• Composites Research
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• v.31 no.5
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• pp.260-266
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• 2018

This study investigates thermal and mechanical characterization of Hafnium carbide coating on the $C_f-C$ composites. The hafnium carbide coatings by vacuum plasma spray on the C/C-SiC composites are prepared to evaluate oxidation and wear resistance. We perform the thermal durability tests by thermal cycling at $1200^{\circ}C$ for 10cycles in air and investigates the weight change of each cycle. We also evaluate the wear and indentation behavior using tungsten carbide ball indenter as a mechanical evaluation. As a result, the HfC coating is beneficial to reduce of weight loss during thermal cycling test and improve the elastic property of C/C-SiC composite. Especially, the HfC coating improves the wear resistance of C/C-SiC composite.

• Journal of Animal Environmental Science
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• v.14 no.1
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• pp.61-68
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• 2008

The roof structural model of liquid manure storage tank was designed to improve a structural safety and an ability of resistance to corrosion by the bad environmental condition with high humidity and high gas concentration. Due to corrosion of a general steel, the 5 years used materials were reduced to one-third of a new material in the result of a bending strength test. Some structural materials were tested to evaluate a strength and an anti-corrosion, and stainless steel pipe (STS439), steel angle with zinc hot dipping, rectangular steel pipe covered with FRP (Fiberglass Reinforced Plastics) resin were selected finally. A stainless steel is more expansive about $3{\sim}5$ times than general structural steel. But its durability under heavy corrosive environment is expected twice as long as general steel. The roof models were designed as closed cone type for each of the three structural materials. In the result of a FEM (Finite Element Method) structural analysis for the developed models, the safe snow depth was higher 2.3 times than a general roof structure, when elements of equal section modulus were used.

• International Journal of Highway Engineering
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• v.3 no.4 s.10
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• pp.93-103
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• 2001

This study focused on the field applicability evaluation of SB latex-modified concrete (LMC) for concrete bridge deck overlay using mobile mixer. The main experimental factors were water-cement ratio(31, 33, 35 37%), latex contents(0, 5, 10, 15, 20%), and fine aggregate ratio(55, 56, 57, 58%) in order to evaluate the workability, mechanical properties, and durability property of LMC. The slump loss, air content, compressive and flexible strength tests were used to evaluate LMC workability and strength properties. Also, the rapid chloride permeability test was used to evaluate the relative permeability of LMC. As a results, the LMC with enough workability and good quality was produced when it was mixed in field using mobile mixer, satisfying the target compressive strength and flexural strength. The required water-cement ratio of LMC for same workability when mixing with mobile mixer was less than that when mixing in laboratory. Increasing the amount of latex produced concrete with increased flexural strength by mobile mixer. The required cement-water ratios for same initial $19{\pm}3cm$ slump were 37% and 33% at laboratory and mobile mixer, respectively. The mobile mixer was accurately calibrated satisfying the required specification.

• Journal of the Korea Concrete Institute
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• v.25 no.6
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• pp.657-665
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• 2013

The purpose of this study is the basic research of self-compacting concrete using Alkali-Activated Slag (AAS) binder in order to emphasize the durability of structures and facilitate casting the fresh concrete in field. The AAS binder emitted low carbon dioxide ($CO_2$) is eco friendly material of new concept because AAS products not only emit little $CO_2$ during production but also reuse the industrial by-products such as ground granulated blast-furnace slag (GGBS) of the steel mill. Until now, almost of domestic and foreign research are using Ordinary Portland Cement (OPC) for self-compacting concrete, and also, nonexistent research about AAS. The self-compacting concrete must get the performance of flowability, segregation resistance, filling and passing ability. Nine concrete mixes were prepared with the main parameter of unit amount of binder (400, 500, 600 $kg/m^3$) and 3 types of water-binder (W/B) ratio. The results of test were that fresh concretes were satisfied with flowability, segregation resistance, and filling ability of JSCE. But the passing ability was not meet the criteria of EFNARC because of higher viscosity of AAS paste than OPC. This high viscosity of AAS paste enables the manufacturing of self compacting concrete, segregation of which does not occur without the using of viscosity agent. It is necessary that the development of high fluidity AAS binders of higher strength and the study of better passing ability of AAS concrete mixes in order to use self compacting AAS concrete in field.

