• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.8 s.227
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• pp.976-983
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• 2004

In high-density hard disk drives, the slider should be made to fly close to the magnetic recording disk to generate better signal resolution and at an increasingly high velocity to achieve better data rate. The slider disk interaction in CSS (contact-start-stop) mode is an important source of particle generation. Contamination particles in the hard disk drive can cause serious problems including slider crash and thermal asperities. We investigated the number and the sizes of particles generated in the hard disk drive, operating at increasing disk rotational speeds, in the CSS mode. CNC (condensation nucleus counter) and PSS (particle size selector) were used for this investigation. In addition, we examined the particle components by using SEM (scanning electron microscopes), AES (auger electron spectroscopy), and TOF-SIMS (time of flight-secondary ions mass spectrometry). The increasing disk rotational speed directly affected the particle generation by slider disk interaction. The number of particles that were generated increased with the disk rotational speed. The particle generation rate increased rapidly at motor speeds above 8000 rpm. This increase may be due to the increased slider disk interaction. Particle sizes ranged from 14 to 200 nm. The particles generated by slider disk interaction came from the lubricant on the disk, coating layer of the disk, and also slider surface.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.3
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• pp.1085-1090
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• 2011

To assure the safety of rolling stock, it is important to perform the fatigue analysis of reduction gear unit in rolling stock considering a variation of velocity and traction motor capability. This paper presents fatigue analysis of the damage of reduction gear unit of railway vehicle under variable amplitude loading(VAL) based on quasi-static fatigue analysis using finite element model and linear Miner's rule. The VAL for the simulation was constructed from the tractive effort curve and train run curves of railway vehicle under commercial operation condition using MSC.ADAMS dynamic analysis. The finite element model for evaluating the carburizing effect on the gear surface was used for predicting the fatigue life of the middle gear based on strain-life based approach. The results showed that the frequent high starting torque due to a quick start as well as increasing numbers of stops at station would decrease the fatigue life of reduction gear unit.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.3
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• pp.29-37
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• 2000

In this paper, the thrust control of PWM Inverter-fed SLIM(Single-sided Linear Induction Motor) is achieved by vector control and PID control with DSP(TMS320C32). SLIM which used as a conveyor has required the quick response and the constant operating without air gap trembling while it conveys load.Thus, SLIM should have the smallest trembling of air gap length. First, voltage equations for SLIM are calculated from the proposed equivalent circuit in this peper, and not only the exciting current but also the thrust component are obtained from them. The thrust current ripple can be reduced by the vector controller using a slip angle frequency, and the PID controller is also use for the position control.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.2
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• pp.74-80
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• 2008

The feasibility study into the development of turbine spinners, which start up the turbo-pump, has been carried out and the design requirements and parameters ranges have been presented. Turbine spinners use the solid propellant as such composite propellant based AN compound with high energy plasticizers, coolants, and phase stabilizer which relieves a sensible volume change due to the phase transformation of AN near room temperature. Propellants which have a homing rate of $0.2{\sim}0.3\;mm/s$ and pressure exponent ranged from 0.3 to 0.6, showed stable burn-out in the standard motor tests. Both the magnitude of ignition energy and its thermal transfer mechanism have been proved to have a tangible effect on the ignition of the pyre starter, and the results of this study showed that a flame temperature of 1400K would be quite adequate to get a stable ignition for the AN composite propellant.

• The Journal of Internal Korean Medicine
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• v.19 no.1
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• pp.168-184
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• 1998

Clinical Observation was made on 120 Cases of CVA that were confirmed through brain CT of Oriental Medical hospital of Se-Myung University from July in 1997 to June in 1998. 1. The CVA cases were classified into the following kinds : cerebral infarction, cerebral hemorrhage, subarachnoid hemorrhage(SAH), and the greatest in number among them were the cases of cerebral infarction. 2. The most cases were 50 of age in all cases, in cerebral infarction were over 70 of age. There is no significant difference in the frequency of strokes between the male and female. the ratio was 1.07 : 1. 3. The frequency of strokes seems to have no relation to month and season. 4. The course of entering hospital, most patients visited this hospital directly(not through any other hospital) within 24hours. 5. The first attack was noted in 80.8%, the recurrance attack in 19.2% and the cerebral infarction had high recurrance ratio compared with cerebral hemorrhage. 6. The average duration of hospitalization was 25.2 days. 7. The most ordinary preceding disease was hypertension. 8. The common symptoms were motor disturbance and dysphasia. 9. The most frequent location of the lesion in cerebral infarction was parietal lobe, in cerebral hemorrhage was basal ganglia. 10. According to electrocardiography findings, abnormality was noted in cerebral infarction more than cerebral hemorrhage, subarachnoid hemorrhage. 11. The hypercholesterolemia and hypertriglyceridemia were found more frequently in cerebral infarction than cerebral hemorrhage, subarachnoid hemorrhage. 12. The average time to start physical theraphy was 7.76 days after admission. 13. The most common complications were pneumonia and bed sore.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.1
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• pp.60-67
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• 2006

