuclear Information System (INIS)

Authors describe the ion beams interaction with liquid electrolyte surface (water solution of sodium chloride) at conditions of atmospheric pressure glow discharge plasma. The glow discharge is ignited between metal anode and liquid electrolyte surface as cathode. It was noted that the increasing dissolved substance concentration leads to abrupt change of discharge view: from 'spreading' at low concentration to 'arc form' at 2.5 times concentration increasing. The 'arc form' is changed without variation of voltage and current. The form changes occur during 0.25 second. It was assumed that there is the back connection between dissolved substances concentration and discharge properties. The estimations of positive ions bombarding liquid surface are presented. The main ion is H3O+. The energetic expenditures on the one water molecule transfer from solution into gas phase were made. The values are 1-2 order less then expenditure for metallic cathode. The suggestion of liquid cathode state in the thin surface layer was made. (authors)

2007-01-01

166

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

International Nuclear Information System (INIS)

The plasma parameters such as electron distribution function and electron density of three atmospheric-pressure transient discharges namely filamentary and homogeneous dielectric barrier discharges in air, and the spark discharge of an argon plasma coagulation (APC) system are determined. A combination of numerical simulation as well as diagnostic methods including current measurement and optical emission spectroscopy (OES) based on nitrogen emissions is used. The applied methods supplement each other and resolve problems, which arise when these methods are used individually. Nitrogen is used as a sensor gas and is admixed in low amount to argon for characterizing the APC discharge. Both direct and stepwise electron-impact excitation of nitrogen emissions are included in the plasma-chemical model applied for characterization of these transient discharges using OES where ambiguity arises in the determination of plasma parameters under specific discharge conditions. It is shown that the measured current solves this problem by providing additional information useful for the determination of discharge-specific plasma parameters. (paper)

2012-03-28

167

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

2002-11-11

168

An EELS and XAS study of cubic boron nitride synthesized under high pressure - high temperature conditions  

International Nuclear Information System (INIS)

Cubic Boron Nitride (c-BN) single-crystals have been synthesized under high pressure and high temperature conditions (HP-HT) using hexagonal Boron-Nitride (h-BN) precursors. We have performed a study of both phases with electron (EELS) and X-ray (XAS) spectroscopy that are compared. The c-BN ELNES spectra at B-K and N-K edges are found to be consistent with the Xanes (XAS) data, although the energy resolution achieved with X-rays is better than that obtained by EELS with a LaB6 filament. However, XAS is at a disadvantage by comparison with EELS owing to the presence o the N-K edge second order. Attempts were made to dope c-BN with carbon atoms. The examination of the EELS spectra reveals that the incorporation of carbon species in the BN material is always accompanied by the addition of oxygen. Several samples were analyzed both with selected area electron diffraction and energy loss spectroscopy. Most probed crystals containing C (and therefore O) were found to be hexagonal. These results emphasized that the range of existence of the cubic phase is very narrow around the binary composition. (authors). 20 refs., 11 figs

1995-01-01

169

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

UK PubMed Central (United Kingdom)

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.

Mondy CP; Usseglio-Polatera P

2013-09-01

170

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

2013-06-15

171

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

CERN Multimedia

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 pressure wave and it not only reproduces the pressure waveform faithfully, but also its sharper nature helps to reliably detect the heart period variability (HPV). We have studied the position-specific (e.g. over carotid or radial artery) nature of change of this pulse wave signal (shape and amplitude) and also the changes at different physiological states.

Sur, S; Sur, Shantanu

2005-01-01

172

COMPARISON OF VENTED AND ABSOLUTE PRESSURE TRANSDUCERS FOR WATER-LEVEL MONITORING IN HANFORD SITE CENTRAL PLATEAU WELLS  

Energy Technology Data Exchange (ETDEWEB)

Automated water-level data collected using vented pressure transducers deployed in Hanford Site Central Plateau wells commonly display more variability than manual tape measurements in response to barometric pressure fluctuations. To explain this difference, it was hypothesized that vented pressure transducers installed in some wells are subject to barometric pressure effects that reduce water-level measurement accuracy. Vented pressure transducers use a vent tube, which is open to the atmosphere at land surface, to supply air pressure to the transducer housing for barometric compensation so the transducer measurements will represent only the water pressure. When using vented transducers, the assumption is made that the air pressure between land surface and the well bore is in equilibrium. By comparison, absolute pressure transducers directly measure the air pressure within the wellbore. Barometric compensation is achieved by subtracting the well bore air pressure measurement from the total pressure measured by a second transducer submerged in the water. Thus, no assumption of air pressure equilibrium is needed. In this study, water-level measurements were collected from the same Central Plateau wells using both vented and absolute pressure transducers to evaluate the different methods of barometric compensation. Manual tape measurements were also collected to evaluate the transducers. Measurements collected during this study demonstrated that the vented pressure transducers over-responded to barometric pressure fluctuations due to a pressure disequilibrium between the air within the wellbores and the atmosphere at land surface. The disequilibrium is thought to be caused by the relatively long time required for barometric pressure changes to equilibrate between land surface and the deep vadose zone and may be exacerbated by the restriction of air flow between the well bore and the atmosphere due to the presence of sample pump landing plates and well caps. The disequilibrium is likely limited to wells screened across the water table (i.e., open to the deep vadose zone) where the depth to water is large or a low-permeability layer occurs in the vadose zone. Such wells are a pathway for air movement between the deep vadose zone and land surface and this sustains the pressure disequilibrium between the well bore and the atmosphere for longer time periods. Barometric over-response was not observed with the absolute pressure transducers because barometric compensation was achieved by directly measuring the air pressure within the well. Users of vented pressure transducers should be aware of the over-response issue in certain Hanford Site wells and ascertain if it will affect the use of the data. Pressure disequilibrium between the well and the atmosphere can be identified by substantial air movement through the wellbore. In wells exhibiting pressure disequilibrium, it is recommended that absolute pressure transducers be used rather than vented transducers for applications that require precise automated determinations of well water-level changes in response to barometric pressure fluctuations.

MCDONALD JP

2011-09-08

173

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

174

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.

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

2010-01-01

175

Navier-Stokes equations with periodic boundary conditions and pressure loss  

CERN Document Server

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, Chérif; Batina, Jean

2007-01-01

176

Heterogeneous catalytic generation of hydrogen from formic acid under pressurized aqueous conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

PtRuBiO x/C catalyst has shown the promise for catalyzing CO-free hydrogen generation from formic acid in aqueous solution at room temperature and atmospheric pressure. In order to produce hydrogen at moderate-pressure to feed into a fuel cell stack, postgeneration compression is needed to overcome ...

Ting, SW; Hu, C; Pulleri, JK; Chan, KY

177

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

International Nuclear Information System (INIS)

[en] 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

1973-01-01

178

Pressure  

Science.gov (United States)

This page contains three Physlets that are able to share data using a connection made by a common superclass, SApplet. The ensemble walls keep track of the change in momentum, i.e., the pressure, during each time step, dt, and provides this data to the DataGraph Physlet and the DataTable Physlet.

Christian, Wolfgang; Belloni, Mario

2008-02-09

179

Seed storage at elevated partial pressure of oxygen, a fast method for analysing seed ageing under dry conditions.  

UK PubMed Central (United Kingdom)

BACKGROUND AND AIMS: Despite differences in physiology between dry and relative moist seeds, seed ageing tests most often use a temperature and seed moisture level that are higher than during dry storage used in commercial practice and gene banks. This study aimed to test whether seed ageing under dry conditions can be accelerated by storing under high-pressure oxygen. methods: Dry barley (Hordeum vulgare), cabbage (Brassica oleracea), lettuce (Lactuca sativa) and soybean (Glycine max) seeds were stored between 2 and 7 weeks in steel tanks under 18 MPa partial pressure of oxygen. Storage under high-pressure nitrogen gas or under ambient air pressure served as controls. The method was compared with storage at 45 °C after equilibration at 85 % relative humidity and long-term storage at the laboratory bench. Germination behaviour, seedling morphology and tocopherol levels were assessed. KEY RESULTS: The ageing of the dry seeds was indeed accelerated by storing under high-pressure oxygen. The morphological ageing symptoms of the stored seeds resembled those observed after ageing under long-term dry storage conditions. Barley appeared more tolerant of this storage treatment compared with lettuce and soybean. Less-mature harvested cabbage seeds were more sensitive, as was the case for primed compared with non-primed lettuce seeds. Under high-pressure oxygen storage the tocopherol levels of dry seeds decreased, in a linear way with the decline in seed germination, but remained unchanged in seeds deteriorated during storage at 45 °C after equilibration at 85 % RH. CONCLUSIONS: Seed storage under high-pressure oxygen offers a novel and relatively fast method to study the physiology and biochemistry of seed ageing at different seed moisture levels and temperatures, including those that are representative of the dry storage conditions as used in gene banks and commercial practice.

Groot SP; Surki AA; de Vos RC; Kodde J

2012-11-01

180

DESIGNED PARAMETERS FOR NOZZLES OF LOCAL SMALL-JET LOW-PRESSURE IRRIGATION NETWORK FOR THE CONDITIONS OF PROTECTED GROUND ????????? ????????? ??????? ????????? ????????????? ????????????? ???????????? ???? ??? ??????? ????????? ??????  

Directory of Open Access Journals (Sweden)

Full Text Available Hydraulic design of water outlets installed (mounted) on water application pipelines of low-pressure small-jet irrigation network when growing gerbera flowers under the conditions of protected ground is given in the paper. Relationships for estimating coefficients of hydraulic resistance and discharge coefficients for different nozzles are deduced

Pavlyukova E. D.; Degtyareva K. A.; Urzhumova Y. S.

2011-01-01

 
 
 
 
181

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

182

The dependence of finger tip touch-pressure upon the condition of Braille reading.  

UK PubMed Central (United Kingdom)

The finger motions and quickness of braille reading were investigated by way of recording the finger tip pressure on the braille and its time process. Subjects were separated into two groups. One group consisted of 5 experienced blinds and the other group consisted of 5 blinds who were beginners in braille reading. The comparison of obtained results from two groups gave some evidence for the following conclusion. The finger tip pressure was considerably increased for careful or difficult reading.

Yamashita E; Matsumoto H

1977-11-01

183

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.)

1977-01-01

184

Valve inlet fluid conditions for pressurizer safety and relief valves in Westinghouse-designed plants. Final report. [PWR  

Energy Technology Data Exchange (ETDEWEB)

The overpressure transients for Westinghouse-designed NSSSs are reviewed to determine the fluid conditions at the inlet to the PORV and safety valves. The transients considered are: licensing (FSAR) transients; extended operation of high pressure safety injection system; and cold overpressurization. The results of this review, presented in the form of tables and graphs, define the range of fluid conditions expected at the inlet to pressurized safety and power-operated relief valves utilized in Westinghouse-designed PWR units. These results will provide input to the PWR utilities in their justification that the fluid conditions under which their valve designs were tested as part of the EPRI/PWR Safety and Relief Valve Test Program indeed envelop those expected in their units.

Meliksetian, A.; Sklencar, A.M.

1982-12-01

185

Using the RELAP5/MOD2 code under low-pressure/low-temperature loss-of-coolant-accident conditions  

Energy Technology Data Exchange (ETDEWEB)

This paper describes how the RELAP5 thermal-hydraulic transient code has been applied to a reactor safety analysis of a loss-of-coolant accident (LOCA) to a reactor with thin fuel plates operating at highly subcooled conditions, --75{sup 0}C below boiling temperatures at operating pressure, 25{sup 0}C below boiling conditions at atmosphere pressure that occurs immediately following the LOCA. Depressurization is not the critical issue in this case, but plate boiling and reflooding and mixing of vapor and liquid streams are the critical aspects of the calculation. The analysis of the results shows the sensitivity of the calculation to the time periods of the steam chugging effects in the water channels between fuel plates. This MOD2 version is the first version which which the authors found consistency and realism in the results calculated for these very difficult transient conditions.

Wang, J.L. (Missouri Univ., Columbia, MO (USA). Research Reactor Facility); Kunze, J.F. (Missouri Univ., Columbia, MO (USA). Dept. of Nuclear Engineering)

1989-06-01

186

High temperature steam oxidation study on Zr-2.5%Nb pressure tube under simulated LOCA condition  

International Nuclear Information System (INIS)

The loss-of-coolant-accident or LOCA has long been an essential part of the defense-in-depth concept used by nuclear power industry and the Atomic Energy Commission (AEC) to ensure the safety of nuclear power plants. LOCA is a highly unlikely postulated accident and the emergency-core-cooling-system (ECCS) is one of the engineered safety features installed to mitigate its consequences. During such a postulated accident in a pressurized heavy water reactor (PHWR), Zircaloy cladding is liable to be severely oxidized in the high temperature steam environment. The pressure tube containing the fuel bundles is also likely to go to very high temperature in steam. One of the exothermic reactions under consideration for LOCA is that of the pressure tube with steam. The objective of this study is to establish the rate law for steam oxidation kinetics of Zr.-2.5%Nb pressure tube. The data on kinetics can later on be used in the assessment of hydrogen generation and its concentration in different compartments of the containment under accidental condition. This decides the possibility of hydrogen detonation risk. This paper discusses the study of high temperature steam oxidation expected for PHWR pressure tubes under postulated loss of coolant accident conditions (LOCA)

2010-01-01

187

Recovery of coal liquids by supercritical fluid extraction. 2. Correlation between extraction yield and extraction conditions (temperature and pressure)  

Energy Technology Data Exchange (ETDEWEB)

Supercritical fluid extraction of coal liquids was carried out using a single solvent such as benzene, toluene or p-xylene, and an equimolecular mixed solvent of benzene and toluene. Correlations between the extraction yield and the temperature and pressure conditions were investigated. Increase in extraction temperature resulted in an increase in extraction yield, as did an increase in density of the extraction solvent. Extraction pressure had an indirect effect through altering the solvent density. An empirical equation was obtained relating extraction yield, temperature and density for a single solvent.

Sakaki, T.

1984-05-01

188

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

International Nuclear Information System (INIS)

[en] 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)

1986-01-01

189

Synthesis of novel Ru2C under high pressure-high temperature conditions  

Science.gov (United States)

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 Å and c = 4.147 Å. 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.

Kumar, N. R. Sanjay; Shekar, N. V. Chandra; Chandra, Sharat; Basu, Joysurya; Divakar, R.; Sahu, P. Ch

2012-09-01

190

Synthesis of novel Ru2C under high pressure-high temperature conditions.  

UK PubMed Central (United Kingdom)

We report here, for the first time, synthesis of the Fe(2)N 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 Ru(2)C at ambient pressure are found to be a = 2.534 Å and c = 4.147 Å. 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 Ru(2)C has significant implications in the synthesis and study of osmium carbides.

Sanjay Kumar NR; Chandra Shekar NV; Chandra S; Basu J; Divakar R; Sahu PCh

2012-09-01

191

Elimination of jamming by electric-osmotic method under conditions of high pressures and temperatures  

Energy Technology Data Exchange (ETDEWEB)

A description is made of a laboratory experimental unit which was used to study the influence of high pressure differentials and temperature on the effectiveness of releasing a jammed drilling tool by electric-osmotic method. Dependences are defined of the force of freeing the bit on the density of direct current and the time of its influence. It was established that the effectiveness of the electric-osmotic method is reduced with high pressure differentials and increases with high temperatures in the jamming zone.

Khasayev, R.M.; Dzhabranlov, G.A.; Kuliyev, R.B.

1983-01-01

192

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

193

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

194

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)

[en] 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)

2003-08-00

195

Liquid pressure amplification and liquid injection in air conditioning and refrigeration systems  

Energy Technology Data Exchange (ETDEWEB)

Liquid pressure amplification and liquid injection are two patented methods of decreasing compressor energy consumption and increasing condenser capacity in an existing reciprocating vapor compression refrigeration system. Although this 6-year-old technology has been installed on thousands of existing systems, it continues to generate controversy in engineering and utility circles.

Yee, B.

1994-06-01

196

Is saturated vapour pressure instantaneously available for damage in accident conditions in FBRs  

International Nuclear Information System (INIS)

The calculations demonstrate that the time scale for the vapour to build up to the saturated vapour pressures (SVP) of liquid fuel is in the milliseconds range. This implies that the presently-followed assumption in fast-reactor safety studies that the SVP is instantaneously available during severe hypothetical accidents in FBRs is incorrect. (author)

1983-01-01

197

Saturated vapour pressure instantaneously available for damage in accident conditions in FBRs  

Energy Technology Data Exchange (ETDEWEB)

The calculations demonstrate that the time scale for the vapour to build up to the saturated vapour pressures (SVP) of liquid fuel is in the milliseconds range. This implies that the presently-followed assumption in fast-reactor safety studies that the SVP is instantaneously available during severe hypothetical accidents in FBRs is incorrect.

Ganesan, S.; Srinivasan, G.M.

1983-01-01

198

Effect of intravenous diazepam on human lower oesophageal sphincter pressure under controlled double blind crossover conditions.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The effect of diazepam on the lower oesophageal sphincter (LOS) pressure is controversial. Therefore, a double-blind crossover study was performed on 18 healthy volunteers to determine the sphincter response to intravenous diazepam--70, 140, 280 microgram/kg, which correspond to a total dose of 5, 1...

Weihrauch, T R; Förster, C F; Köhler, H; Ewe, K; Krieglstein, J

199

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

CERN Multimedia

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

200

Land use change under conditions of high population pressure : the case of Java  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A long history of increases in population pressure in Java has caused agricultural land use to expand and intensify. More recent land use changes caused the conversion of prime agricultural land into residential and industrial area. Results of a dynamic, regional-scale, land use change model are pre...

Verburg, P.H.; Veldkamp, A.; Bouma, J.

 
 
 
 
201

Experimental investigation of sagging of a completely voided pressure tube of Indian PHWR under heatup condition  

International Nuclear Information System (INIS)

Pressure tube (zirconium 2.5 wt.% Nb) serves as a pressure boundary for the coolant that removes nuclear heat generated in the reactor core of Indian Pressurised Heavy Water Reactors (IPHWRs). Under postulated low frequency (-6 per year) accidents like Loss of Coolant Accident (LOCA) along with failure of Emergency Core Cooling System (ECCS) injection, heatup of pressure tube (PT) combined with internal pressure and the weight of the fuel bundle may lead to deformation. The extent and nature of deformation is important from reactor safety point of view. An experimental set-up has been designed and fabricated to simulate sagging (downward deformation) of PT due to its own weight and the weight of fuel bundles for 220 MWe IPHWRs. Experiments are conducted at different heatup rates of voided PTs. It is observed that sagging initiates at a temperature around 450 oC. Contact between PT and calandria tube (CT) occurs at around 585-625 oC, respectively. Once PT-CT contact takes place, PT temperature either decreases or the temperature rise remains controlled whereas CT temperature keeps on increasing for next 20-30 s. The contact location in all the experiments was near the centre of the tube. Structural integrity of PT is retained (no breach) for all the experiments. The PT temperature rise is found to be arrested after the contact between PT and CT, thus establishing that moderator acts as an efficient heat sink for IPHWRs.

2008-10-01

202

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

1992-01-01

203

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 10 ovine aortas and 10 human carotid arteries. Ex vivo measurements (from both locations) were made in 11 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 artery 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

2011-01-04

204

Study on heat transfer and pressure drop characteristics of internal heat exchangers in CO2 system under cooling condition  

Science.gov (United States)

In order to study the heat transfer and pressure drop on four types of internal heat exchangers (IHXs) of a CO2 system, the experiment and numerical analysis were performed under a cooling condition. The configuration of the IHXs was a coaxial type and a micro-channel type. Two loops on the gas cooler part and the evaporator part were made, for experiment. And the section-by-section method and Hardy-Cross method were used for the numerical analysis. The capacity and pressure drop of the IHX are larger at the micro-channel type than at the coaxial type. When increasing the mass flow rate and the IHX length the capacity and pressure drop increase. The pressure drop of the evaporator loop is much larger than that of the gas cooler loop. The performance of the IHX was affected with operating condition of the gas-cooler and evaporator. The deviations between the experimental result and the numerical result are about ±20% for the micro-channel type and ±10% for the coaxial type. Thus, the new CO2 heat transfer correlation should be developed to precisely predict a CO2 heat transfer.

Kim, Dae Hoon; Lee, Jae-Heon; Choi, Jun Young; Kwon, Young Chul

2009-12-01

205

A bare metal reference electrode for application under high-temperature, high-pressure and high-radiation conditions  

Energy Technology Data Exchange (ETDEWEB)

A bare metal electrode device that was used to provide a pseudo reference potential was tested under high-temperature and high-pressure conditions, This reference potential was obtained from the polarization curve of the evolution reaction of hydrogen or oxygen. A cyclic voltammetric method was used in the experiments to obtain the polarization curve for the evolution reactions. Experimental results show that the measured potential of a stainless steel electrode and a stainless steel vessel with respect to the new reference potential were consistent with the values measured against an Ag/AgCl reference electrode. As only bare metal electrodes are required in the reference electrode device, it is robust for applications under high-temperature, high-pressure and high-radiation conditions or in locations difficult to access.

Yang, L.

1999-07-01

206

Multiple-pass high-pressure homogenization of milk for the development of pasteurization-like processing conditions.  

UK PubMed Central (United Kingdom)

Multiple-pass ultrahigh pressure homogenization (UHPH) was used for reducing microbial population of both indigenous spoilage microflora in whole raw milk and a baroresistant pathogen (Staphylococcus aureus) inoculated in whole sterile milk to define pasteurization-like processing conditions. Response surface methodology was followed and multiple response optimization of UHPH operating pressure (OP) (100, 175, 250 MPa) and number of passes (N) (1-5) was conducted through overlaid contour plot analysis. Increasing OP and N had a significant effect (P < 0·05) on microbial reduction of both spoilage microflora and Staph. aureus in milk. Optimized UHPH processes (five 202-MPa passes; four 232-MPa passes) defined a region where a 5-log(10) reduction of total bacterial count of milk and a baroresistant pathogen are attainable, as a requisite parameter for establishing an alternative method of pasteurization. Multiple-pass UHPH optimized conditions might help in producing safe milk without the detrimental effects associated with thermal pasteurization.

Ruiz-Espinosa H; Amador-Espejo GG; Barcenas-Pozos ME; Angulo-Guerrero JO; Garcia HS; Welti-Chanes J

2013-02-01

207

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

International Nuclear Information System (INIS)

[en] 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

1980-01-01

208

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

International Nuclear Information System (INIS)

Highlights: ? Simulating of LOCA at 4 and 6 MPa internal pressures for IPHWR was carried out at IIT Roorkee, India. ? The sagging of PT takes place at 500 °C before the commencement of ballooning. Maximum sagging is less than 2 mm. ? Once PT touches the CT, there is no further rise in PT temperature. ? The maximum PT temperature was below 700 °C. ? 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 °C before the ballooning initiation. The ballooning initiates at a temperature around 625 °C and contact between PT and Calandria Tube (CT) occurs at around 680 °C, respectively, for 4 MPa and the same was at 550 °C and 640 °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.

2012-01-01

209

High-pressure phase transformations of FeS: Novel phases at conditions of planetary cores  

Science.gov (United States)

Iron sulfide (FeS) was investigated using first-principles calculations up to a pressure of 400 GPa. A number of new phase transitions were found. An antiferromagnetic MnP-type structure, FeS II, was confirmed to be stable at low pressures, whereas at high pressures (40-135 GPa) we find a new stable phase, with a non-magnetic MnP-type structure, FeS VI. The observed first-order change in the cell shape between the two phases can be explained by the difference in magnetic configurations. The calculated cell parameters, atomic coordinates, and bulk modulus of non-magnetic MnP-type phase are consistent with those determined from experiment. The upper pressure limit of the stability of the non-magnetic MnP-type phase was calculated to be 135 GPa. A hitherto unsuspected phase transition from the non-magnetic MnP-type to a phase with Pmmn symmetry, FeS VII, was identified using the evolutionary crystal structure prediction (USPEX) method. The structure of the Pmmn phase has no known analogues, but can be described as a distortion of the NaCl-type structure. The Pmmn phase with the distorted NaCl-type structure is stable from 135 GPa at least up to 400 GPa. According to previous experiments and the present study, the transition sequence of FeS at low temperatures is as follows: troilite ? antiferromagnetic MnP-type phase ? monoclinic phase ? non-magnetic MnP-type phase ? Pmmn phase. The calculated volume reduction from the monoclinic to the non-magnetic MnP-type phase is 1.0% at 40 GPa, which is in good agreement with experimental observations. The calculated volume reduction from the non-magnetic MnP-type to the Pmmn phase is 3.7% at 135 GPa.

Ono, Shigeaki; Oganov, Artem R.; Brodholt, John P.; Vo?adlo, Lidunka; Wood, Ian G.; Lyakhov, Andriy; Glass, Colin W.; Côté, Alexander S.; Price, G. David

2008-07-01

210

Acrylic resin water sorption under different pressure, temperature and time conditions  

Directory of Open Access Journals (Sweden)

Full Text Available The purpose of this work was to analyze water sorption by polymerized acrylic resins under different pressure, temperature and time treatments. A thermo-cured acrylic resin was used as the denture base (Classico Ltda.) and ethylene glycol di-methacrylate as a cross-linking agent, with processing carried out in a water bath at 73 °C for nine hours. Forty-five samples were prepared following the criteria and dimensions of specification # 12 of the American Dental Association (ADA), using a matrix in the shape of a stainless steel disc with 50 ± 1 mm diameter and 0.5 ± 0.05 mm thickness. The control group samples were stored in distilled water for 30 days, while groups GII to GIX were placed in a polymerization device with adjustable pressure, time and temperature. An analysis of the variance of the results revealed the influence of different factors on water sorption only, with significant factors being temperature, time, pressure and the interaction between time and temperature. Other interactions exerted no significant influence on water sorption. Neither additional treatments nor the control group (GI) showed any significant difference in comparison to the averages of other treatments.

