In 2006, Alberto Bressan [1] suggested the following problem. Suppose a circular fire spreads in the Euclidean plane at unit speed. The task is to build, in real time, barrier curves to contain the fire. At each time t the total length of all barriers built so far must not exceed $t\cdot v$, where v is a speed constant. How large a speed v is needed? He proved that speed $v>2$ is sufficient, and that $v>1$ is necessary. This gap of $(1,2]$ is still open. The crucial question seems to be the following. When trying to contain a fire, should one build, at maximum speed, the enclosing barrier, or does it make sense to spend some time on placing extra delaying barriers in the fire's way? We study the situation where the fire must be contained in the upper $L_1$ half-plane by an infinite horizontal barrier to which vertical line segments may be attached as delaying barriers. Surprisingly, such delaying barriers are helpful when properly placed. We prove that speed $v=1.8772$ is sufficient, while $v>1.66$ is necessary.

2006年，Alberto Bressan [1]提出了以下问题。假设圆形火焰以单位速度在欧几里得平面内扩散。任务是实时构建屏障曲线以遏制火灾。每次t，到目前为止建造的所有障碍的总长度不得超过$Ť\cdot v$，其中v是速度常数。速度v需要多大？他证明了速度$v>2$ 足够了，那 $v>\mathrm{1个}$有必要的。这个差距$（\mathrm{1个}，2]$仍然开放。关键问题似乎如下。当试图扑灭火焰时，应该以最快的速度建造包围的屏障，还是应该花一些时间在火焰上放置额外的延迟屏障？我们研究了必须将火势控制在上部的情况${\mathrm{大号}}_{\mathrm{1个}}$无限水平障碍的半平面，垂直线段可以作为延迟障碍附加到该障碍上。出人意料的是，如果放置得当，此类延迟障碍物会有所帮助。我们证明了速度$v=1.8772$ 足够，而 $v>1.66$ 有必要的。