Control Structure (control + structure)

Distribution by Scientific Domains


Selected Abstracts


Extended spatial keyframing for complex character animation

COMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 3-4 2008
Byungkuk Choi
Abstract As 3D computer animation becomes more accessible to novice users, it makes it possible for these users to create high-quality animations. This paper introduces a more powerful system to create highly articulated character animations with an intuitive setup then the previous research, Spatial Keyframing (SK). As the main purpose of SK was the rapid generation of primitive animation over quality animation, we propose Extended Spatial Keyframing (ESK) that exploits a global control structure coupled with multiple sets of spatial keyframes, and hierarchical relationship between controllers. The generated structure can be flexibly embedded into the given rigged character, and the system enables the given character to be animated delicately by user performance. During the performance, the movement of the highest ranking controllers across the control hierarchy is recorded in layered style to increase the level of detail for final motions. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Frequency domain modal analysis of earthquake input energy to highly damped passive control structures

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 5 2004
Izuru Takewaki
Abstract A new complex modal analysis-based method is developed in the frequency domain for efficient computation of the earthquake input energy to a highly damped linear elastic passive control structure. The input energy to the structure during an earthquake is an important measure of seismic demand. Because of generality and applicability to non-linear structures, the earthquake input energy has usually been computed in the time domain. It is shown here that the formulation of the earthquake input energy in the frequency domain is essential for deriving a bound on the earthquake input energy for a class of ground motions and for understanding the robustness of passively controlled structures to disturbances with various frequency contents. From the viewpoint of computational efficiency, a modal analysis-based method is developed. The importance of overdamped modes in the energy computation of specific non-proportionally damped models is demonstrated by comparing the energy transfer functions and the displacement transfer functions. Through numerical examinations for four recorded ground motions, it is shown that the modal analysis-based method in the frequency domain is very efficient in the computation of the earthquake input energy. Copyright © 2004 John Wiley & Sons, Ltd. [source]


Inhibition of superior colliculus neurons by a GABAergic input from the pretectal nuclear complex in the rat

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2004
Gesche Born
Abstract The mammalian pretectal nuclear complex (PNC) is a visual and visuomotor control structure which is strongly connected to other subcortical visual structures. This indicates that the PNC also controls subcortical visual information flow during the execution of various oculomotor programs. A prominent, presumably GABAergic, projection from the PNC targets the superficial grey layer of the superior colliculus (SC), which itself is a central structure for visual information processing necessary for the generation of saccadic eye movements. In order to characterize the pretecto-tectal projection in vitro, we performed whole-cell patch-clamp recordings from SC and PNC neurons in slices obtained from 3,6-week-old pigmented rats. Focal glutamate injections into the PNC and electrical PNC stimulation were used to induce postsynaptic responses in SC neurons. Electrical stimulation of the SC allowed electrophysiological identification of PNC neurons that provide the inhibitory pretecto-tectal input. Only inhibitory postsynaptic currents could be elicited in SC neurons both by pharmacological and by electrical activation of the ipsilateral PNC. Concomitantly, a small number of PNC neurons could be antidromically activated from the ipsilateral SC. Most SC cells postsynaptic to the prectectal input showed the dendritic morphology of wide-field and narrow-field cells and are therefore regarded as projection neurons. All inhibitory currents evoked by PNC activation could be completely blocked by bath application of the selective GABAA receptor antagonist bicuculline. Together these results indicate that SC projection neurons receive a direct inhibitory input from the ipsilateral PNC and that this input is mediated by GABAA receptors. [source]


Protecting Minority Shareholders: Listed versus Unlisted Firms

FINANCIAL MANAGEMENT, Issue 1 2010
Claudio Loderer
Listed firms have an incentive to render themselves attractive to investors at large. This paper examines whether listed and unlisted firms differ in their care for minority shareholders and finds supporting evidence. We examine control structure, disclosure, board architecture and processes, and director compensation. The corporate governance package in listed firms differs from that in unlisted firms in terms of levels and mix of the different provisions. The data also suggest that listed firms perform better. [source]


Position-dependent disturbance rejection using spatial-based adaptive feedback linearization repetitive control

