响应曲面法优化无籽刺梨多酚提取工艺研究

文章采用三因素三水平的响应曲面分析方法优选了无籽刺梨多酚的提取工艺.结果表明,提取金刺梨多酚的最佳方案为:酒精浓度72%、固液比1:13、提取时间23 min,用此条件下提取实际测得的平均提取含量为1.8117%.     

公式拟合法计算乙醇水溶液的表面吸附量

建立了乙醇水溶液的表面张力σ与浓度c的关系，由此式求出（Dσ／Dc）r，再由吉布斯吸附公式计算各浓度的表面吸附量г。所求得的г随c的变化规律与文献吻合。     

Academic boredom,approaches to learning and the final-year degree outcomes of undergraduate students

Academic boredom is a largely negative and disabling achievement-related emotion. In this mixed-methods exploration of 224 students attending a single university in England, academic boredom was found to arise at the point of course delivery, while studying at other times and during the completion of assignments for assessment. Quantitative data from the recently adapted Boredom Proneness Scale for use across the UK higher education sector (the BPS-UKHE) and the Approaches and Study Skills Inventory for Students (ASSIST), enriched with qualitative data from 10 semi-structured research interviews, indicate that those with a higher propensity towards academic boredom than others displayed the deep, strategic and surface profiles of ‘less effective learners’. This was reflected in their interest in ideas, their ability to organise resources and manage time, what they had to memorise or do to ‘get by’, their achievement motivation and their sense of purpose. As part of a greater evolving network of other contributing factors, this translated into lower final degree marks and fewer ‘good’ degree awards. Recommendations surrounding boredom mitigation and approaches to learning are suggested which warrant serious consideration. The work presented here makes an important contribution to a surprisingly neglected field of UK higher education research and the student engagement agenda.     

Effect of Shock Wave on Fabricated Anti-Blast Wall and Distribution Law Around the Wall Under Near Surface Explosion

The loads of shock wave effect on fabricated anti-blast wall and distribution law around the wall were investigated by using near surface explosion test method and FEM.The pressure-time histories and variety law on the foreside and backside of the anti-blast wall were adopted in the tests of variety of different explosion distances and dynamites,as well as in the comparison between the test and numerical calculation.The test results show that the loads of shock wave effect on the anti-blast wall were essen-tially consistent with calculation results using criterion under surface explosion when explosion distances exceed 2 m,the distribution of overpressure behind wall was gained according to variety law based on small-large-small.It is also demonstrated that the peak overpressure behind wall had commonly appeared in wall height by 1.5--2.5 multiples,and the peak overpressures of protective building behind wall could be reduced effectively by using the fabricated anti-blast wall.     

Differential response of root morphology to potassium deficient stress among rice genotypes varying in potassium efficiency

Disparity in the root morphology of six rice (Oryza sativa L.) genotypes varying in potassium (K) efficiency was studied with three K levels: 5 mg/L (low),10 mg/L (moderate) and 40 mg/L (adequate) in hydroponic culture.Morphological parameters included root length,surface area,volume and count of lateral roots,as well as fine (diameter<0.2 mm) and thick (diameter>0.2 mm) roots.The results indicate that the root growth of all genotypes was reduced under low K,but moderate K deficiency increased the root length of the efficient genotypes.At deficient and moderate K levels,all the efficient rice genotypes developed more fine roots (diameter<0.2 mm) than the inefficient ones.Both fine root count and root surface area were found to be the best parameters to portray K stress in rice.In accordance with the root morphology,higher K concentrations were noted in shoots of the efficient genotypes when grown at moderate and deficient K levels,indicating that root morphology parameters are involved in root uptake for K and in the translocation of K up to shoots.K deficiency affected not only the root morphology,but also the root ultra-structure.The roots of high-efficient genotypes had stronger tolerance to K deficient stress for root membrane damage,and could maintain the developed root architecture to adapt to the low K growth medium.     

Electroless Co-Zn Surface-Modified Nickel Hydroxide as an Active Material for Pasted Nickel Electrodes

Rechargeablealkalinenickelbatteries (e.g.,Ni/Cd ,Ni/Fe,Ni/Zn,Ni/H2 andNi/MH)areusuallypos itivelimited ,sothatthecapacityandcyclelifeofthecellsaredeterminedmainlybytheperformancesofnickelelectrodes.Withtheirhighenergydensityandlowcostrelativetothatofconventionalsinterednickelelectrodes,pastednickelelectrodeshavenowbeenwidelyusedincommerciallyavailableNi/MHbatteries[1 ,2 ] .Asthedis charged stateactivematerialofthepastednickelelec trodes,thepropertyofsphericalnickelhydroxideisthekeytodeter…     

一种新型常温高效金属清洗剂

介绍了 MC常温高效水基金属清洗剂的构成、去污机理、研制过程、性能特点及其应用情况     

旋转二次曲面成像在物理教学中的应用研究

选择焦点和焦点参数为基本量，将几何光学中只研究球面成像，扩展到旋转二次曲面成像、研究了旋转二次曲面及其透镜的成像规律和成像质量等问题，展现了研制各种旋转二次曲面透镜的必要性，为光学仪器的改进和更新换代奠定了理论基础、将旋转二次曲面的成像理论引入了几何光学教学和新的几何光学教材中。从只研究球面成像扩展到整个旋转二次曲面，从而扩大了学生的知识面，培养了学生的科研能力和创造思维能力。     

An analytical model for predicting sheet springback after V-bending

INTRODUCTION As an important manufacturing method, bending has been widely used in modern industries to produce stamping parts such as frames, channels, braces, brackets and other structural parts. The understanding and development of bending mechanics are aimed at achieving two kinds of information which are very important for industrial production. One is to predict springback for dies design and compensation in order to obtain high dimension accuracy of bending parts. The other is to …     

引力场--有旋的张量场

天文观测表明，宇宙中数以亿万计的星系，绝大多数具有扁平的旋涡结构。在星系内部，绝大多数具有共面性和同向性，这不是偶然的，而是天体在力的作用下长期演化的结果。如果我们仍然把天体问的作用力还叫做引力，那么，引力就不再是个矢量，而是一个张量，引力场应是有旋的张量场。