출처 : itcnaus.net

1. 자연과학자가 바라본 ‘Social Network’
KAIST 바이오및뇌공학과
정재승

2. Paul Erdos: Erdos Numbers

3. 케빈 베이컨의 여섯 단계 게임
(Six degrees of Kevin Bacon)

5. Kevin Bacon Game

6. Small world network
Bullmore and Sporns, 2009

7. Scale-free network

9. Zipf’s Law
George Zipf's 1949 observation that the frequency of words used in the
English language followed a powerlaw distribution is a profound thing. It
not only defined ‘Zipf's Law’, which gives a simple rule to explain why
some words (e.g. the, of, and) are far more commonly used than others.

10. The scale-free nature of the web of sexual contacts.
• They analyze data gathered in a 1996
Swedish survey of sexual behavior. The
survey--involving a random sample of
4781 Swedish individuals (ages 18-74 yr)--
used structured personal interviews and
questionnaires to collect information.
• The response rate was 59 percent,
corresponding to 2810 respondents.
Connections in the network of sexual
contacts appear and disappear as sexual
relations are initiated and terminated.
• To analyze the connectivity of this dynamic
network, whose links may be quite short
lived, we first analyze the number k of sex
partners over a relatively short time
window--the twelve months prior to the
survey.

11. Preferential Attachment

12. 1. Introduction : Self-Organization
- A process of attraction and repulsion in which the internal organization of a system,
normally an open system, increases in complexity without being guided or managed
by an outside source (From Wikipedia)
- Typically displays Emergent Properties
Self-Organized Criticality:
The origin of 1/f in the Brain

13. Complex Systems
• Nonlinear basic unit/individual
• Nonlinear interactions among units
• Complex and ordered structures
• Intrinsic stochastic noises
• Dynamical transition of the states
• Rich phenomena:
chaos, fractal, small-world effect, scale-free behavior,
intermittency, bursting, and synchronization.
• Dynamical adaptation!
• Wake from your reverie “homeostasis and stability.”
• Focus on the complexity of the system!
• Only a short-term prediction is possible.
• Interdisciplinary research will be more preferable and useful.

14. Complex dynamics of heart rate variability

15. Breakdown of a fractal physiological control mechanism can lead
ultimately either to a highly periodic output dominated by a single scale or
to uncorrelated randomness.

16. African Fractal

18. Hub and connectors vs. Weak ties

19. Collective Intelligence
• 여러 사람들이 함께 문제를 해결하고, 서로 의견을 공유하며, 각자 자신
이 가진 것을 기여하고 참여하며, 서로 보완하는 정신 (참여, 공유, 개방).

20. Suggestions
• Social network 은 complex systems 의 전형적인 예 중 하나
다. Complex network 의 창발성을 활용하자!
• 공공캠페인을 위해 Worldwide Web, Blogosphere 등을 적극
적으로 활용하자!
• Diffusion of Buzz: 매력적인 바이러스를 만들자!
• ‘Information Cascade’를 이끌어내자!
• 허브와 커넥터를 공략하자!
• ‘약한 유대의 힘’을 활용하자!
• 자발적인 참여, 공유, 개방을 활용하자!