Cylindrical Diameter Research Articles

EDLC characteristics with high specific capacitance of the CNT electrodes grown on nanoporous alumina templates

Abstract Well-ordered nanoporous alumina templates were fabricated by two-step anodization method by applying a constant voltage of 40 V in oxalic acid solution or of 25 V in sulfuric acid solution. The cylindrical pore diameter and pore density of the templates utilized for the carbon nanotube (CNT) growth were 86 ± 5 nm and 1.2 × 1010 cm−2 in oxalic acid solution and 53 ± 1 nm and 3.1 × 1010 cm−2 in sulfuric acid solution, respectively. The CNTs with uniform diameter of 50 ± 10 nm (oxalic acid) and 44 ± 2 nm (sulfuric acid) were grown on the porous alumina template as electrode materials for the electrochemical double layer capacitor (EDLC). The EDLC characteristics were examined by measuring the capacitances from cyclic voltammograms and the charge–discharge curves. The specific capacitances of the CNT electrodes are 30 ± 1 F/g (Φ = 50 ± 10 nm) and 121 ± 5 F/g (Φ = 44 ± 2 nm). The high specific capacitance of the CNT electrode was achieved by using nanoporous alumina templates with the high pore density and the small and uniform pore diameter.

The performance properties of electrically small resonant multiple-arm folded wire antennas

In this tutorial article, the resonant radiation properties of electrically small, multiple-arm, folded wire antennas are considered and compared as a function of the antenna's height, the cylindrical diameter occupied, the geometry, and the number of folded arms within the antenna structure. The radiation properties considered include resonant resistance, efficiency, radiation patterns, and the operating bandwidth, which is characterized using the antenna's quality factor (Q). It is shown that electrically small, multiple-arm, folded wire antenna designs offer significant performance improvements relative to simple open-ended wire antennas, in terms of increased resonant resistance, bandwidth, and efficiency. However, when multiple-arm, folded wire antennas of the same height and cylindrical diameter, but having significantly different geometries, are made to be self-resonant at the same frequency, they exhibit similar resonant performance properties. This illustrates that the resonant performance properties of these antennas are primarily established by their height and the physical volume occupied relative to the resonant wavelength. Various design parameters are considered and described for achieving self-resonance and a reasonable impedance match with an electrically small, multiple-arm folded wire antenna. Finally, the performance properties of the multiple-arm folded wire configurations are compared with those of an impedance-matched, non-folded, open-ended wire configuration. It is shown that the multiple-arm folded wire configurations exhibit a lower Q than the impedance-matched, non-folded wire configuration.

Extrusion method using nylon 66 fibers for the preparation of porous alumina ceramics with oriented pores

Porous alumina ceramics with unidirectionally oriented pores were prepared using an extrusion method. The paste for extrusion was prepared by mixing alumina and nylon 66 fibers with binder and dispersant. The resulting paste was extruded, dried at room temperature, and after removal of the binder at 600 °C, fired at 1500 °C for 2 h. The pore size in the sintered body, determined from SEM micrographs, was 16 μm, corresponding to the size of the burnt-out nylon 66 fibers. The degree of orientation of the cylindrical pores was evaluated from SEM micrographs to be highly aligned to the extrusion direction. The orientation of the pores decreased with increasing fiber loading because of strong interaction between the fibers. The pore size distribution of the extruded samples showed a peak at 16 μm corresponding to the cylindrical pore diameter and also at 4 and 6 μm corresponding to the pores formed by connection of the fibers.

Cells of Pseudomonas putida and Enterobacter sp. adapt to toxic organic compounds by increasing their size

