Journal articles on the topic 'Liquid Time Constant Networks'
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1
Hasani, Ramin, Mathias Lechner, Alexander Amini, Daniela Rus, and Radu Grosu. "Liquid Time-constant Networks." Proceedings of the AAAI Conference on Artificial Intelligence 35, no. 9 (May 18, 2021): 7657–66. http://dx.doi.org/10.1609/aaai.v35i9.16936.
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We introduce a new class of time-continuous recurrent neural network models. Instead of declaring a learning system's dynamics by implicit nonlinearities, we construct networks of linear first-order dynamical systems modulated via nonlinear interlinked gates. The resulting models represent dynamical systems with varying (i.e., liquid) time-constants coupled to their hidden state, with outputs being computed by numerical differential equation solvers. These neural networks exhibit stable and bounded behavior, yield superior expressivity within the family of neural ordinary differential equations, and give rise to improved performance on time-series prediction tasks. To demonstrate these properties, we first take a theoretical approach to find bounds over their dynamics, and compute their expressive power by the trajectory length measure in a latent trajectory space. We then conduct a series of time-series prediction experiments to manifest the approximation capability of Liquid Time-Constant Networks (LTCs) compared to classical and modern RNNs.
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Hasani, Ramin, Mathias Lechner, Alexander Amini, Lucas Liebenwein, Aaron Ray, Max Tschaikowski, Gerald Teschl, and Daniela Rus. "Closed-form continuous-time neural networks." Nature Machine Intelligence 4, no. 11 (November 15, 2022): 992–1003. http://dx.doi.org/10.1038/s42256-022-00556-7.
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AbstractContinuous-time neural networks are a class of machine learning systems that can tackle representation learning on spatiotemporal decision-making tasks. These models are typically represented by continuous differential equations. However, their expressive power when they are deployed on computers is bottlenecked by numerical differential equation solvers. This limitation has notably slowed down the scaling and understanding of numerous natural physical phenomena such as the dynamics of nervous systems. Ideally, we would circumvent this bottleneck by solving the given dynamical system in closed form. This is known to be intractable in general. Here, we show that it is possible to closely approximate the interaction between neurons and synapses—the building blocks of natural and artificial neural networks—constructed by liquid time-constant networks efficiently in closed form. To this end, we compute a tightly bounded approximation of the solution of an integral appearing in liquid time-constant dynamics that has had no known closed-form solution so far. This closed-form solution impacts the design of continuous-time and continuous-depth neural models. For instance, since time appears explicitly in closed form, the formulation relaxes the need for complex numerical solvers. Consequently, we obtain models that are between one and five orders of magnitude faster in training and inference compared with differential equation-based counterparts. More importantly, in contrast to ordinary differential equation-based continuous networks, closed-form networks can scale remarkably well compared with other deep learning instances. Lastly, as these models are derived from liquid networks, they show good performance in time-series modelling compared with advanced recurrent neural network models.
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Gupta, Anunay, Anindya Gupta, Apoorv Bansal, and Madan Mohan Tripathi. "Solar Power Prediction using LTC Models." International Journal of Electrical and Electronics Research 10, no. 3 (September 30, 2022): 475–80. http://dx.doi.org/10.37391/ijeer.100312.
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Renewable energy production has been increasing at a tremendous rate in the past decades. This increase in production has led to various benefits such as low cost of energy production and making energy production independent of fossil fuels. However, in order to fully reap the benefits of renewable energy and produce energy in an optimum manner, it is essential that we forecast energy production. Historically deep learning-based techniques have been successful in accurately forecasting solar energy production. In this paper we develop an ensemble model that utilizes ordinary differential based neural networks (Liquid Time constant Networks and Recurrent Neural networks) to forecast solar power production 24 hours ahead. Our ensemble is able to achieve superior result with MAPE of 5.70% and an MAE of 1.07 MW.
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Li, Yannanqi, Zhiyong Yang, Ran Chen, Lingchao Mo, Juanli Li, Minggang Hu, and Shin-Tson Wu. "Submillisecond-Response Polymer Network Liquid Crystal Phase Modulators." Polymers 12, no. 12 (November 30, 2020): 2862. http://dx.doi.org/10.3390/polym12122862.
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A submillisecond-response and light scattering-free polymer-network liquid crystal (PNLC) for infrared spatial light modulators is demonstrated. Our new liquid crystal host exhibits a higher birefringence, comparable dielectric anisotropy, and slightly lower visco-elastic constant than a commonly employed commercial material, HTG-135200. Moreover, the electro-optical performance of our PNLCs with different monomer concentrations, cell gaps, and liquid crystal (LC) hosts is compared and discussed from four aspects: operating voltage, hysteresis, relaxation time, and light scattering loss. The temperature effect on hysteresis is also analyzed. Potential applications of PNLCs for laser beam steering and spatial light modulators especially in the infrared region are foreseeable.
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Bouvier, J. M., and M. Gelus. "Diffusion of Heavy Oil in a Swelling Elastomer." Rubber Chemistry and Technology 59, no. 2 (May 1, 1986): 233–40. http://dx.doi.org/10.5254/1.3538196.
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Abstract The swelling of SBR by an aromatic oil has been experimentally studied at temperatures ranging from ambient to 200°C with thermally stable networks. A model based on Fick's law was developed, and the change of geometry of the elastomer sample was taken into account. The proposed approach is global or macroscopic, and a constant diffusion coefficient has been defined. The diffusion number, ND, defined by two characteristics of a solvent-polymer system, tf the swelling time and tD the diffusion time, represents an important result for engineering applications; it allows prediction of the behavior of amorphous elastomers in contact with a diffusing organic liquid.
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Shumate, Justin, Pierre Baillargeon, Timothy P. Spicer, and Louis Scampavia. "IoT for Real-Time Measurement of High-Throughput Liquid Dispensing in Laboratory Environments." SLAS TECHNOLOGY: Translating Life Sciences Innovation 23, no. 5 (April 12, 2018): 440–47. http://dx.doi.org/10.1177/2472630318769454.
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Critical to maintaining quality control in high-throughput screening is the need for constant monitoring of liquid-dispensing fidelity. Traditional methods involve operator intervention with gravimetric analysis to monitor the gross accuracy of full plate dispenses, visual verification of contents, or dedicated weigh stations on screening platforms that introduce potential bottlenecks and increase the plate-processing cycle time. We present a unique solution using open-source hardware, software, and 3D printing to automate dispenser accuracy determination by providing real-time dispense weight measurements via a network-connected precision balance. This system uses an Arduino microcontroller to connect a precision balance to a local network. By integrating the precision balance as an Internet of Things (IoT) device, it gains the ability to provide real-time gravimetric summaries of dispensing, generate timely alerts when problems are detected, and capture historical dispensing data for future analysis. All collected data can then be accessed via a web interface for reviewing alerts and dispensing information in real time or remotely for timely intervention of dispense errors. The development of this system also leveraged 3D printing to rapidly prototype sensor brackets, mounting solutions, and component enclosures.
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Maximean, Doina Manaila, Octavian Danila, Pedro L. Almeida, and Constantin Paul Ganea. "Electrical properties of a liquid crystal dispersed in an electrospun cellulose acetate network." Beilstein Journal of Nanotechnology 9 (January 15, 2018): 155–63. http://dx.doi.org/10.3762/bjnano.9.18.
