Distance metric learning by minimal distance maximization

Classic linear dimensionality reduction (LDR) methods, such as principal component analysis (PCA) and linear discriminant analysis (LDA), are known not to be robust against outliers. Following a systematic analysis of the multi-class LDR problem in a unified framework, we propose a new algorithm, called minimal distance maximization (MDM), to address the non-robustness issue. The principle behind MDM is to maximize the minimal between-class distance in the output space. MDM is formulated as a semi-definite program (SDP), and its dual problem reveals a close connection to “weighted” LDR methods. A soft version of MDM, in which LDA is subsumed as a special case, is also developed to deal with overlapping centroids. Finally, we drop the homoscedastic Gaussian assumption made in MDM by extending it in a non-parametric way, along with a gradient-based convex approximation algorithm to significantly reduce the complexity of the original SDP. The effectiveness of our proposed methods are validated on two UCI datasets and two face datasets.     

Finite element modeling and experimental results of brass elliptic cups using a new deep drawing process through conical dies

This paper introduces a new technique for deep drawing of elliptic cups through a conical die without blank holder or draw beads. In this technique an elliptic-cup is produced by pushing a circular blank using a flat-headed elliptic punch through a conical die with an elliptic aperture in a single stroke. A 3D parametric finite element (FE) model was built using the commercial FE-package ANSYS/APDL. Effects of die and punch geometry including, half-cone angle, die fillet radius, die aperture length and punch fillet radius on limiting drawing ratio (LDR), drawing load and thickness strain of the cup have been investigated numerically for optimal process design. A die with half cone angle of 18° has shown the best drawability for the new technique. An experimental set-up has been designed, manufactured, and used for experimental production of elliptical shaped sheet-metal cups. A total of seven punches having aspect ratios ranging from 2 to 2.25 and a die with an aspect ratio of 2 have been manufactured and used. Tensile tests were carried out to obtain the stress–strain behavior for the formed sheet metal. Experiments were conducted on blanks of brass (CuZn33) with initial thicknesses of 1.5, 1.9, 2.4 and 3 mm at different clearance ratios (c/t). Effects of blank thickness and clearance ratio on limiting drawing ratio, drawing load and thickness strain were numerically and experimentally investigated. Finite element model results showed good agreement with experimental results. An elliptic cup with a limiting drawing ratio (LDR) of 2.28 has been successfully achieved using the proposed technique and set-up.     

低剂量辐射对荷瘤小鼠抑瘤作用及其免疫功能的影响

利用低剂量辐射（ＬＤＲ）对拉处Ｌｅｗｉｓ肺癌细胞小鼠进行全身照射，观察了２０ｄ内肿瘤抑制率免疫学指标的动态变化。研究结果表明，受７５ｍＧｙ剂量单次或分割照射后的肿瘤抑制率分别为４０．３４％和５１．１９％；脾ＮＫ细胞活性在照后１－４ｄ吾一过性升高；外周血Ｔ淋巴细胞表面ＣＤ４、ＣＤ８水平早期不同程度增高，而ＣＤ４／ＣＤ８比值在照后也反映出发升高，提示在本实验条件下，ＬＤＲ对Ｌｅｗｉｓ肺癌的生长有抑制作     

压边力在板料冲压成型中的控制研究

压边力的控制研究是板料冲压成型过程中的一个重要内容。首先分析了国内外对压边力的研究现状。然后提出了压边力曲线的预测和压边力的优化控制是压边力研究的两个主要方面，最后提出了采用模糊控制理论对压边力大小和板料的起皱进行跟踪控制，并给出了一个实例。     

高强度铝合金7075的温成形性能(英文)

对铝合金板料7075在加热状态下的成形性能进行研究。首先,通过单向拉伸试验得到不同温度以及不同应变速率下的应力—应变关系。然后,通过极限拉伸比(LDR)试验和极限拱顶高(LDH)试验对其在不同温度下的拉伸性能和胀形性能进行研究。最后,对不同温度下成形后材料的力学性能进行研究。结果表明:7075铝合金的拉伸和胀形性能在140~220°C均得到较大提升;当温度高于260°C时,由于成形温度对板料热处理状态的影响,成形性能和成形后材料的力学性能均出现下降趋势。     

