Channel-carrier mobility parameters for 4H SiC MOSFETs

In this paper, mobility parameters for enhancement-mode N-channel 4H SiC MOSFETs are extracted and implemented into 2-D device simulation program and SPICE circuit simulator. The experimental data were obtained from lateral N-channel 4H SiC MOSFETs with nitrided oxide–semiconductor interfaces, exhibiting normal mobility behavior. The presence of increasing interface-trap density (D_it) toward the edge of the conduction band is included during the 2-D device simulation. Using measured distribution of interface-trap density for simulation of the transfer characteristics leads to a good agreement with the experimental transfer characteristic.     

A Web‐based and Group Learning Environment for Introductory Environmental Engineering

The use of computer‐based technology is becoming more prevalent in the classroom. As a part of an educational research project sponsored by the GE Foundation, strategies for augmenting a course, Introduction to Environmental Engineering (CE 280), were investigated including cross‐disciplinary experiences in teamwork, design, and the use of advanced teaching technologies such as the web. Interactive tools to assist student learning were developed and refined. Efforts have focused on developing an extensive website, web‐based quizzes and homework assignments, and tutorials. Base groups were used to provide both intellectual and emotional support to students. This paper summarizes the development of this course and the impact of rapid feedback on the progression of student understanding.     

Organic‐acid‐catalyzed sol–gel route for preparing poly(methyl methacrylate)–silica hybrid materials

In this study, a series of organic–inorganic hybrid sol–gel materials consisting of a poly(methyl methacrylate) (PMMA) matrix and dispersed silica (SiO₂) particles were successfully prepared through an organic‐acid‐catalyzed sol–gel route with N‐methyl‐2‐pyrrolidone as the mixing solvent. The as‐synthesized PMMA–SiO₂ nanocomposites were subsequently characterized with Fourier transform infrared spectroscopy and transmission electron microscopy. The solid phase of organic camphor sulfonic acid was employed to catalyze the hydrolysis and condensation (i.e., sol–gel reactions) of tetraethyl orthosilicate in the PMMA matrix. The formation of the hybrid membranes was beneficial for the physical properties at low SiO₂ loadings, especially for enhanced mechanical strength and gas barrier properties, in comparison with the neat PMMA. The effects of material composition on the thermal stability, thermal conductivity, mechanical strength, molecular permeability, optical clarity, and surface morphology of the as‐prepared hybrid PMMA–SiO₂ nanocomposites in the form of membranes were investigated with thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, gas permeability analysis, ultraviolet–visible transmission spectroscopy, and atomic force microscopy, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

6LoWPAN在物联网中的应用仿真

提出了一种基于6LoWPAN的物联网总体方案,同时对协议中的Mesh字段进行了改进,然后在网络模拟环境下对本协议平均传输成功率、平均延迟时间的性能进行了比较分析,并在仿真环境中进行了实验验证工作。实验数据表明,改进后的协议具有更好的性能。     

利用测井资料评价储集层性质的探讨

根据对储集层之简化导电模型的理论分析,提出了一个由电阻率、孔隙度信息表示的、反映储层性质的“孔隙结构参数S”。实际应用表明,S参数在评价储集层性质、计算储层渗透率等方面具有一定的使用价值。     

年最大洪峰流量群居蜘蛛优化投影寻踪预测模型

年最大洪峰流量预测,受较多的复杂因素的影响,不确定性较强,用常规统计方法做出准确预报具有较大困难。从水文序列本身出发,提出将投影回归模型应用于年最大洪峰流量预测,为了更好获得投影寻踪模型参数和预测精度,提出了运用延迟相关系数法确定回归预测因子、群居蜘蛛算法优化投影寻踪模型最佳投影方向参数a、利用最小二乘法确定多项式的权系数c、岭函数个数M的群居蜘蛛优化投影寻踪年最大洪峰流量预测模型,结合长江宜昌站(1882年-2004年)的年最大洪峰流量资料进行实例预测,训练阶段平均绝对相对误差为8.61%,预测阶段平均绝对相对误差为10.51%,该模型预测效果较好,模型结果稳定,可有效应用于年最大洪峰流量预测。     

新版Auto CAD计算机辅助设计在我公司氯碱设计中的应用

随着计算机技术及外围设备的提高和完善 ,计算机辅助设计和计算机辅助工程技术得到了日益广泛应用 ,绘图技术也得到了很大的发展 ,并已成为工程制图发展的必然趋势。我公司应用美国ＡＵＴＯＤＥＳＫ公司推出的新版ＡｕｔｏＣＡＤ2 0 0 2中文版本 ,是当前国际上最为先进和流行的绘图软件之一 ,具有以下增强功能。1　新增设计中心图库 ,在绘图过程中 ,可边绘图 ,边自动将所绘单元图储存在设计中心库中 ,这样可重复和快速使用相同或相近单元图 ,或在绘制新图时 ,可从中心库中随时提取相同或相近单元图形来绘制新图。其次 ,在绘图过程中 ,也可把…     

两亲性聚合物多孔微球的制备研究

合成了具有悬挂双键的苯乙烯-二乙烯基苯多孔微球,在悬挂双键处接枝甲基丙烯酸甲酯,制成了一系列不同接枝度的两亲性聚合物多孔微球。考察了悬挂双键数量、反应时间等因素对接枝率的影响以及接枝率对微球形貌的影响。实验中通过观测澄清点,有效地控制了反应后期自加速现象对接枝率的影响。在反应时间25 m in时,制得了平均孔径为50 nm的两亲性多孔微球。将该微球用于对化妆品活性组分的负载,对极性物的负载率比接枝前高出2倍。     

Synthesis and properties of polyimide (containing naphthalene) nanocomposites with organo‐modified montmorillonites

2,7‐Bis(4‐aminophenoxy) naphthalene (BAPN), a naphthalene‐containing diamine, was synthesized and polymerized with a 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA) to obtain a polyimide (PI) via thermal imidization. To enhance the thermal and mechanical properties of the polymer, PI–Montmorillonite (MMT) nanocomposites were prepared from a DMAc solution of poly(amic acid) and a DMAc dispersion of MMT, which were organo‐modified with various amounts of n‐dodecylamine (DOA) or cetylpyridium chloride (CPC). FTIR, XRD, and TEM (transmission electron microscopy) were used to verify the incorporation of the modifying agents into the clay structure and the intercalation of the organoclay into the PI matrix. Results demonstrated that the introduction of a small amount of MMT (up to 5%) led to the improvement in thermal stability and mechanical properties of PI. The decomposition temperature of 5% weight loss (T_d,5%) in N₂ was increased by 46 and 36°C in comparison with pristine PI for the organoclay content of 5% with DOA and CPC, respectively. The nanocomposites were simultaneously strengthened and toughened. The dielectric constant, CTE, and water absorption were decreased. However, at higher organoclay contents (5–10%), these properties were reduced because the organoclay was poorly dispersed and resulted in aggregate formation. The effects of different organo‐modifiers on the properties of PI–MMT nanocomposite were also studied; the results showed that DOA was comparable with CPC. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006