Content-based image retrieval using block-constrained fractalcoding and nona-tree decomposition

Fractal coding has been proved useful for image compression. In fractal coding, an image is represented by a number of self-transformations (fractal code) by which an approximation of the original image can be reconstructed. The authors present a block-constrained fractal coding scheme and a nona-tree decomposition based matching strategy for content-based image retrieval. In the coding scheme, an image is partitioned into non-overlapped blocks with a size close to that of a query iconic image. The fractal code is generated for each block independently. In the similarity measure of the fractal code, an improved nona-tree decomposition scheme is adopted to avoid matching the fractal code globally in order to reduce computational complexity. The experimental results show that the authors' coding scheme and matching strategy are useful for image retrieval, and compare favourably with two other methods tested in terms of storage usage and computing time     

Dependence of apparent resistance of four-electrode probes on insertion depth

The apparent resistance of a finite-thickness layer measured with a four-electrode plunge probe depends on the electrode insertion depth, electrode spacing, and layer thickness, as well as the resistivity ratio of an underlying layer. A physical model consisting of air, a saline solution layer, and an agar layer simulates the real situation of resistivity measurement. The saline layer represents the finite-thickness layer whose resistivity is to be measured by a plunge electrode probe, and the agar layer represents an underlying perturbing layer. A micropositioner controls the insertion depth of the four electrodes into the saline solution. With the apparent resistance measured on a semi-infinite-thickness layer of saline solution as standard, measurement results show decreasing apparent resistance and increasing error with increasing electrode insertion depth. This information is important for correct measurement of myocardial resistivity in vivo and in vitro.     

Photoconductivity of PbTe:In films with variable microstructure

It is shown that the microstructure and features of formation of surface states in nanocrystalline and polycrystalline PbTe:In films most significantly affect the character of photoconductivity in the spectral range of 1–2.5 THz. We present the results of a study and comparative analysis of the character of conductivity of PbTe:In films in the temperature range from 4.2 to 300 K in a static mode and in variable electric fields with a frequency of up to 1 MHz with illumination with white light and under the effect of high-power terahertz laser pulses with a wavelength of up to 280 μm.     

Phosphotungstic acid-iron-haematoxylin staining method for osteoid, boundary bone and bone components in paraffin sections.

A new staining technique which stains osteoid and bone tissue differentially and also demonstrates boundary bone, pathological osteoid and the changes in ageing, pathological and dead bone matrix in decalcified paraffin or low-viscosity-nitrocellulose bone sections was developed. This phosphotungstic acid-iron-haematoxylin (PTAIH) method is based on pretreating the sections with phosphotungstic acid followed by an iron alum mordant and staining in haematoxylin with subsequent timed differentiation, at certain stages of which the features listed above appear. Van Gieson's picrofuchsin is then used as a counterstain. After standard differentiation osteoid appears red in sharp contrast with the black bone, young and woven bone, old and lamellar bone, and allows one to demonstrate changes in stainability of diseased osteoid and bone matrix, and dead bone. With the differentiation done individually and interrupted at certain stages it is possible to distinguish between various bone components depending on the amount and quality of their in vivo mineralisation. Comparison with controls showed that in this respect the method is more sensitive than the curremt staining techniques of undecalcified bone sections since it demonstrates not only unmineralised and fully mineralised tissues but also shows the poorly calcified, demineralised and ill-calcified bone components. The advantages of the method compared with those using undecalcified sections are its simplicity, suitability for fixed and decalcified material in any unspecialised histological laboratory and the fact that osteoid and other bone components can be studied in sections of unlimited size and in undisturbed relationship to their surrounding soft tissues.     

G-band (140-220-GHz) InP-based HBT amplifiers

We report tuned amplifiers designed for the 140-220-GHz frequency band. The amplifiers were designed in a transferred-substrate InP-based heterojunction bipolar transistor technology that enables efficient scaling of the parasitic collector-base junction capacitance. A single-stage amplifier exhibited 6.3-dB small-signal gain at 175 GHz. Three-stage amplifiers were subsequently fabricated with one design demonstrating 12.0-dB gain at 170 GHz and a second design exhibiting 8.5-dB gain at 195 GHz.     

