High Density Conditions Research Articles

Traffic Awareness-Based Target Wake Time Scheduling in 802.11ax WLANs

In recent years, the rapid growth of mobile communication has led to the continuous expansion of network scale, and the energy consumption of wireless communication has also increased rapidly. Under the high-density networking conditions, frequent communication activities greatly increase the energy consumption. In order to reduce channel competition, optimize resource scheduling and reduce equipment power consumption, the target wake-up time (TWT) mechanism in IEEE 802.11ax system plays an important role through timely scheduling and transmission. To improve channel efficiency for multi-user (MU) transmission and tackle with complicated traffic conditions, this paper presents a traffic awareness-based TWT scheduling scheme (TAT). The traffic is predicted and classified using a spatio-temporal series model for traffic-based TWT parameter generation. Subsequently, the time–frequency scheduling table is developed to adaptively assign Resource Units (RUs) and time slices to active STAs. Simulation results show that TAT can guarantee the Quality of Service (QoS) under dynamic changes in power service and delay requirements while reducing power consumption, effectively meeting the energy-saving demands in the intelligent access scenarios for power terminals.

Molecular dynamics simulations of a multicellular model with cell-cell interactions and Hippo signaling pathway

The transcriptional coactivator Yes-associated protein (YAP)/transcriptional co-activator with PDZ binding motif (TAZ) induces cell proliferation through nuclear localization at low cell density. Conversely, at extremely high cell density, the Hippo pathway, which regulates YAP/TAZ, is activated. This activation leads to the translocation of YAP/TAZ into the cytoplasm, resulting in cell cycle arrest. Various cancer cells have several times more YAP/TAZ than normal cells. However, it is not entirely clear whether this several-fold increase in YAP/TAZ alone is sufficient to overcome proliferation inhibition (contact inhibition) under high-density conditions, thereby allowing continuous proliferation. In this study, we construct a three-dimensional (3D) mathematical model of cell proliferation incorporating the Hippo-YAP/TAZ pathway. Herein, a significant innovation in our approach is the introduction of a novel modeling component that inputs cell density, which reflects cell dynamics, into the Hippo pathway and enables the simulation of cell proliferation as the output response. We assume such 3D model with cell-cell interactions by solving reaction and molecular dynamics (MD) equations by applying adhesion and repulsive forces that act between cells and frictional forces acting on each cell. We assume Lennard-Jones (12-6) potential with a softcore character so that each cell secures its exclusive domain. We set cell cycles composed of mitotic and cell growth phases in which cells divide and grow under the influence of cell kinetics. We perform mathematical simulations at various YAP/TAZ levels to investigate the extent of YAP/TAZ increase required for sustained proliferation at high density. The results show that a twofold increase in YAP/TAZ levels of cancer cells was sufficient to evade cell cycle arrest compared to normal cells, enabling cells to continue proliferating even under high-density conditions. Finally, this mathematical model, which incorporates cell-cell interactions and the Hippo-YAP/TAZ pathway, may be applicable for evaluating cancer malignancy based on YAP/TAZ levels, developing drugs to suppress the abnormal proliferation of cancer cells, and determining appropriate drug dosages. The source codes are freely available.

ÆSOPUS 2.1: Low-temperature Opacities Extended to High Pressure

Abstract We address the critical need for accurate Rosseland mean gas opacities in high-pressure environments, spanning temperatures from 100 K to 32,000 K. Current opacity tables from Wichita State University and ÆSOPUS 2.0 are limited to log ( R ) ≤ 1 , where R = ρ T 6 − 3 in units of g cm − 3 ( 10 6 K ) − 3 . This is insufficient for modeling very low-mass stars, brown dwarfs, and planets with atmospheres exhibiting higher densities and pressures ( log ( R ) > 1 ). Leveraging extensive databases such as ExoMol, ExoMolOP, MoLLIST, and HITEMP, we focus on expanding the ÆSOPUS opacity calculations to cover a broad range of pressure and density conditions ( − 8 ≤ log ( R ) ≤ + 6 ). We incorporate the thermal Doppler mechanism and microturbulence velocity. Pressure-broadening effects on molecular transitions, leading to Lorentzian or Voigt profiles, are explored in the context of atmospheric profiles for exoplanets, brown dwarfs, and low-mass stars. We also delve into the impact of electron degeneracy and nonideal effects, such as ionization potential depression under high-density conditions, emphasizing its notable influence on Rosseland mean opacities at temperatures exceeding 10,000 K. As a result, this study expands the ÆSOPUS public web interface for customized gas chemical mixtures, promoting flexibility in opacity calculations based on specific research needs. Additionally, precomputed opacity tables, inclusive of condensates, are provided. We present a preliminary application to evolutionary models for very low-mass stars.

