This study employs a variety of machine learning models and a wide range of economic and financial variables to enhance the forecasting accuracy of the Korean won–U.S.dollar(KRW/USD)exchange rate and the U.S.and Kore...This study employs a variety of machine learning models and a wide range of economic and financial variables to enhance the forecasting accuracy of the Korean won–U.S.dollar(KRW/USD)exchange rate and the U.S.and Korean stock market returns.We construct international asset allocation portfolios based on these forecasts and evaluate their performance.Our analysis finds that the Elastic Net and LASSO regression models outperform traditional benchmark models in predicting exchange rate and stock market returns,as evidenced by their superior out-of-sample R-squared values.We also identify the key factors crucial for improving the accuracy of forecasting the KRW/USD exchange rate and stock market returns.Furthermore,a machine learning-driven global portfolio that accounts for exchange rate fluctuations demonstrated superior performance.Global portfolios constructed using LASSO(Sharpe ratio=3.45)and Elastic Net(Sharpe ratio=3.48)exhibit a notable performance advantage over traditional benchmark portfolios.This suggests that machine learning models outperform traditional global portfolio construction methods.展开更多
In order to deal with the problem that exists in current teaching of English writing,this thesis aims to explore a new process writing approach which combines process-based approach with portfolios assessment.
Purpose:Interdisciplinarity is a hot topic in science and technology policy.However,the concept of interdisciplinarity is both abstract and complex,and therefore difficult to measure using a single indicator.A variety...Purpose:Interdisciplinarity is a hot topic in science and technology policy.However,the concept of interdisciplinarity is both abstract and complex,and therefore difficult to measure using a single indicator.A variety of metrics for measuring the diversity and interdisciplinarity of articles,journals,and fields have been proposed in the literature.In this article,we ask whether institutions can be ranked in terms of their(inter-)disciplinary diversity.Design/methodology/approach:We developed a software application(interd_vb.exe)that outputs the values of relevant diversity indicators for any document set or network structure.The software is made available,free to the public,online.The indicators it considers include the advanced diversity indicators Rao-Stirling(RS)diversity and DIV*,as well as standard measures of diversity,such as the Gini coefficient,Shannon entropy,and the Simpson Index.As an empirical demonstration of how the application works,we compared the research portfolios of 42“Double First-Class”Chinese universities across Web of Science Subject Categories(WCs).Findings:The empirical results suggest that DIV*provides results that are more in line with one’s intuitive impressions than RS,particularly when the results are based on sampledependent disparity measures.Furthermore,the scores for diversity are more consistent when based on a global disparity matrix than on a local map.Research limitations:“Interdisciplinarity”can be operationalized as bibliographic coupling among(sets of)documents with references to disciplines.At the institutional level,however,diversity may also indicate comprehensiveness.Unlike impact(e.g.citation),diversity and interdisciplinarity are context-specific and therefore provide a second dimension to the evaluation.Policy or practical implications:Operationalization and quantification make it necessary for analysts to make their choices and options clear.Although the equations used to calculate diversity are often mathematically transparent,the specification in terms of computer code helps the analyst to further precision in decisions.Although diversity is not necessarily a goal of universities,a high diversity score may inform potential policies concerning interdisciplinarity at the university level.Originality/value:This article introduces a non-commercial online application to the public domain that allows researchers and policy analysts to measure“diversity”and“interdisciplinarity”using the various indicators as encompassing as possible for any document set or network structure(e.g.a network of co-authors).Insofar as we know,such a professional computing tool for evaluating data sets using diversity indicators has not yet been made available online.展开更多
Equipment selection is an essential work in the research and development planning of equipment.The scientific and rational development of weapons equipment portfolios is of considerable significance to the optimizatio...Equipment selection is an essential work in the research and development planning of equipment.The scientific and rational development of weapons equipment portfolios is of considerable significance to the optimization of equipment architecture design,the adequate resources allocation,and the joint combat performance.From the system view,this paper proposes a method of weapons equipment portfolios selection(WEPS)based on the contribution rate of weapon systems,providing a new idea for weapon equipment portfolio selection.Firstly,we analyze the WEPS problem and the concept of the contribution rate under the systems background.Secondly,we propose a combat network modeling method for weapon equipment systems based on the function chain.Thirdly,we propose a WEPS method based on the contribution rate,fully considering the correlation relationships between potential weapons and the old weapon systems by the combat network model,under the limitation of capability demands and budget resources,with the objective to maximally increasing the combat ability of weapon systems.Finally,we make a case study with a specific WEPS problem where the whole calculation processes and results are analyzed and exhibited to verify the feasibility and effectiveness of the proposed method model.展开更多
