bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Prestrain on Fatigue Crack Growth of Age-Hardened Al 6061-T6
Authors: Ikematsu Koji , Mishima Takuhiro , Kang Minwoo , Aono Yuuta , Noguchi Hiroshi
Published: March 2010

The effect of prestrain on fatigue crack growth characteristic (FCGC) of age-hardened Al 6061-T6 was investigated. Al 6061-T6 specimens were subjected to tension to produce plastic strain. Extruded bars were prepared to investigate FCGC. Specimens with an artificial hole from the bar were used to observe Mode I fatigue crack. On the other hand, coarse-grained plain specimens were used and observed for Mode II fatigue crack. Fatigue tests were performed under a rotating bending load (R=−1). The experimental results showed the Mode I fatigue crack growth rates decelerated a little due to prestrain. However, in the case of Mode II, fatigue crack growth rates of prestrain specimens accelerated about ten times due to prestrain. The Mode II fatigue crack easily propagates on the slip bands, because precipitation particles on the slip bands are sheared by prestrain. The result means the influence of prestrain on Mode II fatigue should be taken into account for damage-tolerant design.
Biaxial Loading Effect on Higher-Order Crack Tip Parameters
Authors: Shlyannikov V. N. , Ilchenko B. V. , Boychenko N. V.
Published: March 2010

The higher-order asymptotic crack-tip fields are considered for a Mode I in power-law plastic and creeping materials under plane strain conditions. Using an asymptotic expansion and separation of variables for the stress function, a series solution is obtained for stress components at a crack tip. In addition, full-field finite element analysis based on a modified layer approach is employed to model the effects of biaxial loading on nonlinear behavior. Loadings were applied related to a range of biaxial stress ratio (−2, +2). The radial and angular stress distributions and higher-order amplitude coefficients for plastic materials are obtained. Crack tip higher-order fields under various conditions of biaxial loading and spanning the range of times from small scale creep to extensive creep are presented. Account is taken of the radial distance accompanying crack tip blunting. The phenomenon of stress redistributions along crack plane on creep time as a function of biaxial stress ratio is stated. The regions of dominance of the HRR-type field under various biaxial stress ratio, crack distance, hardening exponent, and creep time are found. Good agreement analytical findings with finite element results conforms that HRR-solution corresponds only to the equibiaxial tension which is a particular case of biaxial loading. It is further demonstrated that the higher-order both for plastic and creeping fields are controlled through constraint parameter A2 by biaxial stress ratio. By fitting numerical results for plastic and creeping materials, two empirical formulas were obtained to describe the higher-order terms amplitude coefficients A2 distributions depending on biaxial stress ratio, crack distance, hardening exponent, and creep time.
Fatigue Crack Growth in Open and Nut-Loaded Bolts with and without Pretension Loading
Authors: Prakash Raghu V. , Bagla Akash
Published: March 2010

Results of an experimental study to understand crack growth in open threaded bolts and nut-loaded bolts with and without pretension are presented in this paper. Experimental crack growth rates are compared with predicted solutions obtained from known stress intensity factor solutions. For the experiment, a specially designed fixture was used for loading the bolt and the level of pretension was varied by controlling the displacement on the arm of the C section of the fixture. Programmed Hi—Lo fatigue load sequence was applied on a bolt to ensure that decodable marker bands are left behind on the fracture surface, to study the crack growth characteristics. Fatigue crack growth rate was estimated using a scanning electron microscope by identifying crack increment during high stress ratio cycles. This has been compared with predicted crack growth rates using available stress intensity factor solutions. Crack growth at the center of the bolt correlates well with Toribio's (Int. J. Fract., Vol. 53, 1992, pp. 367–385) finite element based predictions for open threaded bolts. Crack growth rate is much higher at the surface than at the center. In case of nut-loaded bolts, available K solutions are found to be inadequate to provide an accurate estimate of crack growth rates at the center of the bolt. Further study is required to characterize the effect of friction, pitch angle, and thread geometry to understand crack growth in bolts.
The Influence of Tank Mix Additives While Making Low Volume Aerial Fungicide Applications
Authors: Wolf Robert , Gardisser Dennis , Bretthaurer Scott , Mauromoustakos Andy , Baxter Lynn
Published: March 2010

