• Journal of Korean Society of Environmental Engineers
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• v.37 no.2
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• pp.120-125
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• 2015

With rapid urbanization, the volume of traffic in urban area has been significantly increased. This in turn led to problem which can be described as Road Traffic Noise. Currently, to alleviate the road traffic noise damage, a demand for installation of soundproofing walls is rising. Among different shapes of soundproof walls being installed, the reflection-type acoustical insulation panel is highly drawing attentions of residents due to the fact that it does not obstruct their field of vision in contrast with the opaque acoustical insulation panel. On the other hand, improving the soundproofing wall of the reflection-type acoustical insulation barrier panel needs to be focused on since it has a possibility to cause a secondary damage by reflected sounds. Therefore, in this research, study has been carried out to improve the forms in order to minimize travelling of reflected sounds through changing the frontal surface shape and geometrical shape of the reflection-type soundproofing panel. A result from comparison between the normal reflection-type soundproofing panel and the improved soundproofing panel, with reduction effects in the noise reflection, showed that the curved type of soundproofing panel has an impact on reducing the noise up to 1.5 dB. Furthermore, from the research conducted, it appears that the increase and decrease in the reflected sounds can be changeable depending on various design factors. Thus, it turns out that the study shows a potential possibility to develop a reduction technology of the reflected sounds pertaining to overall condition on the soundproofing walls.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.9
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• pp.597-603
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• 2014

The aim of the present study is to compare sound performance depending on thickness, materials, and structure of polymer soundproof panels consisting of PC, PMMA, HDPE, and PP, respectively. As a result of comparing sound transmission loss (STL) of single layer panel made of four types of polymer, the better sound transmission loss was obtained in order of PC, PMMA, HDPE, and PP, which was obviously followed mass law. 8 mm of single panel showed 5~6 dB(A) greater STL than that of 4 mm panels and lower frequency for coincidence effect so that STL of 8 mm panels decreased around 4,000~5,000 Hz, indicating less STL of 4 mm panels than those of 8 mm. When it comes to structure, 4 mm panels with air layer appeared similar value of STL with 8 mm single panels under 300 Hz. In range of high frequency above 2,000 Hz, 4 mm panels with air layer performed better than 8 mm of single layer panel while resonance effects were observed at 500~630 Hz. It was found that these results could be practically utilized as fundamental data for noise barriers design considering the change to each condition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.436-444
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• 2017

The purpose of this study is to investigate the research trends related to work rehabilitation in the field of occupational therapy based on studies published in the American Journal of Occupational Therapy (AJOT). Thirty five articles in the AJOT from January, 2000, to June, 2016, were reviewed. Descriptive statistics were used to classify the articles according to their study methodology, evidence level, study subjects, and so on. When they were categorized according to the study methodology, eight studies (22.9%) were published as review or meta-analyses and 7 studies (20%) as qualitative and naturalistic inquiries. Group comparison/correlational and experimental outcome methods were used in 4 studies (11.4%). 3 studies (8.6%) were conducted using a case study/single-subject design or survey. 14 studies (40.0%) were evidence level V ones and 7 studies (33.3%) dealt with mental illness. When they were classified according to the study subjects, 25 studies (71.4%) were related to the work-rehabilitation process and 10 studies (28.6%) were related to the meaning and value of work. Through this study, we were able to determine the main research trends, study methodology, study participants, and evidence level related to vocational rehabilitation in the field of occupational therapy. Additionally, it is necessary to examine studies in the field of vocational rehabilitation, which have a high level of evidence and include various kinds of participants, as well as the process of vocational rehabilitation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.99-110
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• 2017

Improving tracking performance by estimating the status of multiple targets using radar is important. In a clutter environment, a joint event occurs between the track and measurement in multiple target tracking using a tracking filter. As the number increases, the joint event increases exponentially. The problem to be considered when multiple target tracking filter design in such environments is that first, the tracking filter minimizes the rate of false track alarmsby eliminating the false track and quickly confirming the target track. The purpose is to increase the FTD performance. The second consideration is to improve the track maintenance performance by allocating each measurement to a track efficiently when an event occurs. Through two considerations, a single target tracking data association technique is extended to a multiple target tracking filter, and representative algorithms are JIPDAF and LM-IPDAF. In this study, a probabilistic evaluation of many hypotheses in the assignment of measurements was not performed, so that the computation amount does not increase nonlinearly according to the number of measurements and tracks, and the track existence probability based on the track density The LM-IPDAF algorithm was introduced. This paper also proposes a method to reduce the computational complexity by improving the clutter density estimation method for calculating the track existence probability of LM-IPDAF. The performance was verified by a comparison with the existing algorithm through simulation. As a result, it was possible to reduce the simulation processing time by approximately 20% while achieving equivalent performance on the position RMSE and Confirmed True Track.

