• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.821-826
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• 2006

This paper presents a novel type of hybrid dispensing head for IC fabrication and surface mount technology. The proposed mechanism consists of solenoid valve and piezoelectric stack as actuators, and provides positive-displacement and jet dispensing. The positive-displacement dispensing can produce desired adhesive amount without viscosity effect, while the jet dispensing can produce high precision adhesive amount. In order to determine the relationship between required voltage of the piezo actuator and needle displacement, both static and dynamic analysis are undertaken, In addition, finite element analysis is performed in order to find optimal design parameters. Dispensing flow rate and pressure in the chamber are evaluated through fluid dynamic model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.586-591
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• 2004

A load/unload mechanism is applied to most small form factor hard disk drives. Loading velocity is ones of the most important factors to ensure the reliability of the load/unload operations. Especially, the lower the flying height of the head becomes, the more important the accuracy of the loading velocity control becomes. Because there is no sensor during the load/unload operations, BEMF voltage is used to sense the head velocity. To measure BEMF voltage, a simple circuit is added to the load/unload HDD control system. Overall acceptable results are obtained by using the simple PI controller but the errors from the target velocity occur when the head moves along the ramp and then reaches the disk. Feedforward profile and disturbance observer are used to remove those errors effectively.

• Journal of KSNVE
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• v.8 no.6
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• pp.1062-1068
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• 1998

This paper describes the vibration characteristics of a high head pump-turbine runner. with nine blades and an outer diameter of 4.410 mm. of the pumped storage power plant. Mode shapes and natural frequencies were obtained by means of both the finite element analysis and modal testing. both in air and in water. The natural frequencies in air were calculated using the finite element method by ANSYS software. In order to confirm calculation results. the natural frequencies and mode shapes of the runner were measured using a hydraulic exciter both in air and in water. Natural frequencies of the pump-turbine runner were found at 174. 310 Hz in air, and at 107. 184 Hz in water. The first mode shape is flat plate mode with two nodal diameter and the second one is also flat plate mode with three nodal diameter. It can be shown that the natural frequencies of the pump-turbine runner in water is reduced approximately 40 ％ due to additional mass effect. Natural frequencies in air predicted by ANSYS software are in good agreement with test results.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.3
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• pp.171-180
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• 2000

This paper deals with the whole-body vibration and ride quality evaluation in the vertical direction. The responses of the floor, hip, back, and head in four subjects were measured for various seats when the floor was excited by random vibration with r.m.s of 1.2m/s2 in the vertical direction. In the transmissibility between the hip and floor, the fundamental mode is observed at 4.4 Hz. In the transmissibility between the head and floor, the fundamental mode at 4.4Hz and the second mode at 7.6Hz are observed. It is shown that the head motion is 41% larger than the hip motion and the response of female subject is larger than that of male subject. The response without backrest also was compared with that with backrest. From these human responses ride quality of five seats were evaluated by the ride value such as transfer ration having frequency weighting function is the statistical sense. It is observed that the seat having high damping property can reduce the most acceleration exposed to hip in the statistical sense for all ride valves, while the seat having different seat spring doesn't show statistical difference.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.7 s.166
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• pp.1155-1163
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• 1999

This study deals with the vibration ride quality for passenger car when running on straight highway at the speed of 70km/h. Ten accelerations were measured at four positions, three axes each at the feet, hip, and head, and one axis at the back. Five seats that have different static sponge stiffness were used, and two subjects were participated. These accelerations were analyzed to produce the ride values such as component ride value and overall ride value. It was hard to see the difference of ride value by the change of sponge stiffness. However we could rank the ride quality by the total vibration exposed to passengers. From the transfer function between the hip and the foot, the fundamental mode was observed to be around 5.8Hz. Also the transfer function between the head and hip was studied. The optimal damping ratio of the seat was calculated according to the seat natural frequency with human weighting filter which makes the optimal damping ratio different from that without weighting filter.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.2 s.140
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• pp.136-141
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• 2005

An experiment method has been developed to analyse the vibration characteristics of marine propeller blades, and vibration tests have been carried out on the model scale propeller in air and in water. The driving point transfer function(acceleration/excitation force) has been measured and modified by compensating the attachment effect of the impedance head. The measured natural frequencies in air have been compared with the theoretical results by an in-house FEM code PROSTEC. The added masses have been derived by comparing the measured natural frequencies in air and in water, and the results have been compared to the results using existing formula based on experience.

• Journal of Biosystems Engineering
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• v.32 no.3
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• pp.153-159
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• 2007

This study was conducted to measure and analyze the noise from a combine head. The combine head, comprised of a cutting knife assembly, pick-up chains, horizontally conveying chains and vertically conveying chains, had an overall sound level of 101 dBA. The sound levels of each component were, respectively, 98.3 dBA for the cutting knife assembly, 88.9 dBA for the pick-up chains, 79.8 dBA for the horizontally conveying chains and 86.3 dBA for the vertically conveying chains, being equivalent to 54.4%, 18.4%, 6.5% and 13.7% of the overall head noise. The main cause of the head noise was considered the impacts that the joint of the cutting knife assembly made with frame when it oscillated. The impact sound was also generated when the chain lug collided with the chain case. To reduce these impact sound, anti-vibration rubbers were installed on the knife assembly joint and the chain cases. It reduced the head noise by 4 dBA but the overall noise level of the combine head was still high. In order to protect the combine operators more effectively from the noise, a safety cab needs to be installed on the combine.

• Tribology and Lubricants
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• v.23 no.2
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• pp.61-65
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• 2007

It is very important to connect machinery and maintain it. This is usually done by bolt joint. There are two ways in connecting the bolt joint : the angle method and the torque method. The torque method is a method that let the clamping force maintain. The underhead of the bolt's head and the thread friction are the main influences. This study focuses on how the clamping farce and friction coefficient change under the condition in vibrating the underhead of the bolt's head part. As a result, under vibration condition, we found out that the clamping farce increases, while the friction coefficient decreases.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.779-781
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• 2005

In this paper, Firstly, it is shown that the bending mode vibration source of vertical pump system is comparatively large because resonance. Secondly in order to reduce the bending mode vibration of vertical pump, The improvement of some boundary condition have been developed and its effectiveness is investigated as appling it at the vertical pump system pratically.

• 유체기계공업학회:학술대회논문집
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• 1998.12a
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• pp.166-172
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• 1998

This paper describes the shaft vibration phenomena measured on a pump-turbine ofa pumped storage power plant. The pump-turbine runs at a rotational speed of 450 rpm (7.5 Hz). The power output (load) of the pump-turbine was varied from 100 to 300 MW in the generating mode. It was found that the magnitude of the shaft vibration was highly dependent upon the power load. The vibration magnitude of the shaft vibration is very high in the middle load zone from 170 to 210 MW, elsewhere the vibration low. From vibration spectra, it was found that the frequency of major vibration in that load zone was 2.5 Hz which is approximately $34\%$ of the shaft rotating speed in Hz. This frequency component disappeared below and above that load zone. This subsynchronous vibration is caused by the flow induced disturbance due to spiral vortex flow downstream of the pump-turbine runner. Furthermore, it was found that shaft vibration was highly decreased due to the increase of bearing preload.