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This paper presents a novel leader-follower consensus control for a particular class of nonlinear multi-agent mechanical systems in the presence of control input constraints and external disturbances which includes robot system dynamics with a wide range of potential applications in industry. In this case, one of the agents is selected as the leader to direct the other agents in such a way that the whole system can reach consensus within certain prescribed performance transient bounds. Due to the presence of disturbances in most practical systems, the effect of limited disturbance in the consensus control method has been investigated, and actuator saturation is included in the design process. A terminal sliding mode control method has been adapted to ensure the stability of the overall system and fast finite-time leader-follower consensus control. The simulation results of the multi-agent nonlinear robot system in MATLAB environment, in different scenarios with simultaneous consideration of actuator saturation and external disturbance, will show the efficiency of the proposed control method. [ABSTRACT FROM AUTHOR]

For a stochastic PID feedback control system, the uncertainty of the working environment often leads to the unsatisfied performance of the system, which does not meet the profit requirements. The working environment generally includes external disturbance and measurement noise, etc. Gaussian distributed measurement noise and disturbances are widely considered while non-Gaussian distributed measurement noise and disturbances are rarely considered. In this paper, the performance degradation of Gaussian/non-Gaussian disturbances and measurement noise on a stochastic PID feedback system is considered and analyzed. An efficient method, dynamic data reconciliation (DDR) is developed to filter measurement noise and disturbances and improve the performance of the stochastic PID feedback control system. By utilizing model-based and measured information, DDR avoids time delays in output estimation. With the detailed theoretical analysis and simulation verification, the effectiveness of the proposed DDR technology on the stochastic PID feedback control system is verified. Compared with conventional exponential filters, DDR can achieve better control performance. The proposed DDR is also used for the control system of the DC–AC​ converter. The improved effect of DDR on the output quality is demonstrated by the results. • Effect of Gaussian/non-Gaussian disturbances on control performances is analyzed. • Dynamic data reconciliation (DDR) is developed to enhance control performances. • DDR corrects measurements with Gaussian/non-Gaussian disturbances and noises. • SISO, MIMO, and DC–AC converter control systems are used for verification. [ABSTRACT FROM AUTHOR]

Companies operating in global production networks face increasing complexity, uncertainty, and volatility making them more susceptible to disruptions. However, disruption management is characterized by intuitive reactions that focus exclusively on production or logistics, making cross-cutting solutions difficult. Therefore, this paper presents an approach to an integrated disruption management that combines production and logistics perspectives by considering relevant network partners in order to implement efficient, network-optimal (combinations of) countermeasures to disruptions. Using simulation, design of experiments, and metamodeling of cause-effect relationships between disruptions, countermeasures, and network performance, the approach enables fostering network robustness by efficient decision-making in highly complex environments. [ABSTRACT FROM AUTHOR]

The paper is dedicated to the robustness analysis of scalar multi-agent dynamical systems. The open problem we aim to address is the one related to the impact of additive disturbances. Set-theoretic methods are used to achieve the main results in terms of positive invariance and admissible bounds on the disturbances. [ABSTRACT FROM AUTHOR]

The LQR (linear quadratic regulator) control problem subject to singular system constitutes a optimization problem in which one must be find an optimal control that satisfy the singular system and simultaneously to optimize the quadratic objective functional. In this paper we establish a sufficient condition to obtain the optimal control of discounted LQR optimization problem subject to disturbanced singular system where the disturbance is time varying. The considered problem is solved by transforming the discounted LQR control problem subject to disturbanced singular system into the normal LQR control problem. Some available results in literatures of the normal LQR control problem be used to find the sufficient conditions for the existence of the optimal control for discounted LQR control problem subject to disturbanced singular system. The final result of this paper is in the form a method to find the optimal control of discounted LQR optimization problem subject to disturbanced singular system. The result shows that the disturbance is vanish with the passage of time. [ABSTRACT FROM AUTHOR]

• Control scheme design of the benzene/isopropanol/water separation. • Open loop steady-state gain analysis to determine temperature sensitive plates. • Robust control of sensitive plate temperature by the steam separation ratio (β V). • Dynamic performance comparison of CED and DWED. The effective separation of the ternary azeotrope benzene/isopropanol/water has high economic benefits in industry. It is of great significance to study the dynamic controllability of this ternary azeotropic system. In this paper, dynamic control schemes of the conventional extractive distillation (CED) and the dividing wall extractive distillation (DWED) for benzene / isopropanol / water separation with ethylene glycol (EG) as extractant were studied. The open loop steady-state gain analysis is used to guide the control structure improvement, a multi-point temperature control strategy based on the sensitive stage temperatures is proposed to improve the control scheme. In the CED process, the improved control scheme can resist ±20% feed flow and composition disturbances. In addition, it is demonstrated that using the steam separation ratio (β V) to control the sensitive stage temperature shows better dynamic performance compared with using the ratio of the steam side flowrate and the reboiler heat duty (V/R) to control the sensitive stage temperature in the DWED process. Finally, by comparing the integral of squared error (ISE) values, it is found that improved control schemes (CS2 and CS4) have better robustness and dynamic performance. [Display omitted] [ABSTRACT FROM AUTHOR]

Many secondary deciduous forests of eastern North America are approaching a transition in which mature early‐successional trees are declining, resulting in an uncertain future for this century‐long carbon (C) sink. We initiated the Forest Accelerated Succession Experiment (FASET) at the University of Michigan Biological Station to examine the patterns and mechanisms underlying forest C cycling following the stem girdling‐induced mortality of >6,700 early‐successional Populus spp. (aspen) and Betula papyrifera (paper birch). Meteorological flux tower‐based C cycling observations from the 33‐ha treatment forest have been paired with those from a nearby unmanipulated forest since 2008. Following over a decade of observations, we revisit our core hypothesis: that net ecosystem production (NEP) would increase following the transition to mid‐late‐successional species dominance due to increased canopy structural complexity. Supporting our hypothesis, NEP was stable, briefly declined, and then increased relative to the control in the decade following disturbance; however, increasing NEP was not associated with rising structural complexity but rather with a rapid 1‐yr recovery of total leaf area index as mid‐late‐successional Acer, Quercus, and Pinus assumed canopy dominance. The transition to mid‐late‐successional species dominance improved carbon‐use efficiency (CUE = NEP/gross primary production) as ecosystem respiration declined. Similar soil respiration rates in control and treatment forests, along with species differences in leaf physiology and the rising relative growth rates of mid‐late‐successional species in the treatment forest, suggest changes in aboveground plant respiration and growth were primarily responsible for increases in NEP. We conclude that deciduous forests transitioning from early to middle succession are capable of sustained or increased NEP, even when experiencing extensive tree mortality. This adds to mounting evidence that aging deciduous forests in the region will function as C sinks for decades to come. [ABSTRACT FROM AUTHOR]

