bluuebunny/crossref_metadata_2025 huggingface dataset:
The Choice of an Appropriate Information Dissimilarity Measure for Hierarchical Clustering of River Streamflow Time Series, Based on Calculated Lyapunov Exponent and Kolmogorov Measures
Authors: Mihailović Dragutin T. , Nikolić-Đorić Emilija , Malinović-Milićević Slavica , Singh Vijay P. , Mihailović Anja , Stošić Tatijana , Stošić Borko , Drešković Nusret
Published: February 2019

The purpose of this paper was to choose an appropriate information dissimilarity measure for hierarchical clustering of daily streamflow discharge data, from twelve gauging stations on the Brazos River in Texas (USA), for the period 1989–2016. For that purpose, we selected and compared the average-linkage clustering hierarchical algorithm based on the compression-based dissimilarity measure (NCD), permutation distribution dissimilarity measure (PDDM), and Kolmogorov distance (KD). The algorithm was also compared with K-means clustering based on Kolmogorov complexity (KC), the highest value of Kolmogorov complexity spectrum (KCM), and the largest Lyapunov exponent (LLE). Using a dissimilarity matrix based on NCD, PDDM, and KD for daily streamflow, the agglomerative average-linkage hierarchical algorithm was applied. The key findings of this study are that: (i) The KD clustering algorithm is the most suitable among others; (ii) ANOVA analysis shows that there exist highly significant differences between mean values of four clusters, confirming that the choice of the number of clusters was suitably done; and (iii) from the clustering we found that the predictability of streamflow data of the Brazos River given by the Lyapunov time (LT), corrected for randomness by Kolmogorov time (KT) in days, lies in the interval from two to five days.
Unification of Epistemic and Ontic Concepts of Information, Probability, and Entropy, Using Cognizers-System Model
Authors: Nakajima Toshiyuki
Published: February 2019

Information and probability are common words used in scientific investigations. However, information and probability both involve epistemic (subjective) and ontic (objective) interpretations under the same terms, which causes controversy within the concept of entropy in physics and biology. There is another issue regarding the circularity between information (or data) and reality: The observation of reality produces phenomena (or events), whereas the reality is confirmed (or constituted) by phenomena. The ordinary concept of information presupposes reality as a source of information, whereas another type of information (known as it-from-bit) constitutes the reality from data (bits). In this paper, a monistic model, called the cognizers-system model (CS model), is employed to resolve these issues. In the CS model, observations (epistemic) and physical changes (ontic) are both unified as “cognition”, meaning a related state change. Information and probability, epistemic and ontic, are formalized and analyzed systematically using a common theoretical framework of the CS model or a related model. Based on the results, a perspective for resolving controversial issues of entropy originating from information and probability is presented.
Assessment of Landslide Susceptibility Using Integrated Ensemble Fractal Dimension with Kernel Logistic Regression Model
Authors: Zhang Tingyu , Han Ling , Han Jichang , Li Xian , Zhang Heng , Wang Hao
Published: February 2019

The main aim of this study was to compare and evaluate the performance of fractal dimension as input data in the landslide susceptibility mapping of the Baota District, Yan’an City, China. First, a total of 632 points, including 316 landslide points and 316 non-landslide points, were located in the landslide inventory map. All points were divided into two parts according to the ratio of 70%:30%, with 70% (442) of the points used as the training dataset to train the models, and the remaining, namely the validation dataset, applied for validation. Second, 13 predisposing factors, including slope aspect, slope angle, altitude, lithology, mean annual precipitation (MAP), distance to rivers, distance to faults, distance to roads, normalized differential vegetation index (NDVI), topographic wetness index (TWI), plan curvature, profile curvature, and terrain roughness index (TRI), were selected. Then, the original numerical data, box-counting dimension, and correlation dimension corresponding to each predisposing factor were calculated to generate the input data and build three classification models, namely the kernel logistic regression model (KLR), kernel logistic regression based on box-counting dimension model (KLRbox-counting), and the kernel logistic regression based on correlation dimension model (KLRcorrelation). Next, the statistical indexes and the receiver operating characteristic (ROC) curve were employed to evaluate the models’ performance. Finally, the KLRcorrelation model had the highest area under the curve (AUC) values of 0.8984 and 0.9224, obtained by the training and validation datasets, respectively, indicating that the fractal dimension can be used as the input data for landslide susceptibility mapping with a better effect.
Ecological Citizenship Education and the Consumption of Animal Subjectivity
Authors: Spannring Reingard
Published: February 2019

The unfolding of the ecological disaster has led authors to reconsider the position of the human subject and his/her relationship with the earth. One entry point is the concept of ecological citizenship, which emphasizes responsibility, community, and care. However, the discourse of ecological citizenship often reduces the human subject to a critical consumer-citizen and citizenship education to the production of such a subject. The position outlined in this paper provides a more fundamental critique of consumption as a way of being in and relating to the world. In particular, it foregrounds objectification, commodification, and its impacts on human and nonhuman subjectivity and the possibility of care within a multi-species community. The paper brings animal-sensitive work in environmental education research and political theory into dialogue with a more general critique of culture and pedagogy in consumer society. From this perspective, ecological citizenship education seeks to liberate human and nonhuman beings from predetermined behavioral results and functions, and opens the time and space for the subjectification of human and nonhuman citizens within the complex dynamics of a multi-species community. With this proposition, the paper contributes to an ecocentric understanding of ecological citizenship education that builds on the continuity of life and subjective experience.
Exploring Secondary Students’ Alternative Conceptions about Engineering Design Technology
Authors: Asghar Anila , Huang Ying-Syuan , Elliott Kenneth , Skelling Yannick
Published: February 2019

