Estimation of Seasonal Representation of the Sea Water Temperature Profile Using Machine Learning and Its Effect on the Prediction of Underwater Acoustic Detection Performance

박나영,김영규,김경옥,손수욱,박종진,김영호 한국해양과학기술원 2022 Ocean science journal Vol.57 No.3

Seawater temperature and salinity profiles are important physical properties that represent oceanic environments and affect underwater acoustic detection prediction performance. Average ocean data can be used to predict the SONAR detection area in areas where obtaining real-time ocean data or instantly predicting the SONAR detection area is difficult. However, it can yield distorted results. In this study, representative temperature profiles reflecting properties of the vertical structure at various temperatures in the study area were obtained using K-means clustering, an unsupervised machine learning technique. K-means clustering was applied to the temperature profiles obtained from the three stations of the Ulleung Basin in the East Sea. In addition, the physical characteristics of the representative profiles obtained were compared, and the representativeness of the acoustic detection area obtained from the representative profiles was evaluated. In summer, when the mixed layer was thin, each cluster was classified according to the vertical temperature gradient of the thermocline. In winter, the clusters were classified according to the mixed layer and thermocline depths, rather than the vertical temperature gradient of the thermocline. For each obtained cluster, the acoustic detection area was calculated using all the profiles and displayed as a histogram. The acoustic detection area calculated from the representative profile of the cluster was generally close to the average of the acoustic detection area. Thus, K-means clustering can effectively classify temperature profiles physically and acoustically and can potentially be applied in other regions for the classification and analysis of seawater temperature and salinity profiles.

강한 충격파의 온도윤곽에 관한 연구

오영기 배재대학교 자연과학연구소 2013 自然科學論文集 Vol.24 No.1

Strong shock waves are non-equilibrium phenomena far out of equilibrium, which can not be interpreted by the near equilibrium linear thermodynamic theories. One of the obvious problems remained to be answered in this subject is the temperature profile, although many efforts have been done to extend the limit of linear theories. The temperature profile obtained by existing theories and computer experiments of Monte Carlo simulations overshoots in the shock layer. The overshoot does evidently violate the second law of thermodynamics, however, it has not yet been resolved. The problem seems to be arisen by the improper use of heat capacity of gases, which defines the local temperature by the relation (internal energy–heat capacity-temperature). In this study, we use the relation (heat flux-heat conductivity-temperature gradient) to introduce the local temperature. In order to obtain the temperature profile, the iterative method for the solution of Boltzmann equation has been employed. The results of the first iteration gives a temperature profile which does not overshoot in the shock layer, i.e., the result which is consistent with the thermodynamic law. Also the obtained temperature profile shows correct limiting property for weak shocks. The theory provides formulas for transport coefficients in the shock layer, however, the limiting properties of weak shock transport coefficients do not consistent with the linear theory, which should be reexamined in the future study.

고온에서 메가 SRC 기둥의 온도특성

황선웅(Sun-Woong Hwang),최병정(Byong-Jeong Choi) 한국산학기술학회 2021 한국산학기술학회논문지 Vol.22 No.12

