To improve the classical lossless compression of low efficiency, a method of image lossless compression with high efficiency is presented. Its theory and the algorithm implementation are introduced. The basic approach of medical image lossless compression is then briefly described. After analyzing and implementing differential plus code modulation (DPCM) in lossless compression, a new method of combining an integer wavelet transform with DPCM to compress medical images is discussed. The analysis and simulation results show that this new method is simpler and useful. Moreover, it has high compression ratio in medical image lossless compression.
The article proposes a new algorithm to improve the security of image encryption based on two-dimensional chaotic maps. Chaotic maps are often used in encrypting images. However, the encryption has periodicity, no diffusion, and at the same time, the real keys space of encryption are fewer than the theoretical keys space, which consequently results in potential security problems. Thus, this article puts forward several ways to solve the problems including adding diffusion mechanism, changing the design of keys and developing a composite encryption system. It designs an algorithm for the version
Sparse decomposition is a new theory in signal processing, with the advantage in that the base (dictionary) used in this theory is over-complete, and can reflect the nature of a signal. Thus, the sparse decomposition of signal can obtain sparse representation, which is very important in data compression. The algorithm of compression based on sparse decomposition is investigated. By training on and learning electrocardiogram (ECG) data in the MIT-BIH Arrhythmia Database, we constructed an over-complete dictionary of ECGs. Since the atoms in this dictionary are in accord with the character of ECGs, it is possible that an extensive ECG datum is reconstructed by a few nonzero coefficients and atoms. The proposed compression algorithm can adjust compression ratio according to practical request, and the distortion is low (when the compression ratio is 20∶1, the standard error is 5.11%). The experiments prove the feasibility of the proposed compression algorithm.
Focusing on the problem that the ant colony algorithm gets into stagnation easily and cannot fully search in solution space, a text clustering approach based on the fusion of the ant colony and genetic algorithms is proposed. The four parameters that influence the performance of the ant colony algorithm are encoded as chromosomes, thereby the fitness function, selection, crossover and mutation operator are designed to find the combination of optimal parameters through a number of iteration, and then it is applied to text clustering. The simulation results show that compared with the classical
This article presents the formal definition and description of popular topics on the Internet, analyzes the relationship between popular words and topics, and finally introduces a method that uses statistics and correlation of the popular words in traffic content and network flow characteristics as input for extracting popular topics on the Internet. Based on this, this article adapts a clustering algorithm to extract popular topics and gives formalized results. The test results show that this method has an accuracy of 16.7% in extracting popular topics on the Internet. Compared with web mining and topic detection and tracking (TDT), it can provide a more suitable data source for effective recovery of Internet public opinions.
Core system technology is a key factor in the next generation network (NGN). A difference-less mobility management network is proposed to better support the mobility of an IP multimedia subsystem (IMS). This kind of network can provide good service and user mobility, enabling local user access to the network anywhere. User location management and session creation are analyzed. The results show that under this network architecture, the cost of the user location registration and session creation is lower than that of the home control model employed by the IMS.
To coordinate inter-cell interference, a multicell adaptive power allocation scheme is proposed for downlink orthogonal frequency division multiple access (OFDMA) cellular systems. This scheme uses the difference of the signal to interference plus noise ratio (SINR) between the co-subchannels of adjacent cells to balance SINR for coordinating the transmit power in the co-subchannels. The scheme can improve edge user performance, reduce interference between the co-subchannels of adjacent cells and improve radio resource utility. Simulation results show that the scheme can balance system performance and ensure system throughput.
Application layer multicast routing is a multi-objective optimization problem. Three routing constraints, tree's cost, tree's balance and network layer load distribution are analyzed in this paper. The three fitness functions are used to evaluate a multicast tree on the three indexes respectively and one general fitness function is generated. A novel approach based on genetic algorithms is proposed. Numerical simulations show that, compared with geometrical routing rules, the proposed algorithm improve all three indexes, especially on cost and network layer load distribution indexes.
A new mutual coupling compensation method based on a new mutual impedance matrix, as well as its application to dipole arrays, are proposed. This new mutual impedance matrix is deduced by EMF method, based on the current distribution obtained by the characteristic basis function method. It appears in a concise and explicit formulation that facilitates the numerical calculation. The compensation performance is demonstrated and evaluated through its application in DOA estimation. Numerical results show that the proposed method exhibits excellent compensation performance compared with conventional mutual impedance matrix approaches.
Two novel spherical helical antennas are designed by projecting the planar equiangular spiral antenna onto hemisphere and partial sphere surfaces. Their radiation properties are analyzed by the moment method with curved basis and test function, and the curves of the voltage standing wave ratio (VSWR), gain, polarization and pattern that change with frequency are also given, respectively. It can be seen that the circular polarization band of the novel hemispherical helical antenna is broader. The gain curve of the partial spherical helical antenna is flatter and the structure is simpler.
