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As a renewable energy source and potential substitute for fossil fuels, biodiesel plays an increasingly important role in both energy security and environmental protection. Accurate thermal conductivity data of biodiesels and their mixture with diesel are critical to engine design to achieve high combustion efficiency. This study measured the thermal conductivity of binary mixtures of heptane and biodiesel components, specifically methyl myristate, methyl laurate, and methyl caprate, over a temperature range of 298.15–328.15 K, using the two-wire 3ω method. Based on the experimental data, the effect of mass fraction, temperature, and carbon chain length of the fatty acid ester on the thermal conductivity was analyzed. The second-order Scheffé polynomial model, Flippov equation, Jamieson equation, and Chen equation were used to correlate the experimental data and compare to find a better one. The Flippov equation shows the lowest absolute average relative deviation of 0.80% for the binary mixtures of heptane with methyl myristate, methyl laurate, and methyl caprate.

In order to build Beijing into a world-class harmonious and livable capital city, its energy and environmental issues deserve special attention. Considering London’s experience and achievements in tackling smog crisis, New York’s world-class city positioning and influence, and Tokyo’s geographical and cultural characteristics, these three world-class megacities are taken as examples in this study for investigating and analyzing the establishment and optimization of an urban energy system which is clean, efficient, safe, and sustainable. The urban planning strategies, planning experience, and related energy policy of these three megacities for building low-carbon cities are reviewed and their enlightenment to Beijing is discussed. The study of international cases has a certain reference effect on the energy structure adjustment and urban planning practices related to Beijing’s construction of a low-carbon city.

Metallic nanowires (NWs) and their different compounds display incredible prospects for their use in various applications including media storage, sensor and solar cell devices along with the biological drug delivery systems. In this research work, the metallic NWs like nickel nanowires (Ni-NWs) are synthesized successfully by employing electrodeposition process. Anodic aluminum oxide (AAO) templates are employed as a platform with copper metal coating which acts as an active cathode. The synthesized Ni-NWs are examined through various characterization techniques including X-ray diffraction (XRD), scanning electron microscope (SEM) and vibrating sample magnetometer (VSM) to study the crystal structure, surface morphology and magnetic properties, respectively. The XRD analysis shows the development of various diffraction planes like Ni (111), Ni (200), Ni (220) which confirms the formation of polycrystalline nickel NWs. The SEM analysis reveals that the range of diameter and length of nickel NWs are found to be ∼160 to 200 and ∼4 to 11 micron respectively showing high aspect ratio (ranged from ∼200 to 300). The ferromagnetic behavior of Ni-NWs is confirmed by the hysteresis loop carried out for parallel and perpendicular configurations having Hc = 100 and 206 Oe, respectively. The obtained results suggest that the synthesized Ni- NWs may be used for high-density media storage devices.

Ionic liquids (ILs) are promising electrolytes or solvents for numerous applications owing to their unique properties. However, it is a challenge to design the ideal IL with the required properties. Variational autoencoders (VAEs) trained by significantly large datasets have shown good performance in drug discovery. However, low generation efficiency and small sparse datasets prevent their application on IL. In this work, we propose a high generation efficiency molecular design model for IL, which realizes multi-objective optimization on a small dataset. The model combines VAE, multilayer perceptron, and particle swarm optimization for property prediction and molecule optimization. The thermal conductivity and heat capacity of the ILs are chosen as a case to verify the advantages of our model. The results shows that by setting molecular validity judgments to optimization target, 98% output of our method are valid molecules. Besides, the heat capacity and thermal conductivity are improved by 39% and 15%, respectively. Our model improves the applicability to small sparse datasets and the generation efficiency of VAE-like generation model. By multi-objective design ILs for given properties, our model can provide guidance for the design and application of ILs.

Rural energy is related to the domestic energy supply, consumption, and improvement of living standards of more than one-third of the population in China. In the “14th Five-Year Plan,” it has been clearly pointed out that it is necessary to strengthen the clean utilization of coal and implement the construction of rural clean energy projects. At present, the energy consumption structure of rural areas in China is transiting from traditional solid energy to commercial energy and clean energy. Based on this background, this paper reviews the transition trend, influencing factors, and regional differences of China’s rural household energy consumption structure from the 1990s. Taking into account China’s goal of carbon peaking by 2030 and carbon neutrality by 2060, carbon dioxide and pollutant emissions generated in the process of energy consumption and the energy-saving potential of rural households are analyzed and discussed. Moreover, the evolution of rural energy policies in China is presented and related proposals are also made. This review aims to provide reference for relevant researchers and policy makers.

