We introduce a new cryptographic primitive: Proofs of Space-Time (PoSTs) and construct a practical protocol for implementing these proofs. A PoST allows a prover to convince a verifier that she spent a “space-time” resource (storing data—space—over a period of time). Formally, we define the PoST resource as a trade-off between CPU work and space-time (under reasonable cost assumptions, a ration...

The dish-Stirling technology for power generation, using a Stirling engine fed with a renewable energy such as solar, means a promising development regarding electricity generation. The dish-Stirling technology presents the highest efficiency, around 30%, in relation to other solar energy generation systems. However the technology status has not achieved enough advancement to be competitive wit...

Message authentication is considered as a serious bottleneck to multicast security, particular for stream-type of traffic. The techniques of hash chaining and signature amortization have been proposed in many schemes for stream authentication, with or without multicast settings. However, none of them is optimal. They either have a large packet overhead or are not robust to packet loss. Some eve...

We investigate how the adoption of IFRS 3, business combinations, affected reported goodwill and whether the change was relevant for stock market valuation of companies. We use data for all companies listed at the main Swedish stock exchanges. We find some evidence suggesting that aggregated goodwill impairment charges in 2005 are lower than aggregated goodwill amortizations in 2004. Hence, goo...

This study analyzes the evolution of the Financial Accounting Standards Board (FASB)’s Statement of Financial Accounting Standards (SFAS) 141 and 142, through a detailed analysis of comment letters submitted to the FASB on Business Combinations Exposure Drafts 201 and 201 (Revised). Comment letters, an integral part of the standard-setting process, contain valuable insights on the views of part...

We present a distributed efficiently amortizable CPU cost-function with no trap–door. The absence of a trap–door allows us to avoid needing to trust any party. Applications for such cost-functions are in distributed document popularity estimation, and metering of web advertising. None of the servers involved have any advantage over users in computing the cost function. The amortized token has a...

Understanding the complete human influence on maritime space has the central position in the planning process. Maritime spatial planning logically connects on integral planning of coastal area. Applying integral management on coastal and maritime area, together with the establishment of the process of maritime spatial planning makes the coupling regarding managing of the resources; all that is ...

Probabilistic programming languages (PPLs) are a powerful modeling tool, ableto represent any computable probability distribution. Unfortunately, probabilisticprogram inference is often intractable, and existing PPLs mostly rely on expensive,approximate sampling-based methods. To alleviate this problem, one could tryto learn from past inferences, so that future inferences run fa...

Dynamic modeling of osteoarticular system is necessary because the exertion of various actions and natural physiological movements are essentially dynamic. The wide mobility of human body leads to the necessity of modeling the osteoarticular system as a mechanism with a large number of degrees of freedom. The differential equations system obtained are very complex and assume numerical integrati...

PURPOSE Efforts to harmonize the standards of the CSA and the ISO, as they relate to compressed medical gas supply and piping, prompted us to review ten years experience with oxygen concentrators (OCs) in Canada used as a primary hospital oxygen supply. The goals of this study were; 1) To document the number of Canadian OC Hospital sites, 2) to define what impact these units have had on medical...