Uniform Power Distribution Research Articles

A Novel Topology of a 3 × 3 Series Phased Array Antenna with Aperture-Coupled Feeding.

This paper presents a novel 3 × 3 phased array antenna optimized for 4 GHz operation, achieving a realized gain of 13.2 dBi and enabling 30-degree beam steering with a minimal capacitance variation of 1.5 pF. The design features a series aperture-coupled feeding mechanism that not only reduces the antenna's size but also simplifies the fabrication process, making the device both cost-effective and compact. Integrating cost-efficient quadrature-hybrid phase shifters and novel power splitters with cascaded quadrature hybrids ensures uniform power distribution and precise beam steering. The innovative use of these components addresses common challenges in phased array systems, such as space constraints, high costs, and complex power distribution.

Numerical study on benchmark analysis of NACIE-UP facility with uniform and non-uniform power distribution

The NACIE-UP (NAtural Circulation Experiment-Upgrade) facility is located at the ENEA Brasimone Research Centre (Italy) and is designed to investigate the thermal–hydraulic properties of Lead-Bismuth Eutectic (LBE) within a wire-spaced assembly under uniform and non-uniform power distribution conditions. This benchmark exercise proposed by ENEA is based on previous experiment results, intending for development and validation of CFD/TH system code, stand-alone CFD simulation, etc. In this study, the thermal–hydraulic characteristics of Fuel Pin Simulator (FPS) are analyzed, which contains inlet bend and outlet section. ANSYS Fluent solver is applied with the COUPLE algorithm of RANS SSTk-ω model. Cheng&Tak correlation and computational conditions are implanted into Fluent in the form of UDFs. Moreover, calculations were performed for ADP10, ADP06 and ADP07. The results show that the RMSEs of ADP10SS1 and ADP10SS2 are 2.52 K and 3.69 K, 7.05 K and 8.48 K for ADP06SS1 and ADP06SS2, respectively, which indicate that the adopted models have good prediction ability for the temperature of the experimental conditions. Meanwhile, the heat transfer characteristics of different sub-channels and sections are investigated and compared with the correlations of Ushakov, Mikityuk, Kazimi and Carelli. The experimental and simulation values of the uniformly heated ADP10 are in good agreement with the correlations, while there is a large deviation for the non-uniformly heated ADP06. Therefore, it is necessary to develop new correlations for the heat transfer characteristics of LBE in wire-wrapped bundle. Above all, this study provides quantitative and qualitative analysis for verification and validation of CFD/TH system code and stand-alone CFD simulation.

Concurrent performance and security enhancement of ultrahigh-order DSM signals via null subcarriers.

In this paper, we propose leveraging null subcarriers in discrete multi-tone modulation (DMT) to process the DMT signal in both time and frequency domains. Additionally, we employ discrete memory enhanced chaos (DMEC) to scramble the signal in the frequency domain, thereby achieving physical layer signal encryption while ensuring a more uniform power distribution in the time-domain waveform. In our experimental demonstration, we achieved high-security transmission of a DSM-based 65536-QAM signal at a data rate of 16.01 Gb/s over a 25 km single-mode fiber (SMF) in an intensity-modulation direct-detection (IMDD) system. Additionally, in the transmission experiments for 13684-QAM and 65536-QAM signals, the proposed method demonstrated a receiver sensitivity gain of over 0.5 dB compared to the traditional DSM-based ultrahigh-order transmission.

Analytical Model of Natural Circulation with a Sinusoidal Heat Input in a PWR

This research presents the development of a one-dimensional analytical model to investigate the impact of pressure variations in the primary loop on natural circulation (NC). The model takes into account a sinusoidal input heat distribution and derives equations for the parameters of NC. The model covers a broad spectrum of NC patterns, spanning from fully single-phase to fully two-phase flow. The research demonstrates a smooth and continuous transition between various kinds of NC. Moreover, the research demonstrates that NC is capable of efficiently dissipating the decay heat generated inside the core of a pressurized water reactor, encompassing a range from 100% to 60% of the total inventory present within the primary loop. The findings of this study are compared to prior research outcomes and demonstrate a reasonable level of consistency. Additionally, comparisons are made with uniform input power distribution to demonstrate that there are no significant differences in the NC parameters when using sinusoidal heat input.

