摘要：提出了一种在150～165 THz区域内的具有单峰吸收特性的高性能超材料吸收器。设计的吸波器包含两个阵列:双金属颗粒阵列和双空气孔阵列。金属层的阻尼常数在模拟中被优化。发现在模拟中使用2. 3倍的阻尼常数时,可以获得最大吸收率96%。吸收峰由局域表面等离子体(LSP)模式共振激发。为了揭示共振电磁机理,进行了两组模拟,研究结构参数变化对共振吸收峰的影响。发现随着垂直距离V的增加,吸收峰被增强,当V=160 nm时,获得新的吸收带。在第二次模拟中,对于水平距离H的增加,吸收峰也增强,并且当H=190 nm时获得另一个新的吸收带。电场强度分布结果表明LSP模式的激发和LSP模式之间的耦合效应导致吸收峰增强现象。

摘要：研究了基于超磁致伸缩材料实现对光纤布拉格光栅的动态调谐这一方案理论上可获得的最大调谐范围.利用超磁致伸缩换能器的输出特性,进行了超磁致伸缩换能器用于光纤布拉格光栅调谐的实验研究.分析了实验中影响可获得调谐范围的各种因素,如实际可获得的超磁致伸缩材料的特性、光纤布拉格光栅的特性以及换能器结构的设计.进一步讨论了在理论界限的前提下改进该方案可获得调谐范围的措施,并以施加预应力为例进行了实验验证.结果表明,通过给予超磁致伸缩材料合适的预应力,可以较明显地改善最大调谐范围.

摘要：Cancer is characterized by a high fatality rate,complex molecular mechanism,and costly *** microenvironment of a tumor consists of multiple biochemical cues and the interaction between tumor cells,stromal cells,and extracellular matrix plays a key role in tumor initiation,development,angiogenesis,invasion and *** better understand the biological features of tumor and reveal the critical factors of therapeutic treatments against cancer,it is of great significance to build in vitro tumor models that could recapitulate the stages of tumor progression and mimic tumor behaviors in vivo for efficient and patient-specific drug screening and biological *** conventional tissue engineering methods of constructing tumor models always fail to simulate the later stages of tumor development due to the lack of ability to build complex structures and angiogenesis potential,three-dimensional(3D)bioprinting techniques have gradually found its applications in tumor microenvironment modeling with accurate composition and well-organized spatial distribution of tumor-related cells and extracellular components in the past *** capabilities of building tumor models with a large range of scale,complex structures,multiple biomaterials and vascular network with high resolution and throughput make 3D bioprinting become a versatile platform in bio-manufacturing aswell as inmedical *** this review,wewill focus on 3D bioprinting strategies,design of bioinks,current 3D bioprinted tumor models in vitro classified with their structures and propose future perspectives.

摘要：目的:掌握分叉隧道的空气流动特征与阻力损失特性是进行分叉隧道通风设计和控制的关键。本文旨在探讨小角度分叉结构中的流动特征及局部损失机制,并基于流动分离机制构建可供设计使用的分叉隧道分流局部损失系数的理论公式。创新点:1.揭示气流在小角度分叉结构中的流动分离特征及损失机制;2.提出流向偏转角假设,建立可供设计使用的分叉隧道分流局部损失预测模型。方法:1.通过数值模拟,获得隧道分叉处的流动特征(图5、6a和6d),以及分流局部损失系数随分流比及夹角的变化规律(图6b和6c);2.通过理论推导,构建小夹角分叉结构的分流局部损失系数预测公式(公式(18)和(21));3.通过现场实测,验证预测公式的可靠性(图15)。结论:1.空气在隧道分叉处的分流将导致流速和流向的变化;当分流比β较小时,流动分离出现在靠近分叉点一侧的主线边壁和远离分叉点一侧的匝道边壁;当β较大时,流动分离出现在远离分叉点一侧的主线边壁和靠近分叉点一侧的匝道边壁。2.当分流后主线与匝道的流量比q等于两者的面积比?时,主线及匝道的分流局部损失系数ξ12和ξ13最小;当q>?时,ξ12和ξ13均随β的增大而减小,且ξ13随着θ的增大而增大;当q<?时,ξ12和ξ13均随β的增大而增大,且ξ13随着θ的增大而减小。3.基于隧道分叉处的流动分离机制,提出了空气流向偏转角假设,构建了可用于预测分叉隧道分流局部损失系数的理论公式,与已有文献公式相比,具有更好的预测精度。

