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Energies, Volume 5, Issue 9 (September 2012), Pages 3167-3722

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Open AccessArticle Energy and Exergy Analysis and Optimization of Combined Heat and Power Systems. Comparison of Various Systems
Energies 2012, 5(9), 3701-3722; https://doi.org/10.3390/en5093701
Received: 14 July 2012 / Revised: 3 September 2012 / Accepted: 19 September 2012 / Published: 24 September 2012
Cited by 19 | PDF Full-text (516 KB) | HTML Full-text | XML Full-text
Abstract
The paper presents a comparison of various CHP system configurations, such as Vapour Turbine, Gas Turbine, Internal Combustion Engine, External Combustion Engine (Stirling, Ericsson), when different thermodynamic criteria are considered, namely the first law efficiency and exergy efficiency. Thermodynamic optimization of these systems
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The paper presents a comparison of various CHP system configurations, such as Vapour Turbine, Gas Turbine, Internal Combustion Engine, External Combustion Engine (Stirling, Ericsson), when different thermodynamic criteria are considered, namely the first law efficiency and exergy efficiency. Thermodynamic optimization of these systems is performed intending to maximize the exergy, when various practical related constraints (imposed mechanical useful energy, imposed heat demand, imposed heat to power ratio) or main physical limitations (limited heat availability, maximum system temperature allowed, thermo-mechanical constraints) are taken into account. A sensitivity analysis to model parameters is given. The results have shown that the various added constraints were useful for the design allowing to precise the influence of the model main parameters on the system design. Future perspective of the work and recommendations are stated. Full article
(This article belongs to the Special Issue Exergy Analysis of Energy Systems)
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Open AccessArticle A Revisit to the Hydrogen Desorption/Absorption Behaviors of LiAlH4/LiBH4: Effects of Catalysts
Energies 2012, 5(9), 3691-3700; https://doi.org/10.3390/en5093691
Received: 31 July 2012 / Revised: 5 September 2012 / Accepted: 19 September 2012 / Published: 21 September 2012
Cited by 4 | PDF Full-text (296 KB) | HTML Full-text | XML Full-text
Abstract
The hydrogen desorption/absorption behaviors of LiAlH4/LiBH4 with a focus on the effects of catalysts, namely TiCl3, TiO2, VCl3, and ZrCl4, were investigated using a thermal-volumetric apparatus. The hydrogen desorption was performed from
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The hydrogen desorption/absorption behaviors of LiAlH4/LiBH4 with a focus on the effects of catalysts, namely TiCl3, TiO2, VCl3, and ZrCl4, were investigated using a thermal-volumetric apparatus. The hydrogen desorption was performed from room temperature to 300 °C with a heating rate of 2 °C min−1. The LiAlH4–LiBH4 mixture with a molar ratio of 2:1 decomposed between 100 and 220 °C, and the hydrogen desorption capacity reached up to 6.6 wt %. Doping 1 mol % of a catalyst to the mixture resulted in the two-step decomposition and a decrease in the hydrogen desorption temperature. All the doped samples provided lower amountz of desorbed hydrogen than that obtained from the undoped one. No hydrogen absorption was observed under 8.5 MPa of hydrogen pressure and 300 °C for 6 h. Despite the fact each of the catalysts may affect the hydrogen storage behaviors of the mixture differently, none resulted in a change in the sample reversibility. Full article
(This article belongs to the Special Issue Hydrogen Energy and Fuel Cells)
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Open AccessArticle Dispatch Method for Independently Owned Hydropower Plants in the Same River Flow
Energies 2012, 5(9), 3674-3690; https://doi.org/10.3390/en5093674
Received: 23 July 2012 / Revised: 16 August 2012 / Accepted: 13 September 2012 / Published: 19 September 2012
Cited by 6 | PDF Full-text (449 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a coexistence model for two independent companies both operating hydropower plants in the same river flow, based on a case study of the Cetina river basin in Croatia. Companies are participants of the day-ahead electricity market. The incumbent company owns
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This paper proposes a coexistence model for two independent companies both operating hydropower plants in the same river flow, based on a case study of the Cetina river basin in Croatia. Companies are participants of the day-ahead electricity market. The incumbent company owns the existing hydropower plants and holds concessions for the water. The new company decides to build a pump storage hydropower plant that uses one of the existing reservoirs as its lower reservoir. Meeting reservoir water balance is affected by decisions by both companies which are independently seeking maximal profit. Methods for water use settlement and preventing of spillage are proposed. A mixed-integer linear programming approach is used. Head effects on output power levels are also considered. Existences of dispatches that satisfy both companies are shown. Full article
