이온 보존 반응법에 의하여 표면처리된 Polyimide(PI) 표면과 구리박막의 접착력 향상

최성창,석진우,최원국,손용배,정형진,고석근 한국마이크로전자및패키징학회 1997 하이브리드마이크로일렉트로닉스 Vol.4 No.1

Polyimide films are modified by Ar^+ion beam at 1 kV in an oxygen environments. Amounts of ions changed from 5 x 10^(15) to 1 x 10^(17) ions /㎠ and amounts of blowing oxygen from 0 to 8 sccm ml /min. The wettabilities and the surface free energies of modified polyimide were measured by a contact angle meter and the chemical state of the modified polyimide surface was measured by x-ray photoelectron spectroscopy. The wetting angles between water and polyimide films modified by Ar^+ ion without oxygen blowing decrease from 67 to 40 degrees and surface free energies increase from 46 to 64 dyne /㎠. The wetting angle of polyimide films modified by Ar^+ ion in an oxygen environments decrease to 12 degree and surface free energy increase to 72 dyne /㎠. Polyimide surface was modified with various gas environments and ions. Lowest wetting angle was obtained by oxygen ion irradiation in an oxygen gas environment and its value was 8°. In the case of polyimide film modified by Ar^+ ions in an oxygen environment, the wetting angle increase up to 65° when it kept in air and that increase up to 46° when it kept in water after 110 hour. In the case of polyimide film modified by O^+ ions in an oxygen environment, however, the wetting angle of polyimide film dose not increase. From the x-ray photoelectron analysis, it is found that the chemical bonds between polyimide components are severed by ion irradiation and hydrophilic groups such as (C=O)-(ON)-, COH and (C=O)-C are formed by the reaction between newly formed radicals and blowing oxygen. I t was found that the adhesion between Cu and polyimide modified by ion assisted reaction was improved, and the main reason of the enhanced adhesion is due to the reaction between Cu and C-O groups formed by ion assisted reaction on the polyimide surface.

라미부딘과 HBIg 1주일 단기 병합요법은 간이식 후 B형 간염 재발 방지에 HBIg 장기 고용량 투여요법만큼 효과적인가?

김성주,장재권,이석구,도재혁,백승운,최문석,조재원,고광철,이풍렬,이종철,최규완,박상종,이준혁,김재준,임윤정,안병훈 대한소화기학회 2001 대한소화기학회지 Vol.37 No.1

Background/Aims : The aim of this study was to evaluate whether the regimen consisted of lamivudine and one-week HBIg for HBV prophylaxis after liver transplantation is as effective as long-term therapy of high dose HBIg. Methods: Sixty-one patients with HBV infection were randomly divided into two groups: HBIg group of 31 patients and combination group of 30 patients. In the HBIg group, HBIg was given according to the standard dosing schedule. In the combination group, lamivudine was given indefinitely from at least 4 weeks before transplantation, and 10,000 IU of HBIg was given during anhepatic phase and 6 consecutive days. Results: The two groups were not different in HBeAg and HBV DNA positivity. In the HBIg group, the median follow-up of 20 long-term survivors was 12.7 months (range: 4.0 - 48.2) and that of 23 survivors in the combination group was 22.3 months (4.2 - 42.2). Hepatitis B recurred in a patient of the HBIg group and 2 of the combination group. The recurrence-free survival rate of long-term survivors was 66.7% (95% C.I., 39.5% - 93.9%) in the HBIg group and 76.0% (58.6% - 93.4%) in the combination group after 40 months. Conclusions: The combined therapy of lamivudine and one-week HBIg has an effect equivalent to long-term therapy of high dose HBIg in HBV prophylaxis after liver transplantation at a much lower cost.

혈액투석 중인 만성 신부전 환자에서 TT Virus의 감염률과 임상적 의의

이용욱,허우성,도재혁,백승운,최문석,김소정,이준행,고광철,이풍렬,이종철,최규완,박상종,이준혁,김재준,오하영,임윤정 대한소화기학회 2001 대한소화기학회지 Vol.37 No.1