화재로 인한 초고층건물의 큰 피해를 예방하기 위해 적절한 내화설계를 수행하기 위해서는 선행적으로 온도분포를 정확하게 예측하는 것이 매우 중요하다. 하지만, 초고층건물에서 많이 사용되는 단면크기 1,000 mm × 1,000 mm 이상의 메가(mega) SRC(steel reinforced concrete)기둥의 온도분포에 대한 연구는 진행되고 있지 않다. 따라서 본 연구는 비재하 가열실험을 통해 실제 사용되고 있는 단면크기 1,219 mm × 1,219 mm의 메가 SRC 기둥에 대한 깊이별 온도분포 특성을 도출하였다. 화재실험은 메가 SRC 기둥을 화재시간 1, 2, 3시간에 따라 비재하 가열실험을 수행하여 기둥 중앙 높이에서 최대 깊이 432 mm까지 온도분포를 도출하였다. 또한, 화재실험 실험값은 온도 예측식(Wickström, Kodur), 기준 온도프로파일(Eurocode2, ACI216), 유한요소해석 온도 값과 비교하여 온도특성을 검증하였다. 실험 결과, 깊이 150 mm 이하 구간에서 온도는 급격하게 감소하였으며, 깊이 150 mm 초과구간에서는 열이 균일하게 분포되는 것을 확인할 수 있다. 또한 본 연구를 통해 온도 예측식(Wickström, Kodur)과 기준 온도프로파일(Eurocode2, ACI216)로 도출한 온도 값보다 유한요소해석으로 도출한 온도 값이 실험결과와 가장 유사한 것을 확인하였다. Appropriate fire design is necessary to prevent damage to high-rise buildings due to fire. In addition, it is very important to accurately predict the temperature distribution to carry out fire design accurately. However, studies on the temperature distribution of mega SRC columns with a cross-section of 1,000 mm×1,000 mm or more are not actively conducted. Therefore, through a fire test, this study derived the temperature distribution characteristics by depth for mega SRC columns with a cross-section of 1,219 mm×1,219 mm. As part of the fire test, the temperature distribution was derived from the central height of the column to the maximum depth of 432 mm by heating the mega SRC column according to fire times of 1, 2, and 3 hours, respectively. Also, the temperature characteristics from the fire test were verified by comparing them with the temperature equation, the code temperature profile, and the finite element analysis temperature. The result of the test suggests that the temperature rapidly decreased below a depth of 150 mm, and heat was uniformly distributed at depths more than 150 mm. In addition, it was confirmed that the temperature derived from the finite element analysis was more similar to the test than the temperature derived from the temperature equation and the design temperature profile.

적외선 화상처리 장치를 이용한 건조초기 목재 표면 온도 측정

이관영,강호양,이민경,Lee, Kwan-Young,Kang, Ho-Yang,Lee, Min-Kyung 한국가구학회 2006 한국가구학회지 Vol.17 No.3

Temperature of board surface was monitored during drying using an IR image measurement system. Boards were water-saturated and dried at the levels of four temperatures and three air velocities. At higher DB the surface temperature increased more steeply and level off period was significantly short. At the DB temperatures of 70, 80, $90^{\circ}C$ the period where the surface temperature was equivalent to WB temperature was constant regardless of air velocity while at $60^{\circ}C$ it decreased as air velocity increased. It was confirmed that a surface transfer coefficient increased with DB temperature. Variation of temperature profile on a wood surface increased with DB temperature and air velocity.

Influence of tooth profile and surface roughness on wear of spur gears considering temperature

박찬일 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.10

Gear wear is an important failure mode in gear systems that changes the tooth profile. Gear wear is closely related to the sliding friction force, and the temperature rise due to friction may change the lubricant regime. Therefore, this study analyzed the wear characteristics of spur gears considering the temperature for tooth profile and surface roughness. To this end, the spur gear load with friction was obtained by solving simultaneous equations comprising load–deformation equations and a moment balance equation. Subsequently, the contact pressure and the heat flux at the meshing position were calculated. The bulk temperature due to the heat flux was obtained by performing finite element analysis. Further, the flash temperature was calculated. The wear analysis included the parameters accounting for the effects of the temperature rise on the lubricant film properties. The wear depth of spur gears was calculated using the modified Archard wear formula with the parameters. The results indicate that the surface roughness slightly increases the wear depth whereas the temperature effects reduce the wear depth. Wear is altered by the tooth profile and increases transmission error.