In order to study the effect of different risk measures on the efficient portfolios （fron- tier） while properly describing the characteristic of return distributions in the stock market, it is assumed in this paper ...In order to study the effect of different risk measures on the efficient portfolios （fron- tier） while properly describing the characteristic of return distributions in the stock market, it is assumed in this paper that the joint return distribution of risky assets obeys the multivariate t-distribution. Under the mean-risk analysis framework, the interrelationship of efficient portfolios （frontier） based on risk measures such as variance, value at risk （VaR）, and expected shortfall （ES） is analyzed and compared. It is proved that, when there is no riskless asset in the market, the efficient frontier under VaR or ES is a subset of the mean-variance （MV） efficient frontier, and the efficient portfolios under VaR or ES are also MV efficient; when there exists a riskless asset in the market, a portfolio is MV efficient if and only if it is a VaR or ES efficient portfolio. The obtained results generalize relevant conclusions about investment theory, and can better guide investors to make their investment decision.展开更多
This paper makes use of statistical tools of parameter correlation, multi-parameter regression, and does experimental analysis on issues of risk diversification of portfolios entrusted by National Social Security Fund...This paper makes use of statistical tools of parameter correlation, multi-parameter regression, and does experimental analysis on issues of risk diversification of portfolios entrusted by National Social Security Fund (NSSF). The issues are industry related investment fields distribution, the trend of capitalization movement, and investment style factors in stock selection. The results show that there are risk problems with portfolios entrusted by NSSF, which include similar investment fields distribution trend, little difference among portfolios, and high risk preference degree.展开更多
This research aims to compare different strategies that a non-professional investor in exchange-traded funds (ETFs) could employ to reach a good performance both from profits and from a risk perspective. In recent yea...This research aims to compare different strategies that a non-professional investor in exchange-traded funds (ETFs) could employ to reach a good performance both from profits and from a risk perspective. In recent years, especially after the 2008 crisis, a new technique to evaluate the risk has become more popular, the so-called risk parity, which seeks to equalise the contributions to risk of the portfolio constituents. Our study analyses 17 variants of risk parity portfolio design for groups with the minimum variance strategy and equally weighted portfolio over a pool of 56 ETFs—listed on the Italian Stock Exchange—of eight different categories of specialisation. Empirical results confirm the usefulness of the group risk parity strategies in improving outcomes regarding diversification of risks among classes with good out-of-sample performance with respects to the target models.展开更多
This paper is concerned with a study on the efficient frontier characters of portfolio with transaction cost. The conclusion is drawn that all portfolios are of positive correlation on the efficient frontier with tran...This paper is concerned with a study on the efficient frontier characters of portfolio with transaction cost. The conclusion is drawn that all portfolios are of positive correlation on the efficient frontier with transaction cost; the sufficient condition for the derivable efficient frontier has also been achieved. Meanwhile, in comparison with the position of the efficient frontier without transaction cost in the plane (σ 2,R), the conclusion has been made that the efficient frontiers with transaction cost drift and its opening shrinks correspondingly. With this study, the content of the efficient frontier is further enriched. It’s very constructive and important for the practical portfolio investment strategy.展开更多
This paper is trying to make some improvement to Markowitz＇s Mean-Variance Model. In this paper, we try to solve the model of portfolio by using Evolutionary Programming under the condition of the covariance matrix w...This paper is trying to make some improvement to Markowitz＇s Mean-Variance Model. In this paper, we try to solve the model of portfolio by using Evolutionary Programming under the condition of the covariance matrix which is a non-positive matrix, and design a new method which can improve Markowitz＇s model. At last, we give an illustrative example with the new method.展开更多
