A method for off-line compensation of cutting force-induced errors in robotic machining by tool path modification

Industrial robots are promising cost-effective and flexible alternatives for multi-axis milling applications in machining of complex parts of light materials with lower tolerances, having freeform surfaces. As it is well-known, the poor accuracy, stiffness, and the complexity of programming are the most important limiting factors for wider adoption of robotic machining in machine shops. The paper presents the developed method for off-line compensation of machining robot tool tip static displacements as a dominant part of cutting force-induced errors. The developed method is based on modification of programmed trajectory in G-code. Off-line modification of programmed trajectory is performed according to the predicted static tool tip displacements calculated based on developed robot compliance model and cutting forces predicted by mechanistic model. The obtained experimental results show the relevance of developed method since the machining errors could be significantly reduced. This allows the desired accuracy of robot machining to converge towards nominal specifications.     

Model studies of erosion of natural barriers by a wave flow occurring as a result of landslides

Conclusion On the basis of data of model tests it can be stated that substantial deformation of the Usoi landslide will not be observed as a result of a surge overtopping it with the proposed parameters.Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 8, pp. 38–40, August, 1993.     

Preferred color gamut boundaries for wide‐gamut and multiprimary displays

Preferred chroma enhancement and its dependence on hue are studied in a two‐part experiment using a wide‐gamut multiprimary display. Earlier research showed a clear dependence on hue but was limited by the gamut of the display it employed; the present work builds on this while easing the gamut constraints. In the first part of the present experiment, a tuning task was used to refine the preference for chroma boost starting with standard‐gamut (Rec. 709) images. The overall median preferred boost is roughly 20%, but it is not uniform over hues: the preferred boost for orange, yellow, green, and cyan colors is greater than that for blue, magenta, and red colors. Dependence on image content and observer is noted, though a content‐independent chroma boost created by aggregating preference over many images performs well. An adjustment parameter for overall chroma, which incorporates the hue dependence averaged over image content, should be sufficient to handle the vast majority of interobserver variance in preference. In the second part of the experiment, various chroma boost algorithms were evaluated through a paired comparison task. The prescribed hue‐dependent chroma boost is preferred over all other variations, and all hue‐preserving chroma boost variations are preferred over both colorimetrically accurate and na??ve same‐drive‐signal renderings. The results may be applied in display design to select gamut boundaries that maximize satisfaction over the observer population. © 2012 Wiley Periodicals, Inc. Col Res Appl, 39, 169–178, 2014     

BiFeO3 Ceramics: Processing,Electrical, and Electromechanical Properties

Bismuth ferrite (BiFeO₃), a perovskite material, rich in properties and with wide functionality, has had a marked impact on the field of multiferroics, as evidenced by the hundreds of articles published annually over the past 10 years. Studies from the very early stages and particularly those on polycrystalline BiFeO₃ ceramics have been faced with difficulties in the preparation of the perovskite free of secondary phases. In this review, we begin by summarizing the major processing issues and clarifying the thermodynamic and kinetic origins of the formation and stabilization of the frequently observed secondary, nonperovskite phases, such as Bi₂₅FeO₃₉ and Bi₂Fe₄O₉. The second part then focuses on the electrical and electromechanical properties of BiFeO₃, including the electrical conductivity, dielectric permittivity, high‐field polarization, and strain response, as well as the weak‐field piezoelectric properties. We attempt to establish a link between these properties and address, in particular, the macroscopic response of the ceramics under an external field in terms of the dynamic interaction between the pinning centers (e.g., charged defects) and the ferroelectric/ferroelastic domain walls.     

Dependence of the surface morphology of ultrathin bismuth films on mica substrates on the film thickness

The results of studying the surface of 15- to 100-nm-thick bismuth films by atomic-force microscopy are reported. The near-linear character of the dependences of the average surface roughness and the average height of growth patterns on the film thickness is established. It is found that the average crystallite size increases, as the film thickness is increased. A slight dependence of the crystallite size on the film thickness is observed at thicknesses in the range of 27–70 nm.     

Integrated reconfiguration and age-based preventive maintenance decision making

The use of manufacturing system reconfiguration in conjunction with maintenance operations has not been previously reported in the literature. This research attempts to incorporate reconfiguration into Preventive Maintenance (PM) actions for improved system performance in terms of reduced total cost. This paper presents an Integrated Reconfiguration and Age-Based Maintenance (IRABM) policy and applies it to a parallel-serial manufacturing system. The expected total cost of implementing the IRABM policy is estimated and minimized through a simulation-based heuristic optimization procedure. Using this method, it is possible to systematically identify the conditions under which the integration of reconfiguration into maintenance is cost effective. In addition, numerical examples demonstrate that the manufacturing system could have a higher probability of fulfilling production requirements at a lower cost under the IRABM policy compared to the conventional age-based PM policy. The influences of the input parameters associated with reconfiguration, production, and reliability on the performance of IRABM policy also are studied.     

Experimental study of speed of sound in gaseous refrigerant R-507a

The speed of sound in gaseous refrigerants R-134a and R-507a is measured by the method of ultrasonic interferometer in a temperature interval from 293 to 373 K and pressure values from 0.01 to 0.5–2.9 MPa. The errors in measurement of the temperature, pressure, and speed of sound are ±20 mK, ±4 kPa, and ±(0.1–0.2)%, respectively. On the basis of the data obtained, the temperature dependence of the idealgas heat capacity is calculated. The results obtained are compared with calculation of speed of sound from the fundamental state equation for Helmholtz free energy.     

Nanostructured Ti-Cr-B-N and Ti-Cr-Si-C-N coatings for hard-alloy cutting tools

Nanostructured Ti-Cr-B-N and Ti-Cr-Si-C-N coatings with various contents of chromium and nitrogen are obtained by the magnetron sputtering of multiphase composite targets. Their structure and phase composition are investigated by X-ray phase analysis, transmission and scanning electron microscopy, X-ray photoelectron spectroscopy, and optical emission glow-discharge spectroscopy. The Ti-Cr-B-N and Ti-Cr-Si-C-N coatings are based on the fcc phase with texture (100) and crystallite size <25 nm. The Si₃N₄-based hexagonal phase was also revealed in the Ti-Cr-Si-C-N coatings. An investigation into the properties of coatings with the use of methods of nanoindentation, scratch testing, and by performing tribological tests showed that they have a hardness of up to 30 GPa, an adhesion strength no lower than 35 N, and their friction coefficient falls in the range of 0.35–0.57. Coatings also possess high thermal stability, resistance to oxidation, and corrosion stability in a 1N H₂SO₄ solution. The data obtained in tests of hard-alloy cutting tools indicate that the deposition of nanostructured Ti-Cr-B-N and Ti-Cr-Si-C-N coatings increases its resistance by a factor of 11–17.