Neutron irradiation effects on AlGaN/GaN high electron mobility transistors

A1GaN/GaN high electron mobility transistors （HEMTs） were exposed to 1 MeV neutron irradiation at a neutron ftuence of 1 × 10^15 cm-2. The dc characteristics of the devices, such as the drain saturation current and the maximum transconductance, decreased after neutron irradiation. The gate leakage currents increased obviously after neutron irradiation. However, the rf characteristics, such as the cut-off frequency and the maximum frequency, were hardly affected by neutron irradiation. The A1GaN/GaN heterojunctions have been employed for the better understanding of the degradation mechanism. It is shown in the Hall measurements and capacitance voltage tests that the mobility and concentration of two-dimensional electron gas （2DEG） decreased after neutron irradiation. Tbere was no evidence of the full-width at half-maximum of X-ray diffraction （XRD） rocking curve changing after irradiation, so the dislocation was not influenced by neutron irradiation. It is concluded that the point defects induced in A1GaN and GaN by neutron irradiation are the dominant mechanisms responsible for performance degradations of A1GaN/GaN HEMT devices.

Entrance and Exit Defects During Coarse Pitch Orbital Drilling of Carbon Fiber Reinforced Plastic Plates

Formation of entrance and exit defects in coarse pitch orbital drilling(CPOD)of carbon fiber reinforced plastic(CFRP)plates was investigated.Deep observation on entrance and exit morphology shows tear and burr are typical defects.Meanwhile,tear is more obvious than burr,and more entrance tears emerge than exit tears.As one of the major causes of entrance and exit defects in CPOD,cutting forces were substaintially studied by contrast experiments.Then,the effect of cutting parameters on entrance and exit tear was qualitatively analyzed through a single factor test.Experiment results indicate that the variation of rotation speed has little influence on entrance and exit tear.Increasing tangential feed per tooth can enlarge entrance tear,but bring little effect on exit tear.By increasing axial feed pitch,the hole entrance and exit show severe tear.When revolution radius grows bigger and bigger,entrance and exit tear firstly decreases,and then increases.Finally,the models of tear and delamination during CPOD of CFRP were established,the formation mechanisms of entrance and exit defects were revealed,and the control strategies were accordingly put forward.

Size effect of lattice material and minimum weight design

The size effects of microstructure of lattice materials on structural analysis and minimum weight design are studied with extented multiscale finite element method（EMsFEM） in the paper. With the same volume of base material and configuration, the structural displacement and maximum axial stress of micro-rod of lattice structures with different sizes of microstructure are analyzed and compared.It is pointed out that different from the traditional mathematical homogenization method, EMsFEM is suitable for analyzing the structures which is constituted with lattice materials and composed of quantities of finite-sized micro-rods.The minimum weight design of structures composed of lattice material is studied with downscaling calculation of EMsFEM under stress constraints of micro-rods. The optimal design results show that the weight of the structure increases with the decrease of the size of basic sub-unit cells. The paper presents a new approach for analysis and optimization of lattice materials in complex engineering constructions.

Variations of OCT measurements corrected for the magnification effect according to axial length and refractive error in children

Purpose:The aim of this paper was to examine the distribution of macular,retinal nerve fiber layer(RNFL)thickness and optic disc parameters of myopic and hyperopic eyes in comparison withemmetropic control eyes and to investigate their variation according to axial length(AL)andspherical equivalent(SE)in healthy children.Methods:This study included 293 pairs of eyes of 293children(145 boys and 148 girks),ranging in age from 6 to 17 years,Subjects were dividedaccording to SE in control(emmetropia,99 children),myopia(100 children)and hyperopia(94children)groups and according to axial AL in 68 short(<22.00 mm,68),medium(from≥22.00 mmto 25.00 mm,189)and long eyes(>25.00 mm,36).Macular parameters,RNFL thickness and opticdisc morphology were assessed by the Cirrus^(TM) HD-OCT.AL was measured using the IOL-Mastersystem.Littmann's formula was used for calculating the corrected AL-related ocular magnification.Results Mean age(±SD)was 10.84±3.05 years;mean(±SD)SE was+0.14±0.51 D(range from8.75 to+8.25 D)and mean AL(±SD)was 23.12±1.49.Average RNFL thickness,averagemacular thickness and macular volume decreased as AL and myopia increased.No correlationsbetween AL/SE and optic disc parameters were found after correcting for magnification effect.Conclusions:AL and refractive error affect measurements of macular and RNFL thickness inhealthy children.To make a correct interpretation of ocT measurements,ocular magnificationeffect should be taken into account by clinicians or OCT manufacturers.

