Abstract-In order to predict the post-cracking tensile behavior of fiber reinforced concrete, it is necessary to evaluate the fiber orientation factor which indicates the number of fibers bridging a crack. For investigation of fiber orientation factor on a rectangular section, in this paper, dog-bone fiber reinforced concrete specimens were prepared with the variables of concrete compressive strength, rectangular cross-section size, fiber type, and fiber volumetric ratio. After direct tension tests, the fiber orientation factor could be evaluated through counting the number of fibers on a crack. From the test results, it was investigated that the fiber orientation factor was larger than 0.5 which is generally adopted for large members, as fibers distribution is affected by the specimen size. For rational prediction of the fiber orientation factor on a rectangular concrete section, a simple model was derived from the Diverse Embedment Model (DEM), which is a rigorous model to predict the tensile behavior of steel fiber reinforced concrete. From the comparison of the measured data and the predicted values, it was found that the actual fiber orientation factor was well predicted by the proposed model.

Rotten citrus fruits, which spread odor gas during shipping season, pose a severe problem in Jeju Island, Republic of Korea. The existing methods for food waste management such as composting using electro-drying and microorganisms have a high electricity cost and require a precise temperature control, respectively. Herein, we conducted a basic numerical study on a plasma reactor using microwave plasma and liquefied petroleum gas as a combined heat source for drying and composting rotten citrus fruits. To determine the design and operating conditions of the plasma reactor, the thermal flow characteristics inside the reactor were analyzed using a computational fluid dynamics code in ANSYS-fluent. In particular, the temperature distribution in the plasma reactor was simulated at different air flow rates of the centrifugal fan. The numerical simulation accuracy was evaluated by comparing the numerical results and actual experimental data. The temperature of the reactor decreased with the increase in the air flow rate of the centrifugal fan. Above 10 m/s, the temperature of the drying chamber and the exhaust gas remained almost constant at 507 K. In the present work, the calculated temperature shows a difference 1.13 % from the measured temperature at the combustion chamber.