A study of titanium thin films in transmission laser micro-joining of titanium-coated glass to polyimide

Electron beam evaporation (EB-PVD) and cathodic arc physical vapor deposition (CA-PVD) techniques were used for the preparation of titanium (Ti) thin films onto Pyrex borosilicate 7740 glass wafers and the deposited films were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques. The microstructure and surface morphology of the films were studied as a function of the film deposition techniques. Film properties such as, adherence, microstructure and roughness were interconnected to the laser joint strength between Ti coated glass wafers and polyimide films. Ti thin films on glass had a natural oxide layer on the surface as found from XPS. AFM study showed the formation of a uniform Ti coating consisted of packed crystallites with average size of 35 nm by EB-PVD. The root-mean-square surface roughness of the films was 1-2 nm. Whereas, films prepared by CA-PVD had crystallites with an average size of 120 nm and defects in the form of macro-particles which is a common attribute of this deposition system. The surface roughness of the film was 125 nm. The laser joint strength was found to be influenced by the Ti film quality on the glass substrate.     

Synthesis,characterization of poly (4-benzyloxyphenylmethacrylate) and its copolymer with butyl methacrylate and determination of monomer reactivity ratios

The monomer 4-benzyloxyphenylmethacrylate (4-BOPMA) was synthesized by reacting 4-benzyloxy phenol dissolved in methylethylketone (MEK) with methacryloyl chloride in the presence of triethylamine. The homopolymer and various copolymers of 4-BOPMA with butylmethacrylate (BMA) were synthesized by the free radical polymerization in MEK at 70?±?1?°C in nitrogen atmosphere using benzoylperoxide as initiator. The homopolymer and copolymers were characterized by various spectral techniques like IR, ¹H-NMR, ¹³C-NMR spectroscopic techniques. The molecular weights of the polymers were determined by gel permeation chromatography. The glass transition temperatures of polymers were determined by differential scanning calorimeter. The thermal stability of the polymers was performed by thermo gravimetric analysis in inert atmosphere. The monomer reactivity ratios were determined using the conventional linearization methods such as Fineman–Ross (r₁?=?0.438, r₂?=?0.2323), Kelen Tüdös (r₁?=?0.4648, r₂?=?0.2992) and extended Kelen Tüdös (r₁?=?0.4489, r₂?=?0.2616).     

Performance evaluation of polymeric blend of vinyl acetate and acrylate-based copolymers in lubricating oil

Polymer modification processes like blending has attracted much attention as an easy, cost-effective and less time-consuming method for developing new polymeric materials enriched with versatile commercial application. Polymer blends are supposed to carry better thermal and mechanical properties compared to their parent polymers. In this view we have prepared a polymer blend of two copolymers– one of vinyl acetate and octyl acrylate and another of methyl methacrylate and dodecyl acrylate and characterized them by FT-IR and NMR spectroscopy. The molecular weight was determined by Gel Permeation Chromatography (GPC). We represented here a comparative study of their mechanical property as well as their performance as flow improver.     

Vibration of bilayered cylindrical shells with layers of different materials

In this analysis, a comparative study for natural frequencies of two-layered cylindrical shells was presented with one layer composed of functionally graded material and the other layer of isotropic material. Love’s thin shell theory was exploited for the strain-displacement and curvature-displacement relationships. For governing frequency equations, the Rayleigh-Ritz method was utilized to minimize the Lagrangian functional in the form of an eigenvalue problem. Frequency spectra were computed for long, short, thick, and thin cylindrical shells by varying the nondimensional geometrical parameters, length-to-radius and thickness-to-radius ratios for a simply supported end condition. Influence of different configurations of cylindrical shells on the shell frequencies was studied. For validity, the results obtained were compared with some results of isotropic and single-layered functionally graded cylindrical shells from the literature.     