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Electro-optical devices that work in a similar fashion as PDLCs (polymer-dispersed liquid crystals), produced from cellulose acetate (CA) electrospun fibers deposited onto indium tin oxide coated glass and a nematic liquid crystal (E7), were studied. CA and the CA/liquid crystal composite were characterized by multiple investigation techniques, such as polarized optical microscopy, dielectric spectroscopy and impedance measurements. Dielectric constant and electric energy loss were studied as a function of frequency and temperature. The activation energy was evaluated and the relaxation time was obtained by fitting the spectra of the dielectric loss with the Havriliak–Negami functions. To determine the electrical characteristics of the studied samples, impedance measurements results were treated using the Cole–Cole diagram and the three-element equivalent model.
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Kalisiak, Michał, and Wojciech Wiatr. "Complete Meniscus Removal Method for Broadband Liquid Characterization in a Semi-Open Coaxial Test Cell." Sensors 19, no. 9 (May 6, 2019): 2092. http://dx.doi.org/10.3390/s19092092.
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We present a new technique for broadband liquid characterization using a semi-open, vertically oriented test cell that is measured with a calibrated vector network analyzer in three states: the empty one and filled with two different volumes of the liquid under test. Using the measurements, we de-embed a transfer matrix representing a volume increment of the liquid sample and determine its column height with a novel closed-form formula. Thanks to the de-embedding, the method enables one, for the first time, to completely remove effects caused by a reproducible meniscus forming the top surface of a liquid tested in the cell and determine not only the propagation constant, but also characteristic impedance of the liquid sample, from which its permittivity and permeability are calculated. The results are highly consistent, because all the measurements are performed without disassembling the cell. We validate experimental results of the meniscus removal method by comparing them with reference data and outcomes of the Nicolson–Ross–Weir method.
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Promhuad, Khwanchat, and Wirasak Smitthipong. "Effect of Stabilizer States (Solid Vs Liquid) on Properties of Stabilized Natural Rubbers." Polymers 12, no. 4 (March 27, 2020): 741. http://dx.doi.org/10.3390/polym12040741.
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The main objective of this work is to study the effect of hydroxylamine sulfate or stabilizer states (solid vs liquid) on the storage hardening of natural rubber (NR). Several types of natural rubber samples were prepared: unstabilized NR samples and stabilized NR samples: (i) dry NR with 0.2 and 2.0 parts per hundred rubber (phr) of dry hydroxylamine sulfate, and (ii) natural latex with 0.2 and 2.0 phr of liquid hydroxylamine sulfate. The samples were characterized immediately (time 0) and after 12 weeks of storage at room temperature, respectively. We found that the Mooney viscosity, gel content, and Wallace plasticity of NR without a stabilizer increases with storage hardening for 12 weeks. However, two types of stabilized NR samples represent constant values of those three parameters, because hydroxylamine sulfate inhibits network and gel formation in NR. Interestingly, the mixing states (solid vs liquid) between natural rubber and the stabilizer affect the properties of stabilized NR. This could be explained by the better dispersion and homogeneous nature of liquid stabilizers in natural latex (liquid state), and thus the higher loading of the stabilizer in the liquid state. This is important, as the stabilization of NR properties as a function of time is required by rubber industry. This study is a utilization model from theory to application.
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Wang, Xian, Zhengxiang Song, Kun Yang, Xuyang Yin, Yingsan Geng, and Jianhua Wang. "State of Charge Estimation for Lithium-Bismuth Liquid Metal Batteries." Energies 12, no. 1 (January 7, 2019): 183. http://dx.doi.org/10.3390/en12010183.
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Lithium-bismuth liquid metal batteries have much potential for stationary energy storage applications, with characteristics such as a large capacity, high energy density, low cost, long life-span and an ability for high current charge and discharge. However, there are no publications on battery management systems or state-of-charge (SoC) estimation methods, designed specifically for these devices. In this paper, we introduce the properties of lithium-bismuth liquid metal batteries. In analyzing the difficulties of traditional SoC estimation techniques for these devices, we establish an equivalent circuit network model of a battery and evaluate three SoC estimation algorithms (the extended Kalman filter, the unscented Kalman filter and the particle filter), using constant current discharge, pulse discharge and hybrid pulse (containing charging and discharging processes) profiles. The results of experiments performed using the equivalent circuit battery model show that the unscented Kalman filter gives the most robust and accurate performance, with the least convergence time and an acceptable computation time, especially in hybrid pulse current tests. The time spent on one estimation with the three algorithms are 0.26 ms, 0.5 ms and 1.5 ms.
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Zhang, Duo, and Shixing Fan. "Enhancing Methane Recovery with Cryogenic Liquid CO2 Cyclic Injection: Determination of Cyclic Injection Parameters." International Journal of Environmental Research and Public Health 19, no. 20 (October 13, 2022): 13155. http://dx.doi.org/10.3390/ijerph192013155.
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Carbon dioxide (CO2) is both a primary greenhouse gas and a readily available energy source. In this study, a new underground coal permeability enhancement technique utilizing cryogenic liquid CO2 (L-CO2) cyclic injection is proposed. The key parameters that determine the feasibility of this technique are cycle period and cycle number within a fixed working period. The optimal value of these two parameters mainly depends on the pore structure evolution law of coal cores before and after cryogenic L-CO2 cyclic freeze–thaw. Accordingly, nuclear magnetic resonance (NMR) was employed to study the evolution characteristics of the fracture networks and pore structures in coal cores subjected to different freeze–thaw cyclic modes. The results demonstrated that the amplitude and width of all peaks of the T2 spectra of the three coal cores (lignite, gas coal, and 1/3 coking coal) increased with an increase in the number of injection cycles. Additionally, as the number of freeze–thaw cycles (Nc) increased, the total porosity and effective porosity of the coal cores increased linearly before stabilizing, while the residual porosity first steadily diminished and afterwards became constant. Furthermore, the variation in the total porosity and residual porosity of the coal cores continuously diminished with an increase in the level of metamorphism. The NMR permeability of the coal cores showed a similar pattern to the porosity. Accordingly, the optimal parameters for cryogenic L-CO2 cyclic injection during a complete working time were determined to be Nc = 4 and Pc = 30 min. A field test demonstrated that after L-CO2 cyclic freeze–thaw treatment, the average gas drainage concentration of a single borehole in the test region increased by 1.93 times, while the pure flow of a single gas drainage borehole increased by 2.21 times. Finally, the gas attenuation coefficient decreased from 0.036 to 0.012. We concluded that the proposed permeability enhancement technique transformed coal seams from hard-to-drain to drainable.
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Rasmussen, Claus P., Kristian Krejbjerg, Michael L. Michelsen, and Kersti E. Bjurstrøm. "Increasing the Computational Speed of Flash Calculations With Applications for Compositional, Transient Simulations." SPE Reservoir Evaluation & Engineering 9, no. 01 (February 1, 2006): 32–38. http://dx.doi.org/10.2118/84181-pa.
