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U ovom radu je projektirano glavno rebro broda za prijevoz tekućeg tereta u unutarnjoj plovidbi. Analiziran je referentni model dimenzioniran prema pravilima Hrvatskog registra brodova te druge varijante koje su proizašle iz tog modela. Variranjem razmaka uzdužnjaka i okvira analiziran je utjecaj na pojedine konstrukcijske elemente. Naglasak u samoj analizi je na procjeni mase. Nakon modeliranja i analiziranja referentnog modela napravljeno je redimenzioniranje konstrukcijskih elemenata programom Mars Inland u kojemu su implementirana pravila “Rules for the Classification of Inland Navigation Vessels“. Nakon redimenzioniranja predložene su dodatne varijante s različitim razmacima uzdužnjaka i okvira kako bi se za konceptualnu fazu konstruiranja broda pronašla pogodna varijanta koja bi poslužila kao polazna točka za razvoj broda. Dimenzije okvira i rebrenica su preuzete iz tehničkih nacrta za referentni model Hrvatskog registra brodova. S obzirom na procjenu mase, među predloženim varijantama odabrana je varijanta koja teži najmanjoj masi i uspoređena je s referentnim modelom. Nakon analize je razmotren zahtjev uzdužne čvrstoće na primjeru glavnog rebra odabranog modela. In this paper has been made structural design of ship midsection of inland tanker. Reference model designed by the rules of Croatian Register of Shipping and the other suggested models have been analised. By varying the spacing of longitudinals and web frames it has been analyzed how they affect on certain groups of construction elements. The emphasis was on assessment of construction mass. Redimensionating of construction elements has been made after modeling and analysing reference model. Redimensionating has been carried out with the help of Mars Inland program which has Bureau Veritas “Rules for the Classification of Inland Navigation Vessels“ implemented in itself. After redimensionating, other variations have been given with changed spacing of frames and longitudinals so the favorable variant could serve as starting point for conceptual phase of ship development. Dimensions of web frame and floor have been taken from reference model made by Croatian Register of Shipping. With respect to carried out analysis of construction mass, favorable variation has been selected and compared to reference model. After analysis, ultimate longitudinal strength of ship hull criteria has been observed on the example of main frame of selected favorable variant.

Solar energy is a most promising resource of non-conventional energy to utilize for heating. Based on the application there are two kinds of utilization one is water heating and the second one is air heating. This is generally done by flat plate solar collector but due to its limitations to use in higher temperature ranges (i.e., 70–95 °C) and poor performance led to introduce the application of evacuated tube and parabolic trough collector. To fabricate the solar air heater, one ended evacuated tube is used as a receiver of the parabolic trough and U-tube copper pipe is inserted within the evacuated tube. The air heating process is done at various mass flow rates and it was found that the average outlet temperature was more at the minimum mass flow rate, but the average efficiency was less. At maximum mass flow rate, the average outlet temperature was minimum, and the average thermal efficiency was maximum. The maximum thermal efficiency obtained was 24.1% at the 0.0082 kg/s mass flow rate and the maximum temperature that was obtained was 151 °C at 0.0062 kg/s mass flow rate. Hot air being used for different application in space heating, food processing, fruits and vegetable drying and in regeneration of desiccant.

We present new stellar evolutionary sequences of very metal-rich stars evolved with the Monash Stellar Structure code and with MESA. The Monash models include masses of $1-8M_{\odot}$ with metallicities $Z=0.04$ to $Z=0.1$ and are evolved from the main sequence to the thermally-pulsing asymptotic giant branch (AGB). These are the first $Z=0.1$ AGB models in the literature. The MESA models include intermediate-mass models with $Z=0.06$ to $Z=0.09$ evolved to the onset of the thermally-pulsing phase. Third dredge-up only occurs in intermediate-mass models $Z \le 0.08$. Hot bottom burning (HBB) shows a weaker dependence on metallicity, with the minimum mass increasing from 4.5$M_{\odot}$ for $Z=0.014$ to $\approx 5.5 M_{\odot}$ for Z = 0.04, $6M_{\odot}$ for $ 0.05 \le Z \le 0.07$ and above 6.5$ M_{\odot}$ for $Z\ge 0.08$. The behaviour of the $Z=0.1$ models is unusual; most do not experience He-shell instabilities owing to rapid mass-loss on the early part of the AGB. Turning off mass-loss produces He-shell instabilities, however thermal pulses are weak and result in no third dredge-up. The minimum mass for carbon ignition is reduced from 8$M_{\odot}$ for $Z=0.04$ to 7$M_{\odot}$ for $Z=0.1$, which implies a reduction in the minimum mass for core-collapse supernovae. MESA models of similarly high metallicity ($Z=0.06 - 0.09$) show the same lowering of the minimum mass for carbon ignition: carbon burning is detected in a $6 M_{\odot}$ model at the highest metallicity ($Z=0.09$) and in all $7 M_{\odot}$ models with $Z \ge 0.06$. This demonstrates robustness of the lowered carbon burning threshold across codes., 18 pages, 10 figures, accepted for publication in MNRAS

