• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.6
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• pp.1006-1014
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• 2000

Hemisphere type Luneberg lens antenna with a reflector(frequency : 9.375 GHz, -3 dB beam width 6$^{\circ}$, diameter 30.3 cm(about 10 A), which is miniaturized and lightweightized by attaching a reflector on a section of half the Luneberg lens antenna, is designed and fabricated on the basis of Luneberg lens antenna from which easy beam pointing is acquired only by movement of 1st radiator. Measurement shows -3dB beamwidth is 6.1$^{\circ}$ in case of E-plane and 5.5$^{\circ}$ in case of H-plane. These are good agreements with expected value. Gain of this antenna is 26dBi(Aperture efficiency for uniform distribution : $\pi$ = 44.97%) which is greater than that of 1st radiator(Rectangular microstrip antenna) by 20.4 dB. And, after calculating the approximated pattern of the 1st radiator, far-field pattern, whose source is the second aperture source farmed from the approximated pattern of the 1st radiator is computed. Comparing this far-field pattern with the expected pattern, a (relatively) good agreement is observed. Circular polarization Luneberg lens antenna is also manufactured by making 1st radiator so that it has the characteristics of LHCP and RHCP radiation. The results are as followings : -3 dB beamwidth 5.8$^{\circ}$ , side lobe level -15.3 dB, isolation between LHCP and RHCP radiation 2543, axial ratio 2 dB bandwidth about 1.4 GHz(14.9%).

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.1
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• pp.111-120
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• 2010

The policy which encourages people to use cars on the road has been based on the growth of economy in Korea. It has also caused the concentration and overcrowding in Seoul. That's because the increasing number of people possessing cars interconnects with the urban development. The transportation is a derived demand; so many scholars have recognized the importance of understanding the relationship between urban land use and transport. Considering such importance, this study theoretically compared the developed urban land use-transportation models each other and outlined the particular models briefly. Models were categorized by 2 types; optimizing model and predictive mode. Predictive model is also defined by static model, entropy based model, spatial-economic model, and activity model. After studying models, we investigated other major cities in America. This process is the pre-step for transport policy assessment. Through careful literature review, we can finally develop the integrated land-use transportation model in Seoul metropolitan area. In addition, we will be able to deal the changes of traffic demand pattern under U-Society. Consequently, the results of this study can be applied to ITS projects in the future.

• Korean Journal of Optics and Photonics
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• v.24 no.5
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• pp.213-216
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• 2013

This paper presents a combination of linear Fresnel lenses optimized for ${\times}25$ solar concentration. The combined lens consists of $5{\times}5$ linear Fresnel lenses. Each Fresnel lens is of $10{\times}10$ mm and optimized to tilt the incoming light onto a solar cell of the same size. All of the optimized Fresnel segments have the same pattern height of 35 ${\mu}m$, draft angle of $4^{\circ}$, and edge groove round of 1 ${\mu}m$ but with different facet angles varying from $14.1^{\circ}$ to $31.2^{\circ}$. The solar concentrating efficiency of the combination is shown to be over 80% and more robust than a conventional single ${\times}25$ circular Fresnel lens in terms of pointing misalignment and manufacturing errors. A sensitivity analysis finds that the edge groove round should be kept as small as machining allows since the concentrating efficiency drops ~5% per 1 ${\mu}m$ increase of the edge groove.

• Polymer(Korea)
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• v.36 no.2
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• pp.169-176
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• 2012

Based on our experience in developing resistive humidity sensor, interdigital gold electrodes with different fingers and gaps have been fabricated on a glass epoxy (GE) substrate using screen printing techniques. The basic structure of the electrode consisted of a 3-, 4- and 5-fingers with gaps of 310 and 460 ${\mu}m$. Gold electrode/GE was prepared by first printing silver nanopaste, followed by consecutive electroless plating of Cu, Ni and then Au. Copolymer of [2-(methacryloyloxy)ethyl] dimethyl benzyl ammonium chloride (MDBAC) and methyl methacrylate (MMA) was used as a humidity-sensing polyelectrolyte, which was fabricated by a screen printing method on the Au electrode/GE substrate. The flexible humidity sensor showed acceptable linearity between logarithmic impedance and relative humidity in the range of 20-95%RH, low hysteresis of 1.5%RH, good response and recovery time of 75 sec at 1 V, 1 kHz, and $25^{\circ}C$. Electrode construction had a significant influence on the humidity-sensing characteristics of polymeric humidity sensors. The activation energy between electrode and ion conducting polyelectrolyte plays an important role in explaining the differences of humidity sensing characteristics such as temperature dependence, sensitivity, linearity and hysteresis.

