• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.9C
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• pp.888-894
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• 2007

The computational complexity of a sphere decoder (SD) is conventionally reduced by decoding order scheme which sorts candidate symbols in the ascending order of the Euclidean distance from the output of a zero-forcing (ZF) receiver. However, since the ZF output may not be a reliable sorting reference, we propose two types of sorting schemes to allow faster decoding. The first is to use the newly found lattice points in the previous search round instead of the ZF output (Type I). Since these lattice points are closer to the received signal than the ZF output, they can serve as a more reliable sorting reference for finding the maximum likelihood (ML) solution. The second sorting scheme is to sort candidate symbols in descending order according to the number of candidate symbols in the following layer, which are called child symbols (Type II). These two proposed sorting schemes can be combined with layer sorting for more complexity reduction. Through simulation, the Type I and Type II sorting schemes were found to provide 12% and 20% complexity reduction respectively over conventional sorting schemes. When they are combined with layer sorting, Type I and Type II provide an additional 10-15% complexity reduction while maintaining detection performance.

• Ocean Systems Engineering
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• v.10 no.4
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• pp.399-414
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• 2020

A floating bridge is an innovative solution for deep-water and long-distance crossing. This paper presents a curved floating bridge's dynamic behaviors under the wind, wave, and current loads. Since the present curved bridge need not have mooring lines, its deep-water application can be more straightforward than conventional straight floating bridges with mooring lines. We solve the coupled interaction among the bridge girders, pontoons, and columns in the time-domain and to consider various load combinations to evaluate each force's contribution to overall dynamic responses. Discrete pontoons are uniformly spaced, and the pontoon's hydrodynamic coefficients and excitation forces are computed in the frequency domain by using the potential-theory-based 3D diffraction/radiation program. In the successive time-domain simulation, the Cummins equation is used for solving the pontoon's dynamics, and the bridge girders and columns are modeled by the beam theory and finite element formulation. Then, all the components are fully coupled to solve the fully-coupled equation of motion. Subsequently, the wet natural frequencies for various bending modes are identified. Then, the time histories and spectra of the girder's dynamic responses are presented and systematically analyzed. The second-order difference-frequency wave force and slowly-varying wind force may significantly affect the girder's lateral responses through resonance if the bridge's lateral bending stiffness is not sufficient. On the other hand, the first-order wave-frequency forces play a crucial role in the vertical responses.

• Journal of Korean Society of Transportation
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• v.19 no.1
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• pp.17-28
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• 2001

The purpose of this study is to analyze logistics cost of transportation systems on EC(electronic commerce) between company and consumer. Transportation system in logistics is classified by three types on EC. The first type is the direct delivery from supply factory to consumers(type I). The second type is the delivery through distribution center in each area by owner logistics company (type II). The third type is the commission of delivery to the third party logistics company(type III). The logistics of EC has various service characteristics such as dealing with small quantity, various goods, and high frequency. This study assumes that all day's order is delivered on a next day. The logistics cost function is calculated according to the number of orders, delivery distance, transport quantify. and allocated freight trucks for daily order of the subject zone. The logistics cost changes according to the daily order characteristics. Therefore it is simulated to analyze the logistics cost change that considers the type of transportation's order characteristics. As a result of analysis, if the number of order is less than 10 and the quantify of each order is less than 10kg, type III has an advantage over the others And if the number of order is more than 10 and the quantity of each order is more than 10kg, type I has an advantage in the same zone and type II has an advantage in the other zones. This study is limited on the actual application because this study doesn't consider logistics infra of supply company and transport service time. If further study that considers these factors is implemented, it can estimate more accurate logistics cost on EC and propose an efficient freight transport alternatives to the company. This study attributes to estimate the logistics cost change over the frequency of daily order, the quantify of supply goods, and the transport distance on EC.

• Proceedings of the Korea Contents Association Conference
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• 2008.05a
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• pp.289-293
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• 2008

In this study, in order to find out the movement of polluted substance that is flown into the river and the characteristics of dispersion, the experiment that used the RI (Radio Isotope) tracer in the river was undertaken, and by using the experiment result, the figure modelling was undertaken to analyze the general type of pollutant dispersion. In addition, in order to calculate more accurate dispersion range and moving time, the experiment was done in about 2km from the measuring points of Namdaecheon around the Yongdam Dam of the upper Geum River to the lower stream, and modeling was undertaken for the 20km zone from the measuring points to the lower stream. In order to find out the flow of river and dispersion of polluted substance, RMA (Resource Modeling Associates)-2 and RMA-4 program are used in study. The site experiment using the RI was implemented for the experiment in the applied area and the same area, and the distance between each zone was set for 1㎞ with the slight difference for site situation and measured the density date of one second distance through the NaI apparatus to measure the density data of one second interval. On the basis of this measured data, it is compared and analyzed with the result of figure copy of RMA-2 and RMA-4 models to make the comparison and analysis of density distribution following the change in expansion coefficient that makes great influence on expansion range and dispersion in natural rivers. The influence of expansion coefficient on river can be researched and the measured density data, the maximum and minimum density time, and the basic data to calculate the expansion coefficient was prepared in this study.

