关键词： 机械动力设备   检修   管理  

摘要： 随着社会的进步和经济的发展,机械设备的使用率越来越高,很大程度上提高了人们的生活质量和生活水平。机械动力设备的检修管理能够保证机械动力设备的安全运行。但是,近些年来,我国机械动力设备频频发生安全事故,给人们的生产生活埋下了安全隐患,主要原因是机械动力设备的管理工作落实不到位,针对这种情况,本文提出了一些加强机械动力设备检修管理的策略,旨在能够提升机械动力设备的安全运行水平。

关键词： Forced oscillator   Bifurcations   Magnetic force   Chaos  

摘要： In this paper, oscillations in the physical model consisting of two carts mounted on a guide are considered. The movement of the carts is restricted by the repelling permanent magnets. The interaction between carts is provided by a linear spring. The harmonic external loading is applied to one of the carts. According to the experimental studies, the period doubling cascade leading to the creation of a chaotic attractor occurs with an increase in the forcing frequency in the system. Chaotic attractor crises, quasi-periodic regimes, and finite periodic doubling cascade are revealed as well. To describe system's dynamics, the nonlinear mathematical model is developed. Based on the experimental data, the procedure of model validation is introduced. The numerical and qualitative analysis of the mathematical model allows one to identify bifurcation types, reveal unstable modes, and discover phenomena existing beyond the main period doubling cascade. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： 急性呼吸窘迫综合征   俯卧位   机械通气   吸痰  

摘要： 目的观察俯卧位机械通气下不同吸痰深度对ARDS患者吸痰效果及血流动力学、血气指标的影响。方法选取2018年2月-2019年10月在我院接受俯卧位机械通气治疗的80例ARDS患者为研究对象,根据其吸痰方式的不同分为浅部吸痰组和深部吸痰组。比较两组吸痰效果、治疗前后血气指标、APACHEⅡ评分和Murray肺损伤评分、炎症细胞因子(IL-6、IL-10、hs-CRP)水平的差异。结果两组平均吸痰次数和吸痰间隔时间比较差异无统计学意义(P>0.05);两组治疗后MBP和CVP较治疗前增高,HR较治疗前降低,组间比较差异无统计学意义(P>0.05);浅部吸痰组治疗后SPO2高于深部吸痰组,PaCO2低于深部吸痰组;浅部吸痰组治疗后APACHEⅡ评分、Murray肺损伤评分、IL-6、IL-10、hs-CRP低于深部吸痰组(P<0.001)。结论俯卧位机械通气下不同吸痰深度对ARDS的吸痰效果均较好,而浅部吸痰创伤小,且对血气等指标的改善情况优于深部吸痰,可应用于临床。

关键词： Glucose   Hydrogenolysis   1   2-Propylene glycol   Heterogeneous catalysts   ZnO   Ru   C   Optimization of reaction conditions   Kinetic modelling   Thermodynamic analysis  

摘要： Transformations of glucose to 1,2-propylene glycol were studied over a mechanical mixture of ZnO and Ru/C catalysts in the presence of hydrogen. Different reaction conditions were evaluated by changing the reaction temperature and hydrogen pressure. In addition to the cascade mode of operation, also separate steps in the overall reaction network, such as hydrogenation of pyruvaldehyde and hydroxyacetone to 1,2-propylene glycol were investigated. Fructose as a starting material was also studied resulting in a propylene glycol yield of 37.5%. The optimal temperature for glucose transformation to propylene glycol was found to be 165 degrees C. The influence of temperature on the catalytic behavior was more prominent than the effect of hydrogen pressure. Thermodynamic analysis of glucose transformation to 1,2-propylene glycol was performed and a plausible kinetic model reflecting a complex reaction network was developed being able to describe the data in a reliable way.

摘要： Minimal residual disease (MRD) is an important emerging clinical end point in chronic lymphocytic leukemia (CLL). The objective of this research was to develop an integrated mechanistic model to evaluate the impact of venetoclax-rituximab combination therapy on MRD kinetics. Using data from 435 patients with relapsed or refractory CLL, an integrated model was developed and validated that accounted for venetoclax dosing and pharmacokinetics, rituximab treatment, absolute lymphocyte count, and blood and bone marrow (BM) MRD data. Simulations of venetoclax-rituximab (six cycles) combination predicted the proportion (90% confidence interval) of patients with BM MRD below 10(-4)to be 57% (54-61%) and 63% (59-67%) at 12 and 24 months of treatment, respectively. Continued venetoclax treatment to 48 months only increased the predicted rate of negative BM MRD to 66% (63-70%). These results indicate that treatment with venetoclax-rituximab combination for a finite 2-year period would nearly maximize the rate of negative BM MRD (< 10(-4)). Preliminary clinical data agree with these predictions and more long-term follow-up data are awaited to confirm the same.

