Changes In External Pressure Research Articles

Stress Analysis of Radial Compression Disk Based on MATLAB

Elastic mechanics is an important branch of solid mechanics, mainly studies the deformation and internal force of elastic objects under the action of external forces and other external factors, also known as elastic theory. The study object of elasticity is elastomer. The detailed theoretical structure helps us solve more practical engineering problems. We used Matlab software in the data simulation for visualization processing. On the basis of the study of elasticity, this paper explores the stress distribution of the uniform ideal elastic body to the radial compression disk model, and observes the change of the stress of the radial compression disk when the external pressure changes gradually. The expressions of the corresponding stress components , and are obtained by using the theory of normal concentrated force on the boundary of a half plane body. The stress solutions considering the thickness t of the disk are derived. Finally, the drawing software in Matlab software is used to visualize the theoretical derivation results in order to intuitively feel the change of stress. After the data simulation, the data simulation results are compared with the stress analysis results derived from the theoretical deduction, and the conclusion is drawn.

Dynamic characteristics and prediction and control models of subsonic exhaust from a container

This study combines experimental measurements, numerical simulations, and theoretical analysis to investigate the subsonic discharge process in a container under normal temperature and pressure conditions. Experimental data captured the internal pressure dynamics during exhaust at the atmospheric environmental pressure. Numerical simulations using OpenFOAM validated the isothermal exhaust model against the experimental results. Under the assumption of ideal gas and isothermal processes, a nonlinear differential equation was derived to describe the evolution of the container's internal pressure. This equation was simplified for a specific range of pressure ratios, yielding analytical solutions for the internal pressure of the container under both constant and variable external pressures. The effectiveness of the expressions of pressure inside the container was verified by comparing them with experimental and numerical simulation data. We further developed a formula for predicting exhaust mass flow rate, with a prediction error within 9%. An improved formula was subsequently proposed to reduce the error to below 0.4%, enhancing prediction accuracy. For containers with variable external pressure, a method for controlling the exhaust mass flow rate by predicting external pressure changes was proposed, demonstrating its effectiveness in achieving precise control.

Experimental Study on Coal Oxidation and Temperature Rise Under Reciprocating Air Leakage

ABSTRACT Reciprocating air leakage often occurs in the goaf of coal mines because of changes in internal or external pressure. However, its impact on the spontaneous combustion of coal in the goaf is uncertain. Therefore, a comparative study of constant air leakage and reciprocating air leakage was carried out using a self-built system. The results indicate that reciprocating air leakage promotes coal oxidation and produces higher CO levels compared to constant air leakage. Further investigation was carried out to examine the effect of air leakage rate and reciprocating half-cycle (referred to as half-cycle hereafter) on coal oxidation and temperature rise. The results show that there is a linear relationship between resistance and air leakage rate in the coal oxidation heating space; however, the half-cycle length has little effect on resistance. The influence of a fixed air leakage rate on temperature and CO concentration does not always increase, with the maximum value achieved at 1.2 m3/h. Shorter half-cycles result in higher temperatures and CO concentrations. Gradually increasing air leakage rates and shortening half-cycles can promote coal oxidation and temperature rise and lead to higher CO production compared to previous scenarios. Additionally, the effect of using four different air leakage rates or half-cycle lengths is greater than that of using two. These research findings offer a theoretical foundation for preventing and controlling coal spontaneous combustion in goafs under complex air leakage conditions.

Can The Diamond Fraud Model Influence the Occurrence of Fraudulent Financial Reporting?

This research is quantitative in nature and is intended to examine whether can the diamond fraud model influence the occurrence of fraudulent financial reporting. The fraud diamond theory is measured by pressure (financial stability, financial targets, and external pressure), opportunity (ineffective monitoring), rationalization (change in auditor), and capability (change of director). State-owned business (BUMN) registered on the stock exchange of Indonesia between 2016 and 2022 comprise the population considered within this research. Purposive sampling was utilized in this research to select 154 companies for the sample. In this work, logistic regression analysis is the analytical method. The findings within this research show that the variables of financial stability and financial targets have a significant negative impact on the occurrence of fraudulent financial reporting, while the variables of external pressure and director change do not affect the occurrence of fraudulent financial reporting. The variables of ineffective monitoring and change in auditors also affect the occurrence of fraudulent financial reporting .

