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Conformal thermal therapy using planar ultrasound transducers and adaptive closed-loop MR temperature control:: demonstration in gel phantoms and ex vivo tissues

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PHYSICS IN MEDICINE AND BIOLOGY 2007年第10期52卷 2905-2919页

作者： Tang, K. Choy, V. Chopra, R. Bronskill, M. J. Sunnybrook Hlth Sci Ctr Toronto ON M4N 3M5 Canada Univ Toronto Dept Med Biophys Toronto ON Canada

MRI-guided transurethral ultrasound therapy offers a minimally invasive approach for the treatment of localized prostate cancer. Integrating a multi-element planar transducer with active MR temperature feedback can enable three-dimensional conformal thermal therapy of a target region within the prostate gland while sparing surrounding normal tissues. Continuous measurement of the temperature distribution in tissue enables dynamic compensation for unknown changes in blood flow and tissue properties during treatment. The main goal of this study was to evaluate the feasibility of using active temperature feedback on a clinical 1.5 T MR imager for conformal thermal therapy. MR thermometry was performed during heating in both gel phantoms and excised tissue with a transurethral heating applicator, and the rotation rate and power were varied based on the thermal measurements. The capability to produce a region of thermal damage that matched a target boundary was evaluated. The influence of a cooling gradient ( to simulate cooling of the rectum or urethra) on the desired pattern of thermal damage was also investigated in gel phantoms. Results showed high correlation between the desired target boundary and the 55. C isotherm generated during heating with an average distance error of 0.9 mm +/- 0.4 mm (n = 6) in turkey breasts, 1.4 mm +/- 0.6 mm (n = 4) in gel phantoms without rectal cooling and 1.4 mm +/- 0.6 mm (n = 3) in gel phantoms with rectal cooling. The results were obtained using a temporal update rate of 5 s, a spatial resolution of 3 x 3 x 10 mm for the control point, and a temperature uncertainty of approximately 1 degrees C. The performance of the control algorithm under these conditions was comparable to that of simulations conducted previously by our group. Overall, the feasibility of generating targeted regions of thermal damage with a transurethral heating applicator and active MR temperature feedback has been demonstrated experimentally. This method of trea

关键词： Prostate Mm control point Temperature distribution Blood Flow computer algorithms EX-VIVO Heating Gels temperature feedback conformal Thermal techniques Blood Circulation

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A contribution to the exact modal solution of in-plane beam structures

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JOURNAL OF SOUND AND VIBRATION 2009年第4-5期328卷 586-606页

作者： Dias, C. A. N. Alves, M. Univ Sao Paulo Grp Solid Mech & Struct Impact Dept Mechatron & Mech Syst Engn BR-05508900 Sao Paulo Brazil

The exact vibration modes and natural frequencies of planar structures and mechanisms, comprised Euler-Bernoulli beams, are obtained by solving a transcendental. nonlinear, eigenvalue problem stated by the dynamic stiffness matrix (DSM). To solve this kind of problem, the most employed technique is the Wittrick-Williams algorithm, developed in the early seventies. By formulating a new type of eigenvalue problem, which preserves the internal degrees-of-freedom for all members in the model, the present study offers an alternative to the use of this algorithm. The new proposed eigenvalue problem presents no poles, so the roots of the problem can be found by any suitable iterative numerical method. By avoiding a standard formulation for the DSM, the local mode shapes are directly calculated and any extension to the beam theory can be easily incorporated. It is shown that the method here adopted leads to exact solutions, as confirmed by various examples. Extensions of the formulation are also given, where rotary inertia, end release, skewed edges and rigid offsets are all included. (C) 2008 Elsevier Ltd. All rights reserved.

关键词： SYSTEMS engineering MICROELECTROMECHANICAL systems VIBRATION (Mechanics) ENGINEERING mathematics computer algorithms DEGREES of freedom EIGENVALUES SYSTEM analysis DYNAMIC programming

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Three-phase grid-tied single-stage solar energy conversion system using LLMS control algorithm

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IET RENEWABLE POWER GENERATION 2016年第10期10卷 1638-1646页

作者： Agarwal, Rahul Hussain, Ikhlaq Singh, Bhim Indian Inst Technol Delhi Dept Elect Engn New Delhi 110016 India

In this study, a three-phase grid-tied single-stage solar energy conversion system (SECS) is implemented using a leaky least mean square (LLMS) based control algorithm. The SECS extracts the solar energy from the photovoltaic cells and converts it into electrical energy. The SECS makes use of voltage source inverter to invert the extracted DC power into the three-phase AC power. Apart from SECS, this system configures a three-phase grid, ripple filters and connected linear or nonlinear loads. The main objective of this system is to eliminate power quality issues such as harmonics, voltage fluctuations and flickers, unbalancing in loads, reactive power requirement and so on. Moreover, this system operates at unity power factor and zero voltage regulation modes. In this study, SECS employs a single-stage topology controlled by perturb & observe approach of maximum power point tracking technique and for extracting fundamental component of load currents, a LLMS-based adaptive neural network control method is used. This system is modelled, designed and simulated in MATLAB using simpower system toolbox and experimental validation is carried out on a developed prototype in the laboratory.

