Applied Pressure Levels Research Articles

An Efficient Design of the Piezoresistive Pressure Sensor Applied for Micro Aerial Vehicle

In this research, the developing process of a piezoresistive pressure sensor working in the atmosphere environment applied in micro aerial vehicle using the MEMS fabrication method is introduced. The sensor consists of four Au/Cr piezoresistors in a Wheatstone bridge configuration on a wet oxidized silicon diaphragm. To fabricate the sensor, three lithographic steps were conducted: the first one is to define the resistors and Au/Cr lines/pads, the second and the third ones are to determine the width and the thickness of the square SiO2/Si diaphragm, respectively. The sensor diaphragm shape and thickness were defined by the anisotropic etching of Si in tetramethylammonium hydroxide (TMAH) solution, and the resistors array are formed by sputtering and wet etching method. The sensor size is 6000 μm by 6000 μm. The sensor output voltage was measured for various applied pressure levels from -0.9to 1.2 bar with 5V voltage supply. The fabricated pressure sensor also exhibits a sensitivity of 50.1 mV/bar

Time course of optic nerve sheath dilation: In vitro response characteristics to controlled pressure elevations

BackgroundOptic nerve sheath (ONS) dilation indicates intracranial pressure elevation under clinical conditions but limited data exist with regard to the dynamics of sheath expansion. ObjectiveTo assess the time course of ONS widening and its stability under controlled pressure conditions in vitro. MethodsPre-defined pressure steps up to 65 mmHg were applied to the perineural space of ex-vivo human optic nerves (n = 16). Using ultrasound, the optic nerve sheath diameter (ONSD) was monitored over 500 s. Re-tests at low-pressure levels concluded each experimental series. ResultsIn most cases, 50% of the total diameter-change were achieved within 50 s after pressure onset and 95% of the maximal diameter after 200 s. The diametric gains in each experiment were strongly correlated with the applied pressure levels (coefficient of variance 0,96) within preparations with variability of the transfer function across preparations. The time course of the dilation was found to follow an approximate natural logarithmic function (R2 = 0.93–0.99). The re-test condition revealed unchanged time course properties (5% significance level) despite starting regularly from a higher baseline-diameter after preceding exposures. ConclusionsONS dilation commences rapidly after pressure exposure with a predictable time course over 3–4 min. Elasticity changes presumably affecting trabecular structures cause upward shifts of the optic nerve sheath pressure response. Clinically, ONSD shifts should be considered in serial measurements for increasing intracranial pressure monitoring, but relevant response delays are absent for lower or higher changes of intracranial pressure.

Fabrication and characterization of soybean straw and polylactide acid-based hybrid bio-board

Biodegradable bio-board is held together by the self-bonding ability of natural fibre rather than by the synthetic resin adhesives used in traditional fibreboard. This provides a promising way to reduce the use and release of toxic substances. However, the hydrophilic characteristic of natural fibres gives bio-board poor water resistance compared to conventional fibreboards. Therefore, the objective of this study was to fabricate a hybrid bio-board in a wet forming process using soybean straw fibre with polylactic acid (PLA) added as a binder at different mass percentages. The effects of applied pressure during fabrication on the mechanical properties, water resistance properties, and wettability of hybrid bio-board were investigated. The thermal stability, spectroscopic characteristics, and morphological properties were also analysed. The addition of PLA weakened the bending strength and tensile strength of the hybrid bio-board made at each of three applied pressure levels. Fortunately, the hybrid bio-board with 10 and 30% PLA contents could maintain a considerable bending strength higher than 35 MPa when made with 8 MPa of applied pressure. The addition of PLA greatly improves the water-resistant performance of the board. Even with only 10% PLA, the water absorption and thickness swelling rates were reduced by more than half. We argue that PLA could be utilized as a latent natural binder to make hybrid bio-board using agricultural straw fibre; however, an environmentally friendly coupling agent is needed to improve the mechanical properties.

Effect of high hydrostatic pressure on microbial inactivation and quality changes in carrot-orange juice blends at varying pH

This study investigates the effect of high hydrostatic pressure, also known as high pressure processing (HPP), on microbial inactivation and changes in physicochemical characteristics of carrot-orange juice blends at different pH values. HPP conditions (200–400 MPa, up to 5 m) were evaluated to reach at least 5-log inactivation of L. innocua (ATCC 51742) in each blend. HPP at 300 MPa for 2 m, 400 MPa for 1 m, and 400 MPa for 3 m achieved more than 6-log reduction of L. innocua in pH 4, pH 5, and pH 6 blends, respectively. Ascorbic acid (16–45 mg/100g), total carotenoid (66–241 mg/L), and total phenolic (30–44 mg/L) contents did not significantly change after HPP compared to the corresponding untreated blends. The natural microbiota (i.e. aerobic mesophilic bacteria) was kept below 2-log CFU/mL for 28 d of storage. pH and total soluble solids remarkably changed for untreated blends in 10 d while HPP-treated blends were more stable during 28 d. Color attributes (L*, a*, b*) were retained after HPP and during storage. This study identified less intense high pressure processes for carrot-orange juice blends compared to commercially applied pressure levels (i.e. 600 MPa) to produce microbiologically stable blends with preserved quality attributes depending on pH and blend proportion.

