关键词： dissipative particle dynamics   mechanical properties   molecular dynamics   nanocomposites   rubber  

摘要： Dissipative particle dynamics (DPD) is used to predict the mechanical properties of crosslinking-polyisoprene (PI) reinforced by single-walled carbon nanotube (SWCNT). The role of the increasing concentration of SWCNT up to 8% in morphology of PI composite is investigated. The carbon nanotube (CNT) restricts the polymer movement as indicated by the reduction of mean square displacement and the end-to-end distance. The analysis of CNT bundle reveals that the CNT forms bundle of many sizes depending on its concentration. The mechanical reinforcement of the PI composites is attributed to the restricted motion of crosslinked entangled polyisoprene and to the alignment of aggregated CNT along the elongation direction. However, the DPD alone fails to account for the change in Young's modulus of the composite system as a function of the SWCNT concentration. Using the modified segmental repulsive potential (mSRP), which prevents polymeric chain crossing and enhances polymer entanglement, can address this shortcoming. The mSRP is necessary for correct description of mechanical reinforcement in a polymer composite system. To obtain quantitative agreement with the experimental modulus, the polyisoprene interaction parameter is modified from the published value by 10%. This modified parameter is found to work well for the simulation of polyisoprene composites.

关键词： Diffusion   Ketones   Evaporation   Solvents   Water  

摘要： The formation of hard agglomerates during drying has impacts on the product quality, particle size distribution, and downstream formulation. Hence, understanding the cause of hard agglomerates and determining a remedy for them or preventing their formation are necessary. The integrated sorption chamber (ISC) has been successfully applied to the study of hard agglomerate formation. The design and development of this ISC are briefly described. The vapor-phase profile of a binary mixture of acetone and water without active pharmaceutical ingredient (API) was predicted using an analytical solution of a batch distillation and verified via mass spectrometry (MS). The drying of the API wet cake, which is very soluble in water, using a starting point of 5 wt % water in acetone was conducted in the ISC. A significant delay in water removal was observed from both the weight measurement and the MS signal. The slow removal of water was attributed to diffusion of water from a thin crust layer induced by the solution of the API in water and drying, resulting in the formation of hard agglomerates at the end of drying. A wet-cake solvent composition change following a cake wash with acetone reduced the initial water content from 5.5 to 0.5 wt %. This altered wet-cake solvent composition changed the behavior of water removal, leading to a significant reduction of the diffusion time. The dried API contained soft lumps without hard agglomerates.

关键词： Cable galloping   Co-rotational finite element   Quasi-steady theory   Aerodynamic finite element  

摘要： Cables are widely used lightweight and efficient structural members affected by various nonlinearities. This paper is devoted to the development of a finite element approach to the study of the nonlinear dynamic behavior of cable structures under wind loading. Firstly, the formulation of a co-rotational beam-cable element is presented to account for cable geometrical nonlinearities within the context of an Updated Lagrangian approach. The Euler-Bernoulli kinematics is adopted in the co-rotated frame assuming small or moderate displacements and strains. Secondly, the formulation of an aerodynamic element, meant to be superimposed to the mechanical beam element, is developed to fully account for the nonlinearity of the aerodynamic forces. The wind interaction forces are computed within the framework of the quasi-steady theory. Appropriate procedures for applying the aforementioned elements in static and dynamic analyses are presented and applied to the study of the static configuration and the galloping vibrations of a suspended cable under steady and turbulent wind conditions. The results point out the importance of the first anti-symmetric in-plane mode on the galloping response of the iconic selected structure, and reveal the role of the mechanical and aerodynamic model by comparison with a different discretization based on cable finite elements. A mechanical model, such as the proposed co-rotational finite element formulation, which includes the description of torsional rotations is required to properly model the aerodynamic loads in dynamic galloping analyses under steady wind. The mechanical and aerodynamic assumptions, instead, play a less important role in the case of turbulent wind conditions, leading to an eminently buffeting response entailing a strong effect of the swing of the structure.

