Side Leakage Research Articles

Multiple lubricated joints with long and short bearings in multibody mechanical systems - Modeling, simulation, and performance analysis

This study examines the effect of multiple lubricated imperfect long and short bearings on the performance of a multibody mechanical system. Unlike the typical assumption of a single perfect or imperfect lubricated joint due to modeling difficulties, this research considers the practical impacts of clearances in multiple joints. While unlubricated joints generally cause significant performance issues, lubricants reduce these effects, creating more localized peaks. The findings show that as the number of lubricated joints increases, both the magnitude and frequency of these peaks rise. In systems with multiple journal bearings, torque peaks become more noticeable due to the additional degrees of freedom introduced by the clearances. These degrees of freedom amplify acceleration, leading to higher lubricant reaction forces, which in turn require greater motor torque peaks to maintain the system's kinematics. Shorter lubricated joints exhibit more severe peaks than longer ones, mainly due to side leakage causing axial pressure variation and reduced damping capacity. The study highlights the need to replace idealized joints with imperfect ones for more accurate modeling of practical systems.

Non-Newtonian fluids effects on the steady-state performance of two-lobe journal bearings

This research aims to investigate the behavior of non-Newtonian fluid obeying the power law model in a laminar flow regime for a two-lobe journal bearing. The investigation involves calculating the static characteristics in terms; of load-carrying capacity, attitude angle, friction coefficient, friction force, and side leakage, for various values of the power law index and different eccentricity ratios. To determine the static characteristics, the pressure distributions are obtained by the numerical solution of the modified Reynolds equation considering the effect of non-Newtonian behavior of the fluids using the finite difference method. This study reveals that increasing both the eccentricity ratio and power law index produce an increase in the load-carrying capacity, friction force, and side leakage while lead to a decrease in the attitude angle and friction coefficient for the two-lobe journal bearing. In addition, compared to Newtonian fluid the results show that the using of non-Newtonian fluids as lubricants improves the static characteristics of the two-lobe journal bearing especially for the shear-thickening lubricants.

Shield tunnel leakage detection using distributed optical fiber

Leakage in operating tunnels is a serious problem during operating stage. In order to realize non-destructive detection of leakage in an operating shield tunnel, an optical fiber temperature measurement method based on Raman scattering and infrared thermal imaging technology is developed. The working principle of leakage monitoring with Distributed Fiber Optic Temperature Sensor (DTS) combined with time domain reflectometry (OTDR) technology are introduced. The distributed measurement of temperature field is realized in a typical tunnel. Infrared thermal imager is used to perform thermal imaging on the leakage area, and the temperature difference between the leakage area and the non-leakage area is 3.6 °C, which can meet the requirements of distributed optical fiber side leakage temperature accuracy. This illustrates the feasibility of quantitative monitoring of leaks in distributed optical fiber temperature sensing systems. The reasonable arrangement of leakage monitoring fiber in distributed fiber temperature sensing system is discussed in practical engineering.

Effect of chevron-shaped wetting patterns on oil film thickness in cylinder-on-disc contact under starved lubrication or limited lubricant supply

This study addresses the oil starvation problem in roller bearing line contacts and proposes a novel Chevron-shaped wetting/oleophilic pattern on the bearing track to enhance oil replenishment. Validation through optical cylinder-on-disc lubrication film tests reveals the impact of the pattern on inlet oil supply and film thickness. Notably, a Chevron pattern oriented opposite to disc movement significantly increases film thickness. Wetting is more pronounced in oleophilic areas (Chevron pattern), forming an inverted V-shaped "virtual wall" that directs lubricant backflow toward the center and reduces side leakage. A pattern length equal to the bearing track width was found to be more effective compared to smaller sizes, as the oil side ridges are located on the oleophobic and oleophilic boundaries, which capitalizes the wettability step effect more effectively. This research provides a basis for designing oleophobic surfaces with improved anti-wear and anti-friction properties.

