• Journal of Biomedical Engineering Research
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• v.31 no.6
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• pp.464-471
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• 2010

Compressed sensing can be used to reduce scan time or to enhance spatial resolution in MRI. It is now recognized that compressed sensing works well in reconstructing magnitude images if the sampling mask and the sparsifying transform are well chosen. Phase images also play important roles in MRI particularly in chemical shift imaging and magnetic resonance electrical impedance tomography (MREIT). We reconstruct MRI phase images using the compressed sensing technique. Through computer simulation and real MRI experiments, we reconstructed phase images using the compressed sensing technique and we compared them with the ones reconstructed by conventional Fourier reconstruction technique. As compared to conventional Fourier reconstruction with the same number of phase encoding steps, compressed sensing shows better performance in terms of mean squared phase error and edge preservation. We expect compressed sensing can be used to reduce the scan time or to enhance spatial resolution of MREIT.

• Journal of Biomedical Engineering Research
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• v.29 no.5
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• pp.384-391
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• 2008

For use in the guide system for the people who are visually impaired, an obstacle searching device using synchronous ultrasonic wave emission was proposed and developed. Generally, the conventional obstacle detection methods use the ultrasonic distance measuring device with successive scan method. However, the scan method causes a theoretical error and it couldn't estimate accurate obstacle distances. The proposed synchronous firing method use the plural number of ultrasonic sensors which emit ultrasonic wave simultaneously and estimate the distance to the closest obstacle relatively accurately. We analytically analyzed the errors of the conventional and proposed methods and compared the quantitative differences of the errors. The differences verified by obstacle search experiments. Using the proposed ultrasonic wave synchronous firing method, 3 dimensional obstacle location estimating device was designed and implemented. The results of the 3 dimensional obstacle detecting experiments showed the proposed method had good performances and it would be sufficiently use in the guide system for the people who are visually impaired.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.9
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• pp.2080-2089
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• 1997

Recent evolution in compute technology makesthe multimedia processing widely availiable. Conventional storage systems do not meet the requirements of multimedia data. Several approaches were suggested to improve disk storing methods for them. Bocheck proposed a disk partitioning technique for multiple steams assuming that all steams have same retrieval intervals with the same amount data for each access. While Bocheck's one provides a good method for same period, it does not consider the case of different periods of continous media streams. This paper proposes a new partitioning technique in which a fixed number of blocks are assigned for stresms with different retrieval periodicity. The analysis shows this problem is the same as the one scheduling the steams into a given sequence. The simulation was done to compare the proposed m-sequence merge method with the conventional Scan-EDF and Partitioning methods.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.7
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• pp.86-94
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• 1998

The rosette-scan seeker is a device mounted on the infrared guided missile. It offers the positions and iamges of target to missiles servo system by scanning a space about target in rosette pattern with a single detector. An instantaneous field of view (IFOV), which is a diameter of a detector moving along the path of the rosette pattern, has the property that its smaller size provide the less interference of background signals and detector noise. If its size is too small to voer the total field of view (TFOV), however, it produces the invisible regions in the TFOV. In this case, the invisible regions cause the performance of the seeker to deteriorate. For full scan-coverage, it is necessary to design the small IFOV without the invisible regions in the TFOV, as possible. In this paper, we propose the new method of designing the smaller IFOV than the conventional method and verify full coverage of the scanned region. By comparing the nose equivalent flux density (NEFD) of the proposed method with the that of the conventional one, we confirm that the former is better than the latter in terms of performance.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1544-1545
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• 2006

In this paper, we present a new reset waveform for a large-sustain-gap structure in at PDPs. In the driving of the large-sustain-gap structure with a conventional ramp reset waveform, we cannot avoid the condition of an address being a cathode, which causes lots of trouble in stabilizing a reset discharge. To solve these problems, we use the square pulse instead of the conventional rising ramp pulse. Before making a strong discharge between the address (cathode) and scan (anode) electrodes, we make a priming discharge between the address (anode) and the scan (cathode) electrodes to stabilize the strong discharge in which the address electrodes are the cathode. With this scheme, we obtained 60V minimum address voltage and 145V maximum address voltage in $250{\mu}m$ and $350{\mu}m$ gap structures.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.217-224
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• 2014

