Limited by the planar imaging structure,the commercial camera needs to introduce additional optical elements to compensate for the curved focal plane to match the planar image sensor.This results in a complex and bulk...Limited by the planar imaging structure,the commercial camera needs to introduce additional optical elements to compensate for the curved focal plane to match the planar image sensor.This results in a complex and bulky structure.In contrast,biological eyes possess a simple and compact structure due to their curved imaging structure that can directly match with the curved focal plane.Inspired by the structures and functions of biological eyes,curved vision systems not only improve the image quality,but also offer a variety of advanced functions.Here,we review the recent advances in bioinspired vision systems with curved imaging structures.Specifically,we focus on their applications in implementing different functions of biological eyes,as well as the emerging curved neuromorphic imaging systems that incorporate bioinspired optical and neuromorphic processing technologies.In addition,the challenges and opportunities of bioinspired curved imaging systems are also discussed.展开更多
In recent years,the frequent adjustment of the government’s economic policies and the uncertainty of foreign economic situations have made the degree of uncertainty of China’s economic policies rise continuously.The...In recent years,the frequent adjustment of the government’s economic policies and the uncertainty of foreign economic situations have made the degree of uncertainty of China’s economic policies rise continuously.The increasing degree of policy uncertainty will inevitably affect the investment and financing decisions of micro enterprises.Then,how does economic policy uncertainty(EPU)affect mergers and acquisitions(M&A)behavior?What’s the mechanism?Based on the above questions,this paper uses the data of non-financial listed companies in the Shanghai and Shenzhen stock exchanges from 2008 to 2018 as a sample to explore the relationship between EPU and M&A.The study shows that rising EPU will promote corporate M&A behavior,and this effect is more significant in slow-growth companies.The relationship between EPU and M&A is affected by corporate governance,stock price volatility and financing constraints.Specifically,the company’s M&A size is more sensitive to EPU with higher level of corporate governance,higher level of stock price volatility,and lesser financing constraints.Further research shows that the rise of EPU will significantly promote the improvement of M&A performance in the short-term,but this effect does not exist in the long-term.Various robustness checks do not change the empirical results of this paper.展开更多
This study analyzes how economic policy uncertainty affects corporate innovation,and the moderating effects of executive heterogeneity.A threephase dynamic investment and financing model is first built to analyze the ...This study analyzes how economic policy uncertainty affects corporate innovation,and the moderating effects of executive heterogeneity.A threephase dynamic investment and financing model is first built to analyze the mechanism.Empirical analysis confirms that the increase in the degree of economic policy uncertainty promotes enterprise innovation.Further results show that this promotion effect is more significant in enterprises with male executives,low educational level,no financial experience and political background.Moreover,the positive impact is only found in enterprises with moderate executive ability,and the overconfidence of senior executives plays a positive regulating role in it.展开更多
Metal halide perovskites possess intriguing optoelectronic properties,however,the lack of precise control of on-chip fabrication of the large-scale perovskite single crystal arrays restricts its application in integra...Metal halide perovskites possess intriguing optoelectronic properties,however,the lack of precise control of on-chip fabrication of the large-scale perovskite single crystal arrays restricts its application in integrated devices.Here,we report a space confinement and antisolvent-assisted crystallization method for the homogeneous perovskite single crystal arrays spanning 100 square centimeter areas.This method enables precise control over the crystal arrays,including different array shapes and resolutions with less than 10%-pixel position variation,tunable pixel dimensions from 2 to 8 pm as well as the in-plane rotation of each pixel.The crystal pixel could serve as a high-quality whispering gallery mode(WGM)microcavity with a quality factor of 2915 and a threshold of 4.14μJ cm^(-2).Through directly on-chip fabrication on the patterned electrodes,a vertical structured photodetector array is demonstrated with stable photoswitching behavior and the capability to image the input patterns,indicating the potential application in the integrated systems of this method.展开更多
One of the main challenges in stretchable electronics is to achieve high-performance stretchable semiconductors. Here, weintroduce an innovative concept of nanomeshed semiconductor nanomembrane which can be regarded a...One of the main challenges in stretchable electronics is to achieve high-performance stretchable semiconductors. Here, weintroduce an innovative concept of nanomeshed semiconductor nanomembrane which can be regarded almost as intrinsicallystretchable to conventional microelectronic layouts. By making a silicon film into homogeneous nanomeshes with spring-like nanotraces, we demonstrated a high electron mobility of 50 cm^(2)/V·s, and moderate stretchability with a one-time strain of 25% andcyclic strain of 14% after stretching for 1000 cycles, further improvable with optimized nanomesh designs. A simple analytic modelcovering both fractional material and trace sidewall surfaces well predicted the transport properties of the normally on siliconnanomesh transistors, enabling future design and optimizations. Besides potential applications in stretchable electronics, thissemiconductor nanomesh concept provides a new platform for materials engineering and is expected to yield a new family ofstretchable inorganic materials having tunable electronic and optoelectronic properties with customized nanostructures.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.52125205,U20A20166,61805015 and 61804011,52102184,52202181)the National key R&D program of China(Nos.2021YFB3200302 and 2021YFB3200304)the Fundamental Research Funds for the Central Universities。
文摘Limited by the planar imaging structure,the commercial camera needs to introduce additional optical elements to compensate for the curved focal plane to match the planar image sensor.This results in a complex and bulky structure.In contrast,biological eyes possess a simple and compact structure due to their curved imaging structure that can directly match with the curved focal plane.Inspired by the structures and functions of biological eyes,curved vision systems not only improve the image quality,but also offer a variety of advanced functions.Here,we review the recent advances in bioinspired vision systems with curved imaging structures.Specifically,we focus on their applications in implementing different functions of biological eyes,as well as the emerging curved neuromorphic imaging systems that incorporate bioinspired optical and neuromorphic processing technologies.In addition,the challenges and opportunities of bioinspired curved imaging systems are also discussed.
