bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid Pyrolysis of SmBa2Cu3O7-δ Films in CSD-MOD Using Extremely-Low-Fluorine Solutions
Authors: Li Minjuan , Cayado Pablo , Erbe Manuela , Jung Alexandra , Hänisch Jens , Holzapfel Bernhard , Liu Zhiyong , Cai Chuanbing
Published: January 2020

SmBa2Cu3O7-δ (SmBCO) films have been prepared by chemical solution deposition starting from extremely-low-fluorine solutions (7% fluorine with respect to standard full trifluoroacetate solutions). Smooth and homogeneous SmBCO films could be achieved at heating rates of up to 20 °C/min during pyrolysis. The best films were achieved at a crystallization temperature of 810 °C and 50 ppm of oxygen partial pressure. At these conditions, the ~270 nm thick SmBCO films grow mostly c-axis-oriented with J c sf values at 77 K of ~2 MA/cm2 and critical temperatures Tc of up to 95.0 K. These results demonstrate that using extremely-low-fluorine solutions is very attractive since the production rate can be largely increased due to the solutions’ robustness during pyrolysis retaining a remarkable quality of the grown films. Nevertheless, further optimization of the growth process is needed to improve the superconducting properties of the films.
Fabrication of a Thick Crystalline Al2O3 Coating with Insulation and High Thermal Conductivity via Anodic Oxidation and Subsequent Mic Arc Discharge Treatment
Authors: Song Wei , Jiang Bailing , Ji Dongdong
Published: January 2020

Amorphous Al2O3 coating with a thickness of 143 μm was firstly prepared by anodic oxidation, then the amorphous Al2O3 was transformed into crystalline Al2O3 through applying micro arc discharge. The crystal structure of the Al2O3 coatings was analyzed with an X-ray diffractometer. Results indicated that the coating consisted of amorphous and crystalline Al2O3. The microstructure of the coating was characterized by scanning electron microscopy, which showed that the coating had a compact structure. The thermal conductivity of the coating was 23.7 W/m·K, which is significantly higher than that of amorphous Al2O3 coating. The total and specific breakdown voltages of the coating were 3.85 kV and 26.92 kV/mm, which is suitable to apply for high power LED heat sink substrate.
Mechanical and Thermal Properties of Waterborne Polyurethane Coating Modified through One-Step Cellulose Nanocrystals/Graphene Materials Sols Method
Authors: Yang Feng , Wu Yan , Zhang Shuqin , Zhang Haiming , Zhao Suilang , Zhang Jilei , Fei Benhua
Published: January 2020

Developing multifunctional coatings with excellent mechanical and thermal properties is highly desirable for wood-based composite application. The recent development of waterborne coatings for wood products suggests that a promising thermosetting material needs to also have properties like low volatile organic contents (VOCs), hardness, and fast curing. The cellulose nanocrystals/graphene materials (CNC/GM) sols were prepared through the one-step method as the thermally conductive and reinforced modifier for preparing waterborne polyurethane (WPU) coatings. The influence of this modifier on the thermal and mechanical properties such as thermal conductivity, abrasion resistance, and adhesion of WPU coatings was investigated. The results indicated that adding CNC/GM sols increased the hardness, abrasion resistance, and thermal conductivity of the WPU coatings, and meanwhile maintained the coating adhesion at the highest grade (level 1). The highest abrasion resistance value of 0.023 g/100 r was obtained for the modified WPU coating when the addition of GM was 3%.
Enhancing Perovskite Solar Cell Performance through Surface Engineering of Metal Oxide Electron-Transporting Layer
Authors: Lu Gang , Wang Xuhui , Du Juan , Zhang Min , Gao Yali , Liu Yanbo , Ma Jing , Lin Zhenhua
Published: January 2020

Perovskite solar cells have gained increasing interest in recent times owing to the rapidly enlarged device efficiency and tunable optoelectronic properties in various applications. In perovskite solar cells, interface engineering plays an important role in determining the final device efficiency and stability. In this study, we adopted TiCl4 treatment to reduce the surface roughness of the metal oxide layer and improve the perovskite film quality to obtain better device performance. After proper TiCl4 treatment, the efficiencies of TiCl4–TiO2- and TiCl4–ZnO-based devices were significantly enhanced up to 16.5% and 17.0%, respectively, compared with those based on pristine TiO2 and ZnO (13.2% and 10.2%, respectively).
Effects of Bentonite Nanoclay and Cetyltrimethyl Ammonium Bromide Modified Bentonite Nanoclay on Phase Inversion of Water-in-Oil Emulsions
Authors: Ogunlaja Sileola B. , Pal Rajinder
Published: January 2020

