bluuebunny/crossref_metadata_2025 huggingface dataset:
Recent Damage Results on High Reflector Coatings at 355 nm
Authors: Carniglia CK , Hart TT , Rainer F , Staggs MC
Published: December 2008

Several studies of damage induced by 0.6 ns, 355 nm laser pulses have been carried out on thin-film reflectors. The reflectors consisted of dielectric materials vacuumdeposited onto BK7 substrate by evaporation. Each part was damage tested on several sites using one laser shot per site.

Quarterwave stacks of various material combinations were used to make a series of reflectors. Four to six parts were tested for each of four materials combinations. The average damage thresholds obtained for these coatings were 3.5 J/sq. cm for scandia/magnesium fluoride, 3.0 J/sq. cm for zirconia/silica, 2.4 J/sq. cm for tantala/silica and 1 J/sq. cm for hafnia/silica. Interestingly, there was no improvement in those reflectors to which a halfwave silica overcoat was added. This is contrary to previous results at 1064 nm and 248 nm.

A series of zirconia/silica reflectors was made using coating temperatures ranging from 150°C to 300°C. The thresholds were slightly improved by coating at higher temperatures.

Coatings made of zirconia/silica with outer quarterwave layers of samarium fluoride and either silica or magnesium fluoride were also tested. Thresholds for these coatings ranged from 1.7 to 2.8 J/sq. cm and were slightly lower than the thresholds of the zirconia/silica stacks alone.

Scandia/magnesium fluoride coatings with non-quarterwave designs have been shown to be effective in raising the damage threshold of high reflectors at 248 nm. Such designs reduce the electric field intensity in the outer scandia layers. The damage thresholds of several non-quarterwave designs were compared. The highest threshold, 5.1 J/sq. cm, was achieved by reducing the electric field in the two outer scandia layers.
Photothermal Deflection Microscopy of HR and AR Coatings
Authors: Mundy WC , Ermshar JEL , Hanson PD , Hughes RS
Published: December 2008

Last year at this syposium we reported on the initial results of photothermal deflection microscopy (PDM) studies of single layer dielectric thin films [1]. The high spatial resolution, low-level absorption capabilities of PDM were demonstrated in the form of two-dimensional absorption contour maps of such films.

In this paper we report on PDM measurements of a number of HR and AR coatings provided by Lawrence Livermore Laboratory and the Naval Weapons Center. The absorption data obtained from these measurements provide the first phase of absorption/damage correlation studies and as these absorption measurements were recently completed, no correlation data are yet available.

Resolution improvements, measurement methodology and a number of absorption contour maps are presented. Two interesting observations yet to be explained are described and some future experiments are suggested.
Laser Damage in Porous-Silica Antireflection Films
Authors: Lowdermilk WH , Wilder JG , Brown NJ , Gunderson CA , Milam D , Rainer F , Staggs MC
Published: December 2008

We used 355-nm, 0.6-ns pulses to measure laser-damage thresholds of porous-silica antireflection coatings deposited from a polymer solution onto fused silica substrates. For 118 coatings with optical thickness of 500–600 nm, the median threshold was less than 2 J/cm2, and thresholds were not systematically dependent on either the level of filtration of the coating solution or the procedure used to clean the substrates. For coatings 87–90 nm in optical thickness, thresholds were as large as 9 J/cm2, which is the threshold of the bare polished surfaces of the fused silica substrates. The data suggests that carbon residues from the coating solution are responsible for damage in the thicker coatings.
Stress Distributions in Damaged Composites
Authors: Batdorf SB , Ghaffarian R
Published: December 2008

Any micromechanical theory for damage accumulation and ultimate failure in composites must depend on a knowledge of the detailed stress distribution in the damaged state. Lack of this knowledge has been a major roadblock to progress in this field. A shear lag approach to this problem has been proposed by Hedgepeth and Van Dyke for unidirectionally reinforced composites, but it is of limited utility because it contains an unknown parameter.

This paper discusses an experimental technique for finding stress distributions in damaged composites with the aid of an electric analogue. In this approach, a current is passed through a model employing conducting rods to represent fibers and a liquid electrolyte to represent the matrix. The potential distribution in the model is analogous to the longitudinal displacement distribution in the composite, and transverse currents are analogous to shear forces. The analogue is employed in the paper to evaluate the unknown parameter in the Hedgepeth and Van Dyke equation.
A Laboratory Approach for Determining the Effect of Oils and Dispersants on Mangroves
Authors: Getter CD , Baca BJ
Published: December 2008

