摘要：Electronic structures in two kinds of boron structures are investigated by the first-principle density functional theory(DFT) calculations. One structure is from theoretical prediction, and the other is from experimental investigation. Binding energy calculations suggest that the boron structure designed from theory is more stable than that made by experiment. Elastic constants calculations show that both structures are mechanically stable. The electronic structure results show that the theoretical designed structure exhibits semi-metal behavior, while the other structure exhibits metallic character. No magnetic phenomenal is discovered from them. All the calculations are carried out by the first principles calculation through the Mat Cloud platform, which is developed by our research group.

摘要：The design of an ultra-compact SOI-based 1×2 3 dB multimode interference(MMI) coupler is *** symmetric multimode interference structure and deeply-etched parabolically tapered multimode waveguide are used in the *** length of the device is reduced by about 87% compared with general multimode interference straight *** on effective index method(EIM) and two dimensional beam propagation method(2D-BPM),the structure parameters are optimized and the fabrication tolerances are *** results indicate that the performance of the coupler is deeply affected by the coupler's width,etching depth and photolithography alignment error in perpendicular direction.

摘要：All commercial electron spin polarimeters work in single channel mode, which is the bottleneck of researches by spin-resolved photoelectron spectroscopy. By adopting the time inversion antisymmetry of the magnetic field, we developed a multichannel spin polarimeter based on normal incident very low energy electron diffraction （VLEED）. The key point to achieve the multi-channel measurements is the spatial resolution of the electron optics. The test of the electron optics shows that the designed spatial resolution can be achieved and an image type spin polarimeter with 100 times 100, totally ten thousand channels is possible to be realized.

摘要：设计在酸性介质中具有高活性和高稳定性的氧析出反应(OER)催化剂对能量转换和储存技术的发展具有重要意义.然而,在实际OER条件下催化剂的原子结构会发生变化,且目前对其动态活性结构的认识仍然不足.本文中,我们通过退火和蚀刻纳米多孔Co-Ru合金合成了具有优异酸性OER活性和稳定性的原子级Co掺杂纳米多孔Ru O_(2)催化剂.原位X射线吸收光谱证实:蚀刻策略可以在原子级Co掺杂纳米多孔Ru O_(2)的金属中心周围产生丰富的氧空位,从而在实际OER条件下产生收缩的金属-氧配体键.这种动态结构演变降低了催化活性位点在OER过程中的动力学势垒,因而催化剂的催化活性和稳定性大幅提高.本研究结果揭示了催化剂活性结构的原子细节以及它们的结构演化对催化活性的影响.

摘要：离子插层是提高Ti_(3)C_(2)TxMXene电化学性能的有效方法之一.然而,不同的插层离子对MXene的结构和电化学性能的影响是否相同这一问题尚不清楚.本文系统研究了Li+、Na+、K+、Cs+、Zn2+、Mg2+、SO_(4)2-和OH-等一系列离子插层后的MXene的结构特征和电化学性能.研究结果表明,插层离子的半径、电荷数和化学特性对插层效果都会产生影响.在所研究的插层剂中,由离子半径最大的一价阳离子Cs+和具有强碱性的阴离子OH-组成的插层剂CsOH对MXene具有较好的插层效果.插层后的MXene层间距增大,层间容纳了大量游离水,Ti的价态升高,片层表面有利于氧化还原反应的含O官能团增多,这都大大促进了电解液离子H+的扩散与存储.由此制备的电极的质量比电容大幅度提高,为原始MXene电极的7倍多,而且经过20,000次充放电循环后电容保持率未发生下降.本文为具有高电容性能的MXene和MXene基复合电极的合理设计和制备提供了指导.

摘要：This paper discusses the problem of design and optimization of low-energy transfer orbit with multi-body environment. A new integrative method is proposed to effectively solve the problem, in which the parameterized patched manifolds in CR3BP(circular restricted three-body problems), the shape-based method with multi-body environment, the homotopic method with multi-body environment, and the low-thrust capturing and descending algorithm with multi-body environment are all included. Firstly, the parameters describing the patched manifolds in CR3 BP are optimized until the least total absolute velocity increment has been got, including the employment of the shape-based method with multi-body environment. Secondly, the low-thrust control laws of the transfer orbit are optimized employing the homotopic method with multi-body environment that transfers the fuel optimization problem to an easier energy optimization problem. Thirdly, the low-thrust descending orbit around Mars is computed using the laws proposed in this paper. As a typical example, the Earth-Mars transfer orbit design is discussed. The results showed that the parameters describing the patched manifolds could be optimized by the DE(differential evolution) algorithm effectively; the homotopic method with multi-body environment could get the optimal value that meets the first order optimality conditions; and the low-thrust descending orbit could effectively be captured by Mars and finally become a circular parking orbit around it by the hypothesis control laws proposed in this paper. It shows that the final fuel cost is much less than the optimal transfer in the patched two-body problems. In conclusion, the method proposed in this paper could effectively solve the low-energy low-thrust optimal control problem in multi-body environment for the future deep space explorations.

