Ultrasound speckle analysis based on the K distribution

The departure of speckle magnitude from Rayleigh statistics was applied to examine insonated phantoms with both low and high concentrations of scatterers. A mathematical model, the K distribution of Jakeman, was used to characterize non-Rayleigh statistics. This model contains a parameter, alpha, which characterizes the clustering of the scattering sites in a medium. It is shown from phantom experiments that alpha is linearly proportional to the log-scaled scatterer concentration in a range from about 1 to 30 scatterers per sample volume.     

镧与半乳糖醇的两种配合物的FTIR和Raman光谱研究

本文用傅里叶变换红外和拉曼（FTIR和Raman)光谱对镧与半乳糖醇形成的两种配合物进行了研究。结果表明镧可以与半乳糖醇形成1：1和2：1两种配合物，它们的红外与拉曼光谱存在着一定的差别，这表明镧与半乳糖确实形成了两种配合物。     

CONVERGENCE AND OSCILLATION IN A DIFFUSIVE DELAY PARTIAL DIFFERENTIAL EQUATION

ＣＯＮＶＥＲＧＥＮＣＥＡＮＤＯＳＣＩＬＬＡＴＩＯＮＩＮＡＤＩＦＦＵＳＩＶＥＤＥＬＡＹＰＡＲＴＩＡＬＤＩＦＦＥＲＥＮＴＩＡＬＥＱＵＡＴＩＯＮ￥ＷｅｎｇＰｅｉｘｕａｎ（ＳｏｕｔｈＣｈｉｎａＮｏｒｍａｌＵｎｉｖｅｒｓｉｔｙ）Ａｂｓｔｒａｃｔ：Ｓｕｆｆｉｃｉ...     

Crystal structure and fungitoxicity of aquatributyltin N-phthaloylglycinate

The [nBu₃Sn(N-phthaloylglycinate)(OH₂)] compound has been prepared and characterized. The crystal structure reveals the tin atom, in each of the two molecules comprising the asymmetric unit, to exist in a distorted trigonal bipyramidal geometry in which the trigonal plane is defined by the three organic substituents and the axial sites are occupied by an oxygen atom derived from a monodentate carboxylate ligand and a coordinated water molecule. The [nBu₃Sn(N-phthaloylglycinate)(OH₂)] compound and three other triorganotin derivatives of N-phthaloyl-protected amino acids display marked toxicity against several economically important plant pathogenic fungi.     

Single Machine Scheduling with a Common Delivery Window

In this paper we consider the single machine scheduling problem of minimizing the mean absolute deviation (MAD) of job completion times from a restricted common delivery window. This problem is NP-hard. A Lagrangian relaxation procedure is proposed to solve the problem. Two efficient heuristics are also proposed. An experimental study on randomly generated problems is carried out to test the performance of the proposed methods. The computational results show that the obtained lower bounds are very good and the proposed heuristics generate near-optimal solutions.     

Bis[3-(2-pyridyl)-2-thienyl]di-p-tolylstannane,an example of a six-coordinate tetraorganotin compound

The tin atom is bis[3-(2-pyridyl)-2-thienyl]di-p-tolylstannane is six-coordinate in a distortedcis-octahedral geometry owing to coordination by the pyridyl nitrogen atoms (Sn< –N=2.620(5), 2.631(5)Å).     

交替共聚中的自由单体－络合理论

自由基交替共聚理论是共聚合研究中的重要理论问题。本文从交替共聚各种理论中整理出自由单体－络合理论，并从机理、共聚组成和动力学等几方面进行分析和综述，认为该理论能比较全面、真实地反映交替共聚的机理。     

Asymptotic speed of propagation of wave fronts in a lattice delay differential equation with global interaction

In this paper, we derive a lattice model for a single speciesin a one-dimensional patchy environment with infinite numberof patches connected locally by diffusion. Under the assumptionthat the death and diffusion rates of the mature populationare age independent, we show that the dynamics of the maturepopulation is governed by a lattice delay differential equationwith global interactions. We study the well-posedness of theinitial-value problem and obtain the existence of monotone travellingwaves for wave speeds c > c_*. We show that the minimal wavespeed c_* is also the asymptotic speed of propagation, whichdepends on the maturation period and the diffusion rate of maturepopulation monotonically.     

Some current studies on dynamic response of the circular cylindrical sbhells in elastic medium

This paper summarizes and comments on the current situation of study on dynamic response of the circular cylindrical shells in elastic medium. After mentioning a brief introduction about early researches the authers with emphasis recount the general situation about recent development in this field, especially some important and effective methods for solving problems are pointed out. Finally we try to give a look ahead of the study on this subject.Project supported by the Science Foundation of the Chinese Academy of Sciences.     

Semi-insulating GaAs: A possible substrate for a field-assisted positron moderator

Positron lifetime spectroscopy measurements have been carried out for semi-insulating GaAs with applied electric fields in the samples directed towards, and away from the positron injecting contact. The lifetime spectra have been decomposed into two components, the longer of which (400 ps) is characteristic of open volume defects at the metal-semiconductor interface through which positrons are injected. The interesting feature of these experiments is the large increase in the intensity of this interface component as the field is directed towards the contact. We show that this increase is caused by a significant fraction of implanted positrons drifting under the influence of a strong electric field produced by a layer of space-charge formed adjacent to the positron injecting contact. The general trend of the intensity variation is well explained by the proposed model. Experiments involving the application of an ac bias to the samples strengthen the suggestion that the space charge region is largely formed from ionized EL2 donors. The results of the present work indicate that semi-insulating GaAs possesses properties that make it a suitable material for the fabrication of a high efficiency (10%) room-temperature field-assisted positron moderator. The extraction of positrons from the GaAs substrate into the vacuum through a thin metalization is discussed based upon available positron affinities for the GaAs and various elemental metals. These data suggest that a few monolayers of a strongly electronegative metal such as Au or Pd may allow vacuum emission through quantum tunneling.