• The Korean Journal of Nuclear Medicine
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• v.32 no.5
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• pp.414-424
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• 1998

Purpose: Cross-modality coregistration of positron emission tomography (PET) and magnetic resonance imaging (MR) could enhance the clinical information. In this study we propose a refined technique to improve the robustness of registration, and to implement more realistic visualization of the coregistered images. Materials and Methods: Using the sinogram of PET emission scan, we extracted the robust head boundary and used boundary-enhanced PET to coregister PET with MR. The pixels having 10% of maximum pixel value were considered as the boundary of sinogram. Boundary pixel values were exchanged with maximum value of sinogram. One hundred eighty boundary points were extracted at intervals of about 2 degree using simple threshold method from each slice of MR images. Best affined transformation between the two point sets was performed using least square fitting which should minimize the sum of Euclidean distance between the point sets. We reduced calculation time using pre-defined distance map. Finally we developed an automatic coregistration program using this boundary detection and surface matching technique. We designed a new weighted normalization technique to display the coregistered PET and MR images simultaneously. Results: Using our newly developed method, robust extraction of head boundary was possible and spatial registration was successfully performed. Mean displacement error was less than 2.0 mm. In visualization of coregistered images using weighted normalization method, structures shown in MR image could be realistically represented. Conclusion: Our refined technique could practically enhance the performance of automated three dimensional coregistration.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.11
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• pp.1064-1073
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• 2013

In this paper, a compact 370 W high efficiency GaN(Gallium Nitride) HEMT(High Electron Mobility Transistor) power amplifier(PA) using internal harmonic manipulation circuits is presented for cellular and L-band. We employed a new circuit topology for simultaneous high efficiency matching at both fundamental and 2nd harmonic frequency. In order to minimize package size, new 41.8 mm GaN HEMT and two MOS(Metal Oxide Semiconductor) capacitors are internally matched and combined package size $10.16{\times}10.16{\times}1.5Tmm^3$ through package material changes and wire bonded in a new package to improve thermal resistance. When drain biased at 48 V, the developed GaN HEMT power amplifier has achieved over 80 % Drain Efficiency(DE) from 770~870 MHz and 75 % DE at 1,805~1,880 MHz with 370 W peak output power(Psat.). This is the state-of-the-art efficiency and output power of GaN HEMT power amplifier at cellular and L-band to the best of our knowledge.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.41 no.1
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• pp.1-8
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• 2004

The INS(Inertial Navigation System) provides high rate position, velocity and attitude data with good short-term stability while the GPS(Global Position System) provides position and velocity data with long-term stability. By integrating the INS with GPS, a navigation system can be achieved to Provide highly accurate navigation Performance. For the best performance, time synchronization of GPS and INS data is very important in GPS/INS integrated system But, it is impossible to synchronize them exactly due to the communication and computation time-delay. In this paper, to reduce the error caused by the measurement time-delay in GPS/INS integrated systems, error compensation methods using separate bias Kalman filter are suggested for both the loosely-coupled and the tightly-coupled GPS/INS integration systems. Linearized error models for the position and velocity matching GPS/INS integrated systems are Int derived by linearizing with respect to its time-delay and augmenting the delay-state into the conventional state equations for each case. And then separate bias Kalman Inter is introduced to estimate the time-delay during only initial navigation stage. The simulation results show that the present method is effective enough resulting in considerably less position error.

• Journal of Dental Rehabilitation and Applied Science
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• v.34 no.2
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• pp.104-115
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• 2018

Purpose: The purpose of this study is to evaluate the image acquisition ability of intraoral scanners by analyzing the comprehensiveness of scanned images from standardized model, and to identify problems of the model. Materials and Methods: Cast models and 3D-printed models were prepared according to international standards set by ISO12836 and ANSI/ADA no. 132, which were then scanned by model scanner and two different intraoral scanners (TRIOS3 and CS3500). The image acquisition performance of the scanners was classified into three grades, and the study was repeated with varying surface conditions of the models. Results: Model scanner produced the most accurate images in all models. Meanwhile, CS3500 showed good image reproducibility for angled structures and TRIOS3 showed good image reproducibility for rounded structures. As for model ingredients, improved plaster model best reproduced scan images regardless of the type of scanner used. When limited to 3D-printed model, powdered surface condition resulted in higher image quality. Conclusion: When scanning structures beyond FOV (field of view) in standardized models (following ISO12836 and ANSI/ADA 132), lack of reference points to help distinguish different faces confuses the scanning and matching process, resulting in inaccurate display of images. These results imply the need to develop a new standard model not confined to simple pattern repetition and symmetric structure.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.10
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• pp.1378-1383
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• 2011

This study investigated the antioxidant activity of ethanolic extracts of 1~20 kGy-gamma irradiated flowering cherry fruit (Prunus serrulata L. var. spontanea Max. wils.). The total phenolic compound content was highest (30.35 mg/g) in the 10 kGy sample, but there was no consistent trend matching the increase or decrease of gamma irradiation. Radical scavenging activity using DPPH (2,2-diphenyl-1-picrylhydrazyl) showed that gamma-irradiated samples were better than non-irradiated samples and that the 10 kGy-gamma irradiated sample was the best ($IC_{50}$ 327.52 ppm). In reducing power, gamma-irradiated samples induced higher activities than non-irradiated samples at concentrations below 2.5 mg/mL, and the sample with the highest activity was the 20 kGy-gamma irradiated sample. In nitrite-scavenging ability, both gamma-irradiated and non-irradiated samples showed high activity (73~94%) at pH 1.2, 3.0, and 4.2. Also, the nitrite-scavenging ability of gamma-irradiated samples was significantly different from that of the control at pH 1.2. The FRAP value of the 3 kGy-irradiated sample also showed the highest value of 0.38 mM. Our results indicate that gamma irradiating the ethanolic extracts of flowering cherry fruit increases the antioxidant activity at some of the radiation doses. Therefore, it suggests that gamma irradiation could increase biological activity and be used effectively in food manufacturing and related industries.

