A model of coupled thermal, mechanical, and electrostatic field effects in III-N thin film heterostructures

A one-dimensional coupled multi-physics based model has been developed to accurately compute the effects of electrostatic, mechanical, and thermal field interactions on the electronic energy band structure in group III-nitrides thin film heterostructures. Earlier models reported in published literature assumes electro-mechanical field with uniform temperature thus neglecting self-heating. Also, the effects of diffused interface on the energy band structure were not studied. We include these effects in a self-consistent manner wherein the transport equation is introduced along with the electro-mechanical models, and the lattice structural variation as observed in experiments are introduced at the interface. Due to these effects, the electrostatic potential distribution in the heterostructure is altered. The electron and hole ground state energies decrease by 5% and 9%, respectively, at a relative temperature of 700 K, when compared with the results obtained from the previously reported electro-mechanical model assuming constant and uniform temperature distribution. A diffused interface decreases the ground state energy of electrons and holes by about 11% and 9%, respectively, at a relative temperature of 700 K when compared with the predictions based on uniform temperature based electro-mechanical model. (C) 2013 AIP Publishing LLC.

Semi-insulating layer for novel high voltage polysilicon thin film transistors

This work describes the deposition and characterisation of semi-insulating oxygen-doped silicon films for the development of high voltage polycrystalline silicon (poly-Si) circuitry on glass. The performance of a novel poly-Si High Voltage Thin Film Transistor (HVTFT) structure, incorporating a layer of semi-insulating material, has been investigated using a two dimensional device simulator. The semi-insulating layer increases the operating voltage of the HVTFT structure by linearising the potential distribution in the device offset region. A glass compatible semi-insulating layer, suitable for HVTFT applications, has been deposited by the Plasma Enhanced Chemical Vapour Deposition (PECVD) technique from silane (SiH4), nitrous oxide (N2O) and helium (He) gas mixtures. The as-deposited films are furnace annealed at 600°C which is the maximum process temperature. By varying the N2O/SiH4 ratio the conductivity of the annealed films can be accurately controlled up to a maximum of around 10-7 Ω-1cm-1. Helium dilution of the reactant gases improves both film uniformity and reproducibility. Raman analysis shows the as-deposited and annealed films to be completely amorphous. A model for the microstructure of these Semi-Insulating Amorphous Oxygen-Doped Silicon (SIAOS) films is proposed to explain the observed physical and electrical properties.

Predicting the effects of climate change on sea turtle nesting habitat in Florida

Rising global temperatures threaten the survival of many plant and animal species. Having already risen at an unprecedented rate in the past century, temperatures are predicted to rise between 0.3 and 7.5C in North America over the next 100 years (Hawkes et al. 2007). Studies have documented the effects of climate warming on phenology (timing of seasonal activities), with observations of early arrival at breeding grounds, earlier ends to the reproductive season, and delayed autumnal migrations (Pike et al. 2006). In addition, for species not suited to the physiological demands of cold winter temperatures, increasing temperatures could shift tolerable habitats to higher latitudes (Hawkes et al. 2007). More directly, climate warming will impact thermally sensitive species like sea turtles, who exhibit temperature-dependent sexual determination. Temperatures in the middle third of the incubation period determine the sex of sea turtle offspring, with higher temperatures resulting in a greater abundance of female offspring. Consequently, increasing temperatures from climate warming would drastically change the offspring sex ratio (Hawkes et al. 2007). Of the seven extant species of sea turtles, three (leatherback, Kemp’s ridley, and hawksbill) are critically endangered, two (olive ridley and green) are endangered, and one (loggerhead) is threatened. Considering the predicted scenarios of climate warming and the already tenuous status of sea turtle populations, it is essential that efforts are made to understand how increasing temperatures may affect sea turtle populations and how these species might adapt in the face of such changes. In this analysis, I seek to identify the impact of changing climate conditions over the next 50 years on the availability of sea turtle nesting habitat in Florida given predicted changes in temperature and precipitation. I predict that future conditions in Florida will be less suitable for sea turtle nesting during the historic nesting season. This may imply that sea turtles will nest at a different time of year, in more northern latitudes, to a lesser extent, or possibly not at all. It seems likely that changes in temperature and precipitation patterns will alter the distribution of sea turtle nesting locations worldwide, provided that beaches where the conditions are suitable for nesting still exist. Hijmans and Graham (2006) evaluate a range of climate envelope models in terms of their ability to predict species distributions under climate change scenarios. Their results suggested that the choice of species distribution model is dependent on the specifics of each individual study. Fuller et al. (2008) used a maximum entropy approach to model the potential distribution of 11 species in the Arctic Coastal Plain of Alaska under a series of projected climate scenarios. Recently, Pike (in press) developed Maxent models to investigate the impacts of climate change on green sea turtle nest distribution and timing. In each of these studies, a set of environmental predictor variables (including climate variables), for which ‘current’ conditions are available and ‘future’ conditions have been projected, is used in conjunction with species occurrence data to map potential species distribution under the projected conditions. In this study, I will take a similar approach in mapping the potential sea turtle nesting habitat in Florida by developing a Maxent model based on environmental and climate data and projecting the model for future climate data. (PDF contains 5 pages)

