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15℃的空气，流经直径d=1.25m，长度ι=2000m，壁面当量糙粒高度k=1mm的风管，测得沿程水头损失hf=8cm水柱，空气的流量Q=()。
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已知流速场ux=ax，uy=-ay，uz=0，则流函数()。
一管壳式蒸汽—空气加热器，空气在管内，要求将空气由15℃加热到50℃，空气体积流量为υ0=5m3/s。蒸汽为2×105Pa绝对压强的干饱和水蒸气，凝结水为饱和水，已知传热系数k=75W/(m2.k)，则加热器所需面积为()。
Calling to a bully's parent____.
Not long after the telephone was invented. I assume, a call was placed. The caller was a parent saying，“Your child is bullying my child, and I want it stopped!”The bully's parent replied，“You must have the wrong number. My child is a 1ittle angel. ”
A trillion phone calls later. The conversation is the same. When children are teased or tyrannized(欺压)，the parental impulse is to grab the phone and rant. But these days，as studies in the US show bullying on the rise and parental supervision on the decline，researchers who study bullying say that calling morns and dads is more futile than ever. Such calls often lead to playground recriminations(指责)and don't really teach our kids any lessons about how to navigate the world and resolve conflicts.
“When you call parents, you want them to‘extract the cruelty’from their bullying children. ”says Laura Kavesh，a child psychologist in Evanston，Illinois. “But many parents are blown away by the idea of their child being cruel. They won't believe it. ”In a recent police-department survey in Oak Harbor. Washington. 89 percent of local high school students said they had engaged in bullying behavior. Yet only 18 percent of parents thought their children would act as bullies.
In a new US PIA survey, 5 percent of parents support contacting other parents to deal with bullying. But many educators warn that those conversations can be misinterpreted(误解), causing tempers to flare. Instead, they say，parents should get objective outsiders，like principals，to mediate.
Meanwhile, if you get a call from a parent who is angry about your child's bullying, listen without getting defensive. That's what Laura McHugh of Castro Valley, California, did when a caller told her that her then 13-year-old son had spit in another boy's food. Her son had confessed，but the victim's mom“wanted to make sure my son hadn't given her son a nasty disease，”says McHugh，who apologized and promised to get her son tested for AIDS and other diseases. She knew the chance of contracting any disease this way was remote，but her promise calmed the mother and showed McHugh's son that his bad behavior. was being taken seriously. McHugh，founder of Parents Coach Kids，a group that teaches parenting skills，sent the mom the test results. All were negative.
Remember：once you make a call, you might not like what you hear. If you have an itchy dialing finger, resist temptation. Put it in your pocket.
The word“bullying”(Line 2，Para. 1)probably means____.
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