• Journal of Electrical Engineering and Technology
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• v.10 no.6
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• pp.2348-2355
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• 2015

Transformer mineral oil which is normally hydrocarbon based is non- biodegradable and pollutes the environment in all aspects. Though vegetable oils are eco-friendly in nature and potentially could be used in transformers as a replacement for the mineral oil, there usage is restricted because of their oxidative instability. The present work focuses on using rapeseed oil and pongamia (pongamia pinnata) oil as effective alternatives for the traditional mineral oil in power transformer. The oxidative stability of the rapeseed oil and pongamia oil is increased by using combinations of the natural and synthetic anti-oxidants as additives. The parameters like breakdown voltage, viscosity, flash point, fire point are measured for the rapeseed oil and pongamia oil with and without the additives as per IEC and ASTM standards. The results shown encouraging changes in the parameter values and ensures the use of the oils as a potential alternative insulation in power transformers.

• Tribology and Lubricants
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• v.12 no.1
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• pp.36-41
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• 1996

The suitability of a pressure differential scanning calorimetry (PDSC) in monitoring the quality of synthetic base fluids has been investigated using polyalphaolefin (PAO) oils as an example. Induction period meassured at 170, 180 and 19$0^{\circ}C$, and 3.53 MPa oxygen pressure was applied to characterize their oxidation stability. The PDSC method has proven to be simple and repeatable and requires only small sample size for testing. More importantly, it can be applied in differentiating the oxidation performance quality of PAO oils and is versatile enough for use in studying kinetic aspects of PAO oil oxidation which include the effect of temperature and antioxidant concentration. Additionally, the method appears to correlate well with a rotary bomb oxidation test (RBOT).

• Journal of the Korean Ceramic Society
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• v.28 no.2
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• pp.146-152
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• 1991

Ultra fine and homogeneous (Ni0.4Zn0.6)Fe2O4 ferrite powders were prepared by direct-wet, Hydrothermal and coprecipitation methods. In case that specific surface areas of Ni-Zn ferrite powders were over 220㎡/g, 100㎡/g, 30㎡/g individually direct-wet, hydrothermal and coprecipitation methods. The Ni-Zn ferrite magnetic fluids of which Solvents were benzene or kerosene was prepared by making cation surfactant adsorbed on the surface of the (Ni0.4Zn0.6)Fe2O4. The results that measured dispersion and viscosity by making cation surfactant adsorbed were as follows. 1. The adsorption amount of Oleric acid be proportioned the specific surface area of powders. 2. The maximum amount of Oleric acid was 36wt% of dried powders which has 220㎡/g of specific surface area. 3. The stability of fluid by direct-wet synthesis emthod in benzene or kerosene solvent excellent.

• Tunnel and Underground Space
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• v.29 no.3
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• pp.157-171
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• 2019

The fracturing by liquid carbon dioxide ($LCO_2$) as a fracking fluid has been an alternative to mitigate the environmental issues often caused by the conventional hydraulic fracking since it facilitates the fluid permeation owing to its low viscosity. This study presents how $LCO_2$ injection influences the breakdown pressure, acoustic emission, and fracture morphology. Three fracturing fluids such as $LCO_2$, water, and oil are injected with different pressurization rate to the synthetic and porous mortar specimens. Also, the shale which has been a major target formation in conventional fracking practices is also tested to examine the failure characteristics. The results show that $LCO_2$ injection induces more tortuous and undulated fractures, and particularly the larger fractures are developed in cases of shale specimen. On the other hand, the relationship between the fracturing fluids and the breakdown pressure shows opposite tendency in the tests of mortar and shale specimens.

