A Unified Method for First and Third Person Action Recognition

In this paper, a new video classification methodology is proposed which can be applied in both first and third person videos. The main idea behind the proposed strategy is to capture complementary information of appearance and motion efficiently by performing two independent streams on the videos. The first stream is aimed to capture long-term motions from shorter ones by keeping track of how elements in optical flow images have changed over time. Optical flow images are described by pre-trained networks that have been trained on large scale image datasets. A set of multi-channel time series are obtained by aligning descriptions beside each other. For extracting motion features from these time series, PoT representation method plus a novel pooling operator is followed due to several advantages. The second stream is accomplished to extract appearance features which are vital in the case of video classification. The proposed method has been evaluated on both first and third-person datasets and results present that the proposed methodology reaches the state of the art successfully.Comment: 5 page

Mechanical properties of AlSi10Mg alloy fabricated by laser melting deposition and improvements via heat treatment

Process optimization and heat treatment of AlSi10Mg aluminum alloy parts fabricated by laser melting deposition (LMD) based on coaxial powder feeding are conducted in this paper to improve manufacturing quality. The microstructures and mechanical properties of the LMD-built AlSi10Mg alloy parts are systematically investigated. Experimental results show the relative density of the block samples increase to 99.2% without larger pores and cracks after process optimization. The sample microstructures are found to display directional rapid solidification characteristics, with the Al-Si eutectic microstructure containing three microstructures being cellular, columnar dendrites and divergent dendrites. With solution and artificial aging heat treatments, Si atoms are rejected from the supersaturated Al matrix to form small Si granular particles. The heat treated samples display a uniform microstructure without heterogeneities and the microhardness remains stable at 118 HV. When the as-built sample is heat treated for solution time 2h, tensile strength increases from 292 MPa to 342 MPa due to the formation of strengthening phase Mg2Si

Welding of AA6061-T6 Sheets Using High-Strength 4xxx Fillers: Effect of Mg on Mechanical and Fatigue Properties

Al-Si-Mg 4xxx filler metals are widely used in aluminum welding owing to their excellent weldability and capability for strength enhancement by heat treatment. However, weld joints with commercial Al-Si ER4043 fillers often exhibit poor strength and fatigue properties. In this study, two novel fillers were designed and prepared by increasing the Mg content in 4xxx filler metals, and the effects of Mg on the mechanical and fatigue properties were studied under as-welded and post-weld heat-treated (PWHT) conditions. AA6061-T6 sheets were used as the base metal and welded by gas metal arc welding. The welding defects were analyzed using X-ray radiography and optical microscopy, and the precipitates in the fusion zones were studied using transmission electron microscopy. The mechanical properties were evaluated using the microhardness, tensile, and fatigue tests. Compared to the reference ER4043 filler, the fillers with increased Mg content produced weld joints with higher microhardness and tensile strength. Joints made with fillers with high Mg contents (0.6–1.4 wt.%) displayed higher fatigue strengths and longer fatigue lives than joints made with the reference filler in both the as-welded and PWHT states. Of the joints studied, joints with the 1.4 wt.% Mg filler exhibited the highest fatigue strength and best fatigue life. The improved mechanical strength and fatigue properties of the aluminum joints were attributed to the enhanced solid-solution strengthening by solute Mg in the as-welded condition and the increased precipitation strengthening by β″ precipitates in the PWHT condition

Submerged dissimilar friction stir welding of AA6061 and AA7075 aluminum alloys: microstructure characterization and mechanical property

The possibility of underwater dissimilar friction stir welding of AA6061 and AA7075 aluminum alloy was explored to overcome the problem of hardness loss in different microstructural zones. Optical microscopy and electron backscattered diffraction were employed to characterize the microstructure of the joint. Vickers hardness measurements were conducted on the cross-section of the joint to evaluate the mechanical strengths. The results showed that the microstructure of the AA7075 side had undergone the same mechanisms as those occurring during conventional friction stir welding. In the case of the AA6061 side, in addition to typical restoration mechanisms, the grain subdivision was observed. The AA7075 side had finer grains compared to the AA6061 side, which may be related to the different morphology and size of precipitates. Moreover, friction stir welding caused a reduction in the hardness values in all the microstructural areas compared to those of corresponding base materials. For example, it caused a reduction in the hardness of a thermomechanically affected zone from 105 HV to 93 HV in the AA6061 side, and from 187 HV to 172 HV in the AA7075 side. The underwater media improved the overall hardness values in thermo-mechanically affected zones (13% reduction in hardness) compared to those reported in literature (57% reduction in hardness)

