จำนวน Repository ( 194 )

การศึกษาผลของกระแสฮาร์มอนิกส์ต่อค่าสูญเสียของหม้อแปลงไฟฟ้าเลื่อนเฟสและการทำให้เป็นจริงด้วยหม้อแปลงไฟฟ้าเลื่อนเฟส 15 องศา
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.

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ผลของสารสกัดหยาบด้วยเอทานอลจากสมุนไพร 7 ชนิดต่อการไล่มด
ผลของสารสกัดหยาบด้วยเอทานอลจากสมุนไพร 7 ชนิดต่อการไล่มด

This research aims to study the ant repellent effects of the crude ethanolic extracts from 7 herbs; Piper nigrum Linn. Alpinia galanga (L.) Willd Ocimum basilicum L. Cymbopogon citratus Stapf Citrus aurantiifolia (Christm.) Swingle Citrus hystrix DC and Stemona collinsae Craib. Whatman filter paper was dipped with each concentration of the crude ethanolic extracts (0.625 1.25 2.5 and 5 % w/v) and placing the bait on a treated filter paper. The experiments were conducted in the natural. The numbers of weaver ants were recorded at 0 - 30 minutes. From the results the crude ethanolic extracts at 5% w/v of A. galanga was the most effective for repellent the ant (repellent rate; %R = 94.72 ± 2.39) followed with C. citratus (%R = 89.45 ± 3.85) S. collinsae (%R = 82.92 ± 4.47) and P.nigrum (%R = 81.20 ± 5.92). The repellent rates of those crude ethanolic extracts were significantly difference from distilled water which use for the negative control (P < 0.05). The crude ethanolic extract of A. galanga at concentration 5% w/v was prepared as spray cream chalk and powder. At 30 minutes of the observation the ethanolic extracts of A. galanga spray was the best ant repellent effect (%R = 100). The result from questionnaires reveals that a spray preparation was the more satisfaction for the using ant repellent products.

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The Dietary effects on manure characteristics and biogas production from dairy cows feeding with pineapple peel
The Dietary effects on manure characteristics and biogas production from dairy cows feeding with pineapple peel

This study explored the dietary effect on manure characteristics and potential of biogas production from the manure of dairy cows feeding with pineapple peel as a roughage source. Three mid-lactation primiparous crossbred Holstein dairy cows which had an average body weight of 443.5±10.6 kg and average milk production of 9.6±0.3 kg/d were assigned with three different diet types including T1 T2 and T3. T1 was a control diet which consisted of a mixture of dry Pangola grass and commercial pellet (CL). Moreover T2 was a mixture of dry Pangola grass pineapple peel and CL while T3 was a mixture of pineapple peel and CL. Dairy cow manure was collected on the day 10th after feeding and anaerobic digestion of the dairy cow manure was operated with an HRT of 30 days. Results showed that all diet types gave similar manure characteristics of high organic matter and nitrogen. Average concentrations of TS and COD ranged from 82.59 to 85.78 g/L and 85.47 to 91.47 g/L respectively whereas TAN ranged from 1.54 to 1.67 g/L. However a higher pH of 7.50 was found for the manure of dairy cow fed with T1 while a lower pH of 6.50 was obtained with T3. Besides the highest methane yield of 0.20 m3 CH4/kg VSadded was obtained when using the manure of dairy cow fed with T1 as a substrate followed by T2 and T3 which found at 0.14 and 0.11 m3 CH4/kg VSadded respectively. This indicated the efficient potential of biogas production from the manure of dairy cows fed with pineapple peel which will improve sustainable utilization of agricultural wastes and waste produced from dairy cow farm in the future.

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ผลของอุณหภูมิที่มีต่อค่าความต้านทานและความจุไฟฟ้าของข้าวเปลือกที่มีความชื้นแตกต่างกัน
ผลของอุณหภูมิที่มีต่อค่าความต้านทานและความจุไฟฟ้าของข้าวเปลือกที่มีความชื้นแตกต่างกัน

This research proposes an application of resistive and capacitive soil moisture sensors to investigate the influences of paddy temperature on the electrical signal received from sensors when tested with paddy moisture in the range 9.2 - 22.75%wb at 40 - 80ºC to determine the relationship between paddy moisture and electrical signals. It was found that the mean signal values between 20 - 40 seconds from both sensors were inversely linear correlation with the moisture content of the paddy. Temperature is the factors that influence the measured electrical signal. R2 Adjust R2 (95% confidence interval) and RMSEC showed that the model developed from the resistive sensor signals was accurate in calculating the moisture content of paddy between medium to high temperature in range 60 - 80ºC more than the low temperature range. While the capacitive sensor signals model is accurate in calculating paddy moisture between low to medium temperature in range 40 - 60 ºC. Therefore the resistive soil moisture sensor is possible and more suitable for applying as a paddy moisture sensor in the high temperature drying processes than a capacitor soil moisture sensor.

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การปรับปรุงประสิทธิผลโดยรวมของเครื่องจักร ของระบบการกรองน้ำของโรงงานผลิตน้ำขนาดใหญ่ โดยใช้การบำรุงรักษาทวีผลโดยทุกคนมีส่วนร่วม : กรณีศึกษาโรงงานผลิตน้ำประปาแห่งหนึ่ง
การปรับปรุงประสิทธิผลโดยรวมของเครื่องจักร ของระบบการกรองน้ำของโรงงานผลิตน้ำขนาดใหญ่ โดยใช้การบำรุงรักษาทวีผลโดยทุกคนมีส่วนร่วม : กรณีศึกษาโรงงานผลิตน้ำประปาแห่งหนึ่ง

This research objective is to improve the overall equipment effectiveness of the water filtration systems in the case study of the Water Treatment Plant which divides the water production into 4 production lines. The water filtration system has an electric actuator and gear is the main machine in the water filtration system. An electric actuator and gear have more machine breakdowns. That makes the water filtration system is the bottleneck of the water production process. This research study is divided into two steps: the first step is the presentation of the equation and the steps to measure the Overall Equipment Effectiveness of the water filtration system. The equation used data from the computer maintenance management system to analysis on mean time between failure data (MTBF) mean time to repair data (MTTR) and water production process data. The results can be improved the overall equipment effectiveness of the water filtration system increased to 0.11% 0.68% 0.44% and 2.44% respectively in each production process line. And increased Quantity of Filtration Water increased to 328500 m3/year 1168000 m3/year 1022000 m3/year and 3832500 m3/year respectively in each production process line. In this research used the pillar of focus improvement. By adding a protection system to prevent machine breakdown because of the most of the problems are found that the protection system malfunctions. This is the most problem in the 4th And then used engineering knowledge to improve water production and the success factor are required a human resources of all parties to cooperate brainstorm and analyze the causes of various losses in order to eliminate them.

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