Decentralized adaptive generalized predictive control for structural vibration

A decentralized generalized predictive control (GPC) algorithm is developed for strongly coupled multi-input multi-output systems with parallel computation. The algorithm is applied to adaptive control of structural vibration. The key steps in this algorithm are to group the actuators and the sensors and then to pair these groups into subsystems. It is important that the on-line identification and the control law design can be a parallel process for all these subsystems. It avoids the high computation cost in ordinary predictive control,and is of great advantage especially for large-scale systems.     

Active control of structural vibration with on-line secondary path modeling

An active control strategy with on-line secondary path modeling is proposed and applied in active control of helicopter structural vibration. Computer simulations of the secondary path modeling performance demonstrate the superiorities of the active control strategy. A 2-input 4-output active control simulation for a helicopter model is performed and great reduction of structural vibration is achieved. 2-input 2-output and 2-input 4-output experimental studies of structural vibration control for a free-free beam are also carried out in laboratory to simulate a flying helicopter. The experimental results also show better reduction of the structural vibration, which verifies that the proposed method is effective and practical in structural vibration reduction.     

Low-cost oriented preparation of ultra fine xonotlite fibers

Nanometer-sized xonotlite fibers have great potential application in many fields. The traditional method of preparing ultra fine xonotlite fibers uses the ultra fine and highly active silica as the major raw materials, which is not only expensive but also difficult to prepare the xonotlite fibers with diameters around 100 nm. In this study, the ultra fine xonotlite fibers with diameters around 100 nm were prepared by an autoclaving method. The preparation was low-cost oriented by using natural powder quartz and lime as the major raw materials. The intergrowth of the fibers formed thin shell hollow balls or ellipsoids, namely the secondary particles.The length of the nanometer-sized xonotlite fibers was around several microns. The fibers and their secondary particles were produced at 216℃ for 6 h with a continuous stirring of 300-500 r/min. Zirconium oxychloride was used as an additive. The experiments show that zirconium oxychloride has an enormous effect on the growing habit of xonotlite crystals and plays an important role in controlling the diameter of the xonotlite fibers.     

Carbides/nitrides precipitates in a C-Mn strip by CSP technology

The carbides/nitrides precipitates in ferrite grains, on grain boundaries and dislocations were investigated on a hot-rolled C-Mn strip (0.16wt%C-1.22wt%Mn-0.022wt%Ti) produced by the CSP (compact strip production) technology using TEM and X-ray energy dispersive spectroscopy. The Pickering’s equation for the contribution of precipitates to the yield stress was also discussed. It is shown that there are numerous fine and dispersive precipitates TiC in the ferrite grains, on the grain boundaries and dislocations. Also there are a small amount of coarser Ti(C, N) particles and TiC particles associated with MnS. Precipitation strengthening on steels produced by the CSP technology is significant.     

Vector bundle constraint for particle swarm optimization and its application to active contour modeling

Active contour modeling (ACM) has been shown to be a powerful method in object boundary extraction. In this paper, a new ACM based on vector bundle constraint for particle swarm optimization (VBCPSO-ACM) is proposed. Different from the traditional particle swarm optimization (PSO), in the process of velocity update, a vector bundle is predefined for each particle and velocity update of the particle is restricted to its bundle. Applying this idea to ACM, control points on the contour are treated as particles in PSO and the evolution of the contour is driven by the particles. Meanwhile, global searching is shifted to local searching in ACM by decreasing the number of neighbors and inertia. In addition, the addition and deletion of particles on the active contour make this new model possible for representing the real boundaries more precisely. The proposed VBCPSO-ACM can avoid self-intersection during contour evolving and also extract inhomogeneous boundaries. The simulation results proved its great performance in performing contour extraction.     

Fabrication of PLGA coated silica nanorattle for controlling the drug release behavior

Silica nanorattle with hollow and mesoporous structure has been proven to be an excellent drug carrier.However,how to control the drug release from silica nanorattle is still a challenge.In this study,we designed two methods,in-situ polymerization method and water in oil in water(W/O/W) double emulsion method,to coat a nanosized poly(lactic-co-glycolic acid)(PLGA) layer onto the surface of silica nanorattle for controlling the drug release behavior.Hydrophobic antitumor drug docetaxel was loaded into the PLGA coated silica nanorattle(PLGA@SN).The drug release profile,cellular uptake and cytotoxicity on human liver cancer HepG2 cells were evaluated to prove that the PLGA layer plays an effective role in tuning the drug delivery.     

Design and experimental study of thermal control system for AMS cryocoolers

The Alpha Magnetic Spectrometer(AMS) is an instrument for the international scientific experiment,composed of six detectors and 650 micro-electronics.The objective of AMS experiment is to search for dark matter and anti-matter in space.In this paper,the thermal control system for AMS cryocoolers is designed,analyzed and experimentally studied.Using loop heat pipes(LHPs) as the main heat dissipation component,the thermal control system has sufficient heat dissipation capability to prevent the cryocoolers from over temperature(+40℃) in hot environment,meanwhile to ensure temperatures of the cryocoolers higher than their lower limit(-20℃) in cold environment.Experiment results show that the thermal control system for AMS cryocoolers functions stably satisfying design specification.     

