Delay-difference models are intermediate between simple surplus-production models and complicated age-structured models. Such intermediate models are more efficient and require less data than age-structured models. In...Delay-difference models are intermediate between simple surplus-production models and complicated age-structured models. Such intermediate models are more efficient and require less data than age-structured models. In this study, a delay-differ- ence model was applied to fit catch and catch per unit effort （CPUE） data （1975-2011） of the southern Atlantic albacore （Thunnus alalunga） stock. The proposed delay-difference model captures annual fluctuations in predicted CPUE data better than Fox model. In a Monte Carlo simulation, white noises （CVs） were superimposed on the observed CPUE data at four levels. Relative estimate error was then calculated to compare the estimated results with the true values of parameters a and fl in Ricker stock-recruitment model and the catchability coefficient q. a is more sensitive to CV than fl and q. We also calculated an 80% percentile confidence interval of the maximum sustainable yield （MSY, 21756 t to 23408 t; median 22490 t） with the delay-difference model. The yield of the southern Atlantic albacore stock in 2011 was 24122t, and the estimated ratios of catch against MSY for the past seven years were approxi- mately 1.0. We suggest that care should be taken to protect the albacore fishery in the southern Atlantic Ocean. The proposed de- lay-difference model provides a good fit to the data of southern Atlantic albacore stock and may be a useful choice for the assessment of regional albacore stock.展开更多
Although widely used, both the Markowitz model and VAR (Value at Risk) model have some limitations in evaluating the risk and return of stock investment. By the analysis of the conceptions of risk and return, together...Although widely used, both the Markowitz model and VAR (Value at Risk) model have some limitations in evaluating the risk and return of stock investment. By the analysis of the conceptions of risk and return, together with the three hypotheses of technological analysis, a novelty model of metering and evaluating the risk and return of stock investment is established. The major indicator of this model , risk-return ratio K, combines the characteristic indicators of risk and return. Regardless of the form of the risk-return probability density functions, this indicator K can always reflect the risk-return performances of the invested stocks clearly and accurately. How to use the model to make optimum investment and how to make portfolio combined with clustering analysis is also explained.展开更多
Removal of the length ef fect in otolith shape analysis for stock identification using length scaling is an important issue; however, few studies have attempted to investigate the ef fectiveness or weakness of this me...Removal of the length ef fect in otolith shape analysis for stock identification using length scaling is an important issue; however, few studies have attempted to investigate the ef fectiveness or weakness of this methodology in application. The aim of this study was to evaluate whether commonly used size scaling methods and normalized elliptic Fourier descriptors(NEFDs) could ef fectively remove the size ef fect of fish in stock discrimination. To achieve this goal, length groups from two known geographical stocks of yellow croaker, L arimichthys polyactis, along the Chinese coast(five groups from the Changjiang River estuary of the East China Sea and three groups from the Bohai Sea) were subjected to otolith shape analysis. The results indicated that the variation of otolith shape caused by intra-stock fish length might exceed that due to inter-stock geographical separation, even when otolith shape variables are standardized with length scaling methods. This variation could easily result in misleading stock discrimination through otolith shape analysis. Therefore, conclusions about fish stock structure should be carefully drawn from otolith shape analysis because the observed discrimination may primarily be due to length ef fects, rather than dif ferences among stocks. The application of multiple methods, such as otoliths shape analysis combined with elemental fingering, tagging or genetic analysis, is recommended for sock identification.展开更多
Objective： To assess the interobserver agreement on Garden classification of fresh femoral neck fracture and management plan based on anteroposterior （AP） view and also assess if the addition of lateral view change...Objective： To assess the interobserver agreement on Garden classification of fresh femoral neck fracture and management plan based on anteroposterior （AP） view and also assess if the addition of lateral view changes the classification and management plan. Methods： Ten orthopaedic surgeons were asked to classify 35 femoral neck fractures on AP view only and propose the management plan. Then the same films were reshown in conjunction with their lateral view after 10 days. Results were compared with respect to the classification and management plan between two groups. Interobserver agreement was calculated using Fleiss＇ kappa. Results： There was only a fair interobserver agreement （kappa value 0.39） on Garden classification on AP view only which improved to moderate agreement （kappa value 0.52） after adding a lateral view. While there was only a slight improvement in the interobserver agreement on the management plan on AP view only （kappa value 0.50） and AP combined with lateral views （kappa value 0.52）. Supplementation of the lateral view changed the classification in 15.42% of the cases and altered the management plan in 23.14% of the cases. Conclusion： We conclude that lateral view should be obtained routinely on all patients with suspected femoral neck fracture as it definitely has a role in planning treatment of femoral neck fracture.展开更多