Multiple experiments using low volume aerial applications with nine different adjuvants in combination with fungicide were conducted to compare coverage, droplet spectra, yield, and disease control. Four locations were scattered over three states: Arkansas, Kansas, and Illinois. Four aircraft with different nozzle and boom setups were used to complete the studies. Volume median size (DV0.5) ranged from 232 μm to 364 μm. Kromekote® papers used as collectors were placed in the center 9 m of each aerial swath∕treatment (20 m) at three different plant heights: top corn leaf, ear leaf, and the leaf three collars below ear leaf. In each treatment, sampling consisted of 30 papers; 10 corn plants at the three heights, with all papers at 30 cm from the main stalk. DropletScan™, utilizing a high resolution color scanner to digitize the images on the Kromekote® papers, was used to analyze each paper. Means for percent area coverage and DV0.5 were used to separate differences in treatments. Relative span was calculated as an indicator of the range in the droplet spectrum. Yields were taken from the center of each treatment. Three to five replications per treatment were completed and a SAS GLIMMIX analysis was performed. Significant differences were measured among adjuvant treatments for both droplet spectra and deposition∕coverage. Mixed results are reported across all treatments and locations. A mixture of water, Headline, and Crop Oil Concentrate (Treatment 2) was consistently measured with the lowest amount of coverage, and in two of four locations had the largest DV0.5. Overall, droplet spectra were impacted by the addition of adjuvants to the tank mix. The largest droplets were not associated with the best coverage, and the trend was for the lowest coverage to be associated with the smallest droplets. Treatment 5 (NIS + Interlock) had the smallest DV0.5 in three of the test locations. A limited number of significant yield differences were found. This effect could be due to low disease pressure.
Imazapyr Absorption and Translocation in Northern Red Oak and Red Maple as Affected by Herbicide Formulation and the Adjuvant Methylated Seed Oil
Authors: Bernards Mark L. , Penner Donald , Michael Jan
Published: March 2010

Imazapyr-based herbicides are important in removing deciduous hardwood species from conifer plantations. Imazapyr can be applied as a site preparation (pre-establishment) application or as a postestablishment herbaceous or release application. Herbicide efficacy is dependent, in part, on how much herbicide is absorbed and translocated throughout the target weed species. Herbicide absorption can be strongly influenced by herbicide formulation or tank-mix adjuvants. Little data are available on imazapyr absorption and translocation by woody species. The objective of this research was to compare the absorption and translocation of six experimental formulations of imazapyr to a commercial formulation, Chopper®, with and without methylated seed oil (MSO), in northern red oak (Quercus rubra L.) and red maple (Acer rubrum L). Saplings of both species were grown in the greenhouse until they reached a height of approximately 1 m. Trees were blocked according to size, and treatments were randomly assigned within blocks. For the absorption study, five leaves were selected per plant and received two 1-μL drops of 14C-imazapyr-labeled solution. Leaves were rinsed at 2, 8, 24, 72, and 144 h after treatment (HAT). Absorption was quantified as 14C imazapyr that was not collected in the rinse solution. All experimental formulations that were tank-mixed with MSO increased absorption on oak compared to Chopper+MSO. Not all experimental formulations increased absorption in maple, and absorption data were highly variable. Absorption continued for at least 72 HAT in both species for most formulations. For the translocation study, one leaf was treated with two 1-μL drops of 14C-imazapyr-labeled solution. The leaf was rinsed at 144 HAT, and the plant was harvested and divided into sections: above treated leaf, treated leaf, below treated leaf, and roots. The majority (52–91 %) of the applied imazapyr remained in the treated leaf. More imazapyr was translocated from the leaf of red oak than red maple. Translocated 14C accumulated in the tissue above the treated leaf (3–13 % of absorbed) and in the roots (3–34 %). Including the adjuvant MSO and optimizing the herbicide formulation increased the absorption of imazapyr in red maple and northern red oak.
Effect of Processing Shear Time on EW Formulations
Authors: Costello Lauren
Published: March 2010

Concentrated aqueous emulsions, or EWs, are the dispersion of a water insoluble organic liquid into water. The formulation is achieved through the use of polymeric surfactants, which provide multiple anchoring points and steric stabilization to prevent coalescence. Formation of the EW is mechanically driven, requiring high-shear processing to reduce particle size and attain a stable formulation. In this study, the relationship between processing shear time, particle size, and stability was examined. Samples were prepared using a high hydrophile∕lipophile balance (HLB) polymer (butyl block copolymer) paired with a low HLB polymer (nonionic block or random copolymer), varying polymer types and polymer ratios. Shear was applied for 10 min to 40 min. Emulsion dilution stability (ASTM E1116-98), particle size distribution (Malvern Mastersizer), and high temperature stability were used to characterize the samples. It was found that particle size decreased as shear input was increased, reaching an optimum after 25 min to 30 min of shear, depending on the polymer pair used. All samples performed similarly in dilution stability showing improved performance after 10 min of shear. After 1 month at 54°C, all samples showed no separation and demonstrated similar dilution performance, however, D90 values dropped significantly (>20 %) in samples with less than 20 min of shear, whereas samples receiving a minimum of 20 min to 30 min of shear showed decreases in D90 around 10 %. A likely explanation for the decreases in D90 observed after elevated temperature storage is that the addition of heat energy drove the particle surface area toward equilibrium according to the equation ΔA = W∕γ, where ΔA is change in surface area, W is work, and γ is interfacial tension
Development and Testing of a Laboratory Spray Table Methodology to Bioassay Simulated Levels of Aerial Spray Drift
Authors: Fritz Bradley K. , Hoffmann W. Clint , Parker Chris , López Juan D.
Published: March 2010

