Controllable defects implantation in MoS<Subscript>2</Subscript> grown by chemical vapor deposition for photoluminescence enhancement

Photoluminescence (PL) of transition metal dichalcogenides (TMDs) can be engineered by controlling the density of defects, which provide active sites for electron-hole recombination, either radiatively or non-radiatively. However, the implantation of defects by external stimulation, such as uniaxial tension and irradiation, tends to introduce local damages or structural non-homogeneity, which greatly degrades their luminescence properties and impede their applicability in constructing optoelectronic devices. In this paper, we present a strategy to introduce a controllable level of defects into the MoS₂ monolayers by adding a hydrogen flow during the chemical vapor deposition, without sacrificing their luminescence characteristics. The density of the defect is controlled directly by the concentration of hydrogen. For an appropriate hydrogen flux, the monolayer MoS₂ sheets have three times stronger PL emission at the excitonic transitions, compared with those samples with nearly perfect crystalline structure. The defect-bounded exciton transitions at lower energies arising in the defective samples and are maximized when the total PL is the strongest. However, the B exciton, exhibits a monotonic decline as the defect density increases. The Raman spectra of the defective MoS₂ reveal a redshift (blueshift) of the in-plane (out-of-plane) vibration modes as the hydrogen flux increases. All the evidence indicates that the generated defects are in the form of sulfur vacancies. This study renders the high-throughput synthesis of defective MoS₂ possible for catalysis or light emitting applications.

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Molecular dynamics simulation on flow behavior of nanofluids between flat plates under shear flow condition

Molecular dynamic model of nanofluid between flat plates under shear flow conditions was built. The nanofluid model consisted of 12 spherical copper nanoparticles with each particle diameter of 4 nm and argon atoms as base liquid. The Lennard–Jones (LJ) potential function was adopted to deal with the interactions between atoms. Thus, the motion states of nanoparticles during the process of flowing were obtained and the flow behaviors of nanofluid between flat plates at different moments could be analyzed. The simulation results showed that an absorption layer of argon atoms existed surrounding each nanoparticle and would accompany with the particle to move. The absorption layer contributed little to the flow of nanoparticles but much to the heat transferring in nanofluids. Another phenomenon observed during shear flowing process was that the nanoparticles would vibrate and rotate besides main flowing with liquid argon and these micro-motions could strengthen partial flowing in nanofluids.     

Security analysis of two recently proposed RFID authentication protocols

Radio frequency identification (RFID) systems suffer many security risks because they use an insecure wireless communication channel between tag and reader. In this paper, we analyze two recently proposed RFID authentication protocols. Both protocols are vulnerable to tag information leakage and untraceability attacks. For the attack on the first protocol, the adversary only needs to eavesdrop on the messages between reader and tag, and then perform an XOR operation. To attack the second protocol successfully, the adversary may execute a series of carefully designed challenges to determine the tag’s identification.     

公交信号优先策略研究

本文介绍了公交优先策略的概念和分类,阐述了绿灯延长、绿灯提前、相位倒转、相位插入、公交通行专用相位等主动优先控制策略的基本原理,并对其进行了适应性和优缺点分析。     

基于MSP430的二线制高精度表头设计

针对传统的二线制表头在高温下测量精度差、温漂大的特点,提出了一种在高温下的高精度数显表头的设计方案。分别介绍了其软硬件的实现方法,即采用超低功耗微处理器MSP430F4250采集回路中的电流值,采用24位ADC转换器ADS1244进行模数转换,最后将经过运算的变送器输出信号值在LED数码管中加以显示。实测结果证明,该表头在高温下测量精度高、工作可靠、抗干扰性强、实用性强,势必会成为无源二线制仪表的发展方向。     

基于ARM9的分散式数据采集系统的研究

针对传统数据采集系统采集精度与数据处理能力的不足,结合当前广泛应用的嵌入式系统技术和总线技术,基于ARM9处理器S3C2440设计了一种分散式数据采集系统.底层数据采集系统采用了模块化的设计结构,各模块采用统一的总线把数据传送给主控器;最后系统利用ARM9强大的数据处理能力对所有数据进行分析、处理.实际试验证明,该系统数据处理速度快、控制精度高,可满足一般工业现场的要求.     

废气生物处理装置的远程监控系统

为有效控制污水处理设施的恶臭污染问题,设计了一种废气处理装置的监控系统;下位机采用西门子S7-300PLC,运用STEP7编程软件编制了现场PLC控制程序;上位机选用工控机,采用WinCC组态软件对上位机监控功能进行组态,实现现场数据实时记录和监控,并利用WinCC全局脚本开发了模糊自适应PID控制算法,实现了对生物滴滤池循环水pH值的模糊自适应PID控制;实际应用结果表明,该控制系统响应速度快、超调量小,大大改善了pH中和过程的控制效果.     

PKI网络信任模型的分析与研究

信任模型是整个网络安全体系的基础,决定了在网络上采用信任的形式与采用该形式带来的信任风险,并提供了建立和管理信任关系的框架。可见,对于信任模型的研究在网络安全中非常重要。文章着重分析了基于PKI的各类信任模型的信任机制、认证过程及其存在优缺点,指出了各类信任模型对网络信息安全产生影响的主要原因。通过总结与对比,指出了PKI信任模型的设计策略与发展趋势。     

A neural network approach for solving mathematical programs with equilibrium constraints

A neural network approach is presented for solving mathematical programs with equilibrium constraints (MPEC). The proposed neural network is proved to be Lyapunov stable and capable of generating approximal optimal solution to the MPEC problem. The asymptotic properties of the neural network are analyzed and the condition for asymptotic stability, solution feasibility and solution optimality are derived and the transient behavior of the neural network is simulated and the validity of the network is verified with numerical examples.     

The ring authenticated encryption scheme – How to provide a clue wisely

Though cryptography is being used more and more widely in reality, it seems that there exists no scheme or a concatenation of some existing schemes that could deal soundly with such practical situations as providing a clue, where the provider of the clue may want to reserve his beneficial rights while keeping his identity secret. To address this problem, inspired by the two notions of the ring signature and the authenticated encryption signature, we propose a new type of authenticated encryption scheme, which we call the ring authenticated encryption scheme, which can enable any member of a group of persons to provide a clue to some designated recipient wisely.