近红外光谱法测定烷烃分子的拓扑指数

利用近红外光谱法测定了烷径分子的分子连接指数，并探讨了混合烃分子连接指数与单烃分子连接指数之间的关系。结果表明：单烷烃分子连接指数具有可测性，而混合烃分子连接指数与单烃的分子连接指数之间存在线性加和的关系。     

柴油低温流动性质和烃组成的关联

用直馏柴油、催化柴油、加氢精制柴油、加氢裂化柴油调合得到不同柴油样品,分析其烃组成、正构烷烃碳数分布和低温流动性质,找出柴油的低温流动性质与其烃组成的关系,结果表明柴油低温流动性质与其环烷烃含量、芳香烃含量关联不明显,而与高碳数正构烷烃含量有很好的关联,其随着高碳数正构烷烃含量增加而升高。用最小二乘法建立了柴油低温流动性质和高碳数正构烷烃含量的一元、二元回归模型,经验证明二元回归模型计算值与实测值吻合较好。     

不饱和烃的QSPR研究

计算了不饱和烃(烯烃、炔烃、烷基苯)的J指数，并结合最大距离度Sj^max研究了J指数分别与不饱和烃的△Hf(g)^0、△S(g)^0、△Gf(g)^0、ω、tb等一系列分子理化性质之间的相关性和选择性，用计算机回归方法构建了计算不饱和烃的不同理化性质的最优经验公式，结果显示，其相关性和选择性均优于文献。     

北京地区表层土壤中饱和烃类化合物分布特征及污染源分析

对北京地区具代表性的环境功能区表层土壤饱和烃的组成与分布特征进行分析,并讨论了饱和烃污染物的来源.研究结果表明,在不同环境功能区表层土壤样品中均检测到了正构烷烃、类异戊间二烯烷烃、烷基环己烷和甾、萜烷烃等饱和烃化合物,其中正构烷烃和类异戊间二烯烷烃占优势.不同环境功能区和土壤类型的表层土壤样品中饱和烃的组成、分布特征和来源均存在明显差异,其中城区土壤受人为污染最为严重.表层土中饱和烃类化合物的来源比较复杂,既有人为污染源,又有天然来源.其中,中一低碳数正构烷烃主要是人为来源,高碳数正构烷烃主要为生物来源;类异戊间二烯烷烃、烷基环己烷和甾、萜类化合物则主要来源于矿物油、化石燃料和生物质不完全燃烧的产物等.     

部分有机污染物气相色谱保留指数的QSRR研究

用相对键长代替拓扑距离,结合距离矩阵,提出了一个可以表征含多重键、杂原子的距离调和指数Te=(N/∑Si -1)0.5。研究了该指数与烃、醇、醛酮、酯、胺等多种有机污染物气相色谱保留指数的构效关系。结果表明,Te指数与保留指数RI具有良好的相关性,相关系数均在0.99以上,且该指数计算简单,预测值与实验值较好吻合,是预测不同有机污染物分子保留指数的理想参数。     

几何平均连接性指数:一种修正的分子连接性指数

本文试图改进Kier和Hall提出的分子连接性指数,提供一种更加完美的分子表征和分子设计技术。根据分子连接性指数定义,本文对其进行几何平均修正,使其更具解释性和丰富的含义,并命名为几何平均连接性指数(GMCI)。新的分子连接性指数用于一组含3-8个碳原子的烷烃7种性质的QSAR／QSPR研究,统计结果表明,由几何平均连接性指数所建模型普遍比传统的分子连接性指数所建模型要好。     

烷烃保留指数与结构关系的数据挖掘

投影寻踪方法被用来进行烷烃结构和保留指数关系的数据挖掘。发现各种同系物表现了不同性质，它们各自成为一类。因此提出分支变量，用来与部分拓扑指数共同描述结构和保留指数的关系。得到了非常好的模型：R＝0.99995,残差小于4i.u.。     

柴油烃类分子组成预测研究

建立了利用宏观物性数据对柴油烃类组成进行预测的方法,根据对柴油烃类组分的分析和各烃类组分的物性差异,选取分属正构烷烃、异构烷烃、环烷烃和芳烃4个族的168个真实组分来表示柴油的组成,建立了柴油组分表示模板。建立了柴油各宏观物性与组成之间的关联关系,利用柴油常用宏观物性:密度、折射率、十六烷值、分子量以及恩式蒸馏曲线等数据建立方程组,对该方程组求解得到各个组分的含量。结果表明,计算得到的柴油饱和烃组成分布与烃组成分析结果较为吻合,误差在5%以下;三环环烷烃和芳烃的误差相对较大,并对产生误差的原因进行了分析。所建立的方法基本可以对直馏柴油烃类组成进行预测。     

