Unsupervised texture segmentation using multichannel decompositionand hidden Markov models

In this paper, we describe an automatic unsupervised texture segmentation scheme using hidden Markov models (HMMs). First, the feature map of the image is formed using Laws' micromasks and directional macromasks. Each pixel in the feature map is represented by a sequence of 4-D feature vectors. The feature sequences belonging to the same texture are modeled as an HMM. Thus, if there are M different textures present in an image, there are M distinct HMMs to be found and trained. Consequently, the unsupervised texture segmentation problem becomes an HMM-based problem, where the appropriate number of HMMs, the associated model parameters, and the discrimination among the HMMs become the foci of our scheme. A two-stage segmentation procedure is used. First, coarse segmentation is used to obtain the approximate number of HMMs and their associated model parameters. Then, fine segmentation is used to accurately estimate the number of HMMs and the model parameters. In these two stages, the critical task of merging the similar HMMs is accomplished by comparing the discrimination information (DI) between the two HMMs against a threshold computed from the distribution of all DI's. A postprocessing stage of multiscale majority filtering is used to further enhance the segmented result. The proposed scheme is highly suitable for pipeline/parallel implementation. Detailed experimental results are reported. These results indicate that the present scheme compares favorably with respect to other successful schemes reported in the literature.     

A simple method of photomask yield optimization by defect inspection

The quality of the photomask set decides to a large extent the quality and quantity of the device that will be produced. In order to ensure the quality of the photomasks, several sophisticated instruments are commercially available. However, in a research type of environment, the cost of such equipment can be prohibitive. In this paper, we propose a simple method of multiple master mask preparation with subsequent matching of defective die locations to optimize the master mask set. The advantage here is that a very good master mask set can be chosen so that minimum number of dies on the photomask set itself contribute to low wafer yield. The method is based on manual inspection of individual dies on photomasks and can be practically used for a complexity of up to 500 components.     

Role of the stimulated-emission rate in the photostability of solid-state dye lasers

The lasing and photostability characteristics of Rhodamine 6G and Pyrromethene 567 dyes dispersed in polymeric host materials have been investigated as a function of the intensities of incident pump and signal beams in a longitudinally pumped dye laser in an oscillator-amplifier configuration. A substantial reduction in the rate of photodegradation was observed under lasing conditions and with increasing signal intensity in a dye amplifier, establishing that the service lives of these materials improve with an increase in the rate of stimulated emission. We observed approximately 62% amplifier efficiency at 2 Hz operation and 10% reduction in amplifier efficiency at 10 Hz operation after exposure of 72,000 pulses by use of a Pyrromethene disk.     

Studies in isodielectric media Part—I. Standard potentials of the silver—silver chloride electrode in dimethyl formamide + ethylene glycol mixtures at 25°C

Standard potentials (_sE^s) of the silver—silver chloride electrode have been determined at 25°C in some approximately isodielectric media containing ethylene glycol (EG) and 10, 30 and 50% by weight of N-N-dimethyl formamide (DMF) from emf measurements performed on the cell: H₂ (g, 1 atm)/HCl (m). solvent/AgClAg. From these values the activity coefficients (^s_sγ) of HCl at several concentration in each of the mixed solvents and the standard Gibbs energies of transfer (ΔG⁰_t) of HCl from EG to the mixed solvents have been computed. Comparison of the observed ΔG⁰_t (HCl)-composition profile with those for three other related solvent systems studied earlier, reveals that the observed profile results from the opposing effects of the larger proton-accepting and the pronounced anion-desolvating propensities of DMF and its glycolic mixtures compared to pure EG and that the increased stabilization of proton is superseded by the increased desolvation of Cl^? at higher proportions of DMF.     

Curing kinetics of medium reactive unsaturated polyester resin used for liquid composite molding process

The cure kinetics of medium reactivity unsaturated polyester resin formulated for Liquid Composite Molding process simulation was studied by Differential Scanning Calorimetry (DSC) under isothermal conditions over a specific range of temperature. For isothermal curing reactions performed at 100, 110, and 120°C, several influencing factors were evaluated using the heat evolution behavior of curing process. We propose two‐ and three‐parameter kinetic models to describe the cure kinetics of thermoset resins. Comparisons of the model solutions with our experimental data showed that the three‐parameter model was the lowest parameter model capable of capturing both the degree of cure and the curing rate qualitatively and quantitatively. The model parameters were evaluated by a non‐linear multiple regression method and the temperature dependence of the kinetic rate constants thus obtained has been determined by fitting to the Arrhenius equation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Swelling kinetics of linseed oil‐based polymers

