关键词： 传感器   高中物理   动力学   实验平台  

摘要： 基于高中物理实验教学时间和设备有限,有的学校将常规实验教学淡化,学生进行实验基本操作后所得的实验数据也无法及时处理论证等问题,借助信息技术的强大支撑,设计合理的基于传感器的高中物理动力学实验平台,发挥传感器快速测量和同步处理数据的优势。同时,简化实验器材,将器材组合为一体,便于携带和组装,实现在有限的课堂教学时长内完成完整的实验教学。

关键词： 油料作物   农产品成本   机械化   劳动力   产出弹性   替代弹性  

摘要： 油菜是我国最主要的油料作物之一,研究油菜种植机械化发展对劳动力的替代可为油菜产业提升效益、保障食用植物油供给、增强国际竞争力提供参考。本文基于2004-2020年15省油菜产业面板数据,利用超越对数生产函数模型分析油菜种植机械化对劳动力的替代及产出的影响。结果表明:各省份机械投入、劳动力投入对油菜籽产出均有正向影响,劳动力投入是影响油菜籽产量的主要因素;油菜籽生产过程中机械投入对劳动力呈现明显的替代关系。实现油菜生产机械化对于保障国家食用植物油安全具有重要作用,必须通过以下措施推动油菜产业机械化:加大购机补贴扶持力度,为普及油菜机械化生产奠定基础;发展规模化种植,实现机械化与规模化种植协调并进;增强设备稳定性,调整种植方式,进一步推广生产机械化。

关键词： Dynamic mechanical analysis   Rheokinetics   FTIR Spectroscopy   Rigid polyurethane foams   Chemical reactions  

摘要： The modulus build-up and relative density evolution during the reactive foaming of four standard polyurethane formulations was monitored in-situ by Dynamic Mechanical Analysis (DMA) with a customised set-up in parallel plate geometry. The modulus increased from 0.01 MPa in the first minutes to over 1.2 MPa within 20 min. The set-up also enabled the recording of vitrification followed by curing times. These typically occur within 3 min of each other. The results of DMA are corroborated by measurements of the reaction kinetics with Infrared Spectroscopy. This goes to show that the modulus remains nearly unchanged during the stage of swiftest isocyanate conversion, while the point of gel conversion is accompanied by their increase.

关键词： Boron carbide   Nanopillar   Molecular dynamics simulation   Mechanical    property   Amorphous bands evolution  

摘要： Boron carbide is considered as an ideal armor material, but its abnormal failure under high speed impact hinders its application. In order to explore the compression deformation behavior and mechanism of boron carbide, molecular dynamics simulation of reactive force-field (ReaxFF) interatomic potential is adopted to simulate the uniaxial compression deformation of boron carbide nanopillars in different directions at room temperature. The compression deformation behaviors of B11CpCBC nanopillars show significant anisotropy. No twin formation is observed during any compression. The B11CpCBC nanopillars have similar uniaxial compressive strength and corresponding strain along c-axis and b-axis, which are 59.21GPa and 0.185, 54.9GPa and 0.187, respectively, while along d-axis are higher, which are 82.06GPa and 0.234. During the compression along axes of b, c and d, the nanopillars undergo the same deformation processes in sequence as: symmetry reducing region is formed, extends aslant through the model and forms amorphous band. The formation mechanisms of amorphous bands of B11CpCBC nanopillars are as follows. During the compression along axis c, the three-atom chains constantly bend and the bonds among the three polar site B atoms of the icosahedron fracture at large strain leading to icosahedron collapse. During the compression along axes b and d, new bonds are formed between vertical adjacent icosahedrons at large strain leading to icosahedron collapse. In all three compression cases, the collapse extends aslant through the nanopillars under shear stress, during which polar site B atoms of icosahedrons bond with C and B atoms of triatomic chains, and finally forms amorphous bands. The formation of amorphous bands results in the decrease of compressive strength of B11CpCBC.

