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221.
João Paulo Costa 《OR Spectrum》2005,27(4):633-652
Multiple objective linear fractional programming (MOLFP) is an important field of research. Using some branch and bound techniques, we have developed a new interactive method for MOLFP that drastically reduces the computational effort needed, while providing guidance for the decision maker in the choice of his/her preferred solutions. The basic idea of the computation phase of the algorithm is to optimize one of the fractional objective functions while constraining the others. Several linear programming problems, organized in a tree structure, are generated as the search evolves. The whole idea is simple and it results in a fast and very intuitive approach to exploring the non-dominated set of solutions in MOLFP, and eventually to finding the preferred solution.This work was supported by the Fundação para a Ciência e Tecnologia and FEDER, project POCTI/32405/GES/2000. 相似文献
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224.
Paulo Veríssimo 《Real-Time Systems》1994,7(2):105-128
It is significantly difficult to program dependable decentralised computer control systems, since they need to integrate fault-tolerance and real-time with distribution. In consequence, architects and programmers turn to new distributed system tools and paradigms, such as: synchronised clocks, causal order, groups, membership, replication, and so forth, to assist them in that task. Their inappropriate use, however, may lead to unexpected inefficiency or failure of programs. There is a common link between all these tools in real-time uses, and that is the rôle of time and order in the behaviour of the system. The purpose of this paper is to establish the limits to their use, in order that the models programmers rely on are not used beyond their validity boundaries. This paper equates the time and order problems of real-time programs in a unified manner. It recalls known fundamental limits of time and order in distributed systems, and then it shows that these limits can be drastically relaxed, if the system support (clock granularity, order discrimination) can be matched to the ordering and timeliness requirements of programs. It finalises by giving concrete guidelines about the use of clocks and about what a programmer can expect from an ordering by distributed timestamps. 相似文献
225.
This paper proposes a parameter fitting procedure using Markov Modulated Poisson Processes (MMPPs) that leads to accurate estimates of queuing behavior for network traffic exhibiting long-range dependence behavior. The procedure matches both the autocovariance and marginal distribution of the counting process. A major feature is that the number of states is not fixed a priori, and can be adapted to the particular trace being modeled. The MMPP is constructed as a superposition of L 2-MMPPs and one M-MMPP. The 2-MMPPs are designed to match the autocovariance and the M-MMPP to match the marginal distribution. Each 2-MMPP models a specific time-scale of the data. The procedure starts by approximating the autocovariance by a weighted sum of exponential functions that model the autocovariance of the 2-MMPPs. The autocovariance tail can be adjusted to capture the long-range dependence characteristics of the traffic, up to the time-scales of interest to the system under study. The procedure then fits the M-MMPP parameters in order to match the marginal distribution, within the constraints imposed by the autocovariance matching. The number of states is also determined as part of this step. The final MMPP with M2
L
states is obtained by superposing the L 2-MMPPs and the M-MMPP. We apply the inference procedure to traffic traces exhibiting long-range dependence and evaluate its queuing behavior through simulation. Very good results are obtained, both in terms of queuing behavior and number of states, for the traces used, which include the well-known Bellcore traces. 相似文献
226.
Some remarks on multiple-entry finite automata are presented. They deal with the effects of nondeterminism and of other logics on the family of languages accepted, comparison with finite automata (both deterministic and nondeterministic) in terms of number of states and a bound on a decision procedure. 相似文献
227.
Multielectrode microprobes for deep-brain stimulation fabricated with a customizable 3-D electroplating process 总被引:5,自引:0,他引:5
Although deep-brain stimulation (DBS) can be used to improve some of the severe symptoms of Parkinson's disease (e.g., Bradykinesia, rigidity, and tremors), the mechanisms by which the symptoms are eliminated are not well understood. Moreover, DBS does not prevent neurodegeneration that leads to dementia or death. In order to fully investigate DBS and to optimize its use, a comprehensive long-term stimulation study in an animal model is needed. However, since the brain region that must be stimulated, known as the subthalamic nucleus (STN), is extremely small (500 microm x 500 microm x 1 mm) and deep within the rat brain (10 mm), the stimulating probe must have geometric and mechanical properties that allow accurate positioning in the brain, while minimizing tissue damage. We have designed, fabricated, and tested a novel micromachined probe that is able to accurately stimulate the STN. The probe is designed to minimize damage to the surrounding tissue. The probe shank is coated with gold and the electrode interconnects are insulated with silicon nitride for biocompatibility. The probe has four platinum electrodes to provide a variety of spatially distributed stimuli, and is formed in a novel 3-D plating process that results in a microwire like geometry (i.e., smoothly tapering diameter) with a corresponding mechanically stable shank. 相似文献
228.
