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Appl. Sci., Volume 7, Issue 3 (March 2017)

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Cover Story (view full-size image) One of the major challenges in the laser-based additive manufacturing is the severe limitation on [...] Read more.
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Open AccessArticle
Dark Solitons and Grey Solitons in Waveguide Arrays with Long-Range Linear Coupling Effects
Appl. Sci. 2017, 7(3), 311; https://doi.org/10.3390/app7030311
Received: 23 December 2016 / Revised: 14 March 2017 / Accepted: 17 March 2017 / Published: 22 March 2017
Cited by 1 | Viewed by 1114 | PDF Full-text (1456 KB) | HTML Full-text | XML Full-text
Abstract
In J. Phys. Soc. Jpn. 83, 034404 (2014), we designed a scheme of waveguide arrays with long-range linear coupling effects and studied the bright solitons in this system. In this paper, we further study the dynamics of dark and grey solitons in [...] Read more.
In J. Phys. Soc. Jpn. 83, 034404 (2014), we designed a scheme of waveguide arrays with long-range linear coupling effects and studied the bright solitons in this system. In this paper, we further study the dynamics of dark and grey solitons in such waveguide arrays. The numerical simulations show that the stabilities of dark solitons and grey solitons depend on the normalized decay length and the scaled input power. The width of dark solitons and the grey level of grey solitons are studied. Our results may contribute to the understanding of discrete solitons in long-range linear coupling waveguide arrays, and may have potential applications in optical communications and all-optical networks. Full article
(This article belongs to the Special Issue Guided-Wave Optics) Printed Edition available
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Open AccessArticle
Use of the Genetic Algorithm-Based Fuzzy Logic Controller for Load-Frequency Control in a Two Area Interconnected Power System
Appl. Sci. 2017, 7(3), 308; https://doi.org/10.3390/app7030308
Received: 27 February 2017 / Revised: 14 March 2017 / Accepted: 16 March 2017 / Published: 22 March 2017
Cited by 5 | Viewed by 2758 | PDF Full-text (7836 KB) | HTML Full-text | XML Full-text
Abstract
The use of renewable energy resources has created some problems for power systems. One of the most important of these is load frequency control (LFC). In this study, in order to solve the LFC problem, modern control methods were applied to a two [...] Read more.
The use of renewable energy resources has created some problems for power systems. One of the most important of these is load frequency control (LFC). In this study, in order to solve the LFC problem, modern control methods were applied to a two area multi source interconnected power system. A photovoltaic solar power plant (PV-SPP) was also connected, in order to identify the harmful effects on the frequency of the system. A new Genetic-based Fuzzy Logic (GA-FL) controller was designed to control the frequency of the system. For comparison, conventional proportional-integral-derivative (PID), fuzzy logic (FL), and Genetic Algorithm (GA)-PID controllers were also designed. The new control method exhibited a better performance than the conventional and other modern control methods, because of the low overshoot and short settling time. All simulations were realized with the Matlab-Simulink program. Full article
(This article belongs to the Special Issue Distribution Power Systems)
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Open AccessArticle
Experimental Identification and Vibration Control of A Piezoelectric Flexible Manipulator Using Optimal Multi-Poles Placement Control
Appl. Sci. 2017, 7(3), 309; https://doi.org/10.3390/app7030309
Received: 6 January 2017 / Revised: 13 March 2017 / Accepted: 17 March 2017 / Published: 21 March 2017
Cited by 3 | Viewed by 1664 | PDF Full-text (9864 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents experimental identification and vibration suppression of a flexible manipulator with piezoelectric actuators and strain sensors using optimal multi-poles placement control. To precisely identify the system model, a reduced order transfer function with relocated zeros is proposed, and a first-order inertia [...] Read more.
This paper presents experimental identification and vibration suppression of a flexible manipulator with piezoelectric actuators and strain sensors using optimal multi-poles placement control. To precisely identify the system model, a reduced order transfer function with relocated zeros is proposed, and a first-order inertia element is added to the model. Comparisons show the identified model match closely with the experimental results both in the time and frequency domains, and a fit of 97.2% is achieved. Based on the identified model, a full-state multi-poles placement controller is designed, and the optimal locations of the closed loop poles are determined where the move distance of the closed loop poles is the shortest. The feasibility of the proposed controller is validated by simulations. Moreover, the controller is tested for different locations of the closed loop poles, and an excellent performance of the optimal locations of the closed loop poles is shown. Finally, the effectiveness of the proposed controller is demonstrated by experiments. Results show that the vibrations of the expected modes are significantly diminished. Accordingly, multi-mode vibrations of the manipulator are well attenuated. Full article
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Open AccessArticle
Question-Driven Methodology for Analyzing Emergency Room Processes Using Process Mining
Appl. Sci. 2017, 7(3), 302; https://doi.org/10.3390/app7030302
Received: 30 January 2017 / Revised: 7 March 2017 / Accepted: 15 March 2017 / Published: 21 March 2017
Cited by 9 | Viewed by 2091 | PDF Full-text (1193 KB) | HTML Full-text | XML Full-text
Abstract
In order to improve the efficiency and effectiveness of Emergency Rooms (ER), it is important to provide answers to frequently-posed questions regarding all relevant processes executed therein. Process mining provides different techniques and tools that help to obtain insights into the analyzed processes [...] Read more.
In order to improve the efficiency and effectiveness of Emergency Rooms (ER), it is important to provide answers to frequently-posed questions regarding all relevant processes executed therein. Process mining provides different techniques and tools that help to obtain insights into the analyzed processes and help to answer these questions. However, ER experts require certain guidelines in order to carry out process mining effectively. This article proposes a number of solutions, including a classification of the frequently-posed questions about ER processes, a data reference model to guide the extraction of data from the information systems that support these processes and a question-driven methodology specific for ER. The applicability of the latter is illustrated by means of a case study of an ER service in Chile, in which ER experts were able to obtain a better understanding of how they were dealing with episodes related to specific pathologies, triage severity and patient discharge destinations. Full article
(This article belongs to the Special Issue Smart Healthcare) Printed Edition available
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Open AccessCommunication
Universal Voltage Conveyor and its Novel Dual-Output Fully-Cascadable VM APF Application
Appl. Sci. 2017, 7(3), 307; https://doi.org/10.3390/app7030307
Received: 10 February 2017 / Revised: 7 March 2017 / Accepted: 15 March 2017 / Published: 20 March 2017
Cited by 2 | Viewed by 1025 | PDF Full-text (1843 KB) | HTML Full-text | XML Full-text
Abstract
This letter presents a novel realization of a voltage-mode (VM) first-order all-pass filter (APF) with attractive features. The proposed circuit employs a single readily available six-terminal active device called as universal voltage conveyor (UVC) and only grounded passive components, which predict its easy [...] Read more.
