bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Brief History of Dust Explosions
Authors: Verakis HC , Nagy J 
Published: December 2008

This paper summarizes the history and early experimental studies of coal and other dust explosions.
In the 1600s, the explosibility of methane, hydrogen, and other combustible gases was recognized by the scientific and industrial community, but few scholars considered the possibility of a dust explosion. (Although a dust explosion could have occurred several centuries earlier, for example in a boat transporting grain from Egypt to Greece, the first recorded dust explosion occurred in an Italian flour mill in 1785.) In Europe, coal mining became an important industry and the dangers from explosions of fire damp (methane) were quickly recognized. However, most miners and many scientists did not accept the explosibility of coal dust.
It was noted in 1803 that coal dust in passageways had burned and contributed to the flame and violence of a mine explosion in England. In the 1800s, more evidence that coal dust in the absence of fire damp was explosive was obtained by investigators of mine accidents and experimental studies.
The pioneering work during the early 1900s of Taffanel in France and Rice in the United States convinced the mining industry of the danger of coal dust. Full-scale experimental studies of mine explosions began in 1911 in the Bureau of Mines Experimental Mine in Bruceton, PA.
Studies on the explosibility of other industrial dusts followed the recognition of the hazard of coal dust. During the late 1800s, investigations were made to evaluate the explosibility of combustible dusts and the causes of serious dust explosions in U.S. flour mills. Formation of the National Fire Protection Association in 1896 gave impetus to the recognition of the explosion hazard of industrial dusts.
Laboratory experiments on coal and other dusts continue to be made by the U.S. Bureau of Mines, universities, industry, and other research organizations.
Laser Damage in Plastics at the Frank J. Seiler Research Laboratory (FJSRL)
Authors: O'Connell RM , Saito TT , Deaton TF , Siegenthaler KE , McNally JJ , Shaffer AA 
Published: December 2008

In order to study ways to improve the laser damage resistance of transparent polymers and thereby realize their advantages for high power laser system applications (e.g., they are lightweight, inexpensive, and castable), a laser damage program has been established at FJSRL. In this paper we describe the damage facility and present the results obtained during the initial year of the program.
The heart of the damage facility is a 1.06-micron wavelength Q-switched Nd:YAG laser capable of providing 300 mJ, 8 nsec FWHM pulses at repetition rates up to 10 pps. For the results reported here, the beam was focused to a 46 micron 1/e2 spot diameter.
Extensive single and multiple-shot bulk damage studies were made of several commercially available materials including polymethylmethacrylate (PMMA), three grades of polycarbonate (PC), and cellulose acetate butyrate (CAB). Measured single-shot damage thresholds were, respectively, 41 J/cm2, 15 J/cm2, and 15 J/cm2, which correlates with the relative “dirtiness” of the materials. Of the three materials, PMMA also had the greatest multiple-shot damage resistance. However, at fluence levels ≤ 0.1 times its single-shot threshold, CAB appears to be remarkably damage resistant.
Preliminary measurements were also made on PMMA which was synthesized in-house from both unpurified and moderately purified monomers, both with and without unpurified plasticizers. The single-shot damage threshold of the material made from purified monomers (no plasticizer) was 1.6 times that of the material made from unpurified monomers. The multiple-shot behavior of the purified material as compared to that of the unpurified material was even more remarkable.
Optical Properties of Ion-Beam Sputtered TiO2 Films
Authors: Demiryont H , Kerwin DB , Sites JR 
Published: December 2008

Ion-beam sputtered TiO2 films were simultaneously deposited onto Corning 7059 and silicon substrates for ellipsometric and spectrophotometric investigation of optical parameters. Film thicknesses ranged from 5 to 500 nm, and spectrophotometer wavelengths from 400 to 2500 nm. Results from the two techniques agree well at the 632.8 nm wavelength used for ellipsometry.
At thicknesses above 100 nm and wavelengths above 1 μm, the TiO2 refractive index was insensitive to changes in thickness or wavelength. It increased, as expected, at shorter visible wavelengths, and it decreased markedly for films below 100 nm in thickness. The index varied with the oxygen to argon ratio of the ion beam, showing a maximum value of 2.52 for 632.8 nm wavelength light. The extinction coefficient was too small for spectrophotometric measurement in the infrared; previous calorimetric measurements for half wave films at 1.06 μm showed absorption below 100 p/m. The extinction coefficient, however, increased in the visible, typically reaching values corresponding to a few tenths percent absorption at 0.4 μm.
Improvement of the Damage Threshold of High Reflectivity Multidielectric Coatings 1.06 μM
Authors: Geenen B , Malherbes A , Guerain J , Boisgard D , Friart D , Garaude F 
Published: December 2008