A Study on Long-Term Cycling Performance by External Pressure Change for Pouch-Type Lithium Metal Batteries

<p>Lithium dendrite formation is one of the most significant problems with lithium metal batteries. The lithium dendrite reduces the lithium metal batteries’ cycling life and safety. To apply consistent external pressure to a lithium metal pouch cell, we design a press jig in this study. External pressure creates dense lithium morphology by preventing lithium dendrite formation. After 300 cycles at 1 C, the cells with the external pressure perform far better than the cells without it, with a cycling retention of 97.8%. The formation of stable lithium metal is made possible by external pressure, which also enhances safety and cyclability.</p>

Impact of coupled effects of airtight components at variable cross-section location on vehicle airtightness in Wuhan metro

To determine the variation in airtightness performance of metro trains under the coupling state of airtight components, a field-based experimental approach was employed to test the air pressure changes during metro train operations. The study analyzed the impact of the coupling effects of the air conditioning pressure wave protection valve, pneumatic auxiliary door lock devices, and passageway drainage plug on the interior pressure changes of the train while operating in challenging environmental conditions. Following industry standards, the assessment evaluated whether the rate of interior pressure change and the train’s dynamic sealing index met the specified requirements. The findings indicate that, with airtight components in an enabled state, the peak-to-peak value of interior pressure change relative to external pressure change decreased by 15% to 39%. Conversely, when airtight components were not enabled, the reduction was only 0% to 25%. Under enabled airtight component conditions, the train’s dynamic sealing index was within the 2-3 s range, whereas in the disabled state, the dynamic sealing index was less than 1 s. The activation of airtight components plays a crucial role in improving train airtightness by significantly reducing the amplitude of interior pressure changes, thereby ensuring both train airtightness and passenger comfort. The results provide valuable insights for the optimization of train design and operation in order to maintain passenger safety and comfort.

Optical pressure sensor based on Fano resonance in a coupled resonator system

Optical pressure sensor plays a very important role in micro deformation detection, environmental monitoring, and medical fields. However, the quantitative relationship between the applied pressure and the optical response of the resonator before and after deformation is difficult to obtain. In this paper, a coupled resonator system based on metal-insulator-metal waveguide for optical pressure sensor is proposed. The mechanical properties of the system and the optical transmission properties before and after applied pressure are analyzed in detail by using the finite element method. Simulation results show that the maximum deformation of the resonator has a simple linear relationship with the applied pressure. We give a direct definition of the sensitivity of the optical pressure sensor. And based on the Fano resonance phenomenon caused by the coupling the slot cavity with the groove cavity, the optical pressure sensor with a sensitivity of 6.75 nm/MPa is achieved. In addition, we add stub resonator to obtain double Fano resonance phenomenon, and with the change of external pressure, the two Fano line types show different change laws. Specifically, a suitable pressure value can make a double Fano resonance become a single Fano resonance. The special features of our suggested structure are applicable to detecting optical property changes under different pressures, chemical high pressure experimental measurement and study of chemical reaction kinetics process.

NONLINEAR BUCKLING SENSITIVITY ANALYSIS OF THIN-WALLED LINED COMPOSITE PIPE LINER

In order to study the buckling failure of lining delamination of thin-walled lined composite pipe, a numerical analysis model was established by using bilinear cohesion relationship, the buckling mode and critical load of the composite pipe obtained by linear buckling are taken as reference values, the interlayer initial defects were introduced to carry out the nonlinear buckling analysis on the composite pipe lining structure with thin wall lining. The relative displacement curve and deformation morphology of the relative displacement of the lining with the change of external pressure were obtained, and the results are consistent with the existing test results. Based on this model, the buckling sensitivity of lining pipe was analyzed. The results show that the size of interlayer initial defect is the main factor that affects the critical buckling pressure of liner, but it has little influence on the propagation pressure after buckling; However, the increase of interlayer bonding effect significantly improves the buckling resistance and propagation pressure of lining pipe; The ratio of outer tube wall diameter to thickness and liner thickness have significant effects on the critical buckling pressure of liner. The research results provide a reference for determining the interlayer bonding effect and the optimal design of the minimum thickness of the inner liner.

Fabrication of Highly Sensitive Capacitive Pressure Sensors Using a Bubble-Popping PDMS.