关键词： Pipe   Vibration   Two-phase   Slug   Force   Bend   Elbow  

摘要： Slug flow through piping systems may cause severe mechanical vibrations. Finite element models, commonly used to predict dynamic pipe stresses and fatigue, require the slug excitation force as boundary condition. In this paper, a stochastic mechanistic model of the slug force acting on a pipe bend is proposed. The force induced by continuous hydrodynamic two-phase slug flow is modelled by the momentum balance over the bend using slug quantities as liquid holdup and phase velocity. The two-phase flow is described by a train of slug units. Each unit is divided into a film zone with a constant liquid height and a slug zone with aerated liquid. Two-phase flows have a stochastic character, but models based on a fixed slug length cannot predict stochastic force variations. A new approach is introduced that includes the stochastic character of slug flow in the force calculations. A unit slug model is adapted with a log-normal distribution as closure for the slug zone length, resulting in an improved model with stochastic properties. A Lagrangian approach is used to solve the governing equations. Results of the new model are compared with bend force measurements found in the literature. Most of the published measurements were done with air and water under atmospheric conditions. In many field applications, the fluids and operational conditions are different from those used in laboratory experiments. The stochastic mechanistic approach, where the main equations are based on physical laws, increases the models applicability outside the atmospheric air and water conditions used for the validation.

摘要： The applications of translational modeling of local drug concentrations in various organs had a sharp increase over the last decade. These are part of the model-informed drug development initiative, adopted by the pharmaceutical industry and promoted by drug regulatory agencies. With respect to the kidney, the models serve as a bridge for understanding animal vs. human observations related to renal drug disposition and any consequential adverse effects. However, quantitative data on key drug-metabolizing enzymes and transporters relevant for predicting renal drug disposition are limited. Using targeted and global quantitative proteomics, we determined the abundance of multiple enzymes and transporters in 20 human kidney cortex samples. Nine enzymes and 22 transporters were quantified (8 for the first time in the kidneys). In addition, > 4,000 proteins were identified and used to form an open database. CYP2B6, CYP3A5, and CYP4F2 showed comparable, but generally low expression, whereas UGT1A9 and UGT2B7 levels were the highest. Significant correlation between abundance and activity (measured by mycophenolic acid clearance) was observed for UGT1A9 (Rs = 0.65, P = 0.004) and UGT2B7 (Rs = 0.70, P = 0.023). Expression of P-gp approximate to MATE-1 and OATP4C1 transporters were high. Strong intercorrelations were observed between several transporters (P-gp/MRP4, MRP2/OAT3, and OAT3/OAT4);no correlation in expression was apparent for functionally related transporters (OCT2/MATEs). This study extends our knowledge of pharmacologically relevant proteins in the kidney cortex, with implications on more prudent use of mechanistic kidney models under the general framework of quantitative systems pharmacology and toxicology.

关键词： 2-Phenylcyclohexanethiol   Cycloalkyl C-S bond   Desulfurization   Mo/gamma-Al2O3   Ni-Mo/gamma-Al2O3   Co-Mo/gamma-Al2O3   Piperidine  

摘要： The desulfurization of 2-phenylcyclohexanethiol (2-PCHT) was studied over sulfided Mo/gamma-Al2O3, Ni-Mo/gamma-Al2O3, and Co-Mo/gamma-Al2O3 catalysts under 5.0 MPa H-2 or Ar at 240 degrees C. Under H-2, the desulfurization of 2-PCHT proceeded mainly through the hydrogenolysis and beta-elimination pathways. The former was faster than the latter over Mo/gamma-Al2O3. Ni and Co accelerated the beta-elimination pathway but hardly affected the hydrogenolysis pathway. The activity of Mo/gamma-Al2O3 was enhanced by Ni, whereas Co did not show any promoting effect. Under Ar, the desulfurization of 2-PCHT occurred mainly through the beta-elimination and dehydrogenation pathways. The beta-elimination pathway was faster than the dehydrogenation pathway. Both pathways were enhanced by Ni and Co. Ni and Co promoted the dehydrogenation pathway mainly by promoting the dehydrogenation-ring closure reaction. The inhibiting effects of piperidine depended on the reaction and catalyst. Under Ar, Ni-Mo/gamma-Al2O3 was more sensitive to piperidine inhibition. (C) 2021 Elsevier Inc. All rights reserved.

