mlsa-iai-msu-lab/ru_sci_bench_zho_cite_reranking huggingface dataset:
台风双眼墙形成及眼墙替换过程的研究进展

台风双眼墙受到大尺度环境场强迫(如垂直风切变和高空槽/急流等)、海气相互作用和涡旋内部热动力过程共同作用,双眼墙的形成及其演变一直是台风研究中的热点和难点.虽然学术界提出了许多双眼墙形成和眼墙替换的可能机制,但一直未达成共识,尤其在平衡和非平衡、对称与非对称过程对双眼墙形成的相对贡献,以及边界层超梯度风的作用等方面还存在许多争议.本文重点梳理过去十余年来,国内外台风双眼墙统计特征、形成机制和演变机理等方面的发展现状及最新研究进展,讨论分析双眼墙研究中有待进一步解决的问题和发展方向,以期为下一步台风双眼墙研究提供有益的借鉴和参考.
采用奇异能量谱与改进ELM的轴承故障诊断方法

针对滚动轴承故障特征不易提取,进而影响诊断精度的问题,研究一种将信号处理与智能算法相结合的轴承故障诊断方法。首先,利用粒子群算法对变分模态分解(VMD)法进行优化,以确定VMD法的最优输入参数,并利用优化VMD算法对振动信号进行分解得到若干本征模态函数进而建立特征矩阵。然后,对特征矩阵进行奇异值分解,根据不同故障下奇异能量谱的差异构造故障特征向量,并采用改进的极限学习机(ELM)进行故障识别。针对传统ELM输入层权值与隐含层阈值随机选取对分类效果的影响,采用自适应差分进化极限学习机对其进行优化,以保证故障诊断性能。最后,利用实验结果验证所研究故障诊断方法的可行性。
转子微动状态下永磁同步电机初始位置检测

针对表贴式永磁同步电机在无位置传感器情况下难以检测出转子初始位置这一问题,研究了一种基于转子微动的初始位置检测方法。通过分析向定子绕组中注入极低频旋转电压时的电流响应,得出了在电机处于微动状态时可从静止坐标系电流响应中提取出转子初始位置信息的结论,并根据电流响应增幅的变化倍数来获得微动状态下的注入电压信号幅值,进一步提高了该方法的可行性和实用性,最后通过注入正反方向电压矢量并比较电流响应幅值来判断转子极性。实验结果表明,该方法在不同负载情况下均能准确有效地检测出转子初始位置,检测结果均可满足电机启动要求。
多耦合线圈混合谐波滤波器研究

为了研究中高压电网中,混合有源滤波器的有源部分更为安全的接入方式,提出一种多耦合线圈混合谐波滤波器。基于多耦合线圈的无源滤波器用于滤除多次特征谐波,能够减小线圈组的占地面积。在多耦合线圈结构的基础上,增加了一个感应线圈,有源部分的电流流经感应线圈,并通过空间磁路耦合的方式注入电网,用以补偿无源部分补偿之后残余的谐波电流。有源部分和无源部分不需要直接连接,有源部分的开路、短路不影响无源部分的正常工作,安全可靠。分析了多耦合线圈混合谐波滤波器的结构和谐波补偿原理,介绍了其电流跟踪控制技术,搭建了仿真模型和实验平台,验证了所提出滤波器的有效性。本方案为解决电力系统谐波问题提供了更多的选择。
MatriXX测量近距离放疗放射源驻留时间精度的方法研究

目的:应用二维电离室矩阵(MatriXX)测量近距离放疗后装机中192Ir在不同间距驻留点的驻留时间,并与治疗计划系统(TPS)计算的驻留时间作比较,验证放射源驻留时间的精准度。方法:采用不同角度的宫腔管(15°、30°、45 °)分别粘贴在MatriXX表面,通过后装治疗计划系统设计不同计划,计划的治疗长度设为10 cm,各个驻留点权重和时间相等,重复执行5次计划,通过MatriXX记录数据。根据临床后装治疗的要求,用MatriXX测量不同驻留点间距(2.5、5.0、10.0 mm)的时间,开展后装源驻留时间重复性和准确性实验。结果:用MatriXX测量近距离后装源不同驻留间距对应的驻留时间相对于TPS计划系统计算时间的偏差均小于±1%。另外,当驻留点间距为2.5 mm时,其驻留时间偏差最大,为0.9%;驻留点间距为10 mm时,其时间偏差最小为0.3%。结论:在合适的驻留间距范围内用MatriXX验证近距离放疗放射源驻留时间和重复性方法准确可靠,经济适用,同时选择较大的驻留间距可提高测量驻留时间的精度。
云南不同林龄橡胶林土壤有机碳含量变化及影响因子

