• Title/Summary/Keyword: JUMP

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Numerical Simulation of Depth-Averaged Flow with a CDG Finite Element Method (CDG 유한요소법을 이용한 수심적분 흐름의 수치모의)

  • Kim, Tae Beom;Choi, Sung-Uk;Min, Kyung Duck
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.5B
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    • pp.447-457
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    • 2006
  • This paper presents a numerical model for the simulations of 2D depth-averaged flows. The shallow water equations are solved numerically by the Characteristic Dissipative Galerkin (CDG) finite element method. For validation, the developed model is applied to the hydraulic jump. The computed results are compared with the analytical solution, revealing good agreement. In addition, flow in a contracting channel showing standing waves is simulated. The calculated water surface profile appears to be qualitatively consistent with the observed data. The foregoing results indicate that the model is capable of simulating the abrupt change in flow field. Next, the model is applied to the flow in a $180^{\circ}$ curved channel. The simulated results show that the velocity near the inner bank is faster than that near the outer bank and the water depth near the inner bank is shallower than that near the outer bank. However, the simulated results show that the velocity distribution across the channel is almost uniform in the bend except the reach close to the end of the bend. This is due to the limitation of the governing equations in which the transverse convection of momentum by the secondary flows along a channel bend is not taken into account.

Identifying Three-Dimensional Hydraulic Characteristics of the Sea Region Under Combined Tidal Current and Shock Waves (조류와 충격파가 혼재한 해역의 3차원적 수리특성 분석)

  • Kang, Min Goo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.4B
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    • pp.339-346
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    • 2009
  • In this study, the flow characteristics of the sea region, where tidal current and shock waves are combined, are identified using a three-dimensional numerical model (Princeton Ocean Model, POM). The model is adopted and applied for simulating the flows of the sea region near the open sections during the seadike closure work of Sihwa Seadike which was closed in 1994. The simulation results show that the shock waves with high velocities propagate through the sections toward the inside and outside of the seadike during the periods of the spring and ebb tides, respectively. It is found that the phenomena of flow separation occur near the shock waves; as the shock waves extend to wider zones after passing the sections, their effects on the tidal current become weak. In addition, the longitudinal velocity profiles of the flows are revealed to be affected by the shock waves. For all the simulations, at the ebb tide, the drawdown of the water levels occurs in front of the open section, respectively, especially, hydraulic jump occurs when simulating the case of maximum difference in water level between the inside and outside of the seadike. As a result, it is thought that the flow characteristics of the sea region dominated by shock waves need to be identified employing three-dimensional analysis approach, which is expected to provide the information for ocean engineering works and facility management.

Development of 3-D Nonlinear Wave Driver Using SPH (SPH을 활용한 3차원 비선형 파랑모형 개발)

  • Cho, Yong Jun;Kim, Gweon Soo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.5B
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    • pp.559-573
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    • 2008
  • In this study, we newly proposed 3-D nonlinear wave driver utilizing the Navier-Stokes Eq. the numerical integration of which is carried out using SPH (Smoothed Particle Hydrodynamics), an internal wave generation with the source function of Gaussian distribution and an energy absorbing layer. For the verification of new 3-D nonlinear wave driver, we numerically simulate the sloshing problem within a parabolic water basin triggered by a Gaussian hump and uniformly inclined water surface by Thacker (1981). It turns out that the qualitative behavior of sloshing caused by relaxing the external force which makes a free surface convex or uniformly inclined is successfully simulated even though phase error is visible and an inundation height shrinks as numerical simulation more proceeds. For the more severe test, we also simulate the nonlinear shoaling and refraction over uniform beach of wedge shape. It is shown that numerically simulated waves are less refracted than the linear counterpart by Hamiltonian ray theory due to nonlinearity, energy dissipation at the bottom and side walls, energy loss induced by breaking, and the hydraulic jump occurring when breaking waves encounter a down-rush by the preceding wave.

