The influence of specimen geometry and notch on the hydrogen embrittlement of an SA372 steel for pressure vessels was investigated in this study. A slow strain-rate tensile (SSRT) test after the electrochemical hydrogen charging method was conducted on four types of tensile specimens with different directions, shapes (plate, round), and notches. The plate-type specimen showed a significant decrease in hydrogen embrittlement resistance owing to its large surface-to-volume ratio, compared to the round-type specimen. It is well established that most of the hydrogen distributes over the specimen surface when it is electrochemically charged. For the round-type specimens, the notched specimen showed increased hydrogen susceptibility compared with the unnotched one. A notch causes stress concentration and thus generates lots of dislocations in the locally deformed regions during the SSRT test. The solute hydrogen weakens the interactions between these dislocations by promoting the shielding effect of stress fields, which is called hydrogen-enhanced localized plasticity mechanisms. These results provide crucial insights into the relationship between specimen geometry and hydrogen embrittlement resistance.

The effect of Cr and Mo contents on the hydrogen embrittlement of tempered martensitic steels was investigated in this study. After the steels with different Cr and Mo contents were austenitized at 820 °C for 90 min, they were tempered at 630 °C for 120 min. The steels were composed of fully tempered martensite with a lath-type microstructure, but the characteristics of the carbides were dependent on the Cr and Mo contents. As the Cr and Mo contents increased, the volume fraction of film-like cementite and prior austenite grain size decreased. After hydrogen was introduced into tensile specimens by electrochemical charging, a slow strain-rate test (SSRT) was conducted to investigate hydrogen embrittlement behavior. The SSRT results revealed that the steel with lower Cr or lower Mo content showed relatively poor hydrogen embrittlement resistance. The hydrogen embrittlement resistance of the tempered martensitic steels increased with increasing Mo content, because the reduction in the film-like cementite and prior austenite grain size plays an important role in improving hydrogen embrittlement resistance. The results indicate that controlling the Cr and Mo contents is essential to achieving a tempered martensitic steel with a combination of high strength and excellent hydrogen embrittlement resistance.

본 연구는 대목용 호박 계통들의 내냉성을 다양한 방법들로 평가 후 상호 비교하고, 수박과 접목 후 포장에서 나타나는 내냉성 양상과 비교하여 수박 재배용 호박 대목개발에 활용 가능한 내냉성 자원선발 방법을 제시하고자 수행하였다. 그 결과 내냉성 평가에 간접적으로 사용하고 있는 발아검정, 유묘 생육 및 피해검정, 단근삽목 검정법은 접목 후 포장에서 검정한 결과와 상관관계를 보이지 않았다. 포장검정 결과와 상관관계를 보인 검정법은 유묘를 1℃로 1일 처리하고 엽록소형광 값을 측정한 방법과 유묘를 1℃로 2일 처리 후 떡잎의 저온피해 정도를 비교한 방법이었고, 그 중 떡잎의 저온피해 정도를 비교한 방법이 포장검정 결과와 더 높은 상관관계(r=0.480, p=0.002)를 보여 내냉성 대목 선발에 더 적합한 것으로 나타났다.

The impact properties of two austenitic Fe-23Mn-0.4C steels with different Al contents for cryogenic applications are investigated in this study. The 4Al steel consists mostly of austenite single-phase microstructure, while the 5Al steel exhibits a two-phase microstructure of austenite and delta-ferrite with coarse and elongated grains. Charpy impact test results reveal that the 5Al steel with duplex phases of austenite and delta-ferrite exhibits a ductile-to-brittle transition behavior, while the 4Al steel with only single-phase austenite has higher absorbed energy over 100 J at -196 oC. The SEM fractographs of Charpy impact specimens show that the 4Al steel has a ductile dimple fracture regardless of test temperature, whereas the 5Al steel fractured at -100 oC and -196 oC exhibits a mixed fracture mode of both ductile and brittle fractures. Additionally, quasi-cleavage fracture caused by crack propagation of delta-ferrite phase is found in some regions of the brittle fracture surface of the 5Al steel. Based on these results, the delta-ferrite phase hardly has a significant effect on absorbed energy at room-temperature, but it significantly deteriorates low-temperature toughness by acting as the main site of the propagation of brittle cracks at cryogenic-temperatures.

We investigated densities of the bean bug, R. pedestris (Alydidae) and three Pentatomidae stinkbug species, Dolycoris baccarum, Nezera antennata and Halyomorpha halys in an experimental field in Suwon, 2018. Three pheromone traps for R. pedestris adults were installed at distances of more than 50 meters from soybean fields. The adults began to be caught from late March. Its mean number increased from early August, and reached a maximum at early September. The fluctuation aspects of adult number caught, however, were different among trapping sites. Soybean and mungbean were sowed at June 21, and all stages of stinkbugs were scouted from July 18 to late September through direct observation. Adults and eggs of R. pedestris were not observed during the vegetative stage of soybean, but observed first at the flowering stage, mainly early August, of reproductive stage. The results indicated that R. pedestris adults invaded into soybean fields at the flowering stage, despite of inhabitation in the surrounding area during the pre-reproductive stage of soybean. Adults of only D. baccarum in Pentatomid stinkbugs were found at the vegetative stage of soybean. Densities of R. pedestris were compared between two mungbean cultivars, which those seeds have been known to be resistant and susceptible to feeding of the bean bug, respectively. The densities of the third and fifth instar nymphs were higher on the susceptible cultivar than on the resistant cultivar, but densities of egg, adult, and the first and second instar nymphs were not significantly different between the two cultivars.

