Multiple surrogate based optimization of a bidirectional impulse turbine for wave energy conversion

Oscillating water column based wave energy extracting system has a low efficiency due to the poor performance of its principal power extracting component, the bidirectional turbine. In the present work, flow over a bidirectional impulse turbine was simulated using CFD technique and optimized using multiple surrogates approach. The surrogates being problem dependent may produce unreliable results, if a wrong surrogate is selected. Hence, multiple surrogates such as response surface approximation, radial basis function, Kriging and weighted average surrogates were incorporated in this problem. Same design points were used to generate multiple optima via multiple surrogates to enhance the robustness of the optimization process. Numbers of guide vanes and rotor blades were chosen as the design variables, and the objective was to maximize the blade efficiency. Reynolds-averaged Navier–Stokes equations were solved for analyzing the flow physics. The computed results were used to train the surrogates and find the optimal points via hybrid genetic algorithm. The surrogates were further applied to find the optimal flow parameters by changing flow velocity and turbine speed. The relative efficiency enhancement through our present approach was about 16%. Detailed methodologies, analysis of the results and surrogate applicability have been presented in this paper.     

Young’s modulus evolution during heating,re-sintering and cooling of partially sintered alumina ceramics

The Young modulus of partially and fully sintered alumina ceramics, obtained by firing to different temperatures (range 1200–1600°C), has been determined via impulse excitation, and the evolution of Young’s modulus of partially sintered alumina with temperature has been monitored from room temperature to 1600°C. As expected, the room-temperature Young modulus of the partially sintered materials is lower than all theoretical predictions. With increasing temperature Young’s modulus decreases, until the original firing temperature is exceeded and sintering (densification) continues, resulting in a steep Young’s modulus increase. During heating and cooling the temperature dependence obeys a master curve for alumina, unless the temperature of the original firing is excessively low.     

Close-range blast loading on empty recyclable metal beverage cans for use in sacrificial cladding structure

This article deals with the experimental and numerical blast study on a single empty recyclable metal beverage can. The idea is to make a macro-foam (sacrificial cladding structure) out of these cans to protect the main load bearing members of civil engineering structures from the air blast load. Close-range free air blast tests have been conducted to understand the crushing behaviour and the energy absorption of a single empty beverage can in detail. To conduct such an air blast test a special small-scale test set-up was designed and manufactured. The effect of skin plate surface area and its nature on the blast parameters is studied. Furthermore, the effect of inertia of the skin plate on the crushing performance of the beverage can is evaluated. Tests have been conducted with different plates (made of aluminium and sandwich composite materials) with different masses which represent the skin plate of the proposed sacrificial structure. The measured blast parameters from the experimental tests were compared with ConWep predicted data. Furthermore, the influence of the finite surface area of the skin plate on the clearing of the reflected pressure waves was also studied. The deformation behaviour and the corresponding energy absorption of empty beverage cans were captured. During the experimental blast tests it was observed that a part of the total reflected impulse (∼30%) was lost before it transfers to the non-sacrificial structure. Hence, in order to investigate this phenomenon Eulerian-Lagrangian coupled analyses were conducted using Hydrocodes. The results from these analyses showed that the diffraction and ground reflected pressure wave caused the loss in impulse. The results from the numerical studies have been compared and validated with the experimental results.     

耐火材料声发射源信号的盲反卷恢复

声发射信号是表征材料内部损伤状态的重要指标。由于源信号无法直接获取,研究的通常是传播一段距离后已失真的信号,这对材料损伤状态的准确判断带来了影响。为了降低传播路径对声发射源信号的衰减和失真带来的不利影响,假设声发射信号在耐火材料的传递路径为线性系统,对传递通道的冲击响应函数进行了估计,并设计了反卷滤波器。与实验结果对比发现,该方法很好的辨识了传递通道未知的系统,并能一定程度地恢复声发射源信号,为材料损伤状态的准确判断提供参考。     

An efficient algorithm for low-order direct discrete-time implementation of fractional order transfer functions

Fractional order systems become increasingly popular due to their versatility in modelling and control applications across various disciplines. However, the bottleneck in deploying these tools in practice is related to their implementation on real-life systems. Numerical approximations are employed but their complexity no longer match the attractive simplicity of the original fractional order systems. This paper proposes a low-order, computationally stable and efficient method for direct approximation of general order (fractional order) systems in the form of discrete-time rational transfer functions, e.g. processes, controllers. A fair comparison to other direct discretization methods is presented, demonstrating its added value with respect to the state of art.     

