• 한국정밀공학회지
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• 제34권3호
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• pp.167-172
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• 2017

This study proposes a method for identifying correlations between tension and drop height for sessile droplets in a roll-to-roll processing system. The effect of tension and drop height on the contact angle of a sessile droplet is presented. Design of experiment (DOE) methodology and statistical analysis are used to define a correlation between the process parameters. The contact angle is decreased while increasing tension and drop height. The influence of the tension is less significant on the contact angle compared with the effect of the drop height. However, tension should be considered as a major parameter because it is not easy to fix with roll eccentricity and compensating speed of the driven roll. The results of this study show that the effect of tension on the contact angle of a sessile droplet is more important than drop height because the drop height is fixed when the process systems are determined.

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1269-1279
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• 2023

Pool boiling experiments are performed within an isolated bubble regime at inclination angles of 0° and 45°. When a bubble grows and departs from the heating surface, the pressure, buoyancy, and surface tension force play important roles. The curvature and base diameter are required to calculate the pressure force, the bubble volume is required to calculate the buoyancy force, and the contact angle and base diameter are required to calculate the surface tension force. The contact angle, base diameter, and volume of the bubbles are evaluated using images captured via a high-speed camera. The surface tension force equation proposed by Fritz is modified with the contact angles obtained in this study. When the bubble grows, the contact angle decreases slowly. However, when the bubble departs, the contact angle rapidly increases owing to necking. At an inclination angle of 0°, the contact angle is calculated as 82.88° at departure. Additionally, the advancing and receding contact angles are calculated as 70.25° and 82.28° at departure, respectively, at an inclination angle of 45°. The dynamic behaviors of bubble growth and departure are discussed with forces by pressure, buoyancy, and surface tension.

• 반도체디스플레이기술학회지
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• 제12권2호
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• pp.63-66
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• 2013

Carbon Nanotube have been proposed for use in various applications for electromechanical systems. Nano-electromechanical resonators which provide high frequency resolution and long energy storage time, play an important role in wide area fields of science and engineering. Using the control of tension in carbon nanotube, can be made the tunable resonator. In the study, we analysis the tunable frequency change of resonator by tension changes due to the rotation angles of the single-walled carbon nanotube resonator. The frequency characteristics of a resonator as a function of the rotation angle. The tension was found to decrease with increasing rotation angle, and therefore the resonance frequencies could be changed by controlling the single-walled carbon nanotube rotation angle. The resonance frequencies decreased with increasing angle, and when the rotation angle was greater than $60^{\circ}$, these changes were marked.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.169-169
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• 2000

The modeling for the looper of a hot strip finishing mill to control the tension of the strip is presented. The looper is an arm pushing against the strip between stands in a tandem mill to keep the strip tension constant and to isolate the interactions of the adjacent stands. Tension is influenced by the difference in mass flow through the up stream and down-stream rolling stands. Tension is critical to strip quality, influencing width, gauge, and shape. This paper presents how looper angle and strip tension are controlled for a hot strip finishing mill.

• 제어로봇시스템학회논문지
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• 제16권10호
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• pp.1006-1012
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• 2010

The hot rolling process ranks the highest position for production in steel making process. The hot strip manufacturing processes consist of the reheating furnace, roughing and finishing mill and coiler. The reheating furnace heats the slab. The roughing and finishing mill produce the hot strip from slab. The hot strip quality mainly depends on finishing mill, which consists of 4-high 7 stands. The looper is installed between stands and is used for controlling the strip tension by the looper angle for better material flow. It is difficult to control the strip tension with the coupled looper system from interaction between the looper angle and strip tension. Too much deviation of strip tension severely affects the poor width quality of the hot strip. It is important to control simultaneously both the looper angle and strip tension with each of their target values. This paper proposes the fuzzy tension control, which is developed to minimize the width deviation of the hot strip by maintaining the proper strip tension between stands and to achieve the stable operation of the coupled looper system. The fuzzy tension control performance is compared with the conventional PID control by experimental results.

• 대한기계학회논문집B
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• 제27권7호
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• pp.956-962
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• 2003

The Lippmann-Young equation has been widely used in electrowetting to predict the contact-angle change of a droplet on a insulating substrate with respect to the externally-applied electrical voltage. The Lippmann-Young equation is derived by assuming a droplet as a perfect conductor, so that the effect of the electrical double layer and the line tension are not taken into account. The validity of the assumption has never been checked before, systematically. In the present investigation, a modified Lippmann-Young equation is derived taking into account of the effect of the electrical double layer and the line tension. To assess their influence on contact-angle change in electrowetting, the electrostatic field around the three-phase contact line is analyzed by solving the Poisson-Boltzmann equation numerically. The validity of the numerical methods is verified by using the past theoretical results on the electrostatic field around a wedge-shaped geometry, which shows fairly good agreement. The results of the present investigation clearly indicate that the effect of the electrical double layer and the line tension is negligible for a millimeter-sized droplet. On the other hand, for a micron-sized droplet, the effect of the line tension can become a dominating factor which controls the contact-angle change in electrowetting.

• 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).

• 대한물리의학회지
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• 제14권2호
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• pp.137-144
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• 2019

PURPOSE: The continued use of smartphones has resulted in an abnormal body posture and neck alignment changes. Maintaining this posture for a long time weakens the flexor muscles in the neck and shortens the extensor muscles in the neck. This study examined the correlation between the suboccipital muscle tension and deep neck flexor muscle physical endurance according to the craniovertebral angles. METHODS: The craniovertebral angle, tension of the suboccipital muscle and endurance of the deep neck flexor muscle were measured in 58 healthy 20-year-old male and female college students. The tension of suboccipital muscle and endurance of the deep neck flexor muscle were then divided according to the body mass index (BMI). Their correlation with the craniovertebral angle was then examined. Each parameter was measured three times to determine the interrater reliability. RESULTS: The craniovertebral angle and suboccipital muscle tension showed differed significantly. On the other hand, the craniovertebral angle and deep neck flexor muscle physical endurance showed no significant differences. CONCLUSION: The results show that the craniovertebral angle and deep neck flexor muscle physical endurance were not correlated, but a smaller craniovertebral angle resulted in a higher suboccipital muscle tension.

• Fibers and Polymers
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• 제3권2호
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• pp.80-84
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• 2002

Tension control is an important factor in producing high quality knitted products and in maintaining good processing condition. Yarn tension during knitting is subject to be affected from many elements of the machine and process parameters. Several factors including yam feeding speed, feeding angle, and needle gauge that are considered to influence on the tension variation were investigated. Yam feeding speed did not show high contribution to the tension variation but feeding angle of yam did show high correlation with the tension. No or negative correlation of the tension with needle gauge was found from the results. In order to keep well-determined process condition in the knitting manufacturing, it is strongly suggested that all knitting elements and parameters should be in the integrated control circumstance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 B
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• pp.561-563
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• 1999

The looper of a hot strip finishing mill is installed between each pair of stands and plays a key role to enhance the product quality of strip by controlling the tension and height of strip in each inter-stand. Though the conventional looper control has achieved the mass products of strip so far, it has difficulties not only tuning gains by means of errors which are caused by coupling effects between strip tension and looper angle both utilizing tension feedback. Therefore, the non-interactive control employing cross controller and tension feedback has been introduced in looper control system in order to overcome the coupling effects existing between tension and looper angle and track the reference tension efficiently. In this paper, we present the cross controllers which play a role to decouple reciprocal effects between tension and looper angle and show better performance.