bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on Low-Speed Steering Resistance Torque of Vehicles Considering Friction between Tire and Pavement
Authors: Cao Dong , Tang Bin , Jiang Haobin , Yin Chenhui , Zhang Di , Huang Yingqiu
Published: March 2019

Electric power steering (EPS) systems under existing vehicle power systems cannot provide enough power for heavy-duty commercial vehicles under pivot or low-speed steering conditions. To solve this problem, the paper proposes an EPS system that is based on the hybrid power system constituted by the vehicle power system and the supercapacitor in parallel. In order to provide a theoretical basis for the intervention and withdrawal mechanisms of a super-capacitor in the new EPS, the law of steering resistance torque at a low or extremely low vehicle speed should be explored. Firstly, the finite element model of tire/pavement was established to conduct the simulation and calculation of the low-speed steering friction force between the tire and pavement, and to obtain the fitting expression of the equivalent steering friction coefficient with the running speed of the tire. Secondly, the expression of the steering friction torque was deduced based on the calculus theory and mathematical model of the low-speed steering resistance torque, including the steering friction torque and aligning torques, established to conduct the simulation of the equivalent resistance torque applied on a steering column under low-speed condition. Subsequently, the real vehicle experiments were carried out and comparisons of the experimental results and simulation results was performed. The consistency indicated that the model of low-speed steering resistance torque had a high accuracy. Finally, the law of low-speed steering resistance torque with a vehicle speed and steering wheel angle were analyzed according to the 3D surface plot drawn from the simulation results.
Cracking Behavior of RC Beams Strengthened with Different Amounts and Layouts of CFRP
Authors: Saleem Muhammad Umair , Qureshi Hisham Jahangir , Amin Muhammad Nasir , Khan Kaffayatullah , Khurshid Hassan
Published: March 2019

The bending and shear behavior of RC beams strengthened with Carbon Fiber-Reinforced Polymers (CFRP) is the primary objective of this paper, which is focused on the failure mechanisms and on the moment-curvature response prior-to, and post, strengthening with different amounts and layouts of the CFRP reinforcement. Seven reinforced concrete beams were tested in 4-point bending, one without any CFRP reinforcement (control beam, Specimen C1), four with the same amount of CFRP in flexure but with different layouts of the reinforcement for shear (Specimens B1–B4), and two with extra reinforcement in bending, with and without reinforcement in shear (Specimens B6 and B5, respectively). During each test, the load and the mid-span deflection were monitored, as well as the crack pattern. The experimental results indicate that: (a) increasing the CFRP reinforcement above certain levels does not necessarily increase the bearing capacity; (b) the structural performance can be optimized through an appropriate combination of CFRP flexural and shear reinforcement; and (c) bond properties at the concrete–CFRP interface play a vital role, as the failure is very often triggered by the debonding of the CFRP strips. The experimental values were also verified analytically and a close agreement between the analytical and experimental values was achieved.
Large-Scale Whale-Call Classification by Transfer Learning on Multi-Scale Waveforms and Time-Frequency Features
Authors: Zhang Lilun , Wang Dezhi , Bao Changchun , Wang Yongxian , Xu Kele
Published: March 2019

Whale vocal calls contain valuable information and abundant characteristics that are important for classification of whale sub-populations and related biological research. In this study, an effective data-driven approach based on pre-trained Convolutional Neural Networks (CNN) using multi-scale waveforms and time-frequency feature representations is developed in order to perform the classification of whale calls from a large open-source dataset recorded by sensors carried by whales. Specifically, the classification is carried out through a transfer learning approach by using pre-trained state-of-the-art CNN models in the field of computer vision. 1D raw waveforms and 2D log-mel features of the whale-call data are respectively used as the input of CNN models. For raw waveform input, windows are applied to capture multiple sketches of a whale-call clip at different time scales and stack the features from different sketches for classification. When using the log-mel features, the delta and delta-delta features are also calculated to produce a 3-channel feature representation for analysis. In the training, a 4-fold cross-validation technique is employed to reduce the overfitting effect, while the Mix-up technique is also applied to implement data augmentation in order to further improve the system performance. The results show that the proposed method can improve the accuracies by more than 20% in percentage for the classification into 16 whale pods compared with the baseline method using groups of 2D shape descriptors of spectrograms and the Fisher discriminant scores on the same dataset. Moreover, it is shown that classifications based on log-mel features have higher accuracies than those based directly on raw waveforms. The phylogeny graph is also produced to significantly illustrate the relationships among the whale sub-populations.
Optimal Design of Hybrid PV-Battery System in Residential Buildings: End-User Economics, and PV Penetration
Authors: Worighi Imane , Geury Thomas , El Baghdadi Mohamed , Van Mierlo Joeri , Hegazy Omar , Maach Abdelilah
Published: March 2019