Surface planar ion chip for linear radio-frequency Paul traps

We propose a surface planar ion chip which forms a linear radio frequency Paul ion trap. The electrodes reside in the two planes of a chip, and the trap axis is located above the chip surface. Its electric field and potential distribution are similar to the standard linear radio frequency Paul ion trap. This ion trap geometry may be greatly meaningful for quantum information processing.

Localization of sources of human evoked responses

The evoked response, a signal present in the electro-encephalogram when specific sense modalities are stimulated with brief sensory inputs, has not yet revealed as much about brain function as it apparently promised when first recorded in the late 1940's. One of the problems has been to record the responses at a large number of points on the surface of the head; thus in order to achieve greater spatial resolution than previously attained, a 50-channel recording system was designed to monitor experiments with human visually evoked responses.

Conventional voltage versus time plots of the responses were found inadequate as a means of making qualitative studies of such a large data space. This problem was solved by creating a graphical display of the responses in the form of equipotential maps of the activity at successive instants during the complete response. In order to ascertain the necessary complexity of any models of the responses, factor analytic procedures were used to show that models characterized by only five or six independent parameters could adequately represent the variability in all recording channels.

One type of equivalent source for the responses which meets these specifications is the electrostatic dipole. Two different dipole models were studied: the dipole in a homogeneous sphere and the dipole in a sphere comprised of two spherical shells (of different conductivities) concentric with and enclosing a homogeneous sphere of a third conductivity. These models were used to determine nonlinear least squares fits of dipole parameters to a given potential distribution on the surface of a spherical approximation to the head. Numerous tests of the procedures were conducted with problems having known solutions. After these theoretical studies demonstrated the applicability of the technique, the models were used to determine inverse solutions for the evoked response potentials at various times throughout the responses. It was found that reliable estimates of the location and strength of cortical activity were obtained, and that the two models differed only slightly in their inverse solutions. These techniques enabled information flow in the brain, as indicated by locations and strengths of active sites, to be followed throughout the evoked response.

Comunidades de lagartos dos remanescentes de restinga do Estado do Rio de Janeiro: Riqueza, diversidade e onde estão as espécies endêmicas e ameaçadas de extinção