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 12 2009
Cheng-Lun Chen
Abstract In this paper, we propose a new design of spatial-based repetitive control for a class of rotary motion systems operating at variable speeds. The open-loop system in spatial domain is obtained by reformulating a nonlinear time-invariant system with respect to angular displacement. A two-degree-of-freedom control structure (comprising two control modules) is then proposed to robustly stabilize the open-loop system and improve the tracking performance. The first control module applies adaptive feedback linearization with projected parametric update and concentrates on robust stabilization of the closed-loop system. The second control module introduces a spatial-based repetitive controller cascaded with a loop-shaping filter, which not only further reduces the tracking error, but also improves parametric adaptation. The overall control system is robust to model uncertainties of the system and capable of rejecting position-dependent disturbances under varying process speeds. Stability proof for the overall system is given. A design example with simulation is provided to demonstrate the applicability of the proposed design. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Optimal boundary control of cardiac alternans

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 2 2009
Stevan Dubljevic
Abstract Alternation of normal electrical activity in the myocardium is believed to be linked to the onset of life-threatening ventricular arrhythmias and sudden cardiac death. In this paper, a spatially uniform unstable steady state of small amplitude of alternans described by parabolic partial differential equations (PDEs) is stabilized by boundary optimal control methods. A finite dimensional linear quadratic regulator (LQR) is utilized in both a full-state-feedback control structure and in a compensator design with the Luenberger observer, and it achieves global stabilization in a finite size tissue cable length. The ability to realize such control algorithm is analyzed based on the structure of the amplitude of alternans equation and the control methodology applied. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Feedback control design for an anaerobic digestion process

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2002
Jose Alvarez-Ramirez
Abstract An approach for the design of linear feedback controllers for anaerobic digestion systems is presented. The effluent chemical oxigen demand (COD) concentration and the dilution rate are taken respectively as the regulated and the manipulated variables. The control design is based on simple step-response models of the process endowed with an input delay to account for dead-times induced by measurement devices. The resulting feedback controller has a traditional proportional-integral (PI) control structure, so it can be easily implemented with conventional control technologies. Since the concentration of volatile fatty acids can be easily and quickly measured as compared with COD concentration, it is used as a secondary measurement that is incorporated into the feedback loop scheme to enhance the robustness of the control scheme with respect of influent disturbances. The performance of the proposed control scheme is illustrated via numerical simulations and experimental work. © 2002 Society of Chemical Industry [source]


Achieving a cooperative behavior in a dual-arm robot system via a modular control structure

JOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 12 2001
Fabrizio Caccavale
In this paper the problem of achieving a cooperative behavior in a dual-arm robot system is addressed. A control strategy is conceived in which one robot is position controlled and devoted to task execution, whereas a suitable compliance is conferred to the end effector of the other robot to cope with unavoidable misalignment between the two arms and task planning inaccuracies. A modular control structure is adopted that allows the selection of the proper operating mode for each robot, depending on the task requirements. The proposed approach is experimentally tested in two different tasks involving the two robots in the laboratory setup. First, a parts-mating task of peg-in-hole type is executed; the robot carrying the peg is position controlled, whereas the robot holding the hollow part is controlled to behave as a mechanical impedance. Then, a pressure-forming task is executed, in which a disk-shaped tool is required to align with a flat surface while exerting a desired pressure; in this case, the robot carrying the disk is position controlled, whereas the robot holding the surface is force controlled. © 2001 John Wiley & Sons, Inc. [source]


Perfect position/force tracking of robots with dynamical terminal sliding mode control

JOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 9 2001
V. Parra-Vega
According to a given performance criteria, perfect tracking is defined as the performance of zero tracking error in finite time. It is evident that robotic systems, in particular those that carry out compliant task, can benefit from this performance since perfect tracking of contact forces endows one or many constrained robot manipulators to interact dexterously with the environment. In this article, a dynamical terminal sliding mode controller that guarantees tracking in finite-time of position and force errors is proposed. The controller renders a dynamic sliding mode for all time and since the equilibrium of the dynamic sliding surface is driven by terminal attractors in the position and force controlled subspaces, robust finite-time convergence for both tracking errors arises. The controller is continuous; thus chattering is not an issue and the sliding mode condition as well the invariance property are explicitly verified. Surprisingly, the structure of the controller is similar with respect to the infinite-time tracking case, i.e., the asymptotic stability case, and the advantage becomes more evident because terminal stability properties are obtained with the same Lyapunov function of the asymptotic stability case by using more elaborate error manifolds instead of a more complicated control structure. A simulation study shows the expected perfect tracking and a discussion is presented. © 2001 John Wiley & Sons, Inc. [source]


