First-Order Symmetry Energy Induced by Neutron-Proton Mass Difference

The 1st-order symmetry energy coefficient of nuclear matter induced merely by the neutron-proton （n p） mass difference is derived analytically, which turns out to be completely model-independent. Based on this result, （npDM） the 1st-order symmetry energy Esym,1 （A） of heavy nuclei such as 2~spb induced by the np mass difference is investigated with the help of a local density approximation combined with the Skyrme energy density functionals. Although /U（npDM） Esym,1 （A） is small compared with the second-order symmetry energy, it cannot be dropped simply for an accurate estimation of nuclear masses as it is still larger than the rms deviation given by some accurate mass formulas. It is therefore suggested that one perhaps needs to distinguish the neutron mass from the proton one in the construction of nuclear density funetionals.

Inter-stage performance and energy characteristics analysis of electric submersible pump based on entropy production theory

The electric submersible pump(ESP) is a crucial apparatus utilized for lifting in the oil extraction process.Its lifting capacity is enhanced by the multi-stage tandem structure, but variations in energy characteristics and internal flow across stages are also introduced. In this study, the inter-stage variability of energy characteristics in ESP hydraulic systems is investigated through entropy production(EP) analysis,which incorporates numerical simulations and experimental validation. The EP theory facilitates the quantification of energy loss in each computational subdomain at all ESP stages, establishing a correlation between microscopic flow structure and energy dissipation within the system. Furthermore, the underlying causes of inter-stage variability in ESP hydraulic systems are examined, and the advantages and disadvantages of applying the EP theory in this context are evaluated. Consistent energy characteristics within the ESP, aligned with the distribution of internal flow structure, are provided by the EP theory, as demonstrated by our results. The EP theory also enables the quantitative analysis of internal flow losses and complements existing performance analysis methods to map the internal flow structure to hydraulic losses. Nonetheless, an inconsistency between the energy characterization based on EP theory and the traditional efficiency index when reflecting inter-stage differences is identified. This inconsistency arises from the exclusive focus of the EP theory on flow losses within the flow field, disregarding the quantification of external energy input to the flow field. This study provides a reference for the optimization of EP theory in rotating machinery while deeply investigating the energy dissipation characteristics of multistage hydraulic system, which has certain theoretical and practical significance.

Effect of building energy efficiency standards on carbon emission efficiency in commercial buildings

The building sector plays a crucial role in the worldwide shift toward achieving net-zero emissions.Building energy efficiency standards(BEESs)are highly effective policies for reducing carbon emissions.Therefore,exploring the provincial variations in carbon emission efficiency(CEE)in the building sector and identifying the effect of BEESs on CEE is crucial.This study focuses on commercial buildings in China and applies a difference in differences model to evaluate the impact of BEESs on the CEE of commercial buildings.The slacks-based measure–data envelopment analysis model is employed to assess the CEE of commercial buildings in 30 Chinese provinces from 2000 to 2019.Furthermore,heterogeneous tests are used to explore how climate characteristics and economic conditions affect the efficiency of BEESs.The results indicate that BEESs positively influence the CEE of commercial buildings.Specifically,a 1%increase in the intensity of BEESs causes a 0.1484%increase in the CEE of commercial buildings.Moreover,the impact of BEESs is particularly pronounced in the southern and western provinces.This study provides valuable scientific evidence for governments to enhance BEESs implementation.

Microscopic Mechanism of Large Fluctuation in Odd-Even Differences in Moments of Inertia for Actinide Nuclei

The experimental large fluctuation in odd-even differences in moments ofinertia of deformed actinide nuclei is investigated using the particle-number conserving (PNC)method for treating the cranked shell model with monopole and quadrupole pairing interactions. PNCcalculations show that the large odd-even difference in moments of inertia mainly comes from theinterference contributions j(μv) from particles in high j intruder orbitals μ and v quite near theFermi surface, which have no counterpart in the BCS formalism. The effective monopole andquadrupole pairing interaction strengths are determined to fit the experimental odd-even differencesin binding energies and bandhead moments of inertia. The experimental results for the variation ofmoments of inertia with rotational frequency ω are reproduced well by the PNC calculation. Thenearly identical experimental moments of inertia between ~(236)U(gsb) and ~(238)U(gsb) at lowfrequencies hω ≤ 0.20 MeV are also reproduced quite well.

