• Journal of applied mathematics & informatics
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• 제20권1_2호
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• pp.485-489
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• 2006

In this paper, we slightly improve the Baby-step Giant-step for certain elliptic curves. This method gives the running time improvement of $200\%$ in precomputation (Baby-step) and requires half as much storage as the original Baby-step Giant-step method.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2017년도 추계학술대회
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• pp.234-235
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• 2017

기존 고속활주선의 마찰저항을 개선하기 위해 선저에 공기층을 형성하게 하는 계단형식의 선형변환이 연구되어 왔다. 그러나 활주선마다 다른 항주자세와 Step의 효과를 확인하기 위해서 적절한 위치에 대한 연구는 부족한 실정이다. 본 연구에서는 이러한 Step을 길이방향으로 적용시켰을 때 나타나는 항주자세의 변화, Step의 작용효과 및 마찰저항의 변화를 확인하였다.

• 한국재료학회지
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• 제34권2호
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• pp.116-124
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• 2024

In this study, we investigated the microstructure and piezoelectric properties of 0.96(K_0.456Na_0.536)Nb_0.95Sb_0.05-0.04Bi_0.5(Na_0.82K_0.18)_0.5ZrO₃ (KNNS-BNKZ) ceramics based on one-step and two-step sintering processes. One-step sintering led to significant abnormal grain (AG) growth at temperatures above 1,085 ℃. With increasing sintering temperature, piezoelectric and dielectric properties were enhanced, resulting in a high d₃₃ = 506 pC/N for one-step specimen sintered at 1,100 ℃ (one-step 1,100 ℃ specimen). However, for one-step 1,115 ℃ specimen, a slight decrease in d₃₃ was observed, emphasizing the importance of a high tetragonal (T) phase fraction for superior piezoelectric properties. Achieving a relative density above 84 % for samples sintered by the one-step sintering process was challenging. Conversely, two-step sintering significantly improved the relative density of KNNS-BNKZ ceramics up to 96 %, attributed to the control of AG nucleation in the first step and grain growth rate control in the second step. The quantity of AG nucleation was affected by the duration of the first step, determining the final microstructure. Despite having a lower T phase fraction than that of the one-step 1,100 ℃ specimen, the two-step specimen exhibited higher piezoelectric coefficients (d₃₃ = 574 pC/N and k_p = 0.5) than those of the one-step 1,100 ℃ specimen due to its higher relative density. Performance evaluation of magnetoelectric composite devices composed of one-step and two-step specimens showed that despite having a higher g₃₃, the magnetoelectric composite with the one-step 1,100 ℃ specimen exhibited the lowest magnetoelectric voltage coefficient, due to its lowest k_p. This study highlights the essential role of phase fraction and relative density in enhancing the performance of piezoelectric materials and devices, showcasing the effectiveness of the two-step sintering process for controlling the microstructure of ceramic materials containing volatile elements.

• 한국수자원학회논문집
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• 제51권4호
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• pp.313-322
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• 2018

Step의 높이는 하상재료 입경의 크기와 거의 같은 상관관계가 있으며, 하도경사에 따라 증가하고, 하도 폭과 step 파장은 거의 같은 크기로서 하도경사가 증가하면 step 파장은 감소하는 것으로 분석되었다. 하도 폭과 step 폭은 뚜렷한 상관관계가 있으며, 하도 폭의 증가에 따라 step 폭도 증가하는 것으로 분석되었다. 또한, step 파장은 하도 폭에 의하여 규모가 정해지고, step 높이는 step을 형성하는 암석의 크기에 의해 지배되기 때문에 step-pool의 종단면의 하상구조는 하도경사에 따라 변화하는 것으로 판단된다. Pool의 규모는 하도 폭, 입경 및 하도경사와 상관성이 큰 것을 확인하였다. 따라서 하천의 step-pool 구조 특성은 다양한 인자들의 영향을 받지만 대표적으로 입경, 하도 폭 및 하도경사로서 설명할 수 있는 것으로 분석되었다.

• 융합신호처리학회 학술대회논문집
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• 한국신호처리시스템학회 2005년도 추계학술대회 논문집
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• pp.317-320
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• 2005

기존의 블라인드 등화(blind equalization) 알고리즘의 step-size는 임의의 값을 알고리즘에 적용하여 수렴속도와 정상 상태의 특성을 고려하여 최적한 step-size를 결정하였다. step-size를 크게 하면 수렴속도는 빠른 반면에 정상 상태에서 에러가 크고, step-size를 작게 하면 수렴속도는 느린 반면에 정상 상태에서 에러가 작아진다. 그렇기 때문에 수렴속도와 정상 상태를 고려해서 step-size를 결정해야 되고, 특별하게 정해지는 기준이 없기 때문에 연구자의 판단에 의해서 다르게 선택된다. 본 논문에서는 등화기 출력의 잔류 심벌간 간섭에 따라 step-size를 가변함으로서 수렴속도 및 정상 상태 성능을 개선한 가변 step-size를 갖는 블라인드 등화 알고리즘을 제안한다.

