• International Journal of Naval Architecture and Ocean Engineering
• /
• 제12권1호
• /
• pp.468-478
• /
• 2020

The wave interaction problem with a vertical slotted breakwater, consisting of impermeable upper, lower parts and a permeable middle part, has been studied theoretically. An analytical model was presented for the estimation of reflection and transmission of monochromatic waves by a slotted breakwater. The far-field solution of the wave scattering involving nonlinear porous boundary condition was obtained using eigenfunction expansion method. The empirical formula for drag coefficient in the near-field, representing energy dissipation across the slotted barrier, was determined by curve fitting of the numerical solutions of 2-D channel flow using CFD code StarCCM+. The theoretical model was validated with laboratory experiments for various configurations of a slotted barrier. It showed that the developed analytical model can correctly predict the energy dissipation caused by turbulent eddies due to sudden contraction and expansion of a slotted barrier. The present paper provides a synergetic approach of the analytical and numerical modelling with minimum CPU time, for better estimation of the hydrodynamic performance of slotted breakwater.

• Journal of Ginseng Research
• /
• 제29권1호
• /
• pp.19-26
• /
• 2005

The last two decades have shown a marked expansion in publications of diverse effects of Panax ginseng. Ginsenosides, as active ingredients of Panax ginseng, are saponins found in only ginseng. Recently, a line of evidences shows that ginsenosides regulate various types of ion channel activity such as $Ca^{2+},\;K^+,\;Na^+,\;Cl^-$, or ligand gated ion channels (i.e. $5-HT_3$, nicotinic acetylcholine, or NMDA receptor) in neuronal, non-neuronal cells, and heterologously expressed cells. Ginsenosides inhibit voltage-dependent $Ca^{2+},\;K^+,\;and\;Na^+$ channels, whereas ginsenosides activate $Ca^{2+}-activated\;Cl^-\;and\;Ca^{2+}-activated\;K^+$ channels. Ginsenosides also inhibit excitatory ligand-gated ion channels such as $5-HT_3$, nicotinic acetylcholine, and NMDA receptors. This review will introduce recent findings on the ginsenoside-induced differential regulations of ion channel activities and will further expand the possibilities how these ginsenoside-induced ion channel regulations are coupled to biological effects of Panax ginseng.

• Nuclear Engineering and Technology
• /
• 제52권2호
• /
• pp.258-270
• /
• 2020

A new task of using the Jacobian-Free-Newton-Krylov (JFNK) method for the PWR core transient simulations involving neutronics, thermal hydraulics and mechanics is conducted. For the transient scenario of PWR, normally the Picard iteration of the coupled coarse-mesh nodal equations and parallel channel TH equations is performed to get the transient solution. In order to solve the coupled equations faster and more stable, the Newton Krylov (NK) method based on the explicit matrix was studied. However, the NK method is hard to be extended to the cases with more physics phenomenon coupled, thus the JFNK based iteration scheme is developed for the nodal method and parallel-channel TH method. The local gap conductance is sensitive to the gap width and will influence the temperature distribution in the fuel rod significantly. To further consider the local gap conductance during the transient scenario, a 1D mechanics model is coupled into the JFNK scheme to account for the fuel thermal expansion effect. To improve the efficiency, the physics-based precondition and scaling technique are developed for the JFNK iteration. Numerical tests show good convergence behavior of the iterations and demonstrate the influence of the fuel thermal expansion effect during the rod ejection problems.

• Applied Science and Convergence Technology
• /
• 제23권4호
• /
• pp.192-199
• /
• 2014

The electronic property of graphene was investigated by hydrazine treatment. Hydrazine ($N_2H_4$) highly increases electron concentrations and up-shifts Fermi level of graphene based on significant shift of Dirac point to the negative gate voltage. We have observed contact resistance and channel length dependent mobility of graphene in the back-gated device after hydrazine monohydrate treatment and continuously monitored electrical characteristics under Nitrogen or air exposure. The contact resistance increases with hydrazine-treated and subsequent Nitrogen-exposed devices and reduces down in successive Air-exposed device to the similar level of pristine one. The channel conductance curve as a function of gate voltage in hole conduction regime keeps analogous value and shape even after Nitrogen/Air exposure specially whereas, in electron conduction regime change rate of conductance along with the level of conductance with gate voltage are decreased. Hydrazine could be utilized as the highly effective donor without degradation of mobility but the stability issue to be solved for future application.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 하계학술대회 논문집 E
• /
• pp.2195-2197
• /
• 1999

