공기부양반응기 내에서의 액체순환속도를 위한 모델

최근호,Keun Ho Choi 한국화학공학회 2023 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.61 No.3

A mathematical model for predicting the liquid circulation velocity in an airlift reactor was developed based on the mechanical energy balance of the fluid circulation loop. The model considered the energy loss due to a 90° turn, the energy loss due to friction, and the energy loss due to the change in cross-sectional area at each part of the reactor. The model that separately considered the loss coefficients related to friction, direction change, and cross-sectional area change was able to predict the liquid circulation velocity better than the previous model using lumped parameters. The liquid circulation velocity was measured by the tracer pulse method. Most of our experimental results obtained in external-loop airlift reactors, which had the top and bottom connecting pipes, as well as other investigators' results obtained in various types of airlift reactors, were well predicted by the developed model with an error within 20%. Useful empirical equations for the loss coefficient related to the 90° turn of the circulating fluid were obtained in external and internal-loop airlift reactors and used to predict the liquid circulation velocity.

구강악안면영역의 낭종에 대한 6년간의 후향적 임상 연구

최근호,장정록,박영준,문혜원,김영준,유민기,국민석,박홍주,유신열,오희균,Choi, Guen-Ho,Jang, Jung-Rok,Park, Young-Jun,Moon, Hyea-Won,Kim, Young-Joon,Yu, Min-Gi,Kook, Min-Suk,Park, Hong-Ju,Ryu, Sun-Youl,Oh, Hee-Kyun 대한악안면성형재건외과학회 2009 Maxillofacial Plastic Reconstructive Surgery Vol.31 No.5

Purpose : This study was designed to evaluate the clinical aspect of cysts which arised in the oral and maxillofacial region. Patients and Methods : We reviewed clinical record, radiograph, histopathologic and operative report of 155 patients who had been diagnosed as cysts and treated at the department of oral and maxillofacial surgery in Chonnam National University Hospital from January 2003 to December 2008. Gender, age, classifiaction, anatomic distribution, clinical sign and symptoms, treatment, complications and recurrence rate were studied. Results : 1. Among 155 patients, the male patients(64.5%) were more than the female(35.5%). 2. The average age ofthe patients was 37.2 years(ranging from 5 to 79 years). 3. In pathologic classification, radicular cyst and dentigerous cyst were most common cysts, irrespective of 73 cases(48.3%) and 35 cases(23.2%). 4. The frequently involved cystic regions were followed as mandibular molars(38.1%), and maxillary incisors(30.2%). 5. The frequent sequence of clinical symptoms was edema(29.9%), no symptom(18.9%), tenderness(13.9%), pain(11.5%) and abscess(9.4%). 6. The most prevalent treatment was the combination operation, such as cyst enucleation with extraction or endodontic treatment of the causative tooth(76.8%) 7. Among 155 cases, 2 cases that were treated using enucleation method were recurred(1.3%).

다차원 도시시설물 관리를 위한 멀티 텍스처 기법과 다중 스레드 기법의 적용에 관한 연구

최근호,강병준,조홍범,김원철,Choi, Keun-Ho,Kang, Byoung-Jun,Cho, Hong-Beom,Kim, Won-Cheol 한국공간정보학회 2010 한국공간정보학회지 Vol.18 No.1

최근까지 도시시설물 관리를 위해 활용된 GIS 기술은 주로 2차원 기반의 GIS 기술이었다. 하지만 도시시설물은 3차원 공간상에 존재하며 이를 2차원으로 추상화시키면 정보의 손실이 일어나게 된다. 또한 도시 공간 내에 점차 시설물의 수가 증가하고 있고 대부분의 도시시설물이 지하공간에 위치하기 때문에 2차원 기반의 시스템에서 도시 내 모든 시설물의 정보를 통시에 파악하고 관리하는 것이 어려워지고 있다 본 논문에서는 멀티 텍스처 기법을 이용한 다차원 도시시설물 관리 시스템을 제안한다. 제안된 시스템은 3차원 상에서 도시시설물을 가시화하여 데이터의 손실을 줄이고 정보의 가독성을 높이며, 2차원 벡터 데이터의 3차원 라스터 변환을 통한 가시화 기법을 개발하여 다양한 2차원 GIS 의 공간분석 결과를 3차원 데이터와 동시에 활용할 수 있도록 한다. 또한 3차원 데이터를 처리하는 경우에 시스템의 속도 및 성능이 저하되어 활용 효율성이 떨어지는 문제를 해결하기 위하여 다중 스레드 프로세스를 적용하였다. 본 논문에서 제안한 기술은 기존에 텍스처를 통해 보여주던 센서의 상태정보를 3차원 영상, 시설물 데이터와 함께 시각정보로 표출함으로써 직관적인 시설물 모니터링이 가능해졌다는데 의의가 있다. Recently, 2D GIS technology is applied for urban facility management. However, urban facilities are located in 3D space and the information loss is occurring during data abstraction from 3D urban facility to 2D object. Also, the number of urban facilities is increasing steadily and most of urban facilities are located in underground space in the city. Therefore 2D urban facility management system has a limitation on visualization and management for a large number of urban facilities. In this paper, a multi-dimensions urban facility management system based on multi-texture technology is proposed. The proposed system reduces the information loss and improves the readability of information by visualizing urban facilities on 3D virtual space. A multi-texturing technology is applied for integrating of 2D vector data and 3D raster data, and a multi-thread technology is used for improving speed and performance of the system. The proposed technology can be used as a guideline for urban facility monitoring as providing visual information of a facility status with 3D image and facility data.

생물화공 에너지 / 환경 : 교반조 발효기와 공기부양 발효기내에서의 Phellinus linteus 의 액체배양

최근호(Keun Ho Choi),이창우(Chang Woo Lee) 한국화학공학회 2000 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.38 No.2

In this study, to choose a suitable bioreactor type for the mass culture of Phellinus linteus mycelium, we cultured Phellinus linteus mycelium using a stirred tank fermenter and an airlift fermenter and compared the performances of the two fermenters. The effects of aeration rate and agitation speed on the culture of Phellinus linteus mycelium were also investigated in the ranges of 1-4 L/min, 200-300 rpm, respectively. For the batch submerged culture, the dry weight of mycelium, pH, and dissolved oxygen concentration changed in four steps, respectively. But the periods of same steps were not consistent with each other. With an increase in aeration rate, the final dry weight of mycelium, dissolved oxygen concentration and pH value until the third step of pH change were increased. As the time increased, the concentration of glucose decreased. However, the effects of aeration rate and agitation speed on the variation of glucose concentration were negligible. The maximum final dry weight of mycelium was obtained when agitation speed was 300 rpm. The dissolved oxygen concentration was increased with agitation speed. The dry weight of mycelium and dissolved oxygen concentration in the continuous stirred tank fermenter were larger than them those in the airlift fermenter.

