bluuebunny/crossref_metadata_2025 huggingface dataset:
Colorimetric Detection of Multiple Metal Ions Using Schiff Base 1-(2-Thiophenylimino)-4-(N-dimethyl)benzene
Authors: Alorabi Ali Q. , Abdelbaset Mohamed , Zabin Sami A.
Published: December 2019

In this paper, a Schiff base ligand 1-(2-thiophenylimino)-4-(N-dimethyl)benzene (SL1) bearing azomethine (>C=N-) and thiol (-SH) moieties capable of coordinating to metals and forming colored metal complexes was synthesized and examined as a colorimetric chemosensor. The sensing ability toward the metal ions of Cu2+, Cr3+, Fe2+ Ni2+, Co2+, Mg2+, Zn2+, Fe2+, Fe3+, NH4VO3 (V5+), Mn2+, Hg2+, Pb2+, and Al3+ was investigated in a mixture of H2O and dimethylformamide (DMF) solvent using the UV–Visible spectra monitoring method. The synthesized Schiff base ligand showed colorimetric properties with Cr3+, Fe2+, Fe3+, and Hg2+ ions, resulting in a different color change for each metal that could be identified easily with the naked eye. The UV–Vis spectra indicated a significant red shift (~69–288 nm) from the origin after the addition of the ligand to these metal ions, which may be due to ligand-to-metal charge-transfer (LMCT). On applying Job’s plot, it was indicated that the ligand binds to the metal ions in a 2:1 ligand-to-metal molar ratio. SL1 behaves as a bidentate ligand and binds through the N atom of the imine group and the S atom of the thiol group. The results indicate that the SL1 ligand is an appropriate coordination entity and can be developed for use as a chemosensor for the detection of Cr3+, Fe2+, Fe3+, and Hg2+ ions.
Hydrological Modeling Response to Climate Model Spatial Analysis of a South Eastern Europe International Basin
Authors: Skoulikaris Charalampos , Anagnostopoulou Christina , Lazoglou Georgia
Published: December 2019

One of the most common questions in hydrological modeling addresses the issue of input data resolution. Is the spatial analysis of the meteorological/climatological data adequate to ensure the description of simulated phenomena, e.g., the discharges in rainfall–runoff models at the river basin scale, to a sufficient degree? The aim of the proposed research was to answer this specific question by investigating the response of a spatially distributed hydrological model to climatic inputs of various spatial resolution. In particular, ERA-Interim gridded precipitation and temperature datasets of low, medium, and high resolution, i.e., 0.50° × 0.50°, 0.25° × 0.25°, and 0.125° × 0.125°, respectively, were used to feed a distributed hydrological model that was applied to a transboundary river basin in the Balkan Peninsula, while all the other model’s parameters were maintained the same at each simulation run. The outputs demonstrate that, for the extent of the specific basin study, the simulated discharges were adequately correlated with the observed ones, with the marginally best results presented in the case of precipitation and temperature of 0.25° × 0.25° spatial analysis. The results of the research indicate that the selection of ERA-Interim data can indeed improve or facilitate the researcher’s outputs when dealing with regional hydrologic simulations.
Ethanolic Extract of Hippocampus abdominalis Exerts Anti-Melanogenic Effects in B16F10 Melanoma Cells and Zebrafish Larvae by Activating the ERK Signaling Pathway
Authors: Molagoda Ilandarage Menu Neelaka , Choi Yung Hyun , Lee Seungheon , Sung Jiwon , Lee Cho Rong , Lee Hyo Geun , Lim Jongho , Lee Kyeong-Jun , Jeon You-Jin , Ma Jeongin , Kim Gi-Young
Published: December 2019

The big belly seahorse (Hippocampus abdominalis), a well-known ingredient of traditional medicine, possesses anti-inflammatory, anti-aging, anti-fatigue, and anti-thrombotic properties, and also increases male fertility. This study demonstrates that the ethanolic extract of dried H. abdominalis (EEHA) has anti-melanogenic effects in B16F10 melanoma cells and zebrafish larvae. EEHA significantly reduced the α-melanocyte-stimulating hormone (α-MSH)-induced melanogenesis in B16F10 melanoma cells without causing cytotoxicity. At a concentration of 200 µg/mL, EEHA had significant anti-melanogenic activity in zebrafish larvae, accompanied by a severe reduction in the heart rate (118 ± 17 heartbeats/min) compared to that of the untreated group (185 ± 8 heartbeats/min), indicating that EEHA induces cardiotoxicity at high concentrations. Below 100 µg/mL, EEHA significantly reduced melanogenesis in zebrafish larvae in the presence or absence of α-MSH, while the heart rate remained unaltered. Additionally, EEHA downregulated the release of cyclic adenosine monophosphate (cAMP) and the phosphorylation of cAMP response element-binding protein (CREB) in B16F10 melanoma cells, which inhibited microphthalmia-associated transcription factor (MITF), leading to the inhibition of tyrosinase activity. EEHA also increased the phosphorylation of extracellular-signal regulated kinase (ERK). The ERK inhibitor PD98059 interfered with the anti-melanogenic activity of EEHA in B16F10 melanoma cells and zebrafish larvae, indicating that the ERK signaling pathway might regulate the anti-melanogenic properties of EEHA. Altogether, we conclude that EEHA represses the cAMP–CREB–MITF axis, which consequently inhibits tyrosinase-mediated melanogenesis. We propose that at low concentrations, EEHA can serve as a promising anti-melanogenic agent that could be used to prepare whitening cosmetics and for treating melanogenic disorders.
Does Protection Really Matter? A Case Study from Central European Oak Forests
Authors: Reczyńska Kamila , Świerkosz Krzysztof
Published: December 2019

