A symmetric quantum calculus

We introduce the $\alpha,\beta$-symmetric difference derivative and the $\alpha,\beta$-symmetric N\"orlund sum. The associated symmetric quantum calculus is developed, which can be seen as a generalization of the forward and backward $h$-calculus.Comment: Submitted 26/Sept/2011; accepted in revised form 28/Dec/2011; to Proceedings of International Conference on Differential & Difference Equations and Applications, in honour of Professor Ravi P. Agarwal, to be published by Springer in the series Proceedings in Mathematics (PROM

Regenerative braking potencial and energy simulations for a plug-in hybrid electric vehicle under real driving conditions

There are several possible configurations and technologies for the powertrains of electric and hybrid vehicles, but most of them will include advanced energy storage systems comprising batteries and ultra-capacitors. Thus, it will be of capital importance to evaluate the power and energy involved in braking and the fraction that has the possibility of being regenerated. The Series type Plug-in Hybrid Electric Vehicle (SPHEV), with electric traction and a small Internal Combustion Engine ICE) powering a generator, is likely to become a configuration winner. The first part of this work describes the model used for the quantification of the energy flows of a vehicle, following a particular route. Normalised driving-cycles used in Europe and USA and real routes and traffic conditions were tested. The results show that, in severe urban drivingcycles, the braking energy can represent more than 70% of the required useful motor-energy. This figure is reduced to 40% in suburban routes and to a much lower 18% on motorway conditions. The second part of the work consists on the integration of the main energy components of an S-PHEV into the mathematical model. Their performance and capacity characteristics are described and some simulation results presented. In the case of suburban driving, 90% of the electrical motor-energy is supplied by the battery and ultra-capacitors and 10% by the auxiliary ICE generator, while on motorway these we got 65% and 35%, respectively. The simulations also indicate an electric consumption of 120 W.h/km for a small 1 ton car on a suburban route. This value increases by 11% in the absence of ultra-capacitors and a further 28% without regenerative braking.Fundação para a Ciência e a Tecnologia (FCT) - MIT-Pt/EDAMSMS/0030/200

Arthritis in Kawasaki Disease: A Poorly Recognised Manifestation

To determine the prevalence of arthritis in Kawasaki disease (KD) and the clinical characteristics of children with KD and arthritis.info:eu-repo/semantics/publishedVersio

Atypical Presentation of Langerhans Cell Histiocytocis

info:eu-repo/semantics/publishedVersio

Thermoelectric exhaust energy recovery with temperature control through heat pipes

Currently, a great deal of the automotive industry’s R&D effort is focused on improving overall vehicle environmental and energy efficiency. For instance, one of the things that Electric Vehicles (EVs) and Hybrid cars (HEV) have in common is the recovery of waste energy, namely during braking. But, when an I.C. engine is operating (e. g. as a range extender in an EV), a large amount of energy is also wasted within the exhaust gases and with engine cooling, energy that could otherwise be recovered by different methods. This paper reports on the recovery of waste thermal energy using thermoelectric generators (TEG) for application in hybrid, extended range electric vehicles and more generally in any vehicle that could benefit from the generation of a small amount of electric current that would reduce the alternator operation time. Although some manufacturers are trying to develop TEGs to use at exhaust temperatures, there are still no commercially available TEG modules capable of withstanding these extreme temperatures. The present work assesses the potential of the use of heat pipes (HP) as a means of transferring energy from the hot exhaust gases to the TEG modules at a compatible temperature level while minimizing the loss of efficiency due to temperature downgrading. The type of HP used in this study is called Variable Conductance Heat Pipe (VCHP), and its deployment has the advantage of inducing good temperature control. Various types of HPs were designed, manufactured, tested and improved with the aim of enhancing the overall heat transfer process, enabling an optimal level of electric energy recovery from the referred TEG modules. This was accomplished by the testing of different fluids inside the HP and by regulating the pressure of the gas chamber. Although the system is still under improvement, the results indicate that the use of VCHPs in conjunction with thermoelectric generators is a convincing technique for recovering otherwise wasted energy from the exhaust gases.MIT Portugal (MIT-Pt/EDAM-SMS/0030/2008)Fundação para a Ciência e a Tecnologia (FCT) (bolsa SFRH / BPD / 51048 / 2010

Modelling of thermoelectric generator with heat pipe assist for range extender application

Recent trends towards electrification of vehicles favour the adoption of waste energy recovery into electricity. Battery-only Electric Vehicles (BEV) need a very large energy storage system so the use of a Range Extender (RE) may allow a significant downsizing of these bulky components. The Internal Combustion Engines (ICE) have two major discarded energy fluxes, engine cooling and exhaust gas. In Extended Range Electric Vehicles (EREV) and hybrids the potential for heat conversion into electricity is particularly convenient. The direct conversion of thermal energy into electricity, using Thermoelectric Generators (TEG) is very attractive in terms of complexity. However, current commercial TEG modules based on Seebeck effect are temperature limited, so they are unable to be in direct contact with the exhaust gases. A way to downgrade the temperature levels without reducing its potential is to interpose Heat Pipes (HP) between the exhaust gas and the modules. This control of maximum temperature at the modules is achieved by regulating the pressure of phase change of the HP fluid. Such design is convenient for engines with large thermal load variations, such as the RE being developed by the team, with a low (15kW) and a high (40kW) power mode of operation. This system will be able to operate efficiently in both modes. The present work presents the thermal modelling of such a system in order to assess the suitability of this approach. This work is complemented with the experimental work being carried out by the team in this subject, already with some published results. The model was validated with experimental data with a good correlation. Therefore, it was possible to demonstrate the potential of this system for wasted heat recovery.MIT Portugal, Fundação para a Ciência e a Tecnologia (FCT

Temperature controlled exhaust heat thermoelectric generation

The amount of energy wasted through the exhaust of an Internal Combustion Engine (ICE) vehicle is roughly the same as the mechanical power output of the engine. The high temperature of these gases (up to 1000°C) makes them intrinsically apt for energy recovery. The gains in efficiency for the vehicle could be relevant, even if a small percentage of this waste energy could be regenerated into electric power and used to charge the battery pack of a Hybrid or Extended Range Electric Vehicle, or prevent the actuation of a conventional vehicle's alternator.SFRH / BPD / 51048 / 2010MIT-Pt/EDAM-SMS/0030/200

Heat-pipe assisted thermoelectric generators for exhaust gas applications

Millions of hybrid cars are already running on our roads with the purpose of reducing fossil fuel dependence. One of their main advantages is the recovery of wasted energy, namely by brake recovery. However, there are other sources of wasted energy in a car powered by an internal combustion engine, such as the heat lost through the cooling system, lubrication system (oil coolers) and in the exhaust system. These energies can be recuperated by the use of thermoelectric generators (TEG) based on the Seebeck effect, which transform heat directly into electricity To recover the energy from the hot (up to more than 700 ºC) exhaust gases it is possible to use controlled heat transfer, but this would limit the heat transfer potential at partial loads, as commercialy available TEG are limited by their maximum allowable temperature (~250ºC). Therefore Heat Pipes were used as an alternative heat transfer mean, so it would be possible to retain the heat transfer potential, while controlling the maximum temperature at a reasonable level. This is the method to recover the exhaust heat presented in this work. Numerical simulations were performed to assess the potential for this design, involving internal combustion engine simulation, thermoelectric generators simulation and heat transfer modelling. Additionally, the use of variable conductance heat pipes (VCHP) is discussed, as a means of achieving TEG module maximum temperature limitation.MIT Portugal, Fundação para a Ciência e a Tecnologia (FCT