Mechanical Engineering

Rice straw, a renewable feedstock, is recalcitrant and its degree of polymerization makes pretreatment obligatory for subsequent bioconversion. The present study explores an advanced oxidation process i.e. Alkaline Wet Air Oxidation (AWAO) 1 as a pretreatment for rice straw and scrutinizes the effect of operation parameters on cellulose recovery, hemicellulose solubilization and lignin removal through Response Surface Methodology (RSM) 2 . AWAO resulted in 68-90% cellulose recovery, 67-87% hemicellulose solubilization and 32-66% lignin removal while generating limited inhibitors. AWAO caused oxidative delignification, hemicellulose deacetylation and cleavage of carbohydrate-lignin linkages as revealed by FT-IR 3 , thereby improving cellulose accessibility indicated by 42-89% enzymatic cellulose convertibility (%ECC) or % cellulose conversion 4 . The findings of the present study indicate minimization of chemical input and absence of potent inhibitors in the liquor which collectively implies reduction in freshwater requirements, minimization of waste generation and its treatment cost.

In the latest research, the application of three-dimensional electromagnetic tracking system (ETS) for biomechanical and kinesiologic research of cervical spine has been demonstrated. Little information is available regarding coupled movements that accompany the primary movement in vivo. The purpose of the present study was to investigate the feasibility of quantifying the primary movements of the cervical spine and their corresponding coupled motions in healthy subjects by a three-dimensional ETS. Twenty healthy subjects (10 males and 10 females) participated in the study. Cervical extension, flexion, side bending, rotation in neutral position, and rotation in a position of full cervical flexion were analyzed via ETS. All measurements were performed actively except for rotation in a position of full cervical flexion. According to our results, the high intraclass correlation coefficient (ICC (2, 1)) values (greater than 0.791) suggested that ETS is appropriate for measuring primary ...

Sizc!-se parated atmospheric aeroso ls were co llec ted at Kothi (a hill top) and M ohal (a va lley). situated at tho.: foo thill s of western Himalayas during th e summer sea son o f 1999. Bimodal di stributi on of aerosols was observed ::11 both the locat ions. Howeve r. at K othi . fin e si ze parti cles dominated (62 %). wherea s at Mohal . coa rse si ze parti cles co ntributed more (75 "/r•). Th e S0 4 and 0 3 panic le togeth er co ntributed -30% o f the total measured chemical co mposit ion o f aerosols. Burning of biomass and emi ssions from touri st ve hicles could be th e mai n loca l sources for these com ponent s. Ho'' ever. aeroso ls showed alkaline nature (L:•L:+ rati o< I ) clue to th e neutrali zing effec t of so me ca ti ons such as Ca and NH 4 .

The purpose of this research is to broaden the understanding of how resilience influences employee career commitment in the world of work mediated by work engagement and moderated by role modelling. A quantitative study using an online questionnaire was conducted on 415 millennial generation respondents who worked in the Fast-Moving Consumer Goods (FMCG) sector in Indonesia. Structural Equation Method (SEM) using AMOS was used to analyze the hypotheses. The analysis's findings indicated that work engagement's mediating effect on resilience to career commitment had a positive and significant effect. Analysis findings also revealed that the role of role modelling as a moderator was able to strengthen the link between ego-resilience and career commitment through work engagement. FMCG companies need to pay attention to and improve employee resilience which in turn will increase employee work engagement, and ultimately affect employee career commitment.

We have been distributing a new collection of databases and evaluation tools called CENSREC-4, which is a framework for evaluating distant-talking speech in reverberant environments. The data contained in CENSREC-4 are connected digit utterances as in CENSREC-1. Two subsets are included in the data: ''basic data sets'' and ''extra data sets.'' The basic data sets are used for evaluating the room impulse response-convolved speech data to simulate the various reverberations. The extra data sets consist of simulated data and corresponding real recorded data. Evaluation tools are presently only provided for the basic data sets and will be delivered to the extra data sets in the future. The task of CENSREC-4 with a basic data set appears simple; however, the results of experiments prove that CENSREC-4 provides a challenging reverberation speech-recognition task, in the sense that a traditional technique to improve recognition and a widely used criterion to represent the difficulty of recognition deliver poor performance. Within this context, this common framework can be an important step toward the future evolution of reverberant speech-recognition methodologies.

