Microwave photonics (MWP) represents a significant optical signal processing system, standing at the confluence of microwave engineering and photonics. It presents a promising way for meeting the growing demands of contemporary communication systems, radar, sensing, and signal processing. Driving the rapid advancement of MWP are pivotal technologies such as optical frequency combs, photonic integrated circuits, and advanced modulation formats. The integration of photonic integrated circuit technology with hybrid integration techniques holds the promise of realizing MWP systems on a single chip, while comb shaping technology endows MWP systems with programmable and reconfigurable capabilities. In this paper, we present a review of our recent research, which focused on exploring the full spectrum of potential applications for quantum dash lasers in MWP systems. Leveraging principles of finite impulse response filters, our MWP system not only facilitates conventional filtering but also enables instantaneous frequency measurement and waveform generation. A distinguishing feature of MWP filters is their uniform delay. After converting it into a uniform phase difference, it underpins the development of MWP-based phase antenna array systems. Furthermore, this uniform delay finds application in time-interleaved photonic analog-to-digital conversion.
Under the dual carbon target, a large number of new energy sources are connected to the power grid, and relay protection is becoming increasingly important as the primary guarantee for the safe and stable operation of the power system. The research on grid type inverter technology mainly focuses on system stability control, fault ride through, and other aspects, with little attention paid to the characteristics of relay protection. In this regard, this article analyzes the adaptability of transmission line protection under the control strategy of grid type energy storage inverters. Firstly, the synchronous control strategy and fault ride-through control strategy of grid-forming converters are analyzed, with equivalent circuits derived for grid-forming converters under different fault ride-through control strategies in the event of faults. Secondly, an evaluation of the operational performance under grid-forming control strategies is conducted. Additionally, an adaptability analysis is performed for each of these protection configurations. Lastly, a transmission line model incorporating a grid-forming energy storage converter is established in Simulink to validate the relevant theories. Based on the adaptability of transmission line protection, corresponding improvement suggestions are proposed.
Electricity, Production of electric energy or power. Powerplants. Central stations
Eder Hernandez, Esmeralda Campos, Pablo Barniol
et al.
This study presents the development and validation of a novel multiple-choice test designed to assess university students’ conceptual understanding of electric field, force, and flux. The test of understanding of electric field, force, and flux was constructed based on the results of previous studies using a phenomenographic approach to classify common errors in these concepts. The final 10-item test, designed with targeted distractors, was administered to 116 students enrolled in an introductory electricity and magnetism course. Statistical analyses, including item difficulty and discrimination indices, confirmed the reliability and discriminatory power of the test. Students’ performance revealed significant misconceptions in applying the superposition principle, Gauss’s law, and electric force interactions. The results of this study provide valuable insights into students’ learning challenges and offer physics educators and researchers a useful tool for assessing conceptual understanding and guiding instructional improvements.
In this article, a miniaturized, low-profile fractal antenna is designed and prototyped for 6-GHz n104 band 5G advanced communications. Antenna miniaturization is achieved here by considering the random Sierpinski fractal concept and optimizing the structure with the genetic algorithm. Initially, the proposed antenna is designed and optimized using Ansys HFSS. Subsequently, the performance of the antenna is also tested for different atmospheric conditions in MATLAB real-time simulation environment for advanced 5G applications in the presence of foliage and rain. The proposed antenna resonates at 6.5 GHz with an impedance bandwidth of 380 MHz and a gain of 5.21 dBi. The antenna has a low size of 0.39 λ0 x 0.30 λ0 with a size reduction of 76% compared to its conventional design, where λ0 is the free space wavelength. The proposed low-profile antenna with balanced performance characteristics is found to be a suitable candidate for n104 band 5G advanced communications.
P. L. S. Cambalame, B. J. C. Vieira, J. C. Waerenborgh
et al.
