动态无风险折现率
dynamic risk-free discount rate
没有无风险免费午餐
No Free Lunch with Vanishing Risk
无风险阈值
unbiased risk thresholding
一致最小风险无偏估计
uniformly minimum risk unbiased estimator
无实际风险投资
effectively risk-free investment
无风无流靠码头
going alongside with no wind and current