Stability of one-step methods in transient nonlinear heat conduction

International Nuclear Information System (INIS)

Hughes, J.R.

1977-01-01

The purpose of the present work is to ascertain practical stability conditions for one-step methods commonly used in transient nonlinear heat conduction analyses. The class of problems considered is governed by a temporally continuous, spatially discrete system involving the capacity matrix C, conductivity matrix K, heat supply vector, temperature vector and time differenciation. In the linear case, in which K and C are constant, the stability behavior of one-step methods is well known. But in this paper the concepts of stability, appropriate to the nonlinear problem, are thoroughly discussed. They of course reduce to the usual stability criterion for the linear, constant coefficient case. However, for nonlinear problems there are differences and these ideas are of key importance in obtaining practical stability conditions. Of particular importance is a recent result which indicates that, in a sense, the trapezoidal and midpoint families are quivalent. Thus, stability results for one family may be translated into a result for the other. The main results obtained are summarized as follows. The stability behavior of the explicit Euler method in the nonlinear regime is analogous to that for linear problems. In particular, an a priori step size restriction may be determined for each time step. The precise time step restriction on implicit conditionally stable members of the trapezoidal and midpoint families is shown not to be determinable a priori. Of considerable practical significance, unconditionally stable members of the trapezoidal and midpoint families are identified

Radial effects in heating and thermal stability of a sub-ignited tokamak

International Nuclear Information System (INIS)

Fuchs, V.; Shoucri, M.M.; Thibaudeau, G.; Harten, L.; Bers, A.

1982-02-01

The existence of thermally stable sub-ignited equilibria of a tokamak reactor, sustained in operation by a feedback-controlled supplementary heating source, is demonstrated. The establishment of stability depends on a number of radially non-uniform, nonlinear processes whose effect is analyzed. One-dimensional (radial) stability analyses of model transport equations, together with numerical results from a 1-D transport code, are used in studying the heating of DT-plasmas in the thermonuclear regime. Plasma core supplementary heating is found to be a thermally more stable process than bulk heating. In the presence of impurity line radiation, however, core-heated temperature profiles may collapse, contracting inward from the limiter, the result of an instability caused by the increasing nature of the radiative cooling rate, with decreasing temperature. Conditions are established for the realization of a sub-ignited high-Q, toroidal reactor plasma with appreciable output power

Effect of hydrogen peroxide on improving the heat stability of whey protein isolate solutions.

Science.gov (United States)

Sutariya, Suresh; Patel, Hasmukh

2017-05-15

Whey protein isolate (WPI) solutions (12.8%w/w protein) were treated with varying concentrations of H 2 O 2 in the range of 0-0.144 H 2 O 2 to protein ratios (HTPR) by the addition of the required quantity of H 2 O 2 and deionized water. The samples were analyzed for heat stability, rheological properties, denaturation level of β-lactoglobulin (β-LG) and α-lactalbumin (α-LA). The samples treated with H 2 O 2 concentration >0.072 (HTPR) showed significant improvement in the heat stability, and decreased whey protein denaturation and aggregation. The WPI solution treated with H 2 O 2 (>0.072 HTPR) remained in the liquid state after heat treatment at 120°C, whereas the control samples formed gel upon heat treatment. Detailed analysis of these samples suggested that the improvement in the heat stability of H 2 O 2 treated WPI solution was attributed to the significant reduction in the sulfhydryl-disulfide interchange reaction during denaturation of β-LG and α-LA. Copyright © 2016 Elsevier Ltd. All rights reserved.

Impact of source and level of calcium fortification on the heat stability of reconstituted skim milk powder.

Science.gov (United States)

Vyas, H K; Tong, P S

2004-05-01

Calcium enrichment of food and dairy products has gained interest with the increased awareness about the importance of higher calcium intake. Calcium plays many important roles in the human body. Dairy products are an excellent source of dietary calcium, which can be further fortified with calcium salts to achieve higher calcium intake per serving. However, the addition of calcium salts can destabilize food systems unless conditions are carefully controlled. The effect of calcium fortification on the heat stability of reconstituted skim milk was evaluated, using reconstituted skim milks with 2 protein levels: 1.75 and 3.5% (wt/wt) prepared using low and high heat powders. Calcium carbonate, phosphate, lactate, and citrate were used for fortification at 0.15, 0.18, and 0.24% (wt/wt). Each sample was analyzed for solubility, heat stability, and pH. The addition of phosphate and lactate salts lowered the pH of milk, citrate did not have any major effect, and carbonate for the 1.75% protein samples increased the pH. In general, changes in solubility and heat stability were associated with changes in pH. Calcium addition decreased the solubility and heat stability. However, interestingly, the presence of carbonate salt greatly increased the heat stability for 1.75% protein samples. This is due to the neutralizing effect of calcium carbonate when it goes into solution. The results suggested that the heat stability of milk can be affected by the type of calcium salt used. This may be applied to the development of milk-based calcium enriched beverages.

Heat shock modulates the subcellular localization, stability, and activity of HIPK2

International Nuclear Information System (INIS)

Upadhyay, Mamta; Bhadauriya, Pratibha; Ganesh, Subramaniam

2016-01-01

The homeodomain-interacting protein kinase-2 (HIPK2) is a highly conserved serine/threonine kinase and is involved in transcriptional regulation. HIPK2 is a highly unstable protein, and is kept at a low level under normal physiological conditions. However, exposure of cells to physiological stress – such as hypoxia, oxidative stress, or UV damage – is known to stabilize HIPK2, leading to the HIPK2-dependent activation of p53 and the cell death pathway. Therefore HIPK2 is also known as a stress kinase and as a stress-activated pro-apoptotic factor. We demonstrate here that exposure of cells to heat shock results in the stabilization of HIPK2 and the stabilization is mediated via K63-linked ubiquitination. Intriguingly, a sub-lethal heat shock (42 °C, 1 h) results in the cytoplasmic localization of HIPK2, while a lethal heat shock (45 °C, 1 h) results in its nuclear localization. Cells exposed to the lethal heat shock showed significantly higher levels of the p53 activity than those exposed to the sub-lethal thermal stress, suggesting that both the level and the nuclear localization are essential for the pro-apoptotic activity of HIPK2 and that the lethal heat shock could retain the HIPK2 in the nucleus to promote the cell death. Taken together our study underscores the importance of HIPK2 in stress mediated cell death, and that the HIPK2 is a generic stress kinase that gets activated by diverse set of physiological stressors.

Heat shock modulates the subcellular localization, stability, and activity of HIPK2

Energy Technology Data Exchange (ETDEWEB)

Upadhyay, Mamta; Bhadauriya, Pratibha; Ganesh, Subramaniam, E-mail: sganesh@iitk.ac.in

2016-04-15

The homeodomain-interacting protein kinase-2 (HIPK2) is a highly conserved serine/threonine kinase and is involved in transcriptional regulation. HIPK2 is a highly unstable protein, and is kept at a low level under normal physiological conditions. However, exposure of cells to physiological stress – such as hypoxia, oxidative stress, or UV damage – is known to stabilize HIPK2, leading to the HIPK2-dependent activation of p53 and the cell death pathway. Therefore HIPK2 is also known as a stress kinase and as a stress-activated pro-apoptotic factor. We demonstrate here that exposure of cells to heat shock results in the stabilization of HIPK2 and the stabilization is mediated via K63-linked ubiquitination. Intriguingly, a sub-lethal heat shock (42 °C, 1 h) results in the cytoplasmic localization of HIPK2, while a lethal heat shock (45 °C, 1 h) results in its nuclear localization. Cells exposed to the lethal heat shock showed significantly higher levels of the p53 activity than those exposed to the sub-lethal thermal stress, suggesting that both the level and the nuclear localization are essential for the pro-apoptotic activity of HIPK2 and that the lethal heat shock could retain the HIPK2 in the nucleus to promote the cell death. Taken together our study underscores the importance of HIPK2 in stress mediated cell death, and that the HIPK2 is a generic stress kinase that gets activated by diverse set of physiological stressors.

Enhancement of ionic conductivity in stabilized zirconia ceramics under millimeter-wave irradiation heating

International Nuclear Information System (INIS)

Kishimoto, Akira; Ayano, Keiko; Hayashi, Hidetaka

2011-01-01

Ionic conductivity in yttria-stabilized zirconia ceramics under millimeter-wave irradiation heating was compared with that obtained using conventional heating. The former was found to result in higher conductivity than the latter. Enhancement of the ionic conductivity and the reduction in activation energy seemed to depend on self-heating resulting from the millimeter-wave irradiation. Millimeter-wave irradiation heating restricted the degradation in conductivity accompanying over-substitution, suggesting the optimum structure that provided the maximum conductivity could be different between the two heating methods.

Effect of Stabilization Heat Treatment on Time-Dependent Polarization Losses in Sintered Nd-Fe-B Permanent Magnets

Directory of Open Access Journals (Sweden)

Tuominen S.

2013-01-01

Full Text Available Some companies in the motor and generator industry utilizing sintered NdFeB magnets have adopted pre-ageing heat treatment in order to improve the stability of the magnets. The parameters of this stabilization heat treatment are based mainly on assumptions rather than on any published research results. In this work, the effects of pre-ageing treatment on the time-dependent polarization losses of two different types of commercial sintered NdFeB magnets were studied. The material showing the squarer J(H curve did not benefit from the pre-ageing treatment, since it seems to be stable under a certain critical temperature. In contrast, a stabilizing effect was observed in the material showing rounder J(H curve. After the stabilization heat treatment, the polarization of the magnets was found to be at lower level, but unchanged over a certain period of time. The length of this period depends on the temperature and the duration of the pre-ageing treatment. In addition, our analysis reveals that the stabilization heat treatment performed in an open circuit condition does not stabilize the magnet uniformly.

Influence of calcium chelators on concentrated micellar casein solutions : from micellar structure to viscosity and heat stability

NARCIS (Netherlands)

Kort, de E.J.P.

2012-01-01

In practice it is challenging to prepare a concentrated medical product with high heat stability
and low viscosity. Calcium chelators are often added to dairy products to improve heat stability,
but this may increase viscosity through interactions with the casein proteins. The aim of

Effect of nitrite on the microbiological stability of canned Vienna sausages preserved by mild heat treatment or combinations of heat and irradiation

International Nuclear Information System (INIS)

Farkas, J.; Zukal, E.; Incze, K.

1973-01-01

Keeping quality of Vienna sausages packed in No. 1/5 cans (ca 200 g) with salt brine and heat treated with F 0 values in the range of 0.25-0.55 was studied as a function of sodium nitrate addition. In uninoculated cans the heat requirement of preservation proved to be about 0.3 F 0 in the presence of 300 ppm NaNO 2 . A heat treatment of 0.55 F 0 and 200 ppm NaNO 2 resulted in higher microbiological stability of cans inoculated with 2x10 4 /tin Clostridium sporogenes spores than a heat treatment of 1.9 F 0 without nitrite addition. The effect of the combination of heat treatment of 0.35-0.55 F 0 and 0.45 Mrad of gamma irradiation was also studied with inoculated cans. The combination of irradiation plus heat resulted in a higher microbiological stability of the samples than the reversed order of the treatments, but this synergistic effect could not be proved in all experiments. The addition of 200 ppm NaNO 2 was not as effective in increasing the shelf-life of combination treated samples as with the solely heat treated ones. In a medium composed of a 50% extract of Vienna sausages (pH 6.4, asub(w) 0.96) and inoculated with 10 5 per ml Clostridium sporogenes spores 100 ppm or more NaNO 2 was required to ensure microbiological stability of samples heat treated with F 0 0.4. In the range of the permitted concentration level for canned meat products, sodium nitrite did not influence the heat resistance of Clostridium sporogenes, but inhibited the germination of the surviving spores. (F.J.)

Hydrodynamic stability of thermoviscous liquid film inside a rotating horizontal cylinder: Heating and cooling effects

Science.gov (United States)

Kumawat, Tara Chand; Tiwari, Naveen

2018-03-01

Steady two-dimensional solutions and their stability analysis are presented for thin film of a thermoviscous liquid flowing inside a cylinder rotating about its horizontal axis. The inner surface of the cylinder is either uniformly hotter or colder than the enveloping air. The mass, momentum, and energy equations are simplified using thin-film approximation. The analytically obtained film thickness evolution equation consists of various dimensionless parameters such as gravitational number, Bond number, Biot number, thermoviscosity number, and Marangoni number. The viscosity of the liquid is considered as an exponential function of temperature. The viscosity increases (decreases) within the film thickness away from the inner surface of the cylinder when the surface is uniformly hotter (colder) than the atmosphere. For hotter (colder) surface, the film thickness on the rising side decreases (increases) when convective heat transfer at the free surface is increased. The surface tension gradient at the free surface generates Marangoni stress that has a destabilizing (stabilizing) effect on the thin film flow in the case of a hotter (colder) cylinder. The thermoviscosity number stabilizes (destabilizes) the flow on a heating (cooling) surface and this effect increases with an increase in the heat transfer at the free surface. For a hotter surface and in the presence of Marangoni stress, the convective heat transfer at the interface has the destabilizing effect for small values of the Biot number and assumes a stabilizing role for larger values. Non-linear simulations show consistency with the linear stability analysis.

Stabilization of a magnetic island by localized heating in a tokamak with stiff temperature profile

Science.gov (United States)

Maget, Patrick; Widmer, Fabien; Février, Olivier; Garbet, Xavier; Lütjens, Hinrich

2018-02-01

In tokamaks plasmas, turbulent transport is triggered above a threshold in the temperature gradient and leads to stiff profiles. This particularity, neglected so far in the problem of magnetic island stabilization by a localized heat source, is investigated analytically in this paper. We show that the efficiency of the stabilization is deeply modified compared to the previous estimates due to the strong dependence of the turbulence level on the additional heat source amplitude inside the island.

Improved damp heat stability of Ga-Doped ZnO thin film by pretreatment of the polyethylene terephthalate substrate

Science.gov (United States)

Kim, B. B.; Seo, S. G.; Lim, Y. S.; Choi, H.-S.; Seo, W.-S.; Park, H.-H.

2013-09-01

A study on the damp heat stability of transparent conducting ZnO thin film grown on a polyethylene terephthalate substrate (PET) is reported. By thermal annealing of the PET substrate at 100°C with Ar flow in a vacuum chamber prior to the sputtering growth of Ga-doped ZnO (GZO) thin film, significantly enhanced damp heat stability was achieved at 60°C with a 90% relative humidity. Electrical and structural characterizations of the GZO thin films were carried out and the effects of the pretreatment on the improved damp heat stability are discussed.

Stability of one-step methods in transient nonlinear heat conduction

International Nuclear Information System (INIS)

Hughes, J.R.

1977-01-01

The purpose of the present work is to ascertain practical stability conditions for one-step methods commonly used in transient nonlinear heat conduction analyses. In this paper the concepts of stability, appropriate to the nonlinear problem, are thoroughly discussed. They of course reduce to the usual stability critierion for the linear, constant coefficient case. However, for nonlinear problems there are differences and theses ideas are of key importance in obtaining practical stability conditions. Of particular importance is a recent result which indicates that, in a sense, the trapezoidal and midpoint families are equivalent. Thus, stability results for one family may be translated into a result for the other. The main results obtained are: The stability behaviour of the explicit Euler method in the nonlinear regime is analogous to that for linear problems. In particular, an a priori step size restriction may be determined for each time step. The precise time step restriction on implicit conditionally stable members of the trapezoidal and midpoint families is shown not to be determinable a priori. Of considerable practical significance, unconditionally stable members of the trapezoidal and midpoint families are identified. All notions of stability employed are motivated and defined, and their interpretations in practical computing are indicated. (Auth.)

Alfven wave heating and stability

International Nuclear Information System (INIS)

Villard, L.; Brunner, S.; Jaun, A.; Vaclavik, J.

1994-10-01

Alfven waves in fusion plasmas play an important role in a number of situations. First, in Alfven Wave Heating (AWH) schemes. Second, both theory and experiment have demonstrated the existence of Global Alfven Eigenmodes (GAEs). GAEs have been observed in different tokamaks (PRETEXT, TCA, TEXTOR, etc.) and, more recently, in a stellarator (Wendelstein 7-AS) where they were shown to become unstable under intense Neutral Beam injection. Third, the existence and possible destabilization by fast ions of Toroidicity induced Alfven Eigenmodes (TAEs) has been evidenced both theoretically and experimentally. This destabilization could hamper the operation of a magnetically confined fusion reactor by setting a limit on the number of fusion alpha particles in the plasma. It is therefore crucial to understand the mechanisms leading to the occurrence of the instability and also those that can stabilize the TAEs by increasing the strength of the damping. The aim is to be able to devise possible ways to avoid the instability of Alfven eigenmodes in a region of parameter space that is compatible with the functioning of a fusion reactor. A global perturbative approach is presented to tackle the problem of the linear stability of TAEs. Our model computes the overall wave particle power transfers to the different species and thus could also be applied to the study of alpha power extraction in the presence of Alfven waves. We indicate also how to go beyond the perturbative approach. (author) 15 figs., 38 refs

Stability analysis of direct contact heat exchangers subject to system perturbations. Final report, Task 2

Energy Technology Data Exchange (ETDEWEB)

Jacobs, H.R.

1985-01-01

This report includes a project summary, copies of two papers resulting from the work and the Ph.D. Dissertation of Dr. Mehdi Golafshani entitled, ''Stability of a Direct Contact Heat Exchanger''. Specifically, the work deals with the operational stability of a spray column type heat exchanger subject to disturbances typical of those which can occur for geothermal applications. A computer program was developed to solve the one-dimensional transient two-phase flow problem and it was applied to the design of a spray column. The operation and design of the East Mesa 500kW/sub e/ direct contactor was assessed. It is shown that the heat transfer is governed by the internal resistance of the dispersed phase. In fact, the performance is well-represented by diffusion of heat within the drops. 5 refs.

A Policy study on stabilization of heating oil supply and demand

Energy Technology Data Exchange (ETDEWEB)

Lee, Bok Jae [Korea Energy Economics Institute, Euiwang (Korea)

1999-03-01

As a principal heating fuel for household and commercial sector, and a heat source fuel for industry, the heating oil shows its great demand intensively during a specific period (wintertime) due to its characteristics. It represents that the fluctuation of heating oil demand throughout the year is very extreme. Therefore, the stable supply of heating oil has been rising as an important task. It is desirable to develop and supply a new type of heating oil compounded of kerosene and gasoline with appropriate ratio for short- and mid-term to have a stable supply and demand of heating oil. For long-term prospect, it is desirable to supply petroleum products mixing gasoline and B-C oil as heating oil when it is equipped with combustion technology of boiler and distribution system. In this case, it is required to have investment on infrastructure for the supply of new heating oil (mixture of gasoline and B-C oil) and a proper preparatory period for the conversion of equipment (such as a boiler). The vitalization of storing oil is essential to stabilize the supply and demand of heating oil. In order to vitalize it, the price of heating oil should be determined by a market function reflecting the seasonal supply and demand circumstances. (author). 101 refs., 5 figs., 83 tabs.

Heat stability and acid gelation properties of calcium-enriched reconstituted skim milk affected by ultrasonication.

Science.gov (United States)

Chandrapala, Jayani; Bui, Don; Kentish, Sandra; Ashokkumar, Muthupandian

2014-05-01

The aggregation of proteins after heating of calcium-fortified milks has been an ongoing problem in the dairy industry. This undesirable effect restricts the manufacture of calcium rich dairy products. To overcome this problem, a completely new approach in controlling the heat stability of dairy protein solutions, developed in our lab, has been employed. In this approach, high intensity, low frequency ultrasound is applied for a very short duration after a pre-heating step at ⩾70 °C. The ultrasound breaks apart whey/whey and whey/casein aggregates through the process of acoustic cavitation. Protein aggregates do not reform on subsequent post-heating, thereby making the systems heat stable. In this paper, the acid gelation properties of ultrasonicated calcium-enriched skim milks have also been investigated. It is shown that ultrasonication alone does not change the gelation properties significantly whereas a sequence of preheating (72 °C/1 min) followed by ultrasonication leads to decreased gelation times, decreased gel syneresis and increased skim milk viscosity in comparison to heating alone. Overall, ultrasonication has the potential to provide calcium-fortified dairy products with increased heat stability. However, enhanced gelation properties can only be achieved when ultrasonication is completed in conjunction with heating.

Determination of Specific Heat Capacity on Composite Shape-Stabilized Phase Change Materials and Asphalt Mixtures by Heat Exchange System.

Science.gov (United States)

Ma, Biao; Zhou, Xue-Yan; Liu, Jiang; You, Zhanping; Wei, Kun; Huang, Xiao-Feng

2016-05-19

Previous research has shown that composite shape-stabilized phase change material (CPCM) has a remarkable capacity for thermal storage and stabilization, and it can be directly applied to highway construction without leakage. However, recent studies on temperature changing behaviors of CPCM and asphalt mixture cannot intuitively reflect the thermoregulation mechanism and efficiency of CPCM on asphalt mixture. The objective of this paper is to determine the specific heat capacity of CPCM and asphalt mixtures mixed with CPCM using the heat exchange system and the data acquisition system. Studies have shown that the temperature-rise curve of 5 °C CPCM has an obvious temperature plateau, while an asphalt mixture mixed with 5 °C CPCM does not; with increasing temperature, the specific heat capacities of both 5 °C CPCM and asphalt mixture first increase and then decrease, while the variation rate of 5 °C CPCM is larger than that of the asphalt mixture, and the maximum specific heat capacity of 5 °C CPCM appears around the initial phase change temperature. It is concluded that the temperature intervals of 5 °C CPCM are -18 °C-7 °C, 7 °C-25 °C and 25 °C-44 °C, respectively, and that of the asphalt mixture are -18 °C~10 °C, -10 °C~5 °C and 5 °C~28 °C. A low dosage of 5 °C CPCM has little influence on the specific heat capacity of asphalt mixture. Finally, the functions of specific heat capacities and temperature for CPCM and asphalt mixture mixed with CPCM were recommended by the sectional regression method.

Temperature, heat content, mixing and stability in Lake Orta: a pluriannual investigation

Directory of Open Access Journals (Sweden)

Luigi BARBANTI

2001-02-01

Full Text Available This paper describes the overall state of some physical phenomena occurring in Lake Orta, such as thermal stratification and destratification, accumulation and release of heat, vertical winter mixing, and stability of the water mass. The historical series of temperature distribution along the water column in the period 1984-1999, from which the holo-oligomictic character of Lake Orta emerges, is analysed. The monthly evaluation of the heat contents metre by metre from 0 to 143 m depth reveals how the complete winter mixing occurs only when the energy present within the whole column is less than 1,675 MJ m-2; above this value the circulation is only partial, as in the other deep subalpine lakes. A water layer in the deep hypolimnion has been shown to contain a climatic memory, which has generally increased since 1981. Walker’s stability analysis has revealed that when at a depth below 90 metres there is a level where 0.07 J m-2 are exceeded, total mixing cannot take place. In contrast, the Birgean work identifies, during the heating phase, the layers of the lake where energy is stored or lost.

Hydraulic Stability of Heat Networks for Connection of New Consumers

Science.gov (United States)

Seminenko, A. S.; Sheremet, E. O.; Gushchin, S. V.; Elistratova, J. V.; Kireev, V. M.

2018-03-01

Nowadays due to intensive urban construction, there is a need to connect new consumers to existing heating networks. Often the connection of new consumers leads to a hydraulic misalignment of the network, which in turn affects supplying existing consumers with heat. In order to minimize the possibility of misalignment, appropriate recommendations are needed that can be obtained during the research. In the article, the authors carried out a required experiment aimed at revealing the influence of the new consumers’ connection on the hydraulic stability of the entire network. The result of the research is relevant recommendations that will be useful for engineering specialists both for the design of new networks and the reconstruction of the old ones.

Post-sampling release of free fatty acids - effects of heat stabilization and methods of euthanasia.

Science.gov (United States)

Jernerén, Fredrik; Söderquist, Marcus; Karlsson, Oskar

2015-01-01

The field of lipid research has made progress and it is now possible to study the lipidome of cells and organelles. A basic requirement of a successful lipid study is adequate pre-analytical sample handling, as some lipids can be unstable and postmortem changes can cause substantial accumulation of free fatty acids (FFAs). The aim of the present study was to investigate the effects of conductive heat stabilization and euthanasia methods on FFA levels in the rat brain and liver using liquid chromatography tandem mass spectrometry. The analysis of brain homogenates clearly demonstrated phospholipase activity and time-dependent post-sampling changes in the lipid pool of snap frozen non-stabilized tissue. There was a significant increase in FFAs already at 2min, which continued over time. Heat stabilization was shown to be an efficient method to reduce phospholipase activity and ex vivo lipolysis. Post-sampling effects due to tissue thawing and sample preparation induced a massive release of FFAs (up to 3700%) from non-stabilized liver and brain tissues compared to heat stabilized tissue. Furthermore, the choice of euthanasia method significantly influenced the levels of FFAs in the brain. The FFAs were decreased by 15-44% in the group of animals euthanized by pentobarbital injection compared with CO2 inhalation or decapitation. Our results highlight the importance of considering euthanasia methods and pre-analytical treatment in lipid analysis, factors which may otherwise interfere with the outcome of the experiments. Copyright © 2014 Elsevier Inc. All rights reserved.

Stability analysis of a heated channel cooled by supercritical water

International Nuclear Information System (INIS)

Magni, M. C.; Delmastro, D. F; Marcel, C. P

2009-01-01

A simple model to study thermal-hydraulic stability of a heated cannel under supercritical conditions is presented. Single cannel stability analysis for the SCWR (Supercritical Water Cooled Reactor) design was performed. The drastic change of fluid density in the reactor core of a SCWR may induce DWO (Density Wave Oscillations) similar to those observed in BWRs. Due to the similarities between subcritical and supercritical systems we may treat the supercritical fluid as a pseudo two-phase system. Thus, we may extend the modeling approach often used for boiling flow stability analysis to supercritical pressure operation conditions. The model developed in this work take into account three regions: a heavy fluid region, similar to an incompressible liquid; a zone where a heavy fluid and a light fluid coexist, similar to two-phase mixture; and a light fluid region which behaves like superheated steam. It was used the homogeneous equilibrium model (HEM) for the pseudo boiling zone, and the ideal gas model for the pseudo superheated steam zone. System stability maps were obtained using linear stability analysis in the frequency domain. Two possible instability mechanisms are observed: DWO and excursive Ledinegg instabilities. Also, a sensitivity analysis showed that frictions in pseudo superheated steam zone, together with acceleration effect, are the most destabilizing effects. On the other hand, frictions in pseudo liquid zone are the most important stabilizing effect. [es

Complete replication-competent adenovirus 11p vectors with E1 or E3 insertions show improved heat stability

Energy Technology Data Exchange (ETDEWEB)

Mei, Ya-Fang, E-mail: ya-fang.mei@umu.se [Department of Clinical Microbiology and Virology, Umeå University, SE-901 85 Umeå (Sweden); Wu, Haidong, E-mail: haidong.wu@umu.se [Department of Clinical Microbiology and Virology, Umeå University, SE-901 85 Umeå (Sweden); Hultenby, Kjell, E-mail: kjell.hultenby@ki.se [Division of Clinical Research Centre, Department of Laboratory Medicine, Karolinska Institute, SE-14186 Stockholm (Sweden); Silver, Jim, E-mail: jim.silver@umu.se [Department of Clinical Microbiology and Virology, Umeå University, SE-901 85 Umeå (Sweden)

2016-10-15

Conventional adenovirus vectors harboring E1 or E3 deletions followed by the insertion of an exogenous gene show considerably reduced virion stability. Here, we report strategies to generate complete replication-competent Ad11p(RCAd11p) vectors that overcome the above disadvantage. A GFP cassette was successfully introduced either upstream of E1A or in the E3A region. The resulting vectors showed high expression levels of the hexon and E1genes and also strongly induced the cytopathic effect in targeted cells. When harboring oversized genomes, the RCAd11pE1 and RCAd11pE3 vectors showed significantly improved heat stability in comparison to Ad11pwt;of the three, RCAd11pE3 was the most tolerant to heat treatment. Electron microscopy showed that RCAd11pE3, RCAd11pE1, Ad11pwt, and Ad11pE1 Delmanifested dominant, moderate, minimum, or no full virus particles after heat treatment at 47 °C for 5 h. Our results demonstrated that both genome size and the insertion site in the viral genome affect virion stability. -- Highlights: •Replicating adenovirus 11p GFP vectors at the E1 or E3 region were generated. •RCAd11pE3 and RCAd11pE1 vectors manifested significantly improved heat stability. •RCAd11pE3 and RCAd11pE1 showed more full viral particles than Ad11pwt after heating. •We demonstrated that both genome size and the insertion site affect virion stability.

Complete replication-competent adenovirus 11p vectors with E1 or E3 insertions show improved heat stability

International Nuclear Information System (INIS)

Mei, Ya-Fang; Wu, Haidong; Hultenby, Kjell; Silver, Jim

2016-01-01

Conventional adenovirus vectors harboring E1 or E3 deletions followed by the insertion of an exogenous gene show considerably reduced virion stability. Here, we report strategies to generate complete replication-competent Ad11p(RCAd11p) vectors that overcome the above disadvantage. A GFP cassette was successfully introduced either upstream of E1A or in the E3A region. The resulting vectors showed high expression levels of the hexon and E1genes and also strongly induced the cytopathic effect in targeted cells. When harboring oversized genomes, the RCAd11pE1 and RCAd11pE3 vectors showed significantly improved heat stability in comparison to Ad11pwt;of the three, RCAd11pE3 was the most tolerant to heat treatment. Electron microscopy showed that RCAd11pE3, RCAd11pE1, Ad11pwt, and Ad11pE1 Delmanifested dominant, moderate, minimum, or no full virus particles after heat treatment at 47 °C for 5 h. Our results demonstrated that both genome size and the insertion site in the viral genome affect virion stability. -- Highlights: •Replicating adenovirus 11p GFP vectors at the E1 or E3 region were generated. •RCAd11pE3 and RCAd11pE1 vectors manifested significantly improved heat stability. •RCAd11pE3 and RCAd11pE1 showed more full viral particles than Ad11pwt after heating. •We demonstrated that both genome size and the insertion site affect virion stability.

Effect of seasonal variation on some physical properties and heat stability of milk subjected to ultra-high temperature and in-container sterilisation.

Science.gov (United States)

Chen, Biye; Grandison, Alistair S; Lewis, Michael J

2015-08-15

Heat stability was evaluated in bulk raw milk, collected throughout the year and subjected to ultra-high temperature (UHT) or in-container sterilisation, with and without added calcium chloride (2mM), disodium hydrogen phosphate (DSHP, 10mM) and trisodium citrate (TSC, 10mM). More sediment was observed following in-container sterilisation (0.24%) compared with UHT (0.19%). Adding CaCl2 made the milk more unstable to UHT than to in-container sterilisation, while adding DSHP and TSC made the milk more unstable during in-container sterilisation than to UHT processing, although TSC addition increased the sediment formed by UHT processing. Better heat stability was observed in autumn and winter than in spring and summer following UHT. However, following in-container sterilisation, samples with added stabilising salts showed significantly improved heat stability in autumn, whereas with added CaCl2, the best heat stability was observed in spring. No correlation was found between urea and heat stability. Copyright © 2015 Elsevier Ltd. All rights reserved.

Progress in the Study of RF Heating and Stabilization on HANBIT Mirror Device

International Nuclear Information System (INIS)

Kwon, M.; Bak, J.G.; Choh, K.; Choi, J.H.; Choi, J.W.; England, A.C.; Hong, J.S.; Jhang, H.G.; Kim, J.Y.; Kim, S.S.; Ko, W.H.; Lee, D.K.; Lee, J.H.; Lee, S.G.; Lee, H.G.; Lho, T.; Na, H.K.; Park, B.H.; Park, M.K.; Seo, D.C.; Seo, S.H.; Yeom, J.H.; Yoo, S.J.; You, K.I.; Yoon, J.S.; Yoon, S.W.

2005-01-01

The HANBIT device is a simple mirror-type device of which the length, radius, and magnetic field are about 5 m, 0.18 m, and 0.1-0.3 T, respectively, in the central cell. In HANBIT, two antenna systems are used for the plasma production, heating, and MHD stabilization; one is the slot antenna located near the center region with the maximum power of 500 kW and the typical frequency of 3.5 MHz, and the other DHT antenna located near the mirror throat with the maximum power of 100 kW and the frequency of 3.75 MHz. Recent experimental studies in HANBIT indicate that the slot antenna system can produce stable, high-density plasmas in apparently two different regimes; one is the fast wave regime with the ratio w/Wci∼2 and the other is the slow wave regime with w< Wci, where w and Wci are the RF and ion cyclotron resonance frequencies, respectively. The possible stabilization mechanism appears to be the ponderomotive force by the fast wave in the regime of w/Wci∼2, while the RF side-band coupling force by the slow wave in the regime of w< Wci. A clear excitation of the flute-type, interchange modes with the axial mode number n=0 is observed when the RF power is not enough for the stabilization, particularly, in the slow wave regime. Here, we report the results of these experimental and theoretical studies on the RF heating and stabilization processes by the slot antenna in HANBIT. In addition, we introduce briefly the results of the other on-going research works in HANBIT, which include the beach-wave ion heating experiment using DHT antenna, the pre-ionization experiment using the thermal electron cathode or ECH, and the analysis of plasma-wall interaction and neutral transport

Drought and heat stress effects on soybean fatty acid composition and oil stability

Science.gov (United States)

Previous studies have shown that oil concentration and fatty acid profile (composition) change with genotype, environment (mainly heat and drought), and geographical location. The changes in fatty acid composition under these conditions affect fatty acid stability, creating a challenge to oil proces...

A preliminary stability analysis of MYRRHA Primary Heat Exchanger two-phase tube bundle

Energy Technology Data Exchange (ETDEWEB)

Castelliti, Diego [Studiecentrum voor kernenergie – Centre d’étude de l’énergie nucléaire (SCK-CEN), Boeretang 200, Mol (Belgium); GeNERG – DIME/TEC, University of Genova, Via all’Opera Pia 15/a, 16145 Genova (Italy); Lomonaco, Guglielmo, E-mail: guglielmo.lomonaco@unige.it [GeNERG – DIME/TEC, University of Genova, Via all’Opera Pia 15/a, 16145 Genova (Italy); INFN, Via Dodecaneso 33, 16146 Genova (Italy)

2016-08-15

Highlights: • MYRRHA is a pool-type LBE-cooled ADS, operable also as a critical reactor. • MYRRHA is a high priority infrastructure for nuclear research in Europe. • PHX (primary side: LBE, secondary side: two-phase water), is a MYRRHA key component. • The original MYRRHA PHX design does not offer a fully satisfying response to DWO. • The adoption of an orifice allows extending considerably the stability of MYRRHA PHX. - Abstract: The MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) project, started at SCK·CEN since 1999, aims at the construction of a pool-type sub-critical Accelerator-Driven System (ADS) which could also operate as a critical reactor. The primary system, enclosed in the primary vessel, is filled with Lead Bismuth Eutectic (LBE) which acts as primary coolant. The power is then delivered through four heat exchangers to four secondary loops. The secondary cooling fluid is two-phase water operating at relatively low pressure (16 bar). Four aero-condensers act as heat sinks, since MYRRHA design does not foresee any electricity generation. The MYRRHA Primary Heat eXchangers (PHXs) cover a role of fundamental importance in normal operation and accidental conditions, being part of the primary and secondary cooling system and of the Decay Heat Removal (DHR) system. It is thus highly relevant to understand the PHXs behavior under all the potential working conditions. In particular, the stability of the PHXs must be guaranteed under all operating conditions. System code models play an important role in understanding and predicting the behavior of the reactor in all conditions, from steady state to operational and accidental transients, and simulating all the postulated scenarios. A solid PHX design requires a complete assessment of two-phase flow instabilities in the secondary system water tube bundle and the potential implementation of a suitable stabilizing device (orifice) to reduce the impact of the perturbations along

Liquid-Metal/Water Direct Contact Heat Exchange: Flow Visualization, Flow Stability, and Heat Transfer Using Real-Time X-Ray Imaging

International Nuclear Information System (INIS)

Abdulla, Sherif H.; Liu Xin; Anderson, Mark H.; Bonazza, Riccardo; Corradini, Michael L.; Cho, Dae; Page, Richard

2005-01-01

has been given based on two independent procedures. This methodology will allow one to utilize X-ray attenuation for imaging vapor bubbles with acceptable errors (bubbles ∼1 to 5 cm ± 5 to 20%).Subcooled water (T sat - T water [approximately equal to] 10 deg. C) was brought into contact with liquid lead (or lead alloys) at an elevated temperature (T lm = 500 deg. C and T lm - T melting [approximately equal to] 200 deg. C). The study was conducted over a range of ambient pressures (1 to 10 bar) with four different water injection rates (1.5 to 8 g/s; 0.1 to 1 kg/m 2 .s). The results showed that the system pressure has a slight effect on volumetric heat transfer coefficient, the bubble formation time, and the bubble rise velocity. Increasing the system pressure, however, resulted in an increase in the bubble average heat transfer coefficient. Increasing the water injection rate directly had only a small effect on the bubble rise velocity or formation rate. Increasing the water injection rate resulted in a decrease in the local bubble heat transfer coefficient.Direct contact heat transfer also has some key disadvantages; e.g., flow instabilities caused by local vapor explosion is one of the issues related to direct contact heat exchange, particularly for liquid/liquid exchange with high temperature differences. In this study, the region of stable heat transfer was mapped and the effects of the liquid metal temperature, the water injection rate, and the operating pressure were investigated. The pressure required to stabilize the heat exchange process was found to be a function of the water injection rate but generally increasing the system pressure helped stabilize the system. It was also found that the larger the injection rate, the higher the pressure required to stabilize the system

RP-2 Thermal Stability and Heat Transfer Investigation for Hydrocarbon Boost Engines

Science.gov (United States)

VanNoord, J. L.; Stiegemeier, B. R.

2010-01-01

A series of electrically heated tube tests were performed at the NASA Glenn Research Center s Heated Tube Facility to investigate the use of RP-2 as a fuel for next generation regeneratively cooled hydrocarbon boost engines. The effect that test duration, operating condition and test piece material have on the overall thermal stability and materials compatibility characteristics of RP-2 were evaluated using copper and 304 stainless steel test sections. The copper tests were run at 1000 psia, heat flux up to 6.0 Btu/in.2-sec, and wall temperatures up to 1180 F. Preliminary results, using measured wall temperature as an indirect indicator of the carbon deposition process, show that in copper test pieces above approximately 850 F, RP-2 begins to undergo thermal decomposition resulting in local carbon deposits. Wall temperature traces show significant local temperature increases followed by near instantaneous drops which have been attributed to the carbon deposition/shedding process in previous investigations. Data reduction is currently underway for the stainless steel test sections and carbon deposition measurements will be performed in the future for all test sections used in this investigation. In conjunction with the existing thermal stability database, these findings give insight into the feasibility of cooling a long life, high performance, high-pressure liquid rocket combustor and nozzle with RP-2.

Effect of constant heat flux at outer cylinder on stability of viscous ...

African Journals Online (AJOL)

In this paper, the stability of the Couette flow of a viscous incompressible fluid between two concentric rotating cylinders is studied in the presence of a radial temperature gradient, when the outer cylinder is maintained at a constant heat flux. The analytical solution of the eigen-value problem is obtained by using the ...

Validation of accuracy and stability of numerical simulation for 2-D heat transfer system by an entropy production approach

Directory of Open Access Journals (Sweden)

Brohi Ali Anwar

2017-01-01

Full Text Available The entropy production in 2-D heat transfer system has been analyzed systematically by using the finite volume method, to develop new criteria for the numerical simulation in case of multidimensional systems, with the aid of the CFD codes. The steady-state heat conduction problem has been investigated for entropy production, and the entropy production profile has been calculated based upon the current approach. From results for 2-D heat conduction, it can be found that the stability of entropy production profile exhibits a better agreement with the exact solution accordingly, and the current approach is effective for measuring the accuracy and stability of numerical simulations for heat transfer problems.

Chemical Stability Analysis of Hair Cleansing Conditioners under High-Heat Conditions Experienced during Hair Styling Processes

Directory of Open Access Journals (Sweden)

Derek A. Drechsel

2018-03-01

Full Text Available Chemical stability is a key component of ensuring that a cosmetic product is safe for consumer use. The objective of this study was to evaluate the chemical stability of commercially available hair cleansing conditioners subjected to high heat stresses from the styling processes of blow drying or straightening. Two hair cleansing conditioners were subjected to temperatures of 60 °C and 185 °C to simulate the use of a blow dryer or flatiron hair straightener, respectively and analyzed via Gas Chromatography-Mass Spectrometry (GC-MS, High-Performance Liquid Chromatography-UV (HPLC and Fourier-Transform Infrared Spectroscopy (FT-IR to capture a chemical profile of the samples. The resulting spectra from matched heated and unheated samples were compared to identify any changes in chemical composition. Overall, no differences in the spectra were observed between the heated and unheated samples at both temperatures evaluated. Specifically, no new peaks were observed during analysis, indicating that no degradation products were formed. In addition, all chemicals identified during GC-MS analysis were known listed ingredients of the products. In summary, no measurable changes in chemical composition were observed in the hair cleansing conditioner samples under high-heat stress conditions. The presented analytical methods can serve as an initial screening tool to evaluate the chemical stability of a cosmetic product under conditions of anticipated use.

Power Output Stability Research for Harvesting Automobile Exhaust Energy with Heat Capacity Material as Intermediate Medium

Science.gov (United States)

Xiao, Longjie; He, Tianming; Mei, Binyu; Wang, Yiping; Wang, Zongsong; Tan, Gangfeng

2018-06-01

Automobile exhaust energy thermoelectric utilization can promote energy-saving and emission-reduction. Unexpected urban traffic conditions lead to the hot-end temperature instability of the exhaust pipe-mounted thermoelectric generator (TEG), and influence the TEG power generation efficiency. The heat conduction oil circulation located at the hot-end could smooth the temperature fluctuation, at the expense of larger system size and additional energy supply. This research improves the TEG hot-end temperature stability by installing solid heat capacity material (SHCM) to the area between the outer wall of the exhaust pipe and the TEG, which has the merits of simple structure, light weight and no additional energy consumption. The exhaust temperature and flow rate characteristics with various driving conditions are firstly studied for the target engine. Then the convective heat transfer models of SHCM's hot-end and thermoelectric material's cold-end are established. Meanwhile, SHCM thermal properties' effects on the amplitude and response speed of the TEG hot-end temperature are studied. The candidate SHCM with the characteristics of low thermal resistance and high heat capacity is determined. And the heat transfer model going through from TEG's hot-end to the cold-end is established. The results show that the SHCM significantly improves the TEG hot-end temperature stability but slightly reduces the average power output. When the engine working conditions change a lot, the SHCM's improvement on the TEG hot-end temperature stability is more significant, but the reduction of the average power output becomes more remarkable.

Tilt stability and compression heating studies of field-reversed configurations

International Nuclear Information System (INIS)

Rej, D.J.; Tuszewski, M.; Barnes, D.C.; Barnes, G.A.; Chrien, R.E.; Siemon, R.E.; Taggart, D.P.; Webster, R.B.; Wright, B.L.; Milroy, R.D.; Crawford, E.A.; Slough, J.T.; Steinhauer, L.C.; Bailey, A.D.; Baron, M.H.; Cobb, J.W.; Staudenmeier, J.L.; Sugimoto, S.; Takahashi, T.

1990-01-01

The first observations of internal tilt instabilities in field-reversed configurations (FRCs) are reported. Detailed comparisons with theory establish that data from an array of external magnetic probes are signatures of these destructive plasma instabilities. This work reconciles theory and experiments and suggests that grossly stable FRCs are restricted to very kinetic and elongated plasmas. Self-consistent three-dimensional numerical simulations demonstrate tilt stabilization by the addition of a beam ion component. High-power compression heating experiments with stable equilibrium FRCs are also reported. Plasmas formed in a tapered theta-pinch coil have been translated along a guide magnetic field into a new single-turn compression coil where the external field is increased up to 7 times the initial value in 55 μs. Substantial heating is observed accompanied by a decrease in confinement time. 17 refs

Study of an electrical heating system with ductless air supply and shape-stabilized PCM for thermal storage

International Nuclear Information System (INIS)

Lin, Kunping; Zhang, Yinping; Di, Hongfa; Yang, Rui

2007-01-01

A kind of electrical floor heating system with a shape-stabilized phase change material (PCM) which has been studied at Tsinghua University in our previous studies, can provide space heating during the whole day and can be controlled conventionally. However, this is not suitable for office buildings where no space heating is needed at night. The effective control is very important for the heating system in such buildings. In this paper, we studied a kind of new electrical floor heating system with ductless air supply and shape-stabilized PCM for thermal storage in order to overcome the shortcomings of the passive under-floor electric heating system with thermal storage. In this paper, we investigated its thermal performance by experiments and simulation, calculated the effects of various factors and discussed the application feasibility in different climate regions. The results show that the total electrical energy consumption was shifted from the peak period to the off-peak period, which would provide significant economic benefits because of the different day and night electricity tariffs. The system can be designed by choosing PCM with proper melting temperature and be controlled by varying velocity of air supply in different conditions

Stability and fast heat removal with He-II cooling for pulsed superconductive magnets

International Nuclear Information System (INIS)

Desportes, H.

1979-01-01

The use of pressurized superfluid helium between 1.6 K and 1.8 K is being considered for a number of superconducting magnet applications. This type of cooling is particularly interesting in the case of pulsed field magnets where large heat fluxes need to be evacuated in a short time. This paper reviews a few recent experiments on heat transport properties and stability in He-II, which contribute to evaluating its potential use for such an application. Present technology is illustrated by the description of a large test facility recently operated at Saclay

Lifetime prediction of EC, DPA, akardite II and MNA stabilized triple base propellants, comparison of heat generation rate and stabilizer consumption

NARCIS (Netherlands)

Boers, M.N.; Klerk, W.P.C. de

2005-01-01

A lifetime prediction study is carried out on four triple base propellant compositions by artificial ageing. The ageing effects are studied with High Performance Liquid Chromatography (HPLC) and Heat Flow Calorimetry (HFC) in order to find the most effective stabilizer and to evaluate the advantages

Heat Sinking, Cross Talk, and Temperature Stability for Large, Close-Packed Arrays of Microcalorimeters

Science.gov (United States)

Imoto, Naoko; Bandler, SImon; Brekosky, Regis; Chervenak, James; Figueroa-Felicano, Enectali; Finkbeiner, Frederick; Kelley, Richard; Kilbourne, Caroline; Porter, Frederick; Sadleir, Jack;

The response of a harmonically forced premixed flame stabilized on a heat-conducting bluff-body

KAUST Repository

Kedia, Kushal S.

2015-01-01

© 2014 The Combustion Institute. The objective of this work is to investigate the unsteady response of a bluff-body stabilized laminar premixed flame to harmonic inlet velocity excitation. A time series analysis was performed to analyze the physical sequence of events at a fixed longitudinal forcing frequency of 100 Hz for cases with (1) two different equivalence ratios and (2) two different thermal properties of the stabilizing bluff-body. It was observed that conjugate heat exchange between the heat conducting bluff-body and the surrounding reacting flow has a crucial impact on the dynamic response. The flame area and anchoring location, the net conjugate heat transfer and the total heat release underwent significant oscillations. The latter was mean shifted and had multiple frequencies. The burning velocity varied significantly along the flame length and the recirculation zone underwent complex changes in its shape and size during an unsteady cycle. The lower equivalence ratio case exhibited vortex shedding after an initial symmetric response with periodic flame extinction and re-ignition along its surface, unlike the higher equivalence ratio case. The metal/ceramic bluff-body showed a net heat transfer directed from/to the bluff-body, to/from the reacting flow during an unsteady cycle, resulting in a significantly different flame response for the two otherwise equivalent cases.

Factors Affecting Impact Toughness in Stabilized Intermediate Purity 21Cr Ferritic Stainless Steels and Their Simulated Heat-Affected Zones

Science.gov (United States)

Anttila, Severi; Alatarvas, Tuomas; Porter, David A.

2017-12-01

The correlation between simulated weld heat-affected zone microstructures and toughness parameters has been investigated in four intermediate purity 21Cr ferritic stainless steels stabilized with titanium and niobium either separately or in combination. Extensive Charpy V impact toughness testing was carried out followed by metallography including particle analysis using electron microscopy. The results confirmed that the grain size and the number density of particle clusters rich in titanium nitride and carbide with an equivalent circular diameter of 2 µm or more are statistically the most critical factors influencing the ductile-to-brittle transition temperature. Other inclusions and particle clusters, as well as grain boundary precipitates, are shown to be relatively harmless. Stabilization with niobium avoids large titanium-rich inclusions and also suppresses excessive grain growth in the heat-affected zone when reasonable heat inputs are used. Thus, in order to maximize the limited heat-affected zone impact toughness of 21Cr ferritic stainless steels containing 380 to 450 mass ppm of interstitials, the stabilization should be either titanium free or the levels of titanium and nitrogen should be moderated.

Structural stability of hydrogenated amorphous carbon overcoats used in heat-assisted magnetic recording investigated by rapid thermal annealing

KAUST Repository

Wang, N.; Komvopoulos, K.; Rose, F.; Marchon, B.

2013-01-01

Ultrathin amorphous carbon (a-C) films are extensively used as protective overcoats of magnetic recording media. Increasing demands for even higher storage densities have necessitated the development of new storage technologies, such as heat-assisted magnetic recording (HAMR), which uses laser-assisted heating to record data on high-stability media that can store single bits in extremely small areas (∼1 Tbit/in.2). Because HAMR relies on locally changing the coercivity of the magnetic medium by raising the temperature above the Curie temperature for data to be stored by the magnetic write field, it raises a concern about the structural stability of the ultrathin a-C film. In this study, rapid thermal annealing (RTA) experiments were performed to examine the thermal stability of ultrathin hydrogenated amorphous carbon (a-C:H) films deposited by plasma-enhanced chemical vapor deposition. Structural changes in the a-C:H films caused by RTA were investigated by x-ray photoelectron spectroscopy, Raman spectroscopy, x-ray reflectivity, and conductive atomic force microscopy. The results show that the films exhibit thermal stability up to a maximum temperature in the range of 400-450 °C. Heating above this critical temperature leads to hydrogen depletion and sp 2 clustering. The critical temperature determined by the results of this study represents an upper bound of the temperature rise due to laser heating in HAMR hard-disk drives and the Curie temperature of magnetic materials used in HAMR hard disks. © 2013 American Institute of Physics.

Transient Stability Improvement for Combined Heat and Power System Using Load Shedding

Directory of Open Access Journals (Sweden)

Hung-Cheng Chen

2014-01-01

Full Text Available The purpose of the paper is to analyze and improve the transient stability of an industrial combined heat and power (CHP system in a high-tech science park in Taiwan. The CHP system installed two 161 kV/161 kV high-impendence transformers to connect with Taipower System (TPS for both decreasing the short-circuit fault current and increasing the fault critical clearing time. The transient stabilities of three types of operation modes in CHP units, 3G1S, 2G1S, and 1G1S, are analyzed. Under the 3G1S operation mode, the system frequency is immediately restored to 60 Hz after tie line tripping with the TPS. Under the 1G1S and 2G1S operation modes, the system frequencies will continuously decrease and eventually become unstable. A novel transient stability improvement approach using load shedding technique based on the change in frequency is proposed to improve the transient stability.

Linear stability of a fuel channel uniformly heated considering retrofeeding by vacuum. Theoretical study

International Nuclear Information System (INIS)

Gonzalez M, V.; Salinas H, J.G.; Espinosa P, G.

2000-01-01

The Technology, Regulation and Services Management of the National Commission of Nuclear Safety and Safeguards in coordinated form with the IPH Department of the Metropolitan Autonomous-Iztapalapa University, developed the present project to study the linear stability in a fuel channel uniformly heated with effects of retrofeeding by vacuums. In this study the methodology used in the analysis of linear stability of the nuclear reactor unit 1 at Laguna Verde power plant is described which represented by an average channel uniformly heated. The conceptual model consists of two cells which represent the two regions in which is divided the channel according to the cooling is in one and two phases, considering the boiling length dependent in the time. It is used the homogeneous flux models for describing the thermohydraulic behavior of the cooling in the two phases region. The neutron processes with the punctual model of the neutron kinetics with a group of retarded neutrons precursors are described. It is studied the behavior of the system in the frequency domain with the transfer functions obtained and it is characterized in four operation states corresponding to the four corners of the low stability zone in the map power-flow Laguna Verde power plant. For these operation states the characteristic frequency is determined and the corresponding Nyquist diagrams are obtained. The results show that the system stability depends on the power-flow relation and that the operations which implicate a reduction of this relation improve the stability of the system (reducing the power introducing control bars with constant cooling flow or increase cooling flow with bars pattern established). The obtained results with effects of retrofeeding by vacuums show that the value of the characteristic frequency is modified very little with respect to the model without retrofeeding, therefore the thermohydraulic processes seem to determine the response of the stability of the system

The Effects of pH and Heat Treatment Processing on the Stability of ...

African Journals Online (AJOL)

This study was carried out to investigate the effects of pH and heat treatment processing on stability and natural food colours used in dairy products. A repeated laboratory experiment was conducted in which loss of colour intensity or change in shade of natural food colours used in acid and nearly neutral dairy products at ...

Effect of thermal conductivities of shape stabilized PCM on under-floor heating system

International Nuclear Information System (INIS)

Cheng, Wenlong; Xie, Biao; Zhang, Rongming; Xu, Zhiming; Xia, Yuting

2015-01-01

Highlights: • HCE-SSPCM was prepared and used in under-floor heating system. • Enhancing thermal conductivity improved the efficiency of energy and space. • Too high thermal conductivity over a range was meaningless. • The economic benefits of the phase change energy storage system were the best. - Abstract: A kind of heat conduction-enhanced shape-stabilized PCM (HCE-SSPCM) was utilized in the under-floor heating system for house heating in winter. This system charges heat by using cheap nighttime electricity and provides heating needs throughout all day. The effect of thermal conductivity of the PCM on energy savings and economic benefits of the system were theoretically and experimentally studied. HCE-SSPCM plates, made of (solid paraffin + liquid paraffin)/high density polyethylene/expanded graphite, were introduced to a test room with under-floor heating system. And the operating characteristics of the system were compared with that of the non-phase change energy storage system and the conventional air conditioning system. The results showed that enhancing the thermal conductivity of PCM in a certain range could significantly improve the energy efficiency of the heating system and reduce the thickness of thermal insulating materials. But the improving effect was not obvious when the thermal conductivity was beyond 1.0 W/m K. The phase change energy storage system had a comfortable temperature environment and the best economic benefits among the three different heating types especially when the ratio of peak-valley electric price was high. Therefore, increasing the thermal conductivity of SSPCM will be of great significance for house heating

Effect of chitosan on the heat stability of whey protein solution as a function of pH.

Science.gov (United States)

Zhao, Zhengtao; Xiao, Qian

2017-03-01

Chitosan was reported to interact with proteins through electrostatic interactions. Their interaction was influenced by pH, which was not fully characterized. Further research on the interactions between protein and chitosan at different pH and their influence on the thermal denaturation of proteins is necessary. In this research, the effect of chitosan on the heat stability of whey protein solution at pH 4.0-6.0 was studied. At pH 4.0, a small amount chitosan was able to prevent the heat-induced denaturation and aggregation of whey protein molecules. At higher pH values (5.5 and 6.0), whey proteins complexed with chitosan through electrostatic attraction. The formation of chitosan-whey protein complexes at pH 5.5 improved the heat stability of dispersions and no precipitation could be detected up to 20 days. The dispersion with a medium amount of chitosan (chitosan:whey protein 1:5) produced the most stable particles, which had an average radius of 135 ± 14 nm and a zeta potential value of 36 ± 1 mV. In contrast, at pH 6.0 only the dispersion with a high amount of chitosan (chitosan:whey protein 1:2) showed good shelf stability up to 20 days. It was possible to produce heat-stable whey protein beverages by regulating the interaction between chitosan and whey protein molecules. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Lifetime prediction of EC, DPA, Akardite II and MNA stabilized triple base propellants, comparison of heat generation rate and stabilizer consumption

Energy Technology Data Exchange (ETDEWEB)

Boers, Marco N.; Klerk, Willem (Wim) P.C. de [TNO Defence, Security and Safety, P. O. Box 45, 2280 AA Rijswijk ZH (Netherlands)

2005-10-01

A lifetime prediction study is carried out on four triple base propellant compositions by artificial ageing. The ageing effects are studied with High Performance Liquid Chromatography (HPLC) and Heat Flow Calorimetry (HFC) in order to find the most effective stabilizer and to evaluate the advantages and disadvantages of both methods. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

Mechanisms of stabilization and blowoff of a premixed flame downstream of a heat-conducting perforated plate

KAUST Repository

Kedia, Kushal S.

2012-03-01

The objective of this work is to investigate the flame stabilization mechanism and the conditions leading to the blowoff of a laminar premixed flame anchored downstream of a heat-conducting perforated-plate/multi-hole burner, with overall nearly adiabatic conditions. We use unsteady, fully resolved, two-dimensional simulations with detailed chemical kinetics and species transport for methane-air combustion. Results show a bell-shaped flame stabilizing above the burner plate hole, with a U-shaped section anchored between neighboring holes. The base of the positively curved U-shaped section of the flame is positioned near the stagnation point, at a location where the flame displacement speed is equal to the flow speed. This location is determined by the combined effect of heat loss and flame stretch on the flame displacement speed. As the mass flow rate of the reactants is increased, the flame displacement speed at this location varies non-monotonically. As the inlet velocity is increased, the recirculation zone grows slowly, the flame moves downstream, and the heat loss to the burner decreases, strengthening the flame and increasing its displacement speed. As the inlet velocity is raised, the stagnation point moves downstream, and the flame length grows to accommodate the reactants mass flow. Concomitantly, the radius of curvature of the flame base decreases until it reaches an almost constant value, comparable to the flame thickness. While the heat loss decreases, the higher flame curvature dominates thereby reducing the displacement speed of the flame base. For a stable flame, the gradient of the flame base displacement speed normal to the flame is higher than the gradient of the flow speed along the same direction, leading to dynamic stability. As inlet velocity is raised further, the former decreases while the latter increases until the stability condition is violated, leading to blowoff. The flame speed during blow off is determined by the feedback between the

Atmospheric stability inside containments with a heated layer of liquid on the floor

Energy Technology Data Exchange (ETDEWEB)

Vate, J.F. van de [Netherlands Energy Research Foundation, Petten (Netherlands)

1977-01-01

The study of atmospheric stability inside containments with a heated layer of liquid comprised derivation of the boundary condition for stable atmospheric stratifications and the experimental validation of the boundary condition for stable atmospheric stratification. This report includes description of the model for stirred aerosol deposition and the calculation results for maximum aerodynamic diameter of a confined aerosol remaining just well-stirred.

