Aggregate material formulated with MSWI bottom ash and APC fly ash for use as secondary building material

The main goal of this paper is to obtain a granular material formulated with Municipal Solid Waste Incinerarion (MSWI) bottom ash (BA) and air pollution control (APC) ash to be used as secondary building material. Previously, an optimum concrete mixture using both MSWI residues as aggregates was formulated. A compromise between the environmental behaviour and the economy of the process was considered. Unconfined compressive strength and abrasion resistance values were measured in order to evaluate the mechanical properties. From these results, the granular mixture was not suited for certain applications owing to the high BA/APC content and low cement percentages used to reduce the costs of the final product. Nevertheless, the leaching test performed showed that the concentrations of all heavy metals were below the limits established by the current Catalan legislation for their reutilization. Therefore, the material studied might be mainly used in embankments, where high mechanical properties are not needed and environmental safety is assured.

Towards a dynamic model of e-commerce: environmental, technological and organisational drivers of B2C along time

Despite the important benefits for firms of commercial initiatives on the Internet, e-commerce is still an emerging distribution channel, even in developed countries. Thus, more needs to be known about the mechanisms affecting its development. A large number of works have studied firms¿ e-commerce adoption from technological, intraorganizational, institutional, or other specific perspectives, but there is a need for adequately tested integrative frameworks. Hence, this work proposes and tests a model of firms¿ business-to-consumer (called B2C) e-commerce adoption that is founded on a holistic vision of the phenomenon. With this integrative approach, the authors analyze the joint influence of environmental, technological, and organizational factors; moreover, they evaluate this effect over time. Using various representative Spanish data sets covering the period 1996-2005, the findings demonstrate the suitability of the holistic framework. Likewise, some lessons are learned from the analysis of the key building blocks. In particular, the current study provides evidence for the debate about the effect of competitive pressure, since the findings show that competitive pressure disincentivizes e-commerce adoption in the long term. The results also show that the development or enrichment of the consumers¿ consumption patterns, the technological readiness of the market forces, the firm¿s global scope, and its competences in innovation continuously favor e-commerce adoption.

ZigBee/ZigBee PRO security assessment based on compromised cryptographic keys

Sensor networks have many applications in monitoring and controlling of environmental properties such as sound, acceleration, vibration and temperature. Due to limitedresources in computation capability, memory and energy, they are vulnerable to many kinds of attacks. The ZigBee specification based on the 802.15.4 standard, defines a set of layers specifically suited to sensor networks. These layers support secure messaging using symmetric cryptographic. This paper presents two different ways for grabbing the cryptographic key in ZigBee: remote attack and physical attack. It also surveys and categorizes some additional attacks which can be performed on ZigBee networks: eavesdropping, spoofing, replay and DoS attacks at different layers. From this analysis, it is shown that some vulnerabilities still in the existing security schema in ZigBee technology.

Life cycle analysis and life cyle impact assessment methodologies: a state of the art

Life cycle analysis (LCA) is a comprehensive method for assessing the environmental impact of a product or an activity over its entire life cycle. The purpose of conducting LCA studies varies from one application to another. Different applications use LCA for different purposes. In general, the main aim of using LCA is to reduce the environmental impact of products through guiding the decision making process towards more sustainable solutions. The most critical phase in an LCA study is the Life Cycle Impact Assessment (LCIA) where the life cycle inventory (LCI) results of the considered substances related to the study of a certain system are transformed into understandable impact categories that represent the impact on the environment. In this research work, a general structure clarifying the steps that shall be followed ir order to conduct an LCA study effectively is presented. These steps are based on the ISO 14040 standard framework. In addition, a survey is done on the most widely used LCIA methodologies. Recommendations about possible developments and suggetions for further research work regarding the use of LCA and LCIA methodologies are discussed as well.

Assessment of the water chemistry and the macroinvertebrate community changes produced during the creation of the new Llobregat river mouth (Barcelona, NE Spain)

In 1999, a set of coordinated projects and investments whose principal objective was to transform Barcelona into one of the main distribution points of southern Europe resulted in the relocation of the Llobregat River mouth. The mouth was relocated by draining the old river mouth and constructing a new one. The aim of this study was to characterise the physico-chemical properties and the aquatic macroinvertebrate communities of the new river mouth and to monitor the changes experienced by the estuarine environment during its creation. A sampling point was established in the river 1.8 km upstream from its connection with the new mouth, and two sampling points were established in the new mouth. Samples of water and macroinvertebrates were collected every two months from May 2004 to June 2005, covering the periods before (from May to September 2004) and after (from September 2004 to June 2005) the new mouth was connected to the river and the sea. During the period before its connection to the river and the sea, the new mouth was functionally similar to a lagoon, with clear waters, charophytes and a rich invertebrate community. After the connection was completed, seawater penetrated the river mouth and extended to the connection point with the river (approximately 3.9 km upstream). An increase in conductivity from 4-6 mS cm 1 to 24-30 mS cm 1 caused important changes in the macroinvertebrate community of the new mouth. An initial defaunation was followed by a colonisation of the new mouth by brackish-water and marine invertebrate species. Due to its design (which allows the penetration of the sea) and the decreased discharge from the lower part of the Llobregat River, the new mouth has become an arm of the sea

