关键词： 有创无创序贯机械通气   慢性阻塞性肺疾病   呼吸衰竭   血液动力学  

摘要： 目的:分析慢性阻塞性疾病(COPD)致呼吸衰竭应用有创无创序贯机械通气治疗对血液动力学的影响。方法:2017年4月-2018年10月收治COPD致呼吸衰竭患者92例,随机分为两组各46例。两组患者均实施支气管扩张等常规治疗,同时观察组实施有创无创序贯机械通气治疗;对比组实施有创机械通气治疗。比较两组血液动力学指标水平。结果:两组治疗前动脉血二氧化碳分压(PaCO2)、血氧饱和度(PaO2)等血液动力学指标比较,差异无统计学意义(P>0.05);两组出窗时PaCO2、平均动脉压(MAP)、心率(HR)均低于治疗前,PaO2均高于治疗前,差异有统计学意义(P<0.05);观察组出窗时PaCO2、MAP、HR均低于对比组,PaO2高于对比组,差异有统计学意义(P<0.05)。结论:慢性阻塞性疾病致呼吸衰竭患者应用有创无创序贯机械通气治疗有助于改善血液动力学指标,临床应用价值较高。

关键词： HSLA steel   Age hardening   Secondary hardening   Tensile properties   Charpy V-Notch impact test  

摘要： The precipitation kinetics of HSLA-100 steel and the correlation between tensile and impact properties were studied. According to the modified Johnson-Mehl-Avrami-Kolmogorov (JMAK) analysis and based on the analysis of the time corresponding to the transformed fraction of 0.5 (t(0.5)), the activation energy for the precipitation of copper during aging of martensite was determined as similar to 111 and 105 kJ/mol, respectively. These values are much smaller than the activation energy for the diffusion of Cu in alpha-iron, which was related to the effect of high dislocation density of the quenched martensitic microstructure on the aging process. These results were verified based on the diffusional calculations. Based on the analysis of mechanical behavior, no reasonable correlation was found between strength of the material and the impact energy. However, the impact energy was found to be proportional to the UTS-YS, where the latter is an indicator of the work-hardening capability of the material. This revealed that the work-hardening capacity of the material is a much more important factor for determining the impact toughness compared to its strength. (C) 2019 Politechnika Wroclawska. Published by Elsevier B.V. All rights reserved.

关键词： Product design  

摘要： Today, preserving the quality and reducing the losses of agricultural products is an important topic and has attracted the attention of many scholars in the field. This study aims at investigating the engineering properties (physical, mechanical, and hydrodynamic properties) of cantaloupe in order to manage and reduce the losses that is produced postharvest. The results show that the mean values physical properties measured for the geometric mean diameter, arithmetic mean diameter, sphericity, surface area, volume, and true density of the cantaloupes were 130.13 mm, 130.26 mm, 0.94%, 53,367.59 mm(2), 633.30 cm(3), and 0.83 g/cm(3), respectively. Maximum force required for bruising and shearing cantaloupes in the investigation of their mechanical properties were 248.20 and 108.30 N. The hydrodynamic properties of cantaloupes such as the terminal velocity, the cantaloupes' rise time in the water column, the buoyance force and the drag force were obtained to be equal to 0.12 m/s, 4.10 S, 6.21 N, and 0.11 N, respectively. The results obtained through this study can be used in designing harvest machines, optimization, processing, transport, separation of impurities, and grading equipment for the purpose of reducing cantaloupe waste. Practical applications Of the 67 million tons of agricultural production in Iran, 20 million tons of it are turned into waste in the postharvest stage. That is the equivalent of food of 20 million people. Fruits are among the most important horticultural products that play an important role in supplying human nutrition and human health. Failure to review the engineering properties of agricultural products (physical, mechanical, and hydrodynamic properties) are the most important factors in increasing the agricultural waste at the postharvest stage. The physical properties of agricultural products are essential for the design and optimization of harvesting and postharvesting machinery, separating, transferring, grading, and drying processes. M

关键词： Diamond   Chemical mechanical polishing   Removal mechanism   Molecular dynamics simulation   ReaxFF  

