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1 – 10 of over 6000
Article
Publication date: 10 March 2022

Lei Ma, Hanbo Shi, Siyuan Ding, Chao Zhang, Haibing Yuan and Junlin Pan

The purpose of this paper is to study the wear of railway brake disc/pad in low-temperature environment and to explore the damage form of brake disc/pad materials and the…

Abstract

Purpose

The purpose of this paper is to study the wear of railway brake disc/pad in low-temperature environment and to explore the damage form of brake disc/pad materials and the law of temperature rise in braking process and its influence on friction pair material damage.

Design/methodology/approach

The influence of ambient temperature on tribological properties of brake materials was studied by using low-temperature environment simulation device and MM-1000 high-speed brake testing machine. The law of temperature rise in the braking process was simulated by temperature field module of COMSOL.

Findings

The damage of disc sample increases with the decrease of ambient temperature, and the main damage form is furrow. With the decrease of ambient temperature, pitting corrosion, wear, spalling and cracks appear successively. The maximum temperature of brake disc decreases linearly with the decrease of ambient temperature. However, when the ambient temperature is 0 in the experiment, the surface temperature of the disc will increase abnormally because of the increase of abrasive particles caused by the toughening and brittleness transformation of the material.

Originality/value

In this paper, through the study of train braking in low-temperature environment, the damage mechanism and law of train braking pair in low-temperature environment are found, which provide some basis for the development of high-speed railway in low-temperature environment.

Details

Industrial Lubrication and Tribology, vol. 74 no. 5
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 2 January 2018

Muna E. Raypah, Dheepan M.K., Mutharasu Devarajan, Shanmugan Subramani and Fauziah Sulaiman

Thermal behavior of light-emitting diode (LED) device under different operating conditions must be known to enhance its reliability and efficiency in various applications…

Abstract

Purpose

Thermal behavior of light-emitting diode (LED) device under different operating conditions must be known to enhance its reliability and efficiency in various applications. The purpose of this study is to report the influence of input current and ambient temperature on thermal resistance of InGaAlP low-power surface-mount device (SMD) LED.

Design/methodology/approach

Thermal parameters of the LED were measured using thermal transient measurement via Thermal Transient Tester (T3Ster). The experimental results were validated using computational fluid dynamics (CFD) software.

Findings

As input current increases from 50 to 90 mA at 25°C, the relative increase in LED package (ΔRthJS) and total thermal resistance (ΔRthJA) is about 10 and 4 per cent, respectively. In addition, at 50 mA and ambient temperature from 25 to 65°C, the ΔRthJS and ΔRthJA are roughly 28 and 22 per cent, respectively. A good agreement between simulation and experiment results of junction temperature.

Originality/value

Most of previous studies have focused on thermal management of high-power LEDs. There were no studies on thermal analysis of low-power SMD LED so far. This work will help in predicting the thermal performance of low-power LEDs in solid-state lighting applications.

Details

Microelectronics International, vol. 35 no. 1
Type: Research Article
ISSN: 1356-5362

Keywords

Article
Publication date: 1 March 2006

Y. Zhang

Seeks to study the dependence of the shear strength of a fluid on the fluid pressure and the bulk fluid temperature, respectively, theoretically for given bulk fluid…

Abstract

Purpose

Seeks to study the dependence of the shear strength of a fluid on the fluid pressure and the bulk fluid temperature, respectively, theoretically for given bulk fluid temperatures and fluid pressures in the whole ranges of fluid pressure and bulk fluid temperature.

Design/methodology/approach

The analyses are, respectively, carried out with emphasis on the dependence of the shear strength of a fluid in liquid state, i.e. at low pressures on the fluid pressure and the bulk fluid temperature for given bulk fluid temperatures and fluid pressures based on the theory of the compression of the fluid by the pressurization of the fluid.