Purpose： This paper suggests a framework to identify important patents for building potential patent portfolios based on patents owned by different assignees so as to highlight the value of individual patents in tech...Purpose： This paper suggests a framework to identify important patents for building potential patent portfolios based on patents owned by different assignees so as to highlight the value of individual patents in technology transfer and identify potential collaborators for patent assignees. Design/methodology/approach： The analysis framework includes the following steps： l） co-classification analysis based on the International Patent Classification （IPC） codes and Derwent Manual Codes （DMC） to detect sub-tech fields, 2） keyword co-occurrence analysis aiming to understand the core technology information in each patent, and 3） social network analysis used for identifying important technologies and partnerships of key assignees. A case study was conducted with 27,401 chemistry patents filed by a Chinese national research institute. Findings： The results show that this framework is effective in building potential technological patent portfolios based on patents owned by different assignees and identifying future collaborators for the assignees. This integrated approach based on topic identification and correlation analysis that combines network-based analysis with keyword-based analysis can reveal important patented technologies and their connections and help understand detailed technological information mentioned in patents. Research limitations： In keywords analysis, only titles and abstracts of patent documents were used and weights of keywords in different parts of the documents were not considered.Practical implications： The analysis framework provides valuable information for decision- makers of large institutions which have many patents with broad application prospects. Originality/value： Different from previous patent portfolio studies based on the use of a combination of patent analysis indicators, this study provides insights into a method of building patent portfolios to discover the potential of individual patents in technology transfer and promote cooperation among different patent assignees.展开更多
We consider a structural stochastic volatility model for the loss from a large portfolio of credit risky assets.Both the asset value and the volatility processes are correlated through systemic Brownian motions,with d...We consider a structural stochastic volatility model for the loss from a large portfolio of credit risky assets.Both the asset value and the volatility processes are correlated through systemic Brownian motions,with default determined by the asset value reaching a lower boundary.We prove that if our volatility models are picked from a class of mean-reverting diffusions,the system converges as the portfolio becomes large and,when the vol-of-vol function satisfies certain regularity and boundedness conditions,the limit of the empirical measure process has a density given in terms of a solution to a stochastic initial-boundary value problem on a half-space.The problem is defined in a special weighted Sobolev space.Regularity results are established for solutions to this problem,and then we show that there exists a unique solution.In contrast to the CIR volatility setting covered by the existing literature,our results hold even when the systemic Brownian motions are taken to be correlated.展开更多
Mating patterns in angiosperms are typically nonrandom,yet the mechanisms driving nonrandom mating remain unclear,especially regarding the effects of quantitative floral traits on plant mating success across male and ...Mating patterns in angiosperms are typically nonrandom,yet the mechanisms driving nonrandom mating remain unclear,especially regarding the effects of quantitative floral traits on plant mating success across male and female functions.In this study,we investigated how variation in spur length and flower number per plant influences mating patterns in Aquilegia rockii within a natural population.Using marker-based paternity analyses and manipulative experiments,we assessed the role of these traits in mating success across both sexual functions.We found significant variation in the mate composition between male and female function,with spur-length frequency positively associated with female outcrossing rate and mate number,but not with male outcrossing or mate number.Most mating events occurred within 10 m,and spur-length frequency positively correlated with mating distance.Regardless of selfing,there was evidence for assortative mating for spur length.Although spur length did not correlate with pollinator visitation,plants with mid-length spurs had higher seed set than those with shorter or longer spurs when autonomous selfing was excluded.Flowers number per plant was only associated with mating distance and female outcrossing rate.Our results suggest that spur length plays a key role in nonrandom mating by frequency-dependent mating,with implications for stabilizing selection and maintenance of genetic diversity.This study advances our understanding of floral diversity by dissecting the role of quantitative floral traits in plant mating through both female and male functions.展开更多
Improving the quality of life for Earth's growing population is a complex task that requires the development of new technologies and materials. Perhaps the biggest challenge is access to clean and renewable energy...Improving the quality of life for Earth's growing population is a complex task that requires the development of new technologies and materials. Perhaps the biggest challenge is access to clean and renewable energy sources that can drive a sustainable future. Photovoltaics, today mainly represented by silicon-based solar cells, convert solar energy into electricity and is already an important component in the renewable energy portfolio.展开更多