摘要： Management of patients requiring temporary, mechanical hemodynamic support during high-risk percutaneous coronary intervention (PCI) or in cardiogenic shock is rapidly evolving. With the availability of the Impella 2.5, CP, 5.0, LD, and RP percutaneous mechanical circulatory support devices, there is a need for continued surveillance of outcomes. Three factors underline the importance of a registry for these populations. First, large randomized trials of hemodynamic support, involving cardiogenic shock, are challenging to conduct. Second, there is increasing interest in the use of registries to provide "real-world" experience and to allow the flexibility to evaluate individual patient uses and outcomes. Third, current, large databases have not captured the specific impact of mechanical support treatment of cardiogenic shock. The predecessor to the catheter-based ventricular assist devices registry, known as USpella, began in 2009 with paper data acquisition but beginning in 2011 transferred to electronic data capture, enrolling 3,339 patients through 2016. Throughout, registry data have been used to assess the outcomes of Impella therapy, leading to 8 publications and 4 Food and Drug Administration premarket approvals covering multiple indications and Impella devices. Going forward, the registry will continue to assess not only in-hospital outcomes but long-term follow-up to 1 year. In addition, data management will be enhanced to assess quality and clinical experiences. The registry will also provide a mechanism for postmarketing surveillance. This manuscript reviews the ongoing catheter-based ventricular assist devices registry design, management, and contributions of the registry data. The upgraded registry will provide a more robust opportunity to assess acute and late outcomes of current and future device use worldwide.

关键词： C3N   Nanosheet   Molecular dynamics   Defects   Cracks  

摘要： The purpose of this study is to investigate the mechanical properties of a new two-dimensional graphene like material, crystalline carbon nitride with the stoichiometry of C3N. The extraordinary properties of C3N make it an outstanding candidate for a wide variety of applications. In this work, the mechanical properties of C3N nanosheets have been studied not only in the defect-free form, but also with critical defects such as line cracks and notches using molecular dynamics simulations. Different crack lengths and notch diameters were considered to predict the mechanical response at different temperatures under the uniaxial tensile loading. Our simulation results show that larger cracks and notches reduce the strength of the nanosheets. Moreover, it was shown the temperature rise has a weakening effect on the tensile strength of C3N. Our study can provide useful information with respect to the thermomechanical properties of pristine and defective graphene like C3N 2D material. (C) 2018 Elsevier B.V. All rights reserved.

关键词： Closed ecological life support system   Functional-structural plant model   Knowledge-and-data-driven model   Mass balance model   Model evaluation   And model verification  

摘要： Modeling and the prediction of material flows (plant production, CO2/O-2 concentrations, H2O) is an important but challenging task in the design and control of closed ecological life support systems (CELSS). The aim of this study was to develop a novel knowledge-and-data-driven modeling (KDDM) approach for simultaneously simulating plant production and CO2/O-2 concentrations in a closed system of plants and humans by integrating mechanistic and empirical models. The KDDM approach consists of a 'knowledge-driven (KD)' sub-model and a 'data-driven (DD)' sub-model. The KD sub-model describes hourly and up to daily plant photosynthesis, respiration and assimilation partitioning using the components of GreenLab and TomSim models. The DD sub-model describes the dynamics of CO2 production and O-2 consumption by the crew member using a piecewise linear model. The two sub-models were integrated with a mass balance model for CO2/O-2 concentrations in a closed system. The KDDM was applied with a two-person, 30-day integrated CELSS test. This model provides accurate computation of both the dry weights of different plant compartments and CO2/O-2 concentrations. The model also quantifies the underlying material flows among the crew members, plants and environment. This approach provides a computational basis for lifetime optimization of cabin design and experimental setup of CELSS (e.g., environmental control, planting schedule). With extension, this methodology can be applied to a half-closed system such as a glasshouse.