This paper proposes an optimal design for hybrid grid-connected Photovoltaic (PV) Battery Energy Storage Systems (BESSs). A smart grid consisting of PV generation units, stationary Energy Storage Systems (ESSs), and domestic loads develops a multi-objective optimization algorithm. The optimization aims at minimizing the Total Cost of Ownership (TCO) and the Voltage Deviation (VD) while considering the direct and indirect costs for the prosumer, and the system stability with regard to intermittent PV generation. The optimal solution for the optimization of the PV-battery system sizing with regard to economic viability and the stability of operation is found while using the Genetic Algorithm (GA) with the Pareto front. In addition, a fuzzy logic-based controller is developed to schedule the charging and discharging of batteries while considering the technical and economic aspects, such as battery State of Charge (SoC), voltage profile, and on/off-peak times to shave the consumption peaks. Thus, a hybrid approach that combines a Fuzzy Logic Controller (FLC) and the GA is developed for the optimal sizing of the combined Renewable Energy Sources (RESs) and ESSs, resulting in reductions of approximately 4% and 17% for the TCO and the VD, respectively. Furthermore, a sensitivity cost-effectiveness analysis of the complete system is conducted to highlight and assess the profitability and the high dependency of the optimal system configuration on battery prices.
Rheological Characteristics Evaluation of Bitumen Composites Containing Rock Asphalt and Diatomite
Authors: Huang Wentong , Wang Duanyi , He Peiyong , Long Xiang , Tong Bing , Tian Jun , Yu Peng
Published: March 2019

Previous studies have showed that rock asphalt (RA) or diatomite were used to modify the petroleum bitumen. This paper presents the findings from a study conducted to evaluate the potential impact of RA and diatomite on the rheological characteristics of bitumen composites. RA and diatomite with three different dosages were added into the petroleum bitumen: 18% RA, 13% RA+7% diatomite, and 16% RA+9% diatomite by weight. The rheological characteristics of the RA and diatomite modified bitumens were evaluated in this study. The tests conducted included temperature sweep and frequency sweep tests with a dynamic shear rheometer (DSR), a Brookfield rotation viscosity test, and a scanning electron microscope test. The research showed that the addition of RA and diatomite to petroleum bitumen considerably increased the apparent viscosity, dynamic shear modulus, and rutting resistance in bitumen specimens. However, the DSR test indicated a slight reduction in the fatigue performance of composites made of RA and diatomite modified bitumens. Overall, RA and diatomite are good modifiers for petroleum bitumen for a performance improvement.
A Systematic Review of Oxygen Therapy for the Management of Medication-Related Osteonecrosis of the Jaw (MRONJ)
Authors: Sacco Roberto , Leeson Racheal , Nissan Joseph , Olate Sergio , Bettoni Cruz de Castro Carlos Henrique , Acocella Alessandro , Lalli Anand
Published: March 2019

Background: Medication-related osteonecrosis of the jaw (MRONJ) can be a life changing iatrogenic complication of antiresorptive and antiangiogenic drug therapy. It is most often associated with high doses of these medications that are used to prevent skeletal-related events in patients with cancer and bone pathologies. Unfortunately, managing MRONJ lesions has proven difficult and remains a major challenge for clinicians. Due to the lack of efficacy in treating MRONJ by surgical modalities (local debridement and free flap reconstruction), the nonsurgical management of MRONJ is still advocated to aid healing or avoid disease progression. The aim of this systematic review is to identify, analyse and understand the published evidence related to the success of oxygen therapies such as ozone (OT) and hyperbaric oxygen (HBO) in treating MRONJ. Material and methods: A multi-database (PubMed, MEDLINE, EMBASE, CINAHL and Cochrane CENTRAL) systematic search was performed by three authors. The identified articles were independently assessed for their risk of bias. Any type of study evaluating humans treated with antiresorptive and antiangiogenic drugs were considered. The aim is primarily to evaluate the success of OT and HBO in resolving MRONJ and secondarily to identify any improvements in quality of life (QoL), rate of complications, time-to-event and severity of side effects related to these treatments. Results: In total, just 13 studies were eligible for analysis. A pooled total of 313 patients (HBO group n = 82; OT group n = 231) described in these studies have shown good tolerance for oxygen therapies. Complete resolution of MRONJ was reported in 44.58% of OT patients but only 5.17% of the HBO group. Progression of MRONJ was reported only in the HBO studies in 10.34% of cases (6 patients). The quality of evidence was low or very low in all studies. This was due to limitations in how the studies were designed, run and reported. Conclusions: Based on the limited data available, it is difficult to suggest OT is better or worse than HBO or whether it is better than a placebo. As the level of evidence available is low, this necessitates larger well-designed trials to justify these interventions for patients affected by MRONJ.
Research on the Influence of Backlash on Mesh Stiffness and the Nonlinear Dynamics of Spur Gears
Authors: Xiong Yangshou , Huang Kang , Xu Fengwei , Yi Yong , Sang Meng , Zhai Hua
Published: March 2019

