Cyclic Pressure Research Articles

Research on the seepage properties of coal with different particle size proppant under cyclic loading

The selection of proppant particle size significantly impacts the gas output and gas production period of the extracting coalbed methane (CBM). This study combines theoretical analysis and permeability testing, based on the in situ stress distribution characteristics of the coal seam in Wangjiazhai Coal Mine, Guizhou Province, conducted on artificial fractures with different particle size proppant combinations during the cyclic loading and unloading. The findings indicate that the coal sample with two particle sizes of proppant has more permeability and smaller stress sensitivity coefficient than the coal sample with a single particle size proppant; as effective stress increases, the coal sample with the maximum permeability and the smallest stress sensitivity coefficient is placed with a proppant ratio of 20/40 mesh to 40/70 mesh of 1–3. The stress sensitivity coefficient and the permeability decrease with an increase in the number of confining pressure cycles. The increase in the proppant embedding depth has a hysteresis phenomenon with the increase in the effective stress, and the coal sample with a proppant ratio of 20/40 mesh to 40/70 mesh of 1–3 has the smallest embedded depth. The proppant will cause damage to the fracture surface of the coal seam. This study provides technical support for efficiently extracting the CBM resources that are difficult to exploit in Guizhou Province.

Combustion and performance characteristics of a diesel engine fueled with coal-based hybrid fuel at various altitudes

ABSTRACT At high altitude and low pressure, the changes of inlet and exhaust pressure and the combustion environment in the cylinder lead to the deterioration of physicochemical characteristics and combustion in the cylinder of the coal-based mixed fuel. In this research, based on the plateau environment simulation test platform, the combustion characteristics, dynamic performance and fuel economy of the turbocharged diesel engine burned at different simulated altitudes (0 m, 1500 m, 2500 m, 3500 m and 4500 m) were studied. The results revealed that as altitude increased, the coal-based composite fuel caused the diesel engine’s in-cylinder pressure, pressure rise rate, and instantaneous heat release rate to gradually decrease, the flameout period to gradually extend, and the center of gravity of combustion to gradually delay. At low engine speed, the average effective pressure cycle variation rate increased significantly. The coal-based complex fuel diesel engine has increased in-cylinder pressure, torque, and effective thermal efficiency, as well as peak instantaneous heat release rate at high altitude, when compared to diesel combustion. It also causes a reduction in the maximum pressure rise rate, a forward shift in the combustion center of gravity, a reduction in the average effective pressure cycle rate of change, and a shortening of the stall period.

FOSL2 promotes intertumoral infiltration of T cells and increases pathological complete response rates in locally advanced rectal cancer patients

The outcome of neoadjuvant chemoradiotherapy (nCRT) remains highly unpredictable for individuals with locally advanced rectal cancer (LARC). We set out to characterize effective biomarkers that promote a pathological complete response (pCR). We quantified the abundances of 6483 high-confidence proteins in pre-nCRT biopsies of 58 LARC patients from two hospitals with pressure cycling technology (PCT)-assisted pulse data-independent acquisition (PulseDIA) mass spectrometry. Compared with non-pCR patients, pCR patients achieved long-term disease-free survival (DFS) and had higher tumor immune infiltration, especially CD8+ T cell infiltration, before nCRT. FOSL2 was selected as the candidate biomarker for predicting pCR and was found to be significantly upregulated in pCR patients, which was verified in another 54 pre-nCRT biopsies of LARC patients by immunohistochemistry. FOSL2 expression was able to predict pCR by multiple reaction monitoring (MRM) with high efficiency (Area under curve (AUC) = 0.939, specificity = 1.000, sensitivity = 0.850), and high FOSL2 expression was associated with long-term DFS (p = 0.044). When treated with simulated nCRT, FOSL2 sufficiency resulted in more significant inhibition of cell proliferation, and more significant promotion of cell cycle arrest and cell apoptosis. Moreover, CXCL10 secretion with abnormal cytosolic dsDNA accumulation was found in FOSL2-wildtype (FOSL2-WT) tumor cells over nCRT, which might elevate CD8+ T-cell infiltration and CD8+ T-cell-mediated cytotoxicity to promote nCRT-induced antitumor immunity. Our study revealed proteomic profiles in LARC patients before nCRT and highlighted immune activation in the tumors of patients who achieved pCR. We identified FOSL2 as a promising biomarker to predict pCR and promote long-term DFS by contributing to CD8+ T-cell infiltration.