Development of new high power laser for laser-matter interaction in C.E.A. Limeil requires the realization of H.R. coatings with damage thresholds above 8 J/cm2.
MATRA's laboratory “couches minces optiques” (thin optical layers) production commercial mirrors was around 3.5 J/cm2 in 1982. In order to obtain better results we decided to improve the control of evaporation parameters such as:
– vacuum and regulation of oxygene pressure by means of a mass spectrometer
– better measurements of evaporation temperature and regulation of evaporation rate
– measurement and control of substrate temperature by pyrometric observation and to automatize the process.
These different measurements and controls enable us to establish new processing operations giving better evaporation condition.
The result was an increase of damage threshold from 3.5 J/cm2 to 8 J/cm2.
Characterization of Micron-Sized, Optical Coating Defects by Photothermal Deflection Microscopy
Authors: Abate JA , Schmid AW , Guardalben MJ , Smith DJ , Jacobs SD 
Published: December 2008

Information about the localized absorbing defects in optical thin films is required for a better understanding of laser-induced damage. Photothermal deflection microscopy offers a nondestructive optical diagnostic which can yield spatially resolved absorption data on simple and multiple-layer AR and HR dielectric coatings. This paper describes the computer-controlled apparatus used to generate absorption maps of dielectric thin films and an experiment in which a partial correlation between localized absorption sites and damage caused by nanosecond laser irradiation at 351 nm is established.
An absolute calibration of absorption for our measurement technique is presented here. Micron-sized absorbtive defects of Cu were introduced into our coatings to provide a means of calibration. Also presented here are some preliminary data on the modification of the absorption signatures measured by photo-thermal deflection as a function of the location of the defect within the coating layers.
Plasma Deposited Inorganic Thin Films for Optical Applications
Authors: Partlow WD , Heberlein JVR 
Published: December 2008

Plasma deposited thin films, widely used in semiconductor processing, have begun to be used in optical applications such as anti-reflective coatings and optical waveguides. Amorphous films of refractory materials such as SiO2, SiC, and Si3N4 have been applied with high optical perfection on substrates at 200—300°C with this process. Control of index of refraction has been achieved by selecting appropriate deposition parameters.
We describe the plasma deposition process and the properties of these coatings. We present applications and discuss how these coatings may be applied to more demanding optical applications in the future such as graded index films, rugate coatings, and vacuum UV reflecting films. We see that hydrogen inclusion in the films is a factor that must be controlled, and we propose methods to accomplish this.
“Analytical Model for Evaluating Transient, Steady-State, Coating Damage Threshold, Optical Distortion, and Axial Gradient for Externally Cooled Laser Mirrors.”
Authors: Palmer JR 
Published: December 2008

There are a number of requirements in high energy laser systems to provide optical elements that are not integrally cooled. However, there are many instances where a cooling gas, such as helium or nitrogen, may be used to cool the front and back surfaces in order to reduce optical distortion.
In order to evaluate the response of an optic to this type of cooling, first order analytical techniques have been generated to determine transient and steady-state temperature distributions through a fully irradiated optic, an irradiated spot on a large optic, and a toroidal shaped beam (i.e., hole in the beam), on a large optical element.
Cooling temperatures and damage relationships coupled with optical path differences of the flowing gas are treated for evaluation. Optical distortion of the element due to radial and axial temperature gradients are treated for both transient and steady-state conditions and for various gas flow dynamics.
Catastrophic versus Microscopic Damage: Applicability of Laboratory Measurements to Real Systems
Authors: Foltyn SR , Jolin LJ 
Published: December 2008

At ultraviolet wavelengths, damage to both coatings and bare surfaces is dominated by the presence of discrete localized defects. During multiple-shot irradiation, the overwhelming majority of these defects are damaged by the first or first few shots. Initially, damage morphology is that of a crater of approximately 10 μm in diameter; however, upon continued irradiation, one of two events can occur: either the crater grows to catastrophic dimensions or it remains unchanged. In the latter case, the damage is only observable under a microscope, it may be indistinguishable from cosmetic defects present before irradiation, and it is likely that any related degradation in optical performance is unmeasurable.
In view of the generally accepted definition of laser damage (i.e., any visible change in the surface), it is important to consider the implications for real systems. These are discussed in the context of ultraviolet test results for both coatings and surfaces.
Toward Improved Accuracy in Limited-Scale Pulsed Laser Damage Testing Via the “Onset Method”
Authors: Seitel SC , Porteus JO 
Published: December 2008