The objective of this work was to develop a repeatable methodology for bioassaying simulated levels of aerially applied glyphosate at deposition levels ranging from 1∕3 to 1∕100 of labeled rate at droplet sizes of 100 μm in a spray table environment. These drift deposition levels are consistent with downwind drift measurements out to 200 m seen in previous field studies focusing on quantitative drift assessment. Additionally, full rate applications were included for comparative purposes. The deposition levels were obtained by varying nozzle traverse speed and plant location under the nozzle. Ten replications were conducted at each targeted rate applying glyphosate to container grown-plant samples. Deposition was measured on Mylar cards through fluorometric analysis. Plant health measures [height and normalized difference vegetation index (NDVI)] were taken at 0, 1, 3, 5, 7, and 14 days after treatment. An equal number of nontreated control plants were analyzed alongside treated plants. Deposition and plant health data were used to generate dose-response relationships. Dose-response curves relating change in plant height and change in measured NDVI values corresponding to deposition levels were generated. This methodology is one that can be implemented across a wide variety of plant and pesticide combinations. Collected data from this and future studies will be tested under field conditions and ultimately be included in application decision support systems that integrate spray drift modeling results with established dose-response relationships.
Multiple Metal Cations as Spray Deposit Tracers and Evaluation of the AGDISP Ground Boom Spray Drift Model
Authors: Zabkiewicz J. A. , Steele K. D. , Connell R. J.
Published: March 2010

The determination of spray drift by agrichemicals in field applications is laborious and expensive. Dyes have been used as tracers to reduce workloads and costs, but these methods have technical drawbacks. Metal cations have also been used as tracers and this method is promising, especially if a number of distinct cations from consecutive spray applications can be collected cumulatively by the same collectors. This study evaluated the use of various water soluble metal cation salts and plastic tape as a cost-effective collector for spray drift deposits. Measured deposit values were compared with calculated outputs from the AGDISP ground boom spray drift model. The comparisons showed that AGDISP over estimated downwind deposition and under estimated deposition within the last swathe in the spray block. Increasing boom height above the canopy improved within spray block deposition estimates. Varying wind direction had negligible effect; increasing relative humidity gave greater deposition closer to the spray block. These trends are discussed, together with the pros and cons of the metal cation and plastic tape collector system.
A Proposed Qualitative Framework for Heterogeneous Burning of Metallic Materials: The “Melting Rate Triangle”
Authors: Ward Nicholas R. , Steinberg Theodore A.
Published: March 2010

This paper presents a proposed qualitative framework to discuss the heterogeneous burning of metallic materials, through parameters and factors that influence the melting rate of the solid metallic fuel (either in a standard test or in service). During burning, the melting rate is related to the burning rate and is therefore an important parameter for describing and understanding the burning process, especially since the melting rate is commonly recorded during standard flammability testing for metallic materials and is incorporated into many relative flammability ranking schemes. However, while the factors that influence melting rate (such as oxygen pressure or specimen diameter) have been well characterized, there is a need for an improved understanding of how these parameters interact as part of the overall melting and burning of the system. Proposed here is the “melting rate triangle,” which aims to provide this focus through a conceptual framework for understanding how the melting rate (of solid fuel) is determined and regulated during heterogeneous burning. In this paper, the proposed conceptual model is shown to be both (a) consistent with known trends and previously observed results, and (b) capable of being expanded to incorporate new data. Also shown are examples of how the melting rate triangle can improve the interpretation of flammability test results. Slusser and Miller previously published an “extended fire triangle” as a useful conceptual model of ignition and the factors affecting ignition, providing industry with a framework for discussion. In this paper it is shown that a melting rate triangle provides a similar qualitative framework for burning, leading to an improved understanding of the factors affecting fire propagation and extinguishment.
Ignition of Contaminated Aluminum by Impact in Liquid Oxygen—Influence of Oxygen Purity
Authors: Werlen Etienne , Crayssac Frédéric , Longuet Olivier , Willot Fabien
Published: March 2010

Impact tests in liquid oxygen and oxygen enriched liquids have been conducted on aluminum foils (0.2 mm thick) used for heat exchangers of air separation units (ASUs). Some adaptations to the ASTM Standard D2512, “Standard Test Method for Compatibility of Materials with Liquid Oxygen,” have been done to ensure the good control of oxygen content in the cryogenic liquid and to get reproducible results in aluminum ignition with hydrocarbon coating. Modified striker pins with a cavity on the contact surface have been used. The vertical guiding and the centering of the striker pins have been ensured by using two machined guides. Test samples were three layers of aluminum foil, two corrugated and one flat, contaminated by various quantities of hexadecane. The criteria for the identification of aluminum ignition (positive tests) have been validated by performing Scanning electron microscope surface analysis on residuals of a few impact tests performed in copper cups. Criteria have also been defined to check that hexadecane combustion took place in negative tests. A sufficient number of tests have been performed to plot the probability of ignition of the aluminum samples as a function of the average thickness of hexadecane coating and as a function of the oxygen content in the cryogenic liquid varying from 50 % to above 99.95 %. The remaining part in the cryogenic liquid was nitrogen and 2.3 % argon except for one series of tests where the influence of the absence of argon could be identified. The results of these tests can be used to assess the risk of ignition of some aluminum exchangers or structures used in ASU.
Verification of the ASTM G-124 Purge Equation
Authors: Robbins Katherine E. , Davis Samuel Eddie , Herald Stephen D.
Published: March 2010

