• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.302-307
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• 2002

In end milling process, the undeformed chip section area and cutting forces vary periodically with phase change of the tool. However, the real undeformed chip section area deviates from the geometrically ideal one owing to cutter runout and tool shape error. In this study, a method of estimating the real undeformed chip section area which reflects cutter runout and tool shape error was presented during up-end milling of Inconel 718 using measured cutting forces. The specific cutting resistance, K. and $K_t$ are defined as the radial and tangential cutting forces divided by the modified chip section area. Both of $K_r$, and $K_t$ values become smaller as the helix angle increases from $30^\circ$ to $40^\circ$ Whereas they become larder as the helix angle increases from $40^\circ$ to $50^\circ$. On the other hand, the $K_r$, and $K_t$ values show a tendency to decrease with increase of the modified chip section area and this tendency becomes distinct with smaller helix angle.

• 한국정밀공학회지
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• 제19권8호
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• pp.63-70
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• 2002

In end milling process, the undeformed chip section area and cutting forces vary periodically with phase change of the tool. However the real undeformed chip section area deviates from the geometrically ideal one owing to cutter runout and tool shape error. In this study, a method of estimating the real undeformed chip section area which reflects cutter runout and tool shape error was presented in up end milling process using measured cutting forces. The average specific cutting resistance, Ka is defined as the main cutting force component divided by the modified chip section area. Ka value becomes smaller as the helix angle increases from $30^circC \;to\;40\circC$. But it becomes larger as the helix angle increases from $40^\circ$to 50 . On one hand, the Ka value shows a tendency to decrease with increase of the modified chip section area and this tendency becomes distinct with smaller helix angle.

• 지역연구
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• 제15권3호
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• pp.1-13
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• 1999

Since the 1990's, the most important environmental issue on the earth is characterized by "global worming problem". The United Nations Framework Convention on Climate Change (UNFCCC) plays an significant role to solve this problem on a worldwide scale. The main purpose of this paper is to analyse the impact of $CO_2$ reduction on the Daegu regional economy through 1995 regional input-output coefficients derived from the 1995 national input coefficients table by using non-survey method. The sectoral impacts on output, income, and employment were computed under the decline-unequalized assumption in final demand influenced by $CO_2$ reduction. This article has six main sections. Section 1 is an introduction to this paper. Section 2 explains briefly the derivation method of the regional technical coefficients. Section 3 describes the model building through input-output multipliers. In section 4 regional data on output, income, employment and final demand are computed to estimate the regional impacts. Section 5 deals with impact analysis on the Daegu economy. Section 6 contains a brief summary and concludintg remarks. The research findings of this study can be summarized as follows. In 1995, under the assumption of 10% decrease on an average in final demand sectors, the economy of the region studied decreased \3600 billion of output, ￦1114 billion of income, and 49919 man-years of employment. The percent ratios of each value to the total showed 9.4%, 9.7%, and 9.2%, respectively. The dominant sectors associated with impact analysis within the region are chemicals and chemical products, paper, printing and publishing, and textiles and leather, etc; nevertheless, the least dominant sector is non-metallic mineral products. products.

• Structural Engineering and Mechanics
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• 제59권6호
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• pp.993-1017
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• 2016

Helicopters are essential for supporting offshore oil and gas activities around the world. To ensure accessibility for helicopters, helideck structures must satisfy the safety requirements associated with various environmental and accidental loads. Recently, offshore helideck structures have used aluminium because of its light weight, low maintenance requirements, cost effectiveness and easy installation. However, section designs of aluminum pancakes tend to modify and/or change from the steel pancakes. Therefore, it is necessary to optimize section design and evaluate the safety requirements for aluminium helideck. In this study, a design procedure was developed based on section optimization techniques with experimental studies, industrial regulations and nonlinear finite element analyses. To validate and verify the procedure, a new aluminium section was developed and compared strength capacity with the existing helideck section profiles.