Atualmente existe uma contínua perda de biodiversidade, que decorre principalmente devido a intensa modificação das paisagens naturais pelas atividades humanas. O litoral do estado do Rio de Janeiro é ocupado há centenas de anos, e uma das principais ameaças é a crescente taxa demográfica. De forma geral, o conhecimento acerca dos diferentes grupos de vertebrados terrestres e a sua relação com o ambiente de restinga ainda é incipiente. Realizamos o presente estudo em dez áreas de remanescentes de vegetação de restinga no estado do Rio de Janeiro, para compreender a variação das comunidades de lagartos entre os diferentes ambientes e suas estruturas locais, bem como os principais fatores que as afetam negativamente. Realizamos um conjunto de transecções lineares delimitadas por tempo, ao longo de três anos. As espécies de lagartos foram identificadas e quantificadas, e mensuramos a estrutura e os fatores de ameaça antrópica dos ambientes. Registramos no total nove espécies de lagartos compondo as comunidades de restingas amostradas no estado do Rio de Janeiro, incluindo uma espécie exótica e invasora (Hemidactylus mabouia), e duas endêmicas (Liolaemus lutzae e Cnemidophorus littoralis). A maioria das espécies foram registradas em diferentes meso-habitats, e no geral podem ser consideradas oportunistas e generalistas. As restingas diferiram entre si principalmente em termos de abundância e densidade de espécies de lagartos, enquanto a riqueza foi comparativamente menor nos ambientes insulares. Provavelmente essas diferenças são resultados da interação entre processos históricos e ecológicos atuando em sinergia. Na restinga de Grussaí, os dados mostram que, considerando o nicho em suas três dimensões avaliadas (tempo, espaço e dieta), é provável que a comunidade esteja estruturada em seu eixo temporal. A análise dos fatores de ameaça antrópica sobre as restingas mostra que a situação dos fragmentos se manteve a mesma nos últimos anos. Provavelmente, as políticas públicas atuais não parecem ser suficientes para o aumento do grau de preservação e conservação das áreas de restinga do litoral do estado do Rio de Janeiro devido à contínua especulação imobiliária. É necessário o emprego de monitoramentos periódicos para acompanhar a situação das populações das espécies endêmicas e ameaçadas, e promover mudanças físicas (e.g. remoção de lixo depositado e de espécies exóticas), sócio-educativas (e.g. diminuição do acesso de animais domésticos, descarte de material), e de poder público (e.g. aumento das áreas de proteção). Em relação à espécie endêmica e ameaçada L. lutzae, identificamos uma sobreposição de nicho espacial em relação a Tropidurus torquatus, variável entre as localidades amostradas. Provavelmente essa variação resulta da estrutura ambiental que difere entre as restingas e, consequentemente, provoca diferentes respostas em termos de interação entre as espécies que compõem as comunidades de lagartos. Os novos registros de H. mabouia em habitat natural nas restingas foram incluídos aos registros de ocorrência da espécie em ambientes naturais em território brasileiro, no intuito de identificar áreas potenciais de invasão da espécie. Os resultados mostram uma alta probabilidade principalmente na região litorânea. O presente estudo possibilita uma melhor compreensão sobre a ecologia de comunidades de lagartos no estado do Rio de Janeiro.

