scholarly journals Expanding comparative–advantage biological market models: contingency of mutualism on partner's resource requirements and acquisition trade–offs

2003 ◽  
Vol 270 (1518) ◽  
pp. 913-919 ◽  
Author(s):  
Jason D. Hoeksema ◽  
Mark W. Schwartz
Keyword(s):  
Comparative Advantage ◽  
Market Models ◽  
Trade Offs ◽  
Resource Requirements ◽  
Biological Market

scholarly journals MULTI-CLASS RESOURCE SHARING WITH BATCH ARRIVALS

2018 ◽  
Vol 33 (3) ◽  
pp. 348-366
Author(s):  
Paul Ezhilchelvan ◽  
Isi Mitrani
Keyword(s):  
Resource Sharing ◽  
Large Scale ◽  
Virtual Machines ◽  
Cloud Provider ◽  
Batch Arrivals ◽  
Large Scale Systems ◽  
Trade Offs ◽  
Resource Requirements ◽  
Partial Blocking ◽  
Fixed Point Iterations

A cloud provider hosts virtual machines (VMs) of different types, with different resource requirements. There are bounds on the total amounts of each kind of resource that are available. Requests arrive in batches of different sizes. Under the ‘complete blocking’ policy, a request is accepted only if all the VMs in its batch can be accommodated. The ‘partial blocking’ policy would accept a request if there is room for at least one of the VMs in the batch. Blocked requests are lost, with an associated loss of revenue. The trade-offs between costs and benefits are evaluated by means of appropriate models, for which novel solutions based on fixed-point iterations are proposed. The applicability of those solutions is extended, by means of simplifications, to very large-scale systems. Numerical examples and comparisons with simulations are presented.

The effect of cover and food on space use by wintering Song Sparrows and Field Sparrows

1997 ◽  
Vol 75 (10) ◽  
pp. 1636-1641 ◽  
Author(s):  
Christopher W. Beck ◽  
Bryan D. Watts
Keyword(s):  
Predation Risk ◽  
Positive Response ◽  
Distribution Patterns ◽  
Microhabitat Use ◽  
Vegetative Cover ◽  
Song Sparrows ◽  
Trade Offs ◽  
Resource Requirements ◽  
Woody Cover ◽  
Species Specific

The distribution of birds among microhabitats may reflect species-specific resource requirements. Both food availability and predation risk have been shown to influence patterns of microhabitat use by sparrows during winter. We investigated the influence of vegetative cover and food on microhabitat use using a 2 × 2 factorial design. Both woody cover and food were manipulated at the plot level. The presence of screening cover (weed stems) was manipulated within plots. Sparrows showed a positive response to the presence of both cover and food. Within plots, sparrows selected areas with screening cover. The distribution of birds between areas with and without screening cover was influenced by the presence of woody cover and food. Conversely, the presence of screening cover reduced the influence of woody cover on the distribution of birds within patches. Song Sparrows (Melospiza melodia) and Field Sparrows (Spizella pusilla) differed in their response to treatments both within and across plots, suggesting that trade-offs between foraging and predation risk may be important in the structuring of winter sparrow assemblages. Additionally, screening cover appears to moderate predation risk and therefore to affect distribution patterns.

scholarly journals The evolution of competitive ability for essential resources

2019 ◽  
Author(s):  
Joey R. Bernhardt ◽  
Pavel Kratina ◽  
Aaron Pereira ◽  
Manu Tamminen ◽  
Mridul K. Thomas ◽  
...  
Keyword(s):  
Competitive Ability ◽  
Community Dynamics ◽  
Species Coexistence ◽  
Resource Competition ◽  
Environmental Gradients ◽  
Light Limitation ◽  
Major Question ◽  
Trade Offs ◽  
Resource Requirements ◽  
Competitive Abilities

AbstractCompetition for limiting resources is among the most fundamental ecological interactions and has long been considered a key driver of species coexistence and biodiversity. Species’ minimum resource requirements, their R*s, are key traits that link individual physiological demands to the outcome of competition. However, a major question remains unanswered - to what extent are species’ competitive traits able to evolve in response to resource limitation? To address this knowledge gap, we performed an evolution experiment in which we exposed Chlamydomonas reinhardtii for approximately 285 generations to seven environments in chemostats which differed in resource supply ratios (including nitrogen, phosphorus and light limitation) and salt stress. We then grew the ancestors and descendants in common garden and quantified their competitive abilities for essential resources. We investigated constraints on trait evolution by testing whether changes in resource requirements for different resources were correlated. Competitive abilities for phosphorus improved in all populations, while competitive abilities for nitrogen and light increased in some populations and decreased in others. In contrast to the common assumption that there are trade-offs between competitive abilities for different resources, we found that improvements in competitive ability for a resource came at no detectable cost. Instead, improvements in competitive ability for multiple resources were either positively correlated or not significantly correlated. Using resource competition theory, we then demonstrated that rapid adaptation in competitive traits altered the predicted outcomes of competition. These results highlight the need to incorporate contemporary evolutionary change into predictions of competitive community dynamics over environmental gradients.