A chaos genetic algorithm for optimizing an artificial neural network of predicting silicon content in hot metal

A genetic algorithm based on the nested intervals chaos search (NICGA) has been given. Because the nested intervals chaos search is introduced into the NICGA to initialize the population and to lead the evolution of the population, the NICGA has the advantages of decreasing the population size, enhancing the local search ability, and improving the computational efficiency and optimization precision. In a multi-layer feed forward neural network model for predicting the silicon content in hot metal, the NICGA was used to optimize the connection weights and threshold values of the neural network to improve the prediction precision. The application results show that the precision of predicting the silicon content has been increased.     

An Incremental Time—Delay Neural Network for Dynamical Recurrent Associative Memory

An incremental time-delay neural network based on synapse growth,which is suitable for dynamic control and learning of autonomous robots,is prooposed to improve the learning and retrieving performance of dynamical recurrent associative memory architecture.The model allows steady and continuous establishment of associative memory for spatio-temporal regularities and time series in discrete sequence of inputs.The inserted hiddewn units can be taken as the Long-term memories that expand the capacity of network and sometimes may fade away under certain condition.Preliminary experiment has shown that this incremental netwrok may be a promising approach to endow autonomous robots with the ability of adapting to new data without destroying the learned patterns.The system also bendfits from its potential chaos character for emergence.     

Rapid Manufacturing of Sand Molds by Direct Milling

Direct milling of sand molds is an important development in rapid manufacturing of sand molds. Direct milling is an effective method for manufacturing single or small batches of cast parts. This paper describes experimental investigations to find sand blocks with the appropriate strength, to describe wear patterns of different tools (high-speed steel (HSS), carbide, and polycrystalline diamond (PCD) tools), and to analyze sand mold cutting mechanisms. The results show that the PCD tool outperformes the other tools in terms of tool life. Average flank wear and micro-tipping are the dominant tool failure modes in the sand mold milling process. With a flank wear limit of 0.3 mm, the PCD tool works continuously for about 70 h under the experimental conditions. The experimental results show that the cutting mechanism for direct milling sand molds differs from metal cutting.     

Intelligent Scheduling Controller Design for Networked Control Systems Based on Estimation of Distribution Algorithm

The use of communication networks in control loops has gained increasing attention in recent years due to its advantages and flexible applications. The network quality-of-service （QoS） in those socalled networked control systems always fluctuates due to changes of the traffic load and available network resources, This paper presents an intelligent scheduling controller design approach for a class of NCSs to handle network QoS variations, The sampling period and control parameters in the controller are simultaneously scheduled to compensate for the network QoS variations. The estimation of distribution algorithm is used to optimize the sampling period and control parameters for better performance. Compared with existing networked control methods, the controller has better ability to compensate for the network QoS variations and to balance network loads. Simulation results show that the plant setting time with the intelligent scheduling controller is reduced by about 64.0% for the medium network load and 49.1% for high network load and demonstrate the effectiveness of the proposed approaches.     

Magnetic properties of different grain-sized particles of sediments from the Okinawa Trough and their relationships to sedimentary environment

Multiple magnetic parameters were measured for nine different grain-sized fractions separated from the sediment samples that are representatives of four different sedimentary environments of the Okinawa Trough. Based on the measured results, the contributions of different grain-sized particles to total magnetic susceptibility of bulk sediments, the magnetic mineral assemblage and magnetic domain state as well as their relationships to sedimentary environment were discussed. Our research shows that the magnetic mineral is dominated by magnetite with a small amount of hematite and is primarily in pseudo-single-domain state. That indicates that the different sedimentary environments in the Okinawa Trough have certain correlation in material provenance. The magnetic minerals enrich in different grain-sized particles in response to different sedimentary environments. The contribution of the grain sizes from coarse to fine to coarse and fine to the magnetic susceptibility from the west to the east is in accordance with terrigenous material transportation from continental shelf of the East China Sea to the Okinawa Trough. It also shows difference in magnetic properties as a result of some environmental factors.     

Improving the sulfidation-flotation of fine cuprite by hydrophobic flocculation pretreatment

Hydrophobic flocculation pretreatment was performed to assess its effect on the recovery of fine cuprite in sulfidation-flotation. The results of the micro-flotation experiment showed that cuprite recovery is related to the particle size, and that an excessive content of fine particles (<18 μm) impacted the recovery of coarse particles. When hydrophobic flocculation pretreatment was used, the recovery of fine cuprite in sulfidation-flotation increased from 60.3% to 86.3% under optimum conditions (pH 9.5; sodium oleate concentration, 2×10-4 mol·L-1; stirring time, 6 min; stirring speed, 1600 r·min-1). The laser particle size analysis and optical microscopy results indicate that hydrophobic flocculation pretreatment effectively reduces the content of fine cuprite, and augments the apparent particle size in the pulp. We performed the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and extended DLVO theory calculations to further support the interpretation of the results.     

