Change In Radius Research Articles

Quantifying the impact of heat in support seal configuration for aero engines

AbstractLeakage, deformations, power loss, heat generation in the support seal system and other issues are typical when support seals are developed. The design of the support seal system has progressively evolved over recent decades as part of an ongoing effort to provide effective cooling for the aero engine secondary air system. In particular, oil heat management in the oil chamber has strict requirements, which limit the heat generation of the support seal system. The potential of supporting seal research with an oil system is investigated in this work. The combination of the CFD/FEA method and quantifying the heat generation entering the oil chamber allows for improvements not just to the individual buffer air seal unit, but the oil seal together. The analysis relies on the combination of quantifying heat generation entering the oil chamber to provide a mutual influence of neighbouring labyrinth seals. The mutual influence requires further analysis, considering the thermal deformation of the rotor/stator to provide further accurate geometry parameters in preliminary seal designs. The experimental test was conducted to verify the preliminary CFD-FEA loosely coupled analysis result, which reveals that in a turbine support seal system, the radius of the buffer air seal has a significant influence on the leakage flow rate and power loss of the oil seal, which should take into account the integral influence of the pressure difference of the oil seal caused by the radius change of the buffer air seal and the running clearance of the oil seal.

Critical behavior of AdS black holes surrounded by dark fluid with Chaplygin-like equation of state

Supposing the existence of Dark Fluid with a Chaplygin-like equation of state $p=-B/\rho$ (CDF) as a cosmic background, we obtain a static spherically-symmetric black hole (BH) solution to the Einstein gravitational equations. We study the $P-V$ critical behavior of AdS BH surrounded by the CDF in the extended phase space where the cosmological constant appears as pressure, and our results show the existence of the Van der Waals like small/large BH phase transition. Also, it is found that such a BH displays a first-order low/high-$\Phi$ BH phase transition and admits the same criticality with van der Waals liquid/gas system in the non-extended phase space, where the normalization factor $q$ is considered as a thermodynamic variable, while the cosmological constant being fixed. In both $P-V$ and the newly proposed $q-\Phi$ phase spaces, we calculate the BH equations of state and then numerically study the corresponding critical quantities. Moreover, the critical exponents are derived and the results show the universal class of the scaling behavior of thermodynamic quantities near criticality. Finally, we study the shadow thermodynamics of AdS BHs surrounded by the CDF. We find that, there exists a positive correlation between the shadow radius and the event horizon radius in our case. By analyzing the temperature and heat capacity curves under the shadow context, we discover that the shadow radius can replace the event horizon radius to demonstrate the BH phase transition process, and the changes of the shadow radius can serve as order parameters for the small/large BH phase transition, indicating that the shadow radius could give us a glimpse into the BH phase structure from the observational point of view.

Examination of Upper Extremity Length Discrepancy in Patients with Obstetric Brachial Plexus Paralysis.

Since the natural course of obstetric brachial plexus palsy is variable, several problems are encountered. One important question, in considering patients with OBPP under observation in outpatient clinical settings, is whether children will have length discrepancies in their arms. The aim of this study was to determine differences in the length of the affected extremity, in comparison to the opposite upper extremity. As such, 45 patients, aged 6 months to 18 years, with unilateral brachial plexus palsy developed due to obstetric reasons, were included in the study. Affected and healthy side humerus, ulna, radius, 2nd metacarpal and 5th metacarpal lengths were evaluated according to gender, age, side, Narakas classification, primary and secondary surgery. Statistically significant differences were found in the change rates of affected/healthy humerus, radius, 2nd metacarpal and 5th metacarpal lengths according to age (93%, 95%, 92%, 90% and 90%, respectively). Affected/healthy change rates of ulna, radius, 2nd metacarpal and 5th metacarpal lengths were found to differ statistically (p < 0.05) according to the Narakas classification variable (94%, 92%, 95%, 94% and 94%, respectively). There were no statistically significant differences in the ratios of affected/healthy change in the lengths of the humerus, ulna, radius and 5th metacarpal compared to the primary surgery (p > 0.05). The ratios of affected/healthy change in ulna, radius and 5th metacarpal lengths were found to differ statistically (p < 0.05) according to secondary surgeries (93%, 91%, 91% and 92%, respectively). Joint and bone deformities and bone shortening were observed after changes that occurred in the postnatal and growing periods due to obstetric brachial plexus palsy. Every increase in function to be gained in the upper extremity musculature was also potentially able to reduce problems, such as shortness.