Modeling and exploiting spatial locality trade-offs in wavelet-based applications under varying resource requirements

2010 ◽  
Vol 9 (3) ◽  
pp. 1-26 ◽  
Author(s):  
Bert Geelen ◽  
Vissarion Ferentinos ◽  
Francky Catthoor ◽  
Gauthier Lafruit ◽  
Diederik Verkest ◽  
...  
Keyword(s):  
Spatial Locality ◽  
Trade Offs ◽  
Resource Requirements

scholarly journals Stability, Memory, and Messaging Trade-Offs in Heterogeneous Service Systems

2021 ◽  
Author(s):  
David Gamarnik ◽  
John N. Tsitsiklis ◽  
Martin Zubeldia
Keyword(s):  
Broad Class ◽  
Text Messages ◽  
Current State ◽  
Trade Offs ◽  
Resource Requirements ◽  
Decision Epoch ◽  
Message Exchange ◽  
Service Rates ◽  
Finite Memory ◽  
Heterogeneous Service

We consider a heterogeneous distributed service system consisting of n servers with unknown and possibly different processing rates. Jobs with unit mean arrive as a renewal process of rate proportional to n and are immediately dispatched to one of several queues associated with the servers. We assume that the dispatching decisions are made by a central dispatcher with the ability to exchange messages with the servers and endowed with a finite memory used to store information from one decision epoch to the next, about the current state of the queues and about the service rates of the servers. We study the fundamental resource requirements (memory bits and message exchange rate) in order for a dispatching policy to be always stable. First, we present a policy that is always stable while using a positive (but arbitrarily small) message rate and [Formula: see text] bits of memory. Second, we show that within a certain broad class of policies, a dispatching policy that exchanges [Formula: see text] messages per unit of time, and with [Formula: see text] bits of memory, cannot be always stable.

scholarly journals The influence of the steepness of dominance hierarchies on reciprocity and interchange in captive groups of bonobos (Pan paniscus)

Behaviour ◽  
2005 ◽  
Vol 142 (7) ◽  
pp. 941-960 ◽  
Author(s):  
Han de Vries ◽  
Jeroen M.G. Stevens ◽  
Linda Van Elsacker ◽  
Hilde Vervaecke
Keyword(s):  
Side Effect ◽  
Dominance Hierarchy ◽  
Pan Paniscus ◽  
Food Sharing ◽  
Limited Resources ◽  
Dominance Hierarchies ◽  
Market Models ◽  
High Ranking ◽  
Per Se ◽  
Biological Market

AbstractBiological market models explain variability in reciprocity and interchange between groups. In groups with a shallow dominance gradient, grooming will be mostly exchanged for itself (i.e. exchange will occur). In groups with steep dominance hierarchies, interchange is expected: individuals will groom higher ranking individuals to get access to limited resources or commodities such as support in conflicts, and grooming will be traded for these commodities.We examine patterns of reciprocity in grooming and support, and of interchange of grooming for support or for tolerance in six captive groups of bonobos. We test whether differences between groups in patterns of reciprocity and interchange can be attributed to differences in a measure of steepness of dominance hierarchies, which is based on dyadic agonistic interactions.We found that grooming was reciprocal in some, but not all groups. Support was highly reciprocal, but this was a side effect of dominance in most groups. Interchange between grooming and support was observed in some groups. Corroborating earlier findings, this was a side effect of individuals preferring high ranking individuals as grooming and support partners, possibly because these high-ranking individuals provide more efficient support in conflicts. There was no evidence for interchange of grooming for tolerance.Variability in grooming reciprocity was explained by differences in steepness of dominance hierarchies, as predicted by the biological market models. In groups with a shallow dominance hierarchy, grooming was more reciprocal. This was not true for reciprocity in support. There was some evidence that individuals groomed dominants more frequently in groups with a steep dominance hierarchy. The variation in interchange relations between grooming and support did not depend on the steepness of dominance hierarchies. We suggest that grooming in itself is a valuable commodity in bonobos, especially under captive conditions, which can be exchanged reciprocally. Bonobos may interchange grooming for another value equivalent, with food sharing as a very likely candidate. This interchange effects seem more dependent on potential to monopolise food than on steepness of dominance hierarchies per se.

