An Analytically Defined Fire‐Suppressing Foam Formulation for Evaluation of Fluorosurfactant Replacement

A 4‐component, analytically defined, reference fluorosurfactant formulation (Ref‐aqueous film forming foam [AFFF]) composed of 0.3% fluorocarbon‐surfactant concentrate (Capstone 1157), 0.2% hydrocarbon‐surfactant concentrate (Glucopon 215 UP), and 0.5% diethylene glycol mono butyl ether by volume in distilled water was found to have rapid fire extinction comparable to a commercial AFFF in tests conducted on a bench scale and a large scale (28 ft², part of US Military Specification, MIL‐F‐24385F). The Ref‐AFFF was analytically characterized to provide the identity and quantity of the chemical structures of the surfactant molecules that were lacking for commercial AFFF formulations. To arrive at an acceptable Ref‐AFFF formulation, 3 candidate formulations containing different hydrocarbon surfactants in varying amounts were evaluated and ranked relative to a commercial AFFF using a bench‐scale fire‐extinction apparatus; varying the hydrocarbon surfactant was found to affect the fire‐extinction time. The ranking was confirmed by the large‐scale tests suggesting that the bench‐scale apparatus is a reasonable research tool for identifying surfactants likely to succeed in the large‐scale test. In the future, replacing the fluorocarbon surfactant with an alternative surfactant in the Ref‐AFFF enables a direct comparison of fire extinction and environmental impact to identify an acceptable fluorine‐free formulation.     

Development of an intracavity-summed multiple-wavelength Nd:YAG laser for a rugged, solid-state sodium lidar system

A single-cavity solid-state laser that is resonant with sodium D(2) absorption is reported. Simultaneous 1.06- and 1.32-μm emission from a Q-switched Nd:YAG laser is summed with an intracavity type II KTP crystal. A single-intracavity étalon is sufficient to provide a time-averaged linewidth of 1.7 GHz at 589 nm.     

Heat sealing of semicrystalline polymer films. III. Effect of corona discharge treatment of LLDPE

The effects of corona-discharge treatment (CDT) of commercial polyethylene (PE) Linear low-density PE (LLDPE) were studied with special emphasis on the heat-seal behavior of treated films. A range of treat levels, representative of those used in industry, was obtained by varying the applied power to a commercial, on-line treater. Film surfaces were characterized by XPS and wetting-tension measurements. The primary effect of CDT on the heat-sealing behavior of LLDPE films is a transition in the failure mode of heat seals from a normal tearing or inseparable bond to a peelable seal. In addition, CDT increases the seal initiation temperature 5–17°C and decreases the plateau seal strength 5–20% as the treat level, or wetting tension, increases from 31 to 56 dynes/cm. These effects are attributed to cross-linking during corona treatment, which restricts polymer mobility near the surface and limits the extent of interdiffusion and entaglements across the seal interface. Results of heat-sealing studies with electron-beam-irradiated PE, chemically oxidized PE, and CDT polypropylene (PP) provide indirect evidence for the proposed surface cross-linking mechanism. The effect of commercial levels of slip additives on the heat-seal behavior was also investigated. © 1994 John Wiley & Sons, Inc.     

Copper trace fatigue models for mechanical cycling, vibration and shock/drop of high-density PWAs

When assessing the mechanical durability of electronic assemblies, the focus is generally on the solder interconnects. However, in many package styles, such as ball grid arrays (BGAs), land grid arrays (LGAs), micro lead frame (MLFs) and quad flat no-lead (QFNs), the Cu trace emanating from the solder pad may be the weakest failure site, especially if the solder joint is copper-defined rather than mask defined. This is particularly true in situations with cyclic mechanical loading, such as cyclic quasi-static bending, vibration and repetitive drop/shock.This study focuses on quasi-static mechanical cycling durability of LGA assemblies with copper-defined pads. Specimens were cycled to failure under zero-to-max, three-point bending and failure statistics were collected. The failure mode was confirmed to be fatigue cracks in copper traces emanating from the corner solder pads, just at the edge of the solder mask where the solder joint ends. The cracks were identified by lateral polishing after desoldering the component.The cyclic bending of this assembly was modeled with 3D, elastic-plastic, large deformation finite element analysis. Due to the complexity of the geometry, a global-local approach was used to identify the strain history and the mean stress at the failure site.A generalized strain-based fatigue model was used to characterize these failures, and preliminary model constants were iteratively estimated by ensuring that they were simultaneously compatible with both the durability test data and the copper stress-strain curves used in the FEA (finite element analysis).These preliminary model constants were then refined by separately modeling the initiation and progression history of fatigue damage in the cyclic bend tests. Damage progression was modeled in this study by using a technique of ‘successive initiation’ developed earlier by this research group. In this method, finite element simulations are used to progressively ‘kill’ elements that have accumulated sufficient fatigue damage to lose their load-carrying capacity. When the killed elements span the entire cross-section of the copper trace, the trace is assumed to electrically fail.This calibrated model is then used to demonstrate its ability to predict copper trace failures in other situations such as quasi-static four-point bending of LGA assemblies and vibration of BGA assemblies. More important, we demonstrate its use for re-designing of BGA assemblies to prevent copper trace failures under drop/shock loading.The important impact of this study includes insight into copper trace failures in Printed Wiring Assemblies (PWAs) under mechanical cycling, a quantitative model to predict its occurrence, and validated guidelines to prevent it by design.     