Rotating detonation engines (RDEs) have been observed to exhibit several operating modes and instabilities under different operation conditions (reactant mixture, injection pressure, engine geometry, injection mass flow rate, etc.). We develop the simplest model possible describing the operation of an RDE. This model takes into account the dependence of detonation properties on engine conditions, the injection process, and the geometric constraints. Using this model, we predict the lowest allowable reactant injection rates that allow an RDE to operate with a single detonation wave propagating in the annular combustion chamber. This model is compared with experimental results of engines running on H $${}_2$$ /O $${}_2$$ and C $${}_2$$ H $${}_4$$ /O $${}_2$$ .

This paper introduces procedural generation of lattice structures inside predefined volumes for fatigue life enhancement of multiscale constructed structural components. Global optimization is applied to search the design space such that the mass and fatigue damage is minimized given the orientation of the microscopic lattice unit cells and the volume fraction of lattice material. A two-step optimization procedure is applied to avoid local minima. The macro-scale distribution of homogenized lattice material is first determined using a design search method. The second stage employs global optimization with surrogate modeling. Training data is initialized by hypercube sampling to fit a surrogate model so that a genetic algorithm can locate the global minima of the global design space using the lattice rotation and solid volume fraction. New results are applied to the procedural methods to create new testable models which optimize the microscale for minimum mass. New data points are used to enrich the surrogate model database and the model is rebuilt. The procedure iterates until a convergence criterion is met. A case study is presented to demonstrate the proposed methodology to which the mass was reduced by 87%, while fatigue performance was conserved for long life cycles of 106. A comparison between lattice modeled with linear beam elements versus lattice material as a three-dimensional solid is presented to validate the optimal solution. It is found that stresses were underestimated by at most a factor of four, while the difference in deflections was maintained within 8.1%.

In this paper, a linear generalized uncertainty principle (GUP), which suggests a minimum measurable length and a maximal measurable momentum, is used in analyzing COW experiment and Einstein-Bohr’s a photon box experiment. Based in these experiments a modified Schwarzschild metric was obtained in order to calculate a quantum corrections in Schwarzschild black hole thermodynamics and tunneling probability. It was found that GUP placed restrictions on the minimum mass, size and temperature of the black hole, indicating that there was a black hole remnant after the completion of the evaporation process. The resulting values of minimum mass and size of the black hole are identical to that values predicted by quadratic GUP, which points out that the two models are equivalence in Planck scale measurements.

The membrane structures are the potential solution for near term spacecraft systems due to its significant advantages such as lightweight, higher folding and packaging efficiency, ease of deployment, and low on-board volume requirement. For the membrane structures, maintaining the uniform state of stress conditions with a minimum mass penalty of a tensioning system is the most challenging task for space industries. The inflatable planar membrane reflector is attached to the satellite body, used for bidirectional communication between the satellite and earth stations. The aim of the study is to develop the methodology for designing the tensioning system for a planar membrane reflector antenna. The work presents a novel average diagonal stress distribution relation for rectangular membrane reflector. The loading analysis of membrane reflector and tensioning chord is carried out numerically and experimentally to achieve the design goals of the antenna structure. The outcome of the loading analysis is compared and found to be consistent with the method available in the literature. The inflatable torus diameter is calculated based on the tensioning force required at anchor points.

