• Applied Microscopy
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• v.28 no.3
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• pp.415-424
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• 1998

The dependency of long-range order parameter on the ordered structure of $Pb(Mg_{1/3}Nb_{2/3})O_3$ solid solutions has been investigated by means of computer simulations of high-resolution lattice images. The computer image simulations were performed by the multislice method in a wide range of sample thicknesses, defocusing values, and long-range order parameters. It was found that the lattice images of the ordered structures were predominantly dependent on the long-range order parameter, The lattice images in a complete ordered structure showed a pseudo-hexagonal pattern. As the order parameter decreases, the simulated images changed slowly from a pseudo-hexagonal pattern to a rectangular pattern. The lattice images in a complete disordered structure showed a rectangular pattern. Also, the simulated images of the $Pb(Mg_xNb_{1-x})O_3$ with different Mg:Nb ratios obtained at a given long-range order parameter were basically the same patterns, irrespective of Mg and Nb compositions.

• The Journal of the Acoustical Society of Korea
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• v.40 no.5
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• pp.428-438
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• 2021

For long-range communication in deep water, low carrier frequency is efficient due to a decrease in transmission loss. However, there is a limitation in that the data rate decreases due to a narrow bandwith. In order to increase the data rate in an environment with a limited bandwidth, it is necessary to design a higher-order modulation scheme. This paper analyzes the long-range communication data modulated by higher-order modulation schemes. The long-range communication experiment (23 km ~) was conducted in East Sea in October 2020. During the experiment, a vertical line array was utilized and communication sequences were modulated by Phase Shift Keying (PSK) and Quadrature Amplitude Modulation (QAM) schemes and transmitted by a towed source. In more detail, PSK modulation consists of quadrature PSK and 8PSK, QAM modulation consists of 8QAM and 16QAM. Time reversal processing is applied to mitigate inter-symbol interference by utilizing the correlation between received signals and channel impulse responses. All modulation schemes show successful results at 23 km range, demonstrating the feasibility of higher-order modulation in long-range communication.

• 전기의세계
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• v.26 no.1
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• pp.36-44
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• 1977

본고에서는 (1) 대전력장거리송전계통의 안정도향상 문제, (2) 기간송전계통의 단락전력압제 문제, (3) 대전력장거리송전계통의 계통전압과 주파수의 유지 문제, (4) 사고파급에 의한 광범위대정전의 방지 문제의 문제들에 대하여 초고압계통의 운용에 경험이 있는 외국의 전력계통운용방안들을 참고로하여 그의 개요를 기술코자 한다.

• Journal of Radiation Protection and Research
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• v.31 no.1
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• pp.9-15
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• 2006

A long-range atmospheric dispersion model named LADAS has been developed to understand the characteristics of the transport and diffusion of radioactive materials released into atmosphere. The developed numerical model for validation was compared with the results of the ETEX which is the long-range field tracer experiment. As a comparative study, the calculated concentration distributions agreed well in the case of the usage of the mixing heights calculated by the Richardson number than the usage of the constant mixing heights in LADAS model. Also, the calculated concentrations agreed with the time series of the measured ones at some sampling points.

• Korean Journal of Optics and Photonics
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• v.1 no.2
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• pp.142-148
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• 1990

Surface-enhanced Raman scattering (SERS) experiment of pyridine (CsHsN) has been performed at silverpyridine interface by use of long range surface plasmon (LRSP) which is generated in the Sarid-type attenuated total reflection (A TR) structure consisting of prism. dielectric. metal and dielectric media. Generation of LRSP has ben confirmed by observing the propagation of the LRSP. Raman signal of pyridine adsorbed on a silver surface in the above layered structure has been observed and compared with the bulk Raman signal and SERS signal from the chemically adsorbed pyridine. SERS experiment by use of LRSP has not yet reported to the best of our knowledge.wledge.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.3
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• pp.1-15
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• 1993

In response to the growing domestic request and the change of the overseas environment, Hyundai Maritime Research Institute has recently established a three-stage development plan for the high speed marine transportation system. As the first stage plan, the long-range high-speed foil catamaran passenger ship has been designed and constructed for the open-sea serivice of 800 nautical miles round trip with top speed above 40 knots. Extensive theoretical analyses and model tests were systematically carried omit along the course of design for the system optimization and the verification. In this paper, the brief summary of the design and the construction works shall be presented.

