• Polymer(Korea)
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• v.39 no.1
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• pp.130-135
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• 2015

Cellulose has attracted much attention as potential reinforcements in green composites. In this study, polypropylene (PP)/cellulose composites were prepared by melt-blending followed by compression molding. To improve interfacial bonding between PP and cellulose, maleic anhydride-grafted polypropylene (MAPP) was used. Mechanical properties of the PP/cellulose composites were investigated by UTM and izod impact tester. Thermal properties of the PP/cellulose composites were investigated by TGA and DSC. SEM images for the fracture surfaces of the composites showed that the MAPP was effective in improving PP/cellulose interfacial bonding. Tensile strength and modulus of the composite were maxima when MAPP content, based on cellulose content, was 3 wt%. With increasing cellulose content, the impact strength of the composites decreased but the tensile strength and modulus increased.

• The Journal of the Acoustical Society of Korea
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• v.33 no.5
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• pp.335-340
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• 2014

In this paper, we propose a new sign subband adaptive filter to improve the convergence rate of the conventional sign subband adaptive filter which has been proposed to deal with colored input signal under the environment with impulsive noise. The existing sign subband adaptive filter does not increase the convergence speed by increasing the number of subband because each subband input signal is normalized by $l_2-norm$ of all of the subband input signals. We devised a new sign subband adaptive filter that normalizes each subband input signal with $l_2-norm$ of each subband input signal and increases the convergence rate by increasing the number of subband. We carried out a performance comparison of the proposed algorithm with the existing sign subband adaptive filter using a system identification model. It is shown that the proposed algorithm has faster convergence rate than the existing sign subband adaptive filter.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.1
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• pp.53-62
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• 1992

Material can be degraded by using it for a long service under the high temperature and pressure circumstances, Therefore, material degradation can affect the strength of mechanical structures. At present, the life prediction of the degraded structures is considered as an important technical problem. In this paper, the degraded 21/4Cr-lMo steel is the material used for about 10 years around 400.deg. C in an oil refinery plant. The recovered one was prepared out of the above degraded steel by heat treatment for one hour at 650.deg. C. The degradation effect was investigated through the tension test, Hardness test and Charpy impact test. On the smooth surface material, the fatigue crack initiation, growth and coalescence stages of the distributed small cracks were investigated with photographs, and the crack length and density were measured. The measuring results were analyzed by quantative and statistical methods.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.1
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• pp.1-10
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• 2011

Recently harbor remodeling projects are seriously considered to enhance the loading and unloading capability of old container terminals and to make decrepit ports as eco-friendly harbor and waterfront spaces in many countries. In such a case, quantitative and qualitative evaluations on concrete harbor facilities are mandatory to determine the current structural integrity condition of aged materials. Once the remodeling project is determined to be carried out, the reusability of individual structural members and facilities including caissons, cell-blocks, and tetra-pods need to be decided based on the simple and economic visual inspection and/or nondestructive testing. In this study, the systematic quantitative evaluation procedure for determining the structural integrity condition and the reusability is studied based the nondestructive testing and evaluation methods. Conventional methods including Schmidt hammer test and ultrasonicpulse velocity methods and elastic wave based methods including impact echo test and surface wave test are applied to the old harbor facilities in five different sites. The compressive tests are also carried out to determine the elastic modulus and compressive strength of concrete materials.

• Journal of Biomedical Engineering Research
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• v.24 no.1
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• pp.15-21
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• 2003

In this study, for a safetv assessment of light weight wheelchair occupant in frontal crash, we tested a dynamic sled impact test. we carried out total 6 times test and impact speed was 20g/48 km/h. By using Hybrid III 50%ile male dummy, head injury criteria(HIC), neck flexion moment, neck axial tension force, neck shear force. chest acceleration, head, wheelchair and knee excursion were measured, we evaluated light weight wheelchair occupant safety by motion criteria(MC) which proposed in SAE J2249 and combined injury criteria(CIC) which is a voluntary standard(GM-IARV) of General Motors Co.. when we assumed that the maximum injury value in frontal crash was 100%, the result of motion criteria(MC) of wheelchair occupant was 52%, occupant upper body injury index(CIC) was 60.1%.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.5
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• pp.537-548
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• 2006

Statement of problem : The use of mouthguard is important as the leisure life is popular today. Purpose: The purpose of this study is to investigate the effect of a mouthguard on stress distribution in teeth, maxilla and mandible for maxilla impact. Material and methods: The 3-dimensional finite element model was based on a CT scan film of an average korean adult when the subject is using a customized mouthguard which was made with the Signature Mouthguard system of Dreve. The load was applied to the upper central incisor cervical area parellel impact force for 0.1sec(L1). The Von-mises stress analysis with a mouthguard and without a mouthguard was compared. Results: The results of this study were as follows: 1. Without the mouthguard, stress was concentrated on teeth and alveolar bone in all load conditions. 2. With the mouthguard. maximum stress value was decreased and stress was dispersed in all load conditions. 3. Stress extinction with the mouthguard was faster than without the mouthguard in all load conditions. Conclusion: We acknowledged that the mouthguard has a stress buffer effect as the maximum stress value was decreased and stress was dispersed when impact force was applied.

