Showing papers by "James Taylor published in 1987"

An expert system architecture for computer-aided control engineering

Abstract: We propose the development of a rule-based expert system to create a third-generation man/machine environment for computer-aided control engineering (CACE). The breadth of the CACE problem is of particular concern, and provides a major motivation for the use of artificial intelligence. This approach promises to provide a high-level design environment that is powerful, supportive, flexible, broad in scope, and readily accessible to nonexpert users. We focus primarily on the high-level requirements for an improved CACE environment, and on the expert system concepts and structures that we have conceived to fulfill these needs. Our chief goal is to determine what artificial intelligence has to contribute to such an environment, and to provide as definite and credible a vision of an expert system for CACE as possible. The main product of this effort is an expert system architecture for CACE.

Millisecond Pulsar PSR 1937+21: A Highly Stable Clock.

Abstract: The stable rotation and sharp radio pulses of PSR 1937+21 make this pulsar a clock whose long-term frequency stability approaches and may exceed that of the best atomic clocks. Improvements in measurement techniques now permit pulse arrival times to be determined in 1 hour at the Arecibo radio telescope with uncertainties of about 300 nanoseconds relative to atomic time. Measurements taken approximately every 2 weeks since November 1982 yield estimates of fractional frequency stability that continue to improve with increasing averaging time. The pulsar9s frequency stability is at least as good as 6 x 10 -14 for averaging times longer than 4 months, and over the longest intervals the measurements appear to be limited by the stability of the reference atomic docks. The data yield a firm upper limit of 7 x 10 -36 gram per cubic centimeter for the energy density of a cosmic background of gravitational radiation at frequencies of about 0.23 cycle per year. This limit corresponds to approximately 4 x 10 -7 of the density required to close the universe.

Predicting athletic performance with self-confidence and somatic and cognitive anxiety as a function of motor and physiological requirements in six sports.

Abstract: The purpose of the present study is to examine the ability of certain psychological attributes to predict performance in six National Collegiate Athletic Association Division I collegiate sports. Eighty-four athletes from the varsity sports teams of cross country running, alpine and nordic skiing, tennis, basketball, and track and field at the University of Colorado completed a questionnaire adapted from Martens (1977; Martens et al., 1983) that measured their trait levels of self-confidence (Bandura, 1977), somatic anxiety, and cognitive anxiety (Martens, 1977; Martens et al., 1983). In addition, at three to six competitions during the season, the members of the cross country running and tennis teams filled out a state measure (Martens et al., 1983) of the three attributes from one to two hours prior to the competition. Following each competition, subjective and objective ratings of performance were obtained, and, for all sports, coaches' ratings of performance and an overall seasonal team ranking were determined as seasonal performance measures. The sports were dichotomized along motor and physiological dimensions. Results indicate that all three psychological attributes were significant predictors of performance in both fine motor, anaerobic sports and gross motor, aerobic sports. Further, clear differences in these relationships emerged as a function of the dichotomization. In addition, unexpected sex differences emerged. The findings are discussed relative to prior research and their implications for future research.

Use of expert-systems programming techniques for the design of lead-lag compensators

Abstract: The authors discuss the application of expert systems programming techniques to the design of lead-lag compensators for a linear, single-input/single-output, continuous-time plant. A design method based on first adjusting the high-frequency response with lead and constant-gain compensators followed by adjusting the low-frequency response with lag compensators has been developed. This design heuristic is presented and its ability to achieve specifications for a range of different plants is discussed. The heuristic has been implemented using the production rule knowledge representation; examples of production rules are given and their use is discussed. Inference-engine capabilities and extensions to a conventional analysis and design package, required to implement this automatic control system design method, are also outlined.

High-efficiency single-pass solitonlike compression of raman radiation in an optical fiber around 1.4 μm

Abstract: Highly efficient conversion (as great as 60%) into the broad first Stokes Raman band around 1.4 microm the 90-psec pump pulses from a cw mode-locked Nd:YAG laser at 1.32 microm has permitted, through a solitonlike compression mechanism in a single span of standard (lambda(0) = 1.3 microm) single-mode optical fiber, the generation of highly stable pulses of ~100 fsec, with average powers of ~30 mW in the solitary waves, which depend on fiber length and pump power.

