Sink System Research Articles

Active Wave Feedforward Control of a Flexible Beam Using Wave Filter Constructed with Point Sensors

This paper deals with the active wave control of a flexible beam using the wave filter constructed with four point sensors. It is the purpose of this paper to verify the active wave control system with adaptive feedforward technique. Firstly, the active sink method is introduced which is useful as a performance index of active wave control method. If the active sink system is constructed, all vibration modes are made inactive (more than suppressed), and its frequency characteristics are similar to the one of semi-infinite beam. Next, the design procedure of the wave filter using four point sensor is presented, its realization also being presented. Finally, experiment of the active wave feedforward control system is carried out, demonstrating the validity of the proposed method and the robustness against the sensor placement.

The inflationary effects of environmental fluctuations in source-sink systems.

Ecological communities are open to the immigration of individuals and are variable through time. In open habitats immigration may permit populations of a species to persist locally even though local biotic and abiotic processes tend to exclude such "sink" populations. A general model for a sink population reveals that autocorrelated environmental variation can dramatically inflate local abundance and that such populations display a characteristic "outbreak" pattern. An experimental protist microcosm exhibits these predicted effects. Because the many ecological and environmental processes that set the rate of exclusion are typically autocorrelated, these theoretical and empirical results have broad implications for our understanding of community structure and highlight a previously unsuspected potential effect of anthropogenic climate change.

Enzyme catalysis: Transition structures and quantum dynamical aspects: Modeling rubisco's oxygenation and carboxylation mechanisms

Quantum dynamics is introduced with the help of molecular states (MS) for systems decomposable into n electrons and N nuclei. These states, when projected onto the electronic and nuclear configuration spaces, r and R, respectively, are represented as products of electronic and nuclear wave functions of the type Φk(r;αk°)χkj(R;αk°). The 3N coordinates αk° are the positions of positive charges in real space that are equivalent to the nuclear charges. The stationary geometry is derived from quantum chemical analytical gradient optimization procedures. The set {Φk(r;αk°)χkj(R;αk°)} is assumed to contain all cluster partitioning including corresponding asymptotic states. These MSs provide a basis to represent a quantum state as a particular linear superposition. Quantum states are (row) vectors in a dual space whose components are the complex coefficients in the linear superposition of MSs. A reactive system is represented in the direct product space of the MS and surrounding medium: ∣MS〉⊗∣E〉. The surrounding basis states {∣E〉} may be other molecular state systems (protein, solvent) or electromagnetic fields. A chemical reaction is represented as a time evolution of vectors in the dual space driven by the interaction with an energy source or sink system. A theory of catalysis is constructed on this new basis for which the protein–substrate interaction operator drives the quantum change of state. The chemical reaction catalyzed by rubisco is examined and used to introduce the theoretical scheme. The mechanism of carboxylation and oxygenation expressed as sets of transition structures is discussed from this new quantum mechanical perspective. For a protein in thermal equilibrium with a thermal bath at absolute temperature T, in so far as time evolution in the reactant system is concerned, the protein may be replaced by a blackbody radiation field. In real situations, both the protein–substrate and electromagnetic field–substrate interactions provide mechanisms to favor particular time evolutions of the quantum system. A mapping to a unit hypersphere with the axis represented by (orthogonalized) MSs permits a simple “visualization” of all bound quantum states related to the system as points on the surface of the hypersphere. Time evolution of complex systems can be systematized in this new way. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2002

Rate of diffusion-limited reactions in a cluster of spherical sinks

The reaction rate is calculated for a cluster of perfectly absorbing, stationary spherical sinks in a medium containing a mobile reactant. The diffusive interactions are accurately taken into account by employing the first-passage technique. The configurations of the clusters include three spheres, four spheres, regular polygons, linear chains, squares, and finite cubic arrays. For a given number of sinks, the reaction rate is decreased with increasing the compactness of the structure due to the screening effect. For a specified configurations, the asymptotic expressions for the reaction rate varying with the number of sinks are confirmed. By comparing results with these “exact” data, the method of multipole expansions up to the dipole level, which is suitable for a finite system of many sinks, proved to be an excellent approximation.

