Competition Coefficients Research Articles

The analysis and application of competition and cooperation between the bus lines

It is very valuable for planning bus routes and improving transport efficiency to quantify the cooperation and competition between lines. Cooperation modes and competition modes between two lines are defined respectively based on the location of bus stops. Cooperative coefficient and competitive coefficient are proposed to calculate different modes quantitatively in term of the number of overlapped stops and overlapped service area. These coefficients can be used to convert multi-relation transit network into weighted single network to analyze the close degree between lines. Taking Qiqihar City transit network as an example, cooperative coefficient and competitive coefficient between two lines are calculated. The bus network is converted into weighted single network, and the single network is then clustered with social network analysis method. The cluster result indicates that the network can be divided into three groups whose bus lines have different cooperation and competition strength, so distinguish management modes for different group are quite necessary.

Global Dynamics of the Lotka‐Volterra Competition‐Diffusion System: Diffusion and Spatial Heterogeneity I

AbstractIn the first part of this series of three papers, we investigate the combined effects of diffusion, spatial variation, and competition ability on the global dynamics of a classical Lotka‐Volterra competition‐diffusion system. We establish the main results that determine the global asymptotic stability of semitrivial as well as coexistence steady states. Hence a complete understanding of the change in dynamics is obtained immediately. Our results indicate/confirm that, when spatial heterogeneity is included in the model, “diffusion‐driven exclusion” could take place when the diffusion rates and competition coefficients of both species are chosen appropriately.© 2016 Wiley Periodicals, Inc.

Habitat-mediated carry-over effects lead to context-dependent outcomes of species interactions.

When individuals disperse, their performance in newly colonized habitats can be influenced by the conditions they experienced in the past, leading to environmental carry-over effects. While carry-over effects are ubiquitous in animal and plant systems, their impact on species interactions and coexistence are largely ignored in traditional coexistence theory. Here we used a combination of modelling and experiments with two competing species to examine when and how such environmental carry-over effects influence community dynamics and competitive exclusions. We found that variation in the natal habitat quality of colonizing individuals created carry-over effects which altered competitive coefficients, fecundity and mortality rates, and extinction probabilities of both species. As a consequence, the dynamics of competitive exclusion within and across habitat types was contingent on the natal habitat of colonizing individuals, indicating that spatial carry-over effects can fundamentally alter the dynamics and outcome of interspecific competition. Interestingly, carry-over effects persistently influenced dynamics in systems with interspecific competition for the entire duration of the experiment while carry-over effects were transient and only influenced initial dynamics in single-species populations. Thus carry-over effects can be enhanced by species interactions, suggesting that their long-term effects may often not be accurately predicted by single-species studies. Given that carry-over effects are ubiquitous in heterogeneous landscapes, our results provide a novel mechanism that could help explain variation in the structure of natural communities.

Separation of magnesium and lithium from brine using a Desal nanofiltration membrane

Owing to the high ratio of Mg2+ to Li+ in most of the salt lake brines in China, it is difficult to extract lithium. Therefore, the separation efficiency of a nanofiltration membrane was investigated in this study. Operating conditions such as operating pressure, inflow water temperature, pH, and Mg2+/Li+ ratio were investigated. Relationship between the rejection rates of magnesium and lithium was established. Moreover, the extractions of lithium from salt lake brines were also evaluated. The results indicate that the separation of magnesium and lithium was highly dependent on the Mg2+/Li+ ratio, operating pressure, and pH. When the Mg2+/Li+ ratio was <20, the competitive coefficient was sensitive to the Mg2+/Li+ ratio. The permeate flux of membrane for the East Taijiner brine was higher than that for the West Taijiner brine.

Effect of emergent carrying capacity in an eco‐epidemiological system

The paper explores an eco‐epidemiological model of a predator–prey type, where the prey population is subject to infection. The model is basically a combination of S‐I type model and a Rosenzweig–MacArthur predator–prey model. The novelty of this contribution is to consider different competition coefficients within the prey population, which leads to the emergent carrying capacity. We explicitly separate the competition between non‐infected and infected individuals. This emergent carrying capacity is markedly different to the explicit carrying capacities that have been considered in many eco‐epidemiological models. We observed that different intra‐class and inter‐class competition can facilitate the coexistence of susceptible prey‐infected prey–predator, which is impossible for the case of the explicit carrying capacity model. We also show that these findings are closely associated with bi‐stability. The present system undergoes bi‐stability in two different scenarios: (a) bi‐stability between the planner equilibria where susceptible prey co‐exists with predator or infected prey and (b) bi‐stability between co‐existence equilibrium and the planner equilibrium where susceptible prey coexists with infected prey; have been discussed. The conditions for which the system is to be permanent and the global stability of the system around disease‐free equilibrium are worked out. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Simultaneous sorption of 4-nitrophenol and 2-nitrophenol on a hybrid geocomposite based on surfactant-modified pillared-clay and activated carbon

