• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.26 no.1
• /
• pp.93-100
• /
• 2008

The parameters of lens such as focal length, focus, and aperture stop changes while shooting the scenes with zoom lens. Especially, zooming action dramatically changes the geometry of lens system that causes significant change of lens model. We investigated how the lens model changes while zooming in general shooting condition. Each parameters of lens model was estimated and checked whether they can be modeled well in the condition of auto-controlling focus, aperture and vibration reduction. In order to do this, calibration images were taken, modeled in different fecal length setting. And changing patterns of models were inspected to find out if there is some elements that have some particular pattern in changing with respect to focal length. The result showed us that although we didn't control the focus and aperture setting, there's specific changing patterns in radial and do-centering distortion. Especially, the strong linear correlation was found between coefficient of $r^2$ and focal length. It is expected that many parts of distortion can be eliminated without additional self calibration even if zoom operation is done when shooting the scenes if we know its fecal length and model of this coefficient.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.32 no.4_1
• /
• pp.363-371
• /
• 2014

Most space-borne optical scanning systems adopt linear arrayconfigurations. The well-knownthree different types of space-borne sensors arealong-track line scanner, across-track linescanner, and three line scanner. To acquire accurate location information of an object on the ground withthose sensors, the exterior and interior orientation parameters are critical factors for both of space-borne and airborne missions. Since the imaging geometry of sensors mightchange time to time due to thermal influence, vibration, and wind, it is very important to analyze the Interior Orientation Parameters (IOP) effects on the ground. The experiments based on synthetic datasets arecarried out while the focal length biases are changing. Also, both high and low altitudes of the imagingsensor were applied. In case with the along-track line scanner, the focal length bias caused errors along the scanline direction. In the other case with the across-track one, the focal length bias caused errors alongthe scan line and vertical directions. Lastly, vertical errors were observed in the case ofthree-line scanner. Those results from this study will be able to provide the guideline for developing new linearsensors, so as for improving the accuracy of laboratory or in-flight sensor calibrations.

• Journal of the Korea Convergence Society
• /
• v.12 no.2
• /
• pp.95-101
• /
• 2021

The purpose of this study was to investigate the convergence effect of focal vibration stimulation and bilateral upper limb training on the recovery of upper limb function when applied to stroke patients. For 20 stroke patients, divided into an experimental group that performed convergence intervention with focal vibration stimulation and bilateral upper limb training, and a control group who performed only bilateral upper limb training. It was conducted 20 times for 4 weeks, 30 minutes per session. Vibration stimulation was applied to the affected side of the experimental group for 30 minutes during training. Results were measured for the degree of recovery of the affected upper limb function, amount of use on the affected and unaffected sides, the quality and satisfaction in performance on use of both upper limbs. Comparisons were made within groups using a paired-sample t-test and between groups using covariance analysis. As a result of the study, the experimental group showed a significant difference in dexterity and the amount of use on the affected than the control group. The effect size was more than the small effect size in all evaluation items. Through this study, it is thought that the convergence intervention of focal vibration stimulation and bilateral upper limb trainingcan be used clinically as an effective intervention for the recovery of arm function in stroke patients.

• Investigative Magnetic Resonance Imaging
• /
• v.1 no.1
• /
• pp.114-118
• /
• 1997

Purpose: Functional MR imaging is the method of demonstrating changes in regional cerebral blood flow produced by sensory, motor, and any other tasks. Functional MR of visual cortex is performed as a patient stares a photic stimulation, so adaptable photic stimulation is necessary. The purpose of this study is to evaluate whether the size of photic stimulator can affect the degree of visual cortex activation. Materials and Methods: Functional MR imaging was performed in 5 volunteers with normal visual acuity. Photic stimulator was made by 39 light-emitting diodes on a plate, operating at 8Hz. The sizes of photic stimulator were full field, half field and focal central field. The MR imager was Siemens 1.5-T Magnetom Vision system, using standard head coil. Functional MRI utilized EPI sequence (TR/TE= 1.0/51. Omsec, matrix $No.=98{\times}128$, slice thickness=8mm) with 3sets of 6 imaging during stimulation and 6 imaging during rest, all 36 scannings were obtained. Activation images were obtained using postprocessing software(statistical analysis by Z-score), and these images were combined with T-1 weighted anatomical images. The activated signals were quantified by numbering the activated pixels, and activation a index was obtained by dividing the pixel number of each stimulator size with the sum of the pixel number of 3 study using 3 kinds of stimulators. The correlation between the activation index and the stimulator size was analysed. Results: Mean increase of signal intensities on the activation area using full field photic stimulator was about 9.6%. The activation index was greatest on full field, second on half field and smallest on focal central field in 4. The index of half field was greater than that of full field in 1. The ranges of activation index were full field 43-73%(mean 55%), half field 22-40 %(mean 32%), and focal central field 5-24%(mean 13%). Conclusion: The degree of visual cortex activation increases with the size of photic stimulator.

• The Optical Journal
• /
• v.4 no.17 s.17
• /
• pp.42-44
• /
• 1992

• Honam Mathematical Journal
• /
• v.17 no.1
• /
• pp.29-39
• /
• 1995

• 대한핵의학회:학술대회논문집
• /
• 1998.05a
• /
• pp.189-190
• /
• 1998

• Communications of the Korean Mathematical Society
• /
• v.6 no.1
• /
• pp.73-87
• /
• 1991

• Honam Mathematical Journal
• /
• v.12 no.1
• /
• pp.17-25
• /
• 1990

• Proceedings of the KSMRM Conference
• /
• 2000.11a
• /
• pp.64-64
• /
• 2000