• The Journal of Engineering Geology
• /
• v.15 no.3
• /
• pp.337-348
• /
• 2005

Jurassic granite from Pocheon area were tested to investigate the effect of microcracks on mechanical properties of the granite. Three oriented core specimens were used for uniaxial compressive tests and each core specimen are perpendicular to the axes'R'(rift plane),'c'(grain plane) and'H'(hardway plane), respectively Among vacious elastic constants, the variation of Poisson's ratio as function of the directions was examined. From the related chart between ratio of failure strength and Poisson's ratio, H-specimen shows the highest range in Poisson's ratio and Poisson's ratio decreases in the order of C-specimen and R-specimen. The curve pattern is nearly linear in stage $I\simIII$ but the slope increases abruptly in stage H-3. As shown in the related chart, diverging point of a curve is formed when ratio of failure strength is $0.92\sim0.96$ Stage IV -3 is out of elastic region. The behaviour of rock in the four fracturing stages was analyzed in term of the stress-volumetric strain me. From the stress increment-volumetric strain equations governing the behaviour of rock, characteristic material constants, a, n, Q, m and $\varepsilon_v^{mcf}$, were determined. Among these, inherent microcrack porosity$(a, 10^{-3})$ and compaction exponent(n) in the microcrack closure region(stage I ) show an order of $a^R(3.82)>a^G(3.38)>a^H(2.32)\;and\;n^R(3.69)>n^G(2.79)>n^H(1.99)4, respectively. Especially, critical volumetric microcrack strain($\varepsilon_v^{mcf}$) in the stage W is highest in the H-specimen, normal to the hardway plane. These results indicate a strong correlation between two major sets of microcracks and mechanical properties such as Poisson's ratio and material constants. Correlation of strength anisotropy with microcrack orientation can have important application in rock fracture studies.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.7
• /
• pp.325-336
• /
• 2018

The aim of this study was to provide fundamental information on the validity and credibility of the Korean geometric psychological assessment (GEOPIA) by investigating the degree of relation between the GEOPIA and the MBTI. Data was collected from 331 subjects aged 19 to 70, residing in Seoul, Gyeonggi Province, Jeolla Province, or Gyeongsang Province. Participants completed the GEOPIA and the MBTI during the period of May to September 2017. The study calculated Cronbach's ${\alpha}$ to verify the tests' validity and reliability through SPSS. For the relational analysis between the results of the tests, we conducted a one-way analysis of variance on the first group of the GEOPIA's personality types, and the Scheffe Test if significant relationship was found. The study found that the circle type was predisposed to ESFJ, the triangle type to ESTJ, the rectangle type to ISTJ, and S type to INFP. Higher scores of feeling (F) and perceiving (P) corresponded to circle and S types, thinking (T) and judging (J) for triangle and rectangle types, extroversion (E) for circle and triangle types, and introversion (I) for rectangle and S types. These confirmed the substantial relations between the GEOPIA and the MBTI.

• Journal of the Korean Applied Science and Technology
• /
• v.31 no.3
• /
• pp.352-358
• /
• 2014

We were investigated the stability through the electrochemical characteristics of saturated fatty acid(C12, C14, C16, C18) monolayer LB films by cyclic voltammetry. Saturated fatty acid monolayer LB films was deposited on the indium tin oxide(ITO) glass by the LB method. The electrochemical properties were measured by cyclic voltammetry with a three-electrode system in 0.1 N $NaClO_4$ solution. The measuring range was continuously oxidized to 1650 mV, with an initial potential of -1350 mV was reduced. Scanning rates of 50, 100, 150, 200, and 250 mV/s were set. As a result, LB monolayer films of saturated fatty acid were appeared on irreversible processes by the oxidation current from the cyclic voltammogram. Diffusion coefficient(D) of saturated fatty acid(C12, C14, C16, and C18) was calculated 22.231, 2.461, 7.114 and 2.371 ($cm^2s^{-1}{\times}10^{-4}$) in 0.1 N $NaClO_4$ solution, respectively.

• Journal of Advanced Marine Engineering and Technology
• /
• v.25 no.2
• /
• pp.345-345
• /
• 2001

This paper was studied on the characteristics of galvanic corrosion and its protection on heat exchanger tube plate in the sea water. In this paper, behavior of pitting corrosion of Ni-al bronze connected with Ti tube was measured af flow velocity of 0 m/s and 2.4 m/s. To protect galvanic corrosion, the protection characteristics of Ni-Al bronze connected with Ti tube by Zn-base alloys galvanic anode and hexagonal nylon insert was investigated. Main results obtained asre al follows: 1) The galvanic corrosion of Ni-Al bronze connected with Ti-tube is more active than single Ni-al bronze. 2) As the circuit resistance increase under the cathodic protection employing Zn-base alloys galvanic anode, Ni-al bronze connected with Ti tube is cathodically unpolarized. 3) The corrosion of Ni-Al bronze connected with Ti tube by nylon insert controls approximately 73% than not nylon insert.

