The Impact of Soil Moisture Availability upon the Partition of Net Radiation into Sensible and Latent Heat Fluxes

The impact of soil moisture availability on the Bowen ratio and on the partition of net radiation flux into sensible, latent and soil heat fluxes was investigated by using one-dimensional primitive equations with a refined soil parameterization scheme. Simulation results presented that as soil moisture availability increases, the Bowen ratio and the partition of net radiation flux into sensible and soil heat fluxes decrease. The partition of net radiation flux into latent heat flux, however, increases. Quantitative relationships between Bowen ratio and the partitions with soil moisture availability were also given in this study.

Modeling of workpiece temperature suppression in high-speed dry milling of UD-CF/PEEK considering heat partition and jet heat transfer

High-performance carbon fiber-reinforced polyether-ether-ketone(CF/PEEK)has been gradually applied in aerospace and automobile applications because of its high strength-to-weight ratio and impact resistance.The drymachining requirement tends to cause the cutting temperature to surpass the glass transition temperature(Tg),leading to poor surface quality,which is the bottleneck for dry milling of CF/PEEK.Temperature suppression has become an important breakthrough in the feasibility of high-speed dry(HSD)milling of CF/PEEK.However,heat partitioning and jet heat transfer mechanisms pose strong challenges for temperature suppression analytical modeling.To address this gap,an innovative temperature suppression analytical model based on heat partitioning and jet heat transfer mechanisms is first developed for suppressing workpiece temperature via the first-time implementation of an air jet cooling process in the HSD milling of UD-CF/PEEK.Then,verification experiments of the HSD milling of UD-CF/PEEK with four fiber orientations are performed for dry and air jet cooling conditions.The chip morphologies are characterized to reveal the formation mechanism and heat-carrying capacity of the chip.The milling force model can obtain the force coefficients and the total cutting heat.The workpiece temperature increase model is validated to elucidate the machined surface temperature evolution and heat partition characteristics.On this basis,an analytical model is verified to predict the workpiece temperature of air jet cooling HSD milled with UD-CF/PEEK with a prediction accuracy greater than 90%.Compared with those under dry conditions,the machined surface temperatures for the four fiber orientations decreased by 30%–50%and were suppressed within the Tg range under air jet cooling conditions,resulting in better surface quality.This work describes a feasible process for the HSD milling of CF/PEEK.

Effect of friction heat on tribological behavior of M2 steel against GCr15 steel in dry sliding systems

The tribological behavior depends significantly on friction heat under high sliding velocity. Many factors influence the conduction rate of friction heat, such as thermophysical properties of the pairs, the formation components of interface-film, environment mediums, etc. Through theoretical and experimental studies on surface temperature, the heat partition approaches have been applied to the pairs of M2 steel against GCr 15 steel to compare and discuss their tribological behavior in dry sliding contact. The results indicate that the values of the contact pressure have little effect on the heat partition at a high sliding velocity of 40 m/s. Furthermore, the degree of correlation between the dynamic temperature and friction coefficient is obvious, and the correlation degree of parameters increases as the pressure grows. A close correlation exists among the temperatures measured from different points of the pin specimen. At last, X-ray diffraction analysis denotes that the carbides of secondary M6C are separated out during the process of friction.

Effect of sample temperature on laser-induced semiconductor plasma spectroscopy

We investigate the temperature dependence of the emission spectrum of a laser-induced semiconductor（Ge and Si） plasma. The change in spectral intensity with the sample temperature indicates the change of the laser ablation mass. The reflectivity of the target surface is reduced as the sample is heated, which leads to an increase in the laser energy coupled to the surface of the sample and eventually produces a higher spectral intensity.The spectral intensities are enhanced by a few times at high temperatures compared with the cases at low temperatures. The spectral intensity of Ge is enhanced by 1.5 times at 422.66 nm, and 3 times at589.33 nm when the sample temperature increases from 50°C to 300°C. We can obtain the same emission intensity by a more powerful laser or by less pulse energy with a higher sample temperature. Based on experimental observations we conclude that the preheated sample can improve the emission intensity of laser-induced semiconductor plasma spectroscopy.