Amplitude Of Variation Research Articles

A Neural Controller Design for Enhancing Stability of a Single Machine Infinite Bus Power System

This paper examines the formulation and implementation of a neuro-controller for the excitation system of synchronous generators in a Single-Machine Infinite Bus (SMIB) power system. The SMIB model is employed as a fundamental model of a power system, thereby facilitating the assessment and comparison of disparate control strategies with the objective of enhancing system stability. The goal of this study is to enhance the stability of the SMIB power system through the implementation of an Artificial Neural Network (ANN) neuro-controller, providing a comparison of its performance to that of a Power System Stabilizer (PSS) and a Proportional-Integral-Derivative (PID) controller. The proposed neuro-controller will be integrated into the generator's excitation system and will be designed to regulate the excitation voltage in response to fluctuations in the system's operational parameters. To this end, an ANN is calibrated to account for the singularity of the generator's excitation level and terminal voltage. The Levenberg-Marquardt algorithm is employed to ascertain the optimal weight coefficients for the ANN. To assess the performance of the neuro-controller, simulations were conducted using MATLAB/Simulink. The simulations encompass a comprehensive range of operational scenarios, including diverse disturbances and alterations in the reference voltage level. Subsequently, the neuro-controller's outputs are evaluated in comparison to the PSS and PID controllers, as these are the prevailing controllers used to enhance voltage regulation and transient stability in power systems. This paper presents the results of an analysis of the neuro-controller's impact on the system's robustness, voltage variation amplitude, and generator dynamic performance during faults. Simulation results demonstrate that the application of an ANN-based neuro-controller yields superior outcomes in voltage regulation and transient stability compared to the conventional controllers PSS and PID. Furthermore, the neuro-controller is distinguished by accelerated response times and enhanced precision in voltage level regulation. The neuro-controller represents a superior approach to the control of a power system, particularly in the context of SMIB, which would ultimately result in enhanced performance and stability.

Effect of the Lactation Phases on the Amplitude of Variation in Blood Serum Steroid Hormones and Some Hematochemical Analytes in Three Dairy Cow Breeds.

Lactation in dairy cows implies comprehensive endocrine and metabolic changes including a systemic electrolytic reaction. Previous studies have rarely considered these specific demands due to the influence of lactation periods. Therefore, this study aimed to assess the effects of early, middle, and late lactation phases on the dynamic changes in serum concentrations of progesterone (P4), 17β-oestradiol (E2), cortisol, and some electrolytes (Ca++, Mg++, Na+, K+, Cl-, Pi) and biochemical parameters (alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), creatine kinase (CK), total bilirubin, urea, and iron (Fe++) in 10 Holstein, 10 Brown Swiss, and 10 Modicana multiparous healthy dairy cows (4.2 ± 1.7 years of age) sampled at 60-day intervals throughout lactation. Lactation induced significant changes in the concentrations of P4, which peaked at >120-180 days, decreased at >240-300 days, and increased again after 300 days. Cortisol showed an opposite trend to P4, with concentrations progressively decreasing, except for the phase between >240 and 300 days, and a steep drop at >300 days compared to previous phases. Na+ concentrations showed the lowest values at 0-60 d and the highest ones at >180-240 days, whereas Mg++ showed the highest values at >60-120 d and the lowest at >300 d. Significant correlations were found between P4 with cortisol, Cl- and K+, and cortisol with Ca++ and LDH. Significant differences in average concentrations of AST, ALT, LDH, Ca++, Mg++, and Fe++ were observed among different dairy cow breeds. Understanding the dynamic changes in hormone levels, electrolytes, and biochemical parameters during different lactation phases, while considering breed differences in dairy cows, is crucial for improving herd health management and milk production in commercial dairy farms.

Could the Interband Lag of Active Galactic Nucleus Vary Randomly?

