Average Fluctuation Research Articles

Investigation of weather conditions on the output power of various photovoltaic systems

The quantity of solar radiation received by photovoltaic panel surfaces and their efficiency are influenced by environmental factors, including dust buildup and weather changes. This study presents an experimental analysis to determine how dust and rain affected the output of photovoltaic power for five different types and orientations of solar module systems of 5 kW each. All systems are installed at Applied Science Private University in Jordan, and attached to sunny portal system to monitor the PV output power for each type in real time. After one–four weeks of exposure, the effects of dust buildup and weather conditions on the power output of the module systems were examined. The results showed that four weeks of dust buildup resulted in 16.7%, 28%, 16.6%, 26.7%, and 21% reduction in PV power production for Monocrystalline (c-Si)/South, Monocrystalline (c-Si) East/West, Polycrystalline (p-Si)/South, Polycrystalline (p-Si)/East/West, and Thin-film (a-Si, microcrystalline)/South system respectively. In addition, a 20% average decrease and fluctuation in PV output power under wet conditions is observed. Moreover, the results showed that the power sold to the grid would be lower than predicted by 21% after one month of dust accumulation, which should be included in energy management planning.

49 W carrier-envelope-phase-stable few-cycle 2.1 µm OPCPA at 10 kHz.

We demonstrate a mid-infrared optical parametric chirped pulse amplifier (OPCPA), delivering 2.1 µm center wavelength pulses with 20 fs duration and 4.9 mJ energy at 10 kHz repetition rate. This self-seeded system is based on a kW-class Yb:YAG thin-disk amplifier driving a CEP stable short-wavelength-infrared (SWIR) generation and three consecutive OPCPA stages. Our SWIR source achieves an average power of 49 W, while still maintaining excellent phase and average power stability with sub-100 mrad carrier-envelope-phase-noise and 0.8% average power fluctuations. These parameters enable the OPCPA setup to drive attosecond pump probe spectroscopy experiments with photon energies in the water window.

Multimerizations, Aggregation, and Transfer Reactions of Small Numbers of Molecules.

Chemical equilibria of multimerizations in systems with small numbers of particles exhibit a behavior seemingly at odds with that observed macroscopically. In this paper, we apply the recently proposed expression of equilibrium constant for binding, which includes cross-correlations in reactants' concentrations, to write an equilibrium constant for the formation of clusters larger than two (e.g., trimer, tetramer, and pentamer) as series of two-body reactions. Results obtained by molecular dynamics simulations demonstrate that the value of this expression is constant for all concentrations and system sizes, as well as at an onset of a phase transition to an aggregated state, where densities in the system change discontinuously. In contrast, the value of the commonly utilized expression of equilibrium constant, which ignores correlations, is not constant and its variations can reach few orders of magnitude. Considering different paths for the same multimer formation, with elementary reactions of any order, yields different expressions for the equilibrium constant, yet, with exactly the same value. This is also true for routes with essentially zero probability to occur. Existence of different expressions for the same equilibrium constant imposes equalities between averages of correlated, along with uncorrelated, concentrations of participating species. Moreover, a relation between an average particle number and relative fluctuations derived for two-body reactions is found to be obeyed here as well despite couplings to additional equilibrium reactions in the system. Analyses of transfer reactions, where association and dissociation events take place on both sides of the chemical equation, further indicate the necessity to include cross-correlations in the expression of the equilibrium constant. However, in this case, the magnitudes of discrepancies of the uncorrelated expression are smaller, likely because of partial cancellation of correlations, which exist on both the reactant and product sides.