摘要： Diamond has been utilized for various applications such as ultra-precision cutting tools and power semiconductor devices. Chemical mechanical polishing (CMP) is an effective processing method for the planarization of diamond, but the removal mechanism of the carbon atoms in diamond CMP is still under debate. Here, the atomic mechanism of removal in diamond CMP with center dot OH environment was investigated using the molecular dynamics (MD) simulation method of reactive force field (ReaxFF). The simulation results show that with chemical action alone, the substrate surface adsorbs O, H or center dot OH to form C-O, C-H, C-OH, etc., but no carbon atoms are removed from the diamond substrate. However, when the mechanical sliding is added, some carbon atoms are removed in form of CO or CO2, and the other carbon atoms are removed by the attachment to abrasive. The formation of C-C bonds between the diamond substrate and the abrasive or the formation of C-O bonds is a prerequisite for subsequent sliding removal. This work contributes to understanding the removal mechanism of diamond CMP at the atomic level.

关键词： Flow boiling   Critical heat flux   Hydrodynamics   Instability   Gravity   Microgravity  

摘要： CHF is an important design parameter in two-phase thermal management systems utilizing flow boiling schemes. In this study, a new theoretical model for predicting the trigger mechanism for flow boiling CHF is presented. Flow visualization shows that flow boiling on a heated wall is sustained mostly by the region containing discrete vapor bubbles called the wetting front because it allows the heated wall continuous access to the bulk liquid. CHF is triggered when intense evaporation of the liquid in the wetting front causes combined effects of parallel-to-flow direction interfacial stability and perpendicular-to-wall direction Helmholtz instability generating a continuous vapor patch on the wetting front. The new mechanistic CHF model incorporates three sub-models: a separated flow model to calculate two-phase flow parameters, an interfacial instability model to calculate the critical wavelength of parallel-to-flow vapor wave, and a Helmholtz instability model to calculate the critical wavelength of perpendicular-to-wall liquid-vapor interface. The CHF model is used to predict experimental data for a rectangular channel with single-sided heating in Earth gravity and microgravity for a variety of operating conditions. The model predictions show good agreement with experimental data, evidenced by an MAE of 15.36%. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： prostate cancer   prostate-specific antigen dynamics   external beam radiation therapy   mathematical oncology  

摘要： External beam radiation therapy is a widespread treatment for prostate cancer. The ensuing patient follow-up is based on the evolution of the prostate-specific antigen (PSA). Serum levels of PSA decay due to the radiation-induced death of tumour cells and cancer recurrence usually manifest as a rising PSA. The current definition of biochemical relapse requires that PSA reaches nadir and starts increasing, which delays the use of further treatments. Also, these methods do not account for the post-radiation tumour dynamics that may contain early information on cancer recurrence. Here, we develop three mechanistic models of post-radiation PSA evolution. Our models render superior fits of PSA data in a patient cohort and provide a biological justification for the most common empirical formulation of PSA dynamics. We also found three model-based prognostic variables: the proliferation rate of the survival fraction, the ratio of radiation-induced cell death rate to the survival proliferation rate, and the time to PSA nadir since treatment termination. We argue that these markers may enable the early identification of biochemical relapse, which would permit physicians to subsequently adapt patient monitoring to optimize the detection and treatment of cancer recurrence.

关键词： Chlorine compounds  

摘要： Single crystals of thiosemicarbazide cadmium chloride monohydrate (TSCCCM) are grown by slow evaporation solution growth technique (SEST) by utilizing double distilled water as a solvent. Single crystal X-ray diffraction (SXRD) analysis reveals the cell parameters and space group of the grown crystal. FT-IR and FT-Raman spectra were used to assert the presence of various functional groups present in the host material. UV study exhibits high transparency range of TSCCCM crystal and the corresponding optical bandgap is found to be 4.19 eV. The grown crystal exhibits negative photoconductivity. The mechanical strength of the grown crystal was investigated using Vickers microhardness test. The melting point of the grown crystal is determined using thermal analysis. Dielectric studies have been carried out as function of frequency at diverse temperatures. Chemical etching studies were carried out on the grown crystal by using water as an etchant. Second harmonic generation (SHG) efficiency was found to be 13 times higher than that of KDP. The real, imaginary and third order nonlinear susceptibility of the grown crystal is determined using Z-scan analysis.