Portfolios is a well-known investment technique of handling multiple stocks, bonds and securities. However, the previous portfolios investment lack of incorporating the various possible opinions from several experts o...Portfolios is a well-known investment technique of handling multiple stocks, bonds and securities. However, the previous portfolios investment lack of incorporating the various possible opinions from several experts on an given portfolios investment problem. This paper proposes an MC2 linear programming approach to determining weighted coefficients of portfolios that involves multiple experts. The numerical example of the paper shows that the proposed approach likely outperforms the current techniques of portfolios in dealing with the case of multiple experts.展开更多
This study investigates the return dynamics,volatility structure,and risk characteristics of five representative S&P 500 stocks:Johnson&Johnson,Microsoft,NVIDIA,Coca-Cola,and Home Depot,using ARMA-GARCH models...This study investigates the return dynamics,volatility structure,and risk characteristics of five representative S&P 500 stocks:Johnson&Johnson,Microsoft,NVIDIA,Coca-Cola,and Home Depot,using ARMA-GARCH models.Descriptive statistics and diagnostic tests confirm non-normality,negative skewness,fat tails,and volatility clustering,providing strong justification for conditional mean-variance modelling.Optimal model specifications are selected via the Bayesian Information Criterion,with EGARCH frameworks generally outperforming alternative GARCH variants in capturing asymmetric volatility responses.Rolling-window forecasts for 2024Q1 show that the models generate stable and reliable volatility predictions for low-volatility stocks(JNJ,KO),while performance is weaker for highly volatile stocks(NVDA),highlighting structural limitations under extreme market shifts.To evaluate risk management implications,one percent Value-at-Risk and expected shortfall were computed and backtested.Results indicated conservative tail-risk forecasts,with violation rates well within acceptable thresholds.Portfolio applications are further explored by constructing the Global Minimum Variance Portfolio(GMVP)and the Maximum Sharpe Ratio(Max SR)portfolio using rolling covariance estimates.Out-of-sample backtesting demonstrated that the GMVP delivered low volatility but modest returns,whereas the Max SR portfolio achieved significantly higher performance,consistent with the risk-return trade-off.Overall,the findings confirm that ARMA-GARCH models are effective tools for modelling conditional volatility and informing dynamic asset allocation.However,their limited adaptability to jump risk and nonlinear structural breaks underscores the need for more advanced modelling approaches in high-volatility environments.展开更多
Portfolio selection based on the global minimum variance(GMV)model remains a significant focus in financial research.The covariance matrix,central to the GMV model,determines portfolio weights,and its accurate estimat...Portfolio selection based on the global minimum variance(GMV)model remains a significant focus in financial research.The covariance matrix,central to the GMV model,determines portfolio weights,and its accurate estimation is key to effective strategies.Based on the decomposition form of the covariance matrix.This paper introduces semi-variance for improved financial asymmetric risk measurement;addresses asymmetry in financial asset correlations using distance,asymmetric,and Chatterjee correlations to refine covariance matrices;and proposes three new covariance matrix models to enhance risk assessment and portfolio selection strategies.Testing with data from 30 stocks across various sectors of the Chinese market confirms the strong performance of the proposed strategies.展开更多
Project construction and development are an impor-tant part of future army designs.In today’s world,intelligent war-fare and joint operations have become the dominant develop-ments in warfare,so the construction and ...Project construction and development are an impor-tant part of future army designs.In today’s world,intelligent war-fare and joint operations have become the dominant develop-ments in warfare,so the construction and development of the army need top-down,top-level design,and comprehensive plan-ning.The traditional project development model is no longer suf-ficient to meet the army’s complex capability requirements.Projects in various fields need to be developed and coordinated to form a joint force and improve the army’s combat effective-ness.At the same time,when a program consists of large-scale project data,the effectiveness of the traditional,precise mathe-matical planning method is greatly reduced because it is time-consuming,costly,and impractical.To solve above problems,this paper proposes a multi-stage program optimization model based on a heterogeneous network and hybrid genetic algo-rithm and verifies the effectiveness and feasibility of the model and algorithm through an example.The results show that the hybrid algorithm proposed in this paper is better than the exist-ing meta-heuristic algorithm.展开更多
基金supported by the Ministry of Education of the Republic of Korea and the National Research Foundation of Korea(NRF-2022S1A5A8055710).
