Sheath Effects Research Articles

Space-Time Effect Prediction of Blasting Vibration Based on Intelligent Automatic Blasting Vibration Monitoring System

The vibration produced by blasting excavation in urban underground engineering has a significant influence on the surrounding environment, and the strength of vibration intensity involves many influencing factors. In order to predict the space-time effects of blasting vibration more accurately, an automatic intelligent monitoring system is constructed based on the rough set fuzzy neural network blasting vibration characteristic parameter prediction model and the network blasting vibrator (TC-6850). By setting up the regional monitoring network of monitoring points, the obtained monitoring data are analyzed. An artificial intelligence model is used to predict the influence of stratum condition, excavation hole, and high-rise building on blasting vibration velocity and frequency propagation. The results show that the artificial intelligence prediction model based on a rough set fuzzy neural network can accurately reflect the formation attenuation effect, hollow effect, and building amplification effect of blasting vibration by effectively fuzzing and standardizing the influencing factors. The propagation of blasting vibration in a soil–rock composite stratum is closely related to the surrounding rock conditions with a noticeable elastic modulus effect. The hollow effect is regional, which has a significant influence on the surrounding ground and buildings. Besides, the blasting vibration of the excavated area is stronger than that of the unexcavated area. The propagation of blasting vibration on high-rise buildings was complicated, of which the peak vibration velocity is maximum at the lower level of the building and decreased with the rise of the floor gradually. The whip sheath effect appears at the top floor, which is related to the blasting vibration frequency and the building’s natural vibration frequency.

Multi-aspect analysis of ureteral access sheath usage in retrograde intrarenal surgery: A RIRSearch group study

ObjectiveTo evaluate the effect of ureteral access sheath (UAS) use and calibration change on stone-free rate and complications of retrograde intrarenal surgery (RIRS). MethodsData from 568 patients undergoing RIRS for kidney or upper ureteral stones were retrospectively included. Firstly, patients were compared after 1:1 propensity score matching, according to UAS usage during RIRS (UAS used [+] 87 and UAS non-used [−] 87 patients). Then all UAS+ patients (n=481) were subdivided according to UAS calibration: 9.5–11.5 Fr, 10–12 Fr, 11–13 Fr, and 13–15 Fr. Primary outcomes of the study were the success and complications of RIRS. ResultsStone-free rate of UAS+ patients (86.2%) was significantly higher than UAS− patients (70.1%) after propensity score matching (p=0.01). Stone-free rate increased with higher caliber UAS (9.5–11.5 Fr: 66.7%; 10–12 Fr: 87.0%; 11–13 Fr: 90.6%; 13–15 Fr: 100%; p<0.001). Postoperative complications of UAS+ patients (11.5%) were significantly lower than UAS− patients (27.6%) (p=0.01). Complications (8.7%) with 9.5–11.5 Fr UAS was lower than thicker UAS (17.2%) but was not statistically significant (p=0.09). UAS usage was an independent factor predicting stone-free status or peri- and post-operative complications (odds ratio [OR] 3.654, 95% confidence interval [CI] 1.314–10.162; OR 4.443, 95% CI 1.350–14.552; OR 4.107, 95% CI 1.366–12.344, respectively). ConclusionUse of UAS in RIRS may increase stone-free rates, which also increase with higher caliber UAS. UAS usage may reduce complications; however, complications seemingly increase with higher UAS calibration.

Comparison of vacuum-assisted sheaths and normal sheaths in minimally invasive percutaneous nephrolithotomy: a systematic review and meta-analysis

BackgroundA systematic review and meta-analysis was conducted to compare the safety and efficacy of vacuum-assisted sheaths and conventional sheaths in minimally invasive percutaneous nephrolithotomy (MPCNL) in the treatment of nephrolithiasis.MethodsPubMed, Web of Science, Embase, EBSCO, and Cochrane Library databases (updated March 2021) were used to search for studies assessing the effect of vacuum-assisted sheaths in patients who underwent MPCNL. The search strategy and study selection processes were implemented in accordance with the PRISMA statement.ResultThree randomized controlled trials and two case-controlled trials that satisfied the inclusion criteria were enrolled in this meta-analysis. Overall, the stone-free rate (SFR) in patients who underwent vacuum-assisted sheaths was significantly higher than that in patients who underwent conventional sheaths (RR 1.23, 95% CI 1.04, 1.46, P = 0.02), with significant heterogeneity among the studies (I2 = 72%, P = 0.03). In terms of the outcome of complications, vacuum-assisted sheath could bring a benefit to the postoperative infection rate (RR 0.48, 95% CI 0.33, 0.70, P < 0.00001) with insignificant heterogeneity among the studies (I2 = 0%, P = 0.68). There was no significant difference in the blood transfusion rate (RR 0.35, 95% CI 0.07, 1.73, P = 0.17), with significant heterogeneity (I2 = 66%, P = 0.35). Three studies contained operative time data, and the results indicated that the vacuum-assisted sheath led to a shorter operative time (MD = − 15.74; 95% CI − 1944, − 12.04, P < 0.00001) with insignificant heterogeneity (I2 = 0%, P = 0.91).ConclusionThe application of a vacuum-assisted sheath in MPCNL improves the safety and efficiency compared to the conventional sheath. A vacuum-assisted sheath significantly increases the SFR while reducing operative time and postoperative infection.