ASTM G-124 seeks to evaluate combustion characteristics of metals in high-purity (>99 %) oxygen atmospheres. ASTM G-124 provides the following equation to determine the minimum number of purges required to reach this level of purity in a test chamber: n = −4∕log10(Pa∕Ph), where n is the total number of purge cycles required, Ph is the absolute pressure used for the purge on each cycle, and Pa is the atmospheric pressure or the vent pressure. The origin of this equation is not known and has been the source of frequent questions as to its accuracy and reliability. This paper provides the derivation of the G-124 purge equation, and experimentally explores the equation to determine if it accurately predicts the number of cycles required.
Promoted Ignition Testing of Metallic Filters in High-Pressure Oxygen
Authors: Odom Greg A. , Chiffoleau Gwenael J. A. , Newton Barry E. , Fielding J. Ron
Published: March 2010

Currently, no test standard exists for evaluating the ignition tolerance and fault tolerance of metallic filters in high-pressure oxygen. Filters are a critical component in oxygen systems to ensure system cleanliness and mitigate ignitions by particle impact and contamination. However, filters are at risk to these same ignition mechanisms and fires have occurred in service. A new test method was developed using ASTM Standard G175 Phase 2 as a basis. The test subjects a pre-contaminated filter to a forced ignition event using an ignition pill while the filter is maintained at elevated pressure. Prior to testing, contaminant was applied to the filter element and was also placed at the filter inlet. This additional contaminant was based on contaminant that could potentially accumulate in a filter over time. This contaminant consisted of aluminum powder, iron particles, and perfluorinated lubricant. An ignition pill, consistent with ASTM Standard G175 Phase 2, was located on the upstream side of the filter. A back pressure was applied downstream of the ignition pill to ensure that the filter was pressurized during the ignition and burning of the pill. Testing was performed on brass and stainless steel filters of the same design using an oxygen shock to ignite the ignition pill at a test pressure greater than the back pressure applied to the filter. The brass filters safely contained the ignition event without breaching through the filter element or body. For the stainless steel filters, the ignition event kindled the filter element and burned through the filter body. This testing showed that the ignition fault tolerance of the brass filters was far superior to that of the stainless steel filters, which was consistent with the relative flammability of these metallic materials, and therefore verified the test methodology.
Oxygen Compatibility of Brass-Filled PTFE Compared to Commonly Used Fluorinated Polymers for Oxygen Systems
Authors: Herald Stephen D. , Frisby Paul M. , Davis Samuel Eddie
Published: March 2010

Safe and reliable seal materials for high-pressure oxygen systems sometimes appear to be extinct species when sought out by oxygen systems designers. Materials that seal well are easy to find, but these materials are typically incompatible with oxygen, especially in cryogenic liquid form. This incompatibility can result in seals that leak, or much worse, seals that easily ignite and burn during use. Scientists at the Materials Combustion Research Facility (MCRF), part of NASA∕Marshall Space Flight Center, are constantly searching for better materials and processes to improve the safety of oxygen systems. One focus of this effort is improving the characteristics of polymers used in the presence of an oxygen enriched environment. Very few systems can be built which contain no polymeric materials; therefore, materials which have good impact resistance, low heat of combustion, high autoignition temperature, and those that maintain good mechanical properties are essential. The scientists and engineers at the MCRF, in cooperation with seal suppliers, are currently testing a new formulation of polytetrafluoroethylene (PTFE) with brass filler. This brass-filled PTFE is showing great promise as a seal and seat material for high-pressure oxygen systems. Early research has demonstrated very encouraging results, which could rank this material as one of the best fluorinated polymers ever tested. This paper will compare the data obtained for brass-filled PTFE with other fluorinated polymers, such as TFE-polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene 81, Viton® A, Viton® A-500, Fluorel®, and Algoflon®. A similar metal-filled fluorinated polymer, Salox-M®, was tested in comparison to brass-filled PTFE to demonstrate the importance of the metal chosen and relative percentage of filler. General conclusions on the oxygen compatibility of this formulation are drawn, with an emphasis on comparing and contrasting the materials performance to the performance of the current state-of-the-art oxygen compatible polymers.
Effect of Oxygen Concentration on Autogenous Ignition Temperature and Pneumatic Impact Ignitability of Nonmetallic Materials
Authors: Smith Sarah
Published: March 2010

Extensive test data exist on the ignitability of nonmetallic materials in pure oxygen, but these characteristics are not as well understood for lesser oxygen concentrations. In this study, autogenous ignition temperature testing and pneumatic impact testing were used to better understand the effects of oxygen concentration on ignition of nonmetallic materials. Tests were performed using oxygen concentrations of 21, 34, 45, and 100 %. The following materials were tested: PTFE Teflon®, Buna-N, Silicone, Zytel® 42, Viton® A, and Vespel® SP-21.
Liquid Oxygen Rotating Friction Ignition Testing of Aluminum and Titanium with Monel® and Inconel® for Rocket Engine Propulsion System Contamination Investigatio
Authors: Peralta Stephen F. , Rosales Keisa R. , Stoltzfus Joel M.
Published: March 2010

