Fabrication and amplified spontaneous emission spectrum of Er3+-doped tellurite glass fiber with D-shape cladding

Tellurite glass is proposed as a host for broadband erbium-doped fiber amplifiers because of their excellent optical and chemical properties. A single-mode Er3+-doped tellurite glass fiber with D-shape cladding was fabricated in this work. The characterization of amplified spontaneous emission (ASE) from this newly fabricated Er3+-doped tellurite fibers are exhibited. When pumped at 980 nm, a very broad erbium ASE nearly 150 nm around 1.53 mum is observed. The changes in ASE with regard to fiber lengths and pumping power were measured and discussed. The output of 2 mW from Er3+-doped tellurite fiber ASE source was obtained under the pump power of 660 mW. The broad 1.53 mum emission of Er3+ in tellurite glass fiber can be used as host material for potential broadband optical amplifier and tunable fiber lasers. (C) 2004 Elsevier B.V. All rights reserved.

在Sr～2+α_BBO单晶衬底上生长β_BBO薄膜的研究

Crystalline beta-BBO thin films were successfully prepared on (001)-oriented Sr2+-doped alpha-BBO substrates by using liquid phase epitaxy, pulsed laser deposition and vapor transport equilibration techniques. The films were characterized by X-ray diffraction and X-ray rocking curve. The present results manifest that the beta-BBO thin films grown on Sr2+-doped alpha-BBO substrates have larger degree of orientation f value and smaller X-ray rocking curve FWHM than the ones grown on other reported substrates. Compared with other substrates, alpha-BBO has the similar structure, the same UV cutoff and the same chemical properties to beta-BBO. These results reveal that Sr2+-doped alpha-BBO single crystal may be a promising substrate proper to the growth of beta-BBO films.

水热法ZnO晶体特征研究

ZnO具有优良的综合性能使其成为极有前途的下一代光电材料，水热法是一种重要的生长ZnO晶体的方法。本文对水热法生长的面积约150mm^2的ZnO晶体进行了报道，研究了晶体不同方向的生长速度、形貌特征和光学性能。X射线摇摆曲线表明晶体的质量较好。对于光学性质的分析表明晶体生长时加入H2O2能显著提高晶体的质量。494nm附近的发光带可能与氧空位有关。520nm的发光可能与Na或者Si所形成的杂质能级跃迁有关。

典型草原土壤性状变化对灌丛化的响应

以草原和稀树草原中木本植物多度的增加为特征的草地灌丛化，是全球范围普遍发生的现象，但灌丛化的生态学效应目前仍存在争议。对灌丛化草地生态系统特征与过程的研究，将有助于我们进一步了解草地生态系统的退化和恢复机理，为退化草原恢复与管理实践提供理论依据。 本研究以位于内蒙古锡林河流域, 一个经23年围封恢复、具有明显灌丛化特征的草原生态系统为研究对象，通过分析小叶锦鸡儿灌丛及其相邻草本群落下的土壤容重、机械组成、土壤有机碳(SOC)、全氮(TN)和无机氮(IN)的差异，确定小叶锦鸡儿灌丛对草原土壤物理化学性状的影响。主要结果如下： （1）小叶锦鸡儿灌丛化增加了表层土壤（0-5 cm）粗粒级颗粒的比例，降低了浅层土壤（0-20 cm）的容重，较大灌丛下10-20 cm土层仍存在这种现象。这至少部分归因于灌丛对凋落物的截获积聚，以及小叶锦鸡儿的根系分泌物在质和量上较之草本植物的不同，促进了土壤团聚体的发育。 （2）小叶锦鸡儿灌丛斑块引起了典型草原生态系统土壤有机碳、全氮和无机氮的空间分布的变化。在浅层土壤中（0-20cm），由灌丛斑块内部向外部SOC、TN和IN均趋于降低。随小叶锦鸡儿灌丛大小（存在时间）的增加，0-20 cm和60-100cm土层SOC和TN均有增加趋势。 （3）除表层（0-5cm）外，小叶锦鸡儿大灌丛与邻近草地土壤C/N比值无显著差异。 总之，小叶锦鸡儿灌丛不仅改变了草原土壤的物理性状，而且提高了灌丛下土壤有机碳和氮的含量，改变了草原生态系统C、N的空间分布格局，表明草原灌丛化明显改变了草原生态系统的碳氮循环。基于草原约占陆地面积的40%以及全球草地灌丛化普遍存在的事实，这种伴随草原灌丛化发生的土壤有机碳和氮的变化可能会对全球碳氮循环和气候有显著影响。

