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21 – 30 of over 8000Ningbo Liao and Ping Yang
The small dimensions of future device designs also imply a stronger effect of material boundary resistance. For nanoscale devices and structures, especially, interface phenomena…
Abstract
Purpose
The small dimensions of future device designs also imply a stronger effect of material boundary resistance. For nanoscale devices and structures, especially, interface phenomena often dominate their overall thermal behavior. The purpose of this paper is to propose molecular dynamics (MD) simulations to investigate the mechanical and thermal properties at Cu‐Al interface.
Design/methodology/approach
The two‐temperature model (TTM)‐MD model is used to describe the electron‐phonon scattering at interface of different metals. Before the simulation of heat transfer process, a non‐ideal Cu‐Al interface is constructed by simulating diffusion bonding.
Findings
According to the simulation results, in unsteady state, the temperature distribution and the displacements of atoms near the interface tend to generate stress and voids. It reveals the damage mechanics at the interface in heat transfer.
Originality/value
The atomic model proposed in this paper is computationally efficient for interfacial heat transfer problems, and could be used for investigation of other interfacial behaviors of dissimilar materials.
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R. Ben Mansour, N. Galanis and C.T. Nguyen
The aim is to study the conjugate problem of developing laminar mixed convection flow and heat transfer of water‐Al2O3 nanofluid inside an inclined tube submitted to a uniform…
Abstract
Purpose
The aim is to study the conjugate problem of developing laminar mixed convection flow and heat transfer of water‐Al2O3 nanofluid inside an inclined tube submitted to a uniform wall heat flux.
Design/methodology/approach
The set of non‐linear, coupled and fully elliptic governing equations has been solved using a “finite‐control‐volume” numerical method, the classical power‐law scheme for computing heat and momentum fluxes staggered and non uniform grids for spatial discretization of various regions of the tube.
Findings
Numerical results have shown that the presence of nanoparticles slightly intensifies the secondary flow due to buoyancy, in particular in the developing region. It also increases the average Nusselt number and decreases slightly the product ReCf with respect to those of water. For the horizontal inclination, two new correlations have been proposed to calculate these two variables in the fully developed region, for Grashof number ranging from 103 to 105 and particle volume concentrations up to 7 per cent.
Practical implications
The results of this study can be employed for various practical heat transfer and thermal applications using nanofluids.
Originality/value
The present study constitutes an original contribution to the knowledge of nanofluid thermal behaviour.
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Abdelsalam Almarimi and Jaroslav Pokorny
This paper introduces an approach to minimize the total designer effort for building XML data integration systems. Since fully automatic schema mapping generation is infeasible…
Abstract
This paper introduces an approach to minimize the total designer effort for building XML data integration systems. Since fully automatic schema mapping generation is infeasible, in our view such an approach can be used as a semi‐automatic tool for XML schemas mediation. A method is proposed to query XML documents through a mediation layer. Such a layer is introduced to describe the mappings between global XML schema and local heterogeneous XML schemas. It produces a uniform interface over the local XML data sources, and provides the required functionality to query these sources in a uniform way. It involves two important units: the XML Metadata Document (XMD) and the Query Translator. The XMD is an XML document containing metadata, in which the mappings between global and local schemas are defined. The XML Query Translator which is an integral part of the system is introduced to translate a global user query into local queries by using the mappings that are defined in the XMD.
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Sau Fun Frency Ng and Chi Leung Patrick Hui
Pressure garments are mainly made of elastic Lycra fabrics and tailor‐made to individual patients’ measurements to provide an appropriate amount of skin‐garment interface pressure…
Abstract
Pressure garments are mainly made of elastic Lycra fabrics and tailor‐made to individual patients’ measurements to provide an appropriate amount of skin‐garment interface pressure for burn rehabilitation. However, the fabric tension would be different at various locations from the hem edges of pressure garments, and thus the skin‐garment interface pressure cannot be uniformly maintained over the interface surface. Aims to investigate the pattern of interface pressure changes caused by the different types of edge finish used for making pressure garments. The effect of garment sizes on the change of interface pressure was also examined. Experiments were carried out using two selected elastic Lycra fabrics, four types of hem finish and three different garment sizes. The results of the study provide a guideline for designing the edge finish of pressure garments, and a minimum margin from the hem edges of garments to the scar area is also recommended.
