Conductivity Performance Research Articles

Accelerated Microbial Reduction of Azo Dye by Using Biochar from Iron-Rich-Biomass Pyrolysis.

Biochar is widely used in the environmental-protection field. This study presents the first investigation of the mechanism of biochar prepared using iron (Fe)-rich biomass and its impact on the reductive removals of Orange G dye by Shewanella oneidensis MR-1. The results show that biochars significantly accelerated electron transfer from cells to Orange G and thus stimulated reductive removal rate to 72–97%. Both the conductive domains and the charging and discharging of surface functional groups in biochars played crucial roles in the microbial reduction of Orange G to aniline. A high Fe content of the precursor significantly enhanced the conductor performance of the produced biochar and thus enabled the biochar to have a higher reductive removal rate of Orange G (97%) compared to the biochar prepared using low-Fe precursor (75%), but did not promote the charging and discharging capacity of the produced biochar. This study can prompt the search for natural biomass with high Fe content to confer the produced biochar with wide-ranging applications in stimulating the microbial reduction of redox-active pollutants.

Numerical Study on Lightning Current Performance of Striated YBCO-Coated Conductor

Striated YBCO-coated conductor is a variant structure of the second-generation high-temperature superconducting (HTS) tapes. The ac loss is reduced owing to the YBCO layer of the striated YBCO tape is divided into filaments by laser scribing. Hence, it is promising for practical HTS electrical application, such as HTS transformer and cable. However, when the superconducting apparatuses are operated in the power grid, it will possibly experience the lightning impulse current in some extreme working condition. Thus, the performance of striated YBCO tapes suffering from exposure to lightning current is important to be studied. In this paper, a numerical model based on the electromagnetic–thermal coupling is built to analyze the lightning current performance of the striated YBCO tapes. The influence of structural changes on the thermal stability is discussed. The standard lightning current waveform is chosen, i.e., 8/20 μs. The simulated results show that cutting the copper edges of striated YBCO tapes will significantly degrade the lightning current withstand capacity. Instead, the degradation effect of grooves is not so obvious.

Pressure-Induced Formation of Quaternary Compound and In-N Distribution in InGaAsN Zincblende from Ab Initio Calculation.

We present the effects of In−N distribution and high pressure on the zincblende phase (0–5 GPa) of InxGa1−xAs0.963N0.037 (x=0.074, 0.111 and 0.148). Structural, electronic, and optical properties are analyzed, and it is found that non‐isotropic distribution of In−N (type C) possesses the minimum free energy for the InGaAsN conventional cell system. An increasing indium content reduces the formation enthalpy of InGaAsN. The formation enthalpy, conduction band minimum, strength of covalent bonds, and electron density differences in free space of InGaAsN are decreased under high‐pressure conditions. The dielectric performance and static permittivity of InGaAsN are lower than that of GaAs, for which the dielectric performance transforms to conductor performance at high frequency. The optimum photoabsorption coefficient is found at the composition of In0.111Ga0.889As0.963N0.037 (3In−N), which very well relates to the literature.

Performance comparison of 1X versus 4X HTS tapes toward the design a 10‐MW direct drive HTS generator for wind turbine applications

AbstractWith current developments underway at the University of Houston, 4× high‐temperature superconducting (HTS) yttrium barium copper oxide (YBCO) tapes are expected to reach a fourfold critical current density improvement at 30 K and 3 T as part of an Advanced Research Projects Agency‐Energy (ARPA‐E)‐sponsored project. The impetus for this project is to develop and deploy cost‐effective direct drive HTS generators for large offshore wind turbine generators. The improved conductor performance of 4× tapes over 1× tapes is projected to allow for a significant reduction in the amount of HTS tapes required to generate the excitation field and, thus, lead to a reduction of the overall generator cost. It was, however, deduced from simulation results that conventional methods of rotor field enhancement using rotor iron makes 1× conductor competitive enough compared with 4× conductors; hence, commercially available YBCO tapes can provide all the energy density requirements to make wind turbines a competitive energy resource based on energy forecasts. This paper is a presentation of design and optimization work to find the best generator topology from the point of view of both machine design and electricity supply. The generators are numerically modeled and simulated using 1× and 4× YBCO HTS conductors on either or of both the rotor and stator side of the generators.