The supercritical CO2 (SC-CO2) thermodynamic cycle has been a promising and revolutionary technology. Related research has put higher demands on CO2 physical property calculations in terms of computational accuracy and speed. In this study, the deviations between the experimental data and predicted data calculated by several models of CO2 physical property calculation were obtained. According to the comparison results, the Span–Wagner equation of state, the Vesovic model, and the free-volume viscosity model are selected to construct a set of high-precision CO2 property calculation models. For the time-consuming problem of commonly used models, new models were developed by using the polynomial fitting and interpolation method, which improved the speed of the physical property calculation by five orders of magnitude while ensuring high accuracy. On this basis, a physical property calculation program for the SC-CO2 thermodynamic cycle could be developed, which can meet the demands of engineering applications in accuracy and calculation speed.

The coordinated development of the Beijing-Tianjin-Hebei region has become China's national strategy with great and far-reaching significance. The construction of Energy Internet is an important measure to strengthen the coordination of green energy development in Beijing-Tianjin-Hebei region and promote the development of renewable energy. In this paper, based on the development status of renewable energy in the Beijing-Tianjin-Hebei region, the problems and challenges existing in the renewable energy development in the Beijing-Tianjin-Hebei region and related considerations for their solution are reviewed and discussed. Energy Internet has also become a booster for the rapid development of clean and renewable energy. The policies on the Energy Internet Construction issued by Beijing, Tianjin, and Hebei during the 13th Five-Year Plan Period (2016–2020) and at the beginning of the 14th Five-Year Plan Period (2021–2025) are summarized. The focuses of all these policy documents are analyzed. The development status of seven Energy Internet demonstration projects in Beijing-Tianjin-Hebei region is reviewed. On this basis, some considerations on Energy Internet construction in the Beijing-Tianjin-Hebei region are analyzed and proposed.

Energy saving and environmental protection have become the core development concept of China construction industry. There are still a large number of old urban buildings in Beijing, whose energy consumption far exceeds the current building energy efficiency standards. The energy-saving renovation of these old buildings has been becoming the focus and difficulty of urban building energy-saving. In this paper, a calculation model based on the TNM Decree is proposed to calculate and analyze the energy consumption of heating and domestic hot water supply in winter before and after the renovation of old urban buildings in Beijing. The calculation results show that the thermal insulation performance of building envelope is a key factor affecting the energy consumption of old urban buildings. After the renovation, the energy-saving rate of the old urban buildings completed between 1978 and 1985 can reach 65.53%. The energy-saving rate of the buildings completed between 1986 and 1995 and that between 1996 and 2005 can reach 55.04% and 32.79%, respectively.

As a powerful tool to solve nonlinear problems, artificial neural network method (ANN) gets a wide range of applications in data regression. However, the overfitting often occurs during the ANN training process, which results in high accuracy of correlating the training data but poor prediction performance. At the same time, the principle of k-Nearest Neighbor method (kNN) makes it impossible to make an accurate prediction exceeding the range of the training data, but it can confine the overfitting of ANN. In this work, combining ANN and kNN, a new machine learning method called ANN-kNN combination method (AKC) for thermophysical property prediction of material is proposed. To evaluate the performance of AKC, we take the thermophysical properties of natural gas as an example. The inputs of AKC are temperature, pressure and the components of natural gas, the outputs are the compressibility factor, speed of sound and viscosity. AKC not only overcomes the overfitting problem but also needs less training data than ANN. The average absolute relative deviation of AKC for prediction are 2.5%, which are better than ANN (5.9%) and kNN (19.2%).

