This experimental work presents reproducible measurement conditions to allow amplification of the mechanical vibration generated by photo-thermo-acoustics (PTA) effect using the resonance of circular silicon membranes clamped by nitrile o-rings on a diameter of 30 mm (Di ). We use wafers with various thickness (h) between 250 and 1000 μm and with carrier lifetime between 3 and 30 μs. Under the condition to have a resolution of few picometers for the measurement, it is possible to characterize the resonance mechanism obtained without contact by conventional laser vibrometry using a modulated laser diode of only a few milliwatts of power. Compared to perfect clamped membranes, the first Eigen frequency presents a downward shift of some hundreds Hertz due to the circular clamping by o-ring as predicted by our simplified model. The resonance frequency depends linearly on the thickness as long as Di /h > 80. The quality factor (Q) does not exceed ten in agreement with our model for spring loaded membrane in air. The low value of quality factor and its variation according to thickness follow our predictions. Moreover, Q is independent of carrier lifetime whereas first resonance amplitude increases with it but less than prediction for bulks.

In this paper, some of the results of dielectric study carried out using locally produced low cost Fe2O3 powder with 0.5 wt% of Si additive are being summarized. The dielectric properties were studied as a function of composition, frequency and temperature for a series of Mnx Zn1-x Fe2O4 ferrite. The samples were prepared by the usual ceramic technique. It was observed that the values obtained for dielectric constant ∈′ and dielectric loss factor tan δ are much lower than those normally obtained for Mn-Zn ferrite prepared by pure Fe2O3 powder. The low values are attributed to the presence of Si, which suppress the ceramic grain growth. The low dielectric loss makes these samples attractive for use at high frequencies. Each of ∈′ and tan δ increases on increasing the temperature. Abnormal dielectric behavior observed for x = 0.99 due to forced migration of Fe ions from A sites to B sites at this composition.

In this study, Ag/OD-MO/Ag surface-type diode was fabricated by drop-casting orange dye and methyl orange blend thin film from 1.0 wt.% aqueous solution, under the effect of an electric field, on a glass substrate with preliminary deposited silver electrodes. Geometrical length and width of the semiconducting channel between metallic electrodes were equal to 40 μm and 21 mm, respectively. The dark I-V characteristics exhibited strong rectification behaviour though both electrodes were from the same metal. The average value of rectification ratio (RR) was 27 and it was found that RR varies with applied voltage in the range of 1–40. The dark I-V characteristics were simulated by modified Shockley equation and space-charge limited currents (SCLC) approach. Different diode parameters were calculated from current-voltage characteristics. The diode showed non-ideal I-V behaviour with a quality factor greater than unity. Energy band diagram is proposed for the Ag/OD-MO/Ag surface-type diode.

The strain-dependent electronic structure of graphene ribbons is studied based on tight-binding theory. The change of ribbons in applied electric field brought by strain is revealed. In contrast to normal strain, it is found that shear strain yields new transverse electric field which is similar to Hall effect. The conductance of ribbons under uniform uniaxial strain is calculated in Landauer formula. It is obtained that the conductance decreases (increases) 1.62% (1.64%) under the 0.5% uniaxial tension (0.5% compression) for a 200 nm-width ribbon.

The performances of organic photovoltaic cells based on the layer couple electron donor/electron acceptor (ED/EA) are significantly improved when an exciton blocking layer (EBL) is inserted between the organic acceptor and the cathode. A new material, the (Z)-5-(4-chlorobenzylidene)-3-(2-ethoxyphenyl)-2-thioxothiazolidin-4-one, that we called (CBBTZ), has been synthesized, characterized and probed as EBL. The energy levels corresponding to the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the CBBTZ have been determined from the first oxidation and reduction potential respectively, using cyclic voltametric (CV) measurements. From CV curves, CBBTZ in dichloromethane showed a one electron reversible reduction and oxidation waves. The values of its HOMO and LUMO have been estimated to be 6.42 eV and 3.42 eV respectively. Such values show that CBBTZ could be probed as EBL in organic solar cells based on the ED/EA couple copper phthalocyanine(CuPc)/fullerene (C60). The photovoltaic solar cells have been obtained by sequential deposition under vacuum of the different films. The different thin film thicknesses were measured in situ by a quartz monitor. Multilayer solar cells ITO/Au/CuPc/C60/EBL/Al have been probed, where EBL is the aluminium tris(8-hydroxyquinoline) (Alq3), the CBBTZ, the 2-(4-byphenylyl)-5-(4-tert-buthylphenyl)-1,3,4-oxadiazole (butyl PBD) or the bathocuproine (BCP). The optimum film thickness is 8–9 nm whatever the EBL used. When obtained in the same run, the averaged efficiency of the cells using the CBBTZ is of the same order of magnitude than that obtained with BCP and higher than that achieved with Alq3 or butyl PBD. It is shown by XPS study that some aluminium of the cathode is present in the buffer layer. This aluminium could justify the ability of the electrons to cross the insulating exciton blocking layer thick of 9 nm.

The spectroscopic emission of zinc plasma along with CCD imaging profile has been studied. The zinc target has been irradiated with a Q-switched Nd:YAG laser (1064 nm, 290 mJ, 10 ns, 29 MW) in air at atmospheric pressure. The plasma emission is recorded with 100 ns integration time. Boltzmann plot method and Stark broadening profile of the transition line has been used to estimate the electron temperature (Te ) and electron density (Ne ) respectively. Estimated values of Te and Ne is in the range of (5700–6756) K and (1.6 × 1015-3.39 × 1015) cm-3 at three laser shots respectively.

