分布式L_(1/2)正则化

研究数据集被分割并存储于不同处理器时的特征提取和变量选择问题,其中处理器通过某种网络结构相互连接.提出分布式L_(1/2)正则化方法,基于ADMM算法给出分布式L_(1/2)正则化算法,证明了算法的收敛性.算法通过相邻处理器之间完成信息交互,其变量选择结果与数据集不分割时利用L_(1/2)正则化相同.实验表明,所提出的新算法有效、实用,适合于分布式存储数据处理.     

基于稳健统计的新鲜乳腺组织拉曼光谱分析

采用便携式拉曼光谱仪对新鲜乳腺正常组织、良性组织和恶性组织进行检测,通过稳健统计方法对拉曼光谱数据进行分析处理,建立乳腺组织拉曼光谱标准图谱,根据标准图谱特征峰归纳3类组织的主要区别和特征.在3类乳腺组织中,正常组织有明显的脂类特征峰(1078,1297,1437,1653,1746 cm-1),而在良性和恶性组织中则出现了较明显的蛋白特征峰(1259,1530,1650 cm-1),正常、良性和恶性组织的主要区别集中在1340和1534 cm-1处,应归属为蛋白和类胡萝卜素,这一结果并不能由经典统计方法得出.基于稳健统计建立的新鲜乳腺组织拉曼光谱标准图谱为构建数学模型来鉴别乳腺病灶的性质奠定了基础.     

Feasibility of similarity coefficient map for improving morphological evaluation of T2* weighted MRI for renal cancer

The purpose of this paper is to investigate the feasibility of using a similarity coefficient map(SCM) in improving the morphological evaluation of T2* weighted(T2*W) magnatic resonance imaging(MRI) for renal cancer.Simulation studies and in vivo 12-echo T2*W experiments for renal cancers were performed for this purpose.The results of the first simulation study suggest that an SCM can reveal small structures which are hard to distinguish from the background tissue in T2*W images and the corresponding T2* map.The capability of improving the morphological evaluation is likely due to the improvement in the signal-to-noise ratio(SNR) and the carrier-to-noise ratio(CNR) by using the SCM technique.Compared with T2* W images,an SCM can improve the SNR by a factor ranging from 1.87 to 2.47.Compared with T2* maps,an SCM can improve the SNR by a factor ranging from 3.85 to 33.31.Compared with T2*W images,an SCM can improve the CNR by a factor ranging from 2.09 to 2.43.Compared with T2* maps,an SCM can improve the CNR by a factor ranging from 1.94 to 8.14.For a given noise level,the improvements of the SNR and the CNR depend mainly on the original SNRs and CNRs in T2*W images,respectively.In vivo experiments confirmed the results of the first simulation study.The results of the second simulation study suggest that more echoes are used to generate the SCM,and higher SNRs and CNRs can be achieved in SCMs.In conclusion,an SCM can provide improved morphological evaluation of T2*W MR images for renal cancer by unveiling fine structures which are ambiguous or invisible in the corresponding T2*W MR images and T2* maps.Furthermore,in practical applications,for a fixed total sampling time,one should increase the number of echoes as much as possible to achieve SCMs with better SNRs and CNRs.     

超声辐射油溶性氧化剂氧化燃料油中二苯并噻吩的研究

以油溶性过氧化羟基异丙苯(CHP)为氧化剂,Al2O3为催化剂,引入超声作用,以正辛烷为模拟油品对油中二苯并噻吩的氧化进行了研究。考察了反应温度、反应时间、催化剂用量、氧硫比、超声功率对二苯并噻吩(DBT)降解率的影响并进行了正交实验,结果表明,各因素影响程度大小依次为:反应温度>催化剂用量>超声功率>反应时间>氧硫比,在反应温度为70℃,反应时间为45 min,氧硫比为5:1,催化剂用量为0.3 g,超声功率为60 W的最佳氧化条件下,DBT的降解率达到了88.0%。     