Findings

The fluid shear strength versus fluid pressure curve in the whole range of fluid pressure and the fluid shear strength versus bulk fluid temperature curve in the whole range of bulk fluid temperature, respectively, for a given bulk fluid temperature and a given fluid pressure are obtained. It is shown by this fluid shear strength versus fluid pressure curve that, for a given bulk fluid temperature, when the fluid is in liquid state, i.e. at low pressures, the value of the shear strength of the fluid is insensitive to the variation of the pressure of the fluid and is low: when the fluid is in solidification state, i.e. at medium and high but not extremely high pressures, the value of the shear strength of the fluid is the most sensitive to the variation of the pressure of the fluid and is very approximately linearly increased with the increase of the pressure of the fluid; when the fluid is in high solidification state, i.e. at extremely high pressures, the value of the shear strength of the fluid is insensitive to the variation of the pressure of the fluid and is the highest, i.e. approaches the value of the shear strength of the fluid in solid state.

Originality/value

Extends one's knowledge of the shear strength of a fluid in the while ranges of pressure and temperature.

Details

Industrial Lubrication and Tribology, vol. 58 no. 2
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 5 October 2021

Indunil Erandi Ariyaratne, Anthony Ariyanayagam and Mahen Mahendran

This paper presents the details of a research study on developing composite masonry blocks using two types of mixes, conventional and lightweight mix, to enhance their…

Abstract

Purpose

This paper presents the details of a research study on developing composite masonry blocks using two types of mixes, conventional and lightweight mix, to enhance their fire/bushfire resistance and residual compressive strength.

Design/methodology/approach

Composite masonry blocks (390 × 190 × 90 mm) were fabricated using conventional cement–sand mix as the outer layer and lightweight cement–sand–diatomite mix as the inner layer. Material properties were determined, and all the mixes were proportioned by the absolute volume method. After 28 days of curing, density tests, compression tests before and after fire exposure and fire resistance tests of the developed blocks were conducted, and the results were compared with those of conventional cement–sand and cement–sand–diatomite blocks.

Findings

Developed composite blocks satisfy density and compressive strength requirements for loadbearing lightweight solid masonry units. Fire resistance of the composite block is –/120/120, and no cracks appeared on the ambient side surface of the block after 3 h of fire exposure. Residual strength of the composite block is higher compared to cement–sand and cement–sand–diatomite blocks and satisfies the loadbearing solid masonry unit strength requirements.

Practical implications

Composite block developed in this research can be suggested as a suitable loadbearing lightweight solid masonry block for several applications in buildings in bushfire prone areas.

Originality/value

Limited studies are available for composite masonry blocks in relation to their fire resistance and residual strength.

Details

Journal of Structural Fire Engineering, vol. 13 no. 1
Type: Research Article
ISSN: 2040-2317

Keywords

Article
Publication date: 28 December 2020

Ahmad Riaz, Chao Zhou, Ruobing Liang and Jili Zhang

This paper aims to present a numerical study on the natural convection, which operates either as an evaporator or condenser unit of the heat pump system to pre-cool and…

Abstract

Purpose

This paper aims to present a numerical study on the natural convection, which operates either as an evaporator or condenser unit of the heat pump system to pre-cool and pre-heat the ambient fresh air.

Design/methodology/approach

This study focuses on natural air cooling or heating within the air channel considering the double skin configuration. Particular focus is given to the analysis of airflow and the heat transfer processes in an air channel to cool or heat the ambient fresh air. In this study, the physical model consists of one wall, either heated uniformly or cooled uniformly, whereas the other wall is adiabatic.

Findings

The results show that the variation of both velocity and temperature is observed as the flow transition occurs at the evaporator or condenser wall. In either case, the temperature rises in the range of 6.3–8.4°C with an increase in mass flow rate from 0.07–0.08 kg/s in the photovoltaic thermal condenser part, while in the photovoltaic thermal evaporator part, the change in mass flow rate from 0.048–0.061 kg/s causes a decrease in temperature from 7.1–4.5°C.

Practical implications

The solar-assisted photovoltaic thermal heat pump system, in building façade having an air layer application, is feasible for pre-heating and pre-cooling the ambient fresh air and also reduces the energy needed to treat the fresh air.