New generations of hydrophobic composite geomaterials intended to sorb certain hazardous wastes are assembled by mixing surfactant-modified aluminum-pillared montmorillonite (Al-SMPM) with activated carbon (AC). The sorption of 4-nitrophenol (4NP) and 2-nitrophenol (2NP) on these sorbents was studied in both single and binary component systems from aqueous solutions using batch tests. Results showed the efficiency of these composite sorbents relative to the two phenolic compounds, with a dominant contribution from Al-SMPM. In single-component systems, sorption isotherms of 4NP and 2NP as a function of pH were analyzed with the Freundlich equation, whose statistical interpretation was also developed. Sorption capacities sharply decreased when the solution pH value was raised from 3 to 9. In binary-component systems, the fit between measured and predicted simultaneous sorption capacities of both 4NP and 2NP indicated that the Sheindorf–Rebhun–Sheintuch model, an extended Freundlich model, is fully applicable. The 2NP favorably influences the sorption of 4NP. The synergistic effect between these two nitrophenol compounds has been confirmed by the higher competition coefficients, which increase with increasing pH. A number of hypotheses, based on the Abraham’s solvation parameters model, have been advanced to discuss this mechanism.

How to reduce local government decision-making competition in China’s new urbanization process

Purpose – The purpose of this paper is to analyze the impact of local government decision-making competition new urbanization, further to seek measures to weaken the negative effect of local government decision-making competition. Design/methodology/approach – This paper first puts forward the three paths which make local government decision-making competition: construction of new-style urbanization, economic development and construction of people’s livelihood and take China’s new-style urbanization as an example, the authors analyzed the internal mechanism of decision making of local government competition which caused by above three paths. Second, using the prospect theory, risk aversion theory and Cournot duopoly model, the authors analyzed how to avoid the local government decision-making competition and how to reduce the harm caused by local government decision-making competition. Findings – The central government can curb the appearance of local government competition strategy through regulating and controlling the effectiveness of local government protective-investment policy, improving the degree of market competition and punishment coefficient of government decision-making failure and further, the authors can reduce the detriment of decision-making competition between local governments through adjusting the revenue function of local government in the process of new-style urbanization. Originality/value – New-style urbanization is the main driving force of China’s future economic development, however, in the process of new-style urbanization, because of the “principle-agent” relationship between central government and local government, officials achievements appraisal mechanism and promotion game, they all cause competition between local government decision making, and this will weaken the positive effect of urbanization. Although, there are many researches on horizontal and intergovernmental competition, most researches devoted to how to avoid it from the angle of institutional economics, and the suggestions put forward by these researches are hardly applied. Anyone interested in how to avoid local government decision-making competition and reduce the negative influences of it from the angle of unitary government state’s reality will find this paper valuable.

Behave Well: How to Win a Pop Vacant Band via Cooperative Spectrum Sensing

Cooperative spectrum sensing (CSS) for vacant licensed bands is one of the key techniques in cognitive radio networks. However, current CSS schemes focus on ensuring an efficient cooperation among secondary users (SUs), but ignoring their competition. At the same time when several SUs want to a vacant band, how to win this pop vacant band for an SU becomes more and more important. Inspired by the idea that an SU who always behaves well will win a pop vacant band more easily, we propose a competition scheme called BehaveWell (BW) in this paper. By analyzing the main threats against CSS, competitive coefficient is introduced to evaluate each SU’s past behaviors in CSS. A higher competitive coefficient is very helpful for an SU to win a pop vacant band. This BW scheme can not only enhance a healthy competition among SUs, but also improve the security of CSS. Simulations verify the effectiveness of the proposed scheme.

Competitive exclusion and coexistence in an n-species Ricker model

We analyse a discrete-time Ricker competition model with n competing species and give sufficient conditions, which depend on the competition coefficients only, for one species to survive (not necessarily at an equilibrium) and to drive all the other species to extinction. Our results complement and extend similar existing results from the literature. For the model reduced to three species (), we also investigate various scenarios under which all species coexist, in the sense that each species is robustly uniformly persistent. We provide a few numerical simulations to illustrate that coexistence does not necessarily mean convergence to the interior equilibrium, and that the interior dynamics can be quite complex.

