Search

The tilt effects of the mirror–lamp (M–L) system on the shape of the interface of the silicon molten zone formed during growth using the infrared convergent heating floating zone method were studied at various positions of the M–L system. The stability and the interfaces of the molten zone formed in the tilted condition were compared with those in the no tilt condition. The molten zone appeared to be more stabilized in the tilted condition than in the no tilt condition. However, the conventional parameters characterizing the interface shape such as convexities ( h / r ), gap and zone length ( L ) were almost independent of the tilt angle ( θ ) of the M–L system and insufficient to discuss the tilting effects on the molten zone shape. The curvature of the solid–liquid interface was affected by the θ . New characterizing parameters such as the growth interface and triple point angles ( δ and TPA, respectively) were effective to quantitatively describe the tilting effects on the interface shape. With increase of the θ , the δ was decreased and the TPA was increased in both the feed and crystal sides. A silicon crystal of 45 mm in diameter was grown successfully in the tilted condition.

We have investigated various physical properties including phonon dispersion, thermodynamic parameters, optical constants, Fermi surface, Mulliken bond population, theoretical Vickers hardness and damage tolerance of anti-perovskite A3BX phases for the first time by employing density functional theory (DFT) methodology based on first principles method. Initially we assessed nine A3BX phases in total and found that only three phases (Ti3TlN, Ni3SnN and Co3AlC) are mechanically and dynamically stable based on analysis of computed elastic constants and phonon dispersion along with phonon density of states. We revisited the structural, elastic and electronic properties of the compounds to judge the reliability of our calculations. Absence of band gap at the Fermi level characterizes the phases under consideration as metallic in nature. The values of Pugh ratio, Poisson ratio and Cauchy factor have predicted the ductile nature associated with strong metallic bonding in these compounds. High temperature feasibility study of the phases has also been performed using the thermodynamic properties, such as the free energy, enthalpy, entropy, heat capacity and Debye temperature. The Vickers hardness of the compounds are estimated to be around 4 GPa which is comparable to many well-known MAX phases, indicating their reasonable hardness and easily machinable nature. The static refractive index n(zero) has been found around 8.0 for the phases under study that appeals as potential candidate to design optoelectronics appliances. The reflectivity is found above 44 percent for the Ti3TlN compound in the energy range of 0 to 14.8 eV demonstrating that this material holds significant promise as a coating agent to avoid solar heating., 29 pages

The electronic band structures along with Fermi surface, anisotropy, Vickers hardness, analysis of Mulliken populations, optical and thermodynamic properties were studied for the first time. The optimized unit cell parameters are compared with available theoretical and experimental results and a reasonable agreement is recorded. The mechanical stability of these compounds is confirmed. All the compounds herein exhibit metallic conductivity where major contribution comes from d-orbital electrons. The hardness values of 10.71, 12.44, 8.52 and 16.80 GPa were recorded for M2BC (M = V, Nb, Mo and Ta) compounds, respectively. The value of bulk modulus, B is found to increase in the sequence B (V2BC) < B (Nb2BC) < B (Ta2BC) < B (Mo2BC), indicates Mo2BC is highly stiff among all compounds. The Mo2BC and Ta2BC compound might be considered as potential candidates for protection of cutting and forming tools due to the moderately ductile and highly stiff behavior compared to other benchmark hard coating materials such as TiN, TiAlN, Ti0.5Al0.5N and c-BN. Ta2BC compound could also be a promising thermal barrier coating (TBC) material due to the reasonable results of minimum thermal conductivity, Debye temperature and damage tolerance behavior. Various optical functions such as dielectric constants, refractive index, photo-conductivity, absorption, loss function and reflectivity) are calculated and discussed in details. The amount of reflectivity was always more than around 50% with no significant change in the near infrared, visible light and near ultraviolet region (up to ~6 eV), which results a promising coating material to diminish solar heating as well., 26 pages, 10 Figures

Purpose: This study examines the relationship between entrepreneurial competencies (skills that entrepreneurs require to perform their jobs to their full potentials) and firms performance (indicator that includes firms’ growth, profitability and market share). Design/Methodology/Approach: The theoretical model is drawn based on previous literatures and quantitative approach is applied. Data was collected from the 150 owners of the poultry firms (SMEs) in different areas of Khulna concerning 10 specific types of competencies (independent variable) towards firms’ performance (dependent variable). Findings: There remains a positive relationship between the entrepreneurial competencies and firms performance. Thus, if entrepreneurs give more attention to enhance entrepreneurial competencies, then it will result in better firms’ performance. Implications: The findings of this work is important to the entrepreneurship researchers, the practitioners and policy makers because of its concentration towards the fundamental proposition of entrepreneurial competency approach and to have better understanding of the importance of entrepreneurship for economic growth and new job creation. Originality/value: This study is conducted both including the female entrepreneurial domain and emerging economies like Bangladesh which is done for the first time and thus has added special value to this paper. .