In this study, we propose a method of classifying speech under stress using parameters extracted from a physical model to characterize the behavior of the vocal folds. Although many conventional methods have been proposed, feature parameters are directly extracted from waveforms or spectrums of input speech. Parameters derived from the physical model can characterize stressed speech more precisely because they represent physical characteristics of the vocal folds. Therefore, we propose a method that fits a two-mass model to real speech in order to estimate the physical parameters that represent muscle tension in the vocal folds, vocal fold viscosity loss, and subglottal pressure coming from the lungs. Furthermore, combinations of these physical parameters are proposed as features effective for the classification of speech as either neutral or stressed. Experimental results show that our proposed features achieved better classification performance than conventional methods.

Voice activity detection (VAD) plays an important role in speech processing including speech recognition, speech enhancement, and speech coding under noisy environments. We have developed an evaluation framework for VAD under noisy environments, named CENSREC-1-C. We designed this framework for simple isolated utterance detection and hence, this framework consists of noisy continuous digit utterances and evaluation tools for VAD results. We define two evaluation measures, one for frame-level detection performance and the other for utterance-level detection performance. We also provide the evaluation results of a power-based VAD method as a reference.

This qualitative research advocates for prioritizing Critical and Creative Thinking in professional design over empathy. The study involved 74 undergraduate Product Design and Engineering students from Brazil, Portugal, and India to explore the relationship between these thinking skills and sustainability. The students' Critical and Creative Thinking levels were evaluated using rubrics developed by Shively et al. ( ) and a multi-level framework developed by Ceschin & Gaziulusoy (2019) was applied to identify sustainable innovation levels. The research highlights the need to enhance tertiary students' skills in addressing wicked problems, a concern recognized by the Organization for Economic Co-operation and Development for the 21st-century workplace. This research contributes to the ongoing debate on the significance of Critical and Creative Thinking in professional design practice and emphasizes the importance of integrating sustainability considerations into design education.

When evaluated with a spatially uniform irradiance, an imaging sensor exhibits both spatial and temporal variations, which can be described as a three-dimensional (3D) random process considered as noise. In the 1990s, NVESD engineers developed an approximation to the 3D power spectral density for noise in imaging systems known as 3D noise. The goal was to decompose the 3D noise process into spatial and temporal components identify potential sources of origin. To characterize a sensor in terms of its 3D noise values, a finite number of samples in each of the three dimensions (two spatial, one temporal) were performed. In this correspondence, we developed the full sampling corrected 3D noise measurement and the corresponding confidence bounds. The accuracy of these methods was demonstrated through Monte Carlo simulations. Both the sampling correction as well as the confidence intervals can be applied a posteriori to the classic 3D noise calculation. The Matlab functions associated with this work can be found on the Mathworks file exchange ["Finite sampling corrected 3D noise with confidence intervals," .].

This paper introduces the velocity-dependent friction with the Stribeck effect into the moving load model for the vibration of a car disc brake. By solving its corresponding eigenvalue problem, a bounded region of instability is obtained for the rotating speed of the disc versus the friction coefficient at the disc/pads interface, which is compatible with observed squeal phenomenon of a car disc brake.

Rotating cylinder (RC) technique is widely used for flow corrosion testing. However, this test configuration has limitations. Particularly, integrity of corrosion products films formed on the RC surface can be affected. The objective of this work is to show how intense the stresses in corrosion product films can be at high rotation speeds. In such cases, failure of the films is possible due to inertial forces rather than other factors, such as flow, leading to erroneous results. Consequently, theoretical calculation of stresses in films has been performed and a case of corrosion product film failure assessed using a fracture mechanics approach.

En el presente trabajo se estudia el proceso de friction stir spot welding de planchuelas de aleación de aluminio AA6082 utilizando dos métodos de cálculo sucesivos. En una primera etapa se modela la inserción del perno en el material a soldar como un problema unidimensional axisimétrico no estacionario.De este caso se extrae el campo de temperaturas que es utilizado como campo de condiciones térmicas iniciales al momento de modelar el proceso de permanencia en el paso siguiente. Esta segunda etapa del proceso se realiza mediante un modelo bidimensional axisimétrico considerando al material constitutivamenteviscoplástico y, consecuentemente, resolviendo un problema de flujo de Stokes con viscosidades no lineales. Como resultados de este caso se obtienen los campos de velocidades, temperaturas y tensiones para todo el continuo. Las estimaciones realizadas se comparan con resultados experimentales de soldaduras de punto por fricción agitación.In this work, the friction stir spot weldi...

