• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.22 no.2
• /
• pp.310-317
• /
• 2013

In this paper, the contact pressure of the wafer and polishing pad for final polishing process for 300 mm-wafer were investigated through numerical analysis using FEM tool, ANSYS. The distribution of the contact pressure is one of main parameters which affects on the flatness and surface roughness of polished wafers. Two types of polishing head, a hard type head with ceramic disk and a soft type head with air bag were considered. The effects of the deformation and initial shape of table on the contact pressure were also examined. Both heads and tables were modeled as 3D finite element model from solid model, and the material properties of polishing pads and rubber plate for the air-bag head were obtained from tensile tests. The contact pressure deviation on wafer surface was smaller with air bag head than hard type head even when the table had form errors such as convex or concave. From this 3D analysis, it could be concluded that the air-bag head has better uniformity of the contact pressure on wafer. Also, the effects of inner diameter of air bag and radial clearance between wafer and retainer were investigated as view point of contact pressure concentration on the edge of wafer.

• Journal of the Korean Society of Physical Medicine
• /
• v.16 no.2
• /
• pp.1-8
• /
• 2021

PURPOSE: This study examined the effects of changes in the head direction (forward, upward 10° and downward 10°) on the quadriceps, center of pressure (COP), and foot pressure during squat exercises. The aim was to determine if the head direction could better activate the quadriceps muscle and provide a safer and stable squat posture during squat exercise. METHODS: Fifteen healthy college students were asked to stand on a Zebris, and three electrodes for sEMG were attached to their vastus medialis oblique (VMO), vastus lateralis (VL), and rectus femoris (RF) muscles. The participants then performed squatting exercises under three head directions (forward, upward 10°, and downward 10°). Surface electrodes were then used to record the EMG data during exercise. The Zebris FDM-SX was used to measure the foot pressure and COP of the participants. RESULTS: In squat exercise, the upward head direction group showed significantly higher VL activation than the downward head direction group (p < .05). The upward head direction group showed a significant backward change in the deviation of the COP than the downward and forward groups (p < .05). The upward head direction group showed a significant decrease in forefoot pressure than the downward and forward groups (p < .05) and an increase in the hindfoot pressure compared to the downward and forward groups (p < .05). CONCLUSION: The head direction upward in squat exercise has a positive effect on the quadriceps.

• Korean Journal of Hydrosciences
• /
• v.7
• /
• pp.77-86
• /
• 1996

An air chamber is design to keep the pressure from exceeding a predetermined value, or to prevent low pressures and colum separation. Therefore, it can be used to protect against rapid transients in a pipe system following abrupt pump stoppage. In this research, an air chmber was applied to a hypthetical pipe system to analyze attenuation effect of pressure head for different air volumes, locations, chamber areas, coefficients of orifice loss and pollytropic exponents. With an increase of air volume, the maximum pressure head at pump site is decreased and the minimum pressure head is imcreased. For different locations and areas of the chamber, the attenuation effects do not show much difference. Also, as the orifice loss coefficient increases, the maximum pressure head is decreased. For different polytropic exponents, isothermal process shows lower maximum pressure head than that of the adiabatic process.