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Open AccessArticle An Improved Quantum-Behaved Particle Swarm Optimization Method for Economic Dispatch Problems with Multiple Fuel Options and Valve-Points Effects
Energies 2012, 5(9), 3655-3673; https://doi.org/10.3390/en5093655
Received: 2 July 2012 / Revised: 10 August 2012 / Accepted: 22 August 2012 / Published: 19 September 2012
Cited by 15 | PDF Full-text (628 KB) | HTML Full-text | XML Full-text
Abstract
Quantum-behaved particle swarm optimization (QPSO) is an efficient and powerful population-based optimization technique, which is inspired by the conventional particle swarm optimization (PSO) and quantum mechanics theories. In this paper, an improved QPSO named SQPSO is proposed, which combines QPSO with a selective
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Quantum-behaved particle swarm optimization (QPSO) is an efficient and powerful population-based optimization technique, which is inspired by the conventional particle swarm optimization (PSO) and quantum mechanics theories. In this paper, an improved QPSO named SQPSO is proposed, which combines QPSO with a selective probability operator to solve the economic dispatch (ED) problems with valve-point effects and multiple fuel options. To show the performance of the proposed SQPSO, it is tested on five standard benchmark functions and two ED benchmark problems, including a 40-unit ED problem with valve-point effects and a 10-unit ED problem with multiple fuel options. The results are compared with differential evolution (DE), particle swarm optimization (PSO) and basic QPSO, as well as a number of other methods reported in the literature in terms of solution quality, convergence speed and robustness. The simulation results confirm that the proposed SQPSO is effective and reliable for both function optimization and ED problems. Full article
(This article belongs to the Special Issue Hybrid Advanced Techniques for Forecasting in Energy Sector)
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Open AccessArticle An Innovative Reconfigurable Integrated Converter Topology Suitable for Distributed Generation
Energies 2012, 5(9), 3640-3654; https://doi.org/10.3390/en5093640
Received: 30 July 2012 / Revised: 5 September 2012 / Accepted: 13 September 2012 / Published: 18 September 2012
Cited by 19 | PDF Full-text (574 KB) | HTML Full-text | XML Full-text
Abstract
The electricity market and environmental concerns, with wide utilization of renewable sources, have improved the diffusion of distributed generation units changing the operations of distribution grids from passive networks to microgrids. A microgrid includes a cluster of electrical loads, energy storage devices and
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The electricity market and environmental concerns, with wide utilization of renewable sources, have improved the diffusion of distributed generation units changing the operations of distribution grids from passive networks to microgrids. A microgrid includes a cluster of electrical loads, energy storage devices and microsources, which provide both power and heat to their local area. A microgrid has usually one connection point to the utility grid through power electronic converters placed at customers’ sites. This paper analyses a Reconfigurable Integrated Converter (RIC) used for a domestic microgrid with inputs from the AC mains and photovoltaic arrays, and two DC outputs at different voltage levels. A RIC as a dual-boost DC-DC converter is proposed, modelled and analysed in the paper. The advantages of such a topology in comparison with traditional boost converters are outlined. Reported simulations results give evidence on the controllability of this converter and the capability of achieving the desired voltage outputs with reduced ripple. Full article
(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)
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Open AccessArticle Preliminary Ray Tracing and Experimental Study on the Effect of Mirror Coating on the Optical Efficiency of a Solid Dielectric Compound Parabolic Concentrator
Energies 2012, 5(9), 3627-3639; https://doi.org/10.3390/en5093627
Received: 4 May 2012 / Revised: 21 June 2012 / Accepted: 8 September 2012 / Published: 18 September 2012
Cited by 20 | PDF Full-text (1322 KB) | HTML Full-text | XML Full-text
Abstract
This study aims to determine the necessity of applying a mirror coating on the side of a truncated solid dielectric CPC (compound parabolic concentrator) since ray tracing analysis has revealed that part of the incoming rays do not undergo total internal reflection, even
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This study aims to determine the necessity of applying a mirror coating on the side of a truncated solid dielectric CPC (compound parabolic concentrator) since ray tracing analysis has revealed that part of the incoming rays do not undergo total internal reflection, even within the half acceptance angle of the CPC. An experiment was designed and conducted indoors and outdoors to study the effect of mirror coating on the optical performance of a solid dielectric CPC. Ray tracing was also employed for the detailed analysis and its results are compared with the measurements. Based on these, a concept of partial coating is proposed and verified through simulation. The results show that a partly coated solid dielectric CPC may have a better optical efficiency than a solid CPC without coating for a certain range of incidence angles. Full article
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Open AccessArticle Effect of Smart Rotor Control Using a Deformable Trailing Edge Flap on Load Reduction under Normal and Extreme Turbulence
Energies 2012, 5(9), 3608-3626; https://doi.org/10.3390/en5093608
Received: 18 June 2012 / Revised: 20 August 2012 / Accepted: 13 September 2012 / Published: 18 September 2012
Cited by 17 | PDF Full-text (1157 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a newly developed aero-servo-elastic platform for implementing smart rotor control and shows its effectiveness with aerodynamic loads on large-scale offshore wind turbines. The platform was built by improving the FAST/Aerodyn codes with the integration of an external deformable trailing edge
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This paper presents a newly developed aero-servo-elastic platform for implementing smart rotor control and shows its effectiveness with aerodynamic loads on large-scale offshore wind turbines. The platform was built by improving the FAST/Aerodyn codes with the integration of an external deformable trailing edge flap controller in the Matlab/Simulink software. Smart rotor control was applied to an Upwind/NREL 5 MW reference wind turbine under various operating wind conditions in accordance with the IEC Normal Turbulence Model (NTM) and Extreme Turbulence Model (ETM). Results showed that, irrespective of whether the NTM or ETM case was considered, aerodynamic load in terms of blade flapwise root moment and tip deflection were effectively reduced. Furthermore, the smart rotor control also positively affected generator power, pitch system and tower load. These results laying a foundation for a future migration of the “smart rotor control” concept into the design of large-scale offshore wind turbines. Full article
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Open AccessArticle Harmonic Analysis and Fault-Tolerant Capability of a Semi-12-Phase Permanent-Magnet Synchronous Machine Used for EVs
Energies 2012, 5(9), 3586-3607; https://doi.org/10.3390/en5093586
Received: 11 June 2012 / Revised: 1 September 2012 / Accepted: 5 September 2012 / Published: 17 September 2012
Cited by 7 | PDF Full-text (1546 KB) | HTML Full-text | XML Full-text
Abstract
This paper deals with a fault-tolerant semi-12-phase permanent-magnet synchronous machine (PMSM) used for electric vehicles. High fault-tolerant and low toque ripple features are achieved by employing fractional slot concentrated windings (FSCWs) and open windings. Excessive magnetomotive force (MMF) harmonic components can lead to
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This paper deals with a fault-tolerant semi-12-phase permanent-magnet synchronous machine (PMSM) used for electric vehicles. High fault-tolerant and low toque ripple features are achieved by employing fractional slot concentrated windings (FSCWs) and open windings. Excessive magnetomotive force (MMF) harmonic components can lead to thermal demagnetization of rotor magnets as well as high core loss. An improved all-teeth-wound winding disposition that changes the winding factor of each harmonic is applied to suppress harmonics. A relatively large slot leakage inductance that limits the short-circuit current (SCC) induced in the short-circuited winding is proposed to deal with short-circuit fault. Fault-tolerant controls up to two phases open circuited are investigated in this paper based on keeping the same torque-producing MMF. The fault-tolerant control strategies corresponding to each faulty mode are studied and compared to ensure high performance operation. Full article
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Open AccessArticle Performance Analysis and Optimization of a Solar Powered Stirling Engine with Heat Transfer Considerations
Energies 2012, 5(9), 3573-3585; https://doi.org/10.3390/en5093573
Received: 23 July 2012 / Revised: 13 August 2012 / Accepted: 4 September 2012 / Published: 17 September 2012
Cited by 15 | PDF Full-text (417 KB) | HTML Full-text | XML Full-text
Abstract
This paper investigates the optimization of the performance of a solar powered Stirling engine based on finite-time thermodynamics. Heat transference in the heat exchangers between a concentrating solar collector and the Stirling engine is studied. The irreversibility of a Stirling engine is considered
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This paper investigates the optimization of the performance of a solar powered Stirling engine based on finite-time thermodynamics. Heat transference in the heat exchangers between a concentrating solar collector and the Stirling engine is studied. The irreversibility of a Stirling engine is considered with the heat transfer following Newton's law. The power generated by a Stirling engine is used as an objective function for maximum power output design with the concentrating solar collector temperature and the engine thermal efficiency as the optimization parameters. The maximum output power of engine and its corresponding system parameters are determined using a genetic algorithm. Full article
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Open AccessArticle Energy Efficiency in the Brazilian Pulp and Paper Industry
Energies 2012, 5(9), 3550-3572; https://doi.org/10.3390/en5093550