In the face of a rapidly changing global environment, detailed research into the actual role of protected areas (PAs) in preventing the destruction of ecosystems and the loss of biodiversity became particularly important. Using 304 phytosociological relevés of oak forests from SW Poland, we monitored their state of preservation reflected by the share of synanthropes (Ws-c index) in relation to (i) duration of protection, (ii) status of protected area, (iii) main topographic factors, and (iv) bedrock type. We show that the Ws-c index of studied forests depends primarily on the habitat conditions, especially bedrock type, while both the duration and status of protection are not relevant. The most disturbed are forests developing on serpentine substrates regardless of whether they are protected or not. Within the rest of the investigated sites, the Ws-c index is significantly lower and does not meaningfully differ between protected and unprotected areas. On the one hand, our results suggest that the fact of establishing protection does not ensure a favourable state of conservation of forest communities. On the other hand, well-preserved forest communities can also be expected outside PAs what makes them an important target for nature protection in the future.
Performance Characteristics of Automobile Air Conditioning Using the R134a/R1234yf Mixture
Authors: Shin Yunchan , Kim Taejung , Lee Areum , Cho Honghyun
Published: December 2019

In this study, the energy and exergy of an automobile refrigeration system using R134a and R134a/R1234yf were analyzed experimentally with respect to outdoor air temperature and compressor speed. As outdoor air temperature increased from 32.5 °C to 37.5 °C, the coefficient of performance (COP) and total exergy destruction rate of the refrigeration system using Mix30 decreased by 5.19% and 25.8% on average, compared to that of the system using R134a. The exergy efficiency of the Mix30 refrigeration system was on average 21.8% higher than that of the R134a system. As the compressor rotating speed increased from 1000 to 2000 rpm, the cooling capacity of the refrigeration system using R134a and R134a/R1234yf increased, while the COP decreased. The COP and total exergy destruction rate of the refrigeration system using Mix30 decreased by 4.82% and 19.5%, compared to that of the system using R134a. The exergy efficiency of the Mix30 refrigeration system increased on average by 20.7%, compared to that of the R134a system. The total exergy destruction rate of the automobile refrigeration system using R134a/R1234yf decreased with increase in R1234yf, while exergy efficiency increased. In addition, the exergy destruction rate of the automobile refrigeration system decreased as the amount of R1234yf in the R134a/R1234yf automobile refrigeration system increased.
Quantum Reactivity: An Indicator of Quantum Correlation
Authors: Aslmarand Shahabeddin M. , Miller Warner A. , Rana Verinder S. , Alsing Paul M.
Published: December 2019

Geometry is often a valuable guide to complex problems in physics. In this paper, we introduce a novel geometric quantity called quantum reactivity (QR) to probe quantum correlations in higher-dimensional quantum systems. Much like quantum discord, QR is not a measure of quantum entanglement but can be useful in quantum information processes where a notion of quantum correlation in higher dimensions is needed. Both quantum discord and QR are extendable to an arbitrarily large number of qubits; however, unlike discord, QR satisfies the invariance under unitary operations. Our approach parallels Schumacher’s singlet state triangle inequality, which used an information geometry-based entropic distance. We use a generalization of information distance to area, volume, and higher-dimensional volumes and then use these to define a quantity that we call QR, which is the familiar ratio of surface area to volume. We examine a spectrum of multipartite states (Werner, W, GHZ, randomly generated density matrices, etc.) and demonstrate that QR can provide an ordering of these quantum states as to their degree of quantum correlation.
Effective Equilibrium in Out-of-Equilibrium Interacting Coupled Nanoconductors
Authors: Maisel Lucas , López Rosa
Published: December 2019

In the present work, we study a mesoscopic system consisting of a double quantum dot in which both quantum dots or artificial atoms are electrostatically coupled. Each dot is additionally tunnel coupled to two electronic reservoirs and driven far from equilibrium by external voltage differences. Our objective is to find configurations of these biases such that the current through one of the dots vanishes. In this situation, the validity of the fluctuation–dissipation theorem and Onsager’s reciprocity relations has been established. In our analysis, we employ a master equation formalism for a minimum model of four charge states, and limit ourselves to the sequential tunneling regime. We numerically study those configurations far from equilibrium for which we obtain a stalling current. In this scenario, we explicitly verify the fluctuation–dissipation theorem, as well as Onsager’s reciprocity relations, which are originally formulated for systems in which quantum transport takes place in the linear regime.
Tri-polarized Sparse Array Design for Mutual Coupling Reduction in Direction Finding and Polarization Estimation
Authors: Shi Shuli , Xu Yougen , Zhuang Junpeng , Zhao Kang , Huang Yulin , Liu Zhiwen
Published: December 2019