This paper presents the assessment items that were developed by science and technology teachers in Québec to explore their students’ alternative ideas about engineering design technology and technological systems. These assessment items were administered to Secondary Cycle One students in Francophone and Anglophone schools in Québec to elicit their ideas about the foundational technology concepts included in the science and technology curriculum. Students’ responses are presented to share their alternative and scientific explanations. In addition, various approaches to facilitate a deeper understanding of scientific models and mechanistic reasoning in students are also discussed.
Weighted Neighborhood Preserving Ensemble Embedding
Authors: Mehta Sumet , Zhan Bi-Sheng , Shen Xiang-Jun
Published: February 2019

Neighborhood preserving embedding (NPE) is a classical and very promising supervised dimensional reduction (DR) technique based on a linear graph, which preserves the local neighborhood relations of the data points. However, NPE uses the K nearest neighbor (KNN) criteria for constructing an adjacent graph which makes it more sensitive to neighborhood size. In this article, we propose a novel DR method called weighted neighborhood preserving ensemble embedding (WNPEE). Unlike NPE, the proposed WNPEE constructs an ensemble of adjacent graphs with the number of nearest neighbors varying. With this graph ensemble building, WNPEE can obtain the low-dimensional projections with optimal embedded graph pursuing in a joint optimization manner. WNPEE can be applied in many machine learning fields, such as object recognition, data classification, signal processing, text categorization, and various deep learning tasks. Extensive experiments on Olivetti Research Laboratory (ORL), Georgia Tech, Carnegie Mellon University-Pose and Illumination Images (CMU PIE) and Yale, four face databases demonstrate that WNPEE achieves a competitive and better recognition rate than NPE and other comparative DR methods. Additionally, the proposed WNPEE achieves much lower sensitivity to the neighborhood size parameter as compared to the traditional NPE method while preserving more of the local manifold structure of the high-dimensional data.
Structure Function Analysis of Temperature-Dependent Thermal Properties of Nm-Thin Nb2O5
Authors: Mitterhuber Lisa , Kraker Elke , Defregger Stefan
Published: February 2019

A 166-nm-thick amorphous Niobium pentoxide layer (Nb2O5) on a silicon substrate was investigated by using time domain thermoreflectance at ambient temperatures from 25 °C to 500 °C. In the time domain thermoreflectance measurements, thermal transients with a time resolution in (sub-)nanoseconds can be obtained by a pump-probe laser technique. The analysis of the thermal transient was carried out via the established analytical approach, but also by a numerical approach. The analytical approach showed a thermal diffusivity and thermal conductivity from 0.43 mm2/s to 0.74 mm2/s and from 1.0 W/mK to 2.3 W/mK, respectively to temperature. The used numerical approach was the structure function approach to map the measured heat path in terms of a RthCth-network. The structure function showed a decrease of Rth with increasing temperature according to the increasing thermal conductivity of Nb2O5. The combination of both approaches contributes to an in-depth thermal analysis of Nb2O5 film.
Low-Cost Monitoring of Synchrophasors Using Frequency Modulation
Authors: Robson Stephen , Tan Gan , Haddad Abderrahmane
Published: February 2019

A new, low-cost method of simultaneously measuring and communicating voltage and current on distribution networks is presented. Based on Frequency Modulation (FM) of the measured fundamental frequency (and harmonics), followed by immediate re-injection of the modulated waveform back into the network, the proposed method can be implemented using inexpensive and readily available electronics. Furthermore, the method does not require a separate communication media, but instead uses the power line itself to propagate the FM signals back to a central point. EMTP-ATP simulations on a mixed LV/MV network are performed and experimental analysis demonstrates the practicality and robustness of the new method. The low-cost of the method would suit deployment on parts of the network which are otherwise overlooked for monitoring.
Mechatronic Modeling and Frequency Analysis of the Drive Train of a Horizontal Wind Turbine
Authors: Ansoategui Igor , Zulueta Ekaitz , Fernandez-Gamiz Unai , Lopez-Guede Jose Manuel
Published: February 2019

