• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.5
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• pp.98-104
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• 2022

When processing parts, the cutting oil can improve the cooling performance of the workpiece and tool to increase the precision of the workpiece or extend the life of the tool and facilitate chip extraction. Since such cutting oil has a harmful effect on the environment and the human body due to additives such as sulfur, research on a minimum lubrication supply method using an eco-friendly oil is recently underway. The minimum lubrication supply method minimizes the amount of cutting oil used during processing and processes it, which can reduce the amount of cutting oil used, but has a problem in that cooling performance efficiency is poor. Therefore, this study conducted a study on mist cooling of lubricants to reduce the amount of cutting oil used and maximize the cooling effect of processing heat generated during tapping processing. Spray pressure, processing speed, direction, and lubricant spray amount, which are considered to have an effect on cooling performance, were set as process conditions, and the effect on temperature was analyzed by performing an experiment using the box benquin method among experiments were analyzed. Through the experimental analysis results, the optimal conditions for mist and processing that maximize the cooling effect were derived, and the validity of the results derived through additional experiments was verified. In the case of processing by applying the mist lubrication method verified through this study, it is considered that high-precision processing is possible by improving the cooling effect.

• Journal of the Korean Solar Energy Society
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• v.31 no.3
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• pp.57-66
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• 2011

A Photovoltaic/Thermal(PVT) solar system consists of PV module and thermal absorber plate which convert the absorbed solar radiation into electricity and heat. Meaningful researches and development (R&D) on the PVT technologies have been performed since the 1970s. This paper presents a review of the previous works covering the various types of PVT and their performance analysis in terms of electrical and thermal efficiency. This review compares electrical and thermal efficiency of the different types of PVT collectors and analyzes the parameters affecting PVT performance. Based on the literature review, box channel type PVT with unglazed, or flat plate PVT with glazed have the highest efficiency among them. From the literature review, R&D should be carried out aiming at improving their overall electrical and thermal efficiency, cutting down the cost, and making them more competitive in the energy consumption market.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.4
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• pp.27-33
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• 2001

In this study, it is observed that the distribution of combustion chamber volume affects the volumetric efficiency. The distribution ratio was adjusted by controlling combustion chamber volume of head and piston bowl one. Four cases were investigated, which are the combination of different distribution ratios and different compression ratios (9.8-10.0). A commercial SOHC 3-valve engine was modified by cutting the bottom face of the head and/or replacing the piston by the one that has different volume. The result shows that the less the head side volume, the more volumetric efficiency is achieved under the same compression ratio. It is also observed that increasing volumetric efficiency results in early knock occurrence due to increased "real" compression ratio. To consider reliability in estimating the volumetric efficiency, we examined the sensitivity of the AFR equation to possible errors in emission measurements. It is shown that the volumetric efficiency, which is calculated by measuring AFR and fuel consumption, can be controlled in 1% error. 1% error.

• 한국태양에너지학회:학술대회논문집
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• 2011.04a
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• pp.250-255
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• 2011

A Photovoltaic/Thermal(PVT) solar system consists of PV module and thermal absorber plate which convert the absorbed solar radiation into electricity and heat. Meaningful researches and development (R&D) on the PVT technologies have been performed since the 1970s. This paper presents a review of the previous works covering the various types of PVT and their performance analysis in terms of electrical and thermal efficiency. This review compares electrical and thermal efficiency of the different types of PVT collectors and analyzes the parameters affecting PVT performance. Based on the literature review, box charmel type PVT with unglazed, or flat plate PVT with glazed have the highest efficiency among them. From the literature review, R&D should be carried out aiming at improving their overall electrical and thermal efficiency and cutting down the cost, making them more competitive in the energy consumption market.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.5
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• pp.395-409
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• 2022