Landmines can deprive whole areas of valuable resources, and continue to kill and cause injuries years after the end of armed conflicts. Armored vehicles are used for mine clearance, but with limited reliability. The final inspection of minefields is still performed by human deminers exposed to potentially fatal accidents. The aim of this research is to introduce automation as a way to improve the final level of humanitarian demining. This paper addresses mobility and manipulation, while sensing, communication and visualization shall be discussed in detail in a subsequent paper. After analyzing the merits and limitations of previous works, a new approach to tele-operated demining is considered, using off-road buggies equipped with combustion engines, and taking into account actual field requirements. Control of the automated buggies on rough terrain is also discussed, as well as the development of a new weight-balanced manipulator for landmine clearance operations.Paulo Debenest received the B. Eng. degree in mechanical engineering (major in automation and systems) from Polytechnic School of the University of São Paulo (EPUSP), Brazil, in 1998, and the M. Eng. degree in mechanical and aerospace engineering from Tokyo Institute of Technology (Tokyo Tech), Japan, in 2002. He is currently working toward the Ph.D. degree in mechanical science engineering at Tokyo Tech and member of IEEE. His current research activities include development of demining robots and mechanical design of machines for field applications.Edwardo F. Fukushima is an assistant professor in the Department of Mechanical and Aerospace Engineering at Tokyo Institute of Technology (Tokyo Tech). He received the B. Eng. degree in electric engineering (major in electronics and telecommunications) from Federal Center of Technological Education of Paraná (CEFET-PR), Brazil, in 1989, and M. Eng. degree in mechanical science engineering from Tokyo Tech in 1993. In 1994 he became a research associate in the same institute. During Sept.–Dec. 2001 he has been a Visiting Researcher at Stanford University, and during Aug.–Sept. 2004 Visiting Scientist at University of Zurich. He is also member of RSJ. His current research activities include development of demining robots, design of controllers for intelligent robots, and development of new brushless motors and drives.Yuki Tojo is a masters course student in the Department of Mechanical and Aerospace Engineering at Tokyo Institute of Technology (Tokyo Tech). He received the B. Eng. degree in mechanical and aerospace engineering from Tokyo Tech in 2003. His research interests include design and control of weight-compensated manipulator on mobile platform. He is also member of RSJ.Shigeo Hirose was born in Tokyo in 1947. He received his B.Eng. Degree with First Class Honors in Mechanical Engineering from Yokohama National University in 1971, and his M. Eng. and Ph.D. Eng. Degrees in Control Engineering from Tokyo Institute of Technology in 1973 and 1976, respectively. From 1976 to 1979 he was a Research Associate, and from 1979 to 1992 an Associate Professor. Since 1992 he has been a Professor in the Department of Mechanical and Aerospace Engineering at the Tokyo Institute of Technology. Since 2002, he has been Honorary Professor in Shengyang Institute of Technology, the Chinese Academy of Sciences. Fellow of JSME and IEEE. He is engaged in creative design of robotic systems. Prof. Hirose has been awarded more than twenty prizes. 相似文献
229.
Marques F Paulo A Campello MP Lacerda S Vitor RF Gano L Delgado R Santos I 《Radiation protection dosimetry》2005,116(1-4 PT 2):601-604
This work intends to find specific radiopharmaceuticals for cancer therapy based on beta (153Sm and 166Ho) or Auger (99Tc(m)) emitter radionuclides, using cyclic and acyclic polyamines as bifunctional chelators. These chelators are designed to allow the binding of a tumour seeking biomolecule and/or a DNA intercalator. The cyclic amines, such as 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid, 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetic acid and 1,4,7,10-tetraazacyclotridecane-1,4,7,10-tetraacetic acid, were radiolabelled with 153Sm and 166Ho. The radiochemical and biological behaviour of the resulting complexes were evaluated in order to assess their potential as building blocks for the attachment of selected biomolecules, with the aim of further applying them for the development of specific therapeutic radiopharmaceuticals. Novel pyrazolyldiamines, bearing a DNA intercalating anthracenyl fragment, were also explored to synthesize radioactive complexes with the fac-[99Tc(m)(CO)]3]+ moiety. The identity of these 99Tc(m) tricarbonyl complexes was confirmed by high-performance liquid chromatography comparison with rhenium congeners fully characterized. By including a DNA intercalator into the chelator framework, we expect to induce more efficient and selective damage to the DNA of cancer cells by the action of the short-range Auger electrons emitted by 99Tc(m). 相似文献
230.
Simão AG de Mendonça JP Santiago RB de Moraes PC Soares PC Guimarães LG 《Applied optics》2005,44(16):3370-3376
We develop a semiclassical theory to explain the rapid ripple fluctuations in the extinction efficiency of light scattering by a transparent prolate spheroid. The theory is based on uniform asymptotic expansion of spheroidal radial functions. We have calculated the extinction efficiency for normal and oblique incidence. Our results suggest that the excitation of resonant electromagnetic modes inside a spheroidal particle is an important factor in the ripple structure. To verify this assumption and based on a Breit-Wigner formula, we develop a method to fit the peaks that appear in the spheroid's extinction cross section when some scattering parameters vary. In other words, our calculations suggest that narrow resonances are related to ripple fluctuations, whereas broad resonances contribute to extinction cross-sectional background. 相似文献