Peotoemission Study of Si (001) Surfaces Exposed to as Flux

1989 ◽  
Vol 148 ◽  
Author(s):  
H. Okumura ◽  
K. Miki ◽  
K. Sakamoto ◽  
T. Sakamoto ◽  
S. Misawa ◽  
...  
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Temperature Dependence ◽  
Electronic Structures ◽  
Low Temperatures ◽  
Dimer Model ◽  
Surface And Interface ◽  
High And Low Temperatures ◽  
Interface Structures ◽  
Temperature Sample

ABSTRACTPhotoemission spectra (XPS and UPS) of As-covered Si (001) surfaces prepared at high (>600ºC) and low (<450ºC) temperatures and GaAs epilayers subsequently grown on them were measured without exposing to air. It was found that the surface electronic structures of As/Si prepared at the low temperature are different from those of the high temperature sample, the spectra of which can be interpreted as a symmetric dimer model. Differences were also observed between the GaAs epilayers on the As—covered Si surfaces prepared at the high and low temperatures. The temperature dependence of the surface and interface structures are discussed.

Relieving of Residual Stresses in Metal Workpieces at High and Low Temperatures

2021 ◽  
Vol 887 ◽  
pp. 651-656
Author(s):  
Marina V. Polonik
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Residual Stresses ◽  
Low Temperatures ◽  
Creep Properties ◽  
Processing Modes ◽  
Properties Of Materials ◽  
High And Low Temperatures ◽  
Temperature Heating ◽  
High Temperature Heating

On the basis of previously accumulated irreversible deformations, and, consequently, residual stresses, the process of removing residual stresses in metal workpieces under the action of low and high temperatures is simulated. Boundary value problems are solved and here are described regularities that are responsible for removing residual stresses for processing modes: high-temperature heating - cooling, high-temperature heating - holding - cooling, low-temperature heating - holding - cooling. The holding stage is modeled, taking into account the creep properties of materials under Norton creep conditions. According to the dependences of the obtained exact solutions, it is shown that it is the holding process that leads to the relaxation of residual stresses.

scholarly journals Environmental tests of vapor compression heat pump for space applications

2020 ◽  
pp. 240-240
Author(s):  
Xudong Ma ◽  
Rui Ma ◽  
Yilin Ye ◽  
Suying Yan ◽  
Feng Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Heat Pump ◽  
Low Temperatures ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Vapor Compression ◽  
Space Applications ◽  
Suitable Temperature ◽  
High And Low Temperatures

Heat pumps are needed to provide a suitable temperature for both people and equipment in spacecraft. This paper reports on work designed to see if vapor compression heat pumps, in particular, can be expected to function normally in space. A vapor compression heat pump was built and tested under conditions of high temperature (70?C), low temperature (0?C), and near-vacuum (10-4 Pa). It was found that the coefficient of performance of this heat pump was 2.99 at both high and low temperatures, and was 2.1 under near vacuum conditions. The results suggest that vapor compression heat pumps are suitable for use in space.

scholarly journals High and Low Temperatures Differently Affect Infection Density and Vertical Transmission of Male-Killing Spiroplasma Symbionts in Drosophila Hosts

2008 ◽  
Vol 74 (19) ◽  
pp. 6053-6059 ◽  
Author(s):  
Hisashi Anbutsu ◽  
Shunsuke Goto ◽  
Takema Fukatsu
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Vertical Transmission ◽  
Low Temperatures ◽  
Environment Interaction ◽  
Host Genotype ◽  
Male Killing ◽  
Infection Density ◽  
High And Low Temperatures ◽  
Native Host

ABSTRACT We investigated the vertical transmission, reproductive phenotype, and infection density of a male-killing Spiroplasma symbiont in two Drosophila species under physiological high and low temperatures through successive host generations. In both the native host Drosophila nebulosa and the nonnative host Drosophila melanogaster, the symbiont infection and the male-killing phenotype were stably maintained at 25�C, rapidly lost at 18�C, and gradually lost at 28�C. In the nonnative host, both the high and low temperatures significantly suppressed the infection density of the spiroplasma. In the native host, by contrast, the low temperature suppressed the infection density of the spiroplasma whereas the high temperature had little effect on the infection density. These results suggested that the low temperature suppresses both the infection density and the vertical transmission of the spiroplasma whereas the high temperature suppresses the vertical transmission preferentially. The spiroplasma density was consistently higher in the native host than in the nonnative host, suggesting that the host genotype may affect the infection density of the symbiont. The temperature- and genotype-dependent instability of the symbiont infection highlights a complex genotype-by-genotype-by-environment interaction and may be relevant to the low infection frequencies of the male-killing spiroplasmas in natural Drosophila populations.

Thermodynamic Performance Analysis of Ammonia-Water Rankine Cycles Using Heat Sources of High and Low Temperatures

2012 ◽  
Vol 249-250 ◽  
pp. 278-283
Author(s):  
Kyoung Hoon Kim ◽  
Hyung Jong Ko ◽  
Se Woong Kim
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Thermal Efficiency ◽  
Low Temperatures ◽  
Ammonia Concentration ◽  
Working Fluid ◽  
Heat Sources ◽  
Ammonia Water ◽  
High And Low Temperatures ◽  
System Variables

In this study, thermodynamic performances of ammonia-water Rankine (AWR) cycle and regenerative Rankine (AWRR) cycle are comparatively investigated. Special attention is focused on the effects of ammonia concentration and turbine inlet pressure on the performance of system using heat sources of high temperature of 300 oC and low temperature of 150 oC. The behavior of important system variables including mass flow ratio of working fluid, net work production, and thermal efficiency are closely examined. Results show that performance characteristics for heat sources of high and low temperatures are quite different each other. For the high-temperature source, the thermal efficiency has a minimum in AWR system while it has a maximum in AWRR with respect to ammonia concentration in the range of 65% to 75%. For low-temperature source, however, the thermal efficiency decreases with ammonia concentration in the range of ammonia concentration higher than 95% for both AWR system and AWRR system and the effect of regenerator is negligible.

The Microscopic Structure Of Shallow Donors In Silicon Carbide

1996 ◽  
Vol 442 ◽  
Author(s):  
J.-M. Spaeth ◽  
S. Greulich-Weber ◽  
M. März ◽  
E. N. Kalabukhova ◽  
S. N. Lukin
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Temperature Dependence ◽  
Double Resonance ◽  
Epr Spectra ◽  
Electron Nuclear Double Resonance ◽  
Paramagnetic Resonance ◽  
Vacancy Pair ◽  
Temperature Spectra ◽  
Electron Paramagnetic

AbstractThe electronic structure of nitrogen donors in 6H-, 4H- and 3C-SiC is investigated by measuring the nitrogen hyperfine (hf) interactions with electron nuclear double resonance (ENDOR) and the temperature dependence of the hf split electron paramagnetic resonance (EPR) spectra. Superhyperfine (shf) interactions with many shells of 13C and 29Si were measured in 6H-SiC. The hf and shf interactions are discussed in the framework of effective mass theory. The temperature dependence is explained with the thermal occupation of the lowest valley-orbit split A1 and E states. It is proposed that the EPR spectra of P donors observed previously in neutron transmuted 6H-SiC at low temperature (<10K) and high temperature (>60K) are all due to substitutional P donors on the two quasi-cubic and hexagonal Si sites, whereby at low temperature the E state is occupied and at high temperature the A1 state. The low temperature spectra are thus thought not to be due to P-vacancy pair defects as proposed previously.

Environment and Bromoxynil Phytotoxicity

Weed Science ◽  
1986 ◽  
Vol 34 (1) ◽  
pp. 101-105 ◽  
Author(s):  
John D. Nalewaja ◽  
Grzegorz Skrzypczak
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Low Temperatures ◽  
Practical Importance ◽  
Amaranthus Retroflexus ◽  
Controlled Environment ◽  
Growth Stages ◽  
Redroot Pigweed ◽  
Wild Mustard ◽  
Simulated Rain

Experiments in controlled-environment chambers indicated that high temperature, 30 C, increased the phytotoxicity of bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) to wild mustard (Sinapis arvensisL. # SINAR) and redroot pigweed (Amaranthus retroflexusL. # AMARE) compared to low temperature, 10 C, during and after treatment. Bromoxynil phytotoxicity generally was higher at relative humidities of 90 to 95% compared to 40 to 60%, but relative humidity had less influence on bromoxynil phytotoxicity than did temperature. A simulated rain immediately after bromoxynil treatment reduced control of both species, but the reduction was of no practical importance for wild mustard. The data indicate that wild mustard and redroot pigweed control would be reduced by bromoxynil application during a period of low temperatures or to plants in advanced growth stages.

Floral Induction in Growing Buds of Lychee (Litchi chinensis) and Mango (Mangifera indica)

1995 ◽  
Vol 22 (5) ◽  
pp. 783 ◽  
Author(s):  
DJ Batten ◽  
CA Mcconchie
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Low Temperatures ◽  
Floral Induction ◽  
Mangifera Indica ◽  
Litchi Chinensis ◽  
Ambient Temperatures ◽  
Potted Plants ◽  
Whole Process ◽  
Experimental Systems

Buds of potted plants of the terminal flowering tree species lychee (Litchi chinensis) and mango (Mangifera indica) forced to begin growth at high temperatures (florally non-inductive) and then transferred to low temperatures produced inflorescences, so the whole process of floral induction can occur in growing buds. Floral initials were visible in lychee within 39 days of transfer to low temperature and 30 days in mango, indicating that floral induction occurs relatively quickly in both species. In most cases where plants were transferred to winter ambient temperatures for floral induction, pre-activated (growing) buds flowered more consistently than buds that were dormant at the time of transfer. If the buds were small when plants were transferred from high temperature to low temperature, leafless inflorescences formed. If buds were a little larger, leafy inflorescences formed, with leaves basally and flowers terminally. If the buds were larger again, the shoots were purely vegetative. All these observations are consistent with floral induction occuning while the bud is growing and provide for much improved experimental systems for studying the physiology of floral induction in species such as lychee and mango.

35Cl NQR and Structural Studies of Chloroacetanilides C6H3Cl2NHCOCH3-xClx, 1 ≤ x ≤ 3

1992 ◽  
Vol 47 (1-2) ◽  
pp. 160-170
Author(s):  
Dirk Groke ◽  
Shi-Qi Dou ◽  
Alarich Weiss
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Temperature Dependence ◽  
Phenyl Group ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Chlorine Atoms ◽  
Space Group ◽  
Low Temperature Phase

AbstractThe temperature dependence of 35Cl NQR frequencies and the phase transition behaviour of chloroacetanilides (N-[2,6-dichlorophenyl]-2-chloroacetamide, -2,2-dichloroacetamide, -2,2,2-trichloroacetamide) were investigated. The crystal structure determination of N-[2,6-dichlorophenyl]- 2-chloroacetamide leads to the following: a = 1893.8 pm, b = 1110.7 pm, c = 472.1 pm, space group P212121 = D24 with Z = 4 molecules per unit cell. The arrangement of the molecules and their geometry is comparable to the high temperature phase of the acetyl compound N-[2,6-dichlorophenyl]- acetamide. For N-[2,6-diclorophenyl]-2,2,2-trichloroacetamide it was found: a = 1016.6 pm, b = 1194.3 pm, c = 1006.7 pm, ß= 101.79°, space group P21/c = C52h, Z = 4. The structure is similar to the low temperature phase of N-[2,6-dichlorophenyl]-acetamide. Parallelism between the temperature dependence of the 35C1 NQR lines of the CCl3 group and the X-ray diffraction results concerning the different behaviour of the chlorine atoms was observed. The structures of the compounds show intermolecular hydrogen bonding of the N - H • • • O - C type. The phenyl group and the HNCO function are nearly planar. A bleaching out of several 35Cl NQR lines at a temperature far below the melting point of the substances was observed. The different types of chlorine atoms (aromatic, chloromethyl) can be distinguished by their temperature coefficients of the 35Cl NQR frequencies. All the resonances found show normal "Bayer" temperature behaviour. N-[2,6-dichlorophenyl]-2,2-diehloroacetamide shows several solid phases. One stable low temperature phase and an instable high temperature phase (at room temperature) were observed. The different phases were detected by means of 35Cl NQR spectroscopy and thermal analysis

scholarly journals EFFECTS OF LONG-TERM RELATIVELY HIGH AND LOW TEMPERATURE USE ON GROWTH PERFORMANCE AND MEAT QUALITY OF BROILERS

2020 ◽  
pp. 12-17
Author(s):  
Yingying Qiao ◽  
Oleksandr Kyselov ◽  
Changzhong Liu
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Growth Performance ◽  
Meat Quality ◽  
Low Temperatures ◽  
Production Performance ◽  
Control Group ◽  
Temperature Group

The experiment aims to study the effects of long-term relatively high and low temperatures on growth performance and meat quality of broiler chickens. The experiment was carried out in Yunnan Academy of Animal Science, for determine the quality of meat used the laboratories of Henan Institute of Science and Technology. A total of experiment use 240 healthy 1-day-old Avian broiler chickens were randomly divided into three groups: relatively high temperature group, low temperature group and control group. The results of the experiment confirm that at low temperatures, when the energy consumption of the animal decreases, it leads to weight loss, which we can see in the low-temperature group, the average daily weight gain in this experiment was significantly lower than in the control group (P <0.05). It was found that low-temperature stress significantly increased the mortality of broilers, at the age of 42 days in the low-temperature group, the mortality of chickens was higher than in the control group, by 71.4%. Among all evaluated groups on the content of unsaturated fatty acids SFA, PUFA, MUFA and EFA in the muscles of the breasts of broilers, the lowest content was in the lower temperature group than in the control group, by 48.3%, 46.9%, 51.5% and 43.9%. Studies have shown that influence of high-temperature above 30°C causes disturbances in poultry behavior and physiology, leading to reduced production performance. Broilers aged 35-40 days experienced 31°C high-temperature stress and found that their performance and immunity decreased. Broilers feed intake and growth rate at 35°C high temperature were reduced by 13% and 32% than at 20°C. The results showed that: ① Relatively high temperature and low temperature for a long time reduced the growth performance and mortality of broilers, and long-term relatively low temperature decreased the slaughter performance of broilers.② Relatively high and low temperatures for a long period of time reduced the levels of serine, glycine, SFA, PUFA, USFA, EFA and MUFA in broiler breast muscles negative effect on meat quality. ③ The long-term relatively low temperature has a greater adverse effect on broilers than the long-term relatively high temperature. The results provided some theoretical basis for accurately setting the broiler breeding environment temperature, improving broiler quality, maximizing broiler production performance, and increasing the economic benefits of the farm.

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