Simulation and Fabrication of 4H-SiC Separated Absorption Charge and Multiplication Ultraviolet Avalanche Photodiodes

4H-碳化硅（SiC）紫外雪崩光电探测器（APD）已具备取代紫外光电倍增管和Si基紫外光电探测器的可能性，它在光纤通信、高保密的非视距紫外通信及微弱紫外信号检测等特殊领域有重要的应用，已日益成为国际上光电探测领域的研究热点。 近年来已报道的高性能4H-SiCAPDs大多是采用吸收层和倍增层分离结构（SAM）进行制备。虽然SAM结构具有较高的量子效率，但是为了实现有效的吸收层和倍增层分离结构，要求倍增层厚度较薄且掺杂浓度较高，这将会使得器件的暗电流较大且倍增层电场分布梯度过大，不利于雪崩机制，并导致器件雪崩击穿电压过大。为了解决这些问题，本论文改进传统4H-SiCSAM（p+nn-n+）结构，...High performance 4H-SiC ultraviolet (UV) avalanche photodiodes (APDs), as a potential candidate to replace UV photomultiplier tubes and Si-based UV photodiodes, play an important role in the fields such as optical fiber communication, non-line-of-sight covert communications and low-level UV detection, which have increasingly become an research hotspot in the photoelectric detection field. Recentl...学位：理学博士院系专业：物理科学与技术学院_凝聚态物理学号：1982008015050

Convergence acceleration of guide-weight method on solving topology optimization models using Epsilon-algorithm

针对拓扑优化模型求解过程中需要多次迭代才能得到满足一定精度要求的收敛结果的问题,提出了一种基于向量Epsilon算法加速迭代序列收敛的方法。在求解大型连续体结构拓扑优化过程中,依据导重法迭代格式首先迭代了k次,然后对所得到的迭代序列的后m项作Epsilon算法运算,将所得到新向量作为下次导重法迭代的初始值,以此类推直到满足收敛条件。通过两个算例验证了所提出方法的有效性。计算及研究结果表明,用Epsilon算法加速后的迭代格式求解拓扑优化问题能够减少迭代次数,具有更高求解效率。Aiming at the problem of too much times of iterations to get the convergence results satified the accuracy required at the process of solving topology optimization models,a convergence acceleration method was proposed using vector epsilon-algorithm based on Guide-weight method. In the procedure of calculate large continuous structural topology optimization problems,k iterations were done according to the guide-weight method,then vector epsilon-algorithm was applied to the sequence of last m terms to obtain a new vector which was regarded as a initial value of next iteration until convergence. The developed method was verified by two examples. The results indicate that epsilon-algorithm can solve topology optimization problems with less iteration and high efficiency.国家自然科学基金资助项目(51575463

碳纳米管负载Mo-Co-S基HDS/HDN催化剂的制备及其表征研究

用自行制备的多壁碳纳米管(简写为CNTs)作为载体制备负载型Mo-Co-S催化剂,记为:m%MoiCoj/CNTs(m%为质量百分数),用噻吩加氢脱硫(HDS)和吡咯加氢脱氮(HDN)作为探针反应,XRD、XPS和H2-TPD作为表征手段,考察Co/Mo摩尔比、MoiCoj负载量及Co和Mo的浸渍顺序对所制备催化剂的结构和催化性能的影响.研究结果表明,对于本文自行制备CNTs负载的Mo-Co-S催化剂,最佳的Co/Mo摩尔比为1 3,最适宜的Mo3Co1负载量为~7.2%(质量百分数),Co和Mo的浸渍顺序以“先浸渍Co、经干燥焙烧后浸渍Mo”为佳.与AC负载的参比体系相比,CNTs负载催化剂较易于被还原,工作态催化剂表面具有催化活性的Mo物种(Mo4+)在总负载Mo量中所占份额较高;在另一方面,在HDS/HDN反应条件下,作为载体的CNTs的表面存在着数量更加可观的吸附氢物种,这些活泼氢物种通过“溢流”容易传输至Mo-Co-S催化活性位,于是有助于提高表面加氢反应的速率.以上两方面因素对CNTs负载Mo-Co-S催化剂上高的HDS/HDN反应活性都有重要贡献