In light of ignoring the effect of backlash on mesh stiffness in existing gear dynamic theory, a precise profile equation was established based on the generating processing principle. An improved potential energy method was proposed to calculate the mesh stiffness. The calculation result showed that when compared with the case of ignoring backlash, the mesh stiffness with backlash had an obvious decrease in a mesh cycle and the rate of decline had a trend of decreasing first and then increasing, so a stiffness coefficient was introduced to observe the effect of backlash. The Fourier series expansion was employed to fit the mesh stiffness rather than time-varying mesh stiffness, and the stiffness coefficient was fitted with the same method. The time-varying mesh stiffness was presented in terms of the piecewise function. The single degree of freedom model was employed, and the fourth order Runge–Kutta method was utilized to investigate the effect of backlash on the nonlinear dynamic characteristics with reference to the time history chart, phase diagram, Poincare map, and Fast Fourier Transformation (FFT) spectrogram. The numerical results revealed that the gear system primarily performs a non-harmonic-single-periodic motion. The partially enlarged views indicate that the system also exhibits small-amplitude and low-frequency motion. For different cases of backlash, the low-frequency motion sometimes shows excellent periodicity and stability and sometimes shows chaos. It is of practical guiding significance to know the mechanisms of some unusual noises as well as the design and manufacture of gear backlash.
Generation of Orbital Angular Momentum Modes Using Fiber Systems
Authors: Zhang Hongwei , Mao Baiwei , Han Ya , Wang Zhi , Yue Yang , Liu Yange
Published: March 2019

Orbital angular momentum (OAM) beams, characterized by the helical phase wavefront, have received significant interest in various areas of study. There are many methods to generate OAM beams, which can be roughly divided into two types: spatial methods and fiber methods. As a natural shaper of OAM beams, the fibers exhibit unique merits, namely, miniaturization and a low insertion loss. In this paper, we review the recent advances in fiber OAM mode generation systems, in both the interior and exterior of the beams. We introduce the basic concepts of fiber modes and the generation and detection theories of OAM modes. In addition, fiber systems based on different nuclear devices are introduced, including the long-period fiber grating, the mode-selective coupler, microstructural optical fiber, and the photonic lantern. Finally, the key challenges and prospects for fiber OAM mode systems are discussed.
PRGF-Modified Collagen Membranes for Guided Bone Regeneration: Spectroscopic, Microscopic and Nano-Mechanical Investigations
Authors: Ratiu Cristian , Brocks Marcel , Costea Traian , Moldovan Liviu , Cavalu Simona
Published: March 2019

The aim of our study was to evaluate the properties of different commercially available resorbable collagen membranes for guided bone regeneration, upon addition of plasma rich in growth factors (PRGF). The structural and morphological details, mechanical properties, and enzymatic degradation were investigated in a new approach, providing clinicians with new data in order to help them in a successful comparison and better selection of membranes with respect to their placement and working condition. Particular characteristics such as porosity, fiber density, and surface topography may influence the mechanical behavior and performances of the membranes, as revealed by SEM/AFM and nanoindentation measurements. The mechanical properties and enzymatic degradation of the membranes were analyzed in a comparative manner, before and after PRGF-modification. The changes in Young modulus values are correlated with the ultrastructural properties of each membrane type. The enzymatic (trypsin) degradation test also emphasized that PRGF-modified membranes exhibit a slower degradation compared to the native ones.
Omega-3 Fatty Acids Prevent Post-Traumatic Stress Disorder-Induced Memory Impairment
Authors: Alquraan Laiali , Alzoubi Karem H. , Hammad Hana , Rababa’h Suzie Y. , Mayyas Fadia
Published: March 2019

Post-traumatic stress disorder (PTSD) is a psychiatric disorder that can happen after exposure to a traumatic event. Post-traumatic stress disorder is common among mental health disorders that include mood and anxiety disorders. Omega-3 fatty acids (OMGs) are essential for the maintenance of brain function and prevention of cognition dysfunctions. However, the possible effect of OMG on memory impairment induced by PTSD has not been studied. In here, such an effect was explored using a rat model of PTSD. The PTSD-like behavior was induced in animals using a single-prolonged stress (SPS) rat model of PTSD (2 h restraint, 20 min forced swimming, 15 min rest, 1–2 min diethyl ether exposure). The OMG was administered orally at a dose of 100 mg omega-3 polyunsaturated fatty acid (PUFA)/100 g body weight/day. Spatial learning and memory were assessed using the radial arm water maze (RAWM) method. Changes in oxidative stress biomarkers, thiobarbituric acid reactive substances (TBARS), and brain derived neuroptrophic factor (BDNF) in the hippocampus following treatments were measured. The results revealed that SPS impaired both short- and long-term memory (p < 0.05). Use of OMG prevented memory impairment induced by SPS. Furthermore, OMG normalized SPS induced changes in the hippocampus that reduced glutathione (GSH), oxidized glutathione (GSSG), GSH/GSSG ratios, the activity of catalase, glutathione peroxidase (GPx), and TBARSs levels. In conclusion, the SPS model of PTSD-like behavior generated memory impairment, whereas OMG prevented this impairment, possibly through normalizing antioxidant mechanisms in the hippocampus.
Arsenic Trioxide and (−)-Gossypol Synergistically Target Glioma Stem-Like Cells via Inhibition of Hedgehog and Notch Signaling
Authors: Linder Benedikt , Wehle Andrej , Hehlgans Stephanie , Bonn Florian , Dikic Ivan , Rödel Franz , Seifert Volker , Kögel Donat
Published: March 2019

