• 제목/요약/키워드: Mixing Factor

검색결과 471건 처리시간 0.025초

중첩전압(직류+교류 60Hz)에서 산화아연 피뢰기 소자의 누설전류 특성 (The characteristic of leakage current in ZnO surge arrestor elements with mixed direct and 60Hz voltage)

  • 이복희;박건영;강성만;최휘성;오성균
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2003년도 추계학술대회 논문집 전기물성,응용부문
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    • pp.186-188
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    • 2003
  • The ZnO surge arrester is the protective device for limiting surge voltages on equipment by diverting surge current and returning the device to its original status. The occurrence of overvoltage appears in any phase to AC power supply system and it appears in mixing AC and impulse voltages, moreover because HVDC power supply system uses converter in semiconductor, it makes mixed DC and high harmonics voltages. In this study, the various mixed AC and DC voltages was made for investigating the degradation effect of ZnO arrester according to mixed voltage. As a result, the increase of DC component to mixed voltages causes the increase of resistive component of total leakage current to ZnO block. In changing V-I curve for mixed voltages, the cross-over point acts a factor as making the proper capacitor size of an equivalent circuit for ZnO block.

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경면 연삭기 베드를 위한 레진 콘크리트에 관한 연구

  • 김현석;김기수;이대길
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 1993년도 춘계학술대회 논문집
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    • pp.108-113
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    • 1993
  • The material for the machine tool structure should have high static stiffiness and damping in its property to improve both the static and dynamic performances. The static stiffness of a machine tool can be inceased by using either higher modulus material in the structure of a machine tool. However, the machine tool structrue with high stiffness but low damping is vulnerable to vibration at the resonance frequencies of the structure . For the high precision and highsped machine tool structure, therefore, the high damping capacity is most important in order to suppress vibration. The damping of a machine tool can not be increased by increasing the static stiffness. The best way to increase the damping capacity of the machine tool structure is to use a composite material which is composed of on material with high stiffness with low damping and another material with low stiffness with high damping. Therefore, in this paper, the bed of the ultra high precision grinding machine for mirror surface machining of brittle materials such as ceramics and composite materials was designed and manufactured with the epoxy concrete material. The epoxy concrete material was prepared by mixing epoxy resin with different size sands and gravels. The modulus, compressive strength, coefficient of thermal expansion, specific heat, and damping factor were measured by varying the compaction ratio, sizes and contents of the ingredients to assess the effect of the processing parameters on the mechanical properties of the material. Based of the measured properties, the prototype epoxy resin concrete bed for the mirror surface CNC grinding machine was designed and manufactured.

마이크로 역학과 레올로지 제어에 의한 고인성 섬유복합재료 ECC(Engineered Cementitious Composite)의 다양한 타설 공정 구현 (Facilitation of the Diverse Processing of High Ductile ECC (Engineered Cementitious Composite) Based on Micromechanics and Rheological Control)

  • 김윤용;김정수
    • 한국농공학회논문집
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    • 제47권5호
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    • pp.27-39
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    • 2005
  • In the recent design of high ductile fiber-reinforced ECC (engineered cementitious composite), optimizing both processing and mechanical properties for specific applications is critical. This study presents an innovative method to develop new class ECCs, which possess the different fluid properties to facilitate diverse types of processing (i.e., self-consolidating or shotcrete processing) while maintaining ductile hardened properties. In the material design concept, we employ a parallel control of fresh and hardened properties by using micromechanics and cement rheology. Control of colloidal interaction between the particles is regarded as a key factor to allow the performance of the specific processing. To determine how to control the particle interactions and the viscosity of cement suspension, we first introduce two chemical admixtures including a highly charged polyelectrolyte and a non-ionic polymer. Optimized mixing steps and dosages we, then, obtained within the solid concentration predetermined based on micromechanical principle. Test results indicate that the rheological properties altered by this approach were revealed to be highly effective in obtaining the desired function of the fresh ECC, allowing us to readily achieve hardened properties, represented by pseudo strain-hardening behavior in uniaxial tension.

