摘要：单价Ag+或Li+引入到类金刚石结构的MQ22-(M=Ga,In;Q=S,Se)阴离子基团中能合成出良好的二阶非线性光学(NLO)晶体材料.然而,这些晶体分别面临着较低的抗激光损伤阈值(LIDT)或二氧化硅易被腐蚀等缺点,严重限制了其在高功率激光应用中的实用性.在本研究中,基于类金刚石结构的ZnSe,我们采用[Se_(4)Zn_(13)]Se_(2)4→[ClRb_(3)Ba]Se_(24)非常规的聚阳离子取代策略,设计并合成了一种新型的盐包硫属化合物[Rb_(3)BaCl][In_(8)Se_(14)](1).化合物1属于压缩黄铜矿型硒化物并保持了与AgInSe_(2)相同的晶体对称性(I-42d空间群).值得注意的是,由于InSe_(4)四面体结构单元的平行排列,化合物1具有相位匹配的强二次谐波(SHG)响应(2.0倍于AgGaS_(2)@2.90μm).此外,聚阳离子[Rb_(3)BaCl]^(4+)的引入促进了光学带隙(2.02 eV)的增强,有效地避免了对2.09μm激光的双光子吸收;同时结合较低的热膨胀系数,使得化合物1表现出高的LIDT(3.2倍于AgGaS2@2.09μm).本研究验证了在类金刚石结构中进行聚阳离子取代的可行性,并成功获得了性能优异的中远红外NLO材料.

摘要：二维过渡金属硫族化合物(TMDCs)材料被认为是拓展摩尔定律的极具前景的候选材料.然而,该材料的低光致发光效率严重限制了其实际应用,其本质源于材料制备中不可避免引入的缺陷.在本文中,我们报道了一种Sr掺杂单层MoS_(2)的有效缺陷工程策略,该策略在实验上通过简便的化学气相沉积(CVD)一步法成功实现.所制备的具有亚毫米(~324μm)级的大尺寸样品的光致发光可实现高达两个数量级的增强,并伴随着载流子寿命的显著增强.这一现象主要归因于Sr掺杂后MoS_(2)体系中其三激子向激子转换.与此同时,掺杂样品的辐射质量和稳定性也显著提升.第一性原理计算进一步阐明了其调控机制,即在MoS_(2)中引入适当互补缺陷能级与其自身的缺陷能级协同,从而可调节其载流子组分,以实现光致发光的显著增强.此外,我们的缺陷工程策略也适用于其他掺杂剂,如钙掺杂剂.我们的工作报告了一种可以显著提升单层MoS_(2)的荧光性能的有效缺陷工程策略,这为设计和调控二维TMDCs的光电特性提供一种极具前途的方法.

摘要：带隙可调的钙钛矿材料在室内光伏(IPVs)领域具有广阔的应用前景.然而,与室内光相匹配的宽带隙钙钛矿通常导电性较差,缺陷密度较高,往往不利于电荷提取和传输,限制了其光伏特性.在这里,我们通过调节Br/I比,探究了不同带隙三阳离子钙钛矿的IPVs特性.研究表明,宽带隙钙钛矿能充分利用室内光,在低照度下能获得较高的开路电压,但高Br/I比的钙钛矿具有较高的缺陷密度,不利于获得高短路电流密度和填充因子.通过进一步研究不同带隙钙钛矿的结晶动力学、缺陷密度和电荷传输特性,我们发现主流观念中高效IPVs着重考虑室内光伏材料的带隙是不全面的,我们证明了通过适当降低宽带隙晶体中的Br含量可以获得室内光伏特性更优异的器件.也就是说,室内光伏晶体材料的制备需要兼顾带隙和电荷传输特性.在此工作中,平衡带隙和电荷传输的器件(Br 0.23, 1.62 eV)在1035 lux的LED灯照射下取得了40.71%的最佳效率.我们的研究为高效室内光伏的设计提供了新思路.

摘要：Kirigami arts have provided a more promising method for building multiscale structures,which can shape two-dimensional(2D)sheets into three-dimensional(3D)configurations by cutting and ***,we first carried out a theoretical analysis of the mechanical properties of 2D honeycomb lattice structures and experimental verification combined with finite element(FE)***,a series of thick-walled 3D kirigami-inspired honeycomb(TW3KH)structures with different mechanical properties were designed and fabricated on the exploration and optimization of geometric parameters of 2D honeycomb *** investigations of folding feasibility,self-expansion,and self-folding performance experimentally showed that our designed four-dimensional(4D)printing structure had good programmability and shape memory capability and a large volume change ratio during shape ***,research on its compression deformation behavior found that the TW3KH structures can recover load-bearing capacity very well when the angle is ***,these TW3KH structures have great advantages in space-saving smart load-bearing equipment.

摘要：How to increase strength without sacrificing ductility has been developed as a key goal in the manufacture of high-performance metals or alloys. Herein, the double-nanophase intragranular yttrium oxide dispersion strengthened iron alloy with high strength and appreciable ductility was fabricated by solution combustion route and subsequent spark plasma sintering, and the influences of yttrium oxide content and sintering temperature on microstructures and mechanical properties were investigated. The results show at the same sintering temperature,with the increase of yttrium oxide content, the relative density of the sintered alloy decreases and the strength increases. For Fe–2wt%Y_(2)O_(3)alloy, as the sintering temperature increases gradually, the compressive strength decreases, while the strain-to-failure increases. The Fe–2wt%Y_(2)O_(3)alloy with 15.5 nm Y_(2)O_(3)particles uniformly distributed into the 147.5 nm iron grain interior sintered at 650℃ presents a high ultimate compressive strength of 1.86 GPa and large strain-to-failure of 29%. The grain boundary strengthening and intragranular second-phase particle dispersion strengthening are the main dominant mechanisms to enhance the mechanical properties of the alloy.

