Electromechanical resonators from graphene sheets

Nanoelectromechanical systems were fabricated from single- and multilayer graphene sheets by mechanically exfoliating thin sheets from graphite over trenches in silicon oxide. Vibrations with fundamental resonant frequencies in the megahertz range are actuated either optically or electrically and detected optically by interferometry. We demonstrate room-temperature charge sensitivities down to 8 x 10(-4) electrons per root hertz. The thinnest resonator consists of a single suspended layer of atoms and represents the ultimate limit of two-dimensional nanoelectromechanical systems.     

氧化石墨烯对泰乐菌素的吸附特性

通过改良Hummer方法制备了氧化石墨烯(GO),通过批量平衡试验考察了其对泰乐菌素的吸附特性和机制。研究结果表明:GO对泰乐菌素的吸附在24 h可达到动态吸附平衡,吸附动力学可用拉格朗日二级动力学模型较好地拟合;吸附等温线用线性吸附模型可以较好地拟合;吸附随着p H值的升高而降低,随着离子强度的增大而减弱。     

Measurement of the elastic properties and intrinsic strength of monolayer graphene

We measured the elastic properties and intrinsic breaking strength of free-standing monolayer graphene membranes by nanoindentation in an atomic force microscope. The force-displacement behavior is interpreted within a framework of nonlinear elastic stress-strain response, and yields second- and third-order elastic stiffnesses of 340 newtons per meter (N m(-1)) and -690 Nm(-1), respectively. The breaking strength is 42 N m(-1) and represents the intrinsic strength of a defect-free sheet. These quantities correspond to a Young's modulus of E = 1.0 terapascals, third-order elastic stiffness of D = -2.0 terapascals, and intrinsic strength of sigma(int) = 130 gigapascals for bulk graphite. These experiments establish graphene as the strongest material ever measured, and show that atomically perfect nanoscale materials can be mechanically tested to deformations well beyond the linear regime.     

红肖梨丰产优质栽培试验及示范

为推广科学合理的栽培管理技术，北京市怀柔区怀北镇于2004年分别在大水峪、河防口村建立红肖梨丰产优质栽培试验及示范园，总结出一套丰产优质的栽培管理方案，进一步提高红肖梨的品质和产量。     

机电类专业毕业设计指导模式探索

本文从指导教师的角度、基于实际案例阐述了机电类专业毕业设计指导模式。首先分析了毕业设计选题的重要性,指出选题应在学生感兴趣的领域提炼和丰富而成。然后将机电类毕业设计分解为硬件类选题、软件类选题和指导平台建设三部分。指出硬件类选题指导应开阔学生思路,侧重于系统方案设计、元器件选型及可获得性等方面;软件类选题指导应侧重于基于测控系统业界流行的设计工具完成复杂功能的系统设计;毕业设计指导平台建设要求指导教师（课题组）精心选题,保证课题的延续性,同时离不开教学经费支持。研究可为教学管理部门决策提供有意义的依据。     

Wafer-scale graphene integrated circuit

A wafer-scale graphene circuit was demonstrated in which all circuit components, including graphene field-effect transistor and inductors, were monolithically integrated on a single silicon carbide wafer. The integrated circuit operates as a broadband radio-frequency mixer at frequencies up to 10 gigahertz. These graphene circuits exhibit outstanding thermal stability with little reduction in performance (less than 1 decibel) between 300 and 400 kelvin. These results open up possibilities of achieving practical graphene technology with more complex functionality and performance.     

电子机械制动系统的滑模控制研究

建立了基于电子机械制动（EMB）系统的车辆单轮动力学模型，针对制动过程的非线性特征和路面条件的复杂性，设计了基于滑移率的滑模变结构控制器以充分利用地面的附着力及适应制动的全工况要求，并采取了相应的措施削弱抖振现象.在单路面与变路面条件下的仿真计算验证了滑模控制器的可行性和有效性，同时也表明滑模变结构控制器的控制性能及对路面的适应性均优于PID控制器.     

Transformation optics using graphene

Metamaterials and transformation optics play substantial roles in various branches of optical science and engineering by providing schemes to tailor electromagnetic fields into desired spatial patterns. We report a theoretical study showing that by designing and manipulating spatially inhomogeneous, nonuniform conductivity patterns across a flake of graphene, one can have this material as a one-atom-thick platform for infrared metamaterials and transformation optical devices. Varying the graphene chemical potential by using static electric field yields a way to tune the graphene conductivity in the terahertz and infrared frequencies. Such degree of freedom provides the prospect of having different "patches" with different conductivities on a single flake of graphene. Numerous photonic functions and metamaterial concepts can be expected to follow from such a platform.     

Dislocation-driven deformations in graphene

The movement of dislocations in a crystal is the key mechanism for plastic deformation in all materials. Studies of dislocations have focused on three-dimensional materials, and there is little experimental evidence regarding the dynamics of dislocations and their impact at the atomic level on the lattice structure of graphene. We studied the dynamics of dislocation pairs in graphene, recorded with single-atom sensitivity. We examined stepwise dislocation movement along the zig-zag lattice direction mediated either by a single bond rotation or through the loss of two carbon atoms. The strain fields were determined, showing how dislocations deform graphene by elongation and compression of C-C bonds, shear, and lattice rotations.     

