Kinematic analysis of the wire parallel mechanism for full coordinate measuring of industrial robot

This paper presents a wire parallel mechanism for full coordinate measuring of industrial robot. The mechanism is constructed with six parallel wires that act as links. The position and orientation of a robot end-effector are obtained from the wire lengths. The equations of the forward kinematics are solved by a Newton-Raphson method, and the unique solution is determined from the geometric configuration of the mechanism. A method to estimate the workspace is presented. Through simulations, it is verified that the proposed mechanism can measure a robot pose over a large workspace, and can be used effectively for full coordinate measuring of a robot with little cost and effort.     

Elementary School Drinking: The Role of Temperament and Learning.

Drinking in elementary school, despite its low base rate, has been shown to predict alcohol use in middle school (Wilson, Battistich, Syme, & Boyce, 2002), which in turn predicts alcohol abuse or dependence in young adults (Guo, Collins, Hill, & Hawkins, 2000). The authors report 1 of the 1st examinations of the relationship between personality and psychosocial learning risk factors and drinking behavior among elementary school students. Fifth-grade students completed measures of disinhibition, positive and negative alcohol expectancies, and drinking. MIMIC modeling, tests of mediation, and tests of moderation were completed to test these relations. It was found that disinhibition and positive alcohol expectancies were each related to drinking in 5th graders. Disinhibition moderated the relation between positive alcohol expectancies and drinking in some cases. Mediation was not supported. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heterogeneous sympathetic innervation in German shepherd dogs with inherited ventricular arrhythmia and sudden cardiac death

BACKGROUND: Recently, a colony of German shepherd dogs with inherited spontaneous cardiac arrhythmias and associated sudden death has been developed and characterized. Due to the median age of onset of the arrhythmia (4.5 months), the tendency for the arrhythmia to occur during REM sleep or after exercise, and the absence of structural heart disease, we hypothesized a developmental abnormality of the sympathetic innervation to the heart. METHODS AND RESULTS: We studied 11 dogs from this colony, ranging in age from 6 months to 6 years, and four 7-month-old German shepherd dogs unrelated to the colony as controls. We imaged the distribution of functional myocardial sympathetic innervation and perfusion with [123I]metaiodobenzylguanidine (MIBG) and 201Tl, respectively. Sympathetic nerve distribution was evaluated morphologically by immunocytochemical localization of tyrosine hydroxylase. All of the hearts showed evidence of a regional decrease in MIBG uptake, ranging from 5.3% to 53.4% of the myocardium, whereas control dogs showed homogeneous MIBG uptake. Immunocytochemical studies on sections from regions with decreased MIBG uptake showed a striking paucity of nerves compared with regions with normal MIBG uptake, confirming denervation. When the dogs were grouped into those with (n=6) and without (n=5) evidence of ventricular tachycardia on ambulatory ECG, the group with ventricular tachycardia showed 35+/-16.5% denervation, whereas the group without ventricular tachycardia showed 12+/-5.6% denervation (P<.02). CONCLUSIONS: Abnormal heterogeneous sympathetic innervation exists in these dogs with inherited ventricular arrhythmia and sudden cardiac death. Mechanisms relating the presence and extent of regional denervation to the incidence of ventricular arrhythmia remain to be defined.     

The Evolution of As-cast Microstructure of Ternary Mg-Al-Zn Alloys: An Experimental and Modeling Study

A numerical formulation of solidification model which can predict the microsegregation and microstructural features for multicomponent alloys is presented. The model incorporates the kinetic features during solidification such as solute back diffusion, dendrite tip undercooling, and secondary arm coarsening. The model is dynamically linked to thermodynamic library for accurate input of thermodynamic data. The modeling results are tested against the directional solidification experiments for Mg-Al-Zn alloys. The experiments were conducted in the cooling rate range of 0.13 to 2.33 K/s and microstructural features such as secondary arm spacing, primary dendrite arm spacing, second phase fraction, and microsegregation were compared with the modeling results. Based on the model and the experimental data, a solidification map was built in order to provide guidelines for as-cast microstructural features of Mg-Al-Zn alloys in a wide range of solidification conditions.     

Rheological properties of molten polymers. I. Homopolymer systems

Experimental work has been carried out to investigate the influence of molecular weight distribution and long chain branching on both viscous and elastic properties of molten polymers, using a capillary rheometer, as described in a recent paper by Han. The materials used for the study are three high-density polyethylene samples of widely different molecular weight distributions and a low-density polyethylene containing much long-chain branching. For the analysis of the experimental data, and to obtain the information on the melt elasticity, the concept of the exit pressure recently advanced by Han is used. The study shows that the sample containing long-chain branching is much more elastic than the samples containing little or no long-chain branching, and that the broader the molecular weight distribution of the material, the more elastic the material is. These findings are in conformity with those reported in the literature. Also studied were blends of two high-density polyethylenes having widely different molecular weight distributions. The results of the blends systems show a maximum in melt viscosity as well as in elasticity for a certain blending ratio. The results of the present study may be of considerable interest to those who are concerned with modifying the structure of polymer and also with determining optimum processing conditions.     

