• Carbon letters
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• 제15권1호
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• pp.57-66
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• 2014

Three activated carbons (ACs) were prepared using NaOH (N) as an activating agent. Hydrofluoric acid pre-leached rice husk was used as a precursor. After leaching, the precursor was washed with distilled water, dried, crushed, and then sieved; a size fraction of 0.3-0.5 mm was selected for carbonization in the absence of air at $600^{\circ}C$. The carbonization product (LC) was mixed with NaOH at ratios of 1:2, 1:3, and 1:4 (wt of LC: wt of NaOH) and the produced ACs after activation at $800^{\circ}C$ were designated NLC21, NLC31, and NLC41, respectively. Surface and textural properties were determined using nitrogen adsorption at $-196^{\circ}C$, scanning electron microscopy images, thermogravimetric analysis, and Fourier transform infrared spectra. These ACs were used as adsorbents for lead(II) from aqueous solutions. The effects of the textural properties and the chemistry of the carbon surfaces were investigated and the impact of the operation conditions on the capacity for lead(II) sorption was also considered. Modification of NLC41 with $H_2O_2$ and $HNO_3$ gave two other adsorbents, $H_{NLC41}$ and $N_{NLC41}$ respectively. These two new samples exhibited the highest removal capacities for lead(II), i.e.117.5 and 128.2 mg/g, respectively. The adsorption data fitted the Langmuir isotherm and the kinetic adsorption followed pseudo-second order kinetics. The thermodynamic parameters have been determined and they indicated a spontaneous endothermic process.

• Biomaterials and Biomechanics in Bioengineering
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• 제2권1호
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• pp.47-59
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• 2015

A bioactive and multifunctional elastin-like polymer (ELP) was produced by genetic engineering techniques to develop new artificial matrices with the ability to mimic the extracellular matrix (ECM). The basic composition of this ELP is a thermo- and pH-sensitive elastin pentapeptide which has been enriched with RGD-containing domains, the RGD loop of fibronectin, for recognition by integrin receptors on their sequence to promote efficient cell attachment. Hydrogels of this RGD-containing polymer were obtained by crosslinking with hexamethylene diisocyanate, a lysine-targeted crosslinker. These materials retain the "smart" nature and temperature-responsive character, and the desired mechanical behavior of the elastin-like polymer family. The influence of the degree of crosslinking on the morphology and properties of the matrices were tested by calorimetric techniques and scanning electron microscopy (SEM). Their mechanical behavior was studied by dynamical mechanical analysis (DMA). These results show the potential of these materials in biomedical applications, especially in the development of smart systems for tissue engineering.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2005년도 춘계학술발표회
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• pp.179-183
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• 2005

최근 박판부재인 고장력강이 구조물에 폭넓게 사용됨으로서 좌굴이 발생하기 쉽다. 특히 고장력강을 사용하는 선체구조물에서는 좌굴은 중요한 설계기준이 되고 있다. 따라서 좌굴발생 후 거동을 정확하게 파악하는 것은 선체구조의 안정성에 중요하다. 본 연구에서는 선체의 대표적인 구조물인 판을 대상으로 각 선급 룰에서 좌굴강도식의 기준으로 삼고 있는 단순지지조건에서의 여러 가지 항복강도에 따라 압축하중을 받는 박판구조물의 초기좌굴 후 거동과 2차좌굴 후 거동에 대해서 규명하였다. 해석방법으로는 범용 유한요소해석 프로그램인 ANSYS를 이용하였고 2차좌굴과 같은 복잡한 비선형거동을 해석하기 위하여 호장증분법(Arc-length method)을 사용하였다.

• The Journal of Advanced Prosthodontics
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• 제5권2호
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• pp.118-125
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• 2013

PURPOSE. The purpose of this study was to evaluate the effect of the span length on the fit of zirconia framework fabricated using CAD/CAM system. MATERIALS AND METHODS. Abutments for single, 4-unit and 6-unit fixed partial prostheses were fabricated. Ten zirconia frameworks were fabricated for each group. The marginal and internal gap were presented by means of replica technique and measured by measuring microscope ($AXIO^{(R)}$, Carl Zeiss, Rochester, NY) and software (I-$solution^{(R)}$, IMT i-solution Inc., Vancouver, BC, Canada). The results were statistically analyzed by multivariate analysis test and Dunnett T3 test for post hoc test (${\alpha}$=.05). RESULTS. There were statistically significant differences at 2, 4, 7, 8 points (mesio-distal section) and b, d, e, f, g (labio-lingual section). In some marginal reference points of 6-unit group (P<.05), the marginal gap were larger than 120 ${\mu}m$. CONCLUSION. Span length of zirconia core may have an influence on marginal and internal fit. Within the limitation of this study, the increase of span length of zirconia framework of 6 or more-unit fixed partial denture may decrease the marginal and internal fit.

