Power Characteristics Research Articles

Experimental evaluation on the power characteristic of direct-photovoltaic charging for thermal storage equipment

Thermal storage is an essential equipment for storing excessive heat, especially for water heating systems. The present work proposes a preliminary study to maximize the operation of thermal storage using photovoltaics as the primary source for charging the heat storage material. The assessment indicates the concept is feasible, where the output power from photovoltaics can be directly converted to heat using a heating element. The power ratio is considerably high (up to 38.6%), resulting in the maximum temperature of the heat absorber material (water) increasing to 43.2 °C. The final assessment using suitable phase transition material shows that steady phase behavior is essential to maximizing the temperature profile of the material. It is achieved using stabilized-hexadecanoic acid, which shows a transient phase transition at a temperature of 54.2 °C, reducing the possibility of heat loss with an average temperature rate of 0.54 °C/min in the discharge stage. This finding proves the proposed concept is applicable, while further improvement can be done to adjust the suitable power output from photovoltaic and storage tank arrangement for the actual system. Despite that, the result is expected to accelerate the utilization of photovoltaics as reliable solar renewable technology.

High-performance electrocatalyst for PEMFC cathode: Combination of ultra-small platinum nanoparticles and N-doped carbon support

To accelerate the implementation of zero-emission power installations based on proton-exchange membrane fuel cells, it is necessary to maximize the power characteristics of these devices. For this purpose, we have obtained and tested a new N-doped carbon support and a synthesized Pt/C catalyst based on it with a platinum loading of about 37.3 %. A comparison of the degradation resistance of the initial support and the N-doped one has shown greater stability of the latter. At the same time, Raman spectroscopy has confirmed the presence of the C–N bond, which indicates the successful doping of carbon with nitrogen. The resulting Pt/C catalyst based on an N-doped support is characterized by a substantially narrow size dispersion and an ultra-small nanoparticle size of about 2.6 nm. The high-angle annular dark-field scanning transmission electron microscopy images of the synthesized catalyst have confirmed the presence of individual platinum atoms/clusters uniformly distributed over the surface of the support, and their presence is due to nitrogen embedded into the carbon structure. This material is characterized by a 50 m2 gPt-1 larger electrochemically active surface area and a 227 A gPt-1 greater mass activity compared to the commercial JM40 analog (40 % platinum loading). Meanwhile, the electrochemical parameters remaining after the accelerated stress testing are almost 2 times higher than those of JM40. And the power characteristics in the membrane electrode assembly for the catalyst synthesized by the facile one-pot synthesis method are 13 % (575 mW cm-2) higher than those of the commercial analog (500 mW cm-2). The Pt/C catalyst obtained during the research is deemed promising for commercial use in proton-exchange membrane fuel cells.

Increasing efficiency of induction motor

In this work was analyzed induction motor, its advantages and disadvantages, and methods of modify it in way increasing its reliability and power coefficient. Power coefficient is the parameter which shows how much energy is used for yield and which just converting into heat. For analysis used calculation of induction motor which commonly used for developing serial asynchronous motor. Based on that calculation has modulated physical process which conducting in active parts of motor. For calculation of induction in armature and magnetic flux passes in it was used numerical mathematical model. This type of electric motors is common used so increase its efficiency and power characteristics is the one of way to reduce energy consuming. The developed way of modernization of induction motors, and analyzed reliability of it.