The relevance of renewable energies is undeniable, and among them, the importance of wind energy is capital. A lot of literature has been devoted to the control techniques that deal with the optimization of the energy produced, but the maintainability of the individual wind turbines and of the farms in general is also a fundamental factor to take into account. In this paper, the authors address the general problem of knowing in advance the resonance frequencies of the power system of a wind turbine, with the underlying idea being that those frequencies should be avoided and that resonances do not occur only due to mechanical phenomena, but also because of electrical phenomena that in turn are influenced by control and optimization techniques. Therefore, the availability of that information embedded in the optimization techniques that control a wind turbine is of major importance. The main purpose of this paper was accomplished through two related objectives: the first was to obtain a mechatronic model (using a lumped parameters model of two degrees of freedom) of the drive train in the Laplace domain oriented to subsequently perform the described analysis. The second was to use that model to determine analytically the number and the value of the resonance frequencies from the generator angular velocity in such a way that such information could be used by any control algorithm or even by the mechatronic system designers. We assessed through experimental validation using a real 100 kW wind turbine that these two objectives were reached, demonstrating that the different vibration modes were detected using only the generator angular velocity.
An Analysis of Voltage Quality in a Nanogrid during Islanded Operation
Authors: Nömm Jakob , Rönnberg Sarah K. , Bollen Math H. J.
Published: February 2019

Voltage quality data has been collected in a single house nanogrid during 48 weeks of islanded operation and 54 weeks of grid-connected operation. The voltage quality data contains the voltage total harmonic distortion (THD), odd harmonics 3 to 11 and 15, even harmonics 4 to 8, voltage unbalance, short-term flicker severity (Pst) and long-term flicker severity (Plt) values, and voltage variations at timescales below 10 min. A comparison between islanded and grid-connected operation values was made, were some of the parameters were compared to relevant grid standard limits. It is shown that some parameters exceed the defined limits in the grid-standards during islanded operation. It was also found that the islanded operation has two modes of operation, one in which higher values of the short circuit impedance, individual harmonic impedance, harmonic voltage distortion and voltage unbalance were reached.
Hybrid Multilevel Converters: Topologies, Evolutions and Verifications
Authors: Zhang Jianzhong , Xu Shuai , Din Zakiud , Hu Xing
Published: February 2019

Multilevel converters have good potential in high power and high voltage applications due to their advantages of reduced voltage or current stress on power devices. In recent years, hybrid multilevel converter (HMC) have attracted increasing attention since less equipment is required. In this paper, the topologies and evolutions of HMCs are presented, where five topology derivation ways are given by using basic cells in series-parallel/parallel-series. Some general topologies or structures that are used to generate higher levels are also deducted. Then many existing HMCs can be derived, and new topologies of the HMC might be inspired. The capabilities of neutral point and FC voltage balancing control are investigated. The performance of the selected FC-based HMCs is analyzed. Finally, the verifications of operation principle and control strategies for the derived HMCs are carried out.
Mitigating Energy System Vulnerability by Implementing a Microgrid with a Distributed Management Algorithm
Authors: Lujano-Rojas Juan M. , Yusta José M. , Domínguez-Navarro José Antonio
Published: February 2019

This work presents a management strategy for microgrid (MG) operation. Photovoltaic (PV) and wind generators, as well as storage systems and conventional units, are distributed over a wide geographical area, forming a distributed energy system, which is coordinated to face any contingency of the utility company by means of its isolated operation. The management strategy divides the system into three main layers: renewable generation, storage devices, and conventional units. Interactions between devices of the same layer are determined by solving an economic dispatch problem (EDP) in a distributed manner using a consensus algorithm (CA), and interactions between layers are determined by means of a load following strategy. In this way, the complex behaviour of PV and wind generation, the battery storage system, and conventional units has been effectively combined with CA to solve EDP in a distributed manner. MG performance and its vulnerability are deeply analysed by means of an illustrative case study. From the observed results, vulnerability under extreme conditions could be reduced up to approximately 30% by coupling distributed renewable generation and storage capacity with an energy system based on conventional generation.
Testing the Efficiency of Electricity Markets Using a New Composite Measure Based on Nonlinear TS Tools
Authors: Papaioannou George P. , Dikaiakos Christos , Stratigakos Akylas C. , Papageorgiou Panos C. , Krommydas Konstantinos F.
Published: February 2019

In this paper we examine and compare the efficiency of four European electricity markets (NordPool, Italian, Spanish and Greek) of different microstructure and level of maturity, by testing the weak form of the Efficient Market Hypothesis (EMH). To quantify the level of efficiency deviation of each market from the ‘ideal’ or ‘benchmark market of random walk’, we have constructed a Composite Electricity Market Efficiency Index (EMEI), inspired by similar works on other energy commodities. The proposed index consists of linear and nonlinear components each one measuring a different feature or dimension of the market efficiency such as its complexity, fractality, entropy, long-term memory or correlation, all connected to the associated benchmark values of the Random Walk Process (RWP). The key findings are that overall, all examined electricity markets are inefficient in respect to the weak form of EMH and the less inefficient market, as measured by the EMEI is the NordPool, closely followed by the Spanish market, with the Italian being the third. The most inefficient market is the Greek one. These results are in accordance with the predominant view about the maturity of these markets. This study contributes significantly on improving the research framework in developing consistent and robust tools for efficiency measurement, while the proposed index can be a valuable tool in designing improved guidelines towards enhancing the efficiency of electricity markets.
Applying Two-Stage Differential Evolution for Energy Saving in Optimal Chiller Loading
Authors: Lin Chang-Ming , Wu Chun-Yin , Tseng Ko-Ying , Ku Chih-Chiang , Lin Sheng-Fuu
Published: February 2019

