Influence Of Gravity Research Articles

Evaluation of a urine dipstick protein to urine specific gravity ratio for the detection of proteinuria in dogs and cats.

The utility of urine dipsticks for the quantification of proteinuria is limited because of the influence of urine specific gravity (USG). To circumvent the need for urine protein creatinine ratios (UPCR) some have proposed a calculated dipstick urine protein to USG ratio (DUR) for the detection of proteinuria. However, the performance of DUR has not been evaluated in veterinary patients. Evaluate the correlation between DUR and UPCR, while also assessing the effect of urine characteristics on this relationship and evaluating the performance of DUR in detecting proteinuria. Urine samples from 308 dogs and 70 cats. Retrospective cohort study of urinalyses and UPCRs from dogs and cats collected between 2016 and 2021. Both canine and feline urine samples showed a positive moderate correlation between the UPCR and DUR. The correlation was not influenced by the presence of active urine sediment, glucosuria, or urine pH. In detecting canine urine samples with a UPCR >0.5, an optimal DUR of 1.4 had sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 89%, 83%, 96%, and 63%, respectively. In detecting feline urine samples with a UPCR >0.4, an optimal DUR of 2.1 had sensitivity, specificity, PPV, and NPV of 70%, 100%, 100%, and 75%, respectively. Use of the DUR can be a relatively reliable method for identification of proteinuria. However, given its poor NPV, the DUR cannot be recommended for exclusion of proteinuric patients.

Investigation of the stress–strain state of a composite blade in ANSYS WorkBench

In this paper, the static strength of a UAV blade made of composite material was calculated. Composite materials have an advantage over traditional materials (metals and alloys) in the field of aviation - gain in weight, low sensitivity to damage, high rigidity, high mechanical characteristics. At the same time, the identification of vulnerabilities in a layered structure is a difficult task and in practice is solved with the help of destructive control. Composite materials available in the ANSYS materials library were used in the modeling: Epoxy Carbon Woven (230 Gpa) Prepreg woven carbon fiber in the form of a semi–finished prepreg impregnated with epoxy resin carbon fiber with Young's modulus E=230 GPa and Epoxy Carbon (230 Gpa) Prepreg is a unidirectional carbon fiber prepreg impregnated with epoxy resin with a Young's modulus E=230 GPa. Modern software products, such as ANSYS WorkBench, allow comprehensive investigation of the layered structure. Several variants of blade designs with different fillers as the median material were investigated. The forward and reverse destruction criteria based on the Tsai-Hill theory were used. The influence of gravity was not taken into account. It is shown that the developed blade design meets the requirements. Balsa wood, pine, aspen and polyurethane foam were chosen as the middle material of the blade. Pine and aspen wood were selected according to the criteria of their availability and having the lowest density. The materials library of the ANSYS WorkBench software package used does not have characteristics for all of them, so the characteristics of the selected materials (pines and aspens) were added manually. For modeling and calculations in the ANSYS WorkBench program, such characteristics as density, axial elastic modulus, Poisson's coefficients, shear modulus and tensile and compressive strength limits are required.

Stability of buoyancy–thermocapillary convection in molten silicon liquid bridge between two disks with different radii under gravity

By employing a linear stability analysis based on the spectral element method, we investigated the impact of radius ratio (Γr) on the stability of buoyancy–thermocapillary convection in a molten silicon liquid bridge (Pr = 0.011). This liquid bridge was located between two coaxial disks with different radii under the influence of gravity. The aspect ratio of the liquid bridge was maintained at Γ = 1, with a volume ratio Γv = 1 and a fixed height. To explore the physical mechanisms behind convection instability, a perturbation energy analysis was adopted. The free surface shape was determined using the Young–Laplace equation, and two distinct heating strategies were employed. In a top-heated liquid bridge, the convection stability under gravity is always stronger than under zero-gravity. However, in a bottom-heated liquid bridge, the convection stability under gravity is not consistently stronger than under zero-gravity; specifically, when 0.522 < Γr < 0.673, the convection stability under gravity is weaker than under zero-gravity. Despite the small height of the liquid bridge (approximately 2 mm), the maximum relative difference of the critical Marangoni number (Mac) between gravity and zero-gravity conditions reaches as high as 227.8%. In a bottom-heated liquid bridge, oscillatory instability occurs at larger radius ratios (Γr = 0.8) compared to the zero-gravity condition. Furthermore, all instabilities for various radius ratios and heating strategies were found to be of hydrodynamic in nature.