The effects of unmodified and modified bentonite nanoclays (with various degrees of surfactant modification) on the catastrophic phase inversion from water-in-oil (W/O) emulsion to oil-in-water (O/W) emulsion were determined experimentally. The bentonite nanoclay (NC-Bt) was suspended in the aqueous phase, and the critical volume fraction of water where phase inversion from W/O to O/W emulsion took place was determined through conductivity measurements. Cetyltrimethyl ammonium bromide (CTAB) was used as a surfactant to modify the nanoclay. The adsorption of CTAB onto nanoclay had a strong influence on the contact angle and the critical volume fraction of water where phase inversion took place. The modification of the nanoclay brought about by the adsorption of CTAB increased the three-phase contact angle (measured through the aqueous phase), thereby making it more hydrophobic, and prolonged the phase inversion point. CTAB alone and CTAB-modified nanoclay delayed the phase inversion process in a similar manner, showing a strong dependence on the CTAB concentration.
Uniform Hyperbolicity of a Scattering Map with Lorentzian Potential
Authors: Yoshino Hajime , Kogawa Ryota , Shudo Akira
Published: January 2020

We show that a two-dimensional area-preserving map with Lorentzian potential is a topological horseshoe and uniformly hyperbolic in a certain parameter region. In particular, we closely examine the so-called sector condition, which is known to be a sufficient condition leading to the uniformly hyperbolicity of the system. The map will be suitable for testing the fractal Weyl law as it is ideally chaotic yet free from any discontinuities which necessarily invokes a serious effect in quantum mechanics such as diffraction or nonclassical effects. In addition, the map satisfies a reasonable physical boundary condition at infinity, thus it can be a good model describing the ionization process of atoms and molecules.
Quantum Bounds on Detector Efficiencies for Violating Bell Inequalities Using Semidefinite Programming
Authors: Sauer Alexander , Alber Gernot
Published: January 2020

Loophole-free violations of Bell inequalities are crucial for fundamental tests of quantum nonlocality. They are also important for future applications in quantum information processing, such as device-independent quantum key distribution. Based on a detector model which includes detector inefficiencies and dark counts, we estimate the minimal requirements on detectors needed for performing loophole-free bipartite and tripartite Bell tests. Our numerical investigation is based on a hierarchy of semidefinite programs for characterizing possible quantum correlations. We find that for bipartite setups with two measurement choices and our detector model, the optimal inequality for a Bell test is equivalent to the Clauser–Horne inequality.
Sustainable Utilization of Indigenous Goats in Southern Africa
Authors: Monau Phetogo , Raphaka Kethusegile , Zvinorova-Chimboza Plaxedis , Gondwe Timothy
Published: January 2020

Goats have a key role in ensuring food security and economic livelihood to smallholder farmers in rural areas. Women play a vital role in goat rearing, promoting economic autonomy within households. Indigenous goats dominate and are of high significance due to their adaptive traits that are relevant for climate change and low maintenance. However, lack of emphasis on farmer-centered technology development and proper breed characterization remains a hitch to sustainable utilization and breed development of indigenous goats. This can be over come through proper linkage between market and production, workable regional and national agricultural policies, community breeding programs, collaborative research work within the region, and consistent government support.
Overcoming Data Scarcity in Earth Science
Authors: Gorgoglione Angela , Castro Alberto , Chreties Christian , Etcheverry Lorena
Published: January 2020

The Data Scarcity problem is repeatedly encountered in environmental research. This may induce an inadequate representation of the response’s complexity in any environmental system to any input/change (natural and human-induced). In such a case, before getting engaged with new expensive studies to gather and analyze additional data, it is reasonable first to understand what enhancement in estimates of system performance would result if all the available data could be well exploited. The purpose of this Special Issue, “Overcoming Data Scarcity in Earth Science” in the Data journal, is to draw attention to the body of knowledge that leads at improving the capacity of exploiting the available data to better represent, understand, predict, and manage the behavior of environmental systems at meaningful space-time scales. This Special Issue contains six publications (three research articles, one review, and two data descriptors) covering a wide range of environmental fields: geophysics, meteorology/climatology, ecology, water quality, and hydrology.
The VNTR 48 bp Polymorphism in the DRD4 Gene Is Associated with Higher Tobacco Smoking in Male Mexican Mestizo Smokers with and without COPD
Authors: Pérez-Rubio Gloria , García-Carmona Salvador , García-Gómez Leonor , Hernández-Pérez Andrea , Ramírez-Venegas Alejandra , López-Flores Luis Alberto , Sansores Raúl , Falfán-Valencia Ramcés
Published: January 2020

Cigarette smoking is influenced by nicotine’s effects on dopaminergic activity, which appear to be moderated by genetic variation, particularly a variable number tandem repeat (VNTR, 48 bp) polymorphism in the third exon of the dopamine receptor gene (DRD4). Smokers with the VNTR ≥7 repeats (long, L allele) report markedly increased participation in some smoking behaviors; hence, our aim was to evaluate the association of the L allele in Mexican Mestizo smokers with and without COPD. The DRD4 VNTR 48 bp was genotyped in 492 Mexican Mestizo smokers: 164 COPD patients (≥20 cigarettes per day, cpd), 164 heavy smokers without COPD (HS, ≥20 cpd) and 164 light smokers without COPD (LS, 1–10 cpd). In the dominant model analysis (SL + LL vs. SS), men in the COPD and HS groups showed a statistical difference compared to LS (p = 0.01, OR = 2.06, CI 95% 1.17–3.64 and p = 0.05, OR = 1.88, CI 95% 1.03–3.45, respectively). In addition, by clustering smokers >20 cpd (COPD + HS) and comparing with the LS group, we found an association with increased risk of higher tobacco smoking p = 0.01, OR = 1.99, CI 95% 1.18–3.34. In conclusion, the long allele (L) in the VNTR of the DRD4 gene is associated with the risk of presenting higher tobacco smoking in male Mexican Mestizo smokers.
Utility of Contrast-Enhanced Harmonic Endoscopic Ultrasonography for Early Diagnosis of Small Pancreatic Cancer
Authors: Yamashita Yasunobu , Tanioka Kensuke , Kawaji Yuki , Tamura Takashi , Nuta Junya , Hatamaru Keiichi , Itonaga Masahiro , Yoshida Takeichi , Ida Yoshiyuki , Maekita Takao , Iguchi Mikitaka , Terada Masaki , Sonomura Tetsuo , Hirono Seiko , Okada Ken-Ichi , Kawai Manabu , Yamaue Hiroki , Kitano Masayuki
Published: January 2020

