Fundamental Cycle Research Articles

Intelligent construction and optimization based on the heatsep method of a supercritical CO2 brayton cycle driven by a solar power tower system

The current progress in tower-based solar thermal concentrators and receivers enables achieving temperatures within the required range of 500–700 °C for the S–CO2 Brayton cycle. Within this temperature range, the efficiency of the S–CO2 Brayton cycle exceeds that of conventional steam power cycles. This study applies the S–CO2 Brayton cycle to concentrated power generation systems, emphasizing structural and parameter optimization. By utilizing the operational parameters of tower-based solar thermal power generation as boundary conditions and maximizing specific power as the optimization objective, various configurations derived from a maximum of two fundamental cycles are systematically enumerated. Subsequently, an intelligent algorithm optimizes the power cycle flow and parameters for each structure, further optimizing the heat exchanger network. The findings reveal that the optimized configuration shares a common heating and cooling process. This optimization yields a specific power increase of 14.62 kJ/kg compared to the reference case, indicating a 13.26 % enhancement. Additionally, the cycle efficiency improves to 47.45 %, marking a 28.52 % increase. The overall system efficiency for the solar power tower system reaches 32.03 %, with an exergy efficiency of 32.19 %.

Self-consistent field theory for loop-containing polymers: A general algorithm for path-determination

An algorithm was developed for self-consistent field theory (SCFT) simulations of loop-containing polymers (LCPs), where the total number of independent loops (fundamental cycles in the polymer structure) is characterized by the “cycle rank.” Although various multi-ring and cage-like polymers have been reported, there is no explicit SCFT scheme for LCPs with multiple loops. An LCP was cut to open its fundamental cycles to form a pseudo-tree-like polymer. Conventional SCFT calculations for pseudo-tree-like polymers require extra spatial constraints on the pseudo-free endpoints generated by opening the fundamental cycle, which increases the computational cost. A reduction in the computational cost was observed, and the algorithm was applied to microphase-separated structures of small LCPs.

Environmental response characteristics of the carbon and water fluxes above complex urban surfaces of a subtropical megacity in China

Carbon-water cycle represents a fundamental material cycle within urban ecosystems, characterized by interdependence and inseparability. Based on flux measurements in Shenzhen, we analyzed periodical dynamics of carbon and water fluxes and simulated their variations using four machine learning models. The results indicated that hourly carbon fluxes exhibited a typical U-shaped trend, while water fluxes showed an inverse trend. Seasonal carbon sink capacity was strongest in spring and winter and lowest in summer. Human activities influenced carbon and water fluxes, evidenced by shorter duration of carbon sequestration at suburban station (10 h) compared to exurban station (10.5 h). Seasonal mean carbon fluxes ranged from −5.285 to −2.514 μmol m−2∙s−1 at exurban station and from −2.197 to −1.352 μmol m−2∙s−1 at suburban station, while seasonal mean water fluxes of the above stations ranged from −3.454 to −1.136 μmol m−2∙s−1 and from −1.436 to −0.322 μmol m−2∙s−1, respectively. Exurban station demonstrated a greater carbon sequestration capacity and a higher transpiration intensity than suburban station. The environmental factors influencing carbon and water fluxes of the two stations were generally similar and with some differences. At the exurban station, there was a weak negative correlation between photo-synthetic active radiation and carbon flux, whereas at the suburban station, it was weakly positively correlated. Carbon fluxes at both stations displayed a positive correlation with temperature and relative humidity, while exhibiting a significant negative correlation with saturation vapor pressure deficit. The comparative studies are important for revealing the regularities, influencing factors, and mechanisms of carbon and water cycling in subtropical urban ecosystems.