价键理论的对不变式方法——Ⅱ.无自旋价键计算程序Xiamen

发展完善了价键理论的对不变式方法,给出了对不变式的正则展开方法,并证明了对不变式可以展开成任意阶的子对不变式和相应余子式乘积的形式.利用对不变式方法,完成一个新的无自旋价键理论方法从头计算程序——Xiamen.测试计算表明,Xiamen程序比基于传统价键方法的程序计算效率高,为量子化学计算研究提供了一个新工具

Design and application of mechanical rotation pulse device for water depth and water level measurement

针对超声波、光电等水深水位传感器抗污染能力差,无法实现水深水位同时检测的问题,提出了一种机械式旋转脉冲水深水位测量装置,该测量装置分滚筒提升装置、夹紧装置和控制装置三部分。在重锤下降的过程中,通过实时检测光电编码器输出的旋转脉冲数可以得到重锤下降的位移、速度、加速度,找出重锤下降的加速度突变点,由此判断出蓄水池的水面和固液界面两个临界点,进而计算出蓄水池的水深、水位和沉淀物料厚度。测试结果表明:该装置抗污染能力强,在重锤为510 g、采样时间间隔为0.10 S时测量效果最佳,测量误差小于1%。A new type of mechanical rotation pulse measurement device is proposed,aiming at problem that ultrasonic and photoelectric sensors have poor ability to resist pollution and can't realize water depth and water level detection at the same time.The measurement device points cylinder lifting device,clamping device and control device.In falling process of heavy hammer,the downward displacement,velocity,acceleration of heavy hammer can be obtained through real-time detection on output rotation pulse number of photoelectric encoder.Then the two falling acceleration mutation points of heavy hammer can also be founded when heavy hammer gets into the water and arrives at the solid-liquid interface in a reservoir.Thus the reservoir water depth,water level and precipitation material thickness can be calculated.The measurement result shows that the pollution resistance capability of the device is strong and the water depth measurement error of the device is less than 1 % when the weight of heavy hammer is 510 g and the sampling time interval is 0.10 s.国家自然科学基金资助项目(U1204107;51475459); 河南省高等学校精密制造技术与工程重点学科开放实验室开放基金资助项目(PMTE201318A); 河南理工大学博士基金资助项目(B2012—101); 河南理工大学教改项目(2014JG061); 河南省教育厅科技技术研究重点项目(14B460033

H_2在K~0-MWCNTs上储存和吸附/脱附特性研究

利用高压容积法辅以卸压升温脱附排水法,测定金属K修饰多壁碳纳米管对H2的吸附储存容量.结果表明,在室温(25℃),7.25MPa实验条件下,x%K0-MWCNTs(x%=30%～35%,质量百分数)对H2的吸附储存容量可达3.80wt%(质量百分数),是相同条件下单纯MWCNTs氢吸附储量的2.5倍;室温下卸至常压的脱附氢量为3.36wt%(占总吸附氢量的～88%),后续升温至673K的脱附氢量为0.41wt%(占总吸附氢量的～11%).利用LRS和H2-TPD-GC/MS等谱学方法对H2/K0-MWCNTs吸附体系的表征研究表明,H2在K0-MWCNTs上吸附存在非解离(即分子态)和解离(即原子态)两种吸附态;在≤723K温度下,H2/K0-MWCNTs体系的脱附产物几乎全为H2气;723K以上高温脱附产物不仅含H2,也含有CH4,C2H4和C2H2等C1/C2-烃

