Origin of insulating behavior of the p-type LaAlO3/SrTiO3 interface: Polarization-induced asymmetric distribution of oxygen vacancies

It is revealed from first-principles calculations that polarization-induced asymmetric distribution of oxygen vacancies plays an important role in the insulating behavior at p-type LaAlO3/SrTiO3 interface. The formation energy of the oxygen vacancy (V-O) is much smaller than that at the surface of the LaAlO3 overlayer, causing all the carriers to be compensated by the spontaneously formed V-O's at the interface. In contrast, at an n-type interface, the formation energy of V-O is much higher than that at the surface, and the V-O's formed at the surface enhance the carrier density at the interface. This explains the puzzling behavior of why the p-type interface is always insulating but the n-type interface can be conducting.

Optimized design on high-power GaN-based Micro-LEDs - art. no. 684108

The structure of micro-LEDs was optimized designed. Optical, electrical and thermal characteristics of micro-LEDs were improved. The optimized design make micro-LEDs suitable for high-power device. The light extraction efficiency of micro-LEDs was analyzed by the means of ray tracing. The results shows that increasing the inclination angle of sidewall and height of mesa, and reducing the absorption of p and n electrode can enhance the light extraction efficiency of micro-LEDs. Furthermore, the total light output power can be boosted by increasing the density of micro-structures on the device. The high-power flip-chip micro-LEDs were fabricated, which has higher quantum efficiency than conventional BALED's. When the number of microstructure in micro-LEDs was increased by 57%, the light output power was enhanced 24%. Light output power is 82.88mW at the current of 350mA and saturation current is up to 800mA, all of these are better than BALED which was fabricated in the same epitaxial wafer. The IN characteristics of micro-LEDs are almost identical to BALED.

Gate controlled Aharonov-Bohm-type oscillations from single neutral excitons in quantum rings

We report on a magnetophotoluminescence study of single self-assembled semiconductor nanorings which are fabricated by molecular-beam epitaxy combined with AsBr3 in situ etching. Oscillations in the neutral exciton radiative recombination energy and in the emission intensity are observed under an applied magnetic field. Further, we control the period of the oscillations with a gate potential that modifies the exciton confinement. We infer from the experimental results, combined with calculations, that the exciton Aharonov-Bohm effect may account for the observed effects.

An Integrated Solution for Software Process Improvement

Since 1990s, the software industry in China has been developed very rapidly and the total revenue in recent three years of 2005, 2006 and 2007 were 390.0, 480.0, and 583.4 billions RMB respectively, increased by 28.3% annually on an average basis [1]. By the end of 2007, there were about 18,000 software enterprises in China, and the population of software professionals was 1.48 millions roughly. In the global software market, China, with annual revenue about 82.2 billions USD (8.74% of the total: 940 billions USD), currently ranks on the fourth after USA, EU and Japan. However, the software industry in China is still comparatively weak. Most software enterprises have only tens of employees and millions RBM of revenue. And the software development productivity in China varies highly across the software industry in terms of organization, development type, business area, region, language, project size and team size [2]. Co-operative efforts from the government, the industry and the academy are needed [3]. Continuous software process improvement is an effective way to change the challenging situation of the software industry in China.

