基于JMS的一种消息过滤改进算法

本文分析了JMS发布／订阅模式下传统的消息过滤机制,针对其不能快速处理大量相同或相似消息的缺陷,提出了一种改进的消息过滤算法。通过对所有订阅条件进行预处理来优化匹配结果,在此过程中并对相同或相似订阅条件属性进行处理,从而提高消息匹配效率。     

关联规则挖掘算法介绍

数据挖掘是一个多学科交叉融合而形成的新兴的学科,它利用各种分析工具在海量数据中发现模型和数据间的关系。而在大规模事务数据库中,挖掘关联规则是数据挖掘领域的一个非常重要的研究课题。文中介绍了关联规则挖掘的研究情况,描述了经典Apriori算法的实现,并对该算法进行了分析和评价,指出了其不足和原因。描述了FP树挖掘最大频繁项集的算法,通过实例对该算法进行了性能评估,并得到结论:数据库中潜在的最大频繁模式越多,运行时间越长。     

SiC肖特基势垒二极管的反向特性

在n型4H-SiC衬底上的n型同质外延层的Si面制备了纵向肖特基势垒二极管(SBD),研究了场板、场限环及其复合结构等不同终端截止结构对于反向阻断电压与反向泄漏电流的影响。场板(FP)结构有利于提高反向阻断电压,减小反向泄漏电流。当场板长度从5μm变化到25μm,反向阻断电压随着场板长度的增加而增加。SiO2厚度对于反向阻断电压有重要的影响,当厚度为0.5μm,即大约为外延层厚度的1/20时,可以得到较大的反向阻断电压。当场限环的离子注入区域宽度从10μm变化到70μm,反向阻断电压也随之增加。FLR和FP复合结构对于改善反向阻断电压以及反向泄漏电流都有作用,同时反向阻断电压对于场板长度不再敏感。采用复合结构,在10μA反向泄漏电流下最高阻断电压达到1 300V。讨论了离子注入剂量对于反向阻断电压的影响,注入离子剂量和反向电压的关系表明SBD结构不同于传统PIN结构的要求。当采用大约为150%理想剂量的注入剂量时才可达到最高的反向阻断电压而不是其他报道的75%理想剂量,此时的注入剂量远高于PIN结构器件所需的注入剂量。     

Absolute quantification of genetically engineered traits with droplet digital PCR: Effect of DNA treatments and spiking with non-target DNA

Low level presence of unapproved genetically engineered (GE) materials in non-GE grains has been a challenge for grain importers and exporters and many countries also have regulatory requirements for use and cultivation of GE crops. Digital PCR has been used for absolute quantification of GE traits. The need for DNA pre-treatment for droplet digital PCR (ddPCR) has not been well assessed. The effect of non-shearing, QIAshredding and hydroshearing of genomic DNA (300 ng) on quantitative analysis of low concentrations of OXY235 canola, FP967 flax and DP305423 soybean samples was assessed using RainDance RainDrop™ Digital PCR system. 1000 ng DNA was also used for ddPCR to determine if pre-treatment is required for high DNA concentration. The measured percentage values were close to the expected 0.01, 0.1 and 1% values for non-sheared, QIAshredded and hydrosheared samples for three GE traits using 300 ng DNA. The ddPCR results were also similar to the expected 0.01, 0.1 and 1% values for non-sheared and QIAshredded samples for the three GE traits using 1000 ng DNA. The feasibility of absolute quantification of low levels of OXY235 canola, FP967 flax and DP305423 soybean samples spiked in non-GE barley and wheat samples was investigated using ddPCR. Successful quantification of OXY235 canola, FP967 flax and DP305423 soybean DNA samples spiked in barley and wheat DNA samples was achieved at 0.01, 0.1 and 1% levels. ddPCR carried out with DNA extracted from ground DP305423 soybean samples spiked in wheat and barley samples resulted in percentage values close to the expected 0.01, 0.1 and 1% values with some exceptions. The result shows the feasibility of using ddPCR for absolute quantification of low level presence of GE materials in other grain samples.     

High-Performance FP Divider with Sharing Multipliers Based on Goldschmidt Algorithm

Focused on the issue that division is com-plex and needs a long latency to compute, a method to design the unit of high-performance Floating-point (FP) divider based on Goldschmidt algorithm was proposed. Bipartite reciprocal tables were adopted to obtain initial value of iteration with area-saving, and parallel multipliers were employed in the iteration unit to reduce latency. FP divider to support pipeline execution with the control of state m achine is presented to increase the throughput. The design was implemented in Digital signal process (DSP) chip by sharing the existed multipliers.     