文摘This study employs a variety of machine learning models and a wide range of economic and financial variables to enhance the forecasting accuracy of the Korean won–U.S.dollar(KRW/USD)exchange rate and the U.S.and Korean stock market returns.We construct international asset allocation portfolios based on these forecasts and evaluate their performance.Our analysis finds that the Elastic Net and LASSO regression models outperform traditional benchmark models in predicting exchange rate and stock market returns,as evidenced by their superior out-of-sample R-squared values.We also identify the key factors crucial for improving the accuracy of forecasting the KRW/USD exchange rate and stock market returns.Furthermore,a machine learning-driven global portfolio that accounts for exchange rate fluctuations demonstrated superior performance.Global portfolios constructed using LASSO(Sharpe ratio=3.45)and Elastic Net(Sharpe ratio=3.48)exhibit a notable performance advantage over traditional benchmark portfolios.This suggests that machine learning models outperform traditional global portfolio construction methods.
文摘In order to deal with the problem that exists in current teaching of English writing,this thesis aims to explore a new process writing approach which combines process-based approach with portfolios assessment.
基金support from the National Natural Science Foundation of China(Grant No.71573085,71974150).
文摘Purpose:Interdisciplinarity is a hot topic in science and technology policy.However,the concept of interdisciplinarity is both abstract and complex,and therefore difficult to measure using a single indicator.A variety of metrics for measuring the diversity and interdisciplinarity of articles,journals,and fields have been proposed in the literature.In this article,we ask whether institutions can be ranked in terms of their(inter-)disciplinary diversity.Design/methodology/approach:We developed a software application(interd_vb.exe)that outputs the values of relevant diversity indicators for any document set or network structure.The software is made available,free to the public,online.The indicators it considers include the advanced diversity indicators Rao-Stirling(RS)diversity and DIV*,as well as standard measures of diversity,such as the Gini coefficient,Shannon entropy,and the Simpson Index.As an empirical demonstration of how the application works,we compared the research portfolios of 42“Double First-Class”Chinese universities across Web of Science Subject Categories(WCs).Findings:The empirical results suggest that DIV*provides results that are more in line with one’s intuitive impressions than RS,particularly when the results are based on sampledependent disparity measures.Furthermore,the scores for diversity are more consistent when based on a global disparity matrix than on a local map.Research limitations:“Interdisciplinarity”can be operationalized as bibliographic coupling among(sets of)documents with references to disciplines.At the institutional level,however,diversity may also indicate comprehensiveness.Unlike impact(e.g.citation),diversity and interdisciplinarity are context-specific and therefore provide a second dimension to the evaluation.Policy or practical implications:Operationalization and quantification make it necessary for analysts to make their choices and options clear.Although the equations used to calculate diversity are often mathematically transparent,the specification in terms of computer code helps the analyst to further precision in decisions.Although diversity is not necessarily a goal of universities,a high diversity score may inform potential policies concerning interdisciplinarity at the university level.Originality/value:This article introduces a non-commercial online application to the public domain that allows researchers and policy analysts to measure“diversity”and“interdisciplinarity”using the various indicators as encompassing as possible for any document set or network structure(e.g.a network of co-authors).Insofar as we know,such a professional computing tool for evaluating data sets using diversity indicators has not yet been made available online.
基金supported by the National Natural Science Foundation of China(71690233)the Scientific Research Foundation of National University of Defense Technology(ZK19-16)the PLA military graduate student funding project.