We successfully synthesized a novel intermetallic compound $\rm CrFe_2Ge_2$ with the $\rm Fe_{13}Ge_{8}$-type crystal structure. A structural study is presented combining single-crystal X-ray diffraction and Mössbauer spectroscopy analysis, confirming the presence of two distinct Fe sublattices. $\rm CrFe_2Ge_2$ exhibits a metallic ferromagnetic state with $T_C \approx \rm 200~K$. This material does not follow the usual $M^2 \propto H/M$ Arrott law, rather a modified Arrott law is obeyed in this material. The critical exponents determined from detailed analysis of modified Arrott plots were found to be $β= 0.392$, $γ= 1.309$ and $δ= 4.26$ obtained from the critical isotherm at $ T_{\rm C} =\rm 200~K$. Self-consistency and reliability of the critical exponent analysis were verified by the Widom scaling law and scaling equations. Using the results from renormalization group calculation, the critical behavior of $\rm CrFe_2Ge_2$ is akin to that of a $d=3, n=3$ ferromagnet in which the magnetic exhange distance is found to decay as $J(r) \approx r^{-4.86}$ with long-range magnetic coupling. The evaluated Rhodes-Wohlfarth ratio of $\sim 3$ points to an itinerant ferromagnetic ground state. Low-temperature measurements of resistivity, $p(T)$, and specific heat, $C_P(T)$, reveal a pronounced contribution from electron-magnon scattering.
Eberhard Altstadt, Frank Bergner, Jann-Erik Brandenburg
et al.
Neutron irradiation causes embrittlement of reactor pressure vessel (RPV) steels. Post-irradiation annealing is capable of partly or fully restoring the unembrittled condition. While annealing at high temperatures (e.g., 475°C) was successfully applied to extend the lifetime of operating VVER-440 reactors, the benefit of annealing at lower temperatures (e.g., 343°C–the maximum to which the primary cooling water can be heated) is a matter of debate. In this study, neutron-irradiated VVER-440 RPV base metal and weld were exposed to isothermal annealing at 343°C up to 2,000 h. Given the limited amount of material, the degree of recovery was estimated in terms of Vickers hardness, the ductile-brittle transition temperature derived from small punch tests, and the master curve reference temperature derived from fracture mechanics tests of mini samples. For the base metal, small-angle neutron scattering was applied to underpin the findings at the nm-scale. We have found significant partial recovery in both materials after annealing for 300 h or longer. The variations of the degree of recovery are critically discussed and put into the context of wet annealing.
This study proposes a folded cascode CMOS low noise amplifier (LNA) with transformer feedback, implemented using a 0.13-μm CMOS process for wireless local area network front-end module applications. Compared to a conventional cascode inductive source degeneration LNA (ISDLNA), the folded cascode ISDLNA significantly improved the input-referred third-order intercept point (IIP3) as well as the 1-dB compression point (P1dB) by ensuring a large voltage headroom. Furthermore, the designed LNA also achieved a low noise figure (NF), while also saving the silicon area by magnetically coupling the source and folding inductors. When tested experimentally, the proposed LNA showed an S21 of 11.0 dB and an NF of 2.6 dB, while achieving an S11 of −7 dB at the operating frequency of 2.4 GHz. The measured input P1dB and IIP3 were −5.6 dBm and +2.5 dBm, respectively. The power dissipation was 9.6 mW from a 1.2-V supply voltage.
Electrical engineering. Electronics. Nuclear engineering, Electricity and magnetism
In young Maxwell’s eyes, electricity, magnetism and fluid mechanics present analogies that let the first be mathematically grasped in a unitary way similarly to the latter. This entry sketches the first steps of James Clerk Maxwell’s unitary view of electromagnetism and fluid mechanics, with long-lasting effects on understanding the physical world. In his very first paper on the subject, Maxwell interpreted Faraday’s concept of lines of force of both electricity and magnetism as filaments of a flowing fluid. That is, Maxwell suggested to unify the previously distinct fields of electricity and magnetism, considering them as different aspects of the same entity, the ‘electromagnetic field’, which is mathematically described by four partial differential equations. In the literature there are several comprehensive works on Maxwell’s mature exposition of his theory; however, the aim of this entry contribution is rather more limited. Indeed, it is restricted to examining the contributions of Maxwell’s first paper towards developing the idea of electric current as the motion of an incompressible fluid. Thus, this entry highlights the strong connections of Maxwell’s epistemological view with the ‘mechanistic’ approach of the time to every aspect of physical phenomenology. For this purpose, this entry mentions some historical context surrounding the emergence of Maxwell’s innovative concepts.
