• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2016년도 학술발표회
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• pp.370-374
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• 2016

We investigated the three dimensional turbulent flow characteristic around a sidewall-mounted rectangular block using a laboratory flume experiment. The experiment was conducted in the flume which is 18m long and 0.9m wide, and a rectangular block that is 0.3m wide and a height of 0.4m and 0.004m thick is mounted on a sidewall of the flume. Velocity data were collected using Acoustic Doppler Velocimeter(ADV) for the flow rate conditions : $0.0528m^3/s$. The time-averaged velocity and water depth data were analyzed to examine the three-dimensional flow patterns downstream of the rectangular block.

• The Korean Journal of Physiology and Pharmacology
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• 제2권5호
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• pp.611-616
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• 1998

Although the $Ca^{2+}-activated\;K^+\;(I_{K,Ca})$ channel is known to play an important role in the maintenance of resting membrane potential, the regulation of the channel in physiological condition is not completely understood in vascular myocytes. In this study, we investigated the role of cytoplasmic $Mg^{2+}$ on the regulation of $I_{K,Ca}$ channel in pulmonary arterial myocytes of the rabbit using the inside-out patch clamp technique. $Mg^{2+}$ increased open probability (Po), but decreased the magnitude of single channel current. $Mg^{2+}-induced$ block of unitary current showed strong voltage dependence but increase of Po by $Mg^{2+}$ was not dependent on the membrane potential. The apparent effect of $Mg^{2+}$ might, thus, depend on the proportion between opposite effects on the Po and on the conductance of $I_{K,Ca}$ channel. In low concentration of cytoplasmic $Ca^{2+},\;Mg^{2+}$ increased $I_{K,Ca}$ by mainly enhancement of Po. However, at very high concentration of cytoplasmic $Ca^{2+},$ such as pCa 5.5, $Mg^{2+}$ decreased $I_{K,Ca}$ through the inhibition of unitary current. Moreover, $Mg^{2+}$ could activate the channel even in the absence of $Ca^{2+}.\;Mg^{2+}$ might, therefore, partly contribute to the opening of $I_{K,Ca}$ channel in resting membrane potential. This phenomenon might explain why $I_{K,Ca}$ contributes to the resting membrane potential where membrane potential and concentration of free $Ca^{2+}$ are very low.

• The Korean Journal of Physiology and Pharmacology
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• 제22권1호
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• pp.71-80
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• 2018

In patients with epilepsy, depression is a common comorbidity but difficult to be treated because many antidepressants cause pro-convulsive effects. Thus, it is important to identify the risk of seizures associated with antidepressants. To determine whether paroxetine, a very potent selective serotonin reuptake inhibitor (SSRI), interacts with ion channels that modulate neuronal excitability, we examined the effects of paroxetine on Kv3.1 potassium channels, which contribute to high-frequency firing of interneurons, using the whole-cell patch-clamp technique. Kv3.1 channels were cloned from rat neurons and expressed in Chinese hamster ovary cells. Paroxetine reversibly reduced the amplitude of Kv3.1 current, with an $IC_{50}$ value of $9.43{\mu}M$ and a Hill coefficient of 1.43, and also accelerated the decay of Kv3.1 current. The paroxetine-induced inhibition of Kv3.1 channels was voltage-dependent even when the channels were fully open. The binding ($k_{+1}$) and unbinding ($k_{-1}$) rate constants for the paroxetine effect were $4.5{\mu}M^{-1}s^{-1}$ and $35.8s^{-1}$, respectively, yielding a calculated $K_D$ value of $7.9{\mu}M$. The analyses of Kv3.1 tail current indicated that paroxetine did not affect ion selectivity and slowed its deactivation time course, resulting in a tail crossover phenomenon. Paroxetine inhibited Kv3.1 channels in a use-dependent manner. Taken together, these results suggest that paroxetine blocks the open state of Kv3.1 channels. Given the role of Kv3.1 in fast spiking of interneurons, our data imply that the blockade of Kv3.1 by paroxetine might elevate epileptic activity of neural networks by interfering with repetitive firing of inhibitory neurons.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권6호
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• pp.2014-2034
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• 2015

This paper focuses on solving co-channel interference (CCI) issues arising in the open subscriber group (OSG) mode of heterogeneous networks (HetNets). Considering a general framework consisting of arbitrary number of picocells within a macro cell, where the inter-user interference (IUI) is the main CCI to macro user equipments (UEs), while the the inter-cell interference (ICI) is the major CCI to pico UEs. In this paper, three IA based transceiver design schemes are proposed. For macro cell, we uniformly use block diagonalization (BD) scheme to eliminate the IUI. And for picocells, three IA schemes are proposed to mitigate the ICI. The first scheme, named as zero forcing IA (ZF-IA) scheme, aligns the inter picocell interference onto an arbitrary sub-space of the cross-tier interference using ZF scheme. Considering the channel state information (CSI) of the desired channel of pico UEs, the second scheme, named as optimal desired sub-channel selected IA (ODC-IA) scheme, aligns the inter picocell interference onto a certain sub-space of the cross-tier interference, which guarantees the largest channel gain of the desired signal of pico UEs. The third IA scheme, named as maximum cross-tier interference selected IA (MI-IA) scheme, is designed for the system with less receive antennas. The inter picocell interference is aligned onto the space of the strongest cross-tier interference and only the interference on this space is nullified. The complexity analysis and simulations show that the proposed transceiver design schemes outperform the existing IA schemes in the OSG mode of HetNets, and the MI-IA scheme reduces the requirement of the receive antennas number with lower complexity.

