IEEE Int Research Articles

Distilling structure in scientific workflows

Distilling structure in scientific workflows

A digital hardware fast algorithm and FPGA-based prototype for a novel 16-point approximate DCT for image compression applications

The discrete cosine transform (DCT) is the key step in many image and video coding standards. The eight-point DCT is an important special case, possessing several low-complexity approximations widely investigated. However, the 16-point DCT transform has energy compaction advantages. In this sense, this paper presents a new 16-point DCT approximation with null multiplicative complexity. The proposed transform matrix is orthogonal and contains only zeros and ones. The proposed transform outperforms the well-known Walsh–Hadamard transform and the current state-of-the-art 16-point approximation. A fast algorithm for the proposed transform is also introduced. This fast algorithm is experimentally validated using hardware implementations that are physically realized and verified on a 40 nm CMOS Xilinx Virtex-6 XC6VLX240T FPGA chip for a maximum clock rate of 342 MHz. Rapid prototypes on FPGA for a 8-bit input word size show significant improvement in compressed image quality by up to 1–2 dB at the cost of only eight adders compared to the state-of-art 16-point DCT approximation algorithm in the literature (Bouguezel et al 2010 Proc. 53rd IEEE Int. Midwest Symp. on Circuits and Systems).

Overall performance evaluation of adaptive multi rate 06.90 speech codec based on code excited linear prediction algorithm using MATLAB

Today, the primary constrain in wireless communication system is limited bandwidth and power. Wireless systems involved in transmission of speech envisage that efficient and effective methods need to be developed for maintaining quality-of-speech, especially at the receiving end, with maximum saving of bandwidth and power. Amongst all elements of the communication system (transmitter, channel and receiver), transmission channel (carrier of information/data, also called the medium) is the most critical and plays a key role in the transmission and reception of information/data. Channel conditions decide the quality of speech at receiver. Modeling a channel is a complex task. Many techniques are adopted to mitigate the effect of the channel. AMR (Adaptive Multi Rate) is one such technique that counteracts the deleterious effect of the channel on speech. This technique employs variable bit rate that dynamically switches to specific modes of operation (switching bit rates--called modes of operation) depending upon the channel conditions. In this paper, the application of Code Excited Linear Prediction (CELP) source coder on speech followed by AMR codec is investigated and studied. An e-test bench using MATLAB is created to implement the CELP based AMR Codec scheme, and the same studied and investigated through a series of simulation. Here, both subjective and objective evaluations are carried out. Objective evaluations are categorized into waveform based, spectral based and perceptual based analysis. The results of the simulations are recorded and compared in various graphs and tables, which include calculation of various parameters like Absolute Error (ABS), Mean Square Error (MSE), Root Mean Square Error (RMSE), Signal to Noise Ratio (SNR), segmental SNR (segSNR) (Y. Hu and P. Loizou in Proc. IEEE Int. Conf. Acoust., Speech, Signal Process., vol. 1, pp. 153---156, 2006a; Proc. Interspeech, pp. 1447---1450, 2006b), Weighted-Slope Spectral distance (WSS) (Y. Hu and P. Loizou in Speech Commun. 49, 588---601, 2007), Perceptual Evaluation of Speech Quality (PESQ) (ITU-T rec. P.862, 2000), Log-Likelihood Ratio (LLR), Itakura-Saito Distance measure (ISD), Cepstrum Distance Measures (CEP) (V. Turbin and N. Faucheur in Proc. Online Workshop Meas. Speech Audio Quality Netw., pp. 81---84, 2005), Frequency Weighted Segmental SNR (fwSNRseg), Predicted rating of overall Quality (Covl), Rating of Speech Distortion (Csig), Rating of Background Distortion (Cbak) (ITU-T rec. P.835, 2003) and MeanOpinion Score (MOS). Simulation results clearly advocate that, it is possible to producevariable bitrates (tuning to channel conditions) in CELP coder by affecting coefficients of the coder while still maintaining a good quality of speech. Further, higher the bit-rate used, the better is the quality of speech (which can be verified from the results obtained with PESQ and MOS analysis) and at the same time offered simulation delay time also increases.

