scholarly journals A Lamination Model for Pressure-Assisted Sintering of Multilayered Porous Structures

2021 ◽  
Vol 5 (2) ◽  
pp. 53
Author(s):  
Zhi-He Jin ◽  
Corson L. Cramer
Keyword(s):  
Plate Theory ◽  
Applied Pressure ◽  
Porous Structures ◽  
Plane Normal ◽  
Sinter Forging ◽  
Sintering Time ◽  
Out Of Plane ◽  
Force Moment ◽  
The Individual ◽  
Time Required

This work describes a lamination model for pressure-assisted sintering of thin, multilayered, and porous structures based on the linear viscous constitutive theory of sintering and the classical laminated plate theory of continuum mechanics. A constant out-of-plane normal stress is assumed in the constitutive relation. The lamination relations between the force/moment resultants and the strain/curvature rates are presented. Numerical simulations were performed for a symmetric tri-layer laminate consisting of a 10% gadolinia doped ceria (Ce0.9Gd0.1O1.95-δ) composite structure, where porous layers were adhered to the top and bottom of a denser layer under uniaxially-applied pressures and the sinter forging conditions. The numerical results show that, compared with free sintering, the applied pressure can significantly reduce the sintering time required to achieve given layer thicknesses and porosities. Unlike free sintering, which results in a monotonic decrease of the laminate in-plane dimension, pressure-assisted sintering may produce an in-plane dimension increase or decrease, depending on the applied pressure and sintering time. Finally, the individual layers in the laminate exhibit different stress characteristics under pressure-assisted sintering.

Evaluation of the Accuracy of Out-of-Plane Normal Stress Detection Using Novel Piezoresistive CMOS Sensors

2009 ◽  
Author(s):  
Benjamin Lemke ◽  
Rajashree Baskaran ◽  
Oliver Paul
Keyword(s):  
Normal Stress ◽  
Stress Component ◽  
Stress Detection ◽  
Free Surfaces ◽  
Plane Normal ◽  
Uncertainty Sources ◽  
Stress Components ◽  
Normal Stress Component ◽  
Out Of Plane ◽  
The Individual

This paper discusses the measurement opportunities arising from a novel piezoresistance sensor featuring vertical currents. Temperature-compensated measurements of a sum of the three normal stress components including the vertical normal stress, are presented. In specific applications with sensors located at free surfaces where the vertical normal stress component vanishes, a combination of this temperature-compensated measurement and a pseudo-Hall measurement yields the individual in-plane normal stresses. Furthermore, the temperature-uncompensated extraction of the vertical normal stress component is discussed with respect to the new measurement possibilities provided by the presented sensor. A sensitivity analysis illustrates the influence of individual uncertainty sources to the overall uncertainty of the measurement. Based on these results possible improvements in stress detection are suggested.

scholarly journals Statistical Uncertainty of DNS in Geometries without Homogeneous Directions

2021 ◽  
Vol 11 (4) ◽  
pp. 1399
Author(s):  
Jure Oder ◽  
Cédric Flageul ◽  
Iztok Tiselj
Keyword(s):  
Channel Flow ◽  
A Priori ◽  
Time Integration ◽  
Navier Stokes ◽  
Statistical Uncertainty ◽  
Time Step ◽  
Order Of Magnitude ◽  
Averaging Time ◽  
The Individual ◽  
Time Required

In this paper, we present uncertainties of statistical quantities of direct numerical simulations (DNS) with small numerical errors. The uncertainties are analysed for channel flow and a flow separation case in a confined backward facing step (BFS) geometry. The infinite channel flow case has two homogeneous directions and this is usually exploited to speed-up the convergence of the results. As we show, such a procedure reduces statistical uncertainties of the results by up to an order of magnitude. This effect is strongest in the near wall regions. In the case of flow over a confined BFS, there are no such directions and thus very long integration times are required. The individual statistical quantities converge with the square root of time integration so, in order to improve the uncertainty by a factor of two, the simulation has to be prolonged by a factor of four. We provide an estimator that can be used to evaluate a priori the DNS relative statistical uncertainties from results obtained with a Reynolds Averaged Navier Stokes simulation. In the DNS, the estimator can be used to predict the averaging time and with it the simulation time required to achieve a certain relative statistical uncertainty of results. For accurate evaluation of averages and their uncertainties, it is not required to use every time step of the DNS. We observe that statistical uncertainty of the results is uninfluenced by reducing the number of samples to the point where the period between two consecutive samples measured in Courant–Friedrichss–Levy (CFL) condition units is below one. Nevertheless, crossing this limit, the estimates of uncertainties start to exhibit significant growth.