To overcome the limitation of conventional rock excavation methods, the excavation with abrasive waterjet has been actively developed. The abrasive waterjet excavation method has the effect of reducing blasting vibration and enhancing the excavation efficiency by forming a continuous free surface on the rock. However, the waterjet cutting performance varies with rock fracturing characteristics. Thus, it is necessary to analyze the cutting performance for various rocks in order to effectively utilize the waterjet excavation. In this study, cutting experiments with the high pressure waterjet system were performed for basalt and granite specimens. Water pressure, standoff distance, and traverse speed were determined as effective parameters for the abrasive waterjet cutting. The cutting depth and width of basalt specimens were analyzed to compare with granite results. The averaged cutting depth of basalt was shown in 41% deeper than granite; in addition, the averaged cutting width of basalt was formed by 18.5% narrower than granite. The results of this study are expected to be useful basic data for applying rock excavation site with low strength and high porosity such as basalt.

• Horticultural Science & Technology
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• v.30 no.6
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• pp.686-693
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• 2012

To develop a technique for mass-propagation of virus-free sweet potato [Ipomoea batatas (L.) Lam.] plant using nutrient film technique (NFT), the growth characteristics of 4 cultivars as affected by nutrient solution composition and cutting size were investigated. 72 cells (35 mL/cell) plug trays filled with vermiculite and perlite (1:1, v/v) were used. Vine length, fresh and dry weights of virus-free plants were the greatest in the nutrient solution recommended by National Horticultural Research Station in Japan, followed by that recommended by National Institute of Horticultural & Herbal Science in Korea, and Yamazaki's nutrient solution for lettuce. The growth of uppershoot cuttings was the best among 4 subsections of cutting. Vine length, and fresh and dry weights increased in the longer cutting treatments, and were better in 'Shinzami' and 'Yeonhwangmi' than those in 'Mannami' and 'Shincheonmi'. Vine diameter and length of the longest root were not significantly affected by the cutting size and cutting source. The growth characteristics of the single node cutting were not significantly different from those in 2-node cutting. The efficiency of rapid mass-propagation could be promoted with single node cuttings and uppershoot cuttings grown in NFT system.

• Journal of The Korean Society of Grassland and Forage Science
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• v.11 no.2
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• pp.90-96
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• 1991

This experiment was carried out in order to estimate the recovery days of root and stubble to the days after cutting, and contribution of specific stubble weight on the regrowth was examined using the relationships between the dry weight of shoot and yield components, and regrowth parameters by the days after cutting. The varieties examined were Maprima, Manhattan, Tove, Peramo, Caliente, Tempo and P-2 grown under individual plant basis. The results are may be summarized as follows: 1. Dry weight of root and stubble were recovered up to 13.5 and 11 days after cutting, respectively. 2. Dry weight of shoot(regrowth parts+stubble) was affected significantly by the varieties, stages of regrowth and variety x stage of regrowth. 3. The variety with tiller weight type showed higher average productivity of shoot than those of the variety with tiller number type. 4. Absolute growth rate(AGR) of shoot was correlated significantly with regrowth parts, stubble, root and weight of a tiller at the early stage of regrowth(up to 12 days after cutting), and correlated with regrowth parts, stubble, weight of tiller and stubble area at the late stage of regrowth(up to 20 days after cutting). 5. Contribution of specific stubble weight to absolute growth rate of shoot was different between the stages of regrowth. Thus, regrowth parts per specific stubble weight(RP1SSbW) and weight of tiller per specific stubble weight(WT1SSbW) contributed to absolute growth rate of shoot at the early stage of regrowth, and efficiency of specific stubble weight(ESSbW), regrowth parts per specific stubble weight (RPISSbW) and weight of a tiller per specific stubble weight(WT1SSbW) contributed to absolute growth rate of shoot at the late stage of regrowth. 6. Regrowth utilization rate(RUR) was one of the useful regrowth parameter to indicate the regrowth potential of grasses.