Resumen. En los canales de ensayos hidrodinámicos donde la recirculación del fluido se realiza mediante una conducción de sección considerablemente inferior a la de la zona de pruebas, surge el inconveniente de la formación un chorro de alta velocidad que produce condiciones inaceptables de operación. Por lo tanto, es imperativo instalar un elemento disipador ubicado en la zona de vertido, procurando lograr condiciones de uniformidad y regularidad en el campo de velocidades en la zona de mediciones. Dicho disipador de energía cinética consiste usualmente en una serie de mallas o enrejados que actúan como promotores de vórtices de tamaño muy inferior al del chorro principal, que en virtud de sus dimensiones, se disipan rápidamente. Los fenómenos involucrados en este tipo de componente son difíciles de predecir con precisión debido fundamentalmente a las condiciones de flujo turbulento prevalecientes en las inmediaciones del mismo. Esto dificulta los cálculos, motivando la necesidad de realizar modelos computacionales con vistas a obtener criterios razonables para el diseño preliminar. En este trabajo se presenta un modelo por elementos finitos del colector de

El proceso de soldadura de punto por friccion consiste en una herramienta giratoria que, a traves de la presion y el calor generado por el trabajado mecanico, logra la union de las piezas. En este trabajo se modelo dicho proceso utilizando la tecnica de elementos finitos. Se implemento un modelo termomecanico axisimetrico de elementos finitos con el fin de reducir el costo computacional. Se implemento una malla adaptativa para poder simular el proceso de insercion de la herramienta en el material. Los resultados de simulaciones con distintos parametros de proceso nos permitieron reconocer los efectos sobre la zona termomecanicamente afectada, la cual esta relacionada con la resistencia de la soldadura.

Friction stir spot welding (FSSW) is a novel process of metal joining. In the present work, the authors analysed the possibility of using this process to solve current problems in shipbuilding industry regarding small vessels by replacing the current arc welding techniques with the aforementioned process. Numerical simulation was carried out by the multiple purpose solver framework for Finite Element Method with a novel modelling approach. The problem was solved using a coupled mechanics system of equations in an axisymmetric continuum where material velocities were calculated in three dimensions, coupled with pressure and thermal fields. The heat source was calculated as a consequence of internal friction dissipation only. Two boundary conditions were analysed, adiabatic and with heat dissipation. Experimental welding tests were performed using a milling machine. Comparison between numerical modelling results and experimental FSSW testing results was done and analysed in detail.

Rotating cylinder (RC) technique is widely used for flow corrosion testing. However, this test configuration has limitations. Particularly, integrity of corrosion products films formed on the RC surface can be affected. The objective of this work is to show how intense the stresses in corrosion product films can be at high rotation speeds. In such cases, failure of the films is possible due to inertial forces rather than other factors, such as flow, leading to erroneous results. Consequently, theoretical calculation of stresses in films has been performed and a case of corrosion product film failure assessed using a fracture mechanics approach.

In this paper the influence of a surface fatigue crack on vibration behaviour of tee-welded plates was studied and results compared to the influence of machined through-thickness cuts on the dynamic response of cantilever beams. Comparison of experimental data with two and three dimension finite element modelling results was also carried out and discussed. Detection threshold using natural frequencies shift was found and compared to literature. The influence of naturally grown fatigue cracks on the oscillation frequencies was analysed and compared to two and three-dimensional numerical modelling results. An experimental detection threshold was found using the variation of the first mode natural frequencies. The power density spectra of the acceleration signals were analysed. Crack shape was found important for the detection threshold of the method. It was found that small size semicircular fatigue cracks do not noticeably modify the beam natural frequency but generate integer harmonics of the vibration modes that provoked stresses at the samples surface affected by the crack. The harmonics found were found to be generated by the breathing behaviour of the fatigue crack. A detection threshold using this spectral analysis was found to be lower than those found by using frequency shifts. The results obtained showed the ability of the experimental technique to detect cracks from a size of 0.6% of the cross section area, at 55% of the fatigue lifespan, 35% earlier than the other method studied.