Numerical investigation of conjugated heat transfer mechanisms of supercritical hydrogen-helium in PCHE channels

In this study, straight and z-shaped channel PCHEs are employed as hydrogen-helium heat exchangers in Synergistic Air-breathing Rocket Engine (SABER). Conjugated heat transfer mechanisms and characteristics of supercritical hydrogen-helium are studied numerically. The results of the straight channel indicate that when the mass flow rate of the cold (H2)/hot (He) side is 38/280 kg/(m2·s), a greater comprehensive performance of flow and heat transfer can be obtained. The influence of gravity on the hot side is significantly less than that on the cold side. The increase in plate thickness enhances heat transfer, while the effect of rib thickness is the opposite. As the bend angle decreases, the heat transfer coefficient of the z-shaped channel becomes higher. The heat transfer characteristics of the cold side vary more significantly with the bend angle than that of the hot side.

A creative form-finding tool: Deformation of plastic sheets due to the influence of temperature and gravity

A form-finding technique based on the deformation of plastic sheets by the action of gravity and temperature increase is proposed, allowing the exploration of complex geometries to support form-giving processes within architecture projects, both by students and practitioners. Using an analog and computational approach, the ideal material for the technique was selected from a multifactorial experiment. Semi-structured analog experimentation was carried out based on inputs, rules, and outputs previously identified, and the resulting models were morphologically analyzed, to later translate the components of the analog experimentation into a computational algorithm to carry out computational experimentation. The technique can be used as a generator of novel forms possessing adequate transformational qualities. Finally, potential applications of the technique and avenues for future research are presented.

Fabrication of a superhydrophobic cotton fabric with efficient antibacterial properties and asymmetric wettability via synergistic effect of quaternized chitosan/TiO2/Ag

A superhydrophobic cotton fabric with unidirectional moisture transfer ability, antibacterial, and oil-water separation capabilities was fabricated by combining a simple coating method and oxygen plasma etching. Polydimethylsiloxane (PDMS) was employed to impart low surface energy to the cotton fabric, thereby endowing it with hydrophobic characteristics. The synthesized quaternized chitosan/TiO2/Ag (CTA) compound was subsequently applied onto the cotton fabric surface to introduce a desirable level of surface roughness, thus enhancing its hydrophobic properties and conferring excellent antibacterial efficacy. The cotton was subsequently treated by oxygen plasma to trigger asymmetrical wetting on both sides. The experimental findings reveal that the optimally treated cotton fabric exhibits hydrophobic properties on the bottom surface, with a water contact angle (WCA) reaching 162.8°, while the upper surface displays hydrophilic behavior, establishing a wetting gradient along the thickness direction. Notably, even under the influence of reverse gravity, water droplets are capable of transferring from the back to the top surface within 2 s, while preventing reverse penetration of liquid. Moreover, the synthesized compound CTA endows the cotton fabric with efficient and long-lasting antibacterial properties through two modes (contact and release sterilization modes) and three sterilization mechanisms (electrostatic interaction, plasma surface resonance effect, and reactive oxygen species). Remarkably, within a time frame of only 1 h, the modified cotton fabric is able to achieve a kill rate exceeding 99% against Escherichia coli and Staphylococcus aureus. Moreover, the aforementioned properties demonstrate outstanding durability against repeated washing, continuous abrasion, exposure to strong acid/base, and ultraviolet radiation. Additionally, this modified cotton fabric exhibits remarkable efficiency in terms of oil-water separation, effectively separating both light and heavy oil from water. It is worth noting that the preparation process is cost-effective, environmentally friendly, and free from fluorine.

