ScholarBank@NUShttps://scholarbank.nus.edu.sgThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Wed, 30 Nov 2022 18:37:39 GMT2022-11-30T18:37:39Z5081- Plasticity in individual choice in social network evolutionhttps://scholarbank.nus.edu.sg/handle/10635/104608Title: Plasticity in individual choice in social network evolution
Authors: Kah, L.N.
Abstract: Constant re-evaluation of social affiliation is known to cause populations of individuals with different predetermined affiliation preferences to diverge into different network structures. In this study, rather than assigning to each individual a fixed affiliation preference, held throughout the duration of the dynamic network evolution, individuals were allowed an initial "learning period" during which they compared their own relative success, using each of three strategies, at maximizing their social status under three different metrics. Based on the outcomes from this learning period, individuals then chose one particular strategy. The organizational success and stability of the resulting populations was seen to be higher than those of the populations of individuals whose behaviors were predetermined. This indicates that individual-level evaluation and strategy choice in social affiliation preferences can yield strong benefits to the organizational success of the population as a whole. © Finnish Zoological and Botanical Publishing Board 2008.
Tue, 01 Jan 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1046082008-01-01T00:00:00Z
- The role of individual choice in the evolution of social complexityhttps://scholarbank.nus.edu.sg/handle/10635/104344Title: The role of individual choice in the evolution of social complexity
Authors: Fefferman, N.H.; Kah, L.N.
Abstract: Constant re-evaluation of social affiliations and shifting social network structures can profoundly affect the adaptive fitness of individuals within a population, as well as yielding super-additive effects felt by the population as a whole. To evaluate the impact of different social affiliation choices, and the relative ability of individuals to correctly assess the success of other individuals, we have created a set of mathematical models based on network centrality measures. We choose the hypothetical measures of " popularity", "closeness" and "betweenness" to examine the resulting self-organizations of social groups. Our findings suggest that some different types of social behaviors can lead to the same levels of stability and organizational success, suggesting the possibility that complex organizations could have evolved from simpler ones without any change in the selective pressures acting on the population. © Finnish Zoological and Botanical Publishing Board 2007.
Mon, 01 Jan 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1043442007-01-01T00:00:00Z
- A generalization of the firefighter problem on z × zhttps://scholarbank.nus.edu.sg/handle/10635/102655Title: A generalization of the firefighter problem on z × z
Authors: Ng, K.L.; Raff, P.
Abstract: We consider a generalization of the firefighter problem where the number of firefighters available per time step t is not a constant. We show that if the number of firefighters available is periodic in t and the average number per time period exceeds frac(3, 2), then a fire starting at any finite number of vertices in the two dimensional infinite grid graph can always be contained. © 2007 Elsevier B.V. All rights reserved.
Sat, 01 Mar 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1026552008-03-01T00:00:00Z
- The orientation number of two complete graphs with linkageshttps://scholarbank.nus.edu.sg/handle/10635/104329Title: The orientation number of two complete graphs with linkages
Authors: Koh, K.M.; Ng, K.L.
Abstract: For a connected graph G containing no bridges, let D(G) be the family of strong orientations of G; and for any D∈D(G), we denote by d(D) the diameter of D. The orientation number d→(G) of G is defined by d→(G)=min{d(D)|D∈D(G)}. In this paper, we study the orientation numbers of a family of graphs, denoted by G(p,q;m), that are obtained from the disjoint union of two complete graphs Kp and Kq by adding m edges linking them in an arbitrary manner. Define d→(m)=min{d→(G):G∈G(p,q;m)}. We prove that d→(2)=4 and min{m:d→(m)=3}=4. Let α=min{m:d→(m)= 2}. We evaluate the exact value of α when p≤q≤p+3 and show that 2p+2≤α≤2p+4 for q≥p+4. © 2005 Elsevier B.V. All rights reserved.
Sat, 28 May 2005 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1043292005-05-28T00:00:00Z
- How disease models in static networks can fail to approximate disease in dynamic networkshttps://scholarbank.nus.edu.sg/handle/10635/103388Title: How disease models in static networks can fail to approximate disease in dynamic networks
Authors: Fefferman, N.H.; Ng, K.L.
