Flow Separation Dynamics in Three-Dimensional Asymmetric Diffusers

The mean and instantaneous flow separation of two different three-dimensional asymmetric diffusers is analysed using the data of large-eddy simulations. The geometry of both diffusers under investigation is based on the experimental configuration of Cherry et al. (Int J Heat Fluid Flow 29(3):803–811, 2008). The two diffusers feature similar area ratios of $$\mathrm{AR}=4.8$$ AR = 4.8 and $$\mathrm{AR}=4.5$$ AR = 4.5 while exhibiting differing asymmetric expansion ratios of $$\mathrm{AER}=4.5$$ AER = 4.5 or $$\mathrm{AER}=2.0$$ AER = 2.0 , respectively. The Reynolds number based on the averaged inlet velocity and height of the inlet duct is approximately $${\textit{Re}}=10{,}000$$ Re = 10 , 000 . The time-averaged flow in both diffusers in terms of streamwise velocity profiles or the size and location of the mean backflow region are validated using experimental data. In general good agreement of simulated results with the experimental data is found. Further quantification of the flow separation behaviour and unsteadiness using the backflow coefficient reveals the volume portion in which the instantaneous reversal flow evolves. This new approach investigates the cumulative fractional volume occupied by the instantaneous backflow throughout the simulation, a power density spectra analysis of their time series reveals the periodicity of the growth and reduction phases of the flow separation within the diffusers. The dominating turbulent events responsible for the formation of the energy-containing motions including ejection and sweep are examined using the quadrant analysis at various locations. Finally, isourfaces of the Q-criterion visualise the instantaneous flow and the origin and fate of coherent structures in both diffusers.

Quantum Tunnelling based Ultra-compact and Energy Efficient Spiking Neuron enables Hardware Liquid State Machine

Low-power and low-area neurons are essential for hardware implementation of large-scale SNNs. Various novel physics based leaky-integrate-and-fire (LIF) neuron architectures have been proposed with low power and area, but are not compatible with CMOS technology to enable brain scale implementation of SNN. In this paper, for the first time, we demonstrate hardware implementation of LSM reservoir using band-to-band-tunnelling (BTBT) based neuron. A low-power thresholding circuit and current-to-voltage converter design are proposed. We further propose a predistortion technique to linearize a nonlinear neuron without any area and power overhead. We establish the equivalence of the proposed neuron with the ideal LIF neuron to demonstrate its versatility. To verify the effect of the proposed neuron, a 36-neuron LSM reservoir is fabricated in GF-45nm PDSOI technology. We achieved 5000x lower energy-per-spike at a similar area, 50x less area at a similar energy-per-spike, and 10x lower standby power at a similar area and energy-per-spike. Such overall performance improvement enables brain scale computing.

A Novel Guided Anchor Siamese Network for Arbitrary Target-of-Interest Tracking in Video-SAR

Video synthetic aperture radar (Video-SAR) allows continuous and intuitive observation and is widely used for radar moving target tracking. The shadow of a moving target has the characteristics of stable scattering and no location shift, making moving target tracking using shadows a hot topic. However, the existing techniques mainly rely on the appearance of targets, which is impractical and costly, especially for tracking targets of interest (TOIs) with high diversity and arbitrariness. Therefore, to solve this problem, we propose a novel guided anchor Siamese network (GASN) dedicated to arbitrary TOI tracking in Video-SAR. First, GASN searches for matching areas in the subsequent frames with the initial area of the TOI in the first frame are conducted, returning the most similar area using a matching function, which is learned from general training without TOI-related data. With the learned matching function, GASN can be used to track arbitrary TOIs. Moreover, we also constructed a guided anchor subnetwork, referred to as GA-SubNet, which employs the prior information of the first frame and generates sparse anchors of the same shape as the TOIs. The number of unnecessary anchors is therefore reduced to suppress false alarms. Our method was evaluated on simulated and real Video-SAR data. The experimental results demonstrated that GASN outperforms state-of-the-art methods, including two types of traditional tracking methods (MOSSE and KCF) and two types of modern deep learning techniques (Siamese-FC and Siamese-RPN). We also conducted an ablation experiment to demonstrate the effectiveness of GA-SubNet.

Thermal efficiency of metal foams on pool boiling

This paper presents an experimental work on pool boiling using HFE-7100 at saturated conditions, under atmospheric pressure, and copper and nickel foams as the heating surface with four different thicknesses varying between 0.5 mm and 3 mm, followed by an analysis of the effect of foam fin-efficiency based on Ghosh model. All foams showed a better heat transfer coefficient (HTC) than the plain surface; however, as the heat flux increased, the HTC from the thicker nickel foams decreased due to the bubble vapor flow inside the foam. On the other hand, the thinner nickel foam showed better HTC at high heat fluxes with a maximum enhancement of 120%. The foam efficiency presented a similar tendency with the HTC, i.e., as the thickness decreases the efficiency increases; however, as compared with copper foams with a similar area but different porous diameter, the copper foams are 40% more efficient than the nickel ones due to the foam material, which has a thermal conductivity 4.5 times higher.