This letter presents a novel realization of a voltage-mode (VM) first-order all-pass filter (APF) with attractive features. The proposed circuit employs a single readily available six-terminal active device called as universal voltage conveyor (UVC) and only grounded passive components, which predict its easy monolithic integration with desired circuit simplicity. The auxiliary voltage input (W) and output (ZP, ZN) terminals of the device fully ensure easy cascadability of VM APF, since the input and output terminal impedances are theoretically infinitely high and zero, respectively. Moreover, thanks to mutually inverse outputs of the UVC, the proposed filter simultaneously provides both inverting and non-inverting outputs from the same configuration. All of these features make the UVC a unique active device currently available in the literature. The behavior of the filter was experimentally measured using the readily available UVC-N1C 0520 chip, which was produced in cooperation with ON Semiconductor Czech Republic, Ltd. Full article
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Open AccessArticle
Influence of Hard Segments on the Thermal, Phase-Separated Morphology, Mechanical, and Biological Properties of Polycarbonate Urethanes
Appl. Sci. 2017, 7(3), 306; https://doi.org/10.3390/app7030306
Received: 9 December 2016 / Revised: 23 February 2017 / Accepted: 16 March 2017 / Published: 20 March 2017
Cited by 3 | Viewed by 1549 | PDF Full-text (3286 KB) | HTML Full-text | XML Full-text
Abstract
Abstract: In this study, we have fabricated a series of polycarbonate polyurethanes using a two-step bulk reaction by the melting pre-polymer solution-casting method in order to synthesize biomedical polyurethane elastomers with good mechanical behavior and biostability. The polyurethanes were prepared using dibutyltin dilaurate [...] Read more.
Abstract: In this study, we have fabricated a series of polycarbonate polyurethanes using a two-step bulk reaction by the melting pre-polymer solution-casting method in order to synthesize biomedical polyurethane elastomers with good mechanical behavior and biostability. The polyurethanes were prepared using dibutyltin dilaurate as the catalyst, poly(1,6-hexanediol)carbonate microdiols (PCDL) as the soft segment, and the chain extender 1,4-butanediol (BDO) and aliphatic 1,6-hexamethylene diisocyanate (HDI) as the hard segments. The chemical structures and physical properties of the obtained films were characterized by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, gel permeation chromatography (GPC), differential scanning calorimeter (DSC), and mechanical property tests. The surface properties and degrees of microphase separation were further analyzed by water droplet contact angle measurements (CA) and atomic force microscopy (AFM). The materials exhibited a moderate toxic effect on the tetrazolium (MTT) assay and good hemocompatibility through hemolytic tests, indicating a good biocompatibility of the fabricated membranes. The materials could be considered as potential and beneficial suitable materials for tissue engineering, especially in the fields of artificial blood-contacting implants or other biomedical applications. Full article
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Open AccessArticle
Fatigue Life Prediction of High Modulus Asphalt Concrete Based on the Local Stress-Strain Method
Appl. Sci. 2017, 7(3), 305; https://doi.org/10.3390/app7030305
Received: 23 January 2017 / Revised: 13 March 2017 / Accepted: 15 March 2017 / Published: 20 March 2017
Cited by 5 | Viewed by 1858 | PDF Full-text (2031 KB) | HTML Full-text | XML Full-text
Abstract
Previously published studies have proposed fatigue life prediction models for dense graded asphalt pavement based on flexural fatigue test. This study focused on the fatigue life prediction of High Modulus Asphalt Concrete (HMAC) pavement using the local strain-stress method and direct tension fatigue [...] Read more.
Previously published studies have proposed fatigue life prediction models for dense graded asphalt pavement based on flexural fatigue test. This study focused on the fatigue life prediction of High Modulus Asphalt Concrete (HMAC) pavement using the local strain-stress method and direct tension fatigue test. First, the direct tension fatigue test at various strain levels was conducted on HMAC prism samples cut from plate specimens. Afterwards, their true stress-strain loop curves were obtained and modified to develop the strain-fatigue life equation. Then the nominal strain of HMAC course determined using finite element method was converted into local strain using the Neuber method. Finally, based on the established fatigue equation and converted local strain, a method to predict the pavement fatigue crack initiation life was proposed and the fatigue life of a typical HMAC overlay pavement which runs a risk of bottom-up cracking was predicted and validated. Results show that the proposed method was able to produce satisfactory crack initiation life. Full article
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Open AccessArticle
Low Temperature Performance Characteristics of Reclaimed Asphalt Pavement (RAP) Mortars with Virgin and Aged Soft Binders
Appl. Sci. 2017, 7(3), 304; https://doi.org/10.3390/app7030304
Received: 18 January 2017 / Revised: 3 March 2017 / Accepted: 16 March 2017 / Published: 20 March 2017
Cited by 6 | Viewed by 1807 | PDF Full-text (5272 KB) | HTML Full-text | XML Full-text
Abstract
Reclaimed asphalt pavement (RAP) has many advantages and is utilized to improve the high temperature properties of asphalt mixtures. Low temperature cracking is a predominant distress in asphalt pavements containing RAP materials. Thus, the evaluation of fracture resistance for asphalt mixtures containing RAP [...] Read more.
