• KSBB Journal
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• v.31 no.2
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• pp.120-125
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• 2016

Two-dimensional cultivation is typically used for cell growth, but the method reduces the characteristics of chondrocytes and stem cells, and limits culture area. Therefore, development of three-dimensional culture method is needed to mimic in vivo environment, improve quality of cells and scale-up efficiently. Improving proliferation and chondrogenesis is available by co-culture of chondrocytes and mesenchymal stem cells (MSCs) that leads to interaction between two kinds of cells. However, the co-culture has problems that permeability of sphere diminishes as aggregate size increased and ratio of two kinds of cells composing each spheres is different. In this work, co-cultivation method using controlled sphere composed of chondrocytes and MSCs was established and enhanced chondrogenesis. Periosteum-derived progenitor cells (PDPCs) that are appropriate for cell therapy source of articular cartilage were used as MSCs. Controlled spheres were formed in the hanging-drop plates and shifted for being induced chondrogenesis in 35-mm non-adhesive culture dishes at a rotation rate of 60 rpm. After inducing chondrogenesis, gene expressions related with chondrogenesis were found to be improved and it was apparent that the utilization of controlled spheres promoted chondrogenesis. As a result, available numbers of cells per unit area were increased and chondrogenic differentiation ability was improved compared to typical two-dimensional culture. This approach shows the potential in cartilage regeneration as it can provide sufficient numbers of chondrocytes.

• Journal of the Korean Magnetics Society
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• v.25 no.3
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• pp.74-78
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• 2015

We measured the low field microwave absorption (LFMA) and ferromagnetic resonance (FMR) signals at various magnetic field angle in exchange biased CoFe/MnIr thin film. The LFMA signals were dominantly related to the magnetization rotation process. In order to analyze the LFMA signal, we calculated transverse magnetization ($M_{\tau}$) and permeability (${\mu}_{\tau}$) for CoFe/MnIr thin film by using S-W model, which magnetic parameters of exchange bias ($H_{ex}$ = 58.5 Oe) and uniaxial anisotropy field ($H_k$ = 30Oe) was obtained from FMR signals. The LFMA signal at hard axis showed similar behavior compared with that of $M_{\tau}$. As the magnetic field angle approach to the perpendicular to hard axis, the LFMA signals were depending on both of $M_{\tau}$ and ${\mu}_{\tau}$.

• Journal of the Korean Society of Industry Convergence
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• v.21 no.3
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• pp.141-147
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• 2018

In a time when product development cycles are getting shorter and shorter, many companies are making efforts to develop products with high reliability in a short period of time, accelerated life test is widely used as a method to quickly evaluate reliability. Accelerated life test reduces the test life or the life of the product from the observed data by shortening the lifetime of the product or abruptly lowering the performance under the worse condition than the actual condition in order to shorten the test cost or the test time. In this paper, BL3640A-06P+RB35, DC12V model, which is used in the support device of an automatic rotation type digital signage, which display various information such as textures and images on a display screen in a public place or a commercial space, BLDC motors were subjected to a constant stress test and at the rotational speed of 1rpm, $180^{\circ}$ rotation and reverse rotation under actual use conditions, the stress was imposed on the rotating speed of 2rpm and the weight of the actual installed product from 22.2kgf to 10kgf were installed. The lifetime of the actual use environment condition is 23,545 hours and the rotation speed is accelerated. The life time of the acceleration condition with the additional weight is 1,380 hours. The acceleration factor is calculated as 17.06, the one year guarantee test day is 235 days to 14 days, of the period from 470 days to 28 days, and the third year from 704 days to 42 days. The test date of the BLDC motor was tested on the shortened test date, and the rotational speed and the current value were measured. It is found that there is no defect even if it operates as the test date corresponding to the specified one year warranty period and the 3 year accelerated life test which is experimented. Using the statistical technique of the regression analysis the expected time for the motor to defect to #4 samples was 20 years.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.57 no.1
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• pp.89-97
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• 2012

Reduction of greenhouse gas (GHG) emissions from upland crop field as well as paddy field is being required, but little information on GHG emissions according to cultivation practices in upland field is available. Soil GHG emissions during the growing season were investigated in the field of three decades rotation and tillage treatments which were consisted of plow, chiesl tillage and no tillage in west central Indiana, USA in 2006. Seasonal cumulative $CO_2$ emissions were not different among treatments. $CH_4$ emission increased a little in plow tillage during early soybean growing season. Most of $N_2O$ emission occurred during early corn growing season after N-fertilizer application from mid June to mid July, and was significantly affected by tillage practices in which seasonal cumulative $N_2O$ emission was significantly higher under chisel tillage. $N_2O$ emission under no-tillage was lower about 64% and 39% than that under chisel tillage and plow tillage, respectively. No-tillage practice with rotation of corn and soybean seems to be promising in point of less GHG emission and less labor for cultivation without grain yield reduction.

