This paper aims at finding some lessons applicable to successful implementation of ‘The 3D Printing R/D Project’ through both examining the process of adopting overseas industrialized housing production technological knowhow by home builders during the 1970's~1980's period and thereafter until now the various efforts to adjust the technologies efficiently to the Korea‘s unique situation. Some meaningful lessons can be summarized as follows; Ⅰ) Deep understanding of 3DP technological know-why along with its inheritance, Ⅱ) Readjusting of R/D period and goals(cf. Global leader Winsun's 15 years experiment), Ⅲ) Restructuring for more collaborative R/D B&E system among participating researchers Ⅳ) Fostering 3DP expert-engineers and technicians from the early stage, Ⅴ) Clearing legal barriers in users' adopting 3DP methods necessary, Ⅵ) Development of appropriate building material besides concrete. Therefore, it is highly recommended that the above-mentioned 6 lessons positively accepted and applied to the Research Implementation Plan in due course, especially by KICT consortium and KAIA under the guidance of Ministry of Land, Infrastructure and Transport.

SiAlON-based ceramics are some of the most typical ceramic materials used as cutting tools for HRSA(Heat Resistant Super-Alloys). SiAlON can be fabricated using ceramic processing, such as mixing, granulation, compaction, and sintering. Spray drying is a widely-used method for producing a granular powder of controlled morphology and size with flowability. In this study, we report a systematic investigation aimed at optimizing spherical granule morphology by controlling spray-drying parameters such as gas flow and feed rate. Before spray drying, the viscosities of the raw material slurries were also optimized with the amount of dispersant added.

We synthesized YOF(yttirum oxyfluoride) powders through solid state reactions using Y2O3 and YF3 as raw materials. The synthesis of crystalline YOF was started at 300 oC and completed at 500 oC. The atmosphere during synthesis had a negligible effect on the synthesis of the YOF powder under the investigated temperature range. The particle size distribution of the YOF was nearly identical to that of the mixed Y2O3 and YF3 powders. When the synthesized YOF powders were used as a raw material for the suspension plasma spray(SPS) coating, the crystalline phases of the coated layer consisted of YOF and Y2O3, indicating that oxidation or evaporation of YOF powders occurred during the coating process. Based on thermogravimetric analysis, the crystalline formation appeared to be affected by the evaporation of fluoride because of the high vapor pressure of the YOF material.

Reaction-bonded silicon carbide (RBSC) is a SiC-based composite ceramic fabricated by the infiltration of molten silicon into a skeleton of SiC particles and carbon, in order to manufacture a ceramic body with full density. RBSC has been widely used and studied for many years in the SiC field, because of its relatively low processing temperature for fabrication, easy use in forming components with a near-net shape, and high density, compared with other sintering methods for SiC. A radiant tube is one of the most commonly employed ceramics components when using RBSC materials in industrial fields. In this study, the mechanical strengths of commercial RBSC tubes with different sizes are evaluated using 3-point flexural and C-ring tests. The size scaling law is applied to the obtained mechanical strength values for specimens with different sizes. The discrepancy between the flexural and C-ring strengths is also discussed.

Aluminum nitride (AlN) powder specimens are treated by high-energy bead milling and then sintered at various temperatures. Depending on the solvent and milling time, the oxygen content in the AlN powder varies significantly. When isopropyl alcohol is used, the oxygen content increases with the milling time. In contrast, hexane is very effective at suppressing the oxygen content increase in the AlN powder, although severe particle sedimentation after the milling process is observed in the AlN slurry. With an increase in the milling time, the primary particle size remains nearly constant, but the particle agglomeration is reduced. After spark plasma sintering at 1400℃, the second crystalline phase changes to compounds containing more Al2O3 when the AlN raw material with an increased milling time is used. When the sintering temperature is decreased from 1750℃ to 1400℃, the DC resistivity increases by approximately two orders of magnitude, which implies that controlling the sintering temperature is a very effective way to improve the DC resistivity of AlN ceramics.

SiC-based composite materials with light weight, high durability, and high-temperature stability have been actively studied for use in aerospace and defense applications. Moreover, environmental barrier coating (EBC) technologies using oxide-based ceramic materials have been studied to prevent chemical deterioration at a high temperature of 1300℃ or higher. In this study, an ytterbium silicate material, which has recently been actively studied as an environmental barrier coating because of its high-temperature chemical stability, is fabricated on a sintered SiC substrate. Yb2O3 and SiO2 are used as the raw starting materials to form ytterbium disilicate (Yb2Si2O7). Suspension plasma spraying is applied as the coating method. The effect of the mixing method on the particle size and distribution, which affect the coating formation behavior, is investigated using a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) analysis. It is found that the originally designed compounds are not effectively formed because of the refinement and vaporization of the raw material particles, i.e., SiO2, and the formation of a porous coating structure. By changing the coating parameters such as the deposition distance, it is found that a denser coating structure can be formed at a closer deposition distance.

