• 소성∙가공
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• 제12권6호
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• pp.558-565
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• 2003

Rotary swaging is one of the incremental forming process which is a chipless metal forming process for the reduction of cross-sections of bars, tubes and wires. In the present work, the rotary swaging machine and dies were designed to investigate the formability of TDS(Tube Drive Shaft) used in automotive industry. The process variables such as the speed of forming, the shape of the formed materials and the reduction of area were also estimated to study experimental analyses of rotary swaging process using the materials of 34Mn5 and S45C. From experimental results, it was found that the process variables affected the quality of TDS in terms of hardness, the precision of products and the surface roughness. The hardness after swaging approved to be Increased with the increase in the reduction of diameter. And it was found that the grain size became smaller and the elongated grains were formed in the axis direction.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.361-365
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• 2001

Laboratory tests are conducted to validate the mechanical model of a filament-wound composite shaft. Also, design charts are produced by validated analytical calculations based on the Timoshenko beam model of a layered steel/composite structure. The major results found are that steel/composite hybrid shafts can lead to better dynamic and static performances over steel or pure composite shafts of the same volume, and the most effective composite structures contain some steel in the form of a tubular core. These results can be used in the design process of composite boring bars and automotive drive shafts.

• Wind and Structures
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• 제4권2호
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• pp.163-176
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• 2001

Two 12 m high tubular steel lighting columns have been instrumented to determine the wind-induced fatigue loading experienced by such columns. Each column supported a single luminaire mounted on a 0.5 m long bracket. One column was planted in soil, and the other bolted through a welded baseplate to a substantial concrete base. The columns were strain gauged just above the shoulder weld which connected the main shaft to the larger base tube. Forced vibration tests were undertaken to determine the natural frequencies and damping of the columns. Extensive recordings were made of response to winds with speeds from 4 m/s to 17 m/s. Selected records were analysed to obtain stress cycle counts and fatigue lives. Mean drag coefficients were also derived from the strain data to investigate experimentally the effect of Reynolds Number.

• 한국임상수의학회지
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• 제17권1호
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• pp.76-82
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• 2000

This study was undertaken to find out the effect of persimmon leaves on histopathological changes of cadmium toxicity in mice. Seventy two BALB/c mice of male were divided into a control group(A) and five experimental groups (B, C, D, E, F) : group A received tap water and basal diet, group B received tap water and diet supplemented with 3% persimmon leaves alone, group C received basal diet and 300 ppm cadmium, group D, E and F received basal diet supplemented with 1, 3% and 7% persimmon leaves and 300 ppm cadmium respectively. Cadmium dissolved in tap water was used, and the persimmon leaves were mixed with feed. All mice were dissected on the 84th day. Pathological changes in liver, kidney, cortical osseous tissue of femoral shaft, bone trabecular of femur, and epiphyseal cartilage plate of femur were observed. Group B showed no significant changes as the control group. But group C showed the unclearness of specific cells in liver, the loss of architecture and necrosis of hepatocyte, degeneration and necrosis of renal convoluted tubules, desquamation and vacuolization of the greater part of the renal tubular epithelium, marked thinning of the cortical osseous tissue in femoral shaft, reduction of cancellous bone volume and decreaswe of trabecular number, and marked thinning of epiphyseal cartilage plate in femur. On the other hand, persimmon leaves-treated group showed a little convalescent changes an maintained their normal architectures in liver, kidney, cortical osseous tissue of femoral shaft, bone trabecular of femur, and epiphyseal cartilage plate of femur.

• Steel and Composite Structures
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• 제17권6호
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• pp.891-906
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• 2014

This study aims to present a three dimensional finite element model to investigate the wave propagation in a concrete filled steel tubular column (CFSC) due to transient impact load. Both the concrete and steel are regarded as linear elastic material. The impact load is simulated by a semi sinusoidal impulse. Besides the CFSC models, a concrete column (CC) model is established for comparing under the same loading condition. The propagation characteristics of the transient waves in CFSC are analyzed in detail. The results show that at the intial stage of the wave propagation, the velocity waves in CFSC are almost the same as those in CC before they arrive at the steel tube. When the waves reach the column side, the velocity responses of CFSC are different from those of CC and the difference is more and more obvious as the waves travel down along the column shaft. The travel distance of the wave front in CFSC is farther than that in CC at the same time. For different wave speeds in steel and concrete material, the wave front in CFSC presents an arch shape, the apex of which locates at the center of the column. Differently, the wave front in CC presents a plane surface. Three dimensional effects on top of CFSC are obvious, therefore, the peak value and arrival time of incident wave crests have great difference at different locations in the radial direction. High-frequency waves on the waveforms are observed. The time difference between incident and reflected wave peaks decreases significantly with r/R when r/R < 0.6, however, it almost keeps constant when $r/R{\geq}0.6$. The time duration between incident and reflected waves calculated by 3D FEM is approximately equal to that calculated by 1D wave theory when r/R is about 2/3.

