Bulja S.,Bell Labs Ireland |
Mirshekar-Syahkal D.,University of Essex |
James R.,University College London |
Day S.E.,University College London |
Fernandez F.A.,University College London
Microwave and Optical Technology Letters | Year: 2013
The effective dielectric constant of the top grounded coplanar waveguide with a liquid crystal (LC) superstrate for phase shifting applications is investigated in the frequency range of 30-60 GHz. Two nematic LC mixtures, namely E7 and MDA-00-3506, are used as the superstrate. The measurements show that MDA-00-3506 offers higher values of phase shift per millimeter than its E7 counterpart. In particular, the MDA-00-3506 provides 3.14°/mm, whereas E7 gives 2.79°/mm at 60 GHz. The results of the dielectric constants from measurement and computer modeling are found to agree to within 5%. For the modeling, a comprehensive finite element package predicting the local alignment of LC molecules and effective dielectric constant at different bias voltages and frequencies are used. Copyright © 2013 Wiley Periodicals, Inc.
Agency: GTR | Branch: EPSRC | Program: | Phase: Training Grant | Award Amount: 3.57M | Year: 2014
This Centre for Doctoral Training in Embedded Intelligence, the first in the UK, addresses high priority areas for economic growth such as autonomous complex manufactured products and systems, functional materials with high performance systems, data-to-knowledge solutions (e.g. digital healthcare and digitally connected citizens), and engineering for industry, life and health, which are also key priorities for Horizon 2020, the new EU framework programme for research and innovation. Horizon 2020 explicitly spells out ICT and Manufacturing as key industrial technologies. Its remit fits the EPSRC priority areas of ICT for Manufacturing and Data to Knowledge, and has an impact on industrial sectors as diverse as logistics, metrology, food, automotive, oil & gas, chemistry, or robotics. In addition, our world (homes, transport, workplaces, supplies of food, utilities, leisure or healthcare) is constantly seeking for interactive technologies and enhanced functionalities, and we will rely on these graduates who can translate technologies for the end-user. The uniqueness of this Centre resides on the capability to innovatively address a myriad of Embedded Intelligence challenges posed by technical needs ranging from the EI supply chain: the design stage, through manufacturing of embedded or on-bedded devices, to the software behind data collection, as well as integrative technologies, to finally the requirements from end-users. The thematic areas, discussed conjointly with industry during the preparation of this proposal, allow us also to recruit students from a vast range of educational backgrounds. A strong user pull defines the nature of the challenges that this CDT will tackle. The graduates who shall come to alleviate the shortage of skilled engineers and technologists in the field will be exposed to the following thematic areas: > Device design, specification of sensors and measurement devices (power scavenging, processing, wire & wireless communications, design for low power, condition monitoring); > Packaging & integration technologies (reliability and robustness, physical and soft integration of devices, sub-components and wider system environment); > Intelligent software (low level, embedded, system level, database integration, ontology interrogation, service oriented architectures, services design); > Manufacturing solutions (design for manufacture of embedded systems, advanced and hybrid manufacturing processes for embedding, process consolidation technologies, biomimetics and cradle-to-cradle for sustainability production, etc.); > Applications engineering (design and implementation of embedded technologies for in-time, in-line products, processes and supply chains; product and process design for embedded intelligence); > System Services: (i) Service Foundations (e.g., dynamically reconfigurable architectures, data and process integration and semantic enhanced service discovery); (ii) Service Composition (e.g. composability analyses, dynamic and adaptive processes, quality of service compositions, business driven compositions); (iii) Service Management and Monitoring (e.g. self: -configuring, -adapting, -healing, -optimising and -protecting) and (iv) Service Design and Development (e.g. engineering of business services, versioning and adaptivity, governance across supply chains). Our flagship, the Transition Zone training, will facilitate the transition into doctoral studies in the first year of studies, and, closer to the end of the programme, out to industry or self-employment. As employable high calibre individuals with a good understanding of enterprising, commercialisation of research, social responsibility, gender equality and diversity, innovation management, workplaces, leadership and management, our doctorates will grow prosperity bottom up, enjoying a wealthy network of academic and industrial contacts from their years at the CDT, as well as their peers at the Centre.
Lei S.,Bell Labs Ireland |
Mathews I.,Bell Labs Ireland |
Camus J.,University of Nantes |
Bensalem S.,University of Nantes |
And 4 more authors.
Proceedings of the 15th InterSociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems, ITherm 2016 | Year: 2016
In the paper, we aim to solve the thermal problems appearing in integrated silicon photonics by using high thermal conductivity Aluminium Nitride (ALN) as a thermal spreading layer located around the ridge of a hybrid III-V laser on silicon in comparison to the existing encapsulation material benzocyclobutene (BCB). Here, to facilitate the design of reliable hybrid semiconductor lasers, we first develop and implement a multiphysics electro-thermo-mechanical model within a finite element environment COMSOL. A phenomenological model of laser operation is used to numerically capture all the thermal and electrical characteristics of the lasers. In terms of the hybrid devices, the simulated thermal resistance agrees well with our device measurements presented in Part 1 of this work. We also demonstrate that the use of the ALN heat spreader can significantly reduce the thermal resistance. Moreover, a linear elastic model is employed for a mechanical analysis of the entire laser structure. The maximum allowable stress is estimated using the Christensen criterion. We find that the process-dependent residual stress dictates the device stress field. In the current design, the BCB encapsulation layer is at risk of failure around the InP waveguide. For AlN spreaders, lower film processing temperatures are key to reduce the stress in the deposited film. We further perform a parametric study on Tref to determine the maximum allowable deposition temperature of AlN/BCB. The simulations suggest that Tref should not exceed 59 °C and 69 °C for ALN and BCB respectively to avoid mechanical failure in the devices. © 2016 IEEE.
Portolan M.,Bell Labs Ireland |
Van Treurent B.,Alcatel - Lucent |
Goyal S.,Bell Labs Ireland
Proceedings - International Test Conference | Year: 2010
This paper presents the Open-Circuit Deadlock (OCD), a primitive that allows flexible and scalable securization of a JTAG target, from the cell to the system level. © 2010 IEEE.
Egan B.,University of Limerick |
McCarthy M.A.,University of Limerick |
Frizzell R.M.,University of Limerick |
Frizzell R.M.,Bell Labs Ireland |
And 3 more authors.
Composite Structures | Year: 2014
Three-dimensional explicit finite element modelling is used to predict the quasi-static bearing response of typical countersunk composite fuselage skin joints. In order to accurately simulate bearing failure, a user-defined 3D composite damage model was formulated for Abaqus/Explicit and included Puck failure criteria, a nonlinear shear law and a crack band model to mitigate mesh sensitivity. A novel approach was developed to employ characteristic element lengths which account for the orientation of composite ply cracks in the Abaqus/Explicit solver. Resulting models accurately predicted initial joint sticking behaviour and the elastic loading response of single-bolt and three-bolt joints, but preliminary predictions of bearing failure onset were overly-conservative. Improved failure predictions were obtained by utilising a fracture energy for compressive fibre failure which was considered more relevant for simulating bearing damage. The explicit models were exceptionally robust, showing capability to predict extensive hole crushing. Methods of dramatically improving joint model efficiency were highlighted. © 2013 Elsevier Ltd.
Bulja S.,Bell Labs Ireland |
Grebennikov A.,Bell Labs Ireland
IEEE Transactions on Microwave Theory and Techniques | Year: 2012
In this paper, variable reflection-type attenuators based on varactor diodes are introduced and described in detail. Their main components are 3-dB couplers, varactor diodes, and lumped elements. © 2012 IEEE.