Accurate modeling of heat dissipation in pediatric intracorporeal devices is crucial in avoiding tissue and blood thermotrauma. Thermal models of new Maglev ventricular assist device (VAD) concepts for the PediaFlow VAD are developed by incorporating empirical heat transfer equations with thermal finite element analysis (FEA). The models assume three main sources of waste heat generation: copper motor windings, active magnetic thrust bearing windings, and eddy currents generated within the titanium housing due to the two-pole motor. Waste heat leaves the pump by convection into blood passing through the pump and conduction through surrounding tissue. Coefficients of convection are calculated and assigned locally along fluid path surfaces of the three-dimensional pump housing model. FEA thermal analysis yields a three-dimensional temperature distribution for each of the three candidate pump models. Thermal impedances from the motor and thrust bearing windings to tissue and blood contacting surfaces are estimated based on maximum temperature rise at respective surfaces. A new updated model for the chosen pump topology is created incorporating computational fluid dynamics with empirical fluid and heat transfer equations. This model represents the final geometry of the first generation prototype, incorporates eddy current heating, and has 60 discrete convection regions. Thermal analysis is performed at nominal and maximum flow rates, and temperature distributions are plotted. Results suggest that the pump will not exceed a temperature rise of 2°C during normal operation.
Abstract An interfaced GC-thermal atomizer AA system has been developed and used for the speciation and determination of volatile mercury compounds in biological fluids, perspiration and urine. The interfaced system is highly selective to mercury compounds and has high sensitivity. No sample preparation was necessary, avoiding losses during pretreatment procedures such as the cold vapor technique. The levels of inorganic mercury found in urine were from 0.0 to 3.3 ppm, and 0.0 to 0.6 ppm for sweat. Total mercury ranged from 0.6 to 3.9 ppm in urine and 0.2 to 1.0 ppm in sweat. The results also indicated the presence of unidentified non-volatile mercury in the samples. However, inorganic mercury seemed to be the major form of excretion of mercury from human bodies.
Low permeability reservoirs are characterized by low permeability, small pore throat, strong heterogeneity, and poor injection-production ability. High shale content of the reservoir, strong pressure sensitivity, micropore undersaturation, and significant water-lock effect in water injection development lead to increased fluid seepage resistance. There is an urgent need to adopt physical and chemical methods to supplement energy and improve infiltration efficiency, thereby forming effective methods for increasing the production and efficiency. Aiming at the characteristics of ultralow permeability reservoirs, in this paper, a green and environmental friendly biobased profile control and displacement agent (Bio Nano30) has been developed using noncovalent supramolecular interaction. Physical simulation experiments illustrate the profile control and displacement mechanism of Bio-Nano30. Laboratory experiments and field applications show that good results have been achieved in oil well plugging removal, water well pressure reduction and injection increase, and well group profile control and oil displacement. This research has good application prospects in low permeability heterogeneous reservoirs.
Conventional SLAM only requires the construction of sparse maps for localization, while in order to meet the safe driving needs of unmanned vehicles, they need to understand the edges of the road, i.e., with a semantic level of understanding. In addition, unmanned vehicles are more sensitive to lateral errors than longitudinal errors, which requires SLAM algorithms with higher accuracy for lateral errors. We investigate the ORB-SLAM3 algorithm by introducing satellite maps as a priori knowledge, using the corners in satellite maps to initialize the odometer, remove the accumulated errors, and correct the previous positions; using the results of particle filtering and lane line identification to further optimize the localization results of ORB-SLAM3 and to draw maps with lane semantic information. Our experiments show that our algorithm significantly reduces the cumulative error without loopback, improves the localization accuracy, and yields lane line maps with large engineering applications.
The convective dispersion models are derived by the material balance method in an infinitesimal volume. In comparison with the derivation process by the Markov method, they indicate statistical foundation of random particle movement. By numerical method, the mass transport laws are analyzed comparatively for the models.