Ellipsoidal variables present light-curve modulations caused by stellar distortion, induced by tidal interaction with their companions. An analytical approximated model of the ellipsoidal modulation is given as a discrete Fourier series by Morris and Naftilan 1993 (MN93). Based on numerical simulations using the PHOEBE code we present here updated amplitudes of the first three harmonics of the model. The expected amplitudes are given as a function of the mass ratio and inclination of the binary system and the fillout factor of the primary---the ratio between the stellar radius and that of its Roche lobe. The corrections can get up to 30% relative to the MN93 model for fillout factors close to unity. The updated model can be instrumental in searching for short-period binaries with compact-object secondaries in large data sets of photometric light curves. As shown in one OGLE light-curve example, the minimum mass ratio can be obtained by using only the amplitudes of the three harmonics and an estimation of the stellar temperature. High enough amplitudes can help to identify binaries with mass ratios larger than unity, some of which might have compact companions., Comment: 13 pages, 6 figures

In this study, optimal design of two-dimensional functionally graded thick flywheels is obtained by the generalized differential quadrature method (GDQM) and the non-dominated sorting genetic algorithm II (NSGA II). The flywheel cross section is parameterized with the Bezier surface, and a mapping procedure to discretize non-rectangular solution domain by the GDQM is introduced. The results of this novel technique are compared with the results available in open literature and the ANSYS finite element solution, and a very good agreement is observed. Pareto optimal solutions for minimum mass and maximum energy storage capability are obtained for two types of bearing, one being mechanical and the other magnetic. Consequently, the optimal cross-section geometry and the two-dimensional material distribution of functionally graded (FG) flywheel are obtained.

In this work, we report on the implementation of a closed-loop liquid-loaded resonant mass sensor as a test vehicle for the realization of highly sensitive miniaturized biomarker assays. Using thin-film piezoelectric-on-silicon (TPoS) contour-mode disc resonators that are specifically designed and optimized for liquid-phase operation, a liquid-loaded low power (~1.6 mW) oscillator at ~17 MHz is demonstrated with a single transistor. By proper placement of the electrodes and the supporting tethers, a high liquid-loaded quality factor (~380) and a low insertion loss (~19 dB) are concurrently achieved which enable the accurate frequency tracking of the potential mass microbalance. The frequency shifts due to the liquid-loading and the preliminary characterized frequency stability of the oscillator imply a minimum mass detection resolution in the picograms range. [2020-0177]

Dynamic soaring improves the endurance of Unmanned Aerial Vehicles (UAVs) by obtaining energy from the horizontal wind shear gradient. The use of dynamic soaring in small solar UAVs can mitigate the trade-off between energy capacity and battery weight to achieve continuous all-day flight. The goal of this study is to determine the optimal energy acquisition methods for small solar UAVs using dynamic soaring and to decrease the battery weight to achieve all-day flight. A dynamic soaring UAV model that considers the influence of the wind shear gradient and a solar power energy model are established. The conditions to obtain a closed-loop energy system during daytime and nighttime flights are discussed, and the minimum mass of the energy system required for these conditions is determined. Simulations of single-cycle circular flights and a 72-h continuous flight of a small solar UAV are performed. The analyses and simulation results show that: (1) the combination of dynamic soaring and solar technology significantly reduces the energy consumption and reduces the required battery weight, (2) the flight speed and flight attitude angles have significant effects on the optimal total energy acquisition and (3) wind fields with a large horizontal gradient and strong solar illumination provide energy and load advantages.

Lower bracket is an important component in hydro generator. Taking lower bracket as the research object, the strength, the stiffness and the dynamic characteristics of lower bracket have been simulated and analyzed by means of establishing a finite element model. With the two design indexes of maximum normal stress and stiffness as the constraint conditions, aiming at an optimized design with the minimum mass and proposed a lightweight optimization method. The design parameters of the optimized model of hydro generator lower bracket are determined by using the compound form method with optimization iteration. Through lightweight optimization design, the maximum normal stress and maximum displacement of lower bracket are within the allowable value range, modal analysis shows that the dynamic characteristics of the optimized structure also meet the requirements, with the potential of material further utilized. The lightweight optimization design reduced the weight of lower bracket in hydro generator by 790kg and the weight-loss ratio reaches 44.38%, thus achieving the purpose of lightweight. The optimization results are applied in the improvement design of lower bracket and the method is practical and suitable for engineering applications.

Cylindrical grid shells made of modern composite materials by automated continuous winding that have a high degree of weight perfection and are widely used in aerospace engineering are considered. The problem of using such structures as deep-submergence vehicle bodies operating not under external pressure is discussed. The problem of optimal design of cylindrical grid shells based on the criterion of minimum mass under constraints imposed on strength and stability is considered. By minimizing the safety factors for possible forms of destruction, an analytical solution that determines the optimal design parameters of the composite grid shell is obtained.

