In tracking test, discharge is a complicated process and comparative tracking index (CTI) has wide variation. To evaluate tracking resistance, the chaos analysis of discharge current is presented based on the tracking test of phenolic resin in accordance with IEC60112. According to the characteristics of statistical self-similarity and complexity of discharge current, the largest Lyapunov exponent is calculated, and the 2-dimensional attractor of discharge current is reconstructed. Moreover, the attractors of discharge current and recurrence plots of different discharge states are reconstructed. The results indicate that the chaos attractors have different characteristics in evolutionary tracks, the topological structure and grain direction of recurrence plots show significant differences. The chaos attractor can describe the tracking process, the recurrence plot can identify the tracking state clearly, while its arithmetic is simple.

Medically, electrical impedance tomography (EIT) is a relatively inexpensive, safe, non-invasive and portable technique compared with computerized tomography (CT) and magnetic resonance imaging (MRI). In this paper, EIT_TJU_II system is developed including both the data collection system and image reconstruction algorithm. The testing approach of the system performance, including spatial resolution and sensitivity, is described through brine tank experiments. The images of the thorax physical model verify that the system can reconstruct the interior resistivity distribution. Finally, the lung ventilation functional monitoring in vivo is realized by EIT, and the visualized images indicate that the configuration and performance of EIT_TJU_II system are feasible and EIT is a promising technique in clinical monitoring application.

A method was presented to implement the detecting and tracking of moving targets through omnidirectional vision. The method combined optical flow with particle filter arithmetic, in which optical flow field was used to detect and locate moving targets and particle filter was used to track the detected moving objects. According to the circular image character of omnidirectional vision, the calculation equation of optical flow field and the tracking arithmetic of particle filter were improved based on the polar coordinates at the omnidirectional center. The edge of a randomly moving object could be detected by optical flow field and was surrounded by a reference region in the particle filter. A dynamic motion model was established to predict particle state. Histograms were used as the features in the reference region and candidate regions. The mutual information (MI) and Gaussian function were combined to calculate particle weights. Finally, the state of tracked object was computed by the total particle states with weights. Experiment results show that the proposed method could detect and track moving objects with better real-time performance and accuracy.

Optical flow method is one of the most important methods of analyzing motion images. Optical flow field is used to analyze characteristics of motion objects. According to motion features of micro-electronic mechanical system (MEMS) micro-structure, the optical algorithm based on label field and neighborhood optimization is presented to analyze the in-plane micro-motion of micro-structure. Firstly, high speed motion states for each frequency segment of micro-structure in cyclic motion are frozen based on stroboscopic principle. Thus a series of dynamic images of micro-structure are obtained. Secondly, the presented optical algorithm is used to analyze the image sequences, and can obtain reliable and precise optical field and reduce computing time. As micro-resonator of testing object, the phase-amplitude curve of micro-structure is derived. Experimental results indicate that the measurement precision of the presented algorithm is high, and measurement repeatability reaches 40 nm under the same experiment condition.

Partial transmit sequence (PTS) is a promising technique for peak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM). While in optimal PTS, an exhaustive search for all combinations of phase factor sequences is required, this results in huge computation. In this paper, by introducing the orthogonal design, a phase factor sequences algorithm is proposed. The algorithm uses orthogonal table to generate phase factor sequences, and the regular PAPR computation result is then followed by the parameter estimation. The simulation result shows that the proposed algorithm reduces the computation notably and obtains a good PAPR performance approaching the optimal PTS.

A new training symbol weighted by pseudo-noise(PN) sequence is designed and an efficient timing and frequency offset estimation scheme for orthogonal frequency division multiplexing(OFDM) systems is proposed. The timing synchronization is accomplished by using the piecewise symmetric conjugate of the primitive training symbol and the good autocorrelation of PN weighted factor. The frequency synchronization is finished by utilizing the training symbol whose PN weighted factor is removed after the timing synchronization. Compared with conventional schemes, the proposed scheme can achieve a smaller mean square error and provide a wider frequency acquisition range.

The definition of J-integral of interfacial crack was introduced. The three-point bending tests were carried out to obtain the critical loading values when the interfacial crack initiation occurred between coatings and substrates. The finite element analysis (FEA) was adopted to analyze the stress distribution in the specimens and compute the J-integral of the interfacial crack between LX88A coating and Chinese Q345 steel. The results showed that the average value of critical J-integral is 0.70 N/m, which can be taken as the fracture parameter to evaluate the interfacial fracture behavior for the three-point bending specimens of LX88A coating/Q345 steel system.

A mathematical optimization model was set up for a ground-solar combined system based on in-situexperimental results, in which the solar collector was combined serially with a ground-coupled heat pump (GCHP). The universal optimal equations were solved by the constrained variable metric method considering both the performance and economics. Then the model was applied to a specific case concerning an actual solar assisted GCHP system for space heating. The results indicated a system coefficient of performance (COP) of 3.9 for the optimal method under the serial heating mode, and 3.2 for the conventional one. In addition, the optimum solution also showed advantages in energy and cost saving, leading to a 16.7% improvement in the heat pump performance at 17.2% less energy consumption and 11.8% lower annual cost, respectively.