文摘Equipment selection is an essential work in the research and development planning of equipment.The scientific and rational development of weapons equipment portfolios is of considerable significance to the optimization of equipment architecture design,the adequate resources allocation,and the joint combat performance.From the system view,this paper proposes a method of weapons equipment portfolios selection(WEPS)based on the contribution rate of weapon systems,providing a new idea for weapon equipment portfolio selection.Firstly,we analyze the WEPS problem and the concept of the contribution rate under the systems background.Secondly,we propose a combat network modeling method for weapon equipment systems based on the function chain.Thirdly,we propose a WEPS method based on the contribution rate,fully considering the correlation relationships between potential weapons and the old weapon systems by the combat network model,under the limitation of capability demands and budget resources,with the objective to maximally increasing the combat ability of weapon systems.Finally,we make a case study with a specific WEPS problem where the whole calculation processes and results are analyzed and exhibited to verify the feasibility and effectiveness of the proposed method model.
基金Supported by the NNSF of China (10571141) the Key Project of the NNSF of China (70531030).
文摘In order to study the effect of different risk measures on the efficient portfolios （fron- tier） while properly describing the characteristic of return distributions in the stock market, it is assumed in this paper that the joint return distribution of risky assets obeys the multivariate t-distribution. Under the mean-risk analysis framework, the interrelationship of efficient portfolios （frontier） based on risk measures such as variance, value at risk （VaR）, and expected shortfall （ES） is analyzed and compared. It is proved that, when there is no riskless asset in the market, the efficient frontier under VaR or ES is a subset of the mean-variance （MV） efficient frontier, and the efficient portfolios under VaR or ES are also MV efficient; when there exists a riskless asset in the market, a portfolio is MV efficient if and only if it is a VaR or ES efficient portfolio. The obtained results generalize relevant conclusions about investment theory, and can better guide investors to make their investment decision.
文摘This paper makes use of statistical tools of parameter correlation, multi-parameter regression, and does experimental analysis on issues of risk diversification of portfolios entrusted by National Social Security Fund (NSSF). The issues are industry related investment fields distribution, the trend of capitalization movement, and investment style factors in stock selection. The results show that there are risk problems with portfolios entrusted by NSSF, which include similar investment fields distribution trend, little difference among portfolios, and high risk preference degree.
文摘This research aims to compare different strategies that a non-professional investor in exchange-traded funds (ETFs) could employ to reach a good performance both from profits and from a risk perspective. In recent years, especially after the 2008 crisis, a new technique to evaluate the risk has become more popular, the so-called risk parity, which seeks to equalise the contributions to risk of the portfolio constituents. Our study analyses 17 variants of risk parity portfolio design for groups with the minimum variance strategy and equally weighted portfolio over a pool of 56 ETFs—listed on the Italian Stock Exchange—of eight different categories of specialisation. Empirical results confirm the usefulness of the group risk parity strategies in improving outcomes regarding diversification of risks among classes with good out-of-sample performance with respects to the target models.
文摘This paper is concerned with a study on the efficient frontier characters of portfolio with transaction cost. The conclusion is drawn that all portfolios are of positive correlation on the efficient frontier with transaction cost; the sufficient condition for the derivable efficient frontier has also been achieved. Meanwhile, in comparison with the position of the efficient frontier without transaction cost in the plane (σ 2,R), the conclusion has been made that the efficient frontiers with transaction cost drift and its opening shrinks correspondingly. With this study, the content of the efficient frontier is further enriched. It’s very constructive and important for the practical portfolio investment strategy.
文摘This paper is trying to make some improvement to Markowitz＇s Mean-Variance Model. In this paper, we try to solve the model of portfolio by using Evolutionary Programming under the condition of the covariance matrix which is a non-positive matrix, and design a new method which can improve Markowitz＇s model. At last, we give an illustrative example with the new method.
