• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.10A
• /
• pp.1147-1158
• /
• 2004

In this paper we design STBC-OFDM systems by applying several STBC schemes to the OFEM system and show their comparative analysis results obtained through computer simulations under Rayleigh fading environments, considering the effect of channel estimation error. We first consider the space-time coding algorithms of major STBC schemes, together with their demodulation algorithms. We then select the OFDMparameters considering mobile environments and design the STBC-OFDM systems by choosing one of digital modulation schemes such as QPSK, BPSK, 16QAM, 64QAM, and 256QAM according to the transmission rate, and describe the block diagrams of the demodulator and channel estimator. We finally compare and analyze the BER performances of the STBC-OFDM systems according to the transmission rate and the number of receive antennas.

• Proceedings of the SCSK Conference
• /
• 2003.09b
• /
• pp.330-342
• /
• 2003

The formation of emulsions and micelles in water/ceramide PC104/CholE $O_{20}$/C$_{16}$E $O_{20}$ and water/ceramide PC104/CholE $O_{20}$ mixtures was investigated through the phase behavior studies. The phase diagrams showed the existence of micelle and emulsion regions in both systems. The mixed surfactant system (CholE $O_{20}$/C$_{16}$E $O_{20}$) showed the wider micellar and emulsion regions than the single surfactant system (CholE $O_{20}$). From FT-IR measurements, it was found that the polyoxyethylene (POE) groups of surfactants formed the hydrogen bonds with amido carbonyl group in ceramide PC104. This result indicated that the hydrophilic part (EO) of surfactants could stabilize the lamellar structure and emulsion of ceramide PC104. The mixed surfactant system (CholE $O_{20}$/C$_{16}$E $O_{20}$) resulted in the smaller emulsion droplet size due to the effect of curvature at the interface, thus further increasing emulsion stability. With the penetration of $C_{16}$E $O_{20}$into the interfacial layer of surfactants in emulsion, the curvature of the interface might be altered for the formation of smaller emulsion droplets. The mixed surfactant system could incorporate up to 4 wt. % of ceramide PC104 into emulsion more than single surfactant system.ystem.m.

• Spatial Information Research
• /
• v.15 no.3
• /
• pp.203-218
• /
• 2007

The purpose of this article is to set up the scientific and reasonable norm of location and service area determination instead of the pro-administrative lacking availability, so as to propose more practical and reasonable standard of space unit for the location of facilities. This article has accepted the method of Voronoi Diagram as a new scientific and reasonable criteria. The article chooses and realizes a model that can propose a new service area, transform and apply to improve its reality, and assesses which has more reality and compatibility by comparing the models. The result from this procedure can be adapted in objectification of the service area determination and formation of the standard space unit.

• Education of Primary School Mathematics
• /
• v.21 no.2
• /
• pp.237-260
• /
• 2018

This study investigated the models of four countries' elementary mathematics textbooks in Ratio and Rate and identified how multiplicative perspectives on proportional relationships and the structure of proportion situations are reflected in the textbooks. For this, textbooks of 5th and 6th grade textbooks in Korea Japan, Singapore and U.S. are compared and analyzed. As a result, we can find multiplicative perspectives on proportional relationships and the structure of proportion situations on pictorial models, ratio tables, double number lines and double tape diagrams. Also, the development of Japanese textbooks from multiple batches perspectives to variable parts perspectives and the examples of the use with two models together implied the connection and union of two multiplicative perspectives. Based on these results, careful verification and discussion for the next textbook is needed to develop students' proportional reasoning and teach some effective reasoning strategies. And this study will provide the implication for what kinds of and how visual models are presented in the next textbook.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.24 no.4
• /
• pp.331-340
• /
• 2004

Deployment of an advanced on-line monitoring of the component integrity offers a prospect of improved performance, enhanced safety, and reduced overall cost for nuclear power plants. Ultrasonic guided waves have been known as one of the promising techniques that could be utilized for on-line monitoring. The present work is aimed at developing a new method for on-line monitoring of the pipes during the operation period of nuclear power plants. For this purpose, the steam generator (S/G) tube was selected as an object of tile experiment. Dispersion corves and the incident angles corresponding to the specific modes were calculated for the S/G tube. The modes of guided waves were identified by the time-frequency diagrams obtained by the short time Fourier transform. It was experimentally confirmed that there was no mode conversion when the ultrasonic guided waves passed over the curved region of the S/G tube. An optimum mode of guided wave for the S/G tube was suggested and verified by the experiment.

