Search

This study analyzes the consequences of first-order chemical reactions, radiation, and viscous dissipation on the unsteady magnetohydrodynamic natural convective flow of a viscous incompressible fluid over a vertically positioned semi-boundless oscillating plate with uniform mass diffusion and temperature. An implicit finite-difference technique is employed to solve a set of dimensionless, coupled, nonlinear partial differential equations. The numerical results for fluid velocity, concentration, and temperature at the plate under different dimensionless parameters are graphically displayed. Due to first-order homogeneous chemical reactions, it has been discovered that the velocity rises at the time of a generative reaction and drops during a destructive reaction. A decline in velocity is observed with an increase in the phase angle, radiation parameter, and chemical reaction parameter. Further, it has been revealed that plate oscillation, radiation, chemical reactions, and the magnetic field significantly influence the flow behavior. [ABSTRACT FROM AUTHOR]

The pores problem is a challenging problem in laser beam welding titanium alloy TC4. Oscillating laser beam welding, as a new welding process, can effectively control the behavior of the molten pool, and is beneficial to the escape of pores, which holds promise for achieving high quality TC4 joint. Selecting appropriate oscillation parameters is the key to obtaining high quality TC4 joint by LBW. This project will focus on researching the effects of oscillating parameters on weld formation and porosity of TC4 joint by oscillating laser beam welding. Firstly, the oscillating laser beam welding experimental platform was set up, and experiments on oscillating LBW were designed and conducted. Subsequently, the microstructure of TC4 joint was analyzed, and the effects of oscillating frequency and oscillating amplitude on weld formation were studied, and the effects of oscillating frequency and oscillating amplitude on porosity were researched. The results indicate that oscillating laser beam welding with circle trajectory model can achieve high quality TC4 joint. The porosity of weld by oscillating LBW with oscillation amplitude as 1 mm and oscillating frequency as 80 Hz reaches 0.13% in value which is the lowest among the experiment cases under the condition as fixing the oscillation amplitude 1 mm in value and varying the oscillation frequency from 40 Hz to 240 Hz. When the oscillation amplitude exceeds the critical value 2.5 mm, the weld by oscillating LBW exhibits noticeable undercutting and asymmetry. The undercutting occurs on the advancing side in oscillating LBW with circle trajectory model. To a certain extent this study enriches the theory of oscillating LBW, and can provide fundamental data for oscillating laser beam welding on TC4.

AbstractThe control of intermetallic compounds (IMCs) poses a challenge in welding Al–Fe joints. To tackle this issue, power-modulated laser welding was utilized to join 6061 aluminum (6061Al) and AISI-304 stainless steel (304SS) in an overlap configuration. This research compares the impacts of two power modes: constant power (CP) and gradient power (GP) on weld formation and interface IMCs to demonstrate the superior performance of the GP mode. The GP mode alters the energy distribution pattern, resulting in distinct weld formation and interface microstructures compared to the CP mode. Notably, the research confirms that the GP mode enhances the tensile shear strength of the joints, highlighting the effectiveness of the GP mode. [ABSTRACT FROM AUTHOR]

This work investigates performance improvement the of ring voltage-controlled oscillator. Particle swarm optimization (PSO) techniques are used on both the physical and schematic levels to optimize the design parameter values (width of the NMOS " W n " and PMOS " W p "). By utilizing this strategy, multiple time-taking iterations can be reduced and done in a single cycle, thereby increasing the likelihood that the ring VCO will function to the best of its ability. After getting the optimized values for the design parameters of the ring VCO's, the circuit has been designed for the performance analysis. The same is demonstrated by evaluating the performance of the circuit and confirming the results of the transient analysis and noise analysis carried out with Cadence tools under a variety of different operating conditions using the 45 nm technology process. The analysis has been carried out in a variety of PVT corners (fast–fast, slow–slow, fast–slow, and slow–fast). [ABSTRACT FROM AUTHOR]

Follicular unit excision (FUE) has risen to the forefront as the world's most popular hair transplant procedure. However, most writing on this subject has catered to the advanced practitioner. The goal of this article will be to focus on safe planning and decision making along with key technical steps that will guide the beginner surgeon to harvest a graft safely and to harvest the donor area in a uniform way to avoid overharvesting. Topics covered in this article also include instrumentation and decision making between FUE versus linear strip excision. [ABSTRACT FROM AUTHOR]

