Effect Of Wall Material Research Articles

A psychoacoustical investigation into the effect of wall material on the sound produced by lip‐reed instruments

In order to investigate whether a lip‐reed instrument's material of manufacture plays a significant role in determining the timbre of the notes it produces, tests have been conducted on five post horns. These post horns have identical geometry but are manufactured from different copper alloys. Using a laser Doppler vibrometer, the structural resonances of each instrument have been established and the wall vibrations induced in each instrument when artificially blown have been measured. In this paper, these measurements are compared with findings from a series of blindfold playing tests carried out using professional musicians and with listening tests comprising notes produced by the different instruments.

Optimization of the Microencapsulation of Lemon Myrtle Oil Using Response Surface Methodology

Response surface methodology (RSM) was applied to study the effects of types of wall materials (modified starch + maltodextrin and whey protein concentrate + maltodextrin), feed concentration, oil concentration, and outlet air temperature on oil retention and surface oil content of the encapsulated powder. The results revealed that the oil retention was significantly (P < 0.05) affected by the constant term of types of wall materials and the linear term of feed concentration but seemed to be almost independent (P > 0.05) of experimental range of oil concentration and outlet air temperature. The types of wall materials, oil load, and outlet air temperature showed a significant (P < 0.05) influence on surface oil content. The types of wall materials (Hi-Cap and WPC) also influenced significantly the oil retention and surface oil content. Based on the limited range of experimental conditions used in this work, it was not possible to choose the wall materials that can give both high oil retention and low surface oil content. Disregarding the effect of wall material, an optimum response was obtained at 40% of feed concentration (w/w), 18% of oil concentration, and 65°C of outlet air temperature.

Effect of Wall Surface Properties at Different Drying Kinetics on the Deposition Problem in Spray Drying

Current methods in alleviating the wall deposition problem in spray drying emphasize mainly controlling the stickiness of the drying particles and less attention is placed on the properties of the dryer wall. In this experimental study, the effect of wall surface properties on the deposition mechanism has been investigated. Properties considered in classifying different wall materials were surface energy, roughness, and dielectric properties. The model solution contained sucrose, representing low-molecular-weight sugars commonly encountered in spray drying of fruit and vegetable juices. The effect of wall properties on deposition was explored at different drying rates producing particles of different surface rigidity. Larger surface roughness produced higher deposition fluxes for particles with high impact velocity and moisture. Surface energy and surface roughness were found to have no significant effect for dry rigid particles at the middle and bottom elevation of the drying chamber. However, material with lower surface energy (Teflon) exhibited less deposition for rubbery particles at such elevations. Analysis shows that dielectric wall material (Teflon) tends to enhance deposition of dry particles because of attrition at the surface. Higher wall temperature was found to produce slightly more deposition. The results of this work give a general indication of the effect of wall material on the deposition problem and provide the fundamental understanding for further studies along this line. Proper selection of dryer wall material will provide potential alternatives for reducing the deposition problem.

Uncatalyzed Oxidation of 1,5,9-Cyclododecatriene with Molecular Oxygen

Cyclododecatriene was oxidized in liquid phase with molecular oxygen in a batch reactor, and the oxidation kinetics were studied under various reaction conditions. The reaction exhibits strong autocatalysis, thereby yielding epoxycyclododecadiene and cyclododecatryl hydroperoxide as oxidation products. The oxidation is found to exhibit strong selectivity toward epoxide. The batch kinetics were obtained and compared in glass and stainless steel reactors, and the effect of wall material on reaction rate and epoxide selectivity was explored. The kinetic data follows a first order autocatalytic rate equation, and the activation energy was determined and found to be higher for the steel reactor compared to the glass reactor.

Numerical Analysis of Wall Material Effect on Indoor MIMO Channel Capacity

Effects of wall material on the channel capacity of an indoor multiple input multiple output (MIMO) system are investigated using a hybrid technique of the method of moments (MoM) and the finite difference time domain (FDTD) method with consideration of the Ricean K factor and the effective degrees of freedom (EDOF) of multiple paths.

