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Aiming at the weight problem of a light electric commercial vehicle, a lightweight optimization idea is proposed, which is based on the design of the frame structure made of TC4 titanium alloy. Taken the strength, stiffness and stability of the longitudinal beam as the boundary constraints, and the minimum mass of the frame longitudinal beam as the objective function, the mathematical model was established, and the longitudinal beam size was optimized by ant colony algorithm. The influence of different materials on the strength and stiffness of the frame was analyzed from the bending and torsion conditions. The finite element model of the frame before and after optimization was established in ANSYS, and the static conditions before and after optimization were compared and analyzed. The results show that: under the constraint conditions, the frame weight of TC4 material is reduced from 122kg before optimization to 103kg after optimization, which is 15.5% less than that before optimization, and the stress and deformation of the optimized frame meet the service conditions, which has great advantages for reducing the vehicle weight and realizing the lightweight purpose.

In this article, a novel re-entrant octagonal honeycomb (ROH) with negative Poisson's ratio (NPR) configuration is proposed owing to its superior energy absorption and lightweight design performances. Regarding the effects of adjacent unit cells, a mechanics-based homogenization approach is put forward and employed to derive static mechanical properties including elastic modulus and Poisson's ratio of two-dimensional (2D) and three-dimensional (3D) ROHs under axial loading. Based on above, the predominant compression failure mode is explored. Then, the static mechanical properties and finite element model of ROH are validated by experiment and demonstrate high accuracy. Subsequently, to obtain dynamic responses of the ROH under dynamic impact loading, the relations among dynamic plateau stress and quasi-static plateau stress, initial density, dense strain and impact velocities are established under the conditions of mass conservation and momentum theorem based on one-dimensional shock wave theory and ideal rigid-perfectly plastic material model. Besides, dynamic energy absorption models of the ROH under dynamic loading are acquired in consideration of the effects of impact velocities on dense strain, the results show that theoretical models agree quite well with simulation results. On this basis, the application of ROH on automotive energy absorber is studied with the purpose of acquiring superior energy absorption and satisfying lightweight requirements simultaneously. Based on the decoupling thought of stiffness and pedestrian protection, a new design method of carbon fiber reinforced plastics (CFRP) hood with ROH is put forward in consideration of energy absorption and lightweight requirements. Of this, ROH is regarded as sandwich structure to meet the demands of energy absorption, CFRP plates are treated as outer and inner skins to satisfy the needs of stiffness. Firstly, multi-objective optimization models are set up under the constraints of reasonable structural parameters and negative Poisson’s ratio. Then, the NSGA-Ⅱalgorithm is adopted to achieve the optimal Pareto fronts with the targets for maximum unit mass energy absorption and minimum density. Afterwards, the optimization on thicknesses of CFRP layers is carried out to achieve minimum mass under the constraint conditions that the static stiffness of CFRP hood is larger than that of steel hood. In addition, the layering sequence of inner and lower skins are also optimized. Finally, improved overall stiffness, optimized HIC values and similar lightweight space of CFRP hood with ROH are achieved in comparisons with CFRP hood without ROH. Compared with steel hood, the pedestrian protection performance of CFRP hood with ROH is greatly enhanced, 1st free mode increases by 33.9%, and torsional stiffness and bending stiffness increase by 23.1% and 30.8%, respectively. While the weight decreases by 40.1%. The results indicate that the CFRP hood with ROH presents outstanding advantages of pedestrian protection and lightweight design in terms of HIC and stiffness performance.

Many researchers are working in the field of pneumatic slurry transportation, where the rheological parameters involved in the flow. In the present work is a numerical simulation for the study of pressure drop of 30µm particle size of fly ash air mixture flow through a circular pipe was investigated through ANSYS Fluent. The present paper introduces a simplified 3-D Eulerian model along with RNG k-ε turbulent model. It was observed that the pressure drop was maximum for minimum mass flow rate of air and as the mass flow rate increases the pressure drop decreases and it becomes constant at a threshold mass flow rate for this particle size, which qualitatively matches with the experimental results observed by Bansal et al. (2013).

Fractal dimensions can be used to characterize the clustering and lacunarities in density distributions. We use generalized fractal dimensions to study the neutral hydrogen distribution (HI) during the epoch of reionization. Using a semi-numeric model of ionized bubbles to generate the HI field, we calculate the fractal dimensions for length scales $\sim 10 h^{-1}$ cMpc. We find that the HI field displays significant multifractal behaviour and is not consistent with homogeneity at these scales when the mass averaged neutral fraction $\bar{x}_{\rm HI}^M \gtrsim 0.5$. This multifractal nature is driven entirely by the shapes and distribution of the ionized regions. The sensitivity of the fractal dimension to the neutral fraction implies that it can be used for constraining reionization history. We find that the fractal dimension is relatively less sensitive to the value of the minimum mass of ionizing haloes when it is in the range $\sim 10^9 - 10^{10} h^{-1} M_{\odot}$. Interestingly, the fractal dimension is very different when the reionization proceeds inside-out compared to when it is outside-in. Thus the multifractal nature of HI density field at high redshifts can be used to study the nature of reionization., 11 pages, 10 figures, accepted for publication in MNRAS

The purpose of the conducted research was to develop a method for determining parameters of GTE regenerator, which would ensure at the initial stages of designing a minimum mass of the heat exchanger with the assigned values of efficiency. We obtained dependences that establish relationships between the regenerator and the GTE, which allow analyzing the influence of effectiveness and pressure losses in regenerator on the efficiency of GTE and the mass of the regenerator. Relationship between parameters of the regenerator and performance efficiency of regenerative GTE was described by functional dependence, where energy parameters of the regenerator are collected in a single complex. It was established that the magnitude of effectiveness of the regenerator is associated with efficiency by inversely proportional function, and pressure losses – by linear function. Effectiveness of the regenerator is associated with the mass of the heat exchanger and the geometry of heat exchange surface by exponential dependence, and relative pressure losses – by algebraic irrational function. Based on these dependences, the algorithm for selecting rational energy and geometrical parameters of regenerators of GTE was developed. It was found that by selecting rational values of effectiveness of regenerator and pressure losses, it is possible to provide for a significant decrease in mass of the regenerator with a constant value of performance efficiency of GTE. The obtained results of calculations of regenerators of GTE with different structural solutions allow a designer engineer to choose rational values of effectiveness of the regenerator, pressure losses, and initial gas temperature. Comparison of complex regenerative GTE by the mass of regenerator at constant values of performance efficiency was conducted. Based on the analysis of results of calculations, the stage dependence of specific mass of regenerator on the assigned increase in performance efficiency of regenerative GTE was obtained, which gives the possibility to estimate the mass of tubular regenerator at the initial stages of designing. Implementation of the obtained results into the practice of designing regenerative GTE will make it possible to ensure the choice of their rational parameters and to decrease the time of designing.

We present photometric results of the δ Sct star V1162 Ori, which is extensively monitored for a total of 49 nights from mid-December 2014 to early-March 2015. The observations are made with three KMTNet (Korea Microlensing Telescope Network) 1.6 m telescopes installed in Chile, South Africa, and Australia. Multiple frequency analysis is applied to the data and resulted in clear detection of seven frequencies without an alias problem: five known frequencies and two new ones with small amplitudes of 1.2-1.7 mmag. The amplitudes of all but one frequency are significantly different from previous results, confirming the existence of long-term amplitude changes. We examine the variations in pulsation timings of V1162 Ori for about 30 years by using the times of maximum light obtained from our data and collected from the literatures. The O − C (Observed minus Calculated) timing diagram shows a combination of a downward parabolic variation with a period decreasing rate of (1/P)dP/dt = −4.22 × 10 −6 year −1 and a cyclic change with a period of about 2780 days. The most probable explanation for this cyclic variation is the light-travel-time effect caused by an unknown binary companion, which has a minimum mass of 0.69 M ⊙ . V1162 Ori is the first δ Sct-type pulsating star of which the observed fast period decrease can be interpreted as an evolutionary effect of a pre-main sequence star, considering its membership of the Orion OB 1c association.

