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  • Articles  (29,320)
  • MDPI Publishing  (29,320)
  • Energy, Environment Protection, Nuclear Power Engineering  (28,792)
  • Biology  (528)
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  • 11
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    Energies, Vol. 8, Pages 8594-8612: A Real-Time Joint Estimator for Model Parameters and State of Charge of Lithium-Ion Batteries in Electric Vehicles (2015)
    MDPI Publishing
    In: Energies
    Details
    Publication Date: 2015-08-13
    Description: Accurate state of charge (SoC) estimation of batteries plays an important role in promoting the commercialization of electric vehicles. The main work to be done in accurately determining battery SoC can be summarized in three parts. (1) In view of the model-based SoC estimation flow diagram, the n-order resistance-capacitance (RC) battery model is proposed and expected to accurately simulate the battery’s major time-variable, nonlinear characteristics. Then, the mathematical equations for model parameter identification and SoC estimation of this model are constructed. (2) The Akaike information criterion is used to determine an optimal tradeoff between battery model complexity and prediction precision for the n-order RC battery model. Results from a comparative analysis show that the first-order RC battery model is thought to be the best based on the Akaike information criterion (AIC) values. (3) The real-time joint estimator for the model parameter and SoC is constructed, and the application based on two battery types indicates that the proposed SoC estimator is a closed-loop identification system where the model parameter identification and SoC estimation are corrected mutually, adaptively and simultaneously according to the observer values. The maximum SoC estimation error is less than 1% for both battery types, even against the inaccurate initial SoC.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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  • 12
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    Energies, Vol. 8, Pages 8516-8536: An Iterative Method to Derive the Equivalent Centrifugal Compressor Performance at Various Operating Conditions: Part II: Modeling of Gas Properties Impact (2015)
    MDPI Publishing
    In: Energies
    Details
    Publication Date: 2015-08-13
    Description: This is the second part of a study conducted to model the aerothermodynamic impact of suction parameters and gas properties on a multi-stage centrifugal compressor’s performance. A new iterative method has been developed in the first part to derive the equivalent performance at various operating conditions. This approach has been validated to predict the compressor map at different suction pressures and temperatures using the design characteristics as reference values. A further case is included in this paper in order to emphasize the validity of the developed approach to obtain the performance characteristics at various gas compositions. The provided example shows that the performance parameters at different gas mixtures can be predicted to within ±1.34%. Furthermore, the conducted optimization in this paper reveals that the proposed method can be applied for the compressor design evaluation corresponding to the expected variation in suction conditions. Moreover, the examined case study demonstrates the effect of gas properties’ variation on the operating point and aerodynamic stability of the entire compression system. In order to achieve that, a simple approach has been established to assess the contribution of gas properties’ variation to the inefficient and unstable compressor performance based on the available operational data.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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  • 13
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    Energies, Vol. 8, Pages 8537-8561: Torque Distribution Algorithm for an Independently Driven Electric Vehicle Using a Fuzzy Control Method (2015)
    MDPI Publishing
    In: Energies
    Details
    Publication Date: 2015-08-13
    Description: The in-wheel electric vehicle is expected to be a popular next-generation vehicle because an in-wheel system can simplify the powertrain and improve driving performance. In addition, it also has an advantage in that it maximizes driving efficiency through independent torque control considering the motor efficiency. However, there is an instability problem if only the driving torque is controlled in consideration of only the motor efficiency. In this paper, integrated torque distribution strategies are proposed to overcome these problems. The control algorithm consists of various strategies for optimizing driving efficiency, satisfying driver demands, and considering tire slip and vehicle cornering. Fuzzy logic is used to determine the appropriate timing of intervention for each distribution strategy. A performance simulator for in-wheel electric vehicles was developed by using MATLAB/Simulink and CarSim to validate the control strategies. From simulation results under complex driving conditions, the proposed algorithm was verified to improve both the driving stability and fuel economy of the in-wheel vehicle.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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  • 14
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    Energies, Vol. 8, Pages 8482-8496: Measurements of the Aerodynamic Normal Forces on a 12-kW Straight-Bladed Vertical Axis Wind Turbine (2015)
    MDPI Publishing
    In: Energies
    Details
    Publication Date: 2015-08-13
