한국은 1970년대 이후 국가경제에서 농업이 차지하는 비중이 줄어들고, 농업 인구 역시 급속한 감소하였다. 특히 20~30대 청년 농업인력이 급격히 감소하고 있으며, 농업노동생산성의 성장이 정체상태에 있다. 1980년대부터 한국 정부에서는 후계농업경영인육성, 농업대학설립, 농업계 학교 특별프로그램 등 청년 농업인력 확보를 위한 정책 프로그램을 펼쳐왔다. 이러한 프로그램들은 나름의 성과를 내고 있지만, 직업으로서 농업에 대한 국민들의 인식이 긍정적이지 못하고, 농업계 학교 학생들의 농업 분야 진출비율이 저조하고, 농가의 청소년 계층이 지속적으로 줄고 있고, 노령 농업인의 은퇴가 점점 늦어지고, 신규농의 영농진입 연령대가 높아지는 등의 상황을 비추어볼 때, 앞으로 농업인력의 노령화는 지속될 전망이다. 이러한 문제 대한 대안으로 이 연구에서는 농업에 대한 교양 교육 강화, 거점 농업 고등학교에 대한 선별적 집중 지원, 농업계 대학의 농업인력 육성기능 강화, 농업법인을 통한 은퇴농과 신규농의 연결, 지역단위 농업인력 중간지원조직 설치, 신규 청년 농업인의 자본 형성 지원 등을 제시하였다.

Multi-elements doped TiO2 was prepared as a new photocatalyst in order to decrease the band gap of TiO2 by sol-gel process which can provide the large active sites of TiO2. Multi-elements were doped by using a single precursor, tetraethylammonium tetrafluoroborate (TEATFB). By the benefit of large specific surface area of TiO2 prepared by sol-gel process, catalysts showed initial fast removal of dye. The photoactivity showed that the doped catalysts significantly promote the light reactivity than undoped TiO2. The commendable photoactivity of prepared catalysts is predominantly attributable to the doping of anions which may reduce the band gap.

A CNT-TiO2 nano composite was prepared from titanium chloride (TiCl4) via sol-gel process using multi walled carbon nano tube (MWCNT) followed by calcination at 450℃. Spectral analysis revealed that the formed TiO2 resided on the carbon in anatase form. The effect of adsorption was investigated using aqueous solution of methylene blue and procion blue dye. The photochemical reaction of CNT-TiO2 composite in aqueous suspensions was studied under UV illumination in batch process. The reaction was investigated by monitoring the discoloration of the dyes employing UV-Visible spectro-photometeric technique as a function of irradiation time. The catalyst composites were found to be efficient for the photodegradation of the dye.

Cellulose nanofibers from microfibril cellulose (MFC) was prepared by hydrobromic acid (HBr) treatment at different concentrations. Polyvinyl alcohol (PVA) composite films at various loading level of nanofibers were manufactured by a film casting method. The analysis of degree of polymerization (DP), crystallinity (Xc) and molecular weight (Mw) of cellulose after acid treatment was conducted. The mechanical and thermal properties of the cellulose nanofibers reinforced PVA films were characterized using tensile tests and thermogravimetric analysis (TGA). The DP and Mw of MFC by HBr hydrolysis considerably decreased, but Xc showed no significant change. After acid hydrolysis, the diameter of cellulose nanofibers was in the range of 100 to 200 nm. The thermal stability of the films was steadily improved with the increase of nanofiber loading. There was a significant increase in the tensile strength of PVA composite films with the increase in MFC loading. Finally, 5 wt.% nanofiber loading exhibited the highest tensile strength and thermal stability of PVA composite films.

Nanocomposites with polypropylene/clay/wood flour were prepared by melt blending and injection molding. Thermal, mechanical and morphological properties were characterized. The addition of ballmilled clay, compatibilizer and wood flour significantly improved the thermal stability of the hybrids. The tensile modulus and strength of most hybrids was highly increased with the increased loading of clay, maleated polypropylene (MAPP) and wood flour (WF), compared to the PP/WF hybrids. The tensile modulus and strength of most hybrids were highly increased with the increased loading of ballmilled clay, MAPP and wood flour, compared to the hybrids with PP/WF. The transmission electron microscopy (TEM) photomicrographs illustrated the intercalated and partially exfoliated structures of the hybrids with ballmilled clay, MAPP and wood flour.