For short take-off and landing (STOL) aircraft, a parallel hybrid-electric propulsion system potentially offers superior performance compared to a conventional propulsion system, because the short-take-off power requirement is much higher than the cruise power requirement. This power-matching problem can be solved with a balanced hybrid propulsion system. However, there is a trade-off between wing loading, power loading, the level of hybridization, as well as range and take-off distance. An optimization method can vary design variables in such a way that a minimum of a particular objective is attained. In this paper, a comparison between the optimization results for minimum mass, minimum consumed primary energy, and minimum cost is conducted. A new initial sizing algorithm for general aviation aircraft with hybrid-electric propulsion systems is applied. This initial sizing methodology covers point performance, mission performance analysis, the weight estimation process, and cost estimation. The methodology is applied to the design of a STOL general aviation aircraft, intended for on-demand air mobility operations. The aircraft is sized to carry eight passengers over a distance of 500 km, while able to take off and land from short airstrips. Results indicate that parallel hybrid-electric propulsion systems must be considered for future STOL aircraft.

The authors have presented logical and mathematical formulations of the problem of system designing of complex systems by a combined quality criterion. Rocket engines of aircraft and spacecraft have been considered as complex systems. The problem of system designing of a power-supply system has been formulated as a problem of ensuring its minimum mass with assigned constraints on reliability, economic expenditures, and other parameters.

An integrated method for optimization of a welded portion of a high pressure compressor rotor as a single object is developed. The minimum mass criterion is used in the optimization method; limitations are imposed in accordance with strength and stiffness requirements. An example is given of optimization of a typical welded portion of a high pressure compressor rotor resulting in mass reduction and increase of cyclic durability.

In nature, homologues can be seen in structures of common evolutionary origin, which are composed of similar elements in the same zones. Homology shows the relationship of living organisms, which may differ externally, but their structure (bone and muscle) is characterized by significant similarity. The equivalent of homologous transformations in mathematics is homeomorphism, which is one of the basic concepts of the department of contemporary mathematics dealing with the study of the properties of topological geometric figures and solids (properties which do not change even after radical continuous deformation of figures), called topology. Homeomorphism is about transforming figures without tearing them apart and gluing them together, only by stretching, compressing, bending and twisting them, which enables continuity and identity functions to be maintained. Homeomorphic spaces are indistinguishable from the point of view of topology. Homeomorphism of space ensures the preservation of topological invariables, which include a number of features such as closeness, openness, compactness, centrality or cohesion. Optimization searches for solids based on topological transformations, carried out in the scope of architectural and structural criteria can be an important element of analyses in the interdisciplinary design process. On their basis it is possible to make a conscious choice between individual forms inspired by geometry or structures found in nature. The paper presents the results of model analyses of structural forms formed on the basis of topological transformations with determination of their effectiveness in terms of minimum mass. Optimization searches due to the minimum mass are an important element from the design of objects due to the idea of sustainable development.

This article proposes a theoretically substantiated graph analytical method for studying the bearing capacity of orthotropic shell structures of minimum mass. A conceptually new approach to the analysis of optimization processes is considered. It is a rejection of the deterministic approach when exact initial data are specified and the same exact results are expected. In reality, there is some variation in the values of the initial parameters, which can significantly change the extreme values of optimization. Taking into account the sensitivity of orthotropic shells to the choice of the geometry of the force set, in this paper, optimization is carried out by constructing the region of the permissible scatter of its initial values, provided that the probable strength of the structure is ensured with its minimum weight. The numerical calculations presented in the work testify to the efficiency and visibility of the graph-analytical method, as well as its ability to carry out automated calculations. By analogy with structurally orthotropic shells by the graph analytical method, it is possible to construct the regions of optimal values of the initial parameters, when they are scattered, any material products, including objects of military equipment (during their manufacture or repair), which would provide from a given degree of probability to achieve the set goals. The proposed method for calculating the optimal structural parameters allows us to establish in a number of cases the technical requirements for the accuracy of their manufacture, which can be reflected in the DSTU standards., Запропоновано графоаналітичний метод дослідження міцності статично навантажених ортотропних оболонкових конструкцій мінімальної маси. Теоретично обґрунтовано метод дослідження як у детерміністичному стані величин геометричних параметрів оболонки, так і в ймовірному їх розкиді за умов найменшої маси працездатної конструкції.