Rolling bearings working in oscillating applications often suffer from false brinelling and fretting corrosion that limit their service life. At present, the study of oscillation-induced failures is primarily dominated by a large number of sliding and bench tests. However, most of the previous work are not able to fully describe the two closely related but different failure mechanisms. In this study, the origin and evolution of the two failures are thoroughly investigated under strictly controlled oscillating rolling conditions. The results show that failure evolves from false brinelling to fretting corrosion under dry friction conditions regardless of the oscillation amplitude. This process is accompanied by a large area peeling and serious oxidation, and the oxygen content increases from 2.50 wt% to 21.22 wt%. Oxidation is a crucial factor in the evolution of false brinelling into fretting corrosion. However, the distribution of microwear and oxygen content depend on the oscillation amplitude. Under lubrication conditions, the friction coefficient (COF) is smaller in the initial stage and led to local slip or transient instability of rolling elements. Therefore, the size of the wear marks and COF increased and appeared to be larger than those under a dry friction condition. However, grease can separate the contact surfaces, only surface deformation owing to false brinelling and slight damage at the roughness level occurred. The evolution of false brinelling and fretting corrosion is also closely related to residual stress. False brinelling often occurrs with residual stress accomulation, meanwhile, the residual stress increases from 120 to 300 MPa. When peeling occurs, residual stress is released. The failure pattern transformed from false brinelling to fretting corrosion and is accompanied by oxidation. So far, none of investigation is able to show satisfactory evolution of oscillating-induced failures, this study may contribute to more scientific understanding of rolling bearings against long-run reciprocating oscillating wear. [ABSTRACT FROM AUTHOR]

Abstract Rolling bearings working in oscillating applications often suffer from false brinelling and fretting corrosion that limit their service life. At present, the study of oscillation-induced failures is primarily dominated by a large number of sliding and bench tests. However, most of the previous work are not able to fully describe the two closely related but different failure mechanisms. In this study, the origin and evolution of the two failures are thoroughly investigated under strictly controlled oscillating rolling conditions. The results show that failure evolves from false brinelling to fretting corrosion under dry friction conditions regardless of the oscillation amplitude. This process is accompanied by a large area peeling and serious oxidation, and the oxygen content increases from 2.50 wt% to 21.22 wt%. Oxidation is a crucial factor in the evolution of false brinelling into fretting corrosion. However, the distribution of microwear and oxygen content depend on the oscillation amplitude. Under lubrication conditions, the friction coefficient (COF) is smaller in the initial stage and led to local slip or transient instability of rolling elements. Therefore, the size of the wear marks and COF increased and appeared to be larger than those under a dry friction condition. However, grease can separate the contact surfaces, only surface deformation owing to false brinelling and slight damage at the roughness level occurred. The evolution of false brinelling and fretting corrosion is also closely related to residual stress. False brinelling often occurrs with residual stress accomulation, meanwhile, the residual stress increases from 120 to 300 MPa. When peeling occurs, residual stress is released. The failure pattern transformed from false brinelling to fretting corrosion and is accompanied by oxidation. So far, none of investigation is able to show satisfactory evolution of oscillating-induced failures, this study may contribute to more scientific understanding of rolling bearings against long-run reciprocating oscillating wear.

A vertically oscillating plate with a temperature difference and mass diffusion is used to investigate the role of thermal radiation and chemical reaction in the unexpected convection flow of a viscous unstable rotating fluid. The results of the calculations indicate that the fluid is a grey medium that absorbs and emits radiation. With time, both the plate's and the surrounding environment's temperatures and concentrations rise. The Laplace transform method finds solutions to the dimensionless governing equations for a plate, which is oscillating in its own plane. In relation to one another, the phase angle, radiation parameter, Schmidt number, thermal Grashof number, mass Grashof number, and time are all investigated. [ABSTRACT FROM AUTHOR]

