Optimal Sizing of Fixed Capacitor Banks Placed on a Distorted Interconnected Distribution Networks by Genetic Algorithms

In this paper, the optimal sizing of fixed capacitor banks problem in a distorted interconnected distribution system is formulated and solved by a Genetic Algorithm (GA) solution technique to minimize the cost of power production and capacitor banks under the constraints include voltage limits , sizes of installed capacitors and Total Harmonic Distortion (THD), the algorithm is applied on IEEE 30-bus test system and the results are given for different cases: Light and heavy harmonic cases. Computer simulation shows that the harmonic components affect the optimal capacitor sizing

A PC-based magnetometer-only attitude and rate determination system for gyroless spacecraft

This paper describes a prototype PC-based system that uses measurements from a three-axis magnetometer (TAM) to estimate the state (three-axis attitude and rates) of a spacecraft given no a priori information other than the mass properties. The system uses two algorithms that estimate the spacecraft's state - a deterministic magnetic-field only algorithm and a Kalman filter for gyroless spacecraft. The algorithms are combined by invoking the deterministic algorithm to generate the spacecraft state at epoch using a small batch of data and then using this deterministic epoch solution as the initial condition for the Kalman filter during the production run. System input comprises processed data that includes TAM and reference magnetic field data. Additional information, such as control system data and measurements from line-of-sight sensors, can be input to the system if available. Test results are presented using in-flight data from two three-axis stabilized spacecraft: Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) (gyroless, Sun-pointing) and Earth Radiation Budget Satellite (ERBS) (gyro-based, Earth-pointing). The results show that, using as little as 700 s of data, the system is capable of accuracies of 1.5 deg in attitude and 0.01 deg/s in rates; i.e., within SAMPEX mission requirements

Earth horizon modeling and application to static Earth sensors on TRMM spacecraft

Data from Earth sensor assemblies (ESA's) often are used in the attitude determination (AD) for both spinning and Earth-pointing spacecraft. The ESA's on previous such spacecraft for which the ground-based AD operation was performed by the Flight Dynamics Division (FDD) used the Earth scanning method. AD on such spacecraft requires a model of the shape of the Earth disk as seen from the spacecraft. AD accuracy requirements often are too severe to permit Earth oblateness to be ignored when modeling disk shape. Section 2 of this paper reexamines and extends the methods for Earth disk shape modeling employed in AD work at FDD for the past decade. A new formulation, based on a more convenient Earth flatness parameter, is introduced, and the geometric concepts are examined in detail. It is shown that the Earth disk can be approximated as an ellipse in AD computations. Algorithms for introducing Earth oblateness into the AD process for spacecraft carrying scanning ESA's have been developed at FDD and implemented into the support systems. The Tropical Rainfall Measurement Mission (TRMM) will be the first spacecraft with AD operation performed at FDD that uses a different type of ESA - namely, a static one - containing four fixed detectors D(sub i) (i = 1 to 4). Section 3 of this paper considers the effect of Earth oblateness on AD accuracy for TRMM. This effect ideally will not induce AD errors on TRMM when data from all four D(sub i) are present. When data from only two or three D(sub i) are available, however, a spherical Earth approximation can introduce errors of 0.05 to 0.30 deg on TRMM. These oblateness-induced errors are eliminated by a new algorithm that uses the results of Section 2 to model the Earth disk as an ellipse

Consideration of NDVI thematic changes in density analysis and floristic composition of Wadi Yalamlam, Saudi Arabia

Wadi Yalamlam is known as one of the significant wadis in the west of Saudi Arabia. It is a very important water source for the western region of the country. Thus, it supplies the holy places in Mecca and the surrounding areas with drinking water. The floristic composition of Wadi Yalamlam has not been comprehensively studied. For that reason, this work aimed to assess the wadi vegetation cover, life-form presence, chorotype, diversity, and community structure using temporal remote sensing data. Temporal datasets spanning 4 years were acquired from the Landsat 8 sensor in 2013 as an early acquisition and in 2017 as a late acquisition to estimate normalized difference vegetation index (NDVI) changes. The wadi was divided into seven stands. Stands 7, 1, and 3 were the richest with the highest Shannon index values of 2.98, 2.69, and 2.64, respectively. On the other hand, stand 6 has the least plant biodiversity with a Shannon index of 1.8. The study also revealed the presence of 48 different plant species belonging to 24 families. Fabaceae (17&thinsp;%) and Poaceae (13&thinsp;%) were the main families that form most of the vegetation in the study area, while many families were represented by only 2&thinsp;% of the vegetation of the wadi. NDVI analysis showed that the wadi suffers from various types of degradation of the vegetation cover along with the wadi main stream.</p

