Showing papers by "Beijing University of Posts and Telecommunications published in 1997"
TL;DR: It is found that under certain conditions spatiotemporal hyperchaos with a huge number of positive Lyapunov exponents can be synchronized by simply driving a single site, and the mechanism for this efficiency is analyzed.
Abstract: Synchronization of spatiotemporal chaos is investigated, based on the models of one-way coupled map lattice systems. It is found that under certain conditions spatiotemporal hyperchaos with a huge number of positive Lyapunov exponents can be synchronized by simply driving a single site, and the mechanism for this efficiency is analyzed. This approach of spatiotemporal chaos synchronization is applied for multichannel secure communication and secure information storage.
47 citations
TL;DR: In this article, the domain structures of the NdFe10.5Mo1.5 and Nd Fe10.6Mo 1.5Nx were studied by using magnetic force microscopy and a domain structure transition from complex maze to simple stripe was found.
Abstract: We succeed in preparing anisotropic magnetic powders with high performance based on the NdFe10.5Mo1.5Nx nitrides. The properties of these materials are favorable for permanent magnet application. The domain structures of the NdFe10.5Mo1.5 and NdFe10.5Mo1.5Nx were studied by using magnetic force microscopy. Upon nitrogenation, a domain structure transition from complex maze to simple stripe was found. This transition is due to the strongly uniaxial magnetocrystalline anisotropy induced by interstitial nitrogen atoms. Together with magnetic measurements, we have calculated the domain wall energy γ, exchange constant A, domain wall thickness δ, and critical single-domain particle size Dc of NdFe10.5Mo1.5 and NdFe10.5Mo1.5Nx.
36 citations
TL;DR: In this article, the spin-polarized muffin-tin-orbital method was applied to calculate the electronic structures of the lattice of the Fe-Mo lattice.
Abstract: Neutron diffraction was used to determine the crystallographic structures of the ${\mathrm{YFe}}_{10}{\mathrm{Mo}}_{2}$ and ${\mathrm{YFe}}_{10}{\mathrm{Mo}}_{2}X$ $(X$=H,N). The spin-polarized muffin-tin-orbital method was applied to calculate the electronic structures of ${\mathrm{YFe}}_{10}{\mathrm{Mo}}_{2}X$ $(X$=H,B,C,N,O,F) and ${\mathrm{YFe}}_{10}{\mathrm{Mo}}_{2}E$, which is ${\mathrm{YFe}}_{10}{\mathrm{Mo}}_{2}$ with an empty sphere insertion. Both N and H atoms were found to reside on the interstitial $2b$ sites. The magnetovolume effect and chemical bonding effect of interstitial $X$ atoms are investigated by a systematic analysis of the local magnetic moments ${\ensuremath{\mu}}_{\mathrm{loc}},$ Fermi-contact hyperfine fields ${(H}_{\mathrm{FC}})$, and isomer shifts (IS) at different Fe sites in ${\mathrm{YFe}}_{10}{\mathrm{Mo}}_{2}X$ $(X$=H,B,C,N,O,F) and ${\mathrm{YFe}}_{10}{\mathrm{Mo}}_{2}E$. It is found that the insertion of the $X$ atom changes not only Fe-Fe interaction, but also Fe-$X$ interaction, and the latter is dependent on the chemical properties of $X$ atoms. It can be concluded that, based on our results, the chemical bonding effect in $R\ensuremath{-}(\mathrm{F}\mathrm{e},\mathrm{M}{)}_{12}\ensuremath{-}X$ is determined by the features of the Fe-$X$ bonds. The role of the $X$ atom is not only to increase the magnetic moments and hyperfine fields through magnetovolume effects, but also to affect those by chemical-bonding effects. The chemical-bonding effect is strongly dependent on the $X$ atom.
22 citations
04 Jun 1997
TL;DR: This paper presents a robust adaptive controller for time-varying systems with an unknown backlash nonlinearity at the plant input based on the pole assignment strategy, applicable even to systems in the presence of unmodeled dynamics, bounded external disturbances, and time- varying parameters.
Abstract: This paper presents a robust adaptive controller for time-varying systems with an unknown backlash nonlinearity at the plant input. The controller is designed based on the pole assignment strategy, and it is applicable even to systems in the presence of unmodeled dynamics, bounded external disturbances, and time-varying parameters. No minimum phase assumption and no persistence of excitation requirement are needed. The global stability is ensured by the proposed controller.
17 citations
20 Oct 1997
TL;DR: In this paper, the inorganic compounds in the airborne dust collected indoors at Beijing University of Post and Telecommunications have been analyzed by jointly using X-ray powder diffraction (XRPD), electron probe microanalysis (EPMA) and transmission electron microscopy (TEM).
