994 resultados para 700


Relevância:

10.00% 10.00%

Publicador:

Resumo:

本论文选取了斜长角闪岩和榴辉岩作为实验样品,在压力为1.0-3.0 GPa和温度为室温-1300 ℃的条件下,进行了弹性纵波速度和弹性波衰减的实验研究。实验是在YJ-3000吨压力机上进行的,利用超声脉冲透射的方法,首次获得了在压力大于1.0GPa和温度高于800 ℃的条件下的岩石的声波衰减及其各向异性的实验数据。取得如下主要结论:1.榴辉岩的Vp值随压力的升高而增大,在P < 2.0GPa时,上升的速率较快,表明微裂隙逐渐闭合;当P > 2.0GPa时,上升的速率变慢,且表现出很好的线性趋势,这时测得的纵波速度表明了榴辉岩本征的纵波速度,这与前人的实验结果相同。斜长角闪岩的Vp值随压力的变化与榴辉岩的变化相似,不同的是斜长角闪岩的微裂隙闭合压力为1.5GPa。榴辉岩的Vp的Av_p(%)随压力的升高基本保持不变,而斜长角闪岩的Av_p(%)随压力的升高逐渐增大。2.榴辉岩和斜长角闪岩在1.0-3.0 GPa压力下的Vp值随温度的升高而降低,但Vp值在不同的温度阶段,不同的方向上降低的速率和形式不同。如在1.0GPa压力下,当温度小于500 ℃时,Vp值下降较快,说明温度对纵波速度的影响较小;当T > 500 ℃时,Vp值下降的缓慢,说明榴辉岩内部可能发生了结构和应力状态的变化。斜长角闪岩在升温的初始阶段,Vp缓慢下降,并表现出很好的线性趋势。当T > 647 ℃时,Vp下降的速率增大,线性趋势也较好,当T > 1051 ℃时,Vp下降的速率又变小,且比初始时下降的速率要小。榴辉岩Vp的Av_p(%)值随温度的升高而下降,在不同的压力上其下降的速率不同。如在1.0GPa条件下,Av_p(%)随温度的升高而快速下降;在3.0GPa条件下,Av_p(%)值随温度下降缓慢。而斜长角闪岩的Vp的Av_p(%)随温度的变化较复杂,如在1.0GPa条件下,当T < 647 ℃时,Av_p(%)值随温度的升高缓慢增加,当T > 647 ℃时,Av_p(%)值快速增大,当温度达到922 ℃时,Av_p(%)上升到最大值,此后又随温度而减小。3.榴辉岩和斜长角闪岩的弹性波的Q值随压力的升高而增大,其增大的速率和幅度与Vp值的增大形式相同。榴辉岩的Q值的A_Q(%)随压力而升高,而斜长角闪岩的Q值的A_Q(%)随压力基本保持不变。4.榴辉岩和斜长角闪岩的弹性波的Q值随温度的升高而降低,在不同的压力下其降低的速率不同。如在1.0GPa压力下,Q值降低的速率较大;3.0GPa压力下,当T < 300 ℃时,榴辉岩的Q值快速下降,随后下降的幅度减慢,当T > 700 ℃时,榴辉岩的Q值很低,且减小的幅度很小。斜长角闪岩的Q值随温度的变化在1.0-3.0GPa条件下,Q值很小的幅度和趋势相似:当T < 647 ℃时,Q值下降的缓慢,当647 ℃ < T < 1051 ℃时,Q值快速下降,随后下降速率又变小。榴辉岩Q值的A_Q(%)随温度的升高而降低,在1.0和2.0GPa压力下降低较快;3.0GPa压力下A_Q(%)降低较缓慢。斜长角闪岩Q值的A_Q(%)随温度的升高开始缓慢降低,当647 ℃ < T < 105l ℃时,A_Q(%)快速增大,当T > 105l ℃时,A_Q(%)又降低。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