三峡水库蓄水对消落带土壤理化性状的影响

三峡水利枢纽工程的调度运行导致水库水位的涨落，从而在三峡水库周边水陆交错带形成周期性淹没与出露于水面的一段特殊区域，被称为三峡水库消落带。三峡水库消落带生态系统的健康是库岸稳定和水库安全运行的重要保障。土壤养分是三峡库区消落带土壤生态系统的重要组成部分。三峡水库蓄水以来，土壤理化性状发生改变，水土流失日益加剧。土壤是植物的基础，因此，对三峡水库消落带土壤性状的研究对消落带植被恢复有一定的指导意义，也为研究水库消落带水土流失提供依据，为研究水库消落带土壤污染与水体污染提供基础。 本文首先通过对重庆忠县石宝寨水库消落带不同水位、不同时期的表层土壤分析，研究了消落带不同水位土壤容重、酸碱度、有机质、全氮、全磷、全钾、硝态氮、氨态氮、速效磷、速效钾的含量变化。实验结果表明：（1）消落带土壤淹水前各测定指标在不同海拔高程之间的差异均不显著（P>0.05）；（2）三峡水库淹水后消落带土壤由微碱性变为碱性，养分平均含量普遍下降，土壤养分缺乏，淹水易造成养分流失；（3）不同淹水强度下，土壤pH 值、有机质、全氮、全磷、氨态氮、速效钾平均含量差异显著（P＜0.001），经过淹水土壤有机质、全氮、速效钾含量进一步降低；（4）不同淹水时期，土壤全钾、硝态氮、氨态氮平均含量差异显著（P＜0.001），速效氮含量随季节变化较大，与土壤水分有密切关系；（5）干湿交替更容易造成氮、磷解吸释放入水体，从而增加富营养化的风险。 其次，通过对石宝寨消落带5 个时间段6个水位的表层土壤分析，研究了消落带不同时期、不同淹水强度土壤酸碱度及Cu、Zn、Pb、Cr 的含量变化。结果表明（1）淹水土壤pH 显著高于未淹水土壤，长期淹水土壤重金属含量显著高于短期淹水土壤与未淹水土壤，146m 土壤重金属含量最高；（2）经过淹水土壤，pH 先升高后下降，铜含量、锌含量都下降，铬含量先上升后下降，铅含量随着土壤暴露先稍微上升，后又下降，但在08 年9 月达到最大值；（3）各土壤重金属之间均存在显著相关关系，表明三峡消落带土壤存在重金属复合污染隐患；（ 4 ） 以三峡水库土壤背景值为评价标准， 消落带土壤污染程度具有Cu>Pb>Zn>Cr 的特征，其中，铜污染相对最为严重，消落带土壤随着淹水强度的加大与淹水时间的延长，污染程度加重，消落带综合污染指数达到1.24，属于轻度污染级。

Differentiate performance of eight filter media in vertical flow constructed wetland: Removal of organic matter, nitrogen and phosphorus

