Observer-Based Autopilot Heading Finite-Time Control Design for Intelligent Ship with Prescribed Performance

Global cooling in marine climates and local tectonic events in Southwest Japan at the Plio–Pleistocene boundary

Numerical simulations were generated using a nonlinear shallow-water model of velocity potential to study the fundamental processes of tsunami generation and amplification by atmospheric pressure waves. When an atmospheric pressure wave catches up with an existing tsunami that is propagating as a free wave over an abrupt change in water depth, the amplified tsunami propagates in the shallower water. An existing tsunami propagating as a free wave over a sloping seabed is also amplified by being passed by atmospheric pressure waves. When atmospheric pressure waves travel over an abrupt change in water depth, the water surface profile of tsunamis in the shallower water depends on both the interval of the atmospheric pressure waves and the phase of the tsunami-generation process over the change in water depth. Moreover, when atmospheric pressure waves travel over an abrupt change in water depth, the tsunami amplitude in the shallower water increases, as the water depth of the shallower area is decreased and the Proudman resonance is further reduced. When an atmospheric pressure wave train with positive pressure travels over a sloping seabed, the amplification of tsunami crests propagating as free waves is controlled by leaving the forced water waves following the atmospheric pressure waves. Conversely, the amplitudes of tsunami troughs propagating as free waves increase.

<p><br><html></p><p><head><br><title>    A research on initial formation process of intermittent debris flow   </title><br></head></p><p><body><br>Some debris flows are intermittent surges flows with discontinuous changes in water depth.<br>These phenomena are considered to be a kind of nonlinear wave phenomena based on flow instability.<br>The authors show a KdV-Burgers equation as an equation representing the change in water depth.<br>When the phase velocity in the equation is long wave velocity, the equation becomes a Burgers equation.<br>The characteristic of the roll wave is that it has a discontinuous change in water depth and flows down intermittently as many surges. </p><p><br><br>Roll wave experiments were performed using a straight channel with a length of 56m, a width of 10cm, a depth of 15cm and a channel gradient of θ=2.5 deg.<br>The experimental conditions are by a plane water and a flow containing 42% (C=0.42) solid particles.<br>The particles are cylindrical particles with a typical particle size of d = 3 mm and a density of σ=1.04 g/cm<sup>3</sup> made of polystyrene. <br>The flow conditions of the plane water are as follows: mean discharge Q = 1112cm<sup>3</sup>/s, <br>mean depth h<sub>0</sub> = 1.23cm at the downstream end of the channel, <br>mean flow velocity u<sub>0</sub> = 90.2cm/s, <br>and the flow conditions with solid particles Q=1193cm<sup>3</sup>/s, h<sub>0</sub> = 1.35cm, u<sub>0</sub> = 88.4cm/s. <br>To supply water to the flume, a water tank storing 0.5m<sup>3</sup> is placed on the upstream side of the flume, <br>and water or a mixture of water and particles is supplied from the upstream end of the flume.<br>The water tank is closed and the inside is kept at a constant pressure according to the Marriott bottle principle. As a result, the water supply is constant.</p><p><br><br>In the case of plane water, the period is T = 1.12sec at x = 14m from the upstream end of the flume, <br>and at the downstream end x = 56m T = 2.25sec. <br>In the flow including solid particles, T = 1.78sec and T = 3.06sec at the same position.<br>In each case, the surge period becomes longer as the flow goes down. <br>The wave velocity of the surge here in the experimental results is different. <br>Looking at the details of the waveform, the subsequent surge may catch up.<br>Therefore, it is considered that the period of the surge becomes longer as it flows down and combines with other surges. <br>In the Burgers equation, the initial condition waveform is integrated into a waveform with wave number k = 1 by the initial condition of a non-integer multiple waveform and non-fixed boundary conditions at both ends.<br>From the above, it is considered that the initial waveform formation of the roll wave is contributed by the weak shock wave equation such as the Burgers equation.<br>In this Burgers equation, when the waveform is integrated into a waveform with wavenumber k = 1, the analytical solution shows that the phase velocity v<sub>p0</sub> is no longer c<sub>0</sub>.<br>Therefore, the governing equation returns to the KdV-Burgers equation.</p><p><br></body></p><p></html></p>

The microfacies of a Lower Cretaceous carbonate drillcore from Oman are characterized using optimizing matrices of Jaccard's similarity coefficients of community. Other than systems tract boundaries, there is no obvious evidence of individual parasequences in the core. However, diagnostic patterns in microfossil distribution identify environmental gradients recording changes in water depth. These gradients are used to define individual parasequences, parasequence sets, stacking patterns and key surfaces. The patterns suggest that deposition was controlled by successive fourth- to fifth-order (high-frequency) relative sea-level cycles superimposed on an underlying third-order relative sea-level rise. Although the correlation of these depositional subunits to systematic changes in water depth and the rate of carbonate accumulation alone is not incontrovertible proof of such a sea-level control, concurrent multiorder relative sea-level cyclicity provides by far the most likely explanation. A microfacies deposited when the water depth was shallowing is characterized by a relay of microfossils with affinities that shallow upwards. Conversely, a microfacies that records a gradual increase in water depth has a relay of microfossils with affinities that deepen upwards. Microfacies characterized by an assemblage of microfossils with similar affinities record deposition when the benthic environmental conditions remained stable, either because of an equilibrium between shallow water carbonate deposition and rising sea level, or in deeper water where sediment composition was relatively insensitive to changes of water depth. Microfacies characterized by mixed affinity assemblages record syndepositional reworking. During periods of embedded multiorder sea-level changes, individual parasequences within systems tracts are shown to record more complex environmental gradients than simply the repetition of successive shallowing-up units as traditionally represented in carbonate sequence stratigraphic models. The microfacies of an individual parasequence may shallow up, or may record both deepening-up and shallowing-up depositional phases, as well as periods of sedimentation when benthic environments remained stable. Individual parasequence boundaries may be submarine or subaerial unconformities, or be conformable, as part of a predictable stratigraphic pattern related to the temporal position of an individual parasequence within the underlying third-order cycle of relative sea-level change. The hitherto ubiquitous use of assemblages to describe carbonate microfacies, coupled with the widespread use of the metre-scale shallowing-up template to identify parasequences, may have led to such complexities previously being overlooked.

Climate and human modifications, including restoration, are changing freshwater availability in wetland ecosystems. Changes in spatiotemporal variability in water depth can influence biogeochemistry and aquatic metabolism (net ecosystem productivity, gross primary productivity [GPP], and ecosystem respiration [ER]). In subtropical wetlands, flocculent organic matter (floc) is a dominant form of organic matter made up of periphyton, macrophytes, and microbes. How changes in water depth with climate and human modifications of subtropical wetlands influence biogeochemistry and the metabolism of floc is uncertain and necessary to understand the consequences for carbon (C) cycling. We collected seasonal floc samples from shorter‐hydroperiod marshes (Taylor Slough Panhandle [TS/Ph]) and longer‐hydroperiod marshes (Shark River Slough [SRS]) in Everglades National Park (Florida, U.S.A.). We measured floc‐specific metabolism and biogeochemistry during the wet (May–November) and dry seasons (December–April) when marsh conditions differed in water depth, photosynthetically active radiation (PAR), floc chlorophyll a, bulk density, and C and nutrients. Floc biogeochemistry was driven by hydrologic changes in water depth, while floc metabolism was influenced by floc biogeochemistry and PAR in both marshes. Floc‐specific metabolism was more net heterotrophic (GPP < ER) in TS/Ph than in SRS, driven by floc bulk density, total nitrogen, total C, total phosphorus, and total inorganic C. Increasing water depths with freshwater restoration may drive higher rates of C loss in shallower compared to deeper marshes. Understanding how hydrologic changes affect organic matter lability and respiration is important in managing C storage in ecosystems.

Observer-based Adaptive Controller Design for Nonlinear Saturation Systems With Output Constraints

Recent global change occurs within decades and leaves a significant imprint on shallow carbonate platforms. To what extent can rate and synchronicity of environmental changes in the past be evaluated in order to allow comparisons with the processes and products of today? Sections of a carbonate‐dominated platform of Late Oxfordian age have been logged in detail in the Swiss Jura Mountains. The time frame, based on ammonite biostratigraphy and the hierarchical stacking of the sedimentary sequences, suggests that these formed by low‐amplitude, high‐frequency sea‐level changes in tune with the orbital cycles. The smallest unit, the elementary sequence, can thus be attributed to the 20 kyr precession cycle. By identifying sequence‐stratigraphic elements such as maximum‐flooding surfaces within an elementary sequence, an even higher time resolution can be obtained and reconstructions of changes in water depth and sea‐level are attempted. Sedimentation rates were highly irregular and discontinuity surfaces are common. Correlation of such surfaces from one section to the other is tentative because they could also have formed locally and are not necessarily synchronous. On the scale of elementary sequences, the vertical facies evolution permits interpretation of changes in water depth, which were produced by eustatic sea‐level changes (allocyclic) and/or by autocyclic processes. The distribution of clay minerals indicates changes of sea‐level, as well as of rainfall in the hinterland. Biotic changes were controlled by water depth and water quality, and also by nutrient and clay input. Carbon and oxygen isotopes do not show significant shifts within the elementary sequences. The original ecological, mineralogical and geochemical signals have partly been homogenized because of time‐averaging through bioturbation and through reworking by storms, and because of diagenetic modifications. Consequently, there is potential to interpret environmental changes on the studied carbonate platform but the time resolution is not better than a few thousand years. The rates and the synchronicity of the processes leading to the observed environmental changes can thus be estimated only within this time frame.

Cross-sectional-dependent microbial assembly and network stability: Bacteria sensitivity response was higher than eukaryotes and fungi in the Danjiangkou Reservoir.

Surface Effect Ships (SES) have great potential to increase the speed and cargo capacity of modern surface vessels. The resistance characteristics of an SES vary widely as a function of speed, with notable presence of one or more drag humps. The magnitude of these drag humps has been shown to be greatly affected by changes in water depth (Mantle, 1973; Van Dyck, 1972; Doctors, 2006). Additional variations in resistance due to sea state must also be accounted for and consequently, the selection and sizing of an appropriate propulsion system is not trivial. For highly loaded applications, SESs typically employ the use of waterjet propulsion. The propulsion system must satisfy many criteria, including cavitation avoidance, powering limitations, and maximizing fuel efficiency. These three goals are difficult to meet simultaneously, particularly when the performance of the system over the full operational range needs to be considered. Hence, an appropriate methodology is necessary to choose the optimal solution. The objective of this work is to develop a systematic methodology for the first-order design of a waterjet by optimizing the overall efficiency and satisfying all performance requirements over the entire operating regime, as opposed to selecting a discrete number of design points. In this work, a preliminary design of a waterjet propulsion system for a full-scale SES with a top speed of 40 knots is performed with consideration for cavitation inception and variations in resistance due to changes in water depth and sea state. The resistance characteristics are determined from model tests as reported by Van Dyck (1972). The waterjet performance is then predicted for various nozzle sizes using one-dimensional momentum theory. The optimal waterjet size is then selected based on the joint probability distribution of the operational space as functions of the vessel speed and resistance. Finally, the thrust characteristics of the optimal waterjet are presented and compared against ones designed for the endurance speed and top speed.

In this paper, the T-S fuzzy observer-based adaptive tracking control of the biological system with stage structure is studied. First, a biological model with stage structure is established, and its stability at the equilibrium points is analyzed. Considering the impact of reducing human activities on the biological population, an adaptive controller is applied to the system. Since it is difficult to measure density directly, a fuzzy state observer is designed, which is used to estimate the density of biological population. At the same time, the density of predators can track the desired density through the adjustment of adaptive controller. The stability of the biological system is guaranteed, and the observer error and tracking error are shown to converge to zero. Finally, the effectiveness of the proposed adaptive control method is verified by numerical simulation.

Ecosystem functioning is linked to microbial evenness and community composition along depth gradient in a semiarid lake

This paper is focused on the observer-based adaptive fuzzy control problem for nonlinear stochastic systems with the nonstrict-feedback form, in which some complicated and challenging issues including unmeasurable states, input quantization and actuator faults are addressed. The fuzzy logic systems are introduced to approximate the nonlinear functions existing in the control system. A fuzzy observer is designed to observe the unavailable state variables. In order to handle the negative effects resulting from input quantization and actuator faults, a damping term with the estimation of unknown bounds as well as a positive time-varying integral function are constructed, respectively. Furthermore, an observer-based adaptive fuzzy control scheme is proposed for the considered systems to compensate for the effects of input quantization and actuator fault based on adaptive backstepping approach. The proposed control strategy can guarantee that all the signals in the closed-loop system are bounded. Finally, simulation results are provided to illustrate the effectiveness of the proposed adaptive control scheme.

A disturbance observer-based adaptive control approach for flexure beam nano manipulators

Observer-based adaptive neural tracking control for a class of nonlinear systems with prescribed performance and input dead-zone constraints

Observer-based adaptive prescribed performance tracking control for nonlinear systems with unknown control direction and input saturation