In Taiwan, over 45% of the energy in common buildings is used for the air-conditioning system. In particular, the chiller plant consumes about 70% of the energy in air-conditioning system. The electric energy consumption of air-condition system in a clean room of semiconductor factory is about 5–10 times of that in a common building. Consequently, the optimal chiller loading in energy saving of building is a vital issue. This paper develops a new algorithm to solve optimal chiller loading (OCL) problems. The proposed two-stage differential evolution algorithm integrated the advantages of exploration (global search) in the modified binary differential evolution (MBDE) algorithm and exploitation (local search) in the real-valued differential evolution (DE) algorithm for finding the optimal solution of OCL problems. In order to show the performance of the proposed algorithm, comparison with other optimization methods has been done and analyzed. The result shows that the proposed algorithm can obtain similar or better solution in comparison to previous studies. It is a promising approach for the OCL problem.
Accelerated Particle Swarm Optimization for Photovoltaic Maximum Power Point Tracking under Partial Shading Conditions
Authors: Alshareef Muhannad , Lin Zhengyu , Ma Mingyao , Cao Wenping
Published: February 2019

This paper presents an accelerated particle swarm optimization (PSO)-based maximum power point tracking (MPPT) algorithm to track global maximum power point (MPP) of photovoltaic (PV) generation under partial shading conditions. Conventional PSO-based MPPT algorithms have common weaknesses of a long convergence time to reach the global MPP and oscillations during the searching. The proposed algorithm includes a standard PSO and a perturb-and-observe algorithm as the accelerator. It has been experimentally tested and compared with conventional MPPT algorithms. Experimental results show that the proposed MPPT method is effective in terms of high reliability, fast dynamic response, and high accuracy in tracking the global MPP.
Multi-Scenario Analysis of Energy Consumption and Carbon Emissions: The Case of Hebei Province in China
Authors: Li Zeng , Fu Jingying , Lin Gang , Jiang Dong , Liu Kun , Wang Yaxin
Published: February 2019

In view of the complexity of the energy system and its complex relationship with socio-economic factors, this study adopts the Long-range Energy Alternative Planning (LEAP) model, a technology-based, bottom-up approach, scenario-based analysis, to develop a systematic analysis of the current and future energy consumption, supply and associated Green House Gas (GHG) emissions from 2015 to 2050. The impact of various energy policies on the energy system in Hebei Province was analysed by considering four scenarios: a Reference Scenario (REF), Industrial Structure Optimization Scenario (ISO), Terminal Consumption Structure Optimization Scenario (TOS) and Low-carbon Development Scenario (LCD). By designing strategic policies from the perspective of industrial adjustment, aggressive energy structure policies and measures, such as the ISO and the TOS, and even more aggressive options, such as the LCD, where the percentage of cleaner alternative energy sources has been further increased, it has been indicated that energy consumption will have increased from 321.618 million tonnes of coal equivalent (Mtce) in 2015 to 784.88 Mtce in 2050 in the REF, with a corresponding increase in GHG emissions from 920.56 million metric tonnes (Mt) to 2262.81 Mt. In contrast, the more aggressive policies and strategies involved in the LCD, which combines the ISO with the policy-oriented TOS, can lower energy consumption by 50.82% and CO2 emissions by 64.26%. The results shed light on whether and how these scenarios can shape the energy-carbon emission reduction trajectories and develop the low-carbon pathways in Hebei Province.
Reference-Free Dynamic Voltage Scaler Based on Swapping Switched-Capacitors
Authors: Ragheb A. N. , Kim Hyung Won
Published: February 2019

This paper introduces a reference-free, scalable, and energy-efficient dynamic voltage scaler (DVS) that can be reconfigured for multiple outputs. The proposed DVS employs a novel swapping switched-capacitor (SSC) technique, which can generate target output voltages with higher resolution and smaller ripple voltages than the conventional voltage scalers based on switched-capacitors. The proposed DVS consists of a cascaded 2:1 converter based on swapping capacitors, which is essential to achieve both very small voltage ripple and fine-grain conversion ratios. One of the serious drawbacks of the conventional voltage scalers is the need for external reference voltages to maintain the target output voltage. The proposed SSC; however, eliminates the needs for any reference voltages. This significant benefit is achieved by the self-charging ability of the SSC, which can recharge all its capacitors to the configured voltage by simply swapping the two capacitors in each stage. The proposed SSC-DVS was designed with a resolution of 16 output levels and implemented using a 130 nm CMOS (Complementary Metal Oxide semiconductor) process. We conducted measured results and post-layout simulations with an input voltage of 1.5 V to produce an output voltage range of 0.085–1.4 V, which demonstrated a power efficiency of 85% for a load current of 550 µA with a voltage ripple of as low as 2.656 mV for a 2 KΩ resistor load.
A Thermo-Hydro-Mechanical-Chemical Coupling Model and Its Application in Acid Fracturing Enhanced Coalbed Methane Recovery Simulation
Authors: Fan Chaojun , Luo Mingkun , Li Sheng , Zhang Haohao , Yang Zhenhua , Liu Zheng
Published: February 2019

