In this study, we report the microstructure and characterization of Ta20Nb20V20W20Ti20 high-entropy alloy powders and sintered samples. The effects of milling time on the microstructure and mechanical properties were investigated in detail. Microstructure and structural characterization were performed by scanning electron microscopy and X-ray diffraction. The mechanical properties of the sintered samples were analyzed through a compressive test at room temperature with a strain rate of 1 × 10−4 s−1. The microstructure of sintered Ta20Nb20V20W20Ti20 high-entropy alloy is composed of a BCC phase and a TiO phase. A better combination of compressive strength and strain was achieved by using prealloyed Ta20Nb20V20W20Ti20 powder with low oxygen content. The results suggest that the oxide formed during the sintering process affects the mechanical properties of Ta20Nb20V20W20Ti20 high-entropy alloys, which are related to the interfacial stability between the BCC matrix and TiO phase.

본 연구에 이용되는 국내 재래 흑염소는 유전적 자원을 보존하고 품종을 유지하기 위하여 소규모 집단에서 고도의 근친교배를 수행하고 있어 유전적 자질의 다양성이 저해되고 있을 것으로 우려되었다. 따라서 본 연구는 국내 재래흑염소 경상대계통 집단의 유전체 정보를 활용하여 재래흑염소 집단의 유전적 특성과 유효집단의 크기를 추정하고자 실시하였다. 국내 재래 흑염소의 유전체 정보는 Illumina Goat SNP 50k chip (illumina, inc., San Diego, CA)의 정보를 분석하여 연구에 이용하였다. 각 염색체의 인접 표지인자 와의 연관불평형 (Linkage Disequilibrium)은 0.225로 추정이 되었다. 또한, 표지인자 사이의 거리가 증가함에 따라 연관불평형의 값은 감소되는 것으로 나타났다. 국내 재래 흑염소의 유효집단크기는 최근의 세대로 오는 경우 감소하는 추세를 보였으며, 13세대에서 유효집단의 크기는 29두로 추정되었다. 재래 흑염소 경상대계통은 낮은 연관불평형 값과 유효집단 크기를 보여 유전적 자원의 다양성이 낮을 것으로 보이며, 이를 해결하기 위한 계획적인 교배와 품종 집단의 크기를 키우기 위한 대책이 필요할 것으로 사료된다.

Powder characteristics, such as density, size, shape, thermal properties, and surface area, are of significant importance in the powder bed fusion (PBF) process. The powder required is exclusive for an efficient PBF process. In this study, the particle size distribution suitable for the powder bed fusion process was derived by modeling the PBF product using simulation software (GeoDict). The modeling was carried out by layering sintered powder with a large particle size distribution, with 50 μm being the largest particle size. The results of the simulation showed that the porosity decreased when the mean particle size of the powder was reduced or the standard deviation increased. The particle size distribution of prepared titanium powder by the atomization process was also studied. This study is expected to offer direction for studies related to powder production for additive manufacturing.

The Fe-22wt.%Cr-6wt.%Al foams were fabricated via the powder alloying process in this study. The structural characteristics, microstructure, and mechanical properties of Fe-Cr-Al foams with different average pore sizes were investigated. Result of the structural analysis shows that the average pore sizes were measured as 474 μm (450 foam) and 1220 μm (1200 foam). Regardless of the pore size, Fe-Cr-Al foams had a Weaire-Phelan bubble structure, and α-ferrite was the major constituent phase. Tensile and compressive tests were conducted with an initial strain rate of 10−3 /s. Tensile yield strengths were 3.4 MPa (450 foam) and 1.4 MPa (1200 foam). Note that the total elongation of 1200 foam was higher than that of 450 foam. Furthermore, their compressive yield strengths were 2.5 MPa (450 foam) and 1.1 MPa (1200 foam), respectively. Different compressive deformation behaviors according to the pore sizes of the Fe-Cr-Al foams were characterized: strain hardening for the 450 foam and constant flow stress after a slight stress drop for the 1200 foam. The effect of structural characteristics on the mechanical properties was also discussed.