Camille J. Palmer, Jordan Northrop, Todd S. Palmer
et al.
The detailed behavior of neutrons in a rapidly changing time-dependent physical system is a challenging computational physics problem, particularly when using Monte Carlo methods on heterogeneous high-performance computing architectures. A small number of algorithms and code implementations have been shown to be performant for time-independent (fixed source and k-eigenvalue) Monte Carlo, and there are existing simulation tools that successfully solve the time-dependent Monte Carlo problem on smaller computing platforms. To bridge this gap, a time-dependent version of ORNL’s Shift code has been recently developed. Shift’s history-based algorithm on CPUs, and its event-based algorithm on GPUs, have both been observed to scale well to very large numbers of processors, which motivated the extension of this code to solve time-dependent problems. The validation of this new capability requires a comparison with time-dependent neutron experiments. Lawrence Livermore National Laboratory’s (LLNL) pulsed sphere benchmark experiments were simulated in Shift to validate both the time-independent as well as new time-dependent features recently incorporated into Shift. A suite of pulsed-sphere models was simulated using Shift and compared to the available experimental data and simulations with MCNP. Overall results indicate that Shift accurately simulates the pulsed sphere benchmarks, and that the new time-dependent modifications of Shift are working as intended. Validated exascale neutron transport codes are essential for a wide variety of future multiphysics applications.
In order to improve the level of clean energy consumption and the economy of energy storage allocation in parks, an optimal allocation method for energy storage capacity of high-proportion clean energy parks considering demand response is proposed. Firstly, the photovoltaic, wind turbine, and energy storage power models are established. Secondly, a demand response mechanism considering the participation of rigid, transferable and interruptible loads is designed to realize the transfer of loads under a certain time scale. Then, taking the lowest total net present cost of the system as the optimization goal, an energy storage economic allocation model is established with consideration of the constraints such as grid-connected power fluctuations and charge & discharge limits. Case study verifies the effectiveness of the proposed method, and the results show that compared to the traditional method, the proposed allocation method can effectively reduce the economic cost of the system and improve the level of clean energy consumption.
Electricity, Production of electric energy or power. Powerplants. Central stations
In this study, we investigate the possibility to trap an ion particle in a non-uniform electrostatic field generated by two ionic rings, with the aim to obtain and verify general results regarding our proposition. To develop the equation of motion, we first derive the electric field generated by each ring, based on the multipole expansion technique under the azimuthally symmetrical charge distribution speculation and superposition principle. Then, we establish the equation of motion regarding the Lagrangian formalism. From the results, we observe that an ion particle can exhibit harmonic motion, if the stability condition is satisfied by an appropriate parametric setting. The results are confirmed by displacement responses and phase trajectory plots, which validate our belief in the prospect to trap an ion in an electrostatic field. Furthermore, the velocity amplitude is significantly influenced by both the charge concentration of each ring and its size.
Electrical engineering. Electronics. Nuclear engineering, Electricity and magnetism
Abstract In order to improve the sensitivity and accuracy of oil‐paper insulation partial discharge detection by the fibre‐optic Fabry–Perot (FP) ultrasonic sensor, this work studied the ultrasonic signal’s frequency characteristics of typical oil‐paper insulation partial discharges and the vibration characteristics of the FP sensor’s diaphragm in the liquid environment. Based on the works above, a multifrequency FP sensor array is proposed, consisting of several FP sensors with different resonant frequencies to detect partial discharges. The experimental results show that the liquid environment has a significant effect on the vibration characteristics of the FP sensor’s diaphragm, and the sensitivity and accuracy of partial discharge detection can be improved based on the multifrequency FP sensing array, which can also be applied in the pattern recognition and localisation of partial discharges.
