Role of Nitrogen Oxides,Black Carbon,and Meteorological Parameters on the Variation of Surface Ozone Levels at a Tropical Urban Site – Hyderabad,India

In this study, temporal variations of surface ozone (O₃) were investigated at tropical urban site of Hyderabad during the year 2009. O₃, oxides of nitrogen (NO_x = NO + NO₂), black carbon (BC), and meteorological parameters were continuously monitored at the established air monitoring station. Results revealed the production of surface O₃ from NO₂ through photochemical oxidation. Averaged datasets illustrated the variations in ground‐level concentrations of these air pollutants along different time scales. Maximum mean concentrations of O₃ (56.75 ppbv) and NO_x (8.9 ppbv) were observed in summer. Diurnal‐seasonal changes in surface O₃ and NO_x concentrations were explicated with complex atmospheric chemistry, boundary layer dynamics, and local meteorology. In addition, nocturnal chemistry of NO_x played a decisive role in the formation of O₃ during day time. Mean BC mass concentration in winter (10.92 µg m^?3) was high during morning hours. Heterogeneous chemistry of BC on O₃ destruction and NO_x formation was elucidated. Apart from these local observations, long‐range transport of trace gases and BC aerosols were evidenced from air mass back trajectories. Further, statistical modeling was performed to predict O₃ using multi‐linear regression method, which resulted in 91% of the overall variance.     

关于龙游石窟4号洞4-2号岩柱长期抗剪强度反分析问题的讨论

对于地下工程来说,围岩的长期抗剪强度从来是工程设计者和研究者所关心的课题。但历来仅根据持续时间十分 有限的试验来确定。因此从某种意义上说,由这类试验所得到的,并非真正意义上的长期抗剪强度。所以,本文提出的根据 龙游大型古地下工程即龙游石窟岩柱(包括柱础)的剪坏现象反算岩柱的长期抗剪强度的成果,是很有理论价值的。本文将 以龙游石窟4号洞的4-2号岩柱为对象作古地下工程岩柱长期抗剪强度的反演研究。为了在反演中能进一步考虑剪切面上 各部位的应力变化,作者还借助于FLAC-3D分析结果对不同部分分别进行研究,从而取得了较好的反演结果。     

A Practical Indirect Back Analysis Approach for Geomechanical Parameters Identification

Back analysis is a powerful tool to determine geomechanical parameters. In this article, a practical approach that employs the response surface method and MS Excel solver for back analysis is presented. The least square support vector machine (LSSVM)-based response surface is utilized to represent the nonlinear relationship between the geomechanical parameters and the monitored information and Excel solver is used to search the geomechanical parameters based on the monitoring information. We analyze the robustness and search ability of the proposed approach. On the other hand, two numerical cases on a circular tunnel and a slope are used to verify the proposed approach. Results clearly indicate that LSSVM-based response surface is effectively able to be used to identify the geomechanical parameters from the monitoring displacements.     

多层球状物角度稀疏投影CT重建仿真研究

本文主要针对高密度差多层球状物体的角度稀疏投影CT重建问题,进行基于FBP算法的仿真研究。参考特殊工件材料结构特征设计建立检测对象模型,采用C＋＋语言开发完成平行束圆周扫描FBP重建仿真软件平台。分别采用直接补零和紧邻填充两种方法补全缺失的稀疏投影数据,并进行仿真重建和比较分析。对重建图像进行了有针对性地基于边缘和区域的增强处理方法研究,使缺陷特征得以凸显。本文的研究内容和方法可为具有类似特征的CT无损检测提供技术参考。     

The influence of air mass source on the seasonal isotopic composition of precipitation, eastern USA

As part of the AIRMoN program, daily precipitation samples have been collected since the early 1990s throughout the eastern and central United States. Using precipitation stable isotope (δ¹⁸O and δD) and HYSPLIT back trajectory analysis of 591 samples collected by the AIRMoN program from Florida, Illinois, Pennsylvania, Tennessee, Vermont, and West Virginia, amount weighted seasonal average isotopic compositions were calculated for precipitation from Continental, Pacific, Gulf of Mexico, Arctic, North Atlantic, and Mid Atlantic sources. Our results suggest that these sources are isotopically distinct and variable at and among most sites during most seasons. However, in many instances, the isotopic differences of the sources require dramatic changes in precipitation amounts from these sources to modify the seasonal average isotopic composition at a particular site. The relative importance of each source type to the seasonal average isotopic composition is highly variable among and within sites. The largest differences in the isotopic compositions of different sources are in winter and spring precipitation from the high latitude sites. At the Vermont location, the seasonal average isotopic composition is potentially quite sensitive to the relative amounts of precipitation from Arctic and Gulf of Mexico sources.     

