Meroplankton play a crucial role in both benthic and pelagic ecosystems.Existing quantitative research on estimating the quantities of meroplankton groups is both underrepresented and inaccurate.To investigate and eva...Meroplankton play a crucial role in both benthic and pelagic ecosystems.Existing quantitative research on estimating the quantities of meroplankton groups is both underrepresented and inaccurate.To investigate and evaluate the influence of varying mesh sizes(505 and 160μm)on the sampling efficiency of meroplankton,we conducted an examination using two commonly used plankton nets during the spring season in the Southern Yellow Sea(SYS).Our study revealed a total of 12 meroplankton groups,with 9 groups identified in the 505-μm mesh nets and 11 groups in the 160-μm mesh nets.The results demonstrated the superior collection efficiency of the 160-μm net compared to the 505-μm net across the majority of meroplankton groups.Furthermore,we focused on exploring the abundance,distribution patterns,and realized niches of meroplankton collected by the two mesh size nets,and observed that the distribution of meroplankton closely resembled the distribution of possible benthic adults in the SYS.Correlation analysis of the six dominant groups collected in the 160-μm mesh nets revealed that seawater temperature and salinity emerged as the key environmental factors driving variations in meroplankton abundance within the SYS.This study also found that a smaller mesh size net does not necessarily capture meroplankton more comprehensively.A comprehensive understanding of the ecological characteristics of meroplankton requires the combination of two types of nets for research.Our research significantly advances our understanding of the quantification,abundance,and distribution of meroplankton,serving as a valuable contribution to the broader landscape of detailed quantitative meroplankton studies.展开更多
The original whale optimization algorithm(WOA)has a low initial population quality and tends to converge to local optimal solutions.To address these challenges,this paper introduces an improved whale optimization algo...The original whale optimization algorithm(WOA)has a low initial population quality and tends to converge to local optimal solutions.To address these challenges,this paper introduces an improved whale optimization algorithm called OLCHWOA,incorporating a chaos mechanism and an opposition-based learning strategy.This algorithm introduces chaotic initialization and opposition-based initialization operators during the population initialization phase,thereby enhancing the quality of the initial whale population.Additionally,including an elite opposition-based learning operator significantly improves the algorithm’s global search capabilities during iterations.The work and contributions of this paper are primarily reflected in two aspects.Firstly,an improved whale algorithm with enhanced development capabilities and a wide range of application scenarios is proposed.Secondly,the proposed OLCHWOA is used to optimize the hyperparameters of the Long Short-Term Memory(LSTM)networks.Subsequently,a prediction model for Realized Volatility(RV)based on OLCHWOA-LSTM is proposed to optimize hyperparameters automatically.To evaluate the performance of OLCHWOA,a series of comparative experiments were conducted using a variety of advanced algorithms.These experiments included 38 standard test functions from CEC2013 and CEC2019 and three constrained engineering design problems.The experimental results show that OLCHWOA ranks first in accuracy and stability under the same maximum fitness function calls budget.Additionally,the China Securities Index 300(CSI 300)dataset is used to evaluate the effectiveness of the proposed OLCHWOA-LSTM model in predicting RV.The comparison results with the other eight models show that the proposed model has the highest accuracy and goodness of fit in predicting RV.This further confirms that OLCHWOA effectively addresses real-world optimization problems.展开更多
Because the U.S.is a major player in the international oil market,it is interesting to study whether aggregate and state-level economic conditions can predict the subse-quent realized volatility of oil price returns.T...Because the U.S.is a major player in the international oil market,it is interesting to study whether aggregate and state-level economic conditions can predict the subse-quent realized volatility of oil price returns.To address this research question,we frame our analysis in terms of variants of the popular heterogeneous autoregressive realized volatility(HAR-RV)model.To estimate the models,we use quantile-regression and quantile machine learning(Lasso)estimators.Our estimation results highlights the dif-ferential effects of economic conditions on the quantiles of the conditional distribution of realized volatility.Using weekly data for the period April 1987 to December 2021,we document evidence of predictability at a biweekly and monthly horizon.展开更多