白豆杉的地理分布格局及潜在分布区估计

　　根据物种的分布信息结合环境因子估计物种的分布区对珍稀濒危物种的保护有着重要的意义。白豆杉Pseudotaxus chienii为第三纪孑遗植物，我国东南部地区特有，分布区狭窄。本文通过对白豆杉的标本记录研究它的地理分布，找出影响其分布的关键因子并对其潜在分布区进行估计，并解释其分布区形成的原因。全球升温将对物种分布造成重要影响，通过温度升高情况下2100年的气候数据模拟白豆杉未来的潜在分布区，估计温度升高对白豆杉的影响，将对白豆杉的保护有着重要的意义。 　　根据白豆杉的标本信息结合Diva-Gis软件对白豆杉的地理分布进行研究。以海拔图层和植被图层为底图对白豆杉的分布格局进行研究，并对白豆杉种群的多度进行统计分析。用Diva-Gis软件的气候数据提取功能提取白豆杉分布点的气候信息，并运用主成分分析对影响白豆杉分布的气候因子进行分析，找出影响白豆杉分布的主要环境因子。根据白豆杉的分布信息和气候数据，运用Diva-Gis内嵌的BIOCLIM模型和DOMAIN模型对白豆杉在不同气候条件下的潜在分布区进行估计，评价温度升高对白豆杉分布区的影响。 　　白豆杉分布格局研究结果表明，白豆杉分布在我国东南部地区中低海拔山区，白豆杉的分布和植被类型及海拔有着密切的关系。白豆杉的分布与海拔的关系表现为，由东到西，分布的最低海拔升高，海拔范围缩小。白豆杉分布地的植被类型为常绿灌木林，常绿阔叶林及针、阔叶混交林。白豆杉由东向西的海拔变化趋势与植被类型的由东向西的海拔变化趋势相一致。PCA分析结果表明白豆杉的分布与温度相关因子有着密切的关系。 　　现在气候对潜在分布区的估计表明,白豆杉的潜在分布区散布于浙、闽、粤、赣、湘，桂及黔几省各自交界之处即从浙江南部山区沿武夷山山系至南岭山系（向北到沿湘赣交界的罗宵山系）至大瑶山山系（向北沿雪峰山）。潜在分布区南部有三处分布的热点地区，即浙江南部、湖南南部和广西北部地区。三个主要分布区之间仅有有星散的潜在分布区存在，或没有潜在分布区出现，处在一种高度的隔离状态。造成这种潜在分布格局形成的原因可能有二，一是第四纪冰期的到来使白豆杉的分布区向南迁移，局部性气候的变化和地质变化可能导致了部分白豆杉的生境的消失，从而使得原来连续的分布区破碎化，形成了现在的星散分布；二是白豆杉的潜在分布区预测结果与中国东南部地区的山脉走势非常一致，山脉地带小生境多样化能够为白豆杉在垂直地带上的迁移提供更大的可能性。 　　未来气候数据对白都杉的潜在分布区估计表明，温度升高后白豆杉最适生分布区显著缩小。白豆杉的潜在分布区的地理分布格局发生了明显的变化，原来在南部的适生区明显缩小，星散程度更高。除已知的分布地外，在江西西南部武夷山、南岭山脉的湖南、广西、广东三省交界的地方都是白豆杉的适生区。江西和湖南交界的罗宵山山脉北部到井冈山都有白豆杉分布可能性较大，可以作为野外调查的重点地区。气候变化会使白豆杉在浙江、湖南南部的最适生境破碎化从而影响白豆杉的分布。生境保护对白豆杉的保护起着关键作用。