In this paper, a novel active control approach is designed for surge instability in the compressor system using the finite-time fuzzy sliding mode scheme. The primary novelty of this study lies in the development of a finite-time fuzzy sliding mode control for the surge instability in a compressor system in the presence of disturbance and uncertainty in the characteristic curve of the compressor and also throttle valve. To ensure the stability of the closed-loop system in Lyapunov's concept, a finite time active control method is proposed based on fuzzy estimation method and robust adaptive and sliding mode methods. Achieving finite time stability and rapid elimination of deep surge instability occurs through a fast sliding mode design, while fuzzy and adaptive techniques are used to estimate uncertainty and nonlinear terms, as well as to obtain optimal estimation weights. The simulation results in MATLAB environment and comparison show that the suggested method provides better quality control in terms of surge suppression, robustness, and overcoming uncertainty and disturbance effects. [ABSTRACT FROM AUTHOR]

The Cell Transmission Model (CTM) has been widely used to design variable speed limit (VSL) controllers. Since the CTM is an idealization of the actual traffic flow, the issue of robustness of VSL with respect to uncertainties such as disturbances due to modeling and measurement errors is an important problem. In this paper, we modify the CTM to include a constant disturbance term that is unknown and could change over time. The stability properties of the modified open-loop CTM are analyzed and used to motivate the design of a robust VSL controller. The VSL controller is designed to reject external disturbances, which are constant over large intervals of time, while guaranteeing that the density converges to the desired equilibrium state corresponding to high flow and speed. Microscopic simulations based on the commercial software VISSIM are used to demonstrate the effectiveness of the proposed robust VSL controller and associated benefits for traffic scenarios along a large segment of I-710 in Southern California. [ABSTRACT FROM AUTHOR]

Design of an adaptive anti-unwinding finite time sliding mode algorithm for attitude control system of a three-axis satellite is approached in this paper. In the designed controller, some parameters updating laws are proposed to simultaneously obtain the accurate values of inertia moments, the upper values of reaction wheels' failures and disturbances. Accordingly, the combined finite time stability of the control system and convergence of the satellite parameters has been demonstrated. Also, a new sliding surface is suggested to avoid the unwinding problem which is common in sliding mode techniques. It is proved by the Lyaponov methodology that the satellite quaternions and angular velocities always approach to the nearest equilibrium point and so it prevents the excessive satellite slews. Furthermore, the proposed algorithm has been modified in such a way that the singularity problem does not occur, especially when the system states reach around the equilibrium point. Therefore, the finite time convergence of system states and parameters estimation errors are guaranteed subjected to disturbances and actuator failures without occurring singularity and unwinding problems. Besides rigorous theoretical proofs by the Lyapunov theory, different simulations are exhibited to demonstrate the merits of the developed control schemes. • An adaptive finite time sliding mode control is proposed for a rigid satellite. • The finite time stability is ensured despite accurate estimation of parameters. • The upper bound of disturbances and actuator failures are estimated. • The unwinding and singularity problems are prevented. • It is concluded that the suggested controller has superior accuracy and chattering. [ABSTRACT FROM AUTHOR]

This paper deals with the simulation of unexpected disruptions in public transport in the agent-based transport simulation framework of MATSim. A replanning logic for public transport passengers is implemented so passengers can be informed about and react to a disruption and use an alternative route. An unexpected disruption of an underground line in Berlin is simulated to analyze how passengers are affected by the disruption and the information time. It is shown that transport companies can minimize the negative effects of unplanned disruptions by informing their passengers as soon as possible once the disruption has occurred because travel times increase drastically when passengers are informed late. [ABSTRACT FROM AUTHOR]

Offshore surveying from seismic airgun arrays and other intense types of industrial development introduce substantial underwater noise, with potentially serious consequences for marine life. We describe an adaptive spectrum of data collection and analytical methods to evaluate the type, magnitude, and complexity of disturbance associated with industrial activities. Scientists and managers have often been mired in a cycle of mitigation and monitoring plans and data collection schemes that focus solely on the prevention of significant but generally rare instances of injury or death. Increased focus is needed on achieving a refined understanding of the sub-injurious but vastly more common impacts of disturbance on energetics, reproduction, and survivorship at population levels. Approaches that apply and adapt earlier knowledge and integrate tools tuned to exposed species, exposure type, and situational context can provide more insightful understanding of likely effects to inform effective monitoring, and mitigation. Such approaches require multi-disciplinary measurement technologies and individual/population-level statistical models to demonstrate how various types and levels of acute and chronic anthropogenic noise affect marine life. Standardized biological data (e.g., distribution, animal tracking, behavior) should be collected within structured, prioritized, and integrated methodological and analytical frameworks before, during, and after noise-generating activities. This paper sets forth an 'ideal' approach for planning, collecting data, and conducting analyses to test for effects of noise on baleen whales. The approach can range from simple to complex, depending on the context. Further, we discuss and recommend methods for analyzing sampling data using currently available tools and guidelines, including behavioral response severity metrics, acoustic criteria, and bioenergetic and population effects models. [ABSTRACT FROM AUTHOR]

