7,769 research outputs found

    Thermodynamic rarity and the loss of mineralwealth

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    The second law of thermodynamics and, specifically, exergy analysis have been traditionally used for the assessment and optimization of energy systems. Nevertheless, as shown in this paper, exergy could also constitute a powerful tool for the evaluation of mineral commodities. That said, new or re-defined exergy-based concepts need to be developed. This paper presents Thanatia as a baseline for evaluating the exergy of any mineral in the crust and opens the door to discuss the “thermodynamic rarity” concept as a basis for exergy analyses for mineral systems. Thermodynamic rarity is understood as the amount of exergy needed to obtain a given mineral from a completely degraded state, denoted as Thanatia. The rarer the mineral, the greater the associated exergy costs. It quantifies value, as it relates to concentration, chemical composition and cohesion, key aspects that determine whether a mine is exploitable. The theory further allows one to quantify the gradual loss of mineral capital on Earth as a consequence of “rarefaction processes” that occur at a mineral’s end-of-life, when a commodity is wasted, and at its beginning-of-life, where mining ore grades decline after extraction

    The ATLAS TileCal Read-Out Drivers Signal Reconstruction

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    TileCal is the hadronic calorimeter of the ATLAS experiment at the LHC collider at CERN. The Read-Out Drivers (ROD) are the core of the off-detector electronics. The main components of the RODs are the Digital Signal Processor (DSP) placed on the Processing Unit (PU) dautherboards. This paper describes the DSP code and its performance with calibration and real data. The code is divided into two different parts: the first part contains the core functionalities and the second one the reconstruction algorithms. The core acts as an operating system and it controls the configuration, the data reception, transmission, online monitoring and the synchronization between front-end data and the Trigger information. The reconstruction algorithms implemented on the DSP are the Optimal Filtering (OF), Muon Tagging (MTag) and Total Transverse Energy (ET) calculation. The OF algorithm reconstructs the deposited energy and the arrival time of the data on every calorimeter cell within a front-end module. This reconstructed energy is used by the MTag algorithm to tag low transverse momentum muons that may escape the ATLAS muon spectrometer Level 1 trigger whereas the ET algorithm computes the total transverse energy and the projection on X and Y for the entire module that will be used by the Level 2 trigger system. The DSP code performance is being validated with comparisons with offline reconstruction. The DSP performance is evaluated using cali bration data from Charge Injection System

    A physical model suggests that hip-localized balance sense in birds improves state estimation in perching: implications for bipedal robots

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    In addition to a vestibular system, birds uniquely have a balance-sensing organ within the pelvis, called the lumbosacral organ (LSO). The LSO is well developed in terrestrial birds, possibly to facilitate balance control in perching and terrestrial locomotion. No previous studies have quantified the functional benefits of the LSO for balance. We suggest two main benefits of hip-localized balance sense: reduced sensorimotor delay and improved estimation of foot-ground acceleration. We used system identification to test the hypothesis that hip-localized balance sense improves estimates of foot acceleration compared to a head-localized sense, due to closer proximity to the feet. We built a physical model of a standing guinea fowl perched on a platform, and used 3D accelerometers at the hip and head to replicate balance sense by the LSO and vestibular systems. The horizontal platform was attached to the end effector of a 6 DOF robotic arm, allowing us to apply perturbations to the platform analogous to motions of a compliant branch. We also compared state estimation between models with low and high neck stiffness. Cross-correlations revealed that foot-to-hip sensing delays were shorter than foot-to-head, as expected. We used multi-variable output error state-space (MOESP) system identification to estimate foot-ground acceleration as a function of hip- and head-localized sensing, individually and combined. Hip-localized sensors alone provided the best state estimates, which were not improved when fused with head-localized sensors. However, estimates from head-localized sensors improved with higher neck stiffness. Our findings support the hypothesis that hip-localized balance sense improves the speed and accuracy of foot state estimation compared to head-localized sense. The findings also suggest a role of neck muscles for active sensing for balance control: increased neck stiffness through muscle co-contraction can improve the utility of vestibular signals. Our engineering approach provides, to our knowledge, the first quantitative evidence for functional benefits of the LSO balance sense in birds. The findings support notions of control modularity in birds, with preferential vestibular sense for head stability and gaze, and LSO for body balance control,respectively. The findings also suggest advantages for distributed and active sensing for agile locomotion in compliant bipedal robots

