Comparative evaluation of microscopic car-following behavior

Microscopic traffic-simulation tools are increasingly being applied to evaluate the impacts of a wide variety of intelligent transport, systems (ITS) applications and other dynamic problems that are difficult to solve using traditional analytical models. The accuracy of a traffic-simulation system depends highly on the quality of the traffic-flow model at its core, with the two main critical components being the car-following and lane-changing models. This paper presents findings from a comparative evaluation of car-following behavior in a number of traffic simulators [advanced interactive microscopic simulator for urban and nonurban networks (AIMSUN), parallel microscopic simulation (PARAMICS), and Verkehr in Statiten-simulation (VISSIM)]. The car-following algorithms used in these simulators have been developed from a variety of theoretical backgrounds and are reported to have been calibrated on a number of different data sets. Very few independent studies have attempted to evaluate the performance of the underlying algorithms based on the same data set. The results reported in this study are based on a car-following experiment that used instrumented vehicles to record the speed and relative distance between follower and leader vehicles on a one-lane road. The experiment was replicated in each tool and the simulated car-following behavior was compared to the field data using a number of error tests. The results showed lower error values for the Gipps-based models implemented in AIMSUN and similar error values for the psychophysical spacing models used in VISSIM and PARAMICS. A qualitative drift and goal-seeking behavior test, which essentially shows how the distance headway between leader and follower vehicles should oscillate around a stable distance, also confirmed the findings.

Particle tracking in a salinity gradient: A method for measuring sinking rate of individual phytoplankton in the laboratory

This paper presents a new method to measure the sinking rates of individual phytoplankton “particles” (cells, chains, colonies, and aggregates) in the laboratory. Conventional particle tracking and high resolution video imaging were used to measure particle sinking rates and particle size. The stabilizing force of a very mild linear salinity gradient (1 ppt over 15 cm) prevented the formation of convection currents in the laboratory settling chamber. Whereas bulk settling methods such as SETCOL provide a single value of sinking rate for a population, this method allows the measurement of sinking rate and particle size for a large number of individual particles or phytoplankton within a population. The method has applications where sinking rates vary within a population, or where sinking rate-size relationships are important. Preliminary data from experiments with both laboratory and field samples of marine phytoplankton are presented here to illustrate the use of the technique, its applications, and limitations. Whereas this paper deals only with sinking phytoplankton, the method is equally valid for positively buoyant species, as well as nonbiological particles.

Social control and knowledge in democratic societies

In this article we introduce the notions of knowledge policy and the politics of knowledge. These have to be distinguished from the older, well-known terms of research policy, or science and technology policy. While the latter aim to foster the development of innovations in knowledge and its applications, the former is aware of side effects of new knowledge and tries to address them. While research policy takes the aims of innovations as largely unproblematic (insofar as they help improving national competitiveness), knowledge policy tries to govern (regulate, control, restrict, or even forbid) the production of knowledge.

Investigation of research in DEA literature

The present bibliography includes most of the references published in the field of Data Envelopment Analysis (DEA) up to the year 2007. Some publications in 2007 are also listed, but not included in the statistics. To the best of the authors’ knowledge, this listing appears to be the most complete source of references on DEA and its applications in measuring the efficiency and productivity of decision making units (DMUs). The authors hope that this new updated bibliography will assist researchers and other scholars as they develop new frontiers in DEA. The most utilized/relevant journals, a keyword analysis, and selected statistics are also presented.

Acquisition and management of technology in Malaysian companies

This thesis is about the acquisition and diffusion of imported technology. Writers in the field of technology development in developing countries have always recognised that technical progress depends on the diffusion of imported technology and its applications to the provision of products and processes (Rosemberg, 1982). Despite the massive importation of technology by Malaysian companies, little effort has been made to study and understand the diffusion system in local companies. This study analyses: The problems associated with the acquisition of technology, highlighting the technology strategies adopted by the suppliers of technology; the diffusion pattern and key characteristics of the diffusion process; and major factors affecting the diffusion of technology. The policy implications are examined and the framework to manage the diffusion process within the enterprises is suggested. The findings indicated that the diffusion process is not one of passive acceptance but involves systematic efforts to acquire and diffuse the imported technology. A strong system of diffusion in companies had enabled a rapid diffusion of imported technology resulting in higher levels of technical capability. On the other hand, weakness in the company's diffusion system led to limited diffusion and slow technical progress. Characteristics of diffusion system are analysed and discussed extensively. The thesis attempts to develop the idea of `in-house system of diffusion' associated with the acquisition and development of imported technology. It argues for the development ofa stronger theoretical framework on the diffusion and development of technology particularly in countries like Malaysia which relies extensively on the importation of foreign technology.

