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Size effect in the melting and freezing behaviors of Al/Ti core-shell nanoparticles using molecular dynamics simulations 下载免费PDF全文
The thermal stability of Ti@Al core/shell nanoparticles with different sizes and components during continuous heating and cooling processes is examined by a molecular dynamics simulation with embedded atom method. The thermodynamic properties and structure evolution during continuous heating and cooling processes are investigated through the characterization of the potential energy, specific heat distribution, and radial distribution function(RDF). Our study shows that, for fixed Ti core size, the melting temperature decreases with Al shell thickness, while the crystallizing temperature and glass formation temperature increase with Al shell thickness. Diverse melting mechanisms have been discovered for different Ti core sized with fixed Al shell thickness nanoparticles. The melting temperature increases with the Ti core radius. The trend agrees well with the theoretical phase diagram of bimetallic nanoparticles. In addition, the glass phase formation of Al–Ti nanoparticles for the fast cooling rate of 12 K/ps, and the crystal phase formation for the low cooling rate of 0.15 K/ps. The icosahedron structure is formed in the frozen 4366 Al–Ti atoms for the low cooling rate. 相似文献
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Numerical and experimental study of the mesa configuration in high-voltage 4H–SiC PiN rectifiers 下载免费PDF全文
The effect of the mesa configuration on the reverse breakdown characteristic of a SiC PiN rectifier for high-voltage applications is analyzed in this study.Three geometrical parameters,i.e.,mesa height,mesa angle and mesa bottom corner,are investigated by numerical simulation.The simulation results show that a deep mesa height,a small mesa angle and a smooth mesa bottom(without sub-trench) could contribute to a high breakdown voltage due to a smooth and uniform surface electric field distribution.Moreover,an optimized mesa structure without sub-trench(mesa height of 2.2 μm and mesa angle of 20°) is experimentally demonstrated.A maximum reverse blocking voltage of 4 kV and a forward voltage drop of 3.7 V at 100 A/cm~2 are obtained from the fabricated diode with a 30-μm thick N~- epi-layer,corresponding to 85% of the ideal parallel-plane value.The blocking characteristic as a function of the JTE dose is also discussed for the PiN rectifiers with and without interface charge. 相似文献
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利用耦合簇理论CCSD(T)和相关一致基组cc-pVXZ和aug-co-pVXZ(X=2,3,4,5)计算了SH 和SD 的基态平衡几何re、谐振频率ωe和离解能De.计算结果表明,所用基组越大,得到的结果与实验值之间的差别就越小,因此我们选用了大基组aug-cc-pV5Z在0.07~2.50 nm的核间距范围内对SH 和SD 的基态进行单点能计算,并将计算结果拟合成了Murrell-Sorbie函数.利用得到的解析势能函数,计算了SH 和SD 的其余3个光谱常数(ωexe,αe和Be),其结果与实验值符合得相当好. 相似文献
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采用非同时读出条件下晶体两波耦合实验装置,在入射光调制下,研究了调制频率对Ce:KNSBN晶体两波耦合有效增益(G)的影响,结果显示G随调制频率的增大先增大后减小,但入射光波长不同时,G最大值对应的调制频率不同,入射光波长为632.8nm时,G最大值为20.2,对应的调制频率为100Hz;入射光波长为532nm时,G最大值为15.1,对应的调制频率为175Hz.同时研究了入射光参量对增益改善(Gm/Gf)及最佳调制频率的影响,结果显示不同入射光参量下增益改善及最佳调制频率不同,入射光波长为632.8nm时,增益改善最大为1.92,对应的最佳调制频率为100Hz;入射光波长为532nm时,增益改善最大为1.50,对应的最佳调制频率为150Hz.采用运动光栅理论对实验结果进行了解释. 相似文献
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利用完全对角化方法和强场耦合方案,采用半自洽场(semi-SCF)自由Ni2 的d轨道模型,点电荷—偶极子模型和Ni2 -6X-(X=F,Cl,Br,I)络合物的μ-κ-α模型研究,建立了含有过渡族金属离子的晶体的局域结构与吸收光谱和顺磁g因子之间的定量关系,对RbNiCl3晶体的局域结构,吸收光谱和顺磁g因子作出了统一解释,所得理论计算结果与实验值符合得很好.这对进一步研究掺杂顺磁离子晶体的结构,光学,磁学,热学,电子顺磁共振参量,高压,精细结构等性质和了解晶体的结构信息提供了一种可行的方法. 相似文献
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<正>浏览各地2014年中考试题,发现有一类求第2014个点的坐标的问题,立意新颖,形式灵活,下面我们就去2014年中考的花海中采撷几朵,与朋友们共赏.例1(2014年山东省泰安市)如图1,在平面直角坐标系中,将△ABO绕点A顺时针旋转到△AB1C1的位置,点B、O分别落在 相似文献
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依据数理统计理论,对减压氩气环境下,利用CCD数据采集处理系统所获取的激光微区发射光谱数据进行筛选,用以减弱样品表面激光蚀坑变化、样品不均匀性、激光波动性等因素的影响,探讨了激光微区发射光谱定量分析精度的改善方法。实验中以铝合金标样为分析样品,对Cu,Zn,Mg分析表明:分析谱线相对强度RSD分别为1.80%,4.35%,6.29%,定量分析相对标准偏差RSD分别为10.1%,6.98%,8.17%,分析结果平均值的相对误差为-3.76%,3.62%,-1.62%。 相似文献