Mojtaba Sepehrnia, Hossein Khorasanizadeh and Mohammad Behshad Shafii
This paper aims to study the thermal and thermo-hydraulic performances of ferro-nanofluid flow in a three-dimensional trapezoidal microchannel heat sink (TMCHS) under uniform heat…
Abstract
Purpose
This paper aims to study the thermal and thermo-hydraulic performances of ferro-nanofluid flow in a three-dimensional trapezoidal microchannel heat sink (TMCHS) under uniform heat flux and magnetic fields.
Design/methodology/approach
To investigate the effect of direction of Lorentz force the magnetic field has been applied: transversely in the x direction (Case I);transversely in the y direction (Case II); and parallel in the z direction (Case III). The three-dimensional governing equations with the associated boundary conditions for ferro-nanofluid flow and heat transfer have been solved by using an element-based finite volume method. The coupled algorithm has been used to solve the velocity and pressure fields. The convergence is reached when the accuracy of solutions attains 10–6 for the continuity and momentum equations and 10–9 for the energy equation.
Findings
According to thermal indicators the Case III has the best performance, but according to performance evaluation criterion (PEC) the Case II is the best. The simulation results show by increasing the Hartmann number from 0 to 12, there is an increase for PEC between 845.01% and 2997.39%, for thermal resistance between 155.91% and 262.35% and ratio of the maximum electronic chip temperature difference to heat flux between 155.16% and 289.59%. Also, the best thermo-hydraulic performance occurs at Hartmann number of 12, pressure drop of 10 kPa and volume fraction of 2%.
Research limitations/implications
The embedded electronic chip on the base plate generates heat flux of 60 kW/m2. Simulations have been performed for ferro-nanofluid with volume fractions of 1%, 2% and 3%, pressure drops of 10, 20 and 30 kPa and Hartmann numbers of 0, 3, 6, 9 and 12.
Practical implications
The authors obtained interesting results, which can be used as a design tool for magnetohydrodynamics micro pumps, microelectronic devices, micro heat exchanger and micro scale cooling systems.
Originality/value
Review of the literature indicated that there has been no study on the effects of magnetic field on thermal and thermo-hydraulic performances of ferro-nanofluid flow in a TMCHS, so far. In this three dimensional study, flow of ferro-nanofluid through a trapezoidal heat sink with five trapezoidal microchannels has been considered. In all of previous studies, in which the effect of magnetic field has been investigated, the magnetic field has been applied only in one direction. So as another innovation of the present research, the effect of applying magnetic field direction (transverse and parallel) on thermo-hydraulic behavior of TMCHS is investigated.
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Nishant Tiwari and Manoj Kumar Moharana
This paper aims to emphasize on studying various geometrical modification performed in wavy and raccoon microchannel by manipulating parameters, i.e. waviness (γ), expansion…
Abstract
Purpose
This paper aims to emphasize on studying various geometrical modification performed in wavy and raccoon microchannel by manipulating parameters, i.e. waviness (γ), expansion factor (α), wall to fluid thermal conductivity ratio (ksf), substrate thickness to channel height ratio (dsf) and Reynolds number (Re) for obtaining optimum parameter(s) that leads to higher heat dissipation rate.
Design/methodology/approach
A three-dimensional solid-fluid conjugate heat transfer numerical model is designed to capture flow characteristics and heat transfer in single-phase laminar flow microchannels. The governing equations are solved using finite volume method.
Findings
The results are presented in terms of average base temperature, average Nusselt number, pressure drop, dimensionless local heat flux, dimensionless wall and bulk fluid temperature, local Nusselt number and performance factor including axial conduction number. Heat dissipation rate with raccoon microchannel configuration is found to be higher compared to straight and wavy microchannel. With waviness of γ = 0.167, and 0.267 in wavy and raccoon microchannel, respectively, performance factor attains maximum value compared to other waviness for all values of Reynolds number. It is also found that the effect of axial wall conduction in wavy and raccoon microchannel is negligible. Additionally, thermal performance of wavy and raccoon microchannel is compared with straight microchannel.
