• Journal of Biomedical Engineering Research
• /
• v.37 no.5
• /
• pp.186-194
• /
• 2016

In this study, a co-axial flow induced microfluidic chip to fabricate pure collagen type I microfiber via the control of collagen type I and Na-alginate gelation process. The pure collagen type I microfiber was generated by selective degradation of Ca-alginate from 'Core-Shell' structured hydrogel microfiber. To make 'Core-Shell' structure, collagen type I solution was introduced into core channel and 1.5% Na-alginate solution was injected into side channel in microfluidic chip. To evaluatethe 'Core-Shell' structure, the red and green fluorescence substances were mixed into collagen type I and Na-alginate solution, respectively. The fluorescence substances were uniformly loaded into each fiber, and the different fluorescence images were dependent on their location. By immoblizing EpH4-Ras and C6 cells within collagen type I and Na-alginate solution, we sucessfully demonstrated the co-culture of EpH4-Ras and C6 cells with 'Core-Shell' like hydrogel microfiber for 5 days. Only to produce pure collagen type I hydrogel fiber, tri-sodium citrate solution was used to dissolve the shell-like Ca-alginate hydrogel fiber from 'Core-Shell' structured hydrogel microfiber, which is an excellent advantage when the fiber is employed in three-dimensional scaffold. This novel method could apply various application in tissue engineering and biomedical engineering.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.21 no.3
• /
• pp.713-720
• /
• 1996

In recent, the demand of mobile communication system is increasing rapidly. However, since wireless resources is limitted, the protocol to utilize wireless resource efficiently is needed. Up to now, Slotted CDMA_ALOHA(S_CDMA_ALOHA) and Mini-Slotted CDMA_ALOHA(MS_CDMA_ALOHA) methods are proposed as a CDMA_ALOHA mechanism, and it is turned out that MS_CDMA_ALOHA offers betterperformance than S_CDMA_ALOHA mechanism. Also, IS-95 multiple access mechanism has been proposed as common air interface(CAI) protocol of CDMA digital cellular system. However, in former study, the performance evaluations were made without considertion of chnnel characteristics of wireless communication environment. In this paper, a new access mechanism for improring the performance in the DS/CDMA digital cellular environment is suggested. This mechanism is adaptive to the channel condition and based on the conventional MS_CDMA_ALOHA mechanism. Also, the performance of new access mechanism is compared with that of conventional mechanisms, through computer simulation. According tot h simulation results, it is shown that the proposed NA_CDMA_ALOHA(Noise-Adaptation CDMA_ALOHA) mechanism offers better performance than conventional three CDMA_ALOHA mechanisms in view of mean delay time and system throughput characteristics. This phenomenon is due to the fast that NA_CDMA_ALOHA mechanism controls the access attempts efficiently based on the channel condition in heavy traffic environments.

• Korean Journal of Optics and Photonics
• /
• v.11 no.5
• /
• pp.335-339
• /
• 2000

A $1.31/1.55\mu\textrm{m}$ coarse WDM opncal dIrectional coupler that conslsls of two idenlical straight channel waveguides in BK7 glass has been fabricated. The separatIOn between two channel waveguides is $8\mu\textrm{m}$ and the wavegu.ide width is $4\mu\textrm{m}$ . Especlally, we assumed that the index profile is Gaussian function and complementary error function in the width direction and depth direction, respectrvely. This directional coupler operating at $1.31/1.55\mu\textrm{m}$ with crosstalk of 18dB is demonstrated and has the 16 mm long length with 12.6 mm coupling region.region.

• YAKHAK HOEJI
• /
• v.35 no.2
• /
• pp.85-98
• /
• 1991

Verapamil, $Ca^{2+}$-channel blocker, when given into vein or into carotid artery, produced the decrease of urine flow accompanied with the decreased amounts of Na$^{+}$ and $K^{+}$ excreted in urine ($E_{Na}, E_{K}$) and with the decreased clearances of free water (C$_{H_2O}$) and osmolar substance (C$_{osm}$), and then increased reabsorption of Na$^{+}$ and $K^{+}$ in renal tubules (R$_{Na}$, R$_{N}$), glomeruler filtration rate (GFR) and renal plasma flow (RPF) were inhibited when verapamil was given into carotid artery, but were only tendency of reduction when given intravenously. Verapamil, when infused into a renal artery, exhibited diuresis accompanied with the increased GER, RPF, E$_{Na}$ and E$_{K}$, with the decreased filtration fraction (FF) in only infused kidney. At the same time, $C_{H_2O}$ was not changed, R$_{Na}$ and R$_{K}$ were reduced. Antidiuretic action by verapamil administered into vein or into carotid artery in normal kidney was reversed to diuretic action in denervated kidney. At this time, parameters of renal function exhibited the opposite phenomena compared to that elicited by verapamil in normal kidney, wherease renal denervation did not influence the action of verapamil infused into a renal artery. Above results suggest that verapamil produce both antidiuresis through nervous system centrally, not endogenous substances and diuresis by direct action in the kidney. Diurectic action are caused by hemodynamic improvement through dilatioon of vas efferense and by greatly inhibited reabsorption of electrolytes in distal tubules.

• Electrical & Electronic Materials
• /
• v.9 no.2
• /
• pp.174-179
• /
• 1996

We present a new physically based analytical equation for electron effective mobility in MOS inversion layers. The new semi-empirical model is accounting expicitly for surface roughness scattering and screened Coulomb scattering in addition to phonon scattering. This model shows excellent agreement with experimentally measured effective mobility data from three different published sources for a wide range of effective transverse field, channel doping and temperature. By accounting for screened Coulomb scattering due to doping impurities in the channel, our model describes very well the roll-off of effective mobility in the low field (threshold) region for a wide range of channel doping level (Na=3.0*10$^{14}$ - 2.8*10$^{18}$ cm$^{-3}$ ).