The phenol-degrading solvent-tolerant bacterium Pseudomonas putida P8 changed its cell shape when grown in the presence of aromatic compounds such as phenol and 4-chlorophenol. The sizes of cells that had been growing after addition of different concentrations of the toxic compounds were measured using a coulter counter that calculates the sizes of the rod-shaped bacteria to diameters of virtual spheres. The cells showed an increase in the diameter depending on the toxic effects of the applied concentrations of both solvents. The same effect was measured for an alkanol degrading bacterium, Enterobacter sp. VKGH12, in the presence of n-butanol. The reaction of the cells to different concentrations of n-butanol was examined by scanning electron microscopy. With this technique it could be shown that the size of the bacteria increased with increasing concentrations of n-butanol. These changes in cell size were dependent on the cellular activity and occurred only after addition of non-lethal concentrations. In the presence of lethal concentrations that completely inhibited cell growth, the cell sizes were similar to those of cells without intoxication. Taking into account the mathematical formula for spherical and cylindrical diameter and surface, respectively, the cells reacted to the presence of organic solvents by decreasing the ratio between surface and volume of the cells and therefore reducing their relative surfaces. As the cell surface and especially the cytoplasmic membrane are the major targets for the toxic effects of membrane-active compounds, this reduction of the relative surface represents an adaptive response to the presence of such compounds.

Dynamics of water in a molecular sieve by quasielastic neutron scattering

We have investigated the dynamics of water confined in a molecular sieve, with a cylindrical pore diameter of 10 A, by means of quasielastic neutron scattering (QENS). Both the incoherent and coherent intermediate scattering functions I(Q,t) were determined by time-of-flight QENS and the neutron spin-echo technique, respectively. The results show that I(Q,t) is considerably more stretched in time with a slightly larger average relaxation time in the case of coherent scattering. From the Q dependence of I(Q,t) it is clear that the observed dynamics is almost of an ordinary translational nature. A comparison with previous dielectric measurements suggests a possible merging of the alpha and beta relaxations of the confined water at T=185 K, although the alpha relaxation cannot be directly observed at lower temperatures due to the severe confinement. The present results are discussed in relation to previous results for water confined in a Na-vermiculite clay, where the average relaxation time from spin-echo measurements was found to be slower than in the present system (particularly at low temperatures).

Optimal cylindrical handle diameter for grip force tasks

This study tested maximum grip force on cylindrical aluminum handles to evaluate the relationships between handle diameter (25–50 mm diameter handles), perceived comfort, finger and phalange force distribution, and electromyographic efficiency of finger flexor and extensor muscle activity. A force glove system containing 16 thin profile force sensors was developed to measure finger and phalangeal forces on the cylindrical handles. Participants (n=24) rated the mid-sized handles (30, 35 and 40 mm) as the most comfortable for maximum grip force exertions. Using a polynomial regression the handle diameter that maximized subjective comfort was calculated as a function of the user's hand length. This optimal handle diameter was 19.7% of the user's hand length. Total finger force capability was inversely related with handle diameter. Electromyographic amplitude of the primary flexor and extensor was unaffected by handle diameter, so the efficiency of the muscle electrical activity followed the same relationship with handle diameter as total finger force. Individual finger and phalange force distributions were examined to evaluate their relationship with perceived comfort. A non-uniform finger/phalange force distribution, in which finger force was proportional to finger muscle capabilities, exhibited a stronger correlation with subjective ratings of comfort than a uniform finger/phalange force distribution. Results obtained in this study will provide guidelines to hand-tool designers and manufacturers for maximizing handle comfort based on the user's hand size.

Development of Atomization Method in Microchannel and Its Basic Characteristics

A new atomization method in W/O (water in oil) system was developed for liquid sampling system of.μTAS (micro total analysis systems). This device was masufactured using soft MEMS (micro electro mechanical systems) technology and comprised of simple rectangular microchannels made of PDMS (polydimethylsiloxane). Using this device, picoliter-sized cylindrical liquids were generated successfully and sequentially. To investigate the breakup motion of cylindrical liquid in microchannel, a light emitting diode system was developed for the function of the strobe light. Furthermore, theoretical analysis was carried out to predict the size of cylindrical liquids. The effects of continuous phase velocity and microchannel wall on the diameter of cylindrical liquids were clarified experimentally and numerically. The numerical results of cylindrical liquid diameter quantitatively agreed with the experimental results. According to this theoretical model developed here, the device can be optimized to generate smaller and uniform cylindical liquids.