• Journal of Magnetics
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• 제21권2호
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• pp.286-292
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• 2016

This study evaluates the change of computer tomography (CT) number in the case of the metal artifact reduction (MAR) algorithm, using the phantom. The images were obtained from dual CT using a gammex 467 tissue characterization phantom, which is similar to human tissues. The test method was performed by dividing pre and post MAR algorithm and measured CT values of nonmagnetic materials within the phantom. In addition, the changes of CT values for each material were compared and analyzed after measuring CT values up to 140 keV, using the spectral HU curve followed by CT scan. As a result, in the cases of N rod (trabecular bone) and E rod (trabecular bone), the CT numbers decreased as keV increasing but were constant above 90 keV. In the cases of I rod (dense bone) and K rod (dense bone), the CT numbers also decreased as keV increased but were uniform above 90 keV. The CT numbers from 40 keV to 140 keV were consistent in the cases of J rod (liver), D rod (liver), L rod (muscle), and F rod (muscle). For A rod (adipose), G rod (adipose), B rod (breast) and O rod (breast), the CT numbers increased as keV increased but were constant after 90 keV. The CT numbers from 40 keV to 140 keV were consistent in the cases of C rod (lung (exhale)), P rod (lung (exhale)), M rod (lung (inhale)) and H rod (lung (exhale)). Conclusively, because dual CT exhibits no changes in image quality and is able to analyze nonmagnetic materials by measuring the CT values of various materials, it will be used in the future as a useful tool for the diagnosis of lesions.

• International Journal of Automotive Technology
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• 제7권1호
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• pp.25-34
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• 2006

For decades, simulation technique has been well validated in areas such as computer and communication systems. Recently, the technique has been much used in the area of transportation and traffic forecasting. Several methods have been proposed for investigating complex traffic flows. However, the dynamics of vehicles and diversities of driver characteristics have never been considered sufficiently in these methods, although they are considered important factors in traffic flow analysis. In this paper, we propose a traffic simulation tool called Multi-Agent for Traffic Simulation with Vehicle Dynamics Model (MATDYMO). Road transport consultants, traffic engineers and urban traffic control center managers are expected to use MATDYMO to efficiently simulate traffic flow. MATDYMO has four sub systems: the road management system, the vehicle motion control system, the driver management system, and the integration control system. The road management system simulates traffic flow for various traffic environments (e.g., multi-lane roads, nodes, virtual lanes, and signals); the vehicle motion control system constructs the vehicle agent by using various vehicle dynamic models; the driver management system constructs the driver agent capable of having different driving styles; and lastly, the integrated control system regulates the MATDYMO as a whole and observes the agents running in the system. The vehicle motion control system and driver management system are described in the companion paper. An interrupted and uninterrupted flow model were simulated, and the simulation results were verified by comparing them with the results from a commercial software, TRANSYT-7F. The simulation result of the uninterrupted flow model showed that the driver agent displayed human-like behavior ranging from slow and careful driving to fast and aggressive driving. The simulation of the interrupted flow model was implemented as two cases. The first case analyzed traffic flow as the traffic signals changed at different intervals and as the turning traffic volume changed. Second case analyzed the traffic flow as the traffic signals changed at different intervals and as the road length changed. The simulation results of the interrupted flow model showed that the close relationship between traffic state change and traffic signal interval.

• Advances in biomechanics and applications
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• 제1권2호
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• pp.127-141
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• 2014

A preliminary study of a new pulsatile pump that will work to a frequency greater than 1 Hz, is presented. The fluid-structure interaction between a Newtonian blood flow and a piston drive that moves with periodic speed is simulated. The mechanism is of double effect and has four valves, two at the input flow and two at the output flow; the valves are simulated with specified velocity of closing and reopening. The simulation is made with finite elements software named COMSOL Multiphysics 3.3 to resolve the flow in a preliminary planar configuration. The geometry is 2D to determine areas of high speeds and high shear stresses that can cause hemolysis and platelet aggregation. The opening and closing valves are modelled by solid structure interacting with flow, the rhythmic opening and closing are synchronized with the piston harmonic movement. The boundary conditions at the input and output areas are only normal traction with reference pressure. On the other hand, the fluid structure interactions are manifested due to the non-slip boundary conditions over the piston moving surfaces, moving valve contours and fix pump walls. The non-physiologic frequency pulsatile pump, from the viewpoint of fluid flow analysis, is predicted feasible and with characteristic of low hemolysis and low thrombogenesis, because the stress tension and resident time are smaller than the limit and the vortices are destroyed for the periodic flow.

• 방송공학회논문지
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• 제24권5호
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• pp.827-835
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• 2019

완전 참조 영상 화질(full-reference image quality assessment, FR-IQA)측정의 풀링 과정에 있어서, 한 영상의 전역 화질은 각 국부 패치의 측정된 화질값들로부터 측정된다. 그러나 한 영상의 전체 화질 값을 예측함에 있어서 국부 패치의 종류, 왜곡 타입, 왜곡의 인지 민감도, 국부 패치의 관심 집중(saliency) 정도에 따라 국부 패치가 전체 영상에 기여하는 왜곡의 정도가 다를 수 있다. 그 결과, 계산된 국부 패치 화질값에 대한 가중치 풀링 방법이 기존 FR-IQA 방법에서 고려되었다. 본 논문은 기존 FR-IQA 방법에서 고려되지 않은 시각인지시스템의 특성인, 광적응 효과 와 시각 관심 집중 효과를 고려한 새로운 가중치 풀링 방법을 제안한다. 실험 결과, 기존 FR-IQA 방법에 적용될 경우 예측 성능을 향상시킴을 확인하였으며, 이는 제안하는 가중치 풀링 방법은 사람의 시각인지 특성을 효과적으로 반영하기 때문으로 사료된다.