U ovom radu proveden je postupak projektiranja glavnog rebra tankera za prijevoz kemikalija, te su analizirani utjecaji razmaka okvirnih rebara i razmaka uzdužnjaka na masu konstrukcije trupa. Na temelju referentnog modela predloženo je i izrađeno devet varijanti različitog razmaka okvirnih rebara i uzdužnjaka. Prema uzdužnjacima pozicionirani su također uzdužni nosači dvodna i dvoboka. Kod svih varijanti zadovoljeni su svi uvjeti lokalne i globalne čvrstoće s obzirom na propisane kriterije klasifikacijskog društva. Dimenzioniranje uzdužnih konstrukcijskih elemenata konstrukcije provedeno je programom MARS, klasifikacijskog društva Bureau Veritas prema pravilima ˝Rules for the Clasiffication of Steel Ships˝. Dimenzije poprečne konstrukcije preuzete su iz predloška te je provedena studija senzitivnosti masa poprečnih elemenata ovisno o razmaku okvira. Na kraju su uspoređene postignute mase konstrukcije svih varijanti te su dane preporuke vezano za razmak okvira i razmak uzdužnjaka u cilju ostvarenja projekta minimalne mase. Through this papper study structural design of midship section of chemical tanker has been made, and the influence of longitudinals and web frame spacing on construction mass of chemichal tanker was analyzed. Based on reference model, nine models have been made using different combinations of longitudinals and web frame spacing. Double hull girders and double side girders were positined according to longitudinal spacing. In every variant all local and global strength criteria were met regarding classification society criteria. Longitudional construction elements have been designed using software MARS, provided by classification society Bureau Veritas, in accordance with Rules for the Classification of Steel Ships. Dimensions of transverse structure elements were taken from the template, and mass sensitivity study was made depending on the web frame spacing. At the end, all variants were compared to structural mass, and recommendations regarding the longitudinals and web frame spacing to achieve minimum structural mass project were given.

We report initial results of a large radial velocity survey of K dwarfs up to a distance of 50 pc from the Solar System, to look for stellar, brown dwarf, and jovian planets using radial velocities from the CHIRON spectrograph on the CTIO/SMARTS 1.5m telescope. We identify three new exoplanet candidates orbiting host stars in the K dwarf survey, and confirm a hot Jupiter from TESS orbiting TOI 129. Our techniques are confirmed via five additional known exoplanet orbiting K dwarfs, bringing the number of orbital solutions presented here to 9, each hosting an exoplanet candidate with a minimum mass of 0.5--3.0 $M_{jup}$. In addition, we provide a list of 186 nearby K dwarfs with no detected close companions that are ideal for more sensitive searches for lower mass planets. This set of stars is used to determine CHIRON's efficiency, stability, and performance for radial velocity work. For K dwarfs with V = 7--12, we reach radial velocity precisions of 5--20 ms$^{-1}$ under a wide range of observing conditions. We demonstrate the stability of CHIRON over hours, weeks, and years using radial velocity standards, and describe instrumental capabilities and operation modes available for potential users., Published in The Astronomical Journal. 17 pages, 8 figures, 5 tables

Proxima Centauri is our nearest stellar neighbor and one of the most well-studied stars in the sky. In 2016, a planetary companion was detected through radial velocity measurements. Proxima Centauri b has a minimum mass of 1.3 Earth masses and orbits with a period of 11.2 days at 0.05 AU from its stellar host, and resides within the star's Habitable Zone. While recent work has shown that Proxima Centauri b likely does not transit, given the value of potential atmospheric observations via transmission spectroscopy of the closest possible Habitable Zone planet, we reevaluate the possibility that Proxima Centauri b is a transiting exoplanet using data from the Transiting Exoplanet Survey Satellite (TESS). We use three sectors (Sectors 11, 12, and 38 at 2-minute cadence) of observations from TESS to search for planets. Proxima Centauri is an extremely active M5.5 star, emitting frequent white-light flares; we employ a novel method that includes modeling the stellar activity in our planet search algorithm. We do not detect any planet signals. We injected synthetic transiting planets into the TESS and use this analysis to show that Proxima Centauri b cannot be a transiting exoplanet with a radius larger than 0.4 R$_\oplus$. Moreover, we show that it is unlikely that any Habitable Zone planets larger than Mars transit Proxima Centauri., Comment: 14 pages, 5 figures, accepted for publication in Frontiers in Astronomy and Space Sciences

