Large Mass Ratio Research Articles

Analyzing JWST/NIRSpec Hydrogen Line Detections at TWA 27B: Constraining Accretion Properties and Geometry

Hydrogen lines from forming planets are crucial for understanding planet formation. However, the number of planetary hydrogen line detections is still limited. Recent JWST/NIRSpec observations have detected Paschen and Brackett hydrogen lines at TWA 27 B (2M1207b). Although classified as a planetary- mass companison (PMC) rather than a planet due to its large mass ratio to the central star, TWA 27 B’s hydrogen line emissions are expected to be same as the planetary one, given its small mass (≈5M J). We aim to constrain the accretion properties and accretion geometry of TWA 27 B, contributing to our understanding of hydrogen-line emission mechanisms common to both PMCs and planets. We conduct spectral fitting of four bright hydrogen lines (Pa-α, Pa-β, Pa-γ, Pa-δ) with an accretion-shock emission model tailored for forming planets. We estimate the mass accretion rate at Ṁ≈3×10−9MJyr−1 with our fiducial parameters, though this is subject to an uncertainty of up to factor of ten. Our analysis also indicates a dense accretion flow, n ≳ 1013 cm−3 just before the shock, implying a small accretion-shock filling factor f f on the planetary surface (f f ≲ 5 × 10−4). This finding suggests that magnetospheric accretion is occurring at TWA 27 B. Additionally, we carry out a comparative analysis of hydrogen-line emission color to identify the emission mechanism, but the associated uncertainties proved too large for definitive conclusions. This underscores the need for further high-precision observational studies to elucidate these emission mechanisms fully.

Influence of the peel on online detecting soluble solids content of pomelo using Vis-NIR spectroscopy coupled with chemometric analysis

The application of Visible-near infrared spectroscopy (Vis-NIRs) to internal quality detection of pomelo with large sizes and thick peels is still challenging. Considering that the peel has a large mass ratio in pomelo and a great added value in industrial processing, a postharvest processing mode of grading after peeling without affecting consumption of pomelos may be an approach to avoid adverse influence of peel on soluble solids content (SSC) evaluation. In this study, we investigated the performance variation of Vis-NIRs for SSC online determination of pomelos with and without peel for the first time. An online detection system for pomelo spectra acquisition was developed, and the spectral characteristic difference of the intact and peeled pomelos was analyzed. Subsequently, the performance of calibration models was gradually improved and comparatively analyzed by various spectral processing and wavelength selection methods. Furthermore, convolutional neural network (CNN) was utilized to explore its ability for feature extraction. The results showed that combined with standard normal variate (SNV) and second order detrending and changeable-size moving window algorithms, the partial least squares regression (PLSR) model using spectra of peeled pomelos achieved the best prediction results. Specifically, the model attained a determination coefficient of prediction (Rp2) of 0.88, a root mean square error of prediction (RMSEP) of 0.294%, and a residual predictive deviation (RPD) value of 2.57. This study demonstrates that the peel has a significantly negative effect on the prediction performance and the CNN could be an alternative to conventional PLSR method. Our work may open new avenues for the internal quality assessment of agro-products with complex tissue structure.

Multi-species modeling in the particle-based ellipsoidal statistical Bhatnagar-Gross-Krook method including internal degrees of freedom

The implementation of the ellipsoidal statistical Bhatnagar-Gross-Krook (ESBGK) method in the open-source particle code PICLas is extended for multi-species modeling of polyatomic molecules, including internal energies with multiple vibrational degrees of freedom. For this, the models of Mathiaud et al. [1], Pfeiffer [2] and Brull [3,4] are combined. In order to determine the transport coefficients of the gas mixture, Wilke's mixing rules and collision integrals are compared. The implementation is verified with simulation test cases of a supersonic Couette flow as well as a hypersonic flow around a 70° blunted cone. The solutions of the ESBGK method are compared to the Direct Simulation Monte Carlo (DSMC) method to assess the accuracy, where overall good agreement is achieved. In general, collision integrals should be preferred for the determination of the transport coefficients, since the results using Wilke's mixing rules show larger deviations in particular for large mass ratios. Considering the computational efficiency of the methods, a considerable reduction in computational time is possible with the ESBGK model.

