scholarly journals Predicting Compression Pressure of Knitted Fabric Using a Modified Laplace’s Law

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4461
Author(s):  
Yetanawork Teyeme ◽  
Benny Malengier ◽  
Tamrat Tesfaye ◽  
Simona Vasile ◽  
Wolelaw Endalew ◽  
...  
Keyword(s):  
Physical Parameters ◽  
Interface Pressure ◽  
Compression Pressure ◽  
Engineering Strain ◽  
Measuring Device ◽  
Laplace’S Law ◽  
The Difference ◽  
Experimental Pressure ◽  
Laplace's Law

The aim of this study is to develop a mathematical model for the prediction of compression pressure based on fabric parameters, such as engineering stress, engineering strain and engineering modulus of elasticity. Four knitted compression fabrics with different fibrous compositions and knit structures were used. Rectangular-cut strips were employed for the force–elongation characterization of the fabrics. The experimental pressure values between the fabric and rigid cylinder were assessed using a Picopress pressure measuring device. The mechanical and physical parameters of the fabric that influence the interface pressure, such as strain, elasticity modulus/stress and thickness, were determined and integrated into Laplace’s law. A good correlation was observed between the experimental and calculated pressure values for all combinations of fabrics, mounted with variable tension on the cylinder. Over the considered range of pressures, the difference between the two datasets was generally less than 0.5 mmHg. The effect of washing after five, ten and fifteen washing cycles on the fabric–cylinder interface pressure was found to be significant.

scholarly journals Acoustic Characterization of Some Steel Industry Waste Materials

2021 ◽  
Vol 11 (13) ◽  
pp. 5924
Author(s):  
Elisa Levi ◽  
Simona Sgarbi ◽  
Edoardo Alessio Piana
Keyword(s):  
Thermal Characteristic ◽  
Environmental Benefits ◽  
Acoustic Properties ◽  
Physical Parameters ◽  
Industry Waste ◽  
Acoustic Characterization ◽  
Minimization Procedure ◽  
The Difference ◽  
By Products

From a circular economy perspective, the acoustic characterization of steelwork by-products is a topic worth investigating, especially because little or no literature can be found on this subject. The possibility to reuse and add value to a large amount of this kind of waste material can lead to significant economic and environmental benefits. Once properly analyzed and optimized, these by-products can become a valuable alternative to conventional materials for noise control applications. The main acoustic properties of these materials can be investigated by means of a four-microphone impedance tube. Through an inverse technique, it is then possible to derive some non-acoustic properties of interest, useful to physically characterize the structure of the materials. The inverse method adopted in this paper is founded on the Johnson–Champoux–Allard model and uses a standard minimization procedure based on the difference between the sound absorption coefficients obtained experimentally and predicted by the Johnson–Champoux–Allard model. The results obtained are consistent with other literature data for similar materials. The knowledge of the physical parameters retrieved applying this technique (porosity, airflow resistivity, tortuosity, viscous and thermal characteristic length) is fundamental for the acoustic optimization of the porous materials in the case of future applications.

scholarly journals On the Pressure Behavior of Tubular Weft Knitted Fabrics Constructed from Textured Polyester Yarns

2011 ◽  
Vol 6 (2) ◽  
pp. 155892501100600 ◽  
Author(s):  
Homa Maleki ◽  
Marzie Aghajani ◽  
A.H. Sadeghi ◽  
Ali Asghar Asgharian Jeddi
Keyword(s):  
Pressure Reduction ◽  
Knitted Fabrics ◽  
Factors Affecting ◽  
Pressure Behavior ◽  
Interfacial Pressure ◽  
Stitch Length ◽  
Laplace’S Law ◽  
Experimental Pressure ◽  
Theoretical Results ◽  
Laplace's Law

This study attempts to investigate the pressure behavior of tubular knitted fabrics after a long period of time. For this purpose, two kinds of knitted fabric (plain and interlock) with various stitch lengths were chosen and the interfacial pressure and pressure reduction of fabrics after 48 hours were analyzed at different strain percents. The same tests were performed on the same specimens after repeated washing and repeated usage. Finally, the experimental pressure values were compared with the theoretical results obtained from Laplace's law. The results reveal that the stitch length and strain percent are important factors affecting the interfacial pressure and pressure reduction of both plain and interlock fabrics. As the results of statistical analysis, the repeated washing and repeated usage have significant effect on interfacial pressure and pressure reduction of both fabrics. The comparison between experimental pressure values and theoretical values calculated from Laplace's law shows a considerable difference in both plain and interlock fabrics.

