Journal articles on the topic 'Deep Equilibrium Models'
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1
Lafond, Patrick G., R. Gary Grim, and Amadeu K. Sum. "Clathrate hydrate equilibrium modeling: Do self-consistent cell models provide unique equilibrium solutions?" Canadian Journal of Chemistry 93, no. 8 (August 2015): 826–30. http://dx.doi.org/10.1139/cjc-2014-0558.
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When clathrate hydrates of xenon gas are formed deep within the stability field, anomalous melting behavior is readily observed in differential scanning calorimetry (DSC). In the DSC thermograms, multiple dissociation events may be observed, suggesting the presence of more than one solid phase. Following a suite of diffraction and NMR measurements, we are only able to detect the presence of simple structure I hydrate. Recognizing that hydrates are nonstoichiometric compounds, we look back to how the molar composition of a hydrate phase is determined. Making a mean-field improvement to current equilibrium models, we find that some conditions yield multiple solutions to the cage filling of the hydrate phase. Though the solutions are not truly stable, they would result in a kinetically trapped system. If such a case existed experimentally, this could explain the dissociation behavior observed for xenon hydrates. More importantly, this raises the question of how well defined the equilibrium condition is for a cell potential model, and whether or not multiple equilibrium solutions could exist.
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Plant, R. S., and G. C. Craig. "A Stochastic Parameterization for Deep Convection Based on Equilibrium Statistics." Journal of the Atmospheric Sciences 65, no. 1 (January 1, 2008): 87–105. http://dx.doi.org/10.1175/2007jas2263.1.
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Abstract A stochastic parameterization scheme for deep convection is described, suitable for use in both climate and NWP models. Theoretical arguments and the results of cloud-resolving models are discussed in order to motivate the form of the scheme. In the deterministic limit, it tends to a spectrum of entraining/detraining plumes and is similar to other current parameterizations. The stochastic variability describes the local fluctuations about a large-scale equilibrium state. Plumes are drawn at random from a probability distribution function (PDF) that defines the chance of finding a plume of given cloud-base mass flux within each model grid box. The normalization of the PDF is given by the ensemble-mean mass flux, and this is computed with a CAPE closure method. The characteristics of each plume produced are determined using an adaptation of the plume model from the Kain–Fritsch parameterization. Initial tests in the single-column version of the Unified Model verify that the scheme is effective in producing the desired distributions of convective variability without adversely affecting the mean state.
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Azmoon, Behnam, Aynaz Biniyaz, and Zhen (Leo) Liu. "Evaluation of Deep Learning against Conventional Limit Equilibrium Methods for Slope Stability Analysis." Applied Sciences 11, no. 13 (June 29, 2021): 6060. http://dx.doi.org/10.3390/app11136060.
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This paper presents a comparison study between methods of deep learning as a new category of slope stability analysis, built upon the recent advances in artificial intelligence and conventional limit equilibrium analysis methods. For this purpose, computer code was developed to calculate the factor of safety (FS) using four limit equilibrium methods: Bishop’s simplified method, the Fellenius method, Janbu’s simplified method, and Janbu’s corrected method. The code was verified against Slide2 in RocScience. Subsequently, the average FS values were used to approximate the “true” FS of the slopes for labeling the images for deep learning. Using this code, a comprehensive dataset of slope images with wide ranges of geometries and soil properties was created. The average FS values were used to label the images for implementing two deep learning models: a multiclass classification and a regression model. After training, the deep learning models were used to predict the FS of an independent set of slope images. Finally, the performance of the models was compared to that of the conventional methods. This study found that deep learning methods can reach accuracies as high as 99.71% while improving computational efficiency by more than 18 times compared with conventional methods.
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Kollau, Laura J. B. M., Mark Vis, Adriaan van den Bruinhorst, Gijsbertus de With, and Remco Tuinier. "Activity modelling of the solid–liquid equilibrium of deep eutectic solvents." Pure and Applied Chemistry 91, no. 8 (August 27, 2019): 1341–49. http://dx.doi.org/10.1515/pac-2018-1014.
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Abstract Compared to conventional solvents used in the chemical industry, deep eutectic solvents (DESs) are considered as promising potentially sustainable solvents. DESs are binary mixtures and the resulting liquid mixture is characterized by a large melting point depression with respect to the melting temperatures of its constituents. The relative melting point depression becomes larger as the two components have stronger attractive interactions, resulting in non-ideal behavior. The compositional range over which such binary mixtures are liquids is set by the location of the solid–liquid phase boundary. Here we present experimental phase diagrams of various recent and new DESs that vary in the degree of non-ideality. We investigate whether thermodynamic models are able to describe the solid–liquid equilibria and focus on relating the parameters of these models to the non-ideal behavior, including asymmetric behavior of the activity coefficients. It is shown that the orthogonal Redlich–Kister-like polynomial (OP) expansion, including an additional first order term, provides an accurate description. This theory can be considered as an extension of regular solution theory and enables physical interpretation of the fit parameters.
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Yano, Jun-Ichi, and Robert Plant. "Interactions between Shallow and Deep Convection under a Finite Departure from Convective Quasi Equilibrium." Journal of the Atmospheric Sciences 69, no. 12 (December 1, 2012): 3463–70. http://dx.doi.org/10.1175/jas-d-12-0108.1.
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Abstract The present paper presents a simple theory for the transformation of nonprecipitating, shallow convection into precipitating, deep convective clouds. To make the pertinent point a much idealized system is considered, consisting only of shallow and deep convection without large-scale forcing. The transformation is described by an explicit coupling between these two types of convection. Shallow convection moistens and cools the atmosphere, whereas deep convection dries and warms the atmosphere, leading to destabilization and stabilization, respectively. Consequently, in their own stand-alone modes, shallow convection perpetually grows, whereas deep convection simply damps: the former never reaches equilibrium, and the latter is never spontaneously generated. Coupling the modes together is the only way to reconcile these undesirable separate tendencies, so that the convective system as a whole can remain in a stable periodic state under this idealized setting. Such coupling is a key missing element in current global atmospheric models. The energy cycle description used herein is fully consistent with the original formulation by Arakawa and Schubert, and is suitable for direct implementation into models using a mass flux parameterization. The coupling would alleviate current problems with the representation of these two types of convection in numerical models. The present theory also provides a pertinent framework for analyzing large-eddy simulations and cloud-resolving modeling.
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Nick, F. M., and J. Oerlemans. "Dynamics of tidewater glaciers: comparison of three models." Journal of Glaciology 52, no. 177 (2006): 183–90. http://dx.doi.org/10.3189/172756506781828755.
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AbstractA minimal model of a tidewater glacier based solely on mass conservation is compared with two one-dimensional numerical flowline models, one with the calving rate proportional to water depth, and the other with the flotation criterion as a boundary condition at the glacier terminus. The models were run with two simplified bed geometries and two mass-balance formulations. The models simulate the full cycle of length variations and the equilibrium states for a tidewater glacier. This study shows that the branching of the equilibrium states depends significantly on the bed geometry. The similarity between the results of the three models indicates that if there is a submarine undulation at the terminus of a tidewater glacier, any model in which the frontal ice loss is related to the water depth yields qualitatively the same non-linear behaviour. For large glaciers extending into deep water, the flotation model causes unrealistic behaviour.
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Sladkowski, A. V., Y. O. Kyrychenko, P. I. Kogut, and V. I. Samusya. "Innovative designs of pumping deep-water hydrolifts based on progressive multiphase non-equilibrium models." Naukovyi Visnyk Natsionalnoho Hirnychoho Universytetu, no. 2 (April 2019): 51–57. http://dx.doi.org/10.29202/nvngu/2019-2/6.
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Latash, Mark L. "Equilibrium-point control? Yes! Deterministic mechanisms of control? No!" Behavioral and Brain Sciences 18, no. 4 (December 1995): 765–66. http://dx.doi.org/10.1017/s0140525x00040899.
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AbstractThe equilibrium-point hypothesis (the λ-model) is superior to all other models of single-joint control and provides deep insights into the mechanisms of control of multi-joint movements. Attempts at associating control variables with neurophysiological variables look confusing rather than promising. Probabilistic mechanisms may play an important role in movement generation in redundant systems.
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Zalai, Ernő. "The von Neumann Model and the Early Models of General Equilibrium." Acta Oeconomica 54, no. 1 (May 1, 2004): 3–38. http://dx.doi.org/10.1556/aoecon.54.2004.1.2.
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The paper reconstructs the von Neumann model, comments on its salient features and critically reviews some of its generalisations. The issues related to thetreatment of consumption, decomposability and uniqueness of the rate of growth and interest will be especially scrutinised. The most prominent models of general equilibrium that appeared before or roughly at the same time as von Neumann's model will be also reviewed in the paper and compared with it. It will be demonstrated that none of them had any noticeable influence on von Neumann's model, which is genuinely distinct, ideologically free and methodologically fresh and forward-looking. It will be argued that the model can be viewed as a brilliant mathematical metaphor of some deep-rooted old vision, pertaining to the core issues of commodity production.
