Numerical study of microscopic particle arrangement of suspension flow in a narrow channel for the estimation of macroscopic rheological properties

In a narrow channel, the apparent relative viscosity of a suspension with finite-size particles is strongly dependent on its microscopic particle arrangement. Relative viscosity increases when suspended particles flow near the channel wall; thus, a suspension in a narrow channel does not always exhibit the same rheological properties even if the concentration is the same. In this study, we focus on the inertia and concentration of particles in a narrow channel and consider their effects on the microscopic particle arrangement and macroscopic suspension rheology. Two-dimensional pressure-driven suspension flow simulations were performed using a two-way coupling scheme, and normalized particle density distribution (PDD) were implemented to consider their particle arrangements. The results demonstrated that the velocity profiles for the particle suspension were changed by the Reynolds number and particle concentration because of the interactions between particles according to the power-law index. These changes affected the particle equilibrium positions in the channel, and the subsequent changes in solvent layer thickness caused changes in the macroscopic apparent viscosity. The behavior of microscopic particles played important roles in determining macroscopic rheology. Thus, we have confirmed that a normalized PDD can be used to estimate and assess the macroscopic rheology of a suspension.     

Dynamic simulation of hydrogen-based off-grid zero energy buildings with hydrogen storage considering Fanger model thermal comfort

In this study, some locations with different climates, off-grid zero energy buildings with hydrogen energy storage systems are designed, and transient analysis is conducted. These considered buildings supply their electricity consumption without using the electrical grid and PV panels or wind turbines. Also, they supply thermal comfort to occupants by using a vapor compression chiller and humidifier. Domestic hot water of occupants is supplied using solar collectors. For analyzing building's performance and objectives achievement, TRNSYS software is used. Also, for evaluating occupant thermal comfort, the Fanger model is used. The considered building is a one-story building with a 150 m² area. Four occupants are considered. Both of them are seated at rest, and another is seated with light working such as typing. Using the Fanger model equation and MATLAB software, the thermal comfort of occupants is determined. For domestic hot water consumption, verified profiles that vary during 24 h of the day are considered. Achieved results show that for humid and cold cities, PV panels with an area of 73 and 76 m² can be supplied the required electricity of considered building with four occupants and battery state of charge is higher than 50% and 10%, respectively. Moreover, with a suitable air conditioner system, the predicted percentage of dissatisfied (PPD) can be lower than 12% and 8% for humid and cold cities. Therefore, the building can be converted to a zero-energy building using its rooftop area.     

Enhancing the dehydrogenation properties of LiAlH4 using K2NiF6 as additive

Lithium alanate (LiAlH₄) is a material that can be potentially used for solid-state hydrogen storage due to its high hydrogen content (10.5 wt%). Nevertheless, a high desorption temperature, slow desorption kinetic, and irreversibility have restricted the application of LiAlH₄ as a solid-state hydrogen storage material. Hence, to lower the decomposition temperature and to boost the dehydrogenation kinetic, in this study, we applied K₂NiF₆ as an additive to LiAlH₄. The addition of K₂NiF₆ showed an excellent improvement of the LiAlH₄ dehydrogenation properties. After adding 10 wt% K₂NiF₆, the initial decomposition temperature of LiAlH₄ within the first two dehydrogenation steps was lowered to 90 °C and 156 °C, respectively, that is 50 °C and 27 °C lower than that of the аs-milled LiAlH₄. In terms of dehydrogenation kinetics, the dehydrogenation rate of K₂NiF₆-doped LiAlH₄ sample was significantly higher as compared to аs-milled LiAlH₄. The K₂NiF₆-doped LiAlH₄ sample can release 3.07 wt% hydrogen within 90 min, while the milled LiAlH₄ merely release 0.19 wt% hydrogen during the same period. According to the Arrhenius plot, the apparent activation energies for the desorption process of K₂NiF₆-doped LiAlH₄ are 75.0 kJ/mol for the first stage and 88.0 kJ/mol for the second stage. These activation energies are lower compared to the undoped LiAlH₄. The morphology study showed that the LiAlH₄ particles become smaller and less agglomerated when K₂NiF₆ is added. The in situ formation of new phases of AlNi and LiF during the dehydrogenation process, as well as a reduction in particle size, is believed to be essential contributors in improving the LiAlH₄ dehydrogenation characteristics.     

