GaN-based light-emitting diodes with hybrid micro/nano-textured indium-tin-oxide layer

Three types of textured indium-tin-oxide （ITO） surface, including nano-texturing and hybrid micro/nano-texturing with micro-holes （concave-hybrid-pattem） or micro-pillars （convex-hybrid-pattern）, were applied to GaN-based light-emitting diodes （LEDs）. The nano-texturing was realized by maskless wet-etching, and the micro-texturing was achieved by standard photolithography and wet-etching. Compared to LED chips with flat ITO surface, those with nano-pattern, concave-hybrid-pattern, and convex-hybrid-pattern exhibit enhancement of 11.3%, 15.8%, and 17.9%, respectively, for the light-output powers at 20 mA. The electrical performance has no degradation. Moreover, the convex-hybrid-pattern show higher light-output efficiency under small injection current, while the concave-hybrid-pattern exhibit better light-output efficiency at large injection current. The light- extraction efficiency is simulated by use of two-dimensional finite difference time domain method, and the numer- ical results are consistent with the experiments.

Ignition processes and characteristics of charring conductive polymers with a cavity geometry in precombustion chamber for applications in micro/nano satellite hybrid rocket motors

The arc ignition system based on charring polymers has advantages of simple structure,low ignition power consumption and multiple ignitions,which bringing it broadly application prospect in hybrid propulsion system of micro/nano satellite.However,charring polymers alone need a relatively high input voltage to achieve pyrolysis and ignition,which increases the burden and cost of the power system of micro/nano satellite in practical application.Adding conductive substance into charring polymers can effectively decrease the conducting voltage which can realize low voltage and low power consumption repeated ignition of arc ignition system.In this paper,a charring conductive polymer ignition grain with a cavity geometry in precombustion chamber,which is composed of PLA and multiwall carbon nanotubes(MWCNT)was proposed.The detailed ignition processes were analyzed and two different ignition mechanisms in the cavity of charring conductive polymers were revealed.The ignition characteristics of charring conductive polymers were also investigated at different input voltages,ignition grain structures,ignition locations and injection schemes in a visual ignition combustor.The results demonstrated that the ignition delay and external energy required for ignition were inversely correlated with the voltages applied to ignition grain.Moreover,the incremental depth of cavity shortened the ignition delay and external energy required for ignition while accelerated the propagation of flame.As the depth of cavity increased from 2 to 6 mm(at 50 V),the time of flame propagating out of ignition grain changed from 235.6 to 108 ms,and values of mean ignition delay time and mean external energy required for ignition decreased from 462.8 to 320 ms and 16.2 to 10.75 J,respectively.The rear side of the cavity was the ideal ignition position which had a shorter ignition delay and a faster flame propagation speed in comparison to other ignition positions.Compared to direct injection scheme,swirling injection provided a more favorable flow field environment in the cavity,which was beneficial to ignition and initial flame propagation,but the ignition position needed to be away from the outlet of swirling injector.At last,the repeated ignition characteristic of charring conductive polymers was also investigated.The ignition delay time and external energy required for ignition decreased with repeated ignition times but the variation was decreasing gradually.

Erosion Wear Behaviour of Kenaf/Glass Hybrid Polymer Composites

The awareness amongst the researchers to develop an environment friendly sustainable material leads to explore new class of plant-based fiber for making composites. Hybridization of such plant-based fiber with inclusion of engineered fiber is one of the promising methods to not only enhanced the mechanical performance but also suppressed the drawbacks that associate with such plant-based fiber to some extent. A usual hand lay-up method was taken-up in this work to fabricate four layered of hybrid kenaf(K)/glass(G)polyester laminates with different stacking order such as KKKK,KGKG,KGGK,GKKG and GGGG. The erosive character of the laminates was examined under three distinct particle velocities(48m/s, 70m/s,82m/s)and four different impact angles(30°, 45°, 60°, 90°). All fabricated laminates exhibited a semiductile character at lower velocities(48m/s and70m/s)as peak wear rate was observed at45° impact angle. However,they showed a semi-brittle character at high velocity(82m/s)as maximum rate of erosion was noticed at60° impact angle. Again,the influence of stacking order of piles on erosion wear was also clearly noticed. Moreover,the semi-brittle/semi-ductile characterization was also evidenced in accordance to the range of erosion efficiencies. The micro-structures of worn surfaces were inspected thoroughly from the images of scanning electron microscope(SEM)to evident the mechanism of erosion.