• 한국신재생에너지학회:학술대회논문집
• /
• 2005.06a
• /
• pp.64-67
• /
• 2005

A vibration monitoring system for a small size wind turbine (WIT) is established and operated. The monitoring system consists of monolithic integrated chip accelerometer for vibration monitoring, anemometers for wind data acquisition and auxiliary sensors for atmospheric data. Using the monitoring system, vibration response of a 6kW stand alone WIT generator is investigated. Acceleration data of the WIT tower under various operation condition is acquired in real time using LabVIEW and the data are remotely transferred from the test site to the laboratory in school by internet. Vibration response characteristics of the tower structure are diagnosed in the aspect of stability of W/T. Wind data and electrical power performance are also investigated with the stability problem.

• Journal of Korean Society for Quality Management
• /
• v.30 no.4
• /
• pp.106-119
• /
• 2002

The fatigue curve with estimated parameters represents the estimate of the median or mean life at a given applied stress But, in order to assist a designer in making decisions regarding the fatigue failure mode, it is common practice to construct a design curve on the lower or safe side of data. In this study, to overcome the limitations(i.e., no runout, equal variance, and quality of the approximation, etc) of Shen, Wirsching, and Cashman's method which suggested the approximate design curve for nonlinear models using tolerance interval constructed by Owen's method, an algorithm to find design curves under the fatigue model using a parametric bootstrap method, is proposed and illustrated with multiple fatigue data sets.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1998.06a
• /
• pp.156-163
• /
• 1998

During an actual forming operation, a material may undergo considrably large changes in strain path, and these changes can significantly alter the forming limits. So, in this study, modified forming limit curves(FLCs) in complex strain path are determined with specially designed jig to give test specimens with desired prestrains in uniaxial or biaxial deformation mode. In another part of present study, theoretical prediction of FLCs is attempted with MK's theory and Hosford's yield criterion to give forming limit curves in positive minor strain region and with Hill's local necking theory in negative minor strain region. Comparison of these theoretical results with experimental ones will be mentioned for both linear and complex strain path.

• Journal of Sensor Science and Technology
• /
• v.7 no.6
• /
• pp.426-431
• /
• 1998

This paper describes electrochemical etch-stop characteristics in THAH/IPA/pyrazine solution. I-V curves of n- and p-type Si in THAH/IPA/pyrazine solution were obtained. OCP(Open Circuit Potential) and PP (Passivation Potential) of p-type Si were -1.2 V and 0.1 V, and of n-type Si were -1.3 V and -0.2 V, respectively. Both n- and p-type Si, etching rates were abruptly decreased at potentials anodic to the PP. The etch-stop characteristics in THAH/IPA/pyrazine solution were observed. Since accurate etching stop occurs at pn junction, Si diaphragms having thickness of epi-layer were fabricated. Etching rate is highest at optimum etching condition, TMAH 25wt.%/IPA 17vol.%/pyrazine 0.1g/100ml. thus the elapsed time of etch-stop was reduced.

• Journal of Ocean Engineering and Technology
• /
• v.8 no.2
• /
• pp.173-184
• /
• 1994

원자력 압력용기강의 탄소성 파괴인성값 $J_IC$를 CT형 시험편을 이용하여 검토하였으며, 평활 시험편 및 측면홈 시험편의 두께는 각각 $B_O$=25.4mm, $B_N$=20.4mm 이다. 측면홈의 깊이는 19.7% 이며, 홈의 각도는 90 .deg.로 가공하였다. 탄소성 파괴인성시험은 ASTM E813-81과 JSME S001-81의 추천방법에 따라 실시하였다. 두 추천방법으로 실험한 결과 ASTM 방법에 의한 $J_IC$값이 과대평가됨으로써 부대조건에 만족되지 못하였지만 JSME방법은 만족되었다. 측면홈 시험편은 R고선법에 의한 ductile tearing의 결정이 평활 시험편보다 용이하였으며, 이에 따른 $J_IC$값의 정확성을 배가 할 수 있었다. 또한 임계 스트레치존 폭($SZW_C$)은 측면홈에 의한 높은 3축응력이 발생되어 평활시험편보다 적게 나타났으며, 이러한 복합적인 원인에 기인하여 스트레치존법에 의한 $J_IC$평가는 R곡선법에 의한 평가보다 약간 과대평가됨을 알 수 있었다.

• Proceedings of the KAIS Fall Conference
• /
• 2001.05a
• /
• pp.40-46
• /
• 2001

The thermal stability of $Al_2TiO_{5}$ ceramics was improved by formation of solid solution with MgO, such as $MgAl_2O_4$ spinel through electrofusion in an arc furnance, and by limitation of grain size and microcracks with $SiO_2$, $ZrO_2$ and ${\alpha}$-$Al_2O_3$. The low thermal expansion properties of $Al_2TiO_{5}$ composites show the thermal hysteresis curves due to the strong anisotropy of $Al_2TiO_{5}$. These phenomena are explained by the opening and closing of microcracks. The relation between thermal hysteresis, microstructures and sintering temperature were studied by dilatometry.