An experimental approach was developed and applied to testing the effects of oil and dispersant combinations on the growth of mangrove seedlings (trees of the intertidal tropics). A controlled growth chamber was employed to test the effects of different oils and dispersed oils in an array of dosages applied to different parts of the plants. Preliminary test results are reported for two species of mangroves collected from five localities, including both oiled and unoiled estuaries. Differences occurred between species, substances, dosages, the part of the plant dosed, and the presence of chronic oil pollution at localities from which the stocks were collected. Avicennia germinans (L.) L. (black mangrove) was more sensitive than Rhizophora mangle L. (red mangrove) when exposed to almost all substances tested. Light Arabian crude oil (LA) and light Arabian crude oil dispersed (LAD) were the most toxic substances tested. No. 2 fuel oil (N2) and No. 2 fuel oil dispersed (N2D) were as toxic as LA and LAD, except for an increase (an enhancement effect) in foliage and stem growth in Avicennia at lower dosages. Bunker C oil (BC) was the least toxic of the oils tested, resulting in the reduction of foliage and stem growth only at the highest dosage tested in Avicennia. Bunker C oil dispersed (BCD) failed to show effects in either species at any dosage tested. The leaves of Rhizophora were the most sensitive part of the plant tested. Root-dosing had a lesser effect than leaf-dosing but resulted in greater effects with LAD than with any other substance tested. Seedling stock from chronically oiled areas sprouted more rapidly and developed more foliage in response to LA, indicating a possible “preadaptation” to spilled oil; no such effect occurred when dispersant was added to LA. The response of mangroves was specific to the oil type to which the dispersant was added. Dispersant increased the toxicity of LA and N2 but decreased the toxicity of BC.
A Mathematical Model for Predicting the Ecological Impact of Treated and Untreated Oil Spills
Authors: Trudel BK
Published: December 2008

An ecological impact model, designed to estimate the impact of chemically treated and untreated oil spills on seabirds and fish, was developed to aid dispersant-use decision-making. Impact was defined as the proportion of the animal population killed and the length of time required for that population to recover to its prespill condition. Subroutines dealt with the fate of oil, the toxicity of spilled oil, the concentration of organisms at the location of the spill, and the recovery potential of the target population. The model was site-specific. The paper describes briefly the structure and operation of the model, but most of the discussion deals with the modeling of eco-toxicity. The model uses information on oil fate and the sensitivity of organisms to compute the size and location of lethal areas. For fish, the dose of hydrocarbons reaching the organism's tissues is estimated to determine whether this dose is lethal or not. For seabirds, it was assumed that any contact between seabirds and the oil slick would be lethal. Our findings suggest that for some situations, chemically dispersed oil might have greater area of effect and greater environmental impact than undispersed oil. More important, the area of effect of large oil spills, whether treated or not, may be very small relative to the area over which target populations are distributed. Estimates of the size of the zone of lethal conditions made using the exposure dose-response method developed here were similar to those obtained using other methods such as the critical-peak-exposure concentration method and the integrated exposure (Toxicity Index) method.
Oil Spill Dispersants: Does South Africa Have an Alternative?
Authors: Chapman P
Published: December 2008

The role of geographic and socioeconomic factors on the effects of oil pollution in South Africa is discussed. The sparse population and natural mechanisms provide little reason for alarm in the case of an oil spill at sea except for certain higher risk areas. Effects of previous spills are outlined, and government policy with regard to dispersant usage is discussed.
Some Perspectives of Statistical Ecology and Environmental Statistics
Authors: Patil GP
Published: December 2008

The paper sets the scene with historical and professional organizational perspectives briefly describing the activities and publications of groups concerned with statistical ecology and environmental statistics. Then follow the scientific perspectives with examples illustrating certain basic issues and features arising in ecological and environmental work. The observational studies, visibility bias, and inferential recovery constitute a critical problem area. It is discussed at some length with examples and data sets. Extrapolation issues constitute another critical problem area. Different kinds of extrapolation are briefly discussed with examples of low-dose extrapolation and calculated virtually safe dose levels. An example of recruitment distributions and inferences about long-term yields is also given. The issue of single versus several models is touched upon. The present day status of the subject of quantitative risk analysis is briefly described. A need for a focal cooperative program in statistical ecology and environmental statistics is identified.
Design of Efficient Environmental Surveys Over Time
Authors: Smith W
Published: December 2008

Classical survey design and data analysis methods deal with observations at a single time point and cannot be applied directly to time series problems. This paper describes some recent work in the design of environmental surveys conducted over time. A method is given for finding the optimum number of times to repeat a survey over time. It is also shown how time series models can be used to evaluate the utility of base line surveys.
A Simple Apparatus for Measurement of the Hydration Ratio of Plasters and Plaster Rocks
Authors: Karmazsin E
Published: December 2008

In the frame of calcium sulfate β-hemihydrate hydration kinetical studies, a simple experimental set up has been developed to determine the rate of hydration for different species of incompletely hydrated plaster specimens. This apparatus may also be used to determine with accuracy the amount of gypsum contained in plaster rocks, and acquire simultaneously quantitative analysis for six specimens. The apparatus is described, and the effect of vapor pressure is studied.