There are many processes in the business world which are dependent on Critical Infrastructure Systems (CISs) to provide important services. Hence, undesirable behaviors of these processes can provide cascading disturbances and might cause high impacts on criticality infrastructure in Automatic Closed-Loop Supply Chain (A-CLSC). Thus, this level of vulnerability needs to monitor and control the disturbances related to uncertain parameters. In order to develop the controller component inward uncertain Business Process Management System (BPMS), the authors provided adaptive controller considering uncertainty, which could be tuned with an intelligent algorithm called Improved Particle Swarm Optimization (IPSO). In addition to multi-objective optimization, the novel controller has been used to control the two most important activities includes inventory and transportation evolving the criticality infrastructure in A-CLSC at the desired behavior as a simulation and practical case study. Furthermore, the proposed IPSO algorithm has been compared against legendary methods such as adaptive PSO (APSO) and classic PSO. Also, the paper has been provided some metrics to statistical evaluation of proposed method performance. The results indicated the better set response of the new controller to control the A-CLSC as well as effective control of CISs. [ABSTRACT FROM AUTHOR]

It is vital in the prevention of the ferroresonance to consider this phenomenon from new side. The design of the equipment needs deep studies to avoid such disturbance. This paper presents a new way in ferroresonance studies, by the use of the Root Cause Analysis (RCA) in a systematic step by step process to discover the true cause of this problem. A fault tree is built to identify all possible causes leading to the unwanted top event, that is the False Trip Analysis (FTA). Among large statistics of disturbances, the probability of occurrence of ferroresonance is stated, and using the most studied causes of this event, the tree of analysis is built till reaching the main disturbance. In each step, well-known possible causes are shown. Then, a barrier or possible solution corresponding to the cause is presented. The new probability of occurrence is then calculated. The obtained result is compared to the initial probability and a set of protection system is proposed. The advantage of this study is the possibility to reduce the occurrence of the ferroresonance by gathering the maximum detailed amount of possible causes and by choosing the best barrier corresponding to the cause. [ABSTRACT FROM AUTHOR]

The availability of support stations directly affects the departure ability of the fleet. New faulty aircraft will perturb the existing security plan of support stations, so a new security plan needs to be developed to ensure that the effect of disturbance is minimal. The traditional first-come-first-serve (FCFS) algorithm and the priority-weighted scheduling algorithm focus on local adjustments or do not take into full account the global coverage time. Some other optimization algorithms and models, such as heuristic algorithms and mesh flow models, have the disadvantages of high computational costs, over complexity, or low availability. In view of the above problems, this paper proposes to deal with the time relationship of fault aircrafts with the Allen relationship, obtain a set of dominant maintenance programs, and then achieve the best maintenance support program as well as the minimization of the disturbance influence. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we consider the robust observer-based control design problem for discrete nonlinear systems with disturbances. A new approach is proposed to provide less conservative Linear Matrix Inequality control design conditions and enhance the robustness of control designs, where the observer and controller gains are computed independently. Both the one-sided Lipschitz condition and the Linear Parameter Varying approach, which are two well-known alternatives to the classical Lipschitz condition, are considered to address nonlinearities. Two numerical examples are presented to illustrate the superiorities of the new approach over the traditional H ∞ approach as well as relevant works in the literature. [ABSTRACT FROM AUTHOR]

This paper addresses the reachable set bounding for discrete-time switched nonlinear positive systems with mixed time-varying delays and disturbance, which contains switched linear positive systems as a special case. By resorting to a new method that does not involve the common Lyapunov–Krasovskii functional one, explicit criteria to ensure any state trajectory of the system converges exponentially into a prescribed sphere are obtained under average dwell time switching. The results can then be extended to more general time-varying systems. Finally, two numerical examples are used to demonstrate the effectiveness of the obtained results. [ABSTRACT FROM AUTHOR]

Airports, especially international ones, within the urban context should have a specific consideration so they do not affect human lives. The planes fly a few hundred meters above these urban fabrics, and when they are landing, they fly slightly over 20–40 m above the ground. This paper aims to measure aircraft noise, conduct a survey on the subjective reaction of residents to aircraft noise, and present primary data necessary to secure the acoustic performance of residential buildings neighboring an international airport. The methodology used a field survey for six buildings neighboring Dubai International Airport in the United Arab Emirates, analyzed building/window material, and a subjective reaction survey. The result showed that the average equivalent noise level (L eq) was 66.4 dB(A), and the average maximum noise level (L max) was 73.3 dB(A). The indoor noise of the target buildings was found to be in the range of NC-35 to NC-53, exceeding NC-30, the permissible noise standard. The average noise level difference between indoors and outdoors was 13.6–30.5 dB(A). It was statistically proven that aircraft noise is a significant source of sound pollution and occurs all day throughout the year, regardless of the season. The response rate for loudness and noisiness was found to be very high. Regarding the disturbance in daily life due to annoyance, aircraft noise is significantly affected in the order of telephone calls, conversations, listening to TV and radio, sleep disturbance, concentration disturbance, and rest disturbance. This study will serve as primary data to present basic data necessary to secure an optimum acoustic performance of a residential building against aircraft noise. [ABSTRACT FROM AUTHOR]

Abstract: Background: Those at the birth of a baby sometimes speak of the experience as significant and meaningful; an experience in which there is an atmosphere or mood that surrounds the occasion. This paper explores this mood, its recognition, disclosure and how we attune or not to it. The paper is philosophically underpinned by hermeneutic phenomenology. The Heideggerian notion of “attunement to mood” is used to interpret this phenomenon. This paper describes how such a mood becomes visible. Methods: Using a hermeneutic phenomenological approach, 14 tape-recorded transcribed interviews, each about an hour long, were conducted over 8 months from mothers, birth partners, midwives and obstetricians. The stories crafted from these transcripts have been interpreted alongside my own preunderstandings and related literature. Appropriate ethical approval was gained. Findings: Analysis suggests that there is a positively construed mood of joy at birth that can be concealed when disrupted. Disturbing this mood has the effect of exposing the world of birth and its inherent activities and feelings revealing possible meanings inherent in the lived birth experiences. Disturbances at birth provide distinctions and tensions in which a concealed constitutive mood at birth can be seen. This paper provides insight towards a deeper appreciation into how the sacred joy of birth may be protected. Implications for practice: The way in which we attune to birth may have consequences to birth outcomes and to the experience of childbirth. The consequences of these findings for those in the world of birth are discussed. [Copyright &y& Elsevier]

