scholarly journals Transition of Sulphide Self-Heating from Stage A to Stage B

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1133
Author(s):  
Sungjae Moon ◽  
Frank Rosenblum ◽  
Yuehua Tan ◽  
Kristian E. Waters ◽  
James A. Finch
Keyword(s):  
Transition Temperature ◽  
Elemental Sulphur ◽  
Adiabatic Heating ◽  
Heating Process ◽  
Test Apparatus ◽  
Monoclinic Form ◽  
Self Heating ◽  
Adiabatic Conditions ◽  
Adiabatic Mode

Previous work has shown that sulphide self-heating occurs in three distinct stages, referred to as Stage A, Stage B and Stage C. In this publication, the focus is the transition from Stage A to Stage B which occurs at ca. 100 °C. Background literature hints that the transition corresponds to the transformation of the rhombic form of elemental sulphur to the more reactive monoclinic form that occurs at 96 °C. A test apparatus is modified for adiabatic heating to track the transition. The results support this transformation of sulphur as being key to the transition, and the transition temperature is thus modified to 96 °C. Variations in a sample’s response under adiabatic conditions are observed and possible reasons are discussed. Testing in adiabatic mode provides new insights into the sulphide self-heating process that complements the test designed to identify propensity to self-heat.

Numerical modelling of the self-heating process of a wet porous medium

2011 ◽  
Vol 54 (25-26) ◽  
pp. 5200-5206 ◽  
Author(s):  
A. Ejlali ◽  
D.J. Mee ◽  
K. Hooman ◽  
B.B. Beamish
Keyword(s):  
Porous Medium ◽  
Numerical Modelling ◽  
The Self ◽  
Heating Process ◽  
Self Heating

scholarly journals The Semenov formulation of the biological self-heating process in compost piles

2010 ◽  
Vol 51 ◽  
pp. 425 ◽  
Author(s):  
Thiansiri Luangwilai ◽  
Havinder Sidhu ◽  
Mark Nelson ◽  
Dong Chen
Keyword(s):  
Heating Process ◽  
Self Heating

Quantum chemistry calculation of reaction pathways of carboxyl groups during coal self-heating

2017 ◽  
Vol 95 (8) ◽  
pp. 824-829 ◽  
Author(s):  
Xuyao Qi ◽  
Haibo Xue ◽  
Haihui Xin ◽  
Ziming Bai
Keyword(s):  
Quantum Chemistry ◽  
Oxidation Process ◽  
Hydrogen Abstraction ◽  
Thermal Parameters ◽  
Reaction Pathways ◽  
Carboxyl Groups ◽  
Heating Process ◽  
Hydrogen Atoms ◽  
Self Heating ◽  
Quantum Chemistry Calculations

During coal self-heating, reactions of carboxyl groups feature in the evolution of the spontaneous combustion of coal. However, their elementary reaction pathways during this process still have not been revealed. This paper selected the Ar–CH2–COOH as a typical carboxyl group containing structure for the analysis of the reaction pathways and enhancement effect on the coal self-heating process by quantum chemistry calculations. The results indicate that the hydrogen atoms in carboxyl groups are the active sites, which undergo the oxidation process and self-reaction process during coal self-heating. They both have two elementary reactions, namely (i) the hydrogen abstraction of –COOH by oxygen and the decarboxylation of the –COO· free radical and (ii) the hydrogen abstraction of –COOH and its pyrolysis. The total enthalpy change and activation energy of the oxidation process are 76.93 kJ/mol and 127.85 kJ/mol, respectively, which indicate that this process is endothermic and will occur at medium temperatures. For the hydrogen abstraction of –COOH by hydrocarbon free radicals, the thermal parameters are 53.53 kJ/mol and 56.13 kJ/mol, respectively, which has the same thermodynamic properties as the oxidation process. However, for the pyrolysis, the thermal parameters are –42.53 kJ/mol and 493.68 kJ/mol, respectively, and is thus exothermic and would not occur until the coal reaches high temperatures. They affect heat accumulation greatly, generate carbon dioxide, and provide new active centers for enhancing the coal self-heating process. The results would be helpful for further understanding of the coal self-heating mechanism.

scholarly journals Analysis of self-heating of thermally assisted spin-transfer torque magnetic random access memory

2016 ◽  
Vol 7 ◽  
pp. 1676-1683 ◽  
Author(s):  
Austin Deschenes ◽  
Sadid Muneer ◽  
Mustafa Akbulut ◽  
Ali Gokirmak ◽  
Helena Silva
Keyword(s):  
Random Access ◽  
Random Access Memory ◽  
Spin Transfer Torque ◽  
Peltier Effect ◽  
Heating Process ◽  
Tunneling Junction ◽  
Access Memory ◽  
Thermoelectric Effects ◽  
Magnetic Random Access Memory ◽  
Self Heating

Thermal assistance has been shown to significantly reduce the required operation power for spin torque transfer magnetic random access memory (STT-MRAM). Proposed heating methods include modified material stack compositions that result in increased self-heating or external heat sources. In this work we analyze the self-heating process of a standard perpendicular magnetic anisotropy STT-MRAM device through numerical simulations in order to understand the relative contributions of Joule, thermoelectric Peltier and Thomson, and tunneling junction heating. A 2D rotationally symmetric numerical model is used to solve the coupled electro-thermal equations including thermoelectric effects and heat absorbed or released at the tunneling junction. We compare self-heating for different common passivation materials, positive and negative electrical current polarity, and different device thermal anchoring and boundaries resistance configurations. The variations considered are found to result in significant differences in maximum temperatures reached. Average increases of 3 K, 10 K, and 100 K for different passivation materials, positive and negative polarity, and different thermal anchoring configurations, respectively, are observed. The highest temperatures, up to 424 K, are obtained for silicon dioxide as the passivation material, positive polarity, and low thermal anchoring with thermal boundary resistance configurations. Interestingly it is also found that due to the tunneling heat, Peltier effect, device geometry, and numerous interfacial layers around the magnetic tunnel junction (MTJ), most of the heat is dissipated on the lower potential side of the magnetic junction. This asymmetry in heating, which has also been observed experimentally, is important as thermally assisted switching requires heating of the free layer specifically and this will be significantly different for the two polarity operations, set and reset.