• Journal of Korea Water Resources Association
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• v.36 no.4
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• pp.691-703
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• 2003

In this paper, a new and integrated approach easily used to calculate the pollutant loads from agricultural watersheds is suggested. Basic concepts of this empirical tool are based on the hypotheses that variations in event mean concentrations(EMCs) of the pollutants from a given agricultural watershed during rainstorms are only due to the rainfall pattern. This assumption would be feasible to agricultural watersheds whose land uses does not change during the cultivation period overlapped by rainy season and also in which point-sources of the pollutants are rare. Therefore, if EMC data sets through extensive sampling from various rural areas are available, it is possible to establish relationships between EMCs, shapes and land uses of the watersheds, and rainfall events. For this purpose, fifty one sets of EMC values were obtained from nine different watersheds, and those data were used to develop predictive tools for the EMCs of 55, COD, TN and TP in rainfall runoff. The results of the statistical tests for those formulas show that they are not only fairly good in predicting actual EMC values of some parameters, but also useful in terms of calculating pollutant loads on any time-spans such as the day of rainfall event or weekly, monthly, and yearly. Their applicability was briefly demonstrated and discussed. Also, the unit loads calculated from EMCs based on different land uses and real rainfall data over one of the watershed used for this study. were provided, and they are compared with other well-known unit loads.

• Fire Science and Engineering
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• v.28 no.5
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• pp.8-13
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• 2014

The purpose of this study is to analyze the damage pattern when overcurrent is applied to a thermal magnetic type molded case circuit breaker (MCCB) using a Primary Current Injection Test System (PCITS). When an overcurrent of 150 A was applied to the PCITS for 5 seconds with the trip bar of an MCCB being damaged, it was found that the surface of the temperature control device (bimetallic strip) positioned at the right was significantly carbonized. When an overcurrent of 300 A was applied to the PCITS for 5 s under the same conditions, the entire temperature control device was deteriorated, becoming flattened and in close contact with the MCCB. When an overcurrent of 450 A was applied to the PCITS for 5 s, the coil of the temperature control device was melted and disconnected. In addition, it was observed that the contacts, the enclosure and upper cover were deformed and there was a trace of carbonization on them. When approximately 3 s had elapsed after an overcurrent of 600 A was applied, white smoke occurred inside the MCCB and a flame was radiated out, after which the overcurrent supply stopped with "phutt" (whomp) sound. It was observed that when the same type of MCCB is damaged by a general flame, the surfaces of its handle, terminal, arc divider (extinguisher) and temperature control device were carbonized uniformly. In addition, it was found that the trip bar of the operating mechanism was melted down and the metal operation pin was moved while being tripped.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.1
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• pp.12-20
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• 2004

In this paper, the detection of 1 g and 10 g averaged SAR on human head caused by PCS/IMT-2000 handhold phones is analyzed and discussed. Planar structured Single-Semi-disc MPA and double-Semi-disc MPA is designed and resonance characteristics with variety of design parameters are analyzed. As a result, 2.0 ㎓ center frequency, at the bandwidth of single-semi-disc MPA and double-semi-disc MPA are 15.5 ％ and 31 ％, respectively. And monopole antenna with W4 length is designed and compared with double-semi-disc MPA in SARs. The SARs caused by double-semi-disc MPA on folder type handset are 0.811 W/kg and 0.507 W/kg and are about 32.7 ％ lower than monopole-1.206 W/kg and 0.7552 W/kg. While the radiation pattern of the monopole antenna is symmetrical, that of planar structured antenna is asymmetrical and SAR caused by double-semi-disc MPA is less than SAR by the monopole antenna.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7820-7830
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• 2015

Korean households' demand for food consumed away from home is on the steady increase. The ratio of eating-out expenditure of the household income, however, tends to decrease recently irrespective of income groups. This paper, therefore, aims to analyse the food-away-from-home expenditures of salary and wage earners' households by income decile group. The eating-out expenditure is modelled as a function of household income and then estimated using econometric methods such as regression, rolling regression, impulse response, and variance decomposition of forecast error. The regression results indicate that the higher the income decile group is, the lower the income elasticity of eating-out expenditure is, and the high income groups enjoy seasonal eating-out, the low groups do not. The coefficients of dynamic rolling regression are much smaller than those of static one, meaning that households tend to decrease the eating-out expenditure of their income. The impulse response analysis suggests that the eating-out expenditure increase of higher income groups lasts long relative to that of lower income groups. The variance decomposition, also, shows that household income plays much more important role in determining eating-out expenditure at the higher income groups than at the lower income groups.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.416-416
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• 2015