Practical implications
In recent past years, much complex design of microchannel has been proposed for heat transfer enhancement, but the feasibility of available manufacturing techniques to fabricate complex geometries is still questionable. However, fabrication of wavy and raccoon microchannel is easy, and their heat dissipation capability is higher.
Originality/value
This makes the difference in wall and bulk fluid temperature smaller. Thus, present work highlighted the dominance of axial wall conduction on thermal and hydrodynamic performance of wavy and raccoon microchannel under conjugate heat transfer situation.
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Martin Kuehnhausen and Victor S. Frost
Security and accountability within the transportation industry are vital because cargo theft could amount to as much as $60 billion per year. Since goods are often handled by many…
Abstract
Purpose
Security and accountability within the transportation industry are vital because cargo theft could amount to as much as $60 billion per year. Since goods are often handled by many different parties, it must be possible to tightly monitor the location of cargo and handovers. Tracking trade is difficult to manage in different formats and legacy applications Web services and open standards overcome these problems with uniform interfaces and common data formats. This allows consistent reporting, monitoring and analysis at each step. The purpose of this paper is to examine Transportation Security SensorNet (TSSN), the goal being to promote the use of open standards and specifications in combination with web services to provide cargo monitoring capabilities.
Design/methodology/approach
This paper describes a system architecture for the TSSN targeted for cargo monitoring. The paper discusses cargo security and reviews related literature and approaches. The paper then describes the proposed solution of developing a service‐oriented architecture (SOA) for cargo monitoring and its individual components.
Findings
Web services in a mobile sensor network environment have been seen as slow and producing significant overhead. The authors demonstrate that with proper architecture and design the performance requirements of the targeted scenario can be satisfied with web services; the TSSN then allows sensor networks to be utilized in a standardized and open way through web services.
Originality/value
The integration of SOA, open geospatial consortium (OGC) specifications and sensor networks is complex and difficult. As described in related works, most systems and research focus either on the combination of SOA and OGC specifications or on OGC standards and sensor networks. The TSSN shows that all three can be combined and that this combination provides cargo security and monitoring capabilities to the transportation and other industries that have not existed before.
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Rehan Zahid, Masjuki Hj. Hassan, Abdullah Alabdulkarem, Mahendra Varman, Md. Abul Kalam, Riaz Ahmad Mufti, Nurin Wahidah Mohd Zulkifli, Mubashir Gulzar, Muhammad Usman Bhutta, Mian Ashfaq Ali, Usman Abdullah and Robiah H. Yunus
There is a continuous drive in automotive sector to shift from conventional lubricants to environmental friendly ones without adversely affecting critical tribological performance…
Abstract
Purpose
There is a continuous drive in automotive sector to shift from conventional lubricants to environmental friendly ones without adversely affecting critical tribological performance parameters. Because of their favorable tribological properties, chemically modified vegetable oils such as palm trimethylolpropane ester (TMP) are one of the potential candidates for the said role. To prove the suitability of TMP for applications involving boundary-lubrication regime such as cam/tappet interface of direct acting valve train system, a logical step forward is to investigate their compatibility with conventional lubricant additives.
Design/methodology/approach
In this study, extreme pressure and tribological characteristics of TMP, formulated with glycerol mono-oleate (GMO), molybdenum dithiocarbamate (MoDTC) and zinc dialkyldithiophosphate (ZDDP), has been investigated using four-ball wear tester and valve train test rig. For comparison, additive-free and formulated versions of polyalphaolefin (PAO) were used as reference. Moreover, various surface characterization techniques were deployed to investigate mechanisms responsible for a particular tribological behavior.
Findings
In additive-free form, TMP demonstrated better extreme pressure characteristics compared to PAO and lubricant additives which are actually optimized for conventional base-oils such as PAO, are also proved to be compatible with TMP to some extent, especially ZDDP. During cylinder head tests, additive-free TMP proved to be more effective compared to PAO in reducing friction of cam/tappet interface, but opposite behavior was seen when formulated lubricants were used. Therefore, there is a need to synthesize specialized friction modifiers, anti-wear and extreme pressure additives for TMP before using it as engine lubricant base-oil.
