我国理论化学的两位先驱者——孙承谔与王守竞

孙承谔先生是国际知名的化学家,其重要的工作是将过渡态理论成功应用于真实的化学反应速率常数的计算.作为中国理论化学的开拓者和教育家,他为我国化学事业的发展做出了杰出贡献.王守竞先生将新诞生的量子力学应用于氢分子和不对称陀螺的研究,取得了国际公认的成果.之后,又投身应用科技,出任中央机器厂首任总经理,是我国机械工业的奠基人.     

AO3D: A Monte Carlo code for modeling of environmental light propagation

A Monte Carlo radiative transfer program (Atmosphere-Ocean 3-Dimensional, AO3D) for modeling the coupled atmosphere-ocean environment has been developed. The code allows for the specification of optical properties for the atmosphere, land and ocean. Light rays are tracked as they pass between the atmosphere and the ocean, reflect off the ocean surface, the ocean floor, and off land, or are absorbed. In this version the polarization of light rays is not considered. The optical properties of each horizontally homogeneous layer within the atmosphere and ocean can be set on a layer-by-layer basis with a choice of phase functions, absorption and scattering coefficients, and index of refraction. A wind-dependent Cox and Munk ocean surface realization (with whitecaps) is implemented to model refraction and reflection from surface waves. Either spherical- or flat-Earth models can be used, and all refraction and reflection are accounted for. The AO3D model has been tested by parts, and as a whole by comparison with single- and total-scattering calculations from other radiative transfer codes. Comparisons with Monte Carlo calculations by Adams and Kattawar (agreement in TOA radiance within the published precision ∼2%), MODTRAN4 (agreement in spherical-shell atmosphere (SSA) sky radiance within about 2%) and Coupled DIScrete Ordinate Radiative Transfer (COART) (agreement in plane-parallel (PP) sky radiance within 2%) are shown. Sun photometer measurements (including large air mass values) at the Mauna Loa Observatory are compared to AO3D simulations (for a spherical Earth) and suggest that a thin aerosol layer was present above the observatory at the time of the measurements.     

The Hanle effect with partial frequency redistribution. Construction of a frequency-dependent polarization matrix and numerical solution by a PALI method

The polarized approximate lambda iteration (PALI) technique developed for the weak field Hanle effect relies on the decomposition of the Stokes parameters I, Q and U into six cylindrically symmetrical components. It has been applied to complete and partial frequency redistribution with redistribution matrices in which frequency redistribution is decoupled from scattering polarization. For partial frequency redistribution, the decoupling is obtained by an adequate decomposition of the frequency space into several domains. By angle-averaging frequency-dependent terms in the exact weak field Hanle redistribution matrix for a normal Zeeman triplet, we construct a redistribution matrix with coupling between frequency redistribution and polarization and no domain decomposition. The coupling is contained in generalized frequency redistribution functions that depend on the magnetic field. The redistribution matrix is expanded in the Landi Degl’Innocenti spherical tensors for polarimetry and the Stokes parameters are decomposed into cylindrically symmetrical components. A PALI method is set up for the calculation of these components. The Stokes parameters are calculated for different simple atmospheric models. The positive Q direction corresponds to the linear polarization perpendicular to the solar limb. It is shown that the frequency space decomposition may induce large errors on Stokes U in the transition region between line core and line wings but can safely be used for Stokes I and Q, the errors staying less than 1% at all the frequencies.     

Structure and properties of macromolecules in shearflow

A laser light-scattering photometer is presented, the construction of which is based on the principle of a searle-type viscosimeter. It permits registration of the wideangle distribution of the scattered light in an area of 1 sr around the direction of the negative velocity gradient with high resolution (49 · 10^–6 sr).In the investigated range (0–3000 s^–1) the scope of shear-induced intensity changes of diluted solutions of polystyrene in benzene is 0.5–5 %. The alignment, control and measurement of several influencing factors, e. g. the positional and intensity stability of the primary beam, required a relatively high degree of performance.The relation of the intensity changes of the scattered and transmitted light are measured and illustrated as a function of shear cycles. In this way it is possible to recognize both the orientation and the deformation as well as the relaxation of shear-stressed PS-molecules. The discussion of the curves is guided by a simple instructional preview.     

