400,152 research outputs found
Skyhook surface sliding mode control on semi-active vehicle suspension systems for ride comfort enhancement
A skyhook surface sliding mode control method was proposed and applied to the control on the semi-active vehicle suspension system for its ride comfort enhancement. A two degree of freedom dynamic model of a vehicle semi-active suspension system was given, which focused on the passenger’s ride comfort perform-ance. A simulation with the given initial conditions has been devised in MATLAB/SIMULINK. The simula-tion results were showing that there was an enhanced level of ride comfort for the vehicle semi-active sus-pension system with the skyhook surface sliding mode controller
Painlev\'e V and time dependent Jacobi polynomials
In this paper we study the simplest deformation on a sequence of orthogonal
polynomials, namely, replacing the original (or reference) weight
defined on an interval by It is a well-known fact that under
such a deformation the recurrence coefficients denoted as and
evolve in according to the Toda equations, giving rise to the
time dependent orthogonal polynomials, using Sogo's terminology. The resulting
"time-dependent" Jacobi polynomials satisfy a linear second order ode. We will
show that the coefficients of this ode are intimately related to a particular
Painlev\'e V. In addition, we show that the coefficient of of the
monic orthogonal polynomials associated with the "time-dependent" Jacobi
weight, satisfies, up to a translation in the Jimbo-Miwa -form of
the same while a recurrence coefficient is up to a
translation in and a linear fractional transformation
These results are found
from combining a pair of non-linear difference equations and a pair of Toda
equations. This will in turn allow us to show that a certain Fredholm
determinant related to a class of Toeplitz plus Hankel operators has a
connection to a Painlev\'e equation
Hybrid power semiconductor
The voltage rating of a bipolar transistor may be greatly extended while at the same time reducing its switching time by operating it in conjunction with FETs in a hybrid circuit. One FET is used to drive the bipolar transistor while the other FET is connected in series with the transistor and an inductive load. Both FETs are turned on or off by a single drive signal of load power, the second FET upon ceasing conductions, rendering one power electrode of the bipolar transistor open. Means are provided to dissipate currents which flow after the bipolar transistor is rendered nonconducting
Valid and efficient formula for free energy difference from nonequilibrium work
Atomic force microscopes and optical tweezers afford direct probe into the inner working of single biomolecules by mechanically unfolding them.^1-15^ Critical to the success of this type of probe is to correctly extract the free energy differences between the various conformations of a protein/nucleic acid along its forced unfolding pathways. Current studies rely on the Jarzynski equality^16^ (JE) or its undergirding Crooks fluctuation theorem^17^ (CFT), even though questions remain on its validity^17-19^ and on its accuracy.^13,20-21^ The validity of JE relies on the assumption of microscopic reversibility.^17,18^ The dynamics of biomolecules, however, is Langevin stochastic in nature. The frictional force in the Langevin equation breaks the time reversal symmetry and renders the dynamics microscopically irreversible even though detailed balance holds true. The inaccuracy of JE has largely been attributed to the fact that one cannot sample a large enough number of unfolding paths in a given study, experimental or computational.^13,15^ Here I show that both of these questions can be answered with a new equation relating the nonequilibrium work to the equilibrium free energy difference. The validity of this new equation requires detailed balance but not microscopic reversibility. Taking into the new equation equal number of unfolding and refolding paths, the accuracy is enhanced ten folds in comparison to a JE study based on a similar but larger number of unfolding paths
Glycerol Modulates Water Permeation through Escherichia coli Aquaglyceroporin GlpF
Among aquaglyceroporins that transport both water and glycerol across the
cell membrane, Escherichia coli glycerol uptake facilitator (GlpF) is the most
thoroughly studied. However, one question remains: Does glycerol modulate water
permeation? This study answers this fundamental question by determining the
chemical-potential profile of glycerol along the permeation path through GlpF's
conducting pore. There is a deep well near the Asn-Pro-Ala (NPA) motifs
(dissociation constant 14 microM) and a barrier near the selectivity filter
(10.1 kcal/mol above the well bottom). This profile owes its existence to
GlpF's perfect steric arrangement: The glycerol-protein van der Waals
interactions are attractive near the NPA but repulsive elsewhere in the
conducting pore. In light of the single-file nature of waters and glycerols
lining up in GlpF's amphipathic pore, it leads to the following conclusion:
Glycerol modulates water permeation in the microM range. At mM concentrations,
GlpF is glycerol-saturated and a glycerol dwelling in the well occludes the
conducting pore. Therefore, water permeation is fully correlated to glycerol
dissociation that has an Arrhenius activation barrier of 6.5 kcal/mol.
Validation of this theory is based on the existent in vitro data, some of which
have not been given the proper attention they deserved: The Arrhenius
activation barriers were found to be 7 kcal/mol for water permeation and 9.6
kcal/mol for glycerol permeation; The presence of up to 100 mM glycerol did not
affect the kinetics of water transport with very low permeability, in apparent
contradiction with the existent theories that predicted high permeability (0 M
glycerol)
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