Relevant bibliographies by topics / Delayed density-dependence

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  1. Journal articles
  2. Dissertations / Theses
  3. Book chapters
  4. Conference papers

Academic literature on the topic 'Delayed density-dependence'

Author: Grafiati
Published: 4 June 2021
Last updated: 9 February 2022

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Journal articles on the topic "Delayed density-dependence"

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HANSKI, ILKKA, and IAN W.OIWOD. "Delayed density-dependence." Nature 350, no. 6313 (March 1991): 28. http://dx.doi.org/10.1038/350028a0.

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Berryman, Alan, and Peter Turchin. "DETECTION OF DELAYED DENSITY DEPENDENCE: COMMENT." Ecology 78, no. 1 (January 1997): 318–20. http://dx.doi.org/10.1890/0012-9658(1997)078[0318:dodddc]2.0.co;2.

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Williams, David W., and Andrew M. Liebhold. "DETECTION OF DELAYED DENSITY DEPENDENCE: REPLY." Ecology 78, no. 1 (January 1997): 320–22. http://dx.doi.org/10.1890/0012-9658(1997)078[0320:dodddr]2.0.co;2.

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Holyoak, Marcel. "Identifying Delayed Density Dependence in Time-Series Data." Oikos 70, no. 2 (June 1994): 296. http://dx.doi.org/10.2307/3545641.

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Hornfeldt, Birger. "Delayed Density Dependence as a Determinant of Vole Cycles." Ecology 75, no. 3 (April 1994): 791–806. http://dx.doi.org/10.2307/1941735.

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Solow, Andrew R. "OBSERVATION ERROR AND THE DETECTION OF DELAYED DENSITY DEPENDENCE." Ecology 82, no. 11 (November 2001): 3263–64. http://dx.doi.org/10.1890/0012-9658(2001)082[3263:oeatdo]2.0.co;2.

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Gillman, M. P., and M. Dodd. "Detection of delayed density dependence in an orchid population." Journal of Ecology 88, no. 2 (April 2000): 204–12. http://dx.doi.org/10.1046/j.1365-2745.2000.00440.x.

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Неверова, Г. П., and G. P. Neverova. "Dynamic Regimes of Local Homogeneous Population with Delayed Density Dependence." Mathematical Biology and Bioinformatics 10, no. 2 (August 28, 2015): 309–24. http://dx.doi.org/10.17537/2015.10.309.

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It is researched a model of limited homogeneous population size. It is assumed that there is delayed density dependence. It is made the analytical and numerical investigation of the model with different time lag. It is shown there it is the phenomenon of multiregimism. This phenomenon consists in the existence of various dynamic regimes under the same values of parameters. This effect arises in the model that simultaneously possesses several different limit regimes: stable state, regular fluctuations, and chaotic attractor. The research results show if present population dynamics substantially depends on population size of previous years than it is observed quasi-periodic oscillations. Fluctuations with period 2 occur when the growth of population size is regulated by density-dependence in the current year.
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Jiang, Lin, and Nan Shao. "AUTOCORRELATED EXOGENOUS FACTORS AND THE DETECTION OF DELAYED DENSITY DEPENDENCE." Ecology 84, no. 8 (August 2003): 2208–13. http://dx.doi.org/10.1890/02-0557.

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Liz, Eduardo, Victor Tkachenko, and Sergei Trofımchuk. "Global stability in discrete population models with delayed-density dependence." Mathematical Biosciences 199, no. 1 (January 2006): 26–37. http://dx.doi.org/10.1016/j.mbs.2005.03.016.

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Dissertations / Theses on the topic "Delayed density-dependence"

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Hörnfeldt, Birger. "Cycles of voles, predators, and alternative prey in boreal Sweden." Doctoral thesis, Umeå universitet, Ekologi och geovetenskap, 1991. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-100711.