Reclaimed asphalt pavement (RAP) has many advantages and is utilized to improve the high temperature properties of asphalt mixtures. Low temperature cracking is a predominant distress in asphalt pavements containing RAP materials. Thus, the evaluation of fracture resistance for asphalt mixtures containing RAP is of interest. The objective of this research is to explore the low temperature performance characteristics of RAP mortars containing sieved RAP and soft binders at three aged states. The stiffness values and m-values from bending beam rheometer (BBR) tests at three test temperatures of −18 °C, −12 °C and −6 °C were obtained to conduct the minimum low temperature grades. RAP mortar with a higher aged binder content had a higher minimum low temperature regardless of RAP source. In addition, RAP mortars with virgin soft binder had the best low temperature resistance followed by the RAP mortars with rolling thin film oven (RTFO) and pressure-aged vessel (PAV) binders. Full article
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Open AccessArticle
Measurement of Heat Flow Transmitted through a Stacked-Screen Regenerator of Thermoacoustic Engine
Appl. Sci. 2017, 7(3), 303; https://doi.org/10.3390/app7030303
Received: 4 February 2017 / Revised: 9 March 2017 / Accepted: 13 March 2017 / Published: 20 March 2017
Cited by 3 | Viewed by 2272 | PDF Full-text (826 KB) | HTML Full-text | XML Full-text
Abstract
A stacked-screen regenerator is a key component in a thermoacoustic Stirling engine. Therefore, the choice of suitable mesh screens is important in the engine design. To verify the applicability of four empirical equations used in the field of thermoacoustic engines and Stirling engines, [...] Read more.
A stacked-screen regenerator is a key component in a thermoacoustic Stirling engine. Therefore, the choice of suitable mesh screens is important in the engine design. To verify the applicability of four empirical equations used in the field of thermoacoustic engines and Stirling engines, this report describes the measurements of heat flow rates transmitted through the stacked screen regenerator inserted in an experimental setup filled with pressurized Argon gas having mean pressure of 0.45 MPa. Results show that the empirical equations reproduce the measured heat flow rates to a mutually similar degree, although their derivation processes differ. Additionally, results suggest that two effective pore radii would be necessary to account for the viscous and thermal behaviors of the gas oscillating in the stacked-screen regenerators. Full article
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Open AccessFeature PaperArticle
Exergy Analysis of Air-Gap Membrane Distillation Systems for Water Purification Applications
Appl. Sci. 2017, 7(3), 301; https://doi.org/10.3390/app7030301
Received: 13 December 2016 / Revised: 8 March 2017 / Accepted: 15 March 2017 / Published: 20 March 2017
Cited by 6 | Viewed by 1844 | PDF Full-text (2844 KB) | HTML Full-text | XML Full-text
Abstract
Exergy analyses are essential tools for the performance evaluation of water desalination and other separation systems, including those featuring membrane distillation (MD). One of the challenges in the commercialization of MD technologies is its substantial heat demand, especially for large scale applications. Identifying [...] Read more.
Exergy analyses are essential tools for the performance evaluation of water desalination and other separation systems, including those featuring membrane distillation (MD). One of the challenges in the commercialization of MD technologies is its substantial heat demand, especially for large scale applications. Identifying such heat flows in the system plays a crucial role in pinpointing the heat loss and thermal integration potential by the help of exergy analysis. This study presents an exergetic evaluation of air-gap membrane distillation (AGMD) systems at a laboratory and pilot scale. A series of experiments were conducted to obtain thermodynamic data for the water streams included in the calculations. Exergy efficiency and destruction for two different types of flat-plate AGMD were analyzed for a range of feed and coolant temperatures. The bench scale AGMD system incorporating condensation plate with more favorable heat conductivity contributed to improved performance parameters including permeate flux, specific heat demand, and exergy efficiency. For both types of AGMD systems, the contributions of the major components involved in exergy destruction were identified. The result suggested that the MD modules caused the highest fraction of destructions followed by re-concentrating tanks. Full article
(This article belongs to the Special Issue Membrane Distillation) Printed Edition available
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Open AccessArticle
Experimental Study of Imbibition Characteristics of Silica Sol in Coal-Measure Mudstone Matrix
Appl. Sci. 2017, 7(3), 300; https://doi.org/10.3390/app7030300
Received: 28 December 2016 / Revised: 27 February 2017 / Accepted: 16 March 2017 / Published: 20 March 2017
Cited by 3 | Viewed by 1468 | PDF Full-text (2824 KB) | HTML Full-text | XML Full-text
Abstract
Coal-measure mudstone is a typical dual-porosity media, and grouting in a matrix system is dominantly controlled by the imbibition effect for silica sol. This paper studies the imbibition effect using mudstone in the Huaibei mining area and silica sol as grouting material as [...] Read more.
Coal-measure mudstone is a typical dual-porosity media, and grouting in a matrix system is dominantly controlled by the imbibition effect for silica sol. This paper studies the imbibition effect using mudstone in the Huaibei mining area and silica sol as grouting material as an example. Groutability, driving force, and diffusion difficulty affecting the imbibition effect were tested by a mercury porosimeter, nanoparticle size analyzer, optical contact-angle measuring device, surface tension meter, and rotary viscosity meter. After finely grinding a mudstone sample, a pressureless imbibition process was conducted through nuclear magnetic resonance equipment for 216 h to study colloid spontaneous migration and phase characteristics. Results show that silica sol absorption rate follows a power function and that the spectrograms of T2 are distributed in a triple peak pattern, with a tendency to move to the right of vertex time. The paper lays a theoretical and experimental foundation for field grouting in the coal mine. Full article
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Open AccessArticle
Quality Monitoring for Laser Welding Based on High-Speed Photography and Support Vector Machine
Appl. Sci. 2017, 7(3), 299; https://doi.org/10.3390/app7030299
Received: 2 November 2016 / Revised: 14 February 2017 / Accepted: 10 March 2017 / Published: 20 March 2017
Cited by 2 | Viewed by 1229 | PDF Full-text (3102 KB) | HTML Full-text | XML Full-text
Abstract
In order to improve the prediction ability of welding quality during high-power disk laser welding, a new approach was proposed and applied in the classification of the dynamic features of metal vapor plume. Six features were extracted through the color image processing method. [...] Read more.
