Analyzing comovements and connectedness is critical for providing significant implications for crypto-portfolio risk management.However,most existing research focuses on the lower-order moment nexus(i.e.the return and...Analyzing comovements and connectedness is critical for providing significant implications for crypto-portfolio risk management.However,most existing research focuses on the lower-order moment nexus(i.e.the return and volatility interactions).For the first time,this study investigates the higher-order moment comovements and risk connectedness among cryptocurrencies before and during the COVID-19 pandemic in both the time and frequency domains.We combine the realized moment measures and wavelet coherence,and the newly proposed time-varying parameter vector autoregression-based frequency connectedness approach(Chatziantoniou et al.in Integration and risk transmission in the market for crude oil a time-varying parameter frequency connectedness approach.Technical report,University of Pretoria,Department of Economics,2021)using intraday high-frequency data.The empirical results demonstrate that the comovement of realized volatility between BTC and other cryp-tocurrencies is stronger than that of the realized skewness,realized kurtosis,and signed jump variation.The comovements among cryptocurrencies are both time-dependent and frequency-dependent.Besides the volatility spillovers,the risk spillovers of high-order moments and jumps are also significant,although their magnitudes vary with moments,making them moment-dependent as well and are lower than volatility connectedness.Frequency connectedness demonstrates that the risk connectedness is mainly transmitted in the short term(1–7 days).Furthermore,the total dynamic connectedness of all realized moments is time-varying and has been significantly affected by the outbreak of the COVID-19 pandemic.Several practical implications are drawn for crypto investors,portfolio managers,regulators,and policymakers in optimizing their investment and risk management tactics.展开更多
This study investigated the effects of polarized and spectral light interactions on locust polarotaxic behavior and elucidated the regulatory mechanisms of polarized and spectral lights.Locust visual response effect w...This study investigated the effects of polarized and spectral light interactions on locust polarotaxic behavior and elucidated the regulatory mechanisms of polarized and spectral lights.Locust visual response effect was investigated using a combined light source system comprising linear detection polarization violet light with various spectrum lights and a response device to explore the interaction mechanism of polarized and spectral lights on locust visual sensitivity characteristics and the specific sensitivity of locust phototaxis and polartaxis.Results indicated that the polarized vector sensitivity of locusts was related to combined light intensity,showing high visual response sensitivity at 0°and 180°under 1000 lx,whereas under rated illumination(150 mW/cm^(2)),the coupled spectrum attributes induced changes in the locusts’sensitive vectors.UV,violet,and blue lights enhanced the sensitivity at 90°and 270°,and green and orange lights did so at 0°and 180°.Moreover,UV and violet lights enhanced the aggregation and trend sensitivity at 210°and 30°,blue,green and orange lights induced high sensitivity at 0°and 180°.Under increasing illumination,the enhanced effect of light intensity on aggregation sensitivity under blue,green,and orange spectra and on trend sensitivity under orange spectra at 90°and 270°were highly pronounced because of the interaction between heterogeneous spectrum illumination and linear detection polarization vector illumination.Meanwhile,the spectral attribute determined the locust visual response effect,which was affected by the linear detection polarization vector.When illumination increased to rated illumination,coupled light intensity induced a specific vector sensitivity related to optical distance,showing the strongest response sensitivity to 180°under orange spectra and the strongest aggregation and trend sensitivity to 210°under violet spectra due to the interplay of polarization degree,coupling light intensity,and specific vision sensitivity caused by partially polarized light.Then,the locust visual response effect was improved by utilizing the enhancement effect of polarized violet light coupled with violet light at a close range and the inductive effect of polarized violet light coupled with orange light at a long distance,which provide theoretical support for understanding locust polarotactic orientation mechanisms,facilitate the development of polarization induced light sources for attracting locusts.展开更多