Abstract: The inorganic compounds in the airborne dust collected indoors at Beijing University of Post and Telecommunications has been analyzed by jointly using X-ray powder diffraction (XRPD), electron probe microanalysis (EPMA) and transmission electron microscopy (TEM). The results showed that the dust was composed of up to 24 compounds, including quartz, feldspar, mica and calcite etc.. The distilled water separation method effectively enabled size separation of airborne particles. In analysis of airborne particles, combined application of three methods, i.e., XRPD, EPMA and TEM, can provide comprehensive and reliable results. In the studies of dust contamination on electrical contacts, soft dust particles may contribute to the electrical contact failures; their effects can not be ignored.
17 citations
TL;DR: In this article, the dispersion-decreasing-allocated fiber was optimized to realize long amplifier spacing, long-distance soliton transmission, and to realize soliton bidirectional transmission.
Abstract: In order to realize long amplifier spacing, long-distance soliton transmission, dispersion-allocated fiber was optimized. Dispersion-decreasing-allocated fiber is favorable to transmit stable solitons over long distances. Fiber loss plays an important role in stable soliton transmission with the dispersion-allocated fibers. In order to realize soliton bidirectional transmission, symmetrical configuration of the dispersion-allocated fiber within an amplifier spacing must be designed, so the dispersion-decreasing-allocated fiber is not favorable to soliton bidirectional transmission.
13 citations
TL;DR: In this paper, the maximal number of non-principal prime ideals which can divide a square-free element of R with at most k distinct factorizations into irreducible elements was derived.
Abstract: 0. Let K be an algebraic number field with classgroup G and integer ring R. For k ≥ 1 and a real number x > 0, let ak = ak(G) be the maximal number of nonprincipal prime ideals which can divide a squarefree element of R with at most k distinct factorizations into irreducible elements, and let Fk(x) be the number of elements α ∈ R (up to associates) having at most k different factorizations into irreducible elements of R. W. Narkiewicz [8] derived the asymptotic expression
12 citations
TL;DR: In this paper, a reverse force analysis of a spatial three-spring system is presented which determines equilibrium positions when an external force is applied, and corresponding pairs of the remaining two spring lengths are computed, which determine the multiple equilibrium positions.
11 citations
TL;DR: In this paper, the closed-form solution of equilibrium situations of a special planar three-spring system exerted by given static forces was studied, and a 54th degree polynomial in one unknown was obtained.
11 citations
TL;DR: In this paper, the authors proposed an optimum power control and several centralised power control algorithms for CDMA/TDMA cellular systems, which outperformed the perfect average power control algorithm by 1.9 dB under the IS-95 defined radio condition.
Abstract: Efficient power control is of great importance in the design of high capacity cellular radio systems. Optimum power control scheme, in the sense that it minimises the outage probability, has been fully investigated for FDMA/TDMA cellular systems. The authors propose optimum power control and several centralised power control algorithms for CDMA cellular systems. Simulation results indicate that the optimum power control scheme outperforms the perfect average power control algorithm by ~1.9 dB under the IS-95 defined radio condition.
9 citations
TL;DR: Computer simulation results indicate that the Volterra filter behaves better than a linear transverse filter.
Abstract: The Volterra adaptive prediction of the multipath fading channel is studied. The performances of the Volterra filter and the conventional linear transverse filter are compared. Computer simulation results indicate that the Volterra filter behaves better than a linear transverse filter.
12 Oct 1997
TL;DR: An open-loop power control scheme in the CDMA/TDD system is presented, which is based on the adaptive prediction of the multipath fading channel, and the Volterra based nonlinear filter provides the optimum performance.
Abstract: An open-loop power control scheme in the CDMA/TDD system is presented, which is based on the adaptive prediction of the multipath fading channel. The linear and nonlinear adaptive prediction filters are studied. Computer simulations show that this scheme can achieve the precise power control even in the worse fading channel, and the Volterra based nonlinear filter provides the optimum performance.
09 Jun 1997
TL;DR: The multiplex weight to balance the token rate of all services in one multiplexer is proposed and the fuzzy control rules which based on expert experience are suitable to all sorts of services in the authors' example.
Abstract: This paper presents a multiplexer controlled by fuzzy associate memory leaky bucket in ATM networks. It is a good dynamic usage parameter control mechanism. The number of connections and the quality of service can be improved properly. We propose the multiplex weight to balance the token rate of all services in one multiplexer. The fuzzy control rules which based on expert experience are suitable to all sorts of services in our example.
09 Sep 1997
TL;DR: This paper modified this coupled-map spatiotemporal chaos so that it could be implemented by digital hardware and the concept of a cascaded receiver for local synchronization detection was proposed.