Experimental results on incompletely hydrated plaster specimens show that either the weight loss or the integration curves allow the determination of the hydration ratio of the specimen with high accuracy. It has been experimentally shown that the amount of heat involved in the hydration reaction is proportional all along the reaction to the conversion rate.
Rapid Multielement Analysis of Gypsum and Gypsum Products by X-Ray Fluorescence Spectroscopy
Authors: Kocman V
Published: December 2008

A rapid and precise X-ray fluorescence method has been developed for the multielement analysis of gypsum and gypsum products. Gypsum specimens are calcined at 1000°C and then fused with sodium tetraborate flux into flat and transparent disks. The choice of a suitable flux system for the specimen preparation is critical because of a rapid decomposition of anhydrite, CaSO4, in lithium based fluxes at temperatures above 950°C. This decomposition causes not only visible imperfections in the disk surface but also alters considerably the concentrations of the major elements, calcium and sulfur. The procedure used for a fast setup of ten element analysis of gypsum on the Philips PW-1400 spectrometer utilizing synthetic standards and off-line calculated alpha coefficients is presented. Calibrations carried out with chemically analyzed specimens and their mixtures are compared to those performed with synthetic standards prepared by blending pure chemicals and anhydrite into the flux.
Internal Consistency Checks as Part of a Data Validation Process for Chemical Constituents in Ambient Particulate Samples
Authors: Cadle SH
Published: December 2008

Internal consistency checks are an excellent means of validating data obtained during field studies of ambient particulate. The specific method used depends on the purpose and scope of the program. Techniques discussed include inspection of data for outliers, inter-sampler comparisons, and ion balance and mass balance techniques. The use of these methods is illustrated with data collected in a variety of field programs. It is concluded that internal consistency checks should be incorporated into the quality assurance program of all field studies.
Quality Assurance as an Element of Wisconsin's NPDES Program
Authors: Kopecky MJ , Vogen L
Published: December 2008

Wisconsin has a long history of concern about data quality in its Wisconsin Pollution Discharge Elimination System (WPDES) program. Since 1978, operators of municipal sewage treatment plants (STP) have been required to pass written and practical exams in laboratory operations to be certified to operate an STP. The Wisconsin Department of Natural Resources (WDNR) has also developed a program of laboratory evaluations and Performance Audit Inspections (PAI). Results of these evaluations indicate that data quality is improving; however, problems still exist. These problems are related to insufficient operator knowledge of procedures, lack of routine quality control practices at laboratories, and insufficient support of the laboratories by municipal and industrial management. Wisconsin is proposing a laboratory certification program which would certify that a laboratory is actually producing data meeting set standards of accuracy and precision, as opposed to conventional programs which certify a laboratory's capability to produce accurate data.
Monsanto Analytical Testing Program for NPDES Discharge Self-Monitoring
Authors: Hoogheem TJ , Woods LA
Published: December 2008

The Monsanto Analytical Testing (MAT) program was devised and implemented in order to provide analytical standards to Monsanto manufacturing plants involved in the self-monitoring of plant discharges as required by National Pollutant Discharge Elimination System (NPDES) permit conditions. Standards are prepared and supplied at concentration levels normally observed at each individual plant. These levels were established by canvassing all Monsanto plants having NPDES permits and by determining which analyses and concentrations were most appropriate. Standards are prepared by Monsanto's Environmental Sciences Center (ESC) using Environmental Protection Agency (EPA) methods. Eleven standards are currently available, each in three concentrations. Standards are issued quarterly in a company internal round-robin program or on a per request basis or both.

Since initiation of the MAT program in 1981, the internal round-robin program has become an integral part of Monsanto's overall Good Laboratory Practices (GLP) program. Overall, results have shown that the company's plant analytical personnel can accurately analyze and report standard test samples. More importantly, such personnel have gained increased confidence in their ability to report accurate values for compounds regulated in their respective plant NPDES permits.
Quality Assurance for Personal Exposure Monitoring
Authors: Handy RW , Crist HL , Stanley TW
Published: December 2008

A personal exposure monitoring program has been carried out to field-test methodologies for sample collection and analysis. The basic study involved the collection of personal air, breath, and water samples. Quality assurance procedures were implemented during the sampling period and included exposing field controls and blanks and the collection of duplicates, some of which were analyzed by a reference laboratory. The analysis of the air/breath collections on Tenax GC® and water samples were performed by capillary column gas chromatography/mass spectrometry (GC/MS) and GC methods, respectively. Twenty-two volatile halogenated and aromatic compounds were selected as target compounds. Daily checks on instrument performance and calibration were performed, and precision quality control charts were maintained. The analysis of performance audit samples on Tenax GC was a major component of the quality assurance protocol. These results clearly show that background on the sampling devices adversely affect data quality and must be monitored closely.
New Biological Reference Materials—In Vivo Incorporated Toxic Metals in Water Hyacinth Tissues
Authors: Austin JR , Simon SJ , Williams LR , Beckert WF
Published: December 2008

