The division datapath is undoubtedly the most complex operation in a wide range of digital signal processing applications, such as in adaptive filtering algorithms. This paper proposes an optimized ...and approximate integer divider hardware architecture, based on the Newton–Raphson algorithm combining both fixed-point dynamic range and truncation techniques, to speed up that operation. Adaptive filters have been much studied over time, as they comprise one of the most challenging fields in signal processing. This work presents dedicated hardware architectures based on normalized least mean square adaptive filtering algorithms for the power line harmonics interference cancelling. The hardware architectures are based on 2’s complement representation and were described in VHDL and synthesized into a 65 nm CMOS dedicated ASIC. Our results show that the increased approximation level of Newton–Raphson divider approximation presents up to 223 times less power dissipation than the baseline version without our optimization and approximations, providing up to 93 times of power dissipation savings in the complete interference canceller system.
Fast Fourier transform (FFT) is the most common low‐complexity implementation of the discrete Fourier transform, intensively employed to process real‐world signals in smart sensors for the internet ...of things. Butterflies play a central role as the FFT computing core data path since it calculates complex terms employing several multipliers. A low‐power FFT hardware architecture combining split‐radix decimation‐in‐time butterfly and 5‐2 adder compressors (ACs) is proposed and implemented. The circuits are described in Verilog hardware description language and synthesized using the Cadence Genus synthesis tool. The circuits are mapped onto a 65‐nm CMOS ST standard cell library. Results reveal that the proposed FFT hardware architecture using the split‐radix butterfly is 13.28% more power efficient than the radix‐4 one. The results further show that, by combining 5‐2 AC within the split‐radix butterfly, our proposal saves up to 43.1% of the total power dissipation considering the whole FFT hardware architecture, compared with the state‐of‐the‐art radix‐4 butterfly employing the adder automatically selected by the logic synthesis tool.
En este trabajo presento una propuesta metodológica para el mapeo del narcotráfico en el Gran Buenos Aires, Argentina. Es una aproximación, no definitiva y “de abajo para arriba”. Es decir, sale del ...eslabón más “bajo” del narcotráfico para conocer las estructuras superiores. Utilizo 13 entrevistas en profundidad con jóvenes y adolescentes residentes del Gran Buenos Aires y que en noviembre de 2017 estaban bajo tratamiento por consumo de drogas en una comunidad terapéutica de Lomas de Zamora. La metodología utilizada sistematiza en una red semántica y en un mapa síntesis los relatos de interacción con el narcotráfico, reconstruyendo así algunas formas de espacialización, algunas relaciones de poder de su jerarquía interna y algunos de sus actores. Por fin, el esfuerzo desagua en una metodología capaz de iluminar el accionar espacial de otras actividades del crimen organizado como el tráfico de armas y la trata de personas.
Temperature rising is an unavoidable effect on VLSI and has always been a critical issue in any system-on-chip - especially when targeting compute-intensive applications. This effect increases the ...delay in hardware accelerators, resulting in timing errors due to unsustainable clock frequency, whose impact must be carefully evaluated on design time to measure the performance degradation of the hardware accelerator. Further, a hardware operating at a higher temperature accelerates device aging, which incurs in more timing errors. This issue is usually addressed with the inclusion of timing guardbands that compensate for the deleterious effects of temperature, ensuring the hardware accelerator works within a reliable zone, i.e., without any timing errors caused by temperature effects at runtime. However, guardbands directly result in considerable performance and efficiency losses because the circuit will be clocked at a frequency lower than its full potential. Accelerators on edge devices often dismiss such guardbands to explore the full potential of the designed circuits, posing an enormous design challenge as this approach requires a careful evaluation of the impact of timing errors on the quality of the target applications. Many algorithms, such as in multimedia and machine learning applications, are capable of tolerating hardware errors. Yet, these algorithms have a dynamic behavior (i.e., closed-loop) where a timing error can be propagated, affecting subsequent steps. Measuring the degradation-induced errors in these applications is very challenging given that an accurate gate-level simulation to investigate degradation-induced timing errors needs to be coupled dynamically with a system-level simulator to unveil how induced errors in the underlying hardware ultimately impact the algorithm execution in the hardware accelerator. This is the first work to achieve this goal . State-of-the-art works have studied accelerators under timing-errors when removing (or narrowing) guardbands. However, their approach was suitable only for open-loop hardware accelerators which are entirely agnostic of complex interactions of the algorithms . Unlike prior work, this paper investigates temperature- and aging-induced timing-errors in the joint accelerator-algorithm interactions and their runtime impacts. Our framework investigates aging effects across the different layers starting from transistor physics all the way up to the algorithm layer. The hardware accelerator employed as a case study in this work is the sum of absolute differences (SAD), which is the most compute-intensive accelerator on commercial video encoder for mobile applications. Our results demonstrate the runtime behavior impacts of three advanced block-matching algorithms of the video encoder in a joint operation by a SAD accelerator under timing-errors induced by temperature and aging effects considering a 14nm FinFET technology.
