HMCM-56分子筛催化苯酚与异丙醇烷基化反应的研究

研究HMCM-56分子筛上苯酚与异丙醇烷基化反应,探讨了反应条件包括温度,原料配比,催化剂的装填量,空速对催化剂催化性能的影响．通过X射线衍射、研究催化剂的酸性及晶相．得到最佳反应条件：T=220℃,WHSV=3．0h^-1,Catalyst Loading=0．3g,n（IPA）／n（Phenol）=0．8,苯酚的转...     

公务卡实际应用问题对策研究

公务卡报销制度是现代信息化的标志,是电子政务化的必然结果,近几年应用过程中出现的诸多问题影响公务卡的发展。因此,针对目前公务卡应用中存在的问题进行了详细剖析,并从扩大宣传、改善用卡环境,完善公务卡银行服务体系,推动公务卡制度发展等方面提出了一些应对措施。     

《高师理科学刊》2006-2010年载文分析

采用文献计量的方法,对《高师理科学刊》2006-2010年的载文基本信息和作者情况进行统计分析.结果表明,5年出版28期共载文1 014篇,信息密度为4.83,出版时滞148 d,基金论文占38.46％,篇均引文数5.95;论文合著率62.92％;主要作者群为30～40岁的副高级职称和中级职称的研究人员.客观地反映出该...     

An integrated semiconductor device enabling non-optical genome sequencing

The seminal importance of DNA sequencing to the life sciences, biotechnology and medicine has driven the search for more scalable and lower-cost solutions. Here we describe a DNA sequencing technology in which scalable, low-cost semiconductor manufacturing techniques are used to make an integrated circuit able to directly perform non-optical DNA sequencing of genomes. Sequence data are obtained by directly sensing the ions produced by template-directed DNA polymerase synthesis using all-natural nucleotides on this massively parallel semiconductor-sensing device or ion chip. The ion chip contains ion-sensitive, field-effect transistor-based sensors in perfect register with 1.2 million wells, which provide confinement and allow parallel, simultaneous detection of independent sequencing reactions. Use of the most widely used technology for constructing integrated circuits, the complementary metal-oxide semiconductor (CMOS) process, allows for low-cost, large-scale production and scaling of the device to higher densities and larger array sizes. We show the performance of the system by sequencing three bacterial genomes, its robustness and scalability by producing ion chips with up to 10 times as many sensors and sequencing a human genome.     

Skin collagen fiber-based radar absorbing materials

By using skin collagen fiber (CF) as raw material,Schiff base structure containing CF (Sa-CF) was synthesized through CF-salicylaldehyde reaction.Then a novel radar absorbing material (Fe-Sa-CF) was prepared by chelating reaction between Sa-CF and Fe 3+.The coaxial transmission and reflection method was used to analyze the complex permittivity and complex magnetic permeability of these CF-based materials,and the radar cross section (RCS) method was used to investigate their radar absorbing properties in the frequency range of 1.0-18.0 GHz.Experimental results indicated that the conductivity of CF increased from initial 1.08×10-11 to 2.86×10-6 S/cm after being transferred into Fe-Sa-CF,and its dielectric loss tangent (tanδ) in the frequency range of 1.0-17.0 GHz also increased.These facts suggest that the Fe-Sa-CF is electric-loss type radar absorbing material.In the frequency range of 3.0-18.0 GHz,Sa-CF (1.0 mm in thickness) exhibited somewhat radar absorbing property with maximum radar reflection loss (RL) of-4.73 dB.As for Fe-Sa-CF,the absorbing bandwidth was broadened,and the absorbing intensity significantly increased in the frequency range of 1.0-18.0 GHz where a maximum radar RL of-9.23 dB was observed.In addition,the radar absorbing intensity of Fe-Sa-CF can be further improved by increasing membrane thickness.When the thickness reached to 2.0 mm,the RL values of Fe-Sa-CF were-15.0-18.0 dB in the frequency range of 7.0-18.0 GHz.Consequently,a kind of novel radar absorbing material can be prepared by chemical modification of collagen fiber,which is characterized by thin thickness,low density,broad absorption bandwidth and high absorption intensity.     

The effect of nanohybrid materials on the pour-point and viscosity depressing of waxy crude oil

The pipeline transportation of waxy crude oil is a problem both at home and abroad.In this paper,a novel nanohybrid pour-point depressant (PPD) was used to decrease the pour point and viscosity of waxy crude oil.The pour point and apparent viscosity of waxy crude oil was decreased significantly upon addition of the nanohybrid PPD,and the long-term stability of the nanohybrid PPD was superior to that of a conventional ethylene-vinyl acetate copolymer PPD.Polarized optical microscopy and X-ray diffraction were used to study the effect of the nanohybrid PPD on the crystallization of crude oil.Addition of the nanohybrid PPD reduced the amount of wax crystals,prevented their aggregation,and reduced the temperature at which the crude oil started to crystallize.The significant effect of this nanohybrid PPD on the pour point and viscosity depressing of crude oil is of great importance for facilitating the safe,efficient and energy-minimized transportation of waxy crude oil.     

基于Cacti与飞信的网络实时报警平台

针对在无人值守的情况下,如何将网络突发故障及时通知给网络管理人员以便快速响应的问题,提出了基于Cacti与飞信的网络实时故障报警平台.利用Cacti的SNMP信息轮询机制,实时获取当前网络中的设备故障与恢复信息,通过发送飞信的方式将故障信息传递到网络管理人员的手机终端.运行结果表明,网络管理人员排除故障时间大大缩短,管...     

北京市海淀公园绿地CO2通量变化特征

为了定量评估城市绿地吸收CO2改善城市生态环境的效果,2006年4月—2007年3月在北京海淀公园绿地使用涡度相关系统连续观测CO2通量、总辐射、大气温度,并使用冠层分析仪测量叶面积指数,研究CO2通量的变化及其影响因素.结果表明,绿地CO2通量受植被生物活动的影响呈现明显的季节变化特征,晴天天气状况下CO2通量日均值FCO2在4—10月为负值,绿地是CO2汇,在6—9月是CO2强吸收汇,FCO2约-0.100—-0.120mg/m2.s,而在11—3月FCO2为正值,绿地为CO2源,12—2月是CO2强排放源,FCO2约0.100mg/m2.s.绿地CO2通量受总辐射、LAI、大气温度的显著影响,净辐射的影响明显大于大气温度,净辐射越大、LAI越大、大气温度越高,绿地光合作用吸收CO2的能力越强.观测期间一年海淀公园绿地CO2的净吸收量约为615gCO2/m2.     

基于传播因子的分布式信源中心波达方向估计

采用传播因子估计分布式信源中心波达方向的算法,尤其是对于不相干分布式信源,利用泰勒级数将其方向向量进行一阶近似,得到形式上与点信源类似的分布式信源方向向量,再利用传播因子算法来估计其中心波达方向,有效地解决了角度扩散较小且角度信号密度不同的相干和不相干分布式信源中心波达方向估计问题.不仅计算简单,而且适用于多个分布式信源中心波达方向的估计.仿真实验验证了所提算法的有效性,与MUSIC算法相比,本文提出的算法有更好的信噪比性能.     

基于小波分析和集成学习的短时交通流预测

针对短时交通流具有随机性和不确定性等特征,提出一种基于小波分析和集成学习的组合预测模型.首先,对原始交通流数据的平均行程时间序列应用Mallat算法进行多尺度小波分解,且对各尺度上分量进行单支重构;其次,对于各重构的单支序列分别使用极端梯度提升模型(extreme gradient boosting,XGBoost)进...