Stability and robust stability of positive linear Volterra difference equations

We first introduce a class of positive linear Volterra difference equations. Then, we offer explicit criteria for uniform asymptotic stability of positive equations. Furthermore, we get a new Perron–Frobenius theorem for positive linear Volterra difference equations. Finally, we study robust stability of positive equations under structured perturbations and affine perturbations. Two explicit stability bounds with respect to these perturbations are given. Copyright © 2008 John Wiley & Sons, Ltd.     

Drawing Borders Efficiently

A spreadsheet, especially MS Excel, is probably one of the most popular software applications for personal-computer users and gives us convenient and user-friendly tools for drawing tables. Using spreadsheets, we often wish to draw several vertical and horizontal black lines on selective gridlines to enhance the readability of our spreadsheet. Such situations we frequently encounter are formulated as the Border Drawing Problem (BDP). Given a layout of black line segments, we study how to draw it efficiently from an algorithmic view point, by using a set of border styles and investigate its complexity. (i) We first define a formal model based on MS Excel, under which the drawability and the efficiency of border styles are discussed, and then (ii) show that unfortunately the problem is -hard for the set of the Excel border styles and for any reasonable subset of the styles. Moreover, in order to provide potentially more efficient drawing, (iii) we propose a new compact set of border styles and show a necessary and sufficient condition of its drawability.     

Hotspot analysis of COVID-19 infection using mobile-phone location data

Artificial Life and Robotics - Restrictions on outdoor activities are required to suppress the COVID-19 pandemic. To monitor social risks and control the pandemic through sustainable restrictions,...     

Design systems for gear elements made of cotton fiber-reinforced plastics

We look on the cotton fiber reinforced plastics as industrial gear materials, and have been developing design systems for industrial gears made of cotton fiber-reinforced plastics. In this report, we deal with a method estimating for tooth root stresses caused by bending movements under running conditions. The gear material used was cotton fiber plain woven cloth reinforced phenolic resin laminates. Paper-reinforced phenolic resin laminates, a commonly used material, was used as a control for comparison. The main dimensions of the gears were module 3–5 mm and tooth width 25 mm. First, accelerations of gears were measured under running conditions to estimate dynamic performance. Second, fracture tests of gear teeth were carried out under bending loads. Different fracture modes at tooth roots for cotton fiber-reinforced plastics and phenolic resin gears were observed. The fractures occurred at a high position from the tooth root in the case of the cotton fiber-reinforced plastics gear because the cotton fiber-reinforced plastics had excellent cleavage and shear strength. This gear also had higher strength for tooth bending loads. Third, the mechanical properties of the gears were researched by tensile, bending, and shearing tests. It was clear that the cotton fiber-reinforced plastics had excellent properties in cleavage fracture between laminates and shear strength. Finally, we proposed a design method for this gear, which considers the cleavage and shear strength.     

A ( $2-c\frac{1}{\sqrt{N}}$ )-Approximation Algorithm for the Stable Marriage Problem

We consider the problem of finding a stable matching of maximum size when both ties and unacceptable partners are allowed in preference lists. This problem is NP-hard and the current best known approximation algorithm achieves the approximation ratio 2−c(log N)/N, where c is an arbitrary positive constant and N is the number of men in an input. In this paper, we improve the ratio to , where c is an arbitrary constant that satisfies . A preliminary version of this paper was presented at the 16th Annual International Symposium on Algorithms and Computation, ISAAC 2005.     

