Non-ideal Features Research Articles

Stability of THAI in situ combustion process in reservoirs with layers of grading permeabilities and porosities: Detailed qualitative investigations

The world-wide reserves of heavy oil, tar sand, and bitumen, etc., outweigh those of conventional oil by a factor of 7/3. Given that the conventional reserves are being rapidly depleted, the need to develop and produce the unconventional resources has never been so critical. However, the proven most efficient and environmentally-friendly technology, namely the THAI process, still requires further study, and it has no documented design procedures that factor in the non-ideal geological features of heavy oil and bitumen reservoirs. Throughout the literature, there is little reported on the effects of gradations in reservoir petro-physical parameters on the performance of the THAI process. Consequently, this work reports the results of numerical simulations for four different kinds of reservoirs, each having progressive gradations in permeabilities and porosities. The major findings from this in depth study include.(i) In terms of the temperature distribution, regardless of the permeability and porosity gradations, the high temperature zone is always skewed towards the highest permeabilities and porosities zone. Furthermore, it is found that, in any model in which the shoes of the VI wells have no direct communication pathway with the highest permeabilities and porosities zones of the reservoirs, the high temperature zones occur in two chambers, otherwise, there is one high temperature zone.(ii) It is found that generally, the combustion front tends to be lopsided in favour of the most permeable and porous zone. In the case of a bottom-up progressive increase in permeabilities and porosities (model L1), the single combustion front has greatest advance horizontally at the top and axially in the middle of the reservoir, while in model L2 (the converse of model L1), the combustion fronts propagated in two chambers before the chambers overlapped in the toe region of the HP well where it advanced fastest. Therefore, the combustion zone in model L1 was far more stable than in model L2.(iii) It is found that the combustion fronts in model L3, with the lowest permeabilities and porosities at the centre in the longitudinal direction, propagated in two chambers that overlapped each other around the toe region of the HP well and advanced greatest in the HP well and on either lateral edge of the reservoir. In model L4, which has lateral gradation in permeabilities and porosities, however, the thinner edge of the wedge-shape combustion front had advanced fastest along the vertical mid-plane where the HP well was located. Thus, the combustion zone in model L3 was far more stable than that in model L4.(iv) It is found that in all the models except model L4, there exist rich oil saturation zones in the most permeable and porous regions located ahead of the mobile oil zone (MOZ) of each reservoir. These are formed due to restrictions in the pathways via which the mobilised oil can drain into the HP well. In model L4, the HP well is already in the most permeable zone and consequently, the fluids that favourably reach there are rapidly gravity-drained into the HP well.

Energy absorption and resilience in quasi-static loading of foam-formed cellulose fibre materials

To avoid microplastic pollution, there is an urgent need to replace fossil-based cushioning materials in packaging with easily recyclable alternatives. Here, we investigated the potential of lightweight cellulose fibre materials as a solution for mechanical protection. The quasi-static compression was studied among a vast set of 129 different foam-formed trial points with material density ranging from 21 kg/m3 to 123 kg/m3. The trial points included two different fibre types, bleached softwood kraft pulp (BSKP) and bleached chemithermomechanical pulp (CTMP), with varied refining level, pulp consistency, foaming conditions, surfactant type, strength additives, and final material density and thickness. Besides a correlation analysis of factors affecting compression stress and resilience, the results were reflected against a new theoretical prediction of energy absorption for an ideal low-density random fibre network. The theory predicts the initially-high cushion factor to rapidly drop down to the level of 4‒5 at 40‒80% compression. A similar behaviour was seen among the actual samples, despite their various non-ideal features. At 50% compression, the average cushion factor across the whole data set was 4.84 ± 0.10, being close to the theoretical prediction of 4.61 for the ideal case. The smallest cushion factor of 3.6 was found for a CTMP sample. The recovery from compression varied slightly among the samples and appeared highest for the material density of 60‒100 kg/m3, following the predicted proportion of non-buckled fibre segments. According to the results, cellulose fibre-based cushions have a soft initial response, which is preferable for fragile items.Graphical abstract

A method for constructing non-ideal geometric features of thermal insulation tiles based onmeasured data

In the digital assembly of modern aircraft, to meet the higher requirements of aircraft assembly quality, the measurement data of geometric characteristics are used to replace the actual model of the parts for assembly calculation and analysis. However, when analyzing the assembly deviation of parts with complex assembly features, it is difficult to express the non-ideal model clearly by using traditional methods. At the same time, the amount of measured data is large, and the calculation efficiency is low. We propose methods to build geometric feature models based on measurement data to extract and optimize non-ideal features and reduce the data of discrete point sets to address this problem. The experimental results reveal the accuracy and computational efficiency of the geometric feature expression of the model and verify the feasibility of the proposed method.