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Tawfik, Abdel Nasser. "Equilibrium statistical–thermal models in high-energy physics." International Journal of Modern Physics A 29, no. 17 (June 26, 2014): 1430021. http://dx.doi.org/10.1142/s0217751x1430021x.
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We review some recent highlights from the applications of statistical–thermal models to different experimental measurements and lattice QCD thermodynamics that have been made during the last decade. We start with a short review of the historical milestones on the path of constructing statistical–thermal models for heavy-ion physics. We discovered that Heinz Koppe formulated in 1948, an almost complete recipe for the statistical–thermal models. In 1950, Enrico Fermi generalized this statistical approach, in which he started with a general cross-section formula and inserted into it, the simplifying assumptions about the matrix element of the interaction process that likely reflects many features of the high-energy reactions dominated by density in the phase space of final states. In 1964, Hagedorn systematically analyzed the high-energy phenomena using all tools of statistical physics and introduced the concept of limiting temperature based on the statistical bootstrap model. It turns to be quite often that many-particle systems can be studied with the help of statistical–thermal methods. The analysis of yield multiplicities in high-energy collisions gives an overwhelming evidence for the chemical equilibrium in the final state. The strange particles might be an exception, as they are suppressed at lower beam energies. However, their relative yields fulfill statistical equilibrium, as well. We review the equilibrium statistical–thermal models for particle production, fluctuations and collective flow in heavy-ion experiments. We also review their reproduction of the lattice QCD thermodynamics at vanishing and finite chemical potential. During the last decade, five conditions have been suggested to describe the universal behavior of the chemical freeze-out parameters. The higher order moments of multiplicity have been discussed. They offer deep insights about particle production and to critical fluctuations. Therefore, we use them to describe the freeze-out parameters and suggest the location of the QCD critical endpoint. Various extensions have been proposed in order to take into consideration the possible deviations of the ideal hadron gas. We highlight various types of interactions, dissipative properties and location-dependences (spatial rapidity). Furthermore, we review three models combining hadronic with partonic phases; quasi-particle model, linear sigma model with Polyakov potentials and compressible bag model.
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Jansen, Malte F., Louis-Philippe Nadeau, and Timothy M. Merlis. "Transient versus Equilibrium Response of the Ocean’s Overturning Circulation to Warming." Journal of Climate 31, no. 13 (July 2018): 5147–63. http://dx.doi.org/10.1175/jcli-d-17-0797.1.
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Much of the existing theory for the ocean’s overturning circulation considers steady-state equilibrium solutions. However, Earth’s climate is not in a steady state, and a better understanding of the ocean’s nonequilibrium response to changes in the surface climate is urgently needed. Here, the time-dependent response of the deep-ocean overturning circulation to atmospheric warming is examined using a hierarchy of idealized ocean models. The transient response to surface warming is characterized by a shoaling and weakening of the Atlantic meridional overturning circulation (AMOC)—consistent with results from coupled climate simulations. The initial shoaling and weakening of the AMOC occurs on decadal time scales and is attributed to a rapid warming of northern-sourced deep water. The equilibrium response to warming, in contrast, is associated with a deepening and strengthening of the AMOC. The eventual deepening of the AMOC is argued to be associated with abyssal density changes and driven by modified surface fluxes in the Southern Ocean, following a reduction of the Antarctic sea ice cover. Full equilibration of the AMOC requires a diffusive adjustment of the abyss and takes many millennia. The equilibration time scale is much longer than most coupled climate model simulations, highlighting the importance of considering integration time and initial conditions when interpreting the deep-ocean circulation in climate models. The results also show that past climates are unlikely to be an adequate analog for changes in the overturning circulation during the coming decades or centuries.
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Aregba, A. W., and J. P. Nadeau. "Comparison of two non-equilibrium models for static grain deep-bed drying by numerical simulations." Journal of Food Engineering 78, no. 4 (February 2007): 1174–87. http://dx.doi.org/10.1016/j.jfoodeng.2005.12.030.
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Kusochkova, E. V., I. M. Indrupskiy, and V. N. Kuryakov. "Distribution of the Initial Fluid Composition in an Oil-Gas-Condensate Reservoir with Incomplete Gravity Segregation." IOP Conference Series: Earth and Environmental Science 931, no. 1 (December 1, 2021): 012012. http://dx.doi.org/10.1088/1755-1315/931/1/012012.
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Abstract It is known that initial composition of the hydrocarbon fluid in a petroleum reservoir changes significantly with depth due to the influence of gravity and geothermal gradient. Classical models of these phenomena are based on the assumption of equilibrium (quasiequilibrium) distribution of component concentrations in the gravity field with the presence of stationary thermodiffusional flux. However, there are typical situations in gas condensate reservoirs when the quasi-equilibrium conditions are not met. For example, this is true if immobile residual oil exists in the reservoir or for deep tight formations where gravity segregation is not completed. For such cases, modified models are required. They are proposed in this paper to take into account the non-equilibrium conditions of the initial fluid composition distribution in gas condensate (or oil-gas-condensate) reservoirs.
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Ponte, Rui M. "Oceanic Response to Surface Loading Effects Neglected in Volume-Conserving Models." Journal of Physical Oceanography 36, no. 3 (March 1, 2006): 426–34. http://dx.doi.org/10.1175/jpo2843.1.
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Abstract Forcing by freshwater fluxes implies variable surface loads that are not treated in volume-conserving ocean models. A similar problem exists with the representation of volume changes implied by surface heat fluxes. Under the assumption of an equilibrium response, such surface loads merely lead to spatially uniform sea level fluctuations, which carry no dynamical significance. A barotropic model forced by realistic freshwater fluxes is used to test the validity of the equilibrium assumption on seasonal to daily time scales. The simulated nonequilibrium signals have amplitudes much weaker than those of the forcing, with standard deviations well below 1 mm over most of the deep ocean. Larger values (up to ∼1 cm) can be found in shallow and semienclosed coastal areas, where the equilibrium assumption can lead to substantial errors even at monthly and longer time scales. Forcing by mean seasonal river runoff yields similar results, and heat flux effects lead to weaker nonequilibrium signals. In contrast, nonequilibrium signals driven by atmospheric pressure loading are at least an order of magnitude larger than those forced by freshwater fluxes. The exceptions occur for some shallow, coastal regions in the Tropics and at the longest time scales, in general, where forcing by freshwater flux is much stronger than by pressure.
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Toikka, M. A., A. A. Samarov, A. A. Sadaev, A. A. Senina, and O. L. Lobacheva. "CHEMICAL EQUILIBRIUM IN THE PROPIONIC ACID - ETHANOL - ETHYL PROPIONATE - WATER SYSTEM AND EXTRACTION PROCESSES WITH PARTICIPATION OF DEEP EUTECTIC SOLVENTS." Fine Chemical Technologies 14, no. 1 (February 28, 2019): 47–58. http://dx.doi.org/10.32362/2410-6593-2019-14-1-47-58.
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New experimental data on the chemical equilibrium in the propionic acid - ethanol - ethyl propionate - water system at 293.15 K and atmospheric pressure are presented. Chemically equilibrium compositions corresponding to the liquid-liquid equilibrium were obtained by gas chromatographic analysis. Using the method of nuclear magnetic resonance, homogeneous chemically equilibrium compositions were determined and the concentration equilibrium constant is calculated. The surface of chemical equilibrium and the region of splitting chemically equilibrium compositions are represented in the square of the transformed concentration variables. Comparison of the data obtained in the work with the literature was carried out at 303.15 and 313.15 K. It was found that the region of such compositions decreases with increasing temperature, while the surface of chemical equilibrium does not change the shape and position in the concentration space in the temperature range 293.15-313.15 K and atmospheric pressure. Liquid-liquid equilibrium compositions have also been obtained by gas chromatographic analysis for ethanol and ethyl propionate in the pseudo-ternary system using deep eutectic solvents (DES) based on choline chloride and glycerol / urea in whole range of concentration. The analysis of the extraction properties of DES showed the highest efficiency of DES based on choline chloride and urea. Experimental data on phase equilibrium are processed using Othmer-Tobias and Hand models. The calculated correlation coefficient (more than 0.99) indicates a high internal consistency of the experimental data obtained in this work.
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Lin, Jia-Lin, Taotao Qian, Toshiaki Shinoda, and Shuanglin Li. "Is the Tropical Atmosphere in Convective Quasi-Equilibrium?" Journal of Climate 28, no. 11 (May 27, 2015): 4357–72. http://dx.doi.org/10.1175/jcli-d-14-00681.1.