Electron cyclotron resonance harmonics and wall material effects in a microwave discharge

In this article we investigate a 2.45 GHz microwave discharge operated at the electron cyclotron resonance (ECR) and the second harmonic, by applying a divergent magnetic field where the maximum is changed from 1400 to 500 G. The magnetic field is continuously decreased so that the ECR zone is moved axially along the chamber from about 15 cm away to very close to the microwave window. When the field is reduced to below 875 G the ECR disappears and only the second harmonic is present in the source. We observe that the second harmonic is not efficient enough for breakdown at microwave power of less than 500 W and gas pressure of 0.48 Pa, and it is shown that an overdense plasma can not be generated by use of the second harmonic (independent of gas type). It is also shown that the wall material close to the ECR zone is extremely important, probably due to an effect similar to that of the antenna material in capacitively and inductively coupled plasma sources. The possibility of measuring the thickness and location of the effective ionizing resonance zone is discussed. A calculation of the plasma density as a function of the magnetic field is performed, which takes into account the conservation of magnetic flux and the secondary emission from the wall, and excellent agreement with the measured results is obtained.

Wall material effects in stationary plasma thrusters. I. Parametric studies of an SPT-100

The operation of a laboratory version of the flight-qualified SPT-100 stationary plasma thruster is compared for four different discharge chamber wall materials: a boron nitride–silica mixture (borosil), alumina, silicon carbide, and graphite. The discharge is found to be significantly affected by the nature of the walls: changes in operating regimes, up to 25% variations of the mean discharge current, and over 100% variations of the discharge current fluctuation amplitude are observed between materials. Thrust, however, is only moderately affected. Borosil is the only material tested that allows operating the thruster at a low mean current, low fluctuation level and high thrust efficiency regime. It is suggested that secondary electron emission under electron bombardment is the main cause of the observed differences in discharge operation, except for graphite, where the short-circuit current inside the walls is believed to play a major role. It is also suggested that the photoelectric effect, which has apparently not been given attention before in the Hall thruster literature, could increase the cross-field electron current.

Wall material effects in stationary plasma thrusters. II. Near-wall and in-wall conductivity

Simulations and experimental characterizations of a stationary plasma thruster are compared for four different wall materials to investigate near-wall conductivity (dielectric materials) and in-wall conductivity (conducting materials) in such a discharge. Using a one-dimensional transient fluid model that takes into account a possible electron temperature anisotropy, it is shown that electron-wall backscattering plays a crucial role by maintaining a relatively high electron temperature along the magnetic field lines which in turn drives large electron currents toward the walls. The large differences in discharge current observed experimentally for the dielectric materials are qualitatively recovered, confirming that near-wall conductivity results from the combined effects of secondary electron emission and electron backscattering. A clear correlation is found between the appearance of space charge saturation at the walls and a jump of the discharge current observed in experiments when varying the discharge voltage or the magnetic field. The anomalously high values of discharge current observed experimentally with graphite are also correctly recovered in simulations, which highlight a plasma short-circuiting effect resulting from in-wall currents.

Experimental analysis and modelling of particle-wall collisions

A detailed experimental analysis of the particle-wall collision process in a particle-laden horizontal channel flow was performed using particle tracking velocimetry. The particles used in this study were glass beads with a diameter of 100 and 500 μm and quartz particles with a size of about 100 μm. Moreover, the effect of wall material on the collision process was analysed. Special attention was paid to the influence of wall roughness and therefore, untreated stainless steel, polished stainless steel, Plexiglas, and rubber gum were used. It was found that wall roughness considerably alters the rebound behaviour of the particles and causes in average a re-dispersion of the particles, i.e. gravitational settling is reduced. A similar effect was observed for the non-spherical quartz particles and a polished stainless steel wall. The experimental data were used to improve and validate a wall collision model to be used in the frame of the Lagrangian approach. In this model the wall roughness is simulated by assuming that the impact angle is composed of the trajectory angle with respect to the plane wall and a stochastic component caused by wall roughness. A modified normal distribution function was assumed for the roughness angle distribution. All the parameters for the wall collision model, such as restitution coefficient and friction coefficient as functions of the impact angle were obtained from the experiments. The simulations showed a very good agreement with the measurements for the particle rebound properties.