Attempts have been made to introduce microstructures or wrinkles into the elastomer surface to increase the sensitivity of the elastomer. However, the disadvantage of this method is that when a force is applied to the pressure sensor, the contact area with the electrode is changed and the linear response characteristic of the pressure sensor is reduced. The biggest advantage of the capacitive pressure sensor using an elastomer is that it is a characteristic that changes linearly according to the change in pressure, so it is not suitable to introduce microstructures or wrinkles into the elastomer surface. A method of increasing the sensitivity of the capacitive pressure sensor while maintaining the linearity according to the pressure change is proposed. We proposed a bubble-popping PDMS by creating pores inside the elastomer. The sensitivity of the pressure sensor made of the bubble-popping PDMS was approximately 4.6 times better than that of the pressure sensor without pores, and the pressure sensor made of the bubble-popping PDMS showed a high linear response characteristic to the external pressure change. These results show that our pressure sensor can be used to detect applied pressures or contact forces of e-skins.

A hybrid interferometer sensor for simultaneous measurement of temperature and gas pressure based on tapered seven-core fiber and PDMS

A novel hybrid interferometer sensor composed of a tapered seven-core fiber (TSCF) and a polydimethylsiloxane (PDMS) cap at the end face of a TSCF is proposed for simultaneous measurement of temperature and gas pressure. TSCF forms a Michelson interferometer (MI), and the PDMS cap on the end surface of TSCF forms a Fabry–Pérot interferometer (FPI). The sensing head consisted of a cascade of MI and FPI. When the external temperature or gas pressure changes, owing to the thermal effect or elastic deformation of PDMS, the interference spectrum of the FPI shifts significantly, so the FPI is very sensitive to temperature and gas pressure. MI, which is made of quartz optical fiber, is sensitive only to temperature and is not to gas pressure. The experimental results show that FPI has a temperature sensitivity of −0.22 nm °C−1 in the temperature range of 40 °C–80 °C, and a gas pressure sensitivity of −2.27 nm MPa−1 in the gas pressure range of 0–0.3 MPa. MI has a temperature sensitivity of 0.05 nm °C−1 in the temperature range of 40 °C–80 °C, and a gas pressure sensitivity of zero in the gas pressure range of 0–0.3 MPa. Using the temperature and gas pressure sensitivities of FPI and MI to construct a measurement matrix, it is possible to simultaneously measure temperature and gas pressure, eliminating their cross-sensitivity. This sensor has the comprehensive advantages of compact structure, small size, easy manufacturing, low cost, high reliability, and high sensitivity, and is expected to be applied in industrial practice.

Controlling the Structure and Photoproperties of SiV Diamond Nanoslab at Room Temperature by External Pressure for Optical Measurements of Temperature and Pressure

External pressure is one of the key parameters to understand photoemission nanomaterials since the external pressure changes their photoproperties without introducing any chemical treatment. Here, we computationally elucidated the effects of the external pressure on structures, orbitals, photoproperties, and vibrational dynamics of a silicon vacancy (SiV) diamond nanoslab. We studied its attributes not only on the ground state at 0 K but also on the excited state around room temperature (RT) using an ab initio molecular dynamics simulation. We directly and mechanically pressed the SiV diamond nanoslab fluctuating around RT to mimic an actual external pressure usually generated in an anvil cell at RT. We found that the compression induces the shrunk SiV defect structures, the rearranged defect orbital energies, the switch of the optical transition from the SiV–SiV excitation to the nanoslab–SiV excitation, the hybridization of the SiV with nanoslab carbon (C) orbitals, and the blue shift and the smaller intensity of the spectra of the Si atom oscillation and the inner C–C bond vibration. The energies of absorption, emission, and zero-phonon line do not change monotonically but have the maxima below a 7%-compression. Especially, the absorption energy differs more between 0 K and RT as the compression increases, while the largest deviation between 0 K and RT in the emission energy appears below the 7%-compression. It is remarkable that all of these changes are caused only by the mechanical compression and that the compression differently pronounces the temperature effect. The obtained insights will provide a way to effectively control a split-vacancy center to be a promising single-photon source for nanoscale optical measurements of temperature and pressure in a compressed nanoscale material.