Evolution Law of Wellbore Instability Risk under Fluctuating Pressure

The bottom hole fluctuating pressure has a large influence on the wellbore instability. To address this problem, firstly, according to the principle of seepage mechanics, we established a calculation model of the change in pore pressure around the wellbore radius under fluctuating pressure; then, through laboratory rock mechanics test and rock damage mechanics theory analysis, the change law of formation strength under the action of static hydration and dynamic damage are determined; finally, based on the theory of rock mechanics in porous media, a quantitative evaluation method for the risk of wellbore instability under fluctuating pressure is established and the changing pattern of wellbore instability risk is analyzed. The results show that the pore pressure around the well shows a trend of fluctuation increase under fluctuating pressure, and there is a certain lag in the fluctuation of pore pressure inside the formation; the longer the muddy shale is immersed in drilling fluid, the greater the reduction in strength; the reduction is greater in the early stage of immersion, and the reduction in strength in water-based drilling fluid is greater than that in oil-based drilling fluid. At the beginning of the pressure cycle, the formation damage variable and compressive strength gradually increase and decrease with the increase of the pressure cycle number; after several cycles, the magnitude of change gradually decreases with the increase of the cycle number. When the bottom hole pressure fluctuates at a certain period, the greater the fluctuation, the shorter the period of wellbore stability; when the bottom hole pressure fluctuates at a certain range, the smaller the fluctuation period, the faster the borehole enters the high-risk period, while the shortest period of wellbore stability occurs when the fluctuation period is smallest; and when the wave cycle is in the middle, the wellbore stability period is the longest.

Experimental Study on Cyclic Hydraulic Fracturing of Tight Sandstone under In-Situ Stress

Sandstone oil–gas reservoirs in the Junggar Basin, China have great development potential. However, their ultra-deep formation depth leads to high crustal stress and high breakdown pressure. Therefore, in this research, we studied the cyclic hydraulic fracturing of tight sandstone with different combinations of “high-pressure duration + low-pressure duration” under high-stress conditions. Through laboratory experiments, the pump pressure curves, hydraulic fracture morphology, acoustic emission counts, and peak frequency of the samples were obtained. The results showed that: (1) Compared with conventional hydraulic fracturing, the breakdown pressure of cyclic hydraulic fracturing was reduced by more than 30%, the minimum threshold of cyclic pump pressure required for sample breakdown was between 60%Pb and 70%Pb, and cyclic hydraulic fracturing more easily formed complex and diverse hydraulic fractures. (2) In cyclic hydraulic fracturing, under the same upper limit of cyclic pump pressure, the shorter the high-pressure duration, the fewer the cycles required for sample breakdown. (3) Under the same “high-pressure duration + low-pressure duration” condition, the lower the upper limit of the cyclic pump pressure, and the greater the number of cycles required for sample breakdown. (4) The AE cumulative counts curves fluctuated greatly during cyclic hydraulic fracturing, rising in an obvious step-wise manner and the AE peak frequency was banded and mainly divided into three parts: low frequency, medium frequency, and high frequency.

Is obstructive sleep apnea a circadian rhythm disorder?

Obstructive sleep apnea is the most common sleep-related breathing disorder worldwide and remains underdiagnosed. Its multiple associated comorbidities contribute to a decreased quality of life and work performance as well as an increased risk of death. Standard treatment seems to have limited effects on cardiovascular and metabolic aspects of the disease, emphasising the need for early diagnosis and additional therapeutic approaches. Recent evidence suggests that the dysregulation of circadian rhythms, processes with endogenous rhythmicity that are adjusted to the environment through various cues, is involved in the pathogenesis of comorbidities. In patients with obstructive sleep apnea, altered circadian gene expression patterns have been demonstrated. Obstructive respiratory events may promote circadian dysregulation through the effects of sleep disturbance and intermittent hypoxia, with subsequent inflammation and disruption of neural and hormonal homeostasis. In this review, current knowledge on obstructive sleep apnea, circadian rhythm regulation, and circadian rhythm sleep disorders is summarised. Studies that connect obstructive sleep apnea to circadian rhythm abnormalities are critically evaluated. Furthermore, pathogenetic mechanisms that may underlie this association, most notably hypoxia signalling, are presented. A bidirectional relationship between obstructive sleep apnea and circadian rhythm dysregulation is proposed. Approaching obstructive sleep apnea as a circadian rhythm disorder may prove beneficial for the development of new, personalised diagnostic, therapeutic and prognostic tools. However, further studies are needed before the clinical approach to obstructive sleep apnea includes targeting the circadian system.

