In this study, we designed and manufactured a large angular contact ball bearing (LACBB) with low deformation using JIS-SUJ2 steel and analyzed changes in its structural characteristics and chemical composition upon heat treatment. The bearing was produced by hot forging and heat treatment including a quenching and tempering (Q/T) process, and its properties were analyzed using 4 mm thick specimens. A difference in the size distribution of the carbide in the outer and inner parts of the bearing was observed and it was confirmed that large and non-uniform carbide was distributed in the inner part of the bearing. After heat treatment, the hardness value of the outer part increased from 13.4 HRC to 61 HRC and the inner part increased from 8.0 HRC to 59.7 HRC. As a result of X-ray diffraction (XRD) measurements, the volume fraction of the retained austenite contained in the outer part was calculated to be 3.5~4.8 % and the inner part was calculated to be 3.6~5.0 %. The surface chemical composition and the content of chemical bonds were quantified through X-ray photoelectron spectroscopy (XPS), and a decrease in C=C bonds and an increase in Fe-C bonds were confirmed.

The radioactive Sr-90, which is formed from beta decay, is well known as one of the most commonly detected nuclides in radioactive waste. In 2015, it was reported that Sr-90 was observed in some soil and metal wastes among the 516 drums of radioactive waste transferred from the decommissioning site of the Korea Research Reactor (in Seoul) to the disposal site (in Gyeongju). Decontamination and sequestration of radionuclides, including Sr, from nuclear waste is important because they are hazardous and harmful to the ecological environment. Immobilization of these nuclides using a zeolite framework is suitable and simple method that has been widely studied. Therefore, it is still necessary to continuously explore the thermal stability of various zeolites and environmental changes around adsorbed cations in zeolite pore for effective immobilization of these radionuclides. In this study, we observed the thermal stability in fully Sr-exchanged natrolite (Sr-NAT), one of small-pore zeolite, from room temperature to 350°C using the in-situ synchrotron X-ray powder diffraction and thermogravimetric (TGA) analysis. In addition, we investigated the structural changes in Sr-NAT during temperature increase by Rietveld analysis. Sr-NAT exhibited apparent zero thermal expansions (ZTE) with the thermal expansion coefficients of -3(1) × 10-6 at the initial stage of increasing the temperature due to dehydration process. In the section from 250°C to 300°C, a phenomenon like negative thermal expansion (NTE) occurs in which the unit cell volume of Sr-NAT decreases despite the increase in temperature. Sr-NAT maintained well its crystallinity up to 350°C, and it became amorphous at 350°C. In this study, we provide a fundamental understanding of the structural changes and thermal stability mechanism of Sr-exchaged zeolite natrolite with increasing temperature.

Ti3C2Tx MXene, which is a representative of the two-dimensional MXene family, is attracting considerable attention due to its remarkable physicochemical and mechanical properties. Despite its strengths, however, it is known to be vulnerable to oxidation. Many researchers have investigated the oxidation behaviors of the material, but most researches were conducted at high temperatures above 500 oC in an oxidation-retarding environment. In this research, we studied changes in the structural and electrical properties of Ti3C2Tx MXene induced by low-temperature heat treatments in ambient conditions. It was found that a number of TiO2 particles were formed on the MXene surface when it was mildly heated to 200 oC. Heating the material to higher temperatures, up to 400 oC, the phase transformation of Ti3C2Tx MXene to TiO2 was accelerated, resulting in a TiO2/ Ti3C2Tx hybrid. Consequently, the metallic nature of pure Ti3C2Tx MXene was transformed to semiconductive behavior upon heat-treating at ≥ 200 oC. The results of this research clearly demonstrate that Ti3C2Tx MXene may be easily oxidized even at low temperatures once it is exposed to air.

