共查询到19条相似文献,搜索用时 218 毫秒
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利用硫酸镁和造纸草浆黑液制备含镁氧化合物的吸附剂,通过化学分析、表面性质分析、X射线衍射和红外光谱等对吸附剂进行了表征.考察了吸附剂焙烧温度、投加量、吸附时间以及pH值等因素对活性黄ST-4RFN吸附性能的影响,吸附过程可用Freundlich模型来描述. 相似文献
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引言黑体作为标准辐射源,广泛地应用于光学系统校准、各种材料发射率测量及红外探测器定标等等。我们研制的JWHI—Ⅰ型低温黑体(以下简称黑体)是为SWH1—1航空红外测温仪(以下简称测温仪)在空中提供一个辐射温度标准,在利用测温仪大面积航测海表温度中以及研究大气红外辐射中都是不可缺少的辅助仪器。一、仪器的原理一八六○年基尔霍夫在他的绝对黑体理论中指出,在等温密封腔壁上开一个小孔,从小孔发出的辐射就是模拟绝对黑体辐射,绝对黑体辐射的发射率为 相似文献
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利用扫描近场光学显微镜观测并分析了两种表面等离子体激元纳米结构对表面等离子体激元(SPP)的激发和聚焦现象. 用线偏振光照射有半个周期相位差的环状沟槽结构与有半个周期位相差的环状狭缝结构,得到了单点的SPP聚焦. 有限时域差分法的模拟结果验证了实验中观测的现象. 这两种相位错位的表面等离子体激元纳米结构,突破了由于干涉导致的线偏振光不能得到单个聚焦点的限制. 与采用径向偏振光激发而得到单个聚焦点的方法相比,线偏振光不需要聚焦,也不需要将光束中心对准纳米结构的几何中心即可得到单点聚焦. 相似文献
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本文主要介绍对X射线组合折射透镜的制作工艺误差对其聚焦性能影响的研究结果. 首先给出采用深度X射线光刻技术制作的PMMA材料圆柱面型X组合折射透镜的工艺测试结果,得出制作工艺误差值,定性分析制作工艺误差对X射线组合折射透镜聚焦性能的影响. 然后根据实际的制作工艺误差建模,给出详尽的理论分析和定量的理论模拟结果. 最后在北京同步辐射装置(BSRF)上,构建基于PMMA材料的圆柱面型X射线组合折射透镜的微束聚焦实验系统,实际测试了有明显工艺误差和尽量消除工艺误差的两种X射线组合折射透镜的聚焦性能,给出实测结果 相似文献
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利用薄膜模型研究Barriola-Vilenkin黑洞的热辐射,得到了黑洞的热辐射满足广义Stefan-Boltzmann定律的结论,导出的广义Stefan-Boltzmann系数不再是一个恒量,当截断距离以及薄膜厚度取定后,它是一个与黑洞视界附近的时空度规以及辐射粒子的径向平均泻流速率有关的比例系数.得到的Barriola-Vilenkin黑洞视界附近Dirac场的辐射能通量与薄层膜内辐射粒子的径向平均泻流速率成正比,与黑洞的质量平方成反比. 相似文献
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基于线粒体12S rRNA序列探讨4种青蟹系统发育关系及中国沿海青蟹的分类地位 总被引:10,自引:0,他引:10
研究青蟹属4种青蟹的系统发育关系,阐明分布于中国沿海青蟹的分类地位,本研究采集了青蟹属4种青蟹以及中国沿海的青蟹样品,测定分析了其线粒体12S rRNA部分片段序列。结果表明4种青蟹的12S rRNA基因片段长度存在差异,每一种的个体都单独聚为1支,中国沿海的青蟹样品全部与Scylla paramamosain聚为1支,结果提示分布于中国沿海的青蟹主要是S.paramamosain。S.serrata,S.paramamosain和S.tranquebarica3个种间的亲缘关系较近,这3个种形成1个单系群并且具有很高的自展置信值。S.olivacea与其他3个种互为单系,与以上3种青蟹的亲缘关系较远。 相似文献
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A.剂量和剂量率的概念辐射剂量乃是指单位体积或单位质量的被照射物质所吸收的辐射能量。剂量率为单位时间内的剂量。伦琴乃是辐射的物理剂量。它的定义是x射线或γ射线在0.001293克干燥空气中 相似文献
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根据2018年1月冬季航次的水文实测资料,详细分析了大亚湾海水温度(T)、盐度(S)的分布特征。整体而言,观测海区海表相对于海底具有高温低盐的特征;同时,无论是表层还是近底层,大亚湾湾内的海水相对于湾外都呈现高温低盐的特征。观测期间,应是受到大亚湾核电站温排水的影响,湾内西侧存在一个高温中心。盐度的差异在近底层更加明显,低盐中心位于大亚湾的湾顶和大亚湾的中部海域,而高盐中心则主要分布于湾口西侧及惠东以东附近海域。太阳辐射和潮流变化是影响大亚湾温度、盐度变化的两大重要因素。其中,太阳辐射的影响主要局限于表层3~4 m,对近底层海水的影响较小;其加热效应使湾内和湾口附近的表层海水都表现出明显的昼夜变化。由潮汐和温度、盐度的对应关系可知,潮流对湾内温度、盐度的影响较大,而对湾外温度、盐度的影响较小。 相似文献
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Ivana Cerove?ki Mirko Orli? Myrl C. Hendershott 《Deep Sea Research Part I: Oceanographic Research Papers》1997,44(12):2007-2029
A salient feature of sea level records from the Adriatic Sea is the frequent occurrence of energetic seiches of period about 21 h. Once excited by a sudden wind event, such seiches often persist for days. They lose energy either to friction within the Adriatic, or by radiation through Otranto Strait into the Mediterranean.The free decay time of the dominant (lowest mode) seiche was determined from envelopes of handpassed sea level residuals from three locations (Bakar, Split and Dubrovnik) along the Croatian coast during twelve seiche episodes between 