Abstract: In the modeling of infectious disease spread within explicit social contact networks, previous studies have predominantly assumed that the effects of shifting social associations within groups are small. These models have utilized static approximations of contact networks. We examine this assumption by modeling disease spread within dynamic networks where associations shift according to individual preference based on three different measures of network centrality. The results of our investigations clearly show that this assumption may not hold in many cases. We demonstrate that these differences in association dynamics do yield significantly different disease outcomes both from each other and also from models using graph-theoretically accurate static network approximations. Further work is therefore needed to explore under which circumstances static models accurately reflect constantly shifting natural populations. © 2007 The American Physical Society.
Wed, 19 Sep 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1033882007-09-19T00:00:00Z
- On a conjecture concerning the orientation number of a graphhttps://scholarbank.nus.edu.sg/handle/10635/103670Title: On a conjecture concerning the orientation number of a graph
Authors: Ng, K.L.
Abstract: For a connected graph G containing no bridges, let D (G) be the family of strong orientations of G; and for any D ∈ D (G), we denote by d (D) the diameter of D. The orientation number over(d, {combining right arrow above}) (G) of G is defined by over(d, {combining right arrow above}) (G) = min {d (D) | D ∈ D (G)}. Let G (p, q ; m) denote the family of simple graphs obtained from the disjoint union of two complete graphs Kp and Kq by adding m edges linking them in an arbitrary manner. The study of the orientation numbers of graphs in G (p, q ; m) was introduced by Koh and Ng [K.M. Koh, K.L. Ng, The orientation number of two complete graphs with linkages, Discrete Math. 295 (2005) 91-106]. Define over(d, {combining right arrow above}) (m) = min {over(d, {combining right arrow above}) (G) : G ∈ G (p, q ; m)} and α = min {m : over(d, {combining right arrow above}) (m) = 2}. In this paper we prove a conjecture on α proposed by K.M. Koh and K.L. Ng in the above mentioned paper, for q ≥ p + 4. © 2008 Elsevier B.V. All rights reserved.
Mon, 06 Apr 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1036702009-04-06T00:00:00Z
- On optimal orientation of cycle vertex multiplicationshttps://scholarbank.nus.edu.sg/handle/10635/103731Title: On optimal orientation of cycle vertex multiplications
Authors: Ng, K.L.; Koh, K.M.
Abstract: For a bridgeless connected graph G, let D(G) be the family of its strong orientations; and for any D∈D(G), we denote by d(D) its diameter. The orientation number d→(G) of G is defined by d→(G)=min{d(D)|D∈D(G)}. For a connected graph G of order n and for any sequence of n positive integers (si), let G(s1,s2,...,sn) denote the graph with vertex set V* and edge set E* such that V*=∪i=1nVi, where Vi's are pairwise disjoint sets with |Vi|=si, i=1,2,...,n, and for any two distinct vertices x, y in V*, xy∈E* if and only if x∈Vi and y∈Vj for some i,j∈{1,2,...,n} with i≠j such that vivj∈E(G). We call the graph G(s1,s2,...,sn) a G vertex multiplication. In this paper, we determine the orientation numbers of various cycle vertex multiplications. © 2005 Elsevier B.V. All rights reserved.
Thu, 28 Jul 2005 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1037312005-07-28T00:00:00Z
- Systems approach to studying animal sociality: Individual position versus group organization in dynamic social network modelshttps://scholarbank.nus.edu.sg/handle/10635/104242Title: Systems approach to studying animal sociality: Individual position versus group organization in dynamic social network models
Authors: Hock, K.; Ng, K.L.; Fefferman, N.H.
Abstract: Social networks can be used to represent group structure as a network of interacting components, and also to quantify both the position of each individual and the global properties of a group. In a series of simulation experiments based on dynamic social networks, we test the prediction that social behaviors that help individuals reach prominence within their social group may conflict with their potential to benefit from their social environment. In addition to cases where individuals were able to benefit from improving both their personal relative importance and group organization, using only simple rules of social affiliation we were able to obtain results in which individuals would face a trade-off between these factors. While selection would favor (or work against) social behaviors that concordantly increase (or decrease, respectively) fitness at both individual and group level, when these factors conflict with each other the eventual selective pressure would depend on the relative returns individuals get from their social environment and their position within it. The presented results highlight the importance of a systems approach to studying animal sociality, in which the effects of social behaviors should be viewed not only through the benefits that those provide to individuals, but also in terms of how they affect broader social environment and how in turn this is reflected back on an individual's fitness. © 2010 Hock et al.
Fri, 01 Jan 2010 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1042422010-01-01T00:00:00Z