• Journal of Powder Materials
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• v.29 no.1
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• pp.28-33
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• 2022

Aluminum-based powders have attracted attention as key materials for 3D printing owing to their low density, high specific strength, high corrosion resistance, and formability. This study describes the effects of TiC addition on the microstructure of the A6013 alloy. The alloy powder was successfully prepared by gas atomization and further densified using an extrusion process. We have carried out energy dispersive X-ray spectrometry (EDS) and electron backscatter diffraction (EBSD) using scanning electron microscopy (SEM) in order to investigate the effect of TiC addition on the microstructure and texture evolution of the A6013 alloy. The atomized A6013-xTiC alloy powder is fine and spherical, with an initial powder size distribution of approximately 73 ㎛ which decreases to 12.5, 13.9, 10.8, and 10.0 ㎛ with increments in the amount of TiC.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.2
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• pp.90-94
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• 2016

In this work, [$Pb(Mg_{1/2}W_{1/2})_{0.03}(Ni_{1/3}Nb_{2/3})_x(Zr_{0.5}Ti_{0.5})_{0.97-x}O_3-BiFeO_3$] (x=0.02 to 0.12) composition ceramics were fabricated by the conventional soild state reaction method and their microstructure and piezoelectric properties were investigated according to PNN substitution. The addition of small amount of $BiFeO_3$, $Li_2CO_3$, and $CaCO_3$ were used in order to decrease the sintering temperature of the ceramics. The XRD (x-ray diffraction patterns) of all ceramics exhibited a perovskite structure. The sinterability of PMW-PNN-PZT-BF ceramics was remarkably improved using liquid phase sintering of $CaCO_3$, $Li_2CO_3$. However, it was identified from of the X-ray diffraction patterns that the secondary phase formed in grain boundaries decreased the piezoelectric properties. According to the substitution of PNN, the crystal structure of ceramics is transformed gradually from a tetragonal to rhombohedral phase. The x=0.10 mol PNN-substituted PMW-PNN-PZT-BF ceramics sintered at $920^{\circ}C$ showed the optimum values of piezoelectric constant($d_{33}$), piezoelectric figure of merit($d_{33{\cdot}}g_{33}$), planar piezoelectric coupling coefficient($k_p$) and density : $d_{33}=566$ [pC/N], $g_{33}=29.28[10^{-3}mV/N]$, $d_{33{\cdot}}g_{33}=16.57[pm^2/N]$, $k_p=0.61$, density=7.82 [$g/cm^3$], suitable for duplex ultrasonic sensor application.

• Bulletin of the Korean Chemical Society
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• v.29 no.9
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• pp.1769-1773
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• 2008

fThe kinetics and mechanism of the reactions of Y-O-aryl phenylphosphonochloridothioates with X-pyridines are investigated in acetonitrile at 35.0 ${^{\circ}C}$. The negative value of the cross-interaction constant, $\rho$XY = −0.46, indicates that the reaction proceeds by concerted $S_N2$ mechanism. The observed $k_H/k_D$ values involving d-5 pyridine ($C_5D_5N$) nucleophiles are greater than unity (1.05-1.11). The net primary deuterium kinetic isotope effects, $(k_H/k_D)_{net}$ = 1.28-1.35, excluding the increased $pK_a$ effect of d-5 pyridine are obtained. The transition state with a hydrogen bond between the leaving group Cl and the hydrogen (deuterium) atom in the C-H(D) is suggested for the studied reaction system.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.3
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• pp.377-382
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• 2014

Purpose: To investigate the effect of anterior, posterior corneal astigmatism and total corneal astigmatism on posterior corneal astigmatism by analyzing correlation. Methods: Participants were 31 patients (31 eyes) without corneal disease at the age range of 22 to 28 who had visited hospital to receive corneal refractive surgery. The total corneal astigmatism and anterior and posterior corneal astigmatism were measured using a rotating scheimpflug camera before surgery. The magnitude of astigmatism was calculated with the difference between the meridian of the steep refractive power and the flat, and With-The-Rule and inverse astigmatism were divided according to the direction of the meridian that was the steepest. Results: The averages of total corneal astigmatism and anterior and posterior astigmatism were found to be $1.13{\pm}0.76D$, $1.51{\pm}0.84D$, and $-0.59{\pm}0.17D$. The magnitude of posterior corneal astigmatism was distributed between -1.0 D and -0.25 D in all the subjects, and when the magnitude of total corneal astigmatism was set as 100, the magnitude of anterior corneal astigmatism was $142.9{\pm}29.9%$. Total corneal astigmatism indicated the highest correlation with the magnitude of anterior astigmatism (y = 0.871x-0.184, $R^2=0.982$) and high negative correlation with posterior astigmatism (y = -2.974x-0.184, $R^2=0.698$). All the subjects' anterior and posterior corneal astigmatism was classified into With-The-Rule. Conclusions: Anterior and posterior corneal astigmatism in the subjects in their 20's showed the magnitude of -3.8 D in 0.2 D and -0.25 D in -1.0 D separately, and both anterior and posterior astigmatism indicated a high percentage of With-The-Rule.