• 한국공작기계학회논문집
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• 제11권5호
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• pp.45-52
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• 2002

In an end milling process, the undeformed chip section area and cutting forces vary periodically with the phase change of the tool. However, the real undeformed chip section area deviates from the geometrically ideal one owing to the cutter runout and tool shape error. In the current study, a method of estimating the real undeformed chip section area which reflects the cutter runout and tool shape error is presented during up-end milling processes of Inconel 718. The specific cutting forces, $K_r$ and $K_t$ are defined as the radial and tangential cutting forces divided by the modified chip section area, respectively. Both of the $K_{r}$ and $K_t$ values become smaller as the helix angle increases from $30^{\circ}$ to $40^{\circ}$. Whereas they become larger as the helix angle increases from $40^{\circ}$ to $50^{\circ}$. The $K_r$ and $K_t$ values show a tendency to decrease with increase of the modified chip section area.a.

• 한국생산제조학회지
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• 제9권3호
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• pp.48-54
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• 2000

In this study the characteristics of chip formation of the cold drawn Bi-S free machining steels were assessed. And for comparison those of the cold drawn Pb-S free machining steel the hot rolled low carbon steel which has MnS as free machining inclusions and the conventional steels were also investigated. During chip formation the cold drawn free machining steels show relatively little change in thickness and width of chip compare to those of the conventional carbon steels. And a single parameter which indicates the degree of deformation during chip formation chip cross-section area ratio is introduced. The chip cross-section area ratio is defined as chip cross-section area is divided by undeformed chip cross-section area. The variational patters of the chip cross-section area ratio of the materials cut are similar to those of the shear strain values. The shear stress however seems to be dependent on the carbon content of the materials. The cold drawn Bi-S and Pb-S steels show nearly the same chip forming behaviors and the energy consumed during chip formation is almost same. A low carbon steel without free machining aids shows poor chip breakability due to its high ductility. By introducing a small amount of free machining inclusions such as MnS Bi, Pb or merely increasing carbon content the chip breakability improves significantly.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
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• pp.351-356
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• 1999

In this study, the characteristics of chip formation of the cold drawn Bi-S free machining steels were assessed. And for comparison, those of the cold drawn Pb-S free machining steel, the hot rolled low carbon steel which has MnS as free machining inclusions and the conventional steels were also investigated. During chip formation, the cold drawn free machining steels show relatively little change in thickness and width of chip compare to those of the conventional carbon steels. And a single parameter which indicates the degree of deformation during chip formation, 'chip cross-section area ratio' is introduced. The chip cross-section area. The variational patterns of cross-section area is divided by undeformed chip cross-section area. The variational patterns of the chip cross-section area ratio of the materials cut are similar to those of the shear strain values. The shear stress, however, seems to be dependent on the carbon content of the materials. The cold drawn BiS and Pb-S steels show nearly the same chip forming behaviors and the energy consumed during chip formation is almost same. A low carbon steel without free machining aids shows poor chip breakability due to its high ductility. By introducing a small amount of non-metallic inclusions such as MnS, Bi, Pb or merely increasing carbon content the chip breakability improves significantly.

• Journal of Acupuncture Research
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• 제15권2호
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• pp.43-60
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• 1998

This study examined the histomorphomeric and histological changes of the left and right kidney in uninephrectomized rat. The results were as follows: 1. In the control, the right kidney was more prominent than the left in the basement membrane of glomerular capillaries. The podocyte had well developed Golgi apparatus in the left kidney and rough endoplasmic reticulum in the right kidney. 2. At the 30 days after unilateral nephrectomy, the basal lamina of glomerular capillaries was prominently thickened in the right kidney. The cytoplasm of the podocyte of the left kidney was markedly increased and had free ribosomes, developed Golgi apparatus and rough endoplasmic reticulum. 3. At the 30 days, the section of the glomeruli were more enlarged in the left kidney than in the right. 4. At the 20 day, the nuclear section of the podocytes were markedly enlarged in the right kidney, but those of the left kidney were diminished. The mitochondrial section of the podocytes were prominently increased in the right kidney. 5. The nuclear section of the parietal layer lining cells was no significant change in the right kidney. That of the left kidney was increased at the 20 days and decreased at the 40 days. The nuclear section of glomerular endothelium of the left kidney increased earlier than the right. 6. In the morphometry of the control kidney, the section areas, long and short diameters, the nuclear section, the mitochondrial section of the proximal tubule cells, and the changes of those were more large in the right kidney than in the left. 7. The luminal secretory vesicles and peroxisomes of the left kidney were more than the right at the 20 days. The increase of mitochodrial section in the proximal tubule cells of the left kidney was more prominent than the right. The large cytoplasmic vacuoles were more prominent in the left kidney than in the right. 8. The thickness of cytoplasm and brush border was more thick in the control left kidney than in the control right. The change of cytoplasmic thickness of the left kidney was increased earlier than in the right and both kineys were increased in the thickness of brush border at the 30 days.