由于对人体健康的危害,氡越来越受到世界各国的广泛关注。经济的发展,使我国地下公共场所大量涌现,但其空气中氡浓度的大规模调查及系统研究还属空白。本论文采取瞬时法(美国SUN公司的1027型连续测氰仪)与累积法(CR一39SSNTD)相结合的测量方法,对我国23个城市的地下工程进行了为期一年的监测,获得了实测数据700多个。在监测的同时,收集了每个测点的各种相关情况资料。论文以内蒙古自治区的呼和浩特、包头、集宁、鄂尔多斯四个城市为例,从环境地球化学角度出发,在研究了各个测点的各种情况之后,探讨了氧在不同类型工程和不同城市的浓度规律。对长期有人在内工作的地下工程内氛所致工作人员的有效剂量当量进行了估算。最后对氨异常的测点进行了原因分析,并提出了地下工程内氰污染的治理和防范措施。本次研究主要得出以下结论:1、地下工程中氰浓度的季节变化规律为:从总平均值看,夏高冬低。与前人对坑道的调查结果一致,与地上氨浓度的变化规律相反。从两季浓度差来看,两季浓度差从大到小依次为:隧道类工程)单建式铜室类工程>结建式嗣室类工程。2、总体来看内蒙三类工程的氰浓度值:隧道类工程)结建式铜室类工程)单建式铜室类工程。不管是单季还是年平均值,各城市三类工程的氧浓度都遵循隧道类.工程远大于结建式铜室工程和单建式铜室工程的规律。通过对结建式桐室工程和单建式铜室工程的对比分析,发现在地下工程内工程上部有无建筑物阻隔,并不是影响氨浓度高低的重要因素,即氰的纵向扩散作用小于横向扩散作用。3、呼和浩特、包头、集宁、鄂尔多斯四个城市的氛浓度年平均值分别为:190Bq/m3、700Bq/m3、190Bq/m3、270Bq/m3。去掉仅有一季结果的侧点值,包头、鄂尔多斯的氨浓度年平均值为:62oBq/m3、250Bq/m3。呼和浩特、包头、集宁、鄂尔多斯四个城市的氛浓度单季值的范围分别为:31-830Bq/m3、57-3500Bq/m3、26一65oBq/m,、64一69OBq/m',;年平均值的范围分别为:39一580Bq/m:'、94一210oBq/m:,、35-460Bq/m3、110-390Bq/m3。呼和浩特、包头、集宁、鄂尔多斯四个城市分别有30.0%、44.4%、33.3%、50.0%的工程年平均氧浓度在200Bq/时以上。四个城市氦浓度的普遍水平:包头)鄂尔多斯)集宁)呼和浩特。4、对所有单建式铜室类地下工程和结建式铜室类工程内工作人员所受剂量当量进行了估算。单建式地下工程内工作人员所受剂量当量的范围是1.247mSv-6.SOgmsv,平均值是2.610Sv。结建式地下工程内工作人员所受剂量当量的范围是1.195Sv-8.531mSv,平均值是2.572mSv。两类地下工程内工作人员所受氨照射剂量当量都很高,有一半的工程剂量当量是地面上公众人员剂量当量0.924mSv的两倍以上。5、不管是从浓度角度还是从剂量估算角度分析,地下工程内的氛水平都比较偏高,需要采取一定防护措施,对现有状况进行改善。6、通风是地下工程防治氡污染最简便易行、见效最快的措施。使用防氡涂料是最经济的措施。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A newly developed polymer coil shrinking theory is described and compared with the existing entangled solution theory to explain electrophoretic migration behaviour of DNA in hydroxypropylmethylcellulose (HPMC) polymer solution in buffer containing 100 mM tris(hydroxymethyl)aminomethane 100 mM boric acid, 2 mm ethylenediaminetetraacetic acid at pH 8.3. The polymer coil shrinking theory gave a better model to explain the results obtained. The polymer coil shrinking concentration, C-s, was found to be 0.305% and the uniform entangled concentration, C+, 0.806%. The existence of three regions (the dilute, semidilute, and concentrated solution) at different polymer concentrations enables a better understanding of the system to guide the selection of the best conditions to separate DNA fragments. For separating large fragments (700/800 bp), dilute solutions (HPMC < 0.3%) should be used to achieve a short migration time (10 min). For small fragments (200/300 bp), concentrated solutions are preferred to obtain constant resolution and uniform separation. The best resolution is 0.6% HPMC due to a combined interaction of the polymer coils and the entangled structure. The possibility of DNA separation in semidilute solution is often neglected and the present results indicate that this region has a promising potential for analytical separation of DNA fragments.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

