• Elastomers and Composites
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• 제55권2호
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• pp.81-87
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• 2020

Service life prediction and evaluation of rubber components is the foundational technology necessary for securing the safety and reliability of the product and to ensure an optimum design. Even though the domestic industry has recognized the importance thereof, technology for a systematic design and analysis of the same has not yet been established. In order to develop this technology, identifying the fatigue damage parameters that affect service life is imperative. Most anti-vibration rubber components had been damaged by repeated load and aging. Hence, the evaluation of the fatigue characteristics is indispensable. Therefore, in this paper, we propose a method that can predict the service life of rubber components relatively accurately in a short period of time. This method works even in the initial designing stage. We followed the service life prediction procedure of the proposed rubber components. The weak part of the rubber and the maximum strain were analyzed using finite element analysis of the rubber bushing for the tracked vehicles. In order to predict the service life of the rubber components that were in storage for a certain period of time, the fatigue test was performed on the three-dimensional dumbbell specimen, based on the results obtained by the rubber material acceleration test. The service life formula of the rubber bushing for tracked vehicles was derived using both finite element analysis and the fatigue test. The service life of the rubber bushing for tracked vehicles was estimated to be about 1.7 million cycles at room temperature (initial stage) and about 400,000 cycles when kept in storage for 3 years. Through this paper, the service life for various rubber parts is expected be predicted and evaluated. This will contribute to improving the durability and reliability of rubber components.

• Korean Journal of Acupuncture
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• 제31권4호
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• pp.218-224
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• 2014

Objectives : Zizyphus jujuba fruits(ZJF), a traditional Korean medicine has various biological activities such as anti-inflammatory, anti-oxidative and neuro-protective effects. However, it is still unclear whether ZJF has any biological effect on anti-aging. In this study, we examined the effect of ZJF on lifespan and thermal stress in C. elegans. Methods and Results : ZJF water extracts were fermented for 7 days(F7-ZJF) and 14 days(F14-ZJF) by Laetiporus sulphureus to increase secondary metabolites such as aglycone of flavonoids and terpenoids. In the lifespan assay, ZJF water extracts and fermented ZJF were treated on the agar medium plate with age synchronized egg stage of C. elegans. Treatment of F7-ZJF-$200{\mu}g/mL$ with OP-50 E. coli and F14-ZJF-$200{\mu}g/mL$ with OP-50 E. coli significantly increased life span of C. elegans(N2) at thermal stress condition of $25^{\circ}C$. Moreover mRNA levels of lifespan associated HSP 16.1, HSP 70, and HSF-1 were increased at thermal stress condition of $25^{\circ}C$. However, in the equilibration temperature of $20^{\circ}C$ after stress condition of $35^{\circ}C$ for 2 hr, F-14-ZJF-$200{\mu}g/mL$ treatment decreased the levels of heat shock protein in hsp16.2/GFP C. elegans. Conclusions : Our study indicates that prolong role of fermented-ZJF in C. elegans is mediated by control HSPs production.

• 한국재료학회지
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• 제25권10호
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• pp.552-558
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• 2015

The mechanical properties and microstructures of Aluminum 6056 alloys were investigated for their use in the fabrication of a piton block. The EN-AW6056 alloys exhibited a tensile strength of 375 MPa for a solution treatment temperature of $550^{\circ}C$ for 2 h followed by an aging treatment at $190^{\circ}C$ for 4 h. The microstructures of the heat treated specimen showed that the $Mg_2Si$ phase with a size of 3~5 um was dispersed throughout the aluminum matrix when the heat treatment was done. Moreover, in order to identify the forgeability of the specimen, upsetting tests were done. For up to 80 % of the upsetting ratio, the specimen maintained its original shape, and at above 80 % of the upsetting ratio, the specimen underwent crack development. The specimen was successfully forged without any defects with the examined material conditions. The material conditions together with the forging conditions are discussed in terms of the microstructures and mechanical properties.

