72 resultados para WiFi 802.11n


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A new type of phosphor Sr2ZrO4 with one-dimensional structure was prepared by solid reaction and its luminescence is seen at room temperature. The excitation and emission spectra were measured and display broad maximum at 354 nm and 386 nm respectively. The mechanism of this luminescence is ascribed to charge transfer.

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In situ microscopic FTIR spectroelectrochemistry behavior of L-ascorbic acid (H(2)A) in polymer electrolyte is reported for the first time. H(2)A undergoes a two-step oxidation, The oxidation waves shift towards more anodic potential values when the scan rate increases. The peak currents of the oxidation waves are proportional to the square roots of scan rate up to 100 mV/s, The in situ infrared spectra suggest that the product of the oxidation be dehydroascorbic acid, which may exist as a dimer.

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L-抗坏血酸(H2A)由于在生物介质氧化还原过程中的重要作用,其分子及其衍生物已有广泛研究[1~5].聚合物电解质由于能溶解电活性物质和具有离子导电性而成为一种新的溶剂,可用于研究一些物质的电化学行为[6].H2A在聚合物电解质中的电化学及光谱电化学…

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Living planktonic foraminifera (PF) samples from the Okinawa Trough of the northwestern Pacific Ocean were taken for DNA analysis. The SSU rDNA sequences of two PF species, Globigerina sp. and Pulleniatina obliquiloculata collected at Station WP01, were obtained and compared with those from the southwestern Pacific Ocean. Only small differences (< 0.7%-1.2% for P. obliquiloculata, and 0.3% for Globigerina sp.) were found between samples from the north- and south-western Pacific Ocean areas and this molecular evidence supported that these micropaleontological species are the same species, which implies that the West Pacific Ocean circulation system influences the planktonic foraminiferal gene communication.

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热带西太平洋是一个流系和水团分布十分复杂的海域。热带西太平洋是一个在别处形成的几种水团的交汇区。许多起源于中、高纬度海域的次表层和中层水团,由不同流系带入和带出这个海域。热带西太平洋水团分布及其变化,与各种时间尺度的大尺度海洋环流和全球水循环变化密切联系,所在位势密度层次越深,所关联的气候变化时间尺度越长。因此,研究该海域次表层水和中层水的分布、扩散及其变化特征,对大洋环流动力学和气候变化研究有重要意义。本文利用中国ARGO资料中心提供的ARGO延时处理资料和美国NODC提供的WOD01中的高分辨率CTD资料,运用盐度极值法确定水团的核心,通过水团核心位置的分布及变化反映热带西太平洋次表层水和中层水的分布及其起源和归宿问题,试图获得较以往更加准确的NPIW和AAIW以及NPTW和SPTW的向南及向北扩散的特征,以及ITF在不同层次上的水源。对新发现的西太平洋热带水(WPTW)和西太平洋热带中层水(WPTIW)的水团性质、分布特征,成因和起源进行了比较系统的分析。在此基础上,分析上述次表层水和中层水20世纪八九十年代以来的年代变化特征。主要结果如下:(1)SPTW在137°E以西跨越赤道后,仍在很大程度上保持原有盐度,向西北和东北方向发展。SPTW在131°E以东几乎没有越过5°N,但在131°E以西可局部影响到6°N,棉兰老冷涡和哈马黑拉暖涡的涡混合输运在这一局部过程中可能起主要作用。NPTW主要位于10°N-20°N之间,在NEC输送下从东向西一直延伸到菲律宾沿岸,分成向北和向南两个分支,南分支在130°E以西沿棉兰老沿岸向南扩散大约到2°N,部分向西进入苏拉威西海,部分与SPTW相遇后有向东扩散的趋势。(2)AAIW几乎齐头并进地向北扩散到12°N-13°N,在125°E附近向北可以到达13°N左右。NPIW的主体分布在10°N以北、122°E以东,呈东北向西南的扩散趋势,在132°E以西至棉兰老沿岸之间可以到达4°N附近。(3)在已知的NPTW与SPTW之间,发现一个以往从未被报道过的次表层水,称之为WPTW。WPTW存在于3°N-12°N之间,核心盐度低于34.8psu,位势密度约在23.7 -24.7 之间。WPTW源于东太平洋20-25°N附近,由NEC南翼携带向西到达西边界后,部分经MC向南,经NECC向东折回,被局限在NEC与NECC之间的狭长水域。(4)2°N-10°N之间、从170°W到西边界分布着一片盐度比较均匀、呈现垂向盐度极小值特征的中层水。该水体位势密度约为26.0 -26.6 、位于AAIW之上、NPIW以南,核心盐度与AAIW相仿、但高于NPIW,在以往研究中未给予重视。从流场配置来看,这个被本文称为WPTIW的水体恰好处在NEC-NECC-SEC之间的强剪切区,在其北侧的是NPIW与同样起源于东北太平洋的浅的盐度极小值(SSM)之间的混合水,在其南侧相应层次上则是AAIW与SPTW之间的过渡水,两者之间被剪切流充分混合,形成盐度相对均匀的WPTIW。因此,WPTIW是热带西太平洋局地混合和再循环的产物。(5)在20世纪八九十年代和2000年以后这两个时期,本文所关注的次表层水和中层水在热带西太平洋扩散和在西边界附近交织在一起的总体态势基本一致。两个时期相比较,SPTW向西扩散程度变化不大,向北扩散程度有所加大,由前一时期的5°N,进一步扩散到6°N-7°N。NPTW在西边界附近的向南扩散程度有所削弱,在2002-2005年间只向南扩散到4°N,并且被SPTW阻挡于128°E以西,而前一个时期则可向南扩散到2°N,并且在2°N-4°N之间转向东跨过130°E。AAIW在西边界附近向北扩散程度有所加大,在2002-2005年到13°N附近,而前一个时期只到达11°N。NPIW在西边界附近的向南扩散程度有所削弱。(6)ITF的次表层水源基本上可以确定主要来自北太平洋,中层水源既有北太平洋,也有南太平洋。其中北太平洋次表层水和中层水经苏拉威西海、望加锡海峡到达弗罗勒斯海,层次越深趋势越明显。南太平洋次表层水没有进入印度尼西亚海域,AAIW则明显是经哈马黑拉海峡和马鲁古海峡到班达海。在各层次上,南海次表层水和中层水通过苏禄海进入ITF的可能性不大。

