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。     

Interplay of the phase and the chemical composition of the powder feedstock on the properties of porous 8YSZ thermal barrier coatings

Some chemical impurities enhance sintering kinetics of ceramic Thermal Barrier Coatings (TBCs) which can cause their premature failure during operation in gas turbine engine by causing reduction in coating’s strain compliance as well as faster bond-coat oxidation due to increased thermal conductivity. Certain chemical impurities are also believed to suppress resistance to tetragonal to monoclinic phase transformation in 8YSZ, which can also be an important factor regarding TBC’s performance. Most of the impurities and some of the monoclinic phase present in the powder feedstocks can survive into the as-sprayed coating. Therefore, there is a general trend towards OEMs requiring the lowest amounts of chemical impurities and the lowest amounts of monoclinic phase in the powder feedstocks. This paper presents a comprehensive investigation aimed at understanding the role and the relative importance of the chemical and phase purities of the powder feedstock for the properties and performance of thick 8YSZ TBCs.     

Laboratory-scale liquefiers for natural gas: A design and assessment study

Exact knowledge of natural gas composition is essential in custody transfer to determine the energy content of the delivery. However, for liquefied natural gas (LNG), a reliable composition determination is difficult. Here, we describe the design of a laboratory-scale reference liquefier that enables the validation and calibration of optical spectroscopy sensors by providing them with a sample of metrologically traceable composition. Hence, it is crucial to avoid fractionation of the sample during liquefaction. This is realized by supercritical liquefaction of a reference gas mixture in conjunction with a special vapor–liquid-equilibrium (VLE) cell. As this is a demanding high-pressure application, low-pressure condensation as liquefaction method was also assessed. Through experimental investigations and VLE calculations, preservation of the composition of the produced liquid sample during condensation was studied. We conclude that under optimized conditions, validation, and calibration measurements of optical sensors can be performed on condensed liquids, which, however, needs further confirmation.     

Real-time organic aerosol chemical speciation in the indoor environment using extractive electrospray ionization mass spectrometry

Understanding the sources and composition of organic aerosol (OA) in indoor environments requires rapid measurements, since many emissions and processes have short timescales. However, real-time molecular-level OA measurements have not been reported indoors. Here, we present quantitative measurements, at a time resolution of five seconds, of molecular ions corresponding to diverse aerosol-phase species, by applying extractive electrospray ionization mass spectrometry (EESI-MS) to indoor air analysis for the first time, as part of the highly instrumented HOMEChem field study. We demonstrate how the complex spectra of EESI-MS are screened in order to extract chemical information and investigate the possibility of interference from gas-phase semivolatile species. During experiments that simulated the Thanksgiving US holiday meal preparation, EESI-MS quantified multiple species, including fatty acids, carbohydrates, siloxanes, and phthalates. Intercomparisons with Aerosol Mass Spectrometer (AMS) and Scanning Mobility Particle Sizer suggest that EESI-MS quantified a large fraction of OA. Comparisons with FIGAERO-CIMS shows similar signal levels and good correlation, with a range of 100 for the relative sensitivities. Comparisons with SV-TAG for phthalates and with SV-TAG and AMS for total siloxanes also show strong correlation. EESI-MS observations can be used with gas-phase measurements to identify co-emitted gas- and aerosol-phase species, and this is demonstrated using complementary gas-phase PTR-MS observations.     

Numerical study on premixed hydrogen/air combustion characteristics and heat transfer enhancement of micro-combustor embedded with pin fins

Aimed at improving the energy output performance of the Microthermal Photovoltaic (MTPV) system, it is necessary to optimize the structure of the micro combustor. In this paper, micro combustor with in-line pin fins arrays (MCIPF) and micro combustor with both end-line pin fins arrays (MCEPF) were presented to realize the efficient combustion and heat transfer enhancement, and the influence of inlet velocity, equivalent ratio, and materials on thermal performance was investigated. The results showed that pin fins embedding is beneficial to improving combustion, and the combustion efficiency of MCIPF and MCEPF reaches 98.5% and 98.7%, which is significantly higher than that of the conventional cylindrical combustor (MCC). However, with the increase of inlet velocity from 8 m/s to 14 m/s, MCIPF exhibits the highest external wall temperature with a range of (1302–1386 K), while MCEPF maintains the best temperature uniformity. As the inlet velocity increases to 10 m/s, the external wall temperature and temperature uniformity reach the optimum. Besides, under the conditions of different equivalence ratios, both external wall temperature and heat flux increases first and then decreases, meanwhile the temperature uniformity of MCEPF is significantly improved compared with that of MCIPF, they all exhibit the highest external wall temperature with an equivalence ratio of 1.1, and the thermal performance is greatly enhanced. By comparing the heat transfer performance of combustors with different materials based on MCEPF, it is interesting to find that the application of high thermal conductivity materials can not only increase the external wall temperature, but also improve the temperature uniformity. Therefore, materials with high thermal conductivity such as Aluminum, Red Copper and Silicon Carbide should be selected for application in micro combustors and their components. The current work provides a new design method for the enhanced heat transfer of the micro combustor.     

