Search

Hot tensile features in a Ni–Cr–Mo-based superalloy with different notched types are explored. Changes of microstructure and fracture mechanisms with stress triaxiality and tensile parameters are elucidated. Results manifest that the maximum load for the Ni–Cr–Mo-based superalloy in hot tensile ascends with increasing stress triaxiality. The development/interaction of dislocation clusters and subgrains is sensibly boosted, while the dynamic recrystallization (DRX) formation/coarsening behaviors is suppressed with ascending stress triaxiality or strain rate. Nevertheless, the intense generation/development in substructure and DRX grains appear at higher tensile temperature. The primary fracture mode is the ductile facture closely associated with dimples formation/coalescence and the progression of serpentine gliding. The primary fracture mechanism of Ni–Cr–Mo-based superalloy is the shear fracture characterized by the microporous polymerization. The coalescence/growing up in dimples becomes weaken with reducing stress triaxiality. Additionally, the dominant texture components are the E, F and Copper textures for the Ni–Cr–Mo-based superalloy with notched type in high-temperature tensile. With increasing stress triaxiality, the S texture sensibly increases.

The warm flow characteristics and microstructural evolution features in a solution-treated 7075 aluminum alloy are revealed. An elastic-visco-plastic constitutive model is developed to capture the flow stress behavior of 7075 aluminum alloy under warm deformation. The variations of microstructure features, including grain and subgrain size, are also analyzed under warm deformation, and are further incorporated in the proposed unified constitutive model. The results indicate that the dynamic recovery (DRV), related to dislocation annihilation and formation/growth of sub-grains, is the domain softening mechanism. The DRV behavior is enhanced at higher temperatures or lower strain rates. Warm external temperature field assists the plastic deformation by means of activating and accelerating the dynamic softening, while the reduced strain rate also gives sufficient time for the softening. Through experimental validation, the proposed constitutive model successfully captures the grain/subgrain features and flow behavior of the studied 7075 aluminum alloy during warm deformation. The predicted result is in a great agreement with the experimental stress-strain data, demonstrating the excellent predictive performance of the model. Moreover, the proposed model also successfully predicts the average grain/subgrain size.

The formation of prior particle boundaries (PPBs) in a new powder metallurgy superalloy during hot isostatic pressing (HIP) is investigated. Also, the impact of subsequent hot deformation on the elimination of PPBs is systematically studied. The PPBs involves large γ′ phases, carbides (MC and M6C) and oxides (Al2O3, SiO2and ZrO2). The reactions among the superficial oxides, the adsorbed C and O elements on the particle surface and internally-migrated alloying elements are the dominant reasons for the formation of PPBs during HIP. Besides, the existence of surface tension and surface energy induces the carbon segregation, as well as the formation of PPBs. Thus, the density of PPBs decreases when the spacing between powders is shrunk by a rapid deformation. In hot forming process, the PPBs can be efficiently eliminated via raising deformation temperature/true strain or reducing strain rate. The interactions between dislocations and PPBs, as well as the occurrence of dynamic recrystallization (DRX) induced by the strain/orientation gradient, lead to the elimination of PPBs. The thermodynamic stability of carbides declines with the raised temperature. It indicates that the dissolution of carbides and the elimination of PPBs can be accelerated via raising the deformation temperature. The breakage or deformation behavior of PPBs during hot extrusion is investigated by numerical simulation. The deformation degree of PPBs increases with the raised extrusion ratio. The above important findings are useful for developing hot extrusion processing to effectively eliminate PPBs.

