• Journal of the Korean Society for Precision Engineering
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• v.24 no.1 s.190
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• pp.64-70
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• 2007

A long-exposing technique (LET) has been conducted to create nanoscale patterns applicable to diverse micro-devices using two-photon polymerization (TPP). By the weakly-polymerized region via the LET, double-layered embossing patterns can be fabricated simply in a single step. The LET makes possible a voxel and its surrounding to be fully grown into more than 500 nm in lateral size and weakly-polymerized region (WPR), respectively. In the WPR. interconnecting ribs between voxels are generated, and they lead to the creation of double-layered dot patterns. Moreover, by controlling the distance between voxels, various shapes of interconnecting rib can be fabricated when the LET is applied. Various embossing patterns were fabricated to evaluate the usefulness of the proposed technique as a novel nanopatterning technique in TPP.

• Survey Research
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• v.9 no.2
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• pp.51-83
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• 2008

While online surveys are considered to be the viable alternative to face-to-face and telephone surveys, many clients express a strong concern about the possibility of unreliable responses. Given this concern, survey experts hypothesize that amounts of time on responding can represent the extent to which respondents fill out the questions with sincerity. This study examines this hypothesis using data from an online survey sample of 1.052. Results strongly suggest that while "long time" informants are reliable, "short time" informants are not. Those in the short time group spend only 2.4 seconds per question and show very different patterns of responses to 49 Likert -typed questions. Logistic regression results imply that these unreliable respondents are interested in monetary gifts and maybe as a result, participate in surveys much more frequently. In conclusion, we provide some implications of these results to the quality of online surveys.

• Journal of Korean Society of Transportation
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• v.22 no.7 s.78
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• pp.139-146
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• 2004

Road design should be conformed to the expectancy of drivers. The alignment such as long tangent followed by the sharp horizontal curve should be avoided for the road design consistency. Currently, operating speed profile model is generally used to check the consistency of the successive road alignments. In this model, the hypothesis about the drivers' behaviour on the long tangent followed by the sharp horizontal curve is also included. This study compares the hypothesized drivers' behaviour in the existing operating speed profile model with the actual drivers' behaviour observed at the two lane rural roads. In addition to this, comparison between the acceleration for the vehicles approaching and departing horizontal curves suggested by the foreign research and the value observed at this study was made, From this study, it was concluded that the hypothesis in the existing model was well representing the actual drivers' behaviour. The deceleration for vehicles approaching the horizontal curves was ranged $0.39{\sim}1.06m/s^2$ with the average of $0.66m/s^2$. The average acceleration for the vehicles departing horizontal curves was $0.22m/s^2$.

• Journal of the Korean Vacuum Society
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• v.15 no.6
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• pp.594-604
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• 2006

Gas fueling systems operated in the mode of a fixed valve opening at a constant line pressure, and the mode of a constant inlet flow are simulated to establish the relationships between the gas flow pattern and the tube dimensions under various system conditions.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1691-1693
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• 2001

펄스형 Nd:YAG 레이저는 연속형에 비해 효율이 높고 높은 첨두 출력(peak power)이 가능하므로 가공에 있어서 여러 가지 장점이 있다. 더구나 레이저 펄스 모양을 가변시키는 기능은 펄스형 Nd:YAG 레이저로 가공하기 힘든 특수분야에까지 가공을 가능하게 하였다. 본 연구에서는 3개의 플래쉬램프를 순차 점등시키는 MD(multi-discharge)방식의 레이저 시스템을 설계 및 제작하여, 램프 점등 시간의 변화에 따른 레이저 빔의 펄스폭과 펄스 세기(펄스 크기)를 조사하였다. 즉, PIC One-Chip microprocessor를 이용하여 실시간으로 3개의 플래쉬램프를 순차적으로 점등시켜 보다 다양한 펄스 모양을 만드는 기술을 개발하였다. 위 방식의 장점은 램프의 점등 지연시간을 0 $\sim$ 10ms 까지 다양하게 변화시킬 수 있고, 외부의 키보드로 실시간 제어가 가능하므로 보다 편리하게 펄스 모양을 변화시킬 수 있다. 또한 긴 펄스를 만들 수 있어 산업용 가공이나 의료용으로 널리 사용될 수 있을 것이다.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.53.1-53.1
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• 2011

