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PLASMA EFFECTS ON HUMAN LIVER CANCER CELLS
Daeyeon Kim,Bomi Gweon,Danbee Kim,Sukhyun Song,Mina Kim,Se Youn Moon,Wonho Choe,Jennifer H. Shin 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
Low pressure plasma has been widely used in surface treatment of solid materials. In recent years, atmospheric plasma (cold plasma) is introduced in biomedical applications. In general, many types of cellular behaviors depend on the plasma density or intensity. While the plasma-treated cells are detached because of the plasma-induced damage of cell adhesion molecules at low plasma density, the cell membranes are destructed and the necrosis of cells occurs at high plasma density. In this research, we investigate the effects of plasma on cancerous cells. We treat the target human liver cancer cells (HepG2 and SK-Hep1) using a He plasma needle device, which has a pin type plasma jet. We aim to identify the plasma effects on cancerous cells as a function of the treatment time and applied power. This study may contribute to the development of a novel cancer therapy.
Modeling of Eccentricity-Induced Radial Forces in a Permanent-Magnet Synchronous Motor
Daeyeon Kim,Myounggyu D. Noh,Young-Woo Park 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.춘계 No.-
When the rotor of a permanent-magnet (PM) synchronous motor has some eccentricity, the magnetic field distribution in the air gap between the rotor and stator changes. As a result, the radial forces are occurred in a PM synchronous motor and is a common source of noise and vibration. In this paper, we describe a model that predicts the radial forces due to eccentricity in a PM synchronous motor.
Highly stretchable energy harvester using piezoelectric helical structure for wearable applications
Daeyeon Yun,Jungyong Park,Kwang-Seok Yun IET 2015 Electronics letters Vol.51 No.3
<P>Proposed is a helical piezoelectric structure for a highly stretchable energy harvester to be applied on the human body. The proposed device consists of two counter-wound helical structures around a zcore structure made of an elastic fabric string. The inner fabric helix is used to separate the outer piezoelectric helix from the core to obtain a highly stretchable device. When stretched by 60% of its initial length, the device generates a maximum output voltage and power of 140 V<SUB>p-p</SUB> and 0.6 mW, respectively, at an operation frequency of 4 Hz.</P>
Turning mechanism of a smooth body by amplitude and period control in curvature
Daeyeon Kim,Hyejin Hwang,Sungsu Park,Jennifer H. Shin 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10
C. elegans’crawling locomotion including simple running and turning is analyzed with a mathematical model. C. elegans moves forward and backward by propagating dorso-ventral contraction waves toward the opposite direction of its movement. For straight run, the worm maintains a constant amplitude and period in its body curvature. While it changes these quantities during smooth turn. Two types of smooth turn are described theoretically based on the experimental observation. One has the turning strategy to increase both of amplitude and period of the curvature. The other is characterized by decrement of these parameters. Our results may contribute to understanding the lateral undulation of other smooth body animals like snakes and these could further be applied to the developments of bio-inspired robots.
Daeyeon Kim,Jinsil Cheon,Jeonghoon Kim,Daekyun Hwang,Ikpyo Hong,Oh Hyeong Kwon,Won Ho Park,Donghwan Cho 한국탄소학회 2017 Carbon Letters Vol.22 No.-
In the present study, biomass-based lignin was extracted from industrial waste black liquor and the extracted lignin was characterized by means of attenuated total reflectance- Fourier transform infrared spectroscopy and 1H-nuclear magnetic resonance spectroscopy. The extracted lignin was carbonized at different temperatures and then activated with steam at 850oC. The extracted lignin in powder state was transformed into a bulky carbonized lignin due to possible fusion between the lignin particles occurring upon carbonization. The carbonized and then pulverized lignin exhibits brittle surfaces, the increased thermal stability, and the carbon assay with increasing the carbonization temperature. The scanning electron microscopic images and the Brunauer-Emmett-Teller result indicate that the steam-activated carbon has the specific surface area of 1718 m2/g, which is markedly greater than the carbonized lignin. This study reveals that biomassbased activated carbon with highly porous structure can be produced from costless black liquor via steam-activation process.
Recent developments in scale-up of microfluidic emulsion generation via parallelization
Daeyeon Lee,Heon-Ho Jeong,David Issadore 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.6
Microfluidics affords precise control over the flow of multiphasic fluids in micron-scale channels. By manipulating the viscous and surface tension forces present in multiphasic flows in microfluidic channels, it is possible to produce highly uniform emulsion droplets one at a time. Monodisperse droplets generated based on microfluidics are useful templates for producing uniform microcapsules and microparticles for encapsulation and delivery of active ingredients as well as living cells. Also, droplet microfluidics have been extensively exploited as a means to enable highthroughput biological screening and assays. Despite the promise droplet-based microfluidics hold for a wide range of applications, low production rate (<<10mL/hour) of emulsion droplets has been a major hindrance to widespread utilization at the industrial and commercial scale. Several reports have recently shown that one way to overcome this challenge and enable mass production of microfluidic droplets is to parallelize droplet generation, by incorporating a large number of droplet generation units (N>>100) and networks of fluid channels that distribute fluid to each of these generators onto a single chip. To parallelize droplet generation and, at the same time, maintain high uniformity of emulsion droplets, several considerations have to be made including the design of channel geometries to ensure even distribution of fluids to each droplet generator, methods for large-scale and uniform fabrication of microchannels, device materials for mechanically robust operation to withstand high-pressure injection, and development of commercially feasible fabrication techniques for three-dimensional microfluidic devices. We highlight some of the recent advances in the mass production of highly uniform microfluidics droplets via parallelization and discuss outstanding issues.