Zona pellucida (ZP), a primarily representative coat of mammalian egg and embryo, has an extremely heterogeneous morphology during different developmental stages. The objective of the present study was to compare the morphological changes of the ZP surface of immature, in vitro and in vivo matured canine oocytes by using scanning electron microscopy (SEM). Canine ovaries were collected from local veterinary hospitals to recover immature oocytes. The ovaries were sliced and the released cumulus oocyte complexes (COCs) were washed with TL-HEPES. The selected COCs were randomly divided into two groups, first group was processed immediately at immature state and the second group was processed 72 h after in vitro maturation, and compared with in vivo derived oocytes. Oocytes were fixed, critical point dried and examined under SEM. The diameters of oocyte and outer holes of the ZP were measured on a total of 249 oocytes; the results were analyzed using One-way ANOVA. Our results showed that, the diameter of immature oocytes significantly differed (p < 0.05) from that of in vivo matured oocytes (79.60 ± 0.77 μm vs. 101.46 ± 1.07 μm, respectively). Similarly, a significant difference (p < 0.05) in the diameters between those of in vitro and in vivo matured oocytes were found (79.51 ± 2.36 μm vs. 101.46 ± 1.07 μm, respectively). Moreover, the diameters of the outer holes of the ZP were significantly (p < 0.05) larger in in vivo matured (1.48 ± 0.42 μm) than in vitro matured for 72 and immature oocytes (1.10 ± 0.16 and 0.43 ± 0.12 μm, respectively). Taken together, these data indicates that the ZP surface is related to oocyte maturity in canine.

본 연구는 한우 보증씨수소 844두를 출생년도를 기준으로 8개 집단으로 분류하고, 각 개체들의 친자확인용 유전자 마커정보를 농협경제지주 한우개량사업소 홈페이지에서 제공 받아 유전적 다양성 및 구조 변화 분석에 활용하였다. 한우 보증씨수소 전체 집단의 대립유전자수(number of alleles)의 평균은 10.54개, 기대 및 관측 이형접합율(Hex, Hob)의 평균은 각각 0.764, 0.773, 다형성 정보량 지수(PIC)의 평균은 0.727 그리고 Fis의 평균은 –0.014로 확인되었다. 한우 보증씨수소 집단을 출생년도 별로 구분한 8개 집단의 유전적 다양성 및 구조 분석 결과, D집단(2005-2004년)의 기대이형접합율(0.777), 관측이형접합율(0.792) 그리고 다형성정보지수(0.740)가 가장 높은 것으로 확인되었다. C집단(2003-2004년)과 E집단(2007-2008년)에서는 기대이형접합율이 관측이형접합율 보다 큰 것으로 확인되었고, 나머지 그룹 모두에서는 관측이형접합율이 기대이형접합율 보다 큰 것으로 확인되었다. 대립유전자 출현빈도를 기반으로 유전적 조성과 구조를 추론하기 위해 STRUCTURE software를 이용하여 분석한 결과 세대가 지남에 따라 특정 유전적 성분의 변화 또는 비중의 증감을 확인 할 수 있었다. 이는 개량 목표를 설정하고 지속적으로 추진되고 있는 개량 사업이 한우 씨수소 집단의 유전적 구조 변화에 영향을 미치고 있음을 확인 할 수 있는 중요한 자료로, 한우 개량 사업의 효율적인 추진을 위해 유용하게 활용 될것으로 사료된다.

본 연구는 충청남도 보령시에 위치한 보령댐의 도수 전과 후의 저서성 대형무척추동물상을 비교･분석하여 인위적 교란에 대한 영향을 파악하고자 하였다. 조사시기는 2016년 4월부터 2017년 9월까지 총 8회에 걸쳐 조사하였으며, 조사지점은 방류되는 지점부터 총 4개의 지점을 선정하였다. 저서성 대형무척추동물은 총 4문 7강 19목 70과 125종 13,447개체가 출현하였다. 군집분석 결과 우점도 0.55(±0.07)에서 0.47(±0.08), 다양도 2.06(±0.26)에서 2.23(±0.28), 균등도 0.69(±0.05)에서 0.70(±0.04), 풍부도 3.43(±0.72)에서 4.03(±0.91)으로 나타났다. 도수 이후 우점도는 감소하고 다양도, 균등도, 풍부도는 증가하는 안정적인 군집구조로 나타났다. 기능군 분석 결과 도수 이후 섭식기능군은 긁어먹는 무리, 걸러먹는무리의 비율은 증가하고 썰어먹는무리, 주워먹는무리의 비율은 감소하였으며, 서식기능군은 기어오르는 무리와 붙는무리의 비율은 증가하고 굴파는무리와 기는무리의 비율은 감소하는 것으로 나타났다. 군집안정성 분석 결과 도수 이후 St. 1과 St. 2는 저항력과 회복력이 감소하여 Ⅲ특성군에 새로운 종이 출현하였으며, St. 3과 St. 4는 큰 차이를 나타내지 않았다. 다차원척도법 분석 결과 도수 이후 St. 1에서 유사도의 변화가 가장 높은 것으로 나타났으며, St. 4에서 유사도의 변화가 가장 낮은 것으로 나타났다.

