因為微電子技術的進步，近年來無線感測網路 (Wireless Sensor Network) 的應用範圍也越來越廣泛。以無線感測網路應用於土石流監測為例，我們需要先將感測器佈建在河床上，土石流發生的時候，這些感測器會隨著土石流一起移動，同時收集相關的參數 (如震動大小、感測器位置、土石流密度等)，並透過無線網路，將所收集到的資料送回岸邊的接收器。在這類型的應用情境中，感測器會隨著環境一起做非自發性的移動，並且因為應用的需求，需要在一定的區域範圍中，佈一定數量的感測器才能達到所要求的品質。然而因為監測環境的關係，我們必須在土石流發生前就先佈建感測器，所以決定感測器的佈建密度以確保收集資料的品質便成為一個重要的議題。之前相關的研究大致分為兩類，第一類是探討靜態(static)感測器的佈建密度，也就是感測器不會移動的情況。第二類是探討感測器具有自行移動能力時的佈建密度。我們的研究則是屬於第三類，即探討感測器會隨著環境而進行非自主性移動的情況。這個研究提出了一個系統化的模型，可以幫助我們決定感測器會隨著環境漂流時的佈建密度。

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