Around 20 % of world population lives without electricity access, most of them are concentrated in Sub-Saharan rural areas. Traditional approaches to electrify rural areas imply capital intensive infrastructures and large investments, while DC microgrids, based on renewable sources and storage systems, can be easily implementable and lead to cost effective solutions. The use of super efficient appliances can dramatically reduce the households electricity consumption, leading to smaller and cheaper systems. In this study an analysis of the use of efficient DC appliances is performed starting by essential energy services. Solar home system design optimization can be achieved by the evaluation of irradiation variation and the load requirements, finding the most cost-effective solution. Rural electrification can have a major impact to drastically improve the quality of life of millions of people through the sustainable use of solar energy.

Climbing robots that integrate an articulated arm as their main climbing mechanism can eventually take advantage of their arm for plane transition and thus to operate on 3D structures rather than only climbing planar surfaces. However, they are usually slower than wheel based climbing robots. Within this research we address this problem by integration of a light-weight arm and adhesion mechanism into an omnidirectional wheel based climbing robot, thus forming a hybrid mechanism that is agile in climbing and still able to perform plane transition. A 2DOF (Degree of Freedom) plannar mechanism with 2 linear actuators was designed as a light-weight manipulator for the transition mechanism. Furthermore, we customized and developed actuated switchable magnets both for the robot chassis and also as the adhesion unit of the arm. These units allow us to control the amount of magnetic adhesion force, resulting in better adaptation to different surface characteristics. The adhesion units are safe for climbing applications with a very small power consumption. The conceptual and the detailed design of the mechanisms are presented. The robots were developed and successfully tested on a ferromagnetic structure.

This work aims to study the effect of solid lubrication combined with a liquid lubricant in a cooperative lubrication regime. The solid lubricant consists of sintered composites, which contain solid lubricant dispersed in a metallic matrix. The durability of the lubricious regime (μ < 0.2) was studied. The combined action significantly increased the durability of the lubricious regime (3 orders of magnitude). Additionally, the use of 3D triboscopy made it possible, using an original approach, to verify a significant increase in the friction coefficient at the dead centres of the strokes. This difference between the friction coefficients was discussed in terms of the debris accumulation and the change in the lubrication regime. A preponderant role was assigned to the accumulation of debris.

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This work aims to study the effect of solid lubrication combined with a liquid lubricant in a cooperative lubrication regime. The solid lubricant consists of sintered composites, which contain solid lubricant dispersed in a metallic matrix. The durability of the lubricious regime (μ &lt; 0.2) was studied. The combined action significantly increased the durability of the lubricious regime (3 orders of magnitude). Additionally, the use of 3D triboscopy made it possible, using an original approach, to verify a significant increase in the friction coefficient at the dead centres of the strokes. This difference between the friction coefficients was discussed in terms of the debris accumulation and the change in the lubrication regime. A preponderant role was assigned to the accumulation of debris.

The production of self-lubricating composites containing second phase particles is one of the most promising choices for controlling friction and wear in energy efficient modern systems. To gain a better understanding of the wear behaviour of such materials, Fe-Si-C matrix composites containing solid lubricants added during the mixing step were studied in this work. The samples were produced using powder metallurgy route, with total contents of 5, 7.5 and 10% in terms of volume of hexagonal boron nitride (hBN) and graphite mixtures as the solid lubricants. The composite's tribological properties were evaluated under reciprocating sliding conditions and their mechanical properties were tested using tensile tests. Additionally, after interruptions at different stages of the reciprocating tests, the wear scars were characterised by Raman spectroscopy and scanning electronic microscopy, to evaluate the evolution of the wear with test time. Higher total solid lubricant contents greatly increased the scuffing resistance of the composites, but decreased the mechanical properties. Furthermore, increasing the hBN content reduced both properties. Among the composites studied, the samples containing 1% vol hBN and 9% vol graphite showed the best combination of mechanical and tribological properties.

