Increase In Positive Pressure Research Articles

Design of Positive Pressure Re-Acceleration Assisted Seeding Mechanism for Corn Based on CFD-EDEM Gas-Solid Coupling Simulation

This study proposes a positive pressure re-acceleration assisted seeding mechanism and analyzes the motion mechanism of corn seeds during the seeding process. By employing the CFD-EDEM gas-solid coupling simulation analysis method, the fluid characteristics, initial ejection velocity of seeds, seed dropping time difference, and sowing position difference in the seeding mechanism under different structural parameters of the air pressure valve body were investigated. The optimal structural parameters of the air pressure valve body were determined (nozzle gap c = 0.6 mm, throat constriction diameter d = 16 mm, and throat constriction length l = 44 mm). A multi-factor experimental method was used to explore the effects of airflow pressure, forward speed during sowing, and sowing distance on sowing performance, aiming to identify the optimal working parameters for the positive pressure re-acceleration seeding mechanism. High-speed camera technology was used to record and analyze the seed movement process. The results indicate that an increase in positive pressure within the seed guide tube shortens the sowing time of corn seeds, reduces the coefficient of variation of seed dropping time difference, and effectively improves the consistency of sowing distance. The optimal parameters are a forward speed of 8 km/h, sowing distance of 20 cm, airflow pressure of 10 kPa, with a sowing distance coefficient of variation of 7.56%, and a seed dropping time difference coefficient of variation of 5.35%.

Design and test of a pneumatic type of high-speed maize precision seed metering device

This study proposed a pneumatic type of high-speed maize precision seed metering device and analysed the motion mechanism of maize seeds during the filling, cleaning, and seed dropping processes of the device. Single-factor test methods were used to explore the influence of forward velocity, negative pressure of the seed metering device, and positive pressure of the seed guide tube on seeding performance separately. Additionally, based on high-speed camera technology, trajectory analysis was performed on continuously dropping maize seeds under different positive pressures of the seed guide tube. Results showed that an increase in positive pressure of the seed guide tube shortened the seed dropping time of maize seeds and made the time interval between adjacent maize seeds leaving the seed guide tube more uniform. Furthermore, a three-factor five-level orthogonal rotation combination test was used to explore the optimal working parameters of the pneumatic type of high-speed maize precision seed metering device. The results indicated that the optimal parameters were a forward velocity of 10 km/h, negative pressure of the seed metering device of 4.5 kPa, and positive pressure of the seed guide tube of 3 kPa. Verification tests demonstrated that the qualified index was 98.31% and the coefficient variation was 9.26%.

Experimental Study on the Properties of Gas Diffusion in Various Rank Coals under Positive Pressure.

A kind of closed mining and nonventilation working face is proposed, which provides a possibility for eliminating coal mine accidents and extracting high-purity gas. During mining, a confined space above normal pressure is formed in the face. Geological conditions cause significant differences in the physicochemical properties of coal and affect the occurrence and migration of gas in coal seams. The pore structures of five coal samples were obtained by mercury injection and low-temperature nitrogen adsorption. The self-made positive pressure desorption experimental device was used to conduct isothermal desorption experiments under different environmental pressures. An extended Langmuir model was proposed to carry out regression analysis on the curve of positive pressure desorption with time. The effect of coal pore structure on gas diffusion properties was discussed. The results indicate that the development degree of micropores in coal determines the amount of gas adsorption. With the increase of coal rank, both the ultimate desorption quantity and desorption rate first decrease and then increase. The positive pressure enhances the concentration of methane outside the coal and inhibits methane diffusion. With an increase of positive pressure, the desorption capacity of the high-rank ZG was significantly inhibited, and the desorption limit and initial desorption rate decreased by 15.80-44.54 and 16.92-47.93%, respectively. The diffusion coefficient of the middle-rank XS has the greatest decrease rate of 1.56-18.05%. The pore structure of coal is the essential reason that affects methane diffusion.

Desorption and diffusion characteristics of methane in the non-ventilation working face

Based on the rapid development of intelligent unmanned mining technology in coal mines, a new concept of non-ventilation working face is put forward. In the absence of ventilation, it is more possible to extract high purity methane and eliminate coal mine accidents. There are few studies on the desorption and diffusion characteristics of methane under constant positive pressure (higher than atmospheric pressure) in the non-ventilation working face. In this study, a set of self-designed gas positive pressure desorption equipment was used to carry out desorption experiments under various positive environmental pressures. The diffusion coefficient of methane in coal was calculated by using the unipore diffusion model. The results indicate that the extended Langmuir EXT1 model can well describe the variation of methane desorption capacity with time under different positive pressures. Under the same temperature and equilibrium pressure, the limit desorption capacity and desorption rate of methane in coal decrease with the increase of external positive pressure. With the increase of temperature and equilibrium pressure, the negative effect of positive pressure is weakened. At the same temperature and equilibrium pressure, the diffusion coefficient of methane in coal decreases with the increase of positive pressure. The higher equilibrium pressure increases the methane concentration in coal matrix and weakens the influence of positive pressure on the concentration difference, which slows down the decreasing rate of diffusion coefficient. On the contrary, the increase in temperature reduces the methane concentration in coal matrix and accelerates the decreasing rate of diffusion coefficient. These results provide theoretical guidance for the realization of the non-ventilation working face.