A new approach to determine tensile stress-strain evolution in semi-solid state at near-solidus temperature of aluminum alloys

Accurate determination of the materials’ strength and ductility in the semi-solid state at near-solidus temperatures is essential, but it remains a challenging task. This study aimed to develop a new method to determine the stress-strain evolution in the semi-solid state of aluminum alloys within the Gleeble 3800 unit. Stress evolution was determined by the newly developed “L-gauge” method, which converted the displacement of the “restrained” jaw, measured using an L-gauge, into the force. This method gives the possibility to determine the flow stress more accurately, especially for the very low stress rang (1–10 MPa) in the semi-solid state at near-solidus temperatures. The digital image correlation technique implemented in the Gleeble unit allowed effective measurement of the heterogeneous strain fields evolving within the specimen under tensile loading. Therefore, the stress-strain curves measured in the semi-solid state help to better understand the alloy’s susceptibility to hot tearing. The results of an AA6111 alloy under different liquid fractions (2.8% at 535 °C and 5.8% at 571 °C) were demonstrated. The reliable stress-strain data and heterogenous strain distribution are beneficial to develop the thermomechanical models and hot-tearing criteria

Grain Structure Formation and Texture Modification through Multi-Pass Friction Stir Processing in AlSi10Mg Alloy Produced by Laser Powder Bed Fusion

A new strategy is proposed to modify the grain structure and crystallographic texture of laser-powder bed fusion AlSi10Mg alloy using multi-pass friction stir processing (FSP). Accordingly, 1–3 passes of FSP with 100% overlap were performed. Scanning electron microscopy and electron backscattered diffraction were used for microstructural characterization. Continuous dynamic recrystallization and geometric dynamic recrystallization are the governing mechanisms of grain refinement during FSP. The stir zones have bimodal grain structures containing large and fine grains. The multi-pass FSP caused a considerable increase in the volume fraction of the large-grained area in the stir zone, which contained higher values of low-angle boundaries and sharp shear texture components of B(11¯2)[110] and B¯¯¯(1¯12¯)[1¯1¯0]. The formation of low-energy grain boundaries in the stir zone and alignment of the low-energy crystallographic planes with the surface of the sample made the strategy of using multi-pass FSP a promising candidate for corrosion resistance enhancement in future studies. Moreover, the detailed evolution of the grains, texture components, grain boundaries, and Si particles is discussed

