A Theoretical Study on Static Gas Pressure Measurement via Circular Non-Touch Mode Capacitive Pressure Sensor.

A circular non-touch mode capacitive pressure sensor can operate in both transverse and normal uniform loading modes, but the elastic behavior of its movable electrode plate is different under the two different loading modes, making its input-output analytical relationships between pressure and capacitance different. This suggests that when such a sensor operates, respectively, in transverse and normal uniform loading modes, the theory of its numerical design and calibration is different, in other words, the theory for the transverse uniform loading mode (available in the literature) cannot be used as the theory for the normal uniform loading mode (not yet available in the literature). In this paper, a circular non-touch mode capacitive pressure sensor operating in normal uniform loading mode is considered. The elastic behavior of the movable electrode plate of the sensor under normal uniform loading is analytically solved with the improved governing equations, and the improved analytical solution obtained can be used to mathematically describe the movable electrode plate with larger elastic deflections, in comparison with the existing two analytical solutions in the literature. This provides a larger technical space for developing the circular non-touch mode capacitive pressure sensors used for measuring the static gas pressure (belonging to normal uniform loading).

Acid-accelerated hydrolysis of NaBH4: a gas-generation reaction for diverse gas pressure biosensing.

Gas pressure biosensing is a promising portable analysis method. The gas-generation reaction is crucial to its sensitivity, speed, repeatability, and usability. However, very few gas-generation reactions are available for sensitive, safe, and diverse biosensing. Herein, acid-accelerated hydrolysis of sodium borohydride (NaBH4) was explored for the first time to achieve portable and diverse gas pressure biosensing. The slow hydrolysis and hydrogen generation of NaBH4 in alkaline medium is accelerated with increasing acidity, which increased the gas pressure in a small and sealed tube within 10 min. Thus, a label-free bioassay is easily and specifically achieved once analytes can in-situ generate acid to accelerate the hydrolysis rate of NaBH4, such as glucose, acetylcholine (ACh), adenosine triphosphate (ATP) and others. More importantly, analytes without acid generation could be quantitatively and selectively detected by combining target recognition with acid-generated biochemical reactions for enzyme-linked gas pressure biosensing. Inspired by this, aflatoxin B1 (AFB1)-aptamer interaction-triggered strand displacement reaction was combined with glucose oxidation by glucose oxidase (GOD) to detect AFB1 as low as 7.1 pM. Therefore, acid-accelerated hydrolysis of NaBH4 is powerful for developing portable, cheap, and diverse gas pressure biosensing. It opens up a new way for cheap, universal, and portable biosensing.

Advanced IoT Pressure Monitoring System for Real-Time Landfill Gas Management.

This research presents a novel stand-alone device for the autonomous measurement of gas pressure levels on an active landfill site, which enables the real-time monitoring of gas dynamics and supports the early detection of critical events. The developed device employs advanced sensing technologies and wireless communication capabilities, enabling remote data transmission and access via the Internet. Through extensive field experiments, we demonstrate the high sampling rate of the device and its ability to detect significant events related to gas generation dynamics in landfills, such as flare shutdowns or blockages that could lead to hazardous conditions. The validation of the device's performance against a high-end analytical system provides further evidence of its reliability and accuracy. The developed technology herein offers a cost-effective and scalable solution for environmental landfill gas monitoring and management. We expect that this research will contribute to the advancement of environmental monitoring technologies and facilitate better decision-making processes for sustainable waste management.

Compact Harmonic Vernier Sensor Based on an In-Fiber FPI with Three Reflector System for Simultaneous Gas Pressure and Temperature Measurement.

