• International Journal of Aeronautical and Space Sciences
• /
• v.6 no.1
• /
• pp.61-70
• /
• 2005

The currently developed propulsion system(PS) is composed of propellant tank, valves, thrusters, interconnecting line assembly and thermal hardwares to prevent propellant freezing in the space environment. Comprehensive engineering analyses in the structure, thermal, flow and plume fields are performed to evaluate main design parameters and to verify their suitabilities concurrently at the design phase. The integrated PS has undergone a series of acceptance tests to verify workmanship, performance, and functionality prior to spacecraft level integration. After all the processes of assembly, integration and test are completed, the PS is integrated with the satellite bus system successfully. At present, the severe environmental tests have been carried out to evaluate functionality performances of satellite bus system. This paper summarizes an overall development process of monopropellant propulsion system for the attitude and orbit control of LEO(Low Earth Orbit) observation satellite from the design engineering up to the integration and test.

• Journal of the Korean Society of Safety
• /
• v.29 no.4
• /
• pp.61-72
• /
• 2014

The aim of this study is to define the condition of optimal pre-treatment for preferable activated carbon fibers (ACFs), which are based on rayon fibers. This paper shows the ideal path of ACFs preparation process; implies that rayon fibers are pre-treated by various solvents with different times before the heating process. The pre-treated rayon fibers finally turned into desirable rayon fiber-based ACFs through optimal pre-treatment condition by heating processes. The thermal analysis method of pre-treated rayon fibers by thermo-gravimetry analyser (TGA) is an idealized tool, which analyzes the best thermal condition of pre-treatment process. Surface morphologies of resulting rayon fibers based ACFs were examined by scanning electron microscope(SEM). The results of TGA and SEM analyses show that the optimal pre-treatment condition for preparing ACFs was clearly defined, in terms of thermal stability and surface morphology.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09a
• /
• pp.377-378
• /
• 2006

Thermal management technology is a critical element in all new chip generations, caused by a power multiplication combined with a size reduction. A heat sink, mounted on a base plate, requires the use of special materials possessing both high thermal conductivity (TC) and a coefficient of thermal expansion (CTE) that matches semiconductor materials as well as certain packaging ceramics. In this study, nano tungsten coated copper powder has been developed with a wide range of compositions, 90W-10Cu to 10W-90Cu. Powder technologies were used to make samples to evaluate density, TC, and CTE. Measured TC lies among theoretical values predicted by several existing models.

• Membrane and Water Treatment
• /
• v.10 no.5
• /
• pp.387-394
• /
• 2019

Membrane distillation (MD) is one of the water treatment processes which involves the momentum, heat and mass transfer through channels and membrane. In this study, CFD modeling has been used to simulate the heat and mass transfer in the direct contact membrane distillation (DCMD). Also, the effect of operating parameters on the water flux is investigated. The result shows a good agreement with the experimental result. Results indicated that, while feed temperature is increasing in the feed side, water flux improves in the permeate side. Since higher velocity leads to the higher mixing and turbulence in the feed channel, water flux rises due to this increase in the feed velocity. Moreover, results revealed that temperature polarization coefficient is rising as flow rate (velocity) increases and it is decreasing while the feed temperature increases. Lastly, the thermal efficiency of direct contact membrane distillation is defined, and results confirm that thermal efficiency improves while feed temperature increases. Also, flow rate increment results in enhancement of thermal efficiency.

• Korean Journal of Materials Research
• /
• v.33 no.12
• /
• pp.503-510
• /
• 2023

This comprehensive study delves into the intricate process of exfoliating and functionalizing boron nitride nanosheets (BNNSs) extracted from hexagonal boron nitride (h-BN), and meticulously explores their potential application within epoxy composites. The extensive research methodology encompasses a sequence of treatments involving hydrothermal and sonication processes aimed at augmenting the dispersion of BNNSs in solvents. Leveraging advanced analytical techniques such as Raman spectroscopy, X-ray diffraction, and FTIR spectroscopy, the study rigorously analyzes a spectrum of changes in the BNNS's properties, including layer count variations, interlayer interactions, crystal structure modifications, and the introduction of functional groups. The research also rigorously evaluates the impact of integrating BNNSs, specifically glycidyl methacrylate (GMA)-functionalized BNNSs, on the thermal conductivity of epoxy composites. The conclusive findings exhibit notable enhancements in thermal properties, predominantly attributed to the enhanced dispersion of fillers and enhanced interactions within the epoxy matrix. This pioneering work illuminates the wide potential of functionalized BNNSs for significantly enhancing the thermal conductivity of epoxy composites, paving the way for advanced materials engineering and practical applications.

