• 한국기계가공학회지
• /
• 제20권7호
• /
• pp.48-57
• /
• 2021

The main research content of this paper is to evaluate the structural integrity and the cooling performance of 4250 kVA power transformer with ONAN(Oil Natural and Air Natural) mode. The dynamic analysis is used to verify the structural safety of the transformer by seismic loading. The transformer structure is simplified and NX software is used to build a three-dimensional model, and ANSYS commercial software is used to calculate the stress and deformation by applying corresponding load. The analysis result was evaluated whether it satisfies the design requirements according to the IEEE Std 693 standard. In terms of thermal analysis to evaluate the cooling performance, the thermal physical model is used to calculate the heat exchange between the radiator and the tank in the steady state, and the result is input into the Fluent software to calculate the internal temperature field of the transformer tank, which reduces the calculation cost of thermal fluid. Comparing the simulated hot spot temperature and top oil temperature of the transformer with the calculation results of the IEC60076 classic model, it is found that the error is only 1.9%.

• 대한화학회지
• /
• 제24권1호
• /
• pp.80-85
• /
• 1980

N-비닐요소(VU)와 초산비닐(VAc)의 라디칼혼성중합을 $60^{\circ}C$에서 삼종류의 용매중에서 행하였다. VU-VAc혼성중합체를 methanolysis하여 VU-비닐알코올(VA)혼성중합체를 제조하고 이 VU-VA혼성중합체의 질소를 분석함으로써 VU-VAc 혼성중합의 단위체반응성비와 VU의 Q와 $\varrho$값을 구하였다. 중합용매로서 메탄올과 메탄올-티옥산을 사용한 경우에 얻어진 VU의 Q 및 e값은 이중결합에 >NCO-기를 가지는 다른 단위체의 Q 및 $\varrho$ 값과 비교된다. $\varrho$ 값은 VU의 요소기가 전자를 밀어주는 기라는 것을 시사한다. VU-VAc계의 혼성중합 파라미터에 VU는 큰 용매효과를 나타내며 이 결과는 중합온도에서 VU가 tautomer와 평형을 이루고 있는 것으로 하여 해석될 수 있다.

• Korean Chemical Engineering Research
• /
• 제56권3호
• /
• pp.361-369
• /
• 2018

A manufacturing method has been devised to prepare novel heterogeneous cation exchange membranes by mixing ethylene vinyl acetate (EVA) copolymers with a commercial cation exchange resin. Optimum material characteristics, mixture ratios and manufacturing conditions have been worked out for achieving favorable membrane performance. Ion exchange capacity, electrical resistance, water uptake, swelling ratio and tensile strength properties were measured. SEM analysis was used to monitor morphology. Effects of vinyl acetate (VA) content, melt index (MI) and ion exchange resin content on properties of heterogeneous cation exchange membranes have been discussed. An application test was carried out by mounting a selected membrane in a membrane capacitive deionization (MCDI) system to investigate its desalination capability. 0.92 meq/g of ion exchange capacity, $8.7{\Omega}.cm^2$ of electrical resistance, $40kgf/cm^2$ of tensile strength, 19% of swelling ratio, 42% of water uptake, and 56.4% salt removal rate were achieved at best. VA content plays a leading role on the extent of physical properties and performance; however, MI is important for having uniform distribution of resin grains and achieving better ionic conductivity. Overall, manufacturing cost has been suppressed to 5-10% of that of homogeneous ion exchange membranes.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2004년도 춘계학술대회 논문집 방전 플라즈마 유기절연재료 초전도 자성체연구회
• /
• pp.133-137
• /
• 2004

In this paper, we investigated impurities content, absorption properties, and thermal properties showing by changing the content of carbon black which is semiconductive materials for underground power transmission. Specimens were made of sheet form with the three of existing resins and the nine of specimens for measurement. Impurities content of specimens and absorption properties were measured by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer) and Karl Fisher. And high temperature, heat degradation initiation temperature, and heat weight loss were measured by TGA (Thermogravimetric Analysis). The dimension of measurement temperature was 0$[^{\circ}]$ to 800$[^{\circ}]$, and rising temperature was 10$[^{\circ}/min]$. Impurities content was highly measured according to increasing the content of carbon black from this experimental result also absorption amount was increased according to these properties. Specially, impurities content values of the A1 and A2 of existing resins were measured more than 4000[ppm]. Heat degradation initiation temperature from the TGA results was decreased according to increasing the content of carbon black. All over, heat stabilities were EEA>EBA>pEVA. That is, heat stabilities of EVA containing the weak VA(vinyl acetate) against heat was measured the lowest.

• 공업화학
• /
• 제5권5호
• /
• pp.889-898
• /
• 1994

생분해성 고분자의 실용화 검토를 위하여 생분해성 copolyesterethylene(CPEE)과 vinlyacete(VA)기가 15%인 범용 ethylene vinylacetate(EVA)를 0~100%까지 10% 간격으로 전조성에 걸쳐 용융 블랜드하였다. 용융 블랜드한 시료의 녹는점 변화와 결정화 온도를 시차 주사 열량계로 측정하여 miscibility에 관하여 고찰하였으며 만능시험기를 이용하여 인장강도 및 신장률을 측정하였다. 녹는점 변화와 결정화 온도로부터 CPEE 조성이 10%와 90%일 때 약간의 miscibility를 보였으며, 인장강도값으로부터는 CPEE 조성이 50~80%를 제외한 조성에서 유용한 compatibility를 갖는 것을 알았다. SEM 관찰을 통한 각조성에서의 형태학적 모습으로부터 이들 상용성의 결과를 확인하였으며, 또한 CPEE/EVA 블랜드의 생분해성은 미생물접종 전후의 시편의 변화를 Image analyzer로 관찰함으로써 확인하였다.

