Fluid drag-reducing effect and mechanism of superhydrophobic

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.In this paper, drag-reducing property and mechanism of superhydrophobic surface are investigated. Superhydrophobic surfaces with micro-nano textures were fabricated and tested using SEM and contact angle measurement. Experiments on a channel and a flat plate with superhydrophobic surface were conducted separately. For the channel flow, the drag was acquired by measuring the pressure loss. A 54% drag reduction was found both in laminar and turbulent flow over Re range from 500 to 5000. For flow over a plate, PIV measurement was used to obtain the velocity distribution at Reδ=12000. There was a 19% reduction on the total stress in the whole boundary layer. Suppressions of the turbulence intensities and the Reynolds shear stress were found, which may cause the drag reduction

Stability Analysis of Delayed Genetic Regulatory Networks via a Relaxed Double Integral Inequality

Time delay arising in a genetic regulatory network may cause the instability. This paper is concerned with the stability analysis of genetic regulatory networks with interval time-varying delays. Firstly, a relaxed double integral inequality, named as Wirtinger-type double integral inequality (WTDII), is established to estimate the double integral term appearing in the derivative of Lyapunov-Krasovskii functional with a triple integral term. And it is proved theoretically that the proposed WTDII is tighter than the widely used Jensen-based double inequality and the recently developed Wiringter-based double inequality. Then, by applying the WTDII to the stability analysis of a delayed genetic regulatory network, together with the usage of useful information of regulatory functions, several delay-range- and delay-rate-dependent (or delay-rate-independent) criteria are derived in terms of linear matrix inequalities. Finally, an example is carried out to verify the effectiveness of the proposed method and also to show the advantages of the established stability criteria through the comparison with some literature

Infrared carpet cloak designed with uniform silicon grating structure

Through a particularly chosen coordinate transformation, we propose an optical carpet cloak that only requires homogeneous anisotropic dielectric material. The proposed cloak could be easily imitated and realized by alternative layers of isotropic dielectrics. To demonstrate the cloaking performance, we have designed a two-dimensional version that a uniform silicon grating structure fabricated on a silicon-on-insulator wafer could work as an infrared carpet cloak. The cloak has been validated through full wave electromagnetic simulations, and the non-resonance feature also enables a broadband cloaking for wavelengths ranging from 1372 to 2000 nm.Comment: 11 pages, 4 figure

Decision Fusion Network with Perception Fine-tuning for Defect Classification

Surface defect inspection is an important task in industrial inspection. Deep learning-based methods have demonstrated promising performance in this domain. Nevertheless, these methods still suffer from misjudgment when encountering challenges such as low-contrast defects and complex backgrounds. To overcome these issues, we present a decision fusion network (DFNet) that incorporates the semantic decision with the feature decision to strengthen the decision ability of the network. In particular, we introduce a decision fusion module (DFM) that extracts a semantic vector from the semantic decision branch and a feature vector for the feature decision branch and fuses them to make the final classification decision. In addition, we propose a perception fine-tuning module (PFM) that fine-tunes the foreground and background during the segmentation stage. PFM generates the semantic and feature outputs that are sent to the classification decision stage. Furthermore, we present an inner-outer separation weight matrix to address the impact of label edge uncertainty during segmentation supervision. Our experimental results on the publicly available datasets including KolektorSDD2 (96.1% AP) and Magnetic-tile-defect-datasets (94.6% mAP) demonstrate the effectiveness of the proposed method

A 0.76-pJ/Pulse 0.1-1 Gpps Microwatt IR-UWB CMOS Pulse Generator with Adaptive PSD Control Using A Limited Monocycle Precharge Technique

Document Version Author final version (often known as postprint) Link to publication from Aalborg University Citation for published version (APA)

Tetra­aqua­(1,10-phenanthroline)nickel(II) 3,6-dicarboxy­bicyclo­[2.2.2]oct-7-ene-2,5-dicarboxyl­ate

In the title compound, [Ni(C12H8N2)(H2O)4](C12H10O8), the NiII ion is six-coordinated by two N atoms from one phenanthroline ligand and by the O atoms of four water mol­ecules in a distorted octa­hedral geometry. In the crystal, inter­molecular O—H⋯O hydrogen bonds form an extensive three-dimensional network, which consolidates the crystal packing

Lotus-leaf-inspired hierarchical structured surface with non-fouling and mechanical bactericidal performances

Antibiotics, a power tool to combat pathogenic bacterial infection, have experienced their inability to kill drug-resistant bacteria due to the development of antibiotic resistance. As an alternative, nanostructured, mechanical bactericidal surfaces may hold promise in killing bacteria without triggering antimicrobial resistance; however, accumulation of dead bacteria would greatly reduce their antimicrobial activity. In this study, for the first time we report a surprising discovery that the lotus leaf, well known for its superhydrophobicity, has demonstrated not only strong repelling effect against bacteria but also bactericidal activity via a cell-rupturing mechanism. Inspired by this unexpected finding, we subsequently designed and prepared a hierarchically structured surface, comprising microscale cylinders with superimposed nanoneedles on top, which was rendered superhydrophobic (water contact angle: 174°; roll-off angle: 99%) were repelled from the surface (non-fouling), those tenacious bacteria that managed to be in touch of the surface were physically killed completely. Compared to a conventional superhydrophobic surface (non-fouling to some extent, but no bacteria-killing) or a mechanical bactericidal surface (bacteria-killing but not bacteria-repelling), our new structured surface has the great advantage in maintaining long-term effectiveness in antimicrobial activity. We envisage that this study will help develop long-term effective antimicrobial strategies based entirely on physical bactericidal mechanism (thus, avoiding risks of triggering antimicrobial resistance)