Air Pressure Resistance Research Articles

MOF-Embedded Bifunctional Composite Nanofiber Membranes with a Tunable Hierarchical Structure for High-Efficiency PM0.3 Purification and Oil/Water Separation.

Herein, a unique hierarchically structured composite nanofiber membrane, consisting of a zeolitic imidazolate framework-8-embedded polyethersulfone (PES@ZIF8) fiber layer and a polysulfonamide/polyethersulfone (PSA/PES) fiber layer, was successfully developed to cope with the complex environments during the actual filtration/separation process and overcome the conflict between high filtration efficiency and low air pressure resistance. Due to the advantages of the synergistic effect of multicomponents and the bi-layer hierarchical structure, the integrated PES@ZIF8-PSA/PES filter possesses an extremely high air filtration efficiency (up to 99.986%) under a very low pressure drop (only 15 Pa), superior PM0.3 purification capacity (close to 99.95%), long-term recycling ability for purifying real smoke PM2.5 from >800 to <10 μg/m3, extremely high temperature resistance (exceed 200 °C), flame retardancy, good chemical stability, satisfactory transmittance, and robust self-cleaning ability. Apart from these, it achieves effective separation of oil-water mixtures and oil-water emulsions as a result of selective wettability including hydrophobicity and superoleophilicity. In particular, the PES@ZIF8-PSA/PES nanofiber membranes maintain outstanding air filtration and oil/water separation properties under the high temperature or strong acid/alkali conditions. This special comprehensive performance gives the PES@ZIF8-PSA/PES-based filtration/separation membranes a wider application prospect ranging from environmental governance to individual protection and industrial security.

Process enhancement of organic pollutant removal by micro channel excited dielectric barrier discharge

In this study, a micro-channel excited DBD plasma water treatment system is proposed to enhance the discharge and gas-liquid mass transfer processes simultaneously. As the core of the reactor, the micro-channel plays a crucial role in the process intensification. On the one hand, the micro-channel can reduce the initial discharge voltage and enhances the discharge intensity, because of the increased space charge density initiated by the transverse electric field formed by the charges accumulated on the micro-channel wall, as a result, the generation efficiency of active particles can be improved. On the other hand, the micro-channel can also reduce the air pressure resistance and enhance the bubbling process, due to the exciting effect of micro-channel discharge on air flow and plasma-water interaction, as a result, the utilization efficiency of active particles can be improved. Tetrabromobisphenol-S (TBBPS) is used as the target pollutant, with the initial condition of 500 mL, 0.2 mmol/L, the maximum removal is over 98 % after a 30 min treatment under an applied voltage of 18.4 kV. Applied voltage, air flow rate and water flow rate are the key parameters affecting the treatment efficiency. It can be concluded from the results of this study that the micro-channel excited DBD plasma is of significance favorable for the treatment of wastewater.

Prediction of air pressure resistance during the ventilation of wood chips as a function of multiple physical fuel parameters

Air pressure resistance during ventilation was measured experimentally for a high variety of conventional wood chip samples that had been produced using various raw materials, chippers and chipper settings (n = 95). Physical fuel properties such as bulk density or particle size distribution were determined according to international standards for solid biofuels. In addition, particle length and particle shape were determined using a continuously measuring image analysis device. Pressure resistance (in Pa m−1) was determined using a custom-built flow cylinder (2 m height, 0.4 m3 filling volume) and related to air flow rate.Pressure resistance increased exponentially with air flow rate for all samples. Thereby, pressure resistance was highly variable among wood chip samples, ranging from 10 to 107 Pa m−1 at low air flow rates (0.1 m3 s−1 m−2) and from 197 to 1240 Pa m−1 at higher air flow rates (0.5 m3 s−1 m−2). Four common equations to describe pressure resistance (Ramsin, Shedd, Hukill & Ives, Ergun) were compared. Multiple linear regression analysis was applied to express pressure resistance as a function of selected fuel quality parameters. Sensitivity analyses of the resulting equations were performed. Results indicate that pressure resistance strongly depends on bulk density, particle size and particle shape as these parameters determine the number, size and shape of free air voids within wood chip fillings.