Aiming to investigate the rotation effect on the natural convection and heat transfer of nanofluid, which has an important application in the control of heat transfer, the velocity field and temperature distribution inside the square cylinder with the rotating heat source in the center were numerically studied and presented in detail at different Hartman numbers and aspect ratios using the immersed boundary-lattice Boltzmann method. Then, the average Nusselt number on the surface of the heat source was calculated to compare the heat transfer rate in different cases. The results showed that the rotation would reduce the effect of gravity on the flow and suppress the heat transfer between the rotating heat source and nanofluid, while the external magnetic field would reduce the rotation effect on the flow and suppress or promote the heat transfer depending on the rotational speed and aspect ratio. Moreover, the smaller aspect ratio of the heat source to the square cylinder would enhance the heat transfer rate and make the retarding effect of magnetic field on rotation more apparent. In addition, the dimensionless rotational speed was proposed in this work, by which much computational time could be saved during the calculation of the immersed-boundary lattice Boltzmann method for the problem of rotation.

Bus rides have become a routine choice for the large population to travel in Beijing. By the end of November 2020, 82.84% of all buses in Beijing had switched to electric vehicles. A solution to the problem of charging a huge number of battery electric buses (BEBs) in urban areas, especially in crowded cities with large populations, has to be found. In the present paper, a calculation model based on the levelized cost of electricity (LCOE) is established for comparison and analysis of the BEB charging. The calculation results show that the hybrid charging mode is economically feasible. Moreover, from the perspectives of optimizing operation shifts and responding to emergency situations, hybrid charging mode is applicable to the current electric bus system. The calculation results also show that the use of BEBs as the main ground public transportation in Beijing can substantially reduce CO2 emissions and save huge fuel costs. Its application is a very wise choice. The analogy calculation on Tongzhou District, the sub center of Beijing which is under construction, shows that the use of BEBs in Tongzhou can reduce CO2 emissions by about 34.6% on average compared with fuel buses. The population is the main influencing factor of analogy calculation.

The vibration analysis, based on the Donnell thin shell theory, of single-walled carbon nanotubes (SWCNTs) has been investigated. The wave propagation approach in standard eigenvalue form has been employed in order to derive the characteristic frequency equation describing the natural frequencies of vibration in SWCNTs. The complex exponential functions, with the axial modal numbers that depend on the boundary conditions stated at edges of a carbon nanotube, have been used to compute the axial modal dependence. In our new investigations, the vibration frequency spectra are obtained and calculated for various physical parameters like length-to-diameter ratios for armchair and zigzag SWCNTs for different modes and in-plane rigidity and mass density per unit lateral area for armchair and zigzag SWCNTs on the vibration frequencies. The computer software MATLAB is used in order to compute these frequencies of the SWCNTs. The results obtained from wave propagation method are found to be in satisfactory agreement with that obtained through the previously known numerical molecular dynamics simulations.

A modified Evan-Gillan hoinogenous perturbed scheine was employed to measure the thermal response and col-responding normalized plasma thermal conductivity (An) of strongly coupled dusty plasmas (SCDPs). Homogenous perturbed molecular dynamics (HPMD) approach was eniployed to analyze the efficiency and compared the obtained outcomes of perturbed heat flux vector to the outcomes computed through equilibrium molecular dynamics (EMD) approach. Our new outcomes show that the thermal response of heat energy current through HPMD and EMD approaches is an excellent agreement with each other ft}r SCI)Ps at much low value of normalized external perturbation (F'). The obtained HPMD simulations demonstrate that the presented approach provides good outcomes with fast convergence and small system size for low-tointermediate pla,Kma couplings (1') at very weak F'.It was found that the measured plasma Acjoutcoines at nearly equilibrium weak F (- 0.00005) are in reaKon.able agreement with earlier results obtained rom EMD, homogenous and inhomogeneous nonequilihrium molecular dynamics simulations and theoretical predictions and generally overpredicted the plasma 4, by -1%--24% depending on the arrangement of plasma parameters (P, h·).Itwas shown that the HPMDis an excellent approach to calculate the plasma At, and to recognize the elementary patterns in 3D SCDPA. [ABSTRACT FROM AUTHOR]