Breaking the Limitations of Activity and Stability in Powdered Materials for Oxygen Evolution Reaction: The Critical Role of Catalyst-Inducing Seeds

Powdered catalysts are extensively employed in industrial-scale energy conversion devices but struggle with weak powder-substrate adhesion and inherent instability in gas-evolving and highly oxidative oxygen evolution reactions (OER). This work introduces an innovative strategy in which powdered materials serve a critical role as catalyst-inducing seeds to break these limitations. Specifically, powdered Ti2CTx MXene with anchored cobalt single atoms (Co-SAs) shows negligible catalytic activity on its own but serves as catalyst-inducing seeds, significantly enhancing the catalytic activity of the conductive FeNi substrate. Mechanistic studies demonstrate that Co-SAs accelerate the oxidation rate of Ti2CTx, leading to the micro-battery corrosion behavior between oxidized Co/Ti2CTx and FeNi alloy, which generates highly OER-active corrosion products tightly bonded to FeNi alloy, thereby enhancing catalytic activity and ensuring stability. The prepared porous electrode shows a low overpotential of 303mV to deliver an ultra-high current density of 1000mAcm-2 and maintains activity for 1200hours under high current density conditions, rivaling advanced self-supporting electrodes. Moreover, replacing Co in Co/Ti2CTx with metals like Fe, Ni or Mn, yields comparable effects, suggesting the scalability of catalyst-inducing seeds. This approach breaks traditional limitations of powdered materials in OER, offering an effective pathway to engineer advanced catalytic electrodes.

Novel Large-scale Integrated Non-Precious Metal Electrodes for Efficient and Stable Oxygen Evolution Reaction at High Current Density in 2.5 kW Anion Exchange Membrane Water Electrolysis

The utilization of non-precious catalysts to substitute precious metal catalysts on anode side under high current density conditions and with long-term resistance is crucial for the implementation of alkaline anion-exchange membrane water electrolysis (AEMWE) applications. To accommodate industrial applications, a combination of chemical solution and electrodeposition was used to construct NiFeCo layered double hydroxide and NiS nanosheet heterostructures on Ni foam (NiFeCo LDH/NiS/NF). Both experiments and theoretical calculations show that the heterogeneous structure reduces the activation energy barrier of the catalytic reaction and provides an appropriate electronic structure. This not only guarantees the exposure of the active site but also adjusts the local coordination environment and chemisorption properties. Consequently, the reduction in energy barrier affects the rate-determining step (RDS) from *O to *OOH, as well as the energy barriers of all four steps in the oxygen evolution reaction (OER). Consequently, the optimized NiFeCo LDH/NiS/NF catalyst demonstrates a low voltage of 288mV to operate 1.0Acm-2. Additionally, the catalyst was conducted with commercial Pt/C coated onto carbon paper (Pt/C/CP) for 2×2 cm2 AEMWE exhibited 1.63V cell voltag to attain 1Acm−2 and operated for 2100h from 1Acm-2 to 2.5Acm-2 (1.69V to 1.92V). Further, the catalyst was prepared scalable to 15×15 cm2 for application into a 2.5kW AEMWE device, which required only 1.77V at 60 °C to catch 1Acm-2 for 1000h, which shows extremally promising application for stable AEMWE device.

