Adhesion strength of protective and decorative coatings depending on the porosity of the cement substrate

Information provided about long-term bonding strength protective decorative coatings. A method is proposed for assessing the long- term bonding strength of coatings. The method consists in determining the bonding strength before testing and after t hours of testing. The dependence of the long-term bonding strength on the porosity of the cement substrate has been established. With an increase in the surface porosity of the substrate, observed a decrease in the time of maintaining the adhesive contact “coating-substrate». The aging process of coatings is considered from the position accumulation of damage, taking into account the hereditary factor. The influence of the hereditary factor on the kinetics of damage accumulation was established. It is shown that the dependence of the operating time on the level of damage accumulation can be approximated by an exponential dependence. The values of the activation energy of adhesive destruction of coatings are calculated.

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EVALUATION OF THE RESOURCE CHARACTERISTICS OF POLYCRYSTALLINE STRUCTURAL ALLOYS UNDER CYCLIC THERMOMECHANICAL LOADING

Problems of Strength and Plasticity ◽

10.32326/1814-9146-2021-83-4-481-504 ◽

2021 ◽

Vol 83 (4) ◽

pp. 481-504

Author(s):

I.A, Volkov ◽

L.A. Igumnov ◽

D.N. Shishulin ◽

A.A. Belov

Keyword(s):

Fatigue Damage ◽

Damage Accumulation ◽

Mechanical Characteristics ◽

Stress Deviator ◽

Thermomechanical Loading ◽

Effective Stresses ◽

Accumulation Of Damage ◽

Resource Characteristics ◽

Kinetics Of ◽

Physical And Mechanical Characteristics

The main physical regularities of complex thermoviscoplastic deformation and accumulation of damage in structural materials (metals and their alloys) under various modes of cyclic combined thermomechanical loading and mathematical models of these processes are considered. A mathematical model of the mechanics of a damaged medium has been developed, which makes it possible to simulate the cyclic viscoelastoplastic behavior and determine the resource characteristics of polycrystalline structural alloys under the combined action of degradation mechanisms that combine material fatigue and creep. The model is based on the joint integration of equations describing the kinetics of the stress-strain state and damage accumulation processes. The final relation to the model is the strength criterion, the fulfillment of which corresponds to the formation of a macrocrack. The plasticity equations are based on the basic principles of the flow theory. To describe the creep process in the stress space, a family of equipotential creep surfaces of the corresponding radius and having a common center is introduced. The relationship between the creep equations and the thermoplasticity equations describing “instantaneous” plastic deformations is carried out at the loading stage through the stress deviator and the corresponding algorithm for determining and at the loading stage by means of certain relationships between “temporary” and “instantaneous” scalar and tensor quantities. At the stage of development of damage scattered throughout the volume, the effect of damage on the physical and mechanical characteristics of the material is observed. This influence can be taken into account by introducing effective stresses. In the general case, stresses, plastic strains, and creep strains are determined by integrating the thermal creep equations by the four-point Runge-Kutta method with correction of the stress deviator and subsequent determination of stresses according to the thermoplasticity equations, taking into account the average creep strain rate at a new time. The relationships that simulate the accumulation of damage are based on the energy approach to determining the resource characteristics. The kinetics of fatigue damage accumulation is based on the introduction of a scalar parameter of damage to a structural material and a unified model form for representing the degradation mechanism under fatigue and creep conditions. The influence of scattered damage on the physical and mechanical characteristics of the material is taken into account by introducing effective stresses. The results of numerical simulation of cyclic thermoplastic deformation and accumulation of fatigue damage in heat-resistant alloys (Haynes188) under combined thermomechanical loading are presented. Particular attention is paid to the issues of modeling the processes of cyclic thermoplastic deformation and the accumulation of fatigue damage for complex deformation processes accompanied by the rotation of the main areas of stress and strain tensors.

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Kinetics of Damage of Materials under Various Regimes of Re-Changeable Loads

Mechanics and Advanced Technologies ◽

10.20535/2521-1943.2021.5.3.248026 ◽

2021 ◽

Vol 5 (3) ◽

Author(s):

Anatoliy Hrabovsʹkyy ◽

Oleksandr Bondarets ◽

Iryna Babiienko

Keyword(s):

