Unified synthesis of compact planar path-generating linkages with rigid and deformable members

A unified procedure for the synthesis of planar linkages that may take the form of rigid body, fully compliant or partially compliant mechanisms is presented. The procedure automates the selection of mechanism topology as characterized by the number and connectivity of the links as well as the nature of the connections between them, the mechanism shape as characterized by the shapes of the individual links, and the mechanism dimensions which include the locations of the joints and the cross-sectional dimensions of the links. The synthesis task is posed as a constrained optimization problem and is solved by a hybrid, elite-preserving genetic algorithm. Three examples of compact mechanisms that trace different non-smooth paths in response to a single, monotonic and bounded force input are used to illustrate the synthesis capability of the procedure. Prototypes of the designs are built and tested to verify their performance. It is observed that in all three examples, partially compliant mechanism designs offer better conformance with design intent than either rigid body or fully compliant mechanisms.     

Modeling the performance of molten carbonate based direct carbon fuel cell anode

A mathematical model is developed to study the performance of a molten carbonate based direct carbon fuel cell anode. The direct carbon fuel cell(DCFC) is a fuel cell which uses solid carbon as fuel and molten carbonate as electrolyte. The model assumes that the 4 electron carbon oxidation reaction is the primary reaction driving the DCFC. However, the 2 electron CO oxidation reaction and the reverse Boudouard reaction is also considered in this model. The model studies the effect of performance parameters on the performance of the DCFC. The effect of the bulk conductivity in the solid phase, the bulk conductivity in the liquid phase, carbon loading and the thickness of the anode layer on the potential and current distribution in the cell is modeled. Model results are compared with experimental data and found to compare well.     

Growth and transport property measurements of rhenium doped tungsten diselenide single crystal

Single crystals of rhenium doped tungsten diselenide i.e. Re_xW_1−xSe₂ (x = 0, 0.0005, 0.001, 0.05, 0.1) are grown by vapour phase technique. The stoichiometry of grown single crystals is confirmed by energy dispersive analysis of X-rays. X-ray powder diffractograms obtained of these compounds were used for lattice parameter determination based on hexagonal system similar to that of host WSe₂.The crystallite size for each sample for different reflection is calculated using Scherrer's formula. Surface morphology as observed under optical microscope reflects that screw dislocation mechanism is responsible for growth of crystals. Electrical properties viz. Hall effect at room temperature, resistivity measurements at low temperature, and high pressure resistivity measurements indicates the semiconducting behaviour of Re_xW_1−xSe₂ (x = 0, 0.0005, 0.001, 0.05, 0.1) single crystals. Thermoelectric power measurements shows p-type nature of host WSe₂ whereas n-type nature of rhenium doped WSe₂ which matches with the results of Hall effect.     

High input impedance voltage‐mode first‐order all‐pass sections

This paper proposes six new first‐order voltage‐mode all‐pass sections (VM‐APSs) based on three general topologies. Each circuit uses two differential voltage current conveyors and three grounded passive components. All the circuits possess high input impedance and easy control of pole frequency either by a simple matching of resistors (two equal‐valued resistors) for the three canonical circuits or by a single resistor for three non‐canonical circuits. PSPICE simulation results using real device 0.5µ CMOS parameters are given to validate the proposed circuits. Copyright © 2007 John Wiley & Sons, Ltd.     

Obstacles facing the diffusion of drip irrigation technology in the Middle Atlas region of Morocco

We examined how the background (urban/rural) of 282 tertiary students influenced their attitudes and actions including their use of natural areas. Most considered that protection of natural spaces was ‘important’. Childhood residence influenced time spent in natural areas as young adults. When time spent in natural spaces was compared with residence status, non‐urban dwellers more frequently visited natural areas than urban dwellers. Rural residents who visited natural spaces were likely to visit more frequently than urban dwellers. The different types of passive recreation carried out in natural spaces and whether the student was involved in environmental restoration activities were not matters influenced by residence status, although there was a difference as between passive or active recreation in natural spaces. Over 80% of participants considered that ‘protection of the natural environment’ was more important than the cost of fresh produce, reduced taxes, fuel prices or ‘better use of recycled material’.     

Cost-effectiveness of solar thermal and electrical energy production

Solar electricity and also solar thermal energy at moderate temperatures, typically 80 to 90°C, can be used for operating systems to provide cooling and water desalination. We analyze the techno-economic viability of converting solar energy to thermal or electrical form.

The analysis shows that, when compared with the conventional process of electricity production, the conversion of solar energy to electrical form is highly uneconomical. On the other hand, conversion of solar energy to thermal form can compete with oil based thermal energy production.     

Choice of solar collector for applications below 100°C

Non-tracking collectors are the important technology options to harness the solar thermal energy at temperatures below 100°C. Thermal energy below this level has very wide applications in the residential and industrial sectors. Also, energy at this level can be used indirectly to produce cooling, fresh water or electricity. Flat plate and evacuated tube collectors with different design, configuration and cost were considered and their energy collection capabilities were estimated under the Kuwaiti conditions for different applications identified with the temperature. Based on the manufacturers' quotations and other economic parameters, the annual amortized cost of solar collectors were estimated. These values were used to estimate the system cost per unit of energy generation. A domestic solar water heater with an unglazed collector is the only solar system having economic viability at present. Evacuated tube collectors stand a good chance of being economically viable in future with increase in fuel prices and/or reduction in system cost.     

Extraction and Isolation of β‐Glucan from Grain Sources—A Review

A collective report on the extraction and isolation of β‐glucan from grain sources, namely, oat, barley, and wheat is presented. An analysis on the effect of medium, pH, and temperature on the purity and yield of the β‐glucan derived under acidic/alkaline/aqueous/enzymatic conditions is also made. Water extraction and alkali extraction processes are preferred as the yield and recovery of extracted β‐glucan were good. Cost‐effective development of the process for deriving high molecular weight β‐glucan is the current requirement for its wide applications in food and pharmaceutical industries.