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모터 그레이더 평탄작업용 블레이드의 설계개선을 위한 개별요소법 해석
송창헌,오주영,조정우,김문규,석정호,Song, Chang-Heon,Oh, Joo-Young,Cho, Jung-Woo,Kim, Mun-Gyu,Seok, Jeong-Ho 한국터널지하공간학회 2021 한국터널지하공간학회논문집 Vol.23 No.6
모터 그레이더의 블레이드는 도로공사시 골재를 산포하고 평탄화하는 역할을 수행한다. 본 연구는 그레이더의 작업효율을 향상시키기 위하여 블레이드 부품의 설계개선 연구를 진행하였다. 블레이드와 골재 입자의 접촉, 절삭, 산포 과정을 모사하기 위하여 동해석 코드에 개별요소법을 도입하여 전산해석 모델을 수립하였다. 블레이드 설계인자를 4가지 선별한 후 작업 시나리오를 수립하였다. 실험계획의 직교배열을 통해 각 인자의 수준조합별 9개 모델에 대해 평탄화 작업에 대한 동해석을 수행하고, 각 설계인자의 영향도를 분석하였다. 이후 유의한 인자를 분산분석을 통해 선별하여 최적화기법으로 점진적 반응표면법을 적용하였다. 최종적으로 블레이드의 작업 효율성을 향상시킬 수 있도록 설계인자의 최적값을 제안하였다. The blade of motor grader is used for scattering and leveling the aggregates on the foundation of road construction site. The paper performed a design improvement research of the blade part to enhance the working efficiency of motor graders. The scattering works of aggregates by blade driving were simulated by DEM (discrete element method) of a dynamic code. The four design parameters were selected and a specific leveling scenario for the simulation was determined. The nine blade models were numerically experimented, and the sensitivity of each factors was analyzed. Next, the design factors that influence a blade performance have been selected by ANOVA, and these key design factors were applied to the progressive quadratic response surface method (PQRSM). The optimum set of design factors of the blade was finally proposed.
음악 유사도 비교를 위한 Siamese 네트워크 기반 그래프 임베딩의 개선
송창헌,이용현,김형주 한국정보과학회 2020 정보과학회 컴퓨팅의 실제 논문지 Vol.26 No.11
음악 시장의 성장에 따라 사용자는 일부 음악에 국한되어 노출되고 선택하게 된다. 많은 서비스는 메타데이터로 라이브러리를 구성하여 검색 및 추천 문제에 접근하고 있다. 이때, 새로 나오거나 인지도가 없는 음악의 경우 결과에서 제외될 수 있다. 일반적으로 사용되는 오디오 피처는 해상도에 따른 차원의 변화 폭이 크기 때문에 CNN의 입력으로 사용하기에 어려움이 있다. 본 논문에서는 음악 그래프 피처를 추출하고 임베딩하여 유사도를 비교할 수 있는 모델을 제안한다. 모델은 피처 추출과 Siamese 네트워크로 구성된다. 피처 추출에서는 각 음악 신호를 오디오 피처로 변환하고, 각 음악의 그래프 피처를 구성한다. 이후, Siamese 네트워크에서 각 그래프 피처를 GCN과 어텐션 기법을 활용하여 잠재 공간으로 임베딩하고, NTN을 통해 서로 다른 두 벡터의 유사도를 도출한다. 마지막으로 실험을 통해 음악 신호의 유사도 비교를 위한 오디오 피처의 그래프 피처 추출이 효과적인 방식임을 입증하였다. As the music market grows, people are exposed to and provided with selective music. Many services use metadata for building music libraries. In this situation, songs from independent labels and new artists that do not have previous information are still excluded from the result of searches and recommendations. In this paper, we focus on making the music scoring model for calculating the similarity score of two music signals. The model comprises the Siamese network and the scoring layer. The Siamese network embeds audios to small latent vectors and passes them to the scoring layer. The audio feature is difficult to use as an input to the CNN because of the dimensionality problem. Our approach is compared to previous works because it retains the sequence information of the peak frequencies in the spectrogram by transforming it into a graph. The effectiveness of the graphical approach is shown as the result of the experiment.
Computational Fluid Dynamics Simulation of Coal Ash Filling in Underground Mine Cavity
송창헌,조민기,박진영,이재욱,조정우,장항석,이상은,정진태 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.