Multi-polarized antenna arrays have the ability to provide both the direction and polarization information of the incident signals, which is important in radar, sonar, wireless communication, remote sensing, and so on. In this paper, a diversely polarized linear array of sparsely located but identically oriented tri-polarized vector antennas (VAs) is designed for estimating the direction-of-arrival (DOA) and polarization parameters of the incident signals in the presence of antenna mutual coupling (MC). In order to reduce the inter-VA MC, a new type of sparse array geometry is proposed, wherein the minimum inter-VA spacing is constrained to be no less than one signal wavelength. Considering the intra-VA MC effect, a full-wave electromagnetic simulation is introduced to fit the manifold vector of an isolated VA. Based on the sparse VA array, a polarimetric subspace scheme is proposed for DOA and polarization estimation. When the knowledge about the intra-VA MC is a priori unavailable, an algebraic polarimetric blind scheme is also provided for DOA estimation. Computer simulations and real-world experiments (using an S-band 24-channel tri-polarized array system) validate the efficacy of the designed array geometry along with the parameter estimation methods.
Compact Switched-Beam Array Antenna with a Butler Matrix and a Folded Ground Structure
Authors: Kim Young-Jun , Kim Ye-Bon , Dong Hyun-Jun , Cho Yong Soo , Lee Han Lim
Published: December 2019

A compact switched-beam array antenna, based on a switched Butler matrix with four folded ground antennas, is presented for unmanned aerial vehicle (UAV) applications. The folded ground structure, including a slotted patch radiator surrounded by multiple air-gapped ground layers, is adopted to maximize compactness. The extra ground layers provide extra capacitive coupling around the patch antenna, resulting in a down-shift of resonant frequency and a reduction in the antenna size. Also, to optimize aerial operation with a wider beam coverage, the 1 × 4 array is integrated with a switched Butler matrix controlled by a microcontroller unit (MCU). The choice of the Butler matrix reduces the complexity of beamforming circuitry and avoids the use of high-cost phase shifters requiring extra control-bit signals. Further, the array antenna is optimized for high isolation among the antenna ports and a minimal UAV body effect. Then, the proposed structure was verified at 1.96 GHz for test purposes only, and the array size, excluding the antenna case, was 2.16λo × 0.54λo × 0.07λo. The measured 10 dB impedance bandwidth for all antenna elements in the array was always better than 3.4%, and the isolation among the antenna ports was also better than 19 dB. The measured peak gain, excluding the loss of the switched Butler module, was about 9.98 dBi, on average. Lastly, the measured peak scan angles were observed at −39°, −17°, 9° and 31° according to switching modes.
An Ultrasonic Pulse-Echo Method to Detect Internal Defects in Epoxy Composite Insulation
Authors: Tian Fangyuan , Hao Yanpeng , Zou Zhouyiao , Zheng Yao , He Weiming , Yang Lin , Li Licheng
Published: December 2019

Voids or cracks in basin insulators inside a GIS (gas-insulated metal-enclosed switchgear) could trigger partial discharges or surface flashover under electrical stresses, threatening safe GIS operation. For this paper, some epoxy composite specimens were made from similar materials and manufacturing processes to make 252 kV GIS basin insulators. Some voids with different diameters or cracks with different diameters and orientations were artificially made in the specimens with different thicknesses. An ultrasonic pulse-echo system was set up, and ultrasonic tests were carried out on the specimens with voids or cracks. A method to calculate the depth of a defect was proposed by the propagation time of defect reflected waves. The results showed that a depth of 50 mm, a diameter φ of 2 mm void, and a diameter φ of 1 mm crack in epoxy composite insulation were detected by the ultrasonic system using a 1 MHz transducer.
Modeling and Controlling of Temperature and Humidity in Building Heating, Ventilating, and Air Conditioning System Using Model Predictive Control
Authors: Bahramnia Pouria , Hosseini Rostami Seyyed Mohammad , Wang Jin , Kim Gwang-jun
Published: December 2019

Nowadays, by huge improvements in industrial control and the necessity of efficient energy consumption for buildings, unified managing systems are established to monitor and control mechanical equipment and energy usage. One of the main portions of the building management system (BMS) is the cooling and heating equipment called heating and ventilation and air-conditioning (HVAC). Based on temperature slow dynamic and presented uncertainty in modeling, a model predictive control (MPC) strategy to track both temperature and humidity is proposed in this study. The main goal of this study is to provide a framework to describe temperature and humidity elements required for dynamic modeling. Following that, by utilizing a predictive approach, a control strategy is obtained, which optimizes the tracking error of two interactional channel and performs the effort control by minimizing the optimization index. Other articles have mostly only had control over the temperature variable, but in our article, we tried to study the equations of temperature and humidity as well as their interference and according to the ASHRAE standard, both temperature and humidity controls must be accurate. The humidity was the novelty in our article. Simulation results proved the effectiveness of the proposed approach compared to the conventional proportional-integral controller. Evidently, the key idea behind the control objective is providing the comfort condition while consuming the least possible energy.
Enhancement on the Fault Ride through Capability of Power Distribution Systems Linked by Distributed Generation due to the Impedance of Superconducting Fault Current Limiters
Authors: Choi Sang-Jae , Lim Sung-Hun
Published: December 2019