基金supported by the Science and Technology Service Network Initiative of Chinese Academy of Sciences(Grant No.:KFJ-EW-STS-032)the West Light Foundation of Chinese Academy of Sciences(Grant No.:Y4C0091001)the National Social Science Foundation of China(Grant No.:14CTQ033)
文摘Purpose： This paper suggests a framework to identify important patents for building potential patent portfolios based on patents owned by different assignees so as to highlight the value of individual patents in technology transfer and identify potential collaborators for patent assignees. Design/methodology/approach： The analysis framework includes the following steps： l） co-classification analysis based on the International Patent Classification （IPC） codes and Derwent Manual Codes （DMC） to detect sub-tech fields, 2） keyword co-occurrence analysis aiming to understand the core technology information in each patent, and 3） social network analysis used for identifying important technologies and partnerships of key assignees. A case study was conducted with 27,401 chemistry patents filed by a Chinese national research institute. Findings： The results show that this framework is effective in building potential technological patent portfolios based on patents owned by different assignees and identifying future collaborators for the assignees. This integrated approach based on topic identification and correlation analysis that combines network-based analysis with keyword-based analysis can reveal important patented technologies and their connections and help understand detailed technological information mentioned in patents. Research limitations： In keywords analysis, only titles and abstracts of patent documents were used and weights of keywords in different parts of the documents were not considered.Practical implications： The analysis framework provides valuable information for decision- makers of large institutions which have many patents with broad application prospects. Originality/value： Different from previous patent portfolio studies based on the use of a combination of patent analysis indicators, this study provides insights into a method of building patent portfolios to discover the potential of individual patents in technology transfer and promote cooperation among different patent assignees.
基金supported financially by the United Kingdom Engineering and Physical Sciences Research Council (Grant No.EP/L015811/1)by the Foundation for Education and European Culture (founded by Nicos&Lydia Tricha).
文摘We consider a structural stochastic volatility model for the loss from a large portfolio of credit risky assets.Both the asset value and the volatility processes are correlated through systemic Brownian motions,with default determined by the asset value reaching a lower boundary.We prove that if our volatility models are picked from a class of mean-reverting diffusions,the system converges as the portfolio becomes large and,when the vol-of-vol function satisfies certain regularity and boundedness conditions,the limit of the empirical measure process has a density given in terms of a solution to a stochastic initial-boundary value problem on a half-space.The problem is defined in a special weighted Sobolev space.Regularity results are established for solutions to this problem,and then we show that there exists a unique solution.In contrast to the CIR volatility setting covered by the existing literature,our results hold even when the systemic Brownian motions are taken to be correlated.
基金financially supported by the National Natural Science Foundation of China(32271693)the Cultivating Plan Program for the Leader in Science and Technology of Yunnan Province(202405AC350111)to ZQZ.
文摘Mating patterns in angiosperms are typically nonrandom,yet the mechanisms driving nonrandom mating remain unclear,especially regarding the effects of quantitative floral traits on plant mating success across male and female functions.In this study,we investigated how variation in spur length and flower number per plant influences mating patterns in Aquilegia rockii within a natural population.Using marker-based paternity analyses and manipulative experiments,we assessed the role of these traits in mating success across both sexual functions.We found significant variation in the mate composition between male and female function,with spur-length frequency positively associated with female outcrossing rate and mate number,but not with male outcrossing or mate number.Most mating events occurred within 10 m,and spur-length frequency positively correlated with mating distance.Regardless of selfing,there was evidence for assortative mating for spur length.Although spur length did not correlate with pollinator visitation,plants with mid-length spurs had higher seed set than those with shorter or longer spurs when autonomous selfing was excluded.Flowers number per plant was only associated with mating distance and female outcrossing rate.Our results suggest that spur length plays a key role in nonrandom mating by frequency-dependent mating,with implications for stabilizing selection and maintenance of genetic diversity.This study advances our understanding of floral diversity by dissecting the role of quantitative floral traits in plant mating through both female and male functions.