Coal fly ash waste from thermal power plants has recently been considered as a fill material for abandoned coal mine voids in Korea. A volume of fluid method, used in computational fluid dynamics, was adopted to simulate the process of coal ash injection into mine cavities. The difference in the filling efficiency of coal ash versus water using both upper and lower injection points was also investigated. Results show that use of a lower injection point more stably packed the cavity and provided a higher density of fill than use of an upper injection point. Thus, it would be better to place the nozzle of the injection pipe near the bottom of the mine cavity, below the groundwater level.
Design Study of a Rock Particle Flushing Device for a Rock Reaming Machine by CFD Simulation
송창헌,조민기,박진영,이재욱,정명식,조정우,류성훈 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.
A series of multiphase CFD (computational fluid dynamics) simulation was carried out in order to evaluate the design study of flushing device of rock reaming machine. The Star-CCM+ code was adopted for simulating rock particle discharge flow of flushing air during the rock reaming process. The input parameters for the flow simulation of rock particle were obtained from a previously performed in-situ drilling test results. After three design factors (degree of swash plate, radius of curvature of swash plate, and diameter of flushing channel) were determined, the experimental design method (response surface methodology) was applied to determine optimum value of each factor.
CFD를 이용한 굴착용 천공드릴비트의 유로 최적화에 관한 연구
송창헌,권기범,박진영,신대영,조정우 한국암반공학회 2012 터널과지하공간 Vol.22 No.4
본 연구에서는 드릴비트 내부 유로의 최적설계를 위하여 암분유동해석을 수행하였다. 이를 위해 암분과 기체의 다상유동해석이 가능한 전산유체역학 코드인 Star-CCM+을 사용하였다. 실제 천공시험으로부터 획득한 결과값을 기체 및 암분의 해석조건으로 적용하였다. 내부 유로 설계에 관련된 핵심인자를 3가지로 결정한 후, 다구찌 기법을 활용한 실험계획법으로부터 3가지 설계인자에 대한 최적값을 조사하였다. In this study, a series of CFD (Computational Fluid Dynamics) simulations carried out to evaluate the optimum design model of the internal flow path of drill bit. The Star-CCM+ code was adopted to simulate the multi-phase discharge flow of rock particles and flushing air during a drilling process. The input parameters for the flow simulation of rock particles and air were obtained from the in-situ drilling test results. After the three design factors were determined, the experimental design method (Taguchi method) was utilized to evaluate the optimum value of each factor.
Optimum Design of the Internal Flushing Channel of a Drill Bit using RSM and CFD Simulation
송창헌,조정우,권기범,박진영,오주영,이신옥,신대영 한국정밀공학회 2014 International Journal of Precision Engineering and Vol. No.
In this study, a series of computational fluid dynamics (CFD) simulations was conducted to evaluate and optimize the design of theinternal flushing channel for a drill bit. The Star-CCM+ code was used to simulate the multi-phase flow of flushing air and escapingrock particles during drilling work. The values of the input parameters used for the simulation were obtained from in-situ drilling testresults. Finally after choosing three major design factors and determining their appropriate sizes, the experimental design methodknown as response surface methodology (RSM) was used to obtain the optimum value of each factor.
관절 내 주사 치료 후 발생한 Staphylococcus lugdunensis에 의한 화농성 슬관절염
송창헌,손경목,주용범,김민성,천신혜,김연숙,구선회 대한노인병학회 2015 Annals of geriatric medicine and research Vol.19 No.2
Staphylococcus lugdunensis is a coagulase-negative staphylococcus. However, it causes various clinically important human infections and behaves similar to Staphylococcus aureus. S. lugdunensis reportedly causes infective endocarditis, skin and soft tissue infection, bone and joint infection, septicemia, endarteritis, urinary tract infection, ocular infection, and peritonitis. There are no reports of septic arthritis by this organism in Korea. We presented a case of septic arthritis due to S. lugdunensis in an elderly patient with diabetes mellitus after an intra-articular injection.
Development of Lab-Scale Rock Drill Apparatus for Testing Performance of a Drill Bit
송창헌,권기범,조민기,오주영,신대영,조정우 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.
This study experimentally validated the reliability of the lab-scale rock drill apparatus and investigated the effect of bit design factors on the performance of drilling. To test drilling efficiency of a drill bit, a testing system was designed and manufactured. Using the testing system, the drilling rates and specific energy of a conventional drill bit and newly proposed drill bit with different button arrangement were compared. The newly proposed model was tested to be superior in drilling performance than that of the conventional model. The testing system developed in this study could be used to predict and test the performance of newly developed drill bit models. Also, the system has to be improved further for measuring more accurate and quantitative data for future drill bit developments.