Self-healing of workflow activity incidents on distributed computing infrastructures

Distributed computing infrastructures are commonly used through scientific gateways, but operating these gateways requires important human intervention to handle operational incidents. This paper presents a self-healing process that quantifies incident degrees of workflow activities from metrics measuring long-tail effect, application efficiency, data transfer issues, and site-specific problems. These metrics are simple enough to be computed online and they make little assumptions on the application or resource characteristics. From their degree, incidents are classified in levels and associated to sets of healing actions that are selected based on association rules modeling correlations between incident levels. We specifically study the long-tail effect issue, and propose a new algorithm to control task replication. The healing process is parametrized on real application traces acquired in production on the European Grid Infrastructure. Experimental results obtained in the Virtual Imaging Platform show that the proposed method speeds up execution up to a factor of 4, consumes up to 26% less resource time than a control execution and properly detects unrecoverable errors.     

Dynamic positioning of marine craft using a port-Hamiltonian framework

Dynamic positioning of marine craft refers to the use of the propulsion system to regulate the vessel position and heading. This type of motion control is commonly used in the offshore industry for surface vessels, and it is also used for some underwater vehicles. In this paper, we use a port-Hamiltonian framework to design a novel nonlinear set-point-regulation controller with integral action. The controller handles input saturation and guarantees internal stability, rejection of unknown constant disturbances, and (integral-)input-to-state stability.     

A CDMA Dual-Band Zero-IF Receiver With Integrated LNAs and VCOs in an Advanced SiGe BiCMOS Process

This paper describes one of the first dual PCS- and CEL-band CDMA receivers that includes LNAs and VCOs on a single die. The PCS-band LNA achieves a noise figure (NF) of 1.5dB and IP3 of +7.5 dBm at 16-dB gain. The PCS demodulating mixer achieves an NF of 5 dB, IP3 of +5 dBm and uncalibrated IP2 of +60 dBm. The PCS VCO is capable of -134 dBc/Hz phase noise at 3.9 GHz and 1.25-MHz offset. A copper BiCMOS process was chosen for both performance and cost benefits, compared with lower geometry CMOS     

Mechanical and optical dynamic model of lung

A multiscale, multiphysics model generates synthetic images of alveolar compression under spherical indentation at the visceral pleura of an inflated lung. A mechanical model connects the millimeter scale of an indenter tip to the behavior of alveoli, walls, and membrane at the micrometer scale. A finite-difference model of optical coherence tomography (OCT) generates the resulting images. Results show good agreement with the experiments performed using a unique indenter-OCT system. The images depict the physical result with the addition of refractive artifacts and speckle. Compression of the alveoli alters the refractive effects, which introduce systematic errors in the computation of alveolar volume. The complete computational model is useful to evaluate new proposed imaging instrumentation and to develop algorithms for obtaining quantitative data on deformation. Among the potential applications, a better understanding of recruitment of alveoli during inflation of a lung, obtained through a combination of models and imaging could lead to improvements in noninvasive treatment of atelectasis.     

Interfacial Self‐Assembly of Amphiphilic Dual Temperature Responsive Actuating Janus Particles

Amphiphilic Janus particles feature the combination of two different functional materials in one single colloid, as well as the possibility of self‐assembly at interfaces into complex superstructures. In this article, the self‐assembly of dual temperature responsive amphiphilic Janus particles at liquid–liquid interfaces and their subsequent conversion into an actuating layer‐shaped surface are presented. These microparticles are produced in a capillaries based continuous flow microfluidic device by photoinitiated radical polymerization. The hydrophobic part of the Janus particles contains a liquid crystalline elastomer (LCE), which performs a strong actuation up to 95% during the nematic–isotropic phase transition. The other side consists of a p(NIPAAm) hydrogel, which features volumetric expansions up to 280% below the lower critical solution temperature. A multistep molding process is developed to uniformly align the Janus particles at a toluene/water boundary surface and to embed the particles into a hydrogel matrix. A particle covered hydrogel layer is obtained, which features a collective actuation of the rod‐like LCE parts on the surface and a bundling of the resulting forces during the phase transition.     

Towards understanding the influence of porosity on mechanical and fracture behaviour of quasi-brittle materials: experiments and modelling

In this work, porosity-property relationships of quasi-brittle materials are explored through a combined experimental and numerical approach. In the experimental part, hemihyrate gypsum plaster powder (\(\hbox {CaSO}_{4}\cdot 1/2\hbox {H}_{2}\hbox {O}\)) and expanded spherical polystyrene beads (1.5–2.0 mm dia.) have been mixed to form a model material with controlled additions of porosity. The expanded polystyrene beads represent pores within the bulk due to their light weight and low strength compared with plaster. Varying the addition of infill allows the production of a material with different percentages of porosity: 0, 10, 20, 30 and 31 vol%. The size and location of these pores have been characterised by 3D X-ray computed tomography. Beams of the size of \(20 \times 20 \times 150\) mm were cast and loaded under four-point bending to obtain the mechanical characteristics of each porosity level. The elastic modulus and flexural strength are found to decrease with increased porosity. Fractography studies have been undertaken to identify the role of the pores on the fracture path. Based on the known porosity, a 3D model of each microstructure has been built and the deformation and fracture was computed using a lattice-based multi-scale finite element model. This model predicted similar trends as the experimental results and was able to quantify the fractured sites. The results from this model material experimental data and the lattice model predictions are discussed with respect to the role of porosity on the deformation and fracture of quasi-brittle materials.     

Identifying individual single-walled and double-walled carbon nanotubes by atomic force microscopy

We show that the number of concentric graphene cylinders forming a carbon nanotube can be found by squeezing the tube between an atomic force microscope tip and a silicon substrate. The compressed height of a single-walled nanotube (double-walled nanotube) is approximately two (four) times the interlayer spacing of graphite. Measured compression forces are consistent with the predicted bending modulus of graphene and provide a mechanical signature for identifying individual single-walled and double-walled nanotubes.     

Optical study on II-VI semiconductor nanoparticles in Langmuir-Blodgett films

Cadmium sulfide (CdS) nanoparticles formed within Langmuir-Blodgett (LB) films of stearic acid and calix[8]arene were studied with different optical methods including surface plasmon resonance (SPR), ellipsometry and UV-visible absorption and fluorescence spectroscopies. For the first time, the process of formation of CdS nanoparticles within LB films was monitored in-situ with SPR. The results of ellipsometry, SPR and UV-vis absorption spectroscopy were analyzed to evaluate simultaneously the thickness, refractive index and extinction coefficient of LB films. It was shown that all three parameters increase as a result of formation of CdS nanoparticles. Photoluminescence measurements provided direct confirmation directly for previous observation with UV-vis absorption spectroscopy of the blue spectral shift caused by CdS particles formation. The observed large Stoke's shift of the luminescence band is discussed in terms of the formation of "dark excitons" in the platelet-type CdS nanoclusters. AFM study shows the formation of pseudo-two dimensional platelets of CdS with the lateral dimensions in the range of 20-30 nm.