Metallic contaminant was found in the liquid oxygen (LOX) prevalve screen of the shuttle main engine propulsion system on two orbiter vehicles. To investigate the potential for an ignition, NASA Johnson Space Center White Sands Test Facility performed (modified) rotating friction ignition testing in LOX. This testing simulated a contaminant particle in the low-pressure oxygen turbo pump (LPOTP) and the high-pressure oxygen turbo pump (HPOTP) of the shuttle main propulsion system. Monel® K-500 and Inconel® 718 samples represented the LPOTP and HPOTP materials. Aluminum foil tape and titanium foil represented the contaminant particles. In both the Monel® and Inconel® material configurations, the aluminum foil tape samples did not ignite after 30 s of rubbing. In contrast, all of the titanium foil samples ignited regardless of the rubbing duration or material configuration. However, the titanium foil ignitions did not propagate to the Monel and Inconel materials. Based on these results, NASA determined that the risk of a fire occurring in the turbo pumps was acceptably low.
Electrical Arc Ignition Testing for Common Handheld Electrical Devices in Oxygen-Enriched Atmosphere
Authors: Sparks Kyle , Gallus Timothy , Smith Sarah
Published: March 2010

Electrical arc ignition is a concern for materials used in low pressure oxygen-enriched environments such as inside spacecraft. The National Aeronautics and Space Administration (NASA) Johnson Space Center requested that the NASA White Sands Test Facility conduct arc ignition tests to evaluate the hazard of electrical arc ignition of materials that could be in close proximity to batteries for the Constellation Program. Wire-break electrical arc tests were performed to determine the current threshold for ignition of generic cotton with a fixed voltage of 3.7 V, a common voltage for handheld electrical devices. These tests were performed in 34 % oxygen at varying pressures.
Tribocharging of Particle Contaminants Evaluated as an Ignition Source in Oxygen-Enriched Environments
Authors: Oza Aditi , Ghosh Sudipto , Chowdhury Kanchan
Published: March 2010

Contamination particles make an oxygen system more vulnerable to fire hazard as they provide a large surface area with reduced minimum energy of ignition. Adiabatic compression, resonance, solid friction, flow friction, and promoted ignition have acted as the source of ignition in oxygen systems. In this paper, static electricity generated in solid particles is proposed to be another possible source of ignition. It is known that the movement of particles in a system results in the buildup of static charges in them. This static electricity, if supported by suitable geometric configuration and grounding of metal projections, may lead to propagating brush discharge (PBD) and provide the energy needed for initiation of fire. Particles with low auto-ignition temperature, particularly in dispersed state, may help in initiating the fire, while metal particles may aid the propagation because of their high combustion energy. In this paper, we have determined the velocity profile utilizing the FLUENT code and calculated the charge generated in particles, exploring the ignition probability of equipment in oxygen environment through electrostatic discharge. We have also attempted to perform preliminary calculation to determine charge density and the electric field strength required for brush discharge. Computational fluid dynamics analyses on globe valves reveal the presence of probable areas of particulate accumulation in the valve. The decrease in minimum ignition energy (MIE) in the environment of high pressure, high temperature, high purity of oxygen, low humidity, small particles, high dielectric constant, low thickness of insulating layer, and high resistance of the deposited dust layer facilitates occurrence of PBD, which may cause ignition. Adiabatic heating may aid combustion by lowering the MIE of particles. Experiments have been proposed for verification of the hypothesis and analytical calculations presented by the authors. The paper may give a new insight into the possible causes of oxygen fire.
An Approach to Understanding Flow Friction Ignition: A Computational Fluid Dynamics (CFD) Study on Temperature Development of High-Pressure Oxygen Flow Inside Micron-Scale Seal Cracks
Authors: Hooser Jared D. , Wei Mingjun , Newton Barry E. , Chiffoleau Gwenael J. A.
Published: March 2010

Flow friction ignition of non-metallic materials in oxygen is a poorly understood heat-generating mechanism thought to be caused by oxygen flow past a non-metallic sealing surface. Micron-scale fatigue cracks or channels were observed on non-metallic sealing surfaces of oxygen components and could provide a leak path for the high-pressure oxygen to flow across the seal. Literature in the field of micro-fluidics research has noted that viscous dissipation, a heat-generating mechanism, may not be negligible as the flow dimension of the channel is reduced to the micron-scale. Results of a computational fluid dynamics study are presented and used to determine if temperatures developed in high-pressure driven micro-channel oxygen flows are capable of reaching the reported autogenous ignition temperature of non-metallic materials in oxygen.
The Rate-Limiting Mechanism for the Heterogeneous Burning of Cylindrical Iron Rods
Authors: Ward Nicholas R. , Steinberg Theodore A.
Published: March 2010

