Time parameterization and stationary distributions in a relativistic gas

In this paper we consider the effect of different time parameterizations on the stationary velocity distribution function for a relativistic gas. We clarify the distinction between two such distributions, namely the J\"{u}ttner and the modified J\"{u}ttner distributions. Using a recently proposed model of a relativistic gas, we show that the obtained results for the proper-time averaging does not lead to modified J\"{u}ttner distribution (as recently conjectured), but introduces only a Lorentz factor $\gamma$ to the well-known J\"{u}ttner function which results from observer-time averaging. We obtain results for rest frame as well as moving frame in order to support our claim.Comment: 5 pages, 2 figure

IDES-EDU: Comprehensive multidisciplinary education programme to accelerate the implementation of EPBD in Europe

This paper presents a new education and training programme on integrated energy design developed by fifteen European universities collaborating within the IDES-EDU project (2010-2013), funded by Intelligent Energy Europe. IDES-EDU aims to accelerate the implementation of the Energy Performance of Buildings Directive (EPBD) by proposing Master and Post Graduate education and training in multidisciplinary teams. To speed up transition from traditional, sub-optimised building projects with discipline-oriented, segregated budgets and operations, IDES-EDU developed comprehensive, multidisciplinary educational programmes targetting integrated project design at the interface of architecture and engineering. Taking into account local variations in climate, construction and pedagogical approaches, the programme facilitates gradual implementation towards full integration of energy efficiency in building education according to local capacity and legislation. This paper summarises the evaluation process of the first implementation of the educational material in the 15 universities, by academic staff, national industry and professional organisations, and reference students from each university. Included are expected learning outcomes, level of integration in existing curricula and alignment with theory and assessment methods. Measures for improvement as well as further dissemination to other European educational facilities are proposed. In this manner, the project will contribute to make the multiple opportunities for energy efficiency a reality.Intelligent Energy Europe programme for its financial support, Grant agreement no.IEE/09/631/SI2.55822

Improved Safety and Efficiency of Protected/Permitted Right Turns for Bicycles in the Pacific Northwest

DTRT13-G-UTC40Conflict between bicycles and right-turning vehicles on the approaches to intersections is a critical safety concern in urban environments. To understand the safety and operational implications of using protected-permitted right turns (PPRT), a full-scale bicycling simulator experiment was performed. The velocity and lateral position of bicyclists were evaluated during conflicts between bicycles and right-turning vehicles. Two independent variables were analyzed: the signal indication for right-turning vehicles (circular red or green, solid red or green arrow and flashing yellow arrow) and the pavement markings in the conflict area (white lane markings with no supplemental pavement color and white lane markings with solid green pavement applied in the conflict area). Forty-eight participants (24 women and 24 men) completed the experiment. Signal indications and pavement markings had statistically significant effects on bicycle velocity and lateral position, but these effects varied at different levels of the independent variables. Use of PPRT phasing in conjunction with colored pavement markings was associated with increased bicyclist conflict with right-turning vehicles, whereas PPRT phasing with no supplemental colored pavement markings was associated with improved bicyclist safety. The results provide guidance to transportation professionals about how traffic control devices could be applied to conflict areas before signalized intersections