Detailed analysis of bio-oil produced by hydrothermal liquefaction of marine micro algae. Detailed analysis of aqueous phase byproduct from hydrothermal liquefaction of marine micro algae. First application of FT-ICR MS to algal HTL bio-oils. ID of high MW nitrogen compounds and their distribution in HTL oil and aqueous phase byproduct.

Isobaric vapor-liquid equilibria of methyl tert-butyl ether (MTBE)-methanol, MTBE-methanol-calcium chloride, and MTBEmethanol-lithium chloride mixtures were measured at 93.57 kPa using a Malanowski equilibrium still which circulates both the vapor and liquid phases. The experimental results of the salt-free system showed that MTBE-methanol forms a minimum boiling azeotrope of 69.80 mol.-% MTBE at 93.57 kPa and 322.67 K. The experimental results of the salt-free system were predicted using the original UNIFAC and the UNIFAC-Dortmund methods, where the vapor-phase compositions were predicted with root-mean-square deviations (RMSD) of 0.0046 and 0.0091, respectively, and the bubble point temperatures were predicted with RMSD of 0.36 and 0.71 K, respectively. The Wilson and the nonrandom two-liquid (NRTL) models could satisfactorily correlate the experimental data of the salt-free mixtures with RMSD in the vapor-phase compositions calculation of 0.0047 and 0.0059, respectively and in bubble-point temperatures calculation of 0.20 and 0.40 K, respectively. Addition of either calcium chloride or lithium chloride to the MTBE-methanol mixtures resulted in salting-out the MTBE and shifting the azeotropic point to a vapor composition of 76.5 mol.-% and 93.0 mol.-% MTBE, respectively. Both the Tan-Wilson and Tan-NRTL models could satisfactorily predict the bubble-point temperatures of the MTBE-methanol-calcium chloride mixtures with RMSD of 0.143 and 0.130 K, respectively, and the vapor phase compositions with RMSD of 0.0055 and 0.0041, respectively.

The duplex stainless steels are materials, which present a better combination of mechanical properties and stress corrosion resistance than ferritic and/or austenitic stainless steels. However, in the processing of these materials, hot working is a critical step that leads in many cases to the generation of cracks and/or to an unacceptable surface finish. In the present work, it has been observed that severe localisation of plastic flow into superficial shear bands is the responsible for transversal cracking during hot rolling of duplex stainless steels. Torsion is a deformation mode involving pure shear and it has been found to be very useful in tackling the problem of damage formation in these materials under hot working. The effects of the strain, temperature and the strain rate on the damage formation in duplex stainless steels have been analysed in order to improve the hot workab ility of this material. Microstructural observations reveal that cracks mainly concentrate at the f...

Very often Nb contributes to the strength of a microalloyed steel beyond the expected level due to the grain size strengthening resulting from thermomechanical processing. Two different mechanisms are behind this phenomenon, and both of them have to do with the amount of Nb remaining in the solution after hot rolling. The first of them is the increase of the hardenability of the steel due to Nb, and the second one is the fine precipitation of NbC in ferrite. The contribution of the precipitates to the work hardening of two thermally and thermomechanically processed microalloyed steels is addressed in this work and this contribution has been integrated into previously developed models by the authors for ferrite-pearlite microstructures. An L eff is considered through the effective spacing associated to the different obstacles and their interactions with the moving dislocations. The model obtained shows good agreement with the experimental tensile curves from the end of yield point elongation to the onset of necking.

Often, Nb contributes to the strength of a microalloyed steel beyond the expected level because of the grain size strengthening resulting from thermomechanical processing. Two different mechanisms are behind this phenomenon, and both of them have to do with the amount of Nb remaining in solution after hot rolling. The first of them is the increase of the hardenability of the steel as a result of Nb, and the second one is the fine precipitation of NbC in ferrite. Three Nb microalloyed steels were thermomechanically processed in the laboratory and coiled at different temperatures to investigate the effect of Nb content on the tensile properties. The extra strength was linearly related to the Nb remaining in solution after the hot working. The maximum contribution from Nb was reached for a coiling temperature of 873 K (600 °C).