Process control and monitoring of reactive crystallization of L -glutamic acid

AICHE JOURNAL, Issue 8 2010
Hannu Alatalo
Abstract The aim of the present study was to investigate feedback control of a reactive crystallization process. The present study built up a control structure needed to control the driving force of reactive crystallization using the feed rate of added acid. The concentration of the crystallizing compound and pH was used to compute feedback in the closed-loop control of semi-batch precipitation. The concentration of L -glutamic acid was determined from measured MID-IR ATR-FTIR spectra based on a multivariate model. Dynamic change of set value was based on the mass of added sulfuric acid and pH. The studied properties of the product crystals were polymorphism and crystal size. The polymorphic composition was analyzed with a Raman spectrometer and was expressed by mass fraction of the ,-polymorph. The obtained results showed that the developed feedback process control system allows effective control of forming of polymorphs. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]


Robust Neural Network Controller Design For A Biaxial Servo System

ASIAN JOURNAL OF CONTROL, Issue 4 2007
Chih-Hsien Yu
ABSTRACT A robust control method for synchronizing a biaxial servo system motion is proposed in this paper. A new neural network based cross-coupled control and neural network techniques are used together to cancel out the skew error. In the proposed control scheme, the conventional fixed gain PID cross-coupled controller (PIDCCC) is replaced with the neural network cross-coupled controller (NNCCC) to maintain biaxial servo system synchronization motion. In addition, neural network PID position velocity and velocity controllers provide the necessary control actions to maintain synchronization while following a variable command trajectory. This scheme provides strong robustness with respect to uncertain dynamics and nonlinearities. The simulation results reveal that the proposed control structure adapts to a wide range of operating conditions and provides promising results under parameter variations and load changes. [source]


Case-controlled structure validation

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 2 2009
Randy J. Read
Although many factors influence the quality of a macromolecular crystal structure, validation criteria are usually only calibrated using one of these factors, the resolution. For many purposes this is sufficient, but there are times when one wishes to compare one set of structures with another and the comparison may be invalidated by systematic differences between the sets in factors other than resolution. This problem can be circumvented by borrowing from medicine the idea of the case-matched control: each structure of interest is matched with a control structure that has similar values for all relevant factors considered in this study. In addition to resolution, these include the size of the structure (as measured by the volume of the asymmetric unit) and the year of deposition. This approach has been applied to address two questions: whether structures from structural genomics efforts reach the same level of quality as structures from traditional sources and whether the impact factor of the journal in which a structure is published correlates with structure quality. In both cases, once factors influencing quality have been controlled in the comparison, there is little evidence for a systematic difference in quality. [source]


Blending telephony and IPTV: Building the TV-link service package using the Alcatel-Lucent Service BrokerÔ

BELL LABS TECHNICAL JOURNAL, Issue 1 2007
Andre Beck
This paper discusses the design and implementation of blended services, composite services whose base component services interact within a common control structure. The paper focuses on blended services that combine aspects of Internet Protocol television (IPTV) and IP Multimedia Subsystem, (IMS)-based telephony services and, in particular, focuses on a service that blends TV viewing and telephone call-handling functions. If a subscriber to this service receives a telephone call while watching TV, the caller ID is displayed on the subscriber's TV screen and the subscriber can signal call control instructions using the set-top box remote control. In this service blend, functions from each base service are coordinated with actions in the other. The mechanism allowing this service is an information channel that allows status and control information to move between the subscriber's set-top box and the IMS system. The services described in this paper are built upon a software foundation called the Alcatel-Lucent Service BrokerÔ platform, a platform that has unique capabilities to support such an information channel and to serve as the gateway between IMS and digital TV. This foundation offers service developers a set of important functions for the creation of blended services. Specifically, the Alcatel-Lucent Service Broker offers a means of controlling the invocation of base services, a means of communicating through different protocols, and support for large-scale deployment and for service customization. © 2007 Alcatel-Lucent. [source]