Rizzatti-Barbosa Célia Marisa; Fraga Marco Aurélio; Gonçalves Tarcísio de Moraes

2001-01-01

211

Acrylic resin water sorption under different pressure, temperature and time conditions  

Scientific Electronic Library Online (English)

Full Text Available Abstract in english The purpose of this work was to analyze water sorption by polymerized acrylic resins under different pressure, temperature and time treatments. A thermo-cured acrylic resin was used as the denture base (Classico Ltda.) and ethylene glycol di-methacrylate as a cross-linking agent, with processing carried out in a water bath at 73 °C for nine hours. Forty-five samples were prepared following the criteria and dimensions of specification # 12 of the American Dental Associati (more) on (ADA), using a matrix in the shape of a stainless steel disc with 50 ± 1 mm diameter and 0.5 ± 0.05 mm thickness. The control group samples were stored in distilled water for 30 days, while groups GII to GIX were placed in a polymerization device with adjustable pressure, time and temperature. An analysis of the variance of the results revealed the influence of different factors on water sorption only, with significant factors being temperature, time, pressure and the interaction between time and temperature. Other interactions exerted no significant influence on water sorption. Neither additional treatments nor the control group (GI) showed any significant difference in comparison to the averages of other treatments.

Rizzatti-Barbosa, Célia Marisa; Fraga, Marco Aurélio; Gonçalves, Tarcísio de Moraes

2001-01-01

212

Creep behavior of a nuclear pressure vessel under severe accident conditions  

Energy Technology Data Exchange (ETDEWEB)

The results of a study on the creep behavior of the vessel lower head under severe accident conditions are reported. An experimental program aimed at the evaluation of the creep properties of A533grB steel at high temperature (800--1,100 C) and under biaxial loading is summarized and the main results reported. A Finite Element simulation of the lower head under severe accident conditions allows to show the effect of the main parameters affecting the time to rupture.

Beghini, M.; Bertini, L.; Vitale, E. [Dipt. di Costruzioni Meccaniche e Nucleari, Pisa (Italy)

1996-12-31

213

Problems of investigation of HTGR fuel elements under loss-of-pressure accident conditions  

International Nuclear Information System (INIS)

The conditions of operation of fuel elements in emergency situations with the depressurization of the primary circuit and air ingress the latter are discussed for the pebble bed module reactor. The analytical models of light and heavy corrosion of the fuel elements as well as the criterion conditions that determine the nature of corrosion are given. The local differentialities of surface corrosion of the fuel elements in the pebble bed with a natural convection of gas are evaluated. (author). 7 refs, 8 figs

1991-01-01

214

Influence of weather conditions on the onset of primary spontaneous pneumothorax: positive association with decreased atmospheric pressure.  

UK PubMed Central (United Kingdom)

PURPOSE: Primary spontaneous pneumothorax is believed to result from blebs, or from other abnormalities of the pleural surface. There is no consensus as to whether a change in weather conditions can precipitate spontaneous pneumothorax. The aim of the present study was to investigate the influence of weather conditions on the onset of primary spontaneous pneumothorax. METHODS: The case histories of 1051 inpatients with primary spontaneous pneumothorax treated at Nissan Tamagawa Hospital between January 2006 and December 2011 were analyzed retrospectively. Data on weather conditions were collected daily throughout the 6-year period. The data were analyzed to determine differences in weather conditions between days on which primary spontaneous pneumothorax occurred and those on which it did not. RESULTS: Primary spontaneous pneumothorax occurred on 819 (37.3%) of 2191 study days. On days before and the day of primary spontaneous pneumothorax onset, the difference in mean atmospheric pressure was 0.6 hPa lower than on days in which no primary spontaneous pneumothorax occurred. This difference was statistically significant (P = 0.015). There was no statistical difference in mean, maximum, and minimum temperature, hours of sunshine, amount of precipitation, and mean and minimum humidity between days with and those without primary spontaneous pneumothorax. CONCLUSION: This largest study of the literature showed decreased atmospheric pressure might play an important role in the occurrence of primary spontaneous pneumothorax.

Haga T; Kurihara M; Kataoka H; Ebana H

2013-01-01

215

A new transducer for roll gap measurements of the roll pressure distribution and the friction condition in cold flat rolling  

DEFF Research Database (Denmark)

Background/purpose The only way to establish the true rolling pressure and the true friction condition in cold rolling is to conduct measurements in the roll bite. A new transducer design is therefore proposed, this to overcome problems in previous measurements in the past 70 years. Method The new idea is to increase the contact surface of the transducer, to be larger than the arc of contact. This is in the opposite way, compared to the smaller and smaller contact pin design that has been prevailing. Results The measurements where conducted during cold dry rolling of both copper strips and stainless steel strips in a pilot mill. The recordings were selected from a steady state with no disturbance from the material flow. The transducer was able to simultaneously measure both the normal pressure and the friction stress. An estimation of the coefficient of friction was accordingly performed. Conclusions The new transducer works very well, it was seen to be robust and able to avoid signal disturbance. The pressure and friction stress distribution results was as expected by the authors and a good reproducibility, together with a proven agreement between recorded signals and signals simulated. Keywords Friction stress, normal pressure distribution, roll bite measurements, cold flat rolling of metals

Lagergren, Jonas; Wanheim, Tarras

2005-01-01

216

The launching condition of a jet driven by the magnetic field and radiation pressure of an accretion disc  

CERN Document Server

We find that the cold gas can be magnetically launched from the disc surface with the help of the radiation pressure if the angular velocity of the radiation pressure dominated accretion disc is greater than a critical value, which decreases with increasing the disc thickness H/R (radiation pressure). This indicates the force exerted by the radiation from the disc indeed helps launching the outflow. The rotational velocity of the gas in the disc depends on the strength of the magnetic field threading the disc and the inclination B_z/B_r of the field line at the disc surface. The launching condition for the cold gas at the disc surface sets an upper limit on the magnetic field strength, which is a function of the field line inclination B_z/B_r and the disc thickness H/R. This implies a more strict constraint on the maximal jet power can be extracted from a radiation pressure dominated accretion disc than that derived conventionally on the equipartition assumption.

Cao, Xinwu

2012-01-01

217

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)

2009-01-01

218

Pressure condition of brittle to ductile transition in rocks and its significance for predicting dynamic phenomena in rock mass  

Energy Technology Data Exchange (ETDEWEB)

On the basis of the results of conventional tri-axial compression tests on various rocks, the strength criterion, expressed in principal stresses, has been given and the corresponding Mohr's envelope has been described. The expressions defining the angle of internal friction in the function of confining pressure, have been derived. Formulated are the general criterion and special cases of criteria which make it possible to predict the conditions (pressures) under which rocks exhibit the property of brittleness (with a brittle violent failure as its basic attribute), and under which they begin to flow in a ductile manner (without a stress drop) in the stage after passing the ultimate strength (yield point), and possibly pass into the plastic state.

Kwasniewski, M.

1983-01-01

219

Evaluation of hydraulic and mechanical properties of Berea sandstone under different conditions of temperature and confining pressure  

International Nuclear Information System (INIS)

[en] The isotropic compression experiments using Berea sandstone were conducted under the different temperature and confining pressure conditions, and the evolutions of hydraulic and mechanical properties were observed. The temperatures and confining pressures prescribed for the experiments are 20 and 90degC, and 7.5 or 8.0 MPa, respectively. The observed permeability at 20degC did not significantly evolve during the experiment period, while that at 90degC decreased by roughly 20% relative to the original value. This reduction may be attributed to the change of pore-structure induced by mineral dissolution and/or precipitation. Unlikely, the uniaxial compression tests showed no obvious change observed between pre- and post-experimental results. The XRD observation also showed no significant difference of mineralogy between them. (author)

2011-01-01

220

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; A. J. Ridley

2009-01-01

 
 
 
 
221

The application of the Buckingham theorem to modeling high-pressure regenerative heat exchangers in changed conditions  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract The study presents the possibility of applying the Buckingham theorem to modeling high-pressure regenerative heat exchangers in changed conditions. A list of independent parameters on which the water temperature at the outlet of the heat exchanger depends was selected; and by means of the Buckingham theorem a functional relation between two dimensionless quantities, where there is no overall heat transfer coefficient, was obtained. The exact form of the function was determined on the basis of actual measurement data and a linear relation between two dimensionless quantities was obtained. The correctness of the proposed relation was examined for two high-pressure regenerative exchangers for a 200 MW power plant.

Rafal Marcin Laskowski

2011-01-01

222

Optimization of the Operating-conditions of Pressurized-water Reactors Limited By the Dnb Phenomenon  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The replacement of steam generators in a pressurised water reactor (PWR) requires an adaptation of the normal operating conditions imposed by modified characteristics of the replaced steam generators (RSGs). To cover the cost of steam generator replacement, plant uprate is often considered. This is ...

Stievenart, Michel; Lodewijckx, W.; Robeyns, J.; 6th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics (NURETH-6)

223

Deformation conditions in the vicinity of concentrators at low-cycle stress of sizeable samples from reactor pressure vessel material  

International Nuclear Information System (INIS)

Deformation conditions were investigated in a reactor pressure vessel in the vicinity of points where stress and deformation concentrate to a multi-axis stress. The cycle deformation growth in the notch root in the first cycle of low-cycle fatigue stress of a sizeable flat bar with a bore, made from the 15Kh2MFA material, with a transient force cycle may be expressed using the Neuber formula ?sub(H)sup(2)=?sub(delta).?sub(epsilon) considering the deformation curve delta - epsilon. In the second and other cycles the procedure does not yield reliable predictions because it does not consider the strengthening of the plasticized area in the notch root and the formation of inner pressure stress after the first cycle. For a transient cycle of stress of a flat bar with a bore (?sub(H) is approximately 2.6) the pressure stress in the notch root can be considered to attain a level of (0.5 to 0.6).deltasub(0.2) in the second cycle and of (0.2 to 0.35).deltasub(0.2) in a half of service life. Taking into consideration the expression (deltasub(N) - deltasub(NZ)) instead of deltasub(N) in the Neuber hyperbola equation can offer more accurate prediction of cyclic deformation in the notch root and in the second and other cycles than the conventional Neuber method. The results of the study of deformation conditions in the vicinity of the bore in the flat bar can be also applied to the areas of stress concentrators in the pressure vessel and can be used for the rendition of the vessel reliability results more accurate. (B.S.)

1978-11-01

224

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).

1992-01-01

225

An axial flow cyclone to remove nanoparticles at low pressure conditions  

Energy Technology Data Exchange (ETDEWEB)

In this study, the axial flow cyclone used in Tsai et al. (2004) was further tested for the collection efficiency of both solid (NaCl) and liquid (OA, oleic acid) nanoparticles. The results showed that the smallest cutoff aerodynamic diameters achieved for OA and NaCl nanoparticles were 21.7 nm (cyclone inlet pressure: 4.3 Torr, flow rate: 0.351 slpm) and 21.2 nm (5.4 Torr, 0.454 slpm), respectively. The collection efficiencies for NaCl and OA particles were close to each other for the aerodynamic diameter ranging from 25 to 180 nm indicating there was almost no solid particle bounce in the cyclone. The 3-D numerical simulation was conducted to calculate the flow field in the cyclone and the flow was found to be nearly paraboloid. Numerical simulation of the particle collection efficiency based on the paraboloid flow assumption showed that the collection efficiency was in good agreement with the experimental data with less than 15% of error. A semi-empirical equation for predicting the cutoff aerodynamic diameter at different inlet pressures and flow rates was also obtained. The semi-empirical equation is able to predict the cutoff aerodynamic diameter accurately within 9% of error. From the empirical cutoff aerodynamic diameter, a semi-empirical square root of the cutoff Stokes number, {radical}(St{sub 50}*), was calculated and found to be a constant value of 0.241. This value is useful to the design of the cyclone operating in vacuum to remove nanoparticles.

Chen, S.-C.; Tsai, C.-J. [National Chiao Tung University, Institute of Environmental Engineering (China)], E-mail: cjtsai@mail.nctu.edu.tw

2007-01-15

226

An axial flow cyclone to remove nanoparticles at low pressure conditions  

International Nuclear Information System (INIS)

[en] In this study, the axial flow cyclone used in Tsai et al. (2004) was further tested for the collection efficiency of both solid (NaCl) and liquid (OA, oleic acid) nanoparticles. The results showed that the smallest cutoff aerodynamic diameters achieved for OA and NaCl nanoparticles were 21.7 nm (cyclone inlet pressure: 4.3 Torr, flow rate: 0.351 slpm) and 21.2 nm (5.4 Torr, 0.454 slpm), respectively. The collection efficiencies for NaCl and OA particles were close to each other for the aerodynamic diameter ranging from 25 to 180 nm indicating there was almost no solid particle bounce in the cyclone. The 3-D numerical simulation was conducted to calculate the flow field in the cyclone and the flow was found to be nearly paraboloid. Numerical simulation of the particle collection efficiency based on the paraboloid flow assumption showed that the collection efficiency was in good agreement with the experimental data with less than 15% of error. A semi-empirical equation for predicting the cutoff aerodynamic diameter at different inlet pressures and flow rates was also obtained. The semi-empirical equation is able to predict the cutoff aerodynamic diameter accurately within 9% of error. From the empirical cutoff aerodynamic diameter, a semi-empirical square root of the cutoff Stokes number, ?(St50*), was calculated and found to be a constant value of 0.241. This value is useful to the design of the cyclone operating in vacuum to remove nanoparticles

2007-01-01

227

Coordination between ventilatory pressure oscillations and venous return in the cephalopod Sepia officinalis under control conditions, spontaneous exercise and recovery.  

Science.gov (United States)

Venous blood flow was measured for the first time in a cephalopod. Blood velocity was determined in the anterior vena cava (AVC) of cuttlefish S. officinalis with a Doppler, while simultaneously, ventilatory pressure oscillations were recorded in the mantle cavity. In addition, magnetic resonance imaging (MRI) was employed to investigate pulsatile flow in other major vessels. Blood pulses in the AVC are obligatorily coupled to ventilatory pressure pulses, both in frequency and phase. AVC peak blood velocity (v(AVC)) in animals of 232 (+/- 30 SD) g wet mass at 15 degrees C was found to be 14.2 (+/- 7.1) cm s(-1), AVC stroke volume (SV(AVC)) was 0.2 (+/- 0.1) ml stroke(-1), AVC minute volume (MV(AVC)) amounted to 5.5 (+/- 2.8) ml min(-1). Intense exercise bouts of 1-2 min resulted in 2.2-fold increases in MV(AVC), enabled by 1.6-fold increments in both, AVC pulse frequency (f (AVC)) and v(AVC). As increases in blood flow occurred delayed in time by 1.7 min with regard to exercise periods, we concluded that it is not direct mantle cavity pressure conveyance that drives venous return in this cephalopod blood vessel. However, during jetting at high pressure amplitude (> 1 kPa), AVC blood flow and mantle cavity pressure pulse shapes completely overlap, suggesting that under these conditions, blood transport must be driven passively by mantle cavity pressure. MRI measurements at 15 degrees C also revealed that under resting conditions, f (AVC )and ventilation frequency (f (V)) match at 31.6 (+/- 2.1) strokes min(-1). In addition, rates of pulsations in the cephalic artery and in afferent branchial vessels did not significantly differ from f (AVC) and f (V). It is suggested that these adaptations are beneficial for high rates of oxygen extraction observed in S. officinalis and the energy conserving mode of life of the cuttlefish ecotype in general. PMID:16868753

Melzner, Frank; Bock, Christian; Pörtner, Hans-O

2006-07-26

228

Preparation of lanthanum and yttrium cuprates under conditions of high pressures and temperatures  

International Nuclear Information System (INIS)

Lanthanum (La2-xMxCuO4, where M-Ca, Sr, Ba, Pb) and yttrium (YBa2Cu3O7-y) cuprats were synthesized under conditions of all-round compression (p=1.0-5.0 GPa) and heating (t=800-1000 deg C) from initial oxides. It was revealed that lanthanum cuprates (La2CuO4; La1.8Pb0.2CuO4) crystallized in orthorhombic, and phases (La1.8Ca0.2Cu4; La1.8Sr0.2CuO4) in tetragonal syngonies under mentioned experimental conditions. Yttrium cuprate YBa2Cu3O7-y has tetragonal structure.

1991-01-01

229

Factors association and predisposing conditions in the event of pressure ulcers  

Directory of Open Access Journals (Sweden)

Full Text Available Objective: to examine the association between predisposing conditions (CP), intrinsic (FI) and extrinsic factors (EF) with occurrence of PU in bedridden patients in the intensive care unit and wards of a university hospital. Metodology: it’s a descriptive and quantitative study, performed at a University Hospital from Natal/RN city, after approved by the Ethics Committee of Hospital Universitário Onofre Lopes (protocol number135/07) in which data were collected from December 2007 to February 2008, through a structured form, data from medical records and physical examination of the skin. The results were organized using SPSS 15.0 and analyzed using descriptive and inferential statistics. Results: of the 30 patients studied, were diagnosed in 19 UP 43.3% of them. Was found an association of 35.7% of the Predisposing conditions, Intrinsic factors and Extrinsic factors for all patients studied, statistically significant (p-value = 0001), between the average scores in patients with and without PU, with reason chance to 12.0 for the development of PU and there was moderate correlation (r=0618) in the presence of this association. Conclusion: results show the influence of the multiplicity of factors and conditions on the occurrence of PU, which brings us to reflect on the assistance focused on.

Gilson de Vasconcelos Torres; Lucila Corsino de Paiva; Manuela Pinto Tibúrcio; Isabelle Katherinne Fernandes Costa; Gabriela de Sousa Martins Melo; Thalyne Yuri de Araújo Farias

2010-01-01

230

Process for converting a liquid of low boiling point, particularly natural gas or methane under atmospheric pressure, to the gaseous condition with subsequent heating  

Energy Technology Data Exchange (ETDEWEB)

Liquified natural gas or methane under atmospheric pressure and at a low temperature is brought to the required gaseous condition using only one cooling substance, e.g. F12 or propane, by increasing the pressure and introducing heat. In the first stage, the main flow of the gaseous cooling substance is condensed at a certain pressure in a heat exchanger and the liquid of low boiling point is thus converted into the gaseous condition. In the second stage a subsidiary flow of the gaseous cooling substance is condensed in the final heater at a higher pressure produced by a compressor, and the gas is heated.

Dohnt, D.

1981-03-19

231

Pulsatile ex vivo perfusion of human saphenous vein grafts under controlled pressure conditions increases MMP-2 expression.  

UK PubMed Central (United Kingdom)

BACKGROUND: The use of human saphenous vein grafts (HSVGs) as a bypass conduit is a standard procedure in the treatment of coronary artery disease while their early occlusion remains a major problem. METHODS: We have developed an ex vivo perfusion system, which uses standardized and strictly controlled hemodynamic parameters for the pulsatile and non-static perfusion of HSVGs to guarantee a reliable analysis of molecular parameters under different pressure conditions. Cell viability of HSVGs (n = 12) was determined by the metabolic conversion of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) into a purple formazan dye. RESULTS: Under physiological flow rates (10 mmHg) HSVGs remained viable for two weeks. Their exposure to arterial conditions (100 mmHg) was possible for one week without important reduction in viability. Baseline expression of matrix metalloproteinase-2 (MMP-2) after venous perfusion (2.2 ± 0.5, n = 5) was strongly up-regulated after exposure to arterial conditions for three days (19.8 ± 4.3) or five days (23.9 ± 6.1, p < 0.05). Zymographic analyses confirmed this increase on the protein level. Our results suggest that expression and activity of MMP-2 are strongly increased after exposure of HSVGs to arterial hemodynamic conditions compared to physiological conditions. CONCLUSION: Therefore, our system might be helpful to more precisely understand the molecular mechanisms leading to an early failure of HSVGs.

Dummler S; Eichhorn S; Tesche C; Schreiber U; Voss B; Deutsch MA; Hauner H; Lahm H; Lange R; Krane M

2011-01-01

232

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

2013-01-01

233

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

International Nuclear Information System (INIS)

[en] 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

1985-01-01

234

Influence of the external conditions on salt retention and pressure-induced electrical potential measured across a composite membrane  

DEFF Research Database (Denmark)

Transport on single electrolyte solutions (NaCl and MgCl2) due to pressure gradients across a commercial reverse osmosis membrane was studied by measuring volume flux (J(v)), salt rejection (S) and pressure induced electrical potential (Delta E) in a crossflow cell. The influence on these parameters of different external conditions due to hydrodynamic or chemical changes in the feed solutions was also studied. Changes were carried out by variation of the feed solution velocity (Reynolds numbers between 1500 and 3300) or the concentration ratio of mixed electrolytes (r = HCl/NaCl and HCl/MgCl2, r = 1, 0.5 and 0.1), respectively. Results show that J(v), S and Delta E values slightly increase when the velocity of the feed solution increases, but the mixed electrolytes strongly affect both salt rejection and pressure-induced electrical potential. A change in the sign of both parameters with respect to the value determined with single electrolytes at the same concentration was obtained, which is attributed to a strong coupling among the fluxes of individual ions and their distribution in the membrane when transport of mixed salt is studied. (C) 1999 Elsevier Science B.V. All rights reserved.

Benavente, Juana; Jonsson, Gunnar Eigil

1999-01-01

235

Simulation of ATWS conditions in pressurized water reactors; Simulation von ATWS-Transienten in Druckwasserreaktoren  

Energy Technology Data Exchange (ETDEWEB)

Safety analyses of nuclear power plants use ATWS (Anticipated Transients without Scram) as a term covering also events involving assumed failure of the reactor scram system. In this type of failure of the reactor scram system, power development in the reactor core is determined only by neutron kinetics feedback via the fuel temperature, moderator temperature and moderator density. If borated coolant is supplied, there is the additional feedback from the boron concentration. For nuclear power plants, coupled code complexes are developed and used which are made up of a thermohydraulic plant code and a 3D neutron kinetics model of the reactor core. These lend themselves to the use in analyses of ATWS states. The work presented here about the ATWS problem was performed in the interest of a consistent application of the DYN3D 3D neutron kinetics code in combination with the ATHLET thermohydraulic system code, and the quantification of differences resulting from variations of initial and boundary conditions. The DYN3D/ATHLET coupled code complex was validated by recalculation of various operating transients and by solving benchmark problems. The article contains results computed taking into account the influence of systems engineering and neutron kinetics boundary conditions. The calculations shown are methodological studies in no way demonstrating proof. (orig.)

Kliem, Soeren; Mittag, Siegfried; Rohde, Ulrich; Grundmann, Ulrich; Weiss, Frank-Peter [Forschungszentrum Dresden-Rossendorf, Dresden (Germany). Inst. fuer Sicherheitsforschung

2009-02-15

236

Improvement of superconducting properties of MgB{sub 2} by changing the argon ambient pressure and sintering conditions  

Energy Technology Data Exchange (ETDEWEB)

We have investigated various characteristic properties depending on sintering conditions of MgB{sub 2} samples prepared by the standard solid state reaction method. It is inferred from experimental results that the crystallinity of samples were improved when the pressure of the Ar ambient increased. Also, it was found that the sintering temperature above 850 deg. C caused extremely high amount of decomposition of the superconductor phase. Finally, it was considered that the sintering process of MgB{sub 2} must be carried out under the pressure of Ar ambient higher than 8 bar to impede the volatility of Mg in the structure of MgB{sub 2}. The J{sub c} values of samples systematically enhanced with the increase of sintering time and in particular, the sample sintered for 180 min. exhibited the highest J{sub c} (0) of 4.9 x 10{sup 3} A cm{sup -2} at 30 K. The obtained results demonstrate that the sintering conditions of MgB{sub 2} have a significant influence on T{sub c(onset)} and J{sub c}, which are directly related to practical applications of MgB{sub 2} based superconductor components.

Savaskan, Burcu; Ozturk, Kemal; Yanmaz, Ekrem [Department of Physics, Faculty of Arts and Sciences, Karadeniz Technical University, 61080 Trabzon (Turkey); Celik, Sukru, E-mail: savaskanb@hotmail.co, E-mail: turkke@hotmail.co [Department of Physics, Faculty of Arts and Sciences, Rize University, 53100 Rize (Turkey)

2009-03-01

237

Improvement of superconducting properties of MgB2 by changing the argon ambient pressure and sintering conditions  

International Nuclear Information System (INIS)

We have investigated various characteristic properties depending on sintering conditions of MgB2 samples prepared by the standard solid state reaction method. It is inferred from experimental results that the crystallinity of samples were improved when the pressure of the Ar ambient increased. Also, it was found that the sintering temperature above 850 deg. C caused extremely high amount of decomposition of the superconductor phase. Finally, it was considered that the sintering process of MgB2 must be carried out under the pressure of Ar ambient higher than 8 bar to impede the volatility of Mg in the structure of MgB2. The Jc values of samples systematically enhanced with the increase of sintering time and in particular, the sample sintered for 180 min. exhibited the highest Jc (0) of 4.9 x 103 A cm-2 at 30 K. The obtained results demonstrate that the sintering conditions of MgB2 have a significant influence on Tc(onset) and Jc, which are directly related to practical applications of MgB2 based superconductor components.

2009-03-01

238

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.

