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최돈하 ( Don-ha Choi ),박천영 ( Chun-Young Park ),이은정 ( Eunjung Lee ),김지선 ( Gisun Kim ),최진영 ( Jinyoung Choi ),엄창득 ( Chang-deuk Eom ),김민지 ( Min-ji Kim ) 한국목재공학회 2021 한국목재공학회 학술발표논문집 Vol.2021 No.2
우리나라는 국토의 약 64%가 산림이지만 목재자급률은 2019년 기준 16.6%에 머물고 있다. 전 세계적으로 기후변화대응을 위한 탄소중립 실현을 위해 다양한 노력이 전개되고 있으며, 목재의 활용가치가 중요하게 다뤄지고 있다. 이에 국내에서도 목재자급률 상승 및 목재이용 활성화를 통해 탄소중립에 기여하기 위한 논의가 활발하다. 이에 본 연구는 대량의 국산재 수요 창출 및 도시의 환경개선을 위해 적용가능한 거리 목조시설물을 조사·분석하고, 이를 BIM 기초자료로 활용하기 위해 진행되었다. 목조시설물의 조사는 온라인 거래 플랫폼, 현장방문조사 등을 통해 이루어졌다. 조사결과 거리 목조시설물의 유형은 접근성에 따라 도로, 인도, 건축물 등으로 구분되고, 용도에 따라 정보표시, 보도편의, 외장마감, 구조물 등으로 구분된다. 사용된 목재는 주요 구조재가 아닌 단순 부품 또는 마감재가 대부분이며, 색상과 팬턴이 매우 단순하였다. 분석 결과는 일사량(일조시간)에 따른 색상 차이가 있어 지역에 따른 고려하 필요하고, 우수 등 수분과 관련하여 특정 부위에 대한 구조 개선과, 주변과 조화된 패턴과 색의 다양성 확보, 관리매뉴얼의 개발과 적용이 시급하다는 점이다. 각 유형 및 용도별 거리 목조시설물의 개별 사례와 특성은 현재 추가 조사 및 분석 중이며, 최종적으로는 BIM 개발에 반영될 예정이다.
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최돈하(Choi, Don-Ha),이성연(Lee, Seong Youn),손영모(Son, Yeong Mo),박경석(Park, Kyung Seok) 한국신재생에너지학회 2005 한국신재생에너지학회 학술대회논문집 Vol.2005 No.06
Total forest growing stock and growing stock per ha in Korea are 470times10<sup>6</sup>m³;and;73m³, respectively. Those figures mean that forest growing stock was increased 4.7 times more during last 30 years. The annual production of forest biomass comes from forest tending executed by Korea Forest Service was estimated about 1.07times10<sup>6</sup>m³ M/T, which was equivalent to 0.45% of total imported crude oil of Korea at 2002. The production is expected to increase and reach up to 1.9times10<sup>6</sup> M/T till 2008. The analysis of economic feasibility showed that the production cost of wood chip(134,786Won/T) was about 30,389 Won/T higher than heat value of wood chip, 104,397 Won/T estimated from that of kerosene. For the promotion of forest bioenergy utilization, more efforts need to be given for the education and public relations to induce publicity a willingness-to-pay for the environment friendly fuels under the good understanding for the use of bioenergy. In addition, we need to provide a community-based biomass utilization program by region to allocate the role of each participant and to increase the profitability of bioenergy.
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초임계수에 의한 현사시 목분의 분해특성 및 분해산물 분석
최준원(Joon-Weon Choi),임현진(Hyun-Jin Lim),한규성(Kyu Sung Han),강하영(Ha-Young Kang),최돈하(Don-Ha Choi) 한국산림바이오에너지학회 2005 산림바이오에너지 Vol.24 No.1
본 연구에서는 연속형 초임계수 분해장치를 이용하여 처리온도 별로 현사시목재의 당화 가능성과 현사시목재 각 성분의 분해특성을 분석하였다. 미세하게 분쇄한 현사시목분을 물의 초임계압력(23MPa)조건하에서 각각 아임계온도(275℃, 325℃)와 초임계온도(375℃, 415℃)에서 각각 2분간 처리하였다. 갈색을 띤 현사시목분의 액상분해산물에는 어느 정도의 미분해 고형분이 포함되어 있었다. 초임계수 분해온도가 높을수록 현사시목분의 분해율은 증가하여 초임계조건인 375℃에서는 현사시목분의 94%까지 분해되었다. 각 처리조건에서 생성된 환원당량을 DNS법으로 측정한 결과, 처리온도가 상승함에 따라 생성된 환원당량은 점차 감소하는 경향을 나타내었다. 이는 반응 초기에 생성된 환원당들이 높은 온도의 반응기를 통과하면서 열분해와 유사한 화학적 반응에 의해 더욱 분해되어 퓨란계 화합물로 전환된 것으로 예측되었다. 리그닌의 분해특성을 살펴보기 위하여 액상의 분해산물을 ethylacetate로 추출하여 유기용매 가용부를 GC-MS로 분석하였다. 리그닌의 분해산물은 대부분 페놀성 유도체인 vanillin, guaiacol, syringaldehyde, 4-prophenyl syringol과 dihydrosinapyl alcohol 등으로 확인되었으며, 이들의 농도는 처리온도가 상승함에 따라 증가하는 것으로 나타났다. 이러한 리그닌 분해산물은 리그닌고분자의 주요 결합인 에테르 결합이 높은 온도조건하에서 분해에 의한 것으로 예측되었다. In this study, the possibility of sugar conversion of poplar wood(Populus alba×glandulosa) and their degradation features of major wood components were characterized using flow type supercritical water treatment system. The finely ground poplar wood meals were treated for 2min. under subcritical condition(23MPa, 275℃ and 325℃) and supercritical condition(23MPa, 375℃ and 415 ℃), respectively. The degradation products of poplar wood meals appeared brownish colors, including undegraded solids. Increasing the temperature of the system, the degradation rate of poplar wood meals was accelerated and reached up to 94% at 375℃. The total amount of reducing sugars in degradation products determined by DNS method were gradually lowered when the temperature condition became severe. This indicated that the reducing sugars formed were further degraded to furan derivatives by certain side reaction such as pyrolysis under higher temperature. In order to characterize degradation features of lignin, the degradation products were extracted with ethylacetate and the organic phases were subjected to GC-MS analysis. Main lignin degradation products were identified to vanillin, guaiacol, syrinaldehyde, 4-prophenyl syringol and dihydrosinapyl alcohol, which could be formed by the cleavage of ether linkages in lignin polymers by high temperature condition.
