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Operating Mechanism (operating + mechanism)

Distribution by Scientific Domains

Polymers and Materials Science	75%

Selected Abstracts

Creep failure mechanisms of a Ti-6Al-4V thick plate

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 11 2001
F. J. Seco
The creep failure operating mechanisms of a 17-mm thick plate of a Ti,6Al,4V alloy in various heat treating conditions have been investigated. Specimens in the as-received, mill-annealed, condition (50 min maintenance at 720 °C and air cooled as the final step of the thermomechanical process) showed the lowest creep resistance and their metallographic analysis revealed that the temperature-activated dislocation climb was the mechanism responsible for the failure and that observed holes were generated by plastic deformation, rather than by creep cavitation. Conversely, maximum times to failure were recorded in beta-annealed specimens (1030 °C for 30 min, air cooled and aged for 2 h at 730 °C). The fracture surfaces of these broken specimens exhibited an intergranular morphology that was attributed to grain boundary sliding along the former beta grains. Finally, alpha,beta field-annealed samples (940 °C 4 h, and furnace cooled to 700 °C) possessed intermediate lives between those of mill-annealed and beta-annealed specimens and the failure operating mechanism was diffusional creep by the nucleation and coalescence of the creep cavities generated at the alpha,beta interfaces and the triple points. [source]

Hybrid Nanoparticle/Organic Devices with Strong Resonant Tunneling Behaviors

ADVANCED FUNCTIONAL MATERIALS, Issue 16 2009
Tianhang Zheng
Abstract A hybrid nanoparticle/organic device consisting of small molecule organic semiconductors and Ag nanoparticles is reported. The single device exhibits unusual properties of organic resonant tunneling diode (ORTD) at low driving voltage region and offers light emission at high voltage. For ORTD, a strong negative differential resistance behavior is demonstrated at room temperature. The current resonance with the peak-to-valley current ratio of over 4.6 and narrow linewidth of only ,1.4,V is achieved. A detailed operating mechanism of the charging and emission modes is proposed, which can be discussed in terms of the strong charge-trapping effect of Ag nanoparticles. The repeatable operations of hybrid device show the mutual influences between two modes and the light emission properties of the ORTD are also discussed. [source]

Organic Single-Crystal Schottky Gate Transistors

ADVANCED MATERIALS, Issue 36 2009
Toshihiko Kaji
Schottky contacts and Schottky gate transistors on organic single crystals are successfully fabricated, and enable the complete understanding of the operating mechanism as well as a full description of the energy-band diagram. This represents a considerable step forward in the understanding of organic semiconductors, and offers a viable route for organic-device design. [source]

Development of an Algorithm to Regulate Pump Output for a Closed Air-Loop Type Pneumatic Biventricular Assist Device

ARTIFICIAL ORGANS, Issue 12 2009
Kyoung Won Nam
Abstract The closed air space-type of extracorporeal pneumatic ventricular assist device (VAD) developed by the Korea Artificial Organ Center utilizes a bellows-transforming mechanism to generate the air pressure required to pump blood. This operating mechanism can reduce the size and weight of the driving unit; however, the output of the blood pump can be affected by the pressure loading conditions of the blood sac. Therefore, to guarantee a proper pump output level, regardless of the pressure loading conditions that vary over time, automatic pump output regulation of the blood pump is required. We describe herein a pump output regulation algorithm that was developed to maintain pump output around a reference level against various afterload pressures, and verified the pump performance in vitro. Based on actual operating conditions in animal experiments, the pumping rate was limited to 40,84 beats per minute, and the afterload pressure was limited to 80,150 mm Hg. The tested reference pump output was 4.0 L/min. During experiments, the pump output was successfully and automatically regulated within the preset area regardless of the varying afterload conditions. The results of this preliminary experiment can be used as the basis for an automatic control algorithm that can enhance the stability and reliability of the applied VAD. [source]