The possible impact of weather uncertainty on the Dynamic Thermal Rating of transmission power lines: A Monte Carlo error-based approach

Dynamic Thermal Rating (DTR) monitors the temperatures of conductors, or uses weather and load forecasting to estimate their future trend, in order to calculate the actual capacity of a transmission line. By fully exploiting the real performances of conductors corresponding to the current weather conditions, DTR provides Transmission System Operators (TSOs) with additional dispatching flexibility and helps decision-making in case of grid congestions, especially in terms of the amount and timing of required re-dispatching procedures. For this reason, DTR is increasingly used for security assessment and for the reliable operation of power systems.Recently the scientific literature is showing growing interest in applying probabilistic methods to weather-based DTR procedures, in order to account for the stochastic nature of meteorological parameters. In fact, it is evident that the weak point of predicting the ampacity of a transmission line for the next hours is the accuracy of weather forecasting.This paper suggests that the impact of weather uncertainty on the Dynamic Thermal Rating of a transmission line can be assessed through a Monte Carlo technique, used to generate weather scenarios whose Probability Distribution Functions (PDFs) have been carefully pre-tuned, for each meteorological parameter, according to the actual weather forecasting errors made in the proximity of the line. The weather scenarios so obtained are then processed by a thermo-mechanical model of the transmission line, in order to evaluate the impact of weather uncertainty on the confidence interval of thermal and mechanical outputs (conductor’s temperature, tensions, sags).This approach is widely discussed and compared to the conventional method of simply modeling weather quantities with predefined Gaussian PDFs. Afterwards, it is applied to test the robustness of a deterministic DTR procedure developed in the last years by the authors. The DTR procedure under test combines the CIGRE thermal model of conductors and a complex multi-span mechanical model of a transmission line; in fact, it takes into account the mechanical interaction between spans, due to the possible rotation of strings of insulators, as well as that the temperature of conductors can vary span by span, for different weather conditions.Several case studies are discussed, based on weather measures collected near the same overhead lines on which the Italian TSO is obtaining significant benefits from the above-mentioned DTR procedure, especially in terms of increased amount of dispatchable wind energy.

Chemical Control of Correlated Metals as Transparent Conductors

AbstractCorrelated metallic transition metal oxides offer a route to thin film transparent conductors that is distinct from the degenerate doping of broadband wide gap semiconductors. In a correlated metal transparent conductor, interelectron repulsion shifts the plasma frequency out of the visible region to enhance optical transmission, while the high carrier density of a metal retains sufficient conductivity. By exploiting control of the filling, position, and width of the bands derived from the B site transition metal in ABO3 perovskite oxide films, it is shown that pulsed laser deposition‐grown films of cubic SrMoO3 and orthorhombic CaMoO3 based on the second transition series cation 4d2 Mo4+ have superior transparent conductor properties to those of the first transition series 3d1 V4+‐based SrVO3. The increased carrier concentration offered by the greater bandfilling in the molybdates gives higher conductivity while retaining sufficient correlation to keep the plasma edge below the visible region. The reduced binding energy of the n=4 frontier orbitals in the second transition series materials shifts the energies of oxide 2p to metal nd transitions into the near‐ultraviolet to enhance visible transparency. The A site size‐driven rotation of MoO6 octahedra in CaMoO3 optimizes the balance between plasma frequency and conductivity for transparent conductor performance.