The goal of this study was to evaluate effects of various microbial and organic additives on chemical compositions, fermentation indices, and aerobic stability of barley silage. Youngyang barley harvested at 31.5% dry matter (DM), and ensiled into 20 L bucket silo for 0, 1, 3, 7, 48, and 100 d in quadruplicates with four additives following: sterile destilled water at 1% of fresh forage (CON); Lactobacillus plantarum at 1.2 x 105 cfu/g of fresh forage (CL); Lactobacillus buchneri at rate of 1.2 x 105 cfu/g fresh forage (LB); Fermented Persimmon Extract at 1% of fresh forage (FPE); and Essential Oil at 1% of fresh forage (EO). On 100 d of ensiling, CL and FPE silages had lower (p<0.05) DM than CON silage. Additionally, FPE silage had higher (p<0.05) crude protein than CON silage. All silages with additives, except EO, had higher (p<0.05) neutral detergent fiber (NDF) than CON silage. Silage treated with CL, LB, and FPE had lower in vitro DM digestibility than CON silage, and silages treated with LB and FPE had higher in vitro NDF digestibility (IVNDFD) on 100 d of ensiling. The PFE silage produced the highest (p<0.05) lactate during ensiling period, while LB silage produced the highest (p<0.05) acetate. All inoculated silages had higher (p<0.05) LAB count than control silage. Only CL silage had higher (p<0.05) yeast count than control silage, while the other silages were not differ compared to CON silage. The aerobic stability was higher (p<0.05) in LB and FPE silages than in CON silage. In conclusion, FPE could be an alternative additive to increase IVNDFD, fermentation indices, and aerobic stability of barley silage.

본 연구는 한국 정치에서 매니페스토의 지체원인 및 대안을 탐색하고 자 매니페스토 실천 및 문제해결 실천지향성을 학술연구 및 자료를 통해 주로 살펴보았다. 더 나아가 기존의 논의를 구조적, 행위자적, 환경적 차 원으로 구분하여 해당 과제의 대안을 시론적 의미에서 제시하고자 한다. 현대사회는 네트워크 사회로 형상화되며, 각 개인과 집단은 사회의 원자 화된 모듈로서 정체성을 기반으로 자신들의 정치적 의견을 제시하거나 구체적인 목표를 확립시킬 수 있는 조건을 갖추고 있다. 아울러 정치행 위에 대한 상호실패에 대한 대안적 의제를 제시할 수 있는 환경(시민참 여형, 개방형 등)이 활성화된다면 더 큰 정치발전을 이끌어 낼 수 있을 것이다. 한편으로 매니페스토의 약점으로 꼽히는 정치의 현재화, 즉 체제에 대한 보다 긴 안목의 정치적 자세가 결핍되어 단기간의 이익에 몰두 하는 정치행태의 한계에 대해서도 긍정적인 답을 제시할 것으로 기대한다. 매니페스토 가운데 정치참여와 절차, 운영에 대한 자발성이 시민사회 에 뿌리내리고, 이의 해석과 판단에 대한 협업이 운동의 맥락에 내재되 어 학습될 수 있다고 본다. 매니페스토 정책선거가 적극적인 시민참여를 배태할 수 있는 만큼, 성숙한 정치문화의 형성에도 도움을 줄 것으로 본 다.

Phosphorus is an element that plays many important roles in powder metallurgy as an alloy element. The purpose of this study is to investigate the influence of phosphorus addition on the microstructures and mechanical properties of sintered low-alloy steel. The sintered low-alloy steels Fe-0.6%C-3.89%Ni-1.95%Cu-1.40%Mo-xP (x=0, 0.05, 0.10, 0.15, 0.20%) were manufactured by compacting at 700 MPa, sintering in H2-N2 at 1260℃, rapid cooling, and low-temperature tempering in Ar at 160℃. The microstructure, pore, density, hardness, and transverse rupture strength (TRS) of the sintered low-alloy steels were evaluated. The hardness increased as the phosphorus content increased, whereas the density and TRS showed maximum values when the content of P was 0.05%. Based on microstructure observation, the phase of the microstructure changed from bainite to martensite as the content of phosphorus is increased. Hence, the most appropriate addition of phosphorus in this study was 0.05%.