Investigation of North American vegetation variability under recent climate: A study using the SSiB4/TRIFFID biophysical/dynamic vegetation model

AbstractRecent studies have shown that current dynamic vegetation models have serious weaknesses in reproducing the observed vegetation dynamics and contribute to bias in climate simulations. This study intends to identify the major factors that underlie the connections between vegetation dynamics and climate variability and investigates vegetation spatial distribution and temporal variability at seasonal to decadal scales over North America (NA) to assess a 2‐D biophysical model/dynamic vegetation model's (Simplified Simple Biosphere Model version 4, coupled with the Top‐down Representation of Interactive Foliage and Flora Including Dynamics Model (SSiB4/TRIFFID)) ability to simulate these characteristics for the past 60 years (1948 through 2008). Satellite data are employed as constraints for the study and to compare the relationships between vegetation and climate from the observational and the simulation data sets. Trends in NA vegetation over this period are examined. The optimum temperature for photosynthesis, leaf drop threshold temperatures, and competition coefficients in the Lotka‐Volterra equation, which describes the population dynamics of species competing for some common resource, have been identified as having major impacts on vegetation spatial distribution and obtaining proper initial vegetation conditions in SSiB4/TRIFFID. The finding that vegetation competition coefficients significantly affect vegetation distribution suggests the importance of including biotic effects in dynamical vegetation modeling. The improved SSiB4/TRIFFID can reproduce the main features of the NA distributions of dominant vegetation types, the vegetation fraction, and leaf area index (LAI), including its seasonal, interannual, and decadal variabilities. The simulated NA LAI also shows a general increasing trend after the 1970s in responding to warming. Both simulation and satellite observations reveal that LAI increased substantially in the southeastern U.S. starting from the 1980s. The effects of the severe drought during 1987–1992 and the last decade in the southwestern U.S. on vegetation are also evident from decreases in the simulated and satellite‐derived LAIs. Both simulated and satellite‐derived LAIs have the strongest correlations with air temperature at northern middle to high latitudes in spring reflecting the effect of these climatic variables on photosynthesis and phenological processes. Meanwhile, in southwestern dry lands, negative correlations appear due to the heat and moisture stress there during the summer. Furthermore, there are also positive correlations between soil wetness and LAI, which increases from spring to summer. The present study shows both the current improvements and remaining weaknesses in dynamical vegetation models. It also highlights large continental‐scale variations that have occurred in NA vegetation over the past six decades and their potential relations to climate. With more observational data availability, more studies with different models and focusing on different regions will be possible and are necessary to achieve comprehensive understanding of the vegetation dynamics and climate interactions.

Dynamical properties of a biological population with a protected area under ecological uncertainty

In this study, stochastic differential equations with Markovian switching are used to describe the growth of some biological populations with protected areas in a random environment, where both white noise and telegraph noise are included in the ecosystem. In addition, the intrinsic growth rate and intra-specific competition coefficient are both considered to be disturbed by ecological uncertainty. We analyze the asymptotical properties of this system, such as weak persistence and extinction. Moreover, we demonstrate the biological significance and provide some real-life examples to support our main conclusions. Our results show that the establishment of a protection zone has important roles in the biological conservation process, but it is not crucial due to the presence of environmental uncertainty. We describe several theoretically strategies, which are expected to enhance the efficiency of protected areas.

Community diversity and total abundance: Quantitative predictions from competition niche theory

Lotka–Volterra niche competition theory (LVNCT) is based on Lotka–Volterra competition equations with competition coefficients between pairs of species determined by the intensity of their niche overlap though the MacArthur–Levins niche overlap formula. Here I study analytically and numerically the predictions of LVNCT concerning total abundance and biodiversity, measured by the Shannon equitability index. Firstly, a set of simplifying assumptions that render the LVNCT amenable of analytical treatment are considered. In particular I derive an approximated formula for the total abundance, as the inverse of the mean value of the interspecific competition coefficients, which works pretty well both for the transient and steady regime and for a wide range of the typical niche width σ. Secondly, I analyze, by means of simulations, the effect of relaxing the above simplifying assumptions when considering more realistic conditions. It turns out that the approximated formula for the total abundance is quite robust and its potential implications for management are discussed. I also analyze the predicted relationship between community productivity and diversity.