Study on AC Resistance of Layering Enamelled Stranded Conductor

In recent years, with the rapid development of large-length ultra-high-pressure voltage extrusion insulated submarine cable technology, the cable system in the medium-length offshore power grid interconnection project has been gradually replaced by XLPE insulation by traditional oil-paper insulation. There are many large cross-section conductors used in long-distance power transmission cables, and according to the IEC 60287-1-1, it is recommended to use Milliken conductors to reduce the AC resistance of conductors, at the same time, in submarine cables, there is a high requirement on the water-blocking performance of conductors and the water resistance of Milliken conductors is poor, so it is not used in submarine cable conductors. This paper puts forward a layering enamelled stranded conductor and a calculation method of AC / DC resistance ratio for it. The validity of the calculation method is verified by experimental tests. At the same time, the calculation shows that the AC / DC resistance of the conductor at 1800 mm2 nominal cross section can be reduced by 16% compared with the conventional round compacted conductor in the prior art. The effectiveness of this conductor in reducing AC resistance is verified by finite element simulation.

New Gd-Zn co-doping enhanced mechanical properties of BaZrO3 proton conductors with high conductivity for IT-SOFCs

We report here the synthesis and characterization of Gd-Zn co-doped BaZrO3 proton conducting oxides, developed for IT-SOFCs. BaZr0.8Gd0.2−xZnxO3−δ (BZGZn, x = 0, 0.02, 0.04, and 0.06) samples were prepared and then sintered at 1300–1500 °C for characterization of chemical stability, sinterability, mechanical properties, and proton conductivity. Gd-Zn co-doping significantly improved the mechanical performance of BaZrO3-based proton conductors: hardness and compressive strength increased, mainly resulting from improved relative density and the enhancement in grain boundary bonding strength. Importantly, Gd-Zn co-doping dramatically improved the total conductivity, which can achieved a higher conductivity of 2.54 × 10−3 S·cm−1 at 750 °C. A typical anode-supported single cell with Gd-Zn co-doped BaZrO3 electrolyte was tested using humidified hydrogen(∼3% H2O) as fuel, presenting a high maximum power density of 282 mW·cm−2 at 700 °C. Preliminary results demonstrated that Gd-Zn co-doping is an effective way and has a great improvement in sinterability, mechanical properties and conductivity, leading to high electrochemical performance of IT-SOFC.

Non-destructive evaluation of critical current on a Bi-2212 first stage cable based on numerical analysis of the remnant field distributions

The high temperature superconducting material Bi-2212 is considered for use in the next generation of fusion reactors due to an excellent current carrying capacity in a high field. The critical current as well as its inhomogeneity are important factors in evaluating the performance of Bi-2212 wires, cables and conductors. Non-destructive evaluation by using a Hall sensor array is a more effective and faster method for testing the local critical current of a high temperature superconductor compared with a conventional contact-electrical method. In this paper, the coupling and decoupling numerical models of the perpendicular component of the residual magnetic field in Bi-2212 round wire were solved. Then, the perpendicular component of the remnant magnetic field was measured by a Hall sensor array, which was consistent with the results of the coupling model. Our results established the numerical model for a Bi-2212 first stage cable and found that the non-destructive method using four mutual vertical Hall sensor arrays is feasible for evaluation of cable critical current properties.

Hybrid HTS-Nb3Sn-NbTi DEMO CS coil design optimized for maximum magnetic flux generation

The present work is performed within the framework of the EUROfusion DEMO project. Previously, it was demonstrated that for a maintained magnetic flux the use of HTS conductors at highest magnetic field in a layer-wound CS coil would allow the reduction of its outer radius by around 0.5 m as compared to the DEMO reference design using only Nb3Sn conductors. Alternatively, the superior high field performance of HTS conductors can be used to maximize the magnetic flux of a CS coil with a given outer diameter, which could significantly prolong the duration of plasma burn phase and thus the overall power plant efficiency. In the present study, the maximization of the magnetic flux, generated by a layer-wound CS coil of fixed outer radius, is considered. HTS conductors are envisaged to be used at highest field, while Nb3Sn and NbTi are foreseen to be used in intermediate and low field layers, respectively. The inner radius of the CS coil is optimized with respect to the generation of a maximum flux taking into consideration the superconductor properties, the hoop stress and the axial stress. In order to provide reasonable starting values for the finite element analysis, first a simplified model with layer-dependent current densities, however, without stainless steel grading will be considered. In the final outline design of the CS coil a superconductor and stainless steel grading will be implemented.

