Unpicking the signal thread of the sector web spider Zygiella x-notata

Remote sensing allows an animal to extend its morphology with appropriate conductive materials and sensors providing environmental feedback from spatially removed locations. For example, the sector web spider Zygiella x-notata uses a specialized thread as both a structural bridge and signal transmitter to monitor web vibrations from its retreat at the web perimeter. To unravel this model multifunctional system, we investigated Zygiella''s signal thread structure with a range of techniques, including tensile testing, laser vibrometry, electron microscopy and behavioural analysis. We found that signal threads varied significantly in the number of filaments; a result of the spider adding a lifeline each time it runs along the bridge. Our mechanical property analysis suggests that while the structure varies, its normalized load does not. We propose that the signal thread represents a complex and fully integrated multifunctional structure where filaments can be added, thus increasing absolute load-bearing capacity while maintaining signal fidelity. We conclude that such structures may serve as inspiration for remote sensing design strategies.     

Analysis of optimization in an OTEC plant using organic Rankine cycle

This study quantified the effects of evaporation temperature, condensation temperature, and the inlet- and outlet-temperature differences of deep cold seawater and warm seawater on the performance of an ocean thermal energy conversion (OTEC) plant using an organic Rankine cycle (ORC), and also investigated the optimal operations required for the performance. A finite-temperature-difference heat transfer method is developed to evaluate the objective parameter, which is the ratio of net power output to the total heat transfer area of heat exchanger in the system, and R717, R600a, R245fa, R152a, and R134a were used as the working fluids. The optimal evaporation and condensation temperatures were obtained under various conditions for maximal objective parameters in an OTEC system.The results show that R717 performed optimally in objective parameter evaluation among the five working fluids, and that R600a performed better than other fluids in thermal efficiency analysis. The optimal seawater temperature differences between the inlet and outlet of the evaporator and condenser are proposed. Furthermore, the influences of inlet temperatures of warm and cold seawater in the ORC are presented for an OTEC plant. The simulation results should enable the performance of an ORC system to be compared when using various organic working fluids.     

Numerical analysis of partly wrinkled cylindrical inflated beams under bending and shear

This paper is aimed at assessing the nonlinear elastic response of an inflatable cylindrical beam through a simple mechanical model recently proposed by the authors for studying the equilibrium configurations of highly pressurised elastic membranes with general shapes. The attention is focused on beams loaded at mid-span with two different constraints, corresponding to simply-supported ends and built-in ends. The geometrical nonlinearities due to both the cross-sectional ovalization and wrinkling are carefully considered. In particular, the wrinkling of the membrane, clearly visible for load values much lower than the collapse load, is taken into account by means of an equivalent physical non-linearity. A two-states constitutive law for the material is assumed: when a fibre is stretched (the active state), its response is elastic, while when the fibre is contracted, no compressive force can be engendered in it (the passive state). The evolution of the cross-sectional ovalization, the size of the wrinkled regions and the magnitude of longitudinal and transverse stresses in the membrane are accurately determined for increasing levels of loads, up to collapse. The numerical results for the corresponding values of load and internal pressure, obtained through an expressly developed incremental-iterative algorithm, are compared with the experimental ones available in the literature.     

Numerical investigation on influence of diffuser vane height of centrifugal pump

Vaned diffusers are extensively used in centrifugal pumps, but the influence of vane height on internal flow field and overall performance is not explicit. This paper mainly presents numerical investigation on influence mechanism of diffuser vane height in a single-stage centrifugal pump. The head values were carried out on a low specific speed centrifugal pump equipped with different diffuser vane height by numerical simulation and experimental method. And the deviation between numerical results and experimental results were < 5%. The diffuser vane height h/b ratio is changed as 0, 0.3, 0.4, 0.5, 0.6, 0.8, and 1 in this study. The numerical analysis shows that reducing diffuser vane height could eliminate the vortex which appears at tongue region. Meanwhile, the influence of rotor-stator interaction was reduced by reducing the vane height. Consequently, the energy loss in the volute and the diffuser could both be decreased at design flow point and over flow point. In the other hand, the circumferential velocity at partial flow point gets larger which could lead to large frictional loss. In general, reducing the diffuser vane height at design and over flow point could improve the output work of impeller.     

Unwinding of a cholesteric liquid crystal and bidirectional surface anchoring

We examine the influence of bidirectional anchoring on the unwinding of a planar cholesteric liquid crystal induced by the application of a magnetic field. We consider a liquid crystal layer confined between two plates with the helical axis perpendicular to the substrates. We fix the director twist on one boundary and allow for bidirectional anchoring on the other by introducing a high-order surface potential. By minimizing the total free energy for the system, we investigate the untwisting of the cholesteric helix as the liquid crystal attempts to align with the magnetic field. The transitions between metastable states occur as a series of pitchjumps as the helix expels quarter- or half-turn twists, depending on the relative sizes of the strength of the surface potential and the bidirectional anchoring. We show that secondary easy axis directions can play a significant role in the unwinding of the cholesteric in its transition towards a nematic, especially when the surface anchoring strength is large.     