High-Temperature and High-Pressure Fiber Microsphere Fabry–Perot Sensor Based on Vernier Effect and FBG

A pressure and temperature sensor based on dual Fabry-Perot interferometers (F-PIs) using Vernier effect and fiber Bragg grating (FBG) in hollow silica microsphere-cavity (HSMC) structure is demonstrated theoretically and experimentally. The sensor consists of a F-P cavity formed by inserting the FBG into the HSMC and a reference F-P cavity. Two structures are connected by a 50% coupler to generate the Vernier effect. The change of external pressure will change the length of the microsphere F-P cavity. Utilizing the characteristics that FBG is temperature sensitive and not effected by pressure, the simultaneous detection of temperature and pressure can be realized by demodulating equation. With a pressure sensitivity of 49.5nm/MPa and a temperature sensitivity of 14.3pm/°C, the sensor is achieved pressure detection at 300°C ranging from 0 to 0.8 MPa. The sensor has the characteristics of temperature compensation, high production efficiency, low cost, strong robustness, self-encapsulation and so on. It has a broad prospect in the field of high temperature and high pressure detection.

Nonlinear Bending and Buckling of Oblate Ellipsoidal Shells with Variable Thickness Under External Pressure and Temperature Change

Nonlinear Bending and Buckling of Oblate Ellipsoidal Shells with Variable Thickness Under External Pressure and Temperature Change

Rolling flexible double-MXenes Ti3C2Tx/V2CTx hybrid films for microsupercapacitors

Two-dimensional (2D) MXenes with slit-shaped ion diffusion channels have been hot candidates for flexible microsupercapacitors (MSCs), while the large-scale manufacturing of MSCs based on MXene-based films remains a challenge. Herein, different MXenes, Ti3C2Tx and V2CTx nanosheets were stacked and rolled into large-area double-MXenes hybrid films. Then, the large-area hybrid films can be efficiently processed into MSCs by the laser-cutting method. Embedding Ti3C2Tx nanosheets between V2CTx layers to impede the self-restacking of V2CTx and expand the interlayer spacing resulted in high capacitance up to 496F g−1 (2.3F cm−2) and good rate performance of the hybrid films. The assembled all-solid-state MSCs delivered a high energy density of 4.9 mWh g−1 at 350 mW g−1 and long cycling life. Moreover, serving as a power source unit, the MSCs can power a piezoresistive sensor to capture the changes in external pressures. The proposed rolling method for fabricating large-area double-MXenes hybrid films and MSCs was also applicable for other MXenes and 2D nanomaterials, which promoted their applications in flexible MSCs and portable electronic devices.

Financial Statement Fraud, Audit Committee and Audit Quality: Insight into Fraud Diamond Theory

Based on the Fraud diamond theory, the study investigates whether the audit and quality committee can strengthen or weaken financial statement fraud. this study aims to prove the influence of diamond fraud on the potential for financial statement fraud and that the audit and quality committee can strengthen or weaken the effect of diamond fraud on the potential for financial statement fraud. This study sample was selected using the purposive sampling method and obtained 850 observations from 214 companies’ sector non-financial listed on Indonesia Stock Exchange from 2016-2019. Furthermore, this study uses secondary data obtained from www.idx.co.id and each company's website. Data analysis in this study using logistic regression. The result of this study indicates that variable financial stability, board change, and financial target positively affect the detection of fraudulent financial statements. In contrast, variable external pressure, ineffective monitoring, and auditor change do not affect the detection of fraudulent financial statements. As the first variable moderating in this study, the audit committee does not affect weakening the relationship between fraud diamonds and fraudulent financial statements. On the other hand, audit quality, as the second moderating variable in this study, weakens the relationship between external pressure and ineffective monitoring of fraudulent financial statements. But, audit quality does not weaken the relationship between financial stability, financial target, audit change, and board change on the fraudulent financial statement.

FRAUD PENTAGON DAN ANCAMAN KEBANGKRUTAN STUDI PADA PERUSAHAAN PERBANKAN

The purpose of the study was to determine the effect of the fraud pentagon on the threat of bankruptcy in banking companies listed on the Indonesia Stock Exchange in 2018-2020. The fraud Pentagon consists of five indicators namely external pressure, effective monitoring, auditor turnover, director turnover and the number of frequent CEO photos. While the threat of bankruptcy is measured by the X-Score. The method of data analysis is descriptive and hypothesis testing using multiple linear regression analysis. The research sample is 122 financial statements from 42 banking companies listed on the Indonesia Stock Exchange in 2018-2020. The results showed that external pressure variables and changes in auditors had an effect on the threat of bankruptcy. While the variables of effective supervision, the change of directors and the number of CEO photos that often have no effect on the threat of bankruptcy

