Numerical simulation of topography effects on the "00.7" severe rainfall in Beijing

In an effort to study the severe rainfall event of 4-5th July 2000 in Beijing (with 24h accumulated precipitation of 240 mm), we perform numerical simulations to investigate this event using the MM5v3.6 model. The model is initialized with the MM5/WRF 3DVAR analysis, which incorporates the ground-based GPS precipitable water vapor, automatic and conventional meteorological observations in its assimilation step. For 24 h accumulated precipitation forecast, the threat scores are 0.72, 0.76, 0.67 and 0.63, for thresholds of 1, 5, 10, and 20 mm, respectively. Holding other factors unchanged, sensitivity experiments were conducted with different topographic resolutions of 110, 50 and 3.7 km to investigate the topographic effects on precipitation over the Beijing area. In these sensitivity experiments, we attempt to preserve the realistic orographic distribution in the model topography under the condition of keeping the dynamic-thermodynamic consistency of the initial model atmosphere to the extent possible. Results indicate that the unique topographic distribution and variations in the Beijing area play an important role in determining the location, distribution and intensity of heavy precipitation.     

通信信号自动分类方法研究

提出增加信号的频谱作为信号的特征信息之一 ,并采用离散傅里叶变换 (DFT)和小波 (wavelet)方法提取信号的频谱、瞬时幅度、瞬时频率及瞬时相位 ,构成信号的特征向量。为解决运算速度问题 ,对特征向量提出了分类编码方案。最后利用神经网络的方法进行识别。实验结果表明 ,采用这种方法可以显著地改进分类的效果     

三大现代设计理论异同比较

论述现代设计理论的三大流派－一般设计学、设计原理、系统设计论的主要理论与分析，并分析、比较各流派异同点及应用特点，以利于更好地将现代设计理论与方法应用于工程设计。     

基于K-L变换的网络调制识别方法

针对BP网络进行通信信号调制样式识别的场合,在输入层和输出层节点数确定的条件下,提出在网络训练完成后应用K-L变换方法确定网络隐含层的节点数,对网络结构进行优化。利用K-L变换的正交性,去除了网络结构的冗余,给出了该算法的理论推导和具体应用步骤,通过仿真验证了算法的有效性和顽健性。利用BPSK、QPSK、16QAM等数字调制信号,选取了三个特征量,分别用优化前后的网络进行调制识别,实验表明优化前后网络的识别性能基本一致。     

蓬莱19-3溢油运移与归宿数值模拟和分析

通过耦合水动力模型建立渤海海上溢油运移与归宿数学模型,包含漂移、扩散、蒸发、乳化等过程,通过拉格朗日方法模拟漂移过程、蒙特卡罗方法模拟油粒子扩散的随机性,采用变化的紊动扩散系数使溢油所受紊动扩散作用随时间变化.通过率定得到蓬莱19-3溢油模拟中风拖拽系数和扩散系数校正参数b的合理取值范围分别为1.4%~2.3%和0.38~0.42.对蓬莱19-3溢油事故进行了模拟,通过溢油附岸位置与时间验证了模型的准确性.模拟结果表明:由于风速较大、方向变化较小,风对漂浮于水面上的溢油产生较大作用,且溢油漂移方向与主风向一致;渤海海域内的潮流以往复流、旋转流为主且余流小使其对溢油运移的作用弱于风;溢油初期的蒸发速度较快,后期因挥发组分的减少以及乳化作用使溢油含水率增大使得蒸发速度明显减小;蒸发和附岸是溢油漂浮组分减少的主要原因,也是溢油的主要归宿.     

美国工程学学科的评估

本文讨论了影响当今工程学教育的一些问题,其中主要问题是：大众希望高等教育具有可衡量性;企业希望工程学学科能更迅速地调整其研究方向和课程内容以适应技术的发展。《美国新闻与世界报道》基于历年收集的多种数据公布了美国工程学学科排名。在本文中,通过排名结果分析,证实了量可以作为衡量教育质量的尺度的变量。     

IBM GALE中文识别系统

为解决中文音频自动转成文字问题,IBM开发了GALE中文识别系统。该系统采用区分性声学模型训练方法和新颖的基于主题的语言模型自适应技术;为获得最优的识别性能,系统采用多遍解码的识别策略。该文还给出该系统在3个测试集上的识别结果:包括广播新闻和广播访谈节目,结果显示,IBM GALE中文识别系统取得了很好的识别性能;此外,该文还分析了特殊声学现象对识别结果的影响,结果显示,对识别率影响最大的3种声学现象为说话人语速过快、语音交叠和口音问题,这指示了系统下一步的改进方向。     

SOCl2和CF4在光纤MCVD过程中脱氢反应的平衡计算

计算了O₂-H₂O-CH₄-SOCl₂-SiO₂和O₂-H₂O-CH₄-CF₄-SiO₂系统与CVDSiO₂光纤有关组成的多相平衡,给出在1073~2573K温度下沉积SiO₂内的平衡羟基浓度并讨论了SOCl₂与CF₄添加剂在MCVD过程中的脱氢作用.     

Breast metastasis from small cell lung carcinoma

Breast metastases from extramammary neoplasms are very rare. We presented a 66 year-old female with metastasis of small cell lung carcinoma to the breast. She presented with consolidation over the left upper lobe of her lung undetermined after endobronchial or video-assisted thoracoscopic surgery （VATS） biopsy, and this was treated effectively after antibiotic therapy at initial stage. The left breast lumps were noted 4 months later, and she underwent a modified radical mastectomy under the impression of primary breast carcinoma. However, the subsequent chest imaging revealed re-growing mass over the left mediastinum and hilum, and cells with the same morphological and staining features were found from specimens oftransbronchial brushing and biopsy. An accurate diagnosis to distinguish a primary breast carcinoma from metastatic one is very important because the therapeutic planning and the outcome between them are different.