• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.3
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• pp.55-61
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• 2000

In this paper we have discussed on the characteristics and modeling of machined geometry which was established for the case of round shape machining also the effects of externally machined profile are analyzed and its modeling realia-bility was verified by the experiments of roundness testing especially in lathe operation. In this study we established a harmonic geometric model with the parameter harmonic function. In general we can calculate the theoretical roundness profile with an arbitrary multilobe parameter. But in real experiments only 2-5 lobe profile was frequently measured, The most frequently measured ones are 3 and 5 lobe profile in experiments. With these results we can predict that these results may be applied to round shape machining such as turning drilling boring ball screw and cylindrical grinding operation in bearing and shaft making operation with the same method. in this study simulation and experimental work were performed to show the profile behaviors. we can apply these new modeling methods in real process for the predic-tion of part profile behaviors machined such as in round shape machining operation.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.3
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• pp.22-28
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• 2022

In the semiconductor and display component industries, the use of ceramic materials, which are high-strength materials, is increasing for ensuring durability and wear resistance. Among them, alumina materials are used increasingly. Alumina materials are extremely difficult to process because of their high strength; as such, research and development in the area of mineral material processing is being promoted actively to improve their processing. In this study, the processability of an electrodeposition tool is investigated using the electrodeposition method to smoothly process alumina materials. Furthermore, processing is conducted under various processing conditions, such as spindle speed, feed speed, and depth of cut. In addition, the processing characteristics of the workpiece are analyzed based on the tooling.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.1
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• pp.123-128
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• 1994

A high speed spindle system for machine tools can be used to reduce the machining time, to improve the machining accuracy, to perform the machining of light metals and hard materials, and to unite the cutting and grinding processes. In this study, a high speed spindle system is developed by applying the oil-air lubrication method, angular contact ball bearings, injection nozzles with dual orifices, cooling jacket and so on. And an air cooling experiment for evaluating the performance of the spindle system is carried out. Especially, in ofder to establish the air cooling conditions related to the development of a high speed spindle system, the effects of cooling air pressure, oil supply rate, air supply rate and rotational spindle speed are studied and discussed on the bearing temperature rise and frictional torque. Also the effects of cooling air pressure, rotational spindle speed and spindle system structure is investigated on the bearing temperature distribution. The experiment on the test model reveals the usefulness of the air cooling method.

• Journal of the Korean Society of Food Culture
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• v.22 no.5
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• pp.609-614
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• 2007

Quality characteristics of dasik were studied with varied the levels of rice grain particle size and green tea powder and compared them with commercially sold dasik. Among the samples with the same number of grinding times, the sample groups with the higher amount of green tea showed significantly the less mosture content(p<0.05). Hardness was higher in the samples containing higher amount of green tea among the ones with the same grain size (p<0.05). The M13G0.5 was evaluated to have the highest savory aroma with significance (p<0.05), and C1 to have the highest sweetness by sensory analysis. The developed dasik samples with lower rice grain particle size had significantly lower adhesiveness, chewiness, gumminess, and cohesiveness compared to those of commercial sample groups. In sensory tests, the compared groups showed significantly the higher savory aroma and flavor and very lower hardness when compared to those of commercial sample groups. With the results above, dasik with with varied the levels of rice grain particle size and green tea powder were developed with improved qualities compared to those of commercially sold dasik.

• Tribology and Lubricants
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• v.31 no.2
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• pp.62-68
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• 2015

A magnetorheological (MR) fluid is a smart material whose rheological behavior can be controlled by varying the parameters of the applied magnetic field. Because the damping force and shear force of an MR fluid can be controlled using a magnetic field, it is widely employed in many industrial applications, such as in vehicle vibration control, powertrains, high-precision grinding processes, valves, and seals. However, the characteristics of friction caused by iron particles inside the MR fluid need to be understood and improved so that it can be used in practical applications. Surface process technologies such as polytetrafluoroethylene (PTFE) coatings and diamond-like carbon (DLC) coatings are widely used to improve the surface friction properties. This study examines the friction characteristics of an MR fluid with different surface process technologies such as PTFE coatings and DLC coatings, by using a reciprocating friction tester. The coefficients of friction are in the following descending order: MR fluid without any coating, MR fluid with a DLC coating, and MR fluid with a PTFE coating. Scanning electron microscopy is used to observe the worn surfaces before and after the experiment. In addition, energy dispersive X-ray spectroscopy is used to analyze the chemical composition of the worn surface. Through a comparison of the results, the friction characteristics of the MR fluid based on the different coating technologies are analyzed.

