• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.8A
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• pp.777-784
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• 2010

Recently, the necessity of underwater communication and demand for transmitting and receiving various data such as voice or high resolution image data are increasing as well. The performance of underwater acoustic communication system is influenced by characteristics of the underwater communication channels. Especially, ISI(inter symbol interference) occurs because of delay spread according to multi-path and communication performance is degraded. In this paper, we study the OFDM technique to overcome the delay spread in underwater channel and by using CP, we compensate for delay spread. But PAPR which OFDM system has problem is very high. Therefore, we use DFT-spread OFDM method to avoid nonlinear distortion by high PAPR and to improve efficiency of amplifier. DFT-spread OFDM technique obtains high PAPR reduction effect because of each parallel data loads to all subcarrier by DFT spread processing before IFFT. In this paper, we show performance about delay spread through OFDM system and verify method that DFT spread OFDM is more suitable than OFDM for underwater communication. And we analyze performance according to two subcarrier mapping methods(Interleaved, Localized). Through the simulation results, performance of DFT spread OFDM is better about 5~6dB at $10^{-4}$ than OFDM. When compared to BER according to subcarrier mapping, Interleaved method is better about 3.5dB at $10^{-4}$ than Localized method.

• Archives of Pharmacal Research
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• v.28 no.6
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• pp.709-715
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• 2005

The purpose of this study was to investigate the effect of atropine on peripheral vasodilation and the mechanisms involved. The isometric tension of rat mesenteric artery rings was recorded in vitro on a myograph. The results showed that atropine, at concentrations greater than 1$\mu$M, relaxed the noradrenalin (NA)-precontracted rat mesenteric artery in a concentration-dependent manner. Atropine-induced vasodilatation was mediated, in part, by an endothelium-dependent mechanism, to which endothelium-derived hyperpolarizing factor may contribute. Atropine was able to shift the NA-induced concentration-response curve to the right, in a non-parallel manner, suggesting the mechanism of atropine was not mediated via the ${\alpha}_1$-adrenoreceptor. The $\beta$-adrenoreceptor and ATP sensitive potassium channel, a voltage dependent calcium channel, were not involved in the vasodilatation. However, atropine inhibited the contraction derived from NA and $CaCl_2$ in $Ca^{2+}$-free medium, in a concentration dependent manner, indicating the vasodilatation was related to the inhibition of extracellular $Ca^{2+}$ influx through the receptor-operated calcium channels and intracellular $Ca^{2+}$ release from the $Ca^{2+}$ store. Atropine had no effect on the caffeine-induced contraction in the artery segments, indicating the inhibition of intracellular $Ca^{2+}$ release as a result of atropine most likely occurs via the IP3 pathway rather than the ryanodine receptors. Our results suggest that atropine-induced vasodilatation is mainly from artery smooth muscle cells due to inhibition of the receptor-mediated $Ca^{2+}$-influx and $Ca^{2+}$-release, and partly from the endothelium mediated by EDHF.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.6
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• pp.644-653
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• 2013

In this paper, a formulation for obliquely incident electromagnetic wave has been presented for an analysis of highpower electromagnetic pulse penetration into multilayered dispersive media. Based on generalized models of measured dielectric constants and propagation channels reflecting the Earth's general features, the propagation phenomenon of the obliquely incident early-time(E1) high altitude electromagnetic pulse(HEMP) is analyzed. In addition, the polarization and critical angle are also considered. It is found that the total reflection occurs at an incident angle of about 38 degrees at the soil-rock interface, and that the parallel-polarized E1 HEMP penetrates better than the perpendicular-polarized one. The peak level of the penetrating electric field is found to be 5.6 kV/m at normal incidence, regardless of the type of polarization, and E1 HEMP is greatly reduced near the critical angle. Moreover, the penetrating E1 HEMP is analyzed as a variation of moisture content and depth of materials, resulting E1 HEMP could be useful in determining the levels of shielding required for buried facilities.

• Journal of the Korean Society for Marine Environment & Energy
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• v.14 no.2
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• pp.81-92
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• 2011

High resolution seismic profiles (chirp and sparker system) were analyzed for the interpretation of nearshore sedimentary environments of Suyeong Bay, Busan. The sedimentary sequence is classified into three seismic units (SU1a, SU1b, and SU2), overlying acoustic basement, and each units can be defined as erosional and disconformable strata. The lowermost SU1a is characterized by the acoustically parallel and prolonged inner reflections, compared with the upper SU1b displays irregular internal reflectors. The uppermost unit, SU2, is acoustically transparent. The acoustic basement is incised with channels, probably due to the active erosion during the early period of transgression. The acoustic basement deepens eastward in the study area, suggesting primary association with the Suyeong River. The upper SU1a and SU1b units constitute lowland-fill strata. SU2 is widely distributed over the study area. High resolution seismic profiles of Suyeong Bay provide significant information crucial to the interpretation of sedimentary environmental history, which is closely related to the sea level change, estuarine environment and influx of terrestrial sediments from the adjacent rivers.