Polarization sensitive optical side leakage radiometry for distributed characterization of anti-resonant hollow-core fibers.

A novel technique referred to as optical side leakage radiometry is proposed and experimentally demonstrated for non-destructive and distributed characterization of anti-resonant hollow-core optical fibers with high spatial resolution. Through in-depth analysis of the leakage light collection, we discover a unique polarization dependence, which is validated by our experiment. By leveraging this effect and employing Fourier filtering, this method enables accurate quantification of propagation attenuations for fundamental and higher order modes (with the uncertainty of <1 dB/km), identification of localized defects (with the resolution of ∼5 cm), and measurement of ultra-low spectral phase birefringence (at the level of 10-7) in two in-house-fabricated nested antiresonant nodeless hollow-core fibers. Such a fiber characterization approach, boasting unprecedently high accuracy and a potentially wide dynamic range, holds the potential to become an indispensable diagnosis tool for monitoring and assisting the manufacture of high-quality anti-resonant hollow-core fiber.

A Two‐Step Entanglement Concentration for the Less‐Entangled Four‐Photon Cluster States

AbstractEntanglement concentration serves as an essential tool to obtain the maximally entangled states from the less‐entangled states in quantum information processing tasks. An efficient two‐step entanglement concentration protocol (ECP) is proposed to concentrate the less‐entangled four‐photon cluster states with four unknown coefficients into the maximally entangled states in this paper. The protocol utilizes parity‐check gate and photon‐polarized controlled‐Z gate, constructed with a single semiconductor quantum dot in a single optical microcavity (quantum dot‐cavity coupled system) and several linear optical elements. The discarded quantum states can be recycled in the next round concentration to achieve a higher success probability. Under conditions of strong coupling and weak side leakage rate, the ECP can tend toward ideal fidelity and efficiency. Compared to the previously proposed ECPs that utilize various auxiliary tools such as additional entangled states and complex quantum logic gates, the ECP significantly simplifies the analysis process and enables efficient implementation. Thus, the ECP is more economical and feasible in future optical systems.

Magnetic integration of a symmetrical LCL filter in the grid‐tied inverter with reduced EMI noise

AbstractHarmonics and electromagnetic interference (EMI) pose serious threats to the safety and efficiency of grid‐tied inverters. Although the inductor‐capacitor‐inductor (LCL) filter offers commendable harmonic suppression, it does not sufficiently mitigate leakage current and EMI caused by high‐frequency pulse‐width modulation (PWM). This paper examines the use of a symmetrical LCL filter to reduce the AC side leakage current in grid‐tied inverters. The symmetrical structure bolsters the conducted EMI suppression capability of the LCL filter. A magnetic integration scheme for symmetric LCL filters is introduced, and through thoughtful structural design, it achieves filter inductance integration on the EIE magnetic core. An experimental platform, equipped with a high‐frequency SiC‐MOSFET voltage source inverter with a 600 W output, is utilized. The LCL filter, symmetric LCL filter, and magnetic integrated symmetric LCL filter are contrasted, proving the effectiveness and feasibility of the proposed scheme. Furthermore, the experimental results demonstrate that the proposed magnetic integration scheme significantly reduces the filter's volume and weight, thereby enhancing the power density of the grid‐tied inverter system.

Creation of an encryption algorithm resistant to attacks through side channels of leakage

The paper is devoted to.the development of an encryption algorithm resistant to leakage through side channels The objectives of the work were the development and computational-experimental justification of the algorithm. Materials and methods. A new algorithm of encryption resistant to attacks through side channels is proposed.The algorithm resistance to attacks on the basis of numerical experiments is analyzed.As a result of analyzing statistical data before and after modifications of the algorithm it was found that the developed algorithm is resistant to time and energy attacks. Results of the study.The main result of the work is the development of an encryption algorithm resistant to attacks through side leakage channels. The resilience of the algorithm to attacks was confirmed by analyzing the statistical data before and after modifications to the algorithm. The comparisons concluded that the developed algorithm is resistant to timing attack and power consumption attack. Discussion and Conclusion. The resulting algorithm can be applied to counter groups of attacks on cryptographic devices, in which the attacker tries to obtain any information useful to him, through the physical features of the implemented cryptosystem.