A software reliability growth model for component-based software incorporating debugging delay and imperfect debugging

In view of the problems and the weaknesses of component-based software （ CBS ） reliability modeling and analysis, and a lack of consideration for real debugging circumstance of integration tes- ting, a CBS reliability process analysis model is proposed incorporating debugging time delay, im- perfect debugging and limited debugging resources. CBS integration testing is formulated as a multi- queue muhichannel and finite server queuing model （MMFSQM） to illustrate fault detection process （FDP） and fault correction process （FCP）. A unified FCP is sketched, given debugging delay, the diversities of faults processing and the limitations of debugging resources. Furthermore, the impacts of imperfect debugging on fault detection and correction are explicitly elaborated, and the expres- sions of the cumulative number of fault detected and corrected are illustrated. Finally, the results of numerical experiments verify the effectiveness and rationality of the proposed model. By comparison, the proposed model is superior to the other models. The proposed model is closer to real CBS testing process and facilitates software engineer＇ s quantitatively analyzing, measuring and predicting CBS reliability. K

Tunable Reflection Bands and Defect Modes in One-Dimensional Tilted Photonic Crystal Structure

We show theoretically that range of reflection bands and defect modes inside the band gap can be tuned by using a one-dimensional tilted photonic crystal (TPC) structure. A TPC structure is similar to the conventional PC structure with the only difference that in this case alternate layers are inclined at certain angle in the direction of periodicity of the structure. In order to obtain the reflectance spectra of the proposed structure transfer matrix method (TMM) has been employed. From the analysis of the reflectance curve, it is found that 100% reflectance range can be varied and enhanced by using TPC structure for both (TE- and TM-) polarizations. The enhancement in reflection bands increases as the tilt angle increases for both the polarizations and hence the enlarged omni-reflectance bands are obtained. Further, we study the properties of the defect modes in TPC structure by introducing the tilted defect at the different tilt angle. The results show that defect modes (tunneling modes) can be tuned at different wavelengths by changing the tilt angle of the structure without changing other parameters. Finally, the effect of variation thickness of defect layers on the tunneling mode has been studied for both TPC and conventional PC structure. The proposed model might be used as a tunable broadband omnidirectional reflector as well as tunable tunneling or transmission mode, which has potential applications in the field of photonics and optoelectronics.

2008年金融专业英语证书考试(FECT)通知

金融专业英语证书考试(Financial English Certificate Test)是我国第一个国家级的行业性外语证书考试。1994年中国人民银行和原国家教育委员会联合发文,批准在金融行业实施金融专业英语证书考试(FECT)制度。2008年金融专业英语证书综合考试(以下简称金融综合考试)和中级各科考试将于5月31日和6月1日进行。现将有关事项通知如下:

FECT—通向成功的阶梯

知识经济时代,组织的核心竞争力关键在于人才。随着我国金融业改革发展和对外开放的深入进行,提高从业人员自身素质成为当前金融机构人力资源管理中亟待解决的重要问题。

南酸枣多糖的体外抗氧化、降血糖与降血脂作用

以南酸枣多糖体积分数40%乙醇沉淀组分CAP-40为研究对象,初步评价其体外抗氧化、降血糖与降血脂作用。分别利用高效液相凝胶渗透色谱及高效液相离子色谱测定CAP-40的分子量与单糖组成,同时测定其对DPPH·和ABTS+·的清除率,α-葡萄糖苷酶和α-淀粉酶的抑制率,甘氨胆酸钠和牛磺胆酸钠的结合率以及胰脂肪酶的抑制率。结果表明,CAP-40的洗脱曲线为单一对称峰,分子量约156206 Da,单糖主要由葡萄糖、半乳糖醛酸、半乳糖、阿拉伯糖、鼠李糖组成,摩尔百分比分别为40.8%、40.7%、9.3%、5.1%、2.0%。CAP-40浓度为1 mg/mL时,对DPPH·和ABTS^(+)·的清除率分别为(88.85±0.49)%和(87.13±1.63)%。浓度为16 mg/mL时,CAP-40对α-葡萄糖苷酶的抑制率为(71.28±2.34)%;在8 mg/mL处,对α-淀粉酶的抑制率为(72.29±4.85)%。此外,浓度为20 mg/mL时,CAP-40对胰脂肪酶的抑制率为(26.34±1.41)%;在5 mg/mL处,对甘氨胆酸钠和牛磺胆酸钠的结合率分别达到(31.87±4.53)%和(38.98±0.60)%。综上所述,南酸枣多糖CAP-40具有一定的体外抗氧化、降血糖与降血脂作用,为开发天然降糖、降脂功能食品提供理论依据,也为南酸枣资源的综合开发利用提供新的思路。

产融结合的同群效应研究——来自A股上市公司的经验证据

已有关于产融结合的研究较少从同群效应视角考察。本文基于中国沪、深两市A股2008—2020年非平衡面板数据,重点探究产融结合同群效应的存在合理性、产生机制及可能造成的经济后果。研究发现,产融结合分别在深度和广度两方面存在显著的同群效应,采用同群企业股票特质收益率作为工具变量及多项稳健性检验,结果依然成立。领导企业的产融结合同群效应表现为“竞争动机”,追随企业的产融结合同群效应是出于“信息动机”。产融结合同群效应能够降低企业面临的风险,但是会提高社会层面的整体风险水平。本研究拓展了同群效应及产融结合影响因素的研究边界,为政府部门完善有关经济政策、企业制定产融结合决策提供了理论依据与经验证据。

Ce(NO_(3))_(3)和CeO_(2)纳米粒子对APTES膜耐腐蚀性的影响

目的通过对铜箔进行硅烷化处理,增强铜箔的耐腐蚀性能。方法采用化学浸泡法在9μm电解铜箔表面制备γ-氨丙基三乙氧基硅烷偶联剂(APTES)硅烷膜层、Ce^(3+)/APTES膜层、CeO_(2)/APTES膜层和Ce^(3+)/CeO_(2)/APTES膜层,对改性硅烷膜试样与空白试样进行接触角对照实验,对硅烷表面润湿性进行表征。在3.5%(质量分数)NaCl溶液中,对空白样、单一硅烷膜层、Ce^(3+)/APTES硅烷膜层和Ce^(3+)/CeO_(2)/APTES硅烷膜层进行浸泡实验和电化学实验,研究改性膜层前后的耐腐蚀性能。通过扫描电子显微镜(SEM)观察膜层表面形貌,并利用傅里叶变换红外光谱(FTIR)和X射线光电子能谱(XPS)对纳米粒子结构进行分析,探讨改性膜层的钝化机理。结果Ce(NO_(3))_(3)/CeO_(2)/APTES复合膜层的接触角最大,接触角为106.6°,表现出最佳的疏水性。同时,其表面的腐蚀坑数量和面积最小。在盐水浸泡和电化学实验中,各试样的腐蚀电流密度随着浸泡时间的延长而上升,Ce^(3+)/CeO_(2)/APTES试样的腐蚀电位发生正移,具有较低的腐蚀电流密度,并且该试样具有最高的相角和最高的阻抗值,远高于Ce^(3+)/APTES试样。结论与单一硅烷膜层和仅分别添加Ce(NO_(3))_(3)、CeO_(2)2种缓蚀剂的膜层相比,Ce(NO_(3))_(3)/CeO_(2)/APTES复合膜层的防护效果有明显提升,且Ce^(3+)与CeO_(2)之间的协同作用大大提高了硅烷膜层的耐腐蚀性能。