scholarly journals A Wireless Sensor Networks Security Protocol Architecture

2019 ◽  
Vol 9 (2) ◽  
pp. 400-406
Keyword(s):  
Wireless Sensor Networks ◽  
Wireless Sensor Network ◽  
Sensor Networks ◽  
Sensor Network ◽  
Security Protocol ◽  
Wireless Sensor ◽  
Trade Offs ◽  
Resource Requirements ◽  
Save Energy ◽  
The One

A wireless sensor network is made up of extremely small autonomous units capable of sensing, computing and communicating. There are numerous restrictions on wireless sensor networks as the resource available to the wireless sensor network is limited. Thus, a number of clustering protocols in a routing sensor organization of sensor networks have been proposed in the literature which increase the throughput, save energy and decrease the delay in the system. In this paper, we put forward SNP, the one of its type link layer security architecture for wireless sensor networks. In this, the design vulnerabilities which were found in the protocols such as 802.11b and GSM are addressed using SNP. Security protocols have very conservative approach while guaranteeing the security and typically add up around 16-32 bytes as overhead. Owing to the scenario that sensor networks have limited supply of energy, little memory and low power processors, a 30 byte packet is more of unaffordable luxury for the wireless sensor networks. In SNP, the different trade-offs between separate cryptographic algorithms and wireless sensor network limitations are used to find an optimum point where packet overhead, security and resource requirements are met.

scholarly journals The evolution of competitive ability for essential resources

2020 ◽  
Vol 375 (1798) ◽  
pp. 20190247 ◽  
Author(s):  
Joey R. Bernhardt ◽  
Pavel Kratina ◽  
Aaron Louis Pereira ◽  
Manu Tamminen ◽  
Mridul K. Thomas ◽  
...  
Keyword(s):  
Competitive Ability ◽  
Community Dynamics ◽  
Species Coexistence ◽  
Resource Competition ◽  
Environmental Gradients ◽  
Light Limitation ◽  
Major Question ◽  
Trade Offs ◽  
Resource Requirements ◽  
Competitive Abilities

Competition for limiting resources is among the most fundamental ecological interactions and has long been considered a key driver of species coexistence and biodiversity. Species' minimum resource requirements, their R *s, are key traits that link individual physiological demands to the outcome of competition. However, a major question remains unanswered—to what extent are species’ competitive traits able to evolve in response to resource limitation? To address this knowledge gap, we performed an evolution experiment in which we exposed Chlamydomonas reinhardtii for approximately 285 generations to seven environments in chemostats that differed in resource supply ratios (including nitrogen, phosphorus and light limitation) and salt stress. We then grew the ancestors and descendants in a common garden and quantified their competitive abilities for essential resources. We investigated constraints on trait evolution by testing whether changes in resource requirements for different resources were correlated. Competitive abilities for phosphorus improved in all populations, while competitive abilities for nitrogen and light increased in some populations and decreased in others. In contrast to the common assumption that there are trade-offs between competitive abilities for different resources, we found that improvements in competitive ability for a resource came at no detectable cost. Instead, improvements in competitive ability for multiple resources were either positively correlated or not significantly correlated. Using resource competition theory, we then demonstrated that rapid adaptation in competitive traits altered the predicted outcomes of competition. These results highlight the need to incorporate contemporary evolutionary change into predictions of competitive community dynamics over environmental gradients. This article is part of the theme issue ‘Conceptual challenges in microbial community ecology’.

DECISION SUPPORT TOOL TO EVALUATE OPTIONS FOR IMPLEMENTING A SHORT-DURATION VEHICLE CLASSIFICATION COUNT PROGRAM

2020 ◽  
Author(s):  
Puteri Paramita ◽  
Markus Fast ◽  
Giuseppe Grande ◽  
Jonathan D Regehr
Keyword(s):  
Decision Support ◽  
Short Duration ◽  
Decision Support Tool ◽  
Vehicle Classification ◽  
Design Parameters ◽  
Truck Traffic ◽  
Support Tool ◽  
Trade Offs ◽  
Resource Requirements ◽  
Program Options

A short‐duration vehicle classification count program provides essential data for developing a system‐wide understanding of truck traffic volume. In responding to increasingly urgent truck traffic data needs, transportation agencies face the challenge of implementing improvements with constrained resources. Within this context, this paper develops and applies a decision support tool that reveals trade-offs amongst program design parameters. The Tool enables decision‐makers to simultaneously consider two broad and inter‐related program objectives, namely, to achieve a target level of classification count coverage and to minimize changes in resource requirements. The Tool incorporates five decision input parameters (coverage, technology type, count duration, frequency, and counting cycle) and produces information concerning count accuracy, the number of equipment units required to implement the program, the classification counting season duration, costs, and considerations such as count redundancy and data timeliness. The paper presents Manitoba’s short-duration count program as a case study and evaluates three program options.

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