Analysis on The Ageing Mechanism of GaN-based Blue and Green LED by Electrical Stresses

对IngAn/gAn多量子阱蓝光和绿光lEd进行了室温20,40,60 MA加速电流下的电应力老化研究,发现蓝光与绿光样品经过60 MA电流老化424 H后,其电学性能表现出一定的共性与差异性:在小测量电流下,绿光样品的光衰减幅度较蓝光样品大~9%;而在较大测量电流(20 MA)下,两者的光衰减幅度基本相同(18%)。同时,蓝绿光样品的正向电学性能随老化时间的变化幅度基本一致,反映出它们具有相似的退化机制,绿光样品老化后增多的缺陷大部分体现为简单的漏电行为,而并非贡献于非辐射复合中心。在此基础上对gAn基外延结构进行了优化,优化后的lEd长期老化的光衰减幅度较参考样品降低了3%。The behavior of the related reliability of InGaN-based blue and green LED chips were investigated with 20,40,60 mA constant current stress up to 424 h at room temperature.Under 60mA constant current stress,the green LED chip showed more prominent optical power degradation at low measuring current levels than high measuring current levels.While,the blue LED chip showed the consistent optical power decrease at different measuring current levels.It should be pointed out that,at high measured current levels( 20 mA),blue and green LED chips expressed similar optical degradation( 18%) after the aging tests.Meanwhile,the aging stress does not significant affect the forward-bias electrical characteristics of blue and green LED chips,which indicated the similar degradation process in some aging tests.It is believed that the induced defects in blue LED by electrical stress mainly contribute to the nonradiative recombination centers,while in green LED chip the defects contribute to the localized leakage paths rather than the nonradiative recombination centers.Based on the mechanism analysis of blue and green LED,the design of GaN based epitaxial structure was optimized,and the thickness of quantum barrier was reduced to weaken the internal electrical field in the active layer to improve the reliability of LED.国家自然科学基金(61176050、61176092); 华侨大学科研基金(12BS226)资助项

Fabrication and characteristics of Si-based Ge waveguide photodetectors

以外延gE薄膜为吸收区,在SI基上制备了gE波导光电探测器。利用超高真空化学汽相淀积(uHV/CVd)设备,采取低温高温两步法,在SI(100)衬底上外延出厚度约为500nM的高质量纯gE层。探测器采用脊型波导结构,Al电极分别制作在波导的台面上下形成背对背肖特基结。I-V特性测试表明,在-1V偏压下,暗电流密度为0.2MA/CM2。由于SI与gE热失配引起外延的gE薄膜受到0.2%张应变,减小了gE带隙,光响应波长范围扩展到1.60μM以上。在70MW、1.55μM入射光照射下,测得光电流比暗电流高出近1个数量级。A Si-based Ge waveguide photodetector was fabricated and characterized.High-quality tensile strained Ge layer(about 500nm)was epitaxially grown on a Si(100)substrate by low-and high-temperature two-step growth method in ultrahigh vacuum chemical vapor deposition.Two metal-germanium schottky junctions on and under the waveguide were fabricated to form metal-germanium-metal photodetector and the dark current density of 0.2 mA/cm2 at the bias of-1 V is obtained.The photocurrent response in the wavelength range expands to 1.6 μm due to the 0.2% tensile strain in the Ge layer and the photocurrent is higher in one order magnitude than the dark current at 1.55 μm.国家自然科学基金资助项目(60676027);国家重点基础研究发展计划“973”资助项目(2007CB613404);国家自然科学基金委重点基金资助项目(60837001);福建省重点科技资助项目(2006H0036

The shape transformation of Si patterned-substrate in thermal decomposition of native oxide during vacuum annealing

