Basic Transportation Economics

Transportation economics is an integral part of all transportation activities. Refined, detailed, and careful economic analyses consider conduct-performance methodology and the specifications of production, cost and demand functions

Objectives of the Airline Firm: Theory

Theoretical models are formulated for airline firm operations that revolve around alternative formulations of managerial goals which these firms are persuing in practice. Consideration is given to the different objective functions which the companies are following in lieu of profit maximization

The impact of changing technology on the demand for air transportation

Demand models for air transportation that are sensitive to the impact of changing technology were developed. The models are responsive to potential changes in technology, and to changing economic, social, and political factors as well. In addition to anticipating the wide differences in the factors influencing the demand for long haul and short haul air travel, the models were designed to clearly distinguish among the unique features of these markets

An economic model of the manufacturers' aircraft production and airline earnings potential, volume 3

A behavioral explanation of the process of technological change in the U. S. aircraft manufacturing and airline industries is presented. The model indicates the principal factors which influence the aircraft (airframe) manufacturers in researching, developing, constructing and promoting new aircraft technology; and the financial requirements which determine the delivery of new aircraft to the domestic trunk airlines. Following specification and calibration of the model, the types and numbers of new aircraft were estimated historically for each airline's fleet. Examples of possible applications of the model to forecasting an individual airline's future fleet also are provided. The functional form of the model is a composite which was derived from several preceding econometric models developed on the foundations of the economics of innovation, acquisition, and technological change and represents an important contribution to the improved understanding of the economic and financial requirements for aircraft selection and production. The model's primary application will be to forecast the future types and numbers of new aircraft required for each domestic airline's fleet

Examination of Hydrate Formation Methods: Trying to Create Representative Samples

Forming representative gas hydrate-bearing laboratory samples is important so that the properties of these materials may be measured, while controlling the composition and other variables. Natural samples are rare, and have often experienced pressure and temperature changes that may affect the property to be measured [Waite et al., 2008]. Forming methane hydrate samples in the laboratory has been done a number of ways, each having advantages and disadvantages. The ice-to-hydrate method [Stern et al., 1996], contacts melting ice with methane at the appropriate pressure to form hydrate. The hydrate can then be crushed and mixed with mineral grains under controlled conditions, and then compacted to create laboratory samples of methane hydrate in a mineral medium. The hydrate in these samples will be part of the load-bearing frame of the medium. In the excess gas method [Handa and Stupin, 1992], water is distributed throughout a mineral medium (e.g. packed moist sand, drained sand, moistened silica gel, other porous media) and the mixture is brought to hydrate-stable conditions (chilled and pressurized with gas), allowing hydrate to form. This method typically produces grain-cementing hydrate from pendular water in sand [Waite et al., 2004]. In the dissolved gas method [Tohidi et al., 2002], water with sufficient dissolved guest molecules is brought to hydrate-stable conditions where hydrate forms. In the laboratory, this is can be done by pre-dissolving the gas of interest in water and then introducing it to the sample under the appropriate conditions. With this method, it is easier to form hydrate from more soluble gases such as carbon dioxide. It is thought that this method more closely simulates the way most natural gas hydrate has formed. Laboratory implementation, however, is difficult, and sample formation is prohibitively time consuming [Minagawa et al., 2005; Spangenberg and Kulenkampff, 2005]. In another version of this technique, a specified quantity of gas is placed in a sample, then the sample is flooded with water and cooled [Priest et al., 2009]. We have performed a number of tests in which hydrate was formed and the uniformity of the hydrate formation was examined. These tests have primarily used a variety of modifications of the excess gas method to make the hydrate, although we have also used a version of the excess water technique. Early on, we found difficulties in creating uniform samples with a particular sand/ initial water saturation combination (F-110 Sand, {approx} 35% initial water saturation). In many of our tests we selected this combination intentionally to determine whether we could use a method to make the samples uniform. The following methods were examined: Excess gas, Freeze/thaw/form, Freeze/pressurize/thaw, Excess gas followed by water saturation, Excess water, Sand and kaolinite, Use of a nucleation enhancer (SnoMax), and Use of salt in the water. Below, each method, the underlying hypothesis, and our results are briefly presented, followed by a brief conclusion. Many of the hypotheses investigated are not our own, but were presented to us. Much of the data presented is from x-ray CT scanning our samples. The x-ray CT scanner provides a three-dimensional density map of our samples. From this map and the physics that is occurring in our samples, we are able to gain an understanding of the spatial nature of the processes that occur, and attribute them to the locations where they occur