The development, implementation and enforcement of policies involving the rational use of the land and the conservation of natural resources depend on an adequate characterization and understanding of the land cover, including its dynamics. This paper presents an approach for monitoring vegetation dynamics using high-quality time series of MODIS surface reflectance data by generating fraction images using Linear Spectral Mixing Model (LSMM) over South America continent. The approach uses physically-based fraction images, which highlight target information and reduce data dimensionality. Further dimensionality was also reduced by using the vegetation fraction images as input to a Principal Component Analysis (PCA). The RGB composite of the first three PCA components, accounting for 92.9% of the dataset variability, showed good agreement with the main ecological regions of South America continent. The analysis of 21 temporal profiles of vegetation fraction values and precipitation data over South America showed the ability of vegetation fractions to represent phenological cycles over a variety of environments. Comparisons between vegetation fractions and precipitation data indicated the close relationship between water availability and leaf mass/chlorophyll content for several vegetation types. In addition, phenological changes and disturbance resulting from anthropogenic pressure were identified, particularly those associated with agricultural practices and forest removal. Therefore the proposed method supports the management of natural and non-natural ecosystems, and can contribute to the understanding of key conservation issues in South America, including deforestation, disturbance and fire occurrence and management. [ABSTRACT FROM AUTHOR]

This paper considers the design of robust observer for nonlinear uncertain systems affected by sensor fault and subject to external disturbance, represented under the multiple fuzzy model formulation of Takagi-Sugeno with unmeasurable premise variables. Using the technique of descriptor system which considers sensor faults as an auxiliary state variable, we proposed a new less conservative approach in terms of a linear matrix inequality based on Lyapunov theory and H∞ performance to established sufficient conditions for the existence of the considered observer. The observer estimates the previous mentioned variables and attenuates the effect of the modeling uncertainties and the perturbations on the estimation error. The benefits of the proposed approach regarding the classical one are shown through an academic example. An application to a reduced bioreactor model is considered, and the performances of the proposed approach are illustrated through numerical results. [ABSTRACT FROM AUTHOR]

This paper addresses the design of sampled-data output feedback control for nonlinear systems in the presence of exogenous disturbance, which is based on the state feedback control for the continuous-time system. It connects the relationship of uniform regional input-to-state stabilization of sampled-data controller with state feedback control for the original continuous-time system. It shows that not only ISS but also trajectories convergence will be recovered, provided sufficiently small sampling period. Moreover, the advantage of the proposed method of designing a sample-data controller over that of designing a discretized controller for an approximate model is illustrated. An application using high-gain observers to a nonminimum phase single-link flexible robot demonstrates the simplicity of synthesis procedure of the proposed method. [ABSTRACT FROM AUTHOR]

This paper aims at designing observer for single-input-single-output (SISO) linear finite-dimensional systems corrupted by general disturbances. A new observer, referred to as extended dynamics observer (EDO), is proposed to estimate both state and disturbance simultaneously. The only assumption for the observer design is that the plant with unknown disturbance is observable. The disturbance is treated by combination of high-gain and internal model contained in the extended dynamics. The main advantage of the developed method lies in the maximum utilization of the prior information of the disturbance. The more accurate the prior disturbance dynamics we have, the better performance the observer would be. The well-posedness of EDO is established and the theoretical results are validated by numerical simulations. [ABSTRACT FROM AUTHOR]

Wind pressure characteristics on a double tower high-rise structure, which is disturbed by surrounding buildings, were investigated using large eddy simulation (LES) and 1:300 scale wind tunnel experiments. The computational simulation technique and wind tunnel experimental technique were described in detail initially. Comparisons of computational results with the experimental data have subsequently been carried out to validate the reliability of LES. Comparisons have been performed in detail for the mean and fluctuating pressure coefficients. Detailed explanations of each comparison were given in the paper. To study further on the pressure coefficients on the building surfaces, parametric studies on shape coefficient and spatial correlation were performed and investigated. The numerical and experimental results presented in this paper advance understanding on wind field around buildings and the application of LES and wind tunnel tests. [ABSTRACT FROM AUTHOR]

Abstract: The Great Lakes coastal region is a dynamic area at the interface between land and water. It is heavily influenced by the magnitude of the large lakes themselves, by natural abiotic and biotic processes in the watershed, and especially by human activity. This special issue contains a series of 21 papers that are organized into four major themes: 1) landscape characterization and coastal linkage, 2) integration, 3) indicator development, and 4) supporting information. The results of these papers emphasize that many environmental response signals are linked to their physio-biogeographic location in the basin and with human activity in coastal watersheds or in the immediate coastal margin. If lake levels continue to fluctuate and decline, if the climate continues to warm, if agricultural activity expands, if exotic species continue to invade, and if the human population density in the watershed increases, then environmental indicators of the Great Lakes coastal region reported here will point to further degradation of water quality and native amphibian, bird, diatom, fish, macroinvertebrate, and wetland plant communities. These environmental indicators are benchmarks for the current conditions of the Great Lakes coastal region and provide measurable endpoints to assess the success of future management, conservation, protection, and restoration of this important resource. [Copyright &y& Elsevier]

Abstract: Spruce budworm outbreaks are a major disturbance determining boreal forest dynamics in forests dominated by balsam fir. However, these forests have been anthropogenically disturbed in recent decades by clearcutting with protection of advance regeneration and soils which it has been suggested, emulates spruce budworm outbreaks by leaving a seedling bank while removing the overstory. The main objective of this study is to characterize and compare the effects of a spruce budworm outbreak to the effects of this harvesting treatment in balsam fir stands in the Gaspe Peninsula. The study was conducted at two different scales; the stand scale, by field sampling vegetation, and at the landscape scale, through the interpretation of aerial photographs. At the stand scale, results showed a more important structural variability in stands affected by the spruce budworm outbreak. There was a greater diversity of saplings and trees, especially paper birch and white spruce, in post-outbreak stands by comparison to post-logged stands. At the landscape scale, canopy openings created by clearcutting with protection of advance regeneration presented less regular shapes, but still had smaller perimeter/area ratio because of their larger size. Spruce budworm openings are thus more likely to be influenced by the surrounding forest and recolonisation by tree species should be faster than for clearcut openings. Our results suggest that efforts should be made to maintain the associated species (paper birch (Betula papyrifera Marsh.) and white spruce (Picea glauca (Moench) Voss)) by preserving more overstory trees of these species while managing the balsam fir dominated forest. Aggregation of cutting units should be limited and there is a need to create more small canopy openings in the landscape if we are to emulate naturally created patterns. [Copyright &y& Elsevier]