西北干旱区多种植物地理分布与气候的相关性及其可能潜在分布预测

　　作为西部大开发的关键地区，西北干旱区由于地理位置和环境条件的独特性、生态系统的脆弱性以及人类活动的长期干扰，对其周边乃至全国的生态环境有较大的影响，在这一地区研究植物种分布与气候的关系，并模拟预测其可能的潜在分布范围，具有理论上和实践上的重要意义。 　　通过广泛收集了西北干旱区优势种和常见种的地理分布资料，共选择128个植物种，利用Holdridge的生命地带分类系统，计算各植物种的生物温度(BT)、可能蒸散(PE)、降水量(P)及可能蒸散率(PER)，分析植物种与气候的相互关系，并将所有植物种进行经验归纳分类。随后，对这砦植物种及其气候信息进行TWINSPAN定量分类，并与经验分类结果相比较，得出西北干旱区128种植物的生态气候分类，分属于以下几大类型：高寒草甸、森林一草原过渡带、草原（典型草原、荒漠草原）、荒漠（草原化荒漠、荒漠、高寒荒漠）。具体来说，包括以下17个生态气候类型： 1)高寒草甸：异针茅。 2)森林一草原过渡带：牛尾蒿、鬼箭锦鸡儿、沙棘。 3)草原a：沙蒿。 4)草原b：长芒草、百里香（变种）、多叶隐子草、贝加尔针茅、大针茅。 5)草原c：羊茅、小叶锦鸡儿、荒漠锦鸡儿、线叶菊、华北岩黄芪、廿青针茅、碱蒿、内蒙古沙蒿、裂叶蒿、狭叶锦鸡儿、山竹岩黄芪、女蒿、小蓬、两伯利亚杏、沙地柏、角果碱篷、霸王、糙隐子草。 6)草原d：紫狐茅、紫花针茅。 7)草原一荒漠草原a：包括沙竹、琵琶柴、吉尔吉斯针茅。 8)草原一荒漠草原b：华北米蒿、差巴嘎蒿、星星草、长芒针茅、铁竿蒿、柠条锦鸡儿。 9)荒漠草原：沙生冰草、蒙古冰草、羊草、冷蒿、中亚紫菀木、刺旋花、老瓜头、木贼麻黄、西伯利亚白刺、唐古特白刺、戈壁针茅、石生针茅、盐地碱蓬、冰草、蓍状亚菊、油蒿、木蓼、刺针枝蓼、长枝木蓼、中间锦鸡儿、尖叶盐爪爪、黄花琵琶柴、松叶猪毛菜、珍珠猪毛菜、东方针茅、囊果碱蓬、四合木、白滨藜、短脚锦鸡儿。 10)草原化荒漠，荒漠a：川青锦鸡儿、优若藜、苦艾蒿、无芒隐子草、沙冬青、籽蒿、地白蒿、菭草、齿叶白刺、绵刺、盐角草、多枝柽柳、盐生假木贼。 11)草原化荒漠．荒漠b：蒿叶猪毛菜、短花针茅、芨芨草、灌木亚菊、博乐蒿、小蒿、喀什蒿、南山短花菊、盐爪爪、木本猪毛菜、针茅、细枝盐爪爪。 12)草原化荒漠．荒漠c：白梭梭、白羊草、无叶假木贼。 13）干旱荒漠a：戈壁短花菊、荒漠细柄茅、刺蓬、沙生针茅、多花柽柳、细枝柽柳。 14)干旱荒漠b：梭梭柴、铃铛刺、天山猪毛菜、帕米尔麻黄、座花针茅、旱蒿、克氏狐茅、短叶假木贼、准格尔沙蒿、长穗柽柳、刚毛柽柳。 15)高寒荒漠植被：匍生优若藜。 16)干旱荒漠c：粉花蒿、白杆沙拐枣、膜果麻黄、花花柴、灌木紫菀木、裸果木、合头草、塔里木沙拐枣。 17)超干旱荒漠植被：沙拐枣、胡杨、盐穗木、灰杨、盐节木、圆叶盐爪爪。 　　综合分类结果表明：多数植物种的生态气候类型与实际生境相符，但也有少数植物种有明显偏差，主要原因有三点：首先，某些种的分布范围超出了西北干旱区，在东北、华北、甚至全国范围内分布，所计算的植物种的气候范围本身存在局限性;其次，西北干旱区的研究资料如植物种的分布范围、分布点的气象资料等有许多缺失：最后，由于文献中对某些植物种分布范围的描述比较笼统，无法确定其精确的地理分布界限，使得植物种所对应的分类结果与其真正所属的植 被类型有一些偏差。 　　本文还进一步在这128种植物中选取了10种分布明确、资料齐备的代表性植被类型的优势种，根据它们的降水和生物温度指标，模拟预测了它们的可能潜在分布区，包括其主要中心分布区和最大可能分布区，并与实际分布范围进行比较。结果表明．其潜在分布区的分布范围与实际调查所得资料所处范围基本一致，特别是中心分布区的预测图，而最大可能分布区与实际有一定误差。