This study aimed to assess whether contrast-enhanced harmonic endoscopic ultrasonography (CH-EUS), compared to multidetector-row computed tomography (MDCT) and magnetic resonance imaging (MRI), is useful for early diagnosis of small pancreatic cancer (PC). Between March 2010 and June 2018, all three imaging modalities and surgery were performed for patients with a pancreatic solid lesion measuring ≤20 mm; diagnostic ability was compared among modalities. Fifty-one of 60 patients were diagnosed with PC (PC size in 41 patients: 11–20 mm; 10 patients: ≤10 mm). The sensitivity, specificity, and accuracy of CH-EUS, MDCT, and MRI for PC (11–20 mm) detection were 95%/83%/94%, 78%/83%/79%, and 73%/33%/68%, respectively. The diagnostic ability of CH-EUS was significantly superior compared with MDCT and MRI (p = 0.002 and p = 0.007, respectively). The sensitivity, specificity, and accuracy of CH-EUS, MDCT, and MRI for PC (≤10 mm) detection were 70%/100%/77%, 20%/100%/38%, and 50%/100%/62%, respectively. The diagnostic ability of CH-EUS tended to be superior to that of MDCT (p = 0.025). The sensitivity of MDCT for PC (≤10 mm) detection was significantly lower than that for PC (11–20 mm) detection (20% vs. 78%; p = 0.001). CH-EUS, compared to MDCT and MRI, is useful for diagnosing small PCs.
“I Actually Don’t Know What HIV Is”: A Mixed Methods Analysis of College Students’ HIV Literacy
Authors: Avina Robert M. , Mullen Mathew , Mshigeni Salome , Becerra Monideepa B.
Published: January 2020

Objective: Human immunodeficiency virus (HIV) remains a major public health issue with young adults facing a disproportionately higher rate of the burden. Our goal was to address the current literacy related to HIV, including biomedical prevention methods and barriers to care, such as cultural factors, from a sample of college students. Methods: We conducted a convergent parallel mixed methods analysis where both qualitative and quantitative data were collected and analyzed separately. A thematic analysis was conducted to assess qualitative results, while descriptive statistics were conducted to assess quantitative survey results. Results: HIV literacy was limited, with several participants reporting that they did not understand what HIV meant. While the majority knew the use of condoms, knowledge of other biomedical prevention methods was limited, as was the understanding the risk factors of HIV, with participants noting sharing a toilet seat and promiscuity as risk factors. Self-efficacy for HIV prevention was low among participants with many reporting that cultural barriers prevented discussion of risky behaviors and prevention methods in their families and social groups. Conclusion: Targeted, culturally sensitive, health education initiatives are needed to understand the high, low, or no risks of HIV as well as address stigmas related to HIV.
Information Dynamic Correlation of Vibration in Nonlinear Systems
Authors: Wu Zhe , Yang Guang , Zhang Qiang , Tan Shengyue , Hou Shuyong
Published: January 2020

In previous studies, information dynamics methods such as Von Neumann entropy and Rényi entropy played an important role in many fields, covering both macroscopic and microscopic studies. They have a solid theoretical foundation, but there are few reports in the field of mechanical nonlinear systems. So, can we apply Von Neumann entropy and Rényi entropy to study and analyze the dynamic behavior of macroscopic nonlinear systems? In view of the current lack of suitable methods to characterize the dynamics behavior of mechanical systems from the perspective of nonlinear system correlation, we propose a new method to describe the nonlinear features and coupling relationship of mechanical systems. This manuscript verifies the above hypothesis by using a typical chaotic system and a real macroscopic physical nonlinear system through theory and practical methods. The nonlinear vibration correlation in multi-body mechanical systems is very complex. We propose a full-vector multi-scale Rényi entropy for exploring the chaos and correlation between the dynamic behaviors of mechanical nonlinear systems. The research results prove the effectiveness of the proposed method in modal identification, system dynamics evolution and fault diagnosis of nonlinear systems. It is of great significance to extend these studies to the field of mechanical nonlinear system dynamics.
Ordinal Pattern Based Entropies and the Kolmogorov–Sinai Entropy: An Update
Authors: Gutjahr Tim , Keller Karsten
Published: January 2020

