Switching Tendency Research Articles

A Novel Robust MM Filter against Outliers

AbstractAn Interacting Multiple Model (IMM) filter suppresses outliers by integrating model‐conditioned estimation and model mode recognition through adaptive mode switches based on a Bayesian probability update. However, it may face significant outlier‐caused peak errors, which are undesirable or even impermissible in many applications, for example, target tracking. This paper considers that, from the view of the Dempster‐Shafer Theory, the IMM filter actually fuses the Bayesian beliefs of the model mode with Dempster's Rule of Combination, which can deal with uncertainties instead of the evidence conflicts that may exist as outliers appear. Therefore, we propose the adaptive robust multiple model (RMM) filter through introducing practical expert knowledge in the belief function framework, which runs online to reduce outlier‐caused peak errors. In RMM, the Likelihood Temporal Ratio (LTR) is incorporated to provide extra information on the tendency of mode switching. Moreover, expert rules are introduced to construct adaptive belief functions using discount techniques and to select the combination rule that better deals with evidence conflicts when outliers appear. The simulations in target tracking scenarios show that the proposed RMM filter significantly reduces outlier‐caused peak errors and hence obtains a lower rate of track loss in the cluttered environment.

The Impact of Switching on the Dynamics of Prey-Predator Model for a Switching Tendency

The Impact of Switching on the Dynamics of Prey-Predator Model for a Switching Tendency

Asymmetric Multidimensional Scaling of Brand Switching Among Margarine Brands

Brand switching data among 12 margarine brands were analyzed by the asymmetric multidimensional scaling based on the singular value decomposition. A two-dimensional result was adopted as the solution. A configuration based on the left and right singular vectors is given along each dimension. The left singular vector represents an outward tendency of switching from the corresponding brand to the other brands, and the right singular vector represents an inward tendency of being switched to the corresponding brand from the other brands. The configuration along Dimension 1 shows that the three brands with the larger market share compete vigorously with each other. The configuration along Dimension 2 classifies 12 brands into two groups; the brand switching between two groups is small, while that within each group is large.

The Study of Customer Switching Behaviour Toward Carbonated Soft Drink Market

With the continuous growth of competition in the market place, understanding customers has become more and more important in marketing. Moreover, customers are more mobile and knowledgeable than ever before, searching for a best alternative in their purchasing process, and finally switch to best brand. This process can be known as customer switching behaviour. The switching behaviour in products and services are not the same for all categories.The main purpose of this study was to examine whether there is customer switching behaviour in the carbonated soft drink market; and if so, what are the factors that contributed for customers’ switching behaviour. This research was limited to Manmunai -North Divisional secretariat area in Batticaloa district. Customer switching behaviour is operataionalized in terms of four variables; Marketers’ Product Mix, Pricing Strategies, Distributional Strategies, and Promotional Strategies. A quantitative method was applied where for data collection structure questionnaires were used. 200 questionnaires were issued and collected data were analyzed using SPSS v.11.0 and evaluated as low, moderate, and high level influence of research variables on switching behaviour in carbonated soft drink repurchase. Family unit was considered as a unit of analysis. Descriptive analysis was used for data analysis. This study found that most of the customers are switching their brands (85%). Research found that Marketers’ promotional, distributional and product mix are heavily motivating customers’ switching tendency while pricing strategies has moderate influence on customers’ switching tendency. However, most of the respondents agree that marketers’ promotional strategies are attracting them to switch toward their brand. According to the analyzed data, the Coca-Cola Company holds 43.7%, PepsiCo holds 25.1%, and Ceylon Cold Stores Limited holds 21% of Market share.It is advisable for carbonated soft-drink marketers to concentrate more on their pricing and product strategies while maintaining present placing and promotional strategies. Finally recommendations have been given as to how carbonated soft-drink marketers can enhance their markshare further by protecting their customers from competitors’ moves.

Chronic imipramine but not bupropion increases arachidonic acid signaling in rat brain: is this related to ‘switching’ in bipolar disorder?