МЕХАНИЗМЫ РАЗРУШЕНИЯ РАСТИТЕЛЬНОГО СЫРЬЯ В ВАЛКОВОЙ ДРОБИЛКЕ С НАБОРНЫМИ ПЛАСТИНАМИ В ФОРМЕ РК-ПРОФИЛЯ

The purpose of the study is to substantiate the application of a new kinematic scheme for crushing plant materials (cereals and fruit plants) to implement the design of a roller crusher with composite plates in the form of an RT-profile. To achieve the objective of research, a number of tasks were set to study the main object – the kinematic scheme of crushing. The paper examines in detail the specified crushing scheme as a static and kinematic scheme of interaction between the elements of the crusher and the crushed raw material; the possibility of combining a number of different destruction mechanisms in this scheme is noted, namely: compression, tension, abrasion, impact action; the effect of constant change in the direction and magnitude of the forces acting on the crushed material is noted; geometric and power characteristics of the new design of the roller crusher are investigated. The analysis of the new kinematic scheme of grinding allows us to draw the following conclusion: alternating loads appear in the system, ac-ting on the raw material being ground as a result of various destructive forces, which allow us to achieve an additional increase in the intensity of material (raw material) grinding and, as a consequence, an increase in the efficiency of the grinding process as a whole. The substantiation of the kinematic and force effects affecting the raw material being ground in the crushing zone is also given, taking into account the elastic-plastic properties of various types of agricultural products. The result of the analysis of the stress-strain state of the rolls in the grinding zone is given, taking into account the most unfavorable conditions of the impact of substances with different mechanical properties on the working parts of the crusher. The necessity of implementing a new grinding scheme is substantiated and design options are proposed in the form of a crusher with set plates in the form of an RT-profile.

Output Characteristics of External-Cavity Mode-Hop-Free Tunable Laser Source in C+L Band

Tunable laser sources with a wide wavelength tuning range, mode-hop-free (MHF) operation, and high spectral purity are essential for applications such as high-resolution spectroscopy, coherent detection, and intelligent fiber sensing. In this paper, we present a wide-range tunable laser source that operates without mode hopping, based on external cavity feedback using a semiconductor gain chip as the laser gain medium. The wavelength, power, and spectral characteristics of the laser are experimentally measured. A wide MHF continuous wavelength tuning range from 1480 nm to 1620 nm with a side-mode suppression ratio of more than 61.65 dB is achieved. An output optical power of more than 11.14 dBm with good power stability can also be realized in the full C+L band. This proposed external-cavity tunable laser source features a narrow intrinsic linewidth and MHF tunable radiation with a maximum sweep speed of 200 nm/s, enabling practical applications such as high-resolution vector spectrum analysis.

The balance issue of the proportion between new energy and traditional thermal power: An important issue under today's low-carbon goal in developing countries

The stability of the new power system depends on the balance between controllable flexible resources and uncontrollable uncertain resources. For many developing countries and regions lacking advanced flexible resources, thermal power is the main force in solving the problem of new energy consumption. Finding the balance between new energy and traditional thermal power is the key for today's low-carbon goal. To solve this problem, this paper calculates the power range and climbing rate range of thermal power based on physical principles and actual data, and characterizes the characteristics of wind power, photovoltaic power, load and net load based on the five proposed volatility indicators. Then, a logically clear method for determining the required number of thermal power units based on the volatility indicators of new energy from the mechanism and principle perspective is proposed. Finally, under the premise of meeting the power balance and flexibility balance of the power system, the reasonable ratios between the installed capacity of new energy and the number of thermal power units are calculated in four seasons. The results indicate that the judgment system can provide guidance for the energy structure of developing regions.

Living under the same roof: The impact of housemates on sustainable shared housing tenancy in Shanghai’s condominiums

ABSTRACT Young adults with difficulties finding affordable housing have increasingly been choosing to rent in the private sector and share housing with unknown individuals. Shared living arrangements allow these young single tenants to reduce their housing expenses while enjoying a shared lifestyle that encourages social interaction with a diverse group of housemates. However, physical proximity does not guarantee social proximity, as people may encounter undesirable housemates. Using a rich dataset of shared housing tenancies in Shanghai, China, this study examines how the characteristics of housemates influences tenants’ decision to terminate their shared housing tenancy before its expiration. Our results show that the similarity of housemates in age, gender, occupation, and birthplace reduces the probability of an early termination of the shared tenancy. The impact of housemate similarity measured in the four dimensions is further augmented by tenants’ bargaining power and individual characteristics. Since early tenancy termination increases the vacancy rate in shared housing, sharing with undesirable housemates incurs significant social costs. This study sheds light on how residents living in proximity can share urban space effectively to facilitate sustained shared housing tenancies and suggests the need for policy solutions that are tailored to the needs of shared housing renters.

Testing the homogeneity of odds ratio across strata for combined bilateral and unilateral data.

Bilateral and unilateral combined data are commonly involved in clinical trials or observational studies designed to test the treatment effectiveness on paired organs or bodily parts within individual subjects. It is essential to examine if the treatment effect is consistent across different subgroups such as age, gender, or disease severity for understanding how the treatment works for various patient populations. In this paper, we propose three large-sample homogeneity tests of odds ratio in the stratified randomization setting using correlated combined data. Our simulation results show that the score test exhibits robust empirical type I error control and demonstrates strong power characteristics compared to other methods proposed. We apply the proposed tests to real-world datasets of acute otitis media and myopia to illustrate their practical application and utility.

