• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.18 no.10
• /
• pp.945-949
• /
• 2005

We have grown GaN layers with in-situ SiN mask by metal organic chemical vapor deposition (MOCVD) and study the physical properties of the GaN layer. We have also fabricate PN junction light emitting diode (LED) to investigate the effect of the SiN mask on its optical property By inserting a SiN mask, (102) the full width at half maximum (FWHM) decreased from 480 arcsec to 409 arcsec and threading dislocation (TD) density decreased from $3.21{\times}10^9\;cm^{-2}$ to $9.7{\times}10^8\;cm^{-2}$. The output power of the LED with a SiN mask increased from 198 mcd to 392 mcd at 20 mA. We have thus shown that the SiN mask improved significantly the physical and optical properties of the GaN layer.

• Journal of Microbiology and Biotechnology
• /
• v.18 no.3
• /
• pp.397-403
• /
• 2008

Nikkomycins are a group of peptidyl nucleoside antibiotics with potent fungicidal, insecticidal, and acaricidal activities. sanN was cloned from the partial genomic library of Streptomyces ansochromogenes 7100. Gene disruption and complementation analysis demonstrated that sanN is essential for nikkomycin biosynthesis in S. ansochromogenes. Primer extension assay indicated that sanN is transcribed from two promoters (sanN-P1 and sanN-P2), and sanN-P2 plays a more important role in nikkomycin biosynthesis. Purified recombinant SanN acts as a dehydrogenase to convert benzoate-CoA to benzaldehyde in a random-order mechanism in vitro, with respective $K_{cat}/K_m$$ values of $3.8mM^{-1}s^{-1}\;and\;12.0mM^{-1}s^{-1}$ toward benzoate-CoA and NADH, suggesting that SanN catalyzes the formation of picolinaldehyde during biosynthesis of nikkomycin X and Z components in the wild-type stain. These data would facilitate us to understand the biosynthetic pathway of nikkomycins and to consider the combinatorial synthesis of novel antibiotic derivatives.

• Bulletin of the Korean Chemical Society
• /
• v.28 no.12
• /
• pp.2369-2376
• /
• 2007

N2O has been found from experimental and theoretical considerations to bind on-top to the Pd(110) surface in a tilted end-on fashion via its terminal N atom. We use a frontier orbital description of the bonding interactions in the Pd-N2O system to obtain molecular insight into the catalytic mechanism of the activation of N2O by the Pd(110) surface giving rise to the formation of N2 and O on the surface. For the tilted end-on N2O binding mode, the LUMO 3π of N2O has good overlap with the Pd dσ and dπ orbitals which can serve as the electron donors. The donor-acceptor orbital overlap is favorable for electron transfer from Pd to N2O and is expected to dominate the surface reaction pathway of N2O decomposition.

• Journal of the Korean Magnetic Resonance Society
• /
• v.12 no.2
• /
• pp.74-80
• /
• 2008

The local structure of defects in undoped, Si-doped, and neutron irradiated free standing GaN bulk crystals, grown by hydride vapor phase epitaxy, has been investigated by employing electron magnetic resonance(EMR), Raman scattering and cathodoluminescence. The GaN samples were irradiated to a dose of $2{\times}10^{17}$ neutrons in an atomic reactor at Korea Atomic Energy Research Institute. There was no appreciable change in the Raman spectra for undoped GaN samples before and after neutron irradiation. However, a forbidden transition, $A_1$(TO) mode, appeared for a neutron irradiated Si-doped GaN crystal. Cathodoluminescence spectrum for the neutron irradiated Si-doped GaN crystal became much broader or was much more broadened than that for the unirradiated one. The observed EMR center with the g value of 1.952 in a neutron irradiated Si-doped GaN may be assigned to a Si-related complex donor.

• Journal of Navigation and Port Research
• /
• v.46 no.5
• /
• pp.409-417
• /
• 2022

The International Association of Lighthouse Authorities (IALA) utilizes a questionnaire to investigate the status of Aids to Navigation (AtoN) around the world. However, results of the IALA questionnaire have limited use because respondent understanding is inconsistent. In addition, there is uncertainty regarding the appropriateness of the questionnaire content. Furthermore, the overall response rate is low. Therefore, the status of AtoN is not clearly understood. AtoN data from around the world are generated hourly. Thus, big data solutions are required to effectively exploit the information. Digitization of analog data is an important component of building big data. Hence, the IALA has developed a Maritime Resource Name (MRN) scheme and an information exchange standard. Here, we used the AtoN information exchange standard and designed an S-201-based big data construction process that could collect and manage global AtoN information. In this study, construction of an IALA AtoN portal was proposed as the core of the construction of the AtoN big data. The process was divided into three stages. IALA AtoN portal is developed by IALA with the goal to provide various meaningful statistical analysis results based on AtoN data while managing AtoN information around the world based on S-201. If an AtoN portal capable of constructing S-201-based big data is developed, then a data collection and storage system that can gather basic S-201 AtoN data from the IALA and global AtoN management agencies could be achieved. Furthermore, insightful statistical analysis of AtoN status worldwide and changes in manufacturing technology will be possible.