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Bank voles, grey-sided voles, and field voles had synchronous 3-4 year density cycles with variable amplitudes which averaged about 200-fold in each species. Cycles of vole predators (red fox and Tengmalm's owl), and their (foxes') alternative prey (mountain hare and forest grouse) lagged behind the vole cycles. The nomadic Tengmalm's owl responded with a very rapid and strong numerical increase to the initial cyclic summer increase of voles (the owl’s staple food). Owl breeding densities in the springs were highly correlated with vole supply in the previous autumns. This suggested that the number of breeding owls was largely determined in the autumn at the time of the owl's nomadic migrations, and that immigration was crucial for the rapid rise in owl numbers. The owl's numerical response was reinforced by the laying of earlier and larger clutches when food was plentiful. In addition, the owl has an early maturation at one year of age. The transition between subsequent vole cycles was characterized by a distinct shift in rate of change in numbers from low to high or markedly higher values in both summer and winter. Regulation increased progressively throughout the cycle since the rate of change decreased continuously in the summers. Moreover, there was a similar decrease of the rate of change in winter. Rate of change was delayed density-dependent. The delayed density-dependence had an 8 month time-lag in the summers and a 4 month time-lag in the winters relative to the density in previous autumns and springs, respectively. These findings suggest that vole cycles are likely to be generated by a time-lag mechanism. On theoretical grounds, it has been found that a delayed density- dependence of population growth rate with a 9 month time-lag caused stable limit cycles with a period between 3 and 4 years. Some mechanisms for the delayed density-dependence are suggested and discussed. The mechanisms are assumed to be related to remaining effects of vole populations past interactions with predators, food supplies, and/or diseases. Unlike the other voles, the bank vole had regular and distinct seasonal declines in density over winter. These declines are proposed to be due to predation, mainly by Tengmalm's owl. Supranivean foraging for epiphytic tree lichens and conifer seeds most likely explains why this species was frequently taken by the owl under snow-rich conditions. The alternative prey hypothesis predicts that a reduction of predator numbers should increase the number of alternative prey. Alternative prey should be less effectively synchronized to the vole cycle by predation at declining and low vole (main prey) densities; they may also lose their 3-4 year cyclicity. The appearance of sarcoptic mange among foxes in northern Sweden in the mid 1970s provided an opportunity to "test" these ideas, and these were found to be supported. In areas with highest mange infection rates, foxes declined markedly from the late 1970s to mid 1980s, whereas hare numbers rose rapidly and appeared non-cyclic.

Diss. (sammanfattning) Umeå : Umeå universitet, 1991, härtill 7 uppsatser


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Book chapters on the topic "Delayed density-dependence"

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Fogarty, Michael J., and Jeremy S. Collie. "Density-Dependent Population Growth." In Fishery Ecosystem Dynamics, 29–46. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198768937.003.0003.

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The observation that no population can grow indefinitely and that most populations persist on ecological timescales implies that mechanisms of population regulation exist. Feedback mechanisms include competition for limited resources, cannibalism, and predation rates that vary with density. Density dependence occurs when per capita birth or death rates depend on population density. Density dependence is compensatory when the population growth rate decreases with population density and depensatory when it increases. The logistic model incorporates density dependence as a simple linear function. A population exhibiting logistic growth will reach a stable population size. Non-linear density-dependent terms can give rise to multiple equilibria. With discrete time models or time delays in density-dependent regulation, the approach to equilibrium may not be smooth—complex dynamical behavior is possible. Density-dependent feedback processes can compensate, up to a point, for natural and anthropogenic disturbances; beyond this point a population will collapse.
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Turchin, Peter, and Cheryl J. Briggs. "Population Cycles of the Larch Budmoth in Switzerland." In Population Cycles. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195140989.003.0011.

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The population dynamics of the larch budmoth (LBM), Zeiraphera diniana, in the Swiss Alps are perhaps the best example of periodic oscillations in ecology (figure 7.1). These oscillations are characterized by a remarkably regular periodicity, and by an enormous range of densities experienced during a typical cycle (about 100,000-fold difference between peak and trough numbers). Furthermore, nonlinear time series analysis of LBM data (e.g., Turchin 1990, Turchin and Taylor 1992) indicates that LBM oscillations are definitely generated by a second-order dynamical process (in other words, there is a strong delayed density dependence—see also chapter 1). Analysis of time series data on LBM dynamics from five valleys in the Alps suggests that around 90% of variance in Rt is explained by the phenomenological time series model employing lagged LBM densities, R, =f(Ni-1,Ni-2,) (Turchin 2002). As discussed in the influential review by Baltensweiler and Fischlin (1988) about a decade ago, ecological theory suggests a number of candidate mechanisms that can produce the type of dynamics observed in the LBM (see also chapter 1). Baltensweiler and Fischlin concluded that changes in food quality induced by previous budmoth feeding was the most plausible explanation for the population cycles. During the last decade, the issue of larch budmoth oscillations was periodically revisited by various population ecologists looking for general insights about insect population cycles (e.g., Royama 1977, Bowers et al. 1993, Ginzburg and Taneyhill 1994, Den Boer and Reddingius 1996, Hunter and Dwyer 1998, Berryman 1999). These authors generally concurred with the view that budmoth cycles are driven by the interaction with food quality. A recent reanalysis of the rich data set on budmoth population ecology collected by Swiss researchers over a period of several decades, however, suggested that the role of parasitism is underappreciated (Turchin et al. 2002). Before focusing on the roles of food quality and parasitism in LBM dynamics, we briefly review the status of other hypotheses that were discussed in the literature on LBM cycles. First, the natural history of the LBM-larch system is such that food quantity is an unlikely factor to explain LBM oscillations.
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Conference papers on the topic "Delayed density-dependence"

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Tamilporai, P., S. Chandrasekaran, S. Subramaniyam, J. Jancirani, and K. V. Lakshminarayanarao. "Numerical Investigations on Extended Expansion Engine." In ASME 2003 Internal Combustion Engine and Rail Transportation Divisions Fall Technical Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/icef2003-0718.

