This research aimed to determine the optimal sand mold mixture’s ratio by using return sand bentonite water content and new sand component. Then the properties of the mixture according to the standards of American Foundrymen’s Society include the ability of compactability moisture content permeability and green compressive strength. This study applied mixture experiments and response surface methodology to determine an optimal sand mold mixture components condition. After the experiment and linear programming it indicated that the condition was at return sand (95.5387 %) bentonite (1.130102 %) water content (2.331196 %) and new sand (1 %). The green sand mold has compactability (58.37923 %) permeability (73.80148 %) moisture 6.5 % and green compressive strength (0.53 Kg/cm2). At this condition the cost is 11.31579 baths per kilogram.

The objective of this research is to study how rotation speeds affect mechanical properties with friction welding between semi-solid metal 7075 aluminum alloys and semi-solid metal 356 aluminum alloys. The factor of interest is rotation speeds with different conditions at 800 1000 1200 1400 and 1600 rpm respectively. 1.8 millimeter for burn of length 30 seconds for welding time and clockwise rotation are set as a control constant condition for the entire experiment. After friction welding we found that different rotation speeds significantly affected mechanical properties of these alloys. At rotation speed 1400 rpm the maximum tensile strength is 122.24 MPa and the maximum hardness in welded zone is 140.5 HV. The microstructure size is 2.250 µm long and 2.144 µm wide. Its size in welded zone is practically small because of friction force. Moreover this friction force causes the mixture of MgZn2 and Mg2Si in welded zone.

This research aims to study the using cassava pit wastes mixed with cement to particle board walls. The Portland cement type1: fine sand: tap water ratio is equal to 1: 0.5: 0.416 by weight. The ratios of cassava pit wastes to cement are used following: 0.05 0.06 0.07 0.08 0.09 and 0.10 by weight. The cassava pit wastes are crushed by plastic plastics granulators (pass sieve no.4). The casting of particle board walls use the compression machine in room temperature (30 – 35 degree of Celsius) and control 0.75 g/cm3 of density. The TIS 878-2537 standard (cement bonded particle board: high density) is followed to test the properties of particle board wall. Resulting the cassava pit wastes mixed with cement can cast to particle board walls and have good properties especially the thermal insulation property.

This research aims to study strategies required for developing educational game for preschool students and the development processes involved. The sampling groups used in this research included 3 content specialists whose responsibility is to verify the content of the games and 17 specialists on educational game. The sampling groups are selected particularly from the central region of Thailand. The research findings reveal the insights from the majority of specialists on development of educational games for preschool children as follow: games such as picture-matching domino object ordering object categorizing detail observing and number addition & subtraction games are popular for teaching. Moreover the principles for applying educational games with lessons should be incorporated in the development of game strategies. In addition the main objectives and the development process of games should focus primarily on their ability to draw attention from students as well as the fun of playing and allowing students to practice lessons and participate in class activities. The tools used for developing games are computers and devices created by teachers themselves. As for the future of educational game the trend is the more involvement of technology through the use of computer or mobile devices. Problems in game development include limited budget for purchasing hardware and devices. On top of that training on game development is much needed among teachers. The research results can be concluded with the following 5 strategies for preschool students: 1) enhance teachers’ knowledge and skills 2) study details of different kinds of games 3) develop games 4) determine time used for playing game 5) evaluate the process of game development in 4 areas including type of game devices used rules and playing instruction.

The objectives of this research are to propose a Bayesian model for spatial time series analysis to apply the proposed model to forecast a monthly rubber yield in Southern provinces of Thailand and to compare the performance of the proposed model with the classical Holt-Winters Additive Exponential smoothing. The proposed model is a linear mixed model (LMM) with spatial effects which follow a conditional autoregressive model (CAR). Dummy variables are used for seasonal effects. A Bayesian method is used for parameter estimation. The estimated monthly yields are used for the monthly rubber yield forecasting. The dependent variables are the rubber yield in each month of each province. The data are secondary data at a provincial level. The factors considered are spatial effects heterogeneity effects and seasonal effects. The results show that the factors influencing on the amount of rubber yields are spatial heterogeneity and seasonal effects. The proposed model is proper and forecast accurately. Using the mean absolute error (MAE) the proposed model has a better performance compared to the classical Holt-Winters Additive Exponential smoothing in both model fitting and model validating. The proposed model should be the first consideration for spatial time series forecasting.