Retrospect and Prospect of Economic Geography in Korea (한국 경제지리학의 회고와 전망)

  • Lee, Won-Ho;Lee, Sung-Cheol;Koo, Yang-Mi
    • Journal of the Korean Geographical Society
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    • v.47 no.4
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    • pp.522-540
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    • 2012
  • The main aim of the paper is to identify the position or status of Korean economic geography in changing global economic geography by reviewing papers published in Korean geographical journals since the mid-1950s. Since the late 20th century as economic geography has developed significantly with the introduction of new research issues, methodologies, and theory and concepts, economic geography in Korea also has gone through rapid development in terms of both quantitative and qualitative perspectives. The paper attempts to analyze trends in Korean economic geography by reviewing agricultural, industrial, commercial geographies, and others since the mid-1950s. The review of economic geography in Korea would be based on four periods classified by research issues and approaches; foundation (~1950s), positioning (1960s and 1970s), jump and rush (1980s and mid-1990s), and transitional period (late 1990s~). Agricultural geography in Korea has decreased due to increases of the interests in industrial geography since the 1980s. In particular, since the late 1990s industrial geography has undergone a significant transition in accordance with the emergence of new theories of institutional perspectives, centering around issues on value chains, innovative cluster, cooperative and competitive networks, foreign direct investment, flexible specialization and venture ecology. Along with this, there has been changes in the interest of commercial geography in Korea from researches on periodical markets, the structure of store formats, and distributions by commodity, to researches on producer services and retailer's locational behaviors and commercial supremacy according to the emergence of new store formats. Since the late 1990s, many researches and discussions associated with the new economic geography began to emerge in Korea. Various research issues are focused on analyzing changes of local, regional and global economic spaces and their processes in relation to institutional perspectives, knowledge and innovation, production chain and innovative networks, industrial clusters and RIS, and geographies of service. Although economic geography in Korea has developed significantly both in quantitative and qualitative perspectives, we pointed out that it has still limited in some specific scope and issues. Therefore, it is likely to imply that its scope and issues should be diversified with new perspectives and approaches.

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PRC Maritime Operational Capability and the Task for the ROK Military (중국군의 해양작전능력과 한국군의 과제)

  • Kim, Min-Seok
    • Strategy21
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    • s.33
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    • pp.65-112
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    • 2014
  • Recent trends show that the PRC has stepped aside its "army-centered approach" and placed greater emphasis on its Navy and Air Force for a wider range of operations, thereby reducing its ground force and harnessing its economic power and military technology into naval development. A quantitative growth of the PLA Navy itself is no surprise as this is not a recent phenomenon. Now is the time to pay closer attention to the level of PRC naval force's performance and the extent of its warfighting capacity in the maritime domain. It is also worth asking what China can do with its widening naval power foundation. In short, it is time to delve into several possible scenarios I which the PRC poses a real threat. With this in mind, in Section Two the paper seeks to observe the construction progress of PRC's naval power and its future prospects up to the year 2020, and categorize time frame according to its major force improvement trends. By analyzing qualitative improvements made over time, such as the scale of investment and the number of ships compared to increase in displacement (tonnage), this paper attempts to identify salient features in the construction of naval power. Chapter Three sets out performance evaluation on each type of PRC naval ships as well as capabilities of the Navy, Air Force, the Second Artillery (i.e., strategic missile forces) and satellites that could support maritime warfare. Finall, the concluding chapter estimates the PRC's maritime warfighting capability as anticipated in respective conflict scenarios, and considers its impact on the Korean Peninsula and proposes the directions ROK should steer in response. First of all, since the 1980s the PRC navy has undergone transitions as the focus of its military strategic outlook shifted from ground warfare to maritime warfare, and within 30 years of its effort to construct naval power while greatly reducing the size of its ground forces, the PRC has succeeded in building its naval power next to the U.S.'s in the world in terms of number, with acquisition of an aircraft carrier, Chinese-version of the Aegis, submarines and so on. The PRC also enjoys great potentials to qualitatively develop its forces such as indigenous aircraft carriers, next-generation strategic submarines, next-generation destroyers and so forth, which is possible because the PRC has accumulated its independent production capabilities in the process of its 30-year-long efforts. Secondly, one could argue that ROK still has its chances of coping with the PRC in naval power since, despite its continuous efforts, many estimate that the PRC naval force is roughly ten or more years behind that of superpowers such as the U.S., on areas including radar detection capability, EW capability, C4I and data-link systems, doctrines on force employment as well as tactics, and such gap cannot be easily overcome. The most probable scenarios involving the PRC in sea areas surrounding the Korean Peninsula are: first, upon the outbreak of war in the peninsula, the PRC may pursue military intervention through sea, thereby undermining efforts of the ROK-U.S. combined operations; second, ROK-PRC or PRC-Japan conflicts over maritime jurisdiction or ownership over the Senkaku/Diaoyu islands could inflict damage to ROK territorial sovereignty or economic gains. The PRC would likely attempt to resolve the conflict employing blitzkrieg tactics before U.S. forces arrive on the scene, while at the same time delaying and denying access of the incoming U.S. forces. If this proves unattainable, the PRC could take a course of action adopting "long-term attrition warfare," thus weakening its enemy's sustainability. All in all, thiss paper makes three proposals on how the ROK should respond. First, modern warfare as well as the emergent future warfare demonstrates that the center stage of battle is no longer the domestic territory, but rather further away into the sea and space. In this respect, the ROKN should take advantage of the distinct feature of battle space on the peninsula, which is surrounded by the seas, and obtain capabilities to intercept more than 50 percent of the enemy's ballistic missiles, including those of North Korea. In tandem with this capacity, employment of a large scale of UAV/F Carrier for Kill Chain operations should enhance effectiveness. This is because conditions are more favorable to defend from sea, on matters concerning accuracy rates against enemy targets, minimized threat of friendly damage, and cost effectiveness. Second, to maintain readiness for a North Korean crisis where timely deployment of US forces is not possible, the ROKN ought to obtain capabilities to hold the enemy attack at bay while deterring PRC naval intervention. It is also argued that ROKN should strengthen its power so as to protect national interests in the seas surrounding the peninsula without support from the USN, should ROK-PRC or ROK-Japan conflict arise concerning maritime jurisprudence. Third, the ROK should fortify infrastructures for independent construction of naval power and expand its R&D efforts, and for this purpose, the ROK should make the most of the advantages stemming from the ROK-U.S. alliance inducing active support from the United States. The rationale behind this argument is that while it is strategically effective to rely on alliance or jump on the bandwagon, the ultimate goal is always to acquire an independent response capability as much as possible.

