Non-symmetric Conditions Research Articles

Plastic strip strtetching with non-symmetric conditions in bite areas

Plastic strip strtetching with non-symmetric conditions in bite areas

A numerical study on the effect of asymmetry on underwater noise emission in offshore monopile installation

Offshore wind energy holds significant promise as a solution in the energy transition. However, installing offshore pile foundations can generate substantial levels of underwater noise, posing potential risks to marine life. This paper examines the influence of asymmetric impact forces and pile inclination on producing underwater noise and seabed vibrations based on cases of a small- and large-diameter monopile. The study focuses on scenarios involving inclined and eccentric forces and tilted piles. The analysis reveals that non-symmetrical conditions significantly impact the sound pressure levels around the ring frequency of the pile due to various noise generation mechanisms. However, it is observed that the vertical component of the impact force predominantly contributes to the generation of underwater noise, primarily due to its considerably higher amplitude.

Experimental study of the unconstrained melting of a phase change material for air-conditioning applications

This study analyzed the RT8HC melting in a spherical vessel employing air as a heat transfer fluid. The phase change process was followed both visually and by thermal measurements. Photographs and thermographs allow the following phases' evolution and melting mechanisms. We observed that the melting process was not symmetric around the vertical axis; implications of non-symmetric conditions on the melting mechanisms and heat transfer are discussed and analyzed. This work also includes the effects of outer water vapor condensation on heat transfer in the analyses. We proposed a mathematical model to quantify the heat flux that only requires humidity and temperature measurements and considers both heat convection and condensation effects. Results show that condensation significantly affects heat transfer during the initial stage of the melting process. Beside, these effects extend beyond the condensation time due to the liquid film draining from the spherical vessel surface. Regarding thermography, this technique may be a valuable tool for analyzing and following melting processes inside vessels; however, the presence of liquid film over the sphere affects the temperature measurements obtained from the thermograph analysis. This investigation provides relevant information about using phase change materials in cold thermal energy storage applications, latent thermal loads, and humidity control, which are essential aspects of air-conditioning system designs.

Assessment of effectiveness factor in porous catalysts under non-symmetric external conditions of concentration

Abstract the present paper, the effectiveness factor of porous catalytic particles is evaluated in the absence of boundary conditions symmetry over the external surface by computational fluid dynamic (CFD) techniques. The first-order kinetics of decane oxidation, already evaluated experimentally, is taken as a representative reaction. Our study arises from the fact that, in the open literature, the effectiveness factor is usually calculated considering conditions of symmetry of concentration field around particles. However, depending on the fluid dynamics of the system, such conditions are not always established and, thus, our work aims at studying for the first time the behaviour of particle catalysts with non-uniform concentration fields over the surface. In particular, the effectiveness factor of the particles in a catalytic layer is calculated in the absence of symmetry by changing several parameters (temperature, tortuosity and mean pore diameter of particle) using two different methods, named Sphere-by-Sphere (SbS) and Equisized-Volume (EV), respectively. The results of these two methods are then compared to the theoretical one obtained in the presence of spherical symmetry. As a main result, we found that, for moderately low values of Thiele modulus (<1.3 ca.), the analytical expression of the effectiveness factor obtained under spherical symmetry can be also applied in non-symmetric conditions. On the contrary, this cannot be done for higher values of Thiele modulus, for which we propose an empirical correlation of the effectiveness factor based on a corrected Thiele modulus. The efficacy of our approach is stated by the fact that pseudo-homogeneous-mode simulations of the heterogeneous system show results that match very well those obtained in heterogeneous mode, with an important reduction of calculation time and memory. The presented methodology can be also applied to n-order kinetics.

Experimental and Numerical Investigation on the Influence of Thermally Induced Stress Gradients on Fatigue Life of the Nickel-Base Alloy Mar-M247