Different authors have shown strong relationships between ordinal pattern based entropies and the Kolmogorov–Sinai entropy, including equality of the latter one and the permutation entropy, the whole picture is however far from being complete. This paper is updating the picture by summarizing some results and discussing some mainly combinatorial aspects behind the dependence of Kolmogorov–Sinai entropy from ordinal pattern distributions on a theoretical level. The paper is more than a review paper. A new statement concerning the conditional permutation entropy will be given as well as a new proof for the fact that the permutation entropy is an upper bound for the Kolmogorov–Sinai entropy. As a main result, general conditions for the permutation entropy being a lower bound for the Kolmogorov–Sinai entropy will be stated. Additionally, a previously introduced method to analyze the relationship between permutation and Kolmogorov–Sinai entropies as well as its limitations will be investigated.
Numerical Study on the Characteristics of Boger Type Viscoelastic Fluid Flow in a Micro Cross-Slot under Sinusoidal Stimulation
Authors: Yuan Chao , Zhang Hong-Na , Chen Li-Xia , Zhao Jun-Long , Li Xiao-Bin , Li Feng-Chen
Published: January 2020

The cross-slot geometry plays an important role in the study of nonlinear effects of viscoelastic fluids. The flow of viscoelastic fluid in a micro cross-slot with a high channel aspect ratio (AR, the ratio of channel depth to width) can be divided into three types, which are symmetric flow, steady-state asymmetric flow and time-dependent flow under the inlet condition with a constant velocity. However, the flow pattern of a viscoelastic fluid in the cross-slot when a stimulation is applied at inlets has been rarely reported. In this paper, the response of cross-slot flow under an external sinusoidal stimulation is studied by numerical simulations of a two-dimensional model representing the geometry with a maximum limit of AR. For the cases under constant inlet velocity conditions, three different flow patterns occur successively with the increase of Weissenberg number (Wi). For the cases under sinusoidal varying inlet velocity conditions, when the stimulation frequency is far away from the natural frequency of a viscoelastic fluid, the frequency spectrum of velocity fluctuation field shows the characteristics of a fundamental frequency and several harmonics. However, the harmonic frequency disappears when the stimulation frequency is close to the natural frequency of the viscoelastic fluid. Besides, the flow pattern shows spatial symmetry and changes with time. In conclusion, the external stimulation has an effect on the flow pattern of viscoelastic fluid in the 2D micro cross-slot channel, and a resonance occurs when the stimulation frequency is close to the natural frequency of the fluid.
A Speed-Governing System Model with Over-Frequency Protection for Nuclear Power Generating Units
Authors: Wang Li , Sun Wentao , Zhao Jie , Liu Dichen
Published: January 2020

Overspeed is more likely to occur in the process of load rejection or large disturbances for nuclear steam turbines due to the large parameter range and low steam parameters, as well as the power of the low-pressure cylinder accounting for a high proportion of the total power. It is of great significance to study the overspeed characteristics of nuclear power plants (NPPs) to ensure the safe and stable operation of the unit and power grid. According to the characteristics of NPPs, the overspeed protection model and the super-acceleration protection model were established, which were added to the speed-governing system model. The response characteristics of the reactor, thermal system, steam turbine and speed-governing system in the process of load rejection or large disturbances of the power grid were analyzed and simulated. The results were compared using the simulation software personal computer transient analyzer (PCTRAN). The simulation results showed that quickly closing both the high and medium pressure regulating valves could effectively realize frequency control when load rejection or a large grid disturbance occurred. The over-acceleration protection cooperates with the super-acceleration protection to avoid the repeated opening/closing of the valves due to overspeed protection. This could effectively reduce the impact of large disturbances on the reactor, thermal system, and turbine.
Techno-Economic Analysis (TEA) of Different Pretreatment and Product Separation Technologies for Cellulosic Butanol Production from Oil Palm Frond
Authors: Mahmud Nazira , Rosentrater Kurt A.
Published: January 2020

Among the driving factors for the high production cost of cellulosic butanol lies the pretreatment and product separation sections, which often demand high amounts of energy, chemicals, and water. In this study, techno-economic analysis of several pretreatments and product separation technologies were conducted and compared. Among the pretreatment technologies evaluated, low-moisture anhydrous ammonia (LMAA) pretreatment has shown notable potential with a pretreatment cost of $0.16/L butanol. Other pretreatment technologies evaluated were autohydrolysis, soaking in aqueous ammonia (SAA), and soaking in sodium hydroxide solution (NaOH) with pretreatment costs of $1.98/L, $3.77/L, and $0.61/L, respectively. Evaluation of different product separation technologies for acetone-butanol-ethanol (ABE) fermentation process have shown that in situ stripping has the lowest separation cost, which was $0.21/L. Other product separation technologies tested were dual extraction, adsorption, and membrane pervaporation, with the separation costs of $0.38/L, $2.25/L, and $0.45/L, respectively. The evaluations have shown that production of cellulosic butanol using combined LMAA pretreatment and in situ stripping or with dual extraction recorded among the lowest butanol production cost. However, dual extraction model has a total solvent productivity of approximately 6% higher than those of in situ stripping model.
Using Chou’s 5-Step Rule to Evaluate the Stability of Tautomers: Susceptibility of 2-[(Phenylimino)-methyl]-cyclohexane-1,3-diones to Tautomerization Based on the Calculated Gibbs Free Energies
Authors: Dobosz Robert , Mućko Jan , Gawinecki Ryszard
Published: January 2020

