Semantic Understanding of Scenes Through the ADE20K Dataset

International Journal of Computer Vision - Semantic understanding of visual scenes is one of the holy grails of computer vision. Despite efforts of the community in data collection, there are still...     

Effect of residual carbon on the sintering process of M2 high speed steel parts obtained by a modified metal injection molding process

In this article, we present the evolution of the microstructure during sintering of M2 high speed steel (HSS) parts obtained by a modified powder injection molding (PIM) process, which uses a new binder system based on a thermosetting resin. The most important characteristics of this process is that molding is carried out at room temperature by pouring the slurry (resin and tool steel previously mixed) directly into the mold. The mold is then heated to the curing temperature of the resin. The best mixture of polymer and steel powders was 60 pct volume of metal powder. The resin was removed by thermal debinding. The sintering process was carried out under vacuum atmosphere. We tested different debinding temperatures in order to retain residual carbon in the samples coming from the thermal degradation of the polymer. The best results were obtained at low debinding temperature (300 °C). In this case, residual carbon had a beneficial effect, extending the sintering temperature range by 100 deg, making it possible to reach very high density at temperatures as low as 1100 °C. The mechanism of this densification seems to be via supersolidus liquid phase (SPLS). The microstructural study of sintered parts revealed a homogeneous distribution of carbides that change their morphology with increasing temperature. Besides spherical M₆C carbides, which appear in all the temperature ranges studied, a new rodlike M₂C carbide appears.     

Mechanical,intergranular corrosion,and wear behavior of aluminum-matrix composite materials reinforced with nickel aluminides

This article presents experimental results of important properties of aluminum-matrix (AA 2014) composite materials reinforced with different intermetallics of the Ni-Al system. For the present study, the intermetallics are prepared either by mechanical alloying (MA) or by gas atomization (GA). The reinforced composite materials were manufactured by mixing the constituents, followed by uniaxial compacting of a preform and subsequent extrusion without canning or degassing. The present study considered the materials in the extruded state and after T6 heat treatment. Assessments were made from the viewpoint of microstructure (by means of optical and scanning electron microscopy (SEM)) and thermal characteristics (by differential scanning calorimetry (DSC)), with special emphasis on studying the reactions that take place between the matrix and the reinforcement and which produce a highly copper-enriched interphase. A study was also made of the effect of this reactivity on the mechanical properties and wear behavior of the composite materials, as well as the intergranular corrosion resistance of the materials in the extruded state.     

Beta-glucocerebrosidase gene locus as a link for Gaucher's disease and familial hypo-alpha-lipoproteinaemia

BACKGROUND: Gaucher's disease is the most common lysosomal storage disorder, caused by deficiency of glucocerebrosidase resulting from homozygosity for any of several mutations of the glucocerebrosidase gene locus. Affected people have decreased concentrations of LDL cholesterol (LDL-C) and HDL cholesterol (HDL-C). We assessed the association between mutations in the glucocerebrosidase locus and hypo-alpha-lipoproteinaemia. METHODS: We studied 258 people from 43 unrelated Spanish families. 57 participants were affected, 137 were non-affected carriers, and 64 were non-carriers. We determined glucocerebrosidase genotypes and measured plasmid lipids, apolipoproteins A-I, B, and E, and leucocyte glucocerebrosidase activity. FINDINGS: The most common glucocerebrosidase mutations were N370S (45%), L444P (23%), and G377S (5%). Deletions and recombinants accounted for another 5%, and point mutations in exons 5, 6, 9, and 10 were present in 12%. Affected participants had lower LDL-C and HDL-C concentrations than non-affected carriers (p<0.001) and non-carriers (p<0.001). HDL-C values were also significantly different between the non-affected carriers and non-carriers. Mutations at this locus may account for as much as 19.5% of the genetic variability in HDL-C in the population studied. INTERPRETATION: Heterozygosity for these mutations at the glucocerebrosidase locus does not result in clinical expression of Gaucher's disease but can decrease HDL-C concentrations. Given the high frequency of these mutations, the glucocerebrosidase locus might lead to familial low alpha-lipoproteinaemia in up to 2% of the general population and be one of the most common known genetic causes of HDL-C.     

