Yverdon-les-Bains, Switzerland
Yverdon-les-Bains, Switzerland

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Eicher S.,HEIG VD | Hildbrand C.,HEIG VD | Bony J.,HEIG VD | Bunea M.,HEIG VD | And 2 more authors.
Energy Procedia | Year: 2012

In this article, a R&D project is described involving a prototype solar assisted heat pump (HP) designed for domestic hot water preparation for single family dwellings. This project, developed within the framework of Task 44 of the IEA Solar and Cooling Programme, uses solar energy on the HP evaporator side to maximize the performance level of the system. In cases where solar energy is not enough, the HP under investigation has been designed to extract energy from the heating circuit of the building. This study involves both test bench measurements and dynamic simulations of the solar assisted heat pump system. The overall objectives of the project are summarised as follows: • Development of solar thermal technology • Improvement of HP performance for DHW production • Reduction of non-renewable energy consumption • Reduction of environmental impacts This article presents an overview of the project and its current status. © 2012 The Authors.

Ligier J.-L.,HEIG VD | Bonhote P.,HEIG VD
Mechanics and Industry | Year: 2015

The main idea is to present some problems where the friction obeys to regularized Coulomb law. Mathematically, it is usual that the friction law is supposed to be the Coulomb law which is controlled by a function "sign" with discontinuity at the origin. In reality, friction phenomenon corresponds to an average continuous behavior. From a modelling point of view, the simplest way to get this continuity is to regularize friction law. Obviously, friction problems become more complicated due to the fact that the friction law exhibits two phases of behavior. Solving problems with this friction law could bring some special results. To present them, the problems considered in this paper are related to the bending of two beams in contact under a certain pressure and to the transversal strain of an elastic thin strip in contact with a rigid body. For these two problems, analytical solutions are presented and also some finite element simulations for comparison. © AFM, EDP Sciences 2015.

Maalouf E.,University of Applied Sciences and Arts Western Switzerland | Di Zuzio M.,HEIG VD | Sokhn M.,University of Applied Sciences and Arts Western Switzerland
ACM International Conference Proceeding Series | Year: 2014

Business Process Management (BPM) is accepted to be an efficient approach to capture processes in order to improve operational aspects of an enterprise. Business process modeling and design is the first step in BPM. This paper presents a process fragmentation approach that serves to generate process fragments ready for reuse during modeling in a semantic modeling tool. The fragmentation is based on the Refined Process Structure Tree which is an algorithm to decompose processes based on their workflow graphs. Copyright © 2014 ACM.

Melab N.,French Institute for Research in Computer Science and Automation | Van Luong T.,HEIG VD | Boufaras K.,French Institute for Research in Computer Science and Automation | Talbi E.-G.,French Institute for Research in Computer Science and Automation
GECCO 2013 - Proceedings of the 2013 Genetic and Evolutionary Computation Conference | Year: 2013

In this paper, we propose a pioneering framework called Par-adisEO-MO-GPU for the reusable design and implementation of parallel local search metaheuristics (S-Metaheuris-tics) on Graphics Processing Units (GPU). We revisit the ParadisEO-MO software framework to allow its utilization on GPU accelerators focusing on the parallel iteration-level model, the major parallel model for S-Metaheuristics. It consists in the parallel exploration of the neighborhood of a problem solution. The challenge is on the one hand to rethink the design and implementation of this model optimizing the data transfer between the CPU and the GPU. On the other hand, the objective is to make the GPU as transparent as possible for the user minimizing his or her involvement in its management. In this paper, we propose solutions to this challenge as an extension of the ParadisEO framework. The first release of the new GPU-based Par-adisEO framework has been experimented on the permuted perceptron problem. The preliminary results are convincing, both in terms of flexibility and easiness of reuse at implementation, and in terms of efficiency at execution on GPU. Copyright © 2013 ACM.

Ropp J.,HEIG VD | Roethlisberger R.P.,HEIG VD | Roth S.,HEIA FR | Bourgeois J.-P.,HEIA FR
ECOS 2015 - 28th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems | Year: 2015

In order to reduce pollutant emissions, a commercial wood log stove with staged combustion was fitted with an exhaust gas after treatment device based on a metal-based oxidation catalyst coated with platinum and palladium followed by a sintered metal pticle filter (both used on diesel internal combustion engines) and a regulated exhaust gas fan for draft control. The tests were performed with standdised logs (wood species, size and humidity) precisely positioned in the furnace. Further, an exhaust gas draft control based on the pressure at the stove outlet enabled achievement of better operating stability than draft control based on the temperature. Regding the exhaust gas emissions, the use of a catalyst lead to a complete (i.e. 100%) cbon monoxide (CO) oxidation, independently of both its internal structure and length, as well as the draft control pameter (pressure or temperature). In the case of draft control by pressure, the catalyst resulted in a significant reduction of polycyclic omatic hydrocbons (PAH) by 65 to 90 %, increasing with the cell density. The addition of a pticle filter downstream had the same influence on pticles emission as an increase in cell density. On the other hand, the exhaust gas temperature at the level of the catalyst was too low to permit significant methane (CH4) oxidation and reduction of nitrogen oxides (NOx). The use of a pticle filter enabled a minimum of 90 % reduction of the mass emitted. However, this also lead to an important increase of the pressure losses between the stove and the fan inlet, resulting in higher electricity consumption. Globally, an active combustion control by draft regulation combined to an exhaust gas after treatment based on oxidation catalyst and pticle filter appes to be a promising solution to reduce wood log stove exhaust gas emissions and should be further studied.

