127 resultados para 136-843A
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The estimate for the lowest cost of SODL (silicon on defect layer) solar cell is made according to the price standard of present market. The estimate shows that the PV (photovoltaics) energy costs can be reduced from today's 25-30 cents/(kW h) to 7-8 cents/(kW h) which is comparable with the present cost of electricity generated by traditional energy sources such as fossil and petroleum fuels. The PV energy costs could be reduced to a value lower than 7-8 cents(kW h) by developing SODL technology. The SODL solar cell manufacture featuring simple processes is suitable to large scale automated assembly lines with high yield of large area cells. Some new ideas are suggested, favoring the further reduction in the cost of commercial solar cells.
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An ultracompact 3-dB coupler is designed and fabricated in silicon-on-insulator,based on 12 line tapered multimode interference(MMI) coupler.Comparing with the conventional straigth MMI coupler,the device is-40% shorter in length.The device exhibits uniformity of 1.3dB and excess loss of 2.5dB
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用金属有机化学气相淀积技术在蓝宝石衬底上成功外延了高P组分的GaN_(1-x)P_x 三元合金。俄歇电子能谱深度剖面结果表明在GaN_(1-x)P_x 中P的掺入量最高达到20%且分布均匀;X射线光电子能谱价态分析证实了外延层中Ga-P键的存在。对不同P组分的GaN_(1-x)P_x 样品进行了低温光致发光(PL)测试,与来自GaN衬底的带边发射相比,随三元合金中P组分的变化,GaN_(1-x)P_x 的PL峰呈现出了不同程度的红移。在GaN_(1-x)P_x 的PL谱中没有观测到有关GaP的发射峰,表明该合金材料没有发生相分离。
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文章从光子器件功能集成,光子器件面阵集成、光子集成PIC互连等三个方面探讨了半导体集成光学的重大进展。并对今后的发展前景作了展望。
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于2010-11-23批量导入
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于2010-11-23批量导入
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We have studied the spontaneous emission of polarized excitons in the GaInP/AlGaInP VCSEL from 30K to room temperature. It is observed that the spontaneous emission peak enters and leaves the resonant regime. At the resonant regime, the emission intensities of the perpendicular and horizontal polarized exciton are enhanced at different ratio to those in non-resonant regime. These experiment results are explained through the dressed exciton theory of the semiconductor microcavity device. From this theory, the intensity enhancement and the polarization dependence are understood as cooperative emission and the microcavity anisotropy.
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Low threshold current and high temperature operation of 650nm AlGaInP quantum well laser diodes grown by low pressure metal organic chemical vapor deposition (LP-MOCVD) are reported in this paper. 650nm laser diodes with threshold current as low as 22-24mA at room temperature, and the operating temperature over 90 degrees C at CW output power 5 mW were achieved in this study. These lasers are stable during 72 hours burn in under 5mW at 90 degrees C.