利用超高真空化学气相淀积(uHV/CVd)系统,在不同的温度、环境氛围及脱O过程参与等条件下对全息法制备的二维周期图形SI衬底进行退火,通过原子力显微镜(AfM)进行表征与分析,研究真空高温脱O过程对图形衬底表面形态变化的影响。结果表明,真空环境使衬底表面的SI原子可以自由运动,脱O过程增强了SI原子在表面的迁移,温度会影响SI原子的扩散速率,3个因素的共同作用导致图形深度变浅,侧壁坡度变缓。此外,在周期图形台面的边缘,观察到环形有序分布的纳米SI岛。2D-period patterned Si substrate is annealed in ultra-high vacuum chemical vapor deposition(UHV/CVD)under variational conditions including different temperature,environment,thermal decomposition of native silicon oxide.The morphology properties of annealed patterned-substrate are obtained by atomic force microscopy(AFM).The effect of annealing parameters on shape transformation of Si patterned-substrate is studied.The results indicate that the Si atoms can diffuse freely on substrate surface in vacuum and the diffusion is enhanced during thermal decomposition of native oxide.The diffusion velocity is affected by temperature.These effects result in the decrease of the depth of pattern and gradient of side wall.In addition,ordered nanometer Si islands are formed on the mesa of patterned-substrate.国家自然科学基金资助项目(60336010;60676027);国家重点基础研究发展计划“973”资助项目(2007CB613404

补阳还五汤冲洗联合负压封闭引流技术治疗四肢软组织缺损创面的临床研究

目的:探讨补阳还五汤冲洗联合负压封闭引流技术(VSD)治疗四肢软组织缺损创面的临床疗效。方法:将57例慢性四肢软组织缺损创面患者行VSD治疗后随机分为补阳还五汤冲洗组(A组,n=29)和生理盐水冲洗组(B组,n=28),术后观察并比较两组患者的炎症指标变化、细菌培养结果、1周后肉芽组织覆盖率和首次植皮成活率情况。结果:两组患者术后及术后3 d的CRP比较,差异无统计学意义(P>0.05),而术后7 d及14 d,A组患者CRP低于B组(P0.05);A组患者术后14 d的ESR及白细胞计数明显低于B组(P<0.05)。术后1周A、B组平均肉芽组织覆盖率分别为(81.86±5.74)%和(73.11±4.19)%,两组差异有统计学意义(P<0.05)。拆除VSD后细菌培养结果显示:A组阴性为20例(70.0%),明显高于B组的11例(39.3%),差异有统计学意义(P<0.05)。A组有24例(82.8%)首次植皮或皮瓣转移成功闭合创面,B组有16例(57.1%)首次植皮成活,两组首次植皮成活率比较,差异有统计学意义(P<0.05)。结论:补阳还五汤冲洗联合VSD治疗四肢软组织缺损创面能降低炎症反应、促进肉芽组织生长、缩短植皮时间,提高植皮成活率。福建中医药大学校管课题(XB2017079

Effect of Ag loading on soot oxidation for Ag/Ce_(0.75)Zr_(0.25)O_2 catalysts

开发低温下高催化活性的柴油机碳烟颗粒燃烧催化剂是当前环境催化领域的热点问题。利用共沉淀的方法制备了用于碳烟催化燃烧反应的Ag/Ce_(0.75); Zr_(0.25)O_2催化剂。活性评价结果表明,相对于Ce_(0.75)Zr_(0.25)O_2催化剂,Ag的引入可显著降低碳烟催化燃烧温度。; 而且,Ag的负载量存在一个最佳值。以XRD、in-situ; XRD、BET、TPR等表征手段探究了该系列催化剂结构性质及其变化产生的影响。结果表明,Ag与Ce物种间的相互作用可显著降低催化剂(特别是CeO; _2表面氧)的还原温度。该相互作用使Ag/Ce_(0.75)Zr_(0.25)O_2催化剂在一定温度下(>200℃)就表现出Ag+的性质。这些性; 质与该催化剂具有较高的碳烟氧化活性相关。而且,该催化剂也表现出良好的稳定性。It is still important to develop soot oxidation catalysts with excellent; activity under low temperature. Ag/Ce_(0.75)Zr_(0.25)O_2 was synthesized; via coprecipitation method for soot oxidation. Compared with the; catalytic performance of Ce_(0.75)Zr_(0.25)O_2, the introduction of Ag; can lead to the decrease of soot-ignition temperature. Moreover, there; is an optimal Ag loading. Subsequently, several methods such as XRD,; in-situ XRD, BET, TPR were used to characterize the physicochemical; properties of Ag-based catalysts. The results showed that the; introduction of Ag resulted in decreasing the reduction temperature of; surface oxygen species, being due to the interaction of Ag and Ce. The; interaction also brings about the occurrence of Ag~+ nature. And the; feature is linked with the outstanding activity of soot oxidation for; Ag-based catalyst. Furthermore, the Ag-based catalyst possessed fairly; good stability in soot oxidation.国家自然科学基金项目; 中央高校基本科研业务费专项资金项

