Feature extraction using maximum variance sparse mapping

In this paper, a multiple sub-manifold learning method–oriented classification is presented via sparse representation, which is named maximum variance sparse mapping. Based on the assumption that data with the same label locate on a sub-manifold and different class data reside in the corresponding sub-manifolds, the proposed algorithm can construct an objective function which aims to project the original data into a subspace with maximum sub-manifold distance and minimum manifold locality. Moreover, instead of setting the weights between any two points directly or obtaining those by a square optimal problem, the optimal weights in this new algorithm can be approached using L1 minimization. The proposed algorithm is efficient, which can be validated by experiments on some benchmark databases.     

柠檬酸凝胶燃烧法制备GGG∶Eu3+,Bi3+多晶发光粉体及其表征

本文以Gd2O3、Ga2O3、Eu2O3、Bi(NO3)3·5H2O和柠檬酸为原料,采用凝胶燃烧法制备出GGG∶ Eu3+,Bi3+多晶发光粉体,并对样品进行了XRD、SEM、FT-IR、PL测试.XRD和FT-IR分析结果表明合成的发光粉体均形成GGG相.SEM显示样品晶粒呈球形或类球形,直径约60 nm.PL分析显示样品最强发射峰位于592 nm处,属于Eu3+的5D0-7F1磁偶极跃迁.掺杂Bi3+的样品发光强度明显高于未掺杂Bi3+的样品,而发射峰位置不变,当掺杂的Bi3浓度逐渐增加时,样品GGG∶Eu3+0.05,Bi3+x的发光强度先随Bi3+浓度的增加而不断增强,当体系中掺杂Bi3+的摩尔分数达到x=5％时,GGG∶ Eu3+0.05,Bi3+x的发光强度达到最大值.再之后随Bi3+掺杂浓度的增加发光强度减弱,这可能是因为Bi3+和Eu3+之间的能量传递方式主要是偶极-偶极作用,传递效率主要决定于两种离子间距离.     

Effect of Cooling Rate on Microsegregation During Solidification of Superalloy INCONEL 718 Under Slow-Cooled Conditions

Metallurgical and Materials Transactions B - The solidification sequence, microstructural evolution, solid-liquid interface variation, interdendritic segregation, and elemental distribution of...     

凹山采场边坡稳定性监测监控系统

通过对不同区域爆破后雷达监测数据分析,合理划分了凹山采场边帮爆区,选择相适应的爆破方法及装药结构等技术措施,确保了边坡采场地质环境治理及残矿回收工程的安全实施。     

Ionic liquid as an efficient promoting medium for synthesis of dimethyl carbonate by oxidative carbonylation of methanol

The synthesis of dimethyl carbonate by oxidative carbonylation of methanol using Cu salt catalysts in the presence of various room temperature ionic liquids (RTILs) was reported. Among the ionic liquids used, N-butylpyridinium tetrafluoroborate was the most effective promoter in terms of the conversion of methanol and the selectivity to dimethyl carbonate (DMC). The influences of reaction temperature, pressure, time, molar ratio of CO/O₂, and amount of the ionic liquid on the oxidative carbonylation of methanol were investigated. The results indicated that under the reaction conditions of 120 °C and 2.4 MPa of a 2:1 mixture of CO and O₂, 17.2% conversion of methanol, 97.8% selectivity of DMC and a DMC productivity of 4.6 g g⁻¹ cat h⁻¹ were achieved. The N-butylpyridinium tetrafluoroborate-meditated CuCl catalyst system could be reused at least five recycles with the same selectivity and a slight loss of catalytic activity due to loss of the catalyst during handling and transferring the reaction mixture.     

XAFS applications in semiconductors

X-ray absorption fine structure （XAFS） has experienced a rapid development in the last three decades and has proven to be a powerful structural characterization technique nowadays. In this review, the XAFS basic principles including the theory, the data analysis, and the experiments have been introduced in detail. To show its strength as a local structure probe, the XAFS applications in semiconductors are summarized comprehensively, that is, thin films, quantum wells and dots, dilute magnetic semiconductors, and so on. In addition, certain new XAFS-related techniques, such as in-situ XAFS, micro-XAFS, and time-resolved XAFS are also shown.     

ICI cancellation for OFDM communication systems in time-varying multipath fading channels

In orthogonal frequency division multiplexing (OFDM) systems, time-varying multipath fading leads to the loss of subcarrier orthogonality and the occurrence of intercarrier interference (ICI). In this study, an efficient ICI suppression with less noise enhancement for multicarrier equalization is presented by using a parallel canceling scheme via frequency-domain equalization techniques, with the assumption that the channel impulse response (CIR) varies linearly during a block period. In order to avoid performance deterioration due to unreliable initial estimations in the parallel cancellation scheme, a cost function with proper weighting factor is introduced to improve the performance of the proposed equalizer. The proposed equalizer consists of a set of prefilters and a set of ICI cancellation filters, with two stages to perform different functions to achieve minimum mean square error (MMSE) equalization. The prefilters compensate for the multiplicative distortion at the first stage, and the ICI cancellation filters remove the effects of ICI by a parallel cancellation scheme at the second stage. Finally, the performance of the proposed equalizer is analyzed and compared with that of other equalizers, indicating significant performance improvement.     

基于Qt/Embedded嵌入式数字兆欧表GUI的开发与实现

基于Qt/Embedded设计了一款嵌入式数字兆欧表GUI, 与触摸屏结合取代了原有的机械开关, 并建立数据库实现了历史数据保存、打印等现有数字兆欧表没有的功能.