• Journal of Forest and Environmental Science
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• 제38권2호
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• pp.90-101
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• 2022

The study aims to assess composition, diversity and population indices of natural regeneration of woody species in Jebel El Gerrie forest reserve, Blue Nile State, Sudan. We conducted field work between December 2018 and January 2019. We used random sampling to collect vegetation data in the forest where we made a total of 90 circular sample plots (radius 17.84 m) and distributed them proportionally to the area of each of the four density-based vegetation classes of the forest i.e. high density (C1), medium density (C2), low density (C3) and crop land (C4). In each sample plot we identified all regenerating tree species and counted their regeneration frequencies. We calculated ecological metrics of regeneration frequency, density, abundance, richness, evenness, diversity and importance value index (IVI) and drew abundance rank curve. Results revealed that out of fifteen mature tree species present, natural regeneration of 8 species, which belong to 6 families, was observed. The relatively most frequently naturally regenerating and abundant species were Anogeissus leiocarpa and Combretum hartmannianum. Richness, evenness and diversity of regenerating species were 1.33, 0.82 and 1.7, respectively. One-way ANOVA (α=0.05) of mean regeneration densities disclosed that there were significant differences (F_3,86=16.77, p=0.000) between C2 & C3 (p=0.000) and C2 & C4 (p=0.000). While regeneration of seven tree species were absent, two, two and four species were of good, poor and fair regeneration status, respectively. A comparison of mean density of natural regeneration with that of parent trees reflects a poor regeneration status of the forest. The study provides empirical results on the regeneration status of species and signifies the need for management interventions for species conservation and restoration, maintenance of biodiversity and sustainable production.

• 대한토목학회논문집
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• 제3권2호
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• pp.1-15
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• 1983

본(本) 논문(論文)에서는 활성(活性)슬러지법(法)에 의(依)한 분뇨처리방법(糞尿處理方法) 대신 BFB를 이용(利用)한 저희석(低稀釋) 분뇨처리(糞尿處理)의 가능성(可能性)과 수학적(數學的) 해석(解析)을 시도(試圖)하였다. 실험(實驗)은 BFB의 메디아로써 폴리프로필렌계(系) 합성섬유(合成纖維)인 부직포(不織布)를 사용(使用)하였으며, 수온(水溫) $20^{\circ}C$에서 F/M비(比) 및 분뇨(糞尿)의 희석비(稀釋比)를 0.12~0.37/day와 2~10배(倍)로 변화(變化)시켜 연속식(連續式) 반응조(反應槽)에 의해 수행(修行)되었다. 여기서 얻어진 결과(結果)로는 저희석(低稀釋) 분뇨처리(糞尿處理)에 대(對)한 BFB의 적용(適用)은 다른 생물학적(生物學的) 처리법(處理法)에 비(比)해 더 좋은 효과(効果)를 얻을 수 있는 것으로 나타났는데 본연구(本硏究)에서 나타난 분뇨(糞尿)의 최적희석비(最適稀釋比)는 5배(倍)로 나타났고, 그 때의 최적(最適) 체류시간(滯留時間)은 17시간(時間)으로 나타났다. 따라서 반응조(反應槽)의 체적(體積)은 70%, 희석수(稀釋水)는 80%까지 절감(切減)할 수 있는 것으로 계산(計算)되었다. 또 완전혼합(完全混合) 활성(活性)슬러지법(法)에 적용(適用)되는 수학적(數學的) 해법(解法)으로도 BFB의 실험결과(實驗結果)를 해석(解析)할 수 있었다. $20^{\circ}C$에서 McKinney 식(式)($K_m$)과 Eckenfelder 식(式)($K_e$)을 이용(利用)하여 구(求)한 유기물(有機物) 제거속도(除去속도(速度))는 1.784/hr와 $2.0{\times}10^{-3}l/mg{\cdot}day$이었으며, 다른 방법(方法)에 비(比)해 유기물(有機物) 제거(除去)가 빠른 속도(速度)로 진행(進行)되었다. 미생물(微生物) 번식계수(繁殖係數)($a_5$), 내호흡(內呼吸) 계수(係數)(b), 미생물(微生物) 합성(合成)에 필요(必要)한 요소(酸素) 요구율(要求率)($a{_5}^{\prime}$) 및 내호흡(內呼吸)에 필요(必要)한 산소(酸素) 요구율(要求率)(b')은 각각(各各) 0.349, 0.0237/day, 0.495와 0.0336으로 계산(計算)되었다.