Biblio

This paper is about the estimation of the cyber-resilience of CPS. We define two new resilience estimation metrics: k-steerability and l-monitorability. They aim at assisting designers to evaluate and increase the cyber-resilience of CPS when facing stealthy attacks. The k-steerability metric reflects the ability of a controller to act on individual plant state variables when, at least, k different groups of functionally diverse input signals may be processed. The l-monitorability metric indicates the ability of a controller to monitor individual plant state variables with l different groups of functionally diverse outputs. Paired together, the metrics lead to CPS reaching (k,l)-resilience. When k and l are both greater than one, a CPS can absorb and adapt to control-theoretic attacks manipulating input and output signals. We also relate the parameters k and l to the recoverability of a system. We define recoverability strategies to mitigate the impact of perpetrated attacks. We show that the values of k and l can be augmented by combining redundancy and diversity in hardware and software, in order to apply the moving target paradigm. We validate the approach via simulation and numeric results.

The objective of this work is to study, using an analytical approach and a numerical simulation, the dynamic behavior of an oscillating liquid inside a fixed U-tube with open ends used as wave energy converter. By establishing a detailed liquid's motion equation and developing a numerical simulation, based on volume of fluid formulation, we quantified the available power that could be extracted for our configuration. A parametrical study using the analytical model showed the effect of each significant parameter on first peak power and subsequent dampening of this peak power, which constitutes a tool for choosing optimal designs. The numerical simulation gave a more realistic model, the obtained results are in good agreements with those of the analytical approach that underestimates the dampening of oscillations. We focused after on influence of the numerical model formulation, mesh type and mesh size on simulation results: no noticeable effect was observed.

We present results from a vibrating mesh nebulizer for which the mesh is a micro-machined silicon membrane perforated with up to a thousand micron-sized, pyramidal holes. Finite element modelling is used to better understand the measured results of the nebulizer when tested in the dry state as well as when loaded with a liquid. In particular, we found that the frequency response of the system is well represented by the superposition of the frequency response of its two main subcomponents: the piezo driving unit and the silicon membrane. As such, the system is found to have resonance peaks for which the complete assembly flexes in addition to peaks that correspond to the flexural resonance modes of the silicon membrane on its own. Similarly, finite element modelling was used to understand differences observed between the frequency response measured on the nebulizer in the dry condition compared to its wet or liquid loaded operation. It was found that coupling between the structural and the acoustic domains shifts the resonance peaks significantly to the left of the frequency plot. In fact, it was found that at the operating frequency of the nebulizer, the system resonates in a (0,3) when the membrane is loaded with a liquid compared with a (0,2) resonance mode when it is operating in the dry state.

Chemical sensing is an important issue in food, water, environment, biomedical, and pharmaceutical field. Conventional methods used in laboratory for sensing the chemical are costly, time consuming, and sometimes wastes significant amount of sample. Photonic Crystal Fiber (PCF) offers high compactness and design flexibility and it can be used as biosensor, chemical sensor, liquid sensor, temperature sensor, mechanical sensor, gas sensor, and so on. In this work, we designed PCF to sense different concentrations of different liquids by one PCF structure. We designed different structure for silica cladding hexagonal PCF to sense different concentrations of benzene-toluene and ethanol-water mixer. Core diameter, air hole diameter, and air hole diameter to lattice pitch ratio are varied to get the optimal result as well to explore the effect of core size, air hole size and the pitch on liquid chemical sensing. Performance of the chemical sensors was examined based on confinement loss and sensitivity. The performance of the sensor varied a lot and basically it depends not only on refractive index of the liquid but also on sensing wavelengths. Our designed sensor can provide comparatively high sensitivity and low confinement loss.

Underwater communication is vital for a variety of defence and scientific purposes. Current optical and sonar based carriers can deliver high capacity data rates, but their range and reliability is hampered by heavy propagation loss. A vertical Molecular Communication via Buoyancy (MCvB) channel is experimentally investigated here, where the dominant propagation force is buoyancy. Sequential puffs representing modulated symbols are injected and after the initial loss of momentum, the signal is driven by buoyancy forces which apply to both upwards and downwards channels. Coupled with the complex interaction of turbulent and viscous diffusion, we experimentally demonstrate that sequential symbols exhibit a Gaussian velocity spatial distribution. Our experimental results use Particle Image Velocimetry (PIV) to trace molecular clusters and infer statistical characteristics of their velocity profile. We believe our experimental paper's results can be the basis for long range underwater vertical communication between a deep sea vehicle and a surface buoy, establishing a covert and reliable delay-tolerant data link. The statistical distribution found in this paper is akin to the antenna pattern and the knowledge can be used to improve physical security.

In this work, a measurement system is developed based on acoustic resonance which can be used for classification of materials. Basically, the inspection methods based on acoustic, utilized for containers screening in the field, identification of defective pills hold high significance in the fields of health, security and protection. However, such techniques are constrained by costly instrumentation, offline analysis and complexities identified with transducer holder physical coupling. So a simple, non-destructive and amazingly cost effective technique in view of acoustic resonance has been formulated here for quick data acquisition and analysis of acoustic signature of liquids for their constituent identification and classification. In this system, there are two ceramic coated piezoelectric transducers attached at both ends of V-shaped glass, one is act as transmitter and another as receiver. The transmitter generates sound with the help of white noise generator. The pick up transducer on another end of the V-shaped glass rod detects the transmitted signal. The recording is being done with arduino interfaced to computer. The FFTs of recorded signals are being analyzed and the resulted resonant frequency observed for water, water+salt and water+sugar are 4.8 KHz, 6.8 KHz and 3.2 KHz respectively. The different resonant frequency in case different sample is being observed which shows that the developed prototype model effectively classifying the materials.