Update of FRF matrix and physical parameters of finite element model

Numerically simulated results by finite element model of a dynamic system do rarely coincide with the actual responses of the structure due to the modeling, manufacturing errors or other causes. The parameters of the finite element model should be corrected for subsequent proper analysis. Minimizing a cost function by the difference between the analytical and actual dynamic stiffness matrices along with constrained conditions of measured FRFs (Frequency Response Functions), this work provides the mathematical form on the updated FRF. The updated parameter matrices of the structure are derived from the FRF variation within the prescribed frequency range. It is shown that the exactness of the proposed method depends on the number of the measured data. The validity of the proposed method is illustrated in updating the parameter matrices of a planar truss structure

Corner Junction as a Probe of Helical Edge States

We propose and analyze inter-edge tunneling in a quantum spin Hall corner junction as a means to probe the helical nature of the edge states. We show that electron-electron interactions in the one-dimensional helical edge states result in Luttinger parameters for spin and charge that are intertwined, and thus rather different than those for a quantum wire with spin rotation invariance. Consequently, we find that the four-terminal conductance in a corner junction has a distinctive form that could be used as evidence for the helical nature of the edge states.Comment: 4+ pages, 3 figure

Damage detection of truss structure based on the variation in axial stress and strain energy predicted from incomplete measurements

This study derives the static equilibrium equation of a damaged system on the basis of stiffness change due to damage as well as the constraint forces at measurements required for obtaining the measured data. Based on the derived equations, this work provides an analytical method to detect damage from the stress and strain energy variations between intact and damaged truss structures. The applicability of the proposed method is evaluated in detecting multiple damages of low rate in the truss structure from measured data contaminated by external noise. It is demonstrated that it is possible to properly detect damage in an isolated substructure by partitioning the damage-expected substructure from an entire structure and using the displacements measured at the boundary of the partitioned subsystem. The partitioning method has the benefits in reducing the computational time and measured data as well as improving the effectiveness of the damage detection process

Identification of parameter matrices using estimated FRF variation

This study presents an analytical method to predict the dynamic parameters of actual structure from measured FRF (Frequency Response Function) data. The inconsistency due to modeling errors between the actual structure and the finite element model exists. The number of measured data is less than the one of a full set of dofs and should be expanded to estimate the parameters. Considering that the stiffness and mass matrices are related with the real part of the expanded FRF data and the damping matrix with the imaginary part, the variation in the parameter matrices is evaluated. A numerical example evaluates the appropriateness of the proposed method

Competitive Evolutionary Dynamics of Cloud Service Offerings in Korea: A Path-Dependency Perspective

Cloud service for personal users has become more popular world-wide since Apple Inc. launched iCloud storage service in October, 2011. However, such cloud storage service was not new because many global telecom companies, usually called telcos, as well as many portals had already offered similar Internet-based online storage services at that time. As of now, there can be seen hundreds of diverse cloud storage and computing services for both personal and enterprise users in the global market. During last several years, Korean cloud service market has been led by three major telcos, who have launched more advanced and more diversified services competing with each other. Some questions may arise: What makes that happen and what kind of market dynamics affects on the evolution of cloud service offerings? This paper tries to answer these questions by categorizing and analysing 84 cloud services offered by three major telcos in Korea during last three years. As a research framework, Pessemier’s new product classification scheme was employed and precedence relationships among differently positioned service categories were analyzed to figure out the competitive evolutionary dynamics of the market. From the empirical study, path dependency was observed and resource-based view of the market competition was validated. Also, it was found that a player’s next move in service offering to a better position in Pessemier’s product space is quite closely related with the competitive position as well as the company-owned competitive resources like technology competency and company-wide service scope

Damage detection based on the internal force or deformation variation

The presence of damage in an intact structure leads to the change in internal force and deformation due to stiffness deterioration in the region of damage. This study proposes modelbased damage detection methods by deriving the mathematical formulation to describe such changes. The force and deformation variations between the undamaged and damaged systems are derived by minimizing the variation in dynamic strain energy with respect to the internal force and deformation vectors, respectively. They are expressed by the product of a coefficient matrix and the external force vector, and the product of a coefficient matrix and the displacement vector, respectively. Taking singular value decomposition (SVD) on the coefficient matrices of rank-deficiency, this study identifies the damaged elements as belonging to the set of elements whose internal forces or deformations between two adjacent nodes of finite element model are not changed. The validity of the proposed methods is illustrated in a simple application

Flow Characteristics Around Step-Up Street Canyons with Various Building Aspect Ratios

We investigate the flow characteristics around step-up street canyons with various building aspect ratios (ratio of along-canyon building length to street-canyon width, and upwind building height to downwind building height) using a computational fluid dynamics (CFD) model. Simulated results are validated against experimental wind-tunnel results, with the CFD simulations conducted under the same building configurations as those in the wind-tunnel experiments. The CFD model reproduces the measured in-canyon vortex, rooftop recirculation zone above the downwind building, and stagnation point position reasonably well. We analyze the flow characteristics, focusing on the structural change of the in-canyon flows and the interaction between the in- and around-canyon flows with the increase of building-length ratio. The in-canyon flows undergo development and mature stages as the building-length ratio increases. In the development stage (i.e., small building-length ratios), the position of the primary vortex wanders, and the incoming flow closely follows both the upstream and downstream building sidewalls. As a result, increasing momentum transfer from the upper layer contributes to a momentum increase in the in-canyon region, and the vorticity in the in-canyon region also increases. In the mature stage (i.e., large building-length ratios), the primary vortex stabilizes in position, and the incoming flow no longer follows the building sidewalls. This causes momentum loss through the street-canyon lateral boundaries. As the building-length ratio increases, momentum transfer from the upper layer slightly decreases, and the reverse flow, updraft, and streamwise flow in the in-canyon region also slightly decrease, resulting in vorticity reduction

Exploring Cognitive Playfulness Through Zero Interactions

Many emerging technologies, products and services today try to use diverse methods of interaction to provide playful experiences. Increasingly more interactive features and techniques are being introduced to afford users new experiences and enrich our living environment. While many of these playful experiences can be achieved through various types of physical, sensory and social interactions, this paper attempts to focus on how 'no-interaction' can achieve playfulness in relation to our cognitive experience. If there is a way to give someone a playful experience without any physical, sensory and social interactions, where and how can we apply this approach or phenomenon? Here we share a provocation that tries to demonstrate a tangible means whereby such an idea could be used to explore potential user experiences within HCI

Structure and mechanical response of metallized electrospun polymeric mats and foams for filter applications

Polymeric non-woven structures for filters are often formed from wet-laid melt blown or spun-bounded fibers, where the polymeric fibers are on the order of microns in diameter. Ultra-filtration applications use finer diameter fibers (100s to 1000 nm) which can be formed via electrospinning. In these cases, composite filter structures have been shown to enhance flow rates of fluids by tailoring multiple polymeric structures of mixed spacing, diameters, and hydrophobicity [1]. Adding anti-microbial functionality to these filters has been achieved through the addition of metallic nanoparticles, such as silver. The particles have been introduced by a variety of methods, ranging from incorporating silver nitrate and subsequently precipitating silver nanoparticles during electrospinning [2] to simple immersion. Silver is not the only metal that exhibits antimicrobial properties; copper has also been shown to exhibit antimicrobial applications when present in nanoparticle form [3]. Please click Additional Files below to see the full abstract