A study of sandwich foam coextrusion

An experimental study of sandwich foam coextrusion was carried out, using a sheet-forming die with a feedblock. Polymers used for the experiment were low-density polyethylene (LDPE) for the outer layers and ethylene–vinyl acetate (EVA), with the chemical blowing agent azodicarbonamide, for the foamed core component. The present study has shown that the cell size and its distribution in the foamed core and the mechanical properties of the sandwiched foam product can be controlled by a judicious choice of the thickness ratio of the core to skin components, the meltextrusion temperature, and the concentration of chemical blowing agent.     

Influence of the die entry angle on the entrance pressure drop,recoverable elastic energy,and onset of flow instability in polymer melt flow

An experimental study has been carried out to investigate the effects of die entry angle on the entrance pressure drop, recoverable elastic energy, and onset of melt fracture in the flow of viscoelastic polymeric melts through a capillary die. For the study, capillaries with an L/D ratio of 4 and with varying die entry angles, 15°, 30°, 60°, 90°, 120°, and 180°, were used for extruding low-density polyethylene and high-density polyethylene. Measurements were taken of wall normal stresses along the upstream reservoir section, tapered conical section, and straight capillary section.     

Studies of converging flows of viscoelastic polymeric melts. II. Velocity measurements in the entrance region of a sharp-edged slit die

An experimental study has been carried out to measure velocities of viscoelastic polymeric melts flowing into a sharp-edged slit die and in the fully developed region of the slit die. For the velocity measurement, the technique of streak photography was used, in which photographs are made of the movement of tracer particles suspended in a molten polymer. Materials investigated were polypropylene, high-density polyethylene, and polystyrene. From the photographs, local velocities in the entrance region were determined by measuring the streak length, a reference length, and the exposure time of the camera. A comparison was also made of the experimentally determined velocity profiles in the fully developed region with the theoretically predicted ones, showing a reasonable agreement between the two.     

Effect of Co-Deposited Iron on Microstructures and Properties of Electroplated Nanocrystalline Nickel-Iron Alloys

Nickel-iron nanocrystalline alloys with different compositions and grain sizes were fabricated by electroplating for MEMS devices. The iron content of the deposits was changed by varying the nickel/iron ion ratio in the electrolyte. X-ray diffraction (XRD) analysis was applied for measuring the strength of the texture and grain size of the deposits. The nickel/iron atom ratio of the deposits was analyzed by EDS. The hardness of the alloys was evaluated by Vickers hardness indenter. The internal stress of the deposits was measured by thin film stress measurement using Stoney's formula. Surface morphology and roughness were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Hardness and internal stress mechanism of the electroplated structure as a function of Fe ion content and current density were revealed. With increasing the iron content, the hardness and internal stress of the deposits increase. An excellent correlation between the increase in the internal stress and the loss of (200) texture were found.     

Analysis of the performance of plasticating single-screw extruders with a new concept of solid-bed deformation

The performance of plasticating single-screw extruders is analyzed by combining three functional sections: (a) solids-conveying section, (b) melting section, and (c) melt-conveying section. In the analysis of the melting section, we have incorporated a new concept of solid-bed deformation (i.e., the rheology of the solid bed) into Lindt-Elbirli's analysis and included convective heat transfer in the energy equation. Specifically, we have computed stresses on the surfaces of the solid bed, which is surrounded by thin melt films and a melt pool, and, also, computed the apparent modulus of the solid bed in the bulk state as a function of temperature and position within the solid bed, along the extruder axis. From this information, we were able to compute the extent of solid-bed deformation, by assuming a linear stress-strain relationship as the constitutive equation of the solid bed. In this approach, we do not assume a priori whether the solid bed is rigid or freely deformable. The solution of the system equations gives us the following information: (a) whether or not the solid bed deforms and if it does, then, how much; (b) the solid-bed velocity along the extruder axis; (c) pressure profiles along the extruder axis; (d) solid-bed profiles in the melting zone along the extruder axis; (e) temperature profiles along the extruder axis; (f) velocity and temperature distributions in the melt pool along the extruder axis; and (g) thicknesses of thin melt films surrounding the solid bed. Theoretically predicted solid bed and pressure profiles along the extruder axis are compared with experimental results reported in the literature. We have pointed out an urgent need for measurements of the apparent modulus of the solid bed in the bulk state as a function of temperature and pressure, under a combined shear/drag flow field.