Originality/value
In this study, additive-free and formulated versions of bio-lubricant are tested for cam/tappet interface of direct acting valve train system of commercial passenger car diesel engine for the very test time. Another important aspect of this research was comparison of important tribological performance parameters (friction torque, wear, rotational speed of tappet) of TMP-based lubricants with conventional lubricant base oil, that is, PAO and its formulated version.
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This paper aims to compare the reflow and Zn diffusion behaviors in Sn-Zn and Sn-8.5Zn-0.5Ag-0.01Al-0.1Ga (5E) solders during soldering on a Ni/Cu substrate under infrared (IR…
Abstract
Purpose
This paper aims to compare the reflow and Zn diffusion behaviors in Sn-Zn and Sn-8.5Zn-0.5Ag-0.01Al-0.1Ga (5E) solders during soldering on a Ni/Cu substrate under infrared (IR) reflow. The study proposes a model on the effect of various elements particularly Zn diffusion behavior in the solders on the formation of intermetallic compounds (IMCs).
Design/methodology/approach
The melting activities of two solders near their melting points on copper substrates are visualized in an IR reflow furnace. Reflowed solder joints were analyzed using scanning electron microscope and energy dispersive X-ray spectroscopy.
Findings
Reflow behaviors of the solders are similar. During melting, solder balls are first merged into each other and then reflow on the substrate from top to bottom. Both solders show a reduced amount of Zn in the solder. Theoretical calculations demonstrate a higher Zn diffusion in the 5E solder; however, the amount of Zn actually observed at the solder/substrate interface is lower than Sn-9Zn solder due to the formation of ZnAg3 in the solder. A thinner IMC layer is formed at the interface in the 5E solder than the Sn-Zn solder.
Research limitations/implications
The present work compares the 5E solder only with Sn-Zn solder. Additional research work may be required to compare 5E solder with other solders like Sn-Ag, SnAgCu, etc. to further establish its practical applications.
Practical implications
The study ascertains the advantages of 5E solder over Sn-Zn solder for all practical applications.
Originality/value
The significance of this paper is the understanding of the relation between reflow behavior of solders and reactivity of different elements in the solder alloys and substrate to form various IMCs and their influence on the formation of IMC layer at solder/substrate interface. Emphasis is provided for the diffusion behavior of Zn during reflow and respective reaction mechanisms.
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Gloria Yi-Ming Kao and Chi-Chieh Peng
The purpose of this paper is to evaluate the performance of the multi-source book review system (MBRS). MBRS was designed to reduce information overload using the internet and to…
Abstract
Purpose
The purpose of this paper is to evaluate the performance of the multi-source book review system (MBRS). MBRS was designed to reduce information overload using the internet and to accommodate different learner preferences.
Design/methodology/approach
The authors experimentally compared MBRS with the Google search engine. MBRS first gathers reviews from online sources, such as bookstores and blogs. It reduces information overload through an advanced filtering and sorting algorithm and by providing a uniform user interface. MBRS accommodates different learning styles through various sort options and through adding video-mediated reviews.
Findings
Results indicate that, compared with Google, MBRS: reduces the information overload associated with searching for online book reviews; increases users finding satisfactory book reviews; and allows users to find reviews more quickly. In addition, more than half of the participants found video-mediated book reviews more appealing than traditional text-based reviews.
Research limitations/implications
Future studies might examine the effects of other recommendations or sorting methods to fit individual preferences in a more dynamic way.
Practical implications
This study assisted readers with a preference for visual information in locating reviews of personal interest in less time and with finding reviews more aligned with their individual learning preferences.
Originality/value
This study documents an innovative web site featuring video-mediated book reviews and other mechanisms to accommodate individual preferences. Search engine designers could integrate book reviews with different media types to reduce cognitive load allowing readers to focus attention on the reading task. Internet booksellers or library staff may use this as an effective means to enhance reading motivation.
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