一类时滞不确定非线性系统的鲁棒控制器设计

针对一类具有单输入滞后不确定非线性系统 ,采用精确反馈线性化方法和 Lyapunov方法设计出一种使系统终极有界 ( UUB)的无记忆光滑状态反馈鲁棒控制器 .仿真算例表明了本文所采用方法的有效性 .

海洋机器人变参数大时延控制系统补偿方法的研究

本文提出一种变参数大时延系统的补偿方法，具有传输滞后系统的幅相频率特性和时域特性，流体动力学变参数的修正方法和具有传输滞后和零阶保持器滞后的补偿仿真。

计算机辅助带时延多变量系统的离散控制设计

本文将Smith预估技术与逆 Nyquist 阵列法结合对多时延多变量对象进行离散控制系统设计,采用这种方法设计出的控制器易用计算机实现,系统仿真结果也是令人满意的。

磁层-电离层耦合现象的分析研究

The magnetosphere-ionosphere coupling is mainly manifested by the trans- porting processes of energy into the ionosphere , the energy is carried by solar wind and firstly accumulate at the magnetosphere, and the coupling processes also significantly include the interaction between the magnetosphere and ionosphere for mass and energy. At the quiet condition, energy is delivered by the large-scale convection of the geomagnetic field; the huge energy from solar wind bulk will be injected into and consumed at the near magnetosphere and ionosphere by the geomagnetic storm and substorm activities. Aurorae and FACs (Field-aligned currents) are the important phenomena in the coupling processes. In the present work, firstly, we analyze the activity characteristics of auroral precipitating particle, secondly, we study the distribution characters of large-scale field aligned currents (LS FACs) at storm-time using the observations from different satellites at different altitudes. Finally, we investigate the evolution of the geomagnetic field configuration at the nightside sector on the onset of the expansion phase in a substorm event, the substorm event happened at 0430UT to 0630UT on 8th Nov. 2004. The main results as follows： At the first, the data of the estimated power input (EPI) of auroral particles from NOAA/POES (Polar orbiting environmental satellite) for some 30 years have been analyzed. The variation tendencies of the EPI generally coincide with aa, AE and Dst indices. The annual variation of EPI shows equinox peaks and an asymmetric-activity with a higher peak in the winter-hemisphere than in the summer-hemisphere. The diurnal UT variations are different from north and south hemisphere: for north hemisphere, the peak appears at 1200UT, and the relative deviation is 22% to the daily average of the north hemisphere. For south hemisphere, the maximal deviation is 22% at 2000UT. So the diurnal variation of EPI is more dominant than the annual variation which maximal deviation is 3% to 12% for different seasons. Studies on correlations of the hourly average of EPI, Pa, with AE and Dst indices show a correlation coefficient r=0.74 of Pa and AE, and r=-0.55 of Pa and Dst. The hourly EPIs for north and south polar regions, NPa and SPa, show a north-south asymmetry with a higher correlation of SPa and AE (or Dst). Time delays of EPI with respect to magnetic indices are examined, the maximum correlation coefficient of Pa with AE (r=0.78) occurs when the time delay =0, suggesting a synchronous activity of auroral electrojet and auroral precipitating particles, while =1-2h, the correlation coefficient of Pa with Dst is maximum (r=0.57), suggesting that the activity of auroral particle precipitating may influence the ring current on some extent. Sencondly, we use the high-resolution magnetic field vector data of the CHAMP satellite to investigate the distribution of large-scale FACs during the great magnetic storm on 7th to 8th Nov. 2004. The results show that, whether in the northern or southern hemisphere, the number and density of large-scale FACs during the main-phase are more and bigger than these during the recover-phase, and the number of large-scale FACs in morning sector obviously is more than that in afternoon sector. In terms of the magnetic indices, we find that large-scale FACs in morning sector significantly affected by the substorm activities, while in afternoon sector the large-scale FACs mainly indicate the fluctuations of the ring-current in storm time. Accordingly to the former studies, similarly, we find that in the morning sector, the scale of the large-scale FACs move to the high-latitude region, and in the afternoon sector, large-scale FACs distinctly expand to the low-latitude region. During the time periods that the NOAA/POES auroral precipitating particle power data temporally correspond to the large-scale FACs, the more the power of auroral particle is, the more and bigger the number and density of FACs are. At the same time, we use the magnetic field vector data of POLAR obtain a good form of region 1, region 2, and three pieces of cusp FACs during a single transit at 1930UT-2006UT on 07th. And the characteristics of simultaneous electric field and energy particles observations on Polar are coincide with the five FACs pieces. Finally, by means of the observation of Cluster 4 and Goes 10、 Goes 12, we analyze the evolution process of the change of the magnetic field configuration at night sector at the expansion phase of a substorm event which happened during 0430UT to 0630UT on 8th Nov. 2004, we find that the times of the beginning of the polarizations of magnetic field are observed from Goes 10 to Goes 12 then to Cluster 4. So, at the synchronous orbit ( 6.6 RE) to 10RE distance scale of the neutral sheet, the current disruption spread tailward. Simultaneously, the strengthen of the FACs deduced from these satellites’ magnetic field observations are almost consistent with the times of polarizations, as well as the high energy particles injection and the electric field dominant variation. The onset times determined by the magnetic field polarizations from these satellites are all ahead of the onset time that confirmed from the auroral electrojet indices. So, these characters of different observations can be used as the criterions to determine the onset time for the substorms of such type as we studied.