Multidimensional Mission-Profile-Based Lifetime Estimation Approach for IGBT Modules in MMC–HVdc Application Considering Bidirectional Power Transfer

MMC applied in high voltage direct current (HVdc) field consists of numerous submodules (SMs) and supports bidirectional power transfer, leading to the diverse mission and temperature profiles among SMs and IGBT modules. In this paper, an IGBT lifetime estimation approach in terms of the bidirectional power transfer of MMC is proposed. The temperature profile of each module is translated based on the multi-dimensional mission profile, including arm current, heatsink temperature, active power, and reactive power. In this way, the average junction temperature and junction temperature fluctuation of each SM can be readily estimated according to the power transfer direction. Furthermore, both the line-frequency and low-frequency fatigue are considered in the estimation process by using corresponding lifetime models. The proposed lifetime estimation method is compared with the traditional power loss average method and one-direction power transfer method by the application of the multi-dimensional mission profile of the practical Nanao project. The results show the bidirectional power transfer has a big influence on the damage distribution inside SM. The lower IGBT, upper FWD, and lower FWD all suffer considerable degradation under bidirectional power transfer conditions. Moreover, bond wire fatigue is the dominant degradation mechanism in MMC-HVdc application.

Gadolinium dose enhancement determination by unlaminated EBT3 films irradiated with 192Ir brachytherapy source

In this work, Gafchromic® EBT3 films were carefully delaminated and resealed with a thin mylar film of 12 μm for implementing accuracy measurements of Gd dose enhancement by a192Ir brachytherapy source. The intervened dosimeters were previously characterized in terms of their quality intervention (mechanical damage and dosimetry modification). The dose enhancement measurements were implemented in a phantom formed by a set of acrylic slabs of 30 × 30 × 0.5 cm3 machined to contain in the central axis 2 vials of 1.25 × 1.25 × 4.5 cm3 which were filled with a 20 mg/ml solution of Gd agents and with water simulating a tumoral phantom doped and undoped with Gd. In the center of the phantom, a machined acrylic slab was placed to introduce the 2.5 mm flexible guide of GammaMedplus iX equipment to position the source. Fragments of delaminated and resealed EBT3 of 0.9 × 4 cm2 were placed inside the second vial and 0.5 cm away from it, at 1.95 cm and 3.55 cm from the radioactive source respectively, to measure simultaneously the tumor dose enhancement and the radiation shielding produced at a proximal zone. CT images of the phantom were taken to prescribe 5 Gy to 1.95 cm (EBT3 film position) using a Varian BrachyVision™ planning system. Films were read out by a flatbed scanner Epson V750 PRO, 48 h after irradiation. The measurements in both tumor and healthy tissue were repeated ten times in each condition to analyze the uncertainties of the complete experimental realization. The results showed variations in the response of the intervened dosimeters, less than 1.7% for the range of interest and average fluctuations in the readout of 4.6%. The implemented dosimeter showed the feasibility of measuring dose enhancement by 192Ir source of 13 ± 7% for the concentration studied. Additionally, radiation shielding up to 6% was obtained, consistent with what has been reported in the literature.

Thermal analysis of concrete bricks-embedded phase change material: A case study under hot weather conditions

This research experimentally examines the thermal behaviour of concrete brick-based PCM layer/capsules during severe hot summer days in southern Iraq. Three bricks were fabricated in which one brick was integrated with a PCM layer (BL) and another integrated with PCM capsules (BC), while the third was left bare without PCM (BR) for comparison. The thermal performance of bricks was assessed considering the inner and outer surface temperature difference, decrement factor, time lag and average surface temperature fluctuation reduction. Besides, the mechanical strength decline of each brick was investigated to show their applicability in real constructions. Experimental results designated that BL and BC performed better than BR, in which the temperature across the brick was shaved by up to 5 °C with a 30–60 min time lag. Generally, BL exhibited slightly better thermal performance than BC; nonetheless, it showed a sharp decline in compression strength. Conclusively, the brick-based PCM layer was thermally better than that-based PCM capsules, but the latter has superior mechanical properties.

