Gas Penetration of Pit Membranes in the Xylem of Rhododendron as the Cause of Acoustically Detectable Sap Cavitation

1985 ◽  
Vol 12 (5) ◽  
pp. 445 ◽  
Author(s):  
DS Crombie ◽  
MF Hipkins ◽  
JA Milburn
Keyword(s):  
Structural Damage ◽  
Gas Permeability ◽  
Mechanical Damage ◽  
Gas Pressure ◽  
Water Films ◽  
Detached Leaves ◽  
Gas Penetration ◽  
Xylem Conduits ◽  
Gas Pressures

The gas pressure required to force sap from Rhododendron stems was investigated. Sap was expressed from stems, and stem permeability to gas increased, at pressures of 1.3-3.5 MPa. We interpret the changing of permeability as a removal of water films in the pores of the pit membranes which normally limit the length of xylem conduits. Similar pressure differences exist across the pit membranes separating gas and sap-filled conduits when cavitation occurs in Rhododendron. It is suggested that cavitation in detached leaves and shoots of Rhododendron occurs when gas penetrates the pit membranes. The increase in the gas permeability of xylem subjected to high gas pressures was reversed by a soaking in water. It could not therefore have been a consequence of mechanical damage, caused when xylem conduits are subjected to high gas pressures, because such structural damage would be irreversible.

Secondary Electron Imaging of Liquid Water Films in the Environmental Scanning Electron Microscope

1990 ◽  
Vol 48 (1) ◽  
pp. 374-375
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Liquid Water ◽  
Secondary Electron ◽  
Gas Pressure ◽  
Aqueous Environment ◽  
Water Films ◽  
Electron Imaging ◽  
Scanning Electron ◽  
Gas Pressures

High gas pressure scanning electron microscopy is now routinely possible with new microscopes operating between 0.1 and 20 torr gas pressure. Since the specimen chamber is separated from the electron optical column by pressure-limiting apertures, high gas pressures present at the level of the specimen do not affect the high vacuum in the column. The use of a single PLA underneath the last probe-forming lens allows maintainance of ∼0.1 torr. Twenty torr can be stabilized with two PLA, forming two differentially pumped pressure zones which may be incorporated into the last probe-forming lens.One of the most important new features of high gas pressure microscopy is the possibility to alter the type of gas and its pressure over a large range. High gas pressures (>1 torr) are required for charge neutralization on rugged insulators and for gas amplification of the SE signal. Additionally, using water vapors, liquid water can be stabilized. However, the aqueous environment is only one example among many possibilities.The secondary electron imaging of liquid water is a fascinating new aspect of scanning electron microscopy. At saturated water vapor pressures, water is stable indefinitely. Increasing or decreasing the vapor pressure allows condensation or evaporation of water and provides means to generate water films. As can be seer from Fig. 1, the stabilizing pressure for water at 20°C is 17.5 torr. Such a pressure would require a very short working distance for SE imaing. Therefore, it is preferable to reduce the specimen temperature and to establish vapor saturation at lower pressures. However, liquid water can only be stabilized at pressures greater than ∼4.5 torr.

scholarly journals Coupled Effects of Stress, Moisture Content and Gas Pressure on the Permeability Evolution of Coal Samples: A Case Study of the Coking Coal Resourced from Tunlan Coalmine

Water ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1653
Author(s):  
Guofu Li ◽  
Yi Wang ◽  
Junhui Wang ◽  
Hongwei Zhang ◽  
Wenbin Shen ◽  
...  
Keyword(s):  
Moisture Content ◽  
Coalbed Methane ◽  
Gas Permeability ◽  
Axial Stress ◽  
Gas Pressure ◽  
Pressure Curve ◽  
Permeability Evolution ◽  
Confining Stress ◽  
Qinshui Basin ◽  
Gas Seepage

Deep coalbed methane (CBM) is widely distributed in China and is mainly commercially exploited in the Qinshui basin. The in situ stress and moisture content are key factors affecting the permeability of CH4-containing coal samples. Therefore, considering the coupled effects of compressing and infiltrating on the gas permeability of coal could be more accurate to reveal the CH4 gas seepage characteristics in CBM reservoirs. In this study, coal samples sourced from Tunlan coalmine were employed to conduct the triaxial loading and gas seepage tests. Several findings were concluded: (1) In this triaxial test, the effect of confining stress on the permeability of gas-containing coal samples is greater than that of axial stress. (2) The permeability versus gas pressure curve of coal presents a ‘V’ shape evolution trend, in which the minimum gas permeability was obtained at a gas pressure of 1.1MPa. (3) The gas permeability of coal samples decreased exponentially with increasing moisture content. Specifically, as the moisture content increasing from 0.18% to 3.15%, the gas permeability decreased by about 70%. These results are expected to provide a foundation for the efficient exploitation of CBM in Qinshui basin.