Characterisations of Chebyshev sets in c0

A subset MX of a normed linear space X is a Chebyshev set if, for every xX, the set of all nearest points from M to x is a singleton. We obtain a geometrical characterisation of approximatively compact Chebyshev sets in c₀. Also, given an approximatively compact Chebyshev set M in c₀ and a coordinate affine subspace Hc₀ of finite codimension, if M∩H≠, then M∩H is a Chebyshev set in H, where the norm on H is induced from c₀.     

地球只受木星引力作用时的运动轨道的探讨

讨论了如果太阳突然消失,而且地球只受木星引力作用时的运动轨道,结果表明,这时地球相对木星的运动轨道为双曲线或直线．     

用LED灯和乐高积木实现Fe(Ⅲ)的定量测定*

在普通化学实验中引入以LED灯作为单色光源,用乐高积木和简单电子元件搭建简易光度计的教学环节。自制光度计采用2种方法搭建,结构简单,光路直观,成本低廉。将其用于Fe(Ⅲ)的定量测定,测试结果与商用光度计的测试结果进行比较,验证了自制光度计的性能。结果表明,在测试浓度范围内,吸光度与Fe(Ⅲ)浓度具有良好的线性拟合关系,测试结果满足基本的实验教学需求,可替代该实验中惯用的商用分光光度计。教学实践表明,这种自己搭建仪器并用于定量测定的教学模式,易于激发学生的学习兴趣与热情,增强学生的动手能力、独立思考和解决实际问题的能力,改善了教学效果。     

HG-AFS法测定甲鱼肉中硒

采用湿法消解原子荧光光度法对甲鱼肉中硒元素含量进行了分析测定。该方法加标回收率为96.2％～103.0％,相对标准偏差(RSD)为3.69％,猪肉国家标准物质(GBW08552)的测定值与标准值相吻合。结果表明： 甲鱼肉中硒元素的含量非常丰富,硒含量是普通动物鲜肉中的1.2～9.4倍;是新鲜瓜果蔬菜的几十至几百倍。本测定结果可为研制开发富硒甲鱼保健食品提供有价值的和可靠的科学依据。     

Impacts of biomass-burning on aerosol properties of a severe haze event over Shanghai

Anthropogenic aerosols have significant impacts on the environment and human health in the Yangtze River Delta region, one of the most densely populated regions in the world. A biomass-burning plume swept across this area (Shanghai) in May 2009, leading to changes in the physical and optical properties of aerosols, which were investigated using ground-based remote sensing and in situ measurements via comparisons with dust pollution and background conditions. Experiments show that the biomass-burning plume led to an increase in the average aerosol optical depth (AOD) at 500 nm from 0.73 to 1.00 (37% higher), an absorption Angstrom exponent (AAE) of 1.48, and an increase in the Angstrom exponent (α) up to 1.53. Furthermore, local dust aerosols derived from road dust and/or construction dust also led to higher values of AOD (2.68) and AAE (2.16), and a daily average value of α of 1.05. For the biomass-burning plume, the aerosol particles exhibited significant variations in short-wavelength spectra. The single scattering albedo at 670 nm decreased remarkably under the influence of the biomass-burning plume, indicating the significant absorptive ability of the biomass-burning pollution and higher ratio of absorption aerosols within the plume. Under the effects of the biomass-burning, the volume concentration of fine-mode aerosols increased significantly and the PM-fine/PM-coarse volume concentration ratio reached 12.33. This relatively large change in fine-mode particles indicates that biomass-burning has a greater impact on fine-mode aerosols than on coarse-mode aerosols.     

Artificial Sun synchronous frozen orbit control scheme design based on J_2 perturbation

Sun synchronous orbit and frozen orbit formed due to J 2 perturbation have very strict constraints on orbital parameters,which have restricted the application a lot.In this paper,several control strategies were illustrated to realize Sun synchronous frozen orbit with arbitrary orbital elements using continuous low-thrust.Firstly,according to mean element method,the averaged rate of change of the orbital elements,originating from disturbing constant accelerations over one orbital period,was derived from Gauss’ variation of parameters equations.Then,we proposed that binormal acceleration could be used to realize Sun synchronous orbit,and radial or transverse acceleration could be adopted to eliminate the rotation of the argument of the perigee.Finally,amending methods on the control strategies mentioned above were presented to eliminate the residual secular growth.Simulation results showed that the control strategies illustrated in this paper could realize Sun synchronous frozen orbit with arbitrary orbital elements,and can save much more energy than the schemes presented in previous studies,and have no side effect on other orbital parameters’ secular motion.