Tuesday: Faced with international protests, the Chinese government recently released dissident artist Ai Weiwei from prison after nearly three months. In support of Ai's artistic freedom, galleries and museums worldwide have staged what amount to chair sit-ins: gatherings of chairs, in a homage to the artist's 2007 installation "Fairytale: 1001 Qing Dynasty Wooden Chairs," a mass arrangement of antique Chinese chairs symbolizing the historic culture that China has bulldozed in its rapid modernization. This week, Walker Art Center invites people to place chairs on its lawn and join museum staffers in a day of activities celebrating artistic freedom. The Walker will offer free admission all day, and director Olga Viso will explain the meaning of it all at 6 p.m.