Glioblastoma is one of the deadliest malignancies and is virtually incurable. Accumulating evidence indicates that a small population of cells with a stem-like phenotype is the major culprit of tumor recurrence. Enhanced DNA repair capacity and expression of stemness marker genes are the main characteristics of these cells. Elimination of this population might delay or prevent tumor recurrence following radiochemotherapy. The aim of this study was to analyze whether interference with the Hedgehog signaling (Hh) pathway or combined Hh/Notch blockade using small-molecule inhibitors can efficiently target these cancer stem cells and sensitize them to therapy. Using tumor sphere lines and primary patient-derived glioma cultures we demonstrate that the Hh pathway inhibitor GANT61 (GANT) and the arsenic trioxide (ATO)-mediated Hh/Notch inhibition are capable to synergistically induce cell death in combination with the natural anticancer agent (−)-Gossypol (Gos). Only ATO in combination with Gos also strongly decreased stemness marker expression and prevented sphere formation and recovery. These synergistic effects were associated with distinct proteomic changes indicating diminished DNA repair and markedly reduced stemness. Finally, using an organotypic brain slice transplantation model, we show that combined ATO/Gos treatment elicits strong growth inhibition or even complete elimination of tumors. Collectively, our data show for the first time that ATO and Gos, two drugs that can be used in the clinic, represent a promising targeted therapy approach for the synergistic elimination of glioma stem-like cells.
Long-Term Exposure to Oroxylin A Inhibits Metastasis by Suppressing CCL2 in Oral Squamous Cell Carcinoma Cells
Authors: Ku Wei-Ting , Tung Jiun-Jia , Lee Tony Jer-Fu , Lai Kuo-Chu
Published: March 2019

Oroxylin A (Oro-A), the main bioactive flavonoid extracted from Scutellaria radix, has been reported to inhibit migration in various human cancer cell models. In this study, we further explored the anti-migration effects of Oro-A on oral squamous cell carcinoma (OSCC) cells and investigated the underlying mechanisms. A 24-h (short-term) exposure of OSCC cells to non-cytotoxic concentrations (5–20 μM) of Oro-A significantly suppressed cell migration according to a wound-healing assay. Furthermore, a 30-day exposure (long-term) to Oro-A (20 μM), which did not exhibit a cytotoxic effect on OSCC cells, significantly suppressed cell migration more than short-term Oro-A exposure. To uncover the molecular mechanisms underlying the inhibitory effect of long-term Oro-A exposure on OSCC migration, a cDNA microarray and the Ingenuity software were used. Overall, 112 upregulated and 356 downregulated genes were identified in long-term Oro-A-exposed cells compared with untreated OSCC cells. Among them, 75 genes were reported to be associated with cancer cell migration. Consistent with the cDNA microarray results, we found that the expression levels of several cell migration-related genes, such as LCN2, ID-1, MDK, S100A9 and CCL2, were significantly decreased in long-term Oro-A-exposed OSCC cells using a quantitative real-time polymerase chain reaction (Q-PCR) assay. The Western blotting and enzyme-linked immunosorbent assay (ELISA) results also demonstrated that CCL2 expression at the mRNA and protein levels was significantly decreased in long-term Oro-A-exposed OSCC cells compared with untreated OSCC cells. Moreover, the expression levels of downstream CCL2 targets, including p-ERK1/2, NFκB, MMP2, and MMP9, were also decreased in long-term Oro-A-exposed OSCC cells. Further, Oro-A treatment suppressed in vivo metastasis. These results suggest that long-term Oro-A treatment inhibits metastasis via CCL2 signaling in OSCC cells.
Titanium Silicates Precipitated on the Rice Husk Biochar as Adsorbents for the Extraction of Cesium and Strontium Radioisotope Ions
Authors: Zhuravlev Igor
Published: March 2019

The aim of the work was the development of cheap and effective adsorbents based on titanium silicates deposited on the products of thermochemical processing of rice husk to extract cesium and strontium radioisotopes from aqueous media. Synthesis of adsorbents was carried out using the cheapest and widely used titanium water-soluble reagent, titanium sulfate (an intermediate product of white rutile pigment production), as feedstock. After treatment with titanium sulfate and neutralization, hydrothermal treatment was carried out in various ways. The traditional method of processing in an autoclave was used, as well as the blowing at different temperatures by steam. The distribution coefficients and the adsorption capacity for cesium and strontium ions on these sorbents were studied. Along with the chemical composition of adsorbents obtained by those ways, the type and the temperature of hydrothermal treatment also affected the adsorption properties. It was found that the adsorbent obtained by hydrothermal treatment in an autoclave has the highest degree of cesium ions extraction (Kd = 27,500). The highest degree of strontium ions extraction (Kd = 2,095,000) has an adsorbent obtained by hydrothermal treatment with water vapor blowing.
Study on Correlation between Structural and Electronic Properties of Fluorinated Oligothiophenes Transistors by Controlling Film Thickness
Authors: Chang Jui-Fen , Shie Hua-Shiuan , Yang Yaw-Wen , Wang Chia-Hsin
Published: March 2019

