Study on energy output rule on attenuation of small diameter charge detonation wave passing by air-gap

In order to study energy output rule on attenuation of small diameter charge detonation wave passing by air-gap,the detonation shock wave pressures of different charge diameters and confinements,which are attenuated in air-gap,are measured by using the manganin piezoresistance method.Thus the experiential attenuation rule of X booster explosive is obtained with confinement of 45# steel and polymethyl methacrylate(PMMA),the experiential relational expressions in charge diameter and air-gap thickness are gained.The results indicate that exponential rule is obtained in accordance with attenuation of small diameter charge detonation wave passing by air-gap,and the bigger charge diameter,the smaller modulus decay.By changing air-gap thickness,the detonation pressure is also changed.The detonation performance can be controlled by adjusting charge dimension,confinement and air-gap thickness.

A numerical simulation of unsteady flow in small diameter helical grafts

The application of small diameter arterial grafts is limited due to the fact of relatively poor long-time patency which is caused by thrombosis formation in the short term and intimal hyperplasia(IH) in the medium and long term.Thrombosis,obstructing the flow of blood

Study of an Ultrasonic Probe Installed into a Small Diameter-Pipe Using an Electromagnetic Acoustic Transducer

Metal pipes having an inner diameter of about 25 mm or less are frequently used as heat exchangers for power plants, gas pipes, and water pipes. However, erosion and corrosion due to long-term use may cause serious accidents, such as steam leaks, resulting in economic loss and environmental pollution. Therefore, inspection of the entire length and thickness before shipping or monitoring during operation are important technologies. However, no inspection technology including the inside of the wall thickness has been developed. The purpose was to develop an ultrasonic probe that can inspect the inner and outer surfaces from the inside of the pipe at the same time. The developed ultrasonic probe is based on an electromagnetic ultrasonic transducer (EMAT) that does not require a couplant and is then easy to install in a pipe. The EMAT for the longitudinal and for the transverse vibration mode guided wave are connected in series in order to take into account the variety of defects. First, the EMAT was successfully developed for each mode. That is, it was conducted by using the magnetostrictive effect for the longitudinal mode type and by using the Lorentz force for the transverse mode type, and evaluated to improve the performance. The reflected signal from a notch defect was then evaluated in the state that each EMAT was connected in series using any artificial defects and found to be able to detect any notches with about 10% depth or about 15% circumferential length.

Influence of deformation zone length on bending radius of SS304 tubes with small diameters manufactured via free bending-based active motion

In three and six-axis free-bending equipment,the deformation zone length(A)is a fixed mechanical structure parameter modified when the relevant structure is redesigned and manufactured.In this study,a six degree of freedom(6-DOF)parallel mechanism was used as the control mechanism of the bending die,and a new method of changing the deformation zone length(A)was proposed.Firstly,an idealized geometric model of free bending-based active motion was established.Then,the influence of the deformation zone length(A)on the bending moment and the bending radius of the tube was analyzed.In addition,the finite element simulation and a kinematic model of free bending-based active motion controlled by the 6-DOF parallel mechanism were established,and bending processes of the SS304 tube with different deformation zone lengths were investigated.Afterwards,the impact of the deformation zone length(A)on the bending radius,bending moment,wall thickness,and motion of the parallel mechanism were analyzed.Finally,experiments were carried out on the free-bending equipment based on the 6-DOF parallel mechanism.Experiments verified the rules in the theoretical analysis,finite element simulation,and kinematic simulation.

Online tool-wear measurement of small-diameter end mills based on machine vision

The objective of this study was to develop an online tool-wear-measurement scheme for small diameter end-mills based on machine vision to increase tool life and the production efficiency. The geometrical features of wear zone of each end mill were analyzed, and three tool wear criterions of small-diameter end mills were defined. With the uEye camera, macro lens and 3-axis micro milling machine, it was proved the feasibility of measuring flank wear with the milling tests on a 45# steel workpiece. The design of experiment （DOE） showed that Vc was the most remarkable effect factor for the flank wear of small-diameter end mill. The wear curve of the experiments of milling was very similar to the Taylor curve.

