Porous Concrete Design

Porous concrete is a special kind of concrete that has high porosity. The only difference between porous concrete and normal concrete is that a porous concrete mix does not consist of sand or other small particles. The lack of sand and small particles creates voids in the concrete. The voids that area created are the reason why water is able to pass through a porous concrete mix. Porous concrete is used for low traffic areas such as parking lots and pavements. The main purpose of porous concrete is to reduce or even eliminate storm water runoff which has a number of benefits. For this project, the team developed a porous pavement mixture that will be applicable for practical and real life use. This means that the porous concrete mixture must have a certain permeability and compressive strength. There were two main parts to the project. Initially the team found what value of water to cement ratio would give the highest possible compression strength. The team started with experimenting with water to cement ratio due to the fact that it is the only variable that affects compressive strength and barely, if at all, affects permeability. After figuring out what the best water to cement ratio was, the next part of the project was about experimenting with other variables that affect the permeability and compression strength of a porous concrete. After acquiring the best water to cement ratio for the highest compression strength, the second part of the experiment will consist of varying two other variables, which were aggregate size and types of aggregate. By optimizing these variables, an optimal porous concrete mixture was found that could be used for practical use. The hope was to find a mixture that can be used for either pavements or parking lots

Photovoltaics as a terrestrial energy source. Volume 2: System value

Assumptions and techniques employed by the electric utility industry and other electricity planners to make estimates of the future value of photovoltaic (PV) systems interconnected with U.S. electric utilities were examined. Existing estimates of PV value and their interpretation and limitations are discussed. PV value is defined as the marginal private savings accruing to potential PV owners. For utility-owned PV systems, these values are shown to be the after-tax savings in conventional fuel and capacity displaced by the PV output. For non-utility-owned (distributed) systems, the utility's savings in fuel and capacity must first be translated through the electric rate structure (prices) to the potential PV system owner. Base-case estimates of the average value of PV systems to U.S. utilities are presented. The relationship of these results to the PV Program price goals and current energy policy is discussed; the usefulness of PV output quantity goals is also reviewed

On improving security of GPT cryptosystems

The public key cryptosystem based on rank error correcting codes (the GPT cryptosystem) was proposed in 1991. Use of rank codes in cryptographic applications is advantageous since it is practically impossible to utilize combinatoric decoding. This enabled using public keys of a smaller size. Several attacks against this system were published, including Gibson's attacks and more recently Overbeck's attacks. A few modifications were proposed withstanding Gibson's attack but at least one of them was broken by the stronger attacks by Overbeck. A tool to prevent Overbeck's attack is presented in [12]. In this paper, we apply this approach to other variants of the GPT cryptosystem.Comment: 5 pages. submitted ISIT 2009.Processed on IEEE ISIT201