• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.4
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• pp.330-336
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• 2014

The continuous chip generated in cutting process deteriorates workpiece, tool, and machine tool system. It is necessary to treat this continuous chip in ductile material machining condition for stable cutting. This paper deals with the chip control method using acoustic emission(AE) signal in pure copper turning operation. AE raw signals, root mean square(RMS) signals and wavelet transformed signals measured in turning process are introduced to analysis for chip patterns. With analysis of AE signals, it is obtained that the produced chip patterns are correlated with the specified AE signals which are transformed by fuzzy pattern algorithm. By this experimental investigation, the chip patterns can be classified at significant level in pure copper machining process and controlled from continuous chips to reduced-length stable chips.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.94-94
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• 2010

Fiber laser is a heat source which is introduced recently, and so has a little researched data compare with conventional laser processing. Moreover basic data for welding monitoring are also insufficient. Therefore, in this study, the change of signal with measuring position and angle of plasma emission signals were analysed as a basic experiment for real time monitoring in fiber laser welding. As a result, the signals measured from the side, front and rear had the biggest intensity at $60^{\circ}$, and frequency peak to reflect the behavior of keyhole and swing of plasma by shield gas was detected at $45{\sim}60^{\circ}$. However, both intensity of signal and the result of FFT for monitoring were satisfied at the angle of $45^{\circ}$ from the side.

• Tribology and Lubricants
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• v.18 no.5
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• pp.351-356
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• 2002

The surfaces of machine components in sliding contact such as bearing, gears and pistons etc. frequently operate under the condition of mixed lubrication due to high load, high speed and slip. These machine components often undergo the inception of scuffing in practical application. The scuffing failure is a critical problem in modern machine components, especially for the requirement of high efficiency and small size. However, it is difficult to find a universal mechanism to explain all scuffing phenomena because there are so many factors affecting the onset of scuffing. In this study, scuffing experiments are conducted using Acoustic Emission(AE) measurement by an indirect sensing approach to detect scuffing failure. Acoustic Emission(AE) signal has been widely utilized to monitor the interaction at the friction interface. Using AE signals we can get an indication about the state of the friction processes, about the quality of solid and liquid layers on the contacting surfaces in real time. The FFT(Fast Fourier Transform) analyses of the AE signal are sued to understand the interfacial interaction and the relationship between the AE signal and the state of contact is presented.

• 한국가시화정보학회:학술대회논문집
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• 2004.12a
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• pp.65-74
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• 2004

Measurement of concentration distributions of suspended particles in a micro-channel is out of the most crucial necessities in the area of Lab-on-a-chip to be used for various bio-chemical applications. One most feasible way to measure the concentration field in the micro-channel is using micro-LIF(Laser Induced Fluorescence) method. However, an accurate concentration field at a given cross plane in a micro-channel has not been successfully achieved so far due to various limitations in the light illumination and fluorescence signal detection. The present study demonstrates a novel method to provide an ultra thin laser sheet beam having five(5) microns thickness by use of a micro focus laser line generator. The laser sheet beam illuminates an exact plane of concentration measurement field to increase the signal to noise ratio and considerably reduce the depth uncertainty. Nile Blue A was used as fluorescent dye for the present LIF measurement. The enhancement of the fluorescent intensity signals was performed by a solvent mixture of water $(95\%)$ and ethanol (EtOH)/methanol (MeOH) $(5\%)$ mixture. To reduce the rms errors resulted from the CCD electronic noise and other sources, an expansion of grid size was attempted from $1\times1\;to\;3\times3\;or\;5\times5$ pixel data windows and the pertinent signal-to-noise level has been noticeably increased accordingly.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1393-1401
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• 2010

In this experimental study, we have examined the correlation between a human carpal motion and a surface electromyogram. The carpal motion patterns have been identified and the main muscles involved in the carpal motion have been determined by investigating the anatomical structure of a carpal. The torque acting against the carpal motion has been applied by using a device for carpal rehabilitation training, and the surface electromyogram signal corresponding to the torque at the main muscles has been measured. The root-mean-square (RMS) magnitude of the surface electromyogram signal has been calculated and used to analyze the correlation between the surface electromyogram signal and carpal motion. The experimental results have proved that for carpal torque values below $0.1\;N{\cdot}m$, the RMS magnitude of the surface electromyogram signal is linearly proportional to the carpal torque magnitude and that the carpal torque magnitude is linearly proportional to the cross-sectional area of the carpal muscles. Further, the analysis of the contribution of each muscle to the carpal motion has shown that the contribution of the most dominant muscle is consistently 60%. These three results can be applied to develop more sophisticated devices or robots for carpal rehabilitation training.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.3
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• pp.181-189
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• 2015

Powered prosthesis is used to assist walking of people with an amputated lower limb and/or weak leg strength. The accurate gait phase classification is indispensable in smooth movement control of the powered prosthesis. In previous gait phase classification using physical sensors, there is limitation that powered prosthesis should be simulated as same as the speed of training process. Therefore, we propose EMG signal based gait phase recognition method to classify stairs ascending and stairs descending into four steps without using physical sensors, respectively. RMS, VAR, MAV, SSC, ZC, WAMP features are extracted from EMG signal data and LDA(Linear Discriminant Analysis) classifier is used. In the training process, the AHRS sensor produces various ranges of walking steps according to the change of knee angles. The experimental results show that the average accuracies of the proposed method are about 85.6% in stairs ascending and 69.5% in stairs descending whereas those of preliminary studies are about 58.5% in stairs ascending and 35.3% in stairs descending. In addition, we can analyze the average recognition ratio of each gait step with respect to the individual muscle.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.86-89
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• 2015