• Journal of applied mathematics & informatics
• /
• v.42 no.3
• /
• pp.567-582
• /
• 2024

A total coloring of a graph G is an assignment of colors to the elements of a graphs G such that no adjacent vertices and edges receive the same color. The total chromatic number of a graph G , denoted by χ''(G), is the minimum number of colors that suffice in a total coloring. In this paper, we proved the Behzad and Vizing conjecture for certain convex polytope graphs D^p_n, Q^p_n, R^p_n, E_n, S_n, G_n, T_n, U_n, C_n,respectively. This significant result in a graph G contributes to the advancement of graph theory and combinatorics by further confirming the conjecture's applicability to specific classes of graphs. The presented proof of the Behzad and Vizing conjecture for certain convex polytope graphs not only provides theoretical insights into the structural properties of graphs but also has practical implications. Overall, this paper contributes to the advancement of graph theory and combinatorics by confirming the validity of the Behzad and Vizing conjecture in a graph G and establishing its relevance to applied problems in sciences and engineering.

• The Korea Journal of Herbology
• /
• v.21 no.4
• /
• pp.77-84
• /
• 2006

Objectives : To evaluate the neuroprotective effects of modified Bo-Yang-Hwan-O-Tang (BHT), we investigated the neuronal death protection effects to oxidative damages in N2a neuroblastoma cells. Methods : To study the cytotoxic effect of BHT on N2a neuronal cells, the cell viability was determined by MTT assay. To investigate the neuronal death protection of BHT, N2a neuronal cells were induced oxidative damages by H2O2, and assayed the cell viability and DNA fragmentation. We also investigated DPPH free radical scavenging effects of BHT by tube test. Results : In MTT assay, $500{\mu}g/ml$ of BHT was not showed cytotoxic effect on N2a neuronal cells. BHT protected N2a neuronal cells from H2O2-induced cell death in a dose-dependent manner. BHT also protected N2a neuronal cells from H2O2-induced DNA fragmentation. BHT scavenged DPPH free radicals in a dose-dependent manner. Conclusion : These data suggest that BHT may have strong anti-oxidant effects through the free radical scavenging and neuroprotective effects in neuronal cells.

• ETRI Journal
• /
• v.37 no.6
• /
• pp.1120-1128
• /
• 2015

We propose a pseudo optical N-level pulse-amplitude modulation (PO PAM-N) signal using a few externally-modulated lasers (EMLs) operating at different wavelengths, which is suitable for upgrading the transmission speed over an optical link of < 10 km single-mode fiber with low-cost components. To compare a PO PAM-N signal with that of a standard optical PAM-N signal, we perform experiments for evaluating the performance of a 51.56-Gb/s PO PAM-4 signal and standard 51.56-Gb/s optical PAM-4 signal. The receiver sensitivity (at $BER=10^{-5}$) of the PO PAM-4 signal is 1.5 dB better than the receiver sensitivity of a standard optical PAM-4 signal. We also investigate the feasibility of PO PAM-N (N = 4, 8, and 16) signals operating at 103.12 Gb/s, considering relative intensity noise, timing jitter, extinction ratio (ER) of EMLs, and dispersion. From the results, a PO PAM-8 signal performs better than PO PAM-4 and PO PAM-16 signals at 103.12 Gb/s. Finally, we suggest a timing control method to suppress the effect of dispersion in a PO PAM-N signal. We show that the tolerance to dispersion of a 103.12-Gb/s PO PAM-8 signal can be improved to ${\pm}40ps/nm$ by applying a proposed scheme.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.6C
• /
• pp.751-762
• /
• 2004

In this paper, we propose the method to derive new GRM(Generalized Reed-Muller) coefficients for each 2$^n$ polarities using Triangle cell. As the existing methods to generate GRM coefficients, there are Green's method to operate transform matrix with a given RM coefficient and Besslich's method to get other polarities using basic transfer matrices repeatedly. In this paper, Triangle cell is defined so as to obtain GRM coefficients efficiently. After arranging 2$^n$ given RM coefficients of a first row of Triangle cell, sequence modulo sum is peformed in parallel to low column by a fixed numerical formula. To prove the efficiency of proposed arithmetic method, it is compared with Besslich’s method. As the compared result, to calculate GRM coefficients of all polarities to n input variables, Besslich’s method needs 2$^n$$^{-1}$ ${\times}$(2$^n$-1) two-input Ex-ORs and the proposed method needs 2${\times}$(the number of Ex-ORs for n-1 variables)+3$^n$$^{-1}$ for the same system complexity - (lo $g_2$$^n$) $T_{X}$./.

• Journal of the Korean Institute of Navigation
• /
• v.14 no.2
• /
• pp.1-14
• /
• 1990

The Radio Navigation System(R. N. S.) has been progressed consistantly with the development of electric-electronic engineering techniques since the R. D. E had been developed in 1910. The R. N. S. mostly depends on either Hyperbolic Navigation System(H. N. S.) or Spherical Navigation System(S. N. S.) in the ocean, and on Rectangular Navigation System (R. N. S.) in the air near the airport or an a combinations of the above systems in both area. Another effective R. N. S may be the Ellipse-Hyperbola Navigation System(E-H N. S.), which is proposed and named such in this paper. The equations calculating GDOP are derived and the GDOP values are calculated in the case of H. N. S., S. N. S, and E-H. N. S., respectively, for the specified case that four transmitting stations are arranged on the apex of a square, Then the GDOP diagrams of above navigation systems are presented for qualitative comparison in this paper. To measure the distances from the receiver to the stations in S. N. S., and/or the sum of distances to two stations in E-H N. S., the time synchronization between the transmitter clocks and the receiver clock is a major premise. The author has proposed the algorithm for getting this synchronmization utilizing the by S. N. S. or E-H N. S while GDOPs of those are relatively good. Even though clock synchronization error is a voidable due to the fix error used, the simulated results shows that the position accuracy of S. N. S. and E-H N. S. by the proposed method is far upgraded compared with that determined by H. N. S. directly, as far as the outer region of transmitter arrangement is concerned.