Gibbs free energies, based on DFT (Density Functional Theory) calculations, prove that enaminone (2-(anilinemethylidene)cyclohexane-1,3-dione) and ketamine (2-[(phenylimino)-methyl]cyclohexane-1,3-dione) are the most and least stable tautomeric forms of the studied systems, respectively. 1H and 13C NMR spectra prove that 2-(anilinemethylidene)cyclohexane-1,3-diones are the only tautomeric species present in dimethylsulfoxide solution (a very weak signal can be seen only for the p-methoxy derivatives). The zwitterionic character of these enaminones is strengthened by naphthoannulation and by the insertion of the electron-withdrawing substituent into the benzene ring (the latter weakens the intramolecular hydrogen bond in the compound). Substituent and naphtoannulation have no effect on the stability of the studied tautomers. Slight twisting of the benzene ring, with respect to the CArNC plane (seen in the crystalline state), was proven to also take place in vacuum and in solution.
Phasor-Based Control for Scalable Integration of Variable Energy Resources
Authors: von Meier Alexandra , Ratnam Elizabeth L. , Brady Kyle , Moffat Keith , Swartz Jaimie
Published: January 2020

We propose an innovative framework termed phasor-based control (PBC) to facilitate the integration of heterogeneous and intermittent distributed energy resources (DER) on the electric grid. PBC presents a unified approach that is agnostic to optimization criteria and to the particular characteristics of participating resources. It is enabled by synchronized, high-precision voltage phasor measurements that allow stating control objectives in grid-specific, rather than resource-specific, terms. We present qualitative justification and examine the general feasibility of this control approach, including the behavior of candidate control algorithms in simulation. Initial results suggest that PBC has significant potential to support stable and resilient grid operations in the presence of arbitrarily high penetrations of DER.
A Side-Absorption Concentrated Module with a Diffractive Optical Element as a Spectral-Beam-Splitter for a Hybrid-Collecting Solar System
Authors: Wei An-Chi , Chang Wei-Jie , Sze Jyh-Rou
Published: January 2020

In this paper, we propose a side-absorption concentrated module with diffractive grating as a spectral-beam-splitter to divide sunlight into visible and infrared parts. The separate solar energy can be applied to different energy conversion devices or diverse applications, such as hybrid PV/T solar systems and other hybrid-collecting solar systems. Via the optimization of the geometric parameters of the diffractive grating, such as the grating period and height, the visible and the infrared bands can dominate the first and the zeroth diffraction orders, respectively. The designed grating integrated with the lens and the light-guide forms the proposed module, which is able to export visible and infrared light individually. This module is demonstrated in the form of an array consisting of seven units, successfully out-coupling the spectral-split beams by separate planar ports. Considering the whole solar spectrum, the simulated and measured module efficiencies of this module were 45.2% and 34.8%, respectively. Analyses of the efficiency loss indicated that the improvement of the module efficiency lies in the high fill-factor lens array, the high-reflectance coating, and less scattering.
The Effect of Fuel Injection Location on Supersonic Hydrogen Combustion in a Cavity-Based Model Scramjet Combustor
Authors: Jeong Eunju , O’Byrne Sean , Jeung In-Seuck , Houwing A. F. P.
Published: January 2020

Supersonic combustion experiments were performed using three different hydrogen fuel-injection configurations in a cavity-based model scramjet combustor with various global fuel–air equivalence ratios. The configurations tested were angled injection at 15° to the flow direction upstream of the cavity, parallel injection from the front step, and upstream injection from the rear ramp. Planar laser-induced fluorescence of the hydroxyl radical and time-resolved pressure measurements were used to investigate the flow characteristics. Angled injection generated a weak bow shock in front of the injector and recirculation zone to maintain the combustion as the equivalence ratio increased. Parallel and upstream injections both showed similar flame structure over the cavity at low equivalence ratio. Upstream injection enhanced the fuel diffusion and enabled ignition with a shorter delay length than with parallel injection. The presence of a flame near the cavity was determined while varying the fuel injection location, the equivalence ratio, and total enthalpy of the air flow. The flame characteristics agreed with the correlation plot for the stable flame limit of non-premixed conditions. The pressure increase in the cavity for reacting flow compared to non-reacting flow was almost identical for all three configurations. More than 300 mm downstream of the duct entrance, averaged pressure ratios at low global equivalence ratio were similar for all three injection configurations.
Aerodynamic and Thermal Modelling of Disc Brakes—Challenges and Limitations
Authors: Vdovin Alexey , Le Gigan Gaël
Published: January 2020