ТЕОРЕТИЧЕСКИЕ ИССЛЕДОВАНИЯ ДЛИНЫ ПЕРЕМЕЩЕНИЯ СТРУИ ЖИДКОГО НАВОЗА ПРИ ЕГО ПЕРЕМЕШИВАНИИ В НАВОЗОХРАНИЛИЩЕ

There on large livestock farms a nonbedding method of animals’ keeping is common. At such animals’ keeping, liquid and semiliquid manure is obtained. Such manure during storage into three fractions - upper, liquid and lower is stratified. The upper fraction surface contacts with the environment and therefore dries out and forms a crust. This manure heavier part, under the influence of gravity, settles to the manure storage’s bottom, forming a dense layer during prolonged storage. Thus, there in storage manure mass three fractions of different physical-and-mechanical properties are formed, for each of them extraction the different methods are used, by the corresponding machines implementing. As a result, the metal and energy consumption at manure extracting process by the manure storage is increased, and consequently, so as the agricultural products’ cost. The stored manure technological operation’s extracting can be reduced to an energy minimum by a homogeneous mass forming. This can be solved by the farm manure coming into the manure storage facility mixing. This operation can be implemented by the layers’ active movement by hydraulic or mechanical methods organizing. The hydraulic method only if liquid fractions without mechanical impurities presence at the pump entering by the impeller as working organ for they disable it at acting The most widespread mechanical method of manure fractions movement by a propeller agitator, forming a directional flow during rotation is carried out. These theoretical studies results concerning the liquid manure jet movement formed as a result the mixer agitator action in the medium of manure mass stored in a manure storage facility are presented. The relationship between the length of movement of the liquid manure jet, the angle of elevation of the blade’s helical line, this mixer diameter, its angular velocity and the mixer’s inclination in the relative to the horizontal plane has been established.

The effect of circumference on the segregation of objects in a mixture

The size segregation problem refers to the phenomena of larger particles rising to the top of a mixture of variously sized items seemingly against gravity. Upon reviewing the literature on the size-segregation problem, also known as the trail mix quandary, we realized that the reported findings did not account for the apparent adverse behavior of hollow items. Despite geophysical implications, such as erosion sediments, explanations regarding hollow items are necessary to ensure more precise distribution of nanoparticle substances throughout various systems. Additionally, the size segregation of irregularly shaped particles has not been clearly addressed. To address these limitations, we put forth a hypothesis that circumference, rather than size, dictates the arrangement of falling objects. We found that the distribution of hollow particles could be better predicted with a revision of the size-segregation theory. The key observation that motivated us to propose the revision to the model was that hollow beads sometimes trended toward the bottom of the mixing container over their smaller counterparts, contrary to the size-segregation theory. Our findings may increase precision and predictability of particle movement of non-enclosed hollow objects among unrelated items. A better understanding of particle distribution that may explain certain phenomena (i.e., that larger particles tend to rise to the top of a mixture and not sink under the influence of gravity) could be useful for many fields that deal with particulate matter from geology to chemistry.

Impact of alteration corridors on karst reservoir organisation and evolution of groundwater flow path: An example from the southern border of the Larzac Causse, southern France

All the features of karstic reservoirs result from the chemical and/or mechanical erosion of an initial rock volume, which modifies the initial petrophysical properties (i.e., porosity and permeability). The spatial distribution and organisation of the karst system in a carbonate massif are often overlooked in studies on karst hydrological functioning. However, these parameters are key to understand and accurately model dynamic flow. This contribution aims at characterising the nature and impact of alteration corridors on the organisation and evolution of the karstic reservoir and its present-day functioning. We focus on characterising the specific impact of the late onset of pocket valley regressive erosion on the organisation of the present-day drainage system. We used a 3D approach to correlate field observations on the surface and in caves, with remote sensing. The expression of alteration corridors is analysed in a 40 km2 area on the southern border of the Larzac Causse. This Jurassic carbonate massif is affected over its entire thickness by a network of vertically elongated alteration corridors containing dissolution-collapse breccia, mainly oriented in a N-S direction. Ghost-rock karstification played a significant part in the karstic reservoir structure and evolution. Alteration corridors result from the in-situ dissolution of the bedrock along an initial jointing pattern. The dissolution-collapse breccia corridors correspond to ghost-rock corridors selectively emptied of their alterite, under the effect of a hydraulic gradient. The vertically elongated structure of alteration corridors that cross-cut the Jurassic sequence enables fluid circulation from an upper to a lower aquifer, which were initially separated by a Toarcian marly seal unit. The subsequent initiation of pocket valleys led to the rapid evacuation of the residual alterite contained in ghost-rock corridors, under the influence of gravity. These alteration corridors determine the position of present-day pocket valley springs and enhance the regressive erosion dynamics, that progressively capture a north-east flowing watershed (Vis River). Finally, residual alterites are evacuated below the overflow spring altitude during high-flow events by flooding/dewatering of galleries. Such mechanisms of alterite evacuation provide insight into i) the part of the karstic reservoir that is connected to the spring, and ii) the dynamics of the associated flows. This study suggests that corridor networks constitute a substantial volume of porous and permeable materials that plays a major role in the present-day groundwater flow path. Such features should be considered valuable drilling targets for water exploration when located below the piezometric level.

