An ultrasonically levitated noncontact stage using traveling vibrations on precision ceramic guide rails

This paper presents a noncontact sliding table design and measurements of its performance via ultrasonic levitation. A slider placed atop two vibrating guide rails is levitated by an acoustic radiation force emitted from the rails. A flexural traveling wave propagating along the guide rails allows noncontact transportation of the slider. Permitting a transport mechanism that reduces abrasion and dust generation with an inexpensive and simple structure. The profile of the sliding table was designed using the finite-element analysis (FEA) for high levitation and transportation efficiency. The prototype sliding table was made of alumina ceramic (Al2O3) to increase machining accuracy and rigidity using a structure composed of a pair of guide rails with a triangular cross section and piezoelectric transducers. Two types of transducers were used: bolt-clamped Langevin transducers and bimorph transducers. A 40-mm long slider was designed to fit atop the two rail guides. Flexural standing waves and torsional standing waves were observed along the guide rails at resonance, and the levitation of the slider was obtained using the flexural mode even while the levitation distance was less than 10 microm. The levitation distance of the slider was measured while increasing the slider's weight. The levitation pressure, rigidity, and vertical displacement amplitude of the levitating slider thus were measured to be 6.7 kN/m2, 3.0 kN/microm/m2, and less than 1 microm, respectively. Noncontact transport of the slider was achieved using phased drive of the two transducers at either end of the vibrating guide rail. By controlling the phase difference, the slider transportation direction could be switched, and a maximum thrust of 13 mN was obtained.     

Real-time tracking of CO₂ injected into a subsurface coal fire through high-frequency measurements of the ¹³CO₂ signature

CO? was injected into a coal fire burning at a depth of 15 m in the subsurface in southwestern Colorado, USA. Measurements were made of the 13CO? isotopic signature of gas exhaust from an observation well and two surface fissures. The goal of the test was to determine (1) whether CO? with a distinct isotopic signature could be used as a tracer to identify flow pathways and travel times in a combustion setting where CO? was present in significant quantities in the gases being emitted from the coalbed fire, and (2) to confirm the existence of a self-propagating system of air-intake and combustion gas exhaust that has been previously proposed. CO? was injected in three separate periods. The 13CO? isotopic signature was measured at high frequency (0.5 Hz) before, during, and after the injection periods for gas flowing from fissures over the fire and from gas entering an observation well drilled into the formation just above the fire but near the combustion zone. In two cases, a shift in the isotopic signature of outgassing CO? provided clear evidence that injected CO? had traveled from the injection well to the observation point, while in a third case, no response was seen and the fissure could not be assumed to have a flowpath connected with the injection well. High-frequency measurements of the 13CO? signature of gas in observation wells is identified as a viable technique for tracking CO? injected into subsurface formations in real-time. In addition, a chimney-like coupled air-intake and exhaust outlet system feeding the combustion of the coal seam was confirmed. This can be used to further develop strategies for extinguishing the fire.     

Structural optimization methods of nonlinear static analysis with contact and its application to design lightweight gear box of automatic transmission of vehicles

In this paper, we consider lightweight design methods for gear box of automatic transmission of vehicles with contact constraints. Lightweight design is a fundamental requirement for protecting the environment and improving fuel economy. In addition, durability is another important requirement for safe driving. However, in the design of automatic transmissions, these two requirements are usually in a trade-off relationship and engineers spend a long design study time. This paper deals with design approaches using structural optimization method to design lightweight structures and to minimize stress with contact constraints. Stress with contact constraints is solved using the finite element method. Three different structural optimization methods, topometry, topography and freeform optimization, are applied for the design of a lightweight gear box of an automatic transmission. The optimization results show that the optimization methods successfully found the lightweight gear box design and can be used at the early stage of the design process of automatic transmissions.     

Current-perpendicular-to-plane giant magnetoresistance in Co/Cu multilayered nanocylinders electrodeposited into anodized aluminum oxide nanochannels with ultra-large aspect ratio

Journal of Materials Science: Materials in Electronics - An anodized aluminum oxide (AAO) thick film with numerous nanochannels was synthesized by a cathodic exfoliation technique from a metallic...     

The effect of lubricants on deep drawability of zinc-coated steel sheets

The effect of lubricants on deep drawability was studied for two types of zinc-coated steel sheets on a high-speed deep-drawing machine. The drawability of galvannealed steel sheet, GA, at low speeds is significantly improved by friction modifiers, due to reduction in frictional forces around the die radius. In contrast to the results for GA, double layered steel, GAE, which has an Fe-rich alloy coating on the top, and is superior to GA in terms of drawability, is insensitive to changes in the additives. This is mainly because the hardness of the upper coating layer of GAE decreases frictional resistance through a decline in the boundary contact area.