Color differences based fuzzy filter for extremely corrupted color images

In this paper, a color difference based fuzzy filter is presented for fix and random-valued impulse noise. Noise detection scheme of two stages was applied to detect noise efficiently whereas for noise removal an improved Histogram based Fuzzy Color Filter (HFC) is presented. Pixels detected as noisy by the noise detection scheme are deliberated as candidate for the removal of noise. Candidate noisy pixels are then processed using a modified Histogram based Fuzzy Color Filter to estimate their non-noisy values. The idea of using multiple fuzzy membership functions is presented, so that best suitable membership function for local image statistics can be used automatically. In the proposed technique we have used three different types of fuzzy membership functions (bell-shaped, trapezoidal-shaped, and triangular-shaped) and their fuzzy number construction algorithms are proposed. Experimentation is also performed with three, five, and seven membership functions. Type and number of suitable fuzzy membership functions are then identified to remove noise. Comparison with the existing filtering techniques is established on the basis of objective quantitative measures including structural similarity index measure (SSIM) and peak-signal-to-noise-ratio (PSNR). Simulations show that this filter is superior to that of the existing state-of-the-art filtering techniques in removing fix and random-valued impulse noise whereas retaining the details of the image contents.     

How do the internet technological developments shift the consumption pattern of paper products? Evidence from China

Using a monthly data between 2008 and 2019, this study investigated how the development of the Internet technologies has shaped the consumer consumption pattern of different types of paper products in China during this period. In detail, this study covers four major types of paper products in the Chinese market: newsprint, printing paper, household paper, and packaging paper. The developments of Internet technologies were decomposed into two aspects: the communication technology (CT) and the software platform technology (PT). Granger causality analysis was employed to determine whether the consumption pattern of paper products was affected by the development of the Internet. Furthermore, impulse-response analyses were utilized to measure how the consumption pattern of each paper product was shaped by the development of each aspect of Internet technologies, i.e., CT or PT. The empirical results suggested that the Internet developments are causing the consumption patterns shifts of all four paper products. Specifically, the consumptions of newsprint and printing paper were driven by both CT and PT. However, the consumptions of packaging paper and household paper were driven by the PT only. Compared to the development of CT, we found that the quick evolution of PT plays a more significant role in shifting people's consumption of paper products in China. The empirical results revealed by this study could provide valuable economics and policy implications to both academia and relevant industries.     

Does internet dependence affect young people's psycho-social status? Intrafamilial and social relations,impulse control,coping ability and body image

The purpose of this study was to investigate the relation between internet dependence in university students in late adolescence and self-image. The research group consisted of first year university students studying in various departments of the Karadeniz Technical University Fatih Faculty of Education. The study was performed with 623 students, 454 female and 169 male. The Internet Dependence Questionnaire, the Offer Self-Image Questionnaire and a Personal Data Form were used for data collection. Pearson product moment coefficient and multiple linear regression analysis results showed that students' internet dependence was significantly negatively correlated with the self-image subdimensions intrafamilial and social relations, impulse control, coping ability and body image. Multiple linear regression analysis showed that the self-image subdimensions of intrafamilial and social relations and impulse control subdimensions significantly predict internet dependence.     

Arm strength and impulse generation: Initiation of wheelchair movement by the physically disabled

The initiation of wheelchair movement is a function of starting technique, upper extremity strength and the stabilizing potential of the trunk musculature. This study examined the relation between arm strength, activity level, degree of disability and the maximum impulse generated from a resting position while seated in a wheelchair. Two starting techniques were examined using a force platform.

Sixteen male paraplegic adults (age 28·1 ±6·9 year, supine length l·62±0·16m, total body mass 61·2±16·2 kg) performed three grab starts and three strike starts on a Kistler force platform. For each technique, the processed data were averaged together and impulse in the forward/backward and vertical directions was determined. Isokinetic shoulder flexion and elbow extension moments of force were measured at an angular velocity of 60 degs^?1. Peak power and average power were calculated from digitized values of the moment of force-time curves.

Subjects were classified as highly active (HA, >2 exercise periods per week, N = 8) or less active (LA, N = 8). In addition, the site of spinal cord injury was quantified as a high level lesion (HL, above T10, N = 7) or low level lesion (LL, N = 9). There were no differences (p>0·05) between activity or lesion level groups with respect to age, height, total body mass or skinfold thicknesses. Nor were there significant differences between groups for shoulder and elbow power values. However, shoulder flexion scores for the combined groups were greater than those scores for elbow extension (peak power, 72·9 W versus 49·5 W; average power, 51·8 W versus 37·2 W). The grab start produced more forward impulse (the integral of forward force × time) (152·6 N s) than the strike start (119·5 N s, p < 0·05), but the magnitude of this difference was similar for the several groups. Wheelchair impulse scores were well correlated with strength values in both HA and LA subjects (r=0·74 to 0·89). However, the intercepts of the regression lines were dissimilar between activity groups, suggesting an interaction between activity pattern, muscle force and impulse.     

采用C语言FPGA技术实现LDPC码译码算法

针对LDPC码(Low Density Parity Check Codes)译码算法的特点和最新一代Impulse C语言的并行编程技术,提出一种对LDPC码译码器进行FPGA(Field Programmable Gate Array)设计与实现的便捷新方案,以获得译码速率和硬件资源消耗的平衡.在XC2V2000芯片上实现了一种码率1/2,码长2500的(3,6)LDPC码译码器.实验表明当最大迭代次数为10次,主频50MHz时,译码速率可达10Mbps.