A compliant mechanism with variable stiffness achieved by rotary actuators and shape-memory alloy

The aim of this article is to study the consequences of the active stiffening of a compliant mechanism on the workspace created by the deformation of its structure. In connection with recent soft robotics research integrating shape-memory alloys (SMAs), the variation in stiffness over time is here obtained by the thermal activation of a nickel–titanium SMA spring. The workspace is created by the deformation (in the strength of materials sense) controlled by two rotary actuators acting on a structure comprising two angled flexible beams. In addition to a natural variation in the elasticity modulus of the SMA component during its thermal activation, its shape reconfiguration adds a structural deformation modifying the workspace. The existence of a common area between the workspaces of the mechanism corresponding to the non-activated and activated modes of the SMA is preserved. Several compliance maps are determined from measurements using a laser tracker targeting a given position of the loaded structure. The impact of SMA pre-stretch on stiffness variability is compared to that of a change in Young’s modulus. Variations in the stiffness distributions between the two modes reveal interesting properties (stiffness sign inversion, anisotropy) for the future optimal design of compliant mechanisms with high versatility, associating the spatial positions of the effector with variable stiffness values.     

Polymer complexes. Part XVI. Structural chemistry of poly-(5-vinylsalicylidene)aniline complexes

Transition Metal Chemistry - Poly(5-vinylsalicylidene)aniline homopolymer and polymer complexes of 5-vinylsalicylideneaniline with CuII, CoII, NiII, CdII and $? UO_{2}^{2+}$ have been...     

Improving sample preparation of gold-containing ores of the second and third groups for assay analysis

A procedure is proposed for the sample preparation of gold-containing ores of the second and third groups for assay analysis; it allows for an improvement in the accuracy of the results of analysis.     

Vibrational relaxation of CO2(00°1) and N2O(00°1) by NO

The far-from-resonance transfers and the de-excitation processes in CO₂-NO and N₂O-NO systems have been studied by measuring fluorescence decay rate constants of CO₂ or N₂O excited to the (00°1) level by laser radiation. The diagrams giving the variations of these rate constants versus the molar fraction of CO₂ or N₂O have been set out. From these diagrams, the relative importance of the V-V transfer and V-T de-excitation rate constants is discussed. The transfer rate constants have been calculated from a semiclassical theory in which the interaction potential is a sum of four atom-atom Morse potentials. The disagreement observed between calculated and experimental values probably results from the attractive multipolar forces which the theory does not take into account.     

Generalized Weber Problem with Rectangular Regions

The problem of locating one or more new facilities relative to a number of existing rectangular regions is treated for the case where the rectilinear norm is used. The new facilities are to be located such that the total weighted distance is minimized. If there is interfacility interaction among the new facilities, a gradient-free nonlinear search algorithm is utilized. Computational experience suggests that this algorithm is expedient even in the solution of large problems.     

Steiner's problem and fagnano's result on the sphere

This note describes the nature of optimal solutions for the spherical Steiner-Weber location problem for the case of unit weights and either 3 or 4 demand points (requireing 4 demand points to lie in an open hemisphere). Geometrically appealing results which are necessary conditions for optimum solutions and spherical analogs of known planar results are obtained.     

Reliable electron affinities of perfluorocyclopropane and perfluorocyclobutane from convergent ab initio computations

To resolve discrepancies concerning the magnitude of the electron affinities of perfluorocyclopropane and perfluorocyclobutane, quantum chemical calculations have been carried out with the MP2 and CCSD(T) methods in conjunction with augmented correlation consistent basis sets (aug-cc-pVX Z, X = D, T, Q). Though no experimental values have been found for perfluorocyclopropane, we estimate its electron affinity to be 0.17 eV (0.00 eV without zero-point vibrational energy corrections). In addition, determination of the electron affinity of perfluorocyclobutane (0.61 and 0.44 eV with and without zero-point vibrational energy corrections, respectively) is in good agreement with experimental values reported by Miller and co-workers (0.63 +/- 0.05 eV). This study also demonstrates that the widely prescribed B3LYP/DZP++ model chemistry for computing electron affinities does not correctly describe these systems.     

Efficiency analysis in two-stage structures using fuzzy data envelopment analysis

Two-stage data envelopment analysis (TsDEA) models evaluate the performance of a set of production systems in which each system includes two operational stages. Taking into account the internal structures is commonly found in many situations such as seller-buyer supply chain, health care provision and environmental management. Contrary to conventional DEA models as a black-box structure, TsDEA provides further insight into sources of inefficiencies and a more informative basis for performance evaluation. In addition, ignoring the qualitative and imprecise data leads to distorted evaluations, both for the subunits and the system efficiency. We present the fuzzy input and output-oriented TsDEA models to calculate the global and pure technical efficiencies of a system and sub-processes when some data are fuzzy. To this end, we propose a possibilistic programming problem and then convert it into a deterministic interval programming problem using the α-level based method. The proposed method preserves the link between two stages in the sense that the total efficiency of the system is equal to the product of the efficiencies derived from two stages. In addition to the study of technical efficiency, this research includes two further contributions to the ancillary literature; firstly, we minutely discuss the efficiency decompositions to indicate the sources of inefficiency and secondly, we present a method for ranking the efficient units in a fuzzy environment. An empirical illustration is also utilised to show the applicability of the proposed technique.     

Localization from Incomplete Noisy Distance Measurements

We consider the problem of positioning a cloud of points in the Euclidean space ? ^d , using noisy measurements of a subset of pairwise distances. This task has applications in various areas, such as sensor network localization and reconstruction of protein conformations from NMR measurements. It is also closely related to dimensionality reduction problems and manifold learning, where the goal is to learn the underlying global geometry of a data set using local (or partial) metric information. Here we propose a reconstruction algorithm based on semidefinite programming. For a random geometric graph model and uniformly bounded noise, we provide a precise characterization of the algorithm’s performance: in the noiseless case, we find a radius r ₀ beyond which the algorithm reconstructs the exact positions (up to rigid transformations). In the presence of noise, we obtain upper and lower bounds on the reconstruction error that match up to a factor that depends only on the dimension d, and the average degree of the nodes in the graph.