The miniaturisation of systems has widely attracted researchers to contribute to the thermal performance enhancement utilising efficient heat transfer devices. Pulsating heat pipe (PHP) is an inimitable passive two-phase energy conversion/transport device capable of transferring extensive heat energy by oscillating liquid slugs and vapour plugs from hot to cold areas suitable for the management of generation of heat in electronics. Several theoretical, experimental and visualisation studies are made on PHP to understand operational mechanisms and to arrive at optimal conditions. Although PHP has potential application in the field of heat management, its effective utilisation is limited due to complex operational mechanisms.It is observed that PHPs are effective and reliable devices for utilisation in numerous energy systems. It is observed that PHPs are effective and reliable devices for utilisation in numerous energy systems. Advanced research is directed towards numerical simulations on the evaluation of PHP performance with non-conventional working fluids. It is found that the use of ternary hybrid nanofluid in PHP has scope for research work. The objective of this paper is to review the existing methodologies for enhancing the PHP overall performance and its applications. [ABSTRACT FROM AUTHOR]

The flow of an electrically conducting fluid across a vertically positioned oscillating semi-boundless plate with uniform mass diffusion and temperature is examined in this study in terms of the effects of thermal radiation and viscous dissipation. The dimensionless governing equations were solved using an effective and unconditionally stable implicit finite-difference approach known as the Crank-Nicolson method. Based on the numerical results, the impacts of various physical parameter values on concentration, temperature; velocity; Sherwood numbers, Nusselt numbers and skin-friction profiles are displayed graphically and their consequences thoroughly analyzed. We observed that when the magnetic field, radiation and phase angle parameters are increased, the velocity is reduced. This shows that plate oscillation, radiation and magnetic fields affect the flow pattern significantly.

In this paper, we will study the W 1 , p convergence rate for homogenization problems of solutions for both oscillating operator and Neumann boundary data. By introducing the auxiliary periodic problems as well as Neumann correctors, we reduce the setting of both oscillating operator and Neumann boundary data to a fixed operator, which utilize mostly the fact that the Neumann function as well as its gradient pointwise convergence results, respectively. Boundary layer phenomena in periodic homogenization is also considered. [ABSTRACT FROM AUTHOR]

The effects of a trailing-edge active controlled flap on the power output performance of an oscillating wing energy harvester were investigated by numerical analysis. The overset mesh technique was adopted, and a structured mesh was used to simulate multiple moving bodies in close proximity to a wall to improve the accuracy. Sinusoidal motion was applied to both the wings and flaps. The maximum pitch angles for the wing and flap were varied to determine the optimum operating conditions. Numerical results show that the attachment of a flap onto an oscillating wing deflects the incoming flow in flap's direction and increases the vertical momentum change, which consequently increases the pushing force and power. The wing and flap maximum pitch angles significantly affect the power output of the energy harvester. The maximum power output is obtained at maximum pitch angles of 70° and 35° for the wing and flap, respectively. The maximum power is enhanced by 11 % when the flap length is 20 % of the chord length, as compared with the optimum condition of an oscillating wing without a flap. [ABSTRACT FROM AUTHOR]

[Display omitted] Droplet spreading governs various daily phenomena and industrial processes. Insights about microdroplet spreading are limited due to experimental difficulties arising from microdroplet manipulation and substrate wettability control. For droplet sizes approaching the capillary length scale, the gravitational force plays an important role in spreading. In contrast, capillary and viscous forces dominate as the droplet size reduces to smaller length scales. We hypothesize that the dynamic spreading behavior of microdroplets whose radius is far lower than the capillary length differs substantially from established and well understood dynamics. To systematically investigate the spreading dynamics of microdroplets, we develop contact-initiated wetting techniques combined with structuring-independent wettability control to achieve microdroplet (<500 μm) spreading on arbitrary surfaces while eliminating parasitic pinning effects (pining force ∼ 0) and initial impact momentum effects (Weber number ∼ 0). Our experiments reveal that the capillary-driven initial spreading of microdroplets is shorter, with significantly reduced oscillation dampening, when compared to millimeter-scale droplets. Furthermore, spreading along with capillary wave propagation results in coupling between the spreading velocity and dynamic contact angle at the contact line. These findings, along with our proposed microdroplet manipulation platform, may find application in microscale heat transfer, advanced manufacturing, and aerosol transmission studies. [ABSTRACT FROM AUTHOR]