A comparative study was conducted to reveal the differentiate effects of eight different filter media including gravel, zeolites, anthracite, shale, vermiculite, ceramic filter media, blast furnace steel slag and round ceramsite. The study mainly related to the eight different filter media's removal performances of organic matter, nitrogen and phosphorus in the vertical flow constructed wetland simulated system, which treating wastewater at hydraulic loading rate of 1000-2500 mm/d. The results indicated that the removal effects were closely related to the physical and chemical properties of medium materials. Anthracite-filled system had the highest removal rate for the total organic carbon (TOC), up to 70%, and the removal rates of other systems ranged from 20% to 30%. As for the five-day biochemical oxygen demand (BOD5), anthracite-filled and steel slag-filled systems had the highest removal rates, also up to 70%, as well as other systems all exceeded 50%. At the same time, for the total nitrogen (TN) and NH4(+)-N, the zeolites-filled and ceramic-filled systems had the best performances with the removal rates of more than 70%, the other way round, the removal rates of other systems were only about 20%. The distinguishable effects were also observed in removal performances of total phosphorus (TP) and total dissoluble phosphorus (TDP). The removal rates of TP and TDP in steel slag-filled systems were more than 90%, a much higher value, followed by that of the anthracite-filled system, more than 60%, but those of other systems being the less. Our study provided a potential mechanism to optimize the filter media design for the vertical flow constructed wetlands.

Primary succession of algal community structure in desert soil

The microbiotic crust study is among new focuses in investigating on the desertification control. Based on determination of algal crusts with different successive ages (4-, 8-, 17-, 34-, 42-year-old) and unconsolidated sand in the desert area, species composition and clustering analyses were carried out in this study. Results on successional orientation revealed that (1) the abundance of Cyanophyta, specially of Scytonema javanicum gradually decreased; (2) the abundance of Chlorophyta, Bacillariophyta and a species of Cyanophyta, Phormidium tenue increased; (3) the biodiversity increased gradually with the community succession; and (4) biomass of microalgae increased at the early stage, but decreased at the later stage due to the abundance of lichens and mosses. But, the speed of natural succession was so slow that the community-building species was still the first dominant species after 42 years, except that its dominant degree decreased just slightly. However, successive speed and trend were affected by water, vegetation coverage, terrain, time and soil physico-chemical properties as well, especially Mn content in the soil appeared to have a threshold effect.

Effect of desert soil algae on the stabilization of fine sands

Four filamentous cyanobacteria, Microcoleus vaginatus, Phormidium tenue, Scytonema javanicum (Kutz.) and Nostoc sp., and a single-celled green alga, Desmococcus olivaceus, all isolated from Shapotou (Ningxia Hui Autonomous Region of China), were batch cultured and inoculated onto unconsolidated sand in greenhouse and field experiments. Their ability to reduce wind erosion in sands was quantified by using a wind tunnel laboratory. The major factors related to cohesion of algal crusts, such as biomass, species, species combinations, bioactivity, niche, growth phase of algae, moisture, thickness of the crusts, dust accretion (including dust content and manner of dust added) and other cryptogams (lichens, fungi and mosses) were studied. The best of the five species were M. vaginatus and P. tenue, while the best mix was a blend of 80% M. vaginatus and 5% each of P. tenue, S. javanicum, Nostoc sp. and D. olivaceus. The threshold friction velocity was significantly increased by the presence of all of the cyanobacterial species, while the threshold impact velocity was notably increased only by the filamentous species. Thick crusts were less easily eroded than thin crusts, while biomass was more effective than thickness. Dust was incorporated best into Microcoleus crust when added in small amounts over time, and appeared to increase growth of the cyanobacterium as well as strengthen the cohesion of the crust. Microbial crust cohesion was mainly attributed to algal aggregation, while lichens, fungi and mosses affected more the soil structure and physico-chemical properties.