The brake system is a critical component for any passenger vehicle as its task is to convert the kinetic and potential energy of the vehicle into heat, allowing the vehicle to stop. Heat energy generated must be dissipated into the surroundings in order to prevent brake overheating. Traditionally, a lot of experimental testing is performed to ensure correct brake operation under all possible load scenarios. However, with the development of simulation techniques, many vehicle manufacturers today are looking into partially or completely replacing physical experiments by virtual testing. Such a transition has several substantial benefits, but simultaneously a lot of challenges and limitations need to be addressed and understood for reliable and accurate simulation results. This paper summarizes many of such challenges, discusses the effects that can and cannot be captured, and gives a broader picture of the issues faced when conducting numerical brake cooling simulations.
A Refined Loss Evaluation of a Three-Switch Double Input DC-DC Converter for Hybrid Vehicle Applications
Authors: Marchesoni Mario , Passalacqua Massimiliano , Vaccaro Luis
Published: January 2020

In this paper, an accurate efficiency evaluation of an innovative three-switch double input DC–DC converter for hybrid vehicle applications was carried out. The converter was used to interface two storages, (e.g., supercapacitor and battery) to the DC link. A refined model was created in MATLAB/Simulink Plecs environment and it was used to compare the traditional four-switch converter (i.e., two DC–DC converters in parallel connection) with the innovative three-switch converter. Loss and efficiency contour maps were obtained for both converters and a comparison between them was performed. A prototype of the three-switch converter was realized and used to validate the simulation thermal model by comparing both efficiency and current waveforms obtained with simulations and experimental tests.
Measurement of the PMSM Current with a Current Transducer with DSP and FPGA
Authors: Rudnicki Tomasz
Published: January 2020

In the present work, two approaches for the phase current measurement of a permanent magnet synchronous motor (PMSM) were compared. The measured phase current was distorted by glitches, and a software method to eliminate these glitches was necessary. An averaging of samples was carried out, and the experimental results indicated that averaging was essential for further calculations. Moreover, the PMSM operated smoothly, and the difference between the set point and the actual speed was reduced for the full range of loads from the free run up to a full load. The increasing popularity of field-programmable gate array (FPGA) devices has encouraged developments in PMSM controllers using a direct hardware approach and the classic software approach utilizing a digital signal processor unit. In this study, the selected performance of TMS320F2812 and Spartan-3E were compared. This paper proposes an original adaptive correction method for a current transducer.
Effect of Syngas Composition on the Combustion and Emissions Characteristics of a Syngas/Diesel RCCI Engine
Authors: Kousheshi Navid , Yari Mortaza , Paykani Amin , Saberi Mehr Ali , de la Fuente German F.
Published: January 2020

Reactivity controlled compression ignition (RCCI) strategy uses two different fuels with different reactivities which provides more control over the combustion process and has the potential to dramatically lower combustion temperature and NOX and PM emissions. The objective of the present study is to numerically investigate the impact of syngas composition on the combustion and emissions characteristics of an RCCI engine operating with syngas/diesel at constant energy per cycle. For this purpose, different syngas compositions produced through gasification process have been chosen for comparison with the simulated syngas (mixture of hydrogen and carbon monoxide). The results obtained indicate that using syngas results in more soot, CO and UHC emissions compared with simulated syngas. Even though more NOX reduction can be achieved while operating with syngas, the engine could suffer from poor combustion and misfire at low loads due to the presence of nitrogen in the mixture. In terms of exergy, both syngas mixtures lead to more exergy destruction by the increase of syngas substitution. Nevertheless, the magnitude of exergy destruction for simulated syngas is less than the normal syngas.
Optimization of Construction Duration and Schedule Robustness Based on Hybrid Grey Wolf Optimizer with Sine Cosine Algorithm
Authors: Zhao Mengqi , Wang Xiaoling , Yu Jia , Bi Lei , Xiao Yao , Zhang Jun
Published: January 2020

Construction duration and schedule robustness are of great importance to ensure efficient construction. However, the current literature has neglected the importance of schedule robustness. Relatively little attention has been paid to schedule robustness via deviation of an activity’s starting time, which does not consider schedule robustness via structural deviation caused by the logical relationships among activities. This leads to a possibility of deviation between the planned schedule and the actual situation. Thus, an optimization model of construction duration and schedule robustness is proposed to solve this problem. Firstly, duration and two robustness criteria including starting time deviation and structural deviation were selected as the optimization objectives. Secondly, critical chain method and starting time criticality (STC) method were adopted to allocate buffers to the schedule in order to generate alternative schedules for optimization. Thirdly, hybrid grey wolf optimizer with sine cosine algorithm (HGWOSCA) was proposed to solve the optimization model. The movement directions and speed of grey wolf optimizer (GWO) was improved by sine cosine algorithm (SCA) so that the algorithm’s performance of convergence, diversity, accuracy, and distribution improved. Finally, an underground power station in China was used for a case study, by which the applicability and advantages of the proposed model were proved.
Spatiotemporal Characterization and Suppression Mechanism of Supersonic Inlet Buzz with Proper Orthogonal Decomposition Method
Authors: Luo Wenguo , Wei Yuqing , Dai Ke , Zhu Jianfeng , You Yancheng
Published: January 2020

