激光选区熔化成型典型几何特征尺寸精度研究

为了探讨激光选区熔化成型典型几何特征的尺寸精度,并为激光选区熔化直接成型金属零件提供设计参考依据,设计了薄板、尖角、圆柱体、圆孔、方孔等典型几何特征的三维模型,采用华南理工大学研发的激光选区熔化设备(Di Metal-100)在优化的工艺参数下选用316L不锈钢粉末对这些典型几何特征进行激光选区熔化成型。实验结果表明,激光光斑约束、台阶效应、粉末粘附、激光深穿透等因素是影响零件尺寸精度和激光选区熔化成型能力的主要原因。基于对激光选区熔化成型典型几何特征的尺寸精度及成型能力研究,提出了一些适用于激光选区熔化的零件设计规则,为产品的创新设计提供了参考依据。     

光纤激光直接快速成型3l6L不锈钢精密零件研究

为了研究光纤激光在选区激光熔化直接成型316L不锈钢精密零件中的应用,采用扩束镜及f-θ透镜,将光纤激光在成型系统工作面上聚集成30μm~50μm左右的细微聚焦光束;通过分析离焦量、扫描速度、激光功率、扫描路径对比成型实验,获得了激光光斑直径、扫描速度、激光功率等工艺参量及扫描路径对成型精度的影响关系。结果表明,通过优化工艺参量及扫描路径,可成功成型壁厚达0.1mm的316L不锈钢精密零件。     

选区激光熔化中激光束的传输变换及聚焦特性

为了获得光束质量较好、光斑尺寸较小、功率密度较高的、适合于在选区激光熔化快速成型技术中应用的激光束,对应用于选区激光熔化快速成型技术中的高斯光束进行传输与变换。对其传输变换及聚焦特性进行了理论分析与实验验证,实验结果与理论分析的结果相符。取得了功率密度达106W/cm2以上的、光斑尺寸较小的、满足于在选取激光熔化技术中应用的光斑。将其应用于镍基合金(Ni25)和铜磷合金粉末的三维选区激光熔化快速成型。结果表明,这种传输变换及聚焦特性是可行有效的,得到了满足要求的光斑尺寸和功率密度。     

选区激光熔化直接制造网格结构零件

为了实现网格结构零件的制造,在快速成型设备Dimetal-280上经过选区激光熔化(SLM)工艺实验,分析了SLM中能量吸收对零件尺寸的影响、激光深穿透及铺粉装置对成型效果的影响.结果表明,采用实验中优化的工艺参数成型的316L不锈钢网格结构零件孔径大小均匀、孔隙贯通性良好.孔径尺寸在X方向为965 μm,Y方向为975 μm,与设计值相差分别为35 μm及25 μm.研究采用的SLM设备成型网格零件是可行的,在网格零件制造中具有很大的潜力.     

选区激光熔化快速成型过程温度场数值模拟

为了优化铜磷合金粉末选区激光熔化快速成型的工艺参数,采用有限元分析软件ANSYS对其温度场进行了模拟,经理论分析和实验验证,获得了其温度场分布的数据.对材料未知温度范围内的热特性参数用插值法近似获得,采用不等网格剖分方式,用热焓去处理相变潜热问题.结果表明,其温度场的等温线分布为椭圆形,用模拟遴选的工艺参数(在铺粉厚度为0.22mm时,选用激光功率为100W、扫描速度为0.25m/s和激光束半径为0.1mm)能实现选区激光熔化快速成型.这一结果对其它粉末材料的选区激光熔化快速成型也是有帮助的.     