The interband lags among the optical broad-band continua of active galactic nuclei (AGNs) have been intensively explored over the past decade. However, the nature of the lags remains under debate. Here, utilizing two distinct scenarios for AGN variability, i.e., the thermal fluctuation of accretion disk and the reprocessing of both the accretion disk and clouds in the broad line region, we show that, owing to the random nature of AGN variability, the interband lags of an individual AGN would vary from one campaign with a finite baseline to another. Specifically, the thermal fluctuation scenario implies larger variations in the lags than the reprocessing scenario. Moreover, the former predicts a positive correlation between the lag and variation amplitude, while the latter does not result in such a correlation. For both scenarios, averaging the lags of an individual AGN measured with repeated and nonoverlapping campaigns would give rise to a stable lag, which is larger for a longer baseline and gets to saturation for a sufficiently long baseline. However, obtaining the stable lag for an individual AGN is very time-consuming. Alternatively, it can be equivalently inferred by averaging the lags of a sample of AGNs with similar physical properties, and thus can be properly compared with predictions of AGN models. In addition, several new observational tests suggested by our simulations are discussed, as well as the role of the deep high-cadence surveys of the Wide Field Survey Telescope in enriching our knowledge of the lags.

Catalyst pellets with Gaussian activity distribution under forced periodic operation for reactions with Langmuir-Hinshelwood kinetics

This research investigates how combining forced periodic operation with spatially distributed catalyst activity can enhance heterogeneous catalytic processes. It focuses on analyzing reaction-diffusion phenomena within porous catalyst pellets. These pellets exhibit a Gaussian distribution of active sites, and the study investigates how externally forced periodic variations in bulk reactant concentration and temperature affect the reaction process. The paper establishes a mathematical model for a non-isothermal reaction based on Langmuir-Hinshelwood kinetics. This model is then transformed into its dimensionless form for numerical analysis. Numerical simulations are employed to investigate the impact of various parameters on the concentration and temperature profiles within the pellet, as well as on the pellet productivity. These parameters include the position and width of the Gaussian distribution of active sites, the Thiele modulus, the mass and heat Biot numbers, the Arrhenius number for reaction, the energy generation function, the ratio of characteristic times for diffusion and heat conductivity, and frequencies and amplitudes of periodic variations. The simulations reveal complex relationships between the spatial and temporal profiles of concentration and temperature within the pellets. Using porous granules with a non-uniform catalyst activity profile alongside forced periodic operations for reaction-diffusion processes enables higher productivity compared to granules with a uniform activity profile and subject to the steady-state operation. This study demonstrates the potential for optimizing catalytic processes in porous pellets with non-uniform activity profiles under forced periodic operation, offering valuable insights into enhancing process efficiency.

Reduced brain oxygen response to spreading depolarization predicts worse outcome in ischaemic stroke.

Spreading depolarization (SD) describes a propagating neuronal mass depolarization within the cerebral cortex that represents a mediator of infarct development and strongly stimulates the metabolic rate of O2 consumption. Here, we investigated the influence of Spreading Depolarization (SD) on brain tissue partial pressure of O2 (ptiO2) within the peri-infarct tissue of patients suffering malignant hemispheric stroke (MHS). This prospective observational trial included 25 patients with MHS that underwent decompressive hemicraniectomy followed by subdural placement of electrodes for electrocorticography (ECoG) and neighboring implantation of a ptiO2 probe within the peri-infarcted cortex. Continuous side-by-side ECoG + ptiO2 recordings were obtained for 3-6 days postoperatively and analyzed for the occurrence of SD-independent and SD-coupled ptiO2 changes, radiological findings, as well as their association with clinical outcome at 6 months. During the combined ECoG + ptiO2 monitoring period of 2,604 hours and among 1,022 SDs, 483 (47%) SD-coupled ptiO2 variations were identified as biphasic (59%), hypoxic (36%) or hyperoxic (5%) ptiO2 responses that differed significantly (*p<0.0001). Among the remaining 538/1,022 (53%) SDs, no SD-coupled ptiO2 response was detected, which we categorized as 'No response'. The overall infarct progression was 1.7% (IQR -2.5-10.9). Spreading Depolarization characteristics regarding type, duration and frequency, as well as SD-independent baseline ptiO2 had no association with outcome. In contrast, a high occurrence rate and amplitude of SD-coupled variations in ptiO2 were associated with improved outcome at 6 months (occurrence: r=-0.62, *p=0.035; amplitude: r=-0.57, *p=0.024; Spearman correlation). In conclusion, an absent or reduced ptiO2 response to SD could indicate tissue-at-risk and help direct targeted treatment strategies in ischemic stroke, which is further evidence that not all SDs are the same, but that tissue responses coupled to SD such as ptiO2 contain prognostic information. In particular, a lack of SD-coupled ptiO2 variations appears to be a predictor of worse outcome in large hemispheric stroke.