Kinetics of swelling and sorption behavior of copolymers (based on linseed oil, styrene, divinylbenzene, and acrylic acid via cationic and thermal polymerization) is studied in tetrahydrofuran (THF) at different temperatures. The values of n in the transport equation are found to be below 0.4, showing non‐Fickian or pseudo‐Fickian transport in the polymers. The dependence of diffusion coefficient on the composition and temperature has also been studied for the linseed oil‐based polymers. The diffusion coefficient in cationic samples decreases with an increase in the oil contents in the samples. In case of thermal samples, the diffusion coefficient first increases up to 30% oil contents and then decreases. The diffusion coefficient decreases with an increase in temperature for all of the linseed oil polymer samples. The sorption coefficient increases with an increase in the oil contents for all samples. The crosslink density (calculated from the THF swelling) ranges from 20.16 to 92.34 × 10⁶ mol/cm³ for cationic samples and 20.62 to 86.01 × 10⁶ mol/cm³ for thermal samples. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Swelling kinetics of linseed oil‐based nanocomposites

The solvent‐resistance properties of the montmorillonite‐filled conjugated linseed oil‐based nanocomposites are studied in tetrahydrofuran through equilibrium swelling method at different temperatures. The values of “n” in solvent transport equation are found to be below “0.5,” showing the non‐Fickian diffusion in the polymer. The dependence of the diffusion coefficient on the composition, percentage of clay, and temperature has been studied for nanocomposite samples. The diffusion coefficient increases with an increase in the clay contents and temperature. The crosslink density of the nanocomposites ranges from 101.07 to 237.46 × 10⁶ mol/cm³. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Cefuroxime-impregnated calcium phosphates as an implantable delivery system in experimental osteomyelitis

The study aimed to investigate the effectiveness of porous calcium phosphates viz., hydroxyapatite (HAp) and a bi-phasic calcium phosphate (BCP) with predominately β-tricalcium phosphate (β-TCP) prepared by aqueous solution combustion method impregnated with cefuroxime axetil for the treatment of experimental osteomyelitis and compared with parenteral treatment. In vitro release of the drug was tested for its sustained elution characteristics for 21 days in PBS (pH 7.2) and measured by HPLC. In the in vivo study, bone infection was induced in tibia of rabbits by inoculation of 1 ml (3 × 10⁶) CFU Staphylococcus aureus. On the 21st day, after the development of osteomyelitis, six animals were treated by filling the cavity with cefuroxime-impregnated HAp blocks (Group II), six animals with the same drug-impregnated β-TCP (Group III) and in six others, only cefuroxime (15 mg/kg twice daily) was injected parenterally 6 weeks (Group IV). Group I with six animals was kept untreated. Histologically, the signs of infection were found to subside by 3 and 6 weeks. Radiological evaluation with cefuroxime-impregnated HAp and β-TCP pointed out the disappearance of sequestrum and existence of newly formed bony specules. Concentration of cefuroxime in bone and serum as estimated by HPLC showed highest value on day 21 itself which reduced marginally by day 42 in both the groups and these values were higher than minimum inhibitory concentration (MIC) against S. aureus. Our findings suggest that bi-phasic calcium phosphates with predominately β-TCP content is a very efficient carrier material for antibiotic compounds even for refractory infections by S. aureus.     

Effect of drying catalysts on the properties of thermal copolymers from conjugated linseed oil–styrene–divinylbenzene

The effect of addition of a varying concentration of a drying catalyst (cobalt salt as primary drier) and a combination of catalysts such as cobalt, zirconium (secondary drier) and calcium (auxiliary drier) in a fixed concentration (1%) to a 50:20:30 compositions of 87% conjugated linseed oil, styrene (ST), and divinylbenzene (DVB) has been studied by characterizing the resulting polymers from thermal polymerization with various techniques such as soxhlet extraction, ¹H NMR (¹H nuclear magnetic resonance) spectroscopy, dynamic mechanical analysis (DMA), mechanical and thermogravimetric analysis. The thermal polymerization is performed in the temperature range of 85–160 °C. By soxhlet extraction, it is observed that the polymers contain approximately 64–77% crosslinked materials and the crosslinked insoluble fraction increases with an increase in cobalt catalyst concentration. For fixed concentration (1%) of catalysts, the insoluble fraction from the soxhlet extraction is maximum for the cobalt–zirconium mixture and minimum for the cobalt–calcium mixture. The micro-composition of these polymers obtained from the ¹H NMR spectroscopy indicates that the crosslinked materials are composed of both soft oily and hard aromatic phases. The polymers with varying cobalt concentrations up to 0.6 wt% exhibit two separate glass transition temperatures, indicating the presence of two separate phases, one soft rubbery phase with sharp glass transition temperature of −50 °C and a hard brittle plastic phase of broadened glass transition temperature of 70–120 °C. On the other hand, instead of sharp peaks, the polymers with 0.8 and 1.0% cobalt salts exhibit two humps and a distinct peak in between the humps in the tan δ plots, indicating the presence of an additional phase comprised of a copolymer of linseed oil–styrene and DVB. For fixed concentration (1%) of catalysts, the cobalt–calcium combination follows the similar trend in the tan δ as that for the polymers with 0.8–1.0% cobalt whereas other combinations exhibit two phases. These polymers possess crosslink densities of 0.63–0.91 × 10⁴ mol/m³ and compressive strengths of 2.0–26.6 MPa. The catalyzed polymers are thermally stable below 300 °C and exhibit a major thermal degradation with a maximum degradation of 82–88% at a temperature of 500 °C.