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1 – 10 of over 61000Daniela Zavec Pavlinic´ and Jelka Geršak
In transforming fabrics into garment it is necessary to know, besides the manner of processing, the behaviour of the fabric in particular manufacturing processes. It is necessary…
Abstract
In transforming fabrics into garment it is necessary to know, besides the manner of processing, the behaviour of the fabric in particular manufacturing processes. It is necessary to define why and how fabrics behave in a particular way when exposed to various strains. The answers to these questions are obtained by investigating fabric mechanics, as non‐linear mechanical fabric properties at lower strains, which is the case in transforming fabrics into garments. The area to be investigated is quite wide and the investigations presented here deal only with the most important elastic strains occurring in processing fabrics into garments, such as tensile, pressure, shear and bending, as each individual type of strain bears specific importance in studying fabric behaviour, as well as in garment quality control. Strains impacting the fabric, i.e. the reaction of the fabric to these strains, are presented through the parameters of mechanical properties. A relation is also explained between characteristic histeresis curves and fabric behaviour in real garment manufacturing processes, obtained through recording fabric behaviour in particular garment manufacturing processes. Results obtained through the investigations of mechanical properties of the fabrics analysed and their behaviour in garment manufacturing processes helped to determine the so‐called critical, or border values for particular parameters of mechanical properties.
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The purpose of this paper is to explore capital gains, income, and total returns in various property markets in Europe. In a comparative study the nature of returns for different…
Abstract
Purpose
The purpose of this paper is to explore capital gains, income, and total returns in various property markets in Europe. In a comparative study the nature of returns for different commercial and residential properties is investigated. Hereby, total returns, income returns, and capital growth are distinguished. The paper further presents an analysis of the risk‐return relationship of the different markets and investigates the interactions between property markets, other local financial markets, and macroeconomic variables.
Design/methodology/approach
Focusing on the risk‐return relationship of the different asset classes and countries, the Sharpe ratio is used as a risk‐adjusted performance measure to investigate the European markets. Using a simple linear regression model, a comparison of the European commercial property markets with respect to their returns and risk are provided. Finally, a capital asset pricing model (CAPM) and factor models based on arbitrage pricing theory (APT) are used in an effort to further explain the spreads and risk premiums for individual property markets.
Findings
The large differences between the markets regarding spreads, risk premiums, and risk‐return relationships are found. Overall, the Dutch market can be regarded as giving the highest compensation for the risk taken by the investors in the last decade, while the German market performed the worst and was the only market with negative capital growth rates for the considered period. Applying the CAPM, It has also been found total returns in commercial property markets are not significantly related to the performance of stock market indices. On the other hand, factor models using macroeconomic variables are able to explain a higher fraction of property total return spreads over the risk‐free rate in the considered countries. But depending on the country, different macroeconomic variables were estimated to be significant such that there is no single factor model available that could be applied to all European markets. Overall, these findings indicate that classic financial models drawing on existing datasets are unable to satisfactorily explain the performance of property as an asset class. On the other hand, the fact that property office markets yield relatively high returns that exhibit rather low correlations with stock market returns, makes them a very suitable candidate for portfolio diversification.
Originality/value
The paper investigates the risk‐return relationship in various European property markets. The large differences between the markets observed also partly explain the diversity of literature results on this relationship across single countries by, e.g. Goetzmann, Englund, or Bourassa et al. By using classic financial models like the CAPM or APT a contribution to the literature is made by explaining the factors that actually determine property returns over the risk free rate in different countries.
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Index by subjects, compiled by K.G.B. Bakewell covering the following journals: Facilities Volumes 8‐17; Journal of Property Investment & Finance Volumes 8‐17; Property Management…
Abstract
Index by subjects, compiled by K.G.B. Bakewell covering the following journals: Facilities Volumes 8‐17; Journal of Property Investment & Finance Volumes 8‐17; Property Management Volumes 8‐17; Structural Survey Volumes 8‐17.
Compiled by K.G.B. Bakewell covering the following journals published by MCB University Press: Facilities Volumes 8‐17; Journal of Property Investment & Finance Volumes 8‐17;…
Abstract
Compiled by K.G.B. Bakewell covering the following journals published by MCB University Press: Facilities Volumes 8‐17; Journal of Property Investment & Finance Volumes 8‐17; Property Management Volumes 8‐17; Structural Survey Volumes 8‐17.