The optimal control of a Markov jump linear quadratic model with controlled jump probabilities of modes is investigated. Two kinds of mode control policies, i.e., open-loop control policy and closed-loop control policy, are considered. Using the concepts of policy iteration and performance potential, the sufficient condition needed for the optimal closed-loop control policy to perform better than the optimal open-loop control policy is proposed. The condition is helpful for the design of an optimal controller. Furthermore, an efficient algorithm to construct a closed-loop control policy, which is better than the optimal open-loop control policy, is given with policy iteration.
An optimized fault detection observer is designed for a class of Markov jump systems with unknown disturbances. By reconstructing the system, the residual error dynamic characteristics of unknown input and fault signals, including unknown disturbances and modeling error are obtained. The energy norm indexes of disturbance and fault signals of the residual error are selected separately to reflect the restraint of disturbance and the sensitivity of faults, and the design of the fault detection observer is described as an optimization problem. By using the constructed Lyapunov function and linear matrix inequalities, a sufficient condition that the solution to the fault detection observer exists is given and proved, and an optimized design approach is presented. The designed observer makes the systems have stochastic stability and better capability of restraining disturbances, and the given norm index is satisfied. Simulation results demonstrate that the proposed observer can detect the faults sensitively, and the influence of unknown disturbance on residual error can be restrained to a given range.
In this article, the problems of stability and robust stability analysis are investigated for a class of Markovian switching stochastic systems, which has impulses at switching instants. The switching parameters considered form a continuous-time discrete-state homogeneous Markov process. Multiple Lyapunov techniques are used to derive sufficient conditions for stability in probability of the overall system. The conditions are in linear matrix inequalities form, and can be used to solve stabilization synthesis problems. The results are extended to the design of a robust-stabilized state-feedback controller as well. A numerical example shows the effectiveness of the proposed approach.
A model construction of a multi-agent system (MAS) and the basic function of the agent are described. The precision control method using the multi-CPU of a programmable logic controller (PLC) is introduced, and a distributed method using multiple CPUs to control different motion machines is given. The test results indicate that in industrial control fields, the combination of using the credible PLC to control the motion machine and multi-CPU task distributing methods can solve multi-axis machine linkage and implication, providing a more credible method for multi-axis motion units.
This article studies a third-order trajectory planning method for point-to-point motion. All available instances for third-order trajectory planning are first analyzed. To distinguish those, three criteria are presented relying on trajectory characteristics. Following that, a fast preprocessing approach considering the trajectory as a whole is given based on the criteria constructed and system constraints. Also, the time-optimality of the trajectory is obtained. The relevant formulas are derived with the combination of geometrical symmetry of trajectory and area method. As a result, an accurate algorithm and its implementation procedure are proposed. The experimental results show the effectiveness and precision of the proposed method. The presented algorithm has been applied in semiconductor manufacturing equipment successfully.
To improve the tracking accuracy and stability of an optic-electronic target tracking system, the concept of generalized synergic target and an algorithm named error-space estimate method is presented. In this algorithm, the motion of target is described by guide data and guide errors, and then the maneuver of the target is separated into guide data and guide errors to reduce the maneuver level. Then state estimate is implemented in target state-space and error-space respectively, and the prediction data of target position are acquired by synthesizing the filtering data from target state-space according to kinematic model and the prediction data from error-space according to guide error model. Differing from typical multi-model method, the kinematic and guide error models work concurrently rather than switch between models. Experiment results show that the performance of the algorithm is better than Kalman filter and strong tracking filter at the same maneuver level.
The D0h luminescence of ZnO films deposited on p-type Si substrates is produced by metal-organic chemical vapor deposition (MOCVD). After annealing in the air at 700°C for an hour, the photoluminescence (PL) spectra, the
A two-dimensional (2D) model for the subthreshold current in the dual-material gate (DMG) silicon-on-insulator (SOI) MOSFET with a single halo is presented. The model considers single halo doping in the channel near the source and a dual-material gate to derive the channel potential using the explicit solution of the 2D Poisson’s equation. Together with the conventional drift-diffusion theory, this results in the development of a subthreshold current model for the novel structure. Model verification is carried out using the 2D device simulator ISE. Excellent agreement is obtained between the calculations and the simulated results of the model.
A 630-kVA 10.5 kV/0.4 kV three-phase high temperature superconducting (HTS) power transformer was successfully developed and tested in a live grid. The windings were wound by hermetic stainless steel-reinforced multi-filamentary Bi2223/Ag tapes. The structures of primary windings are solenoid with insulation and cooling path among layers, and those of secondary windings consist of double-pancakes connected in parallel. Toroidal cryostat is made from electrical insulating glass fiber reinforced plastics (GFRP) materials with room temperature bore for commercial amorphous alloy core with five limbs. Windings are laid in the toroidal cryostat so that the amorphous core operates at room temperature. An insulation technology of double-half wrapping up the Bi2223/Ag tape with Kapton film is used by a winding machine developed by the authors. Fundamental characteristics of the transformer are obtained by standard short-circuit and no-load tests, and it is shown that the transformer meets operating requirements in a live grid.