An industrial scale dehydration process based on hollow fiber membranes for lowering the dew point of natural gas is described in this paper. A pilot test with the feed flux scale of 12x10(4) Nm(3)/d was carried out. Dew points of -8 degreesC-13 degreesC at a gas transport pressure in the pipeline of 4.6M Pa and methane recovery of more than 98% were attained. The water vapor content of the product gas could be maintained around 0.01 vol% during a continuous run of about 700 hours. The effects of feed flux and operation pressure on methane recovery and water vapor content were also investigated. Additionally, some auxiliary technologies, such as a full-time engine using natural gas as fuel and the utilization of vent gas in the process, are also discussed. A small amount of the vent gas from the system was used as a fuel for an engine to drive vacuum pumps, and the heat expelled from the engine was used to warm up the natural gas feed. The whole system can be operated in a self-sustainable manner from an energy point of view, and has a relatively high efficiency in the utilization of natural gas.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Oxygen spillover and back spillover on Pt/TiO2 catalysts have been studied by a potential dynamic sweep method. The characteristics of I-V profiles of Pt/TiO2 electrodes in the three potential sweep regions are different from those of Pt and TiO2 electrodes. The catalytic role of Pt/TiO2 in oxygen spillover and back spillover is identified. It decreases, and the electrochemical oxygen adsorption (or desorption) increases with elevating temperature of hydrogen post-treatment of Pt/TiO2; to a certain extent (hydrogen post-treatment of Pt/TiO2 at 700 degrees C), the control step of oxygen electrode process (anodic oxidation or cathodic reduction) changes from oxygen diffusion to electrochemical oxygen adsorption or desorption, respectively. Increasing the amount of Pt supported on TiO2 enhances the processes of oxygen spillover and back spillover. (C) 1999 Elsevier Science B.V. All rights reserved.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

According to the influential dual-route model of reading (Coltheart, Rastle et al. 2001), there are two routes to access the meaning of visual words: one directly by orthography (orthography-semantic) and the other indirectly via the phonology (phonology-semantic). Because of the dramatic difference between written Chinese and alphabetical languages, it is still on debate whether Chinese readers have the same semantic activation processes as readers of alphabetical languages. In this study, the semantic activation processes in alphabetical German and logographic Chinese were compared. Since the N450 for incongruent color words in the Stroop tasks was induced by the semantic conflict between the meaning of the incongruent color words and color naming, this component could be taken as an index for semantic activation of incongruent color words in Stroop tasks. Two cross-script Stroop experiments were adopted to investigate the semantic activation processes in Chinese and German. The first experiment focused on the the role of phonology, while the second one focused on the realative importance of orthography. Cultural differences in cognitive processing between individuals in western and eastern countries have been found (Nisbett & Miyamoto, 2005). In order to exclude potential differences in basic cognitive processes like visual discrimination capabilities during reading, a visual Oddball experiment with non-lexical materials was conducted with all participants. However, as indicated by the P300 elicited by deviant stimuli in both groups, no group difference was observed. In the first Stroop experiments, color words (e.g., “green”), color-word associates (e.g., “grass”), and homophones of color words were used. These words were embedded into color patches with either congruent color (e.g. word “green” in green color patch) or incongruent colors (e.g. word “green” in either red or yellow or blue color patch). The key point is to observe whether homophones in both languages could induce similar behavioral and ERP Stroop effects to that induced by color words. It was also interesting to observe to which extent the N450 was related to the semantic conflicts. Nineteen Chinese adult readers and twenty German adult readers were asked to respond to the back color of these words in the Stroop experiment in their native languages by pressing the corresponding keys. In the behavioral data, incongruent conditions (incongruent color words, incongruent color-word associates, incongruent homophones) had significantly longer reaction times as compared to corresponding congruent conditions. All incongruent conditions in the Geman group elicited an N450 in the 400 to 500 ms time window. In the Chinese group, the N450 in the same time window was also observed for the incongruent color words and incongruent color-word associates. These results indicated that the N450 was very sensitive to semantic conflict-even words with semantic association to colors (e.g. “grass”) could elicite similar N450. However, the N450 was absent for incongruent homophones of color words in the Chinese group. Instead, in a later time window (600-800 ms), incongruent homophones elicited a positivity over left posterior regions as compared to congruent homophones. Similar positivity was also observed for color words in the 700 to 1000 ms time window in the Chinese group and 600 to 1000 ms time window for incongruent color words and homophones in the Geman group. These results indicate that phonology plays an important role in Geman semantic activation processes, but not in Chinese. In the second Stroop experiment, color words and pseudowords which had similiar visual shape to color words in both languages were used as materials. Another group of eighteen Chinese and twenty Germans were involved in the Stroop experiment in their native languages.The ERPs were recorded during their performance. In the behavioral data, strong and comparable Stroop effects (as counted by substract the reaction times in the congruent conditions from reaction times in the incongruent conditions) were observed. In the ERP data, both incongruent color words and incongruent pseudowords elicited an N450 over the whole brain scalp in both groups. These results indicated that orthography played an equally important role in semantic activation processes in both languages. The results of the two Stroop experiments support the view that the semantic activation process in Chiense readers differs significantly from that in German readers. The former rely mainly on the direct route (orthography-semantic), while the latter use both direct route and incirect route (phonology-semantic). These findings also indicate that the characteritics of different languages shape the semantic activation processes.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

