Placement of a manipulator for minimum cycle time

Productivity of a manipulator depends, largely, on the time it takes to traverse a path, which is a function of the capacity of the actuators to produce torque. Increasing the torque capacity of the actuators to reduce path traversal time may be unrealistic in many cases. Therefore, this article studies the effects of the manipulator location, within a workcell, on the path traversal time. The article defines the boundaries of the manipulator base locus when the end‐effector path is prescribed. Effects of joint mechanical limits and obstacles on this locus are also considered. The proposed algorithm uses nonlinear programming to search the manipulator base locus for the base location that yields the minimum time to traverse a path, subject to the actuator torque constraints of the manipulator. Detailed examples are included. ©1999 John Wiley & Sons, Inc.     

Study of Fuel Ratios on the Fusion Reactivity in an Inertial Electrostatic Confinement Device Using a Residual Gas Analyzer

Gridded Inertial Electrostatic confinement (IEC) devices are of interest due to their flexibility in burning advanced fuels, their tuning ability of the applied voltage to the reaction cross-section. Although this device is not suitable for power production in its present form, it does have several near term applications. The number of applications of this device increases with increasing fusion reactivity. These devices are simple to operate but are inherently complicated to understand and an effort to incrementally understand the device to improve its operational efficiency is underway at University of Wisconsin, Madison. Of all the parameters under study we are focusing on the effects of flow rate and flow ratio on the fusion reactivity in the present paper. Experiments were conducted to understand the influence of fuel flow ratio on the fusion reactions. The residual gas analyzer (RGA) was used to study the impurity concentration as the flow ratio was changed. It was observed that the higher flow rate resulted in reduced impurity levels and hence an increase in fusion rate. Several different species of gases were detected, some of these molecules formed inside the RGA analyzer. The flow ratio scan revealed that the optimum mixture of D₂ with ³He to be D₂:³He::1:2 for maximum D–³He fusion rate.     

New thiophene‐based donor–acceptor conjugated polymers carrying fluorene or cyanovinylene units: Synthesis,characterization, and electroluminescent properties

Two new thiophene‐based donor–acceptor (D–A) conjugated polymers, PDTOFV and PDTOCN, are synthesized and characterized. The polymers are readily soluble in common organic solvents and exhibit good thermal stability with onset decomposition temperature (T_d) in the range 310?330°C. Cyclic voltammetry studies revealed that polymers possess low‐lying highest occupied molecular orbital (HOMO) energy levels (?5.94 eV for PDTOFV and ?5.86 eV for PDTOCN) and low‐lying lowest unoccupied molecular orbital (LUMO) energy levels (?3.35 eV for PDTOFV and ?3.55 eV for PDTOCN). The optical band gap is calculated from onset absorption edge of the polymer film. The polymers exhibit green fluorescence with fluorescence quantum yields (?_fl) of 38% and 42%, respectively, for PDTOFV and PDTOCN. Polymer light‐emitting diodes (PLEDs) are fabricated using these polymers with a device configuration of ITO/PEDOT:PSS/polymer/Al. The device based on PDTOFV emitted green light with Commission Internationale de I'Eclairage (CIE) coordinate values of (0.25, 0.39). Whereas, the device based on PDTOCN showed white light emission with CIE coordinate values of (0.32, 0.35), which is very close to the values (0.33, 0.33) of standard white light emission. The threshold voltages of the PLEDs are determined by current density‐voltage characteristics and are found to be 7.3 and 3.9 V for PDTOFV and PDTOCN, respectively. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Effect of Zr-SBA-15 support on catalytic functionalities of Mo, CoMo, NiMo hydrotreating catalysts

SBA-15 and ZrO₂ (10–50 wt.%) containing SBA-15 mesoporous materials were prepared by direct and post-synthesis methods. Characterization using low angle XRD, pore size distribution, CO₂ chemisorption indicate that hexagonal mesoporous structure is retained even after ZrO₂ addition (25 wt.%). Mo, CoMo and NiMo catalysts prepared using these supports were examined by XRD, oxygen chemisorption, temperature programmed reduction (TPR). The catalysts were tested for hydrodesulfurization (HDS) of thiophene and hydrogenation (HYD) of cyclohexene. HDS of thiophene for 8%Mo, 3%Co8%Mo, and 3%Ni8%Mo increases with increasing ZrO₂ loading in SBA-15 up to 25 wt.%. Oxygen chemisorption and TPR hydrogen consumption indicated that the molybdenum dispersion and anion vacancies, and catalytic activities are significantly influenced by ZrO₂ content in Zr-SBA-15. A comparison indicated that TiO₂-SBA-15, ZrO₂-SBA-15 supported CoMo catalysts show higher activities for hydrodesulfurization.     