异构烷烃的有效碳数与物性关联研究

多数异构烷烃的物性数据难以获取,且烷烃的物性与其分子结构密切相关.本文分析了异构烷烃与正构烷烃在结构上的差异,提出了用有效碳数描述片构烷烃的分了结构,体现了异构烷烃侧链对其物性的影响.并且根据有效碳数的定义,建立了油品中常见异构烷烃的结构-物性关联方法.对6类异构烷烃的物性计算结果表明,沸点、密度、折光指数的计算值与实测数据的一致性令人满意,沸点的最大绝对误差3.36 K,密度的最大绝对误差0.0056 g/cm3,折光指数的最大绝对误差为0.0028,计算精度优于文献方法,显示了关联方法的有效性.利用该方法,可预测异构烷烃的物性.     

烷烃填充量对纳米胶囊体系微观结构及其扩散的影响

采用分子动力学方法,分别研究了填充量为9个、18个和36个烷烃分子的纳米胶囊复合体系的微观结构和扩散性质。研究表明:三种纳米胶囊复合体系的微观结构发生了一定的变化,分别形成了连续的半周面、连续的单层圆周面和双层圆周面。三种纳米胶囊复合体系在温度升高过程中有序度逐渐降低,在固态时,填充了36个烷烃分子的体系中烷烃分子的有序度低于填充了9个和18个烷烃分子的体系,在液态时,填充了9个烷烃分子的体系,由于其相对自由空间较多和束缚较少,在相变后分子扭曲程度相对较高,有序度也低于填充了18个和36个烷烃分子的体系。三种纳米胶囊复合体系的相变温度分别为325K、325.3K和325.8K,受填充量的影响很小。随着填充量的增加其自扩散系数逐渐减小,这是由于有限的CNTs管内空间限制导致的,而且填充了36个烷烃分子的体系,因为在CNTs管内分为两层,其受到的束缚更大,使得自扩散系数比填充了9个和18个烷烃分子的体系降低了很多。     

脂肪烃类化合物气相色谱保留指数的预测

为了能更好地揭示脂肪烃的气相色谱保留指数与结构的关系,通过对412个脂肪烃类化合物在不同固定相、不同柱温下的1742个样本集的气相色谱保留指数值(RI)与其部分参数相关性的研究,发现RI与拓扑指数(mQ)、分子杂化状态指数(MHSI)、碳原子数(N)、固定液极性(CP)及柱温(T)的关系可表示为:RI=46．6537 15．83520Q 6．02101Q 49．9215MHSI- 62．4378N 2．2836CP 0．6159T(R=0．9954)此式不仅在一定程度上阐明了脂肪烃类化合物RI与其分子结构信息、固定液极性及柱温之间的关系,同时也提供了一种预测脂肪烃类化合物在各种色谱分离条件(不同固定相、不同温度)下RI的新方法。继以留一法(leave-one-out,LOO)进行交互检验,相关系数RLOO=0．9953,说明所建模型具有良好的稳定性和预测能力,较好地揭示了脂肪烃类化合物在不同固定相、不同柱温下气相色谱保留指数的变化规律。     

基于波段反射率日均增量的花生干旱灾情遥感评估

干旱是影响花生产量的主要气象因素之一。开展花生干旱灾情遥感评估对于产量估算、防灾减灾和保险理赔具有重要意义。当前花生旱灾遥感评估主要依赖于光谱指数变化信息,容易受不同地区生育进程干扰,限制了光谱指数方法的普适性。研究在多时相Sentinel-2遥感影像和野外实测样本的支持下,分析时序波段反射率日均增量信息与花生干旱受灾程度之间的内在联系,利用决策树、随机森林、逻辑回归等方法对花生干旱等级进行分类,并以总体精度和Kappa系数评价各种方法的精度。结果表明：单一波段的近红外反射率日均增量对花生受灾情况的指示性较强。多光谱波段组合方式对花生旱灾程度的指示性均优于单个波段,其中红波段、蓝波段、近红外光谱波段反射率日均增量组合的指示性最强,整体精度达到89.93%,Kappa系数0.847 1。与逻辑回归和决策树算法相比,随机森林算法对花生旱灾评估精度最高。在旱情等级最优时相组合分析中,利用花生生长旺盛期（7月～8月）的多波段反射率日均增量信息,灾情等级遥感识别的总体精度可达88.62%,Kappa系数为0.827 4。说明基于生长旺盛期时序多波段反射率日均增量的干旱灾情遥感评估方法能有效提取花...     