笼内金属富勒烯Gd@C_(82)的分离和质谱研究

由于其独特的电子结构，笼内金属富勒烯（碳笼内包容金属原子）的研究一直吸引着人们极大的兴趣，目前已经合成并分离出的笼内金属富勒烯主要包括碳笼内包容铱、钪、镧系原子等。在本论文中我们利用质谱技术对笼内金属富勒烯Gd_2@C_(82)气相离子行为和C_(60)与丙烯酸甲酯气相离子反应进行研究，X光电子能谱对碳笼内轧原子的价态进行研究。笼内金属富勒烯Gd_2@C_(82)是利用电弧放电法合成的。将碳份与三氧化二钆 （C：Gd=1：100, 摩尔比）灌入碳棒，将为棒前处理后，在氦气份保护下进行放电。通过对空心富勒烯在不同沸点的溶解情况进行了研究，发现大碳数的空心富勒烯在高沸点容剂中有较大的溶解度。利用两步高温高压法，既先利用1，2，4－三甲2基苯对大碳数的空心富勒烯进行分离，然后利用吡啶对笼内金属富勒烯进行提取。利用三种不同的质谱电离方式：电喷雾 （ESI），激光解析飞行时间（LDI-TOF），共振电子捕获技术（REC）来研究笼内金属富勒烯的气相离子特征。实验结果表明LDI-TOF和REC电离技术得到的质谱谱图中，笼内金属富勒烯和空心富勒烯均出现分子离子峰，但在电喷雾质谱谱图中只有笼内金属富勒烯出现分子离子峰。结合这一实验结果和理论分析说明碳笼内钆离子偏离碳中心位置。通过对比笼内金属富勒烯Gd@C_(82)和三氧化二钆中钆离子的光电子能谱谱图，Gd@C_(82)的电子结构应表示为Gd~(3+)@C_(82)~(3-)。利用四极杆质谱仪对C_(60)分子[C_(60)H]~+和加成产物为[C_(60)C_4H_3O]~+，后者是丙烯酸甲酯分子经过α短裂后与质子化[C_(60)H]~+ 发生加成反应所得的产物，在限制性Hartree-Fock条件下，采用AM1半经验量子化学计算方法对加成产[C_(60)C_3H_3O]~+八种可能结构的产物进行计算，得出了三种可能的最稳定的环加成同分异构体。

辽宁省生态系统评价与生态功能分区研究

生态系统评价是为了向决策者提供生态系统管理信，息而对生态系统结构、功能进行分析，并根据其变化趋势及驱动力提出相应措施的综合研究过程。生态功能分区是依据生态系统胁迫过程与效应、生态环境质量、敏感性和生态系统服务功能重要性等特征空间分异规律而进行的地理空间分区，目的是辨析区域生态环境问题与生态环境脆弱区和良好区，明确优先保护的生态系统和地区，为生态保护与建设、产业结构调整与优化及区域生态系统分区管理提供科学依据。本研究以辽宁省域生态系统为对象，在生态环境调查的基础上，分析了生态环境状况及变化趋势，进行了生态环境质量、敏感性和生态系统服务功能重要性评价，辨析了存在的生态环境问题及驱动力，明确了生态环境质量、敏感性和生态系统服务功能重要性空间分布格局，然后对辽宁省进行了生态功能区划分，并指出了各功能区生态保护与建设的重点和措施以及产业结构调整与优化的对策和方向研究结果表明，在经济和人口增长的长期胁迫作用下，辽宁省生态环境问题依然严峻，主要表现为：土地退化，地表水污染严重，森林质量下降和功能减弱，草地减少与退化并存，天然湿地萎缩，滩涂和海岸带生境恶化，生物多样性面临威胁，农业面源污染凸显，生态系统抗干扰能力下降，生态灾害加剧。全省生态环境质量超过2／3属于一般以下水平，其中优级面积仅占12.56％，良好级面积占18.71％，主要分布在东部及东南部；一般级面积占34.25％，主要分布在中部、北部和南部；较差级面积占34.48％，主要分布在西部及西北部。全省县级市及县有44个，其中生态环境质量为优的仅有4个市县，占总县数的9.09％；生态环境质量为良的有7个市县，占总县数的15.91％；生态环境质量一般的有19个市县，占总县数的43.18％，生态环境质量较差的有14个市县，占总县数的31.82％。全省处于轻度至高度敏感区域。高度敏感区占34.00％，主要分布在辽东山地丘陵、辽东半岛、辽西低山丘陵、辽西北、柳绕地区和大洼县。辽东山地丘陵、辽东半岛和辽西低山丘陵主要是土壤侵蚀高度敏感。辽西北和柳绕地区主要是土地沙漠化高度敏感。大洼县是土壤盐渍化高度敏感。中度敏感区占能．66％，与高度敏感区相间分布。轻度敏感区占3.34％，零星分布在辽东，在辽西和辽河平原也有少量分布。全省生态服务功能均处于比较重要以上。极重要地区占60.66％，基本分布在辽东、辽西和辽河平原的北部与盘锦滨海地区，辽东主要为水源涵养、生物多样性保护、土壤保持、营养物质保持，辽西主要为土壤保持、生物多样性保护、水源涵养、营养物质保持，辽北主要为土壤保持，盘锦滨海地区主要为生物多样性保护。中等重要地区占37.01%，基本分布在辽河平原，在辽东、辽西也有分布，辽河平原主要为土壤保持、水源涵养，沙漠化控制，辽东和辽西主要为土壤保持，辽西北为沙漠化控制。其它地区为比较重要地区，仅占2.33％，主要分布在辽东和辽河平原，在辽西也有少量分布，主要为土壤保持。在生态系统评价的基础上，首先根据地貌和气候划分出4个生态区，即辽东山地丘陵温带湿润半湿润生态区、辽河平原温带半湿润生态区、辽西低山丘陵温带半湿润生态区、辽南环黄渤海海岸带生态区。在明确生态区的基础上，依据生态系统类型与过程的完整性，以及生态服务功能类型的一致性，划分出21个生态亚区。依据生态环境质量、敏感性及生态服务功能重要性等的一致性，进一步划分出52个生态功能区。