O consumo anual de agrotóxicos no Brasil tem sido superior a 300 mil toneladas de produtos comerciais. Expresso em quantidade de ingrediente-ativo (i.a.), são consumidas anualmente no país cerca de 130 mil toneladas; representando um aumento no consumo de agrotóxicos de 700% nos últimos quarenta anos, enquanto a área agrícola aumentou 78% nesse período (SPADOTTO et al., 2004). Além dos perigos aos seres humanos, nos aspectos ocupacionais, alimentares e de saúde pública, sabe-se que a introdução de agrotóxicos no ambiente pode provocar efeitos indesejáveis, tendo como conseqüência mudanças no funcionamento do ecossistema afetado. De acordo com o Decreto 4.074/2002, é competência do Comitê Técnico de Assessoramento para Agrotóxicos (nele instituído) elaborar ?rotinas e procedimentos visando à implementação da avaliação de risco de agrotóxicos e afins?. O referido Decreto define as competências de órgãos federais e estaduais no processo de registro de novos produtos e de reavaliação dos produtos já registrados, onde a avaliação de risco ambiental aparece como alternativa à avaliação de impacto ambiental propriamente dita.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A Embrapa Mandioca e Fruticultura Tropical iniciou em principios dos anos 80 um Banco de Gemoplasma tendo reunido atualmente um total de quase 700 acessos no campo, do gênero Ananas e outras bromeliáceas, sendo uma das maiores coleções de gemoplasma desse gênero no mundo, reunindo expressiva variabilidade genética intra e interespecífica. A coleção está em condições de campo e uma duplicata vem sendo introduzida na conservação in vitro desde 2003, como cópia de segurança. A variabilidade genética do gênero Ananas, no entanto, é ainda muito pouco explorada, apesar do potencial que essas plantas têm para a geração de diversos produtos. Os genótipos silvestres possuem uma diversidade de formas e cores, que chamam atenção pela beleza e exoticidade. Essas características conferem a essas plantas um grande potencial para serem usadas como planta omamental. O abacaxi já vem se destacando como fruteira omamental, representando, atualmente, o segundo produto mais exportado da floricultura do Ceará. Essa comercialização, no entanto, está pautada em apenas duas cultivares, o Ananas comosus var. erectifolius (=Lucidus) e o Ananas comosus var. bracteatus (=Ananas Porteanus).

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Silver is well known to show peculiar catalytic activities in several oxidation reactions. In the present paper, we investigate the catalytic activity of silver catalysts toward CO-gelective oxidation in H-2. XRD, TEM, TPD, and in situ FTIR techniques were used to characterize the catalysts. The pretreatment of the catalysts was found to have great influence on their performance. The pretreatment in 02 improves the activity of the silver catalyst, whereas He pretreatment at 700 degreesC or direct hydrogen pretreatment shows an inverse effect. Silver catalysts undergo massive structural change during oxygen pretreatment at high temperatures (> 500 degreesC), and there is solid evidence for the formation of subsurface oxygen species. The existence of this silver-subsurface oxygen structure facilitates the formation of active sites on silver catalysts for CO oxidation, which are related to the size, morphology, and exposed crystal planes of the silver particles. Its formation requires a certain temperature, and a higher pretreatment temperature with oxygen is required for the silver catalyst with a smaller particle size. It is observed, for the first time, that adsorbed CO on the surface of silver particles can directly react with subsurface oxygen species at low temperatures (e.g., RT), and the surface oxygen can migrate into and refill these subsurface sites after the consumption of subsurface oxygen by the reaction with CO. This finding provides a new reaction pathway for CO oxidation on silver catalyst. (C) 2004 Published by Elsevier Inc.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

