•A novel PV-TE system was presented.•Mathematical model of the system was built.•Performance under different ambient conditions was analyzed.•New PV-TE and the conventional PV were ...compared.•Preliminary economic analysis was demonstrated.
Photovoltaic-thermoelectric (PV-TE) hybrid system is one typical electrical production based on the solar wide-band spectral absorption. However the PV-TE system appears to be economically unfeasible owing to the significantly higher cost and lower power output. In order to overcome this disadvantage, a novel PV-TE system based on the flat plate micro-channel heat pipe was proposed in this paper. The mathematic model was built and the performance under different ambient conditions was analyzed. In addition, the annual performance and the preliminary economic analysis of the new PV-TE system was also made to compare to the conventional PV system. The results showed that the new PV-TE has a higher electrical output and economic performance.
Modern technology offers many ways to enhance teaching and learning that in turn promote the development of tools for educational activities both inside and outside the classroom. Many educational ...programs using the augmented reality (AR) technology are being widely used to provide supplementary learning materials for students. This paper describes the potential and challenges of using GeoGebra AR in mathematical studies, whereby students can view 3D geometric objects for a better understanding of their structure, and verifies the feasibility of its use based on experimental results. The GeoGebra software can be used to draw geometric objects, and 3D geometric objects can be viewed using AR software or AR applications on mobile phones or computer tablets. These could provide some of the required materials for mathematical education at high schools or universities. The use of the GeoGebra application for education in Laos will be particularly discussed in this paper. Keywords: GeoGebra, Geometry, Mathematic, Learning Media, Augmented Reality
•Different growth rates and variation exist across individuals’ academic achievement.•Children with higher early academic achievement showed faster increases over time.•Initial levels in executive ...function and approaches to learning affect achievement.•Growth rates in executive function and approaches to learning affect achievement.•Approaches to learning mediate the link between executive function and achievement.
For effective promotion of children’s learning and academic achievement, it is important to understand the role of and relationship between children’s cognitive and affective characteristics in their learning and academic achievement. The current study applied latent growth curve modeling to examine trajectories of children’s reading and math achievement, executive function (EF), and approaches to learning (ATLs) from kindergarten year to first grade. We also examined whether and the extent to which the initial levels and growth rate of EF and ATLs independently predicted the initial level and growth rate of reading and math achievement and whether the initial level and the growth rate of ATLs mediate in the relationships between EF and academic achievement. Results from a nationally representative and longitudinal sample of the Early Childhood Longitudinal Study-Kindergarten Cohort of 2011 indicated that children’s levels of reading and math achievement, EF, and ATLs significantly differ in the fall of kindergarten. Significant variances in rates of change of main variables over time suggest that some children showed faster increases than others in some variables, while others may have even shown decreases over time. Children with a higher level and faster growth rate in EF and ATLs showed a faster rate of change in reading and math achievement. Last, EF trajectories influence academic achievement trajectories directly and indirectly through ATL trajectories. Given that this study found an important role of children’s ATLs in academic achievement, we need to promote effective teaching practices and curricula to support students’ ATLs at each grade level in classrooms and schools, with particular attention to at-risk children.