In this work, we proposed a sensitivity-enhanced temperature sensor, a compact harmonic Vernier sensor based on an in-fiber Fabry-Perot Interferometer (FPI), with three reflective interfaces for the measurement of gas temperature and pressure. FPI consists of air and silica cavities formulated by single-mode optical fiber (SMF) and several short hollow core fiber segments. One of the cavity lengths is deliberately made larger to excite several harmonics of the Vernier effect that have different sensitivity magnifications to the gas pressure and temperature. The spectral curve could be demodulated using a digital bandpass filter to extract the interference spectrum according to the spatial frequencies of resonance cavities. The findings indicate that the material and structural properties of the resonance cavities have an impact on the respective temperature sensitivity and pressure sensitivity. The measured pressure sensitivity and temperature sensitivity of the proposed sensor are 114 nm/MPa and 176 pm/°C, respectively. Therefore, the proposed sensor combines ease of fabrication and high sensitivity, making it great potential for practical sensing measurements.

Post-decompression bubble and inflammation interactions: a non-extensive dynamical system model.

Inert gas bubbles in tissues and in blood have been historically considered as the only triggering factors for DCS, but now many other factors are considered to affect the final outcome of a decompression profile for a certain individual. In this sense, inflammation seems to play a relevant role, not only due to the physical damage of tissues by the bubbles, but as a potentiator of the process as a whole. The present study aims to put forward a mathematical model of bubble formation associated with an inflammatory process related to decompression. The model comprises four state-variables (inert gas pressure, inert gas bubbles, proinflammatory and inflammatory factors) in a set of non-linear differential equations. The model is non-extensive: inert gas transitions between liquid and gaseous phases do not change the concentration of the dissolved gas. The relationship between bubbles and inflammation is given through parameters that form a positive feedback loop. The results of the model were compared with the experimental results of echocardiography from volunteers in two dive/decompression profiles; the model shows a very good agreement with the empirical data and previews different inflammatory outcomes for different experimental profiles. We suggest that slight changes in the parameters' values might turn the simulations from a non-inflammatory to an inflammatory profile for a given individual. Therefore, the present model might help address the problem of DCS on a particular basis.

Effect of gas pressure on municipal solid waste landfill slope stability.

Slope failure in municipal solid waste (MSW) landfills is a common environmental disaster that poses serious ecological and health risks. Landfill slope stability (SS) is sensitive to leachate levels and gas pressure (GP) caused by the degradation of organic material, but the extent of these combined effects remains poorly understood. In this study, a simplified landfill GP calculation method is presented and a circular slide method that considers the combined effects of leachate and GP is established. The results show that the landfill GP is mainly affected by the gas production rate, gas conductivity of the solid waste (SW), and landfill depth. The safety factor of landfill SS is also significantly lower when GP is considered. The distribution of GP is affected by the depth of the failure circle and SW. Landfill slope instability can be explained by localized damage caused by GP breakthrough of the filled SW. This study probably provides important guidance for the design, operation, and management of MSW landfills.

Structural Insight of MOFs under Combined Mechanical and Adsorption Stimuli.

External control over the pore size of flexible metal-organic frameworks (MOFs) has recently emerged as an intriguing concept, with possible applications to gas storage and separation. In this work we present a new pressure cell capable for the first time of monitoring through in situ X-ray powder diffraction an adsorbent powder under combined uniaxial applied mechanical stress (up to 1 GPa) and gas pressure (up to 20 bar). The combined stress-pressure clamp (CSPC) cell was successfully exploited to follow the evolution of the CO2 breathing behaviour of the prototypical complex breathing MIL-53(Al) system under mechanical compression obtaining structural evidence that this MOF can be maintained in its closed pore state upon compression, precluding its re-opening at high gas pressure (>7 bar). This novel setup shows potential for the in-operando exploration of flexible systems, in equilibrium and flow configurations.

A modified stability analysis method of landfills dependent on gas pressure.

Excessive gas pressure (GP) in landfills is a potential triggering mechanism for slope failure, which is rarely considered in analytical models. This paper presents a modified analytical model for landfill stability dependent on GP. A two-layered GP model is established to describe the GP above and below the leachate level. The distribution of GP is then used to calculate the factor of safety (FS) using a modified wedge stability analysis method. It is found that the lack of consideration of the GP in landfill stability analysis leads to serious overestimation of the FS. In addition, the GP gas pressure within the landfill accelerates the critical interface of a multilayer liner system shifting from one to another. A new estimation criterion for FS is proposed. The proposed criterion can directly estimate the stability of the landfill by the field-tested pore pressure. Finally, the proposed method is applied to estimate the slope failure of Xiaping landfill in Shenzhen, and the results verify the proposed method.