Generation of 33-fsec pulses at 1.32 μm through a high-order soliton effect in a single-mode optical fiber

Abstract: Pulse shortening by a factor of 2700× at 1.32 μm has been realized by means of a two-stage pulse compression. In the first stage, 90-psec pulses from a cw mode-locked Nd:YAG laser were compressed to ∼1.5 psec by using a standard fiber–grating-pair configuration. Subsequent propagation of these pulses through ∼20 m of single-mode optical fiber with a minimum dispersion at 1.27 μm led to a final pulse width of 33 fsec. This represents the shortest reported pulse generated at 1.32 μm by using the technique described above as well as the largest overall compression factor using optical fibers yet reported.

Optical and structural investigation of Nd3+ in silica-based fibres

Abstract: Le systeme a la composition suivante: 94,5 SiO 2 -5,0 GeO 2 -0,5 P 2 O 5 . Les proprietes du titre sont etudiees par spectrometrie de fluorescence et par microscopie electronique a transmission analytique. Il se forme des clusters lorsque la concentration en Nd(III) est au-dessus de 10 3 ppm

Passively mode locked c.w. dye lasers operating from 490 nm to 800 nm

Abstract: Passively mode locked c.w. dyes lasers now represent an important source of femtosecond optical pulses tunable through the visible and near infra red spectrum. Pulses as short as 70 fs have been obtained from dispersion-optimised CPM cavity configurations using active/passive dyes other than the standard combination of Rhodamine 6G and DODCI.

Femtosecond soliton Raman ring laser

Abstract: Pulses as short as 100 fs have been generated in standard single-mode optical fibre using a high-order soliton compression mechanism of the Raman component, synchronously excited in a ring laser geometry, pumped by a CW mode-locked Nd: YAG laser at 1.32?m.

Passive mode locking of a continuous-wave energy-transfer dye laser operating in the near infrared around 750 nm

Abstract: The passive mode locking of an argon-ion-pumped energy-transfer cw dye laser operating in the near infrared is reported. The dyes 1,1′-diethyl-4,4′-carbocyanine iodide and 1,1′-diethyl-2,2′-dicarbocyanine iodide were used separately to mode lock a gain medium comprising the dyes DCM and Rhodamine 700. Subpicosecond pulses were generated from 732 to 761 nm in a simple linear cavity, and pulses as short as 110 fsec were obtained from a colliding-pulse mode-locked ring cavity that was tuned between 742 and 754 nm.

High-order soliton pulse compression and splitting at 1.32 µm in a single-mode optical fiber

Abstract: The optically compressed pulses from a CW mode-locked Nd:YAG laser operating at 1.32 μm have been further compressed through a high-order soliton generation effect in a 40 m length of single-mode dispersion-shifted optical fiber. Two- and three-fold splitting of the soliton pulses have been demonstrated. Experimental compression factors and spectra for N = 3, 5, 7, 9, 11 , and 13 solitons have been shown to agree qualitatively with theory. In shorter fiber lengths pulses as short as 33 fs have been generated, corresponding to an over-all compression factor of X2700, the largest reported so far.

Passive mode locking of a continuous wave dye laser operating in the blue-green spectral region

Abstract: The passive mode locking of a continuous wave dye laser operating in the blue‐green spectral region is reported for the first time. In a simple linear configuration with no optimization of the intracavity dispersion, coumarin 102, excited by the ultraviolet lines of an argon ion laser, has been mode locked using 3,3’‐diethyl oxacarbocyanine iodide over the spectral range 487–508 nm, yielding pulses as short as 580 fs duration at 498 nm.

Femtosecond single-pass cascade Raman soliton generation at 1.5 μm

Abstract: Highly efficient generation of 130fs pulses at 1.5 μm, through a single-pass cascade Raman soliton-like compression-amplification process in a single-mode fibre, is described. The dispersion-shifted fibre, with a zero-dispersion wavelength at 1.46μm, was pumped by the lOOps pulses from a CW mode-locked Nd : YAG laser operated at 1.32 μm.