• Water for future
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• v.29 no.2
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• pp.249-260
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• 1996

There have been easily found a number of examples that misleading or unreasonable measuring data set of physical variables are often produced in the field and the laboratory. The primary reason is that the specific requirements of civil engineers are initially disregarded in designing the experimental apparatus. It results from a lack of mutual understanding and co-operating between the user group and the maker. Therefore, their fundamental knowledge and apprehension become indispensible in order to obtain measuring data with high confidence and good quality In this study it is shortly explained the basic structure and the operation system of the experimental equipments commonly used at the present. A simple measuring set is developed which is quite easy for a general civil engineer to design and operate without any other specialty of mostly electricity electronics. Based upon this requirement, one of data logger named PPDL8 is newly designed by making use of the parallel port in the personal computer, consisting of multi-channels able to measure 8 different point values simultaneously. It can also use many valuable sub-programs existing in PC because the user makes his own programs necessary for measurement, by himself. Of all things, it has a great advantage to increase the applicability of field measurements much larger when adopting the notebook computer to operate with small battery only. In addition this study gives, in fact, the excellent agreements of in-situ field variables by showing their measuring results of temperature, distance and turbidity.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.11
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• pp.44-52
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• 2011

In this article, we present a QoS-guaranteed IP mobility management scheme of Internet service for fast moving vehicles with multiple wireless network interfaces. The idea of the proposed mechanism consists of two things. One is that new wireless connections are established to available wireless channels whenever the measured data rate at the vehicle equipped with mobile gateway drops below to the required data rate of the user requirement. The other is that parallel distribution packet tunnels between an access router and the mobile gateway are dynamically constructed using multiple wireless network interfaces in order to guarantee the required data rate during the mobile gateway's movement. By doing these methods, the required data rate of the mobile gateway can be preserved while eliminating the possible delay and packet loss during handover operation, thus resulting in the guaranteed QoS. The architecture of the IETF standard HMIPv6 has been extended to realize the proposed scheme, and detailed algorithms for the extension of HMIPv6 has been designed. Finally, simulation has been done for performance evaluation, and the simulation results show that the proposed mechanism demonstrates guaranteed QoS during the handover with regard to the handover delay, packet loss and throughput.

• Nuclear Engineering and Technology
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• v.47 no.6
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• pp.678-699
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• 2015

Although the harsh space environment imposes many severe challenges to space pioneers, space exploration is a realistic and profitable goal for long-term humanity survival. One of the viable and promising options to overcome the harsh environment of space is nuclear propulsion. Particularly, the Nuclear Thermal Rocket (NTR) is a leading candidate for nearterm human missions to Mars and beyond due to its relatively high thrust and efficiency. Traditional NTR designs use typically high power reactors with fast or epithermal neutron spectrums to simplify core design and to maximize thrust. In parallel there are a series of new NTR designs with lower thrust and higher efficiency, designed to enhance mission versatility and safety through the use of redundant engines (when used in a clustered engine arrangement) for future commercialization. This paper proposes a new NTR design of the second design philosophy, Korea Advanced NUclear Thermal Engine Rocket (KANUTER), for future space applications. The KANUTER consists of an Extremely High Temperature Gas cooled Reactor (EHTGR) utilizing hydrogen propellant, a propulsion system, and an optional electricity generation system to provide propulsion as well as electricity generation. The innovatively small engine has the characteristics of high efficiency, being compact and lightweight, and bimodal capability. The notable characteristics result from the moderated EHTGR design, uniquely utilizing the integrated fuel element with an ultra heat-resistant carbide fuel, an efficient metal hydride moderator, protectively cooling channels and an individual pressure tube in an all-in-one package. The EHTGR can be bimodally operated in a propulsion mode of $100MW_{th}$ and an electricity generation mode of $100MW_{th}$, equipped with a dynamic energy conversion system. To investigate the design features of the new reactor and to estimate referential engine performance, a preliminary design study in terms of neutronics and thermohydraulics was carried out. The result indicates that the innovative design has great potential for high propellant efficiency and thrust-to-weight of engine ratio, compared with the existing NTR designs. However, the build-up of fission products in fuel has a significant impact on the bimodal operation of the moderated reactor such as xenon-induced dead time. This issue can be overcome by building in excess reactivity and control margin for the reactor design.

