Design analysis and simulation of an external helical gear

이철희,양진룽,이강희,이철희 사단법인 유공압건설기계학회 2023 드라이브·컨트롤 Vol.20 No.4

This study optimized the parameters of the helical gear based on the original external meshing helical gear pump, combined with the analysis of the stability and flow of the basic parameters of the equipment; herringbone gears were used to eliminate the axial force generated by the helical gears. An optimized helical gear rotor was built with NX. The error between the simulation and calculation results of pump displacement was 3.95% and the simulation results were valid. Analysis of the outlet pressure and lift changes (maximum change rates of 0.38% and 0.25%), pressure analysis of the XY center plane at different times in the same cycle (no pressure surge or drop), and analysis of the axial force of the primary and driven rotors (axis The axial force is close to 0) were performed. The results showed that the flow pulsation of the external gear pump was slight, the operation was smooth, vibration and friction were reduced, the wear of bearings and other components could be diminished, and the service life of the equipment was extended. The simulation results showed that the external gear pump met the design requirements.

한국노동시장 성격에 대한 비교사적 접근

이철희 서울대학교 경제연구소 2013 서울대학교 경제연구소 학술대회 논문집 Vol.2013 No.2

Reliable Fault Diagnosis Method Based on An Optimized Deep Belief Network for Gearbox

이철희,Oybek Eraliev,Ozodbek Xakimov,이철희 사단법인 유공압건설기계학회 2023 드라이브·컨트롤 Vol.20 No.4

High and intermittent loading cycles induce fatigue damage to transmission components, resulting in premature gearbox failure. To identify gearbox defects, numerous vibration-based diagnostics techniques, using several artificial intelligence (AI) algorithms, have recently been presented. In this paper, an optimized deep belief network (DBN) model for gearbox problem diagnosis was designed based on time-frequency visual pattern identification. To optimize the hyperparameters of the model, a particle swarm optimization (PSO) approach was integrated into the DBN. The proposed model was tested on two gearbox datasets: a wind turbine gearbox and an experimental gearbox. The optimized DBN model demonstrated strong and robust performance in classification accuracy. In addition, the accuracy of the generated datasets was compared using traditional ML and DL algorithms. Furthermore, the proposed model was evaluated on different partitions of the dataset. The results showed that, even with a small amount of sample data, the optimized DBN model achieved high accuracy in diagnosis

전화망 음성 데이터를 이용한 향상된 음성 특징 추출 방법

이철희 국제차세대융합기술학회 2017 차세대융합기술학회논문지 Vol.1 No.4

터널의 비접촉 이동식 상태점검 장비: 리뷰

이철희,김동규,Chulhee Lee,Donggyou Kim 한국터널지하공간학회 2023 한국터널지하공간학회논문집 Vol.25 No.3

The purpose of this paper is to examine the most recent tunnel scanning systems to obtain insights for the development of non-contact mobile inspection system. Tunnel scanning systems are mostly being developed by adapting two main technologies, namely laser scanning and image scanning systems. Laser scanning system has the advantage of accurately recreating the geometric characteristics of tunnel linings from point cloud. On the other hand, image scanning system employs computer vision to effortlessly identify damage, such as fine cracks and leaks on the tunnel lining surface. The analysis suggests that image scanning system is more suitable for detecting damage on tunnel linings. A camera-based tunnel scanning system under development should include components such as lighting, data storage, power supply, and image-capturing controller synchronized with vehicle speed.

體格과 體力이 體操學習에 미치는 영향

李喆熙,李勇仁 충남대학교 자연과학연구소 1979 學術硏究誌 Vol.6 No.2

The relationship of the gymnastics competency to the physique and physical fitness was investigated for the students who had finished the gymnastic course in 1978 at Chung Nam National University. The results of this study are as following: 1. In the analysis of the relationship of physique and gymastic learning competency, the correlation cofficients of the horizontal bar learning to body height and body weight were shown as-0.52 and-0.44 (P<0.0l) respectively, 2. In the analysis of the relationship of physical fitness and gymnastic learning competency the shutlle run, standing broad jump, balancing on the pole, and 1000m running to the mat work learning were shown as-0.45, 0.46, 0.44 and-0.41( P<0.01 ) respectively. And the correlation coeffients of the blancing on the pole to the long horse learning was 0.49 ( P<0.01 ).

