The objectives of this study were to calculate the probability of type I error power of a test and to compare the performance of three test statistics: Z Student’s t and Welch’s t. Including the recommending the appropriate test statistic. Classification of the population according to five distribution. The ratios of mean group 1 per group 2 were three levels. The ratios of variance group 1 per group 2 were three levels. The sample sizes of two populations were nine sizes. The significance levels that to study were 0.01 and 0.05. The data were simulated by using SAS programming with 1000 replicates. Results of the research were Z test statistic could control the probability of type I error and had higher power of a test than other test statistics but this test is necessary to know the variances of the two groups. Therefore it was appropriate to apply the other test statistics i.e. Student’s t or Welch’s t. If the variances of the two groups were equal Student’s t was a more appropriate test statistic than Welch’s t. But if the variances of the two groups were not equal Welch’s t was a more appropriate. When both sample sizes were large and the population variances were equal we could use any tests since there is no difference in the performance.

Comparing the protection of the energy curriculum between the European Union (EU) and Thailand demonstrated that the number of curriculum to protect of the energy consumers in EU much more than Thailand 529 courses. The higher education in EU the protection of the energy consumers in master program are more than the undergraduate program. Meanwhile in Thailand is emphasis in undergraduate than graduate program. In addition to the doctoral program in EU there are the course of the protection of the energy consumers much more than Thailand 185 courses. The performance analysis of the role of the EU institutions and Thailand in action and training / increase interdisciplinary knowledge related to protect of the energy consumers. To contribute to the analysis and find ways to improve the system to better meet the EU and the efficient train / increase knowledge of the environmental impact assessment (EIA) was higher than the other side. However the EU is of course the fundamental rights and participation legislation regulations and regulatory standards than Thailand. Therefore the role of educational institutions in the United States and the EU to enhance the training / knowledge to increase the rate for services at first. In Thailand the program should increase the basic rights and participation legislation regulations and regulatory standards including increasing the efficient use of energy and natural resources.

This research aims to compare the mechanical properties of materials made from hyacinth pineapple and sugarcane fibers and also to study the feasibility of producing automotive interior parts from natural fibers. The 9 specimens that made from natural fiber such as water hyacinth pineapple leaf fiber sugar can and husk and there are also three different binders: glue polymer and polymer plus hardener were produced. All of specimens were controlled mass and density. The specimens were classified into 2 types: 1) thin type with a size of 3.5x14x1 cm in order to test the flexibility 2) thick type with a size of 6.5x6.5x20 cm for testing the ability to absorb energy. The test results showed that the specimen produced from sugar cane and husk using adhesive bonding able to receive bending stress and modulus of elasticity more than other specimens up to 80.63% and 69.19% respectively. While the ability to absorb energy from work piece made from pineapple leaf fiber and husks using polymer bender was able to absorb energy more than other work pieces 51.58%.

The damaged propeller shafts caused by the fatigue failure will be repaired by shield metal arc welding process. The service life dependeds on fatigue endurance limit of welding surface. This study was aimed to compare the fatigue resistance of two types of hard facing electrodes using the same arc welding repair process. The investigation of fatigue stress at 517 MPa in failure criteria showed that the propeller shafts repair by Flux core arc welding Process using electrode grade E110T5-K4H4 provided the approximate same service life as that using electrode grade X111-T5-K4 but lowered the repair costs up to thirty-five bath per kilogram electrode. As a result the total maintenance cost decrease 68250 baht per year.

The purpose of this research is to find the relation between stress and strain called as the Flow Stress Curve for 0.4 mm thickness stainless steel (SS 304). Two main methods are used: the Uniaxial tensile test and the Hydraulic Bulge Test (HBT). The relation between stress and strain from both methods would then be compared and simulated into cubic-shaped models by using Finite Element method. Results show that sheet metal formation simulated by using the flow stress curve obtained from Hydraulic bulge test can have the height of up to 40 millimeters before the work piece starts to lacerate. On the other hand if the flow stress curve obtained from Uniaxial tensile test is used the work piece will only be able to form about 15 millimeters before lacerating. The preliminary summary for this research can be said that the analysis for Hydraulic bulge test gives better results than Uniaxial tensile test as it has similar conditions to the actual formation process.