Distributed primal–dual interior-point methods for solving tree-structured coupled convex problems using message-passing

In this paper, we propose a distributed algorithm for solving coupled problems with chordal sparsity or an inherent tree structure which relies on primal–dual interior-point methods. We achieve this by distributing the computations at each iteration, using message-passing. In comparison to existing distributed algorithms for solving such problems, this algorithm requires far fewer iterations to converge to a solution with high accuracy. Furthermore, it is possible to compute an upper-bound for the number of required iterations which, unlike existing methods, only depends on the coupling structure in the problem. We illustrate the performance of our proposed method using a set of numerical examples.     

Variable sampling plan for resubmitted lots based on process capability index and Bayesian approach

Acceptance sampling plans are applied for quality inspection of products. Among the design approaches of sampling plan, the most important one is to use process capability indices in order to improve the quality of manufacturing processes and the quality inspection of products. But, selection of estimators of process capability index and their sampling distribution is very important. Bayesian statistical technique can be used to obtain the sampling distribution. In this paper, a variable sampling plan is developed for resubmitted lots based on process capability index and Bayesian approach. In the proposed sampling plan, lots are inspected several times depending on the quality level of the process. In addition, this paper presents an optimization model for determining the decision parameters of developed sampling plan with regards to the constraints related to the risk of consumer and producer. Two comparison studied have been done including: First, the methods of double sapling plan (DSP), multiple dependent state (MDS) sampling plan, and repetitive group sampling (RGS) plan are elaborated, and also in order to comparing developed sampling plans, an expected number of products as average sample number (ASN) is used for different developed plans; second, a comparison study between Bayesian approach and exact probability distribution is carried out and their results are analyzed. It is observed that the ASN values of MDS sampling plan is less than ASN values of other methods, and also the ASN values of different variable sampling plans based on Bayesian approach is less than ASN values obtained using exact approach.     

A Scenario-Based Management of Water Resources and Supply Systems Using a Combined System Dynamics and Compromise Programming Approach

Water Resources Management - Long-term sustainability in water supply systems is a major challenge due to water resources depletion, climate change and population growth. This paper presents a...     

Forbidden region virtual fixtures from streaming point clouds

Forbidden region virtual fixtures protect objects from unwanted contact with a robot. In this paper, we propose a method for creating forbidden region haptic virtual fixtures for teleoperation from streaming point clouds obtained by an RGB-D camera. Upon violating the protected area, the operator receives force feedback that opposes motion inside the forbidden region. Three architectures for creating virtual fixtures are presented and their advantages and disadvantages are described. The proposed methods have the ability to implement constraints and can handle dynamic environments in real-time. The effectiveness of the methods is demonstrated in experiments with a surgical robot.     

The Influence of KrF Excimer Laser Annealing on Magnetic and Structural Properties of FePt/PtIr Thin Films

A series of 60-nm FePt thin films were deposited by RF magnetron sputtering system on Si/SiO₂ substrate. Platinum–iridium alloy was deposited as a buffer film between the FePt thin film and Si/SiO₂ substrate. These films were annealed by KrF excimer laser annealing with 248 nm of wavelength. The number of laser pulses which were applied on the film was varied from 3 to 20. The A₁ to L₁₀ phase transformation of FePt was confirmed by X-ray diffraction. Three pulses of laser were not sufficient for A₁ to L₁₀ phase transformation. A maximum order parameter of 0.91 was obtained after applying 18 pulses of laser. The roughness of films changed in different pulses, and the films were in the best condition after applying 18 pulses; the roughness was 3.51 nm and its morphology that was observed from AFM was 129 nm. The maximum coercivity was 0.61 MA/m. The coercivity increased with the application of different pulses of laser. Increasing coercivity to the maximum value of 0.61 MA/m related to grain growth. Coercivity of samples in 3, 6, 9, 12, 18, and 20 pulses was 0.24, 0.402, 0.488, 0.522, 0.64, and 0.6 MA/m respectively. Determining the grain growth under condition of annealing was done by field emission scanning electron microscopy (FESEM). Growth of all specimens was calculated with imager software. Grain size in as deposited and 3, 6, 9, 12, and 18 pulses of laser was 15, 20, 29, 44, 47, and 59 respectively.     

