Dimensional Duality

We show that string theory on a compact negatively curved manifold, preserving a U(1)^{b_1} winding symmetry, grows at least b_1 new effective dimensions as the space shrinks. The winding currents yield a "D-dual" description of a Riemann surface of genus h in terms of its 2h dimensional Jacobian torus, perturbed by a closed string tachyon arising as a potential energy term in the worldsheet sigma model. D-branes on such negatively curved manifolds also reveal this structure, with a classical moduli space consisting of a b_1-torus. In particular, we present an AdS/CFT system which offers a non-perturbative formulation of such supercritical backgrounds. Finally, we discuss generalizations of this new string duality.Comment: 25 pages, harvmac. v2: fixed typo. v3: fixed typos and added ref

Importance of understanding variable and transient energy demand in large multi-product industrial plants for process integration

There have been some news releases claiming that Professor Henle in Germany has found the chemical identity of UMF, and that in future chemical analysis will be used instead of assays of antibacterial activity to indicate the level of UMF in manuka honey. Both of these claims are misleading. Because the level of active substance in manuka honey is an unreliable indication of the level of antibacterial activity and can be very misleading, it is hard to see any commercial advantage for it to be used to indicate antibacterial activity other than if someone wanted to fool the consumer into thinking that the higher numbers are giving them a level of antibacterial activity that is far higher than they are really getting

A derivative method for minimising total cost in heat exchanger networks through optimal area allocation

This paper presents a novel Cost Derivative Method (CDM) for finding the optimal area allocation for a defined Heat Exchanger Network (HEN) structure and stream data, without any stream splits to achieve minimum total cost. Using the Pinch Design Method (PDM) to determine the HEN structure, the approach attempts to add, remove and shift area to exchangers where economic benefits are returned. From the derivation of the method, it is found that the slope of the ε-NTU relationship for the specific heat exchanger type, in combination with the difference in exchanger inlet temperatures and the overall heat transfer coefficient, are critical to calculating the extra overall duty each incremental area element returns. The approach is able to account for differences in film coefficients, heat exchanger types, flow arrangements, exchanger cost functions, and utility pricing. Incorporated into the method is the newly defined “utility cost savings flow-on” factor, θ, which evaluates downstream effects on utility use and cost that are caused by changing the area of one exchanger. To illustrate the method, the CDM is applied to the distillation example of Gundersen (2000). After applying the new CDM, the total annual cost was reduced by 7.1 % mainly due to 24 % less HEN area for similar heat recovery. Area reduction resulted from one exchanger having a minimum approach temperature (ΔTmin) of 7.7 °C while the other recovery exchangers had larger ΔTmin values. The optimum ΔTmin for the PDM was 12.5 °C. The CDM solution was found to give a comparable minimum total area and cost to two recently published programming HEN synthesis solutions for the same problem without requiring the increased network complexity through multiple stream splits

Game Theory Analysis of Aircraft Manufacturer Innovation Strategies in the Face of Increasing Airline Fuel Costs

The air transportation system is a vital infrastructure that enables economic growth and provides significant social benefits. Future increases and volatility in crude oil prices, as well as environmental charges, are likely to increase the effective cost of fuel. We investigate the impacts of effective fuel cost increase on the US air transportation system historically and perform a game theory analysis of the impact of manufacturer competition on the introduction of new, more fuel efficient aircraft. The cost of jet fuel increased 244% between July 2004 and July 2008, providing a natural experiment to evaluate how fuel price increase affected continental US networks and fleets. It was found that non-hub airports serving small communities lost 12% of connections, compared to a system-wide average loss of 2.8%. Increased effective fuel costs will provide incentives for airlines to improve fleet fuel efficiency, reducing the environmental impacts of aviation, but may cause an uneven distribution of social and economic impacts if small communities suffer greater loss of mobility. Government action may be required to determine acceptable levels of access as the system transitions to higher fuel costs. Technology innovation may act as a long-term hedge against increasing effective fuel costs, enabling mobility to be maintained. The single aisle commercial aircraft market segment is the largest, but has the longest running product lines. We hypothesize that competition has important effects on manufacturers’ decisions to innovate that must be considered when designing policies to reduce fleet emissions. An aircraft program valuation model is developed to estimate expected payoffs to manufacturers under competitive scenarios. A game theory analysis demonstrates how the incentives to innovate may be altered by subsidies, technology forcing regulations, increased effective fuel costs, the threat of new entrants, and long-term competitive strategies. Increased competition may result in incumbent manufacturers producing re-engined aircraft while increased effective fuel costs may result in new aircraft programs. Incumbents’ optimal strategies may be to delay the entry of new single aisle aircraft until 2020-24, unless technology forcing regulations are implemented.This work was supported by the MIT/Masdar Institute of Science and Technology under grant number Mubadala Development Co. Agreement 12/1/06. The authors wish to thank PARTNER for access to the Piano-X software package and Robert M. Peterson from the Boeing Corporation for his valuable feedback on the aircraft program valuation model. Any errors are the authors’ alone

Transitioning The U.S. Air Transportation System To Higher Fuel Costs

The air transportation system enables economic growth and provides significant social benefits. Future increases and volatility in oil prices, as well as climate change policies, are likely to increase the effective cost of fuel. We investigate the expected impacts of higher fuel costs on the U.S. domestic air transportation system and discuss policy options to reduce negative economic and social effects. The 2004-08 fuel price surge is used as a historical case study. A stochastic simulation model is developed using price elasticity of demand assumptions and flight leg fuel burn estimates to understand the impacts of higher fuel costs. It was found that a 50% increase in fuel prices is expected to result in a 12% reduction in ASMs if all cost increases pass through to passengers. System revenues are expected to decrease marginally for fuel price increases up to 50%, but higher increases may result in significant revenue reductions. Small airports are expected to experience relatively larger decreases and greater volatility in traffic. Older aircraft, flying sectors significantly below their optimal fuel efficiency range, are expected to experience the greatest reductions in capacity. An airline case study demonstrates that a regional carrier may be less sensitive to increased fuel prices than other business models. Policy options to maintain small community access, to manage airport traffic volatility, and to improve fleet fuel efficiency are discussed. To transition the U.S. air transportation system to higher fuel costs, stakeholder action will be required.MIT Partnership for AiR Transportation Noise & Emissions Reduction (PARTNER) provided access to the Piano-X aircraft performance database. The Transportation Research Board’s (TRB) Airport Cooperative Research Program (ACRP) supported this work through the Graduate Research Award Program on Public-Sector Aviation Issues

Water quality in the Illawarra-South Coast region of New South Wales, Australia

Water quality is a serious environmental concern in the South Coast region of New South Wales as many aspects of human ecology and the economy are dependant on good water quality. Apart from drinking water for residents and visitors, tourism and agricultural productivity rely on good quality water. This paper presents an overview of general issues with regard to the development of water quality assessment procedures and programs, and discusses a number of issues considered important for the region. These include the impacts of increasing urbanisation, industrial activity (including mining), the potential wider use of groundwater and the improved management of water quality information. Issues that need further attention include the potential impacts of climate change on water resources and quality, the development of local water quality guidelines, and the provision of more information on organic contaminants