文摘In recent years,the frequent adjustment of the government’s economic policies and the uncertainty of foreign economic situations have made the degree of uncertainty of China’s economic policies rise continuously.The increasing degree of policy uncertainty will inevitably affect the investment and financing decisions of micro enterprises.Then,how does economic policy uncertainty(EPU)affect mergers and acquisitions(M&A)behavior?What’s the mechanism?Based on the above questions,this paper uses the data of non-financial listed companies in the Shanghai and Shenzhen stock exchanges from 2008 to 2018 as a sample to explore the relationship between EPU and M&A.The study shows that rising EPU will promote corporate M&A behavior,and this effect is more significant in slow-growth companies.The relationship between EPU and M&A is affected by corporate governance,stock price volatility and financing constraints.Specifically,the company’s M&A size is more sensitive to EPU with higher level of corporate governance,higher level of stock price volatility,and lesser financing constraints.Further research shows that the rise of EPU will significantly promote the improvement of M&A performance in the short-term,but this effect does not exist in the long-term.Various robustness checks do not change the empirical results of this paper.
基金the support of Humanities and Social Sciences Foundation of the Ministry of Education"Research on policy uncertainty,non-financial enterprises’shadow banking activities and its economic effects"(20YJC790040)School Level Special Research Project of Beijing International Studies University(KYZX20A008).
文摘This study analyzes how economic policy uncertainty affects corporate innovation,and the moderating effects of executive heterogeneity.A threephase dynamic investment and financing model is first built to analyze the mechanism.Empirical analysis confirms that the increase in the degree of economic policy uncertainty promotes enterprise innovation.Further results show that this promotion effect is more significant in enterprises with male executives,low educational level,no financial experience and political background.Moreover,the positive impact is only found in enterprises with moderate executive ability,and the overconfidence of senior executives plays a positive regulating role in it.
基金National Natural Science Foundation of China(No.52125205,U20A20166,52192614,52102184)National key R&D program of China(2021YFB3200302,2021YFB3200304)+2 种基金Natural Science Foundation of Bejing Municipality(Z180011,2222088)Shenzhen Science and Technology Program(Grant No.KQTD20170810105439418)GuangDong Basic and Applied Basic Research Foundation(2020A1515110740).
文摘Metal halide perovskites possess intriguing optoelectronic properties,however,the lack of precise control of on-chip fabrication of the large-scale perovskite single crystal arrays restricts its application in integrated devices.Here,we report a space confinement and antisolvent-assisted crystallization method for the homogeneous perovskite single crystal arrays spanning 100 square centimeter areas.This method enables precise control over the crystal arrays,including different array shapes and resolutions with less than 10%-pixel position variation,tunable pixel dimensions from 2 to 8 pm as well as the in-plane rotation of each pixel.The crystal pixel could serve as a high-quality whispering gallery mode(WGM)microcavity with a quality factor of 2915 and a threshold of 4.14μJ cm^(-2).Through directly on-chip fabrication on the patterned electrodes,a vertical structured photodetector array is demonstrated with stable photoswitching behavior and the capability to image the input patterns,indicating the potential application in the integrated systems of this method.
基金This work was supported by Northeastern University(NU).
文摘One of the main challenges in stretchable electronics is to achieve high-performance stretchable semiconductors. Here, weintroduce an innovative concept of nanomeshed semiconductor nanomembrane which can be regarded almost as intrinsicallystretchable to conventional microelectronic layouts. By making a silicon film into homogeneous nanomeshes with spring-like nanotraces, we demonstrated a high electron mobility of 50 cm^(2)/V·s, and moderate stretchability with a one-time strain of 25% andcyclic strain of 14% after stretching for 1000 cycles, further improvable with optimized nanomesh designs. A simple analytic modelcovering both fractional material and trace sidewall surfaces well predicted the transport properties of the normally on siliconnanomesh transistors, enabling future design and optimizations. Besides potential applications in stretchable electronics, thissemiconductor nanomesh concept provides a new platform for materials engineering and is expected to yield a new family ofstretchable inorganic materials having tunable electronic and optoelectronic properties with customized nanostructures.