Purpose : Conventional, IMRT, at CSI treatment with VMAT, this study compare the treatment plan with dose changes measured at Junction field according to the error of Setup. Materials and Methods : This study established Conventional, the IMRT, VMAT treatment planning for CSI therapy using the Eclipse 10.0 (Eclipse10.0, Varian, USA) and chose person in Seoul National University Hospital. Verification plan was also created to apply IMRT QA phantom for each treatment plan to the film measurements. At this time, the error of Setup was applied to the 2, 4, 6mm respectively with the head and foot direction. ("+" direction of the head, "-" means that the foot direction.) Using IMRT QA Phantom and EBT2 film, was investigated by placing the error of Setup for each Junction. We check the consistency of the measured Film and plan dose distribution by gamma index (Gamma index, ${\gamma}$). In addition, we compared the error of Setup by the dose distribution, and analyzing the uniformity of the dose distribution within the target by calculating the Homogeneity Index (HI). Results : It was figured out that 90.49%-gamma index we obtained with film is agreement with film scan score and dose distribution of treatment plan. Also, depend on the dose distribution on distance, if we make the error of Setup 2, 4, 6mm in the head direction, it showed that 3.1, 4.5, 8.1 at $^*Diff$(%) of Conventional, 1.1, 3.5, 6.3 at IMRT, and 1.6, 2.5, 5.7 at VMAT. In the same way, if we make the error of Setup 2, 4, 6mm in the foot direction, it showed that -1.6, -2.8, -4.4 at $^*Diff$(%) of Conventional, -0.9, -1.6, -2.9 at IMRT, and -0.5, -2.2, -2.5 at VMAT. Homogeneity Index(HI)s are 1.216 at Conventional, 1.095 at IMRT and 1.069 at VMAT. Discussion and Conclusion : The dose-change depend on the error of Setup at the CSI RT(radiation therapy) using IMRT and VMAT which have advantages, Dose homogeneity and the gradual dose gradients on the Junction part is lower than that of Conventional CSI RT. This a little change of dose means that there is less danger on patients despite of the error of Setup generated at the CSI RT.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.5
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• pp.555-563
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• 2011

The goal of image calibration is to find a relation between image and world coordinates. Conventional image calibration uses physical camera model that is able to reflect camera's optical properties between image and world coordinates. In this paper, we try to calibrate images distortion using performance criterion-based polynomial model which assumes that the relation between image and world coordinates can be identified by polynomial equation and its order and parameters are able to be estimated with image and object coordinate values and performance criterion. In order to overcome existing limitations of the conventional image calibration model, namely, over-fitting feature, the performance criterion-based polynomial model is proposed. The efficiency of proposed method can be verified with 2D images that were taken by laser scan camera.

• Imaging Science in Dentistry
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• v.47 no.3
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• pp.141-147
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• 2017

Purpose: The objective of this study was to compare the outcomes of surgical mini-implant placement when potential mini-implant sites were scanned using a lower-dose $180^{\circ}$ acquisition protocol versus a conventional $360^{\circ}$ acquisition protocol. Materials and Methods: Ten dentate human skulls were used to provide sites for potential mini-implant placement. The sites were randomly divided into 2 groups: $360^{\circ}$ and $180^{\circ}$ cone-beam computed tomography (CBCT) acquisition protocols. A small-volume $180^{\circ}$ CBCT scan and a $360^{\circ}$ CBCT scan of each site were acquired using a Morita Accuitomo-170 CBCT machine and then a mini-implant was placed. A follow-up $360^{\circ}$ CBCT scan was done as a gold standard to evaluate the location of the mini-implant and root perforation. Two raters evaluated the scans. Results: Ninety-eight percent of the mini-implants placed did not perforate any root structure. Two percent of the sites had an appearance suggestive of perforation. On a Likert scale, both raters agreed that their subjective evaluation of the diagnostic quality of the protocols, ability to make and read measurements of the sites, and preferences for the specified diagnostic task were comparable. The Cohen kappa showed high inter-rater and intrarater agreement. Conclusion: In this ex vivo study, we found that the $180^{\circ}$ rotational acquisition was as effective as the conventional $360^{\circ}$ rotational acquisition for the preoperative evaluation of potential mini-implant sites.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.4
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• pp.377-385
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• 2002

Ultrasonic tests employing non-ionizing radiation are preferred in nondestructive examinations since they are safe and simple in use. The same principles of the techniques have been taken as valuable tools in medical area for the diagnoses of diseases, in other words, defects of the human body. The paper overviews the principles of the medical diagnosis based on nondestructive ultrasonic tests, and then evaluates experimentally the clinical potential of C scan images not popular in medicine, for detecting the micro fractures of the cortical bone. In the experiment the micro bone fractures were created on the femurs of porks by loading three point bending forces (2-4kN) with the speed of 1 mm/min. As the extent of the fracture was altered, not only X ray images but also ultrasonic C scan images using a focused ultrasonic probe resonated at 25 MHz were obtained. The results showed that ultrasonic C scan images were capable of detecting the micro bone fractures which were not possible to identify by conventional X ray images.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.4
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• pp.73-85
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• 2010

In dense electronic warfare signal environments, the conventional radar identification methods based on the basic parameters such as frequency, pulse width, and pulse repetition interval are confronted by the problem of identification ambiguity. To overcome this critical problem, a new approach introducing scan pattern of radars has been presented. Researches on new identification methods, however, suffer from a practical problem that it is not easy to secure the many radar signals including various scan pattern information and operation parameters. This paper presents a modeling method of radar signals with which we can generate radar signals including various scan pattern types according to the parameters determining the variation pattern of received signal strength. In addition, with the radar signals generated by the proposed model we analyze their characteristics according to the location of an electronic warfare support (ES) system.