• Journal of the Korean Society of Marine Environment & Safety
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• v.11 no.2 s.23
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• pp.77-82
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• 2005

Previously sailing yachts or leisure yachts were mainly made from FRP(Fiber glass reinforced plastic) in the small shipbuilding, but recently there is a trend to replace it for steel or aluminum to substitute FRP for environmental friendly materials. Although It have to need a many checked item in case of hull girder strength and transverse strength normally evaluate base on calculation of class guideline so called direct calculation method. Otherwise. this method of initial structural design considered enough for safety margin on the structure. But, case of small craft must consider for evaluating local strength through rational method. In this paper, check the bow structure members for satisfying results base on allowable stress criterion of damaged bow structure by dynamic load due to slamming and bottom impact load due to pitching motion through finite element analysis. and investigate engine bed structure considering engine weight load and transverse wave load.

• Vending industry
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• v.2 no.4 s.5
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• pp.81-85
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• 2002

담배자판기 규제완화에 대한 산업계의 강력한 의지에도 불구하고 최근 개정을 추진 중인 국민건강증진법 시행령 및 시행규칙 공고(안)에 있어서는 공공지역 흡연구역에 대해 담배자판기를 전면 철거하는 내용이 포함이 되어 있어 산업계에 큰 충격을 주고 있다 이같은 관련입법은 그동안 담배자판기에 성인인증 장치를 부착하는 자율대책으로 규제완화를 적극 주창해 온 산업계 입장과는 전면 대치되는 방향이기에 그 충격이 더욱 클 수밖에 없다. 만약 이 공고안대로 입법통과가 된다면 기존 공공장소 흡연구역에 설치가 된 자판기들마저 전면 철거가 이루어져야 함은 물론 향후 담배자판기 설치로케이션도 극히 제약을 받게 되는 치명적 상황을 맞게 된다. 이같은 사태의 위급성 앞에 협회에서는 ${\ulcorner}$담배자판기 관련 국민건강증진법 시행령 및 시행규칙 개정안${\lrcorner}$에 대해 산업계의 입장을 종합한 소견서를 보건복지부 건강증진과에 제출하고 강력대응을 진행하고 있다. 협회는 이 건의안을 통해 공공장소 흡연구역에 대한 자판기 설치 금지 및 철거 검토 안은 시대적인 조류를 역행함은 물론, 성인인식 담배자판기의 청소년 보호 등 긍정적인 설치효과 측면을 전혀 인정치 않는 초강력 규제로서는 도저히 이 개정안을 수용할 수 없는 산업계 입장을 밝혔다. 아울러 공고안 같은 강력 규제보다는 성인인식 담배자판기가 오히려 합법적인 설치환경을 확보하여 사회적으로 떳떳하고 자신 있게 그 존재가치를 평가받을 수 있게 관련법을 개정해 주길 요청했다. 공고안의 개정통과가 산업계와 협회의 바램과 같이 저지될 수 있을 지는 앞으로 지켜봐야 할 일이다 하지만 분명한 점은 명분과 당위성과 부족한 규제만능주의적인 입법을 산업계가 그대로 수용하고만은 있을 수 없다는 점이다. 따라서 현시점에서 중요한 점은 산업계가 일치단결해 현 관련 공고안에 대한 반대 목소리를 높이는 일이다. 현재의 존립을 위협받는 담배자판기는 발상의 전환과 마인드 변화에 따라서는 얼마든지 합법적인 설치환경을 확보할 수 있기에 산업계의 결속력 있는 대응은 그만큼 중요성을 갖는다. 이번 사안은 결코 포기 할 수 없는 산업계의 권리라는 점은 명심해야 한다. 이러한 취지 하에 금번 정책초점에서는 보건복지부 관련 부처에 제출한 ${\ulcorner}$담배자판기 관련 국민건강증진법 시행령 및 시행규칙 개정안${\lrcorner}$에 대한 업계 소견서 및 건의안 내용을 정리 게재 했다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.4
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• pp.300-306
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• 2002

In this paper the failure mechanisms and Charpy impact tests of carbon fiber polypropylene composites have been studied in the temperature range -5$0^{\circ}C$ to 6$0^{\circ}C$ and 3 different supported length of specimen (span length). There are significant effects of temperature and span length on impact fracture toughness, which shows a peak at ambient temperature and decrease as temperature is reduced. Fracture toughness shows a maximum at span length s=20mm. Failure mechanisms are characterized based on SEM examination, which is correlated the measured fracture toughness. Mafor mechansms of this composites can be classified as fiber matrix debonding, delamination, fiber pull-out and matrix deformation.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.4
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• pp.207-212
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• 2020

To decide a separation distance of the redundant vital equipment in a naval ship, the damage radius due to an aerial explosion should be estimated. In this research, a simplified formula for the damage radius has been developed by using existing empirical formulae for reflected shock pressure and shock lethality value of equipment. As a numerical example, the damage radius for a typical pump aboard a naval ship has been calculated by the developed formula and compared with the results calculated by Measure of Total Integrated Ship Survivability (MOTISS) which is one of survivability analysis codes verified, validated and accredited by the US Navy. Also, comparison with the results calculated by existing other simplified formulae has been made.