Metabolic Control Analysis of Monoclonal Antibody Synthesis

BIOTECHNOLOGY PROGRESS, Issue 2 2001
Ramon Gonzalez
A general route for protein synthesis in eukaryotic cells has been proposed and applied to monoclonal antibody (MAb) synthesis. It takes into account transcription of the gene, binding of ribosomes to mRNA, and polypeptide elongation including binding to SRP (signal recognition particles) and SRP-receptor, competing translocation, folding and glycosylation, assembly of the heavy and light chains in a tetrameric protein and Golgi processing and secretion. A comprehensive model was built on the basis of the proposed pathway. The model takes into account the mechanism of each step. Metabolic control analysis (MCA) principles were applied to the general pathway using the proposed model, and control coefficients were calculated. The results show a shared flux control (of both pathway flux and flux ratio at the branch) among different steps, i.e., transcription, folding, glycosylation, translocation and building blocks synthesis. The steps sharing the control depend on the concentration of building blocks, pathway flux and levels of OST (oligosacharyl transferase), BiP (heavy chain binding protein) and PDI (protein disulfide isomerase). Model predictions compare well with experimental data for MAb synthesis, explaining the control structure of the route and the heterogeneity of the product and also addressing future targets for improvement of the production rate of MAbs. [source]


An Activation-Based Model of Sentence Processing as Skilled Memory Retrieval

COGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 3 2005
Richard L. Lewis
Abstract We present a detailed process theory of the moment-by-moment working-memory retrievals and associated control structure that subserve sentence comprehension. The theory is derived from the application of independently motivated principles of memory and cognitive skill to the specialized task of sentence parsing. The resulting theory construes sentence processing as a series of skilled associative memory retrievals modulated by similarity-based interference and fluctuating activation. The cognitive principles are formalized in computational form in the Adaptive Control of Thought,Rational (ACT,R) architecture, and our process model is realized in ACT,R. We present the results of 6 sets of simulations: 5 simulation sets provide quantitative accounts of the effects of length and structural interference on both unambiguous and garden-path structures. A final simulation set provides a graded taxonomy of double center embeddings ranging from relatively easy to extremely difficult. The explanation of center-embedding difficulty is a novel one that derives from the model' complete reliance on discriminating retrieval cues in the absence of an explicit representation of serial order information. All fits were obtained with only 1 free scaling parameter fixed across the simulations; all other parameters were ACT,R defaults. The modeling results support the hypothesis that fluctuating activation and similarity-based interference are the key factors shaping working memory in sentence processing. We contrast the theory and empirical predictions with several related accounts of sentence-processing complexity. [source]


The Nature and Processing of Errors in Interactive Behavior

COGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 2 2000
Wayne D. Gray
Understanding the nature of errors in a simple, rule-based task,programming a VCR,required analyzing the interactions among human cognition, the artifact, and the task. This analysis was guided by least-effort principles and yielded a control structure that combined a rule hierarchy task-to-device with display-based difference-reduction. A model based on this analysis was used to trace action protocols collected from participants as they programmed a simulated VCR. Trials that ended without success (the show was not correctly programmed) were interrogated to yield insights regarding problems in acquiring the control structure. For successful trials (the show was correctly programmed), steps that the model would make were categorized as matches to the model; steps that the model would not make were violations of the model. The model was able to trace the vast majority of correct keystrokes and yielded a business-as-usual account of the detection and correction of errors. Violations of the model fell into one of two fundamental categories. The model provided insights into certain subcategories of errors; whereas, regularities within other subcategories of error suggested limitations to the model. Although errors were rare when compared to the total number of correct actions, they were important. Errors were made on 4% of the keypresses that, if not detected, would have prevented two-thirds of the shows from being successfully recorded. A misprogrammed show is a minor annoyance to the user. However, devices with the approximate complexity of a VCR are ubiquitous and have found their way into emergency rooms, airplane cockpits, power plants, and so on. Errors of ignorance may be reduced by training; however, errors in the routine performance of skilled users can only be reduced by design. [source]


A Modeling Framework for Supply Chain Simulation: Opportunities for Improved Decision Making,

DECISION SCIENCES, Issue 1 2005
D. J. Van Der Zee
ABSTRACT Owing to its inherent modeling flexibility, simulation is often regarded as the proper means for supporting decision making on supply chain design. The ultimate success of supply chain simulation, however, is determined by a combination of the analyst's skills, the chain members' involvement, and the modeling capabilities of the simulation tool. This combination should provide the basis for a realistic simulation model, which is both transparent and complete. The need for transparency is especially strong for supply chains as they involve (semi)autonomous parties each having their own objectives. Mutual trust and model effectiveness are strongly influenced by the degree of completeness of each party's insight into the key decision variables. Ideally, visual interactive simulation models present an important communicative means for realizing the required overview and insight. Unfortunately, most models strongly focus on physical transactions, leaving key decision variables implicit for some or all of the parties involved. This especially applies to control structures, that is, the managers or systems responsible for control, their activities and their mutual attuning of these activities. Control elements are, for example, dispersed over the model, are not visualized, or form part of the time-indexed scheduling of events. In this article, we propose an alternative approach that explicitly addresses the modeling of control structures. First, we will conduct a literature survey with the aim of listing simulation model qualities essential for supporting successful decision making on supply chain design. Next, we use this insight to define an object-oriented modeling framework that facilitates supply chain simulation in a more realistic manner. This framework is meant to contribute to improved decision making in terms of recognizing and understanding opportunities for improved supply chain design. Finally, the use of the framework is illustrated by a case example concerning a supply chain for chilled salads. [source]