The effect of wall materials on the timbre of brass instruments

It has long been thought by players and instrument makers that the material from which a brass instrument is made influences the tone quality and playing characteristics of the instrument. For instance, the brochure of a maker of custom trombones describes bells made of three alloys: yellow brass (70% Cu, 30% Zn), having the ‘‘clearest sound, sharpest articulation,’’ gold brass (85% Cu, 15% Zn), with ‘‘warm sound, rounded articulation,’’ and red brass (90% Cu, 10% Zn), with ‘‘warmer sound, covered articulation.’’ The bells are made in three metal thicknesses: light weight, with ‘‘flexible tone, rapid response,’’ standard weight, with ‘‘balanced tone, even response,’’ and heavy weight, with ‘‘firm tone, stable response.’’ Most players agree with these statements. This model of trombone is made so that bell sections can be interchanged while leaving the remainder of the instrument intact. The present paper reports the results of measurements under playing conditions on several different bells. Comparisons of steady-state behavior are made via the transfer function between sound pressure in the mouthpiece cup and an on-axis point outside the bell. An attempt will also be made at the rather more difficult task of characterizing the attack transient.

Development and Characterization of a New Compact Microwave Radical Beam Source

For plasma-assisted processing of future semiconductor devices, a new compact microwave plasma source has been specifically designed. The source is versatile in that plasma production is possible over a wide pressure range. Measured plasma parameters include electron densities in excess of 1011 cm-3 and low plasma potential (<10 V). Plasma chemistry was investigated by emission spectroscopy and the main excited species found was atomic oxygen radicals. In determining the absolute density of radical species, titration using NO2 gas was employed to correlate the oxygen atom density with the plasma operating conditions. At a microwave power of 300 W and a O2 partial pressure of 16.6 Pa oxygen atom densities in excess of 1.9×1015 cm-3 have been measured, which gives dissociation rates of O2 of approximately 20%. Effects of wall materials on the oxygen atom density were also investigated. Using a Teflon liner at high pressures provides a 37% increase in oxygen atom density due the lower recombination coefficient of Teflon compared to stainless steel.

Premature Transition to Film Boiling at Stepwise Heat Generation. 2nd Report. Effect of Wall Material and Surface Condition.

The effects of wall material and surface condition on the behavior of an initial boiling bubble of R113 subjected to transient heating is investigated using a heater with a large heat capacity. The behavior of the initial bubble is closely related to the premature transition to film boiling of liquids with high wettability. An initial bubble, which is peculiarly shaped like a 'straw hat' and leads to premature transition in saturated liquid nitrogen as reported in a previous report, appears also on the heated wall with large heat capacity and grows rapidly to cover the entire wall surface. The initial bubble is found to be a coalesced bubble into which small bubbles activated in succession along the heated surface are rolled, from the observation using a high-speed video camera. The growth rate of the initial bubble along the heated surface is not greatly affected by the thermal conductivity of wall material but is affected markedly by the surface roughness.

Premature transition to film boiling with stepwise heat generation 2nd report: Effect of wall material and surface condition

The effects of wall material and surface condition on the behavior of an initial boiling bubble of R113 subjected to transient heating were investigated using a heater with a large heat capacity. The behavior of the initial bubble is closely related to premature transition to film boiling of liquids with high wettability. An initial bubble, which is peculiarly shaped like a straw hat and leads to premature transition in saturated liquid nitrogen (as reported in a previous paper), also appears on a heated wall with large heat capacity and grows rapidly to cover the entire wall surface. From the observations using a high-speed video camera, the initial bubble is found to be a coalesced bubble into which small bubbles activated in succession along the heated surface are rolled. The growth rate of the initial bubble along the heated surface is not greatly affected by the thermal conductivity of the wall material but is affected markedly by the surface roughness.