Chemical analysts need biological reference materials that contain higher levels of toxic elements than are usually present in natural-source materials [e.g., orchard leaves, tomato leaves, or pine needles, available from the National Bureau of Standards (NBS)]. The purpose of this study was to demonstrate that high-quality reference materials, containing high levels of multiple toxic elements, can be produced with in vivo incorporation procedures. The approach taken was to produce water hyacinth tissue materials—leaves and stems containing high levels of arsenic, cadmium, lead, and mercury—as follows: (1) apply a hydroponic feeding procedure for the in vivo incorporation of toxic elements into water hyacinths; (2) dry, blend, and homogenize the plant materials and determine the levels of the incorporated elements and the homogeneity of the generated plant material; (3) demonstrate that low-level control materials can be successfully blended with high-level materials to yield a homogeneous material with intermediate toxicant levels; (4) evaluate the precision of the analytical methods used to determine toxic element levels in the materials; and (5) evaluate the stability of the resulting materials. Sufficient quantities of the parent materials were produced so that characterized reference materials can now be made available on request. Successful application of the in vivo incorporation procedure was demonstrated; therefore additional amounts of such materials could be produced, if needed. Levels of the toxic elements incorporated in water hyacinth leaves were 100, 300, 60, and 27 times the levels present in the control leaves for arsenic, cadmium, lead, and mercury, respectively. Overall precision of sampling, subsampling, and digestion, and chemical analysis of the treated materials, ranged from 3 to 10% relative standard deviation and was generally comparable to that of three NBS biological reference materials tested. Blends of control and high-level materials were found to be homogeneous, and the overall analytical precision was comparable to that achieved for the control or treated materials alone. No significant changes were noted in control and treated materials in long-term (six months or more) stability studies.
The Marine Analytical Chemistry Standards Program of the National Research Council of Canada
Authors: Berman SS , McLaren JW , Jamieson WD
Published: December 2008

The Marine Analytical Chemistry Standards Program (MACSP) of the National Research Council of Canada (NRCC) is described. This program, established in 1976, has resulted in the production, to date, of seven reference materials for the determination of trace metals and organic compounds in marine materials. Significant contributions to the analysis of marine materials have been made in the NRCC laboratories, and through MACSP contracts. Some current projects and plans for future reference materials are also discussed.
Reference Materials and Intercomparison Samples Available from the Environmental Monitoring Systems Laboratory — Las Vegas
Authors: Kantor EJ , Laska PR
Published: December 2008

Reference materials and intercomparison samples may be obtained by laboratories involved in the analysis of environmental samples containing radioactivity, pesticides, toxic inorganic species, or toxic organic species. These reference materials and intercomparison samples are available from the United States Environmental Protection Agency's Quality Assurance Division located at the Environmental Monitoring Systems Laboratory in Las Vegas (EMSL-LV). These materials are useful for incorporation into a laboratory's quality control program for the evaluation of the precision and accuracy of analytical work. Media used for radiation reference materials are pitchblende, Monazite ore, uranium mill tailings, Mancos shale, fly ash, and water spiked with radionuclides. Radioactivity intercomparison samples consist of water, milk, air, urine, and a simulated diet slurry spiked with radionuclides. Media available for toxic organic reference materials are sludge, shale oil, and rag oil, and for intercomparison samples are soil and water. Characterized fly ash, foundry sludge, and river sediment serve as reference materials for toxic inorganics, while spiked soil and water serve as intercomparison samples. Finally, spiked adipose tissue, blood plasma, urine, and water comprise the pesticide intercomparison samples, and, after the disclosure of the true pesticide compositions and concentrations of these samples, the laboratory can use the samples as reference materials. The reference materials are generally available continuously, but the intercomparison samples are distributed on a scheduled basis and in some cases only to certain laboratories.
Resistance to Compaction of Asphalt Paving Mixtures and Its Relationship to Stiffness
Authors: Bissada AF
Published: December 2008

This paper discusses a method of evaluating the compaction characteristics of asphalt concrete mixtures in terms of a coefficient of compactibility or resistance to compaction. Two types of asphalt concrete mixtures have been considered in this study: one is a conventional type with an asphalt cement 60/70 penetration, and the other is an extended sulfur asphalt concrete with 40/60 sulfur to asphalt (S/A) ratio by weight. The effect of mix variables, such as filler content and binder content, is included in the experimental program. Marshall specimens for each mix were subjected to different compaction levels varying between 10 and 100 blows on each face. Bulk density and voids content for each mix at each compaction level were determined. Each specimen was then tested for creep at 40°C under a controlled constant stress (0.1 N/mm2) for 30-min load duration.

Based on the experimental data and using linear regression analysis a relationship between compactibility and stiffness characteristics for each mix is established, which is important in controlling the permanent deformation distresses. The results of this study show that the specifications requirement for a certain percent of laboratory compaction would not be adequate for predicting permanent deformation of the asphalt pavement layer. An additional requirement, such as resistance to compaction, may correlate better with the actual performance of the tested mixture under appropriate conditions of environment and traffic.
Sampling and Analysis in the Production and Consumption of Copper Cathodes
Authors: Dana RL
Published: December 2008

New high-grade cathode specifications are including specific impurity limits to meet the more stringent requirements of the continuous cast rod market. Improved cathode sampling and analytical methods are necessary to confirm specification compliance. A better sampling plan is to collect either saw cuttings or cut sections from the cathodes which would then be melted and cast to obtain adequate impurity representation. Interest in obtaining lower impurity detection limits is leading to more support for the electrothermal and vapor generation methods of atomic absorption spectrometry. Even after the improved methods of sampling and analyzing copper cathodes have been tested and adopted, frequent interaction between the cathode producer and consumer will be important to monitor product quality compliance.
Copper Standard Reference Materials (Benchmark Series)
Authors: Barnes IL , Gills TE , Reed WP
Published: December 2008