SiAlON-based ceramics are some of the most typical oxynitride ceramic materials, which can be used as cutting tools for heat-resistant super-alloys (HRSA). SiAlON can be fabricated by using gas-pressure reactive sintering from the raw materials, nitrides and oxides such as Si3N4, AlN, Al2O3, and Yb2O3. In this study, we fabricate Ybm/3Si12-(m+n)Alm+nOnN16-n (m=0.3, n=1.9, 2.3, 2.7) ceramics by using gas-pressure sintering at different sintering temperatures. Then, the densification behavior, phase formation, microstructure, and hardness of the sintered specimens are characterized. We obtain a fully densified specimen with β- SiAlON after gas-pressure sintering at 1820℃ for 90 min. under 10 atm N2 pressure. These SiAlON ceramic materials exhibited hardness values of ~92.9 HRA. The potential of these SiAlON ceramics for cutting tool application is also discussed.

This study investigated the stress-related metabolites and hormones in blood and compared the muscle structure to identify the reason for blood splash in Hanwoo beef. Five slaughter houses were selected based on the region (Seoul, Gimhae, Jungbu, Naju, and Goryung) and a previous blood splash record. In total, three-hundred eighty blood samples (n=380) and forty-two muscle tissues (n=42) of control and blood splash Hanwoo beef were collected during the slaughter process and beef grading. Blood metabolites were analyzed including glucose, lactate, creatinine, urea-N, and hormones such as cortisol and thyroxin. Muscle fiber, fiber bundle, and capillary wall thickness were measured under microscope. The concentrations of blood glucose, lactate, and urea-N were not significantly different between the control and the blood splash samples. Cortisol and thyroxin levels were not significantly different in both samples. In contrast, the creatinine level was significantly increased (p<0.05) in the blood splash samples. There were also no significant differences observed in muscle fiber, bundles, and capillary wall thickness between the control and the blood splash tissues. In conclusion, blood metabolites, hormones, and muscle fiber showed no differences between the control and the blood splash animal. However, increased creatinine levels may be used as an indicator for identifying blood splash prior to slaughter in Hanwoo.

심리적 계약이란 상호 고용관계를 기반으로 하여 조직과 구성원과의 상호의무에 대하여 가지고 있는 서로의 암묵적 믿음이다. 조직구성원들의 심리적 계약위반 인식에 영향을 주는 요소를 파악하고 이로 인해 조직에 부정적 영향을 줄이는 것은 매우 중요하다 할 수 있다. 이에 본 연구에서는 선행연구들을 바탕으로 첫째, 사회적 교환이론을 바탕으로 심리적 계약 위반이 이직의도에 미치는 영향을 연구하였고 둘째, 조직몰입을 매개변수로 하여 조직몰입의 매개역할을 검증하였다. 마지막으로 사회정체성 이론을 바탕으로 조직의 특성변수로 볼 수 있는 조직 동일시를 심리적 계약위반과 조직몰입간의 조절효과를 검증하고자 하였다. 실증분석을 통해 도출된 결과는 다음과 같다. 심리적 계약위반은 이직의도에 정(+)의 영향 을 주고 있었으며 조직몰입은 심리적 계약위반과 이직의도간의 매개적 역할을 하고 있음을 실증분석을 통해 검증하였다. 마지막으로 심리적 계약위반과 조직몰입간의 관계에서 조직 동 일시의 조절효과를 검증하였다. 연구의 결과 심리적 계약위반은 이직의도에 정(+)의 영향을, 조직몰입에 부(-)의 영향을 주 고 있으며, 조직몰입은 이직의도에 부(-)의 영향을 주고 있음을 보여준다. 또한 조직몰입은 심 리적 계약위반과 이직의도와의 관계를 매개하고 있으며, 조직특성변수인 조직동일시는 심리 적 계약위반과 조직몰입의 관계를 조절하는 것으로 나타났다. 이는 실제로 계약위반이 발생하 지는 않았지만 조직과 다른 구성원들간의 계약위반은 구성원들의 이직의도를 높이고 조직몰 입을 낮추는 결과를 가져와 조직의 성과를 낮추는 결과를 나타내므로, 구성원들의 조직에 대 한 몰입을 높이고 동일시를 할 수 있는 경영정책의 수립이 필요함을 보여주고 있다.

