합성 지표수 용액을 가압식 한외여과 시스템을 통하여 100 L/m2/h 정속 및 0.15bar 정압 조건에서 전량 여과하였다. 공극 크기 0.05μm의 중공사막으로 구성된 가압식 모듈을 통해 실리카(SiO2) 입자 50, 10, 2 mg/L와 알긴산 나트륨(SA) 10, 2, 0.4 mg/L가 혼합된 용액을 여과하였다. 여과 공정은 30분 여과 후 30초 역세와 30초 정세의 주기적 물리 세정과 병행하여 수행되었다. 실험 결과 높은 농도 조건에서 정속 / 정압 여과조건에 따른 파울링 거동은 큰 차이를 보이지 않았으나, 낮은 농도 조건에서는 정속 여과가 정압 여과에 비해 파울링 속도가 빠른 것으로 관찰되었다. 모델링 결과 이는 정속 여과에서 막간 차압 증가에 의한 케이크 층 압축에 의한 것으로 나타났다.

Perfluorinated sulfonic acid (PFSA) ionomers have been used as polymer electrolyte membrane (PEM) materials owing to their excellent chemical durability and proton conductivity. However, the PFSA ionomers are suffering from fast hydrogen crossover and, thereby, chemical degradation in the membrane state. To solve these issues is to make reinforced membranes by filling proton-conductive PFSA ionomers in the pores of chemically robust poly(tetrafluoroethylene) (PTFE) support films. However, it is very difficult to obtain PFSA-PTFE reinforced membranes with improved hydrogen barrier property. In this study, PFSA-PTFE reinforced membranes were fabricated by immersing commercial reinforced membrane in PFSA ionomer dispersions with different chemical architectures and particle sizes and their effects were systematically investigated.

인적오류는 해양사고의 중요한 원인이고, 인적오류의 식별은 해양사고 예방에 근간이 된다. 특히, 선교팀(항해사와 조타수)이 주어진 상황에서 취한 기술적인 행동 패턴은 인적오류 식별에 중요한 정보를 제공한다. 본 연구의 목적은 익수자 구조를 위한 윌리암슨 선회법(Williamson’s Turn)을 이용하여 선교팀들의 기술적인 행동 패턴을 식별하고 분석하기 위한 것이다. 이를 위한 본 연구의 핵심은 실험을 실시하는 과정에서 나타난 선교팀의 인적 행동 요인에 대한 인지모델을 구축하고 분석하는 것이다. 실험환경은 선박조종 시뮬레이터를 이용하여 구축하고, 24개 선교팀으로 구성된 참가자들을 대상으로 실험을 진행하였다. 실험결과, 방향타와 기관을 사용한 항적유지와 선박조종에 대한 행동 패턴을 식별할 수 있었다. 본 연구는 선원의 자격 및 훈련에 적용하여 선교팀의 인적오류를 보완하고 보정하는데 기여할 수 있을 것으로 기대된다.

The purpose of this study was to investigate the dietary habits of smokers and non-smokers among a few male university students residing in Changwon-si and factors that affect their smoking behavior. A self-administered questionnaire was conducted for a duration of one month in June 2015 (n=367). The results of this study showed that the breakfast skipping rate of the smoking group was significantly higher compared to the non-smoking group (p<0.001), and the smoking rate was significantly higher among those with more serious smoking problems (p<0.001). Compared to the non-smoking group, the smoking group showed significantly higher BMI (body mass index) (p<0.05) and demonstrated significant drinking habit of more liquid type yogurt among milk and dairy products and significantly more coffee mixes among fat, oils, and sugars (p<0.05). The results of multiple regression analysis showed the necessity to prepare smoking systems in school (t=－2.87, p<0.05), encumbrances to studies due to smoking (t=－3.59, p<0.001), and variables that affect smoking such as the number of close friends who smoke (t=4.17, p<0.001), BMI (t=3.08, p<0.05), and the level of problematic drinking (t=3.67, p<0.001). The results of this study suggest factors that must be considered in establishing smoking prevention education programs, anti-smoking policies, and strategies for university students.

