Leaching of Uranium from Its Mineralization and Experimental Design of the Process

The central composite design (CCD) of experiments was used to study the leaching of uranium and iron from the mineralized Gabal Al-Aglab uranium ore sample using sulfuric acid solution. The leaching factors were sulfuric acid concentration, contact time, particle size, temperature, solid to liquid ratio, and stirring rate. The uranium and iron leaching efficiencies were 71.6 and 10.8%, respectively. Three factors were taken into consideration in the experimental planning: leaching time, solid/liquid ratio, and stirring rate. The obtained results were statistically analyzed using analysis of variances (ANOVA) to determine the main effects and interactions between the investigated factors.     

Evaluation of the minimum face clearance of a high-speed gas-lubricated bearing with Navier slip boundary conditions under random excitations

Motivated by ongoing developments in aero-engine technology, a model for a coupled gas-lubricated bearing is developed in terms of an extended dynamical system. A slip boundary condition, characterised by a slip length, is incorporated on the bearing faces which can be relevant for operation in non-ideal extreme conditions, notably where external vibrations or disturbances could destabilise the bearing. A modified Reynolds equation is formulated to model the gas flow, retaining the effects of centrifugal inertia which is increasingly important for high-speed operation, and is coupled to the structural equations; spring-mass-damper systems model the axial stator and rotor displacements. A novel model is developed corresponding to a bearing experiencing an external random force to evaluate the resulting induced displacements of the bearing components. The minimum face clearance is obtained from a mapping solver for the modified Reynolds equation and structural equations simultaneously. In the case of random excitations, the solver is combined with a Monte Carlo technique. Evaluation of the average value of the minimum gap and the probability of the gap reaching a prescribed tolerance are provided. Extensive insight is given on the effect of key bearing parameters on the corresponding bearing dynamics.     

Airborne bacterial assemblage in a zero carbon building: A case study

Currently, there is little information pertaining to the airborne bacterial communities of green buildings. In this case study, the air bacterial community of a zero carbon building (ZCB) in Hong Kong was characterized by targeting the bacterial 16S rRNA gene. Bacteria associated with the outdoor environment dominated the indoor airborne bacterial assemblage, with a modest contribution from bacteria associated with human skin. Differences in overall community diversity, membership, and composition associated with short (day‐to‐day) and long‐term temporal properties were detected, which may have been driven by specific environmental genera and taxa. Furthermore, time‐decay relationships in community membership (based on unweighted UniFrac distances) and composition (based on weighted UniFrac distances) differed depending on the season and sampling location. A Bayesian source‐tracking approach further supported the importance of adjacent outdoor air bacterial assemblage in sourcing the ZCB indoor bioaerosol. Despite the unique building attributes, the ZCB microbial assemblage detected and its temporal characteristics were not dissimilar to that of conventional built environments investigated previously. Future controlled experiments and microbial assemblage investigations of other ZCBs will undoubtedly uncover additional knowledge related to how airborne bacteria in green buildings may be influenced by their distinctive architectural attributes.     

低脂芝麻酱制取工艺及品质研究

将清选除杂后的芝麻先经液压榨油机进行不同程度的脱脂,再对半脱脂的整籽芝麻进行适度炒制,之后对炒香芝麻进行磨浆得到低脂芝麻酱。为保证芝麻半脱脂过程籽粒不破损,采用分级压榨脱脂工艺技术(榨油机工作压力10~20 MPa,轻压1次和2次,可脱除芝麻中7%~10%的油脂);经一次压榨半脱脂芝麻的炒籽条件为140℃、40 min,经磨浆后得到的低脂芝麻酱与全脂芝麻酱相比较,性状稳定性和氧化稳定性提高,储存期间析油少,油酱分层现象得到明显改善,上浮指数由8.52%降至1.40%,风味和口感(油腻感)也得到适度改善。     

多层圆片级堆叠THz硅微波导结构的制作

基于微电子机械系统(MEMS)工艺,提出一种多层圆片堆叠的THz硅微波导结构及其制作方法。为了验证该结构在制作THz无源器件中的优势,基于6层圆片堆叠的硅微波导结构,设计了一种中心频率365 GHz、带宽80 GHz的功率分配/合成结构,并对其进行了仿真。研究了制作该结构的工艺流程,攻克了工艺过程中的关键技术,包括硅深槽刻蚀技术和多层热压键合技术,并给出了工艺结果。最终实现了多层圆片堆叠功率分配/合成结构的工艺制作和测试。测试结果表明,尽管样品的插入损耗较仿真值增加3 dB左右,考虑到加工误差和夹具损耗等情况,样品主要技术指标与设计值较为一致。     

Vertically aligned reduced graphene oxide/Ti3C2Tx MXene hybrid hydrogel for highly efficient solar steam generation

Effective utilization of abundant solar energy for desalination of seawater and purification of wastewater is one of sustainable techniques for production of clean water, helping relieve global water resource shortage. Herein, we fabricate a vertically aligned reduced graphene oxide/Ti₃C₂T_x MXene (A-RGO/MX) hybrid hydrogel with aligned channels as an independent solar steam generation device for highly efficient solar steam generation. The vertically aligned channels, generated by a liquid nitrogen-assisted directional-freezing process, not only rapidly transport water upward to the evaporation surface for efficient solar steam generation, but also facilitate multiple reflections of solar light inside the channels for efficient solar light absorption. The deliberate slight reduction endows the RGO with plenty of polar groups, decreasing the water vaporization enthalpy effectively and hence accelerating water evaporation efficiently. The MXene sheets, infiltrated inside the A-RGO hydrogel on the basis of Marangoni effect, enhance light absorption capacity and photothermal conversion performance. As a result, the A-RGO/MX hybrid hydrogel achieves a water evaporation rate of 2.09 kg·m⁻²·h⁻¹ with a high conversion efficiency of 93.5% under 1-sun irradiation. Additionally, this photothermal conversion hydrogel rapidly desalinates seawater and purifies wastewater to generate clean water with outstanding ion rejection rates of above 99% for most ions.

     

Hot corrosion studies of a salt-coated Ni-based superalloy under flowing wet air and sulfur vapor ambient

Corrosion of a salt-coated Ni-superalloy has been studied at 900°C under a wet air and sulfur vapor ambient. The corrosion thickness, after an incubation of ~60 hr, linearly increases with the corrosion time t and the onset of surface spallation occurred at t ≈ 60 hr. The corroded layer consists of a corrosion front dominated by Cr₃S₄ scales and linear precipitate structures, an inner corrosion layer dominated by Ni₃S₂ and NiO, and an outer corrosion layer dominated by Al₂O₃ networks surrounding the Ni₃S₂ and/or NiO scale structures. The corrosion mechanism is discussed based on the coexistence of H₂O, sulfur, and oxygen.     

综采工作面设备快速回撤工艺探讨

神东煤炭集团柳塔煤矿12123综采工作面回采结束后,实际只用9天时间就完成设备快速回撤工作;本文以12123综采工作面设备回撤为实例,探讨了综采工作面设备回撤新工艺;该工艺可以在其他煤矿进行推广,有较强的应用前景。