해창만의 수질환경변동 및 담수방류의 영향평가 (Effect of the Freshwater Discharge on Water Quality Variation and in Haechang Bay, Korea)

  • 이대인;조현서;이문옥
    • 환경영향평가
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    • 제12권5호
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    • pp.341-348
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    • 2003
  • Seasonal characteristics of water quality and effect of the freshwater discharge during open the tide embankment in Haechang Bay were evaluated. In the freshwater, where interior of the tide embankment, COD and Chl-a exceeded about 4mg/L and $10mg/m^3$, respectively, independent of season, while in the seawater they showed high values in April and July in contrast to the other period due to input of freshwater and increase of phytoplankton, respectively. The content of seawater inorganic nitrogen maintained a relatively high level at inner part of the bay, whereas high values of inorganic phosphorus content was distributed at all over the bay. The limiting factor for algal growth was nitrogen with respect to the N/P ratio. The compass of influence by the freshwater discharge in April was quite different with water pollutants. As a result of the salinity variation with time, the freshwater extended strongly to offshore from the surface layer without mixing with depth when open the tide embankment, and reached within about one hour at a station which is 3.5km from the tide embankment. To effective water quality management of Haechang Bay, discharge rate and pollutant loads should be controlled.

Study of Dielectric Properties of a Potential RBD Palm Oil and RBD Soybean Oil Mixture as Insulating Liquid in Transformer

  • Azmi, Kiasatina;Ahmad, Azmier;Kamarol, Mohamad
    • Journal of Electrical Engineering and Technology
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    • 제10권5호
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    • pp.2105-2119
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    • 2015
  • This paper reported the experimental result of dielectric properties of Refined, Bleached and Deodorized Palm Oil (RBDPO) combined with 0-50% of Refined, Bleached and Deodorized Soybean Oil (RBDSO). The dielectric strength and relative permittivity of RBDPO/RBDSO was higher compared to mineral oil at all ranges of ratios and temperatures which indicated a positive sign for its possible use as insulating liquid in a transformer. All ratios of the RBDPO/RBDSO mixture also demonstrated lower dissipation factor compared to mineral oil at 40℃, 70℃ and 90℃. Apart from that, the kinematic viscosity for the oil mixtures shown exceeded the IEC 60296 as well as the mineral oil results. 70%RBDPO/30%RBDSO mixture ratio was chosen as the best mixing percentage after comparison was made with the mineral oil and IEC 60296 standard where the mixture accumulated the most satisfactory of dielectric properties hence making it as the potential candidate for palm and soybean-based transformer oil.

Tape casting 법을 이용한 적층형 세라믹 액츄에이터의 제작 (Fabrication of Multilayer Ceramic Actuator using Tape Casting Method)

  • 하문수;이동만;정순종;김인성;민복기;송재성
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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    • pp.556-560
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    • 2002
  • The rheological characteristics of PNN-PZT ceramics with high electromechanical coupling factor and electricstrictive constant was investigated. Green sheets of piezoelectric PNN-PZT ceramics were made by tape-casting method with controlling the mixing ratio of a dispersant, an organic binder, and a plasticizer. When the dispersant content was 1 wt.%, the slurry showed the best rheological characteristics for tape casting. The amounts of the plasticizer and the binder was simultaneously varied in the ranges of 1.5~18 and 3~9 wt.%, respectively. When both the plasticizer and binder of 6 wt.% mixed in the solution, respectiveley, the highest green density of the sheet was obtained without macrodefects. Multilyered structures of PNN-PZT/Ag-Pd were successfully fabricated using the optimized tape casting condition. The polarization behavior of these actuators seemed to similar to typical electricstrictive polarization behavior. The multilayer ceramic actuator is about $0.6{\times}10^{-3}$ of strain.

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도축우의 근출혈 유발 인자에 관한 연구 (A study on the risk factors associated with blood splash in slaughtered cattle)

  • 구경녀;변병래;심항섭;이호승;김경숙;우종태
    • 한국동물위생학회지
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    • 제32권3호
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    • pp.287-292
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    • 2009
  • This study was conducted to analyse risk factors which can influence on blood splash in slaughtered cattle in D slaughterhouse located in Gyeonggi province in 2008. A total of 13,056 cattle were studied by several risk factors such as species, gender, body weight, meat grade, weather (temperature), transport distance, lairaging time, moving time, mixing cattle from different sources. As the result of analysis, the total mean of blood splash was 0.70% and the rate was highest (0.94%) in castrated Hanwoo. The heavier body weight, the higher blood splash rate. The farms which have had more than one experience of blood splash tend to have high grade in meat quality. As a weather factor, the rate in summer season was lower than in winter season. It increased as transport distance getting longer and decreased when the lairaging time was 2~5 hours. We could know many risk factors strongly related with the occurrence of blood splash from this study.