Thermal stability of quasi-isotropic strands with different cross-sections and with/without metal sheaths

This paper mainly focuses on the thermal stability performance, such as minimum quench energy (MQE) and normal zone propagation velocity (NZPV), of a quasi-isotropic strand (Q-IS) with three different configurations made from 2G high-temperature superconducting (HTS) tapes in the adiabatic approximation. Due to the anisotropic performance of thermal conductivity in 2G HTS tapes, the tensor form of the heat conduction equation was used instead of conventional isotropic forms. We first measured the MQE and NZPV of three strands in the adiabatic approximation. Subsequently, the experimental results were verified by finite element analysis and compared with the values of MQE and NZPV in a liquid nitrogen (LN2) bath. Finally, the effect of a metal sheath on the current distribution and generation of Joule heat during the quench process were analyzed through simulation. The results show that the arc-shaped aluminum filler brings slightly higher thermal stability of Q-IS while the copper sheath largely improves stability. Moreover, compared with the thermal stability of the strand fully exposed to the LN2 bath, for the strand in the adiabatic approximation, the MQE decreases a lot while the maximum of NZPV is increased by 2–3 times.

Effect of non-ionizing reaction rate (assumed to be controllable) on the plasma generation mechanism and communication around RAMC vehicle during atmospheric reentry

Radio frequency (RF) blackout occurs during radio attenuation measurement C (RAMC) vehicle reentry due to the attenuation effect of the plasma sheath on the communication signal. In recent years, the mitigation mechanism of chemical reaction for RF blackout problem has gradually been studied numerically and experimentally. However, the effect of non-ionization reaction rate has been ignored because it does not directly involve the generation of electrons. In the present study, the influence of non-ionizing reaction rate on the plasma generation mechanism and EM wave attenuation was numerically solved by the plasma flow and multilayer transmission model. According to the simulation results, only the reaction rate of NO rightleftharpoons N + O has a significant effect on the electron number density in all non-ionizing reactions, and the degree of influence is less than the ionization reaction rate. The EM wave attenuation decreases with the decrease of the reaction rate of NO rightleftharpoons N + O. When the reaction rate is reduced by 25 times, the maximum attenuation of electromagnetic wave can be reduced by 12 dB. Finally, a potential scheme by reducing the reaction rate of NO rightleftharpoons N + O was proposed to mitigate the RF blackout problem.

Effect of Disposable Sheaths on the Vickers Microhardness of Resin Composites

Objective: The aim of this study was to evaluate the effect of disposable sheaths on microhardness of resin composites.&#x0D; Methods: A total of 40 resin composite specimens were fabricated with perspex molds (5x2 mm). Specimens were divided into 4 groups: Irradiated by 1-Elipar LCU only (EL), 2-Elipar LCU with sheath (ELS), 3-Valo LCU only (VL), 4-Valo LCU with sheath (VLS), (n=10). The specimens were subjected to surface microhardness (SMH) test (Tronic, Digital Microhardness Tester DHV-1000) on the top and bottom surfaces under 200 g load applied for 10 s with a Vickers indenter. The specimens were stored in the distilled water at 37 °C for 24 hours and the same measurements were repeated. One-way ANOVA test, Tukey and Tamhane post-hoc tests were used for intergroup comparisons. Also paired sample t-test was used for comparisons of the different time results. &#x0D; Results: According to the 1st-hour data from the top and bottom SMH measurements, EL and VL groups gave significantly higher microhardness values than VLS and ELS groups (p

I-V characteristics of MgB2 conductors with different metallic sheaths

I-V characteristics of MgB2 superconductors with different metallic sheaths were measured in the range of voltages from 10−7 V up to 10−1 V at liquid helium temperature and external magnetic fields 4.75–8.0 T. R-T measurements of compared superconductors between 20 K and 300 K were also done, which allows to estimate the conductor’s temperature after quench. Quench power density of MgB2 superconductors with different sheaths is compared and analysed. It was found that the tape with Ni sheath reaches higher quench power density in contrast to Ti sheathed one in entire measured range. The quench properties and transport ability were enhanced with adding high conductive strip of metal stabilization. The effect of the metallic sheaths and additional stabilization on the thermal stability of MgB2 conductors carrying DC currents is discussed.

