• Transactions on Electrical and Electronic Materials
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• v.11 no.4
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• pp.194-196
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• 2010

A study is presented of improved road light design for drivers and pedestrians with the use of a ray- or reverse ray-tracing method. Many existing road lights are unsuitable for drivers and pedestrians because of serious problems such as glare effect or randomicity of illuminated areas. This situation has arisen because in customary design methods the emphasis has been on simple factors such as luminance or electrical power. However a high luminance or electrical power consumption, alone, do not guarantee bright and good road lighting. So we have applied a ray-tracing method to the design of a road light reflector with the goals of ensuring that illuminated objects on the road can be seen more clearly and that the illuminating light is more comfortable for the eyes of drivers and pedestrians. We have set design targets for factors such as the uniformity of lighting on the road area per road light, the shading angles and the continuous luminance uniformity on long lengths of road. For set heights of the eyes of drivers and pedestrians eyes we have calculated a design guideline for the achievement of the above design targets. Then we designed a road light reflector using the reverse ray-tracing approach. Also we have achieved the same luminance on the road with almost half the power consumption, through the reduction of lighty loss. In an ideal design optimum parameters are suggested to be a shading angle of 75 degrees and a luminance uniformity of 0.5 on the road area. This reflector performance is achievable with a 250 watt power consumption ceramic discharge metal light source.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.11 s.114
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• pp.1058-1064
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• 2006

In this paper, the channel capacity of a specified wireless indoor multiple-input multiple-output(MIMO) channel is estimated by analyzing spatial characteristics of this channel using the three-dimensional ray tracing method, and a technique for deriving an optimized separation of multi-antenna elements is proposed. At first, the ray paths, the path losses, and the time-delay profile are computed using the three-dimensional ray tracing method in an indoor corridor environment, which has the line of sight(LOS) and non-line of sight(NLOS) regions. The ray tracing method is verified by a comparison between the computation results and the measurements which are obtained with dipole antennas, an amplifier and a network analyzer. Then, an MIMO system is positioned in the indoor channel environment and the ray paths and path losses are computed for four antenna-position combinations and various values of the antenna separation to obtain the channel capacity for the MIMO system. An optimum antenna-separation is derived by averaging the channel capacities of 100 receiver positions with four different antenna combinations.

• Journal of Biomedical Engineering Research
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• v.35 no.5
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• pp.151-159
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• 2014

Computed tomography (CT) is one of the most widely used medical imaging modality. However, substantial x-ray dose exposed to the human subject during the CT scan is a great concern. Region-of-interest (ROI) CT is considered to be a possible solution for its potential to reduce the x-ray dose to the human subject. In most of ROI-CT scans, the ROI is set to a circular shape whose diameter is often considerably smaller than the full field-of-view (FOV). However, an arbitrarily shaped ROI is very desirable to reduce the x-ray dose more than the circularly shaped ROI can do. We propose a new method to make a non-circular convex-shaped ROI along with the image reconstruction method. To make a ROI with an arbitrary convex shape, dynamic collimations are necessary to minimize the x-ray dose at each angle of view. In addition to the dynamic collimation, we get the ROI projection data with slightly lower sampling rate in the view direction to further reduce the x-ray dose. We reconstruct images from the ROI projection data in the compressed sensing (CS) framework assisted by the exterior projection data acquired from the pilot scan to set the ROI. To validate the proposed method, we used the experimental micro-CT projection data after truncating them to simulate the dynamic collimation. The reconstructed ROI images showed little errors as compared to the images reconstructed from the full-FOV scan data as well as little artifacts inside the ROI. We expect the proposed method can significantly reduce the x-ray dose in CT scans if the dynamic collimation is realized in real CT machines.

• Journal of Radiation Industry
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• v.9 no.3
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• pp.137-141
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• 2015

A single-shot dual-energy x-ray imaging technique has been developed using a sandwich detector by stacking two detectors, in which the front and rear detectors respectively produce relatively lower and higher x-ray energy images. Each detector layer is composed of a phosphor screen coupled with a photodiode array. The front detector layer employs a thinner phosphor screen, whereas the rear detector layer employs a thicker phosphor screen considering the quantum efficiency for x-ray photons with higher energies. We have applied the proposed method into the inspection of printed circuit boards, and obtained dual-energy images with background clutter suppressed. In addition, the single-shot dual-energy method provides sharper-edge images than the conventional radiography because of the unsharp masking effect resulting from the use of different thickness phosphors between the two detector layers. It is promising to use the single-shot dual-energy x-ray imaging for high-resolution nondestructive testing. For the reliable use of the developed method, however, more quantitative analysis is further required in comparisons with the conventional method for various types of printed circuit boards.