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Computer Simulation에 의한 FMS의 生産日程 計劃 硏究
최효돈,남현우,문기주,하정진 동아대학교 공과대학 부설 한국자원개발연구소 1992 硏究報告 Vol.16 No.1
An FMS(Flexible Manufacturing System) consists of a group of computer numerically controlled machines linked by and automated material handling system, and which operates under computer control. FMS's are designed for production of small and medium-sized batchs comprising several different part types with the efficiency of automated mass production and the flexiblity of the job shop. In this research, job scheduling for minimizing APT(average processing time) was studied in FMS with 3 machining centers which are served by a cyclic-unidirectional conveyor while the conveyor speed is set to 1, 2, or 3, respectively. The results of this research could be useful to reduce APT in part manufacturing systems in practice.
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A Method for Dynamic Simulation and Detection of Air-Gap Eccentricity in Induction Motors
Don-Ha Hwang,Ki-Chang Lee,Joo-Hoon Lee,Yong-Joo Kim,Kyeong-Ho Choi,Jin-Hee Lee 전력전자학회 2004 ICPE(ISPE)논문집 Vol.- No.-
This paper presents results of the finite-element (FE) analysis of air-gap flux variation in an induction motor when the rotor vibrates due to its eccentricity. An accurate modeling and analysis of rotor vibration in the machine are made using air-gap flux simulation, and search coils are used for measuring the actual air-gap flux. The simulation was done for the induction motor with 380 [V], 5 [HP], 4P, 1,742 [rpm] ratings using the commercial FE analysis tool. The simulation results can be useful for on-line vibration monitoring of an induction motor.
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Heterolayered, One-Dimensional Nanobuilding Block Mat Batteries
Choi, Keun-Ho,Cho, Sung-Ju,Chun, Sang-Jin,Yoo, Jong Tae,Lee, Chang Kee,Kim, Woong,Wu, Qinglin,Park, Sang-Bum,Choi, Don-Ha,Lee, Sun-Young,Lee, Sang-Young American Chemical Society 2014 NANO LETTERS Vol.14 No.10
<P>The rapidly approaching smart/wearable energy era necessitates advanced rechargeable power sources with reliable electrochemical properties and versatile form factors. Here, as a unique and promising energy storage system to address this issue, we demonstrate a new class of heterolayered, one-dimensional (1D) nanobuilding block mat (<I>h</I>-nanomat) battery based on unitized separator/electrode assembly (SEA) architecture. The unitized SEAs consist of wood cellulose nanofibril (CNF) separator membranes and metallic current collector-/polymeric binder-free electrodes comprising solely single-walled carbon nanotube (SWNT)-netted electrode active materials (LiFePO<SUB>4</SUB> (cathode) and Li<SUB>4</SUB>Ti<SUB>5</SUB>O<SUB>12</SUB> (anode) powders are chosen as model systems to explore the proof of concept for <I>h</I>-nanomat batteries). The nanoporous CNF separator plays a critical role in securing the tightly interlocked electrode–separator interface. The SWNTs in the SEAs exhibit multifunctional roles as electron conductive additives, binders, current collectors and also non-Faradaic active materials. This structural/physicochemical uniqueness of the SEAs allows significant improvements in the mass loading of electrode active materials, electron transport pathways, electrolyte accessibility and misalignment-proof of separator/electrode interface. As a result, the <I>h</I>-nanomat batteries, which are easily fabricated by stacking anode SEA and cathode SEA, provide unprecedented advances in the electrochemical performance, shape flexibility and safety tolerance far beyond those achievable with conventional battery technologies. We anticipate that the <I>h</I>-nanomat batteries will open 1D nanobuilding block-driven new architectural design/opportunity for development of next-generation energy storage systems.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2014/nalefd.2014.14.issue-10/nl5024029/production/images/medium/nl-2014-024029_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl5024029'>ACS Electronic Supporting Info</A></P>
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