Transformation rules for CNOT-based quantum circuits and their applications

This paper introduces a simple but nontrivial set of local transformation rules for designingControl-NOT(CNOT)-based combinatorial circuits. We also provide a proof that the rule set iscomplete, namely, for any two equivalent circuits,S ₁ andS ₂, there is a sequence of transformations, each of them in the rule set, which changesS ₁ toS ₂. Two applications of the rule set are also presented. One is to simulate Resolution with only polynomial overhead by the rule set. Therefore we can conclude that the rule set is reasonably powerful. The other is to reduce the cost of CNOT-based circuits by using the transformations in the rule set. This implies that the rule set might be used for the practical circuit design. Currently Graduate School of Information Science, Nara Institute of Science and Technology Kazuo Iwama, Ph.D.: Professor of Informatics, Kyoto University, Kyoto 606-8501, Japan. Received BE, ME, and Ph.D. degrees in Electrical Engineering from Kyoto University in 1978, 1980 and 1985, respectively. His research interests include algorithms, complexity theory and quantum computation. Editorial board of Information Processing Letters and Parallel Computing. Council Member of European Association for Theoretical Computer Science (EATCS). Shigeru Yamashita, Ph.D.: Associate Professor of Graduate School of Information Science, Nara Instutute of Science and Technology, Nara 630-0192, Japan. He received his B.E., M.E. and Ph.D. degrees in information science from Kyoto University, Kyoto, Japan, in 1993, 1995 and 2001, respectively. His research interests include new type of computer architectures and quantum computation. He received the 2000 IEEE Circuits and Systems Society Transactions on Computer-Aided Design of Integrated Circuits and Systems Best Paper Award.     

Dual excitation electrostatic stepping motor

Electrostatic motors have been believed to be weaker than electromagnetic motors which are typically used for mechatronic devices. However, electrostatic motors are preferable to electromagnetic ones for micromechanical applications since their force per volume ratios increase as their dimensions are reduced. It follows that a large output should be obtained if a large number of such small motors with high force per volume ratios are linked and their outputs are aggregated. This paper proposes an electrostatic drive technology which is applicable to such a large-output motor. The element motor, called the dual excitation electrostatic stepping motor, consists of a pair of plastic films, slider and stator. Both films have parallelly located electrodes embedded in them, and the slider moves along the surface of the stator when defined rectangular pulse voltages are applied to the electrodes both in the slider and the stator. The force generation characteristic of the electrostatic motor is calculated by the surface charge method. A prototype fabricated using flexible print board technology weighs 7 g and generates a thrust force of 1.9 N at an excitation of ± 1000 V. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 119(3): 94–103 1997     

A high-power electrostatic motor using skewed electrodes

This paper describes a new type of high-power electrostatic motor equipped with skewed electrodes. The authors have developed several types of high-power electrostatic motors. Among them, the dual excitation multiphase electrostatic drive (DEMED) has the best performance in terms of power. Its power/weight ratio is almost the same as that of the most advanced conventional electromagnetic motors. However, DEMED exhibits a large force ripple leading to such disadvantages as low controllability, high noise, and vibration. To overcome these disadvantages, the authors have proposed to apply the skew technique to DEMED and have analyzed the effects of skewing the electrodes. The analysis has shown that appropriate skewing can reduce the force ripple considerably. In this paper, we further analyze the shape of the electrodes. A new type of motor incorporating the results of the analysis is fabricated and tested. Using the new DEMED with skewed electrodes (V-DEMED), the slider motion becomes much smoother, noise and vibration are reduced, and efficiency improves, without compromising the thrust force. © 1998 Scripta Technica, Electr Eng Jpn, 125(3): 50–58, 1998     

Synthesis and in vitro biodegradation of pure octacalcium phosphate spheres

Octacalcium phosphate (OCP) is a key precursor of biological apatite in hard tissues with excellent osteoconductive and biodegradable properties for bone regeneration. OCP spherical granules are expected to be useful as drug delivery carriers, since OCP has high specific surface area. Although there have been some reports of OCP sphere preparation, methods for preparing pure OCP spheres are limited. The objective of this study is the preparation of spherical granules of pure OCP and assessment of their in vitro biodegradation in physiological conditions. We successfully prepared spherical pure OCP granules with a size of ~500 µm without any organic additives by simple immersion of α-tricalcium phosphate spherical granules in pH 5.0 acetate buffered solutions at 60°C. The granules had core-shell structure composed of OCP crystals different particle size. The spherical granules showed 20%-40% in vitro degradation in physiological conditions; however, the phase transition of OCP was not significantly observed.