Management in fire-prone ecosystems relies widely upon application of prescribed fire and/or fire-surrogate (e.g., forest thinning) treatments to maintain biodiversity and ecosystem function. The literature suggests fire and mechanical treatments proved more variable in their effects on understory vegetation as compared to their effects on stand structure. The growing body of work comparing fire and thinning effects on understory vegetation offers an opportunity to increase the generality of conclusions through meta-analysis. We conducted a meta-analysis to determine if there were consistent responses of understory vegetation to these treatments in North American forests that historically experienced frequent surface fire regimes (<20 years fire return interval, FRI). Means and standard errors were extracted from 32 papers containing data on the response of four understory functional groups (herbaceous, shrub, non-native, and total) to thinning and burning treatments to calculate effect sizes. Lack of replication and inconsistent reporting of results hindered our ability to include many studies in this analysis. For each response variable (species richness and percent cover), we compared three treatment pairs: burn vs control, thin vs control and thin vs burn. We calculated standardized mean differences (Hedges’ g) for each pair and tested if this differed from zero using a random effects model fit with restricted maximum likelihood to account for variation by site. The most consistent effect of the treatments was the increase in non-native species following mechanical thinning and reduction in shrub cover following a burn. These differences suggest the two treatments may not be surrogates in the short-term (less than 5 years). Increase of non-native species due to disturbance is well established but it is not clear if burning and thinning consistently have differential impacts. Response of non-native plants to disturbance is likely a complex function of a variety of site and landscape factors that cannot be evaluated by the current literature. We conclude that prescribed fire and thinning treatments can be used successfully to restore understory species richness and cover, but they can create different conditions and these potentially different outcomes need to be considered in the planning of a fuels reduction treatment. We discuss management options to reduce negative effects of the treatments and we suggest managers use current decision-making frameworks prior to designing an intervention. [ABSTRACT FROM AUTHOR]

Marine coastal ecosystems are affected by a vast array of human-induced disturbances and stresses, which are often capable of overwhelming the effects of natural changes. Despite the conceptual and practical difficulty in differentiating between disturbance and stress, which are often used interchangeably, the two terms bear different ecological meanings. Both are external agents, but the former causes mortality or physical damage (subtraction of biomass), whereas the latter causes physiological alteration (reduction in productivity). Sensitivity of marine organisms may thus have a dual connotation, being influenced in different ways by disturbance and by stress following major environmental change. Coralligenous assemblages, which shape unique biogenic formations in the Mediterranean Sea, are considered highly sensitive to change. In this paper, we propose a method to differentiate between disturbance and stress to assess the ecological status of the coralligenous assemblages. Disturbance sensitivity level (DSL) and stress sensitivity level (SSL) of the sessile organisms thriving in the coralligenous assemblages were combined into the integrated sensitivity level of coralligenous assemblages (ISLA) index. Changes in the coralligenous status were assessed in space, along a gradient of stress (human-induced pressures) at several sites of the western Mediterranean, and in time, from a long-term series (1961–2008) at Mesco Reef (Ligurian Sea) that encompasses a mass mortality event in the 1990s. The quality of the coralligenous assemblages was lower in highly urbanised sites than that in sites in both marine protected areas and areas with low levels of urbanisation; moreover, the quality of the assemblages at Mesco Reef decreased during the last 50 years. Reduction in quality was mainly due to the increase in stress-tolerant and/or opportunist species (e.g. algal turfs, hydroids and encrusting sponges), the disappearance of the most sensitive macroalgae (e.g. Udoteaceae and erect Rhodophyta) and macro-invertebrates (e.g. Savalia savaglia , Alcyonium coralloides and Smittina cervicornis ), and the appearance of invasive alien algal species. Although the specific indices of SSL or DSL well illustrated the changes in the spatial or temporal datasets, respectively, their integration in the ISLA index was more effective in measuring the change experienced by the coralligenous assemblages in both space and time. [ABSTRACT FROM AUTHOR]

Order flows arise as abstractions of discrete manufacturing systems, referred to as transfer probability of orders to each manufacturing cell. In this paper, a dynamic model of production network based on state-space is presented from the order flow point of view. Using perturbation analysis, the transfer probability matrices of disturbances are established for the purpose of analyzing the influences of disturbances on the order flows. Also, a method for recalculating the transfer probability matrix of the order flows is proposed. Results of simulations driven by industrial data are used to illustrate the effect of disturbances on dynamic behavior of the production network. [ABSTRACT FROM AUTHOR]

Marine wildlife-watching is a developing industry in Scotland contributing to overall growth and aspirations of the marine tourism sector. Despite European-level legal protection of cetaceans, and Scottish legislation for the protection of seals at designated haul-out sites, there are currently no formal or mandatory regulations to specifically manage tourism activities in relation to marine wildlife. However, most Scottish wildlife-watching operators adopt one, or more, of the five key voluntary codes of conduct which have been developed in the UK since 2003. In this paper, we review the consistency of policy messages and recommendations across voluntary codes of conduct for the UK and Scotland, taking into consideration global use and effectiveness in the use of similar codes. In this context, we specifically examine the potential impacts of wildlife watching and management of future activities, both within and outwith marine protected areas (MPAs) in Scotland. For this, the research also incorporates data from field surveys, in-situ observations and operator questionnaires conducted in Scotland relating to the implementation of the codes in practice. Key findings highlighting inconsistences in some of the key recommendations across the five UK codes in particular, the distance and speed when approaching an animal. However, all of the codes also have some similarities, including advising against deliberate human interaction, e.g. swimming with marine megafauna, including a separate code on basking sharks, published by the Shark Trust in the UK. In light of the growing network of wildlife-focused MPAs in Scotland (in particular the Sea of Hebrides proposed MPA for mobile species), and national aspirations for the growth of the marine tourism sector, we consider the potential implications of unregulated wildlife watching and the conservation objectives of protected areas for marine mammals and basking sharks. We also provide recommendations on how more formal wildlife-watching regulations could enhance MPA effectiveness and contribute to the emerging processes for Regional Marine Plans across Scotland and provide some insights for global marine wildlife tourism. [ABSTRACT FROM AUTHOR]