Understanding decay resistance, dimensional stability and strength changes in heat treated and acetylated wood

Science.gov (United States)

Roger M. Rowell; Rebecca E. Ibach; James McSweeny; Thomas Nilsson

2009-01-01

Reductions in hygroscopicity, increased dimensional stability and decay resistance of heat-treated wood depend on decomposition of a large portion of the hemicelluloses in the wood cell wall. In theory, these hemicelluloses are converted to small organic molecules, water and volatile furan-type intermediates that can polymerize in the cell wall. Reductions in...

Emulsion stabilizing capacity of intact starch granules modified by heat treatment or octenyl succinic anhydride.

Science.gov (United States)

Timgren, Anna; Rayner, Marilyn; Dejmek, Petr; Marku, Diana; Sjöö, Malin

2013-03-01

Starch granules are an interesting stabilizer candidate for food-grade Pickering emulsions. The stabilizing capacity of seven different intact starch granules for making oil-in-water emulsions has been the topic of this screening study. The starches were from quinoa; rice; maize; waxy varieties of rice, maize, and barley; and high-amylose maize. The starches were studied in their native state, heat treated, and modified by octenyl succinic anhydride (OSA). The effect of varying the continuous phase, both with and without salt in a phosphate buffer, was also studied. Quinoa, which had the smallest granule size, had the best capacity to stabilize oil drops, especially when the granules had been hydrophobically modified by heat treatment or by OSA. The average drop diameter (d 32) in these emulsions varied from 270 to 50 μm, where decreasing drop size and less aggregation was promoted by high starch concentration and absence of salt in the system. Of all the starch varieties studied, quinoa had the best overall emulsifying capacity, and OSA modified quinoa starch in particular. Although the size of the drops was relatively large, the drops themselves were in many instances extremely stable. In the cases where the system could stabilize droplets, even when they were so large that they were visible to the naked eye, they remained stable and the measured droplet sizes after 2 years of storage were essentially unchanged from the initial droplet size. This somewhat surprising result has been attributed to the thickness of the adsorbed starch layer providing steric stabilization. The starch particle-stabilized Pickering emulsion systems studied in this work has potential practical application such as being suitable for encapsulation of ingredients in food and pharmaceutical products.

Mechanisms of stabilization and blowoff of a premixed flame downstream of a heat-conducting perforated plate

KAUST Repository

Kedia, Kushal S.; Ghoniem, Ahmed F.

2012-01-01

The objective of this work is to investigate the flame stabilization mechanism and the conditions leading to the blowoff of a laminar premixed flame anchored downstream of a heat-conducting perforated-plate/multi-hole burner, with overall nearly

Stability, causality, and hyperbolicity in Carter's ''regular'' theory of relativistic heat-conducting fluids

International Nuclear Information System (INIS)

Olson, T.S.; Hiscock, W.A.

1990-01-01

Stability and causality are studied for linear perturbations about equilibrium in Carter's ''regular'' theory of relativistic heat-conducting fluids. The ''regular'' theory, when linearized around an equilibrium state having vanishing expansion and shear, is shown to be equivalent to the inviscid limit of the linearized Israel-Stewart theory of relativistic dissipative fluids for a particular choice of the second-order coefficients β 1 and γ 2 . A set of stability conditions is determined for linear perturbations of a general inviscid Israel-Stewart fluid using a monotonically decreasing energy functional. It is shown that, as in the viscous case, stability implies that the characteristic velocities are subluminal and that perturbations obey hyperbolic equations. The converse theorem is also true. We then apply this analysis to a nonrelativistic Boltzmann gas and to a strongly degenerate free Fermi gas in the ''regular'' theory. Carter's ''regular'' theory is shown to be incapable of correctly describing the nonrelativistic Boltzmann gas and the degenerate Fermi gas (at all temperatures)

Effect of heat-treatment with raw cotton seed oil on decay resistance and dimensional stability of Beech (Fagus orientalis

Directory of Open Access Journals (Sweden)

مریم قربانی

2015-05-01

Full Text Available This research was conducted to determine the effect of heat-treatment with raw cotton seed oil on decay resistance and dimensional stability of beech according to EN113 and ASTM-D1037 standards respectively. The heat treatment with raw cotton seed oil was carried out in the cylinder at the temperatures of 130 and 170oC for 30 and 60 minutes. Oil uptake, density, volumetric swelling, water absorption and weight loss exposed to decay were measured. Oil uptake at 30 and 60 min were determined 10.5 and 13.3 Kg/cm3 respectively. Oil-heat treated samples at 30min and 130°C indicated the maximum density with 87.7% increase. According to results, oil-heat treatment improved water repellency and dimensional stability. Water absorption in 130°C and 60 minutes decreased 76% in comparison with control. Decay resistance of oil soaked samples for 60minutes was 80.2% more than control samples. Oil-heat treatment compared with oil treatment improved decay resistance, this effect was significant at 30 min. The temperature rise of oil–heat treatment at 30 minutes improved decay resistance, but the improvement under same level of temperature with increase time was not significant.

High harmonic ion cyclotron heating in DIII-D: Beam ion absorption and sawtooth stabilization

International Nuclear Information System (INIS)

Heidbrink, W.W.; Fredrickson, E.D.; Mau, T.K.; Petty, C.C.; Pinsker, R.I.; Porkolab, M.; Rice, B.W.

1999-01-01

Combined neutral beam injection and fast wave heating at the fourth cyclotron harmonic produce an energetic deuterium beam ion tail in the DIII-D tokamak. When the concentration of thermal hydrogen exceeds ∼ 5%, the beam ion absorption is suppressed in favour of second harmonic hydrogen absorption. As theoretically expected, the beam absorption increases with beam ion gyro-radius; also, central absorption at the fifth harmonic is weaker than central absorption at the fourth harmonic. For central heating at the fourth harmonic, an energetic, perpendicular, beam population forms inside the q = 1 surface. The beam ion tail transiently stabilizes the sawtooth instability but destabilizes toroidicity induced Alfven eigenmodes (TAEs). Saturation of the central heating correlates with the onset of the TAEs. Continued expansion of the q = 1 radius eventually precipitates a sawtooth crash; complete magnetic reconnection is observed. (author)

Fracture properties and heat resistance of ceramics consisting of microspheres of stabilized zirconium dioxide

International Nuclear Information System (INIS)

Krasulin, Yu.L.; Barinov, S.M.; Ivanov, A.B.; Timofeev, V.N.; Grevtsev, S.N.; Ivanov, D.A.

1980-01-01

Determined were effective specific fracture work, critical coefficient of stress intensity in the upper point of the fracture, strength and heat resistance during heat changes (20-1300 deg C) of the material produced by sintering stabilized zirconium dioxide microspheres. Dependence of these characteristics on granulometric composition of microspheres was determined. It was ascertained that the additional introduction of large microspheres into the bulk of small microspheres increased the metal fracture work. Specific work of material fracture progress exceeded specific work of fracture motion initiation. High value of fracture work together with high strength permits to use the material formed of microspheres as structural ceramics

Stability Analysis and Internal Heating Effect on Oscillatory Convection in a Viscoelastic Fluid Saturated Porous Medium Under Gravity Modulation

Science.gov (United States)

Bhadauria, B. S.; Singh, M. K.; Singh, A.; Singh, B. K.; Kiran, P.

2016-12-01

In this paper, we investigate the combined effect of internal heating and time periodic gravity modulation in a viscoelastic fluid saturated porous medium by reducing the problem into a complex non-autonomous Ginzgburg-Landau equation. Weak nonlinear stability analysis has been performed by using power series expansion in terms of the amplitude of gravity modulation, which is assumed to be small. The Nusselt number is obtained in terms of the amplitude for oscillatory mode of convection. The influence of viscoelastic parameters on heat transfer has been discussed. Gravity modulation is found to have a destabilizing effect at low frequencies and a stabilizing effect at high frequencies. Finally, it is found that overstability advances the onset of convection, more with internal heating. The conditions for which the complex Ginzgburg-Landau equation undergoes Hopf bifurcation and the amplitude equation undergoes supercritical pitchfork bifurcation are studied.

Effects of packaging and heat transfer kinetics on drug-product stability during storage under uncontrolled temperature conditions.

Science.gov (United States)

Nakamura, Toru; Yamaji, Takayuki; Takayama, Kozo

2013-05-01

To predict the stability of pharmaceutical preparations under uncontrolled temperature conditions accurately, a method to compute the average reaction rate constant taking into account the heat transfer from the atmosphere to the product was developed. The average reaction rate constants computed with taken into consideration heat transfer (κ(re) ) were then compared with those computed without taking heat transfer into consideration (κ(in) ). The apparent thermal diffusivity (κ(a) ) exerted some influence on the average reaction rate constant ratio (R, R = κ(re) /κ(in) ). In the regions where the κ(a) was large (above 1 h(-1) ) or very small, the value of R was close to 1. On the contrary, in the middle region (0.001-1 h(-1) ), the value of R was less than 1.The κ(a) of the central part of a large-size container and that of the central part of a paper case of 10 bottles of liquid medicine (100 mL) fell within this middle region. On the basis of the above-mentioned considerations, heat transfer may need to be taken into consideration to enable a more accurate prediction of the stability of actual pharmaceutical preparations under nonisothermal atmospheres. Copyright © 2013 Wiley Periodicals, Inc.

Heat stability of strawberry anthocyanins in model solutions containing natural copigments extracted from rose (Rosa damascena Mill.) petals.

Science.gov (United States)

Shikov, Vasil; Kammerer, Dietmar R; Mihalev, Kiril; Mollov, Plamen; Carle, Reinhold

2008-09-24

Thermal degradation and color changes of purified strawberry anthocyanins in model solutions were studied upon heating at 85 degrees C by HPLC-DAD analyses and CIELCh measurements, respectively. The anthocyanin half-life values increased significantly due to the addition of rose (Rosa damascena Mill.) petal extracts enriched in natural copigments. Correspondingly, the color stability increased as the total color difference values were smaller for anthocyanins upon copigment addition, especially after extended heating. Furthermore, the stabilizing effect of rose petal polyphenols was compared with that of well-known copigments such as isolated kaempferol, quercetin, and sinapic acid. The purified rose petal extract was found to be a most effective anthocyanin-stabilizing agent at a molar pigment/copigment ratio of 1:2. The results obtained demonstrate that the addition of rose petal polyphenols slows the thermal degradation of strawberry anthocyanins, thus resulting in improved color retention without affecting the gustatory quality of the product.

Stress proteins in lymphocytes: Membrane stabilization does not affect the heat shock response

International Nuclear Information System (INIS)

Hughes, C.S.; Repasky, E.A.; Subjeck, J.R.

1987-01-01

Temperatures which have been used to induce heat shock proteins (hsps) have been at the upper physiologic limit or well above this limit. In addition, little attention has been given to the effects of physiologic heat exposures on hsp induction in lymphocytes. The author examined temperatures between 39 0 C and 41 0 C on protein synthesis in the following lymphoid cell lines and cells: BDK, EL-4, JM, DO.11, and in dispersed lymph nodes and thymic tissues. In these studies, 39.5 0 appears to be the threshold for hsp induction (as distinguished by gel electrophoresis). At this temperature the induction of the major hsps at 70 and 89 kDa are observed. Hsp 89 appears to be the most strongly induced in all cells examined. In JM cells, a human cell line, heat shock also induces hsp 68, the non-constitutive hsp at this size. These temperatures do not depress normal levels of protein synthesis. When stearic acid or cholesterol was added to lymphocyte cultures prior to heating (which stabilize membranes), hsp induction appears to occur in a manner indistinguishable from cells heated in normal media. This suggests that membrane fluidity (as influenced by these agents) does not affect or depress the heat shock response in these cells. Finally, the authors observed that 2-deoxyglucose and other inducers of glucose regulated proteins in fibroblasts also induce the major glucose regulated proteins in lymphocytes

Stability Analysis and Internal Heating Effect on Oscillatory Convection in a Viscoelastic Fluid Saturated Porous Medium Under Gravity Modulation

Directory of Open Access Journals (Sweden)

Bhadauria B.S.

2016-12-01

Full Text Available In this paper, we investigate the combined effect of internal heating and time periodic gravity modulation in a viscoelastic fluid saturated porous medium by reducing the problem into a complex non-autonomous Ginzgburg-Landau equation. Weak nonlinear stability analysis has been performed by using power series expansion in terms of the amplitude of gravity modulation, which is assumed to be small. The Nusselt number is obtained in terms of the amplitude for oscillatory mode of convection. The influence of viscoelastic parameters on heat transfer has been discussed. Gravity modulation is found to have a destabilizing effect at low frequencies and a stabilizing effect at high frequencies. Finally, it is found that overstability advances the onset of convection, more with internal heating. The conditions for which the complex Ginzgburg-Landau equation undergoes Hopf bifurcation and the amplitude equation undergoes supercritical pitchfork bifurcation are studied.

Impact of electro-magnetic stabilization, small- scale turbulence and multi-scale interactions on heat transport in JET

Science.gov (United States)

Mantica, Paola

2016-10-01

Heat transport experiments in JET, based on ICRH heat flux scans and temperature modulation, have confirmed the importance of two transport mechanisms that are often neglected in modeling experimental results, but are crucial to reach agreement between theory and experiment and may be significant in ITER. The first mechanism is the stabilizing effect of the total pressure gradient (including fast ions) on ITG driven ion heat transport. Such stabilization is found in non-linear gyro-kinetic electro-magnetic simulations using GENE and GYRO, and is the explanation for the observed loss of ion stiffness in the core of high NBI-power JET plasmas. The effect was recently observed also in JET plasmas with dominant ICRH heating and small rotation, due to ICRH fast ions, which is promising for ITER. Such mechanism dominates over ExB flow shear in the core and needs to be included in quasi-linear models to increase their ability to capture the relevant physics. The second mechanism is the capability of small- scale ETG instabilities to carry a significant fraction of electron heat. A decrease in Te peaking is observed when decreasing Zeff Te/Ti, which cannot be ascribed to TEMs but is in line with ETGs. Non-linear GENE single-scale simulations of ETGs and ITG/TEMs show that the ITG/TEM electron heat flux is not enough to match experiment. TEM stiffness is also much lower than measured. In the ETG single scale simulations the external flow shear is used to saturate the ETG streamers. Multi-scale simulations are ongoing, in which the ion zonal flows are the main saturating mechanism for ETGs. These costly simulations should provide the final answer on the importance of ETG-driven electron heat flux in JET. with JET contributors [F.Romanelli, Proc.25thIAEA FEC]. Supported by EUROfusion Grant 633053.

Microstructural stability of heat-resistant high-pressure die-cast Mg-4Al-4Ce alloy

Energy Technology Data Exchange (ETDEWEB)

Wang, Wei; Zhang, Jinghuai; Li, Guoqiang; Feng, Yan; Su, Minliang; Wu, Ruizhi; Zhang, Zhongwu [Harbin Engineering Univ. (China). Key Laboratory of Superlight Material and Surface Technology; Jiao, Yufeng [Jiamusi Univ. (China). College of Materials Science and Engineering

2017-05-15

The thermal stability of Al-RE (rare earth) intermetallic phases with individual RE for heat-resistant high-pressure die-casting Mg-Al-RE alloys is investigated. The results of this study show that the main strengthening phase of Mg-4Al-4Ce alloy is Al{sub 11}Ce{sub 3}, whose content is about 5 wt.% according to quantitative X-ray diffraction phase analysis. The Al{sub 11}Ce{sub 3} phase appears to have high thermal stability at 200 C and 300 C, while phase morphology change with no phase structure transition could occur for Al{sub 11}Ce{sub 3} when the temperature reaches 400 C. Furthermore, besides the kinds of rare earths and temperature, stress is also an influencing factor in the microstructural stability of Mg-4Al-4Ce alloy.

A stabilized second-order time accurate finite element formulation for incompressible viscous flow with heat transfer

International Nuclear Information System (INIS)

Curi, Marcos Filardy

2011-01-01

In view of the problem of global warming and the search for clean energy sources, a worldwide expansion on the use of nuclear energy is foreseen. Thus, the development of science and technology regarding nuclear power plants is essential, in particular in the field of reactor engineering. Fluid mechanics and heat transfer play an important role in the development of nuclear reactors. Computational Fluid Mechanics (CFD) is becoming ever more important in the optimization of cost and safety of the designs. This work presents a stabilized second-order time accurate finite element formulation for incompressible flows with heat transfer. A second order time discretization precedes a spatial discretization using finite elements. The terms that stabilize the finite element method arise naturally from the discretization process, rather than being introduced a priori in the variational formulation. The method was implemented in the program 'ns n ew s olvec2d av 2 M PI' written in FORTRAN90, developed in the Parallel Computing Laboratory at the Institute of Nuclear Engineering (LCP/IEN). Numerical solutions of some representative examples, including free, mixed and forced convection, demonstrate that the proposed stabilized formulation attains very good agreement with experimental and computational results available in the literature. (author)

Linear Stability Analysis of Flow in an Internally Heated Rectangular Duct

Energy Technology Data Exchange (ETDEWEB)

Uhlmann, M.

2004-07-01

The linear stability of flow in a vertical rectangular duct subject to homogeneous internal heating, constant-temperature no-slip walls and a driving pressure gradient is investigated numerically. A full Chebyshevbased Galerkin method is found to be more reliable than a collocation method, both including the elimination of the pressure and the stream wise velocity from the system of equations and making use of the full symmetry properties. A classification of the mean flow-obtained as a function of Grashof and Reynolds numbers and the geometrical aspect ratio in terms of its inflectional properties is proposed. It is found that the flow loses stability at all aspects rations for a combination of finite thermal buoyancy and pressure forces with opposed sings. In the square duct, the unstable region coincides with the range where additional inflection lines are observed the mean velocity profile. Unstable eigenfunctions are obtained for all basic symmetry modes and their structure can be described as slightly elongated pockets of cross-stream-vertical motion, training each other along the stream wise direction. (Author) 22 refs.

Improved magnetic induction heating of nanoferrites for hyperthermia applications: Correlation with colloidal stability and magneto-structural properties

International Nuclear Information System (INIS)

Khot, V.M.; Salunkhe, A.B.; Ruso, J.M.; Pawar, S.H.

2015-01-01

Nanoferrites with compositions Mn 0.4 Zn 0.6 Fe 2 O 4 , Co 0.4 Zn 0.6 Fe 2 O 4 , Ni 0.4 Zn 0.6 Fe 2 O 4 (MZF, CZF and NZF respectively) coated with polyethylene glycol (PEG) were prepared in a single step. These nanoparticles are highly water dispersible with zeta potential values between 14 and 21 mV. Magnetic induction heating characteristics of these NPs have been studied as a function of magnetic field amplitude from 6.7 to 26.7 kA m −1 (at fixed frequency 265 kHz) and concentration of nanoparticles. Notable enhancement in specific absorption rate (334.5 W g −1 ) by CZF nanoparticles has been observed. This enhanced induction heating properties have been studied and correlated with colloidal stability and magnetostructural properties such as tuned magnetic anisotropy arising from zinc substitution. Cytotoxicity of synthesized mixed ferrites has been evaluated in vitro on HeLa cell lines using MTT assay to explore their use as heating agents in magnetic hyperthermia. - Highlights: • Magnetic nanoferrites (sizes 8–12 nm) with improved specific absorption rate (334.5 W g −1 ) at lowest particle concentration have been prepared • The results have been explained by correlating colloidal stability and magnetostructural properties such as magnetocrystalline anisotropy. • It has been shown that substitution of zinc tunes anisotropy of cobalt iron oxide within the value optimized previously in achieving high throughput in magnetic induction heating. • In vitro cytotoxicity proves nanoparticles are non-toxic suggesting their use as a potential heating agent in hyperthermia therapy

Heat stability evaluations of Co/SiO2 multilayers

International Nuclear Information System (INIS)

Ishino, Masahiko; Koike, Masato; Kanehira, Mika; Satou, Futami; Terauchi, Masami; Sano, Kazuo

2008-01-01

The heat stability of Co/SiO 2 multilayers was evaluated. Co/SiO 2 multilayer samples were deposited on Si substrate by means of an ion beam sputtering method, and annealed at temperatures from 100degC to 600degC in a vacuum furnace. For the structural and optical evaluations, small angle x-ray diffraction (XRD) measurements, soft x-ray reflectivity measurements, and transmission electron microscopy (TEM) observations were carried out. As the results, the Co/SiO 2 multilayer samples annealed up to 400degC maintained the initial multilayer structures, and kept almost the same soft x-ray reflectivities as that of the as-deposited Co/SiO 2 multilayer sample. A deterioration of the multilayer structure caused by the growth of Co grains was found on the Co/SiO 2 multilayer samples annealed over 500degC, and the soft x-ray reflectivity dropped in accordance with the deterioration of the multilayer structure. (author)

Internal structure and stability of an interstellar cloud heated by an external flux of soft X-rays

International Nuclear Information System (INIS)

Sabano, Yutaka; Tosa, Makoto

1975-01-01

We study the properties of an interstellar gas cloud which is heated by an external flux of soft X-rays and has a uniform pressure distribution. The heating flux is significantly attenuated inside the cloud even for a rather small cloud, and the central region of the cloud is much cooler and denser than that heated uniformly, hence the cloud can be compressed easier. The stability of such a gas cloud and its implications for the process of star formation are discussed on the basis of the two-phase model of the interstellar medium. The large scale galactic shock seems important as a triggering mechanism for the formation of a dense cloud and for the gravitational collapse leading to star formation. (author)

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

International Nuclear Information System (INIS)

Sharma, Manish; Pilkhwal, D.S.; Jana, S.S.; Vijayan, P.K.

2013-02-01

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)

Linear stability analysis of flow instabilities with a nodalized reduced order model in heated channel

International Nuclear Information System (INIS)

Paul, Subhanker; Singh, Suneet

2015-01-01

The prime objective of the presented work is to develop a Nodalized Reduced Order Model (NROM) to carry linear stability analysis of flow instabilities in a two-phase flow system. The model is developed by dividing the single phase and two-phase region of a uniformly heated channel into N number of nodes followed by time dependent spatial linear approximations for single phase enthalpy and two-phase quality between the consecutive nodes. Moving boundary scheme has been adopted in the model, where all the node boundaries vary with time due to the variation of boiling boundary inside the heated channel. Using a state space approach, the instability thresholds are delineated by stability maps plotted in parameter planes of phase change number (N pch ) and subcooling number (N sub ). The prime feature of the present model is that, though the model equations are simpler due to presence of linear-linear approximations for single phase enthalpy and two-phase quality, yet the results are in good agreement with the existing models (Karve [33]; Dokhane [34]) where the model equations run for several pages and experimental data (Solberg [41]). Unlike the existing ROMs, different two-phase friction factor multiplier correlations have been incorporated in the model. The applicability of various two-phase friction factor multipliers and their effects on stability behaviour have been depicted by carrying a comparative study. It is also observed that the Friedel model for friction factor calculations produces the most accurate results with respect to the available experimental data. (authors)

Influence of spike lavender (Lavandula latifolia Med.) essential oil in the quality, stability and composition of soybean oil during microwave heating.

Science.gov (United States)

Rodrigues, Nuno; Malheiro, Ricardo; Casal, Susana; Asensio-S-Manzanera, M Carmen; Bento, Albino; Pereira, José Alberto

2012-08-01

Lipids oxidation is one of the main factors leading to quality losses in foods. Its prevention or delay could be obtained by the addition of antioxidants. In this sense the present work intend to monitor the protective effects of Lavandula latifolia essential oil during soybean oil microwave heating. To achieve the proposed goal quality parameters (free acidity, peroxide value, specific coefficients of extinction and ΔK), fatty acids profile, tocopherols and tocotrienols composition, antioxidant activity and oxidative stability were evaluated in soybean oil with and without spike lavender essential oils (EO) submitted to different microwave heating exposure times (1, 3, 5, 10 and 15 min; 1000 Watt) with a standard domestic microwave equipment. Microwave heating induced severe quality and composition losses, mainly above 3 min of microwave heating, regardless the sample tested. However, spike lavender EO addition counteracts the oxidation comparatively to control oils, by presenting enhanced values in quality parameters. A higher protection in unsaturated fatty acids loss was also observed as well as a higher antioxidant activity and oxidative stability. The microwave heating effects were clearly different in the samples with essential oils addition, allowing discrimination from plain soybean oils by a principal component analysis, being also capable to discriminate the different heating times tested within each sample. Copyright © 2012 Elsevier Ltd. All rights reserved.

Improved magnetic induction heating of nanoferrites for hyperthermia applications: Correlation with colloidal stability and magneto-structural properties

Energy Technology Data Exchange (ETDEWEB)

Khot, V.M., E-mail: wish_khot@yahoo.co.in [Center for Interdisciplinary Research, D. Y. Patil University, Kolhapur 416006 (India); Salunkhe, A.B. [Advanced Materials Laboratory, Department of Physics, Savitribai Phule University of Pune (India); Ruso, J.M. [Soft Matter and Molecular Biophysics Group, Applied Physics Department, University of Santiago de Compostela, Santiago de Compostela (Spain); Pawar, S.H. [Center for Interdisciplinary Research, D. Y. Patil University, Kolhapur 416006 (India)

2015-06-15

Nanoferrites with compositions Mn{sub 0.4}Zn{sub 0.6}Fe{sub 2}O{sub 4}, Co{sub 0.4}Zn{sub 0.6}Fe{sub 2}O{sub 4}, Ni{sub 0.4}Zn{sub 0.6}Fe{sub 2}O{sub 4} (MZF, CZF and NZF respectively) coated with polyethylene glycol (PEG) were prepared in a single step. These nanoparticles are highly water dispersible with zeta potential values between 14 and 21 mV. Magnetic induction heating characteristics of these NPs have been studied as a function of magnetic field amplitude from 6.7 to 26.7 kA m{sup −1} (at fixed frequency 265 kHz) and concentration of nanoparticles. Notable enhancement in specific absorption rate (334.5 W g{sup −1}) by CZF nanoparticles has been observed. This enhanced induction heating properties have been studied and correlated with colloidal stability and magnetostructural properties such as tuned magnetic anisotropy arising from zinc substitution. Cytotoxicity of synthesized mixed ferrites has been evaluated in vitro on HeLa cell lines using MTT assay to explore their use as heating agents in magnetic hyperthermia. - Highlights: • Magnetic nanoferrites (sizes 8–12 nm) with improved specific absorption rate (334.5 W g{sup −1}) at lowest particle concentration have been prepared • The results have been explained by correlating colloidal stability and magnetostructural properties such as magnetocrystalline anisotropy. • It has been shown that substitution of zinc tunes anisotropy of cobalt iron oxide within the value optimized previously in achieving high throughput in magnetic induction heating. • In vitro cytotoxicity proves nanoparticles are non-toxic suggesting their use as a potential heating agent in hyperthermia therapy.

Mechanical stability of heat-treated nanoporous anodic alumina subjected to repetitive mechanical deformation

Science.gov (United States)

Bankova, A.; Videkov, V.; Tzaneva, B.; Mitov, M.

2018-03-01

We report studies on the mechanical response and deformation behavior of heat-treated nanoporous anodic alumina using a micro-balance test and experimental test equipment especially designed for this purpose. AAO samples were characterized mechanically by a three-point bending test using a micro-analytical balance. The deformation behavior was studied by repetitive mechanical bending of the AAO membranes using an electronically controlled system. The nanoporous AAO structures were prepared electrochemically from Al sheet substrates using a two-step anodizing technique in oxalic acid followed by heat treatment at 700 °C in air. The morphological study of the aluminum oxide layer after the mechanical tests and mechanical deformation was conducted using scanning electron and optical microscopy, respectively. The experimental results showed that the techniques proposed are simple and accurate; they could, therefore, be combined to constitute a method for mechanical stability assessment of nanostructured AAO films, which are important structural components in the design of MEMS devices and sensors.

Development of a method for the characterization of the oxidation stability of domestic heating oil and domestic heating oil with alternative components using chemiluminescence; Entwicklung einer Analysemethode zur Charakterisierung der Oxidationsstabilitaet von Heizoel EL und Heizoel EL A mittels Chemilumineszenz

Energy Technology Data Exchange (ETDEWEB)

Koch, Winfried; Lukito, Jayadi; Schloss, Heide vom [Oel-Waerme-Institut gGmbH (OWI), Aachen-Herzogenrath (Germany)

2013-04-15

The project's aim was to develop a process that serves to determine the oxidation stability of heating oil - FAME-/ heating oil - vegetable oil-blends clearly. Due to a directed energy input by means of the process of chemiluminescence, statements about the storage stability and the thermal stability of blends can be made. During the process the ageing of blend components and of the heating oil are taken into consideration. As a result, ageing processes and products of pure heating oil as well as biogenic components can be determined. It was shown that the process is applicable to blends up to an admixture of at least 20 % (V/V) of biogenic components, whereby blends with higher admixture shares can be analyzed as well. According to DIN SPEC 51603 - 6 'Heating Oil Alternative' the admixture of FAME is limited to 20 %(V/V) and the admixture of vegetable oil to 5 % (V/V) because of the distillation range. On the basis of these investigations it could be shown how oxidation products influence the signal process of the chemiluminescence radiation and how they can be correlated by a measurable physical value. Moreover, a new evaluation criterion has been developed. By means of this criterion a good reproducibility - regarding the determination of the oxidation stability according to the chemiluminescence methodology for non-aged fuels - can be achieved. The fuel characteristic decrease in the stability of the tested fuels can be represented only partially by the chemiluminescence process, as the measured values are subject to fluctuations. (orig.)

Improvement of stability of Nb₃ Sn superconductors by introducing high specific heat substances

Energy Technology Data Exchange (ETDEWEB)

Xu, X. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Li, P. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Zlobin, A. V. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Peng, X. [Unlisted, US, OH

2018-01-24

High-J_c Nb₃Sn conductors have low stability against perturbations, which accounts for the slow training rates of high-field Nb₃Sn magnets. While it is known that adding substances with high specific heat (C) into Nb3Sn wires can increase their overall specific heat and thus improve their stability, there has not been a practical method that is compatible with the fabrication of long-length conductors. In this work, we put forward a scheme to introduce such substances to distributed-barrier Nb₃Sn wires, which adds minimum difficulty to the wire manufacturing process. Multifilamentary wires using a mixture of Cu and high-C Gd₂O₃ powders have been successfully fabricated along this line. Measurements showed that addition of Gd₂O₃ had no negative effects on residual resitivity ratio or non-Cu J_c, and that flux jumps were remarkably reduced, and minimum quench energy values at 4.2 K, 14 T were increased by a factor of three, indicating that stability was significantly improved. We also discussed the influences of the positioning of high-C substances and their thermal diffusivity on their effectiveness in reducing the superconductor temperature rise against perturbations. Based on these results, we proposed an optimized conductor architecture to maximize the effectiveness of this approach.

Biochemical changes in full fat rice bran stabilized through microwave heating and irradiation treatment

International Nuclear Information System (INIS)

El-Niely, H.F.; Abaullah, M.I.

2007-01-01

The effect of microwave heating and irradiation treatments on proximate composition, lipoxygenase (LOX) activity, free fatty acid (FFA) and fatty acids profile of full fat rice bran were examined. Full fat raw rice bran (FRB) (82.7 g / kg moisture content) was heated in microwave oven at 850 W for up to 4 min or exposed to gamma irradiation up to 25 KGy then packed in polyethylene bags and stored at room temperature for 6 months. Water, protein, fat, ash and crude fiber contents did not change significantly in raw, microwave heated and irradiated samples before and after storage. An exception for this general observation was observed for the moisture content of FRB processed through microwave heating where heating FRB for 4 min dropped the level of moisture to 64.3 g / kg at zero time. Storage of both raw and processed samples had significant (P<0.05) effects on LOX activity. LOX activity of raw samples was significantly increased from its initial value by 43.5% after storage for six months. Microwave heat and irradiated samples showed deactivated LOX and samples exhibited significant changes in LOX activity could be due to treatment dosage. Meanwhile, significant change in LOX activity was observed in processed samples stored for six months. Minor changes were observed due to applied processing methods on FFA and fatty acids composition of full fat rice bran before and after storage. The results suggested that microwave heated or irradiated full fat rice bran packed in polyethylene bags can be stored at room temperature for six months without adverse effect on proximate, fatty acid composition quality and could prevent oxidative and hydrolytic rancidity. However, gamma irradiation treatment at 25 KGy was more effective in this respect. Therefore, it could be concluded that gamma irradiation contributed to optimal processing conditions for FRB stabilization

Bounds of thermal stability of infinite cylindrical structures with non-uniform internal heat generation

International Nuclear Information System (INIS)

Gadalla, M.A.

1992-01-01

This paper presents an overview analyses of the thermal instability or thermal viability of infinite cylindrical structures with non-linear and non-uniform internal heat generation. The structure may be subjected to different and combined boundary conditions. An analytical solution is obtained for the generalized problem in spite of the non-linearity and the non-homogeneity of the source term. Four case studies with different boundary conditions are presented. The analyses show that the critical parameter for thermal stability may be though of as an altitude of surface below which the cylindrical structure will be thermally stable and performance worthy. The results also show that the bounds of thermal stability of a cylindrical structure system (solid or hollow) is eminently determined by the boundary conditions to which the system is subjected and can significantly alter the life-span of the structure

Exponential Stability of the Monotubular Heat Exchanger Equation with Time Delay in Boundary Observation

Directory of Open Access Journals (Sweden)

Xue-Lian Jin

2017-01-01

Full Text Available The exponential stability of the monotubular heat exchanger equation with boundary observation possessing a time delay and inner control was investigated. Firstly, the close-loop system was translated into an abstract Cauchy problem in the suitable state space. A uniformly bounded C0-semigroup generated by the close-loop system, which implies that the unique solution of the system exists, was shown. Secondly, the spectrum configuration of the closed-loop system was analyzed and the eventual differentiability and the eventual compactness of the semigroup were shown by the resolvent estimates on some resolvent sets. This implies that the spectrum-determined growth assumption holds. Finally, a sufficient condition, which is related to the physical parameters in the system and is independent of the time delay, of the exponential stability of the closed-loop system was given.

Extended stability of intravenous 0.9% sodium chloride solution after prolonged heating or cooling.

Science.gov (United States)

Puertos, Enrique

2014-03-01

The primary objective of this study was to evaluate the stability and sterility of an intravenous 0.9% sodium chloride solution that had been cooled or heated for an extended period of time. Fifteen sterile 1 L bags of 0.9% sodium chloride solution were randomly selected for this experiment. Five bags were refrigerated at an average temperature of 5.2°C, 5 bags were heated at an average temperature of 39.2°C, and 5 bags were stored at an average room temperature of 21.8°C to serve as controls. All samples were protected from light and stored for a period of 199 days prior to being assayed and analyzed for microbial and fungal growth. There was no clinically significant difference in the mean sodium values between the refrigerated samples, the heated samples, and the control group. There were no signs of microbial or fungal growth for the duration of the study. A sterile intravenous solution of 0.9% sodium chloride that was heated or cooled remained stable and showed no signs of microbial or fungal growth for a period of 199 days. This finding will allow hospitals and emergency medical technicians to significantly extend the expiration date assigned to these fluids and therefore obviate the need to change out these fluids every 28 days as recommended by the manufacturer.

Contributions to the stability analysis of self-similar supersonic heat waves related to inertial confinement fusion

International Nuclear Information System (INIS)

Dastugue, Laurent

2013-01-01

Exact self-similar solutions of gas dynamics equations with nonlinear heat conduction for semi-infinite slabs of perfect gases are used for studying the stability of flows in inertial confinement fusion. Both the similarity solutions and their linear perturbations are computed with a multi domain Chebyshev pseudo-spectral method, allowing us to account for, without any other approximation, compressibility and unsteadiness. Following previous results (Clarisse et al., 2008; Lombard, 2008) representative of the early ablation of a target by a nonuniform laser flux (electronic conduction, subsonic heat front downstream of a quasi-perfect shock front), we explore here other configurations. For this early ablation phase, but for a nonuniform incident X-radiation (radiative conduction), we study a compressible and a weakly compressible flow. In both cases, we recover the behaviours obtained for compressible flows with electronic heat conduction with a maximal instability for a zero wavenumber. Besides, the spectral method is extended to compute similarity solutions taking into account the supersonic heat wave ahead of the shock front. Based on an analysis of the reduced equations singularities (infinitely stiff front), this method allows us to describe the supersonic heat wave regime proper to the initial irradiation of the target and to recover the ablative solutions which were obtained under a negligible fore-running heat wave approximation. (author) [fr

A comparison of the thermal, emission and heat transfer characteristics of swirl-stabilized premixed and inverse diffusion flames

Energy Technology Data Exchange (ETDEWEB)

Zhen, H.S.; Leung, C.W.; Cheung, C.S. [Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong (China)

2011-02-15

Two swirl-stabilized flames, a premixed flame (PMF-s) and an inverse diffusion flame (IDF-s), were investigated experimentally in order to obtain information on their thermal, emission and heat transfer characteristics. The two flames, having different global air/fuel mixing mechanisms, were compared under identical air and fuel flow rates. Results showed that the two flames have similar visual features such as flame shape, size and structure because the Reynolds number and the swirl number which are important parameters representative of the aerodynamic characteristics of a swirling jet flow, are almost the same for the two flames. The minor dissimilarity in flame color and flame length indicates that the IDF-s is more diffusional. Both the PMF-s and IDF-s are stabilized by the internal recirculation zone (IRZ) and the IDF-s is more stable. Flame temperature is uniformly distributed in the IRZ due to the strong mixing caused by flow recirculation. The highest flame temperature is achieved at the main reaction zone and it is higher for the PMF-s due to more rapid and localized heat release. For the IDF-s, the thermal NO mechanism dominates the NO{sub x} formation. For the PMF-s, both the thermal and prompt mechanisms tend to play important roles in the global NO{sub x} emission under rich conditions. The comparison of EINO{sub x} and EICO shows that the PMF-s has lower level of NO{sub x} emission under lean combustion and lower level of CO emission under all conditions. The reason is that the air/fuel premixing in the PMF-s significantly enhances the mixedness of the supplied air/fuel mixture. The analysis of the behaviors of the impinging PMF-s and IDF-s heat transfer reveals that because the PMF-s has more rapid and localized heat release at the main reaction zone, the peak heat flux is higher than that of the IDF-s and the IDF-s has more uniform heating effect. A comparison of the overall heat transfer rates shows that, due to more complete combustion, the PMF

A comparison of the thermal, emission and heat transfer characteristics of swirl-stabilized premixed and inverse diffusion flames

International Nuclear Information System (INIS)

Zhen, H.S.; Leung, C.W.; Cheung, C.S.

2011-01-01

Two swirl-stabilized flames, a premixed flame (PMF-s) and an inverse diffusion flame (IDF-s), were investigated experimentally in order to obtain information on their thermal, emission and heat transfer characteristics. The two flames, having different global air/fuel mixing mechanisms, were compared under identical air and fuel flow rates. Results showed that the two flames have similar visual features such as flame shape, size and structure because the Reynolds number and the swirl number which are important parameters representative of the aerodynamic characteristics of a swirling jet flow, are almost the same for the two flames. The minor dissimilarity in flame color and flame length indicates that the IDF-s is more diffusional. Both the PMF-s and IDF-s are stabilized by the internal recirculation zone (IRZ) and the IDF-s is more stable. Flame temperature is uniformly distributed in the IRZ due to the strong mixing caused by flow recirculation. The highest flame temperature is achieved at the main reaction zone and it is higher for the PMF-s due to more rapid and localized heat release. For the IDF-s, the thermal NO mechanism dominates the NO x formation. For the PMF-s, both the thermal and prompt mechanisms tend to play important roles in the global NO x emission under rich conditions. The comparison of EINO x and EICO shows that the PMF-s has lower level of NO x emission under lean combustion and lower level of CO emission under all conditions. The reason is that the air/fuel premixing in the PMF-s significantly enhances the mixedness of the supplied air/fuel mixture. The analysis of the behaviors of the impinging PMF-s and IDF-s heat transfer reveals that because the PMF-s has more rapid and localized heat release at the main reaction zone, the peak heat flux is higher than that of the IDF-s and the IDF-s has more uniform heating effect. A comparison of the overall heat transfer rates shows that, due to more complete combustion, the PMF-s has higher overall

Evaluation of microwave oven heating for prediction of drug-excipient compatibilities and accelerated stability studies

DEFF Research Database (Denmark)

Schou-Pedersen, Anne Marie V; Østergaard, Jesper; Cornett, Claus

2015-01-01

, if a microwave oven is applicable for accelerated drug stability testing. Chemical interactions were investigated in three selected model formulations of drug and excipients regarding the formation of ester and amide reaction products. The accelerated stability studies performed in the microwave oven using...... a design of experiments (DoE) approach in order to be able to rank excipients regarding reactivity: Study A: cetirizine with PEG 400, sorbitol, glycerol and propylene glycol. Study B: 6-aminocaproic acid with citrate, acetate, tartrate and gluconate. Study C: atenolol with citric, tartaric, malic, glutaric......, and sorbic acid. The model formulations were representative for oral solutions (co-solvents), parenteral solutions (buffer species) and solid dosage forms (organic acids applicable for solubility enhancement). The DoE studies showed overall that the same impurities were generated by microwave oven heating...

Effect of heat treatment on stability of gold particle modified carbon supported Pt-Ru anode catalysts for a direct methanol fuel cell

International Nuclear Information System (INIS)

Li Xiaowei; Liu Juanying; Huang Qinghong; Vogel, Walter; Akins, Daniel L.; Yang Hui

2010-01-01

Carbon supported Au-PtRu (Au-PtRu/C) catalysts were prepared as the anodic catalysts for the direct methanol fuel cell (DMFC). The procedure involved simple deposition of Au particles on a commercial Pt-Ru/C catalyst, followed by heat treatment of the resultant composite catalyst at 125, 175 and 200 o C in a N 2 atmosphere. High-resolution transmission electron microscopy (HR-TEM) measurements indicated that the Au nanoparticles were attached to the surface of the Pt-Ru nanoparticles. We found that the electrocatalytic activity and stability of the Au-PtRu/C catalysts for methanol oxidation is better than that of the PtRu/C catalyst. An enhanced stability of the electrocatalyst is observed and attributable to the promotion of CO oxidation by the Au nanoparticles adsorbed onto the Pt-Ru particles, by weakening the adsorption of CO, which can strongly adsorb to and poison Pt catalyst. XPS results show that Au-PtRu/C catalysts with heat treatment lead to surface segregation of Pt metal and an increase in the oxidation state of Ru, which militates against the dissolution of Ru. We additionally find that Au-PtRu/C catalysts heat-treated at 175 o C exhibit the highest electrocatalytic stability among the catalysts prepared by heat treatment: this observation is explained as due to the attainment of the highest relative concentration of gold and the highest oxidation state of Ru oxides for the catalyst pretreated at this temperature.

Heat and mass transfer in turbulent chemically nonequilibrium flow in the tube with boundary second kind conditions. The section with the stabilized heat and mass transfer

International Nuclear Information System (INIS)

Kritsuk, E.L.; Mishina, L.V.; Shegidevich, L.N.

1986-01-01

The hydrodynamically stabilized chemically nonequilibrium turbulent flow in a tube with the inert impermeable surface and constant specific heat flow on the wall is considered. The reversible homogeneous reaction of nitrogen dioxide dissociation 2NO 2 ↔ 2NO+O 2 takes place in the flow. Chemically equilibrium flow with homogeneous profile of temperature and concentration arrives into the channel inlet. After application of simplifying assumptions, the expressions for characteristics of heat and mass transfer have been written down, which are valid in the whole range of the flow parameter variation from frozen up to chemically equilibrium flow. An integral transformation method is suggested for a radial coordinate which allows a wall region to be extended, thereby essentially extending the step of integration. A solution in quadratures has been obtained for the heat and mass transfer problem in an inert fluid flow for the developed process section. The elimination method has been employed to solve the boundary-value second-kind problem for the function governing heat and mass transfer in a chemically nonequilibrium turbulent flow over the developed heat and mass transfer section. The results of calculations are presented

Controlling the heating mode of heat pumps with the TRIANA three step methodology

NARCIS (Netherlands)

Toersche, Hermen; Bakker, Vincent; Molderink, Albert; Nykamp, Stefan; Hurink, Johann L.; Smit, Gerardus Johannes Maria

2012-01-01

Heat pump based heating systems are increasingly becoming an economic and efficient alternative for domestic gas heating systems. Concentrations of heat pump installations do consume large amounts of electricity, causing significant grid distribution and stability issues when the diversity factor is

An analytical model for the prediction of the dynamic response of premixed flames stabilized on a heat-conducting perforated plate

KAUST Repository

Kedia, Kushal S.; Ghoniem, Ahmed F.

2013-01-01

The dynamic response of a premixed flame stabilized on a heat-conducting perforated plate depends critically on their coupled thermal interaction. The objective of this paper is to develop an analytical model to capture this coupling. The model

Heat transfer modelling and stability analysis of selective laser melting

International Nuclear Information System (INIS)

Gusarov, A.V.; Yadroitsev, I.; Bertrand, Ph.; Smurov, I.

2007-01-01

The process of direct manufacturing by selective laser melting basically consists of laser beam scanning over a thin powder layer deposited on a dense substrate. Complete remelting of the powder in the scanned zone and its good adhesion to the substrate ensure obtaining functional parts with improved mechanical properties. Experiments with single-line scanning indicate, that an interval of scanning velocities exists where the remelted tracks are uniform. The tracks become broken if the scanning velocity is outside this interval. This is extremely undesirable and referred to as the 'balling' effect. A numerical model of coupled radiation and heat transfer is proposed to analyse the observed instability. The 'balling' effect at high scanning velocities (above ∼20 cm/s for the present conditions) can be explained by the Plateau-Rayleigh capillary instability of the melt pool. Two factors stabilize the process with decreasing the scanning velocity: reducing the length-to-width ratio of the melt pool and increasing the width of its contact with the substrate

On the sensitivity of dimensional stability of high density polyethylene on heating rate

Directory of Open Access Journals (Sweden)

2007-02-01

Full Text Available Although high density polyethylene (HDPE is one of the most widely used industrial polymers, its application compared to its potential has been limited because of its low dimensional stability particularly at high temperature. Dilatometry test is considered as a method for examining thermal dimensional stability (TDS of the material. In spite of the importance of simulation of TDS of HDPE during dilatometry test it has not been paid attention by other investigators. Thus the main goal of this research is concentrated on simulation of TDS of HDPE. Also it has been tried to validate the simulation results and practical experiments. For this purpose the standard dilatometry test was done on the HDPE speci­mens. Secant coefficient of linear thermal expansion was computed from the test. Then by considering boundary conditions and material properties, dilatometry test has been simulated at different heating rates and the thermal strain versus temper­ature was calculated. The results showed that the simulation results and practical experiments were very close together.

Evaluation of microwave oven heating for prediction of drug-excipient compatibilities and accelerated stability studies.

Science.gov (United States)

Schou-Pedersen, Anne Marie V; Østergaard, Jesper; Cornett, Claus; Hansen, Steen Honoré

2015-05-15

Microwave ovens have been used extensively in organic synthesis in order to accelerate reaction rates. Here, a set up comprising a microwave oven combined with silicon carbide (SiC) plates for the controlled microwave heating of model formulations has been applied in order to investigate, if a microwave oven is applicable for accelerated drug stability testing. Chemical interactions were investigated in three selected model formulations of drug and excipients regarding the formation of ester and amide reaction products. In the accelerated stability studies, a design of experiments (DoE) approach was applied in order to be able to rank excipients regarding reactivity: Study A: cetirizine with PEG 400, sorbitol, glycerol and propylene glycol. Study B: 6-aminocaproic acid with citrate, acetate, tartrate and gluconate. Study C: atenolol with citric, tartaric, malic, glutaric, and sorbic acid. The model formulations were representative for oral solutions (co-solvents), parenteral solutions (buffer species) and solid dosage forms (organic acids applicable for solubility enhancement). The DoE studies showed overall that the same impurities were generated by microwave oven heating leading to temperatures between 150°C and 180°C as compared to accelerated stability studies performed at 40°C and 80°C using a conventional oven. Ranking of the reactivity of the excipients could be made in the DoE studies performed at 150-180°C, which was representative for the ranking obtained after storage at 40°C and 80°C. It was possible to reduce the time needed for drug-excipient compatibility testing of the three model formulations from weeks to less than an hour in the three case studies. The microwave oven is therefore considered to be an interesting alternative to conventional thermal techniques for the investigation of drug-excipient interactions during preformulation. Copyright © 2015 Elsevier B.V. All rights reserved.

Effects of heat stress and probiotic supplementation on protein functionality and oxidative stability of ground chicken leg meat during display storage.

Science.gov (United States)

Kim, Hyun-Wook; Kim, Ji-Han; Yan, Feifei; Cheng, Heng-Wei; Brad Kim, Yuan H

2017-12-01

The present study aimed to evaluate the effects of heat stress and probiotic supplementation on protein functionality and oxidative stability of ground chicken leg during display storage. Two hundred and forty, 1-day-old male chicks (5 birds per pen) were subjected to four treatments in a 2 (thermoneutral condition at 21 °C and cyclic heat stress at 32-21-32 °C for 10 h day -1 ) × 2 (regular diet with 0 or 0.25 g kg -1 Bacillus subtilis) factorial design. Chickens were harvested at day 46, and pairs of whole legs were collected at 1 day postmortem. The chicken legs were deboned, ground, tray-packaged with oxygen-permeable film, and displayed for 3 days. Heat stress and probiotic supplementation had no impact on pH, water-holding capacity, color, protein functionality, lipid lipolysis and lipid/protein oxidation stability (P > 0.05). Display storage increased the pH and lipid oxidation of ground chicken legs (P chicken leg meat. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Thermal stability of radiation-modified polyethylene

International Nuclear Information System (INIS)

Vinogradova, T.B.; Sirota, A.G.; Bal'tenas, R.A.; Stanyavichus, V.I.; Knebel'man, A.M.; Sil'chenko, S.A.

1989-01-01

In the work reported here, the authors investigated the thermooxidative resistance, at temperatures from 373 to 473 K, of polyethylene that had been cross-linked by exposure to radiation and formulated with various heat stabilizers. Thus, these studies of the thermooxidative resistance of polyethylene-based compositions that have been cross-linked by the radiation-chemical method have shown that, in this particular series of heat-stabilizers, the greatest effect at temperatures of 373-473 K is given by the FAU-13. The DTPhDMI has the greatest heat-stabilizing effect in the temperature interval 448-473 K, whereas the heat resistance of materials containing Diaphen NN or Phenozan-23 is higher at 373-423 K. These comparative results are in agreement with data for unirradiated and chemically cross-linked polyethylene

Damp heat stability and annealing behavior of aluminum doped zinc oxide films prepared by magnetron sputtering

International Nuclear Information System (INIS)

Tohsophon, T.; Huepkes, J.; Calnan, S.; Reetz, W.; Rech, B.; Beyer, W.; Sirikulrat, N.

2006-01-01

The damp heat stability and subsequent vacuum annealing behavior of aluminum doped zinc oxide (AZO) films was investigated using Hall effect measurements, X-ray diffraction (XRD) and optical spectrometry techniques. The AZO films were deposited on glass or silicon wafers using reactive and non-reactive magnetron sputtering from metallic and ceramic targets, respectively. Additionally, we characterized surface textured AZO films, which are used as light scattering transparent conductive oxide (TCO) in silicon thin film solar cells. For all films a degradation of the electrical film properties was found after the damp heat treatment. For thick compact films, with large grain size, only a small increase in the electrical resistivity was observed, whereas less compact films prepared at high deposition pressures or very thin films (< 300 nm) showed an increase in resistivity by up to a factor of three already after 300 h. The conductivity degradation during damp heat treatment could be largely reversed by annealing in vacuum. However, annealing temperatures of at least 150 deg. C were required. Possible mechanisms explaining the experimental results are discussed

System evaluation of improved thermal stability jet fuels

Energy Technology Data Exchange (ETDEWEB)

Binns, K.E.; Dieterle, G.L.; Williams, T. [Univ. of Dayton Research Institute, OH (United States)

1995-05-01

A single-pass, single-tube heat exchanger device called the Phoenix rig and a single-pass, dual-heat exchanger system called the Extended Duration Thermal Stability Test system are specific devices/systems developed for evaluating jet fuel thermal stability. They have been used extensively in the evaluation of various jet fuels and thermal stability additives. The test results have indicated that additives can substantially improve the thermal stability of conventional jet fuels. Relationships of oxygen consumption, residence time, bulk, and wetted wall temperatures on coking deposits that form in the heated tubes have also been investigated.

Equilibrium, stability and heating of plasmas in linear and toroidal Extrap pinches

International Nuclear Information System (INIS)

Bonnevier, B.; Drake, J.R.; Dalhed, H.E.

1983-01-01

The Extrap scheme consists of a Z-pinch immersed in an octupole field. The total magnetic field has no component along the pinch axis. Globally stable Z-pinch equilibria with a distributed plasma current density and a duration of about 100 Alfven transit times have been observed in linear and toroidal sector experiments. Theoretical studies indicate that this stability can be the result of constraints introduced by the octupole field and the resulting separatrix of the total field, in combination with finite-Larmor-radius effects. A scheme for ICRF heating of the plasma in configurations with a magnetic neutral line, being applicable to Extrap and FRC, is analysed. Wave propagation arises owing to the Hall effect. Particle resonances are responsible for the absorption, owing to a high parallel wavenumber and a weak magnetic field. (author)

Heat pump control method based on direct measurement of evaporation pressure to improve energy efficiency and indoor air temperature stability at a low cooling load condition

International Nuclear Information System (INIS)

Park, Young Sung; Jeong, Ji Hwan; Ahn, Byoung Ha

2014-01-01

Highlights: • New heat pump control method was developed. • Experimental investigation on performance of heat pump with various control method. • New control method appeared to improve the stability of indoor air temperature. • New control method appeared to have a potential to reduce power consumption. - Abstract: The control systems of conventional heat pumps have an input of refrigerant temperature at the evaporator outlet to maintain superheat at proper level. In order to develop a control method that can be used to achieve better indoor thermal comfort and energy efficiency at a low cooling load condition than the current control method, a new method of the evaporation pressure control based on the evaporator outlet pressure reading (EPCP) was developed. The changes in the stability of indoor air temperature and power consumption were measured while changing the compressor frequency in accordance with the new control method. Compared with the evaporation pressure control based on the evaporator outlet temperature reading, the EPCP control method appeared to improve the stability of room air temperature or occupant thermal comfort significantly

Effect of Graphene-EC on Ag NW-Based Transparent Film Heaters: Optimizing the Stability and Heat Dispersion of Films.

Science.gov (United States)

Cao, Minghui; Wang, Minqiang; Li, Le; Qiu, Hengwei; Yang, Zhi

2018-01-10

To optimize the performance of silver nanowire (Ag NW) film heaters and explore the effect of graphene on a film, we introduced poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) and graphene modified with ethyl cellulose (graphene-EC) into the film. The high-quality and well-dispersed graphene-EC was synthesized from graphene obtained by electrochemical exfoliation as a precursor. The transparent film heaters were fabricated via spin-coating. With the assistance of graphene-EC, the stability of film heaters was greatly improved, and the conductivity was optimized by adjusting the Ag NW concentration. The film heaters exhibited a fast and accurate response to voltage, accompanied by excellent environmental endurance, and there was no significant performance degradation after being operated for a long period of time. These results indicate that graphene-EC plays a crucial role in optimizing film stability and heat dispersion in the film. The Ag NW/PEDOT:PSS-doped graphene-EC film heaters show a great potential in low-cost indium-tin-oxide-free flexible transparent electrodes, heating systems, and transparent film heaters.

Heat inactivation kinetics of Hypocrea orientalis β-glucosidase with enhanced thermal stability by glucose.

Science.gov (United States)

Xu, Xin-Qi; Shi, Yan; Wu, Xiao-Bing; Zhan, Xi-Lan; Zhou, Han-Tao; Chen, Qing-Xi

2015-11-01

Thermal inactivation kinetics of Hypocrea orientalis β-glucosidase and effect of glucose on thermostability of the enzyme have been determined in this paper. Kinetic studies showed that the thermal inactivation was irreversible and first-order reaction. The microscopic rate constants for inactivation of free enzyme and substrate-enzyme complex were both determined, which suggested that substrates can protect β-glucosidase against thermal deactivation effectively. On the other hand, glucose was found to protect β-glucosidase from heat inactivation to remain almost whole activity below 70°C at 20mM concentration, whereas the apparent inactivation rate of BG decreased to be 0.3×10(-3)s(-1) in the presence of 5mM glucose, smaller than that of sugar-free enzyme (1.91×10(-3)s(-1)). The intrinsic fluorescence spectra results showed that glucose also had stabilizing effect on the conformation of BG against thermal denaturation. Docking simulation depicted the interaction mode between glucose and active residues of the enzyme to produce stabilizing effect. Copyright © 2015 Elsevier B.V. All rights reserved.

Stability analysis of fluid at supercritical pressure in a heated channel

International Nuclear Information System (INIS)

Gallaway, T.; Podowski, M. Z.

2010-01-01

The Supercritical Water Reactor (SCWR) is one of several reactor design concepts included in the Generation IV International Advanced Reactor Design Program. This reactor design is based upon current light water reactors and supercritical fossil-fuel power plants. Water at supercritical pressures is used as the reactor coolant. At these conditions, there is no phase change in the coolant; however the fluid properties undergo significant variation, particularly in the pseudo-critical region. The fluid density may decrease by a factor of six with increasing temperature. It has been seen before that variations in fluid density can lead to density-wave oscillations in two-phase flow systems in general and boiling water reactors in particular. Such instabilities may cause many undesired problems for reactor operation and safety. Similar issues must be addressed in the design and safety analysis of SCWRs. The objective of the present work has been the development of a detailed one-dimensional model of instabilities in a heated channel corresponding to the geometry and flow conditions in the proposed typical SCWRs. The new model is capable of analyzing in detail transient effects of local property variations in parallel channels subject to a constant pressure drop boundary condition. In particular, such a model can be used to establish SCWR power limits imposed by the onset of instabilities in the hot channel of the reactor. Both time and frequency-domain methods of stability analysis have been developed. The latter method is particularly important since it is not associated with any numerical issues, is very accurate, and allows for establishing general stability boundaries in a computationally effective manner. Model testing has included a study of dependence of the proposed spatial discretization scheme on the accuracy of calculations. A parametric study has also been performed on the effect of channel operating conditions on flow oscillations. Finally, a stability map

Advanced numerical methods for uncertainty reduction when predicting heat exchanger dynamic stability limits: Review and perspectives

International Nuclear Information System (INIS)

Longatte, E.; Baj, F.; Hoarau, Y.; Braza, M.; Ruiz, D.; Canteneur, C.

