An empirical study of vehicle emissions under cordon and distance based road user charging, Leeds, UK.

This paper presents the impact of road user charging (RUC) on vehicle emissions through application of traffic assignment and pollutant emission models. It presents results of an analysis of five RUC schemes on vehicle emissions in Leeds, UK for 2005. The schemes were: a £3 inner ring road cordon charge; a double cordon with a £2 inner ring road and a £1 outer ring road charge; and distance charges of 2, 10 and 20 pence per km levied for travel within the outer cordon. Schemes were compared to a no charge option and results presented here. Emissions are significantly reduced within the inner cordon, whilst beyond the cordon, localised increases and decreases occur. The double cordon exhibits a similar but less marked pattern. Distance charging reduces city-wide emissions by 10% under a 2 p/km charge, 42-49% under a 10 p/km charge and 52-59% under a 20 p/km charge. The higher distance charges reduce emissions within the charge zone, and are also associated with elevated emissions outside the zone, but to a lesser extent than that observed for cordon charging

Effect of model forebody shape on perforated tunnel wall interference

Effect of model forebody shape on perforated supersonic wind tunnel wall interferenc

Airflow control system for supersonic inlets

In addition to fixed and variable bleed devices provided for controlling the position of a terminal shock wave in a supersonic inlet, a plurality of free piston valves are disposed around the periphery of a cowling of a supersonic engine inlet. The free piston valves are disposed in dump passageways, each of which begin at a bleed port in the cowling that is located in the throat region of the inlet, where the diameter of the centerbody is near maximum, and terminates at an opening in the cowling adjacent a free piston valve. Each valve is controlled by reference pressure

Random Matrices and Chaos in Nuclear Physics: Nuclear Reactions

The application of random-matrix theory (RMT) to compound-nucleus (CN) reactions is reviewed. An introduction into the basic concepts of nuclear scattering theory is followed by a survey of phenomenological approaches to CN scattering. The implementation of a random-matrix approach into scattering theory leads to a statistical theory of CN reactions. Since RMT applies generically to chaotic quantum systems, that theory is, at the same time, a generic theory of quantum chaotic scattering. It uses a minimum of input parameters (average S-matrix and mean level spacing of the CN). Predictions of the theory are derived with the help of field-theoretical methods adapted from condensed-matter physics and compared with those of phenomenological approaches. Thorough tests of the theory are reviewed, as are applications in nuclear physics, with special attention given to violation of symmetries (isospin, parity) and time-reversal invariance.Comment: 50 pages, 26 figure

Trade Credit: Theories and Evidence

In addition to borrowing from financial institutions, firms may be financed by their suppliers. Although there are many theories explaining why non-financial firms lend money, there are few comprehensive empirical tests of these theories. This paper attempts to fill the gap. We focus on a sample of small firms whose access to capital markets may be limited. We find evidence that firms use trade credit relatively more when credit from financial institutions is not available. Thus while short term trade credit may be routinely used to minimize transactions costs, medium term borrowing against trade credit is a form of financing of last resort. Suppliers lend to firms no one else lends to because they may have a comparative advantage in getting information about buyers cheaply, they have a better ability to liquidate goods, and they have a greater implicit equity stake in the firm's long term survival. We find some evidence consistent with the use of trade credit as a means of price discrimination. Finally, we find that firms with better access to credit from financial institutions offer more trade credit. This suggests that firms may intermediate between institutional creditors and other firms who have limited access to financial institutions.

Does Distance Still Matter? The Information Revolution in Small Business Lending

The distance between small firms and their lenders in the United States is increasing. Not only are firms choosing more distant lenders, they are also communicating with them in more impersonal ways. After documenting these systematic changes, we demonstrate that they do not stem from small firms locating differently, from simple consolidation in the banking industry, or from biases in the sample. Instead, they seem correlated with improvements in bank productivity. We conjecture that greater, and more timely, availability of borrower credit records, as well as the greater ease of processing these may explain the increased lending at a distance. Consistent with such an explanation, distant firms no longer have to be observably the highest quality credits, suggesting that a wider cross-section of firms can now obtain funding from a particular lender. These findings, we believe, are direct evidence that there has been substantial development of the financial sector in the United States, even in areas such as small business lending that have not been directly influenced by the growth in public markets. From a policy perspective, that small firms now obtain wider access to financing suggests the consolidation of banking services may not raise as strong anti-trust concerns as in the past.

Poppet valve control of throat stability bypass to increase stable airflow range of a Mach 2.5. inlet with 60 percent internal contraction

The throat of a Mach 2.5 inlet with a coldpipe termination was fitted with a stability-bypass system. System variations included several stability bypass entrance configurations. Poppet valves controlled the bypass airflow. The inlet stable airflow range achieved with each configuration was determined for both steady state conditions and internal pulse transients. Results are compared with those obtained without a stability bypass system. Transient results were also obtained for the inlet with a choke point at the diffuser exit and for the inlet with large and small stability bypass plenum volumes. Poppet valves at the stability bypass exit provided the inlet with a stable airflow range of 20 percent or greater at all static and transient conditions

Pressure activated stability-bypass-control valves to increase the stable airflow range of a Mach 2.5 inlet with 40 percent internal contraction

The throat of a Mach 2.5 inlet with a coldpipe termination was fitted with a stability-bypass system. The inlet stable airflow range provided by various stability-bypass entrance configurations in alternate combination with several stability-bypass exit controls was determined for both steady-state conditions and internal transient pulses. Transient results were also obtained for the inlet with a choke point at the diffuser exit. Instart angles of attack were determined for the various stability-bypass entrance configurations. The response of the inlet-coldpipe system to internal and external oscillating disturbances was determined. Poppet valves at the stability-bypass exit provided an inlet stable airflow range of 28 percent or greater at all static and transient conditions

The Effect of Credit Market Competition on Lending Relationships

This paper provides a simple model showing that the extent of competition in credit markets is important in determining the value of lending relationships. Creditors are more likely to finance credit constrained firms when credit markets are concentrated because it is easier for these creditors to internalize the benefits of assisting the firms. The model has implications about the availability and the price of credit as firms age in different markets. The paper offers evidence for these implications from small business data. It concludes with conjectures on the costs and benefits of liberalizing financial markets, as well as the timing of such reforms.

Summary and recent results from the NASA advanced High Speed Propeller Research Program

Advanced high-speed propellers offer large performance improvements for aircraft that cruise in the Mach 0.7 to 0.8 speed regime. The current status of the NASA research program on high-speed propeller aerodynamics, acoustics, and aeroelastics is described. Recent wind tunnel results for five 8- to 10-blade advanced models are compared with analytical predictions. Test results show that blade sweep was important in achieving net efficiencies near 80 percent at Mach 0.8 and reducing near-field cruise noise by dB. Lifting line and lifting surface aerodynamic analysis codes are under development and some initial lifting line results are compared with propeller force and probe data. Some initial laser velocimeter measurements of the flow field velocities of an 8-bladed 45 deg swept propeller are shown. Experimental aeroelastic results indicate that cascade effects and blade sweep strongly affect propeller aeroelastic characteristics. Comparisons of propeller near-field noise data with linear acoustic theory indicate that the theory adequate predicts near-field noise for subsonic tip speeds but overpredicts the noise for supersonic tip speeds. Potential large gains in propeller efficiency of 7 to 11 percent at Mach 0.8 may be possible with advanced counter-rotation propellers