To improve the vehicle fuel economy, various technologies have been studied. Meanwhile it deteriorates fuel economy that the increased driving torque for Power Steering System (PSS) due to weighted vehicle and widened tire for low speed driving and parking. So the larger driving torque for PSS is, the lower fuel economy is. Therefore, the study about the effect of the driving torque for PSS and the engine total friction must be preceded to improve the vehicle fuel economy. In this study, a PSS module separated from the vehicle is used to measure the driving torque for PSS with respect to the pressure of PSS. The result shows that the driving torque for PSS was in direct proportion to the pressure of PSS 3 (N-m) driving torque for PSS vs. 10 (bar) pressure of PSS, and 8 (N-m) vs. 40 (bar). In addition, the driving torque and pressure for PSS was measured according to the engine speed in the component test condition which was in the vehicle condition. Measuring the driving torque for PSP in the vehicle condition was established by using the VeFAS which was a fuel economy analyzer developed in our lab and installing PSS By-pass line. The effect of the driving torque for PSS on the vehicle fuel economy was analyzed with FTP-75 cold start mode.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.3
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• pp.73-82
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• 2011

Most of countries start to restrict the emission gases of vehicles especially CO2 because of the global warming. Many vehicle companies including Toyota have launched various HEVs to satisfy the restriction laws and to improve the vehicle's efficiency. However, development for heavy-duty hybrid system is not plentiful rather than the passenger car. In this study, we choose the optimal size of engine, motor and battery for heavy-duty hybrid systems using dynamic programming. Also we analyze the correlation of the system's cost and efficiency because the added cost of vehicle to make the hybrid system is very important factor for the manufacturing companies. Finally, this study suggests a method to choose the appropriate system components size considering its performance and the cost. With this method, it is possible to select the component size for various systems.

• The Journal of Korean Medicine
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• v.19 no.2
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• pp.59-74
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• 1998

Clinical observation was done on 272 cases of patients who were diagnosed as CVA with brain CT, TCD, MRI scan and clinical observation. They were hospitalized in the oriental medical hospital of Kyung-Won University from 1st January to 31st December in 1997. 1. The cases were classified into the following kinds: cerebral infarction, cerebral hemorrhage. and transient ischemic attack. The most case of them was the cerebral infarction. 2. There is no significant difference in the frequency of strokes in male and female. And the frequency of strokes was highest in the aged over 50. 3. In cerebral infarction the most frequent lesion was the territory of middle cerebral artery, and in cerebral hemorrhage the most frequent lesion was the basal ganglia. 4. The most ordinary preceding disease was hypertension. and the next was diabetes. 5. The rate of recurrence was high in cerebral infarction. 6. The cerebral infarction occurred usually in resting and sleeping, and the cerebral hemorrhage in acting. 7. The common symptoms were motor disability and verbal disturbance. 8 The average time to start physical therapy was 1l.3rd day after stroke in cerebral infarction and it was 15.2th day after stroke in cerebral hemorrhage. 9. The common complications were urinary tract infection, pneumonia, myocardial infarction. 10. Hypercholesterolemia and hypertriglyceridemia are usually found more frequently in cerebral infarction than in hemorrhage. 11. In acute or subacute stage, the methods of smoothening the flow of ki(順氣), dispelling phlegm(祛痰), clearing away heat(淸熱) or purgation(瀉下) were frequently used. and in recovering stage, the methods of replenishing ki(補氣), tonifying the blood(補血) or tranquilization(安神) were frequently used.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.43 no.4
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• pp.161-167
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• 2020

In the process of cutting large aircraft parts, the tool may be abnormally worn or damaged due to various factors such as mechanical vibration, disturbances such as chips, and physical properties of the workpiece, which may result in deterioration of the surface quality of the workpiece. Because workpieces used for large aircrafts parts are expensive and require strict processing quality, a maintenance plan is required to minimize the deterioration of the workpiece quality that can be caused by unexpected abnormalities of the tool and take maintenance measures at an earlier stage that does not adversely affect the machining. In this paper, we propose a method to indirectly monitor the tool condition that can affect the machining quality of large aircraft parts through real-time monitoring of the current signal applied to the spindle motor during machining by comparing whether the monitored current shows an abnormal pattern during actual machining by using this as a reference pattern. First, 30 types of tools are used for machining large aircraft parts, and three tools with relatively frequent breakages among these tools were selected as monitoring targets by reflecting the opinions of processing experts in the field. Second, when creating the CNC machining program, the M code, which is a CNC auxiliary function, is inserted at the starting and ending positions of the tool to be monitored using the editing tool, so that monitoring start and end times can be notified. Third, the monitoring program was run with the M code signal notified from the CNC controller by using the DAQ (Data Acquisition) device, and the machine learning algorithms for detecting abnormality of the current signal received in real time could be used to determine whether there was an abnormality. Fourth, through the implementation of the prototype system, the feasibility of the method proposed in this paper was shown and verified through an actual example.

• Journal of Aerospace System Engineering
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• v.16 no.3
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• pp.93-98
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• 2022

The purpose of this paper was to propose a method for improving the performance of the open-loop control of single-phase permanent magnet synchronous motor (SP-PMSM), based on a square wave voltage injection. Generally, the SP-PMSM driving systems cmprise a full-bridge inverter and asymmetric air-gap structure of magnetic circuit, because a zero torque occurs on the symmetrical air-gap. As a result, it cannot be started at a specific rotor position. Thus, it is possible to cause the start-up failure at an open-loop control for sensorless operation of SP-PMSM. In this paper, the method with square wave voltage injection considering the nonlinearity of the inverter is presented to resolve the problem. The effectiveness of the proposed algorithm is verified through several experiments.