纳米SiO2粉体的制备与研究

纳米SiO2粉体的制备是以硅酸钠和盐酸为原料，添加适宜的稳定剂(非离子表面活性剂)和分散剂，在适宜的pH值和温度下，采用化学沉淀法合成。研究表明，要得到性能优良纳米的SiO2粉体，最佳工艺条件为：温度20～40℃，pH=6，反应液质量浓度P1=20g／L，P2=1．20g／L，反应时间15min。结果表明：制备的纳米SiO2粒径30～50nm，比表面积大，分散性好，质量优良，可达到产业化的生产。     

Studies of structure and cycleability of LiMn2O4 and LiNd0.01Mn1.99O4 as cathode for Li-ion batteries

Lithium manganese oxides LiMn₂O₄ and rare earth elements doped LiNd_0.01Mn_1.99O₄ were synthesized by microwave method. The structure and the electrochemical performances of the samples were characterized. XRD data shows both samples exhibit the same pure spinel phase. But due to the introduction of Nd³⁺ ion into the unit cell, the lattice parameter of the Nd-doped spinel was larger than that of the undoped one. The two samples had a similar morphology including small particle size and homogeneous particle distribution as tested by SEM. The cyclic voltammmetry and constant-current charge-discharge tested that Nd-doped spinel displayed a better reversibility and cycleability.     

Alekseevskii-Tate revisited:An extension to the modified hydrodynamic theory of long rod penetration

The modified hydrodynamic theory of long rod penetration into semi-infinite targets was established independently by Alek-seevskii and Tate over forty years ago and since then many investigators contributed much to the development of the high speed penetration mechanics.However,in all the models proposed so far,the target resistance Rt is not well defined and usually determined by adjusting it until the predicted depth of penetration comes to an agreement with experimental data.In this paper,assumptions are...     

让设计成为科学、艺术、时尚融合的载体——记北京服装学院教师作品展

本文结合北京服装学院2008年在中国美术馆举办的首届教师作品展,就学校的办学理念、办学特色、创新教育、优势互补和理论研讨等方面展开论述。不仅彰显了北京服装学院的学科优势,而且突出了学校在“奥运”和“神七”设计中贡献社会的浓重一笔。同时,也强调了学校对传统与时尚、艺术与科学、民族与世界融为一炉的设计理念的高度重视。     

Research on technology of desktop virtualization based on SPICE protocol and its improvement solutions

Increasingly mature cloud computing technology promotes virtual desktop technology, which can solve many problems existing in traditional computing models. However, virtual desktop solutions introduce the thorny problem of how to deliver a real desktop experience to users, as if they are using it locally, especially when playing video. The SPICE （simple protocol for independent computing environments） virtual desktop solution provides several image compression algorithms to address this problem with the purpose of making virtual desktops as real as possible. Although different compression algorithms can contribute their own abilities to different images to a large extent, switching between them is a big problem that consumes a large amount of resources to detect the different type of image and also causes jitter of the virtual desktop. This paper proposes a new solution, called SPICEx, using the JPEG2000 compression algorithm with dynamic compression ratios to solve the problem and finally validates that the performance is better than that of SPICE. With better quality of user experience and also reducing bandwidth consumption, SPICEx solution is meaningful in virtual desktop fields and can be widely used.     

A Performance Evaluation of Classic Convolutional Neural Networks for 2D and 3D Palmprint and Palm Vein Recognition

Palmprint recognition and palm vein recognition are two emerging biometrics technologies. In the past two decades, many traditional methods have been proposed for palmprint recognition and palm vein recognition, and have achieved impressive results. However, the research on deep learning-based palmprint recognition and palm vein recognition is still very preliminary. In this paper, in order to investigate the problem of deep learning based 2D and 3D palmprint recognition and palm vein recognition in-depth, we conduct performance evaluation of seventeen representative and classic convolutional neural networks (CNNs) on one 3D palmprint database, five 2D palmprint databases and two palm vein databases. A lot of experiments have been carried out in the conditions of different network structures, different learning rates, and different numbers of network layers. We have also conducted experiments on both separate data mode and mixed data mode. Experimental results show that these classic CNNs can achieve promising recognition results, and the recognition performance of recently proposed CNNs is better. Particularly, among classic CNNs, one of the recently proposed classic CNNs, i.e., EfficientNet achieves the best recognition accuracy. However, the recognition performance of classic CNNs is still slightly worse than that of some traditional recognition methods.

     

Improved Computational Model of Grid Cells Based on Column Structure

To simulate the firing pattern of biological grid cells, this paper presents an improved computational model of grid cells based on column structure. In this model, the displacement along different directions is processed by modulus operation, and the obtained remainder is associated with firing rate of grid cell. Compared with the original model, the improved parts include that: the base of modulus operation is changed, and the firing rate in firing field is encoded by Gaussian-like function. Simulation validates that the firing pattern generated by the improved computational model is more consistent with biological characteristic than original model. Besides, the firing pattern is badly influenced by the cumulative positioning error, but the computational model can also generate the regularly hexagonal firing pattern when the real-time positioning results are modified.     

超细Al（OH）3的粒度控制研究

采用铝酸钠种子分解法制备超细Al（OH）3.用X射线衍射仪（XRD）表征了样品的晶相组成,用扫描电子显微镜（SEM）观察了样品的形貌,用激光粒度分析仪测定样品的粒度分布.研究了NaOH浓度、NaOH/Al（OH）3摩尔比,分解温度,分解时间、晶种率和搅拌速率等因素对Al（OH）3的粒度的影响.结果表明：NaOH浓度越高,分解温度越低,NaOH/Al（OH）3摩尔比越小,得到的Al（OH）3颗粒的粒度越小.试验条件为：NaOH浓度180 g/L,NaOH/Al（OH）3摩尔比1.15,分解温度40℃,分解时间26 h,晶种率8％,搅拌速率200 rpm时,氢氧化铝颗粒的平均粒度为2.89 μm.     

时效对接触线用Cu-Ag-Cr合金性能的影响

分析了固溶温度、时效及时效前冷变形量对Cu - 0 1 %Ag - 0 1 %Cr接触线用合金性能的影响 ,结果表明 :经 870℃固溶、 40 %～ 5 0 %冷变形及 480℃× 1 5h时效处理后 ,合金可获得良好的综合性能。