Mathematics is a subject that is full of challenges and practical tasks that students must be able to do, this of course must be in line with the availability of various appropriate and innovative ...learning tools and resources which can then be used by students to deepen the material. Through research that aims to develop an interactive multimedia, it is hoped that it can become one of the appropriate learning media for students to use. This type of research is a Research and Development (RnD) method that adopts a 4D development model (Define, Design, Develop, Disseminate), with a focus on extracting data on Development (D) which contains an assessment of the feasibility of media products, with data collection techniques, namely non- test through a questionnaire, accompanied by a questionnaire instrument validation sheet. The data will be analyzed descriptively using percentage conversion in order to describe the feasibility of multimedia products. The results show that interactive multimedia that has gone through an assessment process from each evaluator with details, namely the assessment of media experts 90.1%, material expert assessments 83.3%, linguistic experts assessment 98%, media developer assessments 89.9% and assessment of elementary school teachers 97%. Through the results of the assessment, it can be concluded that the product of innovation in the form of interactive multimedia for learning in elementary schools is included in the category suitable for use as learning media
The implementation of large-scale intervention and development projects is often problematic, and the impacts of such projects usually fall somewhat short of what was expected. Additionally, the ...rationalities of intervention projects are not carried over into classroom teaching as directly as expected. This problem is generally known, but comprehensive explanations continue to elude the research community at large. Using the theory of cultural-historical activity theory (CHAT), we propose that the heart of the problem lies in the
expansive learning process
that teachers undergo. This process is driven by unrecognised contradictions in terms of cultural and historical origin, which are fundamentally different from the processes governing the projects. We analyze two cases taken from two large Danish professional development projects. In each case, we focus on a teacher as part of two activity systems (‘the project’ and ‘the classroom’) and how the contradictions within and between these shape learning through epistemic actions. The results indicate the importance of making these contradictions apparent and accessible to everyone in the activity systems. Because of these various contradictions, the agency conferred upon teachers leads to unintended outcomes.
With the growing development in demand response, load serving entities (LSEs) may participate in electricity market as strategic bidders by offering coupon-based demand response (C-DR) programs to ...customers. However, due to customers' versatile electricity consumption patterns under C-DR programs as well as the increasing penetration of wind power generation, obtaining the deterministic bidding decision becomes unprecedented complex for LSEs. To address this challenge, a new strategic bidding model for an LSE is proposed in which the primary objective is to maximize the LSE's profit by providing optimal C-DR considering high wind power penetration. The proposed strategic bidding is a bi-level optimization problem with the LSE's net revenue maximization as the upper level problem and the ISO's economic dispatch (ED) for generation cost minimization as the lower level problem. This bi-level model is converted to a stochastic mathematic program with equilibrium constraints (MPEC) by recasting the lower level problem as its Karush-Kuhn-Tucher (KKT) optimality conditions. Then, the stochastic MPEC is transformed to a mixed-integer linear programming (MILP) problem, which is solvable using available optimization software, based on strong duality theory. In addition, the effectiveness of the proposed method has been verified with simulation studies of two sample systems.
•A novel membrane process was investigated to separate NaOH/Na2WO4 continuously.•The alkali recovery ratio here was much higher than that of conventional process.•A model based on irreversible ...thermodynamics was built to simulate the process.•The calculated results of the model fit very well with the experimental results.•The novel membrane process was proved to have the potential to be industrialized.
Conventional diffusion dialysis has two main shortages, including low processing capacity and serious water osmosis. Pressure-concentration double driven (PCDD) diffusion dialysis was proved to cover the two shortages effectively. To further study the PCDD diffusion dialysis, the continuous separation of the common alkali/ metal salt mixture (NaOH/Na2WO4) was realized by adopting it in this work. Results illustrate that 0.04 MPa is an optimum pressure difference. That is because the pressure difference realized the highest recovered NaOH concentration and a high alkali recovery ratio, and a good separation effect were obtained simultaneously. The increment of initial alkali concentration in the feed from 0.5 to 2.0 mol/L can enhance the alkali recovery ratio from 24.93% to 35.15%. As the initial salt concentration in the feed increases from 0.05 to 0.20 mol/L, the recovered NaOH concentration at the operation time of 180 mins improves from 0.24 to 0.36 mol/L, and the alkali recovery ratio increases from 27.86% to 30.34% slowly. Second, a mass transfer mathematical model was established to simulate the continuous PCDD diffusion dialysis separation process. There shows acceptable and satisfactory agreement between the experimental and calculated fluxes, experimental and calculated alkali recovery ratios and salt leakage ratios. The work presented here suggests that the continuous PCDD diffusion dialysis is feasible and promising to be industrialized in the future.
