• 한국통신학회논문지
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• 제31권7C호
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• pp.680-690
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• 2006

본 논문에서는 V-BLAST(Vertical-Bell labs LAyered Space-Time) 검출기를 사용하는 MIMO-OFDM(Multi Input Multi Output-Orthogonal Frequency Division Multiplexing) 시스템에서, 그룹화된 부채널 기반의 간단한 형태의 비트 할당 기법인 SBA-GS(Simplified Bit Allocation based on Grouped Sub-channels)를 제안한다. 2차원 Water Pouring 원리에 기반하여 MIMO-OFDM 시스템 수신단에서 각 부채널별 비트수 및 전력을 결정하여 궤환하는 일반적인 ABPA(Adaptive Bit and Power Allocation)은 비트오율 측면에서 최적의 성능을 보이지만, 수신단에서 송신단으로의 많은 양의 궤환 정보를 필요로 하고 시스템이 복잡하다는 단점을 가진다. 이러한 단점을 보완하기 위해, 상태가 우수한 각 부채널에 동일한 수의 비트를 할당하여 송신단에서 수신단으로의 궤환 정보량과 시스템 복잡도를 감소시킨 SBA가 제안된 바 있다. 본 논문에서 제안하는 SBA-GS 는 부채널들을 그룹화한 뒤 각 그룹별 부채널들의 펑균 신호대잡음비를 구하여 동일한 변조 방식을 적용하는 SBA를 수행한다. 다양한 차세대 이동통신 채널 환경에서의 모의실험 결과, 지연 확산이 작은 다중 경로 채널의 경우에서는 궤환 정보량을 크게 감소하면서도 SBA와 유사한 결과를 얻을 수 있었 으며, 지연확산이 큰 채널 환경에서는 부채널 그룹화에 따른 BER 성능 열화가 상대적으로 증가하였지만 궤환 정보량 감소와의 절충 관계를 감안할 때 실제 시스템 구현시 고려될 수 있는 우수한 결과를 보임을 확인하였다.

• Molecules and Cells
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• 제43권12호
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• pp.1002-1010
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• 2020

Cilia are important eukaryotic cellular compartments required for diverse biological functions. Recent studies have revealed that protein targeting into the proper ciliary subcompartments is essential for ciliary function. In Drosophila chordotonal cilium, where mechano-electric transduction occurs, two transient receptor potential (TRP) superfamily ion channels, TRPV and TRPN, are restricted to the proximal and distal subcompartments, respectively. To understand the mechanisms underlying the sub-ciliary segregation of the two TRPs, we analyzed their localization under various conditions. In developing chordotonal cilia, TRPN was directly targeted to the ciliary tip from the beginning of its appearance and was retained in the distal subcompartment throughout development, whereas the ciliary localization of TRPV was considerably delayed. Lack of intraflagella transport-related proteins affected TRPV from the initial stage of its pre-ciliary trafficking, whereas it affected TRPN from the ciliary entry stage. The ectopic expression of the two TRP channels in both ciliated and non-ciliated cells revealed their intrinsic properties related to their localization. Taken together, our results suggest that sub-ciliary segregation of the two TRP channels relies on their distinct intrinsic properties, and begins at the initial stage of their pre-ciliary trafficking.

• The Korean Journal of Physiology and Pharmacology
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• 제24권1호
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• pp.111-119
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• 2020

In vascular smooth muscle, K⁺ channels, such as voltage-gated K⁺ channels (Kv), inward-rectifier K⁺ channels (Kir), and big-conductance Ca²⁺-activated K⁺ channels (BK_Ca), establish a hyperpolarized membrane potential and counterbalance the depolarizing vasoactive stimuli. Additionally, Kir mediates endothelium-dependent hyperpolarization and the active hyperemia response in various vessels, including the coronary artery. Pulmonary arterial hypertension (PAH) induces right ventricular hypertrophy (RVH), thereby elevating the risk of ischemia and right heart failure. Here, using the whole-cell patch-clamp technique, we compared Kv and Kir current densities (I_Kv and I_Kir) in the left (LCSMCs), right (RCSMCs), and septal branches of coronary smooth muscle cells (SCSMCs) from control and monocrotaline (MCT)-induced PAH rats exhibiting RVH. In control rats, (1) I_Kv was larger in RCSMCs than that in SCSMCs and LCSMCs, (2) I_Kv inactivation occurred at more negative voltages in SCSMCs than those in RCSMCs and LCSMCs, (3) I_Kir was smaller in SCSMCs than that in RCSMCs and LCSMCs, and (4) I_BKCa did not differ between branches. Moreover, in PAH rats, I_Kir and I_Kv decreased in SCSMCs, but not in RCSMCs or LCSMCs, and I_BKCa did not change in any of the branches. These results demonstrated that SCSMC-specific decreases in I_Kv and I_Kir occur in an MCT-induced PAH model, thereby offering insights into the potential pathophysiological implications of coronary blood flow regulation in right heart disease. Furthermore, the relatively smaller I_Kir in SCSMCs suggested a less effective vasodilatory response in the septal region to the moderate increase in extracellular K⁺ concentration under increased activity of the myocardium.

