A developed dual-site Langmuir model to represent the high-pressure methane adsorption and thermodynamic parameters in shale

Comprehending the mechanism of methane adsorption in shales is a crucial step towards optimizing the development of deep-buried shale gas. This is because the methane adsorbed in shale represents a significant proportion of the subsurface shale gas resource. To properly characterize the methane adsorption on shale, which exhibits diverse mineral compositions and multi-scale pore sizes, it is crucial to capture the energy heterogeneity of the adsorption sites. In this paper, a dual-site Langmuir model is proposed, which accounts for the temperature and pressure dependence of the density of the adsorbed phase. The model is applied to the isothermals of methane adsorption on shale, at pressures of up to 30 MPa and temperatures ranging from 40 to 100 ℃. The results show that the proposed model can describe the adsorption behavior of methane on shale more accurately than conventional models, which assume a constant value for the density of adsorbed phase. Furthermore, the proposed model can be extrapolated to higher temperatures and pressures. Thermodynamic parameters were analyzed using correctly derived equations. The results indicate that the widely used, but incorrect, equation would underestimate the isosteric heat of adsorption. Neglecting the real gas behavior, volume of the adsorbed phase, and energy heterogeneity of the adsorption sites can lead to overestimation of the isosteric heat of adsorption. Furthermore, the isosteric heat evaluated from excess adsorption data can only be used to make a rough estimate of the real isosteric heat at very low pressure.

Modeling and Simulation of Coke Combustion Regeneration for Coked Cr2O3/Al2O3 Propane Dehydrogenation Catalyst

A heterogeneous model is developed for the regeneration of the Cr2O3/Al2O3 catalyst for the propane dehydrogenation process by considering the internal mass transfer and external mass/heat transfer during the coke combustion.Simulation shows that under practical operating conditions,multi-steady states exist for the catalyst pellets and the catalyst temperature is sensitive to gas temperature.However,at increased mass flow rate or lowered oxygen concentration,multi-steady states will not appear.Under the strong influences of film diffusion,the coke in the packed bed reactor will first be exhausted at the inlet,while if the film diffusion resistance is decreased,the position of first coke exhaustion moves toward the outlet of the reactor.

Regional Economic Efficiency and Its Influencing Factors of Beijing-Tianjin-Hebei Metropolitans in China Based on a Heterogeneity Stochastic Frontier Model

Using a heterogeneity stochastic frontier model(HSFM),we empirically investigated the economic efficiency of Beijing-Tianjin-Hebei from 2003 to 2016 and its influencing factors.The key findings of the paper lie in:1)in Beijing-Tianjin-Hebei,the overall economic and technological efficiency tended to increase in a wavelike manner,economic growth slowed down,and there was an obvious imbalance in economic efficiency between the different districts,counties and cities;2)the heterogeneity stochastic frontier production functions(SFPFs)of Beijing,Tianjin and Hebei were different from each other,and investment was still an important impetus of economic growth in Beijing-Tianjin-Hebei;3)economic efficiency was positively correlated with economic agglomeration,human capital,industrial structure,infrastructure,the informatization level,and institutional factors,but negatively correlated with the government role and economic opening.The following policy suggestions are offered:1)to improve regional economic efficiency and reduce the economic gap in Beijing-Tianjin-Hebei,governments must reduce their intervention in economic activities,stimulate the potentials of labor and capital,optimize the structure of human resources,and foster new demographic incentives;2)governments must guide economic factors that are reasonable throughout Beijing-Tianjin-Hebei and strengthen infrastructure construction in underdeveloped regions,thus attaining sustainable economic development;3)governments must plan overall economic growth factors of Beijing-Tianjin-Hebei and promote reasonable economic factors(e.g.,labor,resources,and innovations)across different regions,thus attaining complementary advantages between Beijing,Tianjin,and Hebei.

Heterogeneous traffic flow modeling with drivers’ timid and aggressive characteristics

The driver’s characteristics(e.g.,timid and aggressive)has been proven to greatly affect the traffic flow performance,whereas the underlying assumption in most of the existing studies is that all drivers are homogeneous.In the real traffic environment,the drivers are distinct due to a variety of factors such as personality characteristics.To better reflect the reality,we introduce the penetration rate to describe the degree of drivers’heterogeneity(i.e.,timid and aggressive),and proceed to propose a generalized heterogeneous car-following model with different driver’s characteristics.Through the linear stability analysis,the stability conditions of the proposed heterogeneous traffic flow model are obtained based on the perturbation method.The impacts of the penetration rate of drivers with low intensity,the average value and standard deviation of intensity parameters characterizing two types of drivers on the stability of traffic flow are analyzed by simulation.Results show that higher penetration of aggressive drivers contributes to traffic flow stability.The average value has a great impact on the stability of traffic flow,whereas the impact of the standard deviation is trivial.

