• 한국수자원학회논문집
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• 제44권4호
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• pp.275-283
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• 2011

미래 기온변화 정보를 제공하는 General Circulation Model (GCM) 자료, 즉 광역 기온자료를 이용하여 우리나라의 국지 수온변화를 추정하는 연구를 수행하였다. 국지수온 추정은 마산만, 시화호, 낙동강 하구를 대상으로 Two-step 접근방법과 One-step 접근방법을 적용하여 각각의 추정오차를 비교 분석하였다. Two-step 추정방법은 광역 기온으로 국지기온을 추정하는 제1단계에서는 선형회귀분석 기법을 적용하였으며, 모든 지점에서 결정계수가 0.98~0.99 정도로 매우 높게 나타났다. 그리고 국지기온으로 국지수온을 추정하는 제2단계에서는 S-형태함수의 비선형 회귀분석기법을 적용하였으며 이 경우 RMS(Root-mean squared) 오차는 마산만에서 2.07 (온도 증가시기), 1.93 (온도 감소시기), 시화호에서는 2.59, 낙동강 하구에서는 1.58로 파악되었다. 반면 동일한 S-형태함수를 이용한 비선형 회귀분석기법으로 광역기온자료로부터 바로 국지 수온을 추정하는 One-step 접근방법을 적용한 경우, RMS 오차는 마산만이 2.28 (온도증가시기), 1.89 (온도감소시기), 시화호에서는 2.55, 낙동강하구는 1.52로 Two-step 접근방법과 비슷한 수준의 오차를 보이는 것으로 파악되었다. 따라서 광역 기온자료를 이용하여 국지 수온을 추정하는 경우에는 One-step 접근방법도 유용하고 실용적인 것으로 판단된다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2005년도 추계종합학술대회
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• pp.285-288
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• 2005

In this paper, we propose a two step Binary Exponential search algorithm for rapid acquisition time of UWB(Ultra Wide Band) signal on UWB communication systems. Previous proposed timing acquisition algorithm is searching whole frame that consist of the number of n Bins to terminate search, however this paper proposed two step Binary Exponential search algorithm can achieve remarkable reduction of UWB signal acquisition time as limiting search group. Proposed search algorithm is consisting of search group establishment step and Bit Reversing of search group establishment step.

• 전기학회논문지
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• 제56권3호
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• pp.465-471
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• 2007

The one step type pole and two step type pole are used in KEPCO's distribution system. The neutral current increases in three-phase four-wire distribution system due to unbalanced load. Usually, power line and communication line are installed at contiguity by effect of topography in Korea. To this end, the damages such as electrostatic induction, electromagnetic induction and harmonic induction generated by induced voltage and current are occured in power line and communication line. This paper calculates the neutral current in KEPCO's distribution system using EMTP by composing various simulated conditions. Also, these results are verified by vector analysis.

• 전자공학회논문지B
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• 제31B권4호
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• pp.1-8
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• 1994

In this paper, we propose an efficient two-step pattern matching method which promises shape distortion-tolerant recognition of handwritten of handwritten Hangul syllables. In the first step, nonlinear shape normalization is carried out to compensate for global shape distortions in handwritten characters, then a preliminary classification based on simple pattern matching is performed. In the next step, nonlinear pattern matching which achieves best matching between input and reference pattern is carried out to compensate for local shape distortions, then detailed classification which determines the final result of classification is performed. As the performance of recognition systems based on pattern matching methods is greatly effected by the quality of reference patterns. we construct reference patterns by combining the proposed nonlinear pattern matching method with a well-known averaging techniques. Experimental results reveal that recognition performance is greatly improved by the proposed two-step pattern matching method and the reference pattern construction scheme.

