• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.623-628
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• 2011

Micro EDM(Electric Discharge Machining) is one of the most powerful technologies which are capable of fabricating micro-structure without any problems from high cutting force. However, there is a significant defect in the part machining with deep holes or pockets, because debris which are generated by electric discharging may frequently cause a short circuit between an electrode and workpiece material. Vibration flushing can reduce the undesirable phenomena with dynamic flow of EDM fluid in a deep and choked area. In this study, Vibration flushing with solenoid is suggested and the results show that the method can generate a remarkable EDM efficiency with high amplitude at a low frequency in comparison with current vibration flushing methods with high frequency using piezo actuators.

• Korean Journal of Materials Research
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• v.27 no.12
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• pp.716-721
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• 2017

SiAlON-based ceramics are some of the most typical ceramic materials used as cutting tools for HRSA(Heat Resistant Super-Alloys). SiAlON can be fabricated using ceramic processing, such as mixing, granulation, compaction, and sintering. Spray drying is a widely-used method for producing a granular powder of controlled morphology and size with flowability. In this study, we report a systematic investigation aimed at optimizing spherical granule morphology by controlling spray-drying parameters such as gas flow and feed rate. Before spray drying, the viscosities of the raw material slurries were also optimized with the amount of dispersant added.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.6
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• pp.1002-1012
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• 1997

When the presintered ceramics are machined with ceramic tool, the tool life becomes extremely short. The CBN tool exhibits the best performance in dry machining of the ceramics presintered at $1450^{\circ}C$ among all cutting tests. The roughness of the machined surface of the ceramics presintered below $1350^{\circ}C$ is smaller than that of the ceramics presintered at $1450^{\circ}C$ While the performance of the cemented carbide and CBN tools is better in dry than in wet machining, the diamond tool shows adverse tendency. The tool life is not affected by the feed rate and depth of cut. During the following full-sintering after the machining of the presintered ceramics, the surface roughness decreases up to 62%. The finished surface in machining the presintered ceramics is much better than that in machining the full-sintered ceramic.

• Journal of The Korean Society of Grassland and Forage Science
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• v.10 no.3
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• pp.158-163
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• 1990

This experiment was to study the effect of pure mineral nitrogen fertilizing on seasonal distribution of dry matter yield and the advisable mineral nitrogen amounts on grassland. The results were as follows: 1. With longer regrowth periods the absolute dry matter yields and the nitrogen-efficiences due to nitrogen fertilizing increased substantially, whereas the quality declined at the relatively lesser cutting frequencies. 2. The first cut at 3-cut regimes, the first and fourth cut at 4-cut regimes, and the second and last cut at 5-and 6-cut regimes showed the highest nitrogen-efficiency, respectively. 3. By the sigmaformed process of production curve the most efficient mineral N-dressing rate per ha and cut was calculated: 42-56kg N on the 3-cut areas, 39-55kg N on the 4-cut areas, 38-47kg N on the 5-cut areas and 35-48kg N/ha/cut on the &cut areas. 4. In dependence on site and kind of calculation the economical borders were reached with the following dressings of mineral N/ha/cut: 90-100kg on the 3-cut areas, 70-100kg on the 4-cut areas and 50- 90kg on the 5-and 6-cut areas.

• Journal of Biomedical Engineering Research
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• v.24 no.4
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• pp.247-257
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• 2003

This paper proposes a three-dimensional (3D) segmentation algorithm for extracting a diagnostic object from ultrasound images by using a LoG operator In the proposed algorithm, 2D cutting planes are first obtained by the equiangular revolution of a cross sectional Plane on a reference axis for a 3D volume data. In each 2D ultrasound image. a region of interest (ROI) box that is included tightly in a diagnostic object of interest is set. Inside the ROI box, a LoG operator, where the value of $\sigma$ is adaptively selected by the distance between reference points and the variance of the 2D image, extracts edges in the 2D image. In Post processing. regions of the edge image are found out by region filling, small regions in the region filled image are removed. and the contour image of the object is obtained by morphological opening finally. a 3D volume of the diagnostic object is rendered from the set of contour images obtained by post-processing. Experimental results for a tumor and gall bladder volume data show that the proposed method yields on average two times reduction in error rate over Krivanek's method when the results obtained manually are used as a reference data.