Numerical simulation and experiment of laminar heat transfer characteristics in micro-channel collector

In response to the problems of high mass and high thermal resistance in traditional cold plate collectors, the author proposes a shaped and efficient micro-channel collector structure design for non-normal temperature control scenarios such as high power, multiple heat sources, and highly non-uniform power density. The author conducted numerical and experimental studies on the laminar heat transfer in a highly efficient micro-channel shaped collector for non-normal temperature control scenarios such as high power, multiple heat sources, and highly non-uniform power density, the results show that: The relative deviation between the simulated and experimental values of the pressure drop of the micro-channel collector using perfluorotriethylamine as the working fluid is within -20%, and the relative deviation between the simulated and experimental values of the surface temperature is within +3?C, the predicted trend of the pressure drop and temperature field of the collector is in good agreement with the experimental values, indicating the feasibility of using numerical simulation methods for performance analysis and design optimization of 3-D printed micro-channel collectors. As the flow rate increases, the pressure drop of the collector increases approximately linearly, while the value increase of the total heat transfer coefficient gradually decreases, and increasing inlet temperature or heating power will reduce pressure drop of collector and increase total heat transfer coefficient. The influence of gravity on the pressure drop and total heat transfer coefficient of micro-channel collectors is less than 1. The straight through micro-channel collector has lower pressure drop and stronger heat transfer ability compared to the folded type collector.

Gravity impact on viscosity measurements by aerodynamic levitation

This publication deals with the estimation of viscosity of liquid metals. It is proposed to discuss the possibility to determine this parameter during aerodynamic levitation experiments performed in ground laboratory. Once in liquid state, metallic sample is submitted to acoustic waves through the levitation gas making it oscillate and deform. A high speed camera records the radial periodic deformation during the relaxation period, meaning when incident waves stop. The evolutions of the sample radius over time are extracted from records and compared with analytical model based on the damped oscillator. The estimation of viscosity is performed by inverse method and leads to overestimated values by comparison with expected values. Then, numerical simulations (CFD) including or not levitation gas and gravity are performed to show the impact of gravity during measurements. New viscosity estimations show that the damped oscillation model (Lamb’s theory) as it is classically used is not valid in aerodynamic levitation due to the influence of both gravity and gas.

Influence of Shape Index, Specific Gravity, Area-Volume Ratio, and Egg Weight Loss During Incubation on the Hatchability of Eggs from Layer Hen Grandparents

Influence of Shape Index, Specific Gravity, Area-Volume Ratio, and Egg Weight Loss During Incubation on the Hatchability of Eggs from Layer Hen Grandparents

EFFECT OF VARIABLE GRAVITY ON THERMAL CONVECTION IN ROTATING JEFFREY NANOFLUID: DARCY-BRINKMAN MODEL

In this study, we explore the influence of varying gravity on the beginning of thermal instability in a rotating layer of Jeffrey nanofluid with Darcy-Brinkman porous media. The solution of the fluid layer retained between two free-free barriers is determined using linear stability analysis based on the normal mode approach. In this study, we used the Galerkin approach to find the eigenvalue. The influence of exponential and cubic variable gravity on the start of stationary and oscillatory convection is calculated analytically and graphically. The graphs are made with the help of MATLAB R2021b software. For both stationary and oscillatory convection, we've examined how variations in gravity affect the Jeffrey parameter, rotation (Taylor number), Darcy-Brinkman number, Lewis number, moderated diffusivity ratio, porosity of porous media, and nanoparticle Rayleigh number. It is discovered that stationary as well as oscillatory convections are more stabilized by negative exponential variable gravity parameter.

