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1 – 10 of over 55000Beata Witkowska and Iwona Frydrych
The state‐of‐the‐art of existing methods of tear resistance (static and dynamic) of clothing has been described, also presented are the parameters of static tear resistance for…
Abstract
Purpose
The state‐of‐the‐art of existing methods of tear resistance (static and dynamic) of clothing has been described, also presented are the parameters of static tear resistance for protective and work clothing depending on its application.
Design/methodology/approach
For chosen group of fabrics the introduction of a new parameter of dynamic tear resistance was proposed. For research, five static tear test methods and the dynamic one were chosen. In order to find the relationship between the results of mean tear forces for the six described methods Kendall's agreement coefficient was calculated. The comparative measurements for results of static tear resistance and dynamic tear resistance for protective and work clothing were carried out. On the basis of this, the value of tear dynamic force for these fabrics was established.
Findings
When establishing the criteria for the tear strength for protective and work clothing, the most significant was fabric end‐use and the minimal value of tear strength associated.
Practical implications
The value of dynamic tear resistance can be the criterion for assessment of fabrics with regard to textiles exposed to tearing during application. It was the first comparative analysis of the measurement of tear resistance methods.
Originality/value
Investigating test methods for the assessment of clear resistance.
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The purpose of this paper is to present a new method of measuring thermal resistance of power light-emitting diodes (LEDs). Properties of power LEDs strongly depend on their…
Abstract
Purpose
The purpose of this paper is to present a new method of measuring thermal resistance of power light-emitting diodes (LEDs). Properties of power LEDs strongly depend on their internal temperature. The value of this temperature depends on the cooling conditions characterized by thermal resistance.
Design/methodology/approach
The new method of measuring the value of this parameter belongs to the group of electric methods. In this method, the problem of estimating the value of electrical power converted into light is solved. By comparing the values of the case temperature obtained for the LED operating in the forward mode and the reverse-breakdown mode, the thermal power is estimated. On the basis of the measured value of the thermally sensitive parameter (the LED forward voltage) and the estimated value of the thermal power, thermal resistance is calculated.
Findings
The elaborated method was used to measure thermal resistance of the selected types of power LEDs operating at different cooling conditions. The correctness of the elaborated measurement method was proved by comparing the results of measurements obtained with the use of the new method and the infrared method.
Research limitations/implications
On the basis of the obtained results of measurements and the catalog data of the tested diodes, the dependence of the measurement error of thermal resistance of the LED on its luminous efficiency is discussed.
Originality/value
The new measurement method is easy to use and more accurate than the classical method of thermal resistance measurement of the diode.
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Marcus Achenbach and Guido Morgenthal
The purpose of this paper is to develop a method suitable for the design of reinforced concrete columns subjected to a standard fire.
Abstract
Purpose
The purpose of this paper is to develop a method suitable for the design of reinforced concrete columns subjected to a standard fire.
Design/methodology/approach
The Zone Method – a ’simplified calculation method” included in Eurocode 2 – has been developed by Hertz as a manual calculation scheme for the check of fire resistance of concrete sections. The basic idea is to disregard the thermal strains and to calculate the resistance of a cross-section by reducing the concrete cross-section by a “damaged zone”. It is assumed that all fibers can reach their ultimate, temperature dependent strength. Therefore, it is a plastic concept; the information on the state of strain is lost. The calculation of curvatures and deflections is thus only possible by making further assumptions. Extensions of the zone method toward a general calculation method, suitable for the implementation in commercial design software and using the temperature dependent stress–strain curves of the Advanced Calculation Method, have been developed in Germany. The extension by Cyllok and Achenbach is presented in detail. The necessary assumptions of the Zone Method are reviewed, and an improved proposal for the consideration of the reinforcement in this extended Zone Method is presented.
Findings
The principles and assumptions of the Zone Method proposed by Hertz can be validated.
Originality/value
An extension of the Zone Method suitable for the implementation in design software is proposed.
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Tomislav Župan and Bojan Trkulja
The purpose of this paper is to present a method for calculating frequency-dependent resistance when multiple current-carrying conductors are present.
Abstract
Purpose
The purpose of this paper is to present a method for calculating frequency-dependent resistance when multiple current-carrying conductors are present.
Design/methodology/approach
Analytical and numerical formulations are presented. Both skin- and proximity-effects are considered in the numerical approach, whereas only skin-effect can be taken into account in analytical equations. The calculation is done using a self-developed integral equation-based field solver. The results are benchmarked using professional software based on the finite element method (FEM).
