Fluid Stiction From a Contact Condition

2021 ◽  
Author(s):  
Remzija Ćerimagić ◽  
Per Johansen ◽  
Torben Ole Andersen ◽  
Rudolf Scheidl
Keyword(s):  
Reynolds Equation ◽  
High Sensitivity ◽  
Contact Condition ◽  
Initial Contact ◽  
Air Bubbles ◽  
Mechanical Contact ◽  
Strong Force ◽  
Proposed Model ◽  
Force Peak ◽  
Future Work

This paper considers modeling of fluid stiction between two separating plates that start from a mechanical contact condition. Published experimental work on initially contacting plates showed significant variations in stiction force peak values. In order to describe the observed strong force variations with mathematical models, the models should be quite sensitive to some of the input parameters of the stiction problem. The model in this paper assumes that small air bubbles are entrapped between the contact areas of the asperity peaks and that the fluid film flow between the cavitation bubbles is guided by Reynolds equation. The proposed model exhibits high sensitivity to initial bubble size and initial contact force compared to state-of-the art models. A delay of about 1 ms in the simulated stiction force evolution and the experiments was found. Potential causes for this discrepancy are discussed at the end of this paper and an outlook to future work, which can reduce the discrepancy between the model and experimental results is given.

Effect of guide rail profile errors on the motion accuracy for a heavy-duty hydrostatic turntable

2019 ◽  
Vol 233 (15) ◽  
pp. 5350-5362 ◽  
Author(s):  
Yongsheng Zhao ◽  
Hongchao Wu ◽  
Congbin Yang ◽  
Ligang Cai ◽  
Zhifeng Liu
Keyword(s):  
Machine Tool ◽  
Reynolds Equation ◽  
Machining Accuracy ◽  
Guide Rail ◽  
Heavy Duty ◽  
Motion Equations ◽  
Rotating Speed ◽  
Proposed Model ◽  
Reaction Forces ◽  
Profile Errors

The motion accuracy of hydrostatic turntable is the key in improving the machining accuracy of heavy-duty machine tool. However, the motion accuracy of hydrostatic turntable depends not only on the offset load but also on the rotating speed of the turntable as well as the profile errors of the guide rails. In this paper, a simulation model is developed to analyze the effect of guide rail profile errors on the motion accuracy of hydrostatic turntable. The reaction forces of preload thrust bearing and hydrostatic circular oil pads are obtained based on the Reynolds equation of the lubricant film. The motion equations of hydrostatic turntable are derived in which the profile errors of two guide rails are considered. The results show that the motion accuracy of hydrostatic turntable can be affected by wavelength, amplitude of profile errors and speed, and offset load of turntable. Finally, the motion accuracy of heavy-duty hydrostatic turntable used in XCKA28105 type turning and milling composite machine tool is obtained by using the presented method. Comparing with the experimental results, the proposed model can be used to predict the machining accuracy caused by the profile errors of guide rails for any heavy-duty hydrostatic turntable.

scholarly journals Valuation of Guaranteed Maximum Price Contracts in Korea Using the Collar Option Model

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Sanghyo Lee ◽  
Hyeongjae Jang ◽  
Yonghan Ahn
Keyword(s):  
Profit Sharing ◽  
Construction Companies ◽  
Construction Market ◽  
Positive Effects ◽  
Valuation Model ◽  
Maximum Price ◽  
Proposed Model ◽  
Option Model ◽  
Payoff Structure ◽  
Future Work

This study assessed the levels of risk that contractors may be subject to while executing a GMP contract by applying a collar option model to the case study of an apartment project in Korea and identified implications for the application of GMP contracts in Korea. The payoff structure of the GMP contract was defined based on the collar option model and a profit sharing ratio calculated to evaluate the risks involved in GMP contracts. The results showed that an increase in the GMP and a decrease in the expected cost and cost range were accompanied by a decrease in the profit sharing ratio. The proposed valuation model for GMP contracts is expected to help clients and contractors in Korea negotiate reasonable contracts as it enables the contractor to utilize the proposed model as basic data, the client to evaluate the performance of the contractor, and both parties to agree a reasonable profit sharing ratio. Implementing GMP contracts with CMR is likely to have a number of positive effects on the Korean construction market. However, in order to maximize these effects, it is necessary to have the ability to evaluate cost uncertainty. Accordingly, it is very important to analyze the factors that influence cost volatility. In future work, the various factors that have an impact on the GMP must be studied to maximize the positive effects of the framework proposed in this paper. An analysis of the effect of each factor on the change in the GMP will help Korean construction companies who are attempting to introduce GMP contracts to perform their preconstruction services effectively.

