双反馈晶振和石英谐振器低噪声性能的进一步研究

本文进一步探讨了有关双反馈晶振低噪声性能的问题,着重分析了石英谐振器静电容C_0对双反馈晶振电路Q倍增固子、石英谐振器Q值及净噪特性的影响。为验证上述C_0的影响,也对不同C_0的石英谱振器的相噪特性进行了测量并得到了与分析一致的结果。     

钽酸锂晶体宽带滤波器

本文简要介绍钽酸锂晶体及器件的一些特性,对用该材料制作的21.4MHz宽带滤波器的设计、制作和测试结果作了较详细的介绍,滤波器的带宽达225kHz,矩形系数(BW_(?0dB)/BW_(3dB)为2.66,带外衰减在50dB以上。该材料在做宽带滤波器和压控振荡器方面具有优越性。     

呼捷玛斯：前苏联高等艺术与技术创作工作室——被扼杀的现代建筑思想先驱

本文回顾了20世纪初前苏联高等艺术与技术创作工作室（呼捷玛斯）自1920年成立以来至1930年解体，10多年的艰苦历程和对世界现代建筑思想创立的重要贡献。并全面，清晰地勾勒了20世纪初现代建筑运动的两个中心——德国的包豪斯和前苏联的呼捷玛斯的全景。     

金属零件的快速数字化制造

叙述了数字化技术在改造传统铸造工艺中的作用，详细论述了金属零件数字化铸造技术的内涵及其优势。研究表明，金属零件的数字化铸造具有极大的工艺柔性，能够实现虚拟铸造的部分功能；基于快速原型技术的数字化铸造使得常规生产需要2个月时间的金属零件生产周期缩短到一周，大大缩短了金属零件制造的时间，对于快速响应市场需求具有很大的优势。     

中国压铸市场的机遇与挑战

评述了中国压铸市场的现状和发展前景。2002年，全国压铸件总产量为62．4万t，其中：铝合金压铸件产量为41．56万t，锌合金压铸件产量为19．82万t，镁合金压铸件产量为0．50万t，铜合金压铸件产量为0．53万t，分别占66．6％，31．87％，0．8％，0．8％；压铸机年销售量近1800台；2lD02年，全国模具总产值达到360亿元，其中压铸模约占10％；全国压铸行业中，外资企业、民营企业、乡镇企业以及私营企业合计已达到压铸企业总数的80％以上，特大型压铸企业集团开始涌现。     

Hypermedia Support for Software Development: A Retrospective Assessment

Hypermedia technologies have been available for about a decade. Beginning with Douglas Engelbart, researchers have become interested in applying hypermedia concepts and technologies to software development. This paper assesses this symbiosis between hypermedia and software development as described by research contributions; by our count, more than one hundred articles. To date, no collection of, or guide to, this literature has been published. A number of significant contributions are classified, described, and appraised — providing a guide into what has been a rich but perhaps under-reported research area. Hypermedia has made significant contributions to software development in three primary areas: coping with massive amounts of information associated with software development projects; establishing and maintaining linkages between various types of software engineering documents; and enabling development engineers to record, document, and preserve knowledge about development thoughts, processes and rationale. These contributions may help direct the focus of future research towards building on, combining and assessing the resulting contributions. A research agenda is proposed along these lines.     

电子装置的可靠性设计

论述了如何正确选择电子元器件和正确使用电子元器件对电子装置可靠性的影响,同时也论述了正确布线提高系统可靠性问题及电子装置箱体设计应考虑的问题。     

A novel fault-tolerant sensor system for sensor drift compensation

The conventional fault-tolerant sensor systems would fail when outputs from incorporated sensors are either noisy or drifting. This paper presents a novel real-time fault compensation method, which uses state estimation and compensation techniques, that the sensor system can perform robust measurements even when outputs from every incorporated sensor are noisy and drifting. In a simulation example, the proposed design can detect and correct the sensor errors (dc bias and drift) in real time. For the dc bias, the minimum detectable offset value is 0.1, which is the same as the standard deviation of the sensor noise. The compensated sensor output is biased at values smaller than 0.02. For the sensor drifts, the proposed method can compensate drifts for the change rate of drifts up to four times faster than that of the signal to be measured. The highest change rate of drifts, that can be compensated by this method, is determined by the standard deviation of the sensor noise.     

基于马尔可夫模型的JPEG图像隐写分析

论证了通用图像隐写分析是一个类间很聚合、类内很分散的2类模式识别的困难分类问题。提出一种基于JPEG图像量化DCT域的块内和块间2个马尔可夫链获得高维特征,给出2种高维特征的分类器,即改进贝叶斯分类器和CNPCA分类器,后者简单而性能略低,但仍略优于SVM分类器。针对4种公认的JPEG隐藏数据方法,即F5, Outguess, MB1和MB2进行隐写分析,在CorelDraw图像库上做实验,取得了较好的效果。     

基于单幅正面照片的三维人脸重建方法

三维人脸重建算法需要多张照片实现重建且重建效率低下。针对上述问题,提出一种利用单幅正面照片重建三维人脸的方法。采用薄板样条函数对数据库中的三维人脸确立点对点的对应关系,建立平均三维人脸模型,利用LMA算法优化形状系数以恢复其三维形状,人脸颜色纹理信息可通过垂直投影得到。实验结果表明,利用该方法重建得到的三维人脸逼真且时间效率高。