Thermo-Mechanical Fatigue of Compacted Graphite Iron in Diesel Engine Components

Cast iron components in combustion engines, such as cylinder blocks and heads of trucks, are exposed for long periods of time to elevated temperatures. Moreover, the engines are started and stopped frequently during their operational life, constituting a large number of heating and cooling cycles. In geometrical complex components the sudden heating (starting the engine) and cooling (stopping the engine) lead to thermal gradients and thermal mismatch within the material, resulting in the local development of high stress levels. The many start-stop operations and their associated alternating stress levels can lead to a localized cracking phenomenon known as Thermo-Mechanical Fatigue (TMF). Compacted Graphite Iron (CGI) is a common material of choice for diesel engine cylinder heads of heavy trucks and is a type of graphitic cast iron, consisting of vermicular graphite particles embedded in a metal matrix of pearlite. This material provides a suitable combination of thermal and mechanical properties, satisfying the functional requirements of these engine components. The main aim of this research is to identify and understand the damage micro-mechanisms that control thermo-mechanical fatigue phenomena in cast iron (CGI). The acquired knowledge is of relevance for predicting the lifetime, improving the properties and increasing the reliability of diesel truck cylinder heads. The work of this study can roughly be categorized into three main subjects: (i) Microstructural evolutions of CGI at elevated temperatures, (ii) TMF crack growth characterization and (iii) precise microstructural analysis of the TMF-crack path. Microstructural Evolutions of CGI at Elevated Temperatures In a first series of experiments, time and temperature induced microstructural changes in CGI were characterized, in view of their possible role in the TMF behavior of CGI. During open air annealing of CGI at 420 °C microstructural changes take place in the material, which gave rise to volume expansion and weight increase. The weight increase can be explained by considering the formation of an oxide scale whereas the volume expansion can be attributed to the decomposition of pearlite into ferrite and graphite. It was observed that the atmosphere is of crucial importance in this process. Annealing in an open-air atmosphere produced ten times less volume expansion as compared to annealing in vacuum conditions. Internal oxidation was observed during annealing under atmospheric conditions and the presence of an internal oxidation layer largely inhibited the progress of pearlite decomposition. The observed oxide layers at the internal metal/vapour interface of cavities (left behind by denuded graphite) cause the obstruction of carbon diffusion and thus the suppression of the pearlite decomposition process. In addition it was found that the depth of the oxidized zone near the surface (the oxide penetration depth) was of the same order of magnitude as the eutectic cell size, i.e. the volume in which graphite particles are interconnected. This suggests that the interconnectivity of the graphite has a dominant influence on the kinetics of the oxidation process. The microstructural dependence of tensile and fatigue properties of CGI at room temperature were evaluated by an extended annealing treatment of 720 h at 420 °C. This extended annealing treatment leads to better tensile (increase in yield strength, ductility) and dynamic properties (fatigue lifetime) at room temperature. The variations of mechanical properties were observed both after annealing under atmospheric and vacuum conditions, but were more pronounced after vacuum annealing. This can be explained by the decomposition of the pearlite phase during annealing and the formation of new ferrite at the graphite/metal interface. It is assumed that the ferrite/graphite interface exhibits a stronger bond than the pearlite/graphite interface. As this stronger bond will be better resistant to delamination, it will strengthen the material both in static and dynamic loading. Such effects were far less pronounced in the open-air annealed material, which could be associated with the fact that it was shown that internal oxidation strongly reduced the kinetics of decomposition. TMF Crack Growth Characterization An important part of this study was to measure and analyze the TMF lifetime of CGI. For smooth and notched specimens, the TMF lifetime was measured in TMF tests under total-constraint conditions, with temperatures cycling between 50 °C and 420 °C. By considering the notch depth as the initial crack length, TMF lifetimes were reproduced numerically using the Paris equation for fatigue crack growth (da/dN = C (?K)m). The calculated lifetimes were found to be in good agreement with all experimental results, covering a wide range of TMF lifetimes from 30 to 1400 cycles. Also for smooth specimens the Paris model worked well by considering the typical graphite particle size as notch depth. It is one of the main conclusions of this work that graphite particles act as internal notches from which a TMF crack almost immediately starts to grow during the first TMF cycles. Hence, it was established that TMF lifetime in CGI is governed by crack growth and not by crack initiation. The relevance of the Paris growth law was further confirmed by meticulously measuring the actual crack growth rates for three typical values of the stress intensity factor. The resulting crack growth rates proved to be in reasonable agreement with the predicted values according to the Paris model. It was further shown that the cyclic plasticity of the bulk material, accumulated during TMF cycles, does not have a noticeable effect on TMF lifetime (i.e. crack growth rates are not affected). The notched dog-bone specimen geometry is proposed in this work as a valid alternative for monitoring the TMF behavior of CGI. By applying standard TMF tests with notched specimens, it was possible to significantly reduce both testing time and experimental data scatter, whilst preserving a realistic estimation of the lifetime of the smooth sample. The effect of prolonged holding times (HT) on TMF lifetime was studied by using notched specimens and a clear effect was observed. Extended holding times were accompanied by an increased relaxation of compressive stresses, causing higher tensile stresses to develop in the subsequent low temperature stages of the TMF cycles. So, extended HTs had an adverse effect on the sample lifetime with a saturating effect for HTs above 1800 s. The Paris fatigue-crack-growth model was used also to estimate the impact of extended HTs. According to the Paris growth law, using a fixed value of tensile stress at low temperature, it was estimated that an increase of holding time from 30 s to 18000 s (5 h) produced a drop of 45% in lifetime. In reality a 60% drop in lifetime was measured, though, which implies that a combined effect of (tensile) stress and microstructural evolution during TMF is responsible for the reduction of lifetime. Precise Microstructural Analysis of the TMF Crack Path To the purpose of precise characterization of the complex TMF-crack-path morphology in CGI in relation to local microstructural features and to find out how and by which mechanisms the cracks predominantly develop, 2D and 3D orientation contrast imaging was carried out on wide field sample volumes, covering several mm3 of imaged material. The data analysis revealed that the crystal planes that are parallel to the (local) crack plane are essentially of a random orientation. Conversely, it was found that graphite particles do not only play a crucial role in the crack initiation, but also are of primary significance for crack propagation. Quantitative analysis of the EBSD data in 2D and 3D showed that the distribution of graphite particles is very important for the crack propagation, as it was revealed that graphite particles enhance crack growth. It was statistically proven that the density of graphite particles in the crack plane is more than double of the density in an arbitrary plane. Our materials knowledge, based on the interpretation of test results in terms of quantifiable microstructural data functions, is of crucial importance to develop a microstructurally based TMF model.Materials Science & EngineeringMechanical, Maritime and Materials Engineerin

Evaluation and Determination of Silicon Eutectic Modification Level Using Thermal Analysis in 319 Aluminum Alloy

