• 한국정밀공학회지
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• 제14권8호
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• pp.101-107
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• 1997

In general, grinding is one of the final machining processes which determines the surface quality of machined products. Since the ground surface is affected by the states of grains and voids on the grinding wheel surface, the wheel should be dressed before the machined surface deteriorates over a quality limit This paper describes a systematic approach to decide a proper dressing chance and an optimal dressing depth for the working grinding wheel. An eddy current sensor and a laser displacement sensor are used to measure the loading on the working wheel surface and the topography of the dressed wheel surface respec- tively. The dressing chance can be properly decided through the relational locus between the amount of handing and the machined surface roughness. An optimal dressing depth to guarantee the less wheel loss and the higher wheel surface quality is decided through the analysis of the variance of topography for the dressed wheel surface, which decreases at three different rates according to the accumulated dressing depth.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.553-556
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• 2003

End-milling have been used in the industrial world because it is very effective to the manufacture of mechanical parts with various shape. Recently the end-milling processing is needed the high-precise technique with good surface roughness and rapid time in aircraft, automobile part and molding industry. Therefore this study carried to decide the optimum cutting condition for surface roughness and rapid manufacturing time using design of experiment and ANOVA. From the results of experimentation, surface roughness have an effect on cutting direction, spindle speed and depth of cut. And then the optimum condition used Taguchi design is upward cutting in cutting direction, 600rpm in spindle speed, 240mm/min feed rate, 2mm in axial depth of cut and 0.25mm radial depth of cut. By using design of experiment, it is effectively represented shape characteristics of working surface in end-milling.

• Geomechanics and Engineering
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• 제23권1호
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• pp.51-59
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• 2020

In this paper, the WEKA platform was used to mine and analyze measured data of floor failure depth and a prediction system of floor failure depth was developed with Java. Based on the standardization and discretization of 35-set measured data of floor failure depth in China, the grey correlation degree analysis on five factors affecting the floor failure depth was carried out. The correlation order from big to small is: mining depth, working face length, floor failure resistance, mining thickness, dip angle of coal seams. Naive Bayes model, neural network model and decision tree model were used for learning and training, and the accuracy of the confusion matrix, detailed accuracy and node error rate were analyzed. Finally, artificial neural network was concluded to be the optimal model. Based on Java language, a prediction system of floor failure depth was developed. With the easy operation in the system, the prediction from measured data and error analyses were performed for nine sets of data. The results show that the WEKA prediction formula has the smallest relative error and the best prediction effect. Besides, the applicability of WEKA prediction formula was analyzed. The results show that WEKA prediction has a better applicability under the coal seam mining depth of 110 m~550 m, dip angle of coal seams of 0°~15° and working face length of 30 m~135 m.

• 벤처창업연구
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• 제10권5호
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• pp.83-92
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• 2015

최근 새로운 업무문화인 코워킹과 이러한 분위기를 조성해주는 코워킹스페이스가 1인 창조기업 및 스타트업을 지원하는 센터들을 중심으로 급격히 증가하고 있다. 하지만 아직 서울지역을 제외한 나머지 지역에서는 코워킹에 대한 지원과 코워킹스페이스를 수용은 하고 있지만 이에 대한 정확한 인식 및 관련 운영활동에 대해서는 다소 부재한 것으로 나타나고 있다. 따라서 본 연구에서는 이에 대한 탐색적 연구를 진행하기 위하여 큰 연구문제인 '코워킹에 대한 인식 및 사례와 코워킹스페이스 수용'과 작은 연구문제 '코워킹스페이스 운영활동'를 주제로 부산지역의 1인 창조기업 비즈니스센터를 중심으로 현장조사와 매니저 심층인터뷰를 실시하였다. 결과를 종합해보면 먼저 쿤 연구문제에 대한 분석결과는 코워킹에 대한 인식과 사례가 있었지만 성과를 위해 매니저가 인위적으로 진행한 것이 대부분이었고, 코워킹스페이스는 교류공간으로 중요하게 인식하고는 있었지만 사무기기가 지원되는 공용 공간 수준으로 활용되고 있었다. 작은 문제에 대한 분석결과에서는 '공간 및 인테리어', '제휴 및 파트너쉽', '커뮤니티 및 커뮤니케이션'에 대한 인식과 활동이 낮게 나타났는데 이에 대한 개선방안을 우수사례를 통해 제시하였다. 본 연구는 현장방문 및 심층인터뷰를 통해 정성적으로 이루어져 정량적인 분석에서 파악할 수 없는 의견까지 수집하고 분석하여 실제적으로 코워킹스페이스를 수용하고자 하는 이에게 시사점을 제시하고 있다는 점에서 의미가 있다.

• 한국정밀공학회지
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• 제6권3호
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• pp.24-31
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• 1989

By use of the machining center, step-feed drilling was operated under the variety of conditions as to materials, tools and cutting conditions. Based on this study the following conclusions can be drawn : 1) The cutting force can be diminished by utilizing the step-feed working; specially the most effective was it for the brass among the carbon steel, the brass, and the cast iron. 2) Tool life can be enlarged more than double when three-step-feed working is used. 3) For the constant cutting-depth(30mm), the most optimal number of stepping is 3.

