Parameter optimization of an on-chip voltage reference circuitusing evolutionary programming

This paper presents an application of evolutionary programming to parameter optimization in the design of a voltage reference circuit. Designing circuits consists of two steps: topological design and parameter determination. After designing a topology suitable for the circuit, the designer selects an appropriate value for each circuit element from a circuit analysis and his experience. This step is difficult and time consuming because the designer must consider many factors simultaneously. As more precise circuits are required, parameter optimization becomes more complex. The voltage reference circuit, which requires a precise reference voltage independent of power fluctuation and temperature change, is such an example. In this paper, evolutionary programming is used as an effective method of finding good parameter values for the elements of the voltage reference circuit. Simulation results show that this method provides good performance and can be used as an effective method for circuit design     

Knowledge discovery in high-dimensional data: case studies and a user survey for the rank-by-feature framework

Knowledge discovery in high-dimensional data is a challenging enterprise, but new visual analytic tools appear to offer users remarkable powers if they are ready to learn new concepts and interfaces. Our three-year effort to develop versions of the hierarchical clustering explorer (HCE) began with building an interactive tool for exploring clustering results. It expanded, based on user needs, to include other potent analytic and visualization tools for multivariate data, especially the rank-by-feature framework. Our own successes using HCE provided some testimonial evidence of its utility, but we felt it necessary to get beyond our subjective impressions. This paper presents an evaluation of the hierarchical clustering explorer (HCE) using three case studies and an e-mail user survey (n=57) to focus on skill acquisition with the novel concepts and interface for the rank-by-feature framework. Knowledgeable and motivated users in diverse fields provided multiple perspectives that refined our understanding of strengths and weaknesses. A user survey confirmed the benefits of HCE, but gave less guidance about improvements. Both evaluations suggested improved training methods.     

Semi-global observer for multi-output nonlinear systems

We present an explicit form of nonlinear observers for a class of multi-input multi-output systems. Observer construction for multi-output nonlinear systems is not a trivial extension of single output case, especially when the global error convergence is of interest. In this paper, we consider a class of systems in which the subsystem for each output has a triangular dependence on the states of that subsystem itself, and the overall system has a block triangular form for each subsystem. Hence, the contribution is to extend the results existing in the literature in that interconnections between the subsystems are allowed. The construction is based on the saturation of some estimates, which is originated by Khalil and Esfandiari for the use of semi-global output feedback control.     

Energy Efficient Scheduling of Real-Time Tasks on Multicore Processors

Multicore processors deliver a higher throughput at lower power consumption than unicore pro- cessors. In the near future, they will thus be widely used in mobile real-time systems. There have been many research on energy-efficient scheduling of real-time tasks using DVS. These approaches must be modified for multicore processors, however, since normally all the cores in a chip must run at the same performance level. Thus blindly adopting existing DVS algorithms which do not consider the restriction will result in a waste of energy. This article suggests Dynamic Repartitioning algorithm based on existing partitioning approaches of multiprocessor systems. The algorithm dynamically balances the task loads of multiple cores to optimize power consumption during execution. We also suggest Dynamic Core Scaling algorithm which adjusts the number of active cores to reduce leakage power consumption under low load conditions. Simulation results show that Dynamic Repartitioning can produce energy savings of about 8% even with the best energy-efficient partitioning algorithm. The results also show that Dynamic Core Scaling can reduce energy consumption by about 26% under low load conditions.     

Calibration-free augmented reality in perspective

This paper deals with video-based augmented reality and proposes an algorithm for augmenting a real video sequence with views of graphics objects without metric calibration of the video camera by representing the motion of the video camera in projective space. A virtual camera, by which views of graphics objects are generated, is attached to a real camera by specifying image locations of the world coordinate system of the virtual world. The virtual camera is decomposed into calibration and motion components in order to make full use of graphics tools. The projective motion of the real camera recovered from image matches has the function of transferring the virtual camera and makes the virtual camera move according to the motion of the real camera. The virtual camera also follows the change of the internal parameters of the real camera. This paper shows the theoretical and experimental results of our application of nonmetric vision to augmented reality     

Characterization of electromagnetic properties of polymeric composite materials with free space method

The introduction of microwave radars during the second World War altered the air defense scenario significantly, and this led to the development of the “stealth” techniques. By reducing the detectability of aircrafts or warships, of which the radar cross section (RCS) is a measure, they could evade radar detection, which affected not only the mission success rate but also survival of them in the hostile territory. In the very early stage of the research on stealth techniques, many researches were mainly concentrated on the reduction of RCS and development of radar absorbing materials (RAM), but nowadays studies on investigating the radar absorbing structures (RAS) using fiber reinforced polymeric composite materials are becoming popular research field.