Dynamic Forced Performance of an O-Rings Sealed Squeeze Film Damper Lubricated With a Low Supply Pressure and a Simple Method to Quantify Air Ingestion

Abstract Contemporary squeeze film dampers (SFDs) in air-breathing engines are short in length to limit weight and part count and lubricated with a low feed pressure to reduce oil storage and pumping power. In SFDs, O-rings (ORs) restrict side leakage and increase the viscous damping while a adding a modest centering stiffness. Continuing a long-term project characterizing SFDs for aircraft engines and extending the original work (San Andrés and Rodríguez, 2021, “On the Experimental Dynamic Force Performance of a Squeeze Film Damper Supplied Through a Check Valve and Sealed With O-Rings,” ASME J. Eng. Gas Turb. Power, 143(11), p. 111011) the paper details measurements of the forced performance of an OR sealed damper (OR-SFD) with diameter D = 127 mm, land length L = 0.2 D, and radial clearance c = 0.0022 D. Lubricant ISO VG 2 supplied at 0.69 bar(g) fills an upstream oil plenum and flows into the middle of the land through a single orifice configured with a check valve. Measurements of applied single-frequency dynamic loads, along with the ensuing damper displacements and accelerations serve to identify the parameters of the test structure, ORs, and SFD. The tests encompass centered whirl motions with amplitude r = 0.05–0.45c, and a range of whirl frequencies, ω = 10–130 Hz. Note the squeeze velocity vs = rω reaches 102 mm/s. The ORs force coefficients are nearly invariant with frequency but do depend on the orbit amplitude. The ORs' stiffness (KOR) decreases by 75% as the motion amplitude increases, r → 0.45c, likely due to the large elastic deformations and slow recovery of the ORs material. For small amplitude motions (r/c = 0.05 and 0.10), the ORs damping coefficient (COR) is ∼10% of the overall coefficient for the lubricated system (CL), while for r/c &amp;gt; 0.25, COR ∼ 0.03CL. For small amplitudes of whirl (r ≤ 0.25c), the SFD experimental viscous damping (CSFD) and added mass (MSFD) coefficients, identified over a shorter frequency range (vs&amp;lt;30 mm/s) equal theoretical magnitudes for a fully sealed damper. As the orbit size grows to r = 0.45c MSFD drops nearly by 75% and CSFD decreases by ∼40% due to the onset of both lubricant cavitation and air ingestion occurring for squeeze velocities vs ≥ 24.5 mm/s, as also seen in the recorded dynamic pressures and video recordings of a bubbly mixture leaving the damper. A comprehensive flow model predicts CSFD and MSFD about 8% and 12% larger than the experimentally identified coefficients. A novel approach enables the estimation of the gas volume fraction (GVF) generated in the damper which rapidly increases as vs grows. The simple procedure draws into a deflated balloon the material contents in the squeeze film, weighs the sample, and identifies its volume to produce an estimate of the GVF. The procedure to quantify the GFV will assist in the validation of predictive tools.

Analysis of the Turbulent Lubrication of a Textured Hydrodynamic Journal Bearing

In order to investigate the turbulent lubrication performance of a textured hydrodynamic journal bearing (THJB), a model of turbulent lubrication was established in this paper. The variations in the Reynolds number, oil film thickness, oil film pressure, bearing capacity, attitude angle, and side leakage flow with structural and working parameters were studied, and the axis whirl orbit was further analyzed. The results show that turbulent lubrication is suitable for the actual operating conditions of THJBs. The Reynolds number decreases with the eccentricity ratio in the pressure-bearing zone but increases with rotational speeds, whereas the variation in the maximum oil film pressure increases and the minimum oil film thickness decreases with the eccentricity ratio under various Reynolds numbers. The bearing capacity decreases with the dimple diameter, depth, oil film thickness, and clearance ratio but increases with the length/diameter ratio and dimple spacing. As the eccentricity ratio increases, the attitude angle decreases, but the side leakage flow increases. In addition, the system tends to be unstable as the rotational speed and length/diameter ratio increase, and the friction and wear on the surface are three-body friction. This work not only helps in analyzing the characteristics of a THJB under actual operating conditions but also provides support for research on the simulation of THJB’s lubrication mechanism of THJB via computational fluid dynamics.

