Third harmonic generation in LiKB4O7 single crystal

The third order nonlinear optical properties of the lithium potassium borate (LiKB₄O₇) single crystal have been investigated by means of the rotational Maker fringe technique using Nd:YAG laser at 1064 nm working in picosecond regime. The value of the third order nonlinear optical susceptibility was calculated using the theoretical model of Kajzar et al. and was found to be about 1.4 × 10⁻²¹ m² V⁻² that is one order higher than that of fused silica.     

Azo-azulene based compounds-nonlinear optical and photorefractive properties

This work reports on nonlinear optical properties of some azo-functionalized azulene derivatives. Linear and nonlinear optical absorption, second- and third harmonic generation were used as diagnostic tools. It was demonstrated that light induced a surface pattern on thin films containing the studied compounds. The results indicate an important role of thiazole substitution for enhancing NLO properties of the azulene derivatives.     

Combined FPPE–PTR Calorimetry Involving TWRC Technique II. Experimental: Application to Thermal Effusivity Measurements of Solids

Photopyroelectric calorimetry in the front detection configuration (FPPE) and photothermal radiometry (PTR) were simultaneously used, together with the thermal-wave resonator cavity method (TWRC), in order to investigate the thermal effusivity of solids inserted as backing layers in a detection cell. A new combined FPPE–PTR–TWRC setup was designed. It was demonstrated experimentally that the PTR technique, combined with the TWRC method, is able to provide calorimetric information about the third layer of a detection cell. Applications on solids with different values of the thermal effusivity (starting from metals, down to thermal isolators) are presented. The values of the thermal effusivity obtained with the PTR technique are similar to those obtained with the PPE technique, and in agreement with literature values; the two methods reciprocally support each other. The accuracy of both methods is higher when the values of the thermal effusivity of the backing layer and coupling fluid are close.     

Dynamic traffic congestion pricing and electric vehicle charging management system for the internet of vehicles in smart cities

The integration of the Internet of Vehicles (IoV) in future smart cities could help solve many traffic-related challenges, such as reducing traffic congestion and traffic accidents. Various congestion pricing and electric vehicle charging policies have been introduced in recent years. Nonetheless, the majority of these schemes emphasize penalizing the vehicles that opt to take the congested roads or charge in the crowded charging station and do not reward the vehicles that cooperate with the traffic management system. In this paper, we propose a novel dynamic traffic congestion pricing and electric vehicle charging management system for the internet of vehicles in an urban smart city environment. The proposed system rewards the drivers that opt to take alternative congested-free ways and congested-free charging stations. We propose a token management system that serves as a virtual currency, where the vehicles earn these tokens if they take alternative non-congested ways and charging stations and use the tokens to pay for the charging fees. The proposed system is designed for Vehicular Ad-hoc Networks (VANETs) in the context of a smart city environment without the need to set up any expensive toll collection stations. Through large-scale traffic simulation in different smart city scenarios, it is proved that the system can reduce the traffic congestion and the total charging time at the charging stations.     

Techniques for Reducing the Number of Decisions and Backtracks in Combinational Test Generation

Combinational test pattern generation (TPG) is basically a search in a finite state space. In general, the search is performed in a branch-and-bound fashion. The branch-and-bound search builds a decision tree using two basic operations: decision making and backtracking. The size of the decision tree, and hence the efficiency of the branch-and-bound search, is directly dependent on the number of decisions made. This paper proposes a set of novel techniques for reducing the number of decisions and the size of the decision space. These techniques work directly on the maximum number of potential ways of justifying a given logical assignment. This maximum number is reduced by exploiting the properties of prime-and-irredundant covers. These same properties are also used to reduce the number of backtracks by implying a maximum number of necessary assignments. The reduction of the number of decisions and the identification of a maximum of necessary assignments make the proposed TPG method highly efficient as demonstrated by experimental results. This paper also proposes a novel combination of prime-and-irredundant cover extraction and transitive closure computation for a more efficient TPG process.     

