• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.5
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• pp.46-52
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• 2003

End-milling have been used widely in industrial system because it is effective to a material manufacturing with various shape. Recently the end-milling processing is needed the high-precise technique with good surface roughness and rapid time in precision machine part and electronic part. The optimum surface roughness has an effect on end-milling condition such as, cutting direction spindle speed, feed rate and depth of cut, etc. Therefore this study was carried out to presume for mutual relation of end-milling condition to get the optimum surface roughness by regression analysis. The results shown that coefficient of determination($\textrm{R}^2$) of regression equation has a fine reliability of 87.5% and regression equation of surface rough is made by regression analysis.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.2
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• pp.75-80
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• 2021

The crystal grains of polycrystalline diamond vary depending on deposition conditions and growth thickness. The diamond thin film deposited by the CVD method has a very rough growth surface. On average, the surface roughness of a diamond thin film deposited by CVD is in the range of 1-100 um. However, the high surface roughness of diamond is unsuitable for application in industrial applications, so the surface roughness must be lowered. As the surface roughness decreases, the scattering of incident light is reduced, the heat conduction is improved, the mechanical surface friction coefficient can be lowered, and the transmittance can also be improved. In addition, diamond-coated cutting tools have the advantage of enabling ultra-precise machining. In this study, the surface roughness of diamond was improved by thermal diffusion reaction between diamond carbon atoms and ferrous metals at high temperature for diamond thin films deposited by MPCVD.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.2
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• pp.272-285
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• 2003

This study was conducted to observe the microscopic structures of cavities formed after ablation of primary teeth, permanent teeth, enamel and dentin in using a bur and cavities formed after ablation using laser and the following results were obtained after comparing the effects of ablation. Using a #330 bur and Er:YAG laser irradiated at 150 mJ, 200 mJ, 250 mJ and 300 mJ all at the frequency of 5 Hz, 1 mm enamel and dentin samples were ablated and the ablation time was measured. In order to measure the surfaces ablated, 5 each of primary teeth and permanent teeth were ablated using a #330 bur and Er:YAG laser at 150 mJ, 200 mJ, 250 mJ and 300 mJ for 1 sec and the cross section and vertical section were observed. The following results were obtained : 1. Cutting time of Er:YAG laser was longer than that of conventinal high-speed bur regardless of teeth type. 2. Cutting on enamel, Cutting time of conventional high-speed bur in deciduous teeth was longer than in permanent teeth(P<0.05). But Er:YAG laser was not showed any difference between the deciduous and permanent teeth(P>0.05). 3. Cutting on dentin, Cutting time of conventional high-speed bur in permanent teeth was longer than deciduous teeth. Er:YAG laser of 150 mJ, 5 Hz in permanent teeth was longer than in deciduous teeth(p<0.05). But laser of other power did not showed mean difference. 4. The cavity surface treated with the convetional high-speed bur revealed a relatively flat appearance, almost covered with a debris-like smear layer. Cavity wall showed striped appearance because of blade of bur. 5. The cavity surface treated by the Er:YAG laser system was irregular or rough surface with the absence charring, carbonization, or cracking of the dentin. In addition, there was an absence of a smear layer. Cavity floor was round and relatively smooth. According to these results, cutting time of Er:YAG laser was almostly same in permanent and deciduous teeth, but more effective in dentin than enamel. Cutting the sample, Er:YAG laser was needed more time than conventional bur. But SEM findings suggested that laser device produced favorable surface characteristic(i.e, no smear layer, irregular surface, cracking).

• Journal of the Korean Wood Science and Technology
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• v.29 no.2
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• pp.100-108
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• 2001

An understanding of potential lumber cutting yields may lead to increased utilization of the lower grades of lumber in wood industry. Computer simulations of rough-mill operations require a lumber database as input to give reasonable estimates of such yields. The lumber database must contain detailed information regarding the location and type of defects, and then all manufacturing sequences can be tested with the same raw material. However, no suitable lumber database with mapped defects exists for Korean wood industry. In this study lumber databases of Pinus densiflora S. et Z and Quercus acutissima which are the main Korean domestic species were developed to prepare for coming era of "utilization of domestic species" in the near future. These databases were put into lumber cut-up simulation model(gang-rip-first simulator) to investigate the part yields. Gang-rip first simulation showed average part yields of 44.75% and 63.10% for Quercus acutissima and Pinus densiflora lumber database developed, respectively. In most cases process set-up of fixed blade best feed showed the best part yields and the level of acceptable defects could not make significant differences in part yields.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.15
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• pp.61-67
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• 1974

Field experiment was conducted to disclose some effects of leaf defoliation in heading time and the application of different combinations of nitrogen, phosphorus and potassium on the maturity and yield of paddy rice. The results obtained are as follows; 1.All were components considered were increased as the amounts of nitrogen, phospgorus and potassium applied were increased, except the maturity rate had the tendancy to be decreased with the increase of the above fertilizer applications. 2.As the rate of cutting leaves went higher, the weight of rough rice, the maturity rate and the weight of 1, 000 kernels of perferct brown rice were decreased, and there were significant differences among the treatments of leaf blade cutting. 3. The contribution of each leaf to yield through the maturity, number of spikelets per panicle and 1, 000 kernel weight were 61.87-66.18-65.61% respectively for the flag leaf, 17.50-20.65-23.41%for the 2nd leaf, 12-71-12.73-10.11%for the 3rd lead and 7.93-6.44-0.87%for the 4th leaf respectively. This simply indicared that the effects of the leaves to the yield were decreased as their position went down. This tendency was specially emphasized in the case of the weight of 1, 000 kernels of perfect brown rice.

