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Private tutoring has expanded and intensified in China. However, no government statistical data or other empirical studies fully capture its extent and characteristics. This paper analyses private tutoring received by students in Grades 1-12 as indicated by a nationwide representative survey entitled China Family Panel Studies. The paper employs a Hurdle model to examine determinants of demand for tutoring, focusing on factors related to students and their parents. The first step is concerned with the decision to receive tutoring or not; and the second step explores factors influencing expenditures on tutoring among those who decide to receive it.

Dioecious woody species often exhibit male-biased sex ratios under drought habitat, which may result in vulnerability in drying soils. However, whether biased sex ratios are associated with sex-specific responses in growth and defence against insect herbivory under drought stress conditions is unknown. We investigated the sexual responses in terms of growth and defence in Populus yunnanensis Dode in response to two water treatments (40% and 100% field capacity). Drought stress reduced the plant growth (e.g., height increment, gas exchange, photosynthetic nitrogen use efficiency, and water potential) of both sexes and reduced the leaf water content and defensive performance (increased damaged area by leaf-chewing generalists and decreased leaf contents of total phenolics, condensed tannins, and flavonoids) of the females but not the males. Moreover, female defensive performance was lower than that of the males under drought conditions. Additionally, the plant mortality rate increased for both sexes, and it was higher for females than for males during drought stress in response to all leaf defoliation treatments. Our results suggest that sexual responses in terms of growth and defence to drought are significantly different and that P. yunnanensis females have a lower defence capability than males, which may explain the male-biased sex ratio that exists in the natural population. Hence, this study provides new insight into forecasting population dynamics for dioecious plant species in drying habitats. Key words: defence, dioecy, global warming, Populus yunnanensis, sex-biased. On observe souvent un desequilibre dans le rapport des sexes en faveur des individus males chez les especes dioiques dans les habitats sujets a la secheresse, ce quipeutengendrerune vulnerabilite lorsque les sols s'assechent. Cependant, on ne sait pas si le desequilibre dans le rapport des sexes est associe a des reactions specifiques au genre en termes de croissance et de defense contre les insectes herbivores ou en situation de stress du a la secheresse. Nous avons etudie les reponses de croissance et de defense en fonction du genre chez Populus yunnanensis Dode en reaction a deux traitements hydriques (40 et 100 % de la capacite au champ). Le stress du a la secheresse a reduit la croissance (p. ex. accroissement en hauteur, echanges gazeux, efficacite de l'utilisation de l'azote pour la photosynthese, et potentiel hydrique) chez les deux sexes et la teneur en eau ainsi que la performance defensive (plus grande surface endommagee par les generalistes qui broient les feuilles et moins forte teneur en composes phenoliques totaux, tannins condenses et flavonoides) chez les individus femelles mais pas chez les individus males. De plus, la performance defensive des individus femelles etait inferieure a celle des individus males en situation de secheresse. En outre, le taux de mortalite des plants a augmente chez les deux sexes et il etait plus eleve chez les individus femelles que chez les individus males en reponse a tous les traitements de defoliation durant une secheresse. Nos resultats indiquent que les reponses specifiques au genre en termes de croissance et de defense en situation de secheresse sont significativement differentes et que les P. yunnanensis femelles ont une capacite de defense inferieure a celle des males, ce qui pourrait expliquer le desequilibre dans le rapport des sexes en faveur des individus males dans la population naturelle. Par consequent, cette etude fournit de nouvelles informations pour prevoir la dynamique de population des especes vegetales dioiques dans les habitats sujets a la secheresse. [Traduit par la Redaction] Mots-cles: reaction de defense, dioecie, rechauffement global, Populus yunnanensis, desequilibre dans le rapport des sexes., Introduction Despite constituting only 5%-6% of total plant species (Renner 2014), dioecious species such as those of the Salicaceae family play an important role in maintaining the stability of the [...]

Laser-induced ultrasound scanning imaging is proposed and utilized for the detection of the printed circuit board (PCB) delamination defect in this present study. Initially, based on the principle of laser-induced ultrasound scanning imaging, a three-dimensional mathematical model of the ultrasonic excitation by pulsed laser acting on the surface of PCB is established and analyzed. Furthermore, based on the established laser ultrasonic nondestructive testing system, single-point testing is investigated on the PCB specimen. A-scan experiments were carried out by transmission and reflection approaches, respectively. Moreover, the influence of the signal receiving position on the discrimination of defective signals and the effect of wavelet transform denoising parameters on the signal-to-noise ratio were investigated. Eventually, based on the laser-induced ultrasound scanning imaging inspection system, the defects of simulated debonding flat bottom holes are detected and studied. The different algorithms or parameters (Fast Fourier Transform, variance, extremum, and principal component analysis, etc.) are employed to extract the characteristic information are analyzed. The experimental results are compared with the traditional infrared thermal wave imaging (lock-in thermography). The experimental results indicate that laser-induced ultrasound scanning imaging has the advantages of high-resolution imaging for the defect with a small diameter. Therefore, it is of great significance to study a set of feasible laser-induced ultrasound scanning imaging for PCB delamination defect detection. [ABSTRACT FROM AUTHOR]

Constructing a solar-powered photothermal system that can self-regulate temperature without requiring extra energy input is significant for energy saving, but how to achieve zero-energy building remains challenging. Here, a photothermal system that integrates sunlight harvesting, photothermal conversion (PTC), and heat storage was constructed. Well-developed nanoscale pore silica aerogels with high transparency (visible-light transmittance 69.3%, near-infrared transmittance 86.9%), bending resistance (bending angle >30°), and low thermal conductivity were prepared by the interpenetration of C and Si molecular networks using vinyltrimethoxysilane as the silica source, which was used as a window material for the temperature self-regulating system to block heat loss and allow sunlight transmission. Simultaneously, the prepared CsxWO3 (CWO) film with PTC could convert sunlight into heat. Also, PEG 2000 is introduced into the system with a suitable phase transition temperature to further realize temperature self-regulation within a certain range. The outdoor simulation test results showed that the system could heat water to 69.8 °C using sunlight in cold weather around 0 °C, which was 67.6 °C higher than the ambient temperature and can stay above 18 °C for about 20 h, and even in cloudy weather, it could reach 58.2 °C. The highly transparent silica aerogel is given the ability to resist bending, which opens up more application prospects for silica aerogels, and the constructed self-regulating temperature system without additional energy input contributes to the development of the zero-energy building. [ABSTRACT FROM AUTHOR]