Structural Material ◽

Service Life ◽

Damage Accumulation ◽

Load Force ◽

Railway Transport ◽

Damage Factor ◽

Plastic Properties ◽

Effective Stresses ◽

Accumulation Of Damage ◽

Kinetics Of

Kinetics of accumulation of damages in engineering objects, which work at repeated-alternating soft and hard modes of loading of details and elements of constructions of vehicles (cars, cars, railway transport, etc.). When changing the direction of the load force to the opposite in the structural material there is a phenomenon of changing the kinetics of accumulation of damage, ie the damage factor at separation and shear changes, which affects the effective stresses and service life of equipment. This effect of the factor of the influence of repeated variables on the redistribution of the kinetics of damage accumulation is considered experimentally for materials with different plastic properties

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Comparative Labelling and Biokinetic Studies of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn)

Nuklearmedizin ◽

10.1055/s-0037-1620603 ◽

1977 ◽

Vol 16 (01) ◽

pp. 30-35 ◽

Cited By ~ 1

Author(s):

N. Agha ◽

R. B. R. Persson

Keyword(s):

Complex Formation ◽

Significant Influence ◽

Room Temperature ◽

Ph Value ◽

Maximum Activity ◽

Reduction Step ◽

Labelling Yield ◽

Different Temperatures ◽

Kinetics Of

SummaryGelchromatography column scanning has been used to study the fractions of 99mTc-pertechnetate, 99mTcchelate and reduced hydrolyzed 99mTc in preparations of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn). The labelling yield of 99mTc-EDTA(Sn) chelate was as high as 90—95% when 100 μmol EDTA · H4 and 0.5 (Amol SnCl2 was incubated with 10 ml 99mTceluate for 30—60 min at room temperature. The study of the influence of the pH-value on the fraction of 99mTc-EDTA shows that pH 2.8—2.9 gave the best labelling yield. In a comparative study of the labelling kinetics of 99mTc-EDTA(Sn) and 99mTc- DTPA(Sn) at different temperatures (7, 22 and 37°C), no significant influence on the reduction step was found. The rate constant for complex formation, however, increased more rapidly with increased temperature for 99mTc-DTPA(Sn). At room temperature only a few minutes was required to achieve a high labelling yield with 99mTc-DTPA(Sn) whereas about 60 min was required for 99mTc-EDTA(Sn). Comparative biokinetic studies in rabbits showed that the maximum activity in kidneys is achieved after 12 min with 99mTc-EDTA(Sn) but already after 6 min with 99mTc-DTPA(Sn). The long-term disappearance of 99mTc-DTPA(Sn) from the kidneys is about five times faster than that for 99mTc-EDTA(Sn).

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Role of Closed Mitral Commissurotomy for Mitral Stenosis: Mid- and Long-term Surgical Outcome of 36 Patients

The Heart Surgery Forum ◽

10.1532/hsf98.20041137 ◽

2005 ◽

Vol 8 (1) ◽

pp. 55 ◽

Cited By ~ 2

Author(s):

Azman Ates ◽

Yahya �nl� ◽

Ibrahim Yekeler ◽

Bilgehan Erkut ◽

Yavuz Balci ◽

...

Keyword(s):

Mitral Valve ◽

Mitral Regurgitation ◽

Mitral Stenosis ◽

Operating Time ◽

Term Survival ◽

Long Term Outcome ◽

Mitral Commissurotomy ◽

Closed Mitral Commissurotomy

Purpose: To evaluate long-term survival and valve-related complications as well as prognostic factors for mid- and long-term outcome after closed mitral commissurotomy, covering a follow-up period of 14 years. Material and Methods: Between 1989 and 2003, 36 patients (28 women and 8 men, mean age 28.8 6.1 years) underwent closed mitral commissurotomy at our institution. The majority of patients were in New York Heart Association (NYHA) functional class IIB, III, or IV. Indication for closed mitral commissurotomy was mitral stenosis. Closed mitral commissurotomy was undertaken with a Tubbs dilator in all cases. Median operating time was 2.5 hours 30 minutes. Results: After closed mitral commissurotomy, the mitral valve areas of these patients were increased substantially, from 0.9 to 2.11 cm2. No further operation after initial closed mitral commissurotomy was required in 86% of the patients (n = 31), and NYHA functional classification was improved in 94% (n = 34). Postoperative complications and operative mortality were not seen. Follow-up revealed restenosis in 8.5% (n = 3) of the patients, minimal mitral regurgitation in 22.2% (n = 8), and grade 3 mitral regurgitation in 5.5% (n = 2) patients. No early mortality occurred in closed mitral commissurotomy patients. Reoperation was essential for 5 patients following closed mitral commissurotomy; 2 procedures were open mitral commissurotomies and 3 were mitral valve replacements. No mortality occurred in these patients. Conclusions: The mitral valve area was significantly increased and the mean mitral valve gradient was reduced in patients after closed mitral commissurotomy. Closed mitral commissurotomy is a safe alternative to open mitral commissurotomy and balloon mitral commissurotomy in selected patients.