Review of heterogeneous material objects modeling in additive manufacturing

This review investigates the recent developments of heterogeneous objects modeling in additive manufacturing(AM),as well as general problems and widespread solutions to the modeling methods of heterogeneous objects.Prevalent heterogeneous object representations are generally categorized based on the different expression or data structure employed therein,and the state-of-the-art of process planning procedures for AM is reviewed via different vigorous solutions for part orientation,slicing methods,and path planning strategies.Finally,some evident problems and possible future directions of investigation are discussed.

Spatio-temporal Changes and Associated Uncertainties of CENTURYmodelled SOC for Chinese Upland Soils, 1980-2010

Detailed information on the spatio-temporal changes of cropland soil organic carbon(SOC) can significantly contribute to the improvement of soil fertility and mitigate climate change. Nonetheless, information and knowledge on the national scale spatio-temporal changes and the corresponding uncertainties of SOC in Chinese upland soils remain limited. The CENTURY model was used to estimate the SOC storages and their changes in Chinese uplands from 1980 to 2010. With the Monte Carlo method, the uncertainties of CENTURY-modelled SOC dynamics associated with the spatial heterogeneous model inputs were quantified. Results revealed that the SOC storage in Chinese uplands increased from 3.03(1.59 to 4.78) Pg C in 1980 to 3.40(2.39 to 4.62) Pg C in 2010. Increment of SOC storage during this period was 370 Tg C, with an uncertainty interval of –440 to 1110 Tg C. The regional disparities of SOC changes reached a significant level, with considerable SOC accumulation in the Huang-Huai-Hai Plain of China and SOC loss in the northeastern China. The SOC lost from Meadow soils, Black soils and Chernozems was most severe, whilst SOC accumulation in Fluvo-aquic soils, Cinnamon soils and Purplish soils was most significant. In modelling large-scale SOC dynamics, the initial soil properties were major sources of uncertainty. Hence, more detailed information concerning the soil properties must be collected. The SOC stock of Chinese uplands in 2010 was still relatively low, manifesting that recommended agricultural management practices in conjunction with effectively economic and policy incentives to farmers for soil fertility improvement were indispensable for future carbon sequestration in these regions.

Dynamic modeling of a H_2O-permselective membrane reactor to enhance methanol synthesis from syngas considering catalyst deactivation

In this paper, the effect of water vapor removal on methanol synthesis capacity from syngas in a fixed-bed membrane reactor is studied considering long-term catalyst deactivation. A dynamic heterogeneous one-dimensional mathematical model that is composed of two sides is developed to predict the performance of this configuration. In this configuration, conventional methanol reactor is supported by an aluminasilica composite membrane layer for water vapor removal from reaction zone. To verify the accuracy of the considered model and assumptions, simulation results of the conventional methanol reactor is compared with the industrial plant data under the same process condition. The membrane reactor improves catalyst life time and enhances CO2 conversion to methanol by overcoming the limitation imposed by thermodynamic equilibrium. This configuration has enhanced the methanol production capacity about 4.06% compared with the industrial methanol reactor during the production time.

Government intervention model based on behavioral heterogeneity for China’s stock market

Active government intervention is a striking characteristic of the Chinese stock market.This study develops a behavioral heterogeneous agent model(HAM)comprising fundamentalists,chartists,and stabilizers to investigate investors’dynamic switching mechanisms under government intervention.The model introduces a new player,the stabilizer,into the HAM as a proxy for the government.We use the model to examine government programs during the 2015 China stock market crash and find that it can replicate the dynamics of investor sentiment and asset prices.In addition,our analysis of two simulations,specifically the data-generating processes and shock response analysis,further corroborates the key conclusion that our intervention model not only maintains market stability but also promotes the return of risk asset prices to their fun-damental values.The study concludes that government interventions guided by the new HAM can alleviate the dilemma between reducing price volatility and improving price efficiency in future intervention programs.

ZTE Communications Special Issue on Channel Measurement and Modeling for Heterogeneous 5G

While cellular networks have continuously evolved in re- cent years, the industry has clearly seen unprecedented chal- lenges to meet the exponentially growing expectations in the near future. The 5G system is facing grand challenges such as the ever-increasing traffic volumes and remarkably diver- sified services connecting humans and machines alike. As a result, the future network has to deliver massively increased capacity, greater flexibility, incorporated computing capabili- ty, support of significantly extended battery lifetime, and ac- commodation of varying payloads with fast setup and low latency, etc. In particular, as 5G requires more spectrum resource, higher frequency bands are desirable. Nowadays, millimeter wave has been widely accepted as one of the main communication bands for 5G.

ZTE Communications Special Issue on Channel Measurement and Modeling for Heterogeneous 5G

While cellular networks have continuously evolved in recent years, the industry has clearly seen unprecedented challenges to meet the exponentially growing expectations in the near future.

