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991.
Heat transfer for diode side-pumped YAG slabs 总被引:1,自引:0,他引:1
Wenjie Xie Siu. -Chung Tam Hongru Yang Jianhui Gu Gang Zhao Yee-Loy Lam Wilson Tan 《Optics & Laser Technology》1999,31(7):521
Thermal heating is a major limiting factor in scaling the average power of a solid-state laser. The heat transfer coefficient is affected by the coolant flow rate, the physical properties of the laser slab and the coolant, and the pumping cavity geometry. The relationship between the heating effects and the heat transfer coefficient has been studied by considering the variations of thermal conductivity and expansion coefficient of the laser slab with temperature. It is concluded that different heat transfer coefficients should be adopted according to different heat intensities inside the laser slabs in order to obtain better pumping input as well as to optimize the cooling effects. 相似文献
992.
Although plasma torches have been commercially available for about 50 years, areas such as plasma gun design, process efficiency,
reproducibility, plasma stability, torch lives etc. have remained mostly unattended. Recent torch developments have been focusing
on the basic understanding of the plasma column and its dynamics inside the plasma torch, the interaction of plasma jet and
the powders, the interaction of the plasma jet with surroundings and the impingement of the jet on the substrate. Two of the
major causes of erratic and poor performance of a variety of thermal plasma processes are currently identified as the fluctuations
arising out of the arc root movement on the electrodes inside the plasma torch and the fluid dynamic instabilities arising
out of entrainment of the air into the plasma jet. This paper reviews the current state of understanding of these fluctuations
as well as the dynamics of arc root movement in plasma torches. The work done at the author’s laboratory on studying the fluctuations
in arc voltage, arc current, acoustic emissions and optical emissions are also presented. These fluctuations are observed
to be chaotic and interrelated. Real time monitoring and controlling the arc instabilities through chaos characterization
parameters can greatly contribute to the understanding of electrode erosion as well as improvement of plasma torch lifetime. 相似文献
993.
We report new theoretical results and analysis for the transport properties of superconducting UPt3 based on the leading models for the pairing symmetry. We use Fermi surface data and the measured inelastic scattering rate to show that the low-temperature thermal conductivity and transverse sound attenuation in the A- and B-phase of UPt3 are in excellent agreement with pairing states belonging to the two-dimensional orbital E2u representation. 相似文献
994.
The adsorption and dissociation of CH2I2 were studied at 110 K with the aim of generating CH2 species on the Ru(001) surface. The methods used included X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), temperature programmed desorption (TPD), Auger electron spectroscopy (AES) and work function measurements. Adsorption of CH2I2 is characterized by a work function decrease (0.96 eV at monolayer), indicating that adsorbed CH2I2 has a positive outward dipole moment. Three adsorption states were distinguished: a multilayer (Tp=200 K), a weakly bonded state (Tp=220 K) and an irreversibly adsorbed state. A new feature is the formation of CH3I, which desorbs with Tp=160 K. The adsorption of CH2I2 at 110 K is dissociative at submonolayer, but molecular at higher coverages. Dissociation of the monolayer to CH2 and I proceeded at 198–230 K, as indicated by a shift in the I(3d5/2) binding energy from 620.6 eV to 619.9 eV. A fraction of adsorbed CH2 is self-hydrogenated into CH4 (Tp=220 K), and another one is coupled to di-σ-bonded ethylene, which — instead of desorption — is converted to ethylidyne at 220–300 K. Illumination of the adsorbed CH2I2 initiated the dissociation of CH2I2 monolayer even at 110 K, and affected the reaction pathways of CH2. 相似文献
995.
Wenjie Xie Siu-Chung Tam Lam Yee-Loy Jingang Liu Hongru Yang Jianhui Gu Wilson Tan Feng Zhou 《Optics & Laser Technology》2000,32(3):1006
The pump energy distribution in a diode side-pumped solid-state laser, is an overlap of propagating Gaussian beams. A simple model has been developed to calculate the thermal focal length of a diode side-pumped solid-state laser, which is based on a thermal model with a Gaussian heat density in any cross section of a laser rod. It can be seen that as the waists of pump beams increase, the energy distribution tends to be uniform and the thermal focal length tends to be long, which means a smaller thermal focusing. 相似文献
996.
