食品添加剂的应用及安全性探究

近年来,我国食品添加剂行业整体发展态势良好,市场规模逐渐扩大。综述了食品添加剂的研究现状及存在的问题,并针对食品添加剂的发展趋势进行了展望。     

十字轴式双万向铰链机构的传动分析

本文应用矢量函数法分析了十字轴式万向铰链机构的运动,推出传动比的计算公式,并借助Matlab软件绘制出叉面夹角及轴间角对传动比的影响曲线,分析方法和结果对工程技术人员设计、装配及调试双万向铰链机构有指导意义.     

高职学生英语听力训练的问题与对策

详细阐述了听力训练在高职学生的英语学习中的重要作用以及高职学生在英语听力训练中存在的问题及采用的对策与方法。     

PA序列下非参数回归函数估计的相合性

设{εi,i≥1}为PA序列，Eεi=0，supE（ε^2j）〈∞，对某个r〉2及占〉δ，supE｜εj｜^r＋δ〈∞，u（n）=O（n^（r-2）（r＋δ）/2δ，在PA序列误差下，讨论了非参数回归函数加权核估计的相合性．     

新形势下高校辅导员的工作职能探索

高校辅导员肩负着新一代大学生思想政治教育的重要使命,是大学生最为密切的良师益友。对当前新形势下辅导员队伍的工作职能进行了分析,提出了将事务性工作单独划分出来的设想。     

巧用机床

在机床的使用过程中，通过巧妙地利用或适当地改造，不仅可以提高零件的加工精度和生产率，还能扩展机床的功能、扩大机床的使用范围，从而满足企业生产发展的需要。特别是对于一些中小企业，有时通过成本较低的小创新．却可能获得企业生产的大收益。     

森林枯落物的水文功能

从森林枯落物的蓄水量、雨水截留量、阻延径流流速、改善土壤结构、减沙减流作用5个方面,叙述了森林枯落物的水文功能,提出森林经营中,应采取措施,促进林分森林枯落物的积累。     

森林经营对土壤动物影响研究进展

森林经营是实现森林可持续发展的根本途径,土壤动物是森林生态系统的重要组成部分,可对森林经营及其带来的变化及时做出反应。为了探讨土壤动物对森林经营措施的响应,归纳总结了森林经营理念的发展以及森林经营对土壤动物影响的文献资料。结果表明森林经营主要通过对地上结构和微环境的改变对地下土壤动物的群落组成、分解功能及生物指示功能等方面产生影响。在今后研究中应加强森林经营对土壤动物连续长期的动态影响研究,同时利用现代研究技术与方法深入探讨森林经营对土壤动物影响的机制研究。     

Yield, growth and mortality rate of the Thai river sprat, Clupeichthys aesarnensis, in Sirinthorn Reservoir, Thailand

The Thai river sprat, Clupeichthys aesarnensis Wongratana, is a clupeid with a short life span, and supports artisanal fisheries in a number of reservoirs in the Mekong Basin. The growth parameters, mortality rates and the status of the Thai river sprat in Sirinthorn Reservoir (28 800 ha), NE Thailand (15°N; 105°E), are presented. The fishery is based on lured lift‐nets, operated 7–14 days in the new moon period, September to April each year. It was shown that the von Bertalanffy growth function (VBGF) model was L_t (mm) = 78.43[1 ? exp{?0.211[t ? (?0.7996)]}] and its growth conformed to an isometric pattern. Natural mortality rate (month^?1) was 0.13 month^?1. Total mortality rates ranged from 0.69 to 1.53 month^?1 depending on the weather and the fishing season. Recruitment was continuous throughout the year but peaked in June and July. The yield per recruit model indicated that the exploitation rate of this fishery is probably too high.     

Developing scoring functions for soil quality to assess land suitability for irrigated wheat in Southern Algeria

Efficient land-use management could be optimized through appropriate advice regarding land suitability and achieving a reasonable yield while preserving soil and environmental conditions. The main objective of this study was to determine and define those locations capable of wheat cultivation with irrigation in the municipality of N’goussa (Southern Algeria). Expert opinion (EO) method was used for selecting minimum soil data set (MDS_-EO), where six influencing soil properties (sand, pH, salinity, organic matter, gypsum and lime) and other three key parameters (slope, land use/land cover, and proximity to roads and electricity network) were considered important for irrigated wheat cultivation in the study area. Indicators were weighted according to principal component analysis (PCA) loadings and summed. PCA revealed that the selected nine indicators are appropriate for accounting 73.63% of the total variance. Two maps of land suitability were created here (expressed as a soil quality index within a range from 0 to 1) from multivariate analysis and already known standard scoring functions (SSFs) by using two data sets (pure and scored). The distribution of soil quality index (IQI) showed that above 70% of the land was moderately (MS) to highly suitable (HS) for irrigated wheat. The estimation accuracy of soil quality classes has been evaluated using random forests (RF), having as a dependent variable the final class of land suitability used in each map. It was determined that estimation accuracy could reach 60% (pure data set) and 65% (scored data set) at 0.5 cut-off value for soil quality classes. Final prioritizing according to ranks of sensitivity index (SI) and efficiency ratio (ER) showed that IQI obtained from scored data set is the most suitable approach in soil quality assessment of arid areas. Therefore, it could be applied in southern Algeria for land management, integrated planning and environmental assessments.