Effect Of Mass Changes Research Articles

Mechanics mode characteristics analysis and numerical analytical optimization study of a three-stage centrifugal pump

To increase the accuracy of an analytic method based on the concentrated-mass approach for solving the mechanical operating modal characteristics of complete impellers and impellers with balancing holes in a centrifugal-pump rotor system, we establish a mathematical model and a three-dimensional simulation model for a double-supported three-stage centrifugal-pump rotor system. By comparing the modal results obtained from the two models, we propose a mathematical model that integrates the optimization of mass-distribution methods and bending stiffness correction coefficients, and we derive an optimized mathematical model for rotors with balancing holes. The effectiveness of the optimized mathematical model is validated via three-dimensional simulation, and the influence of balancing holes on the wet modes is analyzed. The results show that the wet natural frequencies are lower than the dry ones and that the wet natural frequencies obtained from analytical calculations are consistently higher than those obtained from three-dimensional simulation results. The optimized mathematical model significantly improves the accuracy of the wet modal characteristics for both complete impellers and impellers with balancing holes, with the errors in the low-order natural frequencies reduced by more than 50%. Under the same hole spacing, the natural frequencies of the three-stage centrifugal pump rotor system decrease with increasing hole diameter slightly. Under the same hole diameter, the natural frequencies of the rotor system increase slightly with the hole spacing. The effect of stiffness changes caused by balancing holes on the natural frequencies is larger than the effect of mass changes.

Modelling stellar evolution in mass-transferring binaries and gravitational-wave progenitors with metisse

ABSTRACT Massive binaries are vital sources of various transient processes, including gravitational-wave mergers. However, large uncertainties in the evolution of massive stars, both physical and numerical, present a major challenge to the understanding of their binary evolution. In this paper, we upgrade our interpolation-based stellar evolution code metisse to include the effects of mass changes, such as binary mass transfer or wind-driven mass loss, not already included within the input stellar tracks. metisse’s implementation of mass loss (applied to tracks without mass loss) shows excellent agreement with the sse fitting formulae and with detailed mesa tracks, except in cases where the mass transfer is too rapid for the star to maintain equilibrium. We use this updated version of metisse within the binary population synthesis code bse to demonstrate the impact of varying stellar evolution parameters, particularly core overshooting, on the evolution of a massive (25 and 15 M⊙) binary system with an orbital period of 1800 d. Depending on the input tracks, we find that the binary system can form a binary black hole or a black hole–neutron star system, with primary (secondary) remnant masses ranging between 4.47 (1.36) and 12.30 (10.89) M⊙, and orbital periods ranging from 6 d to the binary becoming unbound. Extending this analysis to a population of isolated binaries uniformly distributed in mass and orbital period, we show that the input stellar models play an important role in determining which regions of the binary parameter space can produce compact binary mergers, paving the way for predictions for current and future gravitational-wave observatories.

Mechanical characteristics analysis and control algorithm for floating raft system with mass variation

The ship floating raft system adopts the integrated design of large liquid tanks and rafts, which can optimize the arrangement in the cabin and increase the intermediate mass of the system to achieve efficient vibration isolation of equipment. One of the major challenges is that the change of liquid mass in the tank will cause displacement of the raft, which will change the modal characteristics of the system and affect the stability of the vibration isolation system performance. This paper establishes a mechanical analysis model of a floating raft system under time-varying liquid mass conditions. Taking a ship variable mass floating raft system as the research object, the effect of mass change on the characteristics of raft displacement, isolator load distribution, and modal frequency of the vibration isolation system is analyzed. The analysis shows that when the liquid tank goes from full load to no-load state, its mass change accounts for 40% of the total mass of the raft, which will cause a large displacement of the raft and change the low order modal frequency of the system, bringing the risk of equipment safety and vibration isolation performance degradation. Therefore, an adaptive variable load control method is proposed to realize the raft attitude balance and load equalization optimization under the variable mass condition of the floating raft air spring system. The test results show that the proposed control method can automatically adapt to the large mass gradual change from full load to no load of the liquid tank on the raft, and control the displacement of the raft structure from about 10 mm to 1.5 mm, which effectively ensures the stability of the air spring system performance.