Flexible Aqueous Cr-Ion Hybrid Supercapacitors with Remarkable Electrochemical Properties in all Climates.

The integration of hostless battery-like metal anodes for hybrid supercapacitors is a realistic design method for energy storage devices with promising future applications. With significant Cr element deposits on Earth, exceptionally high theoretical capacity (1546 mAh g-1), and accessible redox potential (-0.74 V vs. reversible hydrogen electrode) of Cr metals, the design of Cr anodes has rightly come into our focus. This work presents a breakthrough design of a flexible Cr-ion hybrid supercapacitor (CHSC) based on a porous graphitized carbon fabric (PGCF) substrate prepared by K2FeO4 activation. In the CHSC device, PGCF acts as both a current collector and cathode material due to its high specific surface area and superior conductivity. The use of a highly concentrated LiCl-CrCl3 electrolyte with high Cr plating/stripping efficiency and excellent antifreeze properties enables the entire PGCF-based CHSC to achieve well-balanced performance in terms of energy density (up to 1.47 mWh cm-2), power characteristics (reaching 9.95 mW cm-2) and durability (95.4 % capacity retention after 30,000 cycles), while realizing it to work well under harsh conditions of -40 °C. This work introduces a new concept for low-temperature energy storage technology and confirms the potential application of Cr anodes in hybrid supercapacitors.

Flexible Aqueous Cr‐Ion Hybrid Supercapacitors with Remarkable Electrochemical Properties in all Climates

AbstractThe integration of hostless battery‐like metal anodes for hybrid supercapacitors is a realistic design method for energy storage devices with promising future applications. With significant Cr element deposits on Earth, exceptionally high theoretical capacity (1546 mAh g−1), and accessible redox potential (−0.74 V vs. reversible hydrogen electrode) of Cr metals, the design of Cr anodes has rightly come into our focus. This work presents a breakthrough design of a flexible Cr‐ion hybrid supercapacitor (CHSC) based on a porous graphitized carbon fabric (PGCF) substrate prepared by K2FeO4 activation. In the CHSC device, PGCF acts as both a current collector and cathode material due to its high specific surface area and superior conductivity. The use of a highly concentrated LiCl−CrCl3 electrolyte with high Cr plating/stripping efficiency and excellent antifreeze properties enables the entire PGCF‐based CHSC to achieve well‐balanced performance in terms of energy density (up to 1.47 mWh cm−2), power characteristics (reaching 9.95 mW cm−2) and durability (95.4 % capacity retention after 30,000 cycles), while realizing it to work well under harsh conditions of −40 °C. This work introduces a new concept for low‐temperature energy storage technology and confirms the potential application of Cr anodes in hybrid supercapacitors.

The effects of thermalization on the performance of passively Q-switched IC-OPOs

In this paper, we report a new model for passively Q-switched intracavity optical parametric oscillators (IC-OPOs), using Cr:YAG as a Q-switch crystal. The model considers the effects of thermalization in the Nd:YAG laser crystal, excited state absorption in the Cr:YAG saturable absorber, nonlinear loss due to pump depletion in the nonlinear crystal, the thermal lens effect and the mode overlap of the fields within the nonlinear crystal. The calculated pulse width for the 1,064 nm pump light was 6.2 ns compared to the experimental result of 6 ns, while the signal wave was calculated to have a pulse width of 1.75 ns compared to the experimental result of 2 ns. The model is shown to accurately calculate both the temporal and output power characteristics of the IC-OPO, which has not been previously reported to the best of our knowledge.

Experimental and numerical characterization of screw elements used in twin-screw extrusion

Hot melt extrusion by a co-rotating twin screw extruder is an important process in the pharmaceutical industry. Especially for quality by design aspects, a comprehensive process understanding is indispensable. The performance of conveying elements was determined as critical process parameter, and therefore an experimental and numerical framework was developed to analyze and compare variations. A test rig capable of measuring volume flow, pressure and torque with high accuracy and precision was designed and built. The 3D simulation was performed using computational fluid dynamics (CFD). A stationary model with impulse transmission and an apparent motion of the screws was applied. The experimental data were fitted to the model of Pawlowski, and parameters for the pressure (A1, A2) and power characteristics (B1, B2) were determined. Good agreement between experimental data and the model was observed. The simulation was significantly faster compared to common methods, and the results were consistent with the literature. Systematic investigations of a native and worn screw were performed with CFD resulting in a transport capacity increase and a pressure build up decrease for all tested screw elements. An experimental and simulation setup was generated to assess the performance of co-rotating twin screw elements. The experiments provided high-quality data, and the simulations exhibited high flexibility with low computational effort.