scholarly journals Effectiveness of brushing teeth in patients with reduced oral hygiene by laypeople: a randomized, controlled study

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Anna Greta Barbe ◽  
Aya Al-Barwari ◽  
Stefanie Hamacher ◽  
Renate Deinzer ◽  
Ulrike Weik ◽  
...  
Keyword(s):  
Oral Hygiene ◽  
Group Intervention ◽  
Controlled Study ◽  
Care Gap ◽  
Parallel Group ◽  
Dental Professional ◽  
The Individual ◽  
Time Required ◽  
Powered Toothbrush ◽  
Dental Professionals

Abstract Background To evaluate the success of plaque reduction after external toothbrushing by instructed laypeople versus dental professionals using either a manual or powered toothbrush. Longitudinal, randomized, parallel-group intervention study in periodontitis patients with reduced oral hygiene quality undergoing anti-infective therapy. Patients were randomly and equally assigned to one of four groups: laypeople using a manual or powered toothbrush or dental professionals using a manual or powered toothbrush. Plaque reduction (Quigley–Hein-Index (QHI), Marginal Plaque Index (MPI)), gingivitis (papilla bleeding index), and cleaning time (seconds) were investigated. Results Thirty-nine patients participated in the study. Neither the choice of toothbrush (p = 0.399) nor the use of a dental professional (p = 0.790) had a significant influence on plaque levels achieved. However, multivariate modeling indicated statistically significant differences in the external cleaning time between brushing groups, with longer time required by laypeople (p = 0.002) and longer use of the powered toothbrush (p = 0.024). Conclusion When the ability to carry out personal oral hygiene is reduced, external brushing by dental professionals or instructed laypeople who meet previously defined criteria such as sufficient personal oral hygiene at home could help to fill the emerging dental care gap. A combination of oral hygiene approaches adapted to the individual needs of the patients in need of external help is necessary for optimum oral hygiene. Trial registration: German Clinical Trials register (https://www.germanctr.de; number DRKS00018779; date of registration 04/11/2019).

scholarly journals How to Implement Safe, Efficient and Cost-Effective SARS-CoV-2 Testing in Urban and Rural Schools within One Month

COVID ◽  
2021 ◽  
Vol 1 (4) ◽  
pp. 717-727
Author(s):  
Parastoo Kheiroddin ◽  
Magdalena Gründl ◽  
Michael Althammer ◽  
Patricia Schöberl ◽  
Linda Plail ◽  
...  
Keyword(s):  
Data Transfer ◽  
Cost Effective ◽  
Testing System ◽  
Successful Implementation ◽  
Rural And Urban ◽  
Local Involvement ◽  
Working Day ◽  
Set Up ◽  
The Individual ◽  
Time Required

(1) Background: With vaccination and new variants of SARS-CoV-2 on the horizon, efficient testing in schools may enable prevention of mass infection outbreaks, keeping schools safe places and buying time until decisions on feasibility and the necessity of vaccination in children and youth are made. We established, in the course of the WICOVIR (Where Is the COrona VIRus) study, that gargle-based pool-PCR testing offers a feasible, efficient, and safe testing system for schools in Germany when applied by central university laboratories. (2) Objectives: We evaluated whether this approach can be implemented in different rural and urban settings. (3) Methods: We assessed the arrangements required for successful implementation of the WICOVIR approach in a variety of settings in terms of transport logistics, data transfer and pre-existing laboratory set-up, as well as the time required to establish the set-up. (4) Results: We found that once regulatory issues have been overcome, all challenges pertaining to logistics, data transfer, and laboratory testing on different platforms can be solved within one month. Pooling and depooling of samples down to the individual test result were achievable within one working day in all settings. Local involvement of the community and decentralized set-ups were keys for success. (5) Conclusion: The WICOVIR gargle-based pool-PCR system is so robust and simple that it can be implemented within one month in all settings now or in future pandemics.