기후변화는 미래 강수량 변동을 야기하여 하천유량 관리에 큰 영향을 미칠 것으로 예상하고 있다. 이에 본 연구에서는 기후변화에 따른 중장기 하천유량 관리를 위하여 금호강 유역을 대상으로 SWAT 모형을 이용하여 중장기 하천유량을 예측하였다. 임하댐 상류지역의 2008~2012년 유량자료에 대하여 보정 완료된 SWAT 모형을 기반으로, 지역기후모형(RCM)인 HadGEM3-RA모형을 활용한 IPCC 제5차 보고서 RCP 4.5, RCP 8.5 시나리오를 적용하였다. 금호강 표준유역별 기후변화에 의한 영향을 모의하기 위하여 편이보정(Bias Correction)방법을 적용하였으며, 금호강 유역 내 과거 30년(1975~2005년, Baseline) 기상자료와 비교하여 통계적인 유사성을 가지도록 보정을 실시하였다. 기후변화 시나리오 적용결과는 S1(2011~2040년), S2(2041~2070년), S3(2071~2099년)으로 분할하여 월별, 계절별, 연도별 미래 강수량과 기온을 분석하였다. 분석 결과, RCP 4.5 시나리오의 경우 봄철(3~5월)의 강수량은 기준년도에 비해 약 57%가 증가하였으나, 가을철(6~8월)에는 7.9% 감소하였으며, 첨두 강수시기는 8~9월에서 6~7월로 이동하였다. 평균기온은 각 구분 시기별 $0.2^{\circ}C$, $1.1^{\circ}C$, $1.8^{\circ}C$ 정도 상승할 것으로 예측되었다. RCP 8.5 시나리오에서는 기준년도 대비 강우량은 봄철에 61% 증가, 가을철에는 14.9% 감소하는 것으로 모의되었다. 평균기온은 약 $0.4^{\circ}C$, $2.1^{\circ}C$, $4.2^{\circ}C$ 정도 상승하는 것으로 나타났다. 기후변화에 따른 유출량 결과 비교는 2001~2010년을 기준으로 하였으며, RCP 4.5 시나리오에서는 S1, S2, S3 시기별 각각 -10.9%, -7%, -3.6% 감소하였으며, RCP 8.5 시나리오에서는 약 -12.3%, 4.9%, -1.2% 변동하는 것으로 나타냈다. 금호강 유역 전반에 걸쳐 유출량이 감소하는 추세를 보였으며, 특히 본류에 비해 지류유역의 건천화가 심해지는 양상을 보였다. 또한 현재에 비해 여름철 유출패턴 시기가 앞당겨져 봄철 유량이 증가하고 겨울철에 감소하는 경향을 보이고 있다. 기후변화로 인한 수문패턴의 변화로 현재 하천유량관리의 변화가 필요할 것으로 판단되며, 향후 본 연구결과를 바탕으로 물수지 분석을 추가하여 유지유량 만족을 위한 해당유역의 이수기 유량관리 방안 연구를 수행할 예정이다.

• Food Science and Preservation
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• v.12 no.4
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• pp.361-366
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• 2005

An electronic nose equipped with metal oxide sensor(MOS) was used for investigating the quality of reconstitute orange juice added different recoverable oil(cold pressed valencia oil) contents during 21 days of storage at $4^{\circ}C$. Quality changes in orange juice was described in terms of the sensitivity(${\Delta}R_{gas}/R_{air}$) of the sensors. Principal component analysis(PCA) was carried out using data obtained from twelve metal oxide sensors. The flavor of orange juice contained with the different recoverable oil contents($0.01\%{\sim}0.05\%$) was separated in PCA plot, in which the first principal component score was correlated with the content of recoverable oil. As storage periods prolonged, no significantly different sensitivity score of orange juice was observed in electronic nose. The content of recoverable oil in orange juice was reduced rapidly within 14 days, and then the decreasing ratio was slow on the next 7 days during storage at $4^{\circ}C$. The sensory score for overall and orange flavor of orange juice added $0.03\%$ recoverable oil was decreased during the 14 days and then rapidly dropped next 7 days of storage at $4^{\circ}C$.