Abstract Today's and future parameters of stationary gas turbines and aircraft engines require intensive and highly efficient cooling of hot gas path components. High temperature and thermally induced stress gradients with impact on fatigue life are the consequence. Thermally induced stress gradients differ from geometrically induced stress gradients with respect to stress mechanics by the independence from external loads and material mechanics by the influence of temperature on material properties and strength. Regarding the contribution and evaluation on damage, the latter characteristic feature in turbomachinery is currently not fully understood. Therefore, a test facility has been designed, setup, and reported in GTP-18-1482 for the investigation of the influence of stationary temperature, and thus thermally induced stress gradients, on the damage evolution of cooled high-temperature components. To achieve high temperature and thermally induced stress gradients, large heat fluxes are required. A unique radiation heating has been developed allowing very high heat fluxes of q˙ ≥ 1.5 MW/m2 for testing of hollow cylindrical specimens. The conventional cast nickel-base alloy Mar-M247 has been chosen to study the influence of thermally induced stress gradients on fatigue life. The low-cycle fatigue testing of the hollow cylindrical specimens has been conducted both with and without superimposed stationary temperature gradients. In addition, complex low-cycle fatigue (CLCF) tests with symmetric and nonsymmetric loading conditions have been performed to provide the necessary database for the adaptation of a viscoplastic deformation model. To calculate the local stress–strain field and service life of the test specimens, linear elastic and viscoplastic finite element studies have been performed and were assessed by means of a fracture mechanics-based lifetime model. The test results show the considerable influence of the temperature gradient on the low-cycle fatigue life for the investigated material. Both the radial temperature variation over the specimen wall with a hot outer surface and a cooled inner surface as well as the thermally induced stresses are stated to be the main drivers for the change in low-cycle fatigue life. The test results enhance the understanding of fatigue-damage mechanisms under local unsteady conditions and can be used as a basis for improved service life predictions.

Dynamic punching shear failure of a RC flat slab-column connection under a collapsing slab impact

Reinforced concrete flat slabs are very common in residential and office buildings construction. The sensitivity of the flat slab-column connection to punching shear is well known and standards include design rules to ensure the connection safety under static loading. Such failures may occur due to static excessive loading or when buildings are subjected to an extreme event; in such cases, the local failures of the column-slab connections, are followed by the slab collapse downward. The collapsing slab then impacts the slab underneath, and this collision event is critical to the building safety. It may cause dynamic punching shear failure to the impacted slab and initiate a progressive collapse process of the slabs underneath, or it may be arrested by the first impacted slab. This scenario of impact between the two slabs is in the focus of this paper, disregarding the cause of the first slab failure. In this study, the problem is modelled by a representative part of a slab resting on a column; the slab is analyzed under to the impact action of a similar collapsing slab from above. A corner non-symmetrical part of the slab has been selected to represent the more general non-symmetrical conditions of the problem. Many studies have been done on the connection behavior under static loading, but relatively little has been done on the impact shear response of RC column-slab connections despite the major importance of this issue and its relevance to the integrity of the entire building. The behavior of this connection depends on many parameters, and mainly on its longitudinal and shear reinforcements. This paper presents the numerical detailed simulations of a connection under impact conditions, and studies the dynamic response of the RC column-slab connection due to the impact of a falling upper-level slab. The analysis has been performed on slabs with longitudinal reinforcement with (or without) additional shear reinforcement. The paper examines the effects of several major parameters such as the upper slab's falling height, the slab dimensions, the shear reinforcement, and the reinforcement ductility on the column-slab connection behavior and the type of its failure. This paper provides new insight on the impact scenario, the slabs response and the details of the resulting damage.

Quantification of Mg2+, Ca2+ and H+ transport by the gastrointestinal tract of the goldfish, Carassius auratus, using the Scanning Ion-selective Electrode Technique (SIET).

An in vitro gut-sac technique and the scanning ion-selective electrode technique (SIET) were used to characterize Mg2+, Ca2+, and H+ transport at both the mucosal and serosal surfaces of non-everted and everted gastrointestinal tissues obtained from Carassius auratus. As part of the study, two magnesium ionophores were compared (II vs. VI). Unfed animals displayed uniform transport of all ions along the intestine. Feeding resulted in elevated Mg2+ and Ca2+ transport when the gut lumen contained chyme however, under symmetrical conditions this increased transport rate was absent. Furthermore, zonation of divalent cation transport was present for both Ca2+ and Mg2+ under non-symmetrical conditions while the zonation remained for Ca2+ alone under symmetrical conditions. High dietary Mg2+ decreased absorption and induced secretion of Mg2+ in the posterior intestine. Uptake kinetics in the esophagus suggest large diffusive and/or convective components based on a linear relationship between Mg2+ transport and concentration and lack of inhibition by ouabain, an inhibitor of Na+-K+-ATPase. In contrast, kinetics in the rectum were suggestive of a low affinity, saturable carrier-mediated pathway. A decrease in Mg2+ and Ca2+ transport was observed in the posterior intestine (both at the mucosal and serosal surfaces) in response to ouabain. This impact was greatest for Ca2+ transport and when applied to the mucosal fluid and measured in everted preparations. In contrast a putative Mg2+ transport inhibitor, cobalt(III)hexamine-chloride, did not affect Mg2+ transport. This is the first study to use SIET approaches to study ion transport in the gut of teleost fish. This is also the first study to provide characterization of Mg2+ transport in the gut of C. auratus. Due to the limited selectivity of Magnesium ionophore II, subsequent studies of tissues bathed in physiological saline should be made using Magnesium Ionophore VI.

