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[en] Soon after the innovation of the magnetic fluid (Mf), it was found that needle like agglomerates (macro-clusters) were generated in some kind of MFs under an external magnetic field by optical microscope observation. However, the macro-clusters disappeared when the external field was removed. Therefore, many theories were proposed whether or not macro-clusters were simple precipitants of the colloidal particles, or one phase of the two-phase separation, or etc. On the other hand, MFs under an external magnetic field show many peculiar and interesting phenomena in acoustics and magneto optics In order to interpret these peculiar phenomena, an assumption that submicron-order agglomerates of the colloidal particles elongated along the field direction (micro-clusters) was necessary. However, this assumption contradicted the MF's phase transition of second order between the particles monodispersed phase and the phase in which the agglomerates were generated (Landau criterion). In this paper, first, the macro-cluster's nature is explained. The experimental results of the time dependence of the Mf shaft seal's burst pressure, the MF's acoustic properties and magneto-optical effects are explained followed by explaining the necessity of micro-cluster assumption. Proton-NMR experiment of the water-solvent Mf and the latent heat measurement of the Mf phase transition by differential scanning calorimetry are explained. The conventional Mf and 1000-fold diluted Mf were used for the magnetization curve measurement, temperature and Ac magnetic field frequency dependence experiment of the initial complex spastically measurement and frozen MF's magnetic aftereffect experiment. From these experiments, the magnetic colloidal particles interaction in the Mf is discussed. Finally, we show a physical model that the excess surfactant molecules which are isolated and freely dissolved in the MF's solvent make special micelles when the temperature is decreased or the external magnetic field is applied. The magnetic colloidal particles stick to the suffice of the micelles and this applied. The magnetic colloidal particles stick to the surface of the micelles and this micelle with the colloidal particles is the actual micro-cluster. We show that this special micelle model explains all the MF's peculiar phenomena without any contradictions, especially the contradiction between the anisotropic al agglomeration and Landau criterion with respect to the phase transition of second order. (author).
[en] Size, surface and temperature effects of first and second oeder phase transition of ferroelectric (FE) thin films have been discussed in detail in the literature. However, the reversal of polarization by a applied electric field in FE materials is an important phenomennon to the industrial and technological applications, and it is an active research area for experimentalists as well as for theories. The Tilley-Zeks model has well described the polarization profiles of FE thin films in the absence of electric field. Hence we adopt the Tilley-Zeks model of free energy expression and a term P.E., which gives the energy due to the interaction of electric field E and polarization profile for second order FE expression. We study the effects of electric field polarization profile for second order FE thin films with different surface parameters for the case when the direction of electric field is along the direction of polarization (induced polarization phenomenon) and the case when the electric field is in opposite direction with the polarization (polarization reversal phennomenon). We have found that the switching time decreases with increasing the value of external electric field. (author).
[en] Four field emission tubes that have single carbon nano tubes (CN T) as the emitters were tested; two with single-walled CN T and two with multi walled CN T. A tube with a tungsten tip was used for comparison. Fowler-Nordheim analysis of the Dc current-voltage data gave reasonable values for the local fields at the emitters and the sizes of the emitters. Two oscillators were used to superimpose sinusoidal signals on the applied static field, thus increasing the Dc emitted current and causing a mixer current at their difference frequency, in agreement with theory. Square-wave pulses from a single laser diode (20 MW, 658 nm) focused on each emitter increased the emitted current by 5.2% with the CN T and 0.19% with the tungsten tip. (authors).
[en] In this paper, the interacting boson model (IBM-1) is discussed and employed for calculating the energy level and the electromagnetic transition probabilities B(E2) of the even - even 174-180Hf isotopes. These isotopes have been investigated based on two different arrangements; i.e., the dynamical symmetry of 176-180Mf isotopes, SU (3) (deformed nuclei) and the dynamical symmetry of 174Hf isotopein transition region SU(30-O(6). The determined values using the IBM-1 Hamiltonian showed significant agreement with the experimentally reported energy level and B(E2) values. The model provides a fast and accurate predication method of energy level B(E2)values. (authors).