Effects of Ti addition on low carbon hot strips produced by CSP process

Large quantity of fine Ti(C,N) particles, 15-30 nm in size, were observed in low carbon hot strips added to a small amount of Ti and produced by CSP process. The results showed that the precipitation of Ti(C,N) mostly took place during soaking and hot rolling, which is significantly different from that in the conventional production. These fine Ti carbonitride particles could be very effective on the austenite grain refinement by hindering grain growth of recrystallized austenite. Their precipitation behavior was discussed and compared with that of the steels produced in the conventional production.     

Physical mechanism of beam halo-chaos formation for high-current proton beam in a periodic-focusing channels and a nonlinear control strategy

The physical mechanism of the halo-chaos formation for a high intensity proton beam in a periodic-fo cusing channel is analyzed using the transfer mahix theory and a qualiative analysis method.Particles-in-cell simula tims are further used to explore the mechanism of the beam halo-chaos fomation, which concerns not only with thc non linear effect of the beam space charge but also with the lransverse energy exchange belween the particles and the particle core. as well as the chaos generated by the nonlinear resonance ovcrlap. A nonlinear control method is proposed for con trolling tie haho-chaos. Simulation results show lhal the melhod is efhclivc. Somc potemlial applications of the halo chaos conlrol in experimenls are discussed.     

Mechanical Properties of Laterally Driven Microresonance with a One-Side Straight-Leg Suspension

The mechanical properties of lateral polysilicon comb-driven microresonators suspended from one-side straight-leg beams, which are widely used in linear microvibromotors, are investigated in this paper.The lateral vibration of the microresonator was modeled assuming that the symmetry of the microstructures and the applied loads are different. Methods were given to calculate the stress, lateral displacement, spring coefficient, and resonant frequency. The results show that the simple mechanical model is a superfluous system with three unknown variables. The results differ from pervious results for a microresonator suspended from double-side straight-leg beams, which has been commonly used to design linear microvibromotors.     

Research and Development of X70 with an Acicular Ferrite Microstructure for West-East Pipeline Project

It is introduced in this paper that a high strength and high toughness X70 pipeline steel with an ultra-low acicular ferrite microstructure has been researched and developed at Baosteel according to the requirements of the West-East Gas Pipeline(WEGTP) project. The developed steel has higher strength, higher toughness, lower ductile-brittle transition temperature and higher dynamic tear-resistance than the conventional X70 with ferrite and pearlite microstructure. The excellent properties of the steel are benefited from ultralow carbon acicular ferrite consisting of interaction of very fine precipitated particles and high-density dislocation. And the steel has been applied on the WEGTP in China.     

Effect of oxygen content and heat treatment on carbide precipitation behavior in PM Ni-base superalloys

The influence of oxygen content and heat treatment on the evolution of carbides in a powder metallurgy (PM) Ni-base superalloy was characterized. The results reveal that oxygen content has little influence on the precipitation of carbides inside the particles. However, under the consolidated state, stable Ti oxides on the particle surface act as nuclei for the precipitation of prior particle boundaries (PPB). Also, oxygen can diffuse internally along grain boundaries under compressive stress, which favors the precipitation of carbides inside the particles. Therefore, a higher amount of carbides will appear with more oxygen content in the case of consolidated alloys. It is also observed that PPB can be disrupted into discontinuous particles at 1200℃, but this carbide network is hard to be eliminated completely. The combined MC-M₂₃C₆ morphology approves the nucleation and growth mechanism of carbide evolution.     

High-frequency induction heated sintering of ball milled Fe-WC nanocomposites

Fe-WC nanocomposites were successfully fabricated by high-frequency induction heated sintering of ball milled nanostructure powders. The ball milled powders were characterized by X-ray diffraction. Density measurements by the Archimedes method show that all sintered samples have the relative density higher than 95%. Studies on the effects of WC content, milling speed, and milling time indicate that a higher milling speed and a more WC content lead to the improvement of mechanical properties. There is a very good distribution of WC particles in the Fe matrix at the milling speed of 650 r/min. For the sintered sample 20-5-650 (20wt% WC, milling time of 5 h, and milled speed of 650 r/min), the maximum Brinell hardness and yield stress are obtained to be 3.25 GPa and 858 MPa, respectively. All sintered samples have brittle fracture during compression test except the sample 20-5-650.     

Breathing "Trap" Mechanism for C60 Nanocage

A new trap mechanism has been proposed to generate H@C 60 . Buckyball excited by shaped laser pulse could have large Raman-active vibration mode A g (1), which enlarges and shrinks buckyball alternately, and raises and decreases the energy barrier repeatedly, forming a trap to capture the incoming H atom. In this trap mechanism, the A g (1) vibration mode is excited before the encapsulation process of H atom. Simulations of semiclassical electron-radiation-ion dynamics showed that the kinetic energy threshold for H atom in this mechanism was lowered from 17.51 eV to 10.51 eV, and successful encapsulation happened in the range from 10.51 eV to 15.55 eV.