Stochastic macromodeling for hierarchical uncertainty quantification of nonlinear electronic systems

A hierarchical stochastic macromodeling approach is proposed for the efficient variability analysis of complex nonlinear electronic systems. A combination of the Transfer Function Trajectory and Polynomial Chaos methods is used to generate stochastic macromodels. In order to reduce the computational complexity of the model generation when the number of stochastic variables increases, a hierarchical system decomposition is used. Pertinent numerical results validate the proposed methodology

A Review on Internet of Things Solutions for Intelligent Energy Control in Buildings for Smart City Applications

© 2017 The Authors. A smart city exploits sustainable information and communication technologies to improve the quality and the performance of urban services for citizens and government, while reducing resources consumption. Intelligent energy control in buildings is an important aspect in this. The Internet of Things can provide a solution. It aims to connect numerous heterogeneous devices through the internet, for which it needs a flexible layered architecture where the things, the people and the cloud services are combined to facilitate an application task. Such flexible IoT hierarchical architecture model will be introduced in this paper with an overview of each key component for intelligent energy control in buildings for smart cities

2-point functions in quantum cosmology

We discuss the path-integral formulation of quantum cosmology with a massless scalar field as a sum-over-histories, with particular reference to loop quantum cosmology. Exploiting the analogy with the relativistic particle, we give a complete overview of the possible two-point functions, deriving vertex expansions and composition laws they satisfy. We clarify the tie between definitions using a group averaging procedure and those in a deparametrised framework. We draw some conclusions about the physics of a single quantum universe and multiverse field theories where the role of these sectors and the inner product are reinterpreted.Comment: 4 pages, based on a talk given at Loops '11, Madrid, to appear in Journal of Physics: Conference Series (JPCS

2-point functions in quantum cosmology

We discuss the path-integral formulation of quantum cosmology with a massless scalar field as a sum-over-histories, with particular reference to loop quantum cosmology. Exploiting the analogy with the relativistic particle, we give a complete overview of the possible two-point functions, deriving vertex expansions and composition laws they satisfy. We clarify the tie between definitions using a group averaging procedure and those in a deparametrised framework. We draw some conclusions about the physics of a single quantum universe and multiverse field theories where the role of these sectors and the inner product are reinterpreted.Comment: 4 pages, based on a talk given at Loops '11, Madrid, to appear in Journal of Physics: Conference Series (JPCS

2-point functions in quantum cosmology

We discuss the path-integral formulation of quantum cosmology with a massless scalar field as a sum-over-histories, with particular reference to loop quantum cosmology. Exploiting the analogy with the relativistic particle, we give a complete overview of the possible two-point functions, deriving vertex expansions and composition laws they satisfy. We clarify the tie between definitions using a group averaging procedure and those in a deparametrised framework. We draw some conclusions about the physics of a single quantum universe and multiverse field theories where the role of these sectors and the inner product are reinterpreted.Comment: 4 pages, based on a talk given at Loops '11, Madrid, to appear in Journal of Physics: Conference Series (JPCS

Efficient offline outer/inner DAC mismatch calibration in wideband ΔΣ ADCs

Distortion due to feedback DAC mismatch is a key limitation in Delta Sigma ADCs for wideband wireless communications. This article presents an efficient frequency-domain mask-based offline mismatch calibration method of both the outer DAC and the inner DACs in a Delta Sigma ADC. The test stimulus for the calibration is a two-tone signal near the band edge. To avoid the need for high-performance signal generation, a frequency mask is applied to void the stimulus signal and its phase noise. In this way, the method is robust against distortion and jitter in the stimulus signal, which therefore could be combined from two low-quality signal generators. The two-tone band-edge signal has the additional benefit that the number of needed samples of the excitation signal is very modest because as many intermodulations as possible contribute to the calculation of the mismatch errors of the DACs. Experimental results confirming the calibration method are obtained from a prototype chip, designed for an 85MHz signal bandwidth in 28nm CMOS technology. A two-tone stimulus around 78 MHz is applied to calculate the mismatch of the outer DAC and the inner DAC with only 68K samples. With the DACs calibrated, an SFDR improvement of 28.1 dB is achieved for a single-tone input at 5 MHz, while for a two-tone input around 71 MHz, the IM3 is improved from -63.6 dBc to below the noise floor (<-94.1 dBc). This illustrates the effectiveness of the approach