The authors employ the recent stochastic-control-based approach to financial mathematicsto solve a problem of determination of the risk premium for a stochastic interest rate model,andthe corresponding problem of equi...The authors employ the recent stochastic-control-based approach to financial mathematicsto solve a problem of determination of the risk premium for a stochastic interest rate model,andthe corresponding problem of equity valuation.The risk premium is determined explicitly,by meansof solving a corresponding partial differential equation (PDE),in two forms:one,time-dependent,corresponding to a finite time contract expiration,and the simpler version corresponding to perpetualcontracts.As stocks are perpetual contracts,when solving the problem of equity valuation,the latterform of the risk premium is used.By means of solving the general pricing PDE,an efficient equityvaluation method was developed that is a combination of some sophisticated explicit formulas,and anumerical procedure.展开更多
Objective： To evaluate the anatomy of femoral tunnels created by simulated transtibial technique in double-bundle anterior cruciate ligament （ACL） reconstruction. Methods： Two tibial tunnels, anteromedial （AM） ...Objective： To evaluate the anatomy of femoral tunnels created by simulated transtibial technique in double-bundle anterior cruciate ligament （ACL） reconstruction. Methods： Two tibial tunnels, anteromedial （AM） and posterolateral （PL）, were drilled 45° and 55° to tibial plateau respectively. On the femoral side, the AM and PL tunnels were drilled through anteriomedial portal. After the four tun- nels were established, the shaft of a reamer was introduced into the joint through tibial tunnel and reached against the lateral wall of intercondylar notch. The position that the reamer shaft can reach was marked and recorded. Results： Neither femoral AM nor PL tunnel opening can be fully or partially reached by the reamer shaft through the tibial AM tunnel in all cases. The evaluation through the tibial PL tunnel showed that only in 8 of 50 cases （16%） the femoral AM tunnel opening and in 4 cases （8%） the PL opening can be fully reached. On the other hand, in 12 cases （24%） the femoral AM tunnel opening and in 10 cases （20%） the PL opening can be partially reached by the shafts through the tibial PL tunnel. Conclusion： The result strongly suggests that transtibial technique is not well competent for femoral tun- nel drilling in anatomic double-bundle ACL reconstruction as we have hypothesized.展开更多
This paper studies the relationships of the monetary policy, stock market and real investment in China based on Markov-Switching-Vector Error Correction Model. It shows that there is a cointegration relationship among...This paper studies the relationships of the monetary policy, stock market and real investment in China based on Markov-Switching-Vector Error Correction Model. It shows that there is a cointegration relationship among the three ones. We disclose the riddle that the stock market is in recession, but the growth rate of economy is very high in recent years. We also find that Chinese economy operated stably most of the time during the past 8 years. But if the economy is difficult to continue its high growth, it is more likely to appear ＂hard landing＂ than ＂soft landing＂. The impulse response analysis indicates the asymmetry between the ＂too cold＂ economy regime and the ＂too hot＂ regime. And the economy will oscillate during the subsequent time when it is shocked under the ＂too hot＂ regime.展开更多
基金supported by the Fundamental Research Funds for the Central Universities of China (Grant No. 201022001)
文摘Delay-difference models are intermediate between simple surplus-production models and complicated age-structured models. Such intermediate models are more efficient and require less data than age-structured models. In this study, a delay-differ- ence model was applied to fit catch and catch per unit effort （CPUE） data （1975-2011） of the southern Atlantic albacore （Thunnus alalunga） stock. The proposed delay-difference model captures annual fluctuations in predicted CPUE data better than Fox model. In a Monte Carlo simulation, white noises （CVs） were superimposed on the observed CPUE data at four levels. Relative estimate error was then calculated to compare the estimated results with the true values of parameters a and fl in Ricker stock-recruitment model and the catchability coefficient q. a is more sensitive to CV than fl and q. We also calculated an 80% percentile confidence interval of the maximum sustainable yield （MSY, 21756 t to 23408 t; median 22490 t） with the delay-difference model. The yield of the southern Atlantic albacore stock in 2011 was 24122t, and the estimated ratios of catch against MSY for the past seven years were approxi- mately 1.0. We suggest that care should be taken to protect the albacore fishery in the southern Atlantic Ocean. The proposed de- lay-difference model provides a good fit to the data of southern Atlantic albacore stock and may be a useful choice for the assessment of regional albacore stock.
文摘Although widely used, both the Markowitz model and VAR (Value at Risk) model have some limitations in evaluating the risk and return of stock investment. By the analysis of the conceptions of risk and return, together with the three hypotheses of technological analysis, a novelty model of metering and evaluating the risk and return of stock investment is established. The major indicator of this model , risk-return ratio K, combines the characteristic indicators of risk and return. Regardless of the form of the risk-return probability density functions, this indicator K can always reflect the risk-return performances of the invested stocks clearly and accurately. How to use the model to make optimum investment and how to make portfolio combined with clustering analysis is also explained.
