Creep and Long-Time Strength of Compression Elements from Foam Concrete

2018 ◽  
Vol 284 ◽  
pp. 936-943
Author(s):  
M.V. Novikov ◽  
E.E. Prokshits ◽  
A.N. Goykalov
Keyword(s):  
Mechanical Properties ◽  
Structural Modification ◽  
Average Density ◽  
Foam Concrete ◽  
Short Term ◽  
Duration Of Action ◽  
Long Time ◽  
Time Strength ◽  
Strength And Deformation ◽  
Acting Load

In this article discusses the mechanical properties of foam concrete, which submitted based on the experimental data of long force resistance and deformation of compression elements from foam concrete. Also submitted criterion range of strength and deformation characteristics of foam concrete different structural modification with taking into account the permanently acting load, which necessary for calculation and design structures of buildings. In article such characteristics of foam concrete as durability and deformability at the age of 28 days by results of short-term tests and also influence of average density and a type of structure on its durability and deformability are considered. Change of mechanical properties of foam concrete in time by results of short-term tests is analyzed and studied. Experimental and theoretical researches which have in turn allowed to recommend for rationing of value of settlement characteristics the foam of concrete taking into account their variability, aging and duration of action of loading are executed.

Time Window from Visual Images to Visual Short-Term Memory: Consolidation or Integration?

2004 ◽  
Vol 51 (1) ◽  
pp. 45-51 ◽  
Author(s):  
Yuhong Jiang
Keyword(s):  
Short Term Memory ◽  
Time Window ◽  
Short Interval ◽  
Visual Images ◽  
Short Term ◽  
Temporal Window ◽  
Term Memory ◽  
Visual Short Term Memory ◽  
Probe Task ◽  
Long Time

Abstract. When two dot arrays are briefly presented, separated by a short interval of time, visual short-term memory of the first array is disrupted if the interval between arrays is shorter than 1300-1500 ms ( Brockmole, Wang, & Irwin, 2002 ). Here we investigated whether such a time window was triggered by the necessity to integrate arrays. Using a probe task we removed the need for integration but retained the requirement to represent the images. We found that a long time window was needed for performance to reach asymptote even when integration across images was not required. Furthermore, such window was lengthened if subjects had to remember the locations of the second array, but not if they only conducted a visual search among it. We suggest that a temporal window is required for consolidation of the first array, which is vulnerable to disruption by subsequent images that also need to be memorized.

scholarly journals Subway Gearbox Fault Diagnosis Algorithm Based on Adaptive Spline Impact Suppression

Entropy ◽  
2021 ◽  
Vol 23 (6) ◽  
pp. 660
Author(s):  
Zhongshuo Hu ◽  
Jianwei Yang ◽  
Dechen Yao ◽  
Jinhai Wang ◽  
Yongliang Bai
Keyword(s):  
Fault Diagnosis ◽  
Spline Interpolation ◽  
Reference Value ◽  
High Amplitude ◽  
Engineering Practice ◽  
Negative Effects ◽  
Short Term ◽  
Time Domain Signal ◽  
Gearbox Vibration ◽  
Long Time

In the signal processing of real subway vehicles, impacts between wheelsets and rail joint gaps have significant negative effects on the spectrum. This introduces great difficulties for the fault diagnosis of gearboxes. To solve this problem, this paper proposes an adaptive time-domain signal segmentation method that envelopes the original signal using a cubic spline interpolation. The peak values of the rail joint gap impacts are extracted to realize the adaptive segmentation of gearbox fault signals when the vehicle was moving at a uniform speed. A long-time and unsteady signal affected by wheel–rail impacts is segmented into multiple short-term, steady-state signals, which can suppress the high amplitude of the shock response signal. Finally, on this basis, multiple short-term sample signals are analyzed by time- and frequency-domain analyses and compared with the nonfaulty results. The results showed that the method can efficiently suppress the high-amplitude components of subway gearbox vibration signals and effectively extract the characteristics of weak faults due to uniform wear of the gearbox in the time and frequency domains. This provides reference value for the gearbox fault diagnosis in engineering practice.