应用SVM预测杜鹃属（Rhododendron L.）在中国的潜在分布中心

杜鹃属(Rhododendron L.)是中国种子植物中最大的属，其现代分布和分化中心是我国西南部的横断山区和东喜马拉雅地区。我国西部、西南部的云南、四川、西藏等地共有杜鹃达450种，仅特有种就有约300种。对杜鹃属分布的深入研究是横断山区生物多样性保护不可缺少的重要部分。 由于物种分布与环境因子之间存在着紧密的联系，利用环境因子作为预测物种分布模型的变量是当前最普遍的建模思路。但是绝大多数物种分布预测模型都遇到了难以解决的“高维小样本”问题――模型在标本数据不足时无法给出合理的预测，或者模型无法处理大量的环境变量。机器学习领域的理论和实践已经证明，基于结构风险最小化原理的支持向量机(Support Vector Machine, SVM)算法非常适合“高维小样本”的分类问题。为了探索其应用在物种分布预测问题上的可能性，本文创新性的实现了基于SVM算法的物种分布预测系统。然后，本文以30个杜鹃属(Rhododendron L.)物种为检验对象，利用其标本数据和11个1km的栅格环境变量图层作为模型变量，预测其在中国的潜在分布区。本文通过全面的模型评估——专家评估，ROC (Receiver Operator Characteristic)曲线和曲线下方面积AUC (Area Under the Curve)——来比较模型的性能。试验结果表明，我们所实现的以SVM为核心的物种分布预测系统无论在计算速度还是预测效果上都远远优于当前广泛使用的GARP (Genetic Algorithm for Rule-Set Prediction)预测系统。 之后，本文进一步探讨了SVM预测系统预测效果与环境变量维数和标本点个数的关系。试验结果表明，对于只有少量标本点的物种SVM的预测结果仍然具有相当的合理性。由此可见， SVM预测系统很好的解决了以前众多模型无法克服的稀有种和标本点稀少的物种的潜在分布区模拟问题。同时本文发现大的环境维数（高维）对于物种潜在分布区的预测有着决定性的作用，因此模型处理高维问题的能力显得至关重要。 最后，我们使用中国所有可获取的杜鹃属标本数据，以及83个1km的栅格环境变量图层，对400种杜鹃属物种的潜在分布区进行预测。根据预测出来的物种潜在分布区，我们得到了中国杜鹃属物种潜在多样性分布格局，特有物种潜在多样性分布格局，濒危杜物种潜在的分布格局，各亚属物种潜在分布格局，以及不同生活型物种潜在多样性分布格局。这些分布区图不仅可以对杜鹃属起源研究提供分析验证的条件，还能为其引种、保护和新种的搜寻提供有利的空间依据。

落叶栎树在中国的地理替代分布及其气候制约

栎属（Quercus L.）按落叶习性可自然分为落叶类型和常绿类型，我国落叶栎类共有20个种和9个变种。落叶栎是栎属中较为进化的一个类群，源于横断山区和云贵高原;除新疆外，全国各省都有落叶栎的天然分布，一些亲缘关系密切的树种之间呈现出较为明显的地理替代分布格局。本研究的目的在于：（1）应用BIOCLIM模型模拟预测落叶栎类植物的潜在分布区，分析其目前的分布格局以及下一步的发展趋势;（2）分析造成落叶栎树地理替代分布格局的主导气候因子，探讨气候因子对不同落叶栎树种地理分布格局的制约作用。 本文以16个在中国具有成片天然分布区的落叶栎树种（包括变种）为研究对象，利用已核对的标本数据以及13个栅格化环境变量图层（分辨率为1km×1km），按照分类（全国广布型、南方广布型、南方狭域型和北方狭域型）和不分类（全部16种）两种处理方式，通过BIOCLIM模型模拟得出了它们的潜在核心分布区和潜在边缘分布区。在运行模型之前，除必选的海拔高程图层外，采用了主成分分析（PCA）的方法从30个候选的气候变量图层中筛选出对相应落叶栎树种的地理分布格局有较大影响的12个图层作为输入图层。然后，本文通过比较两种处理所得模拟结果的ROC（Receiver Operator Characteristic）曲线下方面积AUC（Area Under the Curve），同时结合文献分析来推测不同落叶栎树种地理分布格局的稳定性及发展趋势。结果表明，在无人类活动干扰且种源传播不受阻碍的情况下，全国广布型和南方广布型落叶栎目前的分布格局在维持稳定的基础上有向周边地区扩展的趋势;南方狭域型和北方狭域型落叶栎的分布格局则基本保持稳定，短期内发生扩散的可能很小。 论文中计算了每个落叶栎树种所在分布范围的气候指标（共11个），以便进行下一步的研究。以蒙古栎（Q. mongolica）、辽东栎（Q. wutaishanica）与槲栎（Q. aliena）、锐齿槲栎（Q. aliena var. acuteserrata）、北京槲栎（Q. aliena var. pekingensis）这两组地理替代系列为研究对象，分别采用独立样本t检验和单因素方差分析的方法，分析了气候因子对其地理替代分布格局的主导作用。结果表明，冬季的低温、较高的气温年较差和大陆度是蒙古栎向东北替代辽东栎的主要原因;槲栎向北被北京槲栎和锐齿槲栎替代的主要原因是生长季高温和冬季高温对其分布的双重制约;除最暖月（7月）最高温外，北京槲栎的各项水热指标与另两种槲栎均存在极显著差异，对冬季低温和较大的年较差的适应可能是限制其向南分布的主要原因。 本研究最后部分的内容是对不同类型落叶栎分布区的气候参数进行的主成分分析。结果表明，生长季温度是制约落叶栎分布的最主要的气候因子;寒冷程度和冬季的低温则对其在大尺度范围的扩散有较大影响;另外，降水、年较差与大陆度对落叶栎的向北分布也起着重要的作用。