6061 Al reinforced with zirconium diboride particles processed by conventional powder metallurgy and mechanical alloying

The homogenous distribution of the reinforcement phase is an essential condition for a composite material to achieve its superior performance. Powder metallurgy (PM) can produce metal matrix composites in a wide range of matrix reinforcement compositions without the segregation phenomena typical of casting processes. Particularly, mechanical alloying can be used to mix the matrix and reinforcement particles, enhancing the homogeneity of the reinforcement distribution. This work investigates the production of aluminium 6061 reinforced with zirconium diboride by mechanical alloying followed by cold pressing and hot extrusion, and compares the results with the same composite produced by conventional PM and hot extrusion. The incorporation of the ZrB₂ particles produces only a small increase in the material hardness, but a small decrease in the UTS when conventional PM is employed. Mechanical alloying breaks the reinforcement particle clusters, eliminates most of the cracks present in the surface of the reinforcement particles, decreases its size and improves its distribution. This enhancement of the composite structure, in addition to the metallurgical aspects promoted by mechanical alloying in the matrix, brings approximately 100% improvements in the composite UTS and hardness, compared with the composites obtained by PM.     

Development of high performance powder metallurgy steels by high-energy milling

High-energy milling is considered to be one of the most efficient techniques for producing materials that have a well-controlled chemical composition and microstructural features that are difficult to obtain using other synthesis routes. In this study, the mechanical alloying technique (MA) was used to develop special powder metallurgy (PM) steels with two different types of properties. The use of this technique is essential for obtaining the target microstructure, which ensures the desired performance of the resulting material. Oxide dispersion strengthened (ODS) ferritic steels were produced using MA based on the prealloyed grade Fe–20Cr–5Al and Fe–14Cr–5Al–3 W steels with the addition of Ti and Y₂O₃ as reinforcements. The incorporation of Y₂O₃ enables a homogeneous dispersion of nano-oxides and nano-clusters in a submicron-grained structure that should enhance the mechanical properties up to 600 °C. In addition, the base alloying system, Fe–Cr–Al (Ti), should enable the development of protective oxide layers through high-temperature treatments, which improves the compatibility with the environment, avoids liquid–metal embrittlement and contributes to the increase of the mechanical response up to 600 °C. Furthermore, microalloyed powders can be obtained using MA and consolidated with a pressure-assisted sintering process in an attempt to control the final grain size, to achieve microalloyed steels, and to achieve an extraordinary balance of properties.     

Tailoring master alloys for liquid phase sintering: Effect of introducing oxidation-sensitive elements

The use of low melting point master alloy (MA) powders contributes beneficially to sintering by increasing the distribution rate of alloying elements, enhancing homogenisation and sometimes also promoting densification. However, working with liquid phases poses important challenges like maintaining a proper dimensional control and minimising the effect of secondary porosity on the final performance of the steel. In this work, three different MA systems are compared: a low dissolutive Cu-based MA, and two systems with a higher degree of iron dissolution but different content in oxidation-sensitive elements. The combination of wetting experiments, step sintering tests and dilatometry studies show how the evolution of the microstructure, dimensional stability and overall densification are strongly affected by the characteristics of the liquid MA and in particular by its ability to dissolve the iron base particles, and by the amount of oxidation-sensitive elements present in the composition of the MA powder.     

Low-power low-voltage differential class-AB OTAs for SC circuits

Two new differential class-AB operational transconductance amplifiers (OTAs) for SC circuits that operate with a supply voltage of less than two transistor threshold voltages are introduced. They make use of a new class-AB pseudodifferential pair to generate signal currents much larger than quiescent currents. Both OTAs have been designed to operate with a supply voltage of V/sub DD/=1.1 V, using a 0.35 /spl mu/m CMOS technology. Simulation results for a load capacitance (C/sub L/) of 1 pF show 15 MHz gain-bandwidth product with a quiescent power consumption of 10 /spl mu/W.     