关键词： Glass  

摘要： This work focused on investigating the mechanical, optical features and gamma-ray shielding parameters of different five glasses coded as W1, W2, W3, W4, and W5 based on 0.8[xBaO (1-x)MgO]-0.2WO(3)-2TeO(2):x = 0, 0.3, 0.5, 0.7, and 1 mol%. According to Makishima-Mackenzie's model, the total ionic packing density (V-t) and the total dissociation energy (G(t)) for the investigated glasses were computed. Then, the main mechanical features (elastic moduli and Poisson's ratio) haven been calculated. The optical features such as optical electronegativity (chi*) and linear dielectric susceptibility (chi((1))) and other related parameters for the W1-W5 glasses were also computed. Utilizing the newly Phy-X/PSD program, mass attenuation coefficient (MAC) has been computed. Based on MAC values, linear attenuation coefficient (LAC), half value layer (HVL), mean free path (MFP), and effective atomic number (Z(eff)) as radiation shielding parameters were evaluated. Results revealed that the (V-t) increased from 0.39 to 0.49, while (G(t)) decreased from 84.94 x 10(6) to 45.33 x 10(6) (KJ/m(3)) for W1 to W5 glasses. The elastic properties varied from 76.21 to 44.32 GPa for Young's modulus, from 29.25 to 18.23 GPa for shear modulus, from 32.29 to 26.00 GPa for bulk modulus, from 70.91 to 50.30 GPa for longitudinal modulus, and from 0.15 to 0.22 for Poisson's ratio. The value of chi* changed from 0.84 to 0.41, while chi((1)) changed from 0.62 to 0.36. HVL and MFP values are in the ascending order of W1 > W2 > W3 > W4 > W5. Therefore, the W5 glass (contains the highest concentration of BaO) has the best radiation shielding efficiency among the other samples W1-W4. Correlations between shielding features (MAC and HVL) at different photon energy are estimated, where MAC and HVL have been improved by increasing the BaO in W1-W5 glasses.

关键词： Quasiperiodic oscillator   Quasiperiodic Mathieu   Quasiperiodic variance   Sub-harmonic resonance   Semi classical-quantum dynamics  

摘要： Quasiperiodically driven quantum parametric oscillators have been the subject of several recent investigations. Here we show that for such oscillators, the instability zones of the mean position and variance (alternatively the mean energy) for a time developing wave packet are identical for the strongest resonance in the three-dimensional parameter space of the quasiperiodic modulation as it is for the two-dimensional parameter space of the periodic modulations. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Flexible mechanical metamaterials   Nonlinear dynamics   Cnoidal waves  

摘要： Flexible mechanical metamaterials have been recently shown to support a rich nonlinear dynamic response. In particular, it has been demonstrated that the behavior of rotating-square architected systems in the continuum limit can be described by nonlinear Klein-Gordon equations. Here, we report on a general class of solutions of these nonlinear Klein-Gordon equations, namely cnoidal waves based on the Jacobi elliptic functions sn, cn and dn. By analyzing theoretically and numerically their validity and stability in the design- and wave-parameter space, we show that these cnoidal wave solutions extend from linear waves (or phonons) to solitons, while covering also a wide family of nonlinear periodic waves. The presented results thus reunite under the same framework different concepts of linear and non-linear waves and offer a fertile ground for extending the range of possible control strategies for nonlinear elastic waves and vibrations.

关键词： Rangeland rehabilitation   Land degradation   Surface runoff   Soil moisture   Erosion  

摘要： Overexploitation and climate change accelerate the degradation of Jordan's arid rangelands. Uncovered and crusted soils increase runoff and erosion and hinder the emergence of the native vegetation. Micro water harvesting combined with shrub-seedling plantation have been widely applied to reverse land degradation trends. However, consequential soil water and vegetation dynamics have been rarely assessed, which constrains further out-scaling of the rehabilitation practice to complex environments. In Jordan, an experiment was set up to study the linkages between local rainfall characteristics, soil moisture and the development of out-planted shrub seedlings. Soil moisture was recorded at approximately weekly time-interval during the rainy and dry season 2017/2018 using a manually operated soil water sensor. Transect monitoring was pursued up and down the slope across four micro water harvesting pits and the interspaces. Data confirmed a significant soil moisture increase inside the pits bridging intra-seasonal dry spells and soil water potentially deep-percolated into the karstic bedrock underneath. The study found that the out-planted shrubs' stem diameter and height predominantly increased during post rainy season, when the interspaces dried up while the pits continued providing moisture. The results are promising and contribute to integrated research towards halting land degradation and sustainable agro-pastoral development.

关键词： Compound "supHopf/homoclinic-fold/supHopf" bursting   Compound "supHopf/supHopf-fold/supHopf" bursting   Fast-slow analysis   Bifurcations   Transition of bursting  

摘要： This paper aims to report complex bursting dynamics in a parametrically and externally excited mechanical system. Typically, two compound bursting patterns, i.e., bursting of "supHopf/homoclinic-fold/supHopf" type and bursting of "supHopf/supHopf-fold/supHopf" type, composed of two different clusters during each period of bursting, can be observed in this system. To begin with, the generation of each of the two clusters in compound bursting of "supHopf/homoclinic-fold/supHopf" type is investigated by the fast-slow analysis. Then, a two-parameter bifurcation diagram is plotted to investigate the transition of the compound bursting. We show that there are two originally disunited active areas, which may inosculate as a whole by homoclinic bifurcations if the system parameter varies properly. Based on this, a different type of compound bursting, i.e., bursting of "supHopf/supHopf-fold/supHopf" type, is revealed. (C) 2020 Elsevier Ltd. All rights reserved.