• Asian-Australasian Journal of Animal Sciences
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• 제25권10호
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• pp.1389-1394
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• 2012

Sheanut cake (SNC), expeller (SNE) and solvent extractions (SNSE) samples were evaluated to determine their suitability in animal feeding. The CP content was highest in SNSE (16.2%) followed by SNE (14.7%) and SNC (11.6%). However, metabolizable energy (ME, MJ/kg) was maximum in SNC (8.2) followed by SNE (7.9) and SNSE (7.0). The tannin phenol content was about 7.0 per cent and mostly in the form of hydrolyzable tannin (HT), whereas condensed tannin (CT) was less than one per cent. The in vitro gas production profiles indicated similar y max (maximum potential of gas production) among the 3 by-products. However, the rate of degradation (k) was maximum in SNC followed by SNE and SNSE. The $t^{1/2}$ (time taken for reaching half asymptote) was lowest in SNC (14.4 h) followed by SNE (18.7 h) and SNSE (21.9 h). The increment in the in vitro gas volume (ml/200 mg DM) with PEG (polyethylene glycol)-6000 (as a tannin binder) addition was 12.0 in SNC, 9.6 in SNE and 11.0 in SNSE, respectively. The highest ratio of $CH_4$ (ml) reduction per ml of the total gas, an indicator of the potential of tannin, was recorded in SNE (0.482) followed by SNC (0.301) and SNSE (0.261). There was significant (p<0.05) reduction in entodinia population and total protozoa population. Differential protozoa counts revealed that Entodinia populations increased to a greater extent than Holotricha when PEG was added. This is the first report on the antimethanogenic property of sheanut byproducts. It could be concluded that all the three forms of SN byproducts are medium source of protein and energy for ruminants. There is a great potential for SN by-products to be incorporated in ruminant feeding not only as a source of energy and protein, but also to protect the protein from rumen degradation and suppress enteric methanogenesis.

• Bulletin of the Korean Chemical Society
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• 제27권9호
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• pp.1423-1428
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• 2006

In this study, we have prepared pitch binded AC (activated carbon)/$AC/TiO_2$ composites photocatalysts through carbon tetrachloride solvent method. The developed samples were characterized with surface properties, structural crystallinity between AC and $AC/TiO_2$, elemental identification and photocatalytic activity. The results of the textural surface properties demonstrate that there are slight increases in the BET surface area and adsorbed volume from adsorption isotherm of composite samples with increasing of the amount of AC. The SEM results present to the characterization of porous texture on the pitch/AC/$AC/TiO_2$ composites and homogenous compositions in the particle for all the materials used. From XRD data, a weak and broad carbon peak of graphene remained rutile peaks kept with anatase structure were observed in the X-ray diffraction patterns for the pitch/AC/$AC/TiO_2$ composites. The EDX spectra show the presence of C, O and S with strong Ti peaks. Most of these samples are richer in carbon and major Ti metal than any other elements. Finally, the excellent photocatalytic activity of the pitch/AC/$AC/TiO_2$ composites between relative concentration ($c/c_o$) of MB and UV irradiation time could be attributed to the both effects between photocatalysis of the supported $AC/TiO_2$ and adsorptivity of the two kinds of carbons.

• Advances in concrete construction
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• 제6권2호
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• pp.103-121
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• 2018

This paper reports the effects of coarse and fine recycled concrete aggregates (RCA) on fresh and hardened properties of self-compacting concrete (SCC) containing ground granulated blast-furnace slag (GGBFS) as cement replacement. For this purpose, three SCC mixes groups, were produced at a constant water to binder ratio of 0.38. Both fine and coarse recycled aggregates were used as natural aggregates (NA) replacement at different substitution levels of 0%, 25%, 50%, 75% and 100% by volume for each mix group. Each group, included 0, 15% or 30% GGBFS as Portland cement replacement by weight. The SCC properties investigated were self-compactability parameters (i.e., slump flow, T500 time, V-funnel flow time, L-box passing ability and sieve stability), compressive strength, capillary water absorption and water penetration depth. The results show that the combined use of RCA with GGBFS had a significant effect on fresh and hardened SCC mixes. The addition of both fine and coarse recycled aggregates as a substitution up to 50% of natural aggregates enhance the workability of SCC mixes, whereas the addition from 50 to 100% decreases the workability, whatever the slag content used as cement replacement. An enhancement of workability of SCC mixes with recycled aggregates was noticed as increasing GGBFS from 0 to 30%. RCA content of 25% to 50% as NA replacement and cement replacement of 15% GGBFS seems to be the optimum level to produce satisfactory SCC without any bleeding or segregation. Furthermore, the addition of slag to recycled concrete aggregates of SCC mixes reduces strength losses at the long term (56 and 90 days). However, a decrease in the capillary water absorption and water permeability depth was noticed, when using RCA mixes with slag.