Fabrication of Micro/Nano-textured Titanium Alloy Implant Surface and Its Infl uence on Hydroxyapatite Coatings

We put forward a protocolcombining laser treatment and acid etching to obtain multiscale micro/nano-texture surfaces of titanium alloy implant.Firstly,the operationalparameters of the laser were optimized to obtain an optimum current.Secondly,the laser with the optimum operationalparameters was used to fabricate micro pits.Thirdly,multiple acid etching was used to clean the clinkers of micro pits and generate submicron and nanoscale structures.Finally,the bioactivity of the samples was measured in a simulated body fluid.The results showed that the micropits with a diameter of 150 μm and depth of 50 μm were built successfully with the optimized working current of 13 A.In addition,submicron and nanoscale structures,with 0.5-2 μm microgrooves and 10-20 nm nanopits,were superimposed on micro pits surface by multiple acid etching.There was thick and dense HA coating only observed on the multiscale micro/nano-textured surface compared with polished and micro-textured surface.This indicated that the multiscale micro/nano-texture surface showed better ability toward HA formation,which increased the bioactivity of implants.

CO_2 laser-micro plasma arc hybrid welding for galvanized steel sheets

A laser lap welding process for zinc-coated steel has a well-known unsolved problem-porosity formation. The boiling temperature of coated zinc is lower than the melting temperature of the base metal, which is steel. In the autogenous laser welding, the zinc vapor generates from the lapped surfaces expels the molten pool and the expulsion causes numerous weld defects, such as spatters and blow holes on the weld surface and porosity inside the welds. The laser-arc hybrid welding was suggested as an alternative method for the laser lap welding because the arc can preheat or post-beat the weldment according to the arrangement of the laser beam and the arc. CO2 laser-micro plasma hybrid welding was applied to the lap welding of zinc-coated steel with zero-gap. The relationships among the weld quality and process parameters of the laser-arc arrangement, and the laser-arc interspacing distance and arc current were investigated using a full-factorial experimental design. The effect of laser-arc arrangement is dominant because the leading plasma arc partially melts the upper steel sheets and vaporizes or oxidizes the coated zinc on the lapped surfaces. Compared with the result from the laser-TIG hybrid welding, the heat input from arc can be reduced by 40%.

Chinese micro-blog sentiment classification through a novel hybrid learning model

With the rising and spreading of micro-blog, the sentiment classification of short texts has become a research hotspot. Some methods have been developed in the past decade. However, since the Chinese and English are different in language syntax, semantics and pragmatics, sentiment classification methods that are effective for English twitter may fail on Chinese micro-blog. In addition, the colloquialism and conciseness of short Chinese texts introduces additional challenges to sentiment classification. In this work, a novel hybrid learning model was proposed for sentiment classification of Chinese micro-blogs, which included two stages. In the first stage, emotional scores were calculated over the whole dataset by utilizing an improved Chinese-oriented sentiment dictionary classification method. Data with extremely high or low scores were directly labeled. In the second stage, the remaining data were labeled by using an integrated classification method based on sentiment dictionary, support vector machine(SVM) and k-nearest neighbor(KNN). An improved feature selection method was adopted to enhance the discriminative power of the selected features. The two-stage hybrid framework made the proposed method effective for sentiment classification of Chinese micro-blogs. Experiments on the COAE2014(Chinese Opinion Analysis Evaluation 2014) dataset show that the proposed method outperforms other schemes.