Strict requirements for the operating conditions for thermally loaded elements of radio-electronic systems contribute to essential relevance of the problem of increasing the indices of reliability of thermoelectric coolers in the implementation of their thermal modes. This leads to the need for increasing the indices of reliability not only through the use of new materials, design and technological solutions, but also optimization of the current modes of thermoelectric modules. The aim of this work is the search for the possibility of increasing the indices of reliability of cascade thermoelectric coolers, without changing their design parameters and material of thermoelements, by the selection of current modes at varied operating conditions. In the work we proposed a mathematical model of interrelation of the relative magnitude of the failure rate of two-stage thermoelectric device with the number of thermoelements, relative operating current, thermal load, and temperature difference in the temperature range of workability of a cooler. We carried out comparative analysis of the main significant parameters and indices of reliability of two-stage thermoelectric coolers for different current modes of operation in a wide range of temperature differences from =60 K to =90 K, taking into account the thermal load. It was demonstrated that with an increase in the general temperature difference, the ratio of the number of thermoelements in the adjacent cascades increases, the total number of thermoelements increases, the refrigeratory coefficient decreases, the relative magnitude of the failure rate grows and the probability of failure-free operation decreases. We obtained expression for determining the optimum relative operating current, at which the minimum value of relative number of thermoelements in the cascades is observed. Comparative analysis of the main parameters and indices of reliability demonstrated the possibility of selection and implementation of different current modes of operation of a cascade thermoelectric cooler for the varied operation conditions. Two extreme (characteristic) modes were proposed: the mode providing a minimum number of thermoelements, that is, minimum mass and overall dimensions of device; and the mode, providing the minimum failure rate and the maximum probability of failure-free operation. The proposed modes may be applied in the process of designing thermoelectric devices of minimum mass and increased reliability.

Recent timing analysis reveals that the orbital period of the first discovered accreting millisecond pulsar SAX J1808.4-3658 is increasing at a rate $\dot{P}_{\rm orb}=(3.89\pm0.15)\times 10^{-12}~\rm s\,s^{-1}$, which is at least one order of magnitude higher than the value arising from the conservative mass transfer. An ejection of mass loss rate of $10^{-9}~\rm M_{\odot}{\rm yr}^{-1}$ from the donor star at the inner Lagrangian point during the quiescence state could interpret the observed orbital period derivative. However, it is unknown whether this source can offer such a high mass loss rate. In this work, we attempt to investigate an evolutionary channel towards SAX J1808.4-3658. Once the accretion disk becomes thermally and viscously unstable, the spin-down luminosity of the millisecond pulsar and the X-ray luminosity during outbursts are assumed to evaporate the donor star, and the resulting winds carry away the specific orbital angular momentum at the inner Lagrangian point. Our scenario could yield the observed orbital period, the orbital period derivative, the peak X-ray luminosity during outbursts. Low-mass X-ray binaries with a $1.0~\rm M_{\odot}$ donor star, and an orbital period in the range of 0.8 - 1.5 d, may be the progenitor of SAX J1808.4-3658. Our numerical calculations propose that the current donor star mass is $0.044 ~\rm M_{\odot}$, which is in approximately agreement with the minimum mass of the donor star. In addition, our scenario can also account for the formation of black widows or the diamond planet like PSR J1719-1438., 7 pages, 5 figures, MNRAS in press

The paper deals with problems of selection of structures and optimum design of multipole permanent magnet synchronous machines (PMSMs) for operation in offshore wind- and wave-power plants under severe conditions for maintenance service. It is shown that multipole PMSMs are a new and very suitable electrical machine for direct connected turbogenerators in power plants and, at the same time, multipole PMSMs meet a number of other important demands, including high reliability, contactless construction, high efficiency, minimum mass and dimensions, and cost effectiveness. With the aim of systematization, an integrated classification scheme of PMSMs is presented to describe the variety of designs of stator and rotor configurations. With the help of a theoretical analysis based on a geometrical approach, analytical expressions for PMSM comparison are derived using the relationship between the criterion of optimization (maximum power density) and the main geometric parameters of PMSMs. Comparative analysis of the PMSMs with radial and axial magnetic fluxes for the case of various numbers of poles and different diameters of rotors has confirmed that axial multipole PMSMs are synchronous machines with maximum power density and an optimum variant for direct connected turbogenerator structures for offshore wind- and wave-power plants. It is noted that the advantage of axial PMSMs over radial PMSMs is monotonic growth in accordance with increasing number of poles p. Under the condition that p ≥ 20, which is strictly necessary for designing direct connected turbogenerators in offshore wind- and wave-power plants, we have more than doubled the power density at axial PMSMs as compared with radial ones.

In this investigation, AA 2618 is taken as the matrix material and Si3N4 (Silicon Nitride), AlN (Aluminium Nitride) and ZrB2 (Zirconium Boride) are taken as the reinforcement material. The reinforcements are mixed with the matrix in various X weight percentages (wt %) (X=0, 2, 4, 6, 8) by stir casting method. According to the ASTM standard AA 2618 composites were prepared with various wt % to find the mass loss in erosion test. The samples were imposed with various input conditions to obtain minimum mass loss for AA 2618 composites. Taguchi method was used to find the maximum influenced process parameter for mass loss and ANOVA (Analysis of Variance) method was adopted for finding the percentage of contribution of each process parameters

In the present study, Multi-objective optimization of composite cylindrical shell under external hydrostatic pressure was investigated. Parameters of mass, cost and buckling pressure as fitness functions and failure criteria as optimization criterion were considered. The objective function of buckling has been used by performing the analytical energy equations and Tsai-Wu and Hashin failure criteria have been considered. Multi-objective optimization was performed by improving the evolutionary algorithm of NSGA-II. Also the kind of material, quantity of layers and fiber orientations have been considered as design variables. After optimizing, Pareto front and corresponding points to Pareto front are presented. Trade of points which have optimized mass and cost were selected by determining the specified pressure as design criteria. Finally, an optimized model of composite cylindrical shell with the optimum pattern of fiber orientations having appropriate cost and mass is presented which can tolerate the maximum external hydrostatic pressure.

Body-in-white (BIW) is the Car body with welded sheet metal parts painted in white. Automobile companies were trying to optimize mass and improve performance with optimal mass addition. In many automotive industries many BIW designs due to aggressive mass optimization, there is a need to have smart solutions to improve BIW structure performance with very little mass increase. In this paper, a new technique of identifying the optimized internal reinforcements in the BIW at conceptual BIW design phase using Deign of experiments and Multi-objective optimization has been investigated. The paper focus on the Bending and torsion stiffness load cases to evaluate the BIW performance. Bulk head designs were designed at the major joints like A-pillar, B-pillar, C-pillar and rocker and their optimal locations to improve stiffness with minimum mass increase were identified using Design of experiments and multi objective techniques. The research shows that the optimized Bulk head design locations using the DOE technique has improved the overall BIW stiffness performance by 3.9% with 1.2% of mass addition in the BIW.