High-temperature flow features of the Al−Zn−Mg−Cu−Zraluminum alloy was revealed by hot compression tests. The evolution mechanisms of dislocation clusters, subgrain, and dynamic recrystallization (DRX) grains, are thoroughly explored by EBSD and TEM analysis. Experimental results suggest that the high strain rate can exacerbate dislocation clusters formation, as well as subgrain nucleation/accumulation, inducing the increasing of flow stress. Nevertheless, the noticeable annihilation of substructures, as well as the growth of DRX grains, emerge at the higher temperature, causing the descending of flow stress. Three types of DRX nucleating mechanisms, i.e., discontinuous DRX (DDRX), geometric DRX (GDRX) and continuous DRX (CDRX) are activated in the Al−Zn−Mg−Cu−Zraluminum alloy during hot compression. Simultaneously, the GDRX often appears at a high compressed temperature or a low strain rate. A physically-based (PB) model is proposed to collaboratively reconstruct true stresses and microstructure evolution features. The estimated values of true stress, DRX fractions and average grain size preferably fit the experimental data, indicating the proposed PB model can precisely catch the thermal compression behaviors and microstructure evolution characteristics of the Al−Zn−Mg−Cu−Zraluminum alloy.

Hot tensile features of a commercial 7046 aluminum alloy are investigated through employing high-temperature tensile tests. The evolving mechanisms of microstructures over high-temperature tensile parameters are systematically revealed. A unified dislocation-density related constitutive model is proposed to reconstruct hot tensile stress–strain behaviors. Results imply that the microstructural evolving features are acutely influenced by tensile parameters. The principal softening mechanism converts from dynamic recovery (DRV) to dynamic recrystallization (DRX), as the tensile temperature reaches 350 °C or above. The combined DRX nucleation features containing discontinuous DRX (DDRX) as well as continuous DRX (CDRX) together emerge. Furthermore, the CDRX behavior characterized by substructural nucleation and interaction becomes apparent at low tensile temperature or high strain rate, while the DDRX process is weaken. Through validation, the reproduced tensile stress, grain size as well as DRX fraction are good accordance with experimented values, which proves the proposed dislocation-density related equation can enjoy an outstanding reproduced capacity for the thermal tensile features of a 7046 aluminum alloy.

The uniform refinement mechanisms and methods of deformed mixed and coarse grains inside a solution-treatment Ni-based superalloy during two-stage annealing treatment have been investigated. The two-stage heat treatment experiments include an aging annealing treatment (AT) and a subsequent recrystallization annealing treatment (RT). The object of AT is to precipitate some δ phases and consume part of storage energy to inhibit the grain growth during RT, while the RT is to refine mixed and coarse grains by recrystallization. It can be found that the recrystallization grains will quickly grow up to a large size when the AT time is too low or the RT temperature is too high, while the deformed coarse grains cannot be eliminated when the AT time is too long or the RT temperature is too low. In addition, the mixed microstructure composed of some abnormal coarse recrystallization grains (ACRGs) and a large number of fine grains can be observed in the annealed specimen when the AT time is 3 h and RT temperature is 980 ℃. The phenomenon attributes to the uneven distribution of δ phase resulted from the heterogeneous deformation energy when the AT time is too short. In the regions with a large number of δ phases, the recrystallization nucleation rate is promoted and the growth of grains is limited, which results in fine grains. However, in the regions with few δ phases, the recrystallization grains around grain boundaries can easily grow up, and the new recrystallization nucleus is difficult to form inside grain, which leads to ACRGs. Thus, in order to obtain uniform and fine annealed microstructure, it is a prerequisite to precipitate even-distributed δ phase by choosing a suitable AT time, such as 12 h. Moreover, a relative high RT temperature is also needed to promote the recrystallization nucleation around δ phase. The optimal annealing parameters range for uniformly refining mixed crystal can be summarized as: 900 ℃×12 h + 990 ℃×(40−60 min) and 900 ℃×12 h + 1000 ℃×(10−15 min). [ABSTRACT FROM AUTHOR]

[Display omitted]

The effects of solution time and cooling rate on microstructures and mechanical properties of 2219 Al alloy for a larger spun thin-wall ellipsoidal head are investigated. It is found that the Al2Cu phases are greatly affected by the solution time. The content of Al2Cu phases first decreases and then stabilizes with increasing the solution time. Moreover, the effects of solution time on the transformation of precipitates are obvious. As the solution time is increased from 35 min to 60 min, almost all the precipitates transfer from GP zones to θ′′ phases. When the solution time is further increased to 110 min, some θ′ phases appear. Meanwhile, the size of θ′′ phases increases, while the density of θ′′ phases drops. These microstructure changes greatly influence the mechanical properties, i.e., the hardness and tensile strengths first increase and then slightly decrease with the continuous increase of the solution time. In addition, if the cooling rate is decreased, the precipitation of coarse equilibrium θ phases is enhanced, but the precipitation of strengthening phases (θ′′, θ′) is restricted. It significantly deteriorates the mechanical properties. Based on the comprehensive analysis, the suitable solution time and cooling method are about 60 min and water cooling.