• Culinary science and hospitality research
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• v.20 no.4
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• pp.310-321
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• 2014

This study investigated the effects of starches(potato, sweet potato, and corn starch) on the quality characteristics of raw and cooked noodles. The moisture content, color, mixogram, texture profile and sensory evaluation were performed. The mixogram showed the addition of starches shortened the kneading time. Mixing tolerance was higher in the noodles with starch than the control group, which indicates that the addition of starch increases dough durability. Moisture content of raw noodles was the highest in the samples with potato starch. L-value of raw noodles was the highest in the samples added with corn starch, whereas that of cooked noodles was the highest in the samples added with potato starch. The hardness of raw noodles was the highest in the control sample, and the chewiness of raw noodles was the highest in the samples added with sweet potato starch. The hardness of cooked noodles was the highest in the samples added with corn starch and the lowest in the control group. The tension distance of raw noodles was the longest in the control group and the tension force of raw noodles was the highest in the noodle with sweet potato starch. The acceptance test indicated that the noodles prepared with the addition of sweet potato starch scored the highest in flavor, taste, texture and overall acceptability.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.15 no.3
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• pp.226-232
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• 1982

The measurements of the jerking force and the tail beat by hooked carp were carried out using a strain gauge at a fish pond from July to August 1981. The maximum jerking force was sustained for a while in the initial state after a carp was hooked, but the jerking force was gradually decreased as a function of the time elapsed until the fish was utterly exhausted, and it converged to the body weight at last. The results are as follows : 1. The maximum jerking force $F_m(g)$ can be expressed with empirical formula : $$F_m=3.23W+105$$ where W (g) is the body weight. 2. Dynamic change of the maximum jerking force $F_n(g)$ by one tail beat with time $t_{n}(-10T/2{\leq}\;t_n{\leq}10T/2)$ can he induced with the equation as follows : $$F_n=(0.27W-6.52)(|t_n|+C)^{-2.10}$$ where the period T (sec) is given by the following equation with the body weight : T=0.000385W+0.193 3. The jerking force at each of the peak points $F_p$ (g) varies with the time elapsed t (sec) as following equation : $$F_{p}=(2.23W+105)e^{-{\beta}t}+W$$. The value of durability index $\beta$ was nearly zero in the initial state and about 1.7 in the exhausted state at last. 4. It was clearly shown that the change of jerking force by hooked carp was closely related to the tail beat from a paired difference T-test.

• Membrane Journal
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• v.21 no.3
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• pp.290-298
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• 2011

The influence of co-existing gases on the hydrogen permeation was studied through a Pd-coated $V_{53}Ti_{26}Ni_{21}$ alloy membrane. The hydrogen permeation characteristics of Pd-coated $V_{53}Ti_{26}Ni_{21}$ alloy membrane have been investigated in the pressure range 1-3 bar under pure hydrogen and hydrogen mixture gas with carbon dioxide and carbon monoxide at $450^{\circ}C$. Preliminary hydrogen permeation experiments have been confirmed that hydrogen flux was $5.36mL/min/cm^2$ for a Pd-coated $V_{53}Ti_{26}Ni_{21}$ alloy membrane (thick: 0.5 mm) using pure hydrogen as the feed gas. In addition, hydrogen fluxes were 4.46, 5.20, $3.91mL /min/cm^2$ for$V_{53}Ti_{26}Ni_{21}$ alloy membrane using $H_2/CO_2$, $H_2/CO$ and $H_2/CO_2/CO$ as the feed gas respectively. Therefore, the hydrogen permeation flux decreased with decrease of hydrogen partial pressure irrespective of temperature and pressure when $H_2/CO_2$, $H_2/CO$ and $H_2/CO_2/CO$ mixture applied as feed gas respectively and permeation fluxes were satisfied with Sievert's law in different feed conditions. It was found from XRD results after permeation test that the Pd-coated $V_{53}Ti_{26}Ni_{21}$ alloy membrane had good stability and durability for various mixtures feeding condition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.697-704
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• 2017