Methane Hydrate Dissociation by Depressurization in a Mount Elbert Sandstone Sample: Experimental Observations and Numerical Simulations

A preserved sample of hydrate-bearing sandstone from the Mount Elbert Test Well was dissociated by depressurization while monitoring the internal temperature of the sample in two locations and the density changes at high spatial resolution using x-ray CT scanning. The sample contained two distinct regions having different porosity and grain size distributions. The hydrate dissociation occurred initially throughout the sample as a result of depressing the pressure below the stability pressure. This initial stage reduced the temperature to the equilibrium point, which was maintained above the ice point. After that, dissociation occurred from the outside in as a result of heat transfer from the controlled temperature bath surrounding the pressure vessel. Numerical modeling of the test using TOUGH+HYDRATE yielded a gas production curve that closely matches the experimentally measured curve

The state-of-the-art in air transportation demand and systems analysis : a report on the proceedings of a workshop sponsored by the Civil Aeronautics Board, Department of Transportation, and National Aeronautics and Space Administration (June 1975)

August 1975Introduction and summary: Forecasting air transportation demand has indeed become a complex and risky business in recent years, especially in view of unpredictable fuel prices, high inflation rates, a declining rate of aggregate population growth, and an uncertainty with respect to the regulatory structure in the aviation industry. Since the stakes are very high, the need for accurate forecasting and for a more complete understanding of the total system of air transportation continues to grow. Past forecasting methods have become inadequate for at least two reasons. First, the trend extrapolation method of forecasting is no longer appropriate due to the significant changes in both the economic and the operating environments in recent years. Second, the more sophisticated econometric forecasting models are only as good as our understanding of the total air transportation system on the one hand, and the availability of data on the other. In light of these deficiencies, the dual needs for improving forecasting methods and for increasing the reliability of data are more critical now than ever before. In short, there is a compelling need to perform basic research to improve both the forecasting methods and the data in the aviation industry. Among the various types of forecasts of aviation activity desired by the government agencies, the air carriers, the airframe and engine manufacturers, the airport authorities, and the financial community, one component that plays a critical role in long-range planning pertains to the future fleet requirements for the aviation industry. Forecast items needed with respect to future fleet requirements include types, configuration, ranges, and technologies of new aircraft so that the industry and government can coordinate their resources to maximize the interests of the producers, regulators and consumers of future air service. The National Aeronautics and Space Administration (NASA), with its twin missions of both aeronautics and astronautics, has been focusing its attention on the aeronautics component in recent years. In this overall responsibility, the Systems Study Division of NASA-Ames Research Center has as one of its main objectives the development of a better understanding of the civil air transportation system in the United States, with emphasis placed on the proper and timely application of new technology. In order to fulfill this objective, the division has a critical need for projections of the growth of demand and for the determination of the role of technology in the future growth of air transportation. Before undertaking an extensive research effort in the area of air transportation demand analysis and forecasting, NASA-Ames attempted to solicit the views of the industry and other government agencies at a one day informal meeting in San Francisco in December 1974. The meeting was attended by about twenty experts from the carriers, airframe and engine manufacturers, U.S. Department of Transportation, universities and NASA. The goals of this mini-workshop were three-fold: the first objective was to determine the ways in which the NASA-Ames Systems Study Division could play a supportive role in this area; second, it was essential to receive an informal endorsement from the industry and other government agencies; and third, it was necessary to determine the direction for the proposed research. This meeting concluded with a general agreement on a definite need for future research, with the belief that not only could NASA-Ames play a supportive role but, more important, that it could play a catalytic role. However, due to the limited participation in this one-day meeting and the assistance that the proposed research could have provided to a wide variety of users, a more extensive workshop was proposed at that time, possibly to be co-sponsored by other government agencies. Subsequent to the December 1974 meeting, further discussions with the U.S. Civil Aeronautics Board (CAB) and the U.S. Department of Transportation (DOT) resulted in a three-day workshop co-sponsored by the CAB, DOT and NASA. The reasons for the joint sponsorship by the CAB and DOT reflected a desire from these agencies to participate in the search for methodologies and information on the long-range benefits, problems and issues of technological advances in aviation and to assist NASA in deploying its funds on these matters in the most productive and efficient ways. The overall objectives of this workshop were four-fold: first, to investigate the state-of-the-art in air transportation demand forecasting; second, to determine the needs of the various government agencies and the industry; third, to assess the possibility of long-term government sponsorship of basic research to improve the forecasting of air transportation activity; and fourth, to determine the most promising areas of research in air transportation and systems analysis. This workshop was organized by the Flight Transportation Laboratory of the Massachusetts Institute of Technology and the Transportation Center at Northwestern University and was held at the Mayflower Hotel in Washington, D.C. on June 2-4, 1975. The meeting was attended by one hundred experts, thirty-three of whom made extensive presentations. This report then is a summary of the highlights of the presentations delivered at the workshop, with appropriate interjections and editorial comments as perceived by its authors

