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      Volume 77, Issue 4

      October 2011,   pages  599-764

    • Evaluation of response matrix of a multisphere neutron spectrometer with water moderator

      Rahim Khabaz Hashem Miri Hakimabad

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      Neutron energy responses of water sphere spectrometers (WSS) to 30 MeV have been calculated by means of Monte Carlo calculations, using the computer code MCNP4C with ENDF/B-VI.0 neutron cross-section. The calculations have been performed for ${}^3$He detector (typical SP9) placed inside 2, 3, 5, 8, 12 and 18-inch diameter moderating spheres composed of water in aluminum shell. These simulations included a detailed description of the geometry of the system. The newly calculated responses have been compared to polyethylene sphere responses.

    • Detection of a periodic structure embedded in surface roughness, for various correlation functions

      V C Vani S Chatterjee

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      This paper deals with surface profilometry, where we try to detect a periodic structure, hidden in randomness using the matched filter method of analysing the intensity of light, scattered from the surface. From the direct problem of light scattering from a composite rough surface of the above type, we find that the detectability of the periodic structure can be hindered by the randomness, being dependent on the correlation function of the random part. In our earlier works, we had concentrated mainly on the Cauchy-type correlation function for the rough part. In the present work, we show that this technique can determine the periodic structure of different kinds of correlation functions of the roughness, including Cauchy, Gaussian etc. We study the detection by the matched filter method as the nature of the correlation function is varied.

    • A near-infrared zero-order achromatic retarder

      Arijit Saha Kallol Bhattacharya Ajoy Kumar Chakraborty

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      Phase retarders normally show strong wavelength dependence. Achromatic retarders which exhibit nearly identical characteristics over a wide wavelength spectrum is used in polychromatic light. The present investigation deals with a technique to design and study the characteristics of an achromatic combination of birefringent plates in 800–2000 nm range. The retarder has been designed using calcite, crystalline quartz and ADP. The thicknesses of the plates are 19.38 𝜇m, 446.14 𝜇m and 12.57 𝜇m respectively. The new arrangement of three birefringent plates proposed has the promise of producing a zero-order quarter wave achromatic combination with fairly good accuracy.

    • Analysis of adiabatic transfer in cavity quantum electrodynamics

      Joyee Ghosh R Ghosh Deepak Kumar

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      A three-level atom in a 𝛬 configuration trapped in an optical cavity forms a basic unit in a number of proposed protocols for quantum information processing. This system allows for efficient storage of cavity photons into long-lived atomic excitations, and their retrieval with high fidelity, in an adiabatic transfer process through the ‘dark state’ by a slow variation of the control laser intensity. We study the full quantum mechanics of this transfer process with a view to examine the non-adiabatic effects arising from inevitable excitations of the system to states involving the upper level of 𝛬, which is radiative. We find that the fidelity of storage is better, the stronger the control field and the slower the rate of its switching off. On the contrary, unlike the adiabatic notion, retrieval is better with faster rates of switching on of an optimal control field. Also, for retrieval, the behaviour with dissipation is non-monotonic. These results lend themselves to experimental tests. Our exact computations, when applied to slow variations of the control intensity for strong atom–photon couplings, are in very good agreement with Berry’s superadiabatic transfer results without dissipation.

    • Numerical modelling of the pump-to-signal relative intensity noise transfer in two-pump fibre optical parametric amplifiers

      H Pakarzadeh A Zakery

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      An accurate numerical model to investigate the pump-to-signal relative intensity noise (RIN) transfer in two-pump fibre optical parametric amplifiers (2-P FOPAs) for low modulation frequencies is presented. Compared to other models in the field, this model takes into account the fibre loss, pump depletion as well as the gain saturation. As a result, the model allows to include a wide range of practical circumstances, both in and beyond the undepleted pump regime, related to different applications of FOPAs. In the small-signal or undepleted pump regime, the model predicts the ripples of the RIN spectrum very well and yields better results than those of other models. It is shown that beyond the small-signal regime, pump power variations do not remain unchanged over the length of the amplifier and for high signal powers, when the FOPA saturates, minimum pump-to-signal RIN transfer occurs. The results of the model are also compared with the available experimental data in the field and a very good agreement can be seen.