Role of Cyclic Negative Pressure Wound Therapy (NPWT) in Pediatric Scald Burn

Burns and related injuries are common causes of death and disability. The highest incidences of burn cases occur in children and adults. In children less than 2 years of age, contact with hot surfaces and scald burns are the most common presentation to the hospital. The practice of cooking at ground level or sleeping with a burning lamp are some of the causes. Early management of this type of burn results in better outcomes. In this case we describe the role of negative pressure wound therapy (NPWT) as an adjuvant in the management of paediatric thermal burns.

Small-Angle Neutron Scattering Investigation of Oil Recovery in Mineralogically Distinct Wolfcamp Shale Strata

Understanding and improving hydrocarbon yields during enhanced oil recovery (EOR) in unconventional reservoirs is complicated by the intrinsic mineralogical and geochemical heterogeneity of shale formations. In this study, we utilized small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS) to investigate the degree of oil retention and its location in the nanoporous shale matrix for two mineralogically distinct shale samples. The two samples, dubbed “dark” and “light” based on their color, were taken from adjacent strata in a Wolfcamp shale core. While both samples contained kerogen, the dark sample contained more kerogen and clay (43.7 wt %) while the light sample contained more calcite (54.9 wt %). Samples were presaturated with decane, a model hydrocarbon, prior to pressure cycling with methane. Results showed significantly more retention of decane in 1.5–10 nm radius pores of both, likely indicating that oil is retained within kerogen nanopores. Although the dark sample had a higher porosity of 8.7%, versus 3.3% for the light sample, more pores were accessible to decane and a higher percentage of the imbibed decane was removable from the light sample compared to the dark sample. The majority of decane was not recoverable for the dark sample, indicating that EOR with methane can be challenging. These new findings can help to model expected recoveries of in-place oil from heterogeneous shale formations, as well as inform improved EOR strategies.

Comparative Analysis of Isochoric and Isobaric Adiabatic Compressed Air Energy Storage

Adiabatic Compressed Air Energy Storage (ACAES) is regarded as a promising, grid scale, medium-to-long duration energy storage technology. In ACAES, the air storage may be isochoric (constant volume) or isobaric (constant pressure). Isochoric storage, wherein the internal pressure cycles between an upper and lower limit as the system charges and discharges is mechanically simpler, however, it leads to undesirable thermodynamic consequences which are detrimental to the ACAES overall performance. Isobaric storage can be a valuable alternative: the storage volume varies to offset the pressure and temperature changes that would otherwise occur as air mass enters or leaves the high-pressure storage. In this paper we develop a thermodynamic model based on expected ACAES and existing CAES system features to compare the effects of isochoric and isobaric storage. Importantly, off-design compressor performance due to the sliding storage pressure is included by using a second degree polynomial fit for the isentropic compressor efficiency. For our modelled systems, the isobaric system round-trip efficiency (RTE) reaches 61.5%. The isochoric system achieves 57.8% even when no compressor off-design performance decrease is taken into account. This fact is associated to inherent losses due to throttling and mixing of heat stored at different temperatures. In our base-case scenario where the isentropic compressor efficiency varies between 55% and 85%, the isochoric system RTE is approximately 10% lower than the isobaric. These results indicate that isobaric storage for CAES is worth further development. We suggest that subsequent work investigate the exergy flows as well as the scalability challenges with isobaric storage mechanisms.

