This study investigates the effect of process stopping and restarting on the microstructure and local nanoindentation properties of 316L stainless steel manufactured via selective laser melting (SLM). We find that stopping the SLM process midway, exposing the substrate to air having an oxygen concentration of 22% or more for 12 h, and subsequently restarting the process, makes little difference to the density of the restarted area (~ 99.8%) as compared to the previously melted area of the substrate below. While the microstructure and pore distribution near the stop/restart area changes, this modified process does not induce the development of unusual features, such as an inhomogeneous microstructure or irregular pore distribution in the substrate. An analysis of the stiffness and hardness values of the nano-indented steel also reveals very little change at the joint of the stop/restart area. Further, we discuss the possible and effective follow-up actions of stopping and subsequently restarting the SLM process.

우리나라 토양으로부터 분리된 (주와 김 2009) poly (butylene succinate-co-butylene adipate; PBSA) 분해균 Burkholderia cepacia PBSA-7, Bacillus licheniformis PBSA-8 및 Burkholderia sp. PBSA-9에서 PBSA 분해효소를 암호화하는 유전자를 분석하였다. PCR을 수행하여 B.cepacia PBSA-7과 Burkholderia sp. PBSA-9는 약

우리나라 서울시와 경기도 일대의 토양으로부터 poly(butylene succinate-co-butylene adipate: PBSA)를 분해하는 중온성세균 3주를 분리하였다. 0.01%의 PBSA film이 유일 탄소원으로 첨가된 변형 Sturm test에서 40일간 PBSA의 생분해도는 각 분리균주가 30%, 55% 및 43%를 나타내었으며, 이 중 Bacillus licheniformis PBSA-5의 경우는 PBSA뿐만 아니라 PVA에도 분해 활

지금까지 개발된 대부분의 세라믹 담체의 재료는 크게 알루미나와 실리카의 두 부류로 나누어지는데 소다유리를 원료로 하는 실리카 담체는 800℃ 정도의 온도에서 소결시켜 제조하나, 알루미나 원료의 담체는 1,300℃이상의 고온에서 소결 제조하여 원재료 및 제조비용이 높아 상업적 이용에 있어 경제성이 비교적 낮다는 단점이 있다. 따라서 본 연구개발은 소성을 하지 않고 무소성으로 압축강도가 향상된 세라믹담체를 제조하고 오염물질을 제거할 수 있는 미생물을 담체 제조시에 같이 혼합 제조하여 미생물담체를 제조하는 것이 1차 목표이며 다음으로 담체를 이용하여 수질오염물질을 제거하는 장치를 개발하는 것이다. 세라믹 담체의 원료가 되는 천연재료에 대한 녹조저감성능에 대한 시간대별로 흡착성능실험을 실시하고 이를 통해 녹조저감에 가장 우수한 재료을 선택하여 무소성 미생물 세라믹 담체를 개발 및 제조하였으며 비표면적과 흡수율, 압축강도, 미생물 균밀도에 대한 성능을 검사하였다. 또한, 개발된 세라믹담체의 수처리 효율을 분석하기 위해 Lab scale과 Pilot plant의 규모로 T-N, T-P, Chl-a, BOD 제거효율을 수질오염공정시험기준에 의거하여 분석하였다. 향후 무소성 세라믹 담체의 제조원료로 하수처리장에서 나오는 슬러지 및 다른 폐기물 등을 활용할 경우 폐기물의 재자원화와 생산단가 절감 등의 효과를 얻을 수 있을 것으로 판단된다.

In reinforced concrete (RC) structures, concrete carbonation depth is an important criterion for the deterioration of durability of RC structures. Concrete carbonation is influenced by multiple factors such as chloride attack, crack, concrete compressive strength, etc. However, due to its complex mechanism, most previous studies considered only one or two deterioration factors to estimate the concrete carbonation depth. In this study, therefore, inspection data were collected from 8 buildings, and the Adaptive Neuro-Fuzzy Inference System (ANFIS) algorithm that estimates the concrete carbonation depth of RC structures has been proposed. The proposed ANFIS model provided good estimations on the carbonation depths.

