• The Journal of the Acoustical Society of Korea
• /
• v.40 no.1
• /
• pp.64-72
• /
• 2021

This paper carried out the optimal design of Tuned Mass Damper (TMD) to attenuate the vibrational energy of pipeline subjected to fluid movement. Under the uncertainty of the vibration source and the specification of a pipeline system, an adaptive approach to design TMD is suggested. A surrogate pipeline system model was designed using MATLAB, and the optimal design method was developed based on the surrogate pipe model. The developed optimization method was validated using Finite Element (FE) model in ANSYS Workbench. And the TMD was designed to account for measurement error and installed on the industrial pipeline system. It showed that the pipeline vibrational amplitude was reduced by 95 % after installing the TMD.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2008.11a
• /
• pp.757-759
• /
• 2008

기존의 웹 서비스가 수동적이고, 단방향 통신을 축으로 뒀다면 현재의 웹 서비스는 점차 능동적이고 변화되었으며, 양방향 통신 환경을 지향하게 되었다. 이러한 웹 서비스 변화의 흐름을 일컬어 웹 2.0이라 한다. 웹 2.0 세대를 살아가는 사용자들은 기존과 다른 다양한 정보의 홍수에 노출되게 되었다. 이들은 일방적이고, 제한적인 정보를 얻는 기존 환경에서 탈피, 스스로 가치 있는 정보를 생산해 내기 시작했고, 이렇게 생산된 정보는 인터넷을 통해 다른 사용자와 교류하며 더욱 가치 있는 정보를 창출해 나가고 있다. 이런 발전 과정에서 지속적으로 더욱 더 커져가는 정보를 더 빠르고 정확하게 공유하는 기술이 필요하게 되었고, 현재 이런 필요성을 충족시키는데 유용한 기술의 한 갈래로 나온 것이 태그와 시맨틱 웹으로 대표되는 온톨로지 이다. 태그는 정보의 주제나 표제를 나타내는 단어를 해당 컨텐츠 정보를 제공하는 사이트에서 정보 분류 단위로 사용, 이를 통한 더 빠른 정보 공유를 할 수 있게 되었다. 시맨틱 웹은 현재의 인터넷과 같은 다양한 리소스에 대한 정보와 자원 사이의 관계-의미 정보를 기계(컴퓨터)가 처리할 수 있는 온톨로지 형태로 표현하고, 이를 자동화된 기계(컴퓨터)가 처리하도록 하는 기술이다. 이 논문에서는 웹 2.0의 대표기술이라 할 수 있는 온톨로지 기법을 이용, 기존 태그의 정보 분류 효율을 높이기 위한 태그와 태그의 의미관계 형성을 제안하였다.

• Journal of Korean Society of Disaster and Security
• /
• v.13 no.2
• /
• pp.27-38
• /
• 2020

Climate variations have become worse and diversified recently, which caused catastrophic disasters for our communities and ecosystem including economic property damages in Korea. Heat wave of summer season is one of causes for such damages of which outbreak tends to increase recently. Related short-term forecasting information has been provided by the Korea Meteorological Administration based on results from numerical forecasting model. As the study area, the ◯◯ province was selected because of the highest mortality rate in Korea for the past 15 years (1998~2012). When comparing the forecasted temperatures with field measurements, it showed RMSE of 1.57℃ and RMSE of 1.96℃ was calculated when only comparing the data corresponding to the observed value of 33℃ or higher. The forecasting process would take at least about 3~4 hours to provide the 4 hours advanced forecasting information. Therefore, this study proposes a methodology for temperature prediction using LSTM considering the short prediction time and the adequate accuracy. As a result of 4 hour temperature prediction using this approach, RMSE of 1.71℃ was occurred. When comparing only the observed value of 33℃ or higher, RMSE of 1.39℃ was obtained. Even the numerical prediction model of the whole range of errors is relatively smaller, but the accuracy of prediction of the machine learning model is higher for above 33℃. In addition, it took an average of 9 minutes and 26 seconds to provide temperature information using this approach. It would be necessary to study for wider spatial range or different province with proper data set in near future.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.4
• /
• pp.409-415
• /
• 2011