Facile preparation of SnS2 nanoflowers and nanoplates for the application of high-performance hybrid supercapacitors

In this work, the SnS₂ nanoflowers (SnS₂ NFs) were solvothermally prepared in the solvent of ethanol, while SnS₂ nanoplates (SnS₂ NPs) were obtained through the identical conditions except for the solvent of water. The flowers were assembled with numerous nanosheets with very thin thickness, and the NPs exhibited hexagonal shape. When used as the battery-type electrode material for supercapacitors, the SnS₂ NFs delivered a specific capacity of as high as 264.4 C g^?1 at 1 A g^?1, which was higher than the 201.6 C g^?1 of SnS₂ NPs. Furthermore, a hybrid supercapacitor (HSC) was assembled with the SnS₂ as positive electrode and activated carbon (AC) as negative electrode, respectively. The SnS₂ NFs//AC HSC exhibited a high energy density of 28.1 Wh kg^?1 at 904.3 W kg^?1, which was higher than the 24.2 Wh kg^?1 at 844.3 W kg^?1 of SnS₂ NPs//AC HSC. Especially, when the power density was enhanced to the highest value of 8666.8 W kg^?1, the NFs-based device could still hold 20.4 Wh kg^?1. In addition, both HSC devices showed an excellent cycling stability after 5000 cycles at 5 A g^?1. The present method is simple and can be extended to the preparation of other transition metal sulfides (TMSs)-based electrode materials with brilliant electrochemical performance for supercapacitors.     

Heterofullerene C48B12-impregnated MOF-5 and IRMOF-10 for hydrogen storage: A combined DFT and GCMC simulations study

The H₂ storage properties of isoreticular metal-organic framework materials (IRMOFs), MOF-5 and IRMOF-10, impregnated with different numbers and types of heterogeneous C₄₈B₁₂ molecules were investigated using density functional theory and grand canonical Monte Carlo (GCMC) calculations. The excess hydrogen adsorption isotherms of IRMOFs at 77 K within 20 bar indicate that suitable number and type of C₄₈B₁₂ molecules play a crucial role in improving the H₂ storage properties of IRMOFs. Among the studied pure and nC₄₈B₁₂ (n = 1, 2, 4, 8) in Ci symmetry impregnating into MOF-5, at 77 K under 6 bar, MOF-5-4C₄₈B₁₂ with a 3.5 wt% and 29.9 g/L hydrogen storage density, and at 77 K under 12 bar, the pure MOF-5 with a 4.9 wt% and 31.0 g/L hydrogen storage density has the best hydrogen storage properties. Whereas, among the studied pure and nC₄₈B₁₂ (n = 1, 2, 4, 8) in S6 symmetry impregnating into IRMOF-10, IRMOF-10-8C₄₈B₁₂ always shows the best hydrogen storage properties among the pure and C₄₈B₁₂-impregnated IRMOF-10 at 77 K within 20 bar. IRMOF-10-8C₄₈B₁₂ has a 6.0 wt% and 34.6 g/L hydrogen storage density at 77 K under 6 bar, and has a 7.1 wt% and 41.4 g/L hydrogen storage density at 77 K under 12 bar. The confinement effect of IRMOFs on C₄₈B₁₂ molecules, and steric hindrance effect of C₄₈B₁₂ molecules on IRMOFs mainly affects the H₂ uptake capacity by comparing the absolute H₂ molecules in individual IRMOFs units, C₄₈B₁₂ molecules, and IRMOFs-nC₄₈B₁₂ compounds. The absolute hydrogen adsorption profiles show that eight C₄₈B₁₂ molecules impregnating into MOF-5 can exert obvious steric effects for H₂ adsorption. The saturated gravimetric and volumetric H₂ densities of IRMOF-10-8C₄₈B₁₂ higher than those of MOF-5-8C₄₈B₁₂ due to with larger free volume.     

Effects of red-wine grape pomace on the quality and sensory attributes of beef hamburger patty

This study was conducted to evaluate the effect of red-wine grape pomaces on the quality and sensory attributes of beef hamburger patties. Both phenolic content and antioxidant activity were assessed using Syrah, Merlot and Cabernet Sauvignon pomaces. Following the assessment, hamburger patties were prepared with Merlot pomace at 0%, 2% and 4% for the patty quality and sensory attributes. Grape seeds possessed significantly higher phenolics and antioxidant activities over the seedless pomace (P < 0.05), whereas no significant difference was found for phenolics and antioxidant activities within the seeds and seedless pomaces. The patty pH decreased as the pomace was added for 2% and 4%. Colour values (L*, a* and b*) of patties lowered as the pomace was added. Allo-Kramer shear force and hardness values increased while cooking yield decreased (P < 0.05) with the addition of pomace. No significant difference between control and Merlot patties was found for flavour, juiciness and colour, whereas lower sensory attributes were observed for texture, taste and overall acceptability. It is observed that the addition of fermented red-wine grape pomace provides hamburger patties with health promoting factors such as antioxidant and other functional components, but it also provided darker, sourer and lower cooking yield.     