제주 남부해역 수온 수직구조의 공간분포 특성 파악

윤동영 ( Dong Young Yoon ),최현우 ( Hyun Woo Choi ) 한국지리정보학회 2012 한국지리정보학회지 Vol.15 No.4

공간적으로 3차원의 특성을 지닌 해양에서 수직적인 수온 자료의 특성을 가시화하기 위해서는 각 수심층별 수평 수온분포도와 같은 2차원적 주제도나 3차원적 공간보간을 통한 입체 모델을 사용하게 된다. 이러한 방법은 해양 현상을 시각적으로 이해하는데 유용하지만, 수직적 수온분포의 공간 패턴 분석이나 수직적 수온의 특성과 다른 해양 요인(해양화학, 해양생물, 기후변화 등)과의 관계분석에는 한계가 있다. 따라서 본 연구는 수온 수직구조의 주요 파라미터인 혼합층의 깊이, 최대수온구배, 수온약층의 두께를 추출하는 알고리즘을 이용하여, 수온의 수직구조 특성을 정량화함으로써 제주남부 해역의 수온 수직구조의 공간분포 특성을 밝히고자 한다. 이를 위해 수온 수직구조를 대표하는 세 가지 파라미터에 대한 공간분포지도 제작을 비롯해 공간자기상관 지수(Moran`s I)를 계산하였다. 아울러, 세 가지 파라미터에 대한 군집분석을 수행하여 제주 남부해역을 4개 지역으로 그룹핑하고, 각 지역에 대한 수직 수온구조의 특성을 정의하였다. To visualize the characteristics of vertical seawater temperature data, in the ocean having 3D spatial characteristics, 2D thematic maps like horizontal seawater temperature distribution map at each depth layer and 3D volume model using 3D spatial interpolation are used. Although these methods are useful to understand oceanographic phenomena visually, there is a limit to analyze the spatial pattern of vertical temperature distribution or the relationship between vertical temperature characteristics and other oceanic factors (seawater chemistry, marine organism, climate change, etc). Therefore, this study aims to determine the spatial distribution characteristics of vertical temperature profiles in the South Sea of Jeju by quantifying the characteristics of vertical temperature profiles by using an algorithm that can extract the thermocline parameters, such as mixed layer depth, maximum temperature gradient and thermocline thickness. For this purpose spatial autocorrelation index (Moran`s I) was calculated including mapping of spatial distribution for three parameters representing the vertical temperature profiles. Also, after grouping study area as four regions by using cluster analysis with three parameters, the characteristics of vertical temperature profiles were defined for each region.

온도 프로파일 가시화를 통한 프랙탈 구조 마이크로채널 히트싱크의 열수력학적 특성 최적화

이한솔,곽노균 한국가시화정보학회 2024 한국가시화정보학회지 Vol.22 No.1

As microchips’ degree of integration is getting higher, its cooling problem becomes important more than ever. One of the promising methods is using fractal microchannel heat sink by mimicking nature’s Murray networks. However, most of the related works have been progressed only by numerical analysis. Perhaps such lack of direct experimental studies is due to the technical difficulty of the temperature and heat flux measurement in complex geometric channels. Here, we demonstrate the direct visualization of in situ temperature profile in a fractal microchannel heat sink. By using the temperature-sensitive fluorescent dye and a transparent Polydimethylsiloxane window, we can map temperature profiles in silicon-based fractal heat sinks with various fractal scale factors (a=1.5–3.5). Then, heat transfer rates and pressure drops under a fixed flow rate were estimated to optimize hydrodynamic and thermal characteristics. Through this experiment, we found out that the optimal factor is a=1.75, given that the differences in heat transfer among the devices are marginal when compared to the variances in pumping power. This work is expected to contribute to the development of high-performance, high-efficiency thermal management systems required in various industrial fields.