This paper presents the findings of an investigation into the rate-limiting mechanism for the heterogeneous burning in oxygen under normal gravity and microgravity of cylindrical iron rods. The original objective of the work was to determine why the observed melting rate for the burning of 3.2-mm-diameter iron rods is significantly higher in microgravity than in normal gravity. This work, however, also provided fundamental insight into the rate-limiting mechanism for heterogeneous burning. The paper includes a summary of normal-gravity and microgravity experimental results, heat transfer analysis, and post-test microanalysis of quenched samples. These results are then used to show that heat transfer across the solid∕liquid interface is the rate-limiting mechanism for melting and burning, limited by the interfacial surface area between the molten drop and solid rod. In normal gravity, the work improves the understanding of trends reported during standard flammability testing for metallic materials, such as variations in melting rates between test specimens with the same cross-sectional area but different cross-sectional shape. The work also provides insight into the effects of configuration and orientation, leading to an improved application of standard test results in the design of oxygen system components. For microgravity applications, the work enables the development of improved methods for lower cost metallic material flammability testing programs. In these ways, the work provides fundamental insight into the heterogeneous burning process and contributes to improved fire safety for oxygen systems in applications involving both normal-gravity and microgravity environments.
Chlorine Trifluoride Exposure Testing and Oxidizer Reactivity Results
Authors: VanOmmeren James
Published: March 2010

Chlorine trifluoride (CIF3) was first synthesized in the 1930s and is one of the most oxidizing and reactive halogen fluorides known. In fact, with the exception of elemental fluorine, CIF3 may represent one of the most oxidizing and reactive materials in existence. Active research and commercial use of CIF3 began in the late 1940s, and CIF3 has been utilized in such diverse applications as military weapons usage, rocket fuel oxidant, nuclear fuels processing, oil well rod cutting, mineral analysis, and electronics manufacturing equipment cleaning. Such fluoride compounds present significant toxic, oxidizing, highly reactive, and environmental challenges in their manufacture, delivery, customer use, handling, disposal treatment, and emergency response. Air Products has been the primary manufacturer of CIF3 in North America for about 40 years, and CIF3 represents one of the strongest oxidizing and highest reactivity materials that Air Products handles worldwide. However, little information has been available in public literature or the industry regarding its oxidizing potential and reactivity strength with specific materials it may routinely or accidentally come in contact with. Therefore, Air Products conducted extensive release testing to expose various materials of construction (metals, plastics, and elastomers), building materials, personal protective equipment, and other common materials to both vapor and liquid phase releases of CIF3. This paper discusses the synthesis, hazards, varied uses, and major incidents involving CIF3. For example, one major CIF3 liquid spill accident from the 1960s is discussed where an eyewitness stated, “The concrete was on fire!” The paper details controlled release exposure testing methods Air Products employed, results, and lessons learned regarding improved handling and usage recommendations for CIF3 suppliers and customers. For example, a significant potential hazard was discovered regarding use of a safety shower if a person's clothing was exposed to CIF3 liquid, which caused Air Products to change their Material Safety Data Sheet and Product Safety hazards training.
The Acceleration-Axonal Strain Relationship and mTBI: Future Directions for Head Protection
Authors: Bishop Patrick J.
Published: March 2010

The primary determinant of helmet suitability in performance standards and certification programs is the head-form acceleration (peak acceleration <275 to 300 g) obtained in the drop tests. This has led to ice hockey helmets that have been very successful in reducing the risk of focal (localized) head injuries. Parallel to this development has been a concomitant increase in the amount and severity of checking about the head that has led to a substantial rise in mTBI at all levels of hockey. While this may be regarded as a behavioral issue, calling for improved player respect, rules enforcement, etc., there are some who believe that mTBI risk reduction can be achieved via helmets. The cause of mTBI is axonal shear strain precipitated by rotational acceleration of the brain. While recent research has indicated that the concussion state is precipitated by a strain of some 2 to 5% and beyond, the level of acceleration needed to produce this amount of strain is unknown. This paper will explore the need for establishing an acceleration-axon strain relationship that may eventually be used to develop head protection strategies that are effective in reducing the concussion risk in hockey.
A Prospective Study of Injuries in NCAA Intercollegiate Ice-Hockey Goaltenders
Authors: LaPrade Robert F. , Wijdicks Coen A. , Spiridonov Stanislav I.
Published: March 2010

While relatively well protected and padded, ice-hockey goaltenders are at risk for impact injuries. There is little information regarding the incidence and mechanism of intercollegiate ice-hockey goaltender injuries. We prospectively studied all NCAA ice-hockey goaltender injuries through the Injury Surveillance System. We analyzed the seasons prospectively starting in 2000–2001 and through 2006–2007. Injury rates were calculated per 1000 player games. The overall rate of NCAA men's ice-hockey goaltender injuries was 0.5∕1000 player games. Fifty-six men's ice-hockey goaltender injuries resulted in further time loss from practices or games. Thirteen injuries resulted in time loss of 1 to 2 days, 18 resulted in time loss of 3–5 days, 10 injuries resulted in time loss of 6–9 days, and 10 injuries resulted in 10 or more days of time loss from competition. The overall rate of NCAA women's ice-hockey goaltender injuries was 0.72∕1000 player games. The most common injuries were nine knee ligament injuries, five on-ice concussions, and four shoulder injuries. Overall, women sustained 23 time-loss game injuries. Five of these resulted in further loss of on-ice practice∕game times of 1 day, eight resulted in 3–5 days of time loss, two resulted in 6–9 days of time loss, and seven injuries resulted in 10 or more days of time loss. Further understanding of the etiology of these on-ice goaltender-player contact injuries should assist in the development of possible interventions to reduce the incidence of NCAA ice-hockey goaltender injuries. The current Injury Surveillance System has shortcomings and does not provide us with enough information to evaluate the effectiveness of goalie equipment and the impact that possible rule changes would have on the game. This paper is the first step in analyzing all participants in hockey with anticipation for future rule and equipment optimization and subsequent injury reduction.
Impact Attenuation Characteristics of Thin Walled Collapsible Air Chambers for Use in Protective Helmets
Authors: Hoshizaki T. B. , Post A.
Published: March 2010

