• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.14 no.4
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• pp.225-247
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• 2010

In this paper, we establish a two-competitive-prey and one-predator Holling type II system by introducing a proportional periodic impulsive harvesting for all species and a constant periodic releasing, or immigrating, for the predator at different fixed time. We show the boundedness of the system and find conditions for the local and global stabilities of two-prey-free periodic solutions by using Floquet theory for the impulsive differential equation, small amplitude perturbation skills and comparison techniques. Also, we prove that the system is permanent under some conditions and give sufficient conditions under which one of the two preys is extinct and the remaining two species are permanent. In addition, we take account of the system with seasonality as a periodic forcing term in the intrinsic growth rate of prey population and then find conditions for the stability of the two-prey-free periodic solutions and for the permanence of this system. We discuss the complex dynamical aspects of these systems via bifurcation diagrams.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.1
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• pp.29-36
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• 2016

Tensairity girder is a light weight inflatable fabric structural concept which can be used in road emergency transportation. It uses low pressure air to stabilize compression elements against buckling. With the purpose of obtaining the comprehensive target of minimum deflection and weight under ultimate load, the cross-section and the inner pressure of tensairity girder was optimized in this paper. The Variable Complexity Modeling (VCM) method was used in this paper combining the Kriging approximate method with the Finite Element Analysis (FEA) method, which was implemented by ABAQUS. In the Kriging method, the sample points of the surrogate model were outlined by Design of Experiment (DOE) technique based on Optimal Latin Hypercube. The optimization framework was constructed in iSIGHT with a global optimization method, Multi-Island Genetic Algorithm (MIGA), followed by a local optimization method, Sequential Quadratic Program (SQP). The result of the optimization gives a prominent conceptual design of the tensairity girder, which approves the solution architecture of VCM is feasible and efficient. Furthermore, a useful trend of sensitivity between optimization variables and responses was performed to guide future design. It was proved that the inner pressure is the key parameter to balance the maximum Von Mises stress and deflection on tensairity girder, and the parameters of cross section impact the mass of tensairity girder obviously.

• Hwankyungkyoyuk
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• v.24 no.2
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• pp.86-98
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• 2011

Water problems recently, not only influence environmental issues such as water quality and water management but also influence socioeconomic issues such as poverty, gender, and regional conflicts. Therefore there is increasing attention on water education as part of the environmental education. Yet water education in formal education is only treated with particular subjects like science and social studies with limited contents which fails to cover the social, economic problems related to water thoroughly. Also, though there is an active water education on the field of informal education. its contents are also very limited. Water education requires the implementation of a comprehensive and holistic approach that can holistically consider economic and social problems as well as environmental problems. Therefore in this research, 'water education for sustainable development' is set up as a direction of contents development which include interdisciplinary and holistic aspects. Contents development of water education for sustainable development is an reflection of the experts and teacher's opinions and contain of: main category dividing into three pillars of sustainable development such as environment, economy, and society, and subcategory covering environmental science's objective including knowledge, skill, attitude, and action as well as local, national, regional, and global issues.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.25
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• pp.243-266
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• 2005

Product liability is becoming a real issue to exporters, manufacturers world wide. The purpose of this study is to examine the product liability of Korean exporters, manufacturers, etc. under Product Liability Laws and Regulations of China. For this purpose, firstly we deal with the Product Liability Laws and Regulations of China. Secondly we analyze the case study concerning the Product Liability in China. From the analysis of case study, Korean exporters, manufacturers, etc. are required to pay close attention to the following : the correspondence of English with Chinese in the warning phrases, the possibility of application of strict global standard in case of existence of product liability, the proper treatment of evidence in the process of litigation, the application of strict liability and the shift of responsibility for evidence on to a defendant, the observance of procedures prescribed by the country in design and manufacture of the product, the manufacture of product to come up to country standard in quality, the consideration of diverse expression in the preparation of warning sign, the importance of quality control and inspection system in case of local procurement of parts and raw materials, Finally, this paper contributes to help the Korean Exporters, Manufacturers, etc. to build up the proper countermeasures regarding product liability under the product liability regulations of China.

• Journal of Korean Society for Atmospheric Environment
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• v.12 no.2
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• pp.189-198
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• 1996

Mercury (Hg) is ubiquitous throughout the earth's atmosphere. The uniqueness of its atmospheric geochemistry is well-known with the high environmental mobility and relatively long atmospheric residence time (c.a., 1 year) associated with its high chemical stability. Despite a growing recognition of the environmental significance of its global cycling, the prexisting Korean database for atmospheric Hg is extremely rare and confined to a number of concentration measurements conducted under relatively polluted urban atmospheric environments. To help activate the research on this suvject, an in-depth analysis on the current development in the measurements of atmospheric mercury and the associated fluxes has been made using the most using the most updated data ests reported worldwide. As a first step toward this purpose, the most reliable techniques commonly employed in the measurements of its concentration in the background atmosphere are introduced in combination with the flux measurement techniques over soil surface such as: dynamic enclosure (or field flux chamber) method and field micrometeorological method. Then the results derived using these measurement techniques are discussed and interpreted with an emphasis on its mobilization across the terrestrial biosphere and atmosphere interface. A unmber of factors including air/soil temperature, soil chemical composition, soil water content, and barometric pressure are found out to be influential to the rate and amount of such exchange processes. Although absolute magnitude of such exchange processes is insignificant relative to that of the major component like the oceanic environment, this exchange process is thought to be the the predominant natural pathway for both the mobilization and redistribution of atmospheric Hg on a local or regional scale.

