Numerical study of flow distribution uniformity for the optimization of gradient porosity configuration of porous copper fiber sintered felt for hydrogen production through methanol steam reforming micro-reactor

A macroscopic numerical method is proposed to study the flow distribution uniformity of a novel porous copper fiber sintered felt (PCFSF), which has gradient porosities and was developed as the methanol steam reforming micro-reactor catalyst support for hydrogen production for fuel cell applications. The macroscopic porous media developed by the ANSYS/FLUENT software is used to represent the PCFSF. Our results indicate that the gradient porosity can reshape the flow distribution of PCFSFs greatly, thus producing significant influence on their performance. It is further revealed that, for a PCFSF with a determined gradient porosity configuration but different reactant feed directions, the velocity uniformity can be used as a quantitative criterion to evaluate the performance of hydrogen production. Furthermore, new gradient PCFSFs are produced according to the flow distribution of original gradient PCFSFs. The preliminary experimental results of the new gradient PCFSFs of 0.8-0.9-0.7 and 0.7-0.9-0.8 exhibit better methanol conversion and H₂ flow rate. This indicates that the numerical method can be used for the optimization of PCFSFs' gradient porosity configuration, which consists of the shape and position of the interfaces between different porosity portions, the number of interfaces and the porosity distribution in different portions.     

A series of Er~(3+)-activated SrLaGa_3O_7 single crystal fibers for mid-infrared laser application

A multidisciplinary approach for the production and characterization of a series of high concentration Er~(3+)activated SrLaGa_3 O_7(abbreviated as Er:SLGO) crystal fibers is shown to have a great promise for implementation in mid-infrared laser applications.The current approach includes the design and formation of unique layered tetrahedral network structures with several kinds of rare earth(RE) ions including Er ions distributing statistically between layers,such as Er:SLGO,Er,Nd:SLGO,Er,Yb,Ho:SLGO,Er,Eu:SLGO and Er,Ho:SLGO.Five kinds of Er:SLGO crystal fibers were designed to grow via a micropulling down method.Spectroscopic analyses show that Er,Yb,Ho:SLGO and Nd,Er:SLGO crystal fibers were superiorly endowed with inhomogeneous broadening absorption and strong emission.The unique structural components design enables the generation of improved absorption and emission recombination,and the inhibition of self-termination as well.Generally,the use of structural components design may warrant high-efficiency emissions in RE-doped crystal fibers.     

柠条的纤维特性及其双螺杆CMP制浆性能研究

以柠条为原料，分析了其化学组分和纤维形态，并探讨了柠条双螺杆CMP法的制浆工艺以及浆料的纤维形态和成纸的物理性能。研究结果表明：与针、阔叶木相比，柠条原料中纤维素和综纤维素质量分数较低，苯醇抽出物和热水抽出物质量分数较高，柠条纤维长度总体偏短，木质部和皮部的纤维质量平均长度分别为0.621和0.819 mm，还存在部分杂细胞。采用3.5% Na₂SO₃和1.5% NaOH常温预浸12 h、90℃汽蒸1 h后再用双螺杆挤浆机在质量分数35%下进行搓丝，并结合高浓盘磨机磨浆，所得CMP浆得率可达73%。柠条CMP浆基本保持了纤维原有的长度，质量平均长度达0.650 mm，长宽比为32.7，纤维解离较好，但分丝帚化情况不理想，含有部分纤维束和杂细胞。当加拿大游离度为300 mL时，柠条CMP浆成纸的环压强度指数和松厚度较高，分别为8.67（N·m）/g和2.56 cm³/g，抗张指数为19.6（N·m）/g，本色浆白度较高，达50%（ISO）。柠条CMP浆适合配抄瓦楞原纸等包装用纸，漂白后可配抄新闻纸和白板纸。     

碳基采暖电热材料研究进展

近几年,由于节能与环保的需求,电取暖的方式得到大力的推广,电热材料的研究与应用受到人们广泛的重视。非金属碳基电热材料是新型的节能型电热采暖材料,本文重点对影响非金属碳基电热材料中的炭黑基电热材料、碳纤维基电热材料、碳晶电热材料电热性能的因素及相关应用进行了综述。     

Phosphorylated cellulose/electrospun chitosan nanofibers media for removal of heavy metals from aqueous solutions

Contamination of water resources by toxic heavy metals has significant impacts on environmental and human health. Their removal from aqueous media is essential to ensure water sustainability and to provide safe freshwater availability to population. Electrospun chitosan (CS) nonwoven mats are efficient at removing heavy metals from aqueous media. However, they suffer from low permeability and low-mechanical strength. They are also unable to remove contaminants in a nonselective way. A bilayer sorbent media made of a porous phosphorylated cellulose substrate covered by electrospun CS nanofibers was developed to overcome those weaknesses. The hydrophilic composite shows good water permeability and mechanical strength with appropriate thermal and chemical characteristics. Adsorption tests with Cd(II) indicate that pseudo-second order and Langmuir models best fitted experimental data, with a maximum adsorption capacity of 591 mg/g at 25°C. Adsorption with multielement samples containing Cr(VI), Cu(II), Cd(II), and Pb(II) also reveal their capability to remove them in a selective way. This mechanically resistant, hydrophilic, and permeable adsorbent media was able to capture both cationic and anionic metallic contaminants.     

