Unstable Cycle Research Articles

Fabrications of Graphene Oxide and Silver Nanowire Hybrid Nanocomposites for Li-Metal Anodes with Dendrite Suppression

Lithium (Li) metal is the most promising anode material for Li-metal batteries due to its high theoretical capacity (3,860 mAh g-1) and low electrochemical potential (-3.04 V vs. the standard hydrogen electrode). However, many of previously studies for Li-metal batteries utilized a relatively thick ~ 50 μm Li metal foils, which lowers overall energy densities of the cells. Therefore, there have been growing research to reduce the thickness of the Li-metal anode to improve the energy density of batteries. Typical anode current collector of a copper foil show low affinity of Li metals with great initial deposition overpotentials when Li-metals are eletrodeposited. Such lithiophobicity accelerate the problems of Li dendritic growth with reduction in cycle life, which has been critical problems in practical applications of pristine Cu current collectors for Li-metal batteries. Therefore, various types of surface modification methods have been reported so far, such as coatings of carbon materials such as GO or metal-based materials such as Ag, Au. However, only carbon or metal modifications have been suffering from the relatively low lithiophilicity of the carbons and pulverizations of metals during cyclings by alloying and dealloying with Li-metals, respectively. Carbon and metal hybrid composites were also studied to mitigate these problems, but there still large rooms for further improvements showing unstable cycle performances at high C-rates.Herein, we report the fabrication of lithiophilic graphene oxide (GO) and silver nanowire (AgNW) nanocomposite anodes by Layer-by-Layer (LbL) assembly methods for uniform Li depositions. GO provides a fast Li ion movement channel with high ionic conductivity, and AgNW shows low nucleation overpotential behavior due to the formation of an alloy with Li. Therefore, we alternately stack these two materials using the LbL assembly method to induce a synergistic effect of their advantages. The resulting GO and AgNW nanocomposite films show uniformly deposited morphology after Li depositions and low nucleation overpotential compared to copper foils when pre-deposited at capacity of 4 mAh cm-2. The symmetric cells with the GO-AgNW composite electrodes with 4 mAh cm-2 of Li pre-depositions show stable behavior for 400 cycles with an overpotential of 10 mV at 1 mA cm-2 and 1 mAh cm-2. In addition, the full cells using LFP cathode materials operate more than 400 cycles at 1 C-rate and 200 cycles even at high 3 C-rate, showing longer cycle life and capacity retention than copper foil. These LbL self-assembled anodes provides a facile route to prepare lithiophillic anode coatings that can be advantageous for the preparations of high energy density Li-metal batteries.

An 11 nW, ＋0.34 °C/−0.38 °C inaccuracy self-biased CMOS temperature sensor at sub-thermal drain voltage

This paper presents a low-power, high-accuracy self-biased full CMOS temperature sensor based on sub-threshold currents at sub-thermal drain voltage. The sensor achieves high accuracy and minimal corner dependence by generating sub-threshold current ratios using NMOS transistors of different sizes operating at sub-thermal drain voltage. The proposed self-biased all-CMOS temperature sensing architecture enhances sensitivity by up to seven times and improves linearity. The overall stability under temperature fluctuations is significantly enhanced by utilizing a substrate diode structure that maintains constant current variation. Additionally, a high-threshold comparator with a fast response compresses the oscillator reset voltage difference, enabling ultra-low power operation. Timing logic control is employed to discard unstable cycle outputs, thereby reducing errors and achieving high-accuracy outputs. Operating at 1 V, the circuit consumes only 11 nW at 27 °C in a 180 nm CMOS process. It achieves a peak-to-peak inaccuracy of ＋0.34 °C/−0.38 °C from −10 to 100 °C after two-point calibration, with a resolution of 40 mK and a resolution FoM as low as 3.7 pJK2.

Dynamics of a slow-fast Leslie-Gower predator-prey model with prey harvesting.