Tether-scanning the kinesin motor domain reveals a core mechanical action

Natural kinesin motors are tethered to their cargoes via short C-terminal or N-terminal linkers, whose docking against the core motor domain generates directional force. It remains unclear whether linker docking is the only process contributing directional force or whether linker docking is coupled to and amplifies an underlying, more fundamental force-generating mechanical cycle of the kinesin motor domain. Here, we show that kinesin motor domains tethered via double-stranded DNAs (dsDNAs) attached to surface loops drive robust microtubule (MT) gliding. Tethering using dsDNA attached to surface loops disconnects the C-terminal neck-linker and the N-terminal cover strand so that their dock-undock cycle cannot exert force. The most effective attachment positions for the dsDNA tether are loop 2 or loop 10, which lie closest to the MT plus and minus ends, respectively. In three cases, we observed minus-end-directed motility. Our findings demonstrate an underlying, potentially ancient, force-generating core mechanical action of the kinesin motor domain, which drives, and is amplified by, linker docking.

REV7-p53 interaction inhibits ATM-mediated DNA damage signaling

ABSTRACT REV7 is an abundant, multifunctional protein that is a known factor in cell cycle regulation and in several key DNA repair pathways including Trans-Lesion Synthesis (TLS), the Fanconi Anemia (FA) pathway, and DNA Double-Strand Break (DSB) repair pathway choice. Thus far, no direct role has been studied for REV7 in the DNA damage response (DDR) signaling pathway. Here we describe a novel function for REV7 in DSB-induced p53 signaling. We show that REV7 binds directly to p53 to block ATM-dependent p53 Ser15 phosphorylation. We also report that REV7 is involved in the destabilization of p53. These findings affirm REV7’s participation in fundamental cell cycle and DNA repair pathways. Furthermore, they highlight REV7 as a critical factor for the integration of multiple processes that determine viability and genome stability.

Local outlier factor based condition monitoring for sub-module capacitors in modular multilevel converters

Modular multilevel converters (MMC) as a key technology for future power grids is rapidly developing. The failure rate of sub-module (SM) capacitors is only lower than that of power devices in MMC, so accurate evaluation of the reliability of capacitors is crucial for the safe operation of MMC. Both the increase of equivalent series resistance (ESR) and decrease of equivalent series capacitance (ESC) are features for capacitor deteriorating. ESC or ESR of the capacitor reaching to limited values indicates that the end of its lifespan and it must be replaced. Most of contemporary researches only focus on ESC or ESR. This article considering the characteristics of both ESC and ESR, proposes a method for monitoring the status of SM capacitors based on machine learning algorithm: local outlier factor (LOF). By utilizing the existing SM switching function and capacitor voltage signals within a fundamental frequency cycle in the control system of MMC, the proposed strategy can not only monitor the faulty capacitors, but also can sort the degrees of abnormal states of capacitors, and the strategy is applicable to MMC with single and multiple types of SM topologies. The proposed method is verified by the hybrid MMC model on Matlab/Simulink.

Bidirectional Power Control Strategy for On-Board Charger Based on Single-Stage Three-Phase Converter

To solve the problems of large switching losses and the need for large-capacity electrolytic capacitances in three-phase DC/AC on-board chargers for vehicle-to-grid (V2G) applications, this paper proposes a single-stage bidirectional high-frequency isolated converter that eliminates the need for large-capacity capacitances. Combined with the proposed modulation scheme, it can theoretically reduce the switching loss by about two-thirds with the three-phase converter compared with the conventional modulation scheme, improving the converter’s operating efficiency and power density. Firstly, based on the characteristics of the proposed topology, a hybrid modulation scheme is proposed, which combines a phase-shift modulation scheme based on double modulation waves and a sawtooth carrier with a 1/3 modulation scheme, and the theoretical feasibility of the hybrid modulation scheme is verified using a mathematical modeling equation. Secondly, this paper provides a detailed analysis of the four operating modes of the two full-bridge circuits and the commutation process of the three-phase converter within 1/6 of the fundamental frequency cycle (P1 modulation interval). Then, the control strategy is given for the constant-current and constant-voltage charging and constant-current discharging for electric vehicle batteries. Finally, simulation results verify the correctness of the proposed topology and modulation scheme in vehicle–grid interaction.