For the past 40 years, helmets have primarily used expanded polystyrene, vinyl nitrile, and expanded polypropylene foams for impact attenuation. Even though the packaging industry has investigated a variety of structures for impact management, the helmet industry has been slow to adopt these types of innovations. More recently, engineered structures have been developed and introduced for use in the helmet industry. This study was intended to describe the impact characteristics of a thin walled collapsible air chambers designed to be used in sport helmets. This study investigated three structures: rigid walls, a chamber with rigid walls and a vent, and a chamber with rigid walls and no vent. Each structure was impacted with a 5 kg weight at three velocities: 1.9, 2.8, and 3.4 m∕s. The three structures were also made using two materials of different stiffnesses. Analysis of the results revealed that the effect of the walls, vent, and material stiffness interacted to produce effective energy management. The results demonstrated that by changing the material stiffness, wall thickness, and vent diameter the performance of the chambers can be engineered to effectively manage different levels of energy.
Concussion in Youth Hockey: Prevalence, Risk Factors, and Management across Observation Strategies
Authors: Williamson I. J. S. , Goodman D.
Published: March 2010

Ice hockey ranks among the highest of all sports for rates of concussion, and estimates from youth hockey appear ominously close to estimates from the NHL (23.15 and 29.59 per 1000 player-hours, respectively), yet concussion is seldom studied in the youth setting, particularly in a way that accounts for under-reporting. To maximize the capture of concussions in youth hockey, we used broad injury inclusion criteria and multiple surveillance strategies, including (a) official injury reports, (b) reports from team personnel, and (c) reports from trained hockey observers. The aims were to (a) better elucidate the prevalence and causes of hockey-related concussions, (b) examine how concussions are reportedly managed in youth ice hockey, and (c) speak to the utility of the different surveillance strategies. Contact between players was the most common mechanism across observation strategies and more than half (51 %) of concussions reported by volunteers were caused by illegal acts (32 % hits from behind, 8 % hits to head, and 7 % crosschecks), though few (23 %) resulted in penalties. According to volunteer and observer reports, many young players are returning to play in the same game they sustained a concussion (34 % and 71 %, respectively), which contravenes Hockey Canada guidelines. Contrary to the literature, there were significantly higher odds (p<0.05) of sustaining a concussion in the youngest age division rather than among older players according to volunteer reports. This study sampled approximately 22 400 youth players and is among the broadest investigations of concussion in youth ice hockey.
Josquin's Qui habitat and the Psalm Motets
Authors: Perkins Leeman L.
Published: March 2010

Traditional methods of stylistic analysis may be useful for delimiting repertories and musical genres on the basis of common features, but they have proved inadequate to the task of distinguishing between general style traits that a composer may choose to cultivate and the compositional voice that is uniquely his own. Particularly relevant in this regard are the questions raised by compositions ascribed to Josquin Desprez. Examples from among the psalm motets that bear his name in the sources illustrate the usefulness of stylistic criteria in establishing affinities shared by a group of works and, conversely, the radically different conclusions that have been drawn by scholars working in the field regarding specific pieces as to their composer and the date of their composition. This circumstance has apparently led to an increased reliance on source-critical criteria for accepting or rejecting Josquin's authorship.

Josquin's Qui habitat in adiutorio Altissimi, one of the most widely circulated and securely attributed of the psalm motets that carry the composer's name, serves as a paradigm for identifying compositional procedures that go beyond the stylistic generalities shared by Josquin and his immediate contemporaries (i.e., traits in use everywhere that could be imitated with comparative ease by a skilled composer) and that can therefore be understood as elements of Josquin's unique compositional voice. The most striking feature of this sort in Qui habitat is a skillful and ingenious use of a variety of iterative procedures, including internal repetitions that appear to be largely wanting in the music of his contemporaries even in their use of syntactic imitation.