Quarkyonic mean field theory

We discuss mean field theory of quarkyonic matter at zero temperature. We treat the nucleons with contact interactions in mean field approximation, discussing both vector and scalar mean field interactions. We treat the quarks without mean field vector interactions, but allow mass terms to be generated consistently from a scalar mean field consistent with the additive quark model for quark masses. Quarkyonic matter is composed of a shell of nucleons that under-occupy the total available phase space associated with the underlying quark degrees of freedom. The fully occupied Fermi sphere beneath this shell of nucleons at high densities is thought of as quarks, but when this fully occupied distribution of states first appears, although the phase space is filled, the matter is at low density. For the transition between this low density and high density saturated matter, we advocate a dual description of the fully filled Fermi sea in terms of hadrons, and make a phenomenological hypothesis for the equation of state of this matter. We then proceed to an example where the mean field interactions are all vector and only associated with the nucleons, ignoring the effects of mass change associated with the scalar interactions. Except for the effects of Pauli blocking, the nucleons and quarks do not interact. To get a reasonable transition to quarkyonic matter the interaction of the quarks among themselves are assumed to be nonperturbative, and a simple phenomenological relation between quark Fermi energy and density is introduced.

Stimuli-responsive shell theory

Soft matter mechanics generally involve finite deformations and instabilities of structures in response to a wide range of mechanical and non-mechanical stimuli. Modeling plates and shells is generally a challenge due to their geometrically nonlinear response to loads; however, non-mechanical loads further complicate matters as it is often not clear how they modify the shell’s energy functional. In this work, we demonstrate how to form a mechanical interpretation of these non-mechanical stimuli, in which the standard shell strain energy can be augmented with potentials corresponding to how a non-mechanical stimulus acts to change the shell’s area and curvature via the natural stretch and curvature. As a result, the effect of non-mechanical stimuli to deform shells is transformed into effective external loadings, and this framework allows for the application of analytical and computational tools that are standard within the mechanics community. Furthermore, we generalize the effect of mass change during biological growth to account for its effect on the stress constitution. The theory is formulated based on a standard, stress-free reference configuration which is known a priori, meaning it can be physically observed, and only requires the solution of a single-field equation, the standard mechanical momentum or equilibrium equation, despite capturing the effects of non-mechanical stimuli. We validate the performance of this model by several benchmark problems, and finally, we apply it to complex examples, including the snapping of the Venus flytrap, leaf growth, and the buckling of electrically active polymer plates. Overall, we expect that mechanicians and non-mechanicians alike can use the approach presented here to quickly modify existing computational tools with effective external loadings calculated in this novel theory to study how various types of non-mechanical stimuli impact the mechanics and physics of thin shell structures.

Effects of Mass Change on Liquid-Liquid Phase Separation of the RNA-Binding Protein Fused in Sarcoma.

In recent years, many experimental and theoretical studies of protein liquid-liquid phase separation (LLPS) have shown its important role in the processes of physiology and pathology. However, there is a lack of definite information on the regulation mechanism of LLPS in vital activities. Recently, we found that the intrinsically disordered proteins with the insertion/deletion of a non-interacting peptide segment or upon isotope replacement could form droplets, and the LLPS states are different from the proteins without those. We believed that there is an opportunity to decipher the LLPS mechanism with the mass change perspective. To investigate the effect of molecular mass on LLPS, we developed a coarse-grained model with different bead masses, including mass 1.0, mass 1.1, mass 1.2, mass 1.3, and mass 1.5 in atomic units or with the insertion of a non-interacting peptide (10 aa) and performed molecular dynamic simulations. Consequently, we found that the mass increase promotes the LLPS stability, which is based on decreasing the z motion rate and increasing the density and the inter-chain interaction of droplets. This insight into LLPS by mass change paves the way for the regulation and relevant diseases on LLPS.

Using a Multiobjective Genetic Algorithm to Design Satellite Constellations for Recovering Earth System Mass Change

The Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) provided twenty years of data on Earth’s time-varying gravity field. Due to their design, GRACE and GRACE-FO are inherently limited in their spatiotemporal coverage, limiting their resolution to a few hundred kilometers and temporally to roughly monthly solutions. To increase the global spatiotemporal resolution and allow for the determination of submonthly time-varying gravity field signals, a constellation of GRACE-type satellite pairs is a possible path forward. Advances in small form factor instrumentation for small satellites have become progressively inexpensive, reliable, and of higher quality. This leads us to consider that a constellation of GRACE-type small satellites could be part of future gravimetric satellite missions. In this work, we investigate the viability and limitations of a genetic-algorithm-based optimization and its objective function to generate satellite constellations to recover daily Earth system mass changes. The developed approach is used to create satellite constellations that are optimally designed to recover gravity variations of sufficient resolution at a range of temporal frequencies (i.e., daily to monthly). We analyze a constellation’s performance using a combination of observability in space, accounting for directionality, and homogeneity in time. This allows us to navigate through a vast search space in a relatively short period of time and estimate the relative performance of constellations to each other. Using evolutionary theory, we converge towards a set of optimally selected orbits. The characteristics of the designed constellations have been validated using high-fidelity numerical simulations. We summarize these results and discuss their implications for possible future constellations of small GRACE-like satellite pairs. The resulting constellations have an inherently improved spatiotemporal performance, which reduces temporal aliasing errors and allows the characterization of daily mass-change effects.