• Design & Manufacturing
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• v.2 no.5
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• pp.1-4
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• 2008

LCD-BLU (Liquid Crystal Display - Back Light Unit) is one of kernel parts of LCD unit and it consists of several optical sheets(such as prism, diffuser and protector sheets), LCP (Light Guide Plate), light source (CCFL or LED) and mold frame. The LGP of LCD-BLU is usually manufactured by forming numerous dots with $50-200{\mu}m$ in diameter on it by erosion method. But the surface of the erosion dots of LGP is very rough due to the characteristics of the erosion process during the mold fabrication, so that its light loss is high along with the dispersion of light into the surface. Accordingly, there is a limit in raising the luminance of LCD-BLU. Especially, the negative and positive micro-lens pattern fabricated by modified LiGA with thermal reflow process was applied to the optical design of LGP.

• Journal of the Korea Fashion and Costume Design Association
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• v.6 no.1
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• pp.25-33
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• 2004

This study is aimed at reviewing how the Orientalism trend is expressed in the modem fashion in terms of silhouette, color, materials, and detail. To this end, the geographic scope of this study is limited to China, Japan, Korea, while data are collected from fashion collections, domestic and foreign magazines since 2000's, literature, and internet sites. The results of this study can be summarized as follows: 1. Silhouette: the basic square silhouette of the Oriental traditional costume do not disturb the body movement and have an effected on design to smoothly follow the body line rather than cutting out materials into several parts or emphasize the curved body. 2. Color: due to the influence of the Oriental Zen thought, color trend seems to pursue simplicity rather than complexity, and natural aesthetics. In addition, the Oriental colorfulness shall not be ignored. 3. Materials: golden embroidered material, polished satin, jersey, tough or rough materials, etc. have used with materials of the Oriental traditional costume came into fashion. In pattern, the Orientalism trend is expressive of pattern by Chinese ink-spread technique, simple brush touch technique, cloud pattern, lotus flower pattern or dragon pattern, all of which feature the Oriental calm aesthetics or those motivated by the Oriental traditional patterns. 4. Detail: the techniques of handicrafts and manual arts such as meticulous embroidery, tassel or patchwork reflect well the Orientalism trend in the modem fashion.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.349-354
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• 2000

A use of Titanium alloy as a structural material is increasing lately. Among those titanium alloys, Ti-6A1-4V alloy is the most popular one with taking 2/3 of it's market. Also, Ti-6A1-4V alloy can get the stability of organization and product measure, and the evaluation of the cutting ability and the mechanical characteristics. The point in titanium alloy work is on how treat the heat generated during grinding. Because the heat conductivity of titanium alloy is unnegligibly low, the grinding heat is accumulated in workpiece, and it cause the increasing of grinding grits' wear and the rough grinding surface. So, these characteristics in grinding of titanium alloy will change the mechanical characteristics of the titanium alloy. From this study, the mechanical characteristics of annealed Ti-6A1-4V alloy after grinding was concerned with checking out the bending strength values, and the factor of the change and the difference was analyzed after analyzing the surface roughness and the image from SEM.

• Journal of the Korean Society of Industry Convergence
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• v.4 no.3
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• pp.237-242
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• 2001

Ti-6Al-4V alloy can be obtained the stability of organization and product treasure, the evaluation of the cutting ability and the mechanical characteristics after the heat treatment of annealing, solution and aging. The difficulty in machining titanium alloy is how treat the heat generated during the process. Because the heat conductivity of titanium alloy is regardfully low, the heat generated during grinding is accumulated in workpiece. and it causes the increasing of grinding wheel grits' wear and makes the ground surface rough. So, these characteristics in grinding of titanium alloy will change the mechanical properties of the titanium alloy. From this study. the mechanical characteristics of annealed one and solution and aging one treated Ti-6Al-4V alloy after grinding was concerned with checking out the bending strength and hardness. For the result, both of bending strength and hardness were increased at the burned area on the surface. Roughness value was remarkably high at the table speed of 10m/min.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.224-230
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• 2005

In order to realize a three-dimensional shape on CAD, the machining process has been widely used because it offers practical advantages such as precision and versatility. However, the traditional machining process needs a large amount of time in cutting a product and the remained material causes trouble such as inconvenience due to cleaning process. This paper introduces a new rapid manufacturing process called Rapid Heat Ablation process (RHA) using the rotary hot tool to overcome limitations of traditional machining process. The rotary hot tool to satisfy requirements of RHA process is designed and produced. In order to examine relationships between kerfwidth and process parameters such as heat input, speed of tool and speed of revolution, experiments were carried out. In addition, relationship between the kerfwidth and the effective heat input was obtained. Based on the experimental results, double-curved shape was ablated to show the validity of proposed process. In the procedure, the rough cut and fine cut were performed according to the conditions of process parameters without tool change process. The practicality and effectiveness of the proposed process have been verified through ablation of three-dimensional shape.