• Proceedings of the KSME Conference
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• 2004.04a
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• pp.7-12
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• 2004

Large-sized pins are usually used to lift and handle large low speed diesel engine crankshaft. There has then been a need to reduce and optimize the weight of the traditionally used pins. Making an hole by cutting the inside of the pin out was investigated in view of static and fracture strength. To compensate the stress increase caused by the introduction of the inner hole, the groove in the circumferential direction pre-existing on the pin is to be removed. Finite element analysis was carried out for both the original model and weight reduced model. Stress intensity factors for semi-elliptical defects assumed on the pin for the original model and weight reduced model was calculated using the ASME method and compared with the fracture toughness test result of the pin material. The diameter of the cutting hole for the revised model was determined based on the analysis results.

• Environmental Engineering Research
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• v.17 no.4
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• pp.191-196
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• 2012

Analysis of hydrological safety as well as the determination of many substance concentrations are necessary when bioreactor systems are introduced to landfill operations. Therefore, hydrological and substance balance model was developed since it can be applied to various bioreactor landfill operation systems. For the final evaluation of the model's effectiveness, four different methods of injections (leachate alone, leachate and organic waste water, leachate and reverse osmosis concentrate, and all the above three combination) was applied to 1st landfill site of Sudokwon landfill. As a result, the water content of the hypothetical cases for four different systematic bioreactors is projected to be increased up to 35.5% in next 10 years, and this indicated that there will be no problems in meeting the hydrological safety. Also, the final $Cl^-$ concentration after 10-yr time period was projected to be between from minimum 126 to maximum 3,238 mg/L, which could be still a decrease from the original value of 3,278 mg/L. According to the proposed model, whether the substance concentration becomes increased or decreased largely depends on the ratio of initial quantity of inner landfill leachate and the rate of injection.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.10
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• pp.1111-1117
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• 2013

In this paper, the shape accuracy of the stamped hat-type product is quantified and analyzed with ultra high strength steel (UHSS) sheets. The shape of the hat-type product is designed in order to simplify the geometry of the side sill and the stamping methodology is proposed in order to verify the effect of the stamping procedure on the springback amount. Experiments and finite element analyses are conducted with four kinds of the forming sequences. The springback amounts are measured and compared according to the forming procedure with the embossing shape. Experimental result in company with analysis one illustrate that the springback amount is reduced with embossing in the padding operation. They also fully demonstrates the proposed forming procedure and the analysis method can be effectively applied to the process design for producing parts with ultra high strength steel.

• Journal of the Korean Society of Safety
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• v.34 no.5
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• pp.139-143
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• 2019

In this study, we tried to derive the most severe scenario and its critical speed by 1-D collision simulation with a variable formation vehicle in order to prepare for the change of demand in Seoul Metropolitan Subway Line 3, which is operated by fixed arrangement. After establishing various collision scenario conditions, the friction coefficient between the wheel and the rail was evaluated as 0.3, which is considered to be severe. As a result of analysis according to all scenarios, the most severe scenario conditions were confirmed by comparing rubber shock absorber performance and vehicle collision deceleration. In addition, a typical wheel-rail friction coefficient was derived through accident cases, and the analysis was performed again and compared. Finally, the criterion of the critical speed in the condition of the friction coefficient of the normal wheel - rail condition was confirmed.

• Journal of Biomedical Engineering Research
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• v.40 no.1
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• pp.15-19
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• 2019

In this study, Theta Gamma Coupling (TGC) analysis was carried out after performing simple and repeated upper limb exercise and comparative experiment to observe changes in the motor cortex of the brain through TGC and to see if mobile rehabilitation therapy is actually effective. As a result, exercise using mobile devices showed higher TGC values in motor cortex as compared with simple repeat upper limb exercise. In addition, paired t-test using SPSS showed statistically significant difference between exercise using mobile devices and simple repeat exercise at P3(t=3.390, df(degree of freedom)=12, p value=0.005). Exercise using mobile devices is effective for rehabilitation because it increases the Theta-Gamma Coupling and activates the motor cortex. Also, since the mobile game contents required the subject to detailed athletic ability adjustment with immersion in the task, it may be thought that brain activation is stronger than simple rehabilitation.

