Investigation of ground vibrations induced by moving loads

The objective of this work indicates and discusses two mathematical models and numerical techniques for solving problems associated with wave propagation in the track and subsoil due to the passage of a train. The Thin Layer Method/Flexible Volume Method (TLM/FVM) and the Boundary Element Method (BEM) are used to analyse the three-dimensional dynamic response of the free field near railway lines induced by the moving loads acting on the surface of a homogeneous or layered half-space. Both simulation models employ the substructuring approach in the frequency domain. The validity of the methods are demonstrated by comparison with results of analytical solution. An extensive numerical investigation has been carried out to show the influence of different parameters on the effectiveness of vibration reduction through open trench barriers.     

Weight optimisation of a salient pole synchronous generator by a new genetic algorithm validated by finite element analysis

In this study, a new approach for genetic algorithm (GA) is proposed and compared with conventional GA (CGA) in the weight optimisation of a 2-MVA salient pole synchronous machine. The main differences between the two algorithms are that, in the newly proposed method, individuals are paired and crossed over based on the Mendelian rules of genetics, and the mutation operator is omitted. The rules concern the segregation of Alleles and the independent assortment of Alleles. This approach is comprehensive and conceptually accurate since its framework uses Mendelian population genetics. The operation CPU time is longer in the new approach when compared to the conventional one but can be ignored in electric machine design since it is not a real-time process. The results of the analytic solution and the new and CGA implementation methods are compared in terms of weight, efficiency and temperature. The results obtained are similar to those of the conventional ones and even better in some cases. A finite element analysis (FEA) is done to realise the machine designs optimised by the new GA (NGA) and CGA for the case of a fixed 24-pole design. Hence the improvement over CGA achieved by NGA has been validated through FEA.     

Radiological characterisation of Artvin and Ardahan provinces of Turkey

Indoor radon concentration measurements were carried out and corresponding annual effective doses due to exposure to indoor radon were determined in Artvin and Ardahan provinces located in the eastern part of Turkey. The measurements were performed for four seasons in order to determine the seasonal fluctuations mostly observed in indoor environments. Indoor radon concentration values were observed to range from 21 to 321 Bq m?3 for the Artvin province and from 53 to 736 Bq m?3 for the Ardahan province. It was observed that minimum indoor radon concentration values were obtained in summer, while the highest ones were observed in winter. Indoor radon concentration values of the current study were compared with those of other provinces in Turkey. As elevated indoor radon concentrations are mostly correlated with high 23?U activity concentrations in soil, a total of 57 and 33 soil samples were collected from the Artvin and Ardahan provinces, respectively, to determine 23?U activity concentration as well as the concentration of 232Th and ??K--naturally occurring radionuclides. It was also observed that soil samples collected from the study areas contained 13?Cs as an artificial radionuclide.     

The effect of sintering temperature on some properties of Cu-SiC composite

Copper matrix composites reinforced with 1 wt.%, 2 wt.%, 3 wt.% and 5 wt.% SiC particles were fabricated by powder metallurgy method. Cu and Cu-SiC powder mixtures were compacted with a compressive force of 280 MPa and sintered in an open atmospheric furnace at 900-950 °C for 2 h. Within the furnace compacted samples were embedding into the graphite powder. The presence of Cu and SiC components in composites was verified by XRD analysis. Optical and SEM studies showed that Cu-SiC composites have a uniform microstructure in which silicon carbide particles are distributed uniformly in the copper matrix. The results of the study on mechanical and electrical conductivity properties of Cu-SiC composites indicated that with increasing SiC content (wt.%), hardness increased, but relative density and electrical conductivity decreased. The highest electrical conductivity of 98.8% IACS and relative density of 98.2% were obtained for the Cu-1 wt.%SiC composite sintered at 900 °C and this temperature was defined as the optimum sintering temperature.     

Small shaking table testing and numerical analysis of free-field site response and soil-structure oscillation under seismic loading

Bulletin of Engineering Geology and the Environment - In this study, the accuracy level of geometric scaling factor (herein, λ = 45) selected for the shaking table test model...     

Characterization of Tantalum–Titanium Powders with Universal Powder Bed (UPB) System for Electron Beam Melting Process

Russian Journal of Non-Ferrous Metals - Electron beam melting (EBM) is a powder bed fusion additive manufacturing (AM) technique that produces three-dimensional (3D) parts by fusing metallic...     

Donor acceptor type neutral state green polymer bearing pyrrole as the donor unit

A new neutral state green polymer, poly (2,3-bis(4-tert-butylphenyl)-5,8-di(1H-pyrrol-2-yl) quinoxaline) (PTBPPQ) was synthesized and its potential use as an electrochromic material was investigated. Spectroelectrochemistry studies showed that polymer reveals two distinct absorption bands as expected for a donor–acceptor type polymer, at 408 and 745 nm. In addition, polymer has excellent switching properties with satisfactory optical contrasts and very short switching times. Outstanding optical contrast in the NIR region and stability make this polymer a great candidate for many applications. It should be noted that PTBPPQ is one of the few examples of neutral state green polymeric materials with superior switching properties. Hence, PTBPPQ can be used as a green polymeric material for display technologies.     

Cross-Modulation Interference and Mitigation Technique for Ultrawideband PPM Signaling

The detection issues of ultrawideband (UWB) signals depend on the type of modulation scheme that is used during the transmission. Cross-modulation interference (CMI) is a problem that is specific to UWB pulse-position-modulation (PPM) signaling. In this paper, the effects of CMI on the performance of noncoherent UWB receivers are analyzed. The probabilities of error for transmitted-reference (TR) and energy detector (ED) receivers in the presence and absence of CMI are derived. Optimal and suboptimal CMI avoidance algorithms, which are based on novel acquisition techniques, are proposed for Rake receivers. The results show that the performance degradation in both receivers, which is due to the CMI effects, can be significant, depending on the modulation index. TR receivers still can be functional in the presence of CMI, and the target performance level determines the modulation index to be used. It is unlikely that effects of CMI on the performance of ED receivers in the presence of CMI are more severe relative to TR receivers, and the performance level is not acceptable. As a result, PPM signaling is not an appropriate modulation technique for ED receivers that are operating in the CMI region, unless CMI mitigation algorithms can be developed. Furthermore, the proposed optimal and suboptimal algorithms are two promising schemes for avoiding the CMI effects and, consequently, for improving the performance of Rake receivers operating in the CMI region.     

Characterization of cemented Cu matrix composites reinforced with SiC

In this study, some properties of copper produced by cementation method and its composites reinforced with 1wt%, 2wt%, 3wt% and 5wt% SiC particles, produced by powder metallurgy method, were investigated. Composite powders were pressed by applying an uniaxial pressure of 280 MPa and sintered at temperatures of 700 °C for 2 h embedding in graphite powder. Scanning electron microscope (SEM-EDS), X-ray diffraction (XRD) techniques were used to characterize the Cu and SiC which are dominant components in the sintered composites. Microstructure studies revealed that SiC particles were located around the copper particles. The relative densities of Cu-SiC composites determined by Archimedes’ principle decreased from 98.11% to 90.93% with increasing reinforcement components. Measured hardness of sintered compacts varied from 127 to155 HVN. Maximum electrical conductivity of test materials ranged from 80.17% IACS to 57.76% IACS.