The global oil and gas exploration targets are gradually moving towards a new field of oil and gas accumulation with nano pore throats, ranging from millimeter scale to micro nano pore throats.There are difficulties in fluid transport in nano confined pore throats, such as strong adsorption, which greatly increases the difficulty of starting crude oil.Therefore, it is necessary to construct a nanoscale fluid with strong diffusion and dispersion, and improve its permeability, suction, and displacement capabilities.This article develops a carbon dioxide responsive graphene dot type surfactant.By characterizing its structure, physical and chemical properties, and conducting infiltration simulation experiments, its infiltration and drainage ability in nanopore throats is elucidated.Infrared spectrum measurement shows that after functional modification exhibit new characteristic peaks at 1600 cm-1 to 1300 cm-1, considering the N-H plane stretching characteristic peak.The fluorescence spectra showed that the fluorescence intensity of F-GQDs was increased after functional modification, which indicated that F-GQDs was successfully synthesized.Through measurements of interfacial activity and adhesion work calculations, the oil-water interfacial tension can achieve ultra-low values within the range of 10-2 to 10-3 mN/m. Oil sand cleaning experiments and indoor simulations of spontaneous imbibition in tight cores demonstrate that F-GQDs exhibit effective oil washing capabilities and a strong response to carbon dioxide. When combined with carbon dioxide, the system enhances both the rate and efficiency of oil washing.Imbibition recovery can reach more than 50%.The research results provide a certain theoretical basis and data reference for the efficient development of tight reservoirs.
Abstract A method based on gel permeation chromatography as sample clean‐up followed by HPLC ‐ fluorescence ‐ UV is successfully developed for measuring the contents of 16 PAHs in airborne particulate after Soxhlet extraction of the samples. The clean‐up process is proved to be efficient by the analysis of SRM from NIST. The HPLC is operated at gradient steps with constant flow followed by UV and optimized multi‐step fluorescence detection. A complete run of HPLC requires less than 30 minutes with satisfactory resolution. The detection limits obtained with UV detection ranged from 0.017 to 2.542 ng/m3, and those of fluorescence are from 0.001 to 0.044 ng/m3. Precision of measurement is within 9.0 %. This method is applied to monitor the PAH contents is the airborne particulate samples collected in Taipei city at ten different sampling sites with particle size distribution measurements.
Based on the development status of low permeability reservoirs, an intelligent nano-flooding agent is needed to improve the displacement efficiency of reservoirs. Janus particles have the characteristics of small size and strong interfacial activity, and the solid surfactant of Janus particles has attracted more and more attention of petroleum researchers. Janus smart nanosheets were developed by Pickering emulsion preparation. Controllable assemblies of Janus smart nanosheets were formed by adjusting the preparation ratio. The structure and properties of smart nanosheets were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and interfacial tensiometer. The nanosheets have hydrophilic and hydrophilic properties. The particle size of silica nanoparticle is 10 nm. After surface modification and high shear stress treatment, nanosheet was formed. The thickness of nanosheet dispersed in aqueous solution was 30.2 nm. Experimental results show that at a given temperature, the Janus nanosheet system with low concentration can achieve ultra-low interfacial tension of 10
An important challenge facing the design of the miniature VADs intended for long term support is the optimization of the flow geometry to maximize hydraulic performance while minimizing shear-stress induced hemolysis and thrombosis. For semi-open centrifugal and mixed-flow pumps, as well as axial flow pumps, the complex flow pattern between the blade tip and casing has a dramatic effect on both efficiency and blood damage. This study employed CFD analyses (Star-CD, Adapco), based on a finite volume method, to simulate the 3-dimensional blood flow within a miniature centrifugal impeller. Turbulence was modeled by the standard k-e turbulence model. A multi-block structured mesh was generated to capture the steep velocity gradient near the blade surface. An implicit method based on multiple reference frames allowed coupling between the rotational impeller and stationary blocks. A periodic boundary condition provided efficient computation within the blade-blade region. A power law function was integrated into the code to estimate hemolysis with the shear history being recorded by the Lagrangian particle tracking method. Simulation results at three different tip clearances of 0.1, 0.05 and 0.02mm revealed the sensitivity upon efficiency, tip leakage flow, secondary flows, and hemolysis. Good agreement with the corresponding experimental results achieved with flow visualization studies was obtained.
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