• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.6
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• pp.395-402
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• 2000

This paper presents the improvement for speed characteristics of a Brushless DC Motor (BLDCM), it was applied to digital PI control for this. The practical PID control has been widely used to velocity control of DC motors. In this paper, a digital PI controller is used in order to decrease the speed error in constant velocity control of BLDCM. A TMS320C31 DSP is used for the microprocessor of digital PI control. The method using the DSP carry out the real-time control. The DSP has the rapid calculation ability and sampling time used lms. Driving BLDCM used 50W, motor input DC 150V and rotation speed 3000rpm. When BLDCM is to approval for discretion velocity at the acceleration and deceleration driving with any load, it was a feasible for stabilization control. Therefore, the experimental results indicate the superiority and validity of the velocity control by digital PI control.

• Fire Science and Engineering
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• v.15 no.1
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• pp.93-99
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• 2001

This study aims to improve the Evacuation Performance o( the I)inc()unto-store in underground that is rapidly new shopping store in Korea. In this paper, The architectural properties of the floor plan and section was reviewed with egress focus, occupant load density of the Discount-store was surveyed and the procedure and method of performance based egress design for this occupancy was analysed with SIMULEX model and calculation method. As a result of modeling, more longer available safe egress time (ASET) is expected than required safe egress time (RSET)in underground discount-store. In order to improve the Evacuation Performance for this type occupancy, egress capacity including escape stair, aisle width, escape door is calculated with based on occupant load density and review of shopping cart's structure and size and maximum escape capacity of the cash counter.

• Smart Structures and Systems
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• v.14 no.4
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• pp.569-594
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• 2014

Damage detection methods based on modal analysis have been widely studied in recent years. However the calculation of mode shapes in real structures can be time consuming and often requires dedicated software programmes. In the present paper the combined application of proper orthogonal decomposition and gapped smoothing method to structural damage detection is presented. The first is used to calculate the dynamic shapes of a damaged structural element using only the time response of the system while the second is used to derive a reference baseline to which compare the data coming from the damaged structure. Experimental verification is provided for a beam case while numerical analyses are conducted on plates. The introduction of a stiffener on a plate is investigated and a method to distinguish its influence from that of a defect is presented. Results highlight that the derivatives of the proper orthogonal modes are more effective damage indices than the modes themselves and that they can be used in damage detection when only data from the damaged structure are available. Furthermore the stiffened plate case shows how the simple use of the curvature is not sufficient when analysing complex components. The combined application of the two techniques provides a possible improvement in damage detection of typical aeronautical structures.

• Bulletin of the Korean Chemical Society
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• v.24 no.9
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• pp.1333-1338
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• 2003

Hollow Fiber flow field-flow fractionation (HF-FlFFF) has been tested in polyacrylonitrile (PAN) membrane channel in order to compare it with polysulfone (PSf) membrane channel. It has been experimentally shown that the separation time of 0.05-0.304 ${mu}m$ polystyrene latex (PSL) standards in PAN membrane channel is shorter than that in PSf channel by approximately 65%. The optimized separation condition in PAN membrane is ${\dot V}_{out}/{\dot V}_{rad}=1.4/0.12\;mL/min$, which is equal to the condition in PSf membrane channel. In addition both the resolution ($R_s$) and plate height (H) in PAN membrane channel are better than that in PSf membrane channel. The membrane radius was obtained by back calculation with retention time. It shows that the PSf membrane is expanded by swelling and pressure, but the PAN membrane doesn't expand by swelling and pressure.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.7
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• pp.1067-1075
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• 2001

The fields at the aperture of conical horn antenna with corrugations parallel to the axis have been analyzed using FDTD(Finite Difference Time Domain). Easy calculation depending on the change of the structure of antenna and time reduction can be achieved by 2-D FDTD coding with the first-order Mur ABC(absorbing boundary condition). It is confirmed that the corrugation can reduce phase difference of field on aperture. also it is investigated that the directivity is increased by 6.1 %, 12.9%, and 28.4% with one corrugation, two corrugations, three corrugations, respectively. It is also found that the improvement of the characteristics of the antenna is not proportional to the number of the corrugation but more dependent on the location of the corrugation near the aperture than that far the aperture.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2008.04a
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• pp.203-208
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• 2008

The purpose of the study is to establish the concept of residential standard, and at the same time to investigate the area of the minimum residential standard in the countries of the world through the preceding studies. In addition, it also aims at establishing the objective residential standard by comparing the residential standard of Korea with that of foreign countries, examining the problems and finding out the matters to be improved through the comparison of the residential standard in advanced countries with the minimum residential standard of Korea. The standard residential area, derived from the process of examining the minimum residential standard, will be used as the basic material for the calculation of the reasonable area in the surface plan for the study of low-cost housing development. The method of the study is to establish the concept of residential standard and at the same time to find out the problems in the minimum residential standard of Korea and improvement methods through the comparison of the residential standards in other countries. As the result of the studies focused on the area among the residential standards, it is found out that the Korea's residential area per capita is established as the least in comparison with that of advanced countries. The real area decided depending on the size of social space suitable for living can play a role in improving the degree of satisfaction in the person's living in the residential area. Therefore, it is urgently necessary to make a depth study on the surface area of the minimum residential standard, and it is also required to propose the residential standard and directions for the improvement of the qualitative level rather the quantitative expansion of residential structures.

