大孔吸附树脂柱色谱法分离纯化重楼皂苷过程中的质量控制与评价

以重楼根茎粉末为原料,加热回流提取粗皂苷后,用近红外在线检测AB-8大孔吸附树脂除杂和洗脱分离的全过程,并以近红外光谱判别变量为表征手段,将分离过程分为四个阶段。分别对每个阶段收集的洗脱液进行比色和水解,通过离线的紫外光谱和高效液相色谱分析,结果显示,用70%的乙醇对大孔吸附树脂中除杂以后的重楼总皂苷进行洗脱,基本能将重楼总皂苷分为几类有效组分群。     

职业院校经济专业高等数学教学改革模式探析

职业院校经济专业高等数学教学具有其自身的特点，教学改革要从教材的编写、教学手段的更新和考核方法的调整等方面进行．     

A 155 Mbps laser diode driver with automatic power and extinction ratio control

An integrated laser diode driver(LDD) driving an edge-emitting laser diode was designed and fabricated by 0.35 μm BiCMOS technology. This paper proposes a scheme which combines the automatic power control loop and temperature com-pensation for modulation current in order to maintain constant extinction ratio and average optical power. To implement tem-perature compensation for modulation current,a novel circuit which generates a PTAT current by using the injecting base current of a bipolar transistor in saturation region,and alternates the amplifier feedback loop(closed or not) to control the state of the current path is presented. Simulation results showed that programmed by choice of external resistors,the IC can provide modu-lation current from 5 mA to 85 mA with temperature compensation adjustments and independent bias current from 4 mA to 100 mA. Optical test results showed that clear eye-diagrams can be obtained at 155 Mbps,with the output optical power being nearly constant,and the variation of extinction ratio being lower than 0.7 dB.     

The limit analysis in soil and rock： a mature discipline of geomechanics

The solution of a slope stability problem can be approached by its least upper-bound and maximum lower-bound with high accuracy. The limit equilibrium methods that employ vertical slices imply a lower bound of the factor of safety. It has been successfully extended to the area of active earth pressure analysis that accounts for different input of locations of earth pressure applications. Those methods that employ slices with inclined interfaces give an upper-bound approach to the stability analysis. It enjoys a sound mechanical background and is able to provide accurate solutions of soil plasticity. It has been successfully extended to the area of bearing capacity analysis in which various empirical coefficients are no longer necessary. The 3D upper- and lower-bound methods under this framework have been made possible and show great potential for solving various engineering problems.     

高等数学中极限概念教学的思考

学生学习极限概念困难的表现主要为：对极限概念存在理解上的问题，在极限概念使用中出现种种不足甚至错误；产生学习困难的原因主要有：极限概念本身的问题和学生的思维特点问题；极限概念教学的主要对策有：在极限教学中融入极限发展的历史，作好铺垫导入；加强语言逻辑结构层次的分析与引导；根据类比迁移原理，适当调整教材中有关极限内容的结构顺序。     

乡村民主的困境和现实出路

村民自治从产生到制度化,对农村的社会生活各方面都带来了巨大的影响。但是,任何制度都离不开现实基层的制约。当前村民自治所依赖的经济、政治、文化条件和历史传统都制约了它发挥自身的优势。因此,必须深化改革,使民主铭刻于乡村社会的内心。     

副词性确认标记词“有”的用法（下）

作为副词，“有”可以和副词、体标记、时间词、形容词等连用，也可以单独运用。通过“有”的运用，进一步验证了将“有”定位作“副词性确认标记词”的准确性。     

《说文解字》“心”部字的文化阐释

《说文解字》的“心”部字在一定程度上反映了汉民族的思想文化传统。通过对“心”与思维、情感的关系以及古代哲学对“心”认识的阐释,我们可以管窥中华思想的独特性与传承性。     

Influences affecting the soil-water characteristic curve

INTRODUCTION The soil-water characteristic curve (SWCC) gives the relationship between the amount of water in the soil (i.e. gravimetric or volumetric water content) and soil suction (i.e. matric suction at low suction and total suction at high suction). Many properties of a partially saturated soil such as the coefficient of permeability, shear strength and volume strain, pore size distribution, the amount of water contained in the pores at any suction, can be obtained from the SWCC. …     

New mode of universal access and Global Memory Net

INTRODUCTION During 1998~2002, I was privileged to serve as a member of the US President’s Information Technol- ogy Advisory Committee (PITAC), and all members were deeply involved in the drafting of several PITAC Reports to the President. The one related to digital libraries was the 2001 Report of the PITAC Digital Library Panel, entitled Digital Libraries: Universal Access to Human Knowledge (PITAC, 2001). It offers an ambitious vision: “All citizens anywhere anytime c…