In this work, the solubilities and diffusion coefficients of refrigerant trans-1-chloro-3,3,3-trifluoropropene (R1233zd(E)) in three imidazolium ionic liquids were measured at temperatures from 303.1 to 343.2 K and pressures up to 0.14 MPa. The ionic liquids include 1-hexyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)amide ([HMIM][Tf2N]), 1-hexyl-3-methylimidazolium trifluoromethanesulfonate ([HMIM][TfO]), and 1-hexyl-3-methyl-imidazolium tetrafluoroborate([HMIM][BF4]). The non-random two-liquid (NRTL) activity coefficient model was employed to correlate the experimental solubility data successfully, the AAD between the measured data and calculated values for the solubilities of R1233zd(E) in [HMIM][Tf2N], [HMIM][TfO], and [HMIM][BF4] are 3.1, 2.5, and 4.0%, respectively. The Wilke-Chang equation was used to correlate diffusion coefficients, the relative deviations between experimental results and the values calculated are most within 10%. Meanwhile, the solubility and diffusivity of refrigerant gases R32, R125, R152a, R161, R143a, R1234yf, R1234ze(E), and R1233zd(E) in ionic liquids [HMIM][Tf2N], [HMIM][TfO], and [HMIM][BF4] were compared and analyzed. [ABSTRACT FROM AUTHOR]

The vibration analysis, based on the Donnell thin shell theory, of single-walled carbon nanotubes (SWCNTs) has been investigated. The wave propagation approach in standard eigenvalue form has been employed in order to derive the characteristic frequency equation describing the natural frequencies of vibration in SWCNTs. The complex exponential functions, with the axial modal numbers that depend on the boundary conditions stated at edges of a carbon nanotube, have been used to compute the axial modal dependence. In our new investigations, the vibration frequency spectra are obtained and calculated for various physical parameters like length-to-diameter ratios for armchair and zigzag SWCNTs for different modes and in-plane rigidity and mass density per unit lateral area for armchair and zigzag SWCNTs on the vibration frequencies. The computer software MATLAB is used in order to compute these frequencies of the SWCNTs. The results obtained from wave propagation method are found to be in satisfactory agreement with that obtained through the previously known numerical molecular dynamics simulations. [ABSTRACT FROM AUTHOR]

Newexperimental data for the vapor–liquid equilibrium of1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([HMIM][Tf2N]) with difluoromethane (R-32), 1,1-difluoroethane (R-152a),and pentafluoroethane (R-125) were presented. Measurements were performedusing an isochoric saturation method at temperatures from (302.3 to344.1) K and at pressures between (0.03 to 1.22) MPa. The relativeexpanded uncertainty in solubility measurement is less than 4 %. Withinthe investigated temperature and pressure range, the order of thesolubilities for R-32, R-152a, and R-125 in [HMIM][Tf2N]is R-152a > R-32 > R-125. The experimental results were successfullycorrelated with the Krichevsky–Kasarnovsky equation. The AADbetween the experimental data and calculated values for the solubilitiesof R-152a, R-32, and R-125 in [HMIM][Tf2N] are 1.4 %, 1.5%, and 0.8 %, respectively. [ABSTRACT FROM AUTHOR]

On the basis of the Mach−Zehnder optical interference model, a digital holographic interferometric experimental system was set up, and a new diffusion cell especially for measuring the binary gas diffusion coefficient was designed and constructed. With the theory for measuring the binary gas diffusion coefficient and the interference fringe processing method introduced before, the binary gas diffusion coefficient can be obtained. In comparison with the reference data of O2in air, the experiment accuracy of the system was verified. The diffusion coefficients of H2, He, NH3, CH4, O2, and CO2in air at T= (278.15 to 343.15) K under normal atmospheric pressure were measured and compared with results of a correlation. The comparison showed that the results are reasonable. [ABSTRACT FROM AUTHOR]

Digital image holographic interferometry has been used to measure the mass diffusion coefficient of fluids. The mass diffusion coefficients of KCl in aqueous solution at a concentration pf 0.33 mol·dm−3as the standard solution was used to verify the precision and reliability of the apparatus. The results show that the absolute average relative deviations is within 1.20 %. The uncertainty in mass diffusion coefficient is estimated to be not greater than ± 0.2 %. The mass diffusion coefficients of three different oxygenated fuel additives, bis(2-methoxyethyl)-ether (diethylene glycol dimethyl ether, DGM), 1,2-dimethoxyethane (ethyleneglycol dimethyl ether, GDME), and ethanol, were determined in both diesel oil and heptane at temperatures between (276 and 333) K. [ABSTRACT FROM AUTHOR]

