Micropatterning of Liquid Metal by Dewetting

Kim, Taehong,Kim, Kwangseok,Kim, Seokbeom,Lee, Jungchul,Kim, Wonjung IEEE 2017 Journal of microelectromechanical systems Vol.26 No.6

<P>Although gallium-based liquid metals are attracting growing interest thanks to its potential applications in deformable, flexible electronic devices, challenges in fabrication associated with the high surface tension and oxide skin remain to be overcome. We report a novel fabrication technique for liquid metal circuits using dewetting. An excessively thin liquid film spontaneously shrinks on a substrate to reduce surface free energy. In the case of a thin liquid metal film on a substrate with microgrooves, the oxide on the microgroove wall and the additional viscous resistance delay the shrinkage in the grooves, which separates the liquid volume inside the microgrooves from the external volume. Utilizing this mechanism, we successfully produced 20-mu m-thick conductive lines of eutectic gallium indium (EGaIn) on polydimethylsiloxane. This fabrication technique is simple, fast, and cost-effective and requires no top covering layer. The resultant metal lines show potentially applicable electrical resistance to flexible and stretchable electronic devices. [2017-0082]</P>

Neighbor Table Based Shortcut Tree Routing in ZigBee Wireless Networks

Taehong Kim,Seong Hoon Kim,Jinyoung Yang,Seong-eun Yoo,Daeyoung Kim IEEE 2014 IEEE transactions on parallel and distributed syst Vol.25 No.3

<P>The ZigBee tree routing is widely used in many resource-limited devices and applications, since it does not require any routing table and route discovery overhead to send a packet to the destination. However, the ZigBee tree routing has the fundamental limitation that a packet follows the tree topology; thus, it cannot provide the optimal routing path. In this paper, we propose the shortcut tree routing (STR) protocol that provides the near optimal routing path as well as maintains the advantages of the ZigBee tree routing such as no route discovery overhead and low memory consumption. The main idea of the shortcut tree routing is to calculate remaining hops from an arbitrary source to the destination using the hierarchical addressing scheme in ZigBee, and each source or intermediate node forwards a packet to the neighbor node with the smallest remaining hops in its neighbor table. The shortcut tree routing is fully distributed and compatible with ZigBee standard in that it only utilizes addressing scheme and neighbor table without any changes of the specification. The mathematical analysis proves that the 1-hop neighbor information improves overall network performances by providing an efficient routing path and distributing the traffic load concentrated on the tree links. In the performance evaluation, we show that the shortcut tree routing achieves the comparable performance to AODV with limited overhead of neighbor table maintenance as well as overwhelms the ZigBee tree routing in all the network conditions such as network density, network configurations, traffic type, and the network traffic.</P>

Distributed Topology Construction in ZigBee Wireless Networks

Kim, Taehong,Kim, Seong Hoon,Kim, Daeyoung Springer-Verlag 2018 Wireless personal communications Vol.103 No.3

Spray-Coated Liquid Metal Reflectors for Transparent Hydrogel Atomic Force Microscope Cantilevers

Kim, Kwangseok,Kim, Seokbeom,Kim, Taehong,Kim, Wonjung,Lee, Jungchul Institute of Electrical and Electronics Engineers 2016 Journal of microelectromechanical systems Vol. No.

<P>This letter reports optical-lever detection with spray-coated liquid metal reflectors for transparent hydrogel atomic force microscope (AFM) cantilevers. Eutectic gallium-indium (EGaIn) filled in an air brush was locally sprayed over poly(ethylene) glycol-diacrylate (PEG-DA) AFM cantilevers with a shadow mask. Oxygen plasma treatment for bare hydrogel cantilevers prior to the EGaIn spray was shown to improve the wetting characteristics between EGaIn and PEG-DA, thus enabled relatively thin coating of similar to 800 nm within similar to 100 ms. PEG-DA AFM cantilevers coated with EGaIn were underwent mechanical characterization, and were employed for AFM imaging in both air and deionized (DI) water. Except the reflectivity degraded down to 40% of the initial value after 1-h dwell in DI water, their overall performance was comparable with those of PEG-DA AFM cantilevers with solid metal reflectors.</P>