中低纬电离层暴的统计分析与经验建模

As a key issue of ionospheric weather study, systemic studies on ionospheric storms can not only further improve our understanding of the response of the ionosphere to solar and geomagnetic disturbances, but also help us to reveal the chemical, dynamic and electro-dynamic mechanisms during storms. Empirical modelling for regional ionospheric storm is also very useful, because it can provide us with tools and references for the forecasting and further practical application of ionospheric activity. In this thesis, we focus on describing and forecasting of ionospheric storms at middle and low latitudes. The main points of my investigations are listed as follows. (1) By using magnetic storms during the period over 50 years, the dependence of the type, onset time and time delay of the ionospheric storms on magnetic latitude, season and local time at middle and low latitudes in the East-Asian sector are studied. The results show that the occurrences of the types of ionospheric disturbances differ in latitude and season. The onset of the ionospheric storms depends on local time. At middle latitudes, most negative phase onsets are within the local time interval from night to early morning, and they rarely occurred in the local noon and afternoon sectors. At low latitudes, positive phases commence most frequently in the daytime sector as well as pre-midnight sector. The average time delays for both the positive and negative ionospheric storms increase with descending latitudes. The time delay has significant dependence on the local time of main phase onset (MPO). The time delay of positive response is shorter for daytime MPO and longer for night-time MPO, whereas the opposite applies for negative response. (2) Based on some previous researches, a primary empirical model for mid-latitude ionospheric disturbance is set up. By fitting to the observed data, we get a high accuracy with a mean RMSE of only 12-14% in summer and equinox. The model output has been compared with the output of STORM model, and the results show that, our model is much better than STORM in summer and a little better for some mid-latitude stations at equinox. Especially, for the type of two-step geomagnetic storm, our model can present twice descending of foF2 very well. In addition, our model can forecast positive ionospheric storms.

保重心脉冲压缩滤波及其在速度自动拾取中的应用

To pick velocity automatically is not only helpful to improve the efficiency of seismic data process, but also to provide quickly the initial velocity for prestack depth migration. In this thesis, we use the Viterbi algorithm to do automatic picking, but the velocity picked usually is immoderate. By thorough study and analysis, we think that the Viterbi algorithm has the function to do quickly and effectually automatic picking, but the data provided for picking maybe not continuous on derivative of its curved surface, viz., the curved face on velocity spectrum is not slick. Therefore, the velocity picked may include irrational velocity information. To solve the problem above, we develop a new method to filter signal by performing nonlinear transformation of coordinate and filter of function. Here, we call it as Gravity Center Preserved Pulse Compressed Filter (GCPPCF). The main idea to perform the GCPPCF as follows: separating a curve, such as a pulse, to several subsection, calculating the gravity center (coordinate displacement), and then assign the value (density) on the subsection to gravity center. When gravity center departure away from center of its subsection, the value assigned to gravity center is smaller than the actual one, but non other than gravity center anastomoses fully with its subsection center, the assigned value equal to the actual one. By doing so, the curve shape under new coordinate breadthwise narrows down compare to its original one. It is a process of nonlinear transformation of coordinate, due to gravity center changing with the shape of subsection. Furthermore, the gravity function is filter one, because it is a cause of filtering that the value assigned from subsection center to gravity center is obtained by calculating its weight mean of subsetion function. In addition, the filter has the properties of the adaptive time delay changed filter, owing to the weight coefficient used for weight mean also changes with the shape of subsection. In this thesis, the Viterbi algorithm inducted, being applied to auto pick the stack velocity, makes the rule to integral the max velocity spectrum ("energy group") forward and to get the optimal solution in recursion backward. It is a convenient tool to pick automatically velocity. The GCPPCF above not only can be used to preserve the position of peak value and compress the velocity spectrum, but also can be used as adaptive time delay changed filter to smooth object curved line or curved face. We apply it to smooth variable of sequence observed to get a favourable source data ta provide for achieving the final exact resolution. If there is no the adaptive time delay-changed filter to perform optimization, we can't get a finer source data and also can't valid velocity information, moreover, if there is no the Viterbi algorithm to do shortcut searching, we can't pick velocity automatically. Accordingly, combination of both of algorithm is to make an effective method to do automatic picking. We apply the method of automatic picking velocity to do velocity analysis of the wavefield extrapolated. The results calculated show that the imaging effect of deep layer with the wavefield extrapolated was improved dominantly. The GCPPCF above has achieved a good effect in application. It not only can be used to optimize and smooth velocity spectrum, but also can be used to perform a correlated process for other type of signal. The method of automatic picking velocity developed in this thesis has obtained favorable result by applying it to calculate single model, complicated model (Marmousi model) and also the practical data. The results show that it not only has feasibility, but also practicability.

序列视觉信息整合的特性与机制

One of the great puzzles in the psychology of visual perception is that the visual world appears to be a coherent whole despite our viewing it through temporally discontinuous series of eye fixations. The investigators attempted to explain this puzzle from the perspective of sequential visual information integration. In recent years, investigators hypothesized that information maintained in the visual short-term memory (VSTM) could become visual mental images gradually during time delay in visual buffer and integrated with information perceived currently. Some elementary studies had been carried out to investigate the integration between VSTM and visual percepts, but further research is required to account for several questions on the spatial-temporal characteristics, information representation and mechanism of integrating sequential visual information. Based on the theory of similarity between visual mental image and visual perception, this research (including three studies) employed the temporal integration paradigm and empty cell localization task to further explore the spatial-temporal characteristics, information representation and mechanism of integrating sequential visual information (sequential arrays). The purpose of study 1 was to further explore the temporal characteristics of sequential visual information integration by examining the effects of encoding time of sequential stimuli on the integration of sequential visual information. The purpose of study 2 was to further explore the spatial characteristics of sequential visual information integration by investigating the effects of spatial characteristics change on the integration of sequential visual information. The purpose of study 3 was to explore the information representation of information maintained in the VSTM and integration mechanism in the process of integrating sequential visual information by employing the behavioral experiments and eye tracking technology. The results indicated that: (1) Sequential arrays could be integrated without strategic instruction. Increasing the duration of the first array could cause improvement in performance and increasing the duration of the second array could not improve the performance. Temporal correlation model was not fit to explain the sequential array integration under long-ISI conditions. (2) Stimuli complexity influenced not only the overall performance of sequential arrays but also the values of ISI at asymptotic level of performance. Sequential arrays still could be integrated when the spatial characteristics of sequential arrays changed. During ISI, constructing and manipulating of visual mental image of array 1 were two separate processing phases. (3) During integrating sequential arrays, people represented the pattern constituted by the objects' image maintained in the VSTM and the topological characteristics of the objects' image had some impact on fixation location. The image-perception integration hypothesis was supported when the number of dots in array 1 was less than empty cells, and the convert-and-compare hypothesis was supported when the number of the dot in array 1 was equal to or more than empty cells. These findings not only contribute to make people understand the process of sequential visual information integration better, but also have significant practical application in the design of visual interface.

Prediction of 30-day mortality in older patients with a first acute myocardial infarction

This study sought predictors of mortality in patients aged >or=75 years with a first ST-segment elevation myocardial infarction (STEMI) and evaluated the validity of the GUSTO-I and TIMI risk models. Clinical variables, treatment and mortality data from 433 consecutive patients were collected. Univariable and multivariable logistic regression analyses were applied to identify baseline factors associated with 30-day mortality. Subsequently a model predicting 30-day mortality was created and compared with the performance of the GUSTO-I and TIMI models. After adjustment, a higher Killip class was the most important predictor (OR 16.1; 95% CI 5.7-45.6). Elevated heart rate, longer time delay to admission, hyperglycemia and older age were also associated with increased risk. Patients with hypercholesterolemia had a significantly lower risk (OR 0.46; 95% CI 0.24-0.86). Discrimination (c-statistic 0.79, 95% CI 0.75-0.84) and calibration (Hosmer-Lemeshow 6, p = 0.5) of our model were good. The GUSTO-I and TIMI risk scores produced adequate discrimination within our dataset (c-statistic 0.76, 95% CI 0.71-0.81, and c-statistic 0.77, 95% CI 0.72-0.82, respectively), but calibration was not satisfactory (HL 21.8, p = 0.005 for GUSTO-I, and HL 20.6, p = 0.008 for TIMI). In conclusion, short-term mortality in elderly patients with a first STEMI depends most importantly on initial clinical and hemodynamic status. The GUSTO-I and TIMI models are insufficiently adequate for providing an exact estimate of 30-day mortality risk.

Extracted Memory from Temporal Patterns Using Adaptive Resonance and Recurrent Network

We can recognize objects through receiving continuously huge temporal information including redundancy and noise, and can memorize them. This paper proposes a neural network model which extracts pre-recognized patterns from temporally sequential patterns which include redundancy, and memorizes the patterns temporarily. This model consists of an adaptive resonance system and a recurrent time-delay network. The extraction is executed by the matching mechanism of the adaptive resonance system, and the temporal information is processed and stored by the recurrent network. Simple simulations are examined to exemplify the property of extraction.

Broadband chaos generated by an optoelectronic oscillator.

We study an optoelectronic time-delay oscillator that displays high-speed chaotic behavior with a flat, broad power spectrum. The chaotic state coexists with a linearly stable fixed point, which, when subjected to a finite-amplitude perturbation, loses stability initially via a periodic train of ultrafast pulses. We derive approximate mappings that do an excellent job of capturing the observed instability. The oscillator provides a simple device for fundamental studies of time-delay dynamical systems and can be used as a building block for ultrawide-band sensor networks.

Developing Single-Laser Sources for Multimodal Coherent Anti-Stokes Raman Scattering Microscopy

Coherent anti-Stokes Raman scattering (CARS) microscopy has developed rapidly and is opening the door to new types of experiments. This work describes the development of new laser sources for CARS microscopy and their use for different applications. It is specifically focused on multimodal nonlinear optical microscopy—the simultaneous combination of different imaging techniques. This allows us to address a diverse range of applications, such as the study of biomaterials, fluid inclusions, atherosclerosis, hepatitis C infection in cells, and ice formation in cells. For these applications new laser sources are developed that allow for practical multimodal imaging. For example, it is shown that using a single Ti:sapphire oscillator with a photonic crystal fiber, it is possible to develop a versatile multimodal imaging system using optimally chirped laser pulses. This system can perform simultaneous two photon excited fluorescence, second harmonic generation, and CARS microscopy. The versatility of the system is further demonstrated by showing that it is possible to probe different Raman modes using CARS microscopy simply by changing a time delay between the excitation beams. Using optimally chirped pulses also enables further simplification of the laser system required by using a single fiber laser combined with nonlinear optical fibers to perform effective multimodal imaging. While these sources are useful for practical multimodal imaging, it is believed that for further improvements in CARS microscopy sensitivity, new excitation schemes are necessary. This has led to the design of a new, high power, extended cavity oscillator that should be capable of implementing new excitation schemes for CARS microscopy as well as other techniques. Our interest in multimodal imaging has led us to other areas of research as well. For example, a fiber-coupling scheme for signal collection in the forward direction is demonstrated that allows for fluorescence lifetime imaging without significant temporal distortion. Also highlighted is an imaging artifact that is unique to CARS microscopy that can alter image interpretation, especially when using multimodal imaging. By combining expertise in nonlinear optics, laser development, fiber optics, and microscopy, we have developed systems and techniques that will be of benefit for multimodal CARS microscopy.