Comparison of conducted emissions due to electric vehicle charging processes under isolated and on-line conditions in the 9–500 kHz frequency range

This paper aims at comparing the conducted emissions generated by Electric Vehicle Charging Processes (EVCPs) under isolated and on-line conditions in the frequency and time domains, covering the 9–500 kHz frequency range. The isolated conditions correspond to the use of a Line Impedance Stabilization Network (LISN), whereas measurements in the Low Voltage (LV) grid where the EV is connected are referred to as on-line conditions. Regarding the frequency analysis, the results lead to conclude that different amplitude and spectral features of the Non-Intentional Emissions (NIEs) are measured depending on the measurement conditions, registering higher-amplitude NIEs when the measurements are conducted in the LV grid. Moreover, the paper also shows that the spectral characteristics of the NIEs correspond to tonal and narrowband emissions at specific frequencies in the 9–150 kHz frequency range, while background noise with low-amplitude emissions (in the case of isolated conditions) and colored noise (in the case of on-line conditions) are reported in the 150–500 kHz band. In the time domain, a periodic time-dependent behavior within the fundamental cycle of the mains (20 ms) is reported in all the analyzed cases, except for the tonal emissions with oscillating central frequency generated by a specific EV model. The time variability between both measurement configurations only differs by more than 3 dB for three out of the twelve analyzed EVCPs, where a higher variability is observed if the measurements are carried out using a LISN. As a conclusion, considering the differences in the frequency and time characteristics of the NIEs under isolated and on-line conditions, evaluating the emissions generated by EVCPs might lead to an underestimation of the NIEs in real LV grids.

Observations key to understanding solar cycles: a review

A paradigm shift is taking place in the conception of solar cycles. In the previous conception, the changing numbers of sunspots over intervals of 9–14 years have been regarded as the fundamental solar cycle although two average 11-year cycles were necessary to account for the complete magnetic cycle. In the revised picture, sunspots are a phase in the middle of two 22-year overlapping solar cycles that operate continuously with clock-like precision. More than 20 researchers have contributed to the initial research articles from 2014 through 2021 which are dramatically altering the perception of solar cycles. The two 22-year cycles overlap in time by 11 years. This overlap is coincidentally the same average duration as the sunspot phase in each 22-year cycle. This coincidence and the relative lack of knowledge of the large numbers of small active regions without sunspots is what led to the previous paradigm in which the 11-year sunspot phases were misinterpreted as a single fundamental solar cycle. The combination of the two 22-year solar cycles, with their large numbers of short-lived active regions and ephemeral active regions are now understood to be the fundamental cycle with the proposed name “The Hale Solar Cycle.” The two 22-year solar cycles each occupy separate but adjacent bands in latitude. The orientations of the majority of bipolar magnetic regions in the two adjacent bands differ from each other by ∼180°. Both bands continuously drift from higher to lower latitudes as has been known for sunspot cycles. However, the polarity reversal occurs at the start of each 22-year cycle and at higher latitudes than it does for the sunspot cycles. This paradigm shift in the concept of solar cycles has resulted in major reconsiderations of additional topics on solar cycles in this review. These are 1) the large role of ephemeral active regions in the origin of solar cycles, 2) the depth of the origin of active regions and sunspots, 3) the mechanisms of how areas of unipolar magnetic network migrate to the solar poles every 11 years, and 4) the nature of the polarity reversal in alternate 22-year cycles rather than 11-year cycles.

Millennial climate variability and organic matter accumulation under icehouse conditions

