Enantiomer separation by CEC——Enantiomer separation by packed-capillary electrochromatography

Three chiral compounds were successfully separated in a short time with two enantiomer separation models on packed-capillary electrochromatography (CEC). (i) 75 μm I.D. capillaries were packed with 5 μm β-cyclodextrin (β-CD) chiral stationary phase (CSP). Effects of voltage, pH and concentration of organic modifier on electroosmotic flow (EOF) and chiral separations were investigated systematically. Enantiomers of a neutral compound (benzoin) and a neutral drug (mephenytoin) were separated within a short time with high efficiency. Efficiency of 32 000 theoretical plates per meter and resolution (R_s) of 1.42 were achieved for enantiomers of benzoin using a βCD packed column with 6.2 cm packed length. Efficiency of 45 000 theoretical plates per meter and R_s of 3.40 were obtained for enantiomers of mephenytoin. Especially, the enantiomer separation of mephenytion was performed in just 3.4 min with R_s of 2.60. (ⅱ) 75 μm I.D. capillary was packed with octadecylsilica particles (ODS). Chiral separat     

全国功率超声会议在无锡召开

１９９９年全国功率超声会议于１９９９年１０月１９日至２１日在江苏省无锡市召开．本次会议是近几年会议中规模较大的一次,全国近４０个单位、团体的约６０名代表出席了会议．会议开得较活泼．除论文报告交流外,会议组织了专题讨论会。会议期间,功率超声分会召开了全体委员会会议,有 ８０％以上的委员出席了会议．中国声学学会名誉理事长、中国科学院资深院士应崇福先生专程出席了本次会议。 功率超声是超声学的一大分支,功率超声技术是一项应用广泛的高新技术。当前,功率超声的应用领域已经扩展和渗透到机械、材料、石油、化工、纺…     

纳米氧化锌的合成及表面改性

以硫酸锌、尿素为原料,采用均相沉淀法合成了纳米氧化锌.研究了硬脂酸对所制的纳米氧化锌粉体表面改性的机理及其对粉体亲油性的影响.实验结果表明,硬脂酸中的羧基与纳米氧化锌粉体颗粒表面的羟基发生了酯化反应,并在表面形成单分子膜.经过表面改性的纳米氧化锌由亲水性转化为亲油性.同时,就纳米氧化锌粉体硬脂酸表面改性反应,探讨了反应摩尔分数、反应温度和反应时间对产物的影响,从而筛选出粉体亲油性最大的反应条件为:硬脂酸质量分数为7%;反应温度为50℃;反应时间为1h.     

模压条件对聚乙烯/碳黑PTC复合材料电阻特性的影响

聚合物基PIE(Positive Temperature Coefficient)复合材料的主要组成为聚合物基体及导电填料,具有室温电阻率低、质软、易加工成形、价格低廉等优点,在医疗、计算机、程控电话交换机、手机电池、汽车配件、家电产品、工业仪表、运载火箭、火灾报警等领域得到了广泛的应用。我们     

An improved effective liquid drop model for cluster radioactivity

The effective liquid drop model(ELDM) is improved by introducing an accurate nuclear charge radius formula and an analytic expression for assaulting frequency. Within the improved effective liquid drop model(IMELDM), the experimental cluster radioactivity half-lives of the trans-lead region are calculated. It is shown that the accuracy of the IMELDM is improved compared with that of the ELDM. At last, the cluster radioactivity half-lives that are experimentally unavailable for the trans-lead nuc...     

新型冠状病毒感染疫情下公众心理健康及影响因素研究进展

新型冠状病毒感染疫情是重大突发公共卫生事件,对全球公共心理健康产生了深远影响.本文对公众心理健康状况、影响心理健康水平的疫情因素(新型冠状病毒感染、隔离、失业和其他应激源)以及个人因素(青少年、女性、医护人员和既往有躯体/精神疾病史)进行综述,并从个人、社会、国家层面分析改善公众心理健康的对策,为应对疫情的长期影响提供参考.     

Direct Microwave Synthesis of 11-Type Fe(Te,Se) Polycrystalline Superconductors with Enhanced Critical Current Density

We report a direct microwave synthesis method for the preparation of 11-type high quality Fe(Te,Se) polycrystalline superconductors. The bulk samples are rapidly synthesized under the microwave irradiation during several minutes, with a subsequent annealing process at 400℃. The samples exhibit a nearly single phase of the tetragonal PbO-type crystal structure with minor impurities. Morphology characterization shows high density, tight grain connectivity and large grain sizes around 100 μm with small cavities inside the sample. Resistivity and magnetization measurements both show similar superconducting transitions above 14 K. The magnetic hysteresis measurements display broad and symmetric loops without magnetic background, and a high critical current density J_c about 1.2 × 10~4 A/cm~2 at 2 K and 7 T is estimated by the Bean model. Compared with the solidstate reaction synthesized samples, these superconducting bulks from microwave-assisted synthesis are possibly free of the interstitial Fe due to smaller c-axis, higher T_c in magnetic transitions, better M–H loops without magnetic background and greatly enhanced J_c, and are promising as raw materials for the non-toxic Fe-based superconducting wires for large currents and high field applications.     

环形正负电子对撞机:物理、技术以及现状

环形正负电子对撞机(CEPC)是中国高能物理学界提议建造的、下一代大型正负电子对撞机。CEPC不仅可作为Higgs粒子工厂而运行,也可产生海量的Z玻色子以及W玻色子,进而从Higgs物理、电弱精密测量、味物理和QCD等各个方面对粒子物理标准模型进行全面、细致的验证,并以此来揭示标准模型背后的物理规律。自倡议以来,我国高能物理学界对CEPC项目的物理潜力及其各项关键技术进行了积极的研究,并于2018年11月正式发布了CEPC的概念设计报告。这意味着CEPC项目的初步设计蓝图已经完成。文章在CEPC《概念设计报告》的基础上简介了其物理潜力及相关技术的研究进展。     

小长径比弹丸加装大展弦比尾翼的气动特性研究

为了提高小长径比弹丸射击质量,设计了一种大展弦比张开式尾翼,采用AUSM+格式、SST(shearstress transport)湍流模型和隐式算法(lower-upper symmetric Gauss-Seidel implicit method, LU-SGS),求解三维RANS 方程,对前体形状完全相同,不同展弦比的3 种尾翼弹进行了数值模拟,得到了三者在马赫数1.5~3.5 下的气动力特性的差异,分析其原因,并给出了不同展弦比张开式尾翼的适用范围. 计算结果表明:C型弹的升阻比较B 型弹在1.5 马赫数区域附近增加了7% 以上,当马赫数达到2.5 以上时,A 型弹的升阻比大于B 型弹和C 型弹,在3.5 马赫数区域附近A 型弹的升阻比较B 型弹增加了5.4% 以上. 3 种弹丸的俯仰力矩系数随着马赫数的增大而负向减少,且减少的趋势随着展弦比的增加而增大. A 型弹、B 型弹、C 型弹的静稳定裕度的变化范围分别为4%~20.3%,8.5%~23.2%,11.4%~25.6%.     

一种基于畸变等效曲面的图像畸变校正

介绍了一种图像畸变的等效曲面模型,用于修正由于光学系统或图像传感器产生的畸变。分析了球形畸变模型的原理,推导出基于球形模型的畸变校正公式,并给出了基于球形模型的畸变校正的具体实现方法,通过实验对这种畸变校正的效果进行了验证。这种曲面畸变模型的校正具有实现简单,不需求解方程组等优点,并可以推广到其他曲面,具有比较广泛的实用性。