Optimization of column-in-column system based on non-conventional TMD concept

Previous studies showed that the non-conventional tuned mass damper (TMD) with large mass ratio outperforms the traditional one in respect to the structural vibration control efficiency and robustness. The authors recently proposed a novel control system based on the non-conventional TMD concept, namely the column-in-column (CIC) system, which was composed of a primary column, a secondary column and a series of interconnected springs/dashpots. In this novel system, the secondary column connected to the primary one with springs/dashpots could act as a large TMD to attenuate adverse vibration of the primary structure, and its control effectiveness was preliminarily verified through numerical investigations. However, the control robustness was found not sufficient based on the existing optimal formulae in the literature for CIC optimization. This paper presents a new design method for optimizing the CIC system for better harnessing its control effectiveness and robustness in reducing structural response. The CIC system consists of two columns with distributed mass and uniform flexural rigidity, connected by springs along the column height. The effective modal mass and modal stiffness of a specific vibration mode of the system can be straightforwardly calculated by using the Euler-Bernoulli beam theory. Considering the fundamental vibration mode of the system as the target response mode for vibration control, the multiple degree-of-freedom (DOF) CIC is simplified into a two DOF with three springs (2DOF3S) structural model, the design parameters, i.e., the optimal tuning frequency ratio and damping ratio of this system are derived to minimize the displacement response of the primary structure. To demonstrate the proposed design method, the effectiveness and robustness of the CIC system in controlling seismic induced structural vibrations are assessed in both the frequency and time domains. Results show that the derived optimum formulae are applicable for optimizing the TMD system with consideration of the distributed mass and deformation of the mass damper, i.e., a column in this study. The optimized CIC system has good control robustness even if the CIC is mistuned with its design parameters deviate from the optimal values by ±50 %. The conventional TMD system with lumped mass as the mass damper is a special case of the proposed CIC system. The optimized CIC system has favorable control efficiency in mitigating the seismic responses of structures with reduction ratios averagely varying within the range of 15 % ∼ 55 % with a probability of 92.67 %. It is concluded that the proposed method is reliable and can be used for the optimum design and control of the CIC system.

Vibration controlling effect of tuned liquid column damper (TLCD) on support structural platform (SSP)

A bidirectional fluid-structure coupling model between tuned liquid column damper (TLCD) and support structural platform (SSP) was developed to study effects of TLCD-SSP mass ratio and tuning ratio on reducing SSP vibration. Laboratory experiments of TLCD interaction with SSP were conducted to validate TLCD-SSP coupling model. Good agreements between numerical results and experimental data are obtained. TLCD/SSP mass ratio increases from 1% to 3%, the maximum amplitude of SSP upper displacement decreases from 43.77% to 78.32%, and the upper acceleration damping rate increases from 43.26% to 77.88%. There is a phase differences between dynamic water pressure offered by sloshing inside TLCD and upper displacement curves, and the damping energy dissipation effect is maximized when the hysteresis phase difference reaches π/2. The larger mass ratio is more effective in suppressing the structural vibration. But it also brings about a fundamental frequency drift. It is advised that the mass ratio of water in TLCD to SSP should be 1.5%, the total mass of water and shell of TLCD should be about 2.5% of the mass of SSP, and the intrinsic frequencies of TLCD and SSP should be tuned the same so that the vibration controlling performance of TLCD can be improved maximally.