For the Leslie-Gower predator-prey model with Michaelis-Menten type prey harvesting, the known results are on the saddle-node bifurcation and the Hopf bifurcation of codimensions 1, the Bogdanov-Takens bifurcations of codimensions 2 and 3, and on the cyclicity of singular slow-fast cycles. Here, we focus on the global dynamics of the model in the slow-fast setting and obtain much richer dynamical phenomena than the existing ones, such as global stability of an equilibrium; an unstable canard cycle exploding to a homoclinic loop; coexistence of a stable canard cycle and an inner unstable homoclinic loop; and, consequently, coexistence of two canard cycles: a canard explosion via canard cycles without a head, canard cycles with a short head and a beard and a relaxation oscillation with a short beard. This last one should be a new dynamical phenomenon. Numerical simulations are provided to illustrate these theoretical results.

Faradaic-dominated intercalation pseudocapacitance in bimetallic ultrathin NiMn-MOF nanosheet electrodes for high-performance asymmetric supercapacitors

Specialized electrochemical characteristics of layered materials are concentrated in the interlayer regions. However, total performance is limited by slow kinetics and unstable cycles. Interfacial alteration of layered materials can significantly enhance charge storage by allowing the development of intercalation pseudocapacitance. The emergence of intercalation pseudocapacitance represents a new energy storage mechanism that bridges the gap between supercapacitors (SCs) and batteries in terms of energy and power density. In this study, bimetallic MOFs of Ni and Mn are synthesized to create a NiMn-MOF electrode with a unique 2D layered structure with ample voids and pores that enable rapid intercalation of electrolyte ions followed by Faradaic redox reactions to promote intercalation pseudocapacitance. Especially, the multiple oxidation states of the metal-ions facilitate better electrochemical activity. The NiMn-MOF electrode material is synthesized by a simple hydrothermal route. The resulting electrode exhibits a high specific capacity of 502 C/g (1025 F/g) at 1 A/g current density, along with 97.5 % capacity retention over 10,000 GCD cycles. Furthermore, an asymmetric supercapacitor (ASC), constructed using NiMn-MOF as the positive electrode and commercially available activated carbon (AC) as the negative electrode, demonstrates a high specific capacitance of 160 F/g, an energy density of 55.0 Wh/kg and a power density of 785 W/kg with a capacitance retention of 94 % over 5000 GCD cycles. This innovative nanocomposite electrode with a novel charge storage mechanism shows great potential for advancing energy density, power density, and rate performance in advanced energy storage systems.

Carbon Cycle Instability for High-CO2 Exoplanets: Implications for Habitability

Implicit in the definition of the classical circumstellar habitable zone (HZ) is the hypothesis that the carbonate-silicate cycle can maintain clement climates on exoplanets with land and surface water across a range of instellations by adjusting atmospheric CO2 partial pressure (pCO2). This hypothesis is made by analogy to the Earth system, but it is an open question whether silicate weathering can stabilize climate on planets in the outer reaches of the HZ, where instellations are lower than those received by even the Archean Earth and CO2 is thought likely to dominate atmospheres. Since weathering products are carried from land to ocean by the action of water, silicate weathering is intimately coupled to the hydrologic cycle, which intensifies with hotter temperatures under Earth-like conditions. Here, we use global climate model simulations to demonstrate that the hydrologic cycle responds counterintuitively to changes in climate on planets with CO2-H2O atmospheres at low instellations and high pCO2, with global evaporation and precipitation decreasing as pCO2 and temperatures increase at a given instellation. Within the Maher & Chamberlain (or MAC) weathering formulation, weathering then decreases with increasing pCO2 for a range of instellations and pCO2 typical of the outer reaches of the HZ, resulting in an unstable carbon cycle that may lead to either runaway CO2 accumulation or depletion of CO2 to colder (possibly snowball) conditions. While the behavior of the system has not been completely mapped out, the results suggest that silicate weathering could fail to maintain habitable conditions in the outer reaches of the nominal HZ.

