Impact of Initial Soil Conditions on Soil Hydrothermal and Surface Energy Fluxes in the Permafrost Region of the Tibetan Plateau

Accurate initial soil conditions play a crucial role in simulating soil hydrothermal and surface energy fluxes in land surface process modeling.This study emphasized the influence of the initial soil temperature(ST)and soil moisture(SM)conditions on a land surface energy and water simulation in the permafrost region in the Tibetan Plateau(TP)using the Community Land Model version 5.0(CLM5.0).The results indicate that the default initial schemes for ST and SM in CLM5.0 were simplistic,and inaccurately represented the soil characteristics of permafrost in the TP which led to underestimating ST during the freezing period while overestimating ST and underestimating SLW during the thawing period at the XDT site.Applying the long-term spin-up method to obtain initial soil conditions has only led to limited improvement in simulating soil hydrothermal and surface energy fluxes.The modified initial soil schemes proposed in this study comprehensively incorporate the characteristics of permafrost,which coexists with soil liquid water(SLW),and soil ice(SI)when the ST is below freezing temperature,effectively enhancing the accuracy of the simulated soil hydrothermal and surface energy fluxes.Consequently,the modified initial soil schemes greatly improved upon the results achieved through the long-term spin-up method.Three modified initial soil schemes experiments resulted in a 64%,88%,and 77%reduction in the average mean bias error(MBE)of ST,and a 13%,21%,and 19%reduction in the average root-mean-square error(RMSE)of SLW compared to the default simulation results.Also,the average MBE of net radiation was reduced by 7%,22%,and 21%.

Laser-assisted synthesis of PtPd alloy for efficient ethanol oxidation

The inefficiency of ethanol oxidation reaction(EOR)presents a significant obstacle in harnessing renewable biofuels with high energy density into electricity.Despite efforts,most Pt-based catalysts still suffer from drawbacks such as poor activity and susceptibility to CO poisoning,particularly in acidic conditions.Herein,we employed a physical laser-assisted approach to synthetize a PtPd alloy with a 1:1 atomic ratio.This alloy demonstrates remarkable performance in acidic EOR,boasting a high mass activity of 1.86 A·mgPt^(−1)and competitive resistance to poisoning.Combining in situ synchrotron radiation infrared spectroscopy with theoretical calculations,we reveal that the synergic interaction between Pt and Pd enhances both the adsorption of OH*intermediate and the dehydrogenation ability of ethanol.This work will prove the feasibility of synthesizing bimetallic alloys by a physical laser-assisted strategy and promote the development of advanced alloy electrocatalysts.

22MnB5/6061异种金属CMT+A+P熔钎焊界面特征及性能研究

22MnB5热成形钢和6061铝合金是汽车工业中常用的材料,两种材料的连接能够同时实现汽车轻量化和安全性的要求,本工作利用CMT Advanced Pulse(CMT+A+P)焊接方法,选用直径为1.2 mm的ER4043焊丝,通过改善工艺实现了6061铝合金和22MnB5热成形钢异种接头有效连接。通过使用金相显微镜(OM)、扫描电子显微镜(SEM)和能谱仪(EDS),研究了熔钎焊接头宏观形貌、界面特征及拉伸性能。研究结果表明,随着焊接热输入的增加,熔钎焊接头熔宽增加,润湿角先增加后减小。铝合金侧热影响区晶粒有粗大倾向;焊缝区组织为α-Al等轴晶和Al-Si共晶,Al-Si共晶均匀分布在α-Al晶界上;界面区附近Al和Fe原子沿着界面层相互扩散,生成多种Fe-Al金属间化合物。当热输入由41.8 J/mm增加至127.6 J/mm时,界面层厚度从1.49μm增加至2.85μm。熔钎焊接头断裂位置分别位于铝合金母材处、焊缝处及界面层三个区域,其断口形貌分别呈现为韧性断裂、韧脆混合断裂和脆性断裂;拉伸强度最高的试样断裂于铝合金母材处,呈韧性断裂,拉剪载荷达3.88 kN。