External Pressure Distribution Research Articles

Junction Piezotronic Transistor Arrays Based on Patterned ZnO Nanowires for High-Resolution Tactile and Photo Mapping.

Recently, a great deal of interest has been focused on developing sensors that can measure both pressure and light. However, traditional sensors are difficult to integrate into silicon (Si)-based integrated circuits. Therefore, it is particularly important to design a sensor that operates on a new principle. In this paper, junction piezotronic transistor (JPT) arrays based on zinc oxide (ZnO) nanowire are demonstrated. And the JPT arrays show high spatial resolution pressure and light mapping with 195 dpi. Because ZnO nanowires are arranged vertically above the p-type Si channel's center of the transistor, the width of the heterojunction depletion region is constricted by the positive piezoelectric potential generated by strained ZnO. In addition, photogenerated charge carriers can be created in the Si channel when JPT is stimulated by light, which increases its electrical conductivity. Consequently, the external pressure and light distribution information can be obtained from the variation in the output current of the device. The prepared JPT arrays can be compatible with Si transistors, which make them highly competitive and make it possible to incorporate both pressure and light sensors into large integrated circuits. This work will contribute to many applications, such as intelligent clothing, human-computer interaction, and electronic skin.

Functionalized Electrode Additive for Simultaneously Reinforcing Chemo‐Mechanical Properties of Millimeter‐Thick Dry‐Electrode for High‐Energy All‐Solid‐State Batteries

AbstractVoids are widely disseminated in a powder when mixed, and hence the typical dry‐electrode preparation method yields a sparse dry‐electrode because the external pressure applied to the surface of the mixed powder is not evenly distributed. Consequently, particle cracking and void remnants appear in the electrode after calendaring. This study introduces a practically applicable bi‐functionalized electrode additive to simultaneously reinforce the chemo‐mechanical properties of millimeter‐thick dry electrodes. The agyrodite Li6PS5Cl solid electrolyte and lithium difluorophosphate (LiPO2F2) additive have different sizes, as demonstrated by their densification from their elaborate bimodal structure, which is densely packed. Because the additive is filled into the interparticle voids in the electrode sheet during electrode fabrication, a decrease in electrode cracking after calendaring is possible because of the uniform distribution of external pressure. Hence, a thin, highly ionic/electronic‐conductive electrode can be constructed by the addition of LiPO2F2 additive. Furthermore, during the formation, the active material surface‐contacted LiPO2F2 promptly produces a surface layer comprising LiF and LixPFy. Thus, the addition of LiPO2F2 further reduces the degradation of Li6PS5Cl solid electrolytes. As a result, the LiPO2F2 additive simultaneously improves the electrochemical and physicochemical properties of millimeter‐thick dry‐electrodes for high‐energy all‐solid‐state battery systems.

Waterproof Flexible Pressure Sensors Based on Electrostatic Self-Assembled MXene/NH2-CNTs for Motion Monitoring and Electronic Skin.

Flexible wearable sensors to monitor human movement and for electronic skins must exhibit high sensitivity, a wide detection range, and waterproof characteristics. This work reports a flexible, highly sensitive, and waterproof sponge pressure sensor (SMCM). The sensor is made by assembling SiO2 (S), MXene (M), and NH2-CNTs (C) on the backbone of melamine sponge (M). The SMCM sensor exhibits excellent sensitivity (10.8 kPa-1), an ultra-short response/recovery time (40 ms/60 ms), a wide detection range (30 kPa), and an extremely low detection limit (4.6 Pa). Benefiting from layer-by-layer self-assembly, the sensor still exhibits excellent stability after 5000 cycles. In addition, the SMCM sensor also has excellent waterproof performance (a water contact angle of 142°), enabling it to operate unaffectedly under wet conditions. The SMCM sensor can accurately detect small body movements such as pulse and swallowing while also accurately detecting finger and elbow movements. In addition, the sensor can be designed as an array to construct an electronic skin for detecting the magnitude and distribution of external pressure. This work holds great application potential in next-generation electronic skin, fitness detection, and flexible pressure sensors.

