• Steel and Composite Structures
• /
• 제32권1호
• /
• pp.59-66
• /
• 2019

Hollow steel-reinforced concrete-filled GFRP tubular member is a new kind of composite members. Firstly set the mold in the GFRP tube (non-bearing component), then set the longitudinal reinforcements with stirrups (steel reinforcement cage) between the GFRP tube and the mold, and filled the concrete between them. Through the axial compression test of the hollow steel-reinforced concrete-filled GFRP tubular member, the working mechanism and failure modes of composite members were obtained. Based on the experiment, when the load reached the ranges of $55-70%P_u$ ($P_u-ultimate$ load), white cracks appeared on the surface of the GFRP tubes of specimens. At that time, the confinement effects of the GFRP tubes on core concrete were obvious. Keep loading, the ranges of white cracks were expanding, and the confinement effects increased proportionally. In addition, the damages of specimens, which were accompanied with great noise, were marked by fiber breaking and resin cracking on the surface of GFRP tubes, also accompanied with concrete crushing. The bearing capacity of the axially compressed components increased with the increase of reinforcement ratio, and decreased with the increase of hollow ratio. When the reinforcement ratio was increased from 0 to 4.30%, the bearing capacity was increased by about 23%. When the diameter of hollow part was decreased from 55mm to 0, the bearing capacity was increased by about 32%.

• 한국초전도ㆍ저온공학회논문지
• /
• 제8권1호
• /
• pp.49-53
• /
• 2006

This paper specifies the new power supply paradigm converting 154kV voltage level into 22.9kV class with equivalent capacity using superconducting rower facilities and analyze the fault current characteristics with and without HTS-FCL (High Temperature Superconducting-Fault Current Limiter). Superconducting new power system is the power system to which applies the 22.9kV HTS cable in parallel to HTS transformer and HTS-FCL with low-voltage and mass-capacity characteristics replacing 154kV conventional cable and transformer. The fault current of superconducting new power system will increase greatly because of the mass capacity and low impedance of HTS transformer and cable. This means that the HTS-FCL is necessary to reduce the fault current below the breaking current of circuit breaker. This paper analyze the fault current and suggests the parallel HTS-FCL scheme complementing the inherent problem of HTS-FCL, that is recovery after quenching is impossible within shorter than a few seconds.

• 전기학회논문지
• /
• 제67권5호
• /
• pp.644-650
• /
• 2018

According to a miniaturization and integration of electric device, a little size of fuse satisfying the current carrying capacity as well as an explosive tolerance and current interrupt rating are required. Fe-Ni alloy is applied to decrease an oxidation of fuse elements. A resistance and T.C.R(temperature coefficient of resistance) of a fuse are analyzed by changing a content of Ni And full rated current I-T curve from 1A to 6.3A has been tested. In order to an explosive energy, a straight wire type is selected to reduce a fuse melting time. An interrupt rating test was conducted by changing a content of Ni and the optimal content of Ni is to be 40%.

• Journal of Advanced Marine Engineering and Technology
• /
• 제36권2호
• /
• pp.315-320
• /
• 2012

일반적으로 저압 회로 보호용 장치로는 ICCB(Insulated case circuit breakers), PCB(Power circuit breakers) 그리고 MCCB(Molded case circuit breakers)를 들 수 있다. 이들 중 가장 보편적으로 사용되는 배선용 차단기(MCCB)는 휴즈 또는 개폐기의 단점인 안전성, 제어성, 협조성 등을 보완한 것이다. 차단기의 성능은 사고전류 발생 시 트립 동작이 순간적이고, 절연능력이 뛰어나야 하므로 매우 중요하다. 따라서 차단기의 개폐 성능은 매우 중요하므로 개폐 기구부의 접촉자 구조 및 접점 그리고 링크구조 등에 대한 기구학적 연구가 필요하다. 본 논문에서는 저압차단기의 기구적 동역학 모델링과 해석을 수행하여 가동자의 개리속도가 빠를수록 차단특성에 유리하다는 결론을 얻었으며, 실제 실험을 통하여 이를 검증하였다.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2006년도 추계학술대회
• /
• pp.438-442
• /
• 2006

The degradation of Nafion membrane by hydrogen peroxide was investigated in polymer electrolyte membrane fuel cell (PEMFC). Degradation tests were carried out in a solution of $10{\sim}30%$ hydrogen peroxide containing 4ppm $Fe^{2+}$ ion which is well known as Fenton's reagent at $80^{\circ}C$ for 48hr. Characterization of degraded membranes were examined through the IR, Water-uptake, Ion exchange capacity, mechanical strength and $H_2$ permeability. After degradation, C-F, S-O and C-O chemical bonds of membrane were broken by radical formed by $H_2O_2$ decomposition. Breaking of C-F bond which is the membrane backbone reduced the mechanical strength of Nafion membrane and hence induced pinholes, resulting in increase of $H_2$ crossover through the membrane. Also the decomposition of C-O and S-O, side chain and terminal bond of membrane, decreased the ion exchange capacity of the membrane.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제54권4호
• /
• pp.149-153
• /
• 2005