The kinematic viscosity, the specific heat capacity at constant pressure, the specific heat capacity at constant volume, and the surface tension of 1,1,1,2-tetrafluoroethane (R134a) refrigerant−oil mixtures in the saturated liquid phase were measured when the lubricant concentrations were (20, 50, 80, and 100) ppm. According to the experimental results, the effect of lubricant concentration on the above four thermophysical properties was analyzed, and the relational expressions describing the relation between these four thermophysical properties and temperature and lubricant concentration were also established. [ABSTRACT FROM AUTHOR]

A method based on digital holographic interferometry for measuring the mutual diffusion coefficients of binary liquid is introduced. With uncertainty analysis and experimental verification, the uncertainties of temperature and mutual diffusion coefficient are estimated to be no greater than ± 0.16 K and ± 0.2 %, respectively. On this basis, the mutual diffusion coefficients for diethyl carbonate and diethyl adipate in heptane were measured from T= (278.15 to 338.15) K under atmospheric pressure, and a polynomial was fitted by the experimental data. [ABSTRACT FROM AUTHOR]

The particle structure of a complex system has been explored through a unique Evans's homogenous nonequilibrium molecular dynamics (HNEMD) simulation technique. The crystalline order–disorder structures (OD-structures) and the corresponding energies of three-dimensional (3D) nonideal complex systems (NICSs) have been measured over a wide range of plasma states (Γ, κ) for a body-centered cubic (BCC) structure. The projected technique provides accurate OD-structures with fast convergence and applicable to very small size effect for different temperatures ( 1 / and constant force field ( values. The OD-structure obtained through HNEMD approach is found to be reasonable agreement and more reliable than those earlier identified by simulation approaches and experimental data of NICSs. New simulations of OD-structures show that dusty plasma remains in crystalline (strongly coupled) state at lower temperature and constant values, for the whole simulation runs. Our investigations show that the crystalline structure is changed and the particle structure switches from intermediate to disorder (nonideal gaseous) state with an increase of the system's temperature. It has been shown that the long range order shifts toward lower temperature with increasing *. The presented technique exhibits that the potential energy has a maximum value when the dusty plasma remains in crystalline states (low temperatures), which confirms earlier 3D simulation results. [ABSTRACT FROM AUTHOR]

Transport properties of di-isopropyl ether are so scarce that it prevents the further studies of di-isopropyl ether as an alternative fuel additive. For this purpose, dynamic light scattering method is used to investigate the thermal diffusivity of di-isopropyl ether (purity: >98%) in the temperature range from 298 to 530 K and at the pressure up to 10 MPa, including saturated liquid and vapor, compressed liquid and the supercritical region. It is estimated that the standard uncertainties are: u(T) = 0.01 K under saturated condition; u(T) = 0.02 K, u(p) = 0.015 MPa for p < 5.5 MPa, u(p) = 0.03 MPa for p > 5.5 MPa under compressed liquid and supercritical conditions; and the relative expanded uncertainty Ur in the thermal diffusivity is Ur(a) = 0.03 with a coverage factor of k = 2. Moreover, the reference relations of thermal diffusivities for saturated liquid, vapor and compressed state are presented by employing the experimental results for interpolation with the average absolute deviation of 0.92%, 1.28% and 0.75%, respectively. [ABSTRACT FROM AUTHOR]

We have discovered unusual behavior of polymer coils in a binary solvent (nitroethane + isooctane) near the critical temperature of demixing. The exceptionally close refractive indices of the solvent components make the critical opalescence relatively weak, thus enabling us to simultaneously observe the Brownian motion of the polymer coils and the diverging correlation length of the critical fluctuations. The polymer coils exhibit a collapse-reswelling-expansion-reshrinking transition upon approaching the critical temperature. While the first stage (collapse) can be explained by the theory of Brochard and de Gennes, the subsequent expansion-reshrinking transition is a new unexpected phenomenon that has not been observed so far. We believe that this effect is generic and attribute it to microphase separation of the solvent inside the polymer coil. [ABSTRACT FROM AUTHOR]