The mishandling of liquid fuels during production, processing or transportation can lead to the formation of combustible two-phase mixtures. These mixtures, with the availability of a suitable energy source, may be ignited generating a deflagration, or even a detonation wave. For military applications, unconfined fuel aerosols are created and detonated with the help of a strong shock generated by a powerful energy source. The minimum energy requirement is expressed in terms of the shock strength, or mass of the high-explosive-based initiator. In this study, the detonability of unconfined aerosols of 4.3 kg propylene oxide was studied by positioning different quantities of cylindrical-shaped initiators of RDX/wax (95/5) at a fixed spatial location in the aerosol cloud, and the minimum mass of the initiator required for detonation initiation was determined. The effect of spatial location and the requirement of initiator mass, especially at farther locations where the fuel concentration is likely to be lower and closer to the lower explosive limit, was also investigated. The experimental findings help identify the detonable zone in unconfined propylene oxide aerosol clouds for different combinations of spatial location and mass of initiator.

This paper produces a design for a minimal mass, deployable support structure for a solar panel covering of water canals. The results are based upon the minimal mass properties of tensegrity structures. The efficient structure is a tensegrity system which has an optimal complexity (i.e. an optimal number of members) for minimal mass. This optimal complexity is derived in this paper, along with deployable schemes which are useful for construction, repairs, for Sun following, and for servicing. It is shown that the minimal structure naturally has deployable features so that extra mass is not needed to add the multifunctional features. The design of bridge structures with tensegrity architecture will show an optimal complexity depending only on material choices and external loads. The minimization problem considers a distributed load (from weight of solar panels and wind loads), subject to buckling and yielding constraints. The result is shown to be a Class 1 Tensegrity substructure (support structure only below the deck). These structures, composed of axially-loaded members (tension and compressive elements), can be easily deployable and have many port-able applications for small spans. The focus of this paper is an application of these minimal mass tensegrity concepts to design shading devices to prevent or reduce evaporation loss, while generating electric power with solar panels as the cover. While the economics of the proposed designs are far from finalized, this paper shows a technical solution that uses the smallest material resources, and shows the technical feasibility of the concept.

The diquark-triquark model is used to explain charmonium-pentaquark states, i.e., $P_c(4380)$ and $P_c(4450)$, which were observed recently by the LHCb collaboration. For the first time, we investigate the properties of the color attractive configuration of a triquark and we define a nonlocal light cone distribution amplitude for pentaquark states, where both diquark and triquark are not pointlike, but they have nonzero size. We establish an effective diquark-triquark Hamiltonian based on spin-orbital interaction. According to the Hamiltonian, we show that the minimum mass splitting between $\frac{5}{2}^+$ and $\frac{3}{2}^-$ is around $100$~MeV, which may naturally solve the challenging problem of small mass splitting between $P_c(4450)$ and $P_c(4380)$. This helps to understand the peculiarities of $P_c(4380)$ with a broad decay width whereas $P_c(4450)$ has a narrow decay width. Based on the diquark-triquark model, we predict more pentaquark states, which will hopefully be measured in future experiments., 7 pages, 3 figures, 1 table; matches the version accepted in Phys.Lett.B

CCD photometry of the eclipsing W Uma binary system V523 Cas in U, B, V and RC filters was carried out during eight nights in 2012. The physical and geometrical parameters of this system are obtained. A possible pulsation period of one of the components is obtained by analyzing the residuals of the ephemeris light curve. Our observations contain 16 times of minimum light. We combined these with all available published times of minimum. By fitting a quadratic curve to the O-C values, a new ephemeris of the system is calculated. By attributing the period change to mass transfer, we find a mass transfer rate of 4 × 10 − 12 M ⊙ y r . Also, Period (80.58 yr) and the minimum mass (0.3 M⊙) of a possible third body is estimated. In addition, the possible existence of a fourth body with a mass of order 0.15 M⊙ is discussed. These third and fourth bodies could be low-mass main-sequence stars (red dwarfs).

Mass is one of the most important parameters for determining the true nature of an astronomical object. Yet, many published exoplanets lack a measurement of their true mass, in particular those detected as a result of radial-velocity (RV) variations of their host star. For those examples, only the minimum mass, or m sin i, is known, owing to the insensitivity of RVs to the inclination of the detected orbit compared to the plane of the sky. The mass that is given in databases is generally that of an assumed edge-on system (~90°), but many other inclinations are possible, even extreme values closer to 0° (face-on). In such a case, the mass of the published object could be strongly underestimated by up to two orders of magnitude. In the present study, we use GASTON, a recently developed tool taking advantage of the voluminous Gaia astrometric database to constrain the inclination and true mass of several hundreds of published exoplanet candidates. We find nine exoplanet candidates in the stellar or brown dwarf (BD) domain, among which six were never characterized. We show that 30 Ari B b, HD 141937 b, HD 148427 b, HD 6718 b, HIP 65891 b, and HD 16760 b have masses larger than 13.5 MJ at 3σ. We also confirm the planetary nature of 27 exoplanets, including HD 10180 c, d and g. Studying the orbital periods, eccentricities, and host-star metallicities in the BD domain, we found distributions with respect to true masses consistent with other publications. The distribution of orbital periods shows of a void of BD detections below ~100 d, while eccentricity and metallicity distributions agree with a transition between BDs similar to planets and BDs similar to stars in the range 40–50 MJ.

Graded core sandwich structures have great potential for designing and optimization under special requirement. In the present work, the dynamic response of clamped square sandwich panel (SP) with layered-gradient metal foam core subjected to blast loading was investigated. A new yield criterion of SP with three-layer metal foam core was proposed, and the analytical solutions for maximum deflection over the center point of the panels were obtained. Furthermore, the corresponding results of finite element simulations and experiments were compared to validate the theoretical model. The numerical simulation and experimental results both show good agreements with theoretical predictions. It is shown that the uniform core SP is better than that of the gradient core one and the negative gradient SP is superior to that with positive gradient core in blast resistance for the same equivalent mass. Finally, the minimum mass designs of three-layer SP are stated by constructing geometry optimization diagram according to analytical formula. The theoretical analysis established is of great important in guiding engineering application of sandwich structure with multi-layer core under air-blast loading.

Since the early 90’s, Composite Curves (CC) and the Grid Diagram (GD) have been among the most popular graphical tools for targeting and design of Mass Exchange Networks (MEN) based on Pinch Analysis technique. However, CC has limitations since it maps rich and lean streams based on composites instead of individual streams on the composition versus mass load (y-M) diagram. Hence, it cannot directly be used for network design. The network design needs to be developed separately using sets of design criteria. This paper presents Stream Composition versus Mass Load Plot (SCMP) as new graphical approach for simultaneous MEN targeting and network design to overcome limitations of CC and GD. The SCMP shows the pinch point, maximum mass recovery, and the minimum Mass Separating Agent (MSA) targets. The network design to achieve these targets can be obtained by graphically translating the SCMP curves into Mass Allocation Network and Targeting (MANT) diagram.

Based on the contact fatigue strength criterion of tooth surface, the mathematical model of gear ratio distribution of the electric vehicle is established. In the process, there are two objective functions. One is the minimum diameter of electric vehicle reducer, the other is the minimum mass of electric vehicle reducer. Through examples, relevant program is compiled with matlab software. It is obtained that there is a distribution method for gear ratio of the electric vehicle reducer.

In order to meet the needs of sludge dewatering treatment in urban areas, a screw extrusion filter with dynamic and static ring was designed. The spiral axis of the filter is simulated by finite element statics. Based on the simulation results, the structure of the spiral axis was topologically optimized, and the optimized mathematical model was established. The minimum mass was taken as the objective function, and the reasonable structure size of the spiral axis was obtained after optimization. Under the condition of satisfying the structural strength, its quality was reduced by 9.7%, and a good optimization effect was achieved.