Marginal quenches and drives in Tomonaga-Luttinger liquids

We study Tomonaga-Luttinger liquids thrown out of equilibrium by marginal deformations in the form of interaction modulations. This is modeled by quenching or periodically driving the Luttinger parameter or, equivalently, the compactification radius of the free boson conformal field theory between two different values. We obtain exact analytical results for the evolution of the Loschmidt echo and observables such as the particle and energy densities. Starting from generic initial states, the quench dynamics are shown to exhibit revivals and temporal orthogonalities. For the periodic drive, we show stability or instability of time-evolved physical quantities dependent on the drive parameters. We also compare the corresponding marginally deformed thermal density matrices by non-perturbatively evaluating their Rényi divergence as a Euclidean quench. All the dynamics are shown to be crucially dependent on the ratio of the Luttinger parameters, which corresponds to the Zamolodchikov distance in the space of marginal deformations. Our setup is equivalently interpreted as the dynamics of the bosonic string upon instantaneous changes of the target-space radius.

Spatially Resolving Size Effects on Diffusivity in Nanoporous Extracellular Matrix-like Materials with Fluorescence Correlation Spectroscopy Super-Resolution Optical Fluctuation Imaging.

It is well documented that the nanoscale structures within porous microenvironments greatly impact the diffusion dynamics of molecules. However, how the interaction between the environment and molecules influences the diffusion dynamics has not been thoroughly explored. Here, we show that fluorescence correlation spectroscopy super-resolution optical fluctuation imaging (fcsSOFI) can be used to accurately measure the diffusion dynamics of molecules within varying matrices such as nanopatterned surfaces and porous agarose hydrogels. Our data demonstrate the robustness of fcsSOFI, where it is possible not only to quantify the diffusion speeds of molecules in heterogeneous media but also to recover the matrix structure with resolution on the order of 100 nm. Using dextran molecules of varying sizes, we show that the diffusion coefficient is sensitive to the change in the molecular hydrodynamic radius. fcsSOFI images further reveal that smaller dextran molecules can freely move through the small pores of the hydrogel and report the detailed porous structure and local diffusion heterogeneities not captured by the average diffusion coefficient. Conversely, bigger dextran molecules are confined and unable to freely move through the hydrogel, highlighting only the larger pore structures. These findings establish fcsSOFI as a powerful tool to characterize spatial and diffusion information of diverse macromolecules within biorelevant matrices.

Seismic Resilience Assessment of Curved Reinforced Concrete Bridge Piers through Seismic Fragility Curves Considering Short- and Long-Period Earthquakes

Curved bridges are commonly used for logistics and emergencies in urban areas such as highway interchange bridges. These types of bridges have complicated dynamic behaviors and also are vulnerable to earthquakes, so their functionality is a critical parameter for decision makers. For this purpose, this study aims to evaluate the bridge seismic resilience under the effects of changes in deck radius (50, 100, 150 m, and infinity), pier height irregularity (Regular and Irregular), and incident seismic wave angle (0°, 45°, and 90°) under short- and long-period records. In the first step, fragility curves are calculated based on the incremental dynamic analysis and probabilistic seismic demand models. Finally, seismic resilience curves/surfaces are constructed and their interpolated values of the log-normal distribution function presented for assessing system resilience. It is found that when long-period records are applied in one given direction, the angle of incidence has the most significant effect on seismic resilience, and bridges are most vulnerable when the angle of incidence tends to 0°. The effect of deck radius on seismic resilience became more remarkable as the angle of incidence increased. Additionally, results indicate that the bridge vulnerability in long-period records is more significant than that under short-period records.

Switchable Double Inversion of Chirality in a Helical Polyelectrolyte.