木质纤维与水泥共同改良软土的力学性能与微观机制分析

通过压实试验、无侧限抗压强度试验和劈裂试验,分析不同木质纤维含量、水泥含量和固化时间对软土力学性能的影响规律,探讨木质纤维、水泥改良软土的微观机制。结果表明,木质纤维的加入对水泥改良软土的击实特性有显著的影响;木质纤维与水泥可有效改善土体的抗压和劈裂抗拉强度,随着木质纤维含量的增加,改良土的抗压和劈裂抗拉强度呈现出明显的“驼峰”现象,并在木质纤维含量为0.25%时最大;木质纤维与水化产物、软土颗粒形成互锁效应,增大了改良土的摩擦力,同时木质纤维还承担一定的拉伸强度,使改良土的劈裂强度增加。     

Encapsulation and characterisation of grape seed proanthocyanidin extract using sodium alginate and different cellulose derivatives

Grape seed proanthocyanidin extract (GSPE) has health benefits. However, these phenolic compounds undergo degradation reactions and have undesirable sensorial characteristics. GSPE was encapsulated using sodium alginate (SA), SA-methyl cellulose (MC) and SA-hydroxypropyl methylcellulose (HPMC) for promoting controlled release, pH stability, temperature and storage period tolerance of GSPE. The microcapsules were characterised using scanning electron microscopy (SEM) and Fourier transform infra-red (FTIR) analysis. The SA-MC and SA-HPMC microcapsules appeared to have a more compact surface than SA-alone microcapsules. FTIR analysis indicated successful immobilisation of GSPE into the polymeric microcapsules. Moreover, the SA-MC and SA-HPMC microcapsules showed higher thermal stability. The microcapsules showed a relatively higher amount of released GSPE at a pH above six than at a lower pH. The SA-MC and SA-HPMC microcapsules could be used to retain more GSPE content in the gastric phase and to release it in the intestinal phase for possible absorption. Furthermore, after 28 days of storage at 25 °C, the GSPE retention rate of the microcapsules was still higher than 80%. GSPE encapsulated in SA-MC and SA-HPMC microcapsules results in lesser degradation and can be absorbed more effectively. This method has potential for the delivery of colon-specific materials while exhibiting a sustained-release characteristic.     

Enhanced hydrogen-assisted cracking of 1,3,5-triisopropylbenzene over fibrous silica ZSM-5: Influence of co-surfactant during synthesis

In this study, unique fibrous silica ZSM-5 was successfully synthesized by using three type of alcohol possessing different alkyl-chain length as the co-surfactant. The effect of diverse co-surfactant was observed in the changes of physical properties, such as crystallinity, inter-dendrimer distances and pore properties. According to the IR and temperature programmed desorption of ammonia (NH₃-TPD) analyses, all catalysts exhibited different acid strengths which could be triggered by the different amount of additional silica species. All catalysts exhibited high catalytic performance in the hydrocracking of 1,3,5-triisopropylbenzene due to the absence of diffusion limitation. However, FZSM5C3 exhibited the highest catalytic activity which corresponded to its high number of Brønsted acid sites. It was observed that different length of co-surfactant alkyl-chain has resulted in different degree of oil penetration into the microemulsion system which subsequently triggered in various inter-dendrimer distances and amount of incorporated silica species. Hence, the altered physicochemical properties led to the difference in catalytic performance due to the presence of different number of Brønsted acid sites.     

Effects of methyl cellulose-based coating on physiochemical properties and chemical hazards of Chinese fried dough cake during storage

Coating has been used as a practical method to ensure the physiochemical properties and reduce the chemical hazard of fried foods. Methyl cellulose (MC) was used as a coating material to pretreat Chinese fried dough cake (CFDC) before frying. The results showed that the water content, hardness and L* value of the 1% MC coated sample were 31.67%, 848.54 g and 51.62, respectively, at the seventh day at 25 °C. Coating contents 1% MC could reduce the oil content, hardness, and extent of browning and improve the physiochemical properties of CFDC on 7 days of storage. Coating contents 1% MC also reduced the acid value, peroxide value, p-anisidine value, malondialdehyde content, 4-hydroxy-2-(E)-hexenal content, 4-hydroxy-2-(E)-nonenal content, acrylamide content and glycidyl ester content in CFDC on 7 days of storage. Our work contributes to the control of the oil content and chemical hazards for fried food during storage by applying an edible coating.     

Analysis of Radio over Fiber system for mitigating four-wave mixing effect

In this paper, an efficient 8-channel 32Gbps RoF (Radio over Fiber) system incorporating Bessel Filter (8/32 RoF-BF) has been demonstrated to reduce the impact of non-linear transmission effects, specifically Four-Wave Mixing (FWM). The simulation results indicate that the proposed 8/32 RoF-BF system provides an optimum result w.r.t. channel spacing (75 GHz), input source power (0 dBm) and number of input channels (8). In comparison with the existing RoF system, the proposed 8/32 RoF-BF system has been validated analytically and it is found that the performance of the proposed system is in close proximity particularly in FWM sideband power reduction of the order of 4 dBm for the 8-channel 32Gbps RoF system.