본 연구는 직경분포에 근거한 잣나무 임분수확표(지위지수 14)를 활용하여 등급별 목재 생산량을 분석하기 위해 수행되었다. 잣나무 임분수확표는 국립산림과학원에서 개발된 직경분포 함수를 이용하여 직경급별 본수를 예측하였으며, 목재 생산량은 말구직경 을 기준으로 3개 등급으로 구분하였다. 연구결과 잣나무 임분수확표를 활용한 원목생산량은 임령이 증가할수록 1등급 생산량이 증가하였고, 1등급(재장 3.6m) 원목은 40년부터 생산 가능한 것으로 분석되었다. 임분단위 원목의 생산량은 직경급별 생산되는 등급별 원목 개수와 직경급별 본수에 따라 생산량에서 차이를 보였다. 임령에 따른 등급별 원목의 이용재적은 원목 생산량에 비례하였 고, 2등급 이용재적비율은 30년과 40년일 때 전체 임분 이용재적의 60% 이상을 차지하였으며, 임령이 증가할수록 1등급 이용재적비율 이 높아짐에 따라 감소하였다. 임분단위 이용재적은 임령이 증가할수록 1등급과 2등급(재장 3.6m) 이용재적은 증가하였고 3등급은 감소하였다. 임분단위 이용재적비율은 3등급의 경우 20년일 때 85% 이상 차지하였고, 2등급은 40년일 때 74% 이상 차지하였으며, 1등급 이용재적이 증가하는 50년 이후 부터 감소하였다.

Recently, the amount of heat generated in devices has been increasing due to the miniaturization and high performance of electronic devices. Cu-graphite composites are emerging as a heat sink material, but its capability is limited due to the weak interface bonding between the two materials. To overcome these problems, Cu nanoparticles were deposited on a graphite flake surface by electroless plating to increase the interfacial bonds between Cu and graphite, and then composite materials were consolidated by spark plasma sintering. The Cu content was varied from 20 wt.% to 60 wt.% to investigate the effect of the graphite fraction and microstructure on thermal conductivity of the Cu-graphite composites. The highest thermal conductivity of 692 W m−1K−1 was achieved for the composite with 40 wt.% Cu. The measured coefficients of thermal expansion of the composites ranged from 5.36 × 10−6 to 3.06 × 10−6 K−1. We anticipate that the Cu-graphite composites have remarkable potential for heat dissipation applications in energy storage and electronics owing to their high thermal conductivity and low thermal expansion coefficient.

호접란 신품종 SM 5225은 2005년 상미원에서 Phal. Golden Peoker와 Phal. Leopard Prince를 모부본으로 인공교배하여 육성한 F1개체 중에서 선발한 바탕은 진적색으로 가장자리가 백색인 이중색 계통의 계통이다. 2006년부터 2007년까지 2년에 걸쳐 실생 300개체를 양성하여 이들 중에서 영양생장과 개화특성이 우수한 개체 05-05-25를 선발하였다. 2008년과 2009년에 1차, 2차 특성검정을 통하여 품종의 안정성과 균일성을 확인하고 SM 5225으로 명명하였다. SM 5225은 화색이 진적색(RHS#69D)이며, 화형은 안아 피기로 안정되어 있다. 꽃의 길이와 폭은 각각 7.3, 9.0cm이다. 총상화서로 꽃의 볼륨이 있으며 중형 분화에 적합하다. 잎의 길이와 폭은 각각 12.0cm, 6.9cm이며, 잎은 반수직으로 배열되어 있다. 기내증식율이 높고 변이가 거의 없으며 영양생장 우수하여 재배관리가 용이하다. 2012년 10월 31일 품종등록(등록번호 제4191호)하여 종자산업법에 의해 보호받고 있다. 신품종 SM 5225는 수입종묘를 대체와 분화시장 발전에 기여할 것으로 판단된다.

In this work, the electrical explosion of wire in liquid and subsequent spark plasma sintering (SPS) was introduced for the fabrication of Ni-graphite nanocomposites. The fabricated composite exhibited good enhancements in mechanical properties, such as yield strength and hardness, but reduced the ductility in comparison with that of nickel. The as-synthesized Ni-graphite (5 vol.% graphite) nanocomposite exhibited a compressive yield strength of 275 MPa (about 1.6 times of SPS-processed monolithic nickel ~170 MPa) and elongation to failure ~22%. The hardness of Nigraphite composite had a value of 135.46 HV, which is about 1.3 times higher than that of pure SPS-processed Ni (105.675 HV). In terms of processing, this work demonstrated that this processing route is a novel, simple, and low-cost method for the synthesis of nickel-graphite composites.