2007-01-01

239

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)

Based on the occurrence of a number of plant incidents during low power and shutdown operating conditions, the Nuclear Regulatory Commission (NRC) has initiated several programs to better quantify risk during these periods. One specific issue of interest is the loss of residual heat removal (RHR) under reduced coolant inventory conditions. This issue is also of interest in the Federal Republic of Germany and an experiment was performed in the integral PKL-3 experimental facility at Siemens-KWU to supply applicable data. Recently, an effort has been undertaken at the Idaho National Engineering Laboratory (INEL) to identify and analyze the important thermal-hydraulic phenomena in pressurized water reactors following loss of vital AC power and consequent loss of the RHR system during reduced inventory operation. The thermal-hydraulic response of a nuclear steam supply system (NSSS) with a closed reactor coolant system (RCS) to loss of residual heat removal cooling capability is investigated in this report. The specific processes investigated include: boiling of the coolant in the core and reflux condensation in the steam generators, the corresponding pressure increase in the reactor coolant system, the heat transfer mechanisms on the primary and secondary sides of the steam generators, the effects of air or other noncondensible gas on the heat transfer processes, and void fraction distributions on the primary side of the system. Mathematical models of these physical processes were developed and validated against experimental data from the PKL 3B 4.5 Experiment

1991-01-01

240

Reactions of possible cellulose liquefaction intermediates under high pressure liquefaction conditions  

Energy Technology Data Exchange (ETDEWEB)

Glucose, methyl and phenyl glucosides, glucitol, levoglucosenone and hydroxymethylfurfural were allowed to react under conditions where cellulose liquefies, with ZnCl/sub 2/, NaH/sub 2/PO/sub 4/ and NaOAc/H/sub 3/BO/sub 3/ as catalysts, to determine whether these compounds could be intermediates in cellulose liquefaction. It was found that: free aldehyde groups and acidity promote charring; these compounds do not fully interconvert before further reaction; levoglucosenone cannot be an intermediate except in acid solutions, glucose and phenyl glucoside give products consistent with their being intermediates; and solvent phenol is incorporated in all products except for hydrocarbons. Dilute aqueous solutions of some of these intermediates can be reacted in the absence of phenol to produce liquids and char. The liquids contain about 90% phenols, and 75% of the liquid products is phenol itself. 18 references, 1 figure, 5 tables.

Miller, I.J.; Saunders, E.R.

1987-01-01

 
 
 
 
241

Mineralogical studies on alteration of barium borosilicate nuclear waste glass under accelerated pressure temperature conditions  

International Nuclear Information System (INIS)

Silicate glass is thermodynamically unstable material hence its dissolution leads to the solubility of glass components, often accompanied by the formation of secondary amorphous gels at low temperatures. Rate of silicate glass dissolution often decreases appreciably as the concentration of silicic acid increases in the solution. Understanding of glass reactions with the environment is required to predict long-term glass dissolution mechanism and rate of radionuclide release in the geological repository. An inactive barium borosilicate glass (reference material for vitrified nuclear waste) was subjected to laboratory induced near hydrothermal conditions at various temperatures ranging between 100 to 300 deg C for different time intervals. Leachates obtained were studied to understand solution chemistry and solubility products of glass dissolution kinetics and the retention of elements. The surface chemistry and morphology of the specimens were studied using XRD and SEM-EDS. The scanning electron microscopic study on the surface of the treated specimens indicates formation of multiple alteration layers as well as secondary products such as smectite, hydrotalcite and saponite. For barium borosilicate glass three material types were distinguished - (a) initial stage of glass dissolution, (b) thin coatings of altered glass which envelope glass grains and (c) thick crust of coalescing alteration products, formed on top of the glass grains. The needle shaped spherulite like Si particles adhering to the grains were also found, but without the crust

2010-01-01

242

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

International Nuclear Information System (INIS)

The catalytic oxidation of C2H4 on Pt catalyst film interfaced with the oxygen-ion conducting yttria-stabilized zirconia solid electrolyte (YSZ) has been studied in the 10-5 and 10-4 mbar range. Photoemission electron microscopy (PEEM) was used as spatially resolving method. Under open circuit conditions (VWR=0 V) the CO2 production increases by rising p(C2H4) 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 CHx layer inhibiting O2 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.

2010-01-01

243

Molecular Studies of Surfaces under Reaction Conditions; Sum Frequency Generation Vibrational Spectroscopy, Scanning Tunneling Microscopy and Ambient Pressure X-Ray Photoelectron Spectroscopy  

Energy Technology Data Exchange (ETDEWEB)

Instruments developed in our laboratory permit the atomic and molecular level study of NPs under reaction conditions (SFG, ambient pressure XPS and high pressure STM). These studies indicate continuous restructuring of the metal substrate and the adsorbate molecules, changes of oxidation states with NP size and surface composition variations of bimetallic NPs with changes of reactant molecules.

Somorjai, G.A.

2009-11-11

244

Investigations of Response Time Parameters of a Pneumatic 3/2 Direct Acting Solenoid Valve Under Various Working Pressure Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available In pneumatic circuits, a solenoid valve is a key component for controlling and directing pneumatic energy. The solenoid valve functional performances are defined as response time parameters with respect to its actuations in terms of direction changing time. This paper aims to present response time parameters of solenoid valves under various working pressures. An experimental setup is employed in order to measure response time with reference to the input signals. The response time plays significant role for evaluating the valve performance in sensitive applications. The response time parameters includes the on delay, the off delay, the on time, the off time, the cycle time and the switching frequency. In this experimental investigation the influence of various input pressure conditions is recorded and tabulated. Valves with varying orifice diameter are employed and the investigation reveals the influence of orifice diameter in response time variations. The newly-proposed six response time parameters can be used to rate and select the appropriate valve for various industrial applications.

K. A. Venkataraman; K. Kanthavel; B. Nirmal Kumar

2013-01-01

245

DNS study of the ignition of n-heptane fuel spray under high pressure and lean conditions  

International Nuclear Information System (INIS)

[en] Direct numerical simulations (DNS) are used to investigate the ignition of n-heptane fuel spray under high pressure and lean conditions. For the solution of the carrier gas fluid, the Eulerian method is employed, while for the fuel spray, the Lagrangian method is used. A chemistry mechanism for n-heptane with 33 species and 64 reactions is adopted to describe the chemical reactions. Initial carrier gas temperature and pressure are 926 K and 30.56 atmospheres, respectively. Initial global equivalence ratio is 0.258. Two cases with droplet radiuses of 35.5 and 20.0 macrons are simulated. Evolutions of the carrier gas temperature and species mass fractions are presented. Contours of the carrier gas temperature and species mass fractions near ignition and after ignition are presented. The results show that the smaller fuel droplet case ignites earlier than the larger droplet case. For the larger droplet case, ignition occurs first at one location; for the smaller droplet case, however, ignition occurs first at multiple locations. At ignition kernels, significant NO is produced when temperature is high enough at the ignition kernels. For the larger droplet case, more NO is produced than the smaller droplet case due to the inhomogeneous distribution and incomplete mixing of fuel vapor

2005-01-01

246

An assessment of the failure rate for the beltline region of PWR pressure vessels during normal operation and certain transient conditions. Technical report  

International Nuclear Information System (INIS)

[en] A study was conducted to assess the failure rate for the beltline region of a generic pressurized-water reactor (PWR) pressure vessel. This assessment included the evaluation of several normal operating and transient reactor conditions. Failure rates were calculated from a computer code that used fracture mechanics methods to model the failure process; random number generation techniques were used to simulate random variables and model their interaction in the failure-process. This investigation had three major objectives: (1) to better define the effect of neutron irradiation, material variation, and flaw distribution on the failure rate for the beltline region of PWR pressure vessels, (2) to estimate the relative margins against failure for normal operation and certain transient conditions associated with nuclear pressure vessels, and (3) to evaluate the current limitations for using fracture mechanics models to predict failure rates for nuclear pressure vessels

1981-01-01

247

Mineralogical Evidence for the Bulk Transformation of Continental Crust to Ultrahigh-Pressure Conditions in Subduction Zones  

Science.gov (United States)

Evidence for (ultra)high-pressure --(U)HP-- metamorphism in modern orogenic belts and the preservation of exhumed (U)HP terranes around the world suggest that subduction and exhumation of continental crust plays an important role in Phanerozoic plate tectonics. The Western Gneiss region (WGR) of Norway, a major (U)HP province extending over 60,000 km2, provides an excellent opportunity to study how subduction to depths >100 km affects continental crust. By studying a ~60 km wide transect bounded to the north by Vartdalsfjorden and Rovdefjorden and the south by the Möre og Romsdal county boundary, we are able to examine mineralogical changes that occurred during subduction and exhumation within a rock composed predominantly of orthogneiss and variably transformed mafic bodies, which indicate the depths to which these rocks were subducted. Previous studies (e.g. Hacker et al., 2005) have suggested that Caledonian deformation in WGR host gneisses is primarily limited to brittle-ductile fabrics characterized by greenschist to lower-amphibolite facies metamorphism; the majority of the deformation in the rocks, including the pervasive foliation and foliation-parallel isoclinal folds, occurred between 1200 and 900 Ma. On the northern half of our study area, however, locally occurring neoblastic garnet crosscuts the foliation in the gneiss. The boundary of this garnet zone coincides with the local HP-UHP boundary, as determined by the presence of coesite in eclogite. Because garnet can retain information about changes in pressure and temperature, as well as the availability of water within the crust to catalyze chemical reactions, our findings suggest that 1) portions of the orthogneiss did transform at high pressures, 2) the presence of garnet within the orthogneiss may indicate conditions that approximate UHP and can therefore be useful in defining the boundaries between UHP and HP conditions, and 3) the growth of garnet during (U)HP metamorphism may be controlled by hydration of the crust, thus explaining the partial transformation to (U)HP mineral assemblages throughout the WGR.

Peterman, E. M.; Hacker, B. R.; Kylander-Clark, A. R.

2005-12-01

248

Metal-silicate partitioning of potassium at high pressure and temperature conditions and implications for thermal history of the Earth  

Science.gov (United States)

The possible presence of potassium in the Earth's core as a radioactive heat source can have a significant influence on the thermal evolution of the Earth (Buffett, 2002 GRL; Labrosse, 2003 PEPI). Core-mantle equilibration at high P-T (e.g. ~30 GPa, ~3450 K [Righter, 2011 EPSL]) was suggested from the mantle contents of siderophile elements. Basal magma ocean (Labrosse et al., 2007 Nature) also should be equilibrated with molten iron at the core-mantle boundary (CMB) (~135 GPa) due to its gravitational stability (Nomura et al., 2011 Nature). Previous experimental studies on potassium partitioning between liquid metal and silicate melt showed contradictory results on the concentration of potassium in the Earth's core because of experimental artifacts (K loss in metal phase), different (simplified) chemical compositions for study and large extrapolations to high P-T which suits for core-mantle equilibration at the base of the magma ocean. Recently, Corgne et al. (2007 EPSL) performed the partitioning experiments up to 7.7 GPa and 2200°C with chemical compositions of CI chondrite doped with moderate amount of S and K and revealed a significant effect of O contents in molten alloy on K partition coefficient while with negligible effect of P-T and S and C contents. The change in electronic structure of potassium from 4s- to 3d-like was predicted by theory (Bukowinski, 1976 GRL) and potassium alloying with nickel and iron was reported by experiments using diamond anvil cell at ~30 GPa and 2200 K (Parker et al., 1997 Science; Lee and Jeanloz, 2003 GRL). So, it is important to investigate the effect of pressure on K partition coefficient at the pressure conditions above ~30 GPa up to 135 GPa. Hirao et al. (2006 GRL) performed melting experiment at 135 GPa and 3500 K using laser-heated diamond anvil cell (LHDAC) and showed the value of partition coefficient Dk is 0.15, but their results lack the elemental mass balances between run products and starting materials. Our melting experiments were performed at high P-T conditions using LHDAC. Fine powdered mixtures of Fe (or Fe-FeS, Fe-FeSi) metal and gels with chemical compositions of KLB-1 peridotite doped with 1wt% K were used as a starting material. The gel powder was dehydrated by heating to 1273 K for 1 h in a H2-CO2 gas mixing furnace, in which oxygen fugacity was controlled to be slightly above the iron-wustite buffer. Pressure was measured after quenching with the Raman shift of diamond anvil. Ar was used as a pressure medium. The sample was heated from double side using Nd:YLF laser. A recovered sample was processed with Ion Slicer (JEOL EM-09100 IS), and subsequently examined by energy-dispersive X-ray spectrometry (EDS) attached with field emission scanning electron microscope (FE-SEM: JOEL JSM-7000F). Our preliminary results at ~20 GPa, fO2 of ~IW-1 and high temperature up to 5000 K with KLB-1 gel and S-free metal shows the clear correlation between O contents in molten iron and K partition coefficients suggested by Corgne et al. (2007). The results of partitioning coefficient at high P-T range up to primordial CMB conditions will be discussed in our presentation.

Nomura, R.; Hirose, K.

2011-12-01

249

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 (

2002-01-01

250

Adduction of solvent molecules by ions isolated within an ion trap mass spectrometer under atmospheric pressure ionisation conditions.  

Science.gov (United States)

Benzylpyridine and papaverine, an alkyl quinoline, both produce product ions containing an azepinium ring during atmospheric pressure chemical ionisation or electrospray multistage mass spectrometry. By controlling the trapping conditions, an isolated azepinium ion was held within the trap for an extended period of time without excitation. A subsequent analytical scan revealed a mass spectrum containing ions at two mass-to-charge (m/z) ratios, the first at the m/z of the isolated product ion and the second at an m/z ratio corresponding to the adduction of a molecule of solvent. Isolation and resonance excitation of the adduct ion remove the solvent molecule, resulting in recovery of the azepinium ion at the same signal intensity as the adduct ion. Isolating and trapping the ion for a further period allowed the solvent adduct ion to be re-formed. Modulation of the solvent flowing into the source while the ion was trapped allowed variation in the solvent molecule adducted to the trapped ion. The proportion of the ion current due to the adduct ion depends on the nature of the isolated ion, the proton affinity of the solvent and the length of time for which the ion was trapped. Adduct ion formation, deliberately maximised in this study, can occur to a significant extent under standard ion trap operating conditions, reducing the ion current of product ions of interest and, ultimately, the response in tandem mass spectrometric assays. PMID:17610242

Wickens, James R; Sleeman, Richard; Keely, Brendan J

2007-01-01

251

Adduction of solvent molecules by ions isolated within an ion trap mass spectrometer under atmospheric pressure ionisation conditions.  

UK PubMed Central (United Kingdom)

Benzylpyridine and papaverine, an alkyl quinoline, both produce product ions containing an azepinium ring during atmospheric pressure chemical ionisation or electrospray multistage mass spectrometry. By controlling the trapping conditions, an isolated azepinium ion was held within the trap for an extended period of time without excitation. A subsequent analytical scan revealed a mass spectrum containing ions at two mass-to-charge (m/z) ratios, the first at the m/z of the isolated product ion and the second at an m/z ratio corresponding to the adduction of a molecule of solvent. Isolation and resonance excitation of the adduct ion remove the solvent molecule, resulting in recovery of the azepinium ion at the same signal intensity as the adduct ion. Isolating and trapping the ion for a further period allowed the solvent adduct ion to be re-formed. Modulation of the solvent flowing into the source while the ion was trapped allowed variation in the solvent molecule adducted to the trapped ion. The proportion of the ion current due to the adduct ion depends on the nature of the isolated ion, the proton affinity of the solvent and the length of time for which the ion was trapped. Adduct ion formation, deliberately maximised in this study, can occur to a significant extent under standard ion trap operating conditions, reducing the ion current of product ions of interest and, ultimately, the response in tandem mass spectrometric assays.

Wickens JR; Sleeman R; Keely BJ

2007-01-01

252

A study on the numerical instability of COBRA-series subchannel analysis codes at low-pressure and low-flow conditions  

International Nuclear Information System (INIS)

[en] The numerical instability at low-pressure and low-flow conditions has been confirmed to be the common problem of the existing COBRA-series subchannel analysis codes. In addition, the range of operating conditions at which the analyses by the codes are impossible has been evaluated. To evaluate the MATRA's inapplicable range of operating conditions of the SMART core that is to be operated at the low flow condition, i.e. about 30% of the flow of the existing commercial pressurized water reactors at the steady-state condition, the analyses of various operating conditions were performed by using several representative COBRA-series subchannel analysis codes including MATRA. TORC of CE, COBRA3CP of Siemens/KWU, COBRA4I of PNL, and MATRA of KAERI were chosen as the subchannel analysis codes to be evaluated. The various operating conditions used in the CHF tests carried out at the Winfrith Establishment of UKAEA were chosen as the conditions to be analyzed. As the result, the numerical instabilities at low-pressure and low-flow conditions occurred in the analyses by all of the codes. It was revealed that the MATRA code, which numerically more stable thatn the other codes, was not able to analyze the conditions of the pressure not more than 100 bar and the mass velocity not more than 300 kg/sec-m2. Hereafter it is required to find out the exact reason for the numerical instability of the existing COBRA-series subchannel analysis codes at low-pressure and low-flow conditions and to devise the new method to get over that numerical problem

2001-01-01

253

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)

2006-01-01

254

Reactive molecular dynamics study of Mo-based alloys under high-pressure, high-temperature conditions  

Science.gov (United States)

Structural metal alloys are of vital importance for a clean energy economy, but the current trial-and-error alloy development methodology is expensive and time consuming. In this study, we demonstrate the capability of the ReaxFF force field model to predict mechanical properties and provide a fully dynamic description of oxidation and sulfidation of Mo-based alloys under high-pressure, high-temperature conditions using molecular dynamics (MD) method. The advantage of the ReaxFF approach is in its ability to model the formation and breaking of chemical bonds within the quantum framework but several orders of magnitude faster than the traditional density functional theory models. ReaxFF-MD predictions were compared to the literature Mo shock compression measurements at 300 K and 1673 K in the pressure range of 0-350 Pa, and densities and Young's modulus in the temperature range of 300-1500 K. Analysis of oxidation of Mo and Ni clusters and surface slabs showed that Mo oxidation proceeded at a significantly higher rate than the Ni oxidation and involved oxygen transport inside the metal cluster coupled to large heat release that caused extensive surface melting. The oxidation simulations of Mo3Ni clusters showed high production of Mo oxides and a low concentration of Ni-oxides in the gas phase. This was attributed to the higher chemical stability of Mo-oxide gas phase species. Modeling of H2S interactions with Mo slab demonstrated that sulfur atoms increasingly agglomerated in the surfaces layers of the slab as the simulation proceeded, diffusing deeper into the slab in their atomic forms. A combined ReaxFF Mo/Ni/C/O/N/S/H parameter set enabled us to obtain a detailed atomistic analysis of complex physical and chemical events during the combustion of a complex fuel molecule on a reactor surface.

Vasenkov, Alex; Newsome, David; Verners, Osvalds; Russo, Michael F.; Zaharieva, Roussislava; van Duin, Adri C. T.

2012-07-01

255

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

Science.gov (United States)

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.

Martin Cabanas, B.; Lützenkirchen, J.; Leclercq, S.; Barboux, P.; Lefèvre, G.

2012-11-01

256

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.

Danny Harel; Hadar Fadida; Shelly Gantz; Kobi Shilo; Hagai Yasuor

2013-01-01

257

The influence of pore fluids on seismic wave velocities under high temperature and high pressure conditions: Development of a new technique with gas apparatus at AIST, Japan  

Science.gov (United States)

In order to study the effects of different pore fluids on elastic-wave velocities, we developed a new system for measuring elastic wave velocities (Vp and Vs ) under high-pressure conditions up to 200 MPa and hightemperature conditions up to 200°C using a gas-medium high-pressure and high-temperature apparatus. During the Vp and Vs measurements, we can also control the pore pressures from outside the rock samples. We measured Vp and Vs of the Berea sandstone samples under three different pore-fluid conditions including dry (without pore- fluids), in the presence of pore water, and in the presence of pore gas. Here we describe our new measurement technique and establish the capacity of the gas apparatus and measurement technique and their potentialities for the solution of geological problems.

Kitamura, K.; Masuda, K.; Takahashi, M.; Nishizawa, O.

2006-11-01

258

The effects of melatonin on anxiety and pain scores of patients, intraocular pressure, and operating conditions during cataract surgery under topical anesthesia.  

UK PubMed Central (United Kingdom)

AIMS: To evaluate the effects of melatonin premedication on anxiety and pain scores of patients, operating conditions, and intraocular pressure during cataract surgery under topical anesthesia. MATERIALS AND METHODS: Sixty patients were randomly assigned to receive either sublingual melatonin 3 mg or placebo 60 min before surgery. Verbal anxiety scores and verbal pain scores, heart rate, systolic and diastolic blood pressure, intraocular pressure, and quality of operating conditions were recorded. RESULTS: Melatonin significantly reduced the anxiety scores (median, interquartile range) from 5 and 5-3 to 3 and 2-4 after premedication and to 3 and 2-3 during surgery and to 0 and 0-1 postoperatively before discharge from the recovery room. There were significant differences between two groups in anxiety scores after premedication (95% CI 3-3.5; P = 0.023), intraoperatively (95% CI 2.5-3.5; P = 0.007), and postoperatively (95% CI 0.5-1; P = 0.007). The surgeon reported better quality of operating conditions in the melatonin group (P = 0.001). No significant difference in intraoperative and postoperative pain scores, intraocular pressure, heart rate, and systolic and diastolic blood pressure between two groups was recorded. CONCLUSION: Sublingual melatonin premedication for patients undergoing cataract surgery under topical anesthesia reduced the anxiety scores in patients and provided excellent operating conditions.

Khezri MB; Merate H

2013-07-01

259

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

260

FINAL REPORT. CHARACTERIZATION OF CONTAMINANT TRANSPORT BY GRAVITY, CAPILLARITY AND BAROMETRIC PUMPING IN HETEROGENEOUS VADOSE REGIMES  

Science.gov (United States)

It is often hoped that the vadose zone will serve as a barrier to the downward transport of contaminants to the water table. Unfortunately, both the degree to which this is true and the conditions under which the vadose zone either functions or fails as a barrier to different kin...

 
 
 
 
261

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

262

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 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 attained after ?10-30 years, due to the infl

2012-01-01

263

The wind energy barometer; Le barometre de l'energie eolienne  

Energy Technology Data Exchange (ETDEWEB)

The year 1999 was particularly good for wind energy. Worldwide capacity grew by 3 695 mw, a record for the industry, exceeding the corresponding measure for newly installed nuclear capacity during the same year. The goal in the year 2000 was to maintain this course in sometimes shifting political and economic conditions. The result: with 22.3% growth and 3 031 mw of additional power, the challenge was met. (author)

Anon

2001-02-01

264

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

265

Dynamic observations of the effect of pressure and temperature conditions on the selective synthesis of carbon nanotubes  

Energy Technology Data Exchange (ETDEWEB)

In situ transmission electron microscopy studies have been carried out to determine the effect of temperature and pressure on the growth of carbon nanotubes by the Ni-catalyzed chemical vapour deposition of acetylene. The temperature range explored was 450-650 deg. C and the acetylene pressure range was 0.8-20 mTorr. Our observations show that straight, single-wall, carbon nanotubes tend to form at higher temperatures and lower pressures while bent, zigzag, multi-wall carbon nanotubes form at lower temperatures and higher pressures. These results can be understood as the result of competition between the arrival rate of carbon and the nucleation rate of carbon hexagons (which increases at high pressure and low temperature), and the annealing rate of the 5-ring and 7-ring defects that are responsible for the nanotube curvature.

Sharma, Renu [Center for Solid State Science, Arizona State University, Tempe, AZ 85287-1704 (United States); Rez, Peter [Department of Physics, Arizona State University, Tempe, AZ 85287-1504 (United States); Brown, Megan [Department of Physics, Arizona State University, Tempe, AZ 85287-1504 (United States); Du, Gaohui [Center for Solid State Science, Arizona State University, Tempe, AZ 85287-1704 (United States); Treacy, M M J [Department of Physics, Arizona State University, Tempe, AZ 85287-1504 (United States)

2007-03-28

266

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

Energy Technology Data Exchange (ETDEWEB)

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.

Kashperskii, V.S. [Kiev Polytechnical Institute (Ukraine)

1995-05-01

267

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

Energy Technology Data Exchange (ETDEWEB)

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. (author)

Maidment, G.G.; Eames, I.W.; Psaltas, M.; Lalzad, A. [Department of Engineering Systems, Faculty of Engineering, Science and the Built Environment, London South Bank University, 103 Borough Road, London SE1 0AA (United Kingdom)

2006-10-15

268

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

2006-01-01

269

Influence of meteorological conditions on the side effects of contrast media during infusion urograms  

Energy Technology Data Exchange (ETDEWEB)

A relationship between certain weather conditions and the frequency of some diseases has been recognised for a long time. During a period of two and a quarter years, the course of infusion urograms in 6862 patients was carefully monitored. At the same time, records were kept of the weather, including the general weather situation, changes in the weather, its dynamics, atmospheric pressure and 'vorticity'. 7.96% of patients showed side effects from the contrast medium. 32.6% of all patients admitted to having been affected by the weather, with an incidence of side effects of 9.7%. Older patients and over-weight patients tended to suffer fewer side effects. There was no correlation with the seasons. As regards the general weather situation, there was an increased incidence associated with changes coming from the east, fewer incidents during the in-flow of cold air and high pressure situations. There were marked differences during periods of high and low pressure ('vorticity'). High pressure situations and periods of increasing barometric pressure had complication rates of 5.3% and 4.7% respectively, low pressure, 11%. Statistical analysis showed no significant difference between the groups, but tendencies were unmistakable. A large number of individual factors are known to have an effect, such as abnormalities of the complement system, antigen-antibody reactions and others, but the importance of each factor remains uncertain. The present results indicate that the reaction of a patient at the moment of the investigation also plays a significant part.

Wolf, K.; Harlfinger, O.; Wedler, E.; Zuckert, D.; Mueller, U.

