• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.4
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• pp.296-301
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• 2016

Using high magnetic flux from a 60 Hz high-current cable, a 2 W wireless-powered energy harvesting receiver for sensor operation, internet of things (IoT) devices, and LED lights inside electrical cable tunnels is proposed. The proposed receiver comprises a copper coil with a high number of turns, a ring-shaped ferromagnetic core, a capacitor for compensating for the impedance of the coil in series, and a rectifier with various types of loads, such as sensors, IoT devices, and LEDs. To achieve safe and easy installation around the power cable, the proposed ring-shaped receiver is designed to easily open or close using a clothespin-shaped handle, which is made of highly-insulated plastic. Laminated silicon steel plates are assembled and used as the core because of their mechanical robustness and high saturation flux density characteristic, in which the thickness of each isolated plate is 0.3 mm. The series-connected resonant capacitor, which is appropriate for low-voltage applications, is used together with the proposed receiver coil. The concept of the figure of merit, which is the product weight and cost of both the silicon steel plate and the copper wire, is used for an optimized design; therefore, the weight of the fabricated receiver and the price of raw material is 750 gf and USD $2 each, respectively. The 2.2 W powering capability of the fabricated receiver was experimentally verified with a power cable current of $100A_{rms}$ at 60Hz.

• Imaging Science in Dentistry
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• v.45 no.2
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• pp.81-87
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• 2015

Purpose: Contrast, sharpness, enhancement, and density can be changed in digital systems. The important question is to what extent the changes in these variables affect the accuracy of caries detection. Materials and Methods: Forty eight extracted human posterior teeth with healthy or proximal caries surfaces were imaged using a photostimulable phosphor (PSP) sensor. All original images were processed using a six-step method: (1) applying "Sharpening 2" and "Noise Reduction" processing options to the original images; (2) applying the "Magnification 1:3" option to the image obtained in the first step; (3) enhancing the original images by using the "Diagonal/"option; (4) reviewing the changes brought about by the third step of image processing and then, applying "Magnification 1:3"; (5) applying "Sharpening UM" to the original images; and (6) analyzing the changes brought about by the fifth step of image processing, and finally, applying "Magnification 1:3." Three observers evaluated the images. The tooth sections were evaluated histologically as the gold standard. The diagnostic accuracy of the observers was compared using a chi-squared test. Results: The accuracy levels irrespective of the image processing method ranged from weak (18.8%) to intermediate (54.2%), but the highest accuracy was achieved at the sixth image processing step. The overall diagnostic accuracy level showed a statistically significant difference (p=0.0001). Conclusion: This study shows that the application of "Sharpening UM" along with the "Magnification 1:3" processing option improved the diagnostic accuracy and the observer agreement more effectively than the other processing procedures.

• The Journal of Advanced Prosthodontics
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• v.8 no.3
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• pp.201-206
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• 2016

PURPOSE. The aim of this study was to compare the radiopacity of 6 modern resin cements with that of human enamel and dentine using the Digora digital radiography system, to verify whether they meet the requirements of ANSI/ADA specification no. 27/1993 and the ISO 4049/2000 standard and assess whether their radiopacity is influenced by the thickness of the cement employed. MATERIALS AND METHODS. Three 3-thickness samples (0.5, 1 and 1.5 mm) were fabricated for each material. The individual cement samples were radiographed on the CCD sensor next to the aluminium wedge and the tooth samples. Five radiographs were made of each sample and therefore five readings of radiographic density were taken for each thickness of the materials. The radiopacity was measured in pixels using Digora 2.6 software. The calibration curve obtained from the mean values of each step of the wedge made it possible to obtain the equivalent in mm of aluminium for each mm of the luting material. RESULTS. With the exception of Variolink Veneer Medium Value 0, all the cements studied were more radiopaque than enamel and dentin (P<.05) and complied with the ISO and ANSI/ADA requirements (P<.001). The radiopacity of all the cements examined depended on their thickness: the thicker the material, the greater its radiopacity. CONCLUSION. All materials except Variolink Veneer Medium Value 0 yielded radiopacity values that complied with the recommendations of the ISO and ANSI/ADA. Variolink Veneer Medium Value 0 showed less radiopacity than enamel and dentin.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.6
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• pp.647-656
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• 2008

In this paper, we present interference power distribution results when radio frequency identification(RFID) and ubiquitous sensor network(USN) systems share the $908.5{\sim}914MHz$ frequency bands. Average interference powers are obtained by simulation and statistical analysis, respectively. Simulation results are then verified by statistical analysis. According to the number of interferers and the diameter of the protection area, the cumulative density functions(CDFs) of interference power are simulated under the various conditions. From the simulation results, the probability that both USN and RFID systems meet the required maximal interference power levels is 95 % on condition that there are 1 low revered RFID reader and several USN nodes and that the minimum distance between a RFID reader and an USN node is greater than 1 m. Our results can be used as an basic research for coexistence analysis of RFID and USN systems in the $908.5{\sim}914MHz$ frequency bands.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.6
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• pp.796-801
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• 2011

The objective of this work presented here was focused on analysis of development trend for the integrated power system of naval vessels to perform the high-power and energy mission load platform. These mission loads are affected by the high level of military technologies, digitalization of the ocean battlefield, high power sensor system for maximization of the ship survivability. All electric power including propulsion power for ship should be controlled by integrated single system in order to carry various high power density weapon system such as Electromagnetic Aircraft Launch System, Electromagnetic Rail Gun[feasible precision striking at long distance 200NM(370km) or over]. As the analyzing the present state of things, mechanical propulsion system is shifted into hybrid or fully electric propulsion systems to realize integrated power system at the developed countries. Such challenges include reduced dependency on foreign-supplied fossil fuel, increasing demand for installed ship power, controlling life-cycle costs.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.393-398
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• 2005