【目的】探讨云南植胶区不同林龄橡胶林土壤有机碳含量变化特征及其影响因子,为天然橡胶产业的可持续发展提供理论依据。【方法】以云南省景洪市、瑞丽市和河口县3个植胶区5种林龄(0~5年、10~15年、16~20年、26~30年和31~35年)橡胶林土壤样品为对象,用pH计法测定土壤pH,烘干法测定土壤含水量,重铬酸钾容量-外加热法测定土壤有机碳含量,并用冗余分析探究影响土壤有机碳含量的影响因子。【结果】(1)云南橡胶林土壤有机碳含量为7.22~22.82 g/kg;其中景洪植胶区土壤有机碳含量最高,平均值为17.90 g/kg;最低的是河口植胶区,平均值为10.62 g/kg。(2)云南各植胶区不同林龄土壤有机碳含量差异比较:景洪0~5年、10~15年和16~20年3个龄级土壤有机碳含量均显著高于26~30年和31~35年2个龄级(P<0.05),瑞丽0~5年土壤有机碳含量显著高于26~30年和31~35年2个龄级(P<0.05),河口各龄级土壤有机碳含量差异不显著(P>0.05);云南各植胶区土壤有机碳含量总体上表现出表层(0~20 cm)高于深层(>20~40 cm)的特征。(3)地理位置(纬度、坡度和海拔)、气温和降水量对植胶区土壤有机碳含量空间差异的影响较大;土壤含水量、土壤pH、郁闭度和树高等的影响次之;不同土地利用类型对土壤有机碳含量的影响差异不显著(P>0.05)。【结论】云南橡胶林土壤有机碳含量存在空间、林龄以及土层之间的变化。
千家寨野生古茶树对不同海拔的生理响应

【目的】研究野生古茶树叶片生理特性对不同海拔的响应机制。【方法】以云南省镇沅县千家寨自然保护区野生古茶树大理茶种(Camellia talinensis)为研究对象,测定在不同海拔(2 050、2200、2350和2500 m)其叶片游离脯氨酸、光合色素、葡萄糖、淀粉和可溶性蛋白的含量以及超氧化物歧化酶(SOD)、过氧化物酶(POD)、抗坏血酸过氧化氢酶(APX)和过氧化氢酶(CAT)活性。【结果】随着海拔的升高,野生古茶树叶片叶绿素a(Chla)和叶绿素a/叶绿素b的比值先增后降,而总叶绿素(Chl a+b)和类胡萝卜素(Car)含量呈现先增后降再增的趋势,均在海拔2 200 m达到最大值;同时,野生古茶树叶片中葡萄糖和淀粉及可溶性蛋白等内含物质含量在海拔2 200 m处亦显著高于其他海拔(P<0.05);此外,随着海拔上升至2 500 m,葡萄糖和淀粉含量降至最低水平,而抗氧化酶POD和APX活性更高。【结论】千家寨自然保护区海拔2 200 m的生境条件更有利于野生古茶树光合生理代谢及光合产物淀粉或糖分的累积。
基于SDF-1/CXCR4途径的骨炎消方体外干预对兔膝骨关节炎软骨组织的保护机制研究

目的:研究骨炎消方体外干预对兔膝骨关节炎(KOA)软骨组织的保护作用。方法:采用生化检测法筛选骨炎消给药浓度,分为骨炎消方360 mg/mL、720 mg/mL、1440 mg/mL组及盐酸氨基葡萄糖10 mmol/L组,分别处理培养KOA家兔软骨组织,观察软骨形态学改变,评估关节软骨蛋白聚糖丢失程度;检测上清液及软骨组织中关于基质细胞衍生因子-1(SDF-1)/CXC趋化因子受体4(CXCR4)信号通路上相关细胞因子的表达水平。结果:与正常对照组比较,模型对照组培养上清液中CXCR4含量显著升高, COL-Ⅱ含量显著下降(P < 0.01);软骨组织中CXCR4蛋白及mRNA、IL-1β mRNA、MMP-13蛋白表达显著上调(P < 0.01) 。与模型对照组比较,骨炎消方各浓度组均能够明显降低KOA模型培养上清液中CXCR4含量,提高COL-Ⅱ含量(P < 0.05或P < 0.01);能明显下调KOA软骨组织中CXCR4蛋白及mRNA、IL-1β mRNA、MMP-13蛋白表达水平(P < 0.05或P < 0.01);能够缓解KOA模型软骨组织番红失染,改善组织畸变的情况。结论:骨炎消方可以通过调节SDF-1/CXCR4信号通路,降低CXCR4水平、促进COL-Ⅱ及蛋白聚糖的合成,减少MMP-13及IL-1β的释放,从而改善KOA引起的软骨组织退化。
基于三角图法的榆林市农业生态系统脆弱性类型变化研究