• Journal of Biosystems Engineering
• /
• v.5 no.2
• /
• pp.1-14
• /
• 1980

This study was carried out to investigate the effects of the counter-pressure setting and the roller speed of a rice whitening machine on the head rice recovery. milling capacity and milling efficiency, and also to find out the optimum operational conditions of the machine. The radial pressure inside the whitening chamber and the outlet axial pressure were measured to study their relationships with the head rice recovery, milling capacity and milling efficiency. The results of the study are summarized as follows. (1) The most important factor in rice whitening was the counter-pressure setting. It significantly affected the head rice recovery. (2) The roller speed significant affected the milling capacity and milling efficiency , but it did not affected the head rice recovery. (3) Both the radial pressure and the outlet axial pressure were affected by the counter-pressure setting but not by the roller speed. Both of them increased almost linearly with the counter-pressure setting. There was a significant correlation between the radial pressure and the outlet axial pressure. (4) The flow rate through the whitening chamber when the feed gate was fully opened increased with the roller speed, but it was not affected by the counter-pressure setting. (5) The head rice recovery decreased as the counter-pressure setting increased , but it was not affected by the roller speed. The reason could be explained by the fact that the radical pressure increased only with the counter-pressure setting. (6) The milling capacity increased with the counter-pressure setting and linearly with the roller speed. The milling efficiency generally increased with both the counter-pressure setting and the roller speed. However, the effect of roller speed was negligible at the higher counter-pressure setting. The temperature rise inside the whitening chamber was moderate with the mean of 11.3℃ (range 5.6-18.3℃) even though it increased slightly with the roller speed. Considering the head rice recovery and milling efficiency, the optimum operational conditions of the machine appeared to be the counter-pressure setting of 67g/㎠ and the roller speed of 1,050rpm. Neglecting the small difference in the head rice recovery , the greater milling capacity could be obtained at the counter-pressure setting of 85g/㎠ with the roller speed of 850-1050rpm.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.21 no.4
• /
• pp.563-569
• /
• 2012

In the semiconductor and display device production processes, the handling of sensitive objects needs new carrying technology. Floating carrying motion is a practical alternative solution for non-contact handling of parts and substrates. This paper presents a study of through paths inside the air pressure pick-up head to generate the floating motion. The air motion by conceptual designed paths inside the head gradually develops positive pressure and vacuum between narrow objects. Positive pressure occurs through the head tip before discharging outside of the head. Negative pressure is developed by evacuating the inside head bottom as result of the radial flow connecting the vertical through-holes. The numerical analysis was done to figure out the stable levitation caused by the two acting forces between surfaces. In comparing with the standard case that the levitation gap gets 0.7-0.9 mm, it confirms the suggested head characteristics to show floating capacity in accordance with the head size, number of through-hole, and locations of through-hole in succession of conceptual design for a prototype.

• The Korean Journal of Physiology
• /
• v.5 no.2
• /
• pp.71-78
• /
• 1971

Anesthetized dogs were tilted from horizontal to the upright and head down position. Tilting to the upright position was followed by an increase in heart rate. In the head down position a decreased heart rate was obtained. The arterial blood pressure was decreased in the upright position and was decreased markedly in the head down position. The central venous pressure was decreased in the upright position and was markedly decreased down to the negative pressure in the head down position. The respiratory rate was slightly increased in the upright position comparing to that in the horizontal position. No remarkable changes were noted in the head down position. From the above results the following factors were discussed The decreased arterial blood pressure during the upright position was supposed to be the secondary effect from the diminished venous return that was suggested by the decreased central venous pressure. The decreased arterial blood pressure in the head down position was also supposed as the above reason as the diminished central venous pressure during the tilt. In addition the cardioinhibitory effects originated from the baroreceptors might have been operated during head down tilting. In the heart rate there was slight tachycardia in the upright position this was assumed as the abolished cardioinhibitory impulses from the baroreceptor in the upright position. On the contrary, despite of the decrease of arterial blood pressure in the head down position as well as in the upright, the bradycardia have been appeared. This was suggestive of cardioinhibitory impulses from the baroreceptors which was stretched during head down tilting. From the above findings there is a possibility of continous cardioinhibitory responses during head down tilting for this kind of the short period of 10 minutes which was chosed in this study.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.16 no.5
• /
• pp.157-165
• /
• 2017

The high-pressure resin transfer molding (HP-RTM) technology has been commercialized for fast production of fiber reinforced composite materials. The high-pressure mixing head was one of the most core component of the HP-RTM process. In this study, a mixing head was systematically designed, manufactured and evaluated. This mixing head was composed of a nozzle, a mixing chamber, a cleaning piston part, and an internal mold release part. In actual, a straight-type structure was newly designed instead of the conventional L-type structure for improving the maximum mixing pressure and mixing ratio precision. The performance of mixing head was showed maximum mixing pressure of 15.22MPa and mixing ratio precision of 0.12%. CFRP molding experiments were successfully obtained a 6~11 laminating carbon sheet using HP-RTM presses and specimen molds.

