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Cause identification of electromagnetic transient events using spatiotemporal feature learning
No full textThis paper presents a spatiotemporal feature learning method for cause identification of electromagnetic transient events in power grids. The proposed method is formulated based on the availability of time-synchronized high-frequency measurements and using the convolutional neural network as the spatiotemporal feature representation along with softmax function for the classification. Despite the existing threshold-based, or energy-based events analysis methods, such as support vector machine autoencoder, and tapered multi-layer perceptron neural network, the proposed feature learning is carried out with respect to both time and space. The effectiveness of the proposed feature learning and the subsequent cause identification is validated through the Electromagnetic Transients Program (EMTP) simulation of different events such as line energization, capacitor bank energization, lightning, fault, and high-impedance fault in the IEEE 30-bus, and the real-time digital simulation of the Western System Coordinating Council (WSCC) 9-bus system. © 2020 Elsevier Lt
Hydrogen as a battery for a rooftop household solar power generation unit
No full textDecentralization of electrical power generation using rooftop solar units is projected to develop to not only mitigate power losses along transmission and distribution lines, but to control greenhouse gases emissions. Due to intermittency of solar energy, traditional batteries are used to store energy. However, batteries have several drawbacks such as limited lifespan, low storage capacity, uncontrolled discharge when not connected to a load and limited number of charge/discharge cycles. In this paper, the feasibility of using hydrogen as a battery is analyzed where hydrogen is produced by the extra diurnal generated electricity by a rooftop household solar power generation unit and utilized in a fuel cell system to generate the required electrical power at night. In the proposed design, two rooftop concentrated photovoltaic thermal (CPVT) systems coupled with an organic Rankine cycle (ORC) are used to generate electricity during 9.5 h per day and the extra power is utilized in an electrolyzer to produce hydrogen. Various working fluids (Isobutane, R134a, R245fa and R123) are used in the ORC system to analyze the maximum feasible power generation by this section. Under the operating conditions, the generated power by ORC as well as its efficiency are evaluated for various working fluids and the most efficient working fluid is selected. The required power for the compressor in the hydrogen storage process is calculated and the number of electrolyzer cells required for the hydrogen production system is determined. The results indicate that the hybrid CPVT-ORC system produces 2.378 kW of electricity at 160 suns. Supplying 65% of the produced electricity to an electrolyzer, 0.2606 kg of hydrogen is produced and stored for nightly use in a fuel cell system. This amount of hydrogen can generate the required electrical power at night while the efficiency of electrolyzer is more than 70%. © 2019 Hydrogen Energy Publications LL
Performance evaluation of a solarized gas turbine system integrated to a high temperature electrolyzer for hydrogen production
No full textIn this paper, the performance of a solar gas turbine (SGT) system integrated to a high temperature electrolyzer (HTE) to generate hybrid electrical power and hydrogen fuel is analyzed. The idea behind this design is to mitigate the losses in the electrical power transmission and use the enthalpy of exhaust gases released from the gas turbine (GT) to make steam for the HTE. In this context, a GT system is coupled with a solar tower including heliostat solar field and central receiver to generate electrical power. To make steam for the HTE, a flameless boiler is integrated to the SGT system applying the SGT extremely high temperature exhaust gases as the oxidizer. The results indicate that by increasing the solar receiver outlet temperature from 800 K to 1300 K, the solar share increases from 22.1% to 42.38% and the overall fuel consumption of the plant reduces from 7 kg/s to 2.7 kg/s. Furthermore, flameless mode is achievable in the boiler while the turbine inlet temperature (TIT) is maintained at the temperatures higher than 1314 K. Using constant amounts of the SGT electrical power, the HTE voltage decreases by enhancing the HTE steam temperature which result in the augmentation of the overall hydrogen production. To increase the HTE steam temperature from 950 K to 1350 K, the rate of fuel consumption in the flameless boiler increases from 0.1 m/s to 0.8 m/s; however, since the HTE hydrogen production increases from 4.24 mol/s to 16 mol/s it can be interpreted that the higher steam temperatures would be affordable. The presented hybrid system in this paper can be employed to perform more thermochemical analyses to achieve insightful understanding of the hybrid electrical power-hydrogen production systems. © 2020 Hydrogen Energy Publications LL
Design and analysis of renewable hydrogen production from biogas by integrating a gas turbine system and a solid oxide steam electrolyzer