An equivalent analysis of unsteady sand transport in a wind tunnel

This study investigates the effect of unsteady wind on sand transport in a wind tunnel using sinusoidally varying wind velocity to represent the unsteady wind. By comparing sand transport fluxes under steady and unsteady winds, we demonstrate that cumulative sand transport flux varies sinusoidally with the sinusoidally varying wind velocity. In addition to the time-averaged wind velocity, the sand transport rate is also affected by the amplitude and period of wind velocity variations. We then propose an ‘equivalent’ steady aeolian sand transport process as a substitute for the actual unsteady transport process. In terms of wind velocity amplitude and period variations, an equivalent wind friction velocity factor u*′ is defined to capture differences caused by wind velocity variations with the same time-averaged wind velocity and friction velocity. Finally, a unified equation for aeolian sand transport is derived, demonstrating applicability for both steady and unsteady flow conditions. The results of this study contribute to a deeper understanding of aeolian sand transport under unsteady flow.

Observational study on the surface radiation budget and energy balance closure of grassland in the eastern arid region of Northwest China

Based on the observation data of the meteorological environment monitoring system (QT-1010) and the open vorticity correlation system (LI-7500DS), we used the block aerodynamics and energy balance ratio method to analyze the surface radiation budget and energy balance closure characteristics of the grassland in the eastern arid region of Northwest China at different time scales.We found that (1) The daily variation curve of the surface radiation flux is unimodal, and the variation amplitude of each component is as follows: Rs↓> RL↑> RL↓> Rs↑. (2) The monthly peak of each radiation component occurs in summer, and the time of reaching the peak of different components has a lag. The changes of radiation components in sunny and cloudy days are multi-modal. In the precipitation weather, the fluctuation of each radiation flux is unimodal.The average annual surface albedo () is 0.24, which is higher in winter than in summer. There is a linear relationship between surface albedo and soil moisture. (3) The Net radiation (Rnet) dominates the sensible heat in spring and the latent heat in summer. H/Rnet and Gn/Rnet are both positive in a day, H/Rnet and LE/Rnet fluctuate wildly before and after sunrise, and Gn is dominant at night. (4) The energy closure is manifested as summer > winter > Autumn > spring, and the energy closure is good throughout the year.

Beryllium ten production and relative paleointensity for the past 1.2 million years

Composite curves of relative paleointensity document the evolution of the geomagnetic field intensity during the past 1.2 Million years. Several records of production of 10Be cosmogenic isotope from the 10Be/9Be ratio (referred to as Be-ratio) covering this period have also been acquired. We add here new 10Be records to the database and produce a first composite curve of beryllium production (Be-1200) for the past 1.2 Myr. We compare Be-1200 with Sint-2000 (Valet et al., 2005) and PISO-1500 (Channell et al., 2009) paleointensity curves. The three curves show similar patterns, but frequently different amplitudes. The variations in dipole moment values derived from the Sint-2000 and PISO-1500 relative paleointensity composite curves were then confronted with the geomagnetic dipole moment record derived from the Be-1200 record. The predicted amplitudes of dipole moment loss during geomagnetic excursions reconstructed from the measured in the Be-1200 record are generally compatible with those deduced from SINT-2000 and PISO-1500. More specifically, the three datasets indicate very low field intensities during the Laschamp, that are consistent with the existence of reverse directions, and to a lesser extent during other events (Iceland basin, Calabrian Ridge/West Eifel events). The two paleointensity curves show a decrease in field intensity of at least 80–90% during the reversals. The Be- derived dipole moment decreases meet the predictions for the Brunhes/Matuyama transition, but are significantly smaller than expected for the two Jaramillo transitions. Such limited variability may result from the impact of environmental factors on the Be ratios, as suggested in a previous study of the last reversal (Savranskaia et al., 2021). This comparative study of 10Be records and relative paleointensity records reveals that, in particular cases, Be ratio records can underestimate the amplitude of virtual geomagnetic dipole variation. With their respective strengths and weakness, these two approaches provide similar first-order patterns relevant to the common control by the geomagnetic moment variation.