A miniaturized low noise quartz crystal oscillator for rubidium atomic frequency standard (RAFS) was designed in this paper, with the oscillation circuit applying Colpitts parallel configuration and SC-cut crystal resonator. The phase noise of quartz crystal oscillator was analyzed based on Leeson model, and the oscillation circuit was simulated by using ADS software, which can provide guidance for oscillator design and debugging. Finally, a low noise crystal oscillator with volume of 22 mm×28.5 mm×13 mm has been completed. Test results show that it reached the phase noise of −102.7 dBc/Hz@1 Hz and −164.2 dBc/Hz@10 kHz, and the short-term stability of 1.73×10−12/s.
The method of symmetrical components is an important mathematical tool for electrical engineering, as it simplifies the analysis of unbalanced electrical circuits. The method is used almost exclusively for three-phase networks, but with the advancement of multiphase electrical systems, it could be convenient to utilize it for such systems as well. In this paper, the method of symmetrical components is used to analyze a generic five-phase electrical system for various short-circuit faults and to determine the sequence networks connections for these faults. The analysis performed covers the derivation of the symmetrical components for voltage/current and of fault currents. The analytical results and the inferred sequence networks connections are validated by computer simulations. This paper therefore extends the literature on short-circuit analysis of multiphase electrical systems using the method of symmetrical components.
A non-thermal plasma, air purification device (PlasmaShield<sup>®</sup>, MD250, Keswick, SA, Australia), was investigated using spatially resolved optical emission spectroscopy. The emission spectra were measured with two spatial dimensions to analyze and identify the transition lines of excited NO–γ (A<sup>2</sup>Σ–X<sup>2</sup>Π), N<sub>2</sub> (C<sup>3</sup>Π–B<sup>3</sup>Π), and N<sub>2</sub><sup>+</sup> (B<sup>2</sup>Σ–X<sup>2</sup>Σ) systems. The N<sub>2</sub> emission band at 337 and 316 nm were used to determine the spatially resolved vibrational temperature of N<sub>2</sub> molecules, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msubsup><mi>T</mi><mrow><mi>v</mi><mi>i</mi><mi>b</mi></mrow><mrow><msub><mi>N</mi><mn>2</mn></msub></mrow></msubsup></mrow></semantics></math></inline-formula>. It was found that the average N<sub>2</sub> vibrational temperatures in the x and y directions are almost the same. Two key operating parameters, supplied power and air flow, influence the N<sub>2</sub> vibrational temperature. The results demonstrate that applying higher supplied power increases the vibrational temperature, while changes in air flow velocity do not affect the vibrational temperature values. The phenomenological plasma temperature (PPT) was also estimated from the N<sub>2</sub> vibrational temperature. It was observed that PlasmaShield<sup>®</sup> generates excited N<sub>2</sub> and NO only within a narrow region around the discharge electrode tip (with peak intensity below 100 µm from the tip). The study also shows no presence of excited OH*, O*, and other radicals.
As a type of zero-discharge technologies, the rotary spray drying technology utilizes hot flue gas to evaporate desulfurization wastewater. In this paper, the evaporation test is carried out for both the raw wastewater with different suspended solid (SS) content and the concentrated high salinity wastewater. Specifically, the evaporation characteristics of the desulfurization wastewater in the drying tower are examined with the aid of visualization techniques. Moreover, the impacts of residence time duration, inlet flue gas temperature and gas-liquid ratio on the evaporation characteristics are also investigated during the spray evaporation process of the desulfurization wastewater. The results show that the rotary spray evaporation process has better adaptability to complex desulphurization wastewater components such as high salinity and high SS content. After sprayed from the rotary atomizer, the desulfurization wastewater evaporates rapidly mainly into the zone of 0.75~1.00 m below the atomization tray, and then the precipitated salt and the incompletely evaporated wastewater droplets are further evaporated until the moisture content is less than 2%. The residence time of the flue gas needs to last at least 20 seconds in the spray drying tower so as to ensure the moisture content of ash particles to be less than 2% at the outlet of the tower. The higher the temperature of the inlet flue gas, the lower the particle moisture content at both the bottom and the outlet of the tower. As for the wastewater with the gas-liquid ratio at 12 000 m3/m3 (standard state), the expected outcome of evaporation of wastewater droplets could hardly be guaranteed with the inlet smoke temperature at 280 ℃. However, if the inlet flue gas temperature is maintained at 340 ℃ and the gas-liquid ratio is greater than 10 000 m3/m3(standard state), the bottom ash moisture content is dropped down below 2%, which shows good evaporation effect.