Optimal eavesdropping on quantum key distribution without quantum memory

We consider the security of the BB84 (Bennett and Brassard 1984 Proc. IEEE Int. Conf. on Computers, Systems, and Signal Processing pp 175–9), six-state (Bruß 1998 Phys. Rev. Lett. 81 3018) and SARG04 (Scarani et al 2004 Phys. Rev. Lett. 92 057901) quantum key distribution protocols when the eavesdropper does not have access to a quantum memory. In this case, Eve’s most general strategy is to measure her ancilla with an appropriate positive operator-valued measure designed to take advantage of the post-measurement information that will be released during the sifting phase of the protocol. After an optimization on all the parameters accessible to Eve, our method provides us with new bounds for the security of six-state and SARG04 against a memoryless adversary. In particular, for the six-state protocol we show that the maximum quantum bit error ratio for which a secure key can be extracted is increased from 12.6% (for collective attacks) to 20.4% with the memoryless assumption.

A 915 MHz SAW Sensor Correlator System

Previous work has been presented on passive wireless surface-acoustic-wave (SAW) sensors using the orthogonal frequency coding (OFC) technique (Malocha et ah, Proc. Int. Soc. Opt. Eng. (SPIE), Aug. 23-27,2004, vol. 2, pp. 1082-1085), Pavlina et al., Proc. IEEE Int. Conf. RFID, 2009, pp. 110-115). This paper will present a SAW sensor correlator system and its key operational parameters. Description of the radio frequency (RF) transceiver system and the OFC SAW temperature sensors is provided for parameter characterization. The system is based on a software radio approach and an analysis of the analog-to-digital converter (ADC) parameters and receiver noise in temperature extraction is presented. Initial experimental results for a four-sensor system operating over a 280°C range are given.

Finite-Element Modeling of Soft Tissue Rolling Indentation

We describe a finite-element (FE) model for simulating wheel-rolling tissue deformations using a rolling FE model (RFEM). A wheeled probe performing rolling tissue indentation has proven to be a promising approach for compensating for the loss of haptic and tactile feedback experienced during robotic-assisted minimally invasive surgery (H. Liu, D. P. Noonan, B. J. Challacombe, P. Dasgupta, L. D. Seneviratne, and K. Althoefer, "Rolling mechanical imaging for tissue abnormality localization during minimally invasive surgery, " IEEE Trans. Biomed. Eng., vol. 57, no. 2, pp. 404-414, Feb. 2010; K. Sangpradit, H. Liu, L. Seneviratne, and K. Althoefer, "Tissue identification using inverse finite element analysis of rolling indentation," in Proc. IEEE Int. Conf. Robot. Autom. , Kobe, Japan, 2009, pp. 1250-1255; H. Liu, D. Noonan, K. Althoefer, and L. Seneviratne, "The rolling approach for soft tissue modeling and mechanical imaging during robot-assisted minimally invasive surgery," in Proc. IEEE Int. Conf. Robot. Autom., May 2008, pp. 845-850; H. Liu, P. Puangmali, D. Zbyszewski, O. Elhage, P. Dasgupta, J. S. Dai, L. Seneviratne, and K. Althoefer, "An indentation depth-force sensing wheeled probe for abnormality identification during minimally invasive surgery," Proc. Inst. Mech. Eng., H, vol. 224, no. 6, pp. 751-63, 2010; D. Noonan, H. Liu, Y. Zweiri, K. Althoefer, and L. Seneviratne, "A dual-function wheeled probe for tissue viscoelastic property identification during minimally invasive surgery," in Proc. IEEE Int. Conf. Robot. Autom. , 2008, pp. 2629-2634; H. Liu, J. Li, Q. I. Poon, L. D. Seneviratne, and K. Althoefer, "Miniaturized force indentation-depth sensor for tissue abnormality identification," IEEE Int. Conf. Robot. Autom., May 2010, pp. 3654-3659). A sound understanding of wheel-tissue rolling interaction dynamics will facilitate the evaluation of signals from rolling indentation. In this paper, we model the dynamic interactions between a wheeled probe and a soft tissue sample using the ABAQUS FE software package. The aim of this work is to more precisely locate abnormalities within soft tissue organs using RFEM and hence aid surgeons to improve diagnostic ability. The soft tissue is modeled as a nonlinear hyperelastic material with geometrical nonlinearity. The proposed RFEM was validated on a silicone phantom and a porcine kidney sample. The results show that the proposed method can predict the wheel-tissue interaction forces of rolling indentation with good accuracy and can also accurately identify the location and depth of simulated tumors.