The reservoir permeability dominates the transport of gas and water in coal seam. However, coal seams rich in gas usually contain various pores and fractures blocked by a large amount of minerals, which leads to an ultra-low permeability and gas extraction rate, and thus an increase of drilling workload. We first propose a thermo-hydro-mechanical-chemical coupled model (THMC) for the acid fracturing enhanced coalbed methane recovery (AF-ECBM). Then, this model is applied to simulate the variation of key parameters during AF-ECBM using a 2D geometry. The effect of different extraction schedules are comparatively analyzed to give an insight into these complex coupling responses in coal seam. Result confirms that the AF-ECBM is an effective way to increase the reservoir permeability and improve the gas production using the proposed model. The range of permeability increment zone increases most dramatically in the way of acid fracturing, followed by none-acid fracturing and acidizing over time. The gas production in order is: acid fracturing (AF-ECBM) > fracturing (F-ECBM) > acidification (A-ECBM)> direct extraction (D-CBM).
Day-Ahead vs. Intraday—Forecasting the Price Spread to Maximize Economic Benefits
Authors: Maciejowska Katarzyna , Nitka Weronika , Weron Tomasz
Published: February 2019

Recently, a dynamic development of intermittent renewable energy sources (RES) has been observed. In order to allow for the adoption of trading contracts for unplanned events and changing weather conditions, the day-ahead markets have been complemented by intraday markets; in some countries, such as Poland, balancing markets are used for this purpose. This research focuses on a small RES generator, which has no market power and sells electricity through a larger trading company. The generator needs to decide, in advance, how much electricity is sold in the day-ahead market. The optimal decision of the generator on where to sell the production depends on the relation between prices in different markets. Unfortunately, when making the decision, the generator is not sure which market will offer a higher price. This article investigates the possible gains from utilizing forecasts of the price spread between the intraday/balancing and day-ahead markets in the decision process. It shows that the sign of the price spread can be successfully predicted with econometric models, such as ARX and probit. Moreover, our research demonstrates that the statistical measures of forecast accuracy, such as the percentage of correct sign classifications, do not necessarily coincide with economic benefits.
The Influence of Apple Orchard Management on Energy Performance and Pruned Biomass Harvesting for Energetic Applications
Authors: Dyjakon Arkadiusz
Published: February 2019

A further increase of biomass share in energy production in the European Union (EU) causes an interest in new sources of this renewable fuel. Agricultural residues coming from permanent crops, such as apple orchards, can support local actions to combat climate change. However, the amount of pruned biomass possible to be harvested from apple orchards and, thus, the energy output, depend mainly on their proper preparation and management. The managing actions are important because they influence the energy balance, the productivity, and the economy of the harvesting process and the potential benefits from the biomass marketing. In this study, two different variants of pruning management in an apple orchard during biomass harvesting applying baling technology were analyzed. The first variant considered the biomass collection in the orchard with scattered prunings. In the second one, the prunings were windrowed in the middle of the inter-rows. The theoretical potential amounted to 2.5 t (fresh mass) FM·ha−1. In the case of scattered pruning in the orchard, the harvesting losses were 69.3% and the energy balance was only 0.76 GJ·ha−1. It resulted in a low biomass yield and a negative economic balance. In turn, for the orchard with windrowed pruning, the harvesting losses were 19.1% and the energy balance was 20.74 GJ·ha−1. Assuming a biomass price of €90 t−1 dry mass (DM), the net benefit excluding transportation of pruned bales was €32.1 ha−1. Other calculated energetic factors, such as energy input share, energy return on the investment, productivity, and pruning intensity, confirmed additionally that proper management of the apple orchard increases its energetic potential to be used in the local market. Baling technology can be also competitive with mulching and chipping processes if a market analysis is carried out and the pruned bale sales are guaranteed.
Analysis of Doubly Fed Induction Generators Participating in Continuous Frequency Regulation with Different Wind Speeds Considering Regulation Power Constraints
Authors: Cai Tingting , Liu Sutong , Yan Gangui , Liu Hongbo
Published: February 2019

Wind turbines (WTs) participate in frequency regulation, which is one of the means to solve the problem of inadequate regulation capacity in power systems with a high proportion of renewable energy. The doubly fed induction generator (DFIG) can reserve part of power to achieve bidirectional regulation capability through rotor over-speed and increasing pitch angle. In this paper, it is pointed out that the available bidirectional regulation power of the WT is constrained by the maximum regulation power under the rotor speed regulation. The regulation power constraints under the pitch regulation considering the time scale are calculated. The adjustment coefficient of WT participating in frequency regulation is designed. Considering the regulation power constraints, the frequency difference interval in which the WT can provide the regulation power according to the adjustment coefficient is analyzed. The rotor speed and pitch coordinated control strategy of DFIG with different wind speeds is designed. Based on 24-hour measured data from a wind farm, the power constraints and their effects of WTs in the wind farm participating in frequency regulation are verified by simulation. The regulation power of the wind farm, frequency quality, and wind power utilization under the different control strategies are analyzed. The results show that the effects of bidirectional power constraints must be taken into account when evaluating the effectiveness of WTs in continuous frequency regulation.
A Novel Magnet-Axis-Shifted Hybrid Permanent Magnet Machine for Electric Vehicle Applications
Authors: Li Ya , Yang Hui , Lin Heyun , Fang Shuhua , Wang Weijia
Published: February 2019