We investigate a possible correlation between the solid surface density Σ of the minimum-mass extrasolar nebula (MMEN) and the host star mass M★ and metallicity [Fe/H]. Leveraging on the precise host star properties from the California-Kepler Survey (CKS), we found that Σ= 50⁺³³₋₂₀ g cm ⁻² (a/1 au)^(−1.75±0.07) (M★/M⊙)^(1.04±0.22) 10^(0.22±0.05[Fe/H]) for Kepler-like systems (1–4R⊕; a < 1 au). The strong M★ dependence is reminiscent of previous dust continuum results that the solid disk mass scales with M★. The weaker [Fe/H] dependence shows that sub-Neptune planets, unlike giant planets, form readily in lower metallicity environment. The innermost region (a < 0.1 au) of an MMEN maintains a smooth profile despite a steep decline of planet occurrence rate: a result that favors the truncation of disks by corotating magnetospheres with a range of rotation periods, rather than the sublimation of dust. The Σ of Kepler multitransiting systems shows a much stronger correlation with M★ and [Fe/H] than singles. This suggests that the dynamically hot evolution that produced single systems also partially removed the memory of formation in disks. Radial-velocity planets yielded a MMEN very similar to CKS planets; transit-timing-variation planets' postulated convergent migration history is supported by their poorly constrained MMEN. We found that lower mass stars have a higher efficiency of forming/retaining planets: for Sun-like stars, about 20% of the solid mass within ~1 au are converted/preserved as sub-Neptunes, compared to 70% for late-K to early-M stars. This may be due to the lower binary fraction, lower giant-planet occurrence, or the longer disk lifetime of lower mass stars.

The paper proposes an approach to the creation of an energy-efficient slow-moving linear magnetoelectric drive of a long-stroke single-stage piston compressor. The problem of optimal design of the magnetic system of the magnetoelectric motor of reciprocating action satisfying the criterion of the maximum of the developed electromagnetic force while ensuring the minimum mass of the active materials used is solved. A mathematical model for calculating the dynamics of a linear magnetoelectric drive is presented and the results of modeling dynamic starting characteristics are presented.

The band gap (BGs) of a material can be manipulated by tailoring its periodic microstructure. The phononic crystals (PnCs), representative of a periodically arranged structural material, are conventionally manufactured from single-phase or two-phase materials. In this study, we investigate the multi-objective topology optimization (MOTO) of periodic three-solid-phase PnCs. With a method of two-stage multi-objective genetic algorithm, the microstructures of the three-solid-phase PnCs were designed to exhibit the desired novel properties. Three case studies were obtained as follows: (1) maximum relative band gap width (RBGW) with a minimum mass, (2) maximum absolute band gap width (ABGW) at two different specified frequencies, and (3) maximum ABGW at specified mid-frequency. All the cases were effective for the MOTO of PnCs, and the Pareto optimal solution set could give the balance of the different competed objectives. Further, the principal mechanisms responsible for the creation of BGs, whether Bragg scattering or local resonance, are discussed. Moreover, comparing with the normal 2-phase materials, suchlike a wider lower-frequency BGs, some important advantages unveiled with the appearance of the three-solid-phase material.

The recently claimed discovery of a massive ($M_\mathrm{BH}=68^{+11}_{-13}\,M_\odot$) black hole in the Galactic solar neighborhood has led to controversial discussions because it severely challenges our current view of stellar evolution. A crucial aspect for the determination of the mass of the unseen black hole is the precise nature of its visible companion, the B-type star LS V+22 25. Because stars of different mass can exhibit B-type spectra during the course of their evolution, it is essential to obtain a comprehensive picture of the star to unravel its nature and, thus, its mass. To this end, we study the spectral energy distribution of LS V+22 25 and perform a quantitative spectroscopic analysis that includes the determination of chemical abundances for He, C, N, O, Ne, Mg, Al, Si, S, Ar, and Fe. Our analysis clearly shows that LS V+22 25 is not an ordinary main sequence B-type star. The derived abundance pattern exhibits heavy imprints of the CNO bi-cycle of hydrogen burning, that is, He and N are strongly enriched at the expense of C and O. Moreover, the elements Mg, Al, Si, S, Ar, and Fe are systematically underabundant when compared to normal main-sequence B-type stars. We suggest that LS V+22 25 is a stripped helium star and discuss two possible formation scenarios. Combining our photometric and spectroscopic results with the Gaia parallax, we infer a stellar mass of $1.1\pm0.5\,M_\odot$. Based on the binary system's mass function, this yields a minimum mass of $2-3\,M_\odot$ for the compact companion, which implies that it may not necessarily be a black hole but a massive neutron- or main sequence star. The star LS V+22 25 has become famous for possibly having a very massive black hole companion. However, a closer look reveals that the star itself is a very intriguing object. Further investigations are necessary for complete characterization of this object., Comment: Accepted for publication in A&A (Astronomy and Astrophysics)

Lattice metamaterials have demonstrated promising characteristics such as having tunable/unconventional properties and being lightweight. This work centers on the design of tensegrity-based lattices, known as “T-bar” structures, capable of supporting compressive loads with minimum mass. Analytical formulas for the calculation of the mass of these structures under externally applied forces and pre-stress are derived. These formulas account for local failure of the T-bar structures (material yielding and buckling of its individual members). A numerical approach is introduced to assess the global stability of the structures under external forces and pre-stress and to account for global buckling in the design process. The mass of the structure is minimized by adjusting its shape and topology while global buckling is simultaneously prevented using two different design methods: i) optimizing the pre-stress distribution in the structure, and ii) optimizing the cross-section areas of the tensegrity members. Using either method, the results show that 2D and 3D T-bars possess a global minimum mass design for a given externally applied force and length. The computed results also show that designs obtained by optimizing the cross-section areas of the members have lower mass than those obtained by optimizing the pre-stress distribution.

It is the goal that the aerospace industry has been continuously pursuing to meet the lightweight design with excellent mechanical properties. A structure-material integrated design framework is proposed to enhance the load-bearing rate of a spacecraft rib significantly, based on the optimization design theory. The structure-material integrated design framework is realized in two steps by commercial software Altair Solidthinking Inspire. The first step is that topology optimization is performed to a spacecraft rib at the macroscopic scale, with the minimum mass and the constraints of the additive manufacturing process and stress; while the second step is to optimally infill the lattice structure at the microscopic scale by minimizing the mass and constraining the additive manufacturing process and stress. Representative samples for the optimal rib structure are then fabricated by the additive manufacturing technique, and the tensile test is finally carried out to obtained the load-bearing rate for the different samples. The results show that the spacecraft rib's load-bearing rate is increased by 122.73% by the proposed structure-material integrated design framework compared to the traditional one; moreover, it is significantly more efficient than the direct topology optimization and lattice optimization design. The structure-material integrated design framework shown in this study can provide an efficient way to aerospace structures with lightweight and superior mechanical properties.