New approaches are required to prevent the plagues of locusts that threaten crop security in many areas of the world. One such approach is to exploit the phototactic response of locusts, enabling their aggregation and...New approaches are required to prevent the plagues of locusts that threaten crop security in many areas of the world. One such approach is to exploit the phototactic response of locusts, enabling their aggregation and effective removal from agricultural sites. This study examined the effect of the dorsal rim area (DRA) of the locust compound eye on the phototactic response of locusts to spectral light. Locusts with intact DRA showed increased phototactic responses to blue, green or orange light but decreased responses to UV and violet light, whereas locusts with blacked-out DRA (non-DRA vision) showed the strongest phototactic responses to orange followed by violet light. The combined results revealed that phototactic push-pull effect triggered by responses of DRA versus non-DRA vision was strongest in response to violet light. Compound vision in the locust is the result of the synergism between DRA versus non-DRA vision, causing a push-pull phototactic effect that is most stimulated by exposure to violet light, with light intensity enhancing this effect. These results provide theoretical support for the induction of phototaxis and polarotaxis in response to light in locusts, which could be useful for the development of light-based control systems in the field.展开更多
This paper investigates the frequency connectedness among economic policy uncertainties of G20 countries using the novel frequency connectedness proposed by Barunik and Krehlik(2018)which can depict the dynamic connec...This paper investigates the frequency connectedness among economic policy uncertainties of G20 countries using the novel frequency connectedness proposed by Barunik and Krehlik(2018)which can depict the dynamic connectedness not only over time but also across different frequencies.The empirical results obtained in this paper demonstrate that,firstly,the connectedness among economic policy uncertainties is significant,and the spillover effects during the financial crisis and the postfinancial crisis period are stronger than the pre-financial crisis period.Secondly,the United States,France,and Australia are the main net-transmitters of the economic policy uncertainty spillovers while Brazil,Italy,Mexico,and Russia act as the main net-recipients of the spillovers.Thirdly,the major international events may significantly enhance the spillover transmissions of economic policy uncertainty among different countries,thus increasing the magnitude of the total connectedness.Finally,the economic policy uncertainty spillovers are mainly transmitted in the short term,i.e.,1~4 months instead of longer time horizons in terms of the magnitude of the frequency connectedness measures.The findings of this paper not only have profound theoretical and practical significance but also provide several significant implications for the policymakers,supervision agents,international traders,and various investors.展开更多
文摘Analyzing comovements and connectedness is critical for providing significant implications for crypto-portfolio risk management.However,most existing research focuses on the lower-order moment nexus(i.e.the return and volatility interactions).For the first time,this study investigates the higher-order moment comovements and risk connectedness among cryptocurrencies before and during the COVID-19 pandemic in both the time and frequency domains.We combine the realized moment measures and wavelet coherence,and the newly proposed time-varying parameter vector autoregression-based frequency connectedness approach(Chatziantoniou et al.in Integration and risk transmission in the market for crude oil a time-varying parameter frequency connectedness approach.Technical report,University of Pretoria,Department of Economics,2021)using intraday high-frequency data.The empirical results demonstrate that the comovement of realized volatility between BTC and other cryp-tocurrencies is stronger than that of the realized skewness,realized kurtosis,and signed jump variation.The comovements among cryptocurrencies are both time-dependent and frequency-dependent.Besides the volatility spillovers,the risk spillovers of high-order moments and jumps are also significant,although their magnitudes vary with moments,making them moment-dependent as well and are lower than volatility connectedness.Frequency connectedness demonstrates that the risk connectedness is mainly transmitted in the short term(1–7 days).Furthermore,the total dynamic connectedness of all realized moments is time-varying and has been significantly affected by the outbreak of the COVID-19 pandemic.Several practical implications are drawn for crypto investors,portfolio managers,regulators,and policymakers in optimizing their investment and risk management tactics.
基金supported by the Scientific and Technological Project of Henan Province,China(Grant No.242102111179)the Natural Science Foundation Project of Henan Province,China(Grant No.232300420024).
