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The paper introduces and illustrates the use of numerical models for the simulation of electromagnetic and thermal processes in an absorbing ceramic layer (susceptor) of a…
The paper introduces and illustrates the use of numerical models for the simulation of electromagnetic and thermal processes in an absorbing ceramic layer (susceptor) of a new millimeter-wave (MMW) heat exchanger. The purpose of this study is to better understand interaction between the MMW field and the susceptor, choose the composition of the ceramic material and help design the physical prototype of the device.
A simplified version of the heat exchanger comprises a rectangular block of an aluminum nitride (AlN) doped with molybdenum (Mo) that is backed by a thin metal plate and irradiated by a plane MMW. The coupled electromagnetic-thermal problem is solved by the finite-difference time-domain (FDTD) technique implemented in QuickWave. The FDTD model is verified by solving the related electromagnetic problem by the finite element simulator COMSOL Multiphysics. The computation of dissipated power and temperature is based on experimental data on temperature-dependent dielectric constant, loss factor, specific heat and thermal conductivity of the AlN:Mo composite. The non-uniformity of patterns of dissipated power and temperature is quantified via standard-deviation-based metrics.
It is shown that with the power density of the plane wave on the block’s front face of 1.0 W/mm2, at 95 GHz, 10 × 10 × 10-mm blocks with Mo = 0.25 – 4% can be heated up to 1,000 °C for 60-100 s depending on Mo content. The uniformity of the temperature field is exceptionally high – in the course of the heating, temperature is evenly distributed through the entire volume and, in particular, on the back surface of the block. The composite producing the highest level of total dissipated power is found to have Mo concentration of approximately 3%.
In the electromagnetic model, the heating of the AlN:Mo samples is characterized by the volumetric patterns of density of dissipated power for the dielectric constant and the loss factor corresponding to different temperatures of the process. The coupled model is run as an iterative procedure in which electromagnetic and thermal material parameters are upgraded in every cell after each heating time step; the process is then represented by a series of thermal patterns showing time evolution of the temperature field.
Determination of practical dimensions of the MMW heat exchanger and identification of material composition of the susceptor that make operations of the device energy efficient in the required temperature regime require and expensive experimentation. Measurement of heat distribution on the ceramic-metal interface is a practically challenging task. The reported model is meant to be a tool assisting in development of the concept and supporting system design of the new MMW heat exchanger.
While exploitation of a finite element model (e.g. in COMSOL Multiphysics environment) of the scenario in question would require excessive computational resources, the reported FDTD model shows operational capabilities of solving the coupled problem in the temperature range from 20°C to 1,000°C within a few hours on a Windows 10 workstation. The model is open for further development to serve in the ongoing support of the system design aiming to ease the related experimental studies.
Aim of the present monograph is the economic analysis of the role of MNEs regarding globalisation and digital economy and in parallel there is a reference and examination…
Aim of the present monograph is the economic analysis of the role of MNEs regarding globalisation and digital economy and in parallel there is a reference and examination of some legal aspects concerning MNEs, cyberspace and e‐commerce as the means of expression of the digital economy. The whole effort of the author is focused on the examination of various aspects of MNEs and their impact upon globalisation and vice versa and how and if we are moving towards a global digital economy.
Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Council, Reports and Technical Memoranda of the United States National Advisory Committee for Aeronautics and publications of other similar Research Bodies as issued
Focuses on two key aspects of the rule of law – equality before the law and the universal application of the same system of law to all people – and examines these requirements in the context of the European Works Council (EWC) Directive, aimed at establishing a European‐wide legal framework for transnational information and consultation. Looks at the philosophy behind the EWC concept, discussing its historical context, the rationale for its adoption, its provisions and certain implementation problems, and considers the implications and consequences of the Directive for the UK, which is in the process of adopting it. Spotlights three problematic areas relating to recognition and employee representation, the potential consequences of late implementation and uniting different employee representative arrangements, and identifies three aspects of inequality relating to both employers and employees that appear to breach the rule of law. Concludes that the Directive represents a first step towards achieving true employee participation and a transnational industrial relations system.
Identifies key activities that network users can perform in order to use the network effectively. Offers recommended reading, from beginner to expert user status. Explains some commonly used terms (e.g. Turbo Gopher with Veronica!). Lists useful Internet resources.
Componentware is a new paradigm in software development that is based on the concept of a software component. Software components are self‐contained, immutable units of…
Componentware is a new paradigm in software development that is based on the concept of a software component. Software components are self‐contained, immutable units of software which can be distributed over large networks or even over the Internet. The distribution of software components requires new, Internet‐based search and retrieval mechanisms. A set of collaborating software components is called componentware. We discuss the architectural requirements and mechanisms of componentware, a technical realisation of a componentware architecture, and identify obstacles in building componentware. Finally, we propose possible solutions for the realisation of componentware and componentware architectures.
We are undergoing a “subtle revolution” (Smith 1979) in the traditional relationship of women to work and family. One indicator of this change is the massive increase in…
We are undergoing a “subtle revolution” (Smith 1979) in the traditional relationship of women to work and family. One indicator of this change is the massive increase in women's economic activity, especially among married women with children. The total labour force of OECD countries increased by around 30 million in the 1950s and 1960s, and by 43 million in the 1970s. In the first two decades women's contribution to the increase was slightly more than half, whereas in the last decade it amounted to 63.8 per cent. In the European OECD countries women's share of labour force change in the 1970s was even higher and amounted to 96.4 per cent (OECD 1984:10, 11).