Silicone Rubber Based Highly Sensitive Fiber-Optic Fabry-Perot Interferometric Gas Pressure Sensor.

A simple, compact, and highly sensitive gas pressure sensor based on a Fabry-Perot interferometer (FPI) with a silicone rubber (SR) diaphragm is demonstrated. The SR diaphragm is fabricated on the tip of a silica tube using capillary action followed by spin coating. This process ensures uniformity of its inner surface along with reproducibility. A segment of single mode fiber (SMF) inserted into this tube forms the FPI which produces an interference pattern with good contrast. The sensor exhibits a high gas pressure sensitivity of -0.68 nm/kPa along with a low temperature cross-sensitivity of ≈ 1.1 kPa/°C.

MEMS-Based Reflective Intensity-Modulated Fiber-Optic Sensor for Pressure Measurements.

A reflective intensity-modulated fiber-optic sensor based on microelectromechanical systems (MEMS) for pressure measurements is proposed and experimentally demonstrated. The sensor consists of two multimode optical fibers with a spherical end, a quartz tube with dual holes, a silicon sensitive diaphragm, and a high borosilicate glass substrate (HBGS). The integrated sensor has a high sensitivity due to the MEMS technique and the spherical end of the fiber. The results show that the sensor achieves a pressure sensitivity of approximately 0.139 mV/kPa. The temperature coefficient of the proposed sensor is about 0.87 mV/°C over the range of 20 °C to 150 °C. Furthermore, due to the intensity mechanism, the sensor has a relatively simple demodulation system and can respond to high-frequency pressure in real time. The dynamic response of the sensor was verified in a 1 kHz sinusoidal pressure environment at room temperature.

Temperature-Independent Gas Pressure Sensor with High Birefringence Photonic Crystal Fiber-Based Reflective Lyot Filter.

A novel temperature-independent gas pressure sensor based on a reflective fiber Lyot filter is presented in this paper. The reflective fiber Lyot filter is simply consist of a fiber polarizer and a segment of hollow-core photonic bandgap fiber (HB-PCF). The HB-PCF plays the role of birefringent cavity in the reflective fiber Lyot filter and works as the sensor head in the gas pressure sensor. Experiment results show that the responses of the sensor to gas pressure and temperature are 3.94 nm/MPa and -0.009 nm/°C, indicating that the proposed gas pressure is sensitive to gas pressure rather than temperature. Coupled with the advantages of simple structure, easy manufacture, high sensitivity and temperature independent, the proposed reflective fiber Lyot filter-based gas pressure sensor holds great potential application in the field of gas pressure monitoring.

Temperature monitoring during a water-injection test using a vertical well in a newly filled MSW layer of a landfill.

High temperature may adversely affect municipal solid waste (MSW) biodegradation and lead to an increase in the deformation of high-density polyethylene (HDPE) pipes used for the collection of leachate and landfill gas in landfills. The test in this study was to change the waste temperature around the vertical injection well by water injection using a vertical well. The test was conducted intermittently with two different flowrates in a newly filled MSW layer of a landfill. The temperature, gas pressure and leachate level in the test area were simultaneously monitored during this study. The results showed that the waste temperature around the vertical injection well was effectively changed by water injection, which did not result in a significant rise in the leachate level. During water injection, the waste temperature influence distance in the horizontal direction increased with depth from the leachate level to the bottom of the injection well. The bottom temperature of the injection well decreased to near the water-injection temperature. The range of influence of the waste temperature caused by intermittent water injections slightly increased in this test. After water injection was stopped, the waste temperature near the vertical injection well increased quickly initially, and then the increments became more gradual with time. When the leachate level recovered stably, there was still a temperature gradient around the injection well within the range of influence. The temperature and gas pressure in the waste above the leachate level and far away from the injection well were slightly influenced by water injection.