• The Journal of the Korea Contents Association
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• v.20 no.12
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• pp.537-546
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• 2020

This study deals with the development and improvement of a particle dispersion model for quick response to water pollutant accidents. The developed model is based on the shear dispersion theory where vertical mixing is done by step by step mixing by vertical and molecular diffusion algorithm. For the quick response to chemical accidents, an algorithm for multi-core modeling for the particle dispersion model is applied. After the application of multi-core operation using OpenMP directives to the model, the relation for the calculation time and particle size were determined along with the number of cores used for parallel programming to determine the model time for chemical accident responses. The results showed the adequate conditions for the modeling of chemical accidents for quick response and to increase the applicability of the model.

• Journal of Cadastre & Land InformatiX
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• v.50 no.2
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• pp.53-68
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• 2020

The Cadastral Renovation is a National project to investigate and survey the registration of Cadastral Record and replace the existing Cadastral Record with a new Cadastral Record by digital, and to correct the registration of Cadastral Record if the registration of Cadastral Record does not match the actual status of the land. The Business Period generally takes about one year and six months to two years. The time required is getting longer due to problems that occur in the course of the Adjustment amount after the cadastral resurvey survey due to complex structure and internal conflict due to the interest between landowners. After Boundary Decision of the real boundary, the land area is confirmed by the landowners, and the cadastral office is to settle the Cadastral Renovation by calculating the Adjustment amount according to the confirmed area and the increase and decrease of the cadastral area. Therefore, the solution plan was suggested so that reasonable Adjustment amount can be applied through empirical research applied to the time of calculation of Adjustment amount and the method of calculation of Adjustment amount. The improvement method showed the expected effect that can lead the agreement with the landowner to the shortest period, and it was also possible to set the real boundary that meets the purpose of the Cadastral Renovation. This study suggests improvements in the method of calculating standard Adjustment amount, the method of imposing Adjustment amount, and the method of boundary adjustment that does not impose adjustment amount through the cadastral Renovation and parallel studies, and it is expected that the Cadastral Renovation will be completed by 2030.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.3 s.345
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• pp.1-9
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• 2006

In this paper, we propose a MIMO-OFDMA (Multi Input Multi Output-Orthogonal Frequency Division Multiple Access) system based on beamforming for performance improvement of downlink real-time traffic transmission in harsh channel conditions with low CIR (Carrier-to-Interference Ratio). In the proposed system, we first consider the M-GTA-SBA (Modified-Grouped Transmit Antenna-Simple Bit Allocation) using effective CSI (Channel State Information) calculation procedure based on spatial resource grouping, which is adequate for the combination of MRT (Maximum Ratio Transmission) in the transmitter and MRC (Maximum Ratio Combining) in the receiver. In addition, to reduce feedback information for the beamforming, we also apply QEGT (Quantized Equal Gain Transmission) based on quantization of amplitudes and phases of beam weights. Furthermore, considering multi-user environments, we propose the P-SRA (Proposed-Simple Resource Allocation) algorithm for fair and efficient resource allocation. Simulation results reveal that the proposed MIMO-OFDMA system achieves significant improvement of spectral efficiency in low CRI region as compared to a typical open-loop MIMO-OFDMA system using pseudo-orthogonal space time block code and H-ARQ IR (Hybrid-Automatic Repeat Request Incremental Redundancy).

• The Journal of Society for e-Business Studies
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• v.10 no.2
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• pp.109-132
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• 2005

With the flood of multimedia contents over the digital TV channels, the internet, and etc., users sometimes have a difficulty in finding their preferred contents, spend heavy surfing time to find them, and are even very likely to miss them while searching. In this paper we suggests two-step clustering technique using time schema on how the system can recommend the user's preferred contents based on the collaborative filtering that has been proved to be successful when new users appeared. This method maps and recommends users' profile according to the gender and age at the first step, and then recommends a probabilistic item clustering customers who choose the same item at the same time based on time schema at the second stage. In addition, this has improved the accuracy of predictions in recommendation and the efficiency in time calculation by reflecting feedbacks of the result of the recommender engine and dynamically update customers' preference.