Quantitative Evaluation of Image Quality using Automatic Exposure Control This it leads, the relationship of control and image between of photographing condition, DR proper use method proposing. Chest phantom acquires Chest PA images which it follows in conditional change, Image evaluation factor (SNR (Signal to Noise Ratio), CNR (Contrast to Noise Ratio), PSNR (Peak Signal to Ratio), RMS (Root Mean Square)). It excepted RMS price, SNR, CNR, PSNR the case which uses AEC it came out being high The fact that the quality of image is better there was a case which does not use AEC. but Price it was slight. Image qualitative it was deficient in AEC use presence. Through this, the overall situation and most efficient use of radiation workers is better suited. But Passive AEC use would be appropriate for use rather than proactive AEC.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.638-642
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• 2005

For gas hydrate exploration, long offset multichannel seismic data acquired using by the 4km streamer length in Ulleung basin of the East Sea. The dataset was processed to define the BSRs (Bottom Simulating Reflectors) and to estimate the amount of gas hydrates. Confirmation of the presence of Bottom Simulating reflectors (BSR) and investigation of its physical properties from seismic section are important for gas hydrate detection. Specially, faster interval velocity overlying slower interval velocity indicates the likely presences of gas hydrate above BSR and free gas underneath BSR. In consequence, estimation of correct interval velocities and analysis of their spatial variations are critical processes for gas hydrate detection using seismic reflection data. Using Dix's equation, Root Mean Square (RMS) velocities can be converted into interval velocities. However, it is not a proper way to investigate interval velocities above and below BSR considering the fact that RMS velocities have poor resolution and correctness and the assumption that interval velocities increase along the depth. Therefore, we incorporated Migration Velocity Analysis (MVA) software produced by Landmark CO. to estimate correct interval velocities in detail. MVA is a process to yield velocities of sediments between layers using Common Mid Point (CMP) gathered seismic data. The CMP gathered data for MVA should be produced after basic processing steps to enhance the signal to noise ratio of the first reflections. Prestack depth migrated section is produced using interval velocities and interval velocities are key parameters governing qualities of prestack depth migration section. Correctness of interval velocities can be examined by the presence of Residual Move Out (RMO) on CMP gathered data. If there is no RMO, peaks of primary reflection events are flat in horizontal direction for all offsets of Common Reflection Point (CRP) gathers and it proves that prestack depth migration is done with correct velocity field. Used method in this study, Tomographic inversion needs two initial input data. One is the dataset obtained from the results of preprocessing by removing multiples and noise and stacked partially. The other is the depth domain velocity model build by smoothing and editing the interval velocity converted from RMS velocity. After the three times iteration of tomography inversion, Optimum interval velocity field can be fixed. The conclusion of this study as follow, the final Interval velocity around the BSR decreased to 1400 m/s from 2500 m/s abruptly. BSR is showed about 200m depth under the seabottom

• Journal of the Korean Society for Nondestructive Testing
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• v.14 no.2
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• pp.122-131
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• 1994

Journal bearings in the rotating machineries are vulnerable to the contamination or the insufficient supply of lubricating oil, which is likely to be the cause of unexpected shutdown or malfunction of these systems. Various destructive and nondestructive testing methods had been used for the reduction of maintenance cost and the operational safety problems due to the accidents related to bearing damages. In this experimental approach, acoustic emission monitoring is employed to the detection of incipient failure caused by intervention of foreign particles most probable in the journal bearing systems. Experimental schedules for the intervention of foreign particles was composed to be more quantitative and systematic than last study in consideration of minimum oil film thickness and particle size. The experiment was conducted under such designed conditions as inserting alumina particles to the lubrication layer in the simulated journal bearing system. Several parameters such as AE rms level, waveform, AE energy distribution and other AE event parameters are used for analysis and characterization of damage source. The results showed that the history of damage was well correlated with the changes of AE rms level and the type of damage source signal can be verified using other informations such as waveform, distributions of AE parameters etc.

• Journal of Radiation Protection and Research
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• v.39 no.2
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• pp.81-88
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• 2014

Recently, a new imaging method, gamma vertex imaging (GVI), was proposed for the verification of in-vivo proton dose distribution. In GVI, the vertices of prompt gammas generated by proton induced nuclear interaction were determined by tracking the Compton-recoiled electrons. The GVI system is composed of a beryllium electron converter for converting gamma to electron, two double-sided silicon strip detectors (DSSDs) for the electron tracking, and a scintillation detector for the energy determination of the electron. In the present study, the modules of a charge sensitive preamplifier (CSP) and a shaping amplifier for the analog signal processing of DSSD were developed and the performances were evaluated by comparing the energy resolutions with those of the commercial products. Based on the results, it was confirmed that the energy resolution of the developed CSP module was a little lower than that of the CR-113 (Cremat, Inc., MA), and the resolution of the shaping amplifier was similar to that of the CR-200 (Cremat, Inc., MA). The value of $V_{rms}$ representing the magnitude of noise of the developed system was estimated as 6.48 keV and it was confirmed that the trajectory of the electron can be measured by the developed system considering the minimum energy deposition ( > ~51 keV) of Compton-recoiled electron in 145-${\mu}m$-thick DSSD.