Kilogram Scale-up Preparation of Catalysts and its Reaction Process in Syngas Methanation

甲烷化催化剂是煤制合成天然气核心技术之一,因此研发合成气完全甲烷化催化剂具有重要意义。研究工作采用实验室小试共沉淀制备甲烷化催化剂的最佳工艺条件; 方法,进行单批次1、5和10; kg级(代号cat-1、cat-5、cat-10)催化剂的制备研究。研究了催化剂制备的控制因素和放大制备催化剂的反应性能及催化反应工艺条件。研究; 显示:催化剂制备的控制因素主要包括Na~+含量及晶型结构;放大制备催化剂具有良好的活性、操作稳定性和耐热性能,与小试制备催化剂具有较好的一致性;; 放大制备催化剂(cat-10)在所考察的还原温度、反应H_2/CO比和10000~40000; mL·h~(-1)*g_(cat)~(-1)反应空速范围内具有良好的甲烷化活性。研究结果表明,该研究单批次公斤级催化剂放大制备是成功的,为实现催; 化剂进一步放大制备提供了良好基础。Methanation catalysts play a vital role in the production of synthetic; natural gas (SNG) from coal. Based on bench-scale optimum; co-precipitation conditions of catalyst preparation, scale up; preparation of catalysts for syngas methanation with single batch of 1,; 5 and 10 kg is studied. Factors affecting catalyst; preparation/performance and scale-up were investigated. The results show; that Na~+ content and crystal structure of the catalysts are the; critical factors, and the catalysts prepared under scale-up conditions; possess excellent operation stability and heat resistance, with; consistent performance as those from bench-scale samples. The 10 kg; batch has good reaction activity under studied conditions. Therefore,; the scale-up preparation is successful for the methanation catalyst in; this study, which is useful for future scale-up preparation of related; catalysts

A Novel Co-training Object Tracking Algorithm Based on Online Semi-supervised Boosting

基于自训练的判别式目标跟踪算法使用分类器的预测结果更新分类器自身,容易累积分类错误,从而导致漂移问题。为了克服自训练跟踪算法的不足,该文提出一种基于在线半监督bOOSTIng的协同训练目标跟踪算法(简称CO-SEMIbOOST),其采用一种新的在线协同训练框架,利用未标记样本协同训练两个特征视图中的分类器,同时结合先验模型和在线分类器迭代预测未标记样本的类标记和权重。该算法能够有效提高分类器的判别能力,鲁棒地处理遮挡、光照变化等问题,从而较好地适应目标外观的变化。在若干个视频序列的实验结果表明,该算法具有良好的跟踪性能。The self-training based discriminative tracking methods use the classification results to update the classifier itself.However,these methods easily suffer from the drifting issue because the classification errors are accumulated during tracking.To overcome the disadvantages of self-training based tracking methods,a novel co-training tracking algorithm,termed Co-SemiBoost,is proposed based on online semi-supervised boosting.The proposed algorithm employs a new online co-training framework,where unlabeled samples are used to collaboratively train the classifiers respectively built on two feature views.Moreover,the pseudo-labels and weights of unlabeled samples are iteratively predicted by combining the decisions of a prior model and an online classifier.The proposed algorithm can effectively improve the discriminative ability of the classifier,and is robust to occlusions,illumination changes,etc.Thus the algorithm can better adapt to object appearance changes.Experimental results on several challenging video sequences show that the proposed algorithm achieves promising tracking performance.国家自然科学基金(61201359;61202143); 福建省自然科学基金(2011J01367;2012J05126); 高等学校博士学科点专项科研基金(20090121110032)资助课

