Formation stabilization and resizing based on the control of inter‐agent distances

We propose a control strategy that could steer the group of mobile agents in the plane to achieve a specified formation. The control law could be implemented in a fully decentralized manner so that each agent moves on their own local reference frame. Under the acyclic minimally persistent graph topology, each agent measures the relative displacements of neighboring agents and then adjusts the distances between them to achieve the desired formation. As well as achieving a fixed formation, we could resize the formation only by changing the leader edge, which connects the leader with the first‐follower in acyclic minimally persistent graph, without changing the structures of the control law. Copyright © 2014 John Wiley & Sons, Ltd.     

Observer‐based decentralized adaptive control for large‐scale pure‐feedback systems with unknown time‐delayed nonlinear interactions

This paper presents an approximation design for a decentralized adaptive output‐feedback control of large‐scale pure‐feedback nonlinear systems with unknown time‐varying delayed interconnections. The interaction terms are bounded by unknown nonlinear bounding functions including unmeasurable state variables of subsystems. These bounding functions together with the algebraic loop problem of virtual and actual control inputs in the pure‐feedback form make the output‐feedback controller design difficult and challenging. To overcome the design difficulties, the observer‐based dynamic surface memoryless local controller for each subsystem is designed using appropriate Lyapunov‐Krasovskii functionals, the function approximation technique based on neural networks, and the additional first‐order low‐pass filter for the actual control input. It is shown that all signals in the total controlled closed‐loop system are semiglobally uniformly bounded and control errors converge to an adjustable neighborhood of the origin. Finally, simulation examples are provided to illustrate the effectiveness of the proposed decentralized control scheme. Copyright © 2013 John Wiley & Sons, Ltd.     

Data generation and representation method for 3D video conferencing using programming by demonstration

Video conferencing provides an environment for multiple users linked on a network to have meetings. Since a large quantity of audio and video data are transferred to multiple users in real time, research into reducing the quantity of data to be transferred has been drawing attention. Such methods extract and transfer only the features of a user from video data and then reconstruct a video conference using virtual humans. The disadvantage of such an approach is that only the positions and features of hands and heads are extracted and reconstructed, whilst the other virtual body parts do not follow the user. In order to enable a virtual human to accurately mimic the entire body of the user in a 3D virtual conference, we examined what features should be extracted to express a user more clearly and how they can be reproduced by a virtual human. This 3D video conferencing estimates the user’s pose by comparing predefined images with a photographed user’s image and generates a virtual human that takes the estimated pose. However, this requires predefining a diverse set of images for pose estimation and, moreover, it is difficult to define behaviors that can express poses correctly. This paper proposes a framework to automatically generate the pose-images used to estimate a user’s pose and the behaviors required to present a user using a virtual human in a 3D video conference. The method for applying this framework to a 3D video conference on the basis of the automatically generated data is also described. In the experiment, the framework proposed in this paper was implemented in a mobile device. The generation process of poses and behaviors of virtual human was verified. Finally, by applying programming by demonstration, we developed a system that can automatically collect the various data necessary for a video conference directly without any prior knowledge of the video conference system.     

An object-based middleware supporting efficient interoperability on a smart home network

This paper proposes a novel object-based home network middleware for supporting the interoperability among home devices and smart grid devices. This middleware provides various types of abstract objects for flexible representation of heterogeneous home devices, which are classified based on their characteristics. It is also flexible enough to allow addition of new protocols and message conversion between different protocols through an abstraction layer, which are not supported by existing home network middlewares so that various protocols can be supported. As a result, it can be utilized to provide the interoperability among a variety of devices from sensors to typical home appliances as well as smart grid devices such as a home electric generator and a battery, which adopt different protocols. In order to demonstrate that home devices and smart grid devices are interoperable through the proposed middleware, we implement applications based on the middleware on a target platform consisting of embedded boards, sensors and laptops for emulation purposes of a home network. According to our emulation, this middleware can provide efficient interoperability among home devices and smart grid devices for future energy efficient home.     

Green practices-IS alignment and environmental performance: The mediating effects of coordination

The problem of environmental sustainability has been growing in recent years with an interest from both researchers and practitioners. A major gap that exists is the absence of empirical studies that addressed business value of green IS (information systems). Thus, drawing on the resource-based view of the firm and IT (information technology) business value literature, this study aims to develop a comprehensive research model of green practice-IS alignment, the key cross-functional coordination of green practices with manufacturing and marketing functions, and firm performance. The study provides a better understanding of the relationship between green practice-manufacturing coordination and green practice-marketing coordination, and how both variables mediated the relationship between green practices-IS alignment and environmental performance. The data used in this study were collected from manufacturing firms. The results show that a firm’s green practices-IS alignment had a positive effect on both green practices-manufacturing coordination and green practices-marketing coordination. In turn, both green practices-manufacturing coordination and green practices-marketing coordination are the significant predictors of environmental performance. Meanwhile, green practices-IS alignment had an indirect effect on environmental performance via both green practices-manufacturing coordination and green practices-marketing coordination. Moreover, the findings of this study show that environmental performance is an important predictor of economic performance.     

