基于NbN，AIN技术的体声波器件研究

体声波滤波器由于其低插损、小尺寸、高带外抑制等特性，随着第三代移动通信以及蓝牙技术的发展而得到广泛研究，而MEMS技术和压电薄膜制备技术的进一步发展使高性能的体声波滤波器制作成为可能．我们以单晶MgO作为器件衬底，MgO/NbN多层结构作为AIN薄膜体声波器件的反射器，NBN／AIN／NbN三层结构为谐振器．在这样的多层结构的设计中由于各种材料之间的晶格失配小，可以获得从几十纳米到几百纳米厚度不等的单晶AIN薄膜．通过控制AIN薄膜和NbN薄膜的不同厚度，可以获得不同频段范围的谐振器．压电薄膜的质量，以及体声波在多层结构界面上的能量损耗，直接影响到谐振器电学性能．基于AIN材料的压电性能，设计了NBN／AIN／NBN三层结构的谐振器，并进行了数值模拟．     

Reverse reconciliation for continuous variable quantum key distribution

An efficient and practical post-processing technique based on reverse reconciliation for continuous variable quantum key distribution is proposed and simulated with low-density parity check (LDPC) codes. MultiLevel Coding/ MultiStage Decoding, which fully utilizes optimization technique such as vector quantization and iterative decoding and the optimal channel coding most close to the Shannon limit, was used to realize efficient reverse reconciliation algorithm. Simulation results showed that the proposed m...     

First-principles study on the structural and electronic properties of ultrathin ZnO nanofilms

Using first-principles density-functional calculations, we have studied the structural and electronic properties of ultrathin ZnO {0001} nanofilms. The structural parameters, the charge densities, band structures and density of states have been investigated. The results show that there are remarkable charge transfers from Zn to O atoms in the ZnO nanofilms. All the ZnO nanofilms exhibit direct wide band gaps compared with bulk counterpart, and the gap decreases with increased thickness of the nanofilms. The decreased band gap is associated with the weaker ionic bonding within layers and the less localization of electrons in thicker films. A staircase-like density of states occurs at the bottom of conduction band, indicating the two-dimensional quantum effects in ZnO nanofilms.     

变量有界半定最小二乘问题

<正>1引言设A_i∈S~n,i=1,…,m,定义线性算子A:S~n→R~m,AX=(A_1·X,…,A_m·X)~T,其相应的伴随算子为A~*:R~m→S~n,且A~*y=sum from i=1 to my_iA_i.X∈S~n,b∈R~m.Malick.J在[6]中讨论了如下标准半定最小二乘问题(SDLS):     

沉积物内多氯联苯测定中有机氯农药的排除及质量控制/质量保证研究

报道了沉积物样品中多氯联苯(PCBs)的分析方法及质量控制/质量保证(QA/QC)研究,结果表明多级复合硅胶柱对有机氯农药去除效果良好.采用25种PCBs同族体标样PCB25对分析方法进行了QA/QC研究,PCBs的平均回收率在97%～118%之间.用本方法测定25种多氯联苯同族体的检测限范围在0.5～1.4ng/g之间.     

聚吡咯/纳米SiO_2复合材料的制备及氧化性能

采用化学氧化法制备聚吡咯/纳米Si O2(PPy/n Si O2)复合材料,通过扫描电子显微镜和红外光谱对其进行表征,并将其应用到对苯二酚的氧化反应中.结果表明,PPy/n Si O2复合材料中,PPy较均匀地负载在纳米Si O2表面.在弱酸性介质中,PPy/n Si O2对对苯二酚具有很好的氧化性能.反应2 h内,对苯二酚的氧化过程符合表观一级反应动力学.结合紫外-可见光谱法分析表明,聚吡咯通过与对苯二酚之间的氢键相互作用形成聚吡咯活性中间体,将对苯二酚氧化为对苯醌,聚吡咯具有氧化剂和催化剂的双重功能.     

Simple Method in Diagnosing Cancer Cells by a Novel Fluorescence Probe BMVC

Different cellular accumulations with distinct fluorescence properties of BMVC in cancer cells from normal cells allow us to establish a simple and economic method for the diagnosis of cancer cells. With using a light emitting diode to excite the BMVC molecule, microarray fluorescence analysis of a cell‐based glass chip provides an easy method towards the detection of a limited number of cancer cells.     

Enhanced mechanical performance and biological evaluation of a PLGA coated β-TCP composite scaffold for load-bearing applications

Porous β-tricalcium phosphate (β-TCP) has been used for bone repair and replacement in clinics due to its excellent biocompatibility, osteoconductivity, and biodegradability. However, the application of β-TCP has been limited by its brittleness. Here, we demonstrated that an interconnected porous β-TCP scaffold infiltrated with a thin layer of poly(lactic-co-glycolic acid) (PLGA) polymer showed improved mechanical performance compared to an uncoated β-TCP scaffold while retaining its excellent interconnectivity and biocompatibility. The infiltration of PLGA significantly increased the compressive strength of β-TCP scaffolds from 2.90 to 4.19 MPa, bending strength from 1.46 to 2.41 MPa, and toughness from 0.17 to 1.44 MPa, while retaining an interconnected porous structure with a porosity of 80.65%. These remarkable improvements in the mechanical properties of PLGA-coated β-TCP scaffolds are due to the combination of the systematic coating of struts, interpenetrating structural characteristics, and crack bridging. The in vitro biological evaluation demonstrated that rat bone marrow stromal cells (rBMSCs) adhered well, proliferated, and expressed alkaline phosphatase (ALP) activity on both the PLGA-coated β-TCP and the β-TCP. These results suggest a new strategy for fabricating interconnected macroporous scaffolds with significantly enhanced mechanical strength for potential load-bearing bone tissue regeneration.     

调质42CrMo钢的棘轮-疲劳交互作用及其耦合损伤粘塑性本构模型

对调质42CrMo钢的棘轮-疲劳交互作用的实验结果进行了分析,揭示了材料在非对称应力循环下的全寿命棘轮变形特征和低周疲劳损伤演化特性.在统一粘塑性循环本构模型框架下,基于连续损伤力学理论,提出一个耦合损伤的牯塑性本构模型.该模型中将损伤分为宏观弹性损伤和塑性损伤两部分,并采用不同的损伤演化方程来描述这两类损伤.针对材料不同的失效模式,分别采用损伤变量门槛值和最大应变作为失效判据.将模型应用于调质42CrMo钢单轴应力循环下全寿命棘轮行为的描述和低周疲劳寿命预测中,模拟结果和实验结果吻合较好.