A gimbal system in observation reconnaissance aircraft was fabricated by assembling many parts and bearings. This system consists of a camera module and a stabilization gimbal that supports the camera module. During the flight for recording images, the gimbal system experiences various accelerations with wide frequencies. Although base excitation of stabilization gimbal results in vibration of the camera module, the camera module must be able to capture the correct and clear image even while vibrating. Hence, it is important to know the natural frequencies and vibration modes of the gimbal system with the camera module. Considering bearings as spring elements, the vibration characteristic of the gimbal system was analyzed by finite element method. In addition, harmonic response analysis was performed to determine the correct transmissibility of acceleration for the camera module in the frequency range of 0-500 Hz.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.10
• /
• pp.1199-1203
• /
• 2011

Nanocomposites were prepared through the compounding of rubber and clay. Measurements of the static and dynamic mechanical properties of different compositions over a temperature range $70-100^{\circ}C$ showed that the mechanical properties of these rubber/clay nanocomposites are superior to those of existing rubber materials. In this study, by using the parameter of the maximum Green.Lagrange strain appearing at certain locations, the relationship between fatigue life and maximum Green.Lagrange strain, and the correlations between test-piece tests and bench tests of actual rubber components are proved. In order to predict the fatigue life of rubber components at the design stage, a simple procedure of life prediction is suggested. The predicted fatigue lives of the rubber engine mounts agree fairly well with the fatigue lives determined experimentally.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.16 no.6
• /
• pp.1363-1372
• /
• 2021

Red tide, defined as the major reproduction of harmful birds, has the characteristics of being generated and diffused in a wide area. This has limitations in detection only with the existing investigation method. Therefore, in this study, red tide was detected using a remote sensing technique. In addition, it was intended to increase the accuracy of detection by using optical characteristics, not just the concentration of chlorophyll. Red tide mainly occurs on the southern coast where sea signals are complex, and the main red tide control species on the southern coast is Cochlodinium polykirkoides. Therefore, it was intended to secure objectivity by reflecting features that could not be found depending on the researcher's observation and experience, not limited to visual judgment using machine learning techniques. In this study, support background machines and random forest were used among machine learning models, and as a result of calculating accuracy as performance evaluation indicators of the two models, the accuracy was 85.7% and 80.2%, respectively.

• Journal of Digital Contents Society
• /
• v.17 no.6
• /
• pp.509-521
• /
• 2016

A novel Samples Balanced Genetic Algorithm combined with Extreme Learning Machine (SBGA-ELM) for Parkinson's Disease diagnosis and detecting bio-markers is presented in this paper. Proposed approach uses genes' expression data of 22,283 genes from open source ParkDB data base for accurate PD diagnosis and detecting bio-markers. Proposed SBGA-ELM includes two major steps: feature (genes) selection and classification. Feature selection procedure is based on proposed Samples Balanced Genetic Algorithm designed specifically for genes expression data from ParkDB. Proposed SBGA searches a robust subset of genes among 22,283 genes available in ParkDB for further analysis. In the "classification" step chosen set of genes is used to train an Extreme Learning Machine (ELM) classifier for an accurate PD diagnosis. Discovered robust subset of genes creates ELM classifier with stable generalization performance for PD diagnosis. In this research the robust subset of genes is also used to discover 24 bio-markers probably responsible for Parkinson's Disease. Discovered robust subset of genes was verified by using existing PD diagnosis approaches such as SVM and PBL-McRBFN. Both tested methods caused maximum generalization performance.

• Current Research on Agriculture and Life Sciences
• /
• v.8
• /
• pp.107-113
• /
• 1990

This study was attempted to develop a remote controllable speed sprayer in order to protect an operator from agricultural chemicals. For the purpose of remote controllable transmission was developed by using one chip microcomputer. The following results could be summarized in this study. 1. Remote controllable transmission developed had not made even a single mistake during the test performed 100 times repeat. Thus, it could that this machine was very accurate. 2. One chip microcomputer was made by machine language and its was with in 3 sec's which was the same as human did. 3. One chip microcomputer which was used in the experiment could be widely used to automation of agricultural machinery, since it is smaller and chiper than any other similar ones such as personal computer, lap tap, one board computer. 4. Since, farm tractor has the same type of transmission as this system, it also could be adapted to farm tractors. 5. In this experiment, transmission lever was remote controll were designed to operate simultaneously. Thus, this system developed was more complicate than conventional system. However, by removing this transmission lever and by mounting the remote controll system at the speed sprayer, it would be higher and easier to handle than the conventional one.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2019.05a
• /
• pp.121-121
• /
• 2019