Erosion and destruction of riverbeds, foundations of flooded engineering structures are accelerated during natural phenomena, accompanied by a significant increase in the rate and wetted perimeter of river flows, the acquisition of mobility by the riverbeds’ particles. We have analyzed the interaction between a water flow and a separate stone of spherical, cylindrical, pyramidal, and other configurations. In particular, we have further developed a traditional approach to determining the force action of fluid on a solid barrier, a stone, for the case of compression of a water jet and taking into consideration the relative flow around a stone with the predefined geometrical characteristics: diameter, volume, and configuration.It has been proposed to employ the following parameters for interaction between the flow of water and rocks of various configurations: a compression ratio and a streamline coefficient. We have derived analytical dependences of the flow rate limit, which sets a stone into motion, its weight, and configuration. For spherical smooth stones these ratios are identical with the classical results. The coefficients, introduced for consideration, were categorized, depending on the configuration of a single stone, in tables and charts, which is convenient to apply when calculating bank­protecting structures. It has been proposed to use a stone shape factor, which is the ratio of the actual flow rate limit, enabling the mobility of a stone of arbitrary configuration taking into consideration its streamlining, to the flow rate limit of a spherical stone of the same mass with a reduced diameter. A shape factor should be applied as an adjustment multiplier in the calculation of the minimum mass of stones for bank­protecting structures and during hydro­engineering works. For the wedge­shaped stones a value of the adjustment coefficient can sometimes amount to 0.170, which indicates high efficiency of applying such stones compared to those of spherical shape. In addition, the proposed coefficient could be used to refine the water flow rate limit in terms of loss of stability by existing bank­protecting structure.We have identified directions for further studies: analysis of the impact interaction between configurable stones and elements of bank­protecting structures; determination of motion parameters for water­stone flows, Ерозія та руйнування русел річок, фундаментів підтоплюваних інженерних споруд пришвидшується під час стихійних явищ, супроводжуваних значним збільшенням швидкості й змоченого периметру річкових потоків, набуттям рухливості частинками русла. Проаналізовано взаємодію потоку води із окремим каменем циліндричної, сферичної, еліпсоїдної, пірамідальної та іншої конфігурації. Зокрема розвинуто традиційний підхід до визначення силової дії рідини на тверду перешкоду – камінь - для випадку стиснення струменю води й врахування відносної обтічності каменю із заданими геометричними характеристиками: діаметр, об`єм та конфігурація.Запропоновано використовувати наступні параметри взаємодії потоку води із каменями різних конфігурацій: коефіцієнт стиснення та коефіцієнт обтічності. Отримано аналітичні залежності між граничною швидкістю потоку, яка спричиняє рух каменя, його масою та конфігурацією. Для сферичних гладких каменів ці відношення співпадають із класичними результатами. Запроваджені коефіцієнти типізовано у залежності від конфігурації окремого каменя у таблицях та графіках, що є зручним для використання у розрахунках берегоукріплень. Запропоновано використовувати коефіцієнт форми каменя – відношення дійсної граничної швидкості потоку, що викликає рухливість каменю довільної конфігурації із врахуванням його обтічності – до граничної швидкості потоку сферичного каменю такої ж маси з приведеним діаметром. Коефіцієнт форми слід використовувати як коригуючий множник у розрахунках мінімальної маси каменів для берегоукріплень та у гідротехнічних роботах. Для каменів клиновидної форми значення коригуючого коефіцієнта може в окремих випадках досягати значення 0,170, що вказує на високу ефективність використання таких каменів у порівнянні із сферичними. Крім того запропонований коефіцієнт може застосовуватися для уточнення граничної швидкості потоку води, з огляду на втрату стійкості існуючого берегоукріплення.Визначено напрями подальших досліджень: аналіз ударної взаємодії конфігуративних каменів із елементами берегоукріплень; визначення параметрів руху водно- каменевих потоків, Эрозия и разрушения русел рек, фундаментов подтопляемых инженерных сооружений ускоряется во время стихийных явлений, сопровождаемых значительным увеличением скорости и смоченного периметра речных потоков, приобретением подвижности частицами русла. Проанализировано взаимодействие потока воды с отдельным камнем цилиндрической, сферической, эллипсоидной, пирамидальной и другой конфигурации. В частности развит традиционный подход к определению силового воздействия жидкости на твердую преграду – камень – для случая сжатия струи воды и учета относительной обтекаемости камня с заданными геометрическими характеристиками: диаметр, объем и конфигурация.Предложено использовать следующие параметры взаимодействия потока воды с камнями различных конфигураций: коэффициент сжатия и коэффициент обтекаемости. Получены аналитические зависимости между предельной скоростью потока, которая приводит в движение камень, его массой и конфигурацией. Для сферических гладких камней эти соотношения совпадают с классическими результатами. Введенные в рассмотрение коэффициенты типизированы в зависимости от конфигурации отдельного камня в таблицах и графиках, что удобно для использования в расчетах берегоукреплений. Предложено использовать коэффициент формы камня - отношение действительной предельной скорости потока, что вызывает подвижность камня произвольной конфигурации с учетом его обтекаемости - к предельной скорости потока сферического камня такой же массы с приведенным диаметром. Коэффициент формы следует использовать как корректирующий множитель в расчетах минимальной массы камней для береговых укреплений и в гидротехнических работах. Для камней клиновидной формы значение корректирующего коэффициента может в отдельных случаях достигать значения 0,170, что указывает на высокую эффективность использования таких камней по сравнению со сферическими. Кроме того, предложенный коэффициент может применяться для уточнения предельной скорости потока воды с точки зрения потери устойчивости существующего берегоукрепления.Определены направления дальнейших исследований: анализ ударного взаимодействия конфигуративных камней с элементами береговых укреплений; определение параметров движения водно - камневых потоков

We address quasinormal modes of compact objects in several alternative theories of gravity. In particular, we focus on black holes and neutron stars with scalar hair. We consider black holes in dilaton-Einstein-Gau\ss -Bonnet theory, and in a generalized scalar-Einstein-Gau\ss -Bonnet theory. In the latter case scalarized black holes arise, and we study the stability of the different branches of solutions. In particular, we discuss how the spectrum of quasinormal modes is changed by the presence of a non-trivial scalar field outside the black hole horizon. We discuss the existence of an (effective) minimum mass in these models, and how the spectrum of modes becomes richer as compared to general relativity, when a scalar field is present. Subsequently we discuss the effect of scalar hair for realistic neutron star models. Here we consider $R^2$ gravity, scalar-tensor theory, a particular subsector of Horndeski theory with a non-minimal derivative coupling, and again dilatonic-Einstein-Gau\ss -Bonnet theory. Because of the current lack of knowledge on the internal composition of the neutron stars, we focus on universal relations for the quasinormal modes, that are largely independent of the equations of state and thus the matter content of the stars., Comment: 38 pages, 14 figures

Giant, wide-separation planets often lie in the gap between multiple, distinct rings of circumstellar debris: this is the case for the HR\,8799 and HD\,95086 systems, and even the solar system where the Asteroid and Kuiper belts enclose the four gas and ice giants. In the case that a debris disk, inferred from an infrared excess in the SED, is best modelled as two distinct temperatures, we infer the presence of two spatially separated rings of debris. Giant planets may well exist between these two belts of debris, and indeed could be responsible for the formation of the gap between these belts. We observe 24 such two-belt systems using the VLT/SPHERE high contrast imager, and interpret our results under the assumption that the gap is indeed formed by one or more giant planets. A theoretical minimum mass for each planet can then be calculated, based on the predicted dynamical timescales to clear debris. The typical dynamical lower limit is $\sim$0.2$M_J$ in this work, and in some cases exceeds 1$M_J$. Direct imaging data, meanwhile, is typically sensitive to planets down to $\sim$3.6$M_J$ at 1'', and 1.7$M_J$ in the best case. Together, these two limits tightly constrain the possible planetary systems present around each target, many of which will be detectable with the next generation of high-contrast imagers., Comment: Accepted for publication in MNRAS. 16 pages, 7 figures