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Summary Approaches are presented for reducing the computation time spent on flash calculations in compositional, transient simulations. In a conventional flash calculation, the majority of the simulation time is spent on stability analysis, even for systems far into the single-phase region. A criterion has been implemented for deciding when it is justified to bypass the stability analysis. With the implementation of the developed time-saving initiatives, it has been shown for a number of compositional, transient pipeline simulations that a reduction of the computation time spent on flash calculations by approximately 85 to 90% can be achieved. Introduction Modeling of oil production requires simulations of transient flow. Examples are miscible-gas displacement in petroleum reservoirs and multiphase flow in pipelines, including slug formation and startup scenarios. In a typical transient-flow simulation, the system is discretized into a number of cells or sections. Phase amounts and phase properties are needed for each cell or section to solve the conservation equations in the model, and specifically for transient pipeline simulations to calculate such properties as heat loss to the surroundings, liquid holdup, and pressure drop. If the overall composition is constant during the simulation, the phase properties can be stored in precalculated tables listing the needed properties as a function of pressure and temperature (Bendiksen et al. 1991; Xu and Shea 2001). This is referred to in the following sections as a noncompositional, table-based simulation. When simulating miscible-gas displacement in reservoirs, the assumption of a constant overall composition is not adequate because the injection gas will dissolve in the reservoir fluid and vice versa. Similarly, in many typical multiphase pipelines, the fluid composition will vary because of velocity differences between phases, interfacial mass transfer, and merging networks. In these situations, a compositional approach is useful. A compositional model has the drawback that the computation time is much higher than that of a noncompositional table-based approach. The phase amounts and properties must be evaluated in each cell or section in each timestep. Furthermore, phase compositions are required to calculate the interfacial mass transfer. Nevertheless, the increased accuracy in the fluid description makes the compositional approach attractive to represent multiphase pipelines and reservoirs with large compositional variations. Flash Equilibrium Calculations in Compositional, Transient Simulations The physical properties of a fluid in a cell or section depend on whether the fluid is present as a single phase or splits into several equilibrium phases. A flash calculation is therefore required in each timestep to determine the number of equilibrium phases and their amounts and compositions. Even with relatively few mixture components, the computation time of a compositional, transient simulation far exceeds that of a corresponding noncompositional, table-based simulation; furthermore, the computation time increases with an increased number of components.
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Pastor, José V., José M. García-Oliver, Carlos Micó, Alba A. García-Carrero, and Arantzazu Gómez. "Experimental Study of the Effect of Hydrotreated Vegetable Oil and Oxymethylene Ethers on Main Spray and Combustion Characteristics under Engine Combustion Network Spray A Conditions." Applied Sciences 10, no. 16 (August 7, 2020): 5460. http://dx.doi.org/10.3390/app10165460.
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The stringent emission regulations have motivated the development of cleaner fuels as diesel surrogates. However, their different physical-chemical properties make the study of their behavior in compression ignition engines essential. In this sense, optical techniques are a very effective tool for determining the spray evolution and combustion characteristics occurring in the combustion chamber. In this work, quantitative parameters describing the evolution of diesel-like sprays such as liquid length, spray penetration, ignition delay, lift-off length and flame penetration as well as the soot formation were tested in a constant high pressure and high temperature installation using schlieren, OH∗ chemiluminescence and diffused back-illumination extinction imaging techniques. Boundary conditions such as rail pressure, chamber density and temperature were defined using guidelines from the Engine Combustion Network (ECN). Two paraffinic fuels (dodecane and a renewable hydrotreated vegetable oil (HVO)) and two oxygenated fuels (methylal identified as OME1 and a blend of oxymethylene ethers, identified as OMEx) were tested and compared to a conventional diesel fuel used as reference. Results showed that paraffinic fuels and OMEx sprays have similar behavior in terms of global combustion metrics. In the case of OME1, a shorter liquid length, but longer ignition delay time and flame lift-off length were observed. However, in terms of soot formation, a big difference between paraffinic and oxygenated fuels could be appreciated. While paraffinic fuels did not show any significant decrease of soot formation when compared to diesel fuel, soot formed by OME1 and OMEx was below the detection threshold in all tested conditions.
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Cherubini, C., C. I. Giasi, and N. Pastore. "On the reliability of analytical models to predict solute transport in a fracture network." Hydrology and Earth System Sciences 18, no. 6 (June 24, 2014): 2359–74. http://dx.doi.org/10.5194/hess-18-2359-2014.
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Abstract. In hydrogeology, the application of reliable tracer transport model approaches is a key issue to derive the hydrodynamic properties of aquifers. Laboratory- and field-scale tracer dispersion breakthrough curves (BTC) in fractured media are notorious for exhibiting early time arrivals and late time tailing that are not captured by the classical advection–dispersion equation (ADE). These "non-Fickian" features are proven to be better explained by a mobile–immobile (MIM) approach. In this conceptualization the fractured rock system is schematized as a continuous medium in which the liquid phase is separated into flowing and stagnant regions. The present study compares the performances and reliabilities of the classical MIM and the explicit network model (ENM), taking expressly into account the network geometry for describing tracer transport behavior in a fractured sample at bench scale. Though ENM shows better fitting results than MIM, the latter remains still valid as it proves to describe the observed curves quite well. The results show that the presence of nonlinear flow plays an important role in the behavior of solute transport. First, the distribution of solute according to different pathways is not constant, but it is related to the flow rate. Second, nonlinear flow influences advection in that it leads to a delay in solute transport respect to the linear flow assumption. However, nonlinear flow is not shown to be related with dispersion. The experimental results show that in the study case the geometrical dispersion dominates the Taylor dispersion. However, the interpretation with the ENM shows a weak transitional regime from geometrical dispersion to Taylor dispersion for high flow rates. Incorporating the description of the flow paths in the analytical modeling has proven to better fit the curves and to give a more robust interpretation of the solute transport.
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Cherubini, C., C. I. Giasi, and N. Pastore. "On the reliability of analytical models to predict solute transport in a fracture network." Hydrology and Earth System Sciences Discussions 10, no. 12 (December 6, 2013): 14905–48. http://dx.doi.org/10.5194/hessd-10-14905-2013.
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Abstract. In hydrogeology, the application of reliable tracer transport model approaches is a key issue to derive the hydrodynamic properties of aquifers. Laboratory and field-scale tracer dispersion breakthrough curves (BTC) in fractured media are notorious for exhibiting early time arrivals and late-time tailing that are not captured by the classical advection–dispersion equation (ADE). These "non-Fickian" features are proved to be better explained by a mobile–immobile (MIM) approach. In this conceptualization the fractured rock system is schematized as a continuous medium in which the liquid phase is separated into flowing and stagnant regions. The present study compares the performances and reliabilities of classical Mobile–Immobile Model (MIM) and the Explicit Network Model (ENM) that takes expressly into account the network geometry for describing tracer transport behavior in a fractured sample at bench scale. Though ENM shows better fitting results than MIM, the latter remains still valid as it proves to describe the observed curves quite well. The results show that the presence of nonlinear flow plays an important role in the behaviour of solute transport. Firstly the distribution of solute according to different pathways is not constant but it is related to the flow rate. Secondly nonlinear flow influences advection, in that it leads to a delay in solute transport respect to the linear flow assumption. Whereas nonlinear flow does not show to be related with dispersion. However the interpretation with the ENM model shows a weak transitional regime from geometrical dispersion to Taylor dispersion for high flow rates. The experimental results show that in the study case the geometrical dispersion dominates the Taylor dispersion. Incorporating the description of the flowpaths in the analytical modeling has proved to better fit the curves and to give a more robust interpretation of the solute transport.
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Denny, E., and R. C. Schroter. "Viscoelastic Behavior of a Lung Alveolar Duct Model." Journal of Biomechanical Engineering 122, no. 2 (October 18, 1999): 143–51. http://dx.doi.org/10.1115/1.429644.
