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Biomedical subjects

Weihong Huang

Publications and source records attributed to Weihong Huang.

8 recordsLinked to original sources
PubMed2006

Operator expansions for polarization mode dispersion analysis and compensation.

We present analytic third- and fourth-order expansions of the Jones matrix as products of exponentials of individual matrices. In our first formalism, these are polarization mode dispersion (PMD) matrices of definite orders. We then discuss an alternative procedure that instead employs exponentials of general skew-Hermitian matrices with a low-order dependence on the deviation of the optical frequency from a central reference frequency. Our expressions correspond to PMD compensators formed from a succession of relatively simple optical components each of which has the frequency response of a single operator in the product.

Journal Article↗
PubMed2006

Polarization mode dispersion in short fiber lengths.

We perform Monte Carlo simulations of the statistical properties of the differential group delay for fiber lengths less than and of the order of the birefringence correlation length. We find that the manner in which quantities related to the polarization mode dispersion evolve along the fiber depends significantly on the model assumed for the form of the birefringence.

Journal Article↗
PubMed2005

Chebyshev and Taylor approximations of polarization mode dispersion for improved compensation bandwidth.

We examine a series of experimentally realizable procedures for wide-bandwidth polarization mode dispersion compensation based on Taylor and Chebyshev approximations to the transfer matrix for light polarization in optical fibers. Our results demonstrate that a symmetric ordering of compensator elements in the Taylor procedure improves performance and that methods based on the Chebyshev approximation can significantly widen the compensation bandwidth.

Journal Article↗
PubMed2005

Multicanonical comparison of polarization-mode dispersion compensator performance.

We employ a modified version of the multicanonical algorithm to evaluate the system penalties and outage probabilities of different polarization-mode dispersion compensators. The procedure determines the optimal operating conditions for each compensator architecture far more efficiently than the standard Monte Carlo algorithm.

Journal Article↗
PubMed2004

On the long-run average growth rate of chaotic systems.

For a discrete dynamical process defined by Xt=F(X(t-1),X(t-2),...,X(t-k)), where Xt subset R+n, the growth rate for the ith endogenous variable is conventionally defined as g(it) identical with (x(it+1)-x(it))/x(it). It is shown that, when the trajectories of x(it) exhibit periodic or aperiodic (chaotic) fluctuations within a bounded range, the long-run average growth rates are always positive, that is, g(it) identical with lim(T--> infinity )1/TSigmaTt=1 g(it) > 0, for all i, so as to induce an illusion of growth. The fact is generic in the sense of being irrespective of the dynamic structure of F. Moreover, the same characteristic exists even if the process is reversed. Economic implications and applications are discussed. It is concluded that the statistical inequalities provide additional measures to check the validity of different discrete models or to test different specifications from empirical time series.

Computer Simulation↗
PubMed2003

An organic solvent-free microwave-assisted extraction of some priority pollutants of phenols in lake sediments.

Alkaline water was used for the microwave-assisted extraction of some priority pollutants of phenols in sediments, i.e. phenol (Ph), 2-chlorophenol (2CP), 2,4-dichlorophenol (2,4DCP), 4-chlorophenol (4CP), 4-dinitrophenol (4NP) and pentachlorophenol (PCP). This organic solvent-free extraction procedure was optimized by studying the parameters such as pH, volume of the alkaline water, extraction pressure and time. Under the optimized conditions, the recoveries of phenols were in the range of 80% to 110%. The extracts were then cleaned-up and concentrated by microcolumn solid phase extraction (SPE) and determined by gas chromatography-flame ionization detection system. The relative standard deviation of the overall-method for most phenol determinations was about 5.0% (n = 6). The proposed method, which needs little volume (1 mL) of ethanol for SPE, has been applied to determine these phenols in sediment samples, and the analytical results are in good agreement with those achieved by Soxhlet extraction.

Journal Article↗
PubMed2002

Stabilizing coupled map lattice systems with adaptive adjustment.

The adaptive adjustment mechanism is applied to stabilization of a general coupled-map lattice system defined by x(i,t+1)=f(x(i,t))+C(i)(x(i,t),x(i-1,t))+D(x(i,t),x(i-1,t)), where f: R-->R is a nonlinear map, and C(i),D(i): R2-->R are coupling functions that satisfy C(i)(x,x)=0 and D(i)(x,x)=0, for all x in R, i=1,2, em leader,n. Sufficient conditions and ranges of adjustment parameters that guarantee the local stability of a synchronized fixed point are provided. Numerical simulations demonstrate the effectiveness and efficiency for this mechanism to stabilize the system to an originally unstable synchronized fixed point or a periodic orbit.

Journal Article↗