Switchable inversion of chirality between opposite handedness by varying pH is discovered for a histidine pendant polymer, polymethyl (4-vinylbenzoyl) histidinate (PBHis), as demonstrated by the circular dichroism as well as the changes of hydrodynamic radius measured by fluorescence correlation spectroscopy at the single molecular level. The polyelectrolyte is found to take an M-helicity below pH 8.0 and change into P-helicity above pH 8.0. Such helicity further inverses into M-chirality above pH 10.6. All these helical structures with opposite handedness can be switched using pH variations. The mechanism of such a unique phenomenon is attributed to the protonation and deprotonation of the imidazole group and the hydroxide-ion-mediated hydrogen bonding, which determine the mutual orientation between the adjacent side groups under the hydrogen bonds and π-π stacking and therefore the handedness of the helical structure.

Solute − solvent repulsion effects on the absorption spectra of anthracene in n-hexane investigated under high pressure

The band positions in the UV–VIS absorption spectra of compressed solution of anthracene in n-hexane significantly depend not only on the dispersive but also on the repulsive solute–solvent interactions, what has so far been omitted. Their strength is determined not only by the solvent polarity but also by Onsager cavity radius changing with pressure. The results obtained for anthracene show that repulsive interactions should be included in the interpretation of barochromic and solvatochromic results of aromatic compounds. We show that the barochromic studies in the liquid solvent can be an alternative to solvatochromic studies, e.g. to determine the polarizability of organic molecules in the electronic excited state. The pressure-induced polarity change in n-hexane exceeds that induced by the exchange of n-alkane solvents between n-pentane and n-hexadecane.

Electrical properties of a high-precision hexagonal spiral silicon drift detector

With the deepening and expansion of semiconductor technology and research, in order to continuously optimize the structure and performance of semiconductor detectors, a high-precision hexagonal spiral silicon drift detector (SDD) is proposed in this paper. In order to obtain a more accurate spiral ring structure, this paper goes beyond the first-order formula in the Taylor expansion for calculating the radius of the spiral ring. Based on the first-order formula, the second-order formula for calculating the radius of the spiral ring is further developed and derived. The point coordinates are obtained by combining the radius, angle, and ring spacing change formula to obtain a more accurate spiral ring structure. The actual number of turns is more accurate than that obtained from first-order approximation, which better solves the problem of accurate calculation of the number of spiral rings and the structure of the spiral SDD in the existing technology, that is, the accurate calculation of the radius of the spiral ring. In order to verify the abovementioned theory, we model this new structure and use Technology Computer-Aided Design to system simulate and study its electrical properties, including potential distribution, electric field distribution, and electron concentration distribution. According to the simulation results, compared with the first-order formula, the second-order formula has better electrical properties; more uniform distribution of potential, electric field, and electron concentration; and a clearer electron drift channel.

Mössbauer and Magnetic Properties Investigation of REFe0.5Cr0.5O3 (RE=La, Y) Perovskite

The synthesis of REFe0.5Cr0.5O3 (RE = La, Y) using the sol–gel method is focused and their structural differences are investigated. The results of X‐ray diffraction show that the change of ion radius at position A leads to varying degrees of octahedral distortion and spatial group structure. The scanning electron microscopy analysis reveals micron‐level particles with clear boundaries, while energy‐dispersive X‐ray spectroscopy and room temperature Mössbauer spectra indicate the presence of Fe/Cr clusters in the sample and the transitional valence of iron. Disorder in the B position leads to a saturation moment that is lower than the theoretical value. The thermomagnetic profile shows a reversal of magnetization due to the interaction between the single‐ion magnetic anisotropy and the antisymmetric Dzyaloshinskii–Moriya (DM) interaction, with a broader peak is observed due to cluster formation. The difference in negative magnetic field is due to the difference in net magnetic moment caused by different DM intensities.