In order to improve the prediction ability of welding quality during high-power disk laser welding, a new approach was proposed and applied in the classification of the dynamic features of metal vapor plume. Six features were extracted through the color image processing method. Three features, including the area of plume, number of spatters, and horizontal coordinate of plume centroid, were selected based on the classification accuracy rates and Pearson product-moment correlation coefficients. A support vector machine model was adopted to classify the welding quality status into two categories, good or poor. The results demonstrated that the support vector machine model established according to the selected features had satisfactory prediction and generalization ability. The classification accuracy rate was higher than 90%, and the model could be applied in the prediction of welding quality during high-power disk laser welding. Full article
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Open AccessArticle
Modeling and Finite Element Analysis of Load-Carrying Performance of a Wind Turbine Considering the Influence of Assembly Factors
Appl. Sci. 2017, 7(3), 298; https://doi.org/10.3390/app7030298
Received: 3 February 2017 / Revised: 28 February 2017 / Accepted: 7 March 2017 / Published: 18 March 2017
Cited by 2 | Viewed by 1410 | PDF Full-text (2670 KB) | HTML Full-text | XML Full-text
Abstract
In this work, a wind turbine shrink disk is used as the research object to investigate load-carrying performance of a multi-layer interference fit, and the theoretical model and finite element model are constructed. According to those models, a MW-level turbine shrink disk is [...] Read more.
In this work, a wind turbine shrink disk is used as the research object to investigate load-carrying performance of a multi-layer interference fit, and the theoretical model and finite element model are constructed. According to those models, a MW-level turbine shrink disk is designed, and a test device is developed to apply torque to this turbine shrink disk by hydraulic jack. Then, the circumferential slip between the contact surfaces is monitored and the slip of all contact surfaces is zero. This conclusion verifies the reasonability of the proposed models. The effect of the key influencing factors, such as machining deviation, assembly clearance and propel stroke, were analyzed. The contact pressure and load torque of the mating surfaces were obtained by building typical models with different parameters using finite element analysis (FEA). The results show that the minimum assembly clearance and the machining deviation within the machining range have little influence on load-carrying performance of multi-layer interference fit, while having a greater influence on the maximum assembly clearance and the propel stroke. The results also show that the load-carrying performance of a multiple-layer interference fit can be ensured only if the key factors are set within a reasonable design range. To avoid the abnormal operation of equipment caused by insufficient load torque, the propel stroke during practical assembly should be at least 0.95 times the designed propel stroke, which is significant in guiding the design and assembly of the multi-layer interference fit. Full article
(This article belongs to the Section Energy)
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Open AccessArticle
Effect of Fibers on Mixture Design of Stone Matrix Asphalt
Appl. Sci. 2017, 7(3), 297; https://doi.org/10.3390/app7030297
Received: 28 December 2016 / Revised: 1 March 2017 / Accepted: 10 March 2017 / Published: 18 March 2017
Cited by 4 | Viewed by 1801 | PDF Full-text (2055 KB) | HTML Full-text | XML Full-text
Abstract
Lignin fibers typically influence the mixture performance of stone matrix asphalt (SMA), such as strength, stability, durability, noise level, rutting resistance, fatigue life, and water sensitivity. However, limited studies were conducted to analyze the influence of fibers on the percent voids in mineral [...] Read more.
Lignin fibers typically influence the mixture performance of stone matrix asphalt (SMA), such as strength, stability, durability, noise level, rutting resistance, fatigue life, and water sensitivity. However, limited studies were conducted to analyze the influence of fibers on the percent voids in mineral aggregate in bituminous mixture (VMA) during the mixture design. This study analyzed the effect of different fibers and fiber contents on the VMA in SMA mixture design. A surface-dry condition method test and Marshall Stability test were applied on the SMA mixture with four different fibers (i.e., flocculent lignin fiber, mineral fiber, polyester fiber, blended fiber). The test results indicated that the bulk specific gravity of SMA mixtures and asphalt saturation decreased with the increasing fiber content, whilst the percent air voids in bituminous mixtures (VV), Marshall Stability and VMA increased. Mineral fiber had the most obvious impact on the bulk specific gravity of bituminous mixtures, while flocculent lignin fiber had a minimal impact. The mixture with mineral fiber and polyester fiber had significant effects on the volumetric properties, and, consequently, exhibited better VMA over the conventional SMA mixture with lignin fiber. Modified fiber content range was also provided, which will widen the utilization of mineral fiber and polyester fiber in the applications of SMA mixtures. The mixture evaluation suggested no statistically significant difference between lignin fiber and polyester fiber on the stability. The mineral fiber required a much larger fiber content to improve the mixture performance than other fibers. Overall, the results can be a reference to guide SMA mixture design. Full article
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Open AccessArticle
Gait Planning Research for an Electrically Driven Large-Load-Ratio Six-Legged Robot
Appl. Sci. 2017, 7(3), 296; https://doi.org/10.3390/app7030296
Received: 12 February 2017 / Revised: 11 March 2017 / Accepted: 16 March 2017 / Published: 18 March 2017
Cited by 2 | Viewed by 1531 | PDF Full-text (3464 KB) | HTML Full-text | XML Full-text
Abstract
Gait planning is an important basis for the walking of a legged robot. To improve the walking stability of multi-legged robots and to reduce the impact force between the foot and the ground, gait planning strategies are presented for an electrically driven large-load-ratio [...] Read more.
