Intelligent and pervasive computing for cyber-physical systems

The Journal of Supercomputing -     

Analyse der Partikelbildung aus der Elektrospray-Flammensprühpyrolyse mittels Scanning Mobility Particle Sizer

Electrospray of liquid precursor coupled to flame spray pyrolysis allows for the synthesis of many different metal oxide nanoparticles. A setup consisting of a moveable burner and a static sampling system gives the possibility of characterizing particle size distributions across and along the flame. The particle formation of iron oxide and silica particles in a flame spray was investigated even for early stages using a 1nm scanning mobility particle sizer. Thereby it was found that even for simple precursor solutions high quality nanopowders could be produced as long as the droplet size is sufficiently small.     

Two-dimensional Darcy–Forchheimer flow of a dusty hybrid nanofluid over a stretching sheet with viscous dissipation

The main objective of the present examination is to design a stable mathematical model of a two-phase dusty hybrid nanofluid flow over a stretching sheet with heat transfer in a porous medium, and the Darcy–Forchheimer flow is taken into account with viscous dissipation and melting effect. The equations of motion are reduced to nonlinear ordinary differential equations by considering suitable similarity variables. These dimensionless expressions are solved by a well-known numerical technique known as Runge–Kutta–Fehlberg fourth–fifth order method. The behavioral study and analysis of the velocity and thermal profile in dual phases (fluid phase and dust phase) for diverse values of parameters are estimated using graphs and tables. The result outcome reveals that the velocity gradient declines in the fluid phase and increases in the dust phase for a rise in values of the velocity interaction parameter. Also, the velocity gradients of the both phases diminish for increasing values of the porosity parameter. Furthermore, it is determined that the increase in the value of melting parameter leads to a decline in the thermal gradient of both phases.     

Mitigating false blocking problem in wireless ad hoc networks

The traditional IEEE802.11 Request-to-Send/Clear-to-Send (RTS/CTS) handshaking in medium access control layer has been widely adopted in wireless ad hoc networks to reduce the hidden node problem. However, it induces the false blocking problem, which occurs when nodes are prevented from replying to any incoming RTS packets when they are in deferring state after overhearing the RTS and/or CTS packets. Worse still, these unreplied RTS packets will then cause other neighbouring nodes to defer blindly which propagates the false blocking problem, resulting in exhaustion of scarce energy resource and throughput degradation. In this paper, we propose an adaptive Ready-to-Send and blocking notification (RSBN) scheme to mitigate the false blocking problem. The adaptive RSBN scheme not only validates the overheard RTS packets to avoid blind deferment but also informs neighbouring nodes of the nodes’ deferring status to block unnecessary RTS packets. We validate the proposed scheme by simulations and the results have shown that the adaptive RSBN scheme can achieve higher performance.     

Biohybrid Photoprotein‐Semiconductor Cells with Deep‐Lying Redox Shuttles Achieve a 0.7 V Photovoltage

Photosynthetic proteins transduce sunlight into biologically useful forms of energy through a photochemical charge separation that has a close to 100% quantum efficiency, and there is increasing interest in their use as sustainable materials in biohybrid devices for solar energy harvesting. This work explores a new strategy for boosting the open circuit voltage of photoelectrochemical cells based on a bacterial photosynthetic pigment‐protein by employing highly oxidizing redox electrolytes in conjunction with an n‐type silicon anode. Illumination generates electron–hole pairs in both the protein and the silicon electrode, the two being connected by the electrolyte which transfers electrons from the reducing terminal of the protein to photogenerated holes in the silicon valence band. A high open circuit voltage of 0.6 V is achieved with the most oxidizing electrolyte 2,2,6,6‐tetramethyl‐1‐piperidinyloxy, and this is further improved to 0.7 V on surface modification of the silicon electrode to increase its surface area and reduce reflection of incident light. The photovoltages produced by these biohybrid protein/silicon cells are comparable to those typical of silicon heterojunction and dye‐sensitized solar cells.     

High stiffness polymer composite with tunable transparency

Biological materials are multifunctional performing more than one function in a perfect synergy. These materials are built from fairly simple and limited components at ambient conditions. Such judicious designs have proven elusive for synthetic materials. Here, we demonstrate a multifunctional phase change (pc) composite from simple building blocks, which exhibits high stiffness and optical transmittance control. We show an increase of more than one order of magnitude in stiffness when we embed paraffin wax spheres into an elastomer matrix, polydimethylsiloxane (PDMS) in a dynamic compression test. High stiffness is mainly influenced by presence of microcrystals within the wax. We further show fast temperature-controlled optical switching of the composite for an unlimited number of cycles without any noticeable mechanical degradation. Through experimental and finite element method, we show high energy absorption capability of pc-composite. Based on these properties, the pc-composite could be used as an effective coating on glasses for cars and windows. This simple approach to multi-functionality is exciting and could pave way for designs of other multifunctional materials at the macro-scale.     