Geophysical effects caused by the bolide fall on September 02, 2023 (Turkey)

We present the results of instrumental observations of acoustic oscillations, geomagnetic variations and variations of the atmospheric electric field during the fall and explosive destruction of the bolide in the southeast of Turkey on September 02, 2023. It is shown that the destruction of the bolide under the action of aerodynamic forces, which occurred in three stages, was accompanied by an acoustic signal of a characteristic shape and manifested in variations of the magnetic and electric fields in the near-surface layer atmosphere. The total energy of the event, estimated by the acoustic effect, was ~ 9×1012 J, which corresponds to about 2.15 kt in TNT equivalent. The maximum amplitude of geomagnetic variations caused by the explosion of the bolide ranged from 0.2 to 2.1 nT depending on the distance. At the same time, the amplitude of variations of the vertical component of the atmospheric electric field at the Mikhnevo observatory (distance ~1900 km) was ~70 V/m. The ionospheric effect of the event under consideration is demonstrated in the form of variations of the critical frequency f0F2 obtained as a result of processing ionograms of height-frequency sounding of the ionosphere at the Rome station.

Resonant Forcing by Solar Declination of Rossby Waves at the Tropopause and Implications in Extreme Precipitation Events and Heat Waves—Part 2: Case Studies, Projections in the Context of Climate Change

Based on the properties of Rossby waves at the tropopause resonantly forced by solar declination in harmonic modes, which was the subject of a first article, case studies of heatwaves and extreme precipitation events are presented. They clearly demonstrate that extreme events only form under specific patterns of the amplitude of the speed of modulated airflows of Rossby waves at the tropopause, in particular period ranges. This remains true even if extreme events appear as compound events where chaos and timing are crucial. Extreme events are favored when modulated cold and warm airflows result in a dual cyclone-anticyclone system, i.e., the association of two joint vortices of opposite signs. They reverse over a period of the dominant harmonic mode in spatial and temporal coherence with the modulated airflow speed pattern. This key role could result from a transfer of humid/dry air between the two vortices during the inversion of the dual system. Finally, focusing on the two period ranges 17.1–34.2 and 8.56–17.1 days corresponding to 1/16- and 1/32-year period harmonic modes, projections of the amplitude of wind speed at 250 mb, geopotential height at 500 mb, ground air temperature, and precipitation rate are performed by extrapolating their amplitude observed from January 1979 to March 2024. Projected amplitudes are regionalized on a global scale for warmest and coldest half-years, referring to extratropical latitudes. Causal relationships are established between the projected amplitudes of modulated airflow speed and those of ground air temperature and precipitation rate, whether they increase or decrease. The increase in the amplitude of modulated airflow speed of polar vortices induces their latitudinal extension. This produces a tightening of Rossby waves embedded in the polar and subtropical jet streams. In the context of climate change, this has the effect of increasing the efficiency of the resonant forcing of Rossby waves from the solar declination, the optimum of which is located at mid-latitudes. Hence the increased or decreased vulnerability to heatwaves or extreme precipitation events of some regions. Europe and western Asia are particularly affected, which is due to increased activity of the Arctic polar vortex between longitudes 20° W and 40° E. This is likely a consequence of melting ice and changing albedo, which appears to amplify the amplitude of variation in the period range 17.1–34.2 days of poleward circulation at the tropopause of the Arctic polar cell.

Evaluating solar-like behavior in turbulent alpha and Babcock-Leighton mechanisms using non-kinematic nonlinear flux-transport solar dynamos.

In this study, we simulate 30,000years of solar activity using turbulent-alpha (TA) and Babcock-Leighton (BL) mechanisms in a non-kinematic, nonlinear mean field flux-transport solar dynamo model. We evaluate their performances against observational data from proxies, like C, and direct solar observations. Both the TA and BL dynamos generate Schwabe-like variations, with the TA dynamo also generating periods that can be related to the QBOs and the Gleissberg cycle. The TA dynamo spends 13.3% (12.2%) of its time in a grand minimum (maximum) state, closely match the historical solar activity reconstructions from proxy records, while the BL dynamo underperforms. For the TA dynamo, the Schwabe cycle length variations during grand minima and the latitudinal and radial dependencies of the amplitude of variations both in Schwabe and QBO timescales align well with C data and solar observations, whereas the BL dynamo fails to reproduce these features.

