一类特殊的奇异级数

讨论了华林问题中一类特殊的奇异级数，在分析的范围内用代数数论的方法对它的下界作出一个估计，从而改进了Vaughan的结果。     

One convenient synthesis route to boron nitride nanotube

We describe one convenient synthesis route to boron nitride (BN) nanotube by the reaction of boron powder, iron oxide, and ammonium chloride at 600 °C for 12 h. Characterized by XRD, FTIR, XPS, TEM and SAED, the composition and morphology of the products are confirmed. The possible reaction mechanism is also discussed.     

医学统计学与流行病学教学模式改革对学生课程认知态度的影响

目的比较新旧医学统计学与流行病学教学模式对学生认知态度的影响。方法以临床医学专业大专班学生为对象，设立改革班和对照班，改革班采用新教学模式，对照班采取传统教学模式，课程结束后比较不同教学模式对于学生有关医学科研及所学课程认知态度的影响。结果改革班与对照班学生的认知态度存在明显差异（P〈0．05）。结论新教学模式可以使学生更好地熟悉医学科研全过程，深刻了解医学统计学与流行病学方法在科研中的具体应用，激发学习的自觉性和兴趣。     

Formation of β‐iPP in isotactic polypropylene/ethylene–propylene rubber blends: Effects of preparation method,composition, and thermal condition

The effects of preparation method, composition, and thermal condition on formation of β‐iPP in isotactic polypropylene/ethylene–propylene rubber (iPP/EPR) blends were studied using modulated differential scanning calorimeter (MDSC), wide angle X‐ray diffraction (WAXD), and phase contrast microscopy (PCM). It was found that the α‐iPP and β‐iPP can simultaneity form in the melt‐blended samples, whereas only α‐iPP exists in the solution‐blended samples. The results show that the formation of β‐iPP in the melt‐blended samples is related to the crystallization temperature and the β‐iPP generally diminishes and finally vanishes when the crystallization temperature moves far from 125 °C. The phenomena that the lower critical temperature of β‐iPP in iPP/EPR obviously increases to 114 °C and the upper critical temperature decreases to 134 °C indicate the narrowing of temperature interval, facilitating the formation of β‐iPP in iPP/EPR. Furthermore, it was found that the amount of β‐iPP in melt‐blended iPP/EPR samples is dependent on the composition and the maximum amount of β‐iPP formed when the composition of iPP/EPR blends is 85:15 in weight. The results through examining the effect of annealing for iPP/EPR samples at melt state indicate that this annealing may eliminate the susceptibility to β‐crystallization of iPP. However, only α‐iPP can be observed in solution‐blended samples subjected to annealing for different time. The PCM images demonstrate that an obvious phase‐separation happens in both melt‐blended and solution‐blended iPP/EPR samples, implying that compared with the disperse degree of EPR in iPP, the preparation method plays a dominant role in formation of β‐iPP. It is suggested that the origin of formation of β‐iPP results from the thermomechanical history of the EPR component in iPP/EPR. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1704–1712, 2007     

水动力学问题的弱可压缩模型求解方法研究

从弱可压缩水动力学方程出发，采用坐标变换的方法处理自由表面，建立了能够模拟有自由表面流动问题的定常、非定常的三维水动力学模型和对流扩散模型，模型采用浮湍流模型进行封闭，并对模型求解的数值方法进行了研究。     

Generation of large fifth-order nonlinear phase shifts by use of lossless χ(2) cascaded nonlinear processes

It is shown that the cascaded fifth-order nonlinear phase shifts will increase with energy loss in the cascaded processes. Essentially different from the multi-photon absorption accompanied with inherent material nonlinearities, the loss of fundamental wave in a cascaded process is controllable and suppressible. By introducing difference frequencies generated from the reaction between the fundamental and its second harmonic after the cascaded processes, the fundamental wave can be free of energy loss, while the large cascaded fifth-order nonlinear phase shift is maintained.     

新型菲涅尔线聚焦聚光太阳电池组件研究

以聚甲基丙烯酸甲脂为材料,采用热压成型工艺加工成型线聚焦菲涅尔聚光透镜(8×),可用于空间、地面光伏系统太阳电池组件的聚光系统,并对在其聚光条件下,太阳电池的电流电压特性进行测试,结果表明,该菲涅尔线聚焦棱镜能有效提高太阳电池的单位输出功率.模具的机械加工精度和光学抛光精度低,是造成其部分聚光率损失的原因.     

Very low thermal expansion in TaO2F

X-ray diffraction data for TaO₂F from 20 to 400 K show a thermal expansion so low that we cannot be certain whether it is positive or negative. We estimate the absolute value of the thermal expansion coefficient to be less than 6×10⁻⁷/K. This then is comparable to that of amorphous SiO₂ and is apparently unique behavior for a cubic material over such a large temperature range.     

对当前建设单位在招投标阶段进行造价控制的思考

指出了当前建设单位在招投标阶段的管理现状及存在的问题,并通过分析这些问题,提出了相应的解决对策。     

国际刑事法院管辖权补充性原则初探

国际刑事法院是世界上第一个常设国际刑事司法机构,其管辖权补充性原则关乎国际义务与国家主权的均衡协调;《规约》对于管辖权补充性原则进行了多层次的规定;针对检察官重复启动调查、起诉程序以及修改、追加指控或代之以较严重的指控的权力,应当实施限制次数和间隔时间的制约措施。