Exploring the reform of the environmental design education model under the OBE theory model of professional and creative depth integration

Abstract To be able to better improve the professional ability of environmental design students and cultivate applied technical talents, this paper proposes an analysis of the OBE theory for the reform of specialized and deeply integrated environmental design education. By establishing a mathematical model, the database is divided into different classes based on the similarity between data. The error value of the objective function is gradually reduced by repeated iterative operations. The data points are randomly selected to calculate the center distance, and the dense area of the input domain is obtained in the data set obeying Gaussian mixture distribution. Through iteration to find the optimal solution, adjust its speed and position so that the fitness function takes the maximum value. The speed is constantly revised according to its own experience and group information to enhance the global seeking ability, improve the local seeking ability of particles and avoid the oscillation phenomenon, and select the particle with the highest adaptability to calculate its average fluctuation value, to analyze the environmental design education reform under OBE theory. The result analysis shows that the correct rate of the algorithm analysis performance of this paper reaches 90.1%, which ensures more complete and accurate environmental design education data.

Transmission-based noise spectroscopy for quadratic qubit-resonator interactions

We develop a theory describing the transient transmission through noisy qubit-resonator systems with quadratic interactions as are found in superconducting and nanomechanical resonators coupled to solid-state qubits. After generalizing the quantum Langevin equations to arbitrary qubit-resonator couplings, we show that only the cases of linear and quadratic couplings allow for an analytical treatment within standard input-output theory. Focussing on quadratic couplings and allowing for arbitrary initial qubit coherences, it is shown that noise characteristics can be extracted from input-output measurements by recording both the averaged fluctuations in the transmission probability and the averaged phase. Our results represent an extension to the field of transmission-based noise spectroscopy with immediate practical applications.

A Bayesian classifier for fractal characterization of short behavioral series.

Serial tasks in behavioral research often lead to correlated responses, invalidating the application of generalized linear models and leaving the analysis of serial correlations as the only viable option. We present a Bayesian analysis method suitable for classifying even relatively short behavioral series according to their correlation structure. Our classifier consists of three phases. Phase 1 distinguishes between mono- and possible multifractal series by modeling the distribution of the increments of the series. To the series labeled as monofractal in Phase 1, classification proceeds in Phase 2 with a Bayesian version of the evenly spaced averaged detrended fluctuation analysis (Bayesian esaDFA). Finally, Phase 3 refines the estimates from the Bayesian esaDFA. We tested our classifier with very short series (viz., 256 points), both simulated and empirical ones. For the simulated series, our classifier revealed to be maximally efficient in distinguishing between mono- and multifractality and highly efficient in assigning the monofractal class. For the empirical series, our classifier identified monofractal classes specific to experimental designs, tasks, and conditions. Monofractal classes are particularly relevant for skilled, repetitive behavior. Short behavioral series are crucial for avoiding potential confounders such as mind wandering or fatigue. Our classifier thus contributes to broadening the scope of time series analysis for behavioral series and to understanding the impact of fundamental behavioral constructs (e.g., learning, coordination, and attention) on serial performance. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

On the Role of Sea Surface Temperature in the Clustering of Global Tropical Cyclone Formation

Abstract This study examines the potential impacts of large-scale atmospheric circulations that are forced by sea surface temperatures (SST) on global tropical cyclone (TC) formation. Using the Geophysical Fluid Dynamics Laboratory (GFDL) global atmosphere and land surface model, version 4 (AM4), under different SST distributions, it is found that the east–west clustering of global TC formation is mainly governed by large-scale circulations in response to given SSTs, instead of direct ocean surface fluxes associated with zonal SST anomalies. Our zonally homogeneous SST simulations in the presence of realistic surface coverage show that TC clusters still emerge as a result of the breakdown of zonal circulations related to land–sea distribution, which produce specific “hotspots” for global TC formation. Sensitivity experiments with different climate warming scenarios and model physics confirm the persistence of these TC clusters in the absence of all zonal SST variations. These robust results offer new insights into the effects of large-scale circulation and terrain forcing on TC clusters beyond the traditional view of direct SST impacts, which are based on the direct alignment of the warmest SST regions and TC clusters. In addition, our experiments also capture internal variability of the global TC frequency, with an average fluctuation of 6–8 TCs at several dominant frequencies of ∼3, 6, and 9 years, even in the absence of all SST interannual variability and ocean coupling. This finding reveals an intrinsic “noise” level of the global TC frequency that one has to take into account when examining the past and future trends in TC activity and their related significance or detectability. Significance Statement In this study, the clustering of global tropical cyclone (TC) formation is investigated, using global simulations under different idealized sea surface temperature (SST) distributions. Our results show that it is the response of the large-scale tropical circulations to SST anomalies that is mostly responsible for the clustering of global TC formation rather than surface flux differences. It is also found that the tropical atmosphere contains inherent fluctuations in the global TC frequency of 6–8 TCs every 3–9 years, even in the absence of all SST interannual and zonal variability. These results offer new insight into the role of tropical dynamics in governing TC climatology and suggest possible mechanisms underlying the clustering of global TC formation under different climate conditions.