Complex dynamics in prey-predator systems with cross-coupling: Exploring nonlinear interactions and population oscillations

This study investigates the problem of ecosystem dynamics in fragmented landscapes, specifically focusing on a two-patch environment with interacting prey and predators. The research examines the impact of cross-predation on these interactions. Using bifurcation analysis, we explored the structural arrangement of attractors and identified complex dynamics such as symmetric, asymmetric, and asynchronous attractors induced by varying cross-coupling levels. Notably, our study describes a novel mechanism for the formation of anti-phase synchrony in the patches. Unlike typical occurrences of a cycle following Hopf bifurcation, our model reveals that the anti-phase cycle stabilizes via Neimark-Sacker (NS) bifurcation of a two-period unstable cycle branch emanating from the synchronous cycle branch. Our findings also demonstrate that cross-feeding can lead to significant ecosystem asymmetry and branching, culminating in the dominance of a single cross-feeding chain. These results challenge traditional models and highlight the presence of multistability and the potential for ecosystem evolution towards distinct subsystem branches due to cross-predation. The study’s insights offer valuable contributions to population and evolutionary biology, enhancing our understanding of the intricate dynamics within fragmented ecosystems.

Intelligent Control System for Wood Drying: Scalable Architecture, Predictive Analytics, and Future Enhancements

This article explores the research and development undertaken as part of a Master’s degree in Computer Engineering, with a primary focus on enhancing control mechanisms for natural wood drying. While this method is known for its cost-effectiveness in terms of labor and energy, it suffers from slower and unstable drying cycles. The project’s objective is to implement an intelligent control system that significantly improves monitoring and recording of humidity levels in each wooden stack. Additionally, the system incorporates the capability to predict humidity based on data sourced from a weather forecasting API. The proposed solution entails a three-layer system: data collection, relay, and analysis. In the data collection layer, low-computing devices, utilizing a Raspberry Pi, measure humidity levels in individual wood stacks. These devices then transmit the data via Low Power Bluetooth to the subsequent layer. The data relay layer incorporates an Android application designed to aggregate, normalize, and transmit collected data. Furthermore, it provides users with visualization tools for comprehensive data understanding. The data storage and analysis layer, developed with Django, serves as the back-end, offering management functionalities for stacks, sensors, overall data, and analysis capabilities. This layer can generate humidity forecasts based on real-time weather information. The implementation of this intelligent control system enables accurate insights into humidity levels, triggering alerts for any anomalies during the drying process. This reduces the necessity for constant on-site supervision, optimizes work efficiency, lowers costs, and eliminates repetitive tasks.

ОЦЕНКА ФУНКЦИОНАЛЬНОГО НАЗНАЧЕНИЯ АКТИВОВ ОРГАНИЗАЦИИ

This article develops tools for assessing the functional purpose of an organization’s as-sets. It assumes the distribution of financial indicators characterizing the functional role of assets by phases of the economic cycle, taking into account the professional judgment of specialists. The assess-ment of assets is a key element in the financial management of an enterprise, especially in an unstable economic cycle. The hypothesis of the study is based on determining the expediency in assessing the purpose of assets to choose indicators characterizing the financial condition of organizations in different phases of the economic cycle. The study revealed that assets of commercial organizations measure the value of the organization's business turnover; characterize the accumulated potential; help in achieving sustainable capital formation; protect against the risk of liquidity loss by highly liquid assets exceeding the minimum mark, guaranteeing the safety margin of equity; influence the level of risky; and assess its financial condition. A methodological toolkit for assessing the functional purpose of assets has been de-veloped, which assumes the distribution of financial indicators characterizing the functional role of as-sets in different phases of the economic cycle taking into account the professional judgment of special-ists. It is only possible to evaluate the asset management of commercial organizations practically, which will determine the direction of subsequent research.

Day-to-day sleep variability with Alzheimer's biomarkers in at-risk elderly.

Measuring day-to-day sleep variability might reveal unstable sleep-wake cycles reflecting neurodegenerative processes. We evaluated the association between Alzheimer's disease (AD) fluid biomarkers with day-to-day sleep variability. In the PREVENT-AD cohort, 203 dementia-free participants (age: 68.3±5.4; 78males) with a parental history of sporadic AD were tested with actigraphy and fluid biomarkers. Day-to-day variability (standard deviations over a week) was assessed for sleep midpoint, duration, efficiency, and nighttime activity count. Lower cerebrospinal fluid (CSF) ApoE, higher CSF p-tau181/amyloid-β (Aβ)42, and higher plasma p-tau231/Aβ42 were associated with higher variability of sleep midpoint, sleep duration, and/or activity count. The associations between fluid biomarkers with greater sleep duration variability were especially observed in those that carried the APOE4 allele, mild cognitive impairment converters, or those with gray matter atrophy. Day-to-day sleep variability were associated with biomarkers of AD in at-risk individuals, suggesting that unstable sleep promotes neurodegeneration or, conversely, that AD neuropathology disrupts sleep-wake cycles.