Secure key rate of the BB84 protocol using finite sample bits**A five page abstract of this paper appeared in: Sano Y, Matsumoto R and Uyematsu T 2010 Secure key rate of the BB84 protocol using finite sample bits ISIT 2010: Proc. IEEE Int. Symp. on Information Theory (13–18 June 2010, Austin, TX, USA) pp 2677–2681.

We improve the non-asymptotic key rate shown by Scarani and Renner by proposing several methods to construct tighter conservative confidence intervals of the phase error rate than one previously shown. In addition, we show that the accurate channel estimation method non-asymptotically increases the key rate over the amplitude damping channel as well as the asymptotic case in the BB84 protocol.

Optimum electrostatic force control for fabricating a hybrid UV-curable aspheric lens**Partially based on the following paper, orally presented at IEEE NEMS 2010 conference: Hung K-Y, Chang L-W, Tseng F-G and Hang N T M 2010 Optimum electrostatic-force control for fabricating a hybrid UV-curable aspheric lens 5th IEEE Int. Conf. on Nano/Micro Engineered and Molecular Systems (Xiamen, China, 20–23 January 2010).

The purpose of this paper is to use a hybrid structure and the electrostatic force to fabricate aspheric lenses with high optical transmittance (95% at 405 nm). The hybrid structure is composed of Norland Optical Adhesive 63 (NOA63) (refractive index: 1.5802 at 405 nm) and BK-7 glass (refractive index: 1.5302). OSLO (Optics Software for Layout and Optimization) and CFD (Computational Fluid Dynamics) software packages were used to simulate the electric field gradient between the top and bottom electrodes and to produce the optimum bottom electrode design. Different electrode designs were also tested in order to optimize the morphology of the lens profile. The resulting lens profiles have clear apertures of approximately 0.92 mm with maximum shape errors of less than 0.18% and the spot size of the fabricated aspheric lenses can be controlled to approximately 0.504 µm. This technology can be used as a generic approach to fabricate lenses for applications in various micro-optical systems.

Practical Issues in Deploying Mobile Agents to Explore a Sensor-Instrumented Environment

When an emergency occurs within a building, it is safer to send autonomous mobile agents instead of human responders, to explore the area and identify hazards and victims. Existing exploration algorithms (Svennebring, J. and Koenig, S. (2004) Building terrain-covering Ant robots: a feasibility study. Auton. Robots, 16, 313–332, Ferranti, E., Trigoni, N. and Levene, M. (2007) Brick&Mortar: An On-Line Multi-Agent Exploration Algorithm. ICRA07: Proc. 2007 IEEE Int. Conf. Robotics and Automation, April, pp. 761–767. IEEE Press) allow mobile agents to make distributed navigation decisions by communicating with nearby fixed sensors embedded in the environment. These algorithms are very efficient in terms of exploration time, but they have only been evaluated in simulation environments, where idealized assumptions were made regarding the ability of agents to localize sensors and move accurately towards them. The objective of this work is to investigate practical issues of building a real testbed of mobile agents and fixed sensors, and implementing exploration algorithms in such a testbed. In particular, we describe our experiences from building a real system consisting of a Surveyor SRV-1 robot and Tmote Sky sensors running the Contiki OS (Dunkels, A., Gronvall, B. and Voigt, T. (2004) Contiki — A Lightweight and Flexible Operating System for Tiny Networked Sensors. Proc. 1st Annual IEEE Int. Workshop on Embedded Networked Sensors, November, pp. 455–462). We select two existing exploration algorithms, Ants (Svennebring, J. and Koenig, S. (2004) Building terrain-covering Ant robots: a feasibility study. Auton. Robots, 16, 313–332) and Brick&Mortar (Ferranti, E., Trigoni, N. and Levene, M. (2007) Brick&Mortar: An On-Line Multi-Agent Exploration Algorithm. ICRA07: Proc. 2007 IEEE Int. Conf. Robotics and Automation, April, pp. 761–767. IEEE Press), and discuss challenges in trying to implement them in our testbed. To address these challenges, we propose practical solutions that allow a mobile agent to: (i) identify and localize fixed sensors deployed in its vicinity and (ii) accurately move towards a carefully selected fixed sensor. Using our real network deployment, we derive realistic models of localization and odometry errors. We then insert these error models into a realistic simulation environment, in order to extensively compare Ants and Brick&Mortar, and measure their performance degradation as a result of introducing realistic errors.

