• Journal of the Korean Society for Heat Treatment
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• v.36 no.4
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• pp.230-236
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• 2023

The current study deals with the effect of cooling rate and temperature for annealing on medium-carbon Cr-Mo alloy steel, especially for cold heading quality wire rod, to derive the optimum micro-structures for plastic deformation. This is to optimize the spheroidization heat treatment conditions for softening the material. Heat treatment was performed under seven different conditions at a temperature between A_c1 and A_c3, mostly within 720℃ to 760℃, and the main variables at this time were temperature, retention time and cooling rate. Microstructure and phase changes were observed for each test condition, and it was confirmed that they were greatly affected by the cooling rate. It was also confirmed that the cooling rate was changed in the range of 0.1℃/min to 5℃/min and affected by phase deformation and spheroidization fraction. The larger the spheroidization fraction, the lower the hardness, which is associated with the increasing connection of ferrite phases.

• Tribology and Lubricants
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• v.38 no.6
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• pp.227-234
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• 2022

Recently, the demand for improving energy efficiency has rapidly increased because of the growing concerns over environmental issues. In this work, the tribo-test and simulation for the initial wear and lubrication performance were performed for the piston pin in the small end system of the connecting rod of a marine engine, to obtain useful data for improving the efficiency of marine engine systems. In addition, a diamond-like carbon (DLC) coating was applied to the piston pin to explore feasibility of eliminating the bush used in the system. The initial wear and lubrication characteristics between the uncoated piston pin and bush were compared with that between the DLC-coated piston pin and connecting rod in the tribo-test. The simulation for the wear and lubrication performance according to the wear progression was conducted based on the data obtained from the test. The wear characteristics were quantitatively assessed by the wear depth and wear volume, and the lubrication performance was characterized with the change of pressure and minimum oil film thickness with respect to the crank angle. It was found that the DLC-coated piston pin may provide better initial wear characteristics and lubrication performance. The results of this work may provide fundamental information for marine engines with improved efficiency.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.292-298
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• 2008

Seoul Metro and Seoul Metropolitan Rapid Transit Corp. have started installing screen doors at subway platforms to improve the environment of subways and prevent passengers' accidents since 2006. They are still installing screen doors at subway platforms and Metropolitan Rapid Transit Corporations in other areas are also proceeding with installment of screen doors or making preparations for it. Grounding is necessary for installing PSD systems. In case that PSD grounding is connected with existing electrical equipment grounding system, it was decided to install separate grounding for safe operation of PSD system and passenger safety. However, it's very difficult to install new grounding at the subway station compound. A way to improve this condition is that we proceed with grounding by composing grounding station by carbon grounding rod. This paper will mainly deal with how to design and construct carbon ground rod, which has been applied to PSD system grounding since 2006, including its experimental examples. In this paper, ways to secure ground resistance below 5 ohms, which is resistance necessary for PSD grounding, and to compose grounding system were also discussed. Furthermore, a ground test to check the ability to fulfill a role of PSD grounding system was conducted. As a result of applying carbon grounding module, PSD system is being operated without any problem and the installment of PSD system will be continuously expanded in the future. It's also thought that a way to integrate grounding of each functional room which has been installed at the subway station compound and to arrange equipotential grounding should be reviewed and performed promptly.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.567-572
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• 2003

An experimental work is presented to evaluate the retrofit method for improving the flexural capacity of shear walls. Fives shear wall specimens are designed and retrofitted by using carbon fiber materials such as rod, sheet and plate. Cyclic horizontal loads are applied to the specimens under constant axial load, $0.1f_{ck}A_g$. Test result shows that specimens with additional flexural reinforcement have the increased initial stiffness and deformation capacity. However, the strength is not improved as much as expected. This is because that the flexural reinforcement is pulled out from the foundation at the latter half of cycles. In order to maximize the flexural retrofit, therefore, it is required to study the anchorage behavior of the flexural reinforcement for retrofit.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.5
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• pp.479-483
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• 2010

9% nickel alloy steels used for LNG, cryogenic liquid, storage tank are welded with dissimilar Inconel or Hastelloy welding rod and the weldment shows similar characteristic with the dissimilar metal weld of low carbon steel and austenitic stainless steel. Band type indications are sometimes shown on the film during radiography test of the weldments. Thus this study identified whether the indications are non-relevant indications through material, radiographic test, ultrasonic test, liquid penetrant test and microstructure analysis and also proposed radiography film interpretation and cause of band type indications.