2013-01-01

Highlights: ► Proposal of hybrid computational methods for investigating dynamical system stability. ► Modeling turbulence disequilibrium due to interaction with moving solid boundaries. ► Providing computational procedure for large size system solution approximation through model reduction. -- Abstract: This article proposes a review of recent and current developments in the modeling and advanced numerical methods used to simulate large-size systems involving multi-physics in the field of mechanics. It addresses the complex issue of stability analysis of dynamical systems submitted to external turbulent flows and aims to establish accurate stability maps applicable to heat exchanger design. The purpose is to provide dimensionless stability limit modeling that is suitable for a variety of configurations and is as accurate as possible in spite of the large scale of the systems to be considered. The challenge lies in predicting local effects that may impact global systems. A combination of several strategies that are suited concurrently to multi-physics, multi-scale and large-size system computation is therefore required. Based on empirical concepts, the heuristic models currently used in the framework of standard stability analysis suffer from a lack of predictive capabilities. On the other hand, numerical approaches based on fully-coupled fluid–solid dynamics system computation remain expensive due to the multi-physics patterns of physics and the large number of degrees of freedom involved. In this context, since experimentation cannot be achieved and numerical simulation is unavoidable but prohibitive, a hybrid strategy is proposed in order to take advantage of both numerical local solutions and empirical global solutions

A Two-Dimensional Numerical Study of Hydrodynamic, Heat and Mass Transfer and Stability in a Salt Gradient Solar Pond

Directory of Open Access Journals (Sweden)

Ali Ben Moussa

2012-10-01

Full Text Available In this work, the problem of hydrodynamic, heat and mass transfer and stability in a salt gradient solar pond has been numerically studied by means of computational fluid dynamics in transient regime. The body of the simulated pond is an enclosure of height H and length L wherein an artificial salinity gradient is created in order to suppress convective motions induced by solar radiation absorption and to stabilize the solar pond during the period of operation. Here we show the distribution of velocity, temperature and salt concentration fields during energy collection and storage in a solar pond filled with water and constituted by three different salinity zones. The bottom of the pond is blackened and the free-surface is subjected to heat losses by convection, evaporation and radiation while the vertical walls are adiabatic and impermeable. The governing equations of continuity, momentum, thermal energy and mass transfer are discretized by finite–volume method in transient regime. Velocity vector fields show the presence of thin convective cells in the upper convective zone (UCZ and large convective cells in the lower convective zone (LCZ. This study shows the importance of buoyancy ratio in the decrease of temperature in the UCZ and in the preservation of high temperature in the LCZ. It shows also the importance of the thickness of Non-Convective Zone (NCZ in the reduction of the upwards heat losses.

Effects of heat stress and probiotic supplementation on protein functionality and oxidative stability of ground chicken leg meat during display storage

Science.gov (United States)

The objective of this study was to evaluate effects of heat stress and probiotic supplementation on protein functionality and oxidative stability of ground chicken leg meat during display storage. Two hundred and forty 1-day-old male chicks (5 bird per pen) were randomly subjected to four treatments...

Numerical simulation and global linear stability analysis of low-Re flow past a heated circular cylinder

KAUST Repository

Zhang, Wei; Samtaney, Ravi

2016-01-01

We perform two-dimensional unsteady Navier-Stokes simulation and global linear stability analysis of flow past a heated circular cylinder to investigate the effect of aided buoyancy on the stabilization of the flow. The Reynolds number of the incoming flow is fixed at 100, and the Richardson number characterizing the buoyancy is varied from 0.00 (buoyancy-free case) to 0.10 at which the flow is still unsteady. We investigate the effect of aided buoyancy in stabilizing the wake flow, identify the temporal and spatial characteristics of the growth of the perturbation, and quantify the contributions from various terms comprising the perturbed kinetic energy budget. Numerical results reveal that the increasing Ri decreases the fluctuation magnitude of the characteristic quantities monotonically, and the momentum deficit in the wake flow decays rapidly so that the flow velocity recovers to that of the free-stream; the strain on the wake flow is reduced in the region where the perturbation is the most greatly amplified. Global stability analysis shows that the temporal growth rate of the perturbation decreases monotonically with Ri, reflecting the stabilization of the flow due to aided buoyancy. The perturbation grows most significantly in the free shear layer separated from the cylinder. As Ri increases, the location of maximum perturbation growth moves closer to the cylinder and the perturbation decays more rapidly in the far wake. The introduction of the aided buoyancy alters the base flow, and destabilizes the near wake shear layer mainly through the strain-induced transfer term and the pressure term of the perturbed kinetic energy, whereas the flow is stabilized in the far wake as the strain is alleviated. © 2016 Elsevier Ltd. All rights reserved.

Numerical simulation and global linear stability analysis of low-Re flow past a heated circular cylinder

KAUST Repository

Zhang, Wei

2016-03-31

We perform two-dimensional unsteady Navier-Stokes simulation and global linear stability analysis of flow past a heated circular cylinder to investigate the effect of aided buoyancy on the stabilization of the flow. The Reynolds number of the incoming flow is fixed at 100, and the Richardson number characterizing the buoyancy is varied from 0.00 (buoyancy-free case) to 0.10 at which the flow is still unsteady. We investigate the effect of aided buoyancy in stabilizing the wake flow, identify the temporal and spatial characteristics of the growth of the perturbation, and quantify the contributions from various terms comprising the perturbed kinetic energy budget. Numerical results reveal that the increasing Ri decreases the fluctuation magnitude of the characteristic quantities monotonically, and the momentum deficit in the wake flow decays rapidly so that the flow velocity recovers to that of the free-stream; the strain on the wake flow is reduced in the region where the perturbation is the most greatly amplified. Global stability analysis shows that the temporal growth rate of the perturbation decreases monotonically with Ri, reflecting the stabilization of the flow due to aided buoyancy. The perturbation grows most significantly in the free shear layer separated from the cylinder. As Ri increases, the location of maximum perturbation growth moves closer to the cylinder and the perturbation decays more rapidly in the far wake. The introduction of the aided buoyancy alters the base flow, and destabilizes the near wake shear layer mainly through the strain-induced transfer term and the pressure term of the perturbed kinetic energy, whereas the flow is stabilized in the far wake as the strain is alleviated. © 2016 Elsevier Ltd. All rights reserved.

The effect of Sn addition on phase stability and phase evolution during aging heat treatment in Ti–Mo alloys employed as biomaterials

Energy Technology Data Exchange (ETDEWEB)

Mello, Mariana G. de, E-mail: marianagm@fem.unicamp.br; Salvador, Camilo F., E-mail: csalvador@fem.unicamp.br; Cremasco, Alessandra, E-mail: alessandra@fem.unicamp.br; Caram, Rubens, E-mail: caram@fem.unicamp.br

2015-12-15

Increases in life expectancy and improvements in necessary healthcare attach great importance to the development of biomaterials. Ti alloys containing β stabilizing elements are often used as biomaterials due to their high specific strength, high corrosion resistance, unusual biocompatibility and low elastic moduli, which benefit bone tissues close to an implant. This study deals with phase stability in β Ti–Mo–Sn alloys processed under different conditions and was performed according to the following steps: a study of the effect of Sn content (a) on phase stability in Ti–Mo alloys, (b) on the suppression of α″ and ω phase precipitation; (c) on α-phase precipitation during aging heat treatments and (d) on mechanical properties, including the elastic modulus, as measured using tensile tests and acoustic techniques. The alloys were prepared by arc melting under a controlled atmosphere followed by homogenization heat treatment and hot rolling. Optical microscopy, scanning and transmission electron microscopy, X-ray diffraction and differential scanning calorimetry were employed for characterization purposes. Samples were also submitted to solution treatment above the β transus temperature and aging heat treatments under a controlled atmosphere. The results suggest that Sn suppresses the formation of the ω and α″ phases in Ti–Mo system. - Highlights: • Sn addition to Ti alloys decreases elastic modulus by suppressing ω phase precipitation. • Sn addition decreases the temperature of martensite decomposition. • Sn addition decreases the temperature of α phase precipitation and β transus. • Mechanical strength decreases with increasing Sn content.

The effect of Sn addition on phase stability and phase evolution during aging heat treatment in Ti–Mo alloys employed as biomaterials

International Nuclear Information System (INIS)

Mello, Mariana G. de; Salvador, Camilo F.; Cremasco, Alessandra; Caram, Rubens

2015-01-01

Increases in life expectancy and improvements in necessary healthcare attach great importance to the development of biomaterials. Ti alloys containing β stabilizing elements are often used as biomaterials due to their high specific strength, high corrosion resistance, unusual biocompatibility and low elastic moduli, which benefit bone tissues close to an implant. This study deals with phase stability in β Ti–Mo–Sn alloys processed under different conditions and was performed according to the following steps: a study of the effect of Sn content (a) on phase stability in Ti–Mo alloys, (b) on the suppression of α″ and ω phase precipitation; (c) on α-phase precipitation during aging heat treatments and (d) on mechanical properties, including the elastic modulus, as measured using tensile tests and acoustic techniques. The alloys were prepared by arc melting under a controlled atmosphere followed by homogenization heat treatment and hot rolling. Optical microscopy, scanning and transmission electron microscopy, X-ray diffraction and differential scanning calorimetry were employed for characterization purposes. Samples were also submitted to solution treatment above the β transus temperature and aging heat treatments under a controlled atmosphere. The results suggest that Sn suppresses the formation of the ω and α″ phases in Ti–Mo system. - Highlights: • Sn addition to Ti alloys decreases elastic modulus by suppressing ω phase precipitation. • Sn addition decreases the temperature of martensite decomposition. • Sn addition decreases the temperature of α phase precipitation and β transus. • Mechanical strength decreases with increasing Sn content.

Fusion reactivity, confinement, and stability of neutral-beam heated plasmas in TFTR and other tokamaks

International Nuclear Information System (INIS)

Park, Hyeon, K.

1996-05-01

The hypothesis that the heating beam fueling profile shape connects the edge condition and improved core confinement and fusion reactivity is extensively studied on TFTR and applied to other tokamaks. The derived absolute scalings based on beam fueling profile shape for the stored energy and neutron yield can be applied to the deuterium discharges at different major radii in TFTR. These include Supershot, High poloidal beta, L-mode, and discharges with a reversed shear (RS) magnetic configuration. These scalings are also applied to deuterium-tritium discharges. The role of plasma parameters, such as plasma current, Isdo2(p), edge safety factor, qsdo5(a), and toroidal field, Bsdo2(T), in the performance and stability of the discharges is explicitly studied. Based on practical and externally controllable plasma parameters, the limitation and optimization of fusion power production of the present TFTR is investigated and a path for a discharge condition with fusion power gain, Q > 1 is suggested based on this study. Similar physics interpretation is provided for beam heated discharges on other major tokamaks

A QTL on the short arm of wheat (Triticum aestivum L.) chromosome 3B affects the stability of grain weight in plants exposed to a brief heat shock early in grain filling.

Science.gov (United States)

Shirdelmoghanloo, Hamid; Taylor, Julian D; Lohraseb, Iman; Rabie, Huwaida; Brien, Chris; Timmins, Andy; Martin, Peter; Mather, Diane E; Emebiri, Livinus; Collins, Nicholas C

2016-04-22

Molecular markers and knowledge of traits associated with heat tolerance are likely to provide breeders with a more efficient means of selecting wheat varieties able to maintain grain size after heat waves during early grain filling. A population of 144 doubled haploids derived from a cross between the Australian wheat varieties Drysdale and Waagan was mapped using the wheat Illumina iSelect 9,000 feature single nucleotide polymorphism marker array and used to detect quantitative trait loci for heat tolerance of final single grain weight and related traits. Plants were subjected to a 3 d heat treatment (37 °C/27 °C day/night) in a growth chamber at 10 d after anthesis and trait responses calculated by comparison to untreated control plants. A locus for single grain weight stability was detected on the short arm of chromosome 3B in both winter- and autumn-sown experiments, determining up to 2.5 mg difference in heat-induced single grain weight loss. In one of the experiments, a locus with a weaker effect on grain weight stability was detected on chromosome 6B. Among the traits measured, the rate of flag leaf chlorophyll loss over the course of the heat treatment and reduction in shoot weight due to heat were indicators of loci with significant grain weight tolerance effects, with alleles for grain weight stability also conferring stability of chlorophyll ('stay-green') and shoot weight. Chlorophyll loss during the treatment, requiring only two non-destructive readings to be taken, directly before and after a heat event, may prove convenient for identifying heat tolerant germplasm. These results were consistent with grain filling being limited by assimilate supply from the heat-damaged photosynthetic apparatus, or alternatively, accelerated maturation in the grains that was correlated with leaf senescence responses merely due to common genetic control of senescence responses in the two organs. There was no evidence for a role of mobilized stem reserves (water

The Influence of Heat Treatments on the Porosity of Suspension Plasma-Sprayed Yttria-Stabilized Zirconia Coatings

Science.gov (United States)

Ekberg, Johanna; Ganvir, Ashish; Klement, Uta; Creci, Simone; Nordstierna, Lars

2018-02-01

Suspension plasma-sprayed coatings are produced using fine-grained feedstock. This allows to control the porosity and to achieve low thermal conductivity which makes the coatings attractive as topcoats in thermal barrier coatings (TBCs). Used in gas turbine applications, TBCs are exposed to high temperature exhaust gases which lead to microstructure alterations. In order to obtain coatings with optimized thermomechanical properties, microstructure alterations like closing of pores and opening of cracks have to be taken into account. Hence, in this study, TBC topcoats consisting of 4 mol.% yttria-stabilized zirconia were heat-treated in air at 1150 °C and thereafter the coating porosity was investigated using image analysis (IA) and nuclear magnetic resonance (NMR) cryoporometry. Both IA and NMR cryoporometry showed that the porosity changed as a result of the heat treatment for all investigated coatings. In fact, both techniques showed that the fine porosity decreased as a result of the heat treatment, while IA also showed an increase in the coarse porosity. When studying the coatings using scanning electron microscopy, it was noticed that finer pores and cracks disappeared and larger pores grew slightly and achieved a more distinct shape as the material seemed to become more compact.

Dimensionless scalings of confinement, heat transport and pedestal stability in JET-ILW and comparison with JET-C

Czech Academy of Sciences Publication Activity Database

Frassinetti, L.; Saarelma, S.; Lomas, P.; Nunes, I.; Rimini, F.; Beurskens, M.N.A.; Bílková, Petra; Boom, J.E.; De La Luna, E.; Delabie, E.; Drewelow, P.; Flanagan, J.; Garzotti, L.; Giroud, C.; Hawks, N.; Joffrin, E.; Kempenaars, M.; Kim, H.-T.; Kruezi, U.; Loarte, A.; Lomanowski, B.; Lupelli, I.; Meneses, L.; Maggi, C.F.; Menmuir, S.; Peterka, Matěj; Rachlew, E.; Romanelli, M.; Stefanikova, E.

2017-01-01

Roč. 59, č. 1 (2017), č. článku 014014. ISSN 0741-3335. [EPS 2016: Conference on Plasma Physics/43./. Leuven, 04.07.2016-08.07.2016] EU Projects: European Commission(XE) 633053 - EUROfusion Institutional support: RVO:61389021 Keywords : JET-ILW * dimensionless scaling * pedestal * confinement * pedestal stability * heat transport Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.392, year: 2016 http://dx.doi.org/10.1088/0741-3335/59/1/014014

Enhancing Oxidative Stability of Sunflower Oil during Convective and Microwave Heating Using Grape Seed Extract

Directory of Open Access Journals (Sweden)

Mariana-Atena Poiana

2012-07-01

Full Text Available This study was performed to investigate the effectiveness of grape seed extract (GSE compared to butylated hydroxytoluene (BHT on retarding lipid oxidation of sunflower oil subjected to convection and microwave heating up to 240 min under simulated frying conditions. The progress of lipid oxidation was assessed in terms of peroxide value (PV, p-anisidine value (p-AV, conjugated dienes and trienes (CD, CT, inhibition of oil oxidation (IO and TOTOX value. In addition, total phenolic content (TP was evaluated in samples before and after heating in order to assess the changes in these compounds relative to the extent of lipid oxidation. The results of this study highlight that GSE showed a significantly inhibitory effect on lipid oxidation during both treatments, although to a different extent. This ability was dose-dependent; therefore, the extent of lipid oxidation was inversely related to GSE level. Convective heating, respective microwave exposure for 240 min of samples supplemented by GSE to a level of 1000 ppm, resulted in significant decreases of investigated indices relative to the control values as follows: PV (48%; 30%, p-AV (29%; 40%, CD (45%; 30%, CT (41%; 36%, TOTOX (35%; 37%. GSE to a level of 600–800 ppm inhibited the lipid oxidation in a similar manner to BHT. These results suggested that GSE can be used as a potential natural extract for improving oxidative stability of sunflower oil during thermal applications.

Developmental stability, age at onset of foraging and longevity of Africanized honey bees (Apis mellifera L.) under heat stress (Hymenoptera: Apidae).

Science.gov (United States)

Medina, Rubén G; Paxton, Robert J; De Luna, Efraín; Fleites-Ayil, Fernando A; Medina Medina, Luis A; Quezada-Euán, José Javier G

2018-05-01

Beekeeping with the western honey bee (Apis mellifera) is important in tropical regions but scant information is available on the possible consequences of global warming for tropical beekeeping. We evaluated the effect of heat stress on developmental stability, the age at onset of foraging (AOF) and longevity in Africanized honey bees (AHBs) in the Yucatan Peninsula of Mexico, one of the main honey producing areas in the Neotropics, where high temperatures occur in spring and summer. To do so, we reared worker AHB pupae under a fluctuating temperature regime, simulating current tropical heatwaves, with a high temperature peak of 40.0 °C for 1 h daily across six days, and compared them to control pupae reared at stable temperatures of 34.0-35.5 °C. Heat stress did not markedly affect overall body size, though the forewing of heat-stressed bees was slightly shorter than controls. However, bees reared under heat stress showed significantly greater fluctuating asymmetry (FA) in forewing shape. Heat stress also decreased AOF and reduced longevity. Our results show that changes occur in the phenotype and behavior of honey bees under heat stress, with potential consequences for colony fitness. Copyright © 2018 Elsevier Ltd. All rights reserved.

Theoretical investigations on two-phase flow instability in parallel channels under axial non-uniform heating

International Nuclear Information System (INIS)

Lu, Xiaodong; Wu, Yingwei; Zhou, Linglan; Tian, Wenxi; Su, Guanghui; Qiu, Suizheng; Zhang, Hong

2014-01-01

Highlights: • We developed a model based on homogeneous flow model to analyze two-phase flow instability in parallel channels. • The influence of axial non-uniform heating on the system stability has been investigated. • Influences of various factors on system instability under cosine heat flux have been studied. • The system under top-peaked heat flux is the most stable system. - Abstract: Two-phase flow instability in parallel channels heated by axial non-uniform heat flux has been theoretically studied in this paper. The system control equations of parallel channels were established based on the homogeneous flow model in two-phase region. Semi-implicit finite-difference scheme and staggered mesh method were used to discretize the equations, and the difference equations were solved by chasing method. Cosine, bottom-peaked and top-peaked heat fluxes were used to study the influence of non-uniform heating on two-phase flow instability of the parallel channels system. The marginal stability boundaries (MSB) of parallel channels and three-dimensional instability spaces (or instability reefs) under different heat flux conditions have been obtained. Compared with axial uniform heating, axial non-uniform heating will affect the system stability. Cosine and bottom-peaked heat fluxes can destabilize the system stability in high inlet subcooling region, while the opposite effect can be found in low inlet subcooling region. However, top-peaked heat flux can enhance the system stability in the whole region. In addition, for cosine heat flux, increasing the system pressure or inlet resistance coefficient can strengthen the system stability, and increasing the heating power will destabilize the system stability. The influence of inlet subcooling number on the system stability is multi-valued under cosine heat flux

Influence of microwave heating on the stability of processed samn

OpenAIRE

Farag, Radwan S.; Taha, Soad H.

1991-01-01

Butter was converted to samn by microwave and conventional heating. The quality of the processed samn by the two methods was followed by determining the acid, peroxide and TBA values over a period of six weeks at 60°C. The fatty acid composition of samn samples was determined by gas-liquid chromatographic technique. The data show that butter conversion to samn by microwave heating was accomplished in about one half of the time that conventional heating requires. Microwave heating obviously in...

ICRF sawtooth stabilization: Application on TFTR and CIT

International Nuclear Information System (INIS)

Hosea, J.C.; Phillips, C.K.; Stevens, J.E.; Wilson, J.R.; Bell, M.; Boivin, R.; Cavallo, A.; Colestock, P.; Fredrickson, E.; Hammett, G.; Hsuan, H.; Janos, A.; Jassby, D.; Jobes, F.; McGuire, K.; Mueller, D.; Nagayama, Y.; Owens, K.; Park, H.; Schmidt, G.; Stratton, B.; Taylor, G.; Wong, K.L.; Zweben, S.

1991-03-01

The use of ICRF heating to stabilize the core plasma sawtooth relaxations has been extended to TFTR where such stabilization has been produced at relatively low power in the L Mode regime at moderate density (P RF = 4 MW, 2.6 MW in helium and deuterium discharges, respectively, for the minority hydrogen ICRF heating regime with bar n e ∼2.5 x 10 13 cm -3 ). These results, as in the case of those obtained on JET, are qualitatively consistent with energetic ion stabilization of the m = 1, n = 1 ideal/resistive kink mode. The relevance of sawtooth stabilization to the primary regimes of interest on TFTR -- the high-Q supershot regime and the high density pellet injection regimes -- and on CIT -- the high density ICRF heated regime -- is considered in the context of the present theory and the projected ICRF power deposition characteristics. 35 refs., 11 figs

Microstructural stability of spark-plasma-sintered Wf/W composite with zirconia interface coating under high-heat-flux hydrogen beam irradiation

Directory of Open Access Journals (Sweden)

M. Avello de Lama

2017-12-01

In this paper, the durability and chemical stability of Wf/W composite specimens under cyclic heat-flux loads up to 20 MW/m² (surface temperature: 1260 °C was investigated using hydrogen neutral beam. The bulk material was fabricated by means of spark-plasma-sintering (SPS method using fine tungsten powder and a stack of tungsten wire meshes as reinforcement where the surface of the wire was coated with zirconia thin film to produce an engineered interface. The impact of plasma beam irradiation on microstructure was examined for two kinds of specimens produced at different sintering temperatures, 1400 °C and 1700 °C. Results of microscopic (SEM and chemical (EDX analysis are presented comparing the microstructure and element distribution maps obtained before and after heat flux loading. Effects of different sintering temperatures on damage behaviour are discussed. The present composite materials are shown to be applicable as plasma-facing material for high-heat-flux components.

Experimental study of nucleate pool boiling heat transfer of water on silicon oxide nanoparticle coated copper heating surface

International Nuclear Information System (INIS)

Das, Sudev; Kumar, D.S.; Bhaumik, Swapan

2016-01-01

Highlights: • EBPVD approach was employed for fabrication of well-ordered nanoparticle coated micro/nanostructure on metal surface. • Nucleate boiling heat transfer performance on nanoparticle coated micro/nanostructure surface was experimentally studied. • Stability of nanoparticle coated surface under boiling environment was systematically studied. • 58% enhancement of boiling heat transfer coefficient was found. • Present experimental results are validated with well known boiling correlations. - Abstract: Electron beam physical vapor deposition (EBPVD) coating approach was employed for fabrication of well-ordered of nanoparticle coated micronanostructures on metal surfaces. This paper reports the experimental study of augmentation of pool boiling heat transfer performance and stabilities of silicon oxide nanoparticle coated surfaces with water at atmospheric pressure. The surfaces were characterized with respect to dynamic contact angle, surface roughness, topography, and morphology. The results were found that there is a reduction of about 36% in the incipience superheat and 58% enhancement in heat transfer coefficient for silicon oxide coated surface over the untreated surface. This enhancement might be the reason of enhanced wettability, enhanced surface roughness and increased number of a small artificial cavity on a heating surface. The performance and stability of nanoparticle coated micro/nanostructure surfaces were examined and found that after three runs of experiment the heat transfer coefficient with heat flux almost remain constant.

STUDY OF THERMAL AND ACID STABILITY OF BENTONITE CLAY

Directory of Open Access Journals (Sweden)

Karna Wijaya

2010-06-01

Full Text Available The thermal and acid stability of the bentonite clays (Na- and Ca-bentonite have been tested. The thermal stability testing has been carried out by heating 5 gram of the clays  for five hours at 200, 300 and 500 °C respectively, meanwhile acid stability testing was performed by immersing 5 gram clays into 100 mL sulphuric acid 1M, 2M and 3M for 24 hours. The tested clays, then were characterized by means of X-Ray difractometry and IR-spectroscopy methods. The characterization results showed that upon heating, both Ca- and Na-bentonites indicated same thermal stability. However, upon acid treatment, Na-bentonite was found relatively stabiler and more resistance then Ca-bentonite.   Keywords: bentonite, clay, thermal stability, acid stability.

Quality of Irrigation Water Affects Soil Functionality and Bacterial Community Stability in Response to Heat Disturbance.

Science.gov (United States)

Frenk, Sammy; Hadar, Yitzhak; Minz, Dror

2018-02-15

Anthropogenic activities alter the structure and function of a bacterial community. Furthermore, bacterial communities structured by the conditions the anthropogenic activities present may consequently reduce their stability in response to an unpredicted acute disturbance. The present mesocosm-scale study exposed soil bacterial communities to different irrigation water types, including freshwater, fertilized freshwater, treated wastewater, and artificial wastewater, and evaluated their response to a disturbance caused by heat. These effectors may be considered deterministic and stochastic forces common in agricultural operations of arid and semiarid regions. Bacterial communities under conditions of high mineral and organic carbon availability (artificial wastewater) differed from the native bacterial community and showed a proteobacterial dominance. These bacterial communities had a lower resistance to the heat treatment disturbance than soils under conditions of low resource availability (high-quality treated wastewater or freshwater). The latter soil bacterial communities showed a higher abundance of operational taxonomic units (OTUs) classified as Bacilli These results were elucidated by soil under conditions of high resource availability, which lost higher degrees of functional potential and had a greater bacterial community composition change. However, the functional resilience, after the disturbance ended, was higher under a condition of high resource availability despite the bacterial community composition shift and the decrease in species richness. The functional resilience was directly connected to the high growth rates of certain Bacteroidetes and proteobacterial groups. A high stability was found in samples that supported the coexistence of both resistant OTUs and fast-growing OTUs. IMPORTANCE This report presents the results of a study employing a hypothesis-based experimental approach to reveal the forces involved in determining the stability of a

Stability analysis for single-phase liquid metal rectangular natural circulation loops

International Nuclear Information System (INIS)

Lu, Daogang; Zhang, Xun; Guo, Chao

2014-01-01

Highlights: • The stability for asymmetric liquid metal natural circulation loops is analyzed. • The Na and NaK loops have higher critical Reynolds number than Pb and LBE loops. • Decreasing the ratio of height to width of loop can increase loop stability. • The length of heater would not affect the loop stability obviously. • Adding the length or heat transfer coefficient of cooler can increase loop stability. - Abstract: Natural circulation systems are preferred in some advanced nuclear power plants as they can simplify the designs and improve the inherent safety. The stability and steady-state characteristics of natural circulation are important for the applications of natural circulation loops (NCLs). A linear stability analysis method was used to study the stability behavior of liquid metal NCLs. The influences of the types of working fluids and loop geometry parameters on the stability of NCLs were evaluated. The liquid sodium (Na) loop and sodium–potassium alloy (NaK) loop would be more stable than lead bismuth eutectics (LBE) loop. The pressure drop could stabilize the loop behavior and also lead an increase of operating temperature for the loop. The NCL with a lower aspect ratio (ratio of vertical center distance between the heating and cooling section to the horizontal length of loop) is supposed to be more stable. It was found that the length of heating section would not have an obvious effect on the stability of NCL. However, the loop behavior could be stabilized by adding the length or heat transfer coefficient of the cooling section

Evaluation of antioxidants stability by thermal analysis and its protective effect in heated edible vegetable oil

Directory of Open Access Journals (Sweden)

Seme Youssef Reda

2011-06-01

Full Text Available In this work, through the use of thermal analysis techniques, the thermal stabilities of some antioxidants were investigated, in order to evaluate their resistance to thermal oxidation in oils, by heating canola vegetable oil, and to suggest that antioxidants would be more appropriate to increase the resistance of vegetable oils in the thermal degradation process in frying. The techniques used were: Thermal Gravimetric (TG and Differential Scanning Calorimetry (DSC analyses, as well as an allusion to a possible protective action of the vegetable oils, based on the thermal oxidation of canola vegetable oil in the laboratory under constant heating at 180 ºC/8 hours for 10 days. The studied antioxidants were: ascorbic acid, sorbic acid, citric acid, sodium erythorbate, BHT (3,5-di-tert-butyl-4-hydroxytoluene, BHA (2, 3-tert-butyl-4-methoxyphenol, TBHQ (tertiary butyl hydroquinone, PG (propyl gallate - described as antioxidants by ANVISA and the FDA; and also the phytic acid antioxidant and the SAIB (sucrose acetate isobutyrate additive, which is used in the food industry, in order to test its behavior as an antioxidant in vegetable oil. The following antioxidants: citric acid, sodium erythorbate, BHA, BHT, TBHQ and sorbic acid decompose at temperatures below 180 ºC, and therefore, have little protective action in vegetable oils undergoing frying processes. The antioxidants below: phytic acid, ascorbic acid and PG, are the most resistant and begin their decomposition processes at temperatures between 180 and 200 ºC. The thermal analytical techniques have also shown that the SAIB antioxidant is the most resistant to oxidative action, and it can be a useful choice in the thermal decomposition prevention of edible oils, improving stability regarding oxidative processes.

Two-phase flow stability structure in a natural circulation system

Energy Technology Data Exchange (ETDEWEB)

Zhou, Zhiwei [Nuclear Engineering Laboratory Zurich (Switzerland)

1995-09-01

The present study reports a numerical analysis of two-phase flow stability structures in a natural circulation system with two parallel, heated channels. The numerical model is derived, based on the Galerkin moving nodal method. This analysis is related to some design options applicable to integral heating reactors with a slightly-boiling operation mode, and is also of general interest to similar facilities. The options include: (1) Symmetric heating and throttling; (2) Asymmetric heating and symmetric throttling; (3) Asymmetric heating and throttling. The oscillation modes for these variants are discussed. Comparisons with the data from the INET two-phase flow stability experiment have qualitatively validated the present analysis.

Influence of heat sterilization on the organoleptic quality of spices

NARCIS (Netherlands)

Maarse, H.; Nijssen, L.M.; Nowak, M.

1982-01-01

Heat sterilization and storage of food products containing spices often results in a change of their organoleptic quality. Our knowledge about the stability of individual spices, however, is low. Therefore the heat stability of 8 different spices most frequently used has been investigated: cinnamon,

Effects of heat and ultraviolet radiation on the oxidative stability of pine nut oil supplemented with carnosic acid.

Science.gov (United States)

Wang, Han; Zu, Ge; Yang, Lei; Zu, Yuan-gang; Wang, Hua; Zhang, Zhong-hua; Zhang, Ying; Zhang, Lin; Wang, Hong-zheng

2011-12-28

The effects of carnosic acid (CA) of different concentrations (0.05, 0.1, and 0.2 mg/g) and two common antioxidants (butylated hydroxytoluene and α-tocopherol) on oxidative stability in pine nut oil at different accelerated conditions (heating and ultraviolet radiation) were compared. The investigation focused on the increase in peroxide and conjugated diene values, as well as free fatty acid and thiobarbituric acid-reactive substances. The changes in trans fatty acid and aldehyde compound contents were investigated by Fourier transform infrared spectroscopy, while the changes in pinolenic acid content were monitored by gas chromatography-mass spectrometry. The results show that CA was more effective in restraining pine nut oil oxidation under heating, UV-A and UV-B radiation, in which a dose-response relationship was observed. The antioxidant activity of CA was stronger than that of α-tocopherol and butylated hydroxytoluene. Pine nut oil supplemented with 0.2 mg/g CA exhibited favorable antioxidant effects and is preferable for effectively avoiding oxidation.

Nonlinear throughflow and internal heating effects on vibrating porous medium

Directory of Open Access Journals (Sweden)

Palle Kiran

2016-06-01

Full Text Available The effect of vertical throughflow and internal heating effects on fluid saturated porous medium under gravity modulation is investigated. The amplitude of modulation is considered to be very small and the disturbances are expanded in terms of power series of amplitude of convection. A weakly nonlinear stability analysis is proposed to study stationary convection. The Nusselt number is obtained numerically to present the results of heat transfer while using Ginzburg–Landau equation. The vertical throughflow has dual effect either to destabilize or to stabilize the system for downward or upward directions. The effect of internal heat source (Ri>0 enhances or sink (Ri<0 diminishes heat transfer in the system. The amplitude and frequency of modulation have the effects of increasing or diminishing heat transport. For linear model Venezian approach suggested that throughflow and internal heating have both destabilizing and stabilizing effects for suitable ranges of Ω. Further, the study establishes that heat transport can be controlled effectively by a mechanism that is external to the system throughflow and gravity modulation.

ICRF stabilization of sawteeth on TFTR

International Nuclear Information System (INIS)

Phillips, C.K.; Hosea, J.; Stevens, J.; Wilson, J.R.; Bell, M.; Bitter, M.; Cheng, C.Z.; Darrow, D.; Fredrickson, E.; Hammett, G.W.; Hill, K.; Hsuan, H.; Jassby, D.; McCune, D.; McGuire, K.; Owens, D.K.; Park, H.; Ramsey, A.; Schilling, G.; Schivell, J.; Stratton, B.; Synakowski, E.; Taylor, G.; Towner, H.; White, R.; Zweben, S.; Phillips, M.W.; Hughes, M.; Bush, C.; Goldfinger, R.; Hoffman, D.; Houlberg, W.; Nagayama, Y.; Smithe, D.N.

1992-01-01

Results obtained from experiments utilizing high power ICRF (ion cyclotron range of frequency) heating to stabilize sawtooth oscillations on TFTR are reviewed. The key observations include existence of a minimum ICRF power required to achieve stabilization, a dependence of the stabilization threshold on the relative size of the ICRF power deposition profile to the q=1 volume, and a peaking of the equilibrium pressure and current profiles during sawtooth-free phases of the discharges. In addition, preliminary measurements of the poloidal magnetic field profile indicate that q on axis decreases to a value of 0.55±0.15 after a sawtooth-stabilized period of ∼0.5 sec has transpired. The results are discussed in the context of theory, which suggests that the fast ions produced by the ICRF heating suppress sawteeth by stabilizing the m=1 MHD instabilities believed to be the trigger for the sawtooth oscillations. Though qualitative agreement is found between the observations and the theory, further refinement of the theory coupled with more accurate measurements of experimental profiles will be required in order to complete quantitative comparisons

Kinetically controlled fabrication of gold nanorods and investigation of their thermal stability via in-situ TEM heating

Science.gov (United States)

Chankhunthod, N.; Aslam, Z.; Critchley, K.; Evans, S. D.; Brydson, R.

2017-09-01

Size controlled CTAB-capped AuNRs with various aspect ratios (ARs) ranging from 1.63±0.13 to 4.12±0.25 were synthesized following a modified seed-mediated method. Their thermal stability was examined by in-situ TEM heating. The results revealed a structural change from rods to spheres with increasing temperature. At lower temperatures 600ºC, particles became increasingly spherical. This behaviour occurred at temperatures lower than the melting point of bulk gold supporting a surface diffusion mechanism with material diffusing from the tips and redepositing at the middle of the rods. The rate of change in AR appeared to increase for thinner AuNRs.

Ring power balance observing plasma stability constraints

International Nuclear Information System (INIS)

Campbell, R.B.; Logan, B.G.

1982-01-01

Ring power balance is performed for an E-ring stabilized tandem mirror reactor, taking into account constraints imposed by plasma stability. The two most important criteria are the stability of the core interchange and hot electron interchange modes. The former determines the ring thickness, the latter determines the minimum hot electron temperature; both quantities are important for power balance. The combination of the hot electron interchange constraint and the fact that the barrier density is low places the operating point on the synchrotron dominated branch of power balance. The reference case considered here requires a reasonable 34 MW of heating power deposited in the rings. We also have examined the sensitivity of the required ring power on uncertainties in the numerical coefficients of the stability constraints. We have found that the heating power is strongly affected

Comminution by hydriding-dehydriding process of the U-Zr-Nb alloys stabilized at different phases by aging heat treatment

International Nuclear Information System (INIS)

Cantagalli, Natalia Mattar; Pais, Rafael Witter Dias; Braga, Daniel Martins; Santos, Ana Maria Matildes dos; Ferraz, Wilmar Barbosa

2011-01-01

Powders of the U-Zr-Nb alloys are raw materials for obtaining plate-type dispersion fuel of high density and medium enrichment for research and test reactors as well as small power reactors. U-2.5Zr-7.5Nb and U-3Zr-9Nb (wt%) alloys, initially homogenized at high temperatures, were transformed at different phases by means aging heat treatments, and then comminuted by hydriding-dehydriding process to powder production. The phases transformations were obtained by the homogenization of the U-2.5Zr-7.5Nb and U-3Zr-9Nb alloys at high temperatures (1000 deg C for 1 and 16 h), followed by aging heat treatment at 600 deg C, in times of 0.5 h, 3.0 h and 24h, and subsequently quenched in water to stabilize the desired phase. The comminution process was performed at 200 deg C for different times ranging from 20 minutes to 4 hours. The powders were then characterized by scanning electron microscopy, X-ray diffraction and determination of particle size distribution by means of laser equipment CILAS. One of the main objectives of this study was to verify the influence of the different phases in the characteristics of the obtained powders. It was found that alloys stabilized in gamma phase produced powders with smaller particles sizes than those with cellular structure of the α and γ phases. Regardless of retained phases, the produced powders consist of agglomerates with irregular morphology. (author)

Comminution by hydriding-dehydriding process of the U-Zr-Nb alloys stabilized at different phases by aging heat treatment

Energy Technology Data Exchange (ETDEWEB)

Cantagalli, Natalia Mattar; Pais, Rafael Witter Dias; Braga, Daniel Martins; Santos, Ana Maria Matildes dos; Ferraz, Wilmar Barbosa, E-mail: ferrazw@cdtn.b [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG) Belo Horizonte, MG (Brazil)

2011-07-01

Powders of the U-Zr-Nb alloys are raw materials for obtaining plate-type dispersion fuel of high density and medium enrichment for research and test reactors as well as small power reactors. U-2.5Zr-7.5Nb and U-3Zr-9Nb (wt%) alloys, initially homogenized at high temperatures, were transformed at different phases by means aging heat treatments, and then comminuted by hydriding-dehydriding process to powder production. The phases transformations were obtained by the homogenization of the U-2.5Zr-7.5Nb and U-3Zr-9Nb alloys at high temperatures (1000 deg C for 1 and 16 h), followed by aging heat treatment at 600 deg C, in times of 0.5 h, 3.0 h and 24h, and subsequently quenched in water to stabilize the desired phase. The comminution process was performed at 200 deg C for different times ranging from 20 minutes to 4 hours. The powders were then characterized by scanning electron microscopy, X-ray diffraction and determination of particle size distribution by means of laser equipment CILAS. One of the main objectives of this study was to verify the influence of the different phases in the characteristics of the obtained powders. It was found that alloys stabilized in gamma phase produced powders with smaller particles sizes than those with cellular structure of the {alpha} and {gamma} phases. Regardless of retained phases, the produced powders consist of agglomerates with irregular morphology. (author)

Stability of matter

International Nuclear Information System (INIS)

Thirring, W.

1985-01-01

Basing on quantum mechanics and the simple Hamiltonian consisting of kinetic energy and Coulomb potential, heuristic arguments and estimates are used to guess the essential stability properties of many-particle systems. In view of applications in astrophysics, gravitation as a second potential and thermodynamic arguments are added. The guesses thus obtained are confronted with known exact results. The connection between the stabilities against explosion and against implosion, and thermodynamic stability is considered. In systems with a particle number larger than approx= 10 54 (corresponding to the Jupiter mass) gravitational energy prevails over the electrostatic energy and determines the history of a star. Negative specific heat accompanies life and death of a star. Finally the role of stability and instability in the universe for life is outlined. (G.Q.)

Remarks on the thermal stability of an Ohmic-heated nanowire

Science.gov (United States)

Timsit, Roland S.

2018-05-01

The rise in temperature of a wire made from specific materials, due to ohmic heating by a DC electrical current, may lead to uncontrollable thermal runaway with ensuing melting. Thermal runaway stems from a steep decrease with increasing temperature of the thermal conductivity of the conducting material and subsequent trapping of the ohmic heat in the wire, i.e., from the inability of the wire to dissipate the heat sufficiently quickly by conduction to the cooler ends of the wire. In this paper, we show that the theory used to evaluate the temperature of contacting surfaces in a bulk electrical contact may be applied to calculate the conditions for thermal runaway in a nanowire. Implications of this effect for electrical contacts are addressed. A possible implication for memory devices using ohmic-heated nanofilms or nanowires is also discussed.

Linear stability of a fuel channel uniformly heated considering retrofeeding by vacuum. Theoretical study; Estabilidad lineal de un canal combustible uniformemente calentado considerando retroalimentacion por vacios

Energy Technology Data Exchange (ETDEWEB)

Gonzalez M, V. [Comision Nacional de Seguridad Nuclear y Salvaguardias, 03000 Mexico D.F. (Mexico); Salinas H, J.G.; Espinosa P, G. [Universidad Autonoma Metropolitana-Iztapalapa, 09000 Mexico D.F. (Mexico)

2000-07-01

The Technology, Regulation and Services Management of the National Commission of Nuclear Safety and Safeguards in coordinated form with the IPH Department of the Metropolitan Autonomous-Iztapalapa University, developed the present project to study the linear stability in a fuel channel uniformly heated with effects of retrofeeding by vacuums. In this study the methodology used in the analysis of linear stability of the nuclear reactor unit 1 at Laguna Verde power plant is described which represented by an average channel uniformly heated. The conceptual model consists of two cells which represent the two regions in which is divided the channel according to the cooling is in one and two phases, considering the boiling length dependent in the time. It is used the homogeneous flux models for describing the thermohydraulic behavior of the cooling in the two phases region. The neutron processes with the punctual model of the neutron kinetics with a group of retarded neutrons precursors are described. It is studied the behavior of the system in the frequency domain with the transfer functions obtained and it is characterized in four operation states corresponding to the four corners of the low stability zone in the map power-flow Laguna Verde power plant. For these operation states the characteristic frequency is determined and the corresponding Nyquist diagrams are obtained. The results show that the system stability depends on the power-flow relation and that the operations which implicate a reduction of this relation improve the stability of the system (reducing the power introducing control bars with constant cooling flow or increase cooling flow with bars pattern established). The obtained results with effects of retrofeeding by vacuums show that the value of the characteristic frequency is modified very little with respect to the model without retrofeeding, therefore the thermohydraulic processes seem to determine the response of the stability of the system

Confinement and stability in JET: recent results

International Nuclear Information System (INIS)

Campbell, D.J.

1990-01-01

The versatility of the JET device allows a wide range of tokamak operating regimes to be explored and plasmas bounded both by material limiters and by a magnetic separatrix have been investigated extensively. This has permitted the confinement and mhd stability properties of plasmas heated to temperatures above 10keV by neutral beam injection or ion cyclotron resonance heating to be studied in detail. The results of recent analyses of transport and confinement in the L- and H-mode regimes in JET are discussed and the properties of H-mode plasmas produced by both major forms of heating are compared. Several aspects of the mhd stability of such plasmas, particularly at high toroidal beta, β θ , and at the density limit, are reviewed. (author)

Heat flow and heat generation in greenstone belts

Science.gov (United States)

Drury, M. J.

1986-01-01

Heat flow has been measured in Precambrian shields in both greenstone belts and crystalline terrains. Values are generally low, reflecting the great age and tectonic stability of the shields; they range typically between 30 and 50 mW/sq m, although extreme values of 18 and 79 mW/sq m have been reported. For large areas of the Earth's surface that are assumed to have been subjected to a common thermotectonic event, plots of heat flow against heat generation appear to be linear, although there may be considerable scatter in the data. The relationship is expressed as: Q = Q sub o + D A sub o in which Q is the observed heat flow, A sub o is the measured heat generation at the surface, Q sub o is the reduced heat flow from the lower crust and mantle, and D, which has the dimension of length, represents a scale depth for the distribution of radiogenic elements. Most authors have not used data from greenstone belts in attempting to define the relationship within shields, considering them unrepresentative and preferring to use data from relatively homogeneous crystalline rocks. A discussion follows.

Stability analysis of high temperature superconducting coil in liquid hydrogen

International Nuclear Information System (INIS)

Nakayama, T.; Yagai, T.; Tsuda, M.; Hamajima, T.

2007-01-01

Recently, it is expected that hydrogen plays an important role in energy source including electric power in near future. Liquid hydrogen has high potential for cooling down superconducting coil wound with high temperature superconductors (HTS), such as BSCCO, YBCO. In this paper, we study stabilities of the coils wound with BSCCO tapes, which are immersed in the liquid hydrogen, and compare stability results with those cooled by liquid helium. We treat a minimum propagation zone (MPZ) theory to evaluate the coil stability considering boiling heat flux of the liquid hydrogen, and specific heat, heat conduction and resistivity of HTS materials as a function of temperature. It is found that the coil cooled by the liquid hydrogen has higher stability margin than that cooled by the liquid helium. We compare the stability margins of both coils wound with Bi-2223/Ag tape and Bi-2212/Ag tape in liquid hydrogen. As a result, it is found that the stability of Bi-2212 coil is equivalent to that of Bi-2223 coil in low and high magnetic field, while the maximum current of Bi-2212 coil exceeds a little bit that of Bi-2223 coil in both magnetic fields

Stability of Ignition Transients

OpenAIRE

V.E. Zarko

1991-01-01

The problem of ignition stability arises in the case of the action of intense external heat stimuli when, resulting from the cut-off of solid substance heating, momentary ignition is followed by extinction. Physical pattern of solid propellant ignition is considered and ignition criteria available in the literature are discussed. It is shown that the above mentioned problem amounts to transient burning at a given arbitrary temperature distribution in the condensed phase. A brief survey...

Effect of heat treatment and packaging systems on the stability of fish sausage

Directory of Open Access Journals (Sweden)

Bruna Rafaela Dallabona

2013-12-01

Full Text Available The purpose of this study was to evaluate the physicochemical and microbiological stability of sausages produced from mechanically separated fish meat (MSM obtained from Nile tilapia filleting residues. Different heat treatments (pasteurization or smoking and packaging systems (conventional or vacuum were used. The sausages were characterized for chemical composition, weight loss, water activity, instrumental texture and sensorial analysis. Additionally, microbiological analysis, instrumental color, pH, thiobarbituric acid reactive substances (TBARS and total volatile base nitrogen (TVB-N were assessed during storage. No presence of Escherichia coli, Salmonella sp. or coagulase-positive Staphylococcus was detected; however, the psychrotrophic count in pasteurized sausages exceeded the limits allowed for consumption. pH and lipid oxidation speed (TBARS values were reduced when vacuum packaging was used. Volatile nitrogenous bases remained virtually constant during the storage period, and higher values were observed in smoked products. Pasteurized sausages remain stable for 10 and 15 days in conventional and vacuum packages, respectively, and smoked sausages remain stable for 25 and 45 days in conventional and vacuum packages, respectively.

Response of eddy activities to localized diabatic heating in Held-Suarez simulations

Science.gov (United States)

Lin, Yanluan; Zhang, Jishi; Li, Xingrui; Deng, Yi

2018-01-01

Widespread air pollutions, such as black carbon over East Asia in recent years, could induce a localized diabatic heating, and thus lead to localized static stability and meridional temperature gradient (MTG) changes. Although effect of static stability and MTG on eddies has been addressed by the linear baroclinic instability theory, impacts of a localized heating on mid-latitude eddy activities have not been well explored and quantified. Via a series of idealized global Held-Suarez simulations with different magnitudes of localized heating at different altitudes and latitudes, responses of mid-latitude eddy activity and circulation to these temperature perturbations are systematically investigated. Climatologically, the localized heating in the lower atmosphere induces a wave-like response of eddy activity near the mid-latitude jet stream. Over the heating region, eddy activity tends to be weakening due to the increased static stability. However, there are cyclonic anomalies over the upstream and downstream of the heating region. The zonal mean eddy activity weakens along the baroclinic zone due to reduced MTG and increased static stability. Furthermore, the response of eddy activity increased as the heating magnitude is increased and moved to higher altitudes. The influence of the heating decreases as the heating is prescribed further away from the climatological mid-latitude jet. This implies that the localized heating is most effective over the region with the maximum baroclinicity. Besides, enhanced storm track downstream of the localized heating area found here suggests that increased aerosols over East Asia might strengthen the North Pacific storm track.

Eddy Heat Conduction and Nonlinear Stability of a Darcy Lapwood System Analysed by the Finite Spectral Method

Directory of Open Access Journals (Sweden)

Jónas Elíasson

2014-01-01

Full Text Available A finite Fourier transform is used to perform both linear and nonlinear stability analyses of a Darcy-Lapwood system of convective rolls. The method shows how many modes are unstable, the wave number instability band within each mode, the maximum growth rate (most critical wave numbers on each mode, and the nonlinear growth rates for each amplitude as a function of the porous Rayleigh number. Single amplitude controls the nonlinear growth rates and thereby the physical flow rate and fluid velocity, on each mode. They are called the flak amplitudes. A discrete Fourier transform is used for numerical simulations and here frequency combinations appear that the traditional cut-off infinite transforms do not have. The discrete show a stationary solution in the weak instability phase, but when carried past 2 unstable modes they show fluctuating motion where all amplitudes except the flak may be zero on the average. This leads to a flak amplitude scaling process of the heat conduction, producing an eddy heat conduction coefficient where a Nu-RaL relationship is found. It fits better to experiments than previously found solutions but is lower than experiments.

Heat activation and stability of amylases from Bacillus species | Ajayi ...

African Journals Online (AJOL)

Leitch and Collier sporulating Bacillus medium was used to isolate some strains of Bacillus species from soil, wastewater and food sources in Ibadan, Oyo State, Nigeria, by heat activation method. Heat treatment at 80oC allowed the growth of sporulating Bacillus species, in the culture sample source without other bacteria ...

Mobility of partially molten crust, heat and mass transfer, and the stabilization of continents

Science.gov (United States)

Teyssier, Christian; Whitney, Donna L.; Rey, Patrice F.

2017-04-01

The core of orogens typically consists of migmatite terrains and associated crustal-derived granite bodies (typically leucogranite) that represent former partially molten crust. Metamorphic investigations indicate that migmatites crystallize at low pressure (cordierite stability) but also contain inclusions of refractory material (mafic, aluminous) that preserve evidence of crystallization at high pressure (HP), including HP granulite and eclogite (1.0-1.5 GPa), and in some cases ultrahigh pressure (2.5-3.0 GPa) when the continental crust was subducted (i.e. Norwegian Caledonides). These observations indicate that the partially molten crust originates in the deep crust or at mantle depths, traverses the entire orogenic crust, and crystallizes at shallow depth, in some cases at the near-surface ( 2 km depth) based on low-T thermochronology. Metamorphic assemblages generally show that this nearly isothermal decompression is rapid based on disequilibrium textures (symplectites). Therefore, the mobility of partially molten crust results in one of the most significant heat and mass transfer mechanisms in orogens. Field relations also indicate that emplacement of partially molten crust is the youngest major event in orogeny, and tectonic activity essentially ceases after the partially molten crust is exhumed. This suggests that flow and emplacement of partially molten crust stabilize the orogenic crust and signal the end of orogeny. Numerical modeling (open source software Underworld; Moresi et al., 2007, PEPI 163) provides useful insight into the mechanisms of exhumation of partially molten crust. For example, extension of thickened crust with T-dependent viscosity shows that extension of the shallow crust initially drives the mobility of the lowest viscosity crust (T>700°C), which begins to flow in a channel toward the zone of extension. This convergent flow generates channel collision and the formation of a double-dome of foliation (two subdomes separated by a steep

Thermomechanical stability of underground installations: significance of the thermophysical properties of rocks

International Nuclear Information System (INIS)

Mirkovich, V.

1981-01-01

When heat is generated in an underground installation, there are several interdependent factors-such as the rate of heat dissipation, changes in this rate with temperature, or the effects of thermal gradients and thermal expansivities-which influence the stability of the rock mass. To evaluate the thermomechanical stability of a proposed site for an underground nuclear power station, rock specimens from a 300 m deep drill core were obtained, and their thermal diffusivity and linear thermal expansion were measured between 25 0 C and 500 0 C. The thermal conductivity was also measured, in the temperature range 100-500 0 C. Under normal operating conditions, heat transfer to the surface of the rock mass surrounding the power installation would be low. However, in some contingencies, this heat load could become large. The results are discussed from the point of view of the stability of a rock enclosure at higher heat fluxes; they indicate that the rocks studied would, in general, not be suitable as an unprotected wall for containment of such a heat source. (author)

The magnetic fluid for heat transfer applications

International Nuclear Information System (INIS)

Nakatsuka, K.; Jeyadevan, B.; Neveu, S.; Koganezawa, H.

2002-01-01

Real-time visual observation of boiling water-based and ionic magnetic fluids (MFs) and heat transfer characteristics in heat pipe using ionic MF stabilized by citrate ions (JC-1) as working liquid are reported. Irrespective of the presence or absence of magnetic field water-based MF degraded during boiling. However, the degradation of JC-1 was avoided by heating the fluid in magnetic field. Furthermore, the heat transfer capacity of JC-1 heat pipe under applied magnetic field was enhanced over the no field case

Study on minimum heat-flux point during boiling heat transfer on horizontal plates

International Nuclear Information System (INIS)

Nishio, Shigefumi

1985-01-01

The characteristics of boiling heat transfer are usually shown by the boiling curve of N-shape having the maximum and minimum points. As for the limiting heat flux point, that is, the maximum point, there have been many reports so far, as it is related to the physical burn of heat flux-controlling type heating surfaces. But though the minimum heat flux point is related to the quench point as the problems in steel heat treatment, the core safety of LWRs, the operational stability of superconducting magnets, the start-up characteristics of low temperature machinery, the condition of vapor explosion occurrence and so on, the systematic information has been limited. In this study, the effects of transient property and the heat conductivity of heating surfaces on the minimum heat flux condition in the pool boiling on horizontal planes were experimentally examined by using liquid nitrogen. The experimental apparatuses for steady boiling, for unsteady boiling with a copper heating surface, and for unsteady boiling with a heating surface other than copper were employed. The boiling curves obtained with these apparatuses and the minimum heat flux point condition are discussed. (Kako, I.)

Nanodiamond stability with friction and heat

International Nuclear Information System (INIS)

Butterworth, J; Briston, K; Claeyssens, F; Inkson, B J

2015-01-01

The structural stability of nanodiamonds (ND) has been investigated as a function of abrasion/friction and thermal annealing. Nanodiamonds examined before and after abrasion by transmission electron microscopy (TEM) are found to have modified surface characteristics. Frictional rubbing generates smaller, non-spherical particles with rougher, cleaner surfaces, and debris consisting of compacted ND+amorphous carbons. Annealing of ND and abraded ND at 1000°C demonstrates that abrasive pre-treatment increases proportion of transformation to onion-like-carbon (OLC) structures with generation of 3-30nm diameter OLC. The OLC achieved are of similar dimensions to those grown from ND annealed with a Ni catalyst but with more defective microstructures. (paper)

LOOP-3, Hydraulic Stability in Heated Parallel Channels

Energy Technology Data Exchange (ETDEWEB)

Davies, A L [AEEW, Dorset (United Kingdom)

1968-02-01

1 - Nature of physical problem solved: Hydraulic stability in parallel channels. 2 - Method of solution: Calculation of transfer functions developed in reference (10 below). 3 - Restrictions on the complexity of the problem: Only due to assumptions in analysis (see ref.)

Heat exchanger, head and shell acceptance criteria

International Nuclear Information System (INIS)

Lam, P.S.; Sindelar, R.L.

1992-09-01

Instability of postulated flaws in the head component of the heat exchanger could not produce a large break, equivalent to a DEGB in the PWS piping, due to the configuration of the head and restraint provided by the staybolts. Rather, leakage from throughwall flaws in the head would increase with flaw length with finite leakage areas that are bounded by a post-instability flaw configuration. Postulated flaws at instability in the shell of the heat exchanger or in the cooling water nozzles could produce a large break in the Cooling Water System (CWS) pressure boundary. An initial analysis of flaw stability for postulated flaws in the heat exchanger head was performed in January 1992. This present report updates that analysis and, additionally, provides acceptable flaw configurations to maintain defined structural or safety margins against flaw instability of the external pressure boundary components of the heat exchanger, namely the head, shell, and cooling water nozzles. Structural and flaw stability analyses of the heat exchanger tubes, the internal pressure boundary of the heat exchangers or interface boundary between the PWS and CWS, were previously completed in February 1992 as part of the heat exchanger restart evaluation and are not covered in this report

Numerical Simulation of Nanofluid Suspensions in a Geothermal Heat Exchanger

Directory of Open Access Journals (Sweden)

Xiao-Hui Sun

2018-04-01

Full Text Available It has been shown that using nanofluids as heat carrier fluids enhances the conductive and convective heat transfer of geothermal heat exchangers. In this paper, we study the stability of nanofluids in a geothermal exchanger by numerically simulating nanoparticle sedimentation during a shut-down process. The nanofluid suspension is modeled as a non-linear complex fluid; the nanoparticle migration is modeled by a particle flux model, which includes the effects of Brownian motion, gravity, turbulent eddy diffusivity, etc. The numerical results indicate that when the fluid is static, the nanoparticle accumulation appears to be near the bottom borehole after many hours of sedimentation. The accumulated particles can be removed by the fluid flow at a relatively high velocity. These observations indicate good suspension stability of the nanofluids, ensuring the operational reliability of the heat exchanger. The numerical results also indicate that a pulsed flow and optimized geometry of the bottom borehole can potentially improve the suspension stability of the nanofluids further.

