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Failure Mechanism of O-Ring Seals under Extreme Operating Conditions

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Modern Mechanical Engineering 2018年第1期8卷 11-30页

作者： Gyorgy Szabó károly váradi Department of Machine and Product Design Budapest University of Technology and EconomicsBudapestHungary

In this paper the behavior of an O-ring made of NBR rubber was investigated under extreme conditions. The effect of the extreme initial compression, operating pressure and extreme temperature conditions were examined. The rubber material was tested in simple tension, pure shear and equibiaxial tension modes complemented with a Dynamic Mechanical Thermal Analysis (DMTA) to capture the viscoelastic behavior of the material. For the investigation, a large-strain viscoelastic material model was developed by the authors, to take into account the large deformations caused by extreme conditions. Insufficient space during installation causes extreme initial compression consequently leading the material to crack on the contacting outer surfaces. It was found that the excessive strain and friction induced shear stress contributes primarily to this phenomenon. Extreme operating pressure causes the seal to penetrate into the gap between the shaft and the housing. This behavior damages the material and cracks appear on the seal. High strain areas were found in the proximity of the gap in the material. The analysis of the extreme operating temperature showed that during cooling the O-ring can completely loose its ability to seal at -70°C. There are three contributing factors: the speed of cooling, the temperature and the coefficient of thermal expansion.

关键词： O-Rings Finite Element Analysis Initial Pressure Overpressure Temperature Extremes

Finite Element Model of a Filament-Wound Composite Tube Subjected to Uniaxial Tension

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Modern Mechanical Engineering 2017年第4期7卷 91-112页

作者： Gyula Szabó károly váradi Dávid Felhos Department of Machine and Product Design Budapest University of Technology and EconomicsBudapestHungary

The aim of this paper is to demonstrate the mechanical behaviour of a filament-wound composite tube subjected to uniaxial tension by finite element analysis. Uniaxial tensile test experiments have been carried out on standard specimen and hose piece in order to verify finite element models and material properties and also to assess failure mode of composite plies. Composite reinforcement plies are modeled as linear orthotropic, while elastomer liners are described by hyperelastic material model. Results of finite element models and experiments show good agreement in the initial phase of uniaxial tension, which justifies utilized material models in the operating range. Results of finite element models show that transverse tension and shear load are dominant under tension. It is determined that principal failure mode of reinforcement plies is intra-ply yarn-matrix debonding caused by intensive shear of rubber matrix.

关键词： Filament-Wound Composite Tube Uniaxial Tension Tensile Test Debonding Damage Finite Element Analysis

Bending Analysis of a Filament-Wound Composite Tube

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Modern Mechanical Engineering 2018年第1期8卷 66-77页

作者： Gyula Szabó károly váradi Dávid Felhos Department of Machine and Product Design Budapest University of Technology and EconomicsBudapestHungary

The aim of this paper is to present finite element model of a filament-wound composite tube subjected to three-point bending and bending in accordance with standard EN?15807:2011?(railway applications-pneumatic half couplings) along with its experimental verification. In the finite element model, composite reinforcement plies have been characterized by linear orthotropic material model, while rubber liners have been described by a two-parameter MooneyRivlin model. Force-displacement curves of three-point bending show fairly good agreement between simulation results and experimental data. Reaction forces of FE simulation and experiment of standard bending test are in good agreement.

关键词： Filament-Wound Composite Tube Three-Point Bending Test Bending Analysis Finite Element Model

Stress Analysis of Bolted Joints Part I. Numerical Dimensioning Method

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Modern Mechanical Engineering 2014年第1期4卷 35-45页

作者： László Molnár károly váradi Balázs Liktor Department of Machine and Product Design Budapest University of Technology and Economics Budapest Hungary

For up-to-date bolted joints, first of all in vehicles, high strength bolts of 10.9 or even 12.9 are used, which are pre-tightened up to 90% or even 100% of the yield strength. The primary aim of this high degree utilization is the weight reduction. For the analytic dimensioning of bolted joints, the vDI 2230 Richtlinien German standard provides support. However, the analytic model can mostly consider the true structural characteristics only in a limited way. The analytic modeling is especially uncertain in case of multiple bolted joints when the load distribution among the bolts depends reasonably upon the elastic deformation of the participating elements in the joints over the geometry of the bolted joint. The first part of this paper deals with the problems of numerical modeling and stress analysis, respectively specifying the analytic dimensioning procedure by applying elastic or rather elastic-plastic material law. The error magnitude in bolted joint calculation was examined in case of omitting the existing threaded connection—between the bolt and the nut—in order to simplify the model. The second part of the paper deals with the dimensioning of stands and cantilevers’ multi-bolt fixing problems, first of all, with the load distribution among the bolts keeping in view the analysis of the local slipping relations. For demonstrating the above technique, an elaborated numeric procedure is presented for a four-bolted cantilever, having bolted joints pre-tightened to the yield strength.