农业生态系统是农业可持续发展的基础,在全球气候变化引发的生态系统脆弱化背景下,开展农业生态系统脆弱性研究对今后制定区域农业生态环境发展政策、实现农业生态系统可持续发展具有重要的现实意义。以陕西省榆林市12个县(区)为研究单元,从农业环境子系统、生产投入子系统和社会经济子系统中选取24项指标构建农业生态系统脆弱性评价体系,运用赋权法、熵值法、综合指数法等数学方法,结合ArcGIS10.2、Grapher12软件,对2004—2017年榆林市农业生态系统脆弱性类型的演变特征分3个阶段研究,并选取2004、2009、2013、2017年4个具有代表性阶段的起始点作为断面节点,运用三角图法分析榆林市12个县(区)农业生态系统脆弱性类型的演变状况。结果表明:2004—2017年榆林市形成了5型农业生态系统脆弱性:①农业环境-生产投入-社会经济子系统均衡脆弱型(EPS型);②生产投入-社会经济子系统脆弱型(PS型);③农业环境-生产投入-社会经济子系统均衡脆弱型向生产投入-社会经济子系统脆弱型,再到农业环境-生产投入-社会经济子系统均衡脆弱型转变(EPS型→PS型 →EPS型);④农业环境-生产投入-社会经济子系统均衡脆弱型向生产投入-社会经济子系统脆弱型转变(EPS型→ PS型);⑤生产投入-社会经济子系统脆弱型向农业环境-生产投入-社会经济子系统均衡脆弱型转变(PS型→EPS型)。各子系统脆弱性程度在各个发展阶段均呈现出南部区域高于北部区域、南6县高于北6县的分布格局,与该地区农业生态环境的实际发展情况基本一致,但区域农业生态系统脆弱性程度总体上表现出逐年降低的趋势,表明了随着社会经济的不断发展,对农业生产和农业科技水平投入的增加,区域内抵抗农业生态系统脆弱性的能力也得到提升。
1975—2018年民勤绿洲沙漠化过程及其驱动机制

根据1975—2018年民勤绿洲土地沙漠化分类体系及遥感影像数据,探究了民勤绿洲沙漠化时空变化过程;选取影响绿洲沙漠化的自然与人为驱动因子,运用主成分分析方法定量评价了民勤绿洲沙漠化过程的主要驱动力。结果表明:1975—2018年沙漠化程度以重度沙漠化为主,轻度、中度、重度和严重沙漠化面积均呈减少趋势,以2000年为界表现为先发展后逆转趋势;1975—2000年,轻度、中度、重度沙漠化重心总体向东北方向迁移,严重沙漠化的重心向西迁移,沙漠化有向绿洲东北部和巴丹吉林沙漠发展的趋势;2000—2018年轻度沙漠化的重心向西北方向迁移,中度、重度和严重沙漠化重心相对稳定,绿洲沙漠化发展得到明显控制。在绿洲沙漠化过程中,人为因素贡献率为39.53%,自然与人为综合贡献率为26.58%,自然因素贡献率为10.77%,人为因素是民勤绿洲沙漠化的主要驱动力。水资源极度匮乏是绿洲沙漠化的决定因素,在以后的防沙治沙工作中,合理调控人类的生产经营活动,优化干旱区水资源配置,可从源头上治理民勤绿洲的沙漠化。
基于沉积物理化性质的雅鲁藏布江中游粉尘物源研究

物源是风沙研究的主要内容。雅鲁藏布江中游风沙区是西藏自治区的主要沙丘分布区和受风沙灾害影响的主要区域。但目前对该地区沙尘物源的研究甚少,从而限制了我们对该地区风沙地貌形成演化过程、防沙治沙工程合理布局和沙尘暴预报预警工作的开展。沉积物理化性质是沉积物物源判别的主要证据。为此,收集了雅鲁藏布江中游河岸、河漫滩、河漫滩沙丘、林地和山麓沙丘沉积物样品,对其进行粒度、常量元素和微量元素(<63 μm)分析,对该地区沙尘物源进行判别。结果表明:(1)不同类型地表沉积物粒度特征存在明显空间差异。沙丘沉积物以>63 μm沙为主(>91%),而河岸和河漫滩粉沙和黏土含量与沙的含量几乎相同。(2)不同地表沉积物的常量元素相似。SiO_2含量最大,MgO含量最小;Fe_2O_3在河岸、河漫滩和林地富集,而在沙丘亏损,其他元素均为亏损。(3)不同地表微量元素差异较大,Ti、Sr和Ba总体为亏损,其他元素为富集。(4)不同地表沉积物的元素比值和风化过程相似,说明了研究区地表沉积物具有相同的物质来源。河岸和河漫滩具有形成风沙灾害的物质条件,是风沙灾害的主要物源。
直线扫描CT检测碳纤维复合芯导线缺陷研究

碳纤维复合芯导线作为常见的增容导线之一,在架空输电线路中应用广泛。由于碳纤维复合芯导线芯棒在施工过程中易受损伤,并诱发导线断股和断线等故障,亟需研究在役碳纤维复合芯导线的无损检测技术。由于传统的X射线检测方法尚无法检测多股铝线和有机复合材料芯棒绞合结构条件下芯棒的损伤,文中提出了一种利用直线扫描CT检测在役碳纤维复合芯导线的方法。此方法采用射线源探测器围绕固定检测对象作相对平行直线运动的扫描方式,具有结构简单、便于安装等优点。设计了一段以及两段直线扫描CT模型,搭建了原理实验平台,在实验室条件下对断裂、劈裂和裂痕3种常见芯棒缺陷进行了小批量检测实验。结果表明,一段直线扫描CT可快速检测较大的芯棒缺陷,两段直线扫描CT可检测微小的芯棒缺陷。相比于传统的X射线透射成像检测,直线扫描CT成像为在役架空导线内部缺陷检测提供了新思路和参考。
普萘洛尔修复即刻消退产生的二次创伤