Electric breakdown in the liquid produces a spark channel. The energy input into the channel causes expansion of a vapor gas cavity. If the power of the discharge is high enough, this expansion is fast enough to produce a shock wave which propagates through the liquid to the subject of destruction. We focused our attention on the correlation between electric parameters and the characteristics of the flash caused by point to-point electrode discharge in the water. By varying firing voltage and gap length, we obtained the features of the flash : amplitude, pulse width, and so on. In this paper, We have known that there is a concrete interrelation between underwater firing voltage and photodiode output.

• 한국통신학회논문지
• /
• 제25권8A호
• /
• pp.1206-1212
• /
• 2000

국내 유선 전화망은 가입자 구간은 한회선씩을 사용하며 전송망 구간은 TDM을 사용하며 음성 한 채널에 64Kbps를 할당하고 있으며 특히 E1의 경우 회선 당 음성 30채널에 2.048Mbps로 구성되어있다 반면에 이동 전화망은 가입자 구간은 수용용량을 늘리고 효율화시키기 위해 CDMA방식을 이용하고 있지만 전송망 구간은 유선망과 마찬가지로 TDM방식을 이용하고 있다 본논문에서는 유선의 가입자 구간에 대해서도 CDM 기법을 이용하여 채널을 증가시켜 회선의 효율성을 증가시키고 비용을 저렴하게 할 수 있음을 보이고 있다.

• 한국방송∙미디어공학회:학술대회논문집
• /
• 한국방송공학회 1996년도 학술대회
• /
• pp.55-59
• /
• 1996

In this paper, we first analyze the influence of interference due to the time variation and delay spread of the mobile channel on an orthogonal frequency division multiplexing (OFDM) system. With the result, we obtain the bit error rate performance of the 16-QAM OFDM system. Second, we investigate the performance of the Reed-Solomon (RS) coded 16-QAM OFDM system when the number of subcarriers varies. In the investigation, we assume that the information transmission rate and the total bandwidth expansion due to coding, guard interval, and the number of subcarriers are fixed. Under this condition, it is observed that there are optimum numbers of subcarriers that minimize the post decoding symbol error probability of RS code for various channel states.

• 경영과학
• /
• 제14권2호
• /
• pp.139-159
• /
• 1997

Recently banking industry is experiencing fundamental changes by advancement of information technology. The traditional role of branches is rapidly being replaced with new electronic service channels such as ATM. Phone and PC for they are time-saving and convenient. Automated service channel strategy of retail banks is divided into two different ways, automation and networking. Automation is mainly focused on cost reduction related to the branch operation, while networking is on expansion of customer contact points. Strategic types of banks can be defined from a matrix model shere the positioning is determined by the extent of automation and networking. The effectiveness of automated channel strategy depends on how separate strategic types show their performance. Results for deposits and productivity will be given to verify the economic performance of each strategic type.

• 한국경영과학회지
• /
• 제14권2호
• /
• pp.139-139
• /
• 1989

Recently banking industry is experiencing fundamental changes by advancement of information technology. The traditional role of branches is rapidly being replaced with new electronic service channels such as ATM. Phone and PC for they are time-saving and convenient. Automated service channel strategy of retail banks is divided into two different ways, automation and networking. Automation is mainly focused on cost reduction related to the branch operation, while networking is on expansion of customer contact points. Strategic types of banks can be defined from a matrix model where the positioning is determined by the extent of automation and networking. The effectiveness of automated channel strategy depends on how separate strategic types show their performance. Results for deposits and productivity will be given to verify the economic performance of each strategic type.

• Archives of Pharmacal Research
• /
• 제18권6호
• /
• pp.402-409
• /
• 1995

The effects of calcium channel blockers (CAB's) verapamil, diltiazem and nicardipine, on erythrocyte ghost membranes have been studied. Using the fluorospectroscopic method, it was observed that the fluidity of the inner layer of ghost membranes was increased with an increase of drug concentrations but did not any changes in the fluidity of the outer layer. These drugs showed protectuve effect against hypotonic hemolysis of erythrocytes. Thus, the expansion of surface area in response to corpuscular volume of erythrocytes in the presence of CAB's is seemed to play an important role in protecting hypotonic hemolysis of erythrocytes.