Eicher S.,HEIG VD | Hildbrand C.,HEIG VD | Kleijer A.,HEIG VD | Bony J.,HEIG VD | And 2 more authors.
Energy Procedia | Year: 2014

Solar heat pumps (SHP) are a class of heating systems combining solar thermal technology with heat pumps. In this article the life cycle impact assessment (LCIA) of a SHP system used to produce domestic hot water (DHW) and space heating (SH) for single family dwellings is presented. This study intends to evaluate the environmental impacts of the energy and material used in a serial SHP installation and identify areas for improvement by applying a "cradle-to-grave" approach when analysing the system. This includes the installation materials both in their manufacturing and disposal phases as well as the energy consumption for DHW and SH throughout a service life of 20 years. In addition, it provides a comparison against two other residential heating systems operating with the same life expectancy. In this LCIA, two environmental related indicators are used, one associated with depletion of non-renewable energy resources (CEDNRE) and the other with climate change (GWP). The impact of the type of electricity used was also investigated by defining, in addition to the European supply mix, an alternative supply mix with electricity deriving from renewable sources. This study shows that SHP have lower environmental impacts than systems operating on electricity only. Installations with large solar collector surfaces are also seen to lead to lower energy consumption related impacts. If the electricity used by these systems derives from renewable sources, the environmental performance improves. However, under these conditions, the SHP impact (material and energy consumption) related to climate change will be of the same order as that of the electric system due to a higher contribution of the infrastructure content of these systems.

Prina Howald E.,HEIG VD | Odier M.,Geotechnique appliquee Deriaz
Rock Mechanics in Civil and Environmental Engineering - Proceedings of the European Rock Mechanics Symposium, EUROCK 2010 | Year: 2010

The publication refers to the rehabilitation of a water diversion tunnel of the streamletVengeron in Geneva. The construction includes a section of 100m drilled and blasted gallery. The swelling behavior of the rock has gradually led to local collapse. The rehabilitation works were carried out in especially difficult conditions since there is no bypass opportunity. The watershed is highly urbanized; the risk of severe flooding was an important parameter in planning the work. © 2010 Taylor & Francis Group.

Junod P.,HEIG VD | Karlov A.,Nagravision | Karlov A.,Ecole Polytechnique Federale de Lausanne
Proceedings of the ACM Conference on Computer and Communications Security | Year: 2010

We describe a new public-key and provably secure attribute-based broadcast encryption scheme which supports complex access policies with AND, OR and NOT gates. Our scheme, especially targetting the implemention of efficient Pay-TV systems, can handle conjunctions of disjunctions by construction and disjunctions of conjunctions by concatenation, which are the most general forms of Boolean expressions. It is based on a modification of the Boneh-Gentry-Waters broadcast encryption scheme in order to achieve attribute collusion resistance and to support complex Boolean access policies. The security of our scheme is proven in the generic model of groups with pairings. Finally, we compare our scheme to several other Attribute-based Broadcast Encryption designs, both in terms of bandwidth requirements and implementation costs. © 2010 ACM.

Romero C.,Ecole Polytechnique Federale de Lausanne | Rachidi F.,Ecole Polytechnique Federale de Lausanne | Paolone M.,Ecole Polytechnique Federale de Lausanne | Rubinstein M.,HEIG VD
IEEE Transactions on Power Delivery | Year: 2013

This paper presents statistical distributions of lightning current parameters based on the lightning current and current-derivative waveforms measured at the Säntis Tower site in 2010 and 2011. The total number of flashes analyzed in this study was 167, which includes nearly 2000 pulses. The statistical distributions refer to upward negative flashes. It is shown that negative flashes are mainly concentrated in the summer months during the convective season. Statistical data on the salient lightning current parameters, namely, peak current, peak current derivative, risetime, pulse charge, pulse duration, interpulse interval, and flash multiplicity are presented and discussed. The obtained data that constitute the largest dataset available to this date for upward negative flashes are also compared with other available statistical distributions. © 1986-2012 IEEE.

Boureanu I.,HEIG VD | Vaudenay S.,Ecole Polytechnique Federale de Lausanne
Scientific Annals of Computer Science | Year: 2013

Based on tamper-evident devices, i.e., a type of distinguishable, sealed envelopes, we put forward weak bit-commitment protocols which are UC-secure. These commitments are weak in that it is legitimate that a party could cheat. Unlike in several similar lines of work, in our case, the party is not obliged to cheat, but he has ability to cheat if and when needed. The empowered party is the sender, i.e., the protocols are also sender-strong. We motivate the construction of such primitives at both theoretical and practical levels. Such protocols complete the picture of existent receiver-strong weak bit-commitments based on tamper-evidence. We also show that existent receiver-strong protocols of the kind are not EUC-secure, i.e., they are only UC-secure. Further, we put forward a second formalisation of tamper-evident distinguishable envelopes which renders those protocols and the protocols herein EUC-secure. We finally draw most implication-relations between the tamper- evident devices, our weak sender-strong commitments, the existent weak receiver-strong commitments, as well as standard commitments. The mechanisms at the foundation of these primitives are lightweight and the protocols yielded are end-to-end humanly veriable. © Scientific Annals of Computer Science 2013.

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