현재 태양전지시장에서 비중이 많은 실리콘 태양전지는 높은 효율에 비해 제조 단가가 비싸다는 단점을 가지고 있다. 이에 비해 칼코파라이트 구조의 $CuInSe_2$ (CIS)계 화합물은 직접 천이형 반도체로서 높은 광흡수 계수($1{\times}105cm-{\acute{e}1$)와 밴드갭 조절의 용이성 및 열적 안정성 등으로 인해 고효율 박막 태양전지용 광흡수층 재료로 많은 관심을 끌고 있다. CIS 계 물질에 속하는 Cu(InGa)$Se_2$ (CIGS) 태양전지의 경우 양산화에 sputtering방식사용하고 Showa Shell에서는 대면적 CIGS 모듈 효율 13.4%를 달성한 바 있다. 현재 CIGS는 열처리하는 방법으로 selenization 공정을 사용하는데 이 공정은 유독한 $H_2Se$ gas를 이용해야 한다는 점과 긴 시간 동안 열처리를 해야 하는 단점을 가지고 있다. 따라서 이러한 단점을 보완하기 위해 본 연구에서는 전자빔을 사용하여 후속 공정을 실시하였다. 전자빔을 사용할 경우 낮은 온도에서 precursor를 처리하며 짧은 시간에 공정이 끝난다는 장점이 있다. 본 연구에서는 sodalime glass위에 조성비(Cu 60.87% Se 38.66%)인 Cu_2Se$ target(4.002"${\times}0.123$") 을 DC sputter를 이용하여 DC power를 50W,100W를 주고 Working pressure를 20,15,10,5,3,1mtorr로 조절하여 증착하였다. 전자빔의 세기 조건을 3Kv, Rf power 200W, Ar 7sccm로 전자빔 조사 시간을 1,2,3,4,5min으로 늘려가며 최적화 실험 하였고 최적화된 조건으로 $Cu_2Se$ target에 조사 하였다. 박막의 특성평가는 전자빔 조사 전/후에 대해 XRD, SEM, XRF, Hall measurement, UV-VIS을 이용하여 분석평가를 하였다. 이 실험은 $Cu_2Se$상이 자라는 특성과 표면 상태에 따라 CIGS박막을 증착하였을 때 나타나는 효율 변화를 알아 보기위한 초기 공정 실험이다.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.5
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• pp.107-116
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• 2011

In this paper, a traffic adaptive sleep based medium access control (TAS-MAC) protocol for wireless sensor networks (WSNs) is proposed. The protocol aims for WSNs which consist of clustered sensor nodes and is based on TDMA-like schema. It is a typical schedule based mechanism which is adopted in previous protocols such as LEACH and Bit-Map Assisted MAC. The proposed MAC, however, considers unexpected long silent period in which sensor nodes have no data input and events do not happen in monitoring environment. With the simple traffic measurement, the TAS-MAC eliminates scheduling phases consuming energy in previous centralized approaches. A frame structure of the protocol includes three periods, investigation (I), transmission (T), and sleep-period (S). Through the I-period, TAS-MAC aggregates current traffic information from each end node and dynamically decide the length of sleep period to avoid energy waste in long silent period. In spite of the energy efficiency of this approach, the delay of data might increase. Thus, we propose an advanced version of TAS-MAC as well, each node in cluster sends one or more data packets to cluster head during the T-period of a frame. Through simulation, the performance in terms of energy consumption and transmission delay is evaluated. By comparing to BMA-MAC, the results indicate the proposed protocol is more energy efficient with tolerable expense in latency, especially in variable traffic situation.

• Journal of Bio-Environment Control
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• v.6 no.3
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• pp.190-197
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• 1997

This study was conducted to determine the optimum hydroponic system and nutrient solution for promoting the growth and flowering of hydroponically grown carnation. DFT (deep flow technique) and NFT (nutrient film technique) systems were employed and four kinds of nutrient solution, which are Cooper solution, Yamasaki solution, balanced nutrient solution by Japanese Horticultural Experiment Station and PTG solution in the Netherlands were used and compared. pH was lowest in the PTG solution compared to the other nutrient solutions used. Plant height was highest in the DFT system in the plot of PTG solution as of 53.0 cm at 88 days after transplanting, while lowest in NFT system with Cooper solution. Stem diameter was more thickened in NFT system with PTG solution as of 7.2 mm at 88 days after transplanting. Days to flowering was shortened to 122.3 days in NFT system when PTG solution was used. This results suggested a combination of NFT system with PTG solution as optimum hydroponic system and nutrient solution for cut carnation production. Further trials as to the management of nutrient solution by glowing stages should be followed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.2
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• pp.90-99
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• 2004

High speed info-communications equipment are required with development of highly information-oriented society, the intelligent industrial facilities and social systems such as administrative, financial and traffic systems, are gradually becoming to automation, which are composed of the integrated circuits and micro-semiconductors, remote control and operation. Thus modern micro-electronic circuits can frequently be damaged by lightning surge. The protection of electronic circuits from lightning overvoltages is concentrated very interesting. In this paper, for the purpose of providing the effective protection method of electronic devices such micro-computers from lightning surges in a residential building, the protection effect of surge protective devices according to types of system groundings were experimentally analyzed. Also the effective installation method of surge protective devices was examined and proposed. The installation of SPDs in retrofits was a high remnant voltage across the protected device owing to the inductance in the long wires to the SPDs. Finally the method of installing the SPD by twisted pain wires is remarkably effective for fast rising transient overvoltages.

• Journal of the Korea Computer Industry Society
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• v.2 no.7
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• pp.975-982
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• 2001

In this study, a solid-state laser system adopting a new real time multi-discharge (RTMD) method in which three flashlamps are turned on consecutively was designed and fabricated to examine the pulse width and the pulse shape of the laser beams depending upon the changes in the lamp rum-on time. That is, this study shows a technology that makes it possible to make various pulse shapes by turning on three flashlamps consecutively on a real-time basis with the aid of a PIC one-chip microprocessor. With this technique, the lamp turn-on delay time can be varied more diversely from 0 to 10 ms and the real-time control is possible with an external keyboard, enabling various pulse shapes. In addition, longer pulses can be more widely used for industrial processing and lots of medical purposes