Experimental Study Wind Turbine Performance of Straight-Savonius and Ice-Wind Type on the Similar proportion Aspect Ratio

The Performance of wind turbines at low speed can be improved by Ice-Wind model, particularly in self-starting conditions. Compared to a traditional wind turbine with two blades of the similar area and material, Ice-Wind can increase efficiency by 19%. Research on the Savonius turbine, particularly the Ice-Wind turbine, is challenging. It is because it has many restrictive parameters, such as the height, diameter, and area of the turbine blades. The Ice-Wind turbine shape is obtained by cutting a Savonius turbine. This process led to research on Ice-Wind turbines only under the similar parameters. The aspect ratio of a Savonius turbine has a significant effect on the speed, mechanical power and static-torque produced by the wind turbine. The research was done on Savonius and Ice-Wind turbines with the similar aspect ratio. The results show that the speed, power factor and efficiency of the Savonius turbine are higher than those of Ice-Wind. However, Savonius produces a smaller static-torque coefficient value than Ice-Wind. The results of this research contrast with other studies comparing Savonius and Ice-Wind turbines. In other researches, Savonius and Ice-Wind turbines have the similar area but different aspect ratios.

A new species of Petta (Annelida, Pectinariidae), with comments on Petta assimilis McIntosh, 1885

The genus Petta Malmgren, 1866 is a small and poorly known genus of the annelid family Pectinariidae Quatrefages, 1866. A previous revision of the genus found that the type material of the species P. assimilis McIntosh, 1885 had been lost. While searching for material from the type locality, we were able to examine material from a similar area but collected in much shallower water from off South Africa which represents another undescribed species of Petta. The new species, Petta brevissp. nov., is described and compared to P. assimilis McIntosh, 1885, and a revised key to all species in the genus is provided.

Salt Marsh and Tidal Flat Area Distributions Along Three Estuaries

Estuarine landscapes form through interactions between fluvio-coastal processes and ecological processes within the boundaries imposed by hard substrate layers and man-made dikes and dams. As estuaries are ecologically valuable areas, monitoring and quantification of trends in habitats is needed for objective comparison and management. However, datasets of tidal flat and saltmarsh habitats along entire estuaries are scarce. The objective was to compare trends of biogeomorphological areas and habitat transitions along three estuaries in the Netherlands and assess whether these are generally comparable or mainly determined by system-specific histories. We present data for these estuaries obtained by automated classification of false-color aerial imagery. The automated method allows objective mapping of entire estuaries at unprecedented resolution. The estuaries are dominated by subtidal areas and tidal flats. The tidal flats have similar area along the estuaries while saltmarsh area decreases. Collective lengths of ecologically important transitions between saltmarsh, low-energy tidal flats and water differ more between the estuaries. These variations are due to presence of mid-channel bars and shore-connected embayments. Saltmarsh area is mainly determined by the different formation and embankment histories of the estuaries, embayments and side-branches. Much of the past saltmarsh flanking the estuaries was lost due to past land reclamation. In one system, ecologically important low-energy tidal flats are reduced by a sudden decrease of tidal amplitude, causing increase of subtidal area at the cost of intertidal area. Large areas of high-energy tidal flats in one estuary remain unexplained. The automated method can be applied in other estuaries, provided that high-quality areal imagery is available. Extensions of the data to other estuaries would allow for system-scale trend comparison between estuaries of ecologically relevant biogeomorphological characteristics.

Textile-Reinforced Concrete Versus Steel-Reinforced Concrete in Flexural Performance of Full-Scale Concrete Beams

The effectiveness of textile-reinforced concrete (TRC) and steel-reinforced concrete (SRC) in the flexural performance of rectangular concrete beams was investigated in this study. To better understand TRC behaviour, large-scale concrete beams of 120 × 200 × 2600 mm were tested and analysed in this work. Cover thickness, anchoring, and various layouts were all taken into consideration to assess the performance of beams. In addition, bi-axial and uni-axial TRC beams and SRC beams were classified according to the sort and arrangement of reinforcements. The findings showed that anchoring the textiles at both ends enhanced load resistance and prevented sliding. The ultimate load of the tow type of textile reinforcement was higher, attributed to the increased bond. Variations in cover thickness also change the ultimate load and deflection, according to the findings. Consequently, in this investigation, the ideal cover thickness was determined to be 30 mm. Furthermore, for the similar area of reinforcements, the ultimate load of TRC beams was noted up to 56% higher than that of the SRC control beam, while the deflection was roughly 37% lower.

The Multi-Criteria Method for the Evaluation of Combat Capabilities of Anti-aircraft Missile Systems Under the NAREW Programme

The selection of weapon systems involves a number of activities to choose the best system in relation to the predefined operational requirements and other vital criteria. In the case of surface to air missile systems competing for the NAREW program, attempts are being made to obtain an asset that will be capable of engaging a spectrum of air threats, under specified conditions, with a predefined high degree of probability. In order to make the right choice, it is necessary to analyze information on performance and combat capabilities. Thus, the aim of this article is to develop a preliminary method of evaluating the capabilities of surface to air missile systems offered under the NAREW program. The theoretical foundation of the empirical study was provided by the method of literature content analysis. Using the methods of comparison and generalization, the author obtained data on the combat capabilities of surface to air missile systems expressed through their tactical and technical parameters. Among the empirical methods, the author applied the algorithm of a multi-criteria analysis and an assessment of the capabilities of surface to air missile systems based on the use of matrix calculus. The diagnostic survey, conducted by means of the questionnaire technique, made it possible to prioritize the adopted evaluation criteria and, consequently, to conduct proper research. The formulation of the final conclusions and establishing the links between the theoretical and empirical part of the study was achieved by means of a synthesis. The results obtained in such a manner may constitute a valuable information database, showing the directions that should be considered when selecting a short-range surface to air missile (SAM) system for Poland. The evaluations and suggestions included in this study can be used for prospective solutions and research conducted in a similar area.