Long-term change to fish assemblages and the flow regime in a southeastern U.S. river system after extensive aquatic ecosystem fragmentation

ECOGRAPHY, Issue 6 2008
Christopher M. Taylor
The upper Tombigbee River in northeastern Mississippi now exists as a fragment, confluencing with and fed by an extensively modified aquatic landscape now called the Tennessee-Tombigbee Waterway (TTW). We examined the changes to fish assemblages and flow regime after waterway construction based on contemporary comparisons to historical fish collections and discharge data. The river's flow regime has changed markedly since TTW construction. Analysis of discharge data from two stations for 15 years, pre- and post-waterway, indicated significant differences in flow regime including increased minimum and base flows, lower spring and higher late summer-autumn flows, and lower high flow durations, post-TTW. These changes corresponded to significantly reduced regional and local species richness, and strong shifts in fish assemblage structure across a 20 yr time span. Post-waterway fish assemblages were related strongly to measured environmental variables characterizing local habitats. Several lentic-adapted species increased their abundances in lower reaches of the river, including a recent invader to the TTW system, the Mississippi silverside Menidia audens. Fragmentation of river ecosystems via disruption to hydrologic regimes is a major threat to aquatic biodiversity worldwide. Because the flow regime of this fragmented river is in part controlled by waterway operations via five minimum flow control structures, adaptive conservation and management efforts could be implemented in order to maintain and potentially restore the natural flow regime and the ecological integrity of the system. [source]


Feuding Families: When Conflict Does a Family Firm Good

ENTREPRENEURSHIP THEORY AND PRACTICE, Issue 3 2004
Franz W. Kellermanns
Using the conflict theory lens and insights from the family business literature, we develop a theoretical model concerning the effects of task, process, and relationship conflict in family firms. Family firms are characterized by different control structures and generational involvement. Accordingly, we discuss the expected effect control concentration has on task, process, and relationship conflict, and propose that generational involvement affects the importance of task and process conflict to a family firm's performance. Furthermore, our model suggests that relationship conflict moderates the outcomes of task and process conflict. The degree of relationship conflict in family firms is in turn influenced by altruism, which characterizes interactions among family members. [source]


Catabolite repression in Escherichia coli, a comparison of modelling approaches

FEBS JOURNAL, Issue 2 2009
Andreas Kremling
The phosphotransferase system in Escherichia coli is a transport and sensory system and, in this function, is one of the key players of catabolite repression. Mathematical modelling of signal transduction and gene expression of the enzymes involved in the transport of carbohydrates is a promising approach in biotechnology, as it offers the possibility to achieve higher production rates of desired components. In this article, the relevance of methods and approaches concerning mathematical modelling in systems biology is discussed by assessing and comparing two comprehensive mathematical models that describe catabolite repression. The focus is thereby on modular modelling with the relevant input in the central modules, the impact of quantitative model validation, the identification of control structures and the comparison of model predictions with respect to the available experimental data. [source]


Adaptive management of an environmental watering event to enhance native fish spawning and recruitment

