• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.28 no.1
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• pp.31-38
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• 2022

Due to the increasing consumer demands for the safety, shelf life, and quality of food, the application and development of active packaging in the food and packaging industry have been improved. According to the standards and specifications of the Republic of Korea for utensils, containers, and packages, the function of active packaging is to remove or alleviate factors that degrade food quality. Although extensive reviews regarding the development and commercialization of active packaging have been conducted, the legal regulations and safety assessments concerning active packaging have rarely been examined. This review provides information regarding the definition, structure, components, operational mechanisms, and applications for active packaging that actively removes oxygen, moisture, carbon dioxide, and ethylene. Furthermore, the legal regulations and research results related to the development of test methods for safety assessments of active packaging are investigated.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.4
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• pp.393-399
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• 2017

In a reciprocating compressor, the piston and connecting rod are important parts. Excess mechanical stress on these parts may cause damage, and broken parts are expensive and difficult to replace. Therefore, it is necessary to analyze the mechanical stress affecting durability and longevity. The main purpose of this study was to identify locations of maximum stress on pistons and connecting rods. Based on dynamic calculation of the working process of a specific air compressor, an analysis of piston and connecting rod performance has been completed. A three-dimensional model for the air compressor's pistons and connecting rods was built separately, and FEM analysis of these components was carried out using a numerical method. The pistons were loaded by pressure which was changed according to crankshaft angle without thermal boundary conditions. The simulation results were used to predict and estimate stress concentration as well as the value of this stress on pistons and connecting rods. The maximum equivalent stress calculated are over 190 MPa on pistons and 123 MPa on connecting rods at crank angle $135^{\circ}$ and $225^{\circ}$ but these are under tensile yield strength. Besides, the calculated safety factors of connecting rods and pistons is higher than 1. Moreover, the results obtained can be used to provide manufacturers with references to optimize the design of pistons and connecting rods for reciprocating compressors.

• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.335-343
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• 2010

Steel corrosion in reinforced concrete (RC) structures is a critical problem to structural safety and many researches are being actively conducted on developing methods to maintain the required performance of the RC structures during their intended service lives. In this study, concrete mixture proportioning technique through genetic algorithm (GA) for RC structures under carbonation, which is considered to be serious in underground site and big cities, is investigated. For this, mixture proportions and diffusion coefficients of $CO_2$ from the previous researches were analyzed and fitness function for $CO_2$ diffusion coefficient was derived through regression analysis. This function based on the 12 experimental results consisted of 5 variables including water-cement ratio (W/C), cement content, sand percentage, coarse aggregate content per unit volume of concrete in unit, and relative humidity. Through genetic algorithm (GA) technique, simulated mixture proportions were proposed for 3 cases of verification and they showed reasonable results with less than relative error of 10%. Finally, assuming intended service life, different exposure conditions, design parameters, intended $CO_2$ diffusion coefficients, and cement contents were determined and related mixture proportions were simulated. This proposed technique is capable of suggesting reasonable mix proportions and can be modified based on experimental data which consider various mixing components like mineral admixtures.

• 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 the Society of Naval Architects of Korea
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• v.32 no.3
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• pp.37-43
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• 1995

The procedure and the results of the full scale strain measurement of the long-range high-speed foil catamaran are described. The wave induced stresses at the center struts of the foils were measured during the sea trials in order to evaluate the hydrodynamic force acting on the foils and to verify the structural safety of the foil structures. From the statistical properties of the measured response of the stress, the most probable maximum values of the lift force and the stresses at the foils in service life of the ship are predicted and compared with the design parameters of the foils which were applied in the design of the subject ship. The available prediction processes of the measured stress are studied and the results of the applied processes are compared with each other.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.5
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• pp.317-326
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• 2013

Probabilistic design methods can consider uncertainties of design variables and are widely used in the design of vertical breakwaters. The probabilistic design methods include a partial safety factor method, reliabilitybased design method, and performance-based design method. Especially the performance-based design method calculates the accumulated sliding distance during the lifetime of the breakwater or during a design storm. Recently a time-dependent performance-based design method has been developed based on the first-passage probability of individual sliding distance during a design storm. However, because the allowable criteria in the first-passage probability method are not established, the stability of structures cannot be quantitatively evaluated. In this study, the allowable first-passage probabilities for two limit states are proposed by calculating the first-passage probabilities for the cross-sections designed with various water depths and characteristics of extreme wave height distributions. The allowable first-passage probabilities are proposed as 5% and 1%, respectively, for the repairable limit state (allowable individual sliding distance of 0.03 m) and ultimate limit state (allowable individual sliding distance of 0.1 m). The proposed criteria are applied to the evaluation of the effect of wave-height increase due to climate change on the stability of the breakwater.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.164.1-164.1
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• 2010

