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Heating ventilating and air-conditioning systems which equip our buildings/rooms represent noise sources unfavorable affecting the people decent living and working conditions. Usually, silencers are used to reduce the annoying sound from these systems. They are lined with different materials and they have various geometries in order to satisfy the consumer needs, in terms of acoustic comfort. Sound absorption and sound transmission loss characterize the materials acoustic properties, but it is not mandatory that a good absorbent material to be also an efficient one from transmission loss (attenuation) point of view. Our paper is focused on an acoustic study of different materials lining three commercial silencers of same geometry and size. We have recorded the sound data according to standards: ISO 10534-1:1998 for the sound absorption coefficient and ISO 7235:2009 for the transmission loss rating. Third octave analysis with LabView soft is used to process the sound information and then the two parameters values are calculated. The acoustic characteristics of the tested materials are discussed and features that recommend them to be used as lining materials for silencers are highlighted.

Traffic microsimulation models use the movement of individual driver-vehicle-units (DVUs) and their interactions, which allows a detailed estimation of the traffic noise using Common Noise Assessment Methods (CNOSSOS). The Dynamic Traffic Noise Assessment (DTNA) methodology is applied to real traffic situations, then compared to on-field noise levels from measurement campaigns. This makes it possible to determine the influence of certain local traffic factors on the evaluation of noise. The pattern of distribution of vehicles along the avenue is related to the logic of traffic light control. The analysis of the inter-cycles noise variability during the simulation and measurement time shows no influence from local factors on the prediction of the dynamic traffic noise assessment tool based on CNOSSOS. A multifractal approach of acoustic waves propagation and the source behaviors in the traffic area are implemented. The novelty of the approach also comes from the multifractal model&rsquo, s freedom which allows the simulation, through the fractality degree, of various behaviors of the acoustic waves. The mathematical backbone of the model is developed on Cayley&ndash, Klein-type absolute geometries, implying harmonic mappings between the usual space and the Lobacevsky plane in a Poincar&eacute, metric. The isomorphism of two groups of SL(2R) type showcases joint invariant functions that allow associations of pulsations&ndash, velocities manifolds type.

Most of electric and hybrid cars are city oriented due to their reduced pollution and small range. In this paper we intend to analyse kinematics and energy distribution during braking in the scope of city use cases. The purpose is to identify optimization criteria based on system limitations. Our proposal is to describe each case from point of view of kinematics (velocity, acceleration), energy (kinematic energy, instantaneous power). Having relations between data and the results helps us to form optimization strategies: a strategy oriented on driver comfort and two resulted from regenerative braking system component limits. Based on results, maximizing acceleration until its comfort value, in city conditions, does not generate unsupported instantaneous power for generator or energy storage system for an average electric car. Power limitation became more important when keeping same strategy for speed higher than 50 kph. In this case electric vehicles with small battery capacity and hybrid vehicles could show lower efficiency, as more kinetic energy will be dissipated by friction brakes. Presented strategies can be used to implement braking system controlling algorithm for regenerative brakes/friction brakes ratio on-the-fly optimization.

Research in deployable structures increased in the last decade, due to the need of building structures that can change their shape or functionality in response to varying of different aspects: climatic conditions, environment, functional requirements or emergency situations. Depending on how the transformation is doing, transformable structures can be deployable or demountable, as a kit-parts system. These structures can be classified in four main groups: structures based on spatial articulated bar mechanisms; foldable plate structures; tensegrity structures; and membrane structures. In this paper, some geometric design aspects of curvilinear bar mechanisms are discussed and a curvilinear structure mechanism is proposed. More results on the geometric design, dimensional synthesis and simulation of this scissor structural mechanism will be presented in future work.

High-pressure pumps are the most important components of modern fuel injection systems. A modern system is the common rail one, equipping vehicles with a diesel or a gasoline engine. Depending on the fuel type, the design of the pumps is completely different, and it is more complex for diesel engines that are more prone to wear. The components subjected to wear are those in contact and continuous motion like drive shaft with roller and shoe, plunger and hydraulic head assembly with valves. Wear is initiated as a result of a process and product deviations or inadequate exploitation of the high-pressure pump. The factors influencing the wear can be improper material hardness, improper coating, incomplete or wrong machining, wrong clearance or misalignment between components, inadequate surface finish, dimensions out of tolerances, wrong assembly process, poor lubrication, contamination or running at high loads and temperatures. Our paper aims to identify, describe and discuss the types of wear encountered at common rail high-pressure pumps, highlighting the effects on their functionality. The wear occurrence can be prevented by paying more attention to the design details, manufacturing processes and correct exploitation of the high-pressure pumps.

Transformable structures in architecture can change their shape or function in response to varying climatic conditions, changing environment and needs for different functional requirements or to emergency situations. Depending on how the transformation is doing, transformable structures can be deployable or demountable, as a kit-parts system. Deployable structures can also be divided in four main groups: spatial bar structures; foldable plate structures; tensegrity structures; and membrane structures. In this paper, some planar bar mechanisms proposed by Ten Fold Engineering company, which can be integrated in deployable structures, will be discussed.