Experimental investigation of a thermoelectric refrigeration system employing a phase change material integrated with thermal diode (thermosyphons)

This paper presents results of tests carried out to investigate the potential application of phase change materials (PCMs) integrated with thermosyphons in a thermoelectric refrigeration system. The work involved design, fabrication and test of a 150 W thermoelectric refrigeration system. The system was first fabricated and tested using a conventional heat sink system (bonded fin heat sink system) at the cold heat sink. In order to improve the performance and the storage capability, the system was reconstructed and tested using an encapsulated PCM as a cold sink. Results of tests of the latter system showed an improved performance compared with the former system. However to improve the storage capability, in particular during off-power periods, it was found necessary to integrate the PCM with a thermal diode, which would allow heat flow in one direction only. Results of tests carried out on the new system showed considerable improvement in the storage capability of the thermoelectric refrigeration system compared with the previous ones. Overall the system suits operation with renewable energies, e.g., solar energy.

A novel thermoelectric refrigeration system employing heat pipes and a phase change material: an experimental investigation

This paper presents results of tests carried out to investigate the potential application of heat pipes and phase change materials for thermoelectric refrigeration. The work involved the design and construction of a thermoelectric refrigeration prototype. The performance of the thermoelectric refrigeration system was investigated for two different configurations. The first configuration employed a conventional heat sink system (bonded fin heat sink) on the cold side of the thermoelectric cells. The other configuration used an encapsulated phase change material in place of the conventional heat sink unit. Both configurations used heat pipe embedded fins as the heat sink on the hot side. Replacement of the conventional heat sink system with an encapsulated phase change material was found to improve the performance of the thermoelectric refrigeration system. In addition, it provided a storage capability that would be particularly useful for handling peak loads and overcoming losses during door openings and power-off periods. Results showed that the heat sink units employing heat pipe embedded fins were well suited to this application. Results also showed the importance of using a heat pipe system between the cold junction of the thermoelectric cells and the cold heat sink in order to prevent reverse heat flow in the event of power failure.

Source–sink dynamics: how sinks affect demography of sources

Models of source–sink population dynamics have to make assumptions about whether, and eventually how, demographic parameters in source habitats are dependent on the demography in sink habitats. However, the empirical basis for making such assumptions has been weak. Here we report a study on experimental root vole populations, where estimates of demographic parameters were contrasted between source patches in source–sink (treatment) and source–source systems (control). In the presence of a sink patch (simulated by a pulsed removal of immigrants), source‐patch populations failed to increase over the breeding season, mainly due to a high spatially density‐dependent dispersal rate from source to sink patches. Theper capitarecruitment rate was almost two times higher in source–sink than in the source–source systems, but this did not compensate for the loss rate due to dispersal from source to sink patches. Sex ratio in the source–sink systems became less female biased, probably as a result of an enhanced frequency of dispersal movements in females. Good knowledge of the degree of density‐and habitat‐dependent dispersal is critical for predicting the dynamics of source–sink populations.

The Logic of Territory Choice: Implications for Conservation and Source-Sink Dynamics