Fracture/matrix flow experiments results

The impact of vapor diffusion and its potential enhancement are of concern with respect to the performance of the potential nuclear waste repository at Yucca Mountain. Under non-isothermal conditions, such as those prevailing in the near-field environment, gas-phase diffusion of water vapor (a condensable component) may be enhanced as compared to isothermal conditions. Two main phenomena are responsible for this enhancement (Philip and DeVries 1957, p. 226). Normally, diffusive transport of water vapor is obstructed by the presence of liquid islands in the pore throats, and diffusion is reduced at higher saturations. However, under a thermal gradient, a vapor-pressure gradient develops in the gas phase, causing water to evaporate from one side of the liquid island and to diffuse in the gas phase to a liquid island of lower temperature, where it condenses (Figure 1). Water flows through the liquid island as a result of differences in meniscus curvature between the two sides. This difference is caused by the temperature gradient between the liquid-vapor interfaces on the two ends of the liquid island. The evaporation-condensation process repeats itself on the other side of the liquid island; the result is an enhanced diffusive flux through the medium

Mobility deficit – Rehabilitate, an opportunity for functionality

There are many pathological conditions that cause mobility deficits and that ultimately influence someone’s autonomy.Aims: to evaluate patients with mobility deficits functional status; to implement a Rehabilitation Nursing intervention plan; to monitor health gains through mobility deficits rehabilitation.Conclusion: Early intervention and the implementation of a nursing rehabilitation intervention plan results in health gains (direct or indirect), decreases the risk of developing Pressure Ulcers (PU) and the risk of developing a situation of immobility that affects patients’ autonomy and quality of life

ESPRAS Survey on Continuing Education in Plastic, Reconstructive and Aesthetic Surgery in Europe

Background Specialty training in plastic, reconstructive and aesthetic surgery is a prerequisite for safe and effective provision of care. The aim of this study was to assess and portray similarities and differences in the continuing education and specialization in plastic surgery in Europe. Material and Methods A detailed questionnaire was designed and distributed utilizing an online survey administration software. Questions addressed core items regarding continuing education and specialization in plastic surgery in Europe. Participants were addressed directly via the European Leadership Forum (ELF) of the European Society of Plastic, Reconstructive and Aesthetic Surgery (ESPRAS). All participants had detailed knowledge of the organization and management of plastic surgical training in their respective country. Results The survey was completed by 29 participants from 23 European countries. During specialization, plastic surgeons in Europe are trained in advanced tissue transfer and repair and aesthetic principles in all parts of the human body and within several subspecialties. Moreover, rotations in intensive as well as emergency care are compulsory in most European countries. Board certification is only provided for surgeons who have had multiple years of training regulated by a national board, who provide evidence of individually performed operative procedures in several anatomical regions and subspecialties, and who pass a final oral and/or written examination. Conclusion Board certified plastic surgeons meet the highest degree of qualification, are trained in all parts of the body and in the management of complications. The standard of continuing education and qualification of European plastic surgeons is high, providing an excellent level of plastic surgical care throughout Europe