Play 2.1或更高版本中的并发性

我已经阅读了一些关于如何在Play中处理并发的教程,并找到了一些例子:

异步工作

import scala.concurrent.{ExecutionContext, future}

def sendEmailAsync(from: String, to: String, subject: String, body: String) = {
  import ExecutionContext.Implicits.global // in scala.concurrent

  future {
    EmailHelper.sendEmail(from, to, subject, body)
  }
}

预定的工作

import play.api.libs.concurrent.{Akka, Execution}

def sendEmailOnSchedule(from: String, to: String, subject: String, body: String) = {
  import scala.concurrent.duration._
  import Execution.Implicits.defaultContext // in play.api.libs.concurrent

  Akka.system.scheduler.scheduleOnce(10 seconds) {
    EmailHelper.sendEmail(from, to, subject, body)
  }
}

好吧,我有点困惑......第一个例子使用,scala.concurrent.ExecutionContext.Implicits.global而第二个例子使用play.api.libs.concurrent.Execution.Implicits.defaultContext.为什么？有人能解释一下幕后发生的事吗？