A series of available equations allows the yield and the tensile strength of low carbon ferrite-pearlite microstructures to be expressed as a function of the optical grain size, steel composition and interstitials in solution. Over the years, as the complexity of steel microstructures has increased, some additional terms have been added to account for precipitation and forest dislocation contributions. In theory, this opens the door for an extension of these equations to bainitic microstructures. Nevertheless, there is a series of difficulties that needs to be overcome in order to improve prediction accuracy. In the present work, different microstructures (ferrite-pearlite, bainite, quenched, and quenched and tempered) were produced and tension tested in a C-Mn-Nb steel. Optical microscopy and EBSD (Electron Back Scattered Diffraction) were applied and the results were compared as a function of the tolerance angle. Based on this work, an adaptation to Pickering's equation is proposed, including its extension to other microstructures rather than ferrite-pearlite.

The EBSD technique is a useful tool to characterize deformation microstructures. In this study a 304 stainless steel was hot deformed to different strains in torsion mode. The application of the above-mentioned technique focused on the characterization of the high angle boundary distribution evolution under strain. Special emphasis was given to the 3 boundaries. It was observed that as the deformation increased the twin character was progressively lost and at the same time, some of the twins appear to be curved in the microstructure. The orientation analysis carried out inside the grains led to a classification of the grains according to the way that in-grain orientation spreads develop.

This study explores a large language model (LLM)-based system enhancing design methodology education, focusing on design for environment (DfE). By integrating GPT-4 with DfE guidelines and a dual-loop structured learning workflow, we developed an interactive system addressing persistent challenges in design method learning. Through personalised exercises and systematic feedback, our system guided beginners in applying DfE strategies while fostering self-directed learning. Experiments involving 30 participants revealed significant improvements across Bloom's taxonomy domains, particularly when learners demonstrated sustained or developing proactiveness. This study analysed how LLM-based systems can support education for various design for X methodologies through generalizable interaction frameworks.

This work is focused on the aerodynamic analysis of a small satellite provided with a deployable aerobrake. The satellite is intended to perform a completely aerodynamic de-orbiting maneuver from Low-Earth-Orbit. A brief discussion about the aerodynamic effects of the position of the aero-brake along the longitudinal axis of a simplified axisymmetric system is presented. Moreover, a more complex architecture, envisaging deployable solar panels for the enhancement of power generation along the orbital path, is proposed and analyzed. The present paper is aimed at the evaluation of the influence of such a configuration on the satellite aerodynamic parameters. Computations have been carried out by means of a Direct Simulation Monte Carlo (DSMC) code at altitude of 150 km, velocity of 7800 m/s and in the interval of angle of attack 0-180 deg with a spacing of 10 deg. The results verified that the deployable solar panels strongly influence Aerodynamics of the satellite. One of the most relevant aspects is the variation of the longitudinal stability equilibrium that becomes more stable. Furthermore, the deployable solar panels increase the aerodynamic drag when the aero-brake is closed, affecting the drag modulation capability.

HyPlane is the Italian aerospaceplane proposal targeting, at the same time, both the space tourism and point-to-point intercontinental hypersonic flights. Unlike other aerospaceplane projects, relying on boosters or mother airplanes that bring the vehicle to high altitude, HyPlane will take off and land horizontally from common runways. According to the current project, HyPlane will fly sub-orbital trajectories under high-supersonic/low-hypersonic continuum flow regimes. It can go beyond the von Karman line at 100 km altitude for a short time, then starting the descending leg of the trajectory. Its aerodynamic behavior up to 70 km have already been studied and the results published in previous works. In the present paper some aspects of the aerodynamic behavior of HyPlane have been analyzed at 80, 90 and 100 km. Computer tests, calculating the aerodynamic parameters, have been carried out by a Direct Simulation Monte Carlo code. The effects of the Knudsen, Mach and Reynolds numbers have been evaluated in clean configuration. The effects of the aerodynamic surfaces on the rolling, pitching and yawing moments, and therefore on the capability to control attitude, have been analyzed at 100 km altitude. The aerodynamic behavior has been compared also with that of another aerospaceplane at 100 km both in clean and flapped configuration.