备孕女性BMI对IVF/ICSI-ET妊娠结局的影响

目的:探讨体外受精/卵胞质内单精子注射-胚胎移植(IVF/ICSI-ET)对不同体质指数(BMI)女性患者临床结局的影响。方法:回顾性分析2020年1月-2023年3月本中心生殖中心接受IVF/ICSI-ET治疗的女性患者临床资料,根据女性BMI分为低体质量组(BMI<18.5kg/m^(2))、正常体质量组(18.5kg/m^(2)≤BMI<24.9kg/m^(2))、超重组(BMI≥24.9kg/m^(2)),比较3组行IVF/ICSI-ET助孕临床结局,logistic回归分析影响IVF/ICSI-ET临床妊娠率和活产率相关影响因素。结果:3组不孕年限、BMI、Gn用量、不孕原因存在差异(P<0.05)。低体质量组(36%,31/86)、正常体质量组(39.8%,276/693)、超重组(43.2%,108/250)临床妊娠率无差异,流产率(16.1%,5/31)、(10.1%,28/276)、(38.0%,41/108)有差异(P<0.05),活产率(30.2%,26/86)、(34.8%,241/693)、(26.4%,66/250)有差异(P<0.05)。logistic多因素回归分析显示,BMI超重和Gn用量多是影响辅助生殖后临床妊娠的因素,Gn用量多是影响辅助生殖后妊娠活产的因素(均P<0.05)。结论:备孕女性行IVF治疗前,使BMI达到或接近正常,以改善IVF/ICSI-ET助孕的妊娠结局。

所有制变更对资产负债率的影响

本文以2012年以来沪深上市公司第一大股东股权性质在国有与非国有之间的转换作为事件的起因,以第一大股东持股比例、股权集中度作为协同变量,以股权性质未在国有与非国有之间发生转换的样本作为控制组,运用因果分析法中的FECT,考察资产负债率在转换前后的变化。研究结果表明:从非国有变为国有后,资产负债率在统计意义上显著增加。

饲料粮期货套期保值与规模生猪养殖主体生产稳定

我国生猪养殖规模化趋势明显,饲料粮期货为规模生猪养殖主体管理饲料粮价格风险、稳定生猪生产提供了金融工具。基于2013-2020年生猪上市公司的经营报告数据,使用双向固定效应模型,实证研究了饲料粮期货套期保值交易对规模生猪养殖主体的隐性与显性稳产作用,并检验了期货交易促进生产稳定的作用机制。研究结果表明:饲料粮期货套期保值交易有助于规模生猪养殖主体扩大生产,且随着生猪营收占比的增加,期货交易的扩产效应有所提高;期货交易有助于规模生猪养殖主体稳定出栏。机制分析结果表明,期货交易稳产的作用机制是降低了生猪养殖主体经营现金流的波动,稳定了收益。基于上述研究结论,从通过期货市场规避风险、金融知识普及、鼓励金融工具创新等方面提出了政策建议。

黄芪桂枝五物汤联合沙丁胺醇治疗缓慢性心律失常64例临床疗效及对动态心电图和心脏功能的影响

目的 探讨黄芪桂枝五物汤联合西药治疗缓慢性心律失常疗效及对病人动态心电图和心脏功能的影响。方法 选取2019年6月至2022年6月河北省沧州中西医结合医院收治的128例缓慢性心律失常病人,按随机数字表法分为对照组(64例)和观察组(64例),对照组给予口服沙丁胺醇片治疗,观察组在对照组的基础上给予黄芪桂枝五物汤治疗。比较两组病人治疗前后中医证候积分、动态心电图(最快心率、最慢心率、平均心率、QT间期、QRS间期、心率变异性相关指标)、心功能指标[心排血量(cardiac output,CO)、心脏指数(cardiac index,CI)、左室射血分数(left ventricular ejection fraction,LVEF)],比较两组病人治疗前、治疗1个月、治疗3个月的血压变化情况以及治疗后的临床疗效。结果 与治疗前比较,对照组和观察组治疗后的中医证候积分[(13.52±2.51)分比(19.54±3.47)分,(10.85±2.04)分比(19.23±3.26)分]、QT间期[(0.412±0.003)s比(0.445±0.003)s,(0.408±0.004)s比(0.446±0.004)s]、QRS间期[(0.09±0.05)s比(0.11±0.02)s,(0.07±0.03)s比(0.10±0.04)s]、正常窦性心律R-R间期标准差(SDNN)、全程相邻正常窦性心律R-R间期之差的均方根值(RMSSD)、正常窦性心律R-R间期平均值的标准差(SDANN)、在一定时间内相邻两正常心动周期差值>50 ms的个数所占的百分比(PNN50)均降低(P<0.05),且观察组更低(P<0.05);治疗后对照组和观察组最快心率[(74.56±3.98)次/分比(66.47±2.87)次/分,(83.23±4.68)次/分比(66.23±2.65)次/分]、最慢心率[(45.32±2.68)次/分比(40.23±1.74)次/分,(47.89±3.54)次/分比(40.46±1.89)次/分]、平均心率、CO、CI、LVEF均升高(P<0.05),且观察组更高(P<0.05);经重复测量方差分析,收缩压(SBP)、舒张压(DBP)在组间、时间及交互方面差异无统计学意义(P>0.05);观察组临床疗效(90.63%)高于对照组(76.56%)(P<0.05)。结论 采用黄芪桂枝五物汤联合西药应用于缓慢性心律失常病人,有利于其临床症状和心功能的改善,还可有效提高心率,具有较好的临床疗效。