α,ω-diperfluorohexylquaterthiophene (DFH-4T) has been an attractive n-type material employed in the development of high-mobility organic field-effect transistors. This paper presents a systematic study of the relationship between DFH-4T transistor performance and film structure properties as controlled by deposited thickness. When the DFH-4T thickness increases from 8 nm to 80 nm, the room-temperature field-effect mobility increases monotonically from 0.01 to 1 cm2·V−1·s−1, while the threshold voltage shows a different trend of first decrease then increase. The morphology of thin films revealed by atomic force microscopy shows a dramatic change from multilayered terrace to stacked rod like structures as the film thickness is increased. Yet the crystallite structure and the orientation of molecular constituent, as determined by X-ray diffraction and near-edge X-ray absorption fine structure respectively, do not differ much with respect to film thickness increase. Further analyses of low-temperature transport measurements with mobility-edge model demonstrate that the electronic states of DFH-4T transistors are mainly determined by the film continuity and crystallinity of the bottom multilayered terrace. Moreover, the capacitance-voltage measurements of DFH-4T metal-insulator-semiconductor diodes demonstrate a morphological dependence of charge injection from top contacts, which well explains the variation of threshold voltage with thickness. The overall study provides a deeper understanding of microstructural and molecular growth of DFH-4T film and clarify the structural effects on charge transport and injection for implementation of high-mobility top-contact transistors.
Examining the Causal Relationship between Tourism and Economic Growth: Spillover Index Approach for Selected CEE and SEE Countries
Authors: Škrinjarić Tihana
Published: March 2019

Debate on tourism-led growth and growth-led tourism is still ongoing today, with much research done for developed countries and those which are popular tourist destinations over the world. Surprisingly, the research is scarce for the Central and Eastern European (CEE) and South and Eastern European (SEE) countries. The contribution of this research is examining the dynamic relationship between spillovers of tourism growth and economic growth for CEE and SEE countries for the first time in the literature. The methodology used in the study (spillover indices) allows for estimating the dynamic relationship throughout rolling indices. Based upon monthly data (with different time spans depending upon availability of data, from January 2000 to January 2003 until December 2017, i.e., October 2018), the following countries were in focus: Bulgaria, Croatia, Czech Republic, Hungary, Poland, Slovenia and Slovakia. Results from dynamic rolling spillover indices indicate mixed results for all of the countries throughout the sample. Dynamic results enable policymakers from individual countries to focus on specifics of their economies to develop even better policies in order to achieve best possible results regarding the tourism growth and related economic growth.
Transformerless Quasi-Z-Source Inverter to Reduce Leakage Current for Single-Phase Grid-Tied Applications
Authors: Choi Woo-Young , Yang Min-Kwon
Published: March 2019

The conventional single-phase quasi-Z-source (QZS) inverter has a high leakage current as it is connected to the grid. To address this problem, this paper proposes a transformerless QZS inverter, which can reduce the leakage current for single-phase grid-tied applications. The proposed inverter effectively alleviates the leakage current problem by removing high-frequency components for the common-mode voltage. The operation principle of the proposed inverter is described together with its control strategy. A control scheme is presented for regulating the DC-link voltage and the grid current. A 1.0 kW prototype inverter was designed and tested to verify the performance of the proposed inverter. Silicon carbide (SiC) power devices were applied to the proposed inverter to increase the power efficiency. The experimental results showed that the proposed inverter achieved high performance for leakage current reduction and power efficiency improvement.
Low Cost Test Pattern Generation in Scan-Based BIST Schemes
Authors: Zhang Guohe , Yuan Ye , Liang Feng , Wei Sufen , Yang Cheng-Fu
Published: March 2019

This paper proposes a low-cost test pattern generator for scan-based built-in self-test (BIST) schemes. Our method generates broadcast-based multiple single input change (BMSIC) vectors to fill more scan chains. The proposed algorithm, BMSIC-TPG, is based on our previous work multiple single-input change (MSIC)-TPG. The broadcast circuit expends MSIC vectors, so that the hardware overhead of the test pattern generation circuit is reduced. Simulation results with ISCAS’89 benchmarks and a comparison with the MSIC-TPG circuit show that the proposed BMSIC-TPG reduces the circuit hardware overhead about 50% with ensuring of low power consumption and high fault coverage.
Defect Estimation in Non-Destructive Testing of Composites by Ultrasonic Guided Waves and Image Processing
Authors: Tiwari Kumar Anubhav , Raisutis Renaldas , Tumsys Olgirdas , Ostreika Armantas , Jankauskas Kestutis , Jakutavicius Julijus
Published: March 2019

The estimation of the size and location of defects in multi-layered composite structures by ultrasonic non-destructive testing using guided waves has attracted the attention of researchers for the last few decades. Although extensive signal processing techniques are available, there are only a few studies available based on image processing of the ultrasonic B-scan image to extract the size and location of defects via the process of ultrasonic non-destructive testing. This work presents an image processing technique for ultrasonic B-scan images to improve the estimation of the location and size of disbond-type defects in glass fiber-reinforced plastic materials with 25-mm and 51-mm diameters. The sample is a segment of a wind turbine blade with a variable thickness ranging from 3 to 24 mm. The experiment is performed by using a low-frequency ultrasonic system and a pair of contact-type piezoceramic transducers kept apart by a 50-mm distance and embedded on a moving mechanical panel. The B-scan image acquired by the ultrasonic pitch-catch technique is denoised by utilizing features of two-dimensional discrete wavelet transform. Thereafter, the normalized pixel densities are compared along the scanned distance on the region of interest of the image, and a −3 dB threshold is applied to the locations and sizes the defects in the spatial domain.
Numerical Analysis of the Influence of Design Parameters on the Efficiency of an OWC Axial Impulse Turbine for Wave Energy Conversion
Authors: Luo Yongyao , Presas Alexandre , Wang Zhengwei
Published: March 2019