Cryostatic stability equation

International Nuclear Information System (INIS)

Sydoriak, S.G.

1976-01-01

Although criteria for cryostatic stability of superconducting magnets cooled by pool boiling of liquid helium have been widely discussed the same cannot be said for magnets cooled by natural convection or forced flow boiling in channels. Boiling in narrow channels is shown to be qualitatively superior to pool boiling because the recovery heat flux equals the breakaway flux for narrow channels, whereas the two are markedly different in pool boiling. A second advantage of channel boiling is that it is well understood and calculable; pool peak nucleate boiling heat flux has been adequately measured only for boiling from the top of an immersed heated body. Peak boiling from the bottom is much less and (probably) depends strongly on the extent of the bottom surface. Equations are presented by which one can calculate the critical boiling heat flux for parallel wall vertical channels subject to either natural convection or forced flow boiling, with one or both walls heated. The one-heated-wall forced flow equation is discussed with regard to design of a spiral wound solenoid (pancake magnet) having a slippery insulating tape between the windings

A stability analysis of ventilated boiling channels

International Nuclear Information System (INIS)

Taleyarkhan, R.P.; Podowski, M.Z.; Lahey, R.T. Jr.

1986-01-01

A mathematical model has been developed for the linear stability analysis of a system of ventilated parallel boiling channels. This model accounts for subcooled boiling, an arbitrary heat flux distribution, distributed and local hydraulic losses, heated wall dynamics, slip flow, turbulent mixing and arbitrary flow paths for transverse ventilation. The digital computer program MAZDA-NF was written for numerical evaluation of the mathematical model. Comparison of MAZDA-NF results with those obtained form both a closed form analytical solution and experiment, showed good agreement. A parametric study revealed that such phenomena as subcooled boiling, the transverse coupling between channels (due to cross-flow and mixing) and power skewing can have a significant impact on predicted stability margins. An analysis of an advanced BWR fuel, of the ASEA-ATOM SVEA design, has indicated that transverse ventilation may considerably improve channel stability. (orig.)

Soybean-derived biofuels and home heating fuels.

Science.gov (United States)

Mushrush, George W; Wynne, James H; Willauer, Heather D; Lloyd, Christopher L

2006-01-01

It is environmentally enticing to consider replacing or blending petroleum derived heating fuels with biofuels for many reasons. Major considerations include the soaring worldwide price of petroleum products, especially home heating oil, the toxicity of the petroleum-derived fuels and the environmental damage that leaking petroleum tanks afford. For these reasons, it has been suggested that domestic renewable energy sources be considered as replacements, or at the least, as blending stocks for home heating fuels. If recycled soy restaurant cooking oils could be employed for this purpose, this would represent an environmental advantage. Renewable plant sources of energy tend to be less toxic than their petroleum counterparts. This is an important consideration when tank leakage occurs. Home fuel oil storage tanks practically always contain some bottom water. This water environment has a pH value that factors into heating fuel stability. Therefore, the question is: would the biofuel help or exacerbate fuel stability and furnace maintenance issues?

The Condensation effect on the two-phase flow stability

International Nuclear Information System (INIS)

Abdou Mohamed, Hesham Nagah

2005-01-01

A one-dimensional analytical model has been developed to be used for the linear analysis of density-wave oscillations in a parallel heated channel and a natural circulation loop.The heater and the riser sections are divided into a single-phase and a two-phase region.The two-phase region is represented by the drift-flux model. The model accounts for aphasic slip and subcooled boiling.The localized friction at the heater and the riser exit is treated considering the two-phase mixture.Also the effects of the condensation in the riser and the change in the system pressure have been studied.The exact equation for the heated channel and the total loop pressure drop is perturbed around the steady state.he stability characteristics of the heated channel and the loop are investigated using the Root finding method criterion.The results are summarized on instability maps in the plane of subcooled boiling number vs. phase change number (i.e., inlet subcooling vs. heater heat flux).The predictions of the model are compared with experimental results published in open literature. The results show that, the treatment effect of localized friction in two-phase mixtures stabilizes the system and improves the agreement of the calculations with the experimental results.For a parallel heated channel, the results indicate a more stable system with high inlet restriction, low outlet restriction, and high inlet velocity. And for a natural circulation loop, an increase in the inlet restriction broadened the range of the continuous circulation mode and stabilized the system, a decrease in the exit restriction or the liquid charging level shifted to the right the range of the continuous circulation mode and stabilized the system and an increase in the riser condensation shifted to the right the range of the continuous circulation mode and stabilized the system.The results show that the model agrees well with the available experimental data. In particular, the results show the significance of

Stearic-acid/carbon-nanotube composites with tailored shape-stabilized phase transitions and light–heat conversion for thermal energy storage

International Nuclear Information System (INIS)

Li, Benxia; Nie, Shibin; Hao, Yonggan; Liu, Tongxuan; Zhu, Jinbo; Yan, Shilong

2015-01-01

Highlights: • A facile preparation of shape-stabilized composite PCMs for thermal energy storage. • The composite PCMs present tunable phase change temperatures and enthalpy. • Sunlight-driven phase change for photothermal conversion and storage. - Abstract: The development of functional materials with both light–heat conversion and thermal energy storage properties is of crucial importance for efficient utilization of sunlight to meet the growing demand for sustainable energy. In this work, the shape-stabilized phase change composites were designed and prepared by integration of stearic acid (SA) and acid-treated carbon nanotubes (a-CNTs). The a-CNTs not only acted as a flexible matrix but also endowed the composites high light–heat conversion ability. The reversible phase transitions shifted from high temperatures (T m = 74 °C, T f = 57 °C) of pure SA to near room temperature (T m = ∼30 °C, T f = ∼22 °C) of SA/a-CNTs composites, probably resulting from the strong interface confinement effect. The phase change enthalpy of the SA/a-CNTs composite could also be tailored by changing the mass ratio of SA and a-CNTs. The composites containing SA of 54.2 wt.%, 67.8 wt.% and 79.5 wt.% presented the melting enthalpy of 76.3 J/g, 98.8 J/g and 111.8 J/g, respectively. Moreover, the phase transition of SA/a-CNTs composite could be driven by sunlight for the energy storage/release. Therefore, this research provides a new platform for improving solar utilization, and understanding the phase transition behaviors of organic PCMs in dimensionally confined environments as well

Stability analysis on the flow and heat transfer of nanofluid past a stretching/shrinking cylinder with suction effect

Science.gov (United States)

Bakar, Nor Ashikin Abu; Bachok, Norfifah; Arifin, Norihan Md.; Pop, Ioan

2018-06-01

The steady boundary layer flow over a stretching/shrinking cylinder with suction effect is numerically studied. Using a similarity transformations, the governing partial differential equations are transformed into a set of nonlinear differential equations and have been solved numerically using a bvp4c code in Matlab software. The nanofluid model used is taking into account the effects of Brownian motion and thermophoresis. The influences of the governing parameters namely the curvature parameter γ, mass suction parameter S, Brownian motion parameter Nb and thermophoresis parameter Nt on the flow, heat and mass transfers characteristics are presented graphically. The numerical results obtained for the skin friction coefficient, local Nusselt number and local Sherwood number are thoroughly determined and presented graphically for several values of the governing parameters. From our investigation, it is found that the non-unique (dual) solutions exist for a certain range of mass suction parameter. It is observed that as curvature parameter increases, the skin friction coefficient and heat transfer rate decrease, meanwhile the mass transfer rates increase. Moreover, the stability analysis showed that the first solution is linearly stable, while the second solution is linearly unstable.

Thermo-hydraulic stability study of a steam generator

International Nuclear Information System (INIS)

Magni, M C; Marcel, C P; Delmastro, D F

2012-01-01

In this work a mathematical model developed to investigate the thermalhydraulic stability of a helically coiled steam generator is presented. Such a steam generator is prone to experiment density wave oscillations. The model is therefore used to analyze the stability of the CAREM-25 reactor steam generators. The model is linear, numerically non-diffusive and nodal. In addition, it is able to represent non-uniform heat transfer fluxes between the primary and secondary coolant circuits. By using this model the marginal stability condition is found by varying the inlet friction coefficient for different conditions. The results are then compared with those obtained with a different model for which a simple uniform heat flux profiled is assumed. It is found that with such simplification the density waves instability mechanism is overestimated in a wide range of operating powers. For very low powers, in the contrary, the so-called uniform model underestimates the stabilizing inlet friction and therefore it gives non-conservative results. With the use of the more realistic non-uniform power profile model, it was possible to determine that, for a CAREM-25 steam generator, the most stable conditions is found at 60MW when the reactor operates at nominal pressure. Moreover, it is found that at high power levels the stability performance is dominated by the two-phase friction component while at low power levels the friction component originated in the over heated steam region prevail (author)

Combined Influence of Strain and Heat Loss on Turbulent Premixed Flame Stabilization

KAUST Repository

Tay-Wo-Chong, Luis

2015-11-16

The present paper argues that the prediction of turbulent premixed flames under non-adiabatic conditions can be improved by considering the combined effects of strain and heat loss on reaction rates. The effect of strain in the presence of heat loss on the consumption speed of laminar premixed flames was quantified by calculations of asymmetric counterflow configurations (“fresh-to-burnt”) with detailed chemistry. Heat losses were introduced by setting the temperature of the incoming stream of products on the “burnt” side to values below those corresponding to adiabatic conditions. The consumption speed decreased in a roughly exponential manner with increasing strain rate, and this tendency became more pronounced in the presence of heat losses. An empirical relation in terms of Markstein number, Karlovitz Number and a non-dimensional heat loss parameter was proposed for the combined influence of strain and heat losses on the consumption speed. Combining this empirical relation with a presumed probability density function for strain in turbulent flows, an attenuation factor that accounts for the effect of strain and heat loss on the reaction rate in turbulent flows was deduced and implemented into a turbulent combustion model. URANS simulations of a premixed swirl burner were carried out and validated against flow field and OH chemiluminescence measurements. Introducing the effects of strain and heat loss into the combustion model, the flame topology observed experimentally was correctly reproduced, with good agreement between experiment and simulation for flow field and flame length.

Zeolite Y Adsorbents with High Vapor Uptake Capacity and Robust Cycling Stability for Potential Applications in Advanced Adsorption Heat Pumps.

Science.gov (United States)

Li, Xiansen; Narayanan, Shankar; Michaelis, Vladimir K; Ong, Ta-Chung; Keeler, Eric G; Kim, Hyunho; McKay, Ian S; Griffin, Robert G; Wang, Evelyn N

2015-01-01

Modular and compact adsorption heat pumps (AHPs) promise an energy-efficient alternative to conventional vapor compression based heating, ventilation and air conditioning systems. A key element in the advancement of AHPs is the development of adsorbents with high uptake capacity, fast intracrystalline diffusivity and durable hydrothermal stability. Herein, the ion exchange of NaY zeolites with ingoing Mg 2+ ions is systematically studied to maximize the ion exchange degree (IED) for improved sorption performance. It is found that beyond an ion exchange threshold of 64.1%, deeper ion exchange does not benefit water uptake capacity or characteristic adsorption energy, but does enhance the vapor diffusivity. In addition to using water as an adsorbate, the uptake properties of Mg,Na-Y zeolites were investigated using 20 wt.% MeOH aqueous solution as a novel anti-freeze adsorbate, revealing that the MeOH additive has an insignificant influence on the overall sorption performance. We also demonstrated that the labscale synthetic scalability is robust, and that the tailored zeolites scarcely suffer from hydrothermal stability even after successive 108-fold adsorption/desorption cycles. The samples were analyzed using N 2 sorption, 27 Al/ 29 Si MAS NMR spectroscopy, ICP-AES, dynamic vapor sorption, SEM, Fick's 2 nd law and D-R equation regressions. Among these, close examination of sorption isotherms for H 2 O and N 2 adsorbates allows us to decouple and extract some insightful information underlying the complex water uptake phenomena. This work shows the promising performance of our modified zeolites that can be integrated into various AHP designs for buildings, electronics, and transportation applications.

Analysis of boundary layer control by heat transfer strips using an asymptotic approach to the PSE

Energy Technology Data Exchange (ETDEWEB)

Brooker, A.M.H.; Severin, J. [Technische Univ. Chemnitz (Germany). Technische Thermodynamik; Herwig, H. [Technische Univ. Hamburg-Harburg, Hamburg (Germany). Abt. Technische Thermodynamik

2002-05-01

The effect of heating strips on the stability of boundary layer flow over a flat plate is investigated. Heating strips alter the flow stability through the temperature dependence of the fluid properties. A stability study is carried out using the parabolized stability equations (PSE) that calculates the effects of temperature dependent fluid properties in terms of asymptotic expansions based on the total heat input. The leading order influence is obtained as a general result and, for the particular Prandtl number taken, is independent of any special set of property laws. In a fluid for which the intrinsic viscosity increases with temperature and the density decreases with temperature (such as air) the results show that the optimal location for a heating strip to stabilise the flow is upstream of the neutral point. The optimal location moves further upstream as the total heat input level is increased. For a given heat input widening the heating strip further stabilises the flow. Finally, the potential of the asymptotic method as a tool for further analysis of the flow is discussed. (orig.)

Automated Hybrid Microwave Heating for Lunar Surface Solidification, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — This SBIR project addresses the need for a system that will provide automated lunar surface stabilization via hybrid microwave heating. Surface stabilization is...

An investigation on the chemical stability and a novel strategy for long-term stabilization of diphenylalanine nanostructures in aqueous solution

Directory of Open Access Journals (Sweden)

H. Nezammahalleh

2015-01-01

Full Text Available The stability of diphenylalanine (FF microwires and microtubes in phosphate buffer solution was investigated and a novel strategy was developed for their chemical stabilization. This stability investigation was carried out by optical microscopy and by high performance liquid chromatography (HPLC. These microstructures dissolve in the solution depending upon their degree of FF saturation. The dissolution mechanisms of the structures in kinetically limited processes were found by accurately fitting the experimental dissolution data to a theoretical kinetic equation. The dissolution data were well fitted to the particular Avrami-Erofe’ev kinetic expression (R2 > 0.98. These findings suggest that the structures can be stabilized by a decrease in the hydration of the constituent molecules thorough a chemical conformational induced transition upon heat treatment. The stable microtubes were fabricated in a novel three step procedure consisting of the reduction of silver ions in unstable FF microtubes by a citrate reductant, the stabilization by chemical conformational induced transition upon heat treatment, and the consequent oxidation of the reduced silver by a persulfate oxidant. These materials were characterized by electron microscopy and powder X-ray diffraction techniques. The long-term stability of both structures was also confirmed by optical microscopy and HPLC.

A study on stability of rotating magnets

International Nuclear Information System (INIS)

Higuchi, N.; Kaiho, K.; Ishii, I.

1996-01-01

Superconducting power generators are being developed in Japan, as a part of a R and D program on energy technology, the New Sunshine Project. In this development, national laboratories are taking a role of fundamental studies to contribute to the R and D being carried out mainly by the manufacturers involved in a research association, Super-GM. Stabilities of magnets in a high gravitational field up to 2,000 G are discussed, based upon the experimental results of forced quench tests in a set of rotating magnets, in order to establish the stability design criterion of field windings of superconducting generators. Relations of propagation velocities, recovery currents, minimum quench energy and heat transfer characteristics are studied, a good agreement between the experimental results and a theory confirmed the improvement of magnet stability in a high gravitational field because of the enhanced heat transfer characteristics

Influence of microwave heating on the stability of processed samn

Directory of Open Access Journals (Sweden)

Farag, Radwan S.

1991-04-01

Full Text Available Butter was converted to samn by microwave and conventional heating. The quality of the processed samn by the two methods was followed by determining the acid, peroxide and TBA values over a period of six weeks at 60°C. The fatty acid composition of samn samples was determined by gas-liquid chromatographic technique. The data show that butter conversion to samn by microwave heating was accomplished in about one half of the time that conventional heating requires. Microwave heating obviously increased the development of samn rancidity compared with the conventional heating. The parameters used for measuring lipid rancidity indicated that the main cause of samn rancidity under the present conditions is an oxidation mechanism.

Mantequilla fue transformada en samn por calentamiento en microonda y convencional. La calidad del elaborado de samn por los dos métodos fue seguida mediante determinación de los índices de acidez, peróxido y TBA durante un período de seis semanas a 60°C. La composición en ácidos grasos de muestras de samn fue determinada por técnica cromatográfica gas-líquido. Los datos mostraron que la conversión de mantequilla a samn por calentamiento en microonda fue realizada en aproximadamente una vez y media el tiempo que exige el calentamiento convencional. El calentamiento en microonda, evidentemente, aumentó el desarrollo de la rancidez del samn comparado con el calentamiento convencional. Los parámetros usados para la medida de la rancidez lipídica indicaron que la causa principal de la rancidez del samn bajo las condiciones presentes es un mecanismo de oxidación.

Thermophysical and heat transfer properties of phase change material candidate for waste heat transportation system

Science.gov (United States)

Kaizawa, Akihide; Maruoka, Nobuhiro; Kawai, Atsushi; Kamano, Hiroomi; Jozuka, Tetsuji; Senda, Takeshi; Akiyama, Tomohiro

2008-05-01

A waste heat transportation system trans-heat (TH) system is quite attractive that uses the latent heat of a phase change material (PCM). The purpose of this paper is to study the thermophysical properties of various sugars and sodium acetate trihydrate (SAT) as PCMs for a practical TH system and the heat transfer property between PCM selected and heat transfer oil, by using differential scanning calorimetry (DSC), thermogravimetry-differential thermal analysis (TG-DTA) and a heat storage tube. As a result, erythritol, with a large latent heat of 344 kJ/kg at melting point of 117°C, high decomposition point of 160°C and excellent chemical stability under repeated phase change cycles was found to be the best PCM among them for the practical TH system. In the heat release experiments between liquid erythritol and flowing cold oil, we observed foaming phenomena of encapsulated oil, in which oil droplet was coated by solidification of PCM.

Transient heat transfer in liquid helium

International Nuclear Information System (INIS)

Shiotsu, Masahiro

1991-01-01

Detailed knowledge on the steady-state and transient heat transfer from solid surfaces in He I and He II is important as a database for the analysis of the influence of local thermal disturbances on the stability of He I or He II cooled large superconducting magnets. In this paper, an overview of the transient heat transfer characteristics on solid surfaces in He I and He II caused by various large stepwise heat inputs, such as the quasi-steady nucleate boiling with a certain lifetime in He I and the quasi-steady Kapitza conductance heat flux with a certain lifetime in He II, are presented in comparison with their steady-state heat transfer characteristics. (author)

Solving the stability-accuracy-diversity dilemma of recommender systems

Science.gov (United States)

Hou, Lei; Liu, Kecheng; Liu, Jianguo; Zhang, Runtong

2017-02-01

Recommender systems are of great significance in predicting the potential interesting items based on the target user's historical selections. However, the recommendation list for a specific user has been found changing vastly when the system changes, due to the unstable quantification of item similarities, which is defined as the recommendation stability problem. To improve the similarity stability and recommendation stability is crucial for the user experience enhancement and the better understanding of user interests. While the stability as well as accuracy of recommendation could be guaranteed by recommending only popular items, studies have been addressing the necessity of diversity which requires the system to recommend unpopular items. By ranking the similarities in terms of stability and considering only the most stable ones, we present a top- n-stability method based on the Heat Conduction algorithm (denoted as TNS-HC henceforth) for solving the stability-accuracy-diversity dilemma. Experiments on four benchmark data sets indicate that the TNS-HC algorithm could significantly improve the recommendation stability and accuracy simultaneously and still retain the high-diversity nature of the Heat Conduction algorithm. Furthermore, we compare the performance of the TNS-HC algorithm with a number of benchmark recommendation algorithms. The result suggests that the TNS-HC algorithm is more efficient in solving the stability-accuracy-diversity triple dilemma of recommender systems.

Effects of Cooling Fluid Flow Rate on the Critical Heat Flux and Flow Stability in the Plate Fuel Type 2 MW TRIGA Reactor

OpenAIRE

H. P. Rahardjo; V. I. Sri Wardhani

2017-01-01

The conversion program of the 2 MW TRIGA reactor in Bandung consisted of the replacement of cylindrical fuel (produced by General Atomic) with plate fuel (produced by BATAN). The replacement led into the change of core cooling process from upward natural convection type to downward forced convection type, and resulted in different thermohydraulic safety criteria, such as critical heat flux (CHF) limit, boiling limit, and cooling fluid flow stability. In this paper, a thermohydraulic safety an...

Design of the inboard passive stabilizer for TPX

International Nuclear Information System (INIS)

Hoffmann, E.; Boonstra, R.; Baxi, C.B.; Chin, E.; Drees, L.; Lee, W.; Redler, K.L.; Reis, E.E.; Bialek, J.

1995-01-01

The Inboard Passive Stabilizer (IPS) is part of the plasma stabilizing system built into the TPX. Its purpose is to provide passive stabilization of the plasma vertical instability on short time scales. With carbon fiber composite (CFC) armor tiles it serves as a startup limiter, protects the vacuum vessel from radiation heat load during steady state operation and also functions as Neutral Beam armor. The inboard passive stabilizer is a saddle coil, constructed of a ring of copper plates, armored with CFC tiles, that surrounds the inner vacuum vessel at the midplane. The design of the plates, the support structure, cooling lines, CFC tiles and tile attach method is described. Tiles that experience only the normal heat load of 0.4 MW/m 2 are attached with mechanical fasteners. Tiles in the neutral beam shine through area are exposed to as much as 1.7 MW/m 2 and are brazed to the IPS. Significant forces are generated in the plates by the stabilization currents as well as during the frequent bakeout cycles. These plates are required to be fully remotely handled, including tile replacement, and the influence of this requirement on the design is discussed

Devoluming and stabilizing method for end piece

International Nuclear Information System (INIS)

Ikeda, Satoshi; Shiotsuki, Msao; Kawamura, Shigeyoshi; Komatsu, Fumiaki.

1991-01-01

As a first method, end pieces and other radioactive metal wastes are filled as a mixture in a vessel, and preliminary compression is conducted. Then, the bulk density of the radioactive metal wastes is reduced and gaps in the end pieces are filled with radioactive metal wastes. If they are applied with heat treatment under high pressure in this state together with the vessel, they are devolumed and stabilized without damaging the vessel. As a second method, metal powders are mixed and filled in the vessel together with the end pieces. The gaps in the end pieces are filled with the metal powders and if they are applied with heat treatment under high pressure in this state together with the vessel, the end pieces are devolumed and stabilized without damaging the vessel in the same manner. This can devolume and stabilize the end pieces separated from nuclear fuel assemblies easily and safely. (T.M.)

A comprehensive review of thermo-physical properties and convective heat transfer to nanofluids

International Nuclear Information System (INIS)

Solangi, K.H.; Kazi, S.N.; Luhur, M.R.; Badarudin, A.; Amiri, A.; Sadri, Rad; Zubir, M.N.M.; Gharehkhani, Samira; Teng, K.H.

2015-01-01

Nanofluids are fluid nanoparticle suspensions that exhibit enhanced properties at modest nanoparticle concentrations. Nanofluids have unique heat transfer properties and are utilized in high heat flux systems (e.g., electronic cooling systems, heat exchanger liquids, solar collectors, and nuclear reactors). However, suspension stability is critical in the development and application of these heat transfer fluids. Reynolds number, mass concentration, and particle size control the heat transfer behavior of fluids. Sedimentation and agglomeration of nanoparticles in nanofluids and their dispersion have rarely been investigated. Therefore, this paper explains the parameters that affect the stability of nanofluids and the different techniques used to evaluate the stability of nanofluids. This paper also presents an updated review of properties of nanofluids, such as physical (thermal conductivity) and rheological properties, with emphasis on their heat transfer enhancement characteristics. Studies on zeta potential as a function of pH are discussed and extended further to identify opportunities for future research. - Highlights: • Comprehensive review of nanofluids and latest methods of preparation. • Parameters that affect the stability of nanofluids and the different techniques are discussed. • Effect of different surfactants on the rheological properties of nanofluids has been presented. • Sedimentation and agglomeration of nanoparticles in nanofluids are discussed in detail. • zeta potential as a function of pH is discussed and opportunities for future research

Stabilizing effect of epoxidized sunflower oil as a secondary stabilizer for Ca/Hg stabilized PVC

Directory of Open Access Journals (Sweden)

2008-01-01

Full Text Available Unsaturated triglyceride oil sunflower was epoxidized and characterized by chemical and spectroscopic methods. Epoxidized sunflower oil (ESO was used as an organic thermal co-stabilizer for rigid poly(vinyl chloride (PVC in the presence of tricalcium dicitrate (Ca3(C6H5O72 and mercury (II acetate (Hg(CH3COO2. The thermo-oxidative degradation of PVC was studied in the presence of these ternary stabilizer systems at 170, 180, 190 and 200°C in N2 atmosphere. The effects of metal carboxylate combination Ca/Hg in the absence and in the presence of epoxidized sunflower oil on static heat treatment of PVC have been studied. The formation of polyene sequences was investigated by UV-visible and FT-IR spectroscopy and by comparing viscosity data obtained in the presence and in the absence of the additives. It was found that the additives retard the rate of degradation and reduce the extent of polymer chain scission associated with the thermal degradation of poly(vinyl chloride. Synergistic effects were found when stabilizer was blended in 50:50 weight ratios with either. It was found that ESO exerted a stabilizing effect on the degradation of PVC. The activation energy for degraded PVC in absence of stabilizers was 38.6 kJ•mol–1 and in the presence of Ca/Hg and Ca/Hg/ESO were 53.3 and 64.7 kJ•mol–1 respectively. In order of compare the efficiency of the epoxidized sunflower oil with these metal soap stabilizers, thermal stabilities were evaluated on the basis of evolved hydrogen chloride determined by conductometry technique and degree of discoloration are discussed.

Natural and Artificial Methods for Regeneration of Heat Resources for Borehole Heat Exchangers to Enhance the Sustainability of Underground Thermal Storages: A Review

Directory of Open Access Journals (Sweden)

Tomasz Sliwa

2015-09-01

Full Text Available The concept of borehole heat exchanger (BHE field exploitation is described, along with problems regarding the sustainability of heat resources in rock masses. A BHE field sometimes has problems with the stability of the heat carrier temperature during long-term exploitation. The main reason for this is an insufficient heat stream with which to transfer heat by conduction in rock. Possibilities for the regeneration of heat in rock masses, based on experiences at the Geoenergetics Laboratory (Drilling, Oil and Gas Faculty, AGH University of Science and Technology, are described.

Synergetic Use of Principal Component Analysis Applied to Normed Physicochemical Measurements and GC × GC-MS to Reveal the Stabilization Effect of Selected Essential Oils on Heated Rapeseed Oil.

Science.gov (United States)

Sghaier, Lilia; Cordella, Christophe B Y; Rutledge, Douglas N; Lefèvre, Fanny; Watiez, Mickaël; Breton, Sylvie; Sassiat, Patrick; Thiebaut, Didier; Vial, Jérôme

2017-06-01

Lipid oxidation leads to the formation of volatile compounds and very often to off-flavors. In the case of the heating of rapeseed oil, unpleasant odors, characterized as a fishy odor, are emitted. In this study, 2 different essential oils (coriander and nutmeg essential oils) were added to refined rapeseed oil as odor masking agents. The aim of this work was to determine a potential antioxidant effect of these essential oils on the thermal stability of rapeseed oil subject to heating cycles between room temperature and 180 °C. For this purpose, normed determinations of different parameters (peroxide value, anisidine value, and the content of total polar compounds, free fatty acids and tocopherols) were carried out to examine the differences between pure and degraded oil. No significant difference was observed between pure rapeseed oil and rapeseed oil with essential oils for each parameter separately. However, a stabilizing effect of the essential oils, with a higher effect for the nutmeg essential oil was highlighted by principal component analysis applied on physicochemical dataset. Moreover, the analysis of the volatile compounds performed by GC × GC showed a substantial loss of the volatile compounds of the essential oils from the first heating cycle. © 2017 Institute of Food Technologists®.

Plate heat exchangers in the power plant industry

International Nuclear Information System (INIS)

Wersel, M.; Ridell, B.

1984-01-01

An increase in heat transfer and stability, small investment, high flexibility, easy maintenance and corrosion resistance are obtained by the design and construction of plate heat exchangers and by the introduction of the herringbone pattern. The plate heat exchanger can be used in nearly 90% of all secondary circuits in powerstations. Examples of its installation are the WYLFA, GENTILLY, RINGHALS and TVO Finland nuclear power-stations. (DG) [de

Controlled fusion and plasma heating

International Nuclear Information System (INIS)

1990-06-01

The contributions presented in the 17th European Conference on Controlled Fusion and Plasma Heating were focused on Tore Supra investigations. The following subjects were presented: ohmic discharges, lower hybrid experiments, runaway electrons, Thomson scattering, plasma density measurements, magnetic fluctuations, polarization scattering, plasma currents, plasma fluctuation measurements, evaporation of hydrogen pellets in presence of fast electrons, ripple induced stochastic diffusion of trapped particles, tearing mode stabilization, edge effects on turbulence behavior, electron cyclotron heating, micro-tearing modes, divertors, limiters

Thermal stability analysis and modelling of advanced perpendicular magnetic tunnel junctions

Science.gov (United States)

Van Beek, Simon; Martens, Koen; Roussel, Philippe; Wu, Yueh Chang; Kim, Woojin; Rao, Siddharth; Swerts, Johan; Crotti, Davide; Linten, Dimitri; Kar, Gouri Sankar; Groeseneken, Guido

2018-05-01

STT-MRAM is a promising non-volatile memory for high speed applications. The thermal stability factor (Δ = Eb/kT) is a measure for the information retention time, and an accurate determination of the thermal stability is crucial. Recent studies show that a significant error is made using the conventional methods for Δ extraction. We investigate the origin of the low accuracy. To reduce the error down to 5%, 1000 cycles or multiple ramp rates are necessary. Furthermore, the thermal stabilities extracted from current switching and magnetic field switching appear to be uncorrelated and this cannot be explained by a macrospin model. Measurements at different temperatures show that self-heating together with a domain wall model can explain these uncorrelated Δ. Characterizing self-heating properties is therefore crucial to correctly determine the thermal stability.

Thermal stability and temperature coefficients of four rare-earth-cobalt matrix magnets heated in dry air

Science.gov (United States)

Strnat, R. M. W.; Liu, S.; Strnat, K. J.

1982-03-01

Flux-loss characteristics during long-term air aging of four rare-earth-cobalt matrix magnet types were measured. Irreversible losses and reversible temperature coefficients on heating above room temperature are reported. Purely magnetic and permanent microstructure-related changes during aging were differentiated by measuring hysteresis curves before and after long-term exposure. Three commercial polymer-bonded magnets using different rare-earth-cobalt-transition metal alloys and a solder-matrix magnet with Sm(Co, Cu, Fe, Zr)7.4 were studied. They were cycled between 25 °C and maximum temperatures to 150 °C (25 ° intervals) as applicable. Aging data at 50 and 125 °C for an exposure time of 3300 h are reported. The 2-17 samples have a stability far superior to bonded 1-5. The soft metal binder imparts significantly better aging behavior on precipitation-hardened 2-17 magnet alloys above 100 °C than an epoxy resin matrix.

Combined Influence of Strain and Heat Loss on Turbulent Premixed Flame Stabilization

KAUST Repository

Tay-Wo-Chong, Luis; Zellhuber, Mathieu; Komarek, Thomas; Im, Hong G.; Polifke, Wolfgang

2015-01-01

relation in terms of Markstein number, Karlovitz Number and a non-dimensional heat loss parameter was proposed for the combined influence of strain and heat losses on the consumption speed. Combining this empirical relation with a presumed probability

Heat- and radiation-resistant scintillator for electron microscopes

International Nuclear Information System (INIS)

Kosov, A.V.; Petrov, S.A.; Puzyr', A.P.; Chetvergov, N.A.

1987-01-01

The use of a scintillator consisting of a single crystal of bismuth orthogermanate, which has high heat and radiation resistance, in REM-100, REM-200, and REM-100U electron microscopes is described. A study of the heat and radiation stabilities of single crystals of bismuth orthogermanate (Bi 4 Ge 3 O 12 ) has shown that they withstood multiple electron-beam heating redness (T ∼ 800 0 C) without changes in their properties

The relationship between fatty acid compositions and thermal stability of extra virgin olive oils

OpenAIRE

Fayegh Moulodi; Peyman Qajarbeigi; Ashraf Haj Hosseini Babaei; Asghar Mohammadpoor Asl

2014-01-01

Background: Fatty acids are one of the most important compounds in edible oils. Further, the stability of oils depends on the composition of fatty acids. So, this study was conducted to investigate the effect of fatty acid composition on the oxidative stability of extra virgin olive oils during the heating process. Methods: In total, eight samples of extra virgin olive oil were studied. To evaluate their thermal stability, the oils were heated at 120 ° C for 4 h and sampling was carried o...

Heat activation and stability of amylases from Bacillus species

African Journals Online (AJOL)

Administrator

2007-05-16

May 16, 2007 ... as Bacillus macerans, Bacillus coagulans Bacillus licheniformis, Bacillus circulans, Bacillus megaterium, Bacillus polymyxa and Bacillus subtilis. Heat treatment at 70oC denatured the β-amylase component of the amylase source while α-amylase retained its potency at this temperature. Calcium.

Crustal heat production and estimate of terrestrial heat flow in central East Antarctica, with implications for thermal input to the East Antarctic ice sheet

Science.gov (United States)

Goodge, John W.

2018-02-01

Terrestrial heat flow is a critical first-order factor governing the thermal condition and, therefore, mechanical stability of Antarctic ice sheets, yet heat flow across Antarctica is poorly known. Previous estimates of terrestrial heat flow in East Antarctica come from inversion of seismic and magnetic geophysical data, by modeling temperature profiles in ice boreholes, and by calculation from heat production values reported for exposed bedrock. Although accurate estimates of surface heat flow are important as an input parameter for ice-sheet growth and stability models, there are no direct measurements of terrestrial heat flow in East Antarctica coupled to either subglacial sediment or bedrock. As has been done with bedrock exposed along coastal margins and in rare inland outcrops, valuable estimates of heat flow in central East Antarctica can be extrapolated from heat production determined by the geochemical composition of glacial rock clasts eroded from the continental interior. In this study, U, Th, and K concentrations in a suite of Proterozoic (1.2-2.0 Ga) granitoids sourced within the Byrd and Nimrod glacial drainages of central East Antarctica indicate average upper crustal heat production (Ho) of about 2.6 ± 1.9 µW m-3. Assuming typical mantle and lower crustal heat flux for stable continental shields, and a length scale for the distribution of heat production in the upper crust, the heat production values determined for individual samples yield estimates of surface heat flow (qo) ranging from 33 to 84 mW m-2 and an average of 48.0 ± 13.6 mW m-2. Estimates of heat production obtained for this suite of glacially sourced granitoids therefore indicate that the interior of the East Antarctic ice sheet is underlain in part by Proterozoic continental lithosphere with an average surface heat flow, providing constraints on both geodynamic history and ice-sheet stability. The ages and geothermal characteristics of the granites indicate that crust in central

Addition of sodium caseinate to skim milk increases nonsedimentable casein and causes significant changes in rennet-induced gelation, heat stability, and ethanol stability.

Science.gov (United States)

Lin, Yingchen; Kelly, Alan L; O'Mahony, James A; Guinee, Timothy P

2017-02-01

The protein content of skim milk was increased from 3.3 to 4.1% (wt/wt) by the addition of a blend of skim milk powder and sodium caseinate (NaCas), in which the weight ratio of skim milk powder to NaCas was varied from 0.8:0.0 to 0.0:0.8. Addition of NaCas increased the levels of nonsedimentable casein (from ∼6 to 18% of total casein) and calcium (from ∼36 to 43% of total calcium) and reduced the turbidity of the fortified milk, to a degree depending on level of NaCas added. Rennet gelation was adversely affected by the addition of NaCas at 0.2% (wt/wt) and completely inhibited at NaCas ≥0.4% (wt/wt). Rennet-induced hydrolysis was not affected by added NaCas. The proportion of total casein that was nonsedimentable on centrifugation (3,000 × g, 1 h, 25°C) of the rennet-treated milk after incubation for 1 h at 31°C increased significantly on addition of NaCas at ≥0.4% (wt/wt). Heat stability in the pH range 6.7 to 7.2 and ethanol stability at pH 6.4 were enhanced by the addition of NaCas. It is suggested that the negative effect of NaCas on rennet gelation is due to the increase in nonsedimentable casein, which upon hydrolysis by chymosin forms into small nonsedimentable particles that physically come between, and impede the aggregation of, rennet-altered para-casein micelles, and thereby inhibit the development of a gel network. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Spin dynamics and thermal stability in L10 FePt

Science.gov (United States)

Chen, Tianran; Toomey, Wahida

Increasing the data storage density of hard drives remains one of the continuing goals in magnetic recording technology. A critical challenge for increasing data density is the thermal stability of the written information, which drops rapidly as the bit size gets smaller. To maintain good thermal stability in small bits, one should consider materials with high anisotropy energy such as L10 FePt. High anisotropy energy nevertheless implies high coercivity, making it difficult to write information onto the disk. This issue can be overcome by a new technique called heat-assisted magnetic recording, where a laser is used to locally heat the recording medium to reduce its coercivity while retaining relatively good thermal stability. Many of the microscopic magnetic properties of L10 FePt, however, have not been theoretically well understood. In this poster, I will focus on a single L10 FePt grain, typically of a few nanometers. Specifically, I will discuss its critical temperature, size effect and, in particular, spin dynamics in the writing process, a key to the success of heat-assisted magnetic recording. WCU URF16.

Stability of High Temperature Standard Platinum Resistance Thermometers at High Temperatures

OpenAIRE

Y. A. ABDELAZIZ; F. M. MEGAHED

2010-01-01

An investigation of the stability of high temperature standard platinum resistance thermometers HTSPRTs has been carried out for two different designs thermometers (with nominal resistance 0.25 Ω and 2.5 Ω) from two different suppliers. The thermometers were heated for more than 160 hours at temperatures above 960 0C using a vertical furnace with a ceramic block. A study was made of the influence of the heat treatment on the stability of the resistance at the triple point of water, and on the...

Analysis of Decentralized Control for Absorption Cycle Heat Pumps

DEFF Research Database (Denmark)

Vinther, Kasper; Just Nielsen, Rene; Nielsen, Kirsten Mølgaard

2015-01-01

Email Print Request Permissions This paper investigates decentralized control structures for absorption cycle heat pumps and a dynamic nonlinear model of a single-effect LiBr-water absorption system is used as case study. The model has four controllable inputs, which can be used to stabilize...... the operation of the heat pump under different load conditions. Different feasible input-output pairings are analyzed by computation of relative gain array matrices and scaled condition numbers, which indicate the best pairing choice and the potential of each input-output set. Further, it is possible...... to minimize the effect of cross couplings and improve stability with the right pairing of input and output. Simulation of selected candidate input-output pairings demonstrate that decentralized control can provide stable operation of the heat pump....

Hyperthermophilic enzymes - stability, activity and implementation strategies for high temperature applications

NARCIS (Netherlands)

Unsworth, L.D.; Oost, van der J.; Koutsopoulos, S.

2007-01-01

Current theories agree that there appears to be no unique feature responsible for the remarkable heat stability properties of hyperthermostable proteins. A concerted action of structural, dynamic and other physicochemical attributes are utilized to ensure the delicate balance between stability and

Sawtooth stability in neutral beam heated plasmas in TEXTOR

NARCIS (Netherlands)

Chapman, I.T.; Pinches, S. D.; Koslowski, H. R.; Liang, Y.; Kramer-Flecken, A.; De Bock, M.

2008-01-01

The experimental sawtooth behaviour in neutral beam injection (NBI) heated plasmas in TEXTOR is described. It is found that the sawtooth period is minimized with a low NBI power oriented in the same direction as the plasma current. As the beam power is increased in the opposite direction to the

Assessing phase stability and element distribution in Co-base superalloys at elevated temperatures by in situ TEM heating experiments

Energy Technology Data Exchange (ETDEWEB)

Eggeler, Yolita; Mueller, Julian; Spiecker, Erdmann [Lehrstuhl fuer Mikro- und Nanostrukturforschung and Center for Nanoanalysis and Electron Microscopy (CENEM), Department Werkstoffwissenschaften, Universitaet Erlangen-Nuernberg, Erlangen (Germany)

2016-07-01

Co-based alloys, of a composition of Co-12Al-9W, form a stable two phase γ/γ{sup '} microstructure at 900 C. γ{sup '} cubes, consisting of the L12 crystal structure are coherently embedded in a solid solution fcc (A1) γ matrix. To ensure precipitate hardening at temperatures, which are relevant to practical applications, 700-1100 C, as experienced in gas turbine applications, the stability of the γ/γ{sup '} phases is of fundamental importance. In this analysis in situ TEM studies with chip-based heating systems (by DENS solution) are applied on new Co-based superalloys. After in situ heating at apr. 900 C and controlled quenching with different quenching rates the elemental distribution at the γ/γ{sup '} interface is measured using ChemiSTEM EDX. Exploiting the driving force for interface movement resulting from temperature-dependent volume fraction of γ and γ{sup '} insight into the diffusion of individual alloying elements and the relationship between local chemistry and ordering can be gained from transient phenomena. The experimental results will be compared with theoretical calculations. This work has been carried out within the framework of the SFB-TR 103 ''Single Crystal Superalloys''.

Chemical and physical aspects of the stability of mica on heating

International Nuclear Information System (INIS)

Muromtsev, V.A.; Arkhangel'skii, S.V.; Egorov, S.V.

1989-01-01

An attempt was made in this study to comparatively determine the degree of hydration and thermal stability of micas and to analyze the possible causes of differences in interpreting the results on establishment of the degree of hydration on the example of phlogopites from the Kovdor and Aldan deposits by methods of flame photometry, γ-radiometric determination of K 2 O, thermal stability, and gravimetric methods of analysis of the moisture content and weight loss in calcination

Structure and phase stability of a Pu-0.32 wt% Ga alloy

Energy Technology Data Exchange (ETDEWEB)

Wheeler, D.W., E-mail: David.Wheeler@awe.co.uk; Ennaceur, S.M.; Matthews, M.B.; Roussel, P.; Bayer, P.D.

2016-08-01

In plutonium-gallium (Pu-Ga) alloys that have a Ga content of 0.3–0.4 wt%, their readiness to transform to α′ renders them of particular interest in efforts to understand the tenuous nature of δ phase stability. The present study is a comprehensive examination of the structure and phase stability of a cast Pu-0.32 wt% Ga alloy, the Ga content being close to the minimum amount needed to retain the δ phase to ambient temperature. The alloy was characterised in both the as-cast condition as well as following a homogenising heat treatment. The 250-h heat treatment at 450 °C was shown to achieve an apparently stable δ-Pu phase. However, the stability of the δ-Pu phase was shown to be marginal: partial transformation to α′-Pu was observed when the alloy was subjected to hydrostatic compression. Similar transformation was also apparent during metallographic preparation as well as during hardness indentation. The results provide new understanding of the nature of δ phase stability. - Highlights: • New insights into the delta phase stability of a Pu-0.32 wt% Ga alloy. • Density and DSC of as-cast alloy both show α-Pu contents of approximately 30%. • The heat-treated alloy has a largely δ-Pu structure at ambient temperature. • Heat-treated alloy susceptible to δ → α transformation during hardness indentation.

Heat shock protein 90β stabilizes focal adhesion kinase and enhances cell migration and invasion in breast cancer cells

International Nuclear Information System (INIS)

Xiong, Xiangyang; Wang, Yao; Liu, Chengmei; Lu, Quqin; Liu, Tao; Chen, Guoan; Rao, Hai; Luo, Shiwen

2014-01-01

Focal adhesion kinase (FAK) acts as a regulator of cellular signaling and may promote cell spreading, motility, invasion and survival in malignancy. Elevated expression and activity of FAK frequently correlate with tumor cell metastasis and poor prognosis in breast cancer. However, the mechanisms by which the turnover of FAK is regulated remain elusive. Here we report that heat shock protein 90β (HSP90β) interacts with FAK and the middle domain (amino acids 233–620) of HSP90β is mainly responsible for this interaction. Furthermore, we found that HSP90β regulates FAK stability since HSP90β inhibitor 17-AAG triggers FAK ubiquitylation and subsequent proteasome-dependent degradation. Moreover, disrupted FAK-HSP90β interaction induced by 17-AAG contributes to attenuation of tumor cell growth, migration, and invasion. Together, our results reveal how HSP90β regulates FAK stability and identifies a potential therapeutic strategy to breast cancer. - Highlights: • HSP90β protects FAK from degradation by the ubiquitin-proteasome pathway. • Inhibition of HSP90β or FAK attenuates tumorigenesis of breast cancer cells. • Genetic repression of HSP90β or FAK inhibits tumor cell migration and proliferation. • Inhibition of HSP90β or FAK interferes cell invasion and cytoskeleton

Heat shock protein 90β stabilizes focal adhesion kinase and enhances cell migration and invasion in breast cancer cells

Energy Technology Data Exchange (ETDEWEB)

Xiong, Xiangyang [Center for Experimental Medicine, The First Affiliated Hospital of Nanchang University, 17 Yongwai Street, Donghu District, Nanchang, Jiangxi 330006 (China); Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Nanchang University, Nanchang, Jiangxi 330006 (China); State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang, Jiangxi 330047 (China); Wang, Yao [Center for Experimental Medicine, The First Affiliated Hospital of Nanchang University, 17 Yongwai Street, Donghu District, Nanchang, Jiangxi 330006 (China); Liu, Chengmei [State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang, Jiangxi 330047 (China); Lu, Quqin [Department of Biostatistics and Epidemiology, School of Public Health, Nanchang University, Nanchang, Jiangxi 330006 (China); Liu, Tao [Center for Experimental Medicine, The First Affiliated Hospital of Nanchang University, 17 Yongwai Street, Donghu District, Nanchang, Jiangxi 330006 (China); Chen, Guoan [Department of Hematology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi 330006 (China); Rao, Hai [Department of Molecular Medicine, University of Texas Health Science Center, San Antonio, TX 78229 (United States); Luo, Shiwen, E-mail: shiwenluo@ncu.edu.cn [Center for Experimental Medicine, The First Affiliated Hospital of Nanchang University, 17 Yongwai Street, Donghu District, Nanchang, Jiangxi 330006 (China)

2014-08-01

Focal adhesion kinase (FAK) acts as a regulator of cellular signaling and may promote cell spreading, motility, invasion and survival in malignancy. Elevated expression and activity of FAK frequently correlate with tumor cell metastasis and poor prognosis in breast cancer. However, the mechanisms by which the turnover of FAK is regulated remain elusive. Here we report that heat shock protein 90β (HSP90β) interacts with FAK and the middle domain (amino acids 233–620) of HSP90β is mainly responsible for this interaction. Furthermore, we found that HSP90β regulates FAK stability since HSP90β inhibitor 17-AAG triggers FAK ubiquitylation and subsequent proteasome-dependent degradation. Moreover, disrupted FAK-HSP90β interaction induced by 17-AAG contributes to attenuation of tumor cell growth, migration, and invasion. Together, our results reveal how HSP90β regulates FAK stability and identifies a potential therapeutic strategy to breast cancer. - Highlights: • HSP90β protects FAK from degradation by the ubiquitin-proteasome pathway. • Inhibition of HSP90β or FAK attenuates tumorigenesis of breast cancer cells. • Genetic repression of HSP90β or FAK inhibits tumor cell migration and proliferation. • Inhibition of HSP90β or FAK interferes cell invasion and cytoskeleton.

Elimination of Oscillations in a Central Heating System using Pump Control

DEFF Research Database (Denmark)

Andersen, Palle; Pedersen, Tom Søndergaard; Stoustrup, Jakob

2000-01-01

In central heating systems with thermostatic valve temperature control it is a well known fact that room temperature oscillations may occur when the heat demand becomes low due to the non-linear behavior of the control loop. This is not only discomforting but it also increases the energy cost...... of heating the room. Using the pump speed as an active part in control is it shown that the room temperature may be stabilized in a wider interval of heat demand. The idea is to control the pump speed in a way that keeps the thermostatic valve within a suitable operating area using an estimate of the valve...... position. The position is estimated from the pump terminals, using the pump flow and the pump differential pressure. The concept is tested on a small central heating test bench. The results show that it is possible to stabilize the room temperature even at part load conditions...

Effect of rotational speed modulation on heat transport in a fluid layer with temperature dependent viscosity and internal heat source

Directory of Open Access Journals (Sweden)

B.S. Bhadauria

2014-12-01

Full Text Available In this paper, a theoretical investigation has been carried out to study the combined effect of rotation speed modulation and internal heating on thermal instability in a temperature dependent viscous horizontal fluid layer. Rayleigh–Bénard momentum equation with Coriolis term has been considered to describe the convective flow. The system is rotating about it is own axis with non-uniform rotational speed. In particular, a time-periodic and sinusoidally varying rotational speed has been considered. A weak nonlinear stability analysis is performed to find the effect of modulation on heat transport. Nusselt number is obtained in terms of amplitude of convection and internal Rayleigh number, and depicted graphically for showing the effects of various parameters of the system. The effect of modulated rotation speed is found to have a stabilizing effect for different values of modulation frequency. Further, internal heating and thermo-rheological parameters are found to destabilize the system.

Ideal MHD Stability Prediction and Required Power for EAST Advanced Scenario

International Nuclear Information System (INIS)

Chen Junjie; Li Guoqiang; Qian Jinping; Liu Zixi

2012-01-01

The Experimental Advanced Superconducting Tokamak (EAST) is the first fully superconducting tokamak with a D-shaped cross-sectional plasma presently in operation. The ideal magnetohydrodynamic (MHD) stability and required power for the EAST advanced tokamak (AT) scenario with negative central shear and double transport barrier (DTB) are investigated. With the equilibrium code TOQ and stability code GATO, the ideal MHD stability is analyzed. It is shown that a moderate ratio of edge transport barriers' (ETB) height to internal transport barriers' (ITBs) height is beneficial to ideal MHD stability. The normalized beta β N limit is about 2.20 (without wall) and 3.70 (with ideal wall). With the scaling law of energy confinement time, the required heating power for EAST AT scenario is calculated. The total heating power P t increases as the toroidal magnetic field B T or the normalized beta β N is increased. (magnetically confined plasma)

Ideal MHD Stability Prediction and Required Power for EAST Advanced Scenario

Science.gov (United States)

Chen, Junjie; Li, Guoqiang; Qian, Jinping; Liu, Zixi

2012-11-01

The Experimental Advanced Superconducting Tokamak (EAST) is the first fully superconducting tokamak with a D-shaped cross-sectional plasma presently in operation. The ideal magnetohydrodynamic (MHD) stability and required power for the EAST advanced tokamak (AT) scenario with negative central shear and double transport barrier (DTB) are investigated. With the equilibrium code TOQ and stability code GATO, the ideal MHD stability is analyzed. It is shown that a moderate ratio of edge transport barriers' (ETB) height to internal transport barriers' (ITBs) height is beneficial to ideal MHD stability. The normalized beta βN limit is about 2.20 (without wall) and 3.70 (with ideal wall). With the scaling law of energy confinement time, the required heating power for EAST AT scenario is calculated. The total heating power Pt increases as the toroidal magnetic field BT or the normalized beta βN is increased.

On a stabilization mechanism for low-velocity detonations

KAUST Repository

Sow, Aliou; Semenko, Roman E.; Kasimov, Aslan R.

2017-01-01

We use numerical simulations of the reactive Lula equations to analyse the nonlinear stability of steady-state one-dimensional solutions for gaseous detonations in the presence of both momentum and heat losses. Our results point to a possible stabilization mechanism for the low-velocity detonations in such systems. The mechanism stems from the existence of a one-parameter family of solutions found in Semenko el al.

On a stabilization mechanism for low-velocity detonations

KAUST Repository

Sow, Aliou

2017-03-08

We use numerical simulations of the reactive Lula equations to analyse the nonlinear stability of steady-state one-dimensional solutions for gaseous detonations in the presence of both momentum and heat losses. Our results point to a possible stabilization mechanism for the low-velocity detonations in such systems. The mechanism stems from the existence of a one-parameter family of solutions found in Semenko el al.

Strain components of nuclear-reactor-type concretes during first heat cycle

International Nuclear Information System (INIS)

Khoury, G.A.

1995-01-01

Strains of three advanced-gas-cooled-reactor-type nuclear reactor concretes were measured during the first heat cycle and their relative thermal stability determined. It was possible to isolate for the first time the shrinkage component for the period during heating. Predictions of the residual strains for the loaded specimens can be made by simple superposition of creep and shrinkage components up to a certain critical temperature, which for basalt concrete is about 500 C and for limestone concrete is about 200-300 C. Above the critical temperature, an expansive ''cracking'' strain component is present. It is shown that the strain behaviour of concrete provides a sensitive indication of its thermal stability during heating and subsequent cooling. (orig.)

Racetrack coil instability resulting from friction-heat generation at fixtures

International Nuclear Information System (INIS)

Yazawa, T.; Urata, M.; Chandratilleke, G.R.; Maeda, H.

1993-01-01

This paper describes racetrack coil instability resulting from friction-heat generation at fixtures and a preventive measure against it using a thermal barrier. Epoxy impregnated racetrack coils sometimes experience premature quenches due to frictional heat produced by coil slides at fixtures that are essential for the coil straight part to withstand the electromagnetic force. Experimentally, we confirmed for a small-sized racetrack coil that coil slides were actually occurring. The coil movements coupled with acoustic emissions were observed several times when the coil was energized. Each of them was about 10 μm, an equivalent of 20 mJ in frictional heat. This frictional heat was almost comparable with the analytical and experimental coil stability margins when an insulation layer was thin. One of the effective measures against the frictional heat is the thermal barrier, which is a thick insulation layer at the interface between the coil and the fixtures. By thickening the insulation layer from 0.36 to 1.00 mm, the coil stability margin increased from 100 to 200 mJ. (orig.)

Stability of nanofluids: Molecular dynamic approach and experimental study

International Nuclear Information System (INIS)

Farzaneh, H.; Behzadmehr, A.; Yaghoubi, M.; Samimi, A.; Sarvari, S.M.H.

2016-01-01

Highlights: • Nanofluid stability is investigated and discussed. • A molecular dynamic approach, considering different forces on the nanoparticles, is adopted. • Stability diagrams are presented for different thermo-fluid conditions. • An experimental investigation is carried out to confirm the theoretical approach. - Abstract: Nanofluids as volumetric absorbent in solar energy conversion devices or as working fluid in different heat exchangers have been proposed by various researchers. However, dispersion stability of nanofluids is an important issue that must be well addressed before any industrial applications. Conditions such as severe temperature gradient, high temperature of heat transfer fluid, nanoparticle mean diameters and types of nanoparticles and base fluid are among the most effective parameters on the stability of nanofluid. A molecular dynamic approach, considering kinetic energy of nanoparticles and DLVO potential energy between nanoparticles, is adopted to study the nanofluid stability for different nanofluids at different working conditions. Different forces such as Brownian, thermophoresis, drag and DLVO are considered to introduce the stability diagrams. The latter presents the conditions for which a nanofluid can be stable. In addition an experimental investigation is carried out to find a stable nanofluid and to show the validity of the theoretical approach. There is a good agreement between the experimental and theoretical results that confirms the validity of our theoretical approach.

Effects of heat, pH, antioxidant, agitation and light on betacyanin stability using red-fleshed dragon fruit (Hylocereus polyrhizus) juice and concentrate as models.

Science.gov (United States)

Wong, Yen-Ming; Siow, Lee-Fong

2015-05-01

Red-fleshed dragon fruit (Hylocereus polyrhizus) is rich in antioxidants. The aim of this study was to determine the effects of heat pasteurization, pH adjustment, ascorbic acid addition as well as storage under agitation and light or dark condition on betacyanin content in red-fleshed dragon fruit (Hylocereus polyrhizus) juice and concentrate. The concentrate was produced by concentrating clarified red-fleshed dragon fruit juice in a rotary evaporator at 40 °C. UV-Visible spectrophotometer was used for analyzing betacyanin content. Addition of 0.25 % ascorbic acid, pH 4.0, and pasteurization at 65 °C for 30 min were selected as the best processing conditions to retain betacyanin content in red-fleshed dragon fruit juice. Storage at the agitation speed of 220 rpm showed that the concentrated samples had higher betacyanin stability compared to juice, while both juice and concentrate had almost similar betacyanin stability when tested for storage in the presence of light. In summary, ascorbic acid stabilized betacyanin in both juice and concentrate at agitated or non-agitated conditions. In contrast, light degraded betacyanin in both juice and concentrate models.

Heat flux management via advanced magnetic divertor configurations and divertor detachment

Energy Technology Data Exchange (ETDEWEB)

Kolemen, E., E-mail: ekolemen@princeton.edu [Princeton University, Princeton, NJ 08544 (United States); Allen, S.L. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Bray, B.D. [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Fenstermacher, M.E. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Humphreys, D.A.; Hyatt, A.W. [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Lasnier, C.J. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Leonard, A.W. [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Makowski, M.A.; McLean, A.G. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Maingi, R.; Nazikian, R. [Princeton Plasma Physics Laboratory, Princeton, NJ 08543 (United States); Petrie, T.W. [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Soukhanovskii, V.A. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Unterberg, E.A. [Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831 (United States)

2015-08-15

The snowflake divertor (SFD) control and detachment control to manage the heat flux at the divertor are successfully demonstrated at DIII-D. Results of the development and implementation of these two heat flux reduction control methods are presented. The SFD control algorithm calculates the position of the two null-points in real-time and controls shaping coil currents to achieve and stabilize various snowflake configurations. Detachment control stabilizes the detachment front fixed at specified distance between the strike point and the X-point throughout the shot.