• 한국전기전자재료학회논문지
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• 제21권12호
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• pp.1063-1070
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• 2008

The performance of an acoustic transducer is determined by the effects of many design variables, and mostly the influences of these design variables are not linearly independent of each other. To achieve the optimal performance of an acoustic transducer, we must consider the cross-coupled effects of the design variables. In this study, the variation of the performances of underwater acoustic transducer in relation to its structural variables was analyzed. In addition, the new optimal design scheme of an acoustic transducer that could reflect not only individual but also all the cross-coupled effects of multiple structural variables, and could determine the detailed geometry of the transducer with great efficiency and rapidity was developed. The validation of the new optimal design scheme was verified by applying the optimal structure design of a flextensional transducer which are the most common use for high power underwater acoustic transducer. With the finite element analysis(FEA), we analyzed the variation of the resonance frequency, sound pressure, and working depth of a flextensional transducer in relation to its design variables. Through statistical multiple regression analysis of the results, we derived functional forms of the resonance frequency, sound pressure, and working depth in terms of the design variables. By applying the constrained optimization technique, Sequential Quadratic Programming Method of Phenichny and Danilin(SQP-PD), to the derived function, we designed and verified the optimal structure of the Class IV flextensional transducer that could provide the highest sound pressure level and highest working depth at a given operation frequency of 1 kHz.

• Journal of Periodontal and Implant Science
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• 제31권3호
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• pp.531-542
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• 2001

Periodontal debridement is most important procedure in periodontal treatment, because periodontal disease is the biofilm infection. The use of ultrasonic instrument has many clinical advantages compared to classical hand instrument. The introduction of newly developed ultrasonic scaler tips made the use of ultrasonic scaler popular. However the study of tooth substance removal according to the working parameters of ultrasonic scaler with newly developed tips is not sufficient. The purpose of this study is to evaluate the effects of working parameters of piezoelectric ultrasonic scaler with curette tip on casting gold removal. The working parameters was standardized by the sledge device which controls lateral force(0.5 N, 1.0 N, 2.0 N) and power setting was adjusted 2, 4, 8 in P mode and S mode and instrumentation time was 5 seconds. The defect depth and width were measured with profile meter and defect surface was examined by SME. The depth of defect was significantly large in S mode( $39.58{\pm}19.35{\mu}m$) compared to P mode( $8.37{\pm}6.98{\mu}m$). There was significant decrease of depth of defect between 1.0N($32.87{\pm}27.18{\mu}m$) and 2.0N( $14.86{\pm}15.04{\mu}m$). The area of defect was also significantly large in S mode($4482.42{\pm}3551.71{\mu}m^2$) compared to P mode( $922.06{\pm}960.32{\mu}m^2$). There was significant decrease of area of defect between 1.0N($3889.12{\pm}3936.00{\mu}m$) and 2.0N( $974.66{\pm}986.01{\mu}m$). The change of mode did not effect on the width of the defect. The change of power setting did not effect on the depth, width, and area of defect. In spite of limitation of this study it could be concluded that the use of piezoelectric ultrasonic scaler with curette tip on S mode could make significant tooth substance loss.

• Tribology and Lubricants
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• 제26권6호
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• pp.329-335
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• 2010

Recently, the End-milling processing is needed the high-precise technique to get a good surface roughness and rapid time in manufacturing of precision machine parts and electronic parts. The optimum surface roughness has an effect on end-milling working condition such as, cutting direction, spindle speed, feed rate and depth of cut, and so on. It needs to form the correlation of working conditions and surface roughness. Therefore this study was carried out to presume of surface roughness on end-milling working condition of Al7075 by regression analysis. The results was shown that the coefficient of determination($R^2$) of regression equation had a fine reliability of 87.5% and nonlinear regression equation of surface rough was made by multiple regression analysis.

• 아동학회지
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• 제27권1호
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• pp.31-44
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• 2006

This study focused on the lives of working mothers in its examination of the meaning of an employer supported educare center. Ethnographic methods including participant observation, in-depth interview, and the analysis of documents were used for the case study at D educare center where management has been entrusted to K University. Results showed that employer supported educare center had significant meanings in the lives of working mothers. Meanings consisted of stories about relieving time conflicts, adapting themselves to life space, putting confidence in the educare center, and organizing community. Meanings gained from this study suggest that D educare center could be a model for employer supported educare centers focused on the lives of working mothers.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2110-2115
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• 2008

In this study, We disigned and manufactured the Hot Chuck which can be operated until $120^{\circ}C$. Its shape is circular, wide is 300mm and depth is 15mm. Two types working fluid was used as working fluid(distilled water, 0.1%-$TiO_2$ nanofluid). The experimental results were compared to each working fluid. The effect of various working fluid, charging volume ratio was investigated. Also we investigated heat transfer rate against each working fluid. By using nanofluid, heat transfer rate can be enhanced and the wick structure can be constructed automatically on smooth surface. The experiment of 40% charged 0.1%-$TiO_2$ nanofluid showed the best performance of thermal accuracy and uniformity. To improve performance of Hot Chuck, more study is needed.