Previous article No AccessNotes and CommentsThe Logic of Territory Choice: Implications for Conservation and Source‐Sink DynamicsHanna Kokko, William J. Sutherland, Rufus A. Johnstone, and Associate Editor: Andrew SihHanna Kokko*Corresponding author; e‐mail: [email protected]. Search for more articles by this author , William J. Sutherland Search for more articles by this author , Rufus A. Johnstone Search for more articles by this author , and Associate Editor: Andrew Sih Search for more articles by this author 1. Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, United Kingdom;2. Institute of Biomedical and Life Sciences, Division of Environmental and Evolutionary Biology, University of Glasgow, Glasgow G12 8QQ, United Kingdom;3. School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, United KingdomPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 157, Number 4April 2001 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/319317 Views: 60Total views on this site Citations: 15Citations are reported from Crossref HistoryReceived January 29, 2000Accepted November 30, 2000 Keywordshabitat selectionsource‐sink dynamicsevolutionarily stable strategybreeding site competitionterritorialityfloating© 2001 by The University of Chicago. PDF download Crossref reports the following articles citing this article:Nathan W. Byer, Brendan N. Reid The emergence of imperfect philopatry and fidelity in spatially and temporally heterogeneous environments, Ecological Modelling 468 (Jun 2022): 109968.https://doi.org/10.1016/j.ecolmodel.2022.109968Subir Ranjan Kundu Shifting of environmental factors related to ecophysiological and adaptive responses of spiders, (Jan 2022): 179–197.https://doi.org/10.1016/B978-0-323-90041-6.00009-7Erik G. Noonburg, Rindy C. Anderson Asymmetric competition and floater dynamics, Ecology 102, no.22 (Dec 2020).https://doi.org/10.1002/ecy.3238Bernt-Erik Sæther, Steinar Engen Towards a predictive conservation biology: the devil is in the behaviour, Philosophical Transactions of the Royal Society B: Biological Sciences 374, no.17811781 (Jul 2019): 20190013.https://doi.org/10.1098/rstb.2019.0013Martijn van de Pol, Yngvild Vindenes, Bernt-Erik Sæther, Steinar Engen, Bruno J. Ens, Kees Oosterbeek, Joost M. Tinbergen Effects of climate change and variability on population dynamics in a long-lived shorebird, Ecology 91, no.44 (Apr 2010): 1192–1204.https://doi.org/10.1890/09-0410.1Jorge Contreras-Garduño, Jorge Canales-Lazcano, Jesús Guillermo Jiménez-Cortés, Nahum Juárez-Valdez, Humberto Lanz-Mendoza, Alex Córdoba-Aguilar Spatial and temporal population differences in male density and condition in the American rubyspot, Hetaerina americana (Insecta: Calopterygidae), Ecological Research 24, no.11 (Mar 2008): 21–29.https://doi.org/10.1007/s11284-008-0476-2 Martijn van de Pol , Ido Pen , Dik Heg , and Franz J. Weissing Variation in Habitat Choice and Delayed Reproduction: Adaptive Queuing Strategies or Individual Quality Differences? M. van de Pol et al., The American Naturalist 170, no.44 (Jul 2015): 530–541.https://doi.org/10.1086/521237J.P. Heath, G.J. Robertson, W.A. Montevecchi Population structure of breeding Harlequin Ducks and the influence of predation risk, Canadian Journal of Zoology 84, no.66 (Jun 2006): 855–864.https://doi.org/10.1139/z06-059 Andrés López‐Sepulcre and Hanna Kokko Territorial Defense, Territory Size, and Population Regulation. A. López‐Sepulcre and H. Kokko, The American Naturalist 166, no.33 (Jul 2015): 317–325.https://doi.org/10.1086/432560 Jean‐François Le Galliard , Régis Ferrière , and Ulf Dieckmann Adaptive Evolution of Social Traits: Origin, Trajectories, and Correlations of Altruism and Mobility. J.‐F. Le Galliard et al., The American Naturalist 165, no.22 (Jul 2015): 206–224.https://doi.org/10.1086/427090Niclas Jonzén, Jonathan R. Rhodes, Hugh P. Possingham TREND DETECTION IN SOURCE–SINK SYSTEMS: WHEN SHOULD SINK HABITATS BE MONITORED?, Ecological Applications 15, no.11 (Feb 2005): 326–334.https://doi.org/10.1890/03-5168Judy A. Stamps, V. V. Krishnan, Mary L. Reid SEARCH COSTS AND HABITAT SELECTION BY DISPERSERS, Ecology 86, no.22 (Feb 2005): 510–518.https://doi.org/10.1890/04-0516 References, (Jan 2004): 599–682.https://doi.org/10.1016/B978-012323448-3/50026-XJason V Watters, Sean C Lema, Gabrielle A Nevitt Phenotype management: a new approach to habitat restoration, Biological Conservation 112, no.33 (Aug 2003): 435–445.https://doi.org/10.1016/S0006-3207(02)00343-9R. M. Sibly, J. Hone, T. H. Clutton–Brock, William J. Sutherland, Ken Norris Behavioural models of population growth rates: implications for conservation and prediction, Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 357, no.14251425 (Sep 2002): 1273–1284.https://doi.org/10.1098/rstb.2002.1127