• Structural Engineering and Mechanics
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• 제23권1호
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• pp.75-95
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• 2006

Two-step identification approaches for effective bridge health monitoring are proposed to alleviate the issues associated with many unknown parameters faced in real structures and to improve the accuracy in the estimate results. It is suitable for on-line monitoring scheme, since the damage assessment is not always needed to be carried out whereas the alarming for damages is to be continuously monitored. In the first step for screening potentially damaged members, a damage indicator method based on modal strain energy, probabilistic neural networks and the conventional neural networks using grouping technique are utilized and then the conventional neural networks technique is utilized for damage assessment on the screened members in the second step. The effectiveness of the proposed methods is investigated through a field test on the northern-most span of the old Hannam Grand Bridge over the Han River in Seoul, Korea.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1772-1775
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• 2000

We have fabricated poly-Si TFTs by two-step crystallizaton. Poly-Si films have been prepared by furnace annealing(FA) and rapid thermal annealing(RTA) followed by subsequent the post-annealing, excimer laser annealing. The measured crystallinity of RTA and FA annealed poly-Si film is 77% and 68.5%, respectively. For two-step annealed poly-Si film, the crystallinity has been drastically to 87.7% and 86.3%. The RMS surface roughness from AFM results have been improved from 56.3${\AA}$ to 33.5${\AA}$ after post annealing. The measured transfer characteristics of the two-step annealed poly-Si TFTs have been improved significantly for the both FA-ELA and RTA-ELA. Leakage currents of two-step annealed poly-Si TFTs are lower than that of the devices by FA and RTA. From these results, we can describe the fact that the intra-grain defects has been cured drastically by the post-annealing.

• 대한의생명과학회지
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• 제17권1호
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• pp.69-77
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• 2011

In this study, we evaluated the protective effects of supercritical extracts and two step ethanol extracts after supercritical extraction from Schizandra chinensis on antioxidant activities and oxidative DNA and cell damages. Supercritical extracts removed DPPH (1,1-diphenyl-2-picryldrazyl) radical by 85.5% at 200 ${\mu}g$/ml, but showed low activities of scavenging and chelating the hydroxyl radical and ferrous iron. However, two step ethanol extracts showed low activities of scavenging the DPPH radical, but removed the hydroxyl radical by 86% at 200 ${\mu}g$/ml. In addition, we tested the activities of extracts for reducing hydroxyl radical-induced DNA and cell damage. Two step ethanol extracts showed protective effect against the oxidative DNA damage by reducing DNA segmentation, inhibiting DNA migration and decreasing the expression of phospho-H2AX. Also, two step ethanol extracts showed protective effect against the oxidative cell damage by inhibiting lipid peroxidation and increasing the expression of p21 protein. Taken together, we suggest that two step ethanol extracts from S. chinensis have a role as useful inhibitors against oxidative damages.

• 대한금속재료학회지
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• 제49권11호
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• pp.868-873
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• 2011

In this study, the fabrication of ultra fine grained Mo bulk was conducted. $MoO_3$ nanopowders were prepared by a high energy ball-milling process and then reduced at the temperature of $800^{\circ}C$ without holding time in $H_2$ atmosphere. The particle size of Mo nanopowder was ~150 nm and grain size was ~40 nm. The two-step process was employed for the sintering of Mo nanopowder to obtain fine grain size. The densification over 90% could be obtained by the two-step sintering with a grain size of less than 660 nm. For higher density, modified two-step sintering was designed. 95% of theoretical density with the grain size of 730 nm was obtained by the modified two-step sintering.

• 한국정밀공학회지
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• 제34권2호
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• pp.83-87
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• 2017

A multi-step warm forging process for subminiature screws is investigated. Due to the low formability of Titanium alloys, bit forming of Titanium screws is difficult by cold forging. In order to overcome this low formability of Titanium alloys, two candidate processes, i.e., multi-step forging and warm forging are introduced. First, a multi-step (two-step) forging process is investigated. The punch shape and stroke of forging during the first step is designed via various analyses. Finally, the bit formability is investigated at different forging temperatures. Analyses are carried out for two-step forging at various temperatures and the formability under these thermal conditions is compared.

• 한국농공학회지
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• 제37권E호
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• pp.1-9
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• 1995

It is shown that two step power transformation is more efficient for the normalization of frequency distribution with the coefficient of skewness of zero in comparison with others including SMEMAX and power transformations. It is confirmed that the design low flows calculated using power and two step power transformations used in this study are generally nearer to the observed data as compared with those of SMEMAX transformation at all return periods in the applied watersheds of the Kum, Naktong and Yongsan rivers in Korea.