    Description: The knowledge of unsteady forces is necessary when designing vertical axis wind turbines (VAWTs). Measurement data for turbines operating at an open site are still very limited. The data obtained from wind tunnels or towing tanks can be used, but have limited applicability when designing large-scale VAWTs. This study presents experimental data on the normal forces of a 12-kW straight-bladed VAWT operated at an open site north of Uppsala, Sweden. The normal forces are measured with four single-axis load cells. The data are obtained for a wide range of tip speed ratios: from 1.7 to 4.6. The behavior of the normal forces is analyzed. The presented data can be used in validations of aerodynamic models and the mechanical design for VAWTs.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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  • 15
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    Energies, Vol. 8, Pages 8497-8515: An Iterative Method to Derive the Equivalent Centrifugal Compressor Performance at Various Operating Conditions: Part I: Modelling of Suction Parameters Impact (2015)
    MDPI Publishing
    In: Energies
    Details
    Publication Date: 2015-08-13
    Description: This paper introduces a new iterative method to predict the equivalent centrifugal compressor performance at various operating conditions. The presented theoretical analysis and empirical correlations provide a novel approach to derive the entire compressor map corresponding to various suction conditions without a prior knowledge of the detailed geometry. The efficiency model was derived to reflect the impact of physical gas properties, Mach number, and flow and work coefficients. One of the main features of the developed technique is the fact that it considers the variation in the gas properties and stage efficiency which makes it appropriate with hydrocarbons. This method has been tested to predict the performance of two multistage centrifugal compressors and the estimated characteristics are compared with the measured data. The carried comparison revealed a good matching with the actual values, including the stable operation region limits. Furthermore, an optimization study was conducted to investigate the influences of suction conditions on the stage efficiency and surge margin. Moreover, a new sort of presentation has been generated to obtain the equivalent performance characteristics for a constant discharge pressure operation at variable suction pressure and temperature working conditions. A further validation is included in part two of this study in order to evaluate the prediction capability of the derived model at various gas compositions.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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  • 16
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    Energies, Vol. 8, Pages 8562-8572: Gasification of a Dried Sewage Sludge in a Laboratory Scale Fixed Bed Reactor (2015)
    MDPI Publishing
    In: Energies
    Details
    Publication Date: 2015-08-13
    Description: This paper presents an investigation of sewage sludge gasification in a fixed bed gasifier. Experiments were conducted on a laboratory scale fixed bed gasifier. In the experiments, two types of dried sewage sludge were tested and their properties were analysed. Parameters such as air ratio λ = 0.12 to 0.27, gasification agent temperature t = 50 to 250 °C and gasification agent composition ( = 0.21 and  > 0.21) were found to influence on temperature distribution, syngas Lower Heating Value (LHV) and syngas composition. The results indicate that the syngas LHV was found to decrease with increased air ratio for all analyzed cases: cold and preheated air and cold enriched air. The increase in the percentage of the main combustible components was accompanied by a decrease in the concentration of carbon dioxide. Increasing oxygen concentration increased the temperature, which tended to favor the formation of smaller molecules in the gas mixture. Thus, the enriched air medium produced a gas with a higher LHV. In contrast to conventional gasification, gasification process with gasification agent preheating causes that the flux of heat necessary to support endothermic gasification reactions is producing more effective. Air preheating causes increases hydrogen and carbon monoxide production.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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  • 17
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    IJERPH, Vol. 12, Pages 9536-9541: Readiness Visual Analog Scale: A Simple Way to Predict Post-Stroke Smoking Behavior (2015)
    MDPI Publishing
    Details
    Publication Date: 2015-08-14
    Description: Background and Purpose: The aim of the present study was to assess a relationship between readiness to quit and post-stroke smoking behavior. Methods: Eighty-six active smokers with first-ever ischemic stroke were recruited in a tertiary-care stroke unit. The question “Are you ready to quit smoking within the next month?” with yes/no responses and the 10-cm readiness visual analog scale (VAS) was administered during the anti-smoking intervention. Smoking status was verified at the 3- and 12-month follow-up. Results: The readiness VAS score at hospitalization was significantly lower in patients classified as smokers as compared to patients classified as non-smokers. The readiness score 〈5 cm was a significant predictor of smoking at the 3-month (OR, 7.3) and 12-month follow-up (OR, 4.9). Conclusions: The present results suggest that the readiness VAS can be used as a simple and inexpensive instrument for early identification of patients who continue to smoke after stroke.