Effect of ultrasound irradiation on solvent extraction process

김형진,Min-Hwan Chi,In-Kwon Hong 한국공업화학회 2009 Journal of Industrial and Engineering Chemistry Vol.15 No.6

The temperature and pressure profiles of four solvents were simulated at various ultrasonic power levels to suggest models for predicting the energy density. The acousticsmode and heat transfer mode of COMSOL MultiphysicsTM were used to predict the temperature and pressure profiles, respectively. For water, the maximumand minimumpressure at 300Wand 450Wof ultrasonic power level were 8.838 × 106 Pa and -9.533 × 106 Pa, and 1.028 × 107 Pa and-1.1167 × 107 Pa, respectively.The pressure gapwasin the order of water,hexane, methanol and ethanol. For ethanol, themaximumand minimumtemperature of 450Win 1200 s was 337.15 K and 298.25 K, respectively. The energy density of ethanol was the highest among solvents while that of water showed the lowest value. The pressure, temperature and energy density increased with increasing ultrasonic power and irradiation time. The energy density was inversely proportional to temperature, but the cavitation density was in proportion to temperature. The solubility increased with increasing temperature. In overall, the temperature-dependent effect was considered in ultrasound-induced extraction process.

Theoretical study of 1D gradient photonic structures with quartic polynomial dielectric profile formed by AllGa1-lAs varying pressure and temperature under oblique incidence

Calvo-Velasco D.M.,Sánchez-Cano Robert 한국물리학회 2022 Current Applied Physics Vol.41 No.-

In this work it is presented a theoretical study of the optical properties of 1D photonic systems with gradient dielectric profile layers of quartic polynomial type, using the dielectric AllGa1-lAs being the Al concentration along the width of the slab as the gradient function, when external parameters as the pressure and the temperature are considered. It is shown that the proposed gradient profile admits an analytic approach supported on the method of series to find the solutions of the wave equations for the TE and TM polarizations. Also, it is proposed a new regression model for the calculation of the dielectric value of AllGa1-lAs as a function of the pressure and temperature. The results showed that the increase in the pressure shifts and changes the transmission bands due to the decrease in the dielectric mean value of the gradient slab. On the other hand, it is found that the increase in the temperature shifts the transmission bands to lower frequencies but without changing their shape distribution. Considering the inclusion of graphene, it is observed its effect on the distribution of the transmission bands at different frequencies depending on the graphene properties. It is expected that the proposed structure can be contribute to the development of new devices when the pressure, the temperature and the chemical potential of graphene are used as external tunable parameters.

Evaluation of Atmospheric Profile Retrieval Algorithm for GK2A Satellite with Dropsonde Observations

김태명,이수정,안명환,정성래 한국기상학회 2020 Asia-Pacific Journal of Atmospheric Sciences Vol.56 No.2

The Korea’s Geostationary Multi-Purpose Satellite-2A (GK2A) was launched in December 2018 with its main payload, Advanced Meteorological Imager (AMI). Using the 9 infrared channels of the AMI, an algorithm has been developed to retrieve vertical profiles of temperature and humidity for the clear-sky. The algorithm, named as AMI Atmospheric Profile (AAP), is based on an optimal estimation method with its a priori information from model forecasts. From the retrieved profiles, total precipitable water and atmospheric instability indices are estimated, while total column ozone is derived as a by-product. Comparisons of the AAP products and radiosonde observations over land surface stations show that the AAP humidity profiles improve the a priori information by about 4%of rootmean square error (RMSE) between 100 and 1000 hPa.However, asmost of radiosonde data used for the validation are also used for the preparation of the a priori data, comparisons with radiosonde data would not reveal full characteristics of the AAP algorithm. Therefore, current study evaluates the AAP using dropsonde data obtained over the ocean. Since the dropsonde data are not used for the preparation of the a priori data, they could be a truly independent reference data set. The validation results with the dropsonde data confirm that the AAP performance over the ocean is almost the same as that on land for the temperature profiles. In the case of the humidity, however, a priori improvements by AAP algorithm is much larger over the ocean than on land (the RMSE is improved by 11% between the surface and 400 hPa). The results also show that the performance of the retrieval algorithm under clear-sky conditions is similar to that at the cloud edges over the sea, suggesting the potential benefits of using AAP temperature and humidity profiles for real-time analysis of the atmospheric conditions over the ocean.