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161.
162.
The growth of young waves along a narrow bay and their directional spectra were studied. The fetch geometry was found to affect the shape of the spectrum already when the waves were young. When compared to the growth from a straight shoreline, the dimensionless energy was reduced, but the change in dimensionless peak frequency was smaller. The behaviour of the young waves was similar to that of the mature waves but the differences between narrow and broad fetch geometries were smaller, which suggests that due to a stronger nonlinear transfer the young waves are less sensitive to the fetch geometry. The directional spectrum of the young waves in the narrow fetch geometry was narrower at all energy containing frequencies than the spectra from broad fetch geometry, which further supports the conclusion that the shape of the spectrum is not independent of the fetch geometry. 相似文献
163.
164.
The extent and mechanisms of adsorption of marine pore water organic matter to montmorillonite were studied in a series of batch and sequential adsorption experiments. Pore water natural organic matter (pNOM) and easily extracted natural organic matter (eNOM) were collected from Liberty Bay (Puget Sound, WA, USA) sediments. The pNOM and eNOM were each divided into two size fractions using a 1000 D ultrafilter. Batch adsorption isotherms were approximately linear, and the >1000 D fractions of both pNOM and eNOM had larger partition coefficients (Kd) than the <1000 D fractions. A two-component fit of the sequential adsorption data indicated that pNOM and eNOM contained a similar amount of NOM (30%) that was not surface reactive toward montmorillonite. After correcting the batch adsorption Kds for the non-reactive components, the Kds estimated by batch and sequential adsorption were identical (2.7 l/kg for >1000 D pNOM and eNOM, and 1.6 l/kg for <1000 D pNOM and eNOM). Mechanisms of adsorption were investigated by systematically changing conditions (pH, temperature and ionic composition) of >1000 D fractions during batch isotherm experiments. Adsorption of NOM was found to decrease with increased temperature, suggesting that hydrophobic effects were not the dominant adsorption mechanisms in this system. Ion exchange was also not an important adsorption mechanism because adsorption increased with ionic strength. The observed enhancement in adsorption with ionic strength indicated that van der Waals interactions were important in the adsorption of NOM. Ligand exchange was found to be a significant mechanism since the presence of SO42− in solution reduced the amount of NOM adsorbed. Ca2+ enhanced adsorption slightly more than Na+, suggesting that cation bridging was involved. The relative contributions of van der Waals interactions, ligand exchange and cation bridging were estimated to be approximately 60%, 35% and 5%, respectively, for adsorption of NOM in a CaCl2 solution. 相似文献
165.
Exact distributions for apparent waves in irregular seas 总被引:2,自引:0,他引:2
We discuss the long-run distributions of several characteristics for the apparent waves in a Gaussian sea. Three types of one-dimensional wave records are considered: 1) the seaway in time at a fixed position; 2) the instantaneous profile along a horizontal line; 3) the encountered seaway. Exact integral forms of the joint long run distributions are derived for the apparent periods, lengths, and heights. Results of numerical approximations of these distributions are presented in examples. For the computations we considered, as the input spectra, empirical estimates of the frequency spectra as well as JONSWAP type spectra. Effective algorithms are discussed and utilized in the form of a comprehensive computer package of numerical routines. 相似文献
166.
煤矿井下水平定向钻进技术的发展 总被引:2,自引:0,他引:2
国内外煤矿井下水平定向钻进技术(HDD)的发展具有不同的技术路线,这涉及钻进设备和钻具、钻孔监测仪器的研发,钻孔轨迹控制理论的研究等。本文阐述了煤矿井下HDD技术在国内外的发展特点及我国在该领域未来几年的发展方向。 相似文献
167.
国外城市轨道交通对房地产价值的影响研究 总被引:13,自引:0,他引:13
从区域的角度分析北美洲、欧洲和东亚的城市轨道交通与房地产价值的相关研究成果,论述轨道交通所带来的巨大的经济、社会和环境效应.国外关于城市轨道交通对商业物业价值的研究较少,这是值得开辟的研究视角;城市轨道交通对房地产价值的影响具有区域性和时效性;对城市轨道交通与房地产价值的研究非常强调定性与定量的结合.这些成果对我国关于城市轨道交通对房地产价值影响研究具有一定的借鉴意义. 相似文献
168.
