通过费米能区重离子碰撞产额分布来研究16O原子核的团簇结构

近几年来,原子核核内的$\alpha$团簇结构引起了人们的广泛关注。本工作的目的是讨论在费米能区下重离子碰撞的碎片产额分布是否可以作为研究轻核中$\alpha$团簇结构的工具。本文基于扩展的量子分子动力学输运模型(EMQD)模拟了16O具有4种不同的初始化$\alpha$构型(长链型、风筝型、四方型以及正四面体型)的16O+16O反应,通过观察碎片产额多重数分布情况研究了具有不同结构的团簇核的核反应。计算结果表明,碰撞后产生的自由质子及4He的产额受不同构型的影响明显,表明4He/proton可以作为团簇结构的一个表征量。此外,自由质子及4He的出射$\theta$和$\phi$角及动能能谱可以用来提取16O的$\alpha$团簇构型信息。     

在椭圆教学中体现数学文化的几个案例

案例背景《普通高中数学课程标准》（实验）指出,数学是人类文化的重要组成部分．数学教学应当反映数学的历史、应用和发展趋势,数学对推动社会发展的作用,以及数学的社会需求,社会发展对数学自身的促进作用,数学的思想体系在人类文明史中的地位和作用,让学生了解数学的应用价值和人文价值．教师在教学中应结合有关内容有意识地强调数学的科学价值、文化价值、美学价值．在这个大背景下,我校数学组承担了市级教育规划课题：《文化视野下的高中数学教学探索》．本文记录了在椭圆教学中体现数学文化的几个案例．     

超声波提取-气相色谱法测定土壤中21种酚类化合物

建立了超声波提取-气相色谱法同时测定土壤中21种酚类化合物的分析方法。用二氯甲烷和正己烷混合溶剂提取土壤中的酚类化合物,提取液经碱性水溶液分配净化,去除非酸性有机杂质,再酸化萃取酚类化合物,浓缩后采用气相色谱-氢火焰离子化检测器进行检测,外标法定量。以10 g土壤样品计,酚类化合物的检出限为0.01~0.06 mg/kg。实际样品添加回收试验的回收率为62.9%~111.4%,相对标准偏差为4.3%~24.0%(n=6),准确度和精密度均较好。结果表明:该法操作方便,净化效果好,可用于土壤中多种酚类化合物的测定。     

Compound buried layer SOI high voltage device with a step buried oxide

A silicon-on-insulator (SOI) high performance lateral double-diffusion metal oxide semiconductor (LDMOS) on a compound buried layer (CBL) with a step buried oxide (SBO CBL SOI) is proposed.The step buried oxide locates holes in the top interface of the upper buried oxide (UBO) layer.Furthermore,holes with high density are collected in the interface between the polysilicon layer and the lower buried oxide (LBO) layer.Consequently,the electric fields in both the thin LBO and the thick UBO are enhanced by these holes,leading to an improved breakdown voltage.The breakdown voltage of the SBO CBL SOI LDMOS increases to 847 V from the 477 V of a conventional SOI with the same thicknesses of SOI layer and the buried oxide layer.Moreover,SBO CBL SOI can also reduce the self-heating effect.     

Partial-SOI high voltage P-channel LDMOS with interface accumulation holes

A new partial SOI (silion-on-insulator) (PSOI) high voltage P-channel LDMOS (lateral double-diffused metal-oxide semiconductor) with an interface hole islands (HI) layer is proposed and its breakdown characteristics are investigated theoretically. A high concentration of charges accumulate on the interface, whose density changes with the negative drain voltage, which increase the electric field (E_I) in the dielectric buried oxide layer (BOX) and modulate the electric field in drift region . This results in the enhancement of the breakdown voltage (BV). The values of E_I and BV of an HI PSOI with a 2-μm thick SOI layer over a 1-μm thick buried layer are 580V/μm and -582 V, respectively, compared with 81.5 V/μm and -123 V of a conventional PSOI. Furthermore, the Si window also alleviates the self-heating effect (SHE). Moreover, in comparison with the conventional device, the proposed device exhibits low on-resistance.     

Improvement on the breakdown voltage for silicon-on-insulator devices based on epitaxy-separation by implantation oxygen by a partial buried n~+-layer

A novel silicon-on-insulator (SOI) high-voltage device based on epitaxy-separation by implantation oxygen (SIMOX) with a partial buried n +-layer silicon-on-insulator (PBN SOI) is proposed in this paper.Based on the proposed expressions of the vertical interface electric field,the high concentration interface charges which are accumulated on the interface between top silicon layer and buried oxide layer (BOX) effectively enhance the electric field of the BOX (E_I),resulting in a high breakdown voltage (BV) for the device.For the same thicknesses of top silicon layer (10 μm) and BOX (0.375 μm),the E I and BV of PBN SOI are improved by 186.5% and 45.4% in comparison with those of the conventional SOI,respectively.     

焦炭特性及成分分析用标准物质的研制

介绍焦炭特性及成分分析用标准物质的研制过程。对标准物质进行了均匀性检验和稳定性考察,8家权威实验室用准确可靠的方法参与协作定值,确定了22个项目的标准值和扩展不确定度。粒度分析和成分分析结果表明该标准物质均匀性良好,在5年内性质稳定。     

Improvement on the breakdown voltage for silicon-on-insulator devices based on epitaxy-separation by implantation oxygen by a partial buried n+-layer

A novel silicon-on-insulator (SOI) high-voltage device based on epitaxy-separation by implantation oxygen (SIMOX) with a partial buried n⁺-layer silicon-on-insulator (PBN SOI) is proposed in this paper. Based on the proposed expressions of the vertical interface electric field, the high concentration interface charges which are accumulated on the interface between top silicon layer and buried oxide layer (BOX) effectively enhance the electric field of the BOX (E_I), resulting in a high breakdown voltage (BV) for the device. For the same thicknesses of top silicon layer (10 μm) and BOX (0.375 upmum), the E_I and BV of PBN SOI are improved by 186.5% and 45.4% in comparison with those of the conventional SOI, respectively.     

Novel high-voltage power device based on self-adaptive interface charge

This paper presents a novel high-voltage lateral double diffused metal--oxide semiconductor (LDMOS) with self-adaptive interface charge (SAC) layer and its physical model of the vertical interface electric field. The SAC can be self-adaptive to collect high concentration dynamic inversion holes, which effectively enhance the electric field of dielectric buried layer (E_I) and increase breakdown voltage (BV). The BV and E_I of SAC LDMOS increase to 612 V and 600 V/μm from 204 V and 90.7 V/μm of the conventional silicon-on-insulator, respectively. Moreover, enhancement factors of η which present the enhanced ability of interface charge on E_I are defined and analysed.