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A great deal of research has been directed towards understanding the dependence of emissions and fuel economy on the operating and design characteristics of spark-ignition homogeneous-charge engine. Several recent investigations have been concerned with modifying the conventional spark-ignition such that the part load BSFC (brake specific fuel consumption) is decreased. Many of the proposed modifications convert the engine from fixed to variable displacement, i.e., the engine size is varied to suit the vehicle needs. Another possible modification to the conventional engine is to control the load of the engine by controlling the timing of the intake-valve closure rather than by variable-density throttling. This investigation examines the delaying intake valve closing as a method of controlling the engine load without incurring the usual part-load throttling losses. The extended expansion engine (EEE) is an engine with the power output regulated by controlling the crank angle at which the intake valve closes (IVC). As in case of a conventional engine the intake valve opens just prior to and remains open through out the intake stroke of the engine. However, the intake valve also remains open over a portion of the compression stroke while the piston pushes part of the cylinder charge back into the intake manifold and stored in a plenum. A one-way valve is provided to prevent the charge from re-entering the carburetor. After the intake valve closes, the actual compression starts and the expansion and exhaust strokes are similar to those of the conventional engine. The effective cylinder volume determines the trapped cylinder charge and therefore the power output, at the time of the intake valve closing. This paper mainly deals with the numerical studies on single cylinder, four stroke, spark ignition, Extended Expansion Engine extended expansion engine with intake valve closure delayed to produce an expansion ratio that is larger than the compression ratio. The Engine processes are simulated on a computer using thermodynamic and global modeling techniques. Further the concept of lean burn technology is applied to the simulated processes and the engine performance and emission characteristics are studied from the simulated results. Two-zone combustion model is adopted for the analysis of combustion. The model is also associated with sub models for calculating the combustion duration and equilibrium composition of five product species. From this investigations and comparison of results, it is concluded that the simulation work developed predicts the performance and emission characteristics of this engine reasonably well. Therefore it is evident that the developed code can be used with confidence for further parametric studies.
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Aghasi, Paul, Ephraim Gutmark, and David Munday. "Dependence of Film Cooling Effectiveness on 3D Printed Cooling Holes." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-56698.

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Film Cooling Effectiveness is closely dependent on the geometry of the hole emitting the cooling film. These holes are sometimes quite expensive to machine by traditional methods so 3D printed test pieces have the potential to greatly reduce the cost of film cooling experiments. What is unknown is the degree to which parameters like layer resolution and the choice among 3D printing technologies influence the results of a film cooling test. A new flat-plate film cooling facility employing oxygen sensitive paint (OSP) verified by gas sampling and the mass transfer analogy and measurements both by gas sampling and OSP is verified by comparing measurements by both gas sampling and OSP. The same facility is then used to characterize the film cooling effectiveness of a diffuser shaped film cooling hole geometry. These diffuser holes are then produced by a variety of additive manufacturing technologies with different build layer thicknesses. Technologies used include Fused Deposition Modeling (FDM), Stereo Lithography Apparatus (SLA) and PolyJet with build layer thicknesses ranging from 0.001D (25 μm) to 0.12D (300 μm). These are compared with an aluminum coupon manufactured by traditional machining methods. The objective is to determine if cheaper manufacturing techniques afford usable and reliable results. Tests are carried out at mainstream flow Mach number of 0.30 and blowing ratios (BRs) from 1.0 to 3.5. The coolant gas used is CO2 yielding a density ratio of 1.5. Surface quality is characterized by an Optical Microscope that measures surface roughness. Test coupons with rougher surface topology generally showed delayed blow off and higher film cooling effectiveness at high blowing ratios compared to the geometries with lower measured surface roughness. At the present scale, none of the additively manufactured parts consistently matched the traditionally machined part, indicating that caution should be exercised in employing additively manufactured test pieces in film cooling work.
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Joshi, Umashankar, Ziliang Zheng, Amit Shrestha, Naeim Henein, and Eric Sattler. "An Investigation on Sensitivity of Ignition Delay and Activation Energy in Diesel Combustion." In ASME 2014 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/icef2014-5587.

