• 항공우주시스템공학회지
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• 제12권3호
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• pp.9-17
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• 2018

지구 관측용 소형 위성카메라의 경우, 중대형 위성에 비해 상대적으로 약한 구조 안정성으로 인해 열악한 발사환경 및 우주환경에서 광부품의 정렬오차가 발생하기 쉽다. 발생한 정렬오차는 위성카메라의 광학 성능 저하를 유발시킨다. 본 연구에서는 소형 위성 카메라의 정렬오차를 보상하기 위하여 3축 포커스 메커니즘을 제안하였다. 이 메커니즘은 3개의 압전 작동기로 구성되어 x-축, y-축 틸트 및 디스페이스(De-space) 보정을 수행할 수 있다. 포커스 메커니즘의 설계 요구조건은 슈미트-카세그레인(Schmidt-Cassegrain) 타입의 목표 광학계 설계에서 도출되었다. 부경 정렬오차 보상을 위하여 부 반사경의 뒤에 포커스 메커니즘을 부착하여 부경의 3축 운동을 제어하였다. 이 때 파면오차로 인한 광학 성능 저하를 최소화하기 위한 플렉셔를 Box-Behnken 실험계획법을 통하여 설계하였으며, ANSYS를 이용하여 파면오차 해석을 수행하였다. 제작된 포커스 메커니즘은 작동기의 수학적 모델링, PID 제어기 설계, 서보 제어실험을 통해 서보성능을 검증하였다.

• International Journal of Concrete Structures and Materials
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• 제9권2호
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• pp.185-206
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• 2015

This paper presents statistical models developed to study the influence of key mix design parameters on the properties of lightweight self-consolidating concrete (LWSCC) with expanded shale (ESH) aggregates. Twenty LWSCC mixtures are designed and tested, where responses (properties) are evaluated to analyze influence of mix design parameters and develop the models. Such responses included slump flow diameter, V-funnel flow time, J-ring flow diameter, J-ring height difference, L-box ratio, filling capacity, sieve segregation, unit weight and compressive strength. The developed models are valid for mixes with 0.30-0.40 water-to-binder ratio, high range water reducing admixture of 0.3-1.2 % (by total content of binder) and total binder content of $410-550kg/m^3$. The models are able to identify the influential mix design parameters and their interactions which can be useful to reduce the test protocol needed for proportioning of LWSCCs. Three industrial class ESH-LWSCC mixtures are developed using statistical models and their performance is validated through test results with good agreement. The developed ESH-LWSCC mixtures are able to satisfy the European EFNARC criteria for self-consolidating concrete.

• 대한토목학회논문집
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• 제33권1호
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• pp.93-100
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• 2013

본 연구에서는 트윈박스 단면인 이순신대교의 레이놀즈수 변화에 따른 공기력의 영향을 살펴보는데 그 목적이 있다. 이를 위하여 1/30 대축척 모형을 제작하여 공군사관학교 아음속 중형 풍동에서 최대 풍속 70m/s까지 풍속을 증가시켜가면서 공기력을 측정하여, 전북대학교 소형풍동에서 수행한 저레이놀즈수 풍동실험 결과와 비교하였다. 본 연구 대상 교량 단면은 레이놀즈수의 영향을 받는 것으로 나타났으며, 고레이놀즈수 실험 결과 기존 저레이놀즈수 실험보다 항력계수는 약 23%정도 낮은 수준인걸로 나타났다. 또한 경계층 촉진장치를 효과적으로 이용하면 기존의 저레이놀즈수 풍동실험 조건에서 고레이놀즈수 모사 실험이 가능한 것으로 판단된다.

• Advances in materials Research
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• 제13권1호
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• pp.1-18
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• 2024

The present experimental investigation focuses on finding optimal parametric data-set of laser micro-drilling operation with minimum taper and Heat-affected zone during laser micro-drilling of Carbon Nanotube/Epoxy-based composite materials. Experiments have been conducted as per Box-Behnken design (BBD) techniques considering cutting speed, lamp current, pulse frequency and air pressure as input process parameters. Then, the relationship between control parameters and output responses is developed using second-order nonlinear regression models. The analysis of variance test has also been performed to check the adequacy of the developed mathematical model. Using the Response Surface Methodology (RSM) and an Accelerated particle swarm optimization (APSO) technique, optimum process parameters are evaluated and compared. Moreover, confirmation tests are conducted with the optimal parameter settings obtained from RSM and APSO and improvement in performance parameter is noticed in each case. The optimal process parameter setting obtained from predictive RSM based APSO techniques are speed=150 (m/s), current=22 (amp), pulse frequency (3 kHz), Air pressure (1 kg/cm²) for Taper and speed=150 (m/s), current=22 (amp), pulse frequency (3 kHz), air pressure (3 kg/cm²) for HAZ. From the confirmatory experimental result, it is observed that the APSO metaheuristic algorithm performs efficiently for optimizing the responses during laser micro-drilling process of nanocomposites both in individual and multi-objective optimization.