Polylactide-based stent coatings: biodegradable polymeric coatings capable of maintaining sustained release of the thrombolytic enzyme streptokinase

2020 ◽  
Vol 92 (8) ◽  
pp. 1329-1340
Author(s):  
A. G. Kolmakov ◽  
A. S. Baikin ◽  
S. V. Gudkov ◽  
K. N. Belosludtsev ◽  
E. O. Nasakina ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Polymer Films ◽  
De Novo ◽  
Membrane Surface ◽  
Aqueous Media ◽  
Polymeric Coatings ◽  
Short Term ◽  
Thrombolytic Activity ◽  
Viable Cells ◽  
Nitinol Stents

AbstractThe paper describes synthesis and testing of novel biodegradable polylactide-based polymer membranes with desired mechanical properties, which are capable of sustained and directed release of biomacromolecules with high molecular weight (in particular, streptokinase; m.w. 47 kDa). Streptokinase is a pharmaceutical agent, possessing a pronounced thrombolytic activity. The membranes synthesized had a percentage elongation of 2–11% and tensile strength of 25–85 MPa. They were biodegradable – yet being stored in aqueous media in the absence of biological objects, would be dissolved by no more than 10% in 6 months. The synthesized membranes were capable of controlled release of streptokinase into the intercellular space, with the enzyme retaining more than 90% of its initial activity. The rate of streptokinase release from the membranes varied from 0.01 to 0.04 mg/day per cm2 of membrane surface. The membrane samples tested in the work did not have any short-term toxic effects on the cells growing de novo on the membrane surface. The mitotic index of those cells was approximately 1.5%, and the number of non-viable cells on the surface of the polymer films did not exceed 3–4% of their total amount. The implantation of the synthesized polymers – as both individual films and coatings of nitinol stents – was not accompanied by any postoperative complications. The subsequent histological examination revealed no abnormalities. Two months after the implantation of polymer films, only traces of polylactide were found in the implant-surrounding tissues. The implantation of stents coated with streptokinase-containing polymers resulted in the formation of a mature and thick connective-tissue capsules. Thus, the polylactide membranes synthesized and tested in this work are biodegradable, possess the necessary mechanical properties and are capable of sustained and directed release of streptokinase macromolecules.

scholarly journals Double-Cross-Linked Networks Based on Methacryloyl Mucin

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1706
Author(s):  
Elena Olăreț ◽  
Brîndușa Bălănucă ◽  
Andra Mihaela Onaș ◽  
Jana Ghițman ◽  
Horia Iovu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Aqueous Solution ◽  
Chemical Modification ◽  
Structural Modification ◽  
Aqueous Media ◽  
Cross Linking ◽  
Ph Values ◽  
Acid Aqueous Solution ◽  
Reaction Media ◽  
Double Cross

Mucin is a glycoprotein with proven potential in the biomaterials field, but its use is still underexploited for such applications. The present work aims to produce a synthesis of methacryloyl mucin single-network (SN) hydrogels and their double-cross-linked-network (DCN) counterparts. Following the synthesis of the mucin methacryloyl derivative, various SN hydrogels are prepared through the photopolymerization of methacrylate bonds, using reaction media with different pH values. The SN hydrogels are converted into DCN systems via supplementary cross-linking in tannic acid aqueous solution. The chemical modification of mucin is described, and the obtained product is characterized; the structural modification of mucin is assessed through FTIR spectroscopy, and the circular dichroism and the isoelectric point of methacryloyl mucin is evaluated. The affinity for aqueous media of both SN and DCN hydrogels is estimated, and the mechanical properties of the systems are assessed, both at macroscale through uniaxial compression and rheology tests and also at microscale through nanoindentation tests.

Application of Tailored Heat Treated Blanks under Quasi Series Conditions

2007 ◽  
Vol 344 ◽  
pp. 383-390 ◽  
Author(s):  
Marion Merklein ◽  
Uwe Vogt
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Local Heat ◽  
Strength Distribution ◽  
Process Window ◽  
Short Term ◽  
Forming Process ◽  
Heat Treated ◽  
Set Up ◽  
The Impact

Tailored Heat Treated Blanks (THTB) are blanks that exhibit locally different strength specifically optimized for the succeeding forming process. The strength distribution is set by a local, short-term heat treatment modifying the mechanical properties of the material. Hence, THTB allow enhancing forming limits significantly leading to shorter and more robust manufacture process chains. In order to qualify the use of THTB under quasi series conditions, the interdependencies of the blank’s local heat treatment and the entire process chain of the car body manufacture have to be analyzed. In this respect, the impact of a short-term heat treatment on the mechanical properties of AA6181PX, a commonly used aluminum alloy in today’s car bodies, was studied. Also the influence of a short-term heat treatment on the coil lubricant, usually already applied by the material supplier, was given a closer look. Based on these experiments process restrictions for the application of THTB in an industrial automotive environment were derived and a process window for the THTB design was set up. In conclusion, strategies were defined how to enhance the found process boundaries leading to a more robust process window.