The theory of substellar evolution predicts that there is a sharp mass boundary between lithium and non-lithium brown dwarfs, not far below the substellar-mass limit. The imprint of thermonuclear burning is carved on the surface lithium abundance of substellar-mass objects during the first few hundred million years of their evolution, leading to a sharp boundary between lithium and non-lithium brown dwarfs, so-called, the lithium test. New optical spectroscopic observations of the binaries DENIS+J063001.4-184014 and DENIS+J225210.7-173013 obtained using the 10.4-m Gran Telescopio de Canarias are reported here. They allow us to re-determine their combined optical spectral types (M9.5 and L6.5, respectively) and to search for the presence of the LiI resonance doublet. The non detection of the LiI feature in the combined spectrum of DENIS\,J063001.4$-$184014AB is converted into estimates for the depletion of lithium in the individual components of this binary system. In DENIS\,J225210.7$-$173013AB we report the detection of a weak LiI feature which we tentatively ascribe as arising from the contribution of the T3.5-type secondary. Combining our results with data for seven other brown dwarf binaries in the literature treated in a self-consistent way, we confirm that there is indeed a sharp transition in mass for lithium depletion in brown dwarfs, as expected from theoretical calculations. We estimate such mass boundary is observationally located at 51.48$^{+0.22}_{-4.00}$ $M_\mathrm{Jup}$, which is lower than the theoretical determinations., 12 pages, 6 figures, accepted for publication in MNRAS

We re-evaluate the outer edge of orbital stability for possible exomoons orbiting the radial velocity planet discovered in the HD 23079 system. In this system, a solar-type star hosts a Jupiter-mass planet in a nearly circular orbit in the outer stellar habitable zone. The outer stability limit of exomoons is deduced using $N$-body and tidal migration simulations considering a large range of initial conditions, encompassing both prograde and retrograde orbits. In particular, we extend previous works by evaluating many values in the satellite mean anomaly to identify and exclude regions of quasi-stability. Future observations of this system can make use of our results through a scale factor relative to the currently measured minimum mass. Using a constant time lag tidal model (Hut 1981), we find that plausible tidal interactions within the system are insufficient to induce significant outward migration toward the theoretical stability limit. While current technologies are incapable of detecting exomoons in this system, we comment on the detectability of putative moons through Doppler monitoring within direct imaging observations in view of future research capacities., 10 pages, 5 figures, 2 tables; accepted for publication in PASA

Suspended polymeric microstructures in the form of microcantilevers and microbeams have seen enormous flux of usage in physical, chemical and biological sensing. Present work investigates more about miniaturized PDMS elastomeric microbeams which can overcome the drawback of conventional rigid silicon based micro-sensors. Static and dynamic methods of analysis for the as-fabricated structures in the lab have been investigated in the present study using COMSOL Multiphysics® 5.3 software to give a better insight about its sensitivity. The study was compared with that of conventional polysilicon microbeams of similar dimensions also and proved to be less effective that polymeric ones. Further, the static and dynamic analysis of the microbeams revealed that the sensors were capable of detecting a minimum mass of almost 70 $\mu$ g and 50 pg respectively, suggesting that the dynamic analysis provided sensitivity than static method.

A numerical comparative analysis of indicators of the technical level of planar rod, armored and spatial armored electromagnetic systems with twisted and laminated magnetic circuits was carried out. To determine the advantages and justify the choice of the design of a single-phase transformer, a universal method of objective functions for optimizing electromagnetic systems with dimensionless indicators of the technical level and relative controlled variables was used. When determining the objective functions based on the condition of electromagnetic equivalence, the materials used, the amplitudes of the magnetic field in the rods and current density of the windings, the average values of yokes, as well as the design and cooling methods of electromagnetic static devices were taken to be the same. It was determined that twisted electromagnetic systems are the best according to the criterion of minimum mass of active materials in comparison with laminated ones.