The flow of an electrically conducting fluid across a vertically positioned oscillating semi-boundless plate with uniform mass diffusion and temperature is examined in this study in terms of the effects of thermal radiation and viscous dissipation. The dimensionless governing equations were solved using an effective and unconditionally stable implicit finite-difference approach known as the Crank-Nicolson method. Based on the numerical results, the impacts of various physical parameter values on concentration, temperature; velocity; Sherwood numbers, Nusselt numbers and skin-friction profiles are displayed graphically and their consequences thoroughly analyzed. We observed that when the magnetic field, radiation and phase angle parameters are increased, the velocity is reduced. This shows that plate oscillation, radiation and magnetic fields affect the flow pattern significantly. [ABSTRACT FROM AUTHOR]

Background: Chronic obstructive pulmonary disease (COPD) is characterized by persistent airflow limitation that is usually progressive and associated with an enhanced chronic inflammatory response in the airway and the lung to noxious particles or gases. Sputum production is a cardinal feature in COPD. Airway clearance techniques have been the mainstay of management. Oscillating positive expiratory pressure (OPEP) devices are handheld devices that provide a combination of positive expiratory pressure (PEP) with high frequency oscillations which involve exhaling against a resistance that is fluctuating. It encourages airflow within secretions, whereas oscillations induce vibrations within airway wall to displace secretions into airway lumen and help in expectoration. Methods: A randomized control trial was conducted at the department of pulmonary medicine, Government Medical College & Hospital, Chandigarh, in which 50 patients with stable COPD were enrolled for one-and-half years. After taking proper history, they were subjected to spirometry, six-minute walk test, and were asked to fill the St. George's Respiratory Questionnaire (SGRQ) and COPD Assessment Test (CAT). These patients were randomized into group A (intervention group) and group B (control group), where group A was prescribed Aerobika OPEP device for daily use for a period of three months. After three months of use of device, the patients were again subjected to assessment parameters and inquired about any exacerbation within the three-month period. Results: At the end of three months were compared with baseline results. The median change in FEV1, FVC, 6MWD from baseline in group A was significantly more as compared to group B (FEV1: P < 0.001; FVC: P < 0.001; 6MWD: P = 0.08), whereas SGRQ score showed a significant improvement in both the intervention and control groups (P < 0.001) and CAT score showed significant improvement in comparison to the control group (P < 0.001). The median change in 6MWD and CAT from baseline in group A was significantly more as compared to group B (SGRQ: P < 0.001; CAT: P < 0.001), whereas it was not significant in case of SGRQ (P = 0.233). There was no significant difference in the incidence of exacerbation in the two groups (P = 0.19). The device did not help in controlling the rate of exacerbation in the present study at three months. Conclusion: Stable COPD patients who were given OPEP therapy as an adjunct to the standard drug therapy showed improvement in the spirometry parameters, exercise capacity and symptom burden in comparison to the drug only group. [ABSTRACT FROM AUTHOR]

Under unprecedented environmental crisis associated with greenhouse gas emission, biomass has attracted a great deal of attention due to renewable and carbon neutral nature. In this study, the premixed combustion of various types of wood and its derived syngases are examined for steady and oscillating sates. For this purpose, the poplar, birch, beech and pin sawdust woods and syngases composing of H 2 , CH 4 and CO are considered. To model dust cloud combustion, a novel and comprehensive flame structure consisting of drying, two-step pyrolysis and homogeneous and heterogeneous reactions is proposed. Afterward, the governing equations and their appropriate boundary conditions are derived and solved analytically-numerically. The oscillating combustion is also modeled by exerting an external perturbation on the velocity field. The results indicate that due to the occurrence of heterogeneous reactions in wood combustion, the flame propagation velocity of wood is higher than that of syngases which contributes to high oscillations amplitude of syngases. When the mixture initial temperature changes between 300 and 550 K, the flame velocities of woods and syngases vary in the ranges of 0.4–0.7 m/s and 0.1–0.27 m/s, respectively. The maximum amplitude of temperature oscillation of syngases is approximately 8 times more than that of woods. • Steady and pulsating flames of various woods and syngases are scrutinized. • Two-step pyrolysis and homogeneous and heterogeneous reactions are considered. • The oscillating combustion is examined via external perturbation on velocity field. • Maximum amplitude of temperature oscillation of syngases is 8 times that of woods. [ABSTRACT FROM AUTHOR]