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A study is conducted into the oscillatory behavior of a finite element model of an alveolar duct. Its load-bearing components consist of a network of elastin and collagen fibers and surface tension acting over the air–liquid interfaces. The tissue is simulated using a visco-elastic model involving nonlinear quasi-static stress–strain behavior combined with a reduced relaxation function. The surface tension force is simulated with a time- and area-dependent model of surfactant behavior. The model was used to simulate lung parenchyma under three surface tension cases: air-filled, liquid-filled, and lavaged with 3-dimethyl siloxane, which has a constant surface tension of 16 dyn/cm. The dynamic elastance Edyn and tissue resistance Rti were computed for sinusoidal tidal volume oscillations over a range of frequencies from 0.16–2.0 Hz. A comparison of the variation of Edyn and Rti with frequency between the model and published experimental data showed good qualitative agreement. Little difference was found in the model between Rti for the air-filled and lavaged models; in contrast, published data revealed a significantly higher value of Rti in the lavaged lung. The absence of a significant increase in Rti for the lavaged model can be attributed to only minor changes in the individual fiber bundle resistances with changes in their configuration. The surface tension was found to make an important contribution to both Edyn and Rti in the air-filled duct model. It was also found to amplify any existing tissue dissipative properties, despite exhibiting none itself over the small tidal volume cycles examined. [S0148-0731(00)00502-1]
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Hopkin, Emma, Anthony J. Illingworth, Cristina Charlton-Perez, Chris D. Westbrook, and Sue Ballard. "A robust automated technique for operational calibration of ceilometers using the integrated backscatter from totally attenuating liquid clouds." Atmospheric Measurement Techniques 12, no. 7 (July 30, 2019): 4131–47. http://dx.doi.org/10.5194/amt-12-4131-2019.
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Abstract. A simple and robust method for calibrating ceilometers has been tested in an operational environment, demonstrating that the calibrations are stable to better than ±5 % over a period of a year. The method relies on using the integrated backscatter (B) from liquid clouds that totally extinguish the ceilometer signal; B is inversely proportional to the lidar ratio (S) of the backscatter to the extinction for cloud droplets. The calibration technique involves scaling the observed backscatter so that B matches the predicted value for S of 18.8±0.8 sr for cloud droplets, at ceilometer wavelengths. For accurate calibration, care must be taken to only use profiles where the range correction is implemented and to exclude any profiles having targets with different values of S, such as drizzle drops and aerosol particles, profiles that do not totally extinguish the ceilometer signal, profiles with low cloud bases that saturate the receiver, and any profiles for which the window transmission or the lidar pulse energy falls below 90 %. A range-dependent multiple-scattering correction that depends on the ceilometer optics should also be applied to the profile. For ceilometers operating at around 910 nm wavelength, a simple correction for water vapour attenuation is applied to the signal using the vapour profiles from a forecast analysis. For a generic ceilometer in the UK the 90 d running mean of the calibration coefficient over a period of 20 months is constant to within 3 % with no detectable annual cycle, thus confirming the validity of the humidity and multiple-scattering correction. For Gibraltar, where cloud cover is less prevalent than in the UK, the 90 d running mean calibration coefficient was constant to within 4 %. The more sensitive ceilometer model operating at 1064 nm is unaffected by water vapour attenuation but is more prone to saturation in liquid clouds; such profiles can be recognised and rejected and, despite the more restricted sample of cloud profiles, a robust calibration is readily achieved. In the UK, the running mean 90 d calibration coefficients varied by about 4 % over a period of 1 year. The consistency of profiles observed by nine pairs of co-located ceilometers in the UK Met Office network operating at around 910 and 1064 nm provided independent validation of the calibration technique. In all cases, if quantitative and reliable backscatter observations are to be obtained it is essential to keep the window clean. This may be a challenge in dusty locations. EUMETNET is currently networking 700 European ceilometers so they can provide ceilometer profiles in near real time to European weather forecast centres and has adopted the cloud calibration technique described in this paper for ceilometers with a wavelength of around 910 nm.
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Sato, Ryoma, Makoto Yamada, and Hisashi Kashima. "Constant Time Graph Neural Networks." ACM Transactions on Knowledge Discovery from Data 16, no. 5 (October 31, 2022): 1–31. http://dx.doi.org/10.1145/3502733.
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The recent advancements in graph neural networks (GNNs) have led to state-of-the-art performances in various applications, including chemo-informatics, question-answering systems, and recommender systems. However, scaling up these methods to huge graphs, such as social networks and Web graphs, remains a challenge. In particular, the existing methods for accelerating GNNs either are not theoretically guaranteed in terms of the approximation error or incurred at least a linear time computation cost. In this study, we reveal the query complexity of the uniform node sampling scheme for Message Passing Neural Networks, including GraphSAGE, graph attention networks (GATs), and graph convolutional networks (GCNs). Surprisingly, our analysis reveals that the complexity of the node sampling method is completely independent of the number of the nodes, edges, and neighbors of the input and depends only on the error tolerance and confidence probability while providing a theoretical guarantee for the approximation error. To the best of our knowledge, this is the first article to provide a theoretical guarantee of approximation for GNNs within constant time. Through experiments with synthetic and real-world datasets, we investigated the speed and precision of the node sampling scheme and validated our theoretical results.
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Jacob, Marek, Felix Ament, Manuel Gutleben, Heike Konow, Mario Mech, Martin Wirth, and Susanne Crewell. "Investigating the liquid water path over the tropical Atlantic with synergistic airborne measurements." Atmospheric Measurement Techniques 12, no. 6 (June 19, 2019): 3237–54. http://dx.doi.org/10.5194/amt-12-3237-2019.
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Abstract. Liquid water path (LWP) is an important quantity to characterize clouds. Passive microwave satellite sensors provide the most direct estimate on a global scale but suffer from high uncertainties due to large footprints and the superposition of cloud and precipitation signals. Here, we use high spatial resolution airborne microwave radiometer (MWR) measurements together with cloud radar and lidar observations to better understand the LWP of warm clouds over the tropical North Atlantic. The nadir measurements were taken by the German High Altitude and LOng range research aircraft (HALO) in December 2013 (dry season) and August 2016 (wet season) during two Next-generation Advanced Remote sensing for VALidation (NARVAL) campaigns. Microwave retrievals of integrated water vapor (IWV), LWP, and rainwater path (RWP) are developed using artificial neural network techniques. A retrieval database is created using unique cloud-resolving simulations with 1.25 km grid spacing. The IWV and LWP retrievals share the same eight MWR frequency channels in the range from 22 to 31 GHz and at 90 GHz as their sole input. The RWP retrieval combines active and passive microwave observations and is able to detect drizzle and light precipitation. The comparison of retrieved IWV with coincident dropsondes and water vapor lidar measurements shows root-mean-square deviations below 1.4 kg m−2 over the range from 20 to 60 kg m−2. This comparison raises the confidence in LWP retrievals which can only be assessed theoretically. The theoretical analysis shows that the LWP error is constant with 20 g m−2 for LWP below 100 g m−2. While the absolute LWP error increases with increasing LWP, the relative one decreases from 20 % at 100 g m−2 to 10 % at 500 g m−2. The identification of clear-sky scenes by ancillary measurements, here backscatter lidar, is crucial for thin clouds (LWP < 12 g m−2) as the microwave retrieved LWP uncertainty is higher than 100 %. The analysis of both campaigns reveals that clouds were more frequent (47 % vs. 30 % of the time) in the dry than in the wet season. Their average LWP (63 vs. 40 g m−2) and RWP (6.7 vs. 2.7 g m−2) were higher as well. Microwave scattering of ice, however, was observed less frequently in the dry season (0.5 % vs. 1.6 % of the time). We hypothesize that a higher degree of cloud organization on larger scales in the wet season reduces the overall cloud cover and observed LWP. As to be expected, the observed IWV clearly shows that the dry season is on average less humid than the wet season (28 vs. 41 kg m−2). The results reveal that the observed frequency distributions of IWV are substantially affected by the choice of the flight pattern. This should be kept in mind when using the airborne observations to carefully mediate between long-term ground-based and spaceborne measurements to draw statistically sound conclusions.
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Milic, Petar, Katarina Rajkovic, Predrag Milicevic, Slavica Milic, Tanja Brdaric, and Vesna Pavelkic. "Comparison, artificial neural network modeling and genetic algorithm optimization of the resinoid and potassium yields from white lady’s bedstraw (Galium mollugo L.) by conventional, reflux and ultrasound-assisted aqueous-ethanolic extraction." Chemical Industry and Chemical Engineering Quarterly 19, no. 1 (2013): 141–52. http://dx.doi.org/10.2298/ciceq120316049m.
