摘要：In terms of lightweight electromagnetic interference(EMI)shielding structural materials,Mg matrix materials have proven to be the best,due to their exciting properties(*** density,high specific strength,good electrical conductivity and excellent EMI shielding properties)and their wide range of applications in lightweighting in electronics,automotive and aerospace *** processing,such as alloying,heat treatment,plastic deformation and composite processing,Mg matrix materials can be obtained with tailorable properties which can play a key role in designing materials for EMI *** work introduces an overview of the research on the EMI shielding properties of Mg matrix materials as well as their EMI shielding mechanisms over the past few decades,focused on the influence of alloying,heat treatment,plastic deformation and composite processing for the EMI shielding properties of Mg matrix *** the end,conclusions and future perspectives are provided.

摘要：区域变电站具有数目众多、类型多样、线损构成及节电特性复杂的特点。为提升区域变电站节电研究效率,实现区域变电站节电特性的科学划分,文中提出了一种基于模糊c-均值聚类(FCM)的变电站节电划分的方法.首先,设计一套变电站节电划分综合指标体系,包括涵盖变电站主变容量、主变台数等基本参数的基本属性指标子体系和涵盖输送电量、站用电量等电气参数的电气属性指标子体系;其次,依据各指标对变电站的损耗及其节电特性的影响程度,应用层次分析法(AHP)确定各指标权重,建立AHP-FCM的变电站节电划分模型;然后,分别应用所设计的节电划分综合指标体系、基本属性指标子体系和电气属性指标子体系从3个不同的角度运用AHP-FCM实现区域变电站的划分,通过对3种节电划分结果及其聚类中心矩阵分析研究,获得对各类变电站损耗及其综合节电特性的深入认识,为变电站后续的研究提供参考依据和重要指导;最后,以某区域90个变电站的实际数据进行实例分析,验证了所提方法的实用性和有效性.

摘要：海洋环境复杂多变,为提升欠驱动无人船(underactuated marine vehicle,UMV)的自主航行与故障应对能力,提出基于有限时间正切漂角视线制导的指令滤波路径跟踪控制策略.在包括内部动力学未知、时变大漂角和执行器故障的复杂情况下,该策略可使UMV在有限时间内遵循所需的路径.首先,构建有限时间漂角观测器,用于快速精准地估计时变大漂角;随后,引入有限时间正切漂角视线制导律,不仅能提升制导性能,还能有效避免因非光滑制导指令产生高频震荡导致UMV失稳;此外,通过采用有限时间指令滤波控制技术降低计算负担,并提出滤波补偿方案减少滤波误差;最后,基于径向基函数神经网络和有限时间理论,设计自适应有限时间容错路径跟踪控制器,使得UMV的纵向速度和艏向角跟踪误差在有限时间内能够收敛到原点附近的小邻域.仿真实验验证了所提出方案的有效性和优越性.

摘要：Energy consumption and acoustic noise can be significantly reduced through perching in the sustained flights of small Unmanned Aerial Vehicles(UAVs).However,the existing flying perching robots lack good adaptability or loading capacity in unstructured *** at solving these problems,a deformable UAV perching mechanism with strong adaptability and high loading capacity,which is inspired by the structure and movements of birds'feet,is presented in this *** elastic toes,an inverted crank slider mechanism used to realize the opening and closing movements,and a gear mechanism used to deform between two configurations are included in this *** experiments on its performance towards different objects,Results show that it can perch on various objects reliably,and its payload is more than 15 times its *** integrating it with a quadcopter,it can perch on different types of targets in outdoor environments,such as tree branches,cables,eaves,and spherical *** addition,the energy consumption of the UAV perching system when perching on objects can be reduced to 0.015 times that of hovering.

摘要：This study presents the RF design of a linear accelerator(linac)operated in single-bunch *** accelerator is powered by a compressed RF pulse produced from a SLED-I type RF pulse *** compressed RF pulse has an unflattened shape with a gradient distribution which varies over the structure *** analytical study to optimize the accelerating structure together with the RF pulse compressor is *** optimization aims to maximize the efficiency by minimizing the required RF power from the generator for a given average accelerating *** study shows that,owing to the compressed RF pulse shape,the constant-impedance structure has a similar efficiency to the optimal structure using varying iris *** constant-impedance structure is easily fabricated and is favorable for the design of a linac with a pulse *** utilize these findings to optimize the RF design of a X-band linac using the constant-impedance accelerating structure for the Tsinghua Thomson X-ray source facility.

摘要：为解决甘薯秧蔓相互交错缠绕、难以分离导致收获困难的问题,设计了一种甘薯秧蔓机械化收获防缠绕割台,并对仿垄型拨禾切割机构、伸缩弹齿捡拾机构的作业过程进行受力及运动分析,得到其作业参数范围。为避免仿垄型拨禾切割机构和伸缩弹齿捡拾机构在作业过程中发生缠绕,搭建了甘薯秧蔓机械化收获防缠绕割台的试验台架,进行单因素试验,以此来确定仿垄型拨禾切割机构和伸缩弹齿捡拾机构的最佳转速范围;利用Design-Expert 13.0软件中Box-Behnken试验设计方法,研究前进速度、切割转速、捡拾转速三因素两两交互作用对甘薯秧蔓回收率、缠绕程度、伤薯率的影响,并建立回归模型,进行试验参数优化,得到最优工作参数组合,即前进速度0.995 m/s、切割转速61.043 r/min、捡拾转速100.939 r/min,此时甘薯秧蔓的回收率为94.553%、缠绕程度为2.169%、伤薯率为0.213%。为验证最优参数的可靠性,将最优工作参数组合数据化零为整,作为田间试验的作业参数,进行田间试验验证,结果表明:甘薯秧蔓的薯秧蔓回收率为93.55%,缠绕程度为2.42%,伤薯率为0.38%。

