MULTIPLE FAILURE CAUSES AND OBSERVATIONS OF TIME DEPENDENT COVARIABLES

In this paper firstly a summary of the theory of competing risks is presented; it shows how cause specific failure time distributions, failure probabilities and failure rate functions relate to the joint survivor function in the presence of various competing failure causes. This first part of the paper gives the insight useful for the second part, which concerns the way in which the dependency of the failure process on given time–dependent observations of covariables is specified and estimated. An application is presented briefly.     

Does paid family leave save infant lives? Evidence from California's paid family leave program

Paid family leave (PFL) aims to help working parents balance their careers and family responsibilities while also improving the well-being of infants. Using linked U.S. birth and infant death data with a difference-in-differences framework, I find that a 6-week PFL in California reduced the post-neonatal mortality rate by 0.135- that is, it saved approximately 339 infant lives. There were fewer deaths from health-related causes and larger effects for infants with married mothers and for infant boys. Additional checks and placebo examinations indicate that the observed effect is not due to contemporaneous shocks but rather is causal.     

基于常数死力有限商品寿命的库存模型研究

将商品寿命的概念用于传统的经济订购批量模型，提出了商品寿命死力的概念，并且基于商品寿命死力。对持统经济订购批量模型进行修正，建立了常数死力有限商品寿命的库存模型．并且对该模型进行分析求解。     

Effects of stream and lake regulation on reproductive success of kokanee in the flathead river system,Montana, U.S.A

Kokanee (Oncorhynchus nerka) provided an important recreational fishery in the Flathead River-Lake system (Columbia River Basin, U.S.A.-Canada) until the late 1970s when populations declined dramatically. The declines coincided with peaking river discharge from Hungry Horse Dam during the autumn spawning period and an increase in the duration of lake drawdown caused by the operation of Kerr Dam on the outlet of Flathead Lake. Redds of both river and lakeshore spawners were, therefore, dewatered in winter, causing high freezing and desiccation mortality of eggs during the incubation period. It appeared that growth rates of kokanee were density dependent. Female kokanee from strong year classes (i.e., those produced during years of favourable water levels and flow conditions during the incubation period) were smaller than those from weak year classes when unfavourable conditions for incubation prevailed. A highly significant relationship (r² = 0.929, p < 0.001) was demonstrated between female kokanee spawner length, river gauge heights, and lake levels during years which produced each year class. The close fit of the relationship was further validated by the strong correlation (r = 0.964) between actual kokanee lengths and predicted lengths. Other factors which could have influenced kokanee year class strength include hatchery plants of kokanee fry, harvest of kokanee by anglers, variations in the carrying capacity of Flathead Lake, and natural fluctuations in egg and fry mortality.