• Journal of the Economic Geographical Society of Korea
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• v.16 no.4
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• pp.613-630
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• 2013

This study attempts to analyze the spatial characteristics of organic agriculture in Korea during the period of 2000~2010, focusing on women's labor contribution to agricultural operations. Spatial distribution and concentration of organic farming have been investigated using Location Quotient(LQ) and Local Indicator of Spatial Association(LISA), it was found that the specialized organic farmland in the Seoul Metropolitan area has decreased significantly over the past decade, while in Chungnam and Kyungpook province it has been rapid growth in the same period. Multilinear regression analysis was also carried out to find out whether the spatial clusters in organic farming depends on women farmers. Results describing the correlation between organic farming and women farmers within identified clusters suggest that the possibility of the transition towards sustainable agriculture and farmland restructuring in Korea, by women.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.1
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• pp.52-60
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• 2002

The purpose of this research is to study the vibration and acoustic pressure radiation from a thin isotropic flat plate stiffened by a rectangular array of beams, and excited by a time harmonic point force. These constructions on aircraft and ship structures are often subjected to fiequency dependent pressure fluctuations and forces. Forces from the these excitations induce structural vibrations in a wide range of fiequencies, which may cause such things as acoustic fatigue and internal cabin noise in the aircraft. It is thus important that the response characteristics and vibration modes of such periodic structures be horn. From this theoretical model, the sound pressure levels(SPL) in a semi-infinite fluid(water) bounded by the plate with the variation in the locations of an external time harmonic point farce on the plate can be calculated efficiently using three numerical tools such as the Gauss-jordan method the LU decomposition method md the IMSL numerical package.

• Tunnel and Underground Space
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• v.8 no.4
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• pp.275-286
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• 1998

The effective permeability and the representative element volume(REV) of fracture network model were evaluated based on the parameters such as permeability tensor, principal permeability and the direction of principal permeability. The effective permeability ranges between the harmonic mean and the arithmetic mean of the local permeabilities of subdivided blocks. From the numerical experiments, which were for investigating the influence of model volume on the variation of flux for the cubic models, it was found that the variation of flux became reduced as the model volume approached REV. The variation of groundwater flux into the tunnel in the fracture network model was mainly dependent on the ratio of the tunnel length to model size rather than REV. And it was found that groundwater flux into the tunnel was not completely consistent between the fracture network model and the equivalent porous media model, especially when the ratio of the tunnel length to model size is small.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.846-853
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• 1995

In order to study electronic structures for locally disordered systems, we have developed a first-principle self-con-sistent-spin-polarized real space band method (TB-LMTO-R), which combines the tight-binding(TB) linear-muffin-tin orbital(LMTO) band rrethod and the recursion(R) rrethod. The TB-LMTO-R rrethod has been applied to fer-romagnetic bec Fe, hcp Co, and fcc Ni. With varying cluster sizes, recursion coefficients, and the order of the TB-Hamiltonian, we have calculated the local density of states(LDOS) and magnetic moments. It is found that the calculation with 5,000 atoms cluster, 40 continued fractions, and the second-order TB-Hamiltonian yields a conver¬gent result in agreement with those from the conventional LMTO. In this way, we have demonstrated a physical transparency of the TB-LMTO-R method as a real space description.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1054-1065
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• 1993

A computer simulation is performed on the effectiveness of the active minimization of harmonically excited enclosed sound fields for producing global reduction in the amplitude of the pressure fluctuations. In this study for the appreciable reductions in total time averaged acoustic potential energy, $E_{pp}$, the transducer location strategies for three dimensional active noise control is presented based on a state space modal which approximates the closed acoustic field.In this study, the above theoretical basis is used to investigate the application of active control to sound fields of low modal density. By the used of room-like 3-dimensional rectangular enclosure it is demonstrated that the reductions in $E_{pp}$ can be achieved by using a single secondary source, provided that the source is placed within the half a wavelength from the primary source and placed away from nodal line of the sound field. Concerning the reductions in $E_{pp}$ by minimzing the pressure in sound fields by the use of 3-dimensional rectangular enclosure, the effects of the number of sensors and the locations of these sensors are investigated. When a few modes dominate the response it is found that if only a limited number of sensors are located away from nodal line and located at the pressure maxima of the sound field such as at each corner of a rectangular enclosure.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.1
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• pp.41-50
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• 1998

The detemination of sound pressure radiated from peoriodic plate structures is fundamental in the estimation of noise levels in aircraft fuselages and ship hull structures. As a robust approach to this problem, here a very general and comprehensive analytical model for predicting the sound radiated by a vibrating plate stiffened by periodically spaced orthogonal symmetric beams subjected to a sinusoidally time varying point load is developed. The plate is assumed to be infinite in extent, and the beams are considered to exert both line force and moment reactions on it. Structural damping is included in both plate and beam materials. A space harmonic series representation of the spatial variables is used in conjunction with the Fourier transform to find the sound pressure in terms of harmonic coefficients. From this theoretical model. the sound pressure levels on axis in a semi-infinite fluid (water) bounded by the plate with the variation in the locations of an external time harmonic point force on the plate can be calculated efficiently using three numerical tools such as the Gauss-Jordan method, the LU decomposition method and the IMSL numerical package.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.732-739
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• 2005

