In this study, changes in the microstructure and mechanical properties of cast and extruded Al-2Li-1Ce alloy materials were investigated as the Mg content was varied. The density decreased to 2.485, 2.46 and 2.435 g/cm3 when the Mg content in the Al-2Li-1Ce alloy was increased to 2, 4 and 6 wt%, respectively. Intermetallic compounds of Al11Ce3 were observed in all alloys, while the β-phase of Al3Mg2 was observed in alloys containing 6 wt% of Mg. In the extruded material, with increasing Mg content the average grain size decreased to 84.8, 71.6 and 36.2 μm, and the fraction of high-angle grain boundaries (greater than 15°) increased to 82.8 %, 88.6 %, and 91.8 %, respectively. This occurred because the increased Mg content promotes dynamic recrystallization during hot extrusion. Tensile test results showed that as the Mg content increased, both the yield strength and tensile strength increased. The yield strength reached 86.1, 107.3, and 186.4 MPa, and the tensile strength reached 215.2, 285, and 360.5 MPa, respectively. However, it is worth noting that the ductility decreased to 27.78 %, 25.65 %, and 20.72 % as the Mg content increased. This reduction in ductility is attributed to the strengthening effect resulting from the increased amount of dissolved Mg, and grain refinement due to dynamic recrystallization.

우리나라는 삼면이 바다로 이루어져 있고, 이에 따라 많은 해양 시설로 인한 위험유해물질이 배출되고 있으나, 배출관리 및 규제 시스템이 미비한 상황이다. 따라서, 위험유해물질(HNS) 관리를 위하여 효율적으로 데이터를 수집할 수 있는 시스템이 필요하 다. 본 연구에서는 HNS 데이터를 효율적으로 관리 및 저장하기 위한 데이터 표준화 시스템을 설계하고 이의 표준화 방안을 제시하고 자 한다.

PURPOSES : Previously, the expansion state of the concrete pavement in which AAR occurred could not be determined. Because the current situation has not been evaluated, it has been difficult to prepare an appropriate response. In this study, a method for calculating the expansion amount of concrete pavement using the stiffness damage test (SDT) is proposed. METHODS : The SDT method was examined through a literature review. For the laboratory tests, specimens that generated AAR were produced based on the mix design (2018) of the Korea Expressway Corporation. SDT was used to calculate various mechanical properties, and their correlation with the expansion amount was reviewed. RESULTS : Using the SDT, various mechanical properties(elastic modulus, hysteresis area, plastic deformation, plastic deformation index, stiffness damage index, and nonlinear index) were calculated based on the expansion rate of the AAR. The elastic modulus was evaluated as the best predictor of the expansion rate. Thus, if the elastic modulus is calculated using SDT, a prediction equation can be used to calculate the amount of AAR expansion. This equation will need to be supplemented by further research. CONCLUSIONS : SDT was used to confirm that the expansion state due to the AAR of the concrete pavement could be indirectly evaluated. Among the mechanical properties related to SDT, the elastic modulus was found to be the most suitable for predicting the amount of expansion.

Benthic attached diatoms (BADs), a major primary producer in lotic stream and river ecosystems are micro-sized organisms and require a highly magnified microscopic technique in the observation work. Thus, it is often not easy to ensure accuracy and precision in both qualitative and quantitative analyses. This study proposed a new technique applicable to improve quality control of aquatic ecosystem monitoring and assessment using BADs. In order to meet the purpose of quality control, we developed a permanent mounting slide technique which can be used for both qualitative and quantitative analyses simultaneously. We designed specimens with the combination of grid on both cover and slide glasses and compared their efficiency. As a result of observation and counting of BADs, the slide glass designed with the color-lined grid showed the highest efficiency compared to other test conditions. We expect that the method developed in this study could be effectively used to analyze BADs and contributed to improve the quality control in aquatic ecosystem health monitoring and assessment.

Cnidium officinale M. is an important crop that is widely used as a raw material for health functional foods. However, it is experiencing cultivation difficulties due to climate change and abnormally high temperatures. In response to this problem, the characteristics and main causes of the high-temperature damage occurring in C. officinale M. cultivation fields were analyzed. A survey of five farmhouse fields in Jecheon and Bonghwa, major C. officinale M. cultivation areas in Korea in 2018, indicated that about 5% to 37% of the cultivation fields in Jecheon and 5% to 15% of the fields in Bonghwa died from wilting. The high-temperature damage of the C. officinale M. fields is divided into two categories: upper leaves drying due to solar radiation and temperature, and lower leaves dying serially to the radiant heat of the vinyl mulch. Damage caused by radiant heat was typically greater. This is due to the greenhouse effect that occurs in the small space between the black vinyl mulching and the soil. The heat radiated to the surface of the ridge creating an environmental condition that greatly exceeded the atmospheric temperature especially on hot days. As a result, short plants with underground parts, such as C. officinale M., can suffer more high-temperature damage than other plants, so it is considered that it is necessary to develop related technologies such as mulching materials that can reduce pavement temperature in the future.

