947 resultados para Wi-fi


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Esta tese consiste no estudo, implementação e desenvolvimento da infra-estrutura para o projecto SEMCABO-WIFI. Este projecto está inserido na empresa Sem¬ Cabo, com o objectivo de levar a Internet aos clientes sob a forma de hotspots ou no acesso à ultima milha (Last Míle Access) à casa dos residentes. O projecto também deu origem à própria empresa, levando esta a ISP desde Setembro de 2007. Numa primeira fase, é feita abordagem a Sistemas de Authentícatíon, Authorization e Ac­countíng para ISPs, na vertente WI-FI e apresentadas possíveis soluções comercias e open source. Em seguida, é apresentado a empresa SemCabo, vertente comercial e tecnológica. O sistema base da SemCabo é referido, contemplando a tecnologia de suporte, rede, equipamentos activos, módulos de emissão de sinal WI-FI, segurança, monitorização e portal de autenticação. Os servidores base são indicados posteriormente, sendo efectuado a apresentação de todos os servidores com suporte ao projecto, incluindo alguns pormenores de configuração. São apresentados equipa­ mentos e sistemas utilizados para controlo de acesso à rede (NAS), sendo igualmente descritos pormenores de configuração. ABSTRACT; This thesis is about the study, implementation and development of the infrastructure created for the SEMCABO-WIFI project. This project is inserted in the company SemCabo, with the objective to bring the Internet to costumers in the form of hots­pots or access in last mile to the house of residents. The project also originated the company and led the company to ISP since September 2007. ln the first fase, the approach is about Systems Authentication, Authorization and Accounting for WISPs and presented possible commercial and open source solutions. ln next, the SemCabo company is presented and described their technological and commercial aspects. The base system of the SemCabo is refered, considering the support technology, network equipment, modules emission signal WI-FI, security, monitoring and portal authentication module. Base servers of the SemCabo project are shown, a presentation of all the servers that support the project is made, including some details of the configuration. The equipment and systems used to control network access (NAS) are presented, details of configuration are also described.

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Dissertação (mestrado)—Universidade de Brasília, Faculdade de Educação, Programa de Pós-Graduação em Educação, 2016.

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During the course of an eight year monitoring effort, the Wisconsin Department of Natural Resources documented a significant decline in milfoil biomass and distribution in Fish Lake, Wisconsin. Average milfoil biomass declined by 40- 50% from 374-524 g dw m -2 during 1991-93 to 265 g dw m -2 during both 1994 and 1995. Milfoil recovered fully in 1996- 98 to 446- 564 g dw m -2 . The size of the milfoil bed, as discerned from aerial photographs, shrank from a maximum coverage of 40 ha in 1991 to less than 20 ha during 1995. During the “crash” of 1994-95, milfoil plants exhibited typical signs of weevil-induced damage, including darkened, brittle, hollowed-out growing tips, and the arching and collapse of stems associated with loss of buoyancy. Monitoring of weevils and stem damage during 1995-98 showed highest densities and heaviest damage occurred near shore and subsequently fanned out into deeper water from core infestation sites each spring. The extent of milfoil stem damage was positively correlated with weevil densities (monthly sampling). However, weevil densities and stem damage were lower during 1995 (when milfoil biomass was in decline) than during 1996-98 (when milfoil biomass was fully recovered).

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Quantum well states of Ag films grown on stepped Au(111) surfaces are shown to undergo lateral scattering, in analogy with surface states of vicinal Ag(111). Applying angle resolved photoemission spectroscopy we observe quantum well bands with zone-folding and gap openings driven by surface/interface step lattice scattering. Experiments performed on a curved Au(111) substrate allow us to determine a subtle terrace-size effect, i.e., a fine step-density-dependent upward shift of quantum well bands. This energy shift is explained as mainly due to the periodically stepped crystal potential offset at the interface side of the film. Finally, the surface state of the stepped Ag film is analyzed with both photoemission and scanning tunneling microscopy. We observe that the stepped film interface also affects the surface state energy, which exhibits a larger terrace-size effect compared to surface states of bulk vicinal Ag(111) crystals