Recently, studies on connecting distributed generation (DG) to power distribution systems through DC links have been actively conducted. When a fault in feeder of this power distribution system occurs, a voltage dip can happen in the grid. In order to prevent voltage dips, there are several solutions such as the application of a superconducting fault current limiter (SFCL). If a SFCL with a larger impedance is applied, the voltage dip of the grid is effectively prevented. However, this action can bring about the malfunction or the delayed operation of the over-current relay (OCR) due to the decreased fault current, which causes another problem of protection coordination between the protective relays. On the other hand, if the impedance of the SFCL is too low, excessive reactive power is supplied by the fault ride-through (FRT) regulation and the active power is reduced. This causes an active power imbalance on the DC link and increases the DC link’s voltage. As previous solutions to prevent the rise of DC links’ voltage, the deloading method and the application of a chopper resistor have been suggested. In this paper, a technique called active power tracking control (APTC), was proposed to suppress the rise of DC links’ voltage. Case studies considering the impedance of SFCL in the constructed power distribution system were carried out, and the rise of DC links’ voltage could be effectively suppressed without any significant delay in the operation of the OCR. This study is expected to solve both the voltage dip of the grid and the rise of DC links’ voltage when distributed generation is connected to a grid.
Roles and Perspectives When Estimating Energy and Environmental Potentials of Urban Consolidation
Authors: Björklund Maria , Simm Niklas
Published: December 2019

Urban consolidation centers (UCCs) are presumed to provide more efficient goods distribution in cities and lead to decreased environmental impact and energy usage. There is, however, limited knowledge as to the actual performance of UCCs, and what roles and perspectives the involved actors have in the performance measurement. The overall aim of this paper is to investigate the roles and perspectives of involved actors when estimating and evaluating the performance of UCCs. The article is based on a study of one case that evaluates the performance of a UCC involving several actors. Interviews were triangulated with documents from the case. The results showed that actors have different roles in performance measurements and even if they share a mutual interest in conducting the measurements, they did not share opinions regarding factors such as system limits or performance indicators. The study provides a deeper understanding of the importance of inter-organizational interaction when conducting performance measurements. The study provides additional insights into the roles of the actors and their perspectives in logistics performance measurement that targets energy usage and environmental impact. These aspects are seldom addressed in less complex estimations or mathematical modelling estimations.
Factors Affecting the Corrosive Behavior of Used Cooking Oils and a Non-Edible Fish Oil That Are in Contact with Ferrous Metals
Authors: Bruun Nina , Demesa Abayneh Getachew , Tesfaye Fiseha , Hemming Jarl , Hupa Leena
Published: December 2019

The corrosion behavior of three used cooking oils and one non-edible fish oil was experimentally investigated by the immersion test of iron rods at room temperature. The corrosivity of the tested oils was indirectly determined from the amount of the dissolved iron in the tested oils after the immersion test. Different factors that affect the corrosive behavior of the tested oils were assessed. Among the tested oils, the fish oil showed the highest amount of dissolved iron owing to its chemical properties such as high water content and acid number. In general, water content and acid number have direct effects on the amount of dissolved iron. The addition of oleic acid to the used cooking oil resulted in a 60% less amount of dissolved iron. It was suggested that the addition of oleic acid prompted the formation of a monolayer, which inhibited the permeation of oxygen and water to the surface of the iron rod. Moreover, the addition of glycerol gave the lowest amount of dissolved iron in the oil sample owing to its ability to bind water molecules and form microemulsions in the presence of a surfactant (for example, oleic acid).
Dynamic Carbon-Constrained EPEC Model for Strategic Generation Investment Incentives with the Aim of Reducing CO2 Emissions
Authors: Valinejad Jaber , Marzband Mousa , Elsdon Michael , Saad Al-Sumaiti Ameena , Barforoushi Taghi
Published: December 2019

According to the European Union Emissions Trading Scheme, energy system planners are encouraged to consider the effects of greenhouse gases such as CO 2 in their short-term and long-term planning. A decrease in the carbon emissions produced by the power plant will result in a tax decrease. In view of this, the Dynamic carbon-constrained Equilibrium programming equilibrium constraints (DCC-EPEC) Framework is suggested to explore the effects of distinct market models on generation development planning (GEP) on electricity markets over a multi-period horizon. The investment incentives included in our model are the firm contract and capacity payment. The investment issue, which is regarded as a set of dominant producers in the oligopolistic market, is developed as an EPEC optimization problem to reduce carbon emissions. In the suggested DCC-EPEC model, the sum of the carbon emission tax and true social welfare are assumed as the objective function. Investment decisions and the strategic behavior of producers are included at the first level so as to maximize the overall profit of the investor over the scheduling period. The second-level issue is market-clearing, which is resolved by an independent system operator (ISO) to maximize social welfare. A real power network, as a case study, is provided to assess the suggested carbon-constrained EPEC framework. Simulations indicate that firm contracts and capacity payments can initiate the capacity expansion of different technologies to improve the long-term stability of the electricity market.
Design and Analysis of a Permanent Magnet Synchronous Motor Considering Axial Asymmetric Position of Rotor to Stator
Authors: Luu Phuong Thi , Lee Ji-Young , Lee Ji-Heon , Woo Byung-Chul
Published: December 2019

