Ant Colony Optimization Inspired Algorithm for 3D Object Segmentation into its Constituent Parts

Neural Processing Letters - This work focuses on the use of an Ant colony optimization (ACO) based approach to the problem of 3D object segmentation. The ACO metaheuristic uses a set of agents...     

Toroidal High-Density Singularity in a Small Plasma Focus

A toroidal singularity in the current sheet of a Plasma Focus operated at tens of joules (PF-50J) leading to the formation of a high-density singularity on the plasma sheath was observed on interferographic images of discharges in 6 mbar of Deuterium gas. The phenomenon was numerically simulated by means of the 2D numerical code Cshock, which was able to reproduce the plasma kinetics and the evolution of the electrical variables, as well as the formation, movement and density of the plasmoid structure.     

Path planning approach based on flock dynamics of moving particles

A novel method based on the behaviour of a flock of moving particles is proposed in order to solve the path planning problem of a mobile robot in two-dimensional dynamical sceneries. The mentioned particles search free obstacles zones into the scenery using a set of collective behaviour rules. The positions of the members of the flock form the search space. A heuristic method, referred to as dynamical particle chain (DPC), is used to join the position of the robot with the target through consecutive connections among the particles of the flock. The result is a free obstacle path, which is able to adapt its structure to environmental changes. The feasibility of the proposed method and its comparison with other algorithms are also discussed and illustrated.     

Explanation of Bitter Taste of Venom of Ponerine Ant, Pachycondyla apicalis

The venom gland of workers of Pachycondyla (= Neoponera) apicalis (Hymenoptera: Formicidae) contains the bitter-tasting cyclic dipeptide of leucine and phenylalanine [cyclo-leu-phe or 3-benzyl-6-(2-methylpropyl)-2,5-piperazinedione]. The venom also contains proteins of undetermined activity. It is suggested that the function of the venom may be both defensive and offensive. The mandibular glands of N. apicalis contains δ-decalactone and benzaldehyde.     

Active sound quality control of engine induced cavity noise

Active control solutions appear to be a feasible approach to cope with the steadily increasing requirements for noise reduction in the transportation industry. Active controllers tend to be designed with a target on the sound pressure level reduction. However, the perceived control efficiency for the occupants can be more accurately assessed if psychoacoustic metrics can be taken into account. Therefore, this paper aims to evaluate, numerically and experimentally, the effect of a feedback controller on the sound quality of a vehicle mockup excited with engine noise. The proposed simulation scheme is described and experimentally validated. The engine excitation is provided by a sound quality equivalent engine simulator, running on a real-time platform that delivers harmonic excitation in function of the driving condition. The controller performance is evaluated in terms of specific loudness and roughness. It is shown that the use of a quite simple control strategy, such as a velocity feedback, can result in satisfactory loudness reduction with slightly spread roughness, improving the overall perception of the engine sound.     

N-[2-[4-(4-Chlorophenyl)piperazin-1-yl]ethyl]-3-methoxybenzamide: a potent and selective dopamine D4 ligand

A series of new 1-aryl-4-alkylpiperazines containing a terminal benzamide fragment or a tetralin-1-yl nucleus on the alkyl chain were synthesized and tested for binding at cloned human dopamine D4 and D2 receptor subtypes. A SAFIR (structure-affinity relationship) study on this series is herein discussed. The most relevant D4 receptor affinities were displayed by N-[omega-[4-arylpiperazin-1-yl]alkyl]-methoxybenzamides (compounds 5, 16-20), their IC50 values ranging between 0.057 and 7.8 nM. Among these, N-[2-[4-(4-chlorophenyl)piperazin-1-yl]ethyl]-3-methoxybenzamide (17) emerged since it exhibited very high affinity for dopamine D4 receptor (IC50 = 0.057 nM) with selectivity of >10 000 for the D4 versus the D2 receptor; compound 17 was also selective versus serotonin 5-HT1A and adrenergic alpha1 receptors.     

In situ syntheses of a suspension agent based on a styrene–acrylic acid copolymer for the suspension polymerization of styrene

We carried out the suspension polymerization of styrene, initiated with benzoyl peroxide at 80°C, in the presence of the simultaneous polymerization of acrylic acid in the water phase, initiated by potassium peroxidisulfate (KPS) at the same temperature. The polymerization in the water phase was started at certain times after the beginning of the polymerization of styrene. Then, a continuous addition of KPS was carried out at a given landing rate and during variable feeding times. The water‐phase polymerization actually produced a copolymer of styrene and acrylic acid, which displayed surface‐active properties. The particle size distribution depended on the variables mentioned earlier (starting time, KPS feeding rate, and addition time), being controlled by the molecular weight, and on the composition of the copolymer produced and its availability at the increasing conversion of styrene. A second distribution of submicronic particles was produced. Both families of particles had about the same molecular weight. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3271–3285, 2002     

Chemical investigation of aggregation behavior ofTriatoma bugs (Hemiptera: Reduviidae)

Nymphs ofTriatoma infestans andTriatoma mazzottii are weakly attracted to their feces and to extracts of feces in polar solvents, but not to nonpolar solvent extracts. The major volatile compounds identified in feces by solvent extraction and thermal desorption wereo-aminoacetophenone, 4-methylquinazoline, and 2,4-dimethylquinazoline, but these showed no attractant activity at a range of concentrations. Choice tests with a moving current of air gave no positive reaction to feces, extracts, or pure compounds.     

Evaluating the LCD algorithm for solving linear systems of equations arising from implicit SUPG formulation of compressible flows

In this work we evaluate the performance of the left conjugate direction method recently introduced by Yuan, Golub, Plemmons and Cecílio for the solution of non‐symmetric systems of linear equations arising from the implicit semi‐discrete SUPG finite element formulation of advective–diffusive and inviscid compressible flows. We extend the original algorithm to accommodate restarts and typical element‐by‐element preconditioners. We also show how to select the first left conjugate vector to start LCD. Several problems are solved, accessing performance parameters such as number of iterations, memory requirements and CPU times, and results are compared with other algorithms, such as GMRES, TFQMR and Bi‐CGSTAB. Copyright © 2004 John Wiley & Sons, Ltd.