Poisson’s ratio of porous and cellular materials with randomly distributed isometric pores or cells

The porosity dependence of Poisson's ratio of materials with random microstructure is investigated via analytical and numerical modeling. It is shown that all analytical models predict porosity independence if the solid Poisson ratio is 0.2 and for low porosities a converging trend toward this value with increasing porosity. From all theory-based relations, only power-law and exponential relations allow for auxetic behavior. Numerical calculations on computer-generated digital microstructures (overlapping and isolated spherical pores, pores between overlapping spherical grains, wall-based cellular materials/closed-cell foams, and strut-based cellular materials/open-cell foams) confirm the general qualitative trends of the analytical models, although a closer look reveals significant quantitative differences. Cellular materials and foams exhibit similar features as porous materials in general, but lack their converging trend toward values around 0.2. Comparison of our results with the classical Roberts-Garboczi results shows good agreement, with subtle differences due to the different microstructures generated.     

Oxidative Stability of Chia (Salvia hispanica L.) and Sesame (Sesamum indicum L.) Oil Blends

Chia and sesame oils are important sources of essential fatty acids; however, their ω-3:ω-6 proportions do not comply with nutritional recommendation. A feasible approach to improve the ratio is to blend different oils, but only after understanding physical and chemical changes of the new matrix. Objective of the investigation was to determine the physico-chemical characteristics and the oxidative stability index (OSI), using the Rancimat method, of chia-sesame oil blends. The four ω-3:ω-6 blends tested (1:4, 1:6, 1:8, and 1:10) were exposed to temperatures of 110, 120, and 130 °C. The OSI values of the mixtures varied between 6.24–8.08, 3.07–4.00, and 1.62–2.01 hours for each temperature, respectively. In addition, their mean activation energy, enthalpy, entropy, and Q₁₀ were 88.4 kJ/mol, 85.2 kJ/mol, −41.1 J/mol K, and 2.0. Finally, a shelf life prediction performed at 25 °C indicated stability times between 80 and 123 days. Therefore, combining chia and sesame oils produced blends with a good balance of essential fatty acids.     

基于旋滚比的电主轴轴承预紧力优化研究

为研究不同工况下轴承预紧力对电主轴轴承动力学的影响规律，基于外轨道控制理论,建立了一种以旋滚比可优化的轴承预紧力动力学模型。通过分析高速状态下滚动体载荷和特征参数动态变化过程，构建综合考虑滚动体滚动、自旋转、陀螺运动和离心力的轴承动力学分析模型，在此基础上，计算旋滚比动态变化结果；研究Jones发现的阈值与旋滚比之间的动态定量映射关系；以轴承滚动体打滑状态为优化目标，使用MATLAB仿真分析不同工况下轴承最佳预紧力。建模分析表明，轴承旋滚比大小可以反映轴承预紧效果，也可实现轴承预紧力动态定量优化。     

温度对膏体充填料浆流变特性影响试验研究

为了探究膏体的流变特性,取某尾砂制备不同质量浓度、灰砂比的尾砂料浆,采用Brookfield R/S+型流变仪和TC-550型制冷/加热式循环浴温度控制设备进行了膏体流变特性测试。结果表明,膏体料浆屈服应力和黏度随温度的变化与灰砂比和浓度有关。当灰砂比一定时,低浓度料浆屈服应力随温度增加不断减小,高浓度料浆屈服应力随温度升高先增加后减小; 当料浆浓度一定时,随着水泥比例增加,屈服应力随温度升高从不断减小到先增加后减小,且水泥比例越大,使屈服应力开始减小的温度越高。黏度变化情况与屈服应力类似。     

氮氩气流量比对磁控溅射氮化钛薄膜微观结构的影响

采用扫描电镜(SEM)和X射线衍射仪(XRD)研究了氮气流量(5、10、25、50 sccm)及氮氩气流量比(4∶1、3∶2、2∶3、1∶4)对磁控溅射TiN薄膜微观形貌和相组成的影响。结果显示,所得样品具有纳米级TiN薄膜的基本特征。当N2与Ar的总流量为5 sccm,而它们的流量比为4∶1时,可以制得品质较好的蓝紫色TiN薄膜。     

Effect of malting and roasting of chickpea on functional and nutritional qualities of its protein fractions

Chickpea is gaining importance as a sustainable plant-based protein source due to its high protein content and protein bioavailability. Malting and roasting, the traditional processing techniques, can be used to improve the protein quality of chickpea. The effect of two processing techniques on the water-soluble albumin fraction, salt-soluble globulin fraction, alcohol-soluble prolamin fraction, and alkali-soluble glutelin fraction was studied. Globulin content decreased from 45.85% to 37.08%, whereas the albumin fraction was found to increase from 4.16% to 7.08%, after 6 days of germination. It was observed that malting and roasting resulted in significant changes in the protein quality parameters and decrease in anti-nutritional factors. Tannin content reduced by 53.18% and 40.44%, and the trypsin inhibitor activity reduced by 14.91% and 34.59% after malting and roasting, respectively. The protein efficiency ratio, biological value, and nutritional index improved due to malting and roasting. The biological value of raw chickpea protein was found to be 74.97%, and it increased to 81.89% and 79.27% on malting and roasting, respectively, and protein digestibility values were also increased. Microstructural and diffraction patterns of chickpea flours were examined. Amino acid scores for infants and adults were calculated, and sulphur-containing amino acids were found to be the limiting amino acids in chickpea.     