1963 and 1986 by taking into consideration only time intervals when the envelopes decreased exponentially in time, when the modelled effects of along-basin winds were smaller than the error of estimation of decay time from the envelopes and when across-basin winds were small. The free decay time thus obtained was 3.2±0.5 d. This value is consonant with the observed width of the spectral peak.The decay caused by both bottom friction and radiation was included in a one dimensional variable cross section shallow water model of the Adriatic. Bottom friction is parameterized by the coefficient k appearing in the linearized bottom stress term ρ0u (where u is the along-basin velocity and ρ0 the fluid density). The coefficient k is constrained by values obtained from linearization of the quadratic bottom stress law using estimates of near bottom currents associated with the seiche, with wind driven currents, with tides and with wind waves. Radiation is parameterized by the coefficient f appearing in the open strait boundary condition ζ =auh/c (where ζ is sea level, h is depth and c is phase speed). This parameterization of radiation provides results comparable to allowing the Adriatic to radiate into an unbounded half plane ocean. Repeated runs of the model delineate the dependence of model free seiche decay time on k and a, and these plus the estimates of k allow estimation of a.The principle conclusions of this work are as follows.
- 1. (1) Exponential decay of seiche amplitude with time does not necessarily guarantee that the observed decay is free of wind influence.
- 2. (2) Winds blowing across the Adriatic may be of comparable importance to winds blowing along the Adriatic in influencing apparent decay of seiches; across-basin winds are probably coupled to the longitudinal seiche on account of the strong along-basin variability of across-basin winds forced by Croatian coastal orography.
- 3. (3) The free decay time of the 21.2 h Adriatic seiche is 3.2±0.5 d.
- 4. (4) A one dimensional shallow water model of the seiche damped by bottom stress represented by Godin's (1988) approximation to the quadratic bottom friction law ρ0CDu|u| using the commonly accepted drag coefficient CD = 0.0015 and quantitative estimates of bottom currents associated with wind driven currents, tides and wind waves, as well as with the seiche itself with no radiation gives a damping time of 9.46 d; radiation sufficient to give the observed damping time must then account for 66% of the energy loss per period. But independent estimates of bottom friction for Adriatic wind driven currents and inertial oscillations, as well as comparisons between quadratic law bottom stress and directly measured bottom stress, all suggest that the quadratic law with CD=0.0015 substantially underestimates the bottom stress. Based on these studies, a more appropriate value of the drag coefficient is at least CD=0. In this case, bottom friction with no radiation leads to a damping time of 4.73 d, radiation sufficient to give the observed damping time then accounts for 32% of the energy loss per period.