Modeling and manufacturability assessment of bistable quantum-dot cells

We have investigated the behavior of bistable cells made up of four quantum dots and occupied by two electrons, in the presence of realistic confinement potentials produced by depletion gates on top of a GaAs/AlGaAs heterostructure. Such a cell represents the basic building block for logic architectures based on the concept of quantum cellular automata (QCA) and of ground state computation, which have been proposed as an alternative to traditional transistor-based logic circuits. We have focused on the robustness of the operation of such cells with respect to asymmetries derived from fabrication tolerances. We have developed a two-dimensional model for the calculation of the electron density in a driven cell in response to the polarization state of a driver cell. Our method is based on the one-shot configuration-interaction technique, adapted from molecular chemistry. From the results of our simulations, we conclude that an implementation of QCA logic based on simple ¿hole arrays¿ is not feasible, because of the extreme sensitivity to fabrication tolerances. As an alternative, we propose cells defined by multiple gates, where geometrical asymmetries can be compensated for by adjusting the bias voltages. Even though not immediately applicable to the implementation of logic gates and not suitable for large scale integration, the proposed cell layout should allow an experimental demonstration of a chain of QCA cells.

Aggregate material formulated with MSWI bottom ash and APC fly ash for use as secondary building material

The main goal of this paper is to obtain a granular material formulated with Municipal Solid Waste Incinerarion (MSWI) bottom ash (BA) and air pollution control (APC) ash to be used as secondary building material. Previously, an optimum concrete mixture using both MSWI residues as aggregates was formulated. A compromise between the environmental behaviour and the economy of the process was considered. Unconfined compressive strength and abrasion resistance values were measured in order to evaluate the mechanical properties. From these results, the granular mixture was not suited for certain applications owing to the high BA/APC content and low cement percentages used to reduce the costs of the final product. Nevertheless, the leaching test performed showed that the concentrations of all heavy metals were below the limits established by the current Catalan legislation for their reutilization. Therefore, the material studied might be mainly used in embankments, where high mechanical properties are not needed and environmental safety is assured.

Fostering Collaborative Knowledge Building by the Effective Provision of Knowledge about the Discussion Process

Peer-reviewed

Building wood debris piles benefits avian seed dispersers in burned and logged Mediterranean pine forests

Salvage logging is a common practice carried out in burned forests worldwide, and intended to mitigate the economic losses caused by wildfires. Logging implies an additional disturbance occurring shortly after fire, although its ecological effects can be somewhat mitigated by leaving wood debris on site. The composition of the bird community and its capacity to provide ecosystem services such as seed dispersal offleshy-fruited plants have been shown to be affected by postfire logging. We assessedthe effects of the habitat structure resulting from different postfire management practices on the bird community, in three burned pine forests in Catalonia (western Mediterranean). For this purpose, we focused on the group of species that is responsible for seed dispersal, a process which takes place primarily during the winter in theMediterranean basin. In addition, we assessed microhabitat selection by seed disperser birds in such environments in relation to management practices. Our results showed a significant, positive relationship between the density of wood debris piles and the abundance of seed disperser birds. Furthermore, such piles were the preferredmicrohabitat of these species. This reveals an important effect of forest management on seed disperser birds, which is likely to affect the dynamics of bird-dependent seed dispersal. Thus, building wood debris piles can be a useful practice for the conservation of both the species and their ecosystem services, while also being compatible with timber harvesting

A Comparison of the Environmental Impact of Different AOPs: Risk Indexes

Today, environmental impact associated with pollution treatment is a matter of great concern. A method is proposed for evaluating environmental risk associated with Advanced Oxidation Processes (AOPs) applied to wastewater treatment. The method is based on the type of pollution (wastewater, solids, air or soil) and on materials and energy consumption. An Environmental Risk Index (E), constructed from numerical criteria provided, is presented for environmental comparison of processes and/or operations. The Operation Environmental Risk Index (EOi) for each of the unit operations involved in the process and the Aspects Environmental Risk Index (EAj) for process conditions were also estimated. Relative indexes were calculated to evaluate the risk of each operation (E/NOP) or aspect (E/NAS) involved in the process, and the percentage of the maximum achievable for each operation and aspect was found. A practical application of the method is presented for two AOPs: photo-Fenton and heterogeneous photocatalysis with suspended TiO2 in Solarbox. The results report the environmental risks associated with each process, so that AOPs tested and the operations involved with them can be compared.