A characteristic-featured shock wave indicator for simulating high-speed inviscid flows on 3D unstructured meshes

In this work, we extend the characteristic-featured shock wave indicator based on artificial neuron training to 3D high-speed flow simulation on unstructured meshes. The extension is achieved through dimension splitting. This leads to that the proposed indicator is capable of identifying regions of flow compression in any direction. With this capability, the indicator is further developed to combine with h-adaptivity of mesh refinement to improve resolution with less computational costs. The present indicator provides an attractive alternative for constructing high-resolution, high-efficiency shock-processing methods to simulate high-speed inviscid flows.

A Characteristic-Featured Shock Wave Indicator for Simulating High-Speed Inviscid Flows on 3D Unstructured Mesh

In this work, we extend the characteristic-featured shock wave indicator based on artificial neuron training to 3D high-speed flow simulation on unstructured mesh. The extension is achieved through dimension splitting. This leads to that the proposed indicator is capable of identifying regions of flow compression in any direction. With this capability, the indicator is further developed to combine with h-adaptivity of mesh refinement to improve resolution with less computational costs. The present indicator provided an attractive alternative for constructing high-resolution, high-efficiency shock-processing method to simulate high-speed inviscid flows.

High flow compression molding for recycling discontinuous long fiber thermoplastic composites

An investigation into high flow compression molding for recycling thermoplastic discontinuous long fiber composites is presented. High flow recycled panels and conventional low flow baseline panels were produced with a large rectangular (2:1 aspect ratio) mold. Flow was induced in the recycled panels by stacking cut sections of conventionally produced baseline panels in the center of the mold cavity, representing 25% initial coverage. High flow compression molded panels were found to exhibit significantly higher than baseline tensile strength (+50%) and modulus (+31%) when tested in the direction parallel to flow. When tested in the direction perpendicular to flow, the opposite effect was found, with reductions in tensile strength (−42%) and modulus (−37%). However, when the average results of both directions are compared to baseline, no significant difference was found between the recycled and baseline panels. This severe anisotropic redistribution of mechanical properties suggests chip orientation is affected by flow. Additionally, micrographic analysis revealed that high flow molding induces intra-ply chip shearing and a reduction in resin rich regions within panels. Baseline panels also exhibited in-plane anisotropy, despite initial random distribution of chips and no or near no flow induced during molding. In this case, mechanical properties favored the direction perpendicular to that of the recycled panels.

Usage of characteristic points to reduce the time of performance of SAD metric calculation during video flow compression by motion compensation method

Today, it is difficult to imagine a video system that does not use compression of the input video stream for transmission or storage, because the uncompressed size of video files can reach several hundred gigabytes. There are many different video stream compression techniques used in various codecs, however, one of the most commonly used is the motion compensation technique, which allows you to transmit video stream frames in the form of compensated inter frame difference, by finding the motion vectors of individual blocks image. Despite the fact that the above-mentioned technique has been used for the last twenty years, it still has two problem-priority places - assessments of the similarity of image blocks and the algorithm for searching blocks. This article focuses on the problem of estimating the similarity of the image, in order to reduce the time of estimating the similarity of the blocks, which in modern algorithms takes from 40 to 80% of the time of the entire process of encoding the video stream. The article considers the usage of metrics for estimating the similarity of images and their importance for the process of motion compensation during video stream compression, such as SSD (standard deviation) and SAD (sum of absolute differences). The temporal contribution of metrics to the video stream encoding process, in particular to the motion compensation process, is estimated. An algorithm combining classical SAD and parameter estimation based on characteristic points is proposed, which will reduce the metric calculation time for estimating block similarity. The reduction of SAD calculation time due to reduction of comparison points is estimated for three proposed comparison templates - HSAD (half SAD), TSAD (third SAD), DSAD (diagonal SAD). For the selected templates, the results of processing the test video sequence were compared with the results obtained during the processing of the video sequence by the classic SAD. The main attention was paid to the assessment of the following parameters: the relative difference SAD, the increase in the number of candidate blocks, the overlap of candidate blocks.

Methods of Delivering Mechanical Stimuli to Organ-on-a-Chip

Recent advances in integrating microengineering and tissue engineering have enabled the creation of promising microengineered physiological models, known as organ-on-a-chip (OOC), for experimental medicine and pharmaceutical research. OOCs have been used to recapitulate the physiologically critical features of specific human tissues and organs and their interactions. Application of chemical and mechanical stimuli is critical for tissue development and behavior, and they were also applied to OOC systems. Mechanical stimuli applied to tissues and organs are quite complex in vivo, which have not adequately recapitulated in OOCs. Due to the recent advancement of microengineering, more complicated and physiologically relevant mechanical stimuli are being introduced to OOC systems, and this is the right time to assess the published literature on this topic, especially focusing on the technical details of device design and equipment used. We first discuss the different types of mechanical stimuli applied to OOC systems: shear flow, compression, and stretch/strain. This is followed by the examples of mechanical stimuli-incorporated OOC systems. Finally, we discuss the potential OOC systems where various types of mechanical stimuli can be applied to a single OOC device, as a better, physiologically relevant recapitulation model, towards studying and evaluating experimental medicine, human disease modeling, drug development, and toxicology.

Investigating the complex velocity structures within dense molecular cloud cores with GBT-Argus

ABSTRACT We present the first results of high-spectral resolution (0.023 km s−1) N2H+ observations of dense gas dynamics at core scales (∼0.01 pc) using the recently commissioned Argus instrument on the Green Bank Telescope (GBT). While the fitted linear velocity gradients across the cores measured in our targets nicely agree with the well-known power-law correlation between the specific angular momentum and core size, it is unclear if the observed gradients represent core-scale rotation. In addition, our Argus data reveal detailed and intriguing gas structures in position–velocity (PV) space for all five targets studied in this project, which could suggest that the velocity gradients previously observed in many dense cores actually originate from large-scale turbulence or convergent flow compression instead of rigid-body rotation. We also note that there are targets in this study with their star-forming discs nearly perpendicular to the local velocity gradients, which, assuming the velocity gradient represents the direction of rotation, is opposite to what is described by the classical theory of star formation. This provides important insight on the transport of angular momentum within star-forming cores, which is a critical topic on studying protostellar disc formation.

Study on the influence factors of impact ejection performance for flexible airbag

In order to improve the impact ejection performance of the flexible airbag and to reveal the airbag inflating mechanism, a simulation model was built and verified by carrying out the flexible airbag impact ejection test. Based on this model, the influence of mass flow, compression displacement, and airbag thickness on flexible airbag ejection impact performance were studied. The results show that the ejection velocity of the flexible airbag increases as mass flow increases, but the excessive air mass flow does not improve the impact ejection performance of the airbag. The simulation results also demonstrate that the flexible airbag will oscillate reciprocally after it has no more contact with the moving rigid body and every node in the flexible airbag model has the same oscillating displacement. The analysis of compression displacement shows that it has a significant effect on the improvement of ejection performance. In conclusion, to improve the impact ejection performance of flexible airbag, the mass flow and compression displacement should be changed in a certain scope, which can provide reference for the topological structure design of the flexible airbag.