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Method for analyzing the kinetics of damage accumulation in the structure of polymer materials under tensile stresses

10.1063/5.0059899 ◽

2021 ◽

Author(s):

Tatyana Nizina ◽

Dmitriy Nizin ◽

Nadezhda Kanaeva ◽

Denis Artamonov

Keyword(s):

Damage Accumulation ◽

Polymer Materials ◽

Tensile Stresses ◽

Kinetics Of

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Electret Filters—From the Influence of Discharging Methods to Optimization Potential

Atmosphere ◽

10.3390/atmos12010065 ◽

2021 ◽

Vol 12 (1) ◽

pp. 65

Author(s):

Maximilian Kerner ◽

Kilian Schmidt ◽

Stefan Schumacher ◽

Christof Asbach ◽

Sergiy Antonyuk

Keyword(s):

Fine Particles ◽

Operating Time ◽

Filtration Efficiency ◽

Long Term Stability ◽

Aerosol Filtration ◽

Charge Decay ◽

The One ◽

Testing Standards ◽

Discharge Efficiency

Electret filters are electrostatically charged nonwovens which are commonly used in aerosol filtration to remove fine particles from gases. It is known that the charge and thus also the filtration efficiency can degrade over time. Thus, many testing standards require to remove the charge by treatment with liquid isopropanol (IPA) or IPA-saturated air. However, the parameters influencing this discharge have not been completely clarified yet. The aim of this work was, on the one hand, to experimentally investigate the influence of the IPA treatment on different electret filters and, on the other hand, to show the optimization potential of electret filters with respect to efficiency and long-term stability by numerical simulations. The experiments revealed that the air permeability is a central influencing parameter. Small pores lead to a reduced discharge efficiency using liquid IPA, while both treatment methods are suitable for larger pores. The simulations showed that a homogeneous charge distribution within the filter depth is advantageous for the initial performance. In contrast, charge penetrating deeper in the filter medium delays the charge decay and thus increases the operating time, with the trade-off of a lower initial performance.

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Minimal Invasive Surgery for Gastroesophageal Reflux Disease and Hiatus Hernia—Our Experience: A Case Series with Review of Literature

International Journal of Recent Surgical and Medical Sciences ◽

10.1055/s-0041-1731115 ◽

2021 ◽

Author(s):

Rafique Umer Harvitkar ◽

Abhijit Joshi

Keyword(s):

Retrospective Study ◽

Gastroesophageal Reflux Disease ◽

Gastroesophageal Reflux ◽

Operating Time ◽

Type I ◽

Type Ii ◽

The Mean ◽

Gerd Symptoms

Abstract Introduction Laparoscopic fundoplication (LF) has almost completely replaced the open procedure performed for gastroesophageal reflux disease (GERD) and hiatus hernia (HH). Several studies have suggested that long-term results with surgery for GERD are better than a medical line of management. In this retrospective study, we outline our experience with LF over 10 years. Also, we analyze the factors that would help us in better patient selection, thereby positively affecting the outcomes of surgery. Patients and Methods In this retrospective study, we identified 27 patients (14 females and 13 males) operated upon by a single surgeon from 2010 to 2020 at our institution. Out of these, 25 patients (12 females and 13 males) had GERD with type I HH and 2 (both females) had type II HH without GERD. The age range was 24 to 75 years. All patients had undergone oesophago-gastro-duodenoscopy (OGD scopy). A total of 25 patients had various degrees of esophagitis. Two patients had no esophagitis. These patients were analyzed for age, sex, symptoms, preoperative evaluation, exact procedure performed (Nissen’s vs. Toupet’s vs. cruroplasty + gastropexy), morbidity/mortality, and functional outcomes. They were also reviewed to examine the length of stay, length of procedure, complications, and recurrent symptoms on follow-up. Symptoms were assessed objectively with a score for six classical GERD symptoms preoperatively and on follow-up at 1-, 4- and 6-weeks postsurgery. Further evaluation was performed after 6 months and then annually for 2 years. Results 14 females (53%) and 13 males (48%) with a diagnosis of GERD (with type I HH) and type II HH were operated upon. The mean age was 46 years (24–75 years) and the mean body mass index (BMI) was 27 (18–32). The range of duration of the preoperative symptoms was 6 months to 2 years. The average operating time dropped from 130 minutes for the first 12 cases to 90 minutes for the last 15 cases. The mean hospital stay was 3 days (range: 2–4 days). In the immediate postoperative period, 72% (n = 18) of the patients reported improvement in the GERD symptoms, while 2 (8%) patients described heartburn (grade I, mild, daily) and 1 (4%) patient described bloating (grade I, daily). A total of 5 patients (20%) reported mild dysphagia to solids in the first 2 postoperative weeks. These symptoms settled down after 2 to 5 weeks of postoperative proton-pump inhibitor (PPI) therapy and by adjusting consistency of oral feeds. There was no conversion to open, and we observed no perioperative mortality. There were no patients who underwent redo surgeries in the series. Conclusion LF is a safe and highly effective procedure for a patient with symptoms of GERD, and it gives long-term relief from the symptoms. Stringent selection criteria are necessary to optimize the results of surgery. Experience is associated with a significant reduction of operating time.