Rare-earth zirconates, such as lanthanum zirconates and gadolinium zirconates, have been intensively investigated due to their excellent properties of low thermal conductivity as well as chemical stability at high temperature, which can make these materials ones of the most promising candidates for next-generation thermal barrier coating applications. In this study, three compositions, lanthanum/gadolinium zirconates with reduced rare-earth contents from stoichiometric RE2Zr2O7 compositions, are fabricated via solid state reaction as well as sintering at 1600oC for 4 hrs. The phase formation, microstructure, and thermo-physical properties of three oxide ceramics are examined. In particular, each oxide ceramics exhibits composite structures between pyrochlore and fluorite phases. The potential of lanthanum/ gadolinium zirconate ceramics for TBC applications is also discussed.

Lanthanum zirconate, La2Zr2O7, is one of the most promising candidates for next-generation thermal barrier coating (TBC) applications in high efficient gas turbines due to its low thermal conductivity and chemical stability at high temperature. In this study, bulk specimens and thermal barrier coatings are fabricated via a variety of sintering processes as well as suspension plasma spray in lanthanum zirconates with reduced rare-earth contents. The phase formation, microstructure, and thermo-physical properties of these oxide ceramics and coatings are examined. In particular, lanthanum zirconates with reduced rare-earth contents in a La2Zr2O7-4YSZ composite system exhibit a single phase of fluorite or pyrochlore after fabricated by suspension plasma spray or spark plasma sintering. The potential of lanthanum zirconate ceramics for TBC applications is also discussed.

2015년 전남 광양, 고흥, 순천, 영광 및 전북 순창의 매실 과수원에서 복숭아씨살이좀벌(Eurytoma maslovskii) 성충의 발생양상을 조사한 결과, 성충 초발생일은 광양 4월 11일, 고흥 4월 15일, 순천 4월 16일, 영광 4월 22일, 순창 4월 23일로 지역별로 최대 12일 정도의 차이를 보였으나, 성충 50% 발생일은 고흥과 순천 4월 25일, 광양 4월 26일, 영광 4월 27일, 순창 4월 28일로 지역별로 큰 차이를 보이지 않았고, 16~17주차에 대부분의 성충이 집중적으로 탈출하였으며, 이 시기의 매실 크기(단경)는 10mm 이상이 되어있었다. 한편, 복숭아씨살이좀벌의 유충은 4번의 탈피과정을 거쳐 5령을 경과한 후 노숙유충으로 하면 및 월동에 들어가는 것으로 조사되었으며, 유충의 영기 구분을 위해 매실 씨앗속 탈피각을 찾아 큰턱 안쪽의 경화된 부분의 길이를 측정하여 비교한 결과, 각각 첫 번째 탈피각은 31.48±6.94㎛, 두 번째 탈피각은 57.96±10.22㎛, 세 번째 탈피각은 90.38±15.35㎛, 네 번째 탈피각은 192.04±10.87㎛로 조사되었다.

RBSC (reaction-bonded silicon carbide) represents a family of composite ceramics processed by infiltrating with molten silicon into a skeleton of SiC particles and carbon in order to fabricate a fully dense body of silicon carbide. RBSC has been commercially used and widely studied for many years, because of its advantages, such as relatively low temperature for fabrication and easier to form components with near-net-shape and high relative density, compared with other sintering methods. In this study, RBSC was fabricated with different size of SiC in the raw material. Microstructure, thermal and mechanical properties were characterized with the reaction-sintered samples in order to examine the effect of SiC size on the thermal and mechanical properties of RBSC ceramics. Especially, phase volume fraction of each component phase, such as Si, SiC, and C, was evaluated by using an image analyzer. The relationship between microstructures and physical properties was also discussed.

매실의 낙과 피해를 일으키는 복숭아씨살이좀벌은 경기도, 충청남북도, 전라남북도 지역의 매실과 살구, 그리고 중국산 복숭아 종자에서 확인되었다. 복숭아씨살이좀벌은 땅에 떨어진 핵과류의 핵 속에서 유충 상태로 월동하고, 노숙유충은 4월 중순까지, 번데기는 3월 하순에서 4월 하순까지 관찰되었으며, 성충은 4월 하순~5월 상순 사이에 90% 이상이 우화하는 것으로 조사되었다. 암컷 성충은 핵이 경화되기 이전 씨앗이 액 상일 때 과실 씨앗의 외피 바로 밑에 산란하였으며, 산란관의 길이가 5 mm를 넘지 않아 산란이 가능한 매실의 크기는 직경이 2 cm를 넘지 않았 다. 하나의 과실에 최대 5개의 알이 관찰되었으며, 알 기간은 2일을 넘지 않았다. 부화한 유충은 먼저 고형화되는 배로 이동하여 이를 섭식하면서 성장하는데 이 과정에서 유충들 사이의 경쟁으로 인해 한 마리의 유충만 생존하였다. 6월 상순경 피해를 받은 과실의 대부분이 부패증상을 보이 며 낙과하였다. 땅에 떨어진 과실의 핵 속에서 이듬해 봄까지 노숙유충으로 월동하였다.

