• Bulletin of the Korean Chemical Society
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• v.34 no.2
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• pp.609-614
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• 2013

Extended H$\ddot{u}$ckel tight-binding band structure calculations are used to address the chemical bonding and elastic properties of $Zr_2AC$ (A=Al, Si, P, and S). Elastic properties are interpreted by analyzing the density of states and the crystal orbital overlap population for the respective phases. Our results show that the bulk modulus of these ternary compounds is determined by the strength of Zr-A bonds.

• Journal of Powder Materials
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• v.22 no.3
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• pp.163-168
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• 2015

Ti alloys are extensively used in high-technology application because of their strength, oxidation resistance at high temperature. However, Ti alloys tend to be classified very difficult to cut material. In this paper, The powder synthesis, spark plasma sintering (SPS), bulk material properties such as electrical conductivity and thermal conductivity are systematically examined on $Ti_2AlN$ and $Ti_2AlC$ materials having most light-weight and oxidation resistance among the MAX phases. The bulk samples mainly consisted of $Ti_2AlN$ and $Ti_2AlC$ materials with density close to theoretical value were synthesized by a SPS method. Machining characteristics such as machining time, surface quality are analyzed with measurement of voltage and current waveform according to machining condition of micro-electrical discharge machining with micro-channel shape.

• Journal of Animal Science and Technology
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• v.53 no.4
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• pp.333-339
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• 2011

The present study was performed to investigate the effects of pre- and post-weaning feeding programs on growth of pigs. A total of 24 litters (avg. 10.6 piglets/litter) born from multiparous (Yorkshire ${\times}$ Landrace) dams ${\times}$ Duroc sires were provided with neither creep feed (CF) nor milk replacer ("CON"), 200 gm CF/litter/d from the 15th day of lactation ("MIN"), or CF and milk replacer ad libitum for 7 h during the daytime from the 7th day ("MAX") through weaning at d 21 of age. Sixty-eight weanling pigs selected randomly from each of CON and MIN were provided with phases 1, 2 and 3 nursery diets for 7, 14, and 13 days, respectively, in two pens; an equal number of piglets from MAX received the same diets for 6, 10, and 18 days, respectively. Subsequently, all pigs were fed grower 1 and 2 diets sequentially up to d 95 and 135, respectively. The entire pre- and post-weaning feeding trial was repeated three times under a split-plot design of experiment. Initial and final weights and ADG of the suckling pigs did not differ between MAX/MIN and CON. However, final wt of MAX adjusted for initial wt, which was 0.17-kg less in MAX than in CON, was greater than that of CON by 0.31kg, whereas the difference between MIN and CON in final wt barely changed after the adjustment. Growth of the animals during the nursery and growing phases was not affected by the feeding program, whereas d 55 and 135 BW, as well as d 6 BW, were highly correlated with weaning weight (r=0.81, 0.57, and 0.76; P<0.001, <0.05, and <0.001, respectively). In conclusion, results suggest that provision of creep feed and milk replacer from early lactation may be effective for increasing weight gain of light piglets, but that limited provision of creep feed during late lactation or extension of the duration of phases 1 and 2 vs. 3 nursery diets for several days is unlikely to influence the growth of pigs during the corresponding and subsequent periods.

• Transactions on Electrical and Electronic Materials
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• v.12 no.2
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• pp.64-67
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• 2011

The effect of Ta substitution on the crystal structure, ferroelectric, and piezoelectric properties of $Bi_{0.5}(Na_{0.82}K_{0.18})_{0.5}Ti_{1-x}Ta_xO_3$ ceramics has been investigated. The Ta doping resulted in a transition from coexistence of ferroelectric tetragonal and rhombohedral phases to an electrostrictive pseudocubic phase, leading to degradations of the remnant polarization, coercive field, and piezoelectric coefficient $d_{33}$. However, the electricfield-induced strain was significantly enhanced by the Ta substitution-induced phase transition and reached a highest value of $S_{max}/E_{max}$ = 566 pm/V under an applied electric field 6 kV/mm when 2% Ta was substituted on Ti sites. The abnormal enhancement in strain was attributed to the pseudocubic phase with high electrostrictive constants.

• Korean Journal of Materials Research
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• v.11 no.10
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• pp.907-911
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• 2001

In order to improve the grindability of magnetic abrasive, Fe-WC magnetic abrasives were made by a plasma melting method after ball milling at various times. This study aims to investigate homogeneously distributed hard phases in Fe matrix and strong bonding between the Fe-matrix and the hard phase. According to XRD, SEM and OM observation, Fe-WC magnetic abrasive powders exhibit the best grindability by plasma melting for 30h ball milling. As a result of magnetic abrasive polishing, the surface roughness, R_{max}$ 5.0$\mu\textrm{m}$, before magnetic abrasive polishing, was reduced to R_{max}$ 2.4$\mu\textrm{m}$. The new magnetic abrasive polishing process is thought to be the useful methods for the automation of three dimensional surface polishing.