실내모형실험을 통한 모래지반에서의 중공블록 보강효과 분석

이철희,신은철,양태철 한국지반공학회 2022 한국지반공학회논문집 Vol.38 No.7

The hollow modular concrete block reinforced foundation method is one of the ground reinforcement foundation methods that uses hexagonal honeycomb-shaped concrete blocks with mixed crushed rock to reinforce soft grounds. It then forms an artificial layered ground that increases bearing capacity and reduces settlement. The hollow modular honeycomb-shaped concrete block is a geometrically economical, stable structure that distributes forces in a balanced way. However, the behavioral characteristics of hollow modular concrete block reinforced foundations are not yet fully understood. In this study, a bearing capacity test is performed to analyze the reinforcement effectiveness of the hollow modular concrete block through the laboratory model tests. From the load-settlement curve, punching shear failure occurs under the unfilled sand condition (A-1-N). However, the filled sand condition (A-1-F) shows a linear curve without yielding, confirming the reinforcement effect is three times higher than that of unreinforced ground. The bearing capacity equation is proposed for the parts that have contact pressure under concrete, vertical stress of hollow blocks, and the inner skin friction force from horizontal stress by confining effect based on the schematic diagram of confining effect inside a hollow modular concrete block. As a result of calculating the bearing capacity, the percentage of load distribution for contact force on the area of concrete is about 65%, vertical force on the area of hollow is 16.5% and inner skin friction force of area of the inner wall is about 18.5%. When the surcharge load is applied to the concrete part, the vertical stress occurs on the area of the hollow part by confining effect first. Then, in the filled sand in the hollow where the horizontal direction is constrained, the inner skin friction force occurs by the horizontal stress on the inner wall of the hollow modular concrete block. The inner skin friction force suppresses the punching of the concrete part and reduces contact pressure.

UAS 영상 및 지상 LiDAR 조합한 3D 수치모형 기반 비탈면 앵커의 손상인자 분석에 관한 연구

이철희,이종현,김달주,강준오,권영훈 한국지반공학회 2022 한국지반공학회논문집 Vol.38 No.7

The current performance evaluation of slope anchors qualitatively determines the physical bonding between the anchor head and ground as well as cracks or breakage of the anchor head. However, such performance evaluation does not measure these primary factors quantitatively. Therefore, the time-dependent management of the anchors is almost impossible. This study is an evaluation of the 3D numerical model by SfM which combines UAS images with terrestrial LiDAR to collect numerical data on the damage factors. It also utilizes the data for the quantitative maintenance of the anchor system once it is installed on slopes. The UAS 3D model, which often shows relatively low precision in the z-coordinate for vertical objects such as slopes, is combined with terrestrial LiDAR scan data to improve the accuracy of the z-coordinate measurement. After validating the system, a field test is conducted with ten anchors installed on a slope with arbitrarily damaged heads. The damages (such as cracks, breakages, and rotational displacements) are detected and numerically evaluated through the orthogonal projection of the measurement system. The results show that the introduced system at the resolution of 8K can detect cracks less than 0.3 mm in any aperture with an error range of 0.05 mm. Also, the system can successfully detect the volume of the damaged part, showing that the maximum damage area of the anchor head was within 3% of the original design guideline. Originally, the ground adhesion to the anchor head, where the z-coordinate is highly relevant, was almost impossible to measure with the UAS 3D numerical model alone because of its blind spots. However, by applying the combined system, elevation differences between the anchor bottom and the irregular ground surface was identified so that the average value at 20 various locations was calculated for the ground adhesion. Additionally, rotation angle and displacement of the anchor head less than 1" were detected. From the observations, the validity of the 3D numerical model can obtain quantitative data on anchor damage. Such data collection can potentially create a database that could be used as a fundamental resource for quantitative anchor damage evaluation in the future.

영사시와 회고시에 대한 시학적 이해 :「이십일도회고시」의 성격 규명을 위하여

이철희 한국어문학연구학회(구, 동악어문학회) 2010 동악어문학 Vol.54 No.-

기계경비시스템의 서비스 품질, 시스템 성능 및 기업 이미지가 고객 만족도에 미치는 영향

이철희 한국사회안전범죄정보학회 2015 한국범죄정보연구 Vol.1 No.1