Pressure-dependent electronic properties of MgO polymorphs: a first-principles study of Compton profiles and autocorrelation functions

The first-principles periodic linear combination of atomic orbitals method within the framework of density functional theory implemented in the CRYSTAL06 code has been applied to explore effect of pressure on the Compton profiles and autocorrelation functions (AF) of MgO. Calculations are performed for the B1, B2, B3, B4, B8₁, and h-MgO polymorphs of MgO to compute lattice constants and bulk moduli. The isothermal enthalpy calculations predict that B4 → B8₁, h-MgO → B8₁, B3 → B2, B4 → B2, and h-MgO → B2 transitions take place at 2, 9, 37, 42, and 64 GPa, respectively. The high-pressure transitions B8₁ → B2 and B1 → B2 are found to occur at 340 and 410 GPa, respectively. The pressure-dependent changes are observed largely in the valence electrons Compton profiles, whereas core profiles are almost independent of the pressure in all MgO polymorphs. Increase in pressure results in broadening of the valence electrons Compton profiles. The principal maxima in the second derivative of Compton profiles shifts toward high-momentum side in all structures. Reorganization of momentum density in the B1 → B2 structural phase transition is seen in the first and second derivatives before and after the transition pressure. Features of the AFs shift toward smaller distances when pressure increases.     

Resin I: Synthesis and characterization of 2,2′‐dihydroxybiphenyl–urea–formaldehyde terpolymers

Terpolymer resins (BPhUF) were synthesized by the condensation of 2,2′‐dihydroxybiphenyl [BPh] and urea [U] with formaldehyde [F] in the presence of an acid catalyst and using varied molar ratios of reacting monomers. Terpolymer resin compositions have been determined on the basis of their elemental analysis and the number average molecular weights of these resins were determined by conductometric titration in nonaqueous medium. Viscometric measurements in dimethyl formamide have been carried out with a view to ascertain the characteristic functions and constants. UV‐VIS, IR, and NMR spectra were studied to elucidate the structure. studied to elucidate the structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1605–1610, 2005     

Illumination normalized based technique for retinal blood vessel segmentation

The Retinal image carries important information about the health of the sensory part of the visual system. In this paper, a new approach is suggested by utilizing the homomorphic filter integrated with Contrast limited adaptive histogram equalization (CLAHE) method for the illumination normalization and contrast enhancement of the retinal images. Then segmentation is done through several steps by using the existing methods such as morphological filtering, a second derivative operator that is followed by a final morphological filtering stage and hysteresis thresholding. The suggested method is verified on DRIVE and CHASE‐DB1 databases and has average accuracy of 72.03% and 64.54%, accordingly. The obtained results demonstrate that the proposed approaches achieve higher accuracy than the traditional method. The suggested approach not only contributes to the successful result, but also minimizes the computing time.     

Facile synthesis,morphological, structural,photocatalytic, and optical properties of ZnFe2O4 nanostructures

Spinel ferrite ZnFe₂O₄ nanostructures have been prepared as sunlight responsive photocatalysts via facile co-precipitation method. The structural, morphological, and optical responses were diligently characterized using XRD, Raman spectroscopy, FESEM, and UV–Vis absorption spectroscopy, respectively. FESEM studies revealed nanoparticles and porous-like nanoparticle aggregates, found to be of cubic spinel ZnFe₂O₄ from XRD and Raman studies. Crystallite size varied from 5 to 13.6 nm, whereas band gap changed from 1.89 to 1.95 eV with CTAB concentration variation. ZnFe₂O₄ nanostructures were employed for sunlight-assisted photodegradation of organic pollutants such as MB, MG, and MO dyes in water. The synthesized ZnFe₂O₄ nanoparticle aggregates with porous-like morphology with crystallite size of 9.2 nm showed superior photocatalytic response and decomposed 80.4% of MB dye in only 40 min. The superiority of the porous-like ZnFe₂O₄ nanoparticle aggregates was mainly ascribed to its optimal crystallite size, narrower band gap, and improved sunlight utilization efficiency. A plausible mechanism of photocatalytic oxidation of dye supported by scavenger studies has also been proposed. The synthesized ZnFe₂O₄ nanostructures have easy magnetic recycling property along with excellent photocatalytic capability and hold potential for the treatment of contaminated water.

     

A novel smart hybrid-Trefftz finite element for smart laminated composite plates

A novel smart hybrid-Trefftz finite element ( HTFE ) has been developed for the analysis of smart laminated composite plates. The substrates of the smart plates are symmetric and antisymmetric cross-ply plates. The derivation of this HTFE is devoid of the complicated task of finding the particular solutions of simultaneous governing partial differential equations. The Trefftz functions are constructed from the finite number of free-field exact solutions of the homogeneous simultaneous governing partial differential equations of the element domain in a straightforward manner without transforming them into a single governing equation. The HTFE is validated with the exact solutions of the smart composite plates. It is observed that this HTFE is an efficient finite element and can be utilized for the analysis of active control of smart composite structures.     