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In this work, the yields of resinoid and potassium obtained from aerial parts of white lady?s bedstraw (Galium mollugo L.) by maceration, reflux extraction and ultrasound-assisted extraction using aqueous ethanol solutions as solvents. The main goal was to define the influence of the extraction technique and the ethanol concentration on the resinoid and potassium yields. The resinoid and potassium yields were determined by the solvent evaporation from the liquid extracts to constant weight and the AAS emission method, respectively. The dependence of resinoid and potassium yields on the ethanol concentration was described by linear and quadratic polynomial models, respectively. The best potassium extraction selectivity of 0.077 g K/g of dry extract was achieved by maceration at the ethanol concentrations of 10 g/100 g. The artificial neural network (ANN) was successfully applied to estimate the resinoid and potassium yields based on the ethanol concentration in the extracting solvent and the time duration for all three extraction techniques employed. The response surface methodology was also used to present the dependence of ANN results on the operating factors. The extraction process was optimized using the ANN model coupled with genetic algorithm. The maximum predicted resinoid and potassium yields of 30.4 and 1.67 g/100 g of dry plant were obtained by the ultrasonic extraction (80 min) using the 10 g/100 g aqueous ethanol solution.
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Lerner, D. N., G. P. Wealthall, and A. Steele. "Assessing Risk from DNAPLs in Fractured Aquifers." Journal of Agricultural and Marine Sciences [JAMS] 7, no. 2 (June 1, 2002): 47. http://dx.doi.org/10.24200/jams.vol7iss2pp47-52.
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Chlorinated solvents are among the most widespread pollutants of groundwater. As DNAPLs (dense nonaqueous phase liquids), they can move rapidly and in complex patterns through fractures to reach and contaminate large volumes of aquifer, and then dissolve to cause significant pollution of groundwater. However, clean-up of DNAPLs in fractured rocks is virtually impossible and certainly expensive. Risk assessment should be used to decide whether the pollution is serious enough to justify major expenditure on clean-up or containment. A key aspect of risk assessment for DNAPLs in fractured aquifers is to understand how deep they are likely to have penetrated through the fracture network. This paper addresses two aspects of such predictions: measuring fracture apertures in situ and the connectivity of fracture networks with respect to DNAPLs. Fracture aperture is an in-situ field technique that has been developed and implemented to measure aperture variability and NAPL entry pressure in an undisturbed, water-saturated rock fracture. The field experiment also provided the opportunity to measure the wetting phase relative permeability at residual non-wetting phase saturation. The RADIO (Radial Aperture Determination by the Injection of Oil) method employs a constant rate injection of a non-toxic NAPL into a fracture isolated by a double packer array. The method was applied at the field site in Scotland, and measured apertures out to ~5m from the borehole. It showed that hydraulic aperture (from packer tests) was a poor estimator of the controlling aperture for DNAPL movement. This is the first time such large-scale aperture measurements have been made, and the technique is the first which can provide useful aperture estimates for risk analysis of DNAPL movement.Network connectivity is a fundamental property of the fracture system. DNAPL connectivity extends the concept to take account of the fluid properties.
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Varin, Remi, Shahsultan Mirshahi, Pehzman Mirshahi, Jean Chidiac, Gerald Kierzek, Jean-Pierre Marie, Massoud Mirshahi, Claudine Soria, and Jeannette Soria. "Effect of Rivaroxaban, An Oral Direct Factor Xa Inhibitor, On Whole Blood Clot Permeation and Thrombolysis: Critical Role of Red Blood Cells." Blood 114, no. 22 (November 20, 2009): 1064. http://dx.doi.org/10.1182/blood.v114.22.1064.1064.
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Abstract Abstract 1064 Poster Board I-86 Introduction: Decreased fibrinolysis has been reported in venous thrombosis. Thrombus degradation depends on its structure: thicker fibrin fibers are permeable to blood flow and highly susceptible to fibrinolytic enzymes, while thinner fibers are poorly permeable to flow and are resistant to fibrinolysis. Thrombin concentration present at the time of gelation profoundly influences fibrin clot structure: decrease in thrombin generation leads to the formation of thick fibrin fibers and to a decrease in activation of thrombin-activated fibrinolysis inhibitor (TAFI). Rivaroxaban, an oral direct factor Xa inhibitor, is in late stage clinical development for the prevention and treatment of venous and arterial thrombosis. The objective of this study was to evaluate the effect of Rivaroxaban on whole blood (WB) clot structure and degradability by t-PA. Compared to plasma clots, WB clots might better represent the in vivo formed thrombi. Methods: 1- Clots were formed by adding to WB or to corresponding plasma, low concentration of tissue factor and calcium in the presence or absence of Rivaroxaban at therapeutic concentrations (0.15 and 0.25 μg/ml). 2- Clot permeability was calculated by measuring the flow rate of liquid through the clot. It was expressed as Darcy constant. 3- Clot degradability was evaluated by D dimers generation during clot perfusion with plasminogen and tissue-type plasminogen activator (t-PA). Results: 1- In the absence of Rivaroxaban, WB clots had a lower porosity than that of corresponding plasma clots: Darcy constant of WB clots was 3.1 –fold lower than that of plasma clots. This decreased porosity of WB clots leads to thrombolysis resistance by preventing access of fibrinolytic enzymes to fibrin network: D dimers generation in t-PA-perfused clots for 60 min was 38 -fold lower in WB clots compared to plasma clots. 2- Rivaroxaban increased the permeation rate of WB clots and thrombolysis by t-PA: the addition of Rivaroxaban at 0.15 μg/ml in WB (corresponding in fact to plasma concentration of 0.25 μg/ml), increased the Darcy constant by 5.5 –fold and the clot degradability in 60 min by 108 -fold. These effects of Rivaroxaban were higher in WB clots than in corresponding plasma clots, as Rivaroxaban at 0.25 μg/ml in plasma clots increased the Darcy constant by 2.5-fold and clot degradation by 9.6-fold. In the presence of Rivaroxaban, the Darcy constant and the degradability of WB clots and of plasma clots were nearly identical. 3- To explain the greater efficacy of Rivaroxaban on WB permeation constants and thrombolysis in comparison to plasma clots a) we tested the possibility for Rivaroxaban to reduce the entrapment of red blood cells (RBC) into the network of fibrin as RBC can be responsible for fibrin pore occlusion. This possibility was excluded since Rivaroxaban had no effect on clot permeation rate in clots formed by clotting purified fibrinogen with thrombin in the presence or in the absence of RBC (condition in which there is no generation of thrombin): RBC induced a 2.5 times decrease in permeation rate due to entrapment of RBC into fibrin network, regardless of presence or absence of Rivaroxaban. b) we analyzed the effect of RBC on thrombin generation and its modification by Rivaroxaban: the addition of 0.1 ml RBC diluted ½ to 0,2 ml plasma increased the thrombin generation (540 % of control without RBC). This is probably due to exposure of phosphatidyl serine at surface of RBC during thrombin generation. The increase in thrombin generation by RBC was reduced to 140 % in presence of Rivaroxaban at 0.15 μg/ml. This is explained by Rivaroxaban's inhibition of factor Xa bound to cells. Conclusion: Thrombin generation was greater in WB than in plasma, leading to a lower porosity and degradability of WB clots as compared to plasma clots. Rivaroxaban, by decreasing thrombin generation, increased clot permeability and degradability to the same level in WB clots and plasma clots. This property of Rivaroxaban may contribute to its antithrombotic effect. This study received a support from Bayer-Schering-Pharma France. Disclosures: No relevant conflicts of interest to declare.
