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The purpose of this paper is to contribute to the existing stock return predictability and idiosyncratic risk literature by examining the relationship between stock returns and components derived from the decomposition of stock returns variance at the portfolio and firm levels.

A theoretical model is used to decompose the variance of stock returns into two volatility and two covariance terms by using a conditional Fama-French three-factor model. This study adopts portfolio analysis and Fama-MacBeth cross-sectional regression to examine the relationship between components of idiosyncratic risk and expected stock returns.

The portfolio analysis results show that volatility terms are negatively related to expected stock returns, and alpha risk has the most significant relationship with stock returns. On the contrary, covariance terms have positive relationships with expected stock returns at the portfolio level. Furthermore, the results of the Fama-MacBeth cross-sectional regression show that only alpha risk can explain variations in stock returns at the firm level. Another finding is that when volatility and covariance terms are excluded from idiosyncratic volatility, the relation between idiosyncratic volatility and stock returns becomes weak at the portfolio level and disappears at the firm level.

This is the first study that examines the relations between all the components of idiosyncratic risk and expected stock returns in equal-weighted and value-weighted portfolios. This research also suggests covariance terms of idiosyncratic volatility as new predictors of stock returns at the portfolio level. Moreover, this paper contributes to the idiosyncratic risk literature by examining whether all the four additional components explain all the systematic patterns included in the unconditional idiosyncratic risk.

The authors investigate how market quality diverges between foreign firms and domestic firms on the US stock market in response to the Russia–Ukraine conflict.

With an event study approach, the authors compare foreign firms with domestic firms in their market responses over the three-day window around the outbreak of the war. Further, with Difference-in-Difference (DID) analyses, the authors study the change in foreign firms' market quality upon this outbreak in comparison with their domestic counterparts. Finally, the authors compare the foreign firms across firm specific characteristics and home country characteristics.

The authors find that foreign stocks listed in the US experience more severe market quality deterioration compared to the stocks' domestic counterparts. This effect is especially strong for companies from countries considered friendlier towards Russia and companies that are not cross-listed. The authors' findings are consistent with the information asymmetry hypothesis concerning market quality. Moreover, US market investors have more concerns over political risks with non-US-aligned political standings during war times.

The authors' findings are consistent with the information asymmetry hypothesis concerning market quality. Moreover, US market investors have more concerns over political risks over non-US-aligned political standings during war time.

Since both countries in the conflict are in Europe, the US stock market, to a certain degree, becomes a safe haven for capital from Europe and other countries. In the meantime, American Depository Receipts (ADRs) have been important for US investors to create a globally diversified portfolio, and the knowledge regarding ADRs' vulnerability to international geopolitical events is valuable. The author' results are informative for stock market investors to understand the market dynamics for international and domestic companies during this extremely uncertain time.

This is the first study that examines the market quality divergence between foreign firms and domestic firms on the US stock market in response to the Russia–Ukraine conflict. The authors provide novel evidence on the change in ADRs' market quality associated with significant political uncertainty. The authors show that ADRs' market quality is more vulnerable to international geopolitical risks relative to otherwise comparable domestic firms.

As a clean and renewable energy source, wind energy will become one of the main sources of new energy supply in the future. Relying on the stable and strong wind resources at sea, wind energy has great potential to become the primary energy. As a critical part of the wind turbine, the gearbox of a wind turbine often bears a large external load. Especially at sea, due to the effects of ocean corrosion, waves and wind, the burden of the wind turbine gearbox is greater, which brings great challenges to its reliability analysis. This study aims to systematically review the reliability research in wind turbine gearboxes and guide future research directions and challenges.

This study systematically reviews some design requirements and reliability analysis methods for wind turbine gearboxes. Then, it summarizes previous studies on wind load uncertainty modeling methods, including the processing of wind measurement data and the summary of three different classifications of random wind speed prediction models. Finally, existing reliability analysis studies on two major parts of the gearbox are described and summarized.

First, the basic knowledge of wind turbine gearboxes and their reliability analysis is introduced. The requirements and reliability analysis methods of wind turbine gearboxes are explained. Then, the processing methods of wind measurement data and three different random wind speed prediction models are described in detail. Furthermore, existing reliability analysis studies on two common parts of wind turbine gearboxes, gears and bearings, are summarized and classified, including a summary of bearing failure modes. Finally, three possible future research directions for wind turbine gearbox reliability analysis are discussed, namely, reliability research under the influence of multiple factors on gears, damage indicators of bearing failure modes and quantitative evaluation criteria for the overall dynamic characteristics of offshore wind turbine gearboxes and a summary is also given.

This paper aims to systematically introduce the relevant contents of wind turbine gearboxes and their reliability analysis. The contents of wind speed data processing, predictive modeling and reliability analysis of major components are also comprehensively reviewed, including the classification and principle introduction of these contents.

This paper aims to explore the developing trend of higher pedagogy, to promote the research of higher pedagogy to be more canonical and scientific and to improve the higher education theory.

The utility research uses a method of quantitative study, namely “content analysis”, to estimate and analyze the higher education theory literature on ten dimensionalities which include theme, author, abstract, keywords, subject, proposing of the issue, definition of key terms, research methods, conclusion, reference and annotations from 1996 to 2006 in China.

The analysis of the selected 250 academic theses and reports in the field of higher education shows that academic research and theoretical standard have been improved, meanwhile academic criterion have been formed by degrees in higher pedagogy within ten years. At the same time, there are still some problems in the papers and reports the authors have selected such as title, key words, proposing of the issue, researching method and conclusion.

This paper sums up the trend of research on higher education in China for the past ten years, and points out the problems in this trend and then proposes ways to improve the research of higher education in China.