댄스뮤직이 케이팝의 세계적 성공과 한류의 확산에 매우 중요한 역할을 했음에도 불구하고, 그동안 한국 댄스뮤직의 역사에 관한 출판기록을 찾아보기 어려웠다. 강원래․박성건의 󰡔댄스: 한국 댄스뮤직 100년사󰡕는 1930년대로부터 시작하는 한국 댄스뮤직의 과거와 현재를 자세하게 상술하고 있다. 비록 각각의 시대마다 기득권 세력의 형태는 다를지라도, 댄스뮤직은 일제강점기, 군사독재 시기, 근대화 시기를 거쳐 기득권이 제도로서 ‘장치’로 작동시키는 ‘실정성’에 대항하여 대중이 저항하는 데 중요한 역할을 담당해왔다. 그것은 본질적으로 원시종교의 의례적 측면을 반영해왔다. 댄스뮤직 가수나 그룹은 의례의 주관자로, 특정 가사를 반복하는 훅송이나 신명 나는 음악은 주문이나 기도로, 노래의 전체를 핵심적으로 표현하는 포인트 안무는 의례 중의 핵심 의례로 해석될 수 있다. 댄스뮤직은 부지 간에 사람들에게 정치적 영성과 초월적 영성의 체험을 할 수 있도록 만든다. 방탄소년단의 대유행에서 나타나듯이, 댄스뮤직의 신성한 예술로서의 승화는 케이팝의 대성공에 핵심적 역할을 하였다.

For fast-built and safe precast concrete (PC) construction, the dry mechanical splicing method is a critical technique that enables a self-sustaining system (SSS) during construction with no temporary support and minimizes onsite jobs. However, due to limited experimental evidence, traditional wet splicing methods are still dominantly adopted in the domestic precast industry. For PC beam-column connections, the current design code requires achieving emulative connection performances and corresponding structural integrity to be comparable with typical reinforced concrete (RC) systems with monolithic connections. To this end, this study conducted the standard material tests on mechanical splices to check their satisfactory performance as the Type 2 mechanical splice specified in the ACI 318 code. Two PC beam-column connection specimens with dry mechanical splices and an RC control specimen as the special moment frame were subsequently fabricated and tested under lateral reversed cyclic loadings. Test results showed that the seismic performances of all the PC specimens were fully comparable to the RC specimen in terms of strength, stiffness, energy dissipation, drift capacity, and failure mode, and their hysteresis responses showed a mitigated pinching effect compared to the control RC specimen. The seismic performances of the PC and RC specimens were evaluated quantitatively based on the ACI 374 report, and it appeared that all the test specimens fully satisfied the seismic performance criteria as a code-compliant special moment frame system.

소형 곤충으로 좁은 틈새에 있는 총채벌레는 종종 살충제 살포에 노출되기 어렵다. 이에 접촉페로몬을 처리하여 은둔행동을 막으려는 행동 교란 방제 전략을 세웠다. 꽃노랑총채벌레(Frankliniella occidentalis)에서 밝혀진 접촉페로몬은 7-methyltricosane (7TM)으로 본 연구에서는 먹이에 이 물질을 처리하여 행동 교란 유무를 생물검정하였다. 이 접촉페로몬은 유충에게 영향을 주지 않았지만 수컷 성충으로 하여금 처리된 먹 이로부터 회피하려는 행동을 유발하였다. 반면에 암컷 성충에게는 오히려 7TM이 처리된 지역으로 이동하는 행동을 유발하였다. 동일한 접촉페 로몬에 대해서 대만총채벌레(Frankliniella intonsa)에서도 유사한 행동 변화가 관찰되었다. 이러한 7TM에 기인한 총채벌레의 행동 변화를 살충 제 처리와 연결하여 고추를 가해하는 총채벌레류를 대상으로 방제효과를 검정하였다. 스피네토람 살충제 단독 처리에 비해 7TM과 혼합하여 처 리하면 총채벌레류 방제효율이 증가하였다. 흥미로운 점은 7TM 단독 처리로도 대만총채벌레 밀도에 일부 감소 효과를 보여 이 물질이 총채벌레 의 행동교란을 주는 것을 뒤받침하였다. 본 연구는 접촉페로몬 처리로 총채벌레의 살충제 회피 행동을 줄여 방제효과를 높인 새로운 해충방제기 술을 제시한다.

횡하중에 작용하는 철근 콘크리트 기둥은 연성능력 확보를 위해 띠철근의 양 단부를 135° 구부려 시공하는 상세가 요구된다. 그러 나 이러한 띠철근 상세는 시공이 매우 까다로와 실제 현장에서는 제대로 시공이 되지 않기도 한다. 이를 대체하기 위해 본 논문에서는 강재 클립형 연결장치가 적용된 철근 콘크리트 기둥에 대해 횡방향 반복가력 실험을 수행하고 그 구조적 성능을 평가하였다. 총 4개 의 실험체가 제작되었으며 주요 실험변수는 강재 클립형 연결장치 및 고강도 콘크리트 사용 여부이다. 또한 대상 구조물에 대해 3차 원 유한요소해석 모델을 개발하고 이에 대한 비선형 해석을 수행하였으며, 해석 및 실험결과를 비교하고 분석하였다. 그 결과 강재 클 립형 연결장치가 설치된 콘크리트 기둥이 반복 횡하중에 대해 기존의 표준갈고리 상세를 지닌 콘크리트 기둥과 동등한 혹은 그 이상 의 성능을 지니고 있으며, 개발된 유한요소해석 모델이 실험결과를 정확히 잘 예측하는 것으로 나타났다.