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辽东山区森林是辽宁省重要的水源涵养基地与用材林资源,在维系区域内生态环境和林产品的可持续供应方面占据十分重要的战略位置。该区的天然林已基本绝迹,因此该区的森林生态恢复具有重要意义。 已有研究表明,影响辽东山区森林更新演替最主要的环境因素是光环境。核桃楸(Juglans mandshurica)、水曲柳(Fraxinus mandshurica)、黄菠萝(Phellodendron amurense)和红松(Pinus koraiensis)是阔叶红松林的优势树种;这些树种幼苗对光环境的适应性差异,在群落演替和森林生态恢复中发挥重要作用。 本论文采用人为控制遮光试验测定了核桃楸、水曲柳和黄菠萝幼苗对光环境的响应,同时,采用自然光环境试验和人为控制遮光试验相结合的手段测定了红松幼苗对光环境的适应性。人为控制遮光试验设置的光环境类似于自然中的典型林窗、林缘和林下的光环境;在人为控制遮光试验中,研究材料于2007年4月末栽植于4个不同光环境(全光、全光的60%、30%和15%,分别记为FI、II、LI和WI处理)下,在2007年7~9月测定了树种幼苗的光合生理、叶片特征、生长和冠层形态特征等方面的变化,结果表明: 1)不同光环境处理区内的光合有效辐射(PAR)具有显著差异,形成一定的光强梯度,而气温,相对湿度和土壤含水量差异并不显著。全光处理区内的日平均PAR为842.4μmol∙m-2∙s-1,最大PAR为1884.1μmol∙m-2∙s-1,显著高于其它处理区。 2)生长在高光强下4个树种幼苗的叶片有较高的光合能力(Amax),随生长光强的下降,Amax显著下降;光补偿点(LCP)和光饱和点(LSP)也表现出随着生长光强的下降而降低的趋势。核桃楸和水曲柳净光合速率Pn的日变化最大值约为16μmol∙m-2∙s-1,黄菠萝的约为13μmol∙m-2∙s-1,这与温带阔叶树种叶片的最大净光合速率Pn在10~15μmol∙m-2∙s-1范围内的结论相符;3个苗龄红松针叶的Pn日变化均呈单峰型,没有光合“午休”现象,峰值出现在11:00~13:00期间。 3)4个树种幼苗的比叶重(LMA)和单位叶面积鲜重(LFA)均随着光环境的降低而下降;三个阔叶树种幼苗的叶长L、叶宽W、叶周长C和单叶面积A均具有随着光强的降低而呈增大的趋势,表明叶片通过调节叶片的形态来适应多变的光环境。 4)不同光环境对阔叶树种幼苗的植株冠形和生长有显著影响,而红松幼苗植株冠形和生长的变化无明显的规律性。 综上,本研究得出以下结论:○1.通过可塑性分析和模糊隶属函数分析,核桃楸和黄菠萝较水曲柳能适应更宽的光强幅度;同时,核桃楸和黄菠萝较水曲柳的需光性更强,核桃楸和黄菠萝的需光性差异不大。○2.与3年、5年生红松相比,7年生红松对光强的适应幅度最小;同时,7年生红松的需光性强于3年和5年生红松。○3.本研究结果支持前人的观点:红松在幼年阶段能耐一定程度的遮光,在全光的20%~60%光条件下生长较好,随着年龄的增大,红松的需光性增加。

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研究辽东山区次生林3种树种幼苗(核桃楸、水曲柳和黄菠萝)对生长光环境的适应性,在生长季测定4种光强下(全光、60%透光、30%透光、15%透光,分别记为FI,II,LI和WI)树种幼苗叶片气体交换参数、净光合速率、单位叶面积叶绿素含量和比叶重(LMA)。结果表明:随着光强的减弱,3个树种的光补偿点(LCP)、光饱和点(LSP)、最大光合速率(Pmax)、暗呼吸速率(Rd)、类胡萝卜素(Car)、LMA、单位叶鲜质量(LFA)均呈下降趋势;全光下单位叶面积的叶绿素Chl含量均低于弱光处理。本研究结果支持水曲柳在幼苗时期具有一定耐荫性的观点。树种生理生态指标的可塑性分析表明:黄菠萝能适应更宽的光强幅度,且黄菠萝的需光性大于核桃楸。不同光环境下3个树种的生理生态变化特征对解释森林生态系统内树种的共生和演替具有重要意义。

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FI催化剂系一近几年发展起来的烯烃聚合高性能催化剂。以它的极高的活性、聚合物分子结构的可控性、多重活性聚合等特性而引人注目。本评述首先进行该催化剂的化学描述,然后分别介绍该催化剂的主要特征、活性中心结构、聚合机理和应用,重点介绍该催化剂的五大特征。