• Korean Journal of Soil Science and Fertilizer
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• v.34 no.6
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• pp.394-400
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• 2001

This experiment was conducted to determine the safety and feasibility of using compost-promoting-bacteria. Compost-promoting-bacteria was isolated from livestock compost containing sawdust. The isolated bacteria was identified as Bacillus subtilis LYH201 by the method of the composition of the fatty acid with MIDI system and Bergey's manual. This Bacillus subtilis LYH201 had the following characteristics : Gram-positive, straight rod ($0.5{\sim}0.7{\mu}m$ width, $2.5{\sim}3.0{\mu}m$ length), facultatively aerobic and product of xylanase, CMCase, catalase, oxidase, protease and $0.5{\sim}0.7{\mu}m$-amylase. Growth of Bacillus subtilis LYH201 at saccharose as carbon source(0.5%) was faster than other carbon source. Activity of cellulase. $0.5{\sim}0.7{\mu}m$-amylase and protease from Bacillus subtilis LYH201 after 24 hours at $50^{\circ}C$ by agar diffusion method was higher than that of low temperature. Optimum growth condition of Bacillus subtilis LYH201 was $50^{\circ}C$ and pH 6.

• Journal of the Korean Society of Tobacco Science
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• v.36 no.1
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• pp.1-11
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• 2014

Cigarette filters containing Brassica Rapa L. seeds of the dark brown and round shaped were evaluated to determine the effect of seed addition on filter degradability. The seeds with germination capability under the tar/nicotine condition in the preliminary test, were put into the active carbon part of the filter(12mm) during filter rod making by the kit. The $4{\pm}2$ pieces of the seeds were put into the opened fiber bundle of the filter tow. In order to test the germination rate of the seeds, seed filters were placed either in a petri dish or test-pot in a conditioned area ($25^{\circ}C$, 70 % RH). The seed filters were placed outdoors exposed to natural conditions with the periodic water supply. The seeds in the smoked filters showed 90 % germination rate after a month under the open air condition. No significant differences in the sensory evaluation and analysis were obtained when the control sample was compared to the same cigarettes with the seeds.

• Smart Structures and Systems
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• v.28 no.6
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• pp.727-735
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• 2021

Recently, non-destructive health monitoring methods such as magnetic flux leakage (MFL) method, have become popular due to their advantages over destructive methods. Currently, numerical study on this field has been limited to simplified studies by only obtaining MFL instead of induced voltage inside coil sensor. In this study, it was proposed to perform a novel numerical simulation of MFL's coil sensor by considering vital parameters including specimen's motion with constant velocity and saturation status of specimen in time domain. A steel-rod specimen with two stepwise cross-sectional changes (i.e., 21% and 16%) was fabricated using low carbon steel. In order to evaluate the results of numerical simulation, an experimental test was also conducted using a magnetic probe, with same size specimen and test parameters, exclusively. According to comparative results of numerical simulation and experimental test, similar signal amplitude and signal pattern were observed. Thus, proposed numerical simulation method can be used as a reliable source to check efficiency of sensor probe when different size specimens with different defects should be inspected.

• Journal of Applied Biological Chemistry
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• v.43 no.2
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• pp.74-78
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• 2000

A strain that produces a high level of carboxymethyl cellulase was isolated from rotten leaves. The isolated strain was revealed to be gram-negative, oxidase-positive, and catalase-negative. From the electron microscopic features, it was identified as a rod-shaped bacterium with peritrichous flagella and did not form spores. Morphological and biochemical characteristics of the strain were found to be similar to the Pseudomonas species. However, carbon utilization test showed different results. Based on the results, this new strain was identified as Pseudomonas sp. CMC-50. CMCase produced by this strain showed a strong activity in neutral and weak acidic conditions and maximum activity at $50^{\circ}C$.

• Journal of the Korean Geotechnical Society
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• v.20 no.9
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• pp.167-176
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• 2004

Underground structures will be affected by the additional surcharge loads such as traffic load et al. Terzaghi (1956) suggested the equation on the influences of surcharge loads in vertically backfilled spaces. In field, the shapes of backfill spaces are not always formed vertically. Then the Terzagi (1956) equation is not suitable to use because of boundary condition. This study suggests equation to calculate the stress in backfilled space caused by surcharge loads when the backfilled space is sloped symmetrically. The suggested equation is verified by carbon box test and numerical analysis. The experimental results show good agreement with the suggested equation but the numerical analysis result shows a little disagreement. The differences are estimated to be caused by the fact that ground made by carbon rod has become more dense and internal frction and wall friction has increased itself as surcharge load is added but that this increase can not be considered in the numerical analysis. The suggested equation shows good agreement with Terzaghi (1956) equation in case of sloped backfill ground. According to the results, it is considered that the suggested equation can be applied not only to sloped space but also to vertical space. Further investigation using full scale experiment is needed.