• Korean journal of applied entomology
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• v.55 no.4
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• pp.329-336
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• 2016

Occurrence of oriental corn borer, Ostrinia furnacalis, and yield in a paddy-upland rotation field for 8 maize (Eolrukchal 1, Heugjeom 2, Miheukchal, Ilmichal, Heukjinjuchal, Chalok 4, Mibaek 2, Daehakchal) and 7 sorghum (Hwanggeumchal, Anzunbaengisusu, Moktaksusu, Sodamchal, DS-202, Nampungchal, Donganme) varieties has been surveyed. In a monitoring study using a pheromone trap carried out from 15 May to 10 September, the density of O. furnacalis adults increased rapidly from about 2 weeks after maize planting and reached the highest density at mid June. After that, their density was fluctuated a little at earlier September. The number of the damaged maize and invasive pores on the stem of 2 maizes and sorghum varieties was examined. The mean number of the damaged maize per 20 plants was 19 and 18 plants, and the number of invasive pores was 1.8 and 1.4 per maize stem in Daehakchal and Mibaek 2, respectively. In a survey carried out at harvest period using 8 maize varieties, the damaged ratio was 94%, 92%, 71%, 64%, 54%, 52%, and 45% in Daehakchal, Mibaek 2, Ilmichal, Eolrukchal 1, Chalok 4, Miheukchal, and Heugjeom 2, respectively. The number of invasive pore per Ilmichal stem was 1.4 and that of the others was less than 1.0 per stem. In addition, the damaged ratio of maize ears was 50% in Ilmichal, 40% in Heukjinjuchal, 37% in Daehakchal, etc. The damage pattern of 2 sorghum varieties, Nampungchal and Donganme, by O. furnacalis larvae was steeply increased from planting to 2 months and the trend was continued up to earlier August. At this time, the mean number of damaged sorghum was 13 and 9.2 plants for Nampungchal and Donganme, and the number of invasive stem pores was 1.06 and 0.46, respectively. In another survey carried out at harvest period for 7 sorghum varieties, their damaged ratio was 95% in DS-202, 76% in Moktaksusu, 75% in Sodamchal, 67% in Nampungchal, 57% in Anzunbaengisusu, 46% in Donganme, and 34% in Hwanggeumchal. The damage of sorghum varieties was much higher and severer than that of maizes by O. furnacalis larvae. The number of invasive pores on a sorghum stem was 1.7 in DS-202, 1.4 in Moktaksusu, 1.3 in Sodamchal, 1.1 in Nampungchal, 1.0 in Anzunbaengisusu, 0.5 in Donganme, and 0.4 in Hwanggeumchal. Meanwhile, there was no distinct connection between damaging results and yields of maizes and sorghums by O. furnacalis larvae in a paddy-upland rotation field. These results from this study can be applicable for the establishment of a management strategy to control Oriental corn borer in paddy-upland rotation fields for maize and sorghum.

• Resources Recycling
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• v.19 no.3
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• pp.24-32
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• 2010

In the present work, a new separation system with rotating rakes has been developed to separate the film-based plastics from the recyclable materials, and environment assessment is also carried out during operation of the device. Capacity of the device was about 5.3 ton/hr at a rakes rotation speed of 26.0 rpm (the number of rakes in the 1st, 2nd and 3rd trials were 39, 52 and 48, respectively) and a belt conveyor speed of 38.5m/min, which satisfied the initial design capacity (5.0 ton/hr). Recovery ratio and purity of the plastic films were 92.6% and 96.5%, respectively at a rotation speed of 28 rpm. The levels of noise, vibration and particulate emission were below material standard regulatory limits. Plastic refused fuel (RPF) was also prepared with the recovered films. The calorific value and chlorine content of the prepared RPF were 9,740 kcal/kg and 0.18%, respectively which satisfy the first grade quality specification of the Korean RPF standard. As a result of this work, recovery of energy resources from the municipal solid waste is possible by adopting the developed separation device.