Regional differences and threshold characters of the impact of energy use efficiency on energy scarcity in China

The improvement of the technical efficiency of energy use has been widely seen as an important way to alleviate energy scarcity.However,the energy rebound effect demonstrates the vulnerability and unsustainability of alleviating energy scarcity relying on technology.Under the background of the consistent development of energy factor market,it is of great importance to explore the paths and differences of energy source allocation constrained by technology and cost to promote the sustainable use of energy.This study analyzed the regional differences and threshold characteristics in the impact of the technical and cost efficiency of energy use on energy scarcity using the instrumental variable-two-stage least square method,based on the panel data of Chinese provinces from 2003 to 2017.The results showed that:①Technology and price were the critical forces of the technical and cost efficiency of energy use.They changed the degree of use of surplus production factors by affecting the complementary and replacement demand relationship between energy and non-energy factors.Meanwhile,the impact of energy use efficiency on energy scarcity showed regional and time features due to the different technology capabilities and different levels of market development in different regions and different time.②The alleviation of energy scarcity at the national level relied on the improvement of energy cost efficiency.At the regional level,the alleviation of energy scarcity in central China came from the improvement of the technical efficiency of energy use.However,the alleviation of energy scarcity in the eastern and western regions was due to the improvement of energy cost efficiency.③Constrained by the economic development,openness,science and technology input and the industrial development structure,the impact of the technical and cost efficiency of energy use on energy scarcity demonstrated a nonlinear feature.And structural mutation occurred after passing a specific‘inflection point’,which showed a significant threshold feature.Therefore,energy price should play an important role in energy use and it is necessary to pay attention to the regional differences and time characteristics of energy economic development to promote the sustainable development of energy resources.

Estimation of Gibbs free energy difference in Pd-based bulk metallic glasses

A new thermodynamic expression for Gibbs free energy difference AG between the under-cooled liquid and the corresponding crystals of bulk metallic glasses was derived. The newly proposed expression always gives results in fairly good agreement with experimental values over entire temperature range between the fusion temperature Tm and the glass transition temperature Tg of Pd40Ni40P20, Pd40Cu30Ni10P20 and Pd43Cu27Ni10P20, which possess different heat capacities. However, the TS and KN expressions cannot always provide results in good agreement with the experimental values. In addition, the deviations between the experimental values and the AG calculated by the proposed expression at Tg are smaller than those given by other expressions for all the bulk metallic glasses studied.

Energy Scaling of Terahertz Pulses Produced through Difference Frequency Generation

We study the energy scaling of terahertz (THz) emission through difference frequency generation of near-infrared pulses, and demonstrate that Gigawatt few-cycle THz transients at the central frequency of 30 THz are produced from GaSe crystal pumped by two pulses at 1.65 and 1.95 micrometers, with the high quantum yield of 28%. Our analysis indicates that the high yield of DFG originates from the largely reduced group velocity mismatch as the long-wavelength pumping pulses are employed.

Two Energy-Preserving Compact Finite Difference Schemes for the Nonlinear Fourth-Order Wave Equation

In this paper,two fourth-order compact finite difference schemes are derived to solve the nonlinear fourth-order wave equation which can be viewed as a generalized model from the nonlinear beam equation.Differing from the existing compact finite difference schemes which preserve the total energy in a recursive sense,the new schemes are proved to per-fectly preserve the total energy in the discrete sense.By using the standard energy method and the cut-off function technique,the optimal error estimates of the numerical solutions are established,and the convergence rates are of O(h^(4)+τ^(2))with mesh-size h and time-step τ.In order to improve the computational efficiency,an iterative algorithm is proposed as the outer solver and the double sweep method for pentadiagonal linear algebraic equations is introduced as the inner solver to solve the nonlinear difference schemes at each time step.The convergence of the iterative algorithm is also rigorously analyzed.Several numerical results are carried out to test the error estimates and conservative properties.

Numerical Verification of Transition’s Energies of Excitons in Quantum Well of ZnO with the Finite Difference Method

This paper shows that the experimental results of quantum well energy transitions can be found numerically. The cases of several ZnO-ZnMgO wells are considered and their excitonic transition energies were calculated using the finite difference method. In that way, the one-dimensional Schrödinger equation has been solved by using the BLAS and LAPACK libraries. The numerical results are in good agreement with the experimental ones.

