• The Korean Journal of Physiology
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• v.27 no.1
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• pp.107-114
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• 1993

Most of voltage operated $Ca^{2+}$ channels can be divided into three types (T-, N-, and L-type), according to the electrical and pharmacological properties. Their distribution is closely related to cell specific functions. Properties of the voltage activated $Ca^{2+}$ current in mouse eggs were examined to classify channel types and to deduce the function by using whole cell voltage clamp technique. $Ca^{2+}$ currents appeared below -40 mV and reached a maximum at -15 mV (half maximum was -31 mV), then decayed rapidly (inactivation time constant ${\tau}=28.2{\pm}9.59$ ms at -10 mV within 50 ms after the onset of step depolarization. Activation and inactivation of the $Ca^{2+}$ channel was steeply dependent on voltage, in a relatively low range of $-70\;mV{\sim}-10 mV,$ half maximum of activation was -31 mV and that of inactivation was -39 mV, respectively. This current was not decreased significantly by nifedipine, a specific dihydropyridine $Ca^{2+}$ channel blocker in the range of $1\;{\mu}M\;to\;100{\mu}M.$ The inhibitory effect of $Ni^{2+}\;on\;Ca^{2+}$ current was greater than that of $Cd^{2+}.$ The conductance of $Ba^{2+}$ through the channel was equal to or lower than that of $Ca^{2+}$ These results implied that $Ca^{2+}$ current activated at a lower voltage in the mouse egg is carried via a $Ca^{2+}$ channel with similar properties that of the T-type channel.

• International Journal of Fluid Machinery and Systems
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• v.10 no.2
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• pp.138-145
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• 2017

The problem of non-uniform inflow exists in many practical engineering applications, such as the elbow suction pipe of waterjet pump and, the channel head of steam generator which is directly connect with reactor coolant pump. Generally, pumps are identical designs and are selected based on performance under uniform inflow with the straight pipe, but actually non-uniform suction flow is induced by upstream equipment. In this paper, CFD approach was employed to analyze unsteady hydrodynamic characteristics of reactor coolant pumps with different inflows. The Reynolds-averaged Naiver-Stokes equations with the $k-{\varepsilon}$ turbulence model were solved by the computational fluid dynamics software CFX to conduct the steady and unsteady numerical simulation. The numerical results of the straight pipe and channel head were validated with experimental data for the heads at different flow coefficients. In the nominal flow rate, the head of the pump with the channel head decreases by 1.19% when compared to the straight pipe. The complicated structure of channel head induces the inlet flow non-uniform. The non-uniformity of the inflow induces the difference of vorticity distribution at the outlet of the pump. The variation law of blade to blade velocity at different flow rate and the difference of blade to blade velocity with different inflow are researched. The effects of non-uniform inflow on radial forces are absolutely different from the uniform inflow. For the radial forces at the frequency $f_R$, the corresponding amplitude of channel head are higher than the straight pipe at $1.0{\Phi}_d$ and $1.2{\Phi}_d$ flow rates, and the corresponding amplitude of channel head are lower than the straight pipe at $0.8{\Phi}_d$ flow rates.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.9
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• pp.688-698
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• 2009

Using the multi-dimensional, multi-phase, nonisothermal Polymer Electrolyte Fuel Cell (PEFC) model presented in Part I, the effects of land/channel flow-field on temperature and liquid saturation distributions inside PEFCs are investigated in Part II. The focus is placed on exploring the coupled water transport and heat transfer phenomena within the nonisothermal and two-phase zone existing in the diffusion media (DM) of PEFCs. Numerical simulations are performed varying the land and channel widths and simulation results reveal that the water profile and temperature rise inside PEFCs are considerably altered by changing the land and channel widths, which indicates that oxygen supply and heat removal from the channel to the land regions and liquid water removal from the land toward the gas channels are key factors in determining the water and temperature distributions inside PEFCs. In addition, the adverse liquid saturation gradient along the thru-plane direction is predicted near the land regions by the numerical model, which is due to the vapor-phase diffusion driven by the temperature gradient in the nonisothermal two-phase DM where water evaporates at the hotter catalyst layer, diffuses as a vapor form and then condenses on the cooler land region. Therefore, the vapor phase diffusion exacerbates DM flooding near the land region, while it alleviates DM flooding near the gas channel.

• Nuclear Engineering and Technology
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• v.37 no.5
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• pp.479-490
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• 2005

The thermalhydraulic performance of a CANDU-6 reactor loaded with various CANFLEX fuel bundles is evaluated by the NUCIRC code, which is incorporated with recent models of pressure drop and critical heat flux (CHF) predictions based on high-pressure steam-water tests for the CANFLEX bundle as well as a 37-element bundle. The distributions of channel flow rate, channel exit quality, critical channel power (CCP), and critical power ratio (CPR) for the CANFLEX bundles (with natural or recycled uranium fuel) in the CANDU-6 reactor fuel channel are calculated by the code. The effects of axial and radial heat flux on CCP are evaluated by assuming that the recycled uranium fuel (CANFLEX-RU) has the same geometric data as the natural uranium fuel bundle (CANFLEX-NU), but a different power distribution due to different fuel composition and refueling scheme. In addition, the effects of pressure tube creep and bearing-pad height are examined by comparing various results of uncrept, and $3.3\%\;and\;5.1\%$ crept channels loaded with CANFLEX bundles with 1.4 mm or 1.7 mm high bearing-pads with those of the 37-element bundle. The distributions of the channel flow rate and CCP for the CANFLEX-NU or -RU bundle show a typical trend for a CANDU-6 reactor channel, and the CPRs are maintained above at least 1.444 (NU) or 1.455 (RU) in the uncrept channel. The enhanced CHF of the CANFLEX bundle (particularly with 1.7mm height bearing-pads) produces a higher thermal margin and considerably less sensitivity to CCP reduction due to the pressure tube creep than the 37-element bundle. The CCP enhancement due to the raised bearing-pads is estimated to be about $3\%\~5\%$ for the CANFLEX-NU and $2\%\~6\%$ for the CANFLEX-RU bundle, respectively.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.46 no.1
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• pp.55-62
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• 2009