Gait planning is an important basis for the walking of a legged robot. To improve the walking stability of multi-legged robots and to reduce the impact force between the foot and the ground, gait planning strategies are presented for an electrically driven large-load-ratio six-legged robot. First, the configuration and walking gait of the electrically driven large-load-ratio six-legged robot are designed. The higher-stable swing sequences of legs and typical walking modes are respectively obtained. Based on the Denavit–Hartenberg (D–H) method, the analyses of the forward and inverse kinematics are implemented. The mathematical models of the articulated rotation angles are respectively established. In view of the buffer device installed at the end of shin to decrease the impact force between the foot and the ground, an initial lift height of the leg is brought into gait planning when the support phase changes into the transfer phase. The mathematical models of foot trajectories are established. Finally, a prototype of the electrically driven large-load-ratio six-legged robot is developed. The experiments of the prototype are carried out regarding the aspects of the walking speed and surmounting obstacle. Then, the reasonableness of gait planning is verified based on the experimental results. The proposed strategies of gait planning lay the foundation for effectively reducing the foot–ground impact force and can provide a reference for other large-load-ratio multi-legged robots. Full article
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Open AccessArticle
Selected Issues of the Indicating Measurements in a Spark Ignition Engine with an Additional Expansion Process
Appl. Sci. 2017, 7(3), 295; https://doi.org/10.3390/app7030295
Received: 1 February 2017 / Revised: 14 March 2017 / Accepted: 14 March 2017 / Published: 17 March 2017
Cited by 7 | Viewed by 1909 | PDF Full-text (11424 KB) | HTML Full-text | XML Full-text
Abstract
The paper presents the results of research on the turbocharged spark ignition engine with additional exhaust expansion in a separate cylinder, which is commonly known as the five-stroke engine. The research engine has been constructed based on the four cylinder engine in which [...] Read more.
The paper presents the results of research on the turbocharged spark ignition engine with additional exhaust expansion in a separate cylinder, which is commonly known as the five-stroke engine. The research engine has been constructed based on the four cylinder engine in which two outer cylinders work as the fired cylinders, while two internally connected inner cylinders constitute the volume of the additional expansion process. The engine represents a powertrain realizing an ultra-expansion cycle. The purpose of the study was to find an effective additional expansion process in the five-stroke engine. Cylinder-pressure indicating measurements were carried out for one of the fired cylinders and the additional expansion cylinder. The study was performed for over 20 different points on the engine operation map. This allowed us to determine a dependence between the pressure indicated in the fired cylinders and in the additional expansion cylinders. A function of the mean pressure indicated in the additional expansion cylinder versus a brake mean effective pressure was also presented. This showed a load threshold from which the work of the cylinders of additional expansion produced benefits for the output of the experimental engine. The issues of mechanical efficiency and effective efficiency of this engine were also discussed. Full article
(This article belongs to the Special Issue Internal Combustion Engines (ICE) for Ground Transport)
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Open AccessArticle
Two- and Three-Photon Partial Photoionization Cross Sections of Li+, Ne8+ and Ar16+ under XUV Radiation
Appl. Sci. 2017, 7(3), 294; https://doi.org/10.3390/app7030294
Received: 14 February 2017 / Revised: 7 March 2017 / Accepted: 9 March 2017 / Published: 17 March 2017
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Abstract
In this work, we present the photon energy dependence of the two- and three-photon cross sections of the two-electron Li+, Ne8+ and Ar16+ ions, following photoionization from their ground state. The expressions for the cross sections are based on [...] Read more.
In this work, we present the photon energy dependence of the two- and three-photon cross sections of the two-electron Li+, Ne8+ and Ar16+ ions, following photoionization from their ground state. The expressions for the cross sections are based on the lowest-order (non-vanishing) perturbation theory for the electric field, while the calculations are made with the use of an ab initio configuration interaction method. The ionization cross section is dominated by pronounced single photon resonances in addition to peaks associated with doubly excited resonances. In the case of two-photon ionization, and in the non-resonant part of the cross section, we find that the 1D ionization channel overwhelms the 1S one. We also observe that, as one moves from the lowest atomic number ion, namely Li+, to the highest atomic number ion, namely Ar16+, the cross sections generally decrease. Full article
(This article belongs to the Special Issue X-Ray Free-Electron Laser) Printed Edition available
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Open AccessReview
A Review of the Application of Zeolite Materials in Warm Mix Asphalt Technologies
Appl. Sci. 2017, 7(3), 293; https://doi.org/10.3390/app7030293
Received: 20 January 2017 / Revised: 4 March 2017 / Accepted: 14 March 2017 / Published: 16 March 2017
Cited by 19 | Viewed by 1356 | PDF Full-text (1176 KB) | HTML Full-text | XML Full-text
Abstract
Among warm mix asphalt (WMA) technologies, asphalt foaming techniques offer high potential in terms of decreasing production temperature. Reluctance of manufacturers to introduce this technology is connected with the concerns of a large investment costs. However, there are known additives which, through asphalt [...] Read more.
Among warm mix asphalt (WMA) technologies, asphalt foaming techniques offer high potential in terms of decreasing production temperature. Reluctance of manufacturers to introduce this technology is connected with the concerns of a large investment costs. However, there are known additives which, through asphalt foaming, allow a decrease in temperatures by approximately 30 °C; the use of these additives do not involve expensive investment in order to change the asphalt mix production method. These additives are zeolites, that is, minerals of the aluminosilicate group, the crystalline structure of which contains water bound in a specific way. Its release, at mix asphalt production temperatures, causes asphalt foaming. It is currently known that zeolites can be used in WMA, including natural and synthetic zeolites obtained using chemical reagents and waste. This review presents the results of studies of WMA technology, including the effects of zeolite addition on asphalt properties and mix asphalt, as well as related environmental, economic, and technological benefits. Full article
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Open AccessArticle
Birch Bark Dry Extract by Supercritical Fluid Technology: Extract Characterisation and Use for Stabilisation of Semisolid Systems
Appl. Sci. 2017, 7(3), 292; https://doi.org/10.3390/app7030292
Received: 31 December 2016 / Revised: 1 March 2017 / Accepted: 3 March 2017 / Published: 16 March 2017
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Abstract
Triterpene compounds like betulin, betulinic acid, erythrodiol, oleanolic acid and lupeol are known for many pharmacological effects. All these substances are found in the outer bark of birch. Apart from its pharmacological effects, birch bark extract can be used to stabilise semisolid systems. [...] Read more.
