Cylinder Apparatus Research Articles

Agitation and its control on excess pore water pressure and debris‐flow behaviour

AbstractExcess water pressure strongly affects the rheology and flow behaviour of debris flows, and the mechanisms for development and persistence of the pressure can be diverse. Using nine experimental slurries prepared with the sediments collected from the deposit of a large‐magnitude debris flow by modifying maximum grain size and solid concentration, the influence of agitation on excess water pressure is investigated with a cylinder apparatus, consisting of a coaxially mounted bucket and impeller driven by a variable‐speed motor. Agitation proceeding in three dynamic stages raises relative excess water pressure (R) by 17%–34% of the peak R in the static stage, showing that agitation can significantly increase excess water pressure. The magnitude of the steady R increases with the level of agitation, which is measured by impeller speed and slurry temperature, and the steady R in a slurry is agitation‐level‐dependent below its potential maximum value. The transfer of particle weight to water in debris flows can occur under zero or very low to extremely low effective stresses. Agitation raises excess water pressure essentially by promoting dispersion of the finest‐grained grains in water and that of progressively larger grains in gradually coarser‐grained slurries. The flow resistance of the tested slurries, characterized by net torque exerted on the impeller by the motor, decreases with increasing liquefaction ratio, demonstrating that agitation enhances debris‐flow mobility by raising excess water pressure. It is of importance to dampen agitation by building proper mitigation measures in remedial practices.

First Determination of Volume Changes and Enthalpies of the High-Pressure Decomposition Reaction of the Structure H Methane Hydrate to the Cubic Structure I Methane Hydrate and Fluid Methane

Pressure-temperature (P-T) conditions of the decomposition reaction of the structure H high-pressure methane hydrate to the cubic structure I methane hydrate and fluid methane were studied with a piston-cylinder apparatus at room temperature. For the first time, volume changes accompanying this reaction were determined. With the use of the Clausius-Clapeyron equation the enthalpies of the decomposition reaction of the structure H high-pressure methane hydrate to the cubic structure I methane hydrate and fluid methane have been calculated.

Ultrasonic detection of bone fragment in mechanically deboned chicken breasts

A piston and cylinder apparatus was designed and fabricated based on pulse–echo technique to perform ultrasound scans for both liquids and solid samples of variable heights. A short time fast Fourier transform program was used to reduce noise in the signal. This apparatus was tested with distilled water. Velocity was accurately measured, whereas values of amplitude ratio varied widely. Chicken breast muscles' density, velocity, impedance and amplitude ratio were determined. Amplitude ratio could successfully discriminate between uncut samples, cut samples, and cut samples with a bone fragment, regardless of bone fragment size from 6 mm 2 to 16 mm 2 projected area. The ratio of amplitude ratios of cut samples with bone fragment to that of cut (or uncut) samples decreased as the ratio of bone fragment projected area to transducer projected area increased. New hygiene regulations now require all food industries to implement a documented safety management system based on hazards analysis and critical control point (HACCP) principles. There is a need to detect and remove bone fragments from deboned poultry products before marketing. The technology developed in this research provides a non-invasive cost effective solution to a food safety concern that is causing production bottlenecks and hazardous situations in deboned poultry meat production.

Independent coding of connected environments by place cells

Place cells are hippocampal neurons that have a strong location-specific firing activity in the rat's current environment. Collectively, place cells also provide a signature of the rat's environment as their ensemble activity is markedly different when recorded in distinct apparatuses. This phenomenon, referred to as 'remapping', suggests that each environment activates a different hippocampal map. In this study, we sought to determine the independence of such maps. In Experiment 1, we used a cylinder apparatus that was divided into two equal halves by a central barrier with an aperture allowing the rat to freely commute between the two sides. A local change in one side failed to induce field remapping in the changed side, thus precluding any significant conclusion to be drawn. We therefore designed Experiment 2 in which place cells were first recorded while rats explored three distinct high-walled boxes. Most cells had distinctive firing fields in each box. A runway was then added to connect two initially unrelated boxes. This manipulation altered the firing of some cells but the fields in each box were still clearly distinguishable. The final manipulation consisted of changing one box and allowing the rat to commute freely between the changed and unchanged boxes. While the firing fields remapped in the changed box, they were most usually unaltered in the unchanged box. These results suggest that the hippocampus holds a set of independent maps for each box, and that each specific map is activated mainly according to the rat's current sensory environment.

