JOURNAL OF PHYSICS MOLECULAR & ATOMIC
Year:2010 | Volume:1 | Issue:3|Papers Count:8

This paper investigates the effect of cell size on density of states of the single wall Carbon nanotube m (2n, 0)/ l (n, n),m (2n, 0) quantum dots. By increasing the length of armchair carbon nanotube in metal-metal system m (12, 0)/l (6, 6)/ m (12, 0) and metal-semiconductor system m (8, 0)/l (4, 4)/m (8, 0), we observe changing in the density of states and increment of oscillation of the density of states. In the presence of the single vacancy and omission of a carbon atomic potential we observe small changes in the density of states in the system. These properties are used in optimization of nanoelectronic devices based on carbon nanotubes.

In this study loss measurements in axial fiber displacements in a fiber-to-fiber design using two different light sources (white lamp & red LED) is reported. A fiber-to-fiber arrangement is used in which the source light is directly coupled to the first fiber and the second fiber delivers the light to a power meter. Using this arrangement the variation of the power and loss as a result of axial (Z-direction) displacements of the second fiber are monitored. Theoretical model is also to evaluate the power transmissions for comparison is made with the experimental results. Our results in general agree with the theoretical predictions and the small deviation is because of the fact that those theoretical formulas are more precise for the case of small core fibers for small axial displacements while we are using large core fibers and relatively long displacements. Important parameters of the reported optical system such as measurements reproducibility (about 0.001%), and hysteresis effect (about 0.034), are also investigated that verify the reasonable operation of such an optical system. The result of this experiment verify that fiber material and other fiber parameters affect the power transmission and such parameters can be investigated experimentally using the reported fiber-to-fiber arrangement.

Cobalt nanocrystals were prepared by precipitation method using cobalt nitrate precursor in the presence of 1) Oxalic acid, 2) KOH, and thus oxidized to grow on varying temperatures. The morphology and crystallite size of cobalt oxide (Co3O4) nanocrystalline were characterized by SEM and XRD patterns.The SEM images of initial powder showed nanorods and second one showed nanoparticles.The XRD patterns studies of these nanopowders indicated a cubic polycrystalline structure for both samples. Purity of polycrystalline powders were investigated by IR spectroscopy. The radius of nanorods of first sample was calculated to be 40 nm approximately by scherrer formula. The particle size of second sample calculated by scherrer equation, and the average particle size become 16.5 nm at 573 K calcinating temperature.

Nowadays One Way Model is one of the most attractive models in Quantum Computation which by tactful measurement on the special qubits in the cluster states, one can easily derive any special quantum gates. Producing any efficient and desirable Hamiltonian according to the necessary evolution in the cluster states also is one of the most significant issues in the Quantum Computation. In this paper in addition to the reviewing how to create any Hamiltonians in the pauli group, we have established as an example, Heisenberg Hamiltonian through One Way Model.

Multi walled Carbon Nanotubes; MWCNTs@Silica nanocomposite was synthesized by sol-gel method. By using the synthesized nanocomposites and also CNTS, as template, Silica-NTs were synthesized. The fabricated nanocomposites and nanotubes were optically characterized. Micro Raman back-scattering, UV/Vis./NIR and FTIR spectroscopies show the presence of CNTs structure in the nanocomposite. UV/Vis./NIR and FTIR spectroscopies also show the presence of silica compounds in the nanocomposite. The recorded data from micro-Raman and FTIR spectroscopies confirm the presence of silica compounds in the nanotubes. The results of SEM imaging indicate that the synthesized silica tubes are nanotube.

Lorentz violation in a brane-world scenario is presented and used to obtain a relationship between the speed of the gravitational waves in the bulk and that on the brane. we considers a typical brane world model and then extracts the Einstein field equations on the brane. Lorentz violation effects would manifest themselves in the gravitational waves travelling with a greater speed in the bulk than on the brane and therefore an observer on the brane can see the Lorentz invariant effects.

Splicing similar and dissimilar optical fibers is an important factor in designing optical cable networks. Therefore, the inspection of loss factors at splice joints of different optical fibers is a major step in enhancing the optical fiber network quality. These factors are divided into two categories of intrinsic and extrinsic. The intrinsic factors are unchangeable after optical fiber fabrication. The influential factors affecting the splicing condition are the extrinsic ones, including transverse and angular misalignments, longitudinal displacement, fusion system, fiber cleaving, and operator workmanship, etc. In this paper, the field measurements of splice loss of similar and dissimilar fibers in some selected domestic optical networks are reported where the influences of aforesaid factors are investigated and the obtained results are compared with theoretical analysis.The reported measurement results can be useful and applicable for the executive and design engineers active in domestic optical communication networks.

Historically, observing anti-bunched photons in Hanbury-Brown&Twiss experiments is the first strict proof on quantum nature of light. These experiments help analyzing the behavior of various light types, namely coherent, bunched or anti-bunched light. Coherent and bunched light can be justified via a classic theory, but to analyze anti-bunched light, we should apply quantum models. Nowadays, anti-bunched light rays are produced using a single photon emitter (e.g. a semiconductor quantum dot, a color center …). At present, the development of single-photon sources is an important subject of research, but they are applied so gradually in modern systems. The reason can be investigated in high sensitivity of single-photon detecting process with respect to loss. This in turn, has motivated rapid development of expensive high efficiency photon detectors. Anti-bunched light is mainly applied in quantum cryptography to highly guaranty the security of data transportation.