High power mid-infrared optically pumped PbSe/PbSrSe multiple-quantum-well vertical-cavity surface-emitting laser operation at 325 K

A high power, mid-infrared (/spl lambda/=3.8 /spl mu/m) lead-salt vertical-cavity surface-emitting laser (VCSEL) operating at 325 K is demonstrated. The laser emission is generated in a half-wavelength microcavity consisting of seven pairs of PbSe/PbSrSe multiple-quantum-wells embedded in two mirrors and optically pumped with 5 ns laser pulses.     

Magnetic properties of Co- and Mn-implanted BaTiO3, SrTiO3 and KTaO3

Implantation of Co or Mn into single-crystal BaTiO₃(K), SrTiO₃ or KTaO₃(Ca), followed by annealing at 700 °C, produced ferromagnetic behavior over a broad range of transition metal concentrations. For BaTiO₃, both Co and Mn implantation produced magnetic ordering temperatures near 300 K with coercivities 70 Oe. The M–T plots showed either a near-linear decrease of magnetization with increasing temperature for Co and a non-Brillouin shaped curve for Mn. No secondary phases were detected by high-resolution X-ray diffraction. The same basic trends were observed for both SrTiO₃ and KTaO₃, with the exception that at high Mn concentrations (5 at.%) the SrTiO₃ was no longer ferromagnetic. Our results are consistent with recent reports of room temperature ferromagnetism in other perovskite systems (e.g. LaBaMnO₃) and theoretical predictions for transition metal doping of BaTiO₃ [Nakayama et al., Jap. J. Appl. Phys. 40 (2001) L1355].     

Algorithms of halftoning color images with edge enhancement

Printers usually generate a limited number of colors and lack the ability of producing continuous-tone color images. Traditional error-diffusion algorithms are used to solve this problem. Compared with other approaches, the approaches of using error-diffusion in general can generate halftoned images of better quality. However, smeared edges and textures may occur in these halftoned images. To produce halftoned images of higher quality, these artifacts due to unstable images, dot-overlap, and error-diffusion must be eliminated or reduced. In this paper, we show that unstable images can be eliminated or reduced through using a proper color difference formula to select the reproduction colors even vector error-diffusion is performed in the RGB domain. We also present a method of using different filters to halftone different components of a color. This approach may have clearer and sharper edges for halftoned color images. Unexpected colors may be generated due to dot-overlap in the printing process. We have presented a method to eliminate this color distortion in the process of error-diffusion. Halftoning a color image by our proposed error-diffusion algorithm with edge enhancement has the following characteristics: the unstable images do not exist; the color-error caused by dot-overlap is corrected; and the smeared edges are sharpened.     

Experimental validation of a thermal modelling method dedicated to multichip power modules in operating conditions

In this paper, we present an implementation of a thermal modelling method applied to a multichip module used as a power converter. Analytical functions of thermal impedances, with original formulations for the mutuals are defined. They are derived from 3D thermal simulations and experimental validations with direct chips temperature measurements. Finally, simulations are performed in order to improve the capability of our model to assess, with fast computation, the thermal constraints applied on the multichip module in a real operating condition.     

The effects of monovacancies on the terrace width during sublimation from the (111) surface of a diamond-like crystal

Using the three-dimensional Monte Carlo model, the effect of monovacancies on the diffusion exchange between the steps on the (111) surface of a diamond-like crystal during sublimation was investigated. The critical terrace width L_cr (the distance from the step edge to the nearest stable vacancy islands) was determined as a function of the relationship between the energy of adatom formation at the smooth terrace E_n and the energy of adatom desorption from the terrace E_d with retention of the sum of these energies E_sub=E_n+E_d, which characterizes the sublimation of a substance. A well-pronounced maximum exists in the dependences L_cr(E_n) obtained. The formula is suggested which well describes the dependences L_cr(E_n) for various values of E_sub. The extrapolation of the dependence L_cr(E_n) to the value E_sub=4.2 eV, which is characteristic of Si, permits us to compare the model results with the experimental data of other authors. The explanation of a threefold increase in the terrace width, which is observed experimentally at about 1500 K, is suggested.