Investigation of effects of plasma sheath on antenna radiation based on ray tracing method

The reason for communication blackout in hypersonic vehicles is strong interference from the plasma sheath on antenna radiation. This paper presents the calculation of the effects of a plasma sheath on microstrip antenna radiation using the ray tracing method, a method comprising an accurate and complex theoretical algorithm. Using an integrated model of a plasma sheath and microstrip antenna, the ray tracing method is used to obtain the disturbed electric field in the sheath with different parameters. This study reveals that the sensitivity of X-band antenna radiation to the alteration of plasma parameters is lower than that of C-band antenna radiation. These numerical results provide a reference guide for the design of antennas for use in hypersonic vehicles.

Study on the Effect of Cement Sheath on the Stress of Gas Storage Well

Compressed natural gas (CNG) has been widely used as an automotive fuel in china, which the service security of CNG storage well (CSW), the main storage equipment in Chinese filling station, is becoming more and more prominent. In order to analyze the stress of CSW and its influencing factors, the mechanical model of CSW + cement sheath + stratum (CCS) processed by both elastic mechanics and finite element method was studied in this work. Using the most common well of Φ177.8× 10.36mm as a calculation case to obtain the analytic solutions and numerical solutions of CCS. The results indicated that the analytic solutions and numerical solutions are very close with relative deviation less than 3%, which verified their reliability each other. The calculation case can prove that the stress of CSW reduced evidently due to the effect of well cementation, which equivalent to the value of circular and axial stress of CSW strengthens to 18% and 20%. And when increasing the elastic modulus of cement sheath, the stress of CSW decreased that the support and potentiation to CSW by cement sheath becomes stronger.

Multi‐Point Measurements of the Plasma Properties Inside an Aurora From the SPIDER Sounding Rocket

AbstractThe Small Payloads for Investigation of Disturbances in Electrojet by Rockets (SPIDER) sounding rocket was launched on February 2nd, 2016 (21:09 UT), deploying 10 free falling units (FFUs) inside a westward traveling auroral surge. Each FFUs deployed spherical electric field and Langmuir probes on wire‐booms, providing in situ multi‐point recordings of the electric field and plasma properties. The analytical retrieval of the plasma parameters, namely the electron density, electron temperature and plasma potential, from the Langmuir probe measurements was non‐trivial due to sheath effects and detailed explanation are discussed in this article. An empirical assumption on the sheath thickness was required, which was confirmed by simulating the plasma environment around the FFU using the Spacecraft Plasma Interaction Software (SPIS). In addition, the retrieved electron density and temperature are also in agreement with the simultaneous incoherent scatter radar measurements from the EISCAT facility. These two independent confirmations provided a good level of confidence in the plasma parameters obtained from the FFUs, and events observed during the flight are discussed in more details. Hints of drift‐wave instabilities and increased currents inside a region of enhanced density were observed by the FFUs.

Effect of opening layout and sheathing on lateral load bearing capacity in wooden shear walls

Effect of opening layout and sheathing on lateral load bearing capacity in wooden shear walls

Analysis of Echo Characteristics of Spatially Inhomogeneous and Time-Varying Plasma Sheath

The “black barrier” phenomenon caused by plasma sheath during the reentry of a high-speed target will seriously affect the detection of radar echo by a ground monitoring station, which is not conducive to making corresponding adjustments to different situations in real-time. The echo reflects the information of the target’s position and speed, which is significant for real-time monitoring and effective strike. In this work, the effect of a high-speed target plasma sheath on electromagnetic wave echo characteristics was investigated by using the proposed spatially inhomogeneous and time-varying plasma sheath model. The Z-transform finite-difference time domain (Z-FDTD) method was adopted to calculate the time domain and frequency domain results of the echo in plasma sheaths with spatially inhomogeneous, uniform and spatially inhomogeneous and time-varying electron density distributions. The effects of different time-varying parameters and plasma parameters on the echo characteristics of the plasma sheath were analyzed. The results show that the reflected echo in spatially inhomogeneous and time-varying plasma is less than that of the other two. The magnitude of the reflected echo is proportional to the time-varying parameter peak coefficient and Gaussian width, and inversely proportional to the collision frequency and plasma thickness. The theoretical results provide important guidance for ground monitoring and anti-stealth.