In this paper, a hybrid controller with observer is introduced for the estimation and rejection of a disturbance. It is based on the combination of the sliding mode technique and the output feedback strategy. It is divided into two designs: (1) the observer and (2) the controller with observer. The observer is selected to reach two objectives: (a) to assure its stability and (b) for the estimation of a disturbance. The controller with observer is selected to reach three objectives: (a) to assure its stability, (b) for the rejection of a disturbance, and (c) for the decreasing of chattering in the sliding mode behavior. The proposed method is applied for the estimation and rejection of the disturbance in a plotter and a suspension system. [ABSTRACT FROM AUTHOR]

The endangered Booroolong Frog Litoria booroolongensis has undergone dramatic declines over the majority of its range, which have largely been attributed to extensive clearing and ongoing modification associated with agricultural practices, disease and introduced pests. This paper presents a small-scale assessment of the distribution and habitat associations of the Booroolong Frog, using data collected during surveys for environmental impact assessments, in areas of likely preferred habitat identified along the Campbells and Macquarie Rivers south of Bathurst and the Turon River at Sofala New South Wales. Seven stream reaches were sampled within study areas, and the Boorolong Frog was recorded in four of those. Thirty-four Booroolong Frogs were recorded, by direct observation and call play back, usually in habitat typically associated with the species. Seven of these were found in highly degraded habitat reinforcing similar observations for this species in the literature. Field data collected during this study and the resulting habitat information will add to the knowledge of the distribution and habitat preferences of this threatened species. This study also provides recommendations to assist in the development of appropriate conservation management actions within the area. [ABSTRACT FROM AUTHOR]

In railway operations, delays are used as one of most important factors to quantify and evaluate the quality of the railway services. However, data about stochastic disturbances and the causes of the delays are hard to be collected and measured. The efforts to manually estimate these disturbances are also considerably high. In this paper, a method for the automatic calibration of disturbance parameters, which are used to generate stochastic disturbances in simulation tools, is developed with the support of the reinforcement learning technique. Simulation and application results show that the efforts for calibrating parameters can be significantly reduced with ensured consistency between simulation models and the actual railway operations. [ABSTRACT FROM AUTHOR]

Assessment of underwater noise is increasingly required by regulators of development projects in marine and freshwater habitats, and noise pollution can be a constraining factor in the consenting process. Noise levels arising from the proposed activity are modelled and the potential impact on species of interest within the affected area is then evaluated. Although there is considerable uncertainty in the relationship between noise levels and impacts on aquatic species, the science underlying noise modelling is well understood. Nevertheless, many environmental impact assessments (EIAs) do not reflect best practice, and stakeholders and decision makers in the EIA process are often unfamiliar with the concepts and terminology that are integral to interpreting noise exposure predictions. In this paper, we review the process of underwater noise modelling and explore the factors affecting predictions of noise exposure. Finally, we illustrate the consequences of errors and uncertainties in noise modelling, and discuss future research needs to reduce uncertainty in noise assessments. [ABSTRACT FROM AUTHOR]

The controlling of robotic arm is really challenging due to the involvement of various uncertainties such as- time varying payload, friction and disturbances. These challenges attract many researchers to develop advanced control strategies for robot arm. However, most of the developed controllers focus on time invariant uncertainties. This paper presents the formulation of a new Sliding Mode Control- Function Approximation Technique (SMC-FAT) based adaptive controller for a robot arm carrying unknown time-varying payload with the presence of time-varying disturbance and friction. The limitation of previous controllers to cope up with wide range time-varying uncertainty is solved using FAT expression. The stability of the controller can be proven by selecting a proper Lyapunov function and the update law can be derived easily. Three different time-varying uncertainties in sinusoidal, sawtooth and random functions have been considered as the payload and disturbance in the computer simulation to evaluate the controller's performance. The results with error less than 0.02 percentages proved the effectiveness of the proposed controller. [ABSTRACT FROM AUTHOR]

The coastal zone is subject to growing recreational human activity, which may compromise the suitability of coastal habitats for coastal wildlife. Waders rely extensively on the coastal zone, and they are easily disturbed by human activity when they congregate in large flocks at communal high tide roost sites. To ensure sustainable future development of outdoor recreational activities, emphasis has been given on differentiating between areas prioritized for nature conservation and areas open to human recreation, but only rarely have nature conservation interests been mapped explicitly on a fine spatial scale. The Danish Wadden Sea has recently been identified as a high-conflict area between outdoor activities and waterbirds, and in this paper, we apply 40 years of bird counts covering 12 wader species to build a priority map identifying the most important areas for the future conservation of waders in the region. We outline the most important areas for roosting waders across the Danish Wadden Sea, describe the preferred habitats used for roosting at high tide and assess the persistence of importance of individual areas across 4 decades. Our analysis indicates that importance changes only little even on long temporal scales, demonstrating that the presented priority map will be a useful tool for managers and policy makers when planning the sharing of the Wadden Sea between humans and waders. As such, spatially referenced long-term monitoring data may significantly improve the scientific basis underpinning decision- and policymaking, and ensure that nature conservation interests are explicitly accounted for. • Mapping important wader roosts ensures sustainable development of outdoor recreation. • Importance of roost areas changed only little across four decades. • Species diversity reflects habitat diversity at the regional scale. [ABSTRACT FROM AUTHOR]

This paper introduces a steering by wired haptic system based on disturbance rejection control techniques. High gain Generalized Proportional Integral (GPI) observers are considered for the estimation of tire and steering wheel dynamic disturbances. These disturbances are on line canceled to ensure tracking between the commanded steering wheel angle and the tire orientation angle. The estimated disturbances at the steering rack are feedback to the steering wheel to provide a haptic interface with the driver. The overall system behaves as a bilateral master-slave system. Very few sensors and minimum knowledge of the dynamic model are required. Experimental results are presented on a prototype platform that consists on: (1) half of the steering rack of a beetle VW vehicle, (2) a steering wheel. [ABSTRACT FROM AUTHOR]