최근 에너지 절감과 환경 문제에 대한 관심이 커지면서 친환경적이고 에너지 효율이 높은 LED에 대한 관심이 대두되고 있으며, 국가 저탄소 녹색성장에 맞는 신성장동력산업의 하나로 LED가 선정되어 적극적으로 육성되고 있다. LED를 활용한 조명등은 현재까지 활발한 연구개발이 진행되었으며 백열전구를 능가하는 조명 효율을 확보하여 조명 광원으로서 이용되고 있다. 그런데 선박용 조명등의 경우에는 아직 관련 기술개발이 초기단계에 머물러있어 대부분의 선박들이 기존의 백열등 및 형광등과 같은 조명등을 사용하고 있다. 이러한 유리 조명등은 고소비전력과 제한된 수명에 따른 높은 유지비 및 제품 누수나 파손 등과 같은 안전성의 문제가 있다. 이에 따라 장기적인 관점에서 선박용 LED 조명 등에 대한 기술 개발이 필요할 것으로 보이며 기술 개발을 저해하는 요소인 방열, 가격 등에 대한 추가적인 기술개발이 뒷받침 되어야 할 것으로 보인다. 한국생산기술연구원에서는 부산광역시 지원사업의 일환으로 선박용 LED 조명등을 개발하고 있으며, 체계적인 연구를 위하여 선박용 LED 조명등의 요소기술에 대한 연구동향과 기술특성을 분석하고 있다. 본 논문에서는 선박용 LED 조명등 개발에서 요구되는 요소기술에 대한 기술개발동향을 살펴보고자 한다. 고효율의 선박용 LED 조명등 개발에 필요한 요소기술로는 방열, SMPS, 광학, 제품 내진동, 제품 방수 등의 설계 및 제작기술이 있다. 이러한 요소기술을 알아보고 선박용 LED 조명등 개발의 방향을 제시하고자 한다.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1997.04a
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• pp.62-68
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• 1997

현재 널리 보급되어 있는 볼베어링은 몇개의 볼에 의해 작동하기에 회전이 불균일하며 진동과 소음이 크다. 이는 고속에서 한계를 갖는 주된 원인이 되고 있다. 또한 그리스의 손실로 인한 수명의 단축이나, 유출된 그리스로 인한 손상은 제품의 내구성에 치명적인 결과를 초래한다. 더욱이 기존에 사용하는 소형 정밀 베어링은 전량 수입에 의존하고 있으며, 기술 선진국의 기술이전 회피로 개발이 어려우며, 수입물량도 확보하기 어려운 상황이다. 이를 극복하기 위한 하나의 방법이 볼과 그리스를 대신해서 유체의 압력을 이용한 유체동압베어링의 개발이다. 유체동압을 이용한 베어링의 장점은 그리스의 누유가 없고, 이로 인한 설계상의 제약이 없으며, 볼베어링으로는 불가능한 고속회전에 적합하고, 안전성이 뛰어나며 회전이 균일하여 제품의 신뢰성을 향상시킬 수 있다. 유체동압 함유소결함유베어링은 진동과 소음이 적고, 저렴하며 구조가 간단하고, 급유기를 필요로 하지 않는 자기윤활(self-lubrication)특성과 생산성 등 많은 장점을 가지고 그 사용범위가 점차 광범위하게 넓어지고 있지만, 저속상태에서의 유막형성, 고속상태에서 기름의 누유, 고하중상태에서 강도와 기공의 눌어붙음과 출발과 정지 시에 발생하는 두 금속간의 직접 접촉을 피할 수 없는 것과 같은 해결해야 하는 문제를 가지고 있다. 본 연구에서는 이러한 단점을 해결하기 위하여 유체동압 함유소결베어링이 마찰특성을 알아보고자 한다.

• Proceedings of the Korean Reliability Society Conference
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• 2011.06a
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• pp.125-130
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• 2011

발전 설비는 기대 수명동안의 안정성을 확보하기 위하여 해당 규격에 부합하도록 설계하여 건설된다. 하지만 가동 중 다양한 복합 환경에 노출됨에 따라 구조물을 이루고 있는 재료의 열화 현상이 가속화되어 예기치 못한 파손이 발생할 수 있다. 기계적 물성은 재료의 기계적 거동을 나타내는 주요 척도가 되며 이는 신뢰성 및 안전과 직결된다. 하지만 기존의 역학물성을 측정하는 대부분의 시험법들은 특정 크기의 시편을 요구하고 파괴적인 시험법이기 때문에 가동 중 시설물에 적용하기가 불가능하였다. 이러한 한계점을 극복하고자 비파괴적이고 정량적인 시험이 가능한 연속압입시험법이 최근 각광받는 시험법으로서 많은 연구자들에 의해 연구되고 있다. 이 시험법은 시험 대상물의 형상에 제약을 받지 않으며 시험 절차가 매우 간단하다는 장점을 가진다. 또한 대상의 국소 부위에 시험할 수 있어 취약 부위 판별이 가능하다. 본 연구에서는 대표응력-대표변형률 기법을 통하여 인장물성을 평가하고, 압입 하중 차이를 이용하여 소재에 존재하는 잔류응력을 평가하는 기법을 소개한다. 또한, 연속압입시험을 이용하여 실제 발전소 파이프의 취약부위로 알려진 용접부에 대하여 인장물성 및 잔류응력을 측정함으로써 실제 산업체의 신뢰성 평가가 적용할 수 있음을 확인하였다.

• Journal of Korean Society of Steel Construction
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• v.10 no.2 s.35
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• pp.187-199
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• 1998

The highspeed railway bridge which support continuous and high moving mass evalute the dynamic state and make the displacement of the bridge makes more or less, but up to this time the bridges are designed by the static design concept. for example when we design bridge we use impact factor, which only times the static load makes dynamic load. But becouse it simples. it can't express all of the effects. And so, in this report we study the modeling method of the moving mass and the dynamic factor.