• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.707-714
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• 2011

The inter-story drift ratio is used to evaluate the damage of buildings by the earthquake. This is known that as the inter-story drift ratio decreases, the seismic damage decreases. Although to reduce the inter-story drift ratio is the important issue in the seismic design, no practical inter-story drift design method has bean developed. This study presents an optimal inter-story drift design method to improve the seismic performance of the steel moment frames using the resizing algorithm. The objective function of the proposed method is to minimize the differences of the inter-story drift ratios so that the inter-story drift ratios of the building could be distributed evenly and be reduced. Because this method redesigns the sectional properties of structural members base on the displacement participation factor calculated by the unit-load method, this can improve the seismic performance of the structure without the iterative structural analysis. The efficiency of this algorithm was demonstrated by the application to steel moment frames.

• The Magazine of the IEIE
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• v.24 no.1
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• pp.86-105
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• 1997

본 글은 이동통신용 안테나의 이해를 돕기 위하여 쓰여진 글이다. I장 서론에는 이동통신용 안테나에 대한 개괄적인 설명을 하고 이어서 II장에서는 이동통신용 안테나의 요구조건에 관하여 약술하였으며 III장에서는 이 분야의 소형안테나로서 널리 사용되는 대표적인 형태의 안테나들의 동작원리 및 설계방식에 대하여 논의하였다. 1절과 2절에서는 각각 헬리컬과 루프 안테나에 대하여 교과서적 수준으로 간략하게 설명하였으며 3절과 4절에서는 마이크로스트립 안테나와 평면형 역-F안테나(PIFA)에 대하여 개념적으로 설명하되 대략적인 설계가 가능하도록 하였고 특히 실험적인 트리밍과정의 중요성을 강조하였다. 5절에서는 자동차용 뒷유리 열선 안테나에 관향 경험적인 설계방법을 간단히 살펴보았다. 이어서 IV장에서는 이동통신용 안테나의 흥미로운 일례로서 비행체에서 광범위하게 사용되는 다양한 형태의 안테나에 대하여 간략하게 설명하였으며 V장에서는 이동통신분야에서 앞으로 그 중요성을 더해갈 다이버시티 기술에 관하여 논의하였으며 VI장에서는 이동통신용 소형안테나의 성능평가 및 설계에 도움이 되는 실험과정에 대하여 논의하여 보았다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.11 s.353
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• pp.95-117
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• 2006

In this paper, we describe the optimization of the link-level performance and the complexity of floating-point and fixed-point methods in IEEE 802.16e OFDMA/TDD mobile modem. In floating-point design, we propose the channel estimation methods for downlink traffic channel and select the optimized method using computer simulation. So we also propose efficent algorithms for time and frequency synchronization, Digital Front End and CINR estimation scheme to optimize the system performance. Furthermore, we describe fixed-point method of uplink traffic and control channels. The superiority of the proposed algorithm is validated using the performances of Detection, False Alarm, Missing Probability and Mean Acquisition Time, PER Curve, etc. For fixed-point design, we propose an efficient methodology for optimized fixed-point design from floating-point At last, we design fixed-point of traffic channel, time and frequency synchronization, DFE block in uplink and downlink. The tradeoff between performance and complexity are optimized through computer simulations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.4
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• pp.714-721
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• 2007

MAC protocol must be necessarily used because the GPON technology has Point-to-Multipoint structure as connecting an OLT with numerous ONUs. And DBA algorithm must be used to support various services too. There are a few researches in DBA algorithm of GPON, referring the DBA algorithm of BPON which has a waste of bandwidth and the fairness problem between T-CONTs. In this paper, we proposed the BR-DBA algorithm to be able to solve the problems of DBA algorithm on BPON and designed that. As a result of evaluating the performance of BR-DBA algorithm using the NS-2 network simulator, we confirm that the problems of DBA algorithm on BPON were solved and increasing the throughput over BR-DBA algorithm.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.1
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• pp.28-36
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• 2016

Theoretical model of a variable thrust solid rocket motor with a pintle nozzle was derived. For the chamber pressure control, classical model linearization and proportional-intergral controller was used. And then two types of gain scheduling controller were suggested to imporve controller performance for the non-linear propulsion model. Considering characteristics of systems, control gains were scheduled by chamber pressure or free volume. Step responses of each controllers were compared. As a result, the proper control algorithm about characteristics of variable thrust rocket motor was suggested.