An electron-losing regulation strategy for stripping modulation towards a highly reversible Zn anode.

The practical application of aqueous zinc-ion batteries (AZIBs) is hindered by their low coulombic efficiency (CE) and unstable cycle life. Numerous electrolyte-additive-related studies have been performed, but most of the focus has been on the Zn plating process. In fact, practical AZIBs undergo stripping in practice rather than plating in the initial cycle, because the commonly used cathodes in the charged state do not have zinc ions, so a uniform stripping process is crucial for the cell performance of AZIBs. Here, we propose an electron-losing regulation strategy for stripping modulation by adding additives. Oxolane (OL) was chosen as the model additive to verify this assumption. It is found that OL adsorbs onto the uneven initial Zn surface and accelerates the dissolution of the Zn tips, thus providing a uniform Zn anode during the stripping process. The oxygen atoms in OL reduce the surface energy of Zn and promote the exposure of the Zn (002) surface during plating. Consequently, cells with the OL electrolyte additive maintained a long lifespan and showed superior reversibility with a high average CE. The findings of this work lead to a deep understanding of the underlying mechanism of Zn anode stripping and provide new guidance for designing electrolyte additives.

Migraine in perimenopausal women

Sex hormones have a significant influence on the course of migraine in women. Perimenopause is accompanied by unstable cycle length, vasomotor, urogenital and other symptoms, while the course of migraine usually worsens. In postmenopause ovarian follicular function decreases, and the course of migraine improves in most cases. However, a number of studies have shown that the course of migraine does not change or even worsen after menopause. Perimenopausal and postmenopausal migraine patients are also more likely to suffer from vasomotor symptoms. Hormone replacement therapy is prescribed to relieve vasomotor symptoms, which may worsen the course of migraine. In this review, the influence of perimenopause and postmenopause on the course of migraine, the use of hormone replacement therapy, and methods to relieve and prevent attacks in patients with migraine are examined in detail.

Effect of surface crack dimension on very low cycle fatigue crack growth behavior of circumferential cracked pipes

In this study, the effects of surface crack depth and length on the fracture behavior of circumferentially cracked pipes under very low cyclic loading were investigated via finite element (FE) damage analysis using an energy-based damage model. The FE analysis method was first validated by comparison with the SA508 Gr.1a surface-cracked pipe test results. Using FE damage analysis, a parametric study was conducted for a surface-cracked pipe with cracks of different depths and lengths, giving the same limit load. The variations in crack penetration and unstable fracture cycles depending on crack depth and length are discussed.

Hydrogen-triggered X-Ray Bursts from SAX J1808.4−3658? The Onset of Nuclear Burning

We present a study of weak, thermonuclear X-ray bursts from the accreting millisecond X-ray pulsar SAX J1808.4−3658. We focus on a burst observed with the Neutron Star Interior Composition Explorer on 2019 August 9, and describe a similar burst observed with the Rossi X-ray Timing Explorer in 2005 June. These bursts occurred soon after outburst onset, 2.9 and 1.1 days, after the first indications of fresh accretion. We measure peak burst bolometric fluxes of 6.98 ± 0.50 × 10−9 and 1.54 ± 0.10 × 10−8 erg cm−2 s−1, respectively, which are factors of ≈30 and 15 less than the peak flux of the brightest, helium-powered bursts observed from this source. From spectral modeling we estimate the accretion rates and accreted columns at the time of each burst. For the 2019 burst we estimate an accretion rate of M ⊙ yr−1, and a column in the range 3.9–5.1 × 107 g cm−2. For the 2005 event the accretion rate was similar, but the accreted column was half of that estimated for the 2019 burst. The low accretion rates, modest columns, and evidence for a cool neutron star in quiescence, suggest these bursts are triggered by thermally unstable CNO cycle hydrogen burning. The post-burst flux level in the 2019 event appears offset from the pre-burst level by an amount consistent with quasi-stable hydrogen burning due to the temperature-insensitive, hot-CNO cycle, further suggesting hydrogen burning as the primary fuel source. This provides strong observational evidence for hydrogen-triggered bursts. We discuss our results in the context of previous theoretical modeling.