关键词： Bolted Joints Numerical Modeling FE Stress Analysis

Stress Analysis of Bolted Joints Part II. Contact and Slip Analysis of a Four Bolt Joint

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Modern Mechanical Engineering 2014年第1期4卷 46-55页

作者： László Molnár károly váradi János Holubán Andor Tamási Department of Machine and Product Design Budapest University of Technology and Economics Budapest Hungary

For up-to-date bolted joints, first of all in vehicles, high strength bolts of 10.9 or even 12.9 are used, which are preloaded up to 90% or even 100% of the yield strength. The primary aim of this high degree utilization is the weight reduction. For the analytic dimensioning of bolted joints, the vDI 2230 Richtlinien German standard [1] provides support. However, the analytic model can mostly consider the true structural characteristics only in a limited way. The analytic modeling is especially uncertain in case of multiple bolted joints when the load distribution among the bolts depends reasonably upon the elastic deformation of the participating elements in the joints over the geometry of the bolted joint. The first part of this paper deals with the problems of numerical modeling and stress analysis, respectively specifying the analytic dimensioning procedure by applying elastic or rather elastic-plastic material law. The error magnitude in bolted joint calculation was examined in case of omitting the existing threaded connection—between the bolt and the nut—in order to simplify the model. The second part of the paper deals with the dimensioning of stands and cantilevers’ multi-bolt fixing problems, first of all, with the load distribution among the bolts keeping in view the analysis of the local slipping relations. For demonstrating the above technique, an elaborated numeric procedure is presented for a four-bolted cantilever, having bolted joints pre-tightened to the yield strength.

关键词： Bolted Joints Numerical Modeling Stress Analysis

Semantic Segmentation of Lumbar vertebrae Using Meijering U-Net(MU-Net)on Spine Magnetic Resonance Images

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Computer Modeling in Engineering & Sciences 2025年第1期142卷 733-757页

作者： Lakshmi S v v Shiloah Elizabeth Darmanayagam Sunil Retmin Raj Cyril Department of Computer Science and Engineering College of Engineering GuindyAnna UniversityChennai600025India Department of Information Technology Madras Institute of TechnologyAnna UniversityChrompetChennai600044India

Lower back pain is one of the most common medical problems in the world and it is experienced by a huge percentage of people *** to its ability to produce a detailed view of the soft tissues,including the spinal cord,nerves,intervertebral discs,and vertebrae,Magnetic Resonance Imaging is thought to be the most effective method for imaging the *** semantic segmentation of vertebrae plays a major role in the diagnostic process of lumbar *** is difficult to semantically partition the vertebrae in Magnetic Resonance Images from the surrounding variety of tissues,including muscles,ligaments,and intervertebral discs.U-Net is a powerful deep-learning architecture to handle the challenges of medical image analysis tasks and achieves high segmentation *** work proposes a modified U-Net architecture namely MU-Net,consisting of the Meijering convolutional layer that incorporates the Meijering filter to perform the semantic segmentation of lumbar vertebrae L1 to L5 and sacral vertebra ***-colour mask images were generated and used as ground truth for training the *** work has been carried out on 1312 images expanded from T1-weighted mid-sagittal MRI images of 515 patients in the Lumbar Spine MRI Dataset publicly available from Mendeley *** proposed MU-Net model for the semantic segmentation of the lumbar vertebrae gives better performance with 98.79%of pixel accuracy(PA),98.66%of dice similarity coefficient(DSC),97.36%of Jaccard coefficient,and 92.55%mean Intersection over Union(mean IoU)metrics using the mentioned dataset.

关键词： Computer aided diagnosis(CAD) magnetic resonance imaging(MRI) semantic segmentation lumbar vertebrae deep learning U-Net model

Autism spectrum disorder:difficulties in diagnosis and microRNA biomarkers

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Neural Regeneration Research 2025年第10期20卷 2776-2786页

作者： Bridget Martinez Philip v.Peplow Department of Pharmacology University of Nevada-RenoRenoNVUSA Department of Medicine University of Nevada-RenoRenoNVUSA Department of Anatomy University of OtagoDunedinNew Zealand

We performed a PubMed search for microRNAs in autism spectrum disorder that could serve as diagnostic biomarkers in patients and selected 17 articles published from January 2008 to December 2023,of which 4 studies were performed with whole blood,4 with blood plasma,5 with blood serum,1 with serum neural cell adhesion molecule L1-captured extracellular vesicles,1 with blood cells,and 2 with peripheral blood mononuclear *** of the studies involved children and the study cohorts were largely *** of the studies had performed microRNA sequencing or quantitative polymerase chain reaction assays to measure microRNA *** five studies had used real-time polymerase chain reaction assay to validate microRNA expression in autism spectrum disorder subjects compared to *** microRNAs that were validated in these studies may be considered as potential candidate biomarkers for autism spectrum disorder and include miR-500a-5p,-197-5p,-424-5p,-664a-3p,-365a-3p,-619-5p,-664a-3p,-3135a,-328-3p,and-500a-5p in blood plasma and miR-151a-3p,-181b-5p,-320a,-328,-433,-489,-572,-663a,-101-3p,-106b-5p,-19b-3p,-195-5p,and-130a-3p in blood serum of children,and miR-15b-5p and-6126 in whole blood of *** important limitations were identified in the studies reviewed,and need to be taken into account in future *** studies are warranted with children and adults having different levels of autism spectrum disorder severity and consideration should be given to using animal models of autism spectrum disorder to investigate the effects of suppressing or overexpressing specific microRNAs as a novel therapy.