Fluid-structure interaction analysis on the response of open-top, squat, circular tank due to wind-driven rain

Wind-driven rain (WDR) is a natural phenomenon, which occurs, when rain droplets descend through a wind flow field, creating an angle with the vertical and affects any structure by impingement through the structural envelope. Existing literatures on wind-driven rain effect on structure, are focused on building envelop only. There is a huge scope, left unexplored, on studying the interaction response of squat, open top, circular tank with wind-driven rain. This available scope is the main motivation of the present authors behind this study. The present study has been conducted through fluid–structure interaction (FSI) analysis, by coupling computational fluid dynamics (CFD) analysis of a multi-phase fluid system involving air and water to simulate wind-driven rain, with the mechanical analysis of the tank structure, by importing the wall pressure, assessed from CFD model of WDR. This study is focused on ground-supported, open-top, squat, circular tank with a slenderness ratio of 0.5. The internal and external pressure distributions on the tank wall have been assessed for WDR and compared with the same caused by wind. The radius (R): thickness (t) ratio of the tank wall has been varied from 125 to 500, in order to understand the impact of wind-driven rain on the tank wall deformation. The comparative study of pressure distribution between WDR and wind (only) cases clearly demonstrates that the wall pressure (internal and external) due to wind-driven rain, is higher than wind (only). It has been observed that the wall deformation is showing an incremental pattern with the decrement of wall thickness. The maximum deformation zone has been observed at the upper half of the frontal area. Higher deformation zone for R/t ratios 500, 250, 166.67, and 125, can be seen for 0° to 40°, 0° to 37°, 0° to 35°, and 0° to 32°, peripherally.

Leakage Analysis and Hazardous Boundary Determination of Buried Gas Pipeline Considering Underground Adjacent Confined Space

Urban underground construction projects are intertwined vertically and horizontally, and adjacent confined spaces such as water supply and drainage pipelines, side ditches and underground canals may exist near buried gas pipelines. Once the buried gas pipeline leaks, the gas will diffuse into the confined space through the soil and even enter the residential room by the confined space, which brings serious potential safety hazards. In this paper, the underground adjacent confined space hazardous boundary (HB) of underground gas pipeline leakage was defined, the distribution properties of gas leakage diffusion flow field were analyzed by numerical simulation and the distribution law of gas entering the confined space was studied. Using the least-squares method and multiple regression theory, the gas concentration prediction model in the adjacent confined space of buried gas pipeline leakage was established, the HB calculation model was further deduced, and the HB drawing board was drawn. The results showed that in the initial stages, the internal and external pressure and velocity distribution of the pipeline near the leakage hole were unstable, reaching a stable state after 60 s, and then the reverse flow occurred in the pipeline downstream of the leak hole. Reducing the minimum construction distance between the buried gas pipeline and the confined space improved the gas distribution concentration in the confined space. When the minimum construction distance increased from 3 m to 9 m, the gas concentration distribution decreased from 90.21% to 0.88%. Meanwhile, increasing the pipeline pressure and leakage diameter enhanced the gas concentration distribution in the confined space. The HB calculation model and HB drawing board realize the rapid determination of the HB between buried gas pipeline and confined space and offer a more reasonable basis for the design of gas pipeline safe distance in urban underground engineering construction.

Research on Influence of Rotation Center Eccentricity on Radial Force of Single-Blade Centrifugal Pump

To estimate the influence of the rotation center eccentricity of the single-blade centrifugal pump impeller on the radial force on it, and to explore the effective radial force balance method, a single blade pump with a power of 2.2 kW is analyzed. The accuracy of Numerical Simulation Methods are verified by tests of external characteristics (under three rotation-speeds of 1470 r/min, 2000 r/min, and 2940 r/min) and pressure distributions. There are five models with different rotation center coordinates (model a with (0,1), model b with (−1,0), model c with (0,−1), model d with (1,0), and model e with (0,0.5)) which are analyzed. The results show that the radial force of model c and model d reduced by 8.1% and 9.8%, respectively, which means the offset of the center of the impeller to the positive direction of the x-axis and the negative direction of the y-axis can effectively reduce the radial force. At the eccentricity of the impeller (2,−2), the radial force under all operating conditions is reduced, most obviously at 1.0 Qd, which is about 17%. The study may prove helpful to designers and pump manufacturers to find a path forward for an optimal eccentricity to minimize the radial force.