Intensity Equalization of Bidirectional Fiber Laser Based on a Non-Reciprocal Optical Attenuator.

The application of a bidirectional laser requires the laser intensity in both directions to be balanced. However, the CW and CCW light intensities in current bidirectional erbium-doped fiber laser experiments differ due to the gain competition effect. There is no report on equalizing the intensity in the CW and CCW directions. This paper proposes a bidirectional non-reciprocal optical attenuator using the Faraday optical rotation effect. Continuous attenuation adjustment is realized by changing the angle between the polarizer's transmission axis and the linear polarized light. In this study, we analyzed the influence of different parameters on the device's performance, built a non-reciprocal attenuator, and tested the bidirectional attenuation curve, which was consistent with the simulation results. The device was integrated into a bidirectional fiber laser, and the light intensity in both directions was balanced through non-reciprocal adjustment. Combined with closed-loop control, the average intensity difference fluctuation between the two directions was controlled at 0.28% relative to the average power, realizing stable long-term bidirectional fiber laser intensity equalization.

Investigations of shock–boundary layer interaction dynamics using high-bandwidth pressure field imaging

The large-scale pulsations of shock-induced separation with length scale that significantly exceeds the incoming boundary layer thickness are investigated. The shock–boundary layer interaction (SBLI) unit is generated by an inward-turning axisymmetric compression ramp at an inflow Mach number of 2.5. A substantial region surrounding the centre azimuth exhibited mean and dynamic flow features that are consistent with two-dimensional separation. Two-dimensional highly resolved maps of surface pressure field are obtained using fast-response pressure-sensitive paint fluorescence imaging at 40 kHz repetition rate. The measurement domain covered significant regions of the incoming boundary layer through the relaxing boundary layer downstream of the reattachment as well as over 25 boundary layer thicknesses in the azimuthal direction. These measurements provide new insights into the spanwise coupling of the SBLI unit in addition to its inherent dynamics. The power spectral density (PSD) of the centreline pressure exhibits very good agreement with theoretical models and complementary measurements using fast-response pressure transducers, which served to validate the pressure field measurements. Detailed examination of the PSD reveals strong agreement with the literature, which includes the peak Strouhal number of the separation and reattachment shock motions as well as the downward frequency shift along the separation bubble. Furthermore, the pressure fluctuation maps reveal streamwise-elongated structures just downstream of the ramp leading edge that persist well downstream of the reattachment. A time sequence of conditional average pressure fluctuation maps is constructed surrounding isolated pressure excursions in the intermittent region. This sequence, along with two-point cross correlation analysis, provides critical information about the flow processes that drive the separation bubble pulsations in the SBLI units with large separation scales. Overall, the imbalance in the mass within the separation bubble appears to be the critical mechanism that drives the separation bubble pulsations. Furthermore, the pressure perturbations originating at azimuthally offset locations are also observed to influence the separation bubble dynamics.

