Near-equilibrium measurements of nonequilibrium free energy

A central endeavor of thermodynamics is the measurement of free energy changes. Regrettably, although we can measure the free energy of a system in thermodynamic equilibrium, typically all we can say about the free energy of a non-equilibrium ensemble is that it is larger than that of the same system at equilibrium. Herein, we derive a formally exact expression for the probability distribution of a driven system, which involves path ensemble averages of the work over trajectories of the time-reversed system. From this we find a simple near-equilibrium approximation for the free energy in terms of an excess mean time-reversed work, which can be experimentally measured on real systems. With analysis and computer simulation, we demonstrate the accuracy of our approximations for several simple models.Comment: 5 pages, 3 figure

On the Solution of a Computable General Equilibrium Model

Many of today's most significant socioeconomic problems, such as slower economic growth, the decline of some established industries, and shifts in patterns of foreign trade, are international or transnational in nature. But these problems manifest themselves in a variety of ways; both the intensities and the perceptions of the problems differ from one country to another, so that intercountry comparative analyses of recent historical developments are necessary. Through these analyses we attempt to identify the underlying processes of economic structural change and formulate useful hypotheses concerning future developments. The understanding of these processes and future prospects provides the focus for IIASA's project on Comparative Analysis of Economic Structure and Growth. Our research concentrates primarily on the empirical analysis of interregional and intertemporal economic structural change, on the sources of and constraints on economic growth, on problems of adaptation to sudden changes, and especially on problems arising from changing patterns of international trade, resource availability, and technology. The project relies on IIASA's accumulated expertise in related fields and, in particular, on the data bases and systems of models that have been developed in the recent past. This paper is concerned with the solution algorithm of a nonlinear multisectoral model. The model has been developed at IIASA and falls into the class of so called computable general equilibrium models. The economic theoretical properties of the model, as well as some results of simulations based on it, have been reported elsewhere

Effect of headlamp area on discomfort glare

This laboratory study evaluated the effect of the size of the glare source on discomfort glare. The subjects performed two simultaneous tasks: continuous compensatory tracking, and evaluation of discomfort from glare stimuli presented periodically in the near visual periphery. The glare stimuli were circles of two sizes (approximately 0.3 and 0.6° in diameter), and produced five illuminance levels (from 0.03 to 3.1 lux) at the observer's eye. Subjects used a nine-point response scale to evaluate discomfort glare. The results indicate that there was a small but statistically significant effect of the size of glare source, with the smaller glare stimuli resulting in more discomfort glare. The mean difference over the range of glare illuminances tested was 0.2 points on the nine-point response scale.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68669/2/10.1177_096032719002200105.pd

Driver Assessment and Training in the 1980s and 1990s: An Analysis of the Most Cited-Publications

This study analyzed the most-cited publications in the area of driverassessment and training. The citation counts were obtained from both the ScienceCitation and Social Science Citation databases, which at the time of the analysiscontained a total of over 27 million items. The search was restricted to items thatwere published during the 20-year period from 1980 through 1999. The focus ofthe search was on the assessment and training of driving-related skills. Inaddition to documenting the most influential publications, the results are alsopresented in terms of changes over time by topic and by publication outlets

Quantitative comparisons of factors influencing the performance of low-beam headlamps

This study compared the quantitative influence of a variety of factors on the performance of low-beam headlamps. The factors included were vertical aim, horizontal aim, mounting height, lateral separation, lens dirt, lamp voltage, number of functioning lamps, vehicle type, beam pattern and light source. The following aspects of headlamp performance were considered: visibility of pedestrians, visibility of road delineation, visibility of vehicle reflex reflectors, visibility of rettoreflective traffic signs, visibility of targets near the road expansion point, glare directed towards oncoming drivers, glare reflected from wet pavement towards oncoming drivers, glare directed towards rearview mirrors of preceding vehicles, and foreground illumination. A sales-weighted average US beam pattern, with lamps mounted at sales-weighted average locations, formed the basis for most of the analyses. The results indicate that, from among the factors studied, vertical aim is overwhelmingly the most important factor in influencing the performance of low-beam headlamps. The second most important factor is the number of functioning lamps. The main implication of this study is that major improvements in current (fixed as opposed to adaptive) low-beam headlighting could be achieved primarily by better control of vertical aim and by use of longer-life headlamps.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68939/2/10.1177_096032719903100403.pd

Effects of voltage drop on the rise time and light output of incandescent brake lamps on trucks

This study evaluated the effects of voltage on rise time and light output from incandescent brake lamps for a range of voltages representing realistic values for large trucks. The findings indicate that, relative to nominal voltage of 12.8 V, realistic voltages for large trucks lead to significant increases in rise time and to decreases in light output. At 9 V, for example, 90% of the asymptotic light output is reached about 113 ms later than at 12.8 V, and the asymptotic light output is about 28% of the output at 12.8 V. Analogous comparisons of 6 V with 12.8 V indicate an increase in the rise time to 90% of asymptotic light output of about 316 ms and a decrease in asymptotic light output to about 5%. The changes obtained in rise time and light output of incandescent lamps as a function of voltage are of practical importance because they can be expected to increase following drivers' reaction times to brake signals and to increase the frequency of missed signals.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68667/2/10.1177_096032719402600202.pd

Influence of truck driver eye position on effectiveness of retroreflective traffic signs

The amount of light reflected from a retroreflective traffic sign decreases with an increase in the observation angle—the angle between the headlamp, the sign, and the eyes of the driver. Mainly because of the increased seated eye height of truck drivers, the actual observation angles are greater for them than they are for car drivers. Consequently, there is concern about the impaired night-time detection and legibility of retroreflective signs for truck drivers. The present study evaluated the relative amount of light reaching drivers of different types of vehicle by using survey data collected in 1989 by the Transport and Road Research Laboratory (TRRL) in England. The TRRL data included driver eye heights and headlamp mounting heights for 445 vehicles. The present analysis considered three sign locations on a straight roadway: left shoulder, centre, and right shoulder. Two viewing distances were included: 152 m (500 feet) (typical of a sign-legibility distance), and 305 m (1000 feet) (typical of a sign-detection distance). The analysis considered both the differential amount of illumination impinging on the signs from headlamps of trucks and cars, as well as the differential amount of the light reflected from the signs in the direction of truck drivers and car drivers. The main results are that for the viewing distance of 152 m, the amount of light reaching a truck driver can be as low as 25% of the light reaching a car driver; the corresponding percentages for the viewing distance of 305 m are as low as 68%. These reductions were then related to the expected effects on sign legibility and detection. The results imply that the increased eye height of truck drivers could have a major effect on the legibility of retroreflective traffic signs, but only a modest effect on their detection.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68794/2/10.1177_096032719302500105.pd

Stochastic control in microscopic nonequilibrium systems

Quantifying energy flows at nanometer scales promises to guide future research in a variety of disciplines, from microscopic control and manipulation, to autonomously operating molecular machines. A general understanding of the thermodynamic costs of nonequilibrium processes would illuminate the design principles for efficient microscopic machines. Considerable effort has gone into finding and classifying the deterministic control protocols that drive a system rapidly between states at minimum energetic cost. But for autonomous microscopic systems, driving processes are themselves stochastic. Here we generalize a linear-response framework to incorporate such protocol variability, deriving a lower bound on the work that is realized at finite protocol duration, far from the quasistatic limit. Our findings are confirmed in model systems. This theory provides a thermodynamic rationale for rapid operation, independent of functional incentives.Comment: 11 pages, 4 figure