A modified two-stage isolated bidirectional buck-DAB converter with a full-load ZVS range

A modified two-stage buck-DAB (MBDAB) converter is proposed to improve the performance of the traditional two-stage buck-DAB (TSBDAB) converter. In the MBDAB converter, the DAB can work with fixed voltage gain and voltage-matched condition under a wide input voltage range. The voltage gain of the converter is adjusted through the added front-end stage, which is similar to a buck converter. Compared with the TSBDAB converter, only part of the transmitted power flows through the front-end stage, so the loss of the buck stage and the burden of zero-voltage switching (ZVS) can be reduced. Detailed analysis of the working principle, partial power characteristics, and the full-load ZVS range design are presented. To verify the effectiveness of the proposed MBDAB converter, experimental results are obtained from a prototype with a rated power of 1 kW.

Developmental trajectories of EEG aperiodic and periodic components in children 2–44 months of age

The development of neural circuits has long-lasting effects on brain function, yet our understanding of early circuit development in humans remains limited. Here, periodic EEG power features and aperiodic components were examined from longitudinal EEGs collected from 592 healthy 2–44 month-old infants, revealing age-dependent nonlinear changes suggestive of distinct milestones in early brain maturation. Developmental changes in periodic peaks include (1) the presence and then absence of a 9-10 Hz alpha peak between 2-6 months, (2) nonlinear changes in high beta peaks (20-30 Hz) between 4-18 months, and (3) the emergence of a low beta peak (12-20 Hz) in some infants after six months of age. We hypothesized that the emergence of the low beta peak may reflect maturation of thalamocortical network development. Infant anesthesia studies observe that GABA-modulating anesthetics do not induce thalamocortical mediated frontal alpha coherence until 10-12 months of age. Using a small cohort of infants (n = 23) with EEG before and during GABA-modulating anesthesia, we provide preliminary evidence that infants with a low beta peak have higher anesthesia-induced alpha coherence compared to those without a low beta peak.

The institutional nature of political power according to new directions in institutional theory

Institutional theory is one of the oldest theories used to analyze political issues and phenomena. In the classical period, this theory emphasized the constitutional and legal aspects, while paying more attention to the official institutions of the state, especially the powers (legislative, executive and judicial). In the 1950s, due to the rise and dominance of the behavioral school, this theory was ignored by researchers in the field. However, the beginning of a new phase of institutional theory in the 1970s; the emergence of all three directions (historical, social, and rational choice) was also a strong factor in attracting researchers to use institutional theory in their studies. At the same time, political power has always been of interest and debate in political analysis, although the concept has often been portrayed in the guise of an individual and a ruling group. But in fact, one of the characteristics of political power is institutionalization. For this purpose, this paper describes political power and new directions of institutional theory. On the other hand, it analyzes the nature of institutionalization and how the process of institutionalizing political power is carried out within the framework of new directions of institutional theory.

Characteristics of Beidou-2 flex power and its impact on precise point positioning with ambiguity resolution

Characteristics of Beidou-2 flex power and its impact on precise point positioning with ambiguity resolution

Ultra-short-term wind power forecasting based on a dual-channel deep learning model with improved coot optimization algorithm

The large-scale integration of wind power to the grid poses some potential challenges to the power system. Accurate wind power forecasts reduce the impact of the nonlinearities and volatility of wind power generation. A two-channel deep learning model based on an improved coot optimization algorithm (ICOA) is proposed. First, the use of long short-term memory (LSTM) builds a channel for the extraction of chronological characteristics of historical power. Second, a temporal convolutional network (TCN) is adopted as a hybrid feature-extraction channel for multi-dimensional meteorological data, and by incorporating the self-attention mechanism (SA), the ability of TCN to extract internal information from meteorological features is enhanced. Finally, the ICOA that introduces nonlinear decision factor, adaptive dynamic boundary, and Cauchy mutation is used to optimize the model hyperparameters. The simulation analysis is carried out on the winter and summer measured data of a wind farm in Xinjiang. The results show that compared with the traditional LSTM model, the root mean square error and the mean absolute error of the proposed method are reduced by 10.35 % and 16.27 % on average, respectively, and the prediction accuracy is higher than that of other comparative models, which verifies the superiority of our proposed model.