• International Journal of Concrete Structures and Materials
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• 제10권sup3호
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• pp.1-17
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• 2016

Recently, advanced transit systems are being constructed to reduce traffic congestions in metropolitan areas. For these projects, curved bridges with various curvatures are required. Many curved bridges in the past were constructed using aesthetically unpleasant straight beams with curved slabs or expensive curved steel box girders with curved slabs. Therefore, many recent studies have been performed to develop less expensive and very safe precast prestressed concrete (PSC) curved girder. One method of reducing the construction cost of a PSC curved girder is to use a reusable formwork that can easily be adjusted to change the curvature and length of a girder. A reusable and curvature/dimension adjustable formwork called Multi-tasking formwork is developed for constructing efficient precast PSC curved girders. With the Multi-tasking formwork, two 40 m precast PSC box girders with different curvatures were constructed to build a two-girder curved bridge for a static flexural test to evaluate its safety and serviceability performance. The static flexural test results showed that the initial cracking load was 1400 kN, exceeding the design cracking load of 450 kN. Also, the code allowed deflection of 50 mm occurred at a load of 1800 kN, verifying the safety and serviceability of the precast PSC curved bridge constructed using the multi-tasking formwork.

• 생명과학회지
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• 제20권2호
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• pp.304-313
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• 2010

J시 소재 K여자고등학교 1학년 중에서 %fat이 30% 이상인 24명을 유의추출법에 의해 운동그룹 A (8명), B (8명) 그룹과 통제그룹(8명)으로 3그룹으로 구분하여 Borg의 주관적운동강도를 이용, A그룹은 RPE 15-17 (hard-very hard; 힘듦-매우 힘듦)${\times}$3 sets, B그룹은 RPE 11-13 (fairly light-somewhat hard; 알맞음-약간 힘듦)${\times}$3 sets로 설정하여 step aerobics (step box: 길이 68 cm, 폭 28 cm, 높이 15 cm, 무게 450 g)를 1일 50-60분간, 주3회(월, 수, 금)로 총 8주간 실시하였다. 본 연구는 step aerobics의 RPE가 비만 여고생의 면역기능(Neutrophil, Lymphocyte, Monocyte, Eosinophil, Basophil, IgG, IgA, IgM)에 어떠한 영향을 미치는가를 알아보는 것이었다. 자료처리는 SPSS Ver. 14.0을 이용하여 집단과 시기 간 상호작용의 효과를 알아보기 위하여 repeated two-way ANOVA를, 집단 내 운동 전 후는 paired t-test를 실시하였고, 집단 간은 변화율(% diff.)을 구하여 one-way ANOVA를 실시하여 다음과 같은 결론을 얻었다. WBC에서, 집단 내 비교에서 A그룹은 Neutrophil, Monocyte, Basophil, Eosinophil 모두 증가하였으나 Lymphocyte는 변화가 없었고, B그룹은 Eosinophil은 감소하였으나 Neutrophil, Lymphocyte, Monocyte, Basophil 모두 변화가 없었으며, 통제군은 Neutrophil, Basophil, Eosinophil은 감소하였으나 Lymphocyte와 Monocyte는 변화가 없었다. 집단 간 비교의 Neutrophil은 A그룹이 B그룹과 통제군보다 더 많이 증가하였고, Lymphocyte는 집단 간 차이가 없었으며, Monocyte는 A, B그룹이 통제군보다 많이 증가하였다. Basophil과 Eosinophil은 A그룹이 B그룹과 통제군보다 더 많이 증가하였다. Immunoglobin에서, 집단 내 비교에서 A그룹은 IgG는 증가하였으나 IgA와 IgM는 변화가 없었고, A그룹은 IgA는 증가하였으나 IgG는 감소하였고 IgM은 변화가 없었다. 통제군은 IgG은 감소하였으나 IgA와 IgM은 변화가 없었다. 집단 간 비교의 IgA는 A그룹이 통제군보다 증가하였고, IgG는 A그룹이 B그룹과 통제군보다 증가하였으나 IgM은 집단 간 차이가 없었다. 요약하면 세 집단 모두 운동프로그램 전 후의 WBC와 Ig 수준이 연령에 맞게 참고치 내의 수준에 머물렀지만 step aerobics를 RPE 15-17로 실시한 A그룹의 경우가 가장 많은 측정항목에서 증가를 보였고, 이 결과는 참고치 범위 내에서 면역기능의 항진을 보여주는 것으로 면역기능의 향상을 위한 step aerobics의 RPE 강도는 힘듦-매우 힘듦(15-17)의 수준으로 실시하는 것이 효과적인 것으로 생각된다.

