scholarly journals Effect of Temperature, Pressure, and Chemical Composition on the Electrical Conductivity of Schist: Implications for Electrical Structures under the Tibetan Plateau

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 961 ◽  
Author(s):  
Wenqing Sun ◽  
Lidong Dai ◽  
Heping Li ◽  
Haiying Hu ◽  
Changcai Liu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
High Pressures ◽  
High Conductivity ◽  
Effect Of Temperature ◽  
The Tibetan Plateau ◽  
Temperature Range ◽  
Electrical Conductivities ◽  
Conductivity Anomalies ◽  
Lower Temperature Range ◽  
Lower Temperature

The experimental study on the electrical conductivities of schists with various contents of alkali ions (CA = K2O + Na2O = 3.94, 5.17, and 5.78 wt.%) were performed at high temperatures (623–1073 K) and high pressures (0.5–2.5 GPa). Experimental results indicated that the conductivities of schist markedly increased with the rise of temperature. Pressure influence on the conductivities of schist was extremely weak at the entire range of experimental temperatures. Alkali ion content has a significant influence on the conductivities of the schist samples in a lower temperature range (623–773 K), and the influence gradually decreases with increasing temperature in a higher temperature range (823–1073 K). In addition, the activation enthalpies for the conductivities of three schist samples were fitted as being 44.16–61.44 kJ/mol. Based on the activation enthalpies and previous studies, impurity alkaline ions (K+ and Na+) were proposed as the charge carriers of schist. Furthermore, electrical conductivities of schist (10−3.5–10−1.5 S/m) were lower than those of high-conductivity layers under the Tibetan Plateau (10−1–100 S/m). It was implied that the presence of schist cannot cause the high-conductivity anomalies in the middle to lower crust beneath the Tibetan Plateau.

Effect of Annealing Temperature on Oxygen Precipitation in Fast Neutron Irradiated CZ-Si

2013 ◽  
Vol 320 ◽  
pp. 403-406
Author(s):  
Qiao Yun Ma ◽  
Zhan Kai Li
Keyword(s):  
Fast Neutron ◽  
Annealing Temperature ◽  
Optical Microscope ◽  
Effect Of Temperature ◽  
Interstitial Oxygen ◽  
Temperature Range ◽  
Oxygen Precipitation ◽  
Lower Temperature Range ◽  
Lower Temperature ◽  
Induced Defects

The effect of annealing temperature on oxygen precipitation was investigated in various dose fast neutron irradiated Czochralski silicon (CZ-Si). Fourier Transform Infrared Absorption Spectrometer (FTIR) was used to measure the concentration of interstitial oxygen ([Oi]). Bulk microdefects (BMDs) were observed by optical microscope. The behavior of oxygen precipitation depends on the annealing temperature and the concentration of irradiation-induced defects. The mount of oxygen precipitates of irradiated samples is more than that in non-irradiation samples and increases with increasing the irradiation dose. Because of the effect of temperature on critical radius rcand the oxygen diffusivity, oxygen precipitation increase with the increase of temperature at the studied lower temperature range, while decrease with the increase of temperature at the studied higher temperature range. High density dislocation and stacking faults generate in irradiated sample.

scholarly journals Spatio-Temporal Variation Characteristics of Snow Depth and Snow Cover Days over the Tibetan Plateau

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 307
Author(s):  
Chi Zhang ◽  
Naixia Mou ◽  
Jiqiang Niu ◽  
Lingxian Zhang ◽  
Feng Liu
Keyword(s):  
Tibetan Plateau ◽  
Snow Cover ◽  
Snow Depth ◽  
Feedback Effect ◽  
Effect Of Temperature ◽  
The Tibetan Plateau ◽  
Reanalysis Dataset ◽  
Spatio Temporal ◽  
The Impact ◽  
Main Factor

Changes in snow cover over the Tibetan Plateau (TP) have a significant impact on agriculture, hydrology, and ecological environment of surrounding areas. This study investigates the spatio-temporal pattern of snow depth (SD) and snow cover days (SCD), as well as the impact of temperature and precipitation on snow cover over TP from 1979 to 2018 by using the ERA5 reanalysis dataset, and uses the Mann–Kendall test for significance. The results indicate that (1) the average annual SD and SCD in the southern and western edge areas of TP are relatively high, reaching 10 cm and 120 d or more, respectively. (2) In the past 40 years, SD (s = 0.04 cm decade−1, p = 0.81) and SCD (s = −2.3 d decade−1, p = 0.10) over TP did not change significantly. (3) The positive feedback effect of precipitation is the main factor affecting SD, while the negative feedback effect of temperature is the main factor affecting SCD. This study improves the understanding of snow cover change and is conducive to the further study of climate change on TP.

