基于正交脉冲波形的高速超宽带通信系统

提出了基于小波函数的两个正交脉冲,其功率谱密度满足美国通信委员会(FCC)对UWB系统的频谱限制。在此基础上提出了使用脉冲波形的极性调制和正交脉冲波形的形状调制相结合的一种高速超宽带通信系统,可以同时传送多个比特信息提高传信率。     

基于谱聚类的在线数据库垂直分区多阶段生成方法

垂直数据分区技术从逻辑上将满足一定语义条件的数据库表属性存放在同一个物理块中,进而降低数据访问成本,提高查询效率.数据库查询负载中的每条查询通常只与数据库表中的部分属性有关,因此只需使用数据库表的某个属性子集便可以得到准确的查询结果.合理的垂直数据分区方式可以使大多数查询负载不需要扫描完整数据库就可以完成查询任务,从而达到减少数据访问量,提高查询处理效率的目的.传统的数据库垂直分区方法主要基于专家设置的启发式规则,分区策略粒度较粗,且不能根据负载的特征进行有针对性的分区优化.同时,当负载规模较大或者属性个数较多时,现有垂直分区方法执行时间过长,尤其无法满足数据库在线实时调优的性能需求.为此,提出在线环境下基于谱聚类的垂直数据分区方法（spectral clustering based vertical partitioning,SCVP）,采用分阶段求解的思想,减少算法时间复杂度,加快分区执行速度.首先通过增加约束条件缩小解空间（即根据谱聚类生成初始分区）,然后对解空间设计算法进行精细的搜索（即采用频繁项集和贪心搜索相结合的策略对初始分区进行优化）.为了进一步提升SCVP在高维属性下的性能,提出了SCVP的改进版本SCVP-R （spectral clustering based vertical partitioning redesign）.SCVP-R通过引入同域竞争机制、双败淘汰机制和循环机制,对SCVP在分区优化过程中的合并方案进行了进一步优化.在不同数据集上的实验结果表明,相比于目前最好的垂直分区方法,SCVP和SCVP-R有着更快的执行时间和更好的性能表现.     

企业文化立体传播系统构建

结合企业的具体实践,提出了应该建立企业文化立体传播系统的观点,给出了企业文化立体传播系统的构建途径,即硬件上要搭建多个传播平台,软件上综合运用多种传播策略。     

An overview of energy consumption of the globalized world economy

For the globalized world economy with intensive international trade, an overview of energy consumption is presented by an embodied energy analysis to track both direct and indirect energy uses based on a systems input–output simulation. In 2004, the total amounts of energy embodied in household consumption, government consumption, and investment are 7749, 874, and 2009 Mtoe (million tons of oil equivalent), respectively. The United States is shown as the world’s biggest embodied energy importer (683 Mtoe) and embodied energy surplus receiver (290 Mtoe), in contrast to China as the biggest exporter (662 Mtoe) and deficit receiver (274 Mtoe). Energy embodied in consumption per capita varies from 0.05 (Uganda) to 19.54 toe (Rest of North America). Based on a forecast for 2005–2035, China is to replace the United States as the world’s leading embodied energy consumer in 2027, when its per capita energy consumption will be one quarter of that of the United States.     

An empirical analysis of the CO2 shadow price in Chinese thermal power enterprises

This paper estimates the shadow price of CO₂ and explores its determinants for thermal power enterprises in China. Using a parametric quadratic directional distance function, we evaluate the inefficiency and shadow price of CO₂ for 124 power enterprises in 2004, applying deterministic and econometric methods. A regression analysis is undertaken to examine the factors that drive shadow prices. Our results indicate that there are large inefficiencies in terms of electricity production and CO₂ emissions. The shadow price is a negative function of firm size, age, and coal share, and is positively correlated with the technology level. This correlation between shadow prices and its determinants is not sensitive to changing assumptions regarding directional vectors, although such changes do alter the distribution of shadow prices. The large variation witnessed in shadow prices across power enterprises argues in favor of market-based regulation such as an emissions trading system as opposed to the command-and-control regulation currently used in China to minimize overall abatement cost.     

Flexible top-emitting warm-white organic light-emitting diodes with highly luminous performances and extremely stable chromaticity

The flexible top-emitting white organic light-emitting diode (FTEWOLED) with a very high efficiency but a significant color alteration is achieved with a blue/red/blue sandwiched tri-emission-layer. The voltage-dependent recombination region alternation and the emission mechanism are systematically investigated through a delta-doping method and the time-resolved transient photoluminescence lifetime measurement. By locating the main exciton recombination region at the 4,4′,4″-Tris(carbazol-9-yl)-triphenylamine (TCTA) and 9,9-spirobifluoren-2-yl-diphenyl-phosphine oxide (SPPO1) interface, replacing the carrier-trapping red dopant guest with an orange guest that utilizes energy transfer mechanism, and using a P–I–N structure together with the FIrpic blue guest dopant to balance the electron and hole carriers, an extremely color stable and a very high efficient FTEWOLED is fabricated, with the resulting high current and power efficiencies of 22.7 cd/A and 14.27 lm/W, and a warm white illumination with a small chromaticity variation of (−0.0087, +0.0015) over a broad luminance range of more than four orders of magnitude. In addition, the performances can be further improved to 23,340 cd/m², 24.49 cd/A and 15.39 lm/W with a slight concentration alteration of the orange emitter.     

Carboxylic acid mediated self-assembly of small molecules for organic thin film transistors

A p-type small molecule bearing dicarboxylic acid functional group (–COOH) is synthesized and evaluated for field-effect transistor properties. We discover and report for the first time, that the –COOH groups assist in the passivation of surface traps on the dielectric layer and simultaneously facilitate the self-assembly of the molecules via inter-molecular hydrogen bonding resulting in crystalline active channels. A 9-fold decrease in the threshold voltage was observed for the transistors made using the –COOH functionalized molecule, QT-DA, compared to its ester analogue, QT-ES, providing an evidence of surface passivation. This resulted in an increase in the hole mobility of QT-DA by up to 2 orders of magnitude. It was shown that QT-DA adopts a vertical alignment with respect to the substrate due to preferential interaction between the –COOH groups and the SiO₂ surfaces.     

An adaptive-weighted two-dimensional data aggregation algorithm for clustered wireless sensor networks

In this paper, an Adaptive-Weighted Time-Dimensional and Space-Dimensional （AWTDSD） data aggregation algorithm for a clustered sensor network is proposed for prolonging the lifetime of the network as well as improving the accuracy of the data gathered in the network. AWTDSD contains three phases： （1） the time-dimensional aggregation phase for eliminating the data redundancy; （2） the adaptive-weighted aggregation phase for further aggregating the data as well as improving the accuracy of the aggregated data; and （3） the space-dimensional aggregation phase for reducing the size and the amount of the data transmission to the base station. AWTDSD utilizes the correlations between the sensed data for reducing the data transmission and increasing the data accuracy as well. Experimental result shows that AWTDSD can not only save almost a half of the total energy consumption but also greatly increase the accuracy of the data monitored by the sensors in the clustered network.     

在校大学生体质调查与中医食疗

体质学说是中医理论的一个重要方面,在一定程度上决定着人体对某种致病因子的易感性及其病变类型的倾向性。而中医思想的另一个重要方面则是"药食同源",运用食物来达到疗疾保健的功效。本文通过分析大学生群体体质调查问卷,了解大学生群体体质差异及表征,并且对应提出一些食疗建议,以期结合体质特点和中医食疗来改善大学生健康状况,做到"治未病"。