Functional micro‐concrete 3D hybrid structures f abricated by two‐photon polymerization

Arbitrary micro-scale three-dimensional(3D)structures fabrication is a dream to achieve many exciting goals that have been pursued for a long time.Among all these applications,the direct 3D printing to fabricate human organs and integrated photonic circuits are extraordinary attractive as they can promote the current technology to a new level.Among all the 3D printing methods available,two-photon polymerization(2PP)is very competitive as it is the unique method to achieve sub-micron resolution to make any desired tiny structures.For the conventional 2PP,the building block is the photoresist.However,the requirement for the building block is different for different purposes.It is very necessary to investigate and improve the photoresist properties according to different requirements.In this paper,we presented one hybrid method to modify the mechanical strength and light trapping efficiency of the photoresist,which transfers the photoresist into the micro-concretes.The micro-concrete structure can achieve±22%strength modification via a silica nano-particles doping.The structures doped with gold nano-particles show tunable plasmonic absorption.Dye doped hybrid structure shows great potential to fabricate 3D micro-chip laser.

Hybrid Micro-forming Processes and Quality Evaluation of Micro-double Gear

Micro-gear is an important actuating component used widely in the micro electro mechanical systems(MEMS) devices.The technologies of micro-forming and precision assembly are urgently developed to manufacture the micro-double gear with central shaft.In the paper,a novel hy-brid-forming process with two kinds of piercing method have been proposed to manufacture the micro-double gear using micro forming technology.The tests of hybrid forming process were carried out with two steps and the micro-double gear was successfully manufactured with good surface quality.The results also show that the hybrid micro-forming process with central piercing method can improve the defects of inclining shaft generated by double-ended piercing method.The quality evaluation of micro-double gear was conducted with surface roughness,micro-hardness and impact tests.The results show that the micro-double gear with good mechanical properties can meet the requirements of application for milli-machines.

Material properties and machining performance of hybrid Ti_2AlN bulk material for micro electrical discharge machining

Mn+1AXn(MAX) phases are a family of nanolaminated compounds that possess unique combination of typical ceramic properties and typical metallic properties.As a member of MAX phase,Ti2 AlN bulk materials are attractive for some high-temperature applications.The synthesis,characteristics and machining performance of hybrid Ti2 AlN bulk materials were focused on in this work.The bulk samples mainly consisting of Ti2 AlN MAX phase with density close to theoretic one were synthesized by a spark plasma sintering method.Scanning electron microscopy results indicate homogenous distribution of Ti2 AlN grains in the samples.Micro-hardness values are almost constant under different loads (6-6.5 GPa).A machining test was carried out to compare the effect of material properties on micro-electrical discharge machining (micro-EDM) performance for Ti2 AlN bulk samples and Ti6242 alloy.The machining performance of the Ti2 AlN sample is better than that of the Ti6242 alloy.The inherent mechanism was discussed by considering their electrical and thermal conductivity.

Voltage Stabilization of Hybrid Micro-Grid Using Super Capacitors

Scarcity of fossil fuel resources has motivated the researchers to develop renewable energy based power projects. Instead of using a single or independent renewable energy source, it is preferable to use the combination of such energy sources in a distributed way to compensate the power fluctuations of the system and this leads to the concept of hybrid micro-grid energy. Voltage stability is an important parameter for the secure operation of the hybrid-micro grid, and IEEE 1547 Standard defines the limit of the voltage for the successful operation of the micro-grid. Although Vanadium Redox Batteries (VRBs) can help the system to stabilize the voltage when voltage sag occurs when a heavy load is suddenly connected to the system, this stabilization process takes some time. This paper discusses the application of super capacitors to the hybrid micro-grid system, as a higher energy density element, to help the system quickly recover its transient voltage.