Analysis of Factors Affecting Strand Tension in Cable-Twisting Equipment and Method for Equilibrated Control

To address the issue of tension fluctuations and deviations among the strands during cable-twisting production, it is necessary to establish a relationship model between the centrifugal force, frictional force, and tension experienced by each strand in a single span range under the state of traveling and rotating. Considering the differences of strand alignment at the distribution reel, the effects of centrifugal force and friction on strand tension under different twisting-deflection paths and cylinder-traveling paths should be analyzed. In our study, different stress states of each strand were applied to simulate and verify the tension fluctuations and deviations of every strand under various traveling and deflection paths. The experimental results show that the increasing travel path of the strand cylinder will cause an increase in the average strand tension. Different deflection paths in the distribution reel will affect the range of the strand tension fluctuation. A sliding mode controller based on a discrete system was designed in MATLAB to control the tension fluctuation and deviation among the strands. The results indicated that this control method can effectively reduce the tension deviation between strands, and the average tension fluctuation range of each strand was reduced by 79.5%.

Control Parameters Optimization of Accumulator in Hydraulic Power Take-Off System for Eccentric Rotating Wave Energy Converter

To improve the efficiency and stability of an eccentric rotating wave energy converter (ERWEC), the adaptive hydraulic power-take-off (PTO) system with an accumulator is designed and developed. Experiments are performed to analyze the effects of trigger pressure, delay time, and open state duration on average output power and power fluctuation index. The results show that the effects of those three control parameters of accumulator on output power are strongly coupled. The experimental examples are designed based on the optimal Latin hypercube sampling (OLHS) method, and the nonparameterized agent models of control parameters to output power indices are established based on the Gaussian process regression (GPR) method. With the help of sensitivity analysis, it is found that the coupled effect of delay time and open state duration on the power fluctuation index is greater than that on the average output power. Furthermore, the optimal combination of control parameters is obtained by non-dominated sorting genetic algorithm-III (NSGA-III), which improves the amount and stability of output power from a hydraulic PTO system. This paper is of important significance for parameter setting of hydraulic PTO systems with an accumulator for wave energy converter, and provides the basis for the real-time adjustment of control parameters under complex sea conditions.

Locality properties of standard homogenization commutator

We study stochastic homogenization for linear elliptic equations in divergence form and focus on the recently developed theory of fluctuations. It has been observed that the fluctuations of averages of the solution are captured by the so-called standard homogenization commutator Ξ ε o . Our aim is to study how Ξ ε o (and its higher-order analogs) decorrelates on large scales when averaged on balls which are far enough. Taking advantage of its approximate locality, we give a quantitative characterization of this decorrelation in terms of both the macroscopic scale and the distance between the balls showing that Ξ ε o inherits the correlation properties of the environment.

Research on Transformer Fault Based on Grey System Theory

A transformer is a kind of power distribution equipment, which plays a vital role in the power system. The concentration of dissolved gas in the oil can predict the fault. Because the prediction accuracy of the classical GM (1, 1) model is not high, a new optimization formula is given according to the reconstruction of its original value and background value. Through the experimental data, it is proved that compared with the original GM (1, 1) model, the average relative error and error fluctuation of the optimized GM (1, 1) model is significantly reduced, and the accuracy is greatly improved.

Compact and highly stable electro-optic Q-switched laser at 1064 nm based on a composite YAG/Nd:YAG crystal

We report a compact and highly stable 1064-nm electro-optic Q-switched laser operating at the repetition rate of 1 kHz. A composite Nd:YAG crystal was used as the gain media and the cavity length was 105 mm. Under the average pump power of 11 W, the output power achieved 2.404 W with the pulse width of 4.558 ns, corresponding to the maximum peak power of 0.527 MW and the optical-to-optical conversion efficiency of 21.85%. The slope efficiency reached 42.69%. The beam quality in the horizontal (Mx2) and vertical (My2) directions were 1.81 and 1.58, respectively. The pulse timing jitter was less than 1 ns, and the average power fluctuation measured within 30 min was 0.83% (RMS). It is believed that such a compact and highly stable pulsed laser with high repetition rate, high peak power, and good beam quality has great potential in the fields of lidar, etc.