Heating and current drive requirements for ideal MHD stability and ITB sustainment in ITER steady state scenarios

Science.gov (United States)

Poli, Francesca

2012-10-01

Steady state scenarios envisaged for ITER aim at optimizing the bootstrap current, while maintaining sufficient confinement and stability to provide the necessary fusion yield. Non-inductive scenarios will need to operate with Internal Transport Barriers (ITBs) in order to reach adequate fusion gain at typical currents of 9 MA. However, the large pressure gradients associated with ITBs in regions of weak or negative magnetic shear can be conducive to ideal MHD instabilities in a wide range of βN, reducing the no-wall limit. Scenarios are established as relaxed flattop states with time-dependent transport simulations with TSC [1]. Fully non-inductive configurations with current in the range of 7-10 MA and various heating mixes (NB, EC, IC and LH) have been studied against variations of the pressure profile peaking and of the Greenwald fraction. It is found that stable equilibria have qmin> 2 and moderate ITBs at 2/3 of the minor radius [2]. The ExB flow shear from toroidal plasma rotation is expected to be low in ITER, with a major role in the ITB dynamics being played by magnetic geometry. Combinations of H&CD sources that maintain reverse or weak magnetic shear profiles throughout the discharge and ρ(qmin)>=0.5 are the focus of this work. The ITER EC upper launcher, designed for NTM control, can provide enough current drive off-axis to sustain moderate ITBs at mid-radius and maintain a non-inductive current of 8-9MA and H98>=1.5 with the day one heating mix. LH heating and current drive is effective in modifying the current profile off-axis, facilitating the formation of stronger ITBs in the rampup phase, their sustainment at larger radii and larger bootstrap fraction. The implications for steady state operation and fusion performance are discussed.[4pt] [1] Jardin S.C. et al, J. Comput. Phys. 66 (1986) 481[0pt] [2] Poli F.M. et al, Nucl. Fusion 52 (2012) 063027.

Comparative evaluation of bivalent malaria rapid diagnostic tests versus traditional methods in field with special reference to heat stability testing in Central India.

Directory of Open Access Journals (Sweden)

Neeru Singh

Full Text Available Malaria presents a diagnostic challenge in areas where both Plasmodium falciparum and P.vivax are co-endemic. Bivalent Rapid Diagnostic tests (RDTs showed promise as diagnostic tools for P.falciparum and P.vivax. To assist national malaria control programme in the selection of RDTs, commercially available seven malaria RDTs were evaluated in terms of their performance with special reference to heat stability.This study was undertaken in four forested districts of central India (July, 2011- March, 2012. All RDTs were tested simultaneously in field along with microscopy as gold standard. These RDTs were stored in their original packing at 25°C before transport to the field or they were stored at 35°C and 45°C upto 100 days for testing the performance of RDTs at high temperature. In all 2841 patients with fever were screened for malaria of which 26% were positive for P.falciparum, and 17% for P.vivax. The highest sensitivity of any RDT for P.falciparum was 98% (95% CI; 95.9-98.8 and lowest sensitivity was 76% (95% CI; 71.7-79.6. For P.vivax highest and lowest sensitivity for any RDT was 80% (95% CI; 94.9 - 83.9 and 20% (95% CI; 15.6-24.5 respectively. Heat stability experiments showed that most RDTs for P.falciparum showed high sensitivity at 45°C upto 90 days. While for P.vivax only two RDTs maintained good sensitivity upto day 90 when compared with RDTs kept at room temperature. Agreement between observers was excellent for positive and negative readings for both P.falciparum and P.vivax (Kappa >0.6-0.9.This is first field evaluation of RDTs regarding their temperature stability. Although RDTs are useful as diagnostic tool for P.falciparum and P.vivax even at high temperature, the quality of RDTs should be regulated and monitored more closely.

Vapor Compression and Thermoelectric Heat Pump Heat Exchangers for a Condensate Distillation System: Design and Experiment

Science.gov (United States)

Erickson, Lisa R.; Ungar, Eugene K.

2013-01-01

Maximizing the reuse of wastewater while minimizing the use of consumables is critical in long duration space exploration. One of the more promising methods of reclaiming urine is the distillation/condensation process used in the cascade distillation system (CDS). This system accepts a mixture of urine and toxic stabilizing agents, heats it to vaporize the water and condenses and cools the resulting water vapor. The CDS wastewater flow requires heating and its condensate flow requires cooling. Performing the heating and cooling processes separately requires two separate units, each of which would require large amounts of electrical power. By heating the wastewater and cooling the condensate in a single heat pump unit, mass, volume, and power efficiencies can be obtained. The present work describes and compares two competing heat pump methodologies that meet the needs of the CDS: 1) a series of mini compressor vapor compression cycles and 2) a thermoelectric heat exchanger. In the paper, the system level requirements are outlined, the designs of the two heat pumps are described in detail, and the results of heat pump performance tests are provided. A summary is provided of the heat pump mass, volume and power trades and a selection recommendation is made.

The physics of sawtooth stabilization

International Nuclear Information System (INIS)

Chapman, I T; Pinches, S D; Graves, J P; Akers, R J; Appel, L C; Budny, R V; Coda, S; Conway, N J; Bock, M de; Eriksson, L-G; Hastie, R J; Hender, T C; Huysmans, G T A; Johnson, T; Koslowski, H R; Kraemer-Flecken, A; Lennholm, M; Liang, Y; Saarelma, S; Sharapov, S E; Voitsekhovitch, I

2007-01-01

Long period sawteeth have been observed to result in low-β triggering of neo-classical tearing modes, which can significantly degrade plasma confinement. Consequently, a detailed physical understanding of sawtooth behaviour is critical, especially for ITER where fusion-born α particles are likely to lead to very long sawtooth periods. Many techniques have been developed to control, and in particular to destabilize the sawteeth. The application of counter-current neutral beam injection (NBI) in JET has resulted in shorter sawtooth periods than in Ohmic plasmas. This result has been explained because, firstly, the counter-passing fast ions give a destabilizing contribution to the n = 1 internal kink mode-which is accepted to be related to sawtooth oscillations-and secondly, the flow shear strongly influences the stabilizing trapped particles. A similar experimental result has been observed in counter-NBI heated plasmas in MAST. However, the strong toroidal flows in spherical tokamaks mean that the sawtooth behaviour is determined by the gyroscopic flow stabilization of the kink mode rather than kinetic effects. In NBI heated plasmas in smaller conventional aspect-ratio tokamaks, such as TEXTOR, the flow and kinetic effects compete to give different sawtooth behaviour. Other techniques applied to destabilize sawteeth are the application of electron cyclotron current drive (ECCD) or ion cyclotron resonance heating (ICRH). In JET, it has been observed that localized ICRH is able to destabilize sawteeth which were otherwise stabilized by a co-existing population of energetic trapped ions in the core. This is explained through the dual role of the ICRH in reducing the critical magnetic shear required to trigger a sawtooth crash, and the increase in the local magnetic shear which results from driving current near the q = 1 rational surface. Sawtooth control in ITER could be provided by a combination of ECCD and co-passing off-axis negative-NBI fast ions

Effect of triethanolamine on the stability of furfurol at elevated temperatures

Energy Technology Data Exchange (ETDEWEB)

Baiburskaya, E.L.; Kalenik, G.S.; Levchenko, E.S.; Martynenko, A.G.; Okhrimenko, N.V.; Shiryaeva, G.P.

1982-01-01

The effect of triethanolamine (I) on the stability of furfurol under the conditions of oil purification was studied. It was shown that (I) shows a stabilizing effect at a temperature of 200/sup 0/, which is considerably weakened on heating the furfurol in the presence of air (at atmospheric pressure). At a temperature of 230/sup 0/ (I) is not a stabilizer for furfurol.

Thermodynamic stability of asymptotically anti-de Sitter rotating black holes in higher dimensions

International Nuclear Information System (INIS)

Dolan, Brian P

2014-01-01

Conditions for thermodynamic stability of asymptotically anti-de Sitter (AdS) rotating black holes in D-dimensions are determined. Local thermodynamic stability requires not only positivity conditions on the specific heat and the moment of inertia tensor but it is also necessary that the adiabatic compressibility be positive. It is shown that, in the absence of a cosmological constant, neither rotation nor charge is sufficient to ensure full local thermodynamic stability of a black hole. Thermodynamic stability properties of AdS Myers–Perry black holes are investigated for both singly spinning and multi-spinning black holes. Simple expressions are obtained for the specific heat and moment of inertia tensor in any dimension. An analytic expression is obtained for the boundary of the region of parameter space in which such space-times are thermodynamically stable. (paper)

Study on the effect of shape-stabilized phase change materials on spacecraft thermal control in extreme thermal environment

International Nuclear Information System (INIS)

Wu, Wan-fan; Liu, Na; Cheng, Wen-long; Liu, Yi

2013-01-01

Highlights: ► A shape-stabilized PCM is used to protect the spacecraft attacked by high energy. ► Taking a satellite as example, it proves the solution given in the work is feasible. ► Low thermal conductivity makes the material above its thermal stability limit. ► It provides guidance on how to choose the shape-stabilized PCM for similar problems. - Abstract: In space, the emergencies such as short-term high heat flux is prone to cause spacecraft thermal control system faults, resulting in temperature anomalies of electronic equipment of the spacecraft and even failures in them. In order to protect the spacecraft attacked by the high energy, a new guard method is proposed. A shape-stabilized phase change material (PCM), which has high thermal conductivity and does not require being tightly packaged, is proposed to be used on the spacecraft. To prove the feasibility of using the material on spacecraft attacked by high energy, the thermal responses for spacecraft with shape-stabilized PCM are investigated in situations of normal and short-term high heat flux, in contrast to that with conventional thermal control system. The results indicate that the shape-stabilized PCM can effectively absorb the heat to prevent the thermal control system faults when the spacecraft’s outer heat flux changes dramatically and has no negative effect on spacecraft in normal heat flux. Additionally the effect of thermal conductivity of PCM on its application effectiveness is discussed

Electron-hole drop (EHD) stability in deformation potential well

International Nuclear Information System (INIS)

Makarov, A.G.; Tikhodeev, S.G.

1984-01-01

In heterogeneously-deformed Ge the stability of electron-hole droplets (EHD) being in a potential well is considered. It is shown that the potential well effect is equivalent to the decrease of effective density of phonon EHD charge. It is pointed out that heating EHD (for example, by IR radiation), can increase the phonon droplet charge and affect its stability

Lunar heat-flow experiment

Science.gov (United States)

Langseth, M. G.

1977-01-01

The principal components of the experiment were probes, each with twelve thermometers of exceptional accuracy and stability, that recorded temperature variations at the surface and in the regolith down to 2.5 m. The Apollo 15 experiment and the Apollo 17 probes recorded lunar surface and subsurface temperatures. These data provided a unique and valuable history of the interaction of solar energy with lunar surface and the effects of heat flowing from the deep interior out through the surface of the moon. The interpretation of these data resulted in a clearer definition of the thermal and mechanical properties of the upper two meters of lunar regolith, direct measurements of the gradient in mean temperature due to heat flow from the interior and a determination of the heat flow at the Apollo 15 and Apollo 17 sites.

Theory of Periodic Conjugate Heat Transfer

CERN Document Server

Zudin, Yuri B

2012-01-01

This book presents the theory of periodic conjugate heat transfer in a detailed way. The effects of thermophysical properties and geometry of a solid body on the commonly used and experimentally determined heat transfer coefficient are analytically presented from a general point of view. The main objective of the book is a simplified description of the interaction between a solid body and a fluid as a boundary value problem of the heat conduction equation for the solid body. At the body surface, the true heat transfer coefficient is composed of two parts: the true mean value resulting from the solution of the steady state heat transfer problem and a periodically variable part, the periodic time and length to describe the oscillatory hydrodynamic effects. The second edition is extended by (i) the analysis of stability boundaries in helium flow at supercritical conditions in a heated channel with respect to the interaction between a solid body and a fluid; (ii) a periodic model and a method of heat transfer sim...

Stability and thermophysical properties of azithromycin dihydrate

Directory of Open Access Journals (Sweden)

S. Timoumi

2014-04-01

Full Text Available The aim of this paper was to describe the temperature effect on the stability and the thermophysical properties of azithromycin (AZ. First, the density, the heat capacity and the solubility of original (commercial AZ were determined. Second, the original samples were heated at 50 °C and 80 °C and their PLM, DSC, TGA and XRD data were compared to those of the original AZ. According to our results, the original AZ was a dihydrate which converted to anhydrate when heated up to 80 °C. The dehydration induced a change of crystal habit while the crystalline lattice remained unchanged.

Propositional Optimal Trajectory Programming for Improving Stability ...

African Journals Online (AJOL)

Propositional Optimal Trajectory Programming for Improving Stability of Hermite Definite Control System. ... PROMOTING ACCESS TO AFRICAN RESEARCH. AFRICAN JOURNALS ONLINE (AJOL) ... Knowledge of systems operation subjected to heat diffusion constraints is required of systems analysts. In an instance that ...

Linear stability of liquid films with phase change at the interface

International Nuclear Information System (INIS)

Spindler, Bertrand

1980-01-01

The objective of this research thesis is to study the linear stability of the flow of a liquid film on an inclined plane with a heat flow on the wall and an interfacial phase change, and to highlight the influence of the phase change on the flow stability. In order to do so, the author first proposed a rational simplification of equations by studying the order of magnitude of different terms, and based on some simple hypotheses regarding flow physics. Two stability studies are then addressed, one regarding a flow with a pre-existing film, and the other regarding the flow of a condensation film. In both cases, it is assumed that there is no imposed heat flow, but that the driving effect of vapour by the liquid film is taken into account [fr

Design concept for vessels and heat exchangers

International Nuclear Information System (INIS)

Elfmann, W.; Ferrari, L.D.B.

1981-01-01

A design concept for vessels and heat exchangers against internal and external loads resulting from normal operation and accident is shown. A definition and explanation of the operating conditions and stress levels are given. A description of the type of analysis (stress, fatigue, deformation, stability, earthquake and vibration) is presented in detail, also including technical guidelines which are used for the vessels and heat exchangers and their individual structure parts. (Author) [pt

Stability and thermophysical properties of non-covalently functionalized graphene nanoplatelets nanofluids

International Nuclear Information System (INIS)

Sarsam, Wail Sami; Amiri, Ahmad; Kazi, S.N.; Badarudin, A.

2016-01-01

Highlights: • The prepared water-based pristine GNPs nanofluids in this research were not stable. • All the surfactants investigated, SDBS, GA, CTAB, and SDS, increased the viscosity. • Thermal conductivity of nanofluids enhanced in the presence of GA, SDBS, and CTAB. • Highest nanofluid stability was obtained using an ultrasonication time of 60 min. • (1–1) SDBS–GNPs nanofluid with 60 min ultrasonication showed the highest stability. - Abstract: A pioneering idea for increasing the thermal performance of heat transfer fluids was to use ultrafine solid particles suspended in the base fluid. Nanofluids, synthesized by mixing solid nanometer sized particles at low concentrations with the base fluid, were used as a new heat transfer fluid and developed a remarkable effect on the thermophysical properties and heat transfer coefficient. For any nanofluid to be usable in heat transfer applications, the main concern is its long-term stability. The aim of this research is to investigate the effect of using four different surfactants (sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), cetyl trimethylammonium bromide (CTAB), and gum Arabic (GA)), each with three different concentrations, and five ultrasonication times (15, 30, 60, 90, and 120 min) on the stability of water-based graphene nanoplatelets (GNPs) nanofluids. In addition, the viscosity and thermal conductivity of the highest stability samples were measured at different temperatures. For this aim, nineteen different nanofluids with 0.1 wt% concentration of GNPs were prepared via the two-step method. An ultrasonication probe was utilized to disperse the GNPs in distilled water. UV–vis spectrometry, zeta potential, average particle size, and Transmission Electron Microscopy (TEM) were helpful in evaluating the stability and characterizing the prepared nanofluids. TEM and zeta potential results were in agreement with the UV–vis measurements. The highest nanofluid stability was

Leaching and heating process as alternative to produce fish protein powder from Kilka (Clupeonella cultiventris caspia

Directory of Open Access Journals (Sweden)

KAVEH RAHMANIFARAH

2014-05-01

Full Text Available Rahmanifarah K, Shabanpour B, Shaviklo AR, Aalami M. 2014. Leaching and heating process as alternative to produce fish protein powder from Kilka (Clupeonella cultiventris caspia. Nusantara Bioscience 6: 1-6. The effect of protein extraction procedures (leached mince and heated suspension on selected properties of fish protein powder (proximate composition, pH, color, density, viscosity, fat adsorption, emulsifying capacity, emulsifying stability, foaming capacity, foaming stability, WBC, protein solubility in water, hygroscopicity, Trichloroacetic acid (TCA-soluble peptides and free sulfhydryl groups was investigated. Results showed that Fish protein powder (FPP produced by leaching mince (LM have higher protein, moisture, ash, pH, L*, viscosity, emulsion capacity, emulsion stability, foam capacity, foam stability, water binding capacity (WBC, protein solubility, hygroscopicity, TCA soluble peptides and free sulfhydryl group content than heated suspension (HS (P0.05. Overall, it was observed that high temperature during heating of suspension in HS method makes possible protein denaturation and aggregation. Consequently, based on functional, chemical and physical properties, extraction of fish protein by leaching process was found to be suitable for the production of fish protein powder.

Transient Thermal Stability of Polymer Nanocomposites

Science.gov (United States)

2012-08-01

modified Montmorillonite, Nanocor masterbatch ) 1 wt % carbon black (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2·nH2O Multiwalled Carbon Nanotubes (Nanocyl... masterbatch ) Twin screw extrusion (190C) Slow Heating Regime Thermogravimetric Analysis Nanospecies improve thermal stability as expected Laser

Chlorophyll loss associated with heat-induced senescence in bentgrass.

Science.gov (United States)

Jespersen, David; Zhang, Jing; Huang, Bingru

2016-08-01

Heat stress-induced leaf senescence is characterized by the loss of chlorophyll from leaf tissues. The objectives of this study were to examine genetic variations in the level of heat-induced leaf senescence in hybrids of colonial (Agrostis capillaris)×creeping bentgrass (Agrostis stolonifera) contrasting in heat tolerance, and determine whether loss of leaf chlorophyll during heat-induced leaf senescence was due to suppressed chlorophyll synthesis and/or accelerated chlorophyll degradation in the cool-season perennial grass species. Plants of two hybrid backcross genotypes ('ColxCB169' and 'ColxCB190') were exposed to heat stress (38/33°C, day/night) for 28 d in growth chambers. The analysis of turf quality, membrane stability, photochemical efficiency, and chlorophyll content demonstrated significant variations in the level of leaf senescence induced by heat stress between the two genotypes, with ColXCB169 exhibiting a lesser degree of decline in chlorophyll content, photochemical efficiency and membrane stability than ColXCB190. The assays of enzymatic activity or gene expression of several major chlorophyll-synthesizing (porphobilinogen deaminase, Mg-chelatase, protochlorophyllide-reductase) and chlorophyll-degrading enzymes (chlorophyllase, pheophytinase, and chlorophyll-degrading peroxidase) indicated heat-induced decline in leaf chlorophyll content was mainly due to accelerated chlorophyll degradation, as manifested by increased gene expression levels of chlorophyllase and pheophytinase, and the activity of pheophytinase (PPH), while chlorophyll-synthesizing genes and enzymatic activities were not differentially altered by heat stress in the two genotypes. The analysis of heat-induced leaf senescence of pph mutants of Arabidopsis further confirmed that PPH could be one enzymes that plays key roles in regulating heat-accelerated chlorophyll degradation. Further research on enzymes responsible in part for the loss of chlorophyll during heat

Studies on thermal properties and thermal control effectiveness of a new shape-stabilized phase change material with high thermal conductivity

International Nuclear Information System (INIS)

Cheng Wenlong; Liu Na; Wu Wanfan

2012-01-01

In order to overcome the difficulty of conventional phase change materials (PCMs) in packaging, the shape-stabilized PCMs are proposed to be used in the electronic device thermal control. However, the conventional shape-stabilized PCMs have the drawback of lower thermal conductivity, so a new shape-stabilized PCM with high thermal conductivity, which is suitable for thermal control of electronic devices, is prepared. The thermal properties of n-octadecane-based shape-stabilized PCM are tested and analyzed. The heat storage/release performance is studied by numerical simulation. Its thermal control effect for electronic devices is also discussed. The results show that the expanded graphite (EG) can greatly improve the thermal conductivity of the material with little effect on latent heat and phase change temperature. When the mass fraction of EG is 5%, thermal conductivity has reached 1.76 W/(m K), which is over 4 times than that of the original one. Moreover, the material has larger latent heat and good thermal stability. The simulation results show that the material can have good heat storage/release performance. The analysis of the effect of thermal parameters on thermal control effect for electronic devices provides references to the design of phase change thermal control unit. - Highlights: ► A new shape-stabilized PCM with higher thermal conductivity is prepared. ► The material overcomes the packaging difficulty of traditional PCMs used in thermal control unit. ► The EG greatly improves thermal conductivity with little effect on latent heat. ► The material has high thermal stability and good heat storage/release performance. ► The effectiveness of the material for electronic device thermal control is proved.

On thermal stability in incompressible slip flow

International Nuclear Information System (INIS)

Bestman, A.R.

1990-12-01

The paper considers the classical problem of the stability of a layer of fluid heated from below, but in the case when the density is low and there is slip flow at the bounding walls. The eigenvalue problem which ensures is tackled by taking cognisance of the orthogonality of Bessel function of the first kind. It is observed that the Rayleigh number for the onset of instability, for the case of marginal stability, is increased by gas rarefication. (author). 2 refs

Determination of the stability limit of a thermoacoustic engine by means of finite elements

NARCIS (Netherlands)

de Jong, Anne; Wijnant, Ysbrand H.; de Boer, Andries

2013-01-01

A finite element model is presented to obtain the stability limit of, as an example, 2D standing wave thermoacoustic engine. The stability limit is the required heating to obtain self-sustained (thermo)acoustic oscillations. The method used to obtain the stability limit is not restricted to the

Heat transfer from the moving heat source of arbitrary shape

International Nuclear Information System (INIS)

Fomin, Sergei A.

2000-01-01

The present research is related to contact melting by a moving heat source of arbitrary shape. Heat conduction in the melting material is governed by 3D differential equation, where the thermal conductivity of the surrounding material is assumed to be strongly temperature dependent. By using the Green's formula, the boundary-value problem is converted to the boundary integral equation. This non-linear equation is solved numerically by interactions utilizing the boundary element method. Different shapes of heat sources are investigated. Since the obtained integral equation is the Fredholm type equation of the first kind and belongs to the family of so-called ill-posed problems, therefore, supplementary computations, that verify the stability of numerical algorithm, are provided. For the special cases associated with thermodrilling technology, some analytical estimations and solutions are obtained. Particularly, if the melting velocity is high (Pe>10), asymptotic solutions are found. In this case the integral equation is significantly reduced, that simplifies the computations. Numerical results are in good agreement with the closed-form solutions available for the elliptical shape of a solid-liquid interface. (author)

Evaluation of Bacteriological Stability of Minced Canned Meat ...

African Journals Online (AJOL)

Evaluation of Bacteriological Stability of Minced Canned Meat Stored Under Simulated ... Thermal inactivation of spoilage microorganisms is one of the widely used ... of the aforesaid strains at 104-106 spores/g prior to the heat treatment.

Stability and quench of dual cooling channel cable-in-conduct superconductors

International Nuclear Information System (INIS)

Blau, Bertrand

1999-11-01

Presently, the most ambitious experimental project towards controlled thermonuclear fusion is the International Thermonuclear Experimental Reactor ITER. All coils of its magnet system will be superconducting since for magnetic fields in the range between 6 - 13 T high current densities are required. During recent years, in particular for fusion applications, a special configuration of superconductor was favoured: the so-called Cable-In-Conduit Conductor (CICC). The CICCs for ITER consist of a superconducting cable made of a large number of superconducting wires (NbTi or Nb 3 Sn) twisted around a central cooling channel, which are tightly jacketed in a metal conduit, providing the desired mechanical stiffness of the conductor against magnetic forces. Pressurized supercritical helium is pumped through the cable interstices and the central channel. The direct contact between the coolant and the cable provides good thermal stability of the conductor against sudden energy inputs. These disturbances can lead to a transition into the normal state (quench) if the released energy is sufficiently high, so that the temperature of the superconductor exceeds locally its critical temperature and if the energy cannot be absorbed efficiently by the surrounding helium. Stability of superconductors against quenches is one of the most important issues in applied superconductivity. The recovery capabilities of a CICC after thermal disturbances are governed by the heat transfer rate from the strands to the helium. The heat transfer is greatly affected by the flow velocity of the coolant. It has been shown theoretically that a temporal thermal disturbance in a CICC can induce an additional strong helium flow, which enhances the heat transfer rate and, hence, the stability. This self-stabilizing effect is believed to play an important role for the recovery capabilities of a CICC. The scope of this thesis is the experimental assessment of the quench and stability behaviour of dual cooling

Stability and quench of dual cooling channel cable-in-conduct superconductors

Energy Technology Data Exchange (ETDEWEB)

Blau, Bertrand [Ecole Polytechnique Federale de Lausanne, Centre de Recherches en Physique des Plasmas (CRPP), CH-1015 Lausanne (Switzerland)

1999-11-01

Presently, the most ambitious experimental project towards controlled thermonuclear fusion is the International Thermonuclear Experimental Reactor ITER. All coils of its magnet system will be superconducting since for magnetic fields in the range between 6 - 13 T high current densities are required. During recent years, in particular for fusion applications, a special configuration of superconductor was favoured: the so-called Cable-In-Conduit Conductor (CICC). The CICCs for ITER consist of a superconducting cable made of a large number of superconducting wires (NbTi or Nb{sub 3}Sn) twisted around a central cooling channel, which are tightly jacketed in a metal conduit, providing the desired mechanical stiffness of the conductor against magnetic forces. Pressurized supercritical helium is pumped through the cable interstices and the central channel. The direct contact between the coolant and the cable provides good thermal stability of the conductor against sudden energy inputs. These disturbances can lead to a transition into the normal state (quench) if the released energy is sufficiently high, so that the temperature of the superconductor exceeds locally its critical temperature and if the energy cannot be absorbed efficiently by the surrounding helium. Stability of superconductors against quenches is one of the most important issues in applied superconductivity. The recovery capabilities of a CICC after thermal disturbances are governed by the heat transfer rate from the strands to the helium. The heat transfer is greatly affected by the flow velocity of the coolant. It has been shown theoretically that a temporal thermal disturbance in a CICC can induce an additional strong helium flow, which enhances the heat transfer rate and, hence, the stability. This self-stabilizing effect is believed to play an important role for the recovery capabilities of a CICC. The scope of this thesis is the experimental assessment of the quench and stability behaviour of dual

Sawtooth stabilization by energetic trapped particles

International Nuclear Information System (INIS)

White, R.B.; Rutherford, P.H.; Colestock, P.; Bussac, M.N.

1988-03-01

Recent experiments involving high power radio-frequency heating of a tokamak plasma show strong suppression of the sawtooth oscillation. A high energy trapped particle population is shown to have a strong stabilizing effect on the internal resistive kink mode. Numerical calculations are in reasonable agreement with experiment. 13 refs., 2 figs

Electron heat transport studies using transient phenomena in ASDEX Upgrade

International Nuclear Information System (INIS)

Jacchia, A.; Angioni, C.; Manini, A.; Ryter, F.; Apostoliceanu, M.; Conway, G.; Fahrbach, H.-U.; Kirov, K.K.; Leuterer, F.; Reich, M.; Sutttrop, W.; Cirant, S.; Mantica, P.; De Luca, F.; Weiland, J.

2005-01-01

Experiments in tokamaks suggest that a critical gradient length may cause the resilient behavior of T e profiles, in the absence of ITBs. This agrees in general with ITG/TEM turbulence physics. Experiments in ASDEX Upgrade using modulation techniques with ECH and/or cold pulses demonstrate the existence of a threshold in R/L Te when T e >T i and T e ≤T i . For T e >T i linear stability analyses indicate that electron heat transport is dominated by TEM modes. They agree in the value of the threshold (both T e and n e ) and for the electron heat transport increase above the threshold. The stabilization of TEM modes by collisions yielded by gyro-kinetic calculations, which suggests a transition from TEM to ITG dominated transport at high collisionality, is experimentally demonstrated by comparing heat pulse and steady-state diffusivities. For the T e ∼T i discharges above the threshold the resilience, normalized by T e 3/2 , is similar to that of the TEM dominated cases, despite very different conditions. The heat pinch predicted by fluid modeling of ITG/TEM turbulence is investigated by perturbative transport in off-axis ECH-heated discharges. (author)

An ecofriendly graphene-based nanofluid for heat transfer applications

DEFF Research Database (Denmark)

Mehrali, Mohammad; Sadeghinezhad, Emad; Akhiani, Amir Reza

2016-01-01

including chemical stability, viscosity, wettability, electrical conductivity and thermal conductivity were investigated in a comprehensive manner. A significant thermal conductivity enhancement amounting to 45.1% was obtained for a volume fraction of 4%. In addition, the convective heat transfer...... that the generated nanofluid will open a new avenue in the pursuit of ecofriendly thermal conductors for heat transfer applications....... coefficient of the nanofluid in a laminar flow regime with uniform wall heat flux was investigated to estimate its cooling capabilities. These results, firmly confirm that the generated graphene-based nanofluid is a formidable transporter of heat and yet ecofriendly. Therefore, it's anticipate...

Single-phase convection heat transfer characteristics of pebble-bed channels with internal heat generation

International Nuclear Information System (INIS)

Meng Xianke; Sun Zhongning; Xu Guangzhan

2012-01-01

Graphical abstract: The core of the water-cooled pebble bed reactor is the porous channels which stacked with spherical fuel elements. The gaps between the adjacent fuel elements are complex because they are stochastic and often shift. We adopt electromagnetic induction heating method to overall heat the pebble bed. By comparing and analyzing the experimental data, we get the rule of power distribution and the rule of heat transfer coefficient with particle diameter, heat flux density, inlet temperature and working fluid's Re number. Highlights: ► We adopt electromagnetic induction heating method to overall heat the pebble bed to be the internal heat source. ► The ball diameter is smaller, the effect of the heat transfer is better. ► With Re number increasing, heat transfer coefficient is also increasing and eventually tends to stabilize. ► The changing of heat power makes little effect on the heat transfer coefficient of pebble bed channels. - Abstract: The reactor core of a water-cooled pebble bed reactor includes porous channels that are formed by spherical fuel elements. This structure has notably improved heat transfer. Due to the variability and randomness of the interstices in pebble bed channels, heat transfer is complex, and there are few studies regarding this topic. To study the heat transfer characters of pebble bed channels with internal heat sources, oxidized stainless steel spheres with diameters of 3 and 8 mm and carbon steel spheres with 8 mm diameters are used in a stacked pebble bed. Distilled water is used as a refrigerant for the experiments, and the electromagnetic induction heating method is used to heat the pebble bed. By comparing and analyzing the experimental results, we obtain the governing rules for the power distribution and the heat transfer coefficient with respect to particle diameter, heat flux density, inlet temperature and working fluid Re number. From fitting of the experimental data, we obtain the dimensionless average

High intensity heat pulse problem

International Nuclear Information System (INIS)

Yalamanchili, R.

1977-01-01

The use of finite-difference methods for the solution of partial differential equations is common in both design and research and development because of the advance of computers. The numerical methods for the unsteady heat diffusion equation received most attention not only because of heat transfer problems but also happened to be the basis for any study of parabolic partial differential equations. It is common to test the heat equation first even the methods developed for complex nonlinear parabolic partial differential equations arising in fluid mechanics or convective heat transfer. It is concluded that the finite-element method is conservative in both stability and monoscillation characteristics than the finite-difference method but not as conservative as the method of weighted-residuals. Since the finite-element is unique because of Gurtin's variational principle and numerous finite-differences can be constructed, it is found that some finite-difference schemes are better than the finite-element scheme in accuracy also. Therefore, further attention is focused here on finite-difference schemes only. Various physical problems are considered in the field of heat transfer. These include: numerous problems in steady and unsteady heat conduction; heat pulse problems, such as, plasma torch; problems arising from machining operations, such as, abrasive cut-off and surface grinding. (Auth.)

Numerical Simulation of Nanofluid Suspensions in a Geothermal Heat Exchanger

OpenAIRE

Xiao-Hui Sun; Hongbin Yan; Mehrdad Massoudi; Zhi-Hua Chen; Wei-Tao Wu

2018-01-01

It has been shown that using nanofluids as heat carrier fluids enhances the conductive and convective heat transfer of geothermal heat exchangers. In this paper, we study the stability of nanofluids in a geothermal exchanger by numerically simulating nanoparticle sedimentation during a shut-down process. The nanofluid suspension is modeled as a non-linear complex fluid; the nanoparticle migration is modeled by a particle flux model, which includes the effects of Brownian motion, gravity, turb...

Modification of heating system on HeaTiNG-02 test section of beta test loop

International Nuclear Information System (INIS)

Sagino; Dedy Haryanto; Riswan Djambiar; Edy Sumarno

2013-01-01

Modifications have been carried out on the heating test section heating-02 on the integration strand Beta Test (UUB). The activities carried out to overcome the obstacles that arise in the test section when used. Constraint that often arises is the fall of the heating source super chantal when it reaches a certain temperature. To mitigate the super chantal is initially converted into a horizontal vertical position. Change from vertical to horizontal position on super chantal aims to stabilize the position of super chantal, so it needs to be modified in the heating system. Modification activities include manufacturing, installation and testing of super chantal and refractory stone as super chantal support. Manufacturing refractory stone formation and assembly into the heater in accordance with design modifications that have been done in electromechanical workshop obtained using some machine tools. Testing results of fabrication has been done by providing voltage 110 volts until it reaches operating temperature 400°C. Test results obtained super chantal stable position when it reaches operating temperature, and heater of heating-02 test section feasible to be used for experiments. (author)

The pH-dependent thermal and storage stability of glycosylated caseinomacropeptide

DEFF Research Database (Denmark)

Siegert, Nadja; Tolkach, Alexander; Kulozik, Ulrich

2012-01-01

of gCMP is strongly influenced by pH. When the pH was decreased from 7 to 2, reduced stability was found even at low heating temperatures. Minimal destabilisation effects were found at neutral pH. Similar observations were found during storage of gCMP. Neu5Ac was released after six days of storage...... manufacturing gCMP can be modified due to processing. Processing conditions, which influence the degree of glycosylation of gCMP lead to alterations of bioactivity and techno-functional properties of gCMP and accordingly gCMP-containing products. Hence, gCMP was studied for its glycan stability during heat......, with a maximum release of 30% at pH 2. Acidic pH conditions were responsible for the hydrolysis of the glycans from the peptide backbone during heat treatment and storage....

Heat pipe solar receiver with thermal energy storage

Science.gov (United States)

Zimmerman, W. F.

1981-01-01

An HPSR Stirling engine generator system featuring latent heat thermal energy storge, excellent thermal stability and self regulating, effective thermal transport at low system delta T is described. The system was supported by component technology testing of heat pipes and of thermal storage and energy transport models which define the expected performance of the system. Preliminary and detailed design efforts were completed and manufacturing of HPSR components has begun.

Surface properties of heat-induced soluble soy protein aggregates of different molecular masses.

Science.gov (United States)

Guo, Fengxian; Xiong, Youling L; Qin, Fang; Jian, Huajun; Huang, Xiaolin; Chen, Jie

2015-02-01

Suspensions (2% and 5%, w/v) of soy protein isolate (SPI) were heated at 80, 90, or 100 °C for different time periods to produce soluble aggregates of different molecular sizes to investigate the relationship between particle size and surface properties (emulsions and foams). Soluble aggregates generated in these model systems were characterized by gel permeation chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Heat treatment increased surface hydrophobicity, induced SPI aggregation via hydrophobic interaction and disulfide bonds, and formed soluble aggregates of different sizes. Heating of 5% SPI always promoted large-size aggregate (LA; >1000 kDa) formation irrespective of temperature, whereas the aggregate size distribution in 2% SPI was temperature dependent: the LA fraction progressively rose with temperature (80→90→100 °C), corresponding to the attenuation of medium-size aggregates (MA; 670 to 1000 kDa) initially abundant at 80 °C. Heated SPI with abundant LA (>50%) promoted foam stability. LA also exhibited excellent emulsifying activity and stabilized emulsions by promoting the formation of small oil droplets covered with a thick interfacial protein layer. However, despite a similar influence on emulsion stability, MA enhanced foaming capacity but were less capable of stabilizing emulsions than LA. The functionality variation between heated SPI samples is clearly related to the distribution of aggregates that differ in molecular size and surface activity. The findings may encourage further research to develop functional SPI aggregates for various commercial applications. © 2015 Institute of Food Technologists®

Inlet throttling effect on the boiling two-phase flow stability in a natural circulation loop with a chimney

International Nuclear Information System (INIS)

Furuya, M.; Inada, F.; Yasuo, A.

2001-01-01

Experiments have been conducted to investigate an effect of inlet restriction on the thermal-hydraulic stability. A Test facility used in this study was designed and constructed to have non-dimensional values that are nearly equal to those of natural circulation BWR. Experimental results showed that driving force of the natural circulation at the stability boundary was described as a function of heat flux and inlet subcooling independent of inlet restriction. In order to extend experimental database regarding thermal-hydraulic stability to different inlet restriction, numerical analysis was carried out based on the homogeneous flow model. Stability maps in reference to the core inlet subcooling and heat flux were presented for various inlet restrictions using the above-mentioned function. Instability region during the inlet subcooling shifted to the higher inlet subcooling with increasing inlet restriction and became larger with increasing heat flux. (orig.)

System identification on two-phase flow stability

International Nuclear Information System (INIS)

Wu Shaorong; Zhang Youjie; Wang Dazhong; Bo Jinghai; Wang Fei

1996-01-01

The theoretical principle, experimental method and results of interrelation analysis identification for the instability of two-phase flow are described. A completely new concept of test technology and method on two-phase flow stability was developed by using he theory of information science on system stability and system identification for two-phase flow stability in thermo-physics field. Application of this method would make it possible to identify instability boundary of two-phase flow under stable operation conditions of two-phase flow system. The experiment was carried out on the thermohydraulic test system HRTL-5. Using reverse repeated pseudo-random sequences of heating power as input signal sources and flow rate as response function in the test, the two-phase flow stability and stability margin of the natural circulation system are investigated. The effectiveness and feasibility of identifying two-phase flow stability by using this system identification method were experimentally demonstrated. Basic data required for mathematics modeling of two-phase flow and analysis of two-phase flow stability were obtained, which are useful for analyzing, monitoring of the system operation condition, and forecasting of two-phase flow stability in engineering system

Characterization, thermal stability studies, and analytical method development of Paromomycin for formulation development.

Science.gov (United States)

Khan, Wahid; Kumar, Neeraj

2011-06-01

Paromomycin (PM) is an aminoglycoside antibiotic, first isolated in the 1950s, and approved in 2006 for treatment of visceral leishmaniasis. Although isolated six decades back, sufficient information essential for development of pharmaceutical formulation is not available for PM. The purpose of this paper was to determine thermal stability and development of new analytical method for formulation development of PM. PM was characterized by thermoanalytical (DSC, TGA, and HSM) and by spectroscopic (FTIR) techniques and these techniques were used to establish thermal stability of PM after heating PM at 100, 110, 120, and 130 °C for 24 h. Biological activity of these heated samples was also determined by microbiological assay. Subsequently, a simple, rapid and sensitive RP-HPLC method for quantitative determination of PM was developed using pre-column derivatization with 9-fluorenylmethyl chloroformate. The developed method was applied to estimate PM quantitatively in two parenteral dosage forms. PM was successfully characterized by various stated techniques. These techniques indicated stability of PM for heating up to 120 °C for 24 h, but when heated at 130 °C, PM is liable to degradation. This degradation is also observed in microbiological assay where PM lost ∼30% of its biological activity when heated at 130 °C for 24 h. New analytical method was developed for PM in the concentration range of 25-200 ng/ml with intra-day and inter-day variability of stability of PM was determined successfully. Developed analytical method was found sensitive, accurate, and precise for quantification of PM. Copyright © 2010 John Wiley & Sons, Ltd. Copyright © 2010 John Wiley & Sons, Ltd.

Quinoa starch granules as stabilizing particles for production of Pickering emulsions.

Science.gov (United States)

Rayner, Marilyn; Sjöö, Malin; Timgren, Anna; Dejmek, Petr

2012-01-01

Intact starch granules isolated from quinoa (Chenopodium quinoa Willd.) were used to stabilize emulsion drops in so-called Pickering emulsions. Miglyol 812 was used as dispersed phase and a phosphate buffer (pH7) with different salt (NaCl) concentrations was used as the continuous phase. The starch granules were hydrophobically modified to different degrees by octenyl succinic anhydride (OSA) or by dry heat treatment at 120 degrees C in order to study the effect on the resulting emulsion drop size. The degree of OSA-modification had a low to moderate impact on drop size. The highest level of modification (4.66%) showed the largest mean drop size, and lowest amount of free starch, which could be an effect of a higher degree of aggregation of the starch granules and, thereby, also the emulsion drops stabilized by them. The heat treated starch granules had a poor stabilizing ability and only the starch heated for the longest time (150 min at 120 degrees C) had a better emulsifying capacity than the un-modified native starch granules. The effect of salt concentration was rather limited. However, an increased concentration of salt slightly increased the mean drop size and the elastic modulus.

A highly stable microchannel heat sink for convective boiling

International Nuclear Information System (INIS)

Lu, Chun Ting; Pan Chin

2009-01-01

To develop a highly stable two-phase microchannel heat sink, we experimented with convective boiling in diverging, parallel microchannels with different distributions of laser-etched artificial nucleation sites. Each microchannel had a mean hydraulic diameter of 120 µm. The two-phase flow visualization and the magnitudes of pressure drop and inlet temperature oscillations under boiling conditions demonstrated clearly the merits of using artificial nucleation sites to further stabilize the flow boiling in diverging, parallel microchannels. The stability map showed the plane of subcooling number versus phase change number. It illustrated that diverging, parallel microchannels with artificial nucleation cavities have a much wider stable region than parallel microchannels with uniform cross-sections or diverging, parallel microchannels without artificial nucleation cavities. In addition, the results revealed that the design with cavities distributed uniformly along the downstream half of the channel presented the best stability performance among the three distributions of nucleation sites. This particular design can be regarded as a highly stable microchannel heat sink for convective boiling

Ground Source Heat Supply in Moscow Oblast: Temperature Potential and Sustainable Depth of Heat Wells

Science.gov (United States)

Vasil'ev, G. P.; Gornov, V. F.; Dmitriev, A. N.; Kolesova, M. V.; Yurchenko, V. A.

2018-01-01

The paper is devoted to a problem of increasing the efficiency of low-potential geothermal heat in heat pump systems of residential buildings the Moscow oblast of Russia, including Moscow. Estimates of a natural geothermal potential in the Moscow oblast (based on climatological data for the period from 1982 to 2011) are presented and a "Typical climatic year of natural soil temperature variations for the geoclimatic conditions of the Moscow oblast, including the city of Moscow" is proposed. Numerical simulation of the influence of geothermal energy potential and the depth of heat wells on the efficiency of ground source heat pump systems for the heat supply of residential buildings is carried out. Analysis of the numerical simulation showed that the operation of a heat pump system in a house heating mode under the geoclimatic conditions of the Moscow oblast leads to a temperature drop of the heat-exchange medium circulating through heat wells to 5-6°C by the end of the first 10 years of operation, and the process stabilizes by the 15th year of operation, and further changes in the heat-exchange medium temperature do not any longer significantly affect the temperature of the heat-exchange medium in the heat well. In this case, the exact dependence of the heat-exchange medium temperature drop on the depth is not revealed. Data on the economically expedient heat well depth for the conditions of the Moscow oblast ensuring a net present value for the whole residential building life cycle are presented. It is found that the heat well depth of 60 m can be considered as an endpoint for the Moscow oblast, and a further heat well deepening is economically impractical.

Thermal Stabilization FY 1999 blend plan

Energy Technology Data Exchange (ETDEWEB)

RISENMAY, H.R.

1999-02-23

This Blend Plan documents the alternate feed material items for the thermal stabilization process that will be used in place of the metal items that were originally planned to be processed. Problems with resolution of the safety basis for the metal items resulted in the decision to run material that already had an established safety basis. Various in process and scrap recovery items stored in gloveboxes, plutonium oxide and plutonium oxide mixed with uranium oxide stored in 2736-Z vaults will be processed through the stabilization furnaces until the safety basis for the metal items has been resolved. The purpose of thermal stabilization is to heat the material to 1000 degrees Celsius to drive off all volatile materials and leave the plutonium and/or uranium as oxides. The stabilized material will be sampled to determine the Loss On Ignition (LOI). The stabilized material must meet LOI of less than 0.5% to be acceptable for storage under DOE-STD-3013-94 specifications. Out of specification material will be recycled through the furnaces until the LOI limits are met.

Thermal Stabilization FY 1999 blend plan

International Nuclear Information System (INIS)

RISENMAY, H.R.

1999-01-01

This Blend Plan documents the alternate feed material items for the thermal stabilization process that will be used in place of the metal items that were originally planned to be processed. Problems with resolution of the safety basis for the metal items resulted in the decision to run material that already had an established safety basis. Various in process and scrap recovery items stored in gloveboxes, plutonium oxide and plutonium oxide mixed with uranium oxide stored in 2736-Z vaults will be processed through the stabilization furnaces until the safety basis for the metal items has been resolved. The purpose of thermal stabilization is to heat the material to 1000 degrees Celsius to drive off all volatile materials and leave the plutonium and/or uranium as oxides. The stabilized material will be sampled to determine the Loss On Ignition (LOI). The stabilized material must meet LOI of less than 0.5% to be acceptable for storage under DOE-STD-3013-94 specifications. Out of specification material will be recycled through the furnaces until the LOI limits are met

Thermal stabilization FY 1999 blend plan

International Nuclear Information System (INIS)

RISENMAY, H.R.

1999-01-01

This Blend Plan documents the alternate feed material items for the thermal stabilization process that will be used in place of the metal items that were originally planned to be processed. Problems with resolution of the safety basis for the metal items resulted in the decision to run material that already had an established safety basis. Various in process and scrap recovery items stored in gloveboxes, plutonium oxide and plutonium oxide mixed with uranium oxide stored in 2736-2 vaults will be processed through the stabilization furnaces until the safety basis for the metal items has been resolved. The purpose of thermal stabilization is to heat the material to 1000 degrees Celsius to drive off all volatile materials and leave the plutonium and/or uranium as oxides. The stabilized material will be sampled to determine the Loss On Ignition (LOI). The stabilized material must meet LOI of less than 0.5% to be acceptable for storage under DOE-STD-3013-94 specifications. Out of specification material will be recycled through the furnaces until the LOI limits are met

Thermal stabilization FY 1999 blend plan

Energy Technology Data Exchange (ETDEWEB)

RISENMAY, H.R.

1999-06-01

This Blend Plan documents the alternate feed material items for the thermal stabilization process that will be used in place of the metal items that were originally planned to be processed. Problems with resolution of the safety basis for the metal items resulted in the decision to run material that already had an established safety basis. Various in process and scrap recovery items stored in gloveboxes, plutonium oxide and plutonium oxide mixed with uranium oxide stored in 2736-2 vaults will be processed through the stabilization furnaces until the safety basis for the metal items has been resolved. The purpose of thermal stabilization is to heat the material to 1000 degrees Celsius to drive off all volatile materials and leave the plutonium and/or uranium as oxides. The stabilized material will be sampled to determine the Loss On Ignition (LOI). The stabilized material must meet LOI of less than 0.5% to be acceptable for storage under DOE-STD-3013-94 specifications. Out of specification material will be recycled through the furnaces until the LOI limits are met.

Stability Analysis for Car Following Model Based on Control Theory

International Nuclear Information System (INIS)

Meng Xiang-Pei; Li Zhi-Peng; Ge Hong-Xia

2014-01-01

Stability analysis is one of the key issues in car-following theory. The stability analysis with Lyapunov function for the two velocity difference car-following model (for short, TVDM) is conducted and the control method to suppress traffic congestion is introduced. Numerical simulations are given and results are consistent with the theoretical analysis. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

HEATING-7, Multidimensional Finite-Difference Heat Conduction Analysis

International Nuclear Information System (INIS)

2000-01-01

problems, surface fluxes may be plotted with H7TECPLOT which requires the proprietary software TECPLOT. HEATING 7.3 runs under Windows95 and WindowsNT on PC's. No future modifications are planned for HEATING7. See README.1ST for more information. 2 - Method of solution: Three steady-state solution techniques are available: point-successive over-relaxation iterative method with extrapolation, direct-solution (for one-dimensional or two-dimensional problems), and conjugate gradient. Transient problems may be solved using any one of several finite-difference schemes: Crank-Nicolson implicit, Classical Implicit Procedure (CIP), Classical Explicit Procedure (CEP), or Levy explicit method (which for some circumstances allows a time step greater than the CEP stability criterion.) The solution of the system of equations arising from the implicit techniques is accomplished by point-successive over-relaxation iteration and includes procedures to estimate the optimum acceleration parameter. 3 - Restrictions on the complexity of the problem: All surfaces in a model must be parallel to one of the coordinate axes which makes modeling complex geometries difficult. Transient change of phase problems can only be solved with one of the explicit techniques - an implicit change-of-phase capability has not been implemented

CsPbBr3 QD/AlOx Inorganic Nanocomposites with Exceptional Stability in Water, Light, and Heat.

Science.gov (United States)

Loiudice, Anna; Saris, Seryio; Oveisi, Emad; Alexander, Duncan T L; Buonsanti, Raffaella

2017-08-28

Herein, the assembly of CsPbBr 3 QD/AlO x inorganic nanocomposites, by using atomic layer deposition (ALD) for the growth of the amorphous alumina matrix (AlO x ), is described as a novel protection scheme for such QDs. The nucleation and growth of AlO x on the QD surface was thoroughly investigated by miscellaneous techniques, which highlighted the importance of the interaction between the ALD precursors and the QD surface to uniformly coat the QDs while preserving the optoelectronic properties. These nanocomposites show exceptional stability towards exposure to air (for at least 45 days), irradiation under simulated solar spectrum conditions (for at least 8 h), and heat (up to 200 °C in air), and finally upon immersion in water. This method was extended to the assembly of CsPbBr x I 3-x QD/AlO x and CsPbI 3 QD/AlO x nanocomposites, which were more stable than the pristine QD films. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of supplementary glycerin on milk composition and heat stability in dairy goats

Directory of Open Access Journals (Sweden)

Deela Thoh

2017-12-01

Full Text Available Objective This experiment was studied the effects of various levels of crude glycerin (CG in dairy goat diet on daily intake, milk yield, milk composition, some physical properties and some quality changes of goat milk after sterilization. Methods Twelve 75% Saanen dairy goats (body weight = 49±3 kg; days in milk = 60±12 d were randomly assigned in a completely randomized design to evaluate the effects of three experimental diets consisting of 0%, 5%, and 10% CG (dry matter basis which were formulated to meet or exceed the nutrient requirements of goats. Experimental dairy goats were evaluated for feed and milk yield. Milk samples were analyzed for their composition, including fatty acids, casein profile, fat globule size, and color, and were sterilized to evaluate milk heat stability. Results There were no significant differences between 0% and 5% CG treatments infeed. Increasing CG supplementation from 0% to 5% increased milk yield from 2.38±0.12 to 2.64±0.23 kg/goat/d. In addition, milk samples from 5% CG treatment had the highest total solids, fat content and lactose content, and largest fat globule size. Increasing CG to 10% resulted in a decrease in milk fat. After sterilizing at 116°C, F0 = 3 min, goat milk samples from 5% CG treatment had slightly higher sediment content and comparatively higher degree of browning. Conclusion Considering milk yield, milk fat content and quality of sterilized milk, 5% CG supplementation in a total mixed ration has a potential for implementation in dairy goats.

THERMOOXIDATIVE STABILITY OF JET FUEL WITH FULLERENES AS AN ADDITIVE

Directory of Open Access Journals (Sweden)

С.В. Іванов

2012-10-01

Full Text Available  Heating of fuels in presence of oxygen reduces their thermal-oxidative stability, leads to a solid phase in the form of sludge and tar, which, sedimented at the details of the fuel system, change its characteristics and cause contamination of fuel filters and injectors, spool control sticking, reduce efficiency of heat exchangers. Nanomaterials, performance of which is considerably superior to the natural materials, are the basis for the movement of humanity's progress. Therefore, with a develpoment of technologies it has become necessary to carry out a research of modified additives – fullerens, to improve an oxidative stability of fuels. We have carried out an investigation of thermal-oxidative stability of fuel RT as a function of additive C60 concentration. The results has shown that even 0,043 g/l fullerene addition as an antioxidant, reduces the amount of sediment in the fuel almost by half. Usage of fullerenes for improvement of petroleum products performance properties is a promising area of research.

Insert Tidal Here: Finding Stability of Galilean Satellite Interiors

Science.gov (United States)

Walker, M.; Bills, B. G.; Mitchell, J.; Rhoden, A.

2017-12-01

The tidal environment is often hypothesized as a cause of surface expression in the satellites of the outer solar system. In two notable cases, Io's volcanism is thought to be driven by tidal heating of its mantle while the shattered surface of Europa's ice shell is said to be generated by tidal stresses in that ice. Being adjacent moons of Jupiter, these satellites give us a unique opportunity to apply a single set of general coupled models at each body to predict how one model can predict the heat generation and flow, strain and stress states, and structural parameters for each body. We include the effects of interior evolution into the tidal environment in addition to an evolving orbit. We find that the interiors of Io and Europa will evolve, as a consequence of the heat transfer from interior to surface, and stable structural and heat flow conditions are found. Then as their orbits evolve, perturbed by the mutual interactions of the Laplace mean motion resonance, those conditions of structural and heat stability also change. In particular, we find that at current orbital conditions there is sufficient heat to completely melt Io models for which a convecting interior is capped by a conducting lid. This argues for the presence of a non dissipating (or barely dissipating) core below the mantle, which future Io structure models should include. For the Europa model at current orbit, we use a silicate interior under an ocean capped by a two layer ice; convecting below with a conducting surface. We find stability in heat and structure occurs when the lower ice melts and recedes until the shell is roughly 50km thick. We present a variety of plausible structures for these bodies, and track how the stability of those structures trend as the orbit (in particular the orbital eccentricity, mean motion, and obliquity) change. We show how the Love numbers, layer thicknesses, surface heat flow, and orbital parameters are all linked. For Europa, upcoming measurements from

Absorption Cycle Heat Pump Model for Control Design

DEFF Research Database (Denmark)

Vinther, Kasper; Just Nielsen, Rene; Nielsen, Kirsten Mølgaard

2015-01-01

Heat pumps have recently received increasing interest due to green energy initiatives and increasing energy prices. In this paper, a nonlinear dynamic model of a single-effect LiBr-water absorption cycle heat pump is derived for simulation and control design purposes. The model is based on an act......Heat pumps have recently received increasing interest due to green energy initiatives and increasing energy prices. In this paper, a nonlinear dynamic model of a single-effect LiBr-water absorption cycle heat pump is derived for simulation and control design purposes. The model is based...... to operational data and different scenarios are simulated to investigate the operational stability of the heat pump. Finally, this paper provides suggestions and examples of derivation of lower order linear models for control design. © Copyright IEEE - All rights reserved....

Stability of High Temperature Standard Platinum Resistance Thermometers at High Temperatures

Directory of Open Access Journals (Sweden)

Y. A. ABDELAZIZ

2010-05-01

Full Text Available An investigation of the stability of high temperature standard platinum resistance thermometers HTSPRTs has been carried out for two different designs thermometers (with nominal resistance 0.25 Ω and 2.5 Ω from two different suppliers. The thermometers were heated for more than 160 hours at temperatures above 960 0C using a vertical furnace with a ceramic block. A study was made of the influence of the heat treatment on the stability of the resistance at the triple point of water, and on the relative resistance W(Ga at the melting point of gallium. The thermometers showed a correlation between the drift note and the values of W(Ga. It was found also that the HTSPRT which has a sensor with strip shaped support and low nominal resistance is more stable than the HTSPRT which has a sensor in the form of a coil wound on silica cross. The 0.25 Ω thermometer has better stability @ 7x10-6 0C (at TPW after 40 hour. Factors affecting the stability and accuracy of HTSPRT also will be discussed.

Thermal stability of hexagonal OsB2

International Nuclear Information System (INIS)

Xie, Zhilin; Blair, Richard G.; Orlovskaya, Nina; Cullen, David A.; Andrew Payzant, E.

2014-01-01

The synthesis of novel hexagonal ReB 2 -type OsB 2 ceramic powder was performed by high energy ball milling of elemental Os and B powders. Two different sources of B powder have been used for this mechanochemical synthesis. One B powder consisted of a mixture of amorphous and crystalline phases and a mixture of 10 B and 11 B isotopes with a fine particle size, while another B powder was a purely crystalline (rhombohedral) material consisting of enriched 11 B isotope with coarse particle size. The same Os powder was used for the synthesis in both cases. It was established that, in the first case, the hexagonal OsB 2 phase was the main product of synthesis with a small quantity of Os 2 B 3 phase present after synthesis as an intermediate product. In the second case, where coarse crystalline 11 B powder was used as a raw material, only Os 2 B 3 boride was synthesized mechanochemically. The thermal stability of hexagonal OsB 2 powder was studied by heating under argon up to 876 °C and cooling in vacuo down to −225 °C. During the heating, the sacrificial reaction 2OsB 2 +3O 2 →2Os+2B 2 O 3 took place due to presence of O 2 /water vapor molecules in the heating chamber, resulting in the oxidation of B atoms and formation of B 2 O 3 and precipitation of Os metal out of the OsB 2 lattice. As a result of such phase changes during heating, the lattice parameters of hexagonal OsB 2 changed significantly. The shrinkage of the a lattice parameter was recorded in 276–426 °C temperature range upon heating, which was attributed to the removal of B atoms from the OsB 2 lattice due to oxidation followed by the precipitation of Os atoms and formation of Os metal. While significant structural changes occurred upon heating due to presence of O 2 , the hexagonal OsB 2 ceramic demonstrated good phase stability upon cooling in vacuo with linear shrinkage of the lattice parameters and no phase changes detected during cooling. - Graphical abstract: The in situ high temperature XRD

The effect of heat transfer on acoustics in burner stabilized flat flames

OpenAIRE

Schreel, K.R.A.M.; Tillaart, van den, E.L.; Janssen, R.W.M.; Goey, de, L.P.H.; Vovelle, C.; Lucka, K.

2003-01-01

Modern central heating systems use low NO$_x$ premixed burners with a large modulation range. This can lead to noise problems which cannot be solved via trial and error, but need accurate modelling. An acoustic analysis as part of the design phase can reduce the time-to-market considerably, but the acoustic response of the flame is an unknown and complex key-factor. In this study, the influence of the heat transfer between the gas and the burner on the acoustic transfer coefficient is studied...