Cascaded-Cavity Fabry-Perot Interferometric Gas Pressure Sensor based on Vernier Effect.

An extrinsic Fabry-Perot interferometer (EFPI) composed of double fiber FP cavities in a glass capillary tube to generate Vernier effect has been fabricated and employed for gas pressure sensing. A lead-in single-mode fiber (LSMF) and a reflective single-mode fiber (RSMF) were inserted into the capillary tube to form a FP cavity. Femtosecond (fs) laser was used to ablate openings on a capillary tube for gas passage to the FP cavity. A fusion hole was also drilled on the end face of a SMF by fs laser. The sensitivity of the sensor is enhanced due to Vernier effect. Experimental results show that the sensitivity was as high as 86.64 nm/MPa in the range of 0~0.6 MPa, which is 32.8 times larger than that of an open-cavity EFPI sensor without Vernier effect. The temperature cross-sensitivity of the sensor was measured to be about 5.18 KPa/°C. The proposed sensor was characterized by its high sensitivity, compact structure and ease of fabrication, and would have extensive application prospects in gas sensing fields.

Diaphragm-Free Fiber-Optic Fabry-Perot Interferometric Gas Pressure Sensor for High Temperature Application.

A diaphragm-free fiber-optic Fabry-Perot (FP) interferometric gas pressure sensor is designed and experimentally verified in this paper. The FP cavity was fabricated by inserting a well-cut fiber Bragg grating (FBG) and hollow silica tube (HST) from both sides into a silica casing. The FP cavity length between the ends of the SMF and HST changes with the gas density. Using temperature decoupling method to improve the accuracy of the pressure sensor in high temperature environments. An experimental system for measuring the pressure under different temperatures was established to verify the performance of the sensor. The pressure sensitivity of the FP gas pressure sensor is 4.28 nm/MPa with a high linear pressure response over the range of 0.1-0.7 MPa, and the temperature sensitivity is 14.8 pm/°C under the range of 20-800 °C. The sensor has less than 1.5% non-linearity at different temperatures by using temperature decoupling method. The simple fabrication and low-cost will help sensor to maintain the excellent features required by pressure measurement in high temperature applications.

Optical Fiber-Tip Sensors Based on In-Situ µ-Printed Polymer Suspended-Microbeams.

Miniature optical fiber-tip sensors based on directly µ-printed polymer suspended-microbeams are presented. With an in-house optical 3D µ-printing technology, SU-8 suspended-microbeams are fabricated in situ to form Fabry⁻Pérot (FP) micro-interferometers on the end face of standard single-mode optical fiber. Optical reflection spectra of the fabricated FP micro-interferometers are measured and fast Fourier transform is applied to analyze the cavity of micro-interferometers. The applications of the optical fiber-tip sensors for refractive index (RI) sensing and pressure sensing, which showed 917.3 nm/RIU to RI change and 4.29 nm/MPa to pressure change, respectively, are demonstrated in the experiments. The sensors and their optical µ-printing method unveil a new strategy to integrate complicated microcomponents on optical fibers toward 'lab-on-fiber' devices and applications.

Penetrating chest trauma caused by a blank cartridge actuated rubber ball projectile: case presentation and ballistic investigation of an uncommon weapon type.

Recently, an increasing number of an uncommon weapon type based on a caliber 6-mm Flobert blank cartridge actuated revolver which discharges 10-mm-diameter rubber ball projectiles has been confiscated by police authorities following criminal offenses. A recent trauma case presenting with a penetrating chest injury occasioned an investigation into the basic ballistic parameters of this type of weapon. Kinetic energy E of the test projectiles was calculated between 5.8 and 12.5 J. Energy density ED of the test projectiles was close to or higher than the threshold energy density of human skin. It can be concluded that penetrating skin injuries due to free-flying rubber ball projectiles discharged at close range cannot be ruled out. However, in case of a contact shot, the main injury potential of this weapon type must be attributed to the high energy density of the muzzle gas jet which may, similar to well-known gas or alarm weapons, cause life-threatening or even lethal injuries.

