题目

阅读下面短文，根据其内容写一篇60词左右的内容概要。Architects have long had the feeling that the places we live in can affect our thoughts,feelings and behaviors.But now scientists are giving this feeling an empirical(实证的）basis.They are discovering how to design spaces that promote creativity,keep people focused and lead to relaxation.Researches show that aspects of the physical environment can influence creativity.In2007,Joan Meyers-Levy at the University of Minnesota,reported that the height of a room's ceiling affects how people think.Her research indicates th11．在平面直角坐标系xOy中，动点P到点D（2，3）的距离为4，设点P的轨迹为C．（Ⅰ）写出C的方程；（Ⅱ）设直线y=kx+1与C交于A，B两点，当k为何值时，$\overrightarrow{DA}$⊥$\overrightarrow{DB}$，此时|$\overrightarrow{AB}$|的值是多少？