关键词： unity power factor maximum power point trackers solar energy conversion Power quality flickers DC power supply MATLAB voltage source inverter spacecraft energy conversion systems alternating current power Photovoltaic cells computer algorithms

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Dynamic modeling of parallel robots for computed-torque control implementation

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INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH 1998年第12期17卷 1325-1336页

作者： Codourey, A ETH Zurich Inst Robot CH-8092 Zurich Switzerland

In recent years, increased interest in parallel robots has been observed. Their control with modern theory, such as the computed-torque method, has, however been restrained, essentially due to the difficulty in establishing a simple dynamic model that can be calculated in real time. In this paper;a simple method based on the virtual work principle is proposed for modeling parallel robots. The mass matrix of the robot needed for decoupling control strategies, does not explicitly appear in the formulation;however it can be computed separately, based on kinetic energy considerations. The method is applied to the DELTA parallel robot, leading to a very efficient model that has been implemented in a real-time computed-torque control algorithm.

关键词： dynamic models Robot Parallel robots mass matrix computer algorithms operating principles Modeling

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Selective encryption for consumer applications

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IEEE COMMUNICATIONS MAGAZINE 2004年第5期42卷 124-129页

作者： Lookabaugh, T Sicker, DC Univ Colorado Dept Comp Sci Boulder CO 80309 USA Univ Colorado INterdisciplinary Telecommun Program Boulder CO 80309 USA

Selective encryption is a technique to save computational complexity or enable interesting new system functionality by only encrypting a portion of a compressed bitstream while still achieving adequate security. Although suggested in a number of specific cases, selective encryption could be much more widely used in consumer electronic applications ranging from mobile multimedia terminals through digital cameras were it subjected to a more thorough security analysis. We describe selective encryption and develop a simple scalar quantizer example to demonstrate the power of the concept, list a number of potential consumer electronics applications, and then describe an appropriate method for developing and analyzing selective encryption for particular compression algorithms. We summarize results from application of this method to the MPEG-2 video compression algorithm.

关键词： Technological innovations Data encryption (computer science) computer security computer algorithms computer science computer network security

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Using high-resolution laboratory and ground-based solar spectra to assess CH₄ absorption coefficient calculations

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JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER 2017年 190卷 48-59页

作者： Mendonca, J. Strong, K. Sung, K. Devi, V. M. Toon, G. C. Wunch, D. Franklin, J. E. Univ Toronto Dept Phys Toronto ON Canada CALTECH Jet Prop Lab Pasadena CA USA Coll William & Mary Dept Phys Williamsburg VA 23185 USA CALTECH Pasadena CA 91125 USA Dalhousie Univ Dept Phys & Atmospher Sci Halifax NS Canada

A quadratic-speed-dependent Voigt line shape (qSDV) with line mixing (qSDV+LM), together with spectroscopic line parameters from Devi et al. [1,2] for the 2v(3) band of CH4, was used to retrieve total columns of CH4 front atmospheric solar absorption spectra. The qSDV line shape (Tran et al., 2013) [3] with line mixing (Levy et al., 1992) [4] was implemented into the forward model of GFIT (the retrieval algorithm that is at the heart of the GGG software (Wunch et al., 2015) [5]) to calculate CH4 absorption coefficients. High-resolution laboratory spectra of CH4 were used to assess absorption coefficients calculated using a Voigt line shape and spectroscopic parameters from the atm line list (Toon, 2014) [6]. The same laboratory spectra were used to test absorption coefficients calculated using the qSDV+LM line shape with spectroscopic line parameters from Devi et al. [1,2] for the 2v(3) band of CH4 and a Voigt line shape for lines that don't belong to the 2v3 band. The spectral line list for lines that don't belong to the 2v(3) band is an amalgamation of multiple spectral line lists. We found that for the P, Q, and R branches of the 2v(3) band, the qSDV+LM simulated the laboratory spectra better than the Voigt line shape. The qSDV+LM was also used in the spectral fitting of high-resolution solar absorption spectra from four ground-based remote sensing sites and compared to spectra fitted with a Voigt line shape. The average root mean square (RMS) residual for 131,124 solar absorption spectra fitted with absorption coefficients calculated using the qSDV+LM for the 2v(3) band of CH4 and the new Spectral line list for lines for lines that don't belong to the 2v(3) band, was reduced in the P, Q and R branches by 5%, 13%, and 3%, respectively when compared with spectra fitted using a Voigt line shape and the atm line list. We found that the average total column of CH4 retrieved from these 131,124 spectra, With the qSDV+LM was 1.1 +/- 0.3% higher than the retrievals perfo

关键词： SOLAR radiation ABSORPTION spectra ABSORPTION coefficients computer algorithms MONOTONIC functions computer software

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Output feedback tracking control of uncertain non-holonomic wheeled mobile robots: a dynamic surface control approach