The Standard Reference Materials Program has experienced increasing demands for new kinds and types of standard materials. In order that the largest number of users be served by these materials and the available resources be used to best advantage, careful planning is required. The planning process helps to ensure that, among other factors, the fewest number of different materials will be produced, a wide range of needs will be met, and production and certification can be accomplished at a level consistent with the intended uses. One output of this process has been the concept of “Benchmark Series” SRMs. These are usually a set of similar materials with varying amounts of a number of elements covering a wide range of concentrations.

Largely through the auspices of ASTM Committee E-2 on Emission Spectroscopy, more than 70 persons from NBS, ASTM, and from throughout the copper industry contributed to the planning of a series of Copper Benchmark Standard Reference Materials. As a result, 12 different materials issued as chips, rods, and cast solids and representing as many as 25 different SRMs have been prepared and certified for as many as 29 elements. The production and certification process and the certified values for this important series are described and the certified values are given.
Analysis and Growth of Cracks in Skins with Variable Thickness
Authors: Ratwani MM , Kan HP
Published: December 2008

Analysis of cracks in skins with variable thickness (skins with lands) was developed. The problem was reduced to the solution of an integral equation by using the Fourier transform technique. The integral equation was solved numerically and stress intensity factors were obtained. The influence of variable skin thickness ratios on stress intensity factors was investigated.

An experimental program was carried out to obtain crack growth data in skins with variable thickness (skins with lands). The crack growth behavior in those skins was predicted using analytical stress intensity factors and a crack growth model. A good correlation between predicted and observed crack growth behavior under constant amplitude as well as spectrum loading was found.
Fatigue Life of Welded Stiffeners with Known Initial Cracks
Authors: Sahli A , Albrecht P
Published: December 2008

The objective of this study was to determine the crack propagation life of a weldment and to assess the significance of the results with regard to the design and inspection of bridge girders. The experimental part consisted of marking initial crack sizes in 68 fillet-welded transverse stiffeners subjected to constant-amplitude loading or spectrum loading typical of highway bridges. The crack propagation lives were then calculated with fracture mechanics methods using average crack growth rates and a reasonably simple method of determining the stress intensity factor. In general, more cycles were needed to grow the crack than were calculated in this study. The predictions were conservative in the sense that they underestimated the observed lives. The results correlated better for the larger than for the smaller marked crack sizes. The propagation life of the specimens tested in this study corresponded to the stage of part-through crack growth in transverse stiffeners welded to the web and the flange of girders, or to the web alone. The generally low crack detection probabilities with ultrasonic and radiographic inspection and the results of this study suggest that it would be prudent to design structures with long service lives, such as highway bridges, to the fatigue limit so that in most cases cracks would not initiate.
On the Use of Compliance for Determining Crack Length in the Inelastic Range
Authors: Nicholas T , Ashbaugh NE , Weerasooriya T
Published: December 2008

Compliance measurements were made during creep and fatigue crack growth to establish crack length. During various tests some of the data from several nickel-base superalloys demonstrated a lack of a one-to-one correspondence between crack length and compliance. In particular, decreases in compliance were observed when going from fatigue to creep and when going from low frequency to higher frequency fatigue cycling. On the other hand, no anomalous behavior was observed in ductile copper when loaded to high K values and subsequently unloaded. It is concluded that a probable cause of the anomalous compliance values during transient loading conditions is due to a complex three-dimensional stress state which may be additionally influenced by environmental factors.
Cryoscopic Determination of the Purity of Benzene by Calorimetry
Authors: Furukawa GT , Piccirelli JH , Reilly ML
Published: December 2008

To test the cryoscopic method for determination of purity, the impurity concentrations of duplicate specimens taken from four prepared lots of benzene were determined on the basis of the van't Hoff law of freezing-point lowering and on the assumption that the phases in equilibrium were composed of pure solid benzene and of liquid benzene containing all of the impurities in ideal solution. The adiabatic calorimeter method was used in conjunction with automatic temperature controls and platinum resistance thermometry. Three of the four lots contained weighted amounts of pure n-heptane as an impurity, known only to the preparer, which were added to portions of the first lot which had been purified to better than 99.999 mol % by a fractional crystallization technique.