Performance evaluation of multilayer thin film coatings under mixed rolling–sliding dry contact conditions

This paper focuses on the application of advanced finite element analysis to simulate the response of complex multilayer coatings when subjected to mixed rolling–sliding dry contact conditions, typical of those experienced by heavily loaded gear tooth flanks. In this study, a versatile model is developed to investigate the response of a variety of complex coatings. Through the investigation of three advanced surface coatings the developed model is shown to offer detailed subsurface stress and strain information, quantifying the benefits provided by the application of each coating.A number of rolling contact fatigue tests were also conducted to complement the computational simulations. An adapted twin disc testing machine was used to investigate the progressive wear rates of the three advanced surface coatings when subjected to mixed rolling–sliding contact at high load and in dry conditions. The result is a clear indication that advanced surface coating techniques can provide significant improvements in wear resistance and surface durability. From the rolling contact fatigue experiments conducted in this study, a multilayer tungsten carbide/carbon coating was shown to provide the most significant increase in surface durability with a 16-fold reduction in measured weight loss compared to the uncoated substrate over the 145,000 cycle test duration investigated.     

Wide-field Fizeau imaging telescope: experimental results

A nine-aperture, wide-field Fizeau imaging telescope has been built at the Lockheed-Martin Advanced Technology Center. The telescope consists of nine, 125 mm diameter collector telescopes coherently phased and combined to form a diffraction-limited image with a resolution that is consistent with the 610 mm diameter of the telescope. The phased field of view of the array is 1 murad. The measured rms wavefront error is 0.08 waves rms at 635 nm. The telescope is actively controlled to correct for tilt and phasing errors. The control sensing technique is the method known as phase diversity, which extracts wavefront information from a pair of focused and defocused images. The optical design of the telescope and typical performance results are described.     

Mobile Web Services

Web Services provide a technology for expressing the interactions between customer and business partners, as part of their business processes. Mobile Web Services apply Web Services technology to the mobile environment, enabling exciting new services to be offered to consumers on their mobile telephones, wireless-LAN-enabled PDAs and laptop computers. This paper provides an overview of mobile Web Services. It proposes an architecture for the deployment of mobile Web Services, highlighting the components required for Web Services to provide a personalised mobile service. Current real world Web Services and the future for mobile Web Services are also discussed.     

Pharmacokinetics of the protease inhibitor KNI-272 in plasma and cerebrospinal fluid in nonhuman primates after intravenous dosing and in human immunodeficiency virus-infected children after intravenous and oral dosing

The aim of this study was to evaluate the feasibility of routine falloposcopy in infertile patients undergoing basic infertility investigations, and to determine its usefulness in comparison with other tubal investigation methods. Seventy-five infertile women were selected based on the following criteria: 2 years of infertility, age between 18 and 40 years, normal ovulation, and partner with normal spermatozoa. Based on the results of the classical means of tubal evaluation (hysterosalpingography and laparoscopy), these patients were classified in one of two groups: tubal or unexplained infertility. All patients underwent a falloposcopy under general anaesthesia. The procedures were performed by the same surgeon with the linear everting catheter. Based on the falloposcopic findings, these patients were then reclassified in one of two other groups: falloposcopic tubal or falloposcopic unexplained infertility. The mean outcome measures were catheterization rate, duration of the procedure, pregnancy rates, complication rate and predictive value of Falloposcopy. The tubal catheterization rate was 94.5%. The mean duration of falloposcopy was 19 min per tube. Based on a standard scoring system, the spontaneous pregnancy rates were 27.6% for a score <20; 11.5% for a score between 21 and 30; and 0% if the score was >30. Complication rate was 5.1% of pinpoint perforations of the tube. With Cox's statistical model, none of the parameters analysed was statistically predictive of intrauterine pregnancy. We conclude that the greater accuracy of diagnosis by falloposcopy may indicate that it should be incorporated into the initial screening of infertile patients.