The physical model of a ten-strand billet caster tundish was established to study the effects of various flow control devices on the melt flow. Before and after the optimization of the melt flow, the inclusion removal...The physical model of a ten-strand billet caster tundish was established to study the effects of various flow control devices on the melt flow. Before and after the optimization of the melt flow, the inclusion removal in the tundish was evaluated by plant trials. The physical modeling results show that when combined with a baffle, the turbulence inhibitor, instead of the impact pad, can significantly improve the melt flow. A turbulence inhibitor with a longer length of inner cavity and without an extending lip at the top of the sidewall seems to be efficient in the improvement of the melt flow. Various types and designs of baffles all influence the flow characteristics significantly. The "V" type baffles are better than the straight baffles for flow control. The "V" type baffle with four inclined holes at the sidewall away from the stopper rods is better in melt flow control than the one with one inclined hole at each sidewall. The combination of a well-designed turbulence inhibitor and an appropriate baffle shows high efficiency on improving the melt flow and an optimal proposal was presented. Plant trials indicate that, compared with the original tundish configuration in prototype, the inclusions reduce by 42% and the inclusion distribution of individual strands is more similar with the optimal one. The optimal tundish configuration effectively improves the melt flow in the ten-strand billet caster tundish.展开更多
AIM:To present statistical tools to model and optimize the cost of a randomized clinical trial as a function of the stringency of patient inclusion criteria.METHODS: We consider a two treatment, dichotomous outcome tr...AIM:To present statistical tools to model and optimize the cost of a randomized clinical trial as a function of the stringency of patient inclusion criteria.METHODS: We consider a two treatment, dichotomous outcome trial that includes a proportion of patients who are strong responders to the tested intervention. Patients are screened for inclusion using an arbitrary number of test results that are combined into an aggregate suitability score. The screening score is regarded as a diagnostic test for the responsive phenotype, having a specific cutoff value for inclusion and a particular sensitivity and specificity. The cutoff is a measure of stringency of inclusion criteria. Total cost is modeled as a function of the cutoff value, number of patients screened, the number of patients included, the case occurrence rate, response probabilities for control and experimental treatments, and the trial duration required to produce a statistically significant result with a specified power. Regression methods are developed to estimate relevant model parameters from pilot data in an adaptive trial design. RESULTS: The patient numbers and total cost are strongly related to the choice of the cutoff for inclusion. Clear cost minimums exist between 5.6 and 6.1 on arepresentative 10-point scale of exclusiveness. Potential cost savings for typical trial scenarios range in millions of dollars. As the response rate for controls approaches 50%, the proper choice of inclusion criteria can mean the difference between a successful trial and a failed trial. CONCLUSION: Early formal estimation of optimal inclusion criteria allows planning of clinical trials to avoid high costs, excessive delays, and moral hazards of Type II errors.展开更多
Objective To understand the real-world study(RWS)and its application in domestic and foreign pharmaceutical device regulatory decision-making,so as to promote its further application in the decision-making of medical ...Objective To understand the real-world study(RWS)and its application in domestic and foreign pharmaceutical device regulatory decision-making,so as to promote its further application in the decision-making of medical devices supervision in China.Methods Literature analysis and comparative analysis were used to compare the real-world evidence(RWE)and randomized controlled trials to obtain the development status of medical devices in China and the United States.Results and Conclusion It is found that the application of RWS in the field of medical devices has many advantages,which can make up for the deficiencies of traditional clinical data.In addition,the RWE has a wide range of applications in the field of medical devices in China.In recent years,the RWE has received extensive attention in the medical field in the United States.The FDA has issued related guidelines,and its applications have gradually formed a complete system.Research on RWE will become the development trend of clinical evaluation of medical devices in the future.While attaching importance to the development of the RWE,China should learn from the specifications of relevant foreign organizations to improve its development in the field of health.展开更多
基金supported by the National Natural Science Foundation of China(No.51474059,No.51204042)the Program for Liaoning Excellent Talents in University(No.LJQ2014031)the Fundamental Research Funds for the Central Universities(No.N140205003)
文摘The physical model of a ten-strand billet caster tundish was established to study the effects of various flow control devices on the melt flow. Before and after the optimization of the melt flow, the inclusion removal in the tundish was evaluated by plant trials. The physical modeling results show that when combined with a baffle, the turbulence inhibitor, instead of the impact pad, can significantly improve the melt flow. A turbulence inhibitor with a longer length of inner cavity and without an extending lip at the top of the sidewall seems to be efficient in the improvement of the melt flow. Various types and designs of baffles all influence the flow characteristics significantly. The "V" type baffles are better than the straight baffles for flow control. The "V" type baffle with four inclined holes at the sidewall away from the stopper rods is better in melt flow control than the one with one inclined hole at each sidewall. The combination of a well-designed turbulence inhibitor and an appropriate baffle shows high efficiency on improving the melt flow and an optimal proposal was presented. Plant trials indicate that, compared with the original tundish configuration in prototype, the inclusions reduce by 42% and the inclusion distribution of individual strands is more similar with the optimal one. The optimal tundish configuration effectively improves the melt flow in the ten-strand billet caster tundish.
文摘AIM:To present statistical tools to model and optimize the cost of a randomized clinical trial as a function of the stringency of patient inclusion criteria.METHODS: We consider a two treatment, dichotomous outcome trial that includes a proportion of patients who are strong responders to the tested intervention. Patients are screened for inclusion using an arbitrary number of test results that are combined into an aggregate suitability score. The screening score is regarded as a diagnostic test for the responsive phenotype, having a specific cutoff value for inclusion and a particular sensitivity and specificity. The cutoff is a measure of stringency of inclusion criteria. Total cost is modeled as a function of the cutoff value, number of patients screened, the number of patients included, the case occurrence rate, response probabilities for control and experimental treatments, and the trial duration required to produce a statistically significant result with a specified power. Regression methods are developed to estimate relevant model parameters from pilot data in an adaptive trial design. RESULTS: The patient numbers and total cost are strongly related to the choice of the cutoff for inclusion. Clear cost minimums exist between 5.6 and 6.1 on arepresentative 10-point scale of exclusiveness. Potential cost savings for typical trial scenarios range in millions of dollars. As the response rate for controls approaches 50%, the proper choice of inclusion criteria can mean the difference between a successful trial and a failed trial. CONCLUSION: Early formal estimation of optimal inclusion criteria allows planning of clinical trials to avoid high costs, excessive delays, and moral hazards of Type II errors.
文摘Objective To understand the real-world study(RWS)and its application in domestic and foreign pharmaceutical device regulatory decision-making,so as to promote its further application in the decision-making of medical devices supervision in China.Methods Literature analysis and comparative analysis were used to compare the real-world evidence(RWE)and randomized controlled trials to obtain the development status of medical devices in China and the United States.Results and Conclusion It is found that the application of RWS in the field of medical devices has many advantages,which can make up for the deficiencies of traditional clinical data.In addition,the RWE has a wide range of applications in the field of medical devices in China.In recent years,the RWE has received extensive attention in the medical field in the United States.The FDA has issued related guidelines,and its applications have gradually formed a complete system.Research on RWE will become the development trend of clinical evaluation of medical devices in the future.While attaching importance to the development of the RWE,China should learn from the specifications of relevant foreign organizations to improve its development in the field of health.