The Role of Fluid Overpressure on the Fracture Slip Mechanism Based on Laboratory Tests That Stimulating Reservoir-Induced Seismicity

A critically stressed fracture will slide in response to the increase in fluid pressure inside the fracture while impounding, which will trigger induced seismicity. The mechanism of fluid overpressure is regarded as a significant factor in the reaction of the fracture slip after water diffusing. This study uses a shearing test with a cylinder of granite, with 100 mm height and 50 mm diameter, under the condition of hydraulic-mechanic (HM) coupling to figure out how fluid overpressure alters the mechanical behavior of the critically stressed fracture. The cyclic water pressurization simulates periodical impounding in the water reservoir. Results show that several slip events happen when water pressure continues to rise higher than the stable state. The change of roughness also indicates the deterioration of the fracture surface while sliding. According to the results, we conclude that the difference between inlet pressure and outlet pressure leads to an overpressure of the fracture, promoting a series of slips and induced seismicity. Hydraulic energy is introduced to explain the relationship between the input and output energy, which is also strong evidence to illustrate that fluid overpressure is a crucial mechanism in reservoir-induced seismicity.

Kombinasi Fermentasi Bakteri Asam Laktat dan Pemanasan Bertekanan-Pendinginan dalam Pembentukan Pati Resisten Tepung Talas Beneng (Xanthosoma undipes K. Koch)

The study aimed to determine the effect of lactic acid bacteria, fermentation time, and pressurized heating-cooling cycle on the formation of resistant starch content of beneng taro (Xanthosoma undipes K. Koch) flour. The materials used were beneng corm, isolates of lactic acid bacteria Lactobacillus casei and Streptococcus thermophilus, and MRSB media. The experimental design was randomized block design factorial with two factors: fermentation time (0, 18, and 24 hours) and pressurized-cooling heating (1, 2, and 3- cycles) in 3 replicates. The data were analyzed using analysis of variance and if necessary continued with Duncan's Multiple Range Test at a level of 95%. The tested parameters were the content of resistant starch, amylose, and amylopectin and the data were treated using variance of analysis. The results showed that the combination of L. casei and S. thermophillus produced the highest resistant starch content of 5.66%. Fermentation time of 18 and 24 hours produced resistant starch content of 4.46% and 4.51%, respectively. Autoclaving-cooling of 1-, 2-, and 3-cycle produced a similar type of resistant starch of 3.81%, 4.26%, and 4.16%, respectively. Therefore, the combination of L. casei and S. thermophillus fermented in 18 hours and 1-cycle of autoclaving-cooling is recommended to produce resistant beneng taro flour starch content.
 
 Keywords: fermentation, autoclaving-cooling, resistant starch, taro beneng, Xanthosoma undipes K. Koch

EFFECT OF HIGH-PRESSURE TREATMENT ON THE STABILITY OF QUINOA PROTEIN-CANOLA OIL NANOEMULSIONS IN TERMS OF DROPLET SIZE AND LIPID OXIDATION

The stability characteristics of soluble nano-sized quinoa protein isolates prepared by different high-pressure homogenization in terms of droplet size and lipid oxidation were studied. Commercial quinoa protein isolates (QPI) were exposed to high-pressure homogenization (HPH) at various pressure (50, 100 and 200 MPa) and pressure cycles (one-cycle and two cycles). The quinoa isolate aggregates were utilized to produce oil-in-water nanoemulsions, which demonstrated the good stabile characteristics for 28 day of storage at 4 oC. While quinoa protein / canola oil nanoemulsions (QPCON) produced with untreated QPI and QPI samples by other HPH treatments were shown a significant increase in terms of droplet size and lipid oxidation in 28 days of storage, QPI samples treated with HPH at 100 MPa for a cycle (100 MPa-1) was found as the most efficient treatment in the stability of protein aggregate sizes and less oxidation level. The sample showed a slight increase from 98 nm to 117 nm for droplet size and from 58 to 102 mmol/kg for lipid oxidation from day 0 to day 28.

