硫含量在出口航煤馏分中分布分析

采用紫外荧光法对切割后航煤各窄馏分油进行了硫含量的测定。结果表明：样品0%-0%窄馏分中硫含量只占整个馏分中硫含量的9.175%-10.451%,而80%-100%窄馏分中硫含量占整个馏分中硫含量的32.538%-45.326%,后者是前者的3.55-4.95倍;样品的平均硫含量与60%-80%窄馏分中硫含量数值接近。该结果对于了解和掌握出口航煤中硫含量在各窄馏分中的分布在数值上提供了依据。     

戊二醛的生产工艺进展及开发与应用前景分析

戊二醛是极为重要的化工中间体和精细化工产品，用途广泛，应用前景广阔，市场潜力大，国内所用戊二醛大部分仍依赖进口，因此我国戊二醛极具开发利用前景。文章介绍了戊二醛的合成方法和在消毒杀菌、皮革制品、石油开采等方面的应用，并对利用C5副产资源开发戊二醛的前景进行了分析。     

K频段斐波那契网格稀疏阵列分析与设计

针对低轨宽带卫星通信网、5G通信网应用中对K/Ka频段多波束有源相控阵天线的需求,对斐波那契网格阵列进行改进,提出一种大规模低旁瓣稀疏阵列的高效设计方法。首先从数学上对斐波那契网格阵列的栅瓣抑制特性进行解释,进而对阵列进行数值计算和全尺寸三维电磁仿真,最后结合实际工程应用给出一种K频段高密度集成有源相控阵多波束天线的阵面及射频芯片的布板方案。这种大间距阵列在大扫描角域和大带宽内具有低副瓣、无栅瓣、高增益等优良特性,非常适用于通信应用中的高密度集成有源相控阵天线。     

分形市场中的汇率协整关系

本文将混沌与分形运用到汇率研究中,运用R/S方法研究了外汇收益率的长记忆性,并将传统的协整理论推广到广义的分数维协整,研究了时间序列之间的长期均衡关系,并以外汇市场中的欧元和新加坡元兑美元的汇率为例进行了实证分析,指出这两种货币收益率服从分形分布,具有相同的分整阶数且二者存在分数维协整关系。     

梁山英雄的宗派观

水泊梁山英雄都有宗派观念。这可以从宋江成为起义军的领袖 ,他对待卢俊义的态度 ,复杂的关系网和英雄排座次的场面中看出来。     

A response surface approach to tolerance design

In spite of Taguchi's robust parameter design (Introduction to quality engineering: designing quality into products and processes, 1986, Asian Productivity Organization, Tokiyo), tolerance design is still important at the design stage of products and processes. Taguchi's proposal and related methods for tolerance design, however, do not efficiently use the information that can be obtained from the parameter design experiment. In this paper, we introduce a new method for tolerance design based on the response surface approach to parameter design. It is a flexible method because non-normal distributions of the noise factors and the quality characteristic are allowed. Moreover, it is unnecessary to perform a new physical experiment. Essentially, tolerances of noise factors are maximized, subject to constraints to ensure that the mean value of the quality characteristic remains on target and the fraction nonconforming is below a pre-specified maximum. Some aspects of model uncertainty are discussed and the method is illustrated by means of an example.     

Effective observation of random processes using derivatives

Metrika - What are optimal observation times of a random process to obtain good prediction or good estimation of the (parametric) trend? In the presented paper we discuss especially the following...     

裂解碳五馏分中戊二烯的提取分离

介绍了国内外裂解碳五馏分分离技术的研究进展。对几种生产工艺的技术特点进行了分析,着重叙述了加热二聚法分离环戊二烯、萃取精馏法分离异戊二烯等工艺。提出优化现有工艺、开发新型萃取剂是今后碳五馏分分离技术发展的新方向。     

控股股东更换是否会提高公司绩效——基于中国上市公司的经验研究

控制权协议转让通常导致上市公司控股股东的更换,然而控股股东的更换是否能提高上市公司的绩效呢?本文对这一问题进行了实证研究.本文认为,控股股东的更换效率受投资者保护环境的影响,由于我国投资者保护环境尚不完善,控制权协议转让中存在较多的无效率交易,因此我国上市公司控股股东的更换并不能有效的提高公司绩效,这在股权转让比例较低...     

Effect of land-use conversion on C and N distribution in aggregate fractions of soils in the southern Loess Plateau,China

The purpose of this study was to assess the effect of grassland (GL) conversion to cropland (CL) and cropland conversion to forest (FL) and orchard (OL) on soil C and N distribution in dry aggregate size fractions in Nihegou catchment of the southern Loess Plateau, China. Four main land-use changes were analyzed in different agronomic management systems in 2006. The soil is wind-deposited loessial parent materials with a rather homogeneous silty clay loam texture classified as Calcic Cambosols. The GL was long-term over-used grassland. The CL was changed from GL after 33 years tillage with conventional tillage and fertilizer. The FL and OL originated from long-term CL after 23- and 7-year planted, respectively. Samples were taken at soil depths of 0–20 cm and 20–50 cm and were subjected to a physical fractionation process by way of aggregate size. Soil aggregate size fractions, total C and N contents and distributions were determined on all soil samples. Three dry aggregate fractions of very coarse (2.0–0.2 mm), coarse (0.2–0.05 mm) and fine (<0.05 mm) were obtained by shaking and sieving for 20 min. After 33 years of tillage, CL had 22% lower content of very coarse aggregates (2.0–0.2 mm) and 34% higher contents of fine aggregates (<0.05 mm) than GL. FL and OL soils had increased 9% and 10% contents of very coarse aggregates, and decreased 2% and 8% contents of fine aggregates compared to the CL. C and N losses in whole CL soils were 31% and 26% higher than those in GL. However, conversion of land uses from CL to FL (after 23 years) and OL (after 7 years) has increased C and N stocks by 76% and 40% in FL soils and by 66% and 63% in OL soils, respectively. This accessorial C and N stocks were higher in very coarse aggregate fractions (1.10 kg C m⁻² and 0.13 kg N m⁻² in FL soils, 1.43 kg C m⁻² and 0.17 kg N m⁻² in OL soils); moreover, the C and N stocks in fine aggregate fraction increased by 8% and 33% in FL soils and by 58% and 69% in OL soils, respectively. This results showed that C and N turnover and loss in aggregate fractions of this silty clay loam soils was very fast. Conversion of land uses from CL to FL and OL has obviously recovered the soil structure, and improved soil quality.