In this paper, we propose a method on the training sequence based on channel estimation issues for relay networks that employ amplify-and-forward(AF) transmission scheme. In $^{[1]}$ and $^{[2]}$, we have to point out that jointly estimating the channel from source to relay and from relay to destination suffers from many drawbacks in fast fading case because the estimation of previous pilots is not suitable for current channel. In this paper, we consider a new joint estimation of overall channel impulse response(CIR) using one OFDM signal without pilots. Using the maximum likelihood(ML) function, we derive a channel estimator by taking the frequency domain of transmitted signal as Gaussian and averaging the ML function over the resulting Gaussian distribution. Simulation results show that our proposed channel estimator performs a fraction of 1dB compared with $^{[1]}$ in high SNR region.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.4
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• pp.367-380
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• 2013

In this paper, an analytical threshold voltage model is developed for a short-channel double-material-gate (DMG) strained-silicon (s-Si) on silicon-germanium ($Si_{1-X}Ge_X$) MOSFET structure. The proposed threshold voltage model is based on the so called virtual-cathode potential formulation. The virtual-cathode potential is taken as minimum channel potential along the transverse direction of the channel and is derived from two-dimensional (2D) potential distribution of channel region. The 2D channel potential is formulated by solving the 2D Poisson's equation with suitable boundary conditions in both the strained-Si layer and relaxed $Si_{1-X}Ge_X$ layer. The effects of a number of device parameters like the Ge mole fraction, Si film thickness and gate-length ratio have been considered on threshold voltage. Further, the drain induced barrier lowering (DIBL) has also been analyzed for gate-length ratio and amount of strain variations. The validity of the present 2D analytical model is verified with ATLAS$^{TM}$, a 2D device simulator from Silvaco Inc.

• Smart Media Journal
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• v.3 no.1
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• pp.9-15
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• 2014

In these days, along with the extreme popularity of online social network services, it becomes an important problem understanding the role of social network in the research of message dissemination. Past studies of message dissemination over online social network services mostly consider the coverage of message dissemination and the methods to maximize it. But, these works lack of the consideration of the impact of multi channel social network, which has multiple communication channel with distinct properties of message transfer and various users with distinct channel preferences. In this paper, the new message dissemination model over multi-modal multi-channel social network, the Delay Weighted Independent Cascade Model, is proposed. The proposed model considers various channels including online social network service, email, SMS messaging, phone and mouth-to-mouth and their distinct message transfer properties. In order to consider the various user properties, the different value of probability of forwarding a message and the different preference of communication channel is considered. Moreover, the proposed model considers the distribution of user location and allows to analyze the properties of message dissemination under various scenarios. Based on the proposed model, a message dissemination simulator is generated and the message disseminations on various scenarios are analyzed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.3B
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• pp.408-422
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• 2000

In this paper, we propose a generalized vector channel model for wireless communication systems using antenna arrays. The proposed channel model reflects path loss. spatial-temporal variation of shadowing, multipath fading , Doppler effect, spatial distribution of local scatterers and delay spread due to remote dominant scatterers. In addition, we use a discrete ray model in which respective ray signal experiences independent shadowing, fading and Doppler shift, and impinges on antenna arrays at a distinct angle. Based on the proposed mode. we derive the relations on the spatial and temporal correlations of the received signals and implement a spatial channel simulator. By comparing the theoretical values with the simulated ones, we verify the effectiveness of the implemented simulator. The simulator is then used to generate an arbitrary channel impulse response and to analyze the channel characteristics under various environments.

• Journal of agriculture & life science
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• v.44 no.1
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• pp.69-80
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• 2010

The purpose of this study is to analyse current marketing practices and marketing efficiency using operational efficiency. Through field survey on marketing situations and channels, we found that major marketing channels of paprika were classified into six types : channels in exporting market included (1) producer's organization leading channel (type I), (2) regional cooperative leading channel (type II), (3) individual producer leading channel (type III), and channels in domestic market included (4) wholesale markets targeting channel (type IV), (5) distribution agents targeting channel (type V), (6) cooperative system selling channel (type VI). According to the estimated result of operational efficiency of marketing channels, marketing efficiency of type III and IV was relatively higher than type I,II and type V, VI respectively.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.6
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• pp.1685-1692
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• 2015

This study examines the mackerel distribution systems in Norway which has a leading mackerel industry, and has the purpose of analyzing the effects of structural improvements for the development of Korea's mackerel industry. The landing and distribution status of Korea and Norway's mackerel industry was compared, and the effects of structural improvements was analyzed under the assumption that a number of factors would be improved after an analysis of competitiveness. Special features of the landing and distribution systems of mackerel in Norway are Reduction of transportation costs and transportation time through E-auctions, fish Pumps, freshness management using state-of-the-art equipment and technology such as sea water cooling systems, direct landing at processing factories and Automation through fully automated sorting & packaging systems. The distribution competitiveness of Korea and Norway's mackerel industry was compared through the qualitative review of landing time and the length of distribution channel, distribution costs due to differences in trading method, quality and hygiene management and merchandising. For Korea's mackerel industry to have international competitiveness, they must have efficiency throughout the phases of landing, processing and distribution systems as observed in case of Norway.