Fast Bolometric Response of Bulk La0.7Sr0.3MnO3Electroceramic Structures

We report on the performance of a microwave electroceramic bolometer of hybrid La0.7Sr0.3MnO3/Al2O3 (0.2 x 2 x 4 mm(3)) structure. The estimated thermal resistance of the bulk ceramic manganite film-single crystal sapphire interface is about 500 K/W at room temperature. This resistance is the main thermal barrier in the heat sink system and has been found to be slightly dependent on temperature, When compared with the high-ire superconducting bolometers, the La0.7Sr0.3MnO3 microwave electroceramic bolometer works in a more wide temperature range, from 77 K to 330 K, excluding the narrow temperature interval at the metal-insulator phase transition (T = 230 K). The microwave electroceramic bolometer sensitivity and the time constant at room temperature have been found to be 0.1 V/W and 100 ms, respectively. To improve the bolometer performance the point contact has been fabricated by a break junction technique. The optimization of a microwave electroceramic bolometer design brought to a considerable improvement of basic bolometer characteristics. The microwave sensitivity was about 0.3 V/W and the time constant was less than 100 ns.

Optimal Vibration Feedback Control of an Euler-Bernoulli Beam: Toward Realization of the Active Sink Method

This paper discusses the optimal vibration feedback control of an Euler-Bernoulli beam from a viewpoint of active wave control making all structural modes inactive (more than suppressed). Using a transfer matrix method, the paper derives two kinds of optimal control laws termed “active sink” which inactivates all structural modes; one obtained by eliminating reflected waves and the other by transmitted waves at a control point. Moreover, the characteristic equation of the active sink system is derived, the fundamental properties being investigated. Towards the goal of implementing the optimal control law that is likely to be non-causal, a “classical” velocity feedback control law (Balas, 1979) widely used in a vibration control engineering is applied, revealing a substantial shortcoming. Introduction of a “classical” displacement feedback to the velocity is found to realize the optimal control law in a restricted frequency range. Finally, two kinds of stability verification for closed feedback control systems are presented for distributed parameter structures.

Irradiation resistance of DS copper/stainless steel joints fabricated by friction welding methods

Copper alloys tubes are assumed to be used for the heat sink system of the ITER first wall and divertor. To join copper tubes with type 316LN stainless steel tubes (for the collector system) various methods are provided, the most promising being the friction welding. Specimens of joints and the base materials were irradiated in the SM-2 mixed spectrum reactor to a dose of 0.2 dpa at T irr=150°C and 300°C. Specimens of GlidCop Al25/316LN friction welded joints have a relatively high level of strength properties and a rather low plasticity after irradiation.

Analytical modeling of spreading resistance in flux tubes, half spaces, and compound disks

A review of previously published models and solutions pertinent to the issue of modeling thermal resistances of diamond on copper heat sink systems is presented. The many particular solutions are shown to be special cases of the comprehensive model developed for a circular heat source in perfect thermal contact with the top surface of a compound disk which consists of two isotropic layers in perfect thermal contact. The bottom surface of the compound disk is subjected to a convective or contact cooling condition. Whenever possible simple models and correlation equations are presented for ease of computation. Bounds are presented for estimating the overall thermal resistance of several important cases.