Effect of Anode Floating Voltage and its Applications in Characterizing Silicon Drift Detectors

Anode floating voltage is predicted and investigated for silicon drift detectors (SDDs) with an active area of 5 mm(2) fabricated by a double-side parallel technology. It is demonstrated that the anode floating voltage increases with the increasing inner ring voltage, and is almost unchanged with the external ring voltage. The anode floating voltage will not be affected by the back electrode biased voltage until it reaches the full-depleted voltage (-50 V) of the SDD. Theoretical analysis and experimental results show that the anode floating voltage is equal to the sum of the inner ring voltage and the built-in potential between the p(+) inner ring and the n(+) anode. A fast checking method before detector encapsulation is proposed by employing the anode floating voltage along with checking the leakage current, potential distribution and drift properties.

THE APPLICATION OF THE MPB4 THEORY TO THE INTERFACE BETWEEN 2 IMMISCIBLE ELECTROLYTE-SOLUTIONS .2. THE DIFFERENTIAL CAPACITANCE OF THE WATER 1,2-DICHLOROETHANE INTERFACE

The MPB4 theory is used to calculate the differential capacitance of the interface between LiCl in water and TBATPB in 1,2-dichloroethane at electrolyte concentrations of 0.005, 0.01 and 0.02 M. The effects of the ion size and the image force, and the influence of the electrolyte concentration, the surface charge density and the solvent effect on the inner layer potential drop are considered simultaneously. These effects can be ascribed to the ionic penetration into the opposite solution and ion-ion correlations across the interface. Our results are in better agreement with experimental data than those obtained using Gouy-Chapman theory. This indicates that the MPB4 theory may also describe the structure of the water \1,2-dichloroethane interface provided that the influence of the electrolyte concentration, the surface charge density and the solvent effect on the inner layer potential distribution are included in the calculation. Comparison of the theoretical results with those of the water \nitrobenzene interface shows that the structure of the water \1,2-dichloroethane interface is similar to that of the water \nitrobenzene interface, except that in the former case the inner-layer potential drop is much higher and the effects of the image force and the ion size are more pronounced.

Electrochemical investigations of micro-droplets formed on metals during the deliquescence of salt particles in atmosphere

CORROSION; WATER; SPECTROSCOPY; CHLORIDE; ZINC; NUCLEATION; INTERFACE; ELECTRODE; SURFACES; GROWTH

Phenomenon of micro-droplets formation on metals during the deliquescence of salt particles in atmosphere

CORROSION; MECHANISM; WATER; ZINC

Boundary Element Method (BEM) Analysis for Galvanic Corrosion of Hot Dip Galvanized Steel Immersed in Seawater

A numerical analysis of galvanic corrosion of hot-dip galvanized steel immersed in seawater was presented. The analysis was based on the boundary element methods (BEMs) coupled with Newton-Raphson iterative technique to treat the nonlinear boundary conditions, which were determined by the experimental polarization curves. Results showed that galvanic current density concentrates on the boundary of steel substrate and zinc coating, and the sacrificial protection of zinc coating to steel substrate results in overprotection of steel cathode. Not only oxygen reduction but also hydrogen reduction could occur as cathode reactions, which probably led up to the adsorption and absorption of hydrogen atoms. Flat galvanized steel tensile sample shows a brittle behavior similar to hydrogen embrittlement according to the SSRT (show strain rate test) in seawater.