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Kwak, SungWon,Kim, Woong-Tae,Rey, Soo-Chang,Kim, Suk American Astronomical Society 2017 The Astrophysical journal Vol.839 No.1
<P>A fraction of early-type dwarf galaxies in the Virgo cluster have a disk component and even possess disk features such as bar, lens, and spiral arms. In this study, we construct 15 galaxy models that resemble VCC856, which is considered to be an infalling progenitor of disk dwarf galaxies, within observational error ranges, and use N-body simulations to study their long-term dynamical evolution in isolation as well as the formation of bar in them. We find that dwarf disk galaxies readily form bars unless they have an excessively concentrated halo or a hot disk. This suggests that infalling dwarf disk galaxies are intrinsically unstable to bar formation, even without any external perturbation, accounting for a population of barred dwarf galaxies in the outskirts of the Virgo cluster. The bars form earlier and stronger in galaxies with a lower fraction of counter-streaming motions, lower halo concentration, lower velocity anisotropy, and thinner disk. Similarly to normal disk galaxies, dwarf disk galaxies also undergo recurrent buckling instabilities. The first buckling instability tends to shorten the bar and to thicken the disk, and drives a dynamical transition in the bar pattern speed as well as mass inflow rate. In nine models, the bars regrow after the mild first buckling instability due to the efficient transfer of disk angular momentum to the halo, and are subject to recurrent buckling instabilities to turn into X-shaped bulges.</P>
Cooperative control of differential wheeled mobile robots for box pushing problem
Sungwon Moon,Dongjun Kwak,H. Jin Kim 제어로봇시스템학회 2012 제어로봇시스템학회 국제학술대회 논문집 Vol.2012 No.10
We present a decentralized cooperative control algorithm for a box pushing problem using two ground robots. The main framework of the algorithm is composed of a sequence of three behaviors, Approach, Align, and Push. We define two rotational and one translational motion primitives to manipulate the box. A point-tracking controller is derived for differential wheeled mobile robots to push the point on the box defined by the motion primitives. For cooperation, robots communicate their status variables and an efficient role assignment scheme is proposed. We present experimental results obtained using our multi-robot testbed.
Mass fabrication of uniform sized 3D tumor spheroid using high-throughput microfluidic system
Kwak, Bongseop,Lee, Yoohwan,Lee, Jaehun,Lee, Sungwon,Lim, Jiseok Elsevier 2018 Journal of controlled release Vol.275 No.-
<P><B>Abstract</B></P> <P> <I>In vivo</I> tumors develop in a three-dimensional manner and have unique and complex characteristics. Physico-biochemical barriers on tumors cause drug resistance and limit drug delivery efficiency. Currently, 2D cancer cell monolayer platforms are frequently used to test the efficiency of new drug materials. However, the monolayer platform generally overestimates drug efficiency because of the absence of physico-biochemical barriers. Many literatures indicated that a 3D tumor spheroid model has very similar characteristics to <I>in vivo</I> tumor models, and studies demonstrated the accurate prediction of drug efficiency using this model. The use of a 3D tumor spheroid model in drug development process remains challenging because of the low generation yield and difficulties in size control. In this study, we developed a droplet-based microfluidic system that can generate cancer cells encapsulated by micro-droplets with very high generation yield (16–20 Hz, 1000 droplets/min). The system can control the number of encapsulated cancer cells in the droplet or diameter of the 3D spheroid model precisely between 50 and 150 μm. Moreover, the formed 3D tumor spheroid model can be cultured for >2 weeks by an additional step of droplet disruption and recollection, and can grow up to 245 μm in diameter.</P> <P><B>Graphical abstract</B></P> <P>The developed droplet based microfluidic system can control the size of 3D tumor spheroid models with very high throughput for the drug test platform.</P> <P>[DISPLAY OMISSION]</P>
주행특성을 이용한 온 마운트 장비 추적 차량의 진동 프로파일 개발
서성원(SungWon Suh),이은호(EunHo Lee),이승한(Seoung-Han Lee),곽도혁(Do-Hyuk Kwak),김창남(Chang-Nam Kim),박노철(No-Cheol Park) 한국소음진동공학회 2020 한국소음진동공학회 논문집 Vol.30 No.4
Military products require more product life considerations than civilian products. Equipment mounted on the operating means is continuously exposed to vibrations. Therefore, vibration is an important environmental factor to consider during product development. However, it is common to proceed with product development by applying the vibration profile obtained from the U.S. military standards because securing actual vibration data related to the product is difficult in terms of cost and time. Moreover, the vibration profile of the tracked vehicle is currently unavailable. In this paper, we propose a methodology that considers the characteristics of military products and transport vibrations for generating the vibration profile of a tracked vehicle. We measured the vibration level of the tracked vehicle during transportation. In addition, by building a finite element model of the product, a vibration profile was created using ANSYS Mechanical, which is a commercial finite element analysis program. In this study, the vibration profile of the tracked vehicle was created, and it is expected to be used for future studies and help in the development of products.