The buzz phenomenon of a typical supersonic inlet is analyzed using the unsteady Reynolds Average Navier-Stokes (RANS) simulation and proper orthogonal decomposition (POD) method. The dominant flow patterns and characteristics of the buzzed flow are obtained by decoupling the computed pressure field into spatial and temporal sub-parts based on the POD method. The supersonic inlet buzz phenomenon could be approximated as a product of decoupled temporal and spatial terms, and the one-dimensional (1D) mathematical model is therefore proposed. The standard deviations of the unsteady pressure fields from both the numerical simulation and the model prediction are compared. The limited discrepancy can be observed, and the good agreement validates the credibility of the proposed 1D model. The numerical simulation and the 1D model prediction are presented to explore the unsteady-jet control with a small perturbation. The results of the 1D model and the numerical simulation achieve good agreements with each other in terms of the overall trend. Finally, POD modal energy is employed to analyze the buzz suppression mechanism. When the jet frequency is identical to the dominant frequency of the buzz and the jet phase is opposite to the oscillation phase of the captured mass flow, the buzz suppression could be more efficient. The buzz suppression mechanism could be explained in two aspects. For one thing, the complex flow structure is suppressed and the first average modal energy in the inlet is increased. For another, the energy redistribution among each POD mode is achieved and the flow stability is gradually enhanced.
NOx Emissions from Euro 5 and Euro 6 Heavy-Duty Diesel Vehicles under Real Driving Conditions
Authors: Ko Sangchul , Park Junhong , Kim Hyungjun , Kang Gunwoo , Lee Jongchul , Kim Jongmin , Lee Jongtae
Published: January 2020

Despite the strengthening of vehicle emissions standards and test methods, nitrogen oxide (NOx) emissions from on-road mobile sources are not being notably reduced. The introduction of real driving emission (RDE) regulations is expected to reduce the discrepancy between emission regulations and actual air pollution. To analyze the effects of RDE regulations on heavy-duty diesel vehicles, pollutants emitted while driving were measured using a portable emission measurement system (PEMS) for Euro 5 and Euro 6 vehicles, which were produced before and after RDE regulations, respectively. NOx emissions were compared as a function of emissions allowance standards, gross vehicle weight (GVW), average vehicle speed, and ambient temperature. NOx emissions from Euro 6 vehicles were found to be low, regardless of GVW; emissions from both vehicular categories increased with a decline in the average speed. To reflect real road driving characteristics more broadly in the RDE test method for heavy-duty vehicles, it is necessary to consider engine power, which is a criterion for classifying effective sections, in the moving average window (MAW) analysis method, as well as including cold start conditions.
Fault Analysis and Design of a Protection System for a Mesh Power System with a Co-Axial HTS Power Cable
Authors: Nguyen Thai-Thanh , Lee Woon-Gyu , Kim Hak-Man , Yang Hyung
Published: January 2020

The uses of high-temperature superconducting (HTS) cables pose a challenge of power system protection since the impedance of the HTS cable is varied during fault conditions. The protection systems should be designed properly to ensure the reliability and stability of the whole system. This paper presents a fault analysis of the co-axial HTS cable in the mesh system and proposes a coordinated protection system. In the proposed protection system, the main protection is the differential current relay whereas the backup protections are the overcurrent and directional overcurrent relays. The normal and abnormal relay operations are considered to analyze the transient fault current in the HTS cable and evaluate the performance of the proposed coordinated protection system. Characteristics of cable impedances and temperatures under various fault conditions are presented. The proposed protection scheme is validated by the simulation in the PSCAD/EMTDC program. Simulation results show that the coordinated protection scheme could successfully protect the HTS cables in both normal and abnormal relay operations.
The Research on a Driving Device for Natural Gas Hydrate Pressure Core
Authors: Ren Ziqiang , Chen Jiawang , Gao Qiaoling , Zhang Peihao , He Kai , Xiao Bo , Geng Xueqiao
Published: January 2020

Precise pressure core motion, including translation and rotation, is the basis and core part of the Analysis and Transfer System of Natural Gas Hydrate Pressure Core, which is crucial to nondestructive analyses, core cutting, and transfer. This paper mainly proposes a driving device, whereby a pressure core, up to 3 m long, can be transferred from pressure core drilling tools to proceed to nondestructive analyses and transferring the cores into other chambers. The lead screw is one of the most important components of this driving device. Therefore, the modal analyses of the lead screw are performed, which can help researchers to analyze the stability of this device. The analyzed data shows that the different positions of the slider have a great impact on the natural frequency of the lead screw. Furthermore, the lead screw with a support slider has a larger natural frequency than that without a support slider. According to data analysis, we can derive that the device with the support slider has a much larger rigidity, which can contribute to the stability of the device. To verify the feasibility of this device, the deformation of the lead screw was tested by the Micro-Electro-Mechanical Systems (MEMS) accelerometer array. Experimental results show that the deformation of the lead screw with the support slider is much less than that without the support slider.
Harvesting Energy from Planetary Gear Using Piezoelectric Material
Authors: Chilabi Haider Jaafar , Salleh Hanim , Supeni Eris E. , As’arry Azizan , Rezali Khairil Anas Md , Atrah Ahmed B.
Published: January 2020