摘要：Recently,Kelly and colleagues[1],inspired by computed tomography(CT),report a“volumetric additive manufacturing”technology via a computed axial lithography(CAL)approach.A related US patent application[2]has also been *** cumulative light exposure solidifies the material in the target area,while the other area remains uncured,resulting in only specific points in the designed 3D objects being *** technology significantly improves the capability of the digital light processing(DLP)***,the lithography approach based on a similar algorithm was already proposed by Xiang Wu in a patent(application ***/CN2016/080097)in 2016[3].

摘要：选择性加氢反应是化学化工领域中最具挑战性的反应之一.针对选择性加氢反应来设计具有工业应用价值的负载型纳米催化剂一直是学术界和工业界的研究热点与难点.载体是负载型催化剂的重要组成部分,在不同类型的载体中,炭载体因其来源广、成本低、耐酸碱、具有高比表面积而被广泛采用.但是,由于炭材料本身相对惰性,炭与负载的金属之间相互作用较弱;此外,碳前驱体的种类甚至产地对炭载体性能影响也非常大,导致催化剂活性及稳定性难以满足工业要求,从而严重限制了炭负载型催化剂的发展.近年来,氮掺杂炭由于其独特的性质受到了广泛的关注,大量的研究证实氮原子的掺入有助于提高炭负载型纳米催化剂的催化效率.本文将重点关注氮掺杂多孔炭负载型催化剂在选择性加氢反应中的应用;最后,将讨论并展望如何基于氮掺杂炭理性设计新型负载型纳米金属催化剂.氮掺杂炭材料中的氮主要可分为石墨氮、吡啶氮、吡咯氮和氨基氮.氮的引入一方面可改变炭材料的局域电子密度,引发电子在载体与活性组分之间的重新分配,电子转移的方向和程度可通过氮掺杂形式(如吡啶型或石墨型氮等)及浓度进行调节,从而实现对活性组分电子结构的调控;另一方面,提供了孤对电子用于形成氢键网络,从而调节了催化剂的亲水性,改善了催化剂在反应体系中的分散性.而且丰富的氮物种可为活性组分提供了稳定的锚定位点,从而提高了活性组分在炭载体上的分散度和稳定性.此外,部分氮物种为催化剂提供了碱性位点,可作为固体碱参与反应,丰富了氮掺杂炭负载型催化剂的应用范围.本文将氮掺杂炭负载型催化剂分为以下四种类型:传统负载型、包覆型、镶嵌型以及单原子催化剂.传统负载型催化剂即以氮掺杂炭材料为载体,采用浸渍法或液相还原法等将活性组分负载其上,该类型催化剂已经被广泛研究和使用.对于包覆型和镶嵌型催化剂,其金属和载体间的相互作用要强于传统炭负载型催化剂,这种强相互作用可有效提升催化剂稳定性,更能使某些高活性亚稳相稳定存在,进而大幅增强催化性能.但是炭层的过度包覆会导致暴露的金属活性位点减少,进而影响催化剂的性能.最近,炭负载型单原子催化剂得到迅速发展,它有着独特的配位环境和微观结构,众多单原子催化剂(如镍、钌、金等)已在选择性加氢反应中展现出优异的催化性能,且在某些反应中表现出独特的选择性.最后,本文讨论了氮掺杂炭负载型加氢催化剂未来的发展方向.原始生物质是氮掺杂炭的理想原料,且制备过程应尽量避免模板剂的使用.丰富氮掺杂炭材料的形貌和微观结构,以应对不同的反应需求是今后的重点发展方向.贵金属催化剂拥有优异的催化性能,如何提升其稳定性是急需解决的问题.非贵金属催化剂的活性相对较低,多组分协同催化是提升其性能的有效方法,进一步的工业应用也值得期待.不含金属的氮掺杂炭直接催化加氢反应需要极为苛刻的反应条件,其工业应用前景相对较低.