A population balance cavitation model

We propose a novel polydisperse cavitation model based on population balances, which seeks to provide the bubble size distribution in addition to the void fraction, enabling natural prediction of transitions from large bubbles to small cavities in regions of massive condensation, or from small bubble to large cavities in regions of strong evaporation. The mass transfer rate is modeled from the asymptotic solution of the Rayleigh-Plesset equation with modifications for the polydisperse approach. Existing breakup and coalescence models, which do not include effects of mass change, are adapted and new models are developed to account for evaporation and condensation. In addition, homogenous and heterogeneous nucleation models are incorporated to treat the activation and size distribution of nuclei. The model is evaluated against data for the Delft twisted foil, showing satisfactory results for the pressure distribution, forces, and shedding frequency. Though no experimental data for the bubble size distribution is available, bubble sizes in different regions of the flow predicted by the model indicate the right trends observed in videos and photographs of the experiments. Refinements to the model based on experiments are necessary, especially to evaluate the ability to properly predict void fraction and bubble size distribution.

Arctic Sea Level Budget Assessment during the GRACE/Argo Time Period

Sea level change is an important indicator of climate change. Our study focuses on the sea level budget assessment of the Arctic Ocean using: (1) the newly reprocessed satellite altimeter data with major changes in the processing techniques; (2) ocean mass change data derived from GRACE satellite gravimetry; (3) and steric height estimated from gridded hydrographic data for the GRACE/Argo time period (2003–2016). The Beaufort Gyre (BG) and the Nordic Seas (NS) regions exhibit the largest positive trend in sea level during the study period. Halosteric sea level change is found to dominate the area averaged sea level trend of BG, while the trend in NS is found to be influenced by halosteric and ocean mass change effects. Temporal variability of sea level in these two regions reveals a significant shift in the trend pattern centered around 2009–2011. Analysis suggests that this shift can be explained by a change in large-scale atmospheric circulation patterns over the Arctic. The sea level budget assessment of the Arctic found a residual trend of more than 1.0 mm/yr. This nonclosure of the sea level budget is further attributed to the limitations of the three above mentioned datasets in the Arctic region.

Influence of processing conditions on crystal structure of BiNbO4 ceramics

Bismuth niobate (BiNbO4) has attracted attention as a low-fired ceramics with promising microwave application potential. It belongs to the bismutocolumbite oxides with similarly to scheelite-like stibiotantalite structure (SbTaO4) A3+B5+O4. The aim of the present research was to fabricate BiNbO4 ceramics by solid state reaction route from the mixture of simple oxides viz. Bi2O3, and Nb2O5, and study its phase composition as well as crystal structure by X-ray diffraction method. The Rietveld refinement method was utilized for analysis of diffraction patterns. It was found that the mass change effects finished at temperature T=500°C and the total mass change was about Δm=-0.78%. It was found that BiNbO4 ceramics sintered in ambient air exhibited multiphase composition, i.e., apart from the major α-BiNbO4 phase, the orthorhombic Bi5Nb3O15, Bi3Nb17O47 and cubic Bi3NbO7 phases were present. An increase in sintering temperature caused an increase in the amount of major α-BiNbO4 phase which adopted an orthorhombic symmetry described well by Pnna(52) space group.

About the Influence of Butt Weld Joints Geometry on the Damage Detection Process

The number and diversity of global nondestructive testing methods applicable to welded structures have rapidly increased in last decades. Vibration-based damage detection methods make possible the evaluation of structures at once; the damage location can be found without having direct access to the structure’s damaged region. Butt welded components often bring complexity in the structures, since the weld introduces cross-section shape changes and alteration of the material’s physical and mechanical characteristics. Moreover, the structure continuity can be interrupted by cracks or cavities. All changes occurring due to the weld induce mutations in the structures dynamical behavior. This paper presents a method to identify structural changes by using information from the modal analysis, actually analyzing the natural frequency shifts. Mathematical relations describing the individual or coupled effect of mass change and geometrical discontinuities are derived and used in the identification process; in fact, finding the mass changes or cracks becomes an inverse problem. The mathematical models are successfully tested on virtual and real structures.

