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- Theoretical Foundation of the Method - An Application of Monte Carlo Method to Computer Simulation of Decision Making Processes in Society - Theoretical Foundation of the Method - Satoru Ozawa and Sarkar Barbaq Quarmal Graduate School of Science and Engineering Ibaraki University Hitachi 316-8511, Japan email@example.com
1) Unit 1: Explosion, roof blown off (12 March, 2011) 2) Unit 2: Explosion (15 March), Contaminated water in underground trench, possible leak from suppression chamber 3) Unit 3: Explosion, most of concrete building destroyed (14 March), Possible plutonium leak 4) Unit 4: Fire (15 March), Water level in spent fuel pools partly restored 5) Multiple trenches: probable source of contaminated water, partly underground, leaked stopped (6 April) Fukushima NPP Accident 11March2011
Before the accident (11March 2011) In Japan, 23% of electricity power supply depended on NPP. The government was trying to increase the ratio up to 30% because of Global Warming Problem. This was supported by most of Japanese. Just after the accident All of the NPP have been shut down. The previous government decided Zero-NPP within 30years. This was not supported in the general election (16 Dec 2012). Today Most of the NPP still being stopped. The new government has not yet decided future energy plan. Question is “Do we depend on NPP for electric power supply?”.
We are not interesting in the conclusion of the problem, but how they conclude is our study. “Computer Simulation of Decision Making Processes in Society” Elements of this work Artificial society modeling to simulate decision making dynamics in society Knowledge function to characterize people’s knowledge Simulation of thinking process based on linkage model in cognitive psychology Method to guess knowledge function Monte Carlo computer simulation
An artificial society modeling describes processes of knowledge-based decision making in society on a given problem. Note: Real society as a whole is too much complicated. We are going to model society regarding one given problem. The problem is expressed in a form of a question, for example, “Do you accept NPP to produce electricity?”
Artificial Society Agent Knowledge Character Agent Knowledge Character Agent Knowledge Character Agent Knowledge Character Agent Knowledge Character Channels Message “Do you accept NPP to produce electricity?”
Artificial Society Model ARTIFICIAL SOCIETY is made of a set of AGENTS. The AGENTS represent groups of similar character people in society regarding a given PROBLEM Each AGENT has a certain KNOWLEDGE regarding the PROBLEM. Each AGENT makes a DECISION of the PROBLEM based on the KNOWLEDGE. Each AGENT has an individual CHARACTER in DESION MAKING. There are CHANNELS between AGENTS. AGENTS produce MESSAGES and send them through the CHANNELS. AGENTS change their KNOWLEDGE as the results of MESSAGE exchanges.
Artificial Society Agent Knowledge Character Agent Knowledge Character Agent Knowledge Character Agent Knowledge Character Agent Knowledge Character Channels Message Looks like physical systems with interactions!
Definition of Knowledge Function Parameter, x is called “preferential parameter”
Knowledge Function is not observable just like wave function in quantum mechanics Quite natural to assume that such function exists and satisfactorily describes a state of brain regarding the given problem
Elemental processes of knowledge modification in artificial society model
Thinking Process (Decision Making) : Linkage Model of Cognitive Psychology Which knowledge come up : nondeterministic It depends also on state of mind (sad or happy) and personal character (optimistic or non-optimistic) : Emotional Factor Question: Do you accept NPP?
Basic Assumption: Principle of equal a-priori probability (Each element of knowledge has equal probability of coming up into mind) Which knowledge come up into mind is stochastic in nature (Neglect Emotional Factor: Rational Thinking)
Various types of thinking Thoughtful rational thinking : Number of elements of knowledge coming up into mind is large. Principle of equal a-priori probability is OK. Emotional thinking: Principle of equal a-priori probability does not work. (For example, negative idea more easily coming up in depressed state of mind). Weighing factor (Emotional factor) is needed. Panic thinking : Only few extreme knowledge coming up into mind. We restrict ourselves for the rational thinking
Let us describe it in terms of mathematics : Algorithm
Algorithm (Step 0) : Selection of Channel Each channel has a band width. One channel is randomly selected with taking into the channel width, i.e., the channel width parameter is the weighing parameter. This work is easily carried out by using random number generator. Thus, a channel from A i to A j is decided. And, two agents are also decided in this step.
Algorithm (Step 1) : Decision making Select N memories randomly with equal probability from all the memories of agent, A i. Then, we have a set of preferential parameters, for. Calculate the mean value and the mean square deviation, Produce a decision function, which is assumed to be a normalized Gaussian type,.
Algorithm (Step 2) : Message making Multiply a psychological factor (authority factor), to the decision function and add it to the knowledge function to produce a message function, Here, the suffix i, j means the message transfer from A i to A j. Then, normalize.
Algorithm (Step 3) : Knowledge Modification Multiply a psychological factor (authority factor, or reliability factor) to the message function and add it to the knowledge function to produce a new knowledge function, Then, normalize.
Multiply an aging factor, to Here, is an parameter of aging. Add it to the knowledge function to produce an aged knowledge function, Then, normalize,. Algorithm (Step 4) : Aging of Received Knowledge
Let us Produce Knowledge Functions Preliminary Study (1) : One Agent Model - How the parameter relates to D(x) -
How the parameter N relates to fluctuation of D(x) Careless Thinking Thoughtful Thinking
Standard deviation of the fluctuation of peak position of D(x) Careless Thinking Thoughtful Thinking
Preliminary Study (2) - How to guess knowledge function - Question: Do you accept NPP? Free description related to the question Examination by keyword analysis method knowledge function
Definition of Knowledge Function Parameter, x is called “preferential parameter”
Examples of Computer Simulation Question in the case of Bangladesh : Do you accept NPP to produce electricity?
Official name People’s Republic of Bangladesh Government Unitary parliamentary democracy Gross national income per capita $700 NationalUrbanRural Population 150 million 38 million 112 million Adult literacy58% 68%54% Newspaper readers40% 50%36% Mobile phone users66% 94%53% The Internet users3.7% 10%1.6% Bangladesh Society To From GPGOVMMSNM GP--12.5 GOV--1.5- MM33-3 SNM3.5- - Number of messages sent by agents per year
Summary (1) Theoretical formulation of Artificial Society Modeling to study decision making processes in society is explained. This model enables to study time variation of knowledge function of agents for a short period. Computer simulations, taking an example of Bangladeshi society, have been carried out under the conditions of thoughtful rational thinking, Even if the thoughtful rational thinking, the results unexpectedly contain fluctuations and an ensemble average is needed to have meaningful results.
Summary (2) This method can be applied any problem of decision making in any society (even on globe), if the needed data are obtainable. One problem is that the model does not include the God’s will. When and where disasters happen is only determined by the God. Cf. Idea of Japanese people on NPP is dramatically changed after 11 March 2011 For this reason, it is not recommended to use the model for the simulations of long time span.
Two kinds of Thinking Logical Thinking : Thinking in conscious part of brain Instinct Thinking : Thinking in non-conscious part of brain “Knowledge coming into mind” should be understood as “Knowledge contributed to decision making both in Logical Thinking and Instinct Thinking”