摘要：提出了一种在轨迹-速度双目标设计要求下优化综合连杆连续轨迹生成机构的方法.利用机构执行末端速度运动规律寻求平面连杆轨迹生成机构插值节点,使所选取的插值节点具有了运动速度要求的信息.基于该方法建立连续轨迹生成机构优化综合模型,以对应轨迹点差值最小作为优化目标函数,采用BFGS(Broyden-Fletcher-Gddfarb-Shanno)拟牛顿非线性优化算法优化计算机构尺寸.在设定曲柄匀速转动前提下,优化计算出了符合轨迹-速度设计要求的平面连杆机构尺寸,实现了预期的设计目标.最后比较了四杆机构和五杆机构实现实例的优化结果,表明了该设计方法的可行性和有效性.

摘要：Treatments for lesions in central nervous system(CNS)are always faced with challenges due to the anatomical and physiological particularity of the CNS despite the fact that several achievements have been made in early diagnosis and precision medicine to improve the survival and quality of life of patients with brain tumors in recent *** the complexity as well as role of the microenvironment of brain tumors may suggest a better revealing of the molecular mechanism of brain tumors and new therapeutic directions,which requires an accurate recapitulation of the complex microenvironment of human brain in ***,a 3D bioprinted in vitro brain matrix-mimetic microenvironment model with hyaluronic acid(HA)and normal glial cells(HEBs)is developed which simulates both mechanical and biological properties of human brain microenvironment in vivo through the investigation of the formulation of bioinks and optimization of printing process and parameters to study the effects of different concentration of gelatin(GA)within the bioink and different printing structures of the scaffold on the performance of the brain matrix-mimetic microenvironment *** study provides experimental models for the exploration of the multiple factors in the brain microenvironment and scaffolds for GBM invasion study.

摘要：natural materials are formed with integral *** on the achievements of our predecessors,the microstructures of some natural materials were decoded,and the configurations of integrated structures were interpreted with graded,porous,fractal and composite *** composition and spatial gradients of multiple kinds of physical parameters,which included elastic modulus,hardness,surface tension,stiffness,damping factor,density,heat conduction,electrical resistance factor,magnetic conductive factor,light penetration factor etc,are *** 2-D and 3-D porous structures were analyzed,which had different types of voids and *** the fractal and gradient fractal rules were described with leaf ***,the particulate and fibrous composite structures were developed with the combination of graded,porous and fractal ***,complex bionic design based on nets of blood vessels and nerves were proposed,which could be applied in structure design of mechanical parts.

摘要：The degumming pretreatment mechanism was investigated to improve degumming performance and the spinnability of degummed fibers. Apocynum was treated with redox system in the degumming pretreatment process and the pretreatment parameters had been optimized, besides the effects of pretreatment on property index of degummed apocynum fiber were investigated. The results showed that the redox system degumming process reduced alkali boiling time and had good advantages over the traditional degumming process in extraction rate, single fiber length and strength. SEM was used to test the longitudinal morphology changes of fibers before and after pretreatment. At the same time, pretreatment solution was analyzed by UV spectra and electron paramagnetic resonance spectrometer (ESR), and its pH value was also tested. The results showed that the pretreatment solution could release acid constantly to keep the stability of the pH which caused the swelling and dissolution of pectic substances in apocynum bast. Meanwhile, pretreatment solution could activate the free radicals from apocynum bast and reduce the activation energy of non-cellulosic composition in apocynum bast.