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Abstract The hypothesis of convective quasi-equilibrium (CQE) has dominated thinking about the interaction between deep moist convection and the environment for at least two decades. In this view, deep convection develops or decays almost instantly to remove any changes of convective instability, making the tropospheric temperature always tied to the boundary layer moist static energy. The present study examines the validity of the CQE hypothesis at different vertical levels using long-term sounding data from tropical convection centers. The results show that the tropical atmosphere is far from the CQE with much weaker warming in the middle and upper troposphere associated with the increase of boundary layer moist static energy. This is true for all the time scales resolved by the observational data, ranging from hourly to interannual and decadal variability. It is possibly caused by the ubiquitous existence of shallow convection and stratiform precipitation, both leading to sign reversal of heating from lower to upper troposphere. The simulations by 42 global climate models from phases 3 and 5 of the Coupled Model Intercomparsion Project (CMIP3 and CMIP5) are also analyzed and compared with the observations.
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Sijp, Willem P., Matthew H. England, and Jonathan M. Gregory. "Precise Calculations of the Existence of Multiple AMOC Equilibria in Coupled Climate Models. Part I: Equilibrium States." Journal of Climate 25, no. 1 (January 1, 2012): 282–98. http://dx.doi.org/10.1175/2011jcli4245.1.
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Abstract This study examines criteria for the existence of two stable states of the Atlantic Meridional Overturning Circulation (AMOC) using a combination of theory and simulations from a numerical coupled atmosphere–ocean climate model. By formulating a simple collection of state parameters and their relationships, the authors reconstruct the North Atlantic Deep Water (NADW) OFF state behavior under a varying external salt-flux forcing. This part (Part I) of the paper examines the steady-state solution, which gives insight into the mechanisms that sustain the NADW OFF state in this coupled model; Part II deals with the transient behavior predicted by the evolution equation. The nonlinear behavior of the Antarctic Intermediate Water (AAIW) reverse cell is critical to the OFF state. Higher Atlantic salinity leads both to a reduced AAIW reverse cell and to a greater vertical salinity gradient in the South Atlantic. The former tends to reduce Atlantic salt export to the Southern Ocean, while the latter tends to increases it. These competing effects produce a nonlinear response of Atlantic salinity and salt export to salt forcing, and the existence of maxima in these quantities. Thus the authors obtain a natural and accurate analytical saddle-node condition for the maximal surface salt flux for which a NADW OFF state exists. By contrast, the bistability indicator proposed by De Vries and Weber does not generally work in this model. It is applicable only when the effect of the AAIW reverse cell on the Atlantic salt budget is weak.
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Zeng, Xubin, and Mark Decker. "Improving the Numerical Solution of Soil Moisture–Based Richards Equation for Land Models with a Deep or Shallow Water Table." Journal of Hydrometeorology 10, no. 1 (February 1, 2009): 308–19. http://dx.doi.org/10.1175/2008jhm1011.1.
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Abstract The soil moisture–based Richards equation is widely used in land models for weather and climate studies, but its numerical solution using the mass-conservative scheme in the Community Land Model is found to be deficient when the water table is within the model domain. Furthermore, these deficiencies cannot be reduced by using a smaller grid spacing. The numerical errors are much smaller when the water table is below the model domain. These deficiencies were overlooked in the past, most likely because of the more dominant influence of the free drainage bottom boundary condition used by many land models. They are fixed here by explicitly subtracting the hydrostatic equilibrium soil moisture distribution from the Richards equation. This equilibrium distribution can be derived at each time step from a constant hydraulic (i.e., capillary plus gravitational) potential above the water table, representing a steady-state solution of the Richards equation. Furthermore, because the free drainage condition has serious deficiencies, a new bottom boundary condition based on the equilibrium soil moisture distribution at each time step is proposed that also provides an effective and direct coupling between groundwater and surface water.
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Ootes, L. S., R. Wijnands, and D. Page. "Long-term temperature evolution of neutron stars undergoing episodic accretion outbursts." Astronomy & Astrophysics 630 (September 26, 2019): A95. http://dx.doi.org/10.1051/0004-6361/201936035.
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Context. Transient neutron star low-mass X-ray binaries undergo episodes of accretion, alternated with quiescent periods. During an accretion outburst, the neutron star heats up due to exothermic accretion-induced processes taking place in the crust. Besides the long-known deep crustal heating of nuclear origin, a likely non-nuclear source of heat, dubbed “shallow heating”, is present at lower densities. Most of the accretion-induced heat slowly diffuses into the core on a timescale of years. Over many outburst cycles, a state of equilibrium is reached when the core temperature is high enough that the heating and cooling (photon and neutrino emission) processes are in balance. Aims. We investigate how stellar characteristics and outburst properties affect the long-term temperature evolution of a transiently accreting neutron star. For the first time the effects of crustal properties are considered, particularly that of shallow heating. Methods. Using our code NSCool, we tracked the thermal evolution of a neutron star undergoing outbursts over a period of 105 yr. The outburst sequence is based on the regular outbursts observed from the neutron star transient Aql X-1. For each model we calculated the timescale over which equilibrium was reached and we present these timescales along with the temperature and luminosity parameters of the equilibrium state. Results. We performed several simulations with scaled outburst accretion rates, to vary the amount of heating over the outburst cycles. The results of these models show that the equilibrium core temperature follows a logarithmic decay function with the equilibrium timescale. Secondly, we find that shallow heating significantly contributes to the equilibrium state. Increasing its strength raises the equilibrium core temperature. We find that if deep crustal heating is replaced by shallow heating alone, the core would still heat up, reaching only a 2% lower equilibrium core temperature. Deep crustal heating may therefore not be vital to the heating of the core. Additionally, shallow heating can increase the quiescent luminosity to values higher than previously expected. The thermal conductivity in the envelope and crust, including the potentially low-conductivity pasta layer at the bottom of the crust, is unable to significantly alter the long-term internal temperature evolution. Stellar compactness and nucleon pairing in the core change the specific heat and the total neutrino emission rate as a function of temperature, with the consequences for the properties of the equilibrium state depending on the exact details of the assumed pairing models. The presence of direct Urca emission leads to the lowest equilibrium core temperature and the shortest equilibrium timescale.
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Ralph, Daniel. "Mathematical programs with complementarity constraints in traffic and telecommunications networks." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 366, no. 1872 (March 6, 2008): 1973–87. http://dx.doi.org/10.1098/rsta.2008.0026.
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Given a suitably parametrized family of equilibrium models and a higher level criterion by which to measure an equilibrium state, mathematical programs with equilibrium constraints (MPECs) provide a framework for improving or optimizing the equilibrium state. An example is toll design in traffic networks, which attempts to reduce total travel time by choosing which arcs to toll and what toll levels to impose. Here, a Wardrop equilibrium describes the traffic response to each toll design. Communication networks also have a deep literature on equilibrium flows that suggest some MPECs. We focus on mathematical programs with complementarity constraints (MPCCs), a subclass of MPECs for which the lower level equilibrium system can be formulated as a complementarity problem and therefore, importantly, as a nonlinear program (NLP). Although MPECs and MPCCs are typically non-convex, which is a consequence of the upper level objective clashing with the users' objectives in the lower level equilibrium program, the last decade of research has paved the way for finding local solutions of MPCCs via standard NLP techniques.
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Roy, Bishwajit, Maheshwari Prasad Singh, Mosbeh R. Kaloop, Deepak Kumar, Jong-Wan Hu, Radhikesh Kumar, and Won-Sup Hwang. "Data-Driven Approach for Rainfall-Runoff Modelling Using Equilibrium Optimizer Coupled Extreme Learning Machine and Deep Neural Network." Applied Sciences 11, no. 13 (July 5, 2021): 6238. http://dx.doi.org/10.3390/app11136238.
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Rainfall-runoff (R-R) modelling is used to study the runoff generation of a catchment. The quantity or rate of change measure of the hydrological variable, called runoff, is important for environmental scientists to accomplish water-related planning and design. This paper proposes (i) an integrated model namely EO-ELM (an integration of equilibrium optimizer (EO) and extreme learning machine (ELM)) and (ii) a deep neural network (DNN) for one day-ahead R-R modelling. The proposed R-R models are validated at two different benchmark stations of the catchments, namely river Teifi at Glanteifi and river Fal at Tregony in the UK. Firstly, a partial autocorrelation function (PACF) is used for optimal number of lag inputs to deploy the proposed models. Six other well-known machine learning models, called ELM, kernel ELM (KELM), and particle swarm optimization-based ELM (PSO-ELM), support vector regression (SVR), artificial neural network (ANN) and gradient boosting machine (GBM) are utilized to validate the two proposed models in terms of prediction efficiency. Furthermore, to increase the performance of the proposed models, paper utilizes a discrete wavelet-based data pre-processing technique is applied in rainfall and runoff data. The performance of wavelet-based EO-ELM and DNN are compared with wavelet-based ELM (WELM), KELM (WKELM), PSO-ELM (WPSO-ELM), SVR (WSVR), ANN (WANN) and GBM (WGBM). An uncertainty analysis and two-tailed t-test are carried out to ensure the trustworthiness and efficacy of the proposed models. The experimental results for two different time series datasets show that the EO-ELM performs better in an optimal number of lags than the others. In the case of wavelet-based daily R-R modelling, proposed models performed better and showed robustness compared to other models used. Therefore, this paper shows the efficient applicability of EO-ELM and DNN in R-R modelling that may be used in the hydrological modelling field.
