จำนวน Repository ( 720 )
ปัจจัยที่ส่งผลต่อความล่าช้าของโครงการก่อสร้าง
The research is aimed to 1) study the level and priority of the factors affecting the delay of construction projects and 2) provide suggestions in relation to the prevention of such delay. The sample is 520 people who were working for different construction projects. They were project managers project engineers field engineers and foremen. The data were collected by using online questionnaires and analyzed to find out mean standard deviation (SD) frequency correlation coefficient and confirmatory factor analysis. The findings reveal two significant aspects. First those who were working in the construction projects concerned about the factors affecting the delay of the projects at high level. Respectively the factors related to design resource external factors and others were taken into consideration. The factor regarding to work performance is regarded affecting the project delay at the highest level. Other factors i.e. the design external factors and others and resource have the affects at the lower level. Second the work-related factors can help prevent the project delay. In other words the construction plan and methods as well as the project management should be well-implemented in accordance with the design. The construction site should be on inspection considering its drawing. Regarding the external factors and others the public voices of those living around the construction site should be taken into consideration. Furthermore the effective use of the resources can be carried out by sufficiently preparing all materials tools and equipment for constructing any project effectively as a consequence.
การจำลองและการทดสอบระบบเติมอากาศแบบน้ำไหลเวียนด้วยพลังงานแสงอาทิตย์
The amount of dissolved oxygen (DO) in aquaculture ponds is considered to be one of the most important aspects for the survival of fishes. The water in aquaculture ponds is stratified into distinct layers with different DO caused by differences in temperature. This temperature difference occurs when the surface layer of water heated by the sun becomes hotter than the lower water layer. Since the top layer is in contact with the air it contains the most DO. On the other hand the deepest layer is isolated from the air it contains the lowest amount of DO. This study proposed an aeration system called a Solar Circulating-Water Aeration System (SCWAS). The SCWAS uses solar thermal energy to create a natural water circulation. In other words it provides an upward current of water from the bottom to the pond surface and a downward current from the surface to the bottom. This circulation creates the movement of surface water and then increases the DO content of the surface water. This water circulation moves highly oxygenated surface water to the bottom layer forcing low oxygen water from the bottom up to the surface where it can absorb oxygen. To evaluate this design concept the numerical simulations of the system were conducted using ANSYS Fluent software. According to the simulation results the SCWAS can provide the natural water circulation. It was found that a flow rate of 2.24 L/s is obtained when the ratio between the draft tube inlet (r) the draft tube outlet (R) the base (L) is 1: 2: 3. In addition an SCWAS prototype was built and installed in a tilapia aquaculture system. A calibrated measuring system was installed to investigate the prototype performance. The experimental results indicate that the average DO values at the water surface and at the bottom of the pond increased by 1.45 and 1.40 times respectively compared with those of a pond without SCWAS. Economic analysis shows that the payback period of SCWAS is 4.58 years and its investment cost is 17.49% less than that of the paddle-wheel aerator.
การศึกษาผลของกระแสฮาร์มอนิกส์ต่อค่าสูญเสียของหม้อแปลงไฟฟ้าเลื่อนเฟสและการทำให้เป็นจริงด้วยหม้อแปลงไฟฟ้าเลื่อนเฟส 15 องศา
The trend of energy savings has been widely interested and phase shift transformers (HMT) have been extensively used. This paper presents the investigation of the effect of harmonic currents on losses of the HMT. In this paper a 15-degree HMT with quad secondary winding is applied to find the relationship between harmonic currents and losses of the HMT. This relation can be met by testing the active power of primary and secondary sides while the HMT supplies for two and four non-linear loads at 25% 50% 75% and 100% rated currents respectively. The results reveal that harmonic currents affect winding eddy current losses significantly and the losses for loading the two secondaries 1 and 2 are the same as loading the two secondaries 1 and 3 while both %THDi are different. However for loading the secondaries 1 and 2 the %THDi is more than 15% so it is not met IEEE 519 Std. while the HMT is supplied with four loads the %THDi has met IEEE 519 Std. and the losses are less than 57% compared to one load. As a result of these if the HMT is applied to an adjustable speed drive system it is not only reduced the harmonics but also saved the energies.
การเปลี่ยนแปลงคุณภาพไข่เค็มพอกขมิ้นทดแทนดินจอมปลวกบางส่วนระหว่างการเก็บรักษา
This research aimed to study the quality changes of coating salted eggs partially replacing soil from termite mound with turmeric powder at the level of 0% 5% 15% and 25% during storage for 4 weeks. The results showed that the increasing in turmeric level caused a decrease in salt content in raw egg yolk and raw egg white which led to decrease in hardening ratio of egg yolk. The hardness values of cooked - salted egg yolk decreased while those of cooked - salted egg white slightly increased. At the same salting period the color values of raw egg yolk and raw egg white coated with different levels of turmeric were slightly different. Egg yolks changed to a yellowish orange color while egg whites showed lightness with a direction of red and slightly yellowish color. The raw egg white coated with higher level of turmeric powder exhibited more yellowness which was in accordance with the increasing in curcumin content. From the results of 9-point hedonic scale in terms of color aroma overall taste and overall liking it was found that salted eggs coated with turmeric powder to partially replace soil at a level of 25% with 2 weeks of preserved duration had high scores of sensory acceptability which did not differ significantly from the control samples (0% turmeric) (p>0.05). The curcumin content analyzed in dry egg white was 3.885 mg/g at week 2 and increased to 13.291 and 18.484 mg/g at week 3 and 4 respectively.
การประยุกต์ใช้ฟิล์มแข็งเคลือบผิวเพื่อยืดอายุพันช์เอียงในกระบวนการตัดขอบ
The objective of this research is to increase the tool life of trimming process by surface coating technology. The procedure of this research consists of two sections. In the first section the friction coefficient was investigated with the ball on disk technique by using a tribometer. Steel ball was produced from cold work tool steel grade SKD11 (JIS) hardened to 60±2 HRC. Two types of surface coating namely AlCrN and TiAlN were conducted by PVD technique. Disk material used in this experiment was made by stainless steel JIS; SUS 304 of 2 mm thickness. For the second section the wear tests of trimming die were performed by using flat punch and inclined punch 45 degrees without surface coating as well as the inclined punch 45 degrees coated with AlCrN and TiAlN (PVD). Workpiece material used for the wear test was stainless steel JIS; SUS 304 of 2 mm thickness. Additionally the finite element analysis was carried out for explanation the deformation of the workpiece during trimming operation. Although the friction coefficient of the surface coating was higher than non-coating it could be extended the tool life ostensibly. As the result of FEM the inclined punch 45 degrees could be generated the long sheared surface more than the flat punch. This is due to the internal stress of workpiece that did not connect from the punch to the die so the crack propagation would be delayed. The inclined punch 45 degrees coated TiAlN has a highly durable which can be used up to 5000 strokes.