A Fluctuation Test for Structural Change Detection in Heterogeneous Panel Data Models

Structural change in panel data is a widespread phenomena. This paper proposes a fluctuation test to detect a structural change at an unknown date in heterogeneous panel data models with or without common correlated effects. The asymptotic properties of the fluctuation statistics in two cases are developed under the null and local alternative hypothesis. Furthermore, the consistency of the change point estimator is proven. Monte Carlo simulation shows that the fluctuation test can control the probability of type I error in most cases, and the empirical power is high in case of small and moderate sample sizes. An application of the procedure to a real data is presented.

Optimal operating conditions of radial flow moving-bed reactors for isobutane dehydrogenation

In this study, radial flow moving bed reactors for isobutane dehydrogenation have been modeled and simulated heterogeneously based on mass and energy conservation laws. The considered reaction networks in the model are isobutene dehydrogenation as main reaction, and hydrogenolysis, propane dehydrogenation as well as coke formation as side reactions that all occur on the catalyst surface. Then, the process condition has been optimized to produce more isobutene under steady state condition. To prove the accuracy of the considered mathematical model and assumptions, simulation results are compared with the plant data. As a powerful method in the global optimization, the genetic algorithm has been used to optimize the considered objective function. The isobutane conversion and isobutene selectivity under optimal conditions are about 40.1% and 91%, respectively.

Researches on the PAM／Cr^3＋ Gel for Deep Profile Control

The profile control hard-gel is composed of polyarylamide (5-6g/L), whose molecular weight is 4,000,000 - 7,000,000 and hydrolysis degree is 17.6%, and cross-linking oxidation-reduction agent (Na2Cr2O7 + NH4Cl), with an delayed organic acid crosslinker which contains lactic acid/propionic acid/ethanoic acid and ethylene glycol. After research of the influence factors, such as pH, temperature, salinity and the dosage of delayed crosslinker, the optimum condition(pH 5.2, temperature 55℃, salinity < 7g/L) was found. Gelation time (12-144h) can be controlled by adjusting the dosage of the delayed crosslinker. Deep profile control experiments are carried out on heterogeneous models, which contains three serial high permeable and low permeable cores arranged in a parallel. After water flooding (total recovery, 24.3%), the first, second and third high-permeable cores each are sealed in turn by the profile control agent, and the total displacement recovery increases to 46.8%, 62.2% and 69.1% respectively. So, the greater the sealed depth, the larger the enhancing recovery will be. Finally, the oil displacement mechanisms of deep profile control are discussed.

Broadband diffuse optical spectroscopy of two-layered scattering media containing oxyhemoglobin,deoxyhemoglobin,water,and lipids

We investigated the relationship between chromophore concentrations in two-layered scattering media and the apparent chromophore concentrations measured with broadband optical spectroscopy in conjunction with commonly used homogeneous medium inverse models.We used diffusion theory to generate optical data from a two-layered distribution of relevant tissue absorbers,namely,oxyhemoglobin,deoxyhemoglobin,water,and lipids,with a top-layer thickness in the range 1–15 mm.The generated data consisted of broadband continuous-wave(CW)diffuse reflectance in the wavelength range 650–1024 nm,and frequency-domain(FD)diffuse reflectance at 690 and 830 nm;two source-detector distances of 25 and 35mm were used to simulate a dual-slope technique.The data were inverted using diffusion theory for a semi-infinite homogeneous medium to generate reduced scattering coeffcients at 690 and 830nm(from FD data)and effective absorption spectra in the range 650–1024nm(from CW data).The absorption spectra were then converted into effective total concentration and oxygen saturation of hemoglobin,as well as water and lipid concentrations.For absolute values,it was found that the effective hemoglobin parameters are typically representative of the bottom layer,whereas water and lipid represent some average of the respective concentrations in the two layers.For concentration changes,lipid showed a significant cross-talk with other absorber concentrations,thus indicating that lipid dynamics obtained in these conditions may not be reliable.These systematic simulations of broadband spectroscopy of two-layered media provide guidance on how to interpret effective optical properties measured with similar instrumental setups under the assumption of medium homogeneity.

Impact of Heterogeneity on Forwarding Schemes in Opportunistic Networks

In the paper, we concentrate on the infl uence of heterogeneity on the performance of forwarding algorithms under opportunistic networks. Therefore, we first describe two different heterogeneous network models, and capture the heterogeneity which concern mobile nodes' contact dynamics under the individual models and the spatial models. Then we investigate inter-contact time is not fully follow exponential distribution and compare the performance of the delivery delay between direct forwarding protocol and three-hop forwarding protocol under three network models. We illustrate the performance of message delivery delay under the spray and wait protocol and prophet protocol from simulation results. Our simulation results show that the heterogeneity should be considered for the performance of forwarding protocols.

