Computational study of transport properties of graphene upon adsorption of an amino acid: importance of including –$$\hbox {NH}_{2}$$ and –COOH groups

The effects of histidine and its imidazole ring adsorption on the electronic transport properties of graphene were investigated by first-principles calculations within a combination of density functional theory and non-equilibrium Greens functions. Firstly, we report adsorption energies, adsorption distances, and equilibrium geometrical configurations with no bias voltage applied. Secondly, we model a device for the transport properties study: a central scattering region consisting of a finite graphene sheet with the adsorbed molecule sandwiched between semi-infinite source (left) and drain (right) graphene electrode regions. The electronic density, electrical current, and electronic transmission were calculated as a function of an applied bias voltage. Studying the adsorption of the two systems, i.e., the histidine and its imidazole ring, allowed us to evaluate the importance of including the carboxyl (–COOH) and amine (–\(\hbox {NH}_{2}\)) groups. We found that the histidine and the imidazole ring affects differently the electronic transport through the graphene sheet, posing the possibility of graphene-based sensors with an interesting sensibility and specificity.     

Theoretical study of structural,electronic and optical properties of novel ternary alloys $$\hbox {MgO}_{1-{x}}{\hbox {Se}}_{{x}}$$ ($$x =$$x= 0.25, 0.50 and 0.75)

We report on the investigation of the structural, electronic, and optical properties of binary compounds (MgO and MgSe) and their ternary \(\hbox {MgO}_{1-{x}}\hbox {Se}_{{x}}\) (\(x=0.25, 0.5, 0.75\)) alloys within the density functional theory based on the full-potential linearized augmented plane wave method as implemented in the WIEN2k code. We have used the revised Perdew–Burke–Ernzerhof generalized gradient approximation (GGA-PBEsol) to calculate the structural properties and analyze the effect of the Se composition on the lattice constant and the bulk modulus of \(\hbox {MgO}_{1-{x}}\hbox {Se}_{{x}}\). The calculated electronic properties by employing the GGA-PBEsol and TB-mBJ approaches show that \(\hbox {MgO}_{1-{x}}\hbox {Se}_{{x}}\) alloys have a direct band gap \(\Gamma \)–\(\Gamma \) for \(x = 0, 0.25, 0.5\) and 0.75, suggesting the possibility of their use in the long wavelength optoelectronic applications. The optical properties such as the real and imaginary parts of the dielectric function, the refractive index, and the reflectivity of \(\hbox {MgO}_{1-{x}}\hbox {Se}_{{x}}\) are computed by using the accurate TB-mBJ potential. The wide band gaps larger than 3.1 eV mean that \(\hbox {MgO}_{1-{x}}\hbox {Se}_{{x}}\) alloys can be used in the applications of the ultraviolet region of the spectrum. Our data for all studied bowing parameters of \(\hbox {MgO}_{1-{x}}\hbox {Se}_{x}\) may serve as references for future experimental studies.     

Single-breath-hold abdominal $${T}_{1}$$ mapping using 3D Cartesian Look-Locker with spatiotemporal sparsity constraints

Objective

Our aim was to develop and validate a 3D Cartesian Look-Locker \({T}_{1}\) mapping technique that achieves high accuracy and whole-liver coverage within a single breath-hold.

Materials and methods

The proposed method combines sparse Cartesian sampling based on a spatiotemporally incoherent Poisson pattern and k-space segmentation, dedicated for high-temporal-resolution imaging. This combination allows capturing tissue with short relaxation times with volumetric coverage. A joint reconstruction of the 3D + inversion time (TI) data via compressed sensing exploits the spatiotemporal sparsity and ensures consistent quality for the subsequent multistep \({T}_{1}\) mapping. Data from the National Institute of Standards and Technology (NIST) phantom and 11 volunteers, along with reference 2D Look-Locker acquisitions, are used for validation. 2D and 3D methods are compared based on \({T}_{1}\) values in different abdominal tissues at 1.5 and 3 T.

Results

\({T}_{1}\) maps obtained from the proposed 3D method compare favorably with those from the 2D reference and additionally allow for reformatting or volumetric analysis. Excellent agreement is shown in phantom [bias\(_{3{\mathrm{T}}}\) < 2%, bias\(_{1.5{\mathrm{T}}}\) < 5% for (120; 2000) ms] and volunteer data (3D and 2D deviation < 4% for liver, muscle, and spleen) for clinically acceptable scan (20 s) and reconstruction times (< 4 min).

Conclusion

Whole-liver \({T}_{1}\) mapping with high accuracy and precision is feasible in one breath-hold using spatiotemporally incoherent, sparse 3D Cartesian sampling.

