Coding Template Of Sensorless Sun Tracking Using Azimuth-Elevation Mode

The next explosion in solar power research was in 1997 as consequence to Kyoto Protocol. This protocol outlined the effect of greenhouse emission which endangers our Earth. As the result, research in solar power field started to take its path again. This work is a part of the UTeM project to build the first CST model in South East Asia and was aimed to develop an azimuth-elevationmode-based template using MATLAB programming for the calculation of the heliostat position with respect to the heat absorber mounted at the top of the CST. This template will serve as the calculation platform to control the movement of the heliostat using a two-axis motion system so that the sun light will be redirected perfectly to the absorber all day long. Since the heliostat normal vector depends on sun position vector, both vectors were calculated by the program and were set as the output of the program. The input from the user will be the Cartesian coordinate of the heliostat and absorber by taking the absorber tower frontal surface and its base as the origin and also the date. The result will be in vector form and will change automatically according to the Sun movement. These values will be programmed in the micro controller which will control the motion system of the heliostat, which will be done by the Control Department of UTeM. The program´s functionality was proved via several verifications and its accuracy which is 0.0005 as stated and verified via comparison with analytical calculations. From the verifications, it can be seen that difference of the numerical and analytical results varied from 0.0000 to 0.0005 which validates the statement of minimum accuracy of the numerical calculated results is 5/10,000

Modelling And Simulation Of A Wind Turbine With Doubly Fed Induction Generator In Full Load Operation

The paper focuses on modelling and simulation of a 5 MW wind turbine with doubly fed induction generator (DFIG) in full load operation. The wind turbine model is described mathematically and presented in simulation blocks. Through a computer simulation, the wind turbine behavior in full load operation is investigated. A speed controller is used to adjust the pitch angle of a rotor blade in high wind speed to limit the wind energy captured by the turbine to the nominal power value. By adjusting the pitch angle to 18.26° at wind speed 20 m/s, the wind turbine is protected from mechanical damage due to torque and power limitation. The simulation results obtained can be used as references for future optimization for the variable speed wind turbine operation

Factors influencing physical activity in pregnancy : a systematic review

Lack of physical activity in pregnancy may lead to poor maternal and perinatal outcomes including gestational diabetes, hypertensive disorders and postpartum depression. Given these risks, identifying factors that influence physical activity in pregnancy is crucial to planning and implementing appropriate interventional programmes and managing this vulnerable group. Peer reviewed articles on factors influencing physical activity in pregnancy were searched using the Pub-Med and Ovid databases, from 2014 to 2019. The selected articles were reviewed by two authors and critically appraised using the Mixed Methods Assessment Tool 2018. A total of 16 articles were included. Factors that positively influenced physical activity in pregnancy were fun, higher economic status, early trimester, and higher body weight. Factors that negatively influenced physical activity in pregnancy were lack of knowledge, lack of social support, multiparity, physical pain and discomfort, ethnic minority status, and concern for the safety of the baby. Fun was one of the most reported motivators of physical activity in pregnancy, and the most reported reason for reduced physical activity was lack of knowledge. Additionally, social support from friends and family played an important role in encouraging pregnant women to be active. This systematic review highlights the need to improve current health education programmes for physical activity in pregnancy, which should ideally be extended and targeted to the whole community, beyond pregnant women themselves for better uptake and acceptance

Effect Of Bio-Based Lubricant Towards Emissions And Engine Breakdown Due To Spark Plug Fouling In A Two-Stroke Engine

Two-stroke also known as two-cycle gasoline engine is a spark ignition engine. Its uniqueness to the four-stroke engine is that this engine does not require lubricant sump, which makes construction lightweight and simple. Its lubricant is mixed with gasoline and burnt together during combustion. There are reports which stated that higher spark plug fouling is due to carbon deposition on the spark plug electrodes on a two-stroke engine when compared to the four-stroke. While many factors could have affected this situation, however, in this paper, the effect of mineral and bio-based lubricants towards carbon deposition and emissions are studied and reported. Idle, half and full throttle operation modes had been conducted on a two-stroke, 43 cubic centimeter engine. To keep combustion temperature below self-cleaning temperature on all three modes of operation, a zero-load test was utilized. This situation accelerates the deposition process as low temperature causes incomplete combustion. This could lead to the accumulation of char, unburned fuel, as well as condensed water and acids as the byproducts blanket the spark plug electrodes and the exhaust system. Five samples had been prepared with a commercially available mineral lubricant (T0) as reference. Trimethylolpropane Trioleate, TMPTO derived from plant origin was used as the bio-based candidate. It was then mixed with T0 which created another four lubricant samples namely T10, T15, T20 and T50 with 10%, 15%, 20% and 50% TMPTO accordingly. Results show that mineral lubricant T0 delivers the lowest hydrocarbon HC, carbon monoxide CO and smoke opacity during idle and half throttle operations. However, it exhibits a greasy deposit on the spark plug circumference and dry carbon deposits on its insulator tip. T0 also emits a liquid residue at the exhaust manifold. T10 and T50 show a wet deposit blanketing both electrodes. Severe deposition was recorded by T50 that caused the engine to fail half way with its emissions had the worst recording. T15 and T20 exhibit only dry carbon deposition on the spark plug circumference. However, T20 has outperformed T15 in terms of emissions with lower CO and CO2 emissions during idling and half-throttling. With better emissions than T15 and better carbon deposition than mineral (T0), T20 could be proposed to be used as a commercial two-stroke lubricant