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The behaviors of lateral propagating modes in the aperture and the oxidized regions are investigated numerically for selectively oxidized vertical-cavity surface-emitting lasers (VCSELs). The results show that the lateral propagating modes in the oxidized region are greatly affected by the oxide layer due to its low index, the modes are divergence for the VCSELs with sufficient thick double oxide layers. So the coupling between the modes in the aperture and oxidized regions is very weak, and we can expect that the lateral spontaneous emission is greatly affected in this case. Ignoring the contribution of the lateral spontaneous emission, we calculate spontaneous emission factor by counting the total number of the guided modes in selectively oxidized VCSELs with double oxide layers. The results agree very well with the reported measurements and are inversely proportional to the lateral index step.
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合叶苔科Scapaniaceae隶属于苔纲Hepaticae叶苔目Jungermanniales,全世界约6属136个现存种,1个化石种。合叶苔科的科和属的特征明显,但物种间变化大,分类比较困难,部分属种的分类位置亦存在争议。本研究前,中国已记录合叶苔科植物有4属,66种3变种,其中9种1变种已归为同物异名,承认的种类共57种2变种。以中国产标本为基础发表的新分类单位共2属16种2变种。目前尚无专门针对中国合叶苔科的系统研究,因此,开展中国合叶苔科的分类、区系和生态研究,对深入认识中国苔类植物多样性、区系和系统具有重要的科学意义。 本研究运用植物学经典分类的基本方法和现代的分支系统分析方法,对国内、外主要苔藓植物标本馆的中国合叶苔科植物的模式标本和有关标本进行了较全面的检查和详细的形态解剖和分类学研究,并开展了野外补充调查采集,完成了对中国合叶苔科植物的分类修订,分析该科的区系成分组成和在中国的地理分布特点及其属种之间的分支系统关系。研究的主要结果如下: (1)在相关模式标本和国内外标本鉴定和研究的基础上,确认中国合叶苔科有3属52种1变种,包括:大褶叶苔属Macrodiplophyllum1种,褶叶苔属Diplophyllum5种,合叶苔属Scapania46种1变种。发现并发表新种2个,即片毛合叶苔S. macroparaphyllia T. Cao, C. Gao & J. Sun(曹同等,2004)和毛茎合叶苔S. paraphyllia T. Cao, C. Gao, J. Sun et B. R. Zuo(Zuo et al., 2007);发现中国新分布记录2种,尖瓣合叶苔S. ampliata Steph.(Zuo & Cao, 2007)和扁平合叶苔S. compacta (Roth) Dum.(首次报道,尚未发表)。完成了对中国合叶苔科植物的分类修订,对每个属、种都进行了文献考证、特征描述、图版绘制和分类讨论,并利用Mapinfo软件绘制了各种在中国的分布图。 (2)对相关模式标本标定和研究,澄清了一些分类问题和中国种的概念。如对东亚分布的若干种类进行了比较和评估,划定其分类界限,确认2种已经被归并为弯瓣合叶苔S. parvitexta Steph.新异名的种类仍然为独立的种,即细齿合叶苔S. parvidens Steph.和灰绿合叶苔S. glaucoviridis Horik.。并对东亚特有属种侧囊苔属的侧囊苔Delavayella serrata Steph.进行了模式标定,探讨了它的地理分布和系统位置,支持将其独立成侧囊苔科Delavayellaceae的观点。 (3)在标本鉴定和野外采集工作的基础上,合叶苔科各种在中国的分布范围大为增加,为开展中国合叶苔科的地理分布格局奠定了基础。对现有的地理分布资料的分析表明,西南地区(西藏,云南,四川,贵州)是中国的合叶苔属植物的分布中心和可能的起源中心,共有合叶苔40种,占该属总数(46种)的86.96%,其中,15种仅分布在西南地区,中国特产9种中,有8种在西南地区分布。此外,东北地区、华东地区及台湾省分布种类较多,分别为16种(34.78%),22种(47.83%)和17种(36.96%)种的分布。 (4)区系成分分析结果表明,合叶苔属Scapania主要由2大区系成分组成:东亚成分25种,占总数的51%,其中,中国-日本分布7种,中国-喜马拉雅分布9种,中国特产种9种。北温带成分22种,占总数的45%,其中有18种在亚洲,欧洲和北美洲均有分布。褶叶苔属Diplophyllum 5种,4种为北温带成分,1种为中国-日本分布的东亚成分。分析结果反映了中国苔藓植物区系的基本特点,即与欧美植物区系有密切联系,同时又体现了较强的东亚区系特色。 (5)对合叶苔属Scapania植物的生态和生境分析表明,47个分类群可分成3种主要类型:1)沼泽或水湿生;2)以腐木生为主,有时生于岩面薄土上的小型种类;3)潮湿岩面或林下土生的中等和大型种类。 (6)选取了39个反映系统发育关系的形态特征,以与合叶苔科相近的裂叶苔科Lophoziaceae中挺叶苔属Anastrophyllum 2种和裂叶苔属Lophozia 1种为外类群,运用外类群比较法对合叶苔科的的属种之间的演化关系进行了分支系统分析。结果表明,原归于合叶苔科的侧囊苔属Dalevayella为单独的一个分支,应为独立的侧囊苔科Dalevayellaceae。大褶叶苔属Macrodiplophyllum和褶叶苔属Diplophyllum植物相近,可归并为一个属,与合叶苔属Scapania同为合叶苔科Scapaniaceae下的属。中国合叶苔属47个分类群可分为若干组,主要与其生境,植物体,叶的结构,无性繁殖等特征有关,结果与目前采用的合叶苔科的分类系统与演化关系基本一致。
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空间生态规划着重于研究城乡土地和空间资源,达到城乡土地和空间资源合理配置。辽宁本溪市南芬区属山地资源型工矿城镇,由于空间用地类型配置不合理,中心城区环境污染严重,而广阔的乡村空间资源未尽其用。为此,有必要对南芬全区城乡空间进行生态规划。本文在理论上补充空间生态规划中生态适宜性评价理论,在方法上提出了基于适宜性评价的空间生态规划方法后,就南芬主要用地类型工业用地、居住用地、作物用地和林业用地分别进行生态适宜性评价和用地配置研究,并综合适宜性评价结果和探讨了南芬空间生态分区及空间生态规划途径。 主要结果为:(1) 工业用地最适宜区、次适宜、勉强适宜和不适宜区面积分别为91.23km2、182.72km2、182.08km2和162.97km2;居住用地分别为208.08km2、169.95km2、149.51km2和91.46km2;作物用地分别为124.23km2、130.65km2、159.02km2和205.1km2;林业用地分别为201.7km2、150.43km2、130.21km2和136.66km2。(2) 工业用地现状位于最适宜区、次适宜区、勉强适宜区、不适宜区的面积分别为9.81km2、10.66km2、6.54km2和11.73km2;居住用地分别为9.05 km2、12.57km2、15.7km2和11.53km2;作物用地分别为16.61km2、7.88km2、22.25km2和24.15km2;林业用地分别为193.91km2、104.88km2、81.74km2和67.27km2。(3)综合评价表明,工业用地、居住用地、作物用地、林业用地适宜区面积分别为46.75km2;71.32km2;94.46km2;406.47km2。南芬生态空间区划为生态保护区、生态居住区(2个)和生态工业区(3个)。(4) 最后详细阐述了南芬城乡空间生态规划途径及其内涵,即:生态优先、整体优化、经济优效和社会持续。