Triterpene compounds like betulin, betulinic acid, erythrodiol, oleanolic acid and lupeol are known for many pharmacological effects. All these substances are found in the outer bark of birch. Apart from its pharmacological effects, birch bark extract can be used to stabilise semisolid systems. Normally, birch bark extract is produced for this purpose by extraction with organic solvents. Employing supercritical fluid technology, our aim was to develop a birch bark dry extract suitable for stabilisation of lipophilic gels with improved properties while avoiding the use of toxic solvents. With supercritical carbon dioxide, three different particle formation methods from supercritical solutions have been tested. First, particle deposition was performed from a supercritical solution in an expansion chamber. Second, the Rapid Expansion of Supercritical Solutions (RESS) method was used for particle generation. Third, a modified RESS-procedure, forming the particles directly into the thereby gelated liquid, was developed. All three methods gave yields from 1% to 5.8%, depending on the techniques employed. The triterpene composition of the three extracts was comparable: all three gave more stable oleogels compared to the use of an extract obtained by organic solvent extraction. Characterizing the rheological behaviour of these gels, a faster gelling effect was seen together with a lower concentration of the extract required for the gel formation with the supercritical fluid (SCF)-extracts. This confirms the superiority of the supercritical fluid produced extracts with regard to the oleogel forming properties. Full article
(This article belongs to the Special Issue The Applications of Supercritical Carbon Dioxide)
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Open AccessArticle
Surface Improvement of Halloysite Nanotubes
Appl. Sci. 2017, 7(3), 291; https://doi.org/10.3390/app7030291
Received: 30 December 2016 / Revised: 14 February 2017 / Accepted: 24 February 2017 / Published: 16 March 2017
Cited by 8 | Viewed by 1586 | PDF Full-text (1256 KB) | HTML Full-text | XML Full-text
Abstract
A novel development on halloysite-polyvinyl alcohol (HNTs-PVA) nanocomposites has been conducted using malonic acid (MA) by crosslinking PVA and HNTs. PVA-MA crosslinking produces smooth surfaces, which play an important role in enhancing the properties of HNTs-PVA nanocomposite. The crystallographic structures of crosslinked HNTs-PVA [...] Read more.
A novel development on halloysite-polyvinyl alcohol (HNTs-PVA) nanocomposites has been conducted using malonic acid (MA) by crosslinking PVA and HNTs. PVA-MA crosslinking produces smooth surfaces, which play an important role in enhancing the properties of HNTs-PVA nanocomposite. The crystallographic structures of crosslinked HNTs-PVA show almost no change as depicted by the X-ray diffraction (XRD)-2θ-peak, suggesting that MA has no or little influence on the crystallographic structure of the HNTs-PVA. Images taken by field emission scanning electron microscope (FESEM) suggest possible effects of MA on the morphology and internal features of HNTs-PVA by reducing the agglomeration of HNTs, which is considered a decisive step in improving the surface qualities of HNTs. Investigating the samples using the Brunauer–Emmelt–Teller (BET) technique showed that the surface area was increased by about 10 times, reaching the second highest recorded results compared to the HNTs, which could be considered a breakthrough step in enhancing the properties of HNTs-PVA due to MA crosslinking. Full article
(This article belongs to the Special Issue Surface Modification of Halloysite Nanotubes)
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Open AccessFeature PaperArticle
Ultrasonic Techniques for Air Void Size Distribution and Property Evaluation in Both Early-Age and Hardened Concrete Samples
Appl. Sci. 2017, 7(3), 290; https://doi.org/10.3390/app7030290
Received: 19 January 2017 / Revised: 6 March 2017 / Accepted: 8 March 2017 / Published: 16 March 2017
Cited by 4 | Viewed by 1895 | PDF Full-text (3832 KB) | HTML Full-text | XML Full-text
Abstract
Entrained air voids can improve the freeze-thaw durability of concrete, and also affect its mechanical and transport properties. Therefore, it is important to measure the air void structure and understand its influence on concrete performance for quality control. This paper aims to measure [...] Read more.
Entrained air voids can improve the freeze-thaw durability of concrete, and also affect its mechanical and transport properties. Therefore, it is important to measure the air void structure and understand its influence on concrete performance for quality control. This paper aims to measure air void structure evolution at both early-age and hardened stages with the ultrasonic technique, and evaluates its influence on concrete properties. Three samples with different air entrainment agent content were specially prepared. The air void structure was determined with optimized inverse analysis by achieving the minimum error between experimental and theoretical attenuation. The early-age sample measurement showed that the air void content with the whole size range slightly decreases with curing time. The air void size distribution of hardened samples (at Day 28) was compared with American Society for Testing and Materials (ASTM) C457 test results. The air void size distribution with different amount of air entrainment agent was also favorably compared. In addition, the transport property, compressive strength, and dynamic modulus of concrete samples were also evaluated. The concrete transport decreased with the curing age, which is in accordance with the air void shrinkage. The correlation between the early-age strength development and hardened dynamic modulus with the ultrasonic parameters was also evaluated. The existence of clustered air voids in the Interfacial Transition Zone (ITZ) area was found to cause severe compressive strength loss. The results indicated that this developed ultrasonic technique has potential in air void size distribution measurement, and demonstrated the influence of air void structure evolution on concrete properties during both early-age and hardened stages. Full article
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Open AccessArticle
An Explicit Approach Toward Modeling Thermo-Coupled Deformation Behaviors of SMPs
Appl. Sci. 2017, 7(3), 289; https://doi.org/10.3390/app7030289
Received: 25 December 2016 / Revised: 9 February 2017 / Accepted: 23 February 2017 / Published: 16 March 2017
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Abstract
A new elastoplastic J2-flow models with thermal effects is proposed toward simulating thermo-coupled finite deformation behaviors of shape memory polymers. In this new model, an elastic potential evolving with development of plastic flow is incorporated to characterize the stress-softening effect at [...] Read more.
A new elastoplastic J 2 -flow models with thermal effects is proposed toward simulating thermo-coupled finite deformation behaviors of shape memory polymers. In this new model, an elastic potential evolving with development of plastic flow is incorporated to characterize the stress-softening effect at unloading and, moreover, thermo-induced plastic flow is introduced to represent the strain recovery effect at heating. It is shown that any given test data for both effects may be accurately simulated by means of direct and explicit procedures. Numerical examples for model predictions compare well with test data in literature. Full article
(This article belongs to the Section Materials)
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Open AccessReview
Enhancement of High-Intensity Focused Ultrasound Heating by Short-Pulse Generated Cavitation
Appl. Sci. 2017, 7(3), 288; https://doi.org/10.3390/app7030288
Received: 28 October 2016 / Revised: 22 February 2017 / Accepted: 3 March 2017 / Published: 16 March 2017
Cited by 6 | Viewed by 2096 | PDF Full-text (10684 KB) | HTML Full-text | XML Full-text
Abstract
A target tissue can be thermally coagulated in high-intensity focused ultrasound (HIFU) treatment noninvasively. HIFU thermal treatments have been clinically applied to various solid tumors. One of the problems in HIFU treatments is a long treatment time. Acoustically driven microbubbles can accelerate the [...] Read more.
