共查询到10条相似文献，搜索用时 46 毫秒
1.
提出直接由MATLAB读入光纤端面图实现复杂结构光子晶体光纤(PCF)模型的快速建立,并综合平面波法(PWM)和频域有限差分(FDFD)法,模拟分析带隙型光子晶体光纤(PBG-PCF)的带隙和模场分布.利用PWM计算得到了在PBG-PCF中传输的光波频率及模式有效折射率范围;基于FDFD法在给定波长及模式有效折射率范围情况下,模拟得到了PBG-PCF中可能存在的模场分布及其他特性.以市售的PBG-PCF为例,验证了数值模拟的正确性,随后系统地分析了结构参数(晶格结构、"原子"占有率、背景材料折射率及"原子 相似文献
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利用INSTANT(The International Nusantara Stratification and Transport,努沙登加拉层结及输运的国际联合观测计划)计划所测得的流场数据,研究了ITF(Indonesian Throughflow,印度尼西亚贯穿流)在主要流出海峡——龙目海峡(Lombok Strait)、翁拜海峡(Ombai Strait)和帝汶海峡(Timor Passage)随深度和时间的变化,并对表层和温跃层的流速进行了功率谱分析。研究发现,ITF流场在龙目和翁拜海峡表层有显著的年循环,在季风转换期间各个层次上海流都会出现反转,从印度洋流向海峡内;而帝汶海峡在300m以下出现反转流。3个海峡的表层流都以年周期为主,温跃层的流以半年变化为主,并且都有丰富的季节内变化。高频部分,除了在龙目海峡表层K1日潮占优外,各海峡均以M2半日潮为主。 相似文献
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A chemoreduction-purge-and-trap gas chromatographic method has been developed for the determination of trace dimethylsulfoxide (DMSO) in seawater. In the analysis procedure, DMSO was first reduced to dimethylsufide (DMS) by sodium borohydride and then the produced DMS was analyzed using the purge-and-trap technique coupled with gas chromatographic separation and flame photometric detection. Under the optimum conditions, 97% DMSO was reduced in the standard solution samples with a standard deviation of 5% (n=5). The detection limit of DMSO was 2.7 pmol of sulfur, corresponding to a concentration of 0.75 nmol/L for a 40 ml sample. This method was applied to determine the dissolved DMSO (DMSOd) and particulate DMSO (DMSOp) concentrations in the surface seawater of the Jiaozhou Bay, and the results showed that the DMSOd and DMSOp concentrations varied from 16.8 to 921.1 nmol/L (mean:165.2 nmol/L) and from 8.0 to 162.4 nmol/L (mean:57.7 nmol/L), respectively. The high concentrations of DMSOp were generally found in productive regions. Consequently, a significant correlation was found between the concentrations of DMSOp and chlorophyll a, suggesting that phytoplankton biomass might play an important role in controlling the distribution of DMSOp in the bay. Moreover, in the study area, the concentrations of DMSOd were significantly correlated with the levels of DMS, implying that the production of DMSOd is mainly via photochemical and biological oxidation of DMS. 相似文献
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The distributions of DMS and its precursor dimethylsulfoniopropionate, in both dissolved (DMSPd) and particulate fractions (DMSPp) were determined in the sea-surface microlayer and corresponding subsurface water of the Jiaozhou Bay, China and its adjacent area in May and August 2006. The concentrations of all these components showed a clear seasonal variation, with higher concentrations occurring in summer. This can be mainly attributed to the higher phytoplankton biomass observed in summer. Simultaneously, the enrichment extents of DMSPd and DMSPp in the microlayer also exhibited seasonal changes, with higher values in spring and lower ones in summer. Higher water temperature and stronger radiant intensity in summer can enhance their solubility and photochemical reaction in the microlayer water, reducing their enrichment factors (the ratio of concentration in the microlayer to that in the corresponding subsurface water). A statistically signi.cant relationship was found between the microlayer and subsurface water concentrations of DMS, DMSP and chlorophyll a, demonstrating that the biogenic materials in the microlayer come primarily from the underlying water. Moreover, our data show that the concentrations of DMSPp and DMS were signi.cantly correlated with the levels of chlorophyll a, indicating that phytoplankton biomass might play an important role in controlling the distributions of biogenic sulfurs in the study area. The ratios of DMS/chlorophyll a and DMSPp/chlorophyll a varied little from spring to summer, suggesting that there was no obvious change in the proportion of DMSP producers in the phytoplankton community. The mean sea-to-air .ux of DMS from the study area was estimated to be 5.70 μmol/(m2 ·d), which highlights the e.ects of human impacts on DMS emission. 相似文献
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Multivariate analysis of fluorescence and source identification of dissolved organic matter in Jiaozhou Bay, China 总被引：1，自引：0，他引：1
Hierarchical clustering analysis and principal component analysis (PCA) methods were used to assess the similarities and dissimilarities of the entire Excitation-emission matrix spectroscopy (EEMs) data sets of samples collected from Jiaozhou Bay, China. The results demonstrate that multivariate analysis facilitates the complex data treatment and spectral sorting processes, and also enhances the probability to reveal otherwise hidden information concerning the chemical characteristics of the dissolved organic matter (DOM). The distribution of different water samples as revealed by multivariate results has been used to track the movement of DOM material in the study area, and the interpretation is supported by the results obtained from the numerical simulation model of substance tracing technique, which show that the substance discharged by Haibo River can be distributed in Jiaozhou Bay. 相似文献
7.