No full textIn this paper, design and performance analysis of a biogas (60%CH4 + 40%CO2) fueled gas turbine (GT) power generation system integrated with a flameless boiler for steam generation for hydrogen production in a solid oxide steam electrolyzer (SOSE) is reported. In this design, the exhaust gases from GT is conducted to a flameless boiler where diluted and preheated exhaust gases are employed as an oxidizer in this process. Using a small amount of biogas in the flameless boiler enables the hybrid system to produce required steam for SOSE process and the whole generated electrical power by GT is employed in SOSE as well to produce hydrogen. The effects of biogas blends and flowrate, turbine inlet temperature (TIT), steam temperature and the electrode characteristics on the performance of the hybrid system are evaluated. The results indicate that by purification of biogas and increasing CH4 concentration up to 80%, the generated electrical power and produced hydrogen of the hybrid system augment 24% and 20% respectively. In GT system, the TIT should be set at the temperatures higher than 1300 K to prepare a desirable circumstance for the operation of flameless mode in the boiler. At the constant electrical power, when steam temperature increases, the overall SOSE potential decreases and consequently the current of the SOSE enhances which result in the enhancement of the overall hydrogen production in high steam temperatures. To increase the steam temperature from 850 K to 1450 K, the rate of overall biogas consumption of the system increases 1% while the amount of overall hydrogen production from SOSE system augments from 0.01 to 0.052 mol/s. The presented analysis in this paper can be employed to perform more analyses to achieve insightful understanding of the green hydrogen production using hybrid systems. © 2020 Elsevier Lt
Predictive Ability of Multiple Factors on Secondary Students\u27 ACT Scores at a Large Suburban High School
Get PDFAs college-bound high school seniors know, the ACT examination is possibly the single most important assessment students take during their academic careers. ACT scores can determine college entrance, scholarship dollars, and whether students will be placed in remedial courses. Parents pay large sums of money to prepare their children for this exam, and states use the scores as a metric to quantify the quality of schools and districts. Since 2015, all high school students in Arkansas take the ACT in the spring of their junior year. Given the significance of this exam, students, parents, and school personnel would benefit from knowing what factors could potentially predict ACT scores. This study measured the predictability of several factors on ACT subject area and Composite scores. The researcher used Multivariate General Linear Hypotheses to measure the predictability of gender, socio-economic status, eighth grade ACT Aspire scores (including Readiness scores), and the number of Pre-AP and AP courses taken on ACT subject area and Composite scores. The data indicated that the students’ eighth grade ACT Aspire Composite score contributed most significantly to ACT score predictability. After the Aspire Composite scores, the number of Pre-AP and AP courses taken was the second greatest contributor to predictability
Alternative Learning Environments as a Tool for Student Success for Struggling Learners in Northwest Arkansas School Districts
Get PDFEducating all students is the foundation of education. However, an epidemic is sweeping throughout America’s schools that is threatening the very underpinning of our society. The number of students that leave school each year without a high school diploma is placing an immense personal and economic burden on the student, as well as the economic impact on society. Alternative learning environments have emerged as an intervention to provide a foundation for success for the struggling learner. This quantitative study was conducted to evaluate the perception of high school alternative learning students and high school alternative learning teachers’ perceptions of program effectiveness. Forty-seven student and 5 teacher respondents completed the 37 question Likert-type survey covering engagement, academic rigor, relationships with teachers, relationships with peers, school culture, academic interventions and behavior interventions. Independent t-tests were used to determine if the means of the variables were statistically different. Cohen’s d was used to evaluate effect size in the sample, due to the large differences in sample size between students and teachers. The findings from the study revealed that engagement, academic rigor, relationships with teachers, academic interventions, and behavior interventions were not significant, while peer relationships and school culture were significant. Cohen’s d results indicated engagement, academic rigor, peer relationships, and school culture had a large effect size, while teacher relationships, academic interventions, and behavior interventions had a medium effect size. No components revealed a small effect size. The results indicate that perception gaps do exist within the individual components, with effect size being a factor in the analysis of the results
Carya texana
No full textWittich Township, AR, USAhttps://orc.library.atu.edu/carya/1048/thumbnail.jp
Cercis canadensis
No full textCR-502, Berryville, AR, UShttps://orc.library.atu.edu/cercis/1018/thumbnail.jp