A new thermomechanical process was applied to a near-β Ti-5Al-5Mo-5V-1Cr-1Fe alloy to induce twinning. The resulting combination of ultrafine grains and heat-treatment twins endowed the alloy with excellent tensile strength (1544MPa) and elongation (13%). β-Field cross-rolling formed micro-sized β grains, and ultrafine α particles precipitated from pre-existing dense dislocation structures and martensites. α-Twinning occurred during heat treatment and continuously evolved with the ongoing heat treatment time. A precisely controlled heat treatment time enabled the distribution of nanosized twins throughout the α laths, simultaneously improving strength and ductility. The results of this study pave the way for the development of customised titanium alloys with significantly improved mechanical properties.

This work gives a comparison on the microstructural characteristics, textural discrepancies, and twinning behaviors of lamellar and equiaxed near β-Ti alloys during multi-pass cross rolling with a rolling reduction of 20 %, 50 % and 80 %. The results showed that the restoration mechanism of the alloy in β phase is strongly dependent on the α morphologies, and in comparison, strain path has weaker influences on the grain refinement of the β matrix. Therefore, the texture intensities of both α and β phases were weakened owing to the dynamic recrystallization (DRX) of the two phases in the equiaxed microstructure. While, with regard to the lamellar microstructure, dynamic recovery (DRV) of the β phase predominated, forming elongated β subgrains. Besides, the α and β matrix in lamellar microstructures obeyed the Burgers orientation relationship, which was gradually broken down until the final reduction. Lastly, the 1 1 ¯ 01 twinning exhibits a strong size effect. With the continuous DRX of α phases, the α-twinning is suppressed owing to progressive grain refinement. The activation of β-twinning, namely 332 〈 113 〉 and 112 〈 111 〉 , in near β-Ti alloys is heavily dependent on the deficient β-stabilizing elements and the local stress concentration. These findings provide an effective way to obtain ultra-fine grain microstructures of this alloy. [ABSTRACT FROM AUTHOR]

A layer of silicon carbide (SiC) will be deposited on the working surface if the kerosene dielectric with silicon powders is applied for the electrical discharge machining (EDM). This SiC layer can enhance the hardness of the machining surface. However, silicon powders are easily reunited and deposited in the bottom of the dielectric, reducing SiC layer to merge on the working surface after EDM. Therefore, the kerosene with silicon powders was replaced by silicone oil as the dielectric to improve the reuniting and the depositing issues of the silicon powders in EDM, since silicone oils contain the liquid silicon elements and not silicon powders. Moreover, silicone oils are the uniformly viscous fluid and not easy to cycle in the small working gap of EDM, thus worth investigating the EDM phenomena of the silicone oils with different viscosities in this study. The results showed that debris by EDM were easily accumulates on the working surfaces of the electrode and the machined material when high viscosity silicone oils were utilized as the dielectrics, and the material removal rate of these dielectrics were small than the kerosene did. However, using the low viscosity silicone oil (100 mPa-S) as dielectric in EDM could transfer higher SiC elements to the steel surface, and the capibility of material removal rate is the best way.