Global dynamics of a competition model with nonlocal dispersal II: The full system

In this paper, we study logistic models with non-local dispersal for two competing species. In the weak competition case, the global asymptotic behavior of solutions is completely classified provided one of the following conditions is valid:•one diffusion rate is small;•one diffusion rate is large;•two diffusion rates are close. This is a continuation of the work [16]. Our results illustrate the effects of non-local dispersals and interspecific competition coefficients in the competition system with spatially heterogeneous environments.

Optimal advertising model in a dynamic marketing with competing brands

We consider a marketing channel consisting of one retailer and two independent and competing manufacturers. One distinctive feature of this paper is that each brand's goodwill evolves according to a modified Nerlove–Arrow dynamics, in such a way that the advertising effort of one brand hurts the competitor's goodwill stock. We obtain the feedback advertising equilibrium policies for the retailer and manufacturers in explicit form for a linear demand formulation and assess the impact of the margin profit and intensity of brand competition on these strategies in different settings. Then the results between the Stackelberg model and cooperative model are compared. Numerical examples show the paths for the evolution of the demand function and for the profits of channel members through the computation of the goodwill state variable trajectory and reveal that the brand competition coefficient has different effects on strategies.

On Lotka--Volterra Equations with Identical Minimal Intrinsic Growth Rate

We investigate the long-run behavior of time-dependent Lotka--Volterra equations $({\rm E}_{\phi}):\frac{dx_i}{dt}=x_i(1+\phi(t)+\sum_{j=1}^na_{ij}x_j)$, $i=1,\ldots,n$, on the positive orthant. It is proved that the system $({\rm E}_{\phi})$ is decomposed into $({\rm E}_0)$ and the logistic equation $({\rm L}):\frac{dg}{dt}=g(1+\phi(t)-g)$ in the sense that $({\rm D}):\Phi(t)=g(t)\Psi(\int_0^tg(s)ds)$, where $\Phi(\cdot)$, $\Psi(\cdot)$, and $g(\cdot)$ are the solutions of $({\rm E}_{\phi})$, $({\rm E}_0)$, and (L), respectively. Suppose that $\phi(t)$ is periodic with the mean value ${\cal M}\{\phi\}>-1$. Then the existence of stable equilibrium, periodic solution, and chaotic motion for $({\rm E}_0)$ implies the existence of stable periodic solution, quasiperiodic solution, and chaotic motion for $({\rm E}_{\phi})$, respectively. The complete dynamical classification for 3-dimensional competitive system $({\rm E}_0)$ is provided in terms of competitive coefficients. There are 37 topological classes, in 34 of which any trajectory converges to an equilibrium. Among the remaining three classes, the first has a heteroclinic cycle attracting all positive points except the ray joining the origin and the positive equilibrium; the second possesses a family of periodic orbits attracting all positive points; the third class, where a family of periodic orbits, an asymptotically stable equilibrium, a heteroclinic cycle, and an invariant noncoordinate plane coexist, is a new type we find for the first time. It is shown that for 3-dimensional periodic competitive system $({\rm E}_{\phi})$, any trajectory for Poincaré mapping tends to a fixed point, a periodic orbit, an invariant minimal closed curve, or a heteroclinic cycle. All their attracting domains, which are all cone-like, are exactly described via (D) and carrying simplex theory. The dynamics can be completely classified into 37 classes corresponding to the autonomous systems. All counterparts hold when $\phi(t)$ is another minimal function, such as a quasiperiodic, almost periodic, or almost automorphic function, via (D), the classification above, and skew-product flow theory.

Investigation of mono/competitive adsorption of environmentally relevant ionized weak acids on graphite: impact of molecular properties and thermodynamics.

The thermodynamics of adsorption and competitive interactions of five weak acids on a graphite surface was assessed in alkaline solutions. Adsorption of the acids in mono- and multicompound solutions followed their Freundlich isotherms which suggest a diversity of graphite adsorption sites as confirmed by the presence of carboxylic and phenolic groups observed on graphite surfaces. Thermodynamic calculations assigned the formation of the negatively charged assisted hydrogen bond (-CAHB) between ionized solutes and adsorbent surface groups as the possible adsorption mechanism. However, the similar pKa values of current acids resulted in comparable free energies for -CAHB formation (ΔG(-CAHB)) being less than solvation free energies (ΔGSolv). Thus, additional ΔG is supplemented by increased hydrophobicity due to proton exchange of ionized acids with water (ΔΔG Hydrophobicity). Adsorption capacities and competition coefficients indicated that ΔΔG Hydrophobicity values depend on the neutral and ionized acid Kow. Competitive adsorption implies that multilayer adsorption may occur via hydrophobic bonding with the CH3 ends of the self-assembled layer which affects the acid adsorption capacities in mixtures as compared to monocompound solutions. The determination of adsorption mechanisms will assist in understanding of the fate and bioavailability of emerging and classical weak acids released into natural waters.

