• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.400-401
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• 2009

Present paper introduces the concepts and R&D activities on the hypersonic vehicles, X-51A by USAF using Dual-Mode Ramjet (DMR) and HyFly by US Navy using Dual-Combustion Ramjet (DCR) both sponsored by DARPA.

• International Journal of High-Rise Buildings
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• v.10 no.4
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• pp.335-344
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• 2021

In structural engineering practice, understanding the performance of composite columns under extreme loading conditions such as high-rise bulding, long span and heavy loads is essential to accuratly predicting of material responses under severe loads such as fires or earthquakes. Hitherto, the combined effect of partial axial loads and subsequent elevated temperatures on the performance of hollow steel column filled fly ash concrete have not been widely investigated. Comprehensive test was carried out to investigate the effect of elevated temperatures on partial axially loaded square hollow steel column filled fly ash concrete as reported in this paper. Four batches of hollow steel column filled fly ash concrete ( 30 percent replacement of fly ash), (HySC) and normal concrete (CFHS) were subjected to four different load levels, n_f of 20%, 30%, 40% and 50% based on ultimate column strength. Subsequently, all batches of the partially damage composite columns were exposed to transient elevated temperature up to 250℃, 450℃ and 650℃ for one hour. The overall stress - strain relationship for both types of composited columns with different concrete fillers were presented for each different partial load levels and elevated temperature exposure. Results show that CFHS column has better performance than HySC at ambient temperature with 1.03 relative difference. However, the residual ultimate compressive strength of HySC subjected to partial axial load and elevated temperature exposure present an improvement compared to CFHS column with percentage difference in range 1.9% to 18.3%. Most of HySC and CFHS column specimens failed due to local buckling at the top and middle section of the column caused by concrete crushing. The columns failed due to global buckling after prolong compression load. After the compression load was lengthened, the columns were found to fail due to global buckling except for HySC02.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.3
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• pp.243-256
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• 2015

As a part of the R&D efforts for the hypersonic vehicles, various flight test programs has been carried out using small launch vehicles or sounding rockets. Australian HyShot program is a representative case of the flight test program for scramjet engines carried by international collaborations. A number of hypersonic flight test programs has followed in a similar way. In USA, Falcon HTV-2 was carried by DARPA, X-51A by AFRL and HyFly by ONR. HyCAUSE and HIFiRE were carried in collaboration with Australia. In France, LEA program is on the way similarly to X-51A. Russia, China and India seems like carrying out flight test programs for the development of hypersonic defense system. The goals, technical elements, the status and the relation between the programs were summarized in this paper as a reference for the similar program of the country in the future.

• Computers and Concrete
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• v.20 no.4
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• pp.449-459
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• 2017

Fresh and hardened behaviors of a new hybrid fiber (steel fiber, polyvinyl alcohol fiber and calcium carbonate whisker) reinforced cementitious composites (HyFRCC) with admixtures (fly ash, silica fume and water reducer) have been studied. Within the limitations of the equipment and testing program, it is illustrated that the rheological properties of the new HyFRCC conform to the modified Bingham model. The relations between flow spread and yield stress as well as flow rate and plastic viscosity both conform well with negative exponent correlation, justifying that slump flow and flow rate test can be applied to replace the other two as simple rheology measurement and control method in jobsite. In addition, for the new HyFRCC with fly ash and water reducer, the mathematical model between the rheological and mechanical properties conform well with the quadratic function, and these quadratic function curves are always concave upward. Based on mathematical analysis, an optimal range of rheology/ flowability can be identified to achieve ideal mechanical properties. In addition, this optimization method can be extended to PVA fiber reinforced cement-based composites.

• Journal of the Korean Ceramic Society
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• v.35 no.11
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• pp.1227-1232
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• 1998

In order to prohibit the delay of early stage hydration activator Na2SO4 was added to Fly Ash blended ce-ment and its effects were investigated. Various measurements such as Compressive strength Heat of hy-dration Pore size distribution Hydration products Microstructure were evaluated and the results show that specimens of Fly Ash(50wt%) with 5% Na2SO4 dramatically improved the compressive strength because pozzolanic reaction of Fly Ash and the formation of ettringite make th microstructure denser than OPC and flyash cement paste.

• Journal of the Korean Ceramic Society
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• v.35 no.10
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• pp.1030-1039
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• 1998

In fly ash-lime system the effects of reaction condition amounts of gypsum and cement and CaO/SiO2 ratio on the hydrates by hydrothermal reaction were investigated. The tobermorite phases were not observed in hy-drothermal reaction of fly ash lime because of the hydrate rate was very slow. The compressive strength and the hydration rate increased with increasing the amount of gypusm and cement and the optimum amounts of gypsumo and cement were 5wt and 20wt% respectively. The specimen which CaO/SiO2 ratio is 0.85 was shown the maximum compressive strength and the tobermorite phase within reaction time 2 hours.

• Animal Bioscience
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• v.35 no.9
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• pp.1408-1417
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• 2022

Objective: The objective of this study was to determine whether dietary black soldier fly (Hermetia illucens, HI) larvae oil (HILO) could serve as an alternative fat source to soybean oil (SBO) in laying hen diets. Methods: We randomly assigned 25-week-old Hy-line Brown laying hens (n = 144) to receive (n = 6 hens/group; eight replicates) a control or an experimental diet in which SBO was replaced with 50% (50HILO) or 100% HILO (100HILO). Results: Dietary HILO did not negatively affect body weight or productive performance during the study. The eggs also had similar quality parameters, proximate composition, and cholesterol levels. However, the yolk color index was significantly higher (p<0.01) in the 100HILO than in the other groups. Dietary HILO significantly altered the composition of fatty acids (FAs) in abdominal fat and eggs. Total saturated fatty acids (SFAs) and total polyunsaturated FAs (PUFAs) were significantly increased and decreased in the 50HILO and 100HILO groups, respectively, compared with those in the control group (p<0.001 and p<0.0001, respectively). Specifically, the medium-chain FAs lauric and myristic acids were remarkably increased in the abdominal fat of laying hens fed HILO (p<0.0001), whereas only myristic acid increased in eggs (p<0.0001). Undesirable heavy metal (aluminum, fluorine, arsenic, lead, mercury, and cadmium) concentrations were below permissible limits in eggs. Conclusion: We considered that HILO could be an alternative dietary fat to SBO for laying hens with maintained productive performance and good egg quality.