龙游牛场古地下洞室群岩柱的长期抗拉强度反演

在龙游县上畈村附近的牛场有一处由2个洞室组成的古地下洞室群。现场调查发现,在其中1号洞的岩柱1上出现了一条竖直的张开裂缝。据分析,这是上覆岩层对该岩柱施加过大荷载的结果,这一发现为本文研究岩体长期抗拉强度提供了条件。作者即以根据牛场古地下洞室群1号洞内岩柱1的拉裂现象为研究对象,根据最大拉应力论来反演岩体的长期抗拉强度。这不仅对长期强度研究具有理论意义,而且在古工程保护方面也具有应用价值。     

The distribution of meiofauna on back‐reef sandy platforms in the Maldives (Indian Ocean)

The Maldivian archipelago comprises some of the most characteristic and significant world atoll systems, but the meiobenthic assemblages of these islands continue to be largely unknown. To investigate variations in meiofaunal spatial distribution and biodiversity in back‐reef platforms, three transects were studied, two at Felidhoo (the north and east sides) and one at South Malé. The sedimentological features of the samples obtained were also analyzed to further current knowledge on the relationships that exist between sediments and meiofauna. Our results reveal that the meiofaunal assemblage at these locations is well diversified and includes 20 major taxa. Nematodes and copepods are dominant, together forming 68% of the total meiofauna, followed by platyhelminthes, polychaetes and ostracods. The nematode assemblage is very rich and composed of 34 families and 123 genera – 96 of which (78%) set new records for the Maldives. The structures of the meiofaunal and nematode assemblages are relatively similar on the ‘large‐scale’ level (i.e. when the different platforms are compared) and reveal a low β‐diversity. However, significant dissimilarities were detected within each platform, emphasizing that such ‘small‐scale’ differences are the main factors determining the structure of the meiofauna and, in particular, the nematode assemblages. Although significant differences were not detected between the transects, greater levels of dissimilarity were recognized at North Felidhoo. Here, the building of inclined deposit layers plays a significant role in increasing the heterogeneity of the platform habitats and sediments, confirming the great importance of sediment granulometry as an environmental variable. Indeed, a close relationship is observed between meiofauna (especially for the nematodes) and grain size, which appears to control the structure, diversity and trophic composition of the Maldivian meiofauna assemblages, thus highlighting the high biodiversity existing in the medium‐coarse sands.     

Using statistical and artificial neural network models to forecast potentiometric levels at a deep well in South Texas

Reliable forecasts of monthly and quarterly fluctuations in groundwater levels are necessary for short- and medium-term planning and management of aquifers to ensure proper service of seasonal demands within a region. Development of physically based transient mathematical models at this time scale poses considerable challenges due to lack of suitable data and other uncertainties. Artificial neural networks (ANN) possess flexible mathematical structures and are capable of mapping highly nonlinear relationships. Feed-forward neural network models were constructed and trained using the back-percolation algorithm to forecast monthly and quarterly time-series water levels at a well that taps into the deeper Evangeline formation of the Gulf Coast aquifer in Victoria, TX. Unlike unconfined formations, no causal relationships exist between water levels and hydro-meteorological variables measured near the vicinity of the well. As such, an endogenous forecasting model using dummy variables to capture short-term seasonal fluctuations and longer-term (decadal) trends was constructed. The root mean square error, mean absolute deviation and correlation coefficient (R) were noted to be 1.40, 0.33 and 0.77 m, respectively, for an evaluation dataset of quarterly measurements and 1.17, 0.46, and 0.88 m for an evaluative monthly dataset not used to train or test the model. These statistics were better for the ANN model than those developed using statistical regression techniques.     

Retrieval study of lake water depth by using multi-spectral remote sensing in Bangong Co Lake

This paper reviewed studies on remote sensing of water depth retrieval. Four water depth retrieval models （single-band, dou- ble-ratio-band, multi-band, and BP network models） were evaluated using TM image and water data from Bangong Co Lake, which is located in China＇s Tibet Autonomous Region and Indian Kashmir. Tested by independent data, comparison of these four models demonstrates that BP network model performed better than the multi-band model, with the single-band model performing the worst. To sum up, this study demonstrates that first, BP network model performed better than the traditional model; second, precise atmospheric correction and radiation study, affected by different water level sand sediment, could improve the precision of water depth retrieval.     

GPS无线电掩星后向传播方法

在大气多路径传播条件下,讨论了两种无线电信号的反演方法:几何光学方法和后向传播方法.当大气存在多路径效应时,采用几何光学方法反演大气参数会引入较大误差.后向传播方法将无线电信号从多路径区域反推至单路径区域,减少了大气多路径效应的影响.为了比较不同的反演方法,利用多相位屏模型,数值模拟了大气多路径条件下无线电信号在大气中...