Narrow-core hollow optical waveguide with nanostructured SOI as ultra-low loss platform for efficient photodetection

A nanostructured hollow optical waveguide based on high-index contrast grating (HCG) embedded SOI is proposed. An ultra-low propagation loss of 1.22 dB/m even at narrow, 1-\(\upmu \)m thick, air-core is reported. A high-performance photodetection is realized by the introduction of hollow core in form of intrinsic region in the photodetection (PIN) layer within HCG-assisted narrow-core waveguide. A sufficiently high responsivity of 0.8 A/W and quantum efficiency of 64% are obtained at 1550-nm which is possible because of the presence of surface modes within HCG which get coupled in the photodetection layer leading to a strong optical confinement in that layer. High reflectivity, small penetration length and coupling of lateral surface modes in HCG make it possible to offer improved waveguiding and hence photodetection.     

Modelling and mitigation of single-event upset in CMOS voltage-controlled oscillator

Single-event effects (SEEs) have been the primary concern in study of radiation effects since late 1970s with the discovery of soft errors in terrestrial and space environments. The interaction of a single ionized particle with electronic devices leads to SEEs. In this paper, single-event upset (SEU) on CMOS devices in designing of a voltage-controlled oscillator (VCO) is analysed. Further, mitigation approaches of SEU are also discussed. To observe the impact of radiation, a VCO was designed in Cadence Virtuoso, and GDSII file of one ring oscillator stage was extracted to incorporate the same design in Silvaco MaskViews. With the help of layer map information file, masks were identified and used to design the CMOS inverter structure file for simulation of SEU condition. The input parameters for SEU simulation were evaluated from linear energy transfer (LET) graph of heavy ion under space conditions. The current profile of CMOS inverter was extracted under influence of a high-energy particle with the help of LET graph of that particle. This current profile was applied to different nodes of VCO and upset conditions were identified. Further, the impact of upset conditions on lock stage of phase-locked loop (PLL) is discussed. Results show that the SEU has significant impact on the logic state of inverters used in ring oscillator stage compared with current starving/biasing stage. The current profile of CMOS device has strong dependence on the energy of ion, its track, angle of incidence and the material. When angle of incidence is very less (\(7^{\circ }-14^{\circ }\)) the channel will be occupied by a funnel of charge and it leads to the maximum degradation of device. This work shows that a device operating at high frequency is more susceptible to SEU. Triple modular redundancy (TMR) and Radiation Hardened By Design (RHBD) can be used to mitigate SEU. TMR consumes more power and is less accurate compared with the RHBD approach.     

Curvilinear Mesh Adaptation Using Radial Basis Function Interpolation and Smoothing

We present a new iterative technique based on radial basis function (RBF) interpolation and smoothing for the generation and smoothing of curvilinear meshes from straight-sided or other curvilinear meshes. Our technique approximates the coordinate deformation maps in both the interior and boundary of the curvilinear output mesh by using only scattered nodes on the boundary of the input mesh as data sites in an interpolation problem. Our technique produces high-quality meshes in the deformed domain even when the deformation maps are singular due to a new iterative algorithm based on modification of the RBF shape parameter. Due to the use of RBF interpolation, our technique is applicable to both 2D and 3D curvilinear mesh generation without significant modification.     

A chaos-based image encryption algorithm based on multiresolution singular value decomposition and a symmetric attractor

ABSTRACT

This paper proposes a new image cryptosystem using multiple chaotic maps and multiresolution singular value decomposition (MR-SVD). The encryption process starts with implementing the MR-SVD to decompose the original image into the four fundamental sub-bands, i.e., Approximation (A), Vertical (V), Horizontal (H), Diagonal (D) sub-bands respectively. Since the approximation part gives the most information about the image, this sub-band is selected to perform permutation and diffusion. The permutation of all the four sub-bands is done by deploying the Baker map. The diffusion of pixels in the permuted approximation part is done by our neighbourhood diffusion scheme that uses the numerical solution of the chaotic Thomas' cyclically symmetric attractor. The final cipher is obtained by combining all the four (A, H, V, D) partial ciphers by performing inverse MR-SVD. The experimental results of our proposed scheme on various benchmarks tests indicate that the algorithm is highly secure and can withstand various attacks.