Evolutionary algorithms for the multi‐objective test data generation problem

Automatic test data generation is a very popular domain in the field of search‐based software engineering. Traditionally, the main goal has been to maximize coverage. However, other objectives can be defined, such as the oracle cost, which is the cost of executing the entire test suite and the cost of checking the system behavior. Indeed, in very large software systems, the cost spent to test the system can be an issue, and then it makes sense by considering two conflicting objectives: maximizing the coverage and minimizing the oracle cost. This is what we did in this paper. We mainly compared two approaches to deal with the multi‐objective test data generation problem: a direct multi‐objective approach and a combination of a mono‐objective algorithm together with multi‐objective test case selection optimization. Concretely, in this work, we used four state‐of‐the‐art multi‐objective algorithms and two mono‐objective evolutionary algorithms followed by a multi‐objective test case selection based on Pareto efficiency. The experimental analysis compares these techniques on two different benchmarks. The first one is composed of 800 Java programs created through a program generator. The second benchmark is composed of 13 real programs extracted from the literature. In the direct multi‐objective approach, the results indicate that the oracle cost can be properly optimized; however, the full branch coverage of the system poses a great challenge. Regarding the mono‐objective algorithms, although they need a second phase of test case selection for reducing the oracle cost, they are very effective in maximizing the branch coverage. Copyright © 2011 John Wiley & Sons, Ltd.     

Radiometric estimation of biomass and nitrogen content of barley grown at different nitrogen levels†

Abstract

Field measurements of red (655 nm) and near-infrared (NIR: 805 nm) canopy reflectance from barley grown at different nitrogen levels are related to changes in biomass accumulation and total nitrogen content of the plant material. Crop biomass and the NIR reflectance or the NIR/red index are highly correlated. The variation in reflectance and index accounted for by the biomass is between 93 and 99 per cent. In the different nitrogen treatments the percentage nitrogen content of the crop is negatively correlated with the biomass accumulation, and the nitrogen content declines in a exponential manner. The correlation coefficient between plant nitrogen content and biomass declines from ?0·99 to ?0·92 with increasing nitrogen application rates. However, at any given chronological age the total plant nitrogen content and the accumulated biomass are strongly correlated in a curvilinear manner. Hence on each sampling date the NIR and NIR/red reflectance are closely related to percentage plant nitrogen in a curvilinear manner similar to the relationship between biomass and percentage plant nitrogen. Sequential reflectance measurements related to the chronological age of the plants are satisfactory for a model assessing the total nitrogen content of the barley plants. Information about the developmental stage of the barley plants should improve the model assessing biomass accumulation by reflectance measurements. The plants should be described by parameters that take the nutritional status of the crop into account. Parameters such as numbers and survival of tillers numbers and duration of leaves, plant height and flowering should be used for a satisfactory definition of the developmental stage of the plants.     

Relationship between remotely sensed variables and tree species diversity in savanna woodlands of Southern Africa

In this study, we test whether and in what way tree species diversity in three savanna woodland sites is related to Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite imagery-derived indices. We test the use of standard deviation of near-infrared (stdev NIR) radiance and tree canopy cover estimated through the soil-adjusted vegetation index (SAVI) in estimating diversity. We use linear regression analysis to test the existence as well as determine the nature of the relationship between tree species diversity estimated from fieldwork data and stdev NIR radiance and SAVI. Our results show that tree species diversity has a significant (p < 0.05) hump-shaped response to variations in stdev NIR radiance and SAVI. Furthermore, results show that the combination of stdev NIR and SAVI explains between 60% and 64% of the variations in tree species diversity, an improvement of between 30% and 54% explained by the indices individually. We conclude that ASTER remotely sensed data can successfully be used to estimate tree species diversity in savanna woodlands.     

