Friction characteristics of three 30 by 11.5-14.5, type 8, aircraft tires with various tread groove patterns and rubber compounds

A test program was conducted to evaluate friction performance and wear characteristics on wet runways of three 30 x 11.5-14.5, type, aircraft tires having two different tread patterns and natural rubber contents. All test tires had the standard three circumferential groove tread, but two had molded transverse grooves which extended from shoulder to shoulder. The tread rubber content of the two tires with transverse grooves differed in that one had a 100 percent natural rubber tread and the other had a rubber tread composition that was 30 percent synthetic and 70 percent natural. The third test tire had the conventional 100 percent natural rubber tread. Results indicate that the differences in tire tread design and rubber composition do not significantly affect braking and cornering friction capability on wet or dry surfaces. Braking performance of the tires decreases with increased speed, with increased yaw angle and, at higher speeds, with increased wetness of the surface

Wear, friction, and temperature characteristics of an aircraft tire undergoing braking and cornering

An investigation to evaluate the wear, friction, and temperature characteristics of aircraft tire treads fabricated from different elastomers is presented. The braking and cornering tests performed on aircraft tires retreaded with currently employed and experimental elastomers are described. The tread wear rate is discussed in relation to the slip ratio during braking and yaw angle during cornering. The extent of wear in either operational mode is examined in relation to the runway surface

The effect of chine tires on nose gear water-spray characteristics of a twin engine airplane

An experimental investigation was performed to evaluate the effectiveness of nose gear chine tires in eliminating or minimizing the engine spray ingestion problem encountered on several occasions by the Merlin 4, a twin-engine propjet airplane. A study of the photographic and television coverage indicated that under similar test conditions the spray from the chine tires presented less of a potential engine spray ingestion problem than the conventional tires. Neither tire configuration appeared to pose any ingestion problem at aircraft speeds in excess of the hydroplaning speed for each tire, however, significant differences were noted in the spray patterns of the two sets of tires at sub-hydroplaning speeds. At sub-hydroplaning speeds, the conventional tires produced substantial spray above the wing which approached the general area of the engine air inlet at lower test speeds. The chine tires produced two distinct spray plumes at sub-hydroplaning speeds: one low-level plume which presented no apparent threat of ingestion, and one which at most test speeds was observed to be below the wing leading edge and thus displaced from the intakes on the engine nacelle

THE IMPACT OF CURRENT COTTON PRICE AND PRODUCTION COSTS ON SKIP-ROW COTTON

According to conventional wisdom, low prices favor skip-row planting patterns while high prices favor solid planted cotton. Production costs have been trending upward for many years. Current high production costs have redefined the point at which a low price becomes a high price relative to skip-row versus solid planting pattern decisions. Growers considering a shift from solid to skip-row cotton must be able to produce high yields, more than 90% of the solid yield on a land acre basis.cotton, no-till yields, returns, Production Economics,

Effect of high-intensity ultrasound on superconducting properties of polycrystalline YBCO

High intensity ultrasonic irradiation (sonication) of alkane slurries of polycrystalline \ybco leads to a significant modification of the grain morphology and, if performed with enforced oxygen flow, results in the increase of the superconducting transition temperature. Sonication with added Fe(CO)$_5$ produces magnetic \fe2o3 nanoparticles deposited on the surface of \ybco (YBCO) granules. Upon sintering these nanoparticles should act as efficient pinning centers utilizing both condensation and magnetic contributions to the free energy. The developed method could become a major technique to produce practically useful high-pinning nanocomposite materials based on \ybco superconductor.Comment: to be presented at LT-25 conferenc

Developments in new aircraft tire tread materials

Comparative laboratory and field tests were conducted on experimental and state-of-the-art aircraft tire tread materials in a program aimed at seeking new elastomeric materials which would provide improved aircraft tire tread wear, traction, and blowout resistance in the interests of operational safety and economy. The experimental stock was formulated of natural rubber and amorphous vinyl polybutadiene to provide high thermal-oxidative resistance, a characteristic pursued on the premise that thermal oxidation is involved both in the normal abrasion or wear of tire treads and probably in the chain of events leading to blowout failures. Results from the tests demonstrate that the experimental stock provided better heat buildup (hysteresis) and fatigue properties, at least equal wet and dry traction, and greater wear resistance than the state-of-the-art stock

Evidence for a glycolate transporter in the envelope of pea chloroplasts

AbstractGlycolate excretion by chloroplasts is essential to the process of photorespiration. Previous transport studies on intact chloroplasts have failed to find evidence for carrier-mediated transport of glycolate. The rate of glycolate uptake, when measured by a rapid silicone oil centrifugation method, saturates at high glycolate concentrations. This rapid glycolate uptake is inhibited by pretreatment of the chloroplasts with N-ethylmaleimide, an inhibition prevented by glycolate. Glyoxylate and glycerate inhibit glycolate uptake when present in the assay medium. These results suggest the existence of a glycolate transporter in the chloroplast envelope

Quarkonium states in a complex-valued potential

We calculate quarkonium binding energies using a realistic complex-valued potential for both an isotropic and anisotropic quark-gluon plasma. We determine the disassociation temperatures of the ground and first excited states considering both the real and imaginary parts of the binding energy. We show that the effect of momentum-space anisotropy is smaller on the imaginary part of the binding energy than on the real part of the binding energy. In the case that one assumes an isotropic plasma, we find disassociation temperatures for the J/psi, Upsilon and chi_b of 1.6 T_c, 2.8 T_c, and 1.5 T_c, respectively. We find that a finite oblate momentum-space anisotropy increases the disassociation temperature for all states considered and results in a splitting of the p-wave states associated with the chi_b first excited state of bottomonium.Comment: 23 pages, 9 figures; v4: subtraction of V_infinity corrected to only subtract Re[V_infinity

A Unit Commitment and Economic Dispatch Model of the GB Electricity Market – Formulation and Application to Hydro Pumped Storage

We present a well calibrated unit commitment and economic dispatch model of the GB electricity market and applied it to the economic analysis of the four existing hydro pumped storage (PS) stations in GB. We found that with more wind on the system PS arbitrage revenue increases: with every percentage point (p.p) increase in wind capacity the total PS arbitrage profit increases by 0.21 p.p.. However, under a range of wind capacity, the PS’ modelled revenue from price arbitrage is not enough to cover their ongoing fixed costs. Analysing the 2015-18 GB balancing and ancillary services data suggests that PS stations were not active in managing transmission constraints and in fact about 60% of constraint payments went to gas-fired units. However, the PS stations are active in provision of ancillary services such as fast reserve, response and other reserve services with a combined market share of at least 30% in 2018. Stacking up the modelled revenue from price arbitrage with the 2018 balancing and ancillary services revenues against the ongoing fixed costs suggests that the four existing PS stations are profitable. Most of the revenue comes from balancing and ancillary services markets – about 75% – whereas only 25% comes from price arbitrage. However, the revenues will not be enough to cover capex and opex of a new 600 MW PS station. The gap in financing will have to come from balancing and ancillary services market opportunities and less so from purely price arbitrage. Finally, we found that the marginal contribution of most of the existing PS stations to gas and coal plant profitability is negative, while from the system point of view, PS stations do contribute to minimizing the total operating cost