恐惧消退能力的受损是创伤后应激障碍(posttraumatic stress disorder, PTSD)的标志之一。以往的研究表明,相较于延迟消退,恐惧获得后短时间内进行的消退训练不能形成长时程的消退记忆,这一现象被称为即刻消退缺损。然而,目前并不清楚这种缺损是一次性的,还是会继续影响其后的重消退。实验1中,大鼠在恐惧习得后1小时(即刻消退)或24小时(延迟消退)开始进行消退训练, 24小时后进行重消退,再24小时后进行消退记忆的测试。结果显示,与延迟消退相比,即刻消退效果缺损,并引起第二天的重消退也出现效果缺损。实验2中,恐惧获得后立即给予大鼠盐水或β-肾上腺素受体阻断剂普萘洛尔(10 mg/kg, i.p.),然后测试即刻消退和重消退的效果。结果显示,普萘洛尔虽没有阻止即刻消退的缺损,但避免了重消退出现缺损。总之,严重创伤后的即刻消退不但无法有效抑制恐惧反应,还可能造成二次创伤,会损害恐惧消退能力,而普萘洛尔可修复即刻消退引起的重消退缺损。这些结果将有助于我们加深对PTSD病理机制和早期干预后果的认识。
外强中瘠、虚饰以财?自我威胁情境下异质性高自尊与物质主义的关系

通过3个研究探讨异质性高自尊与物质主义的关系,以及在自我威胁情境下异质性高自尊与物质主义的关系是否会发生变化。研究1采用问卷法考察异质性高自尊与物质主义的相关关系,结果发现,安全高自尊者的物质主义显著低于脆弱高自尊者;研究2通过要求不同高自尊者与吸引力高/低的同性进行对比操纵自我威胁,然后测量外显物质主义,结果发现,在吸引力威胁情境下,安全高自尊者的外显物质主义显著低于脆弱高自尊者的外显物质主义;研究3通过虚拟的智力测验排名反馈操纵自我威胁,然后测量内隐物质主义。结果发现,在智力威胁情境下,安全高自尊者的内隐物质主义显著低于脆弱高自尊者的内隐物质主义。据此可认为,异质性高自尊既是解开高自尊与物质主义矛盾关系的切入点,也是瓦解自我威胁与物质主义正向关系的突破口。
氧化应激相关酶在心血管疾病中的研究进展

活性氧(ROS)持续产生氧化应激的过程与心血管疾病的发病有关。心血管系统中ROS的主要来源是还原型烟酰胺腺嘌呤二核苷酸磷酸氧化酶(NOX)、解偶联的内皮型一氧化氮合酶、线粒体和黄嘌呤氧化酶。本文就这些氧化酶之间的相互关系在心血管疾病中的作用进行综述,重点论述不同心血管疾病中被激活的NOX特定亚型的核心作用。理解这些机制有助于开发针对氧化应激相关酶系统及其之间相互作用的新型药物,有效预防和治疗心血管疾病。
支持向量机预测可变参数的永磁同步电机快速终端滑模控制

针对永磁同步电机传统滑模控制的调速性能受到电机系统状态变量变化的影响,提出了一种采用支持向量机智能预测永磁同步电机可变参数非奇异快速终端滑模控制策略。首先设计了一种快速收敛的新型可变参数非奇异快速终端滑模面,该滑模面实现了全局快速收敛且消除了奇异现象并且滑模参数随系统状态改变,实现了不同系统状态下,永磁同步电机可以始终保持优异的调速性能;然后,引入支持向量机智能算法对滑模面状态变量参数建模,实现滑模面状态变量参数根据电机系统状态在线调整;最后,采用角速度与q轴定子参考电流二阶模型来设计永磁同步电机可变参数非奇异快速终端滑模速度控制器以减小模型误差。数值仿真结果表明:采用支持向量机建立的滑模面状态变量参数预测模型能够根据电机系统参数变化预测得到滑模面状态变量参数最优值;所提出的可变参数非奇异快速终端滑模控制策略与非奇异快速终端滑模控制策略相比,控制性能不受电机参数变化的影响,具有收敛速度快、鲁棒性好、转速超调小、控制精度高等优点。
梯度结构修饰铜网的毛细特性

如何在有限空间内提高吸液芯的毛细力的同时降低气液流动阻力成为制备超薄热管的关键问题。丝网是一种常用的热管吸液芯结构,当其用于超薄热管时,因厚度较大及毛细力较小而受到限制。为解决这一问题,本文采用电化学沉积法对铜网进行梯度结构修饰。文章对三种不同规格的铜网进行试验,探究不同反应条件对形貌及毛细性能的影响。结果表明,随着反应时间及电流的增加,修饰结构梯度幅度增大,毛细性能增强。以乙醇为工质时,修饰后的最大吸液高度为62.5 mm。与多尺度复合烧结铜粉毛细芯结构相比,在相同的毛细性能条件下,梯度修饰丝网在厚度上减小了90%,从而为其在超薄热管中的使用奠定了基础。
前置部分叶高增压转子风扇气动性能研究