Efficient implementation of x-ray ghost imaging based on a modified compressive sensing algorithm

Towards efficient implementation of x-ray ghost imaging (XGI), efficient data acquisition and fast image reconstruction together with high image quality are preferred. In view of radiation dose resulted from the incident x-rays, fewer measurements with sufficient signal-to-noise ratio (SNR) are always anticipated. Available methods based on linear and compressive sensing algorithms cannot meet all the requirements simultaneously. In this paper, a method based on a modified compressive sensing algorithm with conjugate gradient descent method (CGDGI) is developed to solve the problems encountered in available XGI methods. Simulation and experiments demonstrate the practicability of CGDGI-based method for the efficient implementation of XGI. The image reconstruction time of sub-second implicates that the proposed method has the potential for real-time XGI.     

前言

本期为庆贺著名数学家郭本瑜先生70华诞专辑,是全体弟子献给恩师的生日礼物.郭本瑜教授1942年生于浙江省宁波市,1965年毕业于上海科技大学并留校工作,历任助教、副教授、教授、副校长和校长,组建了上海市应用数学与计算数学研究所,1994年转入新组建的上海大学,任常务副校长,1999年起在上海师范大学工作,组建了上海市高等学校计算科学E-研究院,任首席研究员.他曾任中国计算数学学会和上海市数学会副理事长.他的研究领域是微分方程数值方法.至今发表330多篇论文,出版了学术专著《偏微分方程的差分方法》和《Spectral Methods and Their Applications》等.     

指尖密封靴部结构对气动性能影响的分析

为了研究靴部结构对气动性能的影响,分别建立了光滑、局部开槽、轴向收敛三种指尖密封模型,并对其进行双向流固耦合数值模拟。通过计算,获得了指尖密封的变形规律、泄漏量变化以及指尖靴间隙内流场的运动特性。与普通指尖密封结构相比,对密封靴部进行改进可较大程度地提高密封的性能。根据对泄漏及流场运动特性的分析,初步揭示了指尖密封的泄漏机理,同时阐述了开槽结构影响密封性能的根本原因。     

Elastic and thermodynamic properties of vanadium nitride under pressure and the effect of metallic bonding on its hardness

By the particle-swarm optimization method, it is predicted that tetragonal P42mc, 141md, and orthorhombic Amm2 phases of vanadium nitride （VN） are energetically more stable than NaCl-type structure at 0 K. The enthalpies of the predicted three new VN phases, along with WC, NaC1, AsNi, CsCl type structures, are calculated each as a function of pressure. It is found that VN exhibits the WC-to-CsCl type phase transition at 256 GPa. For the considered seven crystal- lographic VN phases, the structures, elastic constants, bulk moduli, shear moduli, and Debye temperatures are investigated. Our calculated equilibrium structural parameters are in very good agreement with the available experimental results and the previous theoretical results for the NaC1 phase. The Debye temperatures of VN predicted three novel phases, which are all higher than those of the remaining structures. The elastic constants, thermodynamic properties, and elastic anisotropies of VN under pressure are obtained and the mechanical stabilities are analyzed in detail based on the mechanical stability criteria. Moreover, the effect of metallic bonding on the hardness of VN is also investigated, which shows that VNs in P42mc, 141md, and Amm2 phases are potential superhard phases. Further investigation on the experimental level is highly recommended to confirm our calculations presented in this paper.     

A new level set model for cell image segmentation

In this paper we first determine three phases of cell images:background,cytoplasm and nucleolus according to the general physical characteristics of cell images,and then develop a variational model,based on these characteristics,to segment nucleolus and cytoplasm from their relatively complicated backgrounds.In the meantime,the preprocessing obtained information of cell images using the OTSU algorithm is used to initialize the level set function in the model,which can speed up the segmentation and present satisfactory results in cell image processing.     

图G中f-因子的一个结论

在简单图的顶点度和f-因子的关系方面,本文在Tutte定理的基础上给出了图G不存在f-因子时的一个结论.