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Krasting, John P., Ronald J. Stouffer, Stephen M. Griffies, Robert W. Hallberg, Sergey L. Malyshev, Bonita L. Samuels, and Lori T. Sentman. "Role of Ocean Model Formulation in Climate Response Uncertainty." Journal of Climate 31, no. 22 (October 29, 2018): 9313–33. http://dx.doi.org/10.1175/jcli-d-18-0035.1.
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Abstract Oceanic heat uptake (OHU) is a significant source of uncertainty in both the transient and equilibrium responses to increasing the planetary radiative forcing. OHU differs among climate models and is related in part to their representation of vertical and lateral mixing. This study examines the role of ocean model formulation—specifically the choice of the vertical coordinate and the strength of the background diapycnal diffusivity Kd—in the millennial-scale near-equilibrium climate response to a quadrupling of atmospheric CO2. Using two fully coupled Earth system models (ESMs) with nearly identical atmosphere, land, sea ice, and biogeochemical components, it is possible to independently configure their ocean model components with different formulations and produce similar near-equilibrium climate responses. The SST responses are similar between the two models (r2 = 0.75, global average ~4.3°C) despite their initial preindustrial climate mean states differing by 0.4°C globally. The surface and interior responses of temperature and salinity are also similar between the two models. However, the Atlantic meridional overturning circulation (AMOC) responses are different between the two models, and the associated differences in ventilation and deep-water formation have an impact on the accumulation of dissolved inorganic carbon in the ocean interior. A parameter sensitivity analysis demonstrates that increasing the amount of Kd produces very different near-equilibrium climate responses within a given model. These results suggest that the impact of the ocean vertical coordinate on the climate response is small relative to the representation of subgrid-scale mixing.
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Han, Taihao, Sai Akshay Ponduru, Arianit Reka, Jie Huang, Gaurav Sant, and Aditya Kumar. "Predicting Dissolution Kinetics of Tricalcium Silicate Using Deep Learning and Analytical Models." Algorithms 16, no. 1 (December 22, 2022): 7. http://dx.doi.org/10.3390/a16010007.
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The dissolution kinetics of Portland cement is a critical factor in controlling the hydration reaction and improving the performance of concrete. Tricalcium silicate (C3S), the primary phase in Portland cement, is known to have complex dissolution mechanisms that involve multiple reactions and changes to particle surfaces. As a result, current analytical models are unable to accurately predict the dissolution kinetics of C3S in various solvents when it is undersaturated with respect to the solvent. This paper employs the deep forest (DF) model to predict the dissolution rate of C3S in the undersaturated solvent. The DF model takes into account several variables, including the measurement method (i.e., reactor connected to inductive coupled plasma spectrometer and flow chamber with vertical scanning interferometry), temperature, and physicochemical properties of solvents. Next, the DF model evaluates the influence of each variable on the dissolution rate of C3S, and this information is used to develop a closed-form analytical model that can predict the dissolution rate of C3S. The coefficients and constant of the analytical model are optimized in two scenarios: generic and alkaline solvents. The results show that both the DF and analytical models are able to produce reliable predictions of the dissolution rate of C3S when it is undersaturated and far from equilibrium.
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Thi Thanh Chau, Vo, Huynh Thi MinhThanh, Pham Dinh Du, Tran Thanh Tam Toan, Tran Ngoc Tuyen, Tran Xuan Mau, and Dinh Quang Khieu. "Metal-Organic Framework-101 (MIL-101): Synthesis, Kinetics, Thermodynamics, and Equilibrium Isotherms of Remazol Deep Black RGB Adsorption." Journal of Chemistry 2018 (June 24, 2018): 1–14. http://dx.doi.org/10.1155/2018/8616921.
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In the present paper, the synthesis of metal-organic framework-101 (MIL-101) and Remazol Deep Black RGB (RDB) adsorption on MIL-101 were demonstrated. The kinetics of RDB adsorption on MIL-101 was studied using Weber’s intraparticle diffusion model and the pseudo-first- and pseudo-second-order kinetic models. Particularly, the statistical method of piecewise linear regression and multi-nonlinear regression was employed to analyse the adsorption data according to the previously mentioned kinetic models. The results indicated that the adsorption process followed the three-step pseudo-first-order kinetic equation, which was consistent with the results of the intraparticle diffusion model with three linear segments. This model best described the experimental data. In addition, the adsorption isotherm data were studied using five adsorption models, namely, Langmuir, Freundlich, Redlich–Peterson, Toth, and Sips in nonlinear forms, and the Langmuir model is the most appropriate for the experimental data. The values of energies of activation of adsorption were calculated, and they revealed that the adsorption process was of endothermic chemical nature. A statistical comparison using Akaike information criterion to estimate the goodness of fit of the kinetic and isotherm models was presented.
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Primeau, F., and E. Deleersnijder. "On the time to tracer equilibrium in the global ocean." Ocean Science Discussions 5, no. 3 (September 1, 2008): 471–506. http://dx.doi.org/10.5194/osd-5-471-2008.
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Abstract. An important issue for the interpretation of data from deep-sea cores is the time for tracers to be transported from the sea surface to the deep ocean. Global ocean circulation models can help shed light on the timescales over which a tracer comes to equilibrium in different regions of the ocean. In this note, we discuss how the most slowly decaying eigenmode of a model can be used to obtain a relevant timescale for a tracer that enters through the sea surface to become well mixed in the ocean interior. We show how this timescale depends critically on the choice between a Neumann surface boundary condition in which the flux of tracer is prescribed or a Dirichlet surface boundary condition in which the concentration is prescribed. Explicit calculations with a 3-box model and a three-dimensional ocean circulation model show that the Dirichlet boundary condition when applied to only part of the surface ocean greatly overestimate the time needed to reach equilibrium. As a result regional-"injection" calculations which prescribe the surface concentration instead of the surface flux are not relevant for interpreting the regional disequilibrium between the Atlantic and Pacific found in paleo-tracer records from deep-sea cores. For tracers such as δ18O that enter the ocean from melt water, a Neumann boundary condition is more relevant. For tracers that enter the ocean through air-sea gas exchange such as 14C, a prescribed concentration boundary condition can be used to infer relevant timescales, but the Dirichlet Boundary condition must be applied over the entire ocean surface and not only to a patch of limited area. Our three-dimensional model results based on a steady-state modern circulation suggest that the relative disequilibrium between the deep Atlantic and Pacific is on the order of "only" 1200 years or less and does not depend on the size and location of the patch where the tracer is injected.
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Pauluis, Olivier, and Stephen Garner. "Sensitivity of Radiative–Convective Equilibrium Simulations to Horizontal Resolution." Journal of the Atmospheric Sciences 63, no. 7 (July 1, 2006): 1910–23. http://dx.doi.org/10.1175/jas3705.1.
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Abstract This paper investigates the impacts of horizontal resolution on the statistical behavior of convection. An idealized radiative–convective equilibrium is simulated for model resolutions ranging between 2 and 50 km. The simulations are compared based upon the analysis of the mean state, the energy and water vapor transport, and the probability distribution functions for various quantities. It is shown that, at a coarse resolution, the model is unable to capture the mixing associated with shallow clouds. This results in a dry bias in the lower troposphere, and in an excessive amount of water clouds. Despite this deficiency, the coarse resolution simulations are able to reproduce reasonably well the statistical properties of deep convective towers. This is particularly apparent in the cloud ice and vertical velocity distributions that exhibit a very robust behavior. A theoretical scaling for the vertical velocity as function of the grid resolution is derived based upon the behavior of an idealized air bubble. It is shown that the vertical velocity of an ascending air parcel is determined by its aspect ratio, with a wide, flat parcel rising at a much slower pace than a narrow one. This theoretical scaling law exhibits a similar sensitivity to that of the numerical simulations. It is used to renormalize the probability distribution functions for vertical velocity, which show a very good agreement for resolutions up to 16 km. This new scaling law offers a way to improve direct simulations of deep convection in coarse resolution models.
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Primeau, F., and E. Deleersnijder. "On the time to tracer equilibrium in the global ocean." Ocean Science 5, no. 1 (February 3, 2009): 13–28. http://dx.doi.org/10.5194/os-5-13-2009.
