• Tribology and Lubricants
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• v.31 no.6
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• pp.294-301
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• 2015

In this paper, we predict the rotordynamic force coefficients of tilting pad journal bearings (TPJBs) with rocker-back pivots, and we compare the predictions to recently published predictions and test data. The present TPJB model considers the rocker-back pivot stiffness calculated based on the Hertzian contact-stress theory, which is nonlinear with the application of a force . For the five-pad TPJB in load-between-pad and load-on-pad configurations, the predictions show the pressure- and film-thickness distributions, the deflection and stiffness of the individual pivots, and bearing stiffness and damping coefficients. The minimum film thickness and peak pressure occur at the bottom pad on which the applied load is directed. Because of the preload, the pres- sure is positive even at the upper pad in the opposite direction to the applied load. The pivot deflection and stiff- ness are maximum at the bottom pad that receives the heaviest pressure load. The predicted stiffness coefficients increase as the static load and rotor speed increase, while the damping coefficients decrease as the rotor speed increases, but increase as the static load increases. In general, the predicted stiffness coefficients agree well with the test data. The predicted damping coefficients overestimate the test data, particularly for large static loads. In general, the current predictive model considering the pivot stiffness improves the accuracy of the rotordynamic performance compared to previously reported models.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.224-230
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• 2001

A numerical analysis for the gas lubricated flexure-pivot tilting pad journal bearing has been accomplished. The film pressure are obtained by Newton-Raphson method and the dynamic coefficients are evaluated by the pad assembly method. The effects of the pivot position of the pad on the static and dynamic characteristics are presented for three pads journal bearing with LBP. The optimum pivot positions for the static performance is different from that of the dynamic performance.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.433-434
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• 2002

Chemical mechanical polishing refers to a process by which silicon and partially-processed integrated circuits (IC's) built on silicon substrates are polished to produce planar surfaces for the continued manufacturing of IC's. Chemical mechanical polishing is done by pressing the silicon wafer, face down, onto a rotating platen that is covered by a rough polyurethane pad. During rotation, the pad is flooded with a slurry that contains nanoscale particles. The pad deforms and the roughness of the surface entrains the slurry into the interface. The asperities contact the wafer and the surface is polished in a three-body abrasion process. The contact of the wafer with the 'soft' pad produces a unique elastohydrodynamic situation in which a suction force is imposed at the interface. This added force is non-uniform and can be on the order of the applied pressure on the wafer. We have measured the magnitude and spatial distribution of this suction force. This force will be described within the context of a model of the sliding of hard surfaces on soft substrates.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.4
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• pp.7-13
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• 2001

This Study is to investigate the influence of weld residual stresses on the fatigue crack growth behaviors in pressure ves-sel reinforcement. In order to perform this study, the automatically welded specimens are prepared. The material is ASTM A516 grade 60 steel used in pressure vessel mainly. For pad-on-plate of skip welding continuous welding and PWHT specimen, fatigue crack initiation is generally initiat-ed at weld starting and end toe zone, and ruptured at weld starting toe zone, Fatigue life if pad-on-plate continuous speci-men is increased more than that of pad-on-plate skip fillet welding specimene about 85% under low load, about 20% under high load, and decreased than that of two-pad continuous welding specimen about 85%. In da/dN-$\Delta$ Κ curve under low load, pad-on-plate skip fillet welding specimen showed retardation on the initial crack, and the fatigue crack growth rate at the low region of $\Delta$Κ greater specimene E(3.8{\times}10^{-6}$mm/cycle). And the fatigue life of welding specimen was smaller than that of PWHT specimen.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.759-760
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• 2008

• Journal of the Microelectronics and Packaging Society
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• v.5 no.2
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• pp.37-48
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• 1998

The popcorn cracking phenomena in plastic IC packages during reflow soldering are investigated by considering the heat transfer and moisture diffusion through the epoxy molding compound(EMC) along with the mechanics of interface delamination. Heat transfer and moisture diffusion through EMC under die pad are analyzed by finite difference method (FDM)during the pre-conditioning and subsequent reflow soldiering pro-cess and the amounts of moisture mass and vapor pressure at delaminated die pad/ EMC interface are calculated as a function of the reflow soldering time. The energy release rate stress intensity factor and phase angle were obtained under various loading conditions which are thermal crack face vapor pressure and mixed loadings. It was shown that thermal loading was the main driving force for the crack propagation for small crack lengths but vapor pressure loading played more significant role as crack grew.

• Tribology and Lubricants
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• v.9 no.2
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• pp.70-78
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• 1993

Using the finite element method, the film pressure, the transverse force and the firction torque which are distributed over the pad surface of low-friction piston skirt are calculated in order to investigate the dynamic characteristics of the piston. The results indicate that the frictional torque for the low-friction piston pad may increase 3% efficiency in comparison th the conventional one.