Herbivorous insects use plant metabolites to inform their host plant selection for oviposition. These host-selection behaviors are often consistent with the preference-performance hypothesis; females oviposit on hosts that maximize the performance of their offspring. However, the metabolites used for these oviposition choices and those responsible for differences in offspring performance remain unknown for ecologically-relevant interactions. In this time, I will talk about the host-selection behaviors of two sympatric weevils, the Datura (Trichobaris compacta) and tobacco (T. mucorea) weevils in field- and glasshouse-experiments with transgenic host plants specifically altered indifferent components of their secondary metabolism. In addition, I will show that adult females are able to choose the best host plant for their offspring and use chemicals different from those that influence larval performance to inform their oviposition decisions.

The purpose of this study is to review the effects of organizational citizenship behavior on innovative behavior and intention to leave, and the moderating effects of self-efficacy in Korea Politechnics’ teachers and professors. In order to verify and achieve the purposes mentioned above, questionnaire data were gathered and analysed from 206 employees of Korea Politechnics campus. Empirical survey's findings are as follows; First, altruism, conscientiousness, sportsmanship appeared to be positively related with innovative behavior. Second, courtesy, conscientiousness, sportsmanship appeared to be negatively related with intention to leave. Third, self-efficacy moderated negatively the relationship between altruism and intention to leave. Fourth, self-efficacy moderated negatively the relationship between sportsmanship and intention to leave.

The main objective of this paper is to elucidate the present status of Plant Genetic Resources (PGRs), their research, and management system in the genebank of Nepal. PGRs for food and agriculture are the biological basis of world food and nutrition security. The remarkable elevation ranging from 60 meter above sea level (masl) to highest summit Mount Everest (8,848 masl) has created huge geographical and climatic variation which harbor enormous plant species in the country. National Agriculture Genetic Resource Center (NAGRC) or ‘Genebank’ currently conserved 11,051 accessions of more than 110 crops species belonging to cereals (5,850), pseudo cereals (1,150), pulses (1,800), oilseeds (185), and vegetables (565) including other crops (1,501) at ex-situ. Diversity mapping, characterization and evaluation of PGRs, duplicates identification, diversity study, pre-breeding and landrace enhancement are the major research works of NAGRC, and its management strategies include conservation method, types, and groupings of PGRs. Characterization, evaluation and tagging of economically important traits in PGRs are now more important for strengthening their pre-breeding and proper utilization. Additionally, strong communication and collaborative network among public, private, community based organizations and international organizations are important for the effective management of PGRs.

카로티노이드는 항산화 및 항암효과를 가지는 비타민 A의전구물질이다. 농촌진흥청 농업유전자원센터에서 보존하고 있는 호박자원 80자원의 과육에서 카로티노이드를 분석을 하였다. 유전자원은 한국, 멕시코, 인도의 원산지에 따라 호박 과육에서 카로티노이드를 분석하였다. 고성능 액체 크로마토그래피를 이용하여 총 9종의 카로티노이드 (크산토필류 3종과카로틴류 6종)를 분리하였다. 특히 카로티노이드 중 lutein과β-carotene 이 주로 분석이 되었다. 총 카로티노이드 함량 평균은 한국 육성종이 213.69 mg, 멕시코 재래종이 139.07mg, 인도 재래종이 69.13 mg, 그리고 한국 재래종 27.51 mg순으로 나타났다. 총 80 자원중 K188417(멕시코원산) 자원이카로티노이드 성분이 가장 많았다. 본 연구의 결과는 카로티노이드 고함유 호박 품종 개발 뿐 아니라 기능성 식품 개발의기초자료로 활용될 수 있을 것으로 사료된다.

Lettuce is an important annual leafy vegetable and bitterness is its potent flavor character. Lettuce germplasm differ their phenotypic characters and sesquiterpene lactones (SLs) contents which are important for consumer’s acceptance. This study was carried out to evaluate the phenotypic characters and SLs contents in one hundred lettuce germplasm in Jeonju, Korea. Twenty-three agro-morphological (16 qualitative and 7 quantitative) traits and two SLs (lactucin and lactucopicrin) contents were studied in these germplasm. Germplasm exhibited the variation in qualitative and quantitative characters. Average plant weight was 423.9 g with a range from 116.0 to 905.0 g. Lactucin content was varied from 19.7 (IT 294226) to 194.4 ㎍/g (IT 294298) with an average concentration of 84.7 ㎍/g. Lactucopicrin ranged from 82.5 (IT 300134) to 2228.6 ㎍/g (IT 294210) with an average concentration of 586.3 ㎍/g. Total SLs content was ranged from 120.1 (IT 300134) to 2286.6 (IT 294210) ㎍/g with the average concentration of 671.0 ㎍/g. Significant (p≤0.05) differences were found between crisp head and butter head germplasm for lactucin, lactucopicrin and total SLs content. Crisp head germplasm revealed the highest average lactucin (112.9 ㎍/g), lactucopicrin (734.8 ㎍/g) and total SLs content (847.7 ㎍/g). Crisp head and leafy type germplasm exhibited more total SLs content (847.7 and 744.7 ㎍/g, respectively) than cos (524.9 ㎍/g) and butter head type (519.4 ㎍/g). Principal component analyses of the quantitative traits indicated that the first principal component axis accounted more than 91% of the total variation. This study revealed the ample genetic variation in the agro-morphological traits and SLs contents to support the selection for improved lettuce varieties.