Validation of the English-language version of the Morningness-Eveningness-Stability-Scale-improved (MESSi), and comparison with a measure of sleep inertia

ABSTRACT The Morningness-Eveningness-Stability-Scale-improved (MESSi) assesses three components of circadian functioning: Morning Affect (time to fully awaken), Eveningness (orientation/preference for evening activity), and Distinctness (amplitude of diurnal variations in functioning). Following the original German version, translations of the MESSi (including Spanish, Turkish, and Chinese) have been validated, but validity evidence for the English-language version has been lacking. The current study tested the factor structure, internal consistency, and predicted correlations of the English-language MESSi. A sample of 600 adults from an online recruitment platform (aged 18–78, mean = 41.31, SD = 13.149) completed an online survey including the MESSi, reduced Morningness-Eveningness Questionnaire (rMEQ), Sleep Inertia Questionnaire (SIQ), and measures of personality and depressive symptoms. Exploratory factor analysis exactly reproduced the three-component structure of Morning Affect (MA), Eveningness, and Distinctness, with all items loading strongly on their respective component. Confirmatory factor analysis of this structure showed acceptable fit. The three subscales showed good internal consistency and replicated previously reported correlations with depressive symptoms, sleep inertia, sleep quality, and personality. Further factor analysis combining the items of the MESSi, rMEQ, and SIQ replicated a previously found seven-factor structure: Cognitive, Emotional, and Physiological sleep inertia (SI), Responses to SI (including one MA item); Duration of SI (one SIQ item, 3/5 MA items); Morningness-Eveningness (MESSi Eveningness items, plus 3/5 rMEQ items); Distinctness (5/5 MESSi items). In conclusion, the English-language MESSi shows sound psychometric properties, but Morning Affect may be more suitably characterised as a measure of sleep inertia duration, rather than morningness preference.

Some Nutritional Value Aspects of Barley and Oat and Their Impact in Human Nutrition and Healthy Life.

Nowadays, there is a general concern regarding the increasing global talk about functional foods that respond to our demands and needs as consumers in order to maintain health and body weight through a correctly balanced diet. Cereals are key elements of nutrition and a healthy diet, and they also play a significant role in health promotion due to the useful nutrient content. Therefore, this work aims to identify barley and oat genotypes suitable for human nutrition and to achieve practical results for their widespread use in preventing or treating certain chronic diseases by analyzing the nutritional and physical properties of 52 genotypes of oat and barley conserved in Suceava Gene Bank, Romania. The first part of this manuscript is the presentation of these accessions and the evaluation of their most important properties. For oat and barley cultivars, detailed processing was carried out, involving the computation of variation amplitude, coefficients of correlation and cluster analyses, both for biochemical (protein, lysine and tryptophan contents) and physical (test weight and seed weight) properties. The results indicated high variability between oat and barley varieties. Thus, according to the results, the 26 varieties of oat exhibited almost double the content of lysine compared to barley seeds, while tryptophan had higher values in barley than in oat seeds. Overall, both species play an essential role in human nutrition, barley being important because of its high protein content and higher productivity compared to oats, which, although not as productive, have better quality seeds due to their higher lysine content. The results presented are not only of scientific interest but also have practical implications for agriculture, food safety, nutrition and human health. The documented information will facilitate new studies needed to contribute to improving human nutrition and health.

Orbital lifetime design and optimization of CORBES based on lunisolar perturbation

In order to design the orbit for the COntellation of Radiation BElt Survey(CORBES) mission orbit that meets the mission requirements and deorbit constraints, this paper proposed a universal method to design optimal orbital parameters for Highly Elliptic Orbit(HEO). The impact of lunisolar perturbation on perigee altitude is evident, and once a portion of the orbital parameters is determined, the mathematical relationship between the amplitude of the long-period variation in perigee (referred to as “perigee variation”) and the orbital parameters to be designed can be described. The perigee variation exhibits a significant correlation with the orbital lifetime. The initial optimization of orbit parameters is conducted by considering the correlation between lunisolar perturbations and orbital lifetime. Based on this, the orbital parameter RAAN is designed using an improved Decimal Ant Colony Optimization(DACO), and the corresponding launch window is given. The simulation results and comparisons with previous methods validate the effectiveness and efficiency of the initial optimization and the improved DACO in providing optimal feasible solutions, taking into account the law of lunisolar perturbation on orbital lifetime. This method can be well applied to design and estimate the lifetime of orbits dominated by lunisolar perturbation, such as HEO and Geostationary Transfer Orbit(GTO).