Research on 48 V Super Capacitor Micro Hybrid System with 12 V Power Supply Multiplexing Function

48 V lithium battery micro hybrid system is the most fuel economy vehicle which can be mass produced at present.However,with the irreversible internal resistance increase of the key component 48 V lithium battery,and the capacity continues to decline,the system performance deteriorate.Worst case could be the system not functional in the middle and later age of vehicle life cycle.This paper studies the feasibility of using 48 V super capacitor as the replacement to 48 V lithium battery,and uses a 12 V module of 48 V super capacitor as the traditional 12 V power supply,further reducing the number of components or reducing the demand for parts of 48 V micro hybrid system.This paper analyses the 48 V super capacitor micro hybrid system scheme,based on which a prototype is built,and carries out the vehicle comparative test.The results show that:(1)The performance of 48 V super capacitor micro hybrid system perform comparably with 48 V lithium battery micro hybrid system,and 12 V multiplexing function does not cause power loss of super capacitor;(2)The SOC fluctuation of super capacitor is larger than that of lithium battery,but it can satisfy all test conditions through the strategy;(3)The voltage mutation of super capacitor is smaller than that of lithium battery.It can greatly reduce the impact of voltage on vehicle electrical appliances.The 48 V super capacitor micro hybrid system with 12 V multiplexing function is of great significance.

High performance Ga N-based hybrid white micro-LEDs integrated with quantum-dots

Hybrid white micro-pillar structure light emitting diodes(LEDs)have been manufacture utilizing blue micro-LEDs arrays integrated with 580 nm CIS((CuInS2-ZnS)/ZnS)core/shell quantum dots.The fabricated hybrid white micro-LEDs have good electrical properties,which are manifested in relatively low turn-on voltage and reverse leakage current.High-quality hybrid white light emission has been demonstrated by the hybrid white micro-LEDs after a systemic optimization,in which the corresponding color coordinates are calculated to be(0.3303,0.3501)and the calculated color temperature is 5596 K.This result indicates an effective way to achieve high-performance white LEDs and shows great promise in a large range of applications in the future including micro-displays,bioinstrumentation and visible light communication.

Hybrid device for acoustic noise reduction and energy harvesting based on a silicon micro-perforated panel structure

A kind of hybrid device for acoustic noise reduction and vibration energy harvesting based on the silicon micro- perforated panel （MPP） resonant structure is investigated in the article. The critical parts of the device include MPP and energy harvesting membranes. They are all fabricated by means of silicon micro-electro-mechanical systems （MEMS） tech- nology. The silicon MPP has dense and accurate micro-holes. This noise reduction structure has the advantages of wide band and higher absorption coefficients. The vibration energy harvesting part is formed by square piezoelectric membranes arranged in rows. ZnO material is used as it has a good compatibility with the fabrication process. The MPP, piezo- electric membranes, and metal bracket are assembled into a hybrid device with multifunctions. The device exhibits good performances of acoustic noise absorption and acoustic-electric conversion. Its maximum open circuit voltage achieves 69.41 mV.

考虑产消者响应与不确定性的微能网双层混合博弈优化

随着分布式能源的发展,传统用户具备发电能力而成为产消者(production and consumption users,PCU)的趋势愈演愈烈,该文主要研究了同一微能网下大量产消者的协同运行问题。电价不确定性和产消者响应给微能网协同不同利益主体的PCU之间的调度带来困难。在此背景下提出考虑产消者响应与电价不确定性的微能网与产消者混合博弈优化策略。首先,构建产消者响应模型和电价不确定性模型,引入效用函数来描述PCU的满意程度,采用鲁棒优化和机会约束方法描述电价的不确定性与新能源出力的不确定性。其次,构建混合博弈模型,即上层微能网运营商(integrated energy operator,IEO)与下层PCU之间的主从博弈模型和下层PCU联盟之间的合作博弈模型。上层IEO作为主从博弈的领导者以运行成本最小化为目标,通过为产消者制定电价、热价引导产消者的用能需求;下层产消者作为跟随者,以效益最大为目标通过合作方式对IEO的决策进行产消者响应。PCU之间的合作博弈以纳什议价的方式进行,将PCU模型等效为联盟收益最大化和合作分配两个子问题。基于KKT条件利用Big-M法和Mc Cormick包络法将双层问题转换为单层混合整数线性规划问题求解主从博弈,结合交替方向乘子法(alternating direction multiplier method,ADMM)求解下层合作博弈。结果表明,该文所提策略有效协调了微能网与PCU的调度并保证了PCU合作联盟的公平性。

