• Journal of Powder Materials
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• v.9 no.5
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• pp.307-314
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• 2002

The high temperature deformation behavior of the activated sintered W powder compacts was investigated. The W compact showed the relative density of 94% with the average W grain size of $23\mutextrm{m}$ by activated sintering at $1400^{\circ}C$ for 1 hour. Compression tests were carried out in the temperature range of $900-1100^{\circ}C$ at the strain rate range of $10^{0}$/sec - $10^{-3}$/sec. True stress-strain curve and microstructure exhibited the grain boundary brittleness which was dependent on the compression test temperature. The activated sintered W compact showed that the maximum stress as well as the strain at the maximum stress was abruptly decreased as the test temperature increase from $900^{\circ}C$ to 1000 and $1100^{\circ}C$ regardless of the strain rate. The discrepancy of the microstructure in the specimen center was obviously observed with the increase of the test temperature. After compression test at $900^{\circ}C$ the W grain was severely deformed normally against the compression axis. However, after compression test at $1000^{\circ}C$ and $1100^{\circ}C$ the W grain was not deformed, but the microcrack was formed in the W grain boundary. The Ni-rich second phase segregated along the W grain boundary could be partly unstable over $900^{\circ}C$ and affect the poor mechanical property of the activated sintered W compact.

• Applied Chemistry for Engineering
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• v.23 no.6
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• pp.561-566
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• 2012

PtRuW/C catalysts were prepared with the different molar ratios of Pt : Ru : W and their compositions were analyzed by energy dispersive X-ray (EDX). The uniform distribution of particles was observed using transmission electron microscopy (TEM). An average crystalline size of 3.5~5.5 nm was calculated based on x-ray diffraction (XRD) data. The electrochemical properties such as electrochemically active surface areas, current densities, specific activities and poisoning rates, were analyzed via CO stripping, linear sweep voltammetry and chronoamperometry. From the analysis, we observed that ternary alloy catalysts, except $PtRu_2W_2/C$, have higher current densities, specific activities and stabilities than those of commercial binary catalysts. Among all in-house catalysts, Pt5Ru4W/C showed the highest specific activity of $121.05mA{\cdot}m^{-2}$ and the lowest poisoning rate of $0.01%{\cdot}s^{-1}$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.3 no.3
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• pp.187-198
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• 1970

The author succeeded in rearing the young blue crab from the first stage of zoe ato the true crab shape, and during this time he observed their growth and metamorphosis. The relationships between the number of eggs carried by female crabs (E) and the carapace width (C) and body weight (W) are shown as follows: E= 27.9049C-281.8155, E=0.5682 W-116.4606. There are five zoeal stages and a megalopa in the complete larval development of the blue crab. Water temperature in rearing aquaria ranged from 21.4 to $25.2^{\circ}C$. The duration of each zoeal stage was two days on the average. After the fifth moulting, the zoea becomes megalopa and 5 to 6 days later the megalopa moults and develops into the first stage of adult crab shape. The carapace width of megalopa measured about 1.70 mm and the carapace length, from the tip of the rostrum to the posterior dorsal margin of the carapace, was about 2.78 mm on the average. The carapace width and length of the first crab, 18 days after hatching, measured about 4.48 mm and 2.62 mm respectively. After two days, the first crab moulted and grew into the second crab with about 6.47 mm in carapace width and 4.66 mm in carapace length. The larval rearing in the outdoor tank shelved better results than in the indoor aquarium. The highest mortality occurred when the first stage of zoea moulted into the second stage. Percentage of crabs which survived, from the first crab to the ninth crab stages, was about $55\%$. The relationships between rearing days (D) and the carapace width (C), carapace length (L) and body weight (W) of the crab stages during 40 days of rearing are shown as follows. Carapace width, Indoor: C=1.1250D+1.7227 Outdoor C=1.3465D -0.2449 Carapace length, Indoor: L=0.6654D+1.6712 Outdoor: L=0.7893D+0.6919 Body Weight, Outdoor: $$W=1.15e^{0.12423D}$$ Indoor: $$W=6.759\times10^{-2}D^{1.2598}$$ (9-19 day old crabs) Outdoor: $$W=4.136\times10^{-2}D^{1.6024}$$ (21-40 day old crabs) During the crab stage, the following relationships between the number of moulting times and the carapace width (C), carapace length (L) and body weight (W) were found as follows: $$C=5.2e^{0.28119N}$$ $$L=3.65e^{0.26372N}$$ $$W= 0.14e^{0.7037N}$$ The relationships between the carapace length (L) and the carapace width (C) and body weight (W) of the crab stages are shown as follows: Carapace length, mm Formula 2.62-27.17 L=1.6864C-1.0387 7.47-18.53 $$W=9.367\times10^{-5}C^{3.5567}$$ 22.11-27.17 $$W=3.406\times10^{-5}C{3.8571}$$

• Communications of the Korean Mathematical Society
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• v.13 no.4
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• pp.801-810
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• 1998

Let A(z), W(z) and C(z) be power series with operator coefficients such that W(z) = A(z)C(z). Let D(A) and D(C) be the state spaces of unitary linear systems whose transfer functions are A(z) and C(z) respectively. Then there exists a Krein space D which is the state space of unitary linear system with transfer function W(z). And the element of D is of the form (f(z) ＋ A(z)h(z), k(z) ＋ C＊(z)g(z)) where (f(z),g(z)) is in D(A) and (h(z),k(z)) is in D(C).