A cadaveric model for measuring sinonasal continuous positive airway pressure-a proof-of-concept study.

Obstructive sleep apnea is a common respiratory disorder that can have negative effects on health and quality of life. Positive pressure therapy (CPAP) is the primary treatment. There is a lack of consensus on the risk of postoperative CPAP after endoscopic sinus or skull base surgery. We present a proof-of-concept cadaver model for measuring sinonasal pressure delivered by CPAP. Three fresh cadaver heads were prepared by removing the calvaria and brain. Sphenoidotomies were made and sellar bone was removed. Pressure sensors were placed in the midnasal cavity, sphenoid sinus, and sella. CPAP was applied and the delivered pressure was recorded at increasing levels of positive pressure. Paired t tests and intraclass correlation coefficients were used to analyze results. Increases in positive pressure led to increased pressure recordings for all locations. Nasal cavity pressure was, on average, 81% of delivered CPAP. Pressure was highest in the sphenoid sinus. The effect of middle turbinate medialization on intrasphenoid pressure was not statistically significant in 2 heads. Intrasellar pressure was 80% of delivered CPAP with lateralized turbinates and 84% with medialized turbinates. Pressure recordings demonstrated excellent reliability for all locations. All heads developed non-sellar-based cranial base leaks at higher pressures. Cribriform region leaks were successfully sealed with DuraSeal®. Our proof-of-concept cadaver model represents a novel approach to measure pressures delivered to the nasal cavity and anterior skull base by CPAP. With further study, it may have broader clinical application to guide the safe postoperative use of CPAP in this population.

Middle ear pressure: effects on the auditory periphery.

The effects of direct variation in static middle ear pressure were studied in the acute guinea pig. Pressure differences of from −500 to +500 mm of H2O were examined. Pure tones were delivered to the test ear in a closed system and the sound pressure levels monitored with a condenser microphone and probe tube situated 2 mm from the tympanic membrane. The cochlear microphonic was recorded from a round window electrode. Both the relative impedance change and cochlear microphonic were noted at various middle ear pressure levels. The animals were perfused with Prussian blue and cochleas stained with osmic acid and prepared for histopathological study. It was found that negative pressure causes greater changes on impedance and transmission than positive pressure. Increase in positive pressure was found to cause a monotonic increase in input impedance and decrease in transmission. For negative pressures, the effect was nonmonotonic. Observed changes in transmission with both positive and negative pressures could be accounted for only in part by changes in input impedance of the middle ear. Morphological findings showed some discrete dilation of the vessels on the malleus and the tympanic membrane. Subject Classification: [43]65.24, [43]65.40.

Interclavicular air sac pressures and vocalization in mallard ducks anas platyrhynchos

1. Interclavicular air sac pressures were measured in intact, unrestrained mallard ducks. All vocalizations were accompanied by increases in positive pressure in the interclavicular air sac. 2. Opening the sac to the atmosphere reduces the intensity of calling in adults and ducklings. Reducing interclavicular air sac pressures increases the harmonic complexity of the calls and the effect is most pronounced in adult females and ducklings. These results are discussed in terms of normal maturational events during call development in ducklings. 3. In adult males, the effect of reducing interclavicular air sac pressures is minimal. There were no significant changes in the harmonic structure of the call. These differences are related to differences in syringeal structure between adult males and females.

The effects of intermittent positive pressure breathing (IPPB/I) with compressed air in patients with severe chronic nonspecific obstructive pulmonary disease.

The advent of mechanical respirators supplied a useful tool for assisting inadequate respiration (1-4). Segal and Dulfano suggested a practical abbreviated terminology for the various forms of pressure breathing therapy (5). Intermittent positive pressure breathing (IPPB II), producing a gradual increase of positive pressure during inspiration with a rapid fall of expiratory pressure to ambient levels, is considered most effective in producing hyperventilation (6-8). The application of a negative expiratory phase, although considered beneficial in patients with respiratory muscular paralysis (9, 10), has not found favor in the management of patients with b:onchospa~m and chronic diffuse pulmonary dIsease; mamly because the negative expiratory phase mcreases the hazards of bronchiolar collapse and consequent increase in air trapping (11, 12). . The effects of IPPB II in chronic pulmonary dIseases have been studied extensively and found useful by most investigators (13-23). Many of the reports are based on the clinical response without critical attempts to separate the bronchodilator and the oxygen effects from the effect of t~e IPPB/I alone. Moreover, the groups studIed were not clinically homogeneous and the findings not necessarily applicable to all the pulmonary patients. Cullen (16) thought that patients with severe bronchopulmonary obstruction and marked pulmonary failure might not respond as well to IPPB II, but Fraimow disputed this (24). Clinically, the writers have frequently noted that the effects of IPPB II are unsatisfactory in seriously ill patients with chronic diffuse obstructive emphysema. The patient would struggle, resist the machine, and tire easily,