Originality/value

The influence of condensing and evaporating temperature under natural convection mode in double skin conformation is considered for pre-heating and pre-cooling of ambient fresh air.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 5 October 2010

Wei Cao and Rinn Cloud

Surgical gown fabrics are categorized for liquid penetration resistance by standard tests under specified laboratory conditions, which can be different from the conditions…

Abstract

Purpose

Surgical gown fabrics are categorized for liquid penetration resistance by standard tests under specified laboratory conditions, which can be different from the conditions encountered in the surgical environment. The purpose of this paper is to examine the influence of temperature and challenge liquid (CL) type on the effectiveness of liquid penetration resistance of surgical gown fabrics.

Design/methodology/approach

One disposable and one reusable surgical gown fabric were tested for liquid penetration using standard methods required in American Society for Testing Materials F2407 for classifying the materials used in Levels 1‐3 surgical gowns. Standard test conditions were compared to varied conditions of ambient/fabric temperature (AFT), CL type and challenge liquid temperature (CLT). Analysis of variance was used to determine the effects of variables on liquid penetration.

Findings

AFT, CL type and CLT were significant (p<0.05) variables for liquid penetration for at least one of the test fabrics. Higher ambient temperature, fabric and liquid temperature conditions resulted in greater liquid penetration. Use of synthetic blood as the CL resulted in higher liquid penetration than observed with distilled water.

Research limitations/implications

Results suggest that temperatures within the range of body heat or ambient surgical environments are sufficient to affect liquid penetration of surgical gown fabrics. Also, the use of CLs other than distilled water and the use of CLs warmed to body temperature may be needed to accurately assess the liquid penetration resistance of surgical gown fabrics. Level of protection afforded by surgical gowns may be compromised by variability in these conditions.

Originality/value

Conventional wisdom has held that differences between standard testing temperatures and body temperature or ambient temperature in the surgical theatre were insufficient to influence liquid penetration. This study has shown otherwise. No previous studies were found that addressed these variables but our study illustrates their effect on selected materials.

Details

International Journal of Clothing Science and Technology, vol. 22 no. 5
Type: Research Article
ISSN: 0955-6222

Keywords

Article
Publication date: 11 May 2012

Tómas Hafliðason, Guðrún Ólafsdóttir, Sigurður Bogason and Gunnar Stefánsson

Wireless sensor network (WSN) technologies are now available to implement real time temperature monitoring systems in food supply chains. The aim of this paper is to…

1656

Abstract

Purpose

Wireless sensor network (WSN) technologies are now available to implement real time temperature monitoring systems in food supply chains. The aim of this paper is to examine different types of methods and criteria to establish alerts in decision support systems in perishable food supply chains.

Design/methodology/approach

Logistic and temperature mapping was performed in cod supply chains to obtain data to establish criteria for temperature alerts. Data were collected for both ambient temperature and temperature of products packed in expanded polystyrene boxes.

Findings

Alerts based on single criterion for ambient temperature resulted in false alerts when compared to criteria for product temperature. More complex methods that took into account both temperature abuse and the severity of the abuse resulted in more relevant alerts for the chilled cod supply chain.

Research limitations/implications

The research is based on mapping of cod supply chains with a limited number of iterations.

Practical implications

The scope of the research is the application of WSN in an actual supply chain of chilled cod transported from Iceland to Europe, which has relevance in assisting management decision making in the supply chain to prevent losses of quality and minimize waste.

Originality/value

Failure to maintain a low temperature occurs frequently at handover points where alert systems are usually not in place. The theoretical implication of this paper is the development of a conceptual framework for setting up temperature criteria for real time decision support systems in food supply chains.

Details

International Journal of Physical Distribution & Logistics Management, vol. 42 no. 4
Type: Research Article
ISSN: 0960-0035

Keywords

Article
Publication date: 23 March 2010

Patrick S.K. Chua and F.L. Tan

The purpose of this paper is to report an experimental study on the effects of various parameters, such as varying flow velocities of water in the pipe, insulating the…

Abstract

Purpose

The purpose of this paper is to report an experimental study on the effects of various parameters, such as varying flow velocities of water in the pipe, insulating the water pipe, and heating the pipe, to prevent pressurized water in a water hydraulic system from freezing under sub‐zero ambient temperature environment.