Muhammad Aamir, Majid Tolouei-Rad, Israr Ud Din, Khaled Giasin and Ana Vafadar
Tin-Silver-Copper is widely accepted as the best alternative to replace Tin-Lead solders in microelectronics packaging due to their acceptable properties. However, to overcome…
Abstract
Purpose
Tin-Silver-Copper is widely accepted as the best alternative to replace Tin-Lead solders in microelectronics packaging due to their acceptable properties. However, to overcome some of the shortcomings related to its microstructure and in turn, its mechanical properties at high temperature, the addition of different elements into Tin-Silver-Copper is important for investigations. The purpose of this paper is to analyse the effect of lanthanum doping on the microstructure, microhardness and tensile properties of Tin-Silver-Copper as a function of thermal aging time for 60, 120 and 180 h at a high temperature of 150°C and at high strain rates of 25, 35 and 45/s.
Design/methodology/approach
The microstructure of un-doped and Lanthanum-doped Tin-Silver-Copper after different thermal aging time is examined using scanning electron microscopy followed by digital image analyses using ImageJ. Brinell hardness is used to find out the microhardness properties. The tensile tests are performed using the universal testing machine. All the investigations are done after the above selected thermal aging time at high temperature. The tensile tests of the thermally aged specimens are further investigated at high strain rates of 25, 35 and 45/s.
Findings
According to the microstructural examination, Tin-Silver-Copper with 0.4 Wt.% Lanthanum is found to be more sensitive at high temperature as the aging time increases which resulted in coarse microstructure due to the non-uniform distribution of intermetallic compounds. Similarly, lower values of microhardness, yield strength and ultimate tensile strength come in favours of 0.4 Wt.% Lanthanum added Tin-Silver-Copper. Furthermore, when the thermally aged tensile specimen is tested at high strains, two trends in tensile curves of both the solder alloys are noted. The trends showed that yield strength and ultimate tensile strength increase as the strain rate increase and decrease when there is an increase in thermal aging.
Originality/value
The addition of higher supplement (0.4 Wt.%) of Lanthanum into Tin-Silver-Copper showed a lower hardness value, yield strength, ultimate tensile strength, ductility, toughness and fatigue in comparison to un-doped Tin-Silver-Copper at high temperature and at high strain rates. Finally, simplified material property models with minimum error are developed which will help when the actual test data are not available.
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Matthias Michael Lexow, Maximilian Drexler and Dietmar Drummer
Despite the recent progress in basic process understanding considering the selective laser sintering (SLS) of thermoplastics, several aspects of the mechanisms of the beam and…
Abstract
Purpose
Despite the recent progress in basic process understanding considering the selective laser sintering (SLS) of thermoplastics, several aspects of the mechanisms of the beam and powder interaction are not fully understood yet. Recent studies covered the correlation of mechanical properties and part density with the heating rate. The surface roughness of the test specimens was also considered but showed no distinct relation to the part mechanics. The purpose of this paper is to provide a new fundamental model for describing the decreasing mechanical properties with increasing beam speed.
Design/methodology/approach
While the dependence of mechanical properties with total energy input during exposure is well published, the correlation of the exposure speed with the degree of particle melt (DPM) is the subject of the present study. The DPM is accessible through differential scanning calorimetry measurements. Supporting the previously introduced method of the core-peak height, the interpretation via the core-peak area is proposed as a means to ascertain the melting behaviour for different processing conditions. Further support of the observations is given by x-ray computed tomography and microscopy which allows for a correlation with the respective porosity and inner structure of the parts.
Findings
The authors show a novel way of describing the decreasing mechanical properties with increasing speed of energy input by showing the dependence of the DPM on the heating rate during exposure.
Practical implications
The results offer an addition to the understanding considering the reliability and reproducibility of the SLS process.
Originality/value
The paper extends the existing models of the time-dependent material behaviour, which allows for the derivation of new efficient and stable process strategies.
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Wit Stryczniewicz, Janusz Zmywaczyk and Andrzej Jaroslaw Panas
The paper aims to discuss the inverse heat conduction methodology in solution of a certain parameter identification problem. The problem itself concerns determination of the…
Abstract
Purpose
The paper aims to discuss the inverse heat conduction methodology in solution of a certain parameter identification problem. The problem itself concerns determination of the thermophysical properties of a thin layer coating by applying the laser flash apparatus.
Design/methodology/approach
The modelled laser flash diffusivity data from the three-layer sample investigation are used as input for the following parameter estimation procedure. Assuming known middle layer, i.e. substrate properties, the thermal diffusivity (TD) of the side layers’ material is determined. The estimation technique utilises the finite element method for numerical solution of the direct, 2D axisymmetric heat conduction problem.