This paper presents an evaluation method for green jack-up drilling platform(GJDP) design scheme based on the improved grey correlation analysis(IGCA). Under the situation of the low-carbon economy it is important and complicated for jack-up drilling platform design to select the optimum design scheme from the feasible schemes. In this paper, the evaluation index system for GJDP has been proposed which includes 3 factors: advanced technology, economic feasibility and environmental coordination, as well as 13 sub-indices. At the same time, a multi-objective combinatorial optimization model is established by using IGCA, in which the analysis hierarchy process (AHP) is used to obtain the weight values of the indices. The IGCA method is fully considered the connection of the indices reflecting the objective true nature of the things, and the subjective interest of the platform owner and the needs of the designer. This research can not only conduct to green design of jack-up drilling platform, but also can contribute to the development, popularization and application of low-carbon technology on offshore platform. Finally, the case study results demonstrate the feasibility and efficiency of the proposed evaluation method. 相似文献
8.
《Marine Policy》2017
As increasingly large extents of the global oceans are being managed through spatial measures, it is important to identify area characteristics underlying network distributions. Studies discerning spatial patterns in marine management have disproportionately focused on global networks. This paper instead considers the single country context of Japan to illuminate within-country drivers of area-based conservation and fishery management. A dataset containing potentially relevant socioeconomic, environmental, and fisheries factors was assembled and used to model prefecture-level counts of marine protected areas (MPAs) and territorial use rights for fisheries (TURFs) throughout Japan's waters. Several factors were found to significantly influence the number of TURFs in a particular area, whereas MPA patterns of use remain largely unexplained. TURFs are frequently noted as more suitable for managing fisheries of low mobility species and our analysis finds greater use of TURFs in areas that rely heavily on benthic catch. The number of trading ports was also found to be positively related to TURF distributions, suggesting economic infrastructure may influence the use of this fisheries management tool. In-line with global analyses, MPA patterns of use were not found to be significantly related to any of the potential explanatory variables after correcting for the number of statistical comparisons that were carried out. Differences in our ability to model the use of TURFs and MPAs may arise due to the narrower objectives associated with the former (e.g., income, employment) in comparison to the often broad and varied goals that motivate use of the latter. 相似文献
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在快速滤波分解信号为最宽带通本征模态函数方法（简称FFDSI方法）的基础上，引入了主控模态函数的概念。将其应用于Chichijima水文站水位信号，从中分解出3个96．93％-主控模态函数，分别代表着不同于调和分潮，且与天体运行规律更加吻合的3种模态潮型。由此可见，主控模态函数在信号分析中的应用价值。 相似文献
10.
The four-dimensional variational assimilation (4D-Var) has been widely used in meteorological and oceanographic data assimilation. This method is usually implemented in the model space, known as primal approach (P4D-Var). Alternatively, physical space analysis system (4D-PSAS) is proposed to reduce the computation cost, in which the 4D-Var problem is solved in physical space (i.e., observation space). In this study, the conjugate gradient (CG) algorithm, implemented in the 4D-PSAS system is evaluated and it is found that the non-monotonic change of the gradient norm of 4D-PSAS cost function causes artificial oscillations of cost function in the iteration process. The reason of non-monotonic variation of gradient norm in 4D-PSAS is then analyzed. In order to overcome the non-monotonic variation of gradient norm, a new algorithm, Minimum Residual (MINRES) algorithm, is implemented in the process of assimilation iteration in this study. Our experimental results show that the improved 4D-PSAS with the MINRES algorithm guarantees the monotonic reduction of gradient norm of cost function, greatly improves the convergence properties of 4D-PSAS as well, and significantly restrains the numerical noises associated with the traditional 4D-PSAS system. 相似文献