특정 지역에 집중적으로 비가 내리는 현상인 국지성호우가 빈번히 발생함에 따라 하천 주변 사회기반시설의 침수 위험성이 증가하고 있다. 침수 위험성 판단 여부는 주로 수위정보를 이용하며 수위 예측은 대부분 수치모형을 이용한다. 본 연구에서는 빅데이터 기반의 RNN(Recurrent Neural Networks)기법 알고리즘을 활용하여 수위를 예측하였다. 연구대상지는 조위의 영향을 많이 받는 한강 전역을 대상으로 하였다. 2008년~2018년(10개년)의 실제 침수 피해 실적을 조사한 결과 잠수교, 한강대교, 청담대교 등에서 침수 피해 발생률이 높게 나타났고 SNS(Social Network Services)와 같은 비정형화 자료에서는 청담대교가 가장 많이 태그(Tag)되어 청담대교를 연구범위로 설정하였다. 본 연구에서는 Python에서 제공하는 Tensor flow Library를 이용하여 수위예측 알고리즘을 적용하였다. 데이터는 정형화 데이터와 비정형 데이터를 사용하였으며 정형화 데이터는 한강홍수 통제소나 기상청에서 제공하는 최근 10년간의 (2008~2018) 수위 및 강우량 자료를 수집하였다. 비정형화 데이터는 SNS를 이용하여 민간 정보를 수집하여 정형화된 자료와 함께 전체자료를 구축하였다. 민감도 분석을 통하여 모델의 은닉층(5), 학습률(0.02) 및 반복횟수(100)의 최적값을 설정하였고, 24시간 동안의 데이터를 이용하여 3시간 후의 수위를 예측하였다. 2008년~ 2017년 까지의 데이터는 학습 데이터로 사용하였으며 2018년의 수위를 예측 및 평가하였다. 2018년의 관측수위 자료와 비교한 결과 90% 이상의 데이터가 10% 이내의 오차를 나타내었으며, 첨두수위도 비교적 정확하게 예측되는 것을 확인하였다. 향후 수위와 강우량뿐만 아니라 다양한 인자들도 고려한다면 보다 신속하고 정확한 예측 정보를 얻을 수 있을 것으로 기대된다.

• Korean Journal of Agricultural Science
• /
• v.8 no.1
• /
• pp.90-96
• /
• 1981

To design more efficient agricultural machinery, the accurately measuring system among many other factors is essential. A light-beam oscillographic recorder is generally used in measuring dynamic strain but it is not compatible with the extremely high speed measuring system such as 1,000 m/s, also is susceptable to damage due to vibration while using the system in field. The recorder used light sensitive paper for strip chart recording. The reading and analysis of data from the strip charts is very cumbersome, errorneous and time consuming. A microcomputer was interfaced with A/D converter, microcomputer program was developed for measuring, system calibration was done and the strain generated from a cantilever beam vibrator was measured. The results are summarized as follows. 1. Microcomputer program was developed to perform strain measuring of agricultural machine elements and could be controled freely the measuring intervals, no. of channels and no. of data. The maximum measuring speed was $62{\mu}s$. 2. Calibration the system was performed with triangle wave generated from a function generator and checked by an oscilloscope. The sampled data were processed using HP 3000 minicomputer of Chungnam National University computer center the graphical results were triangle same as input wave and so the system have been out of phase distorsion and amplitude distorsion. 3. The strain generated from a cantilever beam vibrator which has free vibration period of 0.019 second were measured by the system controlled to have l.0 ms of time interval and its computer output showing vibration curve which is well filted to theoretical value. 4. Using microcomputer on measuring the strain of agricultural machine elements could not only save analyzing time and recording papers but also get excellent adaptation to field experiment, especially in measurement requiring high speed and good precision.