• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.6
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• pp.569-575
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• 2011

Since the high heat generation of LED chips can cause a reduction in lifetime, degradation of luminous efficiency, and variation of color temperature, studies have been carried out on the optimization of LED packaging and heat sinks. Recently, LED packages have been applied to high-power lights such as car headlamps or street lights, and it is known that cooling using only free convection is not at all efficient. Thus, in this study, a heat pipe with forced convection was examined for the optimization of the cooling performance in high-power LED lights. In addition, optimal on-off control of a fan was adopted to increase the fan lifetime, since the lifetime of the fan is generally shorter than that of the LEDs.

• Smart Structures and Systems
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• v.22 no.6
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• pp.727-741
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• 2018

To mitigate vibrations, tuned mass dampers(TMD) are widely used for long span bridges or high-rise buildings. Due to some durability concerns, such as fluid degradation, oil leakage, etc., the alternative solutions, such as the non-contacted eddy current damping (ECD), are proposed for mechanical devices in small scales. In the present study, a new eddy current damping TMD (ECD-TMD) is proposed and developed for large scale civil infrastructure applications. Starting from parametric study on finite element analysis of the ECD-TMD, the new design is enhanced via using the permanent magnets to eliminate the power need and a combination of a copper plate and a steel plate to improve the energy dissipation efficiency. Additional special design includes installation of two permanent magnets at the same side above the copper plate to easily adjust the gap as well as the damping. In a case study, the proposed ECD-TMD is demonstrated in the application of a steel arch bridge to mitigate the wind-induced vibrations of the flexible hangers. After a brief introduction of the configuration and the installation process for the damper, the mitigation effects are measured for the ambient vibration and forced vibration scenarios. The results show that the damping ratios increase to 3% for the weak axis after the installation of the ECD-TMDs and the maximum vibration amplitudes can be reduced by 60%.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.17 no.1
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• pp.18-27
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• 2021

This study aims to develop an improved evaluation technology for assessing CANDU-6 safety. For this purpose, the multiple steam generator tube rupture (mSGTR) followed by an unmitigated station blackout (SBO) in a CANDU-6 plant was selected as a hypothetical event scenario and the analysis model to evaluate the plant responses was envisioned into the MARS-KS input model. The model includes logic models for controlling the pressure and inventory of the primary heat transport system (PHTS) decreasing due to the u-tubes' rupture, as well as the main features of PHTS with a simplified model for the horizontal fuel channels, the secondary heat transport system including the shell side of steam generators, feedwater and main steam line, and moderator system. A steady state condition was successfully achieved to confirm the stable convergence of the key parameters. Until the turbine trip, the fuel channels were adequately cooled by forced circulation of coolant and supply of main feedwater. However, due to the continuous reduction of PHTS pressure and inventory, the reactor and turbine were shut down and the thermal-hydraulic behaviors between intact and broken loops got asymmetric. Furthermore, as the conditions of low-flow coolant and high void fraction in the broken loop persisted, leading to degradation of decay heat removal, it was evaluated that the peak cladding temperature (PCT) exceeded the limit criteria for ensuring nuclear fuel integrity. This study is expected to provide the technical bases to the accident management strategy for transient conditions with multiple events.

• The Korean Journal of Physiology and Pharmacology
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• v.14 no.2
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• pp.91-97
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• 2010