基于二元堆积理论高致密CuW复合材料制备及耐电弧侵蚀性能研究

目的提高CuW复合材料的致密度及耐电弧侵蚀性能。方法基于二元堆积理论设计并制备了双粒径W颗粒混杂CuW75复合材料,通过微观组织表征、硬度测试、导电率测试及密度测试,重点对比研究了单粒径CuW75复合材料和双粒径混杂CuW75复合材料致密性和微观组织的内在关联,并通过电接触实验研究了双粒径混杂CuW75复合材料耐电弧的侵蚀性能。结果双粒径混杂CuW75复合材料微观组织均匀,W相及Cu相网络连通程度高,致密度高达99.79%,较CuW75复合材料国家标准致密度提升了2.9%,硬度较CuW75复合材料国家标准提升了6.7%。电接触实验结果表明,双粒径混杂CuW75复合材料熔焊力波动幅度小,平均熔焊力(35.06cN)较1μm单粒径CuW75复合材料的降低了11%;平均燃弧能量(147.29mJ)及平均燃弧时间(2.53ms)较1μm单粒径CuW75复合材料的分别下降了38%和36%。双粒径混杂CuW75复合材料受电弧侵蚀面积小,侵蚀坑较浅,耐电弧侵蚀性能优异。结论双粒径混杂W颗粒制备CuW复合材料可以明显提升材料的致密度及微观结构连通性。双粒径混杂CuW复合材料可以更好地分散电弧,具有优异的抗熔焊性能及耐电弧侵蚀性能。

酸性环境下粘接剂对异质压印接头剥离强度的影响

为探究酸性环境下粘接剂对异质压印接头剥离强度的影响,以热轧双相钢DP590和AA5052作为原材料,以0.02 mol·L^(-1)的NaHSO_(3)溶液作为腐蚀液,对异质压印接头(压印接头)和粘接-压印接头(粘-压复合接头)进行了干湿周浸交替腐蚀试验,通过静力学试验、微观失效断口以及能谱分析研究了接头在酸性环境下的静力学性能和失效机理。结果表明:粘接剂的使用显著提高了接头的最大失效载荷,粘-压复合接头的承载能力较压印接头提高了56.3%。粘接剂的使用对接头的失效形式未产生影响,在腐蚀时间为0 h时,压印接头和粘-压复合接头的失效形式均为内锁拉脱失效,但随着腐蚀的进行,失效形式逐渐转变为颈部断裂失效。粘-压复合接头上板的微观断口形貌均表现为韧窝状,下板拉伸失效部位的划痕逐渐加深。酸性腐蚀环境下压印接头搭接区域表面元素特征较粘-压复合接头变化明显,表明粘接剂的使用对压印接头起到了一定的保护作用。

铝/铜蓝-红激光复合焊接头组织及性能

为实现动力电池的高效可靠焊接,文中采用蓝-红复合激光进行了1050 Al/T2 Cu搭接焊,分析了激光功率对接头显微组织、相分布、力学性能及导电性能的影响规律.结果表明,铝/铜搭接接头焊缝表面平整,截面呈现T形,PB(蓝光功率)保持300 W,PR(红光功率)在700~1400 W区间内增加,铜侧熔深由60μm增大到1000μm,在PR=800 W时实现良好的冶金结合.焊缝组织由Al固溶体、Al-Cu共晶相和Al_(2)Cu金属间化合物组成,随激光功率增大,焊缝局部出现Al_(4)Cu_(9)相,边缘出现AlCu,Al_(4)Cu_(9)和AlCu_(3)相.在PR=800 W下抗剪强度达到最高108.6 MPa,接触电阻达到最小94μΩ,裂纹由两极交界处Al_(2)Cu区域萌生,沿焊缝边缘由外层Al_(2)Cu区扩展到底部Al固溶体和Al-Cu共晶区交界处,断裂形式为解理断裂.

