콤바인 예취부 고장진단을 위한 예취 칼날부의 진단 시스템 개발(I) - 진동 및 부하 신호 분석 -

최창현,김용주,김종혁,문정환,Choi, Chang-Hyun,Kim, Yong-Joo,Kim, Jong-Hyuck,Mun, Joung-Hwan 한국농업기계학회 2007 바이오시스템공학 Vol.32 No.3

The purpose of this study is to develop a measurement system of cutter conditions for combine header diagnosis during rice harvesting. A load cell was installed at the locker-arm to measure load fluctuation and an acceleration senor was used to monitor vibration signal of cutter bar. The data were collected from a paddy field during harvesting. The tests were conducted with a normal cutter, a loosened cutter, a broken cutter, and a worn-out connecter pin at the field. The vibration signals converted by FFT (Fast Fourier Transformation), filtered, and normalized. The load data and peak values of vibration signals in four different frequency ranges were used to determine the cutting operation and the cutter conditions of combine. The multiple comparison tests showed that the load data and peak values of vibration signals were important to monitor the cutting operation and cutter conditions of combine header.

BIM기반 MEP공사 시공용 도면 작성 자동화 프로세스 제안

최창현,권대용,조상호,김주형,Choi, Chang-Hyun,Kwon, Dae-Yong,Cho, Sang-Ho,Kim, Ju-Hyung 한국BIM학회 2020 KIBIM Magazine Vol.10 No.4

Shop drawing tasks conducted after finishing coordinated or engineering design have great influences on the quality and cost of a project. However, despite the development of commercial BIM applications, shop drawings have mainly produced manually in certain engineering fields. Incorrect shop drawings with human errors have occurred various problems such as cost overrun, time delay and reworks. An automated shop drawing publishing from BIM is expected to resolve these problems. Despite attempts for automate shop drawing production, the field of mechanical, electrical and plumbing (MEP) is yet regarded challenging due to complexity of components and connection. In this research, we develop a process for automated producing 3D MEP shop drawings in BIM environment as following steps: to analyze conventional MEP shop drawing process, to identify detailed process that can be automated, to classify existing MEP objects and assign codes usable in BIM, and to develop an application. The validation of automated process is conducted against 10 clean room projects in which MEP is more complex and its cost is higher than other projects in terms of productivity and workers' satisfaction. Results show that the number of manpower for shop drawing is reduced by 30%, and the working time is shortened by 31%. Personal opinions of involved practitioners is interpreted as positive as the average rate of agrement on practicability, easy-to-use and necessary retouch tasks is around 66%.

가시광선-근적외선 반사스펙트럼을 이용한 쇠고기의 신선도 평가

최창현,김종훈,김용주,Choi, Chang-Hyun,Kim, Jong-Hun,Kim, Yong-Joo 한국축산식품학회 2011 한국축산식품학회지 Vol.31 No.1

본 연구에서는 유통현장에서 실시간으로 쇠고기 신선도를 측정하기 위해 가시광선-근적외선 반사 스펙트럼을 이용하여 쇠고기 신선도에 영향을 미치는 인자와 설정된 저장기간에 대하여 예측 모델을 개발하고 검증하였다. 쇠고기 시료는 총 216개를 사용하였으며 0-14일의 기간 동안 2일 간격으로 가시광선-근적외선 반사 스펙트럼을 측정한 후, 쇠고기의 신선도에 영향을 미치는 인자인 총균수, pH, VBN, TMA, TBA값을 공인된 방법을 이용하여 측정하였다. 예측모델은 다중회귀분석 방법과 최적 변수 선택이 가능한 stepwise 방법을 이용하여 개발하였으며, 예측모델의 선정은 결정계수, 오차, RPD를 이용하였다. 예측모델의 검증은 미지의 시료를 이용하였으며 그 결과 결정계수, 오차, RPD는 총균수에서 각각 0.74, 0.64, 2.75 Log CFU/$cm^2$, VBN은 각각 0.73, 1.45, 2.00 mg%, TMA는 각각 0.70, 0.19, 2.58 mg%, TBA값은 각각 0.73, 0.13, 2.77 mg MA/kg로 비교적 안정된 예측성능을 보여 주었다. 저장기간에 따른 예측모델의 검증결과는 결정계수, 오차, RPD가 각각 0.77, 1.94일, 2.53으로 실험 시 저장기간이 2일 간격인 점을 고려할 때, 비교적 높은 정밀도를 보이고 있음을 알 수 있다. pH의 예측성능은 결정계수, 오차, RPD가 각각 0.43, 0.10, 1.10로 다른 신선도 인자에 비해 낮은 결과를 보여 주었다. 본 연구에서는 가시광선-근적외선 분광분석법을 이용하여 쇠고기 신선도의 비파괴 평가에 대한 가능성을 제시하였으나 유통현장에서 적용을 위해서는 보다 많은 시료의 확보를 통한 예측모델의 신뢰성 향상과 stepwise방법으로 선정된 파장 영역을 기본으로 하는 부분최소자승법, 인공지능 등의 다양한 알고리즘의 적용을 통한 성능개선이 필요할 것으로 판단된다. The objective of this study was to develop models to predict freshness factors (total viable counts (TVC), pH, volatile basic nitrogen (VBN), trimethylamine (TMA), and thiobarbituric acid (TBA) values) and the storage period in beef using a visible and near-infrared (NIR) spectroscopic technique. A total of 216 beef spectra were collected during the storage period from 0 to 14 d at a $10^{\circ}C$ storage. A spectrophotometer was used to measure reflectance spectra from beef samples, and beef freshness spectra were divided into a calibration set and a validation set. Multi-linear regression (MLR) models using the stepwise method were developed to predict the factors. The MLR results showed that beef freshness had a good correlation between the predicted and measured factors using the selected wavelength. The correlation of determination ($r^2$), standard error of prediction (SEP), and ratio of standard deviation to SEP (RPD) of the prediction set for TVC was 0.74, 0.64, and 2.75 Log CFU/$cm^2$, respectively. The $r^2$, SEP, and RPD values for pH were 0.43, 0.10, and 1.10; those for VBN were 0.73, 1.45, and 2.00 mg%; those for TMA were 0.70, 0.19, and 2.58 mg%; those for TBA values were 0.73, 0.13, and 2.77 mg MA/kg; and those for storage period were 0.77, 1.94, and 2.53 d, respectively. The results indicate that visible and NIR spectroscopy can predict beef freshness during storage.