Electricity, Production of electric energy or power. Powerplants. Central stations
Eric W. Burkholder, Gabriel Murillo-Gonzalez, Carl Wieman
Previous work has looked at the relationship between high school preparation and student performance in calculus-based introductory mechanics (physics 1) courses. Here, we extend that work to look at performance in introductory calculus-based electricity and magnetism (physics 2), and we look at the significance of what college math courses have been completed in addition to high school preparation. Using multiple linear regression including these measures of prior preparation, we examine the correlation between taking various math courses in college and final exam scores in introductory physics courses at a highly selective west coast university. In physics 1, we find that prior college math coursework is not a predictor of physics 1 final exam score. In physics 2, we find that having taken a course in vector calculus is a strong predictor of physics 2 exam performance (effect size=0.58 standard deviations, p<0.001), even when controlling for students’ physics 1 final exam scores (effect size=0.27 standard deviations, p<0.01). These effect sizes are similar in magnitude to other measures of students’ incoming physics and math preparation. Qualitative analysis of student exams from physics 2 reveal that this “vector calculus gap” is due to differences in reasoning about vectors and geometry and some differences in conceptual understanding of circuits, as vector calculus itself is not required to perform well on the final exam. That is, basic reasoning related to vector calculus appears to be important, but the formalisms of vector calculus do not.
Katarina Karlova, Jozef Strecka, Masayuki Hagiwara
Ground-state phase diagrams and magnetization curves of a spin-1 Heisenberg diamond cluster with two different coupling constants and uniaxial single-ion anisotropy are investigated in a presence of the external magnetic field with the help of exact diagonalization methods. It is shown that the spin-1 Heisenberg diamond cluster exhibits several remarkable quantum ground states, which are manifested in zero- and low-temperature magnetization curves as intermediate plateaus at one-quarter, one-half and three-quarters of the saturation magnetization. It is found that the width of the fractional magnetization plateaus depends basically on a relative strength of the coupling constants as well as uniaxial single-ion anisotropy, which may substantially shrink or even cause full breakdown of some intermediate magnetization plateaus. It is evidenced that a relatively weak uniaxial single-ion anisotropy of the easy-axis type considerably improves a theoretical fit of low-temperature magnetization curves of the tetranuclear nickel complex [Ni4(CO3)2(aetpy)8](ClO4)4 in a low-field region without spoiling the previous fit based on the fully isotropic Heisenberg model in a high-field region.
Large amounts of fossil fuel consumption and carbon emissions are the main causes for environmental pollution and climate change. Accelerated devleloping renewable ernergy, reducing reliance on fossil enery, building a clean, low-carbon and efficient energy system is the key to solve environmental pollution and climate change problem and achieve sustainable energy development. In recent years, China has kept its energy saving and emission reduction commitments by developing hydro, wind and PV power, which has already ranked first in the world. Meanwhile, wind and PV power development also has exposed problems such as irrational and insufficient utilization due to uncoordinated development. Focusing on scientific development of wind and PV power in China, this paper analyzes the benefits and impacts of wind and PV power development, and puts forward some reasonable development ideas and policy suggestions from the perspective of energy strategy, planning, management and technology, which can be used as a reference for the high-quality development of wind and PV power.
Electricity, Production of electric energy or power. Powerplants. Central stations