Analytical optimization and performance evaluation of non-traditional tuned mass damper for stochastic base excited structures considering dual solutions

Compared with traditional tuned mass damper (TMD), non-traditional tuned mass damper (NTMD) has higher damping efficiency in some conditions. Nevertheless, the analytical optimization problem of NTMD has not been well solved; especially, multiple optimal solutions are not discussed. In this study, the closed-form optimal expressions of the NTMD using tuning stiffness are derived based on H 2 norm optimization. And the vibration mitigation performance of the NTMD is evaluated considering dual-solutions situation subjected to typical ground motion and impulse excitation. Different from solving the unique optimal frequency ratio, there exist two sets of optimal stiffness and damping ratio derived using tuned spring elements for given mass ratio, and the effective mass ratio is also limited as 1/3. The vibration mitigation or isolation performance and robustness of H 2 optimized NTMD with higher stiffness ratio are far superior to NTMD with lower stiffness ratio. NTMD using larger optimal tuning stiffness ratio also can be seen as an optimized form of Maxwell model using additional mass. Hence, using a large stiffness, namely, a large frequency ratio to design NTMD is recommended, which is different from traditional TMD. The case of NTMD with large stiffness can be adopted when the demands of practical engineering are not met using the optimal parameters of small stiffness. And a compromise scheme can also be provided, which are the combination with a larger mass ratio but is less than the maximum limit value 1/3 and a not very large stiffness ratio but is exceeded 0.5 according to demands of practical engineering.

Effects of important characteristics of earthquake ground motions on probabilistic seismic demand assessment of long-span cable-stayed bridges

The uncertainties of earthquake ground motions have the most important effects on seismic responses of bridge structures, especially long-span bridges, because of complex and special dynamic properties. The nonlinear dynamic time-history analysis is conducted for a two-pylon long-span cable-stayed highway bridge by using real earthquake ground motions rationally selected. The correlation between the important characteristics of earthquake ground motions and the probabilistic seismic demand assessment of the cable-stayed bridge reveals that the geometric means and dispersions of response spectra from selected ground motions have very significant effects on mean values, dispersions and probabilistic distributions of seismic demands of long-span bridges. The spectral shape of geometric mean spectra in the period ranges with large cumulative modal mass participation factors that should be well matched to the target spectrum to improve the precision and computational efficiency of probabilistic seismic demand assessment. If earthquake ground motions are rationally selected, response spectral values at the periods with comparatively large modal participation mass ratios or PGA can be used as intensity measures and even provide more precise probabilistic seismic demand assessment than response spectral values at the fundamental periods.

Weakly nonlinear analysis on synchronization and oscillation quenching of coupled mechanical oscillators

Various oscillatory phenomena occur in the world. Because some are associated with abnormal states (e.g. epilepsy), it is important to establish ways to terminate oscillations by external stimuli. However, despite the prior development of techniques for stabilizing unstable oscillations, relatively few studies address the transition from oscillatory to resting state in nonlinear dynamics. This study mainly analyzes the oscillation-quenching of metronomes on a platform as an example of such transitions. To facilitate the analysis, we describe the impulsive force (escapement mechanism) of a metronome by a fifth-order polynomial. By performing both averaging approximation and numerical simulation, we obtain a phase diagram for synchronization and oscillation quenching. We find that quenching occurs when the feedback to the oscillator increases, which will help explore the general principle regarding the state transition from oscillatory to resting state. We also numerically investigate the bifurcation of out-of-phase synchronization and beat-like solution. Despite the simplicity, our model successfully reproduces essential phenomena in interacting mechanical clocks, such as the bistability of in-phase and anti-phase synchrony and oscillation quenching occurring for a large mass ratio between the oscillator and the platform. We believe that our simple model will contribute to future analyses of other dynamics of mechanical clocks.