Staggered swirler arrangement in two self-excited interacting swirl flames

Interference of acoustic and convective disturbances controls the development of self-excited combustion oscillations of a lean-premixed swirl-stabilized flame with a central bluffbody. How this interference mechanism influences the dynamics of multiple interacting flames in a multi-nozzle environment is currently unknown. Here we present observations of a multi-nozzle system's response to staggered swirler arrangements (ξsw, 1 ≠ ξsw, 2) as compared to non-staggered arrangements; the distance between the swirler and the flame is the dominant length scale of vortical disturbances. Our results demonstrate that a slight modification of the swirler arrangement in the streamwise direction – staggered or non-staggered – has a remarkable influence on the stability map of the whole combustion system. Phase-resolved flame imaging measurements indicate that under non-staggered conditions interacting swirl flames feature a coherent motion during a period of oscillation. By contrast, the staggered swirler combination creates significantly non-symmetric flame dynamics, disturbing the development of well-organized motion over the entire reaction zone. Flame surface modulations in the lateral direction are particularly pronounced due to the formation of non-symmetric convection delays of vortical disturbances between adjacent swirl nozzles. For a given swirler arrangement, the system's response to a wide range of combinations of mean nozzle velocities, including symmetric (u¯1=u¯2) and non-symmetric (u¯1≠u¯2) conditions, were explored to account for the simultaneous effects of the two convection parameters. Our data show that a major determinant of the onset of the instability is the combination of the Strouhal numbers, 〈St1, St2〉, which can be even or uneven depending on the manipulation of the convection time of each nozzle.

Comparative study of laser pulses guiding in capillary waveguides and plasma channels at conditions of non-perfect focusing

For producing of high-quality accelerated electron bunches the structure of laser fields and accelerating wakefields inside the guiding structure should be regular enough to conserve a high value of accelerating longitudinal field throughout the propagation and avoid strong defocusing transverse fields. We had compared the efficiency of capillary waveguides and plasma channels in achieving of this goal, taking in mind different possible nonsymmetric conditions (like non-symmetric shape of laser spot, non-zero angle of incidence of a laser pulse or deviation of a focusing point relatively to the guiding structure axis) of laser pulses focusing in a guiding structure, always available in real experiments. The model for laser pulses propagation in guiding structures for the case of arbitrary dissymmetry of laser focusing is presented.

Axisymmetric and three dimensional flow modeling within thermal vapor compressors

Thermal vapor compressor (TVC) is a device for compressing vapor in water–steam cycles and frequently used in desalination systems. Large amounts of useless vapor can be compressed by this device and the efficiency of a desalination unit is effectively enhanced through this process. Motive steam is injected into the TVC through a convergent–divergent nozzle and accelerated to supersonic velocities. The low pressure steam is entrained at the upstream zone and mixed with this highly compressible motive flow within the TVC. In the current study, the flow field of an experimental TVC is scrutinized in both axisymmetric and three-dimensional approaches and compared with experimental measurements. Since the steam collector at the suction surface of the TVC has a curved shape and may undermine the symmetry of the flow on either side of the central axis, the second objective of this study is to reveal the deviation of the symmetric assumption from the real non-symmetric condition of entering steam flow into the TVC. Results show that the presence of a bending at the inlet side has approximately negligible effects on the mixing phenomenon and the flow remains symmetric around the central axis. Hence, there is no need to consider the collector geometry in further simulations and the performance parameters of the TVC would be sufficiently obtained through an axisymmetric method with a substantial reduction in the computational cost and time.

Temperature fields in thin wide-profile plates obtained from a melt by the Stepanov technique under nonsymmetric conditions of growth

A mathematical model is suggested allowing one to determine the temperature fields in thin wide-profile plates when growing them from a melt by the Stepanov technique depending on the asymmetry in the position of a growing crystal relative to the nearby screens, as well as on the difference between the surface temperatures of the left and right screens. The model contains the heat conduction equation and a system of integral equations that connects the densities of radiant and temperature fluxes.