Second-order optical effects in seed-mediated grown palladium nanoparticles

Palladium nanoparticles deposited on SnO₂-doped In₂O₃ substrate show substantial optical second harmonic generation (SHG) in the spectral range (λ?=?120–160?nm) which is a part of the vacuum ultraviolet (VUV) spectrum. A single crystalline Li₂ B₄ O₇ optical parametric generator (OPG) pumped by nanosecond xenon–fluorine excimer laser (EMG 500/218 (Lambda Physics)) with the wavelength 218?nm, pulse duration about 6–8?ns; pulse rate about 80?hz, average pulse power about 0.2?MW and beam diameter varying within the 1.3–7.5?nm was used to form the fundamental beam. The OPG Li₂ B₄ O₇ single crystal was cut in the XZ optical plane. We have tuned the fundamental wavelengths within the 250–320?nm spectral range varying the angle of the plane with respect to the incident pumping beam. Maximal SHG output (in the reflected SHG geometry) is observed for the incident angles 75^○–80^○ with respect to the surface normal and p-polarized incident fundamental ultraviolet beams. Spectral separation between the vacuum ultraviolet (VUV) SHG intensities and the fundamental beams was performed using a VUV Seya-Numioka vacuum monochromator with spectral resolution 6?nm in the investigated spectral range. We have found that decreasing mean average palladium nanoparticle sizes favour substantial enhancement of the output SHG within the 120–160?nm spectral range. A layer of platinum nanoparticles coated on a layer of palladium nanoparticles suppresses the SHG effect indicating a quenching of the surface plasmon excitation originating from the palladium nanoparticles. The observed effect allows utilizing the palladium nanoparticles as an efficient material for frequency transformation of the UV nanosecond pulses (spectral range 240–310?nm) into the nanosecond laser pulses with wavelengths 120–160?nm.     

Annealing effect on properties of transparent and conducting ZnO thin films

This work presents the effect of postdeposition annealing on the structural, electrical and optical properties of undoped ZnO (zinc oxide) thin films, prepared by radio-frequency sputtering method. Two samples, 0.17 and 0.32 µm-thick, were annealed in vacuum from room temperature to 350 °C while another 0.32 µm-thick sample was annealed in air at 300 °C for 1 h. X-ray diffraction analysis revealed that all the films had a c-axis orientation of the wurtzite structure normal to the substrate. Electrical measurements showed that the resistivity of samples annealed in vacuum decreased gradually with the increase of annealing temperature. For the 0.32 µm-thick sample, the gradual decrease of the resistivity was essentially due to a gradual increase in the mobility. On the other hand, the resistivity of the sample annealed in air increased strongly. The average transmission within the visible wavelength region for all films was higher than 80%. The band gap of samples annealed in vacuum increased whereas the band gap of the one annealed in air decreased. The main changes observed in all samples of this study were explained in terms of the effect of oxygen chemisorption and microstructural properties.     

Combined FPPE–PTR Calorimetry Involving TWRC Technique. Theory and Mathematical Simulations

Photopyroelectric calorimetry in the front detection configuration (FPPE) was combined with photothermal radiometry (PTR), in order to investigate dynamic thermal parameters of different layers of a detection cell. The layout of the detection cell consists of three layers: directly irradiated pyroelectric sensor, liquid layer, and solid backing material; and the scanning parameter is the thickness of the liquid layer (thermal-wave resonator cavity method). The theory developed for the two techniques indicates that both FPPE and PTR signals can lead, in the thermally thin regime for the sensor and liquid layer, to the direct measurement of the thermal diffusivity or effusivity of the sensor and/or liquid layer, or the thermal effusivity of the backing material. The two methods offer complementary results and/or reciprocally support each other.     

Three-dimensional modeling of water transport in PEMFC

A three dimensional two phase flow model is proposed to study transport phenomena in a PEMFC. In order to capture the effects of liquid water on the performance of the fuel cell, all regions are modeled from the anode to the cathode as having finite thickness. The geometry of the bipolar plate is modeled in detail to capture the effect of liquid water accumulation under the channel rib. This model takes into account the effect of temperature and inlet RH of both the anode and cathode. The three-dimensional model uses the finite volume method to solve the equations of mass conservation, momentum, energy, species transfer and protonic potential. These equations include the effect of liquid water on the transport properties as well as the electrochemical source. The effects of water on ohmic losses are presented for different humidity conditions of the anode and cathode at various fuel cell temperatures.     

Promoting social diversity for the automated learning of complex MDE artifacts

Software and Systems Modeling - Software modeling activities typically involve a tedious and time-consuming effort by specially trained personnel. This lack of automation hampers the adoption of...