Investigation on relationship between porosity and spacer content of titanium foams

Titanium foam has been obtained more and more attention due to its combination with porous structure and titanium. The space holder technique was widely used to fabricate this kind of material because of its low cost, easy operation and freely controllable pore structure and properties. However, how to obtain the desired porosities has been a big challenge for this technique, because they are always not equal to the expected ones. Hence, the relationship between porosity (P) and spacer content (S_c) was studied based on theory and practice in this paper. The results show that the relationship between porosity and spacer content was linear, that is P = aS_c + b. It indicates that the volumetric change rate of pores (V_R) is a constant and its value altered in different preparing conditions. Through the research of this paper, the porosity and mechanical properties of a foam material can be predicted by spacer content.     

Nano-wear, nano-hardness and corrosion-resistance of electroplated nickel surfaces after co-implantation of Cr and N2 ions

In this work, a successful sequential co-implantation treatment of Cr⁺ and N₂⁺ ions into electrodeposited nickel plates is presented. The goal of this treatment is the simultaneous enhancement of the wear resistance, mechanical stability and corrosion-protection properties of the Ni surfaces. The ion-implanted surfaces have been characterized by glow-discharge optical-emission spectroscopy, X-ray diffraction, nano-hardness, roughness, nano-wear and potentio-dynamic corrosion tests. It has been observed that the implantation of Cr⁺ or N₂⁺ alone is not sufficient to achieve simultaneously the enhancement of both the wear-resistance and the corrosion-protection properties. Conversely, the sequential implantation of Cr⁺ and N₂⁺ at 140 keV and fluencies of 3 × 10¹⁷ and 1.5 × 10¹⁷ ions/cm² respectively, permits the formation of a functional surface capable of reducing both the corrosion rate and the wear rates, with respect to those exhibited by the un-implanted Ni surfaces.This treatment can be used to protect the surfaces of micro-embossing/stamping dies based on electroformed Nickel, as an alternative to other coating strategies. Furthermore, the ion implantation assures the non-modification of the net-shape and surface finish of these types of dies, which is of crucial importance when they are used for high-precision micro-texturing/imprinting applications.     

风电机组齿轮箱温度趋势状态监测及分析方法

风电机组状态监测对于风电场特别是海上风电场降低维护成本,提高运行水平具有重要的实用价值。采用温度趋势分析的方法对风电机组齿轮箱的运行状态进行监测。利用非线性状态估计（nonlinear state estimate technology,NSET）方法建立齿轮箱正常工作状态下的温度模型并用其进行温度预测。通过合理构造过程记忆矩阵,使模型覆盖齿轮箱的正常工作空间。当齿轮箱工作异常时,其动态特性偏离正常工作空间,NSET温度模型预测残差的分布特性发生改变。采用滑动窗口方法实时计算残差的统计分布特性,当残差的均值或标准差的置信区间超出预先设定的阈值时,发出报警信息,提示运行人员检查设备状态。为模拟齿轮箱的故障情况,在机组数据采集与监视控制系统（supervisory control anddata acquisition,SCADA）数据中加入人为温度偏移。通过对该模拟故障的分析,新的状态监测方法能够及时发现齿轮箱的异常状态,达到实时在线状态监测的目的。     

Ethanol production from energy crops and wastes for use as a transport fuel in Ireland

The Biofuels Directive places an onus on EU member states to ensure biofuels are available on their markets. This paper investigates the use of ethanol derived from biomass type 1 (residues and wastes) and biomass type 2 (energy crops). The technology involved in generating ethanol from energy crops is mature; the same cannot be said for generation of ethanol from residues; many proposals are mooted to generate ethanol from lignocellulosic biomass, but they are not at a commercial scale. Literature is available however on expected yields and economics of ethanol production from lignocellulosic biomass. This paper investigates three options which produce ethanol: 50 million Lpa of ethanol from sugar beet, 50 million Lpa of ethanol from waste paper and 200 million Lpa of ethanol from waste paper. The economics of ethanol production from sugar beet were the worst of the three due to the requirement to buy the sugar beet. Economies of scale are significant: larger plants produce cheaper ethanol. Indeed it was found that for the large plant, the production cost was zero if a gate fee of €100/t was charged for waste paper. The three options were applied to Ireland. It was found that an investment in an ethanol industry of €561 million would produce 5.7% of the energy value of petrol and diesel in Ireland; the reference value for the minimum portion of biofuels placed on the market in 2010 is 5.75%. The greenhouse-gas savings would equate to 18% of the 1990 transport emissions.