• Water for future
• /
• v.28 no.5
• /
• pp.141-150
• /
• 1995

An air chamber is designed to keep the pressure from exceeding a predetermined value, or to prevent low pressures and column separation. Therefore, it can be used to protect against rapid transients in a pipe system following abrupt pump stoppage. In this research, an air chamber was applied to a hypothetical pipe system to analyze attenuation effect of pressure head for different air volumes, locations, chamber areas, coefficients of orifice loss and polytropic exponents. With an increase of air volume, the maximum pressure head at pump site is decreased and the minimum pressure head is increased. For different locations and areas of the chamber, the attenuation effects do not show much difference. Also, as the orifice loss coefficient increases, the maximum pressure head is decreased. For different polytropic exponents, isothermal process shows lower maximum pressure head than that of the adiabatic process.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.21 no.3
• /
• pp.401-407
• /
• 2012

The recent manufacturing process in the thin wafers and flat panel necessitate new approaches to reduce handling fragile and surface-sensitive damage of components. This paper presents a new pneumatic levitation for non-contact handling of parts and substrates. This levitation can achieve non-contact handling by blowing air into an air pressure pick-up head with radial passages to generate a negative pressure region. Negative pressure is caused by the radial air flow by nozzle throat and through holes connecting to the bottom region. The numerical analysis deals with the levitational motion with different design factors. The dynamic motion is examined in terms of force balance(dynamic equilibrium) occurring to the flow field between two objects. The stable equilibrium position and the safe separation distance are determined by analyzing the local pressure distribution in the fluid motion. They make considerable design factors consisting the air pressure pick-up head. As a result, in case that the safe separation distance is beyond 0.7mm, the proposed pick-up head can levitate stably at the equilibrium position. Furthermore, it can provide little effect of torque, and obtain more wide picking region according to the head size.

• Journal of the Ergonomics Society of Korea
• /
• v.30 no.2
• /
• pp.339-347
• /
• 2011

Objective: The purpose of this study was to evaluate of various material of pillows by using biomechanical variables such as the cervical stability, head pressure distribution, and muscle activity. Method: Eight subjects participated in the experiment. Three different materials such as polyester sponge, memory foam and the buckwheat shell used for Korean traditional pillow were tested. Electro-goniometer, six channels of electromyography(EMG), ten channels of the head pressure sensors were used to measure the biomechanical responses. Surface electrodes were attached to the right/left semispinals capitis(RSC, LSC), the right/left sternocleidomastoid(RSM, LSM), the right/left upper trapezius(RUT, LUT). The cervical stability was evaluated by the angle deviated from the standing neck position. The head pressure distribution was evaluated by the pressure per unit area recorded on the sensors and the intensity of peak pressure. Electromyography(EMG) data were analyzed by using root mean square(RMS) and mean power frequency(MPF). Results: The buckwheat shell material showed a higher stability in the cervical spine then the other pillows during spine position. In terms of head pressure distribution, the memory form indicated the lowest pressure at supine position, buckwheat shell material indicated the lowest pressure during lying down to side, and polyester cushion recorded the highest pressure at all postures. Conclusion: The buckwheat shell material has a biomechanical advantage to maintain a healthy neck angle and reduce the pressure on the head, which means the buckwheat shell is a potential material for ergonomic pillow design. The pillow with memory form showed second best biomechanical performance in this study. Application: The shape of the buckwheat shell pillow and the characteristics of materials can be used to design the pillow preventing neck pain and cervical disk problems.