• 한국가정과교육학회지
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• 제11권2호
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• pp.89-110
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• 1999

The purpose of this study was to investigate the perception and eating behaviors of middle school students in Kwangju area about food and nutrition section of Home Economics course. The subjects were 480 middle school students. The major results were as follows： On the perception f food and nutrition section, the 1st graders learned ‘how to settle the problems related to food and nutrition and food choices’. The 2nd graders learned ‘the knowledge and principle of food and nutrition for improving dietary life’. The 3rd graders learned ‘actual dietary life functions like arranging menu and preparing meals’. Consequently, there was a significant difference in each grade and all boy and girl students have the highest response to the item ‘they learn how to settle the nutrition problem and foods choices’. On the interests in food and nutrition section, lower graders and girl students have higher interest than hgiher graders and boy students. The area which was considered as most interesting in food and nutrition sections was ‘cooking’ in all students. The perception of the concern on dietary life after learning food and nutrition section was higher in the 1st graders. On the perception of the area where was a great change in their own dietary life after learning food and nutrition section, the 1st graders responded there was a great change in ‘balanced dietary life’, the 2nd graders in ‘eating habit and nutrition of adolescence’and the 3rd graders in ‘cooking’. Especially, girl students showed more changes. On the perception of degree which food and nutrition section gives a help to actual life, students over 50% responded that it was helpful to their actual life. This showed that the lower the grades, the more help it gave to those students. On the perception of mother’s job, the students with working mother considered that they learned ‘actual dietary life functions like functions like arranging menu and preparing meals’from the food and nutrition section. In addition, they had high interests in the area of ‘cooking’. It was recognized that as the family size was greater, the food and nutrition section gave more helps to actual life. On eating behaviors of breakfast, the higher the grade, the more frequent they don’t have breakfast, boy students have more frequencies of having breakfast than girl students and the primary reason of not having breakfast is poor appetite. On whether going without a meal affects study or not, most of the 1st, 2nd and 3rd graders whether they are boys and girls or not responded it affected their study. On eating behaviors of lunch, most of boy and girl students in the 1st, 2nd 3rd grade have lunch box. On eating behaviors of supper, eating time is usually between 7：00 and 8：00 p.m and eating hour is mostly 10 or 15 minutes. On eating behaviors between meals, frequency of eating between meals is mostly once or twice a day and girl students have more frequencies of eating between meals, and the cause was hunger commonly in boy and girl students and ‘killing time’in girl students. The focus in getting the foods is ‘taste’and favorite food is fruit regardless of the grade.

• 대한기계학회논문집B
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• 제33권4호
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• pp.215-224
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• 2009

Analysis for various driven nozzle position changes. The analysis was done for different Reynolds number in entrance region of jet-pump and for several diameter ratios of driven nozzle. (1) The largest absorption energy was found at the point s=1 in condition of diameter ratio 1:3.21 and point s=0.5 in condition of diameter ratio 1:2.25. (2) The absorption energy was not related to the change of entrance velocity and the driven nozzle position having the largest absorption energy was function for cross section ratio. (3) As the position of driven nozzle moves to the downstream, the absorption energy gets weaker. Because the energy from swirl was lost at the cross section gets smaller. (4) As the position of driven nozzle moves to the downstream, the injection energy leans to the upper direction wall and as the Reynolds number increase, the lean phenomenon is more distinct. (5) The flow quantity of driven nozzle, the diameter ratio 1:3.21, was 32% higher than that of 1 : 2.25 and as the inlet velocity gets faster the efficiency decreased. And as the cross section of the driven nozzle increases.