Oscillating water column (OWC) axial impulse turbines permit the conversion of wave energy into electrical power. Unlike other hydropower units with a mature and well established technology, such turbines have been recently developed, there are still few prototypes operating and therefore there is a large space for optimizing its design. Many recent studies focus on the improvement of the efficiency and transient characteristics by means of experimentation and also simulation techniques. In the present paper we use a 3D numerical simulation model (computational fluid dynamics model with ANSYS-Fluent 18) to analyze the influence of different geometrical parameters on the efficiency of the turbine, which have been less discussed yet. A reference configuration case has been used to validate our simulation model by comparing it with previous experimental results. Then, parametric variations in the guide vane number and type, gaps between the rotating and stationary part and hub to tip ratio have been introduced in the model to discuss the influence of these effects. It is found that some of these parameters have an important influence on the efficiency of the turbine and therefore, the results presented in this paper can help to optimize future designs of OWC impulse turbines.
Is It Possible to Supply Norwegian Apartment Blocks with 4th Generation District Heating?
Authors: Rønneseth Øystein , Holck Sandberg Nina , Sartori Igor
Published: March 2019

Direct electricity is widely used for heating purposes in Norway, leading to significant strain on the electricity grid during the heating season. Conversion to 4th generation district heating (4GDH) is an effective method for reducing the need for large investments in the electricity grid, while simultaneously improving the energy efficiency of district heating systems. This article evaluates the possibility of reducing the supply temperature in existing Norwegian apartment blocks by improving the thermal envelope and reducing the temperature levels for the heating system. The analysis is based on simulations in IDA ICE (IDA Indoor Climate and Energy) focusing on whether the reduced supply temperature guarantees thermal comfort in the building, considering the coldest room with a heating setpoint of 22 °C. Based on a recommended minimum acceptable indoor temperature of 19 °C from the Norwegian building regulations (TEK), it should be possible to lower the radiator supply temperature from 80 to 60 °C for apartment blocks newer than 1971. For older buildings, an “intermediate” renovation is necessary to maintain temperatures above 19 °C, however, a “standard” renovation is recommended to ensure thermal comfort and improve the energy efficiency of the building stock.
Uncertainty Evaluation of Safe Mud Weight Window Utilizing the Reliability Assessment Method
Authors: Ma Tianshou , Tang Tao , Chen Ping , Yang Chunhe
Published: March 2019

Due to the uncertainty of formation properties and improper wellbore stability analysis methods, the input parameters are often uncertain and the required mud weight to prevent wellbore collapse is too large, which might cause an incorrect result. However, the uncertainty evaluation of input parameters and their influence on safe mud weight window (SMWW) is seldom investigated. Therefore, the present paper aims to propose an uncertain evaluation method to evaluate the uncertainty of SMWW. The reliability assessment theory was introduced, and the uncertain SMWW model was proposed by involving the tolerable breakout, the Mogi-Coulomb (MG-C) criterion and the reliability assessment theory. The influence of uncertain parameters on wellbore collapse, wellbore fracture and SMWW were systematically simulated and investigated by utilizing Monte Carlo simulation. Finally, the field observation of well SC-101X was reported and discussed. The results indicated that the MG-C criterion and tolerable breakout is recommended for wellbore stability analysis. The higher the coefficient of variance is, the higher the level of uncertainty is, the larger the impact on SMWW will be, and the higher the risk of well kick, wellbore collapse and fracture will be. The uncertainty of basic parameters has a very significant impact on SMWW, and it cannot be ignored. For well SC-101X, the SMWW predicted by analytical solution is 0.9921–1.6020 g/cm3, compared to the SMWW estimated by the reliability assessment method, the reliability assessment method tends to give a very narrow SMWW of 1.0756–1.0935 g/cm3 and its probability is only 80%, and the field observation for well kick and wellbore fracture verified the analysis results. For narrow SMWW formation drilling, some kinds of advanced technology, such as the underbalanced drilling (UBD), managed pressure drilling (MPD), micro-flow drilling (MFD) and wider the SMWW, can be utilized to maintain drilling safety.
Sliding Mode-Based Robust Control for Piezoelectric Actuators with Inverse Dynamics Estimation
Authors: Chouza Ander , Barambones Oscar , Calvo Isidro , Velasco Javier
Published: March 2019