Multiannuli Solution Uses Intelligent Pipe for Real-Time Monitoring

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 211546, “Intelligent Pipe: A Multiannuli Monitoring Solution,” by Francois-Xavier Bulard, Vallourec; Emmanuel Tavernier, OpenField Technology; and Lucas Kling, Vallourec. The paper has not been peer reviewed. _ The authors describe a multiannular monitoring solution that measures pressure and temperature for each well annulus. These key parameters are captured by sensors based on microelectromechanical-system technology. A transmission methodology is used that allows power supply and data retrieval even for annuli beyond the B annulus. All electronic elements of the solution will be qualified through an international recommendation protocol [Advanced Well Equipment Standards (AWES)] that consists of a series of mechanical and long-term tests to ensure that the system will survive for 20 years at 125°C. The solution could be used in all storage applications, especially those related to the energy transition. Introduction The initial goal of the intelligent-pipe solution was to add functionality to tubulars by embedding miniaturized sensors into the pipe body. The secondary objective was to monitor the pipe’s environment to properly characterize well loads and compare them to its strength resistance. The main application of the solution was then to monitor annulus conditions in real time during the whole life of the well and to anticipate any leakage or annular-pressure-buildup issue that could not be monitored currently on subsea wells. A tubular design was developed to incorporate pressure and temperature sensors without affecting the integrity of the pipe. The design was verified by a testing protocol performed by an in-house testing laboratory. This protocol consisted, first, of finite-element analysis (FEA) performed on different tubular designs with the objective of optimizing the different shapes of the grooves created to incorporate the sensors. The second steps included physical tests performed on a specimen inside test frames that confirmed that the tubular integrity was not affected after several pressure and axial load cycles, even when applying maximum pipe-resistance loads. This mechanical test qualification demonstrated that the monitoring mandrel was able to withstand the constraints observed in a well. The qualification level achieved was the same as that achieved on the premium pipe connection. Much of the complete paper is dedicated to the development of the permanent solution; this synopsis focuses on the system’s pilot deployment and its global system qualification. First Deployment in a Deepwater Subsea Well The operator’s objective was to monitor several annuli of a subsea well to determine the effect of completion operations. This characterization was completed before the well-production phase. The main outputs of the pilot were annuli trapped pressure and temperature. The pilot was defined initially in two stages. The first was to monitor the B and C annuli conditions (pressure and temperature) immediately after casing deployment. The second was to do so again after running completions and various stimulation operations. A secondary objective was to retrieve historical sensor data, pressure, and temperature records from the time of sensor deployment to data-retrieval operation.

N-waves propagating through the Mars atmosphere

One of the particular interest of the SuperCam microphone onboard the NASA’s Perseverance rover is that it is coupled with its own reproducible sound source, the blast waves generated by the SuperCam laser-induced plasma expansion. This unique emission-reception pair on Mars is used to investigate the propagation of spark-induced N-waves through the turbulent CO2-dominated Mars atmosphere. The analysis of waveforms shows large distortions over a burst of 30 subsequent shots, which is consistent with previous laboratory recordings of N-waves through thermal turbulence. Especially, this distortion leads to a scattering of the peak pressure amplitude, whose distribution can be fitted with a generalized gamma function. For bursts recorded farther than 4 m, the distribution gets asymmetric with a shift of the maximum toward the left of the median due to peaks amplified more than twice the median amplitude, likely due to caustics that randomly focus the acoustic wave. On the other hand, over a Martian year, the absolute peak pressure varies by ∼50% due to changes in the acoustic impedance and Rankine-Hugoniot conditions, due to the seasonal cycles of pressure and temperature at the surface of Mars.

Permeability study of water-proofing admixture and fly ash incorporated concrete using standard and own built test

