Landing impact studies of a 0.3-scale model air cushion landing system for a Navy fighter airplane

An experimental study was conducted in order to determine the landing-impact behavior of a 0.3-scale, dynamically (but not physically) similar model of a high-density Navy fighter equipped with an air cushion landing system. The model was tested over a range of landing contact attitudes at high forward speeds and sink rates on a specialized test fixture at the Langley aircraft landing loads and traction facility. The investigation indicated that vertical acceleration at landing impact was highly dependent on the pitch angle at ground contact, the higher acceleration of approximately 5g occurring near zero body-pitch attitude. A limited number of low-speed taxi tests were made in order to determine model stability characteristics. The model was found to have good pitch-damping characteristics but stability in roll was marginal

Studies of some unconventional systems for solving various landing problems

Solutions to various landing problems were obtained through unconventional systems. The first, of these is the air cushion landing system, where efforts were concentrated on development of adequate braking and steering systems and an improved understanding of scaling laws and behavior. The second was concentrated on use of a wire brush skid as a drag producing device, which was shown to have good friction coefficients and reasonable wear rates at ground bearing pressures up to 689 kPa and forward speeds up to 80 km/hr. The third showed great promise in an active control landing gear where significant load reductions were possible during landing impact and subsequent rollout

Experimental and analytical dynamic flow characteristics of an axial-flow fan from an air cushion landing system model

An investigation was conducted to compare the steady-state and dynamic flow characteristics of an axial-flow fan which had been used previously as the air supply fan for some model air cushion landing system studies. Steady-state flow characteristics were determined in the standard manner by using differential orifice pressures for the flow regime from free flow to zero flow. In this same regime, a correlative technique was established so that fan inlet and outlet pressures could be used to measure dynamic flow as created by a rotating damper. Dynamic tests at damper frequencies up to 5 Hz showed very different flow characteristics when compared with steady-state flow, particularly with respect to peak pressures and the pressure-flow relationship at fan stall and unstall. A generalized, rational mathematical fan model was developed based on physical fan parameters and a steady-state flow characteristic. The model showed good correlation with experimental tests at damper frequencies up to 5 Hz

Antitrust Challenge to Non-Profit Certification Organizations: Conflicts of Interest and a Practical Rule of Reason Approach to Certification Programs As Industry-Wide Builders of Competition and Efficiency

The paramount antitrust challenge for nonprofit product certification programs is to demonstrate aggressively that such programs strengthen the competitive market system on an industry-wide basis. This affirmative challenge is, however, limited by another urgent antitrust challenge still closer to the courtroom door. This challenge, requiring advance organizational and litigation planning, is to avoid or defeat a possible plaintiff\u27s claim of antitrust abuses by a certification organization whose decision-making participants may be caught in alleged conflicts of interest. These two challenges must be met for certification programs to survive and progress. The only way successfully to meet these antitrust challenges is to make product performance certification programs synonymous with industry-wide competition and productivity and with systems of safeguards against conflicts of interest. Further, this must be proved to the judge and jury. This Commentary will discuss two critical questions that flow from an analytical approach to these two challenges: First, whether a coherent basis exists for viewing nonprofit certification programs as structural elements in the marketplace hierarchy that advance urgent antitrust goals, including increased competition and productivity; and second, whether a distinct duty to safeguard certification organizations against conflicts of interest would, if met, demonstrate that a certification organization under antitrust scrutiny in court should be found to be without conspiratorial intent

Debt Maturity Choices, Multi-stage Investments and Financing Constraints

We develop a dynamic investment options framework with optimal capital structure and analyze the effect of debt maturity. We find that in the absence of financing constraints short-term debt maximizes firm value. In contrast with most literature results, in the absence of constraints, higher volatility may increase initial debt for firms with low initial revenues, issuing long term debt that expires after the investment option maturity. This effect, which is due to the option value of receiving the value of assets and remaining tax savings, does not hold for short term debt and firms with high profitability, where an increase in volatility reduces the firm value. The importance of short-term debt is reduced in the presence of non-negative equity net worth or debt financing constraints and firms behave more conservatively in the use of initial debt. With non-negative equity net worth, higher volatility has adverse effects on the firm value, while with debt financing constraints higher volatility may enhance firm value for firms with relatively low revenue that have out-of-the-money investment options

Exposure of a population of invasive wild pigs to simulated toxic bait containing biomarker: implications for population reduction

BACKGROUND: An international effort to develop an acute and humane toxic bait for invasive wild pigs (Sus scrofa) is underway to curtail their expansion. We evaluated the ability to expose a population of wild pigs to a simulated toxic bait (i.e., placebo bait containing a biomarker, rhodamine B, in lieu of the toxic ingredient) to gain insight on potential population reduction. We used 28 GPS-collars and sampled 428 wild pigs to examine their vibrissae for evidence of consuming the bait. RESULTS: We estimated that 91% of wild pigs within 0.75 km of bait sites (total area = 16.8 km2) consumed the simulated toxic bait, exposing them to possible lethal effects. Bait sites spaced 0.75–1.5 km apart achieved optimal delivery of the bait, but wild pigs ranging ≥ 3 km away were susceptible. Use of wild pig-specific bait stations resulted in no non-target species directly accessing the bait. CONCLUSION: Results demonstrate the potential for exposing a large proportion of wild pigs to a toxic bait in similar ecosystems. Toxic bait may be an effective tool for reducing wild pig populations especially if used as part of an integrated pest management strategy. Investigation of risks associated with a field-deployment of the toxic bait is needed

