Conventionally, metal materials are produced by subtractive manufacturing followed by melting. However, there has been an increasing interest in additive manufacturing, especially metal 3D printing technology, which is relatively inexpensive because of the absence of complicated processing steps. In this study, we focus on the effect of varying powder size on the synthesis quality, and suggest optimum process conditions for the preparation of AlCrFeNi high-entropy alloy powder. The SEM image of the as-fabricated specimens show countless, fine, as-synthesized powders. Furthermore, we have examined the phase and microstructure before and after 3D printing, and found that there are no noticeable changes in the phase or microstructure. However, it was determined that the larger the powder size, the better the Vickers hardness of the material. This study sheds light on the optimization of process conditions in the metal 3D printing field.

This study examined the eating habits and preferences of foods according to the age of children with autism spectrum disorders and identified the nutritional needs of parents to support their healthy eating habits and provide basic data for the development of educational programs. A survey of 100 parents of children with autism spectrum disorders was conducted on their children’s snack intake, food preferences, and parents’ nutrition education needs. As a result, there were four times more boys than girls, and the body mass index differed according to age (p<0.001). Most children ate snacks more than once a day, and parents found that they wanted to develop nutritious snacks that could replace high-protein, low-calorie meals with the minimal use of additives. For the food preference, there was a significant difference in grains and starches, vegetables/seafood and fruits, milk and dairy products (p<0.05), fats and sugars, and Korean fermented pastes (p<0.01) between the two age groups. Regarding whether nutrition education was required, many parents had a high demand for nutrition education (4.24±0.70), and the intention to participate was 3.62±1.09. The most important content to be dealt with in parent education was ‘Inducing a change in bad eating habits and behaviors’, which was the highest (63%), and mostly face-to-face education was preferred. In conclusion, young children require diet education, and older children need to focus on weight control and obesity.

PURPOSES : It is well known that low temperature cracking is one of the most serious distresses on asphalt pavement, especially for northern U.S. (including Alaska), Canada and the northern part of south Korea. The risk of thermal cracking can be numerically measured by estimating thermal stress of a given asphalt mixture. This thermal stress can be computed by low temperature creep testing. Currently, in-direct tensile (IDT) mixture creep test mentioned in AASHTO specification is used for measuring low temperature creep properties of a given asphalt mixture. However, IDT requires the use of expensive testing equipment for performing the sophisticated analysis process, however, very few laboratories utilize this equipment. In this paper, a new and simple performance test (SPT) method: bending beam rheometer (BBR) mixture creep testing equipment is introduced, and the estimated experimental results were compared with those of conventional IDT tests. METHODS: Three different asphalt mixtures containing reclaimed asphalt pavement (RAP) and roofing shingles were prepared in the Korea Expressway Corporation (KEC) research laboratory. Using the BBR and IDT, the low temperature creep stiffness data were measured and subsequently computed. Using a simple power-law function, the creep stiffness data were converted into relaxation modulus, and subsequently compared. Finally, thermal stress results were computed from relaxation modulus master curve using Gaussian quadrature approach with condierations of 24 Gauss number. RESULTS: In the case of the conventional asphalt mixture, similar trends were observed when the relaxation modulus and thermal stress results were compared. In the case of RAP and Shingle added mixtures, relatively different computation results were obtained. It can be estimated that different experimental surroundings and specimen sizes affected the results. CONCLUSIONS: It can be said that the BBR mixture creep test can be a more viable approach for measuring low temperature properties of asphalt mixture compared to expensive and complex IDT testing methods. However, more extensive research and analysis are required to further verify the feasibility of the BBR mixture creep test.

본 연구의 목적은 협동게임프로그램이 보호관찰대상 청소년들의 정서 및 사회성에 주는 영향을 알아보는 것이다. 이러한 연구 목적을 알아보기 위하여 보호관찰소에서 보호관찰 명령을 받고 있는 12명의 남자청소년들을 대상으로 2주간 8회 프로그램을 적용하였고, 보다 심층적인 결과를 알아보기 위해 심층면담과 참여관찰의 질적연구 방법을 병행하여 실시하였다. 정서와 사회성의 변화를 양적으로 알아보기 위해 질문지는 프로그램 적용 전과 후를 비교하였으며, 질적인 결과를 알아보기 위해 8회의 프로그램 후 실시한 심층면담은 삼각검증법을 통해 결과를 알아보았다. 분석을 통해 나온 결과를 보면 다음과 같다. 양적연구에서, 정서는 현재기분상태, 소외감과 사회비관적태도 중 현재기분상태(p<.05)에서만 유의한 차이를 보였고, 사회성은 사회적 지지와 사회적 갈등에서 유의한 차이가 나타나지 않았다. 질적연구결과, 첫째로 혼자가 아닌 우리라는 인식과, 둘째로 재미와 즐거움을 경험하였고, 셋째로, 도전과 성취로부터 자신감을 얻었고 넷째로, 자기반성의 시간을 갖는 것으로 나타났다.