During middle distillates hydroprocessing, the relationship between feed properties, operating conditions and the deactivation phenomenon is crucial to achieve fuels specification. In this work, an ...accelerated deactivation methodology was employed to in short periods observe and study the deactivation phenomenon. For the stabilization step, 100 h of run were necessary to guarantee that the initial deactivation was achieved. Easy, versatile, and portable tools were employed successfully to monitor and evaluate the hydrotreating process in line, as Fourier Transform Infrared (FTIR) analysis together with density measurements. Besides, process modifications related to hydrotreating reactions were identified using FTIR and it was confirmed that feedstock properties may directly influence the deactivation phenomenon. The feedstock with higher aromatics and olefins concentration required increasing the temperature to 420 °C and the lower H2/oil ratio (150 std m3/m3) to reduce desulfurization and hydrogenation reaction activities by coke formation and deposition.
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•Easy, versatile, and portable tools allowed the hydrotreating reaction monitoring.•Heavy and polyaromatic compounds are correlated to coke formation and deposition.•Aromatic and olefin compounds were associated to enhance the deactivation mechanism.
► Numerical simulation of the start-up flow of thixotropic drilling fluids. ► The thixotropy model accounts for both viscous-plasticity and material elasticity. ► Thixotropy properties, ...compressibility and Reynolds number affect pressure peaks.
This study presents a mathematical model to simulate the start-up flow of drilling fluids in drill pipes. The compressible transient flow approach is based on one-dimensional mass and momentum conservation equations, an equation of state and a thixotropic fluid model. In contrast with prior studies that view gel breaking as a visco-plastic phenomenon, thixotropy is approached as an elasto-visco-plastic problem. Such thixotropy model is fit to rheometer data with reasonable agreement. The start-up flow is then simulated, and the results are compared to Newtonian, Bingham and visco-plastic fluid flow models. It can be anticipated that the pressure overshoots observed in start-up flows depend not only on the thixotropy properties of the fluid but also on the flow compressibility and Reynolds number. In addition, the main differences between the visco-plastic and elasto-visco-plastic thixotropy approaches take place at low shear rates; the higher the shear rates, the more similar are the results. Finally, as expected, the pressure overshoots of the thixotropic fluids are not always larger than those of the Bingham and Newtonian counterparts.
Lanthanum-doped CeO2 is a promising semiconductor for gas sensing. A combined study applying impedance spectroscopy and first-principles calculations was performed for pure and lanthanum-doped ...samples. The results showed a strong influence of the localized Ce 4f states on the electrical conduction processes and an electrical resistance increase as a function of the exposure to vacuum and air atmospheres. After its modification with a rare-earth element along with exposure to reducing and oxidizing atmospheres, the observed behavior suggested the presence of multitraps, which depended on the described equilibrium between the oxygen vacancies (Vo x ↔ VO· ↔ VO· ) in a disordered deep-bulk trap location. According to the DFT results, the multitraps were formed with the creation of an oxygen vacancy far from the doping atom. They were considered to be responsible for the phenomena modifying the Debye-like response. The transfer of electrons from Ce(III) to the adsorbed oxygen species, decreasing the number of electrons in the 4f state, reduced the electrical conductivity by the hopping frequency dependence of the total resistance and capacitances. This was probably due to the interactions between defective oxygen and metallic species.
This study reports the electrical properties of Nd-doped cerium oxide (CeO
2
) films synthesized by microwave assisted hydrothermal using a two-point probe technique. Positron annihilation lifetime ...spectroscopy studies evidenced that, as the Nd content rises, a structural disorder occurs. This is caused by an increase in oxygen vacancies surrounded with Nd (defective clusters), with the mean lifetime components ranging between 290 and 300 ps. Particle size estimation showed values from 8.6 to 28.9 nm. Along with the increase of neodymium impurities, also the conductivity increases, due to the hopping conduction mechanism between defective species. This gives rise to a response time of only 6 s, turning these materials candidates to realize gas sensor devices. Ab initio investigations showed that the improved electric conduction is boosted mostly by the reduced Nd
2+
than the Ce
3+
, where the oxygen vacancies play a fundamental role.
The modification of CeO2 with rare-earth elements opens up a wide range of applications as biomedical devices using infrared emission as well as magnetic and gas-sensing devices, once the structural, ...morphological, photoluminescent, magnetic, electric, and gas-sensing properties of these systems are strongly correlated to quantum electronic transitions between rare-earth f-states among defective species. Quantitative phase analysis revealed that the nanopowders are free from secondary phases and crystallize in the fluorite-type cubic structure. Magnetic coercive field measurements on the powders indicate that the substitution of cerium with lanthanum (8 wt %), in a fluorite-type cubic structure, created oxygen vacancies and led to a decrease in the fraction of Ce species in the 3+ state, resulting in a stronger room-temperature ferromagnetic response along with high coercivity (160 Oe). In addition to the magnetic and photoluminescent behavior, a fast response time (5.5 s) was observed after CO exposure, indicating that the defective structure of ceria-based materials corresponds to the key of success in terms of applications using photoluminescent, magnetic, or electrical behaviors.
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