Fretting Wear Mechanisms and Their Effects on Fretting Fatigue

1988 ◽  
Vol 110 (3) ◽  
pp. 517-524 ◽  
Author(s):  
Y. Berthier ◽  
Ch. Colombie´ ◽  
L. Vincent ◽  
M. Godet
Keyword(s):  
Fretting Fatigue ◽  
Relative Displacement ◽  
Contact Condition ◽  
Fretting Wear ◽  
Initial Contact ◽  
Great Care ◽  
Third Body ◽  
Body Formation ◽  
The Third ◽  
Contact Surfaces

Fretting wear and fretting fatigue are governed by the rate of formation of materials (third-bodies) between the initial contact surfaces. Furthermore, the third-bodies must be maintained within the contact. The issue of the race between third-body formation and subsurface damage conditions the effect of fretting on fatigue. That race lasts for only a few hundred or at best a few thousand cycles. Effective third-bodies (or good anti-fretting lubricants) must adhere strongly to the rubbing surfaces, and be able to accommodate at least part of the relative displacement. Great care in the design of test equipment has to be exercised before definitive results on the effect of amplitude and frequency on either fretting fatigue or fretting wear can be obtained for a given contact condition, given materials and given environments.

scholarly journals Development of a New Bi-Arc Dynamic Numerical Model for Modeling AC Flashover Processes of EHV Ice-Covered Insulators

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2792
Author(s):  
Marouane Jabbari ◽  
Christophe Volat ◽  
Issouf Fofana
Keyword(s):  
Numerical Model ◽  
High Accuracy ◽  
Arc Length ◽  
Calculation Algorithm ◽  
Water Conductivity ◽  
Arc Model ◽  
Proposed Model ◽  
Flashover Voltage ◽  
Extra High Voltage ◽  
Future Work

This paper presents the development of a new bi-arc dynamic numerical model for predicting AC critical flashover voltage (FOV) of ice-covered extra-high voltage (EHV) insulators. The proposed model is based on a generic calculation algorithm coupled with commercial finite element method software designed to solve the Obenaus/Rizk model. The proposed model allows one to implement the Nottingham and Mayr approaches and compare the results obtained as a function of the arcing distance, the freezing water conductivity, and the initial arc length. The validation of the model demonstrated high accuracy in predicting the FOV of ice-covered post-type insulators and its capability to simulate the interaction of the two partial arcs during the flashover process. In particular, the results showed that the Nottingham approach is sensibly more accurate than the Mayr one, especially in simulating the dynamic behavior of the partial arcs during the flashover process. Based on the encouraging results obtained, a multi-arc calculation algorithm was proposed using the bi-arc dynamic numerical model as a basis. The basic idea, which consists in dividing the multi-arc model in several bi-arc modules, was not implemented and validated but will serve as a promising concept for future work.

scholarly journals Modelling the Characteristics of Ring-Shaped Magnetoelastic Force Sensor in Mohri’s Configuration

Sensors ◽  
2020 ◽  
Vol 20 (1) ◽  
pp. 266 ◽  
Author(s):  
Anna Ostaszewska-Liżewska ◽  
Roman Szewczyk ◽  
Peter Raback ◽  
Mika Malinen
Keyword(s):  
Experimental Data ◽  
High Sensitivity ◽  
Force Sensor ◽  
Inhomogeneous Distribution ◽  
The Finite Element Method ◽  
The Core ◽  
Magnetoelastic Effect ◽  
Proposed Model ◽  
Distribution Of Stresses ◽  
Good Agreement

Magnetoelastic force sensors exhibit high sensitivity and robustness. One commonly used configuration of force sensor with a ring-shaped core was presented by Mohri at al. In this configuration force is applied in the direction of a diameter of the core. However, due to inhomogeneous distribution of stresses, model of such sensor has not been presented yet. This paper is filling the gap presenting a new method of modelling the magnetoelastic effect, which is especially suitable for the finite element method. The presented implementation of proposed model is in good agreement with experimental data and creates new possibilities of modelling other devices utilizing magnetoelastic effect.

