静置水解时间对Al-SBA-15介孔分子筛结构的影响

在磷酸介质中,以异丙醇铝为铝源,采用直接合成法合成出Al-SBA-15介孔分子筛.采用XRD、N2吸附-脱附、FT-IR等表征手段,考察了静置时间对Al-SBA-15介孔结构和性能的影响.     

How to consider fractional counting and field normalization in the statistical modeling of bibliometric data: A multilevel Poisson regression approach

The numerical-algorithmic procedures of fractional counting and field normalization are often mentioned as indispensable requirements for bibliometric analyses. Against the background of the increasing importance of statistics in bibliometrics, a multilevel Poisson regression model (level 1: publication, level 2: author) shows possible ways to consider fractional counting and field normalization in a statistical model (fractional counting I). However, due to the assumption of duplicate publications in the data set, the approach is not quite optimal. Therefore, a more advanced approach, a multilevel multiple membership model, is proposed that no longer provides for duplicates (fractional counting II). It is assumed that the citation impact can essentially be attributed to time-stable dispositions of researchers as authors who contribute with different fractions to the success of a publication’s citation. The two approaches are applied to bibliometric data for 254 scientists working in social science methodology. A major advantage of fractional counting II is that the results no longer depend on the type of fractional counting (e.g., equal weighting). Differences between authors in rankings are reproduced more clearly than on the basis of percentiles. In addition, the strong importance of field normalization is demonstrated; 60% of the citation variance is explained by field normalization.     

高校运用有限摄编媒体资源实现多机位摄制高质量教学影片探析

摄制高质量的教学影片是各高校追求的重要目标,部分题材的影片摄制要实现高质量,必须以多台摄影机、多景别、多视角拍摄来实现,然而,部分高校由于经费的原因,不具备这样的条件,这是个矛盾。本文以摄、编、导等多个环节较为详细的阐述了运用有限的摄编媒体资源来实现多机位(15机位)摄制高质量教学影片的思路、方法与技巧,并以实例佐证,以求与同行们切磋。     

人机界面系统输入模块的控制方法

介绍了一种基于P89C51单片机的触摸式人机界面系统中作为系统输入的电阻触摸屏,介绍了8x15行列式电阻触摸屏的结构、工作方式及接口电路的设计,并详细介绍了控制方法。     

第14～15届世锦赛中国男篮若干技术指标的比较与分析

采用文献资料法、数理统计法等方法,对第14、15届世锦赛上中国男篮所参加比赛的若干技术指标进行了横向和纵向的对比分析。结果表明:横向上,两届世锦赛上,中国队与对手在中投次数、抢断和失误方面存在显著性差异。纵向上,在助攻上存在显著性差异。其它方面无显著性差异。中国队的比赛效率下降,而进攻质量却有了提高。应加强中国队员身体和技术的高强度对抗训练;提高个人防守的攻击性、整体的协同性;注重外线队员的培养;提高攻守转换速度;加强欧美强队的交流,借鉴他们的先进经验办好国内的联赛,提高CBA联赛的对抗程度和比赛质量。     

SBA-15固载离子液体催化合成碳酸丙烯酯的研究

采用原位合成法和后嫁接法将[SiPMIm] Cl固载在SBA-15材料上,制得SBA-15固载离子液体催化剂SBA-15-[SiPMIm] Cl.用N2吸附-脱附、透射电镜、小角X射线衍射和红外光谱等手段表征催化剂,并考察其在CO2与环氧丙烷（PO）环加成合成碳酸丙烯酯（PC）反应中的催化性能.结果表明：固载等量离子液体后,原位合成法制备的SBA-15固载离子液体催化剂体系对CO2环加成合成PC反应的催化活性优于后嫁接法制备的SBA-15固载离子液体催化剂体系.在最优工艺条件下,PO的转化率高达52.8％,且反应后催化剂经过滤即可分离回收利用,多次使用仍保持较高的反应活性.     

自然丰度法与同位素稀释法测定植物固氮能力的比较

生物固氮是生态系统有效氮的重要来源,目前存在多种测定和计算方法.以青藏高原高寒草原豆科植物团垫黄芪(Astragalus arnoldii)为对象,对比自然丰度法和同位素稀释法的差异,探讨4种计算方法、4种参考植物和2个取样时间对团垫黄芪生物固氮百分率(％Ndfa)评估的影响.结果 表明:参考植物的δ15N在自然生长状...     

Do you get what you pay for with school-based health programs? Evidence from a child nutrition experiment in rural China

This study uses a randomized controlled trial of a school-based anemia reduction program in rural China to examine how increased school emphasis on health promotion affects academic performance. Although education and health promotion are complementary functions of schools, they do compete for finite school resources. We compare the effects of a traditional program that provided only information about anemia and subsidies to an otherwise identical program that included performance incentives for school principals based on school-level anemia prevalence. By the end of the trial, exam scores among students who were anemic at baseline improved under both versions of the program, but scores among students in the incentive group who were healthy at baseline fell relative to healthy students in the control group. Results suggest that performance incentives to improve student health increase the impact of school-based programs on student health outcomes, but may also lead to reallocation of school resources.     

Periodic solutions for p-Laplacian neutral Liénard equation with a sign-variable coefficient

Using Lu's continuation theorem, the extension one of Manásevich-Mawhin, we study the existence of periodic solutions for p-Laplacian neutral Liénard equation of the form

(?_p(x(t)-cx(t-σ))^′)^′+f(x(t))x^′(t)+β(t)g(x(t-τ(t))=e(t).     

Some properties of submatrices in a solution to the matrix equation AXB=C with applications

Suppose that AXB=C is a consistent matrix equation and partition its solution X into a 2×2 block form. In this article we give some formulas for the maximal and minimal ranks of the submatrices in a solution X to AXB=C. From these formulas, we derive necessary and sufficient conditions for the submatrices to be zero and nonsingular, respectively. As applications, we give a group of formulas for the maximal and minimal ranks of submatrices in generalized inverses of matrices and their properties.