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Warming and depth convergence of the Arctic Intermediate Water in the Canada Basin during 1985-2006 总被引:1,自引:1,他引:0
The warming of the Arctic Intermediate Water (AIW) is studied based on the analyses of hydrographic observations in the Canada Basin of the Arctic Ocean during 1985-2006. It is shown that how the anomalously warm AIW spreads in the Canada Basin during the observation time through the analysis of the AIW temperature spatial distribution in different periods. The results indicate that by 2006, the entire Canada Basin has almost been covered by the warming AIW. In order to study interannual variability of the AIW in the Canada Basin, the Canada Basin is divided into five regions according to the bottom topography. From the interannual variation of AIW temperature in each region, it is shown that a cooling period follows after the warming event in upstream regions. At the Chukchi Abyssal Plain and Chukchi Plateau, upstream of the Arctic Circumpolar Boundary Current (ACBC) in the Canada Basin, the AIW temperature reached maximum and then started to fall respectively in 2000 and 2002. However, the AIW in the Canada Abyssal Plain and Beaufort Sea continues to warm monotonically until the year 2006. Furthermore, it is revealed that there is convergence of the AIW depth in the five different regions of the Canada Basin when the AIW warming occurs during observation time. The difference of AIW depth between the five regions of the Canada Basin is getting smaller and smaller, all approaching 410 m in recent years. The results show that depth convergence is related to the variation of AIW potential density in the Canada Basin. 相似文献
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胶州湾北部水层生态动力学模型与模拟 Ⅰ.胶州湾北部水层生态动力学模型 总被引:1,自引:0,他引:1
建立了一个包括浮游植物、浮游动物、无机氮和磷、溶解态与悬浮有机物及溶解氧七状态变量的浅海水体生态动力学箱式模型,并且考虑了海面太阳辐照度变化、海水与底泥温度变化以及营养盐海底溶出和陆源流入的影响。初步分析了在胶州湾北部浮游生态系统演变的几个特征时期动力学方程中的物流动态特征。结果是比较合理的。 相似文献
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A mooring observation of current velocity, temperature and bottom pressure was carried out approximately 30 km off the coast
of Monbetsu, between August 7 and September 2, 2005, to investigate the characteristics of bottom boundary layer (BBL) off
the Soya Warm Current (SWC). We succeeded in measuring the Ekman veering and bottom Ekman transport in the BBL. On comparing
the observed current velocity with that represented by the classical theoretical equation, the observed alongshore current
velocity in BBL disagreed with that represented by the classical theoretical equation, but the cross-shore one agreed well.
However after applying a linear extrapolation for the alongshore current velocity to estimate the alongshore geostrophic current
velocity above the bottom, we could explain the alongshore current velocity by that represented in the classical theoretical
equation. Consequently, our observations strongly support one of the proposed formation mechanisms of the cold-water belt
observed off the SWC, that is, the convergence of bottom Ekman transport. The volume transport of vertical pumping velocity
was estimated to be (0.12–0.25) Sv. In addition, the vertical profile of average temperature in all observation periods shows
that slightly warmer water lies beneath the homogenous temperature layer, in the BBL. The result is considered to imply that
the down-slope advection due to bottom Ekman transport supplies the SWC water in BBL and the eddy diffusivity of order of
10−3 m2s−1 maintains the oceanic structure in the bottom mixed layer. 相似文献
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南海混合层年循环特征 总被引:22,自引:4,他引:22
通过分析Levitus1994版气候平均温盐资料,得到南海混合层的时空分布特征,剖析了混合层浓度及其内部温度的季节变化规律。资料分析表明:季风通风流场调整对南海混合层的时空分布着明显的影响。这种影响的复杂性在于它不但通过海洋表层Ekman效应来影响混合层深度,而且还通过大尺度环流造成的幅散或辐合来限制或促进混合层深度的发展。研究发现混合层深度与混合层内温度存在着如下关系:夏季最大混合层的形成是28℃等温线与混合层底达到相互贴合的过程;冬季最大混合层的形成是28℃水体完全消失并且等温度线与混合层达到相交最多、相交最为垂直的过程,这时对应着冬季南海北部温跃层的通风;大于或等于28℃的水体总是位于混合层以内。 相似文献
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A. V. Rakitin V. S. Kostsov Yu. M. Timofeev 《Izvestiya Atmospheric and Oceanic Physics》2012,48(9):909-917
The problem of reconstructing the temperature distribution along optical paths from satellite measurements of the Earth’s limb radiation in the CO2 15-μm absorption band with a high spectral resolution is formulated and analyzed on the basis of numerical experiments performed in accordance with the MIPAS experiment. It is shown that the two-dimensional temperature field can be obtained through the processing of radiation measurements on paths with different target heights provided that spectral channels with essentially different optical thicknesses are used. The error in the stratospheric temperature determination varies from 1.8 to 5.6 K and depends on the target height of the optical path and the distance from the target point. The best horizontal resolution is 73–100 km, and it is achieved for optical paths with a target height of about 18–20 km. 相似文献