95 research outputs found

    Charmonium-hadron interactions from QCD

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    The heavy quark system is an excellent probe to learn about the QCD dynamics at finite density. First, we discuss the properties of the J/ψJ/\psi and DD meson at finite nucleon density. We discuss why their properties should change at finite density and then introduce an exact QCD relation among these hadron properties and the energy momentum tensor of the medium. Second, we discuss attempts to calculate charmonium-hadron total cross section using effective hadronic models and perturbative QCD. We emphasize a recent calculation, where the cross section is derived using QCD factorization theorem. We conclude by discussing some challenges for SIS 200.Comment: 8 pages, Presented at 6th International Conference on Strange Quarks in Matter: 2001: A Flavorspace Odyssey (SQM2001), Frankfurt, Germany, 25-29 Sep 2001, submitted to J. Phys.

    Time-dependent density-functional theory for electronic excitations in materials: basics and perspectives

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    Time-dependent density-functional theory (TDDFT) is widely used to describe electronic excitations in complex finite systems with large numbers of atoms, such as biomolecules and nanocrystals. The first part of this paper will give a simple and pedagogical explanation, using a two-level system, which shows how the basic TDDFT formalism for excitation energies works. There is currently an intense effort underway to develop TDDFT methodologies for the charge and spin dynamics in extended systems, to calculate optical properties of bulk and nanostructured materials, and to study transport through molecular junctions. The second part of this paper highlights some challenges and recent advances of TDDFT in these areas. Two examples are discussed: excitonic effects in insulators and intersubband plasmon excitations in doped semiconductor quantum wells.Comment: 15 pages, 2 figures, International Conference on Materials Discovery and Databases: Materials Informatics and DF

    Exploring the role of nanocellulose as potential sustainable material for enhanced oil recovery:New paradigm for a circular economy

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    Presently, due to growing global energy demand and depletion of existing oil reservoirs, oil industry is focussing on development of novel and effective ways to enhance crude oil recovery and exploration of new oil reserves, which are typically found in challenging environment and require deep drilling in high temperature and high-pressure regime. The nanocelluloses with numerous advantages such as high temperature and pressure stability, ecofriendly nature, excellent rheology modifying ability, interfacial tension reduction capability, etc., have shown a huge potential in oil recovery over conventional chemicals and macro/micro sized biopolymers-based approach. In present review, an attempt has been made to thoroughly investigate the potential of nanocellulose (cellulose nanocrystals/nanofibers) in development of drilling fluid and in enhancement of oil recovery. The impact of various factors such as nanocellulose shape, charge density, inter-particle or inter-fibers interactions after surface functionalization, rheometer geometries, additives, post processing techniques, etc., which provides insight into the attributes of nanocellulose suspension and exemplify their behaviour during oil recovery have also been reviewed and discussed. Finally, the conclusion and challenges in utility of nanocellulose for oilfield applications are addressed. Knowing how to adjust/quantify nanocrystals/nanofibers shape and size; and monitor their interactions might promote their utility in oilfield industry.</p

    Dark Matter: A Primer

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    Dark matter is one of the greatest unsolved mysteries in cosmology at the present time. About 80% of the universe's gravitating matter is non-luminous, and its nature and distribution are for the most part unknown. In this paper, we will outline the history, astrophysical evidence, candidates, and detection methods of dark matter, with the goal to give the reader an accessible but rigorous introduction to the puzzle of dark matter. This review targets advanced students and researchers new to the field of dark matter, and includes an extensive list of references for further study.Comment: 26 pages, 6 figure

    Externalities and Taxation/Subsidization Policy of Vehicle Information and Communication System

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    Traffic congestion in urban areas has become serious both in Japan and European countries.This study aims to calculate the optimal penetration level and taxation/subsidization level of VICS. VICS(Vehicle Information and Communication System) is a digital data communication system which promptly provides the latest necessary road traffic information to drivers via car navigation equipment. Drivers can receive real-time road traffic information about congestion and regulation 24 hours a day, 7 days a week. The world's first VICS service started in Japan in April 1996. It is impossible to realize the optimal level of penetration in the market mechanism when a service has technological externalities. VICS must have two type of technological externality. One is positive one-way externality which implies that the higher the level of penetration of VICS, the lower the travel times to the non-equipped drivers because of congestion reducing. The other is negative network externality which implies that a marginal equipped driver adversely affects the already equipped driver by increasing the travel time on alternative routes. Hence taxation or subsidization must be necessary to realize the optimal penetration level of VICS. Many studies explored the effect of market penetrations of PRG(route planning and guidance) on overall system travel time(e.g. Emmerink et al.(1995)). These studies, however, considered market penetration as an exogenous parameter. Recently, Yang (1999) developed the model to calculate the market penetration level endogenously. Lo and Szeto (2002) provided the methodology to analyze penetration level which simultaneously satisfies the three objectives (service providersÂf objective, traffic management agency's objective and usersÂf objective). But there are no studies to explore the optimal penetration level at which the marginal social benefit is equal to marginal social cost. This study develops the partial equilibrium economic model to calculate the optimal penetration level and taxation/subsidization level of VICS and calculate them by applying this model to Kantou-Area where is the most congested area in Japan. The result of our analysis shows that it must be necessary to realize optimal level of penetration of VICS to impose a fixed charge per VICS unit except in the case where the effect of negative externality is very weak.
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