The mean impurity concentration determined by the calorimetric method for duplicate specimens from the lot of purified benzene was found to be 0.000660 mol % with deviations of ±27% from the mean of the two specimens. The results of the duplicate specimens from each of the three lots containing added impurity did not deviate by more than ±2% from their means which were 0.0883, 0.206, and 1.09 mol % impurity. These mean values deviated by −4, +2, and −7%, respectively, from the values calculated from the known amount of n-heptane impurity that was added to each lot. These results demonstrate that the cryoscopic determination of purity by calorimetry yields accurate values.
Droplet Characteristics with Conventional and Holographic Imaging Techniques
Authors: Thompson BJ
Published: December 2008

The basic parameters of both single lens imaging and two-lens imaging systems are discussed with particular emphasis on resolution and depth of field. Holographic methods of imaging particulate volumes are described and illustrated together with some current examples. The extension of the holographic method to the simultaneous measurement of both size and velocity is included.
Hot-Wire Technique for Droplet Measurements
Authors: Mahler DS , Magnus DE
Published: December 2008

An instrument using hot-wire technology to measure droplet size distributions in the 1 to 450 µm size range is discussed. Such instrumentation has several advantages over present techniques which are dominated by a variety of laser light scattering approaches. The major advantages are: (1) the hot-wire instrument is readily portable; (2) no careful alignment is necessary; and (3) the instrument is available at a fraction of the cost of optical instruments.

The present paper discusses some details of the droplet/wire interaction, for example, effects of the wire mounting posts, “grazing” interactions, aerodynamic effects, and liquid variation. Also discussed are the means of raw data corrections to obtain a variety of mean droplet sizes, volume concentration, and volume flow rates.

Limitations will be discussed along with examples of where the instrument can best be utilized.
Industrial Applications of Corrosion-Resistant Tantalum, Niobium, and Their Alloys
Authors: Burns RH , Shuker FS , Manning PE
Published: December 2008

During the period 1960–1982, tantalum, niobium, and their alloys have become increasingly important in industrial applications where superior corrosion resistance is required. These materials are particularly attractive when selected on the basis of “life cycle costing”. This takes into account initial cost, levels of product quality, length of trouble-free operation, and any increase in productivity due to reduced downtime and lower maintenance requirements. The chemical process industry, in particular, has taken advantage of these materials for processing mineral acids at temperatures and concentrations higher than can be withstood by any other materials.

Advances in electron-beam melting technology have also made it possible to manufacture larger and cleaner ingots, resulting in the availability to industry of larger sheets, tubes, and plates with improved property reliability.
Dry Etching Using NF3/Ar and NF3/He Plasmas
Authors: Barkanic J , Hoff A , Stach J , Golja B
Published: December 2008

Dry etching of silicon, silicon dioxide and photoresist has been studied using NF3 plasmas diluted with helium and argon in both reactive ion etch and plasma etch modes. NF3 concentrations in Ar and He ranged from 10 to 80% for these experiments. Power densities varied from 0.02 to 0.8W/cm2 and pressure from 15 to 500 μm depending on the etching mode selected. Etch rates increased with power density in both PE and RIE modes. Si etch rates as high as 14800Å/min. were obtained with an 80% NF3/Ar mixture at 0.8W/cm2 and 500 μm pressure. Oxide etch rates varied from 30 to 1500Å/min. depending on mode selected. Silicon over oxide selectivity tended to be higher for low power densities for all mixtures studied in either PE or RIE mode. Values obtained were ∼ 30 to 40 for low power densities (0.12 W/cm2) and ∼ 5 for the highest power density used. Selectivities were higher in PE than RIE mode. X-ray photoelectron spectroscopy analysis of etched Si, SiO2, and photoresist coated samples indicated that the surface layer had become fluorinated. Photoresist etch rates of ∼ 500Å/min. were measured for positive photoresist etched in a 40% NF3/He plasma. Loading experiments indicated 10 and 13% decreases in Si and SiO2 etch rates respectively, as the area being etched doubled and, the uniformity of etch rate was approximately 7% over the entire batch.
Edge-Controlled, Self-Consistent Proximity Effect Corrections
Authors: Berkowitz HL , Cook CF , Kwiatkowski JH , Goodreau WM
Published: December 2008

A new method for correcting electron-beam lithography pattern data for proximity effects is presented. The method calculates the average dose received by each partition exterior edge to be equal to the critical dose necessary for proper exposure. This method minimizes the number of partitioned rectangles required for acceptable lithography, thus greatly reducing CPU time. Electron-beam dose averages are not only determined for critical edges where exposure conditions are stringent, but also for the rest of the partitioned edges where tolerances are more relaxed. Both simulated and experimental results will be presented.
Evaluation of Gettering Efficiency of Backside Damage by the Use of the “Haze” Test
Authors: Domenici M , Ferrero G , Malinverni P
Published: December 2008

“Haze” test has been used to evaluate gettering efficiency on the wafers damaged by different techniques.

The wafers have been partially back side damaged and then intention ally contaminated by “pure” contaminants, such as the most common 3d transition and noble metals.