This paper presents the design and analysis of a permanent magnet synchronous motor (PMSM) considering the axial asymmetric PM overhang for a smart actuator (SA) application such as an isokinetic exercise machine. This structure helps take advantage of the motor space effectively and makes the system small in size and light in weight. However, two drawbacks related to the performance of motor occur when the axial asymmetric PM overhang is used: (1) an axial attractive force (AAF) is created, which can produce motor noise and vibration; (2) the torque of motor is reduced compared with the symmetric PM overhang model. We used five steps to solve these problems. Firstly, the AAF according to the variation in axial position of the rotor to the stator was calculated and analyzed. Secondly, the torque was calculated under the same conditions to confirm that the system requirements were satisfied. The three-dimensional finite element analysis was used to determine the AAF and torque. Thirdly, the appropriate axial position of the rotor to the stator was suggested considering the analysis results and space inside the housing. Next, the commercial bearing type was chosen so that the total force acting on the bearing was below the bearing load limit to ensure motor stability. Finally, a prototype model was made and tested to confirm the accuracy of the analytical results. Through this study, by using the axial asymmetric PM overhang, the total length of SA was reduced by 5mm and the performance of motor was guaranteed.
Increasing Benefits in High PV Penetration Distribution System by Using Battery Enegy Storage and Capacitor Placement Based on Salp Swarm Algorithm
Authors: Khaboot Nathphol , Srithapon Chitchai , Siritaratiwat Apirat , Khunkitti Pirat
Published: December 2019

This work aims to maximize the benefit of the low-voltage (LV) level distribution system with high photovoltaic (PV) penetration by using an optimal installation of a battery energy storage system (BESS) and capacitor. The 41-bus practical distribution system located in Thailand was focused on. The comprehensive objective function regarding the focused system was proposed. The Salp Swarm and Genetic Algorithms were applied to solve the optimization problem. The total net present value (NPV) of utility was performed as a beneficial indicator, and it was determined by the overall costs and benefits of BESS installation and capacitor placement. A comparison of total NPV in the cases of centralized BESS installation, BESS installation with LV capacitor placement, and decentralized BESS installation was indicated. The results showed that all cases of BESS installation could increasingly flatten the load on the transformer; meanwhile, the voltage profile of the system was significantly improved. Optimal installation of centralized BESS simultaneously with LV capacitor placement provides higher NPV than the case with only centralized BESS installation. In particular, the highest NPV was obtained in the case of installing decentralized BESS. The results can be utilized to maximize the benefits of the utility in the distribution system at a high PV penetration level.
Endurance of Polymeric Insulation Foil Exposed to DC-Biased Medium-Frequency Rectangular Pulse Voltage Stress
Authors: Färber Raphael , Guillod Thomas , Krismer Florian , Kolar Johann , Franck Christian
Published: December 2019

The endurance of polymeric insulation foil is investigated under a mixed medium-voltage stress (DC + medium-frequency rectangular pulse) by means of accelerated lifetime testing. A dedicated setup is used that allows us to selectively eliminate the known risk factors for premature insulation failure under medium-frequency pulse voltage stress: partial discharges (PDs) during pulse transitions, excessive dielectric heating, and systemic overvoltages. The obtained results on polyethylenterephtalat (PET) insulation foil suggest that the adequate consideration of these factors is sufficient for eliminating the adverse effects of the pulse modulation under the investigated conditions. Indeed, if all mentioned risk factors are eliminated, the time to failure observed under a pure DC stress is shorter than with a superimposed pulse (keeping the same peak voltage). There is then no indication of an additional detrimental “per pulse” degradation process (i.e., the time to failure is not dependent on pulse frequency). In contrast, when repetitive PDs are present, the lifetime under combined DC + rectangular pulse stress strongly decreases with increasing pulse switching frequency. PD erosion of the foil is quantified by means of confocal microscopy, and the applicability of the streamer criterion for predicting PD inception is discussed.
Experimental Validation of Total Energy Control System for UAVs
Authors: Jimenez Pedro , Lichota Piotr , Agudelo Daniel , Rogowski Krzysztof
Published: December 2019

This paper presents an analysis of a Total Energy Control System (TECS) introduced by Lambregts to control unmanned aerial vehicle (UAV) velocity and altitude by using the total energy distribution. Furthermore, an extended Kalman filter (EKF) approach was used to predict aircraft response in terms of angular rates and linear acceleration during a test flight campaign. From both approaches, state equations were obtained to model the aircraft using Matlab-Simulink. From an aerodynamic study, airplane characteristics were obtained in terms of non-dimensional derivatives and compared to those obtained from the experimental methods. It was determined that TECS approach was very accurate; however, disturbance errors could be decreased by adjusting some model parameters. On the other hand, it was difficult to obtain a real estimation from the EKF method due to the presence of turbulence during flight and the relatively low inertia of the scale model. Dynamic characteristics were validated using a low-cost inertial sensor that cab be easily integrated in UAV platforms. The gathered data can be used to predict model characteristics by integrating the information into flight simulators for future design development.
ANN-Based Stop Criteria for a Genetic Algorithm Applied to Air Impingement Design
Authors: Sánchez-Chica Ander , Zulueta Ekaitz , Teso-Fz-Betoño Daniel , Martínez-Filgueira Pablo , Fernandez-Gamiz Unai
Published: December 2019