Background/Aims: TT virus (TTV) is a unenveloped, single-stranded and circular DNA virus isolated from the serum of a patient with posttransfusion hepatitis of unknown etiology. We evaluated the prevalence, risk factors, and clinical significance of TTV in patients with chronic renal failure(CCRF) undergoing maintenance hemodialysis (HD). Methods: We examined TTV DNA in serum of HD-undergoing patients and healthy controls using the nested polymerase chain reaction. Results: TTV DNA was detected in 15 (20.0%) of 75 HD-undergoing patients and 10 (13.2%) of 76 healthy controls (p$gt;0.05). The prevalence of TTV did not differ according to the duration of HD or transfusion history of the patients. The prevalence of TTV was higher in IgG anti-HBc positive patients than IgG anti-HBc negative patients (27.5% vs. 4.2%, p=0.03). There was no relationship between TTV infection and liver diseases. Conclusions: The prevalence of TTV infection in CRF patients undergoing HD was similar with that of healthy controls. These results suggest that TTV infection may share the route of transmission with HBV infection in adults.

Forebrain-specific ablation of phospholipase Cγ1 causes manic-like behavior

Yang, Y R,Jung, J H,Kim, S-J,Hamada, K,Suzuki, A,Kim, H J,Lee, J H,Kwon, O-B,Lee, Y K,Kim, J,Kim, E-K,Jang, H-J,Kang, D-S,Choi, J-S,Lee, C J,Marshall, J,Koh, H-Y,Kim, C-J,Seok, H,Kim, S H,Choi, J H,Ch Macmillan Publishers Limited, part of Springer Nat 2017 Molecular psychiatry Vol.22 No.10

<P>Manic episodes are one of the major diagnostic symptoms in a spectrum of neuropsychiatric disorders that include schizophrenia, obsessive-compulsive disorder and bipolar disorder (BD). Despite a possible association between BD and the gene encoding phospholipase C gamma 1 (PLCG1), its etiological basis remains unclear. Here, we report that mice lacking phospholipase C gamma 1 (PLC gamma 1) in the forebrain (Plcg1(f/f); CaMKII) exhibit hyperactivity, decreased anxiety-like behavior, reduced depressive-related behavior, hyperhedonia, hyperphagia, impaired learning and memory and exaggerated startle responses. Inhibitory transmission in hippocampal pyramidal neurons and striatal dopamine receptor D1-expressing neurons of Plcg1-deficient mice was significantly reduced. The decrease in inhibitory transmission is likely due to a reduced number of gamma-aminobutyric acid (GABA)-ergic boutons, which may result from impaired localization and/or stabilization of postsynaptic CaMKII (Ca2+/calmodulin-dependent protein kinase II) at inhibitory synapses. Moreover, mutant mice display impaired brain-derived neurotrophic factor-tropomyosin receptor kinase B-dependent synaptic plasticity in the hippocampus, which could account for deficits of spatial memory. Lithium and valproate, the drugs presently used to treat mania associated with BD, rescued the hyperactive phenotypes of Plcg1(f/f); CaMKII mice. These findings provide evidence that PLC gamma 1 is critical for synaptic function and plasticity and that the loss of PLC gamma 1 from the forebrain results in manic-like behavior.</P>

A Control of Channel Rate for Real-time VBR Video Transmission

Koh, Seok J.,Lee, Chae Y 한국경영과학회 1999 韓國經營科學會誌 Vol.24 No.3

Recent studies on the Constant Bit Rate and Variable Bit Rate transmissions have mainly focused on the frame by frame encoder rate control based on the quantization parameter. With the existing approaches it is difficult to guarantee a consistent video quality. Also, the rate control overhead is too high for the real-time video sources. In this paper, a channel rate allocation scheme based on the control period is proposed to transmit a real-time video, in which the control period is defined by a pre-specified number of frames or group of pictures. At each control period, video traffic information is collected to determine the channel rate at the next control period. The channel rate is allocated to satisfy various channel rate constraints such that the buffer occupancy at the decoder is maintained at a target level if the allocated channel rate approaches the level at which the negotiated traffic descriptions may be violated, the encoder rate is decreased through adjusting quantization parameters in the MPEG encoder. In the experimental result, the video quality and the overflow and underflow probabilities at the buffer are compared at different control periods. Experiments show that the video quality and the utilization of network bandwidth resources can be optimized through the suitable selection of the control period.

