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1.
为了改善GaN HEMT的自热效应,集成高热导率的金刚石衬底有助于增强器件有源区的热量耗散。然而,化学气相淀积(CVD)生长的多晶金刚石(PCD)具有柱状晶粒结构,导致了各向异性的材料热导率,且其热导率值与生长厚度有关。为此,通过建模金刚石生长过程中晶粒尺寸的演变过程,计算了金刚石沿面内和截面方向的热导率。基于该PCD热导率模型,利用计入材料非线性热导率的GaN器件热阻解析模型,计算得到了GaN HEMT沟道温度的波动范围,并分析了其与器件结构(栅长、栅宽、栅间距、衬底厚度)和功耗的依赖关系。最后,通过与有限元(FEM)仿真结果对比,分区域提取了GaN HEMT器件中PCD衬底的有效热导率,分别为260~310 W/(m·K)和1 250~1 450 W/(m·K)。本文的计算为预测金刚石衬底上GaN HEMT器件的沟道温度提供了快速、有效的方法。 相似文献
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针对未来空间天文学应用的超分辨率光谱成像仪器的需求,对低噪声柱面微通道板(MCP)的制备方法及其性能进行了研究. 提出了一种将光学抛光与热成型相结合的新的柱面MCP制备方法,利用不含放射性元素的低噪声MCP玻璃,制备出曲率半径为400mm、尺寸为30mm′46mm、长径比为80:1、通道直径12.5mm、通道间距15mm的柱面MCP,并将其与感应电荷楔条形阳极(WSA)组成光子计数探测器,对其暗计数率、分辨率进行了检测,暗计数率约为0.1counts/cm2×s. 相似文献
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Multilayer membranes prepared via microlayer coextrusion have attracted wide attention due to their unique properties and broad applications. In present study, the foam/film alternating multilayer sheets based on ethylene-vinyl acetate copolymer(EVA) and high-density polyethylene are successfully prepared via microlayer coextrusion. The cells in the sheets are single-cell-array along the foamed EVA layers with uniform cell size. In addition, the effects of layer number and foam relative thickness on morphology, mechanical properties, damping and heat insulation properties are investigated. The cell size decreases significantly with increasing layer number due to the enhanced confine effects. The tensile strength, elongation at break, and heat insulation also increase significantly. However, the mechanical damping properties change little in the observed frequency. Meanwhile, with higher relative thickness of EVA foam, the sheets have lower tensile strength and lower thermal conductivity, while the damping properties are enhanced in a specific frequency scope. The elongation at break of the optimized sample comes to 800% and the thermal conductivity decreases to 61 mW·m~(-1)·K~(-1), which shows high toughness and low thermal conductivity, indicating a possible method for preparing materials with high toughness and heat-insulating properties. 相似文献
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PAN Quan MA Feiyan PU Xinqing ZHAO Manyi WU Qiling ZHAO Na YANG Jun TANG Ben Zhong 《高等学校化学研究》2021,37(1):166-170
In this work,a fluorescent probe(TPEBe-I)was developed for adenosine triphosphate(ATP)detection based on the synergetic effect of aggregation-induced emission and counterion displacement.TPEBe-I gave weak emission in aqueous solution due to the heavy-atom effect of counter iodide ion.However,upon the addition of ATP,the new aggregate complex(TPEBe-ATP)was formed between the cationic unit of TPEBe-I and ATP through electrostatic interactions,which not only restricted the intramolecular motion of luminogen but also eliminated the quenching effect of iodide ion.As a result,the fluorescent light-up detection for ATP was successfully achieved.Moreover,TPEBe-I exhibited high selectivity towards ATP and showed a wide linear detection region towards the logarithm of ATP concentration(5—600μmol/L)with a detection limit of 1.0μmol/L,enabling TPEBe-I as a promising probe for ATP quantitative analysis. 相似文献
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Phase structure and crystallization behavior of polyethylene(PE) in its blends with cis-1,4-butadiene rubber(BR) at different blend ratios and sample preparation conditions were studied. The PE is finely dispersed in the BR matrix. For samples hot pressed at 145 °C, circular PE microdomains with randomly oriented PE lamellar aggregates were produced. The domain size and number increase with increasing PE content. When the PE content is over 10 wt%, most of the PE domains impinged each other. The separated PE domains are connected by PE stripes with parallel arranged lamellar aggregates. For samples hot pressed at 140 °C, elongated PE microdomains with oriented PE lamellar aggregates were obtained due to the shear flow. The crystallization of PE in the blends depends on the phase structure. Confined crystallization of PE occurs in small microdomains at relatively low temperature. With the increase of domain size, the crystallization ability of PE increases while the confined crystallization decreases. 相似文献
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液相色谱-串联质谱同时测定禽肉组织中盐酸金刚烷胺、盐酸金刚乙胺、地塞米松、替米考星及喹乙醇代谢物的残留量 总被引:3,自引:0,他引:3
建立了同时测定禽肉组织中盐酸金刚烷胺、盐酸金刚乙胺、地塞米松、替米考星及喹乙醇代谢物残留量的液相色谱-串联质谱分析方法。样品用2 mol/L氢氧化钠溶液水解,盐酸调节p H值后,以乙腈作为提取溶剂,经C18固相萃取柱净化。各待测物分别经0.1%甲酸甲醇溶液和氨化甲醇(0.1%氨水)洗脱,Phenomenex Kinetex C18(100 mm×4.6 mm,2.6μm)色谱柱进行分离,采用0.1%甲酸(含5 mmol/L乙酸铵)-甲醇作流动相,梯度洗脱,串联质谱法对5种药物含量进行测定。结果表明,5种药物在2~100μg/L范围内线性关系良好,相关系数为0.996 2~0.999 8。在加标浓度为5~50μg/kg的禽肉组织中,这5种药物的加标回收率为73.7%~92.3%,相对标准偏差(n=5)为3.9%~16.6%,检出限为0.2~3.0μg/kg,定量下限为0.7~10μg/kg。方法快速、简便、经济实用,符合法规要求,可满足日常检测的需要。 相似文献
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