Two-Stage Approach for Detection and Reduction of Motion Artifacts in Photoplethysmographic Data

Corruption of photopleythysmograms (PPGs) by motion artifacts has been a serious obstacle to the reliable use of pulse oximeters for real-time, continuous state-of-health monitoring. In this paper, we propose an automated, two-stage PPG data processing method to minimize the effects of motion artifacts. The technique is based on our prior work related to motion artifact detection (stage 1) [R. Krishnan, B. Natarajan, and S. Warren, "Analysis and detection of motion artifacts in photoplethysmographic data using higher order statistics,'' in Proc. IEEE Int. Conf. Acoust., Speech, Signal Process. (ICASSP 2008), Las Vegas, Nevada, Apr. 2008, pp. 613-616] and motion artifact reduction (stage 2) [R. Krishnan, B. Natarajan, and S. Warren, "Motion artifact reduction in photoplethysmography using magnitude-based frequency domain independent component analysis,'' in Proc. 17th Int. Conf. Comput. Commun. Network, St. Thomas, Virgin Islands, Aug. 2008, pp. 1-5]. Regarding stage 1, we present novel and consistent techniques to detect the presence of motion artifact in PPGs given higher order statistical information present in the data. We analyze these data in the time and frequency domains (FDs) and identify metrics to distinguish between clean and motion-corrupted data. A Neyman-Pearson detection rule is formulated for each of the metrics. Furthermore, by treating each of the metrics as observations from independent sensors, we employ hard fusion and soft fusion techniques presented in [Z. Chair and P. Varshney, "Optimal data fusion in multiple sensor detection systems,'' IEEE Trans. Aerosp. Electron. Syst., AES, vol. 1, no. 1, pp. 98-101, Jan. 1986] and [C. C. Lee and J. J. Chao, "Optimum local decision space partitioning for distributed detection,'' IEEE Trans. Aerosp. Electron. Syst., AES, vol. 25, no. 7, pp. 536-544, Jul. 1989], respectively, in order to fuse individual decisions into a global system decision. For stage two, we propose a motion artifact reduction method that is effective even in the presence of severe subject movement. The approach involves an enhanced preprocessing unit consisting of a motion detection unit (MDU, developed in this paper), period estimation unit, and Fourier series reconstruction unit. The MDU identifies clean data frames versus those corrupted with motion artifacts. The period estimation unit determines the fundamental frequency of a corrupt frame. The Fourier series reconstruction unit reconstructs the final preprocessed signal by utilizing the spectrum variability of the pulse waveform. Preprocessed data are then fed to a magnitude-based FD independent component analysis unit. This helps reduce motion artifacts present at the frequencies of the reconstruction components. Experimental results are presented to demonstrate the efficacy of the overall motion artifact reduction method.

Refinement by Interpretation in a General Setting

Refinement by interpretation replaces signature morphisms by logic interpretations as a means to translate specifications and witness refinements. The approach was recently introduced by the authors [M. A. Martins, A. Madeira, and L. S. Barbosa. Refinement via interpretation. In Proc. of 7th IEEE Int. Conf. on Software Engineering and Formal Methods, Hanoi, Vietnam, November 2009. IEEE Computer Society Press] in the context of equational specifications, in order to capture a number of relevant transformations in software design, reuse and adaptation. This paper goes a step forward and discusses the generalization of this idea to deductive systems of arbitrary dimension. This makes possible, for example, to refine sentential into equational specifications and the latter into modal ones. Moreover, the restriction to logics with finitary consequence relations is dropped which results in increased flexibility along the software development process.

The application of particle filters in single trial event-related potential estimation

In this paper, an approach for the estimation of single trial event-related potentials (ST-ERPs) using particle filters (PFs) is presented. The method is based on recursive Bayesian mean square estimation of ERP wavelet coefficients using their previous estimates as prior information. To enable a performance evaluation of the approach in the Gaussian and non-Gaussian distributed noise conditions, we added Gaussian white noise (GWN) and real electroencephalogram (EEG) signals recorded during rest to the simulated ERPs. The results were compared to that of the Kalman filtering (KF) approach demonstrating the robustness of the PF over the KF to the added GWN noise. The proposed method also outperforms the KF when the assumption about the Gaussianity of the noise is violated. We also applied this technique to real EEG potentials recorded in an odd-ball paradigm and investigated the correlation between the amplitude and the latency of the estimated ERP components. Unlike the KF method, for the PF there was a statistically significant negative correlation between amplitude and latency of the estimated ERPs, matching previous neurophysiological findingsSome preliminary results of this work were presented in Mohseni et al (2008b Proc. IEEE Int. Conf. Acoust. Speech Signal Process. (ICASSP) pp 465–68)..