In the case of the visually impaired, in order to pick up an object, the entire shape is grasped while straddling the object first. When we grasp the characteristics of the object sufficiently by using the tactile sense of the hand, we touch the point which is the center of gravity and listen to the object once. When you want to perform object-graping with only the tactile sense under the conditions of other senses, such as vision, a series of actions is repeated. This paper deals with the behavior based control study of the robot hand using the tactile sense and applied to the 4 DOF hand developed by our laboratory by evolving the subsumption architecture (SA) proposed by R.Brooks.

In this study, MgO–CaO–Al2O3–SiO2 (MCAS) nanocomposite glass powder having a mean particle size of 50 nm and a specific surface area of 40 m2/g is used as a sintering additive for AlN ceramics. Densification behaviors and thermal properties of AlN with 5 wt% MCAS nano-glass additive are investigated. Dilatometric analysis and isothermal sintering of AlN-5wt% MCAS compact demonstrates that the shrinkage of the AlN specimen increases significantly above 1,300oC via liquid phase sintering of MCAS additive, and complete densification could be achieved after sintering at 1,600oC, which is a reduction in sintering temperature by 200oC compared to conventional AlN-Y2O3 systems. The MCAS glass phase is satisfactorily distributed between AlN particles after sintering at 1,600oC, existing as an amorphous secondary phase. The AlN specimen attained a thermal conductivity of 82.6 W/m·K at 1,600oC.

This study was conducted to evaluate children’s purchase behavior (frequency of snack consumption and purchase) and preference for high protein snack products developed for weight control and nutritional balance. A total of 80 elementary school students (from the 3rd to 6th graders) in the Gyeonggi-do learning center were participated and 76 were used for the analysis. The most common response for liking snacks was taste (71.4%), and the most preferred types of snacks were chips (42.1%) and puff snacks (34.2%). The highest frequency of snack ingestion was 1-3 times per week (48; 63.2%), and the main purchasers were parents (65.8%). Cheese, corn and chili flavors were more preferred than the control, while yogurt taste was slightly less preferred than the control. The results of this study showed the possibility of commercialization of new protein snacks according to children’s seasoning preference and provide the insights into the snack preferences of children as main consumers.

등기하 해석법을 이용한 고유치 해석은 유한요소를 이용한 결과보다 고차 모드에서 더 정확한 결과를 주는 것으로 알려져 있다. 이는 유한요소법이 차수에 상관없이 요소 간에 C0연속성을 보이는 것과 다르게 등기하 해석법은 p차 요소에 대해서 Cp-1의 연속성을 보장하기 때문이다. 본 논문에서는 이러한 장점을 이용하여 등기하 해석법을 이용하여 모드 기반의 축소 모델을 구성하고 동적 거동 해석을 수행하였다. 축소 모델 구성을 위해 Craig-Bampton(CB) 기법을 적용하였다. 수치 예제를 통해 간단한 봉 요소에 대해 등기하 해석법과 유한요소 해석법을 적용하여 요소의 차수에 따른 고유치 해석 결과를 비교 분석하였다. 등기하 해석법에 중첩 노트를 허용하여 요소 간 연속성을 조절하고, 요소 간 연속성이 줄어듦에 따라 고차 모드에서의 수치 오차가 커짐을 확인하였다. 동적 거동 해석을 위한 축소 모델에 높은 차수의 외력이 주어지는 경우 요소간 연속 성이 높은 등기하해석법을 사용하면, 해의 정확도를 높일 수 있다.