국외여행인솔자 서비스품질의 차이가 관광객의 여행만족도에 미치는 영향

The purpose of this study is to understand the extent to which the gaps between the perceived importance and performance of tour conductors’ service quality impact package tourists’ overall satisfaction with their trip. Previous studies examining tour leaders’ service quality have not specifically investigated the gaps between the importance and performance, which does not appropriately reflect service quality theory in its original version. Accordingly, this study conducted a questionnaire survey to the tourists who have experienced overseas package tours as to their perceptions of tour leaders’ service quality. Data were analyzed through factor analysis according to positive and negative directions. Four factors were drawn for both positive and negative gaps. Multiple regression analysis revealed that two factors(problem solving ability and interpretation ability) significantly affect tourists’ overall satisfaction with the trip, which reflects package tourists’ ambivalent needs of novelty and familiarity. The results of this study provide important implications to increase the competitiveness of tour package by enhancing tourists’ satisfaction.

Analysis of the Icing Accretion Performance of Conductors and Its Normalized Characterization Method of Icing Degree for Various Ice Types in Natural Environments

Icing degree in the severe icing regions for years is an important factor considered in the anti-icing design of transmission lines. However, there is currently no normalized characterization method for the icing degree of transmission lines, which can be used to record the severity of icing at icing areas over the years and guide the design of transmission lines. This study analyzes collision efficiency of water droplets with various diameters of conductors and investigates the ice accretion law of transmission lines with various diameters under four natural ice types. Therefore, the normalized method of standard ice thickness instead of various ice morphologies is creatively used to characterize icing degree of transmission lines and a lot of field tests which have been done at six natural ice observation stations have verified the effective of the method. The results have shown that: The diameters of conductor and the droplet significantly affect collision efficiency; the relation of standard ice thickness with diameter of conductors for four typical ice types complied with the law of power function. The results can provide important references for the design and external insulation selection of transmission lines in ice region.

Improvement of the properties of light metal matrix Micro/Nanocomposite Materials: myth or reality?

The use of materials reinforced by micro-nanoparticles (MMC) is more and more widespread. According to recent studies, the addition of micro-particles in solid materials (polymers, concrete or metal alloys) gives them interesting properties in terms of thermal conductivity, electrical conductivity and mechanical resistance. These properties open new perspectives in terms of environmental consequences. They allow for example to lighten structures while improving their mechanical characteristics, to increase the performance of electrical conductors by reducing energy losses. We provide an example related to light metal alloys widely used in automotive industry and aeronautics. However, the introduction of particles presents several difficulties. The efficiency of particle addition at liquid state depends on many factors, like their dimension, the type of sedimentation forces and the chemical composition of both liquid alloys and particles:(i) at the metallurgical level, the particles are often very reactive and may modify the composition and the micro-structure of the alloy, which can be sometimes beneficial and sometimes damaging,(ii) in terms of scale-up and development of actual processes, the introduction of micro- and especially nanoparticles in liquid phase is a very difficult operation to achieve. Many types of devices are proposed but none is really satisfactory, especially regarding the homogeneity of the materials.We present some application cases related to magnesium alloys that perfectly illustrate the advantages and disadvantages of MMCs.

Influence of voltage polarity on the corona performance of ice-covered conductor

Corona performance of transmission lines in foul weather conditions, icing particularly, have attracted widely attentions. In this research, the influence of voltage polarity on corona performance of two icing categories, glaze and soft rime icing, is studied in corona cage via artificial icing method. The most important finding of this research is that a linear relationship is found between audible noise (AN) and the corona loss (CL) in dB above 1 W/m for the first time, the slopes of the line are voltage polarity-dependent. A 10.4 dBA and 13.7 dBA variation in the AN value for a 10 dB increase in the CL for negative and positive voltage respectively, with little influence icing categories. Moreover, the negative polarity conductors are attending to accumulate much more glaze ice than positive polarity conductors. Taylor cones and hemispheres are observed on the tip of glaze icicles when subjected to DC and AC electric field, respectively. For both icing categories, the CL of negative polarity conductors are bigger than that of positive polarity conductors, the contrary is the case of AN. When the voltage gradient is greater than 18.0 kV/cm, contrary to popular perception, the generated CL and AN of glaze ice-covered conductor are bigger than that of rain condition and fair weather, respectively.