• The Korean Journal of Physiology and Pharmacology
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• v.4 no.1
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• pp.33-40
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• 2000

This study was designed to clarify the mechanism of the inhibitory action of a nitric oxide (NO) donor, 3-morpholino-sydnonimine (SIN-1), on contraction, cytosolic $Ca^{2+}$ level $([Ca^{2+}]_i)$ and ionic currents in guinea-pig ileum. SIN-1 $(0.01{\sim}100\;{\mu}M)$ inhibited 25 mM KCl- or histamine $(10\;{\mu}M)-induced$ contraction in a concentration-dependent manner. SIN-1 reduced both the 25 mM KCl- and the histamine-stimulated increases in muscle tension in parallel with decreased $[Ca^{2+}]_i.$ Using the patch clamp technique with a holding potential of -60 mV, SIN-1 $(10\;{\mu}M)$ decreased peak Ba currents $(I_{Ba})$ by $30.9{\pm}5.4%$ (n=6) when voltage was stepped from -60 mV to +10 mV and this effect was blocked by ODQ $(1\;{\mu}M),$ a soluble guanylyl cyclase inhibitor. Cu/Zn SOD (100 U/ml), the free radical scavenger, had little effect on basal $I_{Ba},$ and SIN-1 $(10\;{\mu}M)$ inhibited peak $I_{Ba}$ by $32.4{\pm}5.8%$ (n=5) in the presence of Cu/Zn SOD. In a cell clamped at a holding-potential of -40 mV, application of $10\;{\mu}M$ histamine induced an inward current. The histamine-induced inward current was markedly and reversibly inhibited by $10\;{\mu}M$ SIN-1, and this effect was abolished by ODQ $(1\;{\mu}M).$ In addition, SIN-1 markedly increased the depolarization-activated outward $K^+$ currents in the all potential ranges. We concluded that SIN-1 inhibits smooth muscle contraction mainly by decreasing $[Ca^{2+}]_i$ resulted from the inhibition of L-type $Ca^{2+}$ channels and the inhibition of nonselective cation currents and/or by the activation of $K^+$ currents via a cGMP-dependent pathway.

• Nuclear Engineering and Technology
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• v.27 no.2
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• pp.176-188
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• 1995

A particle tracking scheme was developed in order to model radionuclide transport through a tortuous flow Held in a rock fracture. The particle tacking method may be used effectively in a heterogeneous flow field such as rock fracture. The parallel plate representation of the single fracture fails to recognize the spatial heterogeneity in the fracture aperture and thus seems inadequate in describing fluid movement through a real fracture. The heterogeneous flow field une modeled by a variable aperture channel model after characterizing aperture distribution by a hydraulic test. To support the validation of radionuclide transport models, a radionuclide migration experiment was performed in a natural fracture of granite. $^3$$H_2O$ and $^{131}$ I are used as tracers. Simulated results were in agreement with experimental result and therefore support the validity of the transport model. Residence time distributions display multipeak curves caused by the fast arrival of solutes traveling along preferential fracture channels and by the much slower arrival of solutes following tortous routes through the fracture. Results from the modelling of the transport of nonsorbing tracer through the fracture show that diffusion into the interconnected pore space in the rock mass has a significant effect on retardation.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.6-6
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• 2022

Prolonged Russia-Ukraine war, and unstable situation of supply and demand of global crops including the COVID-19 pandemic have raised awareness regarding food crisis, and in addition to this situation, export restriction measures imposed by some countries have accelerated the rise in the prices. Since the Republic of Korea depends annual crop consumption (21.32 million tons) mostly on the imports (food self-sufficiency rate in 2020 was 45.8%, crop self-sufficiency rate was 20.2%), our main task is to stably secure food. Now we need to put focus on building capacity to secure stable food supply, and actively manage and respond to risks. To overcome this condition, the Korean government set robust food sovereignty as its policy task, and has been focusing on the policy capacity by providing financial and policy support in parallel. We need to implement mid- to long-term measures to strengthen food security as well as to ensure domestic price stability. While increasing the domestic capacity to supply food in the mid- to long-term perspective, we are implementing projects to bring in crops which are inevitable to be imported by private companies. Specifically, we are making efforts to expand infrastructure for the public reserve and domestic production of wheat and beans which have low self-sufficiency rate, and to secure food sovereignty by providing support to secure global crop supply chain to private companies. The Ministry of Agriculture, Food and Rural Affairs plans to set a target for food self-sufficiency rate and prepare a policy to strengthen mid- to long-term food security by establishing a task force to strengthen mid- to long-term food security in the Ministry. Especially, although wheat is the second staple food, domestic wheat production and the foundation for the industry is poor. Compared to the wheat imports, domestic production of wheat is 30 thousand tons (self-sufficiency rate of 1%), leading to a vulnerable status against internal and external shocks. Through the establishment of the Wheat Industry Promotion Act (Feb. 2020) and the First Master Plan for Wheat Industry Promotion (Nov. 2020), the Korean government has developed a policy basis, and has been providing financial support in overall across the production, distribution and consumption process. In addition, the government established a production complex for Korean wheat and beans in order to supply affordable government-supplied commodities, provide education and consulting services, and create a high-quality stable production system, including facilities and equipment. We are also continuing to increase the public reserve for wheat and beans with the purpose of stable supply and demand as well as food security. The Korean government will establish and implement mid- to long-term measures to strengthen the foundation for domestic production across production, distribution and consumption process, and to stably secure global supply chain including through diversified import channels.