Agents effective against mania in bipolar disorder are reported to decrease turnover of arachidonic acid (AA) in phospholipids and expression of calcium-dependent AA-selective cytosolic phospholipase A(2) (cPLA(2)) in rat brain. In contrast, fluoxetine, an antidepressant that is reported to switch bipolar depressed patients to mania, increases cPLA(2) expression and AA turnover in rat brain. We therefore hypothesized that antidepressants that increase switching to mania generally increase cPLA(2) and AA turnover in brain. To test this hypothesis, adult male CDF-344 rats were administered imipramine and bupropion, with reported high and low switching rates, respectively, at daily doses of 10 and 30 mg kg(-1) i.p., respectively, or i.p. saline (control) for 21 days. Frontal cortex expression of different PLA(2) enzymes and AA turnover rates in brain when the rats were unanesthetized were measured. Compared with chronic saline, chronic imipramine but not bupropion significantly increased cortex cPLA(2) mRNA activity, protein and phosphorylation, expression of the cPLA(2) transcription factor, activator protein-2alpha (AP-2alpha) and AA turnover in phospholipids. Protein levels of secretory phospholipase A(2), calcium-independent phospholipase A(2), cyclooxygenase (COX)-1 and COX-2 were unchanged, and prostaglandin E(2) was unaffected. These results, taken with prior data on chronic fluoxetine in rats, suggest that antidepressants that increase the switching tendency of bipolar depressed patients to mania do so by increasing AA recycling and metabolism in brain. Mania in bipolar disorder thus may involve upregulated brain AA metabolism.

Reputation-based partner choice promotes cooperation in social networks

We investigate the cooperation dynamics attributed to the interplay between the evolution of individual strategies and evolution of individual partnerships. We focus on the effect of reputation on an individual's partner-switching process. We assume that individuals can either change their strategies by imitating their partners or adjust their partnerships based on local information about reputations. We manipulate the partner switching in two ways; that is, individuals can switch from the lowest reputation partners, either to their partners' partners who have the highest reputation (i.e., ordering in partnership) or to others randomly chosen from the entire population (i.e., randomness in partnership). We show that when individuals are able to alter their behavioral strategies and their social interaction partnerships on the basis of reputation, cooperation can prevail. We find that the larger temptation to defect and the denser the partner network, the more frequently individuals need to shift their partnerships in order for cooperation to thrive. Furthermore, an increasing tendency of switching to partners' partners is more likely to lead to a higher level of cooperation. We show that when reputation is absent in such partner-switching processes, cooperation is much less favored than that of the reputation involved. Moreover, we investigate the effect of discounting an individual's reputation on the evolution of cooperation. Our results highlight the importance of the consideration of reputation (indirect reciprocity) on the promotion of cooperation when individuals can adjust their partnerships.

Bifurcation analysis of an ecological food-chain model with switching predator

The present paper deals with the mathematical analysis of a prey–predator model where the prey population is assumed to live in two distinct habitats and the predator consumes prey from both these habitats with a switching tendency . The dynamical behavior of the system is investigated from the point of view of stability and bifurcation aspects. It has been found that the mortality rate of the predator plays an important role in controlling the system dynamics. Finally, a detailed study of the Hopf-bifurcating solutions is carried out and the criteria for subcritical and supercritical Hopf-bifurcation derived. Numerical simulations are performed in support of analytical results.

Spatial dynamics of nonlinear prey–predator models with prey migration and predator switching

The present paper deals with two prey–predator models, one with prey group defence and the other without it. The prey species is assumed to live in two distinct habitats and the predator species has the tendency of switching between the habitats. The models are analyzed regarding stability and bifurcation aspects for the cases where the switching index has the values n = 1 and 2. To model prey dispersal between the habitats, a spatial extension of both the models are considered using physical diffusion of the concerned species. Criteria for diffusion-driven instability are derived and interpreted ecologically. A comparative study of the spatial models are carried out. Numerical simulations are carried out to support analytical findings.

Estimation of Agent-Based Models: The Case of an Asymmetric Herding Model

The behavioral origins of the stylized facts of financial returns have been addressed in a growing body of agent-based models of financial markets. While the traditional efficient market viewpoint explains all statistical properties of returns by similar features of the news arrival process, the more recent behavioral finance models explain them as imprints of universal patterns of interaction in these markets. In this paper we contribute to this literature by introducing a very simple agent-based model in which the ubiquitous stylized facts (fat tails, volatility clustering) are emergent properties of the interaction among traders. The simplicity of the model allows us to estimate the underlying parameters, since it is possible to derive a closed form solution for the distribution of returns. We show that the tail shape characterizing the fatness of the unconditional distribution of returns can be directly derived from some structural variables that govern the traders’ interactions, namely the herding propensity and the autonomous switching tendency.

