图形化蓝宝石衬底工艺研究进展

图形化蓝宝石衬底(PSS)技术是一种提高LED亮度的新技术。结合光刻和刻蚀工艺制作图形化蓝宝石衬底。有关图形化蓝宝石衬底的研究主要集中在对光刻和刻蚀工艺的研究,以及图形化蓝宝石衬底提高LED亮度的机理。目前微米级图形化蓝宝石衬底已经得到普遍的应用,与基于平坦蓝宝石衬底的LED相比,PSS-LED的发光功率提高了30%左右。图形化蓝宝石衬底技术的发展经历了从早期的条纹状图形到目前应用较广的半球形和锥形图形,从湿法刻蚀到干法刻蚀,从微米级到纳米级图形的演变。由于能够显著提高LED亮度,纳米级图形化蓝宝石必将得到广泛的运用。     

关口水电站地下厂房岩壁式吊车梁设计

岩壁式吊车梁是一种新型结构形式，目前尚无规范可循。关口水电站地下厂房岩壁式吊车梁的设计，采用平面力系平衡的方法来分析梁的稳定，其中壁座倾角、锚杆参数选取是岩壁式吊车梁设计的关键。对中小型水电站来讲，按照施工技术要求：把好施工质量关，是岩壁式吊车梁成败的关键。     

Estimation of the Optimal Maximum Beam Angle and Angular Increment for Normal and Shear Strain Estimation

In the current practice of ultrasound elastography, only the axial component of the displacement vector is estimated and used to produce strain images. A method was recently proposed by our group to estimate both the axial and lateral components of a displacement vector using RF echo signal data acquired along multiple angular insonification directions of the ultrasound beam. Previous work has demonstrated that it is important to choose appropriate values for the maximum beam angle and angular increment to achieve optimal performance with this technique. In this paper, we present error propagation analysis using the least-square fitting process for the optimization of the angular increment and the maximum beam steered angle. Ultrasound simulations are performed to corroborate the theoretical prediction of the optimal values for the maximum beam angle and angular increment. Selection of the optimal parameters depends on system parameters, such as center frequency and aperture size. For typical system parameters, the optimal maximum beam angle is around 10deg for axial strain estimation and around 15deg for lateral strain estimation. The optimal angular increment is around 4deg -6deg, which indicates that only five to seven beam angles are required for this strain-tensor estimation technique.     

Analysis of a microstrip dipole antenna

Assuming a quasi-TEM mode of wave propagation and using a conformal transformation technique, accurate and simple analytic expressions for the characteristic wave resistance and the effective dielectric constant of the microstrip dipole antenna in the mixed dielectric medium have been derived. The theoretical values are in close agreement with the experimental results.     

Metalorganic InP and Inx Ga1-x,Asy P1-y,on InP epitaxy at atmospheric pressure

We present a procedure for the MOVPE of InP as simple as the one currently used for GaAs. InP and InGaAsP alloys are grown on InP substrates using trimethy1indium (TMI), phosphine, trimethylgallium (TMG) and arsine. The choice of carrier gas is important ; a mixture of hydrogen and nitrogen allowed us to grow uniform layers over large areas at atmospheric pressure, without pyrolizing the phosphine or separating the input reactants. Preliminary characterization results are presented. Most information contained in this paper was presented at the 1983 Electron Materials Conference as paper Cl.     

Investigation of Contact Electrification between 2D MXenes and MoS2 through Density Functional Theory and Triboelectric Probes

Contact electrification (triboelectrification) (CE) is a universal phenomenon in ambient environment and has been recorded for more than 2600 years. Nonetheless, the intrinsic mechanism of CE still remains controversial. Herein, based on first-principles theory, the underlying mechanism in CE is systematically investigated between metallic MXenes and semiconductive MoS₂. The results show that the work functions of contacting materials dominate the direction of electron transfer during CE process. That is, the electron will be transferred from the material with low work function to the one with high work function. The theoretical prediction is verified experimentally through investigating triboelectric probes based on MXenes and MoS₂ nanomaterials. Additionally, it is noted that the interfacial potential barrier and the work function difference together modulate the amount of transferred electron. Electron transfer mainly occurs in the repulsive forces region where the interaction distance between the two materials is shorter than the normal bonding length. The quantum calculation results agree well with the Wang transition theory. Furthermore, it is also noticed that, due to the wave-particle duality of electron, electron transfer will obviously occur at the attractive force region when the two contacting materials exhibit a larger work function difference.     

Bridging digital divide: Efforts in India

The fruits of Information Technology sector such as the Internet blue chips, online shopping and nanosecond email have failed to cure century-old malaises like illiteracy, poverty and unemployment in India. The paper presents few facts about digital divide based on global and the USA perspective, its definition and types as global, regional and national, and societal implications. It highlights India in the context of digital divide by discussing its infrastructural bottleneck that includes electricity, IT penetration, teledensity and Internet industry, and its enabling policies to transform India as a knowledge society. It discusses various technology options for connectivity, viz. terrestrial wireless, satellite, wireline, etc. and presents snap shots of select successful projects that made an impact in helping to bridge digital divide in India, viz. passenger reservation system, Akashganga, Akshaya e-centres, Bhoomi, etc. It concludes that creation of Information and Communication Technologies infrastructure and content are the core methodologies, and a national agenda on a C-8 thrust towards: connectivity provision, content creation, capacity augmentation, core technologies creation and exploitation, cost reduction, competence building, community participation and commitment to the deprived and disadvantaged would definitely help in bridging digital divide.     

A novel feed for a multifrequency hybrid resonator antenna

A novel feed technique for a hybrid resonator antenna is proposed and developed. The antenna consists of microstrip-patch radiator and a pair of twin resonator slots. The proposed feed mechanism is based on a new coupling aperture technique, in which a single microstrip feed line is etched on the same side of the substrate as the radiating patches. The patches are coupled to the feed line through a twin slots located in the ground plane. By selecting suitable structure parameters for the slots and the patches, multifrequency operation is obtained. The proposed antenna structure is suitable for the development of large antenna arrays.     

A CMOS RF front-end for a multistandard WLAN receiver

This letter describes the design and performance of a dual band tri-mode receiver front-end compliant with the IEEE 802.11a, b, and g standards. The receiver front-end was built in a 0.18-/spl mu/m CMOS process and achieves a noise figure of 4.7 dB/5.1 dB for the 2.4-GHz/5-GHz bands, respectively. The receiver front-end provides a dual gain mode of 5 dB/30 dB with an IIP3 of -1dBm for the low gain mode. The front-end draws 25 mA/27 mA from a 1.8-V supply for the 2.4-GHz/5-GHz bands, respectively.     

Developing decision support for dialysis treatment of chronic kidney failure.

The complexity, variability, quantitative nature, and data density of treatment for chronic kidney failure make dialysis information systems excellent candidates for computerized decision support. We describe the development of an intelligent system building on existing knowledge and susceptible to reconfiguration on the basis of knowledge acquired during the use of the system. Various decision support techniques were used to design and develop the decision support modules. This paper briefly reviews the literature on clinical decision support, discusses some of the problems faced by practitioners in managing chronic kidney failure (end-stage renal disease) patients, and sets forth the decision support techniques used in developing a dialysis decision support system.