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Artificial Intelligence

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  1. Artificial Intelligence Shyh-Kang Jeng Department of Electrical Engineering/ Graduate Institute of Communication Engineering National Taiwan University

  2. Computer vs. Human • Machine • Performs precisely defined tasks with speed and accuracy • Not gifted with common sense • Human • Flounders on complex computations • Capable of understanding and reasoning • More likely to understand the results and determine what to do next

  3. Humanlike Computer • Continue without human intervention when faced with unforeseen situations • Possesses or simulate the ability to reason • Psychologists and their models may be helpful

  4. Related Fields Computer Science Linguistics Artificial Intelligence Psychology Philosophy Mathematics Biology

  5. 監控認知系統 覺知 指揮 知識系統 表徵、儲存 重整、合成 認知策略系統 學習與記憶 思考與解題 No 新知識 或策略 ? 動作系統 Yes Yes 有限的訊息傳遞系統 事件記憶(長期) 事件記憶(短期) 注意與辨識 行為反應 感覺的訊息登錄 訊息刺激 人 類 認 知 系 統 模 式 鄭 昭 明

  6. Two Approaches • Performance oriented • Computer scientists’ main concern • Build more useful machines • Simulation oriented • Psychologists’ focus • Understanding human thought and behavior • Opportunities to test theories

  7. Weak AI vs. Strong AI • Weak AI • Machines programmed to exhibit intelligent behavior • Games and expert systems • Strong AI • Machines programmed to possess intelligence and consciousness • Intelligence and consciousness are internal characteristics that can not be identified directly

  8. Evaluating Intelligent Behavior of Machines • Turing test • A human interrogator communicates with a test subject by means of a typewriter system • A machine behaves intelligently if the interrogator can not distinguish it from a human • Programs DOCTOR and Eliza •

  9. Brain Study

  10. How Brains Think? Cognition 認知 Emotions 情緒 Being, Insight 存在感、洞察力 ? Neurons 神經元 Synapses 突觸 Membranes 細胞膜 Bio Chemistry 生物化學 Chemical Bonds 化學鍵 Quantum Mechanics 量子力學




  14. The Eight-Puzzle

  15. A Puzzle-Solving Machine

  16. Understanding Images • Image processing • Identifying characteristics • Edge enhancement • Region finding • Smoothing • Image analysis • Understanding what these characteristics mean

  17. Production System • Encloses common characteristics of reasoning problems • Major components • A collection of states • Start state and goal state • A collection of productions (rules or moves) • Production is an operation that can be performed to move from one state to another • A control system • Decides which production should be applied next

  18. Portion of the 8-Puzzle’s State Graph

  19. Applications of Production System Framework • Playing games of chess • Drawing logical conclusions from given facts

  20. Deductive Reasoning

  21. Search Trees • Control system • Searches the state graph to find a path from the start node to the goal • A strategy is to build a search tree • Root: start state • Children: states reachable by applying one production • Walking up the tree from the goal

  22. An unsolved 8-Puzzle

  23. A Sample Search Tree

  24. A Sample Search Tree

  25. A Sample Search Tree

  26. A Sample Search Tree

  27. Productions Stack

  28. Tree-Searching Strategies • Breadth-first search • Depth-first search • Heuristics • Constitute a reasonable estimate of the amount of work remaining in the solution if the associated state were reached • Easy to compute

  29. Heuristic Value of An Unsolved 8-Puzzle Heuristic value: 7 (sum of distances)

  30. A Heuristic Algorithm

  31. Beginning of a Heuristic Search

  32. Search Tree After Two Passes

  33. Search Tree After Three Passes

  34. Complete Search Tree

  35. A Neuron in a Living Biological System

  36. Processing Unit

  37. Representation of a Processing Unit

  38. A Neural Network with Two Different Programs

  39. Uppercase C and Uppercase T

  40. Various Orientations of C and T

  41. Character Recognition System

  42. Letter C in the Field of View

  43. The Letter T in the Field of View

  44. Desired Output Actual Output Inputs Adjusting Weights Using Error Back Propagation Network

  45. Associative Memory • Retrieval of information that is associated with, or relevant to, the information at hand • Implementation by Artificial Neural Network • Processor units are interconnected to form a web with no inputs or outputs

  46. Stable and Unstable Configurations • Each unit can be in its excited or inhibited state • Certain configurations are stable in the sense that when the network finds itself in one of these configurations, it will remain in that configuration • If the network is in a non-stable configuration, then the interaction of the processing units will cause the configuration to change

  47. Association of Information • When given a part of a stable configuration, the network is able to complete the configuration • Or, it is able to find the bit pattern that is associated with the partial pattern it is given

  48. A Hopfield Network

  49. Steps Leading to a Stable Configuration

  50. Steps Leading to a Stable Configuration