Pub Date : 2024-01-01Epub Date: 2021-12-20DOI: 10.1080/03610918.2021.2014887
Hui Zeng, Vernon M Chinchilli, Nasrollah Ghahramani
The natural direct and indirect effects in causal mediation analysis with survival data having one mediator is addressed by VanderWeele (2011) [1]. He derived an approach for (1) an accelerated failure time regression model in general cases and (2) a proportional hazards regression model when the time-to-event outcome is rare. If the outcome is not rare, then VanderWeele (2011) [1] did not derive a simple closed-form expression for the log-natural direct and log-natural indirect effects for the proportional hazards regression model because the baseline cumulative hazard function does not approach zero. We develop two approaches to extend VanderWeele's approach, in which the assumption of a rare outcome is not required. We obtain the natural direct and indirect effects for specific time points through numerical integration after we calculate the cumulative baseline hazard by (1) applying the Breslow method in the Cox proportional hazards regression model to estimate the unspecified cumulative baseline hazard; (2) assuming a piecewise constant baseline hazard model, yielding a parametric model, to estimate the baseline hazard and cumulative baseline hazard. We conduct simulation studies to compare our two approaches with other methods and illustrate our two approaches by applying them to data from the ASsessment, Serial Evaluation, and Subsequent Sequelae in Acute Kidney Injury (ASSESS-AKI) Consortium.
{"title":"Causal inference with a mediated proportional hazards regression model.","authors":"Hui Zeng, Vernon M Chinchilli, Nasrollah Ghahramani","doi":"10.1080/03610918.2021.2014887","DOIUrl":"10.1080/03610918.2021.2014887","url":null,"abstract":"<p><p>The natural direct and indirect effects in causal mediation analysis with survival data having one mediator is addressed by VanderWeele (2011) [1]. He derived an approach for (1) an accelerated failure time regression model in general cases and (2) a proportional hazards regression model when the time-to-event outcome is rare. If the outcome is not rare, then VanderWeele (2011) [1] did not derive a simple closed-form expression for the log-natural direct and log-natural indirect effects for the proportional hazards regression model because the baseline cumulative hazard function does not approach zero. We develop two approaches to extend VanderWeele's approach, in which the assumption of a rare outcome is not required. We obtain the natural direct and indirect effects for specific time points through numerical integration after we calculate the cumulative baseline hazard by (1) applying the Breslow method in the Cox proportional hazards regression model to estimate the unspecified cumulative baseline hazard; (2) assuming a piecewise constant baseline hazard model, yielding a parametric model, to estimate the baseline hazard and cumulative baseline hazard. We conduct simulation studies to compare our two approaches with other methods and illustrate our two approaches by applying them to data from the ASsessment, Serial Evaluation, and Subsequent Sequelae in Acute Kidney Injury (ASSESS-AKI) Consortium.</p>","PeriodicalId":48635,"journal":{"name":"Frontiers of Mechanical Engineering","volume":"11 1","pages":"203-218"},"PeriodicalIF":0.9,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10760952/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74582045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-02DOI: 10.1007/s11465-023-0771-1
Changhe Li
{"title":"Revolution and challenges in machining processing aimed at carbon reduction","authors":"Changhe Li","doi":"10.1007/s11465-023-0771-1","DOIUrl":"https://doi.org/10.1007/s11465-023-0771-1","url":null,"abstract":"","PeriodicalId":48635,"journal":{"name":"Frontiers of Mechanical Engineering","volume":"123 17","pages":""},"PeriodicalIF":4.5,"publicationDate":"2023-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138607194","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.1007/s11465-023-0765-z
Alexander Schmidt, Felix Jensch, Sebastian Härtel
{"title":"Multi-material additive manufacturing-functionally graded materials by means of laser remelting during laser powder bed fusion","authors":"Alexander Schmidt, Felix Jensch, Sebastian Härtel","doi":"10.1007/s11465-023-0765-z","DOIUrl":"https://doi.org/10.1007/s11465-023-0765-z","url":null,"abstract":"","PeriodicalId":48635,"journal":{"name":"Frontiers of Mechanical Engineering","volume":" 22","pages":""},"PeriodicalIF":4.5,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138618464","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A new modeling approach for stress–strain relationship taking into account strain hardening and stored energy by compacted graphite iron evolution","authors":"Jiahui Niu, Chuanzhen Huang, Zhenyu Shi, Hanlian Liu, Zhengyi Tang, Binghao Li, Zhen Chen, Guoyan Jiang","doi":"10.1007/s11465-023-0761-3","DOIUrl":"https://doi.org/10.1007/s11465-023-0761-3","url":null,"abstract":"","PeriodicalId":48635,"journal":{"name":"Frontiers of Mechanical Engineering","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135634061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-01DOI: 10.1007/s11465-023-0746-2
Fatma Bayata, S. B. Vatan
{"title":"Mechanical properties of vanadium-alloyed austempered ductile iron for crankshaft applications","authors":"Fatma Bayata, S. B. Vatan","doi":"10.1007/s11465-023-0746-2","DOIUrl":"https://doi.org/10.1007/s11465-023-0746-2","url":null,"abstract":"","PeriodicalId":48635,"journal":{"name":"Frontiers of Mechanical Engineering","volume":" ","pages":""},"PeriodicalIF":4.5,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46564723","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-01DOI: 10.1007/s11465-023-0752-4