• 한국재료학회지
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• 제25권8호
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• pp.403-409
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• 2015

Metastable phase characteristics of beta Ti alloys were investigated to consider the relationship of the microstructure and diffraction pattern in TEM. TEM analysis showed that the microstructure was mottled as a modulated structure, and the diffraction pattern was composed of spot streaks between the main spots of a stable beta phase with a specific lattice relationship. The modulated structure may be induced by short distance slip or atom movement during a very short interval of solution treated and quenched (STQ) materials. The athermal ${\omega}$ phase, which could be precipitated at low temperature aging, is also analysed by the metastable phase. The metastable phases including athermal ${\omega}$ phase had a common characteristic of hardened and brittle behavior because the dislocation slip was restricted by a super lattice effect due to short distance atom movement at the metastable state.

• Preventive Nutrition and Food Science
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• 제15권4호
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• pp.335-339
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• 2010

The effects of baking with broccoli powder on the consumer perception and sensory characteristics were investigated using a model system of cookies incorporated with broccoli powder as a value-added food ingredient. Broccoli powder was incorporated into cookie dough at 5 levels (0%, 1%, 2%, 3%, and 4%, w/w) by replacing equivalent amount of wheat flour of the cookie dough. After aging and sheeting, cookies were baked at $170^{\circ}C$ for 8 min in an oven. The baked cookies were cooled to room temperature for 1 hour and packed in airtight bags prior to all measurements. Control received the most favorable mean score, which was not significantly different from samples with 1% broccoli powder for color preference (p>0.05). Results of the consumer preference on taste showed a similar trend. Consumers did not find any significant differences on aftertaste and flavor among samples prepared by replacing wheat flour with up to 2% broccoli powder (p>0.05). Overall, incorporation of 1% broccoli powder in the formulation would result in the most favorable broccoli cookies for the consumers without sacrificing the sensory qualities, while still taking advantages of health benefits of broccoli. Correlation analysis indicated that broccoli powder concentration was significantly negatively correlated with the consumer preference for color, taste, aftertaste, flavor, overall acceptability and positively correlated with sensory color, taste, and flavor (p<0.05). Consumers' color, taste, aftertaste, and flavor were well correlated with the overall acceptability (p<0.05). Sensory intensity results are also presented.

• 정보보호학회논문지
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• 제29권6호
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• pp.1403-1412
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• 2019

터빈, 배관 및 저장탱크와 같은 물리장치들의 경우 노후화뿐만 아니라 제어장치에 대한 사이버공격으로 인해 PLC(Programmable Logic Controller)와 같은 제어시스템의 보호 및 상태감시기능이 동작하지 않는 경우, 피해파급력이 크고, 가동 중지 시 그 비용 손실 또한 매우 크다. 가동 중인 물리장치의 작동을 중지하지 않고 간접적으로 상태감시를 함으로써 가용성을 유지하기 위한 방안으로써 온도, 가속도, 전류 등을 간접적으로 감지하고, 데이터들을 Influx DB에 저장하여 실시간으로 감시하는 시스템을 설계 및 구현한다. 실제 구현된 시스템으로부터 데이터를 얻고 이를 이용하여 이상상태를 감지할 수 있음을 검증하였다. 간접적 실시간 감시시스템의 범용화를 통해 데이터를 축적해 활용하면, 추가비용 없이 가동을 중지하지 않고 사용할 수 있을 뿐만 아니라 미리 고장을 예측하고 필요한 경우에만 조치를 취하는 고장예지기술, 이상상태를 이중으로 감시하는 신뢰도 높은 건전성 관리 기술을 통해 유지보수비용과 위험도를 대폭적으로 감소시키고, 보안위협에 대한 대비가 가능하다.

• 폴리머
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• 제24권3호
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• pp.382-388
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• 2000

이온전도도가 높으며 균일하고 또 기계적 강도와 전기화학적 안정성이 우수한 전해질막을 얻기 위하여 poly(vinylidenefluoride-hexafluoropropylene) (PVdF-HFP) 공중합체를 전해질의 지지체로 선택하고, LiClO$_4$ 염이 포함된 ethylene carbonate (EC)와 ${\gamma}$-butyrolactone (GBL)의 흔합용매를 사용하여 겔-전해질을 제조하였다. 다양한 조성의 겔-전해질에 대하여 이온전도도, 열분석 및 선형주사전위 실험을 수행하였다. 이온전도도는 30PVdF-HFP+7.8LiClO$_4$+62.2EC/GBL 전해질막에서 3.8$\times$$10^{-3}$ S$cm^{-1}$ /로 가장 높았다. 열분석 결과에서 대부분의 시료는 대략 10$0^{\circ}C$ 정도까지는 안정하였으며, 특히 염은 고분자 사슬과 민감하게 반응하여 PVdF 결정질의 고온용융점을 낮추는 건을 확인하였다. 리튬 금속과 전해질 사이의 부식에 의해 생성된 부동태막에 의해 계면저항이 시간에 따라 계속적으로 증가하는 것을 확인하였으며, anodic stability는 대략 4.5 V vs. Li까지 안정한 것으로 측정되었다.

