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International Workshop on Advanced Motion Control (AMC)

作者： Chunling Du Sam Shuzhi Ge Fan Hong Jingliang Zhang F. L. Lewis Agency for Science Technology and Research Singapore SG Department of Electrical and Computer Engineering National University of Singapore Singapore A*STAR Data Storage Institute(DSI) 5 Engineering Drive 1 117608 Singapore Automation and Robotics Research Institute University of Texas Arlington USA

Compensation for external vibration impact on the positioning accuracy of hard disk drives is considered with the presence of actuator uncertainty in this paper. The low-frequency mode change due to actuator pivot nonlinearity of the voice-coil- motor (VCM) actuator is described as frequency and damping uncertainty. A robust feedforward controller is then designed in continuous time domain by using H infin method to attenuate the impact with the aid of a sensor to detect external vibrations. The linear matrix inequality (LMI) approach is adopted to solve the robust H infin feedforward control design problem. The application results in a 1.8-inch disk drive with an accelerometer to measure acceleration signal show that 27% to 91% reduction of the position error signal is achieved with the robust feedforward controller when the frequency changes in 70 plusmn 50 Hz and damping in 0.4 plusmn 0.3. The effectiveness of the robust feedforward control is also demonstrated to be better than nominal feedforward control.

关键词： Robustness Hard disks Robust control Actuators Uncertainty Frequency Damping Accelerometers Vibration control Linear matrix inequalities

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Spin transverse separation in a two-dimensional electron-gas using an external magnetic field with a topological chirality

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Physical Review B 2008年第24期78卷 245321-245321页

作者： S. G. Tan M. B. A. Jalil Xiong-Jun Liu T. Fujita Data Storage Institute Agency for Science Technology and Research (A*STAR) DSI Building 5 Engineering Drive 1 Singapore 117608 Singapore Department of Electrical and Computer Engineering Information Storage Materials Laboratory National University of Singapore 4 Engineering Drive 3 Singapore 117576 Singapore Department of Physics National University of Singapore 2 Science Drive 3 Singapore 117542 Singapore

We propose a two-dimensional electron-gas (2DEG) system in which an external magnetic field with a small chirality is applied to provide a topological spin gauge field that separates conduction electrons of opposite spins in the transverse direction. Additionally, the vertical electric field in the 2DEG, together with spin-orbit coupling, produces a SU(2) gauge field which reinforces or opposes the effect of the spin gauge. The system thus provides a tunable spin separation effect, where an applied gate voltage on the 2DEG can be used to modulate the transverse spin current. As this method leads to the enhancement or cancellation of spin separation due to the intrinsic spin-orbit coupling effect only, it may naturally distinguish the extrinsic effect from the intrinsic one.

关键词： spin-orbit interactions two-dimensional electron gas

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What we expect from weakly dissipating materials at the range of plasmon resonance frequencies

What we expect from weakly dissipating materials at the rang...

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IEEE PhotonicsGlobal@Singapore, IPGC

作者： B. S. Luk'yanchuk T. C. Chong L. P. Shi M. I. Tribelsky Z. B. Wang L. Li C.-W. Qiu C. J. R. Sheppard J. H. Wu Agency for Science Data Storage Institute Singapore Electronics and Automation Moscow State Institute of Radioengineering Moscow Russia Aerospace and Civil Engineering University of Manchester UK Department of Electrical and Computer Engineering National University of Singapore Singapore Division of Bioengineering National University of Singapore Singapore School of Mechanical Engineering Xi'an Jiaotong University China

Development of modern materials, including nanoclusters, cluster assembled materials and metamaterials is among the actual challenges for the development of future nanotechnologies. Here we discuss the peculiarities of far-field and near-field light scattering by plasmonic nanoparticles, and possible applications of weakly dissipating materials. Over the last few years many peculiarities of light scattering have been found for nanoparticles in the regime of plasmon resonances. Optical excitation of localized plasmons is accompanied by inverse process - transformation of localized resonant plasmons into scattered light. When radiative damping prevails over the dissipative damping, the effects of anomalous light scattering result in sharp giant optical resonances and complicated near-field structure of the Poynting vector field, see e.g. [1-4]. Here we present peculiarities of far-field and near-field light scattering by plasmonic nanoparticles with weak dissipation and anisotropy.

关键词： Plasmons Resonant frequency Resonance light scattering Light scattering Nanoparticles Optical scattering Damping Nanostructured materials Assembly Metamaterials

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Neural networks for disturbance and friction compensation in hard disk drives

Neural networks for disturbance and friction compensation in...