关键词： autism spectrum disorder biomarker blood cells blood plasma blood serum diagnosis microRNA peripheral blood mononuclear cells serum neural cell adhesion molecule L1-captured extracellular vesicles whole blood

MicroRNAs as potential diagnostic biomarkers for bipolar disorder

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Neural Regeneration Research 2025年第6期20卷 1681-1695页

Abnormal expression of microRNAs is connected to brain development and disease and could provide novel biomarkers for the diagnosis and prognosis of bipolar disorder. We performed a PubMed search for microRNA biomarkers in bipolar disorder and found 18 original research articles on studies performed with human patients and published from January 2011 to June 2023. These studies included microRNA profiling in bloodand brain-based materials. From the studies that had validated the preliminary findings,potential candidate biomarkers for bipolar disorder in adults could be miR-140-3p,-30d-5p,-330-5p,-378a-5p,-21-3p,-330-3p,-345-5p in whole blood, miR-19b-3p,-1180-3p,-125a-5p, let-7e-5p in blood plasma, and miR-7-5p,-23b-5p,-142-3p,-221-5p,-370-3p in the blood serum. Two of the studies had investigated the changes in microRNA expression of patients with bipolar disorder receiving treatment. One showed a significant increase in plasma miR-134 compared to baseline after 4 weeks of treatment which included typical antipsychotics, atypical antipsychotics, and benzodiazepines. The other study had assessed the effects of prescribed medications which included neurotransmitter receptorsite binders(drug class B) and sedatives, hypnotics, anticonvulsants, and analgesics(drug class C) on microRNA results. The combined effects of the two drug classes increased the significance of the results for miR-219 and-29c with miR-30e-3p and-526b* acquiring significance. MicroRNAs were tested to see if they could serve as biomarkers of bipolar disorder at different clinical states of mania, depression, and euthymia. One study showed that upregulation in whole blood of miR-9-5p,-29a-3p,-106a-5p,-106b-5p,-107,-125a-3p,-125b-5p and of miR-107,-125a-3p occurred in manic and euthymic patients compared to controls, respectively, and that upregulation of miR-106a-5p,-107 was found for manic compared to euthymic patients. In two other studies using blood plasma,downregulation of miR-134 was observed i

关键词： biomarker bipolar disorder blood leukocytes blood plasma blood plasma extracellular vesicles/exosomes blood serum brain tissue brain tissue extracellular vesicles/exosomes lymphoblastoid cell lines microRNA neural progenitor cells whole blood

MicroRNAs as potential biomarkers for diagnosis of post-traumatic stress disorder

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Neural Regeneration Research 2025年第7期20卷 1957-1970页

Post-traumatic stress disorder is a mental disorder caused by exposure to severe traumatic life ***,there are no validated biomarkers or laboratory tests that can distinguish between trauma survivors with and without post-traumatic stress *** addition,the heterogeneity of clinical presentations of post-traumatic stress disorder and the overlap of symptoms with other conditions can lead to misdiagnosis and inappropriate *** suggests that this condition is a multisystem disorder that affects many biological systems,raising the possibility that peripheral markers of disease may be used to diagnose post-traumatic stress *** performed a PubMed search for microRNAs(miRNAs)in post-traumatic stress disorder(PTSD)that could serve as diagnostic biomarkers and found 18 original research articles on studies performed with human patients and published January 2012 to December *** included four studies with whole blood,seven with peripheral blood mononuclear cells,four with plasma extracellular vesicles/exosomes,and one with serum *** of these studies had also used whole *** studies were excluded as they did not involve microRNA *** of the studies had collected samples from adult male veterans who had returned from deployment and been exposed to combat,and only two were from recently traumatized adult *** measuring miRNA expression levels,many of the studies had used microarray miRNA analysis,miRNA Seq analysis,or NanoString *** six studies had used real time polymerase chain reaction assay to determine/validate miRNA expression in PTSD subjects compared to *** miRNAs that were found/validated in these studies may be considered as potential candidate biomarkers for PTSD and include miR-3130-5p in whole blood;miR-193a-5p,-7113-5p,-125a,-181c,and-671-5p in peripheral blood mononuclear cells;miR-10b-5p,-203a-3p,-4488,-502-3p,-874-3p,-5100,and-7641 in plasma extracellular vesicles/

关键词： biomarker diagnosis microRNA peripheral blood mononuclear cells plasma extracellular vesicles/exosomes post-traumatic stress disorder serum exosomes whole blood whole plasma