• 한국정밀공학회지
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• 제27권4호
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• pp.14-19
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• 2010

In this paper, using interleaved power factor correction how to improve the inverter efficiency studied. Interleaved method can reduce the conduction losses and the inductor energy. Generally, critical conduction mode (CRM) boost PFC converter used low power level because of the high peak currents. if you use the interleaved mode, CRM PFC can be used medium or high power application. interleaved CRM PFC can reduce current ripple for higher system reliability and size of buck capacitor and EMI filter size. Interleaved CRM PFC that is installed in front of inverter can maintain the constant voltage regardless of the input voltage.

• 한국유체기계학회 논문집
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• 제12권6호
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• pp.41-46
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• 2009

This paper deals with the operating-speed (high-speed) balancing of a refinery gasoline HDS (hydrodesulfurization) process recycle-gas 8-stages compressor rotor. A low-speed balancing condition of the rotor was measured as maintaining the G2.5 level. But an inspection run of operating-speed balancing condition, using tilting-pad journal bearings of actual use, showed that while it could be continuously-operated safely at a rated speed of 10,500 rpm, the rotor would not be able to run over 11,000 rpm as the vibration increased very sharply, approaching 11,000 rpm. In order to cure that a series of operating-speed balancing, which first calculated balance correction-weights by applying the influence coefficient measured and calculated at 10,500 rpm and then implemented correction works, was carried-out. The final operating-speed balancing results showed that the vibrations at the bearing pedestals represented very good levels of 0.2 mm/s by decreasing to as much as the 1/10 of the original vibrations and particularly, even at a targeted maximum continuous operating speed, MCS, of 11,500 rpm the vibrations represented about 1 mm/s, which is the operating-speed balancing vibration specification of API. Therefore, the expansion of MCS was successfully accomplished through the operating-speed balancing.

• Geomechanics and Engineering
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• 제19권1호
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• pp.61-70
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• 2019

Yieldable steel ribs have been widely applied in tunnels excavated in rheological rocks. For further understanding the influence of yieldable steel ribs on supporting effect, mechanical behavior of tunnels supported by them in rheological rocks is investigated in this paper. Taking into account the deformation characteristic of yieldable steel ribs, their deformation is divided into three stages. In order to modify the stiffness of yieldable steel ribs in different deformation stages, two stiffness correction factors are introduced in the latter two stages. Viscoelastic analytical solutions for the displacement and pressure in the rock-support interface in each deformation stage are obtained. The reliability of the theoretical analysis is verified by use of numerical simulation. It could be concluded that yieldable steel ribs are able to reduce pressure acting on them without becoming damaged through accommodating the rock deformation. The influence of stiffness correction factor in yielding deformation stage on pressure and displacement could be neglected with it remaining at a low level. Furthermore, there is a linearly descending relationship of pressure with yielding displacement in linear viscoelastic rocks.

• Current Optics and Photonics
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• 제7권2호
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• pp.213-221
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• 2023

The optical window, as a part of the collimator system, is the connector between the outside light source and the optical system inside a vacuum tank. The temperature and pressure difference between the two sides of the optical window cause not only thermoelastic deformation, but also refractive-index irregularities. To suppress the influence of these two changes on the performance of the collimator system, thermo-optical analysis is employed. Coefficients that characterize the deformations and refractive-index distributions are derived through finite-element analysis, and then imported into the collimator system using a user-defined surface in ZEMAX. The temperature and pressure difference imposed on the window seriously degrade the system performance of the collimator. A decentered and tilted lens group is designed to correct both field aberrations and the thermal effects of the window. Through lens-interval adjustment of the lens group, the diffraction-limited performance of the collimator can be maintained with a vacuum level of 10^-5 Pa and inside temperature ranging from -100 ℃ to 20 ℃.