数字经济与农业高质量发展:影响效应与作用路径

文章以2011-2020年中国31个省份的数据为研究样本,运用熵值法测算数字经济发展水平,以DEA方法测算的农业绿色全要素生产率来度量农业高质量发展水平,运用半参数面板数据模型实证分析了数字经济对中国农业高质量发展的影响及其异质性,并采用中介效应模型对农业生产技术效率和农业生产技术水平进行了作用路径检验。结果显示:2011-2020年,中国数字经济发展水平呈逐年递增趋势,但存在明显的地区差异,具体表现为从东部地区向中部和西部地区渐次降低。数字经济与农业高质量发展之间存在“倒U”型关系,拐点为0.60。异质性分析结果表明,数字经济对农业高质量发展的影响存在区域和时间上的异质性。作用路径分析发现,数字经济对农业高质量发展的影响主要是通过农业生产技术效率传导的。

FGH96高温变幅疲劳载荷试验及损伤累积模型研究

针对涡轮盘用镍基高温合金FGH96,开展两级疲劳载荷试验以及谱载荷试验。试验载荷设计参考了涡轮盘关键点载荷及实测飞行任务谱特征。采用常见损伤累积模型对试验结果进行分析。结果显示,FGH96在低-高载荷次序下循环分数和大于1,在高-低载荷次序下循环分数和小于1,符合常见非线性疲劳损伤累积模型的预期;对于谱载荷的疲劳寿命,由Chaboche非线性疲劳损伤模型与时间分数模型组成的损伤累积模型的预测则偏保守,且具有较高的预测精度,预测结果均在2倍偏差带内。

TurboFect介导骨形态发生蛋白2转染CHO细胞的研究

目的:构建真核表达载体p IRES-EGFP-BMP-2,通过Turbo Fect转染得到表达BMP-2蛋白的CHO细胞系。方法:利用逆转录PCR方法扩增获得人的BMP-2基因c DNA,克隆入p MD18-T载体,经PCR、酶切和基因测序分析等方法鉴定重组质粒;将BMP-2连入p IRES-EGFP真核表达载体中,经限制性酶切和PCR扩增鉴定重组质粒。以壳聚糖和Turbo Fect分别作为基因载体转染CHO细胞,荧光显微镜检测分析转染结果;G418筛选富集转染阳性细胞。结果:成功的克隆得到了BMP-2基因,酶切鉴定成功构建了p IRES-EGFP-BMP-2质粒。与壳聚糖组相比,Turbo Fect用量为1:1时,细胞阳性率为(31.92±1.31)%,高于壳聚糖的细胞阳性率(6.33±1.53)%。目的基因与Turbo Fect比例为1:2时转染效率为(42.90±1.10)%高于1:1的(28.59±2.38)%和1:3的(37.52±2.14)%。细胞密度调节到5×103 cells/cm2阳性细胞率可达到(44.43±3.23)%。荧光检测可见荧光阳性细胞得到稳定传代。Western Blot检测可见BMP-2蛋白表达。结论:Turbo Fect成功的介导了p IRES-EGFP-BMP-2载体转染CHO细胞,建立了稳定表达BMP-2和EGFP的CHO细胞株。