• 한국임상수의학회지
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• 제18권2호
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• pp.116-123
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• 2001

This study was undertaken to find out the effect of Korean safflower seed powder on histopathological changes of cadmium toxicity in mice. Fifty BALB/c mice were divided into a control group(A) and four experimental groups(B, C, D, E) : group A received tap water and basal diet, group B received tap water and diet supplemented with 3% Korean safflower seed powder alone, group C received basal diet and 300 $\mu\textrm{g}$/g of cadmium, group D and E received basal diet supplemented with 3% and 10% Korean safflower seed powder and 300$\mu\textrm{g}$/g of cadmium respectively. Cadmium dissolved in tap water was used, and the Korean safflower seed powder were mixed with feed. All mice were dissected on the 56th day. Histopathological changes in liver, kidney, lung, cortical osseous tissue of femoral shaft, bone trabecular of femur, and epiphyseal cartilage plate of femur were observed. Group B showed no significant changes compared with the control group. But group C showed the unclearness of specific cells in liver, the loss of architecture and focal necrosis of hepatocyte, the glomerular swelling, degeneration and necrosis of convoluted tubules, desquamation and vacuolization of the greater part of the renal tubular epithelium, the marked congestion and thickness of the wall of alveolus in lung, slightly thinning of the cortical osseous tissue in femoral shaft, reduction of cancellous bone volume and marked narrowness of bone trabecular, marked thinning of epiphyseal cartilage plate and irregular arrangement of columnar structure of cartilage cells. On the other hand, Korean safflower seed powder-treated group showed a little convalescent changes and maintained their normal architectures in liner, kidney, lung, cortical osseous tissue of femoral shaft, bone trabecular of femur and epiphyseal cartilage plate of femur.

• 대한토목학회논문집
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• 제38권1호
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• pp.51-61
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• 2018

풍력발전기, 송전탑, 굴뚝 등과 같은 타워 구조물의 기초는 기초에서부터 하중 작용점까지의 거리가 멀고 큰 수평하중이 작용하여 매우 큰 전도모멘트에 저항해야 한다. 이러한 구조물을 경제적으로 지지하기 위해서는 암반층이라도 인발력을 받는 말뚝기초를 시공해야 한다. 따라서, 본 연구에서는 암반매입 강관말뚝에 사용되는 주면고정액의 배합비가 주면지지력에 미치는 영향을 평가하기 위하여 물/시멘트비와 잔골재의 배합비를 실험변수로 삼아 모형실험을 수행하였다. 잔골재를 배합하지 않은 시멘트풀의 경우 물/시멘트비의 변화에 관계없이 최대 주면지지력과 잔류 주면지지력은 일정한 범위에 분포하였고, 잔골재가 배합된 경우는 물/시멘트비의 증가에 따라서는 감소하였고 잔골재 배합비의 증가에 따라서는 증가하다 감소하는 경향을 나타내었다. 잔골재가 없는 경우 최대주면지지력은 물/시멘트비에 상관없이 약 540~560kPa을 나타내었고, 잔골재비가 40%인 경우 물/시멘트비에 따라 약 770~870kPa을 보여 잔골재가 없는 경우에 비하여 약 40~55% 증가되었다. 본 실험에서 찾은 최적배합은 잔골재비가 40% 정도, 물/시멘트비가 80~100% 이었다.

• 전기학회논문지
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• 제57권6호
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• pp.966-971
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• 2008

Free-piston engine system is a new type energy converter which uses a linear motion of piston by using linear generator. In free-piston engine system, the piston is not connected to a crank-shaft. The major advantages of free-piston engine system are high efficiency and low mechanical loss from the absence of motion conversion devices. Linear generator of free-piston engine system is used as generator and starting motor. In design step, considering of back-emf and detent force characteristics for generating mode and thrust and control characteristics for starting mode is needed. In this research, generating mode of flat-type linear generator and tubular-type linear generator is analyzed by finite element analysis method and starting mode of both type linear generators is analyzed by using capability curve. Capability curve is plotted from electrical parameters of both type linear generator and motion profile is calculated from mechanical parameters.

• Journal of Korean Neurosurgical Society
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• 제56권5호
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• pp.371-374
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• 2014

Neurosurgeons have been trying to reduce surgical invasiveness by applying minimally invasive keyhole approaches. Therefore, this paper clarifies the detailed surgical technique, its limitations, proper indications, and contraindications for a superciliary keyhole approach as a minimally invasive modification of a pterional approach. Successful superciliary keyhole surgery for unruptured aneurysms requires an understanding of the limitations and the use of special surgical techniques. Essentially, this means the effective selection of surgical indications, usage of the appropriate surgical instruments with a tubular shaft, and refined surgical techniques, including straightforward access to the aneurysm, clean surgical dissection, and the application of clips with an appropriate configuration. A superciliary keyhole approach allows unruptured anterior circulation aneurysms to be clipped safely, rapidly, and less invasively on the basis of appropriate surgical indications.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2006년도 춘계학술대회 논문집
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• pp.395-398
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• 2006

this paper provides a novel method to start the linear engine coupled linear generator from dead stop to its final steady state operation. This method depends mainly to use the linear generator mounted on the shaft of the linear engine to provide the required thrust force to move and oscillate the linear engine from bottom to top dead centers. It is a cost effective approach to start the internal linear combustion engine using its coupled tubular permanent magnet linear generator proposed here. This linear generator operates in this case in motoring mode, providing the required thrust force by feeding this linear generator phases with currents by using a three phase PWM inverter controlled by position feedback scheme. In order to provide the desired thrust force with specific value and direction, a position feedback is required to control the free piston engine motion through controlling the inverter switches using PWM control scheme.