In authors' previous work [Mater. Charact. 141 (2018) 212–222], it was found that the heterogeneous deformed microstructures can be replaced by the relatively homogeneous recrystallized grains through an annealing treatment. However, there are still some relatively large recrystallized grains. To find the reasons for the formation of large grains, some new annealing treatment tests were done, and the cellular automation (CA) simulations were carried out in the present work. The experimental results showed that the microstructural evolution during annealing treatment is significantly affected by the content of δ phase. So, the effects of δ phase on the nucleation and growth of grains are carefully considered in the CA model to accurately simulate the microstructural evolution behavior. By the CA simulation, it is found that the dislocation density rapidly decreases due to the nucleation of static recrystallization (SRX) and the growth of dynamc recrystallization (DRX) nuclei at the early stage of annealing. The high initial dislocation density can provide the high velocity for the growth of DRX nuclei, which is responsible for the formation of coarse grains. However, the growth rate of SRX nuclei is relatively small due to the low dislocation density and pinning effects of δ phase. [ABSTRACT FROM AUTHOR]

Up to now, there are few reports on the yield behavior of Ni-based superalloy during plastic deformation. However, an accurate yield stress model is significant for simulating the plastic forming process by cellular automaton or finite element methods. Therefore, the yield behavior of a solution-treated Ni-based superalloy is studied by hot compression tests. In order to evaluate yield stresses from the measured flow stress curves, the yield process is analyzed in terms of dislocation theory. Then, yield stresses at different deformation temperatures and strain rates are clearly determined. The experimental results show that the yield stresses are highly sensitive to deformation temperature and strain rate. The determined yield stress almost linearly increases with the increase of the logarithm of strain rate or the reciprocal of deformation temperature. A yield stress model is developed to correlate the yield behavior of the studied solution-treated Ni-based superalloy with deformation temperature, strain rate, and strengthening effect of alloying elements. The developed model can well describe the yield behavior of the studied solution-treated Ni-based superalloy.

Isothermal compression experiments were conducted to study the hot deformation behaviors of a Sr-modified Al-Si-Mg alloy in the temperature range of 300–420 °C and strain rate range of 0.01–10 s−1. A physically-based model was developed to accurately predict the flow stress. Meanwhile, processing maps were established to optimize hot working parameters. It is found that decreasing the strain rate or increasing the deformation temperature reduces the flow stress. The high activation energy is closely related to the pinning of dislocations from Si-containing dispersoids. Moreover, the deformed grains and the Si-containing dispersoids in the matrix are elongated perpendicular to the compression direction, and incomplete dynamic recrystallization (DRX) is discovered on the elongated boundaries in domain with peak efficiency. The flow instability is mainly attributed to the flow localization, brittle fracture of eutectic Si phase, and formation of adiabatic shear band. The optimum hot working window is 380–420 °C and 0.03–0.28 s−1.

In hot forming processes, metallic materials often undergo a series of plastic deformation and heat treatments. Hot working parameters, including deformation temperature, strain rate, and strain, exert great impacts on hot deformation behavior of alloys. Work hardening (WH), dynamic recovery (DRV), dynamic recrystallization (DRX), phase transformation, and metadynamic recrystallization (MDRX) often take place, and affect hot deformation behavior of metallic materials. Therefore, a comprehensive investigation on the intrinsic interactions between microstructural evolution and hot deformation behavior is necessary. In this study, a novel unified dislocation-density based model is presented to characterize the hot deformation behavior of a nickel-based superalloy In the Kocks-Mecking model, a new softening item is proposed to represent the impacts of dynamic recrystallization behavior on dislocation density evolution. The grain size evolution and dynamic recrystallization kinetics are incorporated into the developed model. Material parameters of the developed model are calibrated by a derivative-free method in MATLAB toolbox. Comparisons for the experimental and predicted results confirm that the developed unified model can accurately reproduce the hot deformation behavior, DRX kinetics, and grain size evolution in wide scope of initial grain size, deformation temperature, and strain rate.

