A numerical model for estimating groundwater flux from subsurface temperature profiles     

Ashok K. Keshari  Min-Ho Koo 《水文研究》2007,21(25):3440-3448

A simple numerical model is presented for estimating vertical groundwater flux from transient subsurface temperature profiles obtained from field measurements. The model developed utilizes the MacCormack scheme, which is based on the Finite Difference Method (FDM), for solving the governing partial differential equation of convection–diffusion heat transport with appropriate initial and boundary conditions within the subsurface. In order to validate the model, numerical solutions obtained for the study area located in the Nagoka plain, Japan are compared with the published measured data and results obtained by others. Results obtained show good agreement and fit the observed data with a correlation coefficient, R², of 0·88. The estimated groundwater flux is 1·85 × 10⁻⁷ m s⁻¹. Sensitivity analyses were also carried out to investigate the effect of variations in groundwater fluxes, thermal properties and the annual thermal variability due to climatic changes on the transient subsurface temperature profiles and to have a better understanding of the subsurface thermal dynamics. A substantial effect of annual climatic variability is observed on the temporal distributions of temperature depth profiles, and a better estimate of thermal parameters is required to estimate vertical groundwater flux. The largest change in subsurface temperature depth profiles due to groundwater flux over a year is within ± 4 °C. The influence of groundwater flux on subsurface temperature distributions in space and time may be more pronounced in areas where the top of the saturated layer fluctuates considerably. Variation in thermal diffusivity results in temperature change up to ± 1·5% and may cause change in groundwater flux estimate by ± 18%. The model presented has merits over analytical solutions (type curve matching techniques) in terms of suitability and applicability to real field problems, and can be a good asset to hydrological models as quantifying groundwater recharge or deducing it from other quantities, such as rainfall, evapotranspiration and runoff, is often complicated. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Using multiple‐variable indicator kriging to assess groundwater quality for irrigation in the aquifers of the Choushui River alluvial fan     

Cheng‐Shin Jang  Shih‐Kai Chen  Lin Ching‐Chieh 《水文研究》2008,22(22):4477-4489

This work attempted to locate clean and safe groundwater for irrigation use in the Choushui River alluvial fan. Multiple‐variable indicator kriging (MVIK) was adopted to evaluate numerous hydrochemical parameters for a standard of water quality for irrigation in Taiwan. Many hydrochemical parameters in groundwater were distinguished into three main categories—salinity/sodium hazard, nitrogen hazard and heavy metal hazard. Safe and potential hazardous regions of groundwater for irrigation were delineated according to different probabilities estimated by MVIK. The probabilistic results of the classifications gave an opportunity to explore the spatial uncertainty of the hazards and helped government administrators establish a sound policy associated with the development and management of groundwater resources. Analysis of the results indicate that the central distal‐fan and mid‐fan aquifers are the best places to extract clean and safe groundwater for irrigation, and the deep aquifer (exceeding 200 m depth) has wider regions with clean and safe groundwater for irrigation than shallow aquifers. The northern and southern aquifers, with multiple hazards, limit groundwater use for irrigation. Although the proximal‐fan aquifer is a zone of groundwater recharge, the high nitrogen content seriously affects the environment and is not suitable for irrigation use. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Groutability of cement‐based grout with consideration of viscosity and filtration phenomenon     

Jong‐Sun Kim  In‐Mo Lee  Jae‐Hyuk Jang  Hangseok Choi 《国际地质力学数值与分析法杂志》2009,33(16):1771-1797

