• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2352-2358
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• 2012

A high-nitrogen energetic salt, 1-amino-1-hydrazino-2,2-dinitroethylene guanidine salt [G(AHDNE)], was synthesized by reacting of 1-amino-1-hydrazino-2,2-dinitroethylene (AHDNE) and guanidine hydrochloride in sodium hydroxide aqueous solution. The theoretical investigation on G(AHDNE) was carried out by B3LYP/$6-311+G^*$ method. The thermal behaviors of G(AHDNE) were studied with DSC and TG-DTG methods, and the result presents an intense exothermic decomposition process. The enthalpy, apparent activation energy and pre-exponential constant of the process are $-1060J\;g^{-1}$, $148.7kJ\;mol^{-1}$ and $10^{15.90}s^{-1}$, respectively. The critical temperature of thermal explosion of G(AHDNE) is $152.63^{\circ}C$. The specific heat capacity of G(AHDNE) was studied with micro-DSC method and theoretical calculation method, and the molar heat capacity is $314.69J\;mol^{-1}K^{-1}$ at 298.15 K. Adiabatic time-to-explosion of G(AHDNE) was calculated to be a certain value between 60-72 s. The detonation velocity and detonation pressure were also estimated. G(AHDNE) presents good performances.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.6
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• pp.30-37
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• 2013

A ground hot-firing test was conducted to take out the optimal design configurations for the catalyst bed of liquid-monopropellant hydrazine thruster which could be used for primary engine or attitude control thruster of space vehicles. Performance characteristics with the variation of thrust-chamber length are investigated in terms of thrust, specific impulse, chamber pressure, characteristic velocity, and hydrazine decomposition rate. Additionally, the correlations between propellant-supply pressure and performance parameters are given. As results, increase of catalyst-bed length leads to performance degradation in this test condition, and also decreases propellant consumption efficiency with the supply pressure variation.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.1
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• pp.1-8
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• 2020

In this study, a configuration design of a CH₄/LOx small rocket engine was made and test system was established for the performance evaluation. A coaxial swirl injector was chosen because of its remarkable atomization performance and low combustion instability. Three aspect ratios for the combustion chamber configuration, i.e., 1.5, 1.8, and 2.1 were also set for the comparison of the combustion efficiency. The reliability of the thrust measurement rig was enhanced by pre-and post-calibration process. From the preliminary ground hot-firing test, the measured thrust and specific impulse values were 89.2 N and 181.8 s, respectively, which were 21.6% lower than the ideal values. In addition, the efficiency of characteristic velocity was measured as 84.2%.

• Nuclear Engineering and Technology
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• v.21 no.2
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• pp.73-88
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• 1989

Ten methods of the total two-phase pressure drop prediction based on five existing models and correlations have been examined for their accuracy and applicability to pressurized water reactor conditions. These methods were tested against 209 experimental data of local and bulk boiling conditions : Each correlations were evaluated for different ranges of pressure, mass velocity and Quality, and best performing models were identified for each data subsets. A computer code entitled 'K-TWOPD' has been developed to calculate the total two-phase pressure drop using the best performing existing correlations for a specific property range and a correction factor to compensate for the predicted error of the selected correlations. Assessment of this code shows that the present method fits all the available data within $\pm$11% at a 95% confidence level compared with $\pm$25%, for the existing correlations.

• Korean Journal of Food Science and Technology
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• v.11 no.4
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• pp.249-257
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• 1979

Using the whole cell immobilized glucose isomerase which was prepared in the previous work (Korean J. Food Sci. & Technol., 11(3), 192 (1979), the specific activity of the immobilized enzyme was 48.1 units in the batch reaction system and 114 units in the continuous reaction system per g of matrix, respectively. In the continuous reactor the voidity was 0.36, which was suitable for the packed bed reactor. This immobilized enzyme showed a good operational stability of 115 days of half life which was sufficient for the continuous operation. The experimental result showed that 55 % of the substrate was converted to the product in the packed bed reactor. The productivity was dependent on the flow rate, column geometry, enzyme loading, and substrate concentration. An intrapaticle diffusion was observed by the effectiveness factor of 0.75 and interparticle diffusion by the decrease of Km' with increasing the superficial velocity.