Investigation of a chemically treated InP(100) surface during hydrophilic wafer bonding process

Surface micro-roughness, surface chemical properties, and surface wettability are three important aspects of wafer surfaces during a wafer cleaning process, which determine the bonding quality of ordinary direct wafer bonding. In this study, InP wafers are divided into four groups and treated by different chemical processes. Subsequently, the characteristics of the treated InP surfaces are carefully studied by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact angle measurements. The optimal wafer treatment method for wafer bonding is determined by comparing the results of the processes as a whole. This optimization is later evaluated by a scanning electronic microscope (SEM), and the ridge waveguide 1.55 mu m Si-based InP/InGaAsP multi-quantum-well laser chips are also fabricated. (c) 2005 Elsevier B.V. All rights reserved.

间伐对仁用杏园土壤理化性质及生长结果的影响

为了探讨密闭仁用杏园衰败的原因,采用常规的方法研究了间伐对仁用杏园土壤养分、水分及树体生长等方面的影响。结果表明:间伐减小了土壤容重,略微增加了土壤孔隙度;间伐显著提高了0-40 cm土层土壤有机质、0-20 cm土层土壤全氮,略微提高了0-20 cm土层土壤全磷;间伐显著提高了0-80 cm土层土壤速效氮、0-40 cm土层土壤速效磷和0-60 cm土层土壤速效钾,且间伐强度越大土壤养分越高;间伐显著提高了0-500cm土层土壤水分,在干旱的春季、夏季优为显著,且间伐强度越大,土壤水分越高;间伐显著促进了仁用杏生长,提高了坐果率和杏仁产量。白于山山区仁用杏间伐后密度应为167~222株/hm2。

对间隙淋洗长期通气培养条件下黄土高原土壤供氮能力的评价

采用间隙淋洗长期通气培养法,通过对黄土高原物理化学性质差异较大的10种农田土样起始矿质氮、起始提取态总氮、起始可溶性有机氮,以及培养期间淋洗矿质氮、淋洗总氮、可溶性有机氮含量及其与作物吸氮量关系的研究,分析并评价黄土高原主要农田土壤氮素矿化能力以及包括和不包括培养淋洗可溶性有机氮对土壤供氮能力的影响。结果表明,供试土样起始可溶性有机氮平均为N 23.9 mg/kg,是起始提取态总氮的28.8%,土壤全氮的2.4%。在通气培养淋洗总氮中,可溶性有机氮所占比例不高,经过217 d通气培养,淋洗出的可溶性有机氮平均为N 28.8mg/kg,占淋洗总氮量的19.8%。相关分析表明,淋洗可溶性有机氮量与第l季作物吸氮量相关不显著,但与连续2季作物总吸氮量显著相关。淋洗矿质氮、淋洗总氮与两季作物总吸氮量的相关系数明显高于与第一季作物吸氮量的相关系数;与第一季作物吸氮量达显著相关水平,与连续两季作物吸氮量达极显著相关水平。总体上看,可溶性有机氮和土壤全氮、土壤微生物氮不能作为反映短期可矿化氮的指标;间隙淋洗通气培养淋洗液中淋洗矿质氮、淋洗总氮是评价可矿化氮的较好指标,不仅适宜于第一季作物,而且也适用于对连续两季作物土壤供氮...

侵蚀环境人工刺槐林土壤水稳性团聚体演变及其养分效应

采用时空互代法,以典型侵蚀环境纸坊沟流域生态恢复过程中不同年限的人工刺槐林为研究对象,选取坡耕地和天然侧柏林为参照,分析了植被恢复过程中土壤水稳性团聚体变化规律及其与土壤养分状况之间的相互关系。结果表明,侵蚀环境下的坡耕地由于人为耕作干扰,土壤水稳性团聚体含量低下,抗蚀性能较差。营造刺槐林前5 a土壤水稳性团聚体含量较坡耕地显著快速增加,随后增幅变缓,成对数增长,恢复25 a后土壤水稳性团聚体含量已经达到天然侧柏林水平。在植被恢复过程中土壤小粒径的水稳性团聚体逐渐聚集转变形成大粒径的团聚体。相关性分析和回归分析表明,植被恢复过程中>0.25 mm土壤水稳性团聚体与有机碳、全氮、碱解氮、速效钾、容重等相关性达到显著(p<0.05)或极显著水平(p<0.01),与全磷和速效磷相关性较弱。坡耕地退耕营造刺槐林后可以减少人为干扰,增加碳素和氮素供给,提高水稳性团聚体含量,使土壤抗蚀性能提高。