• Journal of Animal Science and Technology
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• v.51 no.2
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• pp.155-162
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• 2009

This study was conducted to determine the protein requirement level in adult Jindo dog (Korea Jindo Dog) through nitrogen balance experiments. 12 female dogs aged 36~38 weeks old (for early stage) or aged 45~49 weeks old (for late stage) were fed one of 3 diets containing 17, 19 and 21% of crude protein. Body weight of dogs were measured during the 12 days of feeding trial, and feces and urine were collected last 3 days of the trial period. In early stage of Jindo dog, average daily gain of dogs fed experimental diets containing 17, 19 and 21% of crude protein were -38.33, -16.25 and -12.71g/d, respectively. There was a significant differences between 17 and 21% of crude protein treatments (p<0.05) and calculated retained nitrogen were -0.29, -0.04 and -0.03g/kg$BW^{.75}$/d, respectively. In late stage of Jindo dog, average daily gain of dogs fed experimental diets containing 17, 19 and 21% of crude protein were -34.05, -28.71 and -28.28g/d, and calculated retained nitrogen were -0.33, -0.06 and 0.09g/kg$BW^{.75}$/d, respectively, and were significantly higher (p<0.05) in dogs fed 21% of crude protein diet than those of other dogs. In early stage and late stage of adult Jindo dog, a calculated linear regression equation for nitrogen intake (x) and nitrogen retention (y) were y = 0.7484x-1.18 ($R^2$ = 0.9923) and y = 0.88231x-1.0894 ($R^2$ = 0.9982) and the requirement of crude protein were estimated as 9.85g/kg$BW^{.75}$/d and 7.72g/kg$BW^{.75}$/d from above equation.

• The Magazine of the IEIE
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• v.29 no.8
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• pp.19-28
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• 2002

본 고에서는 인터넷 가입자의 지속적인 초고속서비스 수요증가에 따라 차세대 xDSL 기술로 부상하고 있는 VDSL기술의 특성과 표준화 동향을 소개한다. VDSL 기술은 FTTC가입자 망의 전화동선 구간에 비대칭 52Mbps/6.4Mbps, 대칭 34Mbps의 데이터 전송이 가능하여 인터넷방송, 주문형 비디오(VoD), 원격과외/교육(EoD), 고화질 TV 등 대용량의 멀티미디어 서비스를 경제적으로 제공할 수 있다. VDSL은 가입자 댁내까지 광선로가 포설되는 FTTH 가입자 망 기술의 경제성 및 사업성이 확보될 때까지 ADSL에 이은 새로운 초고속 인터넷 접속기술로 활용될 것으로 기대된다.

• Journal of the Korean Chemical Society
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• v.39 no.1
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• pp.7-13
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• 1995

The crystal sructures of $X(Ca_{46}Al_{92}Si_{100}O_{384})$ and $Ca_{32}K_{28}-X(Ca_{32}K_{28}Al_{92}Si_{100}O_{384})$ dehydrated at $360^{\circ}C$ and $2{\times}10^{-6}$ Torr have been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at $21(1)^{\circ}C.$ Their structures were refined to the final error indices, R_1=0.096,\;and\;R_2=0.068$ with 166 reflections, and R_1=0.078\;and\;R_2=0.056$ with 130 reflections, respectively, for which I > $3\sigma(I).$ In dehydrated $Ca_{48}-X,\;Ca^{2+}$ ions are located at two different sites opf high occupancies. Sixteen $Ca^{2+}$ ions are located at site I, the centers of the double six rings $(Ca(1)-O(3)=2.51(2)\AA$ and thirty $Ca^{2+}$ ions are located at site II, the six-membered ring faces of sodalite units in the supercage. Latter $Ca^{2+}$ ions are recessed $0.44\AA$ into the supercage from the three O(2) oxygen plane (Ca(2)-O(2)= $2.24(2)\AA$ and $O(2)-Ca(2)-O(2)=119(l)^{\circ}).$ In the structure of $Ca_{32}K_{28}-X$, all $Ca^{2+}$ ions and $K^+$ ions are located at the four different crystallographic sites: 16 $Ca^{2+}$ ions are located in the centers of the double six rings, another sixteen $Ca^{2+}$ ions and sixteen $K^+$ ions are located at the site II in the supercage. These $Ca^{2+}$ ions adn $K^+$ ions are recessed $0.56\AA$ and $1.54\AA$, respectively, into the supercage from their three O(2) oxygen planes $(Ca(2)-O(2)=2.29(2)\AA$, $O(2)-Ca(2)-O(2)=119(1)^{\circ}$, $K(1)-O(2)=2.59(2)\AA$, and $O(2)-K(1)-O(2)=99.2(8)^{\circ}).$ Twelve $K^+$ ions lie at the site III, twofold axis of edge of the four-membered ring ladders inside the supercage $(K(2)-O(4)=3.11(6)\AA$ and $O(1)-K(2)-O(1)=128(2)^{\circ}).$