The Waveform and Spectrum analysis of Tursiops truncatus (Bottlenose Dolphin) Sonar Signals on the Show at the Aquarium (쇼 학습시 병코돌고래 명음의 주파수 스펙트럼 분석)

  • 윤분도;신형일;이장욱;황두진;박태건
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.36 no.2
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    • pp.117-125
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    • 2000
  • The waveform and spectrum analysis of Tursiops truncatus(bottlenose dolphin) sonar signals were carried out on the basis of data collected during the dolphin show at the aquarium of Cheju Pacificland from October 1998 to February 1999. When greeting to audience, the pulse width, peak frequency and spectrum level from the five dolphins'sonar signals were 3.0ms, 4.54kHz and 125.6dB, respectively. At the time of warm-up just before the show, their figures were 5.0㎳, 5.24kHz and 127.0dB, respectively. During the performance of dolphins, with singing, peak frequency ranged 3.28∼5.78kHz and spectrum level ranged 137.0∼142.0dB. With playing ring, pulse width, peak frequency and spectrum level were 7.0㎳, 2.54kHz and 135.9dB, and when playing the ball, the values were 9.0㎳, 2.78kHz and 135.2dB, respectively. The values determined from the five dolphins during jump-up out of water were : pulse width 2.0㎳, peak frequency 4.50kHz and spectrum level 126.8dB. When they responded to trainer's instructions, the values were 2.25㎳, 248kHz and 148.7dB, respectively, and greeting to audience, the peak frequency and spectrum level were 5.84kHz and 122.5dB. During swimming under water, peak frequency and spectrum level were determined to be 10.10kHz and 126.8dB. It was found that there exited close consistencies in pulse width, frequency distribution and spectrum level between whistle sounds and dolphin's sonar signals. Accordingly, the dolphins can be easily trained by using whistle sound based on the results obtained from the waveform and spectrum of the dolphin's sonar signals.