This paper proposes a novel magnet-axis-shifted hybrid permanent magnet (MAS-HPM) machine, which features an asymmetrical magnet arrangement, i.e., low-cost ferrite and high-performance NdFeB magnets, are placed in the two sides of a “▽”-shaped rotor pole. The proposed magnet-axis-shift (MAS) effect can effectively reduce the difference between the optimum current angles for maximizing permanent magnet (PM) and reluctance torques, and hence the torque capability of the machine can be further improved. The topology and operating principle of the proposed MAS-HPM machine are introduced and are compared with the BMW i3 interior permanent magnet (IPM) machine as a benchmark. The electromagnetic characteristics of the two machines are investigated and compared by finite element analysis (FEA), which confirms the effectiveness of the proposed MAS design concept for torque improvement.
Energy Aware Virtual Machine Scheduling in Data Centers
Authors: Qiu Yeliang , Jiang Congfeng , Wang Yumei , Ou Dongyang , Li Youhuizi , Wan Jian
Published: February 2019

Power consumption is a primary concern in modern servers and data centers. Due to varying in workload types and intensities, different servers may have a different energy efficiency (EE) and energy proportionality (EP) even while having the same hardware configuration (i.e., central processing unit (CPU) generation and memory installation). For example, CPU frequency scaling and memory modules voltage scaling can significantly affect the server’s energy efficiency. In conventional virtualized data centers, the virtual machine (VM) scheduler packs VMs to servers until they saturate, without considering their energy efficiency and EP differences. In this paper we propose EASE, the Energy efficiency and proportionality Aware VM SchEduling framework containing data collection and scheduling algorithms. In the EASE framework, each server’s energy efficiency and EP characteristics are first identified by executing customized computing intensive, memory intensive, and hybrid benchmarks. Servers will be labelled and categorized with their affinity for different incoming requests according to their EP and EE characteristics. Then for each VM, EASE will undergo workload characterization procedure by tracing and monitoring their resource usage including CPU, memory, disk, and network and determine whether it is computing intensive, memory intensive, or a hybrid workload. Finally, EASE schedules VMs to servers by matching the VM’s workload type and the server’s EP and EE preference. The rationale of EASE is to schedule VMs to servers to keep them working around their peak energy efficiency point, i.e., the near optimal working range. When workload fluctuates, EASE re-schedules or migrates VMs to other servers to make sure that all the servers are running as near their optimal working range as they possibly can. The experimental results on real clusters show that EASE can save servers’ power consumption as much as 37.07%–49.98% in both homogeneous and heterogeneous clusters, while the average completion time of the computing intensive VMs increases only 0.31%–8.49%. In the heterogeneous nodes, the power consumption of the computing intensive VMs can be reduced by 44.22%. The job completion time can be saved by 53.80%.
Energy, CO2, and AQI Efficiency and Improvement of the Yangtze River Economic Belt
Authors: Ren Fang-Rong , Tian Ze , Shen Yu-Ting , Chiu Yung-Ho , Lin Tai-Yu
Published: February 2019

With the rapid development of its economy, environmental governance is becoming more important in China. The Yangtze River Economic Belt (YREB), as the world’s largest inland shipping channel, can lead the country’s regional green economy development. As most research on China’s environmental efficiency focuses on provinces or the east and west regions, this paper examines its energy input and output and environmental effects from the aspects of YREB and non-YREB, breaking through the limitations of previous studies that only used cross-section or panel data for environmental assessment. This paper employs the meta-frontier dynamic SBM model, selects fixed assets as carry-over indicators, and considers the interrelationships between the dynamics variables during 2014–2016. The results are as follows: The overall energy efficiency and CO2 emission efficiency of YREB are higher than those of non-YREB. The difference in energy consumption, CO2, and AQI efficiency is large, but the performance of YREB is generally better than that of non-YREB. After setting the meta-frontier, non-YREB is better than YREB, for the main reason that the technology gap values of YREB are smaller than those of non-YREB. Our findings thus suggest that YREB should strengthen technical exchanges and promotion within its region, thereby decreasing regional technology differences, while non-YREB should address environment protection and CO2 emissions and advocate a low-carbon production mode.
Production of Oxygenated Fuel Additives from Residual Glycerine Using Biocatalysts Obtained from Heavy-Metal-Contaminated Jatropha curcas L. Roots
Authors: García-Martín Juan Francisco , Alés-Álvarez Francisco Javier , Torres-García Miguel , Feng Chao-Hui , Álvarez-Mateos Paloma
Published: February 2019