Determining the optimal transmembrane gas pressure for nitrification in membrane-aerated biofilm reactors based on oxygen profile analysis.

The goal of this study was to investigate the effect of transmembrane gas pressure (P g) on the specific ammonium removal rate in a membrane-aerated biofilm reactor (MABR). Our experimental results show that the specific ammonium removal rate increased from 4.98 to 9.26 gN m(-2) day(-1) when P g increased from 2 to 20 kPa in an MABR with a biofilm thickness of approximately 600 µm. However, this improvement was not linear; there was a threshold of P g separating the stronger and weaker effects of P g. The ammonium removal rate was improved less significantly when P g was over the threshold, indicating that there is an optimal threshold of P g for maximizing ammonium removal in an MABR. The change in oxygen penetration depth (d p) is less sensitive to P g in the ammonia-oxidizing active layer than in the inactive layer in membrane-aerated biofilm. The location of the P g threshold is at the same point as the thickness of the active layer on the curve of d p versus P g; thus, the active layer thickness and the optimal P g can be determined on the basis of the changes in the slope of d p to P g.

Innovative High Gas Pressure Microscopy Chamber Designed for Biological Cell Observation.

An original high-pressure microscopy chamber has been designed for real-time visualization of biological cell growth during high isostatic (gas or liquid) pressure treatments up to 200 MPa. This new system is highly flexible allowing cell visualization under a wide range of pressure levels as the thickness and the material of the observation window can be easily adapted. Moreover, the design of the observation area allows different microscope objectives to be used as close as possible to the observation window. This chamber can also be temperature controlled. In this study, the resistance and optical properties of this new high-pressure chamber have been tested and characterized. The use of this new chamber was illustrated by a real-time study of the growth of two different yeast strains - Saccharomyces cerevisiae and Candida viswanathii - under high isostatic gas pressure (30 or 20 MPa, respectively). Using image analysis software, we determined the evolution of the area of colonies as a function of time, and thus calculated colony expansion rates.

Heterogeneous Phase Microwave-Assisted Reactions under CO2 or CO Pressure.

The present review deals with the recent achievements and impressive potential applications of microwave (MW) heating to promote heterogeneous reactions under gas pressure. The high versatility of the latest generation of professional reactors combines extreme reaction conditions with safer and more efficient protocols. The double aims of this survey are to provide a panoramic snapshot of MW-assisted organic reactions with gaseous reagents, in particular CO and CO2, and outline future applications. Stubborn and time-consuming carbonylation-like heterogeneous reactions, which have not yet been studied under dielectric heating, may well find an outstanding ally in the present protocol.

Channels formation in cellulose materials by accelerated transport of gas molecules and glycerin.

In this study, a microporous separator was produced using cellulose acetate (CA), which demonstrates heightened thermal stability in comparison to existing materials like polypropylene (PP) or polyethylene (PE). Furthermore, a pliable component was integrated into the CA membrane using glycerin as the plasticizing agent. Subsequently, gas pressure was exerted onto these areas to induce the formation of nano-sized pores. Examination through Scanning Electron Microscopy (SEM) unveiled the presence of abundant pores in the glycerin-plasticized areas. This substantiates that the pores generated under gas pressure were not only more uniform but also smaller than those created under water pressure. The interaction between CA and glycerin was validated using Fourier-Transform Infrared Spectroscopy (FT-IR), offering confirmation that a portion of the glycerin was extracted following the application of gas pressure. Additionally, the application of Thermogravimetric Analysis (TGA) allowed for an assessment of the thermal stability of the CA membrane, along with a verification of glycerin's removal post gas pressure treatment. The findings indicated that the incorporation of glycerin diminished the thermal stability of the CA membrane due to the plasticization effect. Furthermore, it was observed that a minor quantity of glycerin still persisted after the gas pressure treatment. Following the analysis of gas permeation, the porosity of the CA membrane was quantified at 78.8 %, exhibiting an average pore size measuring 224 nm.