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IEEE Conference on Decision and Control

作者： Chow Yin Lai Frank L. Lewis V. Venkataramanan Xuemei Ren Shuzhi Sam Ge Thomas Liew Centre for Life Sciences (CeLS) Graduate School for Integrative Sciences and Engineering (NGS) National University of Singapore Singapore Automation and Robotics Research Institute University of Texas Arlington Fort Worth TX USA Data Storage Institute Engineering Agency for Science Technology and Research Singapore Department of Automatic Control Beijing Institute of Technology Beijing China Department of Electrical and Computer Engineering National University of Singapore Singapore

ISBN: (纸本)9781424431236

In this paper, we show that the tracking performance of a hard disk drive actuator can be improved by using two adaptive neural networks, each of which is tailored for a specific task. The first neural network utilizes accelerometer signal to detect external vibrations, and compensates for its effect on hard disk drive position via feedforward action. In particular, no information on the plant, sensor and disturbance dynamics is needed in the design of this neural network disturbance compensator. The second neural network, designed to compensate for the pivot friction, uses a signum activation function to introduce nonlinearities inherent to pivot friction, thus reducing the neural network¿s burden of expectation. The stability of the proposed scheme is analyzed by the Lyapunov criterion. Simulation results show that the tracking performance of the hard disk drives can be improved significantly with the use of both neural networks compared to the case without compensation, or when only one of the networks is activated.

关键词： Neural networks Friction Hard disks Actuators Adaptive systems Feedforward neural networks Accelerometers Signal detection Stability analysis Stability criteria

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Light Irradiation through Small Particles and Its Applications for Surface Nanostructuring in Near Field

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Chinese Physics Letters 2007年第10期24卷 2947-2950页

作者：周毅洪明辉傅盈西吕力陈凌霄 Lukyanchuk B S Department of Mechanical Engineering National University of Singapore Singapore 117576 Data Storage Institute Agency for Science Technology and Research Singapore 117608 Department of Electrical and Computer Engineering National University of Singapore Singapore 117576

We investigate the light scattering through small particles and its applications in nanostructuring, such as nanobumping, nanopatterning and dry laser cleaning. The theoretical calculation based on Mie theory provides an exact solution for sphere cavity resonance and plasmon resonance, which are two mechanisms for dielectric and metallic particles assisted surface nanostructuring in near field. The experimental results indicate that nanobumps on glass surface and subwavelength holes array on silicon surface can be formed without cracks with the self-assembly of 1 μm silica particle mask under laser irradiation. It is also found that the scattering wave by 40 nm gold particles can propagate 200 times away in terms of particle radius as recorded by photoresist under the UV light irradiation. Meanwhile, dry laser cleaning of 40nm gold particle on silicon wafer is demonstrated at plasmonic resonance frequency. The total cleaning efficiency is estimated to be 80%.

关键词： coated conductor buffer layer self-epitaxy CeO2

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Achieving High Aspect Ratio of Track Length to Width in Molds for Discrete Track Recording Media

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Journal of Nanotechnology 2008年第1期2008卷

作者： K. O. Aung C. Shankaran R. Sbiaa E. L. Tan S. K. Wong S. N. Piramanayagam Data Storage Institute A∗STAR (Agency for Science Technology and Research) 5 Engineering Drive 1 Singapore 117608 Department of Electrical and Computer Engineering National University of Singapore 4 Engineering Drive 3 Singapore 117576

Discrete track media (DTM) fabricated by nanoimprint lithography (NIL) is considered as a potential technology for future hard disk drives (HDD). In the fabrication of a master mold for NIL, patterning the resist tracks with a narrow distribution in the width is the first critical step. This paper reports the challenges involved in the fabrication of high aspect ratio discrete tracks on Polymethylmethacrylate (PMMA) resist by means of electron beam lithography. It was observed that fabrication parameters applied for successful patterning of discrete tracks in nanoscale length were not directly suitable for the patterning of discrete tracks in micron scale. Hence different approaches such as thick layer resist coating, introducing of post exposure baking process, and varying of exposure parameters were used in order to achieve uniform sharp discrete tracks in micron scale length on the resist. The optimal parameters were used to pattern 20 μ m long tracks with 70 nm track pitch on the resist.