A recently reported method for determining the defect damage onset (minimum intensity for defect initiated damage) in optical surfaces offers certain advantages over more conventional methods. First of all, the onset is a more reliable and useful indication of operational performance than conventionally measured thresholds, which may depend strongly on the size of the tested area. Secondly, measurement of damage frequency vs intensity provides valuable information on defect densities. This permits more effective use of a limited test area and provides a basis for defect classification. Effective limited-scale testing is becoming increasingly important as larger optical surfaces and reduced defect densities are made possible by improved coating technology.
In this paper, the onset method is mainly applied to 1.06 μm coatings, tested with a 40 μm (D-1/e2) Gaussian focal spot and 2.7 μm coatings, tested with a 67 μm spot. Comparisons are made between onsets and conventionally measured thresholds, including a demonstration of convergence with large-spot thresholds from other laboratories. Examples of damage frequency distributions indicating the presence of more than one class of defect will also be shown. Finally, the onset model is extended to include flat-topped spatial profiles, and possible advantages over Gaussian profiles are noted.
Precision Reactivation of Antifouling Paints
Authors: Poretz I 
Published: December 2008

Present-day operation of commercial and military ships requires smooth ship bottoms in order to minimize the ship's frictional resistance as it moves through the water. The hydrodynamic advantage of the smoother hull results in lower fuel consumption, which, at current fuel prices, significantly lowers operating costs.
Frequent drydockings to renew antifouling coatings are intended to maintain ship-bottom smoothness. However, they are expensive, interfere with the flexibility of ship operations, are not always completely successful, and do not permit full realization of the economic potential of smooth bottoms for long periods. Recognizing the need to overcome these limitations, the Norwegian Ship Research Institute, with the support of the maritime industry and in close cooperation with paint manufacturers, has developed a successful underwater reactivation technology for an antifouling paint. This technology is described and compared with conventional coatings and another advanced type of coating. Ship-bottom roughness requirements for optimal fuel economy are discussed in numerical terms. The cumulative roughness of underwater hull surfaces during periods between drydockings is compared for conventional and advanced reactivatable antifouling coatings. Finally, a typical program for a ship on a five-year drydocking cycle that is consistent with U.S. regulatory and certification requirements is illustrated.
Minimum Film Thickness for Protection of Hot-Rolled Steel: Results after 23 Years of Exposure at Kure Beach, North Carolina
Authors: Morcillo M 
Published: December 2008

This study was initiated by Dr. Wouter Bosch, University of Missouri at Rolla, in 1957, more than 25 years ago, under the direction of the Corrosion Committee of the Federation of Societies for Paint Technology. It has been continued by the Steel Structures Painting Council (SSPC) from 1966 to the present, under the sponsorship of the Federation.
Originally, the purpose of this study was to determine the optimum film thickness for a few representative coatings in typical atmospheres, with the hypothesis that there were likely to be some differences in film thickness requirements among coatings, surface preparation grades, and atmospheres of varying severity.
Four progress reports have been published, the most recent in 1969 by the Steel Structures Painting Council. This 10-year SSPC report showed clearly (1) an increase of about 20 months of paint life for each additional mil of paint thickness, applicable to all oil-based and alkyd paints in three environments (industrial, marine, and rural); (2) a critical minimum thickness for each generic type of paint; and (3) the value of applying sufficiently heavy films at the beginning rather than undertaking more frequent maintenance painting.
The results given in this work refer only to panel exposure tests in the marine environment of Kure Beach (800-ft lot), North Carolina, while previous studies also considered rural and industrial environments.
The variables studied include type of paint (oil, alkyd, phenolic, vinyl, chlorinated rubber, and epoxy ester), surface condition of steel before and after surface preparation, and a wide range of film thicknesses (primer and topcoat).
The main conclusions of the study are:
• For surface preparation, the degree of cleanliness is much more important to the performance of chemical-resistant coatings than to the performance of conventional coatings.
• Total dry film thickness (primer and topcoat) is the most important factor. Obviously, the minimum paint film thickness required for an effective protection is a function of the required protection duration.
• Nine mils of oil paint film thickness (primer and topcoat) do not afford protection for more than 10 to 12 years (until Rust Grade 8, SSPC-Vis 2/ASTM D 610, Evaluating Degree of Rusting on Painted Steel Surfaces, is reached).
• With other paint systems, film thicknesses of 10 to 12 mils, or even less, afford effective protection after more than 23 years.
Physical Testing of Gypsum Board Per ASTM C 473
Authors: Acker RF 
Published: December 2008