关键词： graphene nanoplatelet (GNP)   aluminum matrix composites   molecular dynamics   strengthening mechanism   mechanical properties  

摘要： The sintering process of graphene nanoplatelet (GNP) reinforced aluminum matrix composite powder was simulated by molecular dynamics method. The effects of Al nanoparticle size and sintering temperature on sintering behavior were studied. Uniaxial tensile simulation was applied to study the mechanical properties of sintered composites. The results show that the nanoparticle size and sintering temperature have significant effects on the sintering behavior of the composites. Smaller size nanoparticle system has lower melting point, which requires lower sintering temperature. Larger size particle system requires longer sintering time and higher sintering temperature. At lower temperatures, the main coalescence mechanisms of nanoparticle systems are surface diffusion and grain boundary diffusion. When the temperature is close to the melting point, volume diffusion and surface diffusion dominate. Tensile simulation results of sintered composites show that the addition of GNP can greatly improve the mechanical properties of the composites. Dislocation reinforcement and stress transfer are the main reinforcement mechanisms.

关键词： air cooling partitioning   hot rolled Q&P steel   industrial coils   mechanical property   retained austenite  

摘要： In this study, an energy-efficient processing route involving hot rolling, direct quenching, and air cooling partitioning (DQ&P) is proposed for the large-scale industrial production. The carbon partitioning is completed through waste heat of the steel coils. The effect of quenching temperature (QT) and the kinetics of non-isothermal carbon partitioning were investigated in a low carbon steel 0.19C-1.5Si-1.6Mn (wt%). A stable volume fraction of retained austenite (RA) approximate to 11.1-13.5% is obtained in the QT range of approximate to 240-360 degrees C, which provides a wide quenching window for industrial production. In addition, when the QT was 320 degrees C, the carbon partitioning was adequate at cooing rate of less than 1 degrees C s(-1) and the volume fraction of RA was more than 11%. When the cooling rate is increased to 5 and 10 degrees C s(-1), approximate to 10% RA with high carbon content of approximate to 1.3 wt% is interestingly obtained. A large scale industrial coils of hot Q&P (Quenched and Partitioned) steel is successfully produced using a commercial steel 0.13C-1.2Si-1.5Mn-0.25Cr (wt%). The mechanical properties are uniform for the entire steel coil with tensile strength of approximate to 1258-1319 MPa and total elongation of approximate to 13.7-16%. The present work confirms the viability to introduce Q&P process in the hot rolling production line.

关键词： Hybrid system   walking robot   lateral dynamics   chaos  

摘要： A detailed mathematical analysis of the two-dimensional hybrid model for the lateral dynamics of walking-like mechanical systems (the so-called hybrid inverted pendulum) is presented in this article. The chaotic behavior, when being externally harmonically perturbed, is demonstrated. Two rather exceptional features are analyzed. Firstly, the unperturbed undamped hybrid inverted pendulum behaves inside a certain stability region periodically and its respective frequencies range from zero (close to the boundary of that stability region) to infinity (close to its double support equilibrium). Secondly, the constant lateral forcing less than a certain threshold does not affect the periodic behavior of the hybrid inverted pendulum and preserves its equilibrium at the origin. The latter is due to the hybrid nature of the equilibrium at the origin, which exists only in the Filippov sense. It is actually a trivial example of the so-called pseudo-equilibrium [Kuznetsov et al., 2003]. Nevertheless, such an observation holds only for constant external forcing and even arbitrary small time-varying external forcing may destabilize the origin. As a matter of fact, one can observe many, possibly even infinitely many, distinct chaotic attractors for a single system when the forcing amplitude does not exceed the mentioned threshold. Moreover, some general properties of the hybrid inverted pendulum are characterized through its topological equivalence to the classical pendulum. Extensive numerical experiments demonstrate the chaotic behavior of the harmonically perturbed hybrid inverted pendulum.