Pressure Assisted Sintering of an Aluminium Alloy

2009 ◽  
Vol 618-619 ◽  
pp. 627-630
Author(s):  
Stephen J. Bonner ◽  
Graham B. Schaffer ◽  
Ji Yong Yao
Keyword(s):  
Aluminium Alloy ◽  
Gas Flow ◽  
Isothermal Holding ◽  
Horizontal Tube ◽  
Elevated Pressure ◽  
Nitrogen Pressure ◽  
Gas Pressure ◽  
Densification Rate ◽  
Conventional Press ◽  
Gas Pressures

An aluminium alloy was sintered using a conventional press and sinter process, at various gas pressures, to observe the effect of sintering gas pressure on the densification rate. Compacts of aluminium alloy 2712 (Al-3.8Cu-1Mg-0.7Si-0.1Sn) were prepared from elemental powders and sintered in a horizontal tube furnace under nitrogen or argon at 590°C for up to 60 minutes, and air cooled. The gas flow was adjusted to achieve specific gas pressures in the furnace. It has been found that increasing the nitrogen pressure at the start of the isothermal holding stage to 160kPa increased the densification rate compared to standard atmospheric pressure sintering. Increasing the nitrogen pressure further, up to 600kPa, had no additional benefit. The densification rate was increased significantly by increasing the gas pressure to 600kPa during both heating and isothermal holding. Under argon the elevated pressure did not increase the densification rate. Results seem to suggest that the beneficial effect of the elevated pressure on the rate of densification is related to nitride formation.

Experimental and Numerical Study of the Influence of Gas Pressure on Gas Permeability in Pressure Relief Gas Drainage

2018 ◽  
Vol 124 (3) ◽  
pp. 995-1015 ◽  
Author(s):  
Cun Zhang ◽  
Lei Zhang ◽  
Shihao Tu ◽  
Dingyi Hao ◽  
Teng Teng
Keyword(s):  
Gas Permeability ◽  
Numerical Study ◽  
Gas Pressure ◽  
Pressure Relief ◽  
Gas Drainage

A Study on Gas Pressure for Superplastic Forming of Titanium Alloy Bellows

2005 ◽  
Vol 475-479 ◽  
pp. 3051-3054 ◽  
Author(s):  
Gang Wang ◽  
Jun Chen ◽  
X.Y. Ruan
Keyword(s):  
Titanium Alloy ◽  
Thin Shell ◽  
Deformation Theory ◽  
Shell Theory ◽  
Superplastic Forming ◽  
Gas Pressure ◽  
Forming Process ◽  
Compressive Axial Load ◽  
Thin Shell Theory ◽  
Gas Pressures

The complex superplastic forming (SPF) technology applying gas pressure and compressive axial load is an advanced forming method for bellows made of titanium alloy, which forming process consists of the three main forming phases namely bulging, clamping and calibrating phase. The influence of forming gas pressure in various phases on the forming process are analyzed and models of forming gas pressure for bellows made of titanium alloy are derived according to the thin shell theory and plasticity deformation theory. Using model values, taking a two-convolution DN250 bellows made of Ti-6Al-4V titanium alloy as an example, a series of superplastic forming tests are performed to evaluate the influence of the variation of forming gas pressure on the forming process. According to the experimental results models are corrected to make the forming gas pressures prediction more accurate.

Effect of Sputtering Gas Pressure and Bias Voltage on Mechanical Properties of TiN Coating Deposited by DC Magnetron Sputtering

2004 ◽  
Author(s):  
Hirotaka Tanabe ◽  
Yoshio Miyoshi ◽  
Tohru Takamatsu ◽  
Hitoshi Awano ◽  
Takaaki Yamano
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Magnetron Sputtering ◽  
Bias Voltage ◽  
Adhesive Strength ◽  
Gas Pressure ◽  
Dc Magnetron Sputtering ◽  
Tin Films ◽  
Bombarding Energy ◽  
Gas Pressures

The mechanical properties of TiN films deposited on carbon steel JIS S45C by reactive dc magnetron sputtering under three sputtering gas pressures, 0.5Pa, 0.8Pa, and 1.76Pa were investigated. The residual stress once increased and then decreased with increasing bias voltage at 0.5Pa and 0.8Pa, but increased monotonously at 1.76Pa. These variations could be explained by the variations of the bombarding energy of a sputtered ion at each gas pressure. The variations of hardness and toughness correlated with the variation of residual stress. The variation of adhesive strength also could be explained by the variation of the bombarding energy with a model proposed in this study. A specific wear rate was also investigated, and it was found that to increase not only the hardness but also the adhesive strength is necessary to improve the wear resistance of TiN films.

The Influence of Processing Parameters on Gas Penetration in GAIM for Thick-Wall Parts

2010 ◽  
Vol 33 ◽  
pp. 669-673
Author(s):  
Hong Lei Shen ◽  
Liu Feng
Keyword(s):  
Quantitative Analysis ◽  
Process Parameters ◽  
Delay Time ◽  
Processing Parameters ◽  
Gas Pressure ◽  
Thick Wall ◽  
Melt Temperature ◽  
Computer Aided ◽  
Short Shot ◽  
Gas Penetration

In this paper, the auto door-handle was taken for an example, the quantitative analysis of the processing parameters (including melt temperature, shot size, delay time and gas pressure) on gas penetration in GAIM process was introduced using the method of orthogonality and computer-aided engineering. The effort in this article is aimed at the effect extent and trend of the four parameters on the molding result. Through the study, the main achievements are as follows: In short shot process for thick-wall parts, the shot size is the most significant factor on the molding result, the delay time is the second and the gas pressure is the last one. The length of gas penetration will increase with the reduction of shot size and delay time, or with the increasing of melt temperature and gas pressure. Then the optimization of the process parameters on the door handle was carried out.