모델을 이용한 음식물퇴비 혼합토양에서의 Pb 흡착 및 이동성 평가 (The assessment of the adsorption and movement of Pb in mixed soil with food compost using model)

  • 주유연;강선홍
    • 상하수도학회지
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    • 제22권2호
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    • pp.251-257
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    • 2008
  • Food compost, having a higher organic contents than soil, could be an alternative material to prevent the proliferation of heavy metals contamination in soil. In this study we used a convection-dispersion local equilibrium sorption model(CDE) and a two-site non-equilibrium sorption model to find the effects on the adsorption and transportation of Pb by mixing food compost with soil and we also tried to find the effect of velocity and concentration of the injected solution on the characteristics of Pb. We measured Pb concentrations in injection-liquid and in effluent, and then applied them to CXTFIT program. As a result of column experiments, some parameters(D, R, ${\beta}$, ${\omega}$) used in two-site non-equilibrium adsorption model were obtained. Characteristics of Pb adsorption and transport were analyzed using the parameters(D, R, ${\beta}$, ${\omega}$) obtained from the CXTFIT program, We could know that mixed soil with food compost showed a higher adsorption capacity from the retardation factor(R) calculated from the breakthrough curve(BTCs) of Pb. Rs of soil and mixed soil are 20.45, 37.45 respectively, indicating that the adsorption and the transportation characteristics could be accessed quantitatively by using of two-site non-equilibrium adsorption model.

콘크리트 초기강도에 영향을 미치는 수화물의 정량분석에 관한 연구 (A Quantitative Analysis on Feature of Hydrate Affecting Early-Age Strength)

  • 송태협;이문환;이세현;박동철
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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    • pp.583-586
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    • 2005
  • Strength of concrete is very important factor in design and quality management and may represent overall quality of concrete. Such strength of concrete may differ depending on amount of cement mixed, water and fine aggregate ratio. Classic concrete products have been produced mainly with ordinary portland cement(hereinafter 'cement'), water and fine aggregate as shown above, but various additives and mixture materials have been used for concrete manufacturing, along with development of high functional concrete and diversification of structures. Various kinds of chemical mixtures agents and mixture materials have been used as it requires concretes with other features which cannot be solved with existing materials only, such as high strength, high flexibility and no-separation in the water. Such addition of various mixture agents may cause change in cement hydrate, affecting strength. Hydration of cement is the process of producing potassium hydroxide, C-S-H, C-A-H and Ettringite, while causing heat generation reaction after it is mixed with water, and generation amounts of such hydrates play lots of roles in condensation and hardening. This study aims to analyze its strength and features with hydrates by making specimen according to curing temperature, types of mixture agent, mixing ratio and ages and by analyzing such hydrates in order to analyze role of cement hydrate on early strength of concrete.

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카올리나이트의 침식특성 (Erosion Characteristics of Kaolinite)

  • 이주형;곽기석;박재현;정문경
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2004년도 춘계학술발표회
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    • pp.533-537
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    • 2004
  • The erodibility of soil is an important factor to scour, especially in fine-grained soils. In this study, the erosion characteristics of kaolinite are quantified through the scour rate tests using the Erosion Function Apparatus called EFA. The basic soil property tests are also performed. The kaolinite samples are prepared by mixing with distilled water and formed to the designed maximum consolidation pressure of 60, 110, 160, 240, 360kPa, respectively. The results of the scour rate tests are presented in a format of a plot showing the relationship between erosion rates and shear stresses. Erosion properties of kaolinite showed a striking contrast according to the maximum consolidation pressure, and a correlation was established between the erosion properties of kaolinite and the soil properties; water content, undrained shear strength, dry density.

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