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This paper reports on the development of constructive EAP CALL courseware, and its integration into blended learning contexts, as a solution to the problems in EAP courses in Chinese universities. A case study of a defining skills package, developed for undergraduates at the University of Science and Technology Beijing (USTB), is used to illustrate the design and integration of the courseware. Guided by constructivist learning theory, the design draws on a synthesis of language-centered, academic skills-centered, content-based and task-based approaches. The integration is evaluated through the quality of students' written work and evidence of their satisfaction with their defining skills improvement and the CALL courseware, based upon the data from a questionnaire survey. Web-based digital tools and multimodal media have been exploited to devise and produce CALL materials on defining skills. After three weeks of blended learning, students' learning outcomes and satisfaction with the courseware and its integration were significantly positive.

This article reports the design of a course blended through a small private online course in a Chinese university EFL context, with an emphasis on the blended learning environment created thereby and on learners' perceptions of their blended learning. In a survey-based approach, 1603 students' experiences of blended EFL learning in two consecutive terms were examined. The questionnaire survey focused on the participants' perceptions of their engagement with blended learning, their motivation, learning autonomy and overall satisfaction. An analysis of students' responses reveals that the blended design can create an efficient EFL learning environment and gain positive learner perceptions.

The ultra-long gravity heat pipe has a long heat transfer distance and narrow working fluid flow channel within its tube. Due to these unique design features, the vapor–liquid counter-flow and heat transfer characteristics of these heat pipes are more complex than those found in conventional-size heat pipes. This paper innovatively proposes the design of a segmented visualization window structure of an ultra-long gravity heat pipe, which successfully overcomes the challenge of visualizing the internal flow during operations. A visualization experimental platform, measuring 40 m in height with an inner diameter of 7 mm and the aspect ratio up to 5714, was built to investigate the evolving characteristics of two-phase flows with an increasing heat input and the impact of the phase change flow characteristics on the thermal performance of ultra-long gravity heat pipes. The results obtained can provide guidance for the development of the internal structure of ultra-long gravity heat pipes that are being applied in exploiting geothermal energy. The results show that, at low heat input (200 W, 250 W), there are separate flow paths between the condensate return and the steam, but the high hydrostatic pressure due to the height of the liquid injection results in the presence of an unsaturated working fluid with a higher temperature in the liquid pool area, which has a lower evaporation rate, limiting the heat transfer through the heat pipe. It is found that if increasing the heat input up to 300 W, the evaporative phase change in the heating section becomes intense and stable. At the same time, despite the intermittent formation of liquid columns in the adiabatic section due to the vapor–liquid rolls, which increases the resistance to the vapor–liquid counter-flow, the liquid columns are blocked for a short period of time, and the path of steam rises and the condensate return is smooth, which does not seriously affect the steam condensation and liquid return evaporation. At this point, the overall temperature of the heat pipe is evenly distributed along the tube and the heat transfer performance is optimal. When the heat input further increases (350 W, 400 W), a large amount of condensate is trapped in the upper part of the adiabatic section and the condensing section by long liquid plugs for a long time. At this point, the condensate flow back to the heating section is significantly reduced, and the steam is seriously prevented from entering the condensation section, resulting in a significant increase in the temperature gradient between the lower part of the evaporating section and the upper part of the adiabatic section and deterioration of the heat transfer performance. [ABSTRACT FROM AUTHOR]

One-dimensional (1D) nanostructures have wide applications in photocatalysts for water splitting. Their surfaces may impact the gas bubble nucleation rate, thus influencing the efficiency of gas evolution. However, the effects of the 1D nanostructured surfaces on the bubble nucleation have not been studied to date. Herein, these effects are theoretically analyzed, based on the changes of free energy for a bubble nucleus forming inside/outside a nanotube. The results show that compared to flat surfaces, the inner tube wall favors the bubble nucleation, while the outer wall has an opposite effect. These differences become increasingly significant with tube radius Rt reducing when Rt < 10r* (r*-bubble equilibrium radius). The size effect is further verified experimentally for bubble nucleation on TiO2 nanotube arrays. The sensitivity of bubble nucleation to nanostructure dimensions should be considered in designing high-efficient photocatalysts. [ABSTRACT FROM AUTHOR]

