•A review of 26 transposition models with complete formulation and code.•Some suboptimal and incorrect implementations in the literature are identified.•Models are evaluated by comparisons with one ...year of measured data from four locations.•Hypothesis testing is used for accuracy comparison and model performance ranking.
Predicting solar radiation on inclined surfaces is a critical task for photovoltaic energy systems design, simulation and performance evaluation. Many transposition models have been proposed in the literature; and there are abundant evaluation studies. However, these models are sometimes used incorrectly. Moreover, these errors tend to propagate through the literature. This paper aims to identify and correct some errors in the literature. It also provides a benchmark on transposition model accuracies. Twenty-six models are described using a consistent nomenclature. Model performance is ranked and pairwise accuracies are evaluated with one year of solar irradiance measurements from four locations. Although no universal model is found in this study, some are recommended. The paper comes with computer code and a small portion of experimental data.
This contribution compares 3-hourly estimates of aerosol optical depth at 550 nm (AOD550) and Ångström exponent (AE) from two similar reanalysis models, ECMWF's CAMS and NASA's MERRA-2, to reference ...remote-sensed observations from the worldwide AERONET network during the period 2003–2017. All data points are first subjected to a thorough quality assessment analysis. All valid AOD550 reanalysis estimates are also corrected to account for the difference in elevation between the nominal grid cell size (0.5 × 0.625°) and the reference AERONET ground station. Comparative results are obtained both on a continental basis and on climate disaggregation basis using the Köppen-Geiger (KG) classification. Based on 793 AERONET stations and ≈1.8 million valid 3-h data points, it is found that CAMS and MERRA-2 behave relatively similarly, with however some regional differences, depending on continent or KG class. AOD550's root-mean-square error (RMSE) varies in the range 0.031–0.268 for CAMS and 0.017–0.232 for MERRA-2, depending on continent. Globally, MERRA-2 performs better than CAMS, achieving an RMSE of 0.126, as compared to 0.144 for CAMS. In contrast, the two reanalyses have very similar overall RMSEs for AE, i.e., 0.382 for CAMS and 0.378 for MERRA-2. For local or regional studies, these results allow users to select the best possible source of data. For global studies, both aerosol products are found appropriate, albeit with different statistical properties.
•Daily aerosol optical depth products from CAMS and MERRA-2 are validated.•Years of reanalysis data are evaluated at 793 AERONET stations.•The validation is conducted based on continents and Köppen-Geiger classification.•For AOD, MERRA-2 performs better than CAMS over most continents and climates.•MERRA-2 and CAMS perform similarly for the Ångström exponent, with regional variance.
Background
Teaching online is a different experience from that of teaching in a face-to-face setting. Knowledge and skills developed for teaching face-to-face classes are not adequate preparation for ...teaching online. It is even more challenging to teach science, technology, engineering and math (STEM) courses completely online because these courses usually require more hands-on activities and live demonstrations. Although the demand for online STEM courses has never been higher, little has been done to develop effective instructional and online course design strategies for teaching STEM courses online. This paper reports the effectiveness of the instructional strategies adopted and the online course design features in a fully online statistics course from the students’ perspectives. The online statistics course was an introductory, quantitative research course that covered common statistical concepts and focused on the application of educational research concepts for graduate students in educational technology. In terms of the statistics concepts covered, the course was similar to an introductory statistics class for students majoring in science, technology, math and engineering (STEM). The participants were mostly K-20 (meaning from kindergarten to college) instructors who had knowledge of instructional strategies.
Results
Data collected from participants’ reflections and course evaluations revealed that a range of instructional strategies and course design features were effective and helped students learn statistics in an online environment. Specifically, case studies, video demonstrations, instructor’s notes, mini projects, and an online discussion forum were most effective. For online course design features, consistent structure, various resources and learning activities, and the application focused course content were found to be effective.
Conclusions
The implications of this study include effective instructional strategies and online course design for application-oriented STEM courses such as physics and engineering. The study results can be used to guide online teaching and learning as well as online course design for instructors, course designers, and students in STEM fields.
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•Leading Ecological Function (LEF) index is proposed.•Maximum Value Composite (MVC) method is used to identify the LEF.•LEF can represent the dominant ecological function of grid ...pixels.•Ecological function zoning based on LEFs is suitable for management practice.
The establishment of scientific and reasonable ecological function regionalization (EFR) plays an important role in giving full play to regional advantages and realizing the benign development of resource exploitation, ecological construction, and environmental protection. However, the existing EFR lacks the identification ability for the leading functions among various ecological functions, and it is difficult to determine the regional ecological advantages, which may hinder the practical application of EFR in ecological environment zoning management. In view of this, we propose a new leading ecological function (LEF) index and the corresponding calculation method to describe the main regional ecosystem services and functions; its application in EFR could enhance the regional spatial guidance effect. We took the Core Area of the Beijing-Hangzhou Grand Canal (CA-BHGC) in China as the study area and used the maximum value composite (MVC) method to identify the LEFs of acquired grid pixels. Furthermore, the LEFs of grid pixels were applied to county-level administrative regions to complete the EFR process. Based on the results, in the CA-BHGC, although the spatial distribution of ecological function values was extremely uneven, the contribution rate of the LEF of grid pixels to the comprehensive ecological function value was usually more than 50%, reliably representing the advantageous ecological functions of grid pixels. The LEFs of the CA-BHGC included biodiversity maintenance, food production, and water retention, with grid proportions of 51.64%, 41.04%, and 6.93%, respectively, highlighting the global ecological resource advantages. The functional areas designated based on LEFs showed a good spatial correlation with the natural geographical environment. The seven biodiversity maintenance areas were mostly located at the river confluence; the two water retention areas were in the south of the Qinling-Huaihe River Line, and the six food production areas were in the central plain. In addition, the EFR process comprehensively considered the LEFs, river reaches, and provincial divisions, and it might be easier to coordinate various conflicts of interest, including economic development and ecological protection, cross-administrative regions, and adjacent functional areas.