Aside from anthropometric data tables, 3D shape models of the human body are becoming increasingly common and call for new product sizing methods based on 3D anthropometry. Though some shape model-based methods exist, most of them focus on mathematical clustering and do not discuss the usability of the clustering results for product design. In this paper, a new shape-model based clustering method for product sizing is presented that takes into account both shape information and usability for designers. The new method, called constrained k-medoids clustering, is applied on a shape model of 100 human heads. It is compared to a partitioning around medoid (PAM) clustering of anthropometric measurements of the same 100 heads (i.e., feature-based), as well as to PAM clustering of the shape model (i.e., shape based). Results show that both shape-based and constrained clustering perform better than feature-based clustering, with an average size-weighted variance (SWV) of 62 × 10 3 ± 16 × 10 3 and 66 × 10 3 ± 26 × 10 3 as compared to 72 × 10 3 ± 12 × 10 3 , respectively. The average point-to-point distances in shape-based and constrained k-medoids were found to be similar to those of feature-based k-medoids, indicating that using 3D-anthropometry for product sizing will not have a negative impact on designer workload and/or a higher cost to implement more sizes. The results suggest that for head-based products, which require accurate shape and size fit, sizing systems should be created using either shape-based or constrained k-medoids, with the latter being slightly less accurate but more intuitive for further design and verification.

The most common monitoring method of metal–oxide surge arrester is based on leakage current measurement, particularly, the component of resistive leakage current. Nowadays, there are several analytical methods used to extract the resistive leakage current. These analytical methods need both current and voltage signals. However, in fact, electrical system voltage contains harmonics and because of these harmonics, it may affect the accuracy of resistive leakage current extraction methods in different ways. The calculated results may be in error or incorrect. It can lead to erroneous evaluation or fault assessment. This paper attempts to clarify the influence of harmonics voltage on current extraction methods. Eventually, the results can be utilized for choosing the extraction method which is suitable for the measured data or limitation of each algorithm.

The exchange coupling between antiferromagnetic/ferromagnetic (AF/FM) materials shifts the hysteresis loop along the field axis by an amount known as exchange bias field. It is believed that the ferromagnetic thickness dependence of the exchange bias field follows an inverse proportionality law. This has experimentally and theoretically been confirmed for FM thicknesses below the FM domain wall width. In this work we demonstrate that this exchange bias dependence is broken for certain FM spin structures, even though in FM layers thinner than the FM domain wall width. We present experimental data of FeF 2 /FeNi bilayers that deviate from the inverse proportionality law, as well as a theoretical calculation that accounts for the results.

Incorporation of clay in polymers is known to improve mechanical properties such as tensile modulus and tensile strength, but to generally decrease elongation at break and toughness. However, recent studies reported an increase in elongation at break for linear low density polyethylene based nanocomposites. In this work, the tensile properties of clay micro-and nanocomposites based on high density polyethylene (HDPE), low density polyethylene (LDPE) and linear low density polyethylene (LLDPE) of similar molecular weights were evaluated. LLDPE micro-and nanocomposites exhibited an extraordinary enhancement in toughness compared to LDPE or HDPE microcomposites. Based on electron microscopy and on acoustic emission and volume strain measurements during tensile testing, micro-mechanisms of deformation in polyethylene/clay micro-and nanocomposites were proposed.

The electrical contact resistance between the Gas Diffusion Layer (GDL) and the BiPolar Plate (BPP) used in Polymer Electrolyte Membrane Fuel cells (PEMFCs) is responsible for a substantial amount of Ohmic losses in the electrical power generator. This contact resistance was measured for a variety of carbon paper GDLs under cyclic mechanical compression between 0 and 8 MPa according to the Transmission Line Method (TLM). Contact resistance and strain hysteresis were noticed as a result of cyclic compression. The effect of GDL structure and composition on the electrical contact resistance and its cyclic behaviour has been evaluated. The contact resistance was found to decrease non-linearly with compression; more than 75% of reduction was attained at 2.5 MPa. The electrical contact resistance's difference between the different cycles of compression decreased with compression loads. Graphitised straight fibre Toray GDLs demonstrated the smallest contact resistance followed by the MicroPorous Layer (MPL) and the felt fibre substrate. The SGL straight fibre substrates exhibited the highest contact resistance. The felt fibre structure exhibited the smallest difference rates between the cycles of compression.