Stability test for a parabolic partial differential equation

NARCIS (Netherlands)

Vajta, Miklos

2001-01-01

The paper describes a stability test applied to coupled parabolic partial differential equations. The PDE's describe the temperature distribution of composite structures with linear inner heat sources. The distributed transfer functions are developed based on the transmission matrix of each layer.

Investigations on hydrodynamic stability of two phase flow in a low pressure natural circulation system

Energy Technology Data Exchange (ETDEWEB)

Shaorong, Wu; Dazhong, Wang; Meisheng, Yao; Jinhai, Bo; Yunxian, Tong; Shengyao, Jiang; Bing, Han [Institute of Nuclear Energy and Technology, Tsingua Univ., Beijing (China)

1997-09-01

Appropriately scaled ``Loop Stability`` tests and ``Channel Stability`` tests were performed with single heated channel system and two parallel channel system separately at the Institute of Nuclear Energy Technology (INET) of the Tsinghua University in China. A broad range of several operational parameters such as heating power, system pressure, test inlet subcooling and resistance coefficient were investigated. It was found that under certain geometric conditions and operating parameters a self-sustaining, low frequency, even amplitude mass flow oscillation may be excited at very low steam qualities and subcooling conditions. Stability maps under different conditions have been provided to assist the design of the NHR. (author). 6 refs, 15 figs.

Heat transfer in pool boiling liquid neon, deuterium and hydrogen, and critical heat flux in forced convection of liquid neon

International Nuclear Information System (INIS)

Astruc, J.M.

1967-12-01

In the first part, free-convection and nucleate pool boiling heat transfer (up to burn-out heat flux) between a platinum wire of 0.15 mm in diameter in neon, deuterium and hydrogen has been studied at atmospheric pressure. These measurements were continued in liquid neon up to 23 bars (Pc ≅ 26.8 b). Film boiling heat transfer coefficients have been measured in pool boiling liquid neon at atmospheric pressure with three heating wires (diameters 0.2, 0.5, 2 mm). All the results have been compared with existing correlations. The second part is devoted to measurements of the critical heat flux limiting heat transfer with small temperature differences between the wall and the liquid neon flowing inside a tube (diameters 3 x 3.5 mm) heated by joule effect on 30 cm of length. Influences of flow stability, nature of electrical current, pressure, mass flow rate and subcooling are shown. In conclusion, the similarity of the heat transfer characteristics in pool boiling as well as in forced convection of liquid neon and hydrogen is emphasized. (author) [fr

Effect of electron irradiation and heat on the structure of hairtail surimi

International Nuclear Information System (INIS)

Lin, Xianping; Yang, Wenge; Xu, Dalun; Wang, Lili

2015-01-01

Hairtail surimi was treated with electron radiation and heat, the chemical interactions, thermal properties and the structural changes were determined. The chemical interaction data indicate that the contribution of disulfide bonds to heat-induced gel formation was decisive. Irradiation promoted the formation of disulfide bonds during the cooking. Differential scanning calorimetry showed that the myosin and actin thermal transitions of irradiated surimi shifted to lower temperatures. And the myosin thermal stability of irradiated surimi was lower than unirradiated surimi. The Fourier transform infrared and Raman results showed the irradiation and heat treatments decreased the α-helix structure content and increased β-sheet structure content. This study may provide useful information for the effect of irradiation on the surimi gel properties. - Highlights: • The effects of irradiation and heat on surimi structure were investigated. • Disulfide bonds were the main chemical interaction of heat-induced gel. • The myosin thermal stability of irradiated surimi was lower than unirradiated surimi. • The decrease in α-helix structure and increase in β-sheet structure were observed

EFFECTS OF VARIOUS STABILIZATION TECHNIQUES ON THE NUTRITIONAL QUALITY AND ANTIOXIDANT POTENTIAL OF BREWER’S RICE

Directory of Open Access Journals (Sweden)

NIK NOR ADILAH MUHAMAD NORDIN

2014-06-01

Full Text Available Brewer’s rice is a nutritionally rich by-product of rice milling industries but remained unutilized due to its high susceptibility to lipid oxidation. Thus, it is desirable to develop certain strategies to stabilize the brewer’s rice for food application. In the present study, the effects of microwave heating, gamma irradiation, and chemical (hydrochloric acid treatments in stabilizing brewer’s rice were investigated. Result showed that microwave-heated brewer’s rice contained lower FFA content as compared with control and irradiation. However, FFA content in brewer’s rice increased significantly (p < 0.05 during storage for all methods, except for hydrochloric acid (HCl treatment. All the stabilizations methods showed non-significant (p < 0.05 effect on protein, fat, and ash content. However, microwave and chemical treatment significantly (p < 0.05 reduced moisture content. All methods showed no significant (p < 0.05 reduction on phenolic contents but significantly (p < 0.05 reduced the γ-oryzanol and α-tocopherol contents. Microwave heating was able to reduce the oxidation of brewer’s rice without affecting other bioactive molecules present in brewer’s rice. Therefore, microwave heating can be considered as the most suitable technique for stabilizing brewer’s rice.

A stabilized second-order time accurate finite element formulation for incompressible viscous flow with heat transfer; Uma formulacao de elementos finitos estabilizada de segunda ordem no tempo para escoamentos viscosos com transferencia de calor

Energy Technology Data Exchange (ETDEWEB)

Curi, Marcos Filardy

2011-07-01

In view of the problem of global warming and the search for clean energy sources, a worldwide expansion on the use of nuclear energy is foreseen. Thus, the development of science and technology regarding nuclear power plants is essential, in particular in the field of reactor engineering. Fluid mechanics and heat transfer play an important role in the development of nuclear reactors. Computational Fluid Mechanics (CFD) is becoming ever more important in the optimization of cost and safety of the designs. This work presents a stabilized second-order time accurate finite element formulation for incompressible flows with heat transfer. A second order time discretization precedes a spatial discretization using finite elements. The terms that stabilize the finite element method arise naturally from the discretization process, rather than being introduced a priori in the variational formulation. The method was implemented in the program 'ns{sub n}ew{sub s}olvec2d{sub av}2{sub M}PI' written in FORTRAN90, developed in the Parallel Computing Laboratory at the Institute of Nuclear Engineering (LCP/IEN). Numerical solutions of some representative examples, including free, mixed and forced convection, demonstrate that the proposed stabilized formulation attains very good agreement with experimental and computational results available in the literature. (author)

Effects of heat treatment on density, dimensional stability and color ...

African Journals Online (AJOL)

The purpose of this study was to evaluate the effect of heat treatment on some physical properties and color change of Pinus nigra wood which has high industrial use potential and large growing stocks in Turkey. Wood samples which comprised the material of the study were obtained from an industrial plant. Samples were ...

On the merits of heating and current drive for tearing mode stabilization

International Nuclear Information System (INIS)

De Lazzari, D.; Westerhof, E.

2009-01-01

Neoclassical tearing modes (NTMs) are magnetohydrodynamic modes that can limit the performance of high β discharges in a tokamak, leading eventually to a plasma disruption. A NTM is sustained by the perturbation of the 'bootstrap' current, which is a consequence of the pressure flattening across a magnetic island. Control and suppression of this mode can be achieved by means of electron cyclotron waves (ECWs) which allow the deposition of highly localized power at the island location. The ECW power replenishes the missing bootstrap current by generating a current perturbation either inductively, through a temperature perturbation (electron cyclotron resonance heating), or non-inductively by direct current drive (electron cyclotron current drive). Although both methods have been applied successfully to experiments showing a predominance of ECRH for medium-sized limiter tokamaks (TEXTOR, T-10) and of ECCD for mid-to-large-sized divertor tokamaks (AUG, DIII-D, JT-60), conditions determining their relative importance are still unclear. We address this problem with a numerical study focused on the contributions of heating and current drive to the temporal evolution of NTMs as described by the modified Rutherford equation. For the effects of both heating as well as current drive, simple analytical expressions have been found in terms of an efficiency fore-factor times a 'geometrical' term depending on the power deposition width w dep , location and modulation. When the magnetic island width w equals the width of the deposition profile, w ∼ w dep , both geometric terms are practically identical. Whereas for current drive the geometric term approaches a constant for small island widths and is inversely proportional to (w/w dep ) 2 for large island widths, the heating term approaches a constant for large island widths and is proportional to (w/w dep ) for small island widths. For medium-sized tokamaks (TEXTOR, AUG) the heating and current drive efficiencies are of the

A phenomenological explanation for the anomalous ion heating observed in the JET alpha-heating experiment of 1997

Science.gov (United States)

Testa, D.; Albergante, M.

2012-08-01

In the so-called ‘alpha-heating’ experiment performed on the JET tokamak during the deuterium-tritium campaign of 1997, the ion temperature was found to be far exceeding (both in absolute value and in its rise time) the level that could have been expected from direct collisional heating by the fusion-born alpha particles themselves and energy equipartition with the electrons. To date, no explanation has been put forward for this long standing puzzle, despite much work having been performed on this subject in the early 2000s. Two analysis methods that have recently become available have been employed to re-analyse these observations of an anomalous ion heating. First, an algorithm based on the sparse representation of signals has been used to analyse magnetic, reflectometry and electron-cyclotron emission measurements of the turbulence spectra in the drift-wave range of frequencies. This analysis has then been complemented with turbulence simulations performed with the GENE code. We find, both experimentally and in the simulations, that the presence of a minority, but sufficiently large, population of fusion-born alpha particles that have not yet fully thermalized stabilizes the turbulence in the ion-drift direction, but practically does not affect the turbulence in the electron-drift direction. We link such stabilization of the ion-drift-wave turbulence to the increase in the ion temperature above the level achieved in similar discharges that did not have (at all or enough) alpha particles. When the fusion-born alpha particles have fully thermalized, the turbulence spectrum in the ion-drift direction reappears at somewhat larger amplitudes, which we link to the ensuing reduction in the ion temperature. This phenomenological dynamics fully corresponds to the actual experimental observations. By taking into account an effect of the alpha particles that had not been previously considered, our new analysis finally presents a phenomenological explanation for the so

A phenomenological explanation for the anomalous ion heating observed in the JET alpha-heating experiment of 1997

International Nuclear Information System (INIS)

Testa, D.; Albergante, M.

2012-01-01

In the so-called ‘alpha-heating’ experiment performed on the JET tokamak during the deuterium–tritium campaign of 1997, the ion temperature was found to be far exceeding (both in absolute value and in its rise time) the level that could have been expected from direct collisional heating by the fusion-born alpha particles themselves and energy equipartition with the electrons. To date, no explanation has been put forward for this long standing puzzle, despite much work having been performed on this subject in the early 2000s. Two analysis methods that have recently become available have been employed to re-analyse these observations of an anomalous ion heating. First, an algorithm based on the sparse representation of signals has been used to analyse magnetic, reflectometry and electron-cyclotron emission measurements of the turbulence spectra in the drift-wave range of frequencies. This analysis has then been complemented with turbulence simulations performed with the GENE code. We find, both experimentally and in the simulations, that the presence of a minority, but sufficiently large, population of fusion-born alpha particles that have not yet fully thermalized stabilizes the turbulence in the ion-drift direction, but practically does not affect the turbulence in the electron-drift direction. We link such stabilization of the ion-drift-wave turbulence to the increase in the ion temperature above the level achieved in similar discharges that did not have (at all or enough) alpha particles. When the fusion-born alpha particles have fully thermalized, the turbulence spectrum in the ion-drift direction reappears at somewhat larger amplitudes, which we link to the ensuing reduction in the ion temperature. This phenomenological dynamics fully corresponds to the actual experimental observations. By taking into account an effect of the alpha particles that had not been previously considered, our new analysis finally presents a phenomenological explanation for the

Diffusive heat transport across magnetic islands and stochastic layers in tokamaks

International Nuclear Information System (INIS)

Hoelzl, Matthias

2010-01-01

Heat transport in tokamak plasmas with magnetic islands and ergodic field lines was simulated at realistic plasma parameters in realistic tokamak geometries. This requires the treatment of anisotropic heat diffusion, which is more efficient along magnetic field lines by up to ten orders of magnitude than perpendicular to them. Comparisons with analytical predictions and experimental measurements allow to determine the stability properties of neoclassical tearing modes as well as the experimental heat diffusion anisotropy.

Stability of Microturbulent Drift Modes during Internal Transport Barrier Formation in the Alcator C-Mod Radio Frequency Heated H-mode

International Nuclear Information System (INIS)

Redi, M.H.; Fiore, C.L.; Dorland, W.; Mikkelsen, D.R.; Rewoldt, G.; Bonoli, P.T.; Ernst, D.R.; Rice, J.E.; Wukitch, S.J.

2003-01-01

Recent H-mode experiments on Alcator C-Mod [I.H. Hutchinson, et al., Phys. Plasmas 1 (1994) 1511] which exhibit an internal transport barrier (ITB), have been examined with flux tube geometry gyrokinetic simulations, using the massively parallel code GS2 [M. Kotschenreuther, G. Rewoldt, and W.M. Tang, Comput. Phys. Commun. 88 (1995) 128]. The simulations support the picture of ion/electron temperature gradient (ITG/ETG) microturbulence driving high xi/ xe and that suppressed ITG causes reduced particle transport and improved ci on C-Mod. Nonlinear calculations for C-Mod confirm initial linear simulations, which predicted ITG stability in the barrier region just before ITB formation, without invoking E x B shear suppression of turbulence. Nonlinear fluxes are compared to experiment, which both show low heat transport in the ITB and higher transport within and outside of the barrier region

Effect of SiO2 addition in the zirconia stabilization

International Nuclear Information System (INIS)

Pessoa, R.C.; Lima, U.R.; Nasar, M.C.; Nasar, R.S.; Yoshida, I.V.P.; Acchar, W.

2006-01-01

The aims of this work was investigated the zirconia stabilization with a mixture of resins based on silico nas promoting the Zr O 2 /Si O 2 formation. The powder was heated and characterized by TGA, DTA, FTIR, XRD and SEM/EDS. The results indicated the tetragonal and cubic phase formation stabilized at 1000 deg C/2 h. The increase of calcing temperature promoted decrease of stabilization. The amorphous silica calcined at 1000 deg C induced defects into the zirconia structure and favour the formation of more stable phases. The decrease of stabilization at high temperatures are related to growth of crystallite above of critical value. (author)

Stabilizing salt-bridge enhances protein thermostability by reducing the heat capacity change of unfolding.

Directory of Open Access Journals (Sweden)

Chi-Ho Chan

Full Text Available Most thermophilic proteins tend to have more salt bridges, and achieve higher thermostability by up-shifting and broadening their protein stability curves. While the stabilizing effect of salt-bridge has been extensively studied, experimental data on how salt-bridge influences protein stability curves are scarce. Here, we used double mutant cycles to determine the temperature-dependency of the pair-wise interaction energy and the contribution of salt-bridges to ΔC(p in a thermophilic ribosomal protein L30e. Our results showed that the pair-wise interaction energies for the salt-bridges E6/R92 and E62/K46 were stabilizing and insensitive to temperature changes from 298 to 348 K. On the other hand, the pair-wise interaction energies between the control long-range ion-pair of E90/R92 were negligible. The ΔC(p of all single and double mutants were determined by Gibbs-Helmholtz and Kirchhoff analyses. We showed that the two stabilizing salt-bridges contributed to a reduction of ΔC(p by 0.8-1.0 kJ mol⁻¹ K⁻¹. Taken together, our results suggest that the extra salt-bridges found in thermophilic proteins enhance the thermostability of proteins by reducing ΔC(p, leading to the up-shifting and broadening of the protein stability curves.

Dissolution and Precipitation Behaviour during Continuous Heating of Al–Mg–Si Alloys in a Wide Range of Heating Rates

Science.gov (United States)

Osten, Julia; Milkereit, Benjamin; Schick, Christoph; Kessler, Olaf

2015-01-01

In the present study, the dissolution and precipitation behaviour of four different aluminium alloys (EN AW-6005A, EN AW-6082, EN AW-6016, and EN AW-6181) in four different initial heat treatment conditions (T4, T6, overaged, and soft annealed) was investigated during heating in a wide dynamic range. Differential scanning calorimetry (DSC) was used to record heating curves between 20 and 600 °C. Heating rates were studied from 0.01 K/s to 5 K/s. We paid particular attention to control baseline stability, generating flat baselines and allowing accurate quantitative evaluation of the resulting DSC curves. As the heating rate increases, the individual dissolution and precipitation reactions shift to higher temperatures. The reactions during heating are significantly superimposed and partially run simultaneously. In addition, precipitation and dissolution reactions are increasingly suppressed as the heating rate increases, whereby exothermic precipitation reactions are suppressed earlier than endothermic dissolution reactions. Integrating the heating curves allowed the enthalpy levels of the different initial microstructural conditions to be quantified. Referring to time–temperature–austenitisation diagrams for steels, continuous heating dissolution diagrams for aluminium alloys were constructed to summarise the results in graphical form. These diagrams may support process optimisation in heat treatment shops.

Dissolution and Precipitation Behaviour during Continuous Heating of Al–Mg–Si Alloys in a Wide Range of Heating Rates

Directory of Open Access Journals (Sweden)

Julia Osten

2015-05-01

Full Text Available In the present study, the dissolution and precipitation behaviour of four different aluminium alloys (EN AW-6005A, EN AW-6082, EN AW-6016, and EN AW-6181 in four different initial heat treatment conditions (T4, T6, overaged, and soft annealed was investigated during heating in a wide dynamic range. Differential scanning calorimetry (DSC was used to record heating curves between 20 and 600 °C. Heating rates were studied from 0.01 K/s to 5 K/s. We paid particular attention to control baseline stability, generating flat baselines and allowing accurate quantitative evaluation of the resulting DSC curves. As the heating rate increases, the individual dissolution and precipitation reactions shift to higher temperatures. The reactions during heating are significantly superimposed and partially run simultaneously. In addition, precipitation and dissolution reactions are increasingly suppressed as the heating rate increases, whereby exothermic precipitation reactions are suppressed earlier than endothermic dissolution reactions. Integrating the heating curves allowed the enthalpy levels of the different initial microstructural conditions to be quantified. Referring to time–temperature–austenitisation diagrams for steels, continuous heating dissolution diagrams for aluminium alloys were constructed to summarise the results in graphical form. These diagrams may support process optimisation in heat treatment shops.

Analysis of water cooled reactors stability; Analiza stabilnosti reaktorskih sistema hladjenih vodom

Energy Technology Data Exchange (ETDEWEB)

Marinkovic, P; Pesic, M [Boris Kidric Institute of Nuclear Sciences, Vinca, Belgrade (Yugoslavia)

1980-07-01

A model for stability analysis of non-boiling water cooled nuclear system is developed. The model is based on linear reactor kinetics and space averaged heat transfer in reactor and heat-exchanger. The transfer functions are defined and the analysis was applied to nuclear reactor RA at 'Boris Kidric' Institute - Vinca. (author)

The Effects of Radiation on the Linear Stability of a horizontal layer ...

African Journals Online (AJOL)

The effect of radiation on the onset of Rayleigh-Benard convection is studied in the case of a radiating Newtonian fluid in a fluid-saturated horizontal porous layer heated from below. The radiative heat transfer is treated using the differential approximation for optically thin limiting case. The linear stability theory is employed ...

Ceramics in engines - Long term stability of transformation toughened zirconia

International Nuclear Information System (INIS)

Marmach, M.; Swain, M.V.

1985-01-01

The long term thermal stability of two types of magnesia partially stabilized zirconia at temperatures below 1000 0 C has been determined. The effect on mechanical properties and phase stability of isothermal heating at 800 0 C and 900 0 C for up to 2000 hours, and with thermal cycling for a similar period between R.T. and 800 0 C in air, was measured. it was found that peak-aged (MS) type Mg-PSZ was much more stable than the thermal shock resistant (TS) type in both tests and showed minimal degradation

Effect of thermal protectants on the stability of bovine milk immunoglobulin G

Energy Technology Data Exchange (ETDEWEB)

Chen, C. C. [National Taiwan University, Taipei, Taiwan (China); Chang, H. M.

1998-09-15

pH stability, thermal stability, and the effect of homogenization and ultrasonic treatment on the stability of bovine milk immunoglobulin G (IgG) in model systems was studied. Separated IgG (0.02 mg/mL) was found to be unstable and susceptible to denaturation when incubated at pH 4 or 10 or thermally treated at temperature 75 degrees C. IgG in the colostrum, on the other hand, was found to be much more stable than in whey or in PBS when thermally treated at temperatures in the range of 75-100 degrees C. The residual IgC content reduced more sharply with increasing heating times, and almost no IgG content was detected when IgG in PBS (0.15 M NaCl/0.01 M phosphate buffer, pH 7.0) was heated at 95 degrees C for 15 s, whereas the corresponding residual IgG contents in whey and colostrum were found to be 42 and 59%, respectively. For IgG in PBS heated at 95 degrees C for 15 s, addition of 5% fructose or maltose displayed most remarkable protection effects by raising the residual IgG content to 31%, followed by sucrose, lactose, glucose, and galactose. However, extravagant addition ( 30%) to IgG in PBS led to a decline in residual IgG content. Addition of 0.4% glutamic acid and 2% glycine to IgG in PBS heated at 95 degrees C for 15 s also remarkably improved the residual IgG content by 13.5 and 26.7%, respectively. Glycerol and sugar alcohol, such as sorbitol, stabilized IgG during the thermal treatment.

Effect of thermal protectants on the stability of bovine milk immunoglobulin G

International Nuclear Information System (INIS)

Chen, C.C.; Chang, H.M.

1998-01-01

pH stability, thermal stability, and the effect of homogenization and ultrasonic treatment on the stability of bovine milk immunoglobulin G (IgG) in model systems was studied. Separated IgG (0.02 mg/mL) was found to be unstable and susceptible to denaturation when incubated at pH 4 or 10 or thermally treated at temperature 75 degrees C. IgG in the colostrum, on the other hand, was found to be much more stable than in whey or in PBS when thermally treated at temperatures in the range of 75-100 degrees C. The residual IgC content reduced more sharply with increasing heating times, and almost no IgG content was detected when IgG in PBS (0.15 M NaCl/0.01 M phosphate buffer, pH 7.0) was heated at 95 degrees C for 15 s, whereas the corresponding residual IgG contents in whey and colostrum were found to be 42 and 59%, respectively. For IgG in PBS heated at 95 degrees C for 15 s, addition of 5% fructose or maltose displayed most remarkable protection effects by raising the residual IgG content to 31%, followed by sucrose, lactose, glucose, and galactose. However, extravagant addition ( 30%) to IgG in PBS led to a decline in residual IgG content. Addition of 0.4% glutamic acid and 2% glycine to IgG in PBS heated at 95 degrees C for 15 s also remarkably improved the residual IgG content by 13.5 and 26.7%, respectively. Glycerol and sugar alcohol, such as sorbitol, stabilized IgG during the thermal treatment

Chinese nuclear heating test reactor and demonstration plant

International Nuclear Information System (INIS)

Wang Dazhong; Ma Changwen; Dong Duo; Lin Jiagui

1992-01-01

In this report the importance of nuclear district heating is discussed. From the viewpoint of environmental protection, uses of energy resources and transport, the development of nuclear heating in China is necessary. The development program of district nuclear heating in China is given in the report. At the time being, commissioning of the 5 MW Test Heating Reactor is going on. A 200 MWt Demonstration Plant will be built. In this report, the main characteristics of these reactors are given. It shows this type of reactor has a high inherent safety. Further the report points out that for this type of reactor the stability is very important. Some experimental results of the driving facility are included in the report. (orig.)

Screening of hydrocarbons as supercritical ORCs working fluids by thermal stability

International Nuclear Information System (INIS)

Dai, Xiaoye; Shi, Lin; An, Qingsong; Qian, Weizhong

2016-01-01

Highlights: • A rapid evaluation method for thermal stability of hydrocarbons for ORCs. • Methane and hydrogen are confirmed to be decomposition indicators. • The decomposition temperatures for some hydrocarbons using the rapid method. • Long carbon chain hydrocarbons are not suitable for supercritical ORCs. - Abstract: Organic Rankine Cycle (ORC) systems are widely used for industrial waste heat recovery and renewable energy utilization. The supercritical ORC is currently one of the main development directions due to its low exergy loss, high thermal efficiency and high work output. The thermal stability is the major limitation of organic working fluid selection with high temperature heat sources. This paper presents a rapid experimental method for assessing the thermal stability of hydrocarbons for ORCs. The fluids were tested in a high temperature reactor with methane and hydrogen theoretically and experimentally confirmed to be the indicators of thermal decomposition. The thermal decomposition temperatures were obtained for n-hexane, n-pentane, isopentane, cyclopentane, n-butane and isobutane using the rapid experimental method. The results show that cycloalkanes are not the good choices by thermal stability and long carbon chain hydrocarbons (longer than C6) are not suitable for supercritical ORCs due to the thermal stability limitation.

Evaluation of thermal stability of paraffin wax by differential scanning calorimetry; Avaliacao da estabilidade termica de parafina por calorimetria diferencial de varredura

Energy Technology Data Exchange (ETDEWEB)

Godinho, K.O.; Silva, A.G.P.; Holanda, J.N.F. [Universidade Estadual do Norte Fluminense (LAMAV/UENF), Campos dos Goytacazes, RJ (Brazil). Grupo de Materiais Ceramicos], Email: holanda@uenf.br

2010-07-01

Phase change materials for heat storage are used as passive solar energy storage materials, which can be impregnated into construction materials. In this work the thermal stability (heating/cooling cycle) of the paraffin wax was investigated using differential scanning calorimetry. The latent heat and fusion temperature were determined for the following thermal cycles: 0, 30, 180 and 360. The thermal stability for paraffin wax infiltrated in support of gypsum was also determined. The experimental results showed that the paraffin wax showed good thermal stability in the states pure and infiltrated for up to 360 thermal cycles. (author)

Phytosterol moiety effects on stability, tocopherol interaction, and anti-polymerization activity of phytosteryl ferulates

Science.gov (United States)

The antioxidant, anti-polymerization, stability, and interaction with tocopherols of corn and rice phytosteryl ferulates have been compared in several heating and frying studies. We have found that corn steryl ferulates are very protective of soybean oil from polymerization during heating and frying...

Thermal analysis on organic phase change materials for heat storage applications

Science.gov (United States)

Lager, Daniel

2016-07-01

In this paper, methodologies based on thermal analysis to evaluate specific heat capacity, phase transition enthalpies, thermal cycling stability and thermal conductivity of organic phase change materials (PCMs) are discussed. Calibration routines for a disc type heat flow differential scanning calorimetry (hf-DSC) are compared and the applied heating rates are adapted due to the low thermal conductivity of the organic PCMs. An assessment of thermal conductivity measurements based on "Laser Flash Analysis" (LFA) and the "Transient Hot Bridge" method (THB) in solid and liquid state has been performed. It could be shown that a disc type hf-DSC is a useful method for measuring specific heat capacity, melting enthalpies and cycling stability of organic PCM if temperature and sensitivity calibration are adapted to the material and quantity to be measured. The LFA method shows repeatable and reproducible thermal diffusivity results in solid state and a high effort for sample preparation in comparison to THB in liquid state. Thermal conductivity results of the two applied methods show large deviations in liquid phase and have to be validated by further experiments.

Two-phase flow instability in a liquid nitrogen heat exchanger, 2

International Nuclear Information System (INIS)

Kondoh, Tetsuya; Fukuda, Kenji; Hasegawa, Shu; Yamada, Hidetomo; Ryu, Hiroyuki.

1988-01-01

Experimental and analytical investigations are conducted on flow instability in a vertically installed liquid nitrogen shell and tube type heat exchanger. The experiments are carried out by making use of water steam as a secondary fluid and it is observed that flow instability occurs in the range of small inlet flow rate. Mode analysis of the flow instability oscillation reveals that there exists a fundamental mode and its higher harmonics up to the fourth. As the period of the fundamental mode is nearly equal to the transit time for a fluid particle to travel through the heated tube, it is suggested that this flow instability is of the density wave type. It is shown that the amount of exchanged heat, as well as the pressure drop, decrease when unstable flow oscillation occurs. An analysis of the static heat transfer and pressure drop characteristics can simulate the experimental results in the stable region. Linear stability analysis is also carried out to yield the stability map as well as the period of flow oscillation, which proved to agree with the experimental data qualitatively. (author)

Stability of superconducting Rutherford cables for accelerator magnets

NARCIS (Netherlands)

Willering, G.P.

2009-01-01

The stability of superconducting magnets has a high priority for particle accelerators, since the operational time and operational collision energy depend strongly on it. Local heat dissipation due to beam loss and conductor movement is inevitable, causing local hot spots in the conductor, possibly

Humid Heat Autoclaving of Hybrid Nanoparticles Achieved by Decreased Nanoparticle Concentration and Improved Nanoparticle Stability Using Medium Chain Triglycerides as a Modifier.

Science.gov (United States)

Gou, Jingxin; Chao, Yanhui; Liang, Yuheng; Zhang, Ning; He, Haibing; Yin, Tian; Zhang, Yu; Xu, Hui; Tang, Xing

2016-09-01

Humid heat autoclaving is a facile technique widely used in the sterilization of injections, but the high temperature employed would destroy nanoparticles composed of biodegradable polymers. The aim of this study was to investigate whether incorporation of medium chain triglycerides (MCT) could stabilize nanoparticles composed of poly (ethylene glycol)-b-polycaprolactone (PEG-b-PCL) during autoclaving (121°C, 10 min). Polymeric nanoparticles with different MCT contents were prepared by dialysis. Block copolymer degradation was studied by GPC. The critical aggregation concentrations of nanoparticles at different temperatures were determined using pyrene fluorescence. The size, morphology and weight averaged molecular weight of pristine/autoclaved nanoparticles were studied using DLS, TEM and SLS, respectively. Drug loading content and release profile were determined using RP-HPLC. The protecting effect of MCT on nanoparticles was dependent on the amount of MCT incorporated. Nanoparticles with high MCT contents, which assumed an emulsion-like morphology, showed reduced block copolymer degradation and particle disassociation after incubation at 100°C for 24 h. Nanoparticles with high MCT content showed the lowest critical aggregation concentration (CAC) under either room temperature or 60°C and the lowest particle concentration among all samples. And the particle size, drug loading content, physical stability and release profile of nanoparticles with high MCT contents remained nearly unchanged after autoclaving. Incorporation of high amount of MCT changed the morphology of PEG-b-PCL based nanoparticles to an emulsion-like structure and the nanoparticles prepared could withstand autoclaving due to improved particle stability and decreased particle concentration caused by MCT incorporation.

Numberical Solution to Transient Heat Flow Problems

Science.gov (United States)

Kobiske, Ronald A.; Hock, Jeffrey L.

1973-01-01

Discusses the reduction of the one- and three-dimensional diffusion equation to the difference equation and its stability, convergence, and heat-flow applications under different boundary conditions. Indicates the usefulness of this presentation for beginning students of physics and engineering as well as college teachers. (CC)

Stability of plasma in static equilibrium

Energy Technology Data Exchange (ETDEWEB)

Krusiial, M D; Oberman, N R [Project Matterhorn, Princeton University, Princeton, NJ (United States)

1958-07-01

Our purpose is to derive from the Boltzmann equation in the small m/e limit, criteria useful in the discussion of stability of plasmas in static equilibrium. At first we ignore collisions but later show their effects may be taken into account. Our approach yields a generalization of the usual energy principles for investigating the stability of hydromagnetic systems to situations where the effect of heat flow along magnetic lines is not negligible, and hence to situations where the strictly hydrodynamic approach is inapplicable. In the first two sections we characterize our general method of approach and delineate the properties of the small m/e limit which we use to determine the constants of the motion and the condition for static equilibrium. In the next two sections we calculate the first and second variations of the energy and conclude with a statement of the general stability criterion. In the final three sections we state several theorems which relate our stability criterion to those of ordinary hydromagnetic theory, we show how to take into account the effect of collisions, and briefly discuss the remaining problem of incorporating the charge neutrality condition into the present stability theory. (author)

Theoretical studying the stability of steady-state regime of a channel with a coolant condensation

International Nuclear Information System (INIS)

Savikhin, O.G.

1987-01-01

Based on the boiling channel stability theory, the channel steady-state stability with the coolant condensation is studied. Condensable coolants are used in the NPP steam-separator superheaters as well as in cryogenic technique. Under certain conditions the coolant flow rate and temperature fluctuations may be excited in the parallel channel system with coolant condensation, which produce a sufficient effect on the heat exchange equipment operation reliability. To describe unsteady processes of heat and mass transfer in the channel, a homogeneous two-phase flow one dimensional model is used. The results obtained allow one to make a conclusion concerning the effect of some parameters on condensing channel steady-state regime stability: reduction of inlet and outlet unheated communication length, pressure drop increase at the outlet plate and its reduction at the inlet one lead to the increase of stability margin

Damping by heat conduction in the Timoshenko system: Fourier and Cattaneo are the same

KAUST Repository

Said-Houari, Belkacem; Kasimov, Aslan R.

2013-01-01

We consider the Cauchy problem for the one-dimensional Timoshenko system coupled with heat conduction, wherein the latter is described by either the Cattaneo law or the Fourier law. We prove that heat dissipation alone is sufficient to stabilize

One-dimensional nonlinear inverse heat conduction technique

International Nuclear Information System (INIS)

Hills, R.G.; Hensel, E.C. Jr.

1986-01-01

The one-dimensional nonlinear problem of heat conduction is considered. A noniterative space-marching finite-difference algorithm is developed to estimate the surface temperature and heat flux from temperature measurements at subsurface locations. The trade-off between resolution and variance of the estimates of the surface conditions is discussed quantitatively. The inverse algorithm is stabilized through the use of digital filters applied recursively. The effect of the filters on the resolution and variance of the surface estimates is quantified. Results are presented which indicate that the technique is capable of handling noisy measurement data

Comparative study of ageing, heat treatment and accelerated carbonation for stabilization of municipal solid waste incineration bottom ash in view of reducing regulated heavy metal/metalloid leaching.

Science.gov (United States)

Santos, Rafael M; Mertens, Gilles; Salman, Muhammad; Cizer, Özlem; Van Gerven, Tom

2013-10-15

This study compared the performance of four different approaches for stabilization of regulated heavy metal and metalloid leaching from municipal solid waste incineration bottom ash (MSWI-BA): (i) short term (three months) heap ageing, (ii) heat treatment, (iii) accelerated moist carbonation, and (iv) accelerated pressurized slurry carbonation. Two distinct types of MSWI-BA were tested in this study: one originating from a moving-grate furnace incineration operation treating exclusively household refuse (sample B), and another originating from a fluid-bed furnace incineration operation that treats a mixture of household and light industrial wastes (sample F). The most abundant elements in the ashes were Si (20-27 wt.%) and Ca (16-19 wt.%), followed by significant quantities of Fe, Al, Na, S, K, Mg, Ti, and Cl. The main crystalline substances present in the fresh ashes were Quartz, Calcite, Apatite, Anhydrite and Gehlenite, while the amorphous fraction ranged from 56 to 73 wt.%. The leaching values of all samples were compared to the Flemish (NEN 7343) and the Walloon (DIN 38414) regulations from Belgium. Batch leaching of the fresh ashes at natural pH showed that seven elements exceeded at least one regulatory limit (Ba, Cr, Cu, Mo, Pb, Se and Zn), and that both ashes had excess basicity (pH > 12). Accelerated carbonation achieved significant reduction in ash basicity (9.3-9.9); lower than ageing (10.5-12.2) and heat treatment (11.1-12.1). For sample B, there was little distinction between the leaching results of ageing and accelerated carbonation with respect to regulatory limits; however carbonation achieved comparatively lower leaching levels. Heat treatment was especially detrimental to the leaching of Cr. For sample F, ageing was ineffective and heat treatment had marginally better results, while accelerated carbonation delivered the most effective performance, with slurry carbonation meeting all DIN limits. Slurry carbonation was deemed the most

Optimizing Glassy Polymer Network Morphology for Nano-particle Dispersion, Stabilization and Performance

Science.gov (United States)

2016-10-03

viscosity and stabilization of MWCNTs within rheological regimes which inhibit re-agglomeration to aid in post processing stabilization of dispersion state...polypropylene- clay nanocomposites subjected to laser pulse heating Bartolucci, Stephen, Supan, Karen, Wiggins, Jeffrey, LaBeaud, Lawrence, Warrender...addition, concurrent chain extension reactions advance prepolymer molecular weights to desired viscosities in less than 2 minutes of mean residence

Thermal stability of ultrasoft Fe-Zr-N films

NARCIS (Netherlands)

Chechenin, NG; van Veen, A; Schut, H; Chezan, AR; Boerma, D; Vystavel, T; De Hosson, JTM

2003-01-01

The thermal stability of nanocrystalline ultrasoft magnetic (Fe98Zr2)(1-x)N-x films with x = 0.10-0.25 was studied using thermal desorption spectrometry, positron beam analysis and high resolution transmission electron microscopy. The results demonstrate that grain growth during the heat treatment

Stabilization of the external kink and the resistive wall mode

International Nuclear Information System (INIS)

Chu, M S; Okabayashi, M

2010-01-01

The pursuit of steady-state economic production of thermonuclear fusion energy has led to research on the stabilization of the external kink and the resistive wall mode. Advances in both experiment and theory, together with improvements in diagnostics, heating and feedback methods have led to substantial and steady progress in the understanding and stabilization of these instabilities. Many of the theory and experimental techniques and results that have been developed are useful not only for the stabilization of the resistive wall mode. They can also be used to improve the general performance of fusion confinement devices. The conceptual foundations and experimental results on the stabilization of the external kink and the resistive wall mode are reviewed. (topical review)

Future heat waves and surface ozone

Science.gov (United States)

Meehl, Gerald A.; Tebaldi, Claudia; Tilmes, Simone; Lamarque, Jean-Francois; Bates, Susan; Pendergrass, Angeline; Lombardozzi, Danica

2018-06-01

A global Earth system model is used to study the relationship between heat waves and surface ozone levels over land areas around the world that could experience either large decreases or little change in future ozone precursor emissions. The model is driven by emissions of greenhouse gases and ozone precursors from a medium-high emission scenario (Representative Concentration Pathway 6.0–RCP6.0) and is compared to an experiment with anthropogenic ozone precursor emissions fixed at 2005 levels. With ongoing increases in greenhouse gases and corresponding increases in average temperature in both experiments, heat waves are projected to become more intense over most global land areas (greater maximum temperatures during heat waves). However, surface ozone concentrations on future heat wave days decrease proportionately more than on non-heat wave days in areas where ozone precursors are prescribed to decrease in RCP6.0 (e.g. most of North America and Europe), while surface ozone concentrations in heat waves increase in areas where ozone precursors either increase or have little change (e.g. central Asia, the Mideast, northern Africa). In the stabilized ozone precursor experiment, surface ozone concentrations increase on future heat wave days compared to non-heat wave days in most regions except in areas where there is ozone suppression that contributes to decreases in ozone in future heat waves. This is likely associated with effects of changes in isoprene emissions at high temperatures (e.g. west coast and southeastern North America, eastern Europe).

Ablative stabilization of Rayleigh-Taylor instabilities resulting from a laser-driven radiative shock

Science.gov (United States)

Huntington, C. M.; Shimony, A.; Trantham, M.; Kuranz, C. C.; Shvarts, D.; Di Stefano, C. A.; Doss, F. W.; Drake, R. P.; Flippo, K. A.; Kalantar, D. H.; Klein, S. R.; Kline, J. L.; MacLaren, S. A.; Malamud, G.; Miles, A. R.; Prisbrey, S. T.; Raman, K. S.; Remington, B. A.; Robey, H. F.; Wan, W. C.; Park, H.-S.

2018-05-01

The Rayleigh-Taylor (RT) instability is a common occurrence in nature, notably in astrophysical systems like supernovae, where it serves to mix the dense layers of the interior of an exploding star with the low-density stellar wind surrounding it, and in inertial confinement fusion experiments, where it mixes cooler materials with the central hot spot in an imploding capsule and stifles the desired nuclear reactions. In both of these examples, the radiative flux generated by strong shocks in the system may play a role in partially stabilizing RT instabilities. Here, we present experiments performed on the National Ignition Facility, designed to isolate and study the role of radiation and heat conduction from a shock front in the stabilization of hydrodynamic instabilities. By varying the laser power delivered to a shock-tube target with an embedded, unstable interface, the radiative fluxes generated at the shock front could be controlled. We observe decreased RT growth when the shock significantly heats the medium around it, in contrast to a system where the shock did not produce significant heating. Both systems are modeled with a modified set of buoyancy-drag equations accounting for ablative stabilization, and the experimental results are consistent with ablative stabilization when the shock is radiative. This result has important implications for our understanding of astrophysical radiative shocks and supernova radiative hydrodynamics [Kuranz et al., Nature Communications 9(1), 1564 (2018)].

Thermal stability of 4-substituted benzenediazonium tetrafluoroborates

International Nuclear Information System (INIS)

Bruner, V.Ya.

1990-01-01

Heating of tetraborates of 4-methyl-, 4-phenyl- and 4-dimethylaminobenzenediazonium at 95, 120 and 148 deg, correspondingly, causes their autocatalytic destruction, two moles of gas (nitrogen, boron fluoride) being liberated. The thermal stability of 4-substituted benzenediazonium tetrafluoroborates increases with the increase of the electron-donor activity of the substituent at benzene ring

Stability considerations and a double-diffusive convection model for solar ponds

Energy Technology Data Exchange (ETDEWEB)

Lin, E.I.H.; Sha, W.T.; Soo, S.L.

1979-04-01

A brief survey is made on the basic principles, current designs and economic advantages of salinity-gradient solar ponds as solar collectors and reservoirs. Solar ponds are well-suited for various AIPH (agricultural and industrial process heat) applications, and as annual storage devices for space heating and cooling. The benefit of an efficient pond is demonstrated via a preliminary economic analysis which suggests the idea of energy farming as a profitable alternative for land usage in the face of rising fuel cost. The economy and reliability of solar-pond operation depend crucially on the stability of the nonconvective gradient zone against disturbances such as generated by a severe weather condition. Attention is focused on the subject of stability, and pertinent existing results are summarized and discussed. Details of the derivation of three-dimensional stability criteria for thermohaline convection with linear gradients are presented. Ten key questions pertaining to stability are posed, whose answers must be sought through extensive analytical and numerical studies. Possible methods of approach toward enhancing solar-pond stability are also discussed. For the numerical studies of pond behavior and stability characteristics, a double-diffusive convection model is proposed. The model can be constructed by extending the three-dimensional thermohydrodynamic computer code COMMIX-SA, following the necessary steps outlined; computational plans are described. Similarities exist between the halothermocline and the thermocline storage systems, and an extended COMMIX-SA will be a valuable tool for the investigation of both.

Heat-pump performance: voltage dip/sag, under-voltage and over-voltage

Directory of Open Access Journals (Sweden)

William J.B. Heffernan

2014-12-01

Full Text Available Reverse cycle air-source heat-pumps are an increasingly significant load in New Zealand and in many other countries. This has raised concern over the impact wide-spread use of heat-pumps may have on the grid. The characteristics of the loads connected to the power system are changing because of heat-pumps. Their performance during under-voltage events such as voltage dips has the potential to compound the event and possibly cause voltage collapse. In this study, results from testing six heat-pumps are presented to assess their performance at various voltages and hence their impact on voltage stability.

Topical gel formulation and stability assessment of platelet lysate based on turbidimetric method

Directory of Open Access Journals (Sweden)

Soliman Mohammadi Samani

2015-06-01

Full Text Available Platelet-rich growth factors have attracted attentions of scientists and clinical practitioners who are involved in wound healing and regenerative medicine extensively, according to their unprecedented potential of promoting and catalyzing healing process. Platelet-rich growth factors are cost-benefit, available and more stable than recombinant human growth factors. These appealing characteristics have converted PRGF to one of the popular candidates for treatment of variety of wounds. According to these valuable properties, we decided to formulate and assess the effect of different excipients on the stability of such valuable protein based formulations. Different excipients have been chosen according to their effective ness on the stability of proteins and their application in other similar formulations. The stabilizing effect of excipients was evaluated by measuring heat-induced aggregation of growth factors by turbidimetric assay. Glycerol, glycine and dextrose were chosen as stabilizing excipients for these formulations. The results show that dextrose has more stabilizing effect on prevention of heat induced aggregation of the platelet lysate growth factors than glycerol and glycine. All of the formulations also contained antioxidant, chelating agents, preservative and carbopol934 in order to form appropriate gel.

Thermal precipitation fluorescence assay for protein stability screening.

Science.gov (United States)

Fan, Junping; Huang, Bo; Wang, Xianping; Zhang, Xuejun C

2011-09-01

A simple and reliable method of protein stability assessment is desirable for high throughput expression screening of recombinant proteins. Here we described an assay termed thermal precipitation fluorescence (TPF) which can be used to compare thermal stabilities of recombinant protein samples directly from cell lysate supernatants. In this assay, target membrane proteins are expressed as recombinant fusions with a green fluorescence protein tag and solubilized with detergent, and the fluorescence signals are used to report the quantity of the fusion proteins in the soluble fraction of the cell lysate. After applying a heat shock, insoluble protein aggregates are removed by centrifugation. Subsequently, the amount of remaining protein in the supernatant is quantified by in-gel fluorescence analysis and compared to samples without a heat shock treatment. Over 60 recombinant membrane proteins from Escherichia coli were subject to this screening in the presence and absence of a few commonly used detergents, and the results were analyzed. Because no sophisticated protein purification is required, this TPF technique is suitable to high throughput expression screening of recombinant membrane proteins as well as soluble ones and can be used to prioritize target proteins based on their thermal stabilities for subsequent large scale expression and structural studies. Copyright © 2011 Elsevier Inc. All rights reserved.

Effects of heat treatment on some physical properties of Douglas fir (Pseudotsuga menziesii) wood

Science.gov (United States)

Xianjun Li; Zhiyong Cai; Qunying Mou; Yiqiang Wu; Yuan Liu

2011-01-01

In this study the effect of heat treatment on some physical properties of Douglas fir (Pseudotsuga menziesii) was investigated. Wood specimens were subjected to heat treatment at 160, 180, 200 and 220°C for 1, 2, 3 and 4h. The results show that heat treatment resulted in a darkened color, decreased moisture performance and increased dimensional stability of...

Controllability and stabilization of parabolic equations

CERN Document Server

Barbu, Viorel

2018-01-01

This monograph presents controllability and stabilization methods in control theory that solve parabolic boundary value problems. Starting from foundational questions on Carleman inequalities for linear parabolic equations, the author addresses the controllability of parabolic equations on a variety of domains and the spectral decomposition technique for representing them. This method is, in fact, designed for use in a wider class of parabolic systems that include the heat and diffusion equations. Later chapters develop another process that employs stabilizing feedback controllers with a finite number of unstable modes, with special attention given to its use in the boundary stabilization of Navier–Stokes equations for the motion of viscous fluid. In turn, these applied methods are used to explore related topics like the exact controllability of stochastic parabolic equations with linear multiplicative noise. Intended for graduate students and researchers working on control problems involving nonlinear diff...

Beneficial effects of microwave-assisted heating versus conventional heating in noble metal nanoparticle synthesis.

Science.gov (United States)

Dahal, Naween; García, Stephany; Zhou, Jiping; Humphrey, Simon M

2012-11-27

An extensive comparative study of the effects of microwave versus conventional heating on the nucleation and growth of near-monodisperse Rh, Pd, and Pt nanoparticles has revealed distinct and preferential effects of the microwave heating method. A one-pot synthetic method has been investigated, which combines nucleation and growth in a single reaction via precise control over the precursor addition rate. Using this method, microwave-assisted heating enables the convenient preparation of polymer-capped nanoparticles with improved monodispersity, morphological control, and higher crystallinity, compared with samples heated conventionally under otherwise identical conditions. Extensive studies of Rh nanoparticle formation reveal fundamental differences during the nucleation phase that is directly dependent on the heating method; microwave irradiation was found to provide more uniform seeds for the subsequent growth of larger nanostructures of desired size and surface structure. Nanoparticle growth kinetics are also markedly different under microwave heating. While conventional heating generally yields particles with mixed morphologies, microwave synthesis consistently provides a majority of tetrahedral particles at intermediate sizes (5-7 nm) or larger cubes (8+ nm) upon further growth. High-resolution transmission electron microscopy indicates that Rh seeds and larger nanoparticles obtained from microwave-assisted synthesis are more highly crystalline and faceted versus their conventionally prepared counterparts. Microwave-prepared Rh nanoparticles also show approximately twice the catalytic activity of similar-sized conventionally prepared particles, as demonstrated in the vapor-phase hydrogenation of cyclohexene. Ligand exchange reactions to replace polymer capping agents with molecular stabilizing agents are also easily facilitated under microwave heating, due to the excitation of polar organic moieties; the ligand exchange proceeds with excellent retention of

Phase stability of TiH{sub 2} under high pressure and temperatures

Energy Technology Data Exchange (ETDEWEB)

Selva Vennila, R.; Durygin, A.; Saxena, S.K. [Center for Study of Matter at Extreme Conditions (CeSMEC), Florida International University, VH-150, University Park, Miami, FL 33199 (United States); Merlini, Marco [European Synchrotron Radiation Facility (ESRF), Grenoble 38043 (France); Wang, Zhongwu [Cornell High Energy Synchrotron Source (CHESS), Wilson Laboratory, Cornell University, Ithaca, NY 14853 (United States)

2008-11-15

Phase stability of titanium hydride (TiH{sub 2}) was studied at high pressure-high temperature conditions using synchrotron radiation under non-hydrostatic conditions. Resistive heating method was used to heat the sample to a maximum temperature of 873 K in a diamond anvil cell (DAC) under pressure up to 12 GPa. Pressure-temperature behavior was studied by varying the temperature upto 823 K in steps of 50 K with pressure variations within 3 GPa. Structural phase transformation from tetragonal (I4/mmm) to cubic (Fm-3 m) was observed with increase in temperature. Tetragonal phase was found to be stabilized when the sample was subjected to pressure and temperature cycle. (author)

Turbulent current heating of dense plasma

International Nuclear Information System (INIS)

Suprunenko, V.A.; Sukhomlin, E.A.; Volkov, E.D.; Perepelkij, N.F.

1976-01-01

Based upon experimental results an attempt is made for systematizing and analysing conditions of experiments in anomalous resistance and turbulent heating of a plasma. The extensive program of such investigations aims at a direct practical study on quasistationary heating and plasma containment in magnetic traps. It has been shown that in real conditions turbulent heating turns out to be a far more complicated phenomenon than that described within the framework of theories developed so far. It has been established that the phenomenon alters in the transition through the critical values of electric and magnetic fields. This makes it possible to separate four characteristic experimental regimes. For all the regimes the stabilization of the electron current drift rate is typical. On the basis of the experimental results obtained an explanation is given of the sporadic character of the ultrathermal radiation in a quasistationary discharge

Note on the cryostatic stability of superconducting composites

International Nuclear Information System (INIS)

Gauster, W.F.

1978-02-01

A careful discussion is given of the ''equal area condition'' developed by Maddock et al. In order to make the essential points as clear as possible, analytical solutions are derived under simplifying assumptions (simple model for heat transfer by nucleate and film boiling liquid helium; constant heat conduction and specific heat) instead of using more realistic but less controllable computer calculations. A quantitative definition of the concept of a long wire is given. Numerical examples for the Maddock transition characterized by the equal area condition are given for a long superconducting composite with linear cooling and for a liquid helium-cooled resistance wire of finite length. In addition, cases are shown where instead of applying the equal area stability condition, time-dependent solutions should be considered

Interacting dark energy model and thermal stability

Energy Technology Data Exchange (ETDEWEB)

Bhandari, Pritikana; Haldar, Sourav; Chakraborty, Subenoy [Jadavpur University, Department of Mathematics, Kolkata, West Bengal (India)

2017-12-15

In the background of the homogeneous and isotropic FLRW model, the thermodynamics of the interacting DE fluid is investigated in the present work. By studying the thermodynamical parameters, namely the heat capacities and the compressibilities, both thermal and mechanical stability are discussed and the restrictions on the equation of state parameter of the dark fluid are analyzed. (orig.)

Interacting dark energy model and thermal stability

International Nuclear Information System (INIS)

Bhandari, Pritikana; Haldar, Sourav; Chakraborty, Subenoy

2017-01-01

In the background of the homogeneous and isotropic FLRW model, the thermodynamics of the interacting DE fluid is investigated in the present work. By studying the thermodynamical parameters, namely the heat capacities and the compressibilities, both thermal and mechanical stability are discussed and the restrictions on the equation of state parameter of the dark fluid are analyzed. (orig.)

Instability of a binary liquid film flowing down a slippery heated plate

Science.gov (United States)

Ellaban, E.; Pascal, J. P.; D'Alessio, S. J. D.

2017-09-01

In this paper, we study the stability of a binary liquid film flowing down a heated slippery inclined surface. It is assumed that the heating induces concentration differences in the liquid mixture (Soret effect), which together with the differences in temperature affects the surface tension. A mathematical model is constructed by coupling the Navier-Stokes equations governing the flow with equations for the concentration and temperature. A Navier slip condition is applied at the liquid-solid interface. We carry out a linear stability analysis in order to obtain the critical conditions for the onset of instability. We use a Chebyshev spectral collocation method to obtain numerical solutions to the resulting Orr-Sommerfeld-type equations. We also obtain an asymptotic solution that yields an expression for the state of neutral stability of long perturbations as a function of the parameters controlling the problem. A weighted residual approximation is employed to derive a reduced model that is used to analyse the nonlinear effects. Good agreement between the linear stability analysis and nonlinear simulations provided by the weighted residual model is found.

Burnout in boiling heat transfer. part I: pool boiling systems

International Nuclear Information System (INIS)

Bergles, A.E.

1977-01-01

Recent experimental and analytical developments in pool-boiling burnout are reviewed, and results are summarized that clarify the dependence of critical heat flux on heater geometry and fluid properties. New analytical interpretations of burnout are discussed, and the effects of surface condition, aging, acceleration, and transient heating (or cooling) are described. The relation of sound to burnout and new techniques for stabilizing electric heaters at burnout are also considered

Non-adiabatic stability analysis of current and magnetic curvature driven modes in cold plasmas penetrated by neutral gas

International Nuclear Information System (INIS)

Ohlsson, D.

1978-08-01

Previous stability theories concerning electrostatic current and magnetic curvature driven modes in cold plasma mantle boundary layers are generalized. In particular the commonly used adiabatic approximation is relaxed. In the general theory presented important new effects associated with heat conduction, ionization and ohmic heating are found. In combination with viscosity and resistivity these effects introduce additional stabilizing as well as destabilizing effects. Furthermore the present theory typically predicts similar stability properties as the adiabatic theory in the limit |d(1nT)/d(1nn)| >1 the general theory predicts less favourable stability properties. One may speculate that these conclusions also apply to more general types of electrostatic modes associated with density and temperature gradients in cold plasma mantel boundary layers. (author)

Current status of research and development for nuclear heating reactor in China

International Nuclear Information System (INIS)

Wang Dazhong; Ma Changwen; Dong Duo

1987-01-01

At present the coal is the main source for district heating in China. It results in serious problems for transportation and pollution. Nuclear district heating reactor can substitute the coal and supply the clear and ecenomic heat energy for the cities. A feasibility studies for a district heating reactor with the power of 450 MW(t) in Harbin were carried out. With cooperation of heating boilers heat demand of 1.2 million pupulation can be satisfied. 600 x 10 3 tons coal per year can be saved. The temperature of the heat grid is 130/70 deg C. The main parameters of the 450 MW(t) and 5 MW(t) heating reactors are given. The technical design, safety aspects, economic analysis and the stability of test loop are also discussed. (Liu)

The role of heat transfer time scale in the evolution of the subsea permafrost and associated methane hydrates stability zone during glacial cycles

Science.gov (United States)

Malakhova, Valentina V.; Eliseev, Alexey V.

2017-10-01

Climate warming may lead to degradation of the subsea permafrost developed during Pleistocene glaciations and release methane from the hydrates, which are stored in this permafrost. It is important to quantify time scales at which this release is plausible. While, in principle, such time scale might be inferred from paleoarchives, this is hampered by considerable uncertainty associated with paleodata. In the present paper, to reduce such uncertainty, one-dimensional simulations with a model for thermal state of subsea sediments forced by the data obtained from the ice core reconstructions are performed. It is shown that heat propagates in the sediments with a time scale of ∼ 10-20 kyr. This time scale is longer than the present interglacial and is determined by the time needed for heat penetration in the unfrozen part of thick sediments. We highlight also that timings of shelf exposure during oceanic regressions and flooding during transgressions are important for simulating thermal state of the sediments and methane hydrates stability zone (HSZ). These timings should be resolved with respect to the contemporary shelf depth (SD). During glacial cycles, the temperature at the top of the sediments is a major driver for moving the HSZ vertical boundaries irrespective of SD. In turn, pressure due to oceanic water is additionally important for SD ≥ 50 m. Thus, oceanic transgressions and regressions do not instantly determine onsets of HSZ and/or its disappearance. Finally, impact of initial conditions in the subsea sediments is lost after ∼ 100 kyr. Our results are moderately sensitive to intensity of geothermal heat flux.

Shear layer flame stabilization sensitivities in a swirling flow

Directory of Open Access Journals (Sweden)

Christopher Foley

2017-03-01

Full Text Available A variety of different flame configurations and heat release distributions exist in high swirl, annular flows, due to the existence of inner and outer shear layers as well a vortex breakdown bubble. Each of these different configurations, in turn, has different thermoacoustic sensitivities and influences on combustor emissions, nozzle durability, and liner heating. This paper presents findings on the sensitivities of the outer shear layer- stabilized flames to a range of parameters, including equivalence ratio, bulkhead temperature, flow velocity, and preheat temperature. There is significant hysteresis for flame attachment/detachment from the outer shear layer and this hysteresis is also described. Results are also correlated with extinction stretch rate calculations based on detailed kinetic simulations. In addition, we show that the bulkhead temperature near the flame attachment point has significant impact on outer shear layer detachment. This indicates that understanding the heat transfer between the edge flame stabilized in the shear layer and the nozzle hardware is needed in order to predict shear layer flame stabilization limits. Moreover, it shows that simulations cannot simply assume adiabatic boundary conditions if they are to capture these transitions. We also show that the reference temperature for correlating these transitions is quite different for attachment and local blow off. Finally, these results highlight the deficiencies in current understanding of the influence of fluid mechanic parameters (e.g. velocity, swirl number on shear layer flame attachment. For example, they show that the seemingly simple matter of scaling flame transition points with changes in flow velocities is not understood.