디지털 매체 활용 탐색을 위한, 대학의 플립드 러닝 효과분석 연구

최근호(Keunho Choi),윤재영(Jaeyoung Yun) 한국HCI학회 2018 한국HCI학회 논문지 Vol.13 No.4

본 연구는, 최근 국내에서 미래형 대학교육 방안으로 부상중인 플립드 러닝 적용의 실증적 사례 연구를 분석 대상으로 한 문헌 연구이다. 연구의 목적은, 현재의 디지털 기반 매체 환경을 고려한 국내 대학의 플립드 러닝 적용 수업에서, 학습자들의 디지털 매체 활용에 대한 탐색이다. 이를 위해, 선행 연구의 측정 변인과 통계적 유의성에 대한 고찰 및 매체 활용에 대한 분석을 진행하였다. 가장 주요한 측정 변인은 ‘학습 성취도’와 ‘수업 만족도’로, 플립드 러닝 적용 수업의 효과성 측정에 대한 척도였다. 분석한 모든 연구는 매체를 활용 하였으나, 대부분의 연구가 교실수업의 효과성 검증에 치중하여, 한 편의 연구에서만 별도의 매체 활용 측정이 이루어졌고, ‘동영상 학습인식’ 변인에 대해 통계적으로 유의한 결과가 도출되었다. 연구 별로 매체 활용 관련한 정성적인 측정 내용은 별도의 분석 결과로 제시하였다. 향후, 플립드 러닝 적용 및 디지털 매체 활용에 대한 실효적인 후속 연구를 위해서는 정확한 효과 측정에 필요한 처치 기간의 확보 등 다섯 가지 주요 논점에 대한 검토가 필요하다. This study is a literature study that analyzes empirical case study of Flipped learning application which has emerged as a method of future university education in Korea. The purpose of the study is to explore the use of digital media by learners in the Flipped learning applied courses in domestic universities considering current digital-based media environment. For this purpose, we analyzed the measurement variables and statistical significance of the preceding studies and analyzed the media utilization. The most important measurement variables were "learning achievement" and "class satisfaction", which were measures of effectiveness on the Flipped learning classes. All studies analyzed used media, but most studies focused on verifying the effectiveness of classroom classes, resulting in separate media utilization measurements in one study and statistically meaningful results for the "video learning recognition" variable. The qualitative measurement related to the use of media for each study was presented as a separate analysis result. In the future, in order for effective follow-up studies on application of Flipped learning and digital media utilization, there are five main issues that need to be studied, which are securing the necessary treatment period for accurate effect measurement, etc.

공정시스템 , 이동현상 , 화학공정안전 : 낮은 다분산성지수를 갖는 폴리에틸렌 왁스의 제조방법

최근호(Keun Ho Choi) 한국화학공학회 2001 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.39 No.6

In this study, to solve the problems of previous techniques, a new thermal degradation method was used for producing polyethylene wax having a low polydispersity index. The thermal degradation method was characterized by putting the preheating stage before the reaction stage. At the preheating stage, to increase the thermal conductivity of raw material, the raw material was heated up to a certain temperature(250-370℃), which was lower than the reaction temperature(380-400℃), and was remained at that temperature for a certain time. Polyethylene wax with a low polydispersity index(less than 3.90) could be produced within 5.40 hr using both the thermal degradation method and an external-loop reactor in which specially designed impellers were installed for more effective heat transfer. The effect of the temperature of preheating stage on the polydispersity of product, the viscosity of medium and the manufacturing time was negligible. An increase in the number of preheating stage only marginally affected the polydispersity index of product. When the reaction temperature increased, the viscosity of medium was more rapidly decreased with time and, hence, the reaction time was decreased. The viscosity of medium was decreased with increasing the reaction time.

플라스틱 코팅 알루미늄 판형 열교환기의 성능에 관한 수치해석적 연구

최근호(Geun-Ho Choi),김영일(Young Il Kim),김명수(Myoung-Soo Kim) 한국지열·수열에너지학회 2018 한국지열에너지학회논문집 Vol.14 No.1

The purpose of this study is to investigate the preliminary thermal performance of a plastic coated aluminum material(PCAM) plate heat exchanger. Plastic coating which has high corrosion resistivity and thermal conductivity can overcome corrosive weakness of aluminum material. The heat exchangers are modeled for STS316, Titanium and PCAM materials, and analyzed numerically using HTRI and ANSYS Fluent CFD softwares. The results show that PCAM heat exchanger is superior in heat transfer performance compared to existing materials. For chevron angle of 60°, thermal performances of Titanium and PCAM are higher by 12.2% and 48.9% when compared to STS316, respectively.