黄土丘陵区不同植被恢复模式对土壤酶活性的影响

为了解侵蚀环境下植被恢复对土壤酶活性的影响,以典型侵蚀环境黄土丘陵区纸坊沟流域生态恢复30a植被长期定位试验点为研究对象,选取坡耕地为参照,分析了植被恢复过程中土壤脲酶、磷酸酶、蔗糖酶、淀粉酶、纤维素酶、过氧化氢酶、多酚氧化酶及理化性质的演变特征。结果表明,黄土丘陵区的坡耕地由于不合理的人为干扰,土壤理化性质和酶活性较弱,通过植被恢复可以有效的改善土壤肥力,不同恢复模式对土壤酶活性和肥力的改善作用不同,恢复30a,脲酶活性增加33%～213%,磷酸酶活性增加275%～394%,蔗糖酶活性增加70%～210%,纤维素酶活性增加24%～48%,过氧化氢酶增加32%～96%,多酚氧化酶降低23%～29%,淀粉酶变化规律不同。不同植被恢复模式其生物特性不同,对土壤酶活性影响也不同。相关性分析说明磷酸酶、蔗糖酶、纤维素酶和多酚氧化酶与其它因子相关性相对较强,可以作为评价土壤质量的生物学指标。

黄土丘陵区封禁对侵蚀土壤微生物生物量的影响

采用时空互代法,以典型侵蚀环境纸坊沟流域不同封禁年限的狼牙刺群落和杂灌群落为研究对象,选取放牧地和天然次生林为参照,分析了生态恢复过程中土壤微生物生物量、呼吸强度、代谢商及理化性质的演变特征。结果表明,封禁后土壤理化性质明显改善;微生物生物量随封禁年限的延长变化显著,阳坡随封禁年限增加土壤微生物生物量逐渐增加,25 a后微生物生物量碳、氮、磷较封禁前分别增加252%、161%和174%,但显著低于天然侧柏林,仅为其39.0%、41.8%和53.7%;阴坡封禁前10年微生物生物量迅速增加,随后增加幅度减缓,呈波动式缓慢上升趋势;封禁25 a后微生物生物量碳、氮、磷分别增加108%、93%和102%,但明显低于天然杂灌丛群落和辽东栎林,仅为辽东栎林的54.4%、49.1%和40.1%。土壤呼吸强度在封禁5 a后增大明显,且随着年限增加逐渐上升,阳坡25 a时达到最大值,而阴坡15 a时达到最大值,随后开始有所下降,25 a后降至最低点,但仍显著高于放牧地,相同封禁年限的土壤呼吸强度阴坡明显高于阳坡。qCO2随着封禁进程逐渐降低,25 a后达到最低值。相关性分析显示微生物生物量碳、氮、磷、呼吸强度、qCO2与土壤养...

几种硫属化合物半导体的电化学与光电化学研究

本文分别用恒电位电沉积和恒电位脉冲电沉积技术在ITO基底上成功地沉积出表面平滑均匀、与基底附着牢固、具有一定光活性的CdS多晶薄膜。系统地考察了CdS薄膜的电性质、光性质及光电化学行为。用电沉积技术在不同基底（Ni、Ti、ITO）上成功地实现了Hg_(1-X)Cd_xTe(MCT)的三元共沉积。初步组装了P-Hg_(1-X)Cd_xTe/n-CdS异质结PV池。研究了层状结构材料n-InSe的PEC行为并考察了多种单晶材料，诸如CdS、CdTe、CdSe、InSe等的光阳极特性和界面行为。