A target tissue can be thermally coagulated in high-intensity focused ultrasound (HIFU) treatment noninvasively. HIFU thermal treatments have been clinically applied to various solid tumors. One of the problems in HIFU treatments is a long treatment time. Acoustically driven microbubbles can accelerate the ultrasonic heating, resulting in the significant reduction of the treatment time. In this paper, a method named “trigger HIFU exposure” which employs cavitation microbubbles is introduced and its results are reviewed. A trigger HIFU sequence consists of high-intensity short pulses followed by moderate-intensity long bursts. Cavitation bubbles induced in a multiple focal regions by rapidly scanning the focus of high-intensity pulses enhanced the temperature increase significantly and produced a large coagulation region with high efficiency. Full article
(This article belongs to the Special Issue Biomedical Ultrasound)
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Open AccessReview
A Review of Flywheel Energy Storage System Technologies and Their Applications
Appl. Sci. 2017, 7(3), 286; https://doi.org/10.3390/app7030286
Received: 10 December 2016 / Revised: 15 February 2017 / Accepted: 9 March 2017 / Published: 16 March 2017
Cited by 40 | Viewed by 3597 | PDF Full-text (1005 KB) | HTML Full-text | XML Full-text
Abstract
Energy storage systems (ESS) provide a means for improving the efficiency of electrical systems when there are imbalances between supply and demand. Additionally, they are a key element for improving the stability and quality of electrical networks. They add flexibility into the electrical [...] Read more.
Energy storage systems (ESS) provide a means for improving the efficiency of electrical systems when there are imbalances between supply and demand. Additionally, they are a key element for improving the stability and quality of electrical networks. They add flexibility into the electrical system by mitigating the supply intermittency, recently made worse by an increased penetration of renewable generation. One energy storage technology now arousing great interest is the flywheel energy storage systems (FESS), since this technology can offer many advantages as an energy storage solution over the alternatives. Flywheels have attributes of a high cycle life, long operational life, high round-trip efficiency, high power density, low environmental impact, and can store megajoule (MJ) levels of energy with no upper limit when configured in banks. This paper presents a critical review of FESS in regards to its main components and applications, an approach not captured in earlier reviews. Additionally, earlier reviews do not include the most recent literature in this fast-moving field. A description of the flywheel structure and its main components is provided, and different types of electric machines, power electronics converter topologies, and bearing systems for use in flywheel storage systems are discussed. The main applications of FESS are explained and commercially available flywheel prototypes for each application are described. The paper concludes with recommendations for future research. Full article
(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems)
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Open AccessArticle
A Finite Element Investigation into the Impact Performance of an Open-Face Motorcycle Helmet with Ventilation Slots
Appl. Sci. 2017, 7(3), 279; https://doi.org/10.3390/app7030279
Received: 11 January 2017 / Revised: 6 March 2017 / Accepted: 6 March 2017 / Published: 16 March 2017
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Abstract
Motorcycle helmets are essential for reducing the risk of head injuries in the event of an impact. However, during the design of helmets, a compromise must be made between user safety and user comfort. Accordingly, the present study proposes a novel open-face helmet [...] Read more.
Motorcycle helmets are essential for reducing the risk of head injuries in the event of an impact. However, during the design of helmets, a compromise must be made between user safety and user comfort. Accordingly, the present study proposes a novel open-face helmet design, in which the helmet features three ventilation slots in the upper-head region. Finite element analysis (FEA) models were constructed for both a prototype helmet design, and three traditional helmet designs (full-face, open-face, and half-face helmets). In simulating the proposed open-face helmet, this study considered three different ventilation slot widths, namely 8, 14, and 18 mm. The simulation results showed that of all the helmet designs, the half-face helmet resulted in the greatest headform acceleration (303 G). The internal ventilation helmet achieved a lower peak acceleration than that of the full-face helmet. By contrast, the proposed open-face helmet with ventilation slots resulted in the lowest acceleration, irrespective of the ventilation slot width. The 8-mm ventilation slot width resulted in the optimal impact performance level (i.e., a peak headform acceleration of 160 G). Overall, the results suggest that the proposed open-face helmet design with ventilation slots provides a promising solution for ensuring both user protection and user comfort in warm climates. Full article
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Open AccessArticle
Optical Coherence Tomography (OCT) for Time-Resolved Imaging of Alveolar Dynamics in Mechanically Ventilated Rats
Appl. Sci. 2017, 7(3), 287; https://doi.org/10.3390/app7030287
Received: 19 January 2017 / Revised: 8 March 2017 / Accepted: 10 March 2017 / Published: 15 March 2017
Cited by 2 | Viewed by 2057 | PDF Full-text (1998 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Though artificial ventilation is an essential life-saving treatment, the mechanical behavior of lung tissue at the alveolar level is still unknown. Therefore, we need to understand the tissue response during artificial ventilation at this microscale in order to develop new and more protective [...] Read more.
Though artificial ventilation is an essential life-saving treatment, the mechanical behavior of lung tissue at the alveolar level is still unknown. Therefore, we need to understand the tissue response during artificial ventilation at this microscale in order to develop new and more protective ventilation methods. Optical coherence tomography (OCT) combined with intravital microscopy (IVM) is a promising tool for visualizing lung tissue dynamics with a high spatial and temporal resolution in uninterruptedly ventilated rats. We present a measurement setup using a custom-made animal ventilator and a gating technique for data acquisition of time-resolved sequences. Full article
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Open AccessArticle
Physics of Prestall Propagating Disturbances in Axial Compressors and Their Potential as a Stall Warning Indicator
Appl. Sci. 2017, 7(3), 285; https://doi.org/10.3390/app7030285
Received: 31 January 2017 / Revised: 3 March 2017 / Accepted: 8 March 2017 / Published: 14 March 2017
Cited by 2 | Viewed by 1955 | PDF Full-text (4798 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Axial compressors in aero engines are prone to suffering a breakdown of orderly flow when operating at the peak of the pressure rise characteristic. The damaging potential of separated flows is why a safe distance has to be left between every possible operating [...] Read more.