Findings
The paper presents methodology developed for a three-layer sample studies and results of the estimation technique testing and evaluation based on simulated data. The multi-parametrical identification procedure results in identification of the out of plane thin layer material diffusivity from the inverse problem solution.
Research limitations/implications
The presentation itself is limited to numerical simulation data, but it should be underlined that the flake graphite thermophysical parameters have been utilised in numerical tests.
Practical implications
The developed methodology is planned to be applied in detailed experimental studies of flake graphite.
Originality/value
In the course of a present study, a methodology of the thin-coating layer TD determination was developed. In spite of the fact that it has been developed for the graphite coating investigation, it was planned to be universal in application to any thin–thick composite structure study.
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Soumya Ranjan Guru, Chetla Venugopal and Mihir Sarangi
This study aims to investigate the behavior of vegetable oil with two additives. Base oil’s tribological qualities can be improved with the help of several additions. In the…
Abstract
Purpose
This study aims to investigate the behavior of vegetable oil with two additives. Base oil’s tribological qualities can be improved with the help of several additions. In the present investigation, soybean oil is served as the foundational oil due to its eco-friendliness and status as a vegetable oil with two additives, named polytetrafluoroethylene (PTFE) and molybdenum disulfide (MoS2).
Design/methodology/approach
As additives, PTFE and MoS2 are used; PTFE is renowned for its anti-friction (AF) properties, while MoS2 is a solid lubricant with anti-wear (AW) properties. This investigation examines the synergistic impact of AF and AW additions in vegetable oil. The lubricity of the base oil is measured by using a four-ball tester, and the wear properties of the oil at different additive amounts are determined by using a universal tribometer.
Findings
PTFE (at 5 Wt.%) and MoS2 (at 1 Wt.%) were found to improve the tribological performance of the base oil. The weld load is significantly increased when 5 Wt.% of PTFE + MoS2 is added to the base oil.
Originality/value
A better tribological characteristic can be achieved by combining additives that amount to less than 1% of the base oil. In experiments with highly concentrated MoS2, the adequate pressure improved dramatically, but the lubricant’s tribological characteristics did not.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2022-0321/
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B. Wiedemann, K.‐H. Dusel and J. Eschl
To facilitate the selection of stereolithography resins, methods have been developed which evaluate photopolymers with respect to dynamics of polymerization and shrinkage, and…
Abstract
To facilitate the selection of stereolithography resins, methods have been developed which evaluate photopolymers with respect to dynamics of polymerization and shrinkage, and also the sensitivity of polymerization with respect to process conditions and ambient influences. To use the whole potential of a resin it is necessary to identify the material behaviour related to the build process. The process parameters have to be adapted to the individual material. Describes how numerical simulation of part distortion can help in understanding the interaction between material properties and process parameters. Concludes by stating that the build process must be optimized to reduce internal stresses and to cater for post‐curing effects.
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Ryan R. Ford, Akhilesh Kumar Pal, Scott C.E. Brandon, Manjusri Misra and Amar K. Mohanty
The fused filament fabrication (FFF) process is an additive manufacturing technique used in engineering design. The mechanical properties of parts manufactured by FFF are…
Abstract
Purpose
The fused filament fabrication (FFF) process is an additive manufacturing technique used in engineering design. The mechanical properties of parts manufactured by FFF are influenced by the printing parameters. The mechanical properties of rigid thermoplastics for FFF are well defined, while thermoplastic elastomers (TPE) are uncommonly investigated. The purpose of this paper is to investigate the influence of extruder temperature, bed temperature and printing speed on the mechanical properties of a thermoplastic elastomer.
Design/methodology/approach
Regression models predicting mechanical properties as a function of extruder temperature, bed temperature and printing speed were developed. Tensile specimens were tested according to ASTM D638. A 3×3 full factorial analysis, consisting of 81 experiments and 27 printing conditions was performed, and models were developed in Minitab. Tensile tests verifying the models were conducted at two selected printing conditions to assess predictive capability.
Findings
Each mechanical property was significantly affected by at least two of the investigated FFF parameters, where printing speed and extruder temperature terms influenced all mechanical properties (p < 0.05). Notably, tensile modulus could be increased by 21%, from 200 to 244 MPa. Verification prints exhibited properties within 10% of the predictions. Not all properties could be maximized together, emphasizing the importance of understanding FFF parameter effects on mechanical properties when making design decisions.
Originality/value
This work developed a model to assess FFF parameter influence on mechanical properties of a previously unstudied thermoplastic elastomer and made property predictions within 10% accuracy.
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