• Journal of Energy Engineering
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• v.16 no.1 s.49
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• pp.46-52
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• 2007

The piecewise constant angular approximation is developed to replace the conventional angular quadrature sets in the solution of the second-order, multi-dimensional $S_{N}$ neutron transport equations. The newly generated quadrature sets by this method substantially mitigate ray effects and can be used in the same manner as the conventional quadrature sets are used. The discrete-ordinates and the piecewise-constant approximations are applied to both the first-order Boltzmann and the second-order form of neutron transport equations in treating angular variables. The result is that the mitigation of ray effects is only achieved by the piecewise-constant method, in which new angular quadratures are generated by integrating angle variables over the specified region. In other sense, the newly generated angular quadratures turn out to decrease the contribution of mixed-derivative terms in the even-parity equation that is one of the second-order neutron transport equation. This result can be interpreted as the entire elimination or substantial mitigation of ray effect are possible in the simplified even-parity equation which has no mixed-derivative terms.

• Textile Coloration and Finishing
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• v.6 no.3
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• pp.52-59
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• 1994

Polyester, polyester/cotton blend, nylon and cotton fabrics were ultraviolet cutting finished with padding method or exhaustion method using several UV absorbers. The transmittance of ultraviolet ray in the textiles can be greatly depressed by the processing and it is expected that human skin can be kept safe from sun-burn or damages by ultraviolet ray.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.2
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• pp.89-98
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• 1987

X-Ray photogrammetry is the method that register and analize the anatomical or physiological information about the human body by the photography form. In this paper, using X-Ray, accuracy of three dimensional coordinates of objects which are deformed and a part of human body is analyzed. An objective of this analysis lies in improving the accuracy of three dimensional coordinates and enhancing the practical use. Through the observation, X-Ray Photogrammetry is used in practical use. And X-Ray photograph is used the reform of graphical model by the determination of the three dimensional coordinates about all sides of object.

• Journal of Welding and Joining
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• v.32 no.6
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• pp.1-7
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• 2014

For the resistance spot welds of CR1180 and GA1180 TRIP steels, the weld quality evaluation method using the digitalized X-ray transmission imaging apparatus was investigated in comparison with the crosssectional examination method. In the case of the resistance spot welding of CR1180, three circular regions, such as WZ(white zone), GZ(grey zone) and DZ(dark zone), appeared on X-ray image and they corresponded to the diameters of indentation mark, nugget and corona bond, respectively. The variation of X-ray transmission thickness due to the thickness variation of the weld seemed to be mainly responsible for the formation of those contrasts. The X-ray image contrast formed from the variation of transmission thickness at the outer border line of DZ could also enable the inspections of the notch shape, nonuniformity of the welding pressure and spatter from its sharpness, concentricity and the normal straight line, respectively. The X-ray image of the resistance spot weld of galvannealed GA1180 TRIP steel was very similar to that of CR1180 TRIP steel except the crown shaped outer border line of DZ which was considered to be due to the melting behavior of zinc having the boiling temperature even lower than the melting temperature of steel.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.8
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• pp.1645-1652
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• 2002

The failure analysis on fractured parts is divided into the qualitative method by naked eyes and metallurgical microscope etc. and the quantitative method by SEM and X-ray diffraction etc. X-ray fractography can be applied to contaminated surface as well as clean surface and gain the plastic deformation and the residual stress near the fractured surface. Turbine blade is subject to cyclic bending force by steam pressure and suffers fatigue damage according to the increasing operating time. Therefore, to clean up the fracture mechanism of torsion-mounted blade in nuclear plant, the fatigue and the X-ray diffraction test was performed on the 12%Cr steel fur turbine blade and the fractured parts. The correlation of X-ray parameter and fracture mechanics parameter was determined, and then the load applied to actual broken turbine blade was predicted. Failure analysis was performed by contact stress analysis and Goodman diagram of torsion-mounted blade.

• Journal of Electrical Engineering and Technology
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• v.11 no.4
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• pp.1035-1041
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• 2016

Internal cracks in products are invisible and can lead to fatal crashes or damage. Since X-rays can penetrate materials and be attenuated according to the material’s thickness and density, they have rapidly become the accepted technology for non-destructive inspection of internal cracks. This paper presents a robust crack filter based on local gray level variation and multiscale analysis for automatic detection of cracks in X-ray images. The proposed filter takes advantage of the image gray level and its local variations to detect cracks in the X-ray image. To overcome the problems of image noise and the non-uniform intensity of the X-ray image, a new method of estimating the local gray level variation is proposed in this paper. In order to detect various sizes of crack, this paper proposes using different neighboring distances to construct an image pyramid for multiscale analysis. By use of local gray level variation and multiscale analysis, the proposed crack filter is able to detect cracks of various sizes in X-ray images while contending with the problems of noise and non-uniform intensity. Experimental results show that the proposed crack filter outperforms the Gaussian model based crack filter and the LBP model based method in terms of detection accuracy, false detection ratio and processing speed.