1981-12-01

270

The influence of meteorological conditions on the side effects of contrast media during infusion urograms  

International Nuclear Information System (INIS)

[en] A relationship between certain weather conditions and the frequency of some diseases has been recognised for a long time. During a period of two and a quarter years, the course of infusion urograms in 6862 patients was carefully monitored. At the same time, records were kept of the weather, including the general weather situation, changes in the weather, its dynamics, atmospheric pressure and 'vorticity'. 7.96% of patients showed side effects from the contrast medium. 32.6% of all patients admitted to having been affected by the weather, with an incidence of side effects of 9.7%. Older patients and over-weight patients tended to suffer fewer side effects. There was no correlation with the seasons. As regards the general weather situation, there was an increased incidence associated with changes coming from the east, fewer incidents during the in-flow of cold air and high pressure situations. There were marked differences during periods of high and low pressure ('vorticity'). High pressure situations and periods of increasing barometric pressure had complication rates of 5.3% and 4.7% respectively, low pressure, 11%. Statistical analysis showed no significant difference between the groups, but tendencies were unmistakable. A large number of individual factors are known to have an effect, such as abnormalities of the complement system, antigen-antibody reactions and others, but the importance of each factor remains uncertain. The present results indicate that the reaction of a patient at the moment of the investigation also plays a significant part. (org.)

1981-01-01

271

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; Zbigniew Koszela

2012-01-01

272

Asthma and climatic conditions: experience from Bermuda, an isolated island community  

Energy Technology Data Exchange (ETDEWEB)

A retrospective study of patients attending the emergency department with acute asthma was performed in Bermuda. Climatic data (barometric pressure, rainfall, humidity, and wind strength and direction) were obtained and compared with frequency of exacerbations of asthma. Three factors - namely, relative humidity, average daily temperature, and northeasterly winds - were found to be related to worsening asthma. Owing to Bermuda's lack of pollution and aeroallergens it was thought that these weather parameters had a direct effect on the asthmatic population.

Carey, M.J.; Cordon, I.

1986-10-04

273

Self-overcoming of the boiling condition by pressure increment in a water target irradiated by proton beam  

Science.gov (United States)

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.

Hong, Bong Hwan; Kang, Joonsun; Jung, In Su; Ram, Han Ga; Park, Yeun Soo; Cho, Hyung Hee

2013-11-01

274

Pulsed laser ablation plasmas generated in CO2 under high-pressure conditions up to supercritical fluid  

Science.gov (United States)

Pulsed laser ablation of solids in supercritical media has a large potential for nanomaterials fabrication. We investigated plasmas generated by pulsed laser ablation of Ni targets in CO2 at pressures ranging from 0.1 to 16 MPa at 304.5 K. Plasma species were characterized by optical emission spectroscopy, and the evolution of cavitation bubbles and shockwaves were observed by time-resolved shadowgraph imaging. Ni and O atomic emissions decreased with increasing gas pressure; however, near the critical point the intensities reached local maxima, probably due to the enhancement of the plasma excitation and effective quenching resulting from the large density fluctuation.

Kato, Toru; Stauss, Sven; Kato, Satoshi; Urabe, Keiichiro; Baba, Motoyoshi; Suemoto, Tohru; Terashima, Kazuo

2012-11-01

275

Study on heat transfer and pressure drop characteristics of internal heat exchangers in CO{sub 2} system under cooling condition  

Energy Technology Data Exchange (ETDEWEB)

In order to study the heat transfer and pressure drop on four types of internal heat exchangers (IHXs) of a CO{sub 2} system, the experiment and numerical analysis were performed under a cooling condition. The configuration of the IHXs was a coaxial type and a micro-channel type. Two loops on the gas cooler part and the evaporator part were made, for experiment. And the section-by-section method and Hardy-Cross method were used for the numerical analysis. The capacity and pressure drop of the IHX are larger at the micro-channel type than at the coaxial type. When increasing the mass flow rate and the IHX length the capacity and pressure drop increase. The pressure drop of the evaporator loop is much larger than that of the gas cooler loop. The performance of the IHX was affected with operating condition of the gas-cooler and evaporator. The deviations between the experimental result and the numerical result are about {+-}20% for the micro-channel type and {+-}10% for the coaxial type. Thus, the new CO{sub 2} heat transfer correlation should be developed to precisely predict a CO{sub 2} heat transfer. (orig.)

Kim, Dae Hoon [Graduate School of Hanyang University, Department of Mechanical Engineering, Seoul (Korea); Lee, Jae-Heon [Hanyang University, School of Mechanical Engineering, Seoul (Korea); Choi, Jun Young [Korea Testing Laboratory, Ansan, Gyeonggi-Do (Korea); Kwon, Young Chul [Sunmoon University, School of Mechanical Engineering, Asan, Chungnam (Korea)

2009-12-15

276

Design of a high-temperature and high-pressure liquid flow cell for x-ray absorption fine structure measurements under catalytic reaction conditions.  

UK PubMed Central (United Kingdom)

The design and performance of a new high-pressure and high-temperature cell for measurement of x-ray absorption fine structure (XAFS) spectra of solid catalysts working in a flowing liquid are presented. The cell has flat, high-purity sintered cubic boron nitride (c-BN) windows which can tolerate high temperature (900 K) and high pressure (10 MPa). The c-BN is a new material which has the highest tensile strength, second only to diamond, and is also chemically and thermally stable. The use of the cell is demonstrated for measurements of PtPdAl(2)O(3) and Ni(2)PSiO(2) hydrodesulfurization catalysts at reaction conditions. A technique called delta chi (Deltachi), involving determining the difference between XAFS spectra of the sample at reaction conditions and the bare sample, is introduced.

Kawai T; Chun WJ; Asakura K; Koike Y; Nomura M; Bando KK; Ted Oyama S; Sumiya H

2008-01-01

277

Design of a high-temperature and high-pressure liquid flow cell for x-ray absorption fine structure measurements under catalytic reaction conditions.  

Science.gov (United States)

The design and performance of a new high-pressure and high-temperature cell for measurement of x-ray absorption fine structure (XAFS) spectra of solid catalysts working in a flowing liquid are presented. The cell has flat, high-purity sintered cubic boron nitride (c-BN) windows which can tolerate high temperature (900 K) and high pressure (10 MPa). The c-BN is a new material which has the highest tensile strength, second only to diamond, and is also chemically and thermally stable. The use of the cell is demonstrated for measurements of PtPdAl(2)O(3) and Ni(2)PSiO(2) hydrodesulfurization catalysts at reaction conditions. A technique called delta chi (Deltachi), involving determining the difference between XAFS spectra of the sample at reaction conditions and the bare sample, is introduced. PMID:18248051

Kawai, Toshihide; Chun, Wang-Jae; Asakura, Kiyotaka; Koike, Yuichiro; Nomura, Masaharu; Bando, Kyoko K; Ted Oyama, S; Sumiya, Hitoshi

2008-01-01

278

Microbial survival rates of Escherichia coli and Deinococcus radiodurans under low temperature, low pressure, and UV-Irradiation conditions, and their relevance to possible Martian life.  

Science.gov (United States)

Viability rates were determined for microbial populations of Escherichia coli and Deinococcus radiodurans under the environmental stresses of low temperature (-35 degrees C), low-pressure conditions (83.3 kPa), and ultraviolet (UV) irradiation (37 W/m(2)). During the stress tests the organisms were suspended in saltwater soil and freshwater soil media, at variable burial depths, and in seawater. Microbial populations of both organisms were most susceptible to dehydration stress associated with low-pressure conditions, and to UV irradiation. However, suspension in a liquid water medium and burial at larger depths (5 cm) improved survival rates markedly. Our results indicate that planetary surfaces that possess little to no atmosphere and have low water availability do not constitute a favorable environment for terrestrial microorganisms. PMID:16689650

Diaz, Benjamin; Schulze-Makuch, Dirk

2006-04-01

279

Cooldown to residual heat removal entry conditions using atmospheric dump valves and auxiliary pressurizer spray following a loss-of-offsite power at Calvert Cliffs, Unit 1  

Energy Technology Data Exchange (ETDEWEB)

An investigation of cooldown using atmospheric dump valves (ADVs) and auxiliary pressurizer spray (APS) following loss-of-offsite power at Calvert Cliffs-1 showed residual heat removal entry conditions could not be reached with the plant ADVs alone. Use of APS with the plant ADVs enhanced depressurization, but still provided insufficient cooldown. Effective cooldown and depressurization was shown to occur when rated steady state flow through the ADVs was increased by a factor of four. 6 refs., 30 figs., 2 tabs.

Jenks, R.P.

1984-11-29

280

Temperature-pressure conditions in coalbed methane reservoirs of the Black Warrior basin: Implications for carbon sequestration and enhanced coalbed methane recovery  

Science.gov (United States)

Sorption of gas onto coal is sensitive to pressure and temperature, and carbon dioxide can be a potentially volatile supercritical fluid in coalbed methane reservoirs. More than 5000 wells have been drilled in the coalbed methane fields of the Black Warrior basin in west-central Alabama, and the hydrologic and geothermic information from geophysical well logs provides a robust database that can be used to assess the potential for carbon sequestration in coal-bearing strata.Reservoir temperature within the coalbed methane target zone generally ranges from 80 to 125 ??F (27-52 ??C), and geothermal gradient ranges from 6.0 to 19.9 ??F/1000 ft (10.9-36.2 ??C/km). Geothermal gradient data have a strong central tendency about a mean of 9.0 ??F/1000 ft (16.4 ??C/km). Hydrostatic pressure gradients in the coalbed methane fields range from normal (0.43 psi/ft) to extremely underpressured (coalbed methane fields are high enough that reservoirs never cross the gas-liquid condensation line for carbon dioxide. However, reservoirs have potential for supercritical fluid conditions beyond a depth of 2480 ft (756 m) under normally pressured conditions. All target coal beds are subcritically pressured in the northeastern half of the coalbed methane exploration fairway, whereas those same beds were in the supercritical phase window prior to gas production in the southwestern half of the fairway. Although mature reservoirs are dewatered and thus are in the carbon dioxide gas window, supercritical conditions may develop as reservoirs equilibrate toward a normal hydrostatic pressure gradient after abandonment. Coal can hold large quantities of carbon dioxide under supercritical conditions, and supercritical isotherms indicate non-Langmiur conditions under which some carbon dioxide may remain mobile in coal or may react with formation fluids or minerals. Hence, carbon sequestration and enhanced coalbed methane recovery show great promise in subcritical reservoirs, and additional research is required to assess the behavior of carbon dioxide in coal under supercritical conditions where additional sequestration capacity may exist. ?? 2003 Elsevier Science B.V. All rights reserved.

Pashin, J. C.; McIntyre, M. R.

2003-01-01

 
 
 
 
281

Analysis of the critical heat flux in round vertical tubes under low pressure and flow oscillation conditions. Applications of artificial neural network  

International Nuclear Information System (INIS)

Artificial neural networks (ANNs) for predicting critical heat flux (CHF) under low pressure and oscillation conditions have been trained successfully for either natural circulation or forced circulation (FC) in the present study. The input parameters of the ANN are pressure, mean mass flow rate, relative amplitude, inlet subcooling, oscillation period and the ratio of the heated length to the diameter of the tube, L/D. The output is a nondimensionalized factor F, which expresses the relative CHF under oscillation conditions. Based on the trained ANN, the influences of principal parameters on F for FC were analyzed. The parametric trends of the CHF under oscillation obtained by the trained ANN are as follows: the effects of pressure below 500 kPa are complex due to the influence of other parameters. F will increase with increasing mean mass flow rate under any conditions, and will decrease generally with an increase in relative amplitude. F will decrease initially and then increase with increasing inlet subcooling. The influence curves of mean mass flow rate on F will be almost the same when the period is shorter than 5.0 s or longer than 15 s. The influence of L/D will be negligible if L/D>200. It is found that the minimum number of neurons in the hidden layer is a product of the number of neurons in the input layer and in the output layer

2003-01-01

282

Biofuels barometer; Barometre biocarburants  

Energy Technology Data Exchange (ETDEWEB)

In 2010 bio-fuel continued to gnaw away at petrol and diesel consumption in the European Union (EU). However its pace backs the assertion that bio-fuel consumption growth in EU slackened off in 2010. In the transport sector, it increased by only 1.7 Mtoe compared to 2.7 Mtoe in 2009. The final total bio-fuel consumption figure for 2010 should hover at around 13.9 Mtoe that can be broken down into 10.7 Mtoe for bio-diesel, 2.9 Mtoe for bio-ethanol and 0.3 Mtoe for others. Germany leads the pack for the consumption of bio-fuels and for the production of bio-diesel followed by France and Spain

Anon.

2011-07-15

283

Photovoltaic barometer; Barometre photovoltaique  

Energy Technology Data Exchange (ETDEWEB)

spain and Germany set the pace for the world photovoltaic market in 2008, which grew to more than twice its 2007 size. The European Union continued to drive photocell installation with an additional 4 592.3 MWp in 2008, or 151.6% growth over 2007. However, European growth prospects for the photovoltaic market in 2009 are being dampened by the global financial crisis and the scheduled slow-down of the Spanish market. (author)

Anon

2009-04-15

284

Photovoltaic barometer; Barometre photovoltaique  

Energy Technology Data Exchange (ETDEWEB)

The photovoltaic sector is continuing on track, just as the extent of solar energy's electricity-generating potential is dawning on the public mind. The annual global installation figure was up more than twofold in 2010 (rising from just short of 7000 MWp in 2009). It leapt to over 16000 MWp, bringing worldwide installed photovoltaic capacity close to 38000 MWp. The photovoltaic power generated in the European Union at the end of 2010 reached 22.5 TWh which means an additional capacity of 13023 MWp during 2010. Concerning the cumulated installed capacity, Germany and Spain rank first and second in the European Union with respectively 17370 MWp and 3808 MWp

Anon.

2011-04-15

285

Influence of operating conditions and ammonia injection on the emission of nitrogenous gases from pressurized fluidized bed combustion of coal  

International Nuclear Information System (INIS)

A coal-fired Pressurized Fluidized Bed Combustor at the Delft University of Technology is being used to study fuel conversion and related environmental aspects. This 'semi-technical' scale combustion test rig with an operating pressure up to 10 bar and a maximum thermal capacity of 1,6 MW is being used to investigate environmental aspects of coal combustion like limiting fly ash concentrations in the flue gas by high temperature/high pressure gas cleaning techniques and the influence of fuel related and operation-dependent parameters on the formation and reduction of noxious oxides, in particular nitrogenous species. The fuels investigated so far were anthracites, bituminous coals and brown coals. The influence of different operating parameters such as coal type, freeboard temperature, pressure and excess air on N2O emissions has been investigated and the effect of Selective Non-Catalytic Reduction (SNCR) using ammonia injection in the exhaust of the combustor on the emission of NO, NO2, CO, NH3 and N2O was determined for a number of mol ratios, injection locations and temperatures using 2 British and 2 German coals. Gas concentrations have been determined at different locations of the PFBC test rig, among others in tile freeboard and downstream of the first cyclone using 'conventional' gas analysis instruments, a Gas Chromatograph (GC) and a Fourier Transform InfraRed (FTIR) spectrometer. The paper describes the PFBC test rig, the ammonia injection system, the sampling systems and the GC and FTIR gas analysis systems. Practical experience gained so far with these measuring systems will be presented and results of the measurements will be given and discussed

1993-01-01

286

Neural reflex regulation of arterial pressure in pathophysiological conditions: interplay among the baroreflex, the cardiopulmonary reflexes and the chemoreflex  

Scientific Electronic Library Online (English)

Full Text Available Abstract in english The maintenance of arterial pressure at levels adequate to perfuse the tissues is a basic requirement for the constancy of the internal environment and survival. The objective of the present review was to provide information about the basic reflex mechanisms that are responsible for the moment-to-moment regulation of the cardiovascular system. We demonstrate that this control is largely provided by the action of arterial and non-arterial reflexes that detect and correct c (more) hanges in arterial pressure (baroreflex), blood volume or chemical composition (mechano- and chemosensitive cardiopulmonary reflexes), and changes in blood-gas composition (chemoreceptor reflex). The importance of the integration of these cardiovascular reflexes is well understood and it is clear that processing mainly occurs in the nucleus tractus solitarii, although the mechanism is poorly understood. There are several indications that the interactions of baroreflex, chemoreflex and Bezold-Jarisch reflex inputs, and the central nervous system control the activity of autonomic preganglionic neurons through parallel afferent and efferent pathways to achieve cardiovascular homeostasis. It is surprising that so little appears in the literature about the integration of these neural reflexes in cardiovascular function. Thus, our purpose was to review the interplay between peripheral neural reflex mechanisms of arterial blood pressure and blood volume regulation in physiological and pathophysiological states. Special emphasis is placed on the experimental model of arterial hypertension induced by N-nitro-L-arginine methyl ester (L-NAME) in which the interplay of these three reflexes is demonstrable

Vasquez, E.C.; Meyrelles, S.S.; Mauad, H.; Cabral, A.M.

1997-04-01

287

Macroscopic electric field and osmotic pressure in ultracentrifugal sedimentation-diffusion equilibria of charged colloids  

International Nuclear Information System (INIS)

Sedimentation-diffusion (SD) equilibria from analytical ultracentrifugation of well-characterized charged silica spheres in ethanol deviate strongly from a barometric profile and demonstrate the existence and substantial effects of a recently predicted internal macroscopic electric field (van Roij 2003 J. Phys.: Condens. Matter 15 S3569). Experimental SD-profiles yield the gradient of the electrostatic potential energy of the colloids, which clearly manifests an almost homogeneous macroscopic electric field. Electrochemical Donnan potential measurements confirm a difference in electrical potential between the top and bottom of the profiles. A 'non-barometric' limiting law derived from electroneutrality explains the trends in the SD-profiles quite well. Our analysis of osmotic pressures (obtained from integrating SD-profiles) beyond this simple law includes, among other things, colloid-ion attractions and extra volume terms in the free energy.

2005-04-20

288

Conditions for Tunnel Formation in LPCVD (Low Pressure Chemical Vapor Deposition) Tungsten Films on Single Crystal Silicon.  

Science.gov (United States)

The occurrence of microscopic filamentary voids (''tunnels'' or ''worm holes'') in silicon beneath chemically vapor deposited tungsten films has been investigated over a wide range of wafer and deposition conditions. The effect of dopant type, concentrati...

M. E. Tracy R. S. Blewer T. J. Headley

1987-01-01

289

Unique rod lens/video system designed to observe flow conditions in emergency core coolant loops of pressurized water reactors  

International Nuclear Information System (INIS)

[en] Techniques and equipment are described which are used for video recordings of the single- and two-phase fluid flow tests conducted with the PKL Spool Piece Measurement System designed by Lawrence Livermore Laboratory and EG and G Inc. The instrumented spool piece provides valuable information on what would happen in pressurized water reactor emergency coolant loops should an accident or rupture result in loss of fluid. The complete closed-circuit television video system, including rod lens, light supply, and associated spool mounting fixtures, is discussed in detail. Photographic examples of test flows taken during actual spool piece system operation are shown

1979-01-01

290

Synthesis and optical property of large-scale centimetres-long silicon carbide nanowires by catalyst-free CVD route under superatmospheric pressure conditions.  

UK PubMed Central (United Kingdom)

Large-scale centimetres-long single-crystal ?-SiC nanowires have been prepared using CH(4) as the carbon source and SiO or the mixture of Si and SiO(2) as the silicon source by a simple catalyst-free CVD route under superatmospheric pressure conditions. The nanowries grown on ceramic boat or corundum substrates, with lengths of several centimetres and the average diameters of around 40 nm, were composed of single-crystal ?-SiC core along the [111] direction and amorphous SiO(2) shell of about 1-30 nm thick depending on the growth position along the flowing direction of the carrier gas. The total gas pressure is an important factor for the synthesis of the large-scale centimetres-long ?-SiC nanowires, which can easily adjust the pressure of the vapors to supersaturation condition. The growth of the nanowires was governed by the Vapor-Solid mechanism. The ?-SiC nanowires showed an intense blue light emission at room temperature.

Lin L

2011-04-01

291

Synthesis and optical property of large-scale centimetres-long silicon carbide nanowires by catalyst-free CVD route under superatmospheric pressure conditions.  

Science.gov (United States)

Large-scale centimetres-long single-crystal ?-SiC nanowires have been prepared using CH(4) as the carbon source and SiO or the mixture of Si and SiO(2) as the silicon source by a simple catalyst-free CVD route under superatmospheric pressure conditions. The nanowries grown on ceramic boat or corundum substrates, with lengths of several centimetres and the average diameters of around 40 nm, were composed of single-crystal ?-SiC core along the [111] direction and amorphous SiO(2) shell of about 1-30 nm thick depending on the growth position along the flowing direction of the carrier gas. The total gas pressure is an important factor for the synthesis of the large-scale centimetres-long ?-SiC nanowires, which can easily adjust the pressure of the vapors to supersaturation condition. The growth of the nanowires was governed by the Vapor-Solid mechanism. The ?-SiC nanowires showed an intense blue light emission at room temperature. PMID:21305091

Lin, Liangwu

2011-02-08

292

In situ Phase Transition Study of Nano- and Coarse-Grained TiO2 Under High Pressure/Temperature Conditions  

Energy Technology Data Exchange (ETDEWEB)

A comparative phase transition study of nanocrystalline and micro-TiO2 has been conducted under high pressure-temperature (P-T) conditions using energy-dispersive synchrotron x-ray diffraction (XRD). Our study reveals that on compression at room temperature, the micro-tetragonal anatase-type TiO2 started to transform to the orthorhombic columbite-type TiO2 near 1.6 GPa. In contrast, we did not observe this phase transition in nano-anatase at pressures of up to 8.5 GPa. At 8.5 GPa, by applying moderate heat, both samples were transformed completely to columbite-type TiO2 almost simultaneously, indicating that heat treatment could significantly expedite this phase transition. These columbite-type TiO2 phases were quenchable because after cooling them to room temperature and decompressing them to 2.0 GPa, the XRD patterns displayed no changes in comparison with those collected at 8.6 GPa and 1270 K. At 2 GPa, we heated the specimens again, and the rutile-type TiO2 started to emerge around 970 K. This phase was also quenchable after cooling and releasing pressure to ambient conditions. The grain size effects on the phase transition were discussed based on the kinetics mechanism. This study should be of considerable interest to the fields of materials science and condensed matter.

Wang,Y.; Zhao, Y.; Zhang, J.; Xu, h.; Wang, L.; Luo, S.; Daemen, L.

2008-01-01

293

Si isotope fractionation between Si-poor metal and silicate melt at pressure–temperature conditions relevant to metal segregation in small planetary bodies  

Science.gov (United States)

Experimental investigations of Si isotope fractionation between Si-bearing metal alloy and silicate phases have to date been limited to high pressure (1–7GPa) and high temperature (1800–2200°C) conditions at highly reducing conditions, to optimize applicability of results to early core formation processes in the Earth. Here, we assess the extent and mechanism of Si isotopic fractionation at conditions relevant to metal segregation in small (km-scale) planetary bodies, using samples obtained from an industrial-scale blast furnace of Tata Steel (IJmuiden, the Netherlands).During the low-pressure, high-temperature process of steelmaking inhomogeneous blast furnace burden consisting of pre- and untreated iron ore, iron silicates and coke is reduced to oxygen fugacities near the C–CO buffer, resulting in the segregation of a metal phase containing only ?0.3wt% Si. Seven sample sets, each comprising a metal alloy and a silicate slag, were taken during tapping of the blast furnace at tapping temperatures between 1400°C and 1600°C. We find large isotopic mass fractionation between metal and silicate, with ?30Sisilicate–metal varying between 0.7‰ and 1.6‰, values that are as high as previously obtained in high-pressure, highly reduced experiments. A model for metal–silicate Si isotope fractionation in blast furnaces can explain both the sense and magnitude of fractionation, if the presence of SiO-bearing vapour is explicitly taken into account. Our data indicate that significant Si isotope fractionation can occur between metal and silicate at low-pressure, high-temperature and only mildly reducing conditions for which Si solubility in molten Fe-rich metal is low. This suggests an important role for SiO at low confining pressures. Our data can be applied to models of aubrite meteorite formation through high-temperature differentiation of an enstatite chondrite parent body. Our calculations suggest a far larger degree of rehomogenisation during differentiation than previously thought on the basis of metal–silicate Si isotopic fractionation measured in natural meteorites that re-equilibrated at low temperature.

Kempl, J.; Vroon, P. Z.; Zinngrebe, E.; van Westrenen, W.

2013-04-01

294

Possibility of regulating the properties of plugging fluids and stone by pheonols under conditions of increased temperatures and pressures  

Energy Technology Data Exchange (ETDEWEB)

Results are presented from studies on the effect of phenols-hydroquinone, methanol, amidol and adurol on the rate of setting of fluids made of Portland cement of the Sterlitamakskiy plant, strengthen permeability of the obtained stone with increased pressures and temperatures. The inhibiting additives were selected according to the sign of greatest efficiency of the effect during standard test at 75/sup 0/C. The fluids were prepared with water-cement ratio of 0.5-0.55, and the reagents were added to the mixing water. With the introduction of phenol additives, the periods for setting of the cement solutions with increased temperatures and pressures are satisfactory for the practice of cementing oil and gas wells. The examined reagents are not scarce and are developed on industrial scales. The technology of using phenols on the whole is common for the entire class and has been mastered in the example of widely known reagents: PFLKh and others. Technical economic evaluation of the efficiency of use must be oriented on the cost of the polyphenols of the type syntans, pich phenols and other polyphenols which include oxidized lignin and sulfite-yeast mash (SYM).

Mamulov, F.G.; Loskutov, D.A.

1980-01-01

295

High temperature steam oxidation study on Zr-2.5%Nb pressure tube under simulated LOCA condition  

Science.gov (United States)

Study of high temperature steam oxidation kinetics and microstructural evolution during the oxidation was carried out on the coupons of Zr-2.5%Nb pressure tube material of Indian Pressurized Heavy Water Reactors (PHWRs) in the temperature range 500-1050 °C. The oxidation kinetics derived from the weight gain measurements showed a parabolic rate law with the parabolic rate constant KP expressed as an Arrhenius equation KP = 10.12 × 108 × exp(?18664/T). 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 °C and 1050 °C.

Banerjee, Suparna; Sawarn, Tapan K.; Alur, V. D.; Rath, B. N.; Kaity, Santu; Pandit, K. M.; Anantharaman, S.; Sah, D. N.