Skin, Veins and Legs

Phlebologie ◽  
2011 ◽  
Vol 40 (06) ◽  
pp. 344-355 ◽  
Author(s):  
H.A.M. Neumann
Keyword(s):  
Plasma Proteins ◽  
Varicose Veins ◽  
Venous Pressure ◽  
Compression Therapy ◽  
Fine Tuning ◽  
Physical Parameters ◽  
Interface Pressure ◽  
Symptom Complex ◽  
The Difference ◽  
Physical Laws

SummarySkin, veins and legs are the three ingredients which compose together the symptom complex know as chronic venous insufficiency (CVI). High ambulatory venous pressure is transferred by simple physical laws to the skin microcirculation. The capillaries are not resistant to this high pressure and will leak water, erythrocytes and plasma proteins into the in-terstitium. The result is oedema, pigmentation, sclerosis, inflammation and ulceration. Although many forms of intervention for incompetent veins are available, compression therapy is still the cornerstone in the treatment of CVI. Beside the interface pressure, the stiffness of the compression material is essential. By increasing the stiffness the difference in pressure during walking increases and with this the massage effect of the therapy.Thermo-ablation is the treatment for varicose veins today. Knowledge about the development and transfer of the intravascular heat is essential to understand this treatment. New experiments, specially about steam development from the heat source in the blood are of great importance for the success rate. Fine tuning in those physical parameters is needed to optimally this treatment.

New approach for the prediction of compression pressure using the cut strip method

2020 ◽  
Vol 90 (15-16) ◽  
pp. 1689-1703 ◽  
Author(s):  
Hafiz Faisal Siddique ◽  
Adnan Mazari ◽  
Antonin Havelka ◽  
Zdenek Kus ◽  
David Cirkl ◽  
...  
Keyword(s):  
Young’S Modulus ◽  
Modulus Of Elasticity ◽  
Young's Modulus ◽  
Compression Pressure ◽  
Engineering Strain ◽  
Measuring Device ◽  
New Approach ◽  
Tensile Tester ◽  
Rectangular Strips ◽  
Pressure Measuring Device

The main objective of the current research is the development of a new mathematical model for the prediction of compression pressure based on the incorporation of some new parameters. These new parameters include deformed width (wf), true stress ([Formula: see text]), true/logarithm strain ([Formula: see text]), true modulus of elasticity ([Formula: see text]), along with measurement of engineering stress ([Formula: see text]), engineering strain ([Formula: see text]) and engineering modulus of elasticity ([Formula: see text]) at ankle position. Various brands of compression socks comprising similar fibrous combinations, as well as knit type, were purchased. Initially they were hand washed, put on the leg for marking, marked in a square, sliced, and cut into rectangular strips. The rectangular cut strips were evaluated for force–elongation characterization at different strain values considering the requisite practical elongation values (circumferential difference between leg and sock at ankle portion). For pressure measurement, a Salzmann MST MK IV pressure measuring device using a standard-sized wooden leg (circumference = 240 mm) was used. For tensile evaluation, a Testometric tensile tester was used. In this research we developed the two mathematical models based on true Young’s modulus and engineering Young’s modulus were compared with Hooke’s law and Laplace’s law. The developed models were also compared with previously existing models statistically.