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IET CONTROL THEORY AND APPLICATIONS 2012年第2期6卷 216-228页

作者： Shojaei, K. Shahri, A. M. Iran Univ Sci & Technol Dept Elect Engn Elect Res Ctr Mechatron & Robot Res Lab Tehran Iran

This study addresses the trajectory tracking control problem of electrically driven wheeled mobile robots under non-holonomic constraints in the presence of model uncertainties without velocity measurement. By defining a suitable set of output equations, a new input-output model of wheeled mobile robots is developed, which helps the designer utilise the classic control algorithms of robot manipulators. An observer-based trajectory tracking controller is proposed for the new wheeled mobile robot (WMR) model. Then, in order to reduce the design complexity, the dynamic surface control approach is effectively exploited to propose a tracking controller considering the actuator dynamics. Adaptive robust techniques are also adopted to cope with the parametric and non-parametric uncertainties in the WMR model. A Lyapunov-based stability analysis is utilised to guarantee that tracking and state estimation errors are uniformly ultimately bounded. Simulation results are presented to illustrate the feasibility and efficiency of the proposed controller.

关键词： Parametric Stability analysis tracking controller Designers trajectory tracking computer algorithms wheeled mobile robots Speed measurement Velocimetry model uncertainty Output feedback Robot Manipulator tracking control State estimation

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Boolean satisfiability from Theoretical hardness to Practical success

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COMMUNICATIONS OF THE ACM 2009年第8期52卷 76-82页

作者： Malik, Sharad Zhang, Lintao Princeton Univ Dept Elect Engn Princeton NJ 08544 USA Microsoft Res Asia Beijing Peoples R China

The article presents a discussion of topics in computer science related to Boolean satisfiability. It focuses on solutions which can be readily used in applications software, and their effectiveness for solving certain types of problems. Topics addressed include the interaction between necessary values and constraints in generating computational complexity. Examples are provided using decision trees solved using various computer algorithms. The increasing commercial use of such programs in fields such as computer hardware and software testing and development is noted.

关键词： ALGEBRA Boolean COMPUTATIONAL complexity computer algorithms DECISION trees computer software computer programming

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Autonomous guidance and control of Earth-orbiting formation flying spacecraft: Closing the loop

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ACTA ASTRONAUTICA 2008年第11-12期63卷 1246-1258页

作者： Hamel, Jean-Francois de Lafontaine, Jean Univ Sherbrooke Dept Elect Engn Sherbrooke PQ J1K 2R1 Canada

Previous work on autonomous formation flying guidance and control identified three key challenges to overcome in order to obtain a fully autonomous guidance and control loop: an accurate but simple model of relative motion about elliptical and perturbed orbits, an efficient way of performing conflicting requirements trade-off with power-limited on-board computers, and finally an optimal or near-optimal control algorithm easy to implement on a flight computer. This paper first summarizes recent developments on each of these subject that help to overcome these challenges, developments which are then used as building blocks for an autonomous formation flying guidance and control system. This system autonomously performs trade-offs between conflicting requirements. i.e. minimization of fuel cost, formation accuracy and equal repartition of the fuel expenditure within the formation. Simulation results show that a complete guidance and control loop can be established using mainly analytical results and with very few numerical optimization which facilitates on-board implementation. (c) 2008 Elsevier Ltd. All rights reserved.

关键词： control ring airborne/spaceborne computers relative motion Guidance Building blocks Formation flight Autonomous guidance computer algorithms

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Toluene removal in an automated cyclical bioreactor

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BIOTECHNOLOGY PROGRESS 2000年第3期16卷 378-384页

作者： Brown, WA Cooper, DG Liss, SN McGill Univ Dept Chem Engn Montreal PQ H3A 2B2 Canada Ryerson Polytech Inst Dept Appl Chem & Biol Sci Toronto ON M5B 2K3 Canada

A control scheme was developed for the automation of toluene removal in a cyclical bioreactor. Toluene was added to the self-cycling fermenter by diffusion across a silicone membrane. Transient dissolved oxygen, carbon dioxide evolution, and oxidation-reduction potential (ORP) were screened as potential control variables. Through experimentation, ORP was deemed most effective. Control algorithms based on realtime estimates of the first and second derivatives of the ORP signal were tested. Although both approaches resulted in stable operation of the reactor, average toluene removal efficiencies of 95% were realized when control was based on the second derivative. This was significantly higher than the 77% efficiencies obtained when the control scheme centered on the first derivative of the transient ORP signal. The system developed was self-regulating, ensuring that a high toluene removal rate, on the order of 1.1 g h(-1), was maintained from cycle to cycle.

关键词： P-xylene. Simultaneous biodegradation. Mathematical-analysis. Degradation. Benzene. Orp. Fermentation. Kinetics. Reactor. System. First Derivative diffusion Standing Orders Self-Control stability operations oxidation reduction potential Toluene computer algorithms REMOVAL RATE Second derivative Real time Fermenters Automation

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