Experimental investigation of quench front propagation during reflooding in 5 × 5 rod bundle channel with axial uniform power distribution

This experimental study delves into the impact of inlet injection velocity, inlet subcooling, and linear power density on the quench front propagation during reflooding in 5x5 rod bundle channel with axial uniform power distribution. The investigation utilized a film boiling test facility constructed by NUclear Safety and Operation Laboratory (NUSOL) of Xi'an Jiaotong University. The findings demonstrate a discernible sensitivity of the quench front to variations in these parameters, wherein higher linear power density, reduced flow rate, and decreased coolant subcooling lead to delayed reflooding. Moreover, the study derived the surface parameters of the heater rod use self-developed Reflooding Experimental Data Analysis code (REDA). The comprehensive experimental data and empirical models generated in this study hold significant potential for enhancing the safety analysis of nuclear reactors.

Neutronic assessment and optimization of ACP-100 reactor core models to achieve unit multiplication and radial power peaking factor

This study focuses on the neutronic and burnup assessment of the PWR-based Chinese ACP-100 SMR core. Four different core models with varying fuel compositions and assembly configurations were analyzed using the Monte Carlo code SERPENT 2. Three of these models shared uniformly enriched fuel assemblies of 3 wt.%, 4 wt.%, and 4.45 wt.% 235U respectively, while the fourth model (the proposed design for the ACP-100 in this study) featured a mix of differently enriched fuel assemblies along with the inclusion of burnable absorbers. The burnup analysis of the cores spanned 1570 EFPDs, evaluating several neutronic parameters (beta effective, reactivity coefficients) as well as fuel cycle characteristics (cycle burnup, discharge burnup and cycle length). Changes in the isotopic concentration of fissile, fertile, and poison materials were observed and the assembly-wise linear power distribution, neutron flux spectra, and radial power peaking factors of the models were determined. In the mixed core, a combination of borated water, IFBAs and control rods were employed to achieve exact criticality (unit keff) and uniform power distribution (unit radial power peaking factor). Insertion of control rods into 41 of the 57 assemblies, in conjunction with IFBAs placed strategically, attained a near unit radial power peaking factor (PPF) of 1.0586. Finally, the combination of IFBAs, sol-bor of 936 ppm concentration, and CRs with rod worth of 414.33 pcm per assembly brought down the keff to 1.000, but increased the PPF to 1.117. While the achievement of uniform power distribution came at the cost of fuel burnup, the proposed mixed core successfully remained critical for over 1.5 years and reached a discharge burnup of 23.37 GWd/t for a two-batch refueling scheme.

Improved Power Sharing Strategy for Parallel Connected Inverters in Standalone Micro-grid

The primary goal of integrating alternative energy systems such as solar and wind turbines into the power grid using power electronic devices is to meet the growing energy demands. Connecting inverters in parallel effectively enhance power capacity, reliability, and overall system efficiency. However, an uneven power distribution among the inverters is a significant limitation in these parallel connected inverters (PCI). This study focuses on a distributed generation (DG) unit comprising a solar photovoltaic system (SPV) and a battery energy storage system (BESS) connected to voltage source inverters (VSI) 1 and 2. The proposed approach aims to achieve uniform load/power distribution among the inverters with power management, maintaining a constant DC link voltage despite variations in solar irradiation and temperature. Additionally, the strategy targets the reduction of total harmonic distortion (THD) in the load current. The conventional droop control method is restricted in its ability to achieve accurate and uniform power distribution during load changes. An enhanced P-f and Q-E-based droop control technique (EDCT) and a fuzzy logic controller (FLC) have been proposed to address these challenges. Performance analysis using MATLAB/Simulink was conducted with two test cases, and a comparative assessment was carried out with a conventional controller, such as a Proportional Integral Controller (PIC) and Sliding Mode Controller (SMC), to showcase the effectiveness of the developed control technique. The proposed control method ensures equal sharing of active power of 2.5 and 4kW, 2.5 and 7.5kW and reactive powers of 2.5 and 4Vars, 2.5 and 7.5Vars among the inverters for the two cases even during the load change at t=0.5seconds. The settling time for DC link voltage and THD is effectively diminished to 0.03 and 0.25 seconds and 1.18% and 2.87% for the two test case studies of the proposed method, which are much lower than those of existing methods available in the literature.