• Mycobiology
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• 제39권1호
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• pp.67-69
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• 2011

A cell-free extract of Saccharomyces cerevisiae containing the angiotensin I-converting enzyme (ACE) inhibitory peptide was treated in a successive simulated gastric-intestinal bioreactor (step 1: amylase digestion, step 2: gastric fluid digestion, step 3: intestinal fluid digestion) to illustrate the absorption pattern of antihypertensive ACE inhibitory peptide, and the ACE inhibitory activities of each step were determined. Total ACE inhibitory activities of step 1, step 2, and step 3 were 55.96%, 80.09%, and 76.77%, respectively. The peptide sequence of each steps was analyzed by MS/MS spectrophotometry. Eleven kinds of representative peptide sequences were conserved in each step, and representative new peptides including RLPTESVPEPK were identified in step 3.

• Journal of applied mathematics & informatics
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• 제28권3_4호
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• pp.773-781
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• 2010

Recently, Yun [8] proposed a new three-step iterative method with the fourth-order convergence for solving nonlinear equations. By using his ideas, we develop a general form of multi-step iterative methods with higher order convergence for solving nonlinear equations, and then we study convergence analysis of the multi-step iterative methods. Lastly, some numerical experiments are given to illustrate the performance of the multi-step iterative methods.

• 한국운동역학회지
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• 제24권1호
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• pp.67-74
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• 2014

This study researched into the left-right inclination of the rear foot at the lower limb joints, knee joint angle, angular velocity of the knee joint, angular acceleration and the max. Based on the analysis of kinematics according to the changes in the height of step box (6, 8, 10 inches) during step aerobics of female college students majoring in physical education. The findings of this study are as follows: Then angle of the knee joint decreased as the height of the step box increased the min. Angle was measured right before the right foot was on the step box, and the angle tended to decrease as the step box get heightened. The left-right inclination of the rearfoot angle according to the height of step box increased as the height increased. In the 'pull-up' stage during which the weight was loaded on the right foot the angle increased, while in the right foot stepping stage during which the right foot was on the ground, the left-right inclination of the rearfoot angle increased as the height of the step box increased. The angular velocity of the knee joint according to the height of step box started increasing when the right foot initially stepped on the step box and during the initial stepping section, the angular velocity decreased as the height of step box increased. The changes in angular acceleration of the knee joint according to the height of step box increased as the height of step box increased.

• 한국임상수의학회지
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• 제35권2호
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• pp.39-45
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• 2018

We evaluated the effects of green tea extract (GTE) supplementation at different dilution steps on boar sperm freezing and in vitro fertilization. Sperm intracellular hydrogen peroxide ($H_2O_2$), motility, viability, acrosome integrity and morphology were determined. In addition, sperm IVF parameters (penetration and monospermy) and glutathione (GSH) levels of presumptive zygotes (PZs) were evaluated. Semen was diluted in lactose egg yolk (LEY) and cooled at $5^{\circ}C$ for 3 h (first dilution step) and then diluted in LEY with 9% glycerol and maintained at $5^{\circ}C$ for 30 min (second dilution step). Four experimental groups were compared: first and second dilution steps without GTE (control), first dilution step with GTE (Step 1), second dilution step with GTE (Step 2) and first and second dilution step with GTE (Step 1+2). The spermatozoa were frozen in nitrogen vapor. Higher sperm motility, viability and acrosome integrity after thawing were observed in Step 1, Step 2 and Step 1+2 groups compared with the control (P < 0.05). Lower $H_2O_2$ level was observed in Step 1+2 compared with control and Step 1 (P < 0.05). For IVF, matured oocytes were co-cultured with spermatozoa frozen according to the experimental groups. GSH levels of PZs were significantly higher in Step 2 and Step 1+2 than in control and Step 1 (P < 0.05) without a significant difference in IVF parameters. In conclusion, supplementation with GTE in both first and second dilution steps during the freezing process resulted in better boar sperm cryopreservation and might be beneficial for further embryo development.

• 한국결정성장학회지
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• 제26권3호
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• pp.89-94
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• 2016

본 연구에서는 HVPE(Hydride Vapor Phase Epitaxy)를 이용하여 각각 다른 V/III ratio를 가지는 multi-step의 성장 시간 변화에 따라 r-plane 사파이어 위에 성장되는 a-plane GaN 에피층의 결정성에 대하여 연구하였다. 또한 이번 연구의 결과를 선행 연구에서 single-step으로 r-plane 사파이어 위에 성장시킨 a-GaN 에피층의 결과와 비교하였다. Multi-step으로 r-plane 사파이어 위에 a-plane GaN 에피층을 성장시켰을 때, source HCl의 유량과 성장 시간이 증가함에 따라 a-plane GaN 에피층에 대한 rocking curve의 FWHM(Full Width at Half Maximum) 값이 감소하였다. 높은 source HCl의 유량을 갖는 first step과 second step의 성장 시간과 source HCl의 유량이 증가할수록 a-plane GaN 에피층 내부의 void가 감소하였다. 결과적으로 first step과 second step의 성장 시간이 가장 긴 조건에서 성장된 a-plane GaN 에피층이 가장 낮은 FWHM 값인 584 arcsec을 가지며, azimuth angle의 의존도가 가장 적은 것으로 확인되었다.