Spectral Method for Multiplexed Phase Retrieval and Application in Optical Imaging in Complex Media

We introduce a generalized version of phase retrieval called multiplexed phase retrieval. We want to recover the phase of amplitude-only measurements from linear combinations of them. This corresponds to the case in which multiple incoherent sources are sampled jointly, and one would like to recover their individual contributions. We show that a recent spectral method developed for phase retrieval can be generalized to this setting, and that its performance follows a phase transition behavior. We apply this new technique to light focusing at depth in a complex medium. Experimentally, although we only have access to the sum of the intensities on multiple targets, we are able to separately focus on each ones, thus opening potential applications in deep fluorescence imaging and light deliver

Interplay between finite resources and local defect in an asymmetric simple exclusion process

When particle flux is regulated by multiple factors such as particle supply and varying transport rate, it is important to identify the respective dominant regimes. We extend the well-studied totally asymmetric simple exclusion model to investigate the interplay between a controlled entrance and a local defect site. The model mimics cellular transport phenomena where there is typically a finite particle pool and non-uniform moving rates due to biochemical kinetics. Our simulations reveal regions where, despite an increasing particle supply, the current remains constant while particles redistribute in the system. Exploiting a domain wall approach with mean-field approximation, we provide a theoretical ground for our findings. The results in steady state current and density profiles provide quantitative insights into the regulation of the transcription and translation process in bacterial protein synthesis. We investigate the totally asymmetric simple exclusion model with controlled entrance and a defect site in the bulk to mimic the finite particle pool and non-uniform moving rates in particle transport processes.Comment: 9 pages, 12 figures; v2: minor format changes; v3: major revision, additional references; v4: minor format change to figures, additional reference

Multiobjective optimization for unidirectional glass and carbon fiber-reinforced hybrid epoxy composites under flexural loading

A multiobjective optimization study for unidirectional carbon fiber- and glass fiber-reinforced epoxy hybrid composites under flexural loading is presented in this paper. The flexural strength of the hybrid composite was conveniently expressed by regression formulas. Two optimization methods—WSM and NSGA-II—were employed for multiobjective optimization with the cost and weight being the objective functions. When WSM was used, two algorithms, viz., interior point algorithm (IPA) and genetic algorithm (GA), were used. The results suggest that positive hybrid effects can be utilized to improve the flexural strength

`Sinking' in a bed of grains activated by shearing

We show how a weak force, $f$, enables intruder motion through dense granular materials subject to external mechanical excitations, in the present case stepwise shearing. A force acts on a Teflon disc in a two dimensional system of photoelastic discs. This force is much smaller than the smallest force needed to move the disc without any external excitation. In a cycle, material + intruder are sheared quasi-statically from $\gamma = 0$ to $\gamma_{max}$, and then backwards to $\gamma = 0$. During various cycle phases, fragile and jammed states form. Net intruder motion, $\delta$, occurs during fragile periods generated by shear reversals. $\delta$ per cycle, e.g. the quasistatic rate $c$, is constant, linearly dependent on $\gamma_{max}$ and $f$. It vanishes as, $c \propto (\phi_c - \phi)^a$, with $a \simeq 3$ and $\phi_c \simeq \phi_J$, reflecting the stiffening of granular systems under shear as $\phi \rightarrow \phi_J$. The intruder motion induces large scale grain circulation. In the intruder frame, this motion is a granular analogue to fluid flow past a cylinder, where $f$ is the drag force exerted by the flow.Comment: 4 pages, 5 figures letter with supplementarie

Coefficient of thermal expansion of single-wall carbon nanotube reinforced nanocomposites

A study on the coefficient of thermal expansion (CTE) of single-wall carbon nanotube (SWCNT)-reinforced nanocomposites is presented in this paper. An interfacial adhesion factor (IAF) is introduced for the purpose of modelling the adhesion between SWCNTs and the matrix. The effective CTE and modulus of SWCNTs are derived using the IAF, and the effective CTE of the nanocomposite is derived by the Mori–Tanaka method. The developed model is validated against experimental data and good agreement is found

Flexural properties of symmetric carbon and glass fibre reinforced hybrid composite laminates

A study on the flexural properties of symmetric carbon and glass fibre reinforced hybrid composite laminates is presented in this paper. A modelling approach was developed with the aid of Finite Element Analysis (FEA). This model was experimentally validated. With this FEA based model, various stacking sequences were studied to find the effects of hybridisation on the flexural properties. A rule of how to arrange the carbon and glass fibres in the hybrid composite was developed. It is shown that the hybrid composite has the highest flexural strength when it contains half carbon/epoxy plies and half glass/epoxy plies. Optimisation was also carried out with the objective functions being the material cost and component weight. It is shown from the optimal hybrid composite has up to half of its plies being glass/epoxy and placed on the inside of the composite

Uncertainties in flexural strength of carbon/glass fibre reinforced hybrid epoxy composites

A study on the flexural behaviours of the of glass and carbon fibre reinforced epoxy hybrid composites is presented in this paper. Two types of glass fibres: S-2 and E, and two types of carbon fibres: T700S and P-100 are investigated. The flexural strength is obtained using an approach based on finite element analysis. Three compressive strength models: Lo-Chim, Budiansky and the shear models are used to obtain the flexural strengths. It is shown from the results that when shear failure occurs, the flexural strength is 20-30% lower compared to other failure modes

On the Design and Analysis of Multiple View Descriptors

We propose an extension of popular descriptors based on gradient orientation histograms (HOG, computed in a single image) to multiple views. It hinges on interpreting HOG as a conditional density in the space of sampled images, where the effects of nuisance factors such as viewpoint and illumination are marginalized. However, such marginalization is performed with respect to a very coarse approximation of the underlying distribution. Our extension leverages on the fact that multiple views of the same scene allow separating intrinsic from nuisance variability, and thus afford better marginalization of the latter. The result is a descriptor that has the same complexity of single-view HOG, and can be compared in the same manner, but exploits multiple views to better trade off insensitivity to nuisance variability with specificity to intrinsic variability. We also introduce a novel multi-view wide-baseline matching dataset, consisting of a mixture of real and synthetic objects with ground truthed camera motion and dense three-dimensional geometry

EbbRT: a framework for building per-application library operating systems

Efficient use of high speed hardware requires operating system components be customized to the application work- load. Our general purpose operating systems are ill-suited for this task. We present EbbRT, a framework for constructing per-application library operating systems for cloud applications. The primary objective of EbbRT is to enable high-performance in a tractable and maintainable fashion. This paper describes the design and implementation of EbbRT, and evaluates its ability to improve the performance of common cloud applications. The evaluation of the EbbRT prototype demonstrates memcached, run within a VM, can outperform memcached run on an unvirtualized Linux. The prototype evaluation also demonstrates an 14% performance improvement of a V8 JavaScript engine benchmark, and a node.js webserver that achieves a 50% reduction in 99th percentile latency compared to it run on Linux