The shape of the silicon crystal, whether spiral or cylindrical, was grown using the infrared convergent-heating floating-zone method, and the stability of the molten zone depended on the position of the mirror-lamp (M-L) system with respect to the grown crystal and molten zone. Through experiment, we studied the changes in the molten zone shape: the melt/feed, melt/gas, and melt/crystal interface shapes of the silicon molten zone under different positions of the M-L system. Although conventional parameters such as convexities (h/r) of the interface toward the melt were found to be independent of the position of the M-L system, the asymmetry of the zone length, L, was found to be inversely proportional to the distance of the M-L system from the center of the molten zone. A spiral crystal would be grown in this case. We introduce some parameters such as growth interface angle (δ), triple point angle (TPA), meniscus angle (MA), and altitude of the interface curvature (aC) to characterize the axis symmetry of the melt/gas and melt/crystal interfaces. The variations in TPA, MA, and aC were significantly reduced when the M-L system was shifted to a distant position from the center of the molten zone. On the other hand, the variations in δ were independent of the position of the M-L system. Thus, a symmetric molten zone was observed when the M-L system was at a distant rather than a close position. These behaviors were validated through observations of the molten zone stability and the crystal shape.

This study was conducted to investigate the status of brucellosis in dairy cattle from five selected dairyfarms in the Mohammadpur Beribadh area of Bangladesh. A cross-sectional study was carried out from October 2010to March 2011 in which a total of 334 serum samples from cattle in five herds were screened by the Rose-Bengalplate-agglutination test (RBPT) and the positives were confirmed using an indirect enzyme-linked immunosorbent assay(I-ELISA). A structured questionnaire was used to collect epidemiological information describing the animals. Overall,4.20% of the animals were RBPT positive, while subsequent confirmatory tests with I-ELISA revealed that the overallanimal-level prevalence derived from the samples was 1.20%. Additionally, the prevalence was relatively higher infemales than in males. A significant association was found between abortion, age of the animals, and the occurrenceof brucellosis (p < 0.05). Considering the overall low prevalence of brucellosis in the selected farms in the presentstudy, a brucellosis eradication program for dairy farms using a test-and-slaughter policy would be possible.Keywords : Bangladesh, brucellosis, indirect enzyme-linked immunosorbent assay, Rose-Bengal plate-agglutination test,seroprevalence

For the first time, we have reported in this study an ab initio investigation on elastic properties, Debye temperature, Mulliken population, Vickers hardness, and charge density of superconducting ScRhP and ScIrP phosphides. The optimized cell parameters show fair agreement with experimental results. The elastic constants and moduli, Poisson's as well as Pugh's ratio and elastic anisotropy factors have also been calculated to understand the mechanical behavior of these ternary compounds. Their mechanical stability is confirmed via the calculated elastic constants. The calculated values for Poisson's and Pugh's ratio indicate the ductile nature of these compounds. ScIrP is expected to be elastically more anisotropic than ScRhP. The estimated value of Debye temperature predicts that ScRhP is thermally more conductive than ScIrP and the phonon frequency in ScRhP is higher than that in ScIrP. The hardness of ScRhP is lower due to the presence of anti-bonding Rh-Rh in ScRhP. The investigated electronic structure predict that the metallic conductivity of ScRhP reduces significantly when Rh is replaced with Ir. The main contribution to the total density of states (TDOS) at Fermi-level (EF) comes from the d-electrons of Sc and Rh/Ir in both compounds. These two ternary compounds are characterized mainly by metallic and covalent bonding with little ionic contribution. As far as superconductivity is concerned, the matrix elements of electron-phonon interaction are noticeably enhanced in ScIrP compared to that in ScRhP., Slightly modified version of the one submitted to the Computational Materials Science

The conditions for bulk silicon crystal growth were examined using the mirror-shifting-type infrared convergent-heating floating zone method. The positions of the mirror-lamp (M-L) systems were systematically shifted to find a suitable position along a horizontal plane, from positions close to the molten zone to those more distant than the conventional position. The required lamp power was found to depend on the position of the M-L system. The system position for the minimum required lamp power also depended on the feed rod diameter and cross-sectional area, with a more distant position being more suitable than the conventional position of the M-L system for larger feed rods. The shape of the grown crystals was also affected by the position of the M-L system. When the system was close to the molten zone, crystals with a spiral shape were grown when larger tetragonal feed rods were used. At more distant positions, however, the growth of spiral-shaped crystals was suppressed. The molten zone length was almo...