Prey switching in four species of carnivorous stoneflies

Summary1. Previous studies compared the functional responses to their prey, and both intraspecific and interspecific interference, in mature larvae of Dinocras cephalotes, Perla bipunctata, Isoperla grammatica and Perlodes microcephalus. The present study examines switching by larvae of the same species presented with different proportions of two contrasting prey types; larvae of Baetis rhodani and Chironomus sp. In each experiment, 200 prey were arranged in nine different combinations of the two prey types (20 : 180, 40 : 160, 60 : 140, 80 : 120, 100 : 100, 120 : 80, 140 : 60, 160 : 40, 180 : 20). Prey were replaced as they were eaten. A model predicted the functional response in the absence of switching and provided a null hypothesis against which any tendency for switching could be tested.2. No evidence for prey switching by Dinocras and Perla was obtained, both species showing a slight preference for Baetis over Chironomus. Prey switching occurred in Isoperla and Perlodes. As the relative abundance of one prey type increased in relation to the alternative, the proportion eaten of the former prey changed from less to more than expected from its availability, the relationship being described by an S‐shaped curve. Isoperla and Perlodes switched to a preference for Baetis when its percentage of the total available prey exceeded 57 and 42%, respectively. Equivalent values for Chironomus were 43 and 58% for Isoperla and Perlodes, respectively. Switching was strongest in Perlodes.3. Non‐switching in Dinocras and Perla was related to their feeding strategy, both species being more successful when using a non‐selective ambush strategy at dusk and dawn rather than a search strategy during the night. Both Isoperla and Perlodes used a search strategy. The smaller Isoperla fed chiefly at dusk and dawn, and preferred Chironomus larvae, whereas most of the larger Perlodes fed continuously from dusk to dawn and preferred Baetis larvae.

Channel evolution of the pre‐channelized Danube River in Bratislava, Slovakia (1712–1886)

AbstractChannel adjustments of the Danube River near Bratislava, Slovakia, are reconstructed from historical river maps for 1712–1886, the period preceding mid‐course channelization. The study reach comprised an anastomosing–meandering planform, characteristic of the upper area of a large alluvial fan. The key mechanisms of channel change were avulsions through channel switching into chute channels, meander development through progression and cutoffs, and abandonment of secondary channels. The gravel‐bed Danube River was characterized by rapid rates of lateral erosion (maxima from 7·5 to 37 m a−1), and extensive areas of point bars and gravel bars. Within three to seven years, new bars were stabilized by Salici–Populetum woodlands which subsequently developed into more stable vegetated islands. Human interventions were relatively common and frequent in the past, though increasing fluvial activity during the 18th century was responsible for their limited effectiveness. Uncontrollable lateral erosion at Petržalka village, terminated only by a switch in position of the Danube River upstream from Bratislava (1766–1774), appears to be closely related to increasing ice‐floods and other high magnitude flood events in the latter half of the 18th century. These events were coincident with the peak of the Little Ice Age. The effect of floods was probably amplified by human works which resulted in stabilization of secondary channels, simplification of the river pattern, and concentration and widening of the main channel. A further sign of channel readjustment to new conditions was the evolution of new large meanders, a tendency for channel switching and production of new anastomosing–meandering parallel channels. Copyright © 2002 John Wiley & Sons, Ltd.