A dataset of the HP filter model-based research on price volatility of solanaceous vegetables in Beijing Xinfadi Market from 2012 to 2018

Solanaceous vegetables are popular dishes for residents, and they are also one type of the important cultivated vegetables in China. The price of solanaceous vegetables is non-steady with large fluctuations. Therefore, it is important to master the historical price trends and fluctuation laws, which can provide scientific guidance and support for ensuring the stability of vegetable supply prices and guiding the orderly operation of the market. Through data collection, stability test and HP filtering method decomposition, we formed a dataset of the HP filter model-based research on price volatility of solanaceous vegetables at Beijing Xinfadi Agricultural and Sideline Products Wholesale Market from 2012 to 2018. The varieties cover five kinds of solanaceous vegetables (eggplant, tomato, green pepper, bean and cucumber), including market, date, weekly/monthly average price, weekly/monthly average volatility, weekly/monthly maximum price, weekly/monthly minimum price, weekly/monthly average HP filter trend value, weekly/monthly average HP filter fluctuation value. The dataset can reflect the weekly and monthly changes of the trading prices of solanaceous vegetables in Beijing Xinfadi Market, and provide scientific data foundation for the research on as well as monitoring and early warning of the price fluctuation of solanaceous vegetables in Beijing.

Statistical properties of fractal type dislocation cell structures

The dislocation microstructure developing during plastic deformation strongly influences the stress-strain properties of crystalline materials. Resent theoretical investigations based on the 2D continuum theory of straight parallel edge dislocations were able to predict a periodic dislocation microstructure. The results obtained, however, can only be considered as a very first step toward the understanding of the origin of dislocation patterning. One of the most challenging problems is the modeling of the formation of the fractal like dislocation microstructure. So, it is crucial to determine the statistical properties of such a structure developing at ideal multiple slip orientation. In the paper, by x-ray line profile analysis and the method of high resolution electron backscatter diffraction (HR-EBSD) a complex experimental characterization of dislocation microstructure developing in uniaxially compressed Cu single crystals is presented. With these methods, the maps of the internal stress, the Nye tensor, and the geometrically necessary dislocation (GND) density were determined at different load levels. It is found from the fractal analysis of the GND maps that the fractal dimension of the cell structure is decreasing with increasing average spatial dislocation density fluctuation. Moreover, it is shown that the evolution of different types of dislocations can be successfully monitored with the HR-EBSD-based technique.

Analysis of the Energy Loss and Performance Characteristics in a Centrifugal Pump Based on Sinusoidal Tubercle Volute Tongue

The energy loss inside a centrifugal pump has a significant effect on its performance characteristics. Based on the structural characteristics of the humpback pectoral fin, a new tongue was designed to improve the performance of the centrifugal pump. The influence of three sinusoidal tubercle volute tongues (STVT) and one original volute tongue (OVT) on energy dissipation using the enstrophy analysis method was investigated. To accomplish this, the pressure fluctuations and performances of four centrifugal pumps were analyzed. The results indicate that enstrophy is primarily distributed at the impeller outlet and near the tongue. The total enstrophy of the profiles of STVT was smaller than that of the profiles of OVT. This difference was more obvious near the tongue. The reductions in the total enstrophy of the pumps were 8% (STVT-1), 8.2% (STVT-2), and 9% (STVT-3). The pressure fluctuations of the STVT profiles also decreased to different degrees. The average pressure fluctuations at the monitoring points decreased by 20.6% (STVT-1), 21.7% (STVT-2), and 23.3% (STVT-3). The performances of the bionic retrofit pumps increased by 1.5% (STVT-1), 2% (STVT-2), and 2.45% (STVT-3) under the design flow rate. This study guides the structural optimization of pumps.