Improving BC Mixing State and CCN Activity Representation With Machine Learning in the Community Atmosphere Model Version 6 (CAM6)

AbstractRepresenting mixing state of black carbon (BC) is challenging for global climate models (GCMs). The Community Atmosphere Model version 6 (CAM6) with the four‐mode version of the Modal Aerosol Module (MAM4) represents aerosols as fully internal mixtures with uniform composition within each aerosol mode, resulting in high degree of internal mixing of BC with non‐BC species and large mass ratio of coating to BC (RBC, the mass ratio of non‐BC species to BC in BC‐containing particles). To improve BC mixing state representation, we coupled a machine learning (ML) model of BC mixing state index trained on particle‐resolved simulations to the CAM6 with MAM4 (MAM4‐ML). In MAM4‐ML, we use RBC to partition accumulation mode particles into two new modes, BC‐free particles and BC‐containing particles. We adjust RBC to make the modeled BC mixing state index (χmode) match the one predicted by the ML model (χML). On a global average, the mass fraction of BC‐containing particles in accumulation mode decreases from 100% (MAM4‐default) to 48% (MAM4‐ML). The globally averaged χmode decreases from 78% (MAM4‐default) to 63% (MAM4‐ML, 19% reduction) and agrees well with χML (66%). The RBC decreases by 52% for accumulation mode and better agrees with observations. The hygroscopicity drops by 9% for BC‐containing particles in accumulation mode, leading to a 20% reduction in the BC activation fraction. The surface BC concentration increases most (6.9%) in the Arctic, and the BC burden increases by 4%, globally. Our study highlights the application of the ML model for improving key aerosol processes in GCMs.

A benchmark white dwarf–ultracool dwarf wide field binary

ABSTRACT We present the discovery and multiwavelength characterization of VVV J1438-6158 AB, a new field wide-binary system consisting of a $4.6^{+5.5}_{-2.4}~{\rm Gyr}$ and $T_{\rm eff} = 9500\pm 125~\mathrm{ K}$ DA white dwarf (WD) and a $T_{\rm eff} = 2400\pm 50~\mathrm{ K}$ M8 ultracool dwarf (UCD). The projected separation of the system is $a = 1236.73~{\rm au}$ ($\sim 13.8\, \mathrm{ arcsec}$), and although along the line of sight towards the Scorpius–Centaurus stellar association, VVV J1438-6158 AB is likely to be a field star, from a kinematic 6D probabilistic analysis. We estimated the physical and dynamical parameters of both components via interpolations with theoretical models and evolutionary tracks, which allowed us to retrieve a mass of $0.62\pm 0.18~\mathrm{ M}_\odot$ for the WD, and a mass of $98.5\pm 6.2~\mathrm{ M}_{\rm Jup}$ ($\sim 0.094\pm 0.006~\mathrm{ M}_\odot$) for the UCD. The radii of the two components were also estimated at $0.01309\pm 0.0003~\mathrm{ R}_{\odot }$ and $1.22\pm 0.05~\mathrm{ R}_{\rm Jup}$, respectively. VVV J1438-6158 AB stands out as a benchmark system for comprehending the evolution of WDs and low-mass companions given its status as one of the most widely separated WD+UCD systems known to date, which likely indicates that both components may have evolved independently of each other, and also being characterized by a large-mass ratio ($q = 0.15\pm 0.04$), which likely indicates a formation pathway similar to that of stellar binary systems.

A Unified Picture of Short and Long Gamma-Ray Bursts from Compact Binary Mergers

The recent detections of the ∼10 s long γ-ray bursts (GRBs) 211211A and 230307A followed by softer temporally extended emission (EE) and kilonovae point to a new GRB class. Using state-of-the-art first-principles simulations, we introduce a unifying theoretical framework that connects binary neutron star (BNS) and black hole–NS (BH–NS) merger populations with the fundamental physics governing compact binary GRBs (cbGRBs). For binaries with large total masses, M tot ≳ 2.8 M ⊙, the compact remnant created by the merger promptly collapses into a BH surrounded by an accretion disk. The duration of the pre-magnetically arrested disk (MAD) phase sets the duration of the roughly constant power cbGRB and could be influenced by the disk mass, M d . We show that massive disks (M d ≳ 0.1 M ⊙), which form for large binary mass ratios q ≳ 1.2 in BNS or q ≲ 3 in BH–NS mergers, inevitably produce 211211A-like long cbGRBs. Once the disk becomes MAD, the jet power drops with the mass accretion rate as , establishing the EE decay. Two scenarios are plausible for short cbGRBs. They can be powered by BHs with less massive disks, which form for other q values. Alternatively, for binaries with M tot ≲ 2.8 M ⊙, mergers should go through a hypermassive NS (HMNS) phase, as inferred for GW170817. Magnetized outflows from such HMNSs, which typically live for ≲1 s, offer an alternative progenitor for short cbGRBs. The first scenario is challenged by the bimodal GRB duration distribution and the fact that the Galactic BNS population peaks at sufficiently low masses that most mergers should go through an HMNS phase.