• 콘크리트학회논문집
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• 제23권4호
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• pp.441-448
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• 2011

이 연구에서는 실리카퓸 및 수축 저감제, 팽창재, 고성능 감수제의 혼입을 변수로 한 초고성능 시멘트 복합체(UHPCC)의 초기 수축 거동을 평가하기 위하여 화학수축 및 자기수축 실험을 수행하고, 응결 측정 결과와 비교하여 UHPCC의 자기건조 시작 시점에 대하여 분석하였다. 실험 결과, 실리카퓸 및 수축 저감제는 초기 화학수축을 증가시키는 경향을 보였으며, 고성능 감수제는 시멘트와 배합수의 수화 반응을 지연시키고 화학수축을 저감시키는 것으로 나타났다. 수축 저감제와 팽창재를 조합하여 적용한 경우 약 49%의 자기수축 저감 효과를 보였으며, 팽창재는 경화를 촉진 시키는 것으로 나타났다. 또한 UHPCC는 다수의 섬유 혼입과 낮은 물-결합재비에 의해 초결 이전부터 자기건조 현상이 발생하는 것으로 나타났다.

• 한국건설순환자원학회논문집
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• 제6권2호
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• pp.87-93
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• 2018

건설 구조물에서의 고강도 콘크리트 사용은 꾸준히 증가하고 있다. 그러나 고강도 콘크리트는 상대적으로 낮은 물-바인더비를 가지고 있어 초기 재령에서 수화과정에 발생하는 수화열 및 수축 등으로 인해 균열 등과 같은 문제점이 발생으로 인해 그 대책이 시급한 실정이다. 최근에 수축을 저감할 수 있는 방법으로 내부양생에 대한 관심이 대두되고 있으며 연구가 활발히 이루어지고 있다. 본 연구에서는 고강도 및 하이볼륨 모르타르에 대해 인공경량골재(LWA)를 이용하여 내부양생 효과를 검증하고 여러 현장조건을 고려하여 양생조건(기중, 습윤, 수중)에 따른 압축강도 영향에 대한 연구를 수행하였다. 자기수축 실험을 통해 고강도 및 플라이애시를 혼입한 하이볼륨 모르타르에서 인공경량골재 혼입률이 증가할수록 수축저감 효과가 커지는 것을 확인하였다. 양생조건에 따라 압축강도 영향은 조금씩 다른 경향을 보이고 있으며, 기중 및 습윤 조건에서는 일반적으로 강도를 증가시키고 수중조건에서는 감소하는 것으로 나타났다.

• 한국재료학회지
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• 제26권8호
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• pp.449-453
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• 2016

$HA(hydroxyapatite)/{\beta}-TCP$ (tricalcium phosphate) biomaterial (BCP; biphasic calcium phosphate) is widely used as bone cement or scaffolds material due to its superior biocompatibility. Furthermore, $NH_4HCO_3$ as a space holder (SH) has been used to evaluate feasibility assessment of porous structured BCP as bone scaffolds. In this study, using a spark plasma sintering (SPS) process at 393K and 1373K under 20MPa load, porous $HA/{\beta}-TCP$ biomaterials were successfully fabricated using $HA/{\beta}-TCP$ powders with 10~30 wt% SH, TiH2 as a foaming agent, and MgO powder as a binder. The effect of SH content on the pore size and distribution of the BCP biomaterial was observed by scanning electron microscopy (SEM) and a microfocus X-ray computer tomography system (SMX-225CT). The microstructure observations revealed that the volume fraction of the pores increased with increasing SH content and that rough pores were successfully fabricated by adding SH. Accordingly, the cell viabilities of BCP biomaterials were improved with increasing SH content. And, good biological properties were shown after assessment using Hanks balanced salt solution (HBSS).