Dissociation of H2+ from a short, intense, infrared laser pulse: proton emission spectra and pulse calibration

The proton energy spectrum from photodissociation of the hydrogen molecular ion by short intense pulses of infrared light is calculated. The time-dependent Schrödinger equation is discretized and integrated. For few-cycle pulses one can resolve vibrational structure, arising from the experimental preparation of the molecular ion. We calculate the corresponding energy spectrum and analyse the dependence on the pulse time delay, pulse length and intensity of the laser for ? ~ 790 nm. We conclude that the proton spectrum is a sensitive probe of both the vibrational populations and phases, and allows us to distinguish between adiabatic and nonadiabatic dissociation. Furthermore, the sensitivity of the proton spectrum from H2+ is a practical means of calibrating the pulse. Our results are compared with recent measurements of the proton spectrum for 65 fs pulses using a Ti:Sapphire laser (? ~ 790 nm) including molecular orientation and focal-volume averaging. Integrating over the laser focal volume, for the intensity I ~ 3 × 1015 W cm-2, we find our results are in excellent agreement with these experiments.

Multi-pulse scheme for enhancing electron localization through vibrational wavepacket manipulation

A novel scheme for enhancing electron localization in intense-field dissociation is outlined. Through manipulation of a bound vibrational wavepacket in the exemplar deuterium molecular ion, simulations demonstrate that the application of multiple phase-locked, few-cycle IR pulses can provide a powerful scheme for directing the molecular dissociation pathway. By tuning the time delay and carrier–envelope–phase for a sequence of pulse interactions, the probability of the electron being localized to a chosen nucleus can be enhanced to above 80%.

Effect of temporal separation on synchronization in rhythmic performance

A variety of short time delays inserted between pairs of subjects were found to affect their ability to synchronize a musical task. The subjects performed a clapping rhythm together from separate sound-isolated rooms via headphones and without visual contact. One-way time delays between pairs were manipulated electronically in the range of 3 to 78 ms. We are interested in quantifying the envelope of time delay within which two individuals produce synchronous per- formances. The results indicate that there are distinct regimes of mutually coupled behavior, and that `natural time delay'o¨delay within the narrow range associated with travel times across spatial arrangements of groups and ensembleso¨supports the most stable performance. Conditions outside of this envelope, with time delays both below and above it, create characteristic interaction dynamics in the mutually coupled actions of the duo. Trials at extremely short delays (corresponding to unnaturally close proximity) had a tendency to accelerate from anticipation. Synchronization lagged at longer delays (larger than usual physical distances) and produced an increasingly severe deceleration and then deterioration of performed rhythms. The study has implications for music collaboration over the Internet and suggests that stable rhythmic performance can be achieved by `wired ensembles' across distances of thousands of kilometers.

Two-colour pulsed Raman studies of the lowest excited singlet state of tetraphenylporphyrin: band assignments and electronic structure

The resonance Raman spectra of the lowest lying singlet (S-1) state of free-base tetraphenylporphyrin and seven of its isotopomers were recorded under pump-and-probe conditions with a time delay of -2 ns between pump and probe laser pulses, In the S-1 spectra of the isotopomers, as in the ground state, there are dramatic splittings of what appear to be single bands in the natural isotopic abundance spectrum. The most structurally significant bands of the S-1 state were assigned on the basis of the isotope data, In some cases it was necessary to curve fit unresolved bands in the excited-state spectra in order to account for observed intensity ratios and to rationalize isotope shifts, The changes in band positions on excitation to the S-1 state were compared with those from earlier studies on the T-1 state. The changes in band positions were found to be similar For both excited states. Most notable was the similar shift in nu(2), the most widely used marker band for orbital character. The data are interpreted as implying that the lowest lying singlet state is a configuration interaction admixture of b(1u)b(2g) + a(u)b(3g) configurations with the coefficients weighted heavily in favour of b(1n)b(2g), which Is the configuration of the T-1 state. Copyright (C) 2000 John Wiley & Sons, Ltd.