Discrete Stiffness Tailoring (DST) is a novel manufacturing concept where stiffness tailoring is achieved using discrete changes in ply angle to favourably redistribute stresses. Resulting performance increases can be exploited to potentially achieve lightweight rapidly manufacturable structures, uninhibited by the minimum tow-turning radii which limit continuous fibre steering approaches. An efficient two-stage optimisation routine is implemented to design a DST minimum-mass stiffened aircraft wing panel subject to buckling and manufacturing feasibility constraints. The panel is manufactured and compression tested to failure, extending the DST design concept to component level for the first time. A weight reduction of 14.4% is achieved compared to a constant stiffness optimum, through redistribution of load to the stiffener region. The optimum design removes material from the skin, between stiffeners. Experimentally, the optimised tailored panel achieved a buckling load, without failure, within 5% of that predicted, validating both the methodology and modelling.

The cut-off mass ratio is under debate for contact binaries. In this paper, we present the investigation of two contact binaries with mass ratios close to the low mass ratio limit. It is found that the mass ratios of VSX J082700.8+462850 (hereafter J082700) and 1SWASP J132829.37+555246.1 (hereafter J132829) are both less than 0.1 ($q\sim0.055$ for J082700, and $q\sim0.089$ for J132829). J082700 is a shallow contact binary with a contact degree of $\sim$19%, and J132829 is a deep contact system with a fillout factor of $\sim$70%. The $O-C$ diagram analysis indicated that both the two systems manifest long-term period decrease. In addition, J082700 exhibits a cyclic modulation which is more likely resulted from Applegate mechanism. In order to explore the properties of extremely low mass ratio contact binaries (ELMRCBs), we carried out a statistical analysis on contact binaries with mass ratios of $q\lesssim0.1$ and discovered that the values of $J_{spin}/J_{orb}$ of three systems are greater than 1/3. Two possible explanations can interpret this phenomenon. One is that some physical processes, unknown to date, are not considered when Hut presented the dynamically instability criterion. The other is that the dimensionless gyration radius ($k$) should be smaller than the value we used ($k^2=0.06$). We also found that the formation of ELMRCBs possibly has two channels. The study of evolutionary states of ELMRCBs reveals that their evolutionary states are similar with those of normal W UMa contact binaries., 26 pages, 9 figures, and 4 tables, accepted by ApJ

The nuclear symmetry energy plays an important role in the description of the properties of finite nuclei as well as neutron stars. Especially, for low values of baryon density, the accurate description of the crust-core interface strongly depends on the symmetry energy. Usually, the well known parabolic approximation is employed for the definition of the symmetry energy without avoiding some drawbacks. In the present paper, a class of nuclear models, suitable for the description of the inner and outer core of neutron stars, is applied in studying the effect of higher orders of the expansion of the energy on the location of the crust-core transition. The thermodynamical and dynamical methods are used for the determination of the transition density $n_{\rm t}$ and pressure $P_{\rm t}$. The corresponding energy density functional is applied for the study of some relevant properties of both nonrotating and slowly rotating neutron stars. We found that the larger the value of the slope parameter $L$, the slower the convergence of the expansion. In addition, a universal relation is presented between $n_{\rm t}$ and $L$, by employing the full expression and dynamical approach. The crustal moment of inertia is very sensitive to the location of the transition while the effects are moderated concerning the critical angular velocity of the $r$-mode instability and minimum mass configuration. The effect on the tidal deformability is less but not negligible. In any case, the use of the parabolic approximation leads to the overestimation of $n_{\rm t}$ and $P_{\rm t}$ and consequently, on inaccurate predictions. Moreover, in some cases, even the matching process at the interface may affect considerably the predictions, introducing errors of the same order with the one due to the employed method., Comment: v1: 10 pages, 5 figures, 3 tables; v2: 15 pages, 7 figures, 6 tables, appendix and updated references; accepted for publication in Physical Review C; v3: matched the published version

The use of industrial robotics in construction poses a number of severe and contradictory requirements, in particular, at high speed it is necessary to provide a given smooth movement and high precision of working out, and at the minimum mass and overall dimensions of actuators wish to receive the highest productivity and the performance of the robot. This increase in accuracy is usually associated with an increase in the mass and moment of inertia of the moving parts, and an increase in performance is achieved by the placement of tight drive mechanisms on the moving links of the robots, which significantly load them, thereby reducing the payload of industrial robots. One of the key factors for efficient use of robots is the optimal selection of their parameters for the specific task, which requires additional research, since scientific works that clearly reflect the relationship between the work environment and the work are virtually absent. To use robots in construction, it is not necessary to have a clear model of understanding the functioning of these systems in the given technological conditions, as on the basis of this the optimal selection of the unit will be performed and the basic units and mechanisms of the work will be constructed. The purpose of this work is to establish the influence of a given working environment on the choice of geometric parameters of a two-link manipulator. The paper presents the dependence by which it is possible to estimate the energy-genetic parameters of the manipulator, which depend on its geometric dimensions. The study used methods of geometric similarity and analytical algebra, Lagrange equations of the 2nd kind, and known optimal laws of motion, which are correct for lifting machines.