High-Performance Fiber-Reinforced Cement Composites (HPFRCC) has outstanding durability, and has attracted interest because of its ductility and development of strength, which allows a reduction of the self-weight of a structural member by substantially decreasing the cross section. Therefore, the present study aimed to improve the economic efficiency of HPFRCC by examining experimentally the flexural performance considering various characteristics of the steel fiber. To find an efficient fiber reinforcement method, the flexural performance was evaluated for different shapes, aspect ratios, and volume ratios of the steel fiber. Straight, hooked, and twisted fiber configurations were considered by adopting a fiber length longer than the usual 13 mm. The test results showed that HPFRCC reinforced by 19.5 nun-long straight fibers with a volume fraction of 1.5% shows better flexural performance than that reinforced by 13 mm-long straight fibers with a volume fraction of 2.0%. Consequently, HPFRCC with enhanced economic efficiency can be produced by adopting a reduced amount of steel fiber.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.1
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• pp.60-65
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• 2014

Recently, lots of researches on alkali-activated slag (AAS) concrete have been carried out to resolve the environmental issues such as recycling by-products and global warming. AAS concrete would have high strength and high level of durability. On the other hand, it is known that large amount of shrinkage occurred in AAS concrete due to rapid alkaline reaction in the early age, and however, the related studies about autogenous shrinkage of high strength AAS mortar are relatively rare. In this study, fresh mortar properties such as flow and setting time, compressive strength and autogenous shrinkage of AAS mortar with W/B=0.40 to 0.50, were measured. AAS mortar was activated with sodium silicate (Ms=1.0) with 5, 6 and 7 % of $Na_2O$. Test results revealed that AAS morar shows larger autogenous shrinkage than OPC mortar and the lower W/B of AAS mortar, the greater autogenous shrinkage. Therefore, the application of appropriate curing and the use of shrinkage reduction admixture would be needed to reduce autogenous shrinkage of AAS mortar.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.3
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• pp.533-544
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• 2015

Unlike the concrete structure built on land, that exposed to the marine environment is greatly degraded in durability due to the exposure to not only the physical action caused by sea wind, tide, and wave, but also the harsh conditions, including the chemical erosion and freeze-thaw which result from $SO_4{^{2-}}$, $Cl^-$ and $Mg^{2+}$ ions in seawater. In the process of the large scaled construction of submerged concrete structures, of course environmental hazardous substance, such as alkaline (pH) and heavy metals, may be leached. Thus, this issue needs to be adequately reviewed and studied. Therefore, this study attempted to develop a CSA (Calcium Sulfo Aluminate) activator using electric arc furnace reducing slags, as well as the eco-friendly concrete for artificial reefs using electric arc furnace oxidizing slag as aggregate for concrete. The strength properties of the eco-friendly concrete exposed to the marine environment were lower than those of the normal concrete by curing 28 days. This suggest that additional studies are needed to improve the early strength of the eco-friendly concrete. With respect to seawater resistance of the eco-friendly concrete, the average strength loss against 1 year of curing days reached 8-9%. the eco-friendly concrete using high volume of ground granulated blast furnace slags and high specific gravity of electronic arc furnace oxidizing slag demonstrated the sufficient usability as a freeze-thaw resistant material. With respect to heavy metal leaching properties of the eco-friendly concrete, heavy metal substances were immobilized by chemical bonding in the curing process through the hydration of concrete. Thus, heavy metal substances were neither identified at or below environmental hazard criteria nor detected, suggesting that the eco-friendly concrete is safe in terms of leaching of hazardous substances.