Do you ever find yourself getting really unhappy for almost no reason? Or suddenly feeling down without knowing why? Going from sadness to anger to joy in a matter of minutes can make many teens feel as though they're losing control. But why is the feeling so common among teens?
Maybe you're starting a new school and not able to see old friends as much. Getting good grades or wanting to be better in sports or other activities can be a concern (关注)for many teens.
Being accepted by friends is important. Teens also may notice, for the first time, a sense of distance from parents and family. You may feel you want to be on your own and make your own decisions, but it can also seem a bit lonely at times.
Another important cause for mood swings is biology. When puberty（青春期）begins, the body starts producing hormones（荷尔蒙）. These hormones cause physical changes in the body. But in some people, they also seem to cause emotional(情绪的)changes.
Here are some things you can do that might make those bad moods a bit easier to deal with.
Recognize you're not alone. Although not every teen experiences mood changes to the same degree, they are common.
Talk to people you trust. Friends can help each other by realizing that they're not alone in their feelings. Talking to parents is important, too. Parents can share their own experiences dealing with bad moods. Teachers are often good resources and a doctor can help to answer questions about development.
Get enough sleep. Though it can be hard to find enough time, getting enough rest is very important. Being tired can lead to more sadness.
Create. Taking part in some kinds of activities, like building something out of wood, or starting an art or music piece. Writing can help you organize and express your thoughts and feelings. Get your thoughts on paper. Do the same thing with paint, music, or other art forms. Put your feelings into your artwork.
小题1:When puberty begins, many teens feel__________.
A．unhappy
B．angry
C．joyful
D．emotional小题2:_______may not make some teens be in bad moods.
A．Study pressure
B．Getting good grades
C．The sense of distance from parents
D．Missing old friends小题3: It’s easier to deal with your mood changes by ___________.
①realizing they are common ②explaining your feelings to people you trust
③playing computer games ④being creative
⑤breaking school rules ⑥getting enough sleep
A．①②③④
B．①②③⑥
C．①②④⑥
D．①③④⑤
，式中，l0为计算跨度，M为梁的最大弯矩，EI为抗弯刚度，S为与荷载类型、支承条件有关的系数，例如，均布荷载作用下的简支梁，S=5／48。对于钢筋混凝土梁，由于其抗弯刚度在开裂之后不再是常数，不但随弯矩增大而减小，而且，由于混凝土的收缩徐变性质，随时间的增长抗弯刚度也会降低。依据《混凝土规范》，将按照标准组合得到的弯矩记作M，按照准永久组合得到的弯矩记作M，短期刚度记作B。M可以认为是一种长期作用，随时间变化不大，因此这一部分产生的弯矩需要乘以挠度增大系数θ，（M-M）这一部分产生短期挠度，不必增大，于是，受弯构件的长期挠度可以按照下式计算：
若将上式只采用M表达，写成
，则需要有下式成立：
可见，在《混凝土规范》中，是利用刚度B考虑长期作用影响的。《公路混凝土规范》中的处理与上述不同：先利用短期刚度求出短期挠度f，然后将f乘以挠度长期增长系数ηθ得到长期挠度。这种做法更容易看出是如何考虑长期作用影响的。若以《混凝土规范》中的符号来表示挠度放大系数，可得
以M代替了M（《公路混凝土规范》中采用频遇组合作为短期效应组合，而非标准组合），以M2代替了M（单纯是符号不同），就成为《公路混凝土规范》6.5.3条条文说明中的公式6-20。可见，两本规范的做法本质上相同。