关键词： Materials Science   general   Characterization and Evaluation of Materials   Polymer Sciences   Solid Mechanics   Crystallography and Scattering Methods   Classical Mechanics  

摘要： Carbon material, because of its high thermal conductivity, ablation resistance and friction resistance, has been widely used in the field of electrical engineering. When confronted strong thermal shock, the interface structure of carbon material would cause thermal shock damage by the rapid temperature difference. In order to systematically and quantificationally study the thermal shock damage of carbon materials, an experimental system that can provide rapid temperature difference was built. The experimental results showed that undergoing a temperature difference of 485 degrees C, more micro-cracks and holes arose in the pure carbon material, resulting in an increase of porosity by 26.39%, an increase friction coefficient by 48.65%, and a decrease of compressive strength by 23.96%. It was also found the ultrasonic velocity linearly decreased with the increase of porosity and the decrease of the compressive strength caused by thermal shock, which meant the non-destructive ultrasonic testing can be used to conveniently and accurately quantify the thermal shock damage. This conclusion also applies when testing copper-impregnated carbon material, making it a potential method to be used in the maintenance of pantograph which can effectively avoid in rail transit accidents.

关键词： mechanical stress   mitochondrial dynamics   mitochondrion   osteoarthritis  

摘要： Mitochondrial dysfunction contributes to osteoarthritis (OA) onset and progress. Mitochondrial dynamics, coupled with mitophagy, is critical for the maintenance of mitochondrial fitness, involving many cellular processes, such as proliferation and apoptosis. Excessive mechanical stress induces chondrocyte apoptosis;however, the effects of mechanical stress on mitochondrial dynamics remain elusive. In this study, we performed fluorescence staining, flow cytometry, transmission electron microscope, Western blot analysis, and RNA-sequencing to assess the effects of different strength of mechanical stimulation on mitochondrial functions of chondrocyte treated with interleukin-1 beta (IL-1 beta). We found that moderate mechanical stress reduced the IL-1 beta-induced apoptosis by maintaining mitochondrial function and scavenging the reactive oxygen species, while excessive mechanical stress induced strong mitochondrial dysfunction and apoptosis. Moreover, RNAsequencing revealed that mitophagy and mitochondrial dynamics were involved in the regulation of mechanical stress on chondrocyte biology. In addition to the elevated mitophagy, moderate mechanical stress also promoted mitochondrial dynamics by enhancing the expression of MFN1/2 and OPA1 and the translocation of dynamin-related protein 1 from the cytoplasm to the mitochondria. However, an uncoupling of mitochondrial dynamics, characterized by strongly elevated fission, resulted in the unfavorable apoptosis of excessive mechanical stress-stimulated chondrocytes. This study revealed the effects of mechanical stress upon mitochondrial dynamics in chondrocyte.

关键词： Citrus processing waste   Extraction kinetics   Green techniques   Pectin   Solid-liquid extraction  

摘要： Pectin as a hydrocolloid has countless functional applications in food and related industries. The extraction techniques considerably influence the composition, characteristic and extractability of the target compound, hence there is an ongoing effort to understand the extraction process using theoretical approaches. This review aims to provide a comprehensive overview of different mathematical approaches reported for describing the solid-liquid extraction process for pectin. As the major source of pectin is citrus waste, the extraction techniques described in this review article have considered citrus processing waste as a major substrate. Chemical rate law, empirical models and mechanistic approaches have been considered in the study. The modelling approaches are based on the hydrolysis, diffusion and degradation of pectin in a homogenous medium, and have been described either as a single or combination of more than one phenomenon. The application of models has been critically reviewed with respect to the influence and interdependencies of the parameters on the extraction kinetics with reference to advance green techniques such as subcritical water, microwave and ultrasonic-assisted extraction processes. Understanding of these models can be used to successfully to predict the properties of extraction systems at a phenomenological scale.