FRESHWATER BIOLOGY, Issue 1 2010
A. J. KING
Summary 1. A common goal of many environmental flow regimes is to maintain and/or enhance the river's native fish community by increasing the occurrence of successful spawning and recruitment events. However, our understanding of the flow requirements of the early life history of fish is often limited, and hence predicting their response to specific managed flow events is difficult. To overcome this uncertainty requires the use of adaptive management principles in the design, implementation, monitoring and adjustment of environmental flow regimes. 2. The Barmah-Millewa Forest, a large river red gum forest on the Murray River floodplain, south-east Australia, contains a wide variety of ephemeral and permanent aquatic habitats suitable for fish. Flow regulation of the Murray River has significantly altered the natural flood regime of the Forest. In an attempt to alleviate some of the effects of river regulation, the Forest's water regime is highly managed using a variety of flow control structures and also receives targeted Environmental Water Allocations (EWA). In 2005, the largest environmental flow allocated to date in Australia was delivered at the Forest. 3. This study describes the adaptive management approach employed during the delivery of the 2005 EWA, which successfully achieved multiple ecological goals including enhanced native fish spawning and recruitment. Intensive monitoring of fish spawning and recruitment provided invaluable real-time and ongoing management input for optimising the delivery of environmental water to maximise ecological benefits at Barmah-Millewa Forest and other similar wetlands in the Murray-Darling Basin. 4. We discuss possible scenarios for the future application of environmental water and the need for environmental flow events and regimes to be conducted as rigorous, large-scale experiments within an adaptive management framework. [source]


Adaptive recurrent neural network control of biological wastewater treatment

INTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 2 2005
Ieroham S. Baruch
Three adaptive neural network control structures to regulate a biological wastewater treatment process are introduced: indirect, inverse model, and direct adaptive neural control. The objective is to keep the concentration of the recycled biomass proportional to the influent flow rate in the presence of periodically acting disturbances, process parameter variations, and measurement noise. This is achieved by the so-called Jordan Canonical Recurrent Trainable Neural Network, which is a completely parallel and parametric neural structure, permitting the use of the obtained parameters, during the learning phase, directly for control system design. Comparative simulation results confirmed the applicability of the proposed control schemes. © 2005 Wiley Periodicals, Inc. Int J Int Syst 20: 173,193, 2005. [source]


Influence of lateral canal water depth on offtake and cross-regulator discharge,

IRRIGATION AND DRAINAGE, Issue 5 2009
Mohammad Ali Shahrokhnia
canal d'irrigation; sensibilité; prise d'eau; régulateur transversal Abstract Monitoring and effective operation of control structures are of importance in a modern irrigation system. Previously developed sensitivity indicators can be useful tools for better management of irrigation systems. The influence of lateral canal water depth on the offtaking and ongoing discharges were simulated and evaluated using a simple model in the Doroodzan irrigation system in south-western Iran. Results confirmed the influence of water level changes in the lateral irrigation canal on offtake and cross-regulator discharge. Results obtained also led us to introduce and evaluate two other sensitivity indicators: offtake sensitivity to downstream water depth, and check sensitivity to tertiary canal water depth. Application of the sensitivity indicators in the Doroodzan irrigation system showed the usefulness of developed sensitivity indicators. The average sensitivity indicators varied from 1.10 to 0.44 (m,1) for offtakes and 0.58 to 0.03 (m,1) for cross-regulators. Copyright © 2008 John Wiley & Sons, Ltd. Dans un système d'irrigation moderne il est important d'assurer un suivi et une exploitation efficace des structures de régulation. Les indicateurs de sensibilité précédemment développés peuvent être des outils utiles pour une meilleure gestion des systèmes d'irrigation. L'influence de la profondeur de l'eau du canal latéral sur le débit de la prise et du canal a été simulée et évaluée avec un modèle simple sur le périmètre irrigué Doroodzan situé au sud-ouest de l'Iran. Les résultats confirment l'influence des changements de niveau de l'eau dans le canal d'irrigation latéral sur le débit des prises et des régulateurs transversaux. Les résultats obtenus nous ont conduits à introduire et évaluer deux autres indicateurs de sensibilité: sensibilité du débit de la prise à la profondeur de l'eau en aval et sensibilité à la profondeur d'eau du canal tertiaire. L'application de ces indicateurs de sensibilité au périmètre Doroodzan a montré l'utilité des indicateurs développés. La moyenne des indicateurs de sensibilité varie de 1.10 à 0.44,m,1 pour les prises et de 0.58 à 0.03,m,1 pour les régulateurs transversaux. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Ultrastructural and histochemical study on gills and skin of the Senegal sole, Solea senegalensis