• 가정과삶의질연구
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• 제28권4호
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• pp.29-42
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• 2010

This study examined the effects of ego-resilience and directors' and fellow teachers' social support on childcare teachers' job stress. The participants were 323 childcare teachers in Chung nam Province and Daejeon Metropolitan City. The research instruments were Job Stress Scale by Cho(2004), Ego-resilience Scale by Park(1996) with CPI and CAQ correction, and Social Support Scale by Park(1985). Collected data were analysed by t-test, F test and Scheff$\acute{e}$ test for post hoc test, Pearson's productive correlation and stepwise multiple regression, and Cronbach's $\alpha$ for reliability by SPSS PC program (17.0 version). The results were as follows: First, the childcare teachers' job stress level was low (M=2.51, SD=.63), while ego-resilience level and social support level of directors and fellow teachers (M=3.68, SD=.58; M=3.62, SD=.94; M=3.83, SD=.69, respectively) were above the average. Second, there were significant differences between different levels of ego-resilience and of social support from directors and fellow teachers. Last, directors' social support and childcare teachers' optimistic attitude of ego-resilience were the most dominant variables that affected childcare teachers' job stress level(R2=38.3% for total score of childcare teachers' job stress).

• Asian Spine Journal
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• 제12권6호
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• pp.1028-1036
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• 2018

Study Design: Single-center, observational, case-control study. Purpose: Comparison and analysis of the metabolic and coagulative profiles in patients with idiopathic scoliosis, patients with congenital scoliosis, and healthy controls. Overview of Literature: Serum melatonin deficiency has been a controversial topic in the etiopathogenesis of scoliosis. Low bone mineral density, low vitamin D3 levels, and high parathyroid hormone levels are common metabolic abnormalities associated with scoliosis that may be responsible for its pathogenesis. In addition to metabolic defects, several studies have shown coagulation defects that either persist from the preoperative period or occur during surgery and usually lead to more than the expected amount of blood loss in patients undergoing deformity correction for scoliosis. Methods: The study population (n=73) was classified into those having congenital scoliosis (n=31), those with idiopathic scoliosis (n=30), and healthy controls (n=12). After detailed clinicoradiological evaluation of all the subjects, 10-mL blood samples were collected, measured, and analyzed for various metabolic and coagulation parameters. Results: The mean serum melatonin levels in patients with idiopathic scoliosis were significantly lower than those in the healthy controls. Although the mean serum melatonin level in the congenital group was also low, the difference was not statistically significant. Serum alkaline phosphatase and parathyroid hormone levels were higher in the scoliosis groups, whereas the vitamin D level was lower. No differences were observed in the coagulation profiles of the different groups. Conclusions: Low serum melatonin levels associated with scoliosis can be a cause or an effect of scoliosis. Moreover, low bone mineral density, high bone turn over, and negative calcium balance appear to play an important role in the progression, if not the onset, of the deformity.

• Archives of Plastic Surgery
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• 제38권6호
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• pp.740-746
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• 2011

Purpose: In the treatment of the unilateral cleft lip nasal deformities, the correction of the low-nostril height and short-columella are very difficult problems. We report the treatment outcomes of web uni-limb Z-plasty used for correction of unilateral cleft lip nasal deformities by using photographic analysis. Methods: A total of 36 patients with unilateral cleft lip nasal deformities were enrolled in this study, who underwent web uni-limb Z-plasty and were followed up for at least 6 months. First, a triangular flap was made on the medial side of alar-columella web. The nostril apex of cleft side was corrected to a higher point compared to noncleft side by 2 mm. The flap was transposed into the defect of the vestibule. To reduce the bulging of the flap, horizontal cinching sutures were added. Postoperative outcomes were evaluated by using photographic analysis. 2 indices and 1 angle were measured on their photographs taken before and after the surgery. Symmetry was also evaluated by means of the noncleft side to cleft side index. For anthropologic assessment, observers described postoperative outcomes, using Ordinary Scale Method. Results: The postoperative values obtained in photographic analysis improved compared to preoperative ones. More improving anthropologic assessment was shown in post-than pre-operative. Conclusion: Although, further long term follow up is needed, we found this technique to be an effective procedure to the symmetry of nostril apex level and the lengthening of columella in the unilateral cleft lip nasal deformities.