Physical and sensory properties of lemon-flavored acidic beverages formulated with nonfat dry milk during storage

Sensory and physical properties of 2 lemon-flavored beverages with 5% and 7.5% wt/wt nonfat dry milk (NFDM) at pH 2.5 were studied during storage. The 2 beverages had similar volatile compounds, but the 5% NFDM had higher aroma and lemon flavor, with a preferred appearance by consumers due to the lower turbidity and viscosity. After 28 d of storage at 4°C, lemon flavor decreased in the 5% NFDM beverage but was still more intense than the 7.5% one. During 70 d of storage, no microorganisms were detected, and the beverages were more stable when stored at 4°C than at room temperature according to changes of physical properties measured for appearance, turbidity, color, particle size, zeta potential, rheological properties, and transmission electron microscopy morphology. Findings of the present study suggest that NFDM may be used at 5% wt/wt to produce stable acidic dairy beverages with low turbidity when stored at 4°C.     

南水北调中线总干渠藻类的生态调度

南水北调中线总干渠无在线调蓄水库,对藻类生态调度过程中出现的问题开展生态调度实现策略和实施方式研究。主要实现策略包括:划定自身的调蓄区,隔离生态调度对下游的影响;采用高效的渠池运行方式,减少生态调度时蓄量的反复调整;综合考虑安全、快速、平稳等需求,设定生态调度实施进程和方式。具体实施方式包括:将总干渠划分为流速调控区、调蓄区和正常运行区,分别实施等体积、控制蓄量和闸前常水位方式运行;将生态调度过程划分为充水阶段和泄水阶段,基于流速调控目标值、持续时长和水位降幅约束条件,确定各阶段时长和各分区的闸门群调控方案等。基于2018年3月输水工况,采用明渠一维非恒定流模型,仿真总干渠上游15个渠池的藻类生态调度过程。结果表明,生态调度可在3.5 d内完成,各渠池的平均流速由0.48 m/s增至0.93 m/s,持续时间超过2 h。在整个生态调度过程中,水位变化平稳,水位变幅符合安全阈值要求,下游渠道的正常运行未受生态调度明显影响。     

基于Hadoop的气象数据分布式存储技术研究

针对目前气象数据存储所面临的海量扩张、高并发读写、结构化和非结构化数据并存以及长时间序列和大数据集检索效率低下等问题,提出了以Hadoop开源框架为基础的气象数据分布式存储方案。通过对气象数据自身属性和特点进行分析,得出了气象数据在经过充分优化的基础上,在分布式存储框架中具有很强的适应性和规模化应用的潜力;并在HBase数据库中的Row Key设计和小文件合并策略方面做了创新。最后针对气象数据中广泛存在的结构化和非结构化这两种主要数据类型,以自动气象站数据和雷达产品数据为具体实例,给出了详细的设计思路和实现方法。     

Direct ink writing of vancomycin-loaded polycaprolactone/ polyethylene oxide/ hydroxyapatite 3D scaffolds

Novel inks were formulated by dissolving polycaprolactone (PCL), a hydrophobic polymer, in organic solvent systems; polyethylene oxide (PEO) was incorporated to extend the range of hydrophilicity of the system. Hydroxyapatite (HAp) with a weight ratio of 55–85% was added to the polymer-based solution to mimic the material composition of natural bone tissue. The direct ink writing (DIW) technique was applied to extrude the formulated inks to fabricate the predesigned tissue scaffold structures; the influence of HAp concentration was investigated. The results indicate that in comparison to other inks containing HAp (55%, 75%, and 85%w/w), the ink containing 65% w/w HAp had faster ink recovery behavior; the fabricated scaffold had a rougher surface as well as better mechanical properties and wettability. It is noted that the 65% w/w HAp concentration is similar to the inorganic composition of natural bone tissue. The elastic modulus values of PCL/PEO/HAp scaffolds were in the range of 4–12 MPa; the values were dependent on the HAp concentration. Furthermore, vancomycin as a model drug was successfully encapsulated in the PCL/PEO/HAp composite scaffold for drug release applications. This paper presents novel drug-loaded PCL/PEO/HAp inks for 3D scaffold fabrication using the DIW printing technique for potential bone scaffold applications.