• Journal of Korean Society for Atmospheric Environment
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• v.10 no.1
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• pp.41-48
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• 1994

A monitoring system for atmospheric CFC-12 and CFC-11 has been established at Mt. Kwan-Ak, Seoul National University (SNU) since July, 1991. The concentrations showed quite a large variation ranging from 495 to 37600 pptv (pptv=part per trillion, 10$^{-12}$ , v/v) for CFC-12 and from 233 to 12100 pptv for CFC-11 due to many local sources. However, monthly medians show rather limited ranges ; 553~765 pptv for CFC-12 and 301~431 pptv for CFC-11. Furthermore minimum concentrations could be defined relatively well during the whole period of observation. The regional background concentrations in 1993 near SNU wer estimated as 533 pptv for CFC-12 and 293 pptv for CFC-11. These values are very comparable to global averages in Northern Hemisphere, 523 pptv for CFC-12 and 287 pptv for CFC-11, reflecting the fast atmospheric mixing processes within the hemisphere. Examinations with meteorological parameters such as wind speed and direction suggest the possible measurement-window at SNU, appropriate for regional monitoring. Studies for improving the monitoring capability of the SNU station such as automation of the analysis system along with correlation with other meteorological parameters, are in progress at the present time.

• Journal of the Korean Society for Marine Environment & Energy
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• v.3 no.2
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• pp.49-59
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• 2000

Wave distribution in Jangjeon Harbour is numerically simulated for an optimum design of the harbour facilities. A deep-water design wave is estimated based on stochastic extreme wave analysis of wind data in the vicinity of the harbour, and it is applied to the boundary condition at open sea. Boussinesq wave theory that includes effects of frequency dispersion and nonlinearity is employed for the wave simulation. The porosity and sponge layer are adapted at beach to depict partial reflection and complete absorption of waves, respectively. The design wave for breakwater is computed in global domain with coarse grids and the wave distribution inside of wharf is simulated in local domain with fine grids.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.2
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• pp.244-250
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• 2020

Microplastic pollution in the marine ecosystem has been emerged as a global issue. In this study, we investigated the abundance of microplastics from clam Meretrix lusoria, blood arkshell Scapharca broughtonii, and warty sea squirt Styela clava obtained from a local market in Busan, Korea. The marine organisms were digested in 10% KOH, and were incubated at 40℃ and 150 rpm, for 7 days. The digest was filtered through standard sieve (5 mm, 1 mm, 300 ㎛, and 100 ㎛), and mciroplastics were identified using a light microscope and microFT-IR. The abundance of microplastics of clam, blood arkshell, warty sea squirt was 0.08 items/g, 0.05 items/g, and 0.12 items/g, respectively. The predominant microplastic size was in the range of 100-300 ㎛, occupying 48%, and the predominant type was fiber. The composition of microplastics was mostly rayon, semi-synthetic cellulosic material and polyester, which are main component of fabric and textile. We strongly believe that this preliminary work may provide useful information for the establishment of the standardized analysis method of microplastics ingested by marine organisms.

• KIEAE Journal
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• v.10 no.3
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• pp.27-35
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• 2010

It has been criticized that the Venice Charter of 1964 characterizes so much of Western value of architecture and its conservation, despite its significant contribution towards an international conservation approach. Since the 1970s some countries have drawn up their own conservation guidelines to supplement the limitations of the Venice Charter. When we review critically those documents, we find a change in the Western dogma of heritage. Although the Burra Charter of 1979(last version in 1999) and the China Principles of 2002 accept the general philosophy and concepts of the Venice Charter but make responses to special local needs. The Burra Charter has redressed a current Western bias which has permeated global conservation practices, responding to the Australian context. The China Principles also meet special national needs but in accordance with recent international practices. For this reason, the Burra Charter and the China Principles are regarded as well established in national conservation practices but also as representing each country's contribution to contemporary international conservation practices.

• English Language & Literature Teaching
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• v.16 no.4
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• pp.91-106
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• 2010

This study examines the use of hedges in cross-cultural communication between EFL learners in an e-learning environment. The study analyzes the use of hedges in a corpus of an interactive web with a bulletin board system through which college students of English at Japanese and Korean universities interacted with each other discussing the topics of local and global issues. It compares the use of hedges in the students' corpus to that of a native English speakers' corpus. The result shows that EFL learners tend to use relatively smaller number of hedges than the native speakers in terms of the frequencies of the total tokens. It further reveals that the learners' overuse of a single versatile high-frequency hedging item, I think, results in relative underuse of other hedging devices. This indicates that due to their small repertoire of hedges, EFL learners' overuse of a limited number of hedging items may cause their speech or writing to become less competent. Based on the result and interviews with the learners, the study also argues that hedging should be understood in its social contexts and should not be understood just as a lack of conviction or a mark of low proficiency. Suggestions were made for using computer corpora in understanding EFL learners' language difficulties and helping them develop communicative and pragmatic competence.