Infiltration in Shallow Water Table Environments: Simple Two-Phase Model Accounting for Air Compression and Counterflow

AbstractA new method is introduced to simulate air compression and counterflow during infiltration into a shallow water table. The method retains the simplicity of Green and Ampt but with one added term, the air pressure resistance below the wetting front. The method differs from existing methods because it couples air compression and counterflow flux dynamically with infiltration. The new method is original and simple, yet it allows the extension of Green and Ampt to simulate infiltration into shallow water environments or a shallow impervious zone where soil-air pressurization is likely to develop. In shallow water table environments, it is shown that neglecting counterflow of air will cause a rapid decline in infiltration due to unrealistic buildup of air pressure below the wetting front. Accounting for air compression and counterflow seemed necessary to bridge between Hortonian (infiltration excess) and Dunne (saturation excess) mechanisms of runoff.

Long Jump Motion Analysis Based on the Aerodynamics

The long jump motion is a traditional track and field event. This sport is not only relevant with athletes congenital physical conditions, but also with the action skills in the long jump process. In the process of long jump, from the run-up to the take-off and landing, relatively large air resistance will be suffered, and the air resistance is affected by the size of the take-off speed and jumping height. Based on this, this article has carried on the detailed analysis of the air dynamic theory in the process of athletes long jump. It also has established the mathematical model of the friction resistance and air pressure resistance in the long jump process, and it has obtained the maximum incident angle when the maximum jump distance was happened by the take-off angle. Finally, through the experiment method, it has established the jumping speed loss curve and loss table under the air resistance effect, and obtained the incident angle and take-off speed in the long jump process, which provides the theory basis for the research of long jump motion.

Design and Implementation of Miniature 3-Axial Fiber Optic Rate Sensor

The key design and implementation methods of Miniature 3-axial Fiber Optic Rate Sensor are described in detail. Based on plenty of theoretical analysis and experimental validation, effective measures and key technology on optical components, fiber coil technics, assembly methods, control circuits and structure solidity are adopt and summarized. Finally, its main engineering performance is tested and listed detailedly. From experimental results and engineering practice, we can conclude that Miniature 3-axial Fiber Optic Rate Sensor has the performance of high reliability, radiation resistance, low air pressure resistance, temperature resistance and high reliability, and can be widely used in some special and professional fields. More importantly, it greatly promotes the development of fiber optic sensing and inertial technology application of China.

A Novel Technique for Natural Orifice Endoscopic Full-Thickness Colon Wall Resection: An Experimental Pilot Study

Natural orifice endoscopic full-thickness colon resection attempts to overcome the need for invasive surgery in selected colorectal indications. Because basic technical requirements have not been met so far, the aim of this study was to develop a novel technique for endolumenal colon-wedge resection addressing current shortcomings. Endoscopic full-thickness colon resection was attempted in a human cadaver model (n = 2), explanted porcine colon stumps (n = 10), and 3 acute pig models. A hypothesized colon lesion was created and retracted into an endoscopic clip closure system (ECCS). Initially used endoscopic graspers (n = 2) were replaced by a T-tag suture approach for retraction (n = 13). T-type anchors were deployed circumferentially to the lesion, which simultaneously marked resection margins. The clip was then applied for pre-resection tissue closure. The inverted tissue was excised by snare resection and was removed together with the sutures. Air leak-pressure of tissue closure was tested. Endoscopic full-thickness colon resection was achieved in 14 of 15 attempts. The mean diameter (±SD) of resected animal specimen, including the predetermined margins, was 26 ± 4 mm. Using the T-tag sutures for retraction, the defined lesion was neither touched by an endoscopic grasper nor compromised by puncturing the center. Leak pressure tests revealed a significantly higher air pressure resistance of the pre-resection ECCS closure (61 ± 5 mmHg) compared with the hand-sewn control (26 ± 7 mmHg). A novel endoscopic technique for full-thickness colon wall resection using tissue anchors for traction and an ECCS for pre-resection tissue closure appears to address several fundamental surgical principles. However, further studies are necessary before initial clinical application.