본 논문에서는 수중폭발(UE: underwater explosion)에 의한 해중터널(SFT: submerged floating tunnel)의 동적거동을 양 해법(explicit)를 이용하는 LS-DYNA에 의한 유한요소해석을 통하여 분석하였다. SFT의 유한요소모델은 원형단면의 강재 라이너에 콘크리트가 채워진 복합재 원형단면으로 고려되었다. 해중터널 시스템의 중앙부 100m 구간은 탄소성재료를 고려 한 솔리드(solid)요소로 상세하게 모델링하였으며, 양측 방향으로 각각 1km 구간에 대해서는 탄성재료를 고려하여 빔(beam) 요소로 이상화하여 모델링하였다. 사선계류시스템은 케이블(cable)요소를 적용하였으며, 수중폭발에 의한 동적거동시 수리동 적질량의 영향을 고려하기 위하여 원형단면에 대한 추가질량을 고려하였다. 또한 부력과 같은 상시하중을 초기조건으로 고려하기 위하여 동적완화해석(dynamic relaxation analysis)를 수행하였다. UE는 부력비(B/W)와 폭발지점으로부터 거리의 변화에 대해서 고려하였으며, 폭발의 규모는 천안함 합동조사보고서(2010)를 참조하여 TNT 360kg로 결정하였다. 수중폭발 해석결과, 폭발지점으로부터 SFT까지 거리는 관입량, 충격압력의 크기와 반비례 관계에 있고, 부력비(B/W)가 커질수록 계류장력도 커짐을 확인하였다. 그러나 사선계류라인의 계류각 변화는 SFT의 수평거동, 관입량, 계류력, 충격압력과의 연관성 을 찾을 수가 없었다.

PURPOSES : The purpose of this study was to investigate the behaviors of the middle slab in a double-deck road tunnel subjected to construction equipment loading from such as a concrete pump car, concrete transmixer, and lifting crane. METHODS: The major construction processes of a middle slab include concrete placement, concrete transportation, and lifting of materials near the emergency passageway section. During the concrete placement, the middle slab is subjected to construction loading due to the presence of the concrete pump car and fully loaded concrete transmixer. During the concrete transportation, the middle slab is subjected to loadings from both the fully loaded and empty concrete transmixer. The emergency passageway section of the middle slab is subjected to crane loading during lifting work. The magnitudes and geometries of these construction loadings are determined and the stresses and deflections of the middle slab under these loadings are analyzed using finite element models of the middle slab. The behaviors of the middle slab under the design truck loadings are also analyzed to compare the results with those under construction loadings. RESULTS : The stresses and deflections of the middle slab under construction loadings are comparable to those under the design truck loadings. Higher stresses can be observed when the concrete transmixers cross paths at the expansion joint section of the middle slab. The behaviors of the middle slab under the construction loadings during concrete placement are very similar regardless of the section types of the middle slab such as the normal, expansion joint, and emergency passageway sections. CONCLUSIONS : When the middle slab is designed, the construction loadings should be considered to determine the primary design loads and to verify the usability of a variety of construction equipment.

PURPOSES : The purpose of this study was to suggest a quantitative trend of the daily and seasonal cyclic movement of transverse crackwidth based on measurements in CRCP(Continuously Reinforced Concrete Pavement) within the first year of construction. METHODS : Crack gauges were installed in eight normal cracks, two induced cracks, and two construction joints of newly constructed CRCP. Crack width movements were continuously collected for about a year to investigate the cyclic behavior after construction. The daily and seasonal crack width movements were quantitatively analyzed and compared. RESULTS: Crack width movement in hot weather was relatively less than in cold weather. As a result of frequency analysis of the daily cyclic behavior, it was revealed by measurement that the minimum crack width from 2 p.m. to 4 p.m. was caused by expansion of the concrete; and that the maximum width from 6 a.m. to 8 a.m. was caused by contraction. Average crack width movements were calculated for every month and showed seasonal cyclic behavior. Maximum crack width was measured from December to January. Average crack width was investigated from March to April. Daily crack width movement in relation to concrete temperature was calculated from -0.00017 to -0.03844 mm/℃ and showed gradual decrease in absolute value with time caused by change in the crack spacing. It was found that the relationships between the monthly average crack width and concrete temperature are from -0.004 to -0.012 mm/℃. CONCLUSIONS : Crack-width movement shows a daily and seasonal cyclic behavior. Crack-width measurement in any time or season will have variance caused by daily and seasonal cyclic movement. Variances and trends were obtained in this study based on measurements for various cracks. The long-term behavior of cracks should be surveyed and compared with these measurements to investigate trends of convergence with time, caused by convergence of crack spacing.