Effects of manufacturing errors and micro-groove surfaces on the static and dynamic characteristics of water-lubricated bearings

In this paper, the effects of manufacturing error and micro-groove on the static, dynamic and stability characteristics of water-lubricated journal bearings (WLJBs) are investigated. Mathematical expressions of manufacturing errors and surface micro-groove are presented, and the Reynolds equations with steady and unsteady states are calculated by using the linear perturbative method and the finite difference technology. According to the developed model, the effects of the waviness magnitude, spatial number, and phase angle for circumferential errors, as well as the concavity, convexity, and taper for axial errors on the film thickness distribution, fluid pressure distribution, bearing capacity, coefficient of friction, side leakage flow rate, attitude angle, stiffness coefficient, damping coefficient, threshold speed and whirl frequency ratio of WLJBs are evaluated. Simulation results demonstrate that fluid film thickness distribution and fluid pressure distribution are significantly affected by manufacturing errors and micro-groove. Compared with axial manufacturing errors, circumferential manufacturing errors cause an inhomogeneous distribution of fluid pressure and morphological transformation in the high-pressure zone. The variation rules for the lubrication performance of bearings with circumferential waviness, concavity, convexity, and taper errors are not consistent at various eccentricity ratios. The magnitude of the concavity and taper errors may have an improving effect on the bearing performance, whereas circumferential waviness and convexity error play a negative role. Moreover, the micro-groove with partial distribution enhances the hydrodynamic effect in the bearing clearance. Numerical simulations can provide a valuable reference for the manufacturing and design of bearing systems.

Compact entanglement concentration for three-electron-spin W states with error-detected parity-check gates

We present a compact entanglement concentration protocol (ECP) for unknown less-entangled three-electron-spin W states, resorting to the interaction rules between the circularly polarized photon and cavity-quantum-dot (QD) system. In the first step of our ECP, the parties utilize two less-entangled three-electron-spin systems not only to obtain one partially entangled three-electron-spin system with two unknown parameters if the odd-parity occurs with the parity-check gate (PCG) but also to get one entangled two-electron-spin system if the even-parity occurs. By exploiting the above three-electron-spin and two-electron-spin systems as the resource for the second step of our ECP, the parties can obtain a standard three-electron-spin W state if the odd parity occurs. Meanwhile, the systems in the even-parity instance can be used as the resource in the next round of our ECP. As the imperfect performances originated from the side leakage and the limited coupling strength of the cavity-QD system can be reflected by clicking the single-photon detectors, the fidelity of the PCG is unit, in principle, immune to strong coupling-strength restriction. Moreover, the success of our ECP not only is heralded by the detectors but also its efficiency further is improved by repeating the operation processes. Therefore, our ECP is useful in the quantum communication network.

Analysis of the Total Leakage Characteristics of Finger Seal Considering Fractal Wear and Fractal Porous Media Seepage Effects