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Шишмарев, Константин Александрович, and Татьяна Ивановна Хабахпашева. "Unsteady deflection of ice cover in a frozen channel under a moving load." Вычислительные технологии, no. 2(24) (April 17, 2019): 111–28. http://dx.doi.org/10.25743/ict.2019.24.2.010.
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Рассмотрена нестационарная задача об изгибно-гравитационных волнах на поверхности замороженного ледового канала, вызванных движением внешней нагрузки. Задача решается методом преобразования Фурье вдоль канала и разложением прогибов льда по модам бегущих изгибно-гравитационных волн в канале. Предложен алгоритм, позволяющий привести решение, полученное с помощью обратного преобразования Фурье, к аналитическим формулам в виде суммы стационарных и нестационарных прогибов при конечных временах в системе координат, движущейся вместе с нагрузкой. Исследована эволюция прогибов во времени для разных скоростей движения нагрузки. Показано, что при увеличении времени решение для нестационарных прогибов ледовой пластины выходит на установившийся режим в системе координат, связанной с нагрузкой. Исследовано влияние коэффициента затухания на образование волн. The non-stationary problem of a moving external load along the surface of a frozen channel is studied in this paper. The channel has a rectangular cross section and is filled with an ideal fluid. The ice cover on the surface of the liquid is modelled by a thin elastic or viscoelastic plate (Kelvin-Voigt model), which is frozen to the channel walls. The external load is modelled by a local pressure moving at a constant speed along the channel. The ice-fluid-load system initially is at rest. The flow caused by both the moving load and the ice deflection is supposed to be potential. The problem is solved using the Fourier transform along the channel and by the method of normal modes. The presence of the channel walls and boundary conditions on them lead to an infinite (countable) number of dispersion relations and critical speeds for the hydroelastic waves propagating in the channel. Depending on the speed of the load, the form of the ice cover oscillations has one of two main cases. When the load moves at a speed lower than the first critical speed, the ice deflection is localised in the vicinity of the load. When the load is moving at supercritical speed, a system of hydroelastic waves propagating from the load is formed. The number of these wave systems is finite and depends on the relation of the speed of the load with the critical speeds for the channel. It is shown that as time increases, the solution for the ice deflection converge to a steady state in the coordinate system moving with the load. The influence of the retardation time on the formation of the ice deflections is investigated.
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Bertossi, A. A., and A. Mei. "Constant time dynamic programming on directed reconfigurable networks." IEEE Transactions on Parallel and Distributed Systems 11, no. 6 (June 2000): 529–36. http://dx.doi.org/10.1109/71.862204.
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Krishnaswamy, P. R., and M. G. Joseph. "Gain and time-constant variations in liquid-fluidized beds." Powder Technology 44, no. 3 (October 1985): 255–59. http://dx.doi.org/10.1016/0032-5910(85)85007-5.
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Hardy, Elaissa, Yumiko Sakurai, Nadia Sanjaya, Alisa S. Wolberg, and Wilbur Lam. "Effect of Locally Applied Electricity On Clot Formation and Hemostasis." Blood 120, no. 21 (November 16, 2012): 2220. http://dx.doi.org/10.1182/blood.v120.21.2220.2220.
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Abstract Abstract 2220 Background: Electricity has historically been used in medical applications such as defibrillators, cauterization, and electrosurgery. Additionally, Kalghatgi et al. [1] demonstrate that high voltage electrical fields (∼30 kilo volts) activate platelets and induce coagulation. However, the exact effect of applied electrical current on clot formation is unknown. We show that upon direct application of electricity (voltages between 5 – 40 volts), platelets are activated immediately and clots rapidly form without excessive heating. This newfound application to induce blood clot formation may enable a new and novel class of therapeutics to achieve hemostasis at sites of bleeding. As newer hemostatic agents are currently derived from animal or human products, which carry risk of blood borne infections and immune dysregulation, a clear need exists for novel therapies to achieve hemostasis. Method: Our experimental setup consisted of a silicone polydimethylsiloxane (PDMS) chamber with embedded metallic wires (Figure 1A). The metallic leads were connected to an Agilent E3649A variable power supply and a constant voltage was applied to the chamber for 1 minute. A Fluke 179 multimeter monitored the temperature with a thermocouple lead inserted into the liquid in the chamber. Experiments were conducted using whole human blood, platelet rich plasma (PRP), platelet poor plasma (PPP), and isolated, washed platelets. Additionally, fluorescently labeled fibrinogen (Alexa Fluor 488) was added to the blood product, 5%v/v, to assess fibrin formation. Experiment: Initial experiments characterized the electrical characteristics of the different components of blood pertinent for clot formation to assess the potential safety concerns. Voltages between 5 – 40 volts (V) result in currents below 0.1 amps (A) and temperatures between 20 – 50°C. Nominally, current values of 0.1A and greater are considered deadly [2], and thermal tissue damage caused by temperatures below 45°C are considered reversible [2], therefore the majority of our work focuses on voltages less than 30V. Figure 1B shows the timeline of fibrin network formation for a control whole blood sample versus a whole blood sample exposed to 30V for 60 seconds. At 30V and immediately after electrical stimulus, platelet aggregation begins to form. At 120 seconds, fibrin polymerization initiates and showed complete coverage at 180 seconds, as well as numerous clusters of platelet aggregates. In the absence of electrical stimulus, no fibrin polymerization or platelet aggregation was detected until greater than 240 seconds and full network coverage was complete by 420 second. Platelet aggregration was more pronouced with electrical stimulus, as compared to the control case. Various voltages were tested with the mean time to complete the fibrin network formation in stimulated and unstimulated whole blood was 170 seconds vs. 320 seconds, respectively (n = 3) indicating a 53% increase in fibrin formation and platelet aggregation. Additional experiments were conducted on anti-coagulated PPP, PRP, and isolated, washed platelets showing no evidence of fibrin polymerization. This suggests that all the components in blood are necessary to create the fibrin scaffold when exposed to electricity. Continued work will focus on unraveling the underlying mechanisms of how electrical stimulation affects platelet aggregation and coagulation. Conclusion: Our results suggest that direct electrical stimulation promotes clot formation and could potentially lead to a new category of hemostatic therapies that are free from the infectious risks and immune effects that encumber current human or animal-derived agents. With the addition of electrical stimulus, fibrin networks form on average 53% faster than control conditions. We anticipate this concept of applying electricity to different processes in the blood will have significant implications for experimental and clinical hematology. Disclosures: No relevant conflicts of interest to declare.
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Lin, Xiaojun, and Shahzada B. Rasool. "Constant-Time Distributed Scheduling Policies for Ad Hoc Wireless Networks." IEEE Transactions on Automatic Control 54, no. 2 (February 2009): 231–42. http://dx.doi.org/10.1109/tac.2008.2010888.
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Mitzenmacher, Michael. "Constant time per edge is optimal on rooted tree networks." Distributed Computing 10, no. 4 (July 28, 1997): 189–97. http://dx.doi.org/10.1007/s004460050036.
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Shen, Yingying, Junkai Chong, Ziniu Huang, Jianke Tian, Wenjuan Zhang, Xingchang Tang, Wanwu Ding, and Xueyan Du. "Viscosity and Structure of a CaO-SiO2-FeO-MgO System during a Modified Process from Nickel Slag by CaO." Materials 12, no. 16 (August 12, 2019): 2562. http://dx.doi.org/10.3390/ma12162562.