The Students’ Needs in Developing EFL Materials ICT Based

In developing English communication skills, the student's needs, wants, and lacks are crucial. The materials given should be suitable for the students' wants. These issues are vital in developing any English materials on ICT-based. This study explores the students' needs, wants, and lacks in learning English by developing suitable materials with the ICT-based. The mixed approach was used in this study. The researchers distributed the survey to 350 students from Indonesia and other countries (Kosovo, Kuwait, Ghana, Pakistan, Philippines, India, and United Kingdom) involved in the Share to Care Community in collecting the data. They were assigned to fill the Google form about their needs in learning English. The result showed that the students need materials that fulfill their needs. It should be related to today's facts, easy enough to share with, and easy to access by the students' technologies devices, then using both target languages L2 and L1 to deliver the materials. While teaching, the lecturers used any method; role-playing is the most common, followed by oral reports, games, outdoor learning, and blended learning. Most of the students from several countries intended to have ICT in their learning process

Design Wind Loads Including Torsion for Rectangular Buildings with Horizontal Aspect Ratio of 1.6

Limited information is available regarding wind-induced torsional loads on buildings. This paper presents results of tests carried out in a boundary-layer wind tunnel using building models with the same plan dimensions (aspect ratio of 1.6) and located in a simulated open terrain exposure for different wind directions. Synchronized wind pressure measurements allowed estimating instantaneous base-shear forces and torsional moments on the tested rigid building models. Results were normalized and presented in terms of shear and torsional coefficients for two load cases, namely: maximum torsion and corresponding shear, and maximum shear and corresponding torsion. Comparison of the wind-tunnel test results with current torsion- and shear-related provisions in the American standard demonstrates good agreement for low-rise buildings but differences for medium-rise buildings

Synthesis, structural and morphological characterizations of nano-Ru-based perovskites/RGO composites

Highly-dispersed Ru-based perovskites supported on reduced graphene oxide (A-RG) nanocomposites are prepared using different A-metal salts (Sr(NO₃)₂, Ba(NO₃)₂ and Ca(NO₃)₂). The procedure is based on a redox reaction between the metal precursors and graphene oxide (GO) using two different routes of reaction initiation: through thermal heating or by microwave-assisted heating. The resulting nanocomposites do not require further calcination, making this method less energy-demanding. In addition, no additional chemical reagents are required for either the GO reduction or the metal precursor oxidation, leading to an overall simple and direct synthesis method. The structure and morphology of the as-prepared A-RG (non-calcined) nanocomposites are characterized using various structural analyses including XRD, XPS, SEM/EDX and HR-TEM. Changing metal A in the perovskite as well as the “activation method” resulted in significant structural and morphological changes of the formed composites. SrRuO₃ and BaRuO₃ in combination with RuO₂ are obtained using a conventional combustion method, while SrRuO₃ (~1 nm size) in combination with Ru nanoparticles are successfully prepared using microwave irradiation. For the first time, a microwave-assisted synthesis method (without calcination) was used to form crystalline nano-CaRuO₃

Comparison of Wind Tunnel Measurements with NBCC 2010 Wind-Induced Torsion Provisions for Low- and Medium-Rise Buildings

The aim of this study is to assess wind-induced torsional loads on low- and medium-rise buildings determined in accordance with the National Building Code of Canada (NBCC 2010). Two building models with the same horizontal dimensions but different gabled-roof angles (0° and 45°) were tested at different full-scale equivalent eave heights (6, 12, 20, 30, 40, 50, and 60 m) in open terrain exposure for several wind directions (every 15°). Wind-induced measured pressures were numerically integrated over all building surfaces and results were obtained for along-wind force, across-wind force, and torsional moment. Torsion load case (i.e., maximum torsion and corresponding shear) and shear load case (i.e., maximum shear and corresponding torsion) were evaluated to reflect the maximum actual wind load effects in the two horizontal directions (i.e., transverse and longitudinal). The evaluated torsion and shear load cases were also compared with the current torsion- and shear-related provisions in the NBCC 2010. The results demonstrated significant discrepancies between NBCC 2010 and the wind tunnel measurements regarding the evaluation of torsional wind loads on low- and medium-rise buildings. Finally, shear and torsion load cases were suggested for evaluating wind loads in the design of low- and medium-rise rectangular buildings