THE OUTPUT NOISE REDUCTION OF THE R-2R RESISTOR LADDER DIGITAL-ANALOG CONVERTER

A new method for reducing output noises in the R-2R resistor ladder digital-analog converter (DAC) is presented. The main reason for the output noises in R-2R resistor ladder DAC is the disadvantages and non-ideal features of the operational amplifier (Op-Amp). In case of the low numbers of the input combination there can be an output voltage without noises, because the voltage-error for the OpAmp in case of low output voltage is very small. But the low output voltage can be not the exact voltage because many times the 0 voltage on the negative input of the OpAmp forms is not clear. The high output voltage of the OpAmp can be more exact, but it will have noises because of the conflict between the voltage corresponding to the difference of the input voltages and the voltage corresponding to the current coming from the R-2R ladder. Using the new method, the output voltage of the R-2R resistor ladder DAC will be exactly in the full input combination range, and it will have almost no noise. In the primary 4-bit R-2R DAC designed in the 32 nm technology the INL (integral nonlinearity error) in case of 0000 input combination is 0.2 V, and the noise-error in case of 0101 input combination is 0.065 V. In the optimized R-2R DAC, the maximum INL error is 0.02 V at 0010 input combination and the maximum noise-error is 0.005 V at 0001 input combination. Using the method, the area of the circuit increases by 7%. As this disadvantage is very small the new approach is very preferable to use for accurate output signal in the R-2R resistor ladder DAC.

Flexible and efficient fabrication of a terahertz absorber by single-step laser direct writing.

Laser direct writing (LDW) is a promising candidate for the fabrication of all-dielectric THz absorbers for its high flexibility and material compatibility. However, multi-step processing or multi-layer materials are required to compensate for the nonideal features of LDW to realize good absorption performance. To further explore the potential of LDW in flexible and cost-effective THz absorber fabrication, in this work, we demonstrate a design method of THz absorbers fully considering and utilizing the characteristics of laser processing. Specifically, we first numerically analyze that by properly combining basic structures processed by single-step LDW, good and adjustable absorption performance can be achieved on a single-layer substrate. Then we experimentally fabricate THz absorbers by processing periodic composite structures, which are combined by grooves and circular holes, on single-layer doped silicon using LDW. Experimental results show that our method can fabricate THz absorbers at a speed of 3.3 mm2/min with an absorptivity above 90% over a broadband of 1.8-3 THz. Our method provides a promising solution for the flexible and efficient fabrication of all-dielectric broadband THz absorbers.

High-Fidelity Induction Motor Simulation Model Based on Finite Element Analysis

This article proposes a new high-fidelity simulation model of an induction motor (IM) based on finite-element analysis (FEA). The proposed model enables fast and accurate IM simulation with the inverter circuit model and control algorithm. That is, the proposed model can represent non-ideal features of IM, such as magnetic saturation, spatial harmonics, skew, and saturation-induced saliency in high accuracy. To construct the proposed model, a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> equivalent circuit of the squirrel cage rotor is introduced. Based on this, the static FEA is conducted which can accelerate the model construction compared to the conventional time-stepping FEA technique. Then, a flux-based IM model is established, which has advantages on speed, accuracy, and memory size in the simulation. To verify the effectiveness of the proposed model, the models are constructed for two commercial IMs used for the industrial drive. IM control algorithms are tested in various operating conditions on the proposed model. The results are compared with the time-stepping FEA and the experiment for the verification of the proposed model.