基金Supported by the National Basic Research Program of China(973 Program)(No.2015CB453302)the NSFC-Shandong Joint Fund for Marine Science Research Centre(No.U1606404)the Aoshan Science and Technology Innovation Project(No.2015ASKJ02-04)
文摘Removal of the length ef fect in otolith shape analysis for stock identification using length scaling is an important issue; however, few studies have attempted to investigate the ef fectiveness or weakness of this methodology in application. The aim of this study was to evaluate whether commonly used size scaling methods and normalized elliptic Fourier descriptors(NEFDs) could ef fectively remove the size ef fect of fish in stock discrimination. To achieve this goal, length groups from two known geographical stocks of yellow croaker, L arimichthys polyactis, along the Chinese coast(five groups from the Changjiang River estuary of the East China Sea and three groups from the Bohai Sea) were subjected to otolith shape analysis. The results indicated that the variation of otolith shape caused by intra-stock fish length might exceed that due to inter-stock geographical separation, even when otolith shape variables are standardized with length scaling methods. This variation could easily result in misleading stock discrimination through otolith shape analysis. Therefore, conclusions about fish stock structure should be carefully drawn from otolith shape analysis because the observed discrimination may primarily be due to length ef fects, rather than dif ferences among stocks. The application of multiple methods, such as otoliths shape analysis combined with elemental fingering, tagging or genetic analysis, is recommended for sock identification.
文摘Objective： To assess the interobserver agreement on Garden classification of fresh femoral neck fracture and management plan based on anteroposterior （AP） view and also assess if the addition of lateral view changes the classification and management plan. Methods： Ten orthopaedic surgeons were asked to classify 35 femoral neck fractures on AP view only and propose the management plan. Then the same films were reshown in conjunction with their lateral view after 10 days. Results were compared with respect to the classification and management plan between two groups. Interobserver agreement was calculated using Fleiss＇ kappa. Results： There was only a fair interobserver agreement （kappa value 0.39） on Garden classification on AP view only which improved to moderate agreement （kappa value 0.52） after adding a lateral view. While there was only a slight improvement in the interobserver agreement on the management plan on AP view only （kappa value 0.50） and AP combined with lateral views （kappa value 0.52）. Supplementation of the lateral view changed the classification in 15.42% of the cases and altered the management plan in 23.14% of the cases. Conclusion： We conclude that lateral view should be obtained routinely on all patients with suspected femoral neck fracture as it definitely has a role in planning treatment of femoral neck fracture.
基金supported in part by the Center for Financial Engineering at the Suzhou University, Chinathe Taft Research Center at the University of Cincinnati, USA
文摘The authors employ the recent stochastic-control-based approach to financial mathematicsto solve a problem of determination of the risk premium for a stochastic interest rate model,andthe corresponding problem of equity valuation.The risk premium is determined explicitly,by meansof solving a corresponding partial differential equation (PDE),in two forms:one,time-dependent,corresponding to a finite time contract expiration,and the simpler version corresponding to perpetualcontracts.As stocks are perpetual contracts,when solving the problem of equity valuation,the latterform of the risk premium is used.By means of solving the general pricing PDE,an efficient equityvaluation method was developed that is a combination of some sophisticated explicit formulas,and anumerical procedure.
文摘Objective： To evaluate the anatomy of femoral tunnels created by simulated transtibial technique in double-bundle anterior cruciate ligament （ACL） reconstruction. Methods： Two tibial tunnels, anteromedial （AM） and posterolateral （PL）, were drilled 45° and 55° to tibial plateau respectively. On the femoral side, the AM and PL tunnels were drilled through anteriomedial portal. After the four tun- nels were established, the shaft of a reamer was introduced into the joint through tibial tunnel and reached against the lateral wall of intercondylar notch. The position that the reamer shaft can reach was marked and recorded. Results： Neither femoral AM nor PL tunnel opening can be fully or partially reached by the reamer shaft through the tibial AM tunnel in all cases. The evaluation through the tibial PL tunnel showed that only in 8 of 50 cases （16%） the femoral AM tunnel opening and in 4 cases （8%） the PL opening can be fully reached. On the other hand, in 12 cases （24%） the femoral AM tunnel opening and in 10 cases （20%） the PL opening can be partially reached by the shafts through the tibial PL tunnel. Conclusion： The result strongly suggests that transtibial technique is not well competent for femoral tun- nel drilling in anatomic double-bundle ACL reconstruction as we have hypothesized.
文摘This paper studies the relationships of the monetary policy, stock market and real investment in China based on Markov-Switching-Vector Error Correction Model. It shows that there is a cointegration relationship among the three ones. We disclose the riddle that the stock market is in recession, but the growth rate of economy is very high in recent years. We also find that Chinese economy operated stably most of the time during the past 8 years. But if the economy is difficult to continue its high growth, it is more likely to appear ＂hard landing＂ than ＂soft landing＂. The impulse response analysis indicates the asymmetry between the ＂too cold＂ economy regime and the ＂too hot＂ regime. And the economy will oscillate during the subsequent time when it is shocked under the ＂too hot＂ regime.