Digital Rock Analysis on the Influence of Coarse Micro-Fractures on Petrophysical Properties in Tight Sandstone Reservoirs

Tight sandstone reservoirs, as typical unconventional reservoirs, have attracted more and more attention worldwide. Compared to conventional reservoirs, the complex microscopic pore structures and micro-fractures of the tight reservoirs are developed, and fluid flow in the tight sandstone reservoir is very complicated. Therefore, studying the influence of fractures on the rock topological structure and the flow characteristics between micro-fractures and the matrix is critical to the development of tight sandstone reservoirs. In light of the intricate nature of micro-fractures, digital rock analysis technology is utilized to address this issue instead of traditional experimental methods. Firstly, the selected tight rock is scanned by X-ray computed tomography (XCT), and then the natural tight digital rock is reconstructed by filtering and binary segmentation. Secondly, micro-fracture with different shapes is added to the digital rock. Then, a pore network model extracted by the maximum ball method is adopted to conduct the flow simulation. The study finds that the distribution of pore throat radius changes with increasing fracture aperture and length and that the permeability and capillary pressure curves are influenced by fracture aperture and length in the direction of connectivity. The impact of micro-fracture dip angle on pore throat structure is significant with changes in permeability and fluid flow in different directions. Overall, the study emphasizes the importance of fracture aperture and length in determining the properties and behavior of tight sandstone reservoirs and highlights the usefulness of digital rock analysis technology in providing insights into complex microstructures.

PRYORTIE: Public on-demand smart transportation service via a scalable fog-based platform

Over the past few years, the on-demand transport services (e.g., Uber) have witnessed an unprecedented popularity due to its easy-to-adopt model (i.e., a passenger orders a taxi, a request is sent to all drivers in the vicinity, drivers accept/reject the order). Nonetheless, such a service is affected directly by multiple urban factors such as traffic, number of existing drivers en-route, and local weather which may cause a huge delay. Dial-A-Ride Problem with Transfers (DARPT) allows passengers to change vehicles during their trip in a bid to minimize the delay. However, DARPT relies solely on using the existing Global Positioning System (GPS) that suffers from delay in propagating raw traffic data (e.g., route coordinates, geodesic distance, and time stamp) on time and ultimately causes traffic disruption and increases ride time constraint. To this end, this work introduces a novel interactive Fog-based navigation simulator, PRYORTIE. PRYORTIE uses roadside smart units in the form of fog nodes as a means for collecting and sharing real-time traffic data comprising of vehicles’ location and speed within the area, they each cover. These nodes can calculate an optimal route for a vehicle using a novel path recommender algorithm that utilizes a vehicle's current position, its destination, and current traffic data. The nodes can update the route in real-time using the same algorithm if traffic conditions within their radius change. A package delivery case study has been implemented and simulated in PRYORTIE to demonstrate the impact of using fog nodes in routing and navigation. Compared with the state-of-the-art, the proposed approach shows on average 46.34% improvement in saving travel time. The proposed method clearly demonstrates tangible benefits of communicating real-time data to drivers and lays the ground for subsequent future work in smart transportation and navigation especially in the context of last mile delivery. It can easily be extended to autonomous vehicles and can be easily integrated into existing transportation frameworks that employ a fog-cloud paradigm for smart transportation.

Effects of rod radius and voltage on streamer discharge in a short air gap

Streamer discharge is the inaugural stage of gas discharge, and the average electron energy directly determines the electron collision reaction rate, which is a key parameter for studying streamer discharge. Therefore, taking into account the average electron energy, this work establishes a fluid chemical reaction model to simulate and study the course of evolution of a streamer discharge in a 5 mm rod–plate gap, considering 12 particles and 27 chemical reactions. It introduces the electron energy drift diffusion equation into the control equation, and analyzes the temporal and spatial changes of average electron energy, electric field intensity and electron density with change in rod radius and voltage. The effects of voltage and rod radius on the course of streamer discharge can be reflected more comprehensively by combining the average electron energies. Three different values of 0.3 mm, 0.4 mm and 0.5 mm are set for the rod radius, and three different values of 5 kV, 6 kV and 7 kV are set for the voltage. The influence of an excitation reaction on the streamer discharge is studied. The findings indicate that, as voltage raises, the streamer head’s electron density, electric field and average electron energy all rise, and the streamer develops more quickly. When the rod radius increases, the electron density, electric field and average electron energy of the streamer head all decrease, and the streamer’s evolution slows down. When an excitation reaction is added to the model, the average electron energy, the magnitude of the electric field and the density of electrons decrease, and the evolution of the streamer slows down. An increase in average electron energy will lead to an increase in electric field strength and electron density, and the development of the streamer will be faster.