Millennial climate variability (MCV) is a prominent feature of the Pleistocene high-resolution climate records and is closely linked to orbital-scale climate variability and glacial-interglacial cycles. However, the origin and internal climate feedback of pre-Quaternary MCV remain poorly constrained. To better understand the nature and evolution of MCV under icehouse conditions, we quantitatively analyzed four sets of paleoclimatic proxies (including natural gamma ray emissions, uranium, and total organic carbon) from mid-latitude lakes (Lucaogou Formation for Early Permian icehouse and Lakes Ohrid and Van for Quaternary icehouse) using amplitude modulation and bi-coherence spectral analysis. Our results suggest that MCV (with periods of 4–8 kyr) is modulated by eccentricity, obliquity, and precession cycles and can be directly generated by the harmonization between fundamental orbital cycles (e.g., obliquity and precession cycles). In both the Early Permian and Quaternary icehouses, the changes in the amplitude of the MCV were more pronounced within an intermediate climate (e.g., glacial-interglacial transition). In addition, robust petrographic evidence and in-phase relationships between total organic carbon and natural gamma ray emissions in millennial-scale cycles suggest that MCV affects mid-latitude organic matter accumulation by modulating hydrological cycles, primary productivity, and redox conditions. Our study highlights a common origin of MCV in two Phanerozoic icehouses and the complex nonlinear response to external orbital forcing of the Earth’s climate system.

Efficient DC Voltage Balancing of Cascaded Photovoltaic System Based on Predictive Modulation Strategy

This paper presents a predictive modulation strategy for dc voltage balancing of cascaded H-bridge-based photovoltaic generation systems (CHB-PV). It is intended for improving the efficiency of CHB-PV by reducing the number of switching events. The strategy enables the charge/ voltage estimation and the design of a real-time discharge-order exchange, ensuring discrete dc voltage balancing. The conventional loss-reduced level-shifted-pulse-width-modulation (LS-PWM) is embedded and used to predict the discharge values and the target dc voltage value. The real-time discharge-order exchange is used to make the individual voltages converge to the target value at intervals of maximum 1/4 fundamental cycle. The voltage spread range introduced by the discrete voltage balancing is also considered and well suppressed by a simple adaptive method. Balancing of the dc voltages is finally achieved in a more discrete way, which makes reduced switching events compared with only using the loss-reduced LS-PWM. Experiment results based on a 2.1 kW/311 V setup are presented to demonstrate the effectiveness of the proposed technologies.

Reproductive Behavior and Development of the Global Insect Pest, Cotton Seed Bug Oxycarenus hyalinipennis.

Understanding the fundamental life cycle and reproductive behavior of a pest insect is essential for developing efficient control strategies; however, much of this knowledge remains elusive for a multitude of insects, including the cotton seed bug, Oxycarenus hyalinipennis. Here, we report the results of our comprehensive study on the cotton seed bug's life cycle, including mating behavior, adult lifespan, and egg-to-adulthood development. Our findings showed that adult males and females began mating as early as three days after emerging (75%), and the frequency of mating increased to 100% by the fifth day. Mated females commenced oviposition on cotton seeds as early as two days after mating, with a cumulative mean number of 151 fertile eggs oviposited during the first oviposition cycle. Furthermore, around 10% of eggs from both mated and unmated females remained unfertilized. The first instar nymphs began emerging approximately seven days following oviposition. To track their development, we monitored the newly hatched nymphs daily until they reached adulthood. There were five nymphal stages, which cumulatively took roughly 28 to 30 days. Notably, mating positively influenced the survivorship and lifespan of adult O. hyalinipennis. Mated males and females exhibited median lifespans of 28 and 25 days, respectively. In contrast, unmated males and females only lived for a median lifespan of 9.5 days, about one-third that of the mated O. hyalinipennis. Our study provides key insights into the O. hyalinipennis life history for new IPM strategies.

A Novel Frequency and Positive Sequence Detector for Utility Applications and Power Quality Analysis.

Based on multi-dimensional representation and vector calculus definitions, this paper proposes two novel and quite simple algorithms for utility applications and power quality analysis. The first one is a synchronizing procedure, based on a digital PLL (Phase Locked Loop). Its design and dynamic behavior are analyzed for single and three-phase systems. The second one is a positive sequence detector, which uses the proposed PLL to ensure that the positive sequence components can be calculated even under distorted waveform conditions or frequency variations. Since it is not based on Fortescue’s classical decomposition and no special input filtering are needed, its dynamic response may be as fast as one fundamental cycle. In order to validate the proposed models, simulations are shown and experimental results were obtained by means of a DSP-based system and a prototype of Power Quality Monitor. Furthermore, the PLL algorithm was implemented in a selective active filter to confirm the expectations in a closed-loop application.