Lianguo Wang, Wei Cai, Yan He, Tao Peng, Jun Xie, Luoke Hu, Li Li
{"title":"Equipment-process-strategy integration for sustainable machining: a review","authors":"Lianguo Wang, Wei Cai, Yan He, Tao Peng, Jun Xie, Luoke Hu, Li Li","doi":"10.1007/s11465-023-0752-4","DOIUrl":"https://doi.org/10.1007/s11465-023-0752-4","url":null,"abstract":"","PeriodicalId":48635,"journal":{"name":"Frontiers of Mechanical Engineering","volume":" ","pages":""},"PeriodicalIF":4.5,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49475690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-01DOI: 10.1007/s11465-023-0756-0
Zheshuai Yang, Laihao Yang, Yu Sun, Xuefeng Chen
Abstract In-situ maintenance is of great significance for improving the efficiency and ensuring the safety of aeroengines. The cable-driven continuum robot (CDCR) with twin-pivot compliant mechanisms, which is enabled with flexible deformation capability and confined space accessibility, has emerged as a novel tool that aims to promote the development of intelligence and efficiency for in-situ aero-engine maintenance. The high-fidelity model that describes the kinematic and morphology of CDCR lays the foundation for the accurate operation and control for in-situ maintenance. However, this model was not well addressed in previous literature. In this study, a general kinetostatic modeling and morphology characterization methodology that comprehensively contains the effects of cable-hole friction, gravity, and payloads is proposed for the CDCR with twin-pivot compliant mechanisms. First, a novel cable-hole friction model with the variable friction coefficient and adaptive friction direction criterion is proposed through structure optimization and kinematic parameter analysis. Second, the cable-hole friction, all-component gravities, deflection-induced center-of-gravity shift of compliant joints, and payloads are all considered to deduce a comprehensive kinetostatic model enabled with the capacity of accurate morphology characterization for CDCR. Finally, a compact continuum robot system is integrated to experimentally validate the proposed kinetostatic model and the concept of in-situ aero-engine maintenance. Results indicate that the proposed model precisely predicts the morphology of CDCR and outperforms conventional models. The compact continuum robot system could be considered a novel solution to perform in-situ maintenance tasks of aero-engines in an invasive manner.
{"title":"Comprehensive kinetostatic modeling and morphology characterization of cable-driven continuum robots for in-situ aero-engine maintenance","authors":"Zheshuai Yang, Laihao Yang, Yu Sun, Xuefeng Chen","doi":"10.1007/s11465-023-0756-0","DOIUrl":"https://doi.org/10.1007/s11465-023-0756-0","url":null,"abstract":"Abstract In-situ maintenance is of great significance for improving the efficiency and ensuring the safety of aeroengines. The cable-driven continuum robot (CDCR) with twin-pivot compliant mechanisms, which is enabled with flexible deformation capability and confined space accessibility, has emerged as a novel tool that aims to promote the development of intelligence and efficiency for in-situ aero-engine maintenance. The high-fidelity model that describes the kinematic and morphology of CDCR lays the foundation for the accurate operation and control for in-situ maintenance. However, this model was not well addressed in previous literature. In this study, a general kinetostatic modeling and morphology characterization methodology that comprehensively contains the effects of cable-hole friction, gravity, and payloads is proposed for the CDCR with twin-pivot compliant mechanisms. First, a novel cable-hole friction model with the variable friction coefficient and adaptive friction direction criterion is proposed through structure optimization and kinematic parameter analysis. Second, the cable-hole friction, all-component gravities, deflection-induced center-of-gravity shift of compliant joints, and payloads are all considered to deduce a comprehensive kinetostatic model enabled with the capacity of accurate morphology characterization for CDCR. Finally, a compact continuum robot system is integrated to experimentally validate the proposed kinetostatic model and the concept of in-situ aero-engine maintenance. Results indicate that the proposed model precisely predicts the morphology of CDCR and outperforms conventional models. The compact continuum robot system could be considered a novel solution to perform in-situ maintenance tasks of aero-engines in an invasive manner.","PeriodicalId":48635,"journal":{"name":"Frontiers of Mechanical Engineering","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135638373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-01DOI: 10.1007/s11465-023-0753-3
Yiming Yan, Shuting Wang, Yuanlong Xie, Hao Wu, Shiqi Zheng, Hu Li
{"title":"Obstacle-circumventing adaptive control of a four-wheeled mobile robot subjected to motion uncertainties","authors":"Yiming Yan, Shuting Wang, Yuanlong Xie, Hao Wu, Shiqi Zheng, Hu Li","doi":"10.1007/s11465-023-0753-3","DOIUrl":"https://doi.org/10.1007/s11465-023-0753-3","url":null,"abstract":"","PeriodicalId":48635,"journal":{"name":"Frontiers of Mechanical Engineering","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135690137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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