     

Series and parallel resistance effects on the C–V and G–V characteristics of $$\mathrm{Al}/\mathrm{SiO}_{2}$$/Si structure

This paper investigates the electrical behavior of the C–V and G–V characteristics of \(\mathrm{Al}/\mathrm{SiO}_{2}/\mathrm{Si}\) structure. The modeling of capacitance and conductance has been developed from complex admittance treatment applied to the proposed equivalent circuit. Poisson transport equations have been used to determine the charge density, surface potential, total capacitance, and flatband and threshold voltages as a function of the gate voltage, frequency (\(\omega )\), and series \(({R}_{\mathrm{s}})\) and parallel \(({R}_{\mathrm{p}})\) resistances. Results showed a frequency dispersion of C–V and G–V curves in both accumulation and inversion regimes. With increasing frequency, the accumulation capacitance is decreased, whereas the conductance is strongly increased. The shape, dispersion, and degradation of C–V and G–V characteristics are more influenced when parallel and series resistances \((\mathrm{R}_{\mathrm{s}}\), \(\mathrm{R}_{\mathrm{p}})\) are dependent to substrate doping density. The variation of \(\mathrm{R}_{\mathrm{s}}\) and \(\mathrm{R}_{\mathrm{p}}\) values led to a reduction of flatband voltage from ?1.40 to ?1.26 V and increase of the threshold voltage negatively from ?0.28 to ?0.74 V. A good agreement has been observed between simulated and measured C–V and G–V curves obtained at high frequency.     

Improved device performance in a CNTFET using La$$_{}$$O$$_{3}$$3 high-$$\kappa $$κ dielectrics

The scaling of MOSFETs is an important and effective way for achieving high performance and low power consumption. One of the bottlenecks for scaling is the physical gate oxide thickness. This paper presents and evaluates a new method for scaling carbon nanotube field-effect transistors (CNTFETs) using \(\hbox {La}_{2}\hbox {O}_{3}\) as a new gate dielectric, which has excellent electrical properties. The proposed CNTFET is simulated using HSPICE. Some of the main digital and analog parameters such as current ratio, subthreshold swing (SS), transconductance, and intrinsic gain have been studied. The simulation results show that the proposed CNTFET outperforms present CNTFETs in terms of current ratio, transconductance, and intrinsic gain.     

2006GE爱迪生奖照明设计大赛{亚太区}

2007年4月，2006GE爱迪生奖照明设计大赛首届亚太大奖在香港颁布。评审团从照明功能优异性，建筑兼容性，照明产品及技术使用有效性，建筑色形及建筑材质的表现性，节能性和成本效率等方面对参赛作品进行评价，最终评选出1个亚太卓越奖及5个亚太优胜奖.[编者按]     

A fast \vec{k}\cdot\vec{p} solver for hole inversion layers with an efficient 2D \vec{k} -space discretization

An efficient discretization of the 2 dimensional (2D) $\vec{k}$ -space and parallelization of the $\vec{k}\cdot \vec{p}$ solver for hole inversion layers is proposed. The 6×6 $\vec{k}\cdot \vec{p}$ Schrödinger equation is solved in parallel for only a small number of grid points in the 2D $\vec{k}$ -space. The subband energy and the generalized probability density function for an arbitrary in-plane wave vector are determined by interpolation based on the resultant eigen states. The fast approach results in accurate inversion densities and also low-field mobilities of holes in unstrained and uniaxially stressed Si channel double-gate MOS structures.     

基于半定规划的{0,1}-经济调度

基于内点半定规划,提出一种直接求解{0,1}-经济调度问题({0,1}-ED)的新方法.通过引入辅助变量,该方法将原整数变量约束转化为凸二次约束,进而将{0,1}-ED问题转化为半定规划问题,并用内点法进行求解.对于大系统整数变量的微小偏差,应用简单的启发式技术调整.ED-420等9个测试系统的仿真结果表明,所提方法能够有效地处理{0,1}-经济调度,对于大多数问题都可以得到较精确的结果,计算时间具有多项式复杂性.     