Does Frequency of Resistance Training Effect Cortical Density at the Tibia in Older Women?: A pQCT Study

ACSM guidelines recommend resistance training (RT) 2 to 3 times/week to optimize bone health. However, the effect of the frequency of RT on bone outcomes has not been evaluated in older community-dwelling women. PURPOSE: Our primary objective was to determine the effect of a 12-month program of three different RT frequencies (0, 1 and 2 times/week) on tibial cortical bone volumetric density (CovBMD) in healthy, community dwelling women aged 65-75 years. METHODS: This was an a priori secondary analysis of a randomized controlled trial (primary outcome was cognitive function). We randomized participants to one of three groups: (i) twice a week balance and tone group (i.e. no resistance other than body weight; BT); (ii) once a week RT program (RT1); and (iii) twice a week RT program (RT2). We used Keiser air-pressure resistance machines (Keiser Corporation, USA) for strengthening the upper and lower extremities. All exercise classes were delivered in groups of 8-10 participants and continued for 12 months. We used peripheral quantitative computed tomography (pQCT; Stratec XCT 2000, Germany) to acquire one 2.5 mm scan at the 50% site of the left tibia. Data were collected at baseline, 6 and 12 months. We used ANCOVA to determine the effect of the exercise intervention on tibial CovBMD at 6 and 12 months. RESULTS: We assessed 140 participants at baseline and 100 women provided data at all three time points (71% compliance). Baseline mean age for RT2 (n=34) and RT1 (n=35) groups was 69±3 years, and 70±3 years for BT (n=31). BMI for RT2 was 27±5, 26±5 for RT1 and 26±4 for BT group. Baseline mean Six-Minute Walk Test (meters) was 508±107 (RT2), 529±61 (RT1), and 537±68 (BT). The baseline mean tibial CovBMD (mg/cm3) at the 50% site was: 1055.8±65.2 (RT2), 1094.7±34.2 (RT1), and 1080.3±44.2 (BT). At 6 months the percent change in tibial CovBMD for the RT2 group= -0.2%; RT1= -0.04%; and BT= 0.2% for BT. From baseline to 12 months the percent change in tibial CovBMD for the RT2 group was -0.3%; RT1= -0.1%; and BT= -0.2%. After adjusting for baseline tibial CovBMD, there were no significant differences between groups at 6 months or 12 months. CONCLUSION: Tibial cortical bone density for all exercise interventions (RT2, RT1 and BT) was maintained in older community dwelling women over 12 months.

Muscle power is related to tibial bone strength in older women

We enrolled 65 to 75 year-old community-dwelling women and measured muscle power, strength, physical activity using accelerometry and tibial bone strength using peripheral quantitative computed tomography (pQCT). Muscle power contributed 6.6% of the variance in the bone strength-strain index and 8.9% in the section modulus after accounting for age, height, weight, and physical activity; moderate to vigorous physical activity was related to muscle power in the lower extremity. Muscle power is associated with DXA measurements of bone mass, but it is not known whether muscle power is associated with bone strength. There are no reports of investigations that have tested the effect of muscle power on bone compartments using advanced imaging. We enrolled 74 community-dwelling women aged 65-75 years. We measured muscle power and strength of leg extension using Keiser air-pressure resistance equipment. All participants wore a waist-mounted Actigraph accelerometer to record physical activity. We used peripheral quantitative computed tomography (pQCT) to measure tibial mid-shaft (50% of the site) bone strength (strength-strain index, section modulus). We used Pearson correlations and multi-level linear regression to investigate the associations between muscle and bone. Muscle power contributed 6.6% (p = 0.007) of the variance in the bone strength-strain index and 8.9% (p = 0.001) the variance in the section modulus in older women after accounting for age, height, weight, and physical activity. Moderate to vigorous physical activity was significantly related to muscle power in the lower extremity (r = 0.260; p = 0.041). Muscle power significantly contributed to the variance in estimated bone strength. Whether power training will prove to be a more effective stimulus for bone strength than conventional strength training will require further studies.