Vibration reduction performance for the novel grounded inerter-based dynamic vibration absorber controlling a primary structure under random excitation

This paper investigates the control performance of a novel grounded inerter-based dynamic vibration absorber (GI-DVA) for random vibration reduction. First, the dynamics equations of the coupled system are written and the transfer function is obtained based on the Laplace transform. Then, assuming that the primary structure is under random white noise excitation, the displacement variance of the primary structure is calculated based on the exact definition of the H2 norm, by solving the Lyapunov equation. By imposing that the partial derivatives of the response variance of the primary structure with respect to the system parameters are simultaneously equal to zero, the optimum design values of the H2 optimized GI-DVA were derived numerically for given different mass ratio. It can be found that the optimal design parameters as the inerter-to-mass ratio, the stiffness ratio and the damping ratio increase, while the frequency ratio decreases with the increase in the mass ratio. Under the optimal conditions, the response analysis showed that the primary structure response controlled by the H2 optimized GI-DVA can decrease with the increase in the mass ratio, but is less sensitive to large mass ratios, and can be robust to the mistuning on the optimum design parameters. Then, the control performance evaluation is first performed in the frequency domain, which reveal that the dynamic response reduction capacity of the H2 optimized GI-DVA are significantly 62% and 48% superior to the H2 optimized classic DVA (CDVA) and high-performance passive nontraditional inerter-based DVA (NIDVA-C4), respectively. Furthermore, for the root mean square response evaluation (H2 performance), the H2 optimized GI-DVA can provide significantly H2 performance 58% and 50% than the H2 optimized CDVA and NIDVA-C4, respectively. To obtain more realistic results, the time domain simulation is performed, which showed that the GI-DVA can provide significantly performance for random vibration reduction.

Inerter location effect on the generalized tuned mass damper inerter control

This paper investigates the inerter location effect on the generalized tuned mass damper inerter (TMDI) control, in which the end of the inerter is located at any position of the primary structure. A good understanding of the inerter location effect can help us achieve an optimal generalized TMDI control. Two mass ratios weighting the mass amplification effect and negative stiffness effect are defined to understand the inerter location effect. Based on the two mass ratios, the relationship between the TMD and generalized TMDI is established, the analytical solution of the optimal tuning frequency is derived, and a high-accuracy prediction equation judging whether the generalized TMDI performs better than the TMD is proposed. Finally, numerical analyses on a 76-story high building equipped with TMD and generalized TMDI are performed. The results show that the the generalized TMDI in fact is a large mass ratio TMD with a frequency-dependent stiffness, the generalized TMDI with larger inertance and smaller physical mass has more inerter location choices, and the damping ratio of the primary structure has no influence on the critical inerter location. The generalized TMDI considering the inerter location effect has better control effect than the TMD in suppressing both the wind-induced vibration and earthquake-induced vibration. The mean reduction ratios of peak floor accelerations for the TMD and TMDI controls are 60.53% and 54.5% under the wind-induced force excitation, and those of maximum floor drift ratios for the TMD and TMDI controls are 94.32%, 87.56% under the earthquake excitation.

