• 감성과학
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• 제11권2호
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• pp.207-214
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• 2008

직물의 결점은 원단손실을 가중시키기 때문에, 검단공정에서 결점부위를 제거한다. 실제공장에서 이뤄지는 검단공정은 육안판정방식과 전자동 방식 중 하나를 채택하는데, 두 방식 나름대로 장단점이 있다. 본 연구에서는 육안판정과 전자동 방식의 장점만을 모아 검출은 사람이 하지만, 결점위치 정보 제공 및 결점정보 기록을 컴퓨터가 하도록 반자동 검단기를 개발하였다. 본 연구에서 개발한 레이저 그리드는 결점의 위치를 검단자가 쉽게 파악하도록 돕는 역할을 하며, 야드미터는 자동으로 결점의 위치를 측정하는 역할을 한다. 컴퓨터는 야드미터로 측정된 직물의 길이와 사람이 검출한 결점의 위치정보를 받아들여 저장하고 직물의 결점정보를 한눈에 보여주는 역할을 한다. 실제 사용되는 직물을 대상으로 특정 패턴으로 재단했을 때의 손실률을 계산하여 개발된 시스템의 성능을 객관적으로 평가하였다.

• 전기학회논문지
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• 제62권10호
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• pp.1383-1389
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• 2013

There were telecommunication noise and malfunctions of the electronic devices occurred over a wide area due to the high harmonic voltage and/or current levels of the Back-to-back converter in the DFIG wind power system even though the magnitude of all harmonics is within the international standards. The triangular carrier signals of the PWM used in the power converter system is related to the telecommunication noise because they are in the range of audible frequencies and amplified by a variety of the standing waves that were excited by harmonic voltage sources in the weak grid system such as a long distance distribution transmission lines. This paper describes the characteristics of the harmonics in the wind turbine-generator, numerical analysis and simulation of the harmonics resonance phenomena in the distribution lines as well as measuring induced voltage of the telecommunication lines in parallel with power lines in order to verify the root cause of the telecommunication noise. These noise problems can occur in a wind turbine power system with a non-linear converter at any time, as well as photovoltaic power system. So, the preliminary review of suitable filter devices and switching frequencies of the PWM have to be required by considering the stability of the controller at the design stage but as part of the measures the effect of the telecommunication cable shields was analyzed by comparing the measured data between multi-conductor with/without shields so as to attenuate the sources of the harmonics voltage induced into the telecommunication lines and to apply the most cost-effective measures in the field.

• 대기
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• 제20권3호
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• pp.343-353
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• 2010

A regional wind network with complex surface conditions must be designed with sufficient space and time resolution to resolve the local circulations. In this study, the spatial variations of the wind field observed in the Seoul and Jeju regional networks were evaluated in terms of annual, seasons, and months to assess the spatial homogeneity of wind fields within the regional networks. The coherency of the wind field as a function of separation distance between stations indicated that significant coherency was sometimes not captured by the network, as inferred by low correlations between adjacent stations. A meso-velocity scale was defined in terms of the spatial variability of the wind within the network. This problem is predictably most significant with weak winds, dull prevailing wind, clear skies and significant topography. The relatively small correlations between stations imply that the wind at a given point cannot be estimated by interpolating winds from the nearest stations. For the Seoul and Jeju regional network, the meso-velocity scale has typically a same order of magnitude as the speed of the network averaged wind, revealing the large spatial variability of the Jeju network station imply topography and weather. Significant scatter in the relationship between spatial variability of the wind field and the wind speed is thought to be related to thermally-generated flows. The magnitude of the mesovelocity scale was significantly different along separation distance between stations, wind speed, intensity of prevailing wind, clear and cloudy conditions, topography. Resultant wind vectors indicate much different flow patterns along condition of contributing factors. As a result, the careful considerations on contributing factors such as prevailing wind in season, weather, and complex surface conditions with topography and land/sea contrast are required to assess the spatial variations of wind field on a regional network. The results in the spatial variation from the mesovelocity scale are useful to represent the characteristics of regional wind speed including lower surface conditions over the grid scale of large scale atmospheric model.