Evaluation of hospital factors associated with hospital postoperative venous thromboembolism imaging utilisation practices

BackgroundRecent research suggests that hospital rates of postoperative venous thromboembolism (VTE) are subject to surveillance bias: the more hospitals ‘look for’ VTE, the more VTE they find. However, little is...

Is different degree of individual specialization in three spider species caused by distinct selection pressures?

Individual specialization (IS), i.e. the relatively narrower niche of individuals compared to their population, can be caused by the interplay between intrinsic and extrinsic factors. We studied IS on prey type and size in three congeneric euryphagous sympatrically occurring species: Philodromus albidus, Philodromus aureolus, and Philodromus cespitum. We performed prey acceptance experiments in standardized laboratory conditions using adult females. We also studied possible factors affecting IS. As intrinsic factors, we measured aggressiveness toward prey and spider size as the measures of behavioral and morphological differences, respectively. As extrinsic factors, we studied the composition of the guild of actively hunting spiders in the area from where the philodromids were collected. We computed the degree of inter- and intraspecific crowding as a measure of inter- and intraspecific competition, respectively. Then we computed competition coefficients from census data in order to estimate the strength of interspecific competition among three species. There was no IS on prey type in any studied species. In terms of prey size, only P. albidus was found to be individually specialized, while there was no IS in the other two species. There was a significant effect of aggressiveness, but no significant effect of body size on IS in P. albidus. This species was the least aggressive of the studied species. The philodromids were the dominant actively hunting spiders in the study area. P. albidus was exposed to a relatively higher degree of interspecific than intraspecific competition, whereas in the other philodromids the situation was reversed. The presence of interspecific competition between P. albidus and the other two species was confirmed by the census data analysis. We documented context-dependent IS in Philodromus species. We argue that the higher degree of IS in P. albidus was influenced by interference competition mainly from the other two philodromid species. The niches of the other two species were influenced by food limitation, which decreased their IS.

Bio-inspired self-adaptive rate control for multi-priority data transmission over WLANs

In Wireless Local Area Networks (WLANs), the unpredictable injection of traffic load and the limitations of DCF based bandwidth allocation may result in network congestion. Also the Quality of Service (QoS) of data flows with different priorities may not be strictly guaranteed. In order to support service differentiation and guarantee QoS of data transmission over WLANs, based on the extended Lotka–Volterra (LV) biological competitive model, a bio-inspired self-adaptive rate control approach for multi-priority data transmission is proposed in this paper. This approach guides data flows to compete for network bandwidth in the way of a native ecosystem. As a result, both service differentiation and QoS can be guaranteed, simultaneously. In particular, it also achieves higher bandwidth utilization. Then the proposed approach is applied to four categories of data flows defined in the EDCA protocol, the allocated bandwidth of each category is optimized through model parameters (i.e. competition coefficients among categories) optimization. Extensive simulation studies have been conducted to show the superior performance of the proposed approach. Under the recommended model parameter values, the total bandwidth utilization is maximized up to 93% compared with 60–70% achieved by the EDCA protocol, whilst maintaining the service differentiation of multi-priority flows.

Evaluating the Effects of competition among different densities of mallov (Malva parviflora) using replacement series method on the yield and yield components of canola (Brassica napus L.)

In order to evaluate the competitive capability of rapeseed and malva towards different densities, experimental planting under vase conditions using replacement series and in perfectly random blocks was carried out in Dezfool City in 2012. Experimental treatments included rapeseed and malva plantings with different ratios (0:100, 25:75, 50:50, 75:25, and 100:0) with the density of eight bushes in each vase. The results showed that the biomass of the farm plant of rapeseed decreased due to an increase in the density of malva weed in the mixed plantations. The highest decrease in the dry mass of one bush of rapeseed comparing to its pure plantation was in the 25 percent density with 68 percent decrease. Moreover the biomass of malva experienced a significant decrease due to raising the share of rapeseed in the combination. Also by increasing the density of malva bushes the seed yields, the number of pods in a bush, the number of seeds in pods and the weight of 1000 seeds were decreased. The relative yielding of rapeseed in density ratios of 50 and 75 percent show the higher competitive capability of this crop plant, while in the lower density of rapeseed (25 percent) the relative yielding of malva was better. Relative competition coefficients of these two species also confirm that in higher densities rapeseed possesses a higher competitive strength.