DETECTING FRAUD FINANCIAL STATEMENTS IN MANUFACTURING COMPANIES INDONESIA

The purpose of this research is toand analyze the influence of the four elements infraud triangle that is pressure, opportunity, and rationalization. to detect the possibility of fraudulent financial statements (financial statement fraud). The four elements will be divided into 5 variables, specifically financial stability,external pressure, ineffective monitoring, nature of industry, and change in auditors.to find the possibility of fraudulent financial statements as measured by the M Score modelin manufacturing companiesin the 2018-2021 period. The results of the study show that of the six variables used in the study, there is one (1) variable, namely the nature of the industry which has a significant effect on the possibility of fraudulent financial statements. While the other five (5) variables financial targets, external pressure, ineffective monitoring, and auditor changes do not affect the likelihood of fraudulent accounts. The contribution of the results of this our riset that manufacturing companies in that year are likely to be more concerned or careful the nature of industry that has a significant impact, this will affect the sustainability of the business in the future.

Experimental Study of the Acoustic Cavitation Threshold in Sunflower Oil Depending on Different Impact Regime

In engineering problems associated with acoustic wave propagation in a liquid, cavitation onset could be an adverse phenomenon, or, conversely, a required process. In both cases, knowledge of the ultrasonic parameters that lead to cavitation onset under given external conditions is relevant and necessary for solving both fundamental and practical problems. The present work proposes experimental results of studying the threshold of acoustic cavitation, which was implemented at different ultrasound frequencies with a change in external pressure, power of transducer and temperature of the liquid. The experiments were carried out for sunflower oil. The test findings demonstrated how the cavitation threshold changes with varying the power of ultrasound exposure in time. In addition, the effect of external pressure fluctuations on cavitation onset was investigated. The obtained results contribute to the understanding of cavitation processes and could be necessary for verification of theoretical models.

Transient flows and migration in granular suspensions: key role of Reynolds-like dilatancy

We investigate the transient dynamics of a sheared suspension of neutrally buoyant particles in pressure-imposed rheology configuration, subject to a sudden change in shear rate or external pressure. Discrete element method simulations show that, depending on the flow parameters (particle and system size, initial volume fraction), the early stress response of the suspension may differ strongly from the prediction of the suspension balance model based on the steady-state rheology. We show that a two-phase model incorporating the Reynolds-like dilatancy law of Pailha & Pouliquen (J. Fluid Mech., vol. 633, 2009, pp. 115–135), which prescribes the dilation rate of the suspension over a strain scale $\gamma _0$ , captures quantitatively the suspension dilation/compaction over the whole range of parameters investigated. Together with the Darcy flow induced by the pore pressure gradient during dilation or compaction, this Reynolds-like dilatancy implies that the early stress response of the suspension is non-local, with a non-local length scale $\ell$ that scales with the particle size and diverges algebraically at jamming. In regions affected by $\ell$ , the stress level is fixed, not by the steady-state rheology, but by the Darcy fluid pressure gradient resulting from the dilation/compaction rate. Our results extend the validity of the Reynolds-like dilatancy flow rule, initially proposed for jammed suspensions, to flowing suspension below the critical volume fraction at which the suspension jams, thereby providing a unified framework to describe dilation and shear-induced migration. They pave the way for understanding more complex unsteady flows of dense suspensions, such as impacts, transient avalanches or the impulsive response of shear-thickening suspensions.

Mathematical Model of the Decomposition of Unstable Gas Hydrate Accumulations in the Cryolithozone

We present a generalization of the mathematical model of gas discharge from frozen rocks containing gas-saturated ice and gas hydrates in a metastable state (due to the self-preservation effect) caused by the drop in external stress associated with various geodynamic factors. These factors can be attributed, for example, to a decrease in hydrostatic pressure on a gas-bearing formation due to glacier melting, causing an isostatic rise, or to the formation of linear depressions in the bottom topography on the shelf due to iceberg ploughing. A change in external pressure can also be associated with seismic and tectonic deformation waves propagating in the lithosphere as a result of ongoing strong earthquakes. Starting from the existing hydrate destruction model, operating at the scale of individual granules, we consider a low-permeable hydrate and ice-saturated horizontal reservoir. Generalization is associated with the introduction of a finite threshold for the external pressure drop, which causes the destruction of the gas hydrate and gas-saturated microcavities of supramolecular size. This makes it possible to take into account the effect of anomalously high pressures occurring in the released gas as a result of partial hydrate dissociation. Numerical and approximate analytical solutions to the problem were found in the self-similar formulation. A parametric study of the solution was carried out, and regularities of the hydrate decomposition process were revealed.