Atmospheric wind pressure distribution on an isolated agricultural silo / Distribuição da pressão atmosférica do vento em um silo agrícola isolado

Storage silos installations are very common in the agricultural areas of Argentina and Brazil. Accidents caused by the action of the wind on the structural components of silos are usually reported. For this reason, the UTN - Regional Rafaela and the Laboratorio de Aerodinámica of the UNNE began to develop experimental studies in a wind tunnel with the objective of analyzing the external pressure distribution on isolated silos and complementing the procedures established in the Argentine Wind Code CIRSOC 102 and in the Brazilian Code NBR 6123. The tests were carried out in the UNNE “Jacek P. Gorecki” wind tunnel, which is a boundary layer tunnel of the Eiffel-type. The total length of the tunnel is 39.65 m, the test section is 2.4 m wide × 1.8 m high × 22.8 m long and an axial fan generates a maximum speed of 25 m/s. Turbulence generators and surface roughness elements were used to simulate atmospheric wind and then a 1:100 scale model of the silo was tested. In this work, results of mean and fluctuating pressure values obtained by wind tunnel tests are presented. The turbulent wind actions defined by the fluctuating pressures are evaluated through the distributions of RMS and peak values.

External hydraulic pressure and invert uplift study in a non-circular shallow tunnel

Water hazards experienced in mountain tunnels have always been associated with inadequacy of waterproof structures and grouting technology applied in the construction stage. But the knowledge of seepage caused by groundwater inflow during the operation stage remains limited despite its importance to tunnel traffic operation and general safety. In this paper, the concept of equivalent permeability lining is introduced and the external hydraulic pressure (EHP) distribution of shallow non-circular tunnel is analytically deduced. A set of numerical and model tests are presented based on the semi-enclosed drained tunnel of a high-speed railway in China. The result shows that the existing circular solution underestimates the invert external hydraulic pressure (EHP) of non-circular shallow tunnel. A staged failure mode of high-EHP semi-enclosed tunnel can be observed in model tests. The vulnerabilities of warning criterion and monitoring put the high EHP tunnel under risk. Based on these, a modified analytical solution, a new warning criterion and a new maintainable monitoring system are built for high EHP tunnel.

Study on pressure distribution of pump chamber and axial force in particle-laden flow of centrifugal pump

To explore the pressure distribution characteristics of pump chambers, and the law governing the axial force in a particle-laden flow centrifugal pump, a semi-open impeller centrifugal pump was selected as the research object. The particle model and heterogeneous model were used to develop the numerical calculations of the particle-laden flow field within the centrifugal pump. For the liquid phase we adopted the shear–stress–transport (SST) turbulence model, while for the solid phase we adopted the discrete phase zero equation model. The external characteristics, pressure distribution and axial forces were compared and analyzed (1) for a constant solid particle diameter, d, of 0.1 mm and particle volume fractions, Cv, of 0, 1, 5, and 10%, and (2) for a constant particle volume fraction, Cv, of 10% and solid particle diameters, d, of 0, 0.01, 0.1, and 0.5 mm. The correlations between the particle volume fractions and solid particle diameters with the pump chamber pressure distributions and axial forces were obtained. The results show that when Cv increased from 1–10%, or d from 0.01–0.5 mm, the pump head and efficiency decreased continuously under the same flow rate. At the same time, larger particle volume fractions resulted in larger pressures at the same radius, while for larger solid particle diameters, smaller pressures were obtained at the same radius. Under the same flow rate, when Cv increased from 1–10%, the total axial force of the centrifugal pump increased, but it was smaller than what was achieved under the clean-water condition. When d increased from 0.01 to 0.5 mm, the total axial force of the centrifugal pump decreased. This study provides a reference for the calculation and balance of the total axial force in a particle-laden flow centrifugal pump.

Aerosol transmission in passenger car cabins: Effects of ventilation configuration and driving speed.