장 정결 후 발생한 정상 신기능에서의 고마그네슘혈증

김태홍 ( Taehong Kim ),김태형 ( Tae Hyung Kim ),이원혁 ( Won Hyuk Lee ),이유진 ( Yoo Jin Lee ),박시형 ( Sihyung Park ),박봉수 ( Bong Soo Park ),김양욱 ( Yang Wook Kim ) 대한내과학회 2016 대한내과학회지 Vol.91 No.3

대장 내시경 검사에서 장 정결은 필수적인 조건이며, 이를 위해선 장 정결제가 반드시 필요하고 정결제는 각기 다른 특성을 지니고 있다. 따라서 정상 신기능을 가진 환자라도 대장 내시경의 목적 및 환자의 증상에 따라 장 정결제 선택에 주의를 해야 할 것으로 생각된다. Most reported cases of hypermagnesemia are related to laxative abuse and impaired renal function, while hypermagnesemia is uncommon without iatrogenic magnesium administration and decreased renal function. Magnesium-containing bowel-cleansing agents are widely used before colonoscopy, usually without complications. However, we experienced a case of symptomatic hypermagnesemia with normal renal function after using a bowel-cleansing agent. A 74-year-old man with normal renal function complained of lethargy and motor weakness after taking a bowel-cleansing agent containing 14 grams of magnesium before a colonoscopy for hematochezia. His magnesium level was 12 mg/dL. Fluid stasis in the gut due to colonic obstruction might have caused the hypermagnesemia. He was treated successfully with a bowel enema and intravenous calcium. We should be cautious when prescribing drugs for colonoscopy if colonic obstruction is suspected. (Korean J Med 2016;91:306-310)

Naringenin Derivative Diethyl (5,4'-dihydroxy flavanone-7-yl) Phosphate Inhibits Cell Growth and Induces Apoptosis in A549 Human Lung Cancer Cells

Jung-Hee Kim,Heejong Kim,Yesol Bak,Jeong-Woo Kang,Dong Hun Lee,Man Sub Kim,박연선,Eun-Jin Kim,정강연,YOONGHO LIM,Jin-TaeHong,윤도영 한국응용생명화학회 2012 Applied Biological Chemistry (Appl Biol Chem) Vol.55 No.1

Anti-cancer effects of naringenin derivative diethyl (5,4'-dihydroxy flavanone-7-yl) phosphate were evaluated in human lung cancer cells. The effect of diethyl (5,4'-dihydroxy flavanone-7-yl) phosphate (dEdHF-7-p) on A549 cell viability was measured using MTS assay and cell counting. Morphological changes were detected using phase-contrast microscopy. Apoptosis was analyzed using Hoechst staining. The influence of dEdHF-7-p on cell cycle distribution was determined using propidium iodide (PI) staining, and protein expression was determined by Western blot analysis. A newly synthesized naringenin derivative dEdHF-7-p suppressed cell growth of A549though mechanisms including inhibition of cell cycle and increased apoptosis. Apoptotic and cell cycle modulators were changed by dEdHF-7-p in A549 cells; cyclins, ppRB, and antiapoptotic factor Bcl-2 were down-regulated, whereas apoptotic factor Bax and cyclin-dependent kinase inhibitors p21 and p53were enhanced, thereby releasing cytochrome c into the cytosol of dEdHF-7-p -treated-A549 cells. dEdHF-7-p treatment processed caspases-3/-8/-9 and cleavage of poly ADP-ribose polymerase. The dEdHF-7-p treatment enhanced Fas expression and decreased expression of cell survival factors such as PI3K and p-Akt in a dose-dependent manner. Taken together, dEdHF-7-p induces apoptosis by inhibiting the PI3K/Akt survival signaling pathway and modulating mitochondria-emanated intrinsic and Fas extrinsic pathways in A549 cells.

Analysis of the 4H-SiC Contact Resistance according to the Composition Ratio of Co to Si

Taehong Kim,Kwangsoo Kim 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.6

In this research, the 4H-SiC contact resistance was analyzed according to the Co to Si composition ratio. The Co to Si composition ratio was split into 1:2, 1:2.5, and 1:3, and two-step annealing was performed to form Co silicide. The specific contact resistivity and the thermal stability characteristics were measured, and the results were analyzed by X-ray diffraction (XRD). As a result, when the composition ratio of Co to Si was 1:2.5, the specific contact resistivity was the smallest, and the variation in temperature. is also the smallest. The reason for this was confirmed based on the results of by the XRD analysis that CoSi2, which is the most thermodynamically stable phase of Co silicide, was formed well when the Co to Si composition ratio was 1:2.5.