• 공업화학
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• 제23권6호
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• pp.567-571
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• 2012

전통회화의 변색은 온도, 습도, 빛, 그리고 대기 오염에 의한 각종 화학 물질들과 사용된 무기 안료와의 화학반응에 의해 일어나기도 한다. 본 연구에서는 조선종이라고 불리는 한지에 석록, 석청 무기 안료를 사용해 전통방법으로 시험편을 제작하고, 인위적인 노화시험을 통해 안료와 환경 요인의 상호 작용에 의한 노화과정을 조사하였다. 석청은 XRD 및 TGA 결과로부터 내후성 시험의 습기와 내염수 시험의 염무에 의해 영향을 받는 것을 알 수 있었다. 하지만 석록은 내후성 시험이나 내자외선 시험 중 주로 자외선에 의해 화학적 변화가 일어나는 것을 색차 및 TGA 결과로부터 볼 수 있었다.

• Steel and Composite Structures
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• 제29권4호
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• pp.527-544
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• 2018

The paper presents the study on a change in modal parameters and structural stiffness of cable-stayed Fiberline Bridge made entirely of Glass Fiber Reinforced Polymer (GFRP) composite used for 20 years in the fjord area of Kolding, Denmark. Due to this specific location the bridge structure was subjected to natural aging in harsh environmental conditions. The flexural properties of the pultruded GFRP profiles acquired from the analyzed footbridge in 1997 and 2012 were determined through three-point bending tests. It was found that the Young's modulus increased by approximately 9%. Moreover, the influence of the temperature on the storage and loss modulus of GFRP material acquired from the Fiberline Bridge was studied by the dynamic mechanical analysis. The good thermal stability in potential real temperatures was found. The natural vibration frequencies and mode shapes of the bridge for its original state were evaluated through the application of the Finite Element (FE) method. The initial FE model was created using the real geometrical and material data obtained from both the design data and flexural test results performed in 1997 for the intact composite GFRP material. Full scale experimental investigations of the free-decay response under human jumping for the experimental state were carried out applying accelerometers. Seven natural frequencies, corresponding mode shapes and damping ratios were identified. The numerical and experimental results were compared. Based on the difference in the fundamental natural frequency it was again confirmed that the structural stiffness of the bridge increased by about 9% after 20 years of service life. Data collected from this study were used to validate the assumed FE model. It can be concluded that the updated FE model accurately reproduces the dynamic behavior of the bridge and can be used as a proper baseline model for the long-term monitoring to evaluate the overall structural response under service loads. The obtained results provided a relevant data for the structural health monitoring of all-GFRP bridge.

• 산업식품공학
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• 제13권2호
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• pp.79-84
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• 2009

딸기 분말의 대체량을 0-6%로 달리하여 쿠키를 제조한 후 물리화학적 품질특성을 측정하고 각 특성사이의 상관관계를 살펴보았다. 딸기 분말 대체량이 증가함에 따라 반죽의 pH와 쿠키의 경도는 유의적으로 감소하였다(p<0.05). 반죽의 수분함량은 딸기 분말의 대체에 따라 유의적인 차이를 나타내지는 않았지만 평균 수분함량은 증가하는 경향을 나타내었다. 딸기 분말의 대체량이 증가할수록 명도와 황색도는 유의적으로 감소한 반면 적색도는 증가하였다(p<0.05). 퍼짐성 지수 역시 유의적인 증가를 나타내었다(p<0.05). 한편 상관분석결과 딸기 분말 대체수준은 모든 물리화학적 품질 특성과 유의적인 상관관계를 나타내었다. 또한 반죽의 수분함량과 퍼짐성 지수 사이에 양의 유의적 상관관계가 관측되었다(p<0.05).