Design of Survivable Communication Networks with High-connectivity Constraints

Koh, Seok J.,Lee, Chae Y. 한국경영과학회 1997 한국경영과학회지 Vol.22 No.3

Designing highly survivable interoffice telecommunication networks is considered. the problem is formulated as a minimum-cost network design problem with three node connectivity constraints. Three valid and facet-defining inequalities for the convex hull of the solutions are presented. A branch and cut algorithm is proposed based on the inequalities to obtain the oprimal solution. With the lower bound by the cutting plane algorithm, a delete-link heuristic is proposed to obtain a good upper bound in the branch and bound procedure. The effectiveness of the branch and cut algorithm is demonstrated with computational results for a variety of problem sets: different lower bounds, two types of link costs and large number of links. The cutting plane procedure based on the three inequalities provides excellent lower bounds to the optimal solutions.

Design of an Optically Controlled MR-Compatible Active Needle

Seok Chang Ryu,Zhan Fan Quek,Je-Sung Koh,Renaud, Pierre,Black, Richard J.,Moslehi, Behzad,Daniel, Bruce L.,Kyu-Jin Cho,Cutkosky, Mark R. IEEE 2015 IEEE TRANSACTIONS ON ROBOTICS Vol. No.

<P>An active needle is proposed for the development of magnetic resonance imaging (MRI)-guided percutaneous procedures. The needle uses a low-transition-temperature shape memory alloy (LT SMA) wire actuator to produce bending in the distal section of the needle. Actuation is achieved with internal optical heating using laser light transported via optical fibers and side coupled to the LT SMA. A prototype, with a size equivalent to a standard 16-gauge biopsy needle, exhibits significant bending, with a tip deflection of more than 14° in air and 5° in hard tissue. A single-ended optical sensor with a gold-coated tip is developed to measure the curvature independently of temperature. The experimental results in tissue phantoms show that human tissue causes fast heat dissipation from the wire actuator; however, the active needle can compensate for typical targeting errors during prostate biopsy.</P>

Corruption-aware adaptive increase and adaptive decrease algorithm for TCP error and congestion controls in wireless networks

Cui, Lin,Koh, Seok J. John Wiley Sons, Ltd. 2009 International journal of communication systems Vol.22 No.5

<P>The conventional TCP tends to suffer from performance degradation due to packet corruptions in the wireless lossy channels, since any corruption event is regarded as an indication of network congestion. This paper proposes a TCP error and congestion control scheme using corruption-aware adaptive increase and adaptive decrease algorithm to improve TCP performance over wireless networks. In the proposed scheme, the available network bandwidth is estimated based on the amount of the received integral data as well as the received corrupted data. The slow start threshold is updated only when a lost but not corrupted segment is detected by sender, since the corrupted packets still arrive at the TCP receiver. In the proposed scheme, the duplicated ACKs are processed differently by sender depending on whether there are any lost but not corrupted segments at present. Simulation results show that the proposed scheme could significantly improve TCP throughput over the heterogeneous wired and wireless networks with a high bit error rate, compared with the existing TCP and its variants. Copyright © 2008 John Wiley & Sons, Ltd.</P>

Enhancement of SCTP Throughput using Chunk Checksum

( Cui Lin ),( Seok J. Koh ),( Yong-geun Hong ) 한국정보처리학회 2006 한국정보처리학회 학술대회논문집 Vol.13 No.1

Stream Control Transmission Protocol (SCTP) uses the 32-bit checksum in the common header, by which a corrupted SCTP packet will be regarded as a lost packet and then discarded. This may result in degradation of SCTP’s throughput performance over wireless networks. This paper proposes a new chunk checksum scheme for SCTP, in which each data chunk contains its own checksum field and SACK chunk carry corresponding Transmission Sequence Number (TSN) with timestamp for every corruption event. The proposed chunk checksum scheme is introduced with the following three purposes: 1) to distinguish the chunk corruptions from the chunk losses; 2) to avoid the unnecessary halving of the congestion window (cwnd) in the case of chunk corruption; 3) to avoid the unwanted timeouts which can be induced in conventional SCTP in the case that the retransmitted data chunks are corrupted again in wireless networks. Simulation results show that the proposed chunk checksum scheme could improve the SCTP throughput in the wireless environments with a high bit error rate.

MMCP: A Control Protocol for IP Multicasting in Mobile Networks

Jaesung Park,Seok J. Koh,Yongjin Kim 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7

This paper proposes a control protocol for IP multicasting in mobile networks, named Mobile Multicast Control Protocol (MMCP). The MMCP is designed to support one-tomany real-time multicast applications running over multicastcapable mobile/wireless networks. This paper dscribes the protocol model, protocol operations and implementation structures of the MMCP.