Mechanism of methanol decomposition on the Pd/WC(0001) surface unveiled by first-principles calculations

In this study, the decomposition of methanol into the CO and H species on the Pd/tungsten carbide (WC)(0001) surface is systematically investigated using periodic density functional theory (DFT) calculations. The possible reaction pathways and intermediates are determined. The results reveal that saturated molecules, i.e., methanol and formaldehyde, adsorb weakly on the Pd/ WC(0001) surface. Both CO and H prefer three-fold sites, with adsorption energies of −1.51 and −2.67 eV, respectively. On the other hand, CH₃O stably binds at three-fold and bridge sites, with an adsorption energy of −2.58 eV. However, most of the other intermediates tend to adsorb to the surface with the carbon and oxygen atoms in their sp³ and hydroxyl-like configurations, respectively. Hence, the C atom of CH₂OH preferentially attaches to the top sites, CHOH and CH₂O adsorb at the bridge sites, while COH and CHO occupy the three-fold sites. The DFT calculations indicate that the rupture of the initial C–H bond promotes the decomposition of CH₃OH and CH₂OH, whereas in the case of CHOH, O–H bond scission is favored over the C–H bond rupture. Thus, the most probable methanol decomposition pathway on the Pd/WC(0001) surface is CH₃OH → CH₂OH → trans-CHOH → CHO → CO. The present study demonstrates that the synergistic effect of WC (as carrier) and Pd (as catalyst) alters the CH₃OH decomposition pathway and reduces the noble metal utilization.     

微弧氧化Mg-3Al-1Zn镁合金应力腐蚀和腐蚀疲劳行为研究

本文主要对微弧氧化Mg-3Al-1Zn镁合金在空气和3.5 wt.%硫酸钠溶液两种环境下的应力腐蚀和腐蚀疲劳行为进行研究，并讨论其相互关系。微弧氧化处理后，Mg-3Al-1Zn镁合金的耐蚀性能得到明显改善。与Mg-3Al-1Zn镁合金基体相比，在空气中，微弧氧化后合金的应力腐蚀和腐蚀疲劳强度均下降了大约10 MPa。在3.5 wt.%硫酸钠溶液环境中，微弧氧化后合金的腐蚀疲劳性能仍然是恶化的，但是应力腐蚀强度却得到了显著改善，从58.24 MPa提高至202.08 MPa。这表明材料的力学性能（应力腐蚀和腐蚀疲劳）并不是与其腐蚀性能完全保持线性关系的。微弧氧化处理后镁合金在空气中的应力腐蚀断口为韧性断裂，在硫酸钠溶液环境中为解理断裂。而其腐蚀疲劳断口不论是在空气中还是在腐蚀环境中均为解理断裂。这主要是由于腐蚀环境和变换循环载荷的影响，两者共同作用将会加速裂纹扩展。这表明，周围环境和加载类型对材料断裂机理有重要影响。     

Textural quality of sweet dumpling: effect of germination of waxy rice

Effects of germination on components and structural changes of rice flours and, in turn, rheological properties and textural attributes of sweet dumplings were investigated in this study. Germination decreased starch, protein and lipid content, while slightly increased free amino acids content. Starch granular surface corroded, crystalline structure disrupted, and short-range ordered structures and helical structures decreased with germination. Moreover, germination resulted in a decreased paste viscosity and gel intensity of flour and a reduction of hardness and adhesiveness of dumplings. According to the Pearson’s correlation analysis, flours components and starch structures were significantly correlated with flours rheological properties that determined textural attributes of sweet dumplings. The germination contributed to significant changes in flours components and starch structures, which suggested the pretreatment of germination of waxy rice could be a promising pathway to control textural properties of sweet dumplings.     

乳铁蛋白纯化和检测方法研究进展

乳铁蛋白是一种具有抗微生物活性的铁离子结合糖蛋白,属于转铁蛋白家族的一员,具有调节炎症反应和激活免疫系统等功能,因此乳铁蛋白被广泛应用于医学和食品领域。本综述汇集了乳铁蛋白纯化和检测方法的研究进展,并比较了各方法之间的优缺点。     

One-step Continuous Phenol Synthesis Technology via Selective Hydroxylation of Benzene over Ultrafine TS-1 in a Submerged Ceramic Membrane Reactor☆

A new route towards phenol production by one-step selective hydroxylation of benzene with hydrogen peroxide over ultrafine titanium silicalites-1 (TS-1) in a submerged ceramic membrane reactor was deve...     

高纯度溴代三嗪的制备方法研究

本文研究了由苯酚与三聚氯氰反应合成2,4,6-三苯氧基-1,3,5-三嗪,然后溴化合成溴代三嗪的反应条件,得到合成2,4,6-三苯氧基-1,3,5-三嗪合适的工艺条件:用氯苯作溶剂,无水三氯化铝做催化剂,苯酚与三聚氯氰在回流温度下保温反应3h。     

Iodothiocyanation/Nitration of Allenes with Potassium Thiocyanate/Silver Nitrite and Iodine

Direct strategies for the iodothiocyanation and iodonitration of allenes have been developed. In this process, potassium thiocyanate/silver nitrite and molecular iodine are used as the source of SCN, ONO₂ and iodine to provide the desired products in moderate to good yields with high stereoselectivity.

     

对建筑设计中突出问题的思考

本文针对目前建筑设计中存在的设计质量差、设计资料不全、设计雷同、不按规定指标设计、出卖图章和招牌、设计未经审查就转入施工、机构人员不到位、不正当竞争等问题,提出要从管理机构、队伍建设和法律规范等几个方面采取相应措施解决好建筑设计中存在的问题。