In order to better understand the thermomechanical behaviors of Ti 3 SiC 2 and Ti 2 AlC ceramics, sintered by spark plasma sintering process (SPS), ultrasonic pulse echography in "long bar mode" (US) and acoustic emission (AE) techniques are applied. High-temperature investigations of the evolution of Young's modulus (E) and AE activity are carried out up to 1 473 and 1 623 K. Results show a decrease of E with increasing temperature which is more marked around maximal temperature of the thermal cycle for Ti 2 AlC material. Moreover, the increase of the maximal temperature of the thermal cycle influences the number of recorded cumulated hits. Both measurements (US þ AE) highlight the role of the plastic deformation mechanism (motion of dislocation) activated over the brittle-to-plastic transition temperature.

Ca 1Àx Pr x MnO 3Àd (x=0, 0.05, 0.15, 0.1, 0.2, 0.4, 0.67; d=0.02) samples were prepared by a solid-state reaction method. X-ray diffraction analysis showed that all samples prepared were of single phase with orthorhombic structure. Electrical resistivity measurements from room temperature to 1300 K showed that a metallic conducting tendency dominated at high temperatures. The hopping nature of the charge carriers was well interpreted in the framework of polaron theory. The Seebeck coefficient was measured in the same temperature interval, and its concentration dependence was analyzed using the high-temperature (HT) thermopower theory proposed by Marsh-Parris. The thermal conductivity and the figure of merit of the prepared samples were also compared with those of other similar perovskite compounds. The observed figure of merit of the sample with x=0.15 was Z=1.5 Â 10 À4 K À1 at T=1100 K, indicating a good potential for application as a HT thermoelectric material.

Ca 1|x Dy x MnO 2.98 (0[x[0.2) m•MdÁ« Pham Xuan ThaoEÒ GE´c¹¹ERº×v k¤ae[ÈwZpåw@åwÞ¿Èw¤ÈEim}eAeNmWZ^[C9231292 Îì §\üSCû¬®ä 11 High temperature thermoelectric properties of Ca 1|x Dy x MnO 2.98 ( x0, 0.05, 0.10, 0.15, 0.20) have been measured in the temperature range from 300 to 1273 K. Ca 1|x Dy x MnO 2.98 ( x0.10, 0.15, 0.20) exhibited the metalinsulator transition in the relation between electrical resistivity and temperature, and the transition temperature increased with increasing x. Electrical resistivity in the metallic region decreased with increas ing x content, reecting the increase of Mn 3{ ions, and the absolute value of Seebeck coecient (a) also decreased. Thermal conductivity ( l) did not considerably change with increasing x content. Among substit uted CaMnO 3 , the highest gure of merit of Z1.05~10 |4 K |1 was obtained for x0.05 and 0.10 at 773 K, while a Z1.63~10 |4 K |1 was obtained for x0.20 at 1273 K.

Constant-curvature solutions lie at the very core of gravitational physics, with Schwarzschild and (anti-) de Sitter being two of the most paradigmatic examples. Although such a kind of solutions are very wellknown in general relativity, that is not the case for theories of gravity beyond the Einsteinian paradigm. In this article, we provide a systematic overview on fðRÞ models allowing for constant-curvature solutions, as well as of the constant-curvature solutions themselves. We conclude that the vast majority of these fðRÞ models suffer, in general, from several shortcomings rendering their viability extremely limited, when not ruled out by physical evidence. Among these deficiencies are instabilities (including previously unforeseen strong-coupling problems) and issues limiting the predictive power of the models. Furthermore, we will also show that most fðRÞ-exclusive constant-curvature solutions also exhibit a variety of unphysical properties.

STRIKE is a diagnostic calorimeter composed of 16 CFC tiles with unidirectional properties used to study the beams of particles generated in the SPIDER experiment. Two thermal cameras will be used to analyze the temperature of the tiles and reconstruct the bidimensional flux of energy striking the calorimeter. Most of the conventional methods used to evaluate the inverse heat flux are unbearably time consuming; since the objective is having a tool for heat flux evaluation for STRIKE real time operation, the need to have a ready-to-go instrument to understand the beam condition becomes stringent. For this reason a neural network was chosen to perform this analysis. During the thesis work an existing convolutional neural network was optimized to retrieve the parameters of the beam from the thermographic images. In particular, starting from a network able to determine the position and the radius of a singular circular shape on a noiseless background, the possibility to recognize the po...