3,058 research outputs found
Analytical study of the frequency response function of a nonlinear spring damper system
A spring damper system with a nonlinear damping element is investigated using the Volterra series method to study the system frequency response function (FRF) characteristics. The relationship between the FRF and the characteristic parameters of the nonlinear damper is determined to produce an analytical description for the system FRF. Simulation studies are used to verify the theoretical analysis. These results provide an important basis for the FRF based analysis and design of nonlinear spring damper systems in the frequency domain
Regularization of point vortices for the Euler equation in dimension two
In this paper, we construct stationary classical solutions of the
incompressible Euler equation approximating singular stationary solutions of
this equation.
This procedure is carried out by constructing solutions to the following
elliptic problem [ -\ep^2 \Delta
u=(u-q-\frac{\kappa}{2\pi}\ln\frac{1}{\ep})_+^p, \quad & x\in\Omega, u=0, \quad
& x\in\partial\Omega, ] where , is a bounded
domain, is a harmonic function.
We showed that if is simply-connected smooth domain, then for any
given non-degenerate critical point of Kirchhoff-Routh function
with the same strength , there is a
stationary classical solution approximating stationary points vortex
solution of incompressible Euler equations with vorticity .
Existence and asymptotic behavior of single point non-vanishing vortex
solutions were studied by D. Smets and J. Van Schaftingen (2010).Comment: 32page
Electrospun medicated shellac nanofibers for colon-targeted drug delivery
Medicated shellac nanofibers providing colon-specific sustained release were fabricated using coaxial electrospinning. A solution of 7.5 g shellac and 1.5 g of ferulic acid (FA) in 10 mL ethanol was used as the core fluid, and a mixture of ethanol and N,N-dimethylformamide (8/10 v/v) as the shell. The presence of the shell fluid was required to prevent frequent clogging of the spinneret. The diameters of the fibers (D) can be manipulated by varying the ratio of shell to core flow rates (F), according to the equation D = 0.52F−0.19. Scanning electron microscopy images revealed that fibers prepared with F values of 0.1 and 0.25 had linear morphologies with smooth surfaces, but when the shell fluid flow rate was increased to 0.5 the fiber integrity was compromised. FA was found to be amorphously distributed in the fibers on the basis of X-ray diffraction and differential scanning calorimetry results. This can be attributed to good compatibility between the drug and carrier: IR spectra indicated the presence of hydrogen bonds between the two. In vitro dissolution tests demonstrated that there was minimal FA release at pH 2.0, and sustained release in a neutral dissolution medium. The latter occurred through an erosion mechanism. During the dissolution processes, the shellac fibers were gradually converted into nanoparticles as the FA was freed into solution, and ultimately completely dissolved
Comparison of Volatile Compounds in Two Brandies Using HS-SPME Coupled with GC-O, GC-MS and Sensory Evaluation
The aim of this study was to compare the volatile compounds between Changyu XO and Hennessy XO. Sensoryevaluation was performed by a panel of tasters. Qualitative and semi-quantitative analysis was achieved byheadspace solid phase micro-extraction (HS-SPME), coupled with gas chromatography-mass spectrometry (GCMS)and gas chromatography-olfactometry (GC-O). A total of 160 volatile compounds were identified in the twobrands of brandy. Of these, 118 compounds were common to both Changyu XO and Hennessy XO; 18 compoundswere specific to Changyu XO and 24 were specific to Hennessy XO. A total of 85 aroma compounds responsiblefor brandy flavour were identified by GC-O, of which 68 were common to both brands, while seven and tenwere specific to Changyu XO and Hennessy XO, respectively. The study provided detailed information aboutthe compounds responsible for the characteristic flavour of specific brandies. According to statistical analysis,significant differences were recorded between Changyu XO and Hennessy XO. Most volatile compounds inChangyu XO occurred at lower concentrations than those in Hennessy XO. Based on sensory evaluation analysis,the floral, alcohol and rancid aroma descriptors achieved higher scores in Changyu XO and Hennessy XO, whilethe lime aroma seemed specific to Hennessy XO. Herb and almond aromas were specific to Changyu XO
Nanofibers fabricated using triaxial electrospinning as zero order drug delivery systems
A new strategy for creating functional trilayer nanofibers through triaxial electrospinning is demonstrated. Ethyl cellulose (EC) was used as the filament-forming matrix in the outer, middle, and inner working solutions and was combined with varied contents of the model active ingredient ketoprofen (KET) in the three fluids. Triaxial electrospinning was successfully carried out to generate medicated nanofibers. The resultant nanofibers had diameters of 0.74 ± 0.06 μm, linear morphologies, smooth surfaces, and clear trilayer nanostructures. The KET concentration in each layer gradually increased from the outer to the inner layer. In vitro dissolution tests demonstrated that the nanofibers could provide linear release of KET over 20 h. The protocol reported in this study thus provides a facile approach to creating functional nanofibers with sophisticated structural features
MIMO free-space optical communication employing subcarrier intensity modulation in atmospheric turbulence channels
In this paper, we analyse the error performance of transmitter/receiver array free-space optical (FSO) communication system employing binary phase shift keying (BPSK) subcarrier intensity modulation (SIM) in clear but turbulent atmospheric channel. Subcarrier modulation is employed to eliminate the need for adaptive threshold detector. Direct detection is employed at the receiver and each subcarrier is subsequently demodulated coherently. The effect of irradiance fading is mitigated with an array of lasers and photodetectors. The received signals are linearly combined using the optimal maximum ratio combining (MRC), the equal gain combining (EGC) and the selection combining (SelC). The bit error rate (BER) equations are derived considering additive white Gaussian noise and log normal intensity fluctuations. This work is part of the EU COST actions and EU projects
The flavor-changing bottom-strange quark production in the littlest Higgs model with T parity at the ILC
In the littlest Higgs model with T-parity (LHT) the mirror quarks induce the
special flavor structures and some new flavor-changing (FC) couplings which
could greatly enhance the production rates of the FC processes. We in this
paper study some bottom and anti-strange production processes in the LHT model
at the International Linear Collider (ILC), i.e.,
and . The results show that the production
rates of these processes are sizeable for the favorable values of the
parameters. Therefore, it is quite possible to test the LHT model or make some
constrains on the relevant parameters of the LHT through the detection of these
processes at the ILC.Comment: 12 pages, 8 figure
Entropy Driven Dimerization in a One-Dimensional Spin-Orbital Model
We study a new version of the one-dimensional spin-orbital model with spins
S=1 relevant to cubic vanadates. At small Hund's coupling J_H we discover
dimerization in a pure electronic system solely due to a dynamical spin-orbital
coupling. Above a critical value J_H, a uniform ferromagnetic state is
stabilized at zero temperature. More surprisingly, we observe a temperature
driven dimerization of the ferrochain, which occurs due to a large entropy
released by dimer states. This dynamical dimerization seems to be the mechanism
driving the peculiar intermediate phase of YVO_3.Comment: 5 pages, 4 figure
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