• Proceedings of the Korean Information Science Society Conference
• /
• 2011.06a
• /
• pp.365-368
• /
• 2011

무선 메쉬 네트워크 (Wireless Mesh Network, WMN)는 인터넷 사용자에게 멀티홉 무선 백본 네트워크로 인터넷 접속을 제공하기 위한 기술로 각광받고 있다. IEEE 802.11에서는 3개 또는 12개의 겹치지 않는 (non-overlapping) 채널을 지원하지만, WMN 환경에서 멀티 채널을 활용하는 디자인은 중요한 이슈이다. 본 논문에서는 멀티 채널 WMN에서의 트래픽 요구에 맞추어 채널 할당과 라우팅을 분산적인 (Distributed) 방식으로 수행하는 OnCAR (On-demand Channel Assignment and Routing) 프로토콜을 제안한다. OnCAR는 트래픽의 요구에 따른 채널 할당이 가능하고, 채널 다양성 (diversity)를 고려한 라우팅 기법을 제공한다. NS-2를 사용한 시뮬레이션을 통해 OnCAR가 기존 멀티 채널 프로토콜에 비해 향상된 네트워크 성능을 보임을 확인하였다.

• 한국방재학회:학술대회논문집
• /
• 2008.02a
• /
• pp.333-336
• /
• 2008

U-Channel Bridge is effective bridge type, because its edge beam performs role of barrier and enables to reduce additional dead loads. Nevertheless, there is possibility of bridge collapse under impact load due to car crash. Also, edge beam must have ability to induce safe driving and prevent falling accidents. Therefore, this study carries out analysis of behavior of edge beam and slab and evaluation of structural stability under impact loads, based on Korean Highway Bridge Design Specifications and AASHTO LRFD Bridge Design Specification. According to analysis result, the maximum stress of edge beam and slab satisfies specification of allowable stress.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.15 no.4
• /
• pp.803-809
• /
• 2011

In this paper, we present a very useful method for updating digital satellite radio broadcast channel information. When a devices equipped with function to receive Digital Satellite Radio such as Home Theater, MP3 player, mobile phones, car audio system and various other types of Digital Devices, receives new Digital satellite radio (will be mentioned as XM radio onwards) broadcast channel information, only the current received XM radio broadcast channel and N number of pre/post nearby broadcast channels are scanned randomly in zigzag manner. Then the previous XM radio broadcast channel information updated with the newly received XM radio broadcast channel information. Since this method can prevent batch update for all XM radio channel, including some channels which less likely did not select by user, update process for real time frequently changed XM radio broadcast channel information can be performed efficiently with minimal or without delay.

• The Korean Journal of Physiology and Pharmacology
• /
• v.7 no.6
• /
• pp.341-348
• /
• 2003

Mechanical stimuli to the cardiac myocytes initiate many biochemical and physiological events. Stretch-activated cation channels have been suggested to mediate these events. In this study, cell-attached and inside-out excised-patch clamp methods were used to identify stretch-activated cation channels in adult rat atrial myocytes. Channel openings were increased in cell-attached configuration when negative pressure was applied to the pipette, and also in inside-out excised patches by negative pressure. The channel was not permeable to $Cl^-$, $Na^+$ and $Cs^+$, but selectively permeable to $K^+$, and the degree of activation was dependent on the magnitude of negative pressure (full activation at ${\sim} -50 mmHg). In symmetrical 140 mM KCl, the slope conductance was $51.2{\pm}3$ pS between the potentials of -80 and 0 mV and $55{\pm}6$ pS between 0 and +80 mV (n=5). Glibenclamide ($100{mu}M$) or ATP (2 mM) failed to block the channel openings, indicating that it is not ATP-sensitive $K^+$ channel. Arachidonic acid ($30{mu}M$), which has been shown to activate a $K^+$ channel cooperatively with membrane stretch, did not affect the channel activity. $GdCl_3$ ($100{mu}M$) also did not alter the activity. These results demonstrate that the mechanical stretch in rat atrial myocytes activates a novel $K^+$-selective cation channel, which is not associated with other $K^+$ channels such as ATP-sensitive and arachidonic acid-activated $K^+$ channel.

• Parasites, Hosts and Diseases
• /
• v.59 no.4
• /
• pp.329-339
• /
• 2021

Ion channels are important targets of anthelmintic agents. In this study, we identified 3 types of ion channels in Ascaris suum tissue incorporated into planar lipid bilayers using an electrophysiological technique. The most frequent channel was a large-conductance cation channel (209 pS), which accounted for 64.5% of channels incorporated (n=60). Its open-state probability (P_o) was ~0.3 in the voltage range of -60~+60 mV. A substate was observed at 55% of the main-state. The permeability ratio of Cl^- to K⁺ (P_Cl/P_K) was ~0.5 and P_Na/P_K was 0.81 in both states. Another type of cation channel was recorded in 7.5% of channels incorporated (n=7) and discriminated from the large-conductance cation channel by its smaller conductance (55.3 pS). Its Po was low at all voltages tested (~0.1). The third type was an anion channel recorded in 27.9% of channels incorporated (n=26). Its conductance was 39.0 pS and P_Cl/P_K was 8.6±0.8. P_o was ~1.0 at all tested potentials. In summary, we identified 2 types of cation and 1 type of anion channels in Ascaris suum. Gating of these channels did not much vary with voltage and their ionic selectivity is rather low. Their molecular nature, functions, and potentials as anthelmintic drug targets remain to be studied further.