Analysis and optimization of a natural draft heat sink system

An analytical solution for a system consisting of a vertical, parallel-plate, isothermal heat sink, and a chimney is presented. The result is applied to problems in which the size of the overall system is constrained. A ridge of maximum total heat transfer is observed with respect to the plate spacing and heat-sink height. The ridge suggests that heat-sink height may be reduced without diminishing the thermal performance for natural draft cooling. The flow characteristics of optimal systems reveal that systems with and without chimneys dissipate maximum heat when the velocity profiles within the heat sink are fully developed and developing, respectively.

Selection of targets and ion sources for radioactive ion beam generation at the Holifield Radioactive Ion Beam Facilitya)

In this article, we describe the performance characteristics for a selected number of target ion sources that will be employed for initial use at the Holifield Radioactive Ion Beam Facility as well as prototype ion sources that show promise for future use for radioactive ion beam applications. A brief review of present efforts to select target materials and to design composite target matrix/heat-sink systems that simultaneously incorporate the short diffusion lengths, high permeabilities, and controllable temperatures required to effect fast and efficient diffusion release of the short-lived species is also given.

Transient survival probability of a particle diffusing in a disordered system of perfectly absorbing spherical sinks

The transient survival probability of a particle diffusing in a disordered system of perfectly absorbing non-overlapping spherical sinks is studied by use of a self-consistent cluster expansion for its Laplace transform. The self-consistent cluster expansion, which in principle is exact, is formulated in two alternative versions, corresponding to different ways of handling the instantaneous absorption of particles created initially inside a sink. In each version of the theory the cluster expansion is truncated at either the singlet or the pair level, so that four different approximations to the exact result are obtained. An approximation on the pair level constitutes an improvement to the corresponding singlet approximation. It is shown that at moderate volume fraction of the sink system the two pair approximations yield almost identical results for the survival probability. All four approximations lead to a band gap in the spectrum of relaxation rates, followed by a continuum extending to infinity.

A Concept of Passive Safety, Pressurized Water Reactor System with Inherent Matching Nature of Core Heat Generation and Heat Removal

The reduction of manpower in operation and maintenance by simplification of the system are essential to improve the safety and the economy of future light water reactors. At the Japan Atomic Energy Research Institute (JAERI), a concept of a simplified passive safety reactor system JPSR was developed for this purpose and in the concept minimization of developing work and conservation of scale-up capability in design were considered. The inherent matching nature of core heat generation and heat removal rate is introduced by the core with high reactivity coefficient for moderator density and low reactivity coefficient for fuel temperature (Doppler effect) and once-through steam generators (SGs). This nature makes the nuclear steam supply system physically-slave for the steam and energy conversion system by controlling feed water mass flow rate. The nature can be obtained by eliminating chemical shim and adopting in-vessel control rod drive mechanism (CRDM) units and a low power density core. In order to simplify the system, a large pressurizer, canned pumps, passive residual heat removal systems with air coolers as a final heat sink and passive coolant injection system are adopted and the functions of volume and boron concentration control and seal water supply are eliminated from the chemical and volume control system (CVCS). The emergency diesel generators and auxiliary component cooling system of “safety class” for transferring heat to sea water as a final heat sink in emergency are also eliminated. All of systems are built in the containment except for the air coolers of the passive residual heat removal system. The analysis of the system revealed that the primary coolant expansion in 100% load reduction in 60 s can be mitigated in the pressurizer without actuating the pressure relief valves and the pressure in 50% load change in 30 s does not exceed the maximum allowable pressure in accidental conditions in regardless of pressure regulation.

A Concept of Passive Safety Pressurized Water Reactor System with Inherent Matching Nature of Core Heat Generation and Heat Removal.

