Applications of Acrylate—based Polymer and Silicone Resin on LPFG—based Devices

Both acrylate-based polymer and silicone resin are proposed as recoating materials surrounding LPFGs for purposes of different applications.For the LPFG recoated with a thin layer of acrylate-based polymer,the range of wavelength shift as much as 60nm is expected when temperature changes from0-100℃.As for that with surrounding material of silicone resin,the temperature stability is greatly improved depicted as the maximum wavelength shift of about 0.6nm with the same temperature variation.The former is potentially a broadband tunable band rejection filter or temperature sensor with enhanced sensitivity.And the latter could be applied as temperature insensitive filter,demultiplexer or strain sensor.     

A novel high-sensitivity pressure sensor: Thinned fiber Bragg grating with pressure-sensing polymer

Based on thinned fiber Bragg grating and polymer material, we propose a novel high-sensitivity pressure sensor and obtained a new contribution to the pressure sensitivity, which is dependent on the derivative of the effective refractive index (RI) of core mode with respect to the surrounding medium RI, as well as on the relationship between the polymer RI and the pressure; moreover, it is inversely proportional to Young’s modulus of the polymer material. For the polymer with Young’s modulus of 1.0 MPa, the total pressure sensitivity 1.54×10-2 MPa-1 can be obtained.     

Multi-type sensor placement and response reconstruction for structural health monitoring of long-span suspension bridges大跨悬索桥结构健康监测多种传感器布置和响应重构的方法

This study is devoted to the experimental validation of the multi-type sensor placement and response reconstruction method for structural health monitoring of long-span suspension bridges. The method for multi-type sensor placement and response reconstruction is briefly described. A test bed, comprising of a physical model and an updated finite element(FE) model of a long-span suspension bridge is also concisely introduced. The proposed method is then applied to the test bed; the equation of motion of the test bed subject to ground motion, the objective function for sensor location optimization, the principles for mode selection and multi-type response reconstruction are established. A numerical study using the updated FE model is performed to select the sensor types,numbers, and locations. Subsequently, with the identified sensor locations and some practical considerations, fiber Bragg grating(FBG) sensors, laser displacement transducers, and accelerometers are installed on the physical bridge model. Finally, experimental investigations are conducted to validate the proposed method. The experimental results show that the reconstructed responses using the measured responses from the limited number of multitype sensors agree well with the actual bridge responses.The proposed method is validated to be feasible and effective for the monitoring of structural behavior of longspan suspension bridges.     

Transmission and demodulation of multi-polarization-multiplexed signals

We propose the configuration of signal multi- plexing with four polarization states and investigate its transmission performance over single-mode fiber links. Using coherent detection and digital signal processing, a demodulation scheme for four-polarization-multiplexed （4PM） system is presented. We discuss the impact of crosstalk from polarization mode dispersion and polarization beam splitter misalignment on the proposed 4PM system. Furthermore, the transmission distance could be doubled to -50 km by employing feedback decision equalizers.     

Cooling hot rolling steel strip using combined tactics

The coiling temperature control of a typical steel strip mill was investigated. Due to the high speed of a strip and complex circumstance, it is very hard to set up a cooling model with high accuracy. A simplified dynamic model was proposed, based on which a cooling control scheme with combined feedforward, feedback and adaptive algorithms was developed. Meanwhile, the genetic algorithms were used for the optimization of model parameters. Simulations with a model validated using actual plant data were conducted, and the results have confirmed the effectiveness of the proposed control methods. At last, a simulation system for coiling temperature control was developed. It can be used for new product trials and newcomer training.     

Optimization of monitoring the stability of surrounding rock in a metal mine

Through analyzing the failure mechanics of rock under blasting effect, the optical fiber sensing system was used to monitor the strain of surrounding rock under blasting effect. Combined with practical exploration, the stability of surrounding rock was computed by numerical simulation using the blasting wave obtained from the site. According to the change regularities of displacement, stress, acceleration, and velocity of tunnels before and after explosion, the layout of key monitoring points was optimized. When disposed the monitoring position of sensors, the regular points should be considered to use as key points and the periodical monitor should be a part of the long-term monitor. In practical application, considering the geology condition in site, monitor points should be added on the area with joints and faults to assure the integrity of monitor data and the preciseness of decision.     