99/02716 Performance characteristic of fluid power converters

The endoreversible thermodynamic theory of heat engines is extended to fluid flow power converters. The useful power can be extracted from the piston and cylinder apparatus. The correlation between power output and efficiency is derived based on a linear flow resistance relationship. The influences of the piston-cylinder friction and nonlinear flow resistance relationships on the performance of the converter are also analyzed in this paper. Performance optimization is undertaken based on the overall size constraints. The paper also develops an analogy among the fluid flow power converters, endoreversible heat engines, endoreversible isothermal chemical engines, classical reversible heat engines, and the ideal motor powered by electrical battery. The results can be applied to the performance analyses and optimization for many steady-flow shaft-powered components.

Reduction in piston-cylinder experiments; the detection of carbon infiltration into platinum capsules

Problems associated with intermittent and variable degrees of sample blackening are often reported for studies involving the preparation of CO 2 -bearing silicate glasses in piston- cylinder apparatus. This phenomenon is generally attributed to H infiltration, which leads to the reduction of CO 2 and the precipitation of graphite with the concomitant formation of water. In this study we demonstrate that carbon diffusion into platinum capsules may be a common cause of blackened glasses and this process may be detected using fourier transform infrared spectroscopy (FTIR) to identify the presence of CO without elevated H 2 O contents. The simulated infiltration of 12 C from a graphite furnace into a 13 C -bearing sample is illustrated using secondary ion mass spectroscopy (SIMS) and micro- FTIR analysis. Careful FTIR monitoring of variable sample reduction has helped to identify the precautions required to reduce C (and H) infiltration in solid media assemblies and it appears that physical barriers can be more important than the chemical buffers traditionally employed.

High-Pressure transport phenomena in [formula omitted

Pressure effect on T c for “Pb-1212” phase is investigated up to 2GPa using a piston- cylinder apparatus. Unusually large pressure coefficient of T c is observed ( dln T c dp =0.65 GPa −1 , T c =16.8K at latm.). Pressure induced-delocalization of holes is discussed.

Compressions of ta10w alloy kennertium w-2, and beryllium oxide to 4.5 GPa

Abstract The volume compressions of a tantalum alloy, tungsten alloy, and beryllium oxide (BeO) have been derived from the measurements of axial shortenings of cylindrical specimens of these materials to 4.5 GPa at room temperature. These measurements were carried out in a solid pressure medium piston- cylinder apparatus.

The Normal Approach, Contact, and Rebound of Lubricated Cylinders

An algorithm has been developed to simulate the normal approach, contact, and rebound of lubricated cylinders. The detailed interaction between the lubricated cylinders is predicted, thus providing the pressure distribution, contact forces, and other variables useful in predicting rates of wear. The present technique improves on the existing elastohydrodynamic (EHD) models in the following areas: (1) during contact a solid-solid model is used; (2) a two-dimensional analysis is used to obtain the pressure distributions in both the circumferential and axial directions; (3) inertia effects are approximated; and (4) any specified load can be treated. The simulated results for the constant load case are compared with the results of Wada and Tsukijihara and a formula developed by Cameron. For sinusoidal loads the results are compared with experimental data from a cylinder and sleeve apparatus.