低剂量辐射（LDR）对淋巴细胞的效应

LDR能刺激成人、儿童和婴幼儿的淋巴细胞转化,对营养不良儿童的刺激效应较低,对脐血则刺激效应较明显。LDR对成人CD4细胞的刺激效应强于CD8细胞,而对同样的刺激效应,NK细胞则需要较大剂量。对淋巴细胞NK活性也有同样规律。肿瘤病人的NK活性的刺激效应低于正常人。LDR增加了小鼠的血和脾内的T辅助／诱导细胞的比例和肿瘤内T细胞毒性细胞。低剂理照射的淋巴细胞外液也能刺激淋巴细胞转化。预先LDR可以减轻随后大剂量照射引起的生物大分子、膜抗原和染色体的损伤。LDR可诱导鼠脾淋巴细胞产生新蛋白,它能增强人和动物的免疫功能。     

基于PSO算法的公路养护决策优化研究

针对公路养护决策中存在的问题,以路面养护为例,借助LDR指数建立养护决策模型,利用粒子群优化算法(PSO)决策模型,对不同路面条件下公路养护决策进行优化分析。研究成果将对公路养护提供决策支持,并提出利于公路养护资金优化的方法。     

低剂量电离辐射对糖尿病小鼠血清中炎症因子表达的影响

目的探讨低剂量电离辐射(LDR)对链尿佐菌素(STZ)诱导的Ⅰ型糖尿病(DM)小鼠血清中炎症因子表达的影响。方法取健康C57BL/6J小鼠,经腹腔注射STZ复制小鼠糖尿病模型,并设空白对照组。将糖尿病模型小鼠分为DM和DM/LDR组,空白对照组分为LDR组及对照组。DM/LDR组和LDR组给予25mGyLDR,隔日照射1次,共照射4周;DM组和对照组不经LDR照射。分别于照射后2、4、8、12及16周,采用ELISA法检测小鼠血清中不同炎症因子的表达水平。结果LDR照射前,4组小鼠血清中ICAM-1和IL-18的表达水平较为接近,而糖尿病小鼠血清中TNFα和MCP-1的表达水平显著高于非糖尿病小鼠;给予LDR照射后,在不同时间点DM/LDR组小鼠血清中IL-18、MCP-1及TNFα的表达水平与DM组相比,均显著降低,LDR组小鼠血清中IL-18、MCP-1及TNFα的表达水平较对照组明显增加。ICAM-1表达的变化与其他因子不同,LDR照射4周时,糖尿病小鼠显著高于非糖尿病小鼠,但在任何时间点,DM/LDR与DM组、LDR与对照组之间差异均无统计学意义。结论在糖尿病状态下,LDR能有效降低血清中IL-18、TNFα和MCP-1的表达水平,缓解糖尿病肾脏中的炎症反应强度;但在正常机体中表现为提高免疫力,促进免疫相关因子的释放。表明LDR针对机体所处的不同状态发挥着不同的生物调节功能。     

小鼠骨髓基质祖细胞低剂量辐射效应研究

采用体外单层和半固体培养方法,研究小鼠骨髓细胞在受到０、２５、５０、７５、１００ｍＧｙ照射后,骨髓基质祖细胞的形成、特性及功能变化。结果表明：各照组组ＣＦＵ－Ｆ有不同程度增多,５０、７５ｍＧｙ组有显著意义;ＣＦＵ－Ｆ基支对粒系祖细胞集落形成单位（ＣＦＵ＿ＧＭ）的支持作用增加;ＣＦＵ－Ｆ基质层对骨髓细胞的粘附能力在５０、７５ｍＧｙ组有显著提高。结论是骨髓基质祖细胞低剂量照射时具有兴奋效应。     

DSP动态加载程序的改进与实现

基于ADSP21160芯片的开发平台,对传统网络动态加载DSP程序的方法进行了改进,完全解决了传统方法的空间浪费问题。该方法已经应用在实际工作中,在类似系统中具有很大的应用前景。