Abstract

Abstract

Abstract

Abstract

The study was designed to evaluate the effects of different dietary levels of rice bran (RB) in laying duck diets on performance, egg quality, oxidation status, egg yolk fatty acid composition, and hepatic expression of fatty acid metabolism-related genes. Longyan females (1080) with similar BW at 19 wk of age were randomly assigned to 6 dietary treatments, each consisting of 6 replicates of 30 birds. The basal diet (I) was a typical corn-soybean ration while the experimental diets (II to VI) substituted RB for corn and wheat bran and a small reduction of soybean meal. The level of substitution in diets (II to VI) was 6%, 12%, 18%, 24%, and 30%, respectively. The experiment lasted for 12 wks. Average egg weight and daily egg mass decreased linearly as the level of RB inclusion increased (P< 0.001) and feed conversion ratio linearly increased (P< 0.001). The proportions of C14:0 and C18:0 and total saturated fatty acids (SFA) in egg yolk linearly decreased with increasing RB, and many of the key polyunsaturated fatty acids (PUFA), like C18:2 n-6and C18:3 n-3, linearly increased (P< 0.001), but not those of C20:5 n-3and C22:6 n-3. There were linear decreases (P< 0.001) in hepatic abundance of FASand SREBP1transcripts, with a substantial reduction to about 30% those of ducks fed the control diet; there were no treatment effects on productive performance, eggshell thickness, strength, Haugh unit, antioxidation status, and egg yolk cholesterol or triglyceride content (P> 0.05). In conclusion, the current study suggests that ducks from 19 to 31 wk could be fed diets with up to about 18% RB without effect on the number of eggs produced, egg quality, and oxidative status. Increasing amounts of RB linearly increased egg yolk concentrations of key fatty acids like C18:2 n-6and C18:3 n-3and decreased the hepatic abundance of FASand SREBP-1transcripts.

To establish the dietary Ca requirements for laying ducks during their peak laying period, 5 Ca levels (2.8, 3.2, 3.6, 4.0, and 4.4%) were used, and laying performance, eggshell quality, serum variables, and bone quality were examined. A total of 1,620 Longyan shelducks with similar BW at 20 wk of age were fed for 13 wk in 5 treatment groups, each with 4 replicates of 81 birds. Dietary Ca increased egg production and egg mass (linear, P< 0.01) and reduced the feed conversion ratio (FCR), but egg weight was not affected. Dietary Ca level did not affect eggshell properties or any reproductive organ index except for shell weight (highest with the 4.0% Ca diet, P< 0.05). Serum concentrations of Ca and calcitonin increased with dietary Ca level (linear, P< 0.01), and a quadratic response (P< 0.01) was seen in alkaline phosphatase activity; the highest values were in ducks fed the 3.6% Ca diet. Tibial fresh weight was affected by dietary Ca (linear and quadratic, P< 0.05) with tibiae from the 2.8% Ca ducks weighing less than those from ducks fed any other Ca level. Other tibial measurements were unaffected by dietary Ca. According to the regression model, the Ca levels required for laying Longyan shelducks during their peak laying period are 3.4 and 3.2% for maximal serum alkaline phosphatase activity and tibial fresh weight, respectively. The results showed that diets containing 3.2 to 3.6% Ca provide for superior productive performance and bone quality in laying Longyan shelducks during their peak laying period.

Internal mass transfer coefficient is considered as a key parameter for open thermochemical sorption heat storage which usually has a large margin between theoretical and actual value. This paper aims to analyze the role of mass transfer on system performance prediction. Al2O3and LiCl composite sorbents are prepared and adsorption behavior is tested through a thermal gravimetric analyzer and a small-scale air duct experiment. An equation of kinetic coefficient is fitted to describe adsorption process more accurate than empirical equation. For simulation, a one-dimensional model is established based on dimensionless number of heat and mass transfer, and similarity theory is built to predict output parameters. Results indicate that the sorbent with 16.44 % salt content reaches 0.39 g·g−1maximum water uptake on the condition of 20 °C, 80 % relative humidity. It is indicated that the system using composite sorbents has a heat storage density of 345.58 kWh·m−3. Parameters that influence system output power and duration are also investigated. By adjusting air flow rate and sorption length of sorption reactor, the system can achieve temperature rise of 30 °C at the exit and a steady output of 6 h. One striking fact is that mass transfer coefficient can be used to well predict the performance of real open adsorption thermal energy storage system which is also conducive to system design and optimization.