One-Hop Neighbor Based Broadcast Scheduling in Wireless Sensor Networks

KIM, Taehong,KIM, Daeyoung,KIT, Chong Poh The Institute of Electronics, Information and Comm 2011 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.eb94 No.1

<P>For wireless sensor networks in which resources are limited and network topology dynamically changes, we propose the one-hop neighbor based broadcast scheduling (ONBS) algorithm to provide reliable delivery service of broadcast packets. The proposed algorithm reduces the scheduling overhead by allowing each joining node to decide its broadcast schedule based on only its one-hop neighbor information in an on-line and distributed manner. Also, once the broadcast schedule is decided, it is not changed to accommodate a newly joining node in order to prevent the consecutive changes of existing schedules. The network simulation results show that the proposed algorithm provides low latency and high reachability despite low overhead and on-line algorithm design.</P>

Analysis of the Cellular Stress Response in MCF10A Cells Exposed to Combined Radio Frequency Radiation

KIM, Han-Na,HAN, Na-Kyung,HONG, Mi-Na,CHI, Sung-Gil,LEE, Yun-Sil,KIM, Taehong,PACK, Jeong-Ki,CHOI, Hyung-Do,KIM, Nam,LEE, Jae-Seon Journal of Radiation Research Editorial Committee 2012 JOURNAL OF RADIATION RESEARCH Vol.53 No.2

<P>Exposure to environmental stressors can be measured by monitoring the cellular stress response in target cells. Here, we used the cellular stress response to investigate whether single or combined radio frequency (RF) radiation could induce stress response in human cells. Cellular stress responses in MCF10A human breast epithelial cells were characterized after exposure to 4 h of RF radiation [code division multiple access (CDMA) or CDMA plus wideband CDMA (WCDMA)] or 2 h RF radiation on 3 consecutive days. Specific absorption rate (SAR) was 4.0 W/kg for CDMA signal alone exposure and 2.0 W/kg each, 4.0 W/kg in total for combined CDMA plus WCDMA signals. Expression levels and phosphorylation states of specific heat shock proteins (HSPs) and mitogen-activated protein kinases (MAPKs) were analyzed by Western blot. It was found that HSP27 and ERK1/2 phosphorylations are the most sensitive markers of the stress response in MCF10A cells exposed to heat shock or ionizing radiation. Using these markers, we demonstrated that neither one-time nor repeated single (CDMA alone) or combined (CDMA plus WCDMA) RF radiation exposure significantly altered HSP27 and ERK1/2 phosphorylations in MCF10A cells (<I>p</I> > 0.05). The lack of a statistically significant alteration in HSP27 and ERK1/2 phosphorylations suggests that single or combined RF radiation exposure did not elicit activation of HSP27 and ERK1/2 in MCF10A cells.</P>

Learning based relay selection for reliable content distribution in smart class application

( Taehong Kim ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.8

As the number of mobile devices such as smart phones and tablets explodes, the need for new services or applications is also rapidly increasing. Smart class application is one of the emerging applications, in which most of contents are distributed to all members of a class simultaneously. It is highly required to select relay nodes to cover shadow area of radio as well as extend coverage, but existing algorithms in a smart class environment suffer from high control packet overhead and delay for exchanging topology information among all pairs of nodes to select relay nodes. In addition, the relay selection procedure should be repeated in order to adapt to the dynamic topology changes caused by link status changes or device`s movement. This paper proposes the learning based relay selection algorithm to overcome aforementioned problems. The key idea is that every node keeps track of its relay quality in a fully distributed manner, where RQI (Relay Quality Indicator) is newly defined to measure both the ability of receiving packets from content source and the ability of successfully relaying them to successors. The RQI of each node is updated whenever it receives or relays broadcast packet, and the node having the higher RQI is selected as a relay node in a distributed and run-time manner. Thus, the proposed algorithm not only removes the overhead for obtaining prior knowledge to select relay nodes, but also provides the adaptability to the dynamic topology changes. The network simulation and experimental results prove that the proposed algorithm provides efficient and reliable content distribution to all members in a smart class as well adaptability against network dynamics.