The reduction of manpower in operation and maintenance by simplification of the system are essential to improve the safety and the economy of future light water reactors. At the Japan Atomic Energy Research Institute (JAERI), a concept of a simplified passive safety reactor system JPSR was developed for this purpose and in the concept minimization of developing work and conservation of scale-up capability in design were considered. The inherent matching nature of core heat generation and heat removal rate is introduced by the core with high reactivity coefficient for moderator density and low reactivity coefficient for fuel temperature (Doppler effect) and once-through steam generators (SGs). This nature makes the nuclear steam supply system physically-slave for the steam and energy conversion system by controlling feed water mass flow rate. The nature can be obtained by eliminating chemical shim and adopting in-vessel control rod drive mechanism (CRDM) units and a low power density core. In order to simplify the system, a large pressurizer, canned pumps, passive residual heat removal systems with air coolers as a final heat sink and passive coolant injection system are adopted and the functions of volume and boron concentration control and seal water supply are eliminated from the chemical and volume control system (CVCS). The emergency diesel generators and auxiliary component cooling system of “safety class” for transferring heat to sea water as a final heat sink in emergency are also eliminated. All of systems are built in the containment except for the air coolers of the passive residual heat removal system. The analysis of the system revealed that the primary coolant expansion in 100% load reduction in 60 s can be mitigated in the pressurizer without actuating the pressure relief valves and the pressure in 50% load change in 30 s does not exceed the maximum allowable pressure in accidental conditions in regardless of pressure regulation.

Generalized rate theory for spatially inhomogeneous systems of point defect sinks

A statistical approach to the derivation of rate equations governing the diffusion of point defects to a dilute random system of sinks in a homogeneous matrix is proposed and discussed. The approach clearly reveals a heirarchical nature of the rate theory. A procedure allowing to reduce this hierarchy to the conventional set of rate equations and to introduce self-consistently the concept of sink strength is described in detail. The resulting set of equations can be quite naturally applied to spatially inhomogeneous sink systems, since the usual assumption of homogeneous sink distribution in the matrix is shown to be unessential for the reduction procedure. Finally, the consecutive procedure for calculation of corrections to sink strength due to close sink configurations is proposed and generalization of the rate theory in order to account for effects of elastic point defect interaction with sinks is discussed.

Diffusion Patterns on Domains Representing Developing Xenopus Retina

The retinotectal map of mature Xenopus frogs has linear metrics. The regions of the Xenopus retina were modeled during embryonic and early larval development with a set of standard geometrical shapes. A disk was used to model the entire early retina, rings of various thickness were used to model the ciliary margin (the growth zone of the larval retina), and portions of a sphere were used to model the entire late embryonic and larval retina. Gradients produced by several reaction-diffusion pattern-generating configurations were considered: Gierer-Meinhardt and Kauffman-type activator-inhibitor systems; an ideal Turing-like two morphogen system; a point source with diffuse sinks; and variously placed point source-point sink combinations. A few special arrangements produced linear metrics: a point source-point sink system produced linear angular metrics on a thin ring; an ideal Turing system produced linear cartesian metrics on a thin ring; and carefully configured multiple sources and sinks produced linear metrics on a disk. These cases could lead to linear map metrics, but are biologically implausible. Thus linear map metrics are probably not a direct consequence of linear positional values, and more generally, most embryonic tissues probably use non-linear gradients of positional information. Formation of linear map metrics may be functionally important for Xenopus frogs, accounting in part for the evolutionary preservation of mechanisms for interactions among neighboring retinal fibers.

Heterogeneous processes of new phase growth in the system of various sinks: ion-beam synthesis of silicon oxynitride

In this paper we continue to model the formation of new phases in silicon after implantation of reactive ions. We generalize our foregoing investigation, and now two different reactive species of similar chemical characteristics are considered. New phase inclusions grow as a result of the impurity diffusion to a distributed sink. This consists of spherical nuclei which have a complex chemical composition and do not touch each other. The numerical results of this model agree with the experimental data, obtained by Auger depth profiling only if we introduce the dependence of the diffusion coefficients of the reactive impurities on the matrix imperfection.