Findings
Results from the numerical approach are in agreement with FEM-based software throughout the whole frequency range. Analytical formulations yield unsatisfactory results in higher frequency range. When multiple conductors are mutually relatively close, the proximity-effect has an impact on effective resistance and has to be taken into account.
Research limitations/implications
The methodology is presented using axially symmetrical conductors. However, the same procedure can be developed for straight conductors as well.
Practical implications
Presented fast and stable procedure can be used in most electromagnetic devices when frequency-dependent resistance needs to be precisely determined.
Originality/value
The value of the presented numerical methodology lies in its ability to take both skin- and proximity-effects into account. As conductors are densely packed in most electromagnetic devices, both effects influence the effective resistance. The method can be easily implemented using a self-developed solver and yields satisfactory results.
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This chapter examines the dynamic of state-society interaction during the events of the winter 2013–2014 Ukrainian Maidan Revolution. Using a new dataset, containing responses…
Abstract
This chapter examines the dynamic of state-society interaction during the events of the winter 2013–2014 Ukrainian Maidan Revolution. Using a new dataset, containing responses from the activists of the dissent movement, the study uncovers the “tipping point” at which revolutionaries were much more likely to support violent tactics. The study adds to the scholarly debate on repression-dissent, showing that social interpretation of state repression is essential in affecting social support for political violence. In addition to the theoretical contribution, this article presents the first systematic scholarly account of the repression-dissent dynamic of the 2013–2014 Ukrainian revolution, implementing original empirical and interview data.
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Zhangyu Wu, Hongfa Yu, Haiyan Ma, Bo Da and Yongshan Tan
Coral aggregate seawater concrete (CASC) is a new type of lightweight aggregate concrete that is becoming widely used in reef engineering. To investigate the corrosion behavior of…
Abstract
Purpose
Coral aggregate seawater concrete (CASC) is a new type of lightweight aggregate concrete that is becoming widely used in reef engineering. To investigate the corrosion behavior of different kinds of rebar in CASC exposed to simulated seawater for 0-270 d, the electrochemical techniques, including linear polarization resistance (LPR) technique and the electrochemical impedance spectroscopy (EIS), were used in the present work.
Design/methodology/approach
The electrochemical techniques, including LPR technique and the EIS, were used in the present work.
Findings
Based on the time-varying law of linear polarization curves, self-corrosion potential (Ecorr), polarization resistance (Rp), corrosion current density (Icorr), corrosion rate (i), and the characteristics of EIS diagrams for different types of rebar in CASC, it can be found that the anti-corrosion property of them can be ranked as epoxy resin coated steel > 2205 duplex stainless steel (2205S) > 316 L stainless steel (316 L) > organic coated steel > ordinary steel. Additionally, the linear regression equation between Rp and charge transfer resistance (Rct) was established. Finally, the EIS corrosion standard of rebar was established from the LPR corrosion standard, which provides a direct standard for the EIS technique to determine the condition of rebar in CASC.
Originality/value
The linear regression equation between polarization resistance and charge transfer resistance was established. And the EIS corrosion standard of rebar was established from the LPR corrosion standard, which provides a direct standard for the EIS technique to determine the condition of rebar in CASC.
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Prior research emphasises that organisational founders have a good deal of influence in organisational development and, where information and communication technogies (ICTs) are…
Abstract
Purpose
Prior research emphasises that organisational founders have a good deal of influence in organisational development and, where information and communication technogies (ICTs) are involved, a generic strategy is usually deployed by managers in order to deal with any resistance that might occur. Cognisant of this, the authors investigated the role played by a managing director of a small to medium‐sized enterprise (SME) consultancy in an ICT project associated with organisational development.
Design/methodology/approach
This study is based on an ethnography of an ICT related change management initiative which, theoretically, takes into account though from the social shaping of technology – specifically the idea that technologies in their broadest sense are subject to ongoing work beyond the design stage.
Findings
The authors argue that Markus' interaction theory of resistance still has relevance today and we extend it by emphasising the problem of homogenising users and downplaying their ability to appropriate resistance strategies in situ.
Research limitations/implications
The study is based upon one group of individuals' experiences. Further case studies of resistance success are required which further highlight how this is achieved and why.
Practical implications
Those engaged with organisational development projects need to be better educated as to the reasons for resistance, particularly positive ones, and the methods by which this might take place.
Originality/value
This study conceptualises strategies for “overcoming” resistance as managerial technologies. Conceptualising them in this way shows the deployment of such technologies to be a complicated and active process where the audience for such things are involved in how they are received and appropriated to suit differing agendas.