A Microstructural Approach Toward the Quantification of Anomaly Bond Coat Surface Geometry Change in NiCoCrAlY Plasma-Sprayed Bond Coat

Three-dimensional behavior of NiCoCrAlY bond coat surface geometry change (known as rumpling) was characterized during 120 h of thermal cycling. The proposed scanning electron microscope (SEM)-based 3D imaging method allows for recording the change in both height and width at the same location during the heat treatment. Statistical analysis using both profile information [two dimensions (2D)] and surface information [three dimensions (3D)] demonstrated a typical nature of rumpling as increase in height and decrease in width. However, it also revealed an anomaly of height reduction between 40 and 80 cycles. Such behavior was further investigated by analyzing the bearing area ratio curve of the surface and attributed to filling of voids and valleys by the growth of thermally grown oxide.     

Direct measurement and modeling relative gas diffusivity of PEMFC catalyst layers: The effect of ionomer to carbon ratio,operating temperature,porosity, and pore size distribution

A modified Loschmidt cell was used to measure the relative gas diffusivity (D¹) of the porous catalyst layers (CLs) of polymer electrolyte membrane fuel cells as a function of CL ionomer/carbon weight ratio (I/C) (0.5, 1.1, and 1.5) and operating temperature (20, 40, and 72 °C). D^* decreased by 80% when I/C was increased from 0.5 to 1.5. While the effective gas diffusivity of CL increased with temperature, D^* decreased because binary diffusion increases more rapidly than Knudsen diffusivity with temperature. The structure of CL was modeled through considering a packed-sphere model for carbon particles within agglomerates, and a network of overlapped spherical agglomerates forming the CL. The gas diffusion problem was solved analytically for the CL structure considering both Knudsen and molecular mechanisms, and, results were validated. Using the model, the effect of porosity, pore size distribution and ionomer coverage on gas diffusivity was evaluated.     

Plate-like structures damage detection based on static response and static strain energy using gaussian process regression (GPR)

This study investigates the applicability of an emergent learning algorithm called Gaussian process regression (GPR) algorithm to predict damage in plate-like structures as an inverse problem. The presented method is based on static responses and static strain energy as input parameters to GPR model. The performance of the presented methods has been evaluated using two numerical examples, namely, four fixed and cantilever plates. Also, an examination has been performed in which only translational DOFs are selected as measured DOFs. In another work, the effect of noise in static data has been investigated. The model results were compared using mean square errors. The obtained results show the effectiveness of GPR in damage detection and estimation of plate-like structures using static data which may be noisy.     

Toughening mechanisms in bioinspired multilayered materials

Outstanding mechanical properties of biological multilayered materials are strongly influenced by nanoscale features in their structure. In this study, mechanical behaviour and toughening mechanisms of abalone nacre-inspired multilayered materials are explored. In nacre''s structure, the organic matrix, pillars and the roughness of the aragonite platelets play important roles in its overall mechanical performance. A micromechanical model for multilayered biological materials is proposed to simulate their mechanical deformation and toughening mechanisms. The fundamental hypothesis of the model is the inclusion of nanoscale pillars with near theoretical strength (σ_th ~ E/30). It is also assumed that pillars and asperities confine the organic matrix to the proximity of the platelets, and, hence, increase their stiffness, since it has been previously shown that the organic matrix behaves more stiffly in the proximity of mineral platelets. The modelling results are in excellent agreement with the available experimental data for abalone nacre. The results demonstrate that the aragonite platelets, pillars and organic matrix synergistically affect the stiffness of nacre, and the pillars significantly contribute to the mechanical performance of nacre. It is also shown that the roughness induced interactions between the organic matrix and aragonite platelet, represented in the model by asperity elements, play a key role in strength and toughness of abalone nacre. The highly nonlinear behaviour of the proposed multilayered material is the result of distributed deformation in the nacre-like structure due to the existence of nano-asperities and nanopillars with near theoretical strength. Finally, tensile toughness is studied as a function of the components in the microstructure of nacre.