Plexiglass Substrates Research Articles

A Comparison of the Machining Efficiency of Two Brands of Stainless Steel Endodontic Hand Files

Abstract The purpose of this study was to compare the machining efficiency of a flexible stainless steel K-type hand file recently introduced by Brasseler USA (“F-Style files”), with that of a well-studied Endodontic instrument (“Flex-o-files,” Maillefer Dentsply), that has been on the market for more than 20 years. The comparison of machining efficiencies of these two brands of files was conducted on both dentin and plexiglas substrates, using an apparatus that allowed a constant force to be applied from each file being tested. The results indicated that the Brasseler instruments had poorer machining efficiency than those of the Maillefer files.

On the neutron reflectivity of Ni-coated mirrors

The work deals with neutron reflectivity measurements performed for five Ni coated mirrors. While one of the mirrors was 58 Ni coated on a glass substrate, the other four mirrors were from two different types of the commercially available plexiglass substrates, coated with either 58 Ni (150 nm thick) or with 700 nm thick NiCr (80% Ni, 20% Cr). The four plexiglass mirrors were prepared at 1991. Some of the mirrors were measured during 1991 and 1993 and are included in the present measurements in order to check the quality of the plexiglass mirrors over years. It has been found, from the present measurements, that plexiglass, as a substrate, successfully substitutes glass and the quality of the Ni coating lasts several years without deterioration.

The neutron reflectivity of different Ni-coated mirrors

The work deals with neutron reflectivity measurements performed for 58 Ni , NiCr and natural Ni films coated on plexiglass substrates of different types and thicknesses. The reflectivities were compared with those measured six years earlier for some of the mirrors. Besides, the reflectivities obtained for 58 Ni and natural Ni films coated on plexiglass were compared with that measured for 58 Ni on glass substrate. The neutron reflectivity behaviours, deduced from experimental measurements were found to be similar, both for glass and plexiglass substrates.

The neutron reflectivity of Ni films coated on plexiglass

The work deals with neutron reflectivity measurements performed for different Ni films coated on different types of plexiglass substrates. The neutron reflectivity behaviours, deduced from experimental measurements, were found to be similar; both for glass and plexiglass substrates. It is concluded that plexiglass can replace glass, as a substrate for neutron mirrors. The quality of the mirror depends on both the Ni coating and the type of plexiglass going to be used as a substrate.

The endodontic file is a disposable instrument

Most cutting and machining tools wear when properly operated on intended substrates. Little is known about endodontic files when machining on human dentin. It was shown earlier that the efficiency of files was very variable when evaluated on Plexiglas substrates. The present study of seven different brands and types of files was undertaken to understand their wear better when machining human dentin. It was shown that all files evaluated rapidly deteriorated when machining dentin. This decline in efficiency was significant but different within, as well as, among brands. It was suggested that endodontic files be disposable.

Neutron reflectivity measurements of different nickel mirrors

Neutron optical devices, such as neutron guides, apply mirrors where multiple total reflections of neutrons takes place. Materials more light and flexible than glass have never been used as a substrate of the neutron mirrors. The present work deals with neutron reflectivity measurements performed for three nickel mirrors. While one of them is a glass plate coated with a NiCr film, the other two mirrors are on plexiglas substrates coated by either NiCr or 58Ni films. The incident beam covered a neutron wavelength range from 0.05-0.4 nm. The results of the present measurements are in favour of the idea of using acrylic glass as a substrate for nickel mirrors.

Photostable solar concentrators based on fluorescent glass films

Efficient luminescent solar concentrators (LSC) were prepared by deposition of organically modified sol-gel films doped by photostable perylimide dyes on plexiglas substrates. The absorption spectra of these dyes extends from 420 to 620 nm covering the visible part of the solar spectrum and the emission is between 550 and 750 nm, close to the optimum response of silicon and gallium arsenide solar cells. The efficiency of this type of collector was calculated from the absorption coefficients, quantum efficiency of the fluorescence and the overlap between emission and absorption spectra by the method of Monte-Carlo and found to be close to 20%. Optimum concentrations are shown to be strongly dependent on the extent of overlap between the absorption and the emission spectra, which also appears to be the limiting factor in respect to the efficiency of the concentrator.

Natural Convection Heat Transfer From an Array of Rectangular Protrusions in an Enclosure Filled With Dielectric Liquid

An experimental investigation of natural convection liquid immersion cooling of a three by three array of rectangular protrusions in an enclosure is presented. The heated elements geometrically simulated 20 pin dual-inline electronic packages and were mounted on a plexiglass substrate, which formed one vertical wall of a dielectric liquid filled rectangular enclosure. The remaining vertical boundaries of the enclosure were insulated, while the top and bottom were maintained at prescribed temperatures using individual heat exchanger plates. Protrusion surface temperatures in steady state are reported for a range of power dissipation levels for three fluorinert liquids spanning a Prandtl number range from about 20 to 1400. The influence of enclosure top and bottom surface boundary conditions and its width on element temperatures is investigated. Non-dimensional heat transfer results are empirically correlated. Changes in component temperatures due to partial powering of the array are also measured.

Effects of power pulsations on natural convection from discrete heat sources

The natural convection heat transfer response of discrete heaters flush mounted on a vertical test surface immersed in water to periodic input power has been investigated. The test surface consisted of a plexiglass substrate containing a single column of fifteen heat sources. Identical periodic input power patterns are generated within selected heaters using a computer controlled DC power supply. The mean power levels were varied in the range 0.2–3.0 W, the amplitude to mean ratios of power pulsations in the range 0.17–1.0 and the pulsation frequencies from 0.025–0.1 Hz. The resulting heater temperatures over several cycles were measured and compared with corresponding responses for steady input power equal to the mean of the periodic variation. For a single heater powered case a triangular wave input power pattern was examined. Two types of periodic input power variations were examined with a column of heat sources powered: a triangular wave and an approximate square wave. The responses clearly indicated heat transfer enhancement due to the power pulsation for certain conditions. With the triangular wave pattern, enhancement was most pronounced when the ratio of amplitude to mean power input was the the largest and for the highest pulsation frequency. For the square wave power input the maximum temperature during the cycle was never below the response to steady input power, in contrast to the triangular input power pattern.

Periphyton Biomass and Species Composition in a Coastal Rainforest Stream in British Columbia: Effects of Environmental Changes Caused by Logging

Periphyton biomass, species composition, and accumulation rates on Plexiglas substrates were determined in a 6-yr study from 1974 to 1979 in Carnation Creek, Vancouver Island, B.C. During the first 2 yr of the study, the watershed was unlogged. Clearcut logging during the remainder of the study resulted in increases in light intensity of over 100% at some sites, slight increases in stream temperature (2–3 °C in summer) and increases in some dissolved ion concentrations. Phosphorus concentrations were similar throughout the study. Diatoms were the most common class of algae, and Achnanthes minutissima and Synedra rumpens were the most common diatoms. Filamentous chlorophytes (predominantly Mougeotia sp. with some Draparnaldia sp., Spirogyra sp., and Zygnema sp.) occurred sporadically throughout the study but were more common after logging, primarily as a result of increased light intensity. Although highest recorded periphyton biomass and accumulation rates occurred after logging, post-logging values were generally similar to those recorded prior to logging. We attributed this to the lack of increase in phosphorus concentrations after logging.