Palyno‐morphological investigations of halophytic taxa of Amaranthaceae through SEM from Salt range of Northern Punjab,Pakistan

The pollen morphology of 11 salt tolerant plant species of family Amaranthaceae from the salt range of Northern Punjab, Pakistan has been studied. The palyno‐morphological characters were examined using light and scanning electron microscope. The examined all salt tolerant species have a slight difference in size but have similarity in shape, pore ornamentation, and polarity. The observed morphological characters of pollen grains were pollen symmetry, size, shape, pore ornamentation, pore size, number of pores, exine thickness, polar and equatorial diameter and, P/E ratio. Apolar type of pollens has been observed in all species. Shape of pollens was spheroidal. Exine sculpturing of pollen grains was scabrate (six spp), microechinate (four spp), and microechinate‐scabrate (one spp). Different pori numbers were observed in different species. The pantoporate aperturate and sunken pore ornamentation have been reported in all species. A pollen taxonomic key was developed using examined morphological characters for the accurate identification of halophytic taxa. The high fertility and low sterility of pollens confirmed that the selected halophytes are well‐established in the salt region. The findings highlight the taxonomic significance of pollen morphology in correct identification and differentiation of salt tolerant plant species.     

Adaptive fusion and co-operative training for classifier ensembles

In this paper, architectures and methods of decision aggregation in classifier ensembles are investigated. Typically, ensembles are designed in such a way that each classifier is trained independently and the decision fusion is performed as a post-process module. In this study, however, we are interested in making the fusion a more adaptive process. We first propose a new architecture that utilizes the features of a problem to guide the decision fusion process. By using both the features and classifiers outputs, the recognition strengths and weaknesses of the different classifiers are identified. This information is used to improve overall generalization capability of the system. Furthermore, we propose a co-operative training algorithm that allows the final classification to determine whether further training should be carried out on the components of the architecture. The performance of the proposed architecture is assessed by testing it on several benchmark problems. The new architecture shows improvement over existing aggregation techniques. Moreover, the proposed co-operative training algorithm provides a means to limit the users’ intervention, and maintains a level of accuracy that is competitive to that of most other approaches.     

Laser fabrication and characterization of sub-millimeter joints between polyimide and Ti-coated borosilicate glass

Laser-fabricated joints of sub-millimeter widths between biocompatible, dissimilar materials have the potential for application as encapsulation of miniature implantable biomedical devices. In this work, we briefly describe the laser joining method of a very promising system, polyimide/titanium-coated borosilicate glass, and present results from characterization of such laser joints by means of mechanical failure (tensile) tests, optical and scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Our results suggest that the formation of the joints is a result of the creation of strong chemical bonds between Ti-containing species and certain polymeric functional groups. Mechanical tensile strength failure testing showed that such joints experience some degradation as a result of soaking in physiological solutions. This degradation is limited and, even after relatively long-term exposure the joints retain considerable strength.     

Electrical,Thermal and Spectroscopic Characterization of Bulk Bi<Subscript>2</Subscript>Se<Subscript>3</Subscript> Topological Insulator

We report the electrical (angular magneto-resistance and Hall), thermal (heat capacity) and spectroscopic (Raman, X-ray photoelectron, angle-resolved photoelectron) characterization of a bulk Bi₂Se₃ topological insulator, which was grown by self-flux method through solid-state reaction from high-temperature (950^°C) melt and slow cooling (2^°C/h) of constituent elements. Bi₂Se₃ exhibited metallic behaviour down to 5 K. Magneto-transport measurements revealed linear up to 400 and 30% magneto-resistance (MR) at 5 K under a 14-T field in perpendicular and parallel field directions, respectively. We noticed that the MR of Bi₂Se₃ is very sensitive to the angle of the applied field. The MR is maximum when the field is normal to the sample surface, while it is minimum when the field is parallel. The Hall coefficient (R _H) is seen nearly invariant with a negative carrier sign down to 5 K albeit having near-periodic oscillations above 100 K. The heat capacity (C _p) versus temperature plot is seen without any phase transitions down to 5 K and is well fitted (C _p = γ T + β T ³) at low temperature with a calculated Debye temperature (?? _D) value of 105.5 K. Clear Raman peaks are seen at 72, 131 and 177 cm^?1 corresponding to A\(_{\mathrm {1g}}^{1}\), E\(_{\mathrm {g}}^{2}\) and A\(_{1\mathrm {g}}^{2}\), respectively. Though two distinct asymmetric characteristic peak shapes are seen for Bi 4f_7/2 and Bi 4f_5/2, the Se 3d region is found to be broad, displaying the overlapping of spin-orbit components of the same. Angle-resolved photoemission spectroscopy (ARPES) data of Bi₂Se₃ revealed distinctly the bulk conduction bands (BCB), surface state (SS), Dirac point (DP) and bulk valence bands (BVB), and 3D bulk conduction signatures are clearly seen. Summarily, a host of physical properties for the as-grown Bi₂Se₃ crystal are reported here.