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Abstract. An important issue for the interpretation of data from deep-sea cores is the time for tracers to be transported from the sea surface to the deep ocean. Global ocean circulation models can help shed light on the timescales over which a tracer comes to equilibrium in different regions of the ocean. In this note, we discuss how the most slowly decaying eigenmode of a model can be used to obtain a relevant timescale for a tracer that enters through the sea surface to become well mixed in the ocean interior. We show how this timescale depends critically on the choice between a Neumann surface boundary condition in which the flux of tracer is prescribed, a Robin surface boundary condition in which a combination of the flux and tracer concentration is prescribed or a Dirichlet surface boundary condition in which the concentration is prescribed. Explicit calculations with a 3-box model and a three-dimensional ocean circulation model show that the Dirichlet boundary condition when applied to only part of the surface ocean greatly overestimate the time needed to reach equilibrium. As a result regional-"injection" calculations which prescribe the surface concentration instead of the surface flux are not relevant for interpreting the regional disequilibrium between the Atlantic and Pacific found in paleo-tracer records from deep-sea cores. For tracers that enter the ocean through air-sea gas exchange a prescribed concentration boundary condition can be used to infer relevant timescales if the air-sea gas exchange rate is sufficiently fast, but the boundary condition must be applied over the entire ocean surface and not only to a patch of limited area. For tracers with a slow air-sea exchange rate such as 14C a Robin-type boundary condition is more relevant and for tracers such as δ18O that enter the ocean from melt water, a Neumann boundary condition is presumably more relevant. Our three-dimensional model results based on a steady-state modern circulation suggest that the relative disequilibrium between the deep Atlantic and Pacific is on the order of "only" 1200 years or less for a Neumann boundary condition and does not depend on the size and location of the patch where the tracer is injected.
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Vuksanovic, Jelena, Nina Todorovic, Mirjana Kijevcanin, Slobodan Serbanovic, and Ivona Radovic. "Experimental investigation and modeling of thermophysical and extraction properties of choline chloride + DL-malic acid based deep eutectic solvent." Journal of the Serbian Chemical Society 82, no. 11 (2017): 1287–302. http://dx.doi.org/10.2298/jsc170316054v.
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The ability of non-toxic and biodegradable deep eutectic solvent (DES) choline chloride + DL-malic acid in mole ratio 1:1, for the breaking of the azeotropes heptane + methanol and toluene + methanol by means of liquid? ?liquid extraction was evaluated. Ternary liquid?liquid equilibrium experiments were performed at 298.15 K and at atmospheric pressure. Densities, viscosities and refractive indices of DES + methanol and water + DES systems were experimentally determined over a wide temperature range and at atmospheric pressure. Additionally, the viscosities of DES + glycerol mixture were - determined at temperatures up to 363.15 K to check how much the addition of glycerol decreases high viscosities of DES. The results indicate that the addition of small amounts of water or glycerol as a third component significantly decreases the viscosity of the investigated deep eutectic solvent. Based on the selectivity and distribution ratio values, the extraction ability of the investigated deep eutectic solvent, in comparison with the conventionally used solvents, yields promising results. Non-random two-liquid (NRTL) and universal quasichemical (UNIQUAC) models were satisfactorily applied for correlation of experimental phase equilibrium data for two ternary mixtures.
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Birchfield, Edward, and Matthew Wyant. "Diverse Limiting Circulations In A Simple Ocean Box Model." Annals of Glaciology 14 (1990): 330. http://dx.doi.org/10.3189/s0260305500008892.
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A coupled ocean-atmosphere model is formulated, incorporating an ocean comprised of two surface and one deep-ocean boxes, horizontal and vertical mixing, a thermohaline circulation, and forcing by latitudinal differential surface heating and evaporation. Surface fluxes are determined through coupling with a two-box steady-state atmospheric energy-balance model The hydrological cycle, thermohaline circulation and latitudinal exchange rate in the atmosphere are each controlled by an independent parameter. For a weak hydrological cycle, a cold low-salinity deep-ocean equilibrium exists with deep water produced in high latitudes, resembling the modern ocean; for a strong hydrological cycle, a warm saline deep ocean is found with deep water produced in lower latitudes, similar to proposed models of a Cretaceous ocean. More complex solutions exist for an intermediate range of parameters. These include co-existence of both of the above limiting circulations as stable steady states and an oscillatory solution about the cold deep-ocean limit case. In general for this model, the cold deep-ocean case appears less stable than the warm saline deep-ocean case.
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Birchfield, Edward, and Matthew Wyant. "Diverse Limiting Circulations In A Simple Ocean Box Model." Annals of Glaciology 14 (1990): 330. http://dx.doi.org/10.1017/s0260305500008892.
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A coupled ocean-atmosphere model is formulated, incorporating an ocean comprised of two surface and one deep-ocean boxes, horizontal and vertical mixing, a thermohaline circulation, and forcing by latitudinal differential surface heating and evaporation. Surface fluxes are determined through coupling with a two-box steady-state atmospheric energy-balance model The hydrological cycle, thermohaline circulation and latitudinal exchange rate in the atmosphere are each controlled by an independent parameter. For a weak hydrological cycle, a cold low-salinity deep-ocean equilibrium exists with deep water produced in high latitudes, resembling the modern ocean; for a strong hydrological cycle, a warm saline deep ocean is found with deep water produced in lower latitudes, similar to proposed models of a Cretaceous ocean. More complex solutions exist for an intermediate range of parameters. These include co-existence of both of the above limiting circulations as stable steady states and an oscillatory solution about the cold deep-ocean limit case. In general for this model, the cold deep-ocean case appears less stable than the warm saline deep-ocean case.
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Sohail, Taimoor, Bishakhdatta Gayen, and Andrew McC. Hogg. "The Dynamics of Mixed Layer Deepening during Open-Ocean Convection." Journal of Physical Oceanography 50, no. 6 (June 2020): 1625–41. http://dx.doi.org/10.1175/jpo-d-19-0264.1.
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AbstractOpen-ocean convection is a common phenomenon that regulates mixed layer depth and ocean ventilation in the high-latitude oceans. However, many climate model simulations overestimate mixed layer depth during open-ocean convection, resulting in excessive formation of dense water in some regions. The physical processes controlling transient mixed layer depth during open-ocean convection are examined using two different numerical models: a high-resolution, turbulence-resolving nonhydrostatic model and a large-scale hydrostatic ocean model. An isolated destabilizing buoyancy flux is imposed at the surface of both models and a quasi-equilibrium flow is allowed to develop. Mixed layer depth in the turbulence-resolving and large-scale models closely aligns with existing scaling theories. However, the large-scale model has an anomalously deep mixed layer prior to quasi-equilibrium. This transient mixed layer depth bias is a consequence of the lack of resolved turbulent convection in the model, which delays the onset of baroclinic instability. These findings suggest that in order to reduce mixed layer biases in ocean simulations, parameterizations of the connection between baroclinic instability and convection need to be addressed.
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COHEN, AVI J. "CAPITAL CONTROVERSY FROM BÖHM-BAWERK TO BLISS: BADLY POSED OR VERY DEEP QUESTIONS? OR WHAT “WE” CAN LEARN FROM CAPITAL CONTROVERSY EVEN IF YOU DON'T CARE WHO WON." Journal of the History of Economic Thought 32, no. 1 (February 25, 2010): 1–21. http://dx.doi.org/10.1017/s105383720999040x.
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The author's path from heterodoxy to economic history to the history of economics is used as a case study to explore tensions between “doing economics” and “doing the history of economics,” between the ideological vision (Schumpeter) motivating a research agenda and the even-handed execution of research. These same tensions appear in the history of capital controversy, which contains deep questions of history and path dependence versus equilibrium models, limitations of aggregate production functions, and the roles of vision and ideology in the reluctance to abandon insights of one-commodity models when results are not robust.
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Ghaly, Ashraf, and Adel Hanna. "Ultimate pullout resistance of single vertical anchors." Canadian Geotechnical Journal 31, no. 5 (October 1, 1994): 661–72. http://dx.doi.org/10.1139/t94-078.
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An investigation into the performance of single vertical screw anchors installed in sands is presented. Models were developed employing the limit equilibrium method of analysis to predict the uplift capacity of anchors installed into shallow, transition, and deep depths. An experimentally observed log-spiral rupture surface was used in the theoretical analysis. Shear stresses were calculated on the surface of rupture using Kötter's differential equation. Weight and shear factors for shallow and deep anchors are established to simplify the calculation of the uplift capacity from the theories developed. These factors are presented in simple graphs as functions of the angle of shearing resistance of the sand and the relative depth ratio of the anchor. The effect of sand overconsolidation resulting from the application of mechanical compaction was introduced by incorporating the overconsolidation ratio in the uplift capacity calculations. Comparisons between the theoretical values and the experimental results of the present investigation as well as field results reported in the literature showed good agreement. Key words : anchors, failure mechanism, limit equilibrium, overconsolidation ratio, theoretical analysis, uplift capacity.