This work aims to shed light on the use of two biochars, obtained from the pyrolysis at 550 °C of heavy-metal-contaminated Jatropha curcas L. roots, as heterogeneous catalysts for glycerol esterification using residual glycerine. To do this, glycerine from biodiesel production was purified. In a first step, H3PO4 or H2SO4 was used to remove non-glycerol organic matter. The glycerol-rich phase was then extracted with ethanol or propanol, which increased the glycerol content from 43.2% to up to 100%. Subsequently, the esterification of both purified glycerine and commercial USP glycerine was assayed with acetic acid (AA) or with acetic anhydride (AH) at 9:1 molar ratio to glycerol using Amberlyst-15 as catalyst. Different reaction times (from 1.5 to 3 h) and temperatures (100–115 °C when using AA and 80–135 °C when using AH) were assessed. Results revealed that the most suitable conditions were 80 °C and 1.5 h reaction time using AH, achieving 100% yield and selectivity towards triacetylglycerol (TAG) almost with both glycerines. Finally, the performance and reuse of the two heterogeneous biocatalysts was assessed. Under these conditions, one of the biocatalysts also achieved 100% TAG yield.
Control Strategies of Full-Voltage to Half-Voltage Operation for LCC and Hybrid LCC/MMC based UHVDC Systems
Authors: Li Gen , Liu Wei , Joseph Tibin , Liang Jun , An Ting , Lu Jingjing , Szechtman Marcio , Andersen Bjarne , Zhuang Qikai
Published: February 2019

With the increasing demand of transmitting bulk-power over long-distance, the ultra high-voltage direct-current (UHVDC) transmission systems become an attractive option. Nowadays, not only the line commutated converter (LCC) based systems, but also the modular multilevel converter (MMC) based systems have reached UHVDC levels. The converter stations of UHVDC systems normally utilize two series-connected valve-groups to reduce the difficulties of device manufacturing and transportation. This high-voltage and low-voltage valve-group configuration allows the UHVDC systems to achieve a full-voltage to half-voltage operation which increases the flexibility of the systems. However, the existing research only focuses on the full-voltage to half-voltage control of LCC-UHVDC systems. The control strategies for hybrid LCC/MMC UHVDC systems are underresearched. Moreover, the approaches to reduce the load-shedding caused by the full-voltage to half-voltage control for both LCC and hybrid LCC/MMC based UHVDC systems have not been investigated. In this paper, full-voltage to half-voltage control strategies for both LCC and hybrid LCC/MMC based UHVDC systems have been proposed. Moreover, to avoid load-shedding caused by the half-voltage operation, a power rescheduling method that re-sets the power references of the half-voltage operating and full-voltage operating poles has been proposed. The proposed full-voltage to half-voltage control strategies and power rescheduling method can achieve a stable and fast control process with a minimum power loss. The proposed methods have been verified through the time-domain simulations conducted in PSCAD/EMTDC.
Narrow Band State of Charge (SOC) Control Strategy for Hybrid Container Cranes
Authors: Bolonne Sheron Ruchiranga Anton , Chandima Dedduwa Pathiranage
Published: February 2019

This paper evaluates possibility of using a new hybrid system based on variable speed diesel generator (VSDG), Li-ion battery bank and supercapacitor bank (SC) for a rubber tire gantry crane (RTGC) used in container terminals. Existing commercial hybrid systems face difficulties producing high efficiencies, higher life span, and lower initial investment cost due to inheriting characteristics of batteries and supercapacitors. In the proposed power system, a variable speed diesel generator act as the principal energy source, while a Li-ion battery bank and SC bank act as an energy storage system. The battery supports the diesel generator during steady demand and further, it absorbs a part of energy during regeneration. The energy management strategy, control the power flow from different sources while maintaining battery state of charge (SOC) level within a narrow band. Unlike most battery systems, this narrow band operation of battery system increases its life span while reducing capacity fade. The originality of this study can be emphasized from this narrow band SOC control technique. Simulation results for real operational load cycles are presented showing a stable system operating under defined current limits which can enhance lifetime of battery system and increase fuel saving by downsizing 400 kW constant speed diesel generator to 200 kW VSDG.
Experimental Study of Particle Deposition on Surface at Different Mainstream Velocity and Temperature
Authors: Zhang Fei , Liu Zhenxia , Liu Zhengang , Liu Yanan
Published: February 2019

The effect of mainstream velocity and mainstream temperature on the behavior of deposition on a flat plate surface has been investigated experimentally. Molten wax particles were injected to generate particle deposition in a two-phase flow wind tunnel. Tests indicated that deposition occurs mainly at the leading edge and the middle and backward portions of the windward side. The mass of deposition at the leading edge was far more than that on the windward and lee sides. For the windward and lee sides, deposition mass increased as the mainstream velocity was increased for a given particle concentration. Capture efficiency was found to increase initially until the mainstream velocity reaches a certain value, where it begins to drop with mainstream velocity increasing. For the leading edge, capture efficiency followed a similar trend due to deposition spallation and detachment induced by aerodynamic shear at high velocity. Deposition formation was also strongly affected by the mainstream temperature due to its control of particle phase (solid or liquid). Capture efficiency initially increased with increasing mainstream temperature until a certain threshold temperature (near the wax melting point). Subsequently, it began to decrease, for wax detaches from the model surface when subjected to the aerodynamic force at the surface temperature above the wax melting point.
Effect of Salts on Interfacial Tension and CO2 Mass Transfer in Carbonated Water Injection
Authors: Hamouda Aly A , Bagalkot Nikhil
Published: February 2019

