• Journal of the Institute of Electronics Engineers of Korea SP
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• v.39 no.4
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• pp.442-454
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• 2002

It's noticed that the SA-DCT (Shape-Adaptive Discrete Cosine Transform) produces different 2-dimensional transform coefficients according as the first 1-dimensional transform is applied in horizontal or vertical direction for an arbitrarily shaped boundary block. Performing the first 1-dimensional transform in the direction, which has higher spatial correlation or smaller shifting distance, can compact the energy on the smaller number of AC coefficients around DC. This paper shows, experimentally, the compaction capability improvement by choosing the first 1-dimensional transform direction with higher spatial correlation or smaller shifting distance. Two adaptive selection methods are proposed to decide efficiently the spatial direction with higher correlation in a boundary block. One is based on the gradients between DC coefficients of neighboring and current blocks, and the other is based on the final coding efficiency that means the number of bits required for coding the block. Using the MPEG-4 video coder, the proposed method shows coding efficiency gain up to 10.87% compared to the conventional SA-DCT method.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.6
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• pp.225-231
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• 2016

The valence band maximum (VBM) and conduction band minimum (CBM) of Al-doped GaInAsSb alloys substrated on GaSb are calculated by using an analytic approximation based on the tight binding method. The relative positions of the VBM and CBM between Al-GaInASSb and GaSb determine band alignement type, valence band offset (VBO) and conductin band offset (CBO) for the heterojunctions. In this study, aluminium doping is assumed to be substituted in the cation site and limited up to 20 % because it can easily oxidize and degrade materials. It is found that the Al-doped alloys exhibit type-II band alignments over the entire composition range and make the band gaps increase, whereas the VBO and CBO decrease. The decreasing rate of VBO is higher than that of CBO, which implies the Al components play a decisive role in controlling electrons at the interface. The Al-dopled GaInAsSb alloy has a direct band gap induced by $E({\Gamma})$ with a considerable distance from the E(L) and E(X), however, $E({\Gamma})$ approaches to E(L) and E(X) in the high Sb concentration (Sb > 0.7-0.8) which might affect the electron mobility and degrade the optical quality.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.3 s.345
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• pp.118-125
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• 2006

Mobile nodes in FHMIPv6 has both advantages of HMIPv6 protocol which reduces signaling delay time and resource consumption during a handover and fast handover algorithm which reduces packet loss. Fast handover algorithm can reduce packet loss by 'tunneling' method ; that transmits a packet from old access router to new access router in case of handover. However, the fast handover algorithm can cause a reordering problem in a receiver between packets tunneled from the previous access router and packets transmitted directly to the new access router, which could degrade the TCP performance due to congestion control. In this paper, we propose two algorithms to solve the reordering problem in fast handover. The first one uses a holding timer for tunneling, the other adds a new algorithm to routers that adopt snoop protocol. We compare the performance of the proposed reseuquencing algorithms with that of the existing FHMIPv6 protocol by simulation. The simulation results show that the proposed algorithms solve the reordering problems and enhance TCP performance by preventing TCP sender entering congestion control.

• Journal of Internet Computing and Services
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• v.15 no.1
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• pp.157-170
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• 2014

As the increase of transaction using mobile banking continues, threat to the mobile financial security is also increasing. Mobile banking service performs the financial transaction using the dedicate application which is made by financial corporation. It provides the same services as the internet banking service. Personal information such as credit card number, which is stored in the mobile banking application can be used to the additional attack caused by a malicious attack or the loss of the mobile devices. Therefore, in this paper, to cope with the mobile financial accident caused by personal information exposure, we suggest outlier detection method which can judge whether the transaction is conducted by the appropriate user or not. This detection method utilizes the user's input patterns and transaction patterns when a user uses the banking service on the mobile devices. User's input and transaction pattern data involves the information which can be used to discern a certain user. Thus, if these data are utilized appropriately, they can be the information to distinguish abnormal transaction from the transaction done by the appropriate user. In this paper, we collect the data of user's input patterns on a smart phone for the experiment. And we use the experiment data which domestic financial corporation uses to detect outlier as the data of transaction pattern. We verify that our proposal can detect the abnormal transaction efficiently, as a result of detection experiment based on the collected input and transaction pattern data.