We report the detection of two exoplanets and a further tentative candidate around the M-dwarf stars Gl96 and Gl617A, based on radial velocity measurements obtained with the SOPHIE spectrograph at the Observatoire de Haute-Provence. Both stars were observed in the context of the SOPHIE exoplanet consortium's dedicated M-dwarf subprogramme, which aims to detect exoplanets around nearby M-dwarf stars through a systematic survey. For Gl96, we present the discovery of a new exoplanet at 73.9 d with a minimum mass of 19.66 earth masses. Gl96 b has an eccentricity of 0.44, placing it among the most eccentric planets orbiting M stars. For Gl617A we independently confirm a recently reported exoplanet at 86.7 d with a minimum mass of 31.29 earth masses. Both Gl96 b and Gl617A b are potentially within the habitable zone, though Gl96 b's high eccentricity may take it too close to the star at periapsis., 22 pages, 23 figures

In order to reduce the mass of satellite deployable umbrella reflector, a structure optimization model of rib was established by analyzing rib’s structure and forces on it. The minimum mass of rib is calculated by optimizing its structure parameters under given rigidity and loads. Optimized structure parameters were obtained by solving the model with Compound Form method. Comparing the original structure, 50.4% mass was successfully reduced after optimization. It was found that increasing the height of the rib's cross section and using variable section are two effective ways to make rib lighter.

“Free-floating, non-deuterium-burning, substellar objects” are isolated bodies of a few Jupiter masses found in very young open clusters and associations, nearby young moving groups, and in the immediate vicinity of the Sun. They are neither brown dwarfs nor planets. In this paper, their nomenclature, history of discovery, sites of detection, formation mechanisms, and future directions of research are reviewed. Most free-floating, non-deuterium-burning, substellar objects share the same formation mechanism as low-mass stars and brown dwarfs, but there are still a few caveats, such as the value of the opacity mass limit, the minimum mass at which an isolated body can form via turbulent fragmentation from a cloud. The least massive free-floating substellar objects found to date have masses of about 0.004 Msol, but current and future surveys should aim at breaking this record. For that, we may need LSST, Euclid and WFIRST.

Rotating systems operating in different foundations structures can present distinct dynamic response. In case of a compliant foundation, interaction between machine and its supports leads to a more complex system with additional degrees of freedom. These degrees of freedom introduce new natural frequencies and vibration modes for the system. When these foundation-induced modes are in the rotor operating range of frequency, a serious problem may arise, since a machine cannot be tested for every different foundation type expected in industry environment, especially in preliminary design phase. Furthermore, foundation replacement or adaptation are costly operations. A significant improvement in machine-foundation compatibility is possible by the introduction of some compensation in machine to change these additional critical frequencies. Therefore, this paper proposes a compensation method for foundation effects through finite element analysis and shape optimization. An optimization is used to find a compromise between minimum mass increase and manufacturing time to ensure a low cost shape, as a result the cost of machine adjustments is reduced. The algorithm is designed to be simple enough to run on cheap micro-controllers. Consequently, the complete system can be embedded in the machine for a negligible amount of its total cost. Simulations’ results show the method as effective in compensating the influence of foundations with minor loss of precision due to simplifications required to make the algorithm less computational intensive than a full-fledged solution designed to run in workstations. In this way, the method is promising for future applications in rotating machines present in industrial plants.

In the past years, the development of morphing wing technologies has received a great deal of interest from the scientific community. These technologies potentially enable an increase in aircraft efficiency by changing the wing shape, thus allowing the aircraft to fly near its optimal performance point at different flight conditions. However, these technologies often present an undesired mass increase due to their inherent complexity. Therefore, the aim of the current work is to ascertain the influence of geometrical and inertial parameters on the structural mass of a Variable-span Wing (VSW). The structural mass prediction is based on a parametric study. A minimum mass optimization problem with stiffness and strength constraints is implemented and solved, being the design variables structural thicknesses and widths, using a parametric Finite Element Model (FEM) of the wing. The study is done for a conventional fixed wing and the VSW, which are then combined to ascertain the VSW mass increment, i.e., the mass penalization of the adopted morphing concept. Polynomials are found to produce good approximations of the wing mass. The effects of the various VSW design parameters in the structural mass are discussed. On one hand, it was found that the span and chord have the highest impact in the wing mass. On the other hand, the VSW to fixed wing mass ratio proved that the influence of span variation ratio in the wing mass is not trivial. It is found that the mass increase does not grow proportionally with span variation ratio increase and that for each combination of span and chord, exists a span variation ratio that minimizes the mass penalty. In the future, the developed polynomials could be used to create a mass prediction model to aid the design of morphing wings during the conceptual design phase.

Detecting exoplanets in clusters of different ages is a powerful tool for understanding a number of open questions, such as how the occurrence rate of planets depends on stellar metallicity, on mass, or on stellar environment. We present the first results of our HARPS long-term radial velocity (RV) survey which aims to discover exoplanets around intermediate-mass (between ~ 2 and 6 Msun) evolved stars in open clusters. We selected 826 bona fide HARPS observations of 114 giants from an initial list of 29 open clusters and computed the half peak-to-peak variability of the HARPS RV measurements, namely DeltaRV/2, for each target, to search for the best planet-host candidates. We also performed time series analysis for a few targets with enough observations to search for orbital solutions. Although we attempted to rule out the presence of binaries on the basis of previous surveys, we detected 14 new binary candidates in our sample, most of them identified from a comparison between HARPS and CORAVEL data. We also suggest 11 new planet-host candidates based on a relation between the stellar surface gravity and DeltaRV/2. Ten of the candidates have less than 3 Msun, showing evidence of a low planet occurrence rate for massive stars. One of the planet-host candidates and one of the binary candidates show very clear RV periodic variations, allowing us to confirm the discovery of a new planet and to compute the orbital solution for the binary. The planet is IC 4651 9122b, with a minimum mass of msini = 6.3 MJ and a semi-major axis a = 2.0 AU. The binary companion is NGC 5822 201B, with a very low minimum mass of msini = 0.11 Msun and a semi-major axis a = 6.5 AU, which is comparable to the Jupiter distance to the Sun., Accepted to Astronomy and Astrophysics. 14 pages, 11 figures

The first stars are known to form in primordial gas, either in minihalos with about $10^6$~M$_\odot$ or so-called atomic cooling halos of about $10^8$~M$_\odot$. Simulations have shown that gravitational collapse and disk formation in primordial gas yield dense stellar clusters. In this paper, we focus particularly on the formation of protostellar binary systems, and aim to quantify their properties during the early stage of their evolution. For this purpose, we combine the smoothed particle hydrodynamics code GRADSPH with the astrochemistry package KROME. The GRADSPH-KROME framework is employed to investigate the collapse of primordial clouds in the high-density regime, exploring the fragmentation process and the formation of binary systems. We observe a strong dependence of fragmentation on the strength of the turbulent Mach number $\mathcal{M}$ and the rotational support parameter $\beta{}$. Rotating clouds show significant fragmentation, and have produced several Pop.~III proto-binary systems. We report maximum and minimum mass accretion rates of $2.31 \times 10^{-1}$~M$_{\odot}$ yr$^{-1}$ and $2.18\times 10^{-4}$~M$_{\odot}$ yr$^{-1}$. The mass spectrum of the individual Pop III proto-binary components ranges from $0.88$~M$_{\odot}$ to $31.96$~M$_{\odot}$ and has a sensitive dependence on the Mach number $\mathcal{M}$ as well as on the rotational parameter $\beta{}$. We also report a range from $\sim0.01$ to $\sim1$ for the mass ratio of our proto-binary systems., Comment: Accepted for publication in MNRAS