Low-temperature heat capacity and thermodynamic functions of vitamin B12

International Nuclear Information System (INIS)

Knyazev, A.V.; Smirnova, N.N.; Plesovskikh, A.S.; Shushunov, A.N.; Knyazeva, S.S.

2014-01-01

Graphical abstract: - Highlights: • Temperature dependence of heat capacity of vitamin B 12 has been measured by precision adiabatic vacuum calorimetry. • The thermodynamic functions of the vitamin B 12 have been determined for the range from T → 0 to 343 K. • The character of heterodynamics of structure was detected. • The thermal stability of cyanocobalamin was studied by differential scanning calorimetry. - Abstract: In the present work temperature dependence of heat capacity of vitamin B 12 (cyanocobalamin) has been measured for the first time in the range from 6 to 343 K by precision adiabatic vacuum calorimetry. Based on the experimental data, the thermodynamic functions of the vitamin B 12 , namely, the heat capacity, enthalpy H°(T) − H°(0), entropy S°(T) − S°(0) and Gibbs function G°(T) − H°(0) have been determined for the range from T → 0 to 343 K. The value of the fractal dimension D in the function of multifractal generalization of Debye's theory of the heat capacity of solids was estimated and the character of heterodynamics of structure was detected. The thermal stability of cyanocobalamin was also studied by differential scanning calorimetry

Effect of Microwave Heating on Phytosterol Oxidation.

Science.gov (United States)

Leal-Castañeda, Everth Jimena; Inchingolo, Raffaella; Cardenia, Vladimiro; Hernandez-Becerra, Josafat Alberto; Romani, Santina; Rodriguez-Estrada, María Teresa; Galindo, Hugo Sergio García

2015-06-10

The oxidative stability of phytosterols during microwave heating was evaluated. Two different model systems (a solid film made with a phytosterol mixture (PSF) and a liquid mixture of phytosterols and triolein (1:100, PS + TAG (triacylglycerol))) were heated for 1.5, 3, 6, 12, 20, and 30 min at 1000 W. PS degraded faster when they were microwaved alone than in the presence of TAG, following a first-order kinetic model. Up to 6 min, no phytosterol oxidation products (POPs) were generated in both systems. At 12 min of heating, the POP content reached a higher level in PSF (90.96 μg/mg of phytosterols) than in PS + TAG (22.66 μg/mg of phytosterols), but after 30 min of treatment, the opposite trend was observed. 7-Keto derivates were the most abundant POPs in both systems. The extent of phytosterol degradation depends on both the heating time and the surrounding medium, which can impact the quality and safety of the food product destined to microwave heating/cooking.

Evaluation of inductive heating energy of sub-size improved DPC-C conductor by calorimetric method

International Nuclear Information System (INIS)

Ito, Toshinobu; Koizumi, Norikiyo; Wakabayashi, Hiroshi; Miura, Yuushi; Fujisaki, Hiroshi; Matsui, Kunihiro; Takahashi, Yoshikazu; Tsuji, Hiroshi

1996-08-01

The improved DPC-U conductor consisting of 648 chrome plated NbTi strands was fabricated and its stability has been investigated using 1/24 sub-size conductor. In the stability experiment, the inductive heating method was applied to originate initial normal zone. Since it is difficult to calculate the inductive heating energy deposited on the conductor because of complicate geometry of the twisted multi-strand cable, inductive heating energy had to be experimentally evaluated using calorimetric method. The heating energy is in proportion to integration of square of an applied sinusoidal wave pulsed current over the heating period. The experimental result shows the proportional constants for the conductor and conduit are 2.062 x 10 -3 [J/A 2 s] and 0.771 x 10 -3 [J/A 2 s], respectively. The coupling between the eddy currents in the strands and conduit might take effect on the heating energy put in the strands. It was shown this effect was however small in this experiment. Consequently, the inductive heating energy applied in the strands was estimated to be the proportional constant of 1.291 x 10 -3 [J/A 2 s] from the difference of the heat energies in the conductor and conduit. (author)

Characterization of cubic yttria-stabilized zirconia obtained by spray pyrolysis

International Nuclear Information System (INIS)

Halmenschlager, Cibele M.; Nunes, Marilia; Vieira, Ramaugusto; Bergmann, Carlos Perez; Falcade, Tiago; Malfatti, Celia de Fraga

2009-01-01

Yttria-stabilized-zirconia (YSZ) has been the object of many studies as a SOFC electrolyte. The aim of this work is to produce, by spray pyrolysis process, thin and dense films of YSZ. A disk of steel 316L, previously heated, was used as substrate. The film was obtained with zirconium acetylacetonate (Zr(C 6 H 7 O 2 ) 4 ) and yttrium chloride (YCl 3.6 H 2 O), dissolved in a mixture of ethanol + butyl carbitol with volume ratio (1:1). ZrO 2 amorphous films were deposited in the substrate heated at many temperatures. After thermal treatment at 700 deg C the films were changed into cubic yttria-stabilized-zirconia structure. The thin films obtained were characterized by thermal analysis, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and micro-Raman spectroscopy. (author)

Study on VCSEL laser heating chip in nuclear magnetic resonance gyroscope

Science.gov (United States)

Liang, Xiaoyang; Zhou, Binquan; Wu, Wenfeng; Jia, Yuchen; Wang, Jing

2017-10-01

In recent years, atomic gyroscope has become an important direction of inertial navigation. Nuclear magnetic resonance gyroscope has a stronger advantage in the miniaturization of the size. In atomic gyroscope, the lasers are indispensable devices which has an important effect on the improvement of the gyroscope performance. The frequency stability of the VCSEL lasers requires high precision control of temperature. However, the heating current of the laser will definitely bring in the magnetic field, and the sensitive device, alkali vapor cell, is very sensitive to the magnetic field, so that the metal pattern of the heating chip should be designed ingeniously to eliminate the magnetic field introduced by the heating current. In this paper, a heating chip was fabricated by MEMS process, i.e. depositing platinum on semiconductor substrates. Platinum has long been considered as a good resistance material used for measuring temperature The VCSEL laser chip is fixed in the center of the heating chip. The thermometer resistor measures the temperature of the heating chip, which can be considered as the same temperature of the VCSEL laser chip, by turning the temperature signal into voltage signal. The FPGA chip is used as a micro controller, and combined with PID control algorithm constitute a closed loop control circuit. The voltage applied to the heating resistor wire is modified to achieve the temperature control of the VCSEL laser. In this way, the laser frequency can be controlled stably and easily. Ultimately, the temperature stability can be achieved better than 100mK.

Irreversibility and Action of the Heat Conduction Process

Directory of Open Access Journals (Sweden)

Yu-Chao Hua

2018-03-01

Full Text Available Irreversibility (that is, the “one-sidedness” of time of a physical process can be characterized by using Lyapunov functions in the modern theory of stability. In this theoretical framework, entropy and its production rate have been generally regarded as Lyapunov functions in order to measure the irreversibility of various physical processes. In fact, the Lyapunov function is not always unique. In the represent work, a rigorous proof is given that the entransy and its dissipation rate can also serve as Lyapunov functions associated with the irreversibility of the heat conduction process without the conversion between heat and work. In addition, the variation of the entransy dissipation rate can lead to Fourier’s heat conduction law, while the entropy production rate cannot. This shows that the entransy dissipation rate, rather than the entropy production rate, is the unique action for the heat conduction process, and can be used to establish the finite element method for the approximate solution of heat conduction problems and the optimization of heat transfer processes.

Impact of the Flameholder Heat Conductivity on Combustion Instability Characteristics

KAUST Repository

Hong, Seunghyuck

2012-06-11

In this paper, we investigate the impact of heat transfer between the flame and the flame-holder on the dynamic stability characteristics in a 50-kW backward facing step combustor. We conducted tests where we use a backward step block made of two different materials: ceramic and stainless steel whose thermal conductivities are 1.06 and 12 W/m/K, respectively. A set of experiments was conducted using a propane/air mixture at Re = 6500 for the inlet temperature of 300 - 500 K at atmospheric pressure. We measure the dynamic pressure and flame chemiluminescence to examine distinct stability characteristics using each flame-holder material over a range of operating conditions. We find that for tests with a flame-holder made of ceramic, the onset of instability is significantly delayed in time and, for certain operating conditions, disappears altogether. Stated differently, for certain operating conditions, the combustor can be stabilized by reducing the thermal conductivity of the flame-holder. As the thermal conductivity of the flame-holder increases, the combustor becomes increasingly unstable over a range of operating conditions. These results imply that the dynamic stability characteristics depend strongly on the heat transfer between the flame and the combustor wall near the flame anchoring region. Copyright © 2012 by ASME.

Two-dimensional simulations of steady perforated-plate stabilized premixed flames

KAUST Repository

Altay, H. Murat

2010-03-17

The objective of this work is to examine the impact of the operating conditions and the perforated-plate design on the steady, lean premixed flame characteristics. We perform two-dimensional simulations of laminar flames using a reduced chemical kinetics mechanism for methane-air combustion, consisting of 20 species and 79 reactions. We solve the heat conduction problem within the plate, allowing heat exchange between the gas mixture and the solid plate. The physical model is based on a zero-Mach-number formulation of the axisymmetric compressible conservation equations. The results suggest that the flame consumption speed, the flame structure, and the flame surface area depend significantly on the equivalence ratio, mean inlet velocity, the distance between the perforated-plate holes and the plate thermal conductivity. In the case of an adiabatic plate, a conical flame is formed, anchored near the corner of the hole. When the heat exchange between themixture and the plate is finite, the flame acquires a Gaussian shape stabilizing at a stand-off distance, that grows with the plate conductivity. The flame tip is negatively curved; i.e. concave with respect to the reactants. Downstream of the plate, the flame base is positively curved; i.e. convex with respect to the reactants, stabilizing above a stagnation region established between neighboring holes. As the plate\\'s thermal conductivity increases, the heat flux to the plate decreases, lowering its top surface temperature. As the equivalence ratio increases, the flame moves closer to the plate, raising its temperature, and lowering the flame stand-off distance. As the mean inlet velocity increases, the flame stabilizes further downstream, the flame tip becomes sharper, hence raising the burning rate at that location. The curvature of the flame base depends on the distance between the neighboring holes; and the flame there is characterized by high concentration of intermediates, like carbon monoxide. © 2010 Taylor

Safety evaluation of interim stabilization of non-stabilized single-shell watch list tanks

International Nuclear Information System (INIS)

Stahl, S.M.

1994-01-01

This report provides results of a review of recently completed safety analyses related to hazards associated with Interim Stabilization of Single analyses related to hazards included oh the Hanford Site Waste Tank-Watch Shell Tanks (SSTs) that are included on the Hanford List. The purpose of the review was to identify and summarize conclusions regarding the safety of interim stabilization of Watch List SSTs, and to highlight applicable limitations, restrictions, and controls. The scope of this review was restricted to SSTs identified List in the categories of flammable gas ferrocyanide, and organic salts. High heat tanks were not included in the scope. A Watch List tank is defined as an underground storage tank containing waste that requires special safety precautions because it may have a serious potential for release of high level radioactive waste because of uncontrolled increases in temperature or pressure. Special restrictions have been placed on these tanks

Thermal and chemical stabilities of some synthesized inorganic ion exchange materials

International Nuclear Information System (INIS)

EI-Naggar, I.M.; Abou-Mesalam, M.M.; El-Shorbagy, M.M.; Shady, S.A.

2006-01-01

Chromium and cerium titanate as inorganic ion exchange materials were synthesized by the reaction of potassium chromate or ammonium eerie nitrate with titanium tetrachloride with molar ratio equal unity. The crystal system of both chromium and cerium titanates were determined and set to be monoclinic and orthorhombic system's, respectively. The chemical composition of both chromium and cerium titanates was determined by X-ray fluorescence technique and based on the data obtained with other different techniques. A molecular formula for chromium and cerium titanates as Cr 2 Ti 12 O 27 . 13H 2 O and Ce 2 Ti 3 O 10 . 7.46H 2 O, respectively, was proposed. Thermal stabilities of both ion exchangers were investigated at different heating temperatures. Also the stability of chromium and cerium titanates for chemical attack was studied in different media. The data obtained showed high thermal and chemical stabilities of chromium and cerium titanate ion exchangers compared with the same group of ion exchange materials. The ion exchange capacities of chromium and cerium titanates at different heating temperature were also investigated

Thermal and chemical stabilities of some synthesized inorganic ion exchange materials

International Nuclear Information System (INIS)

El-Naggar, I.M.; Abou-Mesalam, M. M.; El-Shorbagy, M.M.; Shady, S.A.

2005-01-01

Chromium and cerium titanate as inorganic ion exchange materials were synthesized by the reaction of potassium chromate or ammonium ceric nitrate with titanium tetrachloride with molar ratio equal unity. The crystal system of both chromium and cerium titanates were determined and set to be monoclinic and orthorhombic systems, respectively. The chemical composition of both chromium and cerium titanates were determined by X-ray fluorescence technique and based on the data obtained with other different techniques. We can proposed molecular formula for chromium and cerium titanates as Cr 2 Ti 1 2O27. 13H 2 O and Ce 2 ThO10. 7.46 H 2 O, respectively. Thermal stability of both ion exchangers was investigated at different heating temperatures. Also the stability of chromium and cerium titanates for chemical attack was studied in different media. The data obtained showed high thermal and chemical stabilities of chromium and cerium titanate ion exchangers compared to the same group of ion exchange materials. The ion exchange capacities of chromium and cerium titanates at different heating temperature were investigated

Stability and biocompatibility of photothermal gold nanorods after lyophilization and sterilization

Energy Technology Data Exchange (ETDEWEB)

Gomez, Leyre [Department of Chemical Engineering, Nanoscience Institute of Aragon (INA), C/ Mariano Esquillor, R and D Building, University of Zaragoza, 50018 Zaragoza (Spain); Cebrian, Virginia [CIBER de Bioingeniería, Biomateriales y Nanomedicina, CIBER-BBN, Zaragoza (Spain); Hospital Universitario La Paz-IdiPAZ, Paseo de la Castellana 261, 28046 Madrid (Spain); Martin-Saavedra, Francisco [Hospital Universitario La Paz-IdiPAZ, Paseo de la Castellana 261, 28046 Madrid (Spain); CIBER de Bioingeniería, Biomateriales y Nanomedicina, CIBER-BBN, Zaragoza (Spain); Arruebo, Manuel, E-mail: arruebom@unizar.es [Department of Chemical Engineering, Nanoscience Institute of Aragon (INA), C/ Mariano Esquillor, R and D Building, University of Zaragoza, 50018 Zaragoza (Spain); CIBER de Bioingeniería, Biomateriales y Nanomedicina, CIBER-BBN, Zaragoza (Spain); Vilaboa, Nuria [Hospital Universitario La Paz-IdiPAZ, Paseo de la Castellana 261, 28046 Madrid (Spain); CIBER de Bioingeniería, Biomateriales y Nanomedicina, CIBER-BBN, Zaragoza (Spain); Santamaria, Jesus, E-mail: Jesus.Santamaria@unizar.es [Department of Chemical Engineering, Nanoscience Institute of Aragon (INA), C/ Mariano Esquillor, R and D Building, University of Zaragoza, 50018 Zaragoza (Spain); CIBER de Bioingeniería, Biomateriales y Nanomedicina, CIBER-BBN, Zaragoza (Spain)

2013-10-15

Graphical abstract: - Highlights: • Morphological changes are observed for CTABr capped gold nanorods over time. • Polystyrenesulfonate (PSS) and polyethyleneglycol (PEG) coated nanorods are stable. • Re-suspendible and sterilizable colloids are prepared using those capping agents. • Those materials are efficient heat sinks potentially used in photothermal therapy. - Abstract: Suspensions in phosphate buffered saline (PBS) of gold nanorods stabilized with cetyltrimethyl ammonium chloride (CTABr), polystyrenesulfonate (PSS) and methyl-polyethyleneglycol-thiol (m-PEG-SH) have been prepared and the evolution of their colloidal stability and plasmonic response over time has been evaluated. Their performance after lyophilization, alcoholic sterilization and resuspension has also been characterized. Sub-cytotoxic doses on HeLa cells were calculated for the three surface functionalizations used. Their heating efficiency at different exposure times was also evaluated after being irradiated with near infrared light. The best results were obtained for m-PEG-SH stabilized rods, which were not only stable, sterilizable and lyophilizable, but also biocompatible at all doses tested, showing potential as a stable, re-suspendible and biocompatible hyperthermic agent.

Stability and biocompatibility of photothermal gold nanorods after lyophilization and sterilization

International Nuclear Information System (INIS)

Gomez, Leyre; Cebrian, Virginia; Martin-Saavedra, Francisco; Arruebo, Manuel; Vilaboa, Nuria; Santamaria, Jesus

2013-01-01

Graphical abstract: - Highlights: • Morphological changes are observed for CTABr capped gold nanorods over time. • Polystyrenesulfonate (PSS) and polyethyleneglycol (PEG) coated nanorods are stable. • Re-suspendible and sterilizable colloids are prepared using those capping agents. • Those materials are efficient heat sinks potentially used in photothermal therapy. - Abstract: Suspensions in phosphate buffered saline (PBS) of gold nanorods stabilized with cetyltrimethyl ammonium chloride (CTABr), polystyrenesulfonate (PSS) and methyl-polyethyleneglycol-thiol (m-PEG-SH) have been prepared and the evolution of their colloidal stability and plasmonic response over time has been evaluated. Their performance after lyophilization, alcoholic sterilization and resuspension has also been characterized. Sub-cytotoxic doses on HeLa cells were calculated for the three surface functionalizations used. Their heating efficiency at different exposure times was also evaluated after being irradiated with near infrared light. The best results were obtained for m-PEG-SH stabilized rods, which were not only stable, sterilizable and lyophilizable, but also biocompatible at all doses tested, showing potential as a stable, re-suspendible and biocompatible hyperthermic agent

Physical properties of heat-treated rattan waste binderless particleboard

Science.gov (United States)

Tajuddin, Maisarah; Ahmad, Zuraida; Halim, Zahurin; Maleque, Md Abd; Ismail, Hanafi; Sarifuddin, Norshahida

2017-07-01

The objective of this study is to investigate the effects of heat treatment on the properties of binderless particleboard (BPB) fabricated via hot-pressing process with pressing temperature, pressing time and pressing pressure of 180°C, 5 minutes and 1 MPa, respectively. The fabricated BPB with density in the range of 0.8-0.95g cm-3 was heated in a temperature-controlled laboratory chamber at 80°C, 120°C and 160°C for period of 2 and 8 hours before underwent physical observation, mass loss measurement and thickness swelling test. The samples had remarkable color changes, mainly with samples of treatment temperature of 160˚C, where the color differences were 9.5 and 20.3. This changed the fabricated BPB samples from yellowish brown to dark brown color when treatment conditions increased. Darker color indicates greater mass loss due to severity of chemical component in the powder. Dimensional stability of fabricated BPB was improved with higher treatment temperature as more cellulose cross-linked and hemicellulose degraded that removed the hygroscopicity behavior of powder. These results revealed that heat treatment helped in improving the BPB physical properties, particularly in dimensional stability of boards.

Novel edible oil sources: Microwave heating and chemical properties.

Science.gov (United States)

Hashemi, Seyed Mohammad Bagher; Mousavi Khaneghah, Amin; Koubaa, Mohamed; Lopez-Cervantes, Jaime; Yousefabad, Seyed Hossein Asadi; Hosseini, Seyedeh Fatemeh; Karimi, Masoumeh; Motazedian, Azam; Asadifard, Samira

2017-02-01

The aim of this work was to investigate the effect of various microwave heating times (1, 3, 5, 10, and 15min) on the chemical properties of novel edible oil sources, including Mashhadi melon (Cucumis melo var. Iranians cv. Mashhadi), Iranian watermelon (Citrullus lanatus cv. Fire Fon), pumpkin (Cucurbita pepo subsp. pepo var. Styriaca), and yellow apple (Malus domestica cv. Golden Delicious) seed oils. The evaluated parameters were peroxide value (PV), conjugated diene (CD) and triene (CT) values, carbonyl value (CV), p-anisidine value (AnV), oil stability index (OSI), radical scavenging activity (RSA), total tocopherols, total phenolics, as well as chlorophyll and carotenoid contents. Results showed that extended microwave heating involves decreased quality of the seed oils, mainly due to the formation of primary and secondary oxidation products. Microwave heating time also affects the total contents of chlorophylls, carotenoids, phenolics and tocopherols, which clearly decrease by increasing the exposure time. The order of oxidative stability of the analyzed edible oils was pumpkin>Mashhadi melon>Iranian watermelon>yellow apple. The obtained results demonstrated the promising potential of these novel edible oils for different food applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Methods for improving mechanical properties of partially stabilized zirconia and the resulting product

International Nuclear Information System (INIS)

Aronov, V.A.

1987-01-01

A method for improving mechanical surface properties of a rigid body comprising partially stabilized zirconia as a constituent is described comprising the following steps: (i) providing a rigid body having an exposed surface and an interior volume; (ii) subjecting the exposed surface region of partially stabilized zirconia to external heating to heat the exposed surface region to 1100 0 C-1600 0 C without heating the interior volume above 500 0 C-800 0 C; and (iii) cooling the rigid body to a temperature of less than 500 0 C to cause a portion of the exposed surface region to transform from the tetragonal lattice modification to the monoclinic lattice modification, thereby creating a compressive stress field in the exposed surface region and improving the mechanical surface properties of the exposed surface region. In a ceramic body comprising a first exposed region of a partially stabilized zirconia, and a second region of a partially stabilized zirconia at an interior portion of the ceramic body, the improvement is described comprising the ceramic body having in the first, exposed region a greater percentage of the monoclinic lattice modification than in the second region; having in the first, exposed region 5 percent to 100 percent in the monoclinic lattice modification; and having a molded surface finish in the first, exposed region; the first, exposed region being subjected to a compressive field resulting from the greater percentage of the monoclinic lattice modification

Calculation of cracking under pulsed heat loads in tungsten manufactured according to ITER specifications

International Nuclear Information System (INIS)

Arakcheev, A.S.; Skovorodin, D.I.; Burdakov, A.V.; Shoshin, A.A.; Polosatkin, S.V.; Vasilyev, A.A.; Postupaev, V.V.; Vyacheslavov, L.N.; Kasatov, A.A.; Huber, A.; Mertens, Ph; Wirtz, M.; Linsmeier, Ch; Kreter, A.; Löwenhoff, Th; Begrambekov, L.; Grunin, A.; Sadovskiy, Ya

2015-01-01

A mathematical model of surface cracking under pulsed heat load was developed. The model correctly describes a smooth brittle–ductile transition. The elastic deformation is described in a thin-heated-layer approximation. The plastic deformation is described with the Hollomon equation. The time dependence of the deformation and stresses is described for one heating–cooling cycle for a material without initial plastic deformation. The model can be applied to tungsten manufactured according to ITER specifications. The model shows that the stability of stress-relieved tungsten deteriorates when the base temperature increases. This proved to be a result of the close ultimate tensile and yield strengths. For a heat load of arbitrary magnitude a stability criterion was obtained in the form of condition on the relation of the ultimate tensile and yield strengths.

Thermal stability of butter oils produced from sheep’s non-pasteurized and pasteurized milk

Directory of Open Access Journals (Sweden)

FLAVIA POP

Full Text Available The physical and chemical characteristics and thermal stability of butter oil produced from non-pasteurized and pasteurized sheep’s milk were studied. Thermal stability of samples was estimated by using the accelerated shelf-life testing method. Samples were stored at 50, 60 and 70oC in the dark and the reaction was monitored by measuring peroxide, thiobarbituric acid and free fatty acid values. The peroxide and thiobarbituric acid values increased as the temperature increased. The increase of acid values of the two samples was not significant. A slight increase in free fatty acid value showed that hydrolytic reactions were not responsible for the deterioration of butter oil samples in thermal stability studies. When compared, butter oil produced from pasteurized sheep’s milk has higher thermal stability than butter oil produced from non-pasteurized sheep’s milk. Although butter oil produced from non-pasteurized milk was not exposed to any heat treatment, the shelf-life of this product was lower than the shelf-life of butter oil produced from pasteurized sheep’s milk. Therefore, heat treatment for pasteurization did not affect the thermal stability of butter oil.

Thermal Microstructural Stability of AZ31 Magnesium after Severe Plastic Deformation

Energy Technology Data Exchange (ETDEWEB)

Young, John P.; Askari, Hesam A.; Hovanski, Yuri; Heiden, Michael J.; Field, David P.

2015-03-01

Both equal channel angular pressing and friction stir processing have the ability to refine the grain size of twin roll cast AZ31 magnesium and potentially improve its superplastic properties. This work used isochronal and isothermal heat treatments to investigate the microstructural stability of twin roll cast, equal channel angular pressed and friction stir processed AZ31 magnesium. For both heat treatment conditions, it was found that the twin roll casted and equal channel angular pressed materials were more stable than the friction stir processed material. Calculations of the grain growth kinetics showed that severe plastic deformation processing decreased the activation energy for grain boundary motion with the equal channel angular pressed material having the greatest Q value of the severely plastically deformed materials and that increasing the tool travel speed of the friction stir processed material improved microstructural stability. The Hollomon-Jaffe parameter was found to be an accurate means of identifying the annealing conditions that will result in substantial grain growth and loss of potential superplastic properties in the severely plastically deformed materials. In addition, Humphreys’s model of cellular microstructural stability accurately predicted the relative microstructural stability of the severely plastically deformed materials and with some modification, closely predicted the maximum grain size ratio achieved by the severely plastically deformed materials.

Characterization of zeolite-based coatings for adsorption heat pumps

CERN Document Server

Freni, Angelo; Bonaccorsi, Lucio; Chmielewski, Stefanie; Frazzica, Andrea; Calabrese, Luigi; Restuccia, Giovanni

2015-01-01

This book proposes a radically new approach for characterizing thermophysical and mechanical properties of zeolite-based adsorbent coatings for Adsorptive Heat Transformers (AHT). It presents a developed standard protocol for the complete characterization of advanced coated adsorbers. Providing an in-depth analysis of the different procedures necessary for evaluating the performance of adsorbers, it also presents an analysis of their stability under the hydrothermal and mechanical stresses during their entire life cycle. Adsorptive Heat Transformers (AHT), especially adsorption chillers and

Solid-cryogen-stabilized, cable-in-conduit (CIC) superconducting cables

Science.gov (United States)

Voccio, J. P.; Michael, P. C.; Bromberg, L.; Hahn, S.

2015-12-01

This paper considers the use of a solid cryogen as a means to stabilize, both mechanically and thermally, magnesium diboride (MgB2) superconducting strands within a dual-channel cable-in-conduit (CIC) cable for use in AC applications, such as a generator stator winding. The cable consists of two separate channels; the outer channel contains the superconducting strands and is filled with a fluid (liquid or gas) that becomes solid at the device operating temperature. Several options for fluid will be presented, such as liquid nitrogen, hydrocarbons and other chlorofluorocarbons (CFCs) that have a range of melting temperatures and volumetric expansions (from solid at operating temperature to fixed volume at room temperature). Implications for quench protection and conductor stability, enhanced through direct contact with the solid cryogen, which has high heat capacity and thermal conductivity (compared with helium gas), will be presented. Depending on the cryogen, the conductor will be filled initially either with liquid at atmospheric conditions or a gas at high pressure (∼100 atm). After cooldown, the cryogen in the stranded-channel will be solid, essentially locking the strands in place, preventing strand motion and degradation due to mechanical deformation while providing enhanced thermal capacity for stability and protection. The effect of cryogen porosity is also considered. The relatively high heat capacity of solid cryogens at these lower temperatures (compared to gaseous helium) enhances the thermal stability of the winding. During operation, coolant flow through the open inner channel will minimize pressure drop.

Modelling of flow stabilization by the swirl of a peripheral flow as applied to plasma reactors

International Nuclear Information System (INIS)

Volchkov, E.P.; Lebedev, V.P.; Terekhov, V.I.; Shishkin, N.E.

2000-01-01

The gas-swirl stabilization of plasma jets is one of effective methods of its retention in the near-axial area of channels in generators of low-temperature plasma. Except the effect of gas-dynamic compression, the peripheral swirl allows to solve another urgent problem - to protect the reactor walls from the heat influence of the plasma jet. Swirl flows are also used for the flow structure formation and control of the heat and gas-dynamic characteristics of different power devices and apparatuses, using high-temperature working media: in swirl furnaces and burners, in aviation engines, etc. Investigations show that during swirl stabilization the gas-dynamic structure of the flow influences significantly the spatial stability of the plasma column and its characteristics

Suppression of cyclotron instability in Electron Cyclotron Resonance ion sources by two-frequency heating

International Nuclear Information System (INIS)

Skalyga, V.; Izotov, I.; Mansfeld, D.; Kalvas, T.; Koivisto, H.; Komppula, J.; Kronholm, R.; Laulainen, J.; Tarvainen, O.

2015-01-01

Multiple frequency heating is one of the most effective techniques to improve the performance of Electron Cyclotron Resonance (ECR) ion sources. The method increases the beam current and average charge state of the extracted ions and enhances the temporal stability of the ion beams. It is demonstrated in this paper that the stabilizing effect of two-frequency heating is connected with the suppression of electron cyclotron instability. Experimental data show that the interaction between the secondary microwave radiation and the hot electron component of ECR ion source plasmas plays a crucial role in mitigation of the instabilities

Classical fluids of negative heat capacity

Energy Technology Data Exchange (ETDEWEB)

Landsberg, P.T. [Southampton Univ., (United Kingdom). Faculty of Mathematical Studies; Woodard, R.P. [Florida Univ., Gainesville, FL (United States). Dept. of Physics

1992-06-01

It is shown that new parameters X can be defined such that the heat capacity C{sub X} {equivalent_to} T({partial_derivative}S/{partial_derivative}T)X is negative, even when the canonical ensemble (i.e. at fixed T = ({partial_derivative}U/{partial_derivative}S) and Y {ne} X) is stable. As examples we treat black body radiation and general gas systems with nonsingular {kappa}{sub T}. For the case of a simple ideal gas we even exhibit an apparatus which enforces a constraint X(p,V) = const. that makes C{sub X} < 0. Since it is possible to invent constraints for which canonically stable systems have negative heat capacity we speculate that it may also be possible to infer the statistical mechanics of canonically unstable systems - for which even the traditional heat capacities are negative - by imposing constraints that stabilize the associated, inoncanonical ensembles.

Classical fluids of negative heat capacity

Energy Technology Data Exchange (ETDEWEB)

Landsberg, P.T. (Southampton Univ., (United Kingdom). Faculty of Mathematical Studies); Woodard, R.P. (Florida Univ., Gainesville, FL (United States). Dept. of Physics)

1992-06-01

It is shown that new parameters X can be defined such that the heat capacity C{sub X} {equivalent to} T({partial derivative}S/{partial derivative}T)X is negative, even when the canonical ensemble (i.e. at fixed T = ({partial derivative}U/{partial derivative}S) and Y {ne} X) is stable. As examples we treat black body radiation and general gas systems with nonsingular {kappa}{sub T}. For the case of a simple ideal gas we even exhibit an apparatus which enforces a constraint X(p,V) = const. that makes C{sub X} < 0. Since it is possible to invent constraints for which canonically stable systems have negative heat capacity we speculate that it may also be possible to infer the statistical mechanics of canonically unstable systems - for which even the traditional heat capacities are negative - by imposing constraints that stabilize the associated, inoncanonical ensembles.

Thermal stability of hexagonal OsB{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Xie, Zhilin [Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, FL 32816 (United States); Blair, Richard G. [Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, FL 32816 (United States); Department of Physics, University of Central Florida, Orlando, FL 32816 (United States); Orlovskaya, Nina, E-mail: Nina.Orlovskaya@ucf.edu [Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, FL 32816 (United States); Cullen, David A. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Andrew Payzant, E. [Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

2014-11-15

The synthesis of novel hexagonal ReB{sub 2}-type OsB{sub 2} ceramic powder was performed by high energy ball milling of elemental Os and B powders. Two different sources of B powder have been used for this mechanochemical synthesis. One B powder consisted of a mixture of amorphous and crystalline phases and a mixture of {sup 10}B and {sup 11}B isotopes with a fine particle size, while another B powder was a purely crystalline (rhombohedral) material consisting of enriched {sup 11}B isotope with coarse particle size. The same Os powder was used for the synthesis in both cases. It was established that, in the first case, the hexagonal OsB{sub 2} phase was the main product of synthesis with a small quantity of Os{sub 2}B{sub 3} phase present after synthesis as an intermediate product. In the second case, where coarse crystalline {sup 11}B powder was used as a raw material, only Os{sub 2}B{sub 3} boride was synthesized mechanochemically. The thermal stability of hexagonal OsB{sub 2} powder was studied by heating under argon up to 876 °C and cooling in vacuo down to −225 °C. During the heating, the sacrificial reaction 2OsB{sub 2}+3O{sub 2}→2Os+2B{sub 2}O{sub 3} took place due to presence of O{sub 2}/water vapor molecules in the heating chamber, resulting in the oxidation of B atoms and formation of B{sub 2}O{sub 3} and precipitation of Os metal out of the OsB{sub 2} lattice. As a result of such phase changes during heating, the lattice parameters of hexagonal OsB{sub 2} changed significantly. The shrinkage of the a lattice parameter was recorded in 276–426 °C temperature range upon heating, which was attributed to the removal of B atoms from the OsB{sub 2} lattice due to oxidation followed by the precipitation of Os atoms and formation of Os metal. While significant structural changes occurred upon heating due to presence of O{sub 2}, the hexagonal OsB{sub 2} ceramic demonstrated good phase stability upon cooling in vacuo with linear shrinkage of the lattice

Preparation of nanodispersed titania using stabilized ammonium nitrate melts

KAUST Repository

Raciulete, Monica

2010-10-01

An expedite one-step approach using simple precursors has been proposed to obtain metallic oxide compounds and exemplified by preparation of highly dispersed TiO2. The technique consists in heating to 400500 °C of molten ammonium nitrate stabilized with an organic nitrogen-containing compound (urea, melamine, ammonium oxalate) and containing dissolved metal salt precursor (TiOCl2). The crystallites of the resulting TiO2 demonstrated variable size and shape as a function of stabilizer used. Their activity in photocatalytic oxidation of formic acid also depends on the nature of the stabilizer. The catalysts as-prepared showed high photocatalytic performance, superior to that of the Degussa P25 reference. Nitrogen containing stabilizers play a double role of increasing the process safety and modifying the properties of the solid products. © 2010 Elsevier Inc. All rights reserved.

Pilot Dietary Intervention with Heat-Stabilized Rice Bran Modulates Stool Microbiota and Metabolites in Healthy Adults

Directory of Open Access Journals (Sweden)

Amy M. Sheflin

2015-02-01

Full Text Available Heat-stabilized rice bran (SRB has been shown to regulate blood lipids and glucose, modulate gut mucosal immunity and inhibit colorectal cancer in animal and human studies. However, SRB’s effects on gut microbial composition and metabolism and the resulting implications for health remain largely unknown. A pilot, randomized-controlled trial was developed to investigate the effects of eating 30 g/day SRB on the stool microbiome and metabolome. Seven healthy participants consumed a study meal and snack daily for 28 days. The microbiome and metabolome were characterized using 454 pyrosequencing and gas chromatography-mass spectrometry (GC-MS at baseline, two and four weeks post-intervention. Increases in eight operational taxonomic units (OTUs, including three from Bifidobacterium and Ruminococcus genera, were observed after two and four weeks of SRB consumption (p < 0.01. Branched chain fatty acids, secondary bile acids and eleven other putative microbial metabolites were significantly elevated in the SRB group after four weeks. The largest metabolite change was a rice bran component, indole-2-carboxylic acid, which showed a mean 12% increase with SRB consumption. These data support the feasibility of dietary SRB intervention in adults and support that SRB consumption can affect gut microbial metabolism. These findings warrant future investigations of larger cohorts evaluating SRB’s effects on intestinal health.

Abnormal Grain Growth in the Heat Affected Zone of Friction Stir Welded Joint of 32Mn-7Cr-1Mo-0.3N Steel during Post-Weld Heat Treatment

Directory of Open Access Journals (Sweden)

Yijun Li

2018-04-01

Full Text Available The abnormal grain growth in the heat affected zone of the friction stir welded joint of 32Mn-7Cr-1Mo-0.3N steel after post-weld heat treatment was confirmed by physical simulation experiments. The microstructural stability of the heat affected zone can be weakened by the welding thermal cycle. It was speculated to be due to the variation of the non-equilibrium segregation state of solute atoms at the grain boundaries. In addition, the pressure stress in the welding process can promote abnormal grain growth in the post-weld heat treatment.

Modifications to improve entrance slit thermal stability for grasshopper monochromators

Science.gov (United States)

Wallace, Daniel J.; Rogers, Gregory C.; Crossley, Sherry L.

1994-08-01

As new monochromators are designed for high-flux storage rings, computer modeling and thermal engineering can be done to process increased heat loads and achieve mechanical stability. Several older monochromators, such as the Mark 2 and Mark 5 Grasshopper monochromators, which were designed in 1974, have thermal instabilities in their entrance slit mechanisms. The Grasshoppers operating with narrow slits experience closure of the entrance slit from thermal expansion. In extreme cases, the thermal expansion of the precision components has caused permanent mechanical damage, leaving the slit uncalibrated and/or inoperable. For the Mark 2 and Mark 5 Grasshopper monochromators at the Synchrotron Radiation Center, the original 440 stainless steel entrance slit jaws were retrofitted with an Invar (low expansion Fe, Ni alloy) slit jaw. To transfer the heat from the critical components, two flexible heat straps of Cu were attached. These changes allow safe operation with a 10 μm entrance slit width where the previous limit was 30 μm. After an initial 2 min equilibration, the slit remains stable to 10%, with 100 mA of beam current. Additional improvements in slit thermal stability are planned for a third Grasshopper.

Investigating On Colour Stability Conditions Of Postirradiation Radiochromic Film Dosimeter

International Nuclear Information System (INIS)

Nguyen Nguyet Dieu; Doan Binh; Pham Thu Hong; Cao Van Chung; Nguyen Thanh Duoc

2011-01-01

B3 dosimeter is a thin film with average thickness of 0.0194 mm, which is supplied by the Gex company, the United States. This dosimeter was influenced by many factors: light, temperature, humidity during and after irradiation process. In fact, B3 film dosimeters will be stable under certain conditions such as tightly sealed packs, controlled irradiation and stored temperature after irradiated. Therefore, investigation of the stability effect of postirradiated B3 film dosimeters on the heating temperature, heating time and storing time is carried out before the absorbed dose is read and followed standard reading procedures. When exposed to ionizing radiation, the dosimeters change from colorless to colour. The absorbed doses are read on a Genesys 20 spectrophotometer at a wavelength of 544 nm. Absorbed dose range is investigated from 0.55 to 80 kGy. Experimental results were indicated that colour stability of the postirradiated dosimeters at a temperature of 65 ± 3 o C for 30 minutes and keeping them in desiccator for 5 minutes before read out. Under these conditions, colour stability of B3 film dosimeter has maintained for 3 months. (author)

Analysis of reactor material experiments investigating oxide fuel crust stability and heat transfer in jet impingement flow

International Nuclear Information System (INIS)

Sienicki, J.J.; Spencer, B.W.

1985-01-01

An analysis is presented of the crust stability and heat transfer behavior in the CSTI-1, CSTI-3, and CWTI-11 reactor material experiments in which a jet of molten oxide fuel at approx. 160 0 K above its freezing temperature was impinged normally upon stainless steel plates initially at 300 and 385 K. The major issue is the existence of nonexistence of a stable solidified layer of fuel, or crust, interstitial to the flowing hot fuel and the steel substrate, tending to insulate the steel from the hot molten fuel. A computer model was developed to predict the heatup of thermocouples imbedded immediately beneath the surface of the plate for both of the cases in which a stable crust is assumed to be either present or absent during the impingement phase. Comparison of the model calculations with the measured thermocouple temperatures indicates that a protective crust was present over nearly all of the plate surface area throughout the impingement process precluding major melting of the plate steel. However, the experiments also show evidence for very localized and isolated steel melting as revealed by localized and isolated pitting of the steel surface and the response of thermocouples located within the pitted region

Thermal stability of hexagonal OsB2

Science.gov (United States)

Xie, Zhilin; Blair, Richard G.; Orlovskaya, Nina; Cullen, David A.; Andrew Payzant, E.

2014-11-01

The synthesis of novel hexagonal ReB2-type OsB2 ceramic powder was performed by high energy ball milling of elemental Os and B powders. Two different sources of B powder have been used for this mechanochemical synthesis. One B powder consisted of a mixture of amorphous and crystalline phases and a mixture of 10B and 11B isotopes with a fine particle size, while another B powder was a purely crystalline (rhombohedral) material consisting of enriched 11B isotope with coarse particle size. The same Os powder was used for the synthesis in both cases. It was established that, in the first case, the hexagonal OsB2 phase was the main product of synthesis with a small quantity of Os2B3 phase present after synthesis as an intermediate product. In the second case, where coarse crystalline 11B powder was used as a raw material, only Os2B3 boride was synthesized mechanochemically. The thermal stability of hexagonal OsB2 powder was studied by heating under argon up to 876 °C and cooling in vacuo down to -225 °C. During the heating, the sacrificial reaction 2OsB2+3O2→2Os+2B2O3 took place due to presence of O2/water vapor molecules in the heating chamber, resulting in the oxidation of B atoms and formation of B2O3 and precipitation of Os metal out of the OsB2 lattice. As a result of such phase changes during heating, the lattice parameters of hexagonal OsB2 changed significantly. The shrinkage of the a lattice parameter was recorded in 276-426 °C temperature range upon heating, which was attributed to the removal of B atoms from the OsB2 lattice due to oxidation followed by the precipitation of Os atoms and formation of Os metal. While significant structural changes occurred upon heating due to presence of O2, the hexagonal OsB2 ceramic demonstrated good phase stability upon cooling in vacuo with linear shrinkage of the lattice parameters and no phase changes detected during cooling.

Evaporation and condensation devices for passive heat removal systems in nuclear power engineering

International Nuclear Information System (INIS)

Gershuni, A.N.; Pis'mennyj, E.N.; Nishchik, A.P.

2016-01-01

The paper justifies advantages of evaporation and condensation heat transfer devices as means of passive heat removal and thermal shielding in nuclear power engineering. The main thermophysical factors that limit heat transfer capacity of evaporation and condensation systems have been examined in the research. The results of experimental studies of heat engineering properties of elongated (8-m) vertically oriented evaporation and condensation devices (two-phase thermosyphons), which showed a high enough heat transfer capacity, as well as stability and reliability both in steady state and in start-up modes, are provided. The paper presents the examples of schematic designs of evaporation and condensation systems for passive heat removal and thermal shielding in application to nuclear power equipment

Structure and stabilization of hydrogen-rich transverse.

Energy Technology Data Exchange (ETDEWEB)

Lyra, Sgouria [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Wilde, B [Georgia Inst. of Technology, Atlanta, GA (United States); Kolla, Hemanth [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Seitzman, J. [Georgia Inst. of Technology, Atlanta, GA (United States); Lieuwen, T. C. [Georgia Inst. of Technology, Atlanta, GA (United States); Chen, Jacqueline H. [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

2014-07-01

This paper reports the results of a joint experimental and numerical study of the ow characteristics and flame stabilization of a hydrogen rich jet injected normal to a turbulent, vitiated cross ow of lean methane combustion products. Simultaneous high-speed stereoscopic PIV and OH PLIF measurements were obtained and analyzed alongside three-dimensional direct numerical simulations of inert and reacting JICF with detailed H₂/CO chemistry. Both the experiment and the simulation reveal that, contrary to most previous studies of reacting JICF stabilized in low-to-moderate temperature air cross ow, the present conditions lead to an autoigniting, burner-attached flame that initiates uniformly around the burner edge. Significant asymmetry is observed, however, between the reaction zones located on the windward and leeward sides of the jet, due to the substantially different scalar dissipation rates. The windward reaction zone is much thinner in the near field, while also exhibiting significantly higher local and global heat release than the much broader reaction zone found on the leeward side of the jet. The unsteady dynamics of the windward shear layer, which largely control the important jet/cross flow mixing processes in that region, are explored in order to elucidate the important flow stability implications arising in the reacting JICF. Vorticity spectra extracted from the windward shear layer reveal that the reacting jet is globally unstable and features two high frequency peaks, including a fundamental mode whose Strouhal number of ~0.7 agrees well with previous non-reacting JICF stability studies. The paper concludes with an analysis of the ignition, ame stabilization, and global structure of the burner-attached flame. Chemical explosive mode analysis (CEMA) shows that the entire windward shear layer, and a large region on the leeward side of the jet, are highly explosive prior to ignition and are dominated by non-premixed flame structures after

Impact of Power Ultrasound on Antihypertensive Activity, Functional Properties, and Thermal Stability of Rapeseed Protein Hydrolysates

Directory of Open Access Journals (Sweden)

Asif Wali

2017-01-01

Full Text Available The effects of power ultrasound pretreatments on the degree of hydrolysis (DH, angiotensin-I-converting enzyme (ACE inhibitory activity, amino acid composition, surface hydrophobicity, protein solubility, and thermal stability of ACE inhibition of rapeseed protein hydrolysates were evaluated. Ultrasonic pretreatments before enzymolysis in terms of power and exposure time increased the DH and ACE inhibitory activities over the control (without sonication. In this study, maximum DH 22.07% and ACE inhibitory activity 72.13% were achieved at 600 W and 12 min pretreatment. Compared to the hydrolysates obtained without sonication, the amino acid profile of ultrasound pretreated hydrolysates showed significant changes particularly in the proline content and hydrophobic amino acids with an increased rate of 2.47% and 6.31%, respectively. Ultrasound pretreatment (600 watts, 12 min improved functional properties of protein hydrolysates over control by enhancing surface hydrophobicity and solubility index with an increased rate of 130.76% and 34.22%. Moreover, the stability test showed that the ACE inhibitory activity remains stable against heat treatments. However, extensive heat, prolonged heating time, and alkaline conditions were not in the favor of stability test, while under mild heat and acidic conditions their ACE inhibitory activities were not significantly different from unheated samples.

Neutral insulin solutions physically stabilized by addition of Zn2+.

Science.gov (United States)

Brange, J; Havelund, S; Hommel, E; Sørensen, E; Kühl, C

1986-01-01

Commercial neutral insulin solutions, all of which contain 2-3 zinc atoms per hexameric unit of insulin, have a relatively limited physical stability when exposed to heat and movement, as for example in insulin infusion pumps. Physical stabilization of neutral insulin solutions has been obtained by addition of two extra Zn2+ per hexamer of insulin. This addition stabilizes porcine and human neutral solutions equally well and does not affect the chemical stability of the insulin. The stabilization is probably obtained by a further strengthening of the hexameric structure of insulin, so that the formation of insoluble insulin fibrils (via the dissociation into the insulin monomer or dimer) is impeded or prevented. The addition of an extra 2 Zn2+ has been shown to be without influence on the insulin immunogenicity in rabbits or on the rate of absorption after subcutaneous injection in diabetic patients. It is concluded that neutral insulin solution can be physically stabilized by addition of extra Zn2+ without affecting other qualities of the insulin preparation including chemical stability, immunogenicity, and duration of action after injection.

Investigations on the effect of heater and cooler orientation on the steady state, transient and stability behaviour of single-phase natural circulation in a rectangular loop

International Nuclear Information System (INIS)

Vijayan, P.K.; Bhojwani, V.K.; Bade, M.H.; Sharma, M.; Nayak, A.K.; Saha, D.; Sinha, R.K.

2002-01-01

An instability demonstration facility has been in operation in the heat transfer laboratory of the Reactor Engineering Div. for the past few years. This report deals with the investigations carried out in this facility so far. The facility is essentially a rectangular loop designed to generate single-phase natural circulation data on the steady state and stability behaviour for different orientations of the heat source and the heat sink. Effect of different heat addition paths (i.e. start-up from rest, power raising from initial stable steady and decay of instability due to power step back) and flow direction on the stability behaviour was also studied. The stability map of the system was generated both by the linear and the nonlinear methods

Microwave Heating of a Liquid Stably Flowing in a Circular Channel Under the Conditions of Nonstationary Radiative-Convective Heat Transfer

Science.gov (United States)

Salomatov, V. V.; Puzyrev, E. M.; Salomatov, A. V.

2018-05-01

A class of nonlinear problems of nonstationary radiative-convective heat transfer under the microwave action with a small penetration depth is considered in a stabilized coolant flow in a circular channel. The solutions to these problems are obtained, using asymptotic procedures at the stages of nonstationary and stationary convective heat transfer on the heat-radiating channel surface. The nonstationary and stationary stages of the solution are matched, using the "longitudinal coordinate-time" characteristic. The approximate solutions constructed on such principles correlate reliably with the exact ones at the limiting values of the operation parameters, as well as with numerical and experimental data of other researchers. An important advantage of these solutions is that they allow the determination of the main regularities of the microwave and thermal radiation influence on convective heat transfer in a channel even before performing cumbersome calculations. It is shown that, irrespective of the heat exchange regime (nonstationary or stationary), the Nusselt number decreases and the rate of the surface temperature change increases with increase in the intensity of thermal action.

Heating Development Analysis in Long HTS Objects - Updated Results

Energy Technology Data Exchange (ETDEWEB)

Vysotsky, V S; Repnikov, V V; Lobanov, E A; Karapetyan, G H; Sytnikov, V E [All-Russian Scientific R and D Cable Institute, 5, Shosse Entuziastov, 111024, Moscow (Russian Federation)

2006-06-01

During fault in a grid large overload current, up to 30-times fold, forcibly will go to an HTS superconducting cable installed in a grid causing its quench and heating. The upgraded model has been used to analyse the heating development in long HTS objects during overloads. The model better presents real properties of materials used. New calculations coincide well with experiments and permit to determine the cooling coefficients. The stability limit (thermal runaway current) was determined for different cooling and index n. The overload currents, at which the superconductor will be heated up to 100 K during 250 ms can be determined also. The model may be used for practical evaluations of operational parameters.

Development of thermal stability additive packages for JP-8

Energy Technology Data Exchange (ETDEWEB)

Anderson, S.D.; Harrison, W.E. III; Edwards, T.; Morris, R.W.; Shouse, D.T. [USAF Wright Lab., Wright-Paterson AFB, OH (United States)

1995-05-01

Advanced military aircraft use fuel as the primary heat sink to cool engine and airframe components. As the fuel is thermally stressed, thermal oxidative reactions take place that result in the formation of deposits. These deposits degrade aircraft performance and ultimately lead to premature servicing of the affected components. The frequency of these incidents, coupled with the projected cooling requirements for future systems, demonstrates that current thermal stability limits are inadequate. In response to this situation, the United States Air Force (USAF) has embarked on a program to improve thermal stability using specially formulated additive packages. Results indicate that additives offer significant thermal stability improvement. This paper describes the USAF program to develop and deploy an improved JP-8 for fleet-wide use by 1998.

Evaluation of stabilization techniques for ion implant processing

Science.gov (United States)

Ross, Matthew F.; Wong, Selmer S.; Minter, Jason P.; Marlowe, Trey; Narcy, Mark E.; Livesay, William R.

1999-06-01

With the integration of high current ion implant processing into volume CMOS manufacturing, the need for photoresist stabilization to achieve a stable ion implant process is critical. This study compares electron beam stabilization, a non-thermal process, with more traditional thermal stabilization techniques such as hot plate baking and vacuum oven processing. The electron beam processing is carried out in a flood exposure system with no active heating of the wafer. These stabilization techniques are applied to typical ion implant processes that might be found in a CMOS production process flow. The stabilization processes are applied to a 1.1 micrometers thick PFI-38A i-line photoresist film prior to ion implant processing. Post stabilization CD variation is detailed with respect to wall slope and feature integrity. SEM photographs detail the effects of the stabilization technique on photoresist features. The thermal stability of the photoresist is shown for different levels of stabilization and post stabilization thermal cycling. Thermal flow stability of the photoresist is detailed via SEM photographs. A significant improvement in thermal stability is achieved with the electron beam process, such that photoresist features are stable to temperatures in excess of 200 degrees C. Ion implant processing parameters are evaluated and compared for the different stabilization methods. Ion implant system end-station chamber pressure is detailed as a function of ion implant process and stabilization condition. The ion implant process conditions are detailed for varying factors such as ion current, energy, and total dose. A reduction in the ion implant systems end-station chamber pressure is achieved with the electron beam stabilization process over the other techniques considered. This reduction in end-station chamber pressure is shown to provide a reduction in total process time for a given ion implant dose. Improvements in the ion implant process are detailed across

Turbulent transport stabilization by ICRH minority fast ions in low rotating JET ILW L-mode plasmas

Science.gov (United States)

Bonanomi, N.; Mantica, P.; Di Siena, A.; Delabie, E.; Giroud, C.; Johnson, T.; Lerche, E.; Menmuir, S.; Tsalas, M.; Van Eester, D.; Contributors, JET

2018-05-01

The first experimental demonstration that fast ion induced stabilization of thermal turbulent transport takes place also at low values of plasma toroidal rotation has been obtained in JET ILW (ITER-like wall) L-mode plasmas with high (3He)-D ICRH (ion cyclotron resonance heating) power. A reduction of the gyro-Bohm normalized ion heat flux and higher values of the normalized ion temperature gradient have been observed at high ICRH power and low NBI (neutral beam injection) power and plasma rotation. Gyrokinetic simulations indicate that ITG (ion temperature gradient) turbulence stabilization induced by the presence of high-energetic 3He ions is the key mechanism in order to explain the experimental observations. Two main mechanisms have been identified to be responsible for the turbulence stabilization: a linear electrostatic wave-fast particle resonance mechanism and a nonlinear electromagnetic mechanism. The dependence of the stabilization on the 3He distribution function has also been studied.

Sensing disks for slug-type calorimeters have higher temperature stability

Science.gov (United States)

1967-01-01

Graphite sensing disk for slug-type radiation calorimeters exhibits better performance at high temperatures than copper and nickel disks. The graphite is heat-soaked to stabilize its emittance and the thermocouple is protected from the graphite so repeated temperature cycling does not change its sensitivity.

Effect of plasma rotation on sawtooth stabilization by beam ion

International Nuclear Information System (INIS)

Gorelenkov, N. N.; Nave, M. F. F.; Budny, R.; Cheng, C. Z.; Fu, G. Y.; Hastie, J.; Manickam, J.; Park, W.

2000-01-01

The sawtooth period in JET ELM-free H-Mode plasmas is increasing with Neutral Beam Injection (NBI) power. For injected power PNBI 12MW no large sawtooth crash is observed during the ELM-free period. However, as the edge stability is improved and external kink modes and ELMs are delayed, a possible sawtooth crash at a high plasma beta becomes a concern. In JET DT experiments, delaying sawteeth was found to be crucial in the quest for high fusion power. Fast particles are known to provide stabilizing effect on sawteeth, however, sawtooth stabilization by NBI ions is not clearly understood, since NBI ions are usually not ''fast'' enough to stabilize the m/n = 1/1 internal kink mode which is believed to cause the crash. In order to understand the observed sawteeth stabilization in tokamak experiments with NBI heating, the internal kink m/n = 1/1 mode stability of JET plasmas was modeled using the NOVA-K code, which is also benchmarked with the nonperturbative version of NOVA and the M3D code. Comparison of m/n = 1/1 mode stabilization by NBI ions in JET and TFTR and application of the nonlinear stabilization criteria is given

Dependence of stability of metastable superconductors on copper fraction

International Nuclear Information System (INIS)

Elrod, S.A.; Lue, J.W.; Miller, J.R.; Dresner, L.

1980-12-01

The stability of composite superconductors operating in the metastable regime depends upon such factors as matrix resistivity, cooled surface dimensions, fraction of critical current, and volume fraction of stabilizer. By assuming constant thermophysical properties, we developed analytic expressions for the energy and voltage of the minimum propagating zone (MPZ). With other factors held constant, these expressions have been used to predict composite superconductor stability as a function of copper fraction: lower copper fractions lead to higher MPZ energies. MPZ voltages have been measured for three NbTi/Cu composites having different copper fractions and different critical current densities for several magnetic fields and transport currents. Experimental MPZ voltages have been used to calculate an effective heat transfer coefficient, which is subsequently used to calculate the MPZ energy. The experimental MPZ energies support the theoretical expectation that lower copper fractions lead to higher stability in the metastable regime

Theory-based model for the pedestal, edge stability and ELMs in tokamaks

International Nuclear Information System (INIS)

Pankin, A.Y.; Bateman, G.; Brennan, D.P.; Schnack, D.D.; Snyder, P.B.; Voitsekhovitch, I.; Kritz, A.H.; Janeschitz, G.; Kruger, S.; Onjun, T.; Pacher, G.W.; Pacher, H.D.

2006-01-01

An improved model for triggering edge localized mode (ELM) crashes is developed for use within integrated modelling simulations of the pedestal and ELM cycles at the edge of H-mode tokamak plasmas. The new model is developed by using the BALOO, DCON and ELITE ideal MHD stability codes to derive parametric expressions for the ELM triggering threshold. The whole toroidal mode number spectrum is studied with these codes. The DCON code applies to low mode numbers, while the BALOO code applies to only high mode numbers and the ELITE code applies to intermediate and high mode numbers. The variables used in the parametric stability expressions are the normalized pressure gradient and the parallel current density, which drive ballooning and peeling modes. Two equilibria motivated by DIII-D geometry with different plasma triangularities are studied. It is found that the stable region in the high triangularity discharge covers a much larger region of parameter space than the corresponding stability region in the low triangularity discharge. The new ELM trigger model is used together with a previously developed model for pedestal formation and ELM crashes in the ASTRA integrated modelling code to follow the time evolution of the temperature profiles during ELM cycles. The ELM frequencies obtained in the simulations of low and high triangularity discharges are observed to increase with increasing heating power. There is a transition from second stability to first ballooning mode stability as the heating power is increased in the high triangularity simulations. The results from the ideal MHD stability codes are compared with results from the resistive MHD stability code NIMROD

Electrical stability of Al-doped ZnO transparent electrode prepared by sol-gel method

International Nuclear Information System (INIS)

Tabassum, Samia; Yamasue, Eiji; Okumura, Hideyuki; Ishihara, Keiichi N.

