Discussions of retirement planning and Social Security policy often focus on replacement rates, which represent retirement income or Social Security benefits relative to preretirement earnings. Replacement rates are a rule of thumb designed to simplify the process of smoothing consumption over individuals' lifetimes. Despite their widespread use, however, there is no common means of measuring r...

Mobile location-dependent information services (LDISs) have become increasingly popular in recent years. However, data caching strategies for LDISs have thus far received little attention. In this paper, we study the issues of cache invalidation and cache replacement for location-dependent data under a geometric location model. We introduce a new performance criterion, called caching efficiency...

1 To reduce user-perceived latency in retrieving documents on the world wide web, a commonly used technique is caching both at the client's browser and more gainfully (due to sharing) at a proxy. The eeec-tiveness of Web caching hinges on the replacement policy that determines the relative value of caching diierent objects. An important component of such policy is to predict next-request times....

This article investigates the value of perfect monitoring information for optimal replacement of deteriorating systems in the Proportional Hazards Model (PHM). A continuous-time Markov chain describes the condition of the system. Although the form of an optimal replacement policy for system under periodic monitoring in the PHM was developed previously, an approximation of the Markov process as ...

Joint replacement registries have been in place in Europe and Australia for decades. This registry data have given researchers robust information to evaluate joint replacement volume, utilization patterns, and outcomes. In many instances, registries can also serve as a mechanism for implant surveillance and an early warning system for underperforming implants. As the US health care system evolv...

in this research, 210 concrete cube specimens (15cm) were made replacing 0, 5, 10, 15, 20, 25, 30, 35, 40, 50, and 60 percent of slag powder from isfahan steel mill for cement. the control specimens were made with 350 kg/m3 cement content and the water cement ratio in all specimens was 0.51. the slump value and compressive strength of concrete specimens in 7, 28 and 90 days were obtained and th...

1. Evaluating the economic costs-benefits of a particular selection or breeding decision. By following the flow of genes through a population as a result of a particular breeding decision, it is possible to estimate the net economic cost-benefits of that breeding decision. For example, when looking at the value of the use of a particular bull in a dairy herd, we can note that each replacement h...

Disk space in shared Web caches can be diverted to serve some system users at the expense of others. Cache hits reduce server loads, and if servers desire load reduction to di erent degrees, a replacement policy which prioritizes cache space across servers can provide di erential quality-of-service (QoS). We present a simple generalization of leastfrequently-used (LFU) replacement that is sensi...

In this paper we analyse access traces to a Web proxy, looking at statistical parameters to be used in the design of a replacement policy for documents held in the cache. In the rst part of the paper we present a number of properties of the lifetime and statistics of access to documents, derived from two large trace sets coming from very diierent proxies and spanning over time intervals of up t...

Previous estimates of childhood lead poisoning prevention benefits have quantified the present value of some health benefits, but not the costs of lead paint hazard control or the benefits associated with housing and energy markets. Because older housing with lead paint constitutes the main exposure source today in the US, we quantify health benefits, costs, market value benefits, energy saving...