Gas Pressure Dependence of Photon Emission Accompanying Fracture of Polycrystalline MgO in Nitrogen

2006 ◽  
Vol 317-318 ◽  
pp. 313-316 ◽  
Author(s):  
Tadashi Shiota ◽  
Yasuo Toyoshima ◽  
Kouichi Yasuda ◽  
Yohtaro Matsuo
Keyword(s):  
Pressure Dependence ◽  
Room Temperature ◽  
Photon Emission ◽  
Gas Discharge ◽  
Gas Pressure ◽  
The Other ◽  
Experimental Conditions ◽  
Infrared Photon ◽  
Gas Pressures

The photon emission accompanying fracture of a polycrystalline MgO was investigated at room temperature under N2 gas pressures from 10-4 to 105 Pa. At fracture, the ultraviolet, visible and infrared photon emissions instantaneously increased, and then rapidly decreased in most of the experimental conditions. However, in a N2 gas pressure of around 100 Pa, their peak counts lasted for about 10 milliseconds, and the amount of the UV photon emission was fifteen times larger than those obtained in the other N2 gas pressures. This abrupt increment in the emission was explained by the luminescence due to N2 gas discharge according to the classical Townsend’s theory. In conclusion, the photon emission accompanying fracture of a polycrystalline MgO mainly originated from the excited defects as reported by the authors previously, but the N2 gas discharge had a supplementary effect on the emission around a specific N2 gas pressure.

scholarly journals Thermodynamic Characteristics of Methane Adsorption of Coal with Different Initial Gas Pressures at Different Temperatures

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Tingting Cai ◽  
Zengchao Feng ◽  
Yulong Jiang ◽  
Dong Zhao
Keyword(s):  
Adsorption Process ◽  
Thermodynamic Characteristics ◽  
Methane Adsorption ◽  
Gas Pressure ◽  
Adsorption Heat ◽  
Mathematical Function ◽  
Adsorption Time ◽  
Free Gas ◽  
Different Temperatures ◽  
Gas Pressures

The adsorption of methane in coal depends on both pressure and temperature, and the adsorption gas content decreases as the temperature rises while increases as the pressure increases. When the gas molecule switches between the free state and adsorbed state, energy exchange is accompanied. To study the thermodynamic characteristics (adsorption heat, adsorption content, and adsorption time) of the methane adsorption of coal, the isothermal methane adsorption experiments of coal with different initial free gas pressures at different temperatures (30–90°C) were conducted. In this paper, a well-defined mathematical function of the adsorption heat was established on the basis of the actual gas state equation, Boltzmann energy distribution theory, and the two-state energy model, and the function was verified by the experimental data. The results show that the mathematical function of the adsorption heat can well describe the relationship among the adsorption heat, temperature, and initial free gas pressure in the closed adsorption system, and the adsorption heat involves the initial free gas pressure. The greater the initial free gas pressure, the less the adsorption heat is. In the adsorption process with different initial free gas pressures at different temperatures, the real-time free gas content increases with time and the adsorption system shows desorption process generally. For the adsorption process with the same initial free gas pressure, the adsorption time increases with the rising temperature. For the adsorption process with different initial free gas pressures at the same temperature, the greater the initial free gas pressure, the shorter the adsorption time it takes to reach an equilibrium state. The results help to understand the thermodynamic characteristics and the heat and mass transfer of methane in coal adsorption.

Transportation Risk Analysis

2015 ◽  
pp. 1-31 ◽  
Author(s):  
Dragan Crnčević
Keyword(s):  
Structural Damage ◽  
Measurement Techniques ◽  
Mechanical Damage ◽  
Fluid Flows ◽  
Exclusion Zone ◽  
Radio Communications ◽  
Transportation Risk ◽  
Common Causes ◽  
Tanker Accidents ◽  
Operational Error

Petroleum is transported across the water in barges and tankers, and on land, using pipelines, trucks, and trains. Natural gas is moved, mainly, by pipelines. The most common causes of tanker accidents are: fire/explosions, loading/offloading, structural damage, collision, and grounding. Pipeline accidents are due to: corrosion, third parties activities, mechanical damage, natural events, and operational error. Some of the most commonly applied preventive activities that reduce spills in waterborne transportation are: double-hulled tanker, navigation safety and radio communications equipment, tanker exclusion zone, etc. The pipeline condition can be recorded by using various nondestructive measurement techniques or by chemical analysis of fluid flows. Different types of sensors can be used to locate and determine the size of an anomaly in the pipeline geometry. Mayor methods for detecting leaks are measuring the hydrodynamic parameters or registering abnormal conditions in the fluid flow and detecting phenomena in the immediate vicinity of the pipeline.

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