LiF-enriched interphase promotes Li+ desolvation and transportation enabling high-performance carbon anode under wide-range temperature

Li-ion batteries (LIBs) have made inroads into the electric vehicle area with high energy densities, but they still suffer from slow kinetics of Li+ limited by the graphite anode especially at high current density and low-temperature conditions. Sluggish de-solvation of Li+ at the electrode surface and slow Li+ transfer in solid electrolyte interphase (SEI) are main determining factors that restrict the fast-charging and low-temperature performance of graphite-based LIBs. Here, we construct the sodium lignosulfonate layer with abundant polar functional groups on the lithium-montmorillonite surface, which can make it simple for electrons transfer to promote in-situ formation of LiF-based SEI with high ionic conductivity. The thin and robust LiF-based SEI promotes the de-solvation of Li salts and Li+ transfer as proved by the comprehensive electrochemical studies and density functional theory (DFT) calculations. Consequently, a combination of excellent stability and fast-charging ability for LIBs at room and low temperatures is achieved. The designed anode shows the remarkable capacity of 1500 mAh/g at 0.1 A/g, which was 3–4 times better than the commercial graphite. At the high current density of 5 A/g, it can still keep stable with the capacity retention of 70 % after 7000 cycles. Besides, an impressive 70 % of their room-temperature capacity is attained at −10 °C and 150 mAh/g is achieved under the extremely low temperature of −40 °C. This study establishes the effective strategy to construct the LiF-rich interface on the surface of anode to improve the Li+ kinetics and stability of the battery.

Dual Cocatalytic Sites Synergize NiFe Layered Double Hydroxide to Boost Oxygen Evolution Reaction in Anion Exchange Membrane Water Electrolyzer

AbstractNickel‐iron layered double hydroxide (LDH) is a promising cost‐efficient catalyst to replace noble metals for alkaline oxygen evolution reaction (OER), yet its intrinsic activity under high current density conditions is not satisfactory, which greatly constrains the industrial application of NiFe LDH catalysts. Herein, a new class of integrated Co and W co‐doped NiFe LDH catalysts is reported with dual cocatalytic sites for alkaline OER catalysis. The optimized Co2.8, W3.8‐NiFe LDH integrated catalyst has superior alkaline OER activity (255 mV@1000 mA cm−2) and excellent catalytic stability (200 h@500 mA cm−2). The turnover frequency value of Co2.8, W3.8‐NiFe LDH can reach 4.02 s−1 at 1.49 V versus RHE, which is 9.6 times higher than that of NiFe LDH and superior to the noble metal catalysts. Moreover, it can achieve 1.0 A cm−2 at 1.86 V and maintain 300‐h stable operation in anion exchange membrane water electrolyzer. Theoretical and experimental studies indicate that W sites promote the *OH adsorption and Co sites favor protons desorption of OH*. These dual cocatalytic sites jointly promote *O coverage, effectively accelerating alkaline OER kinetic.

A micro-scale look into pedestrian thermophysiological comfort in an urban environment

Different spatial scales enable the analysis of thermophysiological conditions of pedestrians in an urban environment. A higher resolution hotspot analysis was conceived using GIS technology in some areas of Lisbon with different morphological conditions. Eleven hotspots were found across six study areas, located in high to moderate urban density conditions and in different types of urban spaces. So, six hotspots were found in avenues (high urban density conditions), three in streets, and two in general open spaces (moderate urban density conditions). These spaces are characterized by being busy areas with high anthropogenic influence, with high-absorbing and reflective materials, and with very poor green infrastructure. Environmental conditions, namely, radiation, mean radiant temperature, and air temperature, were the main cause of hotspot existence, and the main propellers for UTCI intensification. The urban density variable was also found to be important, especially in avenues and open spaces. In these areas, the adjusted component for environmental and urban density conditions can increase 0.60 to 1.35 °C in open spaces and 0.30 to 0.60 °C in avenues, each time there is a one-unit increase in the component. Trees, either in the street or in parks, have generally been found to decrease the UTCI.