Received: 29 May 2012 / Revised: 16 August 2012 / Accepted: 21 August 2012 / Published: 17 September 2012
Cited by 8 | PDF Full-text (281 KB) | HTML Full-text | XML Full-text
Abstract
Industrial energy efficiency has received increasing attention in many countries because of its importance in the pursuit of energy supply security, increased economic competitiveness and in the mitigation of greenhouse gases emissions. This paper aimed to evaluate the energy consumption development of the
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Industrial energy efficiency has received increasing attention in many countries because of its importance in the pursuit of energy supply security, increased economic competitiveness and in the mitigation of greenhouse gases emissions. This paper aimed to evaluate the energy consumption development of the Brazilian pulp and paper industry through an energy decomposition analysis and an energy efficiency index approach over a 30 years period. An international comparison with other important paper-producing countries (i.e., Canada, United States of America, Finland and Sweden) was carried out. It was concluded that despite a significant increase in the energy efficiency levels, responsible for 5.6 PJ savings in electricity consumption and for 38.6 PJ savings in fuels consumption between 1979 and 2009, a saving potential of 7.8 PJ and 146.2 PJ related to the annual consumption of electricity and fuels, respectively, could be identified in the Brazilian pulp and paper industry. Among the countries evolved in the international comparison, both the Swedish and Finnish industries were the most efficient, followed by the Brazilian, American and Canadian, the latter being the only one where there was a reduction in the energy efficiency levels from 1979 to 2009. Full article
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Open AccessArticle A Method for Balancing a Single-Phase Loaded Three-Phase Induction Generator
Energies 2012, 5(9), 3534-3549; https://doi.org/10.3390/en5093534
Received: 18 May 2012 / Revised: 23 August 2012 / Accepted: 10 September 2012 / Published: 13 September 2012
Cited by 3 | PDF Full-text (455 KB) | HTML Full-text | XML Full-text
Abstract
When a three-phase induction generator (IG) supplies unbalanced loads, its terminal voltages and line currents are also unbalanced, which may cause the IG to overheat and need to be derated. A single-phase loaded self-excited induction generator (SEIG) works under most unfavorable load unbalance
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When a three-phase induction generator (IG) supplies unbalanced loads, its terminal voltages and line currents are also unbalanced, which may cause the IG to overheat and need to be derated. A single-phase loaded self-excited induction generator (SEIG) works under most unfavorable load unbalance conditions. This paper proposes a three-capacitor circuit scheme and a method to find the values of the self-excitation capacitors that allow the SEIG to be balanced. The SEIG is modeled by a two-port network equivalent circuit that resolves the SEIG into its positive- and negative-sequence circuits associated with the self-excitation capacitors and the load. The network can then be analyzed by common AC circuit analysis techniques. Successful results for balancing the SEIG supplying a single-phase load have been achieved by properly choosing the values of the excitation capacitors. The proposed method has also been validated by experiments on a 0.37 kW SEIG. Full article
(This article belongs to the Special Issue Electrical Power and Energy Systems)
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Open AccessArticle Molecular Dynamics Simulations of Clathrate Hydrates on Specialised Hardware Platforms
Energies 2012, 5(9), 3526-3533; https://doi.org/10.3390/en5093526
Received: 29 June 2012 / Revised: 28 August 2012 / Accepted: 29 August 2012 / Published: 12 September 2012
Cited by 12 | PDF Full-text (191 KB) | HTML Full-text | XML Full-text
Abstract
Classical equilibrium molecular dynamics (MD) simulations have been performed to investigate the computational performance of the Simple Point Charge (SPC) and TIP4P water models applied to simulation of methane hydrates, and also of liquid water, on a variety of specialised hardware platforms, in
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Classical equilibrium molecular dynamics (MD) simulations have been performed to investigate the computational performance of the Simple Point Charge (SPC) and TIP4P water models applied to simulation of methane hydrates, and also of liquid water, on a variety of specialised hardware platforms, in addition to estimation of various equilibrium properties of clathrate hydrates. The FPGA-based accelerator MD-GRAPE 3 was used to accelerate substantially the computation of non-bonded forces, while GPU-based platforms were also used in conjunction with CUDA-enabled versions of the LAMMPS MD software packages to reduce computational time dramatically. The dependence of molecular system size and scaling with number of processors was also investigated. Considering performance relative to power consumption, it is seen that GPU-based computing is quite attractive. Full article
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Open AccessReview Biotechnological Utilization with a Focus on Anaerobic Treatment of Cheese Whey: Current Status and Prospects
