1,721,297 research outputs found
Coupling structural and functional models for interaction design
No full textModel-based interaction design is a promising approach to the problem of building sophisticated interactive systems. Although many models and model-based design methods have been proposed, in practice their effectiveness has tended to be limited to solving fragmented design problems. One factor that has diminished the effectiveness of previous approaches has been their inability to integrate the various models used for different aspects of the overall design problem. This paper proposes a novel approach for combining a structural model and a functional model for complicated interaction design. Formal correspondence between the models is defined and a conversion process to transform from one model to the other and vice versa is introduced. The functional model, OCD, is an efficient technique for representing task procedures, while the structural model, statechart, is well suited to representing system behavior. The usability needs and system requirements are introduced into the design process through either representation. Then, the constraints formed by a decision in a model can be seen by the designer in the other model through transformation. The possibility of automatic conversion between the models warrants the consistence between the models through the design process even when the models should continually evolve. (C) 2003 Elsevier B.V. All rights reserved
Low-power Log-MAP decoding based on reduced metric memory access
No full textDue to the powerful error correcting performance, turbo codes have been adopted in many wireless communication standards such as W-CDMA and CDMA2000. Although several low-power techniques have been proposed, power consumption is still a major issue to be solved in practical implementations. Since turbo decoding is classified as a memory-intensive algorithm, reducing memory accesses is crucial to achieve a low power design. To reduce the number of memory accesses for maximum a posteriori (MAP) decoding, this paper proposes an approximate reverse calculation method that can be implemented with simple arithmetic operations such as addition and comparison. Simulation results show that the proposed method applied to the W-CDMA standard reduces the access rate of the backward metric memory by 87% without degrading error-correcting performance. A prototype log-MAP decoder based on the proposed reverse calculation achieves 29% power reduction compared to a conventional decoder that does not use the reverse calculation.This work
was supported in part by the Institute of Information Technology Assessment
through the ITRC, by the Korea Science and Engineering Foundation through
MICROS center and by IC Design Education Center
A facile preparation of highly interconnected macroporous poly(D,L-lactic acid-co-glycolic acid) (PLGA) scaffolds by liquid-liquid phase separation of a PLGA-dioxane-water ternary system
No full textRegular and highly interconnected macroporous scaffolds ranging in size from 50 to 150 mum were fabricated from poly(D,L-lactic acid-co-glycolic acid) (PLGA)-dioxane-water ternary systems via thermally induced phase separation (TIPS) without any surfactant or other additives. The effect on scaffold morphology of processing parameters including quenching temperature, polymer concentration, solvent composition and molecular weight, was investigated as a function of quenching time. The cloud-point temperature of the polymer solution was found to depend on polymer concentration, solvent composition, and polymer molecular weight. The water content in the solvent mixture had the greatest effect on the cloud-point temperature. The optimal quenching temperature for preparing macroporous interconnected scaffolds from a 9 wt% PLGA solution (dioxane-water = 87/13, by wt) was less than - 7 degreesC. In low viscosity PLGA solutions, sedimentation of the polymer rich phase occurred due to the segregation of the separated phases under gravity. This led to the formation of scaffolds with irregular and closed pores. (C) 2003 Elsevier Science Ltd. All rights reserved.the Korea Research
Foundation Gran
A NEW STATE FEEDBACK-CONTROL OF RESONANT CONVERTERS
No full textA new state feedback control that can be easily implemented is proposed to improve the stability and dynamic characteristics of resonant converters. An important characteristic of the system with the proposed control is the reduction of order in the discrete time domain. The design parameters of the proposed control are reduced by one, compared with those of the conventional linear state feedback control, and the design procedure is similar to that of a variable-structure system control. The proposed control is illustrated by its application to a series resonant converter. The experimental results confirm the validity of the proposed control
A Discrete Time-Domain Modeling and Analysis of Inner-Feedback-Controlled Series Resonant Converter
No full textContinuous generation of hydrogel beads and encapsulation of biological materials using a microfluidic droplet-merging channel
No full textIn this paper, we describe a method for encapsulation of biomaterials in hydrogel beads using a microfluidic droplet-merging channel. We devised a double T-junction in a microfluidic channel for alternate injection of aqueous fluids inside a droplet unit carried within immiscible oil. With this device, hydrogel beads with diameter < 100 mu m are produced, and various solutions containing cells, proteins and reagents for gelation could merge with the gel droplets with high efficiency in the broad range of flow rates. Mixing of reagents and reactions inside the hydrogel beads are continuously observed in a microchannel through a microscope. By enabling serial injection of each liquid with the dispersed gel droplets after they are produced from the oil-focusing channel, the device simplifies the sample preparation process, and gel-bead fabrication can be coupled with further assay continuously in a single channel. Instantaneous reactions of enzyme inside hydrogel and in-situ formation of cell-containing beads with high viability are demonstrated in this report
Immobilization of cell adhesive RGD peptide onto the surface of highly porous biodegradable polymer scaffolds fabricated by a gas foaming/salt leaching method
No full textA cell adhesive peptide moiety, Gly-Arg-Gly-Asp-Tyr (GRGDY), was immobilized onto the Surface of highly porous biodegradable polymer scaffolds for enhancing cell adhesion and function. A carboxyl terminal end of poly(D,L-lactic-co-glycolic acid) (PLGA) was functionalized with a primary amine group by conjugating hexaethylene glycol-diamine. The PLGA-NH2 was blended with PLGA in varying ratios to prepare filius by solvent casting or to fabricate porous scaffolds by a gas foaming/salt leaching method. Under hydrating conditions, the activated GRGDY Could be directly immobilized to the surface exposed amine Groups of the PLGA-NH2 blend films or scaffolds. For the PLGA blend films, the surface density of GRGDY, surface wettability change. and cell adhesion behaviors were characterized. The extent of cell adhesion was substantially enhanced by increasing the blend ratio of PLGA-NH2 to PLGA. The level of an alkaline phosphatase activity, measured as a degree of cell differentiation. was also enhanced as a result of the introduction of cell adhesive peptides. (C) 2004 Elsevier Ltd. All rights reserved.the Korea Science and
Engineering Foundation (R01-2003-000-10362-0) and
the Korea Research Foundation (X01524), Korea
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