This paper is motivated by Bitcoin’s rapid ascension into mainstream finance and recent evidence of a strong relationship between Bitcoin and US stock markets.It is also motivated by a lack of empirical studies on wh...This paper is motivated by Bitcoin’s rapid ascension into mainstream finance and recent evidence of a strong relationship between Bitcoin and US stock markets.It is also motivated by a lack of empirical studies on whether Bitcoin prices contain useful information for the volatility of US stock returns,particularly at the sectoral level of data.We specifically assess Bitcoin prices’ability to predict the volatility of US composite and sectoral stock indices using both in-sample and out-of-sample analyses over multiple forecast horizons,based on daily data from November 22,2017,to December,30,2021.The findings show that Bitcoin prices have significant predictive power for US stock volatility,with an inverse relationship between Bitcoin prices and stock sector volatility.Regardless of the stock sectors or number of forecast horizons,the model that includes Bitcoin prices consistently outperforms the benchmark historical average model.These findings are independent of the volatility measure used.Using Bitcoin prices as a predictor yields higher economic gains.These findings emphasize the importance and utility of tracking Bitcoin prices when forecasting the volatility of US stock sectors,which is important for practitioners and policymakers.展开更多
文章选取上证综指5分钟收盘价序列高频数据,采用ACF拟合、多种损失函数、SPA检验和VaR回测检验对不同误差分布下的包含时变波动、异方差结构和加权已实现极差的Realized HAR GARCH模型进行研究。实证结果表明,新模型相比于以往模型更能...文章选取上证综指5分钟收盘价序列高频数据,采用ACF拟合、多种损失函数、SPA检验和VaR回测检验对不同误差分布下的包含时变波动、异方差结构和加权已实现极差的Realized HAR GARCH模型进行研究。实证结果表明,新模型相比于以往模型更能够捕捉上证综指的波动特征,具有更好的波动率拟合和预测效果,且VaR度量效果更优。研究丰富了时变长记忆高频波动率模型,从时变波动和噪声异方差结构视角为投资者和监管机构进行风险管控提供参考。展开更多
This paper incorporates the Baidu Index into various heterogeneous autoregressive type time series models and shows that the Baidu Index is a superior predictor of realized volatility in the SSE 50 Index.Furthermore,t...This paper incorporates the Baidu Index into various heterogeneous autoregressive type time series models and shows that the Baidu Index is a superior predictor of realized volatility in the SSE 50 Index.Furthermore,the predictability of the Baidu Index is found to rise as the forecasting horizon increases.We also find that continuous components enhance predictive power across all horizons,but that increases are only sustained in the short and medium terms,as the long-term impact on volatility is less persistent.Our findings should be expected to influence investors interested in constructing trading strategies based on realized volatility.展开更多
运用Realized GARCH模型用于期权定价,并考虑隔夜效应的影响及运用Hansen and Lunde(2005a)方法对隔夜效应进行调整,最后将其定价结果与Black-Scholes期权定价结果、GARCH期权定价结果及实际值进行比较。实证结果表明,基于Realized GARC...运用Realized GARCH模型用于期权定价,并考虑隔夜效应的影响及运用Hansen and Lunde(2005a)方法对隔夜效应进行调整,最后将其定价结果与Black-Scholes期权定价结果、GARCH期权定价结果及实际值进行比较。实证结果表明,基于Realized GARCH模型的期权定价结果比经典的Black-Scholes模型和GARCH模型具有更高的定价精确性。展开更多
为了对股票市场的非线性结构进行研究,通过Realized GARCH将高频数据的信息引入到模型之中,并结合Pair Copula分解法对股票指数进行分析,建立股票指数之间的结构关系。计算了AIC(Akaike information criterion)/BIC(Bayesian informatio...为了对股票市场的非线性结构进行研究,通过Realized GARCH将高频数据的信息引入到模型之中,并结合Pair Copula分解法对股票指数进行分析,建立股票指数之间的结构关系。计算了AIC(Akaike information criterion)/BIC(Bayesian information criterion)的值以确定最优Pair Copula函数,最终发现C-Vine的结构更加适合被用来描述股票市场间关系。展开更多
The present study is intended to be an analysis of the main Romanian legal provision in what concerns the impact of foreign exchange differences and potential consequences at the level of financial statements for comp...The present study is intended to be an analysis of the main Romanian legal provision in what concerns the impact of foreign exchange differences and potential consequences at the level of financial statements for companies. In Romanian legislation, the issue of the foreign exchange differences is treated at a general level： these are recognized as a profit and loss item and as a consequence, they are included in the taxable base when booked in the accounting. Our legislation does not provide for specific treatments depending on the ＇realization momenf＇ of these differences or depending on the conditions for recognizing a gain/loss from foreign exchange differences. For the unrealized exchange differences arising from the application of accounting rules on monthly assessment of foreign currency monetary items, there is not a specific event or transaction to determine income or expenditure. This monthly review depending on the National Bank of Romania [BNR] foreign exchange rate valid on the last day of the month aims to bring closer to reality the financial position of an entity. The exchange rate is a monetary policy item set by the central bank and may be influenced by various factors such as： monetary policy of the BNR; inflation target objectives and rate of exchange stabilization or reduction efforts, as is the case of BNR in the last years to fulfill EU criteria for adoption of the EURO; periodical influences of speculative capitals on the exchange rate level; economic status and especially exports and imports. However, a taxpayer should not be charged unless there is evidence of the ＂economic enrichment＂ thereof. However, this enrichment, seen as a rising economic value of the company, depends on the perspective from which is seen： the owner of the company or the tax authorities. The exchange differences impact also the value of the owners＇ equity for which a minimum level is requested under the commercial company law. In case of negative values, this triggers various risks at the level of the continuity principle or even endangers the existence of the company.展开更多
