Analysis of Thermodynamic Characteristic Changes in Direct Expansion Ground Source Heat Pump Using Hydrofluoroolefins (HFOs) Substituting for HFC-134a

HFO-1234yf and HFO-1234ze[E] have low global warming potential and zero ozone depletion potential. If they are used in the direct expansion ground source heat pump system substituting for HFC-134a, the system will be beneficial to mitigating climate change. This study aims to find out the thermodynamic characteristics of the direct expansion ground source heat pump system using HFO-1234yf or HFO-1234ze[E] by theoretical calculation. The results indicate that HFO-1234yf system in an actual cycle has the highest COP. HFO-1234yf and HFO-1234ze[E] have such smaller capacity per unit of swept volume that they need larger compression capacity if providing the same heating or cooling loads. For a given unit when HFC-134a is replaced with HFO-1234yf or HFO-1234ze[E], the capacity will decrease. More refrigerant charge is required in the HFO-1234yf or HFO-1234ze[E] system. The results also present that more refrigerant charge is required in the cooling mode than in the heating mode.

First-principles study of electronic structure and optical properties of Er:Lu_(2)O_(3)

In the present computational study,we found that Er:Lu_(2)O_(3)materials have promise for application in laser applications.The crystal structure and the electronic and optical properties of Er:Lu_(2)O_(3)materials were studied using first-principle calculations under the framework of density functional theory.Based on the experimental and calculated results,the structure of Lu_(2)O_(3)was established.The calculated results show that doping by Er^(3+)can effectively improve its absorption coefficient in the ultraviolet region and improve the static dielectric constant of Lu_(2)O_(3).As the doping concentration of Er^(3+)increases,the energy of the valence band electrons excited to the conduction band decreases,and the transition is more likely to occur.The absorption coefficient,reflectance,and electron energy loss spectroscopy are bathochromic shifted.The Lu_(2-x)Er_(x)O_(3)(0<x<0.09375)system still retains a low absorption coefficient reflectance in the mid-infrared and visible regions.Our calculations therefore show that rare earth doping can effectively regulate the electronic structure and optical properties of Lu_(2)O_(3).

Time series modeling and filtering method of electric power load stochastic noise

Stochastic noises have a great adverse effect on the prediction accuracy of electric power load.Modeling online and filtering real-time can effectively improve measurement accuracy.Firstly,pretreating and inspecting statistically the electric power load data is essential to characterize the stochastic noise of electric power load.Then,set order for the time series model by Akaike information criterion(AIC)rule and acquire model coefficients to establish ARMA(2,1)model.Next,test the applicability of the established model.Finally,Kalman filter is adopted to process the electric power load data.Simulation results of total variance demonstrate that stochastic noise is obviously decreased after Kalman filtering based on ARMA(2,1)model.Besides,variance is reduced by two orders,and every coefficient of stochastic noise is reduced by one order.The filter method based on time series model does reduce stochastic noise of electric power load,and increase measurement accuracy.

Axially Chiral Dodecanuclear Lanthanide Clusters Constructed by“Bottom-Up” Self-assembly for Enantioselective Sensing

Via the bottom-up synthetic strategy,we synthesized a pair of dodecanuclear metal clusters of Eu_(12)(C_(2)O_(4))_(9)(R/S-BNP)_(18)(EtOH)_(6)-(H_(2)0)_(6)·8EtOH-7H_(2)0(complex 2),which represent the largest axial chiral lanthanide metal clusters.In the structure,rare four-pointed star coordination mode of oxalic acid is reported by this work.In addition,as a fluorescence sensor,the complex 2 exhibits high enantioselectivity for R-/S-BINOL-TF_(2)(EF=2.87)and other chiral binaphthyl derivatives.