• The KIPS Transactions:PartA
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• v.18A no.4
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• pp.135-142
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• 2011

This research is to design an effective buffer structure and its management for flash memory based high performance SSDs (Solid State Disks). Specifically conventional SSDs tend to show asymmetrical performance in read and /write operations, in addition to a limited number of erase operations. To minimize the number of erase operations and write latency, the degree of interleaving levels over multiple flash memory chips should be maximized. Thus, to increase the interleaving effect, an effective buffer structure is proposed for the SSD with a hybrid address mapping scheme and super-block management. The proposed buffer operation is designed to provide performance improvement and enhanced flash memory life cycle. Also its management is based on a new selection scheme to determine random and sequential accesses, depending on execution characteristics, and a method to enhance the size of sequential access unit by aggressive merging. Experiments show that a newly developed mapping table under the MBA is more efficient than the basic simple management in terms of maintenance and performance. The overall performance is increased by around 35% in comparison with the basic simple management.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.2
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• pp.30-35
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• 1996

It is well known that the improved methods of the estimation of the service power margin is necessary to design a optimum ship and to operate economically a ship. Unfortunately, most conventional methods of the predicting of the service power margin are not so accurate that attention should be payed to improve this. From this overview, it is importance with. the effects of waves, as recommended by the 15th and 16th International Towing Tank Conference in 1978 and l981. However the progress of research in this field is very slow mainly since it is taken so long time to take data about hull roughness according to ship ages. For instance, it would be taken 17 or 25 years to measure ideally the data for a ship. Moreover it would be also necessary to take data for many types of ships to lead a general solution. A relationship between roughness and ship age are studied in this paper considering full scale data. A comparison is also made between the effects of hull roughness and of weather at sea for the ship.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.183-183
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• 2011

전 국토의 65%가 산악지형으로 이루어져 있는 우리나라는 도로개설 및 산업기지 건설, 대규모 주택단지 개발 등으로 자연사면을 변형시키는 규모나 빈도가 증가하고 있고, 최근에는 기상이변에 의한 집중호우가 빈번히 발생하여 절토사면에서 낙석이 발생할 위험이 점점 높아지고 있는 실정이다. 낙석방지를 위한 대책공법으로는 낙석방지 망, 낙석방지 울타리 등이 있으며 이중에서 낙석방지 울타리는 국내의 국도 낙석방지 대책공법 중 70% 이상을 차지하고 있다. 그러나 국내 설계지침에는 낙석방지 울타리에 대한 다양한 성능등급과 성능평가를 위한 표준화된 시험방법이 제시되어 있지 않아 현장여건을 고려하여 적절한 낙석방지 울타리를 선정하고 낙석방지 울타리들의 성능을 비교검토하기에 어려움이 있다. 유럽의 경우 유럽연합 출범이후 낙석방지 시설에 대한 통합기준의 필요성이 대두되어 유럽 여러 나라의 성능평가 방법과 스위스의 설계지침을 고려하여 2008년에 유럽 통합 지침인 ETAG 27을 제정하였다. ETAG 27에는 낙석방지 울타리의 성능등급이 100kJ~4,500kJ이상 9등급으로 분류되어 있고 성능등급 별로 Service Energy Level과 Maximum Energy Level에 대하여 실물시험을 통한 성능평가 시험과 구성요소에 대한 검증시험을 수행하도록 되어있다. 실물시험은 낙석에너지의 산정과 낙석질량의 타격위치를 정확하게 결정할 수 있는 방법을 이용하여 수행토록 규정되어 있다. 미국의 경우에는 주별로 상이한 설계기준으로 인하여 발생하는 문제를 해소하기 위하여 2003년에 스위스의 설계지침을 준용하여 통합기준인 NCHRP Report 20-07을 결정하였다. NCHRP Report 20-07에는 낙석방지 울타리의 성능등급이 100kJ~5,000kJ까지 9등급으로 분류되어 있고 성능등급 별 낙석질량이 규정되어 있으며 등급별 낙석에너지의 50%와 100%에 대하여 실물시험을 통한 성능평가 시험을 수행하도록 되어 있다. 실물시험은 낙석에너지의 산정과 낙석질량의 타격위치를 정확하게 결정할 수 있는 방법을 이용하여 수행토록 규정되어 있다. 낙석방지 울타리에 대한 국내 설계지침과 유럽과 미국의 설계지침을 비교분석하고 국내에서 수행된 실물실험을 통한 성능평가 연구결과를 검토하였다. 또한 구성요소의 역학적 특성변화가 전체 시스템의 성능에 미치는 영향을 조사하기 위해서 국내 설계 지침에 제시된 낙석방지 울타리에 대하여 컴퓨터 시뮬레이션을 이용한 성능평가를 수행하였다. 이러한 연구결과에 근거하여 국내 설계지침은 현장여건에 따라 적절한 낙석방지 울타리를 선정할 수 있도록 다양한 성능등급을 규정하고, 낙석방지 울타리의 성능을 합리적으로 비교검토 할 수 있게 하는 표준화 성능평가 시험방법과 평가기준을 정립하며, 구성요소의 품질에 대한 신뢰성을 확인하는 구성요소의 검증시험을 포함하는 방향으로 개선될 필요가 있는 것으로 조사되었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.2
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• pp.84-88
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• 2016