• Asia-Pacific Journal of Business
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• v.12 no.2
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• pp.1-24
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• 2021

Purpose - We aim to verify whether CSM activities increase investment efficiency, and to verify whether the influence of CSM activities on investment efficiency is discriminatory depending on whether or not they belong to chaebol. Design/methodology/approach - Using 4,701 Korean firm-year observations over the 2011-2017 period, we used multiple regression analysis. CSM is measured by the evaluation score of the Korea Corporate Governance Service (KCGS). Findings - Our study confirms that CSM is a significantly positive relationship with investment efficiency. This shows that, as a result of CSM, the increased earnings quality acts as an incentive to increase investment efficiency. Next, in analysis of a dataset into two groups (a chaebol, non-chaebol), the results show that the relationship between CSM and investment efficiency differs among detailed indicator activities depending on whether or not they belong to chaebol. Research implications or Originality - It is significant that this study focused on and analyzed CSM as a determinant of investment efficiency, and examined the effects of whether or not it belongs to chaebol in the relationship between CSM and investment efficiency. Our results, which suggested that CSM can increase investment efficiency, are expected to provide important implications not only for managers but also for investors and supervisors.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.17 no.1
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• pp.28-35
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• 2021

The flow accelerated corrosion (FAC) is one of significant aging and degradation mechanism and can affect structural integrity of CANDU feeder pipes. Pipe burst can occur under normal operation pressure (min. 10 MPa) if wall-thinning of the feeder pipe due to FAC is accumulated. Previous studies considered simple shapes of feeder pipe with local wall-thinning in order to conservatively assess structural integrity of wall-thinned feeder pipe. In this paper, a new FE model is developed, having an actual shape of the feeder pipe (double bent) as well as the actual wall-thinning shape and location based on the in-service inspection result. Then, the burst pressure assessment of the wall-thinned feeder pipe is performed using lower bound limit load analysis considering elastic-perfectly plastic material. In addition, an improved formulation to predict the burst pressure of the wall-thinned feeder pipe is presented and the safety margin is compared with an existing assessment method.

• Journal of Surface Science and Engineering
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• v.34 no.5
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• pp.421-428
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• 2001

New WC-CrN superlattice film was deposited on Si substrate (500$\mu\textrm{m}$) using cathodic arc ion plating system. The microstructure and mechanical properties of the film depend on the superlattice period (λ). In the X-ray diffraction analysis (XRD), preferred orientation of microstructure was changed according to various superlattice periods(λ). During the Transmission Electron Microscope analysis (TEM), microstructure and superlattice period (λ) of the WC - CrN superlattice film was confirmed. Hardness and adhesion of the deposited film was evaluated by nanoindentation test and scratch test, respectively. As a result of nanoindentation test, the hardness of WC - CrN superlattice film was gained about 40GPa at superlattice period (λ) with 7nm. Also residual stress with various superlattice period (λ) was measured on Si wafer (100$\mu\textrm{m}$) by conventional beam-bending technique. The residual stress of the film was reduced to a value of 0.2 GPa by introducing Ti - WC buffer layers periodically with a thickness ratio ($t_{buffer}$/$t_{buffer+superlattice}$ ). To the end, for the evaluation of oxidation resistance at the elevated temperature, CrN single layer and WC - CrN superlattice films with various superlattice periods on SKD61 substrate was measured and compared with the oxidation resistance.

• Journal of radiological science and technology
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• v.47 no.1
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• pp.13-19
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• 2024

Control of scattered radiation is one of very important factors in the use of medical radiation. In general X-ray exam, the causes, measurement methods, and the kind of detectors of scattered rays within the radiation area are diverse. In this study, the dose of scattered ray was measured by changing the thickness of the polycarbonate phantom and the tube voltage. As a result of measurement of scattered radiation, the results show that the scattered dose significantly(p<.05) increased with growing of thickness of phantom in the tube voltage 40, 50 and 60 kVp(F(p)<.05, R²>64%). As tube voltage increased at all phantom thicknesses, the scattered dose also significantly(p<.05) increased(F(p)<.05, R²>69%). In cases where a significant correlation was shown, the coefficient of determination of more than 60% was shown in regression analysis. The results of this study can be used as data on scattered radiation dose according to the tube voltage and the object thickness in general X-ray imaging exam.

• Journal of Cadastre & Land InformatiX
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• v.45 no.2
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• pp.161-173
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• 2015

The influence of climate change on rainfall patterns has triggered landslide and debris flow with casualties and property damage. This study constructed DSM and Orthophoto by using UAV surveying technique and evaluated landslide risk area by applying GIS data into the infinite slope stability model. As a result of the estimation of slope stability in a site, the slope instability has $SI{\leq}1.0$ with cover area 46,396m2, and the distribution percentage was 18.2%. The most dangerous section has $SI{\leq}0.0$ with its cover area 7,988m2, and the ratio was 0.8%. The reviews regarding the risk of landslide and debris flow risk by stability index and river channel analysis respectively help being able to designate the hazard zone due to heavy rainfall. Therefore the analysis result of this study will need to reinforce soil slope and plan their safety measures in the future.