Owing to their close identification with the composer's unique idiom, such procedures furnish a touchstone for determining the reliability of the attributions in the sources. Specifically, their presence in the small repertory of psalm motets that appear to have been more or less universally admitted to the Josquin canon provides a basis for comparison with a number of works whose attributions to Josquin have been questioned.
A Longitudinal Analysis of Neighborhood Crime Rates Using Latent Growth Curve Modeling
Authors: Kikuchi George , Desmond Scott A.
Published: March 2010

Although social disorganization theory provides a framework for understanding how changes in neighborhoods can influence crime rates over time, research on neighborhood characteristics and crime has relied primarily on cross-sectional data. Using a latent growth curve model and longitudinal data on residential burglary and vehicle theft in Indianapolis, measured annually between 1992 and 2006 at the census block group level, the authors analyzed the relationships between neighborhood characteristics and crime trends. For both residential burglary and vehicle theft, baseline models revealed that changes in crime rates were best captured by a quadratic function with an initial linear decrease and subsequent deceleration (slowing) of the decrease. When neighborhood characteristics were included as predictors, change in neighborhood disadvantage was significantly related to changes in both residential burglary and vehicle theft over time, while change in residential stability did not have a significant effect on changes in residential burglary or vehicle theft.
Is Rising Earnings Inequality Associated with Increased Exploitation? Evidence for U.S. Manufacturing Industries, 1971–1996
Authors: Sakamoto Arthur , Kim Changhwan
Published: March 2010

Is the trend towards rising earnings inequality associated with increased exploitation? The authors investigate exploitation among workers using data for manufacturing industries. Defined as the underpayment of earnings relative to productivity as evaluated in the market, exploitation is measured for various groups of employees. The results indicate significant levels of exploitation among women, Hispanics, African Americans, and blue-collar workers. By contrast, employees who are overpaid relative to their productivities include middle-aged workers, older workers, and managers. Additional findings suggest that the increase in inequality in recent years has been associated with heightened exploitation due to the underpayment of workers in the lowest two quintiles of the earnings distribution, while workers in the upper two quintiles have become increasingly overpaid. Rising earnings inequality in the manufacturing sector thus appears to be associated with increased exploitation when the latter is measured as the underpayment of market value to workers. A related analysis by Liu, Sakamoto, and Su also investigates patterns of economic underpayment and overpayment but does not link them explicitly to inequality in the distribution of earnings and how the level of inequality has been increasing in recent years.
The Great American Recession: Sociological Insights on Blame and Pain
Authors: Treas Judith
Published: March 2010

The recent recession is likely to rank as the most significant financial crisis in our lifetimes, but sociologists have powerful tools for understanding this devastating development. Drawing on theoretical perspectives and empirical data, this article focuses on ordinary Americans who have suffered during trying times. First, one popular set of political narratives is shown to fit the sociological model of “blaming the victim.” Second, General Social Survey data from 1991 and 2004 are used to counter charges of widespread consumer opportunism and to expose the serious systemic vulnerabilities that existed for Americans before the recession.
Perceptions of Race Relations in Contexts of Ethnic Diversity and Change
Authors: Cohen-Marks Mara A. , Faught Jim
Published: March 2010

Examining public opinion data from a 2007 survey of Los Angeles, the authors consider racial and ethnic variation in perceptions of race relations across neighborhoods in various contexts of demographic composition and change. Using several measures of ethnic diversity, the authors examine whether racial attitudes differ depending on the demographic mix at the census tract level, and if the relative importance of ethnicity and other individual characteristics varies depending on the proportion, ratio, or diversity of ethnic groups within tracts. Only among African Americans do they find a consistent impact of racial/ethnic identity on perception of race relations, although such attitudes do not vary within various measures of neighborhood diversity. The results suggest limitations to the assumed significance—either positive or negative—of neighborhood diversity on individuals of various races and ethnicities.
Outcome of Early-Onset Sepsis in a National Cohort of Very Low Birth Weight Infants
Authors: Klinger Gil , Levy Itzhak , Sirota Lea , Boyko Valentina , Lerner-Geva Liat , Reichman Brian ,   in collaboration with the Israel Neonatal Network
Published: March 2010

BACKGROUND:

Early-onset sepsis (EOS) is associated with significant morbidity and mortality among infants with a very low birth weight (VLBW); however, there is a sparse amount of complete data on large cohorts.

OBJECTIVE:

To evaluate the mortality and major morbidities among VLBW infants with EOS.

METHODS:

This was a population-based observational study. Data were prospectively collected by the Israel Neonatal Network on all VLBW infants born in Israel from 1995 through 2005. Univariate and multivariable analyses were performed to assess the independent association of EOS on morbidity and mortality of VLBW infants.

RESULTS:

The study cohort included 15 839 infants, of whom 383 (2.4%) developed EOS. EOS was associated with significantly increased odds for mortality (odds ratio [OR]: 2.57 [95% confidence interval (CI): 1.97–3.35]), severe intraventricular hemorrhage (OR: 2.24 [95% CI: 1.67–3.00]), severe retinopathy of prematurity (OR: 2.04 [95% CI: 1.32–3.16]), and bronchopulmonary dysplasia (OR: 1.74 [95% CI: 1.24–2.43]). EOS was associated with an increased risk of death and/or severe neurologic morbidity (OR: 2.92 [95% CI: 2.27–3.80]).

CONCLUSIONS:

Although only 2.4% of VLBW infants had an episode of EOS, these infants were at an approximately threefold excess risk of death or major neurologic morbidities.
The Great Crossing
Authors: Levy Beth E.
Published: March 2010

This essay explores how music underscores the twinning of nostalgia and the West at key moments, helping to refine the film’s characterization of family relationships and to deepen its message about manifest destiny.