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本论文主要研究两种重要的调节蜕皮过程的基因—蜕皮激素效应基因E75和RXR在中国明对虾蜕皮中的作用。利用RT-PCR和RACE技术获得了编码FcE75和FcRXR的全长cDNA序列。FcRXR包含7个内含子,在对虾中存在不同的异形体,命名为RXR-1和RXR-2。应用荧光实时定量PCR分析表明FcE75和FcRXR基因在中国明对虾蜕皮前期(D3)其转录表达量明显上调。另外,FcE75和FcRXR基因在不同组织中的转录表达存在明显的差异。利用FcE75和FcRXR基因的双链RNA注射对虾能有效降低FcE75和FcRXR的表达水平。FcE75和FcRXR的体内沉默完全抑制了对虾的蜕皮过程,并且引起对虾的死亡。对不能正常蜕皮个体进行观察的结果表明,FcE75沉默的对虾,其上皮的收缩、新的刚毛及新表皮的形成均收到限制。在FcE75双链RNA沉默后的对虾中,我们检测了与蜕皮相关的一些效应因子,如chitinase等的转录,发现这些效应因子的转录明显受到抑制,说明FcE75和FcRXR在蜕皮过程中起到非常重要的作用。本论文首次阐明了这些基因在十足目甲壳动物蜕皮过程中的功能。

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通过在柴达木盆地盐碱化弃耕地上种植多年生饲草和增施厩肥的试验结果表明:耕作层土壤发含量明显降低,土壤由重度盐碱土变为极轻盐碱化土壤;土壤有机质含量增加,土壤结构得到改善,弃耕地植被得到恢复,第一生产力提高。

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移动式机器人系统的一个重要课题是视觉导航系统的研制。为了通过环境正确导航,移动式机器人必须感知和理解其环境结构,这样就必须提取与景物相关的模型特征。本论文一方面对视觉系统中的关键技术--线性特征抽取进行描述与实施,并将其成果应用在道路边界的检测上;另一方面对视觉系统中的另一重要技术--Hough变换,从理论到实验进行了详细的推导和验证。论文包括两大部分:1、线性特征抽取和道路界检测(包括模拟系统和实时系统)2、Hough变换的发展及其方法研究(包括快速Hough变换的硬件实现方案和用Systolic阵列机Hough变换的模拟实验及其结果)目前,线性特征抽取和道路边界检测的实时系统,己装在自治式导航实验载体上,用于视觉辅助导航。