Contact endoscopy as a novel technique in the detection and diagnosis of oral cavity and oropharyngeal mucosal lesions in the head and neck

2014 ◽  
Vol 128 (2) ◽  
pp. 147-152 ◽  
Author(s):  
S Dowthwaite ◽  
C Szeto ◽  
B Wehrli ◽  
T Daley ◽  
F Whelan ◽  
...  
Keyword(s):  
Sensitivity And Specificity ◽  
High Sensitivity ◽  
Video Data ◽  
Initial Contact ◽  
Benign Lesions ◽  
Video Images ◽  
Malignant Lesions ◽  
Mucosal Lesions ◽  
Detection And Diagnosis

AbstractObjective:We aimed to investigate the diagnostic accuracy of contact endoscopy in evaluating oral and oropharyngeal mucosal lesions.Methods:Between January 2010 and December 2011, 34 patients with lesions of the oral and oropharyngeal mucosa were enrolled in the study. Comparison between initial contact endoscopy results and ‘gold standard’ tissue biopsy was undertaken.Results:Nine patients had histologically confirmed squamous cell carcinoma, 2 had carcinoma in situ, 3 had dysplastic lesions and 20 patients had various benign lesions. Contact endoscopy demonstrated sensitivity and specificity of 89 and 100 per cent respectively in the evaluation of malignant lesions. Benign lesions were correctly categorised in 50 per cent of cases (10/20). The video images from contact endoscopy could not be interpreted in six cases.Conclusions:Contact endoscopy demonstrates high sensitivity and specificity in the imaging of malignant lesions with reduced reliability in the evaluation of benign lesions. Significant shortcomings also exist in the design of current technology that we believe represent a significant barrier to the reliable collection of useful video data.

scholarly journals Elongated Flexuous Plant Virus-Derived Nanoparticles Functionalized for Autoantibody Detection

Nanomaterials ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1438 ◽  
Author(s):  
Yuste-Calvo ◽  
López-Santalla ◽  
Zurita ◽  
Cruz-Fernández ◽  
Sánchez ◽  
...  
Keyword(s):  
High Sensitivity ◽  
Diagnostic Value ◽  
Turnip Mosaic Virus ◽  
Antibody Detection ◽  
Induction Phase ◽  
Proposed Model ◽  
Inflammatory Processes ◽  
Autoantibody Detection ◽  
Very High

Nanoparticles derived from the elongated flexuous capsids of Turnip mosaic virus (TuMV) have been shown to be efficient tools for antibody sensing with a very high sensitivity if adequately functionalized with the corresponding epitopes. Taking advantage of this possibility, TuMV virus-like particles (VLPs) have been genetically derivatized with a peptide from the chaperonin Hsp60, a protein described to be involved in inflammation processes and autoimmune diseases. Antibodies against the peptide have been previously shown to have a diagnostic value in at least one autoimmune disease, multiple sclerosis. The functionalized Hsp60-VLPs showed their significant increase in sensing potency when compared to monoclonal antibody detection of the peptide in a conventional immunoassay. Additionally, the developed Hsp60-VLPs allowed the detection of autoantibodies against the Hsp60 peptide in an in vivo mouse model of dextran sodium sulfate (DSS)-induced colitis. The detection of minute amounts of the autoantibodies allowed us to perform the analysis of their evolution during the progression of the disease. The anti-Hsp60 autoantibody levels in the sera of the inflamed mice went down during the induction phase of the disease. Increased levels of the anti-HSP60 autoantibodies were detected during the resolution phase of the disease. An extension of a previously proposed model for the involvement of Hsp60 in inflammatory processes is considered, incorporating a role for Hsp60 autoantibodies. This, and related models, can now be experimentally tested thanks to the autoantibody detection hypersensitivity provided by the functionalized VLPs.

Prediction of Postpartum Depression Using Multilayer Perceptrons and Pruning

2009 ◽  
Vol 48 (03) ◽  
pp. 291-298 ◽  
Author(s):  
J. M. García-Gómez ◽  
J. Vicente ◽  
J. Sanjuán ◽  
R. de Frutos ◽  
R. Martín-Santos ◽  
...  
Keyword(s):  
Decision Support ◽  
Postpartum Depression ◽  
Decision Support System ◽  
Sensitivity And Specificity ◽  
Support System ◽  
Geometric Mean ◽  
High Sensitivity ◽  
Classification Model ◽  
Multilayer Perceptrons ◽  
Future Work