Evaluation of Repair Welding Influence on GH3535 Superalloy Microstructure and Mechanical Properties

2016 ◽  
Author(s):  
Chaowen Li ◽  
Shuangjian Chen ◽  
Kun Yu ◽  
Zhijun Li
Keyword(s):  
Mechanical Properties ◽  
Arc Welding ◽  
Weld Seam ◽  
Filler Metal ◽  
Short Term ◽  
Weld Repair ◽  
Repair Welding ◽  
Gas Tungsten Arc ◽  
Rolled Plates ◽  
Carbide Precipitate

GH3535 supperalloy, whose grade of ASME is UNS N10003, is currently considered as a candidate material for solid-fuel and fluid-fuel molten salt reactor in china. During the development of procedures for welding GH3535 superalloy, consideration should always be given to the possibility that repair welding may be necessary. This paper presents weld repairs of GH3535 alloy rolled plates using gas tungsten arc welding with filler metal. The purpose of this work is to evaluate the low heat input process for weld repair of GH3535 alloy plates about the microstructure features and mechanical properties. The results demonstrated that sound joints without defects could be obtained after weld repairs. Due to repair thermal cycles on the original weld seam, the size of carbide precipitate became large, but repair welding is found to cause no decrease in short-term time-independent strength.

107 The Role of Tissue Engineering in Auricular Reconstruction: A Critical Review

2021 ◽  
Vol 108 (Supplement_6) ◽  
Author(s):  
F Moura ◽  
R Varley ◽  
C Yao
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Immune Response ◽  
Critical Review ◽  
3D Bioprinting ◽  
Short Term ◽  
Auricular Reconstruction ◽  
Cartilage Reconstruction ◽  
Promising Solution

Abstract Aim Despite several decades of research in tissue engineering, reconstructing a 3D human-sized ear that can stand the test of time has remained a challenge. Autologous cartilage reconstruction remains the main treatment choice despite the associated morbidity. Progress in the field has been made and several studies have used tissue-engineered implants in immunocompetent animals with promising results. Method This study critically reviews and assesses the characteristics that make auricular reconstruction so challenging and how far research has come in addressing the following: mechanical properties; vascularisation; immune response; cell sourcing; surgical attachments; allografts; and cost. Results The question is whether tissue engineering will realistically replace autologous cartilage reconstruction in the short-term, or will advances in other areas, outlined in this article, manage to provide suitable and aesthetically accurate scaffolds. Conclusions Advances in tissue engineering are slowly progressing and utilise advances in both biomaterial design and 3D bioprinting to try and address the challenges of auricular reconstruction. Tissue engineering is still a promising solution to auricular reconstruction but still requires further research before becoming a reality.

Long-time strength of polyethylene in biaxial tension

1977 ◽  
Vol 12 (3) ◽  
pp. 352-360 ◽  
Author(s):  
A. M. Grinman ◽  
A. Ya. Gol'dman
Keyword(s):  
Biaxial Tension ◽  
Long Time ◽  
Time Strength

scholarly journals Biodegradable Flame Retardants for Biodegradable Polymer

Biomolecules ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1038
Author(s):  
Muhammad Maqsood ◽  
Gunnar Seide
Keyword(s):  
Renewable Resources ◽  
Flame Retardants ◽  
Fire Risk ◽  
Polymeric Materials ◽  
Good Choice ◽  
Airborne Particle ◽  
Short Term ◽  
Renewable Materials ◽  
Long Time ◽  
Significant Attention

To improve sustainability of polymers and to reduce carbon footprint, polymers from renewable resources are given significant attention due to the developing concern over environmental protection. The renewable materials are progressively used in many technical applications instead of short-term-use products. However, among other applications, the flame retardancy of such polymers needs to be improved for technical applications due to potential fire risk and their involvement in our daily life. To overcome this potential risk, various flame retardants (FRs) compounds based on conventional and non-conventional approaches such as inorganic FRs, nitrogen-based FRs, halogenated FRs and nanofillers were synthesized. However, most of the conventional FRs are non-biodegradable and if disposed in the landfill, microorganisms in the soil or water cannot degrade them. Hence, they remain in the environment for long time and may find their way not only in the food chain but can also easily attach to any airborne particle and can travel distances and may end up in freshwater, food products, ecosystems, or even can be inhaled if they are present in the air. Furthermore, it is not a good choice to use non-biodegradable FRs in biodegradable polymers such as polylactic acid (PLA). Therefore, the goal of this review paper is to promote the use of biodegradable and bio-based compounds for flame retardants used in polymeric materials.

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