摘要：Hydroxyapatite(HA)nanoparticles and silver(Ag)nanoparticles are expected to enable desirable bioactivity and antibac-terial properties on biopolymer ***,interfacial adhesion between HA/Ag and the biopolymer is poor due to the large physicochemical differences between these *** this study,poly L-lactic acid(PLLA)powder was first surface-modified with bioactive polydopamine(PDA)in an alkaline ***,HA and Ag nanoparticles were grown in situ on the PDA-coated PLLA powder,which was then adhered to the porous bone scaffold using a selective laser-sintering *** showed that HA and Ag nanoparticles were homogenously distributed in the matrix,with enhanced mechanical *** body fluid bioactivity tests showed that the in situ grown HA-endowed scaffold shows excellent *** vitro tests confirmed that the scaffold exhibits favorable biocompatibility with human umbilical cord mesenchymal stem cells,as well as strong antibacterial activity against Gram-negative Escherichia ***,in vivo assays indicated that the scaffold promoted bone generation,with a new bone area fraction of 71.8%after 8 weeks’implantation,without inflammation.

摘要：This work is about the development of a super low noise amplifier with minimum power consumption and high gain for several wireless *** amplifier operates at frequency bands of 0.9-2.4 GHz and can be used in many applications like Wireless local area network(WLAN),WiFi,Bluetooth,ZigBee and Global System for mobile communications(GSM).This new design can be employed for the IEEE 802.15.4 standard in industrial,scientific and medical(ISM) *** enhancement mode pseudomorphic high electron mobility transistor PHEMT is used here due to its high linearity,better performance and less noisy *** common source inductive degeneration method is employed here to enhance the gain of *** amplifier produces a gain of more than 17 dB and noise figure of about 0.5 *** lower values of S11 and S22 reflect the accuracy of impedance matching network placed at the input and output sides of *** Advance Design System(ADS) is used for the design and simulation *** the layout of design is developed on the FR4 substrate.

摘要：量子安全直接通信(QSDC)是通信双方不需要事先共享密钥,直接利用量子信道传输机密信息的一种新型保密通信模式.传统QSDC方案需要在量子信道中分发两轮光子.本文利用极化-空间超纠缠态设计了一种新型的一步QSDC方案,只需在量子信道中分发一轮光子.因此,该方案可简化实验操作并降低信息错误,实现双向通信,且在理论上具有绝对安全性.此外,通过分发一对超纠缠光子能传递2比特的信息,该方案具有较高的通信效率.在极化和空间自由度的纠缠保真度为0.98的情况下,该方案的最大通信距离约为216 ***也可用于远距离分发密钥,与传统的基于纠缠的量子密钥分发(QKD)方案相比,该方案在150 km的通信距离的密钥产生率约为QKD的2.5倍.而且,借助于未来的量子中继技术,采用该方案有望实现任意长距离的安全通信.

摘要：对集成在可编程超表面单元中有源器件的状态进行编程,可以在不重新设计可编程超表面结构的情况下快速改变其电磁特性,从而实时地调控电磁波.但是在远距离控制超表面时,为了传输编码信号需要大量的长导线来连接超表面和现场可编程门阵列(FPGA),使得整个超表面系统十分复杂而且使用不方便.因此,本文提出了红外调控可编程超表面,以此来实现对超表面的远程非接触式编程.红外调控可编程超表面由超表面阵列、FPGA控制器和红外收发模块组成.红外收发模块能够切换存储在FPGA控制器中的编码序列,从而实时控制集成在超表面上的变容管的偏置电压.在微波频段对样品进行实验,测量结果表明利用红外线可以远程改变超表面样品的散射波束.红外调控可编程超表面的成功实现,不仅解决了复杂的长导线连接问题,也为构建一类新的远程调控动态超表面开辟了途径.