Radio pulsars found in binary systems with short orbital periods are usually fast spinning as a consequence of recycling via mass transfer from their companion stars; this process is also thought to decrease the magnetic field of the neutron star being recycled. Here, we report on timing observations of the recently discovered binary PSR J1755$-$2550 and find that this pulsar is an exception: with a characteristic age of 2.1 Myr, it is relatively young; furthermore, with a spin period of 315 ms and a surface magnetic field strength at its poles of 0.88$\times$10$^{12}$ G the pulsar shows no sign of having been recycled. Based on its timing and orbital characteristics, the pulsar either has a massive white dwarf (WD) or a neutron star (NS) companion. To distinguish between these two cases, we searched radio observations for a potential recycled pulsar companion and analysed archival optical data for a potential WD companion. Neither work returned conclusive detections. We apply population synthesis modelling and find that both solutions are roughly equally probable. Our population synthesis also predicts a minimum mass of 0.90 M$_{\odot}$ for the companion star to PSR J1755$-$2550 and we simulate the systemic runaway velocities for the resulting WDNS systems which may merge and possibly produce Ca-rich supernovae. Whether PSR J1755$-$2550 hosts a WD or a NS companion star, it is certainly a member of a rare subpopulation of binary radio pulsars., 13 pages, 11 figures, accepted by MNRAS

We present \emph{Herschel} PACS observations of 8 Classical T Tauri Stars in the $\sim 7-10$ Myr old OB1a and the $\sim 4-5$ Myr old OB1b Orion sub-asscociations. Detailed modeling of the broadband spectral energy distributions, particularly the strong silicate emission at 10 $\mu$m, shows that these objects are (pre)transitional disks with some amount of small optically thin dust inside their cavities, ranging from $\sim 4$ AU to $\sim 90$ AU in size. We analyzed \emph{Spitzer} IRS spectra for two objects in the sample: CVSO-107 and CVSO-109. The IRS spectrum of CVSO-107 indicates the presence of crystalline material inside its gap while the silicate feature of CVSO-109 is characterized by a pristine profile produced by amorphous silicates; the mechanisms creating the optically thin dust seem to depend on disk local conditions. Using millimeter photometry we estimated dust disk masses for CVSO-107 and CVSO-109 lower than the minimum mass of solids needed to form the planets in our Solar System, which suggests that giant planet formation should be over in these disks. We speculate that the presence and maintenance of optically thick material in the inner regions of these pre-transitional disks might point to low-mass planet formation., Comment: 20 pages, 10 figures, 8 tables

Although most of the circumbinary planets detected by the Kepler spacecraft are on orbits that are closely aligned with the binary orbital plane, the systems Kepler-413 and Kepler-453 exhibit small misalignments of $\sim 2.5^\circ$. One possibility is that these planets formed in a circumbinary disc whose midplane was inclined relative to the binary orbital plane. Such a configuration is expected to lead to a warped and twisted disc, and our aim is to examine the inclination evolution of planets embedded in these discs. We employed 3D hydrodynamical simulations that examine the disc response to the presence of a modestly inclined binary with parameters that match the Kepler-413 system, as a function of disc parameters and binary inclinations. The discs all develop slowly varying warps, and generally display very small amounts of twist. Very slow solid body precession occurs because a large outer disc radius is adopted. Simulations of planets embedded in these discs resulted in the planet aligning with the binary orbit plane for disc masses close to the minimum mass solar nebular, such that nodal precession of the planet was controlled by the binary. For higher disc masses, the planet maintains near coplanarity with the local disc midplane. Our results suggest that circumbinary planets born in tilted circumbinary discs should align with the binary orbit plane as the disc ages and loses mass, even if the circumbinary disc remains misaligned from the binary orbit. This result has important implications for understanding the origins of the known circumbinary planets., accepted in MNRAS

Using the "Complexity = Action" framework we compute the late time growth of complexity for charged black holes in Lovelock gravity. Our calculation is facilitated by the fact that the null boundaries of the Wheeler-DeWitt patch do not contribute at late times and essential contributions coming from the joints are now understood arXiv:1803.00172. The late time growth rate reduces to a difference of internal energies associated with the inner and outer horizons, and in the limit where the mass is much larger than the charge, we reproduce the celebrated result of $2M/\pi$ with corrections proportional to the highest Lovelock coupling in even (boundary) dimensions. We find in some cases a minimum mass below which complexity remains effectively constant, even if the black hole contains a non-degenerate horizon., Comment: 7 pages, 1 figure, minor improvements to abstract and discussion, references added

We derive upper and lower limits for the mass-radius ratio of spin-fluid spheres in Einstein-Cartan theory, with matter satisfying a linear barotropic equation of state, and in the presence of a cosmological constant. Adopting a spherically symmetric interior geometry, we obtain the generalized continuity and Tolman-Oppenheimer-Volkoff equations for a Weyssenhoff spin-fluid in hydrostatic equilibrium, expressed in terms of the effective mass, density and pressure, all of which contain additional contributions from the spin. The generalized Buchdahl inequality, which remains valid at any point in the interior, is obtained, and general theoretical limits for the maximum and minimum mass-radius ratios are derived. As an application of our results we obtain gravitational red shift bounds for compact spin-fluid objects, which may (in principle) be used for observational tests of Einstein-Cartan theory in an astrophysical context. We also briefly consider applications of the torsion-induced minimum mass to the spin-generalized strong gravity model for baryons/mesons, and show that the existence of quantum spin imposes a lower bound for spinning particles, which almost exactly reproduces the electron mass., Comment: 21 pages, 3 figures; references added; minor revisions, accepted for publication in EPJC

Given the precision of current neutrino data, priors still impact noticeably the constraints on neutrino masses and their hierarchy. To avoid our understanding of neutrinos being driven by prior assumptions, we construct a prior that is mathematically minimally informative. Using the constructed uninformative prior, we find that the normal hierarchy is favoured but with inconclusive posterior odds of 5.1:1. Better data is hence needed before the neutrino masses and their hierarchy can be well constrained. We find that the next decade of cosmological data should provide conclusive evidence if the normal hierarchy with negligible minimum mass is correct, and if the uncertainty in the sum of neutrino masses drops below 0.025 eV. On the other hand, if neutrinos obey the inverted hierarchy, achieving strong evidence will be difficult with the same uncertainties. Our uninformative prior was constructed from principles of the Objective Bayesian approach. The prior is called a reference prior and is minimally informative in the specific sense that the information gain after collection of data is maximised. The prior is computed for the combination of neutrino oscillation data and cosmological data and still applies if the data improve., 15 pages. Minor changes to match accepted version in JCAP