Forecasting has been an essential part of the power and energy industry. Researchers and practitioners have contributed thousands of papers on forecasting electricity demand and prices, and renewable ...generation (e.g., wind and solar power). This article offers a brief review of influential energy forecasting papers; summarizes research trends; discusses importance of reproducible research and points out six valuable open data sources; makes recommendations about publishing high-quality research papers; and offers an outlook into the future of energy forecasting.
China’s recently announced directive on tackling climate change, namely, to reach carbon peak by 2030 and to achieve carbon neutrality by 2060, has led to an unprecedented nationwide response among ...the academia and industry. Under such a directive, a rapid increase in the grid penetration rate of solar in the near future can be fully anticipated. Although solar radiation is an atmospheric process, its utilization, as to produce electricity, has hitherto been handled by engineers. In that, it is thought important to bridge the two fields, atmospheric sciences and solar engineering, for the common good of carbon neutrality. In this überreview, all major aspects pertaining to solar resource assessment and forecasting are discussed in brief. Given the size of the topic at hand, instead of presenting technical details, which would be overly lengthy and repetitive, the overarching goal of this review is to comprehensively compile a catalog of some recent, and some not so recent, review papers, so that the interested readers can explore the details on their own.
Osteoporotic vertebral compression fracture (OVCF) is a common cause of pain and disability and is steadily increasing due to the growth of the elderly population. To date, percutaneous ...vertebroplasty (PVP) and percutaneous kyphoplasty (PKP) are almost universally accepted as appropriate vertebral augmentation procedures for OVCFs. There are many advantages of vertebral augmentation, such as short surgical time, performance under local anaesthesia, and rapid pain relief. However, there are certain issues regarding the utilization of these vertebral augmentations, such as loss of vertebral height, cement leakage, and adjacent vertebral refracture. Hence, the treatment for OVCF has changed in recent years. Satisfactory clinical results have been obtained worldwide after application of the OsseoFix System, the SpineJack System, radiofrequency kyphoplasty of the vertebral body, and the Kiva VCF treatment system. The following review discusses the development of the current techniques used for vertebral augmentation.
Collective cell migration is a widely observed phenomenon during animal development, tissue repair, and cancer metastasis. Considering its broad involvement in biological processes, it is essential ...to understand the basics behind the collective movement. Based on the topology of migrating populations, tissue-scale kinetics, called the “leader–follower” model, has been proposed for persistent directional collective movement. Extensive in vivo and in vitro studies reveal the characteristics of leader cells, as well as the special mechanisms leader cells employ for maintaining their positions in collective migration. However, follower cells have attracted increasing attention recently due to their important contributions to collective movement. In this Perspective, the current understanding of the molecular mechanisms behind the “leader–follower” model is reviewed with a special focus on the force transmission and diverse roles of leaders and followers during collective cell movement.
► We propose three models to forecast hourly global solar radiation. ► Forecasts use ARIMA models. ► Only having cloud cover data is sufficient for the forecast. ► Increasing meteorological ...information will increase forecast accuracy.
We apply time series analysis to forecast next hour solar irradiance including cloud cover effects. Three forecasting methods are proposed using different types of meteorological data as input parameters, namely, global horizontal irradiance (GHI), diffuse horizontal irradiance (DHI), direct normal irradiance (DNI) and cloud cover. The first method directly uses GHI to forecast next hour GHI through additive seasonal decomposition followed by an Auto-Regressive Integrated Moving Average (ARIMA) model. The second method forecasts DHI and DNI separately using additive seasonal decomposition followed by an ARIMA model and then combines the two forecasts to predict GHI using an atmospheric model. The third method considers cloud cover effects. An ARIMA model is used to predict cloud transients. GHI at different zenith angles and under different cloud cover conditions is constructed using nonlinear regression, i.e., we create a look-up table of GHI regression models for different cloud cover conditions. All three methods are tested using data from two weather stations in the USA: Miami and Orlando. It is found that forecasts using cloud cover information can improve the forecast accuracy.
Strontium ranelate is a newly approved drug that can reduce the risk of vertebral fracture, which is attributed to its dual function in increasing the bone formation and decreasing the bone ...resorption. Strontium-containing hydroxyapatite was also demonstrated to stimulate the osteoblast activity and inhibit the osteoclast activity. However, the molecular mechanisms of strontium underlying such beneficial effects were still not fully understood. In this study, we investigated the effects of strontium on the osteogenic differentiation of human mesenchymal stem cells (MSCs) and its related mechanism; its osteogenic potential was also evaluated using a calvarial defect model in rats. We found that strontium could enhance the osteogenic differentiation of the MSCs, with upregulated extracellular matrix (ECM) gene expression and activated Wnt/β-catenin pathway. After transplanting the collagen-strontium-substituted hydroxyapatite scaffold into the bone defect region, histology and computed tomography scanning revealed that in vivo bone formation was significantly enhanced; the quantity of mature and remodeled bone substantially increased and ECM accumulated. Interestingly, strontium induced an increase of β-catenin expression in newly formed bone area. In this study, we showed for the first time that strontium could stimulate the β-catenin expression in vitro and in vivo, which might contribute to the enhanced osteogenic differentiation of MSCs and in vivo bone formation.
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