• Journal of Electrical Engineering and Technology
• /
• 제12권6호
• /
• pp.2333-2341
• /
• 2017

Mineral oils are commonly used as transformer insulation oils but these oils are obtained from non-renewable and non-sustainable sources, which is highly undesirable. For this reason, natural ester oils are now being used in replacement of mineral oils because of their good biodegradability, high cooling stability, good oxidation stability and excellent insulation performance. Nanotechnology has gained prominence in both academic and industrial fields over the years and it has been shown in previous studies that nanoscale materials are useful for transformers due to their favourable dielectric properties. The objective of this study is to compare the AC breakdown voltage and viscosity of natural ester oil with three types of nanofluids. The natural ester oil-based nanofluids are prepared by mixing palm fatty acid ester (PFAE) oil with three types of nanoparticles at a concentration of 0.01 g/l: (1) $Fe_3O_4$ conductive nanoparticles, (2) $TiO_2$ semi-conductive nanoparticles and (3) $Al_2O_3$ insulating nanoparticles. The AC breakdown voltage of the oil samples is analysed using Weibull statistical analysis and the results reveal that the PFAE oil-based $Fe_3O_4$ nanofluid gives exceptional dielectric performance compared to other oil samples, whereby the AC breakdown voltage increases by 43%. It can be concluded that the PFAE oil-based $Fe_3O_4$ nanofluid is a promising dielectric liquid to substitute mineral oils.

• 신재생에너지
• /
• 제8권4호
• /
• pp.38-43
• /
• 2012

Biodiesel is non-petroleum based fuel produced from vegetable oils or animal fats through transesterification. The compositions of saturated and unsaturated fatty acids in the feedstocks are important factors for biodiesel quality in terms of low-temperature fluidity and oxidative stability. The goal of this study is to improve the cold flow property of biodiesel from vegetable and animal origin containing highly saturated methyl esters (approx. 50%). In this purpose poly-saturated methyl esters in palm and tallow biodiesel were removed via urea-based fractionation and then the recovered fractions (enriched unsaturated fatty acid methyl esters) were supplemented with cold flow improvers. The highest concentration of unsaturated fatty acid methyl esters (93.8%) was obtained using a urea/fatty acid ratio of 3:1 at the crystallization temperature of $0^{\circ}C$ for 17 hours in incubation, with recovery of 71% and the addition of cold flow improver (Flozol$^{(R)}$ 515, 3,000 ppm) to the enriched poly-unsaturated fatty acid methyl esters reduced the CFPP(cold filter plugging point) of palm biodiesel from $12^{\circ}C$ to $-42^{\circ}C$. In tallow biodiesel both the enrichment of unsaturated fatty acid methyl esters (93.71%) and the addition of cold flow improver (Infineum R408, 3,000ppm) reduced the CFPP from $10^{\circ}C$ to $-32^{\circ}C$.

• Korean Chemical Engineering Research
• /
• 제61권2호
• /
• pp.278-286
• /
• 2023

The present work evaluated the production of biohydrogen under mesophilic and thermophilic conditions through dark fermentation of palm oil mill effluent (POME) in batch mode using the design of experiment methodology. Response surface methodology (RSM) was applied to investigate the influence of the two significant parameters, POME concentration as substrate (5, 12.5, and 20 g/l), and volumetric substrate to inoculum ratio (1:1, 1:1.5, and 1:2, v/v.%), with inoculum concentration of 14.3 g VSS/l. All the experiments were analyzed at 37 ℃ and 55 ℃ at an incubation time of 24 h. The highest chemical oxygen demand (COD) removal, hydrogen content (H₂%), and hydrogen yield (HY) at a substrate concentration of 12.5 g COD/l and S:I ratio of 1:1.5 in mesophilic and thermophilic conditions were obtained (27.3, 24.2%), (57.92, 66.24%), and (6.43, 12.27 ml H₂/g COD_rem), respectively. The results show that thermophilic temperature in terms of COD removal was more effective for higher COD concentrations than for lower concentrations. Optimum parameters projected by RSM with S:I ratio of 1:1.6 and POME concentration of 14.3 g COD/l showed higher results in both temperatures. It is recognized how RSM and optimization processes can predict and affect the process performance under different operational conditions.