DEVELOPMENT OF A PREDICTIVE MODEL FOR ARCH DESTRUCTION BY VIBRATION IN STORAGE BINS FOR COHESIVE BULK SOLIDS

A predictive model is developed for arch destruction during vertical vibration in storage bins for cohesive bulksolids. The model is based on the equilibrium of static and inertial forces on an arch. The cohesive bulk material is simulatedas thin layers connected by elastic and damping elements during vibration. The model predicts the minimum accelerationamplitudes and thrust forces required for destructing arches at certain locations in storage bins. A small cylindrical bin of178 mm diameter and 120 mm high was used to conduct an experiment to validate the prediction model. Tests were conductedfor vibration frequencies from 18 to 90 Hz. It is theoretically proven that the optimal vibration frequencies for arch destructionare among the natural frequencies of the cohesive material storage system. The model predictions compared favorably withexperimental results. The average difference between the model predictions and measured acceleration amplitudes for archdestruction was 7%.

Analysis of temporal and spatial temperature gradients at pronouncedly fluctuating cooling conditions

Realised cooling velocities of a probe (cylinder) at discrete radius points during cooling at pronouncedly fluctuating cooling conditions are presented. Submerging the probe into an air-corundum (Al2O3) particles fluidised system of insufficient cooling capacity imposes the fluctuating cooling conditions. The particles have an average granulation of 95 m; the cylindrical probe diameter is 50 mm and its height 175 mm. The probe surface temperature and the temperature 1.5 mm beneath its surface are measured with built-in thermocouples. The thermocouples have a very high sensitivity, which enables temperature variation recording according to the cooling dynamics. The relevant cooling time is 125 seconds. The temperature changes in discrete points of the cylinder radius are determined by the control volume method. The calculation results indicate a shift of the maximum cooling velocity towards the interior of the cylinder.

Electronic device for measuring volume of selected fruit and vegetables

This paper presents the design, construction, and testing of an electronic device for measuring the volumes of selected fruit and vegetables. The device was designed with reference to the principle of capacitance measurement and consists of three parts: cylindrical casing, electronic circuitry and a personal computer. Volumes recorded by the device in experiments with watermelons, large cucumbers, wax gourds and guavas have been compared with measurements obtained from the water displacement (WD) method. The evaluated parameters included: (i) sample shapes, defined by the ratio of minor and major axes, ranging from 0.252 to 0.946, (ii) diameter of the cylindrical casing (25, 50 and 75 cm), and (iii) orientation of the sample in the casing. Results showed that the electronic device measured sample volumes at error margins ranging from 1.1% (watermelons) to 4.7% (large cucumbers). Varying the angular displacement of samples around the longitudinal axis (0, 90, 180 and 270°) did not influence error at the 1% significance level. However, variations in sample shape, cylindrical casing diameter and angular displacement of the sample around the vertical axis (0, 45, 90, 135 and 180°) significantly affected error at the 1% significance level. Minimum error was recorded when a 75-cm diameter casing was used and the longitudinal axis of the sample was aligned to that of the casing.

Experiment on Settling of Slender Particles with Large Aspect Ratio and Correlation of the Drag Coefficient

The drag coefficient of slender particles is an important parameter to operations involved with them. In this paper, settling of slender particles with a large aspect ratio and of different materials in laminar Newtonian fluids is studied. It is observed that the particle orientation oscillates during settling and stabilizes to its equilibrium horizontal orientation eventually. Experiments are conducted in different fluids (water and glycerin solutions, quiescent or flowing) for particles with different densities (from 1125 to 8000 kg·m-3) and aspect ratios (from 4 to 50). It is found that the product of the drag coefficient and cosine of the orientation angle is independent of the particle aspect ratio and the bulk liquid flow. Instead of using the concept of sphericity, the drag coefficient of slender particles is effectively correlated with the orientation and the Reynolds number based on the particle cylindrical diameter. With the aid of the modified Archimedes number, the proposed general correlation CD cos φ = (24/Re)(0.006983 + 0.6224Re-1.046)(ρp/ρl)-1.537(Ar*)0.8524 represents very well the experimental data under various experimental conditions with the average relative error of 9.4%.