Forward kinematic singularity avoiding design of a Schönflies motion generator by asymmetric attachment of subchains

In most of the previous studies on parallel mechanisms (PMs), architectural design mainly relying on symmetric geometry was investigated without in-depth analysis of its performance. This work demonstrates that such a symmetric geometry of multiple subchains sometimes induces a forward kinematic singularity which degrades the overall kinematic performance of PMs within the desired workspace and claims that an asymmetric attachment of those subchains on a moving platform can effectively resolve such a singularity problem. A 4-Degree-of-Freedom (DOF) PM exhibiting Schönflies motions is examined as an example device. First, its mobility analysis and kinematic modeling via screw theory are conducted. Then a singularity analysis based on Grassmann line geometric conditions is carried out, and the forward kinematic singularities of the mechanism are identified and verified by simulations. Based on these analysis and simulations, a forward kinematic singularity-free design is suggested. To show the high potential of the device in practical applications, its output stiffness and dynamic motion capability are examined. Then a prototype is built and its motions capability is verified through experiments.     

Development of a nanofluidic preconcentrator with precise sample positioning and multi-channel preconcentration

A nanofluidic preconcentrator with the capability of rapidly preconcentrating and precisely positioning protein bands in multiple microchannels has been developed for highly sensitive detection of biomolecules. A novel electrical resistive network model is developed to guide the design of the nanofluidic preconcentrator which consists of a PDMS slab bonded with a glass slide. In the prototype design, two microchannels (23 mm long, 25–50 μm wide, and 5–15 μm deep), one preconcentration microchannel and one ground microchannel are connected in the middle via 16 nanochannels (25–50 μm long, 25 μm wide, and 50–80 nm deep). With two sets of optimal voltage settings applied on the opposite ends of the nanofluidic chip, the ion depletion region and electrokinetic trapping were generated to carry out the preconcentration. With the optimal voltage settings (30–30 V) predicted by the model, the ionic current of the nanochannel in our optimized preconcentrator was adjusted to be greater than the threshold value (3.9 nA) needed for the occurrence of the preconcentration, and a preconcentration factor >10⁵ was achieved in 5 min. The sample positioning capability of the preconcentrator was demonstrated by adjusting the applied voltages and moving the preconcentrated protein bands to multiple sites by a distance from several micrometers to several millimeters in the preconcentration channel. The multi-channel preconcentration capability was also demonstrated by preconcentrating two protein bands in two separate microchannels. In this work, the resistive network model was developed and validated to optimize nanofluidic preconcentrators for rapid, high throughput and highly sensitive sensing of low abundance analytes.     

Diameter variability of cycles and tori

The diameter of a graph is an important factor for communication as it determines the maximum communication delay between any pair of processors in a network. Graham and Harary [N. Graham, F. Harary, Changing and unchanging the diameter of a hypercube, Discrete Applied Mathematics 37/38 (1992) 265-274] studied how the diameter of hypercubes can be affected by increasing and decreasing edges. They concerned whether the diameter is changed or remains unchanged when the edges are increased or decreased. In this paper, we modify three measures proposed in Graham and Harary (1992) to include the extent of the change of the diameter. Let D^-k(G) is the least number of edges whose addition to G decreases the diameter by (at least) k, D⁺⁰(G) is the maximum number of edges whose deletion from G does not change the diameter, and D^+k(G) is the least number of edges whose deletion from G increases the diameter by (at least) k. In this paper, we find the values of D^-k(C_m), D^-1(T_m,n), D^-2(T_m,n), D⁺¹(T_m,n), and a lower bound for D⁺⁰(T_m,n) where C_m be a cycle with m vertices, T_m,n be a torus of size m by n.     

Latent-space variational bayes

Variational Bayesian Expectation-Maximization (VBEM), an approximate inference method for probabilistic models based on factorizing over latent variables and model parameters, has been a standard technique for practical Bayesian inference. In this paper, we introduce a more general approximate inference framework for conjugate-exponential family models, which we call Latent-Space Variational Bayes (LSVB). In this approach, we integrate out model parameters in an exact way, leaving only the latent variables. It can be shown that the LSVB approach gives better estimates of the model evidence as well as the distribution over latent variables than the VBEM approach, but in practice, the distribution over latent variables has to be approximated. As a practical implementation, we present a First-order LSVB (FoLSVB) algorithm to approximate this distribution over latent variables. From this approximate distribution, one can estimate the model evidence and the posterior over model parameters. The FoLSVB algorithm is directly comparable to the VBEM algorithm and has the same computational complexity. We discuss how LSVB generalizes the recently proposed collapsed variational methods [20] to general conjugate-exponential families. Examples based on mixtures of Gaussians and mixtures of Bernoullis with synthetic and real-world data sets are used to illustrate some advantages of our method over VBEM.     

Improving children’s reading comprehension and use of strategies through computer-based strategy training

In this study, the attention–selection–organization–integration–monitoring (ASOIM) model, revised from Mayer’s [Mayer, R. E. (1996). Learning strategies for making sense out of expository text: The SOI model for guiding three cognitive processes in knowledge construction. Educational Psychology Review, 8, 357–371] SOI model of text comprehension, was used as a foundation to design a multi-strategy based system, which was named Computer Assisted Strategy Teaching and Learning Environment (CASTLE). CASTLE aims to enhance learners’ abilities of using reading strategies and text comprehension. The effects of CASTLE on students with different reading abilities were empirically evaluated. 130 sixth graders took part in an 11-week computer-based reading strategies course. The results show that CASTLE helps to enhance the students’ use of strategies and text comprehension at all ability levels.