An arithmetical methodology is used to study natural convection with properties of pressure work over a semi-infinite vertical oscillating cylinder. The governing partial differential equations are set up and the resulting equations are changed into a non-dimensional form using the proper non-dimensional quantities. The set of non-dimensional partial differential equations is solved arithmetically using a well-organized method known as the Crank-Nicolson method. The velocity, as well as temperature profiles for different values of parameters are studied with the assistance of graphs.

Raman Effect is the measurement of the intensity and wavelength of the inelastically scattered radiation that falls on a molecule. The electric field of the incident radiation polarizes the molecule on which it falls and this leads to the creation of an oscillating dipole. The incident polarized laser light is inelastically scattered by the molecular sample. The scattered light contains modified wavelengths called the Stokes and anti-Stokes lines or wavelengths. The oscillating electric dipole, created by the incident radiation, creates an oscillating electric field around it. Since the oscillating electric field of the incident radiation creates an oscillating electric dipole that create an oscillating electric field around it, it was surmised that this oscillating electric field can affect the frequency of vibration or oscillation of the oscillating electric dipole that produces it. This novel effect will change the frequency (frequencies) of the scattered radiation resulting in Stokes and anti-Stokes lines with modified frequencies. This theoretical research and its importance can be understood like this. For instance, if there are two cells or molecules, side by side, in which one is a healthy cell and the other is cancerous, or two different types of molecules are sitting side by side, this types of scattering should be able to distinguish one from the other since the Stokes and anti-Stokes lines from the two molecules will not be identical. Thus, the incident radiation of angular frequency ω1 polarizes the charges of the molecule on which it falls and this leads to the creation of an oscillating dipole of frequency ω2. The oscillating dipole creates an oscillating electric field that can create additional frequency of the oscillating dipole that created it, and let this be ωD. Then the Raman lines can have frequencies (ω1+ω2+ωD), (ω1+ω2-ωD), (ω1-ω2+ωD), and (ω1-ω2-ωD). Depending on the relative magnitudes of ω2 and ωD, Raman lines will be designated as Stokes and Anti-Stokes lines. Due to the law of conservation of energy, ωD will be less than ω2 since an oscillating dipole cannot create field of frequency more than its own frequency. Hence the frequencies (ω1-ω2+ωD) and (ω1-ω2-ωD) correspond to Stokes lines, and frequencies. (ω1+ω2+ωD) and (ω1+ω2‑ωD) will correspond to Anti-Stokes lines. Calculations for Stokes and Anti-stokes lines have been done for some molecules, namely Ammonia compound (NH3), Nitrousoxide compound (N2O), Water (H2O), Sulphur dioxide compound (SO2), Ozone compound (O3). Calculations have also been done for compounds containing carbon, such as Dichloromethane compound (CH4Cl2), Formic acid compound (CH2O2), Methanol compound (CH4O), Benzene compound (C6H6), Propane compound (C3H8), and Carbonyl chloride compound (Cl2CO). The theory developed predicts new phenomena of getting Stokes and anti-Stokes lines with modified wavelengths which have not been observed experimentally as of to-day.

A pneumatic oscillating Chinese wolfberry harvester was designed to improve the efficiency of manual harvesting and minimize fruit damage by mechanical harvesting. The shedding model of Chinese wolfberry under pneumatic forces was established based on kinetic analysis, and the flow field characteristics were investigated using computational fluid dynamics (CFD). The position and shape of the fan outlet were determined by comparing the effects of a linear reduction outlet and a Laval reduction outlet on the outlet airflow rate. The size of the oscillating mechanism was optimized with nonlinear constraints to achieve uniform oscillation of the airflow. A three-factor, three-level orthogonal test was conducted on the NingQi 7 wolfberry variety. The flow rate at the outlet, the oscillation frequency, and the outlet distance were the test factors, and the net harvesting rate of ripe fruits, the harvesting rate of green fruits, and the damage rate of ripe fruits were the test indices. The results showed that the net harvesting rate of ripe fruits was 85.21% at an outlet distance of 10 cm, an outlet flow rate of 70 m·s-1, and an oscillation frequency of 2 Hz. This study provides references for the design of pneumatic harvesters for Chinese wolfberry. [ABSTRACT FROM AUTHOR]