基金Supported by the Laoshan Laboratory(Nos.LSKJ 202203700,LSKJ 202203704,LSKJ 202204005)the National Natural Science Foundation of China(NSFC)(Nos.42076166,42130411)the NSFC Ship Time Sharing Project(No.42149901)。
文摘Meroplankton play a crucial role in both benthic and pelagic ecosystems.Existing quantitative research on estimating the quantities of meroplankton groups is both underrepresented and inaccurate.To investigate and evaluate the influence of varying mesh sizes(505 and 160μm)on the sampling efficiency of meroplankton,we conducted an examination using two commonly used plankton nets during the spring season in the Southern Yellow Sea(SYS).Our study revealed a total of 12 meroplankton groups,with 9 groups identified in the 505-μm mesh nets and 11 groups in the 160-μm mesh nets.The results demonstrated the superior collection efficiency of the 160-μm net compared to the 505-μm net across the majority of meroplankton groups.Furthermore,we focused on exploring the abundance,distribution patterns,and realized niches of meroplankton collected by the two mesh size nets,and observed that the distribution of meroplankton closely resembled the distribution of possible benthic adults in the SYS.Correlation analysis of the six dominant groups collected in the 160-μm mesh nets revealed that seawater temperature and salinity emerged as the key environmental factors driving variations in meroplankton abundance within the SYS.This study also found that a smaller mesh size net does not necessarily capture meroplankton more comprehensively.A comprehensive understanding of the ecological characteristics of meroplankton requires the combination of two types of nets for research.Our research significantly advances our understanding of the quantification,abundance,and distribution of meroplankton,serving as a valuable contribution to the broader landscape of detailed quantitative meroplankton studies.
基金The National Natural Science Foundation of China(Grant No.81973791)funded this research.
文摘The original whale optimization algorithm(WOA)has a low initial population quality and tends to converge to local optimal solutions.To address these challenges,this paper introduces an improved whale optimization algorithm called OLCHWOA,incorporating a chaos mechanism and an opposition-based learning strategy.This algorithm introduces chaotic initialization and opposition-based initialization operators during the population initialization phase,thereby enhancing the quality of the initial whale population.Additionally,including an elite opposition-based learning operator significantly improves the algorithm’s global search capabilities during iterations.The work and contributions of this paper are primarily reflected in two aspects.Firstly,an improved whale algorithm with enhanced development capabilities and a wide range of application scenarios is proposed.Secondly,the proposed OLCHWOA is used to optimize the hyperparameters of the Long Short-Term Memory(LSTM)networks.Subsequently,a prediction model for Realized Volatility(RV)based on OLCHWOA-LSTM is proposed to optimize hyperparameters automatically.To evaluate the performance of OLCHWOA,a series of comparative experiments were conducted using a variety of advanced algorithms.These experiments included 38 standard test functions from CEC2013 and CEC2019 and three constrained engineering design problems.The experimental results show that OLCHWOA ranks first in accuracy and stability under the same maximum fitness function calls budget.Additionally,the China Securities Index 300(CSI 300)dataset is used to evaluate the effectiveness of the proposed OLCHWOA-LSTM model in predicting RV.The comparison results with the other eight models show that the proposed model has the highest accuracy and goodness of fit in predicting RV.This further confirms that OLCHWOA effectively addresses real-world optimization problems.
文摘Because the U.S.is a major player in the international oil market,it is interesting to study whether aggregate and state-level economic conditions can predict the subse-quent realized volatility of oil price returns.To address this research question,we frame our analysis in terms of variants of the popular heterogeneous autoregressive realized volatility(HAR-RV)model.To estimate the models,we use quantile-regression and quantile machine learning(Lasso)estimators.Our estimation results highlights the dif-ferential effects of economic conditions on the quantiles of the conditional distribution of realized volatility.Using weekly data for the period April 1987 to December 2021,we document evidence of predictability at a biweekly and monthly horizon.