Clothing Pressure Modeling Using the Modified Laplace’s Law

2019 ◽  
Vol 38 (2) ◽  
pp. 134-147
Author(s):  
H. Barhoumi ◽  
S. Marzougui ◽  
S. Ben Abdessalem
Keyword(s):  
Mechanical Properties ◽  
Human Body ◽  
Elasticity Modulus ◽  
Extended State ◽  
Interface Pressure ◽  
Compression Behavior ◽  
Theoretical Relationship ◽  
Laplace’S Law ◽  
Clothing Pressure ◽  
Laplace's Law

Today, various kinds of pressure garments are designed for specific applications in medical and sports fields. Knitted garments are the most used in these applications due to their high extensibility. The objective of the investigation reported in this article was to develop a theoretical relationship based on Laplace’s law, which describes the compression behavior of knitted compression samples in quasi-static deformation from an initially relaxed state to an extended state. Even though several researchers have used Laplace’s law, there is some discord between theoretical and experimental results. So, it is essential to pinpoint the most important parameters that influence the mechanical properties of the compression knitted garment in order to better describe the interface pressure it applies to the human body. Fabric parameters that influenced the interface pressure, such as elasticity modulus, strain, and thickness, were determined and integrated into Laplace’s law.

Analisis Karakterisasi Teknologi Direct Sequence Spread Spectrum Dan Frequency Hopping Spread Spectrum

2019 ◽  
Vol 2 (2) ◽  
pp. 129-138
Author(s):  
Fawzan Galib Abdul Karim Bawahab ◽  
Elvan Yuniarti ◽  
Edi Kurniawan
Keyword(s):  
Spread Spectrum ◽  
Communication Systems ◽  
Multiple Access ◽  
Frequency Hopping ◽  
Direct Sequence Spread Spectrum ◽  
Direct Sequence ◽  
Frequency Hopping Spread Spectrum ◽  
Two Systems ◽  
The Difference

Abstrak. Pada penelitian ini, telah dilakukan analisa karakterisasi pada teknologi Direct Sequence Spread Spectrum dan Frequency Hopping Spread Spectrum, sebagai salah satu teknik multiple-access pada sistem komunikasi. Karakterisasi dilakukan untuk mencari bagaimana cara meningkatkan keoptimalan kedua sistem tersebut, dalam mengatasi masalah interferensi dengan sistem dan channel yang sama. Dan juga untuk menentukan veriabel apa yang mempengaruhi keoptimalan kedua sistem tersebut. Karakterisasi dilakukan dengan menentukan variabel-variabel yang mempengaruhi keoptimalan keduanya. Hasil dari karakterisasi, diketahui variabel-variabel yang mempengaruhi kemampuan sistem DSSS yaitu nilai frekuensi spreading (). Sedangkan untuk sistem FHSS yaitu nilai frekuensi spreading ( dan ) dan selisih antara frekuensi hopping data dengan frekuensi hopping interferensi . Kata Kunci: BER, DSSS, FHSS, Interference, Spread spectrum. Abstract. In this study, characterization of Direct Sequence Spread Spectrum and Frequency Hopping Spread Spectrum technologies have been done, as one of the multiple-access techniques in communication systems. Characterization is done to find out how to improve the ability of the two systems, in solving interference problems with the same system and channel. And also to determine what veriabel affects the ability of the two systems. Characterization is done by determining the variables that affect the ability of both. The results of the characterization, known variables that affect the ability of the DSSS system are the spreading frequency value (). As for the FHSS system, the spreading frequency value ( and ) and the difference between frequency hopping data with frequency hopping interference .

Characterization of the surface of hydrodesulphurization catalysts by adsorption of hydrocarbons

1984 ◽  
Vol 49 (2) ◽  
pp. 410-420
Author(s):  
Eva Hillerová ◽  
Miroslav Zdražil
Keyword(s):  
Hydrogen Sulphide ◽  
Chromatographic Method ◽  
Supported Catalysts ◽  
Alumina Surface ◽  
Reversible Adsorption ◽  
The Difference

Reversible adsorption of heptane and benzene on model and industrial hydrodesulphurization molybdena catalysts has been studied by elution chromatographic method at 150 °C. An increase in the adsorption of heptane on sulphidation of adsorbents was small for Al2O3 and great for MoO3. Supported catalysts behaved as mixture of Al2O3 and MoO3.The portion of surface which can be transformed by sulphidation into MoS2 ranged from 0 to 65% for individual commercial catalysts, as determined from the change in heptane adsorption after sulphidation of a given sample. The polarity of catalysts, including their acidity, was estimated from the difference between adsorption of benzene and heptane. The polarity of model and industrial catalysts in oxidic form was similar to that of alumina in most cases. The decrease in the polarity after sulphidation of the adsorbents was small for Al2O3 and great for MoO3. The decrease in polarity resulting from sulphidation of supported catalysts was relatively small, since the reaction of MoO3 monolayer with hydrogen sulphide leads to partial reformation of the alumina surface. The acidity of supported sulphided hydrodesulphurization catalysts has been shown by this method to be comparable with the acidity of the support itself.