Characterization and Evaluation of Neuronal Trans-Differentiation with Electrophysiological Properties of Mesenchymal Stem Cells Isolated from Porcine Endometrium

Endometrial stromal cells (EMSCs) obtained from porcine uterus (n = 6) were positive for mesenchymal stem cell markers (CD29, CD44 and CD90), and negative for epithelial marker CD9 and hematopoietic markers CD34, CD45 analyzed by flow cytometry. Further the cells were positive for expression of mesenchymal markers, CD105, CD140b, and CD144 by PCR. Pluripotent markers OCT4, SOX2, and NANOG were positively expressed in EMSCs analyzed by Western blotting and PCR. Further, differentiation into adipocytes and osteocytes was confirmed by cytochemical staining and lineage specific gene expression by quantitative realtime-PCR. Adipocyte (FABP, LPL, AP2) and osteocyte specific genes (ON, BG, RUNX2) in differentiated EMSCs showed significant (p < 0.05) increase in expression compared to undifferentiated control cells. Neurogenic transdifferentiation of EMSCs exhibited distinctive dendritic morphology with axon projections and neuronal specific genes, NFM, NGF, MBP, NES, B3T and MAP2 and proteins, B3T, NFM, NGF, and TRKA were positively expressed in neuronal differentiated cells. Functional analysis of neuronal differentiated EMSCs displayed voltage-dependence and kinetics for transient outward K⁺ currents (I_to), at holding potential of −80 mV, Na⁺ currents and during current clamp, neuronal differentiated EMSCs was more negative than that of control EMSCs. Porcine EMSCs is a suitable model for studying molecular mechanism of transdifferentiation, assessment of electrophysiological properties and their efficiency during in vivo transplantation.     

Cyclopropenoid fatty acids in seed oils ofSida acuta andSida rhombifolia (malvaceae)

Seed oils ofSida acuta andSida rhombifolia were found to contain sterculic (11.0, 10.8%) and malvalic (1.7, 2.0%) acids respectively, in addition to the normal fatty acids. Co-occurrence of these acids was established by gas liquid chromatography of the silver nitrate-methanol-treated methyl esters usingSterculia foetida esters as a reference standard. This gas liquid chromatography technique of quantitation was found most suitable to estimate these acids in low level cyclopropenoid acid-containing seed oils.     

Protein engineering of alcohol dehydrogenase -- 1. Effects of two amino acid changes in the active site of yeast ADH-1

One of the promises held out by protein engineering is the abilityto alter predictably the properties of an enzyme to enable itto find new substrates or catalyse existing substrates moreefficiently, such manipulations being of interest both enzymologicallyand, potentially, industrially. It has been postulated thatin yeast alcohol dehydrogenase (YADH-1) certain amino acidssuch as Trp 93 and Thr 48 constrict the active site due to theirbulky side chains and thus impede catalysis of molecules largerthan ethanol. To study effects of enlarging the active sitewe have made two changes into YADH-1, replacing Trp 93 withPhe and Thr 48 with Ser. Kinetic experiments showed that thisenzyme had marked increases in reaction velocity for the n-alcoholspropanol, butanol, pentanol, hexanol, heptanol, octanol andcinnamyl alcohol compared to the parent, agreeing with the predictionthat expanding the active site should facilitate the oxidationof larger alcohols. The substrate affinities were slightly reducedin the altered enzyme, possibly due to its having reduced hydrophobicityat Phe 93.     

Hydrazine-reduction of graphite- and graphene oxide

We prepared hydrazine-reduced materials from both graphite oxide (GO) particles, which were not exfoliated, and completely exfoliated individual graphene oxide platelets, and then analyzed their chemical and structural properties by elemental analysis, XPS, TGA, XRD, and SEM. Both reduced materials showed distinctly different chemical and structural properties from one another. While hydrazine reduction of graphene oxide platelets produced agglomerates of exfoliated platelets, the reduction of GO particles produced particles that were not exfoliated. The degree of chemical reduction of reduced GO particles was lower than that of reduced graphene oxide and the BET surface area of reduced GO was much lower than that of reduced graphene oxide.     

Effect of deposition orientations on dimensional and mechanical properties of the thin-walled structure fabricated by tungsten inert gas (TIG) welding-based additive manufacturing process

Welding-based additive manufacturing can potentially produce a cost-effective process for the production of dense metallic parts. Tungsten inert gas (TIG) welding-based additive manufacturing process uses wire as a filler material and offers a high deposition rate with low spattering. In this study, different orientations of wire feeding nozzle and TIG welding torch, such as front wire feeding (FWF), back wire feeding (BWF), and side wire feeding (SWF), were investigated for thin-walled metal deposition with enhanced dimensional accuracy and mechanical properties. The dimensional accuracy of thin-walls deposited at four different orientations were investigated in terms of deposition height and deposition width. The FWF orientation with higher wire feeding angle and SWF orientation produced poor dimensional accuracy in the deposition. FWF orientation with normal wire feeding angle and BWF orientation provided a decent dimensional accuracy and surface appearance. The deposited samples exhibited a similar trend for Vickers microhardness, residual stress, and microstructure for the four different wire feeding orientations.