Insight into the dehydration behaviour of scandium-substituted barium titanate perovskites via simultaneous in situ neutron powder thermodiffractometry and thermogravimetric analysis

Hydration-dehydration cycles are critical to the mechanical performance of ceramic proton conductors. The development of in situ methods is desirable in order to study their structural response under conditions that mimic the operating ones. Neutron powder diffraction studies combined with simultaneous thermogravimetric analysis were performed on the hydrated forms of two members of the oxygen deficient perovskite BaTi1−xScxO3−δ series, with x = 0.5 and x = 0.7. Rietveld analyses agreed with in situ gravimetric data, allowing correlation of occupancy factors of the oxygen site to hydration levels and other structural data. Dehydration is an activated process that impacts on structural parameters and the level of Sc substitution was found to control the structural response during in situ dehydration, with higher Sc content leading to significantly greater volume contraction. This was rationalised by the chemical expansion due to hydration of oxygen vacancies within the x = 0.5 sample being anomalously small. Furthermore, the behaviour of the x = 0.5 system revealed an unexpected cell expansion during the early stages of dehydration, suggesting the hydration level may influence the thermal expansion coefficient (TEC).

Reducing sheet resistance of self-assembled transparent graphene films by defect patching and doping with UV/ozone treatment

Liquid phase exfoliation followed by Langmuir-Blodgett self-assembly (LBSA) is a promising method for scalable production of thin graphene films for transparent conductor applications. However, monolayer assembly into thin films often induces a high density of defects, resulting in a large sheet resistance that hinders practical use. We introduce UV/ozone as a novel photochemical treatment that reduces sheet resistance of LBSA graphene threefold, while preserving the high optical transparency. The effect of such treatment on our films is opposite to the effect it has on mechanically exfoliated or CVD films, where UV/ozone creates additional defects in the graphene plane, increasing sheet resistance. Raman scattering shows that exposure to UV/ozone reduces the defect density in LBSA graphene, where edges are the dominant defect type. FTIR spectroscopy indicates binding of oxygen to the graphene lattice during exposure to ozone. In addition, work function measurements reveal that the treatment dopes the LBSA film, making it more conductive. Such defect patching paired with doping leads to an accessible way of improving the transparent conductor performance of LBSA graphene, making solution-processed thin films a candidate for industrial use.

Lev Venediktov’s Creative Laboratory: The School of the Universal Type

The article studies L. Venediktov’s artistic individuality and his creative principles. There is defined the scope of his artist’s activity, characterized as a unique extraordinary multidimensional style phenomenon of a musician and an educator, a teacher and a manager, an opera choirmaster and an artist-interpreter. The study also arranges genesis of N. Venediktov’s spiritual and professional personality.It investigates creative activity of a talented conductor that defined L. Venediktov’s professional orientation. It should be also noted that the perception of the artistic principles of G. Verevka, reflected in the study, was a continuation of the process of L. Venediktov’s professional basis development.The article eludicates the community of the artistic worldview platform of L. Venediktov’s teachers. The one that was formed in keeping traditions of Ukrainian singing culture and church choral music. The latter in turn, determined L. Venediktov’s creative and ethical principles, his artistic content and aesthetically perfect performance style. The research reveals the content of the concept of ‘the creative laboratory’, in its broad universal meaning, which synthesizes L. Venediktov’s manner of performance and his educating techniques as a demonstration of his multidimensional style, i.e. the basis for the Didactic-communicative work of the Master.The article determines extrapolation of opera-choral specificity to the didactically communicative sphere of L. Venediktov’s work as the main component of the choirmaster’s creative method. It casts light on the principle of L. Venediktov’s methodical work, in which dominates synthesis of intellectual-analytical and intuitive approach to musical material. It gives characteristics to the universal style of L. Venediktov’s school, where adjacent didactic-technological methods are used not only in choral and conductor performances but also in the piano one.Didactic and communicative-creative principles of L. Venediktov are as well considered in the context of the continuation of the Byzantine-Russian tradition of ‘encyclios pedia’, that is characterized by a diversified development of personality and reveals a kinship with L. Venediktov’s views, his principles of a great educator, who used to find priorities in all-round intellectual development, revealing, simultaneously, artistic and creative potential of an individual, as well as in the moral and ethical education of a conductor-performer.