Universal many-body properties of one-dimensional mass-imbalanced highly polarized Fermi gases

We investigate the universal properties of mass-imbalanced highly polarized Fermi gases in one-dimensional scenarios. By treating the mass ratio as a parameter, we delve into the binding energy, quasiparticle residue, and correlation functions of the systems. We provide a thorough momentum distribution for impurities and spin-up atoms within the Fermi sea. When the impurity mass is infinite, we discover that the quasiparticle residue approaches to zero and the systems exhibit the signature of the Anderson orthogonality catastrophe in strong coupling regime. We observe an increase in Tan contact under large mass ratios and study density correlations by applying Fourier transform. Crucially, we demonstrate the existence of the molecular state in one-dimensional polaron system with strong attractive interactions, unlike previous conclusions.

Evidence and physical mechanism for vortex-induced vibration of a bluff body without an afterbody

Afterbody—the portion of the body downstream of shear layer separation points—was believed to be essential for the vortex-induced vibration (VIV) of a bluff body. A recent study by Zhao et al. [“Flow-induced vibration of D-section cylinders: An afterbody is not essential for vortex-induced vibration,” J. Fluid Mech. 851, 317–343 (2018)] made an important forward to demonstrate “an afterbody is not required for VIV” through water tunnel experiments of a reversed D-section prism. However, our direct numerical visualization showed that the shear layer separation appears at the curved front surface of the reversed D-section prism, leaving a part of an afterbody, which makes their evidence questionable. The present study aims to provide solid numerical and experimental evidence for the statement “an afterbody is not required for VIV” using an elastically mounted triangular prism with one vertex pointing upstream. By conducting two- and three-dimensional direct numerical simulations and water tunnel experiments, we verified that even without an afterbody, the triangular prism can freely vibrate. Furthermore, the physical mechanisms for the excitation and sustenance of the VIV of a bluff body without afterbody are investigated. By decomposing the lift force into the pressure and viscous parts, we discover that the vibration of a bluff body without an afterbody is excited and sustained by the viscous lift component acting on the forebody, in contrast to the VIV of a circular cylinder with an afterbody in which the viscous component always results in energy dissipation and damps the vibration. Some recent experiments showed that the VIV does not occur for the triangular prism. The reasons are also explained: the absence of VIV is due to either high-Re or large mass ratio (structural damping) but not owing to the lack of an afterbody.

On the behaviour of spin–orbit connection of exoplanets

Star–planet interactions play, among other things, a crucial role in planetary orbital configurations by circularizing orbits, aligning the star and planet spin and synchronizing stellar rotation with orbital motions. This is especially true for innermost giant planets, which can be schematized as binary systems with a very large mass ratio. Despite a few examples where spin–orbit synchronization has been obtained, there is no demographic study on synchronous regimes in those systems yet. Here we use a sample of 1,055 stars with innermost planet companions to show the existence of three observational loci of star–planet synchronization regimes. Two of them have dominant fractions of subsynchronous and supersynchronous star–planet systems, and a third less populated regime of potentially synchronized systems. No synchronous star–planet system with a period higher than 40 days has been detected yet. This landscape is different from eclipsing binary systems, most of which are synchronized. We suggest that planets in a stable asynchronous spin state belonging to star–planet systems in a supersynchronized regime offer the most favourable conditions for habitability. An analysis of 1,055 planets around main sequence stars identifies three subsamples of star–planet synchronization: subsynchronized, dominant for periods shorter than 6.2 days; supersynchronized, for periods longer than 13.5 days; and a transitional regime in between. Synchronized systems are a minority, contrary to eclipsing binaries.

Self-binding of one-dimensional fermionic mixtures with zero-range interspecies attraction

For sufficiently large mass ratios the attractive exchange force caused by a single light atom interacting with a few heavy identical fermions can overcome their Fermi degeneracy pressure and bind them into an N+1N+1 cluster. Here, by using a mean-field approach valid for large NN, we find that N+1N+1 clusters can attract each other and form a self-bound charge density wave, the properties of which we fully characterize. Our work shows that there are no fundamental obstacles for having self-bound states in fermionic mixtures with zero-range interactions.