• Journal of Ginseng Research
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• 제27권3호
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• pp.120-128
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• 2003

Alternative medicines such as herbal products are increasingly being used for preventive and therapeutic purposes. Ginseng is the best known and most popular herbal medicine used worldwide. In spite of some beneficial effects of ginseng on the nervous system, little scientific evidence shows at the cellular level. In the present study, I have examined the direct modulation of ginseng total saponins and individual ginsenosides on the activation of $Ca^{2+}$ channels and NMDA-gated channels in cultured rat dorsal root ganglion (DRG) and hippocampal neurons, respectively. In DRG neurons, application of ginseng total saponins suppressed high-voltage-activated $Ca^{2+}$ channel currents and ginsenoside Rg$_3$, among the 11 ginsenosides tested, produced the strongest inhibition on $Ca^{2+}$ channel currents. Occlusion experiments using selective $Ca^{2+}$ channel blockers revealed that ginsenoside Rg$_3$ could modulate L-, N-, and P/Q-type currents. In addition, ginsenoside Rg$_3$ also proved to be an active component of ginseng actions on NMDA receptors in cultured hippocampal neurons. Application of ginsenoside Rg$_3$ suppressed NMDA-induced [Ca$^{2+}$]$_{i}$ increase and -gated channels using fura-2-based digital imaging and patch-clamp techniques, respectively. These results suggest that the modulation of $Ca^{2+}$ channels and NMDA receptors by ginsenoside Rg$_3$ could be part of the pharmacological basis of ginseng actions in the peripheral and central nervous systems.ous systems.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.259-260
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• 2008

This paper presents fractional frequency reuse (FFR) with sub-channel borrowing to improve spectral efficiency of the wireless broadband (WiBro) system. FFR has constraints on usable sub-channels to balance the interference and cell capacity. Our FFR with sub-channel borrowing allows use of the dedicated sub-channels assigned to neighboring cells. Simulation results show that the proposed FFR with sub-channel borrowing improves the performance of the WiBro system.

• 한국전산유체공학회지
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• 제17권3호
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• pp.93-98
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• 2012

The injection molding process is suitable for manufacturing complicated plastic products. As the customer request higher quality products increase, realization of the precise dimensional and shape controls is getting more important. For this purpose it is important to obtain uniform cooling procedure over the whole surface of the high temperature molded plastic. Failure to this may lead to different shrinkage speed, internal stresses and unwanted shape deformations. It is necessary to distribute coolant flow rates to the main channel and to the sub-channels properly to insure uniform cooling process when there are parallel cooling channels. In this study, three-dimensional turbulent flow simulations for representative parallel cooling channels were performed. To insure the intended flow rate to each sub-channels, various shape designs for the channel system were investigated. The results show that as the Reynolds number increases the effect of shape design is more profound. Through the proper flow distribution, uniform cooling effects would be expected.

• The Korean Journal of Physiology and Pharmacology
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• 제27권1호
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• pp.95-103
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• 2023

Rosiglitazone is a thiazolidinedione-class antidiabetic drug that reduces blood glucose and glycated hemoglobin levels. We here investigated the interaction of rosiglitazone with Kv3.1 expressed in Chinese hamster ovary cells using the wholecell patch-clamp technique. Rosiglitazone rapidly and reversibly inhibited Kv3.1 currents in a concentration-dependent manner (IC₅₀ = 29.8 µM) and accelerated the decay of Kv3.1 currents without modifying the activation kinetics. The rosiglitazonemediated inhibition of Kv3.1 channels increased steeply in a sigmoidal pattern over the voltage range of -20 to +30 mV, whereas it was voltage-independent in the voltage range above +30 mV, where the channels were fully activated. The deactivation of Kv3.1 current, measured along with tail currents, was also slowed by the drug. In addition, the steady-state inactivation curve of Kv3.1 by rosiglitazone shifts to a negative potential without significant change in the slope value. All the results with the use dependence of the rosiglitazone-mediated blockade suggest that rosiglitazone acts on Kv3.1 channels as an open channel blocker.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권8호
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• pp.1876-1889
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• 2013

Packet-based mobile multimedia services for the Internet differ with respect to their resource requirements, performance objectives, and resource usage efficiencies. Nonetheless, each mobile terminal should support a variety of multimedia services, sometimes even simultaneously. This paper proposes a sub-channel allocation scheme based on multi-level priority for supporting mobile multimedia services in an Orthogonal Frequency Division Multiple Access (OFDMA) system. We attempt to optimize the system for satisfying the Quality of Service (QoS) requirements of users and maximize the capacity of the system at the same time. In order to achieve this goal, the proposed scheme considers the Signal-to-Interference-plus-Noise Ratio (SINR) of co-sub-channels in adjacent cells, the Signal-to-Noise Ratio (SNR) grade of each sub-channel in the local cell on a per-user basis, and the characteristics of the individual services before allocating sub-channels. We used a simulation to evaluate our scheme with the performance measure of the outage probabilities, delays, and throughput.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2013년도 임시총회 및 하계학술연구발표회
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• pp.104-105
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• 2013

• The Korean Journal of Physiology and Pharmacology
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• 제27권4호
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• pp.399-406
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• 2023

Voltage-dependent K⁺ (Kv) channels are widely expressed on vascular smooth muscle cells and regulate vascular tone. Here, we explored the inhibitory effect of encainide, a class Ic anti-arrhythmic agent, on Kv channels of vascular smooth muscle from rabbit coronary arteries. Encainide inhibited Kv channels in a concentration-dependent manner with an IC₅₀ value of 8.91 ± 1.75 μM and Hill coefficient of 0.72 ± 0.06. The application of encainide shifted the activation curve toward a more positive potential without modifying the inactivation curve, suggesting that encainide inhibited Kv channels by altering the gating property of channel activation. The inhibition by encainide was not significantly affected by train pulses (1 and 2 Hz), indicating that the inhibition is not use (state)-dependent. The inhibitory effect of encainide was reduced by pretreatment with the Kv1.5 subtype inhibitor. However, pretreatment with the Kv2.1 subtype inhibitor did not alter the inhibitory effects of encainide on Kv currents. Based on these results, encainide inhibits vascular Kv channels in a concentration-dependent and use (state)-independent manner by altering the voltage sensor of the channels. Furthermore, Kv1.5 is the main Kv subtype involved in the effect of encainide.