Uninterrupted power supply is an electrical device that provides emergency power to a load when the input power source, typically the utility mains fails or whenever the line voltage varies outside normal limits. Obviously, uninterrupted power supply (UPS) is an indispensable power unit in every size of establishment. Its features such as noiseless working condition, availability of storage elements, numerous system compatibility, etc. have not in any way marred its acceptance. This device is really dominating computer establishments in most developing countries. It has also been found useful in many other applications in big industries, homes offices, industries and religious centers and places of worship for continuous sustainability of energy supplied to electronic gadgets. The stages of the design were divided into sections. The UPS was switched ON, the bulb started to glow, and the UPS worked properly. The components of the UPS such as MOSFET transistor, relay, inverter, transformer and change over circuit were working properly and efficiently. [ABSTRACT FROM AUTHOR]

Movement learning has been thoroughly investigated in the area of motor learning research. Although existing studies have contributed to a substantial understanding of motor learning, many have been criticized for their reliance on experimental designs where learning is decontextualized, simplified, and investigated in laboratory settings. Researchers have claimed that motor learning theories emanating from such studies are grounded on a dualistic approach to learning and that the theories are often difficult to apply in educational settings. More pedagogically-inspired studies of movement education have investigated movement learning, but the majority of this research has focused on teaching. This focus has left the process of learning somewhat unexplored. There is thus a need for empirical studies that investigate students' learning processes in educational contexts. The aim of this study is to explore, analyze, and understand how learners develop their movement capability when they are provided opportunities to choose different ways of learning activities. We combine Ryle's and Polanyi's ideas concerning practical knowledge with Hirst's and Carlgren's idea of knowing as familiarity with a landscape. Ryle's notion of 'intelligent practice' is used in thinking of the kinds of actions individuals might engage in. Characterizing features of intelligent practice includes being sensitive to one's own actions, changing one's behavior as the result of mistakes, and profiting from the examples of others. We understand the development of movement capability as continuously expanding one's ability to discern nuances and their relationships. This perspective fits well with Polanyi's notion of focal and subsidiary awareness. Taken together Ryle's, Polanyi's, Hirst's, and Carlgren's notions related to knowing and learning inform our perspective on learning in movement education. Based on this perspective on knowing and learning, an action-oriented study was conducted. The researchers created pedagogical modules and collaborated with teachers and university educators to develop learning sequences in line with the needs of their respective groups. With each group, we produced data based on video and field notes. Three successful learners were chosen and followed in-depth with regard to their learning actions. The findings show the learners' varying ways of exploring a movement landscape as playing around in the terrain; checking the map; investigating one chosen path; occupying the vantage point; imitating and actively observing. The findings suggest that oscillating between varying kinds of learning actions is an additional characterizing feature of 'intelligent practice.' The findings demonstrate how the learning of movement capability could occur when providing opportunities to engage in 'intelligent practice' while at the same time directing their focal awareness toward what is most beneficial to them. Opposed to a 'step-by-step' approach to learning, the learners come to know a movement landscape as extending one's capability to discern and differentiate details, nuances, and their relationships. The findings suggest that it may be beneficial for learners to get opportunities to oscillate between different kinds of learning actions. [ABSTRACT FROM AUTHOR]

Undeniably, the Novel Coronavirus 2019, (COVID-19), has disrupted the routine functioning of the global economic and social activities. In particular, vulnerable economies such as the Small Island Developing states (SIDs) are facing unprecedented health and financial crisis. In such critical situation, some in-depth statistical models can be helpful for proper planning in terms of identifying factors that can influence significantly the number of infected COVID-19 cases and for forecasting. Modelling the COVID-19 infected series is a statistical challenge since the series are severely over-dispersed with lots of oscillations. This paper attempts a new integer-valued time series model based on the auto-regressive structure (INAR), with an oscillating Weighted Cosine Geometric (WCG) innovation term. The parameters in the proposed model constitute of the regression effects and serial auto-correlation coefficients and are estimated via likelihood and moment-based approaches. Monte Carlo simulation experiments are implemented to assess the performance and consistency of the different resulting estimators. Thereon, the INAR-WCG is applied to the COVID-19 series of various SIDs countries that include Singapore, Cape Verde, Bahrain, Mauritius and Maldives. The findings reveal that factors such as the transmission mode and the Government Stringency Index are the most influential. In terms of model fitting and forecasting, the INAR-WCG provides slightly better RMSEs than the other competing INAR-based processes. [ABSTRACT FROM AUTHOR]

