High energy constraints on Lorentz symmetry violations

Lorentz violation at high energies might lead to non linear dispersion relations for the fundamental particles. We analyze observational constraints on these without assuming any a priori equality between the coefficients determining the amount of Lorentz violation for different particle species. We focus on constraints from three high energy processes involving photons and electrons: photon decay, photo-production of electron-positron pairs, and vacuum Cerenkov radiation. We find that cubic momentum terms in the dispersion relations are strongly constrained.Comment: 7 pages, 1 figure, Talk presented at CPT01; the Second Meeting on CPT and Lorentz Symmetry, Bloomington, Indiana, 15-18 Aug. 2001. Minor numerical error corrected, gamma-decay constraint update

Identification of terms to define unconstrained air transportation demands

The factors involved in the evaluation of unconstrained air transportation systems were carefully analyzed. By definition an unconstrained system is taken to be one in which the design can employ innovative and advanced concepts no longer limited by present environmental, social, political or regulatory settings. Four principal evaluation criteria are involved: (1) service utilization, based on the operating performance characteristics as viewed by potential patrons; (2) community impacts, reflecting decisions based on the perceived impacts of the system; (3) technological feasibility, estimating what is required to reduce the system to practice; and (4) financial feasibility, predicting the ability of the concepts to attract financial support. For each of these criteria, a set of terms or descriptors was identified, which should be used in the evaluation to render it complete. It is also demonstrated that these descriptors have the following properties: (a) their interpretation may be made by different groups of evaluators; (b) their interpretations and the way they are used may depend on the stage of development of the system in which they are used; (c) in formulating the problem, all descriptors should be addressed independent of the evaluation technique selected

Thermionic research and development program Final report, 15 Jul. 1966 - 15 Jan. 1968

Thermionic research and development program - improvement of performance of low emitter temperature cesium vapor thermionic converter

The development of a model for predicting passenger acceptance of short-haul air transportation systems

Meaningful criteria and methodology for assessing, particularly in the area of ride quality, the potential acceptability to the traveling public of present and future transportation systems were investigated. Ride quality was found to be one of the important variables affecting the decision of users of air transportation, and to be influenced by several environmental factors, especially motion, noise, pressure, temperature, and seating. Models were developed to quantify the relationship of subjective comfort to all of these parameters and then were exercised for a variety of situations. Passenger satisfaction was found to be strongly related to ride quality and was so modeled. A computer program was developed to assess the comfort and satisfaction levels of passengers on aircraft subjected to arbitrary flight profiles over arbitrary terrain. A model was deduced of the manner in which passengers integrate isolated segments of a flight to obtain an overall trip comfort rating. A method was established for assessing the influence of other links (e.g., access, terminal conditions) in the overall passenger trip

Ownership and financing of infrastructure : historical perspective

The authors summarize the rich and varied experiences of private and public provision of urban services in France, Great Britain, and the United States over the past 100 years. Their main focus is on experiences in the United States and on shifts back and forth between the public and private sectors. A few of their observations: (i) The values of politically important actors as well as the working of government, political, and legal institutions have shaped decisions about infrastructure development, the sorts of public goods demanded, and the roles played by private firms. (ii) The range of choices that has historically been made with respect to the ownership, financing, and operation of different infrastructures has been far too varied to be encompassed by simple distinctions between"public"and"private."(iii) Throughout the world, many infrastructures owned and operated by governments have been built by private firms. (iv) In the United States, private firms and property-owners associations of various sorts have owned outright both toll roads and residential streets. Private firms have also collected solid wastes and provided urban transport under a range of franchise, contracting, and regulatory arrangements. The situation with mass transit has been similar in Great Britain. Although water works facilities in France are predominantly government-owned, private firms operate and manage most systems under an array of contracting and leasing arrangements. (v) Even when facilities have been owned by private firms, direct competition has been of limited importance in the provision of many kinds of infrastructure. But market discipline can arise from other sources. (vi) Privatization can get government bureaucracies out of the business of performing entrepreneurial activities for which they may be poorly suited. When market forces are weak, however, and important public interests are at stake, strengthening government institutions may be a prerequisite for successful privatization. (vii) In the electric utility industry, private firms played a far greater role in U.S. electric utilities than in Great Britain, in part because of different views about appropriate roles for government in providing essential services. For similar reasons, the state played a much larger role in furnishing telecommunications services in France than in the United States. (viii) Beliefs about the"publicness"of different goods and services have helped shape the character of regulatory franchise, and contracting arrangements. When a good is seen as mainly private, it is easier for private service providers to be compensated mainly by user fees and for most decisions about price, output, and quality, no matter what the role played by private firms in actually providing services. (ix) Goods defined as"public"have often been provided free to users, even though it would have been easy to exclude nonpayers. Examples in the United States include interstate highway systems, public parks, public libraries, and police and fire protection. Free services have been provided because it is believed that in these domains market relationships should not apply - and that denying nonpayers the public services would be a denial of rights. (x) In Great Britain and the United States, the contracting out of public services has been both supported and opposed because of its potential to break the power of public sector unions and to cut workers'pay. In the United States, privatization has also come under attack on the grounds that opportunities for minority employment may be reduced.Regional Governance,Public Sector Economics&Finance,Decentralization,Public Sector Management and Reform,Urban Governance and Management,Public Sector Management and Reform,Urban Governance and Management,Regional Governance,Town Water Supply and Sanitation,Public Sector Economics&Finance