Plasma Sheath Modelling for Computational Aerothermodynamics and Magnetohydrodynamics

ABSTRACT To date, plasma sheath effects have not been incorporated into most CFD simulations of magnetohydrodynamics (MHD) or aerothermodynamics due to the high computational costs involved. The accurate modeling of both collisional and collisionless plasma sheaths for hypersonic applications is here presented. This is followed by the outline of recent numerical methods that enable the sheaths to be integrated with large time steps and to be incorporated within CFD codes. For the first time, the electron energy transport in non-equilibrium is here integrated in coupled form with the plasma sheath within a MHD process. Some example test problems are then presented including MHD in a scramjet combustor and electron transpiration cooling in a hypersonic flow. Such show that the plasma sheath effects can be added within CFD simulations with little loss in computational efficiency. The inclusion of plasma sheath models is seen to be critical in predicting accurately such problems.

Sheathing-fastener connection strength based design method for sheathed CFS point-symmetric wall frame studs

Cold-formed steel (CFS) in construction delivers cost effectiveness and design flexibility. The instability failures of CFS Structural members significantly influences the failures of sheathing boards attached as an external cover. Therefore, present study experimentally examines the structural behavior of sheathing fastener connection in cold-formed steel wall frame. As a first attempt, strength and stiffness of the sheathing fastener connection is determined against the failure modes of point symmetric CFS wall frame studs. A new test setup has been developed to investigate the individual sheathing fastener failure modes. Parameters investigated include sheathing board types (varying thickness) and different dimensions of point-symmetric CFS studs. A total of forty-one individual fastener connection tests were carried out. The experimental investigation revealed that the fastener connection strength varies depending on the geometric dimensions of CFS stud and material composition of sheathing board. The result indicated that the bracing effect provided by plain gypsum board (fiber less) is insignificant and should not be considered for design. For sheathing boards with fiber composition, a generic parameter [ratio to design moment (Mx or My) to CFS stud depth (h)] is introduced to consider the structural bracing effect in CFS wall panel design. The limitations to consider the bracing effect of sheathing in the design of CFS wall frame studs are suggested for minor axis buckling and major axis buckling.

Effect of Time-Varying Plasma Sheath on Hypersonic Vehicle-Borne Radar Target Detection

Hypersonic vehicle-borne radar target detection will suffer from time-varying plasma sheath which is formed during hypersonic flight. In this study, effect of time-varying plasma sheath on hypersonic vehicle-borne radar target detection is investigated. First, the radar echo model coupling time-varying plasma sheath effect is proposed using an analytical computation method. The regulation of electron density variation is based on flow parameters. Coherent integration result with the present of time-varying plasma sheath effect is derived. The degradations of hypersonic vehicle-borne radar target detection under time-varying plasma sheath are studied through real hypersonic vehicle flight cases. Simulation results shows that high electron density of time-varying plasma sheath will cause significant attenuation, which will lead to decrease of detection probability. In some cases, the signal-noise ratio (SNR) threshold that target can be detected increases more than 40 dB compared with situation without time-varying plasma sheath. Moreover, time-varying plasma sheath will cause time-varying amplitude and phase in pulse and between different pulses, causing intra-pulse and inter-pulse modulation phenomena. These phenomena lead to the disappearance of peak value in range-Doppler plane which will degrade the coherent accumulation as well as target detection performance. By using plasma sheath electron density diagnosis method on vehicle, compensation factor according to the electron density can be established to compensate plasma sheath effect in radar echoes. Simulations results based on real hypersonic vehicle flight flow parameters confirm the conclusions above. The work in this paper will benefit the design and application of hypersonic vehicle-borne radar in the future.

Optimization of a Faraday Cup Collimator for Electric Propulsion Device Beam Study: Case of a Hall Thruster

A Faraday cup (FC) is an instrument dedicated to current measurement in beams, jets and plasmas. It consists of a set of polarized electrodes mounted in such a way plasma sheath effect can be neglected, yielding accurate and reliable results. A FC is composed of three main parts, namely a collector or cup, which collects the current, a collimator, which defines the collection area and can contribute to limit electrons from entering the cup and a housing which protects the instrument from perturbation caused by the surrounding medium. In this paper, we provide experimental results of the effect of the collimator upon the measured ion current within the beam of a low-power Hall thruster. Different collimator materials, aperture diameters and polarization voltages are studied to determine the optimum design. Minimum dimension as well as appropriate materials are given as a conclusion in the case of low-power Hall thruster beam investigation.