Artificial Neural Networks (ANNs) have proven to be a powerful tool in many fields of knowledge. At the same time, evolutionary algorithms show a very efficient technique in optimization tasks. Historically, ANNs are used in the training process of supervising networks by decreasing the error between the output and the target. However, we propose another approach in order to improve these two techniques together. The ANN is trained with the points obtained during an optimization process by a genetic algorithm and a flower pollination algorithm. The performance of this ANN is used as a stop criterion for the optimization process. This new configuration aims to reduce the number of iterations executed by the genetic optimizer when learning the cost function by an ANN. As a first step, this approach is tested with eight benchmark functions. As a second step, the authors apply it to an air jet impingement design process, optimizing the surface temperature and the fan efficiency. Finally, a comparison between the results of a regular optimization and the results obtained in the present study is presented.
Explosion of Microbubbles Generated by the Alternating Polarity Water Electrolysis
Authors: Svetovoy Vitaly B. , Prokaznikov Alexander V. , Postnikov Alexander V. , Uvarov Ilia V. , Palasantzas George
Published: December 2019

Water electrolysis with a fast change of polarity generates a high concentration of bulk nanobubbles containing H 2 and O 2 gases. When this concentration reaches a critical value, a microbubble pops up, which is terminated quickly in an explosion process. In this paper, we provide experimental information on the phenomenon concentrating on the dynamics of exploding microbubble observed from the top and from the side. An initial bubble with a size of 150 μ m expands to a maximum size of 1200 μ m for 150 μ s and then shrinks in the cavitation process. The sound produced by the event is coming from two sources separated in time: exploding bubble and cavitating bubble. The observed dynamics supports expansion of the bubble with steam but not with H 2 and O 2 mixture. A qualitative model of this puzzling phenomenon proposed earlier is refined. It is demonstrated that the pressure and temperature in the initial bubble can be evaluated using only the energy conservation law for which the driving energy is the energy of the combusted gas. The temperature in the bubble reaches 200 ∘ C that shows that the process cannot be ignited by standard combustion, but the surface-assisted spontaneous combustion agrees well with the observations and theoretical estimates. The pressure in the microbubble varies with the size of the merging nanobubbles and is evaluated as 10–20 bar. Large pressure difference between the bubble and liquid drives the bubble expansion, and is the source of the sound produced by the process. Exploding microbubbles are a promising principle to drive fast and strong micropumps for microfluidic and other applications.
Parameter Analysis of Savonius Hydraulic Turbine Considering the Effect of Reducing Flow Velocity
Authors: Yao Jianjun , Li Fengshen , Chen Junhua , Yuan Zheng , Mai Wangeng
Published: December 2019

The Savonius-type hydraulic turbine, mainly known for its good self-starting properties and simple structure, not only has energy capturing characteristics but also has a certain effect on flow velocity reduction. Aside from ensuring energy capture efficiency, studying the effects of parameters on the flow velocity reduction capacity is of great significance for the protection of mariculture, as it can reduce the damage to cages and fishes. In this study, a computational fluid dynamics method was carried out to investigate the hydrodynamic characteristics and variations in the wake of a turbine. The accuracy of the simulation results was verified by experimental comparison. Firstly, the velocity contours and vectors were studied in detail to reveal the mechanism of the flow velocity reduction effect. Secondly, the velocity attenuation coefficient and relative attenuation length were formulated by the variation rule of the velocity field to evaluate the turbine reduction strength and range. Finally, the power coefficient was considered to predict the performance of a turbine under different tip speed ratios, overlap ratios, blade curvatures, and blade numbers. The results showed that the turbine had an obvious flow velocity reduction effect in the rear “sword”-shaped area, where the velocity field distribution had a certain regularity. In addition, by comprehensively comparing the simulation data, it was found that the respective effect trend of tip speed ratio, blade number, overlap ratio, and curvature on the turbine’s energy capture and flow velocity reduction characteristics was basically the same. Considering the effect of reducing flow velocity, a two-bladed turbine with a blade curvature of 0.8 and an overlap ratio of 0.15 is the optimal configuration.
HYRES: A Multi-Objective Optimization Tool for Proper Configuration of Renewable Hybrid Energy Systems
Authors: Donado Katheryn , Navarro Loraine , Quintero M. Christian G. , Pardo Mauricio
Published: December 2019