We have investigated thermal properties showed by changing the content of carbon black which is the component parts of semiconductive shield in underground power transmission cable. Specimens were made of sheet with the nine of those for measurement. Heat capacity (${\Delta}$H), glass transition temperature (Tg) and melting temperature (Tm) were measured by DSC (Differential Scanning Calorimetry). The ranges of measurement temperature were from -100($^{\circ}C$) to 100($^{\circ}C$), and heating rate was 4($^{\circ}C$/min). And then thermal diffusivity was measured by LFA 447. The dimension of measurement temperature was 25[$^{\circ}C$]. Glass transition temperature of specimens was showed near -25[$^{\circ}C$] and the heat capacity and the melting temperature from the DSC results were simultaneously decreased according to increasing the content of carbon black, while thermal diffusivity was increased according to increasing the content of carbon black. Because ionic impurities of carbon black having Fe, Co, Mn, Al and Zn are rapidly passed kinetic energy increasing the number of times breaking during the unit time with the near particles according to increasing vibration of particles by the applied heat energy.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
• /
• pp.160.2-160.2
• /
• 2014

Recently silicon has attracted intense interest as a promising anode material of lithium-ion batteries due to its extremely high capacity of 4200 mA/g (for Li4.2Si) that is much higher than 372 mAh/g (for LiC6) of graphite. However, it seriously suffers from large volume change (even up to 300%) of the electrode upon lithiation, leading to its pulverization or mechanical failure during lithiation/delithiation processes and the rapid capacity fading. To overcome this problem, Si nanowires have been considered. Use of such Si nanowires provides their facile relaxation during lithiation/delithiation without mechanical breaking. To design better Si electrodes, a study to unveil atomic-scale mechanisms involving the volume expansion and the phase transformation upon lithiation is critical. In order to investigate the lithiation mechanism in Si nanowires, we have developed a reactive force field (ReaxFF) for Si-Li systems based on density functional theory calculations. The ReaxFF method provides a highly transferable simulation method for atomistic scale simulation on chemical reactions at the nanosecond and nanometer scale. Molecular dynamics (MD) simulations with the ReaxFF reproduces well experimental anisotropic volume expansion of Si nanowires during lithiation and diffusion behaviors of lithium atoms, indicating that it would be definitely helpful to investigate lithiation mechanism of Si electrodes and then design new Si electrodes.

• 한국전기전자재료학회논문지
• /
• 제32권4호
• /
• pp.327-332
• /
• 2019

Recently, inverter control systems have attracted immense attention to increase the energy efficiency. However, such systems use repeated on/off high currents for linear operation control, instead of the prevalent step variable current control method. Hence, there arise concerns of personal and property damage, especially due to the durability, explosive characteristics, and operating speed of the fuse, which is responsible for safety and is one of the internal components using current control. Therefore, in this paper, we propose an IEC60127-4 SMD sub-miniature fuse, consisting of Ag-Cu alloys and ceramic powder for arc soothing. The IEC60127-4 SMD sub-miniature fuse has high durability and cut-off capacity, and operates safely in dangerous circumstances caused by the inverter control system.

• 동아시아식생활학회지
• /
• 제17권3호
• /
• pp.393-401
• /
• 2007

인삼의 여러 생리 활성 가운데 항산화 정도를 알아보기 위하여 백삼(6 년근), 백삼(5 년근), 피부백삼(5 년근), 피부백삼 (4 년근) 의 80% 에탄올 엑기스, 에틸아세테이트 분획, 수포화 부탄올 분획, 물 분획을 얻은 후 LC/Mass 를 사용하여 사포닌 함량을 조사하고 기존의 여러 가지 항산화 작용 측정 방법들의 오류를 없애고 더욱 정확한 결과를 낼 수 있는 대처 방안으로 선정된 ORAC Assay에 의해 항산화 활성을 검토하였다. 인삼 중 사포닌은 ginsenoside Rg 1 과 Rb1 이 주요 성분으로 다량 함유하고 있었으며, Rc, Rb2, Re 등이 뒤를 이었고, 그밖에도 Rd, Rg3, Rh1가 널리 분포하고 있었다. 피부백삼 5 년근의 경우 에탄올 엑기스와 수포화 부탄올 분획에서 다른 인삼 분획에 비해 높은 함유량을 보였으나 실험의 한계상 인삼 재배기간과 인삼 종류별 각각의 분획에 대한 사포닌 함량 비교는 어려웠다. 인삼의 각 분획별 항산화 활성은 80% 에탄올 엑기스, 에틸아세테이트 분획, 수포화 부탄올 분획, 물 분획 모두에서 나타났고 비교적 전체 유기 용매 분획의 값이 비슷하였으며, 수층 분획이 다소 낮은 활성을 보였다. 검체 인삼들의 각 용매추출 분획 상호간의 유의성 비교에서는 모든 인삼 검체의 에틸아세테이트 분획에서만 유의성을 나타내었다(p>0.05). 인삼 중 항산화 활성은 에틸아세테이트 층으로 이행되는 폴리페놀 계통 성분이나 일부 비극성의 사포닌에 의한 것으로 추측되고 있으나 모든 분획에서 나타난 것으로 보아 이들 외에 산성 다당체, 당 단백질, 수용성 다당류 등 다른 생리활성 물질에 대한 연구가 요구된다.

• 한국생물공학회:학술대회논문집
• /
• 한국생물공학회 2003년도 생물공학의 동향(XIII)
• /
• pp.770-774
• /
• 2003

The effects of pH and/or NaCl concentration on the Fat Binding Capacity (FBC) of rhamnolipid and the physical properties of surimi gel containing rhamnolipid were investigated. The FBC of rhamnolipid was measured 162% of value at pH 7 and 0% NaCl concentration. The whiteness of surimi gel containing rhamnolipid significantly (p< 0.05) lower than control. In contrast, surimi gel containing rhamnolipid compare with control were enhanced significantly(p < 0.05) breaking force and deformation.