A Class of Traveling Wave Solutions to Some Nonlinear Partial Differential Equations

For the Noyes-Fields equations, two-dimenslonal hyperbolic equations of conversation laww and the Burgers-KdV equation, a class of travellng wave solutions has been obtained by constructhag appropriate function transformations. The main idea of solving the equations is that nonlinear partial differential equations are changed into solving algebraic equations. This method has a wide-ranging practicability.

Some Special Types of Solitary Wave Solutions for （3＋1）-Dimensional Jimbo-MiwaEquation

Using the extended homogeneous balance method, we find some special types of single solitary wave solution and new types of the multisoliton solutions of the (3+1)-dimensional Jimbo-Miwa equation.

Baeicklund Transformation and Multiple Soliton Solutions for （3＋1）-Dimensional Potential-YTSF Equation

We study an approach to constructing multiple soliton solutions of the (3+1)-dimensional nonlinear evolution equation. We take the (3+1)-dimensional potential- YTSF equation as an example. Using the extended homogeneous balance method, one can find a Backlund transformation to decompose the (3+1)-dimensional potential-YTSF equation into a set of partial differential equations. Starting from these partial differential equations, some multiple soliton solutions for the (3+1)-dimensional potential-YTSF equation are obtained by introducing a class of formal solutions.

Application of transmit diversity for improved robust watermarking

Many common multimedia signal processing, including cropping, filtering, and perceptual coding, make watermark signal fading-like modification. A scheme that applies transmit diversity technique to improve robustness of digital watermarking is presented. First, the scheme decomposes the original image using wavelet pyramid algorithm and chooses the middle-frequency band for transmission channel that the watermark will be embedded into. Then the watermark is pseudo-randomly permuted. The scheme makes use of space-time coding and differential detection technique to embed and extract watermark. The extracting process has access to neither the original image nor channel state information. Experimental results demonstrate that the scheme improves the performance of robust watermarking.

Abundant Multisoliton Structure of the （3 ＋ 1）-Dimensional Nizhnik-Novikov-VeselovEquation

Using the extended homogeneous balance method, we obtained abundant exact solution structures ofthe (3 + 1)-dimensional Nizhnik-Novikov-Veselov (NNV) equation. By means of the leading order term analysis, thenonlinear transformations of the (3+1)-dimensional NNV equation are given first, and then some special types of singlesolitary wave solution and the multisoliton solutions are constructed.

A New Modified Extended Tanh-Function Method and Its Application

In this paper, a new modified extended tanh-function method is presented for constructing soliton-like,periodic form solutions of nonlinear evolution equation (NEEs). This method is more powerful than the extended tanhfunction method [Phys. Lett. A277 (2000) 212] and the moditied extended tanh-function method [Phys. Lett. A285(2001) 355]. Abundant new solutions of two physically important NEEs are obtained by using this method and symbolic computation system Maple.

Abundant Multisoliton Structure of （3＋1）-Dimensional Breaking Soliton Equation

Using the extended homogeneous balance method, we obtained abundant exact solution structures of the (3+ 1 )-dimensional breaking soliton equation. By means of the leading order term analysis, the nonlinear transformations of the (3t1)-dimensional breaking soliton equation are given first, and then some special types of single solitary wave solutions and the multisoliton solutions are constructed.

New Explicit Exact Solutions for the （2＋1）-Dimensional Higher-Order Broer-Kaup System

Using the modified extended tanh-function method,explicit and exact traveling wave solutions for the(2+1)-dimensional higher-order Broer-Kaup(HBK)system,comprising new soliton-like and period-form solutions,are obtained.

New Families of Exact Solutions for （2＋1）-Dimensional Broer-Kaup System

Using a further modified extended tanh-function method, rich new families of the exact solutions for the (2+ 1)-dimensional Broer-Kaup (BK) system, comprising the non-traveling wave and coefficient functions' soliton-like solutions, singular soliton-like solutions, periodic form solutions, are obtained.

A New Communication Scheme for Threshold Certificate Authority in Ad Hoc Networks

We present a new approach to reduct the com--munication overhead caused bythreshold cryptography using modified multicast protocol and certificate proxy technology. Servernodes maintain a few multicast groups proactively. A client wanting to updateits certificatemulticasts its request to a server nocks group through its certificate proxy. At periodic intervals,server nodes refresh their shares of the private key of certificate authority using multicast.

The Effect of Phase-Shifting between Pumping and Signal Lights on Transmission Performance of Optical Fiber Communication Systems with in-Line PSA

In this paper, the effect of phase-shifting between pumping lightand input signal light in a optical Phase-Sensitive Amplifier(PSA)ondispersion compensation for optical fiber communication systems usingPSA as In-line amplifiers is theoretically analyzed by computersimulation. From ur simulation we've got the result that Theeye-pattern degradation of the high-speed signal increase rapidlywith the accretion of fiber dispersion and also Increase with theincreasing of phase shift. But if the phase shift is controlled in acertain range, it won't affect the System performance. Otherwise, thesystem performance will be seriously degraded. At all events, theshifting Range of PSA's phase, which shifts at both sides of zero,will be half of that which shifts at only one side.

A Study of Handoff in CDMA Systems

Based on the analysis of CDMA handoff, an improved two threshold soft handoff scheme is proposed and analyzed in detail theoretically. Combining with the minimum dwelling time method, we propose a hybrid handoff scheme and compare its performance with that of conventional guard channel scheme and minimum dwelling time scheme, respectively. Results show that the suggested scheme is of good performance.

The Research of ST-OFDM in Physical Layer of IEEE 802.16a

This paper briefly introduces one of the three physical layer implementations of IEEE 802.16a~[1],WirelessMAN-OFDM PHY.Based on the implementation,the combination of Orthogonal Frequency Division Multiplexing(OFDM)and Space-Time Coding(STC)which is briefly called ST-OFDM in IEEE 802.16a,is investigated under thechannel provided in Ref.[2].Especially,this paper is focused on the influence of the optimal decision threshold on the sys-tern Bit-Error-Rate(BER)performance based on unequal probabilities of sources.The simulations show that when Signal-Noise-Ratio(SNR)is low the optimal decision threshold is obviously superior to the usual one;when SNR is high to someextent,such as 10 dB for 4QAM and 16 dB for 16QAM,we can use the usual decision threshold instead of the optimal

Complex dynamical behaviors in modulation-doped GaAs/Al_xGa_(1-x)As heterostructures

We study dynamics of the forced modulation-doped GaAs/AIGaAs heterostructure de-vices . The coupled differential equations governing the dynamical behaviors are numerically simulated. Biased with an appropriate dc field, the system exhibits two states: spontaneous current oscillation and fixed points. By imposing an ac driving force, the dynamical system shows frequency locking, quasiperiodicity, and chaos, which are sensitive to the amplitude and frequency of the externally ap-plied periodical microwave field. The basins of attraction of both ordinary attractors and strange attrac-tors are presented.