As an advanced flexible dynamic sealing technology, the leakage characteristics of a finger seal (FS) is one of the key research areas in this technology field. Based on the fractal theory, this paper establishes a mathematical model of the FS main leakage rate considering the fractal wear effect by taking into account the influence of the wear height on the basis of the eccentric annular gap flow equation. Based on the Hagen-Poiseuille law and the fractal geometry theory of porous media, a mathematical model of the FS side leakage rate considering the fractal porous media seepage effect is developed. Then, a mathematical model of the FS total leakage rate is established. The results show that the mathematical model of the FS total leakage rate is verified with the test results, the maximum error rate is less than 5%, and the mathematical model of the FS total leakage rate is feasible. With the gradual increase in working conditions and eccentricity, the FS main leakage rate gradually increases. In addition, the effects of the fractal dimension, fractal roughness parameters and porosity after loading on the FS main leakage rate are negligible. As the fractal dimension of tortuosity after loading gradually decreases, the fractal dimension of porosity after loading gradually increases, and the FS side leakage rate gradually increases. As the porosity after loading gradually increases, the FS side leakage rate gradually increases. Under different working conditions, different fractal characteristic parameters and different porosities after loading, the weight of the FS main leakage rate is much greater than that of the FS side leakage rate by more than 95%.

Entanglement generation for non-local photonic qubits using quantum dot within the optical micro-cavity

This paper presents the analytical inquisition of photonic entanglement generation circuit (PEGC) for non-local qubits designed using quantum dot within the optical micro-cavity, considering the realistic environment. It is established that the concurrence of the PEGC is considerably contingent on the interplay between the spin of quantum dot and photon within the optical micro-cavity. The maximum concurrence obtained is 0.6124 at normalized coupling strength (g/k) = 0.3 and normalized side leakage rate (ks/k) = 0.1 and 0.9011 at g/k = 4 and ks/k = 0.1 with and without a noisy environment, respectively. Different quantum cryptography-based protocols may be implemented using reported work.

Observation of multiple bulk bound states in the continuum modes in a photonic crystal cavity.

Obtaining bound states in the continuum (BICs) in photonic crystals gives rise to the realization of resonances with high quality factors for lasing and nonlinear applications. For BIC cavities in finite-size photonic crystals, the bulk resonance band turns into discrete modes with different mode profiles and radiation patterns. Here, photonic-crystal BIC cavities encircled by the photonic bandgap of lateral heterostructures are designed. The mirror-like photonic bandgap exhibits strong side leakage suppression to confine the mode profile in the designed cavity. Multiple bulk quantized modes are observed both in simulation and experiment. After exciting the BIC cavity at different positions, different resonance peaks are observed. The physical origin of the dependence between the resonance peak and the illuminating position is explained by analyzing the mode profile distribution and further verified by numerical simulations. Our findings have potential applications regarding the mode selectivity in BIC devices to manipulate the lasing mode in photonic-crystal surface-emitting lasers or the radiation pattern in nonlinear optics.

Study on Characteristics of Two Phase Flow Field in Grinding Zone of Large Spiral Angle Groove Wheel

Aiming at the high specific removal energy and heat generation rate in grinding process, and the low heat transfer efficiency in grinding arc zone of ordinary grinding wheel, the problems of local high temperature and grinding burn are easy to occur. In this paper, the plane grinding of grooving wheel with large spiral Angle is taken as the research object, and the numerical analysis model of gas-liquid two-phase flow field in wedge zone and grinding arc zone is established. The enhancement mechanism of heat transfer performance in grinding arc of large spiral Angle groove wheel was investigated. The results show that the flow of grinding fluid into the grinding arc will be hindered by the airflow around the grinding wheel, resulting in backflow and side leakage. Compared with ordinary grinding wheels without grooves, the backflow and side drainage in grinding zone of big spiral Angle grooves grinding wheels are significantly reduced, and a large amount of grinding fluid is transported in the heat exchange channel. The spiral groove has a good conduction effect on the grinding fluid, and the grinding fluid is easier to enter the grinding zone, thus significantly improving the heat transfer performance of the grinding zone and effectively reducing the grinding temperature during the grinding process.