• Journal of KIISE:Software and Applications
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• v.31 no.1
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• pp.54-60
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• 2004

Face recognition is one of the problems to be solved by appearance based matching technique. However, the appearance of face image is very sensitive to variation in illumination. One of the easiest ways for better performance is to collect more training samples acquired under variable lightings but it is not practical in real world. ]:n object recognition, it is desirable to focus on feature extraction or normalization technique rather than focus on classifier. This paper presents a simple approach to normalization of faces subject to directional illumination. This is one of the significant issues that cause error in the face recognition process. The proposed method, ICR(illumination Compensation based on Multiple Linear Regression), is to find the plane that best fits the intensity distribution of the face image using the multiple linear regression, then use this plane to normalize the face image. The advantages of our method are simple and practical. The planar approximation of a face image is mathematically defined by the simple linear model. We provide experimental results to demonstrate the performance of the proposed ICR method on public face databases and our database. The experimental results show a significant improvement of the recognition accuracy.

• Journal of KIISE:Information Networking
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• v.37 no.1
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• pp.72-83
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• 2010

Group communication in a wireless mesh network is complicated due to dynamic intermediate mesh points, access control for communications between different administrative domains, and the absence of a centralized network controller. Especially, many-to-many multicasting in a dynamic mesh network can be modeled by a decentralized framework where several subgroup managers control their members independently and coordinate the inter-subgroup communication. In this study, we propose a topology-matching decentralized group key management scheme that allows service providers to update and deliver their group keys to valid members even if the members are located in other network domains. The group keys of multicast services are delivered in a distributed manner using the identity-based encryption scheme. Identity-based encryption facilitates the dynamic changes of the intermediate relaying nodes as well as the group members efficiently. The analysis result indicates that the proposed scheme has the advantages of low rekeying cost and storage overhead for a member and a data relaying node in many-to-many multicast environment. The proposed scheme is best suited to the settings of a large-scale dynamic mesh network where there is no central network controller and lots of service providers control the access to their group communications independently.

• Journal of radiological science and technology
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• v.32 no.2
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• pp.195-203
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• 2009

Image registration is a fundamental task in image processing used to match two or more images. It gives new information to the radiologists by matching images from different modalities. The objective of this study is to develop 2D image registration algorithm for PET/CT and CT images acquired by different systems at different times. We matched two CT images first (one from standalone CT and the other from PET/CT) that contain affluent anatomical information. Then, we geometrically transformed PET image according to the results of transformation parameters calculated by the previous step. We have used Affine transform to match the target and reference images. For the similarity measure, mutual information was explored. Use of particle swarm algorithm optimized the performance by finding the best matched parameter set within a reasonable amount of time. The results show good agreements of the images between PET/CT and CT. We expect the proposed algorithm can be used not only for PET/CT and CT image registration but also for different multi-modality imaging systems such as SPECT/CT, MRI/PET and so on.

• Journal of the Korean Vacuum Society
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• v.21 no.5
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• pp.233-241
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• 2012

We have deposited the bilayer consisted of the underlayer and the overlayer by using DC magnetron sputter on Single crystal MgO (001) substrate. This bilayer was fabricated at fixed annealing temperature and time. We have controlled agglomeration effect by changing of the bilayer thickness. Finally, we have made the self-organization and nano-structured film. In this processing, we have made nano-dot which consists of the underlayer and the overlayer, unlike the existing method called the agglomeration effect in the single layer. The underlayer has deposited using Ti, Cr and Co. And the overlayer has deposited with Ag. Through the analysis of Atomic force microscopy (AFM), the microstructure of underlayer is observed by AFM to confirm the formation of nano-dot. As the nano-dot through above processing, we have found that the nano-dot has the different shape. As a result, when we manufactured nano-dot through the agglomeration effect of bi-layer, the best matching material is Ti for underlayer. And also, we have found that MgO/Ti/Ag samples have been grown expitaxially toward the direction of MgO (001) by X-ray Diffraction analysis.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.6
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• pp.25-37
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• 2000

The trajectories of feature points can be defined by the correspondences between points in consecutive frames. The correspondence problem is known to be difficult to solve because false positives and false negatives almost always exist in real image sequences. In this paper, we propose a robust feature tracking algorithm considering incomplete trajectories such as entering and/or vanishing trajectories. The trajectories of feature points are determined by calculating the matching measure, which is defined as the minimum weighted Euclidean distance between two feature points. The weights are automatically updated in order to properly reflect the motion characteristics. We solve the correspondence problem as an optimal graph search problem, considering that the existence of false feature points may have serious effect on the correspondence search. The proposed algorithm finds a local optimal correspondence so that the effect of false feature point can be minimized in the decision process. The time complexity of the proposed graph search algorithm is given by O(mn) in the best case and O($m^2n$) in the worst case, where m and n arc the number of feature points in two consecutive frames. By considering false feature points and by properly reflecting motion characteristics, the proposed algorithm can find trajectories correctly and robustly, which has been shown by experimental results.