Optical Fiber Grating Sensor for Force Measurement of Anchor Cable

The development of the sensor suitable for measuring large load stress to the anchor cable becomes an important task in bridge construction and maintenance. Therefore, a new type of optical fiber sensor was developed in the laboratory - optical fiber grating sensor for force measurement of anchor cable （OFBFMAC）. No similar report about this kind of sensor has been found up to now in China and other countries. This sensor is proved to be an effective way of monitoring in processes of anchor cable installation, cable cutting, cable force regulation, etc, with the accurate and repeatable measuring results. Its successful application in the tie bar cable force safety monitoring for Wuhan Qingchuan bridge is a new exploration of optical fiber grating sensing technology in bridge tie bar monitoring system.     

Constitutive behavior and processing maps of low-expansion GH909 superalloy

The hot deformation behavior of GH909 superalloy was studied systematically using isothermal hot compression tests in a temperature range of 960 to 1040℃ and at strain rates from 0.02 to 10 s-1 with a height reduction as large as 70%. The relations considering flow stress, temperature, and strain rate were evaluated via power-law, hyperbolic sine, and exponential constitutive equations under different strain conditions. An exponential equation was found to be the most appropriate for process modeling. The processing maps for the superalloy were constructed for strains of 0.2, 0.4, 0.6, and 0.8 on the basis of the dynamic material model, and a total processing map that includes all the investigated strains was proposed. Metallurgical instabilities in the instability domain mainly located at higher strain rates manifested as adiabatic shear bands and cracking. The stability domain occurred at 960-1040℃ and at strain rates less than 0.2 s-1; these conditions are recommended for optimum hot working of GH909 superalloy.     

Transient pressure analysis for the reactor core and containment of a HTGR after a primary loop pressure boundary break accident

The pressure variances in the reactor core and containment of a High Temperature Gas-cooled Reactor (HTGR) after a primary loop pressure boundary break accident determine the structural integrity and safety of the reactor. Based on mass conservation, energy conservation and state equations, explicit formulae for the transient pressure and temperature variances in the pressure vessels were deduced, and a set of differential equations for the transient pressure and temperature variances in the containment were developed. Numerical simulation was also conducted to investigate the transient pressure and temperature variances in the pressure vessels and containment. The results show that energy transformation due to expansion work cannot be neglected. The maximum pressure in the containment could increase by 40 percent due to blockage caused by air in the containment. Detailed numerical simulations of the transient pressure and temperature variance in the reactor core flow passages were also conducted. The results show that the pressures acting on the reactor core and containment are below acceptable values.     

Compressive fatigue behavior and failure evolution of additive fiber-reinforced cemented tailings composites

The ordinary cemented tailings backfill(CTB)is a cement-based composite prepared from tailings,cementitious materials,and water.In this study,a series of laboratory tests,including uniaxial compression,digital image correlation measurement,and scanning electron microscope characteristics of fiber-reinforced CTB(FRCTB),was conducted to obtain the uniaxial compressive strength(UCS),failure evolution,and microstructural characteristics of FRCTB specimens.The results show that adding fibers could increase the UCS values of the CTB by 6.90%to 32.76%.The UCS value of the FRCTB increased with the increase in the polypropylene(PP)fiber content.Moreover,the reinforcement effect of PP fiber on the CTB was better than that of glass fiber.The addition of fiber could increase the peak strain of the FRCTB by0.39%to 1.45%.The peak strain of the FRCTB increased with the increase in glass fiber content.The failure pattern of the FRCTB was coupled with tensile and shear failure.The addition of fiber effectively inhibited the propagation of cracks,and the bridging effect of cracks by the fiber effectively improved the mechanical properties of the FRCTB.The findings in this study can provide a basis for the backfilling design and optimization of mine backfilling methods.     

Efficient Method to Achieve Enhanced Thermal Dimensional Stability and Desired Dimensions of Hollow Polyester Fiber

This study has developed an efficient method to achieve excellent thermal dimensional stability and desired dimensions of hollow polyester fiber. Firstly,the influence of thermal treatment temperate( 140-180 ℃) on the degree of shrinkage of fiber was investigated. The influence was also analyzed with a 2nd heating to simulate the application situation. It was discovered that the heat treatment at a temperature which was above the application temperature( 2nd heating) would efficiently remove the internal stress in the fiber and improve the thermal dimensional stability.Secondly,the impact of heat treatment temperature on the fiber diameter and the degree of hollowness were studied. The results implied that with a fixed fiber length, higher treatment temperature led to thinner fiber and a lower degree of hollowness.Last but not least,key parameters that could further influence the fiber dimensions were investigated. The results suggested that the fiber diameters and the degree of hollowness could be further controlled by tuning the drawing speed,the spinning meter pump output and cooling status while the spinneret parameters were fixed.     