~(94)Mo高自旋态能级纲图(英文)

通过重离子融合蒸发反应16 O(82 Se +4n) 94 Mo布局了94 Mo核的高自旋态 .利用多探头探测器阵列GASP进行了在束γ测量 ,从而重新研究了94 Mo核的高自旋态能级结构 .基于新发现的一些重要的连接跃迁 ,对94 Mo核的高自旋态能级纲图做了重要修改 .将新的能级结构与壳模型计算进行了比较和讨论 .结果表明要正确的描述94 Mo核的高自旋态 (自旋值大于 14 )能级结构 ,应考虑价中子在d5/ 2 ,g7/ 2 和h11/ 2 轨道上的激发 .

Elastic Scattering of He-6 + p at 82.3 MeV/nucleon

Differential cross sections for the elastic scattering of halo nucleus He-6 on proton target were measured at 82.3 MeV/u. The experimental results are well reproduced by optical model calculations using global potential KD02 with a reduction of the depth of real volume part by a factor of 0.7. A systematic analysis shows that this behavior might be related to the weakly bound property of unstable nuclei.

Thermodynamic investigation on properties of gasohol

The heat capacities (C-p) of three types of gasohol (which consisted of 20 wt % ethanol and 80 wt % unleaded gasoline 93(#) (system S1), 30 wt % ethanol and 70 wt % unleaded gasoline 931 (system S2), 40 wt % ethanol and 60 wt % unleaded gasoline 930 (system S3), where "93(#)" denotes the octane number) were measured by adiabatic calorimetry in the temperature range of 80320 K. A glass transition was observed at 94.24, 95.15, and 95.44 K for system S1, S2, and S3, respectively. A solid-solid phase transition and solid-liquid phase transition were observed at 135.18 and 151.30 K for system S1, 131.82 and 152.10 K for system S2, and 121.29 and 155.09 K for S3, respectively. The polynomial equations for C, with respect to the thermodynamic temperature (T), and with respect to the content of ethanol (x), were established through the least-squares fitting. The thermodynamic functions and the excess thermodynamic functions of the three samples were derived using these thermodynamic relationships and equations.

黑土侵蚀区生态重建的景观结构与功能分析

以黑龙江省拜泉县为案例,研究了区域生态恢复与生态重建对景观结构及其水土保持功能的调控.在GIS支持下,结合野外调查数据,对县域水平的生态建设成果进行了空间表达和定量辨识.对比分析1989年和2002年类型水平景观指数及13年来景观类型的转移面积和转移方向、林网宏观结构变化、水库塘坝空间分布与数量变化;土地利用和景观结构调整对水蚀、风蚀的控制以及水库塘坝的蓄水功能变化.结果表明,大规模生态建设下,区域景观类型数量和空间配置的变化对发挥其水土保持功能起到很好的调控作用.1989~2002年,耕地面积减少24 731.01 hm2,林草地和水体面积增加了13 567.53 hm2和1 190.97 hm2.全县55%的水土流失面积得到治理,82.2%的农田得到林网防护,43.7%的景观地表超渗径流得到集蓄.景观结构调整应注意增加林草地等类型斑块的聚集度;调节林网连接度、环度及网眼大小;增加水库塘坝的泄洪与灌溉配套设施等.