Eutectic Silicon phases form as the coarse and acicular shape in Aluminum-Silicon alloys. These phases have detrimental effect on mechanical properties of casting parts. Modification process has been used to change the shape of these phases to fibrous morphology. In this research different level of strontium; in the form of Al-10%Sr master alloy; have been added to 319 aluminum alloy to investigate their effects on modification. Thermal Analysis has been used as a technique to study the cooling curves and first derivative curves. Effect of strontium on solidification parameters such as nucleation temperature ((, and growth temperature () of eutectic silicon has been determined. ((and () have been reduced by increasing strontium content. () can be used as a parameter to control the modification of eutectic silicon. The results of this research indicate that thermal analysis technique can be used as an accurate and quick device of on-line quality control in production lines of aluminum casting industries

Design of Wearable Finger Sensors for Rehabilitation Applications

As an emerging technology, smart textiles have attracted attention for rehabilitation purposes or to monitor heart rate, blood pressure, breathing rate, body posture, as well as limb movements. Traditional rigid sensors do not always provide the desired level of comfort, flexibility, anadaptability. To improve this, recent research focuses on the development of textile-based sensors. In this study, knitted strain sensors that are linear up to 40% strain with a sensitivity of 1.19 and a low hysteresis characteristic were integrated into different versions of wearable finger sensors for rehabilitation purposes. The results showed that the different finger sensor versions have accurateresponses to different angles of the index finger at relaxation, 45° and 90°. Additionally, the effect of spacer layer thickness between the finger and sensor was investigated

Role of Sodium Channel on Cardiac Action Potential

Sudden cardiac death is a major cause of death worldwide. In most cases, it's caused by abnormal action potential propagation that leads to cardiac arrhythmia. The aim of this article is to study the abnormal action potential propagation through sodium ion concentration variations. We use a new electrophysiological model that is both detailed and computationally efficient. This efficient model is based on the partial differential equation method. The central finite difference method is used for numerical solving of the two-dimensional (2D) wave propagation equation. Simulations are implemented in two stages, as a single cardiac cell and as a two-dimensional grid of cells. In both stages, the normal action potential formation in case of a single cell and it's normal propagation in case of a two-dimensional grid of cells were simulated with nominal sodium ion conductance. Then, the effect of sodium ion concentration on the action potential signal was studied by reducing the sodium ion conductance. It is concluded that reducing the sodium ion conductance, decreases both passing ability and conduction velocity of the action potential wave front

Improved Safety and Efficiency of Protected/Permitted Right Turns for Bicycles in the Pacific Northwest

Conflict between bicycles and right-turning vehicles on the approaches to intersections is a critical safety concern in urban environments. To understand the safety and operational implications of using protected-permitted right turns (PPRT), a full-scale bicycling simulator experiment was performed. The velocity and lateral position of bicyclists were evaluated during conflicts between bicycles and right-turning vehicles. Two independent variables were analyzed: the signal indication for right-turning vehicles (circular red or green, solid red or green arrow and flashing yellow arrow) and the pavement markings in the conflict area (white lane markings with no supplemental pavement color and white lane markings with solid green pavement applied in the conflict area). Forty-eight participants (24 women and 24 men) completed the experiment. Signal indications and pavement markings had statistically significant effects on bicycle velocity and lateral position, but these effects varied at different levels of the independent variables. Use of PPRT phasing in conjunction with colored pavement markings was associated with increased bicyclist conflict with right-turning vehicles, whereas PPRT phasing with no supplemental colored pavement markings was associated with improved bicyclist safety. The results provide guidance to transportation professionals about how traffic control devices could be applied to conflict areas before signalized intersections.Pacific Northwest Transportation Consortiu

Exploring shape memory alloys in haptic wearables for visually impaired people

Wearable haptic assistive devices can provide tactile information to visually impaired people (VIP) to support independent living. However, electromechanical haptic feedback has a number of disadvantages, including hardware being relatively heavy, large, and producing excessive sound. Here, we present a design-driven investigation of the potential of shape memory alloy-based haptic feedback for VIP. We followed an iterative approach, focusing on hands-on material explorations, in which we identified challenges and subsequent solutions that designers of SMA-based wearable haptic assistive devices may be faced with when incorporating SMAs in their designs. We present several prototype iterations and an initial evaluation with VIP to offer insights into the potential of SMA-based wearable haptic devices for VIP

Review of magnetic shape memory polymers and magnetic soft materials

Magnetic soft materials (MSMs) and magnetic shape memory polymers (MSMPs) have been some of the most intensely investigated newly developed material types in the last decade, thanks to the great and versatile potential of their innovative characteristic behaviors such as remote and nearly heatless shape transformation in the case of MSMs. With regard to a number of properties such as shape recovery ratio, manufacturability, cost or programming potential, MSMs and MSMPs may exceed conventional shape memory materials such as shape memory alloys or shape memory polymers. Nevertheless, MSMs and MSMPs have not yet fully touched their scientific-industrial potential, basically due to the lack of detailed knowledge on various aspects of their constitutive response. Therefore, MSMs and MSMPs have been developed slowly but their importance will undoubtedly increase in the near future. This review emphasizes the development of MSMs and MSMPs with a specific focus on the role of the magnetic particles which affect the shape memory recovery and programming behavior of these materials. In addition, the synthesis and application of these materials are addressed.</p