Experimental and numerical characterization of the transverse dispersion at the exit of a short ceramic foam inside a pipe

The paper theoretically and numerically describes and experimentally studies transverse dispersion of a passive tracer in highly porous ceramic foams of different pore sizes. The pore Reynolds numbers range from 10 to 300. Digital images of the dispersion patterns were recorded and an approximate transverse dispersion coefficient was determined. Numerical solutions of the steady fluid flow and scalar concentrations confirm that the transverse dispersion coefficient models, based on the assumption of dominance of mechanical dispersion and on the linear dependence of the transverse dispersion model on ud, are able to predict satisfactorily the dispersion of a tracer for the range of Reynolds numbers considered. An alternative derivation of this linear dependence based on the closure of the volume averaged scalar transport equation is also presented. The influence of the length of the porous media in the stream direction on transversal and longitudinal dispersion is consistent with findings for packed beds at much lower Peclet and Reynolds numbers.     

Smart Ferrofluid with Quick Gel Transformation in Tumors for MRI‐Guided Local Magnetic Thermochemotherapy

Improved techniques for local administration of anticancer drugs are needed to reduce the side effects of chemotherapy owing to leakage of anticancer drugs from tumors and to enhance therapeutic efficacy. This study presents the development of smart ferrofluid that transforms immediately into a gel in tumors and generates heat in response to an alternating magnetic field (AMF), simultaneously releasing the anticancer drug. The smart ferrofluid, which is synthesized using less toxic magnetic materials (Fe₃O₄ nanoparticles), natural polysaccharides (alginate), and amino acids (cysteine), can also act as a contrast agent for magnetic resonance imaging (MRI). The ferrofluid also incorporates an anticancer drug (i.e., doxorubicin, DOX) via hydrogen bonds. AMF causes heating of gels prepared from the DOX‐containing ferrofluid, resulting in gel shrinkage and DOX release. In vivo experiments demonstrated that the ferrofluid transforms into a gel in the tumor, with the gel remaining in the tumor. Furthermore, magnetic thermochemotherapy using this ferrofluid inhibited tumor growth, while magnetic hyperthermia alone had only a marginal effect. Thus, the combination of magnetic hyperthermia and chemotherapy may be important for suppressing tumor growth. In summary, the ferrofluid presented here has the potential to facilitate MRI‐guided magnetic thermochemotherapy through a combination of endoscopic technologies in the future.     

Calculation of the uniform breakdown field strength of SF6 gas

We calculated the uniform dielectric breakdown field strength of SF₆ gas over the temperature range of 300 to 3000 K. The local thermal equilibrium (ITE) composition of the dissociated gas is connected to the electron impact collision cross sections of the species SF₆, F₂, F and S. The critical reduced electric field strength of the composition is determined by a balancing electron generation and loss modeled by chemical reactions evaluated by the electron energy distribution function (EEDF) derived from the Boltzmann transport equation. At room temperature, pure SF₆ has a critical reduced electric field strength of 362 Td. With increasing temperature and decreasing density we found a small decrease of this value, whereas at temperatures higher than 1500 K, dissociation starts to decrease the dielectric strength of the composition. Furthermore, we found that generation of electrons by (associative) detachment from F ^- starts to play an important role at temperatures >2500 K, where the critical field strength still has a value of 118 Td. This value is found to decrease rapidly afterwards with increasing temperature to the value of 38 Td at 3000 K. The calculated results agree very well with independently predicted values and measured data     

A 1 Mb EEPROM with MONOS memory cell for semiconductor diskapplication

A 1 Mb 5 V-only EEPROM (electrically erasable programmable ROM) with metal-oxide-nitride-oxide-semiconductor (MONOS) memory cells specifically designed for a semiconductor disk application is described. The memory has high endurance to write/erase cycles and a relatively low programming voltage of ±9 V. These advantages result from the structure and the characteristics of the MONOS memory cell. A newly developed dual-gate-type MONOS memory cell has a small unit cell area of 18.4 μm² with 1.2 μm lithography, and the die size of the fabricated chip is 5.3 mm×6.3 mm. A new programming scheme called multiblock erase solved the problem of slow programming speed. A programming speed of up to 1.1 μs/B equivalent (140 ms/chip) was obtained     