Abrasion of plastics

Preliminary data on the effect of the nature of a plastic on its abrasive resistance and the effects of grit size and cutting rate are presented. Abrasion tests were performed on an instrumented pin on cylinder apparatus having removable segments for observing the coated abrasive surface in the scanning electron microscope (SEM); this allowed for direct correlation between measurements of coated abrasive performance and SEM observations of surface morphology. The materials studied were (a) a linen-impregnated phenolic resin, (b) polymethyl methacrylate (Plexiglas) and (c) polytetrafluoroethylene (Teflon). The polymers tested exhibited characteristics which set them apart from one another as far as abrasive wear is concerned. All three showed cutting and scratching of the surface during early stages of abrasion. The phenolic was found to “self-clean” the abrasive by knocking free the previously abraded particles. Frictional heating was sufficient to raise the surface temperature of Plexiglas above its glass transition temperature at high cutting rates introducing significant rate effects. The Teflon fibers were cold-worked by the rolling action at the surface producing a major plastic deformation contribution.

High-field properties of n-InP under high pressure

The high electric field properties of n-InP at 300 K have been studied as a function of pressure. Hydrostatic measurements are made in a piston and cylinder apparatus, using a liquid pressure-transmitting medium. The threshold fields ( E T ) for transferred electron instabilities range from 7.5 to 8.5 kV/cm at atmospheric pressure. The resistivity of the samples increases with increasing pressure. The most reliable results show that E T increases slightly with pressure below 40 kbar. This behavior can be explained qualitatively in terms of possible band structure changes. By using known variations of parameters such as effective mass and sub-band energy gaps, detailed theoretical calculations are carried out to fit the data and to determine the correct mode of operation (two- or three-level operation). The results are also compared with analogous experiments on GaAs.

Melting of germanium to 65 kbar

Melting curve of germanium has been determined to 65 kbar in a single stage piston- cylinder apparatus. The melting curve is slightly concave towards the pressure axis. This trend is apparently in agreement with Bundy's data replotted on the revised pressure scale.

The production of positive ions by field ionization at the surface of a thin wire

Wires of platinum and tungsten 4-10 μm in diameter were used. They were placed along the axis of a coaxial cylinder. When the wire was charged positively with respect to the cylinder and any of the gases ethylene, water, oxygen, nitrogen, nitrous oxide, ammonia, carbon monoxide and hydrogen was present, a current was observed, with a voltage between wire and cylinder less than 20 kv. The current was directly proportional to gas pressure except with water and ammonia. It appeared to be due to field ionization at the surface of the wire. Currents exceeding 10-7 A were obtained with wires 2 cm long. Field ionization was also brought about with a thin wire between parallel plates. With the plates apparatus and with the cylinder apparatus, a fraction of the ions produced could be extracted through a slit cut in one plate, or in the cylinder. The electric field at the wire surface was not great enough, for a smooth surface, to produce field ionization. It is proposed that a considerable local intensification of field occurs because of surface roughness. The field intensification factor for a 10 μm diameter platinum wire was investigated by measuring the field emission of electrons from the wire, first as a function of field at constant temperature and secondly as a function of temperature at constant field. The temperature variation of field emission from 650-1375° k agreed very well with the theory given by Good and Muller (1956). Corrections for thermionic emission at the higher temperatures from the flat parts of the surface were made with a method which used the Schottky equation. The field intensification factor found in this way was 70. Such a value explains the occurrence of field ionization.

Initiation of condensed explosives by compression of the surrounding gas

The rapid compression of gas in a simple piston and cylinder apparatus provides a convenient ignition source for a condensed explosive in contact with the gas. A photomultiplier cell is used to detect initiation of an explosive in the final volume of the cylinder. Partial ignitions are never obtained with tetrazene nor with lead azide, but are fairly common with the other explosive examined at compression ratios intermediate between those always, and those never, causing complete decomposition. The initiating explosives examined are ignited at final gas temperatures between 300 and 1000°C. It is much more difficult to ignite the secondary explosives nitroglycerine and pentaerythritol tetranitrate and complete explosions are rare; the chemical nature of the gas is important.