Modeling and simulation of doubly fed induction generator for wind turbine

The construction of modern wind turbine is costly, complex and risky. In this paper, modeling and simulation of doubly fed induction generator (DFIG) for wind turbine is presented to investigate the dynamic behavior of the system. The behavior of the system is described in mathematical equations, modeled and simulated in MATLAB/Simulink using field orientation principle. Simulation results are presented in two operation modes namely below and above synchronous speed. Measurement obtained from 5 MW wind turbine confirmed the theoretical result. The created modeled can be used to simulate the behavior of DFIG for wind turbine inexpensively, efficiently and safely

Pengurusan fiskal pihak berkuasa tempatan yang berstatus Majlis Bandaraya di Zon Tengah Semenanjung Malaysia

keunikan Majlis bandaraya berbanding dengan pihak berkuasa tempatan yang lain adalah dapat mentadbir kawasan maju dengan kepadatan penduduk dan pendapatan isirumah yang tinggi, dan sekaligus boleh menjana lebih pendapatan fiskal. Namun begitu, permintaan pembayar cukai setempat terhadap barangan awam tempatan turut menjadi semakin kompleks dari masa ke semasa. Maka, pengurusan dan takbir urus belanjawan yang baik adalah penting supaya Majlis Bandaraya tersebut tidak berhadapan dengan defisit fiskal dan hutang awam yang berpanjangan. Justeru, kajian ini bertujuan untuk menguji hubungan jangka panjang (kointegrasi) dan arah hubungan sebab-menyebab antara hasil, belanja, imbangan fiskal dan hutang awam mengikut Majlis Bandaraya di zon tengah Semenanjung Malaysia. Dua kategori data digunakan iaitu data agregat bagi semua pemboleh ubah, dan data mengikut komponen hasil cukai, bukan cukai dan terimaan bukan hasil bagi pemboleh ubah hasil serta belanja mengurus dan pembangunan bagi pemboleh ubah belanja. Penemuan penting kajian dengan menggunakan model auto regresif lat tertabur (autoregressive distributed lag, ArDL) menunjukkan bahawa Dewan bandaraya kuala Lumpur dan Majlis bandaraya Shah Alam menggunakan hipotesis belanja-hasil, manakala Majlis bandaraya Petaling Jaya mempraktiskan hipotesis penyelarasan fiskal dalam jangka pendek dan jangka panjang. Di samping itu, komponen belanja mengurus iaitu belanja perkhidmatan dan bekalan, belanja pembangunan dan jumlah belanja lebih cenderung mempengaruhi hasil cukai. tetapi bagi kes Majlis bandaraya Petaling Jaya, hasil cukai turut mempengaruhi jumlah belanja. Penemuan baharu kajian ini mencadangkan agar Majlis bandaraya perlu meningkatkan kecekapan peruntukan terhadap semua instrumen fiskal, terutama sekali komponen belanja mengurus dan hasil cukai bagi tujuan pengukuhan fiskal pada masa hadapan

Gnielinski method in calculating the heat transfer coefficient for metallic solar tower absorber

This work is done to calculate the heat transfer coefficient of metallic wire mesh to air in an open volumetric thermal absorber. It is aimed to replace the actual ceramic with metallic which latter has better thermal properties in order to increase the efficiency of the concentrating solar power plant. The calculation of the heat transfer coefficient from porous wire structure to the air has been conducted to pursue the purpose. The structure that has been chosen is a set of metallic wires with aligned and shifted configurations. The variations of wire diameter together with various porosities from 0.10 to 0.50 have been calculated to obtain the best configuration for the absorber. The flow characteristic within the mesh structure in terms of Reynolds number and its relationship with the heat transfer coefficient has been obtained. The condition on mass flow rate of heat transfer medium and other aspects which influence the heat transfer are also discussed