Numerical and experimental analysis of stable, unstable, and limit cycle spiral vibrations

In rotating machinery, non-uniform temperature distribution or hot spots on the rotor surface can induce spiral vibrations. In this paper, a novel experimental apparatus is used to analyze the influence of a hot spot on the dynamic behavior of a flexible rotor supported by oil journal bearings. The hot spot is generated using an induction system with controlled amplitude and phase shift with respect to the vibration vector. Hence, it was possible to mimic phenomena like the Morton effect or the Newkirk effect. Different types of spiral vibrations were experimentally reproduced: stable, unstable and limit cycle. In the latter case, the vibration vector describes a closed loop when plotted in a polar plot. Therefore, the present work isolates the phenomenon of spiral vibrations from the complexity of the physics behind the generation of hot spot whether this source is the viscous shearing, rotor rubbing, or eddy current losses in magnetic bearings.Moreover, a theoretical model is derived to gain insight on the mechanisms driving spiral vibrations especially the role that the phase shift between the hot spot and the vibration vector plays in the stability of the system. Theoretical and experimental stability maps obtained for sub-synchronous and super-synchronous angular speeds are in excellent agreement. Additionally, the notion of thermal period, i.e., the period that govern the oscillation of the vibration vector is introduced. A concept never addressed before. It was found that this thermal period depends not only on the thermal inertia of the rotor, but also on the amplitude and phase shift of the hot spot, the distance to the critical speed and the damping ratio.

Relaxation oscillations of a piecewise-smooth slow-fast Bazykin's model with Holling type Ⅰ functional response.

In this paper, we consider the dynamics of a slow-fast Bazykin's model with piecewise-smooth Holling type Ⅰ functional response. We show that the model has Saddle-node bifurcation and Boundary equilibrium bifurcation. Furthermore, it is also proven that the model has a homoclinic cycle, a heteroclinic cycle or two relaxation oscillation cycles for different parameters conditions. These results imply the dynamical behavior of the model is sensitive to the predator competition rate and the initial densities of prey and predators. In order to support the theoretical analysis, we present some phase portraits corresponding to different values of parameters by numerical simulation. These phase portraits include two relaxation oscillation cycles, an unstable relaxation oscillation cycle surrounded by a stable homoclinic cycle; the coexistence of a heteroclinic cycle and an unstable relaxation oscillation cycle. These results reveal far richer and much more complex dynamics compared to the model without different time scale or with smooth Holling type Ⅰ functional response.

TERDAMPAKNYA PENDAPATAN PEDAGANG SAYURAN PADA MASA PANDEMI COVID-19 DI PASAR SHOPPING LIMBOTO KABUPATEN GORONTALO

This research sets out from the phenomenon of decreased income of greengrocers at the Limboto Shopping Market during the Covid-19 pandemic. The purpose of this research is to find out the impact of the Covid-19 pandemic on the greengrocers’ income at the Limboto Shopping Market, Gorontalo Regency. This research applies a qualitative approach. The greengrocers who become subjects in this research are those at the Limboto Shopping Market. The number of informants is 13 people of 22 greengrocers. Data collection involves observation, interview, and documentary techniques. Based on this research, it is found that the income of greengrocers at the Limboto Shopping Market during the pandemic has decreased because people's purchasing power has decreased, while the cost of living has increased. The decreased income has caused the greengrocers to consider whether to continue their business or not, taking into account that there is no reduced fare in the payment for the rental stalls. In addition, the absence of intensive handling causes the business to be threatened with closure and the capital runs out so that traders suffer losses. On the other hand, there is a government policy regarding limiting operating hours which causes an unstable economic cycle.