Modelling study of divertor W leakage for different divertor conditions with Ne seeding in EAST tokamak

Abstract Sequential SOLPS-ITER and DIVIMP simulations are carried out for tungsten (W) edge transport during neon (Ne) injection in EAST, elucidating the pathway of W impurity leakage from the divertor to the core plasma under different dissipative divertor conditions. Divertor conditions from low-recycling to detachment are generated by modulating the Ne injection rate in the SOLPS simulation. With the drift velocities incorporated in DIVIMP, W transport under the drift effect is investigated. For low-density L-mode plasma conditions with favorable Bt direction, the majority of W source originates from the outer divertor target and leaks upstream through the near-SOL EB drift reversed region at both inner and outer divertors. The EB drift is demonstrated to have a significant effect on W leakage and the effect diminishes with the increase of Ne injection rate. Compared to the D2 injection cases, Ne injection helps to achieve a strong dissipative divertor condition at a much lower plasma density, resulting in a higher W leakage ability due to the smaller friction with the background plasma. For Ne injection cases under high-density H-mode conditions, W leaks mostly through the outer divertor region while the inner divertor is fully detached. Compared to the L-mode cases, the shorter power decay lengths in the scrap-off layer (SOL) of the H-mode cases result in smaller parallel EB drift velocities especially in the middle and far SOL region. With the increase of the Ne injection rate, the decrease of the EB drift in the middle SOL leads to a wider near-separatrix W leakage path. Therefore, a worse divertor W screening is expected, which is consistent with the previous published experimental observations [1].

Quiescent cancer cells induced by high-density cultivation reveals cholesterol-mediated survival and lung metastatic traits.

The metastatic cascade, a multifaceted and highly aggressive process, is the primary cause of mortality. The survival of quiescent cancer cells in circulatory system during metastasis is crucial, yet our comprehension is constrained by the absence of universally accepted quiescent cancer models. We developed a quiescent cancer cell model using high-density cultivation. Based on the scRNA-seq analysis, IP-MS, metabolomics, mouse lung metastasis models, cholesterol assay, PLA and other molecular experiments, we explored the molecular mechanism. Immunofluorescence, atomic force microscope, FluidFM, and shear stress stimulation were used to analyze the cytoskeleton and membrane properties contributing to mechanical force resistance. We established a quiescent cancer cell model induced by high-density cultivation. Single-cell RNA sequencing (scRNA-seq) analysis reveals that CDC25A plays a crucial role in the transition to quiescence, with its expression significantly elevated in the quiescent state. Depletion of CDC25A leads to an increased proliferative capacity, and reduced metastasis under high-density conditions. Mechanistically, upregulated CDC25A in quiescent cells enhances cholesterol metabolism via endosome pathways, leading to cell cycle arrest. This increase in cholesterol reinforces the cytoskeleton, alters membrane properties, and improves resistance to mechanical forces in circulatory system. CDC25A significantly increased the cholesterol metabolism through endosome pathway in quiescent cancer cells, leading to the significant changes in cytoskeleton and membrane properties so as to enhance the resistance of mechanical force in circulatory system, facilitating lung metastasis. In high-density cultivation, quiescent cancer cells, up-regulate cholesterol metabolism by CDC25A through endosome pathway, enhancing the resistance to mechanical force in circulatory system, facilitating lung metastasis.

Ego-network characteristics moderates the interaction of structural hole and centrality on market performance: based on coopetition network

This paper establishes a symmetric matrix based on the coopetition relationships among global automobile enterprises, and uses Ucinet software to obtain the visualization chart of the coopetition network of global automobile enterprises. Then, the multiple moderating effect method and two-stage least squares method are adopt to reveal the interaction between structural hole and centrality on enterprise market performance, and how the ego-network characteristics affect this interaction. The results show that structural hole and centrality have a positive interaction on market performance. Compared with high ego-network stability, the positive interaction between structural hole and centrality on enterprise market performance is stronger under the condition of low ego-network stability. And compared with low ego-network density, the positive interaction between structural hole and centrality on market performance is stronger under the condition of high ego-network density. These new findings further strengthen the connection between the overall network and ego-network.

Research Progress in Structure Evolution and Durability Modulation of Ir- and Ru-Based OER Catalysts under Acidic Conditions.

