Spectral clustering with physical intuition on spring–mass dynamics

In this paper, we provide a new insight into clustering with a spring–mass dynamics, and propose a resulting hierarchical clustering algorithm. To realize the spectral graph partitioning as clustering, we model a weighted graph of a data set as a mass–spring dynamical system, where we regard a cluster as an oscillating single entity of a data set with similar properties. And then, we describe how oscillation modes are related with eigenvectors of a graph Laplacian matrix of the data set. In each step of the clustering, we select a group of clusters, which has the biggest number of constituent clusters. This group is divided into sub-clusters by examining an eigenvector minimizing a cost function, which is formed in such a way that subdivided clusters will be balanced with large size. To find k clusters out of non-spherical or complex data, we first transform the data into spherical clusters located on the unit sphere positioned in the (k−1)-dimensional space. In the sequel, we use the previous procedure to these transformed data. The computational experiments demonstrate that the proposed method works quite well on a variety of data sets, although its performance degrades with the degree of overlapping of data sets.     

Synchronization of discrete-time complex dynamical networks with interval time-varying delays via non-fragile controller with randomly occurring perturbation

This paper addresses synchronization problem for discrete-time complex dynamical networks with interval time-varying delays. In order to achieve the synchronization, a feedback controller subjected to randomly occurring perturbations will be considered. The randomly occurring perturbations are assumed to belong to the Binomial sequence. By constructing a suitable Lyapunov–Krasovskii functional, and utilizing reciprocally convex approach and Finsler?s lemma, the synchronization criteria for the networks are established in terms of linear matrix inequalities (LMIs) which can be easily solved by various effective optimization algorithms. The networks are represented by the use of Kronecker product technique. The effectiveness of the proposed methods will be verified via numerical examples.     

Programmed sample delivery on a pressurized paper

This paper reports a method to control the fluid flow in paper-based microfluidic devices simply by pressing over the channel surface of paper, thereby decreasing the pore size and permeability of a non-woven polypropylene sheet. As a result, fluid resistance is increased in the pressed region and causes flow rate to decrease. We characterize the decrease of flow rate with respect to different amounts of pressure applied, and up to 740% decrease in flow velocity was achieved. In addition, we demonstrate flow rate control in a Y-shaped merging paper and sequential delivery of multiple color dyes in a three-branched paper. Furthermore, sequential delivery of multiple fluid samples is performed to demonstrate its application in multi-step colorimetric immunoassay, which shows a 4.3-fold signal increase via enhancement step.     

Interactive Influences of Perceived Social Contexts on the Reading Achievement of Urban Middle Schoolers with Learning Disabilities

This study examined the effects of social influences in the lives of an ethnically diverse sample of fifth through eighth grade students with and without learning disabilities (LD) using survey data and academic achievement scores collected in 19 Chicago public schools from 1993–1997. Similarities and differences in student perceptions of school, family, and peer group contexts were examined. In addition, longitudinal data were analyzed using hierarchical linear modeling (HLM) to identify contextual influences on changes in student reading achievement over time. Comparisons of student responses confirm and extend existing findings in the literature concerning the perceptions of students with LD of their social environments. In particular, having a learning disability was associated with consistent, mostly negative, effects on social relations across the contexts of students’ lives, regardless of gender, race, grade, and socioeconomic status. In addition, student perceptions of their friendship groups were found to have small, but significant, effects on their growth in reading achievement over the course of middle school. While students with and without LD had somewhat different views of their social contexts, the processes working within these environments appeared to affect their reading achievement in similar ways. The results suggest that careful attention should be paid to the social contexts of students’ lives when planning academic interventions.