• 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.

• 전기전자학회논문지
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• 제11권4호
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• pp.340-347
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• 2007

This paper proposes a new class of Space-Time Block Codes, which is manipulated from the existing transmit diversity schemes. We analyze the performance and the receiver complexity of the proposed scheme and confirm that the new diversity scheme can yield performance gain over other existing four-transmit antenna cases. By relaxing the diversity criterion on code designs, the proposed space-time code provides a full transmission rate for four-transmit antennas and makes it possible to approach the open-loop Shannon channel capacity. Outage capacity and simulation results are used to show that substantial improvements in performance while maintaining a simple linear processing receiver structure are obtained in frequency selective channels.

• 한국통신학회논문지
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• 제33권10A호
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• pp.980-986
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• 2008

Spatial multiuser access is investigated for the reverse link of multiuser multiple-input multiple-output (MIMO) systems. In particular, we consider two alternative a aches to spatial multiuser access that adopt the same detection algorithm at the base station: one is a closed-loop approach based on singular value decomposition (SVD) of the channel matrix, whereas the other is an open-loop approach based in space-time block coding (STBC). We develop multiuser detection algorithms for these two spatial multiuser access schemes based on the minimum mean square error (MMSE) criterion. Then, we compare the bit error rate (BER) performance of the two schemes and a single-user MIMO scheme. Interestingly, it is found that the STBC approach can provide much better BER performance than the SVD approach as well as than a single-user MIMO scheme.

• The Korean Journal of Physiology and Pharmacology
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• 제20권2호
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• pp.193-200
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• 2016

Sertraline, a selective serotonin reuptake inhibitor (SSRI), has been reported to lead to cardiac toxicity even at therapeutic doses including sudden cardiac death and ventricular arrhythmia. And in a SSRI-independent manner, sertraline has been known to inhibit various voltage-dependent channels, which play an important role in regulation of cardiovascular system. In the present study, we investigated the action of sertraline on Kv1.5, which is one of cardiac ion channels. The effect of sertraline on the cloned neuronal rat Kv1.5 channels stably expressed in Chinese hamster ovary cells was investigated using the whole-cell patch-clamp technique. Sertraline reduced Kv1.5 whole-cell currents in a reversible concentration-dependent manner, with an $IC_{50}$ value and a Hill coefficient of $0.71{\mu}M$ and 1.29, respectively. Sertraline accelerated the decay rate of inactivation of Kv1.5 currents without modifying the kinetics of current activation. The inhibition increased steeply between -20 and 0 mV, which corresponded with the voltage range for channel opening. In the voltage range positive to +10 mV, inhibition displayed a weak voltage dependence, consistent with an electrical distance ${\delta}$ of 0.16. Sertraline slowed the deactivation time course, resulting in a tail crossover phenomenon when the tail currents, recorded in the presence and absence of sertraline, were superimposed. Inhibition of Kv1.5 by sertraline was use-dependent. The present results suggest that sertraline acts on Kv1.5 currents as an open-channel blocker.

• 한국컴퓨터정보학회논문지
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• 제11권2호
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• pp.201-211
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• 2006

현재 이동통신 시장이 급성장하고 있으며 무선통신 환경에서의 다양한 멀티미디어 서비스의 요구에 부합하고 한정된 주파수를 효율적으로 사용하기 위하여, 데이터 전송의 고속화가 가능하고 다중 안테나를 이용하는 3세대 이동통신 표준화가 진행되고 있다. 본 논문에서는 3세대 이동통신 표준화 기구인 3GPP에서 다루어지는 개루프 송신 다이버시티 기법 중 STTD(Space Time Transmit Diversity) 기법 및 STTD를 기본으로 확장되어진 STTD-OTD, CL-STTD 그리고 4TX-STTD 들에 대한 성능을 분석한다. 그리고 각 기법에서 수신 다이버시티를 추가한 개루프 송신 및 수신 다이버시티 기법을 제안한다. 플랫 페이딩 채널 환경하에서 이들 기법들을 적용하여 모의 수치계산을 수행하고 성능을 비교 분석한다.

• 한국산업정보학회논문지
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• 제27권5호
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• pp.25-36
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• 2022

본 논문은 단일 반송파 변조를 위한 공간 주파수 블록 코드에서의 랜덤 부호 반전 기술을 제안한다. 종래의 시공간 그리고 공간 주파수 블록 코드는 전파 환경이 공개되어 있으므로 심각한 전파 탈취 문제를 극복해야 한다. 이러한 전파 공개 문제를 피하기 위해, 시공간 블록 코드를 위한 랜덤 코드 데이터 보호 방법이 제안되어 있지만, 이 알고리즘은 직교 주파수 분할 다중화 블록별로 채널 결합을 바꿀 수 있는데, 이와 같은 종류의 느린 스위칭은 근처의 수신기들이 전송된 데이터를 검출할 확률을 증가시킨다. 이 논문은 데이터 심볼 기반의 빠른 스위칭 알고리즘 즉, 단일 반송파 변조를 위한 공간 주파수 블록 코드에서의 랜덤 부호 반전 기술을 제안한다. 모의실험 결과는 제안하는 알고리즘이 랜덤 부호 반전 타이밍 시퀀스를 모르는 수신기의 성능과 비교하여 우수한 성능을 보유하고 있다는 것을 나타내었다.