_2Ψ_2的一个变换公式与Eta函数恒等式

应用Ｒａｍａｎｕｊａｎ１Ψ１求和公式及围道积分的方法，得到了２Ψ２的一个变换公式，并由此推出了若干Ｅｔａ函数恒等式     

相差高频保护操作电流(_1+K_2)中_2主导作用的分析

操作元件是相差高频保护的主要元件之一,操作电流是由复合量_1+K_2构成,要求能反应线路上各种类型的短路故障,又能很好地表征线路内部和外部故障。本文分析了在不同的事故类型、故障相别和故障地点中负序量_2在整个操作电流中的主导地位如何得到保证,即如何合理选择_1+K_2中系数K。     

基于LabW{ndows／CVl的多通道测试系统

在高速铁路列车车厢的外形及密封性设计中,需要参考列车在不同速度、不同运行环境下周围流场压力的波动变化。本文在研究被测对象特性的基础上,选用光电式区截测速法和MEMS压力传感器设计了多参数多通道数据采集系统,并基于NILabWindows／CV1开发软件设计数据采集系统的上位机程序,实现了对速度信号和流场压力信号的多通道同步数据采集、数据处理和数据保存及数据回显。经过实际测试,该数据采集系统是简易的、准确的、高效的,能够为高速铁路列车设计提供了理想的参考数据。     

《电机与控制应用}2009增刊即将推出

为了感谢新老读者及广告客户多年来的支持与厚爱，也应众多电机行业生产企业的要求，本刊定于2009年10月增发一期关于“电机配件、材料与检测”的特刊，内容包括风扇、风罩、接线板、出线盒、绝缘材料、电线电缆、硅钢片、各种与电机相关的测试设备、仪器仪表和与电机制造相关的工艺装备等，其中新技术应用、新产品研发、     

铍青铜 Б_(p)Б_4微带的强度和弹性的研究

研究课题的目的,是要查清用各批供货线材制造的微带性能不一致的原因,并拟定出改善性能的方案。选择了两组成分相同,直径为0.2毫米的     

步步高_弦琴300平板影院

市场背景平板电视的高速增长使电视机朝着健康、环保、超薄的方向发展,然而与之配套的家庭影院仍然停留在过去的水平上。开发理念步步高秉承“以人为本”的设计理念,凭借敏锐的市场洞察力和行业领先的研发创新能力,于2005 年5月在行业内率先推出“平板影院”系列产品。既能很好地配合平板电视的外形特点,又能很好地搭配现代家居中流行的地台装修风格,解决了消费者的摆放问题。     

超导发电机_2、~2_2t能力的计算(摘要)

我国关于电机的国家标准中,并未要求对I_2、i_2~2t能力进行考核。由于超导发电机(下称SCG)转子结构异于常规电机,I_2、I_2~2能力成为这种电机的主要性能指标之一。在SCG概念设计工作中,我们不得不付出一定代价去探讨涉及电磁、力、热等学科的I_2、i_2~2t能力的计算方法。本文是在美国通用电气公司和西屋公司的SCG设计基础上开发     

Φ_ρ(G)及其推广

本文给出了Φπ／G的概念，并得到了它的一些结果。     

Spin filtering in a $$\updelta $$-magnetic-barrier nanostructure modulated by Rashba and Dresselhaus spin–orbit couplings

We theoretically investigated the electron-spin transport properties of an antiparallel double \(\updelta \)-magnetic-barrier nanostructure modulated by spin–orbit coupling (SOC), which could be fabricated experimentally by depositing two ferromagnetic stripes with horizontal magnetization on the top and bottom of an InAs/Al\(_{x}\)In\(_{1-x}\)As semiconductor heterostructure. Both Rashba and Dresselhaus SOCs were taken into account, and the transmission coefficient, conductance, and spin polarization calculated analytically by means of the improved transfer matrix method. The electron-spin transport through this nanosystem is found to be strongly dependent on the SOC. The electron-spin polarization is also found to vary with the strength of the SOC, potentially enabling tunable spin filters for use in spintronic applications.     

铂银_(22)合金试制报告

铂银_(22)合金是一种综合性能较好用量较大的张丝材料,它具有强度高、弹性好、弹性后效小、无磁性易焊接并且耐腐蚀以及高温抗氧化等特性。我所从1961年开始试制该合金,并与上海仪表游丝厂协助,试制了铂银_(22)张丝,现在已能小批生产供应国内电表厂的需要,现将铂银合金的性能以及我所铂银_(22)合金的制     

电镀用750~安/8_伏硅整流器

一、前言: 长期以来,用于大型电镀的直流电源,几乎全部采用大功率的电动发电机组。由于电动发电机组运行时的损耗大,噪音响,维修不方便,因此为寻找一种维修简单的直流电源,就成为当前电镀生产上的迫切要求。 我厂在增产节约运动中突出政治,经过15天的奋战,自力更生,技术员、工人相结合,利用一些废旧材料,装制成一台750安/8伏硅整流器,现已投入生产,其性能良好。     

由ω_1ω诱导的几个逻辑系统

给出了由无限长逻辑诱导的一些子系统，讨论了一些重要的模型论性质，然后对它们的强弱作了系统的比较。