• Ocean Science Journal
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• 제42권3호
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• pp.153-163
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• 2007

This study is based on a series of numerical modeling experiments to understand the tidal circulation in the Kangjin Bay (KB). The tidal circulation in the KB is mostly controlled by the inflow from two channels, Noryang and Daebang which introduce the open ocean water into the northern part of the KB with relatively strong tidal current, while in the southern part of the KB, shallowest region of the entire study area, weak tidal current prevails. The model prediction of the sea level agrees with observed records at skill scores exceeding 90 % in terms of the four major tidal constituents (M2, S2, K1, O1). However, the skill scores for the tidal current show relatively lower values of 87, 99, 59, 23 for the semi-major axes of the constituents, respectively. The tidal ellipse parameters in the KB are such that the semi-major axes of the ellipse for M2 range from 1.7 to 38.5 cm/s and those for S2 range from 0.5 to 14.4 cm/s. The orientations of the major-axes show parallel with the local isobath. The eccentricity values at various grid points of ellipses for M2 and S2 are very low with 0.2 and 0.06 on the average, respectively illustrating that the tidal current in the KB is strongly rectilinear. The magnitude of the tidal residual current speed in the KB is on the order of a few cm/s and its distribution pattern is very complex. One of the most prominent features is found to be the counter-clockwise eddy recirculation cell at the mouth of the Daebang Channel.

• 반도체디스플레이기술학회지
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• 제15권4호
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• pp.10-15
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• 2016

In this paper, novel ball grid array (BGA) interconnection process using solderable anisotropic conductive adhesives (SACAs) with low-melting-point alloy (LMPA) fillers have been developed to enhance the processability in the conventional capillary underfill technique and to overcome the limitations in the no-flow underfill technique. To confirm the feasibility of the proposed technique, BGA interconnection test was performed using two types of SACA with different LMPA concentration (0 and 4 vol%). After the interconnection process, the interconnection characteristics such as morphology of conduction path and electrical properties of BGA assemblies were inspected and compared. The results indicated that BGA assemblies using SACA without LMPA fillers showed weak conduction path formation such as solder bump loss or short circuit formation because of the expansion of air bubbles within the interconnection area due to the relatively high reflow peak temperature. Meanwhile, assemblies using SACA with 4 vol% LMPAs showed stable metallurgical interconnection formation and electrical resistance due to the favorable selective wetting behavior of molten LMPAs for the solder bump and Cu metallization.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제1권1호
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• pp.35-43
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• 1997

Handling the emergency problems such as Chemobyl accident require real time prediction of pollutants dispersion. One-point real time sounding at pollutant source and simple model including turbulent-radiation process are very important to predict dispersion at real time. The stability categories obtained by one-dimensional numerical model (including PBL dynamics and radiative process) are good agreement with observational data (Golder, 1972). Therefore, the meteorological parameters (thermal, moisture and momentum fluxes; sensible and latent heat; Monin-Obukhov length and bulk Richardson number; vertical diffusion coefficient and TKE; mixing height) calculated by this model will be useful to understand the structure of stable boundary layer and to handling the emergency problems such as dangerous gasses accident. Especially, this simple model has strong merit for practical dispersion models which require turbulence process but does not takes long time to real predictions. According to the results of this model, the urban area has stronger vertical dispersion and weaker horizontal dispersion than rural area during daytime in summer season. The maximum stability class of urban area and rural area are 'A' and 'B' at 14 LST, respectively. After 20 LST, both urban and rural area have weak vertical dispersion, but they have strong horizontal dispersion. Generally, the urban area have larger radius of horizontal dispersion than rural area. Considering the resolution and time consuming problems of three dimensional grid model, one-dimensional model with one-point real sounding have strong merit for practical dispersion model.

• 대한기계학회논문집
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• 제18권1호
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• pp.139-149
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• 1994

A numerical simulation of unsteady axisymmetric turbulent flow was performed for a reciprocating engine including port/valve assembly. The governing equations based on a nonorthogonal coordinate formulation with Cartesian velocity components were used and discretised by the finite volume method with non-staggered variable arrangements. The modified $\kappa-\xi$. turbulence model which included the effect of compressibility was used. The results of twodimensional transient calculation for the axisymmetric configuration were compared with the experimental data. Although slightly low rms velocity was predicted compared to the experimental data, predicted velocity distributions at the valve exit and in-cylinder region showed good agreements with the experimental data. The flow at the valve exit was separated at the same valve lift position with the experimental data. Two vortices incylinder region were generated during the initial intake process. The clockwise main vortex became strong and moved upward to the top wall. The counter-clockwise second vortex became weak and stick to the upper left corner of the cylinder. After middle intake process, new vortex adjacent to upper cylinder wall appeared by the piston motion and therefore, the in-cylinder flow was formed into three vortices. The cylinder pressure just before bottom dead center of piston was higher than inlet pressure and then the reverse flow occured at the valve exit. The in-cylinder flow characteristics were strongly dependent on piston motion, but insensitive to valve motion.