• KIEAE Journal
• /
• v.12 no.3
• /
• pp.27-32
• /
• 2012

In recent years, the quality of the outdoor thermal environment has come to be regarded as important as that of the indoor thermal environment. Since the outdoor thermal environment is composed of many elements and is affected by many factors, it is not easy to evaluate the impact of each factor separately. Hence, a comprehensive assessment method is required. In order to evaluate the pedestrian level comfort of an outdoor climate, it is necessary to investigate not only wind velocity but also various physical elements, such as temperature, moisture, radiation, etc. Prediction of wind and thermal environment for a large scale buildings is one of the most important targets for research. Wind and thermal change in a city area is a very complicated phenomenon affected by many physical processes. The purpose of this study is to develop a design plan for wind environment at a large Buildings. In this study, we analyze outdoor wind environment and thermal environment on buildings using the CFD (Computational Fluid Dynamics) method. The arrangement of building models is an apartment in Jeonju. These prediction of wind and thermal environment for a large scale buildings is necessary in a plan before a building is built.

• Proceedings of the KWS Conference
• /
• 2007.11a
• /
• pp.76-78
• /
• 2007

• Journal of Technologic Dentistry
• /
• v.36 no.3
• /
• pp.149-158
• /
• 2014

Purpose: Dental casting Co-Cr-Mo based alloys of five kinds of ingot type and two kinds of shot type were analyzed the melting processes with heating time of high frequency induction centrifugal casting machine using infrared thermal image analyzer. Methods: When Co-Cr-Mo based alloys were put about 30g/charge in the ceramic crucible of high frequency induction centrifugal casting machine and heat, Infrared thermal image analyzer and IR thermometer indicated these alloys in the crucible were set and operated. Results: The melting temperatures of alloys measuring infrared thermal image analyzer were deviated ${\pm}10^{\circ}C$ compared to those of manufacturing company. On the other hand, the melting time of alloys were differently appeared with the shape of alloys(ingot and shot type). Conclusion: The melting temperatures of dental Co-Cr-Mo based alloys were measured the degree of $1,360{\sim}1410^{\circ}C$ and the heating time with the alloys of ingot and shot type were deviated ${\pm}10sec$.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.7
• /
• pp.2267-2273
• /
• 2011

A novel energetic material, 1-amino-1-(2,4-dinitrophenylhydrazinyl)-2,2-dinitroethylene (APHDNE), was synthesized by the reaction of 1,1-diamino-2,2-dinitroethylene (FOX-7) and 2,4-dinitrophenylhydrazine in N-methyl pyrrolidone (NMP) at 110 $^{\circ}C$. The theoretical investigation on APHDNE was curried out by B3LYP/6-311+$G^*$ method. The IR frequencies analysis and NMR chemical shifts were performed and compared with the experimental results. The thermal behavior of APHDNE was studied by DSC and TG/DTG methods, and can be divided into two crystal phase transition processes and three exothermic decomposition processes. The enthalpy, apparent activation energy and pre-exponential factor of the first exothermic decomposition reaction were obtained as -525.3 kJ $mol^{-1}$, 276.85 kJ $mol^{-1}$ and $10^{26.22}s^{-1}$, respectively. The critical temperature of thermal explosion of APHDNE is 237.7 $^{\circ}C$. The specific heat capacity of APHDNE was determined with micro-DSC method and theoretical calculation method, and the molar heat capacity is 363.67 J $mol^{-1}K^{-1}$ at 298.15 K. The adiabatic time-to-explosion of APHDNE was also calculated to be a certain value between 253.2-309.4 s. APHDNE has higher thermal stability than FOX-7.

• Korean Journal of Food Science and Technology
• /
• v.27 no.6
• /
• pp.934-938
• /
• 1995

Water soluble fractions (WSF) of wheat bran treated with thermal processes such as autoclaving, microwaving and extrusion were characterized to investigate the structural response of plant cell wall to thermal and mechanical energy. From the chemical analysis and gel filtration chromatography of WSF, gelatinization of starch was found to be the primary solubilizing mechanism of wheat bran, followed by the structural disintegration of fibrous non-starch cell wall materials. It was also found that extrusion process resulted in degrading relatively higher molecular weight non-starch polysaccharides from the cell wall. GC analysis of water soluble non-starch polysaccharides indicates that the arabinoxylan residues of cell wall are the most susceptible site to thermal treatments studied. In particular, the degrading degree of cell wall of wheat bran is the most significant for extrusion accompanying both high temperature and high shear.