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There is a high iron content in nickel slag that mainly exists in the fayalite phase. Basic oxide can destroy the stable structure of fayalite which is beneficial to the treatment and comprehensive utilization of nickel slag. The research was based on the composition of the raw nickel slag, taking the CaO-SiO2-FeO-MgO system as the object and CaO as a modifier. The effect of basicity on the melting characteristics, viscosity and structure of the CaO-SiO2-FeO-MgO system was studied. The relationship between the viscosity and structure of the CaO-SiO2-FeO-MgO system was also explored. The results show as follows: (1) When the basicity is lower than 0.90, the primary phase of the slag system is olivine phase. When the basicity is greater than 0.90, the primary phase of the slag system transforms into monoxide. When the basicity is 0.90, olivine and monoxide precipitate together as the temperature continues to decrease. At the same time, the liquidus temperature, softening temperature, hemispherical temperature, and flow temperature all reach the lowest value. (2) With the increase of basicity, the critical viscosity temperature of the CaO-SiO2-FeO-MgO system decreases first and then increases. Critical viscosity temperature is the lowest at the basicity of 0.90, which is 1295 °C. (3) When the slag system is heterogeneous, the viscosity of the molten slag increases rapidly because of the quantity of solid phase precipitated from the CaO-SiO2-FeO-MgO system. (4) When the slag system is in a homogeneous liquid phase, the molar fraction of O0 decreases with the increase of basicity and the mole fraction of O−, and O2− increases continuously at the basicity of 0.38~1.50. The silicate network structure is gradually depolymerized into simple monomers, resulting in the degree of polymerization, and the viscosity, being reduced. The mole fraction of different kinds of oxygen atoms is converged to a constant value when the basicity is above 1.20.
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Kvamme, Håvard, and Ørnulf Borgan. "Continuous and discrete-time survival prediction with neural networks." Lifetime Data Analysis 27, no. 4 (October 2021): 710–36. http://dx.doi.org/10.1007/s10985-021-09532-6.
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AbstractDue to rapid developments in machine learning, and in particular neural networks, a number of new methods for time-to-event predictions have been developed in the last few years. As neural networks are parametric models, it is more straightforward to integrate parametric survival models in the neural network framework than the popular semi-parametric Cox model. In particular, discrete-time survival models, which are fully parametric, are interesting candidates to extend with neural networks. The likelihood for discrete-time survival data may be parameterized by the probability mass function (PMF) or by the discrete hazard rate, and both of these formulations have been used to develop neural network-based methods for time-to-event predictions. In this paper, we review and compare these approaches. More importantly, we show how the discrete-time methods may be adopted as approximations for continuous-time data. To this end, we introduce two discretization schemes, corresponding to equidistant times or equidistant marginal survival probabilities, and two ways of interpolating the discrete-time predictions, corresponding to piecewise constant density functions or piecewise constant hazard rates. Through simulations and study of real-world data, the methods based on the hazard rate parametrization are found to perform slightly better than the methods that use the PMF parametrization. Inspired by these investigations, we also propose a continuous-time method by assuming that the continuous-time hazard rate is piecewise constant. The method, named PC-Hazard, is found to be highly competitive with the aforementioned methods in addition to other methods for survival prediction found in the literature.
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SAWAI, Shujiro. "Numerical Estimation of Nutation Divergence Time Constant owing to Liquid Propellant." Transactions of the Society of Instrument and Control Engineers 37, no. 10 (2001): 993–95. http://dx.doi.org/10.9746/sicetr1965.37.993.
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Elmasry, Amr, Mostafa Kahla, Fady Ahdy, and Mahmoud Hashem. "Red–black trees with constant update time." Acta Informatica 56, no. 5 (May 21, 2019): 391–404. http://dx.doi.org/10.1007/s00236-019-00335-9.
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Weller, René, Nicole Debowski, and Gabriel Zachmann. "kDet: Parallel Constant Time Collision Detection for Polygonal Objects." Computer Graphics Forum 36, no. 2 (May 2017): 131–41. http://dx.doi.org/10.1111/cgf.13113.
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Kunte, Anagha A., and Arun N. Gaikwad. "Boxed Ring Resonator for Liquid Dielectric Constant Measurement." International Journal on Communications Antenna and Propagation (IRECAP) 8, no. 6 (December 31, 2018): 477. http://dx.doi.org/10.15866/irecap.v8i6.15170.
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CHEN, SHYAN-SHIOU, and CHIH-WEN SHIH. "DYNAMICS FOR DISCRETE-TIME CELLULAR NEURAL NETWORKS." International Journal of Bifurcation and Chaos 14, no. 08 (August 2004): 2667–87. http://dx.doi.org/10.1142/s0218127404011053.
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This presentation investigates the dynamics of discrete-time cellular neural networks (DT-CNN). In contrast to classical neural networks that are mostly gradient-like systems, DT-CNN possesses both complete stability and chaotic behaviors as different parameters are considered. An energy-like function which decreases along orbits of DT-CNN as well as the existence of a globally attracting set are derived. Complete stability can then be concluded, with further analysis on the sets on which the energy function is constant. The formations of saturated stationary patterns for DT-CNN are shown to be analogous to the ones in continuous-time CNN. Thus, DT-CNN shares similar properties with continuous-time CNN. By confirming the existence of snap-back repellers, hence transversal homoclinic orbits, we also conclude that DT-CNN with certain parameters exhibits chaotic dynamics, according to the theorem by Marotto.
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Malinowski, Adam. "Efficient Byzantine Agreement in Networks with Random Faults." Parallel Processing Letters 07, no. 01 (March 1997): 69–76. http://dx.doi.org/10.1142/s0129626497000097.
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We consider the Byzantine Agreement problem under the assumption that nodes and links of a synchronous network fail independently with constant probabilities p < 1/3 and q< 1 - 1/2(1-p), respectively. In a unit of time any node can send or receive a single bit of information. We present an asymptotically time-optimal agreement protocol, whose probability of correctness exceeds 1 - n-∊, where n is the number of nodes and ∊ > 0 an arbitrary constant.
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Funke, Stefan, Domagoj Matijevic, and Peter Sanders. "Constant Time Queries for Energy Efficient Paths in Multi-hop Wireless Networks." Journal of Computing and Information Technology 16, no. 2 (2008): 119. http://dx.doi.org/10.2498/cit.1001047.
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Thanh, Vo Hong, Roberto Zunino, and Corrado Priami. "Efficient Constant-Time Complexity Algorithm for Stochastic Simulation of Large Reaction Networks." IEEE/ACM Transactions on Computational Biology and Bioinformatics 14, no. 3 (May 1, 2017): 657–67. http://dx.doi.org/10.1109/tcbb.2016.2530066.
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Le, Long Bao, and Ravi R. Mazumdar. "Control of wireless networks with flow level dynamics under constant time scheduling." Wireless Networks 16, no. 5 (September 19, 2009): 1355–72. http://dx.doi.org/10.1007/s11276-009-0208-8.
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Ogier, Richard G. "Minimum-delay routing in continuous-time dynamic networks with Piecewise-constant capacities." Networks 18, no. 4 (1988): 303–18. http://dx.doi.org/10.1002/net.3230180405.
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Leggieri, Alberto, Davide Passi, and Franco Di Paolo. "A true-time-delay networks design technique." International Journal of Microwave and Wireless Technologies 8, no. 2 (November 6, 2014): 155–64. http://dx.doi.org/10.1017/s1759078714001408.
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This paper proposes a technique to design wide band switched-line (SL) true-time-delay (TTD) networks, commonly used for phased array antenna (PAA) applications. This study investigates the constant-delay behavior of switched-line phase shifters based on single-pole double-throw (SPDT) switches. Circuit sizing starts by considering the effective S-parameters of the switches, to use their non-idealities as an integral part of the phase shift linearly dependent to the frequency and by considering, from the beginning, the possible spatial positioning of elements that allows the circuit feasibility as a design target. The aim of this study is to provide a technique suitable for the design of well-matched TTD networks with a flat delay in wide bandwidth. In this paper, we propose new design formulas for which we show a single-frequency implementation. A computational strategy is used to obtain numerical solutions of the derived equations with this study. Finally, a monolithic X-band TTD circuit example is shown.