Core design: Review & perspectives in Spain

In Core Fuel Management (ICFM) is an essential part of the operation of all commercial nuclear reactors. At the beginning of each fuel cycle (BOC), an optimal loading pattern is required to produce safe and economical operating conditions, such as uniform power distribution and a high degree of fuel burnup. These operating conditions are sought to achieve maximum useful life at minimum cost and the highest levels of safety, which leads to maximization of benefits. This article describes the work done by Spanish nuclear related organizations, which are currently involved in core design and core analyses from industrial, research and safety perspectives. In many instances, achieving enhanced accident tolerance would provide significant opportunities for outstanding research and improvements in operational cost benefits for the industry.

ОПТИМІЗАЦІЯ ГРАФІКІВ ЕЛЕКТРИЧНОГО НАВАНТАЖЕННЯ АГРЕГАТОРОМ У ЛОКАЛЬНИХ ЕЛЕКТРОЕНЕРГЕТИЧНИХ СИСТЕМАХ

The market operation of the electricity distribution system has gained significant expansion due to the growing use of renewable and distributed sources. This paper presents strategies for optimizing load schedules by aggregators of local systems. Optimization of load schedules is to minimize the total costs of the supplier to reduce the cost of electricity and lower prices for the consumer. In local systems, which include diesel generators, the main component that most affects the price per 1 kW is the consumption of primary fuel of diesel generators. The objective function proposed in this study minimizes the supplier's primary fuel consumption by optimally redistributing power to each generator. The basic load schedule and application of schedule optimization strategies were studied: load reduction, load transfer, increase of minimum loads, flexible load change. When using the optimal algorithm, the costs are 5-6% relative to the uniform power distribution. Ref. 8, fig. 4, table. Key words: local system, diesel-generator, load schedule, aggregator.

An attempt to find the optimal loading pattern of minor actinides in the PWR fuel rods

Three approaches of minor actinide (MA) loading in the fuel rods of a pressurized water reactor were examined. They comprised inserting MAs and fuel mixture in the center of duplex fuel rods, coating of MAs and fuel mixture in the outer layer of fuel rods and lastly, mixing MAs homogeneously with the entire fuel rod elements. AP1000 fuel assembly was chosen as the reference design. Two fuel types namely conventional UO2 and UTh MOX fuel were selected as the base fuel models for the study. Although shorter cycle length than the UO2 fuel design was achieved by the UTh fuel design, UTh fuel exhibited more favorable FTC and yielded a lower plutonium stockpile at the end of the fuel cycle. When MAs were added in the outer layer of fuel rods, it resulted in higher rate of transmutation, however it had an adverse impact on the fuel reactivity, discharge burnup and pin power distribution. On the contrary, when MAs were loaded in the central region, it led to incomplete incineration of MAs. Therefore, based on the satisfactory transmutation rate, MTC, most negative FTC and uniform pin power distribution, the homogenous MA loading strategy can be concluded as the optimal loading pattern for the AP1000 nuclear reactor.