AlN single crystals were grown by the PT (Physical vapor transport) method with position-changable induction coil. And the graphite crucible dimensioned ${\Phi}90{\times}H120$ was used on processing. The temperature was $1950{\sim}2050^{\circ}C$ and ambient pressure was 150~1 Torr. And the hot-zone was changed according to times on growing for result comparison. When hot-zone by coil is located below far enough (> 40 mm) from AlN crystal concentration position, the as-grown crystals physical size is better ($300{\mu}m/hr$) than another condition, but the condition-reproducibility was very poor. However the closer the distance between hot-zone and AlN growing posion, the smaller the size of as-grown crystal and the rarer the generation of the crystal nuclear, but the crystal growing condition is stable for quality. The best condition for both growth rate and quality is gained when the starting position of hot-zone coil is about 20 mm distance from growing position. For the best growth condition, the position of hot-zone is very sensitive factor and the further more the condition of speed of coil shift also must control.

• Journal of Digital Convergence
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• v.15 no.10
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• pp.437-444
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• 2017

Christopher Nolan's film "Inception (2012)", which depicts the world of dreams as a unique space-time and opens a new chapter in the expression of dreams, portrays the dreamy world of unconsciousness. However, I can find limitations and contradictions in the expression of the actual dreams and essence of unrealistic structures and forms. I can find David Lynch's movies "Mulholland drive (2001)", which are closer to Freud's psychoanalysis in expressing the actual presentation process of dreams Through comparative analysis, I try to analyze the interpretation and context of the dream mentioned by Freud. The film "Inception" can be appreciated in terms of space time and rich imagination created from the point of view of science fiction movies, but it shows that logical reasonability is weak in view of applying the essence of dream. On the other hand, the film "Mulholland Drive" describes the illogical, confusing and unhappy feeling of unconsciousness by giving logic and order based on the interpretation of Freud's psychoanalytic dreams, is. In this way, it is possible to portray more realistic scenes of dreams only through the portrayal of dreams and unconsciousness based on Freud's psychoanalytic viewpoint.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.3 s.43
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• pp.9-22
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• 2005

The allowed operation space for the mass damper in an active tuned mass damper (ATMD) system is limited for most civil structures. In this study, a restrained stroke active tuned mass damper (RS-ATMD) system with a end-spring and a holder that reduces the stroke of the mass damper with maintaining the control effect durably is proposed. This new control system functions as a conventional ATMD within the predetermined stroke limitation under small excitation and as an RS-ATMD beyond that limitation under large excitation. A new control algorithm considering such an operation principle of the RS-ATMD are also provided. Parameteric study for the various design factors of the RS-ATMD is conducted and the control effectiveness are investigated in comparison with the ATMD. Exposed to sinusoidal or impact load, the RS-ATMD system shows the considerable reduction of the maximum stroke of the mass damper with the slight diminution in the control effectiveness. Excited by random load, it also shows the considerable reduction of the maximum stroke of the mass damper not allowing the diminution in the control effectiveness.