Formability and Process Conditions of Magnesium Alloy Sheets

2005 ◽  
Vol 488-489 ◽  
pp. 453-456 ◽  
Author(s):  
Shi Hong Zhang ◽  
Yong Chao Xu ◽  
G. Palumbo ◽  
S. Pinto ◽  
Luigi Tricarico ◽  
...  
Keyword(s):  
Deep Drawing ◽  
Tensile Tests ◽  
Process Conditions ◽  
Drawing Ratio ◽  
Temperature Range ◽  
Fine Grained ◽  
Axial Tensile ◽  
Die Surface ◽  
Lower Temperature Range ◽  
Lower Temperature

Comparing the formability with each other, extrusion and various rolling experiments were carried out to make fine-grained AZ31 Mg sheets, and uni-axial tensile tests were carried out at different strain rates and temperatures to investigate the effect of different variables. A warm deep drawing tool setup with heating elements, which were distributed under the die surface and inside the blank holder, was designed and manufactured, and deep drawing was performed. Extruded Mg alloy AZ31 sheets exhibit the best deep drawing ability when working in the temperature range 250-350°C. Extruded and rolled sheets of 0.8 mm thick were also deep drawn in the lower temperature range 105-170°C，showing good formability and reaching a Limit Drawing Ratio up to 2.6 at 170°C for rolled sheets. At last, a sheet cup 0.4 mm thick was deep drawn successfully at 170 °C.

Effect of Microstructure and Zr Addition on the Crystallographic Orientation Relationships among Phases related to the Eutectoid Decomposition of Nb3Si in near Eutectic Nb-Si alloy

2004 ◽  
Vol 842 ◽  
Author(s):  
Seiji Miura ◽  
Kenji Ohkubo ◽  
Tetsuo Mohri
Keyword(s):  
Eutectic Alloy ◽  
Crystallographic Orientation ◽  
Eutectoid Decomposition ◽  
Orientation Relationships ◽  
Temperature Range ◽  
Zr Addition ◽  
Heat Treated ◽  
Lower Temperature Range ◽  
Lower Temperature ◽  
Nose Temperature

ABSTRACTThe authors have reported in the previous study that the sluggish decomposition of Nb3Si phase is effectively accelerated by Zr addition [1]. This is obvious at lower temperature range than the nose temperature of the TTT curve. In the present study a eutectic alloy containing 1.5 % of Zr was investigated. The crystallographic orientation relationships among phases, such as eutectic Nb and product phases formed by eutectoid decomposition of Nb3Si (eutectoid Nb and Nb5Si3phases) in the Zr-containing sample which was heat treated at 1300°C were investigated by FESEM/EBSD for further understanding of the decomposition process in alloy with a different microstructure.

scholarly journals Characteristics of Coherent Optical Phonons in a Hexagonal YMnO3 Thin Film

2019 ◽  
Vol 9 (4) ◽  
pp. 704 ◽  
Author(s):  
Takayuki Hasegawa
Keyword(s):  
Thin Film ◽  
Optical Phonon ◽  
Laser Pulses ◽  
Generation Process ◽  
Neel Temperature ◽  
Optical Phonons ◽  
Néel Temperature ◽  
Temperature Range ◽  
Lower Temperature Range ◽  
Lower Temperature

This paper reviews our recent study on a coherent optical phonon in a hexagonal YMnO3 thin film together with related optical studies in hexagonal RMnO3 (R = Y, Lu, Ho) compounds. Coherent phonons have been observed in RMnO3 compounds by pump-probe spectroscopy with subpicosecond laser pulses, whereas the observation of coherent optical phonons was reported only in LuMnO3. Recently, we succeeded in the observation of the coherent optical phonon in a YMnO3 thin film. The generation process of the coherent optical phonon is assigned to a displacive mechanism, which is identical to that in LuMnO3. The coherent optical phonon is observed in the temperature range from 10 K to room temperature, while the oscillation intensity strongly decreases as the temperature increases to the Néel temperature of ~70 K from a lower temperature range. It is interesting that the temperature dependence is largely different from that in LuMnO3. We describe that the result can be qualitatively explained by the property of an isostructural transition around the Néel temperature in RMnO3 compounds. In addition, we briefly discuss ultrafast incoherent responses of excited electronic states from the viewpoint of the excitation photon energy of laser pulses.