Epidermal keratinocytes overgrow in response to ultraviolet-B (UVB), which may be associated with skin photoaging and cancer development. Recently, we found that HIF-$1{\alpha}$ controls the keratinocyte cell cycle and thereby contributes to epidermal homeostasis. A further study demonstrated that HIF-$1{\alpha}$ is down-regulated by UVB and that this process is involved in UVB-induce skin hyperplasia. Therefore, we hypothesized that the forced expression of HIF-$1{\alpha}$ in keratinocytes would prevent UVB-induced keratinocyte overgrowth. Among several agents known to induce HIF-$1{\alpha}$, pyrithione-zinc (Py-Zn) overcame the UVB suppression of HIF-$1{\alpha}$ in cultured keratinocytes. Mechanistically, Py-Zn blocked the degradation of HIF-$1{\alpha}$ protein in keratinocytes, while it did not affect the synthesis of HIF-$1{\alpha}$. Moreover, the p21 cell cycle inhibitor was down-regulated after UVB exposure, but was robustly induced by Py-Zn. In mice repeatedly irradiated with UVB, the epidermis became hyperplastic and HIF-$1{\alpha}$ disappeared from nuclei of epidermal keratinocytes. However, a cream containing Py-Zn effectively prevented the skin thickening and up-regulated HIF-$1{\alpha}$ to the normal level. These results suggest that Py-Zn is a potential agent to prevent UVB-induced photoaging and skin cancer development. This work also provides insight into a molecular target for treatment of UVB-induced skin diseases.

• Agribusiness and Information Management
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• v.10 no.1
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• pp.1-15
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• 2018

Many paddy cultivating farmers in the country are forced to use their limited resources to produce adequate food for their family, leading to the degradation and reduction in potential of these resources. The yield levels of paddy at the farmers' level and in the Front Line Demonstrations (FLDs) conducted in the farmers' fields is not at par with potential yield of the paddy variety. The gap between potential yield of crop variety and yield realized in FLDs refers to Research gap and the yield gap between FLDs and due to farmers' practice refers to Extension gap. The earlier studies conducted in India in general and in Andhra Pradesh in particular highlighted the existence of both research and extension gaps with reference to paddy. It is essential that, the narrowing of both research and extension gaps is not static, but dynamic considering the influence of technological interventions in boosting paddy yields at FLDs level and at farmers' level and also with the improvement of the yield potential of paddy varieties. This calls for integrated and holistic approaches to address these two gaps and with this background, the researcher aimed at this in depth study. The findings revealed that, research gaps are high with reference to weed management and pest management and extension gaps are high with reference to farm mechanization followed by fertilizer management. Reliable source of seed, capital use and frequency of meetings with Scientists or Agricultural Officers significantly influence the extension gaps in paddy. Farmers also prioritized socio-economic and technical constraints and the analysis infers that, it is high time now for the farmers to adopt the planned technological interventions on scientific scale to minimize the extension gaps to the extent possible. As the enabling environment in the State of Andhra Pradesh is highly encouraging for the farmers with relevant policy instruments in the form of subsidized inputs, free power, credit at concessional rates of interest, constructing irrigation projects etc., the adoption of the proposed technological interventions significantly contribute to minimizing both research and extension gaps in paddy cultivation in Kurnool district of Andhra Pradesh.

• Journal of the Korean GEO-environmental Society
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• v.15 no.2
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• pp.17-25
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• 2014

In the present study, it were performed an unconfined compression test and a field applicability test according to a mixed ratio of SS, soil type and curing period to analyze strength and deformation characteristic in order to evaluate engineering characteristics of soil mixed pavements using the eco-friendly soil stabilizer (SS). The test results revealed that SS mixed soil shows fast strength development at the initial curing time while 28-day strength amounted for 97% of the final strength. Furthermore, coarse-grained dredged sand (DS) and weathered granitic soil (WGS) have a larger ratio of deformation coefficient with respect to unconfined compressive strength than fine-grained dredged clay (DC) and organic soil (OS). Moreover, a comparison test between natural and forced drying conditions was conducted and test result showed 54% to 67% of strength degradation while having 55% to 63% of strength degradation in the freezing and thawing test result. Finally, a repeated loading test result showed that DS experiences up to 35% of strength reduction compared to initial strength under 10,000 times loading in maximum. Thus, it was validated that an appropriate amount of fine-grained sand is necessary to secure resistance capability to repeated loading.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.1
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• pp.200-214
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• 1993