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The auto-ignition process plays a major role in the combustion, performance, fuel economy and emission in diesel engines. The auto-ignition quality of different fuels has been rated by its cetane number (CN) determined in the CFR engine, according to ASTM D613. More recently, the Ignition Quality Tester (IQT), a constant volume vessel, has been used to determine the derived cetane number (DCN) to avoid the elaborate, time consuming and costly engine tests, according to ASTM D6890. The ignition delay period in these two standard tests and many investigations has been considered to be the time period between start of injection (SOI) and start of combustion (SOC). The ignition delay (ID) values determined in different investigations can vary due to differences in instrumentation and definitions. This paper examines the different definitions and the parameters that effect ID period. In addition the activation energy dependence on the ID definition is investigated. Furthermore, results of an experimental investigation in a single-cylinder research diesel engine will be presented while the charge density is kept constant during the ID period. The global activation energy is determined and its sensitivity to the charge temperature is examined.
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Thompson, Corey, Matt Gordon, Ajay P. Malshe, and Deep Gupta. "Development of Thermal Interface Materials for Harsh Environment Packaging of Superconducting Integrated Circuits." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-40527.

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Superconducting integrated circuits (SCICs) require cooling to about 4 K for proper circuit operation. Current efforts are being made to transfer SCIC technology from lab experiments to viable consumer and military products. In order for this to be feasible, SCICs must function in cryogen-free closed-cycle refrigerator (or cryocooler) based systems. Design constraints for SCICs utilizing rapid single-flux-quantum (RSFQ) logic require a maximum temperature gradient across the package of less than 50 mK for proper circuit operation when implemented in cryocooler mounted systems. Also, to achieve increased functional density and decreased signal delays, it is desired to implement multichip module (MCM) SCICs in which RSFQ signals are passed from chip-to-chip through a common MCM substrate. Satisfying these constraints requires innovative packaging and thermal interface materials for harsh environment packaging (low temperature, high vacuum). The objective of this modeling work is to: explain the role of underfill in harsh environment cryogenic packages, explore the role of polymers and nanocomposites in filling this role, and anticipate the role of manufacturing defects on thermal management of 4 K packages. A characteristic model is developed in COMSOL MultiPhysics that allows for investigation of the dependence of temperature gradients across the package on these variables. It is found that at 4 K thermal interface resistances act as major bottlenecks to heat removal from the active die. It is also shown that as bump diameter decreases below 100 microns due to device miniaturization, the need for effective thermal interface materials is exacerbated. A novel nanoengineered cryogenic adhesive (nECA) comprised of nanoparticles dispersed in an epoxy matrix is proposed to act as a heat transfer medium between chip and substrate. Incorporation of nECA into the FEA model of a single chip package reduces the overall temperature gradient from 78 mK to 44 mK. This advance in thermal management of low temperature SCICs is paramount for the advancement of MCM packaging requiring efficient removal of heat from densely packaged chips.
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de Risi, Arturo, Teresa Donateo, and Domenico Laforgia. "Theoretical Investigation on the Influence of Physical Parameters on Soot and NOx Engine Emissions." In ASME 2001 Internal Combustion Engine Division Spring Technical Conference. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/ices2001-120.

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Abstract CFD simulations need a certain number of parameters to calibrate both empirical and analytical models. The present investigation aims at identifying the effects of these parameters on the numerical prediction of a modified version of Kiva 3V code, which includes the use of the RNG k-ε model for turbulence, the gas/wall convective heat transfer model proposed by Han, Kelvin-Helmholtz Rayleigh-Taylor spray injection and breakup models. Ignition delay was modeled with the Shell model, whereas the laminar-turbulent characteristic time model was used for combustion. Soot formation and oxidation were calculated using Hiroyasu and Nagle and Strickland-Constable models, respectively. NOx was predicted by using the extended Zel’dovich mechanism. This study was carried out for a common-rail direct injection, small-bore Diesel engine, including the investigation of both numerical and physical parameters. Numerical parameters are intended to be variables related to breakup, turbulence, and combustion models that are adjusted according to grid resolution, engine and injection system geometry, and operating conditions. In particular, the effect of laminar and turbulent time scales, characteristic breakup length and time scales, initial turbulence kinetic energy density, initial swirl velocity profile, on engine emissions was analyzed. The investigated physical parameters were initial swirl ratio, air water content, Schmidt number for mass diffusion. All simulations were performed by changing one of the above parameters at each run and keeping approximately the same pressure and heat release rate curves. Results show that similar pressure vs. crank angle curves can be obtained with different values of these parameters but they lead to very different values of predicted emissions levels. In particular, changes of laminar and turbulent characteristic time resulted in a strong influence on NOx emissions but their effects on soot levels were minor. Mass diffusion characteristics (e.g. Schmidt number) were found to strongly affect both soot and NOx emissions. Spray parameters were found mainly to affect soot formation. Furthermore, NOx and soot emissions showed a dependence on swirl ratio and velocity profile.
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