Integration of dynamic, aerodynamic, and structural optimization of helicopter rotor blades

Summarized here is the first six years of research into the integration of structural, dynamic, and aerodynamic considerations in the design-optimization process for rotor blades. Specifically discussed here is the application of design optimization techniques for helicopter rotor blades. The reduction of vibratory shears and moments at the blade root, aeroelastic stability of the rotor, optimum airframe design, and an efficient procedure for calculating system sensitivities with respect to the design variables used are discussed

The importance of steady and dynamic inflow on the stability of rotor-body systems

The induced flow field of a rotor responds in a dynamic fashion to oscillations in rotor lift. This was long known to affect the stability and control derivatives of the rotor. More recently, however, it was also shown that this dynamic inflow also affects rotor and rotor-body aeroelastic stability. Thus, both the steady and unsteady inflow have pronounced effects on air resonance. Recent theoretical developments were made in the modeling of dynamic inflow, and these were verified experimentally. Thus, there is now a simple, verified dynamic inflow model for use in dynamic analyses

Underrepresented groups

The problem with the shortage of under represented groups in science and engineering is absolutely crucial, especially considering that U.S. will experience a shortage of 560,000 science and engineering personnel by the year 2010. Most studies by the National Science Foundation also concluded that projected shortages cannot be alleviated without significant increases in the involvement of Blacks, Hispanics, Native Americans, handicapped persons, and women

Cold Storage: Why Doha Failed

The WTO negotiations on agriculture were placed in cold storage in July 2008 although 18 of the 20 major agenda items had been agreed. The sticking point was the safeguard measures to control import surges, while the final issue, relating to domestic support for US cotton, was not addressed. Quantitative analysis of the numbers on the table indicate that improvements in market access in the European Union and Japan drive changes in exports and welfare, whereas special safeguard measures, export subsidies, domestic support and special products appear to be of lesser importance. Many developing countries, including most LDCs, would enjoy export gains but experience welfare losses because of higher import prices.

MAKING SENSE OF AGRICULTURAL TRADE POLICY REFORM

Proposals for agricultural trade reform put forward by the main protagonists remain far apart, with little sign of convergence. In an attempt to progress the negotiations towards a successful outcome, the chairman of the WTO Committee on Agriculture has proposed a compromise. The alternative proposals by the United States, the European Union and the WTO are analysed with the Agricultural Trade Policy Simulation Model, a static, multi-commodity, multi-region, partial equilibrium trade model. The estimated annual global welfare gains are $26 billion,$12 billion and $17 billion respectively. Least developed countries, as a group, gain from the US proposal but are made worse off under the WTO and EU proposals. Furthermore, in the best case many individual countries experience welfare losses. However, all countries enjoy increased export revenues and tariff revenues hold up quite well under the two less stringent proposals.agriculture, trade, modelling, negotiations, International Relations/Trade, F13, Q17,

Impact of Tariff Reductions in NAMA and Agriculture WTO Negotiations on GCC Common External Tariffs

The Gulf countries (Bahrain, Kuwait, Oman, Qatar, Saudi Arabia and United Arab Emirates) have a common external tariff that is unusually low with the exception of selected products such as alcohol and tobacco. As exporters of oil and gas and importers of agricultural products, the GCC is interested in the impacts of tariffs reductions in these products following the eventual completion of the Doha round. Of particular interest are four sectors (raw materials, gas-related goods, fisheries and chemicals), in which it is hoped tariffs will be eliminated. This will improve market access for the GCC countries, but it may also increase the competition depending on the initial bilateral tariffs. In agriculture, rising import prices driven by policy changes occurring elsewhere will increase import costs in the GCC countries. Potential gains and losses are identified using a bilateral trade model.International Relations/Trade,

Do Sensitive Products Undermine Ambition?

The long-running WTO negotiations remain unresolved. Agriculture is the main stumbling block. Members have agreed to linear tariff reductions within bands, but proposed exemptions for sensitive products, while providing for much needed flexibility, threaten to undermine the ambition. A detailed partial equilibrium global agricultural trade model is used to analyse the likely impact of exemptions from the formula tariff reductions. Applying one third of the formula cuts to the five per cent of lines with the highest tariffs increases the final developed country average agricultural tariff from 16 to 24 per cent but the negative impacts on trade and welfare are less dramatic.agriculture, trade, tariffs, WTO, International Relations/Trade, F13, Q17,

Characterization of the novel ene reductase Ppo-Er1 from paenibacillus polymyxa

Ene reductases enable the asymmetric hydrogenation of activated alkenes allowing the manufacture of valuable chiral products. The enzymes complement existing metal- and organocatalytic approaches for the stereoselective reduction of activated C=C double bonds, and efforts to expand the biocatalytic toolbox with additional ene reductases are of high academic and industrial interest. Here, we present the characterization of a novel ene reductase from Paenibacillus polymyxa, named Ppo-Er1, belonging to the recently identified subgroup III of the old yellow enzyme family. The determination of substrate scope, solvent stability, temperature, and pH range of Ppo-Er1 is one of the first examples of a detailed biophysical characterization of a subgroup III enzyme. Notably, Ppo-Er1 possesses a wide temperature optimum (Topt: 20–45 °C) and retains high conversion rates of at least 70% even at 10 °C reaction temperature making it an interesting biocatalyst for the conversion of temperature-labile substrates. When assaying a set of different organic solvents to determine Ppo-Er1′s solvent tolerance, the ene reductase exhibited good performance in up to 40% cyclohexane as well as 20 vol% DMSO and ethanol. In summary, Ppo-Er1 exhibited activity for thirteen out of the nineteen investigated compounds, for ten of which Michaelis–Menten kinetics could be determined. The enzyme exhibited the highest specificity constant for maleimide with a kcat/KM value of 287 mM−1 s−1. In addition, Ppo-Er1 proved to be highly enantioselective for selected substrates with measured enantiomeric excess values of 92% or higher for 2-methyl-2-cyclohexenone, citral, and carvone

Optimization of rotor blades for combined structural, performance, and aeroelastic characteristics

The strategies whereby helicopter rotor blades can be optimized for combined structural, inertial, dynamic, aeroelastic, and aerodynamic performance characteristics are outlined. There are three key ingredients in the successful execution of such an interdisciplinary optimization. The first is the definition of a satisfactory performance index that combines all aspects of the problem without too many constraints. The second element is the judicious choice of computationally efficient analysis tools for the various quantitative components in both the cost functional and constraints. The third element is an effective strategy for combining the various disciplines either in parallel or sequential optimizations