关键词： hemodynamic monitoring   mechanical circulatory support   left ventricular assist device   heart failure   pulmonary wedge pressure   heart transplantation  

摘要： Proper timing of left ventricular assist device (LVAD) implantation in advanced heart failure patients is not well established and is an area of intense interest. In addition, optimizing LVAD performance after implantation remains difficult and represents a significant clinical need. Implantable hemodynamic monitoring systems may provide physicians with the physiologic information necessary to improve the timing of LVAD implantation as well as LVAD performance when compared with current methods. The CardioMEMS Heart sensor Allows for Monitoirng of Pressures to Improve Outcomes in NYHA Class III heart failure patients (CHAMPION) Trial enrolled 550 previously hospitalized patients with New York Heart Association (NYHA) class III heart failure. All patients were implanted with a pulmonary artery (PA) pressure monitoring system and randomized to a treatment and control groups. In the treatment group, physicians used the hemodynamic information to make heart failure management decisions. This information was not available to physicians for the control group. During an average of 18 month randomized follow-up, 27 patients required LVAD implantation. At the time of PA pressure sensor implantation, patients ultimately requiring advanced therapy had higher PA pressures, lower systemic pressure, and similar cardiac output measurements. Treatment and control patients in the LVAD subgroup had similar clinical profiles at the time of enrollment. There was a trend toward a shorter length of time to LVAD implantation in the treatment group when hemodynamic information was available. After LVAD implantation, most treatment group patients continued to provide physicians with physiologic information from the hemodynamic monitoring system. As expected PA pressures declined significantly post LVAD implant in all patients, but the magnitude of decline was higher in patients with PA pressure monitoring. Implantable hemodynamic monitoring appeared to improve the timing of LVAD implantatio

关键词： Silicene   Nanoindentation   Mechanical properties   Molecular dynamics  

摘要： In the present study, molecular dynamics simulations were carried out to study the mechanical behavior and response of a single layer, rectangular, planar and pristine silicene sheet during nanoindentation process. The nanoindentation simulation on the silicene sheet was done using a spherical diamond indenter and the different force vs depth of indentation curves at different conditions of temperature, indenter radius and depth of indentation were obtained. The variation of mechanical properties like maximum force, hardness and Young's modulus were studied with respect to temperature, indenter radius and depth of indentation by varying one parameter while keeping the other two parameters constant. The deformation behavior of the silicene sheet up to failure was thoroughly studied and the mechanical properties like maximum force bearing capacity, maximum hardness and Young's modulus of the silicene sheet were calculated. The maximum force and hardness of the silicene sheet at its maximum indentation depth of 39.5 angstrom are found to be 286.3 nN and 461.2 GPa respectively. The Young's modulus of the silicene sheet is found to be 176.9 GPa which is in close agreement with the existing literature reported value of 178 GPa. (C) 2018 Elsevier B.V. All rights reserved.

关键词： Hybrid   TENG   Self-powered multifunctional sensors  

摘要： Collecting mechanical energy in the surrounding environment to power small electronic devices is an ideal method as a green and clean power source. Based on the working mechanism and the advantages of triboelectric nanogenerator (TENG), a robust rolling friction contact-separation mode TENG (CS-TENG) has been fabricated for harvesting vertical rotation energy by utilizing the integrated cylindrical surface with the conjunction of rolling contact electrification and electrostatic induction. The output current of the CS-TENG can maintain 96% (origin: 1.72 mu A, final: 1.66 mu A) after two days continuous work a rotation speed of 300 r/min. Furthermore, an electromagnetic and triboelectric hybrid contact-separation mode nanogenerator (HCS-TENG) has been further designed by coupling magnets in the rolling cylinders with copper coils as an electromagnetic generator (EMG) in the acrylic cylinder to implement the multi-functional properties. The gear transmission structure makes the device more facile to be installed on the rotation objects. The output performances of CS-TENG and EMG under various rotation speeds were systematically studied. It shows that the CS-TENG with six units can deliver an output power of 0.15 mW/cm(2) and the 100 mu F capacitor can be charged to 6 V in less than 1 min by the hybridized nanogenerator at a rotating rate of 700 r/min. In addition, utilizing the output signal's intrinsic characteristics of CS-TENG, a self-powered rotation speed and displacement sensor using the dual cylinder structure TENG has been achieved for these rotating mobile devices that are inconvenient to get an additional power supply in the grimmest circumstances such as moon car or other celestial and tough environment detection equipment. This multifunctional TENG device reveals a significantly potential application in the grimmest circumstances as power source, self-powered electronics and sensor systems.