• Journal of the Korean Chemical Society
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• v.45 no.5
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• pp.442-447
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• 2001

The charge-transfer compound (OMTTF)AuCl$_4$ was prepared from the direct reaction of octamethylenethiafulvalene (OMTTF) with HAuCl$_4{\cdot}xH_2$O in THF. (OMTTF)$_2PtCl_4$, (OMTTF)_2IrCl_6{\cdot}2H_2$O, and (OMTTF)Os$Cl_5{\cdot}THF$ were also formed using $H_2PtCl_6{\cdot}xH_2O$, $H_2IrCl_6{\cdot}xH_2O$ and $H_2OsCl_6$, respectively. The prepared compounds were characterized by magnetic (EPR, magnetic susceptibility), spectroscopic (IR, UV-Vis), electrochemical (CV) methods, and the powdered electrical conductivity measurement. The powdered electrical conductivities at room temperature were ~$10^{-7}S{\cdot}cm^{-1}$. The experimental results show that $OMTTF^+$ monocation radicals exist in all of the prepared compounds. The redox potential of OMTTF supports that $OMTTF^+$ is relatively stable. The magnetic properties indicate that there are significant magnetic interactions between the localized odd electrons on the central metal (Ir and Os) ions and the odd electrons resided on $OMTTF^+$ cation radicals in both (OMTTF) $_2IrCl_6{\cdot}2H_2O$ and (OMTTF)$OsCl_5{\cdot}THF$.

• Journal of Astronomy and Space Sciences
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• v.14 no.2
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• pp.312-319
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• 1997

The magnetometer is one of the most important payloads for scientific satellite to monitor the near-earth space environment. The electromagnetic variations of the space environment can be observed with the electric and magnetic field measurements. In practice, it is well known that the measurement of magnetic fields needs less technical complexities than that of electric fields in space. Therefore the magnetometer has long been recognized as one of the basic payloads for the scientific satellites. In this paper, we discuss the scientific fluxgate magnetometer which will be on board the KITSAT-3. The main circuit design of the present magnetometer is based on that of KITSAT-1 and -2 but its facilities have been re-designed to improve the resolution to about 5nT for scientific purpose. The calibration and noise level test of this circuit have been performed at the laboratory of the Tierra Tecnica company in Japan.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.4
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• pp.665-670
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• 2020

Buffer layer in CIGS thin-film solar cells improves energy conversion efficiency through band alignment between the absorption layer and the window layer. ZnS is a non-toxic II-VI compound semiconductor with direct-transition band gaps and n-conductivity as well as with excellent lattice matching for CIGS absorbent layers. In this study, the structural and optical properties of ZnS thin films, deposited by RF magnetron sputtering method and subsequently performed by the rapid thermal annealing treatment, were investigated for the buffer layer. The zincblende cubic structures along (111), (220), and (311) were shown in all specimens. The rapid thermal annealed specimens at the relatively low temperatures were polycrystalline structure with the wurtzite hexagonal structures along (002). Rapid thermal annealing at high temperatures changed the polycrystalline structure to the single crystal of the zincblende cubic structures. Through the chemical analysis, the zincblende cubic structure was obtained in the specimen with the ratio of Zn/S near stoichiometry. ZnS thin film showed the shifted absorption edge towards the lower wavelength as annealing temperature increased, and the mean optical transmittance in the visible light range increased to 80.40% under 500℃ conditions.

• Journal of IKEEE
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• v.27 no.1
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• pp.103-108
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• 2023

This research was carried out experiments with changing processes and design parameters to optimally design a SiC-based 1200V power MOSFET, and then, essential electrical characteristics were derived. In order to secure the excellence of the trench gate type SiC power MOSFET device to be designed, electrical characteristics were derived by designing it under conditions such as planner gate SiC power MOSFET, and it was compared with the trench gate type SiC power MOSFET device. As a result of the comparative analysis, the on-resistance while maintaining the yield voltage was 1,840mΩ, for planner gate power MOSFET and to 40mΩ for trench gate power MOSFET, respectively, indicating characteristics more than 40 times better. It was judged that excellent results were derived because the temperature resistance directly affects energy efficiency. It is predicted that the devices optimized through this experiment can sufficiently replace the IGBT devices generally used in 1200V class, and that since the SiC devices are wide band gap devices, they will be widely used to apply semiconductors for vehicles using devices with excellent thermal characteristics.