Lithium Battery SoC Estimation Based on Improved Iterated Extended Kalman Filter

With the application of lithium batteries more and more widely, in order to accurately estimate the state of charge (SoC) of the battery, this paper uses the iterated extended Kalman filter (IEKF) algorithm to estimate the SoC. The Levenberg–Marquardt (LM) method is used to optimize the error covariance matrix of IKEF. Based on the hybrid pulse power characteristics experiment, a second-order Thevenin model with variable parameters is established on the MATLAB platform. The experimental results show that the proposed model is effective under the constant current discharge condition, the Federal Urban Driving Schedule (FUDS) condition, and the Beijing dynamic stress test (BJDST) condition. The results show that the simulation error of the improved LM-IEKF algorithm is less than 2% under different working conditions, which is lower than that of the IKEF algorithm. The improved algorithm has a fast convergence speed to the true value, and it has a good estimation accuracy in the case of large changes in external input current. Additionally, the fluctuation of error is relatively stable, which proves the reliability of the algorithm.

Вимоги до вибору значень параметрів радарів із синтезованою апертурою на базі малих космічних апаратів дистанційного зондування Землі

Present-day small satellites for Earth remote sensing have found wide practical application in solving different problems in the socio-economic and defense areas. The use of small satellites is justified as a basis for the formation both of large constellations and constellations of several spacecraft or single spacecraft with the aim to reduce the cost of Earth remote sensing information. The miniaturization of electron components and the latest technological advances have made radar systems compatible with small satellites. The goal of this paper is to present, based on small satellites, expressions for calculating the key parameters of radar systems and their analysis and to calculate possible values of the parameters considered. Possibilities in principle of using synthetic aperture radars (SARs) are considered. The paper presents an overview of Internet sources that give broad information on the recent trends, technologies, and use SAR-equipped satellites. Particular attention is paid to the development of mini- and microspacecraft with X-band SARs operating, in particular, in the stripmap and spotlight modes. The key parameters that have an effect on the SAR possibility of producing high-quality images are presented. By the example of the ICEYE constellation of small satellites, important technical characteristics and parameters of modern radar systems equipped with an active phased array antenna are presented. A model of SAR imaging in the stripmap mode is considered. In the approximation of a rectangular antenna aperture, expressions are given to estimate the slant and the horizontal range resolution and the azimuthal resolution. The available range of the small-satellite SAR pulse repetition frequency is estimated. Relationships between the maximum swath width and the minimum SAR pulse repetition frequency are presented. Expressions are given to estimate the antenna dimensions, the SAR sensitivity, and the signal-to-noise ratio. The presented expressions allow one to analyze the effect of the main technical characteristics and parameters of minisatellite SARs on the design and power characteristics of small satellites and the orbit parameters. The obtained results make it possible to develop recommendations on the design of imaging equipment for home low-orbit satellites and their constellations.

Modeling end-to-end delays in TSCH wireless sensor networks using queuing theory and combinatorics

Wireless communication offers significant advantages in terms of flexibility, coverage and maintenance compared to wired solutions and is being actively deployed in the industry. IEEE 802.15.4 standardizes the Physical and the Medium Access Control (MAC) layer for Low Power and Lossy Networks (LLNs) and features Timeslotted Channel Hopping (TSCH) for reliable, low-latency communication with scheduling capabilities. Multiple scheduling schemes were proposed to address Quality of Service (QoS) in challenging scenarios. However, most of them are evaluated through simulations and experiments, which are often time-consuming and may be difficult to reproduce. Analytical modeling of TSCH performance is lacking, as only one-hop communication with simplified traffic patterns is considered in state-of-the-art. This work proposes a new framework based on queuing theory and combinatorics to evaluate end-to-end delays in multihop TSCH networks of arbitrary topology, traffic and link conditions. The framework is validated in simulations using OMNeT++ and shows below 6% root-mean-square error (RMSE), providing quick and reliable latency estimation tool to support decision-making and enable formalized comparison of existing scheduling solutions.