Orbital evolution of binaries in circumbinary discs

ABSTRACT We present the to-date largest parameter space exploration of binaries in circumbinary discs (CBDs), deriving orbital evolution prescriptions for eccentric, unequal mass binaries from our suite of hydrodynamic simulations. In all cases, binary eccentricities evolve towards steady state values that increase with mass ratio, and saturate at an equilibrium eccentricity eb,eq ∼ 0.5 in the large mass ratio regime, in line with resonant theory. For binaries accreting at their combined Eddington limit, a steady state eccentricity can be achieved within a few megayears. Once at their steady state eccentricities, binaries with qb ≳ 0.3 evolve towards coalescence, while lower mass ratio systems expand due to CBD torques. We discuss implications for population studies of massive black hole binaries, protostars in binary systems, and post-common envelope binaries observed by ground-based gravitational wave detectors.

Optimal design of a parallel assembling robot with large payload-to-mass ratio

• Kinematic, stiffness and mass modeling of a parallel assembling robot is conducted. • A meta modeling method is proposed to consider topological variation of the base. • Optimal design towards large payload-to mass ratio is carried out. • Different objective arrangements are discussed based on Pareto-based optimizations. Assembly in a confined space, such as the cabin of an aircraft or train, demands the assembling device to be with compact structure, satisfactory kinematics and excellent load carrying capability. A six degree-of-freedom (DoF) parallel robot is proposed and designed for such assembling tasks in this paper. Specially, internal structure changes introduced by topology optimization are considered and the multi-objective optimization reaching large load-to-mass ratio is implemented. First, external dimensions of the base and the ratio of the remaining volume to the complete volume are the inputs. Once a set of input variables are given, the topology optimization will be performed by FEA software to form the structure of the base. The stiffness and mass of the base, being the outputs, are obtained numerically by software. Then, the meta models are established by the response surface model (RSM) method. On this basis, stiffness and mass models of the robot are built by the semi-analytical method. The optimal design is implemented by Pareto-based multi-objective optimization. Different arrangements of the objectives are compared. The results show that kinematic indices on the Pareto fronts are all at a satisfactory level. The optimization having payload-to-mass ratio as objective leads to the optimum with higher stiffness along z -axis and smaller mass. The design 6-DoF parallel assembly robot can carry up to 42.06 kg loads while the mass is only 12.002 kg.

Photometric binaries, mass functions, and structural parameters of 78 Galactic open clusters

Context. Binary stars play a crucial role in our understanding of the formation and evolution of star clusters and their stellar populations. Aims. We use Gaia Data Release 3 to homogeneously analyze 78 Galactic open clusters and the unresolved binary systems they host, each composed of two main sequence (MS) stars. Methods. We first investigated the structural parameters of these clusters, such as the core radius and the central density, and determined the cluster mass function (MF) and total mass by interpolating the density profile of each cluster. We measured the fraction of binaries with a large mass ratio and the fraction of blue straggler stars (BSSs), and finally investigated possible connections between the populations of binary stars and BSSs with the main parameters of the host cluster. Results. Remarkably, we find that the MFs of 78 analyzed open clusters follow a similar trend and are well reproduced by two single power-law functions, with a change in slope around masses of 1 M⊙. The fraction of binary stars ranges from ∼15% to more than ∼60% without significant correlation with the mass and the age of the host cluster. Moreover, we detect hints of a correlation between the total fraction of binary stars and the central density of the host cluster. We compared the fraction of binary stars with that of BSSs, finding that clusters with high and low central density exhibit different trends. The fraction of binaries does not significantly change with the mass of the primary star and the mass ratio. The radial distribution of binary stars depends on cluster age. The binaries of clusters younger than ∼800 Myr typically show a flat radial distribution, with some hints of a double peak. In contrast, the binaries of the remaining clusters are more centrally concentrated than the single stars, which is similar to what is observed in globular clusters.