纳米尺寸团簇Ni_nZr_n(n=3～5)的几何结构与成键规律研究

根据化学键理论与拓朴原理 ,设计了团簇 Nin Zrn(n=3～ 5 )的可能几何构型 ,并用从头算方法进行构型优化 .结果表明 :由 Ni Zr组成的团簇原子间的 Zr—Zr和 Zr— Ni键明显较强 ,而 Ni—Ni的成键较弱 ;并发现 Nin Zrn(n=3～ 5 )团簇电子性质与有机烯烃分子等瓣相似 ,原子之间的成键按照强弱相间的规则分

Study of storage and adsorption/desorption characteristics of H-2 on MWCNTs modified by metal potassium

Storage capacity of H-2 in a kind of potassium-modified multiwalled carbon nanotubes, K-0-MWCNTs, was measured by using high-pressure volumetric method combined with desorption water-displacement method. It was experimentally shown that appropriate incorporation of a certain amount of metallic potassium into the MWCNTs could significantly increase the storage capacity of hydrogen. Under conditions of 7.25 MPa and ambient temperature, H-2 uptake of 3.8 wt% could be achieved by the x%K-0-MWCNTs (x%=30%-35%, mass percentage), which was 2.5 times as high as that by the KO-free MWCNTs under the same conditions. It was also indicated that adsorption of 99% of the H2 was reversible, and that 88% of the stored hydrogen (equalling storage capacities of 3.36 wt%) could be desorbed while the pressure was relieved to atmospheric pressure and similar to 11% of the stored hydrogen (equalling storage capacities of 0.41 wt%) was desorbed in the following process of elevating temperature from room temperature to 673 K. The Raman-spectroscopic and TPD-MS/GC investigations of the H-2/K-0-MWCNTs adsorption systems showed that adsorption of H-2 on the MWCNTs could occur in associative and dissociative forms, with the observed v(s)(C-H) for CH2, v(C-H) for CH and v(H-H) for H-2 (a) at 2856, 3228 and 3946 cm(-1), respectively, and that H-2 Was the predominant products desorbed at temperatures lower than 723 K, whereas in addition to H-2, light hydrocarbons such as CH4, C2H4, C2H2, etc. were also involved in the products desorbed at temperatures higher than 723 K

Development of Metal Oxide Microelectrodes for Measuring Sediment pH

用改进的高温熔融碳酸盐法制备了铱和钨氧化物PH微电极,表征了金属氧化物电极的各项性能.所制备电极对PH有较好的线性响应,斜率在40--60 MV/PH,接近理想能斯特响应.实验表明,铱氧化物微电极在长时间工作稳定性方面优于钨氧化物微电极,90%响应时间为5 S.铱氧化物微电极受盐度和氧气浓度影响很小,且经nAfIOn修饰后不受沉积物间隙水中还原性S2-的影响.把铱氧化物微电极应用于测量厦门西海域和九龙江河口的沉积物PH垂直剖面,发现PH在沉积物有氧和无氧深度界面(4--5 MM)达到最小,20 MM以深趋于稳定,符合沉积物生物地球化学规律.Iridium oxide and tungsten oxide pH microelectrodes were fabricated by oxidizing the metal wires in sodium carbonate or lithium carbonate molten at high temperature.Experiments were carried out to characterize their working performance.The microelectrodes show good linear response to pH in buffer solution with a slope between 40 and 60 mV/pH,close to Nernst slope.Experimental results indicate that iridium oxide microelectrode has better performance than tungsten oxide microelectrode in long-time working stability.Iridium oxide microelectrode has a 90% response time of about 5 s,shorter than that of tungsten oxide microelectrode.Iridium oxide microelectrode is little affected by oxygen concentration,salinity,and the reducing agent of S2-ions in the pore water of sediments after being coated with a Nafion film.Iridium oxide microelectrodes were applied to measure pH profiles of sediment cores sampled from Xiamen Western Bay and Jiulong River Estuary.It was found that pH reach minimum values at oxic-anoxic interface of 4～5 mm depths within the sediments and tended to be stable at depths deeper than 20 mm.These results agree with the prediction of biogeochemistry in coastal sediments.国家自然科学基金(40476035);教育部留学回国基金资