The influence of frequency and gravity on the orientation of active metallo-dielectric Janus particles translating under a uniform applied alternating-current electric field.

Theoretical and numerical models of active Janus particles commonly assume that the metallo-dielectric interface is parallel to the driving applied electric field. However, our experimental observations indicate that the equilibrium angle of orientation of electrokinetically driven Janus particles varies as a function of the frequency and voltage of the applied electric field. Here, we quantify the variation of the orientation with respect to the electric field and demonstrate that the equilibrium position represents the interplay between gravitational, electrostatic and electrohydrodynamic torques. The latter two categories are functions of the applied field (frequency, voltage) as well as the height of the particle above the substrate. Maximum departure from the alignment with the electric field occurs at low frequencies characteristic of induced-charge electrophoresis and at low voltages where gravity dominates the electrostatic and electrohydrodynamic torques. The departure of the interface from alignment with the electric field is shown to decrease particle mobility through comparison of freely suspended Janus particles subject only to electrical forcing and magnetized Janus particles in which magnetic torque is used to align the interface with the electric field. Consideration of the role of gravitational torque and particle-wall interactions could account for some discrepancies between theory, numerics and experiment in active matter systems.

Dynamic model of the influence of gravity, ventilation with positive and negative pressure on ventilation-perfusion ratio in lungs

Dynamic model of the influence of gravity, ventilation with positive and negative pressure on ventilation-perfusion ratio in lungs

Pengenalan Mengenai Gerak Vertikal Kebawah dengan Mengamati Media Mainan Terjun Payung

Vertical downward motion is a phenomenon in physics that occurs when an object falls freely under the influence of gravity without any external force affecting it. In this article, we will look at how vertical downward motion can be observed through the use of skydiving toys. Parachuting toys are used as a safe simulation to observe vertical downward motion. This research uses a descriptive qualitative approach. This approach explains in detail the subject of vertical downward movement through parachuting. The purpose of this article is to introduce an example of vertical downward motion for elementary school children. With this article in order to introduce and invite children to play and know that what is played is an example of vertical downward motion. These toys are often designed with designs and materials that allow the opening or slowing of the fall speed. This ensures that skydiving toys are safer for children to play with. Through observing skydiving toys, we can understand the basic concepts of vertical downward motion and its characteristics such as constant acceleration, terminal velocity, and the design and material factors that affect it. In conclusion, this article shows the importance of vertical downward motion in physics and how skydiving toys can be used to observe this phenomenon.

Gravity-Based Kinetostatic Modeling of Parallel Manipulators Using Screw Theory

The pose accuracy of parallel manipulators (PMs) is a key index to measure their performance. Establishing the gravity-based kinetostatic model of a parallel robot provides an important basis for its error composition and accuracy improvement. In this paper, a kinetostatic modeling approach that takes real gravity distribution into consideration is proposed to analyze the influence of gravity on the infinitesimal twist and actuator forces of PMs. First, the duality of the twist screw and constraint wrenches are used to derive the gravity-attached constraint wrenches independent of the external load and the limb stiffness matrix corresponding to the kinematics-based constraint wrenches. Second, the gravity model of the mechanism is established based on the screw theory and the principle of virtual work. Finally, the analytical formulas of the infinitesimal twist and the actuator force of PMs are obtained, and the influences of the external load, platform gravity, and rod gravity on the stiffness of the mechanism are decoupled. The non-overconstrained 3RPS and overconstrained 2PRU-UPR PMs are taken as examples to verify the proposed method. This research proposes a methodology to analyze the infinitesimal deformation of the mechanism under the influence of gravity.

