Simultaneous size and geometry optimization of steel trusses under dynamic excitations

During the past decades, the main focus of the research in steel truss optimization has been tailored towards optimal design under static loading conditions and limited work has been devoted to investigating the optimum structural design considering dynamic excitations. This study addresses the simultaneous size and geometry optimization problem of steel truss structures subjected to dynamic excitations. Using the well-known big bang-big crunch algorithm, the minimum-weight design of steel trusses is conducted under both periodic and non-periodic excitations. In the case of periodic excitations, in order to examine the effect of the exciting period of the dynamic load on the final results, the design instances are optimized under different exciting periods and the obtained results are compared. It is observed that by increasing the excitation period of the considered sinusoidal loading as well as the finite rise time of the non-periodic step force, the optimization results approach the minimum design weight obtained under the static loading counterpart. However, in the case of the studied rectangular periodic excitation, the results obtained do not approach the optimum design associated with the static loading case even for higher values of the exciting period.     

Evaluate and control service and transaction dependability of complex IoT systems

Observing and controlling the dependability of service provision of complex IoT systems is challenging. In practice, many organizations struggle to derive consumer needs related to quality and to observe and quantify the service provision in the context of the dynamic behavior of a complex distributed system. In this paper, we present an approach to define and evaluate the dependability of complex IoT systems. Our approach is an adaptation of the ISO/IEC 25040, an international standard for the evaluation process for system and software quality, which is part of the systems and software quality requirements and evaluation (SQuaRE) series. Our approach was designed and evaluated with action research in an industrial study at Robert Bosch GmbH. Based on the framework of the SQuaRE series, we integrated different elements of site reliability engineering (SRE) and combined them with distributed tracing as a promising measurement method. Our approach introduces the IoT transaction concept to reduce modeling and observation efforts while increasing operationalization to measure performance against dependability targets. Our adaption was effectively applied, consumer-centricity along different system stakeholders were enhanced, and negative consequences of organizational silos were reduced. This has improved the dependability evaluation of service provision to enable fast feedback cycles for service performance control and improvement.

     

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.     

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.     

Experimental and numerical analysis of aerodynamic effects of repair patches on damaged airfoils

This investigation assesses the change of aerodynamic characteristics of triangular and star-shaped damaged airfoils with repair patches. Both experimental and numerical methods to determine aerodynamic coefficients are used in this study. The test model is a NACA 64₁-412 airfoil full span, which is considered by using five schematics: Clean model, damaged model, upper repaired model, lower repaired model, and fully repaired model. Repair patches are chosen based on the Aircraft battle damage repair (ABDR) manuals. Various effects of repair schemes on triangular and star-shaped damages are quantitatively and qualitatively illustrated. A novel visualization method by paint and oil is used in wind tunnel tests to study the effects of repair patches on the damaged airfoil.