This work was performed to investigate modernization of the equipment used for the physical testing of gypsum board that has not been basically changed over a period of many years and is not commercially available. A comprehensive study has been made using a commercially available machine for three strength tests, with the expectation that this type of equipment might be incorporated into ASTM methods and specifications in the future. Technical advances in the methods of evaluating gypsum board are desirable in a progressive industry.
The procedure used was to run the three major physical tests: flexural strength; core, end, and edge hardness; and nail pull resistance on a machine using constant strain rate loading and compare those results with those obtained on the commonly used ASTM specified machine that uses a constant stress rate. A TM 51008 tester made by Testing Machines, Inc. was used for the work reported in this paper. Comparative tests were made on equipment conforming to the specifications of ASTM Physical Testing of Gypsum Board Products, Gypsum Lath, Gypsum Partition Tile or Block, and Precast Reinforced Gypsum Slabs (C 473). Preliminary work was done in a research laboratory to develop the fixtures and procedures necessary to use the new equipment. The machine was then placed in a manufacturing plant and duplicate tests on all types of board products were run for a period of several months.
Data will be presented to show that the constant strain rate method of testing can give equally precise results with a very substantial saving in time and physical effort. For flexural strength, nail pull resistance, and core hardness there is a simple linear correlation between the results with the two machines. The constant strain rate machine can more accurately determine the maximum load causing failure than the constant stress rate machine. Correlation between the results of tests on either machine shows that the core hardness and nail pull resistance tests tend to duplicate information on core properties.
Gypsum Analysis with the Polarizing Microscope
Authors: Green GW 
Published: December 2008

The fastest and most accurate method for the qualitative analysis of gypsum is use of the polarizing microscope. Five bits of optical data can be used for identification of gypsum and its most common impurities such as natural anhydrite, calcite, dolomite, and silica. The optical data are morphology, refractive index, birefringence, angle of extinction, and dispersion staining. Gypsum can be identified by its refractive index of 1.521 and 1.530, its oblique extinction angle, its birefringes of 0.009, and a blue dispersion staining color when mounted in a refractive index liquid of 1.528. Natural anhydrite is normally seen as blocky crystals with a refractive indices of 1.570 and 1.614. The birefringence of 0.044 gives it much higher order polarizing colors than gypsum, and it has parallel extinction. Silica has the same birefringence as gypsum; so it is hard to distinguish with crossed polars. However its refractive index of 1.544 is higher than gypsum and has a yellow dispersion color to contrast with the blue of gypsum when mounted in 1.528. Limestone may be either calcite or dolomite. Limestone may be distinguished mainly by its very high birefringence of 0.172, which renders even very fine particles colorful with crossed polars—larger particles are high order white. Calcite may be distinguished from dolomite by mounting in a refractive index liquid of 1.660 rendering the dolomite orange with the calcite blue.
The phases of gypsum can be distinguished also. Beta hemihydrate has the same shape as the dihydrate from which it was made but is porous and cloudy rather than clear and solid. Alpha hemihydrate may be blocky or acicular and has a refractive index of 1.558 and 1.586. The birefringence is 0.028. When mounted in 1.564 liquid, the dispersion colors will change from orange to blue as the stage is rotated. Soluble anhydrite is difficult to identify, but dead-burned gypsum has a refractive index close to natural anhydrite, and the dispersion colors are red and blue when mounted in a liquid of 1.596. The qualitative analysis of natural anhydrite may be done by direct estimation, or by estimating a series of fields and averaging the results. A more precise method is to count and measure the diameters of all particles then calculate the weight percent of each.
Determination of Sulfur Trioxide in Gypsum
Authors: Goswami S , Chandra D 
Published: December 2008

This paper deals with the various sources of error in different steps of the procedure for determination of sulfur trioxide in gypsum samples, using hydrochloric acid as solvent for gypsum and barium chloride to precipitate barium sulfate. The paper suggests reduction in the amount of acid and barium chloride used in order to minimize errors. Thus, it justifies the need for the revision of Section 12 of ASTM, Chemical Analysis of Gypsum and Gypsum Products (C 471).
ASTM C 471 recommends use of 50 mL of 1 + 5 hydrochloric acid (sp gr 1.19) as solvent for a 0.5-g gypsum sample and 20 mL of 10% barium chloride as precipitant. This results in too high a concentration of acid and chloride ions in reaction solution before and after precipitation, justifiable only for dissolution of impure gypsum samples and formation of coarse barium sulfate crystals to give rapid filtering. The method is silent about the final volume to be made of reaction solution, which determines the acidity before precipitation. It is also silent about the use of and the type of filtering crucibles.
The greatest source of error is the occlusion of chloride ions caused by both hydrochloric acid and barium chloride in addition to adsorption of H+, coprecipitation of barium chloride and Ca++ ions, and increased solubility of barium sulfate in acidic solution.
Therefore, the following suggestions have been made (1) reduce the initial amount of hydrochloric acid used as solvent to 25 mL of 1 + 5 hydrochloric acid for the 0.5-g test sample, (2) use 20 mL of 6% barium chloride solution (preferably old), (3) make the volume of the reaction solution up to 400 to 500 mL before precipitation of barium sulfate, and (4) use filtering crucibles. These changes will increase the accuracy of the sulfate determination by minimizing error caused by high acid and chloride concentration and by maintaining quick dissolution and filtering. Analyses performed with these changes have been found to be consistent and accurate.