Premature transition to film boiling with stepwise heat generation 2nd report: Effect of wall material and surface condition

Premature transition to film boiling with stepwise heat generation 2nd report: Effect of wall material and surface condition

Performance characteristics of an oxygen radical beam radio-frequency source

An oxygen radical beam source discharged by radio frequency was newly designed and constructed. Effects of wall materials on the optical emission intensity of the oxygen plasma and the atomic oxygen flux were measured. The optical emission intensity correlated well with the intensity of the atomic oxygen flux. An atomic oxygen flux as high as 1.4×1016 atoms/(cm2 s) was achieved at 50 mm away from an end plate, with nine orifices, of the radical beam source by using a sleeve made of pyrolytic boron nitride in the beam source.

Wall Material and Capping Effects on Microlysimeter Temperatures and Evaporation

AbstractThe microlysimeter (ML) is useful for measurements of evaporation from soil but questions persist regarding correct ML design. We studied the effects of length and wall material on evaporation and the effects of wall material and capping on ML temperatures. Cylindrical steel and plastic MLs of 10‐, 20‐, and 30‐cm lengths and 8.8‐cm o.d. were used in two field experiments on a bare Pima clay loam (fine‐silty, mixed, thermic Typic Torrifluvent). Steel MLs significantly underestimated 8‐d cumulative evaporation compared with plastic MLs for 20‐cm lengths. Steel MLs conducted heat more easily and their surfaces were significantly cooler during the day and warmer at night than either plastic MLs or the adjacent field soil. Capping the bottoms with 0.6‐cm‐thick plastic disks caused accumulation of heat in the MLs. For plastic MLs, only the 20‐ and 30‐cm lengths were long enough for continuous use for 9 d under our conditions. It was unclear if cumulative evaporation varied with length for steel MLs. We recommend that walls be constructed of material with low thermal conductivity and that end caps be designed to maximize thermal transfer between the soil inside and below the ML. A length of at least 30 cm is recommended if measurements are needed at the same location for several days.

Effect of wall material on H− production in a multicusp source

The effect of wall material on volume H− production in a magnetically filtered multicusp source has been investigated. Under the same discharge conditions, Al and Cu generally produce the highest H− ion current. It is shown that secondary electrons emitted from wall surfaces can account for the difference in H− yield.

The effect of wall materials on hydrogen recycling in JT-60

A model calculation on hydrogen recycling at the wall in JT-60 has been made for three different wall materials (molybdenum, Inconel 625 and titanium carbide) for the case when the plasma is heated by neutral beam injection. It has been assumed that only charge exchange neutrals hit the wall. Values of the recycling coefficient required to keep constant plasma densities for two different flux densities 1 × 10 16 and 3 × 10 16 H/cm 2·s onto the wall have been estimated to be 0.75 and 0.92, respectively. By assuming Maxwellian energy distributions (200 and 400 eV), the recycling coefficients have been calculated as a function of time and wall temperature by taking account of particle re-emission due to backscattering, diffusion and saturation overflow. The wall temperature regions which satisfy the above criteria for 5 and 10 s discharges have been discussed for the three materials.

Wall material and wall temperature effects on negative ion production in a hydrogen plasma

The effect of wall material and wall temperature on negative ion production in a hydrogen plasma has been studied. Under the same plasma conditions, within the combined uncertainties of the measurements, the same negative ion densities were found for Pyrex, stainless steel, copper and molybdenum. However, there seems to be a trend for stainless steel walls to produce somewhat higher negative ion densities. Contamination of the walls with hydrocarbons was found to reduce the negative ion density. It was also found that cooling the Pyrex walls leads to an increase in the negative ion density.

Tube viscometry of blood: effects of wall material.

ArticleTube viscometry of blood: effects of wall material.G M Chisolm, and J L GainerG M Chisolm, and J L GainerPublished Online:01 Aug 1971https://doi.org/10.1152/jappl.1971.31.2.313MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformationCited ByThe viscosity and viscoelasticity of blood in small diameter tubesMicrovascular Research, Vol. 11, No. 2 More from this issue > Volume 31Issue 2August 1971Pages 313-7 https://doi.org/10.1152/jappl.1971.31.2.313PubMed5105130History Published online 1 August 1971 Published in print 1 August 1971 Metrics