数字视频广播有线系统中的解调与信道解码

讨论了数字视频广播有线系统标准中正交幅度解调和信道解码的基本原理和具体实现方案．在专用硬件和应用软件的配合下,实现了一个数字有线接收前端系统．该系统与符合数字视频广播标准的解码系统相连接,即可组成一个数字有线电视机顶盒,通过有线电视网,该盒可接收占用频带资源少、具有演播室质量的数字电视节目．     

“快”带电离子通过固体时的“尾流”效应

简略介绍了“尾流”效应（ｗａｋｅｅｆｆｅｃｔ）的等离子体模型，并依之模拟计算了１．９１５ＭｅＶＨ、２．０６０ＭｅＶＨ在１００Ａ碳膜中分解后０°方向的能谱形式。给出了相同条件下的实验结果，将两者做了比较。     

Statistical mechanics and the Gauss principle

In an essentially statistical approach to statistical mechanics, it is seen that the Gauss principle of the arithmetic mean may be taken as the starting point. The equations from which the subject can be built up are deduced from the Gauss principle of the arithmetic mean.     

Synthesis and Characterization of Li‐containing Boron Carbide r‐Li~1B13C2

Transparent and nearly colorless single crystals of r‐LiB₁₃C₂ were obtained by reaction of boron with Li₂CO₃ in a Cu melt at 1250–1300 °C. The structure analysis [R3 m, a = 5.6535(1), c = 12.5320(2) Å, 421 independent reflections, 22 parameters, R₁ = 0.034, wR₂ = 0.093] revealed a crystal structure that can be described as a filling variant of rhombohedral B₁₃C₂. Li⁺ is located in a void above or below the linear CBC unit. The site occupation is close to 50 % resulting in an electron‐precise composition according to Wade's rules if a positive charge is given to the CBC entity: Li⁺(B₁₂)^2–(CBC)⁺. The displacement parameters of the CBC unit indicate disorder in the [001] direction, that relates to the short Li–C distance and the partial occupation of the Li⁺ site. The composition is confirmed by EELS measurements of single crystals. Band gap calculations give a value of 2.94 eV, which is in agreement to the crystals being colorless. The evaluation of the electron density by application of the QTAIM formalism as proposed by Bader modifies the assignment pictured above according to Wade's rules. In agreement to the electronegativities the carbon atoms carry a negative charge (–2.31/–2.42) and the effective charges are: Li^+0.81(B₁₂)^+2.02(CBC)^–2.83.     

用于合成纯硅分子筛 AST 和 LTA 的动态有机结构导向剂(英文)

Pure-silica-zeolite(PSZ) AST and LTA are synthesized successfully by using the same structure-directing agent(SDA) molecule,but at different concentrations.A dynamic organic SDA is proposed to discuss the mechanism of phase discrimination between AST and LTA.Data suggest that the SDA molecules can self-assemble into dimer or trimer complexes at different concentrations by π-π interactions,and these differences can be taken advantage of to selectively synthesize either PSZ AST or LTA.These deviations from the Liebau's rules indicate that small changes in SDA chemistry,structure,and order in solution can have a great impact on the structure selectivity of the zeolite synthesis.     

遵照国家法制规定大力开发强化食品

介绍了我国食品营养强化剂使用卫生标准,特别是对其中一些重要备注和规定进行了归纳和说明.     

高分子单链凝聚成与线团相互穿透的多链凝聚态

高分子单链凝聚态由于链内链结构单元间存在范德化吸引作用,高分子链呈打圈链构象,而多链凝聚态由于链内链单元间的吸引作用被与相互穿透的近邻链的单元间吸引作用所屏蔽,高分子链呈高斯链构象。本文简要介绍单链凝聚态试样的制备方法,单链单晶体、单链玻璃体、溶胀的单链高弹态拉伸等的实验观察,并提出从单链凝聚态到多链凝聚态的转变过程问题,即高分子线团的相互穿透过程,目前还缺少基础了解。     

Al_(70)Cu_(30)合金液态RDF高斯分解与局域结构计算

运用密度泛函B3LYP方法对AlmCun(m,n≤4)团簇结构进行量子化学计算,得到团簇的稳定构型。对不同温度下X-射线衍射实验所得的径向分布函数(RDF)在0.2～0.4nm范围内做高斯分解,结合计算结果对高斯峰的意义做了解释,认为计算所得部分团簇构型可以代表Al70Cu30合金熔体的内部局域结构。     

Radial quadrature for multiexponential integrands

We introduce a Gaussian quadrature, based on the polynomials that are orthogonal with respect to the weight function ln(2)x on the interval [0, 1], which is suitable for the evaluation of radial integrals. The quadrature is exact if the non-Jacobian part of the integrand is a linear combination of a geometric sequence of exponential functions. We find that the new scheme is a useful alternative to existing approaches, particularly for integrands that exhibit multiexponential behavior.     

基于改进Alopex算法的烷基化生产过程的优化

为了提高Alopex算法的全局搜索能力,本文提出了一种改进的Alopex算法。该算法将混沌算法引入到Alopex的初始化过程中,提出了具有停滞行为的步长操作方法,在个体连续一定代数没有更新时,引入了高斯变异操作。最后利用改进的Alopex算法求解了烷基化生产过程的最优化问题,优化结果表明了本文算法的有效性。