Identifying the potential routes of airborne transmission during transportation is of critical importance to limit the spread of the SARS-CoV-2 virus. Here, we numerically solve the Reynolds-averaged Navier–Stokes equations along with the transport equation for a passive scalar in order to study aerosol transmission inside the passenger cabin of an automobile. Extending the previous work on this topic, we explore several driving scenarios including the effects of having the windows fully open, half-open, and one-quarter open, the effect of opening a moon roof, and the scaling of the aerosol transport as a function of vehicle speed. The flow in the passenger cabin is largely driven by the external surface pressure distribution on the vehicle, and the relative concentration of aerosols in the cabin scales inversely with vehicle speed. For the simplified geometry studied here, we find that the half-open windows configuration has almost the same ventilation effectively as the one with the windows fully open. The utility of the moonroof as an effective exit vent for removing the aerosols generated within the cabin space is discussed. Using our results, we propose a “speed–time” map, which gives guidance regarding the relative risk of transmission between driver and passenger as a function of trip duration and vehicle speed. A few strategies for the removal of airborne contaminants during low-speed driving, or in a situation where the vehicle is stuck in traffic, are suggested.

Use of Artificial Neural Networks to Predict Wind‐Induced External Pressure Coefficients on a Low‐Rise Building: A Comparative Study

Wind flow on a bluff body is a complex and nonlinear phenomenon that has been mainly studied experimentally or analytically. Several mathematical methods have been developed to predict the wind‐induced pressure distribution on bluff bodies; however, most of them result unpractical due to the mathematical complexity required. Long‐short term memory artificial neural networks with deep learning have proven to be efficient tools in the solution of nonlinear phenomena, although the choice of a more efficient network model remains a topic of open discussion for researchers. The main objective of this study is to develop long‐short term memory artificial neural network models to predict the external pressure distribution of a low‐rise building. For the development of the artificial neural network models, the multilayer perceptron and the recurrent neural network were also employed for comparison purposes. To train the artificial neural networks, a database with the external pressure coefficients from boundary layer wind tunnel tests of a low‐rise building is employed. The analysis results indicate that the long‐short term memory artificial neural network model and the multilayer perceptron neural network outperform the recurrent neural network.

Sensitive Mechanofluorochromic Carbon Dot‐Based AIEgens: Promising Reporting Components for Self‐Sensing Plastics

AbstractMechanofluorochromic carbon dot‐based aggregation‐induced emission luminogens (M‐CD‐AIEgens) are attracting much attention because of their many potential practical applications. However, the mechanofluorochromic response of current M‐CD‐AIEgens only occurs under high pressure, which greatly hinders their practical applications. To overcome this shortcoming, more pressure‐sensitive M‐CD‐AIEgens are now developed, which show approximately fivefold enhancement of photoluminescence quantum yield after grinding. This enhancement of photoluminescence is attributed to the weakening of π–π stacking interactions between the carbon dots, which is caused by the grinding process. To illustrate a potential application of their interesting properties, M‐CD‐AIEgens are incorporated into a poly(e‐caprolactone) matrix to prepare self‐sensing sustainable plastics, which are able to dynamically sense the external pressure distribution when subjected to strain.

A novel analytical study on the buckling of cylindrical shells subjected to arbitrarily distributed external pressure

A completely new analytical method to solve the fourth-order governing partial differential equations with variable coefficients is proposed for the buckling of cylindrical shells subjected to distributed external pressure. Unlike the present energy method in literatures, pressure distribution needs not be assumed beforehand and be simple, which is arbitrary in this manuscript. The present novel method makes the buckling analysis for the complicated external pressure distributions (including discontinuous loads) possible. Furthermore, general buckling load formulas related to geometrical sizes of the shell and pressure distribution functions are obtained by the combined perturbation method and Fourier series expansion for the first time. The first and second order asymptotic terms of buckling loads are directly given for the purpose of engineering application. Based on the presented method, three types of external pressure loads (namely, linear liquid pressure, wind type pressure and discontinuous stepwise external pressure)are considered. Validity and accuracy are demonstrated by comparing with the results in published literatures for linear liquid pressure and wind type pressure, and it is also the first time to derive the buckling load for a shell under discontinuous stepwise external pressure. Parametric discussion is also performed to investigate the effects of load distribution types and parameters on buckling resistance capacity.