scholarly journals Nonlinear stability of two-layer shallow water flows with a free surface

2020 ◽  
Vol 476 (2236) ◽  
pp. 20190594
Author(s):  
Francisco de Melo Viríssimo ◽  
Paul A. Milewski
Keyword(s):  
Free Surface ◽  
Initial Data ◽  
Nonlinear Stability ◽  
Mathematical Proof ◽  
Passive Layer ◽  
Physical Parameters ◽  
Immiscible Fluid ◽  
Dimensional System ◽  
The Cauchy Problem ◽  
The Difference

The problem of two layers of immiscible fluid, bordered above by an unbounded layer of passive fluid and below by a flat bed, is formulated and discussed. The resulting equations are given by a first-order, four-dimensional system of PDEs of mixed-type. The relevant physical parameters in the problem are presented and used to write the equations in a non-dimensional form. The conservation laws for the problem, which are known to be only six, are explicitly written and discussed in both non-Boussinesq and Boussinesq cases. Both dynamics and nonlinear stability of the Cauchy problem are discussed, with focus on the case where the upper unbounded passive layer has zero density, also called the free surface case. We prove that the stability of a solution depends only on two ‘baroclinic’ parameters (the shear and the difference of layer thickness, the former being the most important one) and give a precise criterion for the system to be well-posed. It is also numerically shown that the system is nonlinearly unstable, as hyperbolic initial data evolves into the elliptic region before the formation of shocks. We also discuss the use of simple waves as a tool to bound solutions and preventing a hyperbolic initial data to become elliptic and use this idea to give a mathematical proof for the nonlinear instability.

Synthesis and characterization of a series of 1-methyl-4-[2-aryl-1-diazenyl]piperazines and a series of ethyl 4-[2-aryl-1-diazenyl]-1-piperazinecarboxylates

2004 ◽  
Vol 82 (8) ◽  
pp. 1294-1303 ◽  
Author(s):  
Vanessa Renée Little ◽  
Keith Vaughan
Keyword(s):  
Free Energy ◽  
Chemical Shifts ◽  
Linear Free Energy Relationship ◽  
Piperazine Ring ◽  
Linear Free Energy ◽  
In Series ◽  
Methylene Groups ◽  
Diazonium Coupling ◽  
The Difference

1-Methylpiperazine was coupled with a series of diazonium salts to afford the 1-methyl-4-[2-aryl-1-diazenyl]piperazines (2), a new series of triazenes, which have been characterized by 1H and 13C NMR spectroscopy, IR spectroscopy, and elemental analysis. Assignment of the chemical shifts to specific protons and carbons in the piperazine ring was facilitated by comparison with the chemical shifts in the model compounds piperazine and 1-methylpiperazine and by a HETCOR experiment with the p-tolyl derivative (2i). A DEPT experiment with 1-methylpiperazine (6) was necessary to distinguish the methyl and methylene groups in 6, and a HETCOR spectrum of 6 enabled the correlation of proton and carbon chemical shifts. Line broadening of the signals from the ring methylene protons is attributed to restricted rotation around the N2-N3 bond of the triazene moiety in 2. The second series of triazenes, the ethyl 4-[2-phenyl-1-diazenyl]-1-piperazinecarboxylates (3), have been prepared by similar diazonium coupling to ethyl 1-piperazinecarboxylate and were similarly characterized. The chemical shifts of the piperazine ring protons are much closer together in series 3 than in series 2, resulting in distortion of the multiplets for these methylenes. It was noticed that the difference between these chemical shifts in 3 exhibited a linear free energy relationship with the Hammett substituent constants for the substituents in the aryl ring. Key words: triazene, piperazine, diazonium coupling, NMR, HETCOR, linear free energy relationship.

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