Abstract: This paper studied the driving synchronization behavior of coupled logistic-map spatiotemporal chaos. Under appropriate parameters, we modified this coupled-map spatiotemporal chaos so that it could be implemented by digital hardware. We applied this synchronization behavior to a CDMA communication system. For local synchronization detection, we proposed the concept of a cascaded receiver. The computer simulation showed that the digital hardware implementation and cascaded receiver synchronization detection are possible.
04 May 1997
TL;DR: In this article, a closed-form formula is derived to show an important fact that 1 dB standard deviation of the received SIR corresponds to 2.3 dB reduction of the CDMA reverse link capacity.
Abstract: With fast close-loop power control, slowly varying power control errors, which cannot be eliminated by coding and interleaving, have been found lognormally distributed in the received SIR and may result in great performance reduction. In this paper, a closed-form formula is derived to show an important fact that 1 dB standard deviation of the received SIR corresponds to 2.3 dB reduction of the CDMA reverse link capacity.
09 Jun 1997
TL;DR: In this article, the properties of a lossless bandpass ladder network composed of two kinds of resonant sections consisting of lumped and distributed elements are investigated and necessary and sufficient conditions for realization are given.
Abstract: This paper investigates the properties of a lossless bandpass ladder network composed of only two kinds of resonant sections consisting of lumped- and distributed-elements and gives the necessary and sufficient conditions for realization. These conditions can be regarded as a direct generalization of the necessary and sufficient conditions for LC bandpass ladder networks proposed previously.
08 Jun 1997
TL;DR: This paper proposes the customer-oriented and network engineer-oriented definitions of restoration mechanism availability and proves that two availabilities can evaluate restoration mechanisms more sufficiently and more meaningfully.
Abstract: Network/service survivability is an important problem demanding prompt solution in the design and planning of new telecommunications networks (e.g., SDH networks and ATM networks). Different restoration mechanisms for SDH and ATM networks have already been developed. The previous literature comparing and evaluating the restoration mechanisms only uses a simple method. In order to overcome the shortcomings in the traditional method, this paper proposes the customer-oriented and network engineer-oriented definitions of restoration mechanism availability. In the second definition, the extra spare capacity requirement in the network is taken into account in the availability analysis. Because an exact measurement of the availability is not feasible due to the large number of failure states in the network, an ORDER algorithm (Li and Silverter 1984) to get a reasonable subset to approximately measure the availability is recommended. Then, applications of the definitions are given. One application is how this definition is used by network planner/engineer to construct a cost-effective survivable network. Another application is that a new group of parameters-survivability quality of service (SQoS) is defined and added to CAC (connection admission control) of the ATM survivable network. Finally, a simulation using two definitions is performed. The simulation results prove that two availabilities can evaluate restoration mechanisms more sufficiently and more meaningfully.
04 May 1997
TL;DR: In this article, the authors proposed an optimum power control and several centralized power control algorithms for CDMA/TDMA cellular systems, and the simulation results indicate that the optimal power control scheme outperforms the perfect average power control algorithm by approximately 1.9 dB under IS-95 defined radio condition.
Abstract: Efficient power control is of great importance in the design of high capacity cellular radio systems. An optimum power control scheme, in the sense that it minimizes the outage probability, has been fully investigated for FDMA/TDMA cellular systems. In this paper, the optimum power control and several centralized power control algorithms are proposed for CDMA cellular systems. Simulation results indicate that the optimum power control scheme outperforms the perfect average power control algorithm by approximately 1.9 dB under IS-95 defined radio condition.
01 Jan 1997
TL;DR: The concept of SLB is given, and the service is formally described in the syntax, behavior, and semantics way, which provides an approach to resolve the service interaction in the service specification phase.
Abstract: On the basis of reviewing the basic concept of IN and life cycle of the service, this paper gives the concept of SLB, and formally describes the service in the syntax, behavior, and semantics way, which provides an approach to resolve the service interaction in the service specification phase.
09 Jun 1997
TL;DR: A high throughput ATM switch is proposed which consists of neural network controlled Banyan network with input-output-queueing, and a method of hardware implementation is given.
Abstract: The Banyan network is a kind of multistage interconnection networks (MINs), and the most popular to be used as a basic building block in ATM switch fabric designs. The neural networks scheduling of MINs has been proposed in some papers, but its hardware implementation is complicated. In this paper we propose a high throughput ATM switch which consists of neural network controlled Banyan network with input-output-queueing, and give a method of hardware implementation. Its neural network controller is very simple.
01 Jul 1997
TL;DR: This work presents six mechanisms using priority leaky buckets to police traffic with different priority-classes of cells in ATM networks, using two token generators and two token pools.
Abstract: There are different priority classes of cells in ATM networks. The policing mechanisms seen in the literature only can police total traffic amount or total rate because they only use one token generator and one token pool. We present six mechanisms using priority leaky buckets to police traffic with different priority-classes of cells. All the policing mechanisms use two token generators and two token pools. They can distinguish the classes of arriving cells. They can police the rate of class-0 traffic as well as the total rate of the priority traffic. Their performance are studied through simulations.