Comparison between PCA and KPCA methods in comprehensive evaluation of robotic kinematic dexterity

Due to the correlation and diversity of robotic kinematic dexterity indexes, the principal component analysis （PCA） and kernel principal component analysis （KPCA） based on linear dimension reduction and nonlinear dimension reduction principle could be respectively introduced into comprehensive kinematic dexterity performance evaluation of space 3R robot of different tasks. By comparing different dimension reduction effects, the KPCA method could deal more effectively with the nonlinear relationship among different single kinematic dexterity indexes, and its calculation result is more reasonable for containing more comprehensive information. KPCA＇ s calculation provides scientific basis for optimum order of robotic tasks, and furthermore a new optimization method for robotic task selection is proposed based on various performance indexes.     

Plastic theory for the multi-crystal metals-From infinitesimal deformation to finite deformation

Multi-crystal metals have the property of volume conservation in the plastic state. In the infinitesimal deformation plasticity the strain tensor can be split into a deviator part and a volumetric part. The vanishing of the first variant of the strain tensor is equivalent to the volume conservation. Furthermore, the split of the strain into an elastic part and a plastic part is also adopted widely. The flow rule is thus established. These two splits are not confirmed in the finite deformation plasticity. The plasticity criterion and the flow rule are thus facing great challenge. There are various definitions of strain measures in the finite deformation theory. Though the choosing of strain measure is arbitrary in the elastic problem, it is strongly restricted in the plastic problem. By theoretical and experimental studies, it is shown that the logarithmic strain is the only suitable strain measure in the metal forming problem.     

A Switch Agent for Wireless Sensor Nodes with Dual Interfaces: Implementation and Evaluation

Data generation in wireless sensor networks could be bursty as it is dictated by the presence or absence of events of interest that generate these data. While conventional sensor nodes possessed only one radio interface, next generation sensor nodes are expected to have two (possibly more) radio interfaces, each with different ranges, capacities, and power consumptions. Equipping sensor nodes with dual radios has its own benefits and can be quite useful in handling bursty traffic while at the same time satisfying the application’s delivery requirements. In this paper, we propose an adaptive interface switch agent that intelligently selects the interface to be used for data transmission at a sensor node based on the data burst length or end-to-end delay while taking into consideration power consumption and throughput. The proposed work generalizes earlier works in this area to enable both the source nodes and intermediate data forwarding nodes to initiate the activation of high power radios so that they can be utilized to a higher degree for converge-cast communication. We have performed extensive simulations with sensor nodes containing both IEEE 802.15.4 and IEEE 802.11 compatible radios. Our simulation results indicate that the switch agent yields throughput, delay, and packet delivery ratio comparable to the higher bandwidth interface alone, without incurring much energy wastage.     

A separate two-stage pulse tube cooler working at liquid helium temperature

A novel 4 K separate two-stage pulse tube cooler (PTC) was designed and tested. The cooler consists of two separate pulse tube coolers, in which the cold end of the first stage regenerator is thermally connected with the middle part of the second regenerator. Compared to the traditional coupled multi-stage pulse tube cooler, the mutual interference between stages can be significantly eliminated. The lowest refrigeration temperature obtained at the first stage pulse tube was 13.8 K. This is a new record for singlestage PTC. With two compressors and two rotary valves driving mode, the separate two-stage PTC obtained a refrigeration temperature of 2.5K at the second stage. Cooling capacities of 508mW at 4.2K and 15W at 37.5K were achieved simultaneously. A one-compressor and one-rotary valve driving mode has been proposed to further simplify the structure of separate type PTC.     

