He arranged for a ballistics expert to be available.他安排人去请一位弹道学专家。Photographer in Residence required. There are no specific teaching commitments but he will be expected to be available to students on an informal basis.招聘驻校摄影师。不要求摄影师担任具体教职，但希望能在非正式雇用的基础上随时为学生服务。