The conjugal violence and the divorce in Iran

Dans les sociétés patriarcales comme l'Iran où l'inégalité entre les hommes et les femmes est élevée, l'exercice de la violence pour résoudre les conflits familiaux a donc une légitimité implicite. Ainsi les hommes pensent que la violence est une façon légitime et plus simple et plus efficace. Cependant, aujourd'hui le fait de la violence, en tant qu'une façon appropriée de résoudre les conflits dans les familles, va perdre petit à petit sa légitimité dans les sociétés patriarcales aussi ; parce que les femmes ne se soumettent plus, facilement à la violence. Comme le montre l'augmentation des femmes qui se présentent aux tribunaux pour demander le divorce en raison de violence conjugale, ou les femmes qui se suicident, ou s'enfuient de leur domicile, la société traditionnelle iranienne confirme ces faits. Concernant l'influence de la violence sur la déstabilisation des familles en Iran, nous avons introduit deux hypothèses principales dans ce mémoire de thèse. Première hypothèse, il s'agit de l'existence d'une relation significative entre le divorce et la violence conjugale physique dans la société actuelle d'Iran. En deuxième hypothèse, nous avons conclu qu'aujourd’hui dans la société iranienne le niveau de la violence qui cause le divorce est encore assez élevé. Selon notre hypothèse, ce niveau de violence est dépendant de plusieurs éléments démographiques et socio-économiques. Pour vérifier la vraisemblance de nos hypothèses, nous avons effectué une enquête. Les résultats de notre enquête montrent que le Degré de la Violence qui Cause une demande du Divorce (DVCD) en tant que la variable dépendante diffère significativement des sept variables indépendantes, à savoir : le niveau d'études de femmes, leur opinion sur la violence conjugale, le niveau des études des pères des femmes, le lieu d'habitation, le lieu d'habitation parentale, l'âge des femmes et le nombre d'enfantsIn the patriarchal societies like Iran, the disparity between men and women is high and thus the exercise of the violence to resolve the family conflicts has an implicit legitimacy. There, man assumes that the violence is a simpler and more effective and justifiable way. However, today even in patriarchal society the women do not easily slender to the violence and the trend of resolving the family conflicts through violence is becoming less common. According to the Iranian traditional society, this attitude has increased the number of women who contact the courts to get the divorce or commit suicide, or run away from their house. Concerning the influence of the violence on the destabilization of families in Iran, we have proposed two main hypotheses in this report. First hypothesis, it is about the existence of a significant relation between the divorce and the physical conjugal violence in the current society of Iran. In the second hypothesis, we have concluded that there is a high ratio of violence that is causing the divorce. According to our hypothesis, this level of violence depends on several demographic and socioeconomic elements. To verify the credibility of our hypotheses we have conducted a survey. The results show that the degree of the violence which causes a request of the divorce as a dependent variable varies significantly with seven independent variables, namely: the level of women education, their opinion on the conjugal violence, the education level of the women's fathers, living place, parental living place, the age of the women and the number of childre

Effect of Cu, Mg and Fe on solidification processing and microstructure evolution of Al-7Si based foundry alloys