• The Journal of Asian Finance, Economics and Business
• /
• 제3권3호
• /
• pp.79-91
• /
• 2016

This paper is the first of its kind using a non-linear approach based on cross-correlation function (CCF) to investigate the information arrival hypothesis in crude palm oil (CPO) futures market. Based on daily data from 1986 to 2010, our empirical results reveal that: First, the volume of volatility is not a proxy of information flow. Second, dependence causality running from current return to future volume in conditional variance exhibit an asymmetric pattern of time span with different signs of correlation between price and volume series. This finding indicates the presence of noise traders' hypothesis of price-volume interaction in CPO futures market. Both findings suggest that this futures market is weak-form inefficiency. In terms of investors' behavior, they tend to change their expectations on current return based on errors made in previous trade in generating abnormal volume in the subsequent period. As implied, it is advisable for the investors devise their future trading strategies according to time span and changes of return.

• Journal of Microbiology and Biotechnology
• /
• 제20권12호
• /
• pp.1664-1671
• /
• 2010

A new biosurfactant producer was isolated from palm-oil-contaminated soil and later identified through morphology and DNA sequencing as the yeast-like fungus Exophiala dermatitidis. Biosurfactant production was catalyzed by vegetable oil, supplemented with a basal medium. The culture conditions that provided the biosurfactant with the highest surface activity were found to be 5% palm oil with 0.08% $NH_4NO_3$, at a pH of 5.3, with shaking at 200 rpm, and a temperature of $30^{\circ}C$ for a 14-day period of incubation. The biosurfactant was purified, in accordance with surfactant properties, by solvent fractionation using silica gel column chromatography. The chemical structure of the strongest surface-active compound was elucidated through the use of NMR and mass spectroscopy, and noted to be monoolein, which then went on to demonstrate antiproliferative activity against cervical cancer (HeLa) and leukemia (U937) cell lines in a dose-dependent manner. Interestingly, no cytotoxicity was observed with normal cells even when high concentrations were used. Cell and DNA morphological changes, in both cancer cell lines, were observed to be cell shrinkage, membrane blebbling, and DNA fragmentation.

• Journal of Korean Vacuum Science & Technology
• /
• 제6권1호
• /
• pp.36-39
• /
• 2002

Molybdena powder was heated at both 660$^{\circ}C$ and 700$^{\circ}C$ for half-hour in an evaporation-deposition device. The molybdena thin films deposited on the surfaces of alumina ceramics displayed two kinds of fractal aggregates, i.e., the stackings of ribbon-like crystals and ramified palm-like structures. It is revealed from the experimental results that the microstructures of these fractal aggregates depended strongly on their growth conditions. The dynamics of fractal growth of molybdena thin film is discussed.

• 한국균학회지
• /
• 제16권4호
• /
• pp.204-206
• /
• 1988

Chemical analysis of both sclerotia and the fruits of Pleurotus tuber-regium showed higher values for such elements as calcium(Ca), iron(Fe), zine(Zn) in the fruits than in the sclerotia. On the contrary magnessium(Mg) was found to be higher in sclerotia than in the fruits. protein and carbohydrate were also found to be more in the fruits. There was no significant difference between the chemical values of old(1 year) and fresh sclerotia. Oil palm fruit fibre substrate produced sporophores with higher values for the minerals, protein and carbohydrate than those on riversand substrate.

• Journal of Chest Surgery
• /
• 제32권5호
• /
• pp.461-464
• /
• 1999

배경: 흉강경을 이용한 T2 교감신경절단술은 수장부다한증의 효과적인 치료법이다. 교감신경을 절단하면 다한증 증상이 소실되는 것은 물론 피하혈관의 확장으로 동측 손바닥 온도가 올라간다. 그러나 반대측 손바닥의 온도 변화에 대해서는 밝혀진 바가 적다. 저자들은 수장부다한증 환자에서 교감신경절단술 과정에 나타나는 양측 손바닥 온도의 변화양상을 알아보고자 하였다. 대상 및 방법: 일차성 수장부다한증 환자 15명에서 T2 교감신경절단술을 시행하였다. 수술중 양측 손바닥에 피부온도감지패취를 부착하여 손바닥의 온도를 관찰기록하였다. 결과: 먼저 좌측 2번 흉부교감신경을 절단하자 동측 손바닥의 온도는 상승하고 반대측 손바닥의 온도는 감소하였다. 두 손바닥의 온도차는 우측 교감신경절단전에 가장 컸으며(좌측 34.6$\pm$0.9 $^{\circ}C$, 우측 31.6$\pm$1.3$^{\circ}C$, P < 0.0001) 반대쪽(우측) 교감신경을 절단하자 감소하였던 우측 손바닥의 온도가 상승하여 수술종료시 두 손바닥의 온도차가 없어졌다(좌측 34.7$\pm$1.0 $^{\circ}C$, 우측 34.4$\pm$1.0 $^{\circ}C$, P=0.415). 결론: 수장부 다한증에서 교감신경절단술을 시행할 때는 상지에 분포하는 교감신경이 정확히 차단되었는가를 확인하는 것이 중요하다. 이를 위해서 수술중 손바닥 피부온도를 측정하여 온도상승을 확인한다. 반대측 손바닥 온도가 감소하는 기전인 혈관수축에는 교차억제효과(Cross inhibitory effect)가 관계될 것으로 생각되며 향후 이에 대한 많은 연구가 이루어져야 할 것으로 생각된다.