One of the most important factors influencing concrete's age is its permeability. Many commercially available water-proofing chemicals claim to be helpful in water-proofing concrete while improving other attributes such as compressive strength, modulus of rupture, durability, and density. Furthermore, the mineral admixtures also improve concrete's mechanical and durability properties. DIN 1048 (Part 5), EN 12390 – 8, and IS 516 (Part 2): 2018 are standard codes for determining the water permeability of concrete. These codes lack information on the drying conditions of concrete samples between the pressure cycles of water permeability tests and leads to an inability to evaluate the effectiveness of using admixtures in concrete. Some more limitations of these codes are fixed duration of testing and bulky apparatus. In this study, the one- and four-cycle test with oven drying and the air-drying combination is carried out. The present study also focuses on evaluating the effectiveness of fly ash and waterproofing admixture as an additive in concrete to reduce the water permeability of concrete. Further, limitations of the previous test are taken into consideration, and the own built apparatus is developed. The own-built apparatus (water penetration test) works at the same pressure (5 kg/cm2) as the standard method. The own-built apparatus reduces the testing duration, and a more significant number of samples can be tested at a time compared to the traditional method. The results of water penetration depth for the different samples prepared at a common effective w/c ratio have given an insightful effect, as the concrete with similar strength was compared for permeability evaluation. Therefore, the present paper will enlighten the testing procedure, duration, and comparison of (0, 15, 25, and 35%) fly ash and (0.8 and 1.2%) waterproofing admixture concrete. The 15%, 25% and 35% fly ash incorporated concrete was found effective by 18 to 27% in reducing the penetration depth, whereas 0.8 and 1.2% water proofing admixture concrete reported 9 and 14% effective compared to control concrete. This study will help researchers to evaluate the comparative effectiveness of the ability of water-proofing and mineral admixtures in improving the permeability of the concrete and ultimately enhancing the durability of the concrete structure.

Combustion Variability Monitoring in Engines Using High-Speed Exhaust Temperature and Pressure Measurements

AbstractThe diagnostic merits of high-speed (HS) exhaust gas temperature and pressure measurements for indexing engine stability and identifying abnormal combustion cycles are explored through experimental investigations on a low speed, single-cylinder engine. Exhaust temperature and pressure are measured using a fine wire 50 μm thermocouple and a piezoresistive pressure transducer, respectively. Synchronously recorded cylinder pressure data is used to continuously index combustion variations, and then anomalous combustion event detection and engine stability monitoring are attempted using HS exhaust temperature and pressure measurements. Two types of abnormal combustion cycles, namely, misfiring and overload cycles are used to typify low and high intensity anomalous combustion cycles, respectively. The results demonstrate that if suitable cyclic exhaust pressure and temperature metrics are used, anomalous combustion cycles can be identified, and overall combustion variability levels can be indexed. The comparative diagnostic performance of HS measured exhaust pressure and temperature and slow speed measured exhaust temperature are also discussed. A thermodynamic simulation of the engine and the HS thermocouple is used to provide theoretical support for the discussion by comparing measured and simulated “actual” exhaust temperature and identifying the flow, heat transfer, and thermodynamic influences that act as limits to the thermocouple's dynamic performance.

Nanofluidic Attenuation of Metal-Organic Frameworks

Porous materials with energy absorption characteristics have been used for attenuation against hazardous vibrations and noises. The intrusion of liquid water and aqueous solutions into hydrophobic nanoporous materials such as metal-organic frameworks (MOFs) present an attractive pathway to engineering new attenuation technologies. In this process, hydrostatic pressure forces water to intrude hydrophobic nanopores, thereby converting mechanical work into interfacial energy through nanoscale interfacial interactions. Once the external pressure is removed, water molecules can flow out of the nanopores spontaneously, making the system reversible. We envision that this mechanism has the potential of innovating attenuation technologies, so in this work we provided a preliminary study in this direction. We investigated a material system consisting of water and a commonly used MOF, zeolitic imidazolate framework-8 (ZIF-8), and demonstrated its reversibility and stability under cyclic pressurization, considered its performance at various peak pressures and frequencies, its tunability in terms of intrusion pressure, and its potential in hydrogel forms. These features are important for potential attenuation technologies based on this novel mechanism.

Decompression and degassing, repressurization, and regassing during cyclic eruptions at Guagua Pichincha volcano, Ecuador, 1999–2001

