The Effect of the Range of a Modulating Phase Mask on the Retrieval of a Complex Object from Intensity Measurements

In many fields of science, it is often impossible to preserve the information about the phase of the electromagnetic field, and only the information about the magnitude is available. This is known as the phase problem. Various algorithms have been proposed to recover the information about phase from intensity measurements. Nowadays, iterative algorithms of phase retrieval have become popular. Many of these algorithms are based on modulating the object under study with several masks and retrieving the missing information about the phase of an object by applying mathematical optimization methods. Several of these algorithms are able to retrieve not only the phase but also the magnitude of the object under study. In this study, we investigate the effect of the range of modulation of a mask on the accuracy of the retrieved magnitude and phase map. We conclude that there is a sharp boundary of the range of modulation separating the successfully retrieved magnitude and phase maps from those retrieved unsuccessfully. A decrease in the range of modulation affects the accuracy of the retrieved magnitude and phase map differently.

Methodology for Increasing the Competences of Housing Managers in Climate Change Issues

In order to identify the necessary competences and develop the study course programme, within the framework of the EUKI (The European Climate Initiative; Die Europäische Klimaschutzinitiative) project “From Housing Manager to CLImate Manager”, research [1] has been conducted, describing the Latvian residential fund, analysing the principles and activities of multi-apartment residential buildings, as well as identifying and describing the parties involved in shaping the housing policy. Special attention is paid to energy efficiency issues for buildings – looking at Latvia’s potential for climate changes, analysing energy consumption in buildings in relation to energy efficiency requirements, as well as assessing the medium and long-term objectives of buildings in Latvia and the obstacles to achieving them. In order to clarify more precisely the necessary competences of housing managers for the successful implementation of the residential renovation process, a survey has been carried out for stakeholders in the project. Based on an analysis of the situation and the performed survey results, a methodology has been developed to increase the competences of housing managers in relation to the renovation of residential buildings in order to mitigate climate change.

Investigation of the Flow-Based Fast Reroute Model with Implementation of a Multimedia Quality Protection Scheme

In this paper, a tensor flow-based fast reroute model with multimedia quality protection is proposed. In the model, the conditions for implementing a multipath routing strategy and flow conservation are introduced taking into account possible packet loss at the network nodes and preventing overloading communication links both when using the primary and backup routes. At the same time, the novelty of the proposed solution is the formalization of the conditions of protection of the Quality of Experience level in terms of multimedia quality along the primary and backup routes. These conditions have been obtained during the tensor formalization of the network, which made it possible to calculate the quality of service indicators: packet loss probabilities, as well as the average end-to-end delay for audio and video flows transmitted in the multimedia session using the primary and backup routes, respectively. As a criterion for the optimality of the obtained solutions, a condition has been selected related to maximizing the overall performance of the infocommunication network. The results of the research of the proposed model confirm the adequacy of the numerical research results obtained for solving the problem of fast rerouting with link/node protection.

Three Stages of Composite Specimen Destruction in Static Failure

The paper presents the results of standard specimen fracture made of anisotropic carbon fiber plastic with an epoxy matrix. Static stepwise loading of the specimen was carried out on an Instron 8801 testing machine to determine the characteristics of ductile fracture G1C in the first mode in accordance with ASTM D5528. During loading, the parameters of acoustic emission (AE) signals, such as AE impulse amplitudes and their energy were synchronously recorded. At the same time, the magnitude of the opening and the growth of the crack initiated by the artificial cut at the end of the specimen were recorded. According to the analysis of the acoustic emission signals, three zones with different G1C behaviour were identified: initial crack propagation, its stationary growth and accelerated fracture of the specimen. The zonal character of the change in the acoustic emission signals made it possible to determine the energy of the acoustic emission signals as diagnostic evidence for the onset of rapid destruction of the specimen. The amplitude of the AE-signals in the zones, however, remained constant. Online monitoring of changes in the energy of acoustic emission signals will prevent the onset of rapid destruction of an object in places of its deformations. The paper does not aim at defining G1C as usual. It presents the investigation of the fracture stages for a composite material using an acoustic emission method.

WO3 as Additive for Efficient Photocatalyst Binary System TiO2/WO3

Two different methods of synthesis of TiO2/WO3 heterostructures were carried out with the aim to increase photocatalytic activity. In this study, anodic TiO2 nanotube films were synthesized by electrochemical anodization of titanium foil. WO3 particles were applied to anodic Ti/TiO2 samples in two different ways – by electrophoretic deposition (EPD) and insertion during the anodization process. Structural and photocatalytic properties were compared between pristine TiO2 and TiO2 with incorporated WO3 particles. Raman mapping was used to character-ise the uniformity of EPD WO3 coating and to determine the structural composition. The study showed that deposition of WO3 onto TiO2 nanotube layer lowered the band gap of the binary system compared to pristine TiO2 and WO3 influence on photo-electrochemical properties of titania. The addition of WO3 increased charge carrier dynamics but did not increase the measured photo-current response. As the WO3 undergoes a phase transition from monoclinic to orthorhombic at approximately 320 ℃ proper sequence WO3 deposition could be beneficial. It was observed that secondary heat treatment of WO3 lowers the photocurrent.