Modelling of laser-material interaction using semi-analytical approach

In this paper different aspects of laser-material interaction were considered. Semi-analytical method was developed and applied to analysis of spatial and temporal distribution of temperature field inside bulk materials. In particular, cases with cylindrical geometry, finite diameter and infinite length as well as cylindrical geometry, finite diameter and finite length were considered. For solving the governing partial differential equations (PDEs) the Laplace transform and the Fourier method of variables separation were used. In this way instead of the original governing PDEs, ordinary differential equations were solved. Particular solutions of the ordinary differential equations were used for evaluating the general solution, which was expressed in terms of series of particular solutions. The unknown coefficients in the series of particular solutions were determined using the boundary and initial conditions. The laser-material interaction was represented using the thermal model. These interactions for the cases of the high power laser in pulse and continuous regime were analysed. The incident intensity of laser radiation was under critical intensity.Using these methods the temperature field distribution was obtained in the Laplace transform domain. The convolution integral and the Green function were used to determine the temperature field in time domain. General semi-analytical methods and numerical solutions of appropriate transcendent equations were considered and numerical results for Al specimens were presented. The influences of laser beam parameters to the temperature field distribution and isothermal curves inside the bulk material were evaluated.

Improved EDLC Characteristics of the CNTs Grown on the Nanoporous Alumina Templates

AbstractThe specific capacitance of the carbon nanotube (CNT) electrode can be increased by using nanoporous alumina templates with the high pore density and the small and uniform pore diameter. The surface area of the CNTs was controlled and increased by preparing them with uniform diameters. The well-ordered nanoporous alumina templates were fabricated by a two-step anodization method. The cylindrical pore diameter, length, and density of the template utilized for the CNT growth was 53 ± 1 nm, 2 μm, and 3.1×1010 cm−2, respectively. The CNTs with uniform diameter of 44 ± 2 nm were grown on the porous alumina template as electrode materials for the electric double-layer capacitor (EDLC). The EDLC characteristic of the CNT electrodes was examined by measuring the capacitances from the cyclic voltammograms. The specific capacitance of the CNT electrodes can be increased to the value of 121 ± 5 F/g.

Experimental Study of the Impact of Boundary Conditions on Oil Recovery by Co-Current and Counter-Current Spontaneous Imbibition

Spontaneous imbibition (SI) is a very important oil recovery mechanism from low-permeability fractured reservoirs. The impact of different sample shapes and boundary conditions on oil recovery by counter-current and co-current SI into low-permeability (2 mD) strongly water-wet outcrop chalk have been investigated. The experimental program was divided into two parts. In part 1, counter-current SI was studied by submerging cubic, cylindrical, and irregular rock samples totally in the aqueous phase, whereas co-current SI was investigated in part 2 by exposing different portions of a cubic rock sample to an oil-phase. The scaling law of Ma et al. -1 was used to correlate counter-current SI data with all parameters than the characteristic length, L C , held essentially constant. The results confirm the ability for L C to account for cylindrical (diameters in the range from 2 to 10 cm) and cubic sample shapes and different no-flow surface boundary conditions (2, 4 and 5 faces were coated with polyester on the cubic rock samples; top and bottom faces on the cylindrical cores). Rock samples having irregular shapes (increasing and decreasing cross-sectional areas were investigated) could not be scaled according to L C because the overall shape of the imbibition curves deviated from curves generated by rock samples having regular shape. No scaling law correlating imbibition data for different boundary conditions exists for tests performed under co-current flow conditions; hence the results in part 2 of the experimental program are interpreted qualitatively. When using the SI rate for a cube with all faces open to imbibition as the reference (counter-current flow conditions), the results show that depending on the area fraction of the cube covered by oil, co-current SI can either be faster (water-oil area-ratio (WOAR) > 1), equal (WOAR = 1) or slower (WOAR < 1)) than the reference system. In all cases, ultimate recovery is significantly higher for tests performed under co-current flow conditions than under counter-current (70% of initially oil in place (IOIP) vs 58% IOIP for counter-current). The results indicate that when evaluating oil recovery potential on reservoir rock samples due to SI experimentally, tests should be performed both under co-current and counter-current flow conditions because the latter one might under certain circumstances predict too low rates and ultimate recoveries.