Three-dimensional simulation of flows through a rectangular sudden expansion

Detailed three-dimensional numerical predictions of the effect of vortex generators on vorticity dynamics and the phenomenon of axis switching are presented for the laminar incompressible flows through a rectangular sudden expansion. As a special case, the axis switching mechanism for flows through a square sudden expansion has also been investigated. The physical domains consist of 2:1 and 1:1 aspect-ratio channels which undergo a sudden expansion such that the backward facing step height is uniform, and equal to 0.75 times the minor width (or width, for the 1:1 aspect-ratio channel) of the inlet channel. The rectangular-shaped protrusions into the flow (“rectangular tabs”) are used as vortex generators, placed on the plane of the expansion. Passive forcing was provided by the system geometry and particularly due to the presence of the tabs. Suitable placement of the tabs could either stop or augment the axis switching mechanism. The rectangular vortex rings formed in the shear layer of the expanding jet undergo nonuniform self-induction and a complex three-dimensional deformation of the jet takes place in its downstream location. Such a deformation of the jet leads to the generation of streamwise vortices. Two mechanisms, the ωθ-dynamics, originated from the difference in induced velocities for different segments of a rolled-up azimuthal vortical structure; and the ωz-dynamics, caused due to the induced velocities of streamwise vortex pairs in the flow, co-exist and are identified to be active in flows through a rectangular sudden expansion. The tendency of axis switching initiated by the ωθ-dynamics are either resisted or enhanced by the ωz-dynamics. While ωθ-dynamics is known to be responsible for axis switching in periodically forced asymmetric jets, the ωz-dynamics mostly govern the effect of tabs. The results of the present simulation reveal the flow features closely consistent with the axis switching mechanism suggested by the laboratory flow visualization.

Axis switching and spreading of an asymmetric jet: the role of coherent structure dynamics

The effects of vortex generators and periodic excitation on vorticity dynamics and the phenomenon of axis switching in a free asymmetric jet are studied experimentally. Most of the data reported are for a 3:1 rectangular jet at a Reynolds number of 450 000 and a Mach number of 0.31. The vortex generators are in the form of ‘delta tabs’, triangular-shaped protrusions into the flow, placed at the nozzle exit. With suitable placement of the tabs, axis switching could be either stopped or augmented. Two mechanisms are identified governing the phenomenon. One, as described by previous researchers, is due to the difference in induced velocities for different segments of a rolled-up azimuthal vortical structure. The other is due to the induced velocities of streamwise vortex pairs in the flow. While the former mechanism, referred to here as the ωθ-dynamics, is responsible for a rapid axis switching in periodically forced jets, e.g. screeching supersonic jets, the effect of the tabs is governed mainly by the latter mechanism, referred to as the ωx-dynamics. Both dynamics can be active in a natural asymmetric jet; the tendency for axis switching caused by the ωθ-dynamics may be, depending on the streamwise vorticity distribution, either resisted or enhanced by the ωx-dynamics. While this simple framework qualitatively explains the various observations made on axis switching, mechanisms actually in play may be much more complex. The two dynamics are not independent as the flow field is replete with both azimuthal and streamwise vortical structures which continually interact. Phase-averaged measurements for a periodically forced case, over a volume of the flow field, are carried out in an effort to gain insight into the dynamics of these vortical structures. The results are used to examine such processes as the reorientation of the azimuthal vortices, the resultant evolution of streamwise vortex pairs, as well as the redistribution of streamwise vortices originating from secondary flow within the nozzle.

Haloperidol- and apomorphine-induced changes in pup searching behaviour of house mice.

Maternal pup searching behaviour of lactating house mice treated with apomorphine, haloperidol or saline was examined on a running board with a central depression as a nest. Pup searching was elicited by artificial ultrasonic stimuli: a female moved out from the nest either towards a 50 kHz tone (key stimulus) which is adequate to activate species specific pup searching behaviour or towards a 20 kHz tone (neutral stimulus), thus showing her preference for one of these stimuli. Under apomorphine (0.00625; 0.0125; 0.025 mg/kg) the females preferred the key stimulus. Nevertheless apomorphine (0.00625-0.025 mg/kg) prolonged response latencies and shortened the duration of pup searching. At the highest dose (0.05 mg/kg), apomorphine induced stereotyped sniffing. Haloperidol (0.025; 0.05; 0.1 mg/kg) had opposite effects to apomorphine: it lowered the threshold for elicitation, shortened response latencies and prolonged the duration of pup searching. Females treated with haloperidol (0.025-0.1 mg/kg) did not prefer the key stimulus. Changes in response elicitation and in the performance of pup searching induced by apomorphine and haloperidol, respectively, were assumed to be due to i) a reduced and an increased responsiveness to external stimuli respectively, ii) an enhanced and a reduced tendency for response switching respectively, and iii) a preference for spontaneous behaviour in apomorphine-treated females, with an increased dependence on exteroceptive stimuli following haloperidol.