In 1999–2001, Guagua Pichincha volcano, Ecuador, produced a series of cyclic explosive and effusive eruptions. Rock samples, including dense blocks and pumiceous clasts collected during the eruption sequence, and ballistic bombs later collected from the crater floor, provide information about magma storage, ascent, decompression, degassing, repressurization, and regassing prior to eruption. Pairs of Fe-Ti oxides indicate equilibrium within 1.2–1.5 log units above the NNO oxidation buffer and equilibrium temperatures from 805 to 905 °C. Melt inclusions record H2O contents of 2.7–4.6 wt% and CO2 contents (uncorrected for CO2 segregation into bubbles) from 19 to 310 ppm. Minimum melt inclusion saturation pressures fall between 69 and 168 MPa, or equilibration depths of 2.8 and 6.8 km, the lower end of which is coincident with the maximum inferred equilibration depths for the most vesicular breadcrust bombs sampled. Amphibole phenocrysts lack breakdown rims (except for one sample) and plagioclase phenocrysts have abundant oscillatory compositional zones. Plagioclase areal microlite number densities (Na) range over less than one order of magnitude (8.9×103–8.7×104 mm-2) among all samples, with the exception of a dense, low crystallinity sample (Na = 3.0×103 mm−2) and a pumiceous sample erupted on 17 December 1999 (Na = 1.7×103 mm−2). Plagioclase microlite shapes include tabular, hopper, and swallowtail forms. Taken together, the relatively high plagioclase microlite number densities, the high number of oscillatory zones in plagioclase phenocrysts, the presence of CO2 in groundmass glass, seismicity, and time-varying tilt cycles provide a picture of sudden evacuation of magma residing at different levels in the shallow conduit. Explosive eruptions punctuate inter-eruptive repose periods marked by time-varying rates of degassing (volatile fluxing) and re-pressurization. Shallow residence time in the conduit was sufficient to allow precipitation of silica-phase in the groundmass, but insufficient to allow breakdown of hornblende phenocrysts, with the one exception of the final dome sample from 2000, which has the longest preceding repose time. These results support a model of cyclic pressure cycling, volatile exsolution and regassing, and magma decompression decoupled from ascent.

Harnessing Nonuniform Pressure Distributions in Soft Robotic Actuators

Herein, complex motion in soft, fluid‐driven actuators composed of elastomer bladders arranged around a neutral plane and connected by slender tubes is demonstrated. Rather than relying on complex feedback control or multiple inputs, the motion is generated with a single pressure input, leveraging viscous flows within the actuator to produce nonuniform pressure between bladders. Using an accurate predictive model coupling with a large deformation Cosserat rod model and low‐Reynolds‐number flow, all dominating dynamic interactions including extension and curvature are captured with two governing equations. Given insights from this model, five design elements are described and demonstrated in practice. By choosing the relative timescales between the solid, fluid, and input pressure cycles, the tip of the actuator can obtain almost any desired trajectory and can be placed anywhere temporarily within its 2D workspace. Finally, the benefits of viscous‐driven soft actuators are showcased in a six‐legged untethered robot able to walk 0.05 body lengths per second. The foundation is laid for a new class of morphologically intelligent, soft robotic actuators that enables complex deformations and multifunctionality without explicit drivers; whereby generating nonuniform pressure distributions, their infinite degrees of freedom can be exploited.

Flexible Pressure Sensor with an Excellent Linear Response in a Broad Detection Range for Human Motion Monitoring.

Pressure sensing is highly demanding in wearable devices, robotics, and artificial intelligence, whereas it is still a big challenge to develop a pressure sensor with an excellent linear response in a broad detection range. Herein, a flexible and porous carbon nanotube (CNT)/carbon black (CB)/carbonyl iron powder (CIP)/silicone composite is proposed by a simple strategy of mixing, curing, and washing. Due to the porous structure induced by the sacrifice of sugar particles, an excellent linear response (R2 = 0.999) is achieved for the composite sensor by manipulating the contributions of contact resistance and tunnel resistance to the sensing performance via the alternation of CB and CNT contents. Moreover, the porous structure donates the composite sensor a low compressive modulus at a low pressure level, while the CIPs introduced lead to a high compressive modulus at a high pressure level with the assistance of an external magnetic field. As a result, the sensor produced has a wide linear response range of 80 Pa to 220 kPa, much wider than most of the linear response pressure sensors reported previously. The wide detection range is demonstrated by cyclic pressure tests in the frequency range of 0.1-5 Hz, durability tests, and monitoring human or robot motions including breathing, walking, lifting, and boxing, etc. Taking the advantages of low cost, high sensitivity, and excellent linear response in a wide pressure range, the current composite sensor is promising for precise monitoring of human motions and delicate controlling of robots.