On the Characterization of the Dynamic Performances of Planar Manipulators

The characterization of the dynamic performances of a manipulator is important both to compare different manipulators and to improve the dynamic performances of a manipulator during the design stage. In a previous paper the concepts of swiftness and of dynamic isotropy were used to characterize some dynamic performances of 3-dof manipulators. This paper analyzes the usefulness of these concepts for three-dof planar manipulators and shows that the concept of swiftness is still significant, whereas the concept of dynamic isotropy has no practical interest. Moreover, it introduces three new dynamic properties that are useful in the design of a 3-dof planar manipulator. Finally, it proposes some indices that measure both the swiftness and the three new dynamic properties and shows how to use them, both for evaluating the dynamic performances of a given 3-dof planar manipulator and for improving the dynamic performances during its design.     

Convergence of the Law of the Environment Seen by the Particle for Directed Polymers in Random Media in the <Emphasis Type="Italic">L</Emphasis><Superscript>2</Superscript> Region

We consider the model of directed polymers in an i.i.d. Gaussian or bounded environment (Imbrie and Spencer in J. Stat. Phys. 52(3/4), 609–626, 1988; Carmona and Hu in Probab. Theory Relat. Fields 124(3), 431–457, 2002; Comets et al. in Adv. Stud. Pure Math. 39, 115–142, 2004) in the L ² region. We prove the convergence of the law of the environment seen by the particle.     

Reflecting diffusions and hyperbolic Brownian motions in multidimensional spheres

We consider diffusion processes $ {{\left( {{{{\underline{\mathrm{X}}}}_d}(t)} \right)}_{{t\geqslant 0}}} $ moving inside spheres $ S_R^d $ ? ? ^d and reflecting orthogonally on their surfaces. We present stochastic differential equations governing the reflecting diffusions and explicitly derive their kernels and distributions. Reflection is obtained by means of the inversion with respect to the sphere $ S_R^d $ . The particular cases of Ornstein–Uhlenbeck process and Brownian motion are examined in detail. The hyperbolic Brownian motion on the Poincaré half-space ? _d is examined in the last part of the paper, and its reflecting counterpart within hyperbolic spheres is studied. Finally, a section is devoted to reflecting hyperbolic Brownian motion in the Poincaré disc D within spheres concentric with D.     

A Size‐Flexible Organometallic Box for the Encapsulation of Fullerenes

A palladium‐cornered molecular square with four pyrene‐bis(imidazolylidene) bridging ligands is reported. This metallo‐polygon can encapsulate C₆₀ and C₇₀. The X‐ray diffraction structures of the empty cage as well as the cages complexed with both fullerenes are described. The fullerene encapsulation produces perturbations in the structural parameters of the metallo‐square, showing that it can adjust the shape of its cavity to the size of each fullerene.     

Maximal Partial Spreads and Flocks

Denote by a flock of a quadratic cone of PG(3,q) by S() the spread of PG(3,q) associated with and by l the common line of the base reguli. Suppose that there are two lines not transversal to a base regulus which share the same lines of S() Then we prove that is either linear or a Kantor-Knuth semifield flock. Using this property we can extend the result of J3 on derivable flocks proving that, if a set of q + 1 lines of S() defines a derivable net different from a base regulus-net, then is either linear or a Kantor-Knuth semifield flock. Moreover if l is not a component of the derivable net, then is linear.     

Mirror fibrations and root stacks of weighted projective spaces

We show that the orbifold Chow ring of a root stack over a well-formed weighted projective space can be naturally seen as the Jacobian algebra of a function on a singular variety.     

Determination of zearalenone and its metabolites in urine samples by liquid chromatography with electrochemical detection using a carbon nanotube-modified electrode

A simple and sensitive method for the separation and determination of zearalenone (ZON) and its secondary metabolites, namely beta-zearalenol (beta-ZAL), beta-zearalanol (beta-ZOL), alpha-zearalenol (alpha-ZAL), alpha-zearalanol (alpha-ZOL) and zearalanone (ZAN) in urine (human, bovine and swine) samples is proposed. The method comprises previous clean-up and pre-concentration on C(18) adsorption cartridges of the analytes followed by liquid chromatographic separation and direct electrochemical detection at +0.85mV using a carbon nanotube-modified glassy carbon electrode (CNT-GCE). This method allows the determination of beta-ZAL, beta-ZOL, alpha-ZAL, alpha-ZOL, ZAN and ZON in a linear range between 5 and 50ngmL(-1), with relative standard deviation values lower than 6.9% (intra-day) and 7.1% (inter-day), in all cases. Detection limits ranging between 1.3ngmL(-1) (beta-ZOL, alpha-ZAL, alpha-ZOL) and 1.4ngmL(-1) (beta-ZAL, ZAN, ZON) were achieved. The usefulness of the proposed method was demonstrated by the analysis of spiked and natural samples of human, bovine and swine urine samples.     

Cu2+ ions as a paramagnetic probe to study the surface chemical modification process of layered double hydroxides and hydroxide salts with nitrate and carboxylate anions

A layered zinc hydroxide nitrate (Zn5(OH)8(NO3)2.2H2O) and a layered double hydroxide (Zn/Al-NO3) were synthesized by coprecipitation and doped with different amounts of Cu2+ (0.2, 1, and 10 mol%), as paramagnetic probe. Although the literature reports that the nitrate ion is free (with D3h symmetry) between the layers of these two structures, the FTIR spectra of two zinc hydroxide nitrate samples show the C2v symmetry for the nitrate ion, whereas the g ||/A || value in the EPR spectra of Cu2+ is high. This fact suggests bonding of some nitrate ions to the layers of the zinc hydroxide nitrate. The zinc hydroxide nitrate was used as matrix in the intercalation reaction with benzoate, o-chlorobenzoate, and o-iodobenzoate ions. FTIR spectra confirm the ionic exchange reaction and the EPR spectroscopy reveals bonding of the organic ions to the inorganic layers of the zinc hydroxide nitrate, while the layered double hydroxides show only exchange reactions.     

Continuous Bulk Process for the Production of High‐Impact Polystyrene: Recent Developments in Modeling and Control

This work presents (in a wider perspective), some of our recent developments in the mathematical modeling and control of bulk polymerization for the production of HIPS. The recent model by Casís assumes the polymerization to be heterogeneous, and it calculates (in two phases) the global molecular structure of the three polymeric components of HIPS (free polystyrene, unreacted polybutadiene, and graft copolymer). At present, a model is being developed capable of estimating the average particle morphology (salami or core‐shell). Assuming a continuous bulk HIPS process as homogeneous, Luciani estimated the evolution of the MFI of the final product during changes of grade, with the aim of minimizing the intermediate off‐spec product. Finally, an unpublished simulation is presented that describes the transitions between the steady state of a HIPS‐grade and that of a general‐purpose polystyrene.