Redox‐Active Polymer Integrated with MXene for Ultra‐Stable and Fast Aqueous Proton Storage

AbstractProton is a charge carrier with the smallest ionic size and quickest kinetics, making aqueous proton batteries (APBs), a promising technology for safe and profitable energy storage systems. Despite being potential electrode materials, organic compounds have not yet been fully investigated in terms of proton storage properties and APB applications due to their low capacity and unstable cycle life in aqueous electrolytes. Herein, a novel redox‐active polymer (PDPZ) with diquinoxalino‐phenazine as the structural unit has been designed, which is further integrated with MXene nanosheets to construct a flexible PDPZ@MXene electrode material with a rapid and ultra‐stable proton storage behavior. In‐operando monitoring techniques, i.e., in situ Raman and in situ FTIR, demonstrate the highly reversible redox reaction between CN and CN/NH bonds in electro‐active PDPZ molecule with the strong proton absorption ability. Theoretical calculation further proves the electron transfer from MXene to PDPZ promotes the redox reaction of the PDPZ@MXene electrode. As a result, a flexible APB device is developed with a considerable energy density (64.3 mWh cm−3), a supercapacitor‐level power density (6000 mW cm−3), and a record lifespan with ≈98.2% capacity retention over 10 000 cycles, revealing its potential applications in satisfying the various requirements of energy storage systems.

CO2 Ocean Bistability on Terrestrial Exoplanets.

Cycling of carbon dioxide between the atmosphere and interior of rocky planets can stabilize global climate and enable planetary surface temperatures above freezing over geologic time. However, variations in global carbon budget and unstable feedback cycles between planetary sub-systems may destabilize the climate of rocky exoplanets toward regimes unknown in the Solar System. Here, we perform clear-sky atmospheric radiative transfer and surface weathering simulations to probe the stability of climate equilibria for rocky, ocean-bearing exoplanets at instellations relevant for planetary systems in the outer regions of the circumstellar habitable zone. Our simulations suggest that planets orbiting G- and F-type stars (but not M-type stars) may display bistability between an Earth-like climate state with efficient carbon sequestration and an alternative stable climate equilibrium where CO2 condenses at the surface and forms a blanket of either clathrate hydrate or liquid CO2. At increasing instellation and with ineffective weathering, the latter state oscillates between cool, surface CO2-condensing and hot, non-condensing climates. CO2 bistable climates may emerge early in planetary history and remain stable for billions of years. The carbon dioxide-condensing climates follow an opposite trend in pCO2 versus instellation compared to the weathering-stabilized planet population, suggesting the possibility of observational discrimination between these distinct climate categories.

Representation of gene regulation networks by hypothesis logic-based Boolean systems

Boolean Dynamical Systems (BDSs) are networks described by Boolean variables. A new representation of BDSs is presented in this article by using modal non-monotonic logic (\({\mathcal {H}}\)). This approach allows Boolean Networks to be represented by a set of modal formulas and therefore can be used to describe and learn their properties. The study of a BDS focuses in particular on the search of stable configurations, limit cycles and unstable cycles, which help to characterize a large type of Gene Networks. In this article is presented the identification of such asymptotic properties by introduction of a new concept, ghost extensions. Using ghost extensions, it is possible to translate BDSs in propositional calculus and consequently to use SAT algorithms.

Dynamic Analysis of a Novel 3D Chaotic System with Hidden and Coexisting Attractors: Offset Boosting, Synchronization, and Circuit Realization

To further understand the dynamical characteristics of chaotic systems with a hidden attractor and coexisting attractors, we investigated the fundamental dynamics of a novel three-dimensional (3D) chaotic system derived by adding a simple constant term to the Yang–Chen system, which includes the bifurcation diagram, Lyapunov exponents spectrum, and basin of attraction, under different parameters. In addition, an offset boosting control method is presented to the state variable, and a numerical simulation of the system is also presented. Furthermore, the unstable cycles embedded in the hidden chaotic attractors are extracted in detail, which shows the effectiveness of the variational method and 1D symbolic dynamics. Finally, the adaptive synchronization of the novel system is successfully designed, and a circuit simulation is implemented to illustrate the flexibility and validity of the numerical results. Theoretical analysis and simulation results indicate that the new system has complex dynamical properties and can be used to facilitate engineering applications.