There is a fast increase of information and data generation in virtual environments due to microblogging sites such as Twitter, a social network that produces an average of 8, 000 tweets per second, and up to 550 million tweets per day. That's why this and many other social networks are overloaded with content, making it difficult for users to identify information topics because of the large number of tweets related to different issues. Due to the uncertainty that harms users who created the content, this study proposes a method for inferring the most representative topics that occurred in a time period of 1 day through the selection of user profiles who are experts in sports and politics. It is calculated considering the number of times this topic was mentioned by experts in their timelines. This experiment included a dataset extracted from Twitter, which contains 10, 750 tweets related to sports and 8, 758 tweets related to politics. All tweets were obtained from user timelines selected by the researchers, who were considered experts in their respective subjects due to the content of their tweets. The results show that the effective selection of users, together with the index of relevance implemented for the topics, can help to more easily find important topics in both sport and politics.

本研究旨在探討圖像輔助呈現時機對台灣國中生聽力的影響，而圖像輔助呈現時機則分為在聽力活動前與在聽力活動進行中。同時為了深入探究其效益，本研究更著重於其對高、中、低三個不同能力組別學生的影響。除此之外，並對於二份學生問卷的回答加以探討： （1）問卷一有關學生們先前學習英語的背景資料。 （2）問卷一有關學生們在聽力過程中主要遭遇的問題，涵蓋聽力內容、聽者本身與外在因素等。 （3）問卷二有關學生們對圖像式聽力測驗的反應與他們對實施聽力測驗時，圖片展示時間的看法。 本研究以台中縣光正國中一個國三班級42位同學為對象，經過英語聽力能力測驗後，他們被分為高中低三組。實驗前，學生們先填寫第一份問卷。隨後，三組學生一起接受兩種實驗: (1)邊聽邊看圖片; (2)先展示圖片再聽。在完成所有實驗後，隨即填寫第二份問卷。本研究主要結果如下： （1）大多數的受試者已學習英語3年以上，卻對自己的聽力缺乏信心。此現象乃肇因於學生們有限的練習時間。也因此，他們大多不贊成將來升高中大考有聽力測驗的項目。另外，眾多的學生表達了希望獲得老師在聽力方面指導的強烈需求。 （2）聽力能力愈差的學生，遇到更多的聽力問題，尤其在聽力內容與聽者本身方面問題為最。 （3）以整體學生的聽力表現而言，聽前呈現圖片對學生的幫助比邊聽邊呈現圖片的效果來的顯著。 （4）以各個組別學生的聽力表現而言，聽前呈現圖片最能彌補中低程度學生聽力的不足。 （5）超過半數以上的學生表達較喜愛圖像式的英語聽力測驗，尤其是圖像呈現在正式的聽力活動之前為最。 根據研究的結果，聽前呈現圖像輔助對不同程度的學生均有助益，尤其對中低程度者聽力理解的幫助更為顯著。因此，本論文呼籲，國中英語老師可在實施英語聽力測驗時，多善用圖像輔助以引發學生的學習動機並藉由聽前呈現圖片技巧來提昇學生們的英語聽力理解。 / The purpose of the present study is to explore the effects of pictures as cues supplied at different time periods, the picture before listening comprehension test (BLCT) and during listening comprehension test (DLCT). More specific, it is focused on the comparisons of the effects of BLCT and DLCT on the high, middle and low proficiency groups. Also probed are students’responses to two questionnaires on the following issues. (1) The subjects’ previous English learning background as shown in Questionnaire One; (2) The main listening problems the subjects encounter in the process of listening, including the oral text, the listener and external aspects; (3) The subjects reactions to the listening comprehension with the picture format and their preference for the timing of picture-giving. The subjects of this study are 42 students of nine-grade junior high school students in Kuang-cheng Junior High School in Taichung County. They are divided into three proficiency groups—the high proficiency group (HPG), the intermediate proficiency group (MPG) and the low proficiency group (LPG) according to the scores of the listening comprehension test in the subjects’ second mid-term examination. At the beginning of the overall experiment, they are demanded to finish Questionnaire One. After that, they are assigned to take two listening comprehension tests: a listening comprehension test with a picture before listening and during listening. After receiving the two treatments, the subjects are asked to complete Questionnaire Two to reveal their attitudes toward the listening comprehension tests with visual cues. The major findings of the present study are summarized as follows: (1) Although most of the subjects have learned English for more than three years, they do not establish much confidence in their own listening ability due to the limited time of practice in listening. Many of them do not support the idea of incorporating the listening comprehension test into the future high school entrance exam. However, they express their eagerness for obtaining the teacher’s guidance in listening. (2) The worse the listeners achieve, the more listening difficulties they would come across, especially in the oral text and the listener himself/herself. (3) BLCT is more effective than DLCT. This can be proved by the mean scores and standard deviation of BLCT and DLCT respectively. (4) As the three different proficiency groups are taken into consideration, BLCT lends itself to the low proficiency groups (LPG) and the intermediate proficiency groups (MPG). (5) Most of the subjects prefer the listening comprehension test with the picture format, particularly the visual cue before the listening activity. Based on the results of the study, the picture before listening benefits all of the three proficiency groups, especially the lower achievers. The researcher suggests that English teachers in junior high school try to make good use of visual cues in constructing listening comprehension tests to arouse students’ motivation and thus improve students’ listening comprehension.