短期微流水处理对池塘养殖杂交鲌“先锋1号”肌肉品质的影响

以池塘养殖杂交鲌“先锋1号”为对象,采用短期微流水处理,研究处理时间(0、4、8和12d)对杂交鲌“先锋1号”色度、肌纤维直径、肌肉质构特性、常规营养成分、氨基酸和脂肪酸含量的影响,以评价短时间微流水处理对杂交鲌“先锋1号”品质的提升作用。结果显示,微流水条件下,8 d和12 d皮的黄度值(b^(*))显著升高,各实验组肌肉的红度值(a^(*))显著降低(P<0.05,下同)。处理8 d时,肌纤维密度、肌肉硬度、咀嚼性和弹性显著提升,分别较对照组提升了70.96%、92.04%、198.99%和35.71%。随着处理时间的延长,粗蛋白和粗脂肪含量显著降低,灰分在处理过程中无显著差异(P>0.05,下同);杂交鲌“先锋1号”在处理4d时的鲜味氨基酸总量(DAA)显著高于8d和12d;氨基酸总量(TAA)和必需氨基酸总量(EAA)变化不显著,各组必需氨基酸指数(EAAI)分别为77.33%、74.91%、76.56%和76.75%。第8天时,肌肉中顺-15-二十四碳一烯酸(C24:1)、花生三烯酸(C20:3n6)和花生四烯酸(C20:4n6)含量分别为6.85、41.05和53.84 mg/100 g显著高于其他各组,而α-亚麻酸含量,单不饱和脂肪酸总量和n-6多不饱和脂肪酸(n-6PUFAs)总量分别为48.05、1336.43和524.43 mg/100 g显著高于4 d和12 d。研究表明,短期微流水处理8 d时,在保证肌肉营养品质的同时,可有效改善其体色和肌肉颜色,增加肌肉口感,为池塘养殖淡水产品品质提升提供新的思路。

胃癌组织中microRNA-224阳性表达与患者预后相关性分析

目的:探讨micro RNA-224于胃癌组织中的阳性表达与患者临床病理特征及预后的相关性。方法:应用原位杂交技术检测micro RNA-224在50例石蜡固定癌旁非肿瘤胃黏膜组织及112例石蜡胃肿瘤组织切片中的表达情况,分析其与肿瘤患者各病理参数及预后的相关性。原位杂交按照原位杂交试剂盒的说明书进行。结果:micro RNA-224在胃癌组织中阳性表达率49.1%(55/112),癌旁非肿瘤胃黏膜组织中阴性表达。其阳性表达与TNM分期、淋巴结转移、远处转移及浸润深度存在相关性(P<0.05),而与性别、年龄、肿瘤大小、肿瘤的部位、分化程度、Lauren分型无关(P>0.05)。micro RNA-224阴性表达比阳性表达者5年生存率高,差异有统计学意义(P<0.001)。经COX多因素分析显示:micro RNA-224的表达是影响胃癌患者预后的独立因素之一(P<0.05)。结论:micro RNA-224在肿瘤组织中阳性表达与TNM分期、淋巴结转移、远处转移及浸润深度密切相关,是影响胃癌患者预后的独立因素之一。

面向直流微电网的混合级联多电平逆变器阶梯波控制策略研究

级联多电平变换器将数个全桥逆变模块以级联方式进行连接并予以控制,适用于中压大功率输出场景下的直流微电网,广泛应用于能量路由器、智能电能网关、固态变压器等电力电子装置中.传统级联多电平变换器所级联的每一路逆变模块的电压相同,限制了多电平输出电压的电平数量.为解决上述问题,将传统的母线电压相等的三路级联7电平逆变器改造成母线电压为2的倍数关系(20∶21∶22)的三路混合级联15电平逆变器,通过采用阶梯波控制方法,并针对最近电平逼近法进行了改良以产生开关器件的触发信号,可有效降低开关器件的开关频率和开关损耗,并将输出电压由7电平增加到15电平,有效降低谐波.从混合级联15电平逆变器工作原理、阶梯波调制方法、输出电压谐波等角度开展了理论分析与计算,最终搭建样机进行实验,有效验证了所提出的分析和研究.