Observed trend of diurnal temperature range in the Tibetan Plateau in recent decades

2015 ◽  
Vol 36 (6) ◽  
pp. 2633-2643 ◽  
Author(s):  
Qinglong You ◽  
Jinzhong Min ◽  
Yang Jiao ◽  
Mika Sillanpää ◽  
Shichang Kang
Keyword(s):  
Tibetan Plateau ◽  
Diurnal Temperature Range ◽  
The Tibetan Plateau ◽  
Diurnal Temperature ◽  
Temperature Range

Scanning UV microspectrophotometry as a tool to study the changes of lignin in hydrothermally modified wood

Holzforschung ◽  
2016 ◽  
Vol 70 (3) ◽  
pp. 215-221 ◽  
Author(s):  
Bruno Andersons ◽  
Guna Noldt ◽  
Gerald Koch ◽  
Ingeborga Andersone ◽  
Anete Meija-Feldmane ◽  
...  
Keyword(s):  
Cell Wall ◽  
Degradation Products ◽  
Middle Lamella ◽  
Temperature Range ◽  
Wood Protection ◽  
Lower Temperature Range ◽  
Lower Temperature ◽  
The One ◽  
S2 Layer ◽  
Uv Microspectrophotometry

Abstract Thermal modification (TM) of wood has occupied a relatively narrow but stable niche as an alternative for chemical wood protection. There are different technological solutions for TM and not all details of their effects on wood tissue have been understood. The one-stage hydrothermal modification (HTM) at elevated vapour pressure essentially changes the wood’s composition and structure. In the present paper, the changes in three hardwood lignins (alder, aspen, and birch) were observed within the cell wall by means of cellular UV microspectrophotometry. The lignin absorbances in the compound middle lamella (CML) of unmodified wood are 1.7- to 2.0-fold higher than those in the fibre S2 layer. The woods were modified in the temperature range from 140 to 180°C, while in the lower temperature range (140°C/1 h), the UV absorbances are little affected. Essential changes occur in the range of 160–180°C and the UV data reflect these by absorbtion changes, while the absorbances at 278 nm rise with factors around 2 more in the S2 layer than in the CML. The absorbance increments are interpreted as polycondensation reactions with furfural and other degradation products of hemicelluloses with the lignin moiety of the cell wall.

scholarly journals The influence of pressure on the spontaneous ignition of inflammable gas-air mixtures—the simpler olefines

1937 ◽  
Vol 160 (901) ◽  
pp. 174-187 ◽  
Keyword(s):  
Internal Combustion Engines ◽  
Chemical Reactivity ◽  
Time Lag ◽  
Spontaneous Ignition ◽  
Combustion Engines ◽  
Temperature Range ◽  
Cool Flames ◽  
Lower Temperature Range ◽  
Lower Temperature ◽  
Short Time

The investigations described in previous papers on this subject have related mainly to the paraffin hydrocarbons (Townend and Mandlekar 1933 a,b ; Townend, Cohen and Mandlekar 1934; Townend and Chamberlain 1936, 1937). It has been found that mixtures with air of the members containing three or more carbon atoms, while not spontaneously ignitible at low pressures below about 500° C., give rise abruptly to ignition at higher pressures in a temperature range between about 310 and 370° C., where normally only cool flames are initiated; and although neither methane- nor ethane-air mixtures appear to develop cool flames, the latter are ultimately ignitible in a lower temperature system which is less complex than that characteristic of the higher paraffins. Moreover, it is now recognized that “knock” in internal combustion engines arises in circumstances responsible for pronounced chemical reactivity in the unburnt explosive medium characteristic of that occurring in the lower temperature range (cf. Egerton and Ubbelohde 1935; Ubbelohde 1935), and the investigations referred to have indicated that the “knock-ratings” of the paraffins when used as fuels in such engines are related to the pressures requisite for the occurrence of spontaneous ignition in this range within an appropriate short time lag (Townend and Chamberlain 1936, p. 104, cf. Prettre 1936 a and b )

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