Temporal variations in productivity and planktonic ecological structure in the East Sea (Japan Sea) since the last glaciation     

Kyung?Eun?LeeEmail author  Jang?Jun?Bahk  Hisashi?Narita 《Geo-Marine Letters》2003,23(2):125-129

We investigated the biogenic components (biogenic opal, calcium carbonate, and organic carbon) of the marine sediments in core TY99PC18 recovered from the southeastern part of the Ulleung Basin, East Sea (Japan Sea). Our results indicate that primary productivity by diatoms increased after the last glaciation (15,000 ¹⁴C years b.p.) probably because of the onset of vertical mixing of seawater and nutrient supply from the deep water. Between 5,000 and 10,000 ¹⁴C years b.p. a shift in the dominant primary producer, i.e. from diatoms to coccolithophores, coincides with decreased productivity, which could be related to the influx of warm, low-nutrient waters at that time. During the late Holocene (after 5,000 ¹⁴C years b.p.) the productivity of diatoms increased once more probably due to renewed ventilation and vertical mixing.  相似文献   

Time-lapse borehole radar monitoring of an infiltration experiment in the vadose zone     

S. Kuroda  H. Jang  H.J. Kim   《Journal of Applied Geophysics》2009,67(4):361

Ground-penetrating radar (GPR) is an effective tool for imaging the spatial distribution of water content. An artificial groundwater recharge test was conducted in Nagaoka City in Japan, and time-lapse crosshole GPR data were collected to monitor the infiltration process in the vadose zone. Since electromagnetic wave velocities in the vadose zone are largely controlled by variations in water content, an increase in traveltime is interpreted as an increase in saturation. In the test zone, the infiltrated water penetrated downward with an average velocity of about 2.7 m/h. A finite-difference time-domain method using two-dimensional cylindrical coordinates is applied to simulate radargrams associated with the advancing wetting front and to quantify the effects of critical refraction. Standard zero-offset profiling for which all first-arrivals are assumed to be direct waves results in an underestimation of water content in the transition zone above the wetting front. As a result, correct velocity analysis requires identification of first-arriving critically refracted waves from the traveltime profile to accurately determine a water content profile.  相似文献   

由多震相走时和波形作三维地震成像   总被引：1，自引：1，他引：0  

金昭九  李清河  Jung-in Lee  Ho Sung Jang 《CT理论与应用研究》2000,9(4):44-47

本项成果包括：提出天然地震走时反演层析成像技术,采用下列方法使得处理结果得以改善：１）利用３２个地震,４０４条射线的Ｐｇ,Ｓｇ,Ｐｍ,Ｓｍ,Ｐｎ,Ｓｎ等震相增加约束条件：２）用已有精度较高的人工地震测深化结果作速度约束;３）用波形反演来修改模型,把波源,介质吸收,散射等物理特征集中反映在记录中,把诸多物理量开发出来互为约束,以修改后的模型再作反演,使解的稳定性大大提高;４）采用最优化过程,选择遗传  相似文献   

Advances in computational morphodynamics using the International River Interface Cooperative (iRIC) software     

Yasuyuki Shimizu  Jonathan Nelson  Kattia Arnez Ferrel  Kazutake Asahi  Sanjay Giri  Takuya Inoue  Toshiki Iwasaki  Chang-Lae Jang  Taeun Kang  Ichiro Kimura  Tomoko Kyuka  Jagriti Mishra  Mohamed Nabi  Supapap Patsinghasanee  Satomi Yamaguchi 《地球表面变化过程与地形》2020,45(1):11-37

Results from computational morphodynamics modeling of coupled flow–bed–sediment systems are described for 10 applications as a review of recent advances in the field. Each of these applications is drawn from solvers included in the public-domain International River Interface Cooperative (iRIC) software package. For mesoscale river features such as bars, predictions of alternate and higher mode river bars are shown for flows with equilibrium sediment supply and for a single case of oversupplied sediment. For microscale bed features such as bedforms, computational results are shown for the development and evolution of two-dimensional bedforms using a simple closure-based two-dimensional model, for two- and three-dimensional ripples and dunes using a three-dimensional large-eddy simulation flow model coupled to a physics-based particle transport model, and for the development of bed streaks using a three-dimensional unsteady Reynolds-averaged Navier–Stokes solver with a simple sediment-transport treatment. Finally, macroscale or channel evolution treatments are used to examine the temporal development of meandering channels, a failure model for cantilevered banks, the effect of bank vegetation on channel width, the development of channel networks in tidal systems, and the evolution of bedrock channels. In all examples, computational morphodynamics results from iRIC solvers compare well to observations of natural bed morphology. For each of the three scales investigated here, brief suggestions for future work and potential research directions are offered. © 2019 The Authors Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd  相似文献   

Spatiotemporal Distribution of Dissolved Heavy Metals in Gyeonggi Bay,Korea     

Sojung Park  Mansik Choi  Dongjun Jang  Dongjin Joe  Kyunggue Park  Hyojin Lee  Junsik Woo  Taeha Kim  Jongkyu Park 《Ocean Science Journal》2020,55(1):69-84

In this study, we investigated the spatial and temporal distribution of heavy metals and nutrients in Gyeonggi Bay, Korea, to determine their present statu  相似文献   

Molecular and Morphometric Variations in the Sea Raven,Hemitripterus villosus from Korea,with its Implication on Fisheries Management     

Jang  Seo-Ha  Lee  Jang-Won  Kim  Jin-Koo 《Ocean Science Journal》2019,54(3):419-433

Ocean Science Journal - To understand and clarify the geographic variations of the Korean sea raven, Hemitripterus villosus, we investigated the molecular and morphometric characteristics of 147...  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   

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   

Integrated Data Assimilation and Distance-Based Model Selection with Ensemble Kalman Filter for Characterization of Uncertain Geological Scenarios     

Lim  Seojin  Park  Changhyup  Kim  Jaejun  Jang  Ilsik 《Natural Resources Research》2020,29(2):1063-1085

Natural Resources Research - This paper develops a reliable workflow for multi-objective history matching coupled with a distance-based model selection and ensemble-based data assimilation at a...  相似文献