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Lee Seunghee,Kim Hyun Woo,임진오,Kim Seok Ki,Kim Yong Tae,Chang Hyunju,Ko Tae-Wook,Lee Jonggul,Hyon YunKyong 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.8
Molecular dynamics (MD) simulations are useful in understanding the interaction between solid materials and molecules. However, performing MD simulations is possible only when interatomic potentials are available and constructing such interatomic potentials usually requires additional computational work. Recently, generating interatomic potentials was shown to be much easier when machine learning (ML) algorithms were used. In addition, ML algorithms require new descriptors for improved performance. Here, we present an ML approach with several categories of atomic descriptors to predict the parameters necessary for MD simulations, such as the potential energies and the atomic forces. We propose several atomic descriptors based on structural information and find that better descriptors can be generated from eXtreme gradient boosting (XGBoost). Moreover, we observe fewer descriptors that perform better in predicting the potential energies and the forces during methane activation processes on a catalytic Pt(111) surface. These results were consistently observed in two different ML algorithms: fully-connected neural network (FNN) and XGBoost. Taking into account the advantages of FNN and XGBoost, we propose an efficient ML model for estimating potential energies. Our findings will be helpful in developing new ML potentials for long-time MD simulations.
OPTIMAL STRATEGIES FOR PREVENTION OF ECSTASY USE
SUNHWA CHOI,JONGGUL LEE,EUNOK JUNG 한국산업응용수학회 2014 Journal of the Korean Society for Industrial and A Vol.18 No.1
We have investigated optimal control strategies for prevention of ecstasy use. Ecstasy use has continued at raves and nightclubs in recent years and the reduction of ecstasy use has become one of the important issues in society. We apply optimal control theory to a model of the peer-driven dynamics of ecstasy use. Our goal is to minimize the ecstasy use class and the intervention cost. Optimal control is characterized in terms of the solution of optimality system, which is the state system coupled with the adjoint system and the optimality equations. The numerical simulations show the optimal prevention policies of ecstasy use in various scenarios.
MULTIDIMENSIONAL OPEN SYSTEM FOR VALVELESS PUMPING
JUNG, EUNOK,KIM, DO WAN,LEE, JONGGUL,LEE, WANHO Korean Mathematical Society 2015 대한수학회보 Vol.52 No.6
In this study, we present a multidimensional open system for valveless pumping (VP). This system consists of an elastic tube connected to two open tanks filled with a fluid under gravity. The two-dimensional elastic tube model is constructed based on the immersed boundary method, and the tank model is governed by a system of ordinary differential equations based on the work-energy principle. The flows into and out of the elastic tube are modeled in terms of the source/sink patches inside the tube. The fluid dynamics of this system is generated by the periodic compress-and-release action applied to an asymmetric region of the elastic tube. We have developed an algorithm to couple these partial differential equations and ordinary differential equations using the pressure-flow relationship and the linearity of the discretized Navier-Stokes equations. We have observed the most important feature of VP, namely, the existence of a unidirectional net flow in the system. Our computations are focused on the factors that strongly influence the occurrence of unidirectional flows, for example, the frequency, compression duration, and location of pumping. Based on these investigations, some case studies are performed to observe the details of the ow features.
전해 산성수 및 차량 번호판 인식을 이용한 방재 관제 시스템 구현에 관한 연구
곽윤식(Yoonsik Kwak),이정재(Jungjae Lee),이윤수(Yunsou Lee),김태환(Taehwan Kim),우종걸(Jonggul Woo),조남형(Namhyung Joo),신희종(Heejong Shin),송석일(Seokil Song) 한국정보기술학회 2012 한국정보기술학회논문지 Vol.10 No.9
In this paper, we present that it is about the monitoring system for disaster prevention using an antiseptic water production device and a car license plate recognition system. The antiseptic water production devices consist of a storage, spray, connection part, and an antiseptic water unit. The car license plate recognition systems consist of an automatic recognition system for cars and license plate recognition system. Using the above described components, we could implement the monitoring system for disaster prevention that consist of realtime monitoring, objects, configuration, user, login/out management part. As the results, we could prove the function of disinfection for an antiseptic water and monitor the information about cars to be used for disinfection. Simultaneously we could get the information about cars and drivers. Also, using the functionality of implemented systems integration management, we could obtain usability and efficiency in agriculture to be characteristics.
Ko Youngsuk,Mendoza Victoria May,Mendoza Renier,Seo Yubin,Lee Jacob,Lee Jonggul,Kwon Donghyok,Jung Eunok 대한의학회 2022 Journal of Korean medical science Vol.37 No.26
Background: The most recent variant of concern, omicron (B.1.1.529), has caused numerous cases worldwide including the Republic of Korea due to its fast transmission and reduced vaccine effectiveness. Methods: A mathematical model considering age-structure, vaccine, antiviral drugs, and influx of the omicron variant was developed. We estimated transmission rates among age groups using maximum likelihood estimation for the age-structured model. The impact of non-pharmaceutical interventions (NPIs; in community and border), quantified by a parameter μ in the force of infection, and vaccination were examined through a multi-faceted analysis. A theory-based endemic equilibrium study was performed to find the manageable number of cases according to omicron- and healthcare-related factors. Results: By fitting the model to the available data, the estimated values of μ ranged from 0.31 to 0.73, representing the intensity of NPIs such as social distancing level. If μ < 0.55 and 300,000 booster shots were administered daily from February 3, 2022, the number of severe cases was forecasted to exceed the severe bed capacity. Moreover, the number of daily cases is reduced as the timing of screening measures is delayed. If screening measure was intensified as early as November 24, 2021 and the number of overseas entrant cases was contained to 1 case per 10 days, simulations showed that the daily incidence by February 3, 2022 could have been reduced by 87%. Furthermore, we found that the incidence number in mid-December 2021 exceeded the theory-driven manageable number of daily cases. Conclusion: NPIs, vaccination, and antiviral drugs influence the spread of omicron and number of severe cases in the Republic of Korea. Intensive and early screening measures during the emergence of a new variant is key in controlling the epidemic size. Using the endemic equilibrium of the model, a formula for the manageable daily cases depending on the severity rate and average length of hospital stay was derived so that the number of severe cases does not surpass the severe bed capacity.