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Exarchou, Eleftheria, Till Kuhlbrodt, Jonathan M. Gregory, and Robin S. Smith. "Ocean Heat Uptake Processes: A Model Intercomparison." Journal of Climate 28, no. 2 (January 15, 2015): 887–908. http://dx.doi.org/10.1175/jcli-d-14-00235.1.
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Abstract The quasi-equilibrium heat balances, as well as the responses to 4 × CO2 perturbation, are compared among three global climate models with the aim to identify and explain intermodel differences in ocean heat uptake (OHU) processes. It is found that, in quasi equilibrium, convective and mixed layer processes, as well as eddy-related processes, cause cooling of the subsurface ocean. The cooling is balanced by warming caused by advective and diapycnally diffusive processes. It is also found that in the CO2-perturbed climates the largest contribution to OHU comes from changes in vertical mixing processes and the mean circulation, particularly in the extratropics, caused both by changes in wind forcing and by changes in high-latitude buoyancy forcing. There is a substantial warming in the tropics: a significant part of which occurs because of changes in horizontal advection in extratropics. Diapycnal diffusion makes only a weak contribution to the OHU, mainly in the tropics, because of increased stratification. There are important qualitative differences in the contribution of eddy-induced advection and isopycnal diffusion to the OHU among the models. The former is related to the different values of the coefficients used in the corresponding scheme. The latter is related to the different tapering formulations of the isopycnal diffusion scheme. These differences affect the OHU in the deep ocean, which is substantial in two of the models, with the dominant region of deep warming being the Southern Ocean. However, most of the OHU takes place above 2000 m, and the three models are quantitatively similar in their global OHU efficiency and its breakdown among processes and as a function of latitude.
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Parker, Jonathan A. "On Measuring the Effects of Fiscal Policy in Recessions." Journal of Economic Literature 49, no. 3 (September 1, 2011): 703–18. http://dx.doi.org/10.1257/jel.49.3.703.
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We do not have a good measure of the effects of fiscal policy in a recession because the methods that we use to estimate the effects of fiscal policy—both those using the observed outcomes following different policies in aggregate data and those studying counterfactuals in fitted model economies—almost entirely ignore the state of the economy and estimate “the” government multiplier, which is presumably a weighted average of the one we care about—the multiplier in a recession—and one we care less about—the multiplier in an expansion. Notable exceptions to this general claim suggest this difference is potentially large. Our lack of knowledge stems significantly from the focus on linear dynamics: vector autoregressions and linearized (or close-to-linear) dynamic stochastic general equilibrium (DSGE) models. Our lack of knowledge also reflects a lack of data: deep recessions are few and nonlinearities hard to measure. The lack of statistical power in the estimation of nonlinear models using aggregate data can be addressed by exploiting estimates of partial-equilibrium responses in disaggregated data. Microeconomic estimates of the partial-equilibrium causal effects of a policy can discipline the causal channels inherent in any DSGE model of the general equilibrium effects of policy. Microeconomic studies can also provide measures of the dependence of the effects of a policy on the states of different agents, which is a key component of the dependence of the general-equilibrium effects of fiscal policy on the state of the economy. (JEL E12, E13, E32, E62, H50)
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Sessions, Sharon L., Stipo Sentić, and David J. Raymond. "Balanced Dynamics and Moisture Quasi-Equilibrium in DYNAMO Convection." Journal of the Atmospheric Sciences 76, no. 9 (August 23, 2019): 2781–99. http://dx.doi.org/10.1175/jas-d-18-0173.1.
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AbstractTropical convection that occurs on large-enough space and time scales may evolve in response to large-scale balanced circulations. In this scenario, large-scale midtropospheric vorticity anomalies modify the atmospheric stability by virtue of thermal wind gradient balance. The convective vertical mass flux and the moisture profile adjust to changes in atmospheric stability that affect moisture and entropy transport. We hypothesize that the convection observed during the 2011 DYNAMO field campaign evolves in response to balanced dynamics. Strong relationships between midtropospheric vorticity and atmospheric stability confirm the relationship between the dynamic and the thermodynamic environments, while robust relationships between the atmospheric stability, the vertical mass flux, and the saturation fraction provide evidence of moisture adjustment. These results are important because the part of convection that occurs as a response to balanced dynamics is potentially predictable. Furthermore, the diagnostics used in this work provide a simple framework for model evaluation, and suggest that one way to improve simulations of large-scale organized deep tropical convection in global models is to adequately capture the relationship between the dynamic and thermodynamic environments in convective parameterizations.
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Ju, Yiyi, Masahiro Sugiyama, Etsushi Kato, Ken Oshiro, and Jiayang Wang. "Job creation in response to Japan’s energy transition towards deep mitigation: An extension of partial equilibrium integrated assessment models." Applied Energy 318 (July 2022): 119178. http://dx.doi.org/10.1016/j.apenergy.2022.119178.
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Nonato, Fábio, and Katia L. Cavalca. "An approach for including the stiffness and damping of elastohydrodynamic point contacts in deep groove ball bearing equilibrium models." Journal of Sound and Vibration 333, no. 25 (December 2014): 6960–78. http://dx.doi.org/10.1016/j.jsv.2014.08.011.
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Huang, Xiaoxin, and Xiuxiu Chen. "A Quantitative Model of International Trade Based on Deep Neural Network." Computational Intelligence and Neuroscience 2022 (May 31, 2022): 1–11. http://dx.doi.org/10.1155/2022/9811358.
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This paper is an in-depth study of international trade quantification models based on deep neural networks. Based on an in-depth analysis of global trade characteristics, a summary of existing problems, and a comparative analysis of various prediction methods, this paper constructs the ARIMA model, BP neural network (BPNN) model, and deep neural network (DNN) model to make a comprehensive comparison of international trade quantification. The results show that the nonlinear model has a global trade quantification has some advantages over linear models, and the deep model shows better prediction performance than the shallow model. In addition, preprocessing of the time series is considered to improve the prediction accuracy or shorten the model training time. The empirical modal analysis method (EMD) is introduced to decompose the time series into eigenmodal functions (IMFs) of different scales. Then the decomposed IMF series are arranged into a matrix using principal component analysis (PCA) to reduce the dimensionality and extract the data containing the most stock index information features; these features are then input into BPNN and DNN for combined prediction, thus constructing the combined models EMD-PCA-BPNN and EMD-PCA-DNN. Based on Melitz’s heterogeneous firm trade theory and its development by Chaney, a quantitative trade model incorporating production heterogeneity is constructed through a multisector extension. This paper adopts a general equilibrium analysis, which makes the modeling process pulse clear. The completed model has high flexibility and scalability, which can be applied to quantitative analysis of various problems.
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Iklima, Zendi, Trie Maya Kadarina, and Eko Ihsanto. "Realistic image synthesis of COVID-19 chest X-rays using depthwise boundary equilibrium generative adversarial networks." International Journal of Electrical and Computer Engineering (IJECE) 12, no. 5 (October 1, 2022): 5444. http://dx.doi.org/10.11591/ijece.v12i5.pp5444-5454.
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<span>Researchers in various related fields research preventing and controlling the spread of the coronavirus disease (COVID-19) virus. The spread of the COVID-19 is increasing exponentially and infecting humans massively. Preliminary detection can be observed by looking at abnormal conditions in the airways, thus allowing the entry of the virus into the patient's respiratory tract, which can be represented using computer tomography (CT) scan and chest X-ray (CXR) imaging. Particular deep learning approaches have been developed to classify COVID-19 CT or CXR images such as convolutional neural network (CNN), and deep convolutional neural network (DCNN). However, COVID-19 CXR dataset was measly opened and accessed. Particular deep learning method performance can be improved by augmenting the dataset amount. Therefore, the COVID-19 CXR dataset was possibly augmented by generating the synthetic image. This study discusses a fast and real-like image synthesis approach, namely depthwise boundary equilibrium generative adversarial network (DepthwiseBEGAN). DepthwiseBEGAN was reduced memory load 70.11% in training processes compared to the conventional BEGAN. DepthwiseBEGAN synthetic images were inspected by measuring the Fréchet inception distance (FID) score with the real-to-real score equal to 4.3866 and real-to-fake score equal to 4.4674. Moreover, generated DepthwiseBEGAN synthetic images improve 22.59% accuracy of conventional CNN models.</span>
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Wang, Yingqi, Wenfeng Du, Hui Wang, and Yannan Zhao. "Intelligent Generation Method of Innovative Structures Based on Topology Optimization and Deep Learning." Materials 14, no. 24 (December 13, 2021): 7680. http://dx.doi.org/10.3390/ma14247680.