World bank endorses water resources strategy

Gas cyclones have many industrial applications in solid–gas separation. The vortex finder is an essential part in gas cyclones where the shape and diameter highly affect the cyclone performance. Many optimization studies have been conducted to optimize the cylindrical vortex finder diameter. This study introduces a new vortex finder shape optimized for minimum pressure drop using the discrete adjoint method. The new optimum cyclone will save 66% from the driving power needed for the Stairmand cyclone. To efficiently perform the grid independence study for the new cyclone, a new framework using the adjoint solver and the grid convergence index is proposed and tested. The proposed framework relies on local mesh adaptation instead of the global mesh refinement approach. A comparison of numerical simulation of the new cyclone and the Stairmand cyclone confirms the superior performance of the new vortex finder shape for the pressure drop and the cut-off diameter. The results of this study open a new era gas cyclones geometry optimization by using the adjoint method instead of the traditional surrogate based optimization technique. Moreover, the computational costs for the grid independence studies will be reduced via the application of the adjoint methods.

Synthesis of Nanostructured Titania Powders via Hydrolysis of Titanium Isopropoxide in Supercritical Carbon Dioxide

Titania powders were synthesized via hydrolysis of titanium(IV) isopropoxide (TIP) in supercritical carbon dioxide (SCCD). Injection of TIP into water-in-CO2 (w/c) dispersions resulted in precipitation of spherical titania particles, and free-flowing white titania powders were isolated in 65−70% yield by slow isothermal depressurization. Qualitatively similar results were obtained with and without the addition of an anionic phosphate fluorosurfactant (DuPont Zonyl FSP) to stabilize the w/c dispersions. The titania powders had broad particle size distributions (20−800 nm) and specific surface areas in the 100−500 m2/g range. Addition of Zonyl FSP resulted in a decrease in specific surface area at a given water-to-alkoxide molar ratio (hydrolysis level). The specific surface area increased as the hydrolysis level was increased, irrespective of the presence of surfactant. The surface area is associated primarily with internal porosity of the spherical titania particles, as evidenced by scanning transmission electron microscopy and N2 porosimetry. Calcination of a surfactant-free titania powder at 300 °C in air decreased the specific surface area from ∼300 to 65 m2/g and increased the mean cylindrical pore diameter from 2.6 to 4.9 nm, consistent with collapse of micropores. Titania nanoparticle synthesis via TIP hydrolysis in SCCD was attempted using w/c microemulsions formed with ammonium carboxylate perfluoropolyether (PFPE-NH4); however, injection of TIP into PFPE-NH4-stabilized microemulsions resulted in precipitation of 0.3−2 μm titania particles. The use of other CO2-soluble titanium(IV) alkoxides gave qualitatively similar results.

159. The speed modulation of the patient's rotation in TSEI-RD to improve the homogeneity of the dose distribution in the horizontal plane. In phantom's results

Purpose The aim of this study was to reduce the differences in doses accumulated in the points, localised in the same horizontal plane, on the patient's skin, during the rotary-dual total skin electron irradiation (TSEI RD). Material and Method During the standard TSEI RD technique, the patient was standing on the slowly and continuously rotating platform while the irradiation with two dual electron fields was performed. In this study a non-continuous platform movement was implemented. One cylindrical (diameter of 30 cm) and two elliptical (diameters of 20/40 cm and 25/35 cm) wax phantoms were used. The one full circle (360 degree) of the platform was divided into eight fractions. The platform speed was calculated individually for the each fraction. The total time of one rotation in both modes of the movements: continuous and non-continuous were equal. Phantoms were irradiated with two dual fields: size of 36×36 cm at the isocenter each, source-phantom distance of 300 cm, and with 6 MeV electrons’ energy (output). Doses were measured with the semiconductor detectors which were placed equidistantly (distance between dosimetrical points by 45 degree) on the same horizontal plane on the phantom's surface. Results The respective measured doses after normalisation to those previously calculated were as follows: 1/ for the cylindrical phantom (diameter of 30 cm) – 100.1%, 99.8%, 100.3%, 99.4%, 100.1%,99.8%, 100,3%,99.4%;2/ for the elliptical phantom of 25/35 cm – 98.3%, 99.6%, 103.2%, 99.2%, 97.8%, 99.6%, 103.2%, 100.7% and 3/ for the elliptical phantom of 20/40 cm – 95.8%, 99.9%, 105%, 98.8%, 95.8%, 100.2%, 105%, 99.3%. The modulation of the speed during platform's rotation resulted in the decrease of the dose discrepancies. The respective measured doses after the normalization performed with the same as above way were equal to: 1/ for the elliptical phantom of 25/35 cm – 99.4%, 99.9%, 101.3%, 100.5%, 100.1%, 100.9%, 101.1%, 99.7%; 2/ for the elliptical phantom of 20/40 cm – 98.9%, 100.2%, 102.4%, 99.8%, 99%, 99.9%, 102.1%, 100.5%. Conclusion Results of the dose inphantom measurements showed that the speed modulation of the platform reduced the dose inhomogeneity at the horizontal plane on the phantom's surface.