In the particular case of contamination by iron we are calibrating our qualitative results by parallel measurements using neutron activation analysis: this is done utilizing thermal as well as epithermal and fast neutrons to transmute Fe-54 into *Mn-54.
Ion Channeling Study of Damage in Neutron Transmutation Doped Semiconductors: Application to GaAs
Authors: Yahagi M , Satoh M , Kuriyama K , Iwamura K , Kim C , Shiraishi F
Published: December 2008

Neutron irradiation at a flux of 5 × 1011 neutrons /cm2 sec for 18 hr has been performed on n-type GaAs with 5.9 × 10−2Ω-cm (n= 2.1 × 1016/cm3). In annealing experiments for electrical properties, it is found that neutron irradiated-induced damages are removed by the annealing temperature at 800°C. The recovery of radiation damage is also confirmed from the improvement of photoluminescence for GaAs annealed at 800°C. The magnitude of the average displacement damage introduced during neutron irradiation is estimated to be 0.15 A by the measurement of Rutherford Backscattering channeling.
A New Silicon Irradiation Facility in the Pluto Mtr at Harwell
Authors: Baxter J , Crick NW
Published: December 2008

The full use of the existing silicon irradiation facilities in the Harwell Material — Testing reactors over the last three years has encouraged the installation and commissioning of a new irradiation facility in the PLUTO reactor. This paper includes a description of the facility which uses a horizontal hole positioned tangentially to the reactor core. Included are some details of nuclear parameters and the mode of operation. It is conservatively estimated that the facility in full-time operation has a capacity in excess of 20 tonnes per annum.
Optimization Criteria for the Stabilization of Sewage Sludge and Biogas Production Through Anaerobic Digestion: An Example of an Environmental Biotechnology Application
Authors: Ferraiolo G , del Borghi M , Solisio C , Gardi G
Published: December 2008

According to environmental protection and energy conservation principles, anaerobic digestion of activated sludges should have two main purposes: to stabilize the sludge within allowable limits and to increase biogas production as much as possible, in order to meet ecological requirement without neglecting a particular energy source. This implies optimization procedures for the design of the process, based upon its actual kinetics.

This optimization has been developed in the present paper on the basis of experimental results on anaerobic digestion kinetics achieved in previous research.

In particular, optimal biogas production has been determined under ecological constraint due to sludge stabilization.

This procedure has proved that the volatile solids (VS) concentration in the digester feed must be kept above an allowable limit, which has been determined in the authors' research.

If the process design is also required to keep the pollutant concentrations of the outlet supernatant liquor within allowable limits, optimization of biogas “production factors” is no longer feasible because, in this instance, a single digester would work as a purifier rather than a biogas productive unit.
Three-Dimensional Analysis of Short-Bar Chevron-Notched Specimens by the Boundary Integral Method
Authors: Mendelson A , Ghosn LJ
Published: December 2008

An analysis was performed, of the three-dimensional elastic problem of the chevron-notched short-bar specimen, using the boundary integral equation method. This method makes use of boundary surface elements only in obtaining the solution. Results were obtained for various notch geometries, and included displacement and stress fields. Load line displacements, and stress-intensity factors determined both from strain calculations and compliance calculations were compared with experimental values obtained at NASA Lewis Research Center. Good agreement was obtained.
Photoelastic Calibration of the Short-Bar Chevron-Notched Specimen
Authors: Sanford RJ , Chona R
Published: December 2008

The geometric shape function calibration of the short-bar chevron-notched specimen has been determined using a hybrid experimental-numerical technique. The results are in good agreement with those obtained by other methods. The hybrid method, which is rapid and low in cost compared to purely numerical methods, also provides additional information about the stress state in the neighborhood of the crack tip. This additional information has been used to determine the size and shape of the singularity dominated zone.
A Computer-Assisted Technique for Measuring KI-V Relationships
Authors: Coyle RT , Buhl ML
Published: December 2008

We developed a computer-assisted data collection technique for flatjackloaded, short-rod specimens to readily obtain crack velocity V as a function of stress intensity factor KI. The technique facilitates the study of stress corrosion in glass and ceramic materials and allows us to determine the crack velocity at which the critical stress intensity factor is evaluated. The experimental apparatus included (1) a stepper motor to automate pressurization of the flatjack and (2) a digital oscilloscope to acquire information about the flatjack pressure and sample displacement at preselected time intervals.

We conducted fracture experiments using samples of soda-lime-silicate float glass and alumino-borosilicate glass (Corning 7809 Solar Glass) in an environmental chamber at 25°C and 30% relative humidity. We found that the critical stress-intensity factor for float glass, extrapolated to a crack velocity of 0.1 m/s, was 0.77 MPa m1/2 compared to 0.81 MPa m1/2 for the solar glass. Comparison of KI versus V data for the two glasses showed that the coefficient n in the empirical relationship V = AKIn is 27.5 for the solar glass and 18 for float glass.
The Effect of Binder Chemistry on the Fracture Toughness of Cemented Tungsten Carbides
Authors: Tingle JR , Shumaker CA , Jones DP , Cutler RA
Published: December 2008

The fracture toughness of WC-10Co compositions with varying carbon concentrations were investigated. Both the material property, KIcSR and the apparent toughness, KQ, decreased rapidly upon the appearance of eta carbides in the microstructure. The amount of tungsten in the cobalt binder, as well as the presence of free carbon or eta carbides in the microstructure, affected the magnitude of the macroscopic residual stresses in the cermet.