Automated self-assembly programming paradigm: The impact of network topology

In our previous work Li et al., in Proc of 3rd IEEE Int Workshop on Engineering of Automatic & Automation Systems, Potsdam, Germany, 2006, pp 25–34; Li et al., in Proc Workshop on Nature Inspired Cooperative Strategies for Optimization, Granada, Spain, 2006, pp 123–134, we introduced automated self-assembly programming paradigm (ASAP2) using unguided self-assembly and swarm-inspired methodologies. We investigated how external environment settings affect software self-assembly speed and diversity of the generated programs. In this paper, we extend our previous work with a diversified compartments approach based on general graphs. This diversified compartments approach is integrated into a network structure such that each compartment can be seen as a node in the network. We investigate how structures of the network impacts on software self-assembly speed, complexity, and diversity of generated programs. Results indicate that network structure can substantially affect the dynamics, diversity, and complexity of generated programs. © 2009 Wiley Periodicals, Inc.

Calculating a near time-optimal jerk-constrained trajectory along a specified smooth path

This article presents a near time-optimal and jerk-constrained trajectory planner. The presented work is an extension to the “proximate time-optimal algorithm” (Pardo-Castellote and Cannon, IEEE Int Conf Robot Autom 2:1539–1546, 1996), which is used to determine smooth and near time-optimal path-constrained trajectories, to problems where not only the velocity and the acceleration but also the jerk are explicitly constrained. It is shown that the constraint on the jerk translates into limits for the curvature of the phase-space velocity. As high-speed motion systems become more and more accurate, the trend goes clearly towards jerk-constrained trajectory calculation to avoid large deviations from the planned trajectory during the complete move. The proposed algorithm is nonperturbative and its calculation time is linear with respect to the length of the path.

State-of-the-art of 3D facial reconstruction methods for face recognition based on a single 2D training image per person

3D facial reconstruction systems attempt to reconstruct 3D facial models of individuals from their 2D photographic images or video sequences. Currently published face recognition systems, which exhibit well-known deficiencies, are largely based on 2D facial images, although 3D image capture systems can better encapsulate the 3D geometry of the human face. Accordingly, face recognition research is gradually shifting from the legacy 2D domain to the more sophisticated 2D to 3D or 2D/3D hybrid domain. Currently there exist four methods for 3D facial reconstruction. These are: Stochastic Newton Optimization method (SNO) [Blanz, V., Vetter, T., 1999. A morphable model for the synthesis of 3D faces. In: Proc. 26th Annu. Conf. on Computer Graphics and Interactive Techniques, SIGGRAPH. pp. 187–194; Blanz, V., Vetter, T., 2003. Face recognition based on fitting a 3D morphable model. IEEE Trans. Pattern Anal. Machine Intell. 25(9), 1063–1074; Blanz, V., 2001. Automatische Rekonstruction der Dreidimensionalen Form von Gesichtern aus einem Einzelbild. Ph.D. Thesis, Universitat Tubingen, Germany] inverse compositional image alignment algorithm (ICIA) [Romdhani, S., Vetter, T., 2003. Efficient, robust and accurate fitting of a 3D morphable model. In: IEEE Int. Conf. on Computer Vision, vol. 2, no. 1. pp. 59–66], linear shape and texture fitting algorithm (LiST) [Romdhani, S., Blanz, V., Vetter, T., 2002. Face identification by fitting a 3D morphable model using linear shape and texture error functions. In: Proc. ECCV, vol. 4. pp. 3–19], and shape alignment and interpolation method correction (SAIMC) [Jiang, D., Hu, Y., Yan, S., Zhang, L., Zhang, H., Gao, W., 2005. Efficient 3D reconstruction for face recognition. Pattern Recogn. 38(6), 787–798]. The first three, SNO, ICIA + 3DMM, and LiST can be classified as “analysis-by-synthesis” techniques and SAIMC can be separately classified as a “3D supported 2D model”. In this paper, we introduce, discuss and analyze the difference between these two frameworks. We begin by presenting the 3D morphable model (3DMM; Blanz and Vetter, 1999), which forms the foundation of all four of the reconstruction techniques described here. This is followed by a review of the basic “analysis-by-synthesis” framework and a comparison of the three methods that employ this approach. We next review the “3D supported 2D model” framework and introduce the SAIMC method, comparing it to the other three. The characteristics of all four methods are summarized in a table that should facilitate further research on this topic.