This paper presents an improved control approach to be used for piezoelectric actuators. The proposed approach is based on sliding mode control with estimation perturbation (SMCPE) techniques. Also, a proportional–integral–derivative (PID)-type sliding surface is proposed for position tracking. The proposed approach has been studied and implemented in a commercial actuator. A model for the system is introduced, which includes the Bouc–Wen (BW) model to represent the hysteresis, and it is identified by means of the System Identification Toolbox in Matlab/Simulink. Experimental data show that the proposed controller has a better performance when compared to a proportional-integral (PI) controller or a conventional SMCPE in motion tracking. Furthermore, a sub-micrometer accuracy tracking can be obtained while compensating for the hysteresis effect.
A Simplified Methodology for Existing Tertiary Buildings’ Cooling Energy Need Estimation at District Level: A Feasibility Study of a District Cooling System in Marrakech
Authors: Charani Shandiz Saeid , Denarie Alice , Cassetti Gabriele , Calderoni Marco , Frein Antoine , Motta Mario
Published: March 2019

In district energy systems planning, the calculation of energy needs is a crucial step in making the investment profitable. Although several computational approaches exist for estimating the thermal energy need of individual buildings, this is challenging at the district level due to the amount of data needed, the diversity of building types, and the uncertainty of connections. The aim of this paper is to present a simplified measurement-based methodology for estimating the cooling energy needs at the district level, which can be employed in the preliminary sizing and design of a district cooling network. The methodology proposed is suitable for tertiary buildings and is based on building electricity bills as historical data to calculate the yearly cooling demand. Then, the developed method is applied to a real case study: the feasibility analysis of a sustainable district cooling network for a hotel district in the city of Marrakech. The designed system foresees a 23-MWcold district cooling network that is 4 km long, supplying 26 GWh of cooling to the tourist area. The results show that the proposed methodology for cooling demand estimation is coherent with the other existing methods in the literature.
Coordinated Control for Operating Characteristics Improvement of UHVDC Transmission Systems under Hierarchical Connection Scheme with STATCOM
Authors: Rehman Atiq Ur , Guo Chunyi , Zhao Chengyong
Published: March 2019

Ultra-high voltage direct current (UHVDC) systems under hierarchical connection schemes (HCSs) linked to AC grids with different voltage levels (500 and 1000 kV) have been a great concern for power utilities to transfer bulk power. They have some operating issues like cascaded commutation failures and longer fault recovery time under certain fault conditions. Since STATCOM has the ability to effectively regulate AC busbar voltages, thus it is considered in this paper to improve the operating characteristics of UHVDC-HCS systems. To further improve the operating characteristics, a coordinated control between an UHVDC-HCS system and STATCOM is presented. To validate the effectiveness of coordinated control, the comparison between different control modes such as reactive power control (Q-control) and voltage control (V-control) in the outer loop control of STATCOM are conducted in detail. Various indices like commutation failure immunity index (CFII) and commutation failure probability index (CFPI) are also comprehensively evaluated in order to investigate robustness of the adopted coordinated control. An UHVDC-HCS system with multiple STATCOMs on the inverter side (500 kV bus) is developed in PSCAD/EMTDC. The impact of coordinated control on commutation failure phenomena and fault recovery time during single and three phase AC faults is analyzed. The analysis shows that coordinated control with V-control mode of STATCOM exhibits better performance in enhancing the operating characteristics of UHVDC-HCS system by improving the CFII, effectively reducing the CFPI and fault recovery time under various AC faults.
Prediction of Electric Vehicle Range: A Comprehensive Review of Current Issues and Challenges
Authors: Varga Bogdan Ovidiu , Sagoian Arsen , Mariasiu Florin
Published: March 2019

Electric vehicles (EV) are the immediate solution to drastically reducing pollutant emissions from the transport sector. There is a continuing increase in the number of EVs in use, but their widespread and massive acceptance by automotive consumers is related to the performance they can deliver. The most important feature here (a hot topic at present in EV research) is related to the possibility of providing a more accurate prediction of range. Range prediction is a complex problem because it depends on a lot of influence factors (internal, external, constant, variables) and the present paper aims to investigate the effect of these factors on the range of EVs. The results and aspects of current worldwide research on this theme are presented through the analysis of the main classes of influence factors: Vehicle design, the driver and the environment. Further, the weight and effect of each potential factor which influences EV range was analyzed by presenting current issues. An exhaustive and comprehensive analysis has made it possible to identify future research and development directions in the EV research field, resulting in massive future and immediate EV penetration in the automotive market.
HyFlow—A Hybrid Load Flow-Modelling Framework to Evaluate the Effects of Energy Storage and Sector Coupling on the Electrical Load Flows
Authors: Böckl Benjamin , Greiml Matthias , Leitner Lukas , Pichler Patrick , Kriechbaum Lukas , Kienberger Thomas
Published: March 2019