IP-2형 운반용기는 정상운반조건에서의 자유낙하시험 및 적층시험을 수행한 후에 운반내용물의 분산 및 유실이 없어야 하며 외부표면에서의 방사선량률이 20%이상 증가할 수 있는 차폐능력의 상실이 없어야 한다. 본 연구에서는 두꺼운 철판을 구조재로 사용하며 볼트체결방식의 뚜껑을 가진 IP-2형 운반용기에 대한 구조 안전성을 평가하기 위한 해석적인 방안을 제안하였다. 해석적인 방법을 통하여 원자력발전소에서 발생된 방사성폐기물 드럼을 폐기물 처리시설에서 임시저장고까지 운반하기 위한 두 종류의 IP-2형 방사성폐기물 운반용기에 대하여 자유낙하조건에서 운반내용물의 분산 및 유실과 차폐손실이 없음을 확인하였다. 자유낙하조건에서 운반내용물의 분산 및 유실을 평가하기 위하여 최대 볼트단면 평균응력값과 최대 뚜껑열림량을 볼트의 인장강도와 뚜껑부에 존재하는 단차와 비교 평가하였다. 또한 최대 차폐두께 감소량을 이용하여 차폐손실을 평가하였다. 자유낙하조건에 대한 동적충돌해석을 검증하고 구조 안전성을 시험적으로 평가하기 위하여 자유낙하시험을 다양한 방향으로 실시하였다. 자유낙하시험에서는 운반내용물의 분산 및 유실은 볼트체결방식의 뚜껑에서 볼트의 파손 및 플랜지의 변형 등을 검사하여 평가하였으며, 차폐손실은 초음파 두께 측정기를 이용한 차폐두께를 측정하여 평가하였다. 해석에 대한 검증을 위하여 시험에서 취득한 변형률과 가속도를 동일한 위치에서 얻어진 해석결과와 비교하였다. 해석결과는 시험결과에 비하여 보수적인 결과를 보여주므로 해석에서 입증한 IP-2형 방사성폐기물 운반용기의 안전성은 보수적인 결과이다. 마지막으로 유한요소해석을 통하여 적층조건에 대한 IP-2형 방사성폐기물 운반용기는 안전함을 입증하였다. 적층해석에서 차폐체의 응력은 항복응력에 비하여 1/3정도의 작은 값을 보였다. 두 종류의 IP-2형 방사성폐기물 운반용기는 정상운반조건에서의 자유낙하시험 및 적층시험에 대하여 안전함을 입증하였다.

The purpose of this study was to examine the interfacial reaction between diamond grits and Ni-based, Ag-based, brazing filler metal, respectively. The morphology of the interface between diamond grits and Ni-based, filler metal exhibited a very good condition after this heat treatment. Cr-carbide and Ni-rich compounds were detected by XRD analysis in the vicinity of the interface between diamond grits and Ni-based, filler metal after vacuum induction brazing. Chromium carbide is considered to play an important role in the high bonding strength achieved between diamonds grits and the brazing alloy.

An efficient plant regeneration of C. asiatica was achieved from organogenesis using petiole explants of in vitro plantlet on MS basal medium controled with different plant growth regulators (NAA,2,4-D, IAA kinetin, and BA). Best results that 50%, efficiency of regeneration per explant for regeneration were obtained with IAA 17.13 μM and BA 8.9 μM. Formation of adventitious shoots via organogenesis from the petiole explant was verified by histological sectioning of plantlets. Regenerated plants were transplanted into soil.

Laboratory sorption isotherm batch studies have been attempted to elucidate interaction of synthetic pyrethroids (bifenthrin and permethrin) with sediments and their fractions. As a nonlinear isothermal model, the Freundlich equation was applied to sorption results obtained from sediments to investigate the relationship between synthetic pyrethroids and sediments containing different amounts of organic carbon. Results demonstrated that the sorption capabilities of bifenthrin and cis- and trans-permethrin was in the order of bifenthrin, cis-permethrin and trans-permethrin, respectively, indicating that adsorbed bifenthrin was the most stable followed by cis- and trans-permethrin in all sediments. Their sorption capability was closely related to organic carbon contents in sediments. Higher sorption was observed in sediments containing higher organic carbon contents. Sorption study extended into the fractions, clay and humic acids, extracted from a sediment, indicated that higher sorption capacity in humic acids occurred than in the clay of both examined bifenthrin and permethrin. This study demonstrates the sorption of synthetic pyrethroids with sediments, and will help in the understanding of the transport and fate of synthetic pyrethroids existing in field sediments.