3,817 research outputs found
Effect of the Berendsen thermostat on dynamical properties of water
The effect of the Berendsen thermostat on the dynamical properties of bulk
SPC/E water is tested by generating power spectra associated with fluctuations
in various observables. The Berendsen thermostat is found to be very effective
in preserving temporal correlations in fluctuations of tagged particle
quantities over a very wide range of frequencies. Even correlations in
fluctuations of global properties, such as the total potential energy, are
well-preserved for time periods shorter than the thermostat time constant.
Deviations in dynamical behaviour from the microcanonical limit do not,
however, always decrease smoothly with increasing values of the thermostat time
constant but may be somewhat larger for some intermediate values of ,
specially in the supercooled regime, which are similar to time scales for slow
relaxation processes in bulk water.Comment: 21 pages, 5 figures, To be published in Mol. Phy
Study of Microstructure of Chill Cast Aluminium Bronzes (Cu-Al-Fe-Mn)
Substantial information is available on the microstr-uctures of high tensile aluminium bronzes but most of the literature is pertaining to the alloys containing nickel. In the present paper authors have studies and presented the microstructures of various nickel-free aluminium bronze alloys containing iron and manganese. As an exhau-stive amount of work had been done at National Metall-urgical Laboratory to study the mechanical properties of such aluminium bronze alloys in the chill cast condition, the present microstructure study is also limited to the as cast alloys
Study of microstructure of chill cast aluminium bronzes (Cu-AI-Fe-Mn)
SUBSTANTIAL information is available on the microstru-ctures of high tensile aluminium -bronzes but most of
the literature is pertaining to the alloys containing nickel. Exhaustive amount of work was carried out by Gupta et al. at the National Metallurgical Laboratory
to study the mechanical properties of aluminium-bronze alloys in the chill-cast condition without nickel addition, the results of which have already been reported in an earlier paper. The present paper relates
to the study of microstructures of these chill-cast aluminium-bronze alloys. A few microstructures of
Cu-Al-Fe system have been given by Copper Development Association in their recent publication on aluminium-bronzes.
Excess entropy, Diffusivity and Structural Order in liquids with water-like anomalies
The excess entropy, Se, defined as the difference between the entropies of
the liquid and the ideal gas under identical density and temperature
conditions, is shown to be the critical quantity connecting the structural,
diffusional and density anomalies in water-like liquids. Based on simulations
of silica and the two-scale ramp liquids, water-like density and diffusional
anomalies can be seen as consequences of a characteristic non-monotonic density
dependence of Se. The relationship between excess entropy, the order metrics
and the structural anomaly can be understood using a pair correlation
approximation to Se.Comment: 9 pages, 5 figues in ps forma
Ambiguity and Accident Law
Environmental accidents often involve ambiguous risks, i.e., the relevant probabilities are unknown. This paper studies how liability rules are affected by ambiguity. The injurer and the victim choose a level of care, which is observable, and an unobservable action. Both actions may affect the size and/or likelihood of loss. We analyze the welfare implications of tort rules. First, we show that with ambiguity, negligence is likely to perform better than strict liability. Second, we propose a tort rule of negligence and punitive damages, which gives the efficient levels of both care and unobserved actions
Quantum Hall plateau transition in the lowest Landau level of disordered graphene
We investigate, analytically and numerically, the effects of disorder on the
density of states and on the localization properties of the relativistic two
dimensional fermions in the lowest Landau level. Employing a supersymmetric
technique, we calculate the exact density of states for the Cauchy (Lorentzian)
distribution for various types of disorders. We use a numerical technique to
establish the localization-delocalization (LD) transition in the lowest Landau
level. For some types of disorder the LD transition is shown to belong to a
different universality class, as compared to the corresponding nonrelativistic
problem. The results are relevant to the integer quantum Hall plateau
transitions observed in graphene.Comment: 18 pages and 11 figure
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LinkWidth: A Method to measure Link Capacity and Available Bandwidth Using Single-End Probes
We introduce LinkWidth, a method for estimating capacity and available bandwidth using single-end controlled TCP packet probes. To estimate capacity, we generate a train of TCP RST packets "sandwiched" between two TCP SYN packets. Capacity is obtained by end-to-end packet dispersion of the received TCP RST/ACK packets corresponding to the TCP SYN packets. Our technique is significantly different from the rest of the packet-pair-based measurement techniques, such as CapProbe, pathchar and pathrate, because the long packet trains minimize errors due to bursty cross-traffic. TCP RST packets do not generate additional ICMP replies preventing cross-traffic interference with our probes. In addition, we use TCP packets for all our probes to prevent some types of QoS-related traffic shaping from affecting our measurements. We extend the Train of Packet Pairs technique to approximate the available link capacity. We use pairs of TCP packets with variable intra-pair delays and sizes. This is the first attempt to implement this technique using single-end TCP probes, tested on a wide range of real networks with variable cross-traffic. We compare our prototype with pathchirp and pathload, which require control of both ends, and demonstrate that in most cases our method gives approximately the same results
Dynamical simulation of current fluctuations in a dissipative two-state system
Current fluctuations in a dissipative two-state system have been studied
using a novel quantum dynamics simulation method. After a transformation of the
path integrals, the tunneling dynamics is computed by deterministic integration
over the real-time paths under the influence of colored noise. The nature of
the transition from coherent to incoherent dynamics at low temperatures is
re-examined.Comment: 4 pages, 4 figures; to appear in Phys. Rev. Letter
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