Carbonated water injection (CWI) is a promising enhanced oil recovery (EOR) and CO2 sequestration method, which overcomes the problems associated with CO2 EOR. CO2 mass transfer and interfacial tension (IFT) are important parameters that influence oil recovery efficiency. This study addresses the impact of MgCl2 and Na2SO4 in carbonated water (CW) on CW/hydrocarbon IFT and CO2 mass transfer. An axisymmetric drop shape analysis was used to estimate the IFT and the CO2 diffusion coefficient. It was found that CW+MgCl2 reduced both the CW/n-decane IFT (36.5%) and CO2 mass transfer, while CW+Na2SO4 increased both the IFT and CO2 mass transfer (57%). It is suggested that reduction in IFT for CW+MgCl2 brine is mainly due to the higher hydration energy of Mg2+. The Mg2+ ion forms a tight bond to the first hydration shell [Mg(H2O)6]2+, this increases the effective size at the interface, hence reduce IFT. Meanwhile, the SO42− outer hydration shell has free OH groups, which may locally promote CO2 mass transfer. The study illustrates the potential of combining salts and CW in enhancing CO2 mass transfer that can be the base for further investigations. Furthermore, the contribution and proposed mechanisms of the different ions (SO42− and Mg2+) to the physical process in carbonated water/hydrocarbon have been addressed, which forms one of primary bases of EOR.
Inter-Criteria Dependencies-Based Decision Support in the Sustainable wind Energy Management
Authors: Ziemba Paweł
Published: February 2019

Decision problems related to the wind energy require considering many, often interrelated and dependent on each other, criteria. To solve such problems, decision systems based on Multi-Criteria Decision Analysis (MCDA) methods are usually used. Unfortunately, most methods assume independence between the criteria, therefore, their application in decision problems related to the wind energy is debatable. This paper presents the use of the Analytic Network Process (ANP) method to solve a decision problem consisting in selecting the location and design of a wind farm. The use of the ANP method allows capturing the complexity of the decision problem by taking into consideration dependencies between criteria. As part of the verification of the solution, the results of the ANP method were compared with those of the Analytic Hierarchy Process (AHP) method, which uses only hierarchical dependencies between criteria. The conducted verification showed that the inter-criteria dependencies may have a significant influence on the obtained solution. On the basis of the conducted sensitivity analysis and the research into robustness of the rankings to the rank reversal phenomenon, it has been found out that the ranking obtained with the use of the ANP is characterized by a higher quality than by means of the AHP.
Power Flow Analysis of the Advanced Co-Phase Traction Power Supply System
Authors: He Xiaoqiong , Ren Haijun , Lin Jingying , Han Pengcheng , Wang Yi , Peng Xu , Shu Zeliang
Published: February 2019

The development of the traction power supply system (TPSS) is limited by the existence of the neutral section in the present system. The advanced co-phase traction power supply system (ACTPSS) can reduce the neutral section completely and becomes an important research and development direction of the railway. To ensure the stable operation of ACTPSS, it is necessary to carry out an appropriate power analysis. In this paper, the topology of advanced co-phase traction substation is mainly composed by the three-phase to single-phase cascaded converter. Then, the improved PQ decomposition algorithm is proposed to analyze the power flow. The impedance model of the traction network is calculated and established. The power flow analysis and calculation of the ACTPSS with different locations of locomotive are carried out, which theoretically illustrates that the system can maintain stable operation under various working conditions. The feasibility and operation stability of the ACTPSS are verified by the simulations and low power experiments.
Study on the Cooling Effect of Attached Fins on PV Using CFD Simulation
Authors: Kim Jaemin , Nam Yujin
Published: February 2019

The issue of efficiency decrease according to temperature increase is a pending problem in the PV market. Several active and passive technologies have been suggested but few quantitative studies on the estimation of the cooling effect have been carried out. In this study, a CFD (computational fluid dynamics) simulation model was developed to analyze a passive cooling technology using fins attached to the back of the PV module. Furthermore, a method to improve airflow at the back of the PV module by forming slits in the frame was analyzed. The simulation model reproduced the indoor test that uses a solar simulator and the cooling performance was analyzed according to the shape of the fins and the presence of slits. In the simulation results, the surface temperature and expected electrical efficiency without cooling were 62.78 °C and 13.24% respectively under nominal operating cell temperature conditions. Moreover, the temperature reduced by approximately 15.13 °C because the fins attached at the bottom of the PV module increased the heat transfer area with airflow. Thus, the electrical efficiency according to the PV module temperature was predicted as 14.39%. Furthermore, when slits were installed between the fins, they increased the airflow velocity and accelerated the formation of turbulence, thereby improving the cooling performance of the fins. The simulation results showed that the temperature could be further reduced by approximately 8.62 °C at a lower air velocity. As the fins and slits can also reduce the non-uniformity of the temperature, they are expected to supplement the efficiency and durability reduction of the PV modules caused by the hot spot phenomenon. In addition, it was shown that slits in the frame could further improve the cooling performance of the fins at a low-velocity airflow.