Design and Implementation of Transformer-less Common-Ground Inverter With Reduced Components

Nowadays, common-ground-type (CGT) based transformer-less inverters (TIs) are gaining more popularity in photovoltaic (PV) applications owing to their low cost, weight of the systems, losses and zero ground leakage current. For PV applications, a separate boost converter is often used to boost the low PV array voltage, resulting in increased component count, cost and lower efficiency. To resolve this issue, switched-capacitor (SC) based CGT inverter with reduced component count is proposed in this paper. The proposed amalgamation of CGT and SC technique, results in inherent boosting and zero ground leakage current. In the proposed inverter, SCs are connected in series/parallel with the dc voltage source for several instances in a fundamental cycle preserving the self-voltage balancing ability. Therefore, the proposed topology is devoid of voltage sensors to balance the voltage across SCs. Further, A simplified logic gatebased pulse-width-modulation strategy is developed. In addition, the benefits of proposed inverter are highlighted and compared with the other recent SC inverter topologies with regard to boosted voltage, elimination of leakage current and reduced component count. A laboratory prototype is developed by using DS1202/1302 dSPACE controller and experimental results are presented for both steady state and dynamic conditions and verifying the feasibility of the proposed TI.

Using of the contour method to solving the problem of optimal traffic dis-tribution in the network

The purpose of this work is to create a method for solving the problem of optimal traffic distribution in a network using the contour data analysis method. In the first section of the work, the principle of converting any available network to a contour form is explained, and the case is considered both for networks without loss and for networks with losses. The second section shows in a general way the method of bringing the network in contour form to a system of non-linear inequalities, by solving which one can obtain a certain distribution of traffic in the system. In the final section, using the M/M/1/N queuing system as an example, the solution of the problem of optimal traffic distribution according to the loss minimization criterion is shown. The initial data for the task were the incidence matrix, service intensity and buffer dimension for communication channels. A feature of the proposed algorithm is the search for a contour matrix, for the compilation of which it is proposed to use loss edges as elements of the spanning tree of the graph, which allows you to immediately determine the contour matrix using the concept of a fundamental cycle of a graph. This approach to optimal traffic distribution reduces the number of variables used compared to the known methods based on loopless routes, and also does not require their preliminary search, since they are determined from the dimension of the incidence matrix of the simulated network graph.

Minimum spanning tree cycle intersection problem on outerplanar graphs

We study the minimum spanning tree cycle intersection (MSTCI) problem on outerplanar graphs in this paper. Consider a connected simple graph G=(V,E) and any spanning tree T=(V,ET) of G, it is well-known that each non-tree edge e∈E∖ET induces a fundamental cycle in T∪{e}. We say that two distinct fundamental cycles intersect if they share at least one edge. The MSTCI problem seeks a spanning tree such that the number of pairwise cycle intersections is minimized. We provide a linear-time algorithm to solve the problem on outerplanar graphs by exploiting the cycle-cut duality on plane graphs. Besides, we show that the minimum cycle intersection number is bounded by O(n) for outerplanar graphs with n vertices.

Cut‐set matrix methods for frequency response analysis curves of lumped parameter equivalent circuit model of three‐winding power transformer