One-dimensional (1D) arrayed photoelectrodes usually present superior performance in photoelectrochemical (PEC) water splitting. This superiority is known to be attributed to directional transport of photogenerated charge carriers. Herein, we show that in addition to this intrinsic charge transport property, a 1D arrayed structure introduces nanoscale capillary wetting, which is also believed to contribute to the improved PEC performance. Our theoretical model predicts that this morphology-dependent capillarity leads to the formation of a liquid film between the photoelectrode surface and the adhered bubble (the generated H2/O2 bubble), thus largely reducing the blockage of active sites at the bubble base. This prediction has been experimentally demonstrated by taking arrayed TiO2 nanorods as a model photoelectrode, with the observation of the PEC activity within the bubble base. This work extends our knowledge toward hydrodynamic functionality involved in morphology-controlled photoelectrodes for enhanced PEC performance. [ABSTRACT FROM AUTHOR]

The installation and operation of enhanced geothermal systems (EGS) involves many challenges. These challenges include the high cost and high risk associated with the investment capital, potential large working-fluid leakage, corrosion of equipment, and subsiding land. A super-long heat pipe can be used for geothermal exploitation to avoid these problems. In this paper, a high aspect-ratio heat pipe (30 m long, 17 mm in inner diameter) is installed vertically. Experiments are then carried out to study its heat-transfer performance and characteristics using several filling ratios of deionized water, different heating powers, and various cooling-water flowrates. The results show that the optimal filling-ratio is about 40% of the volume of the vaporizing section of the heat pipe. Compared with a conventional short heat pipe, the extra-long heat pipe experiences significant thermal vibration. The oscillation frequency depends on the heating power and working-fluid filling ratio. With increasing cooling-water flow rate, the heat-transfer rate of the heat pipe increases before it reaches a plateau. In addition, we investigate the heat-transfer performance of the heat pipe for an extreme working-fluid filling ratio; the results indicate that the lower part of the heat pipe is filled with vapor, which reduces the heat-transfer to the top part. Based on the experimental data, guidelines for designing a heat pipe that can be really used for the exploitation of earth-deep geothermal energy are analyzed. [ABSTRACT FROM AUTHOR]

• Heat transfer experiments of an extra-long gravity heat pipe are conducted. • The heat pipe is long (40 m in length) and thin (7 mm in diameter). • Heat pipe performance is correlated with the four multiphase flow regimes inside. • Heat pipe working in the film boiling regime performs the best. • Using water as working fluid is better than ethanol and acetone at high heat load. The exploitation of deep geothermal energy has created a great demand for super-long distance heat transportation technology. As one of the most highly-efficient heat transfer devices, the super-long gravity-assisted heat pipe is promising to achieve this heat transportation. The performance of the super-long heat pipe is related to the multiphase flow status inside, the details of which are yet unknown. In this paper, a systematic experimental study on the multiphase flow regimes and the performance of an extra-long heat pipe was conducted. The experimental heat pipe is 40 m in length, 7 mm in diameter, which mimics the major geometric characteristic of the super-long heat pipes that can be practically used for geothermal heat extraction. Thermal performance and surface temperature of the extra-long heat pipe using water, ethanol or acetone as working fluid were measured and analyzed. Particular focus was placed on correlating the heat transfer performance of the heat pipe with the multiphase flow regime inside it. It was found that the extra-long heat pipe works in the following four different flow regimes successively with the increase in inflow heat: (1) nucleating pool boiling regime; (2) geyser boiling regime; (3) evaporating film boiling regime; and (4) overheated boiling regime. The thermal performances of extra-long heat pipe are significantly affected by the flow regimes, while the transition between these flow regimes is influenced by the properties of working fluid, the fluid fill height, and the heat load. It is found that the heat pipe working in the evaporation film boiling regime shows the best thermal performance and the heat pipe using water as working fluid is more suitable for relatively high heat load use. The reachable maximum axial heat fluxes for the water, ethanol, and acetone heat pipes are found to be about 6.5 × 106, 2.21 × 106, 2.08 × 106 W·m−2, respectively. These characteristics of heat transfer and multiphase flow provide very useful hints for the design and development of super-long geothermal heat pipes. [ABSTRACT FROM AUTHOR]