KM UMa: An Active Short-period Detached Eclipsing Binary in a Hierarchical Quadruple System

Abstract The first detailed photometric and spectroscopic analysis of the G-type eclipsing binary KM UMa is presented, which indicates that the system is a short-period detached eclipsing binary. The radial velocity curves were calculated using the cross-correlation function method based on Large Sky Area Multi-Object Fiber Spectroscopic Telescope, Sloan Digital Sky Survey, and our observations, which determined the mass ratio as q = 0.45 (±0.04). Based on the light curves from the Transiting Exoplanet Survey Satellite, other survey data, and our multiband observations, the positive and negative O’Connell effects have been detected evolving gradually and alternately over the last 20 yr, which can be explained by the presence of spots on the primary component. A superflare event was detected in the SuperWASP data on 2007 February 28, further indicating that KM UMa is a very active system. We calculated its energy to be 5 × 1034 erg by assuming it occurred on the primary star. Utilizing hundreds of medium-resolution spectra and one low-resolution spectrum, the equivalent width variations of the H α line were calculated, indicating the presence of a 5.21 (±0.67) yr magnetic activity cycle. The orbital period variations were analyzed using the O–C method, detecting a long-term decrease superimposed with a periodic variation. The amplitude of the cyclic variation is 0.01124 (±0.00004) day, with a period of 33.66 (±0.0012) yr, which exceeds the 5.21 yr activity cycle, suggesting that this is more likely attributable to the light travel time effect of a third body. Simultaneously, a visual companion has been detected based on the Gaia astrometric data, indicating that KM UMa is actually in a 2+1+1 hierarchical quadruple system.

3D modeling for effect of tool eccentricity on coupled thermal and material flow characteristics during friction stir welding

A novel three-dimensional numerical model is proposed to investigate the effect of tool eccentricity on the coupled thermal and material flow characteristics in friction stir welding (FSW) process. An asymmetrical boundary condition at the tool−workpiece interface, and the dynamic mesh technique are both employed for the consideration of the tool eccentricity during tool rotating. It is found that tool eccentricity induces the periodical variation of the heat densities both at the tool−workpiece interface and inside the shear layer, but the fluctuation amplitudes of the heat density variations are limited. However, it is demonstrated that tool eccentricity results in significant variation of the material flow behavior in one tool rotating period. Moreover, the material velocity variation at the retreating side is particularly important for the formation of the periodic characteristics in FSW. The modeling result is found to be in good agreement with the experimental one.

The YMDB catalog: Young massive detached binaries for the determination of high-precision absolute stellar parameters

Context. Massive stars play a crucial role in the cosmic dynamics and chemical evolution of galaxies. Despite their significance, our understanding of their evolution and properties remains limited. An accurate determination of stellar parameters, such as the mass and radius, is essential for advancing our knowledge. Detached eclipsing binaries (DEBs) are particularly valuable for these determinations due to the minimal interaction between their stellar components, allowing for precise measurements. Aims. This study aims to introduce the Young Massive Detached Binary (YMDB) catalog, designed to address the gap in the high-precision absolute parameter determination for young massive stars. By focusing on DEBs within the spectral range O9-B1, this catalog seeks to provide a reliable database for future astronomical studies and improve our understanding of massive star evolution. Methods. We conducted a photometric analysis of 87 young massive stars in detached eclipsing systems using TESS light curves (LCs) that were processed through a custom pipeline. This analysis involved determining the amplitude of magnitude variations, orbital periods, times of minima, eccentricities, and the presence of apsidal motion and heartbeat phenomena. A thorough literature review was performed to obtain MK spectral classifications. We performed our own spectral classification of 19 systems to support the sample where a new classification was lacking or inconclusive. Results. The analysis identified 20 previously unreported binary systems, with 13 newly recognized as variable stars. Among the 87 stars examined, 30 are confirmed as YMDB members, and 25 are candidates pending spectral classification. The exclusion of the remaining 32 stars is attributed to unsuitable spectral types or their nondetached binary nature. Notable findings include the identification of new LC classifications, eccentricities in 13 systems, and heartbeat phenomena in several targets. Conclusions. The YMDB catalog offers a resource of high-quality LCs and reliable stellar classifications, serving as a valuable tool for the astronomical community.