Thermal effect on magnetoexciton energy spectra in monolayer transition metal dichalcogenides

It is widely comprehended that temperature may cause phonon-exciton scattering, enhancing the energy level's linewidth and leading to some spectrum shifts. However, in the present paper, we suggest a different mechanism that allows the thermal motion of the exciton's center of mass (c.m.) to affect the magnetoexciton energies in monolayer dichalcogenides (TMDCs). By the nontrivial but precise separation of the c.m. motion from an exciton in a monolayer TMDC with a magnetic field, we obtain an equation for the relative motion containing a motional Stark term proportional to the c.m. pseudomomentum, related to the temperature of the exciton gas but neglected in the previous studies. Solving the Schr\"odinger equation without omitting the motional Stark potential at room temperature shows approximately a few meV thermal-magnetic shifts in the exciton energies, significant enough for experimental detection. Moreover, this thermal effect causes a change in exciton radius and diamagnetic coefficient and enhances the exciton lifetime as a consequence. Surprisingly, the thermoinduced motional Stark potential breaks the system's SO(2) symmetry, conducting new peaks in the exciton absorption spectra at room temperature besides those of the $s$ states. This mechanism could be extended for other magnetoquasiparticles such as trions and biexcitons.

An Active Compliance Adsorption Method for Climbing Machining Robot on Variable Curvature Surface

This article proposes an active compliance adsorption method for a negative pressure adsorption climbing robot with 3 active compliance suction units which integrate 3 degree of freedom active compliance actuators along with flexible adsorption chambers. This method enables the climbing robot to adsorb and move stably on the surface of large and complex components with variable curvature for machining purposes. The main contribution lies in two aspects. First, an adsorption performance indicator (API) depicting the stretch of the flexible sealing lip is proposed by analyzing the leaked airflow of the climbing robot's suction unit. Second, the pose control method of the suction chamber based on the real-time estimated adsorbed surface is proposed, where the API is used as the optimization target. The experiments have been performed and the results show that a 10 kg-weight climbing robot with three active compliance suction units can keep adsorption force over 1000 N when the surface's curvature radius changes continuously from 1.1 to 14.6 m, with a significant increase in the adsorption force up to 156% compared with only pure passive compliance adsorption method.

Study on the influence of uneven settlement and small curve radius on metro train running safety and riding comfort

Shield tunnels are susceptible to large uneven settlements owing to their low longitudinal stiffnesses, which can lead to structural defects and unfavorable wheel–rail interactions. These conditions may even worsen if uneven settlement occurs in curved track sections with small radii. Therefore, the running safety and riding comfort of metro trains should be considered when dealing with curved tunnel sections with differential settlements. In this study, a train–curved-track–tunnel dynamic interaction model was established to evaluate the influence of uneven settlement and a small curve radius on the running safety and riding comfort of a metro train under different curve radii, vehicle speeds, and settlement ranges and amplitudes. Considering initial random irregularities with respect to the longitudinal level and alignment, the dynamic responses of the vehicle were determined, including the wheel–rail forces, accelerations of the vehicle, wheel load reduction rate, derailment coefficient, and stability index. In addition, the characteristics of uneven settlement when the vehicle responses reached peak values were illustrated. The results revealed that the wheel–rail lateral and vertical forces increased significantly with an increase in velocity. The wheel load reduction rate, derailment coefficient, and lateral comfort were negatively correlated with the curve radius, whereas vertical comfort was not very sensitive to changes in the curve radius. Additionally, the outer wheel exhibited a greater load reduction than the inner wheel, thus leading to a greater likelihood of derailment. More attention should therefore be directed toward the settlement wavelengths and amplitudes at which the wheel load reduction rate, derailment coefficient, and vertical and lateral riding comfort indexes achieve their maximum values.