Rapid and Efficient Wet Fixation by the Use of Steam

1969 ◽  
Vol 39 (6) ◽  
pp. 497-504 ◽  
Author(s):  
Norman R. S. Hollies ◽  
Steven R. Chafitz ◽  
Karen A. Farquhar
Keyword(s):  
Fiber Surface ◽  
Strong Acid ◽  
Strength Properties ◽  
Fiber System ◽  
Resin Solution ◽  
Speed Up ◽  
Drying Properties ◽  
The Individual ◽  
Time Required ◽  
Finishing Processes

The impregnation of cotton fabrics with a solution consisting of strong acid and a combination of N-methylol resins having polymer-forming and cross-linking properties distinguishes the wet-fixation system from conventional durable-press processes, and this finish results in an improved balance of smoothness and strength properties during wear and laundering. Swelling of the fibers in a steam atmosphere, following padding in the resin solution can serve to speed up the impregnation process. In addition, with controls to minimize resin migration back to the fiber surface, steaming can substantially improve the efficiency of the use of resin for producing these smooth drying properties. The degree of penetration of resin is influenced by a number of process variables, such as predrying before steaming, steaming time, fabric tension and rapidity of neutralization. The optimum in fabric performance is achieved with both sufficient resin of both types in the fiber system and even distribution of resin within the individual fibers, Steaming acts to improve both these factors over that achieved in conventional hot wet fixation and so reduces the time required for wet fixation by a factor of 20–30. There is a corresponding increase in efficiency of resin use so that resin solids in the bath can be reduced two- to three-fold. These findings appear to have general application to a variety of cotton finishing processes involving fiber impregnation with reactive resins.

scholarly journals Non-Helicobacter pylori Gastric Intestinal Metaplasia in Children: A Series of Cases and Review of the Literature

2018 ◽  
Vol 2018 ◽  
pp. 1-5 ◽  
Author(s):  
Sandra Mabel Camacho-Gomez ◽  
Anas Bernieh ◽  
Ali G. Saad ◽  
Neelesh Ajit Tipnis
Keyword(s):  
Helicobacter Pylori ◽  
Intestinal Metaplasia ◽  
Pediatric Population ◽  
Duodenogastric Reflux ◽  
Clinical Implications ◽  
Review Of The Literature ◽  
Gastric Intestinal Metaplasia ◽  
The Individual ◽  
Time Required

In the pediatric population, Gastric Intestinal Metaplasia (GIM) is a finding with unknown frequency and, more importantly, unknown clinical implications. The relationship between Helicobacter pylori (HP) infection and GIM is well documented, as well as an association between duodenogastric reflux and GIM. We present two cases of pediatric patients with GIM along with a review of the literature. The diagnosis of GIM may have adverse clinical implications and should be made with caution in a child. The association of GIM and adenoma/dysplasia and carcinoma is rarely seen in children, primarily because the time required for these to develop takes the individual into adulthood. Treatment, long-term consequences, and surveillance protocols are not well established in the pediatric population. Studies to evaluate the long-term natural history, treatment, and surveillance protocols in children with GIM are needed.

Spectra of the 1:1 and 3:1 solid complexes of coronene-TCNQ

1977 ◽  
Vol 55 (21) ◽  
pp. 3712-3716 ◽  
Author(s):  
Kim Doan Truong ◽  
André D. Bandrauk
Keyword(s):  
Charge Transfer ◽  
Absorption Spectra ◽  
Electronic Absorption ◽  
Ground State ◽  
Electronic Absorption Spectra ◽  
Charge Transfer Band ◽  
Out Of Plane ◽  
The Individual ◽  
A Charge ◽  
Solid Complexes

Two new solid TCNQ complexes have been isolated, coronene–TCNQ 1:1 and 3:1. The infrared and electronic absorption spectra are presented for the two different stoichiometries. From these spectra we infer that the complexes are covalent in the ground state with a charge transfer band appearing at 730 nm. The out of plane vibrations of the individual molecules are noticeably perturbed upon complexation.

Thermal Property Measurement of Thin Aluminum Oxide Layers for Giant Magnetoresistive (GMR) Head Applications

2003 ◽  
Author(s):  
Bahareh Behkam ◽  
Yizhang Yang ◽  
Mehdi Asheghi
Keyword(s):  
Thermal Conductivity ◽  
Areal Density ◽  
Dielectric Constants ◽  
Recording Head ◽  
Magnetic Disks ◽  
Low Dielectric ◽  
Plane Normal ◽  
Thin Aluminum ◽  
Out Of Plane ◽  
Property Measurement

In recent years, the magnetic recording storage industry has developed a growing interest in increasing recording density of the magnetic disks. Since dimensions of the recording head read transducer have been scaled down to increase areal density, all other parameters being equal, the energy required to cause damage by an ElectroStatic Discharge (ESD) event is reduced substantially. The reduction of insulator thickness between the leads and shields, to increase linear density, further lowers the threshold for ESD breakdown voltage. This problem will become increasingly acute with use of a large number of new and exotic passivation materials having low dielectric constants and thermal conductivities. The present work characterizes the thermal transport properties of Al2O3 Gap layer, which are essential to address the ESD failure in GMR head. This study provides data for out-of-plane (normal) thermal conductivity of thin Al2O3 layers. Thermal conductivity data is obtained using steady-state Joule heating and electrical-resistance thermometry technique.

