地下连拱隧道施工地表沉降分析及预测

本文以重庆彭家花园双连拱隧道为工程背景,方法条件下,针对不同埋深、断面大小进行回归分析,的预测公式,并结合三维数值模拟验证了回归效果。就矿山法双连拱隧道施工引起的地表变形进行研究;在不同施工从理论上弄清地表沉降的规律,提出矿山法施工条件下地表沉降     

What can we learn from the return predictability over the business cycle?

In this paper, we forecast stock returns using time‐varying parameter (TVP) models with parameters driven by economic conditions. An in‐sample specification test shows significant variation in the parameters. Out‐of‐sample results suggest that the TVP models outperform their constant coefficient counterparts. We also find significant return predictability from both statistical and economic perspectives with the application of TVP models. The out‐of‐sample R² of an equal‐weighted combination of TVP models is as high as 2.672%, and the gains in the certainty equivalent return are 214.7 basis points. Further analysis indicates that the improvement in predictability comes from the use of information on economic conditions rather than simply from allowing the coefficients to vary with time.     

小行星采样返回任务的选址方法进展与启发

针对小行星采样返回任务,回顾不同小行星采样选址任务中的选址方法,阐述日本的隼鸟二号和美国的奥西里斯号采样返回任务中从初选采样区中选出最终采样区L08-E1和夜莺区的流程、采样选址涉及的工程和科学价值因素的分析方法与采样选址结果,并介绍了其他小行星附着任务的选址过程;对不同小行星采样返回任务的选址方法进行了对比分析与归纳,阐释了隼鸟二号和奥西里斯号采样选址所用到的载荷、选址方法以及得到的选址结果,并对选址方法进行对比分析,可作为今后小行星采样返回任务中采样选址方法的参考。结合我国小行星探测任务规划,展望了今后小行星采样返回任务中的选址方案。     

Optimal forecast error as an unbiased estimator of abnormal return: A proposition

In the event studies, the accuracy of the abnormal returns assessment is highly dependent on the accuracy of the preceding expected return model. If the expected return model is inadequate, there is a possibility that a part of returns is labeled as abnormal returns even though they are not. Currently, we have a variety of options to set up an expected return model. To obtain unbiased abnormal returns, one should pay attention to the performance of the expected return model. In this research, we propose that the optimal forecast lemma can be consulted beforehand so that minimizing the optimal forecast error in the expected return model will yield unbiased abnormal returns. We introduce and prove a proposition that the optimal forecast error is an unbiased estimator for abnormal return. The proposition induces assessing the performance of abnormal return estimation to preemptively evaluate the out-sample forecast accuracy of the model employed. In an illustrative dataset, we examine various models. The approach requires preliminary computational effort; however, it is useful for accurately obtaining the abnormal return predictions.     

随机需求下考虑顾客策略行为的预售和退货策略

预售策略目前已成为季节性产品零售商普遍采用的一种销售策略。策略型顾客在预售期购买商品尽管可以享受折扣的预售价格,但同时也面临着因不确定估值而可能带来的损失,所以顾客可能不愿意提前购买或提前购买了产品的顾客会选择在正常销售期间退货。此时零售商有两种策略可以选择:不进行预售、提供可退货服务的预售策略。针对市场需求不确定和顾客估值不确定并存的情况,利用均衡分析方法和理性预期理论分别建立了零售商不进行预售、允许顾客退货的预售策略的最优决策模型,并对这两种模型进行了求解与对比分析,以及敏感性分析。研究显示,当顾客对商品的估值较低时,零售商最好不要采取预售的方式。如果采取预售,则零售商的期望利润是退货补偿的严格凹函数。     

教育收益率的地区、性别差异:基于CGSS2013的研究

本文使用中国综合社会调查CGSS2013的数据,利用明瑟方程及OLS回归方法,发现性别和地区差异对教育收益率存在显著的影响,应优化对教育资源的配置,加强劳动力市场的市场化程度,减少社会性的劳动力市场分割.