• KSBB Journal
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• v.21 no.1 s.96
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• pp.49-53
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• 2006

The aim of this research is to estimate the values of biological kinetic parameters of pharmaceutical wastewater for understanding biochemical properties. Maximum specific growth rate (${\mu}m$), yield coefficient (Y), and half-velocity coefficient (KS) were determined using oxygen uptake rate (OUR), and the results were 10.49/day (0.437/hr), 0.655, and 38.89 mg/L, respectively. Measured ${\mu}max$ by nonlinear regression of Monod equation was 10.63/day (or 0.443/hr), and this value was similar with above result. These parameters may be used to increase efficiency of pharmaceutical wastewater treatment and to determine amount of oxygen needed to removal BOD and dissolved oxygen in activated sludge process.

• Journal of the Korean Institute of Rural Architecture
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• v.17 no.2
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• pp.51-58
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• 2015

10 years ago, in Sijeon-ri, Dogo-myeon, Asan-si, the existing stream was repaired to develope Mt. Dogo trail and irrigation systems through road expansion pavement construction and small stream repair construction. The trees such as persimmon and willow are eliminated that rowed on both sides of the stream and dredging work to dig the rock and sand have been performed. As a result, wide asphalt road was built, also flood damage worries were reduced. 10 years passed and now, how did local residents think about the stream repaired before and after? Village residents, public officials, and the stream construction engineer were interviewed. Villagers indicated a problems that brook became a place where water peppers were taking over and water was stagnating due to the slow velocity so nothing could live and natural landscape like a wash place and the cascade disappeared, because rock and sand were taken out brought soil into the brook. Public officials and engineers were aware of the problems at the time of the stream. Now that construction is completed after 10 years, Both realistically and budgetary to restoration would be difficult. However, it is necessary to seek for waterfront space which can be restored or replaced by a part of the stream like similarly before. In addition, it is necessary to restore to the progression of a natural stream which connect with stairs(or slope) - small waterfalls - pools - wash place. In this paper, we hope to take a lesson from the Sijeon-ri model and make rural stream construction be prepared with consideration about not only distinct characteristics of specific area but also the opinion of local resident.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.181-186
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• 2006

In this paper, generation mechanisms of ocean freak waves are briefly introduced in the context of wave-current interaction phenomena. The present model of the fluid motion is based on the Navier-Stokes equations incorporating velocity-pressure formulation because of need to model the nonlinear wave interaction with spatially non-uniform current field. In order to deal with the free surface motion, an Arbitrary Lagrangian-Eulerian (ALE) description is adopted. As an accurate and efficient numerical tool, the spectral element method is presented with general features and specific treatment for the wave-current interaction problem. As an intermediate stage of development, solution procedure and characteristics aspects of the present modeling and numerical method are addressed in detail, and preliminary numerical results prove its accuracy and convergence.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.1
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• pp.25-38
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• 1993

Numerical models of directional wave spectra for the analysis of offshore structural cable responses are verified. Alternative spreading models are used to predict wave-induced flows in water and for mooring systems. Hydrodynamic wave forces upon cable are estimated. using a Morison formula encompassing considerations for drag and for inertial forces both parallel and tangential to the slope of the cable. Numerical analysis for directional random waves. including consideration of displacement and velocity, trajectory, phase plane response. and tension are shown for mooring system cable responses at both the tether point for a buoy and at the anchor point. The effects of wave forces far different drag coefficients, various significant wave heights, and selected wave parameters are considered in the analysis. For the specific systems considered in the examples, it is demonstrated that wave period and height as well as wave spreading function parameters and drag coefficients, have an important effect upon the dynamic responses of the cable-buoy systems.

• Journal of Korean Society of Disaster and Security
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• v.11 no.1
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• pp.1-5
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• 2018

Power plant is the important infrastructure to generate electricity. This plant in normally located next to river and seashore in order to take cooling water through intake. However, the plant is stopped when marine organism blocks the intake, and it caused damages by social and commercial. Therefore, air bubble barrier has been used to block marine organism in order to operate the plant properly. The aim of this study was to test the rates of cut off of floating substance by air bubble barrier to develop the facility for the plant. The test was conducted by current velocity, pressure of air, specific gravity of the substance and the layer of the barrier, and the result showed the blocking rates by the condition. It will be used as basic data to develop the air bubble barrier and to operate power plant properly from the marine organism.