Geum’yeok-dang house in Andong was originally constructed in 1558. The original floor plan of the upper base featured a 90-degree tilted ‘日’ shape, and had inner court(內庭) on each side of ‘Jungdang(中堂, center hall)’ building that was placed on the south-north axis. When designing the building, the Neo-Confucian client of Geum’yeok-dang applied his understanding of how Ga’rye(家禮) defined the structure of ritual space. Consequently, ‘Daecheong(大廳)’, the place where guests were greeted and ancestral rites and coming of age ceremonies for male were held, was built in a protruding fashion. ‘Jungdang’[otherwise known as ‘Jeongchim(正寢)’], where coming of age ceremonies for females were held, the master of the house faced death, and memorials for close ancestors were held, was placed at the center of the residence on the south-north axis. The Geum’yeok-dang today was greatly renovated in the early and mid 18th century, due to the spread of ‘Ondol’ heating system. As the Ondol heating system became popular, the pre-existing drawbacks and the inconvenience of the house stood out clearly. As a result, the house was renovated into today’s structure consisting of ‘口’ shape ‘Anchae’ and ‘Daecheongchae’ in separate building.

본 연구는 지역 농지자원의 효율적인 이용을 위해 경상남도 농경지의 이용구조의 변화요인을 분석하고 전망하는 것을 목적으로 하고 있다. 이를 위해 전체 작물을 쌀, 하계 식량작물류, 하계 채소 및 특용작물류, 과일, 보리쌀, 동계 노지채소류, 동계 시설채소류의 7개 작물 그룹으로 구분하였으며, 이들에 대한 작물별 경작지 배분모형을 개발하여 추정하였다. 추정결과 자체가격과 재배면적 간에는 양의 상관관계가 존재하였으며, 대체가격에 있어서는 하계작물의 경우 쌀과 과일 등 모든 작물간에 경합관계가 존재하고 있으며, 동계작물의 경우, 노지 채소류와 시설채소류간에 경합관계가 뚜렷한 것으로 나타났다. 한편 재배면적의 자체가격과 농업노임에 대한 탄성치도 연도별로 추정하였다. 마지막으로 시나리오 분석 하에 경남지역 작물의 총재배면적은 2010년 15만 9천 ha에서 2020년에는 14만 3천 ha∼15만 3천 ha에 이를 것으로 전망된다. 작물그룹별로 쌀, 기타식량작물류, 보리쌀은 재배면적의 감소가 예상되며, 하계채소․특용작물류, 과일, 동계노지채소류, 동계시설채소류는 재배면적의 정체가 예상된다.

Thermal emissivity of nuclear graphite was measured with its oxidation degree. Commercial nuclear graphites (IG-110, PECA, IG-430, and NBG-18) have been used as samples. Concave on graphites surface increased as its oxidation degree increased, and R value (Id/Ig) of the graphites decreased as the oxidation degree increased. The thermal emissivity increased depending on the decrease of the R (Id/Ig) value through Raman spectroscopy analysis. It was determined that the thermal emissivity was influenced by the crystallinity of the nuclear graphite.

월동기간 동안 zoysiagrass[Zoysia matrella(L.) Merr]와 creeping bentgrass(Agrostis palustris Hunds)의 저온 스트레스에 대한 탄수화물 대사 반응을 구명하기 위해 11월부터 이듬해 4월까지의 식물체내의 탄수화물 대사산물의 변화를 비교 분석하였다. Creeping bentgrass의 녹색도와 뿌리 성장은 온도변화와 거의 평행하게 변화하였으나 zoysiagrass는 뿌리 성장에 거의 변화가 없이