• International Journal of Precision Engineering and Manufacturing
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• 제3권3호
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• pp.76-81
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• 2002

In order to study the fatigue crack and retardation mechanism in variable loading, the effects of crack tip branching in crack growth retardation were examined. The characteristics of crack tip branching behavior were considered with respect to microstructure and crack tip branching angle was examined. Crack tip branching was observed along the grain boundary of finite and pearlite structure. It was found that the branching angle ranges from 25 to 53 degrees. Using the finite element method, the variable of crack driving farce to branching angle was examined. The effective crack driving farce (K$\_$eff/) decreased as the branching angle increased. The rate of decrease was 33% for kinked type and 29% for forked one. It was confirmed that the effect of crack tip branching is a very important factor in crack growth retardation. Therefore, crack branching effect should be considered in building the hypothetical model to predict crack growth retardation.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1441-1445
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• 2008

Insect flight is adapted to cope with each circumstance by controlling a variety of the parameters of wing motion in nature. Many researchers have struggled to solve the fundamental concept of insect flight, but it has not been solved yet clearly. In this study, to find the most effective flapping wing kinematics, we conducted to analyze CFD data on fixing some of the optimal parameters of wing motion such as stoke amplitude, flip duration and wing rotation type and then controlled the deviation angle by fabricating wing tip motion. Although all patterns have the similar value of lift coefficient and drag coefficient, pattern A(pear-shape type) indicates the highest lift coefficient and pattern H(pear-shape type) has the lowest lift coefficient among four wing tip motions and three deviation angles. This result suggest that the lift and drag coefficient depends on the angle of attack and the deviation angle combined, and it could be explained by delayed stall effect.

• 한국자동차공학회논문집
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• 제12권5호
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• pp.180-186
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• 2004

The simulator of a vehicle equipped with mechanical transmission and hydraulic accumulator type-braking energy regeneration system is developed using a PC. The simulator receives the shift lever position, the accelerator pedal angle and the brake pedal angle generated by the operator using the keyboard, updates the state variables of the energy regeneration system responding to the input signals, and draws the moving pictures of the accumulator piston and pump/motor plate angle every drawing time on the PC monitor. Also, the operator can observe the shift lever position, the accel pedal angle, brake pedal angle, pressures of accumulators, vehicle speed, hydraulic torque, engine torque and air brake torque representing the operation of braking energy regeneration system through the PC monitor every drawing time. The simulator can be a very useful tool to design and improve the braking energy regeneration system.

• Nuclear Engineering and Technology
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• 제53권6호
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• pp.1878-1886
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• 2021

For industrial package (IP)-type transport containers for radioactive materials, a free drop test should be conducted under regulatory conditions. Owing to various uncertainties observed during the drop test, errors in drop angles inevitably occur. In IP-type metal transport containers in which the container directly impacts onto a rigid target without any shock absorbing materials, the error in the drop angle due to a slight misalignment makes a significant difference from the ideal drop. In particular, in a vertical drop, the error in the drop angle causes a strong secondary impact. In this paper, a numerical method is proposed to estimate the error in the drop angle occurring during the test. To determine this error, an optimization method accompanying a computational drop analysis is proposed, and a surrogate model is introduced to ensure calculation efficiency. Effectiveness of the proposed method is validated by performing the verification and comparison between the test and the analysis applied with the drop angle error.

• Journal of Advanced Marine Engineering and Technology
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• 제33권1호
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• pp.52-61
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• 2009

This experiment was conducted in attempt of improving hydrodynamic efficiency of the propulsion mechanism by installing a spring to the wing so that the opening angle of the wing in one stroke can be changed automatically, compared to the existing method of fixed maximum opening angle in Weis-Fogh type ship propulsion mechanism. Average thrust coefficient was almost fixed with all velocity ratio with the prototype, but with the spring type, thrust coefficient increased sharply as velocity ratio increased. Average propulsive efficiency was larger with bigger opening angle in the prototype, but in the spring type, the one with smaller spring coefficient had larger value. In the range over 1.0 in velocity ratio where big thrust can be generated, spring type had more than twice of propulsive efficiency increase compared to the prototype.