• 한국농림기상학회지
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• 제3권1호
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• pp.37-43
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• 2001

Crop status monitoring and yield prediction at higher spatial resolution is a valuable tool in various decision making processes including agricultural policy making by the national and local governments. A prototype crop forecasting system was developed to project the size of rice crop across geographic areas nationwide, based on daily weather pattern. The system consists of crop models and the input data for 1,455 cultivation zone units (the smallest administrative unit of local government in South Korea called "Myun") making up the coterminous South Korea. CERES-rice, a rice crop growth simulation model, was tuned to have genetic characteristics pertinent to domestic cultivars. Daily maximum/minimum temperature, solar radiation, and precipitation surface on 1km by 1km grid spacing were prepared by a spatial interpolation of 63 point observations from the Korea Meteorological Administration network. Spatial mean weather data were derived for each Myun and transformed to the model input format. Soil characteristics and management information at each Myun were available from the Rural Development Administration. The system was applied to the forecasting of national rice production for the recent 3 years (1997 to 1999). The model was run with the past weather data as of September 15 each year, which is about a month earlier than the actual harvest date. Simulated yields of 1,455 Myuns were grouped into 162 counties by acreage-weighted summation to enable the validation, since the official production statistics from the Ministry of Agriculture and Forestry is on the county basis. Forecast yields were less sensitive to the changes in annual climate than the reported yields and there was a relatively weak correlation between the forecast and the reported yields. However, the projected size of rice crop at each county, which was obtained by multiplication of the mean yield with the acreage, was close to the reported production with the $r^2$ values higher than 0.97 in all three years.

• 디지털융복합연구
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• 제17권3호
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• pp.227-234
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• 2019

본 연구는 교육인프라가 취약한 아프리카 국가들의 교육 콘텐츠, 교실환경, 그리고 ICT기술에 대한 종합적인 보급을 위한 블록형 스마트교실 모델 제시를 목표로 한다. 수업관리시스템, 전력관리시스템 및 교실환경 관리시스템을 통합하는 상황별 솔루션을 제시하고, 아프리카 지역의 국가별 경제적, 비경제적 여건에 최적화가 가능한 융합 모델이 될 것이다. 이는 기존의 서비스, 콘텐츠, 솔루션에 대한 독립적 연구개발이나 단일 컨테이너로 보급된 기존교실과는 차별화되는 효율적인 모델이 될 수 있을 것이다. 이러한 통합 연구 과정을 통해 기존 컨테이너교실에서 나타나는 공간과 기능적 한계를 극복하고 이러닝 기술 고도화에 대비한 융통성 있는 공간을 구축한다. 향후 보다 다양한 지역의 교육 및 인프라 여건에 부합하는 성능과 모델에 대한 탐구로 후속 연구의 깊이와 범위의 확장이 가능할 것이다.

• 한국문헌정보학회지
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• 제19권
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• pp.63-112
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• 1990

The environment of the modern library is changing rapidly with advancements in information technology, massive increse in information, and with the changing needs of users for information in order to keep up with developments in science and technology. The library should also be in a constant state of change in accordance with the changing environment. But the current situation is that library organizations in Korea do not show any change. Here arises the need to diagnose the health of these organization. Organizational innovations can be achieved either by change in the organizational structure or administrative methods or in personal attitudes. In making organizational innovations, however, it is not sufficient only to change the organizational structure or the administrative methods without changing personal attitudes. The purpose of this thesis is to diagnose the health of university library organizations in Korea and to suggest prescriptions based on the results of this diagnosis, by means of organization development theory. In this study, the action research model and the diagnostic model were developed for the health of university library organization in Korea. The action research model consisted of 3 steps: diagnosis, intervention and evaluation. The diagnostic model comprised diagnostic criterion and diagnostic indicators. The health of an organization was selected as the diagnostic criterion. Diagnostic indicators were divided into 3 levels: personal job-satisfaction at the individual level, cohesiveness at the group level, and the organizational climate at the organizational level. Both the interview and the questionaire were used as diagnostic methods. The questionaire form was designed according to the Likert typle 5-point scale. For the investigation, 10 university libraries were selected from the private universities in Seoul, and questionaire sheets were sent to their 156 librarians and responses were received from 116 persons. An interview was carried out with a selected chief of departments of the library concerned. The results of the diagnosis show that the average personal job­satisfaction was 3.57, the group cohesiveness was 3.15 and organizational climate was 2.93, and accordingly the comprehensive health indicator was 3.22. The health of university library organizations in Korea was generally on the decline at all 3 levels. In particular, the organizational climate was in a very weak state. Most problems concern dissatisfaction with personnel policy, communications and non-professionally qualified directors. As the prescriptions, the following was suggested: institutionalization of the staff meeting for resolving problems with communication, appointement of professional directors, performance appraisal, conferring faculty status for librarians, and a suggest system. And for the improvement of the organizational climate, managerial grid training was suggested as one of the educational strategies for organizational development.