Secondary current distribution in a two-dimensional model cell composed of an electrode with an open part

On the assumption that the relation between the overpotential and the current density is expressed by linear and Butler-Volmer equations, secondary current distributions were obtained in a two-dimensional model cell in which a working electrode with an open part serving to release gas bubbles to the back side of the electrode is located parallel to a counter electrode or a separator. Cell resistances or cell voltage in the model cell were evaluated for various combinations of geometrical parameters and heterogeneous kinetic parameters by means of the finite element method. As a result, when the kinetic equation was the linear approximation, the cell resistance or cell voltage varied mainly with two geometrical parameters (the interelectrode distance and the electrode surface ratio) and the kinetic parameters. On the other hand, when the kinetic equation was of the Butler-Volmer type the cell voltage varied with the kinetic parameters and the percentage of open area instead of the electrode surface ratio. In order to facilitate estimation of cell voltage for an industrial productiontype cell composed of electrodes with voids or holes, the computed cell voltages were expressed as functions of these parameters in simple approximate equations. A criterion for estimating whether the cell voltage is controlled by the overpotential or the ohmic drop is presented.     

Development of a “volume heat-trap” type solar collector using a fine-particle semitransparent liquid suspension (FPSS) as a heat vehicle and heat storage medium Unsteady, one-dimensional heat transfer in a horizontal FPSS layer heated by thermal radiation

The objective of this work is to develop a “volume heat-trap” solar collector in which a fine-particle semitransparent liquid suspension (FPSS) is used as a heat vehicle and heat storage fluid.In the first step of our fundamental research, a multiband model, taking into consideration the effect of fine particle suspension in a continuous fluid on radiation and absorption characteristics, was formulated to analyze the unsteady one-dimensional heat transfer in a horizontal FPSS layer heated by thermal radiation.The experiments were conducted for three kinds of suspensions: diethylphthalate-graphite, -carborundum and -silicon dioxide. The time-changes of temperature distributions within the suspension layer were measured under step- and intermittent-radiative heating conditions, using an infrared lamp bundle as a simulated model of solar radiation.The experimental data obtained for the rate and efficiency of heat collection, as well as for the unsteady temperature distribution within the FPSS layer, show satisfactory agreement with calculations based on the proposed theoretical analysis.It is the feelings of the authors that the FPSS used as a heat collection fluid in this work has a good heat transfer characteristics to enable the development of high efficient solar collector.     

A simplified tensile damage analysis method for composite laminates using a quasi-three-dimensional model

Measurement of the strength of laminated composites is very difficult because their failure processes imply various failure modes, which are, for example, an interlaminar delamination, a destruction of matrix and an interfacial fracture between fiber and matrix. However, that strength is one of the most important characteristics in structural design using laminated composites. Hence we try a fractural progress analysis of laminated composites using a quasi-three-dimensional analysis method under a tensile load. The quasi-three-dimensional model is constructed of shell elements and beam elements which represent fiber and matrix respectively. The fractural progress analyses of the laminated composites are carried out to evaluate this proposed model. The precision is very good. Therefore we confirm that this proposed model can simulate a transverse crack and an interlaminar delamination.     

Primary current distribution in a two-dimensional model cell composed of an electrode with an open part

A two-dimensional model for industrial production-type cells in which electrodes have holes for releasing gas bubbles to the back side of the electrodes and a separator located between the working- and counter-electrodes is proposed in conjunction with some geometrical parameters of the electrode and the cell. The primary current distribution in this model was calculated for a series of values of the parameters by the finite element method. The current distribution in the cell with the separator is quite different from that without the separator. Variations of the ohmic potential drop with the parameters reveal that the cell resistance is determined not only by the interelectrode distance but also by the per cent open area and in some cases by the superficial surface area. The partitions of the total current into the currents on the front, the back and the intermediate sides of the working-electrode are obtained as functions of the per cent open area and the superficial surface area. These results may be useful for estimating the performance of the electrode.Nomenclature b distance from the back wall to the back side of the working-electrode - d ₁ distance between the front side of the working-electrode and the separator (or the counter electrode when cell has no separator) - d ₂ width of the separator - I total current per half pitch - L length of a real electrolysis cell - n coordinate perpendicular to the boundary of the model cell - o _p per cent open area, given by Equation 1 for the present model - p pitch, i.e. twice the length of the unit cell - R equivalent unit-cell resistance defined by Equation 13 - R _t total cell resistance - r ratio of the average current density on each side of the working-electrode to that of the counter-electrode - s superficial surface area, given by Equation 2 for the present model - t thickness of the working electrode - u _k function defined by Equation 10 - test function - w width of the working electrode - x abscissa located on the cell model - y ordinate located on the cell model - d infinitesimal length on the boundary - ₁ resistivity of the solution phase - ₂ resistivity of the separator - potential - ^* potential at the working electrode - linear integration contour along I0, AH or EFDH - double integration space in the solution or the separator phase     

Electron Microscopic Study of Heat-Treated Carbon Nanotubes

Carbon nanotubes, which were made by DC arc discharge of a graphite electrode, were heat-treated at about 250°C in intermediate vacuum of 10^-4 Torr and 10^-2 Torr. Considerable thickening of carbon nanotubes and periodic morphology like that of living organisms were observed by scanning electron microscopy.     

Computation of primary current distribution and cell resistance at model electrodes with circular perforations

A model of a gas-evolving production-type cell with a circularly perforated anode is described. A unit of the model was composed of a disk cathode, a separator and a ring anode in turn. These were located in a cylindrical cell filled with solution. Primary current and potential distributions in the unit cell were computed by solving the Laplace equation in cylindrical coordinates by the finite element method. Geometric parameters determining the distributions were primarily the interelectrode distance and the percentage open area. Current distribution in the open part was larger than that in a rectangular cell with the same geometric parameters because of the cylindrically concentrated supply of the current from the inner part of the ring and the back side of the anode. The unit cell resistance was evaluated as a function of the geometric parameters. It exhibited a linear variation of the interelectrode distance and the square of the percentage open area. There was, however, a slight dependence of the percentage open area on the unit cell resistance and hence it is concluded that circularly perforated electrodes provide higher performance than louvre-type electrodes.     

An Optimally Controlled Respirator

An optimally controlled respirator was developed. It has three main features: 1) ventilation is controlled by the patient's metabolic rate from continuously measured C02 output, 2) physiologic dead space approximated as a linear function of tidal volume is used to estimate alveolar ventilation, and 3) respiratory rate is computed to minimize ventilatory work.