본 연구는 유아들이 한국 전통음식에 대해 알아보고, 오감을 이용하여 음식 재료를 탐색해 보고, 한국 전통음식을 직접 만들어 다른 사람과 음식을 나누는 활동에 참여하면서 나타나는 유아들의 경험이 어떠한지를 알아보는 것이다. 이를 위해 충청북도 C군 O어린이집 꿈꾸는반 만5세 유아 10명을 대상으로 2013년 7월 9일부터 2013년 9월 9일까지 8주에 걸쳐 주 2회씩 총 16회 한국 전통음식 만들기 활동을 실시하였고, 녹화자료의 전사와 교사저널, 사진, 유아 기록물 등의 자료를 수집, 분석하였다. 연구결과 첫째, 유아들은 연구 초기 한국 전통음식에 대해 생소함을 느꼈지만 점차 한국 전통음식에 관심가지기 시작했다. 둘째, 한국 전통음식 만들기에 참여하면서 다양한 음식재료를 오감을 이용해 탐색하고, 전통 도구를 이용하여 음식을 만드는 경험을 통해 즐거움을 느꼈다. 셋째, 한국 전통음식에 자부심을 갖게 되고, 유아가 만든 음식을 나누는 과정 속 에서도 유아 혼자에서 유아 주변 사람으로, 더 나아가 많은 사람으로 확대되었고, 나눔의 즐거움을 경험하였다. 넷째, 유아들은 한국 전통음식에 담긴 조상들의 지혜를 알게 되고, 조상들의 생활양식에도 관심 갖게 되면서 점차 전통 문양, 전통 의복 등 한국 전통문화로의 관심을 확대해 나갔다.

The remaining service life (RSL) of the concrete structures built in the past has become a social issue with the concerns of the sustainable construction. In the previous studies, some simple methods for estimation of the RSL of the concrete structures were proposed. However, most of the existing studies on the RSL evaluation method have focussed on the investigation of the single deteriorating factor. In this study, the combination effect of various factors related with durability performances of the concrete structure, such as concrete carbonation and chloride penetration were considered by utilizing the fuzzy and reliability theory.

Experimental studies on prestressed steel-concrete composite beams with various types of innovative webs have been conducted to improve prestress efficiency and composite action. These researches observed that the efficiency of prestress introduced into the flanges of composite beams with corrugated webs or discontinuous webs significantly increased due to accordion effect. In this study, nonlinear finite element analysis has been performed to evaluate the local behavior of specimens that are very difficult or sometimes impossible to observe. A suitable modeling method for PS composite beam has been developed, which can consider the loading stages along construction sequences and the interface interaction between different materials such as concrete and steel. The analysis results have been compared to test results for verification.

Existing approaches on flexural analysis of unbonded post-tensioned concrete beams are very difficult to be applied to estimation of service load behavior up to failure. In this study, theorectical flexural behavior model for post-tensioned members with unbonded tendons was, therefore, proposed based on the basic concept of idealization of curvature distribution within maximum moment region in a simple manner, which was previously developed by authors. The proposed model can predict the service load behavior as well as ultimate strength, and it is confirmed that this concept can be extended to estimate the flexural behavior of continuous unbonded post-tensioned members.

In this study, the unique material characteristics of steel fiber-reinforced concrete were introduced to extend the application of the compression field models to evaluations of shear capacity and behavior of steel fiber-reinforced concrete (SFRC) members. To achieve this purpose, nonlinear finite element program is developed using secant stiffness-based formulations, and the proposed numerical model was verified using basic experimental results of SFRC shear panels.

The Non-Shrinkage Epoxy using Silanol(Si-OH) was developed for repairing and strengthening, and it has excellent material properties that overcomes many limits of other existing epoxy products. In this study, direct shear strength tests were conducted to investigate the superior bond and shear capacity of the Non-Shrinkage Epoxy. The test results showed that the specimens with Non-Shrinkage Epoxy applied to their shear plane had higher shear strength than those with other existing epoxy.

Various type of composite beams have been developed to utilize advantages of reinforced concrete and steel structural system with making up for their weaknesses. In this study, prestressed composite beams with discontinuous corrugated webs are presented, in which discontinuous web plates improve the introduction efficiency of prestress by accordion effect and enhance composite action between steel beam and concrete compared to typical plane webs. Two prestressed composite beam with discontinuous corrugated webs, four prestressed composite beam with trapezoidal corrugated webs, and one corrugated webbed composite beam without prestress were fabricated and tested to evaluate their serviceability, ductility and flexural strength.