High-temperature ultra-strength of dual-phase Re0.5MoNbW(TaC)0.5 high-entropy alloy matrix composite

The dual-phase Re0.5MoNbW(TaC)0.5 composite,consisting of refractory body-centered cubic(BCC)high-entropy alloy and carbide with many fine eutectic structures,was successfully synthesized by arc melting.The phase stability,high-temperature mechanical properties and strengthening mechanism of the as-cast composite were studied.The microstructure of the composite remained stable after annealing at 1300℃for 168h.It exhibited remarkably high-temperature strength,yield strength～901 MPa,and true ultimate compressive strength～1186 MPa at 1200℃.The BCC phase and carbide exhibited a semi-coherent interface with good bonding after severe deformation at 1200℃.The dipolar dislocation walls in BCC phase,restricted dynamic interaction between defects in carbide,and the pinning effect of semi-coherent interface offered effective strengthening effects.     

Microstructure,mechanical properties,and cytotoxicity of low Young’s modulus Ti–Nb–Fe–Sn alloys

Journal of Materials Science - Ti–26Nb–2Fe–(0, 2, 4, 6, 8)Sn alloys were prepared by arc melting and subjected to homogenization, cold rolling, and solution treatment. The β...     

Release behavior of 1‐methylcylopropene coated paper‐based shellac solution in response to stepwise humidity changes to develop novel functional packaging for fruit

1‐Methylcyclopropene (1‐MCP) has been shown to be a suitable inhibitor of ethylene production in fruit and vegetables during preservation and distribution. In this study, a 1‐MCP controlled‐release system on coated paper was produced using shellac as the coating material. The effect of humidity and temperature on the release of 1‐MCP from the coated paper was investigated using a dynamic sorption system (DVS) with stepwise humidity changes (initial 20% relative humidity (RH) for 2 h, then increased to 40%, 50%, 60%, and 80% RH for 2 h, respectively). The release rate kinetic data were simulated using an Avrami equation with a mechanism release number n of 1.26. The results showed that the dynamic release of 1‐MCP from the coated paper was mainly affected by humidity, for which the release rate constant could be correlated with moisture concentration in humid air. The highest humidity condition (80% RH) resulted in the highest apparent activation energy of 46.8 kJ/mol. The effect of 1‐MCP coated paper on apple storage was evaluated by measuring the ethylene production rate, flesh firmness, and titratable acidity (TA) of apple. Ethylene production rates of apple were significantly affected with 1‐MCP coated paper. The values were 0.22 nL/g FW/h at 50 mg of 1‐MCP powder and 44.7 nL/g FW/h at 0 mg of 1‐MCP powder after 15 days at 4°C and 15 days at 20°C. The other properties of apple such as flesh firmness and TA also indicated that 1‐MCP coated paper could delay fruit softening during storage time. Based on these results, the release of 1‐MCP could be controlled by coating paper with shellac solution and promising to produce functional packaging for fruit.     

Stable operation of induction-type bearingless motors under loadedconditions

A control method, which realizes stable operation in induction-type bearingless motors under loaded conditions, is proposed. Without a proposed control method, both the amplitude and the direction of radial force vary in accordance with loads. These variations result in interferences of radial force commands in two perpendicular axes. The interferences become a serious problem as a load increases. A shaft finally touches down without proper compensation. It is found that a decoupling of the radial force commands can be realized with compensation of both amplitude and phase angle of four-pole motor current. A decoupling controller is proposed with the principle of a field-oriented controller of conventional induction motors. The results of experiments show the validity of compensations. It is shown that induction-type bearingless motors can be operated stably under loaded conditions, as well as transient conditions     

Markov-type velocity field for efficiently animating water stream

In computer graphics, one of the most challenging tasks is continuously varying phenomena such as waving, swaying, and flowing motions. In this paper, we present a novel hybrid model (physical-stochastic) to create an endless animation in which offline simulation is used to produce an infinitely varying real-time animated result. In this particular case, a water stream model is proposed. Most fully 3D physically based simulation methods for depicting fluid flows are very time and memory consuming. Thus, these methods are still reserved for offline simulations and small-domain real-time simulations, especially in the case of fluid flows with irregularly repeating patterns. The proposed model is based on the tracer particle technique, uses a non-static velocity field, and consists of two main phases. In the first phase, we construct the stochastic velocity field by using the physically based method. The second phase is the main part, in which we create real-time endless animation. Here, we introduce a new type of velocity field which we refer to as a Markov-type velocity field (MTVF). MTVF allows us to animate a water stream endlessly in real-time by avoiding the time-consuming process of solving the corresponding equations for every simulation step.     

Java heap protection for debugging native methods

Java virtual machine (JVM) crashes are often due to an invalid memory reference to the JVM heap. Before the bug that caused the invalid reference can be fixed, its location must be identified. It can be in either the JVM implementation or the native library written in C invoked from Java applications. To help system engineers identify the location, we implemented a feature using page protection that prevents threads executing native methods from referring to the JVM heap. This feature protects the JVM heap during native method execution; if the heap is referred to invalidly, it interrupts the execution by generating a page-fault exception. It then reports the location where the exception was generated. The runtime overhead for using this feature depends on the frequency of native method calls because the protection is switched on each time a native method is called. We evaluated the runtime overhead by running the SPECjvm98, SPECjbb2000, VolanoMark, and JFCMark benchmark suites on a PC with two Intel Xeon^® 1.6 GHz processors. The performance loss was less than 2% for the benchmark items that do not call native methods so frequently (10⁴ times per second) and 5%–20% for the benchmark items that do (10⁴–10⁵ times per second). The worst performance loss was 54%, which was recorded for a benchmark item that calls native methods 2.0×10⁶ times per second.     

Decentralized autonomous control of a quadrupedal locomotion robot using oscillators

This article deals with the design of a control system for a quadrupedal locomotion robot. The proposed control system is composed of a leg motion controller and a gait pattern controller within a hierarchical architecture. The leg controller drives actuators at the joints of the legs using a high-gain local feedback control. It receives the command signal from the gait pattern controller. The gait pattern controller, on the other hand, involves nonlinear oscillators. These oscillators interact with each other through signals from the touch sensors located at the tips of the legs. Various gait patterns emerge through the mutual entrainment of these oscillators. As a result, the system walks stably in a wide velocity range by changing its gait patterns and limiting the increase in energy consumption of the actuators. The performance of the proposed control system is verified by numerical simulations. This work was presented in part at the Fifth International Symposium on Artificial Life and Robotics, Oita, Japan, January 26–28, 2000     

Efficient Nd:YAG laser end pumped by a high-power multistripe laser-diode bar with multiprism array coupling

A 10-W laser-diode bar, a multistripe monolithic laser-diode array, has been used to end pump Nd:YAG. Twelve beams emitted from 12 stripes, spaced 800 μm apart, of a 1-cm linear diode array were collimated with a multiprism array consisting of 14 prismlets with 800-μm width to pump the Nd:YAG facet. The maximum Nd:YAG cw output power at 1064 nm of 3 W was obtained at 10-W laser-diode-bar power with a slope efficiency of 35%, and a TEM(00) spatial mode with values of beam-quality factor M(2) of 1.29 and 1.76 in the planes perpendicular and parallel to the junction, respectively. A pulse width of 25.2 ns (1-kHz repetition) was obtained in acousto-optic Q-switched operation.