Implantable wireless device for study of entrapment neuropathy

BackgroundDisease processes causing increased neural compartment pressure may induce transient or permanent neural dysfunction. Surgical decompression can prevent and reverse such nerve damage. Owing to insufficient evidence from controlled studies, the efficacy and optimal timing of decompression surgery remains poorly characterized for several entrapment syndromes. New methodWe describe the design, manufacture, and validation of a device for study of entrapment neuropathy in a small animal model. This device applies graded extrinsic pressure to a peripheral nerve and wirelessly transmits applied pressure levels in real-time. We implanted the device in rats applying low (under 100 mmHg), intermediate (200–300 mmHg) and high (above 300 mmHg) pressures to induce entrapment neuropathy of the facial nerve to mimic Bell’s palsy. Facial nerve function was quantitatively assessed by tracking whisker displacements before, during, and after compression. ResultsAt low pressure, no functional loss was observed. At intermediate pressure, partial functional loss developed with return of normal function several days after decompression. High pressure demonstrated complete functional loss with incomplete recovery following decompression. Histology demonstrated uninjured, Sunderland grade III, and Sunderland grade V injury in nerves exposed to low, medium, and high pressure, respectively. Comparison with existing methodsExisting animal models of entrapment neuropathy are limited by inability to measure and titrate applied pressure over time. ConclusionsDescribed is a miniaturized, wireless, fully implantable device for study of entrapment neuropathy in a murine model, which may be broadly employed to induce various degrees of neural dysfunction and functional recovery in live animal models.

Experimental testing of pneumatically forced actuated compressor-expander valves

The possibility of forced actuation of valves enables new operation modes for existing reciprocating compressors, e.g. capacity control or reverse operation as expander. A pneumatically forced actuated valve was tested within a reciprocating compressor and a quite complex behaviour was found, as shown in previous publications. A test rig outside of the compressor was set up for a better understanding of the system. Two measurement techniques were used to observe the sealing element motion over the time at varying operating conditions, like applied pressure levels and actuation time. The dependency of the valve motion to those operation conditions is evaluated and discussed. Improvements to the test bench and measurement techniques are also proposed to achieve more accurate results.

Effect of process variables on the calorific value and compressive strength of the briquettes made from high moisture Empty Fruit Bunches (EFB)

In this study, the manual hydraulic press was designed to prepare the briquettes from selected biomass waste. Each biomass was sun-dried and milled into small particle sizes before mixing with crude glycerol that used as a biomass binder. The effects of applied pressure levels of 100, 110, 120 bars, the particle size of 60, 80 and 100 mesh and the binder composition on the density, compressive strength and calorific heating value of the prepared briquettes were investigated using response surface methodology (RSM). Results showed that the briquettes have an average inside diameter, average outside diameter, and height of 12, 38, and 25-30 mm, respectively. The density of the briquettes increased with increasing the applied pressure, was in the range of 623-923 kg/m3. The densest briquettes were obtained at 80 mesh of particle size, 53:47 binder composition ratio and 110 bars of pressurizing. The heating value of the briquette reached up to 28.99 MJ/kg obtained on the particle size of 80 mesh, 53:47 binder composition, and 110 bars and the best compressive strength of 6.991 kg/cm2 obtained at a particle size of 100 mesh, 60:40 binder composition, and 120 bars. Process conditions influence the calorific value significantly.

Carbon-Based Pressure Sensors With Wavy Configuration

We demonstrate all-solution-processed pressure sensors consisting of carbon-based nano-composites with a wavy configuration using patterned polydimethylsiloxane molds. The sensitivity of the proposed sensors was increased by 36% at the applied pressure levels of 1 k N/ $\text{m}^{2}$ . Significantly, the resistance was mostly recovered after a release from 3 M N/ $\text{m}^{2}$ without conspicuous hysteresis, and a very stable and robust operation was secured during the pressure and release cycle. Compared with the as-supplied pressure-sensitive rubber films, the carbon-based nano-composite with a wavy configuration exhibited gradual changes, including a linear change in the low-pressure regime.