맥류 연구의 과거, 현재, 그리고 미래

김경민(Kyeong-Min Kim),강천식(Chon-Sik Kang),김양길(Yang-Kil Kim),김경훈(Kyeong-Hoon Kim),박종호(Jong-Ho Park),윤영미(Young-Mi Yoon),박형호(Hyoung-Ho Park),정한용(Han-Yong Jeong),최창현(Chang-Hyun Choi),박진희(Jinhee Park),김영진(You 한국육종학회 2020 한국육종학회지 Vol.52 No.S

Barley and wheat are a major food crop of humans, along with rice, soybean and corn. A systematic breeding program for Korean barley began in 1906 with selection and introduction breeding. In 1908, landrace barley was collected, and breeding focused on selection and introduction for high yielding varieties until the 1970s. In the 1980s and 1990s, breeding was carried out for diversity; thereafter, we aimed to improve quality, productivity and lodging tolerance that can be applied to the paddy field in Korea. Since 2010, the major result of breeding was shortening cultivation to approximately 6–12 days, making a double cropping system possible in the paddy field in Korea. Yield has increased by 1.2 times from 438 kg/10 a in the 1960s to 536 kg/10 a in the 2010s, and farm yield has increased by 1.7 times. In addition, as cultivation safety has been enhanced, the varieties have also improved, such as the covered barley used in making tea and other processing products. In case of wheat, up to now forty cultivars have been developed in Korea. In the early stage, we developed a domestic wheat variety that was early maturing and high yielding. As a result, the maturation time of wheat planted in the 1970s to 2010 was shortened (from 13 to 30 days), while productivity increased by 30% from 408 kg/10 a in the 1970s to 532 kg/10 a in 2010. In recent years, there have been remarkable efforts for a more stable production by focusing on increasing disaster and pest resistance due to climate change. In addition, a wheat variety discrimination marker was developed using a variety-specific marker, and selection was made using a trait-specific marker at the early stage of breeding to enhance breeding efficiency. In the 2000s, winter cereals for forage have been promoted to expand forage production and to replace imported feed grains. Therefore, winter cereal that is useful for feed, such as rye, oat, and triticale, have had various varieties and safe production techniques developed. Currently, our research goal for winter cereals for feed is to develop a double-cropping adaptation and abiotic stress tolerance cultivar, and safe production in paddy field. Hence, aggressive action is needed to support the strategic survival of the Korean wheat and barley industry. Barley is a health food that requires a multifaceted effort to improve breeding efficiency, develop varieties that contain large amounts of functional components and are more resistant to stronger biotic and abiotic stresses in response to climate change. It is necessary to recognize the role of wheat and barley as the second main crop after rice, and to improve the self-sufficiency rate of these crops for the health and food industry crisis of Korea.