• The Journal of Engineering Geology
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• v.17 no.4
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• pp.577-587
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• 2007

The length of study area was about 450m, and it was shown the geological condition of distinguished change of rock by cutting slope. In order to establish a slope stability, we carried out an engineering geological investigations about rock constituent, rock structure and a direction of discontinuous plane. The study area was divided into six section considered by direction of cutting slope, height of slope and geological condition. Analysis of cutting slope stability was carried out with stereo-graphic projection method by DIPS program which was feasible of stability analysis with geometrical correlation for a direction of discontinuous plane and direction of cutting slope. From analysis of cutting slope stability considered by construction, stability and economical efficiency, the slope stability countermeasures such as a high tensile wire net, slope protection method and enhanced retaining wall were established and operated which minimized effect caused by lower end of road on a relaxation of huge rock.

• Journal of Animal Science and Technology
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• v.62 no.6
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• pp.912-921
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• 2020

We examined the rates of pathogenic bacterial cross-contamination from gloves to meat and from meat to gloves during pork processing under meat-handling scenarios in transfer rate experiments of inoculated pathogens. The inoculated pork contained ~5-6 Log10 CFU/g pathogenic bacteria like Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Listeria monocytogenes (L. monocytogenes), and Salmonella enterica subsp. enterica (Sal. enteritidis). On cotton gloves, after cutting the pork, the cutting board, knife, and cotton gloves showed 3.07-3.50, 3.29-3.92 and 4.48-4.86 Log10 CFU/g bacteria. However, when using polyethylene gloves, fewer bacteria (3.12-3.75, 3.20-3.33, and 3.07-3.97 Log10 CFU/g, respectively) were transferred. When four pathogens (6 Log10 CFU/g) were inoculated onto the gloves, polyethylene gloves showed a lower transition rate (cutting board 2.47-3.40, knife 2.01-3.98, and polyethylene glove 2.40-2.98 Log10 CFU/g) than cotton gloves. For cotton gloves, these values were 3.46-3.96, 3.37-4.06, and 3.55-4.00 Log10 CFU/g, respectively. Use of cotton gloves, polyethylene gloves, knives and cutting boards for up to 10 hours in a meat butchering environment has not exceeded HACCP regulations. However, after 10 h of use, 3.09, 3.27, and 2.94 Log10 CFU/g of plate count bacteria were detected on the cotton gloves, cutting board, and knives but polyethylene gloves showed no bacterial count. Our results reveal the transfer efficiency of pathogenic bacteria and that gloved hands may act as a transfer route of pathogenic bacteria between meat and hands. The best hand hygiene was achieved when wearing polyethylene gloves. Thus, use of polyethylene rather than cotton gloves reduces cross-contamination during meat processing.

• Geomechanics and Engineering
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• v.34 no.1
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• pp.103-113
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• 2023

This study focused on understanding the relationship between the design of a tunnel boring machine disc cutter ring and its rock-breaking efficiency, as well as the applicable conditions of different cutter ring types. The discrete element method was used to establish a numerical model of the rock-breaking process using disc cutters with different ring types to reveal the development of rock damage cracks and variation in cutter penetration load. The calculation results indicate that a sharp-edged (V-shaped) disc cutter penetrates a rock mass to a given depth with the lowest load, resulting in more intermediate cracks and few lateral cracks, which leads to difficulty in crack combination. Furthermore, the poor wear resistance of a conventional V-shaped cutter can lead to an exponential increase in the penetration load after cutter ring wear. In contrast, constant-cross-section (CCS) disc cutters have the highest quantity of crack extensions after penetrating rock, but also require the highest penetration loads. An arch-edged (U-shaped) disc cutter is more moderate than the aforementioned types with sufficient intermediate and lateral crack propagation after cutting into rock under a suitable penetration load. Additionally, we found that the cutter ring wedge angle and edge width heavily influence cutter rock-breaking efficiency and that a disc cutter with a 16 to 22 mm edge width and 20° to 30° wedge angle exhibits high performance. Compared to V-shaped and U-shaped cutters, the CCS cutter is more suitable for soft or medium-strength rocks, where the penetration load is relatively small. Additionally, two typical case studies were selected to verify that replacing a CCS cutter with a U-shaped or optimized V-shaped disc cutter can increase cutting efficiency when encountering hard rocks.