• Tuberculosis and Respiratory Diseases
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• v.43 no.6
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• pp.842-851
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• 1996

Background : Rifampicin(RFP) is a key component of the antituberculous shon-course chemotherapy and the RFP-resistance is a marker of multi-drug resistant(MDR) M. tuberculosis. rpoB gene encodes the ${\beta}$-subunit of RNA polymerase of M. tuberculosis which is the target of RFP. Recent reports show that rpoB gene mutations are the cause of RFP resistance of M. tuberculosis and the main mechanism of rpoB gene mutation is point mutation. And PCR-SSCP is a rapid and easy method for detecting point mutations. So we performed PCR-SSCP of rpoB gene of M. tuberculosis and compared the result with traditional RFP sensitivity test. Method : The 27 RFP sensitive M. tuberculosis culture isolates and 25 RFP resistant isolates were evaluated. The RFP sensitivity test was done at the Korean Tuberculosis istitute. The DNA was extracted by bead beater method and was amplified with primers TR-8 and TR-9 in a 20ul PCR reaction containing 0.1ul(luCi) [${\alpha}-^{32}P$] - dCTP. After amplification, SSCP was done using non-denaturaring polyacrylamide gel electrophoresis. Then direct sequencing was done in cases of different eletrophoretic mobility compared with that of H37Rv. In 19 cases, we compared PCR-SSCP results with patient's clinical course and the results of traditional RFP sensitivity test. Results : 1) All 27 RFP sensitive M. tuberculosis isolates showed the same electrophoretic mobility compared with that of H37Rv. And all 25 RFP resistant M. tuberculosis isolates showed different electrophoretic mobility. 2) The mechanism of rpoB gene mutation of M. tuberculosis is mainly point mutation. 3) The PCR-SSCP results correlate well with traditional RFP sensitivity and patient's clinical response to antituberculous treatment. Conclusion: The PCR-SSCP of rpoB gene is a very sensitive and rapid mehod in detecting RFP- resistant M. tuberculosis.

• Journal of radiological science and technology
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• v.35 no.2
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• pp.141-149
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• 2012

The aims of this study are to assess external radiation exposed doses of body and hands of nuclear medicine workers who handle radiation sources, and to measure radiation exposed doses of the hands induced by a whole body bone scan with high frequency and handling a radioactive sources like $^{99m}Tc$-HDP and $^{18}F$-FDG in the PET/CT examination. Skillful workers, who directly dispense and inject from radiation sources, were asked to wear a TLD on the chest and ring finger. Then, radiation exposed dose and duration exposed from daily radiation sources for each section were measured by using a pocket dosimeter for the accumulated external doses and the absorbed dose to the hands. In the survey of four medical institutions in Incheon Metropolitan City, only one of four institutions has a radiation dosimeter for local area like hands. Most of institutions uses radiation shielding devices for the purpose of protecting the body trunk, not local area. Even some institutions were revealed not to use such a shielding device. The exposed doses on the hands of nuclear medicine workers who directly handles radioactive sources were approximately twice as much as those on the body. The radiation exposure level for each section of the whole body bone scan with high frequency and that of the PET/CT examination showed that radiation doses were revealed in decreasing order of synthesis of radioactive medicine and installation to a dispensing container, dispensing, administering and transferring. Furthermore, there were statistically significant differences of radiation exposure doses of the hands before and after wearing a syringe shielder in administration of a radioactive sources. In this study, although it did not reach the permissible effective dose for nuclear medicine, the occupational workers were exposed by relatively higher dose level than the non-occupational workers. Therefore, the workers, who closely exposed to radioactive sources should be in compliance with safety management regulations, and take actions to maximally reduce locally exposed dose to hands monitoring with ring TLD.