Summary Objective: The main goal of this paper is to obtain a classification model based on feed-forward multilayer perceptrons in order to improve postpartum depression prediction during the 32 weeks after childbirth with a high sensitivity and specificity and to develop a tool to be integrated in a decision support system for clinicians. Materials and Methods: Multilayer perceptrons were trained on data from 1397 women who had just given birth, from seven Spanish general hospitals, including clinical, environmental and genetic variables. A prospective cohort study was made just after delivery, at 8 weeks and at 32 weeks after delivery. The models were evaluated with the geometric mean of accuracies using a hold-out strategy. Results: Multilayer perceptrons showed good performance (high sensitivity and specificity) as predictive models for postpartum depression. Conclusions: The use of these models in a decision support system can be clinically evaluated in future work. The analysis of the models by pruning leads to a qualitative interpretation of the influence of each variable in the interest of clinical protocols.

scholarly journals A Spatially Explicit Capture–Recapture Model for Partially Identified Individuals When Trap Detection Rate Is Less than One

2019 ◽  
Vol 71 (1) ◽  
pp. 1-20 ◽  
Author(s):  
Soumen Dey ◽  
Mohan Delampady ◽  
K. Ullas Karanth ◽  
Arjun M. Gopalaswamy
Keyword(s):  
Detection Probability ◽  
Credible Interval ◽  
Camera Traps ◽  
Spatially Explicit ◽  
Panthera Tigris ◽  
Partial Identity ◽  
Proposed Model ◽  
Estimation Problems ◽  
Capture Recapture ◽  
Future Work

Spatially explicit capture–recapture (SECR) models have gained enormous popularity to solve abundance estimation problems in ecology. In this study, we develop a novel Bayesian SECR model that disentangles two processes: one is the process of animal arrival within a detection region, and the other is the process of recording this arrival by a given set of detectors. We integrate this complexity into an advanced version of a recent SECR model involving partially identified individuals (Royle JA. Spatial capture-recapture with partial identity. arXiv preprint arXiv:1503.06873, 2015). We assess the performance of our model over a range of realistic simulation scenarios and demonstrate that estimates of population size N improve when we utilize the proposed model relative to the model that does not explicitly estimate trap detection probability (Royle JA. Spatial capture-recapture with partial identity. arXiv preprint arXiv:1503.06873, 2015). We confront and investigate the proposed model with a spatial capture–recapture dataset from a camera trapping survey of tigers (Panthera tigris) in Nagarahole study area of southern India. Detection probability is estimated at 0.489 (with 95% credible interval (CI) [0.430, 0.543]) which implies that the camera traps are performing imperfectly and thus justifying the use of our model in real world applications. We discuss possible extensions, future work and relevance of our model to other statistical applications beyond ecology. AMS classification codes: 62F15, 92D40

scholarly journals Antecedents of absorptive capacity: a new model for developing learning processes

2016 ◽  
Vol 23 (1) ◽  
pp. 77-91 ◽  
Author(s):  
Mohammad Rezaei-Zadeh ◽  
Tamer K Darwish
Keyword(s):  
Absorptive Capacity ◽  
Relevant Literature ◽  
Learning Processes ◽  
Environmental Turbulence ◽  
Content Type ◽  
Proposed Model ◽  
Exploitative Learning ◽  
Modes Of Governance ◽  
Future Work ◽  
Practical Implications

Purpose – The purpose of this paper is to provide an integrated framework to indicate which antecedents of absorptive capacity (AC) influence its learning processes, and to propose testing of this model in future work. Design/methodology/approach – Relevant literature into the antecedents of AC was critically reviewed and analysed with the objective of categorising and explaining the influence of AC on learning processes, including exploratory, transformative and exploitative learning. Findings – By considering the level of learning, the proposed model demonstrates that the antecedents of AC vary, comprising exploratory, transformative and exploitative learning processes. Moreover, this study reveals the complex interplay between the antecedents of AC. Research limitations/implications – The proposed model was developed theoretically, thus pending further empirical validation according to environmental turbulence, knowledge characteristics and modes of governance. This study also urges researchers to explore whether or not the antecedents of AC differ based on organisational outcomes. Practical implications – The model can be put into a testable template for use by researchers. It further guides managers in developing effective processes for learning to use external knowledge. Originality/value – It is the first work to schematically bring together and discuss the antecedents of AC and its influence on learning processes, and further provides a framework capable of facilitating the empirical testing of this nexus.

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