2013-08-01

296

Experience with monitoring of corrosion and failure conditions in pressurized-water reactor loop using electrochemical methods  

International Nuclear Information System (INIS)

[en] An experimental program of electrochemical measurement was implemented using the pressurized water loop of the WWR-S research reactor with the aim of verifying the suitability of the said methods for continuous surveillance of the water regimen in the primary circuits of WWER reactors. Four TIV probes were used for the electrochemical measurements. A probe with a gold redox electrode was placed in the active channel of the loop, one probe with an electrode of low-carbon non-alloyed steel and one probe with an electrode of zirconium alloy were placed in the measuring circuit outside the reactor. The fourth probe was used as a reference. Briefly presented are the results of the experiments which proved that electrochemical measurement in the reactor core is technically feasible. The probes provide a great number of useful data even when only partial time courses of potential in non-polarized state are computer processed. (Z.M.). 3 refs

1987-01-01

297

Dependence of electronic structure of cerium in Ce1-xScx on ambient conditions (composition, temperature, pressure)  

International Nuclear Information System (INIS)

Dependence of population density of Ce 4f-shell (of m valence) in Ce1-xScx on composition, temperature and pressure (x = 0.02 - 0.99, T 300 and 77 K, P ? 0 - 1.4 GPa) is studied using X-ray line shifting technique. Increase of Ce valence is detected to occur at isomorphous phase transition in Ce1-xScx (Tt ? 150 K or Pt ? 0.6 GPa). The value of the effect depends on the way transition is been initiated and decreases at approximation to xcr ? 0.18 critical concentration. Ce3+ ? Ce4+ new electron transition is detected at x ? 0.8, T = 300 K. 12 refs., 4 figs.

1995-01-01

298

Rapid ascent conditions of diamond-bearing kimberlitic magmas: Findings from high pressure–temperature experiments and finite element modeling  

Science.gov (United States)

This paper deals with the problem of rapid ascent mechanism of kimberlite magmas with a multi-directional approach: 1) the kinetics of diamond–graphite transition; 2) settling velocity of diamond phenocrysts in magmas and 3) formation of ruptures required for magma ascent with a high speed. Based on the diamond–graphite transition, we present an estimate of the ascent rates from high pressure and temperature experiments using Walker-type multi-anvil apparatus. The experiments were conducted with diamond, placed within a synthetic kimberlitic assemblage, keeping an initial pressure and temperature of 6 GPa and 1350 °C, respectively. It was observed that the volume fraction of diamond to graphite conversion strongly depended on the ascent rates. Using electrical resistivity and X-ray diffraction studies, we measured the degree of graphitization as a function of the ascent rate (u). For u graphitization (conversion > 90%), whereas it remained nearly intact (conversion 10 m/s. Our theoretical calculations of the settling velocity of mantle xenoliths again confirm that diamond can exist when u > 3 m/s. We performed numerical experiments with finite element (visco-elastic) models to analyze the dynamics of tensile failure at the tip of magma pools, leading to dilatational vertical fractures for magma transport. Considering the tensile strength of mantle in the order of 0.5 kb, our models show this failure process as a function of the critical shape (Ar: ratio of vertical and horizontal dimensions) and density contrast (??) of magma pools. The critical ?? is estimated nearly 200 kg/m3 when Ar is very large (> 4).

Baruah, Amiya; Gupta, Alok K.; Mandal, Nibir; Singh, Rishi Narain

2013-05-01

299

Urban tree species show the same hydraulic response to vapor pressure deficit across varying tree size and environmental conditions.  

UK PubMed Central (United Kingdom)

BACKGROUND: The functional convergence of tree transpiration has rarely been tested for tree species growing under urban conditions even though it is of significance to elucidate the relationship between functional convergence and species differences of urban trees for establishing sustainable urban forests in the context of forest water relations. METHODOLOGY/PRINCIPAL FINDINGS: We measured sap flux of four urban tree species including Cedrus deodara, Zelkova schneideriana, Euonymus bungeanus and Metasequoia glyptostroboides in an urban park by using thermal dissipation probes (TDP). The concurrent microclimate conditions and soil moisture content were also measured. Our objectives were to examine 1) the influence of tree species and size on transpiration, and 2) the hydraulic control of urban trees under different environmental conditions over the transpiration in response to VPD as represented by canopy conductance. The results showed that the functional convergence between tree diameter at breast height (DBH) and tree canopy transpiration amount (E(c)) was not reliable to predict stand transpiration and there were species differences within same DBH class. Species differed in transpiration patterns to seasonal weather progression and soil water stress as a result of varied sensitivity to water availability. Species differences were also found in their potential maximum transpiration rate and reaction to light. However, a same theoretical hydraulic relationship between G(c) at VPD = 1 kPa (G(cref)) and the G(c) sensitivity to VPD (-dG(c)/dlnVPD) across studied species as well as under contrasting soil water and R(s) conditions in the urban area. CONCLUSIONS/SIGNIFICANCE: We concluded that urban trees show the same hydraulic regulation over response to VPD across varying tree size and environmental conditions and thus tree transpiration could be predicted with appropriate assessment of G(cref).

Chen L; Zhang Z; Ewers BE

2012-01-01

300

A comparison of experimental and numerical studies performed on a low-pressure turbine blade cascade at high-speed conditions, low reynolds numbers and various turbulence intensities  

Science.gov (United States)

This paper focuses on a comparison of experimental and numerical investigations performed on a low-pressure mid-loaded turbine blade at operating conditions comprised of a wide range of Mach numbers (from 0.5-1.1), Reynolds numbers (from 0.4e+5-3.0e+5), flow incidence (-15-15 degrees) and three levels of free-stream turbulence intensities (2, 5 and 10%). The experimental part of the work was performed in a high-speed linear cascade wind tunnel. The increased levels of turbulence were achieved by a passive grid placed at the cascade inlet. A two-dimensional flow field at the center of the blade was traversed pitch-wise upstream and downstream the cascade by means of a five-hole probe and a needle pressure probe, respectively. The blade loading was measured using the surface pressure taps evenly deployed at the blade mid-span along the suction and the pressure side. The inlet turbulence was investigated using the constant temperature anemometer technique with a dual sensor probe. Experimentally evaluated values of turbulent kinetic energy and its dissipation rate were then used as inputs for the numerical simulations. An in-house code based on a system of the Favre-averaged Navier-Stokes equation closed by a two-equation k-? turbulence model was adopted for the predictions. The code utilizes an algebraic model of bypass transition valid both for attached as for separated flows taking in account the effect of free-stream turbulence and pressure gradient. The resulting comparison was carried out in terms of the kinetic energy loss coefficient, distributions of downstream wakes and blade velocity. Additionally a flow visualization was performed by means of the Schlieren technique in order to provide a further understanding of the studied phenomena. A few selected cases with a particular interest in the attached and separated flow transition are compared and discussed.

Michalek, Jan; Straka, Petr

2013-10-01

 
 
 
 
301

High-temperature, high-pressure in situ reaction monitoring of heterogeneous catalytic processes under supercritical conditions by CIR-FTIR  

Energy Technology Data Exchange (ETDEWEB)

An in situ cylindrical internal reflection infrared technique (CIR-FTIR) was developed, which permits the real time analysis of supercritical fluids and heterogeneous catalytic processes at temperatures up to 500{degrees}C and 1000 psi pressure (1 psi = 6850 Pa). High-quality spectra were obtained at both high temperatures and high pressures under in situ reaction conditions. The molecular thermal transitions that a hydrocarbon undergoes in the supercritical regime, the properties of a hydrocarbon within the pores of a zeolite, and the interactions of a hydrocarbon with the active acid sites of the zeolite during catalytic cracking were studied by this technique. The results showed that the stretching frequency of the C-H bonds was altered in supercritical heptane, probably due to intermolecular hydrogen bonding. IR data also demonstrated an increased heptane concentration within the micropores of a commercial catalytic cracking, Y-type zeolite (promoted Octacat) during catalytic cracking at supercritical conditions. This method also enabled a determination of the types of hydroxyl groups contained within the zeolite (i.e., Bronsted acid sites in the supercages and sodalite cages, terminal silanols, and superacid sites) and their relative concentration changes with increasing temperature. Finally, the alteration of the concentrations of the various catalytic active sites together with the appearance of new bands was also monitored in situ during catalytic cracking of heptane at 475{degrees}C under subcritical and supercritical conditions. 38 refs., 11 figs.

Dardas, Z.; Suer, M.G.; Ma, Yi.H.; Moser, W.R. [Worcester Polytechnic Institute, Worcester, MA (United States)

1996-03-01

302

Using Atmospheric Pressure Tendency to Optimise Battery Charging in Off-Grid Hybrid Wind-Diesel Systems for Telecoms  

Directory of Open Access Journals (Sweden)

Full Text Available Off grid telecom base stations in developing nations are powered by diesel generators. They are typically oversized and run at a fraction of their rated load for most of their operating lifetime. Running generators at partial load is inefficient and, over time, physically damages the engine. A hybrid configuration uses a battery bank, which powers the telecoms’ load for a portion of the time. The generator only operates when the battery bank needs to be charged. Adding a wind turbine further reduces the generator run hours and saves fuel. The generator is oblivious to the current wind conditions, which leads to simultaneous generator-wind power production. As the batteries become charged by the generator, the wind turbine controller is forced to dump surplus power as heat through a resistive load. This paper details how the relationship between barometric pressure and wind speed can be used to add intelligence to the battery charger. A Simulink model of the system is developed to test the different battery charging configurations. This paper demonstrates that if the battery charger is aware of upcoming wind conditions, it will provide modest fuel savings and reduce generator run hours in small-scale hybrid energy systems.

Shane Phelan; Paula Meehan; Stephen Daniels

2013-01-01

303

Conditions for tunnel formation in LPCVD (low pressure chemical vapor deposition) tungsten films on single crystal silicon  

Energy Technology Data Exchange (ETDEWEB)

The occurrence of microscopic filamentary voids (''tunnels'' or ''worm holes'') in silicon beneath chemically vapor deposited tungsten films has been investigated over a wide range of wafer and deposition conditions. The effect of dopant type, concentration, and infusion method, dry and wet etch pretreatment, deposition temperature, reaction sequence, deposition time and phase of the tungsten film have all been studied. Three deposition techniques (two selective and one non-selective) have been identified which avoid tunnel formation for the wafer conditions considered in this investigation, thus providing an operational regime in which tunnel formation is not an issue. 14 refs., 10 figs., 1 tab.

Blewer, R.S.; Headley, T.J.; Tracy, M.E.

1987-01-01

304

The role of water chemistry for environmentally assisted cracking in low-alloy reactor pressure vessel and piping steels under boiling reactor conditions  

International Nuclear Information System (INIS)

[en] The environmentally assisted initiation and propagation of cracks in structural materials is one of the most important degradation and ageing mechanisms in light water reactors (LWR) and may seriously affect plant availability and economics. In the first part of this paper a short general introduction on environmentally assisted cracking (EAC) and its significance for LWR is given. Then the important role of water chemistry control in reducing the EAC risk in LWR is illustrated by current research results about the effect of chloride transients and hydrogen water chemistry on the EAC crack growth behaviour of low-alloy reactor pressure vessel and piping steels under boiling water reactor conditions. (author)

2005-01-01

305

Cooldown to residual heat removal entry conditions using atmospheric dump valves and auxiliary pressurizer spray following a loss-of-offsite power at Calvert Cliffs, Unit 1  

International Nuclear Information System (INIS)

[en] An investigation of cooldown using atmospheric dump valves (ADVs) and auxiliary pressurizer spray (APS) following loss-of-offsite power at Calvert Cliffs-1 showed residual heat removal entry conditions could not be reached with the plant ADVs alone. Use of APS with the plant ADVs enhanced depressurization, but still provided insufficient cooldown. Effective cooldown and depressurization was shown to occur when rated steady state flow through the ADVs was increased by a factor of four. 6 refs., 30 figs., 2 tabs

1984-01-01

306

Pressure Fluctuations on the Bed of Surge Tank at the H.P. Zimapan, Hgo., with Different Arrangements Studied on Hydraulic Model, with the Lowest Operation Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, the pressure fluctuations of the surge tank in the Zimapan Hydroelectric Project are compared in a hydraulic model. The shaft is located lateral, over the conduction tunnel and in the simple form (permitting the tunnel entering the shaft), with and without orifice plates taking into account the demand and supply condition of energy with the minimum level of water of the conduction. It was determined the hydraulic efficiency and it was found that it was the best constructive option.

H. Marengo–Mogollón; F.J. Ochoa–Álvarez; C. Cortés–Cortés

2009-01-01

307

High temperature steam oxidation study on Zr-2.5%Nb pressure tube under simulated LOCA condition  

International Nuclear Information System (INIS)

The kinetic rate equation for steam oxidation reaction of Zr-2 .5%Nb pressure tube can be used in the assessment of hydrogen generation during postulated loss of coolant accident or LOCA in a nuclear reactor. Experiments were carried out in the temperature range from 500 to 1050 deg C for different time periods. Heating was carried out at a rate of 30 to 40 deg C/sec. Isothermal heating was followed by air cooling. The oxidation kinetics derived from the mass gain showed a parabolic rate law having 'n' of the equation, ?W = ktn, in the range from 0.53 to 0.6. The experimentally measured parabolic rate constants have been expressed as Arrhenius type of function. The micro structural observation showed the presence of an oxide layer, an underlying coarse oxygen stabilized ?-Zr(O) platelets interspersed with prior ?-Zr, a transformed ?-Zr phase and hydride precipitates for the specimens heated above the a? -Zr + ?-Zr/?-Zr transition temperature. Specimens heated below the transition temperature but above the monotectoid temperature revealed a microstructure containing ?-Zr and ?-Zr and hydride precipitates. As fabricated microstructure with no significant modification was observed in case of coupons heated below the monotectoid temperature. (author)

2011-01-01

308

A hybrid Markov chain Monte Carlo method for generating permeability fields conditioned to multiwell pressure data and prior information  

Energy Technology Data Exchange (ETDEWEB)

In order to properly evaluate the uncertainty in reservoir performance predictions, it is necessary to construct and sample the a posteriori probability density functions for the rock property fields. In this work, the a posteriori probability density function is constructed based on prior means and variograms (covariance function) for log-permeability and multiwell pressure data. Within the context of sampling the probability density function, we argue that the notion of equally probable realizations is the wrong paradigm for reservoir characterization. If the simulation of Gaussian random fields with a known variogram is the objective, it is shown that the variogram should not be incorporated directly into the objective function if simulated annealing is applied either to sample the a posteriori probability density function or to estimate a global minimum of the associated objective function. It is shown that the hybrid Markov chain Monte Carlo method provides a way to explore more fully the set of plausible log-permeability fields and does not suffer from the high rejection rates of more standard Markov chain Monte Carlo methods.

Bonet-Cunha, L.; Oliver, D.S.; Redner, R.A. [and others

1996-12-31

309

High temperature post-irradiation performance of spent pressurized-water-reactor fuel rods under dry-storage conditions  

Energy Technology Data Exchange (ETDEWEB)

Post-irradiation studies on failure mechanisms of well characterized PWR rods were conducted for up to a year at 482, 510 and 571/sup 0/C in unlimited air and inert gas atmospheres. No cladding breaches occurred even though the tests operated many orders of magnitude longer in time than the lifetime predicted by Blackburn's analyses. The extended lifetime is due to significant creep strain of the Zircaloy cladding which decreases the internal rod pressures. The cladding creep also contributes to radial cracks, through the external oxide and internal FCCI layers, which propagated into and arrested in an oxygen stabilized ..cap alpha..-Zircaloy layer. There were no signs of either additional cladding hydriding, stress-corrosion cracking or fuel pellet degradation. Using the Larson-Miller formulization, a conservative maximum storage temperature of 400/sup 0/C is recommended to ensure a 1000-year cladding lifetime. This accounts for crack propagation and assumes annealing of the irradiation-hardened cladding.

Einziger, R.E.; Atkin, S.D.; Stellrecht, D.E.; Pasupathi, V.

1981-06-01

310

Monitoring of prestressed concrete pressure vessels. II. performance of selected concrete embedment strain meters under normal and extreme environmental conditions  

International Nuclear Information System (INIS)

Unique types of instrumentation are used in prestressed concrete pressure vessels (PCPVs) to measure strains, stresses, deflections, prestressing forces, moisture content, temperatures, and possibly cracking. Their primary purpose is to monitor these complex structures throughout their 20- to 30-year operating lifetime in order to provide continuing assurance of their reliability and safety. Numerous concrete embedment instrumentation systems are available commercially. Since this instrumentation is important in providing continuing assurance of satisfactory performance of PCPVs, the information provided must be reliable. Therefore, laboratory studies were conducted to evaluate the reliability of these commercially available instrumentation systems. This report, the second in a series related to instrumentation embedded in concrete, presents performance-reliability data for 13 types of selected concrete embedment strain meters which were subjected to a variety of loading environments, including unloaded, thermally loaded, simulated PCPV, and extreme environments. Although only a limited number of meters of each type were tested in any one test series, the composite results of the investigation indicate that the majority of these meters would not be able to provide reliable data throughout the 20- to 30-year anticipated operating life of a PCPV. Specific conclusions drawn from the study are: (1) Improved corrosion-resistant materials and sealing techniques should be developed for meters that are to be used in PCPV environments. (2) There is a need for the development of meters that are capable of surviving in concretes where temperatures in excess of 660C are present for extended periods of time. (3) Research should be conducted on other measurement techniques, such as inductance, capacitance, and fluidics

1978-01-01

311

Preparation and Formation Mechanism of New PdHx-Pd/C Catalyst through Hydrazine-reducing Method under Atmospheric Pressure and H2-free Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available PdHx is an important reactive species for the Pd/C catalyst. Without H2, it can not exist stably at room temperature. This species is usually prepared through reaction of Pd with H2 under certain pressure. PdHx-Pd/C catalyst was prepared through hydrazine-reducing method under atmospheric pressure and H2-free conditions. The microstructure, morphology and chemical state of PdHx and Pd particles were investigated by XRD, TEM and XPS characterization methods. The formation mechanism of PdHx particles in the hydrazine-reducing method was proposed. Experimental results show that the average particle size of PdHx is 3.9 nm, and the d spacing of PdHx(111) is slightly larger than that of Pd(111). The PdHx particles derive from the reduction process of PdO by hydrazine. Their particle size is closely related to the particle size and structural imperfection of PdO. The PdHx-Pd/C catalyst demonstrates better catalytic performance than the conventional Pd/C catalyst in the amination reaction to produce 2, 6-dimethylaniline under H2-free condition.

HUAN Chang-Yong, MA Lei, L- De-Yi, ZHENG Yi-Fan, JI Lai-Jun, LI Xiao-Nian

2013-01-01

312

Heat transfer for flow-boiling of water and Critical Heat Flux in half-heated round tube under low-pressure condition  

International Nuclear Information System (INIS)

[en] Heat transfer for flow-boiling of water and Critical Heat Flux (CHF) experiments in the half-circumferentially heated round tube under low pressure condition were carried out. In order to clarify the flow patterns in the heated section the experiments in the round tube under the same condition were also carried out, and their results were compared. The experiments were conducted with atmospheric-pressure water in the test sections with inner diameter D=6 mm, heated length L=360 mm, inlet water subcooling ?Tin=80 K and mass velocity G from 0 to 2000 kg/(m2·s) for the half-circumferentially heated tube and from 0 to 7000 kg/(m2·s) for the full-circumferentially heated tube. The experiment data demonstrated that the wall temperature near the outlet of the half-circumferentially heated tube continued almost the same until CHF. And it was found that the burnout occurred when the flow regime changed from churn flow to annular flow, and the liquid film on the heated wall dried out nevertheless the liquid film on the unheated wall remained. (author)

2000-01-01

313

On the existence of negative excess isotherms for argon adsorption on graphite surfaces and in graphitic pores under supercritical conditions at pressures up to 10,000 atm.  

UK PubMed Central (United Kingdom)

In this paper, we consider in detail the computer simulation of argon adsorption on a graphite surface and inside graphitic slit pores under supercritical conditions. Experimental results in the literature for graphitic adsorbents show that excess isotherms pass through a maximum and then become negative at high pressures (even for adsorption on open surfaces) when a helium void volume is used in the calculation of the excess amount. Here we show that, by using the appropriate accessible volume (which is smaller than the helium void volume), the excess isotherms still have a maximum but are always positive. The existence and the magnitude of this maximum is because the rate of change of the adsorbed density is equal to that of the bulk gas, which has a large change in bulk gas density for a small variation in pressure for temperatures not far above the critical point. However for temperatures far above T(c), this change in the bulk gas density is no longer significant and the maximum in the surface excess density becomes less pronounced and even disappears at high enough temperatures. The positivity of the adsorption excess persists for all pressures up to 10,000 atm for adsorption on surfaces and in slit pores of all sizes. For adsorption on a surface, the surface excess density eventually reaches a plateau at high pressures as expected, because the change in the adsorbed phase is comparable to that of the bulk gas. Positive excess lends support to our physical argument that the adsorbed phase is denser than the bulk gas, and this is logical as the forces exerted by the pore walls should aid to the compression of the adsorbed phase.

Do DD; Do HD; Fan C; Nicholson D

2010-04-01

314

Microbial Community Dynamics in Uranium Contaminated Subsurface Sediments under Biostimulated Conditions with High Nitrate and Nickel Pressure  

Energy Technology Data Exchange (ETDEWEB)

The subsurface at the Oak Ridge Field Research Center represents an extreme and diverse geochemical environment that places different stresses on the endogenous microbial communities, including low pH, elevated nitrate concentrations, and the occurrence of heavy metals and radionuclides, including hexavalent uranium [U(VI)]. The in situ immobilization of U(VI) in the aquifer can be achieved through microbial reduction to relatively insoluble U(IV). However, a high redox potential due to the presence of nitrate and the toxicity of heavy metals will impede this process. Our aim is to test biostimulation of the endogenous microbial communities to improve nitrate reduction and subsequent U(VI) reduction under conditions of elevated heavy metals.

Moreels,D.; Crosson, G.; Garafola, C.; Monteleone, D.; Taghavi, S.; Fitts, J.; van der Lelie, D.

2008-01-01

315

Application of Structural Reliability to support deterministic integrity analyses of Reactor Pressure Vessel subjected to transient conditions  

International Nuclear Information System (INIS)

The benefits of a probabilistic approach compared to the more conventional deterministic method are the clear treatment of uncertainties and the possibility to perform sensitivity studies from which it is possible to identify and quantify the effect of key factors and mitigative actions. They thus provide information to support optimal decisions related to in-service inspection planning and maintenance strategies, lifetime prediction or reassessment, integrity assessment of degradation and definition of in-service acceptability criteria. Apart from a clear modelling of fracture mechanics concept and detailed knowledge of the input data, application of this type of analysis requires a tool capable of making a reasonably easy numerical estimate of the probability of failure. For this purpose a benchmark problem has been performed by EDF, Framatome and CEA to clarify the difficulties and differences in numerical processes. In this study, general state-of-the-art structural reliability methods known as First and Second Order Reliability Methods (FORM/SORM) along with Monte Carlo Simulation and Importance Sampling were tested on a rather complex mechanical model. This model concerns the risk of brittle rupture of a PWR vessel subjected to transient conditions. The objective of this paper is to present the results of this benchmark exercises used also to validate the probabilistic model and its input random parameters. By performing sensitivity studies and analyzing the coordinate value of the design point (most probable failure point given by FORM method), the most influential parameters have been identified on this case study. Special data base have therefore been collected and sophisticated statistical treatment performed to update more precisely the probability distribution of these parameters (the fracture toughness transition curve, the irradiation-induced shift prediction, the flaw size, the reliability of NDE...). Results from these probabilistic analyses can now be used to calibrate explicit safety factors in relation to implicit safety margins, and define in-service acceptability criteria. The 'deterministic' approach is then treated as a special case of the more detailed 'probabilistic' formulation of the problem

1996-03-01

316

Analysis of fuel rod behaviour within a rod bundle of a pressurized water reactor under the conditions of a loss of coolant accident (LOCA) using probabilistic methodology  

International Nuclear Information System (INIS)

[en] The assessment of fuel rod behaviour under PWR LOCA conditions aims at the evaluation of the peak cladding temperatures and the (final) maximum circumferential cladding strains. Moreover, the estimation of the amount of possible coolant channel blockages within a rod bundle is of special interest, as large coplanar clad strains of adjacent rods may result in strong local reductions of coolant channel areas. Coolant channel blockages of large radial extent may impair the long-term coolability of the corresponding rods. A model has been developed to describe these accident consequences using probabilistic methodology. This model is applied to study the behaviour of fuel rods under accident conditions following the double-ended pipe rupture between collant pump and pressure vessel in the primary system of a 1300 MW(el)-PWR. Specifically a rod bundle is considered consisting of 236 fuel rods, that is subjected to severe thermal and mechanical loading. The results obtained indicate that plastic clad deformations with circumferential clad strains of more than 30% cannot be excluded for hot rods of the reference bundle. However, coplanar coolant channel blockages of significant extent seem to be probable within that bundle only under certain boundary conditions which are assumed to be pessimistic. (orig./RW)

1980-01-01

317

Multi-well CO2 Injectivity: Impact of Boundary Conditions and Brine Extraction on Geologic CO2 Storage Efficiency and Pressure Buildup.  

UK PubMed Central (United Kingdom)

CO2 storage efficiency is a metric that expresses the portion of the pore space of a subsurface geologic formation that is available to store CO2. Estimates of storage efficiency for large-scale geologic CO2 storage depend on a variety of factors including geologic properties and operational design. These factors govern estimates on CO2 storage resources, the longevity of storage sites, and potential pressure buildup in storage reservoirs. This study employs numerical modeling to quantify CO2 injection well numbers, well spacing, and storage efficiency as a function of geologic formation properties, open-versus-closed boundary conditions, and injection with or without brine extraction. The set of modeling runs is important as it allows the comparison of controlling factors on CO2 storage efficiency. Brine extraction in closed domains can result in storage efficiencies that are similar to those of injection in open-boundary domains. Geomechanical constraints on downhole pressure at both injection and extraction wells lower CO2 storage efficiency as compared to the idealized scenario in which the same volumes of CO2 and brine are injected and extracted, respectively. Geomechanical constraints should be taken into account to avoid potential damage to the storage site.