摘要：In this study,we designed an oil-filled motor that can be used at full-ocean depths,and investigated the friction losses caused by the rotating seal and the properties of the *** direct current(DC)motor is encapsulated in an aluminum alloy housing.A rubber diaphragm is used to balance the internal and external pressures so that the motor can work on the seabed without pressure *** study the resistance caused by the rotating seal,a numerical model of the Glyd ring and the rotating shaft was *** from a rotational torque test agreed with those from numerical *** kinematic viscosity of four oils was measured at 1-25℃.Oil bath experiments in an incubator showed that the resistance from oil is highly correlated with its dynamic *** appears to be very suitable as an insulating oil for these *** working characteristics of the motor were tested in a high-pressure *** results showed that the motor needs to overcome higher oil resistance under higher pressure.A prototype of a pressure-adaptive motor was designed and applied successfully in the hadal zone at a water depth of more than 10000 m.

摘要：为探究黄土高原区长期覆盖措施对农田土壤酶活性与微生物养分限制的响应特征,基于2008年开展的长期田间定位试验,研究采用随机区组设计,设置常规无覆盖(NM)、秸秆覆盖(SM)、地膜覆盖(PM)和起垄地膜覆盖(RPM)这4种田间管理措施,以常规无覆盖(NM)为对照,利用单因素方差分析、土壤胞外酶化学计量学模型和冗余分析(RDA)等方法研究不同覆盖措施下土壤养分和胞外酶活性及其生态化学计量的变化规律及影响因子.结果表明,覆盖处理显著影响土壤基础养分(P<0.05),其中可溶性有机碳(DOC)、速效氮(AN)和有效磷(AP)随作物生长呈显著动态变化;C、N和P循环胞外酶活性呈现积极响应,分别增加变化21.03%~161.14%、1.11%~60.68%和17.55%~37.66%,以SM和RPM效果更为显著;长期耕作措施下土壤微生物整体面临C、N养分限制,覆盖处理下矢量角度在作物生长前期显著增大11.52%~23.17%,表明缓解了微生物氮限制,而矢量长度整体呈增加趋势,变化10.38%~84.38%,覆盖处理加剧了微生物碳限制,且随时间发展碳限制程度愈发强烈;RDA分析显示,土壤含水量(SWC)、AN和AP含量为黄土高原区驱动酶活性及其计量比变化的关键因子.综上所述,黄土高原区实施SM和RPM耕作处理对土壤养分特征及酶活性影响更强,可相结合推行以达到更佳效果,同时,应考虑适量施用氮肥以缓解当地农田养分限制,研究结果可有助于深入了解覆盖措施对农田土壤微生物养分利用策略的影响及其调控机制,为黄土高原丘陵区长期可持续发展提供理论依据.

摘要：The key to managing fracture is to achieve stable internal fixation,and currently,biologically and mechanically appropriate internal fixation devices are urgently *** excellent biocompatibility and corrosion resistance,titanium–niobium alloys have the potential to become a new generation of internal fixation materials for ***,the role and mechanism of titanium–niobium alloys on promoting fracture healing are still ***,in this study,we systematically evaluated the bone-enabling properties of Ti45Nb via in vivo and in vitro *** vitro,we found that Ti45Nb has an excellent ability to promote MC3T3-E1 cell adhesion and proliferation without obvious *** phosphatase(ALP)activity and alizarin red staining and semiquantitative analysis showed that Ti45Nb enhanced the osteogenic differentiation of MC3T3-E1 cells compared to the Ti6Al4V *** the polymerase chain reaction experiment,the expression of osteogenic genes in the Ti45Nb group,such as ALP,osteopontin(OPN),osteocalcin(OCN),type 1 collagen(Col-1)and runt-related transcription factor-2(Runx2),was significantly higher than that in the control ***,in the western blot experiment,the expression of osteogenic-related proteins in the Ti45Nb group was significantly increased,and the expression of PI3K–Akt-related proteins was also higher,which indicated that Ti45Nb might promote fracture healing by activating the PI3K–Akt signaling *** vivo,we found that Ti45Nb implants accelerated fracture healing compared to Ti6Al4V,and the biosafety of Ti45Nb was confirmed by histological ***,immunohistochemical staining confirmed that Ti45Nb may promote osteogenesis by upregulating the PI3K/Akt signaling *** study demonstrated that Ti45Nb exerts an excellent ability to promote fracture healing as well as enhance osteoblast differentiation by activating the PI3K/Akt signaling pathway,and its good biosafety has been confirmed

摘要：心肌肥厚(hypertrophiccardiomyopathy,HCM)主要病理表现为心肌细胞体积增大等,是心力衰竭发生的重要原因之一,易导致心律失常和猝死[1],由于HCM病因和发病机制的复杂性,目前并没有有效的防治方法。异丙肾上腺素(isoprenaline,ISO)是一种β肾上腺素受体激动剂,已成为大鼠心肌肥厚动物模型造模的常用方案之一。但目前ISO注射剂量和注射时间并不统一差异较大,并未明确一个可重复、固定的造模方法。因此,建立一个可靠的ISO药物注射HCM模型,探究ISO造模心肌肥厚更加有效的注射剂量,选取1、3和5 mg·kg^(-1) ISO剂量,探究大鼠心肌肥厚模型的建立方法。