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P. Alotto, M. Guarnieri, F. Moro and A. Stella
The purpose of this paper is to simulate in the time domain three‐dimensional electrical, thermal, mechanical coupled contact problems arising in electric resistance welding (ERW…
Abstract
Purpose
The purpose of this paper is to simulate in the time domain three‐dimensional electrical, thermal, mechanical coupled contact problems arising in electric resistance welding (ERW) processes.
Design/methodology/approach
A three‐dimensional multiphysical numerical model for analyzing contact problems is proposed. Electrical and thermal field equations in bulk domains are discretized with the cell method (CM). Welding resistance at contact interfaces is described locally by synthetic statistic parameters and contacting domains are matched together by a non‐overlapping domain decomposition method. Contact pressure distribution is resolved by a finite‐element procedure. The model is validated with 3D FEM software package.
Findings
The semi‐analytical model describing the electric and thermal resistances at contact interfaces can be easily embedded in CM formulations, where problem variables are expressed directly in integral form. Compatibility conditions between contact members are enforced by a domain decomposition approach. System conditioning and computing time are improved by a solution strategy based on the Schur complement method.
Research limitations/implications
The electrical‐thermal analysis is not coupled strongly with the mechanical analysis and contact pressure distribution is assumed to be not depending on thermal stresses, which can be considerable near the contact area where localized joule heating occurs.
Practical implications
Resistance welding processes involve mechanical, electrical, and thermal non‐linear coupled effects that cannot be simulated by standard commercial software packages. The proposed numerical model can be used instead for designing and optimizing ERW processes.
Originality/value
The paper shows that numerical modeling of ERW processes requires a careful prediction of the localized joule heating occurring at the electrode‐material interface. This effect is reconstructed by the proposed approach simulating coupled electrical, thermal, and mechanical effects on different spatial scales.
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The purpose of this paper is to describe how a traditional metal base plate is replaced with a vapour chamber, a two‐phase flow heat transfer module with high heat transfer…
Abstract
Purpose
The purpose of this paper is to describe how a traditional metal base plate is replaced with a vapour chamber, a two‐phase flow heat transfer module with high heat transfer efficiency, to effectively reduce the temperature of heat sources as graphic processing unit (GPU) of smaller area and higher power.
Design/methodology/approach
As a first step, the nature of flow field of a vapour chamber‐based thermal module with heat sink is simulated and analysed through computational numerical method. Second, a sample is prepared according to the theoretical results and the performance of thermal modules is tested together with thermal performance experiment.
Findings
The results show that when the fin height from vapour chamber top to fan bottom area is more than 3 mm and not more than 8 mm, the vapour chamber‐based thermal module can achieve the optimum heat dissipation and the maximum heat flux may exceed 90 W/cm2. Also, when copper fins are 3 mm in height, 0.2 mm in thickness, 53 in number and spaced out 1.0 mm apart, the optimum total thermal resistance of a vapour chamber‐based thermal module is 0.28 ○C/W.
Originality/value
The Sapphire Atomic HD3870 of Video Graphics Array module for AMD RV670XT using MicroLoops vapour chamber has greater thermal performance than the AMD reference dual slot thermal module. So, AMD latest GPU is considered to be the vapour chamber thermal cooler to solve the higher power consumption.
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Fei Shang, Bo Sun and Dandan Cai
The purpose of this study is to investigate the application of non-destructive testing methods in measuring bearing oil film thickness to ensure that bearings are in a normal…
Abstract
Purpose
The purpose of this study is to investigate the application of non-destructive testing methods in measuring bearing oil film thickness to ensure that bearings are in a normal lubrication state. The oil film thickness is a crucial parameter reflecting the lubrication status of bearings, directly influencing the operational state of bearing transmission systems. However, it is challenging to accurately measure the oil film thickness under traditional disassembly conditions due to factors such as bearing structure and working conditions. Therefore, there is an urgent need for a nondestructive testing method to measure the oil film thickness and its status.
Design/methodology/approach
This paper introduces methods for optically, electrically and acoustically measuring the oil film thickness and status of bearings. It discusses the adaptability and measurement accuracy of different bearing oil film measurement methods and the impact of varying measurement conditions on accuracy. In addition, it compares the application scenarios of other techniques and the influence of the environment on detection results.
Findings
Ultrasonic measurement stands out due to its widespread adaptability, making it suitable for oil film thickness detection in various states and monitoring continuous changes in oil film thickness. Different methods can be selected depending on the measurement environment to compensate for measurement accuracy and enhance detection effectiveness.
Originality/value
This paper reviews the basic principles and latest applications of optical, electrical and acoustic measurement of oil film thickness and status. It analyzes applicable measurement methods for oil film under different conditions. It discusses the future trends of detection methods, providing possible solutions for bearing oil film thickness detection in complex engineering environments.
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