In this study, we investigated the effects of precipitates and oxide dispersoids on the high-temperature mechanical properties of oxide dispersion-strengthened (ODS) Ni-based super alloys. Two ODS Ni-based super alloy rods with different chemical compositions were fabricated by high-energy milling and hot extrusion process at 1150℃ to investigate the effects of precipitates on high-temperature mechanical properties. Further, the MA6000N alloy is an improvement over the commercial MA6000 alloy, and the KS6000 alloy has the same chemical composition as the MA6000 alloy. The phase and microstructure of Ni-based super alloys were investigated by X-ray diffraction and scanning electron microscopy. It was found that MC carbide precipitates and oxide dispersoids in the ODS Ni-based super alloys developed in this study may effectively improve high-temperature hardness and creep resistance.

한국에서는 특정 연령과 성별 및 직업군에서 과다 대표되는 현상이 반 복되고 있다. 이에 정치대표성에서의 결함을 해소하고, 시민들의 다양한 정치적 의사와 이익을 대변하여 보다 균형적이고 안정적인 정치대표성의 확보가 필요하다. 특히, 산술적 대표성(descriptive representation)의 균형적인 확보가 요구됨으로 본 논문에서는 과소 대표되는 청년의 정치대표성을 OECD국가들을 중심으로 검토하였다. OECD국가에서 유럽 국가들은 비교적 청년 의원 비율이 높은 반면에 한국의 청년의원 비율을 ‘30세 이 하’(0.0%), ‘40세 이하’(2.3%), ‘45세 이하’(5.6%)로 세 연령에서 최하위 수준을 보이며, 대부분의 OECD 국가들보다도 현저하게 낮아 이를 해결 할 수 있는 선거제도의 개편 논의가 필요하다. 최근 한국은 정치개혁법 안인 패스트트랙 선거법을 통해 병립형 비례대표제를 부분(준)연동형 비 례대표제로 변화시켰으나 직접적인 행위자 주체로서 청년의 이익을 대변 할 수 있는 청년의 정치대표성에 대한 논의는 미흡함으로 청년이 선출직으로 대표할 수 있는 제도적 개선 논의가 절실하다.

장내 미생물과 숙주의 면역시스템은 상호 조절을 통해서 공진화 되어 왔다. 미생물은 부분적으로 대사물질을 생산하여 숙주 면역시스템을 조절한다. 면역세포는 대사 특이적인 수용체로서 P2X7, GPR41, GPR43, GPR109A, AhR, PXR, FXR, TGR5 등을 발현한다. 대변 은행은 rCDI 환자 치료를 위해 2013년부터 세계 각국에서 설립되고 있으며, 2017년 유럽에서 기증자 선발, 대변 준비, 대변 전이와 임상 관리, FMT 센터 운영을 위한 기본 요소 기준에 대하여 실무 중심의 의견 보고서를 발표하였다. CDI를 제외한 다른 질병 치료를 위한 FMT의 이용은 미국 식품의약국(FDA)으로부터 시험용 신약(IND) 승인을 받아야 한다. 따라서 FMT는 항생제로 제거가 불가능한 CDI 치료를 위하여 임상 실무에서 이용이 증가하고 있다. 비만에 대한 FMT 이용은 쥐에 대한 결과가 대부분이며, 비만쥐에서 Bacteroidetes가 감소하고 Firmicutes가 증가하였다. 동물의 생산성 향상을 위하여 사람 FMT의 표준 방법을 이용할 수 있다. 동물에서는 대변 미생물의 구강 투여가 적절한 방법이며, 동물 산업의 잠재적 대규모 수요를 충족시키기 위해서 품종에 따른 대변 은행의 설립이 필요하다.