Hydroxylation mechanism of phase regulation of nanocrystal BaTiO3 synthesized by a hydrothermal method

Understanding the phase regulation mechanism of BaTiO₃ synthesized by a hydrothermal method is a complicated and challenging task. Here, we successfully prepared cubic and tetragonal BaTiO₃ single nanocrystals by changing the ratio of water and ethanol in the solvent. We confirm that the BaTiO₃ phase is mainly affected by the hydroxylation process due to the reaction with solvent. In particular, ethanol can be catalytically oxidized by titanium atoms, cause BaTiO₃ hydroxylation and promote the formation of a cubic phase. In the mixed solution of ethanol and water, the hydroxylation process is suppressed, which facilitates the formation of the tetragonal phase. The relationship framework between the solvent ratio, phase structure and hydroxyl defects of BaTiO₃ is established. Tetragonal BaTiO₃ with fewer hydroxyl defects can promote charge transfer and surface reaction after polarization, thereby enhancing their photoelectric catalytic performance. This work provides references for the controllable synthesis of ferroelectric nanocrystals by hydrothermal methods and new insight for the utilization of polarization in photoelectrocatalysis applications.     

The high-fertility cycle: How timely pregnancies in one lactation may lead to less body condition loss,fewer health issues,greater fertility,and reduced early pregnancy losses in the next lactation

Body condition loss during early lactation varies among cows in the herd and is associated with future health and reproductive outcomes. The objective of this study was to gain a greater understanding of the relationship between previous calving interval and body condition change during the first 30 d in milk (DIM) and their relationship to subsequent fertility and health variables and sex ratio at birth. Dry cows and heifers (n = 851) from a single farm entered the study approximately 25 d before the due date. They were evaluated and given a body condition score on a 1-to-5 scale with 0.1-point increments weekly until parturition. Body condition score was assessed within 1 wk of parturition and then again 27 to 33 DIM. Previous calving interval, gestation length, periparturient health events (giving birth to twins, dystocia, retained placentas, ketosis, metritis, and displaced abomasum), sire net merit ($), and milk data were used for each cow as recorded in PCDART (Dairy Records Management Systems, Raleigh, NC) by the herd managers. Longer previous calving intervals were related to greater body condition at parturition and body condition loss during the first 30 DIM. A 75% greater proportion of cows with a calving-to-pregnancy interval shorter than 130 d maintained or gained body condition during the first 30 DIM compared with cows with calving-to-pregnancy intervals longer than 130 d. Multiparous cows that maintained or gained body condition (n = 144) had greater pregnancies per AI following first service compared with cows that lost body condition (n = 577) during the first 30 DIM when health events were considered or removed. When cows with health events were considered, multiparous cows that maintained or gained body condition had a greater percentage pregnant by 130 DIM compared with cows that lost body condition (67 vs. 55%; n = 522). Cows that lost body condition during the first 30 DIM regardless of health events experienced greater pregnancy loss (n = 224) between 35 and 60 d after first AI (0.0 vs. 6.7%) compared with cows that maintained or gained body condition (n = 69) during that period. Based on data in this study from a single herd, maintaining a cycle of pregnancy before 130 DIM may reduce the amount of body condition lost after the next parturition, enhance subsequent pregnancies per AI, and reduce the possibility of early pregnancy loss. We refer to this phenomenon as the high-fertility cycle.     

Investigation of Nafion series membranes on the performance of iron‐chromium redox flow battery

To boost the performance of the iron‐chromium redox flow battery (ICRFB), opting an appropriate proton exchange membrane (PEM) as the core component of ICRFB is of great importance. For the purpose, in this paper, various widely adopted commercial Nafion membranes with a different thickness of 50 μm (Nafion 212, N212), 126 μm (N115), and 178 μm (N117) are chosen for the sake of evaluating the influence of membrane thickness on the ICRFB single‐cell performance. Physicochemical properties, electrolyte utilization, cell efficiency, long‐term cycling stability, and the self‐discharge process of ICRFBs based on a series of Nafion membranes are contrasted comprehensively. The cycling test of ICRFBs is carried out under the current density range of 40 to 120 mA/cm² for the charge‐discharge process. As a result of the good equilibrium of membrane resistance and electro‐active species permeability, Nafion 212 membrane exhibits the highest electrolyte utilization and energy efficiency during the operation, accompanied by the lowest overpotential. In the final part, the selection of Nafion membrane thickness was optimized on the basis of single‐cell performance and the overall cost of the system.     

Electrochemical performance and modeling of lithium‐sulfur batteries with varying carbon to sulfur ratios

Lithium‐sulfur batteries have attracted much research interest because of their high theoretical energy density and low‐cost raw materials. While the electrodes are composed of readily available materials, the processes that occur within the cell are complex, and the electrochemical performance of these batteries is very sensitive to a number of cell processing parameters. Herein, a simple electrochemical model will be used to predict, with quantitative agreement, the electrochemical properties of lithium‐sulfur cathodes with varying carbon to sulfur ratios. The discharge capacity and the polarization were very similar for the lowest sulfur loadings, while above 23.2 wt% sulfur the gravimetric capacity dropped significantly, and there was an increase in the cell polarization. In addition, a transition in the electrode morphology, from well dispersed to aggregated sulfur at the surface, will be reflected in the change in a critical model parameter demonstrating the sensitivity and functionality of even this simple model in predicting complex behavior in the lithium‐sulfur cells.