基于嵌入式系统的机电控制系统开发研究

近年来,社会的不断进步与发展,使嵌入式系统在机电控制领域中的应用变得越来越广泛,嵌入式系统的应用在很大程度上促进了机电控制领域的发展,提高了机电控制设备的工作性能。鉴于此,本文便基于嵌入式系统对机电控制系统的开发进行深入的研究,以期能够为机电控制领域的进一步发展做出贡献。     

智能制造中机电一体化技术的应用研究

随着如今科技的快速发展,在社会经济的发展过程中有更多的制造产业也都开始应用全新的科技手段来帮助企业进行更好的生产制造。在企业制造过程中出现的这些全新的技术手段中,智能制造已经算作最前沿的科技手段,智能制造的应用有效的提高了我国企业的机械制造水平和产品制造能力,帮助我国企业得到更好的发展。而在智能制造中,机电一体化的技术也得到了更多的研究和关注,对我国智能制造的研究有着非常重要的意义。     

纤维打包机机电控制系统的改进设计

为了提高纤维打包机的工作效率,对原电控系统进行了改进。改进后的控制系统,采用双速电机,实现了对不同工作行程速度的控制,同时提供手动与自动两种控制方式。试验结果表明:打包工作效率提高了19.4%,且操作方便安全,减少了能量损耗。     

福建与东盟机电产品出口贸易竞争性分析

随着中国—东盟自由贸易区的正式建立,区域经贸合作进入一个新阶段。机电产业是福建和东盟国家的贸易的主要产业。当前福建机电产品的出口和东盟主要国家相比,竞争性大于互补性,出口额及国际市场占有率逐年上涨,增速不断提升,产品的出口竞争力整体上不断增强,但和新加坡及菲律宾相比依然存在着差距。福建应扬长避短,着力于机电产业结构的升级与调整、科研投入的增加与研发能力的提升、产品科技含量的提高、跨地区产业集聚的发展,实施“走出去”战略,加大对东盟国家的投资,进一步提升机电产品的出口竞争力。     

Gate-variable optical transitions in graphene

Two-dimensional graphene monolayers and bilayers exhibit fascinating electrical transport behaviors. Using infrared spectroscopy, we find that they also have strong interband transitions and that their optical transitions can be substantially modified through electrical gating, much like electrical transport in field-effect transistors. This gate dependence of interband transitions adds a valuable dimension for optically probing graphene band structure. For a graphene monolayer, it yields directly the linear band dispersion of Dirac fermions, whereas in a bilayer, it reveals a dominating van Hove singularity arising from interlayer coupling. The strong and layer-dependent optical transitions of graphene and the tunability by simple electrical gating hold promise for new applications in infrared optics and optoelectronics.     

基于非线性分析的复杂机电系统故障特征提取

针对复杂机电系统振动信号呈现复杂非平稳性的特点,采用Hilbert-Huang变换(HHT)和基于小波包分解的频带能量比例非线性分析方法,对机电转子系统碰摩和不对中故障试验信号进行分析.分析结果表明:基于非线性分析的HHT和小波包频带能量比例方法弥补了原有传统频谱分析的不足,可以清晰的表征故障的瞬时和局部特性,实现故障特征的有效提取.     

Layer-by-layer removal of graphene for device patterning

The patterning of graphene is useful in fabricating electronic devices, but existing methods do not allow control of the number of layers of graphene that are removed. We show that sputter-coating graphene and graphene-like materials with zinc and dissolving the latter with dilute acid removes one graphene layer and leaves the lower layers intact. The method works with the four different types of graphene and graphene-like materials: graphene oxide, chemically converted graphene, chemical vapor-deposited graphene, and micromechanically cleaved ("clear-tape") graphene. On the basis of our data, the top graphene layer is damaged by the sputtering process, and the acid treatment removes the damaged layer of carbon. When used with predesigned zinc patterns, this method can be viewed as lithography that etches the sample with single-atomic-layer resolution.     

Carbon-based supercapacitors produced by activation of graphene

Supercapacitors, also called ultracapacitors or electrochemical capacitors, store electrical charge on high-surface-area conducting materials. Their widespread use is limited by their low energy storage density and relatively high effective series resistance. Using chemical activation of exfoliated graphite oxide, we synthesized a porous carbon with a Brunauer-Emmett-Teller surface area of up to 3100 square meters per gram, a high electrical conductivity, and a low oxygen and hydrogen content. This sp(2)-bonded carbon has a continuous three-dimensional network of highly curved, atom-thick walls that form primarily 0.6- to 5-nanometer-width pores. Two-electrode supercapacitor cells constructed with this carbon yielded high values of gravimetric capacitance and energy density with organic and ionic liquid electrolytes. The processes used to make this carbon are readily scalable to industrial levels.     

Controlling the electronic structure of bilayer graphene

We describe the synthesis of bilayer graphene thin films deposited on insulating silicon carbide and report the characterization of their electronic band structure using angle-resolved photoemission. By selectively adjusting the carrier concentration in each layer, changes in the Coulomb potential led to control of the gap between valence and conduction bands. This control over the band structure suggests the potential application of bilayer graphene to switching functions in atomic-scale electronic devices.