Subchannel thermal–hydraulic analysis of a wire-wrapped 19-pin rod bundle in the NACIE-UP facility

Based on the experimental campaign performed on the NACIE-UP (NAtural Circulation Experiment-Upgraded) facility, the benchmark activity was proposed by ENEA to qualify and validate the numerical tools for the Heavy Liquid Metal (HLM) system. Xi’an Jiaotong University participated in the benchmark exercise of subchannel validation and the self-developed subchannel code YAOGUANG was applied to the thermal hydraulic analysis. The performed two tests with different power distributions on the Fuel Pin bundle Simulator (FPS) were simulated, characterized by transition from forced to natural circulation. The applicability of this code to the stable state and mass flow rate transient was evaluated by comparing the numerical outcomes with the experimental results. Then the effect of the non-uniform heating on the thermal field was analyzed. The results indicate that this subchannel code has good accuracy in simulating both steady state and transient conditions with uniform power distribution. For the non-uniform case, the subchannel calculations can capture the general trend of temperature distributions, with a larger simulation deviation observed. This discrepancy is mainly due to the limitations of existing models adopted because they didn’t consider the impacts of non-uniform conditions on the flow and heat transfer in rod bundles. Finally, the influence of non-uniform heating is mainly manifested as the increase of axial and radial temperature gradients and it helps to flatten the radial thermal field to some degree.

High Isolation Wideband MIMO Antenna without Decoupling Technique for IoT Applications

This paper presents a method a high isolation wideband MIMO antenna without using any decoupling technique. This is achieved by transforming a strip line to a 1 ×2 MIMO antenna using Hilbert transform and Defected Ground structure is used in the antenna to resonate the antenna in for IOT and 5G sub-6 GHz bands. The proposed antenna has a size of 50 × 49.8 × 1.6 mm 3 and operates in the frequency band of 4.6 GHz to 5.94 GHz. The antenna simulated in ANSYS HFSS showed that its parameters Envelope correlation coefficient (ECC), Total Active Reflection Coefficient (TARC), Diversity gain (DG) and Channel Capacity Loss (CCL) are less than 0.04, -25 dB, 9.98 to 10 dB and less than 0.4 bits/s/Hz respectively. The radiation pattern of the antenna in both E-plane and H-plane has been simulated which the uniform distribution of power in the space.

Multiphysics assessment of a PWR-type SMR core using Spherical Cermet fuel through a neutronic and thermohydraulic coupled study

In this paper, a multiphysics assessment of the performance of a PWR-type SMR core using Spherical Cermet Fuel is carried out, through a coupled neutronic-thermohydraulic study using Serpent and Ansys CFX codes. The most important results related to the core performance are compared with those obtained when TRISO fuel is used. Correlations (Cp, k) were developed as function of temperature for the fuel region, which are unique and specific for the fuel of this study. The results obtained show that the neutronic-thermohydraulic coupled calculation converges from the fourth iteration, with Keff being the convergence indicator that converges more slowly. An extended fuel cycle of 1448 days was achieved with a uniform power distribution. With this new core configuration, a lower production of plutonium isotopes was obtained. Temperatures below the safe operation limit were obtained in all the studied zones, as well as basic negative safety parameters such as fuel temperature and moderator temperature coefficients, and the full coolant void coefficient.

Neutronic and thermal analysis of heat pipe cooled graphite moderated micro reactor

Heat pipe micro reactors are drawing a lot of interest lately due to their distinct features, including the elimination of moving parts required for transferring the heat, as they do so passively through heat pipes, combined with the ability of such reactors to provide energy to remote locations. This present study introduces a proposed design for heat pipe cooled graphite moderated micro reactor suitable for remote locations and space applications. The main requirements of the design include long core lifetime, two shutdown mechanisms, uniform power distribution, and strong negative temperature coefficient. Neutronic calculations were performed using MCNP 6.2 code. Criticality analysis demonstrated the ability of both control devices incorporated in the design to independently control and shutdown the reactor. Calculations of the flux and power distribution showed that, for a thermal power of 0.25 MW, the maximum flux at mid-plane of the reactor is in the order of 1012n/(cm2·s), while radial and axial power peaking factors were found to be 1.2 and 1.13, respectively. The results also showed that the reactor has an overall negative temperature coefficient. Additionally, burnup calculations were carried out to calculate the core lifetime which was estimated to be more than 70 years. A preliminary steady-state thermal analysis was conducted for the reactor using ANSYS FLUENT, assuming 1/12th symmetry. The obtained temperature distribution of the reactor showed that the operating temperatures are within the accepted limits where the highest temperature reached in the fuel was 1074 K. Furthermore, soft coupling of MCNP and ANSYS FLUENT was conducted through an iterative process of performing neutronic and thermal simulation using updated results for the temperatures and power distributions in each iteration.

