• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.1
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• pp.43-50
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• 2005

This test was performed to evaluate the change of the unconfined compressive strength, strength parame¡?ters which resulted from direct shear test and oil residue percents analyzed by GC-MS as time lapse, oil addition. Unconfined compression strength of $10\%$ kerosene added by weight of dry soil recovered as time passed. In the case of $5\%$ kerosene added, the strength recovered as much as clean clayey soil after about 50 days passing. For the case of diesel added, the recovery of unconfined compressive strength was not shown even though about 60 days passed. The strength parameters (c, $\psi$) of kerosene added not changed but for diesel added, the cohesion was very decreased as diesel addition increased. Residual percent of kerosene in the soil was less than that of diesel as time passed.

• Journal of the Korea Institute of Military Science and Technology
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• v.2 no.2
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• pp.251-260
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• 1999

The stiffness of joint parts in the finite element beam model are corrected by the direct comparison between the modal test and analysis model. The corrected stiffness are reviewed according to the boundary conditions of modal testing. For the improved modal test/analysis correction, more modes measured than acceleration sensors are used to make a minimal order system model. In addition, the initial F.E. model is reduced to the degrees of freedom of a minimal order system model, keeping the dynamics of the initial model. Finally, for the parametric correction of the reduced model, the submatrices are used to model the initially assumed stiffness.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.11
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• pp.1626-1630
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• 2015

This paper reflected the Temperature test value and compare the Computational Fluid Dynamic analysis value on particular characteristics of the multi-winding transformer's cooling apparatus equipped by heat pipe with excellent heat transfer ability on design Particularly if you look at multi-winding transformers that supply high-quality Direct current power to silicon production apparatus, heat generation due to high current supply is excessive thus, an innovative cooling apparatus is required in particular for reduced size transformer.

• Journal of Korean Society for Quality Management
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• v.35 no.1
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• pp.61-72
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• 2007

The purpose of this research is to identify causalities among service quality, service value, customer satisfaction and customer loyalty. A Structural Equation Model is used to test the hypothesis of conceptual model. To test the model, we collect data by conducting a survey with 508 patients. Empirical result indicates that three factors such as tangibles, assurance, and empathy have direct impact on service value and customer satisfaction. Especially, customer loyalty is positively related not with service value but with customer satisfaction.

• Ocean Systems Engineering
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• v.9 no.1
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• pp.1-19
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• 2019

Latching control was applied to a Wave Energy Converter (WEC) buoy with direct linear electric Power Take-Off (PTO) systems oscillating in heave direction in waves. The equation of the motion of the WEC buoy in the time-domain is characterized by the wave exciting, hydrostatic, radiation forces and by several damping forces (PTO, brake, and viscous). By applying numerical schemes, such as the semi-analytical and Newmark ${\beta}$ methods, the time series of the heave motion and velocity, and the corresponding extracted power may be obtained. The numerical prediction with the latching control is in accordance with the experimental results from the systematic 1:10-model test in a wave tank at Seoul National University. It was found that the extraction of wave energy may be improved by applying latching control to the WEC, which particularly affects waves longer than the resonant period.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.336-337
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• 2019

본 논문에서는 MMC (Modular Multilevel Converter) 기반 HVDC (High Voltage Direct Current) 시스템을 위한 서브모듈 시험회로를 제안한다. 서브모듈 시험회로는 MMC 기반 HVDC 시스템의 한 암(arm)의 전류를 모사한 서브모듈 시험전류를 만들어 서브모듈 성능시험을 하기 위한 것이다. 본 논문에서는 시험회로의 인덕턴스를 줄이기 위해 5 레벨 인버터를 사용한 새로운 방식의 회로를 제안한다. 시뮬레이션을 통하여 제안하는 서브모듈 시험회로의 타당성을 검증하였다.

• Women's Health Nursing
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• v.8 no.1
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• pp.69-84
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• 2002

The purpose of this study was to develope and test the structural model for depression in middle-aged women. A hypothetical model was constructed on the basis of previous studies and a review of literatures. The conceptual framework was built around eight constructs. Exogenous variables included in this model were volunteer activity, health status & economic status. Endogenous variables were meaning of life, self-esteem, perceived life stress & depression. Empirical data for testing the hypothetical model was collected using a self-report questionnaire from 216 middle-aged women in Pusan City. The Data was collected from May to June, 1999. Reliability of the seven instruments tested with Cronbach's alpha was ranged from .86-.94. For the data analysis, SPSS 7.5 WIN Program and LISREL 8.12 WIN Program were used for descriptive statistics and covariance structural analysis. The results of covariance structure analysis were as follows: 1. The hypothetical model showed a good fit with the empirical data. [$x^2$/df=2.87(p=.72), GFI=1.00, AGFI=.98, RMSR=.025, NFI=.99, standardized residuals ($-1.44{\sim}1.44$)]. 2. To heighten for the parsimony and fitness of the model, a modified model was constructed by deleting according to the criteria of statistical significance and meaning. 3. The modified model also showed a good fit with the data. [$x^2$=5.26(01=7,p=.63), GFI=.99, AGFl=.97, RMSR=.025, NFI=.99, standardized reslduals ($-1.50{\sim}1.45$)] Results of the testing of the hypothesis were as follows : 1. Self-esteem(${\beta}_{42}$=-.48, t=-5.64) had a negative and perceived life stress(${\beta}_{43}$=.20, t=3.21)had a positive direct effect on depression. Meaning of life had a negative direct(${\beta}_{41}$=-.17, t=-2.19) and a negative indirect effect through self-esteem on depression. Volunteer activity had a negative indirect effect through meaning of life, meaning of life and self-esteem on depression. Health status had a negative direct and a negative indirect effect through meaning of life, meaning of life and self-esteem on depression. Economic status had a negative indirect effect through perceived life stress on depression. Self-esteem was the most significant variable. 2. Volunteer activity(${\gamma}_{11}$=.43, t=6.78) and health status(${\gamma}_{12}$=.35, t=4.88) had positive direct effect on meaning of life. 3. Meaning of life(${\beta}_{21}$=.50, t=6.53) had a positive direct effect on self-esteem. Volunteer activity had a positive indirect effect through meaning of life on self-esteem. Health status had a positive direct(${\gamma}_{22}$=.18, t=2.23) and a indirect effect through meaning of life on self-esteem. Meaning of life was the most significant variable. 4. Economic status (${\gamma}_{33}$=-.44, t값=-6.01) had a positive direct effect on perceived life stress. The results of this study showed that self-esteem had the most significant direct effect on depression. Meaning of life and health status had significant direct effect on this self-esteem. Volunteer activity and health status had direct effect on meaning of life. The results of this study suggested that there is a need to develope intervention to promote degree of self-esteem and alleviate degree of depression in middle-aged women.