In this paper, it is shown that the problem of automatic control is, in essence, that of disturbance rejection, with the notion of disturbance generalized to symbolize the uncertainties, both internal and external to the plant. A novel, unifying concept of disturbance rejector is proposed to compliment the traditional notion of controller. The new controller–rejector pair is shown to be a powerful organizing principle in the realm of automatic control, leading to a Copernican moment where the model-centric design philosophy is replaced by the one that is control–centric in the following sense: the controller is designed for a canonical model and is fixed; the difference between the plant and the canonical model is deemed as disturbance and rejected. [ABSTRACT FROM AUTHOR]

Copyright of Basic & Applied Ecology is the property of Urban & Fischer Verlag and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Existing methods for maintaining pressure gradient in a pharmaceutical cleanroom rely on the condition of steady air supply. When the air supply volume in a cleanroom changes considerably from one state to another, the pressure gradient inside the cleanroom becomes turbulent, reducing the robustness associated with the existing methods. Therefore, a variable residual air volume tracking method is proposed in this paper to maintain the pressure gradient in a multi-compartment cleanroom under variable air volume conditions. By establishing a data relationship model between the cleanroom air supply volume (or damper opening degree) and residual air volume compensation coefficient, a fixed leakage air volume is maintained in the cleanroom under a given pressure gradient. Furthermore, the air volume inside the cleanroom and the residual air volume are adjusted in real-time. The balancing of return air volume overcomes various errors and interferences in the system, to achieve pressure gradient stability under variable air volume. Experimental results show that when the air supply volume changes within ±10%, the pressure amplitude change in each room with the proposed method is significantly reduced compared with usage of the traditional fixed residual air volume method. The study could guide the comprehensive maintenance of differential pressure inside cleanrooms. • Variable residual air volume tracking method for pharmaceutical cleanrooms. • Data relationship model with air supply volume and residual air volume compensation coefficient. • A fixed leakage air volume is maintained under a given pressure gradient. • Room air supply volume and residual air volume in cleanrooms are maintained in real-time. • Pressure gradient is controlled under variable air supply volume for pressure gradient stability. [ABSTRACT FROM AUTHOR]

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As a regional artificial disturbance component, road exerts great effects on vegetation types, and plays a substantial role in defining vegetation distribution to a certain extent. Aiming at the tropical rainforest degradation and artificial forest expansion in Yunnan Province of Southwest China, this paper analyzed the effects of road network extension on regional vegetation types. In the Province, different classes of roads had different effects on the vegetation types, but no obvious regularity was observed in the effects on the patch areas of different vegetation types due to the great variations of road length and affected distance. However, the vegetation patch number was more affected by lower class roads because of their wide distribution. As for different vegetation types, the vegetations on cultivated land were most affected by roads, followed by Castanopsis hystrix and Schima wallichii forests. Road network formation contributed most to the vegetation fragmentation, and there existed significant correlations between the human disturbance factors including village- and road distributions. [ABSTRACT FROM AUTHOR]

Abstract: The paper deals with manipulator end-effector position control. At first the problem of inverse kinematics is introduced. The dynamic model of manipulator by Euler – Lagrange method is derived. In order to achieve required end-effector position the feedback control method is introduced for non-linear differential equations system. In the conclusion all mentioned methods are demonstrated on 2 DOF planar manipulator. [Copyright &y& Elsevier]

The technology of eco-bag slope is widely used as the soft structure in the slope protection system because of its characteristic of structure and plants cover. In this paper, the practical application effect of the technology of applying the eco-bags to deal with the reservoir collapsed bank slope has been introduced through the practical engineering cases and experimental data. The results show that, by using reasonable structure and eco-bag filling materials, the eco-bags not only can be used as a general bank slope protection structures to play the role of soil conservation and vegetation-friendly performance as well as to achieve the purpose of barren slope restoration ecology effectively but also can be used to protect the steep and collapse bank slope of reservoirs. The results also indicated that the eco-bag bank slope can achieve good anti-erosion, anti-frost performance and vegetation-friendly in seasonal frozen soil zone for ecological hydraulic projects. [ABSTRACT FROM AUTHOR]

Taking seven plots of coastal saline soil under different vegetation cover in North Jiangsu as study sites, this paper studied the seasonal fluctuations of soil basic physicochemical and biological characteristics, and analyzed the relationships between these fluctuations and vegetation cover. In the test plots, there was a greater variability of soil basic physicochemical and biological characteristics. The average soil electrical conductivity was lower in crop plots (0郾95 dS·m-1 ) than in natural vegetation plots (2郾77 dS·m-1), but parts of the crop plots showed an increased soil electrical conductivity compared with pre鄄planting. Overall, the soil fertility of the plots was generally at a low level, with the hydrolysable nitrogen content averagely lower than 50 mg·kg-1, available phosphorus content (except fertilized plots) lower than 3 mg·kg-1, and organic matter content less than 1%. Due to fertilization, the soil conditions in crop plots somewhat improved. For the test coastal saline soil, its electrical conductivity and nutrient level were the key factors affecting the vegetation distribution and plant growth, and soil electrical conductivity was most important. There existed close correlations between soil nitrogen and phosphorus contents and soil microbial amount. The seasonal fluctuations of soil characteristics were closely related with vegetation type and human disturbance, being relatively stable under higher vegetation coverage and lesser human disturbance, and dramatic in bare land and castor experimental plots. [ABSTRACT FROM AUTHOR]