Cascade Raman soliton fiber ring laser

Abstract: Pulses as short as 200 fsec at 1.5 microm and 230 fsec at 1.6 microm have been generated through a cascade Raman, solitonlike process in a fiber ring oscillator. A dispersion-shifted (lambda(0) = 1.46 microm) single-mode fiber was used as the gain medium, which was synchronously pumped by a cw mode-locked Nd:YAG laser operated at 1.32 microm.

Conventional and Expert-Aided Data-Base Management for Computer-Aided Control Engineering

Abstract: There has been substantial recent progress in the development of software for computer-aided control engineering. This includes both "conventional" software as well as environments based on the use of expert systems. One major area has not received much attention until very recenty: data-base management. In this paper, we define a framework for database management, describe a set of design assumptions and corresponding functional requirements, and describe several roles that an expert system can play in this activity.

Rule-based real-time control systems

Abstract: The premise that one can obtain more effective control systems with less engineering effort, less technical risk, and less cost via the use of artificial intelligence techniques is explored in this paper. In particular, we discuss, develop, and illustrate the use of a rule-based system for real-time control as a software environment that can be used for control system implementation, relieving the design engineer of much of the burden of taking a basic control algorithm and making it work in a real-world application. We show that the rule-based systems approach can be used to provide substantial support for the above task. A rule-based system provides the environment in which the designer can develop and test all of the required heuristic logic and control, using a programming language (production rules) that is ideally suited for the task. We develop the details of such an implementation methodology, and illustrate its application to failure detection and isolation.

Effect of diazepam on the speed of mental rotation.

Abstract: The effect of diazepam on spatial visualization was studied using a double-blind crossover design. Diazepam 10 mg (or placebo) was given orally to 12 healthy young men at bedtime, followed again by 10 mg (or placebo) the next morning. One hour after the administration of the morning dose, the subjects performed a mental rotation task. Diazepam effects were analyzed in terms of an information processing model previously constructed to account for performance of the task. Using this method, the slope and intercept parameters of a linear function relating reaction time to task condition (i.e., angular difference in orientation between two identical stimulus figures) were computed for diazepam and placebo conditions. Diazepam significantly increased the slope and intercept of the mental rotation function (P<0.05). These results suggest that diazepam impairs spatial visualization ability.

Dynamic data acquisition, reduction, and analysis for the identification of high-speed compressor component post-stability characteristics

Abstract: A compressor test was conducted in which transient data were obtained for the purpose of identifying the high-speed post-stability characteristics. The transient, surge-cycle nature of high-speed post-stability operation precludes the possibility of obtaining the characteristics in a steady-state manner, as is possible during low-speed poststability operation, which is characterized by quasi-steady rotating-stall behavior. Specialized compressor instrumentation was developed and was used to obtain the necessary surge-cycle performance data, which were then digitized, filtered, and analyzed. The high-speed post-stability characteristics were obtained through the use of a maximum likelihood-parameter estimation technique. The estimated characteristics were found to be insensitive to the presence of measurement noise and unmodelled system dynamics, but the compressor time-response constants, which were also estimated, were more sensitive to these same disturbances.

Optical pulse compression of raman-depleted picosecond pulses and spectrally windowed self-phase modulated pulses at 1.06 μm

Abstract: Two pulse-shortening schemes based on the nonlinear propagation of picosecond pulses from a Nd: YAG laser in single-mode optical fibres are described. In the first experiment, a spectral-windowing technique was employed to compress self-phase modulated pulses exiting 100 m of optical fibre, and compression factors of 2.5 were recorded in good agreement with theoretical predictions. The technique was adapted to enable the time-dependent frequency shift occurring after pulse propagation through 2 km of fibre to be measured. In the second experiment, cascaded stimulated Raman generation, occurring when a high-power pump pulse propagated in 4 m of fibre, was studied. Lower-order components in the cascade were severely depleted through generation of higher-order Stokes signals, leaving negatively chirped pulse fragments. These were compressed with a dispersion-tunable Gires-Tournois interferometer and compression ratios of times 4 were obtained.