• Asian-Australasian Journal of Animal Sciences
• /
• 제26권6호
• /
• pp.820-826
• /
• 2013

The objective of this study was to determine the effect of rain tree pod meal with palm oil supplementation on feed intake, digestibility, microbial protein synthesis and microbial populations in dairy cows. Four, multiparous early-lactation Holstein-Friesian crossbred (75%) lactating dairy cows with an initial body weight (BW) of $405{\pm}40$ kg and $36{\pm}8$ DIM were randomly assigned to receive dietary treatments according to a $4{\times}4$ Latin square design. The four dietary treatments were un-supplementation (control), supplementation with rain tree pod meal (RPM) at 60 g/kg, supplementation with palm oil (PO) at 20 g/kg, and supplementation with RPM at 60 g/kg and PO at 20 g/kg (RPO), of total dry matter intake. The cows were offered concentrates, at a ratio of concentrate to milk production of 1:2, and chopped 30 g/kg of urea treated rice straw was fed ad libitum. The RPM contained condensed tannins and crude saponins at 88 and 141 g/kg of DM, respectively. It was found that supplementation with RPM and/or PO to dairy cows diets did not show negative effects on feed intake and ruminal pH and BUN at any times of sampling (p>0.05). However, RPM supplementation resulted in lower crude protein digestibility, $NH_3$-N concentration and number of proteolytic bacteria. It resulted in greater allantoin absorption and microbial crude protein (p<0.05). In addition, dairy cows showed a higher efficiency of microbial N supply (EMNS) in both RPM and RPO treatments. Moreover, NDF digestibility and cellulolytic bacteria numbers were highest in RPO supplementation (p<0.05) while, supplementation with RPM and/or PO decreased the protozoa population in dairy cows. Based on this study, supplementation with RPM and/or PO in diets could improve fiber digestibility, microbial protein synthesis in terms of quantity and efficiency and microbial populations in dairy cows.

• 콘크리트학회논문집
• /
• 제21권5호
• /
• pp.565-572
• /
• 2009

이 연구에서는 전기화학적 기법을 사용하여 혼합콘크리트의 일종인 palm oil fuel ash(POFA) 콘크리트의 부식저항성을 평가하였다. POFA는 야자수로부터 야자유를 정제하고 난후 야자수 재로 추출되어진 산업 재생 폐기물을 일컫는다. POFA 콘크리트의 기본 물성 특성분석을 위해서 초기재령에서의 POFA 콘크리트의 압축강도, 슬럼프, 중량감소율, 블리딩 및 팽창비 특성 분석실험을 수행하였다. 한편, 내구성 특성분석을 위해서 염소이온침투시험 및 중성화 침투시험도 수행하였다. 마지막으로 전기화학적 균열치유기법을 사용하여, 가압전압 특성분석, 갈바닉 전류특성분석 및 선형분극저항 평가 등의 부식저항성 평가를 실시하였다. 실험 결과로부터, 장기재령의 강도, 블리딩, 슬럼프 특성, 팽창비, 염소이온 확산성, 탄산화 저항성 및 부식저항성의 향상 효과가 활성화 되어진 POFA 콘크리트의 포졸란 반응에 기인하여 이루어지고 있음을 확인하였다. 따라서 POFA 콘크리트는 그린-재생 자원으로서 시멘트계 대체 결합재로서의 이용가능성이 있음을 확인할 수 있었다.