Heath JE; McKenna SA; Dewers T; Roach JD; Kobos PH

2013-08-01

318

Single-crystal diffraction at the Extreme Conditions beamline P02.2: procedure for collecting and analyzing high-pressure single-crystal data.  

Science.gov (United States)

Fast detectors employed at third-generation synchrotrons have reduced collection times significantly and require the optimization of commercial as well as customized software packages for data reduction and analysis. In this paper a procedure to collect, process and analyze single-crystal data sets collected at high pressure at the Extreme Conditions beamline (P02.2) at PETRA III, DESY, is presented. A new data image format called `Esperanto' is introduced that is supported by the commercial software package CrysAlis(Pro) (Agilent Technologies UK Ltd). The new format acts as a vehicle to transform the most common area-detector data formats via a translator software. Such a conversion tool has been developed and converts tiff data collected on a Perkin Elmer detector, as well as data collected on a MAR345/555, to be imported into the CrysAlis(Pro) software. In order to demonstrate the validity of the new approach, a complete structure refinement of boron-mullite (Al5BO9) collected at a pressure of 19.4?(2)?GPa is presented. Details pertaining to the data collections and refinements of B-mullite are presented. PMID:23955034

Rothkirch, André; Gatta, G Diego; Meyer, Mathias; Merkel, Sébastien; Merlini, Marco; Liermann, Hanns Peter

2013-07-25

319

Closeout of IE Bulletin 80-05: vacuum condition resulting in damage to low-pressure tanks which may contain primary-system water  

International Nuclear Information System (INIS)

[en] In early 1977, low pressure tanks at the Trojan and Rancho Seco Nuclear Stations buckled because of accidental conditions resulting from a partial vacuum. Both of these damaged tanks released radioactive gases. IE Circular 77-10 was issued on July 15, 1977 to caution PWR facility personnel about providing adequate protection for low pressure tanks which may contain primary system water. However, because similar tank failures occurred later at Turkey Point 3 and Salem 1, despite issuing the Circular, Bulletin 80-05 was issued on March 10, 1980 to require further action by utilities. Utility responses and IE inspection reports are evaluated on the basis of closeout criteria, for 49 facilities with operating licenses and 39 facilities with construction permits. Followup items are proposed for 30 of these 88 current PWR facilities. Therefore, the Bulletin has been closed out for 66% of the current facilities. A search conducted by the Nuclear Safety Information Center at the Oak Ridge National Laboratory indicates that none of these tanks has failed since the issuance of IE Bulletin 80-05 on March 10, 1980, and provides assurance that the Bulletin has been effective

1983-01-01

320

Single-crystal diffraction at the Extreme Conditions beamline P02.2: procedure for collecting and analyzing high-pressure single-crystal data.  

UK PubMed Central (United Kingdom)

Fast detectors employed at third-generation synchrotrons have reduced collection times significantly and require the optimization of commercial as well as customized software packages for data reduction and analysis. In this paper a procedure to collect, process and analyze single-crystal data sets collected at high pressure at the Extreme Conditions beamline (P02.2) at PETRA III, DESY, is presented. A new data image format called `Esperanto' is introduced that is supported by the commercial software package CrysAlis(Pro) (Agilent Technologies UK Ltd). The new format acts as a vehicle to transform the most common area-detector data formats via a translator software. Such a conversion tool has been developed and converts tiff data collected on a Perkin Elmer detector, as well as data collected on a MAR345/555, to be imported into the CrysAlis(Pro) software. In order to demonstrate the validity of the new approach, a complete structure refinement of boron-mullite (Al5BO9) collected at a pressure of 19.4?(2)?GPa is presented. Details pertaining to the data collections and refinements of B-mullite are presented.

Rothkirch A; Gatta GD; Meyer M; Merkel S; Merlini M; Liermann HP

2013-09-01

 
 
 
 
321

Radionuclides release from re-irradiated fuel under high temperature and pressure conditions. Gamma-ray measurements of VEGA-5 test  

Energy Technology Data Exchange (ETDEWEB)

The VEGA (Verification Experiments of radionuclides Gas/Aerosol release) program is being performed at JAERI to clarify mechanisms of radionuclides release from irradiated fuel during severe accidents and to improve source term predictability. The fifth VEGA-5 test was conducted in January 2002 to confirm the reproducibility of decrease in cesium release under elevated pressure that was observed in the VEGA-2 test and to investigate the release behavior of short-life radionuclides. The PWR fuel of 47 GWd/tU after about 8.2 years of cooling was re-irradiated at Nuclear Safety Research Reactor (NSRR) for 8 hours before the heat-up test. After that, the two pellets of 10.9 g without cladding were heated up to about 2,900 K at 1.0 MPa under the inert He condition. The experiment reconfirmed the decrease in cesium release rate under the elevated pressure. The release data on short-life radionuclides such as Ru-103, Ba-140 and Xe-133 that have never been observed in the previous VEGA tests without re-irradiation was obtained using the {gamma} ray measurement. (author)

Hidaka, Akihide; Kudo, Tamotsu; Nakamura, Takehiko; Kanazawa, Toru; Kiuchi, Toshio; Uetsuka, Hiroshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

2003-03-01

322

An on-line electrical resistance corrosion monitor for studying flow assisted corrosion of carbon steel under high-temperature and high-pressure conditions  

Energy Technology Data Exchange (ETDEWEB)

An in-situ corrosion rate monitor using a carbon steel tube, a carbon steel rod or a carbon steel wire as the sensing element has been developed. The monitor was tested both in an inert system at room temperature and in a high-temperature and high-pressure loop with LiOH solution. Experimental results from the room temperature tests showed that the calculated corrosion rate or thinning rate based on the resistance signal of the carbon steel sensing element agreed well with the measured values. Experimental results from the high-temperature tests showed that the corrosion monitor responded to the corrosion rate changes when air or sulfuric acid was added. The precision of the monitor under the simulated nuclear coolant conditions was found to be {+-}0.04 {micro}m to {+-}1 {micro}m in terms of thickness change. The variation in precision is dependent upon the dimension of the sensing element.

Yang, L.; Sun, X.; Steward, F.

1999-07-01

323

Modifications to tough and analysis of build-up data of PTS (Pressure/Temperature/Spinner) logging in a two-phase condition  

Energy Technology Data Exchange (ETDEWEB)

The original version of TOUGH (Pruess, 1987) requires a large amount of CPU time for large 2D or 3D problems. This has prevented us from using the original TOUGH on several actual field simulations. Therefore, we have modified the original TOUGH to make less CPU time and allow us to use new TOUGH on large problems. For reducing the CPU time, two new matrix inversion methods were implemented on the original TOUGH. In this report, first we summarize new matrix inversion method implemented in new TOUGH and second we show inspection results of the accuracy and improvements of speed, and then we show the case study results. Before conducting this case study, the porous medium model for the case study is optimized. As the case study we tried to analyze build-up data acquired by PTS (Pressure/Temperature/Spinner) logging in a two-phase condition. We have been successful in obtaining a good match to PTS data.

Okabe, T.; Osato, K.; Takasugi, S.

1991-01-01

324

Preliminary design of coal-fired supercritical sliding-pressure boilers for turbine steam conditions of 4500 psi, 1100 degree F  

Energy Technology Data Exchange (ETDEWEB)

Significant heat rate improvements in pulverized coal power plants are possible through the use of advanced thermodynamic conditions. This report presents the results of a study which shows that a steam generator featuring 4500 psi, 1100{degree}F (31 MPa, 593{degree}C) throttle steam, two reheats, each with 1100{degree}F (593{degree}C) steam, and capable of sliding pressure cyclic duty is available to the utility industry. Design and performance of contemporary subcritical single reheat boilers designed for 2400 psi, 1005{degree}F/1005{degree}F (16.55 MPa/540/540{degree}C) are provided for information and comparison. 4 refs., 69 figs., 9 tabs.

Palkes, M.; Salem, A. (ABB/Combustion Engineering, Inc., Windsor, CT (United States) Sulzer Bros. Ltd., Winterthur (Switzerland))

1991-10-01

325

Effect of SG Modeling on Primary Side Pressure and Temperature Trend During Long Term Station Black Out Conditions in VVER Using RELAP5 and CATHARE2 System Codes  

International Nuclear Information System (INIS)

Although station black out conditions (i.e. loss of off-site power with simultaneous failure of all diesel generators) over a period of several hours are very unlikely, analysis of station black out transients and possible countermeasures are important. A well planned emergency operating procedure, utilizing just equipment powered by batteries, can extend the grace period considerably, and mitigate severe accident progression. Until the occurrence of core damage best estimate thermal hydraulic system codes like Relap5 or Cathare2 can give a good picture of the development of the transient. Heat transfer from the primary to the secondary side is one of the dominant phenomena during the first hours of a station black out transient. Primary side pressure stays high, and the decay heat is transferred by natural circulation to the secondary side. The steam generator inventory boils off, and the steam generator level decreases. Modelling of the steam generator therefore is of special importance. The current paper presents an analysis for VVER-1000 type steam generators (horizontal) with different nodalization detail and different codes (Cathare2 and Relap5). The nodalization approach has been verified by comparing calculated results to PSB-VVER steam generator experiments. The results show that codes like Relap5 and Cathare2, by assuming uniform bulk flow properties over the flow cross section and within volume units, introduce a distortion compared to the real physics in case station black out conditions. The reason lies in the specifics of the horizontal steam generator. While the heat transfer surface decreases continuously in the actual steam generator, the necessity of modelling the steam generator with nodes of finite volume creates a step-wise reduction of the heat transfer surface. The effects on the primary side temperature and pressure trends are not negligible, and decrease with increasing detail of modelling.(author).

2008-01-01

326

Real-world operation conditions and on-road emissions of Beijing diesel buses measured by using portable emission measurement system and electric low-pressure impactor.  

UK PubMed Central (United Kingdom)

On-road measurement is an effective method to investigate real-world emissions generated from vehicles and estimate the difference between engine certification cycles and real-world operating conditions. This study presents the results of on-road measurements collected from urban buses which propelled by diesel engine in Beijing city. Two widely used Euro III emission level buses and two Euro IV emission level buses were chosen to perform on-road emission measurements using portable emission measurement system (PEMS) for gaseous pollutant and Electric Low Pressure Impactor (ELPI) for particulate matter (PM) number emissions. The results indicate that considerable discrepancies of engine operating conditions between real-world driving cycles and engine certification cycles have been observed. Under real-world operating conditions, carbon monoxide (CO) and hydrocarbon (HC) emissions can easily meet their respective regulations limits, while brake specification nitrogen oxide (bsNO(x)) emissions present a significant deviation from its corresponding limit. Compared with standard limits, the real-world bsNO(x) emission of the two Euro III emission level buses approximately increased by 60% and 120% respectively, and bsNO(x) of two Euro IV buses nearly twice standard limits because Selective Catalytic Reduction (SCR) system not active under low exhaust temperature. Particle mass were estimated via particle size distribution with the assumption that particle density and diameter is liner. The results demonstrate that nanometer size particulate matter make significant contribution to total particle number but play a minor role to total particle mass. It is suggested that specific certified cycle should be developed to regulate bus engines emissions on the test bench or use PEMS to control the bus emissions under real-world operating conditions.

Liu Z; Ge Y; Johnson KC; Shah AN; Tan J; Wang C; Yu L

2011-03-01

327

Real-world operation conditions and on-road emissions of Beijing diesel buses measured by using portable emission measurement system and electric low-pressure impactor.  

Science.gov (United States)

On-road measurement is an effective method to investigate real-world emissions generated from vehicles and estimate the difference between engine certification cycles and real-world operating conditions. This study presents the results of on-road measurements collected from urban buses which propelled by diesel engine in Beijing city. Two widely used Euro III emission level buses and two Euro IV emission level buses were chosen to perform on-road emission measurements using portable emission measurement system (PEMS) for gaseous pollutant and Electric Low Pressure Impactor (ELPI) for particulate matter (PM) number emissions. The results indicate that considerable discrepancies of engine operating conditions between real-world driving cycles and engine certification cycles have been observed. Under real-world operating conditions, carbon monoxide (CO) and hydrocarbon (HC) emissions can easily meet their respective regulations limits, while brake specification nitrogen oxide (bsNO(x)) emissions present a significant deviation from its corresponding limit. Compared with standard limits, the real-world bsNO(x) emission of the two Euro III emission level buses approximately increased by 60% and 120% respectively, and bsNO(x) of two Euro IV buses nearly twice standard limits because Selective Catalytic Reduction (SCR) system not active under low exhaust temperature. Particle mass were estimated via particle size distribution with the assumption that particle density and diameter is liner. The results demonstrate that nanometer size particulate matter make significant contribution to total particle number but play a minor role to total particle mass. It is suggested that specific certified cycle should be developed to regulate bus engines emissions on the test bench or use PEMS to control the bus emissions under real-world operating conditions. PMID:21295821

Liu, Zhihua; Ge, Yunshan; Johnson, Kent C; Shah, Asad Naeem; Tan, Jianwei; Wang, Chu; Yu, Linxiao

2011-02-04

328

Optimisation of the hot conditioning of carbon steel surfaces of primary heat transport system of Pressurized Heavy Water Reactors using electrochemical impedance spectroscopy  

Energy Technology Data Exchange (ETDEWEB)

Hot conditioning operation of the primary heat transport system is an important step prior to the commissioning of Pressurized Heavy Water Reactors. One of the major objectives of the operation is to develop a stable and protective magnetite layer on the inner surfaces of carbon steel piping. The correlation between stable magnetite film growth on carbon steel surfaces and the period of exposure to hot conditioning environment is generally established by a combination of weight change measurements and microscopic/morphological observations of the specimens periodically removed during the operation. In the present study, electrochemical impedance spectroscopy (EIS) at room temperature is demonstrated as an alternate, quantitative technique to arrive at an optimal duration of the exposure period. Specimens of carbon steel were exposed for 24, 35 and 48 h during hot conditioning of primary heat transport system of two Indian PHWRs. The composition and morphology of oxide films grown during exposure was characterized by X-ray diffraction and optical microscopy. Further, ex situ electrochemical impedance spectra of magnetite films formed after each exposure were measured, in 1 ppm Li{sup +} electrolyte at room temperature as a function of potential in a range of -0.8 to +0.3 V{sub SCE}. The defect density of the magnetite films formed after each exposure was estimated by Mott-Schottky analysis of capacitances extracted from the impedance spectra. Further the ionic resistance of the oxide was also extracted from the impedance spectra. Defect density was observed to decrease with increase in exposure time and to saturate after 35 h, indicating stabilisation of the barrier layer part of the magnetite film. The values of the ionic transport resistance start to increase after 35-40 h of exposure. The quantitative ability of EIS technique to assess the film quality demonstrates that it can be used as a supplementary tool to the thickness and morphological characterizations of samples during hot conditioning.

Kiran Kumar, M., E-mail: mkiran@barc.gov.i [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Gaonkar, Krishna; Ghosh, Swati; Kain, Vivekanand [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Bojinov, Martin [Department of Physical Chemistry, University of Chemical Technology and Metallurgy, Kl. Ohridski Blvd. 8, 1756 Sofia (Bulgaria); Saario, Timo [VTT Materials and Building, VTT Technical Research Centre of Finland, P.O. Box 1000, Kemistintie 3, FIN-02044 VTT, Espoo (Finland)

2010-06-15

329

Optimisation of the hot conditioning of carbon steel surfaces of primary heat transport system of Pressurized Heavy Water Reactors using electrochemical impedance spectroscopy  

International Nuclear Information System (INIS)

Hot conditioning operation of the primary heat transport system is an important step prior to the commissioning of Pressurized Heavy Water Reactors. One of the major objectives of the operation is to develop a stable and protective magnetite layer on the inner surfaces of carbon steel piping. The correlation between stable magnetite film growth on carbon steel surfaces and the period of exposure to hot conditioning environment is generally established by a combination of weight change measurements and microscopic/morphological observations of the specimens periodically removed during the operation. In the present study, electrochemical impedance spectroscopy (EIS) at room temperature is demonstrated as an alternate, quantitative technique to arrive at an optimal duration of the exposure period. Specimens of carbon steel were exposed for 24, 35 and 48 h during hot conditioning of primary heat transport system of two Indian PHWRs. The composition and morphology of oxide films grown during exposure was characterized by X-ray diffraction and optical microscopy. Further, ex situ electrochemical impedance spectra of magnetite films formed after each exposure were measured, in 1 ppm Li+ electrolyte at room temperature as a function of potential in a range of -0.8 to +0.3 VSCE. The defect density of the magnetite films formed after each exposure was estimated by Mott-Schottky analysis of capacitances extracted from the impedance spectra. Further the ionic resistance of the oxide was also extracted from the impedance spectra. Defect density was observed to decrease with increase in exposure time and to saturate after 35 h, indicating stabilisation of the barrier layer part of the magnetite film. The values of the ionic transport resistance start to increase after 35-40 h of exposure. The quantitative ability of EIS technique to assess the film quality demonstrates that it can be used as a supplementary tool to the thickness and morphological characterizations of samples during hot conditioning.

2010-01-01

330

Effect of meal volume and calorie load on postprandial gastric function and emptying: studies under physiological conditions by combined fiber-optic pressure measurement and MRI.  

Science.gov (United States)

This study assessed the effects of meal volume (MV) and calorie load (CL) on gastric function. MRI and a minimally invasive fiber-optic recording system (FORS) provided simultaneous measurement of gastric volume and pressure changes during gastric filling and emptying of a liquid nutrient meal in physiological conditions. The gastric response to 12 iso-osmolar MV-CL combinations of a multinutrient drink (MV: 200, 400, 600, 800 ml; CL: 200, 300, 400 kcal) was tested in 16 healthy subjects according to a factorial design. Total gastric volume (TGV) and gastric content volume (GCV = MV + secretion) were measured by MRI during nasogastric meal infusion and gastric emptying over 60 min. Intragastric pressure was assessed at 1 Hz by FORS. The dynamic change in postprandial gastric volumes was described by a validated three-component linear exponential model. The stomach expanded with MV, but the ratio of GCV:MV at t(0) diminished with increasing MV (P TGV followed those of GCV. Intragastric pressure increased with MV, and this effect was augmented further by CL (P = 0.02); however, the absolute pressure rise was <4 mmHg. A further postprandial increase of gastric volumes was observed early on before any subsequent volume decrease. This "early" increase in GCV was greater for smaller than larger MV (P < 0.01), indicating faster initial gastric emptying of larger MV. In contrast, volume change during filling and in the early postprandial period were unaffected by CL. In the later postprandial period, gastric emptying rate continued to be more rapid with high MVs (P < 0.001); however, at any given volume, gastric emptying was slowed by higher CL (P < 0.001). GCV half-emptying time decreased with CL at 18 +/- 6 min for each additional 100-kcal load (P < 0.001). These findings indicate that gastric wall stress (passive strain and active tone) provides the driving force for gastric emptying, but distal resistance to gastric outflow regulates further passage of nutrients. The distinct early phase of gastric emptying with relatively rapid, uncontrolled passage of nutrients into the small bowel, modulated by meal volume but not nutrient composition, ensures that the delivery of nutrients in the later postprandial period is related to the overall calorie load of the meal. PMID:19779010

Kwiatek, Monika A; Menne, Dieter; Steingoetter, Andreas; Goetze, Oliver; Forras-Kaufman, Zsofia; Kaufman, Elad; Fruehauf, Heiko; Boesiger, Peter; Fried, Michael; Schwizer, Werner; Fox, Mark R

2009-09-24

331

Effect of meal volume and calorie load on postprandial gastric function and emptying: studies under physiological conditions by combined fiber-optic pressure measurement and MRI.  

UK PubMed Central (United Kingdom)

This study assessed the effects of meal volume (MV) and calorie load (CL) on gastric function. MRI and a minimally invasive fiber-optic recording system (FORS) provided simultaneous measurement of gastric volume and pressure changes during gastric filling and emptying of a liquid nutrient meal in physiological conditions. The gastric response to 12 iso-osmolar MV-CL combinations of a multinutrient drink (MV: 200, 400, 600, 800 ml; CL: 200, 300, 400 kcal) was tested in 16 healthy subjects according to a factorial design. Total gastric volume (TGV) and gastric content volume (GCV = MV + secretion) were measured by MRI during nasogastric meal infusion and gastric emptying over 60 min. Intragastric pressure was assessed at 1 Hz by FORS. The dynamic change in postprandial gastric volumes was described by a validated three-component linear exponential model. The stomach expanded with MV, but the ratio of GCV:MV at t(0) diminished with increasing MV (P < 0.01). Postprandial changes in TGV followed those of GCV. Intragastric pressure increased with MV, and this effect was augmented further by CL (P = 0.02); however, the absolute pressure rise was <4 mmHg. A further postprandial increase of gastric volumes was observed early on before any subsequent volume decrease. This "early" increase in GCV was greater for smaller than larger MV (P < 0.01), indicating faster initial gastric emptying of larger MV. In contrast, volume change during filling and in the early postprandial period were unaffected by CL. In the later postprandial period, gastric emptying rate continued to be more rapid with high MVs (P < 0.001); however, at any given volume, gastric emptying was slowed by higher CL (P < 0.001). GCV half-emptying time decreased with CL at 18 +/- 6 min for each additional 100-kcal load (P < 0.001). These findings indicate that gastric wall stress (passive strain and active tone) provides the driving force for gastric emptying, but distal resistance to gastric outflow regulates further passage of nutrients. The distinct early phase of gastric emptying with relatively rapid, uncontrolled passage of nutrients into the small bowel, modulated by meal volume but not nutrient composition, ensures that the delivery of nutrients in the later postprandial period is related to the overall calorie load of the meal.

Kwiatek MA; Menne D; Steingoetter A; Goetze O; Forras-Kaufman Z; Kaufman E; Fruehauf H; Boesiger P; Fried M; Schwizer W; Fox MR

2009-11-01

332

Effects of pre- or post-processing storage conditions on high-hydrostatic pressure inactivation of Vibrio parahaemolyticus and V. vulnificus in oysters.  

UK PubMed Central (United Kingdom)

The effects of storage conditions on subsequent high-hydrostatic pressure (HHP) inactivation of Vibrio parahaemolyticus and Vibrio vulnificus in oysters were investigated. Live oysters were inoculated with V. parahaemolyticus or V. vulnificus to ca. 7-8 log MPN/g by feeding and stored at varying conditions (i.e., 21 or 35 °C for 5h, 4 or 10 °C for 1 and 2 days and -18 °C for 2 weeks). Oyster meats were then treated at 225-300 MPa for 2 min at 4, 21 or 35 °C. HHP at 300 MPa for 2 min achieved a >5-log MPN/g reduction of V. parahaemolyticus, completely inactivating V. vulnificus (negative by enrichment) in oysters. Treatment temperatures of 4, 21 and 35 °C did not significantly affect pressure inactivation of V. parahaemolyticus or V. vulnificus (P>0.05). Cold storage at -18, 4 and 10 °C, prior to HHP, decreased V. parahaemolyticus or V. vulnificus populations by 1.5-3.0 log MPN/g, but did not increase their sensitivity to subsequent HHP treatments. The effects of cold storage after HHP on inactivation of V. parahaemolyticus in oysters were also determined. Oysters were inoculated with V. parahaemolyticus and stored at 21 °C for 5h or 4 °C for 1 day. Oyster meats were then treated at 250-300 MPa for 2 min at 21 or 35 °C and stored for 15 days in ice or in a freezer. V. parahaemolyticus populations in HHP-treated oysters gradually decreased during post-HHP ice or frozen storage. A validation study using whole-shell oysters was conducted to determine whether the presence of oyster shells influenced HHP inactivation of V. parahaemolyticus. No appreciable differences in inactivation between shucked oyster meat and whole-shell oysters were observed. HPP at 300 MPa for 2 min at 21 °C, followed by 5-day ice storage or 7-day frozen storage, and HPP at 250 MPa for 2 min at 21 °C, followed by 10-day ice or 7-day frozen storage, completely inactivated V. parahaemolyticus in whole-shell oysters (>7 log reductions). The combination of HHP at a relatively low pressure (e.g., 250 MPa) followed by short-term frozen storage (7 days) could potentially be applied by the shellfish industry as a post-harvest process to eliminate V. parahaemolyticus in oysters.

Ye M; Huang Y; Gurtler JB; Niemira BA; Sites JE; Chen H

2013-05-01

333

Effects of pre- or post-processing storage conditions on high-hydrostatic pressure inactivation of Vibrio parahaemolyticus and V. vulnificus in oysters.  

