• Journal of the Korean Society of Propulsion Engineers
• /
• v.19 no.3
• /
• pp.96-102
• /
• 2015

Traditional propellants emit toxic gases such as carbon dioxide and hydrogen chloride during combustion which are harmful to the environment. This study established a synthetic process of a high nitrogen containing derivative of tetrazine, 3,3-Azobis(6-Amino-1,2,4,5-Tetrazine) (DAAT), which can be applied as solid fuels for a solution to environmental concerns. Also, this paper described the detailed process and the analytic results of properties, which were not mentioned in previous reports. The compound was characterized by NMR, IR spectroscopy, and thermal, impact, and friction stability were measured. In addition, the heats of formation (${\Delta}H_f$) and detonation properties (pressure and velocity) of DAAT were calculated using Gaussian 09 and EXPLO5 programs.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.7A
• /
• pp.682-687
• /
• 2010

The IEEE 802.15.4a specification targets the low-rate (LR) Impulse-radio (IR) ultra-wideband (UWB) system which is now widely applied in the WPANs considering rather short distance communications with low complexity and power consumption. The physical (PHY) layer uses concatenated coding with mixed binary phase-shift keying and binary pulse-position modulation (BPSK-BPPM), and direct sequence spreading with time hopping in order that both coherent and non-coherent receiver architectures are supported. In this paper, the performances of multiple access schemes compliant with IEEE 802.15.4a specification are investigated with energy detection receiver, which allow avoiding the complex channel estimation needed by a coherent receiver. However, the performance of energy detection receiver is severely degraded by multi-user interference (MUI), which largely diminishes one of the most fascinating advantages of UWB, namely robustness to MUI as well as the possibility to allow parallel transmissions. So as to improve the performance of multiple access schemes, we propose to apply the novel TH sequences as well as to increase the number of TH positions. The simulation results show that our novel multiple access schemes significantly improve the performance against MUI.

• Journal of the Korean Wood Science and Technology
• /
• v.36 no.6
• /
• pp.49-58
• /
• 2008

This research was carried out to use green tea leaves powder for scavenging effects of volatile organic compounds on the UV varnishes and adhesives of fancy cherry veneer overlaid on the PF resin bonded Meranti plywood. The results are as follows: 1) Green tea leaves contained 9.85% of polyphenol compounds. 2) FT-IR results showed green tea leaves had effects to react with benzaldehyde and ethyl hexyl alcohol to form a chemical bond. 3) 2.5% of green tea leaves powder content was proper for scavenging effect on the UV varnishes and adhesives of fancy veneer overlaid on the PF resin bonded plywood 4) 20 liters small chamber test indicated excellent emission speed results such as $0.089mg/m^2hr$ of TVOC and $0.001mg/m^2hr$ of HCHO (on 7th day), as compared with standard (less than $0.1mg/m^2hr$ of TVOC and $0.015mg/m^2hr$ of HCHO emission are the excellent grade).

• Journal of the Korean Chemical Society
• /
• v.31 no.3
• /
• pp.258-270
• /
• 1987

A series of new thorium nitrate complexes with crown ethers have been synthesized from the reaction of the hydrated thorium nitrate, with the appropriate crown ethers of different cavity sizes in various solvents such as methanol, ethanol, butanol, methylacetate, acetone, tetrahydrofuran and acetylacetone. CHN elemental analysis, ICPAS, thermal analysis and Karl-Fischer method have been used to characterize their compositions, and the spectroscopic methods of IR, UV, $^1H-NMR$, and X-ray diffraction have been employed to determine the structures and solvolysis phenomena of these complexes. and the electrical conductances were measured in DMSO, and water solvent. The solvolysis have been observed only in the complexes synthesized in acetylacetone solvent. In the solvated complexes of 15-crown-5 and 18-crown-6, the mole ratio of $Th^{4+}$: ligand : acetylacetone is found to be 1:1:1, but in the non-solvated complexes of 12-crown-4 and 15-crown-5, the mole ratios of Th:L are 1:2 and 2:3, respectively, and that in the complexes of both 18-crown-6 and dicyclohexano-18-crown-6 is 1:1. All complexes which were not solvated have shown $n{\to}{\sigma}^{\ast}$ electronic transitions of crown ether whereas complexes solvated have exhibited both $n{\to}{\sigma}^{\ast}$ of crown ether and $n{\to}{\pi}^{\ast}$ transitions of acac. The dissociation mole ratio of $Th^{4+}$ and nitrate ion is found to be 1:1 in aprotic solvent, and 1:4 in protic solvent like water.

• Food Science and Biotechnology
• /
• v.14 no.2
• /
• pp.268-274
• /
• 2005

Novel antimicrobial substance was isolated from seed coat of Canavalia gladiata by extraction with 75% methanol. Isolation and purification were conducted with solvent fractionation and chromatography on silica gel and sephadex LH-20 columns. Each fraction of antimicrobial activity was tested by paper disc method. Single compound was obtained from the 4th fraction of sephadex LH-20 column chromatography using chloroform/methanol (1:4, v/v), and identified as 3,4,5-trihydroxybenzoic acid methyl ester (methyl gallate) based on HPLC, GC/MS, FT-IR, $^1H$ NMR, and $^{13}C$ NMR analyses. This is the first report describing the presence of methyl gallate in C. gladiata.

• International Journal of Advanced Culture Technology
• /
• v.8 no.4
• /
• pp.299-305
• /
• 2020

With the advancement of the 4th Industrial Revolution(4IR), microprocessor education is on the rise due to the explosive demand for IoT (Internet of Things) and M2M devices. However, it is difficult due to many constraints to efficiently transfer training on hardware assembly and implementation through online training. Thus, we developed a cost-effective online content based on Arduino simulations, Atmel Studio 7, and WinAvr simulator that are required for the utilization of AVR 128. These Camtasia videos overcame the limitation of theory focused on-line education by visually introducing the practical utilization of an actual AVR 128. In this paper, the proposed educational content was provided to university students, and the results of student feedback show that it has a strong effect.

• Computers and Concrete
• /
• v.29 no.4
• /
• pp.237-246
• /
• 2022

The concrete quality relies on general factors like preparation technique, uniformity of the compaction, amount and appropriateness of the additives. The current article investigates the impact of a well knows amino acid, L-arginine as an additive on water requirements, setting durations and characterization of various cement samples. Compressive strength tests of reference and L-arginine added cements at age of 2, 7 and 28 days were carried out according to TS-EN 196-1. Samples were blended by incorporating various amounts of L-arginine (25 ppm, 50 ppm and 75 ppm) in the cement water mixture which were tested with Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermo-gravimetric analysis (TG), scanning electron microscopy (SEM) and the energy-dispersive X-ray spectroscopy (EDS) on the 28th day. Results revealed that L-arginine does not affect the setting time, volume expansion of cement and water demands negatively; rather it imparts enhanced sustainability to the samples. It was determined that the highest value belonged to the 75L mortar with an increase of 2.6% compared to the reference sample when the compressive strengths of all mortars were compared on the 28th day. Besides, it has been observed that the development of calcium silicate hydrate or C-S-H gel, calcium hydroxide or CH and other hydrated products are associated with each other. L-arginine definitely has a contribution in the consumption of CH formed in the hydration process.

• The Journal of Korean Medicine
• /
• v.30 no.4
• /
• pp.79-92
• /
• 2009

Objectives: The aim of the present study was to explore the neuroprotective effect and the possible mechanism of the PD-1 extracts on 1-methyl-4-phenyl-1,2,3,6-tetrahydrophridine (MPTP)-lesioned C57BL/6 mouse model of Parkinson's disease (PD). Methods: The mice were supplemented (or not) with 50 or 100 mg/kg/day of PD-1 for 2 weeks, after which MPTP was injected intraperitoneally. We observed that daily administration of PD-1 prevented MPTP-induced depletion of striatal DA, and maintained striatal and nigral tyrosine hydroxylase (TH) protein levels. Results: Our results demonstrated that mice treated with PD-1 prior to MPTP administration showed more abundant TH-immunopositive (TH-ir) fibers and neurons than mice given only MPTP, indicating that PD-1 protects dopaminergic striatal fibers and nigral neurons from MPTP insults. Possible neuroprotective effect of PD-1 was further studied by the detection of antiapoptotic protein (bcl-2) and proapoptotic protein (Bax). In this assay, MPTP elevated the Bax protein and decreased the bcl-2 protein, while these expressions were prevented by PD-1 pre-treatment. Conclusions: The present results suggest that PD-1 is able to protect dopaminergic neurons from MPTP-induced neuronal injury with anti-apoptotic activity being one of the possible mechanisms.

• Electrical & Electronic Materials
• /
• v.10 no.3
• /
• pp.210-216
• /
• 1997

The th ermal and optical properties of multicomponent oxide glass optical fiber by adding heavy metal oxide Ga$_{2}$O$_{3}$(0-20wt%) were investigated. The fiber samples were made by the method of rod in tube. The optical loss of fiber was measured in 0.3-1.8.mu.m wavelength region. As Ga$_{2}$O$_{3}$ increased up to 20wt%, the transition and softening temperature of bulk glass were increased from 495.deg. C to 579.deg. C and from 548.deg. C to 641.deg. C, respectively. Whereas the thermal expansion coefficient was decreased from 102 to 79.1x10$^{-7}$ /.deg. C. The refractive index was increased from 1.621 to 1.665, and IR cut-off wavelength was enlarged from 4.64.mu.m to 6.1.mu.m. The optical loss of fiber was remarkably decreased in 1.146.mu.m-1.8.mu.m wavelength region.

• Applied Microscopy
• /
• v.30 no.2
• /
• pp.193-204
• /
• 2000

Nowadays, mongolian gerbil is widely utilized in the research of brain and water deprivation because of congenitally incomplete Willis' circle, audiogenic seizure in low noise, and special cholesterol metabolism without water absorption for a long time. In this study, we intended to identify the time lapse changes in the general morphoogy and ultrastructure of the catecholaminergic neurons of mongolian gerbil brain in after long-term water deprivation. Fifteen mongolian gerbils were divided into 3 groups (5, 10, and 20-day water deprivation groups), each with 5 mongolian gerbils. Additional 5 mongolian gerbils which received water without limitation were used as a control. The brain sections were immunostained using tyrosine hysroxylase (TH), $ dopamine-\beta-hydroxylase$ (DBH), and phenylethanolamine-N-methyltrasferase (PMNT) antibodies. And immunoreactive cells were observed by electromicroscopy for the ultrastructural changes . The TH-immunoreactive (TH-IR) nerve cells were observed in the para- and peri-ventricular nucleus of the 3 rd ventricle in the hypothalamus and the substantia nigra. The number of TH-IR neurons in these areas was decreased from the 5th day of the water deprivation to the 10 th day and reincreased until 20 th day water deprivation. The shape and density of the dopamine-secreting cells identified by immunohistochemistry showed changes in the continuous water deprivation. Electron microscopy revealed a round nucleus in the neurons of control group but 5-day water deprivation group showed a dense and irregularly shaped nucleus. Also in the 5-day water-deprived group, mitochondria was decreased in number and junctins were disappered. Endoplasmic reticulum, Golgi complex did not show changes after water-deprivation. In this results, we can conclude that dopamine are involved in the water metabolism in mongolian gerbil, and mongolian gerbil could be used as an animal model for the researches of water deprivation.