Green hydrogen energy, as one of the most promising energy carriers, plays a crucial role in addressing energy and environmental issues. Oxygen evolution reaction catalysts, as the key to water electrolysis hydrogen production technology, have been subject to durability constraints, preventing large-scale commercial development. Under the high current density and harsh acid-base electrolyte conditions of the water electrolysis reaction, the active metals in the catalysts are easily converted into high-valent soluble species to dissolve, leading to poor structural durability of the catalysts. There is an urgent need to overcome the durability challenges under acidic conditions and develop electrocatalysts with both high catalytic activity and high durability. In this review, the latest research results are analyzed in depth from both thermodynamic and kinetic perspectives. First, a comprehensive summary of the structural deactivation state process of noble metal oxide catalysts is presented. Second, the evolution of the structure of catalysts possessing high durability is discussed. Finally, four new strategies for the preparation of stable catalysts, "electron buffer (ECB) strategy", combination strength control, strain control, and surface coating, are summarized. The challenges and prospects are also elaborated for the future synthesis of more effective Ru/Ir-based catalysts and boost their future application.

Maize-Tripsacum-Teosinte allopolyploid (MTP), a novel dwarf mutant inducer tool in maize.

Dwarf plant architecture facilitates dense planting, and increased planting densities boost the maize yield. However, breeding applications of dwarfing materials for maize are currently limited. There is an urgent need remove the obstacles to applying dwarf resources. Here, we innovated a new method to add a novel maize dwarf germplasm through the distant hybridization of Maize-Tripsacum-Teosinte allopolyploid (MTP) with maize. We identified ten independent dwarf families with unique characteristics. Five germplasms in our library were controlled by their respective dwarf genes. However, no allele was controlled by Br2. Subsequently, d024 in the library was successfully fine mapped, revealing its linkage to indel-4 in ZmCYP90D1. The indel-4 polymorphism regulates the expression of ZmCYP90D1 and is controlled by an upstream transcription factor (ZmBES1/BZR1-5). The indel-4 of ZmCYP90D1 allele, which reduces plant height, originated from Tripsacum, a wild variety of maize. However, d024 exhibits sensitivity to brassinosteroids (BRs), with lower castasterone levels in the internodes than that in the wild type. Furthermore, ZmCYP90D1 interacted with ZmFDXs and ZmNAD(P)H to positively regulate the downstream BR synthesis pathway. Additionally, we showed that introgressing the indel-4 of the Tripsacum allele into modern hybrids ensures yield potential and improves the harvest index under high-density conditions. Overall, as we begin to manufacture highly engineered dwarf materials using the MTP, this approach will solve the problems faced by corn dwarfs.

Investigation of fuel temperature and injection timing effects on ammonia direct injection in an optical engine

This work investigates the effects of fuel temperature and injection timing on ammonia direct injection in an optical engine using a multi-hole injector. Flash-boiling may occur over various engine-relevant conditions due to ammonia’s high vapor pressure. This phenomenon impacts spray characteristics and, in severe cases, facilitates cavitation inside the nozzle. Both fuel temperature and injection timing (i.e., ambient conditions during injection) impact the intensity of flash-boiling during fuel injection. Therefore, this work varies fuel temperature (from 320K to 388K) and injection timing (from −60CADaTDC (crank angle degrees after top dead center) to −6CADaTDC) to assess their impact on injection mass flux, discharge coefficients, and macroscopic spray characteristics using an ammonia injection pressure of 200bar. For this purpose, the injection mass is measured by analyzing exhaust gas compositions during engine operation with ammonia injections but without combustion. In addition, diffuse background illumination (DBI) images capture the liquid phase of the fuel spray to characterize spray behavior. The findings reveal that increasing fuel temperature decreases ammonia’s injection mass by up to 12.8% but has little impact on discharge coefficients for late injection timings and high in-cylinder pressures. However, discharge coefficients decrease by up to 17.4% (from 0.58 to 0.48) for early injection timings if fuel temperatures are high. The individual sprays of the 6-hole GDI injector may collapse into a uniform spray at high-density conditions without flash-boiling or under strongly flash-boiling conditions. The findings clarify the impact of ammonia’s high vapor pressure on injection mass and prove the relevance of different spray collapse mechanisms in ammonia direct injection engines.