Barnard’s star is a red dwarf, and has the largest proper motion (apparent motion across the sky) of all known stars. At a distance of 1.8 parsecs, it is the closest single star to the Sun; only the three stars in the α Centauri system are closer. Barnard’s star is also among the least magnetically active red dwarfs known and has an estimated age older than the Solar System. Its properties make it a prime target for planetary searches; various techniques with different sensitivity limits have been used previously, including radial-velocity imaging, astrometry and direct imaging, but all ultimately led to negative or null results. Here we combine numerous measurements from high-precision radial-velocity instruments, revealing the presence of a low-amplitude periodic signal with a period of 233 days. Independent photometric and spectroscopic monitoring, as well as an analysis of instrumental systematic effects, suggest that this signal is best explained as arising from a planetary companion. The candidate planet around Barnard’s star is a cold super-Earth, with a minimum mass of 3.2 times that of Earth, orbiting near its snow line (the minimum distance from the star at which volatile compounds could condense). The combination of all radial-velocity datasets spanning 20 years of measurements additionally reveals a long-term modulation that could arise from a stellar magnetic-activity cycle or from a more distant planetary object. Because of its proximity to the Sun, the candidate planet has a maximum angular separation of 220 milliarcseconds from Barnard’s star, making it an excellent target for direct imaging and astrometric observations in the future. © 2018, Springer Nature Limited., The results are based on observations made with the CARMENES instrument at the 3.5-m telescope of the Centro Astronomico Hispano-Aleman de Calar Alto (CAHA, Almeria, Spain), funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Cientificas (CSIC), the European Union and the CARMENES Consortium members; the 90-cm telescope at the Sierra Nevada Observatory (Granada, Spain) and the 40-cm robotic telescope at the SPACEOBS observatory (San Pedro de Atacama, Chile), both operated by the Instituto de Astrofisica de Andalucia (IAA); and the 80-cm Joan Oro Telescope (TJO) of the Montsec Astronomical Observatory (OAdM), owned by the Generalitat de Catalunya and operated by the Institute of Space Studies of Catalonia (IEEC). This research was supported by the following institutions, grants and fellowships: Spanish MINECO ESP2016-80435-C2-1-R, ESP2016-80435-C2-2-R, AYA2016-79425-C3-1-P, AYA2016-79245-C3-2-P, AYA2016-79425-C3-3-P, AYA2015-69350-C3-2-P, ESP2014-54362-P, AYA2014-56359-P, RYC-2013-14875; Generalitat de Catalunya/CERCA programme; Fondo Europeo de Desarrollo Regional (FEDER); German Science Foundation (DFG) Research Unit FOR2544, project JE 701/3-1; STFC Consolidated Grants ST/P000584/1, ST/P000592/1, ST/M001008/1; NSF AST-0307493; Queen Mary University of London Scholarship; Perren foundation grant; CONICYT-FONDECYT 1161218, 3180405; Swiss National Science Foundation (SNSF); Koshland Foundation and McDonald-Leapman grant; and NASA Hubble Fellowship grant HST-HF2-51399.001. J.T. is a Hubble Fellow.

A multi-parameter optimization software tool for active cooling panel with high thermal load is established and validated. It can be quickly solved in the constraint range and setting margin, and automatically select the basic geometry size. The minimum mass for active cooling structure matching the complex thermal environment and fuel cooling capacity of the engine is obtained. With the minimum mass as the optimization objective, the constraints such as the allowable stress of the structure, the allowable temperature of the structure, the coking temperature of the cooling fuel, the loss of the cooling fuel flow resistance and the processing limit are considered. The material is available in the thermal environment with a gas convection heat transfer coefficient of 445∼1800W/m2-K. The feasible solution is converted into a material design space map, which can be used to compare a variety of materials to the safety margin of a given active cooling structure, or to intuitively compare the feasibility of a given material to a variety of active cooling structures. Using these design space maps, the active cooling structure design can be quickly determined according to the given conditions. The feasible solution can be converted to a material weight map, and a minimum weight structural scheme can be visually determined from a variety of scenarios.

We age-date the stellar populations associated with 12 historic nearby core-collapse supernovae (CCSNe) and 2 supernova impostors, and from these ages, we infer their initial masses and associated uncertainties. To do this, we have obtained new HST imaging covering these CCSNe. Using these images, we measure resolved stellar photometry for the stars surrounding the locations of the SNe. We then fit the color-magnitude distributions of this photometry with stellar evolution models to determine the ages of any young existing populations present. From these age distributions, we infer the most likely progenitor mass for all of the SNe in our sample. We find ages between 4 and 50 Myr, corresponding to masses from 7.5 to 59 solar masses. There were no SNe that lacked a young population within 50~pc. Our sample contains 4 type Ib/c SNe; their masses have a wide range of values, suggesting that the progenitors of stripped-envelope SNe are binary systems. Both impostors have masses constrained to be $\lesssim$7.5 solar masses. In cases with precursor imaging measurements, we find that age-dating and precursor imaging give consistent progenitor masses. This consistency implies that, although the uncertainties for each technique are significantly different, the results of both are reliable to the measured uncertainties. We combine these new measurements with those from our previous work and find that the distribution of 25 core-collapse SNe progenitor masses is consistent with a standard Salpeter power-law mass function, no upper mass cutoff, and an assumed minimum mass for core-collapse of 7.5~M$_{\odot}$., Comment: 12 pages, 4 tables, 4 figures, accepted for publication in ApJ

Current planet formation theories provide successful frameworks with which to interpret the array of new observational data in this field. However, each of the two main theories (core accretion, gravitational instability) is unable to explain some key aspects. In many planet formation calculations, it is usual to treat the initial properties of the planet forming disc (mass, radius, etc.) as free parameters. In this paper, we stress the importance of setting the formation of planet forming discs within the context of the formation of the central stars. By exploring the early stages of disc formation, we introduce the concept of the Maximum Mass Solar Nebula (MMSN), as opposed to the oft-used Minimum Mass Solar Nebula (here mmsn). It is evident that almost all protoplanetary discs start their evolution in a strongly self-gravitating state. In agreement with almost all previous work in this area, we conclude that on the scales relevant to planet formation these discs are not gravitationally unstable to gas fragmentation, but instead form strong, transient spiral arms. These spiral arms can act as efficient dust traps allowing the accumulation and subsequent fragmentation of the dust (but not the gas). This phase is likely to populate the disc with relatively large planetesimals on short timescales while the disc is still veiled by a dusty-gas envelope. Crucially, the early formation of large planetesimals overcomes the main barriers remaining within the core accretion model. A prediction of this picture is that essentially all observable protoplanetary discs are already planet hosting., 6 pages, no figures, accepted for publication in MNRAS

We rehearse the physical and theoretical considerations that define the nature of Brown Dwarfs, in particular the maximum mass for a Brown Dwarf (set by the Hydrogen-Burning Limit) and the minimum mass for a Brown Dwarf (set by the Opacity Limit). We then review the range of mechanisms that have been invoked to explain the formation of Brown Dwarfs and their statistical properties. These include turbulent fragmentation, fragmentation of filaments and discs, dynamical ejection of stellar embryos, and photoerosion. The primary contenders would seem to be turbulent fragmentation and disc fragmentation, and the observations needed to evaluate their relative importance may soon be available.

Using the star formation histories (SFHs) near 94 supernova remnants (SNRs), we infer the progenitor mass distribution for core-collapse supernovae. We use Bayesian inference and model each SFH with multiple bursts of star formation (SF), one of which is assumed to be associated with the SNR. Assuming single-star evolution, the minimum mass of CCSNe is $7.33^{+0.02}_{-0.16}$ $\text{M}_\odot$, the slope of the progenitor mass distribution is $\alpha = -2.96^{+0.45}_{-0.25}$, and the maximum mass is greater than $\text{M}_\textrm{max} > 59$ $\text{M}_\odot$ with a 68% confidence. While these results are consistent with previous inferences, they also provide tighter constraints. The progenitor distribution is somewhat steeper than a Salpeter initial mass function ($\alpha$ = -2.35). This suggests that either SNR catalogs are biased against the youngest SF regions, or the most massive stars do not explode as easily as lower mass stars. If SNR catalogs are biased, it will most likely affect the slope but not the minimum mass. The uncertainties are dominated by three primary sources of uncertainty, the SFH resolution, the number of SF bursts, and the uncertainty on SF rate in each age bin. We address the first two of these uncertainties, with an emphasis on multiple bursts. The third will be addressed in future work., Comment: 15 pages, 8 figures