Surface interaction and chemical imaging in plasma spectrometry induced with a line-focused laser beam

An experimental line imaging arrangement for surface characterization of solid samples in air at atmospheric pressure using laser-induced plasma spectrometry (LIPS) is presented. A microline plasma was formed by focusing a Nd:YAG laser beam operating at 532 nm with a cylindrical lens on the sample surface. The spatial resolution was investigated as a function of beam focal parameters including cylindrical lens focal length, beam diameter and pulse energy. While focal length affected lateral resolution only slightly, a strong dependence of crater width on beam diameter and laser pulse energy was observed. For routine sample imaging the crater width obtained was close to 15 μm while the spatial resolution along the spectrometer slit was 17.4 μm. Compositional distribution maps of inclusion constituents (Mg, Ca, Si, Al and Ti) in stainless steel are shown. The results demonstrate the potential of microline imaging for fast analysis of large area samples and for screening purposes.

Characterising the packing and dead-end filter cake compressibility of the polymorphic yeast Kluyveromyces marxianus var. marxianus NRRLy2415

Suspensions of the polymorphic yeast Kluyveromyces marxianus var. marxianus NRRLy2415 were grown in batch and continuous culture, producing broths with a range of mean cell morphologies. The mean cell aspect ratio, L dm, defined as the mean ratio of total cell length to equivalent cylindrical diameter, was measured for each broth by image analysis and ranged from 1.7 to 51. The porosity of the cell pellet formed in a bench-top centrifuge was measured for each broth and in all cases, the pellet porosity decreased linearly with increasing centrifuge speed. This decrease became more pronounced as L dm increased. The extrapolated zero-speed pellet porosity, ε 0, was correlated with L dm by the expression ε 0=1−1/(1.24+0.062 L dm). The dead-end specific cake resistance, α, was measured for each broth in the pressure range 30–180 kPa. The cake compressibility constant, k c, defined by the expression α=α 0(1+k c ΔP) was found to increase with increasing values of L dm. The increase was most rapid in the region, L dm<10. Microscopic observations indicate that cell deformation at branching points may contribute to cake compressibility.

A composite resonator for simultaneous NMR and EPR imagingexperiments

Electron paramagnetic resonance imaging (EPRI) and nuclear magneticresonance imaging (NMRI) are currently used for in vivo spectroscopyand imaging. A multimodal apparatus based on the simultaneous observation ofelectronic and nuclear signals is very desirable because it combines theability of NMRI to provide an accurate description of the internal structureof a sample with the ability of EPRI to detect the presence of free radicalsand map their distribution. At a given value of the magnetic field B0, the electronic and nuclear transitions have very different resonancefrequencies. This required the development of a multimodal spectrometer thatcombined the two spectroscopic modalities. In spite of the complexity of theelectronic apparatus involved, the main requirement was for a resonator thatallowed the simultaneous irradiation and observation of the signals at the twofrequencies with good sensitivity. The EPR section of the composite resonatorconsists of a one-loop, two-gap resonator tuned to 1 GHz and the NMR sectionis a solenoid, coaxial to the EPR section, tuned to 1.52 MHz. Both sectionshave been designed to produce a homogeneous rf field in a cylindrical regionof diameter 3 cm and length 4 cm. The rf magnetic fields B1e and B1nare directed along the axis of the magnet. The probe was tested on a phantomcomprising two separate regions containing 0.73 g of lithium phthalocyanine(LiPtc) powder and 20 ml of an aqueous solution of CuSO4, respectively, andboth EPR and NMR signals have been collected. Measurements of the sensitivityhave also been made.