本論文主旨在為基於日常生活活動產生之加速度訊號開發晝夜節律估測演算法，並利用此演算法的分析結果做為探討作息型態和社會授時因子對晝夜節律產生影響的依據。在晝夜節律的參數計算上，我們利用配戴於慣用手腕及腳踝之三軸加速度感測器收集使用者的日常活動訊號進行晝夜節律的分析，基於本論文發展的分析方法，可得到下列資訊：1)每日晝夜節律的資訊，以及2) 一星期內天與天間晝夜節律的規律性和平均週期。
在晝夜節律估測演算法當中，量測之加速度訊號首先經過重力移除與特徵擷取等訊號前處理程序，接下來再進行後續的資料分析。在特徵擷取時，本論文以count來做為代表人類活動量的主要特徵；24小時之count值經過睡/醒週期分析及餘弦分析後可得到每日晝夜節律的資訊，7天之count值經過龐卡萊圖分析和自相關分析後可得到一星期內天與天間晝夜節律的規律性和平均週期。
接下來，本論文將晝夜節律估測演算法所產生的參數應用於探討作息型態和社會授時因子對晝夜節律產生的影響。我們首先以日夜作息型態量表從一群大學生中挑選出作息型態屬於早晨型或夜晚型的人做為實驗受測者。受測者於實驗期間配戴加速度感測器記錄晝夜節律參數，並定時填寫主觀量表，以了解受測者的睡眠品質和日間嗜睡程度。根據加速度訊號所分析出的晝夜節律參數，我們可以發現不同作息型態受測者的晝夜節律確實存在差異，其差異為：1)早晨型睡眠中點出現的時間約比夜晚型早了2個小時、2)早晨型的晝夜節律比夜晚型規律，縱然早晨型和夜晚型於晝夜節律有所差異，但兩種類型於主觀量表所表現的睡眠品質和日間嗜睡程度並沒有差異。另一方面，我們透過比較早晨型或夜晚型於平日和假日間的晝夜節律差異，來探討社會授時因子對晝夜節律的影響。社會授時因子確實會對晝夜節律產生影響，但影響程度會依個體之作息型態不同，而有所不同。早晨型於平日和假日間之晝夜節律較無差異；夜晚型於平日和假日間的入睡時間無差異，但是平日的醒來時間比假日早了約一小時，因此壓縮到了夜晚型於平日的睡眠長度，但睡眠品質和日間嗜睡程度所受的影響有限。
由上述結果我們可以得知，不同作息型態間的晝夜節律確實存在差異，睡眠中點出現的時間是最明顯的差異；此外，社會授時因子確實會對晝夜節律產生影響，但此影響會依作息型態的不同而有所不同，早晨型受到的影響較小，夜晚型受到的影響較大。

This thesis aimed at developing a circadian rhythm estimation algorithm by daily activity accelerations. With the help of the indices derived from the proposed circadian rhythms estimation algorithm, we investigated the influence of chronotype and social zeitgebers on circadian rhythms. Based on the accelerations collected from domain wrist and ankle, the proposed circadian rhythm estimation algorithm generates circadian rhythm information including: 1) the circadian rhythms indices of each day and 2) regularity of circadian rhythms among days and the average period in a week.
The proposed circadian rhythm estimation algorithm first removes gravitational component and filters noise, then extract the count value: a feature derived from activity acceleration signal. The count value of each day is used to generate the circadian rhythm information of each day by sleep/wake cycle analysis and cosinor analysis. The count value of a week (7 days) is analyzed via Poincaré plot analysis and autocorrelation analysis to represent the regularity of circadian rhythms among days and the average period in a week.
Based on the indices obtained from circadian rhythms estimation algorithm, we further investigate the influence of chronotype and social zeitgebers on circadian rhythms. Both morning type and evening type subjects are included in our experiment to represent different chronotypes. Based on the indices of the proposed circadian rhythms estimation algorithm, we can conclude that there are some differences on circadian rhythms between various chronotype, the differences are: 1) morning types have earlier occurrence of sleep midpoint than evening types (approximate two hours) and 2) morning types’ circadian rhythms are more regular to that of evening types. Although there are some differences between morning type and evening type, these differences on circadian rhythm do not lead to the differences on their sleep quality and daytime sleepiness (measured by subjective questionnaires). In addition to investigate the differences between various chronotypes, we also compare the circadian rhythms indices between weekday and weekend to investigate the influence of social zeitgebers on circadian rhythms. Social zeitgebers also impact our circadian rhythms, but the influence of social zeitgebers has different impact to the subjects with various chronotype. In the subjects of morning type, there are no differences on the circadian rhythm between weekday and weekend. However, the subjects of evening type reveal the different circadian rhythm in the sleep-wake cycle between weekday and weekend. The sleep onset time of evening type subjects are similar between weekday and weekend, but the wake up time on the weekday are earlier than that of the weekend (approximate one hour).
Based on the observed phenomenon, we can know that chronotype have indeed influence on circadian rhythms; the most significant characteristic is sleep midpoint. On the other hand, social zeitgebers also have impact on circadian rhythms of evening type subjects.

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