Effects of organism preparation in metallothionein and metal analysis in marine invertebrates for biomonitoring marine pollution

Metallothionein (MT) is established as a potentially useful biomarker for monitoring aquatic pollution. This paper addresses widespread inconsistencies in storage conditions, tissue type selection and pre-treatment of samples before MT and metal analysis in biomarker studies. This variation hampers comparability and so the widespread implementation of this monitoring approach. Actively sampled Mytilus edulis in Southampton Water, UK were exposed to different storage temperatures, a variety of tissue types were analysed, and various pre-treatments of transportation on ice, transportation in seawater, depuration, and rapid dissection in the field were examined. Storage temperatures of −20°C were found to be adequate for periods of at least ten weeks, as MT was not reduced by protein degradation compared with samples kept at −80°C. Whole tissue and digestive gland concentrations of MT and metals were significantly positively correlated and directly relatable. MT in the digestive gland appeared to be more responsive to metals than in whole tissue, where it may be diluted, masking MT responses. However, longer study periods may suffer the effects of mass changes to the digestive gland, which alters MT concentration, and it may therefore be advisable to measure whole tissue. Depuration and transportation in seawater reduced both MT and metal concentrations in the digestive gland, and few correlations between MT and metals were identified for these treatments. It is therefore recommended that: i) samples are transported to the laboratory on ice and dissected as soon as possible thereafter, ii) depuration should not be used when examining MT response to metal exposure until further research clarifying its utility is reported, iii) either whole tissue or the digestive gland can be used to measure MT, though whole tissue may be preferable on long-term studies, and iv) organisms can be stored at −20°C before analysis for up to ten weeks. These practices can be applied to future biomonitoring studies and will improve the comparability and repeatability of using MT as a biomarker.

Persistence of bending and torsional modes in piezoelectric-excited millimeter-sized cantilever (PEMC) sensors in viscous liquids - 1 to 103 cP

Cantilever sensors consisting of only a piezoelectric layer express both bending and torsional modes near ∼25 kHz that persist with reasonable Q-values (∼15) in liquids of high viscosity (>100 cP). Responses of both bending and torsional modes in liquids (1−1019 cP) were measured simultaneously. The bending mode response was more sensitive to mass-change effects than the torsional mode, and the response in liquids <70 cP matched theoretical values within 0.9%. At 1019 cP the bending mode response was within 10.4% of theory. The bending and torsional modes in PEMC can potentially be used simultaneously for bio-chemical sensing in very viscous samples.

What are the limits of the discrete stringed instrument model?

Many different analytical models for stringed instruments have appeared in the technical literature, but one of the most widely used is a simple discrete model presented by Christensen and Vistisen in 1980. This model accounts, in a simple and approximate way, for the first two or three modes of a typical stringed instrument such as a guitar and includes coupling between the structure and the enclosed air. For the model to be used in predicting the effect of design changes, it is important to understand its limits. In order to explore the applicablity of the model, we have constructed a fixture that models the volume of an acoustic guitar with rigid side walls and flexible top and back plates, which can be changed quickly. A group of different tops was tested to show the effect of changes in mass and stiffness. Additionally, different soundhole geometries were used. In order to change the interior volume of the body, rigid plates were inserted into the body cavity. We report on the ability of tuned discrete models to account for changes to the geometry and the structure. Further, we show the experimentally determined trends in dynamic response of the guitar fixture.

Real-time measurement of photocatalytic reactions using a monolithic QCM array

This paper reports a real-time measurement of photocatalytic reactions by using a miniaturized quartz-crystal microbalance (QCM) array. The QCM was miniaturized and integrated on the same quartz plate using microfabrication techniques. Two QCMs were located close to each other, with one of the QCMs used as a reference sensor for the accurate and independent determination of mass change effects and environmental change effects. The QCM output was compensated for frequency shifts induced by ultra violet (UV) irradiation by subtracting the frequency shift of the reference sensor. The minimum detectable frequency shift under the irradiation was within 1 Hz. The measured photodecomposition speed of methylene blue dye on a TiO2-coated QCM agreed well with that evaluated by the standard optical testing method under dry condition. The developed method enabled us to measure the photodecomposition of a surfactant on a TiO2-coated QCM with sub-nanogram mass resolution in real time.