Characterizing Nitrogen Saturation of the Wuchuan Headwater Stream in the Southeast of China

以九龙江流域典型的农业源头溪流——五川溪为研究区域,开展每月一次共2年的nO3-采样用于溪流氮饱和特征的研究.结果表明,2005年和2007年溪流的nO3-浓度分别为35.5~319.5μEQl-1和5.0~353.6μEQl-1,根据STOddArd和TrAAEn提出的氮饱和划分准则,五川流域分别处于氮饱和阶段2/3和阶段2,接近氮饱和.氮饱和阶段随着nO3-浓度的增加而上升,五川溪流的氮饱和阶段存在着时间上的变化.河流生态系统中氮负荷增加,使河流达到氮饱和状态,并最终改变溪流系统硝化和反硝化等氮的生物地球化学循环过程.随着nO3-浓度的增加,五川源头溪流已成为流域内重要的nO3-源.NO3-concentrations sampled monthly in the Wuchuan stream,which is a small agricultural headwater stream in the southeast of China,within two years,were used to study the stream′s nitrogen saturation characteristics.Results showed that NO3-concentrations varied from 35.5 to 319.5 μeqL-1 in 2005 and from 5.0 to 353.6 μeqL-1 in 2007.And,according to the criteria proposed by Stoddard and Traaen,the nitrogen saturation status of the stream was at stage 2 or 3,and stage 2,respectively.Both stages were closed to saturation.It was found that the saturation stage would increase with the NO3-concentration,which caused the change of nitrogen saturation stage in the Wuchuan stream over time.The increasing of nitrogen loadings has led to the stream nitrogen saturation and eventually can alter nitrification,denitrification and other nitrogen biogeochemical cycles in the stream ecosystem.国家自然科学基金资助项目(41175130);教育部新世纪优秀人才支持计

A Perspective Invariant Image Matching Algorithm

针对ASIfT(AffInE SCAlE InVArIAnT fEATurE TrAnSfOrM)算法存在的仿射采样策略、采样点离散设置等问题,提出了一种基于粒子群优化的图像透视不变特征PSIfT(PErSPECTIVE SCAlE InVArIAnT fEATurE TrAnSfOrM)算法.该算法通过虚拟相机的透视采样来模拟景物在多视角图像中的变形.在此基础上,将图像匹配问题转换为透视变换的优化问题,并以粒子群算法为工具,研究了虚拟相机旋转参数搜索空间、适应值函数的合理设定.针对三组不同类型低空遥感图像的实验结果表明,该算法比ASIfT、SIfT(SCAlE InVArIAnT fEATurE TrAnSfOrM)、HArrIS AffInE和MSEr(MAXIMAlly STAblE EXTrEMAl rEgIOnS)等算法获得更多的特征匹配对,有效地提高了算法对视角变化的鲁棒性.To solve the problem of affine transform and discrete sampling in ASIFT(Affine scale invariant feature transform),the PSIFT(Perspective scale invariant feature transform),which is based on particle swarm optimization,is proposed in this paper.The proposed algorithm uses a virtual camera and homographic transform to simulate perspective distortion among multi-view images.Therefore,particle swarm optimization is employed to determine the appropriate homography,which is decomposed into three rotation matrices.Experimental results obtained on three categories of low-altitude remote sensing images show that the proposed method outperforms significantly the state-of-the-art ASIFT,SIFT,Harris-affine and MSER,especially when images suffer severe perspective distortion.国家自然科学基金(61103052;61202143); 国家教育部博士点基金(20090121110032); 福建省产学重大科技项目(2011H6020); 福建省自然科学基金项目(2011J01013;2013J01245;2013J05100); 深圳市科技计划项目(JC200903180630A;ZYB200907110169A); 厦门市科技计划项目(3502Z20123022;3502Z20110010); 福建省教育厅基金项目(JK2012025)资助~