一种基于PCA的MPSK信号码元速率估计方法

针对MPSK信号的码元速率估计问题, 研究了有限数据条件下循环谱的谱线特征受到背景色噪声干扰的现象, 提出了一种基于主分量分析(PCA)的循环谱特征码元速率估计方法。PCA变换抑制了信号循环谱中的背景色噪声, 提高了估计精度, 减小了估计方差。仿真表明, 该方法在有限数据条件下具有良好的估计性能, 适用于不同成形滤波系数的MPSK信号。     

基于身份密码体制的电子病历系统安全方案

针对目前电子病历系统存在病历信息泄露、数据被窜改、身份验证不严格等问题, 分析了该系统采用公钥基础设施（public key infrastructure, PKI）存在的不足, 提出了一种基于身份密码体制的改进方案。利用基于身份的加密、签名、认证等技术解决了电子病历系统中所遇到的一系列安全问题, 与已有PKI方案相比, 具有成本低、实现简单、效率高等优点。理论分析和实验结果表明, 该方案是保证电子病历系统安全运行的一种有效解决方案。     

Oxygen enrichment from air through multilayer thin low‐density polyethylene films

Several multilayer thin low‐density polyethylene (LDPE) films were fabricated by blown thin film having a thickness of 7 μm and an area of 130 cm². They were characterized for their oxygen‐enrichment performance from air by a constant pressure–variable volume method in a round permeate cell with an effective area of 73.9 cm². The relationship between oxygen‐enrichment properties, including oxygen‐enriched air (OEA) flux, oxygen concentration, permeability coefficients of OEA, oxygen, nitrogen, as well as separation factor through the multilayer LDPE films, and operating parameters, including transfilm pressure difference, retentate/permeate flux ratio, temperature, as well as layer number, are all discussed in detail. It is found that all of the preceding oxygen‐enrichment parameters increase continuously with an increase of transfilm pressure difference from 0.1 to 0.65 MPa, especially for the trilayer and tetralayer LDPE films. The oxygen concentration and separation factor appear to rapidly increase within the retentate/permeate flux ratio below 200, and then become unchangeable beyond that, whereas the OEA flux and the permeability coefficients of OEA, oxygen, and nitrogen seem to remain nearly constant within the whole retentate/permeate flux ratio investigated, especially for the monolayer and bilayer LDPE films. The selectivity becomes inferior, whereas the permeability becomes superior, as the operating temperature increases from 23 to 31°C. The highest oxygen concentration was found to be 44.8% for monolayer LDPE film in a single step with air containing oxygen of 20.9% as a feed gas and operating pressure of 0.5 MPa at a retentate/permeate flux ratio of 340 and 23°C. The results demonstrate a possibility to prepare an oxygen‐enriching membrane directly from air, based on the easily obtained thin LDPE films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3013–3021, 2002; DOI 10.1002/app.2331     

Identification of organochlorines and organobromines in coals

Four Chinese bituminous coals were extracted with CS₂, n-hexane, benzene, methanol, acetone, tetrahydrofuran (THF) and THF/methanol (1: 3 vol/vol) mixed solvent sequentially. The resulting 28 extracts were analyzed with GC/MS. Six organochlorines (OCs) and two organobromines (OBs) were identified in eight extracts from the coals. Our experiments provide, for the first time, the information on the molecular structure of OCs and OBs in coals.     

自含砷合碳难处理金矿中提取金的研究─Ⅰ.氨水脱砷-石灰加压氧化-氰化

针对甘肃省坪定金矿含金、砷高、金部分地赋存于脉石、脉石为碱性、属于难选难冶矿的特点，提出了氨水脱砷－石灰加压氧化－氰化新工艺．当原矿含金8．7g／t及13．0％砷时，砷可脱除95％，金可浸出85％．技术及经济指标预计均较满意．     

C5石油树脂在橡胶中应用的探讨

将Ｃ５石油树脂应用于丁苯橡胶（ＳＢＲ）和天然橡胶（ＮＲ）／顺丁橡胶（ＢＲ）并用胶中进行了全面性能试验。结果表明：国产和进口树脂的各项性能基本一致；适量加入树脂对胶料物理性能无明显影响；Ｃ５树脂对胶料具有明显增粘效果，是一种值得大力推广的产品。     

HDPE／炭黑导电复合材料的改性

本文研究了导电炭黑的品种、含量及其对高密度聚乙烯（ＨＤＰＥ）性能的影响，以及动态硫化对改善ＨＤＰＥ／导电炭黑复合材料物性的贡献。结果表明，ＨＧ－４型导电炭黑填充ＨＤＰＥ具有很好的导电性，复合材料力学性能较差；ＡＣＥＴ炭黑导电性较差，复合材料力学性能最好。炭黑并用能有效地降低生产成本，而且保持了材料的性能。动态硫化法可以克服复合材料物性差的弱点，并能保持改性材料的高导电性。在ＨＧ－４型炭黑含量为７份时，材料的拉伸强度１３ＭＰａ，断裂伸长率３５０％，体积电阻率为２．１Ω·ｃｍ。     

Bidirectional Label Propagation over Graphs

Graph-Based label propagation algorithms are popular in the state-of-the-art semi-supervised learning research. The key idea underlying this algorithmic family is to enforce labeling consistency between any two examples with a positive similarity. However, negative similarities or dissimilarities are equivalently valuable in practice. To this end, we simultaneously leverage similarities and dissimilarities in our proposed semi-supervised learning algorithm which we term Bidirectional Label Propagation (BLP). Different from previous label propagation mechanisms that proceed along a single direction of graph edges, the BLP algorithm can propagate labels along not only positive but also negative edge directions. By using an initial neighborhood graph and class assignment constraints inherent among the labeled examples, a set of class-specific graphs are learned, which include both positive and negative edges and thus reveal discriminative cues. Over the learned graphs, a convex propagation criterion is carried out to ensure consistent labelings along the positive edges and inconsistent labelings along the negative edges. Experimental evidence discovered in synthetic and real-world datasets validates excellent performance of the proposed BLP algorithm.     

基于改进A*算法的越野路径规划研究

针对车辆的越野路径规划问题, 研究并分析了地形坡度和地表属性对于车辆路径规划的综合影响。引入了窗口移动法对地形进行先期的坡度计算和通行性分析, 就轮式车辆和履带式车辆分别建立了地表属性的粗糙度评价指标, 并采用面积占优法将地表属性栅格化。通过建立禁忌表, 叠加了坡度与粗糙度的约束影响以减少搜索范围, 提高搜索效率。构造了改进A*算法的估价函数, 并结合expand表、open表、closed表以及path表设计了考虑坡度和粗糙度约束的路径优化算法。仿真结果表明, 该算法能够快速有效地实现符合真实地形环境的越野路径规划。     

弹性条缝筛网用聚氨酯弹性体的研制

采用预聚法常压浇注制备煤矿用聚氨酯筛网，考察了聚醚多元醇、甲苯二异氰酸酯异构体种类、预聚体的NCO质量分数、扩链反应温度、后熟化温度及时间等条件对制筛网用的浇注型聚氨酯弹性体体系操作性能及物理性能的影响。实验表明，采用聚四氢呋喃二醇与聚氧化丙烯二醇的混合二醇(质量比为80：20)，制得的预聚体NCO质量分数控制在4．5％左右；再以MOCA和一种三官能度扩链剂的混合扩链剂进行扩链，制得的浇注型聚氨酯弹性体满足洗煤用筛网的性能要求。