Abstract: As silvicultural objectives have changed over the last several decades, managers are increasingly designing cutting regimes that mimic natural disturbance with the hopes that such systems will restore forests to a more natural condition while optimizing harvest yield. Treefall gaps, canopy openings caused by the death of one or more trees, are the dominant form of disturbance in many forest systems worldwide. These gaps play an important role in forest ecology by helping to maintain bio- and pedo-diversity, influencing nutrient cycling, and preserving the uneven-age nature of late-successional forests. In gap literature, there are inconsistencies with regard to gap terminology, methods for identifying and studying gaps, and modeling gap disturbances. From the papers reviewed, the size of treefall gaps ranges widely from 10 to >5000m2; we suggest that the maximum gap size should be set at 1000m2. Larger openings tend to have microclimates and return intervals significantly different than smaller treefall gaps. Two main definitions of treefall gaps exist: canopy gap: a ‘hole’ in the forest through all levels down to an average height of 2m above ground and extended gap: canopy gap plus the area that extends to the bases of surrounding canopy trees. Although researchers have assumed a variety of gap shapes to simplify measuring gap size, gaps are often irregularly shaped and so we recommend that gap areas and shapes be determined from detailed field measurements. Gap age may be determined from tree ring analysis of released trees in or near the gap edge, the spacing of whorls on released saplings, or from decomposition of gap-making trees. Windthrow is the main cause of canopy gaps in a variety of ecosystems; other causes include insects, diseases, acidic deposition, drought, and climate change. Treefall-gap models have been developed to predict the following processes during gap making or infilling: (i) gap abundance, (ii) forest structure, (iii) spatial and temporal variations in light levels, (iv) canopy dynamics, and (v) soil nutrient and water regimes. We recommend a protocol for gap studies and identify future research topics. [Copyright &y& Elsevier]

Historical range of variability (HRV) characterizes the fluctuations of ecosystem structure and processes under natural disturbances, and is helpful in understanding the causes and consequences of ecosystem change, providing the researchers and managers a reference to evaluate the present status of ecosystems and guiding managers to develop effective management strategies to ultimately drive ecosystems to a sustainable state. In recent years, HRV has played an increasingly important role in forest ecosystem management, and has been successfully used in indicating the causes of ecosystem change, conservation of biological diversity and endangered species, and restoration of ecosystem function, etc. This paper outlined the concept of HRV, and discussed the applications, limitations (lack of data, environmental change, and human impacts, etc.), and challenges of applying HRV in forest ecosystem management. Strengthening data mining, focusing on the changes of natural environment and human society, and increasing the public's recognition of HRV would benefit the improvement of the application efficacy of HRV in forest ecosystem management, and make the forest ecosystem ultimately achieve a sustainable state. [ABSTRACT FROM AUTHOR]

The homing ability of non-marine turtles has been studied in a variety of taxa, and many species appear to be capable of short- range homing on the scale of several hundred meters or a few kilometers following experimental displacement. However, the behavioral response of turtles following a naturally caused displacement has seldom been reported. In this paper, we describe the effect of displacement ranging from 1.4 to 16.8 km (average = 4.8 km) by severe floods in a stream system in Massachusetts. We radio-tracked 38 adult Wood Turtles (Glypteinys inscuipta) at five separate sites in Franklin County, Massachusetts, for periods ranging from one to four activity seasons and documented the displacement of a total of 12 Wood Turtles during seven floods between 2004 and 2008. Based on the average rate of displacement per flood and annual flood frequency, we estimate that, during our study, floods displaced over 40% of this Wood Turtle subpopulation annually. We present evidence that displace- ment results in elevated mortality rates and that displaced Wood Turtles mate and nest in the year following displacement at rates well below average; on a longer time scale, however, displacement by flooding may be an important mechanism of population connectivity in some areas. We also present evidence that most Wood Turtles avoid stream segments with stream gradient steeper than 1%; this may in part reflect an adaptation to avoid severe floods. Regional models and empirical data from stream gages suggest that flood intensity may currently be on an increasing trend. Conversion of upland from forest and fields to impervious surfaces and hardening of upstream riverbanks may have exacerbated recent flooding and decreased the resiliency of the riparian system to increased precipitation. [ABSTRACT FROM AUTHOR]

Abstract: Multivariate statistical analysis is a powerful method of examining complex datasets, such as species assemblages, that does not suffer from the oversimplification prevalent in many univariate analyses. However, identifying whether data points on a multivariate plot are clustered is subjective, as there is no determination of significant differences between the points and no indication of the level of confidence in those points. The validity of drawing such conclusions may therefore be considered suspect. This paper describes a method of bootstrapping calculated principal components to estimate a confidence radius, similar to confidence intervals in univariate techniques. Plotting 3D scatterplots of the principal components, with the size of the spherical point representative of the level of confidence of the estimate, gives a clear and visual indication of significant difference between the points — where the spheres overlap there is no significant difference. We apply the technique to mammal assemblages at sites in Epping Forest (Essex, UK) that differ in the level of disturbance present and find that differences between some sites that appear large using traditional principal components analysis are actually not significantly different at the 95% confidence level, while other sites do differ significantly. Sites that differ most in anthropogenic disturbance are not significantly different in terms of assemblage structure. [Copyright &y& Elsevier]

Abstract: Old growth forest has become a major and increasingly prevalent research topic over the past two decades. However, there is no generic definition that can be applied uncritically to all forest types. This is because a precise definition of old growth is ecologically meaningful only when it is applied to a specific vegetation type. This is demonstrated in this paper using the Mountain Ash (Eucalyptus regnans) forests of the Central Highlands of Victoria, south-eastern Australia as a case study. These forests have been the target of extensive and intensive research over the past 25 years. That work has shown that a number of attributes of stand structure and composition can be crudely used to distinguish old growth forest from other age cohorts of Mountain Ash forest. However, it is not unusual for some of these characteristics also to be recorded in regrowth stands. A key feature of stands of old growth Mountain Ash forest was that the overstorey was rarely even aged. Rather, there was strong evidence of at least two cohorts of overstorey trees in old growth stands. This highlighted the existence of multiple disturbance pathways. Thus, although an absence of disturbance is typically one of the criteria for defining old growth forest, extensive evidence was found to suggest that most stands of old growth Mountain Ash have been subject to several previous natural disturbance events. Current management policies in Mountain Ash forests preclude the harvesting of old growth stands. The ecological importance of living and dead biological legacies for many elements of biodiversity in Mountain Ash forests indicates that naturally disturbed old growth stands also should be exempt from salvage logging, particularly salvage logging using traditional clearfelling methods. [Copyright &y& Elsevier]