2016-01-01

Highlights: • Al-doped ZnO thin film was deposited by sol-gel method in different annealing temperature and duration. • We examined the environmental stability in ambient and damp heat condition. • We investigated chemical state of thin film. • Better stability was observed in the film annealed at high temperature (600 °C) along with longer duration (120 min). • An ultrathin aluminum oxide layer formation was predicted by XPS measurement which protects further oxidation and improves stability. - Abstract: Al-doped zinc oxide (AZO) thin films have been considered as a promising alternative to tin doped indium oxide (ITO), which is currently used in various optoelectronic applications. However, the environmental stability of AZO film is not satisfactory, in that the resistivity is significantly increases in air. Here, we investigate the resistivity stability of AZO thin films prepared by sol-gel method using various annealing temperatures and durations. The degradation of resistivity property was observed for AZO films stored in ambient or damp heat environment, where the degradation rate was influenced by annealing temperature. A significant improvement of electrical stability was attained in AZO films that were prepared at high annealing temperature. The films, which showed the highest and the lowest increasing rate of resistivity, were further characterized in detail to shed light on the possible mechanisms explaining the improved stability through crystallinity, surface morphology and elemental state of the thin film.

Electrical stability of Al-doped ZnO transparent electrode prepared by sol-gel method

Energy Technology Data Exchange (ETDEWEB)

Tabassum, Samia, E-mail: shawon14@gmail.com; Yamasue, Eiji; Okumura, Hideyuki; Ishihara, Keiichi N.

2016-07-30

Highlights: • Al-doped ZnO thin film was deposited by sol-gel method in different annealing temperature and duration. • We examined the environmental stability in ambient and damp heat condition. • We investigated chemical state of thin film. • Better stability was observed in the film annealed at high temperature (600 °C) along with longer duration (120 min). • An ultrathin aluminum oxide layer formation was predicted by XPS measurement which protects further oxidation and improves stability. - Abstract: Al-doped zinc oxide (AZO) thin films have been considered as a promising alternative to tin doped indium oxide (ITO), which is currently used in various optoelectronic applications. However, the environmental stability of AZO film is not satisfactory, in that the resistivity is significantly increases in air. Here, we investigate the resistivity stability of AZO thin films prepared by sol-gel method using various annealing temperatures and durations. The degradation of resistivity property was observed for AZO films stored in ambient or damp heat environment, where the degradation rate was influenced by annealing temperature. A significant improvement of electrical stability was attained in AZO films that were prepared at high annealing temperature. The films, which showed the highest and the lowest increasing rate of resistivity, were further characterized in detail to shed light on the possible mechanisms explaining the improved stability through crystallinity, surface morphology and elemental state of the thin film.

Heat Treatment of Cr- and Cr-V ledeburitic tool steels

Directory of Open Access Journals (Sweden)

Peter Jurči

2014-11-01

Full Text Available Cr- and Cr-V ledeburitic cold work tool steels belong to the most important tool materials for large series manufacturing. To enable high production stability, the tools must be heat treated before use. This overview paper brings a comprehensive study on the heat treatment of these materials, starting from the soft annealing and finishing with the tempering. Also, it describes the impact of any step of the heat treatment on the most important structural and mechanical characteristics, like the hardness, the toughness and the wear resistance. The widely used AIS D2- steel (conventionally manufactured and Vanadis 6 (PM are used as examples in most cases.

The relationship between fatty acid compositions and thermal stability of extra virgin olive oils

Directory of Open Access Journals (Sweden)

Fayegh Moulodi

2014-11-01

Full Text Available Background: Fatty acids are one of the most important compounds in edible oils. Further, the stability of oils depends on the composition of fatty acids. So, this study was conducted to investigate the effect of fatty acid composition on the oxidative stability of extra virgin olive oils during the heating process. Methods: In total, eight samples of extra virgin olive oil were studied. To evaluate their thermal stability, the oils were heated at 120 ° C for 4 h and sampling was carried out in 2-hour intervals. Then, fatty acid composition, peroxide value, anisidine value and totox value were evaluated according to Iranian national standards. Results: Results showed a significantly direct correlation between Palmitoleic acid and Totox index in the second (r=0.786 and fourth hours (r=0.762, and between linoleic and Totox index in the second (r=0.643 and fourth hours (r=0.786. However, there was a significantly inverse relationship between oleic acid and Totox index in the fourth hour (r=-0.833. Conclusion: Result indicated that linoleic and Palmitoleic acids had a reducing effect on thermal stability of extra virgin olive oil after the second hour. But, Oleic acid caused a positive effect on thermal stability after the fourth hour. Thus, it is concluded that unsaturated fatty acids especially oleic acid affect the thermal stability at final hours.

Composite bulk Heat Insulation Made of loose Mineral and Organic Aggregate

Directory of Open Access Journals (Sweden)

Namsone Eva

2015-12-01

Full Text Available The task of building energy-efficiency is getting more important. Every house owner wishes to save up exploitation costs of heating, cooling, hot water production, ventilation, etc. and find cost-effective investments. One of the ways to reduce greenhouse gas emissions (GHGE is to minimize the heat transfer through the building by insulating it. Loose heat insulation is a good alternative to traditional board insulation, it is simple in use and cost-effective. Main drawback of this insulation is tendency to compact during exploitation. In the frame of this research composite loose heat insulation is elaborated, consisting on porous mineral foamed glass aggregate and local organic fiber materials (hemp and flaxen shives. Composite bulk insulation is an alternative solution which combines heat insulating properties and mechanical stability.

No Heat Spray Drying Technology

Energy Technology Data Exchange (ETDEWEB)

Beetz, Charles [ZoomEssence, Inc., Hebron, KY (United States)

2016-06-15

No Heat Spray Drying Technology. ZoomEssence has developed our Zooming™ spray drying technology that atomizes liquids to powders at ambient temperature. The process of drying a liquid into a powder form has been traditionally achieved by mixing a heated gas with an atomized (sprayed) fluid within a vessel (drying chamber) causing the solvent to evaporate. The predominant spray drying process in use today employs air heated up to 400° Fahrenheit to dry an atomized liquid into a powder. Exposing sensitive, volatile liquid ingredients to high temperature causes molecular degradation that negatively impacts solubility, stability and profile of the powder. In short, heat is detrimental to many liquid ingredients. The completed award focused on several areas in order to advance the prototype dryer to a commercial scale integrated pilot system. Prior to the award, ZoomEssence had developed a prototype ‘no-heat’ dryer that firmly established the feasibility of the Zooming™ process. The award focused on three primary areas to improve the technology: (1) improved ability to formulate emulsions for specific flavor groups and improved understanding of the relationship of emulsion properties to final dry particle properties, (2) a new production atomizer, and (3) a dryer controls system.

Quinacrine pretreatment reduces microwave-induced neuronal damage by stabilizing the cell membrane

Science.gov (United States)

Ding, Xue-feng; Wu, Yan; Qu, Wen-rui; Fan, Ming; Zhao, Yong-qi

2018-01-01

Quinacrine, widely used to treat parasitic diseases, binds to cell membranes. We previously found that quinacrine pretreatment reduced microwave radiation damage in rat hippocampal neurons, but the molecular mechanism remains poorly understood. Considering the thermal effects of microwave radiation and the protective effects of quinacrine on heat damage in cells, we hypothesized that quinacrine would prevent microwave radiation damage to cells in a mechanism associated with cell membrane stability. To test this, we used retinoic acid to induce PC12 cells to differentiate into neuron-like cells. We then pretreated the neurons with quinacrine (20 and 40 mM) and irradiated them with 50 mW/cm2 microwaves for 3 or 6 hours. Flow cytometry, atomic force microscopy and western blot assays revealed that irradiated cells pretreated with quinacrine showed markedly less apoptosis, necrosis, and membrane damage, and greater expression of heat shock protein 70, than cells exposed to microwave irradiation alone. These results suggest that quinacrine stabilizes the neuronal membrane structure by upregulating the expression of heat shock protein 70, thus reducing neuronal injury caused by microwave radiation. PMID:29623929

Microtopographic patterns in an arctic baydjarakh field: do fine-grain patterns enforce landscape stability?

International Nuclear Information System (INIS)

Gamon, John A; Kershaw, G Peter; Williamson, Scott; Hik, David S

2012-01-01

Recent observations suggest that while some arctic landscapes are undergoing rapid change, others are apparently more resilient. In this study, we related surface cover and energy balance to microtopography in a degraded polygonal peat plateau (baydjarakh field) near Churchill, Manitoba in mid-summer 2010. The landscape consists of remnant high-centered polygons divided by troughs of varying widths. Historical aerial photos indicate these topographical features have been stable for over 80 years. Our goal was to explore patterns that might explain the apparent stability of this landscape over this time period and to evaluate remote sensing methods for characterizing microtopographic patterns that might resist change in the face of climate warming. Summertime surface albedo measurements were combined with several years of winter snow depth, snow heat flux, summer thaw depth and annual surface temperature, all of which had striking contrasts between wet troughs and high polygon centers. Measurements of albedo and the snowpack heat transfer coefficient were lowest for wet troughs (areas of standing water) dominated by graminoids, and were significantly higher for high polygon centers, dominated by dwarf shrubs and lichens. Snow depth, surface temperature and thaw depth were all significantly higher for wet troughs than high polygon centers. Together these patterns of cover and energy balance associated with microtopographic variation can contribute to the stability of this landscape through differential heat transfer and storage. We hypothesize that local thermal feedback effects, involving greater heat trapping in the troughs than on the baydjarakh tops, and effective insulation on the baydjarakh edges, have ensured landscape stability over most of the past century. These results suggest that high-resolution remote sensing, combined with detailed field monitoring, could provide insights into the dynamics or stability of arctic landscapes, where cover often varies

Thermal stabilization and plasticization of poly(vinyl chloride) by ester thiols: Update and current status

International Nuclear Information System (INIS)

Starnes, William H.; Du, Bin; Kim, Soungkyoo; Zaikov, Vadim G.; Ge, Xianlong; Culyba, Elizabeth K.

2006-01-01

Poly(vinyl chloride) (PVC) is one of the most important medical plastics. Recently, however, the safety of flexible PVC containing the common plasticizer, di(2-ethylhexyl) phthalate, has been called into question. Widely used heat stabilizers for PVC that incorporate toxic heavy metals also have fallen into disfavor. In order to address these problems, we have synthesized and tested, as potential replacements, several organic thiols that contain one or more carboxylate ester functions and thus are highly compatible with the polymer. When introduced into PVC at high loading levels (e.g., 30-35 parts by weight), the ester thiols are extremely effective as heat stabilizers and also useful as primary plasticizers. When used at a low loading level (e.g., 3 parts by weight), they still are excellent heat stabilizers for both plasticized and rigid PVC. Importantly, their high potency is achieved in the absence of any costabilizers that incorporate heavy metals. Their syntheses are simple and straightforward, and their odors are not offensive, because their volatilities are low. Described here are some typical results obtained with this new additive technology, which was licensed for commercialization in 2005

Non-equilibrium phase stabilization versus bubble nucleation at a nanoscale-curved Interface

Science.gov (United States)

Schiffbauer, Jarrod; Luo, Tengfei

Using continuum dynamic van der Waals theory in a radial 1D geometry with a Lennard-Jones fluid model, we investigate the nature of vapor bubble nucleation near a heated, nanoscale-curved convex interface. Vapor bubble nucleation and growth are observed for interfaces with sufficiently large radius of curvature while phase stabilization of a superheated fluid layer occurs at interfaces with smaller radius. The hypothesis that the high Laplace pressure required for stable equilibrium of very small bubbles is responsible for phase stability is tested by effectively varying the parameter which controls liquid-vapor surface tension. In doing so, the liquid-vapor surface tension- hence Laplace pressure-is shown to have limited effect on phase stabilization vs. bubble nucleation. However, the strong dependence of nucleation on leading-order momentum transport, i.e. viscous dissipation, near the heated inner surface is demonstrated. We gratefully acknowledge ND Energy for support through the ND Energy Postdoctoral Fellowship program and the Army Research Office, Grant No. W911NF-16-1-0267, managed by Dr. Chakrapani Venanasi.

Investigation of temperature stability of ITO films characteristics

Directory of Open Access Journals (Sweden)

Troyan Pavel

2018-01-01

Full Text Available The paper represents research of thermal stability of optical and electro-physical parameters of ITO films deposited using various techniques. Variation of optical and electro-physical parameters was recorded using spectroscopy, and Hall’s and four-probe measurements. The best thermal stability was demonstrated by ITO films deposited by metal target sputtering In(90%/Sn(10% in mixture of gases O2 (25% + Ar (75% with further annealing in air atmosphere. This enables to apply this technique for production of thin film transparent resistive elements capable to heat the translucent structures up to 100°C without deterioration of their parameters.

Effects of roasting, blanching, autoclaving, and microwave heating on antigenicity of almond (Prunus dulcis L.) proteins.

Science.gov (United States)

Venkatachalam, M; Teuber, S S; Roux, K H; Sathe, S K

2002-06-05

Whole, unprocessed Nonpareil almonds were subjected to a variety of heat processing methods that included roasting (280, 300, and 320 degrees F for 20 and 30 min each; and 335 and 350 degrees F for 8, 10, and 12 min each), autoclaving (121 degrees C, 15 psi, for 5, 10, 15, 20, 25, and 30 min), blanching (100 degrees C for 1, 2, 3, 4, 5, and 10 min), and microwave heating (1, 2, and 3 min). Proteins were extracted from defatted almond flour in borate saline buffer, and immunoreactivity of the soluble proteins (normalized to 1 mg protein/mL for all samples) was determined using enzyme linked immunosorbent assay (ELISA). Antigenic stability of the almond major protein (amandin) in the heat-processed samples was determined by competitive inhibition ELISA using rabbit polyclonal antibodies raised against amandin. Processed samples were also assessed for heat stability of total antigenic proteins by sandwich ELISA using goat and rabbit polyclonal antibodies raised against unprocessed Nonpareil almond total protein extract. ELISA assays and Western blotting experiments that used both rabbit polyclonal antibodies and human IgE from pooled sera indicated antigenic stability of almond proteins when compared with that of the unprocessed counterpart.

Fuels for the oil-fuelled heating system of the future; Brennstoffe fuer die Oelheiztechnik der Zukunft

Energy Technology Data Exchange (ETDEWEB)

Rheinberg, O. van [Oel-Waerme-Institut GmbH, An-Institut der RWTH Aachen, Herzogenrath (Germany). Abt. Energietraeger

2011-02-15

For ecological and political reasons bio-heating-oil of up to 10.9 vol.% of Fatty-Acid-Methyl-Ester (FAME) is available in the market. For new installations the appliance industry has approved their products for the use of this bio-heating-oil. For existing oil firing plants minor changes are necessary. These are the use of qualified oil burner pumps, oil tubes, oil pre-filter and the change to single chord system in order to avoid the continuous circulation of heating oil. Due to the chemical and physical properties an admixture of up to 20.9 vol.% of FAME in heating oil sulphur low is feasible. One of the main requirements to introduce such fuel in the market is the guarantee of storage stability over several years even by such high levels of FAME. To reach this goal an accurate predictability of fuel stability and different actions for the stabilisation of such bio-heating oil are necessary. Hence several investigations are undertaken at Oel-Waerme-Institut to ensure higher levels of FAME or of other alternative fuels in the future. (orig.)

The stability of second sound waves in a rotating Darcy–Brinkman porous layer in local thermal non-equilibrium

Energy Technology Data Exchange (ETDEWEB)

Eltayeb, I A; Elbashir, T B A, E-mail: ieltayeb@squ.edu.om, E-mail: elbashir@squ.edu.om [Department of Mathematics and Statistics, College of Science, Sultan Qaboos University, Muscat 123 (Oman)

2017-08-15

The linear and nonlinear stabilities of second sound waves in a rotating porous Darcy–Brinkman layer in local thermal non-equilibrium are studied when the heat flux in the solid obeys the Cattaneo law. The simultaneous action of the Brinkman effect (effective viscosity) and rotation is shown to destabilise the layer, as compared to either of them acting alone, for both stationary and overstable modes. The effective viscosity tends to favour overstable modes while rotation tends to favour stationary convection. Rapid rotation invokes a negative viscosity effect that suppresses the stabilising effect of porosity so that the stability characteristics resemble those of the classical rotating Benard layer. A formal weakly nonlinear analysis yields evolution equations of the Landau–Stuart type governing the slow time development of the amplitudes of the unstable waves. The equilibrium points of the evolution equations are analysed and the overall development of the amplitudes is examined. Both overstable and stationary modes can exhibit supercritical stability; supercritical instability, subcritical instability and stability are not possible. The dependence of the supercritical stability on the relative values of the six dimensionless parameters representing thermal non-equilibrium, rotation, porosity, relaxation time, thermal diffusivities and Brinkman effect is illustrated as regions in regime diagrams in the parameter space. The dependence of the heat transfer and the mean heat flux on the parameters of the problem is also discussed. (paper)

The critical state stability in textured Bi2Sr2CaCu2O8+δ superconductor

International Nuclear Information System (INIS)

Nabialek, A.; Niewczas, M.

2006-01-01

The influence of parameters such as temperature, density of the critical current j c , sample dimensions and heat exchange conditions on the critical state stability has been studied in thin samples of textured Bi 2 Sr 2 CaCu 2 O 8+δ (BSCCO) superconductor, in an external magnetic field perpendicular to the wide surface of the samples. The results show that stability of the superconductor against flux jumps increases with decreasing sample thickness. A composite-like sample consisting of two superconducting slabs glued together exhibits critical state stability as a bulk sample of the same thickness while it is less stable against flux jumping than the unit slab. The field of the first flux jump H fj1 decreases with increasing magnetic field sweep rate. For a given temperature there exists a critical sweep rate below which flux jumps vanish. These observations are interpreted in terms of the current distribution in thin superconducting samples characterized by a strong demagnetizing factor. The results are compared with a model developed for samples characterized by negligible demagnetizing effects. The critical state stability in BSCCO has been discussed in terms of the diffusion of heat and of the magnetic flux within the superconductor and the influence of heat exchange on these conditions

Stability Study of the RERTR Fuel Microstructure

Energy Technology Data Exchange (ETDEWEB)

Jian Gan; Dennis Keiser; Brandon Miller; Daniel Wachs

2014-04-01

The irradiation stability of the interaction phases at the interface of fuel and Al alloy matrix as well as the stability of the fission gas bubble superlattice is believed to be very important to the U-Mo fuel performance. In this paper the recent result from TEM characterization of Kr ion irradiated U-10Mo-5Zr alloy will be discussed. The focus will be on the phase stability of Mo2-Zr, a dominated second phase developed at the interface of U-10Mo and the Zr barrier in a monolithic fuel plate from fuel fabrication. The Kr ion irradiations were conducted at a temperature of 200 degrees C to an ion fluence of 2.0E+16 ions/cm2. To investigate the thermal stability of the fission gas bubble superlattice, a key microstructural feature in both irradiated dispersion U-7Mo fuel and monolithic U-10Mo fuel, a FIB-TEM sample of the irradiated U-10Mo fuel (3.53E+21 fission/cm3) was used for a TEM in-situ heating experiment. The preliminary result showed extraordinary thermal stability of the fission gas bubble superlattice. The implication of the TEM observation from these two experiments on the fuel microstructural evolution under irradiation will be discussed.

Heat-Treatment of Defective UiO-66 from Modulated Synthesis: Adsorption and Stability Studies

International Nuclear Information System (INIS)

Jiao, Yang; Liu, Yang; Zhu, Guanghui; Hungerford, Julian T.; Bhattacharyya, Souryadeep

2017-01-01

Defect engineering in metal-organic frameworks (MOFs) is an emerging strategy that can be used to control physical or chemical characteristics of MOFs, including adsorption behavior and textural, mechanical, and conductive properties. Understanding the impact of defects on textural properties and chemical stability of MOFs is imperative to the development of MOFs with tunable defect sites. In this work, systematic adsorption measurements were performed with three adsorbate molecules (SO 2 , benzene, and cyclohexane) to investigate changes in the pore size of defective UiO-66. Compared to the parent UiO-66, the defective UiO-66 shows significant changes in adsorption capacities among the selected adsorbate molecules, demonstrating that pore size is significantly enlarged by the missing cluster defects. BET surface area analysis and DFT calculations were also performed to interrogate the chemical stability of the defective MOFs after exposure to water and acidic environments. This work shows that pore size can be tuned as a function of defect concentration. Further, it is shown that the structural incorporation of trifluoroacetate groups in defective UiO-66 leads to an increase in average pore size without sacrificing chemical stability toward water and acidic species. The results of this work advance the understanding of textural properties and chemical stability of defect-engineered MOFs and also suggest a preparation method for synthesizing defective but stable MOFs.

Progress in understanding heat transport at JET

International Nuclear Information System (INIS)

Mantica, P.; Garbet, X.; Angioni, C.

2005-01-01

This paper reports recent progress in understanding heat transport mechanisms either in conventional or advanced tokamak scenarios in JET. A key experimental tool has been the use of perturbative transport techniques, both by ICH power modulation and by edge cold pulses. The availability of such results has allowed careful comparison with theoretical modelling using 1D empirical or physics based transport models, 3D fluid turbulence simulations or gyrokinetic stability analysis. In conventional L- and H-mode plasmas the issue of temperature profile stiffness has been addressed. JET results are consistent with the concept of a critical inverse temperature gradient length above which transport is enhanced by the onset of turbulence. A threshold value R/L Te ∼5 has been found for the onset of stiff electron transport, while the level of electron stiffness appears to vary strongly with plasma parameters, in particular with the ratio of electron and ion heating: electrons become stiffer when ions are strongly heated, resulting in larger R/L Ti values. This behaviour has also been found theoretically, although quantitatively weaker than in experiments. In plasmas characterized by Internal Transport Barriers (ITB), the properties of heat transport inside the ITB layer and the ITB formation mechanisms have been investigated. The plasma current profile is found to play a major role in ITB formation. The effect of negative magnetic shear on electron and ion stabilization is demonstrated both experimentally and theoretically using turbulence codes. The role of rational magnetic surfaces in ITB triggering is well assessed experimentally, but still lacks a convincing theoretical explanation. Attempts to trigger an ITB by externally induced magnetic reconnection using saddle coils have shown that MHD islands in general do not produce a sufficient variation of ExB flow shear to lead to ITB formation. First results of perturbative transport in ITBs show that the ITB is a narrow

Thermo-physical stability of fatty acid eutectic mixtures subjected to accelerated aging for thermal energy storage (TES) application

International Nuclear Information System (INIS)

Fauzi, Hadi; Metselaar, Hendrik S.C.; Mahlia, T.M.I.; Silakhori, Mahyar

2014-01-01

The thermo-physical stability of fatty acids eutectic mixtures subjected to accelerated number of melting/solidification processes has been identified using thermal cycling test in this study. Myristic acid/palmitic acid (MA/PA) (70/30, wt.%) and myristic acid/palmitic acid/sodium stearate (MA/PA/SS) (70/30/5, wt.%) were selected as eutectic phase change materials (PCMs) to evaluate their stability of phase transition temperature, latent heat of fusion, chemical structure, and volume changes after 200, 500, 1000, and 1500 thermal cycles. The thermal properties of each eutectic PCMs measured by differential scanning calorimetric (DSC) indicated the phase transition temperature and latent heat of fusion values of MA/PA/SS has a smallest changes after 1500 thermal cycles than MA/PA eutectic mixture. MA/PA/SS also has a better chemical structure stability and smaller volume change which is 1.2%, compared to MA/PA with a volume change of 1.6% after 1500 cycles. Therefore, it is concluded that the MA/PA/SS eutectic mixture is suitable for use as a phase change material in thermal energy storage (TES) such as solar water heating and solar space heating applications. - Highlights: •The prepared MA/PA and MA/PA/SS were used as eutectic phase change materials (PCM). •Thermo-physical reliability of eutectic PCMs evaluated using a thermal cycling test. •MA/PA/SS has a great thermo-physical stability than MA/PA after 1500 thermal cycles

Observations of ELM stabilization during neutral beam injection in DIII-D

Science.gov (United States)

Bortolon, Alessandro; Kramer, Gerrit; Diallo, Ahmed; Knolker, Matthias; Maingi, Rajesh; Nazikian, Raffi; Degrassie, John; Osborne, Thomas

2017-10-01

Edge localized modes (ELMs) are generally interpreted as peeling-ballooning instabilities, driven by the pedestal current and pressure gradient, with other subdominant effects possibly relevant close to marginal stability. We report observations of transient stabilization of type-I ELMs during neutral beam injection (NBI), emerging from a combined dataset of DIII-D ELMy H-mode plasmas with moderate heating obtained through pulsed NBI waveforms. Statistical analysis of ELM onset times indicates that, in the selected dataset, the likelihood of onset of an ELM lowers significantly during NBI modulation pulses, with the stronger correlation found with counter-current NBI. The effect is also found in rf-heated H-modes, where ELMs appear inhibited when isolated diagnostic beam pulses are applied. Coherent average analysis is used to determine how plasma density, temperature, rotation as well as beam ion quantities evolve during a NB modulation cycle, finding relatively small changes ( 3%) of pedestal Te and ne and toroidal and poloidal rotation variations up to 5 km/s. The effect of these changes on pedestal stability will be discussed. Work supported by US DOE under DE-FC02-04ER54698, DE-AC02-09CH11466.

Effects of Heat-treatments on the Mechanical Strength of Coated YSZ: An Experimental Assessment

DEFF Research Database (Denmark)

Toftegaard, Helmuth Langmaack; Sørensen, Bent F.; Linderoth, Søren

2009-01-01

The mechanical strength of thin, symmetric sandwich specimens consisting of a dense yttria-stabilized zirconia (YSZ) substrate coated with a porous NiO–YSZ layer at both major faces was investigated. Specimens were loaded in uniaxial tension to failure following heat treatments at various...... temperatures. In comparison with the YSZ material, the failure strength of coated specimens was found to increase for heat treatments at 1100°C, but decreased again with further increased heat-treatment temperatures....

The effect of heat transfer on acoustics in burner stabilized flat flames

NARCIS (Netherlands)

Schreel, K.R.A.M.; Tillaart, van den E.L.; Janssen, R.W.M.; Goey, de L.P.H.; Koehne, H.; Lucka, K.

2003-01-01

Modern central heating systems use low NOx premixed burners with a largemodulation range. This can lead to noise problems which cannot be solved viatrial and error, but need accurate modelling. An acoustic analysis as part ofthe design phase can reduce the time-to-market considerably, but the

Heat-flow and temperature control in Tian–Calvet microcalorimeters: toward higher detection limits

International Nuclear Information System (INIS)

Vilchiz-Bravo, L E; Pacheco-Vega, A; Handy, B E

2010-01-01

Strategies based on the principle of heat flow and temperature control were implemented, and experimentally tested, to increase the sensitivity of a Tian–Calvet microcalorimeter for measuring heats of adsorption. Here, both heat-flow and temperature control schemes were explored to diminish heater-induced thermal variations within the heat sink element, hence obtaining less noise in the baseline signal. PID controllers were implemented within a closed-loop system to perform the control actions in a calorimetric setup. The experimental results demonstrate that the heat flow control strategy provided a better baseline stability when compared to the temperature control. The effects on the results stemming from the type of power supply used were also investigated

Ultra-High Pressure Homogenization enhances physicochemical properties of soy protein isolate-stabilized emulsions.

Science.gov (United States)

Fernández-Ávila, C; Escriu, R; Trujillo, A J

2015-09-01

The effect of Ultra-High Pressure Homogenization (UHPH, 100-300MPa) on the physicochemical properties of oil-in-water emulsions prepared with 4.0% (w/v) of soy protein isolate (SPI) and soybean oil (10 and 20%, v/v) was studied and compared to emulsions treated by conventional homogenization (CH, 15MPa). CH emulsions were prepared with non-heated and heated (95°C for 15min) SPI dispersions. Emulsions were characterized by particle size determination with laser diffraction, rheological properties using a rotational rheometer by applying measurements of flow curve and by transmission electron microscopy. The variation on particle size and creaming was assessed by Turbiscan® analysis, and visual observation of the emulsions was also carried out. UHPH emulsions showed much smaller d 3.2 values and greater physical stability than CH emulsions. The thermal treatment of SPI prior CH process did not improve physical stability properties. In addition, emulsions containing 20% of oil exhibited greater physical stability compared to emulsions containing 10% of oil. Particularly, UHPH emulsions treated at 100 and 200MPa with 20% of oil were the most stable due to low particle size values (d 3.2 and Span), greater viscosity and partial protein denaturation. These results address the physical stability improvement of protein isolate-stabilized emulsions by using the emerging UHPH technology. Copyright © 2015 Elsevier Ltd. All rights reserved.

Stability, structure, and evolution of cool loops

International Nuclear Information System (INIS)

Cally, P.S.; Robb, T.D.

1991-01-01

The criteria for the existence and stability of cool loops are reexamined. It is found that the stability of the loops strongly depends on the form of the heating and radiative loss functions and that if the Ly-alpha peak which appears in most calculations of the radiative loss function is real, cool loops are almost certainly unstable. Removing the hydrogen contribution from the recent loss function Q(T) by Cook et al. (1989) does not produce the much-used result, Q proportional to T-cubed, which is so favorable to cool loop stability. Even using the probably unrealistically favorable loss function Q1 of Cook et al. with the hydrogen contribution removed, the maximum temperature attainable in stable cool loops is a factor of 2-3 too small to account for the excess emission observed in lower transition region lines. Dynamical simulations of cool loop instabilities reveal that the final state of such a model is the hot loop equilibrium. 26 refs

Stability and forcing of the Iceland-Faroe inflow of water, heat, and salt to the Arctic

Directory of Open Access Journals (Sweden)

B. Hansen

2010-12-01

Full Text Available The flow of Atlantic water across the Greenland-Scotland Ridge (Atlantic inflow is critical for conditions in the Nordic Seas and Arctic Ocean by importing heat and salt. Here, we present a decade-long series of measurements from the Iceland-Faroe inflow branch (IF-inflow, which carries almost half the total Atlantic inflow. The observations show no significant trend in volume transport of Atlantic water, but temperature and salinity increased during the observational period. On shorter time scales, the observations show considerable variations but no statistically significant seasonal variation is observed and even weekly averaged transport values were consistently uni-directional from the Atlantic into the Nordic Seas. Combining transport time-series with sea level height from satellite altimetry and wind stress reveals that the force driving the IF-inflow across the topographic barrier of the Ridge is mainly generated by a pressure gradient that is due to a continuously maintained low sea level in the Southern Nordic Seas. This implies that the relative stability of the IF-inflow derives from the processes that lower the sea level by generating outflow from the Nordic Seas, especially the thermohaline processes that generate overflow. The IF-inflow is an important component of the system coupling the Arctic region to the North Atlantic through the thermohaline circulation, which has been predicted to weaken in the 21st century. Our observations show no indication of weakening.

Influence of the doping additives on heat stability and heat transfer of nickel coverings of cases IC

Directory of Open Access Journals (Sweden)

Novosyadly S. P.

2008-04-01

Full Text Available With the help of modern diagnostic microanalysis tools, the regularities are established for variation of electrophysical parameters of Ni-B galvanic coating of IC packages in the process of ultrasonic welding of internal Al leads and package seal. The optimal composition of the electrolyte which provides heat resistance increase of IC packages with alloyed Ni coating is selected. This, combined with the local gilding, enables mounting of crystals through a eutectic Si-Au sublayer.

Plasma equilibrium and stability in stellarators

International Nuclear Information System (INIS)

Pustovitov, V.D.; Shafranov, V.D.

1987-01-01

A review of theoretical methods of investigating plasma equilibrium and stability in stellarators is given. Principles forming the basis of toroidal plasma equilibrium and its stabilization, and the main results of analytical theory and numerical calculations are presented. Configurations with spiral symmetry and usual stellarators with plane axis and spiral fields are considered in detail. Derivation of scalar two-dimensional equations, describing equilibrium in these systems is given. These equations were used to obtain one-dimensional equations for displacement and ellipticity of magnetic surfaces. The model of weak-elliptic displaced surfaces was used to consider the evolution of plasma equilibrium in stellarators after elevation of its pressure: change of profile of rotational transformation after change of plasma pressure, current generation during its fast heating and its successive damping due to finite plasma conductivity were described. The derivation of equations of small oscillations in the form, suitable for local disturbance investigation is presented. These equations were used to obtain Mercier criteria and ballon model equations. General sufficient conditions of plasma stability in systems with magnetic confinement were derived

Promising materials for HTGR high temperature heat exchangers

International Nuclear Information System (INIS)

Kuznetsov, E.V.; Tokareva, T.B.; Ryabchenkov, A.V.; Novichkova, O.V.; Starostin, Yu.D.

1989-01-01

The service conditions for high-temperature heat-exchangers with helium coolant of HTGRs and requirements imposed on materials for their production are discussed. The choice of nickel-base alloys with solid-solution hardening for long-term service at high temperatures is grounded. Results of study on properties and structure of types Ni-25Cr-5W-5Mo and Ni-20Cr-20W alloy in the temperature range of 900 deg. - 1,000 deg. C are given. The ageing of Ni-25Cr-5W-5Mo alloy at 900 deg. - 950 deg. C results in decreased corrosion-mechanical properties and is caused by the change of structural metal stability. Alloy with 20% tungsten retains a high stability of both structure and properties after prolonged exposure in helium at above temperatures. The alloy has also increased resistance to delayed fracture and low-cycle fatigue at high temperatures. The developed alloy of type Ni-20Cr-20W with microalloying is recommended for production of tubes for HTGR high-temperature heat-exchangers with helium coolant. (author). 3 refs, 8 figs

A simple stability criterion for CANDU figure-of-eight flow oscillations

International Nuclear Information System (INIS)

Gulshani, P.; Spinks, N.J.

1983-01-01

Potential flow oscillations in CANDU reactor primary heat transport system are analyzed in terms of a simple, linearized model. A simple, algebraic stability criterion is obtained. The model predictions are found to be in good agreement with those of thermohydraulic codes for high pressure natural circulation conditions. For normal operating conditions the criterion predicts the correct trend but overlooks important stabilizing effects. The model clarifies the instability mechanism; namely the response of enthalpy and, hence, pressure in the boiling region to flow change

Climatic effects of nuclear war: The role of atmospheric stability and ground heat fluxes

International Nuclear Information System (INIS)

Mitchell, J.F.B.; Slingo, A.

1988-01-01

Most studies of the climatic effects of nuclear war have used atmospheric models with simple representations of important physical processes. In this work, a model is used which treats the diurnal cycle of insolation, and includes surface and boundary layer parameterizations which take into account static stability and a four-layer soil model. Three idealized experiments are described in which a band of smoke is prescribed over northern mid-latitudes in In the experiment, the standard model is used, in the second the effect of deep soil layers is ignored and in the third the stability dependence in the surface and boundary layer processes is removed. It is found that the inclusion of deep soil layers decreases the surface cooling by about 20%, whereas the inclusion of stability effects increases the cooling by about the same amount, though conclusions will depend to some extent on the model used. copyright American Geophysical Union 1988

Multi-Temperature Heat Pump with Cascade Compressor Connection

Directory of Open Access Journals (Sweden)

Sit M.L.

2017-08-01

Full Text Available The object of the study is a multifunctional heat pump with several evaporators and condensers designed for simultaneous provision of technological processes with heat and cold. The aim of the work is the development and study of the scheme for this type of heat pumps, which ensures minimum irreversibility in the "compressor-gas coolers" chain, without the use of adjustable ejectors installed after evaporators and used as flow mixers. The obtained technical solution ensures the stabilization of the heat pump coefficient of performance (COP and prescribed thermal regimes of heat exchangers at a variable flow rate of the refrigerant. The novelty of the elaboration is inclusion a compressor of the first stage with a serially connected intermediate heat exchanger and a control valve that are located before the compressor inlet of the second stage of the heat pump, which allows to establish a rational pressure after the first stage of the compressors. A scheme is proposed for regulating the temperature at the inlet of the first stage compressors by regulating the flow through the primary circuits of the recuperative heat exchangers. The first stage compressor control system allows providing the required modes of operation of the heat pump. It is established, because of the exergetic analysis of the sections of the hydraulic circuit of heat pump located between the evaporators and gas coolers that the reduction of irreversible losses in the heat pump is ensured due to the optimal choice of the superheat value of the gas after the evaporators.

Development of Latent Heat Storage Phase Change Material Containing Plaster

Directory of Open Access Journals (Sweden)

Diana BAJARE

2016-05-01

Full Text Available This paper reviews the development of latent heat storage Phase Change Material (PCM containing plaster as in passive application. Due to the phase change, these materials can store higher amounts of thermal energy than traditional building materials and can be used to add thermal inertia to lightweight constructions. It was shown that the use of PCMs have advantages stabilizing the room temperature variations during summer days, provided sufficient night ventilation is allowed. Another advantage of PCM usage is stabilized indoor temperature on the heating season. The goal of this study is to develop cement and lime based plaster containing microencapsulated PCM. The plaster is expected to be used for passive indoor applications and enhance the thermal properties of building envelope. The plaster was investigated under Scanning Electron Microscope and the mechanical, physical and thermal properties of created plaster samples were determined.

An analytical model for the prediction of the dynamic response of premixed flames stabilized on a heat-conducting perforated plate

KAUST Repository

Kedia, Kushal S.

2013-01-01

The dynamic response of a premixed flame stabilized on a heat-conducting perforated plate depends critically on their coupled thermal interaction. The objective of this paper is to develop an analytical model to capture this coupling. The model predicts the mean flame base standoff distance; the flame base area, curvature and speed; and the burner plate temperature given the operating conditions; the mean velocity, temperature and equivalence ratio of the reactants; thermal conductivity and the perforation ratio of the burner. This coupled model is combined with our flame transfer function (FTF) model to predict the dynamic response of the flame to velocity perturbations. We show that modeling the thermal coupling between the flame and the burner, while accounting for the two-dimensionality of the former, is critical to predicting the dynamic response characteristics such as the overshoot in the gain curve (resonant condition) and the phase delay. Good agreement with the numerical and experimental results is demonstrated over a range of conditions. © 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

CsPbBr{sub 3} QD/AlO{sub x} inorganic nanocomposites with exceptional stability in water, light, and heat

Energy Technology Data Exchange (ETDEWEB)

Loiudice, Anna; Saris, Seryio; Buonsanti, Raffaella [Department of Chemical Sciences and Engineering, EPFL Valais Wallis, Sion (Switzerland); Oveisi, Emad; Alexander, Duncan T.L. [Interdisciplinary Centre for Electron Microscopy (CIME), EPFL, Lausanne (Switzerland)

2017-08-28

Herein, the assembly of CsPbBr{sub 3} QD/AlO{sub x} inorganic nanocomposites, by using atomic layer deposition (ALD) for the growth of the amorphous alumina matrix (AlO{sub x}), is described as a novel protection scheme for such QDs. The nucleation and growth of AlO{sub x} on the QD surface was thoroughly investigated by miscellaneous techniques, which highlighted the importance of the interaction between the ALD precursors and the QD surface to uniformly coat the QDs while preserving the optoelectronic properties. These nanocomposites show exceptional stability towards exposure to air (for at least 45 days), irradiation under simulated solar spectrum conditions (for at least 8 h), and heat (up to 200 C in air), and finally upon immersion in water. This method was extended to the assembly of CsPbBr{sub x}I{sub 3-x} QD/AlO{sub x} and CsPbI{sub 3} QD/AlO{sub x} nanocomposites, which were more stable than the pristine QD films. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Decreased stability of DNA in cells treated with alkylating agents

Energy Technology Data Exchange (ETDEWEB)

Frankfurt, O.S. (Cedars Medical Center, Miami, FL (United States))

1990-12-01

A modified highly sensitive procedure for the evaluation of DNA damage in individual cells treated with alkylating agents is reported. The new methodology is based on the amplification of single-strandedness in alkylated DNA by heating in the presence of Mg{sup 2+}. Human ovarian carcinoma cells A2780 were treated with nitrogen mustard (HN2), fixed in methanol, and stained with monoclonal antibody (MOAB) F7-26 generated against HN2-treated DNA. Binding of MOAB was measured by flow cytometry with indirect immunofluorescence. Intensive binding of MOAB to control and drug-treated cells was observed after heating in Tris buffer supplemented with MgCl{sub 2}. Thus, the presence of phosphates and MgCl{sub 2} during heating was necessary for the detection of HN2-induced changes in DNA stability. Fluorescence of HN2-treated cells decreased to background levels after treatment with single-strand-specific S{sub 1} nuclease. MOAB F7-26 interacted with single-stranded regions in DNA and did not bind to dsDNA or other cellular antigens. It is suggested that alkylation of guanines decreased the stability of the DNA molecule and increased the access of MOAB F7-26 to deoxycytidines on the opposite DNA strand.

Effects of Heat Acclimation on Photosynthesis, Antioxidant Enzyme Activities, and Gene Expression in Orchardgrass under Heat Stress

Directory of Open Access Journals (Sweden)

Xin Xin Zhao

2014-09-01

Full Text Available The present study was designed to examine the effects of heat acclimation on enzymatic activity, transcription levels, the photosynthesis processes associated with thermostability in orchardgrass (Dactylis glomerata L..The stomatal conductance (Gs, net photosynthetic rate (Pn, and transpiration rates (Tr of both heat-acclimated (HA and non-acclimated (NA plants were drastically reduced during heat treatment [using a 5-day heat stress treatment (38/30 °C ‒ day/night followed by a 3-day recovery under control conditions (25/20 °C ‒ day/night, in order to consolidate the second cycle was permitted]. Water use efficiency increased more steeply in the HA (4.9 times versus the NA (1.8 times plants, and the intercellular CO2 concentration decreased gently in NA (10.9% and HA (25.3% plants after 20 d of treatments compared to 0 days’. Furthermore, heat-acclimated plants were able to maintain significant activity levels of superoxide disumutase (SOD, catalase (CAT, guaiacol peroxidase (POD, and transcription levels of genes encoding these enzymes; in addition, HA plants displayed lower malondialdehyde content and lower electrolyte leakage than NA plants. These results suggest that maintenance of activity and transcription levels of antioxidant enzymes as well as photosynthesis are associated with variable thermostability in HA and NA plants. This likely occurs through cellular membrane stabilization and improvements in water use efficiency in the photosynthetic process during heat stress. The association between antioxidant enzyme activity and gene expression, both of which may vary with genetic variation in heat tolerance, is important to further understand the molecular mechanisms that contribute to heat tolerance.

Flexible low-voltage organic transistors with high thermal stability at 250 °C.

Science.gov (United States)

Yokota, Tomoyuki; Kuribara, Kazunori; Tokuhara, Takeyoshi; Zschieschang, Ute; Klauk, Hagen; Takimiya, Kazuo; Sadamitsu, Yuji; Hamada, Masahiro; Sekitani, Tsuyoshi; Someya, Takao

2013-07-19

Low-operating-voltage flexible organic thin-film transistors with high thermal stability using DPh-DNTT and SAM gate dielectrics are reported. The mobility of the transistors are decreased by 23% after heating to 250 °C for 30 min. Furthermore, flexible organic pseudo-CMOS inverter circuits, which are functional after heating to 200 °C, are demonstrated. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Elliptically Bent X-ray Mirrors with Active Temperature Stabilization

International Nuclear Information System (INIS)

Yuan, Sheng; Church, Matthew; Yashchuk, Valeriy V.; Goldberg, Kenneth A.; Celestre, Rich; McKinney, Wayne R.; Kirschman, Jonathan; Morrison, Greg; Noll, Tino; Warwick, Tony; Padmore, Howard A.

2010-01-01

We present details of design of elliptically bent Kirkpatrick-Baez mirrors developed and successfully used at the Advanced Light Source for submicron focusing. A distinctive feature of the mirror design is an active temperature stabilization based on a Peltier element attached directly to the mirror body. The design and materials have been carefully optimized to provide high heat conductance between the mirror body and substrate. We describe the experimental procedures used when assembling and precisely shaping the mirrors, with special attention paid to laboratory testing of the mirror-temperature stabilization. For this purpose, the temperature dependence of the surface slope profile of a specially fabricated test mirror placed inside a temperature-controlled container was measured. We demonstrate that with active mirror-temperature stabilization, a change of the surrounding temperature by more than 3K does not noticeably affect the mirror figure. Without temperature stabilization, the surface slope changes by approximately 1.5 ?mu rad rms (primarily defocus) under the same conditions.

Elliptically Bent X-Ray Mirrors with Active Temperature Stabilization

International Nuclear Information System (INIS)

Yuan, S.; Church, M.; Yashchuk, V.V.; Celestre, R.S.; McKinney, W.R.; Morrison, G.; Warwick, T.; Padmore, H.A.; Goldberg, K.A.; Kirschman, J.; Noll, T.

2010-01-01

We present details of design of elliptically bent Kirkpatrick-Baez mirrors developed and successfully used at the advanced light source for submicron focusing. A distinctive feature of the mirror design is an active temperature stabilization based on a Peltier element attached directly to the mirror body. The design and materials have been carefully optimized to provide high heat conductance between the mirror body and substrate. We describe the experimental procedures used when assembling and precisely shaping the mirrors, with special attention paid to laboratory testing of the mirror-temperature stabilization. For this purpose, the temperature dependence of the surface slope profile of a specially fabricated test mirror placed inside a temperature-controlled container was measured. We demonstrate that with active mirror-temperature stabilization, a change of the surrounding temperature by more than 3 K does not noticeably affect the mirror figure. Without temperature stabilization, the rms slope error is changed by approximately 1.5 μrad (primarily defocus) under the same conditions

Thermal stability and phase transformation in fully indium oxide (InO{sub 1.5}) stabilized zirconia

Energy Technology Data Exchange (ETDEWEB)

Piva, R.H., E-mail: honorato.piva@ua.pt; Piva, D.H.; Morelli, M.R.

2017-01-15

Indium oxide (InO{sub 1.5}) stabilized zirconia (InSZ) is an attractive material as electrolyte, or electrode, in solid oxide fuel cells (SOFCs), and as corrosion resistant top coat in thermal barrier coatings. However, little is known about the phase stability of cubic InSZ at temperatures that simulate the conditions in an operating SOFC or turbine. This article provides an investigation of the phase stability and phase transformations in cubic InSZ after heat treatments at 800, 1000, and 1200 °C for periods up to 2000 h. The results revealed that cubic InSZ is not stable during annealing at 1000 and 1200 °C, owing to a fast destabilization of the initial cubic phase to tetragonal, and eventually to monoclinic (c → t → m). The c → t → m transition in InSZ is intimately associated with the indium volatilization. On the other hand, cubic InSZ remained stable for 2000 h at 800 °C, although the partial formation of the tetragonal phase was observed along with a 0.25% contraction in the unit cell volume of the cubic phase, caused by short-range ordering. These results demonstrate that technological applications of cubic InSZ are restricted to temperatures at which the volatilization of the InO{sub 1.5} stabilizer does not occur. - Highlights: •Phase stability of fully InO{sub 1.5} stabilized zirconia (cubic InSZ) was evaluated. •Cubic InSZ is instable at temperatures ≥ 1000 °C, owing to the cubic-to-tetragonal-to-monoclinic destabilization. •Cubic InSZ undergoes the cubic-to-tetragonal transformation at ~ 800 °C. •Owing to the low phase stability, applications of cubic InSZ in TBCs or SOFCs are restricted.

Effectiveness of the Vertical Gas Ventilation Pipes for Promoting Waste Stabilization in Post-Closure Phase

Directory of Open Access Journals (Sweden)

Yasumasa Tojo

2015-06-01

Full Text Available To make inside of the municipal solid waste (MSW landfill aerobic as much as possible is thought to be preferable for promoting waste stabilization, reducing pollutant's load in leachate, minimizing greenhouse gas emission and shortening post-closure-care period. In Japan, installation of semi-aerobic landfill structure has widely spread in order to promote waste stabilization in MSW landfill from 1980s. In semi-aerobic landfill structure, outlet of main leachate collection pipe is opened to atmosphere. Heat generated by aerobic degradation of waste causes natural convection and natural aeration arises from the outlet of leachate collection pipe to the gas vents. It is so-called stack effect. This air flow is thought to be effective for purifying leachate flowing through drainage layer and leachate collection pipes. And it is also thought to be contributing to expanding aerobic region in waste layer in landfill. Recently, measures attempting the promotion of waste stabilization are taken at several landfills at where stabilization of waste delays, in which many vertical gas vents are newly installed and close structure to semi-aerobic landfill is created. However, in many cases, these gas vents are not connected to leachate collection pipes. Many vertical gas vents are just installed without scientific proof regarding whether they can contribute for waste stabilization. In this study, how such installation of gas vents is effective for waste stabilization and aerobization of waste layer was discussed by numerical analysis. In numerical analysis, heat transfer, gas movement by pressure, gas diffusion, biological degradation of organic matter, and heat generation by biodegradation were taken into account. Simulations were carried out by using the general purpose simulator of finite element method. Three types of landfill structure were assumed. As the results, the following information were obtained. In dig-down type landfill, installation of gas

Utilizing whey protein isolate and polysaccharide complexes to stabilize aerated dairy gels.

Science.gov (United States)

O'Chiu, Emily; Vardhanabhuti, Bongkosh

2017-05-01

Heated soluble complexes of whey protein isolate (WPI) with polysaccharides may be used to modify the properties of aerated dairy gels, which could be formulated into novel-textured high-protein desserts. The objective of this study was to determine the effect of polysaccharide charge density and concentration within a WPI-polysaccharide complex on the physical properties of aerated gels. Three polysaccharides having different degrees of charge density were chosen: low-methoxyl pectin, high-methoxyl type D pectin, and guar gum. Heated complexes were prepared by heating the mixed dispersions (8% protein, 0 to 1% polysaccharide) at pH 7. To form aerated gels, 2% glucono-δ-lactone was added to the dispersions of skim milk powder and heated complex and foam was generated by whipping with a handheld frother. The foam set into a gel as the glucono-δ-lactone acidified to a final pH of 4.5. The aerated gels were evaluated for overrun, drainage, gel strength, and viscoelastic properties. Without heated complexes, stable aerated gels could not be formed. Overrun of aerated gel decreased (up to 73%) as polysaccharide concentration increased from 0.105 to 0.315% due to increased viscosity, which limited air incorporation. A negative relationship was found between percent drainage and dispersion viscosity. However, plotting of drainage against dispersion viscosity separated by polysaccharide type revealed that drainage decreased most in samples with high-charge-density, low-methoxyl pectin followed by those with low-charge-density, high-methoxyl type D pectin. Aerated gels with guar gum (no charge) did not show improvement to stability. Rheological results showed no significant difference in gelation time among samples; therefore, stronger interactions between WPI and high-charge-density polysaccharide were likely responsible for increased stability. Stable dairy aerated gels can be created from WPI-polysaccharide complexes. High-charge-density polysaccharides, at

The effect of heat transfer on acoustics in burner stabilized flat flames

NARCIS (Netherlands)

Schreel, K.R.A.M.; Tillaart, van den E.L.; Janssen, R.W.M.; Goey, de L.P.H.; Vovelle, C.; Lucka, K.

2003-01-01

Modern central heating systems use low NO$_x$ premixed burners with a large modulation range. This can lead to noise problems which cannot be solved via trial and error, but need accurate modelling. An acoustic analysis as part of the design phase can reduce the time-to-market considerably, but the

Effect of Gradual Heating and Fat/Oil Type on Fat Stability, Texture, Color, and Microstructure of Meat Batters.

Science.gov (United States)

Barbut, S; Youssef, M K

2016-09-01

The effects of endpoint cooking temperature (40, 50, 60, 70, 80, and 90 °C) on emulsion stability, texture, color, and microstructure of meat batters prepared with different fats/oils were studied. Canola oil treatments showed the highest cooking loss whereas hydrogenated palm oil provided the most stable meat batters. Rendered beef fat was less stable than regular beef fat. Increasing endpoint cooking temperatures resulted in a progressive reduction of water holding capacity in all treatments. As temperature was raised, meat batters showed higher hardness and cohesiveness values, but no appreciable changes in cohesiveness above 60 °C. Canola and hydrogenated palm oil treatments showed the highest hardness and chewiness values. Lightness (L(*) ) values of all meat batters increased significantly with increasing temperature from 40 to 60 or 70 °C; no major changes observed above 70 °C. Light microscopy revealed no substantial changes in the microstructure of all the stable meat batters cooked to between 50 and 70 °C. Heating to 90 °C changed the microstructure in all meat batters except the hydrogenated palm oil treatments, which still showed nonround fat particles and a less aggregated protein matrix. © 2016 Institute of Food Technologists®

NIM gas controlled sodium heat pipe

Science.gov (United States)

Yan, X.; Zhang, J. T.; Merlone, A.; Duan, Y.; Wang, W.

2013-09-01

Gas controlled heat pipes (GCHPs) provide a uniform, stable and reproducible temperature zone to calibrate thermometers and thermocouples, and to realize defining fixed points using a calorimetric method. Therefore, to perform such investigations, a GCHP furnace using sodium as its working fluid was constructed at the National Institute of Metrology (NIM), China. Also, investigations into the thermal characteristics of the NIM gas controlled sodium heat pipe were carried out. The temperature stability over 5 hours was better than ±0.25 mK while controlling the pressure at 111250 Pa. The temperature uniformity within 14 cm from the bottom of the thermometer well was within 0.3 mK. While keeping the pressure stable at the same value, 17 temperature determinations were performed over 14 days, obtaining a temperature reproducibility of 1.27 mK. Additionally, the NIM gas controlled sodium heat pipe was compared with the sodium heat pipe produced by INRiM. The temperature in the INRiM sodium heat pipe operating at 111250 Pa was determined, obtaining a difference of 21 mK with respect to the NIM GCHP. This difference was attributed to sodium impurities, pressure controller capabilities and reproducibility, and instabilities of high temperature standard platinum resistance thermometers (HTSPRTs). Further investigations will be carried out on extending the pressure/temperature range and connecting both GCHPs to the same pressure line.

Optimization study of using PTC for human body heating dissipation

Directory of Open Access Journals (Sweden)

Tiberiu Adrian SALAORU

2014-06-01

Full Text Available A better knowledge of the human body heat loses mechanisms is important for both diminishing the number of deaths during the surgical procedures of the patients under effect of full anaesthesia and increasing the efficiency of the Heating, Ventilation and Air Conditioning (HVAC systems. For these studies it is necessary to manufacture a human body mannequin having its surface temperature maintained on a value close to the real human body temperature. A number of PTC (Positive Temperature Coefficient thermistors placed on the entire external surface of the mannequin can be used for this purpose. This paper presents a study of the transient heating regime and the stability of the maintained temperature, performed on these devices.

Microwave heating device for internal heating convection experiments, applied to Earth's mantle dynamics.

Science.gov (United States)

Surducan, E; Surducan, V; Limare, A; Neamtu, C; Di Giuseppe, E

2014-12-01

We report the design, construction, and performances of a microwave (MW) heating device for laboratory experiments with non-contact, homogeneous internal heating. The device generates MW radiation at 2.47 GHz from a commercial magnetron supplied by a pulsed current inverter using proprietary, feedback based command and control hardware and software. Specially designed MW launchers direct the MW radiation into the sample through a MW homogenizer, devised to even the MW power distribution into the sample's volume. An adjustable MW circuit adapts the MW generator to the load (i.e., the sample) placed in the experiment chamber. Dedicated heatsinks maintain the MW circuits at constant temperature throughout the experiment. Openings for laser scanning for image acquisition with a CCD camera and for the cooling circuits are protected by special MW filters. The performances of the device are analyzed in terms of heating uniformity, long term output power stability, and load matching. The device is used for small scale experiments simulating Earth's mantle convection. The 30 × 30 × 5 cm(3) convection tank is filled with a water‑based viscous fluid. A uniform and constant temperature is maintained at the upper boundary by an aluminum heat exchanger and adiabatic conditions apply at the tank base. We characterize the geometry of the convective regime as well as its bulk thermal evolution by measuring the velocity field by Particle Image Velocimetry and the temperature field by using Thermochromic Liquid Crystals.

Low-temperature heat capacity and thermodynamic functions of vitamin B{sub 12}

Energy Technology Data Exchange (ETDEWEB)

Knyazev, A.V., E-mail: knyazevav@gmail.com; Smirnova, N.N.; Plesovskikh, A.S.; Shushunov, A.N.; Knyazeva, S.S.

2014-04-01

Graphical abstract: - Highlights: • Temperature dependence of heat capacity of vitamin B{sub 12} has been measured by precision adiabatic vacuum calorimetry. • The thermodynamic functions of the vitamin B{sub 12} have been determined for the range from T → 0 to 343 K. • The character of heterodynamics of structure was detected. • The thermal stability of cyanocobalamin was studied by differential scanning calorimetry. - Abstract: In the present work temperature dependence of heat capacity of vitamin B{sub 12} (cyanocobalamin) has been measured for the first time in the range from 6 to 343 K by precision adiabatic vacuum calorimetry. Based on the experimental data, the thermodynamic functions of the vitamin B{sub 12}, namely, the heat capacity, enthalpy H°(T) − H°(0), entropy S°(T) − S°(0) and Gibbs function G°(T) − H°(0) have been determined for the range from T → 0 to 343 K. The value of the fractal dimension D in the function of multifractal generalization of Debye's theory of the heat capacity of solids was estimated and the character of heterodynamics of structure was detected. The thermal stability of cyanocobalamin was also studied by differential scanning calorimetry.

Thermodynamics and stability of hyperbolic charged black holes

International Nuclear Information System (INIS)

Cai Ronggen; Wang Anzhong

2004-01-01

In AdS space the black hole horizon can be a hypersurface with a positive, zero, or negative constant curvature, resulting in different horizon topology. Thermodynamics and stability of black holes in AdS spaces are quite different for different horizon curvatures. In this paper we study thermodynamics and stability of hyperbolic charged black holes with negative constant curvature horizon in the grand canonical ensemble and canonical ensemble, respectively. They include hyperbolic Reissner-Nordstroem black holes in arbitrary dimensions and hyperbolic black holes in the D=5,4,7 gauged supergravities. It is found that associated Gibbs free energies are always negative, which implies that these black hole solutions are globally stable and the black hole phase is dominant in the grand canonical ensemble, but there is a region in the phase space where the black hole is not locally thermodynamically stable with a negative heat capacity for a given gauge potential. In the canonical ensemble, the Helmholtz free energies are not always negative and heat capacities with fixed electric charge are not always positive, which indicates that the Hawking-Page phase transition may happen and black holes are not always locally thermodynamically stable

Simultaneous rough rice drying and rice bran stabilization using infrared radiation heating

Science.gov (United States)