997.
《Particuology》2023
Comprehensive analyses on thermal runaway mechanisms are critically vital to achieve the safe lithium–sulfur (Li–S) batteries. The reactions between dissolved higher-order polysulfides and Li metal were found to be the origins for the thermal runaway of 1.0 Ah cycled Li–S pouch cells. 16-cycle pouch cell indicates high safety, heating from 30 to 300 °C without thermal runaway, while 16-cycle pouch cell with additional electrolyte undergoes severe thermal runaway at 147.9 °C, demonstrating the key roles of the electrolyte on the thermal safety of batteries. On the contrary, thermal runaway does not occur for 45-cycle pouch cell despite the addition of the electrolyte. It is found that the higher-order polysulfides (Li2Sx ≥ 6) are discovered in 16-cycle electrolyte while the sulfur species in 45-cycle electrolyte are Li2Sx ≤ 4. In addition, strong exothermic reactions are discovered between cycled Li and dissolved higher-order polysulfide (Li2S6 and Li2S8) at 153.0 °C, driving the thermal runaway of cycled Li–S pouch cells. This work uncovers the potential safety risks of Li–S batteries and negative roles of the polysulfide shuttle for Li–S batteries from the safety view. 相似文献
998.
采用液氮冷却以及气体增压技术,制备了~30MPa及~90K初始状态的氢、氦等摩尔混合气体样品.以二级轻气炮作为加载工具,用不同灵敏度设置的两套多通道瞬态高温计系统获得完整、清晰的稠密氢、氦混合气体多次冲击压缩过程的光谱辐射强度信号.并建立起相应的实验数据处理和分析技术,获得了5—140GPa范围内氢、氦混合气体一至五次冲击雨贡纽物态方程,以及一次、二次和四次冲击温度实验数据.流体变分理论和离解模型用来分析和解释所获得的测量结果.
关键词:
氢、氦混合气体
多次冲击压缩
光谱辐射强度历史
物态方程 相似文献
999.
Patricia A. M. Williams Evelina G. Ferrer Karina A. Pasquevich Enrique J. Baran Zulema Chaia Eduardo E. Castellano Oscar E. Piro 《无机化学与普通化学杂志》2000,626(12):2509-2514
The crystal structure of the complexes [Cu(sac)2(bzim)2(H2O)] ( 1 ) and [Cu(sac)2(bzim)(H2O)(EtOH)] · 2 EtOH ( 2 ) (sac = saccharinate anion; bzim = benzimidazole; EtOH = ethanol) was determined by single crystal X‐ray diffractometry. Complex 1 crystallizes in the monoclinic C2/c space group with Z = 8 whereas complex 2 belongs to the triclinic P1 space group with Z = 2. Room temperature magnetic susceptibilities as well as electronic and IR spectra of both complexes were discussed. Their thermal behaviour was investigated by means of TG and DTA methods. 相似文献
1000.
Jie Chen Yan Kou Shihui Zhang Xinyu Zhang Hanqing Liu Huiming Yan Quan Shi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(16):e202400759
Solar thermal fuels (STFs) have been particularly concerned as sustainable future energy due to their impressive ability to store solar energy in chemical bonds and controllably release thermal energy. However, currently studied STFs mainly focus on molecule-based materials with high photochemical activity, toxicity, and compromised features, which greatly restricts their applications in practical scenarios of solar energy utilization. Herein, we present a novel erythritol-based composite phase change material (PCM) as a new type of STFs with an outstanding capability to store solar energy as latent heat in its stable supercooling state and release thermal energy as needed. This composite PCM with stored thermal energy can be maintained stably at room temperature and subsequently release latent heat as high as 224.9 J/g during the crystallization process triggered by thermal stimuli. Remarkably, solar energy can be converted into latent heat stored in the composite PCM over months. Through mechanical stimulations, the released latent heat can increase the temperature of the composite up to 91 °C. This work presents a new concept of using spatiotemporal storage and release of latent heat in PCMs for solar energy utilization, making it a potential candidate as STFs for developing future clean energy techniques. 相似文献