Advantages of binary stochastic synapses for hardware spiking neural networks with realistic memristors

Hardware implementing spiking neural networks (SNNs) has the potential to provide transformative gains in energy efficiency and throughput for energy-restricted machine-learning tasks. This is enabled by large arrays of memristive synapse devices that can be realized by various emerging memory technologies. But in practice, the performance of such hardware is limited by non-ideal features of the memristor devices such as nonlinear and asymmetric state updates, limited bit-resolution, limited cycling endurance and device noise. Here we investigate how stochastic switching in binary synapses can provide advantages compared with realistic analog memristors when using unsupervised training of SNNs via spike timing-dependent plasticity. We find that the performance of binary stochastic SNNs is similar to or even better than analog deterministic SNNs when one considers memristors with realistic bit-resolution as well in situations with considerable cycle-to-cycle noise. Furthermore, binary stochastic SNNs require many fewer weight updates to train, leading to superior utilization of the limited endurance in realistic memristive devices.

Fracture and fatigue of entangled and unentangled polymer networks

Entanglement of polymer chains is ubiquitous in elastomers, gels, and biological tissues. While the effects of chain entanglement on elasticity and viscoelasticity of polymer networks have been intensively studied, it remains elusive how chain entanglement affects fracture and fatigue of polymer networks. In this paper, using polyacrylamide hydrogels as a model material, we systematically compare fracture toughness and fatigue threshold of polymer networks with various levels of chain entanglement. We find that the fracture toughness and fatigue threshold of an unentangled polymer network are almost the same, although the unentangled polymer network still contains non-ideal features including topological defects (i.e., dangling chains and cyclic loops) and structural heterogeneity (i.e., non-uniform chain lengths and non-uniform functionalities). In contrast, the fracture toughness of an entangled polymer network can be over ten times (up to 16 times) higher than its fatigue threshold, indicating substantial toughness enhancement due to chain entanglement. Different from the conventional toughness enhancement due to bulk dissipation of polymer networks, the toughness enhancement by chain entanglement requires low stress–stretch hysteresis (<10%) of the bulk entangled polymer networks. We attribute the toughness enhancement in entangled polymer networks to a new dissipation mechanism, near-crack dissipation, which is possibly induced by pull-out of chains and/or delocalized damage of chains around the crack tip.

Chua circuit based on the exponential characteristics of semiconductor devices

The use of non-ideal features of semiconductor devices is an interesting option for implementations of nonlinear electronic systems. This paper analyzes the Chua circuit with nonlinearity based on the exponential hyperbolic characteristics of semiconductor devices. The stability analysis using describing functions predicts the dynamics of this nonlinear system, which is corroborated by numerical investigations and experimental results. The dynamic behaviors and bifurcations of this nonlinear system are mapped in parameter space in order to create a base for studies, analyses, and designs. The dynamic behavior of the experimental high speed implementation of this version of Chua circuit differs from the expected dynamics for a conventional Chua circuit due to effects of unmodelled non-idealities of the real semiconductor devices, displaying that new and different dynamics for the Chua circuit can be obtained exploring different nonlinearities.

Estimating the Chirp Mass of Eccentric Inspiraling Binary Systems from Time-Frequency Representations of their Gravitational Radiation

Using the simplest yet meaningful Peters-Mathews model describing the orbital damping of a compact binary system under the emission of gravitatonal radiation, we show that the chirp-mass of an eccentric inspiraling binary, and its (Keplerian) orbital eccentricity at some reference time, can be estimated from the time-frequency skeleton of its gravitational wave signal. The estimation algorithm is nicely simple, and is robust against the non-ideal (non Gaussian, non stationary) features of detector noise.

Beam Drift in Millimeter Wave Links: Beamwidth Tradeoffs and Learning Based Optimization

Millimeter wave (mmwave) communications, envisaged for the next generation wireless networks, rely on large antenna arrays and very narrow, high-gain beams. This poses significant challenges to beam alignment between transmitter and receiver, which has attracted considerable research attention. Even when alignment is achieved, the link is subject to beam drift (BD). BD, caused by non-ideal features inherent in practical beams and rapidly changing environments, is referred to as the phenomenon that the center of main-lobe of the used beam deviates from the real dominant channel direction, which further deteriorates the system’s performance. To mitigate the BD effect, in this paper we first theoretically analyze the BD effect on the performance of outage probability as well as effective achievable rate, which takes practical factors (e.g., the rate of change of the environment, beam width, transmit power) into account. Then, different from conventional practice, we propose a novel design philosophy where multi-resolution beams with varying beam widths are used for data transmission while narrow beams are employed for beam training. Finally, we design an efficient learning based algorithm which can adaptively choose an appropriate beam width according to the environment. Simulation results demonstrate the effectiveness and superiority of our proposals.