Effect of Applied Pressure and Binder Proportion on the Fuel Properties of Holey Bio-Briquettes

In this study, the manual hydraulic press was designed to prepare the holey briquettes from selected biomass wastes. Each biomass was sun dried and milled into the smaller particle size before mixing with 20wt% of palm fiber, and molasse was used as the binder. The effects of applied pressure levels of 40, 50, 60 and 70kg/cm2 and of the binder amount on the density, calorific heating value and burning rate of the prepared briquettes were investigated. Results showed that briquettes have the average inside diameter, average outside diameter and height of 12, 38 and 25-30mm, respectively. The density of the briquettes increased with the increasing of applied pressure, was in the range of 260-416kg/m3. The most densified briquettes were obtained from bamboo sawdust at the use of 20wt% molasse and pressure of 70kg/cm2. The heating value of bamboo briquette reached upto 21.26MJ/kg, and rubber wood residue briquette obtained the slowest burning rate of 2.01g/min.

Effect of High Pressure on the Porcine Placenral Hydrolyzing Activity of Pepsin, Trypsin and Chymotrypsin.

This study investigated the effects of protease treatments (trypsin, chymotrypsin, and pepsin) under various pressure levels (0.1-300 MPa) for the characteristics of porcine placenta hydrolysates. According to gel electrophoretic patterns, the trypsin showed the best placental hydrolyzing activity followed by chymotrypsin, regardless of the pressure levels. In particular, the peptide bands of tryptic-digested hydrolysate were not shown regardless of applied pressure levels. The peptide bands of hydrolysate treated chymotrypsin showed gradual decreases in molecular weights (Mw) with increasing pressure levels. However, the pepsin did not show any evidences of placental hydrolysis even though the pressure levels were increased to 300 MPa. The gel permeation chromatography (GPC) profiles showed that the trypsin and pepsin had better placental hydrolyzing activities under high pressure (particularly at 200 MPa), with lower Mw distributions of the hydrolysates. Pepsin also tend to lower the Mw of peptides, while the major bands of hydrolysates being treated at 300 MPa were observed at more than 7,000 Da. There were some differences in amino acid compositions of the hydrolysates, nevertheless, the peptides were mainly composed of glycine (Gly), alanine (Ala), hydroxyproline (Hyp) and proline (Pro). Consequently, the results indicate that high pressure could enhance the placental hydrolyzing activities of the selected proteases and the optimum pressure levels at which the maximum protease activity is around 200 MPa.

Simulation of pressure effects on hot isostatic pressing of stainless steel powder

To investigate the effects of pressure on the hot isostatic pressing (HIP) process of a stainless steel powder, density distribution and deformation of the powder at four different applied pressure levels were predicted and compared by using finite element method (FEM). Constitutive relations of porous compacts during HIP process were derived based on the yield criterion of porous metal materials. Thermo-mechanical coupling calculations were carried out by the MSC.Marc. Densification mechanisms were studied through evolutions of relative density, equivalent plastic strain and equivalent viscoplastic strain rate for compacts. The simulation results were also compared with experimental data. The results show that the densification rate and final density of compacts increase dramatically with the increase in the applied pressure level when it is below 100 MPa during HIP process, and the creep for compacts evolves into steady stage with the improvement of density.

Influence of Applied Pressure on Tensile Behaviour and Microstructure of Squeeze Cast Mg Alloy AM50 with Ca Addition

The development of alternative manufacturing processes is essential for the success in applying Ca-containing magnesium alloys for automotive applications due to their relatively poor die castability. Squeeze casting with its inherent advantages has been demonstrated capable of minimizing the formation of casting defects in Mg-Al-Ca alloys. In this study, the effect of applied pressures on tensile behavior and microstructure of squeeze cast Mg-5wt.%Al-1%wt.%Ca alloy (AMX501) was investigated with the applied pressure varying from 3 to 90 MPa. The results of tensile testing indicate that the tensile properties of AMX501 alloy including ultimate tensile strength, yield strength, and elongation (Ef) increase from 153.7, 80 MPa and 3.26% to 183.7, 90.5, and 5.42% with increasing applied pressure levels from 3 to 90 MPa, respectively. The analysis of true stress versus strain curves shows that an increase in applied pressure levels result in high straining hardening rates during the plastic deformation of the alloy. Microstructural analysis and density measurements indicate that, as the applied pressure increases, the porosity levels of the alloy decrease considerably, despite of almost no significant reduction in grain sizes of the squeeze cast alloys due to their high aspect ratio of cylindrical castings. Hence, the improvement in tensile properties should be primarily attributed to casting densification resulting from applied pressures. The scanning electron microscopy observation on fractured surfaces reveals that the fracture modes of the squeeze cast alloys transit to ductile from brittle with increasing applied pressures.