• 대한전기학회논문지:전력기술부문A
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• 제54권3호
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• pp.133-138
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• 2005

This paper presents a characteristics of horizontal swing angle in V type suspension string sets for 765kV T/L. The design of V type suspension string set does not differ from that of general string set for general towers, but it prevents instabilities from swing motion by the horizontal angle and by the wind pressure. We were designed specially 6 conductor yoke, arcing horn and earth horn. And we were decided to 550mm for a distance of strings. We were carried out characteristics of horizontal swing test and movement of mass center test for V-string sets of 400kN single, 300kN double and 400kN double. This products will be used for 765kV T/L of 1 circuit in suspension towers.

• The Journal of Korean Physical Therapy
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• 제14권1호
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• pp.117-124
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• 2002

Poor posture of the neck and head long been recognized as a factor contributing to the onset and perpetuation of pain in the head and neck region. The purposes of the study were to evaluate the changes in forward head posture and pressure pain threshold in tension type headache group and control group. Forward head posture were measured to craniovertebral angle and cranial rotation angle. Craniovertebral angle was smaller in tension type headache group(p<0.05), and cranial rotation angle was larger in tension type headache group(p<0.05). Pressure pain threshold was similar between tension type headache group and control group with the exception of right suboccipitalis and left temporalis(p<0.05).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.627-629
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• 2004

V type suspension string sets prevent instabilities from swing motion by the horizontal angle and by wind pressure. These installation conditions are controled mainly 3 items - normal swing angle by horizontal angle of line, unusual swing angle by strong wind, minimum vertical loads. We calculated and analysed that factors for the 765kV transmission line condition. And we were tested swing characteristics of V-string sets in real size test situation. So, we find to installation condition for the V type suspension string sets. This results will be used to design of V type suspension string set and to decision of the installation condition.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.668-673
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• 2000

Spud angle( ${\alpha}$ ) and fuel injection angle ( ${\beta}$ ) have strong influence on spud type gas burner combustion. A wide range of flame stability is shown at ${\alpha}=60^{\circ}$, but at ${\alpha}=30^{\circ}$ is narrow. Optimum condition of flame stability swirl angle( ${\gamma}$ ) is $40^{\circ}$. At condition of ${\alpha}=30^{\circ}$ flame shape is relatively narrow and long, on the other hand, at ${\alpha}=60^{\circ}$ flame is wide and short. Regardless of spud angle, maximum flame temperature shows in the range of Z=200mm and R=0mm. Flame temperature, on the whole, is high at ${\alpha}=45^{\circ}$. At ${\alpha}=45^{\circ}$, NOx emission is higher than other conditions that may be concerned with flame temperature. At ${\beta}=60^{\circ}$ and ${\gamma}=40^{\circ}$, NOx emission is reduced due to fuel injection angle.

• Journal of Biosystems Engineering
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• 제30권3호
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• pp.161-165
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• 2005

In this study, peeling test of the Altari radish on kimchi pre-processing system for mechanization was performed with the longitudinal plane peeling type with wider cutting blade than that of the peeled chip's. To determine the optimum cutter shape to match this plane peeling type, the peeling tests depending on variable cutting speed, rake angle and blade angle using the blade with thickness as 2 m and width as 50mm were performed, and the patterns of the peeled chips and peeling resistances were investigated. As the result of the tests, the rake angle of the blade with clean peeled surface of the Altari radish was over $45^{\circ}$, and the blade angle and rake angle with the minimum peeling resistance was $20^{\circ}\;and\;60^{\circ}$, respectively. The optimum peeling conditions were; the peeling speed 0.2m/s, blade angle $20^{\circ}$ and the rake angle $60^{\circ}$, and the peeling resistance of each blade was 15 N.