scholarly journals Characterization of Self-Heating Process in GaN-Based HEMTs

Electronics ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 1305 ◽  
Author(s):  
Daniel Gryglewski ◽  
Wojciech Wojtasiak ◽  
Eliana Kamińska ◽  
Anna Piotrowska
Keyword(s):  
Communication Systems ◽  
Accurate Determination ◽  
Heating Process ◽  
Equivalent Circuits ◽  
High Electron ◽  
Thermal Impedance ◽  
Self Heating ◽  
Gan Hemt

Thermal characterization of modern microwave power transistors such as high electron-mobility transistors based on gallium nitride (GaN-based HEMTs) is a critical challenge for the development of high-performance new generation wireless communication systems (LTE-A, 5G) and advanced radars (active electronically scanned array (AESA)). This is especially true for systems operating with variable-envelope signals where accurate determination of self-heating effects resulting from strong- and fast-changing power dissipated inside transistor is crucial. In this work, we have developed an advanced measurement system based on DeltaVGS method with implemented software enabling accurate determination of device channel temperature and thermal resistance. The methodology accounts for MIL-STD-750-3 standard but takes into account appropriate specific bias and timing conditions. Three types of GaN-based HEMTs were taken into consideration, namely commercially available GaN-on-SiC (CGH27015F and TGF2023-2-01) and GaN-on-Si (NPT2022) devices, as well as model GaN-on-GaN HEMT (T8). Their characteristics of thermal impedance, thermal time constants and thermal equivalent circuits were presented. Knowledge of thermal equivalent circuits and electro–thermal models can lead to improved design of GaN HEMT high-power amplifiers with account of instantaneous temperature variations for systems using variable-envelope signals. It can also expand their range of application.

Decomposition mechanism scenarios of CL-20 co-crystals revealed by ReaxFF molecular dynamics: similarities and differences

2020 ◽  
Vol 22 (5) ◽  
pp. 2827-2840 ◽  
Author(s):  
Chunxing Ren ◽  
Han Liu ◽  
Xiaoxia Li ◽  
Li Guo
Keyword(s):  
Molecular Dynamics ◽  
Decomposition Mechanism ◽  
Self Heating ◽  
Adiabatic Conditions ◽  
Product Distributions ◽  
Similar Product ◽  
Similarities And Differences

Overall scenarios first revealed clearly by ReaxFF MD for self-heating, similar product distributions and altered kinetics in the three-stage decomposition of CL-20 and its cocrystals under adiabatic conditions.

Low-Frequency Inelastic Light Scattering of Glassy Ba2TiGe2O8 during Heating Process

2010 ◽  
Vol 445 ◽  
pp. 225-228
Author(s):  
Yoshihiro Takahashi ◽  
Hirokazu Masai ◽  
Takumi Fujiwara ◽  
Minoru Osada
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Light Scattering ◽  
Low Frequency ◽  
Structural Heterogeneity ◽  
Heating Process ◽  
In Situ Observation ◽  
Inelastic Light Scattering ◽  
Crystallization Tendency

In-situ observation of inelastic light scattering of boson region in glassy Ba2TiGe2O8 (BTG) was performed during heating process. The in-situ boson observation revealed structural relaxation below glass-transition temperature in the as-quenched sample, suggesting the nanometric structural heterogeneity. Relation of the boson behavior to crystallization tendency is also discussed.

Investigation of Airflow Influence on Self-Heating Process of Linseed Oil Using Safety Calorimeter SEDEX

2013 ◽  
Vol 690-693 ◽  
pp. 1340-1344
Author(s):  
Ivan Hrušovský ◽  
Karol Balog ◽  
Jozef Martinka ◽  
Tomáš Chrebet
Keyword(s):  
Heating Rate ◽  
Unsaturated Fatty Acids ◽  
Linseed Oil ◽  
Heating Process ◽  
Scanning Calorimetry ◽  
Temperature Range ◽  
Self Heating ◽  
Air Inlet ◽  
Standard Pressure ◽  
Sequential Scanning

The oxidative self-heating process of vegetable oil with high content of unsaturated fatty acids was investigated by the means of sequential scanning calorimetry in safety calorimeter SEDEX. The oil was applied on the cotton, and was put to the standard pressure sample vessel, which was modified for air inlet. The behavior of sample was studied under three rates of air flow. First experiment was carried out in the temperature range between approximately 30 and 350°C at a heating rate of 45°C/h. Second scanning was carried out in the temperature range from 30 to 200°C at heating rate of 10°C/h.

scholarly journals Self-heating process influence on efficiency of luminescence of nitride-based heterostructures

2013 ◽  
Vol 461 ◽  
pp. 012027 ◽  
Author(s):  
E A Menkovich ◽  
S A Tarasov ◽  
I A Lamkin ◽  
S Yu Kurin ◽  
A A Antipov ◽  
...  
Keyword(s):  
Heating Process ◽  
Self Heating
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