JOURNAL OF APPLIED ICHTHYOLOGY, Issue 6 2004
J. M. Arellano
Summary This study was undertaken to identify the normal ultrastructural features of gills and skin of the Senegal sole, Solea senegalensis, for a comparative measure to morphological alterations caused by environmental stressors such as reduced water quality and diseases. In the Senegal sole skin, four morphologically distinct layers were identified: cuticle, epidermis, dermis and hypodermis. The epidermis was composed of stratified epithelium containing three cellular layers: the outermost or mucosa layer, the middle or fusiform layer and the stratum germinativum or the basal layer. In the mucosa, two mucous cell types were differentiated: type A cells containing several round vesicles of different electron density and type B cells containing mucosomes of uniform electron density. Senegal sole have five pairs of gill arches, each containing two rows of well-developed and compactly organized primary filaments and secondary lamellae. Fingerprint-like microridges were observed on the surface of epithelial cells. The branchial lamellae epithelium consisted of different cell types: pavement, mucous and chloride. Between the chloride cells and the larger pavement cells, accessory cells were observed. Complexes of tight junctions and desmosomes were frequently observed between adjacent chloride and epithelial cells. Neutral mucosubstances and/or glycoconjugates were observed in the epidermis, dermis and hypodermis of S. senegalensis skin. Proteins rich in different amino acids, such as arginine and cysteine, reacted negatively or weakly positive in the epidermis, dermis and hypodermis. In gills, some mucous cells responded weakly positive to periodic acid-Schiff (PAS) reaction but were strongly stained with Alcian Blue at pH 0.5, 1 and 2.5. When Alcian Blue pH 2.5,PAS reaction was performed, most mucous cells were stained blue (carboxylated mucins) and some mucocytes stained purple, indicating a combination of neutral and acid mucins. Proteins rich in cysteine-bound sulphydryl (-SH-) and cystine disulphide (-S-S-) groups were strongly detected in branchial and epidermal mucous cells, whereas lysine, tyrosine and arginine containing proteins showed very weak staining in both epidermal and branchial mucous cells. Protein reactions were strongly positive in the pillar cells, except for those rich in tryptophan, whereas the branchial cartilaginous tissue did not show an important reaction. The performed lipid reactions were negative in goblet and chloride cells. It is concluded from this study that ultrastructural and cytohistochemical features of the Senegal sole skin and gills may serve as control structures in both natural and aquaculture systems to monitor or detect environmental stress responses at the histological level. [source]


INTEGRATED MANAGEMENT OF IN-FIELD, EDGE-OF-FIELD, AND AFTER-FIELD BUFFERS,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 1 2006
Seth M. Dabney
ABSTRACT: This review summarizes how conservation benefits are maximized when in-field and edge-of-field buffers are integrated with each other and with other conservation practices such as residue management and grade control structures. Buffers improve both surface and subsurface water quality. Soils under permanent buffer vegetation generally have higher organic carbon concentrations, higher infiltration capacities, and more active microbial populations than similar soils under annual cropping. Sediment can be trapped with rather narrow buffers, but extensive buffers are better at transforming dissolved pollutants. Buffers improve surface runoff water quality most efficiently when flows through them are slow, shallow, and diffuse. Vegetative barriers - narrow strips of dense, erect grass - can slow and spread concentrated runoff. Subsurface processing is best on shallow soils that provide increased hydrologic contact between the ground water plume and buffer vegetation. Vegetated ditches and constructed wetlands can act as "after-field" conservation buffers, processing pollutants that escape from fields. For these buffers to function efficiently, it is critical that in-field and edge-of-field practices limit peak runoff rate and sediment yield in order to maximize contact time with buffer vegetation and minimize the need for cleanout excavation that destroys vegetation and its processing capacity. [source]


Controlling International Joint Ventures: An Investigation of Australian Parent Partners

AUSTRALIAN ACCOUNTING REVIEW, Issue 2 2009
Francesco Giacobbe
International joint ventures (IJVs) are an important modern organisational form, with their complexity presenting significant management and control issues. Our research uses a cross-sectional survey of Australian parent partners of IJVs to provide insights into the characteristics of Australian companies and their IJVs, performance outcomes and choices of parent partners management control systems (MCS) design in terms of operational areas they seek to control (focus), the extent to which they exercise control (extent) and the mechanisms of control used (formal and informal). Australian parent partners of IJVs generally are, partnering in countries close to Australia in the Asia-Pacific, in activities similar to those they undertake in Australia, contributing a significant amount of resources, but overall have only limited IJV experience. Australian parent partners focus on a limited set of controls, often with tighter formalised control structures. Finally, overall they are satisfied with the performance of their IJVs, with higher satisfaction for organisational learning and product/customer dimensions than financial performance. [source]