The fracture toughness of compositions in which varying amounts of nickel had been substituted for cobalt were also investigated. It was found that up to 25% nickel could be substituted for cobalt without adversely affecting the fracture toughness or the hardness of the cermet.
Fiberglass Epoxy Laminate Fatigue Properties at 300 and 20 K
Authors: Toth JM , Bailey WJ , Boyce DA
Published: December 2008

A subcritical liquid hydrogen orbital storage and supply experiment is being designed for flight in the Space Shuttle cargo bay. The Cryogenic Fluid Management Experiment (CFME) includes a liquid hydrogen tank supported in a vacuum jacket by two fiberglass epoxy composite trunnion mounts. The ability of the CFME to last for the required seven missions depends primarily on the fatigue life of the composite trunnions at cryogenic temperatures. To verify the trunnion design and test the performance of the composite material, fatigue property data at 300 and 20 K were obtained for the specific E-glass fabric/S-glass unidirectional laminate that will be used for the CFME trunnions. The fatigue life of this laminate was greater at 20 K than at 300 K, and was satisfactory for the intended application.
Analytical Applications of Proton-Transfer Spectroscopy. Detection of Trace Hydrogen-Bonding Impurities in Hydrocarbon Solvents Using 3-Hydroxyflavone as a Fluorescence Probe
Authors: McMorrow D , Kasha M
Published: December 2008

The photo-excitation steps in 3-hydroxyflavone leading to proton-transfer are described. The consequence of the ultra-rapid (<8 ps) phototautomerization is the emission of a unique yellow-green tautomer fluorescence (λmax 525 nm) in hydrocarbon solution, instead of the violet fluorescence expected from the first UV absorption (onset λ 370 nm, first peak λ 354 nm). The tautomerization is intramolecular, involving the transfer of the hydroxyl hydrogen to the neighboring carbonyl group of the 3-hydroxyflavone molecule.

The analytical applications suggested by the qualitative spectroscopic features investigated result from the extreme sensitivity of the intramolecular H-bond to external solvent perturbations, which appear most strikingly in low-temperature spectroscopic studies as induced violet fluorescences of the H-bonded solvates. Using solute concentrations of 10−5 to 10−7 M, H-bonding impurities are detectable at substoichiometric concentrations. In the case of water in hydrocarbon solvents, the present experiments suggest that 10−7 to 10−9 M water may be detectable.

Ethers, alcohols, water, and other H-bonding solvents give characteristic violet solvate fluorescence band contours and peak positions, permitting qualitative discrimination of trace contaminants. The use of 3-hydroxyflavone as a fluorescence probe for solvent impurities is suggested. An application is made of isolated-site crystal matrix spectroscopy to determine the intrinsic low-temperature spectroscopic behavior of solutes, such as quinones and ketones, which can H-bond with trace impurities.
Comparison of Techniques for Generating Room Temperature Phosphorescence in Fluid Solution
Authors: Weinberger R , Rembish K , Cline Love LJ
Published: December 2008

Four techniques for inducing room temperature phosphorescence (RTP) in fluid solution are discussed, and the general requirements of molecular association for observation of RTP are presented. These methods are micelle-stabilized RTP, microcrystalline/colloidal RTP, cyclodextrin-induced RTP, and sensitized/quenched RTP. Examples of results using the different techniques for several classes of molecules, including carbocyclic and heterocyclic aromatic hydrocarbons and drugs, are used to illustrate the capabilities of these methods. The analytical utility of the four methods is compared and contrasted.
Impact Resistance of Fiber Composites: Energy-Absorbing Mechanisms and Environmental Effects
Authors: Chamis CC , Sinclair JH
Published: December 2008

Energy-absorbing mechanisms are identified and evaluated using several approaches. The energy-absorbing mechanisms considered are those in unidirectional composite beams subjected to impact. The approaches used include mechanistic models, statistical models, transient finite-element analysis, and simple beam theory. Predicted results are correlated with experimental data from Charpy impact tests. The environmental effects on impact resistance are also evaluated. Working definitions for energy-absorbing and energy-releasing mechanisms are proposed and a dynamic fracture progression is outlined. Possible generalizations to angleplied laminates are described.
Viscoelastic Buckling Analysis of Laminated Composite Columns
Authors: Wilson DW , Vison JR
Published: December 2008

A linear viscoelastic buckling analysis for laminated composite columns was developed using the quasi-elastic approach. The analysis includes transverse shear deformation (TSD), transverse normal deformation (TND), and bending-extensional coupling. The Rayleigh-Ritz method of solution was employed to solve the governing equation derived from the Theorem of Minimum Potential Energy. Viscoelastic column buckling behavior was investigated for four laminate configurations, [0]24, [0/±45/0]3s, [0/±45/90]3s, [±45]6s, and for column length-to-thickness ratios (ℓ/t) ranging between 35.8 and 150.0. The results for graphite/epoxy show that viscoelastic effects are significant, reducing the critical buckling load by 10% to 20%, depending upon laminate configuration. For geometries where TSD is important (ℓ/t < 50.0), the effects of viscoelasticity are magnified by the matrix-controlled shear stiffness contribution.