Effect of Gap Size on Coating Extrusion of Pb-GF Composite Wire by Theoretical Calculation and Experimental Investigation

A new method using lead coated glass fiber to produce continuous wire for battery grid of electric vehicles （EVs） and hybrid electric vehicles （HEVs） was introduced. Under equal flow, both the maximum and minimum theoretical value of gap size were studied and estimation equation was established. The experimental results show that the gap size is a key parameter for the continuous coating extrusion process. Its maximum value （Hmax） is 0.24 mm and the minimum one （Hmin） is 0.12mm. At a gap size of 0.18 mm, the maximum of metal extrusion per unit of time and optimal coating speed could be obtained.

Photosynthesis adaption in Korean pine to gap size and position within Populus davidiana forests in Xiaoxing’anling, China

Forest gaps restrict the restoration of temperate secondary forest to broad-leaved Korean pine forest in zonal climax vegetation by affecting the growth of Korean pine(Pinus koraiensis).However,the photo synthetic adaptability of Korean pine to gap size and position within the gap is unclear.In order to explore the adaptability of young Korean pine(35 years) to different gap sizes in Xiaoxing’anling,photo synthetic capacity and microenvironmental factors(leaf temperature,light transmittance) of Korean pine needles in three positions in the gap(central,transition,and edge areas) were investigated.Three gaps were identified in the secondary Populus davidiana forest:a large 201 m^(2) gap,a middle 112 m^(2) gap,and a small 50 m^(2) gap;12 m^(2) of the understory was sampled as a control.The results show that:(1) maximum net photosynthetic rate(P_(max)) in needles of Korean pine growing in the large gap was higher than in the small gap,and P_(max) in the centre in the same gap was higher than in the transition and edge areas;(2) light saturation point(LSP) and photosynthetic quantum yield(AQY)of needles in the large gap were higher than in the small gap,while the light compensation point(LCP) and chlorophyll contents of needles were lower in the small gap;and,(3)P_(max) had a significant positive correlation with temperature and light transmittance.It is suggested that the larger the gap in secondary Populus davidiana forests,the greater the change in light intensity and temperatures,the stronger the light adaption of Korean pine needles and the higher the photosynthetic capacity.Therefore,in the recovery of broadleaved/Korean pine forests,suitable gaps should be created and gap microhabitats fully utilized to accelerate the restoration process.

Optimization analysis on gap size of molding for Pb-GF composite wire

Under the condition of equal flow, the maximum and minimum theoretical values of gap size were studied and an estimation equation was established for the clad extrusion of the brittle core cladded by plastic metal materials. The results show that the gap size is a key parameter for the continuous clad extrusion and the molding speed. Its maximum value (Hmax) is 0.24mm and the minimum one (Hmin) is 0.12mm. At a gap size of 0.18mm, the maximum of metal extrusion per unit of time and the optimal coating speed can be obtained.

Natural regeneration in logging gaps of different sizes in Subri River Forest Reserve(Ghana)

Subri River Forest Reserve(SR)is the most extensive forest area in Ghana with an accompanying rich floral species.Over the years,logging from both legally prescribed and illegal operations remain the predominant forest disturbance in SR.Gap creation following logging is crucial in determining tree species composition and diversity.Hence,the study evaluated the composition and diversity of naturally regenerated tree species in logging gaps of different sizes and,again examined the roles of these tree species in fulfilling the economic and ecological agenda of sustainable forest management after logging in SR.Twelve gaps were randomly selected:4 each were grouped into small size(≤200 m^(2)),medium size(201–300 m^(2)),and large size(≥300 m^(2)).Data were gathered from 1 m^(2) circular area at gap centres and repeatedly inside 1 m width strip along 20 m individual N-S-E-W transects.Species diversity differed significantly between gap sizes.Higher diversity indices were measured in large size gaps.Gap sizes shared similar species.There were significant differences among various height groupings of tree species across all three gap sizes.Pioneers preferred medium to large size gaps,while shadetolerant tree species preferred small size gaps for their abundance.Vulnerable and Lower Risk Near Threatened tree species under Conservation Status and,Premium and Commercial tree species under Utilisation Status preferred small size gaps for their proliferation and conservation.Therefore,we recommend the single tree-based selective logging for ensuring creations of small to medium size(200–300 m^(2))gaps through adjustments to the logging permit process,revision of Allocation Quota Permit,strict adherence to the 40-year polycyclic selection system,along with more dedicated enforcement and monitoring.Changes along these protocols would tremendously facilitate natural regeneration of different suites of timber species resulting in the improvement of the overall biodiversity conservation associated with the forest,more sustainable forest harvests and more income to those who receive permits.