    Print ISSN: 1661-7827
    Electronic ISSN: 1660-4601
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Published by MDPI Publishing
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  • 18
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    Water, Vol. 7, Pages 4446-4476: Simulation of Water Level Fluctuations in a Hydraulic System Using a Coupled Liquid-Gas Model (2015)
    MDPI Publishing
    In: Water
    Details
    Publication Date: 2015-08-14
    Description: A model for simulating vertical water level fluctuations with coupled liquid and gas phases is presented. The Preissmann implicit scheme is used to linearize the governing equations for one-dimensional transient flow for both liquid and gas phases, and the linear system is solved using the chasing method. Some classical cases for single liquid and gas phase transients in pipelines and networks are studied to verify that the proposed methods are accurate and reliable. The implicit scheme is extended using a dynamic mesh to simulate the water level fluctuations in a U-tube and an open surge tank without consideration of the gas phase. Methods of coupling liquid and gas phases are presented and used for studying the transient process and interaction between the phases, for gas phase limited in a chamber and gas phase transported in a pipeline. In particular, two other simplified models, one neglecting the effect of the gas phase on the liquid phase and the other one coupling the liquid and gas phases asynchronously, are proposed. The numerical results indicate that the asynchronous model performs better, and are finally applied to a hydropower station with surge tanks and air shafts to simulate the water level fluctuations and air speed.
    Electronic ISSN: 2073-4441
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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  • 19
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    IJERPH, Vol. 12, Pages 9639-9657: Prevalence of Polyherbacy in Ambulatory Visits to Traditional Chinese Medicine Clinics in Taiwan (2015)
    MDPI Publishing
    Details
    Publication Date: 2015-08-15
    Description: Patients with a polyherbal prescription are more likely to receive duplicate medications and thus suffer from adverse drug reactions. We conducted a population-based retrospective study to examine the items of Chinese herbal medicine (CHM) per prescription in the ambulatory care of traditional Chinese medicine (TCM) in Taiwan. We retrieved complete TCM ambulatory visit datasets for 2010 from the National Health Insurance database in Taiwan. A total of 59,790 patients who received 313,482 CHM prescriptions were analyzed. Drug prescriptions containing more than five drugs were classified as polyherbal prescriptions; 41.6% of patients were given a polyherbal prescription. There were on average 5.2 ± 2.5 CHMs: 2.3 ± 1.1 compound herbal formula items, and 3.0 ± 2.5 single Chinese herb items in a single prescription. Approximately 4.6% of patients were prescribed 10 CHMs or more. Men had a lower odds ratio (OR) among polyherbal prescriptions (OR = 0.96, 95% confidence interval [CI] 0.92–0.99), and middle-aged patients (35–49 years) had the highest frequency of polyherbal prescription (OR = 1.19, 95% CI = 1.13–1.26). Patients with neoplasm, skin and subcutaneous tissue disease, or genitourinary system disease were more likely to have a polyherbal prescription; OR = 2.20 (1.81–2.67), 1.65 (1.50–1.80), and 1.52 (1.40–1.64), respectively. Polyherbal prescription is widespread in TCM in Taiwan. Potential herb interactions and iatrogenic risks associated with polyherbal prescriptions should be monitored.
    Print ISSN: 1661-7827
    Electronic ISSN: 1660-4601
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
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  • 20
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    Energies, Vol. 8, Pages 8704-8715: CO2 Fixation by Membrane Separated NaCl Electrolysis (2015)
    MDPI Publishing
    In: Energies
    Details
    Publication Date: 2015-08-15
    Description: Atmospheric concentrations of carbon dioxide (CO2), a major cause of global warming, have been rising due to industrial development. Carbon capture and storage (CCS), which is regarded as the most effective way to reduce such atmospheric CO2 concentrations, has several environmental and technical disadvantages. Carbon capture and utilization (CCU), which has been introduced to cover such disadvantages, makes it possible to capture CO2, recycling byproducts as resources. However, CCU also requires large amounts of energy in order to induce reactions. Among existing CCU technologies, the process for converting CO2 into CaCO3 requires high temperature and high pressure as reaction conditions. This study proposes a method to fixate CaCO3 stably by using relatively less energy than existing methods. After forming NaOH absorbent solution through electrolysis of NaCl in seawater, CaCO3 was precipitated at room temperature and pressure. Following the experiment, the resulting product CaCO3 was analyzed with Fourier transform infrared spectroscopy (FT-IR); field emission scanning electron microscopy (FE-SEM) image and X-ray diffraction (XRD) patterns were also analyzed. The results showed that the CaCO3 crystal product was high-purity calcite. The study shows a successful method for fixating CO2 by reducing carbon dioxide released into the atmosphere while forming high-purity CaCO3.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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