基于LMDS的固定无线接入技术

介绍LMDS（Local Multipoint Distribute Service本地多点分配业务）的基本概念和它的结构,重点分析LMDS所采用调制解调技术和OFDM（Optical Frequency Division Mulfiplexing正交频分复用）高速传输技术,以及LMDS优缺点;将LMDS技术应用于电信领域很好解决了瓶颈问题,应用效果良好,且特别适用于中国电信这样拥有众多光缆资源的老牌营运商。     

新水土保持法主要制度解读

2011年3月1日起施行的《中华人民共和国水土保持法》确立和强化了水土保持目标责任制和考核奖惩制度等20多项制度。这些制度的建立和完善,保证了新时期水土保持事业的健康、有序、持续发展,并成为今后水土保持改革和发展的强劲动力。本刊专题约请水利部水土保持司副司长牛崇桓对主要制度进行深入解读。     

内燃机缸内气体流动与燃烧的大型计算程序向微机移植

介绍了将大型计算机使用的内燃机缸内气体流动与燃烧数值计算程序向４８６微机移植过程中，由于运行环境的改变所出现的问题及其解决的途径与方法。     

我国南方红壤分布区1:20万水土流失遥感调查方法探讨

介绍了水土流失区土壤流失1:20万比例尺遥感调查过程,建立了权重模型和判别条件,可用来评估土壤流失强度。认为所获得的 Landsat TM3,4,7波段的假彩色合成影像是解译和识别影响因子的主要手段。在流失区面积估测中,利用大比例尺航片,解译量算流失区中的“非流失区系数”,通过非流失区系数扣除,可大大提高面积量算的精度。     

紫外激光辐照非纯7-DHC研究

本文报道用KrF准分子激光和N_2分子激光分别辐照含杂质的7-去氢胆留醇合成维生素D_3的实验研究。维主素D_3的前身P_3的转化率～63％。     

A novel application recommendation method combining social relationship and trust relationship for future internet of things

Traditional collaborative filtering methods always utilize Cosine and Pearson methods to calculate the similarity of users. When the nearest neighbor doesn’t comment the predicted item, then the nearest neighbor has no influence on results, thus affecting the accuracy of collaborative filtering recommendation. And the traditional recommendation systems always have the problems of data sparsity, cold start and so on. In this paper, we consider social relationship and trust relationship, and put forward a novel application recommendation method that combines users’ social relationship and trust relationship. Specifically, we combine social relationship and user preference towards applications to calculate similarity score, we fuse the trust relationship based on familiarity and user reputation to calculate trust score. The final prediction score is calculated by fusing similar relationship and trust relationship properly. And the proposed method can effectively improve accuracy of recommendations.

     

结合自助抽样的动态数据流贝叶斯分类算法

动态数据流具有数据量大、变化快、随机存取代价高、详细数据难以存储等特点,挖掘动态数据流对计算能力与存储能力要求非常高。针对动态数据流的以上特点,设计了一种基于自助抽样的动态数据流贝叶斯分类算法,算法运用滑动窗口模型对动态数据流进行处理分析。该模型以每个窗口的数据为基本单位,对窗口内的数据进行处理分析;算法采用自助抽样技术对待分类数据中的属性进行裁剪和优化,解决了数据属性间的多重线性相关问题;算法结合贝叶斯算法的特点,采用动态增量存储树来解决动态样本数据流的存储问题,实现了无限动态数据流无信息失真的静态有限存储,解决了动态数据流挖掘最大的难题——数据存储;对优化的待分类数据使用all-贝叶斯分类器和k-贝叶斯分类器进行分类,结合数据流的特性对两个分类器进行实时更新。该算法有效克服了贝叶斯分类属性独立性的约束和传统贝叶斯只对静态数据分类的缺点,克服了动态数据流最大的难题——数据存储问题。通过实验测试证明,基于自助抽样的贝叶斯分类具有很高的时效性和精确性。     

Atmospheric HCH concentrations over the Marine Boundary Layer from Shanghai, China to the Arctic Ocean: role of human activity and climate change

From July to September 2008, air samples were collected aboard the research expedition icebreaker XueLong (Snow Dragon) as part of the 2008 Chinese Arctic Research Expedition Program. Hexachlorocyclohexane (HCH) concentrations were analyzed in all of the samples. The average concentrations (± standard deviation) over the entire period were 33 ± 16, 5.4 ± 3.0, and 13 ± 7.5 pg m?3 for α-, β- and γ-HCH, respectively. Compared to previous studies in the same areas, total HCH (ΣHCH, the sum of α-, β-, and γ-HCH) levels declined by more than 10 × compared to those observed in the 1990s, but were approximately 4 × higher than those measured by the 2003 China Arctic Research Expedition, suggesting the increase of atmospheric ΣHCH recently. Because of the continuing use of lindane, ratios of α/γ-HCH showed an obvious decrease in North Pacific and Arctic region compared with those for 2003 Chinese Arctic Research Expedition. In Arctic, the level of α-HCH was found to be linked to sea ice distribution. Geographically, the average concentration of α-HCH in air samples from the Chukchi and Beaufort Seas, neither of which contain sea ice, was 23 ± 4.4 pg m?3, while samples from the area covered by seasonal ice (～75°N to ～83°N), the so-called "floating sea ice region", contained the highest average levels of α-HCH at 48 ± 12 pg m?3, likely due to emission from sea ice and strong air-sea exchange. The lowest concentrations of α-HCH were observed in the pack ice region in the high Arctic covered by multiyear sea ice (～83°N to ～86°N). This phenomenon implies that the re-emission of HCH trapped in ice sheets and Arctic Ocean may accelerate during the summer as ice coverage in the Arctic Ocean decreases in response to global climate change.     

拖拉机阻力控制系统的统计分析计算方法

本文介绍了阻力控制系统的统计分析计算方法。这个计算方法,根据给定的系统随机输入的统计特征,可计算各犁铧耕深的方差、发动机转速和扭矩的方差。适用于上拉杆传感式、先导回油阀卸载油路阻力控制系统的统计分析。     

基于社会网络协同过滤的社会化电子商务推荐研究

随着社会网络关系的不断复杂化,商品是否推荐成功,除了基于商品本身的特征外,还受社会网络关系的影响。很多用户更加信任来自朋友的推荐,而非机器通过单因素计算出来的推荐结果。因此,设计了一个融入社会网络关系的电子商务推荐系统。其中,构建了社会网络关系强度、兴趣偏好强度和商品流行性与声望强度3个关键因子,每个一级因子又由若干个二级因子构成。实验结果验证了社会网络关系会对其中成员的网购等网络行为产生影响,构建的基于社会网络的电子商务推荐策略的效果比其他单因素推荐策略好且稳定,具有很好的实际应用效果。