Improvement in the Number of Velocity Vector Acquisitions Using an In-Picture Tracking Method for 3D3C Rainbow Particle Tracking Velocimetry

Particle image velocimetry and particle tracking velocimetry (PTV) have developed from two-dimensional two-component (2D2C) velocity vector measurements to 3D3C measurements. Rainbow particle tracking velocimetry is a low-cost 3D3C measurement technique adopting a single color camera. However, the vector acquisition rate is not so high. To increase the number of acquired vectors, this paper proposes a high probability and long-term tracking method. First, particles are tracked in a raw picture instead of in three-dimensional space. The tracking is aided by the color information. Second, a particle that temporarily cannot be tracked due to particle overlap is compensated for using the positional information at times before and after. The proposed method is demonstrated for flow under a rotating disk with different particle densities and velocities. The use of the proposed method improves the tracking rate, number of continuous tracking steps, and number of acquired velocity vectors. The method can be applied under the difficult conditions of high particle density (0.004 particles per pixel) and large particle movement (maximum of 60 pix).

Numerical simulation study of boiling heat transfer of R290 flow in horizontal microtubes

Abstract R290 is considered to be an excellent alternative refrigerant for domestic air conditioners in the future. In this paper, CFD numerical simulation was used to obtain the flow field distribution of R290 in a micro-fine circular tube with an inner diameter of 2mm under a specific range of working conditions, and the effects of saturation temperature, mass flow density, heat flow density and tube type on the boiling heat transfer characteristics of R290 tube were investigated. The results show that the boiling heat transfer coefficient increases with the increase of saturation temperature, and the maximum value of the heat transfer coefficient increases by 8.1% when the saturation temperature increases from 284K to 286K. The boiling heat transfer coefficient increases with the increase of mass flow density, and the maximum value appears in the medium dryness range. The boiling heat transfer coefficient in the tube increases and then decreases when the heat flow density increases from 10 kW/m2 to 20 kW/m2 and increases faster at high heat flow density conditions. In addition, compared with the circular tube, the boiling heat transfer coefficient in the elliptical tube with an aspect ratio of 1.56 increases by 2.78% for R290 under the same flow area.

Study on forming process and performance of nano-La2O3 reinforced tungsten-based composites by selective laser melting

In this study, La2O3 nanoparticles were incorporated into a tungsten (W) matrix to enhance the microstructure and properties of pure W. The selective laser melting (SLM) process for W-2wt% La2O3 was optimized, and the influence of SLM processing parameters on the relative density and internal defects of the samples was examined. Challenges such as uneven powder layering and layer-by-layer thickening during the SLM process were addressed by incorporating a homogeneous material support formed with low laser energy density beneath the sample. This approach widened the process window for sample formation, resulting in a 2.38 % increase in the average relative density of supported samples compared to unsupported ones.With optimized parameters of 240W laser power, 200 mm/s scanning speed, and 80 μm hatch spacing, the sample achieved a relative density of 98.32 % with minimal internal pores, though some microcracks remained. Further investigation revealed that surface roughness decreased with increasing laser power and scanning speed. High laser power combined with low scanning speed yielded good surface quality. Under conditions of high relative density (over 96 %), samples processed with low laser power and high scanning speed (200W, 200 mm/s) exhibited fine and uniform grain morphology, few internal defects, and excellent mechanical properties, with a microhardness of 474HV and a compressive strength of 2237 MPa.

Accelerated development of maize inbred lines suitable for high density through doubled haploid technology

Aim: Doubled haploid technology was utilized to accelerate the development of maize lines with traits suitable for high planting density, enabling the identification of potential parental lines for hybrid development under these conditions. Methodology: Two F1 populations (PML-119 x PML-185 and PML-95 x PML-172) were used to generate doubled haploid lines, confirmed using polymorphic markers phi115 and umc1887. These lines were phenotypically evaluated under high density (60 cm x 15 cm) and normal density (60 cm x 20 cm) conditions. Results: Using doubled haploid technology, 67 lines were developed from two source populations with traits such as narrow leaf angle, moderate plant height, and sparse tassel for high planting density stress tolerance. Molecular marker screening confirmed the homozygosity of these lines. Agronomic evaluation under narrow plant-to-plant spacing (15 cm) identified eight potential donor lines amenable to high planting density stress, ready for use as parents in breeding high-density tolerant hybrids. Interpretation: Potential donor doubled haploid lines viz. DH2-4, DH2-8, DH2-9, DH2-11, DH2-14, DH2-15 derived from Population-3 X CIM2GTAIL P2 and DH2-4, DH2-23 derived from Population-9 X CIM2GTAIL P2 were identified for utilization as putative parents of hybrids suitable for planting under high planting density conditions. Key words: Doubled haploid, High plant density, Maize, Plant architecture, Yield