Toward non-default partitioning for compound feature identification in engineering design

Geometrical operations, such as extraction, partitioning and reconstruction, are defined in ISO standards on Geometrical Product Specifications and Verification (GPS) in order to obtain ideal and non-ideal features on mechanical parts. Default partitioning enables to decompose the workpiece into independent surface portions regarding kinematic invariance classes. For both specification and verification purposes, non-default partitioning is utilized to create compound features and assist functional tolerancing in the design process. Therefore, it is essential to formalize non-default partitioning and exploit it for supporting further operations within the design activities. In this paper, after a state-of-the-art survey of partitioning and segmentation methods for both default and non-default partitioning, a non-default partitioning process is proposed from both rule-based (explicit knowledge) and data-driven (implicit knowledge) perspectives. The rule-based process addresses non-default partitioning by using Technologically and Topologically Related Surfaces (TTRS) concept while the data-driven method benefits from the recent developments brought by a convolutional neural network (CNN) on point sets. A pre-labeled dataset of mechanical parts is established in the paper for training the network. Experiments and results on CAD models are presented to illustrate the effectiveness of the proposed non-default partitioning method.

Kant’s Nonideal Theory of Politics by Dilek Huseyinzadegan

Reviewed by: Kant’s Nonideal Theory of Politics by Dilek Huseyinzadegan Elaine P. Miller (bio) Dilek Huseyinzadegan, Kant’s Nonideal Theory of Politics Northwestern University Press, 2019, 204 pp. ISBN 978-0-8101-3987-9 The opening pages of Kant’s Nonideal Theory of Politics present the controversial central claim of the book head on: Kant’s teleological arguments in political philosophy, which have a contentious reputation in Kant circles, not only should not be omitted from scholarly inquiry but form an essential part of what Dilek Huseyinzadegan calls “Kant’s nonideal theory,” or the second prong of his dual-focused political philosophy. Nonideal theory, a term Huseyinzadegan borrows from Charles Mills, is anchored, on her argument, in the regulative principle of Zweckmässigkeit, or purposiveness, and has as its purview the contingent variables of politics such as history, culture, and geography. Accordingly, she names “nonideal” the part of his political philosophy that takes up not a priori ideals and political goals but the messiness of actual, empirical history. In The Racial Contract, Mills describes the aim of examining a nonideal contract, such as Rousseau’s in “Discourse on the Origin of Inequality,” in order to “explain and expose the inequities of the actual nonideal polity” (Mills 1997, 9). The racial contract, in relation to social contract theory, starts with “uncomfortable reality” in order not to have to continually “retreat into illusory idealizing abstraction,” and so that it can readily shift between the hypothetical and the actual (Mills 1997, 130). Part of the historical support for Mills’s argument that the racial contract constructs not only racial exploitation but also race [End Page 238] itself can be directly traced to Kant. Huseyinzadegan’s work is not an apologia for Kant, but a demonstration of the ways in which Kant countenanced the nonideal features of his own description of geography and peoples as a part of political philosophy that concerned itself with empirical, historical reality alongside the principles of political right. Huseyinzadegan locates Kant’s political philosophy not only in the obvious “political writings” but in a range of critical and noncritical texts, focusing notably on the Critique of Judgment, a work that some may feel has nothing to do with politics. Of course, Hannah Arendt’s Lectures on Kant’s Political Philosophy argued convincingly for the relevance of the “Critique of Aesthetic Judgment” to a Kantian political philosophy, and spurred a whole line of interpretations in this vein, but this is not Huseyinzadegan’s focus. She draws attention rather to the relatively neglected “Critique of Teleological Judgment,” fully aware of the controversy to which this focus might give rise. In emphasizing purposiveness as a regulative principle that informs Kant’s political philosophy, she argues that Kant’s use of teleology does not render up an unsavory narrative of world history moving inexorably toward a European end, but rather foregrounds the gap between the ideals put forward by his theory of Recht and the realities of current culture that fail to live up to them. It is in her identification of Zweckmässigkeit, which operates as a link, in the manner of reflective judgment, between the ideals of Recht and the nonideality of actual history, that Huseyinzadegan makes a decisive contribution to the interpretation of Kantian political philosophy. Chapters 1–3 of Kant’s Nonideal Theory of Politics cover Kant’s essay “What is Orientation in Thinking?”; “Idea for a Universal History with a Cosmopolitan Aim”; “What is Enlightenment?”; and the Doctrine of Right. Huseyinzadegan starts by identifying in the Critique of Pure Reason a precursor to the concept of reflective judgment. Here Kant talks about ideas of reason as providing an “imaginary focus” that allows for a greater unity and extension between the concepts of the understanding and the sensible experience they constitute. This hypothetical unity gives rise to a hope that, despite all the diversity and seeming infinitude of empirical experiences, it still might be possible for us to draw them all together as if they belonged to this imaginary focal point. The regulative use of this imaginary point serves to orient us in an otherwise bewildering or overwhelming amount of sensible experience. We cannot dogmatically assert the...