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Computer-aided design has been widely used in structural calculation and analysis, but there are still challenges in generating innovative structures intelligently. Aiming at this issue, a new method was proposed to realize the intelligent generation of innovative structures based on topology optimization and deep learning. Firstly, a large number of structural models obtained from topology optimization under different optimization parameters were extracted to produce the training set images, and the training set labels were defined as the corresponding load cases. Then, the boundary equilibrium generative adversarial networks (BEGAN) deep learning algorithm was applied to generate numerous innovative structures. Finally, the generated structures were evaluated by a series of evaluation indexes, including innovation, aesthetics, machinability, and mechanical performance. Combined with two engineering cases, the application process of the above method is described here in detail. Furthermore, the 3D reconstruction and additive manufacturing techniques were applied to manufacture the structural models. The research results showed that the proposed approach of structural generation based on topology optimization and deep learning is feasible, and can not only generate innovative structures but also optimize the material consumption and mechanical performance further.
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Long, Zhao, Yilei Shi, Weili Li, and Shuaihua Ye. "Soil Pressure and Deformation Analysis of Small Size Deep Foundation Pit." Journal of Physics: Conference Series 2148, no. 1 (January 1, 2022): 012061. http://dx.doi.org/10.1088/1742-6596/2148/1/012061.
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Abstract In this paper, the influence of space effect on soil pressure and deformation of deep foundation pit was considered, and the finite soil pressure calculation model was established. The soil pressure of deep foundation pit was calculated by assuming the slip surface and using the finite soil limit equilibrium theory. Then, PLAXIS 3D finite element software was used to establish finite element models of different plane sizes and depths. The distribution regulation of side wall soil pressure and deformation of deep foundation pit was calculated. Finally, the results of finite soil pressure calculation was compared with finite element method. The results shown that: The soil pressure of small deep foundation pit was affected by space effect, and the soil pressure and deformation decrease significantly along the foundation pit depth. Shear fracture Angle was related to the ratio of width to depth of foundation pit, and it was no longer a constant value of 45°+φ/2. Therefore, the spatial effect should be considered in the calculation of soil pressure of small deep foundation pit. The research results can provide some guidance for the design and calculation of similar small size deep foundation pit.
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Bai, Fang, Chao Hua, Yongzhi Bai, and Mengying Ma. "Design Optimization of Deep Eutectic Solvent Composition and Separation Performance of Cyclohexane and Benzene Mixtures with Extractive Distillation." Processes 9, no. 10 (September 23, 2021): 1706. http://dx.doi.org/10.3390/pr9101706.
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Deep eutectic solvents (DESs) have properties that make them suitable candidates to be used as entrainers for extractive distillation. In the previous work, it was proven that DES(1:2) (tetrabutylammonium bromide: levulinic acid, 1:2, molar ratio) can break the cyclohexane-benzene azeotrope. In the present work, the HBA and HBD ratio and molar concentration of DES were optimized to obtain a better constitute and condition of DES to be utilized in cyclohexane and benzene extractive distillation. The physical properties and structure of the prepared DESs were characterized. Vapor–liquid equilibrium data of the ternary system (benzene + cyclohexane + DESs) were also measured at atmospheric pressure. All experimental equilibrium data were correlated with Wilson, nonrandom two-liquid (NRTL), and universal quasichemical (UNIQUAC) activity coefficient models, from which the coefficient of determination (R2) of the three pseudo-ternary systems fitting was calculated. From the obtained results, the best HBA and HBD ratio in the DESs is elucidated as 1:2, the best molar concentration of DES is 0.1, and the NRTL model predicts the experimental data more accurately than the Wilson and UNIQUAC models. From the derived mechanism, the formation of stronger hydrogen bond and π–π bond interactions between DES and benzene is obtained when HBA and HBD ratio in DES is 1:2. In other conditions, the azeotrope cannot be broken, or the efficiency is low. The present work provides an environmentally friendly method to separate aromatic/aliphatic mixtures and act as a guide for further study of DESs in extractive distillation.
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Jiang, Donglei, Yi Yu, Yi Huang, Wenbo Meng, Jianbo Su, and Zhenggang Gong. "Gas Hydrate Formation Risk and Prevention for the Development Wells in the Lingshui Gas Field in South China Sea." Geofluids 2021 (July 30, 2021): 1–13. http://dx.doi.org/10.1155/2021/9122863.
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Hydrate formation risk is an important challenge in the development of deep-water gas field. Considering the characteristics of the Lingshui (LS) gas field in the South China Sea and the difference of well structures, a model for calculating wellbore temperature and pressure in deep-water gas production well is proposed and verified by the field data. Combining the hydrate equilibrium models with varied gas components, the prediction method of hydrate formation region in deep-water gas well in the South China Sea is obtained. The hydrate formation regions under different operating conditions for a deep-water gas well in the South China Sea were given by the proposed model. The results show that no hydrate formation risk exists in the production operation, but the risk exists in the shut-in and testing operations. Meanwhile, the determination of the hydrate inhibitor injection parameters during the testing operation is studied, and the influence of the inhibitors’ injection concentration and pressure on preventing gas hydrates is analyzed. This work provides useful advice for the prediction and prevention of hydrate formation risk in the development of deep-water gas fields, especially in the South China Sea.
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Smiljanic, R., P. Donati, A. Bragaglia, B. Lemasle, and D. Romano. "Deep secrets of intermediate-mass giants and supergiants." Astronomy & Astrophysics 616 (August 2018): A112. http://dx.doi.org/10.1051/0004-6361/201832877.
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Context. Recent observational results have demonstrated an increase in the surface Na abundance that correlates with stellar mass for red giants between 2 and 3 M⊙. This trend supports evolutionary mixing processes as the explanation for Na overabundances seen in some red giants. In this same mass range, the surface Al abundance was shown to be constant. Aims. Our main aim was to extend the investigation of the Na and Al surface abundances to giants more massive than 3 M⊙. We sought to establish accurately whether the Na abundances keep increasing with stellar mass or a plateau is reached. In addition, we investigated whether mixing can affect the surface abundance of Al in giants more massive than 3 M⊙. Methods. We obtained new high-resolution spectra of 20 giants in the field of 10 open clusters; 17 of these stars were found to be members of 9 clusters. The giants have masses between 2.5 M⊙ and 5.6 M⊙. A model atmosphere analysis was performed and abundances of up to 22 elements were derived using equivalent widths. Additionally, abundances of C, N, and O were determined using spectrum synthesis. The abundances of Na and Al were corrected for non-local thermodynamic equilibrium (non-LTE) effects. Moreover, to extend the mass range of our sample, we collected from the literature high-quality C, N, O, and Na abundances of 32 Galactic Cepheids with accurate masses in the range between 3 M⊙ and 14 M⊙. Results. The surface abundances of C, N, O, Na, and Al were compared to predictions of stellar evolution models with and without the inclusion of rotation-induced mixing. The surface abundances of most giants and Cepheids of the sample can be explained by models without rotation. For giants above Ȉ2.5 M⊙, the Na abundances reach a plateau level of about [Na/Fe] ~ 0.20–0.25 dex (in non-LTE). This is true for both Cepheids and giants in open clusters. Regarding Al, the non-LTE [Al/Fe] ratios are mostly close to solar and suggest that Al is not affected by the first dredge-up up to ~5.0 M⊙. Our results support previous works that found models with rotation to overestimate the mixing effects in intermediate-mass stars.
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Abdallah, Maha M., Simon Müller, Andrés González de Castilla, Pavel Gurikov, Ana A. Matias, Maria do Rosário Bronze, and Naiara Fernández. "Physicochemical Characterization and Simulation of the Solid–Liquid Equilibrium Phase Diagram of Terpene-Based Eutectic Solvent Systems." Molecules 26, no. 6 (March 23, 2021): 1801. http://dx.doi.org/10.3390/molecules26061801.
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The characterization of terpene-based eutectic solvent systems is performed to describe their solid–liquid phase transitions. Physical properties are measured experimentally and compared to computed correlations for deep eutectic solvents (DES) and the percentage relative error er for the density, surface tension, and refractive index is obtained. The thermodynamic parameters, including the degradation, glass transition and crystallization temperatures, are measured using DSC and TGA. Based on these data, the solid–liquid equilibrium phase diagrams are calculated for the ideal case and predictions are made using the semi-predictive UNIFAC and the predictive COSMO RS models, the latter with two different parametrization levels. For each system, the ideal, experimental, and predicted eutectic points are obtained. The deviation from ideality is observed experimentally and using the thermodynamic models for Thymol:Borneol and Thymol:Camphor. In contrast, a negative deviation is observed only experimentally for Menthol:Borneol and Menthol:Camphor. Moreover, the chemical interactions are analyzed using FTIR and 1H-NMR to study the intermolecular hydrogen bonding in the systems.
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Pa´dua, K. G. O. "Nonisothermal Gravitational Equilibrium Model." SPE Reservoir Evaluation & Engineering 2, no. 02 (April 1, 1999): 211–17. http://dx.doi.org/10.2118/55972-pa.