Abstract This paper is concerned with homogenization of p-Laplace equations with rapidly oscillating periodic coefficients. The main difficulty of this work is due to the nonlinear structure in this field concerning p-Laplace equations itself. Utilizing the layer and co-layer type estimates as well as homogenization techniques, we establish the desired error estimates. As a consequence, we obtain the rates of convergence for solutions in W01,p $W_{0}^{1,p}$ as well as Lp $L^{p}$. Meanwhile, our convergence rate results do not involve the higher derivatives any more. This may be viewed as rather surprising. The novelty of this work is that it seems to find a new analysis method in quantitative homogenization.

An experimental investigation is presented of an oscillating disk submerged in water. The system is adapted from one modeled by the Bagley-Torvik equation, being modified to more closely approximate idealizations in the derivation. The modified system eliminates alignment problems that would violate the assumption of fluid forces being due only to shear in the fluid. An implicit finite difference model based on the Riemann-Liouville fractional derivative was used to model the observed oscillatory free response resulting from a non-homogeneous initial condition. The numerical model accounted for motion well until the amplitude was small. MSC 2010: 26A33, 34A08, 76A99, 34K11 [ABSTRACT FROM AUTHOR]

The unsteady flow of a viscous incompressible electrically conducting fluid due to non-coaxial rotations of a porous disk subjected to a periodic suction and the fluid at infinity in the presence of applied transverse magnetic field has been studied. The fluid at infinity passes through a fixed point. The velocity field, shear stresses are obtained in a closed form.

The unsteady flow of a viscous incompressible fluid due to non-coaxial rotations of a porous disk and a fluid at infinity subjected to a periodic suction through a porous medium has been studied. The velocity field, shear stresses are obtained in closed form. The variations of primary and secondary velocities for different values of non dimensional parameters are depicted in figures.

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fishes interact with the fluid environment using various surfaces. These multiple control surfaces work in combination to produce the thrust and the balance torques in a steady swimming, to maneuver and to position themselves accurately even in turbulent flows. These motivate us to embark on a research program designed to develop an agile biologically inspired robotic fish based on the performance of multiple fins. To accomplish this goal, a mechanical ray-like fin actuated by the shape memory alloy (SMA) is developed, which can realize the oscillating motion, the undulating motion or even the complex three dimensional motion. The basic unit is the two opposite side SMA-driven plate, namely the fin ray. As a result, a lightweight bio-inspired fin is constructed by placing radially multiple SMA fin rays. A biologically inspired underwater vehicle (BIUV) is later built using the above multiple lightweight bio-inspired fins. Two common arrangement styles of multiple fins on the BIUV are considered here: one is the posterior fin (for the oscillating motion) that is parallel to the anterior fins (for the undulating motion), another one is the posterior fin that perpendicular to the anterior fins. The kinematic modeling, the deformation modeling and the detecting of the SMA fin are made. The thrust generation is also established. Finally, an experiment is conducted to test the performance of the proposed two arrangement styles, including the comparison of the averaged propulsion velocity and the averaged thrust under certain kinematic parameters. Meanwhile, the influence of the frequency and the amplitude of the SMA fin ray on the propulsion performance is also investigated. [ABSTRACT FROM AUTHOR]