Sensors in Spray Processes

This paper presents what is our actual knowledge about sensors, used in the harsh environment of spray booths, to improve the reproducibility and reliability of coatings sprayed with hot or cold gases. First are described, with their limitations and precisions, the different sensors following the in-flight hot particle parameters (trajectories, temperatures, velocities, sizes, and shapes). A few comments are also made about techniques, still under developments in laboratories, to improve our understanding of coating formation such as plasma jet temperature measurements in non-symmetrical conditions, hot gases heat flux, particles flattening and splats formation, particles evaporation. Then are described the illumination techniques by laser flash of either cold particles (those injected in hot gases, or in cold spray gun) or liquid injected into hot gases (suspensions or solutions). The possibilities they open to determine the flux and velocities of cold particles or visualize liquid penetration in the core of hot gases are discussed. Afterwards are presented sensors to follow, when spraying hot particles, substrate and coating temperature evolution, and the stress development within coatings during the spray process as well as the coating thickness. The different uses of these sensors are then described with successively: (i) Measurements limited to particle trajectories, velocities, temperatures, and sizes in different spray conditions: plasma (including transient conditions due to arc root fluctuations in d.c. plasma jets), HVOF, wire arc, cold spray. Afterwards are discussed how such sensor data can be used to achieve a better understanding of the different spray processes, compare experiments to calculations and improve the reproducibility and reliability of the spray conditions. (ii) Coatings monitoring through in-flight measurements coupled with those devoted to coatings formation. This is achieved by either maintaining at their set point both in-flight and certain spray parameters (spray pattern, coating temperature…), or defining a good working area through factorial design, or using artificial intelligence based on artificial neural network (ANN) to predict particle in-flight characteristics and coating structural attributes from the knowledge of processing parameters.

Transient model of induction machine using rotating magnetic field approach

Most simulation models of electric machines use the coupled circuit approach, where the machine is considered as an electric circuit element with time-varying inductances ( abc model) or with constant inductances ( dq0 model). On the other hand, the rotating magnetic field approach, which considers the electric machine as two groups of windings producing rotating magnetic fields and can give insight into internal phenomena of the machines, has not yet received much attention in electric machines modeling, especially for machine transient analysis. Based on the rotating magnetic field approach, this paper presents a transient model of the induction machine including main flux saturation effect. Based on the direct computation of the magnetizing fluxes of all machine windings, the model represents instantaneous main flux saturation by simply introducing a main flux saturation factor. No iteration process is involved to incorporate the saturation effects. The model combines the advantages of the dq0 and abc models advantages, such as rapid computation time and nonsymmetrical conditions simulation, respectively. The simulation results and the experimental tests show advantages and verification of the model.

Permanent Strains in Clay-Like Material During Drying

One of the characteristic features of clay-like materials is the change of their mechanical properties during drying as the moisture content is changed. At high moisture contents they are viscoelastic and then become elastic-plastic and finally brittle-elastic or even stiff. Elastic strains are reversible but viscous and plastic strains are not reversible. The permanent strains are usually undesirable in dried products because they cause warping. In brittle materials, on the other hand, microcracks and cracks are generated. The number of cracks depends on the material properties, sample shape, and drying conditions. The aim of this work is to examine experimentally the permanent strains during drying. The samples used in experiments were made of different materials (two types of clay and kaolin) and were dried convectively. Constant but nonsymmetric drying conditions were applied. The strains of the samples were measured online using a video camera.

3‐D Numerical Mode‐Matching (NMM) Method for Resistivity Logging Responses in Nonsymmetric Conditions

AbstractThree‐dimension (3‐D) Numerical Mode‐Matching (NMM) is selected to deal with resistivity logging responses in nonsymmetric conditions. First, an appropriate Descartes's reference frame is set up: the plane of deviated borehole and normal of formation is regarded as plane XOY , and formation strike is regarded as Z axis direction. In the plane XOY the finite‐element method (FEM) is used and a series of two‐dimension (2‐D) generalized eigenvalue problems are solved; whereas vertical analytic is adopted along Z axis. In analytical section, the medium is sliced into some layers artificially, and the relationship between adjacent layers is derived according to the electromagnetic field continuity, namely boundary transition matrices rather than reflection and transmission matrices theory in the 2‐D NMM method. Finally, a system of linear equations is constructed according to the natural boundary conditions that the topmost layer bed has no up‐going wave or the bottommost layer has no down‐going wave, and the potential of every point of formation is solved and the apparent resistivity is computed. In the given formation model, the results of 3‐D NMM agree well with previous ones of 2‐D NMM and FEM in symmetry conditions. Furthermore, the algorithm also applies to with formations titled angle and elliptical borehole; and some examples illustrate how all kinds of formation models with tilt angles affect logging response results.