The Finite Element Method (FEM) is used to analysis multiply asperity sliding contact surface. The various distributions of stress and strain along the asperity contact profile are shown for various pressure, roughness, sliding velocity, friction coefficient, and thermal conductivity. The results show that equivalent strain increases as the friction coefficient decreases. Similar results are found for the shear stress. However, the maxima equivalent stress at the center peak increases as the roughness, thermal conductivity, or loading force increases. Instead of the peak point, maxima equivalent stress and strain can be found at the contact/non-contact interchange point of the contact profile. The equivalent stress and strain increase as the loading force increases. In addition, the normal stress increases as the friction coefficient and loading force increase. The maxima normal stress can be found at the center peak point.

In recent years, the position location applications have increasingly. In this paper, we will use multiple Back-Propagation neural networks with genetic algorithm (GA) for a radio frequency identification (RFID) indoor location system to provide location services named indoor location with multiple neural networks and genetic algorithms (ILMNGA). In Section 1, we collect received signal strength (RSS) information from reference points to train the neural network models. In Section 2, genetic algorithm (GA) is used to find the weight of each neural network based on the performance of each neural network. Finally, we input the RSS information of each tracking object into the model that will provide the location of tracking objects based on the RSS information. The location will be integrated using the weights produced by the GA. The experiment conducted our methodology can provide better accuracy than a single neural network.

Three-dimensional crystal plasticity finite element (CPFE) simulations are performed to study the coupled thermo-mechanical response of aluminium alloy 7075 under hot compression loadings. To improve the computational efficiency, a grain-scale representative volume element model with periodic boundary conditions is adopted to represent the macroscopic response. The initial grains are created using Voronoi tessellation method, and the grain orientations are obtained from the electron back-scatter diffraction test. The simulated results indicate that the effects of the grain properties on the local deformation and temperature distribution of the alloy are significant during the hot deformation. The temperature continuity can be found across some grain boundaries while there is a temperature gap at other grain boundaries. The proposed coupled thermo-mechanical CPFE model is able to provide detailed microstructure evolution and temperature distribution in the studied alloy during the hot deformation, which cannot be easily obtained by experiments.

AbstractHigh temperature creep and useful creep life behavior of Al-Cu-Mg (2124-T851 aluminum) alloy was investigated by conducting constant stress uniaxial tensile creep tests at different temperatures (473–563 K) and at stresses ranging from 80 to 200 MPa. It was found that the stress and temperature dependence of minimum creep rate could be successfully described by the power-law creep equation. The power-law stress exponent, n= 5.2 and the activation energy for secondary creep, Q= 164 kJ mol−1, which is close to that observed for self diffusion of aluminum (~140 kJ mol−1). The observed values of nand Qsuggest that the secondary creep of 2124-T851 aluminum alloy is governed by the lattice diffusion controlled dislocation climb process. A Monkman-Grant type relationship between minimum creep rate and time for reaching 1.5% creep strain is proposed and could be employed for predicting the useful creep life of 2124-T851 aluminum alloy.

n order to study the workability and optimize hot forming processing parameters for GH4169 superalloy, the hot deformation behaviors are investigated. The results show that the flow stress strongly depends on the strain rate, deformation temperature and strain. With the increase of strain rates and the decrease of deformation temperature, the flow stress increases. The flow stress exhibits an initial increase with the strain until a peak stress value, showing a obvious work hardening. After the peak stress, increasing strain results in the decrease of stress, indicating a dynamic flow softening. A revised constitutive equation incorporating the effects of temperature, strain rate and work-hardening rate of the material is established by compensation of strain. A good agreement between the measured and predicted results shows that the established model can give an accurate prediction of the flow behavior of GH4169 superalloy.

The cyclic deformation behaviors of hotrolled AZ91 magnesium alloy are studied by asymmetrical cyclic stresscontrolled experiments at room temperature. The ratcheting behavior and fatigue failure mechanism are discussed. Results show that: (1) The ratcheting strain increases sharply with the increase of cycle number at the initial stage, and then tends to be a constant after certain cycles. (2) The fatigue crack initiation and stable propagation regions are flat with lamellar structures, while the unstable propagation and rapid fracture regions are coarse with ductile dimples and tearing edges. (3) The residual twins can be seen as potential damage to fatigue failure of the material, due to its irreversibility of cyclic plastic deformation and damage to grain boundaries.