• Proceedings of the Korean Environmental Health Society Conference
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• 2003.06a
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• pp.213-216
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• 2003

This study was conducted to estimate if the level of several chemical ingredients including alkanolamines or ethanolamines (EA) examined in the specific synthetic metalworking fluid (MWF) “A” can cause anti-microbial activity and health effect. Three water-based MWF products (“A”, “B”, and “C”) were studied every week for two months (from June 1, 2002 to July 30, 2002). Chemical ingredients such as formaldehyde, boron, EA, and copper were examined. In the sump where MWF “A” was used, not only the total level of EA, monoethanolamine(MEA), diethanolamine(DEA) and triethanolamine(TEA), but also boron level were significantly higher than those of the other MWFs. ANOVA statistical tests indicated that levels of pH, alkalinity, boron, MEA, DEA and TEA in MWF A were significantly higher than those in other MWF types. Correlation tests also found that levels of pH, alkalinity, boron, MEA, DEA and TEA in MWF “A” are significantly correlated. We suggested the assumptions that excessive concentrations of EA, and borate at a high pH level, may cause anti-microbial resistance synergically, To demonstrate this assumption, additional study is needed to examine the relationship between the levels of microbes and excessive concentrations of EA, and borate at a high pH level.

• Korean Journal of Veterinary Research
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• v.35 no.2
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• pp.263-270
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• 1995

Creatine(Cr) and phosphocreatine(PCr), the important mediators of intracellular high-energy phosphate buffer system, were found in the tissues of mouse seminal vesicle and also in the extracellular fluids of seminal vesicle secretion. This study was performed m confirm that the secretion and accumulation of Cr and PCr is regulated by testosterone and its $5{\alpha}$-reduced metabolite, $5{\alpha}$-dihydrotestosterone(DHT). In addition, the effect of nandrolone decanoate(ND), a synthetic anabolic steroid, on the levels of Cr and PCr in the seminal vesicle was compared with those of testosterone propionate(TP) and DHT. Male Swiss-Webster mice were castrated and three groups of the castrates were treated with daily injection(sc) of same molar dose($1.45{\times}10^{-8}mol/g\;BW$) of TP, DHT, or ND. All three androgens rapidly increased weights of seminal vesicle tissue and fluid, and also increased concentrations of Cr and PCr in the tissue and fluid. However, ND was least effective in increasing seminal vesicle weights, whereas ND was as effective as, or in some cases, more effective than, TP or DHT in increasing Cr and PCr levels in the tissue and fluid. The results confirm that the accumulation of Cr and PCr in the seminal vesicles is regulated by testosterone and DHT, and also suggest that the effects of androgens on seminal vesicle growth and secretory activity may be differentiated.

• Molecules and Cells
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• v.46 no.1
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• pp.33-40
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• 2023

RNAs are versatile molecules that are primarily involved in gene regulation and can thus be widely used to advance the fields of therapeutics and diagnostics. In particular, circular RNAs which are highly stable, have emerged as strong candidates for use on next-generation therapeutic platforms. Endogenous circular RNAs control gene regulatory networks by interacting with other biomolecules or through translation into polypeptides. Circular RNAs exhibit cell-type specific expression patterns, which can be altered in tissues and body fluids depending on pathophysiological conditions. Circular RNAs that are aberrantly expressed in diseases can function as biomarkers or therapeutic targets. Moreover, exogenous circular RNAs synthesized in vitro can be introduced into cells as therapeutic molecules to modulate gene expression networks in vivo. Depending on the purpose, synthetic circular RNA sequences can either be identical to endogenous circular RNA sequences or artificially designed. In this review, we introduce the life cycle and known functions of intracellular circular RNAs. The current stage of endogenous circular RNAs as biomarkers and therapeutic targets is also described. Finally, approaches and considerations that are important for applying the available knowledge on endogenous circular RNAs to design exogenous circular RNAs for therapeutic purposes are presented.

• New & Renewable Energy
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• v.19 no.4
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• pp.53-60
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• 2023

The Computational Fluid Dynamics (CFD) model is a method of studying the flow phenomenon of fluid using a computer and finding partial differential equations that dominate processes such as heat dispersion through numerical analysis. Through CFD, a lot of information about flow disorders such as speed, pressure, density, and concentration can be obtained, and it is used in various fields from energy and aircraft design to weather prediction and environmental modeling. The simulation used for fluid analysis in this study utilized Gexcon's (FLACS) CODE, such as Norway, through overseas journals, for the accuracy of the analysis results through many experiments. It was analyzed that a technology for treating two or more catalysts with physical properties under low-temperature atmospheric pressure conditions could not be found in the prior art. Therefore, it would be desirable to establish a continuous plan by reinforcing data that can prove the effectiveness of producing efficient synthetic oil (renewable oil) through the application that pyrolysis under low-temperature and atmospheric pressure conditions.