This paper presents the results of fluidelastic instability analysis performed for the U-tube bundle of a Westinghouse model 51 steam generator, one of the recirculating types designed at an early stage, in which the principal region of external cross-flow is associated with the U-bend portion of tube. The prerequisites for this analysis are detailed informations of the secondary side flow conditions in the steam generator and the free vibration behaviours of the U-tubes. In this study, the three-dimensional two-phase flow field in the steam generator has been calculated employing the ATHOS3 steam generator two-phase flow code and the ANSYS engineering analysis code has been used to calculate the free vibration responses of specific U tubes under consideration. The assessment of the potential instability for the suspect U-tubes, which is the final analysis process of the present work, has been accomplished by combining the secondary side velocity and density distributions obtained from the ATHOS3 prediction with the relative modal displacement and natural frequency data calculated using the ANSYS code. The damping of tubes in two-phase flow has been deduced from the existing experimental data by taking into account the secondary side void fraction effect. In operation of the steam generator, the tube support conditions at the tube-to-tube support plate intersections due to either tube denting degradation or deposition of tube support plate corrosion products or ingression of dregs. Thus, various hypothetical cases regarding the tube support conditions at the tube-to-tube support plate intersections have been considered to investigate the clamped support effects on the forced vibration response of the tube. Also, the effect of anti-vibration bars support in the curved portion of tube has been examined.

• Development and Reproduction
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• v.12 no.3
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• pp.297-303
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• 2008

BCL-2 family members are essential protein for the regulation of cell death and survival consisting both antiapoptotic and pro-apoptotic proteins. In the present study, we designed and cloned a new apoptotic molecule MCL-1ES BH3M coding a modified protein of MCL-1L. Compared to MCL-1L protein, MCL-1ES BH3M lacks the PEST motifs known to be involved in MCL-1L protein degradation and has seven mutated residues in BH3 domain critical for dimerization with BCL-2 family members. Overexpression of MCL-1ES BH3M induced death of different cells, and its cell killing effect was not blocked by forced expression of the pro-survival protein MCL-1L. Expression of MCL-1ES BH3M protein led to the activation of caspase 9 and caspase 3, suggesting apoptotic cell death, and confocal fluorescent microscopic analyses showed that MCL-1ES BH3M was partially localized in mitochondria. In conclusion, we reported a new apoptotic molecule and determined its cell death activity in cells.

• Journal of the Korea Organic Resources Recycling Association
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• v.2 no.2
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• pp.19-29
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• 1994

A large volume of paper mill sludge(PMS) is produced every day from paper industries after treatments of waste water and it costs too much to dispose of the sludge. Since PMS consists mostly of biodegradable organic matter, cellulose, it is desirable to recycle it by proper treatments such as composting. In this study, experiments were conducted using a small scale reactor(12l) to establish optimum conditions for efficient composting of PMS of which initial pH, C/N ratio, and moisture content were 7.1, 28~30, and 60~65%, respectively. No heavy metals such as mercury, cadmimum, and lead were not detected in the PMS. Various levels of forced aeration, 1 minute aeration per every 30, 60, 120, 240, and 480 minutes were applied and 1 minute aeration per 60 and 120 minutes found to be proper for composting of 8l PMS in this system. Relationship between $CO_2$ production and temperatures was positively correlated with r> 0.82 suggesting that the normal decomposition of PMS by microorganisms occurred. However, under the condition of aeration interval over than 240 minutes, a negative relationship between two parameters was found indicating the occurrence of abnormal(maybe anaerobic) degradation. The amount of added nitrogen also affected composting of PMS resulting in the increase of $CO_2$ production and temperature. Semi-field tests using 100kg PMS in a static pile sysem showed that PMS could be composted efficiently under optimal environmental conditions. The parameters determining efficiency of composting such as C/N ratio, aeration, moisture content, and pH need to be monitored.