Residual uncertainty in processed line-of-sight returns from nacelle-mounted lidar due to spectral artifacts

An uncertainty quantification technique for nacelle-mounted lidar is developed that extends conventional error analyses to precisely account for residual uncertainty due to observed non-ideal features in processed Doppler lidar spectra. The technique is applied after quality assurance/quality control (QAQC) processing to quantify residual error, both bias and random, from solid-body interference, shot noise, and any additional uncertainty introduced to the data from the QAQC process itself. The approach follows from the one-time construction of a high-dimensional parametric database of synthetic lidar spectra and subsequent processing with an existing QAQC technique. A model of the correspondence between the spectral shape and the associated residual errors due to non-ideal features is then developed for quantities of interest (QOIs) including the geometric median and spectral standard deviation of line-of-sight velocity. The model is preliminarily implemented within a neural network framework that is then applied in post-processing to sample returns from a DTU SpinnerLidar. The initial analysis uncovers the effects of specific sources of uncertainty in the context of both individual spectra and full-field maps of the measurement domain. The technique is described in terms of application to continuous wave (CW) lidar, though it is also relevant to pulsed lidar.

Probing Coulomb Interactions on Charge Transport in Few‐Layer Organic Crystalline Semiconductors by the Gated van der Pauw Method

AbstractA general understanding of the nature of the charge motions at the organic/dielectric interface requires an accurate examination on the influence from the Coulomb interactions among carriers. However, difficulties on this substantial issue are due to complicated interpretation and extraction of the intrinsic electrical parameters for the organic films. Here, the carrier transport in highly ordered, few‐layer organic crystalline semiconductors is studied by a geometry‐independent gated van der Pauw method, confining the charge carrier distribution at the precision of molecular layers and minimizing the effects of extrinsic factors. The characteristics of carrier transport are varied in different film layers and show nonideal features. The Fröhlich polaron model well explains the features and suggests that the Coulomb interactions among carriers should be considered at a high carrier density, which is manifested by the characteristic parameter 〈ξ 〉/2 measuring the extra potential for polaron transport. This understanding of the physical process between Coulomb interactions and polaron transport in organic crystalline semiconductors can enable promising strategies for achieving more ideal transistor performance and new device physics.

Toward a Mathematical Definition of Reconstruction Operation for ISO GPS Standards

Abstract ISO standards on geometrical product specifications and verification (GPS) define several geometrical operations, such as extraction, partitioning, filtration, and association. These operations are required for obtaining ideal or non-ideal features and acts at both specification and verification domains. Recently, another operation called reconstruction has become an important topic of discussion in the ISO GPS standards committee ISO/TC 213. The operation of reconstruction produces a continuous surface from a finite number of points. Different from association, which is an operation used to fit pre-defined ideal features to non-ideal features or point-cloud, the main challenge of reconstruction is to guarantee that the topology of the underlying surface is preserved and its boundaries are well defined. This paper takes some initial steps toward a mathematical definition of the reconstruction operation and explores fundamental concepts for specification and verification. Challenges and future research are also highlighted.