A Study on Heterogeneous Cellular Automaton Simulation of the Influencing Factors on Seismicity

For the purpose of investigating conditions of earthquake pregnancies,a heterogeneous 2-D single fault model with 81 × 81 cells is set up. By using cellular automata models and changing the model heterogeneity and correlation parameters, we compute and get different synthetic event catalogues for analyzing general seismic activity and intensity distribution properties. The results show that different heterogeneous structures produce different seismic sequence types and G-R relationship,so the heterogeneity is an important influencing factor on seismicity. Nevertheless,both the coefficients of stress redistribution and local friction loss can also influence seismicity to some extent. This is possibly useful for further understanding of the complexity of earthquake processes.

Theoretical Study on Auto-Oscillating Combustion in Self-propagating High Temperature Synthesis

Oscillating combustion is one of classic phenomenon in SHS.But the cause of its formation in a set of complex processes is unclear yet.With a two-step chemical reaction assumption and effects of other thermal dynamic factors,an auto-oscillating combustion has been gained in a solid SHS process on the macro-homogenous and micro-heterogonous model.Numerical solution shows that the change of chemical reaction is the main cause of the oscillating combustion.

Upgrading Siberian(Russia) crude oil by hydrodesulfurization: Kinetic parameter estimation in a trickle-bed reactor

Hydrodesulfurization(HDS) of sour crude oil is an effective way to address the corrosion problems in refineries and is an economic way to process sour crude oil in an existing refinery built for sweet oil.Siberian crude oil transported through the Russia-China pipeline could be greatly sweetened and could be refined directly in local refinery designed for Daqing crude oil after the effective HDS treatment.In this study,the HDS of Siberian crude oil was carried out in a continuous flow isothermal trickle-bed reactor over Ni-Mo/γ-Al_2 O_(3).The effects of temperature,pressure and LHSV were investigated in the ranges of 320-360℃,3-5 MPa and 0.5-2 h^(-1),keeping constant hydrogen to oil ratio at 600 L·L^(-1).The HDS conversion could be up to 92.89% at the temperature of 360℃, pressure of 5 MPa,and LHSV of 0.5 h^(-1), which is sufficient for local refineries(>84%).A three phase heterogeneous model was established to analyze the performance of the trickle-bed reactor based on the two-film theory using Langmuir-Hinshelwood mechanism.The order of sulfur component is estimated as 1.28,and the order of hydrogen is 0.39.By simulating the reactor using the established model,the concentration of H_(2), H_(2) S and sulfur along the catalyst bed is discussed.The model is significantly useful for industrial application with respect to reactor analysis,optimization and reactor design,and can provide further insight of the HDS of Siberian crude oil.

Simultaneous production and utilization of methanol for methyl formate synthesis in a looped heat exchanger reactor configuration

In this investigation, a novel thermally coupled reactor （TCR） containing methyl formate （MF） production in the endothermic side and methanol synthesis in the exothermic side has been investigated. The interesting feature of this TCR is that productive methanol in the exothermic side could be recycled and used as feed of endothermic side for MF synthesis. Other important advantages of the proposed system are high production rates of hydrogen and MF. The configuration consists of two thermally coupled concentric tubular reactors. In these coupled reactors, autothermal system is obtained within the reactor. A steady-state heterogeneous model is used for simulation of the coupled reactor. The proposed model has been utilized to compare the performance of TCR with the conventional methanol reactor （CMR）. Noticeable enhancement can be obtained in the performance of the reactors. The influence of operational parameters is studied on reactor performance. The results show that coupling of these reactions could be feasible and beneficial. Experimental proof-of-concept is required to validate the operation of the novel reactor.

A tour-based analysis of travel mode choice accounting for regional transit service

The aim of this work is to explore the impact of regional transit service on tour-based commuter travel behavior by using the Bayesian hierarchical multinomial logit model, accounting for the spatial heterogeneity of the people living in the same area.With two indicators, accessibility and connectivity measured at the zone level, the regional transit service is captured and then related to the travel mode choice behavior. The sample data are selected from Washington-Baltimore Household Travel Survey in 2007,including all the trips from home to workplace in morning hours in Baltimore city. Traditional multinomial logit model using Bayesian approach is also estimated. A comparison of the two different models shows that ignoring the spatial context can lead to a misspecification of the effects of the regional transit service on travel behavior. The results reveal that improving transit service at regional level can be effective in reducing auto use for commuters after controlling for socio-demographics and travel-related factors.This work provides insights for interpreting tour-based commuter travel behavior by using recently developed methodological approaches. The results of this work will be helpful for engineers, urban planners, and transit operators to decide the needs to improve regional transit service and spatial location efficiently.