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1986.04a
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• pp.119-124
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• 1986

This paper describes the development of the KORNET that may be regarded as the latest public packet-swiched computer communication network. The KORNET project included the development of the network management center (NMC), a network concentrator. For the KORNET we use the virtual circuit(VC) method, a distributed adaptive routing algorithm, and a dynamic buffer management algorithm. The NMC acts as a nerve center of the network, performing such function as network monitoring, subscriber and network management and routing management, etc. As for the NNP and NC hardware, we have implemented them with the 16-bit multitask/multiprocessor technology using MC68000 microprocessors. Softwares have been developed using C language is required for real time processing. All the network protocols we have developed comply completely with the latest CCITT recommendations including X.25, X,3 , X.28 and X.29.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.6
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• pp.29-34
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• 2007

It is important to analyse the frequency spectrum for the measurement of modulated signal, distortion, and noise. The frequency spectrum analysis is performed by the execution of Radix-2 DIT DFT i.e. FFT algorithm. The discrete input signal converted by A/D converter from the input signal in time domain is mathematically transformed to the frequency spectrum by FFT algorithm. In this study, we design the digital spectrum analyser by the hardware based on the TMS320F2812 DSP and AD9244 converter, and by the software based on the C28x S/W modules. We can timely analyse the frequency spectrum in mobile communication system by the digital frequency analyser based on the high performance DSP and S/W modules. This real-time analysing capability is the important performance in the internet-based mobile communication server system.

• Asian-Australasian Journal of Animal Sciences
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• v.29 no.2
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• pp.250-256
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• 2016

The objective of this study was to investigate the effects of graded levels of isomaltooligosaccharides (IMO) on the performance, immune function and intestinal microflora and intestinal mucosal morphology of weaned pigs. In a 28-day experiment, one hundred eighty, twenty eight-day-old, crossbred (Duroc${\times}$Large White${\times}$Landrace), weaned pigs, with an initial body weight of $8.19{\pm}1.45kg$, were fed either an unsupplemented corn-soybean meal based diet or similar diets supplemented with 0.2%, 0.4%, 0.6%, or 0.8% IMO added at the expense of corn. Each treatment was replicated six times with six pigs (three barrows and three gilts) per pen. From day 0 to 14, weight gain was linearly increased (p<0.05), while gain:feed (p<0.05) was linearly improved and diarrhea rate (p = 0.05) linearly declined as the IMO level increased. On d 14, the level of the immunoglobulins IgA, IgM, and IgG in the serum of pigs were linearly increased (p<0.05) with increasing IMO supplementation. Interleukin-6 (IL-6) was linearly (p<0.05) and quadratically (p<0.05) decreased as IMO intake increased. From day 15 to 28, there was a trend for weight gain to be linearly increased, and IL-2 was linearly (p<0.05) increased as IMO supplementation increased on d 28. Over the entire experiment, weight gain was linearly increased (p<0.05), while gain:feed (p<0.05) was linearly improved and diarrhea rate (p<0.05) was linearly decreased as the IMO level increased. Supplementation with IMO had no effect on the intestinal microflora of pigs in the ileum and cecum of pigs, as well as the villus height and crypt depth in the ileum and jejunum (p>0.05). These results indicate that dietary inclusion of IMO increases weight gain, gain:feed and enhanced the immune status of pigs, and could be a valuable feed additive for use in weaned pigs, particularly during the period immediately after weaning.