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Experimental Study on the Softening Characteristics of Sandstone and Mudstone in Relation to Moisture Content

Shock and Vibration ◽

10.1155/2017/4010376 ◽

2017 ◽

Vol 2017 ◽

pp. 1-14 ◽

Cited By ~ 2

Author(s):

Gui-chen Li ◽

Chong-chong Qi ◽

Yuan-tian Sun ◽

Xiao-lin Tang ◽

Bao-quan Hou

Keyword(s):

Moisture Content ◽

Vertical Displacement ◽

Surface Porosity ◽

Shear Tests ◽

Moisture Contents ◽

Dynamic Finite Element ◽

Rock Types ◽

Underground Roadway ◽

The Stability ◽

Kinetics Of

The kinetics of fluid-solid coupling during immersion is an important topic of investigation in rock engineering. Two rock types, sandstone and mudstone, are selected in this work to study the correlation between the softening characteristics of the rocks and moisture content. This is achieved through detailed studies using scanning electron microscopy, shear tests, and evaluation of rock index properties during exposure to different moisture contents. An underground roadway excavation is simulated by dynamic finite element modeling to analyze the effect of moisture content on the stability of the roadway. The results show that moisture content has a significant effect on shear properties reduction of both sandstone and mudstone, which must thus be considered in mining or excavation processes. Specifically, it is found that the number, area, and diameter of micropores, as well as surface porosity, increase with increasing moisture content. Additionally, stress concentration is negatively correlated with moisture content, while the influenced area and vertical displacement are positively correlated with moisture content. These findings may provide useful input for the design of underground roadways.

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Automated Microscopy: Macro Language Controlling a Confocal Microscope and its External Illumination: Adaptation for Photosynthetic Organisms

Microscopy and Microanalysis ◽

10.1017/s1431927616000556 ◽

2016 ◽

Vol 22 (2) ◽

pp. 258-263 ◽

Cited By ~ 4

Author(s):

Gábor Steinbach ◽

Radek Kaňa

Keyword(s):

Light Sources ◽

Light Conditions ◽

Photosynthetic Organisms ◽

Automated Microscopy ◽

Photosynthetic Microorganisms ◽

Arduino Microcontroller ◽

Microscopy Data ◽

Kinetics Of ◽

Photosynthetic Cells

AbstractPhotosynthesis research employs several biophysical methods, including the detection of fluorescence. Even though fluorescence is a key method to detect photosynthetic efficiency, it has not been applied/adapted to single-cell confocal microscopy measurements to examine photosynthetic microorganisms. Experiments with photosynthetic cells may require automation to perform a large number of measurements with different parameters, especially concerning light conditions. However, commercial microscopes support custom protocols (throughTime Controlleroffered by Olympus orExperiment Designeroffered by Zeiss) that are often unable to provide special set-ups and connection to external devices (e.g., for irradiation). Our new system combining an Arduino microcontroller with theCell⊕Findersoftware was developed for controlling Olympus FV1000 and FV1200 confocal microscopes and the attached hardware modules. Our software/hardware solution offers (1) a text file-based macro language to control the imaging functions of the microscope; (2) programmable control of several external hardware devices (light sources, thermal controllers, actuators) during imaging via the Arduino microcontroller; (3) theCell⊕Findersoftware with ergonomic user environment, a fast selection method for the biologically important cells and precise positioning feature that reduces unwanted bleaching of the cells by the scanning laser.Cell⊕Findercan be downloaded fromhttp://www.alga.cz/cellfinder. The system was applied to study changes in fluorescence intensity inSynechocystissp. PCC6803 cells under long-term illumination. Thus, we were able to describe the kinetics of phycobilisome decoupling. Microscopy data showed that phycobilisome decoupling appears slowly after long-term (>1 h) exposure to high light.

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