Contribution of soil fauna to the degradation of recalcitrant components in Cinnamomum camphora foliar litter in different-sized gaps in Pinus massoniana plantations

Forest gaps are important in forest dynamics and management, but little is known about how soil fauna influence the degradation of recalcitrant litter components in different-sized forest gaps. This investigation uses litterbags with two different mesh sizes (0.04 and 3 mm) to control the meso- and microfauna entering the bags to quantify the contribution of soil fauna to the degradation of recalcitrant components (including condensed tannins, total phenol, lignin and cellulose) during litter decomposition. The experiment was conducted in seven different forest gap sizes in Pinus massoniana plantations over 1 year. One closed-canopy site (CC) and forest gap sizes of 100, 225, 400, 625, 900, 1225 and 1600 m^2 were created in a P. massoniana plantation in the Sichuan basin of China;the CC was treated as the control. Cinnamomum camphora foliage from local native trees was used in all forest gap experiments. We found the following:(1) Gap size had significant effects on the degradation rates (E) of condensed tannins and lignin and on the contributions of soil fauna;medium-sized gaps also presented high degradation rates. Soil fauna obviously contributed to the degradation of recalcitrant foliar litter components in medium-sized gaps.(2) The highest contribution to degradation (40.98%) was recorded for lignin, and the lowest contribution (0.29%) was recorded for condensed tannins. The results indicate that medium-sized gaps (900 m^2) were conducive to the degradation of recalcitrant litter components by soil fauna.

GAP/PET/RDX基推进剂的动态冲击及点火响应行为

针对含不同粒度环三亚甲基三硝胺(RDX)的叠氮缩水甘油醚(GAP)推进剂和聚对苯二甲酸乙二醇酯(PET)推进剂,利用分离式霍普金森压杆装置开展高应变率(1000~6000s^(-1))动态冲击实验,同时结合高速摄影和数字全息光学测量技术,采用3台高速摄像机同步观测推进剂在撞击条件下损伤演化、点火响应和能量增长过程。结果表明,GAP基推进剂在高应变率压缩下的强度极限较PET基推进剂最大提升了一倍,弹性模量在不同应变率下均提升了一倍以上;中等粒度RDX较粗粒度RDX推进剂的强度极限最大提升了80%,弹性模量最大提升了148%;此外,GAP基推进剂较PET基推进剂、粗粒度较中粒度推进剂在高应变率压缩条件下更易点火,但中粒度推进剂的燃烧反应较粗粒度更加剧烈和完全。

Effects of gaps on regeneration of woody plants: a meta-analysis

Forest gaps, openings in the canopy caused by death of one or more trees, have a profound effect on forest regeneration and drive the forest growth cycle. It is therefore necessary to understand the effects of forest gaps on regeneration for modern forest management. In order to provide a quantitative assessment of the effects of forest gaps on regen-eration of woody plants, we conducted this review of gap effects on woody plant regeneration on the basis of 527 observations from 42 indi-vidual papers, and reported the results of these data in a meta-analysis. Overall, densities of regenerated woody plants were significantly greater （359%） in forest gaps than on the closed-canopy forest floor. The regen-eration density in gaps of plantation forests was significantly greater （P＆lt;0.05） than that of natural forest because the regeneration in gaps of plan-tation forests was improved by both gap effects and experimental meas-ures. Similarly, in comparison to natural gaps, regeneration was better enhanced in artificial gaps. Regeneration density exhibited a significantly positive correlation with gap size, but a negative correlation with gap age because the gap size decreased with increasing gap age. Shade tolerance of woody plants affected regeneration density in gaps and understory. Average regeneration density of shade-tolerant species exhibited a sig-nificantly positive response to gaps but densities remained lower in total than those of intermediate and shade-intolerant species. Gap effects on regeneration decreased in response to increasing temperature and pre-cipitation because of the limiting effects of lower temperature and moisture on woody plant regeneration. In summary, forest gaps enhance woody plant regeneration, and the effects of gaps varied by forest type, gap characteristics, environmental factors and plant traits. The results of this meta-analysis are useful for better understanding the effects and roles of gaps on forest regeneration and forest management.