    • Effect of low-temperature plasma treatment on tailorability and thermal properties of wool fabrics

      V S Goud J S Udakhe

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      Dielectric barrier discharge type of plasma reactor was used for the low-temperature plasma (LTP) treatment of the wool fabrics. Air was used as the non-polymerizing gas for the plasma treatment at different time intervals. Low-stress mechanical properties of the treated and untreated wool fabrics were evaluated using Siro-fast technique which revealed that the tensile, bending, compression, shear, dimensional stability and surface properties were altered after the LTP treatment. Other properties such as thermal conductivity, thermal resistance and pilling propensity were also evaluated. The surface topographical changes of the wool fibres after LTP treatment were analysed by scanning electron microscopy. The changes in these properties are supposed to be related closely to the interfibre and interyarn frictional force and increased surface area of the fibres induced by the etching effect of plasma.

    • The effect of complexing agent on the crystallization of ZnO nanoparticles

      S A Ketabi A S Kazemi M M Bagheri-Mohagheghi

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      In this work, some structural and optical properties of the zinc oxide (ZnO) nanoparticles were studied. The highly crystalline ZnO nanoparticles were produced by the hydrothermal and sol–gel methods. The analyses of the XRD patterns, STEM images and UV spectroscopy showed that the size of the nanoparticles prepared by oxalic acid was smaller than the ones by urea. The properties of oxalic acid and urea were also investigated to determine the most effective crystallization process of ZnO nanoparticles. It has been shown that pH, decomposition temperature and activity coefficient of the complexing agent have certain effects on crystallization process.

    • A simple model for calculating the bulk modulus of the mixed ionic crystal: NH4Cl1−xBr$_x$

      Vassiliki Katsika-Tsigourakou

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      The ammonium halides are an interesting systems because of their polymorphism and the possible internal rotation of the ammonium ion. The static properties of the mixed ionic crystal NH4Cl$_{1−x}$ Br$_x$ have been recently investigated, using the three-body potential model (TDPM) by applying Vegard’s law. Here, by using a simple theoretical model, we estimate the bulk modulus of the alloys NH4Cl$_{1−x}$ Br$_x$, in terms of the bulk modulus of the end members alone. The calculated values are comparable to those deduced from the three-body potential model (TDPM) by applying Vegard’s law.

    • Quantum information entropies of ultracold atomic gases in a harmonic trap

      Tutul Biswas Tarun Kanti Ghosh

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      The position and momentum space information entropies of weakly interacting trapped atomic Bose–Einstein condensates and spin-polarized trapped atomic Fermi gases at absolute zero temperature are evaluated. We find that sum of the position and momentum space information entropies of these quantum systems containing 𝑁 atoms confined in a $D(\leq 3)$-dimensional harmonic trap has a universal form as $S^{(D)}_t = N(a D − b ln N)$, where $a \sim 2.332$ and $b = 2$ for interacting bosonic systems and a $a \sim 1.982$ and $b = 1$ for ideal fermionic systems. These results obey the entropic uncertainty relation given by Beckner, Bialynicki-Birula and Myceilski.

    • Opto-chemical response of Makrofol-KG to swift heavy ion irradiation

      Ambika Negi R V Hariwal Anju Semwal R G Sonkawede D Kanjilal J M S Rana R C Ramola

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      In the present study, the effects of swift heavy ion beam irradiation on the structural, chemical and optical properties of Makrofol solid-state nuclear track detector (SSNTD) were investigated. Makrofol-KG films of 40 𝜇m thickness were irradiated with oxygen beam ($O^{8+}$) with fluences ranging between 1010 ion/cm2 and 1012 ion/cm2. Structural, chemical and optical properties were investigated using X-ray diffraction, FTIR spectroscopy and UV–visible spectroscopy methods. It is observed that the direct and indirect band gaps of Makrofol-KG decrease after the irradiation. The XRD study shows that the crystalline size in the films decreases at higher fluences. The intensity plots of FTIR measurements indicate the degradation of Makrofol at higher fluences. Roughness of the surface increases at higher fluence.

    • Effect of hybridization and dispersion of quasiparticles on the coexistent state of superconductivity and antiferromagnetism in 𝑅Ni2B2C

      B K Sahoo B N Panda

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      The effect of hybridization of conduction electrons and f-level on superconductivity (SC) and antiferromagnetism (AFM) in the coexistent phase of rare-earth nickel borocarbide superconductors (𝑅Ni2B2C) is reported. The Hamiltonian of the system is a mean field one and has been solved by writing equations of motion for the single-particle Green functions. It is assumed that superconductivity arises due to BCS pairing mechanism in the presence of antiferromagnetism in nickel lattices of Ni2B2 plane. The expressions for superconducting and antiferromagnetic order parameters are derived using double time electron Green functions. The quasiparticle energy bands are plotted and the nature of band dispersion of the quasiparticles is studied.