Influence of “Productive” Impurities (Cd, Na, O) on the Properties of the Cu2ZnSnS4 Absorber of Model Solar Cells

The study focuses on the optical properties of the CZTS multicomponent semiconductor absorber with 3 % “production” impurities of Cd, Na, O within the framework of the density functional theory using the generalized gradient approximation and the SCAPS program, as well as investigates their influence on the performance and efficiency of CZTS-solar cells. The results showed that the introduction of Cd, Na, O impurities would lead to a decrease in the intensity of the absorption bands at 2.06 eV and 2.55 eV. The density of states CZTS: (Cd, Na, O) was determined from first principles, and it was revealed that impurities of Cd and O atoms would lead to a decrease in the band gap (to 0.9 eV and 0.79 eV), and an increase in Na impurity absorption (1.2 eV). It was also found that a decrease in the band gap led to a decrease in the open circuit voltage, and it was also shown that “industrial” impurities led to a decrease in the efficiency of energy conversion of solar cells to 2.34 %.

Damage Detection of the Rod in the Crossflow Using Surrogate-Based Modelling

An effective and accurate methodology is developed to create an inverse surrogate model for the mass reduction analysis of the rod in the rod bundle inserted in the crossflow. The performance of two surrogate modelling approaches has been evaluated. These models are the Response Surface Method and Legendre polynomial approximations. The relationship between dominant frequencies, support stiffness and rod mass derived from Computational Fluid Dynamics simulations is used as input data for approximations. The selection of sample points is implemented with a new type of orthogonal design. The results have shown that the proposed methodology can reliably replace the finite volume model and drastically reduce computational time.

Application of 3D Roughness Parameters for Wear Intensity Calculations

In this paper, calculations of 3D parameter Vm (material volume) of surfaces with irregular roughness and comparison with experimental data were performed, with further application of this parameter in calculations of wear intensity. First, using Mountains Map software for profilometric measurements, 3D roughness processing and determination of material volume Vm at specific relative levels γ were performed. The next step was an additional analysis of the distribution of surface ordinates using a theoretical and experimental Laplace function. The given check confirmed that for mostly surfaces with irregular roughness the ordinate distribution corresponds to the normal Gaussian distribution law, but in cases when the asymmetry of the ordinate distribution function goes outside the permissible limits (|∆Ssk|> 10%), errors> 10 % occur. On this basis, the mathematical formula of the material volume Vm was derived, and the obtained calculations were compared with the measured values. The results showed that the calculated values of the parameter Vm were very close to the experimental data (|∆Vm|<10 %), while at the relative level γ=+3, errors occurred that was related to the deviation from the normal distribution law. It was concluded that the given parameter could be used in the calculations of linear wear intensity, knowing the relative level γ.

Modelling of Drag Force Reduction for a Waterjet Propulsion System

The paper provides simulation results for SUP (Stand Up Paddle) board appendage resistance. Additional propulsion is added to the SUP board. It is equipped with a waterjet. The waterjet is attached to the board rudder. This increases the drag coefficient for rudder five times. To reduce the drag variable, design options for the waterjet duct were proposed. The simulation tests were performed using SolidWorks Flow software using two types of simulations, namely, the pressure on the body and the flow around the body. The objective was to streamline the bluff duct of the waterjet and thus to create the appendage design with minimum drag force from fluid flow and possibly greater Inlet Velocity Ratio. Calculations showed that rounding-off the edges of waterjet duct resulted in 35 % of drag coefficient reduction, while further streamlining reduced it by additional 10 %.

Research of Kinematic Stepping Mechanism

In this paper, a kinematic analysis of Theo Jansen’s stepping mechanism has been carried out and an algorithm for finding the output link trajectory from the given dimensions of the stepping mechanism elements, implemented by Mathcad program, has been developed. It is possible to output characterising parameters of all intermediate links with any number of intermediate links of a step cycle of the mechanism. The dimensions of the mechanism elements have been selected so that they provide the optimal smooth trajectory of the stepping point, minimising the mechanism oscillations in the vertical plane. A comparison of the trajectories of the foot in this study with the classical trajectory of Theo Jansen and the trajectory from article [7] has been provided. A minimum swing of the oscillation of the centre of mechanism masses in the vertical plane has been selected as an optimality criterion, combined with the maximum smoothness of the trajectory, provided that maximization of the step height is not required.