O objetivo do trabalho foi realizar o estudo dos solos de uma área montanhosa na região de influência do médio alto curso do Rio Grande, região Serrana do Estado do Rio de Janeiro, na escala 1:100.000, visando proceder à identificação, caracterização e cartografia dos solos. Predomina na área relevo forte ondulado a montanhoso e amplitude altimétrica entre 700 e 1.300 metros, podendo registrar picos mais elevados. O tipo climático predominante é o Aw, tropical mesotérmico úmido, de Köppen, com temperatura média anual de 17,8ºCº e precipitação pluviométrica variável de 1.327 mm a 1.585 mm anuais. Os procedimentos utilizados consistiram basicamente na delimitação dos principais domínios e/ou padrões fisiográficos, a partir de dados de sensores remotos e do modelo digital de elevação (MDE), principalmente dos dados de altimetria e de declividade. No domínio das baixadas, foram identificados Neossolos Flúvicos, ocupando as várzeas do Rio Grande e Cambissolos Flúvicos nas posições ligeiramente mais elevadas das baixadas. No domínio das terras altas, foram identificados Argissolos Vermelhos, Vermelho-Amarelos e eventualmente Amarelos, restritos às partes mais suavizadas da paisagem. Na classe do Argissolo Vermelho-Amarelo há ocorrência de solos com caracteristicas intermediárias para a classe dos Latossolos, e apenas na classe do Argissolo Vermelho ocorrem solos eutróficos, relacionados a diques de rochas básicas. Latossolos Vermelhos, Vermelho-Amarelos, Amarelos e eventualmente Latossolos Amarelos húmicos e, mais raramente, ácricos, que gradativamente dão lugar a Cambissolos Háplicos e Neossolos Litólicos, que ocorrem associados a afloramentos de rochas, à medida que a vertente fica mais íngreme. Excluindo os solos representativos das áreas de várzea, o restante, assim como os afloramentos de rochas, ocorrem em toda a área de estudo em diferentes posições da paisagem. As principais restrições pedológicas observadas na área compreendem a baixa fertilidade natural dos solos e a elevada suscetibilidade à erosão, em consequência da elevada precipitação e do relevo vigoroso da área. Essas características influenciam no comportamento dos solos frente aos diferentes tipos de usos e práticas de manejo, devendo ser consideradas no planejamento de uso dos solos.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Durbin, J. & Urquhart, C. (2003). Qualitative evaluation of KA24 (Knowledge Access 24). Aberystwyth: Department of Information Studies, University of Wales Aberystwyth. Sponsorship: Knowledge Access 24 (NHS)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

B.M. Brown, M. Marletta, S. Naboko, I. Wood: Boundary triplets and M-functions for non-selfadjoint operators, with applications to elliptic PDEs and block operator matrices, J. London Math. Soc., June 2008; 77: 700-718. The full text of this article will be made available in this repository in June 2009 Sponsorship: EPSRC,INTAS

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Nkiruka, A., Multiple Principles and the Obligation to Obey the Law, Deakin Law Review. Vol. 10. No. 2. 2005. p. 524 RAE2008

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Scott, L. (2006). Labour and the Bomb: The First Eighty Years. International Affairs. 82(4), pp.685-700 RAE2008

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The following article appeared in Torres, V., Beruete, M., Del Villar, I., & Sánchez, P. (2016). Indium tin oxide refractometer in the visible and near infrared via lossy mode and surface plasmon resonances with Kretschmann configuration. Applied Physics Letters, 108(4), doi:10.1063/1.4941077, and may be found at http://dx.doi.org/10.1063/1.4941077.