Characteristics of sewer biofilms in aerobic rural small diameter gravity sewers

Small diameter gravity sewers(SDGS)are extensively used to collect rural sewage as they are low in cost and quick to construct.However,the characteristics of biofilms in rural SDGS are still not clear.In this study,biofilms characteristics of aerobic rural SDGS were investigated using simulations in a lab under different flow conditions and slopes.Results indic ated that the average thickness of aerobic rural SDGS biofilms was in the range of 350-650μm,decreasing at locations with variable flow and high slopes.Protein was the most abundant substance in extracellular polymeric substance of SDGS biofilms.The most abundant bacteria,Proteobacteria,Actinobacteria,and Bacteroidetes,and functional bacteria showed different distributions when analyzed through Illumina HiSeq sequencing of 16 S rRNA.The relative abundances of denitrifying bacteria,nitrite-oxidizing bacteria,and sulfate-reducing bacteria(SRB)were lower during variable flow than during stable flow.High slopes(15‰)decreased SRB presence,which could be used to mitigate H2 S accumulation in aerobic SDGS.Overall,this study describes the characteristics of aerobic rural SDGS biofilms and provides valuable suggestions for the optimal design of SDGS based on these characteristics.

Fucoidan and topography modification improved in situ endothelialization on acellular synthetic vascular grafts

Thrombogenesis remains the primary failure of synthetic vascular grafts.Endothelial coverage is crucial to provide an antithrombogenic surface.However,most synthetic materials do not support cell adhesion,and transanastomotic endothelial migration is limited.Here,a surface modification strategy using fucoidan and topography was developed to enable fast in situ endothelialization of polyvinyl alcohol,which is not endothelial cell-adhesive.Among three different immobilization approaches compared,conjugation of aminated-fucoidan promoted endothelial monolayer formation while minimizing thrombogenicity in both in vitro platelet rich plasma testing and ex vivo non-human primate shunt assay.Screening of six topographical patterns showed that 2μm gratings increased endothelial cell migration without inducing inflammation responses of endothelial cells.Mechanistic studies demonstrated that fucoidan could attract fibronectin,enabling integrin binding and focal adhesion formation and activating focal adhesion kinase(FAK)signaling,and 2μm gratings further enhanced FAK-mediated cell migration.In a clinically relevant rabbit carotid artery end-to-side anastomosis model,60%in situ endothelialization was observed throughout the entire lumen of 1.7 mm inner diameter modified grafts,compared to 0%of unmodified graft,and the four-week graft patency also increased.This work presents a promising strategy to stimulate in situ endothelialization on synthetic materials for improving long-term performance.

In vitro biocompatibility evaluation of silk-fibroin/ polyurethane membrane with cultivation of HUVECs

In order to investigate the in vitro biocompatibility of a novel polyurethane （PU） membrane modified by incorporation of superfine silk-fibroin powder （SFP）, which was prepared for small-diameter vascular grafts, with the cultivation of human umbilical vein endothelial cells （HUVECs）, PU and SFP were mixed with the ratios of 9：1, 7：3, 5：5, 3：7 （PU：SFP） to make four composite materials. Unmodified PU and polytetrafluoroethylene （PTFE） were added as control groups. CCK-8 assay was used to evaluate the cytotoxicity of these biomaterials. Data were processed using SPSS, and P〈 0.05 was considered to be statistically significant. Adherence and spreading of HUVECs on the surface of specimens was observed using direct contact cultivation. The toxicity ratings of the novel composites were grade 0-1, which is in the acceptable range. In all the experimental groups except control, SFP/PU with ratio of 1：9 had the least cytotoxicity property, and more content of SFP in the composite showed no improvement of the biocompatibility. HUVECs strongly attached to and grew on the surface of the biomaterials, and proliferated rapidly. The proliferation ability increased with increased proportion of SFP; however the cell quantity on the surface of the materials decreased when the proportion of SFP was equal to or larger than that of PU in the composite. It is concluded that this novel material has excellent cellular affinity with no cytotoxicity to HUVECs. Adding SFP gives PU better biocompatibility, while further research on optimum blend ratios is still needed.