无限大电力系统三相短路，短路电流由周期分量和______组成。
题型：填空题
问题：
无限大电力系统三相短路，短路电流由周期分量和______组成。
题型：填空题
CPR is cardiopulmonary resuscitation (心肺复苏). It forces air into the lungs and pumps(用泵抽) blood and oxygen to the brain in order to increase the chances that a person whose heart stops will survive. It increases the chances that he or she will suffer little or no brain damage.
The American Heart Association suggests two ways to perform CPR. One combines the use of hands to pump the victim’s chest with rescue breathing. The other method is called “Hands-Only CPR”, which is for people who are unwilling or unable to perform rescue breathing. Some people fear infection(感染). Others say they are afraid of making the patient worse.
But the American Heart Association strongly asks people in contact with a victim(受害者) to take action and tells how to take it. It says you can recognize a person needing CPR. He or she is unconscious(无意识) -- unable to communicate or react to surroundings or speech. His or her skin has lost color. The person is not breathing. If such conditions describe the situation, chances are the heart has stopped beating.
You should act by calling for help, or sending someone else. Even if you cannot do mouth-to-mouth rescue breathing, you can perform Hands-Only CPR. You can do chest compressions(压迫) that help to keep blood flowing to the brain and the heart. To perform the compressions, place one hand over the other and press firmly on the center of the victim’s chest. Push down about five centimeters. Aim for one hundred compressions each minute.
Doctor Sayre suggests that medical workers do both the breathing method and chest compressions as usual. He says some victims, including babies, need the mouth-to-mouth breathing with the compressions. Still, the doctor says it is better to do just chest compressions than to do nothing.
