利用LED的投影系统光源设计

设计了利用多颗LED(Light Emitting Diode,发光二极管)阵列组成的扩展面光源.经过合理的聚光设计使之符合某些投影设备对亮度要求不是很高,但结构紧凑、性能稳定、使用寿命长的要求.结合数学建模和软件模拟的方式设计了一种小巧的反光杯,利用反光杯把LED近180°的发散光束汇聚到60°左右;然后再用一一对应的透镜阵列汇聚为平行光;最后采用柯勒照明方式把较大的面光源阵列汇集到LCD投影屏幕上,从而达到了较高亮度且具有很高均匀性的目的.     

利用计算机软件确定电位滴定法中的滴定终点

采用Origin，Statistica，MS Excel等软件处理电位滴定法中的滴定数据，与传统的终点确定方法进行比较，提出较为精确的滴定终点确定方法。     

论彝族火把节中的传统体育活动

火把节是彝族的盛大传统节日。在火把节期间除了开展宗教祭祀活动外,还开展民族传统体育活动。本文对彝族火把节期间开展的传统体育活动和功能加以分析,认为彝族火把节是连接彝族传统体育、传播彝族传统体育的重要形式,它深刻影响着彝族传统体育的发展。     

高等数学中的自然对数

本文主要阐述了自然对数在高等数学课程中各个章节中的作用,由此提示高等数学理论体系的内在联系。     

Numerical modelling of unsteady convective–diffusive heat transfer with a control volume hybrid method

Presented in this paper is a numerical methodology for the solution of the parabolic governing partial differential equation that describes unsteady advection–diffusion heat transfer. The formulation presented here is shown to be free from the numerical oscillation commonly associated with advection–diffusion heat transfer regardless of the value of the Peclet number. The formulation involves the absorption of the advection term in the unsteady heat equation into the capacitance term. This process is achieved with the use of a control volume methodology applied to each nodal element on a finite-volume mesh. This is shown to ensure that spurious energy losses and gains are avoided and provides for consistency between temperature and energy change. This approach provides unconditional stability and it is shown that good accuracy is achievable with relatively large time-steps.     

熔铸民族性:土家族饮食禁忌的人类学考察

禁忌作为一种典型的民俗文化现象 ,往往渗透着人类初民的思维意识 ,同时显示出文化的民族性特征。全面考察土家族饮食禁忌的各种形态及其文化成因 ,认为这些禁忌形态是土家人构建民族性的外化形式之一 ,体现了双重建构的民族文化心理 :表层结构是把饮食本身作为首要生存要素的饮食天命观 ,深层结构是个体融入民族总体之中构建民族性的生命意识。     

Estimation of DUR and source utilization efficiency for changing product dimensions and source activities in gamma irradiator

This paper discusses the application of the developed analytical method (Reji George, Jain, Pradhan, A.S., 2008. Theoretical evaluation of dose distribution in product in radiation processing plants. Radiat. Phys. Chem. 77, 186–191), for determining the activity loading pattern in a radiation processing plant to get the desired dose uniformity ratio (DUR) for processing mangoes and how the method was used to evaluate the expected source utilization efficiency for the redesigned source–product configuration.     

On the pfaffianized-KP equation with self-consistent sources

A new procedure called ‘source generation’ is applied to the pfaffianized KP equation. As a result, the pfaffianized-KP equation with self-consistent sources (ESCS) is obtained. This coupled system cannot only be reduced to the pfaffianized KP equation, but also reduced to the KP equation with self-consistent sources (KPESCS). So the pfaffianized-KP ESCS can be viewed as a pfaffian version of the KPESCS, which indicates the commutativity of the ‘source generation’ procedure and pfaffianization.     

First neutron Bragg-edge imaging experimental results at CSNS

The neutron Bragg-edge imaging is expected to be a new non-destructive energy-resolved neutron imaging technique for quantitatively two-dimensional or three-dimensional visualizing crystallographic information in a bulk material, which could be benefited from pulsed neutron source. Here we build a Bragg-edge imaging system on the General Purpose Powder Diffractometer at the China Spallation Neutron Source. The residual strain mapping of a bent Q235 ferrite steel sample has been achieved with a spectral resolution of 0.15% by the time-of-flight neutron Bragg-edge imaging on this system. The results show its great potential applications in materials science and engineering.     

Amplification of chirality as a pathway to biological homochirality

Amplification of enantiomeric enrichment is a key feature for the chemical evolution of biological homochirality from the origin of chirality. The aggregations of the enantiomers by diastereomeric interactions enable the modification of their enantiomeric excess during some chemical processes. Fluorine-containing chiral compounds possess large amplification effect via distillation, sublimation and achiral chromatography by self-disproportionation. Asymmetric amplifications in enantioselective catalysis occur by the differential formation and reactivity between homochiral and heterochiral aggregate in solution.We described the amplification of ee in asymmetric autocatalysis of 5-pyrimidyl alkanol in the reaction between diisopropylzinc and pyrimidine-5-carbaldehdye. During the reactions extremely low ee (ca. 0.00005% ee) can be amplified to achieve more than 99.5% ee. Since the proposed origins of chirality such as CPL, quartz, chiral organic crystals of achiral compounds and statistical fluctuation of ee can initiate the asymmetric autocatalysis with amplification of ee, the proposed origin of chirality can be linked with enantiopure organic compound in conjunction with amplification of ee by asymmetric autocatalysis. In addition, we described that the carbon isotopically chiral compound triggers the asymmetric autocatalysis of 5-pyrimiodyl alkanol to afford the enantioenriched product with the absolute configuration correlated with that of carbon isotope chirality, that is, isotope chirality including hydrogen isotopes can control the enantioselectivity of asymmetric addition of alkyl metal reagent to aldehyde.