Effects of breed,farm intensiveness,and cow productivity level on cheese-making ability predicted using infrared spectral data at the population level

Fourier-transform infrared (FTIR) spectra collected during milk recording schemes at population level can be used for predicting novel traits of interest for farm management, cows' genetic improvement, and milk payment systems. The aims of this study were as follows. (1) To predict cheese yield traits using FTIR spectra from routine milk recordings exploiting previously developed calibration equations. (2) To compare the predicted cheese-making abilities of different dairy and dual-purpose breeds. (3) To analyze the effects of herds' level of intensiveness (HL) and of the cow's level of productivity (CL). (4) To compare the patterns of predicted cheese yields with the patterns of milk composition in different breeds to discern the drivers of cheese-making efficiency. The major sources of variation of FTIR predictions of cheese yield ability (fresh cheese or cheese solids produced per unit milk) of individual milk samples were studied on 115,819 cows of 4 breeds (2 specialized dairy breeds, Holstein and Brown Swiss, and 2 dual-purpose breeds, Simmental and Alpine Grey) from 6,430 herds and exploiting 1,759,706 FTIR test-day spectra collected over 7 yr of milk sampling. Calibration equations used were previously developed on 1,264 individual laboratory model cheese procedures (cross-validation R² 0.85 and 0.95 for fresh and solids cheese yields, respectively). The linear model used for statistical analysis included the effects of parity, lactation stage, year of calving, month of sampling, HL, CL, breed of cow, and the interactions breed × HL and breed × CL. The HL and CL stratifications (5 classes each) were based on average daily secretion of milk net energy per cow. All effects were highly significant. The major conclusions were as follows. (1) The FTIR-based prediction of cheese yield of milk goes beyond the knowledge of fat and protein content, partially explaining differences in cheese-making ability in different cows, breeds and herds. (2) Differences in cheese yields of different breeds are only partially explained by milk fat and protein composition, and less productive breeds are characterized by a higher milk nutrient content as well as a higher recovery of nutrients in the cheese. (3) High-intensive herds not only produce much more milk, but the milk has a higher nutrient content and a higher cheese yield, whereas within herds, compared with less productive cows, the more productive cows have a much greater milk yield, milk with a greater content of fat but not of protein, and a moderate improvement in cheese yield, differing little from expectations based on milk composition. Finally, (4) the effects of HL and CL on milk quality and cheese-making ability are similar but not identical in different breeds, the less productive ones having some advantage in terms of cheese-making ability. We can obtain FTIR-based prediction of cheese yield from individual milk samples retrospectively at population level, which seems to go beyond the simple knowledge of milk composition, incorporating information on nutrient retention ability in cheese, with possible advantages for management of farms, genetic improvement of dairy cows, and milk payment systems.     

Comparative study of the phenolics,antioxidant and metagenomic composition of novel soy whey-based beverages produced using three different water kefir microbiota

Water kefir microbiota was used to develop novel soy whey-based beverages that have antioxidant activity. In the present study, comparative phenolics, antioxidant and metagenomic composition of the soy whey beverages fermented using three different water kefir microbiota, named WKFS-A, WKFS-B and WKFS-C were investigated. WKFS-B beverage had the highest concentrations of isoflavone aglycones (208.73 ± 2.78 mg L⁻¹) and phenolic acids (132.33 ± 3.41 mg L⁻¹) compared with WKFS-A (193.88 ± 1.15 mg L⁻¹) and (91.73 ± 2.34 mg L⁻¹) and WKFS-C (160.63 ± 1.76 mg L⁻¹) and (97.13 ± 2.63 mg L⁻¹), respectively. The WKFS-B also showed higher DPPH and ABTS radical scavenging activity and ferric reducing antioxidant power compared with WKFS-A and WKFS-C beverages. Microbial species diversity index analysis showed that a higher concentration of isoflavone aglycones, phenolic acids and increased antioxidant activity in the WKFS-B beverage correlates with the higher relative abundance of Lactobacillus genus. This study thus revealed that Lactobacillus dominated water kefir microbiota produces soy whey beverages with high phenolic acids, isoflavone aglycones and antioxidant activity.     

Microemulsion synthesis of ms/tz-BiVO4 composites: The effect of pH on crystal structure and photocatalytic performance

In this work, BiVO₄ composites, containing the tetragonal zircon phase (tz-BiVO₄), and monoclinic scheelite phase (ms-BiVO₄), were synthesized using the microemulsion method. The effect of pH on phase composition and photocatalytic activity were investigated. Based on X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), a ms/tz-BiVO₄ composite forms at pH = 1.0 and pure ms-BiVO₄ is obtained in the pH range 4.0–10.0. The three primary steps in preparing BiVO₄ were monitored by optical microscopy and the role played by the microemulsion on the phase composition of BiVO₄ is explained. Photoluminescence spectroscopy (PL), UV–visible diffuse reflectance spectroscopy (UV-DRS), Brunauer-Emmett-Teller (BET), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were employed to characterize the physical and chemical properties of BiVO₄ composites. The composite formed at pH = 1 exhibited the lowest hole-electron (h⁺-e^-) recombination rate, resulting in the highest photocatalytic activity towards microcystin-LR (MC-LR), with near 100% removal of MC-LR in 5 h. ESR and trapping experiments indicated that MC-LR degradation was mediated primarily by hydroxyl radicals (•OH), superoxide radicals (O₂^•−) and photogenerated holes (h⁺).