Evolutionary algorithms (EAs) are population-based global search methods. They have been successfully applied to many complex optimization problems. However, EAs are frequently incapable of finding a convergence solution in default of local search mechanisms. Memetic Algorithms (MAs) are hybrid EAs that combine genetic operators with local search methods. With global exploration and local exploitation in search space, MAs are capable of obtaining more high-quality solutions. On the other hand, mixed-integer hybrid differential evolution (MIHDE), as an EA-based search algorithm, has been successfully applied to many mixed-integer optimization problems. In this paper, a memetic algorithm based on MIHDE is developed for solving mixed-integer optimization problems. However, most of real-world mixed-integer optimization problems frequently consist of equality and/or inequality constraints. In order to effectively handle constraints, an evolutionary Lagrange method based on memetic algorithm is developed to solve the mixed-integer constrained optimization problems. The proposed algorithm is implemented and tested on two benchmark mixed-integer constrained optimization problems. Experimental results show that the proposed algorithm can find better optimal solutions compared with some other search algorithms. Therefore, it implies that the proposed memetic algorithm is a good approach to mixed-integer optimization problems.

The article develops multi-pattern formation exchange using A* searching algorithm, and programs the shortest motion paths for mobile robots. The system contains an image recognition system, a motion platform, some wireless RF modules and five mobile robots. We use Otsu algorithm to recognize the variety 2D bar code to classify variety pattern, and control five mobile robots to execute formation exchange, and present the movement scenario on the motion platform. We have been developed some pattern formations according to game applications, such as hook pattern formation, T pattern formation, L pattern formation, rectangle pattern formation, sward pattern formation and so on, and develop the user interface of the multi-robot system to program motion paths for variety pattern formation exchange on the supervised computer. The supervised computer programs pattern formation exchange according to the image recognition results, and controls mobile robots moving on the motion platform via wireless RF interface. In the experimental results, mobile robots can receive the pattern formation command from the supervised computer, and change the original pattern formation to the assigned pattern formation on the motion platform, and avoid other mobile robots on real-time.

The present study uses a heat sink plate to conduct natural convection in order to examine different areas of the heat sink and the effects of mounting different quantities of LEDs on the same surface on the thermal mechanism performance. Based on the experimental results, when a heat sink plate is arranged vertically, the channel flow between the fins is parallel to gravity. The LED substrate plate temperature is different from that at the end of the fin, and rises with the increase of total power. The thermal resistance rises slowly and then declines with the increase of LED electric power. As for temperature change of the LED substrate and at the end of the fin, when the temperature difference is increased, it also increases the natural convection thrust. For thermal resistance, the environmental thermal resistance at the bottom of the heat sink plate is lower than at the middle and top sections. These LED power emissions will be changed synchronously.

The compressive deformation experiments of 2124-T851 aluminum alloy were carried out over a wide range of temperature and strain rate. An artificial neural network (ANN) model is developed for the analysis and simulation of the correlation between the flow behaviors of hot compressed 2124-T851 aluminum alloy and working conditions. The input parameters of the model consist of strain rate, forming temperature and deformation degree whereas flow stress is the output. A three layer feed-forward network with 15 neurons in a single hidden layer and back propagation (BP) learning algorithm has been employed. Good performance of the ANN model is achieved. The predicted results are consistent with what is expected from fundamental theory of hot compression deformation, which indicates that the excellent capability of the developed ANN model to predict the flow stress level, the strain hardening and flow softening stages is well evidenced.