Effect of Plasma Sheath on the Design of Electric Field Instrument Detecting Magnetosheath

The distribution of plasma potential and density around spacecraft is affected by the coupling of spacecraft and plasma, resulting in disturbing the detection of space electric field. In this paper, Spacecraft Plasma Interaction Software (SPIS for short) is used to provide a reference to design the electric field instrument detecting magnetosheath on future missions. The interaction of plasma with the spacecraft platform and the probe is simulated to investigate the thickness of plasma sheath and the relationship between current and voltage drop under different plasma conditions. Our results indicate that the thickness of plasma sheath covered spacecraft is smaller than the Debye radius, and this difference is larger at higher temperature conditions caused by photoelectrons and secondary electrons. Moreover, the current collected by the probe at a different voltage drop is also simulated. The simulated results show that the influence of current disturbance on measuring potential can be reduced by the probe with a bias current. Furthermore, the estimated optimum bias current is also listed corresponding to the detected region.

Variation in Tensile Properties of Single Vascular Bundles in Moso Bamboo

Abstract Moso bamboo (Phyllostachys edulis), an apt example of an anisotropic, functionally graded composite material, is the most important commercial bamboo species of China. This species has excellent mechanical properties due to its unique vascular bundle structure. This article examines the variation in mechanical properties of single vascular bundles with respect to their location within a bamboo culm. The mechanical exfoliation method was used to prepare the single vascular bundle. This study found that moso bamboo has superior stiffness and strength. Additionally, the variation in properties was large in the radial direction but minimal in longitudinal direction. The large variation in mechanical properties of vascular bundles can be ascribed to the synergistic effect of the fibrous sheath and parenchyma rather than to changes in fibrous sheath properties. This study provides a basis for the structure application for moso bamboo.

Separation and Enrichment of Yeast Saccharomyces cerevisiae by Shape Using Viscoelastic Microfluidics.

Yeast Saccharomyces cerevisiae (S. Cerevisiae) is one of the most attractive microbial species used for industrial production of value-added products and is an important model organism to understand the biology of the eukaryotic cells and humans. S. Cerevisiae has different shapes, such as spherical singlets, budded doublets, and clusters, corresponding to phases of the cell cycle, genetic, and environmental factors. The ability to obtain high-purity populations of uniform-shaped S. Cerevisiae cells is of significant importance for a wide range of applications in basic biological research and industrial processes. In this work, we demonstrate shape-based separation and enrichment of S. Cerevisiae using a coflow of viscoelastic and Newtonian fluids in a straight rectangular microchannel. Due to the combined effects of lift inertial and elastic forces, this label-free and continuous separation arises from shape-dependent migration of cells from the Newtonian to the non-Newtonian viscoelastic fluid. The lateral position of S. Cerevisiae cells with varying morphologies is found to be dependent on cell major axis. We also investigate the effects of sheath and sample flow rate, poly(ethylene oxide) (PEO) concentration and channel length on the performance of the viscoelastic microfluidic device for S. Cerevisiae enrichment and separation by shape. Moreover, the separation efficiency, cell extraction yield, and cell viability after sorting operations are studied.

Short-Frame Fountain Code for Plasma Sheath With “Communication Windows”

The surface of a hypersonic vehicle traveling at a speed exceeding Mach 10 is covered by a plasma sheath. The plasma sheath is a complex dynamic random medium that seriously attenuates electromagnetic (EM) waves and generates the so-called blackout phenomenon. However, owing to changes in vehicle flight parameters, such as the angle of attack, speed, and altitude, or the effects of plasma weakening control measures, the attenuation effect of the plasma sheath on EM waves weakens for a short time. At times, the amplitude of the EM waves is higher than the communication threshold, and the EM waves penetrate the plasma sheath in a so-called “communication window”. However, the random temporal variance of the plasma sheath parameters causes the required parameters of the “communication windows” to appear randomly, resulting in the traditional communication methods that needs to keep the communication link open for a long time being no longer applicable. To maximize the use of these “communication windows”, this paper proposes a short-frame fountain code (SFFC), constructs a time-varying plasma sheath channel model, and studies the relationship between the SFFC parameters and the transmission performance of this particular channel. Simulation and experimental results show that the use of SFFC improves the reliability of communication through the plasma sheath. The uninterrupted and correct transmission of information can be achieved even when the plasma equivalent frequency is close to the carrier frequency.