Control of Robot Manipulators in Terms of Quasi-Velocities

In this paper we present new control algorithms for robots with dynamics described in terms of quasi-velocities (Kozlowski, Identification of articulated body inertias and decoupled control of robots in terms of quasi-coordinates. In: Proc. of the 1996 IEEE International Conference on Robotics and Automation, pp. 317---322. IEEE, Piscataway, 1996a; Zeitschrift fur Angewandte Mathematik und Mechanik 76(S3):479---480, 1996c; Robot control algorithms in terms of quasi-coordinates. In: Proc. of the 34 Conference on Decision and Control, pp. 3020---3025, Kobe, 11---13 December 1996, 1996d). The equations of motion are written using spatial quantities such as spatial velocities, accelerations, forces, and articulated body inertia matrices (Kozlowski, Standard and diagonalized Lagrangian dynamics: a comparison. In: Proc. of the 1995 IEEE Int. Conf. on Robotics and Automation, pp. 2823---2828. IEEE, Piscataway, 1995b; Rodriguez and Kreutz, Recursive Mass Matrix Factorization and Inversion, An Operator Approach to Open- and Closed-Chain Multibody Dynamics, pp. 88---11. JPL, Dartmouth, 1998). The forward dynamics algorithms incorporate new control laws in terms of normalized quasi-velocities. Two cases are considered: end point trajectory tracking and trajectory tracking algorithm, in general. It is shown that by properly choosing the Lyapunov function candidate a dynamic system with appropriate feedback can be made asymptotically stable and follows the desired trajectory in the task space. All of the control laws have a new architecture in the sense that they are derived, in the so-called quasi-velocity and quasi-force space, and at any instant of time generalized positions and forces can be recovered from order $O({\cal N})$ recursions, where ${\cal N}$ denotes the number of degrees of freedom of the manipulator. This paper also contains the proposition of a sliding mode control, originally introduced by Slotine and Li (Int J Rob Res 6(3):49---59, 1987), which has been extended to the sliding mode control in the quasi-velocity and quasi-force space. Experimental results illustrate behavior of the new control schemes and show the potential of the approach in the quasi-velocity and quasi-force space.

Post electrochemical Cu deposition anneal impact on stress-voiding in individual vias

Stress-voiding is a critical reliability issue in Cu dual-damascene interconnects which could induce via openings. In our case, voids are typically observed at the edges at the bottom of vias. This location is correlated to a local delamination at Cu/Ta interface [E.T. Ogawa, J.W. McPherson, J.A. Rosal, M.J. Dickerson, T.-C. Chiu, L.Y. Tsung, M.K. Jain, T.D. Bonifield, J.C. Ondrusek, W.R. McKee, IEEE Int. Rel. Phys. Symp. Proc. (2002) 312–321; Y.K. Lim et al., Stress-induced voiding in multi-level copper/low-k interconnects, IEEE Int. Rel. Phys. Symp. Proc. (2004) 240–245]. Then, Cu/Ta interface properties at the bottom of via seem to be in the critical path for stress-voiding. In this paper, stress-voiding on 300 mm wafers in individual vias for different post electrochemical Cu deposition (ECD) anneals is studied. Electrical results show the clear benefit of hot plate and short furnace annealings. Microstructural characterizations indicate that impurities accumulation at Cu/Ta interface during long annealings could drive preferred void nucleation.

Robotic execution of everyday tasks by means of external vision/force control

In this article, we present an integrated manipulation framework for a service robot, that allows to interact with articulated objects at home environments through the coupling of vision and force modalities. We consider a robot which is observing simultaneously his hand and the object to manipulate, by using an external camera (i.e. robot head). Task-oriented grasping algorithms (Proc of IEEE Int Conf on robotics and automation, pp 1794–1799, 2007) are used in order to plan a suitable grasp on the object according to the task to perform. A new vision/force coupling approach (Int Conf on advanced robotics, 2007), based on external control, is used in order to, first, guide the robot hand towards the grasp position and, second, perform the task taking into account external forces. The coupling between these two complementary sensor modalities provides the robot with robustness against uncertainties in models and positioning. A position-based visual servoing control law has been designed in order to continuously align the robot hand with respect to the object that is being manipulated, independently of camera position. This allows to freely move the camera while the task is being executed and makes this approach amenable to be integrated in current humanoid robots without the need of hand-eye calibration. Experimental results on a real robot interacting with different kind of doors are presented.