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Application of Principle in Metal-Ligand Complexation to Remove Heavy Metals : Effects of Metal Concentration, pH and Temperature (금속(金屬)-Ligand 착염형성(錯鹽形成)에 의한 중금속(重金屬) 제거방법(除去方法)에 관(關)한 연구(硏究) : 중금속(重金屬) 농도(濃度), pH 및 온도(溫度)의 효과(效果))

  • Yang, Jae-E;Shin, Yong-Keon;Kim, Jeong-Je
    • Korean Journal of Soil Science and Fertilizer
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    • v.26 no.1
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    • pp.37-42
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    • 1993
  • Influences of metal concentration, pH and temperature on metal-ligand precipitate formation were investigated, as a part of projects for removing heavy metals from aqueous solution employing the principles in metal-ligand complexation. Aqueous solutions of HA or FA were reacted with those of heavy metals with 1:1 ratio. Efficiency of humic (HA) or fulvic acid (FA) on removing metals was evaluated by separating the precipitates from soltuions with the filtering method. When HA was a counter ligand, there existed three ranges of metal concentrations affecting precipitation : precipitate fromation was not available, was reached to the maximum, and afterwards was decreased again. The concentration ratios of metal to HA for initiating complexation were dependent upon kinds of metal and concentrations of ligand. Amount of Pb to form maximum precipitates per unit mg of HA was 1.3 times higher than that of Cu. When FA was a counter ligand, concentrations of metal-FA precipitates were increased proportionally with the treated metal concentrations. Efficiency of FA fro removing Pb was nearly 100%, but it was ranged from 12 to 19% for Cu, depending on FA concentration. pH exerted a considerable effect on complexation between Pb and FA, showing precipitates were increased six times at most per unit increase of pH. Ranges of pH increasing significantly the mounts of precipitates were coincied with pH jump ranges of the titration curve of organic ligands. As increasing temperature from 15 to $55^{\circ}C$, increases of FA-Cu precipitates were doubled, but those of FA-Pb were accounted for only 6%, However, HA-metal complexation was not affected by temperature.

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Sixty Years History of the Korean Geographical Society as a Numerical Record (숫자로 본 대한지리학회 60년)

  • Hyong, Kie-Joo
    • Journal of the Korean Geographical Society
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    • v.40 no.6 s.111
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    • pp.748-761
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    • 2005
  • This study attempts to describe and periodinate the sixty years history of Korean Geographical Society. For the purpose, several numerical records concerned with the society were employed. The Korean Geographical Society was established in 1945 as a first academic society in geography. The international participation of Korean geographers started when it applied for the IGU membership in 1959. Next year, Korean's application was approved at the 19th IGC in Stockholm. The 40 years later, Korea came to host the 29th IGC in Seoul. This means that the activity of Korean geographers has been vigorous during the 40 years in accordance with high growth of Korean economy. The number of the society member reached 116 in the latter part of 1960s. It grew steadily from 1970s to 1990s and now amounts to around one thousand. It is believed that such trend is associated with the increase of geographical department and the development of graduate programs during past 40 years in Korea. The number of the advanced degree holders was only 2 in 1960, and now reachs 338 among which 166($43\%$) obtained from the foreign country. The Int issue of the society journal 'Geagraphy' -the title was changed to 'Journal of the KGS' in 1993-was published in 1963. It has gradually developed into the annual for $1966{\~}1973$, the semi-annual for $1974{\~}1990$, the quaterly for $1991{\~}1997$, and the hi-monthly until 2005. One issue per year has been published in English since 1993. The annual number of papers accepted by the editorial board has increased from 7 in 1960s-1970s to 52 in the new millennium. In terms of the specialty distribution of total 725 papers after 1963, many Korean geographers have been preferable to the field of socio-economic and urban geography as their major, and next histro-cultural and physical geography. Recently, a growing number of younger geographers are more interested in such diversified fields as ecological geography, socio-historical geography, applied geography concerned with GIS technic, geography education and so on. Such trend is a reflection of the new era which is characterized by diversity, software, high technology, globalization and others. The sixty years history of the society nay be summarized into the five phases of periodization: (1) establishment and chaos($1945{\~}1959$), (2) reconstruction(1960${\~}$1969), (3)reorganization(1970${\~}$1989), (4) jump and rush($1990{\~}1999$), (5)globalization($2000{\~}\;$).