• The Journal of Korean Physical Therapy
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• v.32 no.1
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• pp.29-33
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• 2020

Purpose: This study examined the effects of the weight-bearing pattern and calcaneal taping on the heel width and plantar pressure in standing. Methods: Fifteen healthy subjects with normal feet participated in this study. The heel width was measured using a digital caliper, and a pedoscan was used to measure the plantar pressure of the rear foot while standing. The participants were instructed to stand in three weight-bearing patterns (anterior, middle, and posterior weight bearing) before and after calcaneal taping. The heel width and plantar pressure were measured three times before and three times after calcaneal taping, with the three weight-bearing patterns applied in random order. A 2 (non-taping vs. taping) × 3 (anterior, middle, posterior weight bearing) two-way repeated ANOVA with a Bonferroni post hoc correction was used to assess the differences in heel width and plantar pressure. Results: The results revealed a significant main effect of the weight-bearing pattern (p<.01), but not of calcaneal taping (p>.05). Greater weight bearing applied to the heel resulted in a significantly increased heel width and planter pressure of the rear foot (p<.01). Conclusion: In standing, a posterior weight-bearing pattern increases the heel width due to side-to-side shifting of the plantar heel pad, which increases the heel plantar pressure. Therefore, to prevent high stress on the heel pad and plantar heel pain, it is important to refrain from posterior weight bearing while standing during the activities of daily living.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1016-1021
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• 2004

The need for developing a mathematical model for pad-pivot friction in tilting pad proceeding bearings has been well-recognized, since previous experimental work about the performances of the bearings hypothesized that the friction in the bearings is closely related to their performances. Especially, the sliding friction between pad and pivot in the ball and socket type of the bearings can influence the performance of the bearing. We propose a mathematical model for pad-pivot friction in the ball and socket type, which considers the geometrics of the pad and pivot of the bearings, by assuming the sliding friction in the ball and socket bearing as Coulomb friction. By utilizing the proposed model for pad-pivot friction, we show the analysis of Reynolds equation and energy equation, which explain the thermo-hydrodynamic characteristics of tilting pad proceeding bearings, by taking into account the turbulence and inlet pressure building as well. The results of the study show that the performance of titling-pad proceeding bearings can be greatly influenced by the pad-pivot friction. In particular, we have shown that the analysis of the pad-pivot friction is useful to explain the static proceeding loci and the dynamic characteristics of the ball and socket type of the bearings. Furthermore, for a given operating condition, we can obtain various equilibrium states which satisfy the static equilibrium conditions, by considering the pad-pivot friction.

• Journal of Korean Academy of Nursing
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• v.4 no.3
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• pp.93-104
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• 1974

Regardless of a patient's diagnosis, the care of his skin has been a primary concern of nurses throughout the years. Nurses has washed, dried, and rubbed the skin and have changed his position so as to keep the patient's skin in good condition and to protect him from pressure sores. However, we still find many-patients suffering from the pressure sores which may take many mothers or years of treatment and cost a lot to be repaired. In view of expensive cost for treatment of the sores and low ratios of nursing staff per patient for intensive nursing care, prophylaxis of the bed sores with sufficient aids is extremely important both for patients and for nurses. Therefore, the unique purpose of this study was to determine whether sponge is good enough to treat and prevent the pressure sore as compared with gel pad and sheepskin. Sixty patients in the age range of 15 through 45 who were in unconscious status or have difficulty of mobility were chosen between January and March of 1974 at Seoul National University Hospital. They were randomly assigned to each treatment and observed on every 4th day with regard to level of consciousness, status of mobility, moisture or dryness of the bed, general skin condition, intake of nutrition, vital signs and intervals of position change in comparison with the changes of skin over the bony prominences. The study results were reviewed in a statistical method analysis of valiance-to obtain the following findings: 1. There was no significantly different changes of skin over the sanctum or the trochanter in each group using get pad, sheepskin or sponge. It means that we may substitute sponge for expensive gel pad or sheepskin. 2. There was no significant difference among mean changes of patient's skin in relation to sheepskin, gel pad and sponge. 3. There was no significant changes of patient's akin in relation to level of consciousness, status of mobility, intake of nutrition, general skin condition, temperature, blood pressure or interval of position change. 4. There were no meaningful interactions between each treatment and level of consciousness, moisture or dryness of the bed, intake of nutrition, general skin condition, temperature or blood pressure. 5. Sheepskin and gel pad had significantly better influence on patients with limited mobility than on patients with immobility, and sponge on patients with immobility on than patients with limited mobility, 6. Sheepskin and sponge had meaningfully totter influence on patients changing position at below 2-hour interval, gel pad at 2-4-hour interval, sheepskin at 4-6-hour interval, and three of them at above 6-hour interval.