Science.gov (United States)

The effects of storage conditions on subsequent high-hydrostatic pressure (HHP) inactivation of Vibrio parahaemolyticus and Vibrio vulnificus in oysters were investigated. Live oysters were inoculated with V. parahaemolyticus or V. vulnificus to ca. 7-8 log MPN/g by feeding and stored at varying conditions (i.e., 21 or 35 °C for 5h, 4 or 10 °C for 1 and 2 days and -18 °C for 2 weeks). Oyster meats were then treated at 225-300 MPa for 2 min at 4, 21 or 35 °C. HHP at 300 MPa for 2 min achieved a >5-log MPN/g reduction of V. parahaemolyticus, completely inactivating V. vulnificus (negative by enrichment) in oysters. Treatment temperatures of 4, 21 and 35 °C did not significantly affect pressure inactivation of V. parahaemolyticus or V. vulnificus (P>0.05). Cold storage at -18, 4 and 10 °C, prior to HHP, decreased V. parahaemolyticus or V. vulnificus populations by 1.5-3.0 log MPN/g, but did not increase their sensitivity to subsequent HHP treatments. The effects of cold storage after HHP on inactivation of V. parahaemolyticus in oysters were also determined. Oysters were inoculated with V. parahaemolyticus and stored at 21 °C for 5h or 4 °C for 1 day. Oyster meats were then treated at 250-300 MPa for 2 min at 21 or 35 °C and stored for 15 days in ice or in a freezer. V. parahaemolyticus populations in HHP-treated oysters gradually decreased during post-HHP ice or frozen storage. A validation study using whole-shell oysters was conducted to determine whether the presence of oyster shells influenced HHP inactivation of V. parahaemolyticus. No appreciable differences in inactivation between shucked oyster meat and whole-shell oysters were observed. HPP at 300 MPa for 2 min at 21 °C, followed by 5-day ice storage or 7-day frozen storage, and HPP at 250 MPa for 2 min at 21 °C, followed by 10-day ice or 7-day frozen storage, completely inactivated V. parahaemolyticus in whole-shell oysters (>7 log reductions). The combination of HHP at a relatively low pressure (e.g., 250 MPa) followed by short-term frozen storage (7 days) could potentially be applied by the shellfish industry as a post-harvest process to eliminate V. parahaemolyticus in oysters. PMID:23545264

Ye, Mu; Huang, Yaoxin; Gurtler, Joshua B; Niemira, Brendan A; Sites, Joseph E; Chen, Haiqiang

2013-03-05

334

Analysis Of The Atlantic Ocean Response To Pressure Variations  

UK PubMed Central (United Kingdom)

The sea level response to fluctuations in barometric pressure is currently modelled by the inverted barometer (IB)approximation which implies a change of approximately 1 cm in sea level for 1 mb change in atmospheric pressure(isostatic assumption). Therefore, sea level gradients perfectly compensate the horizontal gradients in atmosphericpressure fields and there is no pressure gradient at the sea surface. As a consequence, pressure-induced sea levelslopes are not dynamically significant and are usually subtracted from altimetric records of sea surface height. Thevalidity of the IB assumption and the character of the sea level response to barometric forcing is dependant on thetime and space scales considered. In this work the magnitude of the Atlantic Ocean response to pressure variationswill be quantified, in order to verify the validity of the isostatic assumption. To do that, we will calculate thecorrelation coefficients () between the sea level anomaly (SLA) and pressure variations (P), which should beapproximately-1 cm/mb if the oceanic response is isostatic. The altimeter data used cover a time period from May1995 to June 1996 during which ERS-1 and ERS-2 satellites were put in the same ground track (the so-calledTandem Mission) with a time lag of approximately one day. Two different techniques will be applied to quantifythe coefficients above mentioned, simple regression analysis and empirical orthogonal function decomposition(eofd) analysis. The SLA time series has been produced following the recommendations of the Ocean Product UserManual and cycle validation reports applying the suggested instrumental and geophysical corrections. Apart fromthat, several corrections have been also applied, such as a new orbital altitude which significantly redu...

Gmez-enri J; Villares P; Bruno M; Benveniste J; Avate A

335

Modelling the chemical behaviour of tellurium species in the reactor pressure vessel and the reactor cooling system under severe accident conditions  

International Nuclear Information System (INIS)

This state of the art report contains information on the behaviour of tellurium and its compounds in the reactor pressure vessel and the reactor coolant system under light water reactor severe accident conditions. To characterise tellurium behaviour, it is necessary the previous knowledge of the species of tellurium released from the core, and simultaneity of its release with that of other materials which can alter the transport, for instance, control rod and structural materials. Release and transport experiments have been reviewed along with the models implemented in the codes which are used in the international community: TRAPMELT, RAFT, VICTORIA and SOPHIE. From the experiments, it can be concluded that other species different to Te2, such as tin telluride and cesium telluride, may be released from the fuel. That is why they must be considered in the transport phenomena. There is also experimental evidence of the strong interaction of Te2 with Inconel 600 and stainless steel of the pipe walls and structures, however this strong interaction is in competition with the interaction of tellurium with aerosols, which under severe accident conditions may represent an area greater than that of the primary system. It is for the absence of significant tellurium species in the transport models, and also for the interaction of tellurium with aerosols, for which some codes show the greatest deficiencies.

1991-01-01

336

Alkyne-azide cycloadditions with copper powder in a high-pressure continuous-flow reactor: high-temperature conditions versus the role of additives.  

UK PubMed Central (United Kingdom)

A safe and efficient flow-chemistry-based procedure is presented for 1,3-dipolar cycloaddition reactions between organic azides and acetylenes. This simple and inexpensive technique eliminates the need for costly special apparatus and utilizes Cu powder as a plausible Cu(I) source. To maximize the reaction rates, high-pressure/high-temperature conditions are utilized; alternatively, the harsh reaction conditions can be moderated at room temperature by the joint application of basic and acidic additives. A comparison of the performance of these two approaches in a series of model reactions has resulted in the formation of useful 1,4-disubstituted 1,2,3-triazoles in excellent yields. The risks that are associated with the handling of azides are lowered, thanks to the benefits of flow processing, and gram-scale production has been safely implemented. The synthetic capability of this continuous-flow technique is demonstrated by the efficient syntheses of some highly functionalized derivatives of the antifungal cispentacin.

Ötvös SB; Mándity IM; Kiss L; Fülöp F

2013-04-01

337

An application of liquid sublayer dryout mechanism to the prediction of critical heat flux under low pressure and low velocity conditions in round tubes  

International Nuclear Information System (INIS)

Based on several experimental evidences for nucleate boiling in annular film and the existence of residual liquid film flow rate at the critical heat flux (CHF) location, the liquid sublayer dryout (LSD) mechanism under annular film is firstly introduced to evaluate the CHF data at low pressure and low velocity (LPLV) conditions, which would not be predicted by a normal annular film dryout (AFD) model. In this study, the CHF occurrence due to annular film separation or breaking down is phenomenologically modelled by applying the LSD mechanism to this situation. In this LSD mechanism, the liquid sublayer thickness, the incoming liquid velocity to the liquid sublayer, and the axial distance from the onset of annular flow to the CHF location are used as the phenomena-controlling parameters. From the model validation on the 1406 CHF data points ranging over P = 0.1 - 2 MPa, G = 4 - 499 kg/m2s, L/D = 4 - 402, most of CHF data (more than 1000 points) are predicted within ±30% error bounds by the LSD mechanism. However, some calculation results that critical qualities are less than 0.4 are considerably overestimated by this mechanism. These overpredictions seem to be caused by inadequate CHF mechanism classification criteria and an insufficient consideration of the flow instability effect on CHF. Further studies for a new classification criterion screening the CHF data affected by flow instabilities and a new bubble detachment model for LPLV conditions are needed to improve the model accuracy. (author)

1997-10-04

338

An application of liquid sublayer dryout mechanism to the prediction of critical heat flux under low pressure and low velocity conditions in round tubes  

Energy Technology Data Exchange (ETDEWEB)

Based on several experimental evidences for nucleate boiling in annular film and the existence of residual liquid film flow rate at the critical heat flux (CHF) location, the liquid sublayer dryout (LSD) mechanism under annular film is firstly introduced to evaluate the CHF data at low pressure and low velocity (LPLV) conditions, which would not be predicted by a normal annular film dryout (AFD) model. In this study, the CHF occurrence due to annular film separation or breaking down is phenomenologically modelled by applying the LSD mechanism to this situation. In this LSD mechanism, the liquid sublayer thickness, the incoming liquid velocity to the liquid sublayer, and the axial distance from the onset of annular flow to the CHF location are used as the phenomena-controlling parameters. From the model validation on the 1406 CHF data points ranging over P = 0.1 - 2 MPa, G = 4 - 499 kg/m{sup 2}s, L/D = 4 - 402, most of CHF data (more than 1000 points) are predicted within {+-}30% error bounds by the LSD mechanism. However, some calculation results that critical qualities are less than 0.4 are considerably overestimated by this mechanism. These overpredictions seem to be caused by inadequate CHF mechanism classification criteria and an insufficient consideration of the flow instability effect on CHF. Further studies for a new classification criterion screening the CHF data affected by flow instabilities and a new bubble detachment model for LPLV conditions are needed to improve the model accuracy. (author)

Lee, Kwang-Won; Yang, Jae-Young; Baik, Se-Jin [NSSS Engineering and Development, Korea Power Engineering Company, Inc., Taejon (Korea, Republic of)

1997-12-31

339

Modelling the chemical behaviour of tellurium species in the reactor pressure vessel and the reactor cooling system under severe accident conditions  

Energy Technology Data Exchange (ETDEWEB)

This state of the art report contains information on the behaviour of tellurium and its compounds in the reactor pressure vessel and the reactor coolant system under light water reactor severe accident conditions. To characterise tellurium behaviour, it is necessary the previous knowledge of the species of tellurium released from the core, and simultaneity of its release with that of other materials which can alter the transport, for instance, control rod and structural materials. Release and transport experiments have been reviewed along with the models implemented in the codes which are used in the international community: TRAPMELT, RAFT, VICTORIA and SOPHIE. From the experiments, it can be concluded that other species different to Te{sub 2}, such as tin telluride and cesium telluride, may be released from the fuel. That is why they must be considered in the transport phenomena. There is also experimental evidence of the strong interaction of Te{sub 2} with Inconel 600 and stainless steel of the pipe walls and structures, however this strong interaction is in competition with the interaction of tellurium with aerosols, which under severe accident conditions may represent an area greater than that of the primary system. It is for the absence of significant tellurium species in the transport models, and also for the interaction of tellurium with aerosols, for which some codes show the greatest deficiencies

Alonso, A.; Gonzalez, C. [Universidad Politecnica de Madrid (Spain). Escuela Tecnica Superior de Ingenieros Industriales

1991-07-01

340

Distinguishing HIV-1 drug resistance, accessory, and viral fitness mutations using conditional selection pressure analysis of treated versus untreated patient samples  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background HIV can evolve drug resistance rapidly in response to new drug treatments, often through a combination of multiple mutations 123. It would be useful to develop automated analyses of HIV sequence polymorphism that are able to predict drug resistance mutations, and to distinguish different types of functional roles among such mutations, for example, those that directly cause drug resistance, versus those that play an accessory role. Detecting functional interactions between mutations is essential for this classification. We have adapted a well-known measure of evolutionary selection pressure (Ka/Ks) and developed a conditional Ka/Ks approach to detect important interactions. Results We have applied this analysis to four independent HIV protease sequencing datasets: 50,000 clinical samples sequenced by Specialty Laboratories, Inc.; 1800 samples from patients treated with protease inhibitors; 2600 samples from untreated patients; 400 samples from untreated African patients. We have identified 428 mutation interactions in Specialty dataset with statistical significance and we were able to distinguish primary vs. accessory mutations for many well-studied examples. Amino acid interactions identified by conditional Ka/Ks matched 80 of 92 pair wise interactions found by a completely independent study of HIV protease (p-value for this match is significant: 10-70). Furthermore, Ka/Ks selection pressure results were highly reproducible among these independent datasets, both qualitatively and quantitatively, suggesting that they are detecting real drug-resistance and viral fitness mutations in the wild HIV-1 population. Conclusion Conditional Ka/Ks analysis can detect mutation interactions and distinguish primary vs. accessory mutations in HIV-1. Ka/Ks analysis of treated vs. untreated patient data can distinguish drug-resistance vs. viral fitness mutations. Verification of these results would require longitudinal studies. The result provides a valuable resource for AIDS research and will be available for open access upon publication at http://www.bioinformatics.ucla.edu/HIV Reviewers This article was reviewed by Wen-Hsiung Li (nominated by Eugene V. Koonin), Robert Shafer (nominated by Eugene V. Koonin), and Shamil Sunyaev.

Chen Lamei; Lee Christopher

2006-01-01

 
 
 
 
341

Solubility of Uranium in Fe-S-Si Melts at High Pressure and Temperature and at Highly Reducing Conditions: Uranium as a heat source in the Earth's Core?  

Science.gov (United States)

The presence of Uranium and its role as a radioactive heat source in the Earth's Fe-metallic core has been controversial (e.g., Wheeler et al., 2006; Bao et al., 2005). We report here on partitioning of U between molten enstatite chondrite and Fe-S-Si melts at about 4 log units below the Iron-Wustite oxygen buffer and pressures between 3 and 8 GPa. All experiments were performed at super-liquidus temperatures in the range of 2000- 2400 C. Both the metal and silicates were completely molten, in keeping with the concept of an early global magma ocean. At these pressures and temperatures, the partition coefficient, DU (U concentration in metallic sulfide liquid/U concentration in molten silicate) is in the range of 0.03-0.08. DU is positively correlated with S as observed in prior studies (Bao et al., 2005; Wheeler et al., 2006), but is inversely correlated with Si in metallic liquid. In metal with little or no sulfur, DU is lower by an order of magnitude or more. In the range of our measurements, no strong effect of either T or P on the partition coefficient is observed. U shows no correlation with Ca suggesting that U is not carried via CaS at these highly reducing conditions, as has been suggested (Murrell and Burnett, 1982; Furst et al., 1982). Nor does the U content of metal-sulfide have any discernible dependency on the O content of the metallic liquid. Thus it appears that neither Ca nor O act as carriers or catalytic agents for the entry of U into Fe-S melts. Rather, we suggest that the reaction UO2 +2 FeS = US2 +2FeO proceeds to the right at elevated P and T and highly reducing conditions, facilitating the incorporation of U in Fe-S liquids. Assuming that the behavior of DU is not significantly changed at the much higher P and T relevant to the magma ocean, our data permit 0.6-1.8 ppb of U in the core with heat production capacity of 0.1-0.3 TW at present, a small fraction of the 6-12 TW total heat flux from the core (Buffet, 2003). We conclude that under highly reducing conditions uranium might be incorporated into the Earth's metallic core.

Murthy, V.; Draper, D. S.; Agee, C. B.

2006-12-01

342

Ferric iron content of ferropericlase as a function of composition, oxygen fugacity, temperature and pressure: Implications for redox conditions during diamond formation in the lower mantle  

Science.gov (United States)

We investigated the ferric iron (Fe3+) concentration in (Mg,Fe)O ferropericlase using the flank method applied to Mg-Fe interdiffusion couples of ferropericlase. Diffusion couples with Mg/(Mg+Fe) in the range 0.44 to 1 were annealed at temperatures of 1673-1873 K and pressures of 5-24 GPa over a wide range of oxygen fugacities. Oxygen fugacity was controlled by Fe, Ni, Mo, and Re metal capsules and their corresponding oxide phases. Based on our results and available experimental data, we derived an equation for the Fe3+ solubility in ferropericlase applicable to depths at the top of the lower mantle: [Fe3+]=C (XFe4fO2)m exp{-((1-XFe)E*Mg+XFeE*Fe+PV*)/RT}, where C=2.6(1)×10-3, m=0.114(3), E*Mg=-35(3) [kJ/mol], E*Fe=-98(2) [kJ/mol], and V*=2.09(3) [cm3/mol]. The value of the oxygen fugacity exponent m implies that Fe3+ mostly occupies tetrahedral sites under these conditions, which is consistent with the results of previously reported Mössbauer spectroscopy studies. Based on this relationship, we calculated the redox conditions of ferropericlase inclusions in diamonds believed to have come from the lower mantle. The estimated oxygen fugacities are close to the upper stability limit of diamond in mantle peridotite at the top of the lower mantle at adiabatic or slightly superadiabatic temperatures, which suggests that ferropericlase inclusions recorded and preserved the conditions at which diamond was precipitated from carbonates or carbonatite melts near the top of the lower mantle.

Otsuka, Kazuhiko; Longo, Micaela; McCammon, Catherine A.; Karato, Shun-ichiro

2013-03-01

343

Referenced dual pressure- and temperature-sensitive paint for digital color camera read out.  

Science.gov (United States)

The first fluorescent material for the referenced simultaneous RGB (red green blue) imaging of barometric pressure (oxygen partial pressure) and temperature is presented. This sensitive coating consists of two platinum(II) complexes as indicators and a reference dye, each of which is incorporated in appropriate polymer nanoparticles. These particles are dispersed in a polyurethane hydrogel and spread onto a solid support. The emission of the (oxygen) pressure indicator, PtTFPP, matches the red channel of a RGB color camera, whilst the emission of the temperature indicator [Pt(II) (Br-thq)(acac)] matches the green channel. The reference dye, 9,10-diphenylanthracene, emits in the blue channel. In contrast to other dual-sensitive materials, this new coating allows for the simultaneous imaging of both indicator signals, as well as the reference signal, in one RGB color picture without having to separate the signals with additional optical filters. All of these dyes are excitable with a 405 nm light-emitting diode (LED). With this new composite material, barometric pressure can be determined with a resolution of 22 mbar; the temperature can be determined with a resolution of 4.3 °C. PMID:23070744

Fischer, Lorenz H; Karakus, Cüneyt; Meier, Robert J; Risch, Nikolaus; Wolfbeis, Otto S; Holder, Elisabeth; Schäferling, Michael

2012-10-15

344

Referenced dual pressure- and temperature-sensitive paint for digital color camera read out.  

UK PubMed Central (United Kingdom)

The first fluorescent material for the referenced simultaneous RGB (red green blue) imaging of barometric pressure (oxygen partial pressure) and temperature is presented. This sensitive coating consists of two platinum(II) complexes as indicators and a reference dye, each of which is incorporated in appropriate polymer nanoparticles. These particles are dispersed in a polyurethane hydrogel and spread onto a solid support. The emission of the (oxygen) pressure indicator, PtTFPP, matches the red channel of a RGB color camera, whilst the emission of the temperature indicator [Pt(II) (Br-thq)(acac)] matches the green channel. The reference dye, 9,10-diphenylanthracene, emits in the blue channel. In contrast to other dual-sensitive materials, this new coating allows for the simultaneous imaging of both indicator signals, as well as the reference signal, in one RGB color picture without having to separate the signals with additional optical filters. All of these dyes are excitable with a 405 nm light-emitting diode (LED). With this new composite material, barometric pressure can be determined with a resolution of 22 mbar; the temperature can be determined with a resolution of 4.3 °C.

Fischer LH; Karakus C; Meier RJ; Risch N; Wolfbeis OS; Holder E; Schäferling M

2012-12-01

345

Restriction of transpiration rate under high vapour pressure deficit and non-limiting water conditions is important for terminal drought tolerance in cowpea.  

UK PubMed Central (United Kingdom)

Drought stress is a major constraint on cowpea productivity, since the crop is grown under warm conditions on sandy soils having low water-holding capacity. For enhanced performance of crops facing terminal drought stress, like cowpea, water-saving strategies are crucial. In this work, the growth and transpiration rate (TR) of 40 cowpea genotypes with contrasting response to terminal drought were measured under well-watered conditions across different vapour pressure deficits (VPD) to investigate whether tolerant and sensitive genotypes differ in their control of leaf water loss. A method is presented to indirectly assess TR through canopy temperature (CT) and the index of canopy conductance (Ig). Overall, plants developed larger leaf area under low than under high VPD, and there was a consistent trend of lower plant biomass in tolerant genotypes. Substantial differences were recorded among genotypes in TR response to VPD, with tolerant genotypes having significantly lower TR than sensitive ones, especially at times with the highest VPD. Genotypes differed in TR response to increasing VPD, with some tolerant genotypes exhibiting a clear VPD breakpoint at about 2.25?kPa, above which there was very little increase in TR. In contrast, sensitive genotypes presented a linear increase in TR as VPD increased, and the same pattern was found in some tolerant lines, but with a smaller slope. CT, estimated with thermal imagery, correlated well with TR and Ig and could therefore be used as proxy for TR. These results indicate that control of water loss discriminated between tolerant and sensitive genotypes and may, therefore, be a reliable indicator of terminal drought stress tolerance. The water-saving characteristics of some genotypes are hypothesised to leave more soil water for pod filling, which is crucial for terminal drought adaptation.

Belko N; Zaman-Allah M; Diop NN; Cisse N; Zombre G; Ehlers JD; Vadez V

2013-03-01

346

An utilization of liquid sublayer dryout mechanism in predicting critical heat flux under low pressure and low velocity conditions in round tubes  

Energy Technology Data Exchange (ETDEWEB)

From a theoretical assessment of extensive critical heat flux (CHF) data under low pressure and low velocity (LPLV) conditions, it was found out that lots of CHF data would not be well predicted by a normal annular film dryout (AFD) mechanism, although their flow patterns were identified as annular-mist flow. To predict these CHF data, a liquid sublayer dryout (LSD) mechanism has been newly utilized in developing the mechanistic CHF model based on each identified CHF mechanism. This mechanism postulates that the CHF occurrence is caused by dryout of the thin liquid sublayer resulting from the annular film separation or breaking down due to nucleate boiling in annular film or hydrodynamic fluctuation. In principle, this mechanism well supports the experimental evidence of residual film flow rate at the CHF location, which can not be explained by the AFD mechanism. For a comparative assessment of each mechanism, the CHF model based on the LSD mechanism is developed together with that based on the AFD mechanism. The validation of these models is performed on the 1406 CHF data points ranging over P=0.1-2 MPa, G=4-499 kg m{sup -2} s{sup -1}, L/D=4-402. This model validation shows that 1055 and 231 CHF data are predicted within {+-}30 error bound by the LSD mechanism and the AFD mechanism, respectively. However, some CHF data whose critical qualities are <0.4 or whose tube length-to-diameter ratios are <70 are considerably overestimated by the CHF model based on the LSD mechanism. These overestimations seem to be caused by an inadequate CHF mechanism classification and an insufficient consideration of the flow instability effect on CHF. Further studies for a new classification criterion screening the CHF data affected by flow instabilities as well as a new bubble detachment model for LPLV conditions, are needed to improve the model accuracy.

Lee, Kwang-Won E-mail: jimlee@ns.kopec.co.kr; Baik, Se-Jin; Ro, Tae-Sun

2000-08-01

347

Optimum condition of thermal cycle for temper bead weld repair of SQV2A pressure vessel steel. Fundamental investigation in Gleeble simulation test  

International Nuclear Information System (INIS)

Temper bead welding technique is one of the most important repair welding methods for large structures for which post weld heat treatment (PWHT) is difficult to perform. In this study the optimum condition of weld thermal cycles to carry out temper bead weld repair for pressure vessel steel SQV2A are investigated taking interest in the improvement of the characteristics of coarse grained heat affected zone (CGHAZ) re-heated to the temperature between 670degC (Acl temperature) and 837degC (Ac3 temperature). Thermal/mechanical simulator Gleeble 1500 is employed to give specimens repeated thermal cycles. Improvability of the Charpy absorbed energy and the hardness for the thermal cycles is discussed. The temper bead thermal cycles were suggested that the peak temperature in the second thermal cycle should be selected as lower than Acl but near Acl. In this case triple thermal cycles temper bead process are enough to improve the characteristics of CGHAZ. When the other peak temperatures (that is, higher than Acl) in the succeeding thermal cycle are applied to CGHAZ, quadruple or more thermal cycle temper bead process should be applied. (author)

2003-01-01

348

Self-diffusion in supercritical water and benzene in high-temperature high-pressure conditions studied by NMR and dynamic solvation-shell model  

Energy Technology Data Exchange (ETDEWEB)

The self-diffusion coefficients of water and organic solvents in the high-temperature high-pressure conditions are studied by using high-temperature NMR and MD simulation methods. The experimental results are analyzed using a scheme based on the solvation shell relaxation time obtained by MD simulation. The dynamic effect of hydrogen bonding is discussed through the comparison between water and a nonpolar organic solvent, benzene, over a wide range of density and temperature. The hydrogen-bonding effects are as follows: (1) the self-diffusion coefficient of water depends on density more weakly than that of benzene, (2) the self-diffusion coefficient of water at the ambient density depends on temperature more strongly than that of benzene at the density, (3) the turnover from the mobile-shell type to the in-shell type with increasing density does not occur in supercritical water up to the ambient density, whereas such turnover is observed in benzene. These contrasts are reflecting the dynamic effect of the anisotropic attractive interactions.

Yoshida, Ken; Uosaki, Yasuhiro [Department of Chemical Science and Technology, Faculty of Engineering, University of Tokushima, 2-1 Minamijosanjima-cho, Tokushima 770-8506 (Japan); Matubayasi, Nobuyuki; Nakahara, Masaru, E-mail: yoshida@chem.tokushima-u.ac.j [Institute for Chemical Research, Kyoto University, Uji, Kyoto, 611-0011 (Japan)

2010-03-01

349

An utilization of liquid sublayer dryout mechanism in predicting critical heat flux under low pressure and low velocity conditions in round tubes  

International Nuclear Information System (INIS)

From a theoretical assessment of extensive critical heat flux (CHF) data under low pressure and low velocity (LPLV) conditions, it was found out that lots of CHF data would not be well predicted by a normal annular film dryout (AFD) mechanism, although their flow patterns were identified as annular-mist flow. To predict these CHF data, a liquid sublayer dryout (LSD) mechanism has been newly utilized in developing the mechanistic CHF model based on each identified CHF mechanism. This mechanism postulates that the CHF occurrence is caused by dryout of the thin liquid sublayer resulting from the annular film separation or breaking down due to nucleate boiling in annular film or hydrodynamic fluctuation. In principle, this mechanism well supports the experimental evidence of residual film flow rate at the CHF location, which can not be explained by the AFD mechanism. For a comparative assessment of each mechanism, the CHF model based on the LSD mechanism is developed together with that based on the AFD mechanism. The validation of these models is performed on the 1406 CHF data points ranging over P=0.1-2 MPa, G=4-499 kg m-2 s-1, L/D=4-402. This model validation shows that 1055 and 231 CHF data are predicted within ±30 error bound by the LSD mechanism and the AFD mechanism, respectively. However, some CHF data whose critical qualities are

2000-01-01

350

A detailed TEM and SEM study of Ni-base alloys oxide scales formed in primary conditions of pressurized water reactor  

International Nuclear Information System (INIS)

The oxide film formed on nickel-based alloys in pressurized water reactors (PWR) primary coolant conditions (325 oC, aqueous media) is very thin, in the range of 1-100 nm thick, depending on the surface state and on the corrosion test duration. The nature and the structure of this scale have been investigated by Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). TEM observations revealed an oxide layer divided in two parts. The internal layer was mainly composed of a continuous spinel layer, identified as a mixed iron and nickel chromite (Ni(1-x)FexCr2O4). Moreover, nodules of Cr2O3, with a size about 5 nm, were present at the interface between this spinel and the alloy. No chromium depletion was observed in the alloy, at the alloy/oxide interface. The external layer is composed of large crystallites corresponding to a spinel structure rich in iron (Ni(1-z)Fe(2+z)O4) resulting from precipitation phenomena. SEM and TEM observations showed a link between the nucleation and/or the growth of crystallites of nickel ferrite and the crystallographic orientation of the substrate. A link between the presence of surface defects and the nucleation of the crystallites was also underlined by SEM observations. Partially hydrated nickel hydroxide, was also observed by TEM in the external scale. Based on these results, some considerations about the mechanism of formation of this oxide layer are discussed.