文摘This study investigated the effects of polarized and spectral light interactions on locust polarotaxic behavior and elucidated the regulatory mechanisms of polarized and spectral lights.Locust visual response effect was investigated using a combined light source system comprising linear detection polarization violet light with various spectrum lights and a response device to explore the interaction mechanism of polarized and spectral lights on locust visual sensitivity characteristics and the specific sensitivity of locust phototaxis and polartaxis.Results indicated that the polarized vector sensitivity of locusts was related to combined light intensity,showing high visual response sensitivity at 0°and 180°under 1000 lx,whereas under rated illumination(150 mW/cm^(2)),the coupled spectrum attributes induced changes in the locusts’sensitive vectors.UV,violet,and blue lights enhanced the sensitivity at 90°and 270°,and green and orange lights did so at 0°and 180°.Moreover,UV and violet lights enhanced the aggregation and trend sensitivity at 210°and 30°,blue,green and orange lights induced high sensitivity at 0°and 180°.Under increasing illumination,the enhanced effect of light intensity on aggregation sensitivity under blue,green,and orange spectra and on trend sensitivity under orange spectra at 90°and 270°were highly pronounced because of the interaction between heterogeneous spectrum illumination and linear detection polarization vector illumination.Meanwhile,the spectral attribute determined the locust visual response effect,which was affected by the linear detection polarization vector.When illumination increased to rated illumination,coupled light intensity induced a specific vector sensitivity related to optical distance,showing the strongest response sensitivity to 180°under orange spectra and the strongest aggregation and trend sensitivity to 210°under violet spectra due to the interplay of polarization degree,coupling light intensity,and specific vision sensitivity caused by partially polarized light.Then,the locust visual response effect was improved by utilizing the enhancement effect of polarized violet light coupled with violet light at a close range and the inductive effect of polarized violet light coupled with orange light at a long distance,which provide theoretical support for understanding locust polarotactic orientation mechanisms,facilitate the development of polarization induced light sources for attracting locusts.
基金supported by the Scientific and Technological Project of Henan Province,China(Grant No.242102111179,222102210116,222102320080)the Natural Science Foundation Project of Henan Province,China(Grant No.232300420024)the National Natural Science Foundation of China(Grant No.31772501).
文摘New approaches are required to prevent the plagues of locusts that threaten crop security in many areas of the world. One such approach is to exploit the phototactic response of locusts, enabling their aggregation and effective removal from agricultural sites. This study examined the effect of the dorsal rim area (DRA) of the locust compound eye on the phototactic response of locusts to spectral light. Locusts with intact DRA showed increased phototactic responses to blue, green or orange light but decreased responses to UV and violet light, whereas locusts with blacked-out DRA (non-DRA vision) showed the strongest phototactic responses to orange followed by violet light. The combined results revealed that phototactic push-pull effect triggered by responses of DRA versus non-DRA vision was strongest in response to violet light. Compound vision in the locust is the result of the synergism between DRA versus non-DRA vision, causing a push-pull phototactic effect that is most stimulated by exposure to violet light, with light intensity enhancing this effect. These results provide theoretical support for the induction of phototaxis and polarotaxis in response to light in locusts, which could be useful for the development of light-based control systems in the field.
基金Supported by the National Natural Science Foundation of China(71573042)the Natural Science Foundation of Fujian Province(2017J01794)
文摘This paper investigates the frequency connectedness among economic policy uncertainties of G20 countries using the novel frequency connectedness proposed by Barunik and Krehlik(2018)which can depict the dynamic connectedness not only over time but also across different frequencies.The empirical results obtained in this paper demonstrate that,firstly,the connectedness among economic policy uncertainties is significant,and the spillover effects during the financial crisis and the postfinancial crisis period are stronger than the pre-financial crisis period.Secondly,the United States,France,and Australia are the main net-transmitters of the economic policy uncertainty spillovers while Brazil,Italy,Mexico,and Russia act as the main net-recipients of the spillovers.Thirdly,the major international events may significantly enhance the spillover transmissions of economic policy uncertainty among different countries,thus increasing the magnitude of the total connectedness.Finally,the economic policy uncertainty spillovers are mainly transmitted in the short term,i.e.,1~4 months instead of longer time horizons in terms of the magnitude of the frequency connectedness measures.The findings of this paper not only have profound theoretical and practical significance but also provide several significant implications for the policymakers,supervision agents,international traders,and various investors.