A Study on the Volatility of Global Stock Markets using Markov Regime Switching model (마코브국면전환모형을 이용한 글로벌 주식시장의 변동성에 대한 연구)

  • Lee, Kyung-Hee;Kim, Kyung-Soo
    • Management & Information Systems Review
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    • v.34 no.3
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    • pp.17-39
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    • 2015
  • This study examined the structural changes and volatility in the global stock markets using a Markov Regime Switching ARCH model developed by the Hamilton and Susmel (1994). Firstly, the US, Italy and Ireland showed that variance in the high volatility regime was more than five times that in the low volatility, while Korea, Russia, India, and Greece exhibited that variance in the high volatility regime was increased more than eight times that in the low. On average, a jump from regime 1 to regime 2 implied roughly three times increased in risk, while the risk during regime 3 was up to almost thirteen times than during regime 1 over the study period. And Korea, the US, India, Italy showed ARCH(1) and ARCH(2) effects, leverage and asymmetric effects. Secondly, 278 days were estimated in the persistence of low volatility regime, indicating that the mean transition probability between volatilities exhibited the highest long-term persistence in Korea. Thirdly, the coefficients appeared to be unstable structural changes and volatility for the stock markets in Chow tests during the Asian, Global and European financial crisis. In addition, 1-Step prediction error tests showed that stock markets were unstable during the Asian crisis of 1997-1998 except for Russia, and the Global crisis of 2007-2008 except for Korea and the European crisis of 2010-2011 except for Korea, the US, Russia and India. N-Step tests exhibited that most of stock markets were unstable during the Asian and Global crisis. There was little change in the Asian crisis in CUSUM tests, while stock markets were stable until the late 2000s except for some countries. Also there were stable and unstable stock markets mixed across countries in CUSUMSQ test during the crises. Fourthly, I confirmed a close relevance of the volatility between Korea and other countries in the stock markets through the likelihood ratio tests. Accordingly, I have identified the episode or events that generated the high volatility in the stock markets for the financial crisis, and for all seven stock markets the significant switch between the volatility regimes implied a considerable change in the market risk. It appeared that the high stock market volatility was related with business recession at the beginning in 1990s. By closely examining the history of political and economical events in the global countries, I found that the results of Lamoureux and Lastrapes (1990) were consistent with those of this paper, indicating there were the structural changes and volatility during the crises and specificly every high volatility regime in SWARCH-L(3,2) student t-model was accompanied by some important policy changes or financial crises in countries or other critical events in the international economy. The sophisticated nonlinear models are needed to further analysis.

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The Efficiency and Improvement of the Highway Wild-Life Fences for Decrease of Mammals Road-kill - In Case of Manjong~Hongchun Section on Jungang Highway - (포유류 로드킬 저감을 위한 고속도로 유도울타리 효율성 및 개선방안 연구 - 중앙고속도로 만종~홍천 구간을 사례로 -)

  • Song, Jeong-Seok;Lee, Kyong-Jae;Ki, Kyong-Seok;Jun, Ik-Yo
    • Korean Journal of Environment and Ecology
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    • v.25 no.5
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    • pp.649-657
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    • 2011
  • This study had targeted the Manjong Junction~Hongchun interchange section of Jungang highway in order to analyze the efficiency and improvement of the highway wild-life fences. Being analyzed wild-life fence as an effective facility for the prevention of road-kill, it had founded that the wild animals did not jump over even the two layer guardrail, concrete barrier and noise barrier, fence for rock fall. For the section with high road-kill decrease effect after installing the wild-life fence, the effect was higher at wild-life fence with the height of 1.0m where the door had not been installed and the well connected points of road facility than the area with fence height of 1.5m. The road-kill decrease effect was also high at the well managed areas even if the door has not been installed. Also, road-kill had occurred by concentrating around the end of wild-life fence after installing the fence, Moreover road-kill had also occurred around the cutting section. The door of wild-life fence had higher amount of road-kill occurrence as the installation interval was closer. it was analyzed that the door management has a lot of effect on road-kill decrease. The fence for rock fall, two layer guardrail and concrete barrier having the effect of wild-life fence installed on the road would have to be installed by connecting with wild-life fences through proper facility improvement. Although the door should not be installed if possible, it should be installed as automatic door or gravity door to prevent the door from leaving the door open. An escape route has to be formed for the prompt escape away from the road for the animals entered through the ending section of the fence. The eco-corridor has to be made by restoring the soil layer of dual purpose eco-corridor forming a planting area. Also, the dead body after the accident has to be disposed to the outer section of the road immediately in order to prevent the secondary road-kill by the predator from the road-kill. The fence has to be installed as 500m or longer in both ways, in other words 1,000m or longer, from the targeted spot of minimum accident prevention while connecting up to the bridge or box culvert, etc that are next road facilities if possible to guide wild animals safely to the eco-corridor.