Acceleration and filtering in the generalized Landweber iteration using a variable shaping matrix

The generalized Landweber iteration with a variable shaping matrix is used to solve the large linear system of equations arising in the image reconstruction problem of emission tomography. The method is based on the property that once a spatial frequency image component is almost recovered within in in the generalized Landweber iteration, this component will still stay within in during subsequent iterations with a different shaping matrix, as long as this shaping matrix satisfies the convergence criterion for the component. Two different shaping matrices are used: the first recovers low-frequency image components; and the second may be used either to accelerate the reconstruction of high-frequency image components, or to attenuate these components to filter the image. The variable shaping matrix gives results similar to truncated inverse filtering, but requires much less computation and memory, since it does not rely on the singular value decomposition.     

塑料加工应用情报检索体系的建立与应用

介绍了塑料加工应用情报检索体系的组成与功能.该体系拥有PE、PP、PS等5个专题文献数据库;开通了3个国际联机情报检索系统和4个国内联机情报检索系统.累计已检索课题310个,打印输出信息12000条.产生了较好的经济效益和社会效益.     

一台用于环境样品分析的γ谱仪系统的性能与评论

本文介绍和评论了我所建立的环境实验室Ge(Li)γ谱仪系统的性能和应用。提出了一般环境实验室中使用一个中等体积和性能的高分辨率锗或Ge(Li)γ谱仪,加上适当的物质屏蔽就可以满足一般环境或生物样品中γ谱分析。     

ZnO薄膜光谱计算与颜色预测

简述了色彩形成的物理过程,建立一较有效的材料光谱特性仿真与色彩预测模型.采用密度泛函理论,计算了纤锌矿ZnO的复折射率,计算结果与实验结果相符.计算并分析了ZnO薄膜的反射光谱性质,预测了ZnO薄膜颜色为黄色,与实际样品相符.研究了薄膜厚度对ZnO薄膜色彩的影响,结果表明,在相干长度范围内(＜1300 nm),膜厚对ZnO薄膜颜色调制作用显著,膜较厚时(＞1300 nm),色彩及明度趋于稳定.     

Tracking mobile users in wireless networks via semi-supervised colocalization

Recent years have witnessed the growing popularity of sensor and sensor-network technologies, supporting important practical applications. One of the fundamental issues is how to accurately locate a user with few labeled data in a wireless sensor network, where a major difficulty arises from the need to label large quantities of user location data, which in turn requires knowledge about the locations of signal transmitters or access points. To solve this problem, we have developed a novel machine learning-based approach that combines collaborative filtering with graph-based semi-supervised learning to learn both mobile users' locations and the locations of access points. Our framework exploits both labeled and unlabeled data from mobile devices and access points. In our two-phase solution, we first build a manifold-based model from a batch of labeled and unlabeled data in an offline training phase and then use a weighted k-nearest-neighbor method to localize a mobile client in an online localization phase. We extend the two-phase colocalization to an online and incremental model that can deal with labeled and unlabeled data that come sequentially and adapt to environmental changes. Finally, we embed an action model to the framework such that additional kinds of sensor signals can be utilized to further boost the performance of mobile tracking. Compared to other state-of-the-art systems, our framework has been shown to be more accurate while requiring less calibration effort in our experiments performed on three different testbeds.     

DNA immobilization and SAW response in ZnO nanotips grown on LiNbO3 substrates.

DNA immobilization enhancement is demonstrated in a structure consisting of ZnO nanotips on 128 degrees Y-cut LiNbO3. The ZnO nanotips are grown by metalorganic chemical vapor deposition (MOCVD) on the top of a SiO2 layer that is deposited and patterned on the LiNbO3 SAW delay path. The effects of ZnO nanotips on the SAW response are investigated. X-ray diffraction and scanning electron microscopy are used to analyze the ZnO nanotips, which are of single crystalline quality, and they are uniformly aligned with their c-axis perpendicular to the substrate surface. The photoluminescence (PL) spectrum of the ZnO nanotips shows strong near bandedge transition with insignificant deep level emission, confirming their good optical property. DNA immobilization enhancement is experimentally validated by radioactive labeling tests and SAW response changes. The ZnO nanotips enhance the DNA immobilization by a factor of 200 compared to ZnO film with flat surface. DNA hybridization with complementary and noncomplementary second strand DNA oligonucleotides is used to study the selective binding of the structure. This device structure possesses the advantages of both traditional SAW sensors and ZnO nanostructures.     

Study of hybrid optical burst networks

We propose the hybrid optical burst switching (HOBS), and investigate the HOBS-based ring topology with numerical simulation. Results indicate that the packet loss ratio in HOBS is much less than that in optical burst switching(OBS) and its performance depends on some parameters such as the packet proportion, the electronic buffer size and the processing speed in the node. __________ Translated from Journal on Communications, 2005, 26(11): 7–11 (in Chinese)     

500kV曲北甲线误跳闸事故分析

本文针对500kV曲北甲线线路开关由于厂家二次接线错误而引起跳闸事故,分析其产生原因并提出防范措 施。     

我国空气中氡及其短寿命子体产生的照射

本文收集、分析和研究了我国已发表的空气中氡及其短寿命子体的资料。室外和室内^222Rn浓度按人口加权平均值的典型值分别为14Bq.m^-3和24Bq.m^-3。省市室外平均值最高和最低值相差约12倍，室内相差约6倍。室内和室外最高的都是福建。室外最低的是台湾，室内最低的是吉林。室内钍射气子体引起的照射值得引起注意，其中特别是以泥土为墙体的建筑物，在很多情况下钍射气子体所致年有效剂量高于(有时甚至远高于)氡及其子体所产生的剂量。     

"辐射防护体系演进"中一些问题的讨论

从中国辐射防护的实践看，现行辐射防护体系进行适当简化和更加协调一致是必要的。仅仅基于保护人的防护举措不是在各种情况下均能满足环境的要求。辐射防护的含意应该包括保护环境免受电离辐射的影响。集体剂量是一个有用的但需要明确其应用范围的指标。它的应用有利于促进辐射防护水平的提高，但应明确其应用的条件，如时间和空间等。天然辐射是人类所受照射的最大来源。有必要控制天然辐射产生的职业照射，如地下矿工和航空机组人员。加强控制人工辐射和天然辐射对孕妇和儿童的照射是重要的，其中特别是放射诊断和治疗。