在航空发动机更高推重比的需求牵引下,风扇需进一步提高其通流能力和内涵增压能力。本文以某宽弦复合掠跨音风扇为研究对象,对前置部分叶高增压转子风扇开展了深入细致的性能和流动机理研究。结果表明:高通流风扇中串列转子叶片的周向相对布局对风扇性能有决定性影响,在λs=20%周向布局下,风扇最大通流能力在外径、效率以及裕度基本不变的前提下增大5.83%,同时峰值效率点下总压比提升8.38%,压比提升主要来源于内涵压比的提升。研究证实前置部分叶高增压转子风扇有效提升了风扇级的性能水平,展现出巨大应用前景。
离子液体[BMP] [Tf_2N]基本物性的实验研究

针对离子液体[BMP] [Tf_2N]的物性数据缺乏的问题,本文在101.325 KPa下对[BMP] [Tf_2N]在温度范围为278.15~338.15 K的黏度和温度范围为298.15~338.15 K的密度、电导率进行了实验测定,结果表明:黏度、密度和电导率均受温度的影响较大,当压力一定时,[BMP] [Tf_2N]的黏度、密度随温度的升高而减小;而电导率随温度的升高而增大;通过选择分别用Arrhenius方程、自然对数方程和VFT方程关联[BMP] [Tf_2N]的黏度、密度和电导率;结果表明:模型值与实验值的最大相对误差和平均相对误差分别是2.25%和0.94%; 5.74%和5.39%; 4.41%和4.24%。
用于锌-空气电池的MnO_2纳米片@Ni-氮掺杂石墨烯气凝胶

在锌-空气电池中,电池正极的氧还原反应(oxygen reduction reaction, ORR)动力学缓慢,影响其功率密度等性能,需催化剂提高电极反应速率.常用的贵金属基催化剂(如Pt/C)成本高,而低成本的MnO_2具有ORR催化活性,但导电性差,影响ORR过程中的电子转移速率,限制了其ORR催化活性的充分发挥.将MnO_2与高导电性金属或碳材料组装、引入氧空位(oxygen vacancies, OVs)等都可提高其导电性,从而提高ORR催化活性.本研究在氮掺杂石墨烯气凝胶(nitrogen doped graphene aerogel, NGA)上均匀负载Ni纳米颗粒得到Ni-NGA,然后在Ni-NGA上均匀生长MnO_2纳米片,得到了具有丰富OVs的MNSs@Ni-NGA.由于Ni、NGA和OVs皆可提高共组装体的导电性,且Ni、 NGA和MnO_2均具有ORR催化活性,其中MnO_2纳米片保证了活性位点与O2等反应物的充分接触;同时, NGA防止Ni和MnO_2纳米结构在ORR过程中的脱落和聚集,进一步保证活性位点的暴露.因此,通过Ni、NGA、MnO_2和OVs的协同作用, MNSs@Ni-NGA具有优异的ORR催化活性,其起始电位(0.98 V)和半波电位(0.84 V)接近商业Pt/C(0.98和0.85 V),且优于已报道MnO_x-基催化剂.以MNSs@Ni-NGA作为正极材料组装的锌-空气电池的功率密度为114.8 mW cm-2,比容量为801.9 mAh gZn -1,比能量为962.3 Wh kgZn -1(约为理论比能量的88.8%),性能优于商业Pt/ C+IrO_2和已报道的MnO_x-基材料作为正极材料组装的锌-空气电池.
中国晚新生代猫科剑齿虎的分类述评及古生态探讨

猫科剑齿虎类是晚新生代哺乳动物群中最常见且重要的化石组分之一,它的研究对分析和对比动物群具有极其重要的生物地层学意义和古生态意义.中国晚新生代陆相地层中出产了非常丰富的剑齿虎类化石,然而在前人的报道中,受限于有限的化石材料,一些属种的有效性有待讨论.基于对经典材料的实地观测,以及对部分近年来未受关注类群的探讨,结合最新的研究进展,中国的剑齿虎类得到了一次全面的梳理.最终确认有效属种共6属13种,分别是:恐剑齿虎Machairodus horribilis、巴氏剑齿虎Ma. palanderi、钝齿锯齿虎Homotherium crenatidens 、最后锯齿虎H. ultimum、欧亚副剑齿虎Paramachaerodus transasiaticus、马氏副剑齿虎Par. maximiliani、巨颏巨颏虎Megantereon megantereon、泥河湾巨颏虎Meg. nihowanensis、意外巨颏虎Meg. inexpectatus、大后猫Metailurus major、最晚后猫Met. ultimus、横断山后猫Met. hengduanshanensis和冠恐猫Dinofelis cristata.分析了剑齿虎类尤其是那些中间形态类型的系统关系及存在的问题.结合不同地点的动物群组合特征,对中国相关剑齿虎类的古生态进行了探讨.恐剑齿虎的生态位很可能与现生虎近似,主要捕食中大型有蹄类.副剑齿虎类和巨颏虎类与现生美洲豹相似,两者分别以中小型及大型食草动物为主要取食对象,上述类群主要生活在林地环境.巴氏剑齿虎和锯齿虎类则与现生狮近似,以捕食中大型猎物为主,后猫类与现生豹近似,偏好于捕食与自身体型相当或稍大的猎物,这些类群主要生活在相对更加开阔的地带.恐猫类的生境尚不十分明了,其捕猎习性可能近似于现生的狮或虎.
石墨烯/离子液体体系静电吸附机理及非平衡热力学模型