• Korean Journal of Optics and Photonics
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• v.19 no.6
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• pp.429-434
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• 2008

We propose a wavelength filter based on long-range surface plasmon-polaritons (LR-SPP) supported by a asymmetric doubleelectrode LR-SPP structure. For the case of the asymmetric double-layered LR-SPP waveguide, LR-SPPs exist with a much broader range of index mismatches between core and clad materials. Thus, the asymmetric double-electrode LR-SPP waveguide is adequate to form a plasmonic band-gap device as we report in this paper by studying Bragg-reflection wavelength filter based on it. The structure for wavelength filter operating telecommunications wavelength is designed by using the method of line (MoL) and the transfer matrix method. The fabricated device shows a relatively high extinction ratio of 50 dB with a bandwidth of 2 nm, and the performance is very consistent with numerical simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6C
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• pp.626-633
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• 2009

ISO/IEC/WD 24753 defines new modem specifications for a long-range RFID communications and application protocol for a sensor tag system. According to the standard, the frequency offset of the tag is 4%. In general wireless communications systems, it is known that a coherent receiver is superior to a non-coherent receiver. However, if the frequency offset is large, it is difficult to restore the original data accurately with a coherent receiver, and the performance of a coherent receiver is easily degraded. In this paper, a non-coherent receiver structure is adopted to solve the frequency offset problem of long-range RFID communications. We designed a frequency estimation block to find an optimal frequency from the received signal with 4% frequency offset and proposed a start frame delimiter (SFD) detection algorithm to determine the start position of the payload. The frequency estimation block finds the optimal frequency from the received signal using 9-correlators. And the SFD detection block searches the received signal to find the start position of the payload with dual correlator. We implemented a long-range RFID reader with the proposed methods and evaluated its performance in a wired/wireless test network. The implemented long-range RFID reader showed more superior performance than the commercial RFID reader in terms of recognition range.

• Journal of Energy Engineering
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• v.19 no.3
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• pp.195-202
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• 2010

A third of primary energy is lost as a waste heat. To improve this inefficient use of energy, systems using chemical reaction have been suggested and studied. In this study, methanol decomposition/synthesis reaction as a chemical reaction was selected for long time heat storage and long distance heat transport system because of safe, cheap and gaseous product. The purpose of this study is to find the optimal conditions in the methanol decomposition and synthesis reactions for long distance heat transport. Several parameters such as reaction temperature, pressure, $H_2$/CO ratio, space velocity, catalyst particle size were tested to find the effects on the reaction rates for the methanol synthesis. And the reaction temperature, space velocity, catalyst particle size were tested to find the effects on the production concentration for the methanol decomposition.

• Journal of Korean Society of Transportation
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• v.21 no.3
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• pp.7-14
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• 2003

Statistics shows that 80% of freeway users travel less than 50km, and only 8% of them do over 100km. It means that the freeway is used for commuting. As a result, the freeway is not used efficiently and social cost is high. The current toll system aims for the efficient usage of the freeway by restraining short-distance trips and inducing long-distance ones. Thus, policies such as minimum toll system and discount for long-distance trips have been carried out. However. these two policies take no account of demand management between the freeway and alternative roads. They merely consider the compensation for charge on users, so the assessment of discount rate and distinction of distance are not reasonable. Consequently, not only the effective demand management but also the evaluation of those policies has been difficult to be achieved. The objective of this paper is to analyze those problematic policies and to establish a reasonable and improved toll system. In addition, this study presents the methodology to minimize social cost, which can be achieved by reducing short trips and encouraging long ones on the freeway. A new methodology of freeway toll system is applied and the results are presented.