准确预测GaN半导体材料的热导率对GaN基功率电子器件的热设计具有重要意义. 本文基于第一性原理计算和经典Debye-Callaway模型,通过分析和完善Debye-Callaway模型中关于声子散射率的子模型, 建立了用于预测温度、同位素、点缺陷、位错、薄膜厚度、应力等因素影响的GaN薄膜热导率的理论模型. 具体来说, 对声子间散射项和同位素散射项基于第一性原理计算数据进行了系数拟合, 讨论了两种典型的处理点缺陷和位错散射的散射率模型, 引入了应用抑制函数描述的各向异性边界散射模型,并对应力的影响进行了建模. 热导率模型预测值和文献中典型实验数据的对比表明, 基于第一性原理计算数据拟合的热导率模型和实验测量值总体符合较好, 300 K温度附近热导率数值及其随温度变化的趋势存在20%左右的偏差. 结合实验数据和热导率模型进一步确认了第一性原理计算会高估同位素散射的影响, 给出了薄膜热...

We present a strictly three-dimensional modeling technique as a basis for numerical simulations. These simulations range from a high-resolution indoor air flow modeling using the so-called thermal lattice Boltzmann method to a multi-zone network model for building energy simulation. Within this paper, an intermediate geometric model is derived from the IFC building product model standard with r...

This paper considers the design and optimization of thermal systems on the basis of the mathematical and numerical modeling of the system. Many complexities are often encountered in practical thermal processes and systems, making the modeling challenging and involved. These include property variations, complicated regions, combined transport mechanisms, chemical reactions, and intricate boundar...

Not least due to the widespread use of meta modeling concepts, model transformation techniques have reached a certain level of maturity (Czarnecki and Helsen, 2006). Nevertheless, defining transformations in some application areas in our case business process modeling is still a challenge because current transformation languages provide general solutions but do not support issues specific to a ...

Learning progressions (LPs) are a recent educational theory pertaining to student modeling. LPs argue that students with equal test scores may nonetheless have different conceptualizations of the material, with varying degrees of maturity. However, there is little empirical validation for LPs. To this end, we mapped two physics LPs (one predefined, one described in the paper) onto the answer ch...