Two-dimensional MX Dirac materials and quantum spin Hall insulators with tunable electronic and topological properties

We propose a novel class of two-dimensional(2D)Dirac materials in the MX family(M=Be,Mg,Zn and Cd,X=Cl,Br and I),which exhibit graphene-like band structures with linearly-dispersing Dirac-cone states over large energy scales(0.8–1.8 eV)and ultra-high Fermi velocities comparable to graphene.Spin-orbit coupling opens sizable topological band gaps so that these compounds can be effectively classified as quantum spin Hall insulators.The electronic and topological properties are found to be highly tunable and amenable to modulation via anion-layer substitution and vertical electric field.Electronic structures of several members of the family are shown to host a Van-Hove singularity(VHS)close to the energy of the Dirac node.The enhanced density-of-states associated with these VHSs could provide a mechanism for inducing topological superconductivity.The presence of sizable band gaps,ultra-high carrier mobilities,and small effective masses makes the MX family promising for electronics and spintronics applications.     

低临界胶束浓度PEGMA-b-PCL的制备及其 药物缓释性能

以ε-己内酯（ε-CL）为疏水链段,聚乙二醇甲醚甲基丙烯酸酯（PEGMA）为亲水链段,4-氰基-4-[(十二烷基硫基硫羰基)硫基]戊酸（CDPA）为可逆加成-断裂链转移（RAFT）试剂,在以甲苯为溶剂、N2氛围、80 ℃、反应24 h的条件下,通过RAFT聚合法制备了两嵌段聚合物PEGMA-b-PCL。将其自组装为胶束用作纳米药物载体,并以姜黄素（Cur）为胶束负载药物。考察了两嵌段聚合物结构、分子量及分布,表征了胶束载体粒径、形貌,测试了胶束载体的载药和释药性能。结果表明,不同嵌段聚合物相对分子质量范围为478~7318,此类聚合物具有较低的临界胶束浓度（CMC）,在常规条件下（pH=7.4）其范围为0.920~1.600 μg/mL。胶束载体粒径范围为:68.34~186.30 nm。当n(CDPA)∶n(ε-CL)=1∶200时,胶束载药量和包封率最高,可达12.05%和75.26%。在不同pH值环境下,药物缓释性能可达15 d,其中pH=5.0时释药量可达35.38%。     

Biomimetic Modification of Water-Borne Polymer Coating with Carnauba Wax for Controlled Release of Urea

Benefitting from the special structure of the leaf cuticle layer, plants have natural hydrophobicity and anti-fouling abilities. Inspired by the leaf surface structure, a biomimetic modification strategy was raised to improve the surface hydrophobicity of polyacrylate coating for controlled release fertilizer. Double-layer (polyacrylate and carnauba wax) coated fertilizer was obtained after biomimetic modification. The quality of controlled release fertilizer modified with the carnauba wax was greatly enhanced, and the coating material was effectively saved. The surface appearance of polyacrylate-coated fertilizer was improved for the surface blemish was repaired by the loaded carnauba wax. The characterizations by Fourier transform infrared spectroscopy indicated that the hydrogen bonds were formed between the water-based polyacrylate membrane and the carnauba wax layers. By optimizing the content of polyacrylate and carnauba wax, the release duration of the fertilizer was effectively prolonged, which was improved from 1 month to more than 2 months after the biomimetic modification. Therefore, biological wax as an environmentally-friendly natural material that has showed a broad potential in the application of coated controlled release fertilizer.     

我国混凝土空心砌块节能建筑案例分析

通过我国混凝土空心砌块节能建筑案例分析,提出外保温、内保温、夹芯保温各有优缺点,应因地制宜,依据建筑功能要求采取适合的保温方式,并根据多年的研究和应用实践经验,提出了我国不同气候区域混凝土空心砌块节能建筑的外墙构造设计方案。     

浅谈零缺陷与质量成本

阐述零缺陷在工作中的行动准则和零缺陷管理所要达到的最终目标,分析了零缺陷在实际生产中对质量成本的影响。     

小型无人直升机的纵向横向解耦优化控制

论文根据小型无人直升机的机理建立了数学模型,并在悬停状态下近似线性化,运用Matlab的非线性控制工具箱(NCD)设计了具有很强鲁棒性的控制器,实现了对于小型无人直升机的纵向和横向的解耦控制,仿真结果证明了方法的有效性。     

Performance of Channel-Aware Scheduling Algorithms for HDR-WPAN

In this paper, we consider the performances in terms of system throughput and response time of various channel-aware scheduling algorithms for both MPEG streams and non-MPEG flows in a high-data-rate (HDR) wireless personal area network (WPAN). The algorithms under investigation are the shortest remaining processing time rule, the exponential rule, the modified largest weighted delay first rule, the maximum rate rule, and the proportionally fair rule. Decodability issues are taken care of by means of the frame-decodability aware technique and the burst transfer eligibility decision mechanism. The impacts of a number of factors including deadline and interference-plus-noise level are also examined. The investigations are carried out through extensive ns-2 simulations. Based on the numerical results, we propose a heuristic scheduling algorithm for MPEG streams that outperforms the above algorithms in terms of system throughput. The findings are useful for system designers.     

多通道高速实时数据采集与处理平台的设计

针对红外导引头多元信息探测和实时数据处理要求,设计了基于FPGA和DSP的多通道高速实时数据采集和处理平台;在该平台中,通过FPGA实现了DSP的引导、多通道高速A/D、D/A、大容量存储器(SDRAM和FLASH)和数字I/O等功能模块的无缝链接及逻辑控制;利用时序分配和EDMA(扩展的直接存储器访问)技术以及McBSP(多通道缓冲串口)和HPI(主机口),实现了FPGA和DSP之间实时传输与通信控制;实际应用表明在该平台中A/D与FPGA之间串行传输速率可达20MHz,FPGA与DSP之间串行传输速率可达70MHz,且平台运行稳定、可靠,满足了红外导引头的实时信号处理要求。     

炸药冲击波激励氩气闪光实验研究

建立了对可见光和近红外的瞬态测试记录系统。用实验方法研究了氩气在炸药冲击小励下产生的可见光光强。测得了不同压力下氩气的辐射强度,分析了气体压力对光强的影响。     

Cytokinin Confers Brown Planthopper Resistance by Elevating Jasmonic Acid Pathway in Rice

Plants have evolved a sophisticated defense system that employs various hormone pathways to defend against attacks by insect pests. Cytokinin (CK) plays an important role in plant growth and stress tolerance, but the role of CKs in plant–insect interaction remains largely unclear. Here, we report that CKs act as a positive regulator in rice resistance against brown planthopper (BPH), a devastating insect pest of rice. We found that BPH feeding promotes CK biosynthesis and signaling in rice. Exogenous application of CKs significantly increased the rice resistance to BPH. Increasing endogenous CKs by knocking out cytokinin oxidase/dehydrogenase (OsCKXs) led to enhanced resistance to BPH. Moreover, the levels of the plant hormone jasmonic acid (JA) and the expression of JA-responsive genes were elevated by CK treatment and in OsCKXs knockout plants. Furthermore, JA-deficient mutant og1 was more susceptible to BPH, and CK-induced BPH resistance was suppressed in og1. These results indicate that CK-mediated BPH resistance is JA-dependent. Our findings provide the direct evidence for the novel role of CK in promoting insect resistance, and demonstrate that CK-induced insect resistance is JA-dependent. These results provide important guidance for effective pest management strategies in the future.