• Journal of Korean Orthopaedic Sports Medicine
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• v.2 no.1
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• pp.62-70
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• 2003

Purpose: We examined the kinematics and kinetics of the shoulder in youth baseball pitchers in light of the mechanisms of development of little league shoulder and humeral retrotorsion. Materials and Methods: The joint kinematics and the net force and torque acting on the humerus were calculated in fourteen youth pitchers throwing in a simulated game. Results: The major force component acting on the humerus was a tensile force of 378$\pm$81 N that peaked just after ball release. The predominant torque on the humerus was an external rotation torque about the long axis of the humerus. This torque reached a peak value of 35.3$\pm$6.7 Nm about 73$\%$through the pitching motion. This torque is approximately 66$\%$ of the torque required to fracture of the adult humerus. Conclusions: The direction of the humeral torque was consistent with the development of increased humeral retrotorsion in the throwing arm. Shear stress arising from the high torque during the late cocking phase likely leads to deformation the relatively weak proximal humeral epiphysis. The external rotation torque applied to the humerus during the pitch also agrees with the proposed mechanism for development little league shoulder, which has been hypothesized to be due to rotational stresses acting on the epiphysis during the throwing motion.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.451-463
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• 2022

Whenever a mineshaft accidentally collapses, speedy risk assessment is both required and crucial. But onsite safety diagnosis by humans is reportedly difficult considering the additional risk of collapse of the unstable mineshaft. Generally, drones equipped with high-speed lidar sensors can be used for such inspection. However, the drone technology is restrictively applicable at very shallow depth, failing in mineshafts with depths of hundreds of meters because of the limit of wireless communication and turbulence inside the mineshaft. In previous study, a three-dimensional (3D) scanning system with a single channel lidar was fabricated and operated using towed cable in a mineshaft to a depth of 200 m. The rotation and pendulum movement errors of the measuring unit were compensated for by applying the data of inertial measuring unit and comparing the similarity between the scan data of the adjacent depths (Kim et al., 2020). However, the errors grew with scan depth. In this paper, a multi-channel lidar sensor to obtain a continuous cross-sectional image of the mineshaft from a winch system pulled from bottom upward. In this new approach, within overlapped region viewed by the multi-channel lidar, rotation error was compensated for by comparing the similarity between the scan data at the same depth. The fabricated system was applied to scan 0-165 m depth of the mineshaft with 180 m depth. The reconstructed image was depicted in a 3D graph for interpretation.

• Journal of the Korean Electrochemical Society
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• v.16 no.1
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• pp.52-58
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• 2013

In order to overcome the cost issue for commercialization of polymer electrolyte membrane fuel cell (PEMFC), this research was conducted for replacing platinum cathode catalyst with non-precious metal catalyst. The non-precious metal catalyst (Co-PANI-C) was synthesized by the simple reduction method with polyaniline (PANI), carbon black, and cobalt precursor without any heat treatment. Characterization of new Co-PANI-C composite catalysts was done by the measurement of X-ray diffraction (XRD) and thermogravimetric analysis (TGA) for structure analysis and performed by rotating disk electrode (RDE) and rotating ring disk electrode (RRDE) for electrochemical analysis. As a result, Co-PANI-C catalyst showed 60 mV lower on-set potential for oxygen reduction reaction (ORR) than Pt/C catalyst, but the overall reduction current of Co-PANI-C catalysts by ORR was still smaller than that of Pt/C. In addition, the ORR behavior of Co-PANI-C catalysts depending on the rotation speed of electrode and the stability of Co-PANI-C catalyst under potential cycling and the performance of fuel cell conditions are also discussed.

• Corrosion Science and Technology
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• v.17 no.2
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• pp.68-73
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• 2018

Substitution of hip and knee joints by CoCr alloys is in great demand due to their high wear resistance and good biocompatibility. Understanding of tribocorrosion in joint replacements requires study of variables such as coefficient of friction and the choice of a proper corrosive medium in wear-corrosion tests carried out in the lab. The objective of this study was to characterize tribocorrosion behaviour of CoCr alloy with low (LCCoCr) and high carbon (HCCoCr) contents in several corrosive media: NaCl, Phosphate Buffer Solution (PBS), and PBS with hyaluronic acid (PBS-HA). Tribocorrosion tests were carried out on a pin-on-disk tribometer with an integrated electrochemical cell. A normal load of 5N was applied on the alumina ball counterpart at a rotation rate of 120 rpm. Coefficient of friction (COF) was measured and tribocorrosion behaviour was characterized by in situ application of electrochemical techniques. HCCoCr alloy immersed in PBS-HA showed the best tribocorrosion behaviour with the lowest COF. In this case, in situ measurement of corrosion potential and the impedance data under wear corrosion process showed an active state while passive film was continuously destroyed without possibility of regeneration.