In the present study, a rotational piezoelectric (PZT) energy harvester has been designed, fabricated and tested. The design can enhance output power by frequency up-conversion and provide the desired output power range from a fixed input rotational speed by increasing the interchangeable planet cover numbers which is the novelty of this work. The prototype ability to harvest energy has been evaluated with four experiments, which determine the effect of rotational speed, interchangeable planet cover numbers, the distance between PZTs, and PZTs numbers. Increasing rotational speed shows that it can increase output power. However, increasing planet cover numbers can increase the output power without the need to increase speed or any excitation element. With the usage of one, two, and four planet cover numbers, the prototype is able to harvest output power of 0.414 mW, 0.672 mW, and 1.566 mW, respectively, at 50 kΩ with 1500 rpm, and 6.25 Hz bending frequency of the PZT. Moreover, when three cantilevers are used with 35 kΩ loads, the output power is 6.007 mW, and the power density of piezoelectric material is 9.59 mW/cm3. It was concluded that the model could work for frequency up-conversion and provide the desired output power range from a fixed input rotational speed and may result in a longer lifetime of the PZT.
Supplementary Control of Air–Fuel Ratio Using Dynamic Matrix Control for Thermal Power Plant Emission
Authors: Lee Taehyun , Han Eungsu , Moon Un-Chul , Lee Kwang Y.
Published: January 2020

This paper proposes a supplementary control for tighter control of the air–fuel ratio (AFR), which directly affects the environmental emissions of thermal power plants. Dynamic matrix control (DMC) is applied to the supplementary control of the existing combustion control loops and the conventional double cross limiting algorithm for combustion safety is formulated as constraints in the proposed DMC. The proposed supplementary control is simulated for a 600-MW drum-type power plant and 1000 MW ultra-supercritical once-through boiler power plant. The results show the tight control of the AFR in both types of thermal power plants to reduce environmental emissions.
Integral Sliding-Mode Control-Based Direct Power Control for Three-Level NPC Converters
Authors: Lin Hao , Leon Jose I. , Luo Wensheng , Marquez Abraham , Liu Jianxing , Vazquez Sergio , Franquelo L. G.
Published: January 2020

Three-level neutral-point-clamped (NPC) converter is widely used in energy conversion systems due to its good properties for high-power systems presenting output waveforms with reduced harmonic distortion. To obtain better system performance, an integral sliding-mode control (ISMC)-based direct power control (DPC) strategy is proposed for NPC converters. The controller achieves three objectives. First, an extended state observer (ESO)-based ISMC strategy, to enforce the active and reactive power to their reference values, is applied in the power tracking loop. ESO is used to reduce the influence of parameter uncertainties. Next, in the voltage regulation loop, a radial basis function neural network (RBFNN)-based adaptive ISMC strategy is applied to regulate the DC-link voltage. RBFNN is used to estimate the load variation, which is considered as a disturbance, to improve the system disturbance rejection ability. An adaptive law is used in the controller to reduce the chattering of reference active power which can reduce the current harmonic distortion. Finally, a proportional-integral (PI) control strategy is applied in the voltage balancing loop to achieve voltage balance between two DC-link capacitors. Experimental results show the effectiveness and superiority of the proposed control strategy for the NPC power converter compared with PI-based DPC strategy.
VMD-KFCM Algorithm for the Fault Diagnosis of Diesel Engine Vibration Signals
Authors: Bi Xiaobo , Lin Jiansheng , Tang Daijie , Bi Fengrong , Li Xin , Yang Xiao , Ma Teng , Shen Pengfei
Published: January 2020

Accurate and timely fault diagnosis for the diesel engine is crucial to guarantee it works safely and reliably, and reduces the maintenance costs. A novel diagnosis method based on variational mode decomposition (VMD) and kernel-based fuzzy c-means clustering (KFCM) is proposed in this paper. Firstly, the VMD algorithm is optimized to select the most suitable K value adaptively. Then KFCM is employed to classify the feature parameters of intrinsic mode functions (IMFs). Through the comparison of many different parameters, the singular value is selected finally because of the good classification effect. In this paper, the diesel engine fault simulation experiment was carried out to simulate various faults including valve clearance fault, fuel supply fault and common rail pressure fault. Each kind of machine fault varies in different degrees. To prove the effectiveness of VMD-KFCM, the proposed method is compared with empirical mode decomposition (EMD)-KFCM, ensemble empirical mode decomposition (EEMD)-KFCM, VMD-back propagation neural network (BPNN), and VMD-deep belief network (DBN). Results show that VMD-KFCM has advantages in accuracy, simplicity, and efficiency. Therefore, the method proposed in this paper can be used for diesel engine fault diagnosis, and has good application prospects.
Modelling Selected Parameters of Power Grid Network in the South-Eastern Part of Poland: The Case Study
Authors: Hadaj Piotr , Strzałka Dominik
Published: January 2020

In this paper, a case study is conducted based on the real data obtained from the local Distribution System Operator (DSO) of electrical energy. The analyzed network represents connections and high-voltage switchgears of 110 kV. Selected graph parameters—vertex degree distribution, the average vertex degree, the graph density, network efficiency, the clustering coefficient, the average path length, and the graph diameter were examined, taking into account that in the analysis, some nodes were removed due to the different failures. For each failure, the possible effects on network parameters were tested. As a final result, it was shown that in the analyzed case, the removal of only five nodes could cause a significant (almost four times) fall of graph efficiency. In turn, this means that the whole analyzed network cannot be considered as a fault-tolerant.