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Editorial: Knowledge engineering, semantics, and signal processing in audio - visual information retrieval

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IEEE Transactions on Circuits and Systems for Video Technology 2007年第3期17卷 257-258页

作者： Izquierdo, Ebroul Zhang, Jian Sikora, Thomas Huang, Thomas S. Department of Electrical Engineering Queen Mary University of London London El 4NS United Kingdom Sydney Australia School of Computer Science and Engineering University of New South Wales Australia Communication Systems Group Technical University Berlin Berlin Germany ITG University of Illinois at Urbana-Champaign United States Department of Electrical and Computer Engineering Coordinated Science Laboratory United States Image Formation and Processing Group Beckman Institute for Advanced Science and Technology United States Institute's Major Research Theme Human Computer Intelligent Interaction National Academy of Engineering Chinese Academies of Engineering and Sciences China International Association of Pattern Recognition Optical Society of American United States

No abstract available

关键词： Special issues and sections Knowledge engineering Information retrieval Audio-visual systems

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View-dependent visibility estimation for tree models

View-dependent visibility estimation for tree models

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IEEE International Conference onMultimedia and Expo, ICME 2007

作者： Lee, Jessy Peng, Jingliang Kuo, C.-C. Jay Ming Hsieh Department of Electrical Engineering Signal and Image Processing Institute University of Southern California Los Angeles CA 90089-2564 United States Department of Computer Science Sun Yat-sen University Guangzhou 510275 China

ISBN: (纸本)1424410177

A view-dependent visibility estimation technique for tree models is proposed in this work. While most previous work focused on visibility estimation of large objects in architectural walkthroughs, we consider the visibility estimation problem of tree leaves in complex natural scenes such as forests. Exact calculation of how each leaf object blocks another from a given viewpoint is difficult due to the large amount of computational cost. To address this issue, we propose three simple yet effective methods for efficient visibility estimation of tree leaves: the distance-based, the normal-based, and the layer-plus-normal-based methods. Experimental results show that the distance-based method always produces the best analytical performance, the normal-based method works better in preserving volumetric visual quality at low budget constraints, and the layer-plus-normal-based method preserves volumetric visual quality while yielding excellent analytical performance. © 2007 IEEE.

关键词： Budget control

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Cooperation of Cars and Formation of Cooperative Groups

Cooperation of Cars and Formation of Cooperative Groups

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IEEE Symposium on Intelligent Vehicle

作者： Christian Frese Jurgen Beyerer Peter Zimmer Lehrstuhl für Interaktive Echtzeitsysteme Institute of Computer Science and Engineering Department of Computer Science Universität Karlsruhe Karlsruhe Germany Lehrstuhl für Interaktive Echtzeitsysteme Institute of Computer Science and Engineering Department of Computer Science Fraunhofer Institute for Information and Data Processing IITB Universität Karlsruhe Karlsruhe Germany Data Processing IITB Fraunhofer Institute for Information and Data Processing Karlsruhe Germany

Cooperation of cars capable to communicate bears a high potential with respect to safety in critical situations. Following a top-down design, cars form cooperative groups, exchange information available to them and establish a common relevant picture upon which critical situations are detected, optimal decisions for the groups are derived and are distributed in form of individual action sequences. This paper focuses on the formation of cooperative groups. To this end, a graph-based spatiotemporal distance measure is developed, using the concept of virtual meeting points within the road infrastructure. The distance measure is analyzed and it serves to define cooperative groups of cognitive automobiles.

关键词： computer science data processing Remotely operated vehicles Road safety data engineering Intelligent vehicles Vehicle safety Spatiotemporal phenomena Automobiles Adaptive systems

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Optical limiting phenomena of carbon nanoparticles prepared by laser ablation in liquids

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Journal of Physics: Conference Series 2007年第1期59卷 289-292页

作者： Chen, G.X. Hong, M.H. Tan, L.S. Chong, T.C. Elim, H.I. Chen, W.Z. Ji, W. Data Storage Institute DSI Building Singapore 117608 5 Engineering Drive 1 Singapore Department of Electrical and Computer Engineering National University of Singapore Singapore 117576 4 Engineering Drive 3 Singapore Department of Physics National University of Singapore Singapore 117542 2 Science Drive 3 Singapore

We report optical limiting properties of carbon nanoparticles, which were made in liquids by laser ablation of a bulk carbon target. The carbon nanoparticles were analyzed with micro-Raman spectroscopy, UV-Vis spectroscopy and Electron microscopy. Optical limiting responses towards 532-nm wavelength were measured with a 7-ns Nd:YAG laser. Nanoparticle size and laser pulse repetition rate effects on optical limiting behaviour were studied. A model was proposed to explain the physical origin of this nonlinear optical process. This work can provide useful information for designing carbon nanoparticle based optical limiters. © 2007 IOP Publishing Ltd.

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