Applied Mechanics and Materials Vols. 66-68

Abstract: Harmful algal blooms (HABs) are generally known as excessive phytoplankton growth or rapidly concentrate to high biomass. This study summarized the situation of HABs in China, and discussed possible dominant factors stimulating algal blooms by analyzing several actual HABs cases. It was manifested nutrients may affect algae concentration principally, but such impact tended to decease with degradation of background water. Meanwhile the hydrological and meteorological factors expressed greater correlation to chlorophyll concentration under multiple coupling effects of complex environmental factors. For the complex mechanisms, the determination of principle factors which stimulate excessive algal blooms effectively still need further researches, which are suggested to conduct under overall considerations on 3 scales: macro dimension, medium dimension and micro dimension.

Abstract: Mg₂Si particle reinforced hypereutectic Al-Si composite was prepared by direct melt reaction, and the effects of Mg₂Si content on the microstructure of the composite were researched. The results indicated that the morphology of Mg₂Si obviously changed with Mg₂Si contents increasing, in which the morphology of Mg₂Si in the composite had changed from polygon block to characters like and finally became coarse dendrite. Formation of α-Al grains in the composites with the high Si and Mg content was discussed.

Abstract: A numerical model has been build up to study temperature evolution and metal flow for the indirect extrusion of 6005A aluminium alloy. Model validation was carried out by comparison between experiments and simulations. Results show a good agreement with each other. The influence of the extrusion parameters on the profile temperature and metal flow were studied according to the real industrialized process. It was found that the profile temperature increases with the ram speed as well as the peak load of the total press force. However, a too slow extrusion process would cause increasing of the total force at the end of the extrusion because of heat dissipation to the environment. In addition the dead metal zone at the top of the billet was shrunk during the extrusion process. The ram speed would have little influence on the distribution and shape changing of dead metal zone. Once the extrusion went into steady stage, the strain rate of metal flow would keep a stable situation relatively.

Abstract: Two novel polyurethanes (PU) with alternating and random block architectures, hydroxyl-terminated polybutadiene (HTPB)/polyethylene glycol (PEG) block copolymers, HTPB-alt-PEG and HTPB-co-PEG, were synthesized via a coupling reaction route between hydroxyl groups and isocyanate groups. The structural and crystal characterization was conducted by means of FTIR, and phase behavior was examined by SEM and DSC. The biodegradation in a simulated human body fluid was investigated through mass loss and SEM. The experimental results indicate that all polyurethane samples form the microphase separation structure, and the separation degree depended on their sequence structure and the molecular weight (MW) of PEG, and further affecte their in-vitro degradation.

Abstract: In the recent two decades, Advanced Manufacturing Technology (AMT) has been deeply applied in every aspect of manufacturing system, which has made great impacts on manufacturing industry and caused great changes. This paper has studied the deep impacts of AMT on manufacturing industry at the aspects of modeling mode, design mode, design test and evaluation method, working mode and production organization mode.

Abstract: Based on NGSIM empirical trajectory data, we focus on verifying the correlations among various parameters in car-following models. The data is preprocessed primarily by symmetric exponential moving average filter. Then, based on SPSS, we explore the preprocessed NGSIM trajectory data by plotting scatter diagram and correlation analysis. The results show that the acceleration of the following vehicle is obviously proportional to the velocity difference and acceleration difference between the following and the preceding (next preceding) vehicle, as well as the product of such velocity difference and the following vehicle’s velocity. Furthermore, we analyze the delay time by using time series correlation formula and modified R/S and V/S statistics methods.

Abstract: According to the rule of non-sinusoidal oscillation of continuous casting mold, a mathematical model was established to study the effects of oscillation parameters on the consumption rate of mold flux. The results indicated that the mold flux consumption rate is remarkably affected by the non-sinusoidal factor. This proves that the non-sinusoidal oscillation of mold contributes to increase the flux consumption. Moreover, the amplitude and frequency of mold oscillation have effects on mold flux consumption rate. The non-sinusoidal oscillation parameters must be optimized.

Abstract: A transient analysis mathematic model was established via ANSYS. The variation laws of magnetic induction density, induced eddy current and electromagnetic force in molten steel changing with the high frequency sine exciting current were investigated. The results indicate that the magnetic induction density and induced eddy current in molten steel vary at the same frequency as exciting current. Moreover, the variations of magnetic induction density and induced eddy current are not in step with exciting current. This proves that the high frequency electromagnetic field in mold and steel is not a time-harmonic wave. The electromagnetic force varies at the double frequency of the exciting current. When the exciting current reaches the amplitude value, the electromagnetic force is close to the max value, whereas when the exciting current returns to zero, the electromagnetic force is not zero. At the same time, there is partial electromagnetic force reversing its direction. If the reversed electromagnetic force is expanded seriously, the fluctuation of liquid level is induced, so it must be controlled.

Abstract: Parametric effect on bidirectional moving vehicle load identification from plate bridge responses is studied in this paper. The equation of motion of a plate bridge-bidirectional vehicle system is formulated based on Hamilton principle and is rewritten in a state space form, the bidirectional moving load identification problem is considered as a damped least-squares problem and further solved with the regularization method. Finally, the effect of parameters on identification accuracy is investigated in order to evaluate the effectiveness and robustness of the bidirectional moving load identification method proposed in a companion paper. Some numerical simulations show that the proposed method is correct and effective for identifying the bidirectional moving vehicle loads from bridge responses with an acceptable accuracy, but the selection of parameters should be carefully considered in the identification process.

Abstract: The stabilization problem of a system without parameter uncertainties can always be transferred to a tracking problem if it is no need to consider the robustness requirement of a system. But those two questions are not the same for a missile control systems. In this paper, the uncertainties of parameters are considered, and we found that the stabilization problem can not be transferred to a tracking problem.