The effects of lamp power and mirror position on the feed–melt and crystal–melt interfaces during the growth of a silicon crystal were examined using the mirror-shifting-type infrared convergent-heating floating-zone (IR-FZ) method. The lamp power used to form the molten zone was carefully changed. The positions of the mirrors along a horizontal plane were also systematically shifted from positions close to the molten zone to more distant positions as compared with the conventional mirror position. The solid–liquid (S–L) interfaces at both the feed–melt and the crystal–melt sides were examined carefully at the different mirror positions under the different lamp powers using a feed rod 15 mm in diameter, and it was found that the convexities (h/r) of the S–L interface shapes at both sides decreased with increasing lamp power. It was also found that the interface shapes were independent of the mirror position. A lower lamp power was enough to maintain the stable molten zone during the crystal growth at the closer mirror position. Therefore, effective heating was realized at the closer mirror position.

An investigation of U2Ti, a potentially safe and heavy metal-based storage material for radioactive tritium for fusion reactor, has been performed using pseudopotential density functional theory. The analysis of the elastic constants and other moduli calculated for the first time shows large anisotropy on elasticity and brittle behavior. A quasi-harmonic Debye model, which considers the vibrational contribution to the total free energy of the system, has been used to investigate the finite-temperature and finite-pressure thermodynamic properties of U2Ti. The electronic band structure reveals metallic conductivity and the major contribution comes from U-5f states. By analyzing the optical spectra, the origin of the various structures is also explained in terms of the calculated electronic structure. Further the reflectivity spectrum shows that the material is a perfect reflector within the energy range 8–12.5 eV.

First principles pseudopotential calculations have been performed for the first time to investigate the phonon dispersion, thermodynamic and optical properties including charge density, Fermi surface, Mulliken population analysis, theoretical Vickers hardness of predicted MAX phase Sc2InC. We revisited the structural, elastic and electronic properties of the compound which assessed the reliability of our calculations. The analysis of the elastic constants and the phonon dispersion along with phonon density of states indicates the mechanical stability and dynamical stability of the MAX phase. The Helmholtz free energy, internal energy, entropy specific heat capacity and Debye temperature have also been calculated from the phonon density of states. Mulliken population analysis indicates the existence of prominent covalency in chemical bonding of Sc2InC. The electronic charge density mapping shows a combination of ionic, covalent and metallic bonding in the compound. The Fermi surface is comprised due to the low dispersive Sc 3d and C 2p states from the [ScC] blocks. The phase is expected to be a soft material and easily mechinable due to its low Vicker hardness value. Furthermore, the analysis of various optical properties (such as dielectric function, refractive index, photoconductivity, absorption coefficients, loss function and reflectivity) suggests that the nanolaminate Sc2InC is a promising candidate for optoelectronic devices in the visible and ultraviolet energy regions and as a coating material to avoid solar heating., Comment: Submitted for publication, 15 pages, 6 figure

Of seven species of polychaetous annelids collected from the intertidal zone of Sitakunda coast, Chittagong, Bangladesh, five were new records for the country. The seven are listed, with brief notes on these, some previously recorded species and others housed in the collections of the Natural History Museum, London. Keys are given to the recorded species of Phyllodocidae, Nereididae, Lumbrineridae, Nephtyidae and Capitellidae of the “Northern Bay of Bengal Ecoregion”, and to the recognised species of Glyceridae from the Bay of Bengal. The worms in this Ecoregion are subject to the outflows of the Irrawaddy, Ganges, Hooghly and Mahanadi Rivers, and many of them are known to be freshwater tolerant.

The structural parameters with stability upon Si incorporation and elastic, electronic, thermodynamic and optical properties of Ti3Al1-xSixC2 (0 \leq x \leq 1) are investigated systematically by the plane wave psedudopotential method based on the density functional theory (DFT). The increase of some elastic parameters with increasing Si-content renders the alloys to possess higher compressive and tensile strength. The Vickers hardness value obtained with the help of Mulliken population analysis increases as x is increased from 0 to 1. The solid solutions considered are all metallic with valence and conduction bands, which have a mainly Ti 3d character, crossing the Fermi level. The temperature and pressure dependences of bulk modulus, normalized volume, specific heats, thermal expansion coefficient, and Debye temperature are all obtained through the quasi-harmonic Debye model with phononic effects for T = 0-1000K and P = 0-50GPa. The obtained results are compared with other results where available. Further an analysis of optical functions for two polarization vectors reveals that the reflectivity is high in the visible-ultraviolet region up to ~ 10.5 eV region showing promise as good coating material. Keywords: Ti3Al1-xSixC2; First-principles; Quasi-harmonic Debye model; Mechanical properties; Band structure; Optical properties, Comment: 12 pages, 8 figures