한국 지방정부의 정책수용에 관한 연구 -음식물쓰레기종량제를 중심으로-

최근호 ( Geun ho Choi ),엄태호 ( Tae ho Eom ) 한국정책학회 2015 韓國政策學會報 Vol.24 No.4

본 연구의 목적은 한국 지방정부의 중앙정부 정책에 대한 수용을 분석하는 것이다. 구체적으로, 2006년부터 2013년까지의 폐기물관리지역 기초자치단체를 대상으로 중앙정부에서 추진한 음식물쓰레기종량제에 대한 지방정부의 수용 행태에 영향을 미치는 요인들을 실증분석하는 것을 목적으로 한다. 음식물쓰레기종량제는 중앙정부차원에서 추진한 정책으로서, 지방정부에게 시행에는 법적 책무성을 부여하되, 시행방식에는 자율성을 부여한 제도이다. 따라서 지방정부가 시행수준을 스스로 결정하게 되고, 중앙정부의 권고안에 대한 각 지방정부의 수용태도에 차이가 발생한다. 이와 같은 지방정부의 정책수용 행태를 분석하기 위해 본 연구에서는 정책수용과 정책도입에 관한 선행연구를 검토해 지방정부의 수용동기요인과 수용능력요인을 도출하였다. 그리고 한국의 중앙-지방정부간 관계를 나타내는 정책수단인 시행지침을 변수로 조작화하여 분석에 포함하였다. 고정효과 패널 순위형 로짓 분석을 실시하여 추정한 결과, 음식물쓰레기 종량제의 시행수준은 수용동기요인, 시행지침요인과 정(+)의 관계가 있는 것으로 나타났으며, 수용능력요인 중 재정력과는 부(-)의 관계가 있는 것으로 나타났다. 이러한 결과는 환경정책 중 하나인 음식물쓰레기종량제의 경우, 수용동기가 높을 경우에는 중앙정부의 정책에 높은 수용 태도를 보이지만, 수용능력이 높을 경우에는 낮은 수용 태도를 가질 가능성이 있음을 시사한다. This study aims to analyze the policy compliance behavior of local governments; more concretely, this is empirical research on the determinants of Korean local government' compliance with the Korean central government's policies. The object of this study is “The Measured Rate System of Food Waste.” Some characteristics of the measured rate system of food waste, such as accountability of implementation and selectivity for the methods of implementing policy that are produced by central government, have created diverse local government compliance behavior. For this reason, the measured rate system of food waste gives the opportunity to analyze local government policy compliance. I brought two different theories to build a research model: A theory of policy compliance(or regulatory compliance), and the policy adoption and diffusion of local governments. I combined these two theoretical perspectives and added special factors; Guidelines. I designed estimated models to analyze policy compliance using a fixed-effect panel ordered logit model. According to the analysis results, motivation factors have significant positive influences on compliance level. In contrast, fiscal capacity has a significant negative influence on compliance level. This means the higher the local government' motivations, the higher the probability of the local government complying closely and the stronger a local government' fiscal capacity, the less it complies with the central government policy.

외부순환 공기부양반응기에서 낮은 주파수의 압력 변동

최근호 ( Keun Ho Choi ) 한국화학공학회 2020 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.58 No.4

Low-frequency pressure fluctuations in an external-loop airlift reactor were investigated. Low-frequency pressure fluctuations could be measured by shooting videos about liquid levels in the four piezometric tubes which were installed at the lower and upper parts of the riser and downcomer using a cellular phone. The periodic characteristics of pressure fluctuations were proved by the calculation of their auto-correlation function and cross-correlation function. Even if the riser superficial gas velocity was constant, the riser and downcomer gas holdups as well as wall pressures were periodically changed due to the inertia of circulating liquid. In general, the intensity of pressure fluctuations increased with an increase in the gas velocity. When the unaerated liquid height was 0.04 m, the maximum period of pressure fluctuations was found at the specific gas velocity (0.14 ms^-1). It was because the maximum inertia of circulating liquid resulted from a reduction in the increasing rate of the liquid circulation velocity and a decrease in the volume of the effectively circulating liquid with an increase in the gas velocity.

생물화공 : 차가버섯의 균사체 성장에 대한 배지성분의 영향

최근호 ( Keun Ho Choi ) 한국화학공학회 2005 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.43 No.3