• 한국분말재료학회지
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• 제19권2호
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• pp.140-145
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• 2012

This paper describes the manufacturing process of tilting pad gas bearing with a diameter of 5 mm and a length of 0.5-1 mm for power MEMS (Micro Electomechanical Systems) applications. The bearing compacts with nanopowder feedstock were prepared by Ni-metal mold with 2-mold system using LIGA process. The effect of the manufacturing conditions on sintering properties of nanopowder gas bearing was investigated. In this work, Fe-45 wt%Ni nanopowder with an average diameter of 30-50 nm size was used as starting material. After mixing the nanopowder and the wax-based binders, the amount of powder was controlled to obtain the certain mixing ratio. The nanopowder bearing compacts were sintered with 1-2 hr holding time under hydrogen atmospheres and under temperatures of $600^{\circ}C$ to $1,000^{\circ}C$. Finally, the critical batch of mixed powder system was found to be 70% particle fraction in total volume. The maximum density of the sintered bearing specimen was about 94% of theoretical density.

• 농약과학회지
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• 제10권1호
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• pp.28-35
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• 2006

Flucetosulfuron 수면부상성 입제의 제형요소 및 효능을 최적화하기위한 일련의 실험을 실시하였다. SPA와 xanthan gum을 혼합하여 입제로 제제한 경우 조립성과 부상성이 우수하여 점착제로 선발하였으며 증량제는 조립성, 부상성 및 붕괴성이 우수한 KCl을 선발하였다. 또한 습윤 및 분산제로는 분산성이 가장 우수한 Surfynol 440을 선발하였다. 입제의 입경은 부상성과 분산성을 고려 1.0 mm로 결정하였다. 본 연구로 선발된 부제를 이용해 조제한 flucetosulfuron 수면부상성 입제를 실내 간이 포장 및 야외 포장에서 제초활성을 평가한 결과 잡초를 처리지점에서 15 m에 다다르는 지점까지 우수하게 방제하였다. 따라서 본 수면부상성 입제 기술은 flucetosulfuron을 비롯한 노동력 절감형 제초제 개발에 사용될 수 있을 것으로 기대된다.

• 공업화학
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• 제20권5호
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• pp.561-564
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• 2009

화학적 바인더를 사용하여 활성탄을 고정화시킨 필터 여재(filter media)와 바인더를 사용하지 않고 니들펀치 공정으로 제조한 필터여재를 비교해 보았다. 제조된 콤비네이션 필터는 실차의 내용적과 비슷한 크기의 챔버 내부의 차량용 송풍기에 장착하여 가스제거 효과를 평가하여 보았다. 화학적 바인더를 사용한 캐빈에어필터는 바인더에 의해 활성탄의 흡착기공이 막혀 아세트알데히드 제거 효과가 감소하리라는 예측과 반대로 니들펀칭 공정으로 제조한 필터에 비해 아세트알데히드 1 min 및 30 min 제거효율이 더 높게 나타났다. 니들펀칭 공정에 따르면 활성탄의 소수성결합력(hydrophobic interaction)으로 인해 화학적 바인더를 사용한 캐빈에어필터보다 공극면적(void area)이 상대적으로 더 넓은 것으로 나타났다.

• 한국재료학회지
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• 제25권4호
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• pp.165-170
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• 2015

Ceramics biomaterials are useful as implant materials in orthopedic surgery. In this study, porous HA(hydroxyapatite)/${\beta}$-TCP(tricalcium phosphate) composite biomaterials were successfully fabricated using HA/${\beta}$-TCP powders with 10-30 wt% $NH_4HCO_3$ as a space holder(SH) and $TiH_2$ as a foaming agent, and MgO powder as a binder. The HA/${\beta}$-TCP powders were consolidated by spark plasma sintering(SPS) process at $1000^{\circ}C$ under 20 MPa conditions. The effect of SH content on the pore size and distribution of the HA/${\beta}$-TCP composite was observed by scanning electron microscopy(SEM) and a microfocus X-ray computer tomography system(SMX-225CT). These microstructure observations revealed that the volume fraction of the pores increased with increasing SH content. The pore size of the HA/${\beta}$-TCP composites is about $400-500{\mu}m$. The relative density of the porous HA/${\beta}$-TCP composite increased with decreasing SH content. The porous HA/${\beta}$-TCP composite fabricated with 30%SH exhibited an elastic modulus similar to that of cortical bone; however, the compression strength of this composite is higher than that of cortical bone.