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Online learning has become the new educational pattern during the COVID-19 pandemic and is likely to supplement conventional schooling in the post-pandemic world. Lacking prior online learning experiences, the population of K-12 students deserves our special attention. Using purposeful sampling, this study investigated K-12 online learning experiences in China based on a large-scale survey (N = 118,589). Leveraging both quantitative and qualitative evidence, this study supported online learning as a flexible alternative to conventional schooling in emergency situations with a discussion of its benefits and limitations, and revealed key findings regarding K-12 students' online learning pattern, experiences, and engagement, as well as the influencing factors. The research findings can inform the future design and implementation of online learning programs in primary and secondary schools.

The proliferation of massive open online courses (MOOCs) highlights the necessity of developing accurate and diagnostic evaluation methods to assess the courses' quality and effectiveness. Hence, this study proposes a diagnostic MOOC evaluation (DME) method that combines the Analytic Hierarchy Process algorithm and learner review mining to integrate expert opinions, standardized rubrics, and learner feedback into the evaluation process. For this purpose, 30 MOOCs from the Coursera website were purposively selected and evaluated using the DME method and the results compared with expert evaluation and learner rating scores. The preliminary findings, in general, support the feasibility, accuracy, and diagnostic utility of the DME method and its suitability as a low-cost, sophisticated, and accurate method for MOOC evaluation. Finally, the study discusses several limitations and technical issues of the DME method that should be addressed in future research and practice.

For offshore HPHT wells, the string has been serving in a harsh environment for a long time, which leads to string mechanical properties degradation and a worse wellhead growth phenomenon. In this article, the mechanical properties of P110 and N80 strings varied with temperature through the MTS experiment. And based on wellbore temperature and pressure conduction method, a new high-accuracy wellhead growth calculation model is established combined with thermal-induced string mechanical properties degradation. The difference between the calculated results and the measured data is less than 8%. And the influence of string mechanical properties degradation on wellbore safety is studied. The results show that high temperature leads to a sudden drop in wellbore safety factors and a sharp increase in wellhead growth. And the maximum critical safety production is recommended to be 85 × 10 4 m 3 / d when the case well is worked for 500 days. Attenuation of the string elastic modulus leads to a slight decrease in axial force and a slight increase in wellhead growth. The increase in the thermal expansion coefficient of string has a noticeable influence on wellhead growth. Reducing string thermal expansion capacity and increasing material stiffness can alleviate the wellhead growth phenomenon. [ABSTRACT FROM AUTHOR]

Sustaining the steady state for highly active non‐stoichiometric iridium (Ir)‐based oxide (IrOx) at low Ir loading remains challenging primarily due to the continuous oxidation and sequent dissolution of Ir active sites during the oxygen evolution reaction (OER). In this context, a new iridium–cerium (Ce) substitution solid solution oxide (SSO) has been developed, featuring uniformly dispersed Ir atoms within Ce dioxide (CeO2) matrix as electron buffer, which delivers remarkable acidic OER catalytic activity and enhanced stability. The electron‐buffering capacity of CeO2 facilitates the charge transfer toward Ir atoms, leading to abundant active low‐valence Ir sites and effectively prevent their oxidation and dissolution. As a result, Ir─Ce SSO demonstrates an overpotential of merely 238 mV@10 mA cm−2. Proton exchange membrane water electrolyzer employing Ir─Ce SSO at a low Ir loading of 396 µgIr cm−2 operates consistently for over 100 h@500 mA cm−2. Density functional theory (DFT) calculations corroborate that the electron‐buffering effect of CeO2 enriches the density of IrIII and substantially increases the dissolution energy barrier of Ir atoms. This study presents a viable approach to addressing the issues of instability and low efficiency in Ir‐based OER electrocatalysts for acidic water electrolysis. [ABSTRACT FROM AUTHOR]

Due to the high cost and complex challenges faced by offshore wind power transmission, economic research into offshore wind power transmission can provide a scientific basis for optimal decision-making on offshore wind power projects. Based on the analysis of the topology structure and characteristics of typical wind power transmission schemes, this paper compares the economic benefits of five different transmission schemes with a 3.6 GW sizeable onshore wind farm as the primary case. Research includes traditional high voltage alternating current (HVAC), voltage source converter high voltage direct current transmission (VSC-HVDC), a fractional frequency transmission system (FFTS), and two hybrid DC (MMC-LCC and DR-MMC) transmission scenarios. The entire life cycle cost analysis model (LCCA) is employed to thoroughly assess the cumulative impact of initial investment costs, operational expenses, and eventual scrap costs on top of the overall transmission scheme's total cost. This comprehensive evaluation ensures a nuanced understanding of the financial implications across the project's entire lifespan. In this example, HVAC has an economic advantage over VSC-HVDC in the transmission distance range of 78 km, and the financial range of a FFTS is 78–117 km. DR-MMC is better than the flexible DC delivery scheme in terms of transmission capacity, scalability, and offshore working platform construction costs in the DC delivery scheme. Therefore, the hybrid DC delivery scheme of offshore wind power composed of multi-type converters has excellent application prospects. [ABSTRACT FROM AUTHOR]

GPS has a sharp performance decline in terms of accuracy indoors due to the complex building structure. A combined algorithm, targeting at received signal strength indication (RSSI) calibration optimisation, depending on deep neural network training via input vector Γ and the target output vector Ψ, termed reference signal optimisation algorithm (RSOA) is proposed to improve the positioning accuracy in the indoor Bluetooth positioning networks. Experimental results show that the relative error of the proposed RSOA between the estimated results and the measured ones can reach as low as 0.2%, and the absolute errors can be reduced to 0.13 m at most within 10 m.

This study investigates the effect of geographic distance on students' distance learning experience with the aim to provide tentative answers to a fundamental question--does geographic distance matter in distance education? Using educational outcome data collected from an online master's program in Geographic Information Systems, this study calculates the distance between students' residences and the program location, and employs three hierarchical multiple regression models to examine how well geographic distance can predict a student's online learning performance, satisfaction with the program, and length of time to complete, when controlling for other relevant factors. Our research findings provide empirical evidence to support the claim that the development of information and communication technologies (ICTs) has in fact overcome the potential barriers that may be associated with distance in education and has provided an effective bridge between students and educational programs. The study also reveals interesting discoveries regarding the relationship between students' distance learning experience and certain student characteristics such as age, gender, and previous academic achievement.