The groutability depends on the properties of the grout, its injection processes, and on the mechanical properties of the soil formation. During the process of pouring cement‐based grouting into a porous medium, a variation with time occurs in the viscosity of grout suspension. In addition, the particle filtration phenomenon will limit the expansion of the grouted zone because cement particles are progressively stagnant within the soil matrix. In this paper, a closed‐form solution was derived by implementing the mass balance equations and the generalized phenomenological filtration law, which can be used to evaluate the deposition of cement‐based grout in the soil matrix. The closed‐form solution relevant to a particular spherical flow was modified by a step‐wise numerical calculation, considering the variable viscosity caused by a chemical reaction, and the decrease in porosity resulting from grout particle deposition in the soil pores. A series of pilot‐scale chamber injection tests was performed to verify that the developed step‐wise numerical calculation is able to evaluate the injectable volume of grout and the deposition of grout particles. The results of the chamber injection tests concurred well with that of the step‐wise numerical calculation. Based on the filtration phenomenon, a viable approach for estimating the groutability of cement‐based grout in a porous medium was also suggested, which might facilitate a new insight in the design of the grouting process. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

滩涂水边线Landsat-5影像提取方法   总被引：1，自引：0，他引：1  

杨立君  张荣春  姜杰  苗立志  施佳凤 《海洋学报》2021,43(3):146-156

快速获取遥感影像水边线时空变化信息具有重要意义,滩涂水边线提取一直是遥感技术应用的难点问题。水边线在遥感影像上具有独特的空间关系与光谱特征。本文综合使用颜色模型变换法、信息熵计算法、最大类间方差法及边缘检测方法。以长江口崇明东滩为研究区,研究了Landsat-5卫星影像海陆对比度增强及不同尺度下的边缘提取,重点给出了基于热红外波段的水边线空间特征与光谱特征的计算方法,在面向对象技术框架下提出了一种顾及空间关系和光谱特征的遥感影像水边线快速提取方法。实验结果表明:(1)基于最大类间方差法的局部阈值分割法能够自动提取band 6的水边线,水边线连续、完整,空间信息丰富;(2)综合使用最佳指数法、离散度方法及颜色模型变换方法,能够有效增强海陆对比度,基于最大类间方差法的局部自适应Canny算子能够自动检测出增强后遥感影像高精度边缘;(3)利用水边线的空间关系和光谱特征,能够由计算机自动实现水边线的识别与连接工作;(4)本文提出的水边线提取方法速度快、自动化程度高,分别继承了阈值分割法的连续性强的优点和Canny算子定位精度高、细节呈现能力强的优势。研究结果对于海岸带动态变化、陆海相互作用机制、海岸带资源保护与开发及近海工程管理等研究具有重要的参考价值。  相似文献   

Sources of plastic marine debris on beaches of Korea: More from the ocean than the land     

Yong Chang Jang  Jongmyoung Lee  Sunwook Hong  Jong Su Lee  Won Joon Shim  Young Kyoung Song 《Ocean Science Journal》2014,49(2):151-162

Reduction of marine debris requires knowledge of its sources. Sources of plastic marine debris found on six beaches of Korea were estimated. Samples larger than 25 mm were collected from 10 quadrats of 5 × 5 m for each beach in spring 2013. The total 752 items (12,255 g) of debris comprised fiber and fabric (415 items, 6,909 g), hard plastic (120 items, 4,316 g), styrofoam (93 items, 306 g), film (83 items, 464 g), foamed plastic other than styrofoam (21 items, 56 g), and other polymer (20 items, 204 g). With the probable sources allocated to each of 55 debris types, the source of 56% of all the collected debris appeared to be oceanbased and 44% was land-based. Priorities of policy measures to reduce marine debris should be different from regions to regions as the main sources of debris may differ.  相似文献   

Impacts of marine debris on wild animals in the coastal area of Korea     

Sunwook Hong  Jongmyoung Lee  Yong Chang Jang  Young Jun Kim  Hee Jong Kim  Donguk Han  Sang Hee Hong  Daeseok Kang  Won Joon Shim 《Marine pollution bulletin》2013,66(1-2):117-124