Assessment of Mask Effectiveness to Prevent the Spread of SARS-Cov-2: A Review

Background: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes coronavirus diseases 2019 (COVID-19) is mainly spread person-to-person through droplets and aerosols. It is often recommended that healthcare workers and other people take precautionary measures to reduce their exposure to SARS-CoV-2 by wearing masks. However, the effectiveness of the masks is not well understood at the community level. Methods: To assess the effectiveness of the masks against the SARS-CoV-2 virus, we searched electronic databases (Pubmed, Scopus, and Web of Science) for studies that assessed mask or respirator effectiveness in the prevention of SARS-CoV-2 transmission. Results: The majority of studies reviewed suggested that all types of masks (e.g., N95 respirators, surgical masks, and cloth masks) protect the human respiratory system against airborne viral pathogens, such as SARS-CoV-2. The quality and effectiveness of the masks vary depending on the materials, structures, and methods used for construction. The data shows that both surgical masks and N95 respirators can provide similar protection against airborne respiratory infections, including SARS-CoV-2, for healthcare workers, but due to its better facial fit, N95 is recommended for high-risk environments. However, although masks reduce the spread of SARS-CoV-2, they may not entirely provide proper protection against biologic particles, which are considerably smaller than the accepted most penetrating particle size used in certification tests. Conclusion: While all types of masks have technical pros and cons, wearing them correctly can significantly improve their effectiveness since a complete seal of respiratory particles is unlikely due to side leakage of aerosols of different sizes.

Novel shear thickening gel/high‐performance fiber reinforced flexible composites: Multi‐velocity impact and functional properties

AbstractShear thickening gel (STG) is a promising substrate used for flexible protective materials, which has superior dimensional stability without gel side leakage and delamination when sustaining long‐standing time. STG/high‐performance fiber flexible composites exhibit high‐energy absorption capacity for multi‐velocity impact. This article reveals the shear thickening mechanism of STG that lays a theoretical foundation for the performance analysis of STG composites. The preparation methods of STG/high‐performance fiber flexible composites, including impregnation, hand lay‐up, filling, and lamination methods, are compared. The energy absorption principle of STG/high‐performance fiber flexible composites on multi‐velocity impact and the destruction morphology was analyzed. The coupling effects and functional applications of STG functional composites with nanoparticles, magnetic particles, and conductive particles are summarized. It provides more suitable conditions for designing new multifunctional protective equipment and manufacturing advanced intelligent, protective devices.

Three-Dimensional Thermohydrodynamic Analysis of Journal Bearing Lubricated by Magnetic Fluids with Couple Stresses

Couple stresses because of magnetic particles additives on the lubrication performance of a journal bearing system was embraced and scrutinized in the current examinations theoretically. The governing equations of Reynolds (pressure field), energy (temperature field), and heat conduction (temperature field through the solids) are coupled and solved instantaneously in term of temperature and viscosity. After these set of equation pressure is obtained, it is used to obtain the bearing characteristic. It was found that the load currying capacity and maximum pressure are increased due the employing of magnetic fluids along with the couple stresses, as well as side leakage flow and the friction coefficient are decreased. It can be also concluded that the magnetic fluids with couple stresses are better lubricant than magnetic fluid only (l = 0), Newtonian fluids, and couple stress fluid (ʎ = 0).

Analiza performansi eliptičnog ležaja podmazanog eksperimentalno karakterizovanim nano-mazivom s obzirom na toplotni efekat korišćenjem CFD tehnike

This study uses computational fluid dynamics (CFD) to quantitatively examine the performance of an elliptical journal bearing (EJB) lubricated with TiO2 and ZnO nano-lubricant considering thermal effect. In an experiment, nanoparticles with particle concentrations varying from 0 to 2 weight percent are mixed with SAE15W40 engine oil to create these lubricants. The impact of weight fractions, rotational speed, eccentricity, and ellipticity ratios on the thermal performance of the EJB has been examined. The Kreger-Dougherty model is employed to understand the effects of oil film temperature as well as nanoparticle concentration on lubricant viscosity. The pressure and temperature determined by (Dang 2020) and (Wang 2021were evaluated against the CFD model with good agreement. The findings show that for 2 wt% nanoparticles, e of 0.6 and N of 5000 rpm, the load-carrying capacity increased by 5.5% and 4% and the side leakage flow decreased by 24.4% and 18%.