• Journal of the Korean Orthopaedic Association
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• v.55 no.2
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• pp.143-153
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• 2020

Purpose: To evaluate the timing of the improvement in surgical skills of the direct anterior approach for hip arthroplasty through an analysis of the clinical features and learning curve in 58 cases. Materials and Methods: From November 2016 to November 2018, 58 patients, who were divided into an early half and late half, and underwent hip arthroplasty by the direct anterior approach, were enrolled in this retrospective study. The operation time and complications (fracture, lateral femoral cutaneous nerve injury, heterotopic ossification, infection, and dislocation) were assessed using a chi-square test, paired t-test, and cumulative sum (CUSUM) test. Results: The mean operation times in total hip arthroplasty (26 cases) and bipolar hemi-arthroplasty were 132.1 minutes and 79.7 minutes, respectively, demonstrating a significant difference between the two groups. CUSUM analysis based on the results revealed breakthrough points of the operation time, decreasing to less than the mean operation time because of the 16th case in total hip arthroplasty and 14th case in bipolar hemiarthroplasty. Complications were encountered in the early phase and late phase: five cases of fractures in the early phase, no case in the late phase; eight and two cases of lateral femoral cutaneous nerve injury, respectively; three and two cases of heterotopic ossification, respectively; and one case of dislocation, one case of infection and three cases of others in the early phase. The CUSUM chart for the fracture rate during operation in the early phase revealed the following: five cases fracture (17.2%) in the early phase and no case in the late phase (0%). This highlights the learning curve and the need for monitoring the inadequacy of operation based on the complications. Conclusion: Hip arthroplasty performed by the direct anterior approach based on an anatomical understanding makes it difficult to observe the surgical field and requires a learning curve of at least 30 cases.

• International Journal of Automotive Technology
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• v.6 no.1
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• pp.1-8
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• 2005

Recently, the HSDI (High Speed Direct Injection) diesel engine has been spotlighted as a next generation engine because it has a good potential for high thermal efficiency and fuel economy. This study was carried out to investigate the in-cylinder flow characteristics generated in a HSDI diesel engine with a 4-valve type cylinder head. The four kinds of cylinder head were manufactured to elucidate the effect of intake port geometry on the in-cylinder flow characteristics. The steady flow characteristics such as coefficient of flow rate $(C_{f})$, swirl ratio (Rs), and mass flow rate (m,) were measured by the steady flow test rig and the unsteady flow velocity within a cylinder was measured by PIV. In addition, the in-cylinder flow patterns were visualized by the visualization experiment and these results were compared with simulation results calculated by the commercial CFD code. The steady flow test results indicated that the mass flow rate of the cylinder head with a short distance between the two intake ports is $13\%$ more than that of the other head. However, the non-dimensional swirl ratio is decreased by approximately $15\%$. As a result of in-cylinder flow characteristics obtained by PIV and CFD calculation, we found that the swirl center was eccentric from the cylinder center and the position of swirl center was changed with crank angle. As the piston moves to near the TDC, the swirl center corresponded to the cylinder center and the velocity distribution became uniform. In addition, the results of the calculation are in good agreement with the experimental results.

• Geomechanics and Engineering
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• v.16 no.4
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• pp.385-397
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• 2018

This study evaluates the interfacial properties of composite specimens consisting of shotcrete and sprayed waterproofing membrane. Two different membrane prototypes were first produced and tested for their waterproofing ability. Then composite specimens were prepared and their interfacial properties assessed in direct shear and uniaxial compression tests. The direct shear test showed the peak shear strength and shear stiffness of the composites' interface decreased as the membrane layer became thicker. The shear stiffness, a key input parameter for numerical analysis, was estimated to be 0.32-1.74 GPa/m. Shear stress transfer at the interface between the shotcrete and membrane clearly emerged when measuring peak shear strengths (1-3 MPa) under given normal stress conditions of 0.3-1.5 MPa. The failure mechanism was predominantly shear failure at the interface in most composite specimens, and shear failure in the membranes. The uniaxial compression test yielded normal stiffness values for the composite specimens of 5-24 GPa/m. The composite specimens appeared to fail by the compressive force forming transverse tension cracks, mainly around the shotcrete surface perpendicular to the membrane layer. Even though the composite specimens had strength and stiffness values sufficient for shear stress transfer at the interfaces of the two shotcrete layers and the membrane, the sprayed waterproofing membrane should be as thin as possible whilst ensuring waterproofing so as to obtain higher strength and stiffness at the interface.