Hydrostatic burst test 0F X80 grade steel pipe

To evaluate the future application of X80 steel pipe in high-pressure oil and gas pipelines in China, hydrostatic burst tests were performed. The deformation and yield strength of longitudinal submerged arc-welding steel pipe Ф1016 × 18.4 mm under five applied pressure levels were measured. When the hoop stress is lower than 1.1SMYS, the pipe normally deforms elastically and uniformly with the maximum strain less than 0.3%. The slope offsets of the pressure–volume plot of pipe were discussed.

Tribological performance of A206 aluminum alloy containing silica sand particles

The dry-sliding tribological behavior of A206 aluminum alloy containing silica sand was investigated using a three pin-on-disk tribometer against an SAE 1045 steel counterface. The worn surfaces of the pins were then analyzed by optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS). The test results showed that the addition of silica sand particles decreased the friction coefficient of Mg modified A206 alloy. The wear rate of the composites increased with increases in the applied pressure from 0.35 to1.75MPa and with increases in the silica sand content from 0% to 13%. The wear rate variation with the applied pressure is attributed to the shift in the dominant wear mechanisms from oxidation and mild abrasive wear at applied pressures at and below 0.35MPa to delamination accompanied by severe abrasive wear at applied pressure levels above 0.35MPa. The high wear rate may be as a result of an overall decrease of the fracture toughness of the composites containing silica particles. The temperature near the counterface surface increased with increases in both silica content and the applied pressure due to the lower thermal conductivity of silica sand and greater abrasion that occurs at higher silica contents. A T6 heat treatment did not significantly decrease the friction coefficient or the wear rate of either the A206 matrix alloys or the composite containing silica sand.

Compression and Shear Behavior of Mudstone Aggregates

In this paper, a staged compression-immersion-direct shear test was conducted on compacted samples of crushed mudstone aggregates and its compressive and shear behavior are discussed with a focus on cementation effects. Compression behavior of the compacted samples was influenced significantly by the compaction degree as expected, as were shear behavior and shear strength. Immersion caused an additional compression and a reduction in mobilized shear stress and in the dilatant nature during shear at low applied pressure levels. Moreover, immersion significantly reduced the peak shear strength parameter c with only a little change in phi. The compression and critical state lines of the nonimmersed and immersed specimens seem to parallel each other, and the compression line of the nonimmersed and the critical state line of the immersed form the upper and lower bounds, respectively. A gap between shear stress-void ratio lines of the specimens with and without immersion is considered to represent a combined effect of cementation retained in a crushed mudstone aggregate itself and an interlocking effect of aggregates.

Treatment of Tar Sand Wastewaters with Activated Carbon, Ozone and Reverse Osmosis

Tar sand deposits offer long-term potential for satisfying future energy needs. Two large field-scale extraction experiments near Vernal, Utah, employed either a sequenced reverse-forward combustion technique (TS-2C) or a steam flooding procedure (TS-1 S) to recover in-place bitumen. This report documents the evaluation of activated carbon, ozone and reverse osmosis in treating the two types of tar sand wastewaters. Substrates included untreated and pretreated (filtration, foam fractionation, chemical treatment with ferric chloride) TS-1S and TS-2C wastewaters. Activated carbon, at a dose of 1,000 mg/L, reduced the Total Organic Carbon (TOC) of TS-1 S wastewater after treatment by 350 mg/L of ferric chloride to 2.3 mg/L TOC, a reduction of 91.6%. At the same adsorbent dos, activated carbon reduced the TOC in TS-2C wastewater from 678 mg/L to 546 mg/L. A study of the six commercially available adsorbents yielded little difference in adsorption capability for either wastewater. Ozonation of TS-lS wastewater after pretreatment by either foam fractionation or chemical treatment with ferric chloride then activated carbon yielded residual TOC levels of less than 1.2 mg/L. Reverse osmosis (RO) studies included investigation of four membrane types (cellulose acetate, poly-ether amide, poly-ether urea and a noncellulosic on a poly-sulfone base), three applied pressure levels (250, 400 and 550 psig) and two solution pH levels (5.5 and 7.8) with 5.0 µ (micron) filtered TS-2C wastewater as the substrate. A two-stage RO process achieved maximum organic and inorganic rejections of 98% and 97%, respectively.