Steady Wind Load on External Surface and Its Effect on Wind-Induced Response for a 200 m High Natural-Draught Cooling Tower

Wind tunnel tests were carried out to measure the wind pressure of a 200 m high natural-draught cooling tower. An analysis of the distribution characteristics of external pressure was then conducted to determine the pressure coefficients Cp(θ, z) in a given wind profile. Finally, the effect on the response of the shell and the buckling safety of the shell, applying the simplified height-constant pressure coefficient Cp(θ) and the realistic pressure Cp(θ, z), was determined. Taking the wind load specified in the code as an example, the influence of the distribution of external pressure on the wind-induced response was further analyzed. The results indicate that the pressure distribution varies with not only the height z but also the circumferential angle θ, and the wind load of both ends of the tower is significantly greater than that of its middle. Moreover, the wind-induced static responses of the tower under the action of the realistic pressure distribution Cp(θ, z) and the simplified approach Cp(θ) are basically consistent, because the wind load distribution is more important than its magnitude for the wind-induced response of cooling tower, and the wind-induced response of the cooling tower is dominated by the local shell deformation.

The Influence of Pipe Bending Curvature on H2-O2 Gaseous Detonation Wave Front

The influence of different bend curvatures on the detonation wave propagation was analyzed by an advanced numerical simulation system. The mechanism of propagation properties is revealed by cellular structure, internal and external boundary pressure distribution, propagation process of detonation wave and chemical reaction. The cellular structure and detonation wave front of bend with different curvature are very different. The simulation results show that the detonation wave with regular cell structure propagating through the curved parts induces detonation cell size increased by diffraction near the inner wall while detonation reflected on the bottom surface resulting in decrease of cell size. Detonation wave was affected by the rarefaction wave and compression wave in the bent pipe. The pressure distribution of the bend shows that the peak pressure in the 450 curvature is the largest, which should be paid more attention in industrial design. The chemical reaction could indicate the propagation characteristics of detonation wave, and different propagation characteristics have different profiles of chemical components.

Integration of 3D Printed Flexible Pressure Sensors into Physical Interfaces for Wearable Robots.

Sensing pressure at the physical interface between the robot and the human has important implications for wearable robots. On the one hand, monitoring pressure distribution can give valuable benefits on the aspects of comfortability and safety of such devices. Additionally, on the other hand, they can be used as a rich sensory input to high level interaction controllers. However, a problem is that the commercial availability of this technology is mostly limited to either low-cost solutions with poor performance or expensive options, limiting the possibilities for iterative designs. As an alternative, in this manuscript we present a three-dimensional (3D) printed flexible capacitive pressure sensor that allows seamless integration for wearable robotic applications. The sensors are manufactured using additive manufacturing techniques, which provides benefits in terms of versatility of design and implementation. In this study, a characterization of the 3D printed sensors in a test-bench is presented after which the sensors are integrated in an upper arm interface. A human-in-the-loop calibration of the sensors is then shown, allowing to estimate the external force and pressure distribution that is acting on the upper arm of seven human subjects while performing a dynamic task. The validation of the method is achieved by means of a collaborative robot for precise force interaction measurements. The results indicate that the proposed sensors are a potential solution for further implementation in human–robot interfaces.

Searching for irregular pin-fin shapes for high temperature applications using deep learning methods

Pin-fins have been widely used in cooling channels to enhance internal heat transfer. For over thirty years, the literature has been using regular pin-fin shapes or identical pin-fins arrays. However, it was expected that an efficient pin-fin channel should have irregular pin-fin shapes and localized changing shapes along the streamwise direction. These new degrees of freedom for pin-fins were not well explored due to the lack of data processing method in the past. With the aid of the advanced deep learning techniques arising in these years, this study proposed a new optimization approach for pin-fins using the pix2pix networks and the Genetic Algorithms. A simulation dataset with 300 random spline pin-fin shapes was generated using Computational Fluid Dynamics. Two surrogated models were trained and tested to predict the temperature distributions on the external surfaces and pressure distributions in the middle section of the channel. Five optimized geometries were generated using different combinations of cooling objectives and pressure objectives. Based on the comprehensive results proliferated by the machine leaning methods, detailed sensitive analysis and response analysis were conducted for each input parameter. The optimized results indicated several general suggestions for pin-fin designs under different objectives: (a) square pin-fins could fit better with the cooling requirement and pressure constraints for the most upstream regions, (b) enlarging the opening area of middle stream pin-fins could elevate the uniformity of temperature, (c) streamlined pin-fins helped reduce the pressure drop. This effort was expected to provide a reference to explore cooling channel configurations geometries within a larger degree of freedom.