Design/methodology/approach

An experimental test rig was designed, fabricated, and set up to conduct several experiments to investigate the time taken for water to freeze under sub‐zero ambient temperature at −20°C and with the water initially at a higher temperature than the ambient.

Findings

The experiments show that it would take about 90 min for water in the pipe to freeze completely when there is no flow, or water is flowing at slow speed, in the pipe. The results also show that the use of insulation on the pipe would delay the freezing of water inside the pipe; and if used together with heating at several locations on the pipe, freezing of water inside the pipe could be prevented completely.

Originality/value

This paper usefully shows that insulation and heating in a water hydraulic system can prevent freezing of water in the pipe. The promising results of the experimental work mean that water might be able to replace oil in hydraulic systems on aircraft and other low‐temperature applications.

Details

Aircraft Engineering and Aerospace Technology, vol. 82 no. 2
Type: Research Article
ISSN: 0002-2667

Keywords

Article
Publication date: 25 September 2009

Frances D. Bryant and Ming C. Leu

The purpose of this paper is to develop a physics‐based model that can predict how a main build material of water interacts with a water‐soluble sacrificial support…

Abstract

Purpose

The purpose of this paper is to develop a physics‐based model that can predict how a main build material of water interacts with a water‐soluble sacrificial support material in the rapid freeze prototyping (RFP) process.

Design/methodology/approach

RFP uses water freezing into ice in a layer‐by‐layer manner as a main build material to create ice structures with complex geometries in a sufficiently cool environment. A eutectic dextrose‐water solution is used as a sacrificial support material. The supported areas in an ice structure are removed by placing the fabricated structure in an environment of appropriate temperature.

Findings

Two methods of concentration modeling have been developed to predict the interaction between the main and support materials around their interface region. The two models are described in detail and their predictions are compared to experimentally measured data. The experimental height data compared to the simulation result based on the concentration models agrees to within 6 percent for various build ambient temperatures. As ambient temperatures decreased, diffusion between the two materials also decreased.

Originality/value

The results obtained from this paper can be used as an aid in building complex ice parts in the RFP process so that minimal interaction between the main and support materials can be attained. An understanding of the interaction occurring during fabrication is provided with the concentration models. The method used to develop the concentration models can be applied to other layered manufacturing processes when using two miscible materials.

Details

Rapid Prototyping Journal, vol. 15 no. 5
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 18 January 2013

Dominik Jurków and Grzegorz Lis

The purpose of this paper is to present the application of low temperature cofired ceramics (LTCC) technology in the fabrication of a novel electronic device, which…

Abstract

Purpose

The purpose of this paper is to present the application of low temperature cofired ceramics (LTCC) technology in the fabrication of a novel electronic device, which consists of an antenna amplifier integrated with temperature stabilizer. The temperature controller consists of a thick‐film thermistor and heater, which has been optimized using geometry to achieve uniform temperature distribution on the whole electronic substrate.

Design/methodology/approach

LTCC technology was applied in the fabrication process of the novel device. The temperature distribution on the ceramic substrate and temperature stabilization time were analyzed using an IR camera. The heating ability of the heater was tested in a climatic chamber. The heater and thermistors parameters variability were estimated using a basic mathematical statistic.

Findings

The integrated device ensures proper temperature conditions of electronic components if the ambient temperature is lower than −40°C.

Research limitations/implications

The presented device is just a first prototype. Therefore, the fabrication of the next structures and further experiments will be needed to improve structural drawbacks and to analyze precisely the device reliability and parameters repeatability.

Practical implications

The device presented in the paper can be applied in systems working at very low ambient temperatures (even at −5°C). Moreover, a temperature stabilizer can increase the temperature of the whole device above −40°C, therefore, standard electronic components (which can work down to −40°C) can be used instead of specialized ones (which can work below −40°C).

Originality/value

This paper presents a novel temperature stabilizer.

Details

Microelectronics International, vol. 30 no. 1
Type: Research Article
ISSN: 1356-5362

Keywords

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