The San Antonio River Mammoth Site: Archaeological Testing Investigations for the Interstate 37 Bridge at the San Antonio River Improvement Project, Bexar County, Texas

On behalf of the Texas Department of Transportation (TxDOT), SWCA Environmental Consultants (SWCA) conducted test excavations on the San Antonio River Mammoth site (41BX1239) and 41BX1240 and surveys in the area of potential effects (APE) of the Interstate Highway (IH) 37 bridge project at the San Antonio River in southeastern Bexar County, Texas. Work was initiated to address the requirements of Section 106 of the National Historic Preservation Act (1966) as Amended and the Antiquities Code of Texas. The purpose of the investigations was to identify, delineate, and evaluate the significance of all archaeological and historic properties potentially affected by the undertaking and, if warranted, recommend the scope of additional work. Of particular concern, site 41BX1239 contains the remains of at least two mammoths with possible evidence of cultural association based on the initial investigations by Texas A&M in 1997. However, subsequent faunal analysis, conducted by Olga Potapova and Larry D. Agenbroad of the Mammoth Site in Hot Springs, North Dakota, found inconclusive evidence for definite or valid cultural modification to the specimens studied. The testing investigations on the San Antonio River Mammoth site included the re-exposure of the original Texas A&M 1997 site trench; limited hand-excavated units to further assess the prior interpretations of the deposits and recover a sample of bone; and a detailed geomorphological assessment. The work identified a bone bed consisting of the remains of at least two mammoths. Flotation of recovered sediments from these hand excavations identified flakes of siliceous material that are consistent with micro-debitage produced by the use and retouch of stone tools. Although at the highest thresholds of certainty, the cumulative evidence is likely yet insufficient to conclusively prove human interaction with the mammoth remains, the additional data gathered herein lend some credence to the prior interpretation of the site as archaeological rather than strictly paleontological. Concurring with the previous determination, the site is considered eligible for inclusion to the National Register of Historic Places (NRHP) and for listing as a State Archeological Landmark (SAL). However, the investigations determined the site deposits are located outside the APE of the current undertaking, and therefore the project will not affect deposits associated with the San Antonio River Mammoth site. The investigations of 41BX1240 identified only a very sparse scatter of primarily surficial materials in a heavily disturbed context with no associated features or diagnostic materials. Accordingly, the site is not recommended as eligible for listing on the NRHP or for designation as a SAL. The survey identified no new archaeological sites. Based on the avoidance of 41BX1239, it is SWCA’s recommendation that no archaeological properties will be affected by the IH 37 bridge rehabilitation

Delays in IP routers, a Markov model

Delays in routers are an important component of end-to-end delay and therefore have a significant impact on quality of service. While the other component, the propagation time, is easy to predict as the distance divided by the speed of light inside the link, the queueing delays of packets inside routers depend on the current, usually dynamically changing congestion and on the stochastic features of the flows. We use a Markov model taking into account the distribution of the size of packets and self-similarity of incoming flows to investigate their impact on the queueing delays and their dynamics

European Sea Bass (Dicentrarchus labrax) immune status and disease resistance are impaired by arginine dietary supplementation

Infectious diseases and fish feeds management are probably the major expenses in the aquaculture business. Hence, it is a priority to define sustainable strategies which simultaneously avoid therapeutic procedures and reinforce fish immunity. Currently, one preferred approach is the use of immunostimulants which can be supplemented to the fish diets. Arginine is a versatile amino acid with important mechanisms closely related to the immune response. Aiming at finding out how arginine affects the innate immune status or improve disease resistance of European seabass (Dicentrarchus labrax) against vibriosis, fish were fed two arginine-supplemented diets (1% and 2% arginine supplementation). A third diet meeting arginine requirement level for seabass served as control diet. Following 15 or 29 days of feeding, fish were sampled for blood, spleen and gut to assess cell-mediated immune parameters and immune-related gene expression. At the same time, fish from each dietary group were challenged against Vibrio anguillarum and survival was monitored. Cell-mediated immune parameters such as the extracellular superoxide and nitric oxide decreased in fish fed arginine-supplemented diets. Interleukins and immune-cell marker transcripts were down-regulated by the highest supplementation level. Disease resistance data were in accordance with a generally depressed immune status, with increased susceptibility to vibriosis in fish fed arginine supplemented diets. Altogether, these results suggest a general inhibitory effect of arginine on the immune defences and disease resistance of European seabass. Still, further research will certainly clarify arginine immunomodulation pathways thereby allowing the validation of its potential as a prophylactic strategy.European Union's Seventh Framework Programme AQUAEXCEL (Aquaculture Infrastructures for Excellence in European Fish Research) [262336]; AQUAIMPROV [NORTE-07-0124-FEDER-000038]; North Portugal Regional Operational Programme (ON. 2 - O Novo Norte) , under the National Strategic Reference Framework, through the European Regional Development Fund; North Portugal Regional Operational Programme (ON. 2 - O Novo Norte), under the National Strategic Reference Framework through the COMPETE - Operational Competitiveness Programme; Fundacao para a Ciencia e Tecnologia; Fundacao para a Ciencia e Tecnologia [SFRH/BD/89457/2012, SFRH/BPD/77210/2011]; Generalitat Valenciana through the project REVIDPAQUA [ISIC/2012/003]; [PEst-C/MAR/LA0015/2013]; [UID/Multi/04423/2013]info:eu-repo/semantics/publishedVersio