• This paper designs a linear oscillating electromagnetic energy harvester with hollow spheres as buoys. • Transient analysis of the oscillator permanent magnet is performed by kinematic and electromagnetic induction simulations. • Spherical buoys can provide resilience for the oscillating permanent magnet, which is sensitive to the wave vibration form. • The collector output power is sufficient for low power wireless sensor devices. The power supply method of low-power sensors has partly restricted the exploration and utilization of marine resources. Low-density wave energy can be harvested and used to power low-power wireless sensor devices and promote the coordinated development of the marine environment. This paper designs a linear oscillating electromagnetic energy harvester with hollow spheres as buoys. Spherical buoys can provide resilience for the oscillating permanent magnet, which is sensitive to the wave vibration form. Under wave excitation with wide-amplitude and stochastic low-frequency distribution, the oscillating permanent magnet with intrinsic frequency of 1.1 Hz is forced to move reciprocally in the rolling slot. Multiple groups of induction coils used in series make the output voltage of the harvester more balanced and smooth, improving the conversion rate of wave energy. According to the experimental results, the harvester can generate a maximum output power of 18.4 mW and an average output power of 4.44 mW under the excitation of water waves with a maximum acceleration of 1.21 m/s2. The output power is sufficient for low-power wireless sensor devices. [ABSTRACT FROM AUTHOR]

In this work, a numerical study of two dimensional laminar incompressible flow around the flexible oscillating NACA0012 airfoil is performed using the open source code OpenFOAM. Oscillatory motion types including pitching and flapping is considered. Reynolds number for these motions is assumed fixed at 12000. One of the important issues that must be considered in designing air structures, in particular the aircraft wing, is the interaction between the air and the elastic aircraft wings that is known as the Aeroelastic phenomenon. For this purpose, the effect of airfoil flexibility and flow induced vibration in these motion types is investigated and compared with the case of rigid airfoil. It is observed that the flexibility in both types of motions causes improvement of the thrust which is boosted with increasing the frequency. Contrary to thrust, the significant improvement of lift is only achievable in high frequencies. It was also found that the effect of flexibility on the flapping motion is higher than the pitching motion. For flow control on the airfoil, Dielectric Barrier Discharge plasma actuator is used in the trailing edge of a flexible airfoil, and its effect on the flexible airfoil is also investigated.

We study the mixing dynamics of a dyed and a clear miscible fluid by an oscillating flow inside an Hele-Shaw cell with randomly distributed circular obstacles. A transparent setup allows us to analyze the distribution of the two fluids and the reversible and irreversible mixing components. At the lower Péclet numbers Pe (based on the averaged absolute fluid velocity), geometrical dispersion due to the disordered flow field between the obstacles is dominant: the corresponding dispersivity is constant with Pe and, at constant Pe, increases with the amplitude of the oscillations and is negligible at small ones. Compared to echo dispersion with only one injection-suction cycle, oscillating flows are shown to provide additional information when the number of oscillations and, as a result, the distance of transverse mixing are varied. Geometrical dispersion is dominant up to a limiting Pe increasing with the amplitude. At higher Pe′s, the results are similar to those of Taylor dispersion in cells with smooth walls. [ABSTRACT FROM AUTHOR]

Oscillating method has been applied to bulk forming process due to the load reduction and high yield. The main cause of load reduction is the rebuilding of lubricating film during the back stroke of the die. A chemical corrosion method using an oscillating T-shape compression (OTC) test was employed to analyze re-lubrication and real contact area (RCA) in oscillating bulk forming process. Conventional T-shape compression (CTC) test and OTC test with three different frequencies were compared. Moreover, lubrication in compression and extrusion, which are two typical plastic deformations in T-shape test, were analyzed separately. The differences in RCA and re-lubrication were analyzed by optical microcoordinate measurement (OMC) and confocal scanning laser microscopy (CSLM). The mixed lubrication condition and re-lubrication degree were analyzed by measuring 3D roughness parameters and specimen geometry. By applying the corrosion method, the two main problems (i.e., the effective re-lubrication observation and the actual friction condition under load) can be expressed by the different degrees of corrosion. Re-lubrication was confirmed by the chatter marks expanding in the circumferential direction. Unlike in conventional forming, mixed lubrication condition was guaranteed by the re-lubrication, and the thick lubricant film prevented the generation of scratches. Furthermore, the RCA and lubrication condition were subjected to oscillating frequency. Results showed that a higher frequency produced more sufficient lubrication. [ABSTRACT FROM AUTHOR]

Heat transfer in an oscillating vertical annular fluid column flowing through a porous domain in the single phase or bubbly flow two