Preparation of Ba2YCu3O7-δ Thin Films with Preferred Orientation through an Organometallic Route

Superconducting Ba₂YCu₃O_7-δ thin films were prepared through an organometallic route. Single-phase Ba₂YCu₃O_7-δ thin films with preferred orientation were successfully prepared on SrTiO₃ (100) single-crystal substrates at 800°C by a dip coating method using partially hydrolyzed Ba-Y-Cu organometallic solutions. Preferentially oriented Ba₂YCu₃-O_7-δ thin films were also prepared on MgO (100) substrates. By controlling the partial hydrolysis conditions, a coating solution for precursor thin films was kept accurately at the stoichiometric composition. The use of ozone gas during the pyrolysis of the precursor thin films was found to suppress the formation of BaCO₃. Ba₂YCu₃O_7-δ thin films with c -axis orientation perpendicular to a SrTiO₃ (100) substrate, which were heat-treated at 900°C for 15 min, exhibited a superconductivity transition with an onset of 90 K and an end of 75 K.     

Toughening of a Particulate-Reinforced Ceramic-Matrix Composite by Thermal Residual Stress

The micromechanics involved in increased crack growth resistance, K _R, due to the addition of TiB₂ particulate in a SiC matrix was analyzed both experimentally and theoretically. The fractography evidence, in which, the advancing crack was attracted to adjacent particulates, was attributed to the tensile region surrounding a particulate. Countering this effect is the compressive thermal residual stress, which results in the toughening of the composite, in the matrix. This thermal residual stress field in a particulate-reinforced ceramic-matrix composite is induced by the mismatch in the coefficients of thermal expansion of the matrix and the particulate when the composite is cooled from the processing to room temperature. The increase in K _R of the composite over the monolithic matrix, which was measured by using a hybrid experimental-numerical analysis, was 77%, and compared well with the analytically predicted increase of 52%. The increase in K _R predicted by the crack deflection model was 14%. Dependence of K _R on the volume fraction of particulates, f _p, and of voids, f _v, is also discussed.     

Nondestructive readout mode static induction transistor (SIT) photosensors

The nondestructive readout (NDRO) performance of two static induction transistor (SIT) photosensors, a 40×40 pixel area array and a 140-b linear array, is examined. NDRO operation in the SIT sensors is demonstrated by imaging with the area array and by examining the output waveform of the linear array. The charge lost per NDRO cycle in the linear array was 0.014% near the saturation signal level, and no charge loss could be detected at the ⩽0.5 saturation level. NDRO performance in the area array was degraded compared to the linear array, due to the larger value of the load capacitance connected to the output electrode of the SIT. NDRO operation also enables the cancellation of both the photosite reset noise and the signal nonuniformity by subtracting the first NDRO output from the following NDRO outputs, as well as the advantage of monitoring the signal state during the integration period     

Radiation from the transmission line with an acute bend

The transmission and radiation characteristics at an acute bend of a transmission line are investigated analytically. First, in consideration of the strong coupling to the adjacent conductor, the current distributions are decomposed into even and odd modes. Applying the traveling-wave mode method to these modes, it is shown that transmission characteristics of the line with an acute bend can be easily obtained. The abrupt variation of the voltage near the bend is noted. Next, the discontinuities of the traveling wave currents are regarded as radiating sources and the radiation field from the bend in the transmission line is derived by the summation of fields created by each of the discontinuities. It is found that there exist the electric field component radiating strongly in the directions of propagation of the current and another electric field component radiating strongly into the intermediate direction. Finally, by comparing with the former method and experimental results, the validity of the method is confirmed     

Durable write-once optical disk memories for 800 nm using silverisland films

Durable write-once (WO) optical disk media have been demonstrated by using silver island films with a protection layer of fluorine-contained polymers. The reflectance of the silver island films is high at the wavelength of 800 nm and can be greatly lowered by laser irradiation, owing to the thermal deformation or the islands. Laser writing has been experimentally confirmed at almost the same line speed as that of compact discs (CDs). Therefore it is expected that a CD-compatible write-once optical disc can be realised