• 한국세라믹학회지
• /
• 제53권3호
• /
• pp.301-305
• /
• 2016

We investigate proton conduction in a nonstoichiometric ${\Sigma}3$ $BaZrO_3$ (210)[001] tilt grain boundary using density functional theory (DFT). We employ the space charge layer (SCL) and structural disorder (SD) models with the introduction of protons and oxygen vacancies into the system. The segregation energies of proton and oxygen vacancy are determined as -0.70 and -0.54 eV, respectively. Based on this data, we obtain a Schottky barrier height of 0.52 V and defect concentrations at 600K, in agreement with the reported experimental values. We calculate the energy barrier for proton migration across the grain boundary core as 0.61 eV, from which we derive proton mobility. We also obtain the proton conductivity from the knowledge of proton concentration and mobility. We find that the calculated conductivity of the nonstoichiometric grain boundary is similar to those of the stoichiometric ones in the literature.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
• /
• pp.647-652
• /
• 1998

Recently, many strengthening methods are developed and used to rehabilitate existing structure. One of the popualr methods is the strengthening with steel plate. But steel plate have a defect that is a debondig at the end of the steel plate due to stress concentration. The objective of this paper is an experimental study for improving bonding properties of a strengthening plate. The two normally reinforced beams and ten strengthened beams steel plate, which has various notches were tested. The test results show that the notches of strengthening plate improve post-yield behavior significantly compared. It is proved that the notch in a strengthening plate increase of ulimate strength after the yield strength 9% more than ordinary strengthening method.

• 소성∙가공
• /
• 제15권5호
• /
• pp.382-386
• /
• 2006

Preform design is an effective means of achieving the homogeneous deformation of workpiece materials and decreased load in metal forming. However, this approach has not been applied to equal channel angula. pressing (ECAP). In this paper, plastic deformation behavior of workpieces having four different preform shapes during ECAP was investigated using finite element analyses. The results indicated that a preform design of the workpiece head has a beneficial effect on homogeneous deformation, reducing the maximum pressing load at the initial stage and eliminating folding defects at strain concentration points.

• The Korean Journal of Ceramics
• /
• 제4권2호
• /
• pp.136-140
• /
• 1998

This work demonstrates a method for modeling of electrical conductivity in high-temperature proton-conducting oxides. Total conductivity was calculated assuming that it comprises partial conductivities contributed by protons, oxygen ions and electron holes. From the polt $\sigma_{tot}$ vs. $po_2\;{1/4}$ in wet atmosphere, thermodynamic and kinetic parameters were obtained representing transport properties such as concentration and mobility of the charge-carrying defects. The formulas for the calculation of partial conduction were derived based on the defect structure of HTPCs. Illustrative calculation were made for $SrCe_{0.95}Yb_{0.05}O_{2.975}$ system.

• Structural Engineering and Mechanics
• /
• 제53권5호
• /
• pp.1017-1030
• /
• 2015

In this study, the finite element method was used to analyze the distribution of the adhesive shear stresses in the single-lap bonded joint of two plates 2024-T3 aluminum with and without defects. The effects of the adhesive properties (shear modulus, the thickness and the length of the adhesive were highlighted. The results prove that the shear stresses are located on the free edges of the adhesively bonding region, and reach maximum values near the defect, because the concentration of high stress occurs near this area.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권2호
• /
• pp.1551-1554
• /
• 2007

To overcome defect due to large surface of nanoparticle, a redispersible Eu doped $LnPO_4:LnPO_4$ core/shell nanoparticles were prepared in a highboiling coordinating solvent. The particle size of the synthesized core/shell nanophosphors was estimated to be about 8 nm by TEM. In this core/shell nanoparticle, the concentration of Eu ion was optimized on the basis of the emission intensity under UV ray excitation. Also, the PL properties of the nanophosphors have been compared with those of the $LnPO_4:Eu$ nanoparticles.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2004년도 춘계학술대회 논문집
• /
• pp.1084-1089
• /
• 2004

Recently, Orthotropic steel deck bridges, which have long span decks, have been regarded as one of economical as well as durable bridge types. However, Orthotropic steel deck bridge is used by a lot of welding, which may cause welding defect and deformation of connections. This kind of system happens some damages by the fatigue cracks of welding. The cross-connection of longitudinal rib and transversal rib is one of the weakest point because of the fatigue. The secondary stresses which are from the out-plane deformation of transversal rib and the torsion of longitudinal rib make the topical stress concentration phenomenon. But, it is principle that a Bulkhead Plate is not established in the domestic design standard. Therefore, it is estimated that a study for the installing of Bulkhead Plate is needed. This study with considering these circumstances proves efficiency of Bulkhead Plate and will be presented optimal design details through finite element analysis according to change the geometrical system of Bulkhead Plate and the cross-connection area of longitudinal and transversal rib

• 한국전기전자재료학회논문지
• /
• 제29권5호
• /
• pp.307-311
• /
• 2016

Although there are existing Residual Current Protective Device (RCD) including detect electric leakage and elements such as short circuit and surge, the occurrence of incidents caused by electric faults, including fire, are still constant. The purpose of this study is to analyze the causes of accidents through the electric field distribution in the interpretation of the fault contact breaker. Simulation results by the arc fault has shown the convergence of temperature and electric field to the defect. Through their simulation results, the main cause of erosion phenomena in circuit breaker bar is the electric arc by concentration of electric field not due to dissolve by temperature.

• 한국산업융합학회 논문집
• /
• 제7권1호
• /
• pp.69-82
• /
• 2004

Recently, in the food, paper, steel and plastic industries, plate or sheet type products have been produced by the rolling drum. Steam heating drums are introduced into plastic products facilities in order to keep the density, microstructure, and strength of material uniformly. The drum journal can not help being concentrated by stresses due to the bending and torsion. Especially the drum, heated by high pressure steam, might be exposed in the steam leakage accident. First of all, the stresses on the steam drum journal are to be analyzed, and a case study proper to the subject was performed with a scraped journal, in order to investigate the failure characteristics as well as the initiation and propagation of fatigue cracks, and most probable circumstances of crack initiation. As the result of this study, it is suggested that newly installed drum journal be thoroughly inspected at the next periodic maintenance intervals for evidence of cracking, the microstructure examination and hardness measurements to prevent steam drum from the failure accident.

• 한국세라믹학회지
• /
• 제34권10호
• /
• pp.1015-1020
• /
• 1997

In the Nd;YAG crystal growth by Czochralski method, the relationship between the core formation and the solid-liquid interface was observed by controlling the temperature gradient in the furnace. When the crystal was grown along<111> direction, defects and core area were reduced as the temperature gradient increased. The optimum temperature gradient was found to be higher than 4$0^{\circ}C$/cm. The Nd3+ concentration analysis by ICP-Mass showed that the segregation coefficient was about 20% higher in the core region than core-free region, where the segregation coefficients of core region and core-free region were 0.22 and 0.18, respectively.