• Applied Chemistry for Engineering
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• v.21 no.2
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• pp.148-153
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• 2010

This study was carried out to investigate the effect of extraction methods on the physicochemical characteristics using seed oil of wild green tea (Camellia sinensis). When the solvent extraction method after grinding and steam treatment (SGS) was used for oil extraction, the yield was highest. The specific gravity was a range of $0.91{\sim}0.94g/cm^{3}$ irrespective of extraction methods of oil. However, the light in the solvent extraction method after grinding (SG), the red in the pressure extraction method after grinding and roasting treatment (PGR), and the yellow in SG method were highest. Among various fatty acids, the concentrations of C16 : 0, C18 : 1 and C18 : 2 were highest, irrespective of extraction methods. Especially, the C16 : 0 concentration was in the order of SG (34.78%), SGS (23.04%), and PRGS method (23.01%), the C18 : 1 concentration was in the order of PGR (43.35%), SGS (42.7%), SG method (39.0%), and in the case of C18 : 2, it was in order of PGR (23.15%), SGS (23.03%), and SG method (15.01%). The saturated fatty acid concentration was in the order of SG (40.59%), PGR (31.61%), and SGS method (30.1%). On the other hand, in the case of the unsaturated fatty acid, it was in the order of SGS (69.9%), PGR (68.39%), and SG method (59.41%). The acid values in the SGS and SG method after 10 days of storage were in the range of 6~8 mgKOH/g. However, in the case of PGR method, it was increased with the increase of storage time and was 49.3 mgKOH/g after 60 days. The peroxide values in the SGS and SG method were in the range of 60~100 mEq/g from 10 to 60 days of storage. On the other hand, when the storage time was increased from 10 to 30 days, it was sharply increased from 60 to 240 mEq/g. The rancidity was in the order of $Fe^{2+}$, $Cu^{2+}$, $Cr^{2+}$, $Zn^{2+}$ and $Ni^{2+}$, irrespective of extraction methods. Especially, when butylated hydroxyanisole (BHA) was added into oil containing 1.0 ppm of <$Fe^{2+}$, the peroxide value was decreased from 539.4 to 216.6%. These results show that seed oil of Camellia sinensis grown in Iksan can be applied as sources for cosmetics, detergents, food, and pharmaceuticals.

• Journal of Conservation Science
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• v.21
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• pp.5-20
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• 2007

The stone artifacts in Bronze age from the Hyocheon sites in the Gwangju, Korea were studied on the basis of material characteristics and provenance presumptions. The use and rock names of the artifacts are a stone shovel by andesite, the stone grinding pestle by pyrophyllite, the stone sickle by schist and four stone semifinished artifacts by slates. Andesitic stone shovel could be observed easily around the Hyocheon relic site. But, rocks of the stone grinding pestle, the stone sickle, the stone arrowhead and the stone semifinished artifacts could be confirmed typical occurrences of the all kinds of rocks around the Hwasun coal mine area above 10km from the site. These are made the coupled samples with each stone artifact to the same kinds of raw material rocks based on analysis of the lithology and geochemistry. As a result a geochemical evolution trends of both a stone artifact and the rock showed very similar patterns based on normalization using the behavior, enrichment, compatibility and incompatibility of the elements. Therefore, the source rock of the stone shovel was convey from Mudeung mountain possible interpreted that the domestic-type artifacts are distributed in the vicinity of the Hyocheon site. On the other hand, the stone grinding pestle, the stone sickle, the stone arrowhead and the stone semifinished artifacts were convey from the Hwasun coal mine area possible foreign-type stone artifacts interpreted that the source rocks. Consequently, in the foreign-type stone artifacts are should archaeologic research which it can examine various possibilities clearly that the possibility to coming the introduction with the mankind migration, diffusion to dealings of tribe, the captured enemy equipment through the war and the trade with the behavior of the materials.