The effects of particle size of Li-Si alloy and LiCl-KCl addition as a binder phase for raw material of anode were investigated on the formability of the thermal battery anode. The formability was evaluated with respect to filling density, tap density, compaction density, spring-back and compressive strength. With increasing particle size of Li-Si alloy powder, densities increased while spring-back and compressive strength decreased. Since the small spring-back is beneficial to avoiding breakage of pressed compacts, larger particles might be more suitable for anode forming. The increasing amount of LiCl-KCl binder phase contributed to reducing spring-back, improving the formability of anode powder too. The control of particle size also seems to be helpful to get double pressed pellets, which consisted of two layer of anode and electrolyte.

소나무재선충병의 생물학적 방제인자를 탐색하기 위하여 소나무 고사목, 토양 등에서 선충 포획 능력이 있는 선충포식성 곰팡이를 소나무 고사목 및 토양 시료에 서 40균주를 선발하여 배양 특성 및 재선충병 감염목 내 재선충 밀도 저하 효과 등을 조사하였다. 소나무재선충은 1/6 nutrient agar에 소나무 고사목 및 토양 샘플을 치 상하고, 500마리의 소나무재선충을 접종한 후, 25℃ 항온기에서 배양하면서 1~2일 간격으로 선충 포획기관을 형성하는 곰팡이에 의해 치사된 균주가 형성하는 분생 포자를 순수 분리하여 PDA배지를 이용하여 계대배양을 실시하였다. 분리된 40균 주는 25~30℃ 온도 조건에서, pH 5~8의 범위에서 생육이 양호하였으며, 1/6 nutrient agar에서 분생포자를 유도하여 Ø 5㎜ 드릴로 천공한 후 배지와 함께 1g의 균주를 접종하여 60일 경과 후 최종 선충 밀도를 조사하였으며 4개 균주가 현저한 소나무재선충 억제효과를 보여 소나무재선충병 방제 이용 가능성을 시사하였다.

매실의 낙과 피해를 일으키는 복숭아씨살이좀벌은 경기도, 충청남북도, 전라남 북도 지역의 매실과 살구, 그리고 중국산 복숭아 종자에서 확인되었다. 복숭아씨살 이좀벌은 이들 핵과류의 핵 속에서 애벌레 상태로 월동하며, 노숙유충은 4월 중순 까지, 번데기는 3월 하순에서 4월 하순까지 관찰되었고, 성충은 4월 하순～5월 상 순 사이에 90% 이상이 우화하는 것으로 조사되었다. 암컷 성충은 핵(endocarp)이 경화되기 이전 씨앗이 액상일 때 과실의 씨앗 껍질(seed coat) 바로 밑에 산란하였 다. 산란관의 길이는 5mm를 넘지 않아 산란이 가능한 매실의 직경은 2cm를 넘지 않았다. 하나의 과실에 최대 5개의 알이 관찰되었으며, 알 기간은 2일을 넘지 않았 다. 부화한 유충은 먼저 고형화되는 배(embryo)로 이동하여 이를 섭식하면서 성장 하는데 이 과정에서 유충들 사이의 경쟁으로 인해 한 마리의 유충만 생존하였다. 6 월 상순 경이되면 유충은 배젖(endosperm)까지 섭식하게 되고 이때 피해 받은 과 실의 대부분이 부패증상을 보이며 낙과하였다. 땅에 떨어진 과실의 핵 속에서 이듬 해 봄까지 노숙유충으로 월동하였다.

FeS2 has been widely used for cathode materials in thermal battery because of its high stability and currentcapability at high operation temperature. Salts such as a LiCl-KCl were added as a binder for improving electrical per-formance and formability of FeS2 cathode powder. In this study, the effects of the addition of Li2O in LiCl-KCl binderon the formability of FeS2 powder compact were investigated. With the increasing amount of Li2O addition to LiCl-KClbinder salts, the strength of the pressed compacts increased considerably when the powder mixture were pre-heat-treatedabove 350oC. The heat-treatment resulted in promoting the coating coverage of FeS2 particles by the salts as Li2O wasadded. The observed coating as Li2O addition might be attributed to the enhanced wettability of the salt rather than itsreduced melting temperature. The high strength of compacts by the Li2O addition and pre-heat-treatment could improvethe formability of FeS2 raw materials.