On the space-charge effects in the beam extraction process of ion thrusters: the roles of compensating electrons and changing beam radius

Space-charge effects limit the beam-extraction capability of the ion optics and thus hinder the miniaturization and other performance improvements of ion thrusters. This paper presents numerical studies of the space-charge effects in ion optics using hybrid and full particle-in-cell (PIC) simulations, and proposes a modified Child–Langmuir (CL) law. As the injected current increases, the parallel-plane electrode system which corresponds to the classical CL law will reach an unstable and oscillatory state, while the ion optics system remains stable because the electrons from the bulk plasma compensate for the space-charge effects. Furthermore, the radial expansion of the ion beam and the loss of ions on the grids can counteract the space-charge effects when the injected current increases. In general, the space-charge effects in ion optics are self-consistently adjusted by the compensating electrons and the variation of the beam radius. Accordingly, we identify a region in ion optics where, generally, no electrons exist to exclude the influence of electron compensation, and then we modify the CL law of this region by taking into account the effect of the change in the beam radius. We validate the modified CL law and demonstrate its effectiveness in predicting the operating points of the ion optics, such as the perveance-limit point.

Laboratory study of Kelvin–Helmholtz instability at ion kinetic scales

Kelvin–Helmholtz instability (KHI) is considered important in transporting energy and mass at the magnetopause of Earth and other planets. However, the ion kinetic effect influences the generation and evolution of KHI, as the spatial length of the magnetopause may be smaller than the Larmor radius of the ion; this influence is not yet fully understood. In this investigation, laboratory experiments were designed to study the excitation of KHI at the ion kinetic scale. The ion kinetic scale was modeled by controlling the ratio of the Larmor radius and the electric scale length ρ i / L E &amp;gt; 1, and the KHI was excited at the spatial scale of LE by a controllable sheared E × B flow. It was found that the ion kinetic effect on KHI growth manifests as the ion Larmor radius reaches the shear length scale, and the KHI is suppressed as the ion Larmor radius increases. Incorporating a theoretical analysis by substituting our experimental parameters, the suppression of the KHI was attributed to the fact that the KHI linear growth rate decreases with the ratio change of the ion Larmor radius because the relative orientations of the ion diamagnetic drift velocity ( V d) and the shear flow velocity ( V 0) are opposite. Our experimental conditions ( V d / V 0 &amp;lt; 0) are similar to the dusk-side conditions of the magnetospheres of Earth and Mercury under northward interplanetary magnetic fields; therefore, this result can be extended to understand the evolution of KHI in the planetary boundary layer.

Dynamics of the truncated conical thin-wall turning process

Dynamics of the rotational truncated conical thin-walled workpieces, which are widely used in predicting stability of turning process, was seldom reported. This article presents a systematical method to study the dynamic behaviors of these kinds of workpieces under the practical clamping conditions of their turning processes. Mathematical derivations, which consider the radius change along the conical direction, are detailed to predict the instantaneous dynamic characteristics of the workpieces by comprehensively considering the influence of rotation factor. The boundary condition of a clamping and free combination, which corresponds to the actual clamping requirement in turning, is well considered in the derivation. The frequencies and modal shapes of the workpiece under different rotating speeds are solved by the generalized differential quadrature algorithm. A series of modal impact tests, conducted with the workpiece under both static and rotating states, are used to confirm the method’s accuracy in predicting the in-process dynamic behavior. It is theoretically found that in contrast to the conventional turning processes, this thin-walled workpiece’s turning process undergoes clear multi-mode effects, which further significantly influence the process stability. After that, the aforementioned derivations are incorporated into the dynamic governing formulation of the turning process for solving the stability lobe diagrams (SLDs). Finally, actual truncated conical thin-wall turning tests confirm the reasonability of the proposed method, and find that the first three modes dominate the stability of the process but not only the first one.

Front Cover: A Thermodynamic Model for the Insertion Electrochemistry of Battery Cathodes (ChemElectroChem 7/2023)

The Front Cover illustrates a crystal layer of nickel hydroxide that undergoes phase separation during electrochemical ion deinsertion (oxidation) and its corresponding cyclic voltammogram (CV). This phase separation phenomenon is revealed by a thermodynamic modelling of solid-solution and phase-separation reaction modes in battery cathodes. Furthermore, according to this model, the hysteresis observed during charge-discharge in the CV curves results from this phase separation which itself is a consequence of large radius changes in the crystal's central metal ion. More information can be found in the Research Article by K. Malaie, F. Scholz and U. Schröder.