• Applied Chemistry for Engineering
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• v.16 no.6
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• pp.834-841
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• 2005

Polyethylene glycol esters (PEG-esters) were synthesized by condensation reaction of dicarboxylic acid such as adipic acid and sebacic acid and several PEGs. The PEG-esters were analyzed by FT-IR, $^1H-NMR$ and HPLC for structure analysis, and by GPC for molecular weight. Through the analysis of surface tension, critical micelle concentration (CMC), aluminum contact angle of water solution containing the PEG-ester, the synthetic PEG-esters are proven to exhibit surfactant properties. The surface tension ranged from 45 to 50 dyn/cm depended on the concentration and structures of the PEG-esters. The surface tension of PEG-esters with sebacic acid moiety and short polyoxyethylene unit resulted in lower value than that of PEG-ester with adipic acid moiety and long polyoxyethylene unit. The CMC of water solution containing 2.5 wt% PEG-ester with sebacic acid moiety estimated at $0.9{\times}10^{-5}{\sim}5.3{\times}10^{-3}mol/L$ depended on the structures of PEG-esters. The CMC of PEG-esters with long polyoxyethlene unit showed a higher value than that of PEG-esters with short polyoxyethylene unit. Meanwhile, the CMC of PEG-esters with adipic acid moiety was not distinct due to their high hydrophilic character. As the results of contact angle and cutting time aginst aluminum, the contact angle ranged from $45^{\circ}$ to $53^{\circ}$ depended on the concentration of PEG-esters. The cutting time of aluminum showed the shortest value at CMC, but the longest value above CMC. This fact indicates that the CMC of PEG-esters is a very important factor in drilling aluminum.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.17 no.4
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• pp.282-288
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• 2007

그 동안 많은 역학연구를 통해서 금속가공유(metalworking fluid, MWFs) 노출과 여러 조직에서 암 발생 위험과의 관계를 밝혔지만, 금속가공유 종류(비수용성, 수용성, 합성, 준합성)별로 구분된 위험은 아직 완전하게 규명되지 않았다. 역학조사에서 금속가공유 노출을 대체할 수 있는 인자(surrogate)로서 정성적(qualitative), 명목적(ordinal) 혹은 준정량적인(semi-quantitative) 변수들(금속가공유에 대한 노출 유무, 노출 정도: 높음, 낮음 등, 직업 유무, 근무기간 등)을 이용하여 금속가공유 노출을 평가하였다. 이러한 노출평가방법은 기본적으로 금속가공유 노출 강도(intensity)가 고려되지 않을 뿐만 아니라 노출 분류 오류(misclassification)도 항상 존재할 수 있어 금속가공유 노출은 물론이고 종류별 위험을 밝히기 어렵다. 일부 역학연구에서 금속가공유 종류별 누적 노출양(cumulative exposure level)과 암위험과의 관계를 밝혔다. 이러한 연구결과들은 모두 금속가공유 종류별로 과거노출을 추정할 수 있는 자료(정량적인 노출평가자료, 과거직업력, 취급했던 금속가공유 종류 등)가 잘 기록되어 있는 1개의 대규모 자동차공장에서 나온 것들이다. 따라서 금속가공유에 대한 노출자료가 부족하고 사용특성에 대한 기록이 없거나 부족한 일반 인구나 산업을 대상으로 한 역학연구에서는 금속가공유의 종류별 위험을 밝히는것은 불가능하다. 금속가공유 종류별로 과거 노출에 대한 확률(probability)을 추정하는데 일반적으로 활용할 수 있는 노출확률 메트릭스를 개발하는 것이 필요하다.