• Progress in Superconductivity and Cryogenics
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• v.23 no.3
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• pp.5-9
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• 2021

Comprehensive utilization of sulfur-containing iron tailings (SIT) not only solves environmental problems but also creates certain economic value. The iron element from SIT was enriched by the superconducting high gradient magnetic separation (S-HGMS) technology in this study. In the experiments, the total iron content (TFe) was increased from 26.3% to 60.5% with the total sulfur content (TS) of 5.9% under the optimal parameters, i.e., a magnetic flux density of 0.4 T, a slurry flow rate of 1500 mL/min. The high-quality sulfur-containing material with TFe of more than 60% was obtained, which can be used for preparing high-sulfur free cutting steel. The S-HGMS technology can realize the resource utilization of iron tailings with high added value.

• The Korean Journal of Food And Nutrition
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• v.34 no.1
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• pp.123-131
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• 2021

This study investigated the current status of foodservice management and the importance and performance of foodservice management according to the level of knowledge of workers. A survey was conducted between February 2015 and March 2015 for 329 foodservice workers at Community Child Centers in Chungbuk Area. Of these respondents, the majority (78.4%) of them were females. Most of them were in their 40s (40.4%) or 50s (33.4%). If the respondent's correct answer rate of knowledge was 0~50% or 51~100%, the respondent was classified into a 'Low Group (LG, n=175)' or a 'High Group (HG, n=154)'. Among a total of 14 foodservice management questions, 6 items (personal hygiene: 1 item; food material: 2 items; and food processing: 3 items) had relatively higher performance scores for workers in HG than for workers in LG. As a result of Importance-Performance analysis, 'Use different knives and cutting boards for fish, meat, and vegetables' was a variable of high importance but low performance. It was found that improvement was most urgently needed. Results of this study can be used to derive important items for improving foodservice management and policy development for foodservice workers at Community Child Centers.

• Journal of Surface Science and Engineering
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• v.54 no.3
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• pp.133-138
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• 2021

Ternary Ti-X-N coatings, where X = Al, Si, Cr, O, etc., have been widely used for machining tools and cutting tools such as inserts, end-mills, and etc. Ti-Al-N-O coatings were deposited onto silicon wafer and WC-Co substrates by a cathodic arc evaporation (CAE) technique at various negative substrate bias voltages. In this study, the influence of substrate bias voltages during deposition on the microstructure and mechanical properties of Ti-Al-N-O coatings were systematically investigated to optimize the CAE deposition condition. Based on results from various analyses, the Ti-Al-N-O coatings prepared at substrate bias voltage of -80 V in the process exhibited excellent mechanical properties with a higher compressive residual stress. The Ti-Al-N-O (-80 V) coating exhibited the highest hardness around 30 GPa and elastic modulus around 303 GPa. The improvement of mechanical properties with optimized bias voltage of -80 V can be explained with the diminution of macroparticles, film densification and residual stress induced by ion bombardment effect. However, the increasing bias voltage above -80 V caused reduction in film deposition rate in the Ti-Al-N-O coatings due to re-sputtering and ion bombardment phenomenon.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.9
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• pp.12-20
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• 2022

Delamination and burr defects are important problems in drilling fiber reinforced plastics. A method for measuring FRP drilling defects has been studied. Delamination and burr factors were defined as the relative length or area. Using these factors, the effects of tool shape and drilling conditions on delamination and burr were studied. In this study, the defects that occur when drilling a glass-carbon fiber hybrid composite were compared in terms of three factors. In the glass-carbon fiber hybrid composite, the effects of the feed rate and tool point angle on the delamination and burr factors were similar to those in previous studies. The diameter of the tool did not affect the defect factor. A circular burr was generated in a drill tool with a point angle of 184°, and a relatively small deburring factor was observed compared with a tool with a point angle of 140°.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.1
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• pp.138-149
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• 1994

This paper introduces a new monitoring technique which utilizes an adaptive signal processing for feature generation, coupled with a multilayered merual network for pattern recognition. The cutting force signal in face milling operation was modeled by a low order discrete autoregressive model, shere parameters were estimated recursively at each sampling instant using a parameter adaptation algorithm based on an RLS(recursive least square) method with discounted measurements. The influences of the adaptation algorithm parameters as well as some considerations for modeling on the estimation results are discussed. The sensitivity of the extimated model parameters to the tool state(new and worn tool)is presented, and the application of a multilayered neural network to tool state monitoring using the previously generated features is also demonstrated with a high success rate. The methodology turned out to be quite suitable for in-process tool wear monitoring in the sense that the model parameters are effective as tool state features in milling operation and that the classifier successfully maps the sensors data to correct output decision.