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Summary This work presents a new computational model for the non-isothermal gravitational compositional equilibrium. The works of Bedrikovetsky [Mathemathical Theory of Oil and Gas Recovery, Kluwer Academic Publishers, London, (1993)] (gravity and temperature) and of Whitson and Belery ("Compositional Gradients in Petroleum Reservoirs," paper SPE 28000, presented at the 1994 University of Tulsa Centennal Petroleum Engineering Symposium, Tulsa, 29-31 August) (algorithm) are the basis of the mathematical formulation. Published data and previous simplified models validate the computational procedure. A large deep-water field in Campos Basin, Brazil, exemplifies the practical application of the model. The field has an unusual temperature gradient opposite to the Earth's thermal gradient. The results indicate the increase of oil segregation with temperature decrease. The application to field data suggests the reservoir could be partially connected. Fluid composition and property variation are extrapolated to different depths with its respective temperatures. The work is an example of the application of thermodynamic data to the evaluation of reservoir connectivity and fluid properties distribution. Problem Compositional variations along the hydrocarbon column are observed in many reservoirs around the world.1–4 They may affect reservoir/fluid characteristics considerably leading to different field development strategies.5 These variations are caused by many factors, such as gravity, temperature gradient, rock heterogeneity, hydrocarbon genesis and accumulation processes.6 In cases where thermodynamic associated factors (gravity and temperature) are dominant (mixing process in the secondary migration), existing gravitational compositional equilibrium (GCE) models7,8 provide an explanation of most observed variations. However, in some cases8,9 the thermal effect could have the same order of magnitude as the gravity effect. The formulation for calculating compositional variation under the force of gravity for an isothermal system was first given by Gibbs10 $$\mu {ci}(p, Z, T)=\mu {i}(p {{\rm ref}}, Z {{\rm ref}}, T {{\rm ref}}) - m {i}g(h - h {{\rm ref}}),\eqno ({\rm 1})$$ $$\mu {ci}=\delta [nRT\,{\rm ln}(f {i})]/\delta x,\eqno ({\rm 2})$$ $$f {i}=f({\rm EOS}),\eqno ({\rm 3})$$where p =pressure, T=temperature, Z=fluid composition, m=mass, ? c=chemical potential, h=depth, ref=reference, EOS=equation of state, i=component indices, R=real gas constant, n=number of moles, f=fugacity, ln=natural logarithm, x=component concentration, and g=gravitational acceleration. In 1930 Muskat11 provided an exact solution to Eq. (1), assuming a simplified equation of state and ideal mixing. Because of the oversimplified assumptions, the results suggest that gravity has a negligible effect on the compositional variation in reservoir systems. In 1938, Sage and Lacey12 used a more realistic equation of state (EOS), Eq. (3), to evaluate Eq. (2). At that time, the results showed significant composition variations with depth and greater ones for systems close to critical conditions. Schulte13 solved Eq. (1) using a cubic equation of state (3) in 1980. The results showed significant compositional variations. They also suggested a significant effect of the interaction coefficients and the aromatic content of the oil as well as a negligible effect of the EOS type (Peng-Robinson and Soave-Redlich-Kwong) on the final results. A simplified formulation that included gravity and temperature separately was presented by Holt et al.9 in 1983. Example calculations, limited to binary systems, suggest that thermal effects can be of the same magnitude as gravity effects. In 1988, Hirschberg5 discussed the influence of asphaltenes on compositional grading using a simplified two component model (asphaltenes and non-asphaltenes). He concluded, that for oils with oil gravity <35°API, the compositional variations are mainly caused by asphalt segregation and the most important consequences are the large variations in oil viscosity and the possible formation of tar mats. Montel and Gouel7 presented an algorithm in 1985 for solving the GCE problem using an incremental hydrostatic term instead of solving for pressure directly. Field case applications of GCE models were presented by Riemens et al.2 in 1985, and by Creek et al.1 in 1988. They reported some difficulties in matching observed and calculated data but, in the end, it was shown that most compositional variations could be explained by the effect of gravity. Wheaton14 and Lee6 presented GCE models that included capillary forces in 1988 and 1989, respectively. Lee concluded that the effect of capillarity can become appreciable in the neighborhood of 1 ?m pore radius. In 1990, an attempt to combine the effects of gravity and temperature for a system of zero net mass flux was presented by Belery and Silva.15 The multicomponent model was an extension of earlier work by Dougherty and Drickamer16 that was originally developed in 1955 for binary liquid systems. The comparison of calculated and observed data from Ekofisk field in the North Sea is, however, not quantitatively accurate (with or without thermal effect). An extensive discussion and the formal mathematical treatment of compositional grading using irreversible thermodynamics, including gravitational and thermal fields, was presented by Bedrikovetsky17 in 1993. Due to the lack of necessary information on the values of thermal diffusion coefficients, which in general are obtained experimentally only for certain mixtures in narrow ranges of pressure and temperature, simplified models were proposed. In 1994, Hamoodi and Abed3 presented a field case of a giant Middle East reservoir with areal and vertical variations in its composition.
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Cohen, Avi J., and G. C. Harcourt. "Retrospectives Whatever Happened to the Cambridge Capital Theory Controversies?" Journal of Economic Perspectives 17, no. 1 (February 1, 2003): 199–214. http://dx.doi.org/10.1257/089533003321165010.
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We argue that the Cambridge capital theory controversies of the 1950s to 1970s were the latest in a series of still-unresolved controversies over three deep issues: explaining and justifying the return to capital; Joan Robinson's complaint that, due to path dependence, equilibrium is not an outcome of an economic process and therefore an inadequate tool for analyzing accumulation and growth; and the role of ideology and vision in fuelling controversy when results of simple models are not robust. We predict these important and relevant issues, latent in endogenous growth and real business cycle theories, will erupt in future controversy.
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Liu, Ying, Rodrigo Caballero, and Joy Merwin Monteiro. "RadNet 1.0: exploring deep learning architectures for longwave radiative transfer." Geoscientific Model Development 13, no. 9 (September 21, 2020): 4399–412. http://dx.doi.org/10.5194/gmd-13-4399-2020.
Full textAbstract:
Abstract. Simulating global and regional climate at high resolution is essential to study the effects of climate change and capture extreme events affecting human populations. To achieve this goal, the scalability of climate models and efficiency of individual model components are both important. Radiative transfer is among the most computationally expensive components in a typical climate model. Here we attempt to model this component using a neural network. We aim to study the feasibility of replacing an explicit, physics-based computation of longwave radiative transfer by a neural network emulator and assessing the resultant performance gains. We compare multiple neural-network architectures, including a convolutional neural network, and our results suggest that the performance loss from the use of conventional convolutional networks is not offset by gains in accuracy. We train the networks with and without noise added to the input profiles and find that adding noise improves the ability of the networks to generalise beyond the training set. Prediction of radiative heating rates using our neural network models achieve up to 370× speedup on a GTX 1080 GPU setup and 11× speedup on a Xeon CPU setup compared to the a state-of-the-art radiative transfer library running on the same Xeon CPU. Furthermore, our neural network models yield less than 0.1 K d−1 mean squared error across all pressure levels. Upon introducing this component into a single-column model, we find that the time evolution of the temperature and humidity profiles is physically reasonable, though the model is conservative in its prediction of heating rates in regions where the optical depth changes quickly. Differences exist in the equilibrium climate simulated when using the neural network, which are attributed to small systematic errors that accumulate over time. Thus, we find that the accuracy of the neural network in the “offline” mode does not reflect its performance when coupled with other components.
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Windows-Yule, C. R. K. "Do granular systems obey statistical mechanics? A review of recent work assessing the applicability of equilibrium theory to vibrationally excited granular media." International Journal of Modern Physics B 31, no. 10 (April 20, 2017): 1742010. http://dx.doi.org/10.1142/s0217979217420103.
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Driven granular media — assemblies of discrete, macroscopic elements exposed to a source of mechanical energy — represent inherently out-of-equilibrium systems. Although granular media are ubiquitous in both nature and industry, due to their dissipative nature and resultant complex behaviors they remain startlingly poorly understood as compared to classical, thermodynamic systems. Nonetheless, in recent years it has been observed that the behaviors of granular media can, under certain circumstances, closely resemble those of equilibrium systems. One of the most important contemporary questions in the field of granular physics is whether these similarities are merely superficial, or whether the parallels run deep enough that the behaviors of these nonequilibrium systems can in fact be successfully captured using analogs to existing theoretical models developed for classical systems. In this review, we draw together the findings of a variety of recent studies where this question has been addressed, comparing and contrasting the results and conclusions presented. We focus our attention on vibrated and vibrofluidized granular beds, which provide a canonical system representative of various equilibrium and nonequilibrium physical systems, and whose simple dynamics offer a valuable testing ground for exploring the fundamental physics of the granular state.