The international standard ISO 10303, called STEP, has been used to deal with problems in the exchange of product models and the associated data between different computer-aided systems. A platform based on STEP for managing product information is presented. This platform includes three components: a product geometry information model, a product feature model and a product visualization model. An information extracting pattern, in which information is extracted from low level elements to high level ones, is adopted in establishing the product geometry information model. Relative elements lists are created based on the extracted product information. With the traversing of these lists, feature extraction methods are proposed, which take advantage of boundary information in product model and avoid the determination of concavity and convexity of curves. Information correlating to features is stored in a structure named as feature block and the product visualization model is founded from it. The feature block is used in the platform for information communication and synchronous update among the three components.

The fracture behavior of a ceramic reinforced metal-base coating prepared by high velocity arc spraying (HVAS) technology in three-point bending test was studied. Moreover, finite element analysis (FEA) was adopted to analyze the stress distribution in the crack front. It can be found that the crack normal to the interface in the coatings occurred at the location where a fixed moment of force was reached. So the critical moment can be taken as the coating cracking criterion, which was confirmed by FEA results. In addition, the stress levels at three different locations where cracks occurred near the interface are almost the same. The results will provide reference for the design of coatings and the structure integrity evaluation of coating/substrate systems.

Based on the comprehensive forces balance model, a modified model of the formation of a single bubble in non-Newtonian fluid under constant flowrate was developed by taking account of the effect of the ingoing gas through orifice as well as its variation on the radial expansion of bubble. The modified model involves the radial expansion equation of bubble surface and the forces balance equation in vertical direction of the bubble respectively. The shape variation of bubbles formed in polyacrylamide (PAM) aqueous solutions under various conditions was predicted numerically. The practical formation of bubbles was real-time visualized and recorded by a CCD camera and a computer by means of a special laser image measurement system. Results show that the predicted shapes of the bubbles by the present model agree well with experimental observation.

In order to reduce economic and life losses due to terrorism or accidental explosion threats, reinforced concrete (RC) slabs of buildings need to be designed or retrofitted to resist blast loading. In this paper the dynamic behavior of RC slabs under blast loading and its influencing factors are studied. The numerical model of an RC slab subjected to blast loading is established using the explicit dynamic analysis software. Both the strain rate effect and the damage accumulation are taken into account in the material model. The dynamic responses of the RC slab subjected to blast loading are analyzed, and the influence of concrete strength, thickness and reinforcement ratio on the behavior of the RC slab under blast loading is numerically investigated. Based on the numerical results, some principles for blast-resistant design and retrofitting are proposed to improve the behavior of the RC slab subjected to blast loading.

Indoor environment separated with down-feed air curtain was numerically simulated and experimentally researched. Indoor airflow and temperature fields separated with air curtain were numerically simulated. Results show that both polluted airflow and thermal air current can be separated with a down-feed air curtain to prevent contaminants from spreading in the room space. In a test chamber, the smoke of burning Tibetan incense served as the source of contaminants, and the probe test shows that 1.0 μm is the prevailing diameter of the smoke particles. During the release of the smoke, the particle concentration of the indoor air was tested with a laser particle counter at the points of three different heights from the floor when the air curtain was running or not. Experimental results show that the higher the test point is located, the lower the particle concentration is, implying that the separating or isolating effect decreases as the air velocity of the curtain reduces along with the height descends. According to both simulation and experimental results, down-feed air curtain can separate indoor environment effectively when the supply air velocity of air curtain is not less than 3 m/s. In order to strengthen separation effect, it is suggested that the supply air velocity be speeded up to 5 m/s.

A system dynamics approach to urban water demand forecasting was developed based on the analysis of urban water resources system, which was characterized by multi-feedback and nonlinear interactions among system elements. As an example, Tianjin water resources system dynamic model was set up to forecast water resources demand of the planning years. The practical verification showed that the relative error was lower than 10%. Furthermore, through the comparison and analysis of the simulation results under different development modes presented in this paper, the forecasting results of the water resources demand of Tianjin was achieved based on sustainable utilization strategy of water resources.

Nonlinear m-term approximation plays an important role in machine learning, signal processing and statistical estimating. In this paper by means of a nondecreasing dominated function, a greedy adaptive compression numerical algorithm in the best m-term approximation with regard to tensor product wavelet-type basis is proposed. The algorithm provides the asymptotically optimal approximation for the class of periodic functions with mixed Besov smoothness in the L _q norm. Moreover, it depends only on the expansion of function f by tensor product wavelet-type basis, but neither on q nor on any special features of f.