• Journal of Korean Institute of Industrial Engineers
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• v.20 no.4
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• pp.51-63
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• 1994

Many themes have been studied for FMS problems. But most researches have focused on specific themes; Machine selection, Loading, Routing, Machine layout, etc. So many decision makers who want to introduce FMS to his factory, have many problems, because they do not know either what size of FMS should be introduced or what amount of money should be invested. The objective of this research is to help the decision makers who want to introduce FMS. This research consists of three major part, first, Machine selection, second, Loading, and third, Machine Layout. In the first part of the research, machines are selected with minimum cost satisfying the given demand of each part. In the second part, each operations with its required tools are allocated to those machines. In the third part the locations of each selected machines are determined. And dissimilarity coefficients between each pair of machines are calculated as the measure of distance. With above three steps, we have selected machines, allocated operations to those machines, and the layout configuration of those machines. And for each three steps, Mixed Integer Programming models are formulated. In order to solve the large problems and reduce the computer execution time, three heuristic algorithms are developed for the three mixed integer programming models.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.347-349
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• 1997

In this study, we designed a vascular occlusion device based on the principle that slowing blood flow would induce thrombosis. Tungsten, stainless steel and platinum were tested for finding a good embolic metallic coil. The primary coil and the second coil were done with heat treatment or different time. The pitch distance and the shape retention capability of second coil were characterized by SEM. To increase thrombogenicity, we tried to treat different proteins on steel coils: thrombin, gelatin and both gelatin and thrombin. To verify protein materials treated on coils, the surface of coil treated with different proteins were characterized using Laser Raman Spectrophotometer. After observation of embolic coils, the peptides bonds on theirs' surface were found. In order to compare the thrombogenicity of different embolic agents, we measured whole blood clotting time.

• Journal of the Society of Disaster Information
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• v.8 no.1
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• pp.71-80
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• 2012

It is necessary to establish guidelines when we selecting the civil defense evacuation facilities through quantitative analysis by civil defense evacuation facilities volume. The purpose of this study is to evaluate according to population density and distribution of the capacity of evacuation facilities. The results of this study are as follows. First, it is necessary to consider the capacity of evacuation facilities in order to set up the exact districts of civil defense evacuation facilities. Second, basic data based on to compare the condition of civil defense evacuation facilities is produced by an analysis on evacuation status of the target region. Third, it is proved to consider topographical conditions which do not move the shortest distance. Fourth, in order to create a realistic model, it is necessary to consider the model set various parameters.

• Journal of Advanced Navigation Technology
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• v.23 no.4
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• pp.265-272
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• 2019

In this paper, we selected commuting scenarios in the most congested metropolitan area in Korea, and conducted noise analysis during personal air vehicle (PAV) operation using aviation environmental design tool (AEDT)software which was developed by Federal Aviation Administration (FAA). Noise is the second important factor after safety in order to operate PAVs through concepts such as ODM (on-demand mobility) introduced by National Aeronautics and Space Administration (NASA). Noise analysis were performed by modeling low-noise ePAVs as commercial helicopters and predicted residential suitability in order to resolve problems in which accurate NPD (noise power distance) data from PAVs were not released. The application of noise reduction technology such as electric propulsion has significantly reduced noise exposure levels and has reached the conclusion that commuting with PAVs is feasible without noise problems in the metropolitan area.

• Journal of Urban Science
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• v.6 no.2
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• pp.29-34
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• 2017

Although the supply of public parking lots in major cities is steadily increasing, there is still a shortage of parking spaces that take into account the characteristics of actual available parking spaces. These parking problems are caused by conflicts between users, illegal occupation and privatization of roads, interference with traffic roads, and business stagnation in commercial areas and illegal parking problems. In addition, despite various parking demand management policies and continuous supply of public parking facilities, the solution to the parking problem is uneasy due to increased construction costs and changes in social conditions. In order to solve this problem, it was judged that it would be necessary to utilize the existing public parking lots efficiently. Therefore, we collect the variables expected to affect the turnover, and use multiple regression models. The results are summarized as follows. Firstly, public parking lots can be classified into four types using utilization rate and turnover rate. Secondly, influencing factors are found including index of public transportation usage convenience, index of illegal parking, and land use characteristics in central commercial district. Thirdly, it was shown that there was little impact by the size of public parking lots, separation distance to subway distance, separation distance to bus stops, transfer zone, residential zone, and second-rated lots by parking costs. Finally, it is found that public parking lots can be improved by proving accessibility of public transit, enforcement of illegal parking, active approaches supporting public parking lots. It is also recommended that public parking cost rating system based mainly on land use characteristics should be remedied and rearranged.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.360-365
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• 2008

We propose an efficient robot name registration and recognition method in order to enable a Call-and-Come service for home robots. In the proposed method for the name registration, the search space is first restricted by using monophone-based acoustic models. Second, the registration of robot names is completed by using triphone-based acoustic models in the restricted search space. Next, the parameter for the utterance verification is calculated to reduce the acceptance rate of false calls. In addition, acoustic models are adapted by using a distance speech database to improve the performance of distance speech recognition, Moreover, the location of a user is estimated by using a microphone array. The experimental result on the registration and recognition of robot names shows that the word accuracy of speech recognition is 98.3%.