• The Journal of the Petrological Society of Korea
• /
• v.28 no.2
• /
• pp.71-83
• /
• 2019

The volcanic rocks in Saryangdo area are composed of Witseom Andesite, Punghwari Tuff, Araetseom Andesite, Obido Formation, Namsan Rhyolite and Saryangdo Tuff in ascending order. The volcanic rocks has a range of andesite-rhyodacite-rhyolite, which indicates calc-alkaline series and volcanic arc of orogenic belt. In Harker diagrams for trace element and REE pattern, these are also distinguished into so three groups(Witseom Andesite, Araetseom Andesite and Saryangdo Tuff) that each unit is interpreted to have originated in different magma chamber. The Saryangdo Tuff exhibits systematically(chemical zonations that gradually change) from lower dacite to upper rhyolite in section. The systematic sequence of compositional variations suggests that the tuffs were formed by successive eruptions of upper to lower part of a zoned magma chamber in which relatively dacitic magma is surrounded around rhyolitic magma of the central part. The zoned magma chamber was formed from marginal accretion and crystal settling that resulted form magmatic differentiations by fractional crystallization.

• Journal of Industrial Convergence
• /
• v.16 no.2
• /
• pp.1-14
• /
• 2018

The interconnectedness of all things is continuously expanding. For example, bluetooth low energy (BLE) beacons are wireless radio transmitters that can send an identifier to nearby receivers and trigger a number of applications, from proximity marketing to indoor location-based service. iBeacon technology which is one of the newest technologies in the smart tourism field, is reckoned as being very useful for travelers in enhancing the experience with visiting places. However, there is consequently not much existing research yet about the connection between iBeacon technology and tourism destination. Considering that, this study analyzes the adoption of iBeacon in tourism destination, this study examine the interrelationships and feedback structures of key factors in iBeacon adoption. To serve the purpose, this study used system dynamics approach to develop a model of iBeacon adoption in tourism destination. The analysis results showed that the concept of 'Social Influences' is one of the significant predictors for individual's intention behavior to accept iBeacon, and word of mouth (WOM), subjective norm, privacy concern, and perceived usefulness are key factors influencing the iBeacon adoption.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.23 no.3
• /
• pp.183-190
• /
• 2019

Recent changes in the construction method of piles to minimize noise, along with the development of high-strength reinforcement, have provided an economical high performance RC pile development to compensate for the disadvantages of existing PHC piles. In this study, a methodology for the development of cross - section details of high performance RC piles of various performances is presented by freely applying high strength steel and concrete. This study suggested a technique for calculating bending moments for a given axial force corresponding to the allowable crack widths and this can be used for serviceablity check. In calculating the design shear force, the existing design equation applicable to the rectangular or the I section was modified to be applicable to the hollow circular section. In particular, in the limit state design method, the shear force is calculated in proportion to the axial force, and the procedure for calculating PV diagram is established. Last, the section details are determined through PM diagrams that they have the similar flexural and axial-flexural performances of the PHC pile A, B and C types with a diameter of 500 mm. To facilitate the application of the selected standard sections to the practical tasks, the design PM diagram and design shear forces are proposed in accordance with the strength design method and limit state design method.

• Journal of Soil and Groundwater Environment
• /
• v.27 no.spc
• /
• pp.1-18
• /
• 2022

A conceptual site model is used to support decision-making of response strategy development, determination, and implementation within a risk-based contaminated site management system. It aims to provide base information of the relevant site characteristics and surface/subsurface conditions in order to understand the contaminants of concern and the associated risk they pose to the receptors. This study delineated the technical details of conceptual site model development, and discussed the possibility of applying it in domestic subsurface contamination management. Conceptual site models can be developed in various formats such as tables, diagrams, flowcharts, and figures. Contaminated sites are managed for a long period of time following the steps of investigation, remediation design, remediation, verification, and post-remedation management. The conceptual site model can be enhanced in each stage of the contaminated site management based on the continuously updated information on the site's subsurface environment. In the process of enhancement for conceptual site model, precision is gradually improved, and it can evolve from a conceptual and qualitative form to a more quantitatvive and three-dimensional model. In soil pollution management, it is desirable to incorporate the conceptual site model into the soil scrutiny system to better assess the current status of the contaminated site and support follow-up investigation and management.

• Composites Research
• /
• v.19 no.6
• /
• pp.8-15
• /
• 2006

In this study, computational rotor dynamic analyses of a composite roller used for large LCD panel manufacturing process have been conducted. The present computational method is based on the general finite element method with rotating gyroscopic effects of rotor systems. General purpose commercial finite element code, SAMCEF which has special rotordynamics analysis module is applied. For the purpose of numerical verification, comparison study for a benchmark dual rotor model with support bearings is also presented. Detailed finite element models for composite roller with optimized lamination angles are constructed and analyzed considering gravity effect in order to investigate vibration characteristics in actual operation environment. As results of the present study, rotor stability diagrams and mass unbalance responses are presented for different rotating conditions.