SummaryTo accurately and efficiently calculate the frequency response of the lumped parameter equivalent circuit model (LPECM) of a transformer winding is the basis for studying the simulation method of the frequency response analysis (FRA). In this paper, two different cut‐set matrix (CSM) methods, including fundamental cut‐set (FCS) and independent cut‐set (ICS) matrix methods, are proposed to calculate the FRA curves of the LPECM of a three‐winding power transformer. First, based on graph theory and electrical circuit laws, the basic CSM equation is deduced. Second, four different FCS matrix selection methods of the LPECM are introduced and the best FCS matrix is determined by deeply analyzing their characteristics. Then, an ICS matrix method is proposed to obtain the ICS of the LPECM. Furthermore, FCS and ICS are taken into the CSM equation to calculate the FRA results of the LPECM, respectively. Finally, the accuracy of the proposed methods is validated by Multisim software and the performance of these two methods is compared with node voltage matrix (NVM) method by analyzing the calculation time. The results show that FCS and ICS matrix methods both can be used to accurately obtain the FRA results of the LPECM of the three‐winding power transformer, but ICS is more simple than FCS matrix method due to avoiding the procedure for the selection of the tree. In addition, since ICS matrix method has the shortest running time among these methods, it can be used to improve the calculation efficiency of the FRA curves of the LPECM of a three‐winding power transformer.

Clustering Schizophrenia Genes by Their Temporal Expression Patterns Aids Functional Interpretation.

Schizophrenia is a highly heritable brain disorder with a typical symptom onset in early adulthood. The 2-hit hypothesis posits that schizophrenia results from differential early neurodevelopment, predisposing an individual, followed by a disruption of later brain maturational processes that trigger the onset of symptoms. We applied hierarchical clustering to transcription levels of 345 genes previously linked to schizophrenia, derived from cortical tissue samples from 56 donors across the lifespan. We subsequently calculated clustered-specific polygenic risk scores for 743 individuals with schizophrenia and 743 sex- and age-matched healthy controls. Clustering revealed a set of 183 genes that was significantly upregulated prenatally and downregulated postnatally and 162 genes that showed the opposite pattern. The prenatally upregulated set of genes was functionally annotated to fundamental cell cycle processes, while the postnatally upregulated set was associated with the immune system and neuronal communication. We found an interaction between the 2 scores; higher prenatal polygenic risk showed a stronger association with schizophrenia diagnosis at higher levels of postnatal polygenic risk. Importantly, this finding was replicated in an independent clinical cohort of 3233 individuals. We provide genetics-based evidence that schizophrenia is shaped by disruptions of separable biological processes acting at distinct phases of neurodevelopment. The modeling of genetic risk factors that moderate each other's effect, informed by the timing of their expression, will aid in a better understanding of the development of schizophrenia.

The Impact of Processing Time Variations on Swap Sequence Performance in Dual-Armed Cluster Tools

The performance of a swap sequence is analyzed by assuming cyclic scheduling in dual-armed cluster tools with processing time variations. A dual-armed cluster tool consists of multiple processing modules (PMs), one material handling robot that can hold two wafers at the same time, and loadlocks where wafer cassettes are loaded or unloaded. The swap sequence in a dual-armed cluster tool is widely used in practice and known to be optimal with deterministic processing times when the bottleneck PM’s workload is larger than the robot workload. However, in practice, processing times on a PM can have a small variation, which leads to a different processing time of each wafer on the PM. Hence, when the processing time variation is introduced, the performance of the swap sequence needs to be analyzed. This paper first defines a fundamental cycle and analyzes its cycle time. It then proposes optimality conditions of the swap sequence and performs numerical experiments to show the effectiveness of the sequence. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —A dual-armed cluster tool used for semiconductor manufacturing processes is usually operated with a swap sequence because it is simple, easy to control, and proven to be optimal with deterministic processing times. However, studies on the performance of the swap sequence are still limited with processing times varying in PMs which often occur in practice. Hence, this study shows the effectiveness of the swap sequence with the processing time variations by analyzing cycle times, optimality conditions, and performing numerical experiments.

Problem solution of telecommunication networks parametric synthesis by the loop method

An algorithm for the parametric synthesis of telecommunication networks based on the criterion of minimizing the total throughput of communication channels is proposed. The problem is formulated in terms of linear programming. A feature of the proposed algorithm for obtaining a mathematical model is the use of the contour method of analysis that describes the distribution of information flows through flows in the fundamental cycles of the graph. A numerical example of the operation of the algorithm is given as well as an analysis of the results obtained.