In-plane thermal diffusivity determination using beam-offset frequency-domain thermoreflectance with a one-dimensional optical heat source

We present an innovative contactless method suitable to study in-plane thermal transport based on beam-offset frequency-domain thermoreflectance using a one-dimensional heat source with uniform power distribution. Using a one-dimensional heat source provides a number of advantages as compared to point-like heat sources, as typically used in time- and frequency-domain thermoreflectance experiments, just to name a few: (i) it leads to a slower spatial decay of the temperature field in the direction perpendicular to the line-shaped heat source, allowing to probe the temperature field at larger distances from the heater, hence, enhancing the sensitivity to in-plane thermal transport; (ii) the frequency range of interest is typically <100 kHz. This rather low frequency range is convenient regarding the cost of the required excitation laser system but, most importantly, it allows the study of materials without the presence of a metallic transducer with almost no influence of the finite optical penetration depth of the pump and probe beams on the thermal phase lag, which arises from the large thermal penetration depth imposed by the used frequency range. We also show that for the case of a harmonic thermal excitation source, the phase lag between the thermal excitation and thermal response of the sample exhibits a linear dependence with their spatial offset, where the slope is proportional to the inverse of the thermal diffusivity of the material. We demonstrate the applicability of this method to the cases of: (i) suspended thin films of Si and PDPP4T, (ii) Bi bulk samples, and (iii) Si, glass, and highly-oriented pyrollitic graphite (HOPG) bulk samples with a thin metallic transducer. Finally, we also show that it is possible to study in-plane heat transport on substrates with rather low thermal diffusivity, e.g., glass, even using a metallic transducer. We achieve this by an original approach based on patterning the transducer using focused ion beam, with the key purpose of limiting in-plane heat transport through the thin metallic transducer.

Research on the deep peak-shaving cost allocation mechanism considering the responsibility of the load side

With the goal of carbon reduction, China has carried out a series of institutional reforms and innovations in renewable energy consumption. However, the existing allocation rules for peak-shaving costs concentrate on the power side only. In the context of high energy penetration rates, peak-shaving cost significantly increases, and the economic pressure on the power side sharply increases. As the beneficiaries of peak shaving, the load side, while enjoying clean energy, also needs to bear the responsibility of peak shaving and share part of the peak-shaving cost. In this regard, this paper proposes a peak-shaving cost allocation mechanism considering load-side participation. First, it uses the marginal contribution theory to establish the peak-shaving value evaluation model of the power and load. Then, based on the waveform similarity theory, it sets two indicators “Fluctuation Trend Similarity” and “Waveform Amplitude Difference” to evaluate each load’s renewable energy consumption responsibility. Finally, the peak-shaving cost allocation rules on the power source side and the load side are obtained. An example shows that the proposed allocation mechanism can initially realize the uniform distribution of power and load in peak-shaving cost. Furthermore, the method can promote the fairness of the peak-shaving market and guide users to reasonably participate in the peak-shaving market.