• 천문학회지
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• 제48권4호
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• pp.213-228
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• 2015

The Horizon Run 4 is a cosmological N-body simulation designed for the study of coupled evolution between galaxies and large-scale structures of the Universe, and for the test of galaxy formation models. Using 6300³ gravitating particles in a cubic box of L_box = 3150 h⁻¹Mpc, we build a dense forest of halo merger trees to trace the halo merger history with a halo mass resolution scale down to M_s = 2.7 × 10¹¹h⁻¹M_⊙. We build a set of particle and halo data, which can serve as testbeds for comparison of cosmological models and gravitational theories with observations. We find that the FoF halo mass function shows a substantial deviation from the universal form with tangible redshift evolution of amplitude and shape. At higher redshifts, the amplitude of the mass function is lower, and the functional form is shifted toward larger values of ln(1/σ). We also find that the baryonic acoustic oscillation feature in the two-point correlation function of mock galaxies becomes broader with a peak position moving to smaller scales and the peak amplitude decreasing for increasing directional cosine μ compared to the linear predictions. From the halo merger trees built from halo data at 75 redshifts, we measure the half-mass epoch of halos and find that less massive halos tend to reach half of their current mass at higher redshifts. Simulation outputs including snapshot data, past lightcone space data, and halo merger data are available at http://sdss.kias.re.kr/astro/Horizon-Run4.

• Korean Journal of Chemical Engineering
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• 제35권11호
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• pp.2241-2255
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• 2018

RSM methodology was applied to present mathematical models for the fabrication of polyvinylidene fluoride (PVDF) dual-layer hollow fibers in membrane distillation process. The design of experiments was used to investigate three main parameters in terms of polymer concentration in both outer and inner layers and the flow rate of dope solutions by the Box-Behnken method. According to obtained results, the optimization was done to present the proper membrane with desirable properties. The characteristics of the optimized membrane (named HF-O) suggested by the Box-Behnken (at the predicted point) showed that the proposed models are strongly valid. Then, a morphology study was done to modify the fiber by a combination of three types of a structure such as macro-void, sponge-like and sharp finger-like. It also improved the hydrophobicity of outer surface from 87 to $113^{\circ}$ and the mean pore size of the inner surface from 108.12 to 560.14 nm. The DCMD flux of modified fiber (named HF-M) enhanced 62% more than HF-O when it was fabricated by considering both of RSM and morphology study results. Finally, HF-M was conducted for long-term desalination process up to 100 hr and showed stable flux and wetting resistance during the test. These stepwise approaches are proposed to easily predict the main properties of PVDF dual-layer hollow fibers by valid models and to effectively modify its structure.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권7호
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• pp.1841-1857
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• 2023

CenterNet, a novel object detection algorithm without anchor based on key points, regards the object as a single center point for prediction and directly regresses the object's height and width. However, because the objects have different sizes, directly regressing their height and width will make the model difficult to converge and lose the intrinsic relationship between object's width and height, thereby reducing the stability of the model and the consistency of prediction accuracy. For this problem, we proposed an algorithm based on the regression of the diagonal half-length and the center angle, which significantly compresses the solution space of the regression components and enhances the intrinsic relationship between the decoded components. First, encode the object's width and height into the diagonal half-length and the center angle, where the center angle is the angle between the diagonal and the vertical centreline. Secondly, the predicted diagonal half-length and center angle are decoded into two length components. Finally, the position of the object bounding box can be accurately obtained by combining the corresponding center point coordinates. Experiments show that, when using CenterNet as the improved baseline and resnet50 as the Backbone, the improved model achieved 81.6% and 79.7% mAP on the VOC 2007 and 2012 test sets, respectively. When using Hourglass-104 as the Backbone, the improved model achieved 43.3% mAP on the COCO 2017 test sets. Compared with CenterNet, the improved model has a faster convergence rate and significantly improved the stability and prediction accuracy.

• 한국균학회지
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• 제3권2호
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• pp.19-23
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• 1975

한국산(韓國産) 생송용(生松茸)의 선도보존(鮮度保存)을 하기 위하여 드라이아이스를 넣은 송이 상자 내부의 기온변화(氣溫變化)에 관(關)한 연구(硏究)가 1975(年) 8월(月) 1일(日)부터 동월(同月) 30일(日)까지 서울에서 이루어졌다. 정미(正味) 5kg의 생송용(生松茸)를 24시간(時間)동안 선도(鮮度)를 보존(保存)하여 안전수송(安全輸送)하려면 8월중(月中)에는 후지상자(厚紙箱子)(송용상자(松茸箱子))내(內)에 송이를 채우고, 4.5kg의 드라이아이스를 그상자안의 최상부(最上部)와 중간부(中間部)에 약(約) 반(半)씩 나누어 넣고 밀봉(密封)하면 되었다. 송용상자(松茸箱子)의 체적(體積)은 $0.066m^3$ $(0.33{\times}0.4{\times}0.5m)$이고, 두께 3mm의 이중포장지(二重包裝紙)로 만들었다. 추계(秋季)에 기온(氣溫)이 하강(下降)함에 따라 넣는 드라이아이스양(量)도 감소(減少)시켜, 실제(實際)로 9월(月)에는 $2{\sim}3kg$, 10월(月)에는 $0.3{\sim}1.5kg$의 드라이아이스를 넣으면 되었다. 이 방법(方法)을 써서 일본국(日本國) 동경(東京), 대판(大阪)으로 생송용(生松茸)를 부패(腐敗)함이 없이 다량수출(多量輸出)하여 대성과(大成果)를 거두었다.