• Journal of the Korean Magnetics Society
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• v.16 no.1
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• pp.75-78
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• 2006

In case of contacts between semiconductor and metal in semiconductor circuits, they become unstable because of thermal budget. To prevent these problems, we use diffusion barrier that has a good thermal stability between metal and semiconductor. So we consider the diffusion barrier to prevent the increase of contact resistance between the interfaces of metals and semiconductors, and the increase of resistance and the reaction between the interfaces. In this paper we deposited tungsten boron carbon nitride (W-B-C-N) thin film on silicon substrate. The impurities of the $1000\;{\AA}-thick$ W-B-C-N thin films provide stuffing effect for preventing the inter-diffusion between metal thin films $(Cu-2000\;{\AA})$ and silicon during the high temperature $(700\~1000^{\circ}C)$ annealing process.

• Elastomers and Composites
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• v.40 no.3
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• pp.174-180
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• 2005

Sonochemical synthesis of fullerene oxides $[C_{70}O_n](n=1{\sim}2)$ by fullerene$[C_{70}]$ and metal hexacarbonyl complexes $M(CO)_6$(M=Cr, Mo, W) took place under air atmosphere. The reactivity of fullerene$[C_{70}]$ and several metal hexacarbonyl complexes $M(CO)_6$(M=Cr, Mo, W) under same ultrasonic condition increased in the order of $Mo(CO)_6$ > $W(CO)_6$ > $Cr(CO)_6$. The MALDI-TOF-MS, UV-visible spectra, and HPLC analysis confirmed that the products of sonochemical reaction were $[C_{70}O_n](n=1{\sim}2)$.

• Journal of the Korean Vacuum Society
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• v.20 no.3
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• pp.200-204
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• 2011

In this paper, we deposited the tungsten carbon nitride (W-C-N; nitrogen gas flow of 2 sccm) and tungsten carbon (W-C) thin film on silicon substrate using rf magnetron sputter. Then the thin films annealed at $800^{\circ}C$ during 30 minute ($N_2$ gas ambient) for thermal damage. Nano-indenter was executed 16 points on thin film surface to measure the thermal stability, and we also propose the elastic modulus and the Weibull distribution, respectively. This nanotribology method provides statistically reliable information. From these results, the W-C-N thin film included nitrogen gas flow is more stable for film uniformities, physical properties and crystallinities than that of not included nitrogen gas flow.

• Nuclear Engineering and Technology
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• v.5 no.1
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• pp.3-12
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• 1973

Some physical and chemical properties of wood-plastic combinations(W.P.C.) made of domestic soft woods such as pinus densiflora, pinus rigida and poplus deltoides were measured. The rates of improvement in properties were roughly proportional to the contents of polymer or polymer mixtures in W.P.C. For the W.P.C. obtained by means radiation curing and containing 80% of polymer or polymer mixture, the hardness and water absorptirity were improved 2.2 times and 4 times those of the original wood, respectively. The improvement of hardness was especially remarkable in the W.P.C. made of pinus densiflora and polystyrene(120%) to show 7 times increased hardness. For the W.P.C. obtained by means of thermal curing and containing 80% of polymer or polymer mixture, the hardness and water absorptivity were improved 2.4 times and 3.4 times those of the non-treated woods, respectively. These data indicate that the properties of W.P.C. prepared by means of radiation curing are not much different from those of W. p. C. prepared by means of thermal curing. Both of acid resistancy and alkali resistancy of the W.P.C. were also improved remarkably in comparison with the non-treated wood.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.3
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• pp.83-91
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• 2019

The purpose of this study is to assess a fire-damaged concrete structure using a digital camera and image processing software. To simulate it, mortar and paste samples of W/C=0.5(general strength) and 0.3(high strength) were put into an electric furnace and simulated from $100^{\circ}C$ to $1000^{\circ}C$. Here, the paste was processed into a powder to measure CIELAB chromaticity, and the samples were taken with a digital camera. The RGB chromaticity was measured by color intensity analyzer software. As a result, the residual compressive strength of W/C=0.5 and 0.3 was 87.2 % and 86.7 % at the heating temperature of $400^{\circ}C$. However there was a sudden decrease in strength at the temperature above $500^{\circ}C$, while the residual compressive strength of W/C=0.5 and 0.3 was 55.2 % and 51.9 % of residual strength. At the temperature $700^{\circ}C$ or higher, W/C=0.5 and W/C=0.3 show 26.3% and 27.8% of residual strength, so that the durability of the structure could not be secured. The results of $L^*a^*b$ color analysis show that $b^*$ increases rapidly after $700^{\circ}C$. It is analyzed that the intensity of yellow becomes strong after $700^{\circ}C$. Further, the RGB analysis found that the histogram kurtosis and frequency of Red and Green increases after $700^{\circ}C$. It is analyzed that number of Red and Green pixels are increased. Therefore, it is deemed possible to estimate the degree of damage by checking the change in yellow($b^*$ or R+G) when analyzing the chromaticity of the fire-damaged concrete structures.

• Journal of the Korean Society for Heat Treatment
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• v.31 no.4
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• pp.165-170
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• 2018

W, Fe, and carbon powders were mechanical alloyed to produce $W_{35}Fe_{43}C_{22}$ ternary alloy powders containing nanocrystal W embedded within amorphous matrix. When the powder samples were heated to the primary crystallization temperature of $735^{\circ}C$, most parts of their amorphous region were fully crystallized to [W,Fe]-rich $M_6C$ carbides. Interestingly, a little portion of the carbides changes to stoichiometric line compounds ($M_{12}C$ and $W_6Fe_7$) and a solution phase (Fe-rich bcc), and remaining parts of the crystallites were amorphized again. The resulting microstructure was retained even by cyclic heating between room temperature of $1,200^{\circ}C$, and thus we found that the amorphous structure can be irreversibly formed at above glass transition temperature.