Based on the vector angular spectrum theory of electromagnetic waves and the method of stationary phase, analytical vector structures of four-petal Gaussian beams (FPGB) in the far field are derived. The energy flux for the TE term, TM term and the whole beam are represented and illustrated with numerical examples. Effects of beam orders and paraxial degrees on energy flux distributions are discussed in detail, and the corresponding analytical explanations are also given. These results may provide a new approach to manipulate other higher-order laser beams in the far field.

Zn1-x Mnx O (x = 0.01, 0.02, 0.05, 0.1, and 0.15) powders were prepared by solid-state reaction processes. The structural and magnetic properties of the powders were investigated. X-ray diffraction (XRD) analysis of the samples indicates the presence of wurtzite crystal structure similar to pure ZnO and absence of any other secondary phase till 5% Mn doping. This suggests that doped Mn2+ ions substitute Zn2+ sites. However, Raman results revealed the presence of secondary phase even at very low Mn doping (2%), which demonstrates that Mn does not incorporate completely the ZnO lattice. The powders exhibit ferromagnetism at low temperatures and paramagnetic at room temperature. Transition from ferromagnetic to paramagnetic is highlighted by measurements at 230 K.

Perovskites BaTi1 - z Mz O3 + δ (M = Fe, Cr, Mn, Co) has been sol-gel synthesized. Their transformation point of ferroelectric to paraelectric and the latent heat of the transformation were found a little lower than those for pure BaTiO3 (BTO), respectively. Layered composites Tb1 - x Dyx Fe2 - y –BaTi1 - z Mz O3 + δ have been fabricated. Their magnetoelectric (ME) effect has been investigated. All the bilayers containing the doped BTO displayed a stronger ME effects than that containing pure BTO does. The bilayer Tb1 - x Dyx Fe2 - y –BaTi0.99Cr0.01O3+δ was observed to show a larger ME coupling in the composites containing other doped BTO. While Tb1 - x Dyx Fe2 - y –BaTi0.985Fe0.015O3 + δ showed the largest ME effects in the bilayers Tb1 - x Dyx Fe2 - y –BaTi1 - z Fez O3 + δ (0 ≤z ≤ 0.02). Additionally, the ME voltage coefficient for the trilayers Tb1 - x Dyx Fe2 - y –BaTi0.99M0.01O3 + δ –Tb1 - x Dyx Fe2 - y was observed to be two or three times larger than that observed in the bilayers composed by the same substances. Theoretical analyses have been given for these observations. All the results suggest that the doped BTO can be a new choice of piezoelectrics in fabricating layered ME composites.

The high order perturbation formulas of the electron paramagnetic resonance (EPR) parameters (the g factors and the hyperfine structure constants) are established for a 3d 9 ion in orthorhombically compressed octahedra. These formulas are applied to the investigations of the EPR spectra and local structures for the substitutional Cu2+ centers in the wolframite-type tungstates AWO4 (where A = Cd, Zn, Mg). Based on the studies, the [CuO6]10- clusters are found to experience the local planar bond length variations δR' (≈0.096, 0.021 and 0.028 Å for CdWO4, ZnWO4 and MgWO4, respectively) along X and Y-axes. These values are quite different from the host planar bond length variations δR (≈0.013, 0.069 and 0.005 Å) for the A2+ sites in the pure tungstates. The above local bond length variations in the impurity centers can be attributed to the Jahn-Teller effect and size mismatching substitution. The theoretical EPR parameters based on the above local structures agree well with the experimental data. By adopting the uniform theoretical formulas and fewer adjustable parameters in this work, the improvements are achieved for the EPR parameters as compared with the previous calculation results.

In a calculation of demonstrative type collective, laser-like behavior of low energy nuclear fusion reaction of deuterons in crystalline environment is investigated. It is found that the reported extra 4He production can be appropriately described with a model well known in quantum electronics in which the quantized boson (4He) field interacts with an ensemble of two-level systems in a crystal resonator. The estimated life times of the two levels indicate that population inversion may be achieved. Thresholds of the deuteron number of the sample and of the electric current density of the pumping electrolysis are estimated in the calculation by analyzing the gain parameter and some other characteristics of the process. An explanation for the experimentally observed threshold behavior of the electric current density is given. A loss of a special type, that is the degenerate parametric amplifier mechanism, is suggested to be responsible for the difference between the expected and observed energies of the outgoing charged particles.

This paper, which deals with the winding modeling of ac multi-phase machines with a regular distribution of the stator slots, details an original matrix modeling of the stator winding. First, the properties of the balanced multi-phase windings (with integral-slot and fractional-slot patterns) are analysed. The winding function approach, one of the most common way to model the winding distribution effects on the stator rotating field, is then introduced. For multi-phase machines, it will be shown that the pole number generated by the winding distribution depends on a new parameter: the circularity index. The discrete nature of the winding, imposed by the stator slots, leads to the development of a discrete modeling of the winding obtained from sampling the winding function: two matrices, the winding function matrix and the distribution function matrix, are introduced to characterize the multi-phase winding. This matrix approach is thus a concise way to calculate the winding factors and to estimate the set of self and mutual stator inductances for smooth air gap multi-phase machines. A particularly original method of obtaining an analytical expression for the leakage mutual inductance is described. The results are validated with two experimental 5-phase PM machines by using experimental measurements and numerical simulations.

In this paper, the transportation principles of a sine-modulated spherical light coming from a point light source in an optically homogeneous scattering media are present for the first time to our knowledge. Both a focused ultrasound pulse and a broadened light beam are employed to produce the point light source emitting the sine-modulated light. Firstly, based on the transportation principles, the penetration depth of the media is deduced by moving the ultrasound beam and detecting the changes of the ultrasound-modulated light signal outside the media. Then, the diffuse reflection ratio of the media is deduced by measuring the reflected light outside the media. At last, with the combinations among the penetration depth, the diffuse reflection ratio and other optical properties, the optical properties of the media are determined by mathematic calculating.