TL;DR: The following results are proven in this paper: 1) neither periodic autonor cross-correlation of the truncated Costas optical orthogonal code (TC OOC) is upper bounded by 1; 2) TC OOC is a class of (/spl omega/(2p-3), /spl omega/,2,2) optical Orthogonal codes.
Abstract: The following results are proven in this paper: 1) neither periodic autonor cross-correlation of the truncated Costas optical orthogonal code (TC OOC) is upper bounded by 1; 2) TC OOC is a class of (/spl omega/(2p-3), /spl omega/,2,2) optical orthogonal codes.
02 Dec 1997
TL;DR: The threshold of visibility of MPEG-2 ES, PES and TS in the form of bit error rate (BER) are studied, compared and analyzed and the error code performance is evaluated.
Abstract: The transmission error code performance of an MPEG-2 transport system is studied, by analyzing the sensitivity of MPEG-2 ES, PES and TS to the transmission error code. The reconstructed images decoded from ES, PES and TS with the transmission error code are used to evaluate the error code performance. On this basis, the threshold of visibility (TOV) of MPEG-2 ES, PES and TS in the form of bit error rate (BER) are studied, compared and analyzed.
21 May 1997
TL;DR: In this article, a new concept, power flux turning, is proposed to analyze the absorbing materials' characteristics by the method of the power flux, and found that power flux turns relates strongly with the absorbing material's characteristics.
Abstract: Presently the electromagnetic characteristics of absorbing materials have been partly studied on basis of Maxwell equations. However, a thorough study for a physics view-point is obviously insufficient. A new concept, power flux turning, is proposed. We analyzed the absorbing materials' characteristics by the method of the power flux, and found that power flux turning relates strongly with the absorbing materials' characteristics. Power flux turning keeps the absorbing materials' characteristics against improving.
TL;DR: In ATM networks, bursty sources can be described as the Interrupted Bernoulli Process (IBP), and it is proposed that the leaky bucket output process can be approximately described as this process.
Abstract: In ATM networks, bursty sources can be described as the Interrupted Bernoulli Process(IBP). With the use of the thin process theory, the Probability Generating Function(PGF) of the IBP is obtained. An iterative algorithm, which can be used to calculate the IBP probability distribution, is presented. The bursty source’s equivalent description is discussed. It is proposed that the leaky bucket output process can be approximately described as the IBP. The accuracy of the analytical results has been largely validated by means of the simulation approach. Moreover, how to improve its accuracy is discussed. The smoothing function of the leaky bucket algorithm is quantitatively analyzed.
03 Nov 1997
TL;DR: An integrated restoration application (IRA) in the ATM network is proposed, which combines a VP protection switching (VP PS) mechanism, a distributed restoration algorithm (DRA) and a centralized restoration algorithms (CRA) on the ATM VP level.
Abstract: This paper proposes an integrated restoration application (IRA) in the ATM network, which combines a VP protection switching (VP PS) mechanism, a distributed restoration algorithm (DRA) and a centralized restoration algorithm (CRA) on the ATM VP level. The IRA can achieve cost-effective survivability performance inter-working with the service classes of survivability and the restoration plan. The implementation of the IRA in the Alcatel ATM test environment is presented, and the relative test results and analysis are also given. Finally, the issues of standardization are discussed.
TL;DR: In this paper, explicit formulas for cross-correlation functions of linearly related generalized geometric sequences are derived, thus an open problem proposed by Klapper et al. (1993) is partially solved.
29 Jun 1997
TL;DR: In this paper, a family of p-ary sequences called pseudo-generalized geometric sequences (PGGS) are constructed, and correlations of PGGSs and geometric sequences are also calculated.
Abstract: A family of p-ary sequences called pseudo-generalized geometric sequences (PGGS) are constructed, and correlations of PGGSs and geometric sequences are also calculated. The main result shows that the correlation property is good if the functions from GF(q) to GF(p) are permutation polynomials.
21 Apr 1997
TL;DR: A new efficient image coding scheme, based on quadtree representation and block entropy coding (QRBEC), for encoding the wavelet transform coefficients of images is presented and the property of HVS is incorporated into the quantization process.
Abstract: A new efficient image coding scheme, based on quadtree representation and block entropy coding (QRBEC), for encoding the wavelet transform coefficients of images is presented. The property of HVS is also incorporated into the quantization process. In addition, how to flexibly control the quantization level as well as output bitrate of the coder is also investigated. The coding efficiency of the coder is quite competitive with the well-known EZW coder, and requires less computation burden. The proposed coding scheme can also be applied in image sequence coding, resulting in satisfactory performance.