Risk Based Strategy for the Development of an Emergency Pipeline Repair System (EPRS)

2016 ◽  
Author(s):  
Ali Alani ◽  
Graham D. Goodfellow ◽  
Dennis Keen
Keyword(s):  
Economic Consequences ◽  
Third Party ◽  
Repair System ◽  
Pipeline Network ◽  
Expected Time ◽  
Emergency Repair ◽  
Offshore Pipeline ◽  
Timely Access ◽  
The Individual ◽  
Time Required

This paper presents an overview of the various components of an emergency pipeline repair system which should be in place in order to act effectively and efficiently during an emergency pipeline repair scenario. The condition of pipelines during operation is typically monitored by means of external and internal inspections. These inspections allow for planned intervention when a pipeline is found to be deteriorating. A failure to inspect adequately for time dependent threats, or randomly occurring events such as third party interaction, could result in a pipeline failure, leading to a requirement to rapidly return to operation and thus the need for an emergency repair. An Emergency Pipeline Repair System (EPRS) is therefore an essential part of a pipeline integrity management system. The primary purpose of the EPRS is to ensure that pipeline operators have the necessary level of readiness to allow an emergency repair to be carried out, thus minimising the economic consequences of having a pipeline out of service, whilst optimising the cost of purchasing and maintaining equipment and spares. In general, pipeline operators will have some emergency repair procedures to cater for unplanned or unexpected incidents. However, to complete an emergency repair efficiently and effectively, the availability of adequate spare materials and timely access to the damage location is required. For a large pipeline network, satisfying these requirements can be challenging. This paper discusses some basic elements of an EPRS and describes a case study of the development of a risk based EPRS strategy for an offshore pipeline operator. This approach involves the identification of credible hazards that can lead to damage requiring an emergency repair, and identification of repair options. The relative importance of the individual pipelines, in terms of their availability requirement, and the expected time required to complete an emergency repair are then taken into account. This enables the pipelines to be ranked based on the consequence of failure. Pipelines with consequence rankings that are considered unacceptable are therefore highlighted, and EPRS readiness related to those pipelines can subsequently be optimised. Recommendations for the development of an EPRS for an onshore or offshore pipeline network are also made.

A Prediction of Total Cutting Time When Crosscutting Rounds, Pipe, and Rectangular Bar With a Portable Bandsaw

2012 ◽  
Author(s):  
Thomas P. James ◽  
Amrit Sagar ◽  
Joseph P. Domblesky
Keyword(s):  
Cross Sections ◽  
Feed Rate ◽  
Thrust Force ◽  
Mechanistic Model ◽  
Applied Pressure ◽  
Lithium Ion ◽  
Steel Tube ◽  
Workpiece Material ◽  
Software Application ◽  
Time Required

Portable bandsaws are gaining in popularity for their use on jobsites to efficiently crosscut structural materials such as bar, pipe, angle, and channel. Some of the increased popularity is also due to the recent introduction of lithium ion batteries, which has further improved the portability of bandsaws by making them cordless. However, with cordless portable bandsaws, knowledge of cutting rates becomes more important as battery runtime limits productivity. Unlike industrial bandsaws that typically have feed rate control, portable bandsaws use operator applied pressure and gravity to control feed rate. While some research has highlighted the cutting mechanics of bandsaws and related wear processes, there is a lack of progress in the area of predicting total cutting time as a function of sawing parameters, such as applied thrust force, blade speed, workpiece material properties, and geometry of the cross section. This paper presents research that was conducted to develop and experimentally verify a mechanistic model to predict cutting rates of various cross sections with a gravity fed portable bandsaw. The model was used to predict the time required to cut steel tube for several conditions of thrust force and blade speed. Model predictions were verified by experiment to a reasonable degree of accuracy. The model serves as the algorithm for a software application to assist contractors in developing jobsite estimates of time and material.

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