辽西油松纯林林分改造效益的综合评价

针对辽西地区大面积油松纯林的松毛虫危害严重、水土保持功能差、生态和经济效益低的现状 ,自 1982年起 ,在辽西地区通过采用带状皆伐后栽植阔叶树方法对油松纯林进行了更新改造试验 .试验结果表明 ,油松纯林改造成针阔混交林近 2 0年后 ,林分的小气候逐渐向良性转变 ,相对湿度提高 2 0 %～ 5 7%,气温降低 0 4～ 1 9℃ ,松毛虫虫口密度降低了 2～ 2 0头 株 ;同时水土保持功能增加 ,油松树高增加 16 8%,胸径增长 2 2 94%;经济效益有了较大提高 ,每公顷利润平均增加了 2 1倍 .因此 ,油松纯林改造成混交林是根治松毛虫危害 ,提高林分生态功能 ,增加林分经济效益的有效措施 ,应进行大面积推广 .

人工潜流湿地处理稠油采出水的实验研究

人工潜流湿地由 3个面积各为 90 0m2 的芦苇床组成 ,平均布水量分布为 6m3 d、18m3 d和 30m3 d .进水污染物平均浓度为 :COD 40 1 0 8mg L ,BOD531 88mg L ,矿物油 2 4 6 7mg L ,TN 11 6 7mg L .经潜流湿地处理后上述污染物分别减少了COD6 7 2 5 %— 80 77% ,BOD580 0 2 %— 89 0 5 % ,石油类 78 0 0 %— 88 45 % ,TN 75 32 %— 82 43 % .经检测 ,试验期间潜流湿地的渗透率为 0 5 2m d ,在这种条件下潜流湿地的耐冲击负荷强 ,出水水质稳定

沈阳西郊污灌区农田铜锌铅污染特征分析

为评价污水灌溉区农田土壤重金属污染状况,采用单因子指数和综合多因子指数法,对沈阳西郊污灌区农田土壤重金属铜锌铅的污染特征进行了研究。结果表明,于洪区宁官、高明、胡孤家和四台子四个样点土壤均受到三种重金属污染,其中宁官点0～10 cm土层铜、锌、铅含量分别达到69.74 mg.kg-1、275.09 mg.kg-1和81.83mg.kg-1,分别是当地土壤背景值的2.82、4.59和3.60倍。各样点土壤有效态铜、锌、铅含量也远高于未受污染地区的平均含量,土壤铜、锌、铅有效态含量占全量的比例分别为4.65%～15.46%、1.36%～3.84%和5.46%～18.86%。说明沈阳西郊污灌区农田土壤重金属污染较严重,必须通过工程、生物及化学措施进行长期的污染治理。

蔬菜温室土壤某些化学性质的演变特征

To explore the changes of soil chemical properties in vegetable greenhouse,a comparative study was carried out with the samples gathered from vegetable greenhouse fields and their adjacent upland fields in Damintun Town,Xinming County,Liaoning Province.The results showed that compared with upland fields,the contents of soil organic carbon and total nitrogen in greenhouse fields increased significantly.At the depth of 0～30 cm,soil organic carbon in greenhouses of 1-,4-and 10-year increased by 31.09%,35.44%,and 66.80%,respectively,compared with the upland soil.Soil nitrate content at the depth of 0～30 cm in greenhouse fields was 5.05～12.49 times as much as that in upland fields.The nitrate content in different soil layers increased with the increasing age of greenhouse field.,e.g.,at the depth of 20～30 cm,soil nitrate content was significantly higher in 10-year than in 1-and 4-year greenhouse field,with an increase of 65.73% and 50.89%,respectively,and 6.55 times as much as that in upland field,which indicated that soil nitrate transported downwards,and obviously enriched in deeper soil layers under heavy application of fertilizer.Also with the increasing age of greenhouse field,soil pH decreased,while soil soluble salts accumulated.

Gas phase derivatization of endohedral metallofullerenes R@C-82 and R-2@C-80 (R = Nd, Ce)

Endohedral metallofullerenes Ce@C-82, Ce-2@C-80, Nd@C-82 and Nd-2@C-80 undergo gas phase ion/molecule reactions with the ion system from self-chemical ionization of vinyl acetate, and exohedral derivatives are thus generated, A new heterocycle is formed from metallofullerenes and a C2H3O+ cation, Endohedral metallofullerenes show much higher reactivities than empty fullerenes during the association and the charge and proton transfer processes, The strong electron-donating character of endohedral metallofullerenes is due to their unique super-atom-like electronic structures. (C) 1997 by John Wiley & Sons, Ltd.