This paper presents the Hybrid Renewable Energy System (HYRES), a powerful tool to contribute to the viability analysis of energy systems involving renewable generators. HYRES considers various input parameters related to climatic conditions, statistical reliability, and economic views; in addition to offering multi-objective optimizations using Genetic Algorithms (GAs) that have a better cost-benefit ratio than mono-objective optimization, which is the technique used in several commercial systems like HOMER, a worldwide leader in microgrid modeling. The use of intelligent techniques in HYRES allows optimal sizing of hybrid renewable systems with wind and solar energy generators adapted to different conditions and case studies. The elements that affect the system design like buying and selling energy from/to the grid and the use of storage units can be included in system configuration according to the need. Optimization approaches are selectable and include Initial Cost, Life Cycle Cost, Loss of Power Probability, and Loss of Power Supply Probability.
Coordinated Control of RSC and GSC for DFIG System under Harmonically Distorted Grid Considering Inter-Harmonics
Authors: Pang Bo , Dai Hui , Li Feng , Nian Heng
Published: December 2019

For improving the performance of a doubly fed induction generator (DFIG) system under a harmonically distorted grid, this paper proposes a coordinated control strategy which is effective for grid inter-harmonics as well as grid integer harmonics. In order to suppress the negative impacts caused by grid harmonics, including inter-harmonics, this paper introduces an additional harmonics suppression controller, which contains a Chebyshev high-pass filter and a modified lead element considering the delay compensation. The proposed controller is employed in the rotor side converter (RSC) and grid side converter (GSC). Based on the proposed harmonics suppression controller, a coordinated control strategy between RSC and GSC is developed, in which the control targets, including the sinusoidal output current, constant power, or steady generator torque, can be achieved for DFIG, while GSC is responsible for maintaining the sinusoidal total current to guarantee the power quality of the grid connection. The effectiveness of the proposed method is verified by the theoretical analysis, and the experimental results derived using a 1 kW DFIG system validate the correctness of the theoretical analysis.
Frequency Response Quality Index for Assessing the Mechanical Condition of Transformer Windings
Authors: Kornatowski Eugeniusz , Banaszak Szymon
Published: December 2019

Frequency response analysis (FRA) is a popular method for assessing a transformer’s mechanical condition. The paper proposes a new method for interpreting the frequency response measurement results. The currently used numerical indices only give one value, which may be misleading in the analysis, while the proposed frequency response quality index (FRQI) tool analyses three separate features in the whole frequency range. The applied numerical calculations technique allows for estimations of not only the values of the average quality indices, but also locally for given frequency ranges of the analysed spectrum. It allows for determination of the problems that can be found in the active part of a transformer. The presented results come from three transformers, representing cases of typical faults. Two of them are from industry, while one was used for deformational tests in laboratory conditions. The proposed FRQI method showed its usefulness in FRA test results analysis and may be introduced into the automated assessment of such data. Each of the component parameters is sensitive to other types of differences observed between the compared frequency response curves, and may be used as a good quality detection tool.
Direct AC/DC Heating of Oxygen Transport Membranes
Authors: Kovalev Ivan , Vorobyev Alexander , Bagishev Artem , Popov Mikhail , Sharafutdinov Marat , Titkov Alexander , Bychkov Sergey , Nemudry Alexander
Published: December 2019

This article is devoted to the development of the direct resistive heating of oxygen transport membranes technique. In this case, DC was selected to perform direct heating. The effect of DC on the oxygen fluxes and the microstructure of the membrane was studied. It is shown that in the short-term experiment with DC, a positive significant effect on the oxygen transport was found, while sample exposure under the influence of DC for a long period of time had a significant negative effect on the microstructure of the membrane.
Solar UV Irradiance in a Changing Climate: Trends in Europe and the Significance of Spectral Monitoring in Italy
Authors: Fountoulakis Ilias , Diémoz Henri , Siani Anna-Maria , Laschewski Gudrun , Filippa Gianluca , Arola Antti , Bais Alkiviadis F. , De Backer Hugo , Lakkala Kaisa , Webb Ann R. , De Bock Veerle , Karppinen Tomi , Garane Katerina , Kapsomenakis John , Koukouli Maria-Elissavet , Zerefos Christos S.
Published: December 2019

Review of the existing bibliography shows that the direction and magnitude of the long-term trends of UV irradiance, and their main drivers, vary significantly throughout Europe. Analysis of total ozone and spectral UV data recorded at four European stations during 1996–2017 reveals that long-term changes in UV are mainly driven by changes in aerosols, cloudiness, and surface albedo, while changes in total ozone play a less significant role. The variability of UV irradiance is large throughout Italy due to the complex topography and large latitudinal extension of the country. Analysis of the spectral UV records of the urban site of Rome, and the alpine site of Aosta reveals that differences between the two sites follow the annual cycle of the differences in cloudiness and surface albedo. Comparisons between the noon UV index measured at the ground at the same stations and the corresponding estimates from the Deutscher Wetterdienst (DWD) forecast model and the ozone monitoring instrument (OMI)/Aura observations reveal differences of up to 6 units between individual measurements, which are likely due to the different spatial resolution of the different datasets, and average differences of 0.5–1 unit, possibly related to the use of climatological surface albedo and aerosol optical properties in the retrieval algorithms.
Production of D-Lactic Acid by the Fermentation of Orange Peel Waste Hydrolysate by Lactic Acid Bacteria
Authors: Bustamante Daniel , Tortajada Marta , Ramón Daniel , Rojas Antonia
Published: December 2019