This paper deals with two optimisation problems related to axisymmetric membrane shells made of homogeneous, linear and isotropic materials and subjected to an internal pressure. The design variables are the meridian shape and the thickness distribution (possibly not constant). In the first part of the paper, a general background on the mechanics of thin-walled shells is presented and the two optimisation problems concerning the search for meridian profile and thickness distribution which minimise the mass once fixed the internal volume (which, in the present work, is called direct problem) and which maximise the volume once fixed the mass (the dual problem) are formulated. The direct problem is studied and solved in closed form in several works available in the literature. All these works refer to the case of shells made of brittle materials. Herein, an extension to ductile materials is proposed. Moreover, the dual problem is solved in closed form, highlighting that the domain of boundary conditions for which a solution exists is more restricted with respect to that of the direct problem.

In protoplanetary discs (PPDs) consisting of gas and dust particles, fluid instabilities induced by the drag force, including secular gravitational instability (SGI) can facilitate planet formation. Although SGI subject to the axisymmetric perturbations was originally studied in the absence of gas feedback and it then generalized using a two-fluid approach, the fate of the nonaxisymmetric SGI, in either case, is an unexplored problem. We present a linear perturbation analysis of the nonaxisymmetric SGI in a PPD by implementing a two-fluid model. We explore the growth of the local, nonaxisymmetric perturbations using a set of linearized perturbation equations in a sheared frame. The nonaxisymmetric perturbations display significant growth during a finite time interval even when the system is stable against the axisymmetric perturbations. Furthermore, the surface density perturbations do not show continuous growth but are temporally amplified. We also study cases where the dust component undergoes amplification whereas the gas component remains stable. The amplitude amplification, however, strongly depends on the model parameters. In the minimum mass solar nebula (MMSN), for instance, the dust fluid amplification at the radial distance 100 au occurs when the Stokes number is about unity. But the amplification factor reduces as the dust and gas coupling becomes weaker. Furthermore, perturbations with a larger azimuthal wavelength exhibit a larger amplification factor., accepted for publication in MNRAS

Efficiency improving of the forest sector cannot be achieved without development of the forest machines design methods. Analysis of the studies devoted to this issue shows that insufficient attention was paid to it. The research objectives were to analyze the influence of the probabilistic nature of tree parameters on the load from moving tree bundle acting on a chokerless skidding system, and to determine the range of values of the necessary load-carrying capacity of the system’s chassis based on the analysis results. The research was based on computer experiment consist of tree bundle generating necessary for the full filling of the skidding system chain grapple. The parameters of generated trees were determined by the taxation conditions of the Karelian Republic forest stands. Forty five variation series characterizing the mass distribution of a skidding tree bundle were obtained based on the computer experiment results processing. The variation curve shifted to the right side along the mass axis of a tree bundle, and its shape changed with the increase of chain grapple size. The curve was stretched slightly and became more flat; the maximum value of the relative frequency of tree bundle mass decreased. Tree bundle mass fluctuated significantly at the same size of chain grapple. The difference between the maximum and minimum mass values of tree bundles was in the range of 3.7–5.6 tons. It increased with the increase of chain grapple size. The analytical dependence of tree bundle mass necessary for determina-tion the load-carrying capacity of the chokerless skidding system chassis on the chain grapple size was found. The recommended values of the chassis load-carrying capacity in the considered range of chain grapple sizes (1–2.2 m2) are in the range of 5.5–12.4 tons. The obtained results can be used at antecedent design stage of forest machines, as well as at technical and economic assessment of chokerless skidding systems operating in the Republic of Karelia.For citation: Shegelman I.R., Budnik P.V. Features of Calculated Truck Load Estimation at Antecedent Design Stage of Chokerless Skidding System Based on Computer Experiment. Lesnoy Zhurnal [Forestry Journal], 2019, no. 3, pp. 82–96. DOI: 10.17238/issn0536-1036.2019.3.82Funding: the research was carried out within the framework of the grant of the President of the Russian Federation no. MK-5321.2018.8.