Comparative study of surface energy and land-surface parameters in different climate zones in Northwest China

Based on observational data of arid,semi-arid and semi-humid areas in Northwest China,the characteristics of surface-wa ter heat transfer and land-surface parameters were compared and analyzed.The results show that the annual mean net radi ation was largest in the semi-humid area,followed by the semi-arid area,and then the arid area:77.72 W/m^2,67.73 W/m^2,and 55.47 W/m^2,respectively.The annual mean sensible heat flux was largest in the arid area,followed by the semi-arid and semi-humid areas,while latent heat flux showed the reverse.The annual mean sensible heat flux in arid,semi-arid,and semi-humid areas was 85.7 W/m^2,37.59 W/m^2,and 27.55 W/m^2,respectively.The annual mean latent heat flux was 0 W/m^2,26.08 W/m^2,and 51.19 W/m2,respectively.The annual mean soil-heat flux at the 5-cm soil layer in arid,semi-arid,and semi-humid areas was 1.00 W/m^2,0.82 W/m^2,and 1.25 W/m^2,respectively.The annual mean surface albedo was larg est in the arid area,followed by the semi-humid area;and the smallest was in the semi-arid area:0.24,0.21,and 0.18,re spectively.The annual mean Bowen ratio in the semi-arid area was about 2.06,and that in semi-humid area was about 0.03.The annual mean soil thermal conductivity in the arid,semi-arid,and semi-humid areas was 0.26 W/(m k),1.15 W/(m k),and 1.20 W/(m k),respectively.

THE UPWIND FINITE DIFFERENCE METHOD FOR MOVING BOUNDARY VALUE PROBLEM OF COUPLED SYSTEM

Coupled system of multilayer dynamics of fluids in porous media is to describe the history of oil-gas transport and accumulation in basin evolution.It is of great value in rational evaluation of prospecting and exploiting oil-gas resources.The mathematical model can be described as a coupled system of nonlinear partial differential equations with moving boundary values.The upwind finite difference schemes applicable to parallel arithmetic are put forward and two-dimensional and three-dimensional schemes are used to form a complete set.Some techniques,such as change of variables,calculus of variations, multiplicative commutation rule of difference operators,decomposition of high order difference operators and prior estimates,are adopted.The estimates in l~2 norm are derived to determine the error in the approximate solution.This method was already applied to the numerical simulation of migration-accumulation of oil resources.

Modified characteristic finite difference fractional step method for moving boundary value problem of nonlinear percolation system

A fractional step scheme with modified characteristic finite differences run- ning in a parallel arithmetic is presented to simulate a nonlinear percolation system of multilayer dynamics of fluids in a porous medium with moving boundary values. With the help of theoretical techniques including the change of regions, piecewise threefold quadratic interpolation, calculus of variations, multiplicative commutation rule of differ- ence operators, multiplicative commutation rule of difference operators, decomposition of high order difference operators, induction hypothesis, and prior estimates, an optimal order in 12 norm is displayed to complete the convergence analysis of the numerical algo- rithm. Some numerical results arising in the actual simulation of migration-accumulation of oil resources by this method are listed in the last section.

A Compact Difference Scheme for Multi-point Boundary Value Problems of Heat Equations

In this paper,a compact difference scheme is established for the heat equations with multi-point boundary value conditions.The truncation error of the difference scheme is O(τ2+h^4),where t and h are the temporal step size and the spatial step size.A prior estimate of the difference solution in a weighted norm is obtained.The unique solvability,stability and convergence of the difference scheme are proved by the energy method.The theoretical statements for the solution of the difference scheme are supported by numerical examples.

Different Charging-Induced Modulations of Highest Occupied Molecular Orbital Energies in Fullerenes in Comparison with Carbon Nanotubes and Graphene Sheets

The highest occupied molecular orbital（HOMO） energies of fullerenes are found by quantitative first-principles calculations to be raised by negative charging, and the rising rate rank of the fullerenes is C60 >C70 >C80 >C90>C100 >C180. Then we compare fullerenes with carbon nanotubes（CNTs） and graphene sheets（GSs） and find that the increase of the HOMO energy of a fullerene is much faster than that of CNTs and graphene sheets with the same number of C atoms. The rising rate rank is fullerene>CNT>GS, which holds no matter what the number of C atoms is or which structure the fullerene isomer is. This work paves a new path for developing all-carbon devices with low-dimensional carbon nanomaterials as different functional elements.