Lactic acid is one the most interesting monomer candidates to replace some petroleum- based monomers. The application of conventional poly-lactic acid (PLA) is limited due to insufficient thermal properties. This limitation can be overcome by blending poly-D and poly-L-lactic acid. The main problem is the limited knowledge of D-lactic acid (D-LA) production. Efficient biochemical processes are being developed in order to synthesize D-LA from orange peel waste (OPW). OPW is an interesting renewable raw material for biorefinery processes of biocatalytic, catalytic or thermal nature owing to its low lignin and ash content. Bioprocessing of the pretreated OPW is carried out by enzymatic hydrolysis and fermentation of the released sugars to produce D-LA. Several strains of the species Lactobacillus delbrueckii ssp. bulgaricus have been evaluated for the production of D-LA from OPW hydrolysate using Lactobacillus delbrueckii ssp. delbrueckii CECT 286 as a reference strain since its performance in this kind of substrate have been widely reported in previous studies. Preliminary results show that Lactobacillus delbrueckii ssp. bulgaricus CECT 5037 had the best performance with a yield of 84% w/w for D-LA production and up to 95% (e.e.).
Polyolefin-Supported Hydrogels for Selective Cleaning Treatments of Paintings
Authors: Freese Silvia , Diraoui Samar , Mateescu Anca , Frank Petra , Theodorakopoulos Charis , Jonas Ulrich
Published: December 2019

Surface decontamination is of general concern in many technical fields including optics, electronics, medical environments, as well as art conservation. In this respect, we developed thin copolymer networks covalently bonded to flexible polyethylene (PE) sheets for hydrogel-based cleaning of varnished paintings. The syntheses of acrylates and methacrylates of the surfactants Triton X-100, Brij 35, and Ecosurf EH-3 or EH-9 and their incorporation into copolymers with acrylamide (PAM) and N-(4-benzoylphenyl)acrylamide are reported. Photocrosslinked polymer networks were prepared from these copolymers on corona-treated PE sheets, which can be swollen with aqueous solution to form hydrogel layers. The cleaning efficacy of these PE-PAM hydrogel systems, when swollen with appropriate cleaning solutions, was evaluated on painting surfaces in dependence of the PAM copolymer composition and degree of crosslinking. Specifically, soil and varnish removal and varnish surface solubilization were assessed on mock-ups as well as on paintings, indicating that even surfactant-free cleaning solutions were effective.
‘I’ve Put a Yule Log on Your Grate’: Lynette Roberts’s ‘Naïve’ Modernism
Authors: McAvoy Siriol
Published: December 2019

In this article, I suggest that Lynette Roberts develops a ‘naïve’ modernism that emphasizes tropes of folk art, home-made craft, and creative labour as a therapeutic response to war and a means of carving out a public role for the woman writer in the post-war world. Bringing high modernist strategies down to earth through an engagement with localized rural cultures, she strives to bridge the divide between the public and the private in order to open up a space for the woman writer within public life. As part of my discussion, I draw on Rebecca L. Walkowitz’s contention that literary style—conceived broadly as ‘attitude, stance, posture, and consciousness’—is crucial to modernist writers’ attempts to think in—and beyond—the nation. Embracing a liberating openness to experience and ‘amateurish’ passion, Roberts’s ‘home-made’ style challenges imperial constructions of nationhood centred in authority and control with a more collective, constructivist, improvisatory concept of belonging (Roberts 2005, p. xxxvi). Probing the intersections between folk art, national commitments, and global feminist projects in British modernism, I investigate how a radically transformed ‘naïve’ subtends the emergence of a new kind of feminist modernism, rooted in concepts of collective making and creative labour.
The Role of Hospital Transfer in Reexamination Computed Tomography Scans: A Nationwide Cohort Study of Gastric Cancer Patients Undergoing Surgery
Authors: Shin Jaeyong , Choi Yoon Jung , Choi Young , Lee Sang Gyu , Kim Ji Man
Published: December 2019

Because the high-cost of medical imaging can cause a tremendous economic burden across the health care system, we investigated factors associated with taking additional computed tomography (CT) scans. Data of gastric cancer patients were eligible for analysis if the patient underwent a gastrectomy during the study period (2002–2013). We defined initial CT scans as those taken within 90 days from the surgery date. If there was an additional CT scan between the date of an initial CT scan and the surgery date, we regarded it as a reexamination. We used multivariate logistic regression analysis for reexamination CT scans. Among 3342 gastrectomy patients, 1165 participants underwent second CT scans. Transfer experience (adjusted odds ratio (OR) = 23.87, 95% confidence interval (CI) = 18.15–31.39) was associated with higher OR for reexamination. Among transferred patients, an increased number per 100 beds at the initial CT hospital was associated with a decreased OR for reexamination (OR = 0.88, 95% CI = 0.83–0.94), but increased beds in surgery hospitals was related to an increased OR for reexamination (OR = 1.29, 95% CI = 1.20–1.36). In our study, transfer experience, initial CT scan in a low-volume hospital, and surgical treatment in a high-volume hospital were associated with reexamination CT scans.