Stability analysis on Nb3Sn sample conductor of CFETR central solenoid model coil

The magnet system of China fusion engineering test reactor (CFETR) includes toroidal field, central solenoid (CS) and poloidal field coils. The design and fabrication of CS coil are most significant and challenging for China due to the lack of experience. As the core technique of CS coil, cable-in-conduit-conductor (CICC) has been chosen to ITER CS conductor with the short twist pitch (STP) cable pattern. STP cable pattern has been demonstrated to avoid the performance degradation of conductor after electromagnetic cycling and warm-up-cool-down thermal cycles during operation. For qualifying the manufacturing process and performance of conductor, two short sample conductors were manufactured at ASIPP and tested at Swiss Plasma Center. Performance tests include DC test, Tcs, AC loss and MQE (Minimum Quench Energy) measurements. This paper is mainly about the stability analysis, and the energy margins of the conductor at various operation conditions are investigated with test data and model simulation.

Improved Flux Pinning for High-Field Applications in BaHfO3-Doped SmBa2Cu3 Oy-Coated Conductors With High Density of Random Pinning Centers Induced by BaHfO 3 Nanorods

The critical current performance of REBa 2 Cu 3 Oy-coated conductors must be isotropically improved for use in high-field coil-based applications operated at low temperatures less than 50 K. The high and isotropic critical current densities (Jc) with respect to the directions of the magnetic field under these operating conditions were achieved by a 3.8 vol.% BaHfO3 (BHO)-doped SmBa 2 Cu 3 Oy (SmBCO) film on a metallic substrate deposited with low-temperature growth (L-BHO film). In particular, the L-BHO film attained a high flux pinning force density over 1.5 TN/m 3 at a temperature of 4.2 K. From the anisotropic scaling approach based on the effective mass model, a high density of random pinning centers in the L-BHO film plays an important role in achieving the high J c performance at 4.2 K. In order to reveal the reason why the L-BHO film includes high density of random pinning centers, we compared the flux pinning properties and the dominant flux pinning centers between the L-BHO film and the other two samples: a 3.8 vol.% BHO-doped SmBCO film fabricated with relatively high-temperature growth, and a nondoped SmBCO film fabricated with low-temperature growth. From the comparison, it is revealed that the random pinning centers are induced by BHO nanorods.

Effects of chemical etching on structure and properties of Y0.5Gd0.5Ba2Cu3O7-z coated conductors

Corrosion resistance is a crucial property to achieve successful superconducting joints of Y0.5Gd0.5Ba2Cu3O7-z (YGdBCO) coated conductors (CCs). Cu and Ag metallic layers need to be fully removed from the area of conductor to be joint to allow for a superconducting path across the joint. Therefore, when using a wet etching process to remove the metallic layers, the joint performance can be significantly influenced by the etching conditions. The effects of chemical etching with ammonia water and hydrogen peroxide mixture on crystal structure, surface microstructure and critical current (Ic) of YGdBCO CCs were systematically investigated. We found the set of etching parameters that does not affect conductor performance, leaving the Ic of the YGdBCO conductor unchanged upon etching. However, when the etching conditions are not optimal, decrease in Ic was found and the underlying reasons driving the degradation were investigated. Raman spectroscopy and XRD analysis indicated that the reduced Ic is mainly due to oxygen deficiency in the YGdBCO crystal lattice.