Au cours de la dernière décennie, les alliages de fonderie Al-Si ont été utilisés de plus en plus comme une alternative appropriée à la fonte dans la fabrication de composants de moteurs (par exemple les culasses). Les objectifs du projet étaient d'étudier l'effet des éléments tels que le cuivre, le magnésium et le fer sur les défauts de solidification, et sur l'évolution des phases poste-eutectiques les alliages de fonderie Al-Si. Tout d’abord, les travaux antérieurs sont soigneusement examinés afin de mieux comprendre les charges de fatigue thermomécanique, les caractéristiques, les exigences et les matériaux applicables dans les composantes du moteur. Par la suite, les défauts de solidification (tendance de fissuration à chaud (HTS) et microporosité) des alliages à base d’Al-Si ont été évalués. En augmentant la teneur en Cu et en Fe des alliages, la valeur de HTS et de microporosité ont été augmentées. Les indices théoriques de fissuration à chaud ont été simulés avec un modèle de microségrégation multiphasique avec rétrodiffusion dans la phase primaire «multiphase back diffusion model». La corrélation obtenue entre les résultats expérimentaux (HTS) et les résultats simulés est excellente. L’effet de la composition chimique (Cu, Mg et Fe contenu) dans les alliages Al-Si sur l'évolution de la microstructure ont donc été étudiées. Les microstructures à l'état de coulée et à l'état de traitement thermique de mise en solution (SHT) ont été évaluées par les microscopies optique/électronique. Deux intermétalliques contenant du Mg (Q-Al5Cu2Mg8Si6, π-Al8FeMg3Si6) qui apparaissent avec une couleur grise sous le microscope optique ont été discriminés par des attaques chimiques que nous avons développées. L’analyse calorimétrique différentielle à balayage (DSC) a été utilisée pour examiner les transformations de phase survenant au cours du processus de chauffage et de refroidissement. Les calculs thermodynamiques ont été effectués pour évaluer la formation de la phase à l'état d'équilibre et hors-équilibre. Les résultats ont démontré que la séquence de solidification et la stabilité des intermétalliques contenant du Cu/Mg ont été fortement influencée par la composition chimique des alliages. La phase Q-Al5Cu2Mg8Si6 a été solidifiée soit à la même température ou plus tôt que la phase θ-Al2Cu en fonction de la teneur en Cu de l'alliage. Par ailleurs, les phases Q-Al5Cu2Mg8Si6 et π-Al8FeMg3Si6 qui étaient solubles à 505℃ dans l'alliage Al-7Si-1.5Cu-0.4mg, sont restées presque intactes dans l'alliage Al-7Si-1.5Cu-0.8mg wt.-%. Bien que l’intermétallique-AlCuFe a été à peine observé dans la microstructure de coulée, la réaction entre la phase primiare α-Al avec la phase β-Al5FeSi a causé la formation de la phase N-Al7Cu2Fe au cours de la mise en solution. La transformation de phase à l'état solide de la phase β-Al5FeSi à la phase N-Al7Cu2Fe a également été étudiée.Over the past decade, Al-Si based foundry alloys have increasingly been used as a suitable alternative for cast iron in the fabrication of engine components. This project was aimed to study the effect of Cu, Mg and Fe elements on solidification defects (hot rearing tendency and microporosity), and on evolution of post eutectic phases in the Al-7Si (wt.-%) based alloys. Initially, the previous works and the most pertinent literatures were thoroughly reviewed to elaborate the thermo-mechanical fatigue loads, characteristics, requirements and materials applicable in engine components (mainly cylinder-head). Subsequently, the solidification defects of the Al-Si based alloys were evaluated. By increasing Cu and Fe content of the alloys, the hot tearing sensitivity and the microporosity content of the alloys were both enhanced. Multiphase back diffusion model was utilized to simulate the theoretical hot tearing indices. A very good correlation was obtained between the experimental and the theoretical hot tearing indices. Effect of the chemistry (Cu, Mg and Fe content) on microstructure evolution of the Al-Si foundry alloys was consequently studied. As-cast and solution heat treated (SHT) microstructures of the alloys were evaluated by optical- and electron-microscopy. Two etchants were developed to discriminate the Mg-bearing intermetallics (Q-Al5Cu2Mg8Si6, π- Al8FeMg3Si6) under optical microscope. Differential scanning calorimetry (DSC) was utilized to examine the phase transformations occurring during heating/cooling process. Thermodynamic computations were carried out to assess the phase formation in the equilibrium/non-equilibrium conditions. According to the predicted/experimental results, the solidification sequence and the stability of Cu/Mg bearing intermetallics are strongly influenced by the chemistry of the alloys. Q-Al5Cu2Mg8Si6 phase was solidified either at the same temperature or earlier than θ-Al2Cu phase depending the Cu content of the alloy. Moreover, Q-Al5Cu2Mg8Si6 and π- Al8FeMg3Si6 which were soluble at 505℃ in the alloy Al-7Si-1.5Cu-0.4Mg, remained almost intact in the alloy Al-7Si-1.5Cu-0.8Mg wt.-%. Tough the AlCuFe- intermetallic was barely observed in the as-cast microstructure, the reaction of α-Al with the β-Al5FeSi phase caused the formation of the N-Al7Cu2Fe phase during SHT. The solid state phase transformation (precipitation temperature and mechanism) of β-Al5FeSi to the N-Al7Cu2Fe phase was also investigated

Application of cast Al–Si alloys in internal combustion engine components

Excellent thermal conductivity and lower density make Al–Si alloys a suitable alternative for cast iron in the fabrication of engine components. The increase in the maximum operation temperature and pressure of engines necessitates improving the thermomechanical fatigue performance of Al–Si alloys. This paper has two major parts focussing on the use of Al–Si based alloys in cylinder heads and engine blocks. In the first part, the structural stress–strain and material property requirements of cylinder heads are discussed. In addition, the physical and mechanical properties of different competing materials used in the manufacture of engine components are reviewed. The physical metallurgy, solidification sequence and thermal conductivity of Al–Si based alloys are reviewed. Also discussed is the effect of microstructural features on thermomechanical fatigue lifetime. This part also includes an overview of the strengthening mechanisms of cast Al–Si alloys, by dispersed phases and heat treatment. Demands to improve fuel economy and reduce emissions necessitate modifications in the materials and design of engine blocks. Wear resistance and low friction coefficient are the major characteristics required for engine block materials. In the second part, the most promising alternative approaches to manufacturing liner-less Al–Si alloy cylinder blocks are elaborated