The novel triangular spectral indices for characterizing winter wheat drought

Agricultural drought threatens food security and agricultural sustainable development. There have been numerous spectral indices from remote sensing images developed for monitoring crop drought. However, most present spectral indices are focusing on crop growth and Land Surface Temperature (LST), and the crop canopy water content are in less consideration simultaneously. Additionally, the Normalized Difference Vegetation Index (NDVI) is used for characterizing crop growth in almost all spectral drought indices, with the spectral saturation problem of NDVI for closed crop canopy. When vegetation cover is high, NDVI values tend to saturate, which makes them insensitive to further changes in crop health. Therefore, the NDVI saturation phenomenon may lead to an underestimation of the extent of crop drought, as it is not effective in identifying subtle changes in crops under high-density vegetation conditions. Hence, we propose three novel triangular spectral indices for characterizing winter wheat drought using three features including LAI, Land Surface Water Index (LSWI) and LST. For validating the proposed spectral indices, we compared the agreement between these indices with measured Relative Soil Moisture (RSM) and Volumetric Water Content (VWC) of soil in agricultural meteorological station and present popular indices including Crop Water Stress Index (CWSI), Temperature-Vegetation Drought Index (TVDI), and Vegetation Health Index (VHI). The results revealed that our proposed indices including Euclidean distance Crop Health Index (ECHI), Difference Crop Health Index (DCHI) and Perpendicular Water Stress Index (PWSI) outperformed the popular CWSI, TVDI and VHI, with stronger correlations with measured RSM and VWC in agricultural meteorological station. Secondly, there are spatial consistencies for characterizing winter wheat drought between proposed ECHI, DCHI and PWSI with popular CWSI, TVDI and VHI. In addition, our proposed ECHI, DCHI and PWSI have achieved good performance of drought monitoring both in irrigated and rainfed croplands. All these results suggest that our proposed indices have great potential in crop drought monitoring.

Magnetosonic waves in the Martian ionosphere driven by upstream proton cyclotron waves: Two-point observations by MAVEN and Mars Express

Recent observations from the Mars Atmosphere and Volatile EvolutioN (MAVEN) and Mars Express (MEX) spacecraft have suggested that pressure pulses originating from upstream proton cyclotron waves (PCWs) can “ring” the Martian magnetopause at the same frequency and drive magnetosonic waves in the upper ionosphere of Mars, thereby transporting energy from the solar wind into the ionosphere. However, the limitation of single-spacecraft measurements prevents simultaneous observations of the driver and response of this “ringing” process of the Martian magnetosphere. Here we utilize two-point measurements from MAVEN and MEX to characterize the ringing probability at which upstream PCWs drive compressional fluctuations in the ionospheric magnetic field. We develop an algorithm to identify PCW-driven magnetosonic waves in the upper ionosphere of Mars from the two-point magnetic field data. The derived ringing probability is higher on the dayside, outside strong crustal magnetic fields, and under high solar wind density conditions. We also show that the median power of dayside ionospheric magnetic field fluctuations is enhanced by a factor of ∼2 at corresponding frequencies in the presence of upstream PCWs compared to the median power in the absence of upstream PCWs. These results demonstrate the prevalence of energy deposits into the dayside Martian ionosphere from the solar wind mediated by the PCW-driven ringing of the magnetosphere. Future studies, possibly with new multi-point observations, should address the detailed processes of wave propagation and energy transport through the system and the long-term impact of this chain of processes on the planetary ion heating in the ionosphere and atmospheric loss from Mars.