A nuclear density probe:isobaric yield ratio difference

We report our recent progress on the nuclear symmetry energy probe,which is called the isobaric yield ratio difference(IBD),and its application in neutron density determination in experiments.The results obtained by the IBD,from which the isobaric yields in the measured 140 A MeV ^(40.48)Ca + ~9Be and ^(58.64)Ni + ~9Be reactions,and the calculated 80 A MeV ^(38-52)Ca +^(12)C reactions by using a modified statistical abrasion-ablation model,show the sensitivity of the IBD to the density differences between reactions.

计及多重需求响应的综合能源系统多时间尺度低碳运行

为挖掘需求侧资源响应潜力,文中提出一种计及多重需求响应的综合能源系统(integrated energy system,IES)多时间尺度低碳调度策略。首先,考虑到需求侧资源在不同时间尺度下的响应差异性,建立计及价格型和激励型的多重综合需求响应(integrated demand response,IDR)模型。然后,为减少源、荷预测误差对IES运行的影响,分别构建日前低碳经济调度模型和日内双时间尺度滚动优化平抑模型。最后,算例仿真设置不同场景进行对比分析。结果表明,相比传统IDR,多重IDR能有效挖掘用户响应潜力,提升系统经济性。此外,计及多重IDR的多时间尺度调度策略能有效缓解源、荷误差带来的功率波动并降低系统碳排放量,实现IES低碳、经济和稳定运行。

数字经济、绿色技术创新与能源效率提升——基于城市面板数据的实证分析

提高能源效率是我国经济绿色转型和实现双碳目标的必然要求,当下数字经济已成为能源效率提升的新动能。本文基于数字经济的“四化”框架,在理论分析的基础上,运用2011~2020年我国284个地级市的面板数据,实证检验了数字经济影响能源效率提升的机制、特征和路径。结果表明:(1)数字经济及各维度对能源效率提升的总体效应为正,其中产业数字化促进作用最强,且数字经济对能源效率的提升具有区域异质性;(2)数字经济对能源效率的提升存在双门槛,呈现中间波动但总体促进的“N”型特征;(3)数字经济可通过促进绿色技术创新进而提升能源效率,且绿色技术创新水平的提高有助于城市跨越数字经济的第二个门槛,实现数字经济发展与能源效率提升的共赢。

用能权交易制度对城市碳排放绩效改善的影响研究

用能权交易制度作为我国实现绿色发展的一项重要制度创新,对改善城市碳排放绩效具有重要意义。本文基于2006~2022年我国281个地级市的面板数据,采用双重差分模型检验用能权交易制度对城市碳排放绩效的作用机制及其溢出效应。研究发现:(1)用能权交易制度显著降低城市碳强度和提升碳全要素生产率;(2)用能权交易制度有利于非老工业基地和资源型城市碳强度的降低,同时也有利于非老工业基地和非资源型城市碳全要素生产率的提高;(3)用能权交易制度主要通过结构效应、创新效应和监管效应等途径改善城市碳排放绩效;(4)用能权交易制度的碳排放改善作用存在显著的正向空间溢出,能够实现环境红利和社会福利相容发展。因此,稳步扩大试点政策范围,积极探索实现路径和推进区域协同是实现绿色低碳的重要保障。

低碳城市试点政策能否有效促进可再生能源技术创新?

低碳城市试点政策是中国促进经济社会绿色低碳发展的一项重要举措,而可再生能源技术创新是其中的关键技术路径。基于2006—2020年的城市数据,采用渐进双重差分法考察低碳试点城市对可再生能源技术创新发展的作用机制与影响差异。结果显示,低碳城市试点政策主要通过影响城市产业结构和绿色金融发展促进可再生能源技术创新发展,且对不同资源禀赋城市的可再生能源技术创新具有异质性影响。研究建议持续扩大低碳城市试点政策推行范围,促进可再生能源技术创新发展,从而推动社会绿色转型。

多执行器载荷差异储能均衡系统特性

针对阀控多执行器复合作业系统节流损失大、动势能浪费严重等问题,提出一种多执行器载荷差异储能均衡原理。首先对多执行器系统功率分配特性进行分析,明确了载荷差异产生节流损失的原因是动力源压力与最大负载相匹配,导致其他执行器控制阀产生过大的压力损失。然后建立了载荷储能均衡液压挖掘机联合仿真模型。并设计电液储能单元控制各执行器进油腔的压力相等,从而消除执行器载荷差异造成的节流损失。在动臂、铲斗同时动作时,与流量匹配系统相比,所提系统节流损失降低达75%,系统效率提升39%;同时,电液储能单元实现了传统压力补偿器的压差调控功能,显著提升了系统运行平稳性。