• Journal of the Korean institute of surface engineering
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• v.47 no.1
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• pp.33-38
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• 2014

Nanoindentater tests were conducted to conducted nanoindentation microhardness of the individual phase of ferrite and martensite of 680MPa dual-phase (DP) steel charged with hydrogen. Hydrogen was charged by electrochemical method with current densities of 150, $200mA/cm^2$ for charging times of 5, 10, 25, 50 hours, respectively. Nanoindenter test results showed that the nanoindentation microhardnesses of ferrite phase of DP steel were varied from min. 1.58 GPa to max. 2.82 GPa, and the nanoindentation microhardnesses of martensite phase varied from min. 3.19 GPa to max. 5.16 GPa with the variation of hydrogen charging conditions. It was observed that the variations of the nanoindention microhardnesses of martenstie phase were higher than those of ferrite phases. It was thought that martensite phase in the 680MPa DP steel was more sensitive than ferrite phase to hydrogen embrittlement.

• Journal of the Korean Geosynthetics Society
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• v.13 no.4
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• pp.69-75
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• 2014

The shear strength characteristics of an unsaturated earth material are highly important not only for evaluating the seepage characteristics but also the stability of levee for a lifelong. In this study, unsaturated strength characteristics of Nak-dong river sand and clay that frequently used for the levee construction in southern province of Korea were analyzed using unsaturated triaxial compressive test. The strength characteristics due to the variation of matric suction were analyzed using multi-stage compression technique and the results were directly compared with the non-linear formulation for the apparent cohesion ($C_{max}$), and the friction component ${\varphi}^b$ were determined and evaluated from the test for the application of linear Mohr-Coulomb failure criteria. Cohesion and friction characteristics of the unsaturated levee material under various suction phases were also explored during this study.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.412-415
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• 1995

By adding 1wt.% $HfB_{2}$ into $Nd_{3-4}Fe_{77-78.5}B_{18.5}$ alloys, the grain growth of $Fe_{3}B/Nd_{2}Fe_{14}B$ composite phases during annealing was found to be hindered by 40~50%. It is proposed that the addition of $HfB_{2}$ leads to the formation of fine dispersoids of $HfB_{2}$ in the $Fe_{3}B/Nd_{2}Fe_{14}B$ composite magnet. The maximum energy product($(B.H)_{max}$) as well as intrinsic coercivity($_{i}H_{c}$) for the $Nd_{3}Fe_{78.5}B_{18.5}\;+\;1wt.%\;HfB_{2}$ alloy were enhanced by more than 25% $(B.H)_{max}=10\;MGOe,\;_{i}H_{c}=2.5\;kOe)$ due to the addition of $HfB_{2}$ while remanent magntization($B_{r}$) was reduced slightly. Itis deduced that the formation of fine dispersoids will also play a role of magnetic domain pinning.

• Current Applied Physics
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• v.18 no.11
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• pp.1289-1293
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• 2018

The influence of crystallization treatment on the structure, magnetic properties and magnetocaloric effect of $Gd_{71}Ni_{29}$ melt-spun ribbons has been investigated in detail. Annealing of the melt-spun samples at 610 K for 30 min, a majority phase with a $Fe_3C$-type orthorhombic structure (space group, Pnma) and a minority phase with a CrB-type orthorhombic structure (space group, Cmcm) were obtained in the amorphous matrix. The amorphous melt-spun ribbons undergo a second-order ferromagnetic to paramagnetic phase transition at 122 K. For the annealed samples, two magnetic phase transitions caused by amorphous matrix and $Gd_3Ni$ phases occur at 82 and 100 K, respectively. The maximum magnetic entropy change $(-{\Delta}S_M)^{max}$ is $9.0J/(kg{\cdot}K)$ (5T) at 122 K for the melt-spun ribbons. The values of $(-{\Delta}S_M)^{max}$ in annealed ribbons are 1.0 and $5.7J/(kg{\cdot}K)$, corresponding to the two adjacent magnetic transitions.

• Smart Media Journal
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• v.10 no.4
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• pp.15-20
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• 2021

The distributed trigger counting problem is to notify the user when the total number of triggers received from a distributed system consisting of n nodes reaches a predefined value w. The distributed trigger counting problem is used for monitoring and global snapshots in various distributed systems. In this paper, we propose a simple and efficient algorithm for the distributed trigger counting problem. The proposed algorithm operates based on a tree structure of degree $\sqrt{n}$ and height 2. The proposed algorithm operates in three different phases based on the remaining number of triggers. Experimental results show that the proposed algorithm has a smaller message complexity than CoinRand, and MaxRcv also performed better when the number of nodes is not large.