The determination of sound pressure radiated from periodic plate structures is fundamental in the estimation of noise level in aircraft fuselages or ship hull structures. As a robust approach to this problem, here a very general and comprehensive analytical model is developed for predicting the sound radiated by a vibrating plate stiffened by periodically spaced orthogonal symmetrical beams subjected to a sinusoidally time varying point load. In this these, we experiment with the numerical analysis using the space harmonic series and the SYSNOISE for measuring the vibration mode and character of response caused by sound radiation with adding the harmonic point force in the thin isotropic plate supported by the rectangular lattice reinforcement. We used the reinforcements, beams of open type section like the style of 'ㄷ' letter; the space of the beams were chosen to be 0.2m, 0.3m, 0.4m. We studied the behavior of sound pressure levels, analysis of vibration mode between support points, connection between frequency function and sound pressure levels, and connection between position function and sound pressure levels.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.12
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• pp.2818-2826
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• 2010

To study the spatial and temporal variations of sea surface temperature(SST) in the Northeast Asia sea during the period of 1985 to 2009. At first, the buoy data from Korea Meteorological Administration(KMA) and the satellite data have been matched up eight points. The root mean square error and the bias were increased towards the coastal shallow region. The study area which is divided 7 regions from Japan Meteorological Agency(JMA). We analyzed NOAA/AVHRR data by harmonic analysis which is comparison and analysis the center of the each regions. The mean SST varied between $8^{\circ}C$ to $26.0^{\circ}C$. The annual amplitude varied between $7^{\circ}C$ to $24^{\circ}C$. And the annual phase varied between end of July to end of August. Cross-correlation coefficients of mean SST, annual amplitude, and annual phase varied 0.57 to 0.85, -0.04 to 0.81 and 0.35 to 0.80 at all study area, respectively.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.377-381
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• 2011

지구는 지속적으로 변화하는 동력학적 시스템이며, 지표면 형상 및 지구 내부의 질량분포도 계속 변화하고 있다. 지구시스템의 질량재분배 과정에서 발생되는 밀도 차이는 중력장의 미세한 변이를 초래한다. 미 항공우주센터(NASA)와 독일 국립 항공우주연구센터(DLR)에서 공동으로 개발한 GRACE (Gravity Recovery And Climate Experiment) 인공위성은 지구의 중력장을 측정하는 위성으로, 2002년부터 현재까지 9년 동안 활동해왔다. 본 연구에서는 한반도(북위 $37.5^{\circ}\sim41.5^{\circ}$, 동경 $125.5^{\circ}\sim130.5^{\circ}$)의 월평균 수자원변화량(TWSC: Terrestrial Water Storage Change)을 산정하기 위해 미국 텍사스대학교 공간연구센터(CSR)에서 가우시안 필터링을 통해 구면조화함수의 계수 형태로 제공된 총 94개월(2002 년 8월~2010년 6월)의 자료(Level-2)를 이용하였다. Level-2 자료는 해양조석, 고체지구조석 및 지구자전으로 인한 극조석 등 조석의 영향과 대기와 해양의 변동성으로 인한 비조석 영향을 보정한 것이다. 이렇게 산정한 TWSC를 수자원관리정보시스템(WAMIS)과 전지구지표동계화시스템(GLDAS)을 통해 제공되는 자료와 비교 분석하였다. 본 연구를 통해 GRACE 중력장 자료가 수자원총량의 산정과 검증을 위한 대안으로 활용될 수 있음과, 수문요소의 불확실성을 낮출 수 있는 새로운 수문자료로의 활용 가능성을 확인하였다.

• Journal of the Korean Association of Geographic Information Studies
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• v.13 no.2
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• pp.94-106
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• 2010

Understanding of the amount of energy resources and site selection are required prior to develop Ocean Thermal Energy (OTE). It is necessary to calculate the appearance probability of difference of seawater temperature(${\Delta}T$) between sea surface layer and underwater layers. This research mainly aimed to calculate the appearance probability of ${\Delta}T$ using frequency analysis(FA) and harmonic analysis(HA), and compare the advantages and weaknesses of those methods which has used in the South Sea of Korea. Spatial scale for comparison of two methods was divided into local and global scales related to the estimation of energy resources amount and site selection. In global scale, the Probability Differences(PD) of calculated ${\Delta}T$ from using both methods were created as spatial distribution maps, and compared areas of PD. In local scale, both methods were compared with not only the results of PD at the region of highest probability but also bimonthly probabilities in the regions of highest and lowest PD. Basically, the strong relationship(pearson r=0.96, ${\alpha}$=0.05) between probabilities of two methods showed the usefulness of both methods. In global scale, the area of PD more than 10% was less than 5% of the whole area, which means both methods can be applied to estimate the amount of OTE resources. However, in practice, HA method was considered as a more pragmatic method due to its capability of calculating under various ${\Delta}T$ conditions. In local scale, there was no significant difference between the high probability areas by both methods, showing difference under 5%. However, while FA could detect the whole range of probability, HA had a disadvantage of inability of detecting probability less than 10%. Therefore it was analyzed that the HA is more suitable to estimate the amount of energy resources, and FA is more suitable to select the site for OTE development.