Over the last decade, marine debris has become a major factor affecting the coastal ecosystem of Korea. This study compiled information regarding how marine debris impacts wildlife in Korea. Cases of marine debris impacting wildlife were collected from experts of various fields and from local participants through an open access website from February 2010 to March 2012. A total of 21 species were affected by marine debris: 18 species of birds, 2 species of mammals, and 1 species of crustacean. Five threatened or protected species were identified: black-faced spoonbill, finless porpoise, water deer, whooper swan, and greater painted snipe. Recreational fishing gears were the types of debris that most frequently impacted wildlife, especially birds. Black tailed gulls were the most vulnerable species to recreational fishing hooks and lines. Although it was preliminary, this study revealed that recreational fishing activities should be prioritized when managing marine debris in Korea.  相似文献   

Three-dimensional visualization of an emotional map with geographical information systems: a case study of historical and cultural heritage in the Yeongsan River Basin,Korea     

Mun-Hyun Jang 《International journal of geographical information science》2013,27(8):1393-1413

The objective of this study is the production and visualization of an emotional map to reveal the unique emotions inherent to the areas surrounding the Yeongsan River, which is often referred to as ‘the cradle of civilization’ in Korea. The sites selected for this study are the 11 cities and districts (5667.6 km²) that cut across the vast granary in the southeastern region of Korea, near the Yeongsan River. The emotional map was produced by extracting features of historical and cultural heritage distributed throughout this region and by using a geographic information systems program and its functions for spatial analysis. A database was constructed through interviews with locals and Global Positioning System to index 4318 pieces of cultural heritage to achieve the visualization of emotions. Among the 558 historical relics considered for representing the regional culture, 100 with the largest emotional impact were selected. It was determined that loyalty (), justice (), courtesy (), resentment (), and anger () should be the major emotional elements. Methodologically, a set of regional, periodic, historical, and emotional classification codes were first systematized. After subjecting this data to inverse distance weight interpolation and vertical exaggeration coefficients, the three-dimensional emotional map could be visualized.  相似文献   

Photometric behaviour of the Be star EW Lacertae     

Jang Hae Jeong  Chang Won Suh  Il-Seong Nha 《Astrophysics and Space Science》1986,119(1):73-76

The night-to-night and short-term variations inUBV light curves of EW Lac which were made during 1982–1984 at Yonsei University Observatory are discussed. The long-term variability in the photometric behaviour of the star is examined with our own data as well as those of Harmanecet al. (1980).Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.Yonsei University Observatory Contribution No. 23.  相似文献   

Evaluation of seismic displacements of quay walls   总被引：2，自引：0，他引：2  

Sung-Ryul Kim  In-Sung Jang  Choong-Ki Chung  Myoung-Mo Kim   《Soil Dynamics and Earthquake Engineering》2005,25(6):451-459

A new simplified dynamic analysis method is proposed to predict the seismic sliding displacement of quay walls by considering the variation of wall thrust, which is influenced by the excess pore pressure developed in backfill during earthquakes. The method uses the Newmark sliding block concept and the variable yield acceleration, which varies according to the wall thrust, to calculate the quay wall displacement.A series of 1 g shaking table tests were executed to verify the applicability of the proposed method, and a parametric study was performed. The shaking table tests verified that the proposed method properly predicts the wall displacement, and the parametric study showed that the evaluation of a realistic wall displacement is as important as the analysis of liquefaction potential for judging the stability of quay walls.  相似文献   

新疆黑孜断层现今活动特征研究及有关问题的讨论   总被引：3，自引：0，他引：3  

蒋靖祥  温和平  尹光华  刘辉 《中国地震》2001,17(3):246-252

在前人研究的基础上，用近年黑孜水库的形变测量资料重新计算了黑孜断层的微量位移，表明自1973年以来黑孜断层活动特征发生了变化，大致经历了4个阶段；其中第3个阶段有正断层特征，其余3个阶段属逆断层特征。水库大坝的修建及水库的蓄水对断层的现今活动具有重要影响，甚至改变了某个阶段断层活动的性状。地震活动对形变测量资料、断层活动也有一定程度的影响。  相似文献