Analysis of the contact between cubic profiles

The contact between cubic profiles with continuous relative curvatures has been analyzed and solutions in closed form were obtained for both symmetric and non-symmetric conditions. Analytical solutions have allowed a complete parametric study to be performed, showing the effects of the gradient of relative curvature. The accuracy of approximate ‘equivalent’ Hertzian solutions has been verified.

Rapidly inactivating and non-inactivating calcium-activated potassium currents in frog saccular hair cells.

1. Using a semi-intact epithelial preparation we examined the Ca(2+)-activated K(+) (K(Ca)) currents of frog (Rana pipiens) saccular hair cells. After blocking voltage-dependent K(+) (K(V)) currents with 4-aminopyridine (4-AP) an outward current containing inactivating (I(transient)) and non-inactivating (I(steady)) components remained. 2. The contribution of each varied greatly from cell to cell, with I(transient) contributing from 14 to 90 % of the total outward current. Inactivation of I(transient) was rapid (tau approximately 2-3 ms) and occurred within the physiological range of membrane potentials (V(1/2) = -63 mV). Recovery from inactivation was also rapid (tau approximately 10 ms). 3. Suppression of both I(transient) and I(steady) by depolarizations that approached the Ca(2+) equilibrium potential and by treatments that blocked Ca(2+) influx (application Ca(2+)-free saline or Cd(2+)), suggest both are Ca(2+) dependent. Both were blocked by iberiotoxin, a specific blocker of large-conductance K(Ca) channels (BK), but not by apamin, a specific blocker of small-conductance K(Ca) channels. 4. Ensemble-variance analysis showed that I(transient) and I(steady) flow through two distinct populations of channels, both of which have a large single-channel conductance (~100 pS in non-symmetrical conditions). Together, these data indicate that both I(transient) and I(steady) are carried through BK channels, one of which undergoes rapid inactivation while the other does not. 5. Inactivation of I(transient) could be removed by extracellular papain and could later be restored by intracellular application of the 'ball' domain of the auxiliary subunit (beta2) thought to mediate BK channel inactivation in rat chromaffin cells. We hypothesize that I(transient) results from the association of a similar beta subunit with some of the BK channels and that papain removes inactivation by cleaving extracellular sites required for this association.

Interannual variations in the stratospheric circulation with a perfectly steady troposphere

The seasonal and interannual variations of the stratospheric circulation are investigated using a quasi‐geostrophic, β‐plane channel model of the middle atmosphere. In the horizontal the model truncation retains at most two zonal and meridional wavenumbers. There are 27 layers in the vertical. All conditions at the model's lower boundary in the lower stratosphere are constant in time. No interannual variations are found if the flow is forced to a radiative equilibrium condition that is annually periodic with a radiative damping time of ∼20 days in the lower stratosphere. The seasonal evolution of the stratospheric circulation differs for different amplitudes of zonal wavenumbers 1 and 2 prescribed at the model's lower boundary (hB1 and hB2, respectively). When hB2 is small (50 m), variations are weak during winter and strong during spring, thus resembling the southern stratosphere. When hB2 is larger (150 m), variations have significant intensity during the entire winter, thus resembling the northern stratosphere. It is demonstrated that interannual variations can be obtained during winter and spring if two requirements are met. First, the radiative damping time is doubled in the lower stratosphere to a value in closer agreement with observational estimates. Second, if the model's truncation includes the antisymmetric mode about the channel center. The two requirements complement each other in the following way: Larger radiative damping times imply that the system can “remember” different conditions at the beginning of the previous summer, when otherwise the system memory is lost. Nonsymmetric conditions about the channel center imply that the critical level of the mean zonal wind in early winter does not extend across the entire domain. It is concluded that intraseasonal and interannual variations in the stratospheric circulation could exist even in the presence of planetary waves with constant amplitude in the troposphere and radiative forcing in the stratosphere, which is annually periodic.

Equations of strip equilibrium during asymmetrical flat rolling

The paper presents the equations of equilibrium of a flat rolled strip, generalized for non-symmetrical conditions in the roll-gap and for the cases of forces and moments operating on the strip sections beyond the roll-gap. The dependencies and assumptions imposed here are complete, which enables using them, e.g. to establish, simplified relationships useful for analytical solutions. In the discussion, the limitations of the solutions presented are indicated and the problems demanding further research defined.

On properties of Abel integral operators

It is shown that an Abel integral operator establishes isomorphisms between the Nikol'skii and Besov spaces with nonsymmetric conditions at the endpoints of the interval.