In this study, electromagnetic characteristics of unidirectional E-glass fiber reinforced epoxy composites were tested with free space methods, which can overcome drawbacks of conventional cavity and waveguide methods. Complex relative permittivities of low-loss composite were measured with respect to the angle between the fiber orientation and the electric field vector of EM wave in X-band frequency range. From the experimental data, empirical relation between the dielectric properties of composites and test variable was suggested and verified.     

Modeling and analysis for the development of Lightweight Piezoceramic Composite Actuators (LIPCA)

This paper focuses on the modeling and analysis of Lightweight Piezoceramic Composite Actuators (LIPCA) for developmental purposes. A simple analytical model and a numerical model for predicting the displacement of the actuators due to both an applied input voltage and transverse load to the piezoelectric ceramic layer are presented. The analytical model describing the laminated beam actuation results in two primary design parameters, an actuation coefficient of a laminated beam C_ulb and the bending stiffness of a laminated beam EI_lb. The C_ulb is a parameter when maximum displacement is required. The bending stiffness affects the displacement performance when a transverse load is applied to the actuators. An experiment was performed to verify the proposed laminated beam model. The numerical model, a NASTRAN finite element model, is used to assess the effect of initial dome heights of actuators on the displacement. An increase in the initial dome height produces a positive effect for the low anisotropic actuators and gives a negative effect for the high anisotropic actuators. In conclusion, the results indicate that designing to maximize the C_ulb, the EI_lb, and the initial dome height of the low anisotropic actuators could generate LIPCA-type actuators with larger displacement and higher force.     

AFM study of phase-separated morphology in immiscible blend thin films

Phase-separation behavior of polystyrene (PS) and poly(methyl methacrylate) (PMMA) 1:1 blend film has been studied as a function of film thickness and component by adding PS-b-PMMA diblock copolymer. After annealing, PS is phase-separated into circular-shaped bumps on a PMMA layer. The bump number is inversely proportional to the film thickness in log-log plot while the slope is invariable for the blends with and without 5% PS-b-PMMA diblock copolymer. The bump size and inter-bump spacing are also affected by both the film thickness and addition of the block copolymer.     

Inward torque and high-friction handles can reduce required muscle efforts for torque generation

OBJECTIVE: The effects of handle friction and torque direction on muscle activity and torque are empirically investigated using cylindrical handles. BACKGROUND: A torque biomechanical model that considers contact force, friction, and torque direction was evaluated using different friction handles. METHODS: Twelve adults exerted hand torque in opposite directions about the long axis of a cylinder covered with aluminum or rubber while grip force, torque, and finger flexor electromyography (EMG) were recorded. In addition, participants performed grip exertions without torque, in which they matched the EMG level obtained during previous maximum torque exertions, to allow us to determine how grip force was affected by the absence of torque. RESULTS: (a) Maximum torque was 52% greater for the high-friction rubber handle than for the low-friction aluminum handle. (b) Total normal force increased 33% with inward torque (torque applied in the direction fingertips point) and decreased 14% with outward torque (torque in the direction the thumb points), compared with that with no torque. Consequently, maximum inward torque was 45% greater than maximum outward torque. (c) The effect of torque direction was greater for the high-friction rubber handle than for the low-friction aluminum handle. CONCLUSION: The results support the proposed model, which predicts a large effect of torque direction when high-friction handles are gripped. APPLICATION: Designing tasks with high friction and inward rotations can increase the torque capability of workers of a given strength, or reduce required muscle activities for given torque exertions, thus reducing the risk of fatigue and musculoskeletal disorders.     

Analyzing the impact of a firm's capability on outsourcing success: A process perspective

We investigated the effect of a firm's resource capabilities and interaction processes on the success of IT outsourcing. Grounded in available literature on outsourcing relationship and process theory as well as a resource-based view of the IT resource capability, a conceptual model was composed to examine the causal structure of capability, process, and relationship in IT outsourcing. We identified the firm's resource capability factors and, based on the premise that relationship intensity should be affected by the IT outsourcing process, we developed a first-order factor analysis of resource capabilities in the interactions between the outsourcer and provider. Results of empirical testing using responses from 267 IT outsourcing project teams in Korea supported most of our hypotheses. The integration of corporate IT resource and capability theories with social exchange theory distinguishes our research from that of others, who have generally treated these theories separately.