Class-dependent PCA, MDC and LDA: A combined classifier for pattern classification

Several pattern classifiers give high classification accuracy but their storage requirements and processing time are severely expensive. On the other hand, some classifiers require very low storage requirement and processing time but their classification accuracy is not satisfactory. In either of the cases the performance of the classifier is poor. In this paper, we have presented a technique based on the combination of minimum distance classifier (MDC), class-dependent principal component analysis (PCA) and linear discriminant analysis (LDA) which gives improved performance as compared with other standard techniques when experimented on several machine learning corpuses.     

Distortion cancellation performance of miniature delay filters for feed-forward linear power amplifiers

The technique of feed-forward amplitude control has been widely used in the linearization of power amplifiers for wireless communication systems. In this technique, an error signal due to third order intermodulation distortion (IMD) is extracted, amplified, and used to correct the delayed main line distorted signal. For example, a miniature prototype base station for the Global System for Mobile Communications/Code Division Multiple Access (GSM/CDMA) cellular system uses feed-forward amplifiers with bulky and expensive coaxial cables, about 20 feet in length, to provide about 25 ns of delay. This paper shows alternate space-saving approaches of achieving these delays using three different types of delay filters: electromagnetic interdigital/lumped (<2.5"), ceramic (<1.8"), and ladder-type surface acoustic wave (SAW) (0.15"). The delay lines introduce phase and amplitude imbalance and delay mismatch in the linearization loop due to fabrication tolerances. These adversely affect the IMD cancellation. Using an RF system simulation tool, this paper critically compares the IMD cancellation performance achieved using the three technologies. Simulation results show that the optimization of delay mismatch can achieve the desired cancellation more easily than other parameters. It is shown that, if the critical system parameter (phase deviation from linearity), is maintained at <2.5/spl deg/ peak-to-peak over a 20 MHz bandwidth in the frequency range 855 MHz to 875 MHz, one can achieve 25 dB of IMD cancellation performance. This paper concludes with the suggestion of a set of realistic specifications for a miniature delay filter for the low power loop of the feed-forward amplifier.     

A practical alternative to conventional five-field irradiation postmastectomy for locally advanced breast cancer

BACKGROUND: This study reports the results of Neodymium-Yttrium-Aluminum Garnet (Nd-YAG) laser resection on benign and malignant obstructing airway diseases which has been done in our hospital for four years. The effect of this treatment on patients' arterial blood gases, during and after the process is also analyzed. The benefit of adjuvant therapy with radiotherapy and/or chemotherapy after laser vaporization is discussed. METHODS: Fiberoptic bronchoscopic Nd-YAG laser therapy was performed in 32 cases of lung cancer (primary 27, secondary 5) and 11 cases of benign tracheobronchial diseases with total or near total airway obstruction. The therapy was performed through the oral route under local anesthesia. The result of therapy was classified as "excellent", "fair" or "poor" depending upon the degree of recanalization and clinical improvement. A cannula was inserted into the radial artery in lung cancer patients before the procedure. Samples of blood to determine arterial blood gas levels were drawn before, during and after treatment. After bronchoscopic laser therapy, radiotherapy and/or chemotherapy were given to the patients of lung cancer. RESULTS: The effective rate (excellent and fair) was 75% in lung cancer and 81.8% in benign airway obstruction. In the lung cancer group, significant decline of PaO2 was noted during and after Nd-YAG laser therapy. Decrease of PaO2 was not recovered even 5 hours after laser vaporization. After bronchoscopic Nd-YAG laser therapy, 21 of 32 lung cancer patients received radiotherapy (at least 3000 rads) and/or chemotherapy (at least 3 times). The median survival time was 5.5 months. The other 11 patients received laser therapy only, with median survival time was 2.9 months (p < 0.05). CONCLUSIONS: Endobronchial Nd-YAG laser therapy of obstructing lesions has been proved to be effective and relatively safe in well-trained hands. Oxygen supplementation was suggested in patients with hypoxemia before laser therapy. After endobronchial Nd-YAG laser therapy, better survival and life quality result if radiotherapy and/or chemotherapy are added for the lung cancer group.     

Quadtree-based classification in subband image coding

Classification of blocks of subband samples according to their energy and variable bit allocation within the subsequent classes has demonstrated considerable gains in coding efficiency. The gains due to classification increase as smaller blocks are used; however, this increases the overheads for transmitting the classification information. In this paper, a quadtree based method is proposed. This method allows for more efficient classification by using variable-sized blocks in order to maximize the classification gain, while maintaining a limit on the classification overheads. This method is applied for subband coding of images and the results indicate that it performs better than the other methods currently available in the literature.     

Effect of the nature and mole fraction of acidic comonomer on the stabilization of polyacrylonitrile

Differential scanning calorimetry (DSC) and thermogravimetric analysis measurements were used to study the influence of the acidic comonomers acrylic acid, methacrylic acid, and itaconic acid on the exothermic reactions occurring during the heat treatment of acrylonitrile copolymers under air atmosphere. The presence of these reactions was noticed in the DSC exotherms of the copolymers, which appear as doublets. These doublets were resolved into their constituent peaks, arising due to the occurrence of oxidative and cyclization reactions, and the area under the resolved peaks was considered as the extent of the reaction. The comonomers under study were found to enhance the secondary oxidation reactions and retard the extent of cyclization reactions. The degree of cyclization decreases abruptly with the increase in the comonomer content beyond ⋍ 2 mol %. © 1996 John Wiley & Sons, Inc.