Mass transfer in fluidized bed drying of moist particulate

Bubbling fluidized bed technology is one of the most effective mean for interaction between solid and gas flow, mainly due to its good mixing and high heat and mass transfer rate. It has been widely used at a commercial scale for drying of grains such as in pharmaceutical, fertilizers and food industries. When applied to drying of non-pours moist solid particles, the water is drawn-off driven by the difference in water concentration between the solid phase and the fluidizing gas. In most cases, the fluidizing gas or drying agent is air. Despite of the simplicity of its operation, the design of a bubbling fluidized bed dryer requires an understanding of the combined complexity in hydrodynamics and the mass transfer mechanism. On the other hand, reliable mass transfer coefficient equations are also required to satisfy the growing interest in mathematical modelling and simulation, for accurate prediction of the process kinetics. This chapter presents an overview of the various mechanisms contributing to particulate drying in a bubbling fluidized bed and the mass transfer coefficient corresponding to each mechanism. In addition, a case study on measuring the overall mass transfer coefficient is discussed. These measurements are then used for the validation of mass transfer coefficient correlations and for assessing the various assumptions used in developing these correlations.

Metformin - The gold standard:a scientific handbook

Metformin may play in important role in the future in helping to prevent the development of diabetes: it is a strong candidate therapy for delaying the onset of the disease and potentially as part of a treatment programme to correct features of the metabolic syndrome. This book celebrates 50 years of research into metformin and its use in the treatment of diabetes. Metformin is still the drug of choice for managing patients with type 2 diabetes and all new drugs are tested in comparison with this, the gold standard. Comprising seven sections, addressing different aspects of research on metformin and its applications, this book is edited by a world class team of expert diabetologists and beautifully presented in two colour throughout. It also includes a bibliography of all papers published on metformin and a complete list of all authors on those papers.

NLSE-based model of a random distributed feedback fiber laser

In this work we propose a NLSE-based model of power and spectral properties of the random distributed feedback (DFB) fiber laser. The model is based on coupled set of non-linear Schrödinger equations for pump and Stokes waves with the distributed feedback due to Rayleigh scattering. The model considers random backscattering via its average strength, i.e. we assume that the feedback is incoherent. In addition, this allows us to speed up simulations sufficiently (up to several orders of magnitude). We found that the model of the incoherent feedback predicts the smooth and narrow (comparing with the gain spectral profile) generation spectrum in the random DFB fiber laser. The model allows one to optimize the random laser generation spectrum width varying the dispersion and nonlinearity values: we found, that the high dispersion and low nonlinearity results in narrower spectrum that could be interpreted as four-wave mixing between different spectral components in the quasi-mode-less spectrum of the random laser under study could play an important role in the spectrum formation. Note that the physical mechanism of the random DFB fiber laser formation and broadening is not identified yet. We investigate temporal and statistical properties of the random DFB fiber laser dynamics. Interestingly, we found that the intensity statistics is not Gaussian. The intensity auto-correlation function also reveals that correlations do exist. The possibility to optimize the system parameters to enhance the observed intrinsic spectral correlations to further potentially achieved pulsed (mode-locked) operation of the mode-less random distributed feedback fiber laser is discussed.

Nonlinear mixing and mode correlations in a short Raman fiber laser

In the present paper we experimentally demonstrate a generation in a short Raman fiber laser having 10 000 different longitudinal modes only. We design the laser using 12 meters of commercially available fiber. Contrary to the recently demonstrated single longitudinal mode DFB Raman laser and short DBR Raman laser, in the laser under study the number of modes is high enough for efficient nonlinear interactions. Experimentally measured time dynamics reveals the presence of mode correlations in the radiation: the measured extreme events lasts for more than 10 round-trips.

Influence of the generated power, measurement bandwidth, and noise level on intensity statistics of a quasi-CW Raman fiber laser

In the present paper we numerically study instrumental impact on statistical properties of quasi-CW Raman fiber laser using a simple model of multimode laser radiation. Effects, that have the most influence, are limited electrical bandwidth of measurement equipment and noise. To check this influence, we developed a simple model of the multimode quasi- CW generation with exponential statistics (i.e. uncorrelated modes). We found that the area near zero intensity in probability density function (PDF) is strongly affected by both factors, for example both lead to formation of a negative wing of intensity distribution. But far wing slope of PDF is not affected by noise and, for moderate mismatch between optical and electrical bandwidth, is only slightly affected by bandwidth limitation. The generation spectrum often becomes broader at higher power in experiments, so the spectral/electrical bandwidth mismatch factor increases over the power that can lead to artificial dependence of the PDF slope over the power. It was also found that both effects influence the ACF background level: noise impact decreases it, while limited bandwidth leads to its increase. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.