基于Ansys取能电流互感器铁心气隙仿真分析

针对取能电流互感器存在的启动电流大、铁心易饱和、无法适应较宽的输电线路电流等问题,对铁心部分进行设计与改进。依据初始磁导率、饱和磁通密度、铁心损耗以及成本等参数确定铁心材料,从铁心的选材上进行预处理;利用Ansys软件对铁心气隙形状进行设计并仿真,通过铁心在不同气隙形状下的磁泄露情况得出矩形半开口效果最优;采用控制变量法对气隙尺寸进行仿真,对铁心气隙尺寸进行了定量的分析,并对比分析了铁心的饱和特性以及二次侧输出功率情况,为电流互感器取能电源铁心的结构设计和参数的实际选取提供了良好的工程价值。

GAP改性单基球形药的表征

采用内溶法制备了由聚叠氮缩水甘油醚(GAP)改性的单基球形药,用扫描电子显微镜(SEM)、假密度测定器、激光粒度仪和傅里叶变换红外(FT-IR)对GAP改性单基球形药进行表征。结果表明,所制得的GAP改性单基球形药圆球率较高,颗粒间无粘结,流散性好;在驱溶时采取缓慢升高真空度和温度的方法可制得较好的GAP改性单基球形药,驱溶时间从10min增长至60min时,假密度从0.5467g/cm3增大至0.8315g/cm3,适宜的驱溶时间为40～50min;搅拌速度从700r/min提高至1 500r/min时,GAP改性单基球形药的中位粒径d50从134.53μm减小至59.80μm,适宜的搅拌速度为1 000～1 500r/min。

HNIW/GAP混合物燃速的实验研究与数值模拟

制备了HNIW/GAP二元混合物,在6～15MPa压强范围测试了其静态燃速,研究了HNIW含量和压强对混合物燃速的影响;分析了HNIW粒径与预热层厚度对HNIW/GAP混合物燃速的影响规律;基于Relay-Race模型对燃速进行了模拟;分析了燃速控制机理,并采用DSC对HNIW/GAP混合物进行了热分析研究。结果表明,Relay-Race模型可以预测HNIW低含量时的部分燃速,在6～9MPa下,混合物燃速随HNIW含量的增加而增大,在12～15MPa下,混合物燃速随HNIW含量增加先减小后增大;在压强低于约0.2MPa下,粒径62μm的HNIW颗粒低于预热层厚度,不经历自持燃烧,增大HNIW粒径可以促进混合物燃烧;在HNIW与GAP质量比为1∶1条件下,模拟的燃速增幅会随着粒径的增大而减小。当HNIW质量分数在0～30%时,混合物燃烧过程的反应控制区域由GAP转移至HNIW燃烧区域,从而导致燃速变化。

农村中小金融机构发展对城乡收入差距的影响效应研究

缩小城乡收入差距,实现城乡融合发展的关键在于实现农业农村优先发展。在坚持“金融机构的属性特征和数量分布对资金规模和供给流向具有重要影响”的基础上,文章基于2008—2021年中国省级面板数据实证检验农村中小金融机构发展对城乡收入差距的影响。结果发现,不同于以往大多数关于农村金融发展扩大城乡收入差距的结论,以农村每万人拥有的中小银行网点数衡量的农村中小金融机构发展显著缩小城乡收入差距。该作用在经过一系列内生性及稳健性检验后依然成立。对该作用的机制分析和检验表明,农村中小金融机构通过增加第一产业增加值、提高农业生产率和促进农村中小企业发展三个渠道对城乡收入差距起到缩小作用。这一研究发现深化了金融发展理论,为金融市场体制改革提供了一定理论依据,有利于从全新的角度理解城乡收入差距的影响因素,对经济高质量发展和收入分配状况的改善亦具有重要参考价值。