    Exergy assessment of topsoil fertility

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    Soil degradation, affecting around 38% of the world''s cropland, threatens the global food supply. Due to the soil''s complexity, the measure of soil degradation that involves the loss of soil fertility due to crop system management processes represents an unsolved problem. Exergy is a property with the potential to be used in soil fertility and/or degradation analysis. A methodology to determine the exergy value fenced in a fertile soil due to its inorganic and organic components is established in this study and will be applied to evaluate soil fertility, degradation, and quality. As a first step, the exergy of perfect topsoil with optimum characteristics called "OptSOIL" is determined. The "OptSOIL" is established by agronomic expertise and will allow establishing a general theoretical reference suitable to execute exergy assessments of soils and compare the degradation grade of any soil concerning the best possible. Consequently, we introduce a perfect fertile planetary crust made of “OptNUT” and “OptSOM” invariant and independent of the different local textures, but not independent of their water content and aeration. We call this imaginary crust -copiously fertile- Pristinia as opposed to Thanatia, a dead state referring to abiotic resources. Thus, any real agricultural soil will be an intermediate soil between Pristinia and Thanatia. This idea might serve to quantitatively diagnose an assessment of all the concepts by which soil is degraded. The methodology has been validated through laboratory agronomic tests for different soils, concluding that exergy is a rigorous indicator to measure topsoil fertility. © 2021 The Author

    Exergoecology assessment of mineral exports from Latin America: Beyond a tonnage perspective

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    Latin America has traditionally been a raw material supplier since colonial times. In this paper, we analyze mineral exports from an exergoecology perspective from twenty countries in Latin American (LA-20). We apply material flow analysis (MFA) principles along with the concept of the exergy replacement cost (ERC), which considers both quantity and thermodynamic quality of minerals, reflecting their scarcity in the crust. ERC determines the energy that would be required to recover minerals to their original conditions in the mines once they have been totally dispersed into the Earth''s crust, with prevailing technology. Using ERC has helped us identify the importance of certain traded minerals that could be overlooked in a traditional MFA based on a mass basis only. Our method has enabled us to determine mineral balance, both in mass (tonnes) and in ERC terms (Mtoe). Using indicators, both in mass and ERC, we have assessed the self-sufficiency and dependency of the region. We have also analyzed the mineral exports flows from Latin America for 2013. Results show that half of the mineral production from LA-20 was mainly exported. High-quality minerals, such as, gold, silver, and aluminum were largely exported to China and the United States. Extraction of high-quality minerals also implies higher losses of natural stock and environmental overburdens in the region

    Mining energy consumption as a function of ore grade decline: the case of lead and zinc

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    Demand for raw materials is increasing exponentially. To satisfy that demand, more minerals need to be mined from the Earth’s crust. As a result, minerals are being exhausted, and ore grades decline. Lower ore grade mines also mean more energy, which in turn entails fossil fuel emissions and more climate change. This paper estimates the specific energy for the beneficiation process of metals lead and zinc as case studies. The evaluation is performed with specialized software, HSC Chemistry which assesses the specific energy for every stage: comminution, flotation, and refining. Different scenarios have been established to simulate the behavior of a mine when it approaches depletion. Preliminary results show that energy consumption for lead would increase by five times when compared to the current situation if ore grades decrease until the level of tailings, while for zinc by almost two

    Exergy-based assessment of polymers production and recycling: An application to the automotive sector

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    In the last century, the economic growth has been accompanied by a worldwide diffusion of polymers for multiple applications. However, there is a growing attention to the environmental pollution and energy consumption linked to the unconditional use of plastic. In the present work, exergy is used as a measure of the resource consumption during the life cycle of polymers. Nine commercially diffused polymers are chosen, and their production chains are identified according to the “grave to cradle” approach. The global Embodied Exergy (EE) is calculated as the sum of the contribution of each step of the chain, including the production process and the Exergy Replacement Cost (ERC) of the fossil fuel. Then, recycling routes and the associated exergy consumption are analysed. Thermodynamic recycling indexes are developed depending on the final product, namely the crude polymeric material and the oil derivatives or structural molecules. The main results show that some commonly used polymers have a considerable impact in terms of EE (e.g., PET). Recycling indexes encourage the recycling processes, which are always energetically convenient (from 10% to 60% of exergy savings) compared with the production from virgin raw material. Results from EE calculation are used for the thermodynamic assessment of the plastic content of vehicle components, to obtain useful information for recycling practices development. Copyright