基金financially supported by the National Science Foundation of China grant (62322407, 22279034, 52261145698, W2421103)Shanghai Science and Technology Innovation Action Plan (22ZR1418900, 24110714100)+1 种基金the Swedish Research Council (project grant no. 2020-04538)the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Link?ping University (Faculty Grant SFO Mat LiU no. 2009 00971)。
文摘Improving the quality of life for Earth's growing population is a complex task that requires the development of new technologies and materials. Perhaps the biggest challenge is access to clean and renewable energy sources that can drive a sustainable future. Photovoltaics, today mainly represented by silicon-based solar cells, convert solar energy into electricity and is already an important component in the renewable energy portfolio.
基金Thisresearch is supported by Naiton Excellent Youth Science Foundation of China (No.7972 50 0 2 )
文摘Portfolios is a well-known investment technique of handling multiple stocks, bonds and securities. However, the previous portfolios investment lack of incorporating the various possible opinions from several experts on an given portfolios investment problem. This paper proposes an MC2 linear programming approach to determining weighted coefficients of portfolios that involves multiple experts. The numerical example of the paper shows that the proposed approach likely outperforms the current techniques of portfolios in dealing with the case of multiple experts.
文摘This study investigates the return dynamics,volatility structure,and risk characteristics of five representative S&P 500 stocks:Johnson&Johnson,Microsoft,NVIDIA,Coca-Cola,and Home Depot,using ARMA-GARCH models.Descriptive statistics and diagnostic tests confirm non-normality,negative skewness,fat tails,and volatility clustering,providing strong justification for conditional mean-variance modelling.Optimal model specifications are selected via the Bayesian Information Criterion,with EGARCH frameworks generally outperforming alternative GARCH variants in capturing asymmetric volatility responses.Rolling-window forecasts for 2024Q1 show that the models generate stable and reliable volatility predictions for low-volatility stocks(JNJ,KO),while performance is weaker for highly volatile stocks(NVDA),highlighting structural limitations under extreme market shifts.To evaluate risk management implications,one percent Value-at-Risk and expected shortfall were computed and backtested.Results indicated conservative tail-risk forecasts,with violation rates well within acceptable thresholds.Portfolio applications are further explored by constructing the Global Minimum Variance Portfolio(GMVP)and the Maximum Sharpe Ratio(Max SR)portfolio using rolling covariance estimates.Out-of-sample backtesting demonstrated that the GMVP delivered low volatility but modest returns,whereas the Max SR portfolio achieved significantly higher performance,consistent with the risk-return trade-off.Overall,the findings confirm that ARMA-GARCH models are effective tools for modelling conditional volatility and informing dynamic asset allocation.However,their limited adaptability to jump risk and nonlinear structural breaks underscores the need for more advanced modelling approaches in high-volatility environments.
基金National Natural Science Foundation of China(Project No.:12201579)。
文摘Portfolio selection based on the global minimum variance(GMV)model remains a significant focus in financial research.The covariance matrix,central to the GMV model,determines portfolio weights,and its accurate estimation is key to effective strategies.Based on the decomposition form of the covariance matrix.This paper introduces semi-variance for improved financial asymmetric risk measurement;addresses asymmetry in financial asset correlations using distance,asymmetric,and Chatterjee correlations to refine covariance matrices;and proposes three new covariance matrix models to enhance risk assessment and portfolio selection strategies.Testing with data from 30 stocks across various sectors of the Chinese market confirms the strong performance of the proposed strategies.
基金supported by the National Natural Science Foundation of China(724701189072431011).
文摘Project construction and development are an impor-tant part of future army designs.In today’s world,intelligent war-fare and joint operations have become the dominant develop-ments in warfare,so the construction and development of the army need top-down,top-level design,and comprehensive plan-ning.The traditional project development model is no longer suf-ficient to meet the army’s complex capability requirements.Projects in various fields need to be developed and coordinated to form a joint force and improve the army’s combat effective-ness.At the same time,when a program consists of large-scale project data,the effectiveness of the traditional,precise mathe-matical planning method is greatly reduced because it is time-consuming,costly,and impractical.To solve above problems,this paper proposes a multi-stage program optimization model based on a heterogeneous network and hybrid genetic algo-rithm and verifies the effectiveness and feasibility of the model and algorithm through an example.The results show that the hybrid algorithm proposed in this paper is better than the exist-ing meta-heuristic algorithm.