2010-07-31

351

CFD-tool for assessment of the reactor pressure vessel integrity in pressure thermal shock conditions for lifetime evaluation. Qualification phasis and thermal-hydraulic study of a safety injection in a PWR plant  

International Nuclear Information System (INIS)

[en] Integrity evaluation methods for nuclear Reactor Pressure Vessels (RPVs) under Pressurised Thermal Shock (PTS) loading are applied by French Utility. They are based on the analysis of the behaviour of relatively shallow cracks under PTS loading conditions due to the emergency cooling during SBLOCA transients. This paper presents the Research and Development program started at Electricity De France (EDF) on the CFD determination of the cooling phenomena of a PWR vessel during a Pressurised Thermal Shock. The numerical results are obtained with the thermal-hydraulic tools N3S and Code Saturne, in combination with the thermal-solid computer code SYRTHES to take into account the coupled effect of heat transfer between the fluid flow and the vessel. We first explain the recent improvement of the thermal-hydraulic analysis with the global definition of the SBLOCA transient and the local analysis in the down comer. Then, the qualification task of the EDF numerical tools is described. In order to reach this purpose, we have investigated several configurations related to an injection of cold water and focused our analysis particularly in the cold leg but also in a the down comer. Two experiment test cases have been studied. A comparison between experiment and numerical results in terms of temperature field is presented. On the whole, the main purpose of the numerical thermal-hydraulic studies is to accurately estimate the distribution of fluid temperature in the down comer and the heat transfer coefficients on the inner RPV surface for a fracture mechanics computation which will subsequently assess the associated RPV safety margins. (author)

2004-01-01

352

Breeding pond selection and movement patterns by eastern spadefoot toads (Scaphiopus holbrookii) in relation to weather and edaphic conditions.  

Energy Technology Data Exchange (ETDEWEB)

Cathryn H. Greenberg and George W. Tanner. 2004. Breeding pond selection and movement patterns by eastern spadefoot toads (Scaphiopus holbrookii) in relation to weather and edaphic conditions. J. Herp. 38(4):569-577. Abstract: Eastern Spadefoot Toads (Scaphiopus holbrookii) require fish-free, isolated, ephemeral ponds for breeding but otherwise inhabit the surrounding uplands, commonly xeric longleaf pine (Pinus palustris) ?wiregrass (Aristida beyrichiana). Hence both pond and upland conditions can potentially affect their breeding biology, and population persistence. Hardwood invasion due to fire suppression in sandhills could alter upland and pond suitability by higher hardwood density and increased transpiration. In this paper we explore breeding and neonatal emigration movements in relation to weather, hydrological conditions of ponds, and surrounding upland matrices. We use 9 years of data from continuous monitoring with drift fences and pitfall traps at 8 ephemeral ponds in 2 upland matrices: regularly-burned, savanna-like sandhills (n = 4), and hardwood-invaded sandhills (n = 4). Neither adult nor neonate captures differed between ponds within the 2 upland matrices, suggesting that they are tolerant of upland heterogeneity created by fire frequency. Explosive breeding occurred during 9 periods and in all seasons; adults were captured rarely otherwise. At a landscape-level rainfall, maximum change in barometric pressure, and an interaction between those 2 variables were significant predictors of explosive breeding. At a pond-level, rainfall, change in pond depth during the month prior to breeding, and days since a pond was last dry were significant predictors of adult captures. Transformation date, rather than weather, was associated with neonatal emigrations, which usually were complete within a week. Movement by first-captured adults and neonates was directional, but adult emigrations were apparently not always toward their origin. Our results suggest that Spadefoot Toads are highly adapted to breeding conditions and upland habitat heterogeneity created by weather patterns and fire frequency in Florida sandhills.

Greenberg, Cathyrn, H.; Tanner, George, W.

2004-08-31

353

Territorial characterisation considering geo morphological properties of subsoil as well as climatic and meteorological conditions for the evaluation of the effects of radiological nature on the environment  

International Nuclear Information System (INIS)

The composition and origin of the rocky substratum, the permeability of the ground, its degree of humidity and the particle size are the main factors that influence radon concentration in the subsoil and in the water stratums as well as its upward migration. The climatic and meteorological conditions, particularly the moisture, the barometric pressure and the temperature, can influence more or less directly the underground emanation and diffusion properties of radon and thoron giving rise to short-term modifications of radiological nature in the subsoil, closely related to the presence of these elements. The great concentration of some radioisotopes, in some particular areas, can also induce high dose rates caused by the radiation coming from emergent rocks, due for instance to activities related to building works, with consequent possible exposure of the personnel involved in underground excavations. In such situations it is possible to carry out systematical radiometric measurements, which provide instantaneous and time integrated data, using fixed or movable instrumentation. The stratigraphical structure of the subsoil and the related variations of lithological nature as well as the lack of homogeneity in the land, due also to the unevenness of the ground outline and to the presence of fault planes, increase considerably the complexity of analytical evaluations based upon the chemical and physical characteristics of the subsoil and upon the meteorological and climatic properties.

2002-01-01

354

Cyclic Acyloxonium Ions as Diagnostic Aids in the Characterization of Chloropropanol Esters under Electron Impact (EI), Electrospray Ionization (ESI), and Atmospheric Pressure Chemical Ionization (APCI) Conditions.  

Science.gov (United States)

During mass spectrometric analysis of various lipids and lipid derivatives such as the chlorinated counterparts of triacylglycerols, the detailed structure of the characteristic and common ions formed under electron impact (EI), electrospray ionization (ESI), and atmospheric pressure chemical ionization (APCI) conditions by the loss of a single fatty acid remains ambiguous. These ions are designated in the literature as "diacylglyceride ions" and are frequently depicted with a molecular formula without showing any structural features and sometimes represented as cyclic acyloxonium ions. Characterization of these ions is of considerable importance due to their utility in structural identification of lipid derivatives. This study provides complementary evidence on the cyclic nature of "diacylglyceride ions" through the use of the simplest 3-monochloropropanediol diester as a model and the use of isotope labeling technique. Tandem MS/MS studies have indicated that the ion at m/z 135.6 generated from 1,2-bis(acetoyl)-3-chloropropane through the loss of an acetyl group was identical to the ion at m/z 135.6 generated from 4-chloromethyl-2,2-dimethyl-1,3-dioxolane, the latter being generated from a cyclic precursor through the loss of a methyl radical, keeping the dioxolane ring structure intact, thus confirming the cyclic nature of these ions. The corresponding cyclic oxonium ions generated from longer chain chloropropanol diesters, such as the ion at m/z 331.2 originating from 3-monochloropropanediol (3-MCPD) diesters containing palmitic acid(s), could serve as chemical markers for the presence chloropropanol esters. PMID:23734847

Rahn, Anja K K; Yaylayan, Varoujan A

2013-06-13

355

Structural controls, temperature-pressure conditions and fluid evolution of orogenic gold mineralisation at the Betam mine, south Eastern Desert, Egypt  

Science.gov (United States)

The Betam gold deposit, located in the southern Eastern Desert of Egypt, is related to a series of milky quartz veins along a NNW-trending shear zone, cutting through pelitic metasedimentary rocks and small masses of pink granite. This shear zone, along with a system of discrete shear and fault zones, was developed late in the deformation history of the area. Although slightly sheared and boudinaged within the shear zone, the auriferous quartz veins are characterised by irregular walls with a steeply plunging ridge-in-groove lineation. Shear geometry of rootless intra-folial folds and asymmetrical strain shadows around the quartz lenses suggests that vein emplacement took place under a brittle-ductile shear regime, clearly post-dating the amphibolite-facies regional metamorphism. Hydrothermal alteration is pervasive in the wallrock metapelites and granite including sericitisation, silicification, sulphidisation and minor carbonatisation. Ore mineralogy includes pyrite, arsenopyrite and subordinate galena, chalcopyrite, pyrrhotite and gold. Gold occurs in the quartz veins and adjacent wallrocks as inclusions in pyrite and arsenopyrite, blebs and globules associated with galena, fracture fillings in deformed arsenopyrite or as thin, wire-like rims within or around rhythmic goethite. Presence of refractory gold in arsenopyrite and pyrite is inferred from microprobe analyses. Clustered and intra-granular trail-bound aqueous-carbonic (LCO2 + Laq ± VCO2) inclusions are common in cores of the less deformed quartz crystals, whereas carbonic (LCO2 ± VCO2) and aqueous H2O-NaCl (L + V) inclusions occur along inter-granular and trans-granular trails. Clathrate melting temperatures indicate low salinities of the fluid (3-8 wt.% NaCl eq.). Homogenisation temperatures of the aqueous-carbonic inclusions range between 297 and 323°C, slightly higher than those of the intra-granular and inter-granular aqueous inclusions (263-304°C), which are likely formed during grain boundary migration. Homogenisation temperatures of the trans-granular H2O-NaCl inclusions are much lower (130-221°C), implying different fluids late in the shear zone formation. Fluid densities calculated from aqueous-carbonic inclusions along a single trail are between 0.88 and 0.98 g/cm3, and the resulting isochores suggest trapping pressures of 2-2.6 kbar. Based on the arsenopyrite-pyrite-pyrrhotite cotectic, arsenopyrite (30.4-30.7 wt.% As) associated with gold inclusions indicates a temperature range of 325-344°C. This ore paragenesis constrains f S2 to the range of 10-10 to 10-8.5 bar. Under such conditions, gold was likely transported mainly as bisulphide complexes by low salinity aqueous-carbonic fluids and precipitated because of variations in pH and f O2 through pressure fluctuation and CO2 effervescence as the ore fluids infiltrated the shear zone, along with precipitation of carbonate and sericite. Wallrock sulphidation also likely contributed to destabilising the gold-bisulphide complexes and precipitating gold in the hydrothermal alteration zone adjacent to the mineralised quartz veins.

Zoheir, Basem A.

2008-01-01

356

The relationship between meteorological conditions and index acute coronary events in a global clinical trial.  

UK PubMed Central (United Kingdom)

BACKGROUND: Considerable uncertainty exists concerning the interaction between climate and human health. We explored this issue by evaluating the relationship between meteorological events and acute coronary syndrome (ACS) events. METHODS: 9406 patients in 29 countries at 440 Early versus Delayed, Provisional Eptifibatide in Acute Coronary Syndromes (EARLY ACS) clinical trial sites were linked to a weather station by location. Temperature, barometric pressure, precipitation, wind speed and combined temperature and relative humidity were normalized by location for the 37days prior to the index ACS event that precipitated study enrollment. A meteorological event was defined as a change in any weather metric that was expected to occur in less than 10% of the exposure intervals: four separate 48-hour intervals within the seven days prior to an ACS event (T1, day of event and -1day; T2, -2 to -3days; T3, -4 to -5days; and T4, -6 to -7days). Results are reported as ratio of observed to expected events for the meteorological parameter. RESULTS: There were 10% more drops in temperature observed in T4 (95%CI: 3-17%), and more increases in temperature observed during T1 (4%; 95%CI -2-9%). An excess number of wind speed increases (9%;95%CI 2-16%) and relative humidity increases (6%; 95%CI 0.1-14%) occurred during T4. Additionally, female patients in this cohort presented less often than male patients following drops in average temperature. CONCLUSIONS: Using a new method for integrating meteorological data into a clinical trial dataset, we identified associations between changes in weather conditions and the likelihood of an ACS event.

Ezekowitz JA; Bakal JA; Westerhout CM; Giugliano RP; White H; Keltai M; Prabhakaran D; Tricoci P; Van de Werf F; Califf RM; Newby LK; Armstrong PW

2013-02-01

357

Analysis report of the thermal-hydraulic characteristics of the high temperature/high pressure thermal-hydraulic test facility (VISTA) in steady state conditions  

International Nuclear Information System (INIS)

The VISTA (Experimental Verification by Integral Simulation of Transients and Accidents) is an experimental facility to verify the performance and safety issues of the SMART-P (Pilot plant of the system-integrated modular advanced reactor). The basic design of the SMART-P has been completed by KAERI. The present report describes the experimental results on the water inventory distribution, the pressure distribution, and the differential pressure characteristics of the VISTA facility and on the heat transfer characteristics of the core simulating heater and the steam generator of the VISTA facility. There were little differences of their water inventories between the designed and the measured data. The pressure of the VISTA primary system kept near the steady-state operating pressure of 147 bar, and the differential pressures through the primary and secondary systems increased with the increase of their flow rates. Also the surface temperatures of core simulating heaters were measured, and the overall heat transfer coefficient of the VISTA steam generator was calculated to show a little higher values than that of the SMART-P

2004-01-01

358

Analysis report of the thermal-hydraulic characteristics of the high temperature/high pressure thermal-hydraulic test facility (VISTA) in steady state conditions  

Energy Technology Data Exchange (ETDEWEB)

The VISTA (Experimental Verification by Integral Simulation of Transients and Accidents) is an experimental facility to verify the performance and safety issues of the SMART-P (Pilot plant of the system-integrated modular advanced reactor). The basic design of the SMART-P has been completed by KAERI. The present report describes the experimental results on the water inventory distribution, the pressure distribution, and the differential pressure characteristics of the VISTA facility and on the heat transfer characteristics of the core simulating heater and the steam generator of the VISTA facility. There were little differences of their water inventories between the designed and the measured data. The pressure of the VISTA primary system kept near the steady-state operating pressure of 147 bar, and the differential pressures through the primary and secondary systems increased with the increase of their flow rates. Also the surface temperatures of core simulating heaters were measured, and the overall heat transfer coefficient of the VISTA steam generator was calculated to show a little higher values than that of the SMART-P.

Park, Hyun Sik; Choi, Ki Yong; Cho, Seok; Lee, Sung Jae; Song, Chul Hwa; Park, Chun Kyong; Chung, Moon Ki

2004-01-01

359

Electrical resistivity of YbRh2Si2 and EuT2Ge2 (T=Co,Cu) at extreme conditions of pressure and temperature  

International Nuclear Information System (INIS)

This investigation addresses the effect that pressure, p, and temperature, T, have on 4f states of the rare-earth elements in the isostructural YbRh2Si2, EuCo2Ge2, and EuCu2Ge2 compounds. Upon applying pressure the volume of the unit cell reduces, enforcing either the enhancement of the hybridization of the 4f localized electrons with the ligand or a change in the valence state of the rare-earth ions. Here, we probe the effect of a pressure-induced lattice contraction on these system by means of electrical-resistivity measurements, ?(T), from room temperature down to 100 mK. (orig.)

2006-01-01

360

Basic investigation into the burn-out of various coal types under pressurized pulverized coal combustion conditions; Grundlegende Untersuchungen zum Umsatz verschiedener Kohlen unter Druckkohlenstaub-Feuerungsbedingungen  

Energy Technology Data Exchange (ETDEWEB)

The development of pressurized p.f. combustion is still in the bud. Major importance is attributed to the understanding of the chemo-physical processes in the combustion chamber; the findings made here are the basis for an optimized combustion process with a view to economy and environmental acceptability. Experiments with various coal types in a pressurized entrained-flow reactor at an industrial level and a kinetic modelling of degasification, gas phases reactions and coke burn-out under pressure showed the relation of coke burn-out reactions with dwell time, O{sub 2} partial pressure, pressure and gas temperature. From the experimentally determined data (particle temperature, size and density, burn-out degree) the reaction rates of the coke burn-out were determined and served as basic data for the kinetic modelling. Basic statements regarding the fuel combusted under pressure could be deduced from the results. (orig.) [Deutsch] Die Druckkohlenstaubfeuerung steht am Anfang ihrer Entwicklung. Dem Verstaendnis der chemisch-physikalischen Vorgaenge im Feuerraum kommt eine wesentliche Bedeutung zu. Die hier gewonnenen Erkenntnisse sind Grundlage fuer einen hinsichtlich Wirtschaftlichkeit und Umweltvertraeglichkeit optimierten Verbrennungsprozess. Experimente mit verschiedenen Kohlen an einem druckaufgeladenen Entrained-Flow-Reaktor im Technikumsmassstab und eine kinetische Modellierung von Entgasung, Gasphasenreaktionen und Koksabbrand unter Druck zeigten die Abhaengigkeit der Koksabbrandreaktionen von Verweilzeit, O2-Partialdruck, Druck und Gastemperatur. Aus den experimentell ermittelten Daten (Partikeltemperatur, -groesse und -dichte, Ausbrandgrad) wurden die Reaktionsraten des Koksabbrandes bestimmt und dienten als Eingangsgroesse fuer die kinetische Modellierung. Aus den Ergebnissen wurden grundlegende Aussagen zum Brennstoffumsatz unter Druck abgeleitet. (orig.)

Bauer, C.; Spliethoff, H.; Hein, K.R.G. [Stuttgart Univ. (Germany). Inst. fuer Verfahrenstechnik und Dampfkesselwesen

1999-03-01

 
 
 
 
361

1/5-scale experiment of a Mark I boiling-water reactor pressure-suppression system under hypothetical LOCA conditions  

International Nuclear Information System (INIS)

[en] Experimental results show the sensitivity of hydrodynamically generated vertical loads to changes in the drywell pressurization rate, downcomer submergence, and vent-line loss coefficient. Insignificant effects on peak vertical loads were observed when the vent-line loss was varied. Peak vertical loads can be reduced by adding initial drywell overpressure so that the downcomers are partly cleared of water. Spatial variation of pressure at about the time of vent clearing is seen in comparisons of data from locations along the axis of the toroidal wetwell

1977-08-05

362

Test report: Preliminary tests for the High Flux Reactor: Experimental determination of flow redistribution conditions at pressures between 4 and 5 kg/cm2 abs in a rectangular channel 2 mm thick and 60 cm long  

International Nuclear Information System (INIS)

In the context of safety research for the OSIRIS reactor, tests have been performed on the Super BOB cell with a view to determining experimentally the internal characteristics (or ''S'' curves) of a channel with a rectangular heating cross-section 2 x 38 mm and 600 mm long. During these tests the maximum pressure at the channel exit was brought to 3 kg/cm2 abs. The pressurization level in the High Flux Reactor will be higher. That is why tests have been carried out at maximum pressure of 5 kg/cm2 abs allowable on the ''super BOB'' loop without modifying it. The first objective of this test series was to determine the ''S'' curves and the exchange coefficients experimentally. This document discusses the test conditions and test results.

1989-01-01

363

Decomposition of carbon monoxide and its reaction with hydrogen on iron films under static conditions at pressures between 2 and 25 mbar and at temperatures between 373 and 573 K  

Energy Technology Data Exchange (ETDEWEB)

When carbon monoxide is adsorbed on iron films at temperatures T >= 373 K carbon dioxide and carbon are formed. The Boudouard equilibrium is, however, not established at the chosen reaction conditions. In the presence of hydrogen the carbon monoxide adsorption leads to the formation of methane, carbon dioxide, and water. There is no correlation between the formation of water and of methane. The methane formation increases with both the increase in the total pressure and the increase in the partial pressure ratio psub(H2):psub(CO). The ratio of the partial pressures of CO, H/sub 2/, CO/sub 2/, and H/sub 2/O point to the establishment of the water gas equilibrium at medium temperatures.

Wedler, G.; Koerner, H.

1981-04-01

364

Wind power barometer; Barometre eolien  

Energy Technology Data Exchange (ETDEWEB)

The global wind power market not only repelled the strictures of the financial crisis, but saw the installation of 37 GW in 2009, which is almost 10 GW up on 2008. China and the United States registered particularly steady growth and the European Union also picked up momentum to break its installation record. A total capacity of 158 GW of wind power are now installed across the world from which 74.8 GW in the European Union. Among the European countries Denmark has the highest wind capacity per inhabitant in 2009: 627.5 kW/1000 inhabitants. Spain seeks to limit its market's growth in order to better manage the development of wind energy across the country. German growth is back, Italy chalks up a new record for installation and the French market is becoming increasingly regulated. United-Kingdom is developing offshore wind farms: the offshore capacity could reasonably rise to 20000 MW by 2020. The last part of the article reports some economical news from the leading players: Vestas, GE-Energy, Gamesa, Enercon, Sinovel and Siemens. (A.C.)

Anon.

2010-03-15

365

Changes in entrapped gas content and hydraulic conductivity with pressure.  

UK PubMed Central (United Kingdom)

Water table fluctuations continuously introduce entrapped air bubbles into the otherwise saturated capillary fringe and groundwater zone, which reduces the effective (quasi-saturated) hydraulic conductivity, K(quasi), thus impacting groundwater flow, aquifer recharge and solute and contaminant transport. These entrapped gases will be susceptible to compression or expansion with changes in water pressure, as would be expected with water table (and barometric pressure) fluctuations. Here we undertake laboratory experiments using sand-packed columns to quantify the effect of water table changes of up to 250 cm on the entrapped gas content and the quasi-saturated hydraulic conductivity, and discuss our ability to account for these mechanisms in ground water models. Initial entrapped air contents ranged between 0.080 and 0.158, with a corresponding K(quasi) ranging between 2 and 6 times lower compared to the K(s) value. The application of 250 cm of water pressure caused an 18% to 26% reduction in the entrapped air content, resulting in an increase in K(quasi) by 1.16 to 1.57 times compared to its initial (0 cm water pressure) value. The change in entrapped air content measured at pressure step intervals of 50 cm, was essentially linear, and could be modeled according to the ideal gas law. Meanwhile, the changes in K(quasi) with compression-expansion of the bubbles because of pressure changes could be adequately captured with several current hydraulic conductivity models.

Marinas M; Roy JW; Smith JE

2013-01-01

366

A model for the effective diffusion of gas or the vapor phase in a fractured media unsaturated zone driven by periodic atmospheric pressure fluctuations  

Energy Technology Data Exchange (ETDEWEB)

There is evidence for migration of tritiated water vapor through the tuff in the unsaturated zone from the buried disposal shafts located on a narrow mesa top at Area G, Los Alamos, NM. Field data are consistent with an effective in-situ vapor phase diffusion coefficient of 1.5x10{sup {minus}3} m{sup s}/s, or a factor of 60 greater than the binary diffusion coefficient for water vapor in air. A model is derived to explain this observation of anomolously large diffusion, which relates an effective vapor or gas phase diffusion coefficient in the fractured porous media to the subsurface propagation of atmospheric pressure fluctuations (barometric pumping). The near surface (unattenuated) diffusion coefficient is independent of mode period under the simplified assumptions of a complete {open_quote}mixing mechanism{close_quote} for the effective diffusion process. The unattenuated effective diffusion driven by this barometric pumping is proportional to an average media permeability times the sum of the square of pressure mode amplitudes, while the attenuation length is proportional to the squarer root of the product of permeability times mode period. There is evidence that the permeability needed to evaluate the pressure attenuation length is the in-situ value, approximately that of the matrix. The diffusion which results using Area G parameter values is negligible in the matrix but becomes large at the effective permeability of the fractured tuff matrix. The effective diffusion coefficient predicted by this model, due to pressure fluctuations and the observed fracture characteristics, is in good agreement with the observed in-situ diffusion coefficient for tritium field measurements. It is concluded that barometric pumping in combination with the enhanced permeability of the fractured media is a likely candidate to account for the observed in-field migration of vapor in the near surface unsaturated zone at Area G.

Vold, E.L.

1997-03-01

367

Development of Simulation System for Hot Gas Filtration by Ceramic Candle Filters on High Temperature and/or High Pressure Conditions  

Energy Technology Data Exchange (ETDEWEB)

Hot gas filtration from industrial processes offers various advantages in terms of improvement of process efficiencies, heat recovery and protection of plant installation. Especially hot gas filtration is an essential technology for pressurized fluidized bed combustion (PFBC) and integrated gasification combined cycle (IGCC).

Park, S.J.; Lim, J.H.; Kim, S.D.; Choi, H.K.; Park, H,S.; Park, Y.O.

2002-09-19

368

Special video diagnostics and optical temperature measurements by means of pressure sensors for thermal reactors also in extreme conditions; Spezial-Videodiagnostik und optische Temperaturmessung mittels Drucksonden fuer thermische Reaktoren, auch unter extremsten Bedingungen  

Energy Technology Data Exchange (ETDEWEB)

In order to make thermal utilisation of refuse economically efficient, optimized control of the thermal processes is required. The authors` own work on process monitoring in thermal waste utilisation showed that combustion space analyses are possible with special sensor systems that can be used at full-load operating conditions (i.e. pressures up to 30 bar, temperatures above 1000degreeC, aggressive media etc.) without interfering with the combustion process. (orig./AKF)

Werschy, M.; Groeschel, L.

1997-12-31

369

Intraosseous phlebography, intraosseous pressure measurements and sup(99m)Tc-polyphosphate scintigraphy in patients with various painful conditions in the hip and knee  

International Nuclear Information System (INIS)

[en] Twenty-five patients with pain in the knee or hip were examined by means of bilateral intraosseous phlebography, intraosseous pressure measureme