选区激光熔化直接成型个性化牙冠牙桥研究

为了探索应用数字化反求设计结合选区激光熔化快速成型技术制作个性化牙冠牙桥的可行性,通过Laser-denta扫描系统测量牙列模型并 3 维重建其数字化外形,采用计算机辅助设计了牙冠牙桥。利用自主研发的选区激光熔化快速成型设备Dimetal-280进行了316L不锈钢粉末的正交实验工艺研究,获得优化参量,并用该参量加工设计了牙冠牙桥。结果表明,该方法能快速而精确地制造出形状复杂的个性化牙冠牙桥,且成型速度快、尺寸精度高、表面质量好、误差在±0.15mm以内,未经打磨表面粗糙度达到20μm;与传统加工方式相比,反求工程结合选区激光熔化快速成型的方法能快速而精确地制造出形状复杂的个性化金属牙冠牙桥,为其应用于口腔修复体的计算机辅助设计与制造提供了科学依据。     

新型L式双向智能刮刀的设计及应用

激光选区熔化技术在实际应用中会出现熔点突出、工件翘曲等问题,影响铺粉质量及最终成型工件质量.为了提高激光选区熔化的铺粉质量,该文设计了一款基于PZT-5 H阵列的L式双向智能刮刀,并对其传感器性能、单路信号灵敏度、铺粉模拟等进行了测试.结果表明,测试得到刮刀整体灵敏度为100μm,有效地提高了智能刮刀在激光选区熔化中的...     

选区激光熔化直接成型个性化舌侧托槽的研究

为了探讨应用选区激光熔化快速成型技术直接制造个性化金属舌侧托槽的可行性,采用3维激光扫描仪采集与重建牙颌模型数据,并以该数字模型为基础,应用3维软件进行了个性化舌侧托槽的CAD设计,再通过自主研发的选区激光熔化快速成型机直接制造出个性化金属舌侧托槽,并对托槽的直接成型质量进行了理论分析和实验验证。结果表明,3维激光扫描仪获得的牙颌模型数据可以满足个性化舌侧托槽设计要求;应用选区激光熔化技术能够制造出与实际牙颌模型相一致的个性化舌侧托槽,取得了个性化前牙槽沟宽度为0.471mm±0.009mm数据,前牙槽沟宽度CAD设计值为0.460mm,两者间没有统计学上的差异(p0.05)。这一结果对选区激光熔化技术直接制造个性化金属舌侧托槽的实际应用是有帮助的。     

激光选区熔化成型腔内流场优化及飞溅去除研究

为减少激光选区熔化过程中飞溅物的残留,提高成型零件的质量,构建EOS M290型激光选区熔化设备成型腔的计算流体力学模型和流体流动颗粒追踪模型,研究不同进气速度、进气孔直径、进气孔拉伸长度和出气口栅格数量对成型腔内流场分布和飞溅颗粒去除概率的影响。结果表明,当316L不锈钢飞溅颗粒直径为10～100μm范围内的4种正态分布时,原模型在进气速度为3 m/s时,去除概率仅为69.25%;延长进气孔可以改善成型腔内流场的均匀性和抑制Coanda效应,进气速度为3 m/s,进气孔拉伸长度为90 mm时,去除概率提高到74.64%;进气速度为3 m/s时,出气口栅格数量从5增加到9,出气口中心平面均匀性指数从64.42%增加到78.57%;在粉床不被破坏的情况下,优化模型(进气孔直径4 mm、进气孔拉伸长度90 mm、出气口栅格数量8)的最大进气速度为4.46 m/s,飞溅颗粒去除概率提升至82.11%。     

铜磷合金粉末选区激光熔化成型研究

为了应用选区激光熔化技术直接制造金属零件,采用Dimetal 240快速成型机对平均直径为75μm的铜磷合金粉末进行了工艺试验。成型机配备200W半导体抽运Nd:YAG激光器,激光功率为103W～117W,内部扫描速度为0.25m/s～0.41m/s,边框扫描速度为0.15m/s,铺粉厚度为0.2mm。所得试样用扫描电镜和光学显微镜进行了微观组织分析。试样层问结合为冶金结合,致密度达到90%以上,层内组织为细长枝晶,层问组织为细小等轴晶。结果表明,通过设定合适的工艺参量,选区激光熔化技术可以直接成型金属零件。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks