• Elastomers and Composites
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• 제59권2호
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• pp.73-81
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• 2024

In the field of electronic components, the potting material, which is a part of the electronic circuit package, plays a significant role in protecting circuits from the external environment and reducing signal interference among electronic devices during operation. This significantly affects the reliability of the components. Therefore, the accurate prediction and assessment of the lifespan of a material are of paramount importance in the electronics industry. We conducted an accelerated thermal aging evaluation using the Arrhenius technique on elastic potting material developed in-house, focusing on its insulation, waterproofing, and contraction properties. Through a comprehensive analysis of these properties and their interrelations, we confirmed the primary factors influencing molding material failure, as increased hardness is related to aggregation, adhesion, and post-hardening or thermal-aging-induced contraction. Furthermore, when plotting failure times against temperature, we observed that the hardness, adhesive strength, and water absorption rate were the predominant factors up to 120 ℃. Beyond this temperature, the tensile properties were the primary contributing factors. In contrast, the dielectric constant and loss tangent, which are vital for reducing signal interference in electric devices, exhibited positive changes(decreases) with aging and could be excluded as failure factors. Our findings establish valuable correlations between physical properties and techniques for the accurate prediction of failure time, with broad implications for future product lifespans. This study is particularly advantageous for advancing elastic potting materials to satisfy the stringent requirements of reliable environments.

• 한국양식학회지
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• 제21권2호
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• pp.70-75
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• 2008

본 연구는 입이 작은 어류들의 초기 먹이생물로 이용 가능성이 있는 초소형 rotifer Synchaeta kitina의 대량배양을 위한 최적 염분 및 수온을 규명하는데 그 목적이 있다. S. kitina를 대상으로 6개(5, 10, 15, 20, 25 및 30 psu)의 염분구와 5개(16, 20, 24, 28 및 $32^{\circ}C$)의 수온구를 두어 이들의 성장을 비교해 보았다. 이 때 모든 실험은 밀집 및 개체배양으로 나누어 행하였다. 염분 및 수온에 따른 실험결과, 밀집배양 시 최고밀도는 저온, 저염분 일 때 높은 경향을 5 psu, $16^{\circ}C$에서 유의적으로 가장 높게 나타났다. 또한 개체배양을 통한 생식 전 단계, 순 생식 단계, 산란수 및 수명 등의 성장요인들도 저온, 저염분 일수록 유의적으로 높게 나타나는 것으로 조사되었다. 따라서 초소형 rotifer S. kitina의 대량배양을 위한 최적 염분 및 수온 조건은 밀집배양 시 최고밀도를 보이고, 개체배양 시 생식, 평균수명과 같은 성장요인이 유의적으로 높게 나타난 5 psu, $16^{\circ}C$라 판단된다.

• 생태와환경
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• 제36권2호통권103호
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• pp.208-214
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• 2003

국내산 물벼룩의 배양조건에 따른 개체 생산특성을 비교하고 최적 배양환경 조건을 도출하기 위하여 배양조건에 따른 물벼룩의 개체생산특성을 조사하였다. Daphnia magna, D. pulex, Moina macrocopa는 퇴비를 이용한 배양액으로 배양하는 것이 생존기간과 개체 발생 수 측면에서 가장 효과가 좋았으며 D. galeata는 이와는 달리 비료를 이용한 배양액에서 가장 성장률이 좋았다. D. galeata는 전반적으로 배양이 어려웠으며 배양기간 동안의 새끼 발생도 적어 인공 배양시에 상당한 관심이 요구되었다. 남조류 Microcystis sp.의 microcystin이라는 독소는 포유류를 비롯한 여러 생물에게 직접적인 영향을 미치는 것으로 밝혀졌으나 금번 실험에서는 물벼룩의 생존여부에 대해서는 독소의 영항이 크게 나타나지 않았다. 또한 남조류 Microcystis sp.를 공급받은 물벼룩은 제한된 먹이 제공으로 적은 양의 Microcystis sp.를 불가피하게 섭취함으로써 상대적으로 생존기간이 짧았으며 개체 생산율도 낮았다. Scenedesmus sp.를 먹이로 공급한 경우는 물벼룩의 종류와 배양액의 종류에 상관없이 Microcystis sp.를 먹이로 공급한 경우보다 생존기간이 길고 개체발생수도 많았다. 각 물벼룩은 $20^{\circ}C$에서보다 더 생존기간이 길고 더 많은 개체를 발생하여 물벼룩 배양은 $15^{\circ}C.$보다 $20^{\circ}C$가 적절함이 확인되었다. 이러한 결과를 토대로 볼 때 D. galeata와 M. macrocopa는 물벼룩을 이용한 수질감시와 독성실험에 사용하기에 어려움이 많은 종이며 기존에 사용하고 있는 D. magna와 국내에서도 분포하고 있는 D. pulex를 사용하는 것이 용이할 것으로 사료된다.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2010년도 한국컴퓨터종합학술대회논문집 Vol.37 No.2(A)
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• pp.165-166
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• 2010

• Journal of applied mathematics & informatics
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• 제28권1_2호
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• pp.425-430
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• 2010

In this work, We consider an initial boundary value problem for a class of nonlinear hyperbolic equations. We establish a blow-up result for certain solutions with a dissipative term.

• Molecules and Cells
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• 제28권3호
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• pp.209-213
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• 2009

Caenorhabditis elegans is a free living soil nematode and thus in its natural habitat, C. elegans encounters many different species of soil bacteria. Although some soil bacteria may be excellent sources of nutrition for the worm, others may be pathogenic. Thus, we undertook a study to understand how C. elegans can identify their preferred food using a simple behavioral assay. We found that there are various species of soil bacteria that C. elegans prefers in comparison to the standard laboratory E. coli strain OP50. In particular, two bacterial strains, Bacillus mycoides and Bacillus soli, were preferred strains. Interestingly, the sole feeding of these bacteria to wild type animals results in extended lifespan through the activation of the autophagic process. Further studies will be required to understand the precise mechanism controlling the behavior of identification and selection of food in C. elegans.

• 전기학회논문지
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• 제62권11호
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• pp.1550-1559
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• 2013

Light emitting diode(LED) lighting has been applied various industry fields because of its high efficiency, low power consumption, long life time, and environment friendly characteristics. Generally, LED lighting needs a driver to maintain constant current. Most popular driver is the switching converter. In the converter, there are several electrolytic capacitors. However the lifespan of the electrolytic capacitor is much shorter than LED. Therefore the lifespan of LED lighting with electrolytic capacitor is decreased. Also, LED lighting needs dimming control because of various needs and energy saving. This paper presents the dimmable single-stage PFC DCM flyback converter without electrolytic capacitor and parallel LC resonant filter for reducing 120[Hz] ripple on the output. The type 2 controller is used to maintain constant current and the analog dimming control is used. The proposed converter is verified through simulation and experimental works.

• 한국생산제조학회지
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• 제22권5호
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• pp.767-773
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• 2013

A high-pressure, high-pressure drop control valve, which transforms the power transfer of a system by reducing the inlet pressure of 345bartothe outlet pressure of 112bar, is a fundamental component in an offshore plant process. With the increasingly growing market share of the maritime industry, this valve has been expected to be a high-value-added product. This study not only analyzes the relation between pressure drop and fluid velocity in a trim by using fluid analysis, but also examines the possibility of cavitation in a valve in addition to the plot for the extension of lifespan. Based on the analysis results, the design and production method of the valve are established, and accordingly, performance evaluation is carried out. It is demonstrated that the pressure drop from 345bar to 112bar is more feasible in the presence of the trim, which can induce a continuous and diminutive pressure drop in order to prevent cavitation in a high-pressure drop control valve. Furthermore, despite the fluid velocity near a seatring being found to be over 30m/s, the lifespan of the valve is determined to be adequate considering the operation condition of a prototype valve of 80%.

• 재활간호학회지
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• 제15권2호
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• pp.73-82
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• 2012

Purpose: The purpose of this study was to identify the influencing factors on mental health related quality of life (MHRQoL) in adults across the lifespan. Methods: A total of 688 Korean adults aged 19 years and older were selected. Data were collected by personal interviews or self report using structured questionnaires. For data analysis, t-test, ANOVA, Pearson's correlation coefficients and Stepwise multiple regression were used. Results: Mental health related quality of life (MHRQoL) differed significantly according to life cycle, especially showing a lower score in the elderly than others. In addition, elderly adulthood reported the highest stress and depression. The most significant predictors of MHRQoL in young and middle aged people were stress, depression, and subjective health status. Predictors of MHQoL in the elderly were stress and religion. Conclusion: The results indicate that MHRQoL of adult is associated with stress and depression. When the programs are developed to enhance mental health in elderly adulthood, religion should be considered as well as stress.

• 전기학회논문지
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• 제65권4호
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• pp.601-610
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• 2016

The light-emitting diode (LED) has been used in a variety of industrial fields and for general 0lighting purposes on account of its high efficiency, low power consumption and long lifespan. The LED is driven by direct current; therefore, an AC/DC converter is typically required for its use. An electrolytic capacitor is generally used for stabilizing DC voltage during use of the AC/DC converter. However, this capacitor has a short lifespan, which makes it a limiting factor in LED lighting. Furthermore, LED lighting requires a dimmable control to enable energy savings and fulfil a growing consumer demand. In this paper, the dimmable single-stage power factor correction (PFC) continuous conduction mode (CCM) flyback converter that employs no electrolytic capacitor is presented. The LC resonant filter is alternatively applied to reduce the 120[Hz] ripple on the output. And the optimum value of the LC resonant filter parameters considering both efficient and performance is analysed. Simulation and experimental results verify the satisfactory operation of the converter.