Using a 2.5D boundary element model to predict the sound distribution on train external surfaces due to rolling noise

In order to be able to predict train interior noise, it is first important to calculate the external sound pressure distribution on the floor, sidewalls and roof. This can then be combined with the transmission loss of the train panels to determine the interior noise. Traditional techniques such as the finite element and boundary element (FE/BE) methods in three dimensions (3D) can achieve this result but are computationally very expensive. In this paper, a wavenumber-domain boundary element (2.5D BE) approach is instead adopted to predict the propagation of rolling noise from the wheels, rails and sleepers to the train external surfaces. In the 2.5D models, only the cross-section of the vehicle is represented by using boundary elements, while the third direction is considered in terms of a spectrum of wavenumbers. The rail is treated directly in the wavenumber domain but, to include the wheel, a method of representing point sources in a 2.5D approach is developed. An inverse Fourier transform is applied to obtain the spatial distribution of the sound pressure on the train surfaces. The validity of this approach has been verified by comparison with experimental data. The 2.5D BE method was first used to predict the sound distribution on a 1:5 scale train surfaces due to a point source below the vehicle, and later it was used to predict the sound pressure on a full-scale metro vehicle due to a loudspeaker. Comparisons of predictions with measurements on the scale model and on the metro vehicle showed good agreements. For a point source below the vehicle, the sound pressure levels on the train floor were found to be around 20 dB higher than on the sides, and the sound pressure on the train roof was negligible. The 2.5D BE method was also used to predict the sound pressure on the metro vehicle surfaces in running operation, in which the predicted sound pressure levels on the train external surfaces agreed with measurements to within 3 dB and similar trends were found in terms of spectra and longitudinal distribution of pressure.

High-Sensitivity Flexible Pressure Sensor With Low Working Voltage Based on Sphenoid Microstructure

Flexible pressure sensors have attracted significant attention in field of electronic skin, medical equipment, and soft robotics. However, the poor sensing performance and high working voltage have hindered their practical applications. Here, a low-voltage wearable pressure sensor with high sensitivity in a large useable range is demonstrated. The pressure sensor has been designed with a random distributed sphenoid surface and highly conductive silver films, exhibiting an excellent sensitivity of 5.9 kPa <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> with a wide linearity of 0-15 kPa and ultralow operating voltage of 20 mV. Meanwhile, the flexible pressure sensor could be used for sensitively monitoring human physiological signals, such as wrist pulse, voice recognition, and human activities. Furthermore, a resistive pressure sensor array has been applied for detecting the spatial distribution of external pressure, indicating huge potential as wearable detectors for self-powered real-time monitoring human healthcare.

Low-frequency observations of the Giant Radio Galaxy NGC 6251

Abstract We present LOFAR observations at 150 MHz of the borderline FRI/FRII giant radio galaxy NGC 6251. This paper presents the most sensitive and highest-resolution images of NGC 6251 at these frequencies to date, revealing for the first time a low-surface-brightness extension to the northern lobe, and a possible backflow associated with the southern lobe. The integrated spectra of components of NGC 6251 are consistent with previous measurements at higher frequencies, similar to results from other LOFAR studies of nearby radio galaxies. We find the outer structures of NGC 6251 to be either at equipartition or slightly electron dominated, similar to those of FRII sources rather than FRIs; but this conclusion remains tentative because of uncertainties associated with the geometry and the extrapolation of X-ray measurements to determine the external pressure distribution on the scale of the outer lobes. We place lower limits on the ages of the extension of the northern lobe and the backflow of the southern lobe of t ≳ 250 Myr and t ≳ 210 Myr respectively. We present the first detection of polarisation at 150 MHz in NGC 6251. Taking advantage of the high Faraday resolution of LOFAR, we place an upper limit on the magnetic field in the group of B &amp;lt; 0.2 (ΛB/10 kpc)−0.5 μG for a coherence scale of ΛB &amp;lt; 60 kpc and B &amp;lt; 13 μG for ΛB = 240 kpc.