Application of Variational a-Posteriori Multiscale Error Estimation to Higher-Order Elements

An explicit a-posteriori error estimator based on the variational multiscale method is extended to higher-order elements. The technique is based on a recently derived explicit formula of the fine-scale Green’s function for higher-order elements. For the class of element-edge exact methods, the technique is able to predict the error exactly in any desired norm. It is shown that for elements of order k, the exact error depends on the k−1 derivative of the residual. The technique is applied to one-dimensional examples of fluid transport computed with stabilized methods.     

A new CMOS comparator robust to process and temperature variations for SAR ADC converters

This paper presents a novel comparator being robust to temperature and process variations. The new comparator is confronted to a conventional topology used in most of the Successive Approximations Analog to Digital Converters (SAR ADCs) for biomedical applications. To verify the benefits of the new comparator, it was designed on a CMOS 65 nm process and characterized with post layout simulations under conditions of process and temperature fluctuations. With the proposed circuit, a SAR ADC exhibits 83.11 dB of Signal to Noise Ratio at 1.28 MS/s and \(375\,\upmu\hbox {W}\) of power consumption. The PT variations for critical corners are less than 0.58 bits.     

Analysis of Pressure Waves Generation in Gun Combustion Chambers During the Propellant Ignition Process

At certain conditions, propelling charges for artillery – either because of their low heat of combustion, a low vulnerability, or due to other reasons – require relatively high initiation thresholds. This phenomenon, combined with large gun chambers, high initial charge densities of materials with granular geometry and low porosity powder beds, give rise to delays and irregularities in the initiation times at various points of the propelling charges. These irregular behaviors or failures in the initiation cause pressure waves within the chambers of the weapons. This paper focuses on experimental studies and tests carried out on the processes taking place in the initiation of propelling charges, which can lead to pressure waves in the bore of howitzers and cannons. Pressure waves during initiation are considered to be particularly dangerous to the safety of users and weapons. The behavior of the initiator systems, the flame volume and its distribution throughout the length of the bore are analysed by means of pressure‐time diagrams, obtained from experimental shooting. The data are processed using the standard Fourier transform and the “discrete wavelet transform”, by means of the Daubechies functions. This allows to identify when these events occur during shooting and to determine some of the causes in order to achieve virtual elimination of the pressure waves.     

Implementing Thermometry on Silicon Surfaces Functionalized by Lanthanide‐Doped Self‐Assembled Polymer Monolayers

The thermal gradients generated at submicrometer scale by the millions of transistors contained in integrated circuits are becoming the key limiting factor for device integration in micro‐ and nanoelectronics. Noncontact thermometric techniques with high‐spatial resolution are, thus, essential for noninvasive off‐chip characterization and heat management on Si surfaces. Here, the first ratiometric luminescent molecular thermometer implemented in a self‐assembled polymer monolayer functionalized Si surface is reported. The functionalization of Si surfaces with luminescent thermometers constitutes a proof‐of‐concept that foretells a wide range of applications in Si‐based micro‐ and nanostructures. The thermometric functionalization of the Si surface with Tb³⁺ and Eu³⁺ complexes leads to a thermal sensitivity up to 1.43% K^?1, a cycle–recycle reliability of 98.6%, and a temperature uncertainty of less than 0.3 K. The functionalized surface presents reversible bistability that can be used as an optically active molecular demultiplexer.     

润滑和污染对轴承寿命的影响(一)

轴承寿命受许多因素影响,两个最重要的因素是润滑和污染。通过更好地认识这些因素是如何导致轴承寿命缩短的机理,我们就能改善轴承设计和运行。本文是两个部分的系列之一,首先研究润滑的影响。     

A Multi-Shared Register File Structure for VLIW Processors

The available instruction level parallelism allowed by current register file organizations is not always fully exploited by media processors when running a multimedia application. This paper introduces a novel register file organization, called multi-shared register file, that eliminates this superfluous instruction scheduling flexibility by reducing the number of read and write ports and partitioning the register file in a special ring structure. A parameterized generic VLIW architecture is used to explore different configurations of our proposed register file structure in terms of estimated silicon area, minimum clock period, estimated power consumption, and multimedia task processing performance. Moreover, a metric highly related to multimedia applications is introduced to study trade-offs between hardware cost and performance. The results show that by substituting a monolithic register file with an equivalent multi-shared register file, the estimated area and the power consumption are considerably reduced at the cost of a negligible performance degradation.     

Adaptive internal model control: the discrete‐time case

This paper considers the design and analysis of a discrete‐time H₂ optimal robust adaptive controller based on the internal model control structure. The certainty equivalence principle of adaptive control is used to combine a discrete‐time robust adaptive law with a discrete‐time H₂ internal model controller to obtain a discrete‐time adaptive H₂ internal model control scheme with provable guarantees of stability and robustness. The approach used parallels the earlier results obtained for the continuous‐time case. Nevertheless, there are some differences which, together with the widespread use of digital computers for controls applications, justifies a separate exposition. Copyright © 2001 John Wiley & Sons, Ltd.     

Thermal stabilization by polyols of β-xylanase from Bacillus amyloliquefaciens

Purified endo-β-1,4-xylanase of Bacillus amyloliquefaciens MIR 32 retained 100% of its activity after 4 days of incubation at 50°C. Sorbitol (400 mg cm⁻³) produced a 63-fold increase in the half-life of the enzyme at 65°C, which was only 29 min at this temperature in the absence of the polyol. This thermal stabilizing activity increased exponentially in respect to sorbitol concentration in the range 250–400 mg cm⁻³ and was dependent on the pH, showing a maximum at pH values between 5·25 and 8·0. The circular dichroism (CD) thermal scanning profile (50°C h⁻¹) at 224 nm showed that changes in the secondary structure of xylanase started at 65°C, while in the presence of sorbitol (400 mg cm⁻³) these modifications started at 80°C. This study indicated that sorbitol might be a valuable stabilizer for the use of β-xylanase from B. amyloliquefaciens at high temperatures. © 1998 SCI