Measuring the Spot Variability of T Tauri Stars Using Near-infrared Atomic Fe and Molecular OH Lines

As part of the Young Exoplanets Spectroscopic Survey, this study explores the spot variability of 13 T Tauri Stars (TTSs) in the near-infrared H band, using spectra from the Immersion GRating INfrared Spectrometer. By analyzing effective temperature (T eff) sensitive lines of atomic Fe i at ∼1.56259 μm and ∼1.56362 μm, and molecular OH at ∼1.56310 and ∼1.56317 μm, we develop an empirical equivalent width ratio (EWR) relationship for T eff in the range of 3400–5000 K. This relationship allows for precise relative T eff estimates to within tens of Kelvin and demonstrates compatibility with solar metallicity target models. However, discrepancies between observational data and model predictions limit the extension of the T eff–EWR relationship to a broader parameter space. Our study reveals that both classical and weak-line TTSs can exhibit T eff variations exceeding 150 K over a span of 2 yr. The detection of a quarter-phase delay between the EWR and radial velocity phase curves in TTSs indicates spot-driven signals. A phase delay of 0.06 ± 0.13 for CI Tau, however, suggests additional dynamics, potentially caused by planetary interaction, inferred from a posited 1:1 commensurability between the rotation period and orbital period. Moreover, a positive correlation between T eff variation amplitude and stellar inclination angle supports the existence of high-latitude spots on TTSs, further enriching our understanding of stellar surface activity in young stars.

Modeling the Effects of Temperature and Limiting Nutrients on the Competition of an Invasive Floating Plant, Pontederia crassipes, with Submersed Vegetation in a Shallow Lake.

The potential for a non-native plant species to invade a new habitat depends on broadscale factors such as climate, local factors such as nutrient availability, and the biotic community of the habitat into which the plant species is introduced. We developed a spatially explicit model to assess the risk of expansion of a floating invasive aquatic plant species (FAV), the water hyacinth (Pontederia crassipes), an invader in the United States, beyond its present range. Our model used known data on growth rates and competition with a native submersed aquatic macrophyte (SAV). In particular, the model simulated an invasion into a habitat with a mean annual temperature different from its own growth optimum, in which we also simulated seasonal fluctuations in temperature. Twenty different nutrient concentrations and eight different temperature scenarios, with different mean annual amplitudes of seasonal temperature variation around the mean of the invaded habitat, were simulated. In each case, the ability of the water hyacinth to invade and either exclude or coexist with the native vegetation was determined. As the temperature pattern was changed from tropical towards increasingly cooler temperate levels, the competitive advantage shifted from the tropical FAV to the more temperate SAV, with a wide range in which coexistence occurred. High nutrient concentrations allowed the coexistence of FAV, even at cooler annual temperatures. But even at the highest nutrient concentrations in the model, the FAV was unlikely to persist under the current climates of latitudes in the Southeastern United States above that of Northern Alabama. This result may have some implications for where control efforts need to be concentrated.

Improvement of wire marks on the surface of Si3N4 ceramics cut by diamond wire saw

The presence of wavy wire marks on the cut surface of silicon nitride (Si3N4) ceramics reduces the mechanical properties of the slices and increases the workload of subsequent grinding and polishing processes. To improve the wire marks, a workpiece reciprocating movement-assisted diamond wire sawing (RMA-DWS) technology is proposed in this paper. While diamond wire sawing the Si3N4 ceramics, the workpiece is moved back and forth in the direction of the saw wire movement to assist in sawing. Single factor and orthogonal experiments were carried out to analyze the characteristics of the surface created by this sawing technology. The effects of workpiece reciprocating movement distance, workpiece reciprocating movement speed, saw wire speed and feed speed on the sawn surface morphology, surface roughness Ra and wire marks PV value, as well as the primary and secondary relationships of the effects, were investigated. And the optimal parameter combinations were explored. The results show that within the range of process parameters studied in this paper, the surface morphology of Si3N4 ceramics slices shows a comprehensive effect of material ductility and brittleness removal, the RMA-DWS technology can improve wire marks on the slice surface. Surface wire marks PV value can be reduced by increasing the workpiece reciprocating movement distance and saw wire speed, reducing the feed speed, while increasing the reciprocating movement speed of the workpiece, the PV value shows a trend of first decreasing and then increasing. The variation amplitude of surface roughness Ra value is not significant, and the variation trend is roughly similar to the change trend of PV value. It was determined that the experiment with the process parameters combination of 0.1 m/min feed speed, 90 mm workpiece reciprocating distance, 15 mm/s workpiece reciprocating speed and 1400 m/min saw wire speed yielded the optimal result, significantly improving the wire marks of the sliced surface. The results of this paper provide ideas for the development of sawing wire marks improvement technology.