Ceramic bismuth titanate for high – temperature electro-acoustic transducers

Bismuth titanate Bi4Ti3O12 (BIT), which belongs to the Aurivillius family, is one of the most interesting compounds among the bismuth-based layered ceramics. BIT is a ferroelectric material with wide applications in the electronic industry, as capacitors, transducers, memory devices and sensors. BIT ceramics materials with m= 3 were prepared by conventional mixed-oxide method by solid-state reaction. Thermal and mass change effects were analyzed in air by thermogravimetric and differential thermal analysis. The crystal structure of Bi4Ti3O12 was examined at room temperature with an X-ray diffraction method using the Rietveld method. Microstructure and chemical composition were analyzed. The investigation of dielectric proprieties of Bi4Ti3O12 ceramics shows that the BIT is ferroelectric with Tc about 675○C. Due to this high transition temperature, BIT ceramics is a good material for high temperature piezoelectric applications.

High temperature corrosion of metallic materials in simulated waste incineration environments at 300–600 °C

AbstractThe durability of the materials employed in waste incineration plants is affected by different factors that together result in severe degradation of the materials. The effects of alloying elements, as well as deposit composition and temperature range are investigated in this work. Different alloys were exposed in laboratory experiments to a specifically simulated waste incineration atmosphere N2 – 8 vol.% O2 – 2000 vppm HCl – 15 vol.% H2O – 200 vppm SO2 at 300–600 °C. The samples are covered with different salt mixtures especially chlorides and sulphates. Experiments with PbCl2‐KCl‐ZnCl2 at 450 °C, which is molten, showed catastrophic corrosion, but this was not observed in the case with KCl, which is solid. Mixtures of five different sulphates did not cause significant mass losses at 600 °C, but sulphate‐chlorided mixtures caused bigger mass losses. The presence of Al and Si in the alloys decreased mass change effects, the presence of Mo in alloys tested showed a negative effect.

Synthesis and dielectric properties of A m−1 Bi 2B mO 3 m+3 ceramic ferroelectrics with m=1.5

Bismuth containing ceramic materials of molecular formula Bi 5TiWNbO 15, Bi 5Ti 1/2W 1/2Nb 2O 15, Bi 5Nb 3O 15 have been synthesised and fabricated. The materials are known as the Aurivillius phases. The Aurivillius phases are a family of oxide ferroelectrics generally formulated as A m−1 Bi 2B m O 3 m+3 . The process of preparation was investigated by X-ray diffraction method as well as the simultaneous thermal analysis, in which both thermal (DTA) and mass change effects (TG) were measured on the same sample. The synthesis of the Aurivillius phases was carried out according to the solid state reaction from the conventional mixture of oxides (Nb 2O 5, WO 3, Bi 2O 3, and TiO 2). DTA and TG traces showing the synthesis effects have been recorded. Investigations of the crystalline structure, microstructure and basic dielectric properties were performed.

A temperature insensitive quartz microbalance

Mass deposition onto a microbalance is generally accompanied by a temperature change. By measuring a single frequency only, it is not possible to separate the frequency change due to mass change from that due to temperature change. In the temperature insensitive microbalance technique, measurements of two frequencies, the fundamental mode and third overtone frequencies of an SC-cut resonator, yield two equations with two unknowns. This allows the separation of mass change effects from temperature change effects. Dual mode excitation can be used for highly accurate resonator self-temperature sensing over wide temperature ranges. SC-cut resonators are also thermal transient compensated. These unique properties allowed the development of a temperature compensated microbalance that is highly sensitive to mass changes, which can be used in rapidly changing thermal environments, over wide temperature ranges, and which requires neither temperature control nor a thermometer other than the resonator. To demonstrate the performance of this microbalance, SC-cut resonators were coated with thin polymethylmethacrylate (PMMA) photoresist films then placed into a UV-ozone cleaning chamber that initially was at about 20 degrees C. When the UV lamp was turned on, the UV-ozone removed PMMA from the surfaces while the chamber temperature rose to about 60 degrees C. The frequency changes due to mass changes could be accurately determined, independently of the frequency changes due to temperature changes.

Stress-dependent hole effective masses and piezoresistive properties ofp-type monocrystalline and polycrystalline silicon

Piezoresistive effects of $p$-type polycrystalline silicon underline that longitudinal and transversal piezoresistive properties in monocrystalline silicon do not have the same physical origin, which is not accounted for in current models. This difference is highlighted by the study of the mechanical stress effect on the valence band, which shows that piezoresistive properties of $p$-type monocrystalline silicon can be explained in terms of both hole transfer between heavy- and light-hole valence bands and stress-dependent hole effective masses. The quantification of these phenomena points out that longitudinal piezoresistive properties are mainly due to the hole transfer, whereas transversal ones are mainly attributed to the effective mass change effects. This enables one to model $p$-type polycrystalline silicon piezoresistivity, in particular the sign change of the transversal gauge factor at high doping level.