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Towards a Unified Single Analysis Framework Embedded with Multiple Spatial and Time Discretized Methods for Linear Structural Dynamics

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Computer Modeling in Engineering & Sciences 2023年第5期135卷 843-885页

作者： David Tae Kumar K.tamma Department of Mechanical Engineering University of MinnesotaTwin CitiesMinneapolis55455USA

We propose a novel computational framework that is capable of employing different time integration algorithms and different space discretized methods such as the Finite Element Method,particle methods,and other spatial methods on a single body sub-dividedintomultiple *** is in conjunctionwithimplementing thewell known Generalized Single Step Single Solve(GS4)family of algorithms which encompass the entire scope of Linear Multistep algorithms that have been developed over the past 50 years or so and are second order accurate into the Differential Algebraic Equation *** the current state of technology,the coupling of altogether different time integration algorithms has been limited to the same family of algorithms such as theNewmarkmethods and the coupling of different algorithms usually has resulted in reduced accuracy in one or more variables including the Lagrange ***,the robustness and versatility of the GS4 with its ability to accurately account for the numerical shifts in various time schemes it encompasses,overcomes such barriers and allows a wide variety of arbitrary implicit-implicit,implicit-explicit,and explicit-explicit pairing of the various time schemes while maintaining the second order accuracy in time for not only all primary variables such as displacement,velocity and acceleration but also the Lagrange multipliers used for coupling the *** selecting an appropriate spatialmethod and time scheme on the area with localized phenomena contrary to utilizing a single process on the entire body,the proposed work has the potential to better capture the physics of a given *** method is validated by solving 2D problems for the linear second order systems with various combination of spatial methods and time schemes with great *** accuracy and efficacy of the present work have not yet been seen in the current field,and it has shown significant promise in its capabilities and effectiveness for ge

关键词： Time integration structural dynamics multiple scale and multiple methods ordinary differential equations differential algebraic equations

High voltage power transformer condition assessment considering the health index value and its decreasing rate

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High Voltage 2021年第2期6卷 314-327页

作者： Winanda Riga tamma Rahman Azis Prasojo Suwarno School of Electrical Engineering and Informatics Institut Teknologi BandungBandungIndonesia Electrical Engineering Department Politeknik Negeri MalangMalangIndonesia

A health index method is a useful tool for the transformer assessment *** method has been used in several previous ***,most of them have not observed the health index decreasing rate as an aspect to improve the transformer con-dition assessment.A health index method with different approaches is proposed,considering the values and decreasing rate to assess the transformer *** data from in-service and out-of-service 150 kV power transformers provided by the Indonesian electric company are *** correlation between operating age and Health Index value and Health Index decreasing rate was also *** increasing operation age,the Health Index value tends to decrease with a correlation coefficient R2 of *** analysis was conducted to power transformers with historical data of 3 years or more,which showed that the tendency of the Health Index value decreasing rate is higher with older *** paper also illustrates the Health Index analysis of 35 out-of-service transformers,resulting in a more suitable Health Index value compared to the previous *** study proposes the transformer risk assessment based on its health index value and the decreasing rate.

关键词： value power service

The Fundamentals Underlying the Computations of Acceleration for General Dynamic Applications:Issues and Noteworthy Perspectives

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Computer Modeling in Engineering & Sciences 2015年第2期104卷 133-158页

作者： M.Shimada A.Hoitink K.K.tamma Department of Mechanical Engineering University of Minnesota111 Church St.SEMinneapolisMN55455USA.

To-date,with the exception of the Newmark method and the midpoint rule,most computational algorithms under the umbrella of LMS methods,which are predominantly employed in research and commercial software fail to properly evaluate acceleration computations accurately for conducting the numerical dynamic ***,this is not trivial and a sound theoretical basis of the fundamental underlying issues is described in *** this paper,we provide a resolution and point-out several noteworthy perspectives to address the proper evaluation of acceleration computations for structural dynamics applications with focus on the class of LMS methods as an illustration.

关键词： acceleration trivial illustration

A Consistent Time Level Implementation Preserving Second-Order Time Accuracy via a Framework of Unified Time Integrators in the Discrete Element Approach

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Computer Modeling in Engineering & Sciences 2023年第3期134卷 1469-1487页

作者： Tao Xue YazhouWang Masao Shimada David Tae Kumar tamma Xiaobing Zhang School of Energy and Power Engineering Nanjing University of Science and TechnologyNanjing210094China'2Department of Mechanical EngineeringUniversity of Minnesota-Twin CitiesMinneapolis55455USA

In this work,a consistent and physically accurate implementation of the general framework of unified second-order time accurate integrators via the well-known GSSSS framework in the Discrete Element Method is *** improved tangential displacement evaluation in the present implementation of the discrete element method has been derived and implemented to preserve the consistency of the correct time level evaluation during the time integration process in calculating the algorithmic tangential *** numerical examples have been used to validate the proposed tangential displacement evaluation;this is in contrast to past practices which only seem to attain the first-order time accuracy due to inconsistent time level implementation with different algorithms for normal and tangential *** comparisons with the existing implementation and the superiority of the proposed implementation are given in terms of the convergence rate with improved numerical accuracy in ***,several schemes via the unified second-order time integrators within the framework of the GSSSS family have been carried out based on the proposed correct *** the numerical results demonstrate that using the existing state-of-the-art implementation reduces the time accuracy to be first-order accurate in time,while the proposed implementation preserves the correct time accuracy to yield second-order.

关键词： Computational dynamics time integration Discrete Element Method(DEM)

Plastic multilayered closure versus orthopedic surgeon closure after spinal instrumentation in pediatric neuromuscular scoliosis

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World Journal of Pediatric Surgery 2023年第1期6卷 30-35页

作者： Ekene U Ezeokoli Poornima L tamma Neritan Borici Ifeoma Inneh Edward P Buchanan Brian G Smith Department of Orthopedic Surgery Texas Children's HospitalHoustonTexasUSA Baylor College of Medicine HoustonTexasUSA Department of Plastic Surgery Texas Children's HospitalHoustonTexasUSA Department of Orthopedic Surgery Baylor College of MedicineHoustonTexasUSA

Objective To compare wound complication rates between orthopedic closure(OC)and plastic multilayered closure(PMC)in patients undergoing primary posterior spinal fusion for neuromuscular scoliosis(NMS).We hypothesize that multilayered closure will be associated with better postoperative *** We collected data on pediatric patients diagnosed with NMS who underwent first time spinal instrumentation between 1 January 2018 and 31 May *** demographics,length of surgery,spinal levels fused and operative variables,wound complication rate,treatments,and need for wound washout were reviewed in depth and *** In total,86 patients were reviewed:46 with OC and 40 with *** was a significant increase in operating room(OR)time with PMC compared with OC(6.7±1.2 vs 7.3±1.3,p=0.016).There was no difference in complication rate,mean postoperative day of complication or unplanned return to the OR for OC and PMC,*** was a slightly significant increase in the number of patients going home with a drain in the PMC cohort compared with the OC cohort(2.1%vs 15%,p=0.046).Conclusions PMC demonstrated longer OR times than OC and did not demonstrate a statistically significant reduction in wound complications or unplanned returns to the ***,other studies have demonstrated statistical and clinical significance with these *** programs should review internal patient volumes and outcomes for spinal fusion in NMS patients and consider if PMC after spinal fusions in pediatric patients with NMS or other scoliosis subtypes is an appropriate option in their institution to minimize postoperative wound complications.

关键词： wound pediatric closure