基于国产处理器增量式实时交通流预测算法及实现

针对城市交通难以处理大量数据且实时性差等问题,提出了根据增量式城市交通流数据预测拥堵情况的一种基于国产处理器的L-BFGS(limited-memory BFGS)算法。该算法通过存储向量序列计算Hessian矩阵,改进Two-Loop算法求下降方向,在Spark集群中并行处理时收敛速度快,适用于实时性要求强的城市交通场景。实验结果证明,L-BFGS预测算法完全可以在国产平台上对大规模的实时交通数据流进行快速建模、预测,在改善城市交通管理水平提供有效支撑的同时也丰富了国产芯片的应用领域。     

Polybrominated Diphenyl Ethers in Surface Sediment from Songhua River Basin, Northeast of China

Sixty sediment samples were collected from the main Songhua River in three years. Twelve polybrominated diphenyl ether ( PBDE) congeners ( BDE17, 28, 47, 66, 99, 100, 153, 154, 138, 183, and BDE?209) w...     

Accelerated electrospark deposition and the wear behavior of coatings

Electrospark deposition (ESD) is a coating process that is featured by low heat input to the substrate. Low coating efficiency and other limitations influence its wider application. The present paper introduces newly designed ESD equipment, by which a higher coating rate can be reached. The relationship among coating thickness, surface roughness, and process parameters such as pulse energy, pulse frequency, and deposition time are presented. Electrospark deposition coating by the new equipment on AISI 1045 steel (with WC-8% Co as electrode) increases the wear resistance by 5 to 8 times. The micromechanism is investigated by scanning electron microscopy observation.     

AGING BEHAVIOUR OF PARTICULATE REINFORCED ALUMINUM ALLOY MATRIX COMPOSITES

The process of aging precipitation in SiC_p/6061 and Al_2O_3/6061 composites were investigated. Hardness testing, differential scanning calorimetry(DSC) and transmission electron microscopy were employed. Results showed that the precipitation phase form directly along dislocation lines in the composites because the particles produce high densities of dislocations which makes vacancy densities in the composites decrease, and the main precipitation phase at peak hardness was β′ phase.     

含Cl^-溶液中SO4^2-对316不锈钢临界点蚀温度的影响

采用外加恒电位下腐蚀电流-温度扫描方法研究了在0．5％Cl^-溶液中，SO4^2-浓度对316不锈钢点腐蚀行为的影响．结果表明，随着SO4^2-浓度的增加，钝化电流增加，开路电位降低．当SO4^2-浓度低于0．42％时，316不锈钢的临界点蚀温度比不存在SO4^2-时的临界点蚀温度低；当SO4^2-浓度大于0．42％时，临界点蚀温度比不存在SO4^2-时的临界点蚀温度高．从离子竞争吸附的角度进行分析，对SO4^2-加速与抑制点蚀两种作用规律的形成原因进行了解释．     

An improved NDVI-based threshold method for estimating land surface emissivity using MODIS satellite data

This work estimated the land surface emissivities (LSEs) for MODIS thermal infrared channels 29 (8.4–8.7 μm), 31 (10.78–11.28 μm), and 32 (11.77–12.27 μm) using an improved normalized difference vegetation index (NDVI)-based threshold method. The channel LSEs are expressed as functions of atmospherically corrected reflectance from the MODIS visible and near-infrared channels with wavelengths ranging from 0.4 to 2.2 μm for bare soil. To retain the angular information, the vegetation LSEs were explicitly expressed in the NDVI function. The results exhibited a root mean square error (RMSE) among the estimated LSEs using the improved method, and those calculated using spectral data from Johns Hopkins University (JHU) are below 0.01 for channels 31 and 32. The MODIS land surface temperature/emissivity (LST/E) products, MOD11_L2 with LSE derived via the classification-based method with 1 km resolution and MOD11C1 with LSE retrieved via the day/night LST retrieval method at 0.05° resolution, were used to validate the proposed method. The resultant variances and entropies for the LSEs estimated using the proposed method were larger than those extracted from MOD11_L2, which indicates that the proposed method better described the spectral variation for different land covers. In addition, comparing the estimated LSEs to those from MOD11C1 yielded RMSEs of approximately 0.02 for the three channels; however, more than 70% of pixels exhibited LSE differences within 0.01 for channels 31 and 32, which indicates that the proposed method feasibly depicts LSE variation for different land covers.     

飞腾平台中硬件数据压缩的驱动设计与实现

数据压缩是有效处理大数据的关键技术,在飞腾处理器平台上基于zlib库的数据压缩通常采用软件的方式实现,在数据处理量大而且实时性要求较高的情况下,已经难以满足需求。针对这个问题,通过研究zlib编程函数库,结合飞腾处理器的特性,完成了飞腾平台中硬件数据压缩的驱动设计与实现,其中提出了双向DMA传输技术和基于一致性内存的命令环机制,从而进一步提高了基于硬件的数据压缩的效率。通过实验证实了飞腾平台中采用硬件数据压缩改进的有效性。     

面向电子商务的秒杀系统设计与实现

根据互联网服务的特色,从可靠性、可扩展性和安全性的角度着手,提出了一套面向电子商务领域的网络秒杀系统的架构设计方案。同时分析了秒杀系统的业务特点,设计了一套相应的业务体系,并给出了主要业务流程的具体实现方法。基于该解决方案的秒杀系统可以达到高并发、高可靠、易扩展以及高安全性的设计目标。     

Extended minimum-squared error algorithm for robust face recognition via auxiliary mirror samples

The changes of face images with poses and polarized illuminations increase data uncertainty in face recognition. In fact, synthesized mirror samples can be recognized as representations of the left–right deflection of poses or illuminations of the face. Symmetrical face images generated from the original face images also provide more observations of the face which is useful for improving the accuracy of face recognition. In this paper, to the best of our knowledge, it is the first time that the well-known minimum squared error classification (MSEC) algorithm is used to perform face recognition on an extended face database using synthesized mirror training samples, which is titled as extended minimum squared error classification (EMSEC). By modifying the MSE classification rule, we append the mirror samples to the training set for gaining better classification performance. First, we merge original training samples and mirror samples synthesized from original training samples per subject as mixed training samples. Second, EMSEC algorithm exploits mixed training samples to obtain the projection matrix that can best transform the mixed training samples into predefined class labels. Third, the projection matrix is exploited to simultaneously obtain transform results of the test sample and its nearest neighbor from the mixed training sample set. Finally, we ultimately classify the test sample by combining the transform results of the test sample and the nearest neighbor. As an extension of MSEC, EMSEC reduces the uncertainty of the face observation by auxiliary mirror samples, so that it has better robustness classification performance than traditional MSEC. Experimental results on the ORL, GT, and FERET databases show that EMSEC has better generalization ability than traditional MSEC.