Off-line Bangla handwritten word recognition: a holistic approach

Neural Computing and Applications - Due to the cursive nature, segmentation of handwritten Bangla words into characters and also recognition of the same sometimes become a very challenging problem...     

Estimation of fracture toughness of 20MnMoNi55 steel in the ductile to brittle transition region using master curve method

Fracture toughness is an important material property to assess the critical load for structural integrity of reactor pressure vessel steel. In this paper, master curve method proposed by Kim Wallin is used to estimate the fracture toughness of 20MnMoNi55 steel in the ductile to brittle transition regime. Reference temperature (T₀) is evaluated using both single temperature and multi-temperature method for one inch thick compact tension (1T-CT) specimens. Reference temperature (T₀) is also determined from Charpy V-notch test data and compared. Effect of selection of temperature range and number of test temperatures on the value of T₀ is also studied. It is observed that Charpy test results yield lower values of unirradiated T₀ compared to 1T-CT specimen tests. It is also observed that most of the fracture toughness values fall between 5% and 95% boundary of fracture toughness curves for all the evaluations.     

Disorder Induced BCS–BEC Crossover in an Ultracold Fermi Gas

We develop the formalism for BCS–BEC crossover in the presence of weak random impurity and calculate the effect of the random potentials on the basic mean-field quantities. The disorder has been included through the Nozières and Schmitt–Rink theory of superconducting fluctuations, and we obtain the disorder induced superfluid order parameter and chemical potential through a self-consistent calculation. We also calculate the condensate fraction which reveals a distinct nonmonotonic behavior. The downturn in the latter result occurs at the crossover regime with gradual depletion on the BEC side. The non-monotonic feature in the condensate fraction data has been measured in clean systems. Motivated by the above result, we discuss the stability of a disordered fermionic superfluid in the crossover regime.     

Synthesis and characterization of poly(pyridinium salt)s derived from various aromatic diamines

Several poly(pyridinium salt)s containing various aromatic diamine moieties and tosylate counterions were prepared by the ring-transmutation polymerization reaction of bis(pyrylium tosylate) with aromatic diamines in dimethyl sulfoxide at 130?135 °C for 48 h and their tosylate counterions were exchanged to triflimide polymers by a metatheses reaction in an organic solvent. Their chemical structures were established by using various spectroscopic techniques. Their number-average molecular weights (M_n) were in the range of 38–46 kg/mol and polydispersities in the range of 1.13–1.43 as determined by gel permeation chromatography. They showed excellent thermal stabilities in nitrogen in the range of 326–477 °C. They exhibited lyotropic liquid-crystalline phase in polar aprotic and protic organic solvents above their critical concentrations depending on their microstructures and counterions. Their optical properties were examined by using UV–Vis and photoluminescent spectroscopy, which revealed that some polymers emitted UV light, some emitted blue light, and some emitted green light (both in solutions and solid states) depending on their microstructures, counterions, and on solvent polarity of organic solvents.     

Characterization and calibration of a SSNTD for heavy-ion detection and strangelet search in cosmic rays

A commercially available grade of polymer was investigated for its suitability as a solid state nuclear track detector (SSNTD) to look for rare events in cosmic rays at very high mountain altitudes. It was identified to be polyethylene terephthalate (PET) and found to have a higher detection threshold compared to many other widely used SSNTDs. Hence it is particularly suited for rare event search in cosmic rays by eliminating the dominant low Z background. Systematic studies were carried out to determine the ideal etching condition. Also the charge response of PET was studied using various ion beams from accelerators. The results of such studies were combined to obtain the calibration curve for PET as SSNTD, by which one can identify and characterize charged particles.     

Determining seasonal optimum tilt angles,solar radiations on variously oriented,single and double axis tracking surfaces at Dhaka

The performance of a solar radiation conversion system is affected by its orientation and tilt angle with the horizontal plane. This is because both of these parameters change the amount of solar energy received by the surface of solar system. Three mathematical models- the Isotropic, the Klucher and the Perez model for the point source with parameters optimized for a variety of climatic conditions have been employed to determine hourly and seasonal optimum tilt angles. Theoretical optimum tilt angles (10° for Mar–Sep and 40° for Oct–Feb) were compared with measured data for Nov 2007 to Oct 2008 at Dhaka. The anisotropic Perez model showed least rmse of 0.09 for monthly tilt factor estimation. This model was also used for theoretical study of solar radiation on variously oriented, single axis and double axis tracking surfaces.     

Grain size dependent magnetization, electrical resistivity and magnetoresistance in mechanically milled La0.67Sr0.33MnO3

We have studied magnetization, ac susceptibility, resistivity and magnetoresistance in mechanically milled La_0.67Sr_0.33MnO₃. The material with grain size micron to nanometer scale has stabilized in rhombohedral crystal structure with space group R3C. We have found various grain size effects, e.g., decrease of ferromagnetic moment, increase of surface spin disorder, and appearance of insulator/semiconductor type resistivity. In addition to these conventional features, we have identified a magnetic anomaly at 45 K in bulk sample. Ferromagnetic to paramagnetic transition temperature (T_C) is above room temperature for all samples. The samples are typical soft ferromagnet that transformed from multi-domain state to single domain state in nanocrystalline samples. The remarkable observation is that low temperature freezing of ferromagnetic domains/clusters does not follow the conventional spin glass features. Experimental results clearly showed the enhancement of high field magnetoresistance in nanocrystalline samples below 200 K, whereas low field magnetoresistance gradually decreases above 200 K and almost absent at 300 K. We have discussed few more magnetic and electrical changes, highly relevant to the progress of nanomaterial research in ferromagnetic manganites.     

Performance prediction of 60 kWp PV power plant in an educational institute

Due to government initiatives, many solar photovoltaic (PV) power plants of different sizes will be set up in India in the near future. In this context, the performance of a 60?kW_p PV power plant is discussed in this paper which is installed at National Institute of Technology (a centrally funded institute of Government of India), Agartala, located in a small state (Tripura) of North East India where supply of grid electricity is a critical issue. This article examines the various parameters for performance prediction of this solar power plant.     

Structural and Optical Characterizations of Electrochemically Grown Connected and Free-Standing TiO2 Nanotube Array

A TiO₂ nanotube array was grown electrochemically by using single and mixed electrolyte/s with 20 V constant potential at room temperature. Anodization was carried out for 120 min using five different electrolytes, e.g., H₃PO₄, NH₄F, HF, NH₄F with H₃PO₄ and HF with H₃PO₄. Structural characterizations of the grown titania nanotubes were conducted by using x-ray diffraction and field emission scanning electron microscopy. Optical properties of the grown nanotubes were investigated through photoluminescence (PL) spectroscopy. In the case of the 4 M H₃PO₄ electrolyte, no perceptible growth of nanotubes was observed. The individual electrolytes of 0.3 M NH₄F and 1 M HF resulted into the formation of the wall-connected nanotubes. In contrast, the mixed electrolytes comprising the strong (NH₄F, HF) and weak (H₃PO₄) electrolytes have been found to be efficient for the growth of wall-separated titania nanotubes. The results of the PL spectroscopy have demonstrated that the free-standing nanotubes offer low PL intensity compared to its connected counterpart owing to the lower carrier recombination rate of free-standing nanotubes.