    • Affect of the electrical characteristics depending on the hole and electron injection materials of red organic light-emitting diodes

      Jong-Yeol Shin Hyun-Min Choi Hyeon-Seok Han Jin-Woong Hong

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      This study examined the electrical and optical properties of red OLEDs (organic lightemitting diodes) with a four-layer structure, ITO/amorphous fluoropolymer (AF)/$N,N'$--diphenyl$N,N'$-bis(3-methylphenyl)-1, 1-biphenyl-4,$4'$-diamine (TPD)/R-H:R-D/lithium fluoride (LiF)/Al, containing a hole injection material, AF (amorphous fluoropolymer) and an electron injection material, LiF. Compared to the basic structure (two-layer structure), the brightness and luminous efficiency of the four-layer structure, ITO/TPD/R-H:R-D/Al, increased approximately 100 times (30,000 lm/m2) and 150 times (51 lm/W), respectively, with an applied voltage. The excellent efficiency of the external proton was also increased 150 times (0.51%). That is, the hole and electron injection layers improved the surface roughness of ITO and Al, and the interfacial physical properties. In addition, these layers allowed the smooth injection of holes and electrons. The luminance, luminous efficiency and external quantum efficiency were attributed to an increase in the recombination rates.

    • Structural evolutions of the mechanically alloyed Al70Cu20Fe10 powders

      Musa Göğebakan Bariş Avar

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      Elemental mixtures of Al, Cu, Fe powders with the nominal composition of Al70Cu20Fe10 were mechanically alloyed in a planetary ball mill for 80 h. Subsequent annealing of the as-milled powders were performed at 600–800°C temperature range for 4 h. Structural characteristics of the mechanically alloyed $Al$_{70}Cu20Fe10 powders with the milling time and the heat treatment were investigated by X-ray diffraction (XRD), differential scanning calorimeter (DSC) and differential thermal analysis (DTA). Mechanical alloying of the Al70Cu20Fe10 did not result in the formation of icosahedral quasicrystalline phase (i-phase) and a long time milling resulted in the formation of 𝛽-Al(Cu,Fe) solid solution phase (𝛽-phase). The i-phase was observed only for short-time milled powders after heat treatment above 600°C. The 𝛽-phase was one of the major phases in the Al70Cu20Fe10 alloy. The w-Al7Cu2Fe1 phase (w-phase) was obtained only after heat treatment of the short-time milled and unmilled samples. The present investigation indicated that a suitable technique to obtain a large amount of quasicrystalline powders is to use a combination of short-time milling and subsequent annealing.

    • Seasonal variation of radon level and radon effective doses in the Catacomb of Kom EI-Shuqafa, Alexandria, Egypt

      M Abdelzaher

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      Inhalation of radon has been recognized as a health hazard. In the present work radon concentration was measured, in the atmosphere of the archaeological place, namely Catacomb of Kom El-Shuqafa, in Alexandria, Egypt, which is open to the public, using time-integrated passiveradon dosimeters containing LR-115 solid-state nuclear track detector. The measurements were performed throughout winter and summer. Seasonal variation of radon concentration, with the maximum in summer ranging from 243 to 574 Bq m-3 and minimum in winter ranging from 64 to 255 Bq m-3 was observed. Because of the variations of the catacomb ventilation system, the equilibrium factor between radon and its progeny ranges from 0.14 to 0.48. The tour guides are exposed to an average estimated annual effective dose ranging from 0.21 to 0.52 mSv y-1 and the visitors from 0.88 to 2.28 𝜇Sv y-1. The effective doses the catacomb workers are exposed to ranged from 0.20 mSv y-1 in winter to 4.65 mSv y-1 in summer which exceeds the lower bound of the recommended level (3–10 mSv y-1) (ICRP, 1993).

    • The classification of single travelling wave solutions to the Camassa–Holm–Degasperis–Procesi equation for some values of the convective parameter

      Chun-Yan Wang Jiang Guan Bao-Yan Wang

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      By the complete discrimination system for the polynomial, we give the classification of single travelling wave solutions to the Camassa–Holm–Degasperis–Procesi equation for some values of the convective parameter.

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