Exploring the mechanical response of functionally graded hollow disks: insights from rotation, gravity and variable heat generation

PurposeThe purpose of the study is to perform elastic stress and deformation analysis of a functionally graded hollow disk under different conditions (rotation, gravity, internal pressure, temperature with variable heat generation) and their combinations.Design/methodology/approachThe classical method of solution, Navier's equation, is used to solve the governing equation. The analysis considers thermal and mechanical boundary conditions and takes into account the variation of material properties according to a power law function of the radius of the disk and grading parameter.FindingsThe findings of the study reveal distinct trends and behaviors based on different grading parameters. The influence of gravity is found to be negligible, resulting in similar patterns to the pure rotation case. Variable heat generation introduces non-linear temperature profiles and higher displacements, with stress values influenced by grading parameters.Practical implicationsThe study provides valuable insights into the behavior of displacement and stresses in hollow disks, offering a deeper understanding of their mechanical response under varying conditions. These insights can be useful in the design and analysis of functionally graded hollow disks in various engineering applications.Originality/valueThe originality and value of this study lies in the consideration of various loading combinations of rotation, gravity, internal pressure and temperature with variable heat generation. Furthermore, the study of effect of various angular rotations, temperatures and pressures expands the understanding of the mechanical behavior of such structures, contributing to the existing body of knowledge in the field.

VERIFICATION OF THE MATHEMATICAL FLIGHT MODEL THE PROJECTILE AS A MODIFIED MODEL OF THE MATERIAL POINT

The analysis of mathematical models of the flight of projectiles has been carried out, it is shown that the nature of their provision varies depending on the degree of reliability of the representation of the real physical process of its flight by a mathematical model, the adequate consideration of certain forces (moments) acting on the projectile, as well as the level of information about external flight conditions. In the simplest mathematical model with three degrees of freedom, the projectile is considered as a material point that moves in the atmosphere under the influence of gravity and full aerodynamic force. The dynamics of projectile flight is most completely described by the mathematical model of the movement of a solid body with six degrees of freedom. In the intermediate model with four degrees of freedom, all aerodynamic forces are taken into account, the orientation of the projectile is characterized by taking into account the angle of nutation, and the kinetic energy of the rotational movement is taken into account through the angular velocity of the projectile around its axis of symmetry. The process of restori ng the coefficients of aerodynamic forces using the material point model does not provide the necessary accuracy and adequacy of the description of the projectile flight process; of the modified material point model is much simpler (the least complex) compared to the model of the motion of a rigid body with six degrees of freedom due to the smaller number of coefficients and differential equations included in its composition. The differential equations of the modified material point model are provided - the equation of motion of the center of mass and the equation of nutational oscillations of the projectile in scalar form; an assessment of its accuracy (adequacy) was carried out on the example of the 155-mm PF projectile M2000, one of the family of projectiles of the company Denel Naschem – Assegai M200X Series 155-mm Projectiles. A comparison of the characteristics of the 155-mm PF of the M2000 projectile calculated according to the 6DoF model and the modified material point model showed their high convergence; the error does not exceed 1%. Keywords: aerodynamic forces (moments), projectile, mathematical models, modified model, aerodynamic coefficients, simulation, accuracy, flight parameters.

Study on Rheological Properties and Pouring Process of Hydroxyl-Terminated Polybutadiene (HTPB) Propellants.

The process of solid propellant production, which is the most widely used high-energy material, has garnered significant attention from researchers. However, there have been relatively few studies on its processing, due to the unique nature of the casting process. This paper aims to further analyze the pouring process of the propellant slurry. Initially, we obtained a sample of the propellant slurry and measured its rheological parameters using a rotary rheometer. From the analysis of the experimental results, we derived the viscosity parameters and the yield values of the propellant slurry. Subsequently, we simulated the pouring process, setting the slurry parameters based on the data obtained from the rheological measurement experiment. The simulation results demonstrated that the flower plate significantly impacts upon the cutting and separating effect on the slurry during pouring. Upon leaving the flower plate, the slurry descends onto the core mold platform under the influence of gravity, gradually flowing along the edge of the core mold. Although there may be some small voids in the pouring process, the voids will disappear completely at the end of pouring. A comparison with the actual pouring situation revealed a higher consistency between the simulation results and reality, thus establishing the reliability of the simulation method as a reference for analyzing the pouring process.