Microstructural evolution during ultra-rapid annealing of severely deformed low-carbon steel: strain,temperature, and heating rate effects

An interaction between ferrite recrystallization and austenite transformation in low-carbon steel occurs when recrystallization is delayed until the intercritical temperature range by employing high heating rate. The kinetics of recrystallization and transformation is affected by high heating rate and such an interaction. In this study, different levels of strain are applied to low-carbon steel using a severe plastic deformation method. Then, ultra-rapid annealing is performed at different heating rates of 200–1100℃/s and peak temperatures of near critical temperature. Five regimes are proposed to investigate the effects of heating rate, strain, and temperature on the interaction between recrystallization and transformation. The microstructural evolution of severely deformed low-carbon steel after ultra-rapid annealing is investigated based on the proposed regimes. Regarding the intensity and start temperature of the interaction, different microstructures consisting of ferrite and pearlite/martensite are formed. It is found that when the interaction is strong, the microstructure is refined because of the high kinetics of transformation and recrystallization. Moreover, strain shifts an interaction zone to a relatively higher heating rate. Therefore, severely deformed steel should be heated at relatively higher heating rates for it to undergo a strong interaction.     

基于液芯光纤和CCD的分光光度法测定河水中的Cr(VI)

A convenient and sensitive spectrometric system based on a liquid core optical fiber and a charge coupled device was constructed for the determination of chromium(VI) in river water.Diphenylcarbazide was added to Cr(VI) solution to form colored complex in the medium of perchloric acid.With a 35 cm long Teflon optical fiber,the limit of detection(LOD) was 0.4 μg·L~(-1),ten times lower than that of Chinese National Standard Procedure(GB7467-87).The method was applied to determine Cr(VI) in river water without...     

Modeling an Elastic-Demand Bimodal Transport Network with Park-and-Ride Trips

This paper presents a network equilibrium formulation for modeling commuters＇ travel choices in a bimodal transport system with park-and-ride （P＆R） trips while the total demand is elastic to the congestion level of the network. A super-network approach is adopted in the proposed model. It is assumed that commuters＇ trips are categorized into two types, auto mode only and a combined mode with both auto and transit modes. The former is referred to as the pure mode trip and the latter as the P＆R mode trip. The proposed model simultaneously considers the commuter＇s choice of the pure mode versus the P＆R mode, the choice of parking location for the pure mode, the choice of transfer point for the P＆R mode, as well as the route choice for each mode. The demand elasticity of transport system, the capacity constraints of transport facilities, and the congestion interaction throughout the super-network are also explicitly incorporated into the proposed model. The results of the numerical experiment show the following key findings： （i） traditional parking/P＆R models may overestimate or underestimate travel demand distribution over network; （ii） parking/P＆R, transit scheduling, and carpooling schemes bring significant impacts on commuters＇ travel behavior and network performance; and （iii） different transport policies may be to some extent mutually substituted .     

Integrated TEM/transmission-EBSD for recrystallization analysis in nickel-based disc superalloy

Turbine discs in gas-turbine engines always experience high-temperature and high-stress environment. Extensive investigations have been performed towards achieving high performance. Deformation behaviors and degradation factors above normal service temperature are important to be comprehensively understood for further development and optimization of turbine disc superalloys. In this study, the low cycle fatigue behaviors were investigated under total strain amplitude control in U720 Li disc superalloys. The results revealed that with the increasing strain, the number of dislocation increased and dislocation configuration transferred from pile-up at the matrix/γ′ precipitates interfaces to penetrating into γ′ precipitates. The great extent of recrystallization was found above the normal service temperature through transmission-EBSD combined with TEM analysis. The low cycle fatigue property above the normal service temperature was weakened to a large extent after recrystallization of small-angle grains formed by the dislocation substructures and movements. Large extent of local recrystallization could also provide much more sites for the crack initiation and propagation.     

Improved area-difference-based recovery information placement

<正> In mobile computing systems,message logging can be used to provide fault tolerance for mobilehosts.Due to the mobility of mobile hosts,their recovery information,including logged messages andcheckpoints,may spread throughout mobile support stations.During recovery,there will be a considerablecost for the collection of recovery information.To speed up recovery and to reduce the failure-freeoverhead,an improved area-difference-based scheme is proposed.It tries to keep recovery informationevenly spreading over an area.Only part of recovery information needs to be migrated for controlling thedistribution of recovery information.To reduce the migration cost,a light-weight migration is also proposed.In the performance study,we give an analysis of the probability that the light-weight migrationtakes place.