Axial compressors in aero engines are prone to suffering a breakdown of orderly flow when operating at the peak of the pressure rise characteristic. The damaging potential of separated flows is why a safe distance has to be left between every possible operating point and an operating point at which stall occurs. During earlier investigations of stall inception mechanisms, a new type of prestall instability has been found. In this study, it could be demonstrated that the prestall instability characterised by discrete flow disturbances can be clearly assigned to the subject of “Rotating Instabilities”. Propagating disturbances are responsible for the rise in blade passing irregularity. If the mass flow is reduced successively, the level of irregularity increases until the prestall condition devolves into rotating stall. The primary objective of the current work is to highlight the basic physics behind these prestall disturbances by complementary experimental and numerical investigations. Before reaching the peak of the pressure rise characteristic flow, disturbances appear as small vortex tubes with one end attached to the casing and the other attached to the suction surface of the rotor blade. These vortex structures arise when the entire tip region is affected by blockage and at the same time the critical rotor incidence is not exceeded in this flow regime. Furthermore, a new stall indicator was developed by applying statistical methods to the unsteady pressure signal measured over the rotor blade tips, thus granting a better control of the safety margin. Full article
(This article belongs to the Special Issue Gas Turbines Propulsion and Power)
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Open AccessArticle
Construction of Compact Finite Difference Schemes by Classic Differential Quadrature
Appl. Sci. 2017, 7(3), 284; https://doi.org/10.3390/app7030284
Received: 20 February 2017 / Revised: 10 March 2017 / Accepted: 10 March 2017 / Published: 14 March 2017
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Abstract
Using classic differential quadrature formulae and uniform grids, this paper systematically constructs a variety of high-order finite difference schemes, and some of these schemes are consistent with the so-called boundary value methods. The derived difference schemes enjoy the same stability and accuracy properties [...] Read more.
Using classic differential quadrature formulae and uniform grids, this paper systematically constructs a variety of high-order finite difference schemes, and some of these schemes are consistent with the so-called boundary value methods. The derived difference schemes enjoy the same stability and accuracy properties with correspondent differential quadrature methods but have a simpler form of calculation; thus, they can be seen as a compact format of classic differential quadrature methods. Through systematic Fourier stability analysis, the characteristics such as the dissipation, dispersion and resolution of the different schemes were studied and compared. Full article
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Open AccessArticle
Development of a Preliminary Design Method for Subsonic Splittered Blades in Highly Loaded Axial-Flow Compressors
Appl. Sci. 2017, 7(3), 283; https://doi.org/10.3390/app7030283
Received: 31 January 2017 / Revised: 8 March 2017 / Accepted: 10 March 2017 / Published: 14 March 2017
Cited by 3 | Viewed by 2187 | PDF Full-text (8637 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a model for predicting the reference minimum-loss incidence and deviation angles of a blade arrangement with splitter vanes, which is probably a solution for future ultra-highly loaded axial compressor designs. The motivation of the modeling is to guide the blading [...] Read more.
This paper presents a model for predicting the reference minimum-loss incidence and deviation angles of a blade arrangement with splitter vanes, which is probably a solution for future ultra-highly loaded axial compressor designs. The motivation of the modeling is to guide the blading design in splittered compressor design processes where the additional splitter vanes must be specially considered. The development of the model is based on a blade performance database from systematic numerical simulations. Basic correlations of the model are firstly proposed, which consider dominant blade geometry parameters related to blade loading, including camber angle and solidity. Secondly, geometric and aerodynamic corrections about orientation parameter, blade maximum thickness, inlet Mach number, and three-dimensional (3D) effects are empirically incorporated into the basic correlations. Eventually, a subsonic 3D splittered rotor is designed using the correlations coupled with the corrections obtained from the validation of the model. The results indicate that the model is able to achieve a good agreement within an error band of ±1.0° for the predictions of both reference minimum-loss incidence and deviation angles, and the rotor designed using the model accomplishes the desired work input and flow deflection. Full article
(This article belongs to the Special Issue Gas Turbines Propulsion and Power)
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Open AccessArticle
Application of a High-Power Reversible Converter in a Hybrid Traction Power Supply System
Appl. Sci. 2017, 7(3), 282; https://doi.org/10.3390/app7030282
Received: 24 December 2016 / Revised: 25 February 2017 / Accepted: 7 March 2017 / Published: 14 March 2017
Cited by 7 | Viewed by 2595 | PDF Full-text (8382 KB) | HTML Full-text | XML Full-text
Abstract
A high-power reversible converter can achieve a variety of functions, such as recovering regenerative braking energy, expanding traction power capacity, and improving an alternating current (AC) grid power factor. A new hybrid traction power supply scheme, which consists of a high-power reversible converter [...] Read more.
A high-power reversible converter can achieve a variety of functions, such as recovering regenerative braking energy, expanding traction power capacity, and improving an alternating current (AC) grid power factor. A new hybrid traction power supply scheme, which consists of a high-power reversible converter and two 12-pulse diode rectifiers, is proposed. A droop control method based on load current feed-forward is adopted to realize the load distribution between the reversible converter and the existing 12-pulse diode rectifiers. The direct current (DC) short-circuit characteristics of the reversible converter is studied, then the relationship between the peak fault current and the circuit parameters is obtained from theoretical calculations and validated by computer simulation. The first two sets of 2 MW reversible converters have been successfully applied in Beijing Metro Line 10, the proposed hybrid application scheme and coordinated control strategy are verified, and 11.15% of average energy-savings is reached. Full article
(This article belongs to the Special Issue Energy Saving)
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