Models of subjective response to in-flight motion data

Mathematical relationships between subjective comfort and environmental variables in an air transportation system are investigated. As a first step in model building, only the motion variables are incorporated and sensitivities are obtained using stepwise multiple regression analysis. The data for these models have been collected from commercial passenger flights. Two models are considered. In the first, subjective comfort is assumed to depend on rms values of the six-degrees-of-freedom accelerations. The second assumes a Rustenburg type human response function in obtaining frequency weighted rms accelerations, which are used in a linear model. The form of the human response function is examined and the results yield a human response weighting function for different degrees of freedom

Passenger ride quality determined from commercial airline flights

The University of Virginia ride-quality research program is reviewed. Data from two flight programs, involving seven types of aircraft, are considered in detail. An apparatus for measuring physical variations in the flight environment and recording the subjective reactions of test subjects is described. Models are presented for predicting the comfort response of test subjects from the physical data, and predicting the overall comfort reaction of test subjects from their moment by moment responses. The correspondence of mean passenger comfort judgments and test subject response is shown. Finally, the models of comfort response based on data from the 5-point and 7-point comfort scales are shown to correspond

Application of ride quality technology to predict ride satisfaction for commuter-type aircraft

A method was developed to predict passenger satisfaction with the ride environment of a transportation vehicle. This method, a general approach, was applied to a commuter-type aircraft for illustrative purposes. The effect of terrain, altitude and seat location were examined. The method predicts the variation in passengers satisfied for any set of flight conditions. In addition several noncommuter aircraft were analyzed for comparison and other uses of the model described. The method has advantages for design, evaluation, and operating decisions

Hardware development for the surface tension driven convection experiment aboard the USML-1 spacelab mission

The Surface Tension Driven Convection Experiment is a Space Transportation System flight experiment to study both transient and steady thermocapillary fluid flows aboard the USML-1 Spacelab mission planned for March 1992. Hardware is under development to establish the experimental conditions and perform the specified measurements, for both ground based research and the flight experiment in a Spacelab single rack. Major development areas include an infrared thermal imaging system for surface temperature measurement, a CO2 laser and control system for surface heating, and for flow visualization, a He-Ne laser and optical system in conjunction with an intensified video camera. For ground based work the components of each system were purchased or designed, and tested individually. The three systems will be interfaced with the balance of the experimental hardware and will constitute a working engineering model. A description of the three systems and examples of the component performance is given along with the plans for the development of flight hardware

On the orientational ordering of long rods on a lattice

We argue that a system of straight rigid rods of length k on square lattice with only hard-core interactions shows two phase transitions as a function of density, rho, for k >= 7. The system undergoes a phase transition from the low-density disordered phase to a nematic phase as rho is increased from 0, at rho = rho_c1, and then again undergoes a reentrant phase transition from the nematic phase to a disordered phase at rho = rho_c2 < 1.Comment: epl.cl