• Journal of the Korean Society of Food Culture
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• v.20 no.6
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• pp.738-743
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• 2005

This study was performed to investigate the quality characteristics of pine mushroom yanggaeng prepared with different additions and different preparations of pine mushroom. Yanggaeng was prepared with three concentration of pine mushroom after different preparations of pine mushroom, A hot wind drying 0.1%, 0.3%, 0.5%, Frozen pine mushroom grinding 0.1%, 0.3%, 0.5%, Freezed drying 0.1%, 0.3%, 0.5%, to which was added cooked red bean, agar, oligosaccharide, salt and water. Proximate composition, hunter's color, texture profile analysis and sensory evaluation of yanggaeng were examined. Lightness of pine mushroom yangaeng increased with increasing pine mushroom content and frozen pine mushroom grinding products were higher than those of the preparation products. In the texture profile analysis, hardness of pine mushroom yangaeng increased with increasing pine mushroom content and cohesiveness, springiness of Frozen pine mushroom grinding 0.1% were the highest. In sensory evaluation, the taste and viscosity scores of Freezed drying 0.1% higher than those of the other products. Also the overall acceptability of freezed drying 0.1% pine mushroom yanggaeng was the highest of the all products.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.115-116
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• 2002

This study was carried out as one of efforts to overcome difficulties in air bearing design due to low stiffness and low damping. Hydrodynamic effects on hydrodynamic stiffness of a fluid film in a high speed air bearing with tow-row air sources are investigated. The hydrodynamic effects by the high speed over DN 1,000,000 and eccentricity of a proceeding which are not considered in conventional design of an air bearing need to be reconsidered. The hydrodynamic effects, which dominantly influence on the load capacity of air bearing, are caused mainly by proceeding speed, eccentricity, and the source positions. The two-row source arrangement in the air bearing produces quite unique hydrodynamic effects with respect to pressure distribution of the air film. Optimal arrangement of the two-row sources improves performance of an air bearing in film reaction force and loading capacity of high speed spindles. This study compares the pressure distribution by numerical simulation as a function of eccentricity of proceeding and the source positions. The air source position 1/7L form one end of an air bearing was found to be superior to source position of 1/4L. The dynamic stiffness were obtained using a two-dimensional cutting method which can directly measure the cutting reaction forces and the displacements of the spindle in two directions using a tool dynamometer and transducer sensors. Heat generation in the air film can not be negligible over the speed of DN 2,000,000. In order to analysis effects of heat generation on the characteristics of air bearing, high cooling bearing spindle and low cooling bearing spindle were tested and compared. Characteristics of the frequency response of shaft and motion of run out errors were different for the spindle. The test results show that, in the case of low cooling bearing spindle, the stiffness became smaller due to heat generation. The results, which were obtained for high speed region, may be used as a design information for spindle which can be applied to precision devices such as ultra precision grinding and ultra high speed milling.

• Journal of Ocean Engineering and Technology
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• v.16 no.6
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• pp.60-64
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• 2002

This paper describes the machining characteristics of the MoSi$_2$--based composites through the process of electric discharge drilling with various tubular electrodes. In addition to hardness characteristics, microstructures of Nb/MoSi$_2$laminate composites were evaluated from the variation of fabricating conditions, such as preparation temperature, applied pressure, and pressure holding time. MoSi$_2$-based composites have been developed in new materials for jet engines of supersonic-speed airplanes and gas turbines for high-temperature generators. These high performance engines may require new hard materials with high strength and high temperature-resistance. Also, with the exception of grinding, traditional machining methods are not applicable to these new materials. Electric discharge machining (EDM) is a thermal process that utilizes a spark discharge to melt a conductive material. The tool electrode is almost -unloaded, because there is n direct contact between the tool electrode and the work piece. By combining a non-conducting ceramic with more conducting ceramic, it was possible to raise the electrical conductivity. From experimental results, it was found that the lamination from Nb sheet and MoSi$_2$ powder was an excellent strategy to improve hardness characteristics of monolithic MoSi$_2$. However, interfacial reaction products, like (Nb, Mo)SiO$_2$and Nb$_2$Si$_3$formed at the interface of Nb/MoSi$_2$, and increased with fabricating temperature. MoSi$_2$composites, with which a hole drilling was not possible through the conventional machining process, enhanced the capacity of ED-drilling by adding MbSi$_2$, relative to that of SiC or ZrO$_2$reinforcements.