Designing PMF with negative tap coefficient

DIRECT global optimization algorithm is innovatively used in design of PMF. Tap coefficient is attained by achieving DIRECT algorithm with C language and Matlab language is employed to simulate the amplitude response of filters. We have designed PMF (photonic microwave filter) with negative tap coefficient and then optimize the design. The minimum shape factor is as low as 1.3180. The results show that the algorithm is highly efficient in designing filter and can produce necessary passband and stopband response characteristics. In the meantime, transition band becomes steeper in the process of further optimization and the shape factor is closer to 1.     

Electrodisintegration of 3He

Double differential cross sections for electron-³He scattering leading to continuum states were measured between break-up threshold and the region of quasi-free interaction in a momentum transfer range of $\text{1}\text{fm}{}^{\mathrm{?2}}\text{< ¦}\text{q}\text{¦}{}^2\text{< 2.5}\text{fm}{}^{\mathrm{?2}}$. The cross sections for the quasi-free scattering calculated in plane-wave impulse approximation were found to be in good agreement with the experimental results for momentum transfer $\text{¦}\text{q}\text{¦ > 1.5}\text{fm}{}^{\mathrm{?1}}$.     

Discrete Approximation of a Mixture Distribution via Restricted Divergence

Mixture distributions arise in many application areas, for example, as marginal distributions or convolutions of distributions. We present a method of constructing an easily tractable discrete mixture distribution as an approximation to a mixture distribution with a large to infinite number, discrete or continuous, of components. The proposed DIRECT (divergence restricting conditional tesselation) algorithm is set up such that a prespecified precision, defined in terms of Kullback–Leibler divergence between true distribution and approximation, is guaranteed. Application of the algorithm is demonstrated in two examples. Supplementary materials for this article are available online.     

Design of URAs by DIRECT global optimization algorithm

Coded aperture imaging (CAI) has evolved as a standard technique for imaging high-energy photon sources and has found numerous applications. Coded aperture arrays (CAAs) are the most important devices in the applications of CAI. In recent years, many approaches were presented to design optimum or near-optimum CAAs. Uniformly redundant arrays (URAs) are the most successful CAAs for their cyclic autocorrelation consisting of a sequence of delta functions on a flat sidelobe, which can easily be subtracted when the object has been reconstructed. Unfortunately, the existing methods can only be used to design URAs with limited number of array sizes and fixed autocorrelative sidelobe-to-peak ratio. In this paper, we presented a method to design more flexible URAs by means of a global optimization algorithm named DIRECT. By our approaches, we obtain various types of URAs including the filled URAs which can be constructed by existing methods and the sparse URAs which have never been constructed and mentioned by existing papers as far as we know.     

雪胆甲素在碱中的乙酰基转移反应

在研究雪胆甲素(1)的过程中,试图用氢氧化钾的乙醇溶液进行皂解,以期得到雪胆乙素(2)。但所得为另一物质,与甲素、乙素的突出区别是具有紫外光谱270nm(3.98)与红外光谱1615cm~(-1)(强)等峰,推测可能产生了β-二羰体系的烯醇式结构(-CO-C=C-OH),~1H核磁共振谱82.24(3H,s)表明仍保留乙酰基。雪胆甲素(1)为叔醇酯,皂解反应的速度较低。但12及23位碳在碱性条件下均易形成碳负离子,其中23位的碳负离子对乙酰羰基进行分子内部的进攻(形成五元环中间体),可远超过皂解的反应速度,从而使乙酰基由氧向碳转移。结合光谱数据,可以判定产     

Design and implementation of a massively parallel version of DIRECT

This paper describes several massively parallel implementations for a global search algorithm DIRECT. Two parallel schemes take different approaches to address DIRECT’s design challenges imposed by memory requirements and data dependency. Three design aspects in topology, data structures, and task allocation are compared in detail. The goal is to analytically investigate the strengths and weaknesses of these parallel schemes, identify several key sources of inefficiency, and experimentally evaluate a number of improvements in the latest parallel DIRECT implementation. The performance studies demonstrate improved data structure efficiency and load balancing on a 2200 processor cluster.     

Measurement of the 50Cr(γ, n)49Cr cross section with monochromatic γ-rays

The ⁵⁰Cr(γ, n)⁴⁹Cr cross section has been measured over the energy range E_γ = 20.43 to E_γ = 22.22 MeV using monochromatic γ-rays from the ³H(p, γ)⁴He reaction and detecting the resulting ⁴⁹Cr positon activity. The γ-rays were monitored by a 12.7 cm × 15.2 cm NaI(Tl) crystal. The positon activity was determined by a coincidence detector consisting of two 7.62 cm × 7.62 cm NaI(Tl) crystals set on the annihilation radiation photopeaks. The γ-ray energy resolution was less than 110 keV over the whole energy range. Structure in the cross section was not observed.     

华佗豆生物碱间的相互转化

我国广西省植物华佗豆Ipomoea hardwickii Hemsl(Convolvulaceae)在民间用来镇痛。从其中分离到甲、乙、戊、丁四种生物碱,其结构分别为1,2,3,4。     

金属羰基化合物M(CO)6(M=Cr,Mo, W)氧原子转移反应动力学与机理

本文研究了PPh3存在与不存在的情况下, M(CO)6(M=Cr, Mo, W)与三甲胺氧化物me3NO在CH2Cl2中的氧原子转移反应动力学. 反应速率遵循: r=k[M(CO)6][Me3NO], 并且rW>rMo>rCr, 并根据实验结果提出了反应机理, 讨论了溶剂对反应速率的影响.