The NiO-Au composite films with Au contents of 0 to 33.7 at.% are deposited on glass substrates. The high electrical resistivity (ρ) of Au-doped NiO films with Au contents below 1.0 at.% is difficlut to measure by four point probe. The ρ value could be reduced to 30.4 Ω-cm as Au content of 1.4 at.% is added into NiO film. It is reduced significantly to 0.375 Ω-cm as Au content is increased to 13.6 at.%. Further increasing the Au content to 33.7 at.%, the ρ value of NiO film is further decreased to 4 x 10-4 Ω-cm. On the other hand, the transmittance of Au doped NiO films also decreases with increasing Au contents. The transmittance for pure NiO film is as high as 96 %. As the Au contents of 1.4, 13.6, and 33.7 % are added into NiO film, they are decreased drastically to 45 %, 20 %, and 9 % respectively. The XRD patterns of Au-doped NiO films with Au content below 9.6 at.% only appear NiO peaks and their (200) peaks shift slightly to low angle as Au content is increased. When Au content is added to above 9.6 at.%, the NiO crystalline become worse. In addition, further increasing the Au content to above 13.6 at.%, the (111) peak of Au also appears in XRD patterns. This indicating that the Au atoms instead of part of Ni atoms results in the enlargement of NiO lattice for Au-doped NiO film with lower Au contents, but large amount of Au atoms are precipitated from the NiO lattice when the content of Au in the NiO film is increased to above 13.6 at.%.

The NiO-Cu composite films with various Cu contents of 0 – 18.17 at.% are deposited on glass substrate. An ultra high electrical resistivity (ρ) is obtained and cannot be detected by four point probe measurement when the Cu contents in the films are lower than 6.97 at.%. The ρ value is reduced significantly to 35.8 Ω-cm as Cu content is increased to 9.18 at.%, and it further decreases to 0.02 Ω-cm when the Cu content further increases to 18.17 at.%. The Hall measurement for all Cu-doped NiO films show p-type conduction. In addition, the transmittance of NiO films also decreases continuously from 96 % to 43 % as Cu content increases from 0 to 18.17 at.%. The XRD patterns of Cu-doped NiO films only appear NiO peaks and the crystallinity of NiO films becomes worse as Cu content is added to above 6.97 at.%. Large amount of lattice sites of Ni2+ ions in NiO crystalline are replaced by the Cu+ ions that leads to p-type conduction and result in the degradation of crystallinity for NiO-Cu composite films having higher Cu content.

Networks of the cytoskeletal biopolymer actin cross-linked by the compliant protein filamin form soft gels that stiffen dramatically under shear stress. We demonstrate that the elasticity of these networks shows a strong dependence on the mean length of the actin polymers, unlike networks with small, rigid cross-links. This behavior is in agreement with a model of rigid filaments connected by multiple flexible linkers.

Muon-induced neutrons are one of the major backgrounds to various underground experiments, such as dark matter searches, low-energy neutrino oscillation experiments and neutrino-less double beta-decay experiments. Previous experiments on the underground production rate of muon-induced neutrons were mostly carried out either at shallow sites or at very deep sites. The Aberdeen Tunnel experiment aims to measure the neutron production rate at a moderate depth of 611 meters water equivalent. Our apparatus comprises of six layers of plastic-scintillator hodoscopes for tracking the incident cosmic-ray muons, and 760 L of gadolinium-doped liquid-scintillator for both neutron production and detection targets. In this paper, we describe the design and the performance of the apparatus. The preliminary result on the measurement of neutron production rate is also presented.

The experimental result shows that the preferred orientations of NiO thin films are closely related to the working pressure of argon. All of NiO(111), NiO(200), and NiO(220) diffraction peaks are observed in the XRD patterns and exhibited random orientation of NiO film when the film is deposited in low Ar pressure of 5 mTorr. As the Ar pressure is increased to 20 mTorr, only NiO(200) peak appears and shows (200)-textured NiO films. However, the lattice parameter of NiO film deposited in high Ar pressure of 20 mTorr is 0.424 nm, which is much larger than that of NiO bulk (0.417 nm). The lattice parameter can be decreased by post-annealing the film due to the interstitial Ar atoms are released from the NiO lattice and it reduces continuously from 0.423 to 0.417 nm as the NiO films are annealed from 300 to 600 °C. Therefore, post-annealing the NiO film deposited in higher Ar pressure will reduce the lattice misfit between the NiO and L10 FePt film that is beneficial to improve the perpendicular magnetic anisotropy of FePt film.