文摘This paper is motivated by Bitcoin’s rapid ascension into mainstream finance and recent evidence of a strong relationship between Bitcoin and US stock markets.It is also motivated by a lack of empirical studies on whether Bitcoin prices contain useful information for the volatility of US stock returns,particularly at the sectoral level of data.We specifically assess Bitcoin prices’ability to predict the volatility of US composite and sectoral stock indices using both in-sample and out-of-sample analyses over multiple forecast horizons,based on daily data from November 22,2017,to December,30,2021.The findings show that Bitcoin prices have significant predictive power for US stock volatility,with an inverse relationship between Bitcoin prices and stock sector volatility.Regardless of the stock sectors or number of forecast horizons,the model that includes Bitcoin prices consistently outperforms the benchmark historical average model.These findings are independent of the volatility measure used.Using Bitcoin prices as a predictor yields higher economic gains.These findings emphasize the importance and utility of tracking Bitcoin prices when forecasting the volatility of US stock sectors,which is important for practitioners and policymakers.
文摘文章选取上证综指5分钟收盘价序列高频数据,采用ACF拟合、多种损失函数、SPA检验和VaR回测检验对不同误差分布下的包含时变波动、异方差结构和加权已实现极差的Realized HAR GARCH模型进行研究。实证结果表明,新模型相比于以往模型更能够捕捉上证综指的波动特征,具有更好的波动率拟合和预测效果,且VaR度量效果更优。研究丰富了时变长记忆高频波动率模型,从时变波动和噪声异方差结构视角为投资者和监管机构进行风险管控提供参考。
基金This work is supported by the National Natural Science Foundation of China(71790594,71701150,and U1811462).
文摘This paper incorporates the Baidu Index into various heterogeneous autoregressive type time series models and shows that the Baidu Index is a superior predictor of realized volatility in the SSE 50 Index.Furthermore,the predictability of the Baidu Index is found to rise as the forecasting horizon increases.We also find that continuous components enhance predictive power across all horizons,but that increases are only sustained in the short and medium terms,as the long-term impact on volatility is less persistent.Our findings should be expected to influence investors interested in constructing trading strategies based on realized volatility.
文摘运用Realized GARCH模型用于期权定价,并考虑隔夜效应的影响及运用Hansen and Lunde(2005a)方法对隔夜效应进行调整,最后将其定价结果与Black-Scholes期权定价结果、GARCH期权定价结果及实际值进行比较。实证结果表明,基于Realized GARCH模型的期权定价结果比经典的Black-Scholes模型和GARCH模型具有更高的定价精确性。
文摘为了对股票市场的非线性结构进行研究,通过Realized GARCH将高频数据的信息引入到模型之中,并结合Pair Copula分解法对股票指数进行分析,建立股票指数之间的结构关系。计算了AIC(Akaike information criterion)/BIC(Bayesian information criterion)的值以确定最优Pair Copula函数,最终发现C-Vine的结构更加适合被用来描述股票市场间关系。
文摘The present study is intended to be an analysis of the main Romanian legal provision in what concerns the impact of foreign exchange differences and potential consequences at the level of financial statements for companies. In Romanian legislation, the issue of the foreign exchange differences is treated at a general level： these are recognized as a profit and loss item and as a consequence, they are included in the taxable base when booked in the accounting. Our legislation does not provide for specific treatments depending on the ＇realization momenf＇ of these differences or depending on the conditions for recognizing a gain/loss from foreign exchange differences. For the unrealized exchange differences arising from the application of accounting rules on monthly assessment of foreign currency monetary items, there is not a specific event or transaction to determine income or expenditure. This monthly review depending on the National Bank of Romania [BNR] foreign exchange rate valid on the last day of the month aims to bring closer to reality the financial position of an entity. The exchange rate is a monetary policy item set by the central bank and may be influenced by various factors such as： monetary policy of the BNR; inflation target objectives and rate of exchange stabilization or reduction efforts, as is the case of BNR in the last years to fulfill EU criteria for adoption of the EURO; periodical influences of speculative capitals on the exchange rate level; economic status and especially exports and imports. However, a taxpayer should not be charged unless there is evidence of the ＂economic enrichment＂ thereof. However, this enrichment, seen as a rising economic value of the company, depends on the perspective from which is seen： the owner of the company or the tax authorities. The exchange differences impact also the value of the owners＇ equity for which a minimum level is requested under the commercial company law. In case of negative values, this triggers various risks at the level of the continuity principle or even endangers the existence of the company.