• 한국컴퓨터그래픽스학회논문지
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• 제23권3호
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• pp.95-103
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• 2017

본 논문은 딥 러닝(deep learning)을 이용하여 입력 영상의 기울어진 정도를 측정하고 수평에 맞게 바로 세우는 방법을 제시한다. 기존 방법들은 일반적으로 영상 내에서 선분, 평면 등 하위 레벨의 특징들을 추출한 후 이를 이용해 영상의 기울어진 정도를 측정한다. 이러한 방법들은 영상 내에 선이나 평면이 존재하지 않는 경우에는 제대로 동작하지 않는다. 본 논문에서는 대규모 데이터 셋을 통해 영상의 다양한 특징들에 대해 학습 가능한 Convolutional Neural Network (CNN)를 이용하여 인물이나 복잡한 배경으로 구성된 기울어진 영상에 대해서도 강인하게 동작하는 프레임워크를 제시한다. 또한, 네트워크에 가변 공간적 (adaptive spatial) pooling 레이어를 추가하여 영상의 다중 스케일 특징을 동시에 고려할 수 있게 하여 영상의 기울어진 정도를 측정하는 성능을 높인다. 실험 결과를 통해 다양한 콘텐츠를 포함한 영상의 기울어짐을 높은 정확도로 바로 세울 수 있음을 확인할 수 있다.

• 한국통신학회논문지
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• 제33권12C호
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• pp.1014-1020
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• 2008

메모리 등의 저장 장치는 다양한 전자제품에 널리 이용되면서 높은 메모리 집적도가 요구되고 있으며 멀티 레벨로 데이터를 저장하는 단계에 이르렀다. 그 결과 데이터의 오류율은 더 높아지게 되었다. 본 논문에서 우리는 저장장치의 낮은 오류율을 만족시키기 위하여 통신시스템에서 널리 사용되고 있는 오류정정부호 기법을 적용하였다. 평균 오류율 (BER)이 $10^{-5}$ 또는 $5{\times}10^{-6}$인 AWGN 채널에서 4-level cell을 이용한 저장장치에 대하여 목표 부호율 0.99과 목표 오류율 (BER) $10^{-11}$과 $10^{-13}$를 만족시킬 수 있는 방법을 알아본다. 높은 부호율에서는 연접부호의 성능이 블록 부호만 사용한 경우보다 좋지 않은 경우도 많으며, 이때 천공을 많이 한 경우에도 성능 열화가 덜한 안쪽 부호를 선정하는 것이 중요함을 확인하였다. 일반적인 feedfoward systematic 길쌈 부호를 이용한 연접부호는 복잡도를 고려하지 않더라도 블록 부호를 단독으로 사용한 경우보다 성능이 좋지 않음을 확인하였고, 높은부호율 에서도 성능이 우수한 천공 길쌈 부호를 만들기 위해서는 RSC 부호를 사용해야 한다는 것을 모의실험 결과를 통해 보여준다.

• 융합신호처리학회논문지
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• 제11권3호
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• pp.244-249
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• 2010

차세대 멀티 레벨 셀 플래시 메모리들을 위해 복잡도가 낮은 에러 정정 코드 구현에 대한 요구가 커지고 있다. 일반적으로 부 표현 (sub-expression) 들을 공유하는 것은 복잡도와 칩 면적을 줄이기 위한 효과적인 방법이다. 본 논문에서는 직렬 선형 귀환 쉬프트 레지스터 구조를 기반으로 부 표현들을 이용한 저 복잡도 m-비트 병렬 BCH 인코더 구현 방법을 제안한다. 또한, 부 표현들을 탐색하기 위한 일반화된 방법을 제시한다. 부 표현들은 패리티 생성을 위해 사용하는 행렬(생성 행렬, generator matrix)의 부 행렬 (sub-matrix)과 다른 변수들의 합과의 행렬 연산에 의해 표현된다. 부 표현들의 수는 개로 한정되며, 탐색된 부 표현들은 다른 병렬 BCH 인코더 구현을 위해 공유되어질 수 있다. 본 논문은 구현 과정에서 다수의 팬 아웃에 의해 발생하는 문제점(지연)의 해결이 아닌 복잡도(로직 사이즈) 감소에 그 목적이 있다.