경부고속선 절연구간에서 KTX 운행중 모터블럭의 동작특성 분석

최창현(Chang Hyun Choi),노영환(Young Hwan Lho) 대한전기학회 2015 전기학회논문지 Vol.64 No.10

Traction power is supplied by three-phase alternating current of 154 kV power grid and electric trains are operated on single phase feeding system. It becomes important to use all the three phases equally and convert them into two-phase electric power (90 degree phase rotation) for traction supply. This is achieved by special transformer from the adjacent traction substation which is separated by a neutral section. Neutral section locations are in front of the substation and between the two substations. The first stage of the Seoul-Busan high-speed railway, design curve radius is larger than 7,000 m and the greatest slope is 25‰. The railway track conditions are evaluated as good enough to install a neutral section at the first stage, but a few factors of coasting operation of the train should be considered at the second stage of Seoul-Busan high-speed railway. The neutral section was located at Kim-cheon substation, which made some neutral section problems produced by the operating train, and the neutral section was moved about 1.5 km to the south toward Dong Dae-gu station due to the track operation condition. Some of the trains which stopped at the existing Kim-cheon Gu-mi station produced another motor block failure after moving the neutral section. In this paper, power quality, system performance and track condition, etc. are suggested to solve the problems.

주성분 분석과 로지스틱 회귀모형을 이용한 호우피해 예측함수 개발

최창현(Choi Chang hyun),김종성(Kim Jong sung),이명진(Lee Myung jin),김정환(Kim Jeong hwan),이우주(Lee Woo joo),김형수(Kim Hung Soo) 한국방재학회 2017 한국방재학회논문집 Vol.17 No.6

본 연구에서는 낙동강 권역을 대상으로 주성분 분석과 로지스틱 회귀모형을 적용하여 호우피해 예측함수를 개발하였다. 주성분 분석을 통해 상관성이 높은 설명변수를 사용할 수 있는 방안을 제시하였고, 로지스틱 회귀모형을 이용하여 피해액이 큰 집단과 작은 집단으로 분류한 다음, 구분된 각 집단에서 호우피해 예측함수를 개발하였다. 최종적으로 선정된 모델의 예측력을 실제피해액과 예측피해액을 비교하여 NRMSE(Normalized Root Mean Squared Error)로 평가한 결과, 12.44%로 낙동강 권역의 호우피해를 적절하게 예측하는 것으로 나타났다. 따라서 본 연구에서 개발한 낙동강 권역의 호우피해 예측함수를 활용하면, 호우피해 발생 전에 사전 대비 차원의 재난관리를 실시할 수 있을 것이다. In this study, we developed heavy rain damage prediction functions for Nakdong river basin by using principal component analysis and logistic regression model. The principal component analysis can be used for the determination of explanatory variables which are highly correlated with the damage. Then the determined variables could be used as the independent variables for the development of heavy rain damage prediction functions. The logistic regression model classified heavy rain damages into two data groups of small and large damage values. Then the functions for two data groups could be developed. Finally, the function performances were assessed by comparing the observed damages and predicted damages. And we obtained NRMSE(Normalized Root Mean Squared Error) of 12.44%. Therefore, we can use the developed heavy rain damage prediction functions in the Nakdong river basin area for preparing for disaster occurred by heavy rainfall and also for the effective disaster management for damage reduction.

ISBM - PP 기술의 현황과 전망

최창현(Chang Hyun Choi),김영우(Young Woo Kim) 한국고분자학회 1995 고분자 과학과 기술 Vol.6 No.6

BIM 전환설계 생산성 향상을 위한 설계오류 검토 자동화 프로그램 구현

최창현(Choi Chang-Hyun),주문부(Joo Moon-Boo),이명도(Lee Myungdo),김주형(Kim Ju-Hyung) 대한건축학회 2023 대한건축학회 학술발표대회 논문집 Vol.43 No.1

머신러닝을 이용한 호우피해 예측함수 개발

최창현(Choi, Chang Hyun),김종성(Kim, Jong Sung),김동현(Kim, Dong Hyun),김경훈(Kim, Kyung Hun),김형수(Kim, Hung Soo) 대한토목학회 2017 대한토목학회 학술대회 Vol.2017 No.10

다상 유동 Void Fraction 가시화 장치 설계 및 성능 평가

최창현(Chang-Hyun Choi),최성원(Seong-Won Choi),송시몬(Simon Song) 한국가시화정보학회 2017 한국가시화정보학회지 Vol.15 No.1

A two-phase flow observed in a heat exchanger or nuclear power generation often has a profound effect on undesirable noise or flow characteristics. Void fraction, which refers to the ratio of gas (or liquid) to the total fluid, affects heat transfer coefficient, vibration and so forth. In other words, void fraction is one of most important parameters in two-phase flow since it contributes to comprehend the characteristics of two-phase flow. We developed a two-phase flow visualization system to measure cross-sectional and volumetric void fractions by using quick closing valves and image processing software. With this system, we could observe the plug, slug, and stratified flow patterns of two-phase flow and measure a myriad of void fractions. As a consequence of the experiment, we found that the estimated void fractions were largely coincident with the predictive values by Chisholm model.