[en] Radon concentration were measured using passive dosimeters, Snidest Cr-39 in As-Salt city and its surrounding. 300 dosimeters were distributed over the study area dwell ins according to the fraction of the population. The exposure time started from April 2004 and lasted for 100 days. Radon concentrations were found to vary from region to region, ranging from 31 to 501 Bq m-3 with a mean value of 111 ± 4 Bq m-3. The concentration of radon short-lived daughters was estimated at 44 ± 2 Bq m-3 or around 0.012 Working Level (Wl). The ground floors were found to have the highest radon concentrations with a mean value of 118 Bq m-'3, while the upper floors were found to have a higher mean radon concentration than living or setting rooms; these concentration were 117 ± 16 and 105 ± 5 Bq m-3, respectively . It was found that As-salt dweller is exposed annually to 0.49 Working Level Month (Wilm) from radon gas and its short-lived daughters. Hence, a person takes on the average an annual effective dose equivalent to 2.7 mSv according to UNSCEAR and 1.9 mSv according to ICRP. This implies an expected value for lung cancer probability of 0.004%. (authors).
[en] We have studied the structural and magnetic properties of (Ni1χMgχ)Fe2 O4 ferrite. X-ray diffraction and magnetization measurements were performed for all samples. x-ray results showed that a single phase ferrite was obtained for all samples. The lattice parameter, a, was estimated from the X-ray results and we found that the lattice parameter increases slightly at high Mg2+ contents (χ > 0.4). Magnetic hysteresis measured for all samples showed that the coercivity (Hc) shows an appreciable change at low (χ=0.2) and high (χ=1.0)Mg2+ content. It was also found that the saturation magnetization (Ms) and the reman ece (Mr) decreases with increasing Mg. (authors).
[en] Composite materials containing both ferroelectric and ferromagnetic phases from barium titanate (BaTiO3) and barium ferrite (BaFe12o19) have been studied. The coexistence of ma genetic hysteresis in the composite material has been observed un the temperature range 90-300 K.It is found that both remnant magnetization Mr and the saturation magnetization Ms decrease with increasing the temperature and they increase with decreasing the concentration of Ba Tio-3 in the system. The coercive field Hc increases almost linearly with inr easing the temperature and with increasing the concentration of BaTiO3 in the system. (authors).
[en] Recent theoretical and experimental studies demonstrated the ability of space technologies to identify and monitor the spcific variations an near-earth space plasma and atmosphere associted with approaching severe earthquaks, named as earthquake precursors, which appear several days before the seismic shock over the seismically active areas . This paper aims at determining the relationship between ionosphere scintillation of radio waves and earthquakes. Data for GPS (Global Positioning System) S4 index have been examined through spatial and temporal correlation. The results showed that the pre-seismic activity can be considered as a source of ionosphere scintillation. (authors).
[en] This work reports the preparation of thin films of amorphous tin nitride (a-Sn:N) by a novel implementation of simulttaneous ion beam assisted deposition (IBAD) and reactive DC magnetic sputtering of a metal tin target in pure nitrogen plasma. The work also reports the optical characterization and determination of the optical constants of a-Sn:N thin films material. The refractive index n varies only slighly over spectral range of 400-900 nm while the extinction coefficient k displays a gradual but significant increase starting at ∼470nm. We have estimated the optical energy gao, Eopt, be 2.23 ±0.047 eV deduced from the transmittance measurements. Other impoetant optical characteristics, such as the high frequency dielectric constant ε∞ , the average oscillator's wavelength λo, the average oscillator strength So tangent loss ( tan δ) and the optical conductivity σ, are also determined. Determination and interpretation of some of the optical properties are based on the single oscillator model proposed by Wemple and DiDominico. (Author) 45refs, 8 fig
[en] This work describes the results of measurements on the concentrations of radon (222 Rn) found in seven mineral water samples collected from some natural mineral springs at seven sites in Nenevah govern orate of north region in Iraq. Heat drying method was used to concentrate the radioactive nuclides in measured samples. Test tubes technique employed to measure (222Rn) using (Cr - 39) plastic nuclear track detectors. The activity density of (222Rn) ranges from (3.82 P Ci/L) to (9.999 P Ci/L); while the average value was (5.8054 P Ci/L). All results were below the maximum contaminant level (Mc) for (222Rn) in drinking water as reported by Environmental Protection Agency (EPA). (author).