• The Journal of Korea CHUNA Manual Medicine
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• v.2 no.1
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• pp.133-142
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• 2001

Objectives : The aim of this study is to investigate the relationship between spinal distortion and pain in elementary and middle school students. Methods : Using the phase-shifting moire developed by KAIST(Korea Advanced Institute of Science and Technology) we measured the back surface distortion, and using questionnaire investigation, we investigated the partial pain in 1008 elementary and middle school students(532 boy students(52.8%), 476 girl students(47.2%)) in Seoul in 1999. And, we statistically analyzed the relationship between spinal distortion and partial body pain Results : This study show that the more age increase, the more the pain in head, neck, shoulder, back and low back Increase considerably among the students aged 9 to 15. The ratio of each partial body pain was 28.4%, 19.7%, 18.2%, 18.7%. 16.0% at the age of 9 and 59.7%, 67.4%, 51.8%, 51.8%, 64.4% at the age of 15 respectively. And, it was shown there was a significant correlation between spine distortion and partial body pain area. When the spinal distortion was found at the upper thoracic and cervical area, the students complained the more pain on head, neck and shoulder(p<0.05) and when the spinal distortion was found at the sacral base, the more headache(p<0.05) Conclusions : It is suggested that the significant correlation exist between the spinal distortion and pain and the pain related to spine disorder get more increase as students grow. We have to study further more about Juvenile postural distortion and it's prevention.

• International Journal of Quality Innovation
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• v.5 no.1
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• pp.68-84
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• 2004

The measured values of a same object should remain constant regardless of the object's position in the image. In other words, its measured values should not vary as its position in the image changes. However, lens' image distortion, heterogeneous light source, varied angle between the measuring apparatus and the object, and different surroundings where the testing is set up will all cause variation in the measurement of the object when the object's position in the image changes. This research attempts to compensate the machine vision image distortion caused by the object's position in the image by developing the compensation table. The compensation is accomplished by facilitating users to obtain the correcting object and serves the objective of improving the precision of measurement.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.2
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• pp.125-131
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• 1994

This paper describes a method to measure the distortion level of loudspeaker using a LMS(Least Mean Square) adaptive filter. Conventional technique to measure the distortion level uses a band-pass filter with a sharp cut-off frequency characteristics. However. such the band-pass filter has a bed time response characteristics. On the other hand, the proposed method offers us an easy way to measure the specified harmonic distortion level with a small hardware. Moreover, our method is not affected by noise which has no correlation with the test signal, and the measurement can be carried out in a noisy environment. The effectiveness of the proposed method is confirmed by experiment using a loudspeaker in a noisy room.

• Journal of the Optical Society of Korea
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• v.20 no.1
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• pp.140-149
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• 2016

For visual measurement under dynamic scenarios, a zoom lens camera is more flexible than a fixed one. However, the challenges of distortion prediction within the whole focal range limit the widespread application of zoom lens cameras greatly. Thus, a novel sequential distortion correction method for a zoom lens camera is proposed in this study. In this paper, a distortion assessment method without coupling effect is depicted by an elaborated chessboard pattern. Then, the appropriate distortion correction model for a zoom lens camera is derived from the comparisons of some existing models and methods. To gain a rectified image at any zoom settings, a global distortion correction modeling method is developed with bundle adjustment. Based on some selected zoom settings, the optimized quadratic functions of distortion parameters are obtained from the global perspective. Using the proposed method, we can rectify all images from the calibrated zoom lens camera. Experimental results of different zoom lens cameras validate the feasibility and effectiveness of the proposed method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.503-504
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• 2009

• Journal of Broadcast Engineering
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• v.14 no.2
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• pp.210-218
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• 2009

The 3D shape as well as the depth of an object presented on a 3D display is perceptually distorted depending on viewing distance. It is quite undesirable that different observers perceive different depth and shape from an object displayed on a 3D monitor. To resolve the problem of perceptual distortion of 3D depth and shape, the degree of the distortion should be measured appropriately. As a basis for resolving these problems, the present research suggests an instrument for measuring the degree of the perceptual distortion of 3D depth and shape.

• Journal of the Korean Institute of Intelligent Systems
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• v.27 no.2
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• pp.144-149
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• 2017

In this paper, we developed an intelligent and wideband RF-receiver module to represent a high dynamic range and good linearity characteristics up to 650MHz-2700MHz frequency band. and implemented an intelligent digital-RF- distorted signal measuring system for the RF distortion (intermodulation) signals. Broadband RF-receive module was designed to represent the optimized linear parameters of the receiver to meet the low noise and wide dynamic range. The designed intelligent digital-distortion(intermodulation) signal measument system measured by applying the 1MHz IF of third intermodulation signal of DUT and Measured data was recorded by program on the PC monitor with GUI interface. By variable up to 650MHz-2700MHz measured data showed up to -127.8dBc to -138dBc of the distortion (intermodulation) signal. And developed intelligent digital- distortion signal measurement system can be used to measure intermodulation distortion signal of wireless system widely.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.12
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• pp.649-654
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• 2003

The simplest method for measuring output currents of the three phase inverters is to measure them with three current sensors such as hall sensors. This method requires at least two current sensors, and these types of sensors are somewhat expensive. More economical method is measuring DC link current with a simple shunt resistor, then, reconstructing output current using the DC link current value and the switching status. However, in low speed region, the measurement becomes difficult and even impossible due to the requirement of minimum switching duration for A/D conversion. These problems can be overcome by limitation of switching duration. Limitation of switching, however, causes voltage and current distortion. Owing to compensation, distortion can be effectively suppressed. However these increase acoustic noise due to increment of current ripple. In this paper, a current measurement method is proposed, which can reduce minimum switching duration resulting in reduction of acoustic noise. The validity of proposed method is confirmed through experiment.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.137-142
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• 2001

Since recent production system becomes that of the small quantity, large volume with high quality production, accurate and high speed inspection system is required. In such situation, noncontact 3D measurement system which utilized CCD cameras is useful technique in terms of system cost, speed of data acquisition, measuring accuracy and application. However, it has low accuracy compared with contact 3D measurement system because of the camera distortion, non uniformity of laser distribution and so on. For those reasons, in this paper precision enhancement method is studied considering radial camera distortion, and laser distribution. A distortion correction method is applied even to the standard lens. The laser slit beam trajectory is determined by 3 method: based of the Gaussian function signal approximation, the median method, the center of gravity method and the peak point of the Gaussian function method.

• Journal of the Semiconductor & Display Technology
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• v.8 no.4
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• pp.7-13
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• 2009

The slender device(long length and thin width) manufactured by stereolithography process suffers from large curl distortion. This paper adapts two control parameters such as a critical exposure and a penetration depth. The measurement of the test parts dimension are carried out by reverse engineering method with the optical 3-dimensional measurement equipment. We investigate how each parameter contributes to the part accuracy and estimates the optimal set of parameters which minimizes the dimensional error of the test parts. Finally, As being an the RAM slot as being an example of the slender device, the RAM slot is made with the optimal values of control parameter and the results are investigated