Comparison among digital fundamental groups and its applications

The notion of digital fundamental group was originated by Khalimsky [E. Khalimsky, Motion, deformation, and homotopy in finite spaces, Proc. IEEE Int. Conf. Syst. Man Cybernet. (1987) 227–234]. Motivated by this notion, three kinds of digital k-homotopies as well as the relative k-homotopy were established [R. Ayala, E. Domínguez, A.R. Francés, A. Quintero, Homotopy in digital spaces, Discrete Appl. Math. 125 (1) (2003) 3–24; L. Boxer, A classical construction for the digital fundamental group, J. Math. Imaging Vis. 10 (1999) 51–62; S.E. Han, Connected sum of digital closed surfaces, Inform. Sci. 176 (3) (2006a) 332–348; T.Y. Kong, A digital fundamental group, Comput. Graphics 13 (1989) 159–166; R. Malgouyres, Homotopy in 2-dimensional digital images, Theor. Comput. Sci. 230 (2000) 221–233]. These four notions contributed to the development of three kinds of k-fundamental groups of a digital image ( X , k ) . One was established by Kong [Kong, 1989] and Malgouyres [Malgouyres, 2000], and we denote by π KM k ( X ) this digital fundamental group. Another was developed by Boxer [Boxer, 1999] and extended by Han [Han, 2006a; S.E. Han, Discrete Homotopy of a closed k -surface, LNCS 4040, Springer-Verlag, Berlin, 2006b, pp. 214–225; S.E. Han, Equivalent ( k 0 , k 1 ) -covering and generalized digital lifting, Inform. Sci. 178 (2) (2008) 550–561] by using both the k-homotopic thinning [Han, 2006b; S.E. Han, Remarks on digital k -homotopy equivalence, Honam Math. J. 29 (1) (2007) 101–118] and Han’s digital covering theory [S.E. Han, Digital coverings and their applications, J. Appl. Math. Comput. 18 (1–2) (2005) 487–495; Han, 2006b], which is denoted as π BH k ( X ) in this paper. The other was established by Ayala et al. by using the framework of a multilevel architecture [Ayala, 2003]. Since each of these digital k-fundamental groups has an intrinsic feature of its own and its usages depend on the situation. This study is focused on the first two notions, π KM k ( X ) and π BH k ( X ) , and intended to show the strong merits of π BH k ( X ) in relation to the classification of digital images.

Wire Retiming Problem With Net Topology Optimization

In this paper, we study the retiming problem of sequential circuits with net topology optimization. Both interconnect and gate delay are considered in retiming. Most previous retiming algorithms have assumed ideal conditions for the nonlogical portions of data paths, which are not sufficiently accurate to be used in high-performance circuits today. In our modeling, we assume that the delay of a wire is directly proportional to its length. This assumption is reasonable since the quadratic component of a wire delay is significantly smaller than its linear component when the more accurate Elmore delay model is used. A simple experiment was conducted to illustrate the validity of this assumption. We present two approaches to solve the retiming problem, both of which have polynomial time complexity. The first one can compute the optimal clock period, while the second one is an improvement over the first one in terms of practical applicability. The second approach gives solutions that are very close to the optimal (0.06% more than the optimal on average) but in a much shorter runtime. The optimally retimed circuit will then be realized physically by placing the registers and finding the net topologies. In contrast to many previous works [Proc. IEEE Int. Conf. Comput.-Aided Des., p. 136, 1998], [IEEE Trans. Comput.-Aided Design Integr. Circuits Syst., 22(7) Jul. 2003] that performed simple calculations to determine the register positions, our approach can preserve the optimal clock period that is obtained by the retiming step and utilize as few registers as possible. Minimization of register number saves both area and power in register and clock loading. Our topology optimization step is shown to be optimal for nets with four or fewer pins, and this type of nets constitutes over 90% of the nets in a sequential circuit on average. Using the ISCAS89 benchmark, we tested our algorithm with a 0.35-mum complementary metal-oxide-semiconductor standard cell library. Silicon Ensemble was used to layout the design with a row utilization of 50%. Experimental results showed that our algorithm could find the best sharing of registers for a net in most of the cases, i.e., using the minimum number of registers while preserving the target clock period that is obtained by the retiming step, within a minute run on an Intel Pentium IV 1.5 GHz PC with 512 MB RAM.