Time-encoding analog-to-digital converters : bridging the analog gap to advanced digital CMOS : part 1: basic principles

The scaling of CMOS technology deep into the nanometer range has created challenges for the design of highperformance analog ICs. The shrinking supply voltage and presence of mismatch and noise restrain the dynamic range, causing analog circuits to be large in area and have a high power consumption in spite of the process scaling. Analog circuits based on time encoding [1], [2] and hybrid analog/digital signal processing [3] have been developed to overcome these issues. Realizing analog circuit functionality with highly digital circuits results in more scalable design solutions that can achieve excellent performance. This article reviews the basic principles of time encoding applied, in particular, to analog-to-digital converters (ADCs) based on voltage-controlled oscillators (VCOs), one of the most successful time-encoding techniques to date

Time-encoding analog-to-digital converters : bridging the analog gap to advanced digital CMOS? Part 2: architectures and circuits

The scaling of CMOS technology deep into the nanometer range has created challenges for the design of highperformance analog ICs: they remain large in area and power consumption in spite of process scaling. Analog circuits based on time encoding [1], [2], where the signal information is encoded in the waveform transitions instead of its amplitude, have been developed to overcome these issues. While part one of this overview article [3] presented the basic principles of time encoding, this follow-up article describes and compares the main time-encoding architectures for analog-to-digital converters (ADCs) and discusses the corresponding design challenges of the circuit blocks. The focus is on structures that avoid, as much as possible, the use of traditional analog blocks like operational amplifiers (opamps) or comparators but instead use digital circuitry, ring oscillators, flip-flops, counters, an so on. Our overview of the state of the art will show that these circuits can achieve excellent performance. The obvious benefit of this highly digital approach to realizing analog functionality is that the resulting circuits are small in area and more compatible with CMOS process scaling. The approach also allows for the easy integration of these analog functions in systems on chip operating at "digital" supply voltages as low as 1V and lower. A large part of the design process can also be embedded in a standard digital synthesis flow

An interferometric study of the post-AGB binary 89 Herculis. II Radiative transfer models of the circumbinary disk

The presence of disks and outflows is widespread among post-AGB binaries. In the first paper of this series, a surprisingly large fraction of optical light was found to be resolved in the 89 Her post-AGB system. The data showed this flux to arise from close to the central binary. Scattering off the inner rim of the circumbinary disk, or in a dusty outflow were suggested as two possible origins. With detailed dust radiative transfer models of the disk we aim to discriminate between these two configurations. By including Herschel/SPIRE photometry, we extend the SED such that it now fully covers UV to sub-mm wavelengths. The MCMax radiative transfer code is used to create a large grid of disk models. Our models include a self-consistent treatment of dust settling as well as of scattering. A Si-rich composition with two additional opacity sources, metallic Fe or amorphous C, are tested. The SED is fit together with mid-IR (MIDI) visibilities as well as the optical and near-IR visibilities of Paper I, to constrain the structure of the disk and in particular of its inner rim. The near-IR visibility data require a smooth inner rim, here obtained with a two-power-law parameterization of the radial surface density distribution. A model can be found that fits all the IR photometric and interferometric data well, with either of the two continuum opacity sources. Our best-fit passive models are characterized by a significant amount of mm-sized grains, which are settled to the midplane of the disk. Not a single disk model fits our data at optical wavelengths though, the reason being the opposing constraints imposed by the optical and near-IR interferometric data. A geometry in which a passive, dusty, and puffed-up circumbinary disk is present, can reproduce all the IR but not the optical observations of 89 Her. Another dusty, outflow or halo, component therefore needs to be added to the system.Comment: 15 pages, in pres