• Smart Media Journal
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• v.11 no.9
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• pp.21-29
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• 2022

Ultra Violet(UV) is gradually being replaced with LED instead of general UV lamps. However, the light efficiency of UV LED is still lower than that of the general lamp, and the light efficiency is also low. Due to the current environment and technical problems of UV lamps, the LED replacements are gradually being made. In this study, a new package design and analysis were performed to increase the lifetime and performance of UV LEDs. A new packaging for UV LED were designed and implemented. The new packaging for UV LED was constructed to improve light efficiency. And the electrical and optical characteristics were analyzed respectively. To improve the optical efficiency in UV LED package, the Al has been used based on high reflectivity and applying the optimal lens focusing. Compared to the existing silver Ag, the light efficiency was improved by about 30% or more, and it was confirmed that the light output degradation characteristic was improved by about 10% in the newly applied optical device chip.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.3
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• pp.215-225
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• 2011

During the past decade, the performance-based design method of caisson breakwaters has been developed, which allows a certain damage while maintaining the function of the structure. However, the existing method does not consider the changing coastal environment due to climate change impacts so that the stability of the structure is not guaranteed over the lifetime of the structure. In this paper, a time-dependent performance-based design method is developed, which is able to estimate the expected sliding distance and the probability of failure of a caisson breakwater considering the influence of sea level rise and wave height increase due to climate change. Especially, time-dependent probability of failure is calculated by considering the sea level rise and wave height increase as a function of time. The developed method was applied to the East Breakwater of the Hitachinaka Port which is located on the east coast of Japan. It was shown that the influence of wave height increase is much greater than that of sea level rise, because the magnitude of sea level rise is negligibly small compared with the water depth at the breakwater site. Moreover, investigation was made for the change of caisson width due to climate change impacts, which is the main concern of harbor engineers. The longer the structure lifetime, the greater was the increase of caisson width. The required increase of caisson width of the Hitachinaka breakwater whose width is 22 m at present was about 0.5 m and 1.5 m respectively for parabolic and linear wave height increase due to climate change.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.4
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• pp.53-58
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• 2023

As smartphones increasingly support the execution of various applications, the function of virtual memory swapping is becoming important. However, unlike traditional computer systems, mobile platforms do not basically support swapping. This is because swapping results in frequent writes to flash memory, which may degrade the performance of smartphone's storage significantly. To cope with this situation, this paper suggests two multi-swap architectures, hierarchical swapping and hybrid swapping, and compares their performance quantitatively. Specifically, this paper shows that hybrid swapping with the consideration of single-access data can reduce swapping traffic to flash memory, and improve the performance compared to traditional swapping.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.5
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• pp.151-160
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• 2022

Owing to the recent increase in the frequency of explosion accidents, blast resistive design has garnered attention to reduce the damage of important structural elements. However, domestic research on the blast resistive structures is still insufficient, and domestic design guideline against blast loads are not documented yet. In this study, a numerical study on the RC blast resistive walls, where the test variable was the presence of FRP sheet, was performed using LS-DYNA program. Based on the numerical results, displacement-time hysteretic curve, pressure-impulse diagram, and fragility curve of the test specimens were derived. It was shown that the FRP sheet strengthening method is efficient to improve the blast resistive performance of the RC wall. Also, the strengthening effect of FRP sheet on the RC wall was stronger when the magnitude of the blast load was greater.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.6
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• pp.64-71
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• 2018

It is essential to understand the characteristics of gas turbine components in order to carry out an off-design analysis of a gas turbine engine. In this study, a micro gas turbine engine test system was constructed to understand the performance characteristics of gas turbines. The temperature and pressure in the flow path of the micro gas turbine was collected by measuring the engine spool speed, and a compressor map was constructed by using the experimental data. The exhaust gas was collected at the turbine outlet and the combustion efficiency was calculated. An off-design performance analysis at ground static was performed using GasTurb software by applying the compressor map and combustion efficiency obtained from the experimental data. Futhermore, we compared and evaluated the analysis results with engine operating data.