热风返修台拆除QFP和FP及3D类器件工艺研究

热风返修台采用非接触热风对流热传递方式,加热系统包括底部加热、顶部加热和局部加热,适于表贴器件返修;目前,QFP、FP和3D类器件返修多采用热风枪加热,待引腿焊点融化后,将器件取下,手工焊接替换器件。使用热风枪加热拆除器件效率低,热量不易控制。通过探索,适当的工艺条件下,热风返修台可以高效拆除QFP、FP和3D类表贴器件,同时不会对周围器件、焊盘及印制板造成损伤。     

基于法布里-珀罗标准具的双环路光电振荡器

设计了一种基于法布里-珀罗(FP)标准具的双环路光电振荡器(OEO),该振荡器能将连续的光功率转换为稳定的频谱纯净的微波信号。FP标准具具有滤波的特性,因此可以替代普通OEO中的电滤波器从而降低电噪声,此外,FP标准具是一种高Q值的光学器件,可以缩短普通OEO所使用的光纤长度。双环路结构的引入能够更好地保证振荡器的单模输出,进一步降低相位噪声。仿真结果证明这种新型结构的OEO可以实现20GHz范围内振荡频率为15GHz的单模起振,边模抑制比超过150dB,使用的两条光纤环路长度分别为5m和36m。     

Predicting blood lead levels from current and past environmental data in Europe

The present case study on lead in Europe illustrates the use of the Integrated Monitoring Framework Strategy to assess the health outcome of environmental pollution by evaluating the associations between lead in various environmental compartments (air, soil, dust, drinking water and diet) and lead concentrations in blood (B-Pb) for various age-related sub-populations. The case study was aimed to investigate whether environmental, exposure and biomonitoring data at general population level, covering all EU member states, could be integrated. Although blood lead has been monitored extensively in Europe, consistent datasets are not yet available. Data diverge with regard to objectives, regional scale, sampling years, gender, age groups and sample size.Significant correlations were found between B-Pb and the concentrations of Pb in air and diet. The significant decrease of the Pb in air over time from 0.31 μg/m³ (P95: 0.94; n = 98) prior to 1990 to 0.045 μg/m³ (P95: 0.11; n = 256) in 2007 (latest observations included) (Δ = − 85%) corresponds to a decline in B-Pb by 48% and 57% in adult women and adult men, respectively. For pre-school children a more shallow decline in B-Pb of 16% was calculated over the same period. Similarly, the reduction in Pb-dietary intake from on average 68.7 μg/d (P95: 161.6; n = 19) in 1978 to 35.7 μg/d (P95: 82.3; n = 33) in the years post 2000 (Δ = − 48%) is paralleled by a decline in B-Pb of 32, 33 and 19% in adult women, primary- and pre-school children, respectively. Insufficient data exist for other age groups to calculate statistically significant correlations.Although regression models have been derived to predict B-Pb for different sub-populations in Europe based on Pb concentrations in air and soil as well as dietary intake, it is concluded that the available data are insufficient to accurately predict actual and future simultaneous exposure to Pb from various environmental compartments, and as a consequence the health impact of Pb for various target populations at EU scale. At least due to data availability, air Pb remains the best predictor of B-Pb in the population. However, lead emission sources have largely been reduced and inhalation of lead in air is not causal to B-Pb levels. Therefore, there is a need of adequate data for Pb in soil and house dust, and in diet and drinking water as these are causal exposure sources with a longer Pb half-life than air. An extended and more harmonized surveillance system monitoring B-Pb, especially in children, is urgently required in order to identify, quantify and reduce still remaining sources of Pb exposure.     

基于重叠写入啁啾光栅的Fabry-Perot腔的研究

以两段重叠写入的啁啾光栅作为反射面,构成光纤光栅Fabry-Perot(FP)腔.分别采用施加应力法和移动相位掩模板法,在同一段光纤中重叠写入啁啾光栅形成FP腔.使用啁啾量为1 nm的相位掩模板进行实验,两种方法曝光后的重叠啁啾光栅都可以形成明显梳状透射光谱.使用移动相位掩模板法,透射光谱的自由光谱范围(FSR)可达0...     

Design and implementation of the OFELIA FP7 facility: The European OpenFlow testbed

The growth of the Internet in terms of number of devices, the number of networks associated to each device and the mobility of devices and users makes the operation and management of the Internet network infrastructure a very complex challenge. In order to address this challenge, innovative solutions and ideas must be tested and evaluated in real network environments and not only based on simulations or laboratory setups.OFELIA is an European FP7 project and its main objective is to address the aforementioned challenge by building and operating a multi-layer, multi-technology and geographically distributed Future Internet testbed facility, where the network itself is precisely controlled and programmed by the experimenter using the emerging OpenFlow technology. This paper reports on the work done during the first half of the project, the lessons learned as well as the key advantages of the OFELIA facility for developing and testing new networking ideas.An overview on the challenges that have been faced on the design and implementation of the testbed facility is described, including the OFELIA Control Framework testbed management software. In addition, early operational experience of the facility since it was opened to the general public, providing five different testbeds or islands, is described.