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Yarom, Yuval, Daniel Genkin, and Nadia Heninger. "CacheBleed: a timing attack on OpenSSL constant-time RSA." Journal of Cryptographic Engineering 7, no. 2 (February 11, 2017): 99–112. http://dx.doi.org/10.1007/s13389-017-0152-y.
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SUNDARARAJAN, A., and L. K. JU. "LIQUID-FILM TIME CONSTANT ASSESSMENT FOR kLa MEASUREMENTS IN RESPIRING FERMENTATION BROTHS." Chemical Engineering Communications 131, no. 1 (January 1995): 161–71. http://dx.doi.org/10.1080/00986449508936289.
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Pralet, Cédric, and Gérard Verfaillie. "Time-Dependent Simple Temporal Networks: Properties and Algorithms." Proceedings of the International Conference on Automated Planning and Scheduling 24 (May 11, 2014): 536–39. http://dx.doi.org/10.1609/icaps.v24i1.13656.
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Simple Temporal Networks (STNs) allow minimum and maximum distance constraints between time-points to be represented. They are often used when tackling planning and scheduling problems that involve temporal aspects. This paper is a summary of the journal article "Time-dependent Simple Temporal Networks: Properties and Algorithms" published in RAIRO - Operations Research. This journal article introduces an extension of STN called Time-dependent STN (TSTN), which covers temporal constraints for which the temporal distance required between two time-points is not necessarily constant. Such constraints are useful to model time-dependent scheduling problems, in which the duration of an activity may depend on its starting time. The paper introduces the TSTN framework, its properties, resolution techniques, as well as examples of applications.
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Ludwig, R., D. S. Gill, and M. D. Zeidler. "Molecular Reorientation in Liquid Methanol." Zeitschrift für Naturforschung A 46, no. 1-2 (February 1, 1991): 89–94. http://dx.doi.org/10.1515/zna-1991-1-214.
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AbstractOxygen-17 enriched methanol CD317OH was synthesized and 1H as well as 17O nmr relaxation rates were measured in the temperature range 180-310 K. By varying the 17O-content different contributions to the proton relaxation rate could be separated and from the 17O-H dipolar interaction contribution the correlation time of the OH bond was determined. These results are compared to recent computer simulation data. Additional deuteron relaxation measurements on CH3OD yielded the quadrupole coupling constant which increases with falling temperature. The 17O quadrupole coupling constant shows a similar trend with temperature but not as pronounced.
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Kuhn, Fabian, and Roger Wattenhofer. "Constant-time distributed dominating set approximation." Distributed Computing 17, no. 4 (May 2005): 303–10. http://dx.doi.org/10.1007/s00446-004-0112-5.
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Ben-Asher, Yosi, and Assaf Schuster. "Single Step Undirected Reconfigurable Networks." VLSI Design 9, no. 1 (January 1, 1999): 17–28. http://dx.doi.org/10.1155/1999/71739.
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The reconfigurable mesh (RN-MESH) can solve a large class of problems in constant time, including problems that require logarithmic time by other, even shared memory, models such as the PRAM with a similar number of processors [3]. In this work we show that for the RN-MESH these constants can always be reduced to one, still using a polynomial number of processors. Given a reconfigurable mesh that computes a set of values in constant time, we show that it can be simulated by a single step reconfigurable mesh with maximum size that is polynomial in the size of the original mesh. The proof is constructive, where the construction of the single step RN-MESH holds for the relatively weak undirected RN-MESH model. In this model broadcasts made on buses arrive at all nodes that belong to the undirected connected component of the transmitting processor. A result similar to the one that is obtained in this work was previously obtained for the directed reconfigurable mesh model (DRN) [5]. However, the construction for the DRN-MESH relies on the fact that the buses are directed, and thus cannot be applied to the undirected case. In addition, the construction presented here is simpler and uses significantly fewer processors than the one obtained for the DRN-MESH.
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LIU, YURONG, ZIDONG WANG, and XIAOHUI LIU. "ON SYNCHRONIZATION OF DISCRETE-TIME MARKOVIAN JUMPING STOCHASTIC COMPLEX NETWORKS WITH MODE-DEPENDENT MIXED TIME-DELAYS." International Journal of Modern Physics B 23, no. 03 (January 30, 2009): 411–34. http://dx.doi.org/10.1142/s0217979209049826.
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In this paper, the synchronization problem is investigated for a new class of discrete-time complex networks. Such complex networks involve the Markovian jumping parameters, mode-dependent discrete and distributed time-delays, constant and delayed couplings, as well as multiple stochastic disturbances. The stochastic disturbances influence the constant coupling term, the delayed coupling term, as well as the overall network dynamics, which could better describe the dynamical behavior of a coupled complex network presented within a noisy environment. With help from the Lyapunov functional method and the properties of Kronecker product, we employ the stochastic analysis techniques to derive several delay-dependent sufficient conditions under which the coupled complex network is asymptotically synchronized in the mean square. The criteria obtained in this paper are in the form of LMIs whose solution can be easily calculated using the standard numerical software. It is shown that our main results can cover many existing ones reported in the literature. A numerical example is presented to illustrate the usefulness of our results.
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Wang, Xiaoqian, Meifeng Dai, Yufei Chen, Yue Zong, Yu Sun, and Weiyi Su. "Determining entire mean first-passage time for Cayley networks." International Journal of Modern Physics C 29, no. 01 (January 2018): 1850009. http://dx.doi.org/10.1142/s0129183118500092.
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In this paper, we consider the entire mean first-passage time (EMFPT) with random walks for Cayley networks. We use Laplacian spectra to calculate the EMFPT. Firstly, we calculate the constant term and monomial coefficient of characteristic polynomial. By using the Vieta theorem, we then obtain the sum of reciprocals of all nonzero eigenvalues of Laplacian matrix. Finally, we obtain the scaling of the EMFPT for Cayley networks by using the relationship between the sum of reciprocals of all nonzero eigenvalues of Laplacian matrix and the EMFPT. We expect that our method can be adapted to other types of self-similar networks, such as vicsek networks, polymer networks.
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Li, Fangwei, Yue Wu, Yifang Nie, and Ce Shi. "Time Allocation and Optimization in Time-Reversal Wireless Powered Communication Networks." International Journal of Antennas and Propagation 2020 (July 22, 2020): 1–8. http://dx.doi.org/10.1155/2020/8906438.
Full textAbstract:
This paper studies optimal resource allocation in the wireless powered communication networks (WPCN) combined with time reversal (TR) in which one hybrid access point (H-AP) broadcasts constant wireless energy to a set of distributed users in the downlink (DL) and receives information from the users via space division multiple access (SDMA) in the uplink (UL). Inevitable interferences will occur when users transmit information in the UL simultaneously and the special space-time focusing of TR is used to suppress the interferences. An efficient protocol is proposed to support wireless energy transfer (WET) and TR in the DL and wireless information transmission in the UL for the proposed TR-WPCN. We optimize the time allocations to the H-AP for DL WET, DL TR, and UL WIT to maximize the sum throughput. Due to the nonconvexity of the studied optimization problem, we optimize variables successively, where the nonconvex optimization problem is transformed into the convex optimization problem. The approximate convex optimization problem can then be solved iteratively combined with the dichotomy method. Simulation results show that the proposed scheme can effectively suppress interferences and improve system performance.