A new partitioning process for geometrical product specifications and verification

In ISO Geometrical Product Specifications and Verification Standards (GPS), Feature operations are used to obtain ideal and non-ideal features. The formalization of such operations enables to reduce ambiguity and uncertainty within the activities of design, manufacture and metrology of mechanical products, and their scientific investigation contributes to develop a sound mathematical framework and formalisms for the comprehension of engineering practices and the development of new standards. Partitioning is a fundamental operation defined in ISO GPS standard which aims at decomposing a part into independent features or surface portions for further processing and analysis. In this paper, a state-of-the-art survey of partitioning and segmentation methods and techniques reported in the literature is conducted and a comprehensive classification is proposed. Thereafter, a new partitioning process is developed for partitioning into regions and recognizing each region as one of the seven invariance classes of surfaces. It proceeds in three main steps: initial partitioning based on shape index and curvedness, refined partitioning by slippage analysis and invariance class recognition by statistical evaluation. An intuitive shape color wheel is defined to visualize the partitioned features according to their corresponding invariance classes. Experiments and results on both nominal models and measured point clouds are presented to demonstrate the effectiveness of the proposed method.

Effects of nonideal features of silicon photomultiplier on the measurements of quantum correlations

We analyze the effects of some stochastic deviations from the ideal response in silicon photomultipliers that prove to be detrimental for the measurement of quantum properties of light. We demonstrate that an optimized operation mode can overcome some limitations of the detectors allowing the characterization of entanglement in mesoscopic twin-beam states.

Fabrication of Two-Dimensional Crystalline Organic Films by Tilted Spin Coating for High-Performance Organic Field-Effect Transistors.

We developed a facile method for fabricating large-area, two-dimensional (2D), organic, highly crystalline films and extended it to organic thin-film transistor arrays. Tilted spinning provided oriented flow at the three-phase contact line, and a 2D crystalline film that consisted of layer-by-layer stacked 2,7-diocty[1]benzothieno[3,2- b]benzothiophene (C8-BTBT) was obtained facilely for organic thin-film transistors (OTFTs). The extracted field-effect mobility is 4.6 cm2 V-1 s-1, but with nonideal features. By applying this method to microdroplet arrays, an oriented crystal was fabricated, and the channel region for OTFTs was covered by adjusting the spinning speed. By tuning the tilt angle (θ) of the revolving substrate, we fabricated high-performance OTFT arrays with average and maximum mobilities of 7.5 and 10.1 cm2 V-1 s-1, respectively, which exhibited high reliability factors of over 90% and were close to that of ideal transistors. These results suggest that high-quality crystalline films can be obtained via a facile tilted-spinning method.

Mapping the mechanical properties of a graphene drum at the nanoscale

The operation of graphene-based nanoelectromechanical systems (NEMS) crucially depends on the local mechanical characteristics of the graphene drum resonator. In particular, inhomogeneity in the residual strain (pre-strain) of the graphene membrane may affect the vibration dynamics as well as the energy dissipation. Despite its importance, achieving a precise local mapping of the pre-strain of a graphene membrane remains challenging. Here, we correlate scanning-probe force microscopy and Raman spectroscopy to map the local mechanical properties of circular monolayer-graphene drums. At odds with other techniques, we obtain maps of the membrane pre-strain with nanometric resolution and measure the effective Young’s modulus in a non-invasive way. Moreover, we show that the common topographic artefacts stemming from tip-induced deformations can be precisely corrected using the information derived from force-spectroscopy data. As a result, the local map of the pre-strain can be correlated with the true morphology of the graphene drum. Our analysis demonstrates that graphene resonators can be characterized by a non-flat morphology and a non-uniform pre-strain distribution, as a consequence of complex boundary conditions at the edge of the membrane and in correlation with local material defects. Since these non-ideal features are strictly related to the growth and the fabrication procedures, our method can provide a useful screening tool for the development of 2D materials-based NEMSs.