Suspended fine mineral particles are deposited at the areas with low flow velocity and low transportation capacity in rivers, reservoirs and lakes. It can be contaminated by heavy metals. Examples of problem fields art dredging of sediment, water pollutants, and maintenance of navigation channels and construction works. To deal with the settling problems it is necessary to understand tile physico-chemical characteristics of cohesive sediment under varying density of particle and ion addition(NaOH, HCl, NaCl), which is dissolved in river, because fine-grained cohesive sediment can lead to flocculation with the physico-chemical influences and takes different characteristics. Experiments with fresh and saline water are followed with fine-grained sediments(alumina and quartz) in settling columns. Settling velocity of suspended fine particles in still water was measured with a pressure sensor(maximum 10 mbar). Until the initial concentration of 20,000 mg/1 of alumina and quartz the settling velocity was on the increase. Above this initial concentration was it on the decrease. In an acid condition, which causes strong flocculation, average settling velocity of quartz powder was high. In an alkaline water low average settling velocity of it was observed. However, alumina behaved exactly contrarily.

• Korean Journal of Materials Research
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• v.21 no.3
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• pp.133-137
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• 2011

Gold have been used as an electrode materials having a good mechanical flexibility as well as electrical conductivity, however the stretchability of the gold on a flexible substrate is poor because of its small elastic modulus. To overcome this mechanical inferiority, the reinforcing gold is necessary for the stretchable electronics. Among the reinforcing materials having a large elastic modulus, carbon nanotube (CNT) is the best candidate due to its good electrical conductivity and nanoscale diameter. Therefore, similarly to ferroconcrete technology, here we demonstrated gold electrodes mechanically reinforced by inserting fabrics of CNTs into their bodies. Flexibility and stretchability of the electrodes were determined for various densities of CNT fabrics. The roles of CNTs in resisting electrical disconnection of gold electrodes from the mechanical stress were confirmed using field emission scanning electron microscope and optical microscope. The best mechanical stability was achieved at a density of CNT fabrics manufactured by 1.5 ml spraying. The concept of the mechanical reinforced metal electrode by CNT is the first trial for the high stretchable conductive materials, and can be applied as electrodes materials in various flexible and stretchable electronic devices such as transistor, diode, sensor and solar cell and so on.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.2
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• pp.155-160
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• 2014

In this paper, an algorithm using RGB-depth camera is proposed to detect smoke in interrior. RGB-depth camera, the Kinect provides RGB color image and depth information. The Kinect sensor consists of an infra-red laser emitter, infra-red camera and an RGB camera. A specific pattern of speckles radiated from the laser source is projected onto the scene. This pattern is captured by the infra-red camera and is analyzed to get depth information. The distance of each speckle of the specific pattern is measured and the depth of object is estimated. As the depth of object is highly changed, the depth of object plain can not be determined by the Kinect. The depth of smoke can not be determined too because the density of smoke is changed with constant frequency and intensity of infra-red image is varied between each pixels. In this paper, a smoke detection algorithm using characteristics of the Kinect is proposed. The region that the depth information is not determined sets the candidate region of smoke. If the intensity of the candidate region of color image is larger than a threshold, the region is confirmed as smoke region. As results of simulations, it is shown that the proposed method is effective to detect smoke in interior.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.7
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• pp.1583-1590
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• 2011

As the existing radiation scanning systems use 2-dimensional radiation scanned images, the low accuracy has been pointed out as a problem of it. This research analyzes the applicability of the stereo image processing technique to X-ray scanned images. Two 2-dimensional radiation images which have different disparity values are acquired from a newly designed stereo image acquisition system which has one additional line sensor to the conventional system. Using a matching algorithm the 3D reconstruction process which find the correspondence between the images is progressed. As the radiation image is just a density information of the scanned object, the direct application of the general stereo image processing techniques to it is inefficient. To overcome this limitation of a stereo image processing in radiation area, we reconstruct 3-D shapes of the edges of the objects. Also, we proposed a new volume based 3D reconstruction algorithm. Experimental results show the proposed new volume based reconstruction technique can provide more efficient visualization for cargo inspection. The proposed technique can be used for such objects which CT or MRI cannot inspect due to restricted scan environment.

• Journal of the Korean Institute of Gas
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• v.3 no.2 s.7
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• pp.43-52
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• 1999

An experimental chamber was fabricated to observe the gas diffusion behavior of leak gas from underground city-gas pipeline. It was made of acryl so that feeding of gas and the measuring points of the gas could be varied in each experiment. The MOS sensors were used to measure the concentrations of leak gas. The soil media such as the Jumunjin standard sand and the granite weathered soil were used to measure the gas diffusion and the change of leak gas concentrations was measured with time for various gas flow rate. As the distance between the leak point of gas and the measuring point of MOS sensor decreases, or the leak rate increases, the detection time of gas at a measuring points decreases and the gas concentration increases quickly and the concentration of the gas at steady state also increases. As the density of granite weathered soil is higher than that of Jumunjin standard sand for compaction, the detection time of leak gas in the granite weathered soil was longer than that in the Jumunjin standard soil. The leak gas concentrations in the granite weathered soil were lower than those in the Jumunjin standard sand at the beginning of gas leaking from a pipe, but inverse phenomenon was occured at steady state.