Background This study aims to identify predictors of smoking initiation and nicotine dependence (ND) to develop a comprehensive risk-factor model based on Kendler’s development model for major depression. Methods Data were drawn from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), Wave 2 (n = 34,653). Risk factors were divided into 5 developmental tiers according to Kendler’s model (childhood, early adolescence, late adolescence, adulthood, past-year). Hierarchical logistic regression models were built to predict the risk of smoking initiation and the risk of ND, given initiation. The continuation ratio (CR) was tested by ordinal logistic regression to examine whether the impact of the predictors was the same on smoking initiation or ND. Results The final models highlighted the importance of different tiers for each outcome. The CR identified substantial differences in the predictors of smoking initiation versus ND. Childhood tier appears to be more determinant for smoking initiation while the effect of more distal tiers (i.e. childhood and early adolescence) was tempered by more proximal ones (i.e. late adolescence, adulthood and past-year) in ND, with few sex differences. Conclusions The differential effect of some predictors on each outcome shows the complexity of pathways from smoking initiation to ND. While some risk factors may be shared, others impact only at one stage or have even an inverse effect. An adaptation of Kendler’s developmental model for major depression showed high predictive power for smoking initiation and ND.

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Promoting the intelligent upgrades of small and medium-sized enterprises is one of the important tasks of implementing “Made in China 2025” in China. As a front runner of nation-level reform, Zhejiang Province has provided much room for innovation and development, along with the emergence of a new type of ecology, accelerated formation of two ecosystems and international cooperation, and a supportive policy environment. Therefore, this paper uses 173 Small and Medium-sized Enterprises (SMEs) from Zhejiang Province as the research objects, builds a binary selection model, and analyzes the dynamic and constraining mechanism of intelligent upgrades of SMEs with regard to employee qualification, technology, capital, policy environment, and so on. The study finds that: First, among three main industries, manufacturing is the major industry for the intelligent upgrades of SMEs and there are significant demonstration effects and industry heterogeneity. Secondly, the willingness to upgrade intelligently for SMEs is relatively strong. More than half of SMEs that have not intelligently upgraded show willingness to implement intelligent upgrades. Thirdly, factors such as corporate profitability, human capital quality, and industry intelligence level have significantly promoted the intelligent upgrades of SMEs, while the impact of labor cost, capital structure, government subsidies, and other variables are not significant. This conclusion still works after a number of robustness tests. Last but not least, based on the above conclusions, this paper proposes corresponding policy recommendations which are practically beneficial to the development of SMEs in China.

A method of deicing using microwave heating is proposed to make scientific and economical road deicing in a cold area, and to make up for deficiencies in the existing methods for melting snow and ice. This paper proposes to define microwave deicing efficiency as the heating rate of a concrete surface when heated to 0 °C (the efficiency of deicing is equal to the difference divided by heating time, which is between 0 °C and the initial temperature at the junction of ice and concrete). Based on the mechanism of microwave heating and deicing, a method combining the finite element simulation model with indoor experiments was proposed to study the deicing efficiency of microwaves, and the effects of different microwave frequencies and different road structure materials on microwave deicing efficiency were analyzed. The results show that the microwave frequency and road structure materials have a great influence on microwave deicing. For asphalt concrete, the ice melting efficiency of 5.8 GHz is 4.31 times that of 2.45 GHz, but the heating depth is less than that of 2.45 GHz. At 2.45 GHz, the melting efficiency of cement concrete is 3.89 times that of asphalt concrete. At 5.8 GHz, the melting efficiency of cement concrete is 5.23 times that of asphalt concrete. Through the consistency of the simulation and experimental results, the validity of the simulation model based on the finite element theory is verified. The results provide theoretical guidance and a practical basis for future applications of microwave deicing.