Effect of size on characteristic of acoustic emission in rock specimen

A series of uniaxial-compression tests were conducted on some granite speci- mens.A multi-channel,high-speed AE signal acquiring and analyzing system was em- ployed to acquire and record the characteristics of AE events and demonstrate the tem- poral and spatial distribution of these events during the failure process.The test results show that in the primary stage,many low amplitude AE events are developed rapidly and distributed randomly throughout the entire specimens.In the second stage,the number of AE increases much slower than that in the first stage,while the amplitude of most AE events became greater.Contrarily to the primary stage,AE events clusteres in the middle area of the specimen and distributes vertically conformed to the orientation of compres- sion.The most distinct characteristic of this stage is a vacant gap formed approximately in the central part of the specimen.In the last stage,the number of AE events increases sharply and their magnitude increases accordingly.The final failure location coincidently inhabited the aforementioned gap.The main conclusion is that most macrocracks are de- veloped from the surrounding microcracks existed earlier and their positions occupy the earlier formed gaps,and the AE activity usually becomes quite acute before the main rup- ture occurs.

Acoustic beam splitting in a sonic crystal around a directional band gap

Beam splitting upon refraction in a triangular sonic crystal composed of aluminum cylinders in air is experimentally and numerically demonstrated to occur due to finite source size, which facilitates circumvention of a directional band gap. Experiments reveal that two distinct beams emerge at crystal output, in agreement with the numerical results obtained through the finite-element method. Beam splitting occurs at sufficiently-small source sizes comparable to lattice periodicity determined by the spatial gap width in reciprocal space. Split beams propagate in equal amplitude, whereas beam splitting is destructed for oblique incidence above a critical incidence angle.

Modification of Optical Band-Gap of Si Films After Ion Irradiation

Amorphous silicon （a-Si）, nanocrystalline silicon （nc-Si） and hydrogenated nanocrys- talline silicon （nc-Si：H） films were fabricated by using chemical vapor deposition （CVD） system. The a-Si and nc-Si thin films were irradiated with 94 MeV Xe-ions at fluences of 1.0 × 10^11 ions/cm2, 1.0 × 10^12 ions/cm^2 and 1.0 × 10^13 ions/era2 at room temperature （RT）. The nc-Si：H films were irradiated with 9 MeV Xe-ions at 1.0 ×10^12 Xe/cm^2, 1.0 × 10^13 Xe/cm2 and 1.0×10^14 Xe/cm2 at RT. For comparison, mono-crystalline silicon （c-Si） samples were also irradiated at RT with 94 MeV Xe-ions. All samples were analyzed by using an UV/VIS/NIR spectrometer and an X-ray powder diffractometer. Variations of the optical band-gap （Eg） and grain size （D） versus the irradiation fluence were investigated systematically. The obtained results showed that the optical band-gaps and grain size of the thin films changed dramatically whereas no observable change was found in c-Si samples after Xe-ion irradiation. Possible mechanism underlying the modification of silicon thin films was briefly discussed.

华西雨屏带马尾松人工林林窗大小对植物多样性与土壤理化性质的影响

【目的】旨在揭示马尾松人工林不同林窗大小下植物多样性与土壤理化性质之间的关系。【方法】以25年树龄的马尾松人工林内5种不同大小林窗(50~100、100~150、200~250、400~450、600~650 m^(2))为研究对象,以马尾松纯林为对照(CK),调查分析不同林窗下植被组成、物种多样性和土壤理化性质;使用冗余分析(RDA)研究了土壤因子与植物多样性的关系。【结果】(1)不同林窗内枹栎、青榨槭、柃木和野桐等乡土树种的重要值均位于前列;随着林窗面积的增加,耐荫物种数呈上升趋势,半耐荫物种数趋势平稳且占据重要地位。(2)G4(400~450 m^(2))林窗面积下呈最高的物种多样性,灌木层的物种丰富度和多样性与土壤理化性质存在极强正相关关系。(3)在G4林窗下土壤全钾(45.41 mg/kg)、速效钾(191.29 mg/kg)和有机质(68.42 mg/kg)的含量达到最高,速效钾含量显著高于其余林窗(P<0.05);土壤有机质、全氮和全钾是影响马尾松人工林林窗下植物分布的主要环境因子。【结论】G4林窗(400~450 m^(2))最有利于此地区植物群落的更新组成和土壤养分循环。

GAP高能推进剂体积开裂尺寸效应

以体积开裂试验和热失重试验数据为基础,结合有限元热分析模块计算药柱中气体的累积规律,研究了GAP高能推进剂体积开裂的尺寸效应。结果表明,GAP高能推进剂产气过程为零级反应扩散方程,密封与敞开条件对体积开裂结果影响不明显;体积开裂时间受样品边长影响明显,边长越长即尺寸越大,发生体积开裂时间越短,样品边长与体积开裂时间呈指数衰减关系。可采用小尺寸样品体积开裂试验建立体积开裂时间与药柱边长指数衰减方程,为预测大型发动机药柱体积开裂时间提供参考。

海滩也缺乏砂-砾过渡粒级的沉积物

沉积物的粒度是最重要的沉积物参数之一,在河床中,表层沉积物缺乏砂–砾过渡粒级(即1~10 mm)的沉积物,被称为Grain size gap,得到广泛关注。海滩沉积物是否也是如此,是一个基本而又未知的问题。本文分析了中外228处海滩共456个表层沉积物平均粒径数据,发现海滩大概率或是平均粒径几十毫米的砾石滩,或是平均粒径几百微米的砂滩,也缺乏砂–砾过渡粒级沉积物,其粒度范围是−3.5~−1ϕ(2~11 mm),这一结果和河床的情况基本相同。造成砂–砾过渡粒级缺乏的原因应从物源、颗粒磨损和分选以及广义的物质收支分析中去寻找。

长三角城市群高质量城镇化进程中的工资差距研究

长三角城市群正由快速城镇化向高质量城镇化演进,其中的劳动力由同质性集聚向异质性集聚转变如何影响城市间工资差距和共同富裕?通过理论模型和计量检验,研究阐释城市规模、市场潜力和高技能劳动力比重对长三角城市工资收入的影响,结果发现:人口规模和市场潜力对中小城市的名义工资有显著促进作用,而大城市的名义工资主要表现为高技能劳动力的工资溢价,人口规模和市场潜力的作用不明显;对于真实工资,城市规模、市场潜力和高技能劳动力的工资溢价影响都不显著。这表明长三角城市群初步实现空间一般均衡,正进入高质量城镇化和共同富裕的发展阶段。

海拔2200m地区正极性操作冲击下大尺寸球–板间隙放电转化特性

在我国中西部海拔超2000m地区,曲率半径达0.25~1m的屏蔽球金具在特高压直流输电换流站阀厅中应用广泛,其与地面、墙壁形成的球–板间隙直接影响整个输电系统的绝缘安全及经济成本,因此研究高海拔地区大尺寸球–板长间隙放电转化特性具有重要的理论意义和工程价值。该文在海拔2200m的青海特高压试验基地开展3m间隙距离下,曲率半径为0.30、0.65、0.80m的球–板间隙正极性操作冲击放电试验;对比分析3种电极结构各放电阶段的瞬时光功率、空间电场强度、高电位电流等光电特征物理参量;计算其初始流注注入电荷量、电场强度空间分布、初始流注长度、流注茎温度等物理特征值;研究间隙结构对大尺寸电极放电转化特性的影响。结果表明:间隙距离一致,球电极曲率半径越大时,初始流注长度越长、产生空间电荷量越多、流注茎温度上升速率越快、流注逐渐成为放电过程的主导。研究结果可为今后高海拔地区换流站阀厅选择合适的屏蔽结构、有效增强间隙操作冲击绝缘水平及减小设备尺寸等提供参考。

高管团队薪酬差距、投资效率与企业全要素生产率

基于社会比较理论与委托代理理论,从投资效率角度切入,研究高管团队水平薪酬差距对企业全要素生产率的影响及传导机制。研究发现:高管团队水平薪酬差距的拉大,会导致全要素生产率降低。作用机制表明,非效率投资在两者间发挥中介作用。进一步区分投资不足与投资过度后发现,高管团队水平薪酬差距主要通过投资过度路径对企业全要素生产率产生负面影响。企业异质性发现,在较大规模董事会的企业和非国有企业中,高管团队水平薪酬差距对全要素生产率的负面影响更为严重。研究结论为改善企业治理结构提供了相关经验证据。