• 한국연초학회지
• /
• 제7권2호
• /
• pp.111-121
• /
• 1985

The present study was carried out to obtain some basic informations of the breeding of tobacco varieties. Genetically divergent 8 varieties, 3 flue-cured, 2 burley and 3 sun-cured tobaccos, were used in half diallel cross. In order to analyze the heterosis, combining abilities, modes of inheritance and correlations for some agronomic and chemical characters, 8 parents and 28 $F_2$ were tested. The results obtained were summarized as follows: The percentages of heterosis for yield, stem diameter, internode length and total sugar content in $F_2$ hybrid were positive , where-as those for the other characters were negative. Yield had significant positive genotypic and phenotypic correlations with plant height, days to flower, leaves per plant, leaf length, leaf width and leaf shape index (Leaf length/leaf width). General (GCA) and specific combining abilities (SCA) for all characters of $F_2$ hybrid were significant. In the effect of GCA, yield was greater in combinations of Bulgaria and Xanthi, days to flower and leaves per plant were those of Burley 21 and Va 528, leaf length and width were those of Coker 139, respectively. In the effect of SCA, the major part of characters were greater than those of others in the combinations of Burley 21, Va 528, Hicks.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제55권12호
• /
• pp.570-575
• /
• 2006

In this paper, we have investigated thermal properties by changing the content of carbon nanotube, which is component part of semiconductive shield in underground power transmission cable. Heat capacity (${\Delta}H$), glass transition temperature (Tg) and melting temperature (Tm) were measured with the samples of eight, through DSC (Differential Scanning Calorimetry), and the measurement ranges of temperature selected from $-100[^{\circ}C]\;to\;100[^{\circ}C]$ with heating temperature selected per $4[^{\circ}C/min]$ Also, high temperature, heat degradation initiation temperature, and heat weight loss were measured by TGA (Thermogravimetric Analysis) in the temperature from $0[^{\circ}C]\;to\;700[^{\circ}C]$ with rising temperature of $10[^{\circ}C/min]$. As a result, the Glass transition temperatures of the sample were showed near $-20[^{\circ}C]{\sim}25[^{\circ}C]$, and the heat capacity and melting temperature from the DSC was increased according to increasing the content of carbon nanotube, while, thermal diffusivity was increased according to increasing the content of carbon nanotube. Also, heat degradation initiation temperature from the TGA results was increasing according to increasing the content of carbon nanotube with CNT/EEA. Therefore, heat stabilities of EVA, which contained the we VA (vinyl acetate), showed the lowest.

• 한국정보과학회논문지:데이타베이스
• /
• 제37권5호
• /
• pp.228-237
• /
• 2010

고차원 데이터에 대한 다양한 색인 구조가 제안되어 왔음에도 불구하고, 인터넷 서비스로서 이미지 및 동영상의 내용 기반 검색을 지원하기 위해서는 고확장성 지원 및 k-최근접점 검색 성능 향상을 지원하는 새로운 고차원 데이터의 색인 구조가 절실히 요구된다. 이에 우리는 다중 컴퓨팅 노드를 바탕으로 구축되는 분산 색인 구조로 분산 벡터 근사 트리(Distributed Vector Approximation-tree)를 제안한다. 분산 벡터 근사 트리는 대용량의 고차원 데이터로부터 추출한 샘플 데이터를 바탕으로 hybrid spill-tree를 구축하고, hybrid spill-tree외 말단 노드 각각에 분산 컴퓨팅 노드를 매핑하여 VA-file용 구축하는 두 레벨의 분산 색인 구조이다. 우리는 다중 컴퓨팅 노드들 상에 구축된 분산 벡터 근사 트리를 바탕으로 병렬 k-최근접점 검색을 수행함으로써 검씩 성능을 향상시킨다. 본 논문에서는 서로 다른 분포의 데이터 집합을 바탕으로 한 성능 시험 결과를 통하여, 분산 벡터 근사 트리가 기존의 고확장성을 지원하는 색인 구조와 비교하여 검색 정확도에 대한 손실 없이 더 빠른 k-최근접점 검색을 수행함을 보인다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1995년도 춘계학술대회 논문집
• /
• pp.115-119
• /
• 1995

Electrical conduction characteristics of Polyethylene/Ethylene vinyl acetate blends of varing vinyl acetate content(1% and 4%) were investigated at electric fields ranging from 10$\^$6/ to 10.$\^$8/ V/cm over the temperature range of 30 and 85$^{\circ}C$. It was obser-ved that the extent of current density was changed at the blends and the rate of change of current den-sity was slightly suppressed at high field range, but PE and EVA were not shown. The change of con-duction characteristics and a suppression in rate of change of current density were attributed to the VA content in PE.EVA blends.

• Elastomers and Composites
• /
• 제52권1호
• /
• pp.27-34
• /
• 2017

In this experiment, blends of ethylene vinyl acetate rubber (EVM) with a vinyl acetate (VA) content greater than 40 wt% and ethylene propylene rubber (EPM) were prepared by mechanical mixing; a number of parameters of the blends, including oil resistance, morphological and dynamic mechanical properties and flame retardancy, were subsequently measured. In the $100^{\circ}C$ oil resistance test, both the ammonium polyphosphate/dipentaerythritol/expandable graphite (APP/DPER/EG) and aluminum hydroxide (ATH) flame retardant systems showed an increase in volume change with increasing EPM content. For the ATH system, the dispersion shape was coarse and aggregation was observed. The results of a dynamic mechanical test showed slightly higher E' and E'' for the APP/DPER/EG flame retardant system when compared to the single ATH system. For both the APP/DPER/EG and ATH systems, the limited oxygen index (LOI) tests performed at increasing content of EPM showed a LOI value higher than 30, indicating excellent flame resistance.