Rationalization and evaluation of a Phenomenon-driven improved bundle CHF model under PWRs condition with different axial power distributions

In this paper, based on the bubble crowding bundle critical heat flux (CHF) mechanistic model proposed earlier by the author, which is applicable to the pressurized water reactors (PWRs) condition, more reasonable processes are considered, and a phenomenon-driven improved model was proposed. Firstly, the improved model describes the relationship between the latest visualization experimental results within PWRs ranges and bubble crowding concept, and clarifies the theoretical basis of the model. Secondly, based on the grid-effect CHF experiment, a more mechanistic turbulence mixing intensity factor was proposed in the process of model construction. Finally, the validation of the improved model for uniform axial power distribution (APD) CHF shows good prediction ability, and the previous tendentious problem about quality was eliminated. The model’s assessment of non-uniform APD CHF is performed for the first time, which shows that the improved model has good potential for predicting non-uniform APD CHF, and the CHF model needs to consider the upstream heating effect.

Theoretical Impact of Intraocular Lens Design Variations on the Accuracy of IOL Power Calculations.

To ascertain the theoretical impact of optical design variations of the intraocular lens (IOL) on the accuracy of IOL power formulas based on a single lens constant using a thick lens eye model. This impact was also simulated before and after optimization. We modeled 70 thick-lens pseudophakic eyes implanted with IOLs of symmetrical optical design and power comprised between 0.50 D and 35 D in 0.5-step increments. Modifications of the shape factor resulting in variations in the anterior and posterior radii of an IOL were made, keeping the central thickness and paraxial powers static. Geometry data from three IOL models were also used. Corresponding postoperative spherical equivalent (SE) were computed for different IOL powers and assimilated to a prediction error of the formula due to the sole change in optical design alone. Formula accuracy was studied before and after zeroization on a uniform and non-uniform realistic IOL power distribution. The impact of the incremental change in optic design variability depended on the IOL power. Design modifications theoretically induce an increase in the standard deviation (SD), Mean Absolute Error (MAE), and Root Mean Square (RMS) of the error. The values of these parameters reduce dramatically after zeroization. While the variations in optical design can affect refractive outcomes, especially in short eyes, the zeroization of the mean error theoretically reduces the impact of the IOL's design and power on the accuracy of IOL power calculation.

Powell lens-based line-field spectral domain optical coherence tomography system for cellular resolution imaging of biological tissue.

A Powell lens is used in a line-field spectral domain OCT (PL-LF-SD-OCT) system to generate a line-shaped imaging beam with almost uniform distribution of the optical power in the line direction. This design overcomes the severe sensitivity loss (∼10 dB) observed along the line length direction (B-scan) in LF-OCT systems based on cylindrical lens line generators. The PL-LF-SD-OCT system offers almost isotropic spatial resolution (Δx and Δy ∼2 µm, Δz ∼1.8 µm) in free space and sensitivity of ∼87 dB for 2.5 mW imaging power at 2,000 fps imaging rate with only ∼1.6 dB sensitivity loss along the line length. Images acquired with the PL-LF-SD-OCT system allow for visualization of the cellular and sub-cellular structure of biological tissues.

Integrated Phased Array for Scalable Vortex Beam Multiplexing

Orbital angular momentum (OAM) modes have low model interactions during fiber propagation at data center distances, and thus are suitable for ultra-high capacity systems at low digital signal processing. Generating OAM modes using free-space setups is useful for proof-of-concept experiments, but is not a scalable solution. We use an optical phased array (OPA) with two-dimensional antennas for on-chip circularly polarized OAM beam generation. Our previous work demonstrated an OAM multiplexer for lower-order modes. In this work, we demonstrate an OAM multiplexer that supports a record of 46 (23 per polarization) simultaneous spatial modes up to OAM order 11. We also improve the crosstalk performance of our multiplexer. We incorporate an intensity tuning capability that substantially improves the OAM quality by enabling a uniform power distribution across the antennas. The worst-case crosstalk for the supported OAM5 to OAM11 are found experimentally to be better than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-12$</tex-math></inline-formula> dB, with OAM10 achieving <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-17.2$</tex-math></inline-formula> dB.