1.1 V Low-Power ΣΔ Modulator for 14-bit, 16 KHz A/D Conversion Using a New Low-Voltage Class-AB Op-amp

This paper presents the implementation of a second order modulator for a 1.1 V supply voltage. A new class-AB CMOS operational amplifier has been designed in order to achieve high-resolution under very-low-voltage operation. The modulator has been implemented using a 0.35 m CMOS technology with 0.65 V transistor threshold voltage. Experimental results show 14 bits of resolution over 16 kHz nyquist rate with an oversampling ratio of 160.Fernando Muñoz Chavero was born in El Saucejo, Sevilla, Spain. He received the Telecommunications Engineering and Ph.D. degrees from the University of Seville, Seville, Spain, in 1998 and 2002, respectively. Since 1997, he has been with the Department of Electronic Engineering, School of Engineering, University of Seville, where he has been an Associate Professor (1999). His research interests are related to low-voltage low-power analog circuit design, A/D and D/A conversion, and analog and mixed signal processing.Alfredo Pérez Vega-Leal was born in Seville, Spain. He received the Telecommunications Engineering and Ph.D. degrees from the University of Seville, Seville, Spain, in 1998 and 2003, respectively. Since 1995, he has been with the Department of Electronic Engineering, School of Engineering, University of Seville, as research student and became an Associate Professor in 1999. His research interests are related to low-voltage low-power analog circuit design, A/D and D/A conversion.Ramón González Carvajal was born in Seville, Spain. He received the Electrical Engineering and Ph.D. degrees from the University of Seville, Seville, Spain, in 1995 and 1999, respectively. Since 1996, he has been with the Department of Electronic Engineering, School of Engineering, University of Seville, where he has been an Associate Professor (1996), and Professor (2002). He has published more than 100 papers in International Journals and Conferences. His research interests are related to low-voltage low-power analog circuit design, A/D and D/A conversion, and analog and mixed signal processing.Antonio Torralba was born in Seville, Spain. He received the electrical engineering and Ph.D. degrees from the University of Seville, Seville, Spain, in 1983 and 1985, respectively. Since 1983, he has been with the Department of Electronic Engineering, School of Engineering, University of Seville, where he has been an Assistant professor, Associate Professor (1987), and Professor (1996). He has published 30 papers in journals and more than 80 papers in conferences. His research interests are in the design and modeling of low-voltage analog circuits, analog and mixed-signal design, analog to digital conversion, and electronic circuits and systems with application to control and communication.Jonathan Noel Tombs was born in Oxford, UK. He received the Electrical Engineering and Ph.D. degrees from Oxford University, UK, in 1987 and 1991, respectively. Since 1993, he has been with the Department of Electronic Engineering, School of Engineering, University of Seville, where he has been an Associate Professor (1997), and Professor (2002). He has published more than 50 papers in International Journals and Conferences. His research interests are related to Digital Design and system verification with VHDL, low-voltage low-power analog circuit design, A/D and D/A conversion and analog and mixed signal processing.Jaime Ramírez-Angulo is currently Klipsch Distinguished Professor, IEEE fellow and Director of the Mixed-Signal VLSI lab at the Klipsch School of Electrical and Computer Engineering, New Mexico State University (Las Cruces, New Mexico), USA. He received a degree in Communications and Electronic Engineering (Professional degree), a M.S.E.E. from the National Polytechnic Institute in Mexico City and a Dr.-Ing. degree form the University of Stuttgart in Stuttgart, Germany in 1974, 1976 and 1982 respectively. He was professor at the National Institute for Astrophysics Optics and Electronics (INAOE) and at Texas A&M University. His research is related to various aspects of design and test of analog and mixed-signal Very Large Scale Integrated Circuits.