Low mathematical literacy is one of the causes of the lack of interest and motivation in learners. Mathematical literacy and realistic mathematical approaches have relevant characteristics. This ...research aims to develop memes as learning media with a realistic mathematical approach to develop mathematical literacy in elementary school students. The research consists of several steps, which are: analysis, design, development, implementation, and evaluation. The methods used are descriptive, evaluative, and experimental with a pre-experimental design. The instruments used were expert validation questionnaires, student response questionnaires, teacher observation sheets, and evaluation assessments. The results obtained from material experts were 79% and 78% from media expert, both in the appropriate category. Assessments of mathematical content obtained the validation results from the material experts and media experts with scores of 79% and 78%; both belong to the decent category. In large-scale trials, the results of the student response questionnaire after learning obtained a score of 73% while the evaluation results obtained a score of 60%. The students' evaluation scores are evenly distributed from the lower limit of 25 to the upper limit of 95. Based on the results, it can be concluded that meme teaching media with a realistic mathematical approach develop students’ mathematical literacy even though it is not a high level.
•A novel T-form hydraulic conductivity (kw) function of frozen soils (HCFF) is proposed.•The proposed T-form HCFF is extended to consider vapor flow and bimodality.•HCFF prediction is supported by ...statistical kw models and thermodynamic equilibrium.•HCFF prediction is clarified as 3 routes: single SWCC, single SFCC and combining two.
Hydraulic conductivity function for frozen soils (HCFF) is crucial for accurately simulating the water transfer process in cold regions, impacting hydrological states and frost heave diseases. However, the HCFF model capturing the relation between hydraulic conductivity and unfrozen water content (θ) or temperature (T) remains an open question. This study delves into HCFF encompassing both empirical and prediction models. This study begins with introducing θ-form and innovative T-form empirical HCFF models, showcasing their solid performance in fitting measured hydraulic conductivity data. Furthermore, the extension of the T-form empirical model to incorporate vapor flow and bimodal soils, through the introduction of maximum vapor conductivity and weighting factors, demonstrates a closer alignment with physical mechanisms and observed trends. In terms of predicting HCFF, the study provides a theoretical foundation through statistical hydraulic conductivity models and thermodynamic equilibrium in frozen soils. Additionally, it clarifies three routes for HCFF prediction—single Soil Freeze Characteristic Curve (SFCC), single Soil Water Characteristic Curve (SWCC), and a combination of the two—and validates their effectiveness through test results and comparison of HCFF prediction outcomes using SWCC and SFCC data from specific soil samples. In practice, the empirical and prediction models are recommended for available hydraulic conductivity data and available SFCC or SWCC data, respectively. Overall, this study not only lays the theoretical groundwork for most prediction models but also presents a valid empirical equation for modeling hydraulic conductivity function tailored specifically for frozen soils.
Executive functions (EFs) are linked to children’s overall math performance, although few studies have considered the joint role of prior math abilities for specific math subskills, such as ...arithmetic. The current study examined the longitudinal contributions of preschool EFs and early math abilities to children’s accuracy and reaction time on arithmetic problems. Two hundred and eighty-three children completed EF and numeracy assessments at 5.25 years old. Children completed an arithmetic problem task in first (Mage = 7.14), second (Mage = 8.09), and third grade (Mage = 9.08). Results indicated that preschool EFs and math abilities are uniquely linked to children’s accuracy and reaction time at age 7, whereas preschool EFs alone continue to predict accuracy at age 8 and reaction time at age 9, even after accounting for intervening arithmetic performance. The study highlights the sustained, unique importance of early EFs for children’s arithmetic acquisition.
•Early executive functions linked to accuracy on arithmetic problems at age 7.•Early math skills linked to accuracy and speed on arithmetic problems at age 7.•Cascading benefits of EFs and math for arithmetic skills later in elementary school.•Unique importance of EFs for later arithmetic acquisition at ages 8 and 9.•Implications for joint interventions to support early EF and math skills.
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