• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.2
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• pp.111-117
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• 2011

Vibration monitoring is required for reliable thermosonic testing to decide whether sufficient vibration is achieved in each test for the detection of cracks. From a practical point of view, a cheaper and convenient monitoring method is better for the application to real tests. Therefore, the performance of different sensors for vibration monitoring was investigated and compared in this study to find a convenient and acceptable measurement method for thermosonics. Velocity measured by a laser vibrometer and strain provide an equivalent HI when measured at the same position. The microphone can provide a cheaper vibration monitoring device than the laser and the heating index calculated by a microphone signal shows similar characteristics to that calculated from velocity measured by the laser vibrometer. The microphone frequency response shows that it underestimates high frequency components but it is applicable to practical tests because it gives a conservative value of HI.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.807-811
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• 2002

As the requirements on precision and speed of motion in chip mounter increase, vibration forces are always exerted on operating conditions. To insure safety of the chip mounter, the vibration must be kept within an acceptable limit. The focus of this paper is on the identification of dynamic load characteristics and the estimation of static and dynamic stiffness characteristics for Frame Base by judicious selection of the number and the location of the support points. This study carried an analytical and experimental method to estimate the dynamic characteristics in structure.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.474-477
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• 2005

In tactical theater, it is crucial to detect ground moving targets and to locate them precisely. This problem can be resolved by using SAR (Synthetic Aperture Radar) sensors providing GMTI (Ground Moving Target Indication) capability. In general, to implement a robust GMTI sensor is not simple because of the strong competitions between target signals and clutter signals on the ground, and low speed of moving targets. Contrary to the case that a delay canceller is mostly suitable for ground surveillance radars, DPCA (Displaced Phase Centered Antenna) or STAP (Space Time Adaptive Processing) techniques have been adapted for GMT! function of modem airborne radars. In this paper, anew scheme of DPCA using two passive antennas with vertical separation is proposed, which also provides good clutter cancellation performance. The proposed scheme enables us to scan straight ahead of the carrying platform that is impossible with typical DPCA configuration. Simulations using various conditions have been performed to validate the proposed scheme, and the results are acceptable.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.3
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• pp.68-75
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• 2000

The flexibility of a manipulator inevitably yields vibration at the end effector. In this work, position and vibration control for a flexible robot arm was studied using a separate voice coil type actuator to raise the accuracy and speed of end tip. A flexible robot arm with a tip mass is modeled as an Euler-Bernoulli beam. An $H_$\infty$$ controller is adapted to get a robust control against unmodeled higher-order mode vibration, output sensor noise, and etc. Simulations and experiments show that the modeling of the system is acceptable and robust vibration control is also achieved.

• KSTLE International Journal
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• v.6 no.1
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• pp.17-20
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• 2005

The object of the present work is the natural lre%uency analysis of femto slider, HeaHdisk interaction during starustop and constant speed were detected by using the acoustic emission (AE) test system. The frequency spectrum analysis wasperformed using the AE signal obtained during the head/disk interaction. The FFT (Fast Fourier Transform) analysis of the AEsignals is used to understand the interaction between the AE signal and the state of contact. Natural frequency analysis wasperformed using the ANSYS program. The results indicate acceptable accordance of finite element calculation results with theexperimental results.

• Proceedings of the KOSOMBE Conference
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• v.1994 no.05
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• pp.88-91
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• 1994

We develope a assistant system of foot pressure distribution for improvement gait Pattern, adapted working speed, and minimitation of muscle fatigue of the sensory feedback type FES system(SEFES). This measurement system consist of mat type pressure sensor with piezo electric films. The pressure data signal multiflexed input scanning method processed A/D conversion after two step amplify and integrate. Matrix sensor interface to PC for pseudo color display by level of Pressure distribution data. This measurement system clinically evaluated in hemiplegic patients. It has produced acceptable results with optimal location of the food sensor's pressure point and avoid the muscle fatigue.

• Journal of Pharmaceutical Investigation
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• v.35 no.4
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• pp.243-247
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• 2005

Although many scientists have used pectin, its feasibility in terms of tablet manufacturability with a high speed machine has never been evaluated. Therefore, compactibility of different pectin types for large scale tableting operation has been evaluated. The compactibility behavior of powder pectins was studied by a compaction simulator. It was found that pectin on its own does not produce tablets of acceptable quality even at a punch velocity as low as 20 rpm (e.g. low tensile strengths, capping and lamination irrespective of applied compression force). Thus, dwell time was introduced and more hard compact was produced as relaxation time in die increases. It was concluded that frequent structural failure observed in both pectin types was due to lack of plastic deformation, poor compactibility and high elastic recovery.

• Journal of the korean Society of Automotive Engineers
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• v.5 no.2
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• pp.48-55
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• 1983

The prediction of performance and emissions is presented for a spark ignition engine. a two zone, zero-dimensional model was employed which included thermodynamics, combustion and hear transfer, and a kinetic model employed for NOx. The model was used to analyze the processes of compression, combustion and expansion. Cylinder pressures and temperatures were calculated as a function of crankangle as well as engine performance and emissions. Predictions made with the simulation were compared with experimental data from a four cylinder spark ignition engine. Calculated pressures and, Co and Co$_{2}$ concentrations showed acceptable quantitative agreement with data. But calculated No concentrations were slightly different. A parametric study of the effect of variations in speed, combustion duration and spark timing was carried out. This simulation can be useful for design of spark ignition engines.

• Journal of Biomedical Engineering Research
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• v.7 no.1
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• pp.53-58
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• 1986

This paper represent the design of a digital modem which transmits the ECG data from an ambulatory arrhythmia monitor over the telephone lines to a large hospital for the instantaneous interpretations. The digital modem provides on-line communications between the patient and the central computer located near cardiologists. For commercial telephone lines, the transmitting error rates of the digital modem were measured 200 times at a speed of 300 baud. In those measurements, the block errors-results, due to the misinterpretation of start and stop bits, did not occur, The data bit errors which were due to a single bit interpreted incorrectly were 0.78 (bits/10 ) . Since the acceptable data bit error limit is 10 per 106 bits transmitted, the digital modem designed in this paper can be used for the clinical applications without any difficulty.

• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.1449-1453
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• 1987

A microprogrammable Bit Slice Sinal Processor for image processing is implemented. Processing speed is increased by the parallelism in horizontal microprogram using 120bits microcode, pipelined architecture, 2 bank memory switching that interfaces with the Host through DMA, a variable clock control, overflow checking H/W,look-up table method and cache memory. With this processor, a DCT algorithm which uses 2-D FFT is performed. The execution time for $512{\times}512{\times}8$ image is 12 sec when 16 bit operation is runned, and the recovered image has acceptable quality with MSE 0.276%.