In this research, a new medium-entropy alloy with an equiatomic composition of FeCuNi was designed using a phase diagram (CALPHAD) technique. The FeCuNi MEA was produced from pure iron, copper, and nickel powders through mechanical alloying. The alloy powders were consolidated via a high-pressure torsion process to obtain a rigid bulk specimen. Subsequently, annealing treatment at different conditions was conducted on the four turn HPT-processed specimen. The microstructural analysis indicates that an ultrafine-grained microstructure is achieved after post-HPT annealing, and microstructural evolutions at various stages of processing were consistent with the thermodynamic calculations. The results indicate that the post-HPT-annealed microstructure consists of a dual-phase structure with two FCC phases: one rich in Cu and the other rich in Fe and Ni. The kernel average misorientation value decreases with the increase in the annealing time and temperature, indicating the recovery of HPT-induced dislocations.

The transition from “More-of-Less” markets (economies of scale) to “Less-of-More” markets (economies of scope) is supported by advances of disruptive manufacturing and reconfigurable-supply-chain management technologies. With the prevalence of cyber-physical manufacturing systems, additive manufacturing technology is of great impact on industry, the economy, and society. Traditionally, backbone structures are built via bottom-up manufacturing with either pre-fabricated building blocks such as bricks or with layer-by-layer concrete casting such as climbing form-work casting. In both cases, the design selection is limited by form-work design and cost. Accordingly, the tool-less building of architecture with high design freedom is attractive. In the present study, we review the technological trends of additive manufacturing for construction-scale additive manufacturing in particular. The rapid tooling of patterns or molds and rapid manufacturing of construction parts or whole structures is extensively explored through uncertainties from technology. The future regulation still has drawbacks in the adoption of additive manufacturing in construction industries.

High-entropy alloys (HEAs) are generally defined as solid solutions containing at least 5 constituent elements with concentrations between 5 and 35 atomic percent without the formation of intermetallic compounds. Currently, HEAs receive great attention as promising candidate materials for extreme environments due to their potentially desirable properties that result from their unique structural properties. In this review paper, we aim to introduce HEAs and explain their properties and related research by classifying them into three main categories, namely, mechanical properties, thermal properties, and electrochemical properties. Due to the high demand for structural materials in extreme environments, the mechanical properties of HEAs including strength, hardness, ductility, fatigue, and wear resistance are mainly described. Thermal and electrochemical properties, essential for the application of these alloys as structural materials, are also described.

In the development of advanced ceramic tools, material improvements and design freedom are critical in improving tool performance. However, in the die press molding method, many factors limit tool design and make it difficult to develop innovative advanced tools. Ceramic 3D printing facilitates the production of prototype samples for advanced tool development and the creation of complex tooling products. Furthermore, it is possible to respond to mass production requirements by reflecting the needs of the tool industry, which can be characterized by small quantities of various products. However, many problems remain in ensuring the reliability of ceramic tools for industrial use. In this study, alumina inserts, a representative ceramic tool, was manufactured using the digital light process (DLP), a 3D printing method. Alumina inserts prepared by 3D printing are pressurelessly sintered under the same conditions as coupon-type specimens prepared by press molding. After sintering, a hot isostatic pressing (HIP) treatment is performed to investigate the effects of relative density and microstructure changes on hardness and fracture toughness. Alumina inserts prepared by 3D printing show lower relative densities than coupon specimens prepared by powder molding but indicate similar hardness and higher fracture toughness values.

Macro-porous carbon foams are fabricated using cured spherical phenolic resin particles as a matrix and furfuryl alcohol as a binder through a simple casting molding. Different sizes of the phenolic resin particles from 100– 450 μm are used to control the pore size and structure. Ethylene glycol is additionally added as a pore-forming agent and oxalic acid is used as an initiator for polymerization of furfuryl alcohol. The polymerization is performed in two steps; at 80oC and 200oC in an ambient atmosphere. The carbonization of the cured body is performed under Nitrogen gas flow (0.8 L/min) at 800oC for 1 h. Shrinkage rate and residual carbon content are measured by size and weight change after carbonization. The pore structures are observed by both electron and optical microscope and compared with the porosity results achieved by the Archimedes method. The porosity is similar regardless of the size of the phenolic resin particles. On the other hand, the pore size increases in proportion to the phenol resin size, which indicates that the pore structure can be controlled by changing the raw material particle size.