Energies 2012, 5(9), 3492-3525; https://doi.org/10.3390/en5093492
Received: 30 May 2012 / Revised: 9 August 2012 / Accepted: 5 September 2012 / Published: 10 September 2012
Cited by 27 | PDF Full-text (537 KB) | HTML Full-text | XML Full-text
Abstract
Cheese whey utilization is of major concern nowadays. Its high organic matter content, in combination with the high volumes produced and limited treatment options make cheese whey a serious environmental problem. However, the potential production of biogas (methane), hydrogen or other marketable products
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Cheese whey utilization is of major concern nowadays. Its high organic matter content, in combination with the high volumes produced and limited treatment options make cheese whey a serious environmental problem. However, the potential production of biogas (methane), hydrogen or other marketable products with a simultaneous high COD reduction through appropriate treatment proves that cheese whey must be considered as an energy resource rather than a pollutant. The presence of biodegradable components in the cheese whey coupled with the advantages of anaerobic digestion processes over other treatment methods makes anaerobic digestion an attractive and suitable treatment option. This paper intends to review the most representative applications of anaerobic treatment of cheese whey currently being exploited and under research. Moreover, an effort has been made to categorize the common characteristics of the various research efforts and find a comparative basis, as far as their results are concerned. In addition, a number of dairy industries already using such anaerobic digestion systems are presented. Full article
(This article belongs to the Special Issue Biomass and Biofuels 2012)
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Open AccessArticle Experimental Study on Frost Height of Round Plate Fin-Tube Heat Exchangers for Mobile Heat Pumps
Energies 2012, 5(9), 3479-3491; https://doi.org/10.3390/en5093479
Received: 23 May 2012 / Revised: 4 June 2012 / Accepted: 9 July 2012 / Published: 10 September 2012
Cited by 6 | PDF Full-text (515 KB) | HTML Full-text | XML Full-text
Abstract
The objective of this study was to provide experimental data that could be used to predict frost growth and frost performance of a round plate fin-tube heat exchanger for low temperature heat pumps used in zero emission vehicles under cold weather conditions. In
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The objective of this study was to provide experimental data that could be used to predict frost growth and frost performance of a round plate fin-tube heat exchanger for low temperature heat pumps used in zero emission vehicles under cold weather conditions. In this study, round plate fin-tube heat exchangers were tested with variation of the fin space, air flow rate, relative humidity, and inlet air temperature. Frost height was measured and considered with the boundary layer interruption between fins. Frost height for 8.0 mm of fin space was increased by approximately 91.9% with an increase of relative humidity from 50.0% to 80.0%. The growth rate of frost height at 1.2 m3/min was observed to be 13.0% greater than that at 0.8 m3/min. Finally, the variation of the blockage ratio with fin space would be an important reference for designing advanced heat exchangers that operate under cold weather conditions. Full article
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Open AccessArticle The Economic Cost of Unsupplied Diesel Product in Korea Using Input-Output Analysis
Energies 2012, 5(9), 3465-3478; https://doi.org/10.3390/en5093465
Received: 20 May 2012 / Revised: 27 August 2012 / Accepted: 27 August 2012 / Published: 6 September 2012
Cited by 1 | PDF Full-text (245 KB) | HTML Full-text | XML Full-text
Abstract
Diesel is an essential factor in industrial production and development, and thus its stable supply is a crucial element for economic growth. The supply shortage of diesel has massive economic costs, namely supply shortage costs. This paper attempts to apply input-output (I-O) analysis
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Diesel is an essential factor in industrial production and development, and thus its stable supply is a crucial element for economic growth. The supply shortage of diesel has massive economic costs, namely supply shortage costs. This paper attempts to apply input-output (I-O) analysis to measuring the supply shortage cost of industrial diesel in Korea by finding an optimal way of allocating the limited diesel resources to different sectors according to the objective of maximizing overall value-added. To this end, a static I-O framework is presented using a recently published I-O table. The results indicate that the marginal cost of unsupplied diesel ranges from KRW 716 (USD 0.65) to KRW 113,376 (USD 103.07) per liter and these costs depend not only on the shortage rate of each non-diesel sector but also on the level of its own final demand. The quantitative results are useful for policy-makers to set economic reliability standards, develop optimum curtailment levels and priorities, and plan curtailment strategies for diesel supply and demand. Full article
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