题干

下列做法不符合安全用电的是()

A:将电水壶的金属外壳接地

B:在家庭电路中插座与电灯连接必须是并联

C:家庭电路布线时熔断器应在总开关之后

D:使用测电笔时手不能接触笔尾金属体

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答案(点此获取答案解析)

D

同类题1

阅读理解

    Many students want to give gifts to their teachers, and they often wonder what gifts to give to their teachers. After almost two decades as a teacher, here are some thoughts.

    First, not giving your teacher anything is perfectly fine. Teachers do not expect to receive a gift and are often surprised when they receive a gift. Believe it or not, the gift that a teacher receives (or does not receive) has no influence on his or her opinion of the child. No teacher will ever remember which child arrived at school with a gift and which did not. Trust me. In fact, many schools do not allow teachers to accept gifts from parents, so offering a gift can place a teacher in a difficult situation. As a result, no gift is sometimes just easier for a teacher.

    But if you're going to give your teacher a gift, here are a few suggestions:

    The best gift I ever received from students was given to me when my daughter was born. Each student in my class bought his or her favorite childhood book and signed the inside cover with a message to Clara. These books were then put into a library and gathered to me after Clara's birth. The books in that library are still some of Clara's favorites today, and we always take a moment to read the messages.

    Two things to take away from this: Books make excellent gifts. Gifts for a teacher's children make excellent gifts.

    But when it comes to gifts, I believe that the best gift that you can give a teacher is simply a note expressing your appreciation for all that he or she has done for you. I have letters from students that I appreciate (感激) as much as any other object in my life. I read these letters after difficult days in the classroom. They lift my spirits beyond measure.

同类题4

阅读下面的文字,完成下列各题。

    在大自然中,悦耳动听的鸟鸣声给人们带来无限的愉悦。每一类鸟的鸣声都不尽相同。乌鸦呱呱叫,山雀的鸣声如嘹亮的哨响,隐夜鸫的叫声则似长笛声般悠扬。那么在复杂的背景噪声下,如何识别鸟鸣声?是否存在可以识别每一类鸟鸣的应用程序?

    针对上述问题,英国牛津大学的蒂莫•帕帕多普洛斯和他的同事,提出了一种能够识别各类鸟叫声的鸟鸣识别算法。

    一般情况下,自然资源保护论者需要通过定期的徒步旅行或者直升机旅行的方式,对生存在特定区域内的鸟类数目进行统计和总结。然而,如果通过音频录制鸟鸣,再将音频转化为物种计数,采用此方法代替旅行统计方式,将使得鸟类追踪的研究变得轻而易举,为研究鸟类种群数目是否下降或者鸟类的迁徙模式是否改变等,带来很大便利。

    英国伦敦大学玛丽女王学院的丹•斯托博士称:“鸟鸣极其复杂,这些最简单的声音通常难以分辨,因为它们听起来如此相似。”毕竟我们无法听清远处的,特别是在嘈杂环境中的鸟叫声。

    牛津大学的研究团队在亚洲和欧洲共收录了15种不同鸟类的鸣叫声,包括新疆歌鸲、大山雀、画眉等。他们收录的鸟鸣声中混杂了不同的音频环境,如市区公园中较为平缓的背景噪声或者露天市场中密集人群的喧嚣声。

    如此多样化的混合声音,用于机器学习算法的训练过程,通过训练后的机器来选择包含鸟鸣声的音频段。尽管鸟鸣声与部分噪声频率相近,影响算法的准确性,但这些学习算法仍能成功地从噪声中区分出鸟鸣声。

    目前国内福州大学的研究团队,对于低信噪比鸟鸣识别的算法是将声音信号转化为图象,对图象进行处理得到一串被称作特征值的数字,并用这串数字代替声音进行识别。

    国外其他研究团队也在致力于研究自己的鸟鸣识别算法,尤其是那些能够识别不同鸟类物种的算法。斯托和他的同事正在测试名为Warblr的应用程序,在最佳状态下,Warblr进行鸟类识别的准确度可以高达95%,该数据已经得到巴西一家鸟类鉴定组织的认证。美国威斯康星大学的研究团队研发了一个相似的应用程序,命名为WeBIRD,是针对本地鸟类而设计的。美国康奈尔大学鸟类学实验室研发的Merlin应用程序,通过对鸟类的大小、颜色、位置等简单情况的了解,以利于人们对鸟类进行区分。

    斯托博士认为,对鸟鸣识别应用技术进行探索的最终目标不仅仅用于识别鸟类,更是想要破译鸟类之间真正的“人际关系”,如果音频能够转换为物种计数,那么我们可以更方便地监测鸟类种群的变化。德国动物声音档案自然历史博物馆的马里奥说,类似牛津大学团队提出的鸟鸣识别算法,对研究自然环境是很有价值的。

(摘编自李应编译《鸟鸣识别》)