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Increasing attentions have been paid to the subsurface geological storage for CO2 in view of the huge storage capacity of subsurface reservoirs. The basic requirement for subsurface CO2 storage is that the CO2 should be sequestrated as supercritical fluids (physical trapping), which may also interact with ambient reservoir rocks and formation waters, forming new minerals (chemical trapping). In order to the effective, durable and safe storage for CO2, enough storage space and stable sealing caprock with strong sealing capacity are necessitated, in an appropriate geological framework. Up till now, hydrocarbon reservoirs are to the most valid and appropriate CO2 storage container, which is well proven as the favorable compartment with huge storage capacity and sealing condition. The thesis focuses on two principal issues related to the storage and sealing capacity of storage compartment for the Qingshankou and Yaojia formations in the Daqingzijing block, Southern Songliao Basin, which was selected as the pilot well site for CO2-EOR storage. In the operation area, three facies, including deltaic plain, deltaic front and subdeep-deep lake facies associations, are recognized, in which 11 subfacies such as subaqueous distributary channel, river- mouth bar, interdistributary bay, sheet sandbody, crevasse splay and overflooding plain are further identified. These subfacies are the basic genetic units in the reservoir and sealing rocks. These facies further comprise the retrogradational and progradational depositional cycles, which were formed base- level rise and fall, respectively. During the regressive or lake lowstand stage, various sands including some turbidites and fans occurred mostly at the bottom of the hinged slope. During the progradation stage, these sands became smaller in size and episodically stepped backwards upon the slope, with greatly expanded and deeped lake. However, most of Cretaceous strata in the study area, localized in the basin centre under this stage, are mainly composed of grey or grizzly siltstones and grey or dark grey mudstones intercalated with minor fine sandstones and purple mudstones. On the base of borehole and core data, these siltstones are widespread, thin from 10 to 50 m thick, good grain sorting, and have relative mature sedimentary structures with graded bedding and cross- lamination or crossbeds such as ripples, which reflect strong hydrodynamic causes. Due to late diagenesis, pores are not widespread in the reservoirs, especially the first member of Qingshankou formation. There are two types of pores: primary pore and secondary cores. The primary pores include intergranular pores and micropores, and the secondary pores include emposieus and fracture pores. Throat channels related to pores is also small and the radius of throat in the first, second and third member of Qingshankou formation is only 0.757 μm, 0.802 μm and 0.631 μm respectively. In addition, based on analyzing the probability plot according to frequency of occurrence of porosity and permeability, they appear single- peaked distribution, which reflects strong hetero- geneity. All these facts indicate that the conditions of physical property of reservoirs are not better. One reason may be provided to interpret this question is that physical property of reservoirs in the study area is strong controlled by the depositional microfacies. From the statistics, the average porosity and permeability of microfacies such as subaqueous distributary channel, channel mouth bar, turbidites, is more than 9 percent and 1md respectively. On the contrary, the average porosity and permeability of microfacies including sand sheet, flagstone and crevasse splay are less than 9 percent and 0.2md respectively. Basically, different hydrodynamic environment under different microfacies can decide different physical property. According to the reservoir models of the first member of Qingshankou formation in the No. well Hei47 block, the character of sedimentary according to the facies models is accord to regional disposition evolution. Meantime, the parameter models of physical property of reservoir indicate that low porosity and low permeability reservoirs widespread widely in the study area, but the sand reservoirs located in the channels are better than other places and they are the main sand reservoirs. The distribution and sealing ability of fault- fractures and caprock are the key aspects to evaluate the stable conditions of compartments to store CO2 in the study area. Based on the core observation, the fractures widespread in the study area, especially around the wells, and most of them are located in the first and second member of Qingshankou formation, almost very few in the third member of Qingshankou formation and Yaojia formation instead. In addition, analyzing the sealing ability of eleven faults in the three-dimensional area in the study area demonstrates that most of faults have strong sealing ability, especially in the No. well Hei56 and Qing90-27. To some extent, the sealing ability of faults in the No. well Hei49, Qing4-6 and Qing84-29 are worse than others. Besides, the deposition environment of most of formations in the study area belongs to moderately deep and deep lake facies, which undoubtedly take advantage to caprocks composed of mudstones widespread and large scale under this deposition environment. In the study area, these mudstones distribute widely in the third member of Qingshankou formation, Yaojia and Nenjiang formation. The effective thickness of mudstone is nearly ~550m on an average with few or simple faults and fractures. In addition, there are many reservoir beds with widely- developed insulated interbeds consist of mudstones or silty mudstone, which can be the valid barrier to CO2 upper movement or leakage through diffusion, dispersion and convection. Above all, the closed thick mud caprock with underdeveloped fractures and reservoir beds can be taken regard as the favorable caprocks to provide stable conditions to avoid CO2 leakage.