有机化合物性质与键极性诱导指数的关系(一) —烃类裂化与键极性诱导指数

用作者过去建议的极性诱导指数的概念和计算方法,以计算机程序在计算机上对一些烃类化合物的键极性诱导指数进行了计算,并讨论了此类化合物在放电中裂解稳定性与键极性诱导指数的关系。     

LabVIEW DAQ在学生实验中的应用

简要介绍了在实验室虚拟仪器集成环境LabVIEW中,对国产模拟量数据采集卡AD7202进行驱动的三种方法,包括直接用Inport和Outport图标编程、利用Code Interface Node(CIN)图标调用C语言编写的代码以及利用Call Library Functions图标调用数据采集卡的动态链接库函数。该文采用了调用动态链接库函数(adcard．du)的方法驱动,分别在单缓冲区方式和多缓冲区方式下进行实时数据采集(DAQ),并比较了两种方式的优劣,最后通过设计一个虚拟示波器,在多缓冲区方式下完成了LabVIEW DAQ在学生实验中的应用。该虚拟示波器具有存储示波器的功能。     

烃类物质闪点定量构效的关系

应用CODESSA软件计算300种烃类物质的分子结构描述符,用启发式回归(HM)、最佳多元线性回归(B-MLR)法,以筛选出来的分子描述符建立线性回归模型.用B-MLR法所选4个描述符作为支持向量机(SVM)的输入,建立非线性模型.预测结果表明:所建模型稳健,泛化能力强,预测误差小.非线性模型(R2=0.9884,RMSE=8.7570)的性能优于线性回归模型(HM:R2=0.9815,RMSE=11.0653;B-MLR:R2=0.9814,RMSE=11.1041),预测的效果令人满意.     

Land Surface Water Index (LSWI) response to rainfall and NDVI using the MODIS Vegetation Index product

For more than 20 years the Normalized Difference Vegetation Index (NDVI) has been widely used to monitor vegetation stress. It takes advantage of the differential reflection of green vegetation in the visible and near-infrared (NIR) portions of the spectrum and provides information on the vegetation condition. The Land Surface Water Index (LSWI) uses the shortwave infrared (SWIR) and the NIR regions of the electromagnetic spectrum. There is strong light absorption by liquid water in the SWIR, and the LSWI is known to be sensitive to the total amount of liquid water in vegetation and its soil background. In this study we investigated the LSWI characteristics relative to conventional NDVI-based drought assessment, particularly in the early crop season. The area chosen for the study was the state of Andhra Pradesh located in the Indian peninsular. The Moderate Resolution Imaging Spectroradiometer (MODIS) Vegetation Index (VI) product from the Aqua satellite was used in the study. The analysis was carried out for the years 2002 (deficit year) and 2005 (normal year) using the NDVI from the MODIS VI product and deriving the LSWI using the NIR and SWIR reflectance available with the MODIS VI product. The response of LSWI to rainfall, observed in the rate of increase in LSWI in the subsequent fortnights, shows that this index could be used to monitor the increase in soil and vegetation liquid water content, especially during the early part of the season. The relationship between the cumulative rainfall and the current fortnight LSWI is stronger in the low rainfall region (<500 mm), while the one-fortnight lagged LSWI had a stronger relationship in the high rainfall region (>500 mm). The relationship between LSWI and the cumulative rainfall for the entire state was mixed in 2002 and 2005. The strength of the relationship was weak in the high rainfall region. When LSWI was regressed directly with NDVI for three LSWI ranges, it was observed that the NDVI with the one-fortnight lag had a strong relationship with the LSWI in most of the categories.     

Objective and subjective responses of seated subjects while reading Hindi newspaper under multi axis whole-body vibration

Train passengers often read newspapers while traveling. Vibration is one of the key factors that may occasionally inhibit this activity. An experimental study was, therefore, conducted to investigate the extent of interference perceived in reading task by seated subjects in two postures under random vibration. 30 healthy male subjects were exposed to vibration magnitudes of 0.4, 0.8 and 1.2 m/s² in mono, dual and multi axis in the low frequency range 1–20 Hz. The task required subjects to read a given paragraph of Hindi national newspaper, in two seated postures (lap posture with backrest support and table posture with leaning over the table). The reading performance was evaluated by both degradation in performance in terms of time required to complete the task and subjective rating using Borg CR10 scale. Both the methods of reading performance evaluation exhibit progressive increase with an increase in vibration magnitude for both the subject postures in all the direction of vibration and are found to be higher in lateral and vertical direction among mono axes. The effects of multi axis vibration on perceived difficulty have been found to be similar to dual axes vibration and greater than mono axes vibration; however degradation in reading performance in multi axis vibration was also found to be similar to that for lateral direction. A comparison of the effect of postures by both evaluation methods revealed that the reading performance was adversely affected for table posture in all direction of vibration, however for lap posture, only the X-axis vibration effect was more severe.

Relevance to industry

Available ride comfort standards for vehicles do not include the effects of vibrations on passenger activities. Assessment of activity discomfort would be useful for vehicle design optimization to facilitate activity comfort.