HyFlow is a grid-based multi-energy system (MES) modelling framework. It aims to model the status quo of current energy systems, future scenarios with a high share of fluctuating energy sources or additional consumers like electric vehicles, and to compare solution strategies if certain parts of the infrastructure are congested. In order to evaluate the congestion limits and the feasibility and suitability of solution strategies (e.g., energy storage, sector coupling technologies, demand response (DR)), load flow calculations of all three main grid-bound energy carriers are implemented in one single modelling framework. In addition to the implemented load flow models, it allows the interaction of these grids with the use of hybrid elements. This measure enables a proper assessment of future scenarios, not only for the infrastructure of one energy carrier, but for the overall energy system. The calculation workflow of HyFlow, including the implemented load flow calculations, as well as the implementation of the flexibility options, is described in detail in the methodology section. To demonstrate the wide range of applicability of HyFlow with different spatial ranges, two case studies referring to current research problems are presented: a city and a region surrounding the mentioned city. The calculations for the mentioned case studies are performed for three levels. A “status quo” level, a “high-stress” level with added fluctuating energy sources and consumers, and an “improvement” level, where flexibility options are introduced to the system. The effect of the flexibility options on future energy grids is, therefore, analyzed and evaluated. A wide variety of evaluation criteria can be selected. For example, the maximum load of certain power lines, the self-sufficiency of the overall system, the total transport losses or the total energy consumption.
Dissolution Kinetics of R-Glass Fibres: Influence of Water Acidity, Temperature, and Stress Corrosion
Authors: Krauklis Andrey E. , Gagani Abedin I. , Vegere Kristine , Kalnina Ilze , Klavins Maris , Echtermeyer Andreas T.
Published: March 2019

Glass fibres slowly degrade due to dissolution when exposed to water. Such environmental aging results in the deterioration of the mechanical properties. In structural offshore and marine applications, as well as in the wind energy sector, R-glass fibre composites are continuously exposed to water and humid environments for decades, with a typical design lifetime being around 25 years or more. During this lifetime, these materials are affected by various temperatures, acidity levels, and mechanical loads. A Dissolving Cylinder Zero-Order Kinetic (DCZOK) model was able to explain the long-term dissolution of R-glass fibres, considering the influence of the p H , temperature, and stress corrosion. The effects of these environmental conditions on the dissolution rate constants and activation energies of dissolution were obtained. Experimentally, dissolution was measured using High Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS). For stress corrosion, a custom rig was designed and used. The temperature showed an Arrhenius-type influence on the kinetics, increasing the rate of dissolution exponentially with increasing temperature. In comparison with neutral conditions, basic and acidic aqueous environments showed an increase in the dissolution rates, affecting the lifetime of glass fibres negatively. External loads also increased glass dissolution rates due to stress corrosion. The model was able to capture all of these effects.
Equations for Deep Water Counter Streaming Waves and New Integrals of Motion
Authors: Dyachenko Alexander
Published: March 2019

The waves on a free surface of 2D deep water can be split into two groups: the waves moving to the right, and the waves moving to the left. A specific feature of the four-wave interactions of water waves allows to describe the evolution of the two groups as a system of two equations. The fundamental consequence of this decomposition is the conservation of the “number of waves” in each particular group. The envelope approximation for the waves in each group of counter streaming waves is obtained.
Quality Aspects of Insects as Food—Nutritional, Sensory, and Related Concepts
Authors: Elhassan Mohammed , Wendin Karin , Olsson Viktoria , Langton Maud
Published: March 2019

In the search for another appealing source of future food to cover the increasing need for nutrients of a growing global population, this study reviewed the potential of insects as human food. Most previous reviews have dealt with insects as a group, making it difficult to evaluate each individual insect species as food because of the generalized data. This study assessed some common edible insects, but concentrated on mealworms. Insects, especially mealworms, have a similar or higher nutritional value than many conventional food sources. For example, the protein content of mealworm larvae is reported to be almost 50% of dry weight, while the fat content is about 30% of larval dry weight. Mealworms can be cooked by different methods, such as hot air drying, oven broiling, roasting, pan frying, deep frying, boiling, steaming, and microwaving. Oven broiling in particular gives a desirable aroma of steamed corn for consumers. Changes in the flavor, taste, and texture of mealworm products during storage have not been studied, but must be determined before mealworms can be used as a commercial food source. Factors controlling the shelf-life of mealworms, such as their packaging and storage, should be identified and considered with respect to the feasibility of using mealworms on a commercial scale.
Ancient Mitochondrial Genomes Reveal the Absence of Maternal Kinship in the Burials of Çatalhöyük People and Their Genetic Affinities
Authors: Chyleński Maciej , Ehler Edvard , Somel Mehmet , Yaka Reyhan , Krzewińska Maja , Dabert Mirosława , Juras Anna , Marciniak Arkadiusz
Published: March 2019

Çatalhöyük is one of the most widely recognized and extensively researched Neolithic settlements. The site has been used to discuss a wide range of aspects associated with the spread of the Neolithic lifestyle and the social organization of Neolithic societies. Here, we address both topics using newly generated mitochondrial genomes, obtained by direct sequencing and capture-based enrichment of genomic libraries, for a group of individuals buried under a cluster of neighboring houses from the classical layer of the site’s occupation. Our data suggests a lack of maternal kinship between individuals interred under the floors of Çatalhöyük buildings. The findings could potentially be explained either by a high variability of maternal lineages within a larger kin group, or alternatively, an intentional selection of individuals for burial based on factors other than biological kinship. Our population analyses shows that Neolithic Central Anatolian groups, including Çatalhöyük, share the closest affinity with the population from the Marmara Region and are, in contrast, set further apart from the Levantine populations. Our findings support the hypothesis about the emergence and the direction of spread of the Neolithic within Anatolian Peninsula and beyond, emphasizing a significant role of Central Anatolia in this process.