高分五号卫星大气参数探测综述 总被引:3,自引:0,他引:3
高分五号卫星搭载了大气痕量气体差分吸收光谱仪、主要温室气体探测仪、大气多角度偏振探测仪、大气环境红外甚高分辨率探测仪、可见短波红外高光谱相机和全谱段光谱成像仪共6台载荷,对全球环境监测及中国大气气溶胶、臭氧、二氧化硫、二氧化氮、二氧化碳、甲烷和云等多个环境与气象综合监测方面有着重要的意义。为了更好的了解高分五号卫星任务的大气监测内容,本文对高分五号卫星其中的4个大气探测载荷特征和数据处理算法进展进行了总结,涉及各个载荷参数信息、算法介绍和产品初步结果等相关内容。高分五号卫星是中国专门用于大气环境监测任务的遥感卫星,随着后续卫星的发射升空,将对中国乃至全球大气环境监测提供强有力的数据支撑。 相似文献
169.
Current meter data from a series of oceanographic moorings spanning a total of five years was analyzed to quantify the tidal and subtidal exchange of water between Prince William Sound and the adjacent continental shelf in the northern Gulf of Alaska. Velocity profiles were used to quantify the exchange in terms of a transport through each of the two largest passages: Montague Strait and Hinchinbrook Entrance. Buoy wind and atmospheric pressure observations, as well as bottom pressure records, are then used to elucidate the role of atmospheric forcing on the exchange.An EOF analysis shows that the barotropic component accounts for 62% or more of the variance in the velocity profiles even after tides are removed by low-pass filtering, and thus the analysis is concerned primarily with depth-integrated transport. The estimated depth-integrated transport can reach ±0.6 Sv in Montague Strait, and ±1.5 Sv in Hinchinbrook Entrance. The largest fluctuations occur in response to the semidiurnal tides. Transport variations on subtidal time scales, which can reach −0.2 Sv in Montague Strait, and +0.6 Sv in Hinchinbrook Entrance, are shown by a frequency domain analysis to be dominated by easterly wind stress events which occur at periods of 2–5 days in both summer and winter. Atmospheric pressure has much less impact on transport, but there is some evidence that it might play a small role on time scales of a few weeks.Bottom pressure records suggest that easterly wind events set up a sea level height gradient in Hinchinbrook Entrance such that it tilts up to the east, which under geostrophy drives a barotropic flow into Prince William Sound. The same winds also raise the sea level in Hinchinbrook Entrance relative to Montague Strait, encouraging an outflow there in agreement with the ADCP observations. There is no evidence that the wind drives a vertically sheared bi-directional flow in either entrance, as has been observed in some estuaries. It is hypothesized that the lack of such a flow is possible because Prince William Sound has two major connections to the shelf, which alters the mass conservation requirement for each passage when compared to a system with just one entrance. 相似文献
170.
Introduced species may outcompete or hybridize with native species, resulting in the loss of native biodiversity or even alteration of ecosystem processes. In this study, we reported an alien distromatic Ulva species, which was found in an embayment (Holly Pond) connected with Long Island Sound, USA. The morphological and anatomical observations in combination with molecular data were used for its identification to species. Anatomy of collected specimens showed that the cell shape in rhizoidal and basal regions was round and the marginal teeth along the basal and median region were not found. These characteristics were primarily identical to the diagnostic characteristics of Ulva laetevirens Areschoug (Chlorophyta). The plastid-encoding tufA and nucleusencoding ITS1 were used for its molecular identification. Phylogenetic analysis for the tufA gene placed the specimens from Holly Pond in a well-supported clade along with published sequences of U. laetevirens identified early without any sequence divergence. In ITS tree, the sample also formed well-supported clades with the sequences of U. laetevirens with an estimated sequence divergence among the taxa in these clades as low as 1%. These findings confirmed the morpho-anatomical conclusion. Native to Australia, this species was reported in several countries along the Mediterranean coast after the late of 1990s. This is the first time that U. laetevirens is found in the northeast coast of United States and the second record for Atlantic North America. 相似文献