摘要：局部电荷的强离域和强偶极矩是影响共价有机框架(COFs)基光催化剂催化析氢性能的两个关键因素.然而,基于精确的调控结构模型来系统研究这种构效关系的报告相对较少.本研究提出了一种新的策略,通过合理的设计,制备了三种三芴酮基COFs,通过在分子水平上调控单体的结构和偶极来提高局部电荷离域指数.我们重点研究这三种三芴酮基COF的局部电荷离域与光催化性能之间的构效关系.在不同三芴酮基COF中,1,3,5-三(对甲酰基苯基)苯基COF(TeTpb-COF)展现出21.6 mmol g^(-1)h^(-1)的最高析氢速率,与2,4,6-三(4-醛基苯基)-1,3,5-三嗪基COF(TeTt-COF,0.2mmol g^(-1)h^(-1))相比,光催化析氢性能提高了108倍.这种性能的增强可归因于其强大的分子内置电场提高了供体-受体嵌段单元中光生电荷的有效分离效率.这项工作证实了调整构建块可以极大增强三芴酮基COFs中的局部偶极矩,从而显著改善光催化析氢性能.构建模块的调控策略为创建高效的新型COF基光催化析氢平台提供了新机会.

摘要：The H_(∞)control method is an effective approach for attenuating the effect of disturbances on practical systems, but it is difficult to obtain the H_(∞)controller due to the nonlinear Hamilton-Jacobi-Isaacs equation, even for linear systems. This study deals with the design of an H_(∞)controller for linear discrete-time systems. To solve the related game algebraic Riccati equation(GARE), a novel model-free minimax Q-learning method is developed, on the basis of an offline policy iteration algorithm, which is shown to be Newton’s method for solving the GARE. The proposed minimax Q-learning method, which employs off-policy reinforcement learning, learns the optimal control policies for the controller and the disturbance online, using only the state samples generated by the implemented behavior policies. Different from existing Q-learning methods, a novel gradient-based policy improvement scheme is proposed. We prove that the minimax Q-learning method converges to the saddle solution under initially admissible control policies and an appropriate positive learning rate, provided that certain persistence of excitation(PE)conditions are satisfied. In addition, the PE conditions can be easily met by choosing appropriate behavior policies containing certain excitation noises, without causing any excitation noise bias. In the simulation study, we apply the proposed minimax Q-learning method to design an H_(∞)load-frequency controller for an electrical power system generator that suffers from load disturbance, and the simulation results indicate that the obtained H_(∞)load-frequency controller has good disturbance rejection performance.

摘要：Si C nanowires are excellent high-temperature electromagnetic wave (EMW) absorbing materials. However, their polymer matrix composites are difficult to work at temperatures above 300℃, while their ceramic matrix composites must be prepared above 1000℃ in an inert atmosphere. Thus, for addressing the abovementioned problems, SiC/low-melting-point glass composites were well designed and prepared at 580℃ in an air atmosphere. Based on the X-ray diffraction results, SiC nanowires were not oxidized during air atmosphere sintering because of the low sintering temperature. Additionally, SiC nanowires were uniformly distributed in the glass matrix material. The composites exhibited good mechanical and EMW absorption properties. As the filling ratio of SiC nanowires increased from 5wt%to 20wt%, the Vickers hardness and flexural strength of the composite reached HV 564 and 213 MPa, which were improved by 27.7%and 72.8%, respectively, compared with the low-melting-point glass. Meanwhile, the dielectric loss and EMW absorption ability of SiC nanowires at 8.2–12.4 GHz were also gradually improved. The dielectric loss ability of low-melting-point glass was close to 0. However, when the filling ratio of SiC nanowires was 20wt%, the composite showed a minimum reflection loss (RL) of-20.2 dB and an effective absorption (RL≤-10 dB) bandwidth of2.3 GHz at an absorber layer thickness of 2.3 mm. The synergistic effect of polarization loss and conductivity loss in SiC nanowires was responsible for this improvement.

摘要：A storage system is the core of a computer,and plays an important role in the sustainable development of emerging strategic industries,such as artificial intelligence,big data,cloud computing,and the Internet of *** stack access is a major factor restricting the performance of data-intensive systems because of the increasing performance of processors and network devices.

摘要：Understanding the influence of purities on the electrochemical performance of pure aluminum(Al)in alkaline media for Al–air batteries is ***,we comprehensively investigate secondary phase precipitate(SPP)-induced localized corrosion of pure Al in NaOH solution mainly based on quasi-in-situ and cross-section observations under scanning electron microscopy coupled with finite element *** experimental results indicate that Al–Fe SPPs appear as clusters and are coherent with the Al *** alkaline media,Al–Fe SPPs exhibit more positive potentials than the substrate,thus aggravating localized galvanic corrosion as cathodic ***,finite element simulation indicates that the irregular geometry coupled with potential difference produces the non-uniform current density distribution inside the SPP cluster,and the current density on the Al substrate gradually decreases with distance.