超级电容是基于固液界面静电吸附原理的先进储能技术.石墨烯和高浓度离子液体被认为是超级电容储能的理想材料和电解液工质,但是其静电吸附过程中能量载子间具有复杂交互作用、纳米尺度效应和非平衡热力学特征,显著区别于常规低浓度、低黏度和非受限体系,无法通过经典理论和模型进行解释.本文通过分子动力学模拟,结合恒定电势和热力学方法,系统研究了离子液体在石墨烯纳米通道内的静电吸附机理,包括热力学平衡态结构和非平衡传递过程;提出了可在分子动力学模拟中量化离子传递的判据,发现离子液体在纳米通道内传递与电势、受限效应、粒子间交互作用密切相关;基于时间微元原理,建立了描述纳米通道静电吸附过程的非平衡热力学模型,更为真实地描述了静电吸附充/放电过程;发现纳米受限状态下高密度异性离子和低密度同性离子间相界面的形成会阻碍同性离子的传输,进而造成高充/放电速率下储能容量下降,不同于传统观点所提出的异性离子吸附滞后的机理.研究结果揭示了高浓度离子液体在纳米通道内的特殊静电吸附机理,为构筑高性能超级电容提供了理论指导.
硝酸锂添加剂在锂硫电池中作用的新理解

硝酸锂(LiNO_3)作为锂硫(Li-S)电池电解液添加剂获得了广泛的关注,对其作用机理也进行了深入研究.本研究通过新的实验方案,对LiNO_3添加剂的作用机理提出了新的理解.该实验方案中,利用含LiNO_3添加剂电解液循环过的锂金属负极和新的硫电极,与不含LiNO_3添加剂电解液重新组装电池.该电池在充电过程中却存在严重过充现象,发生了多硫离子的穿梭.这说明LiNO_3抑制“穿梭效应”的作用机制不仅是生成固体电解质界面膜(solid electrolyte interphase,简称SEI膜);而且通过离子迁移数测试,发现加入LiNO_3添加剂后,锂离子(Li~+)迁移数增加.由此得出,加入LiNO_3添加剂的另一个作用是增加Li~+迁移数,从而降低多硫离子迁移数,有效抑制“穿梭效应”.
锂枝晶的生长理论模型及其抑制方法

锂金属由于其具有极高的理论比容量、较低的密度和极低的氧化还原电位等特性,是实现下一代高比能锂电池的理想负极材料.然而,在锂金属电池实际充放电循环过程中,锂金属负极表面易产生枝晶状结构锂,这些锂枝晶不仅能够引起锂金属电池的安全隐患,而且极大地降低锂金属电池的库伦效率,缩短电池的使用寿命.这些问题严重阻碍了锂金属电池的应用发展.因此,充分认识锂枝晶的形成和生长机理,同时精确调控金属锂的电化学溶解/锂沉积过程,进而有效地抑制锂枝晶的形成生长,是实现下一代锂金属电池商业化应用的首要前提.本文综述了近年来锂枝晶生长理论与抑制方法的研究进展,在此基础上,从热力学与动力学角度加深对锂枝晶生长机理的认识,将为开发锂枝晶的抑制策略和加快锂金属电池的实用化提供科学理论借鉴.
Mid-infrared single photon detector with superconductor Mo_(0.8)Si_(0.2) nanowire

Mid-infrared(mid-IR) single photon detectors have broad applications in science and technology, such as biomolecular spectrum analysis [1] and astronomical observations [2].Unfortunately, it is much more difficult than detecting near-infrared photons due to the significantly reduced energy of mid-IR single photon.Superconducting nanowire single photon detectors(SNSPDs) have shown a great potential in mid-IR single photon detection relied on the low energy gap(~meV) of superconductor materials.In 2011, Marsili et al.[3] extended the response bandwidth of SNSPD to 0.5-5 lm band by reducing the width of NbN nanowire to 30 nm, resulting in a saturated internal detection efficiency at wavelengths λ <3 lm.The reduced width of 30 nm increased the probability of the transition from the superconducting state to the non-superconducting state.In 2019, Verma et al.[4] reported a SNSPD based on WSi films, a superconductor material with low energy gap, achiving a response cut-off wavelength at 9.9 lm.The lower energy gap of WSi enhanced the efficiency of the photon-induced Cooper pair decoupling.As can be seen above, it is an effective way to develop mid-IR SNSPD through ultranarrow nanowires patterned on superconductor films with low energy gap.
Interfacial stabilization for inverted perovskite solar cells with long-term stability

Perovskite solar cells(PSCs) commonly exhibit significant performance degradation due to ion migration through the top charge transport layer and ultimately metal electrode corrosion.Here, we demonstrate an interfacial management strategy using a boron chloride subphthalocyanine(Cl_6SubPc)/fullerene electron-transport layer, which not only passivates the interfacial defects in the perovskite, but also suppresses halide diffusion as evidenced by multiple techniques, including visual element mapping by electron energy loss spectroscopy.As a result, we obtain inverted PSCs with an efficiency of 22.0%(21.3% certified), shelf life of 7000 h, T_(80) of 816 h under damp heat stress(compared to less than 20 h without Cl_6SubPc), and initial performance retention of 98% after 2000 h at 80 C in inert environment, 90% after 2034 h of illumination and maximum power point tracking in ambient for encapsulated devices and 95% after 1272 h outdoor testing ISOS-O-1.Our strategy and results pave a new way to move PSCs forward to their potential commercialization solidly.
Cationic intermediates assisted self-assembly two-dimensional Ti_3C_2T_x/ rGO hybrid nanoflakes for advanced lithium-ion capacitors

Two-dimensional(2D) material MXenes have been intensively concerned in energy-storage field due to these unique properties of metallic-like conductivity, good hydrophilicity and high volumetric capacity.However, the self-restocking of ultra-thin 2D materials seriously hinders these performances, which significantly inhibits the full exploitation of MXenes in the field of energy storage.To solve this issue, a strategy to prepare delaminated Ti_3C_2T_x(MXene) nanoflakes/reduced graphene oxide(rGO) composites is proposed using the electrostatic self-assembly between positively charged Ti_3C_2T_x with tetrabutylammonium ion(TBA~+) modification and negatively charged graphene.The nanoflakes of Ti_3C_2T_x/rGO are well dispersed and arranged in a face-to-face structure to effectively alleviate the self-restacking and provide more electroactive sites for accessible of electrolyte ions.The prepared delaminated Ti_3C_2T_x/rGO anode shows a high reversible capacity up to 1394 mAh g~(-1) at a current density of 50 mA g~(-1).Moreover, a lithium-ion capacitor(LIC) was assembled with delaminated Ti_3C_2T_x/rGO anode and activated carbon(AC) cathode which can exhibit a specific capacity of 70.7 F g~(-1) at a current density of 0.1 A g~(-1) and deliver an ultrahigh energy density of 114 Wh kg~(-1) at a relatively high power density of 3125 W kg1.These good electrochemical performances demonstrate the potential of delaminated Ti_3C_2T_x/rGO as an anode material for lithium-ion capacitors.
On the understanding of dielectric elastomer and its application for all-soft artificial heart

Although dielectric elastomer(DE) with substantial actuated strain(AS) has been reported 20 years ago, its scientific understanding remains unclear.The most accepted theory of DE, which is proposed in 2000, holds the view that AS of DE is induced by the Maxwell stress.According to this theory, materials have similar ratios of permittivity and Young's modulus should have similar AS, while the experimental results are on contrary to this theory, and the experimental AS has no relationship with ideal AS.Here, a new dipole-conformation-actuated strain cross-scale model is proposed, which can be generally applied to explain the AS of DE without pre-strain.According to this model, several characteristics of an ideal DE are listed in this work and a new DE based on polyphosphazene(PPZ) is synthesized.The AS of PPZ can reach 84% without any pre-strain.At last, a PPZ-based all soft artificial heart(ASAH) is built, which works in the similar way with natural myocardium, indicating that this material has great application potential and possibility in the construction of an ASAH for heart failure(HF) patients.
Engineering of multiferroic BiFeO_3 grain boundaries with head-to-head polarization configurations

Confined low dimensional charges with high density such as two-dimensional electron gas(2DEG) at interfaces and charged domain walls in ferroelectrics show great potential to serve as functional elements in future nanoelectronics.However, stabilization and control of low dimensional charges is challenging, as they are usually subject to enormous depolarization fields.Here, we demonstrate a method to fabricate tunable charged interfaces with ~77, 86 and 94 head-to-head polarization configurations in multiferroic BiFeO_3 thin films by grain boundary engineering.The adjacent grains are cohesively bonded and the boundary is about 1 nm in width and devoid of any amorphous region.Remarkably, the polarization remains almost unchanged near the grain boundaries, indicating the polarization charges are well compensated, i.e., there should be two-dimensional charge gas confined at grain boundaries.Adjusting the tilt angle of the grain boundaries enables tuning the angle of polarization configurations from 71 to 109, which in turn allows the control of charge density at the grain boundaries.This general and feasible method opens new doors for the application of charged interfaces in next generation nanoelectronics.
Vapor-deposited CsPbI_3 solar cells demonstrate an efficiency of 16%

Hybrid organic-inorganic perovskite solar cells(PSCs) have made rapid progress in efficiency from 3.8% to 25.5% in the past decade [1-3].The hybrid perovskite materials possess a 3D crystal structure with a chemical formula as ABX3, where A is a monovalent cation such as methylammonium(CH3NH_3+, MA~+) and formamidinium(HC(NH_2)~(2+), FA~+), and B is a divalent metal cation such as Pb~(2+), and X is a halide(I, Br, Cl or their mixed) [4].However, the long-term stability issue has hindered large-scale commercialization of PSCs owing to the degradation and volatilization of organic cations(i.e., MA~+and FA~+) [5,6].Therefore, replacing the volatile organic cations with inorganic cesium(Cs~+) cation have drawn significant attention for achieving highly stable perovskite materials and devices [7,8].
Eliminating the electric field response in a perovskite heterojunction solar cell to improve operational stability

Intrinsic and extrinsic ion migration is a very large threat to the operational stability of perovskite solar cells and is difficult to completely eliminate due to the low activation energy of ion migration and the existence of internal electric field.We propose a heterojunction route to help suppress ion migration, thus improving the operational stability of the cell from the perspective of eliminating the electric field response in the perovskite absorber.A heavily doped p-type(p~+) thin layer semiconductor is introduced between the electron transporting layer(ETL) and perovskite absorber.The heterojunction charge depletion and electric field are limited to the ETL and p~+layers, while the perovskite absorber and hole transporting layer remain neutral.The p+~layer has a variety of candidate materials and is tolerant of defect density and carrier mobility, which makes this heterojunction route highly feasible and promising for use in practical applications.
Origin of the electrocatalytic oxygen evolution activity of nickel phosphides: in-situ electrochemical oxidation and Cr doping to achieve high performance

Zinc-air batteries(ZnABs) with high theoretical capacity and environmental benignity are the most promising candidates for next-generation electronics.However, their large-scale applications are greatly hindered due to the lack of high-efficient and cost-effective electrocatalysts.Transition metal phosphides(TMPs) have been reported as promising electrocatalysts.Notably,(Ni_(1-x)Cr_x)_2P(0 ≤ x ≤ 0.15) is an unstable electrocatalyst, which undergoes in-situ electrochemical oxidation during the initial oxygen evolution reaction(OER) and even in the activation cycles, and is eventually converted to Cr-NiOOH serving as the actual OER active sites with high efficiency.Density functional theory(DFT) simulations and experimental results elucidate that the OER performance could be significantly promoted by the synergistic effect of surface engineering and electronic modulations by Cr doping and in-situ phase transformation.The constructed rechargeable ZnABs could stably cycle for more than 208 h at 5 mA cm~2, while the voltage degradation is negligible.Furthermore, the developed catalytic materials could be assembled into flexible and all-solid-state ZnABs to power wearable electronics with high performance.
On-site building of a Zn~(2+)-conductive interfacial layer via short-circuit energization for stable Zn anode

Aqueous zinc ion batteries(ZIBs) show great potential in large-scale energy storage systems for their advantages of high safety, low cost, high capacity, and environmental friendliness.However, the poor performance of Zn metal anode seriously hinders the application of ZIBs.Herein, we use the zinc-ion intercalatable V_2O_5nH_2O(VO) as the interface modification material, for the first time, to on-site build a Zn~(2+)-conductive Zn_xV_2O_5nH_2O(ZnVO) interfacial layer via the spontaneous short-circuit reaction between the pre-fabricated VO film and Zn metal foil.Compared with the bare Zn, the ZnVO-coated Zn anode exhibits better electrochemical performances with dendrite-free Zn deposits, lower polarization, higher coulombic efficiency over 99% after long cycles and 10 times higher cycle life, which is confirmed by constructing Zn symmetrical cell and Zn|ZnSO_4+Li_2SO_4|LiFePO_4 full cell.
Passivation with crosslinkable diamine yields 0.1 V non-radiative Voc loss in inverted perovskite solar cells

Organic-inorganic hybrid perovskite solar cells(PSCs) have attracted continually increasing attention in recent years due to its outstanding photoelectric properties and bright commercial prospect [1-6].So far, the certified power conversion efficiency(PCE) record of PSCs increased up to be 25.2% [7].However, the efficiency for PSCs with inverted structure was generally lower(~22.3%) [8].A major reason for the relatively lower PCE in inverted solar cells was that the achieved open-circuit voltage(V_(oc)) was generally lower than that of conventional PSCs based on the same photoactive layers [9-11].The V_(oc) of solar cells was determined by the splitting of quasi-Fermi levels of electrons(E_(Fn)) and holes(E_(Fp)) [12].Non-radiative recombination assisted by trapping effect would reduce the energy difference between E_(Fn) and E_(Fp), hence leading to additional V_(oc) loss beyond radiative recombination [13,14].Nowadays, the obtained grain size of hybrid perovskites could easily reach the micron-scale, successfully reducing the non-radiative recombination channels caused by defects located on grain boundaries.However, surface defects were not necessarily reduced with enlarged grain size.A recent study pointed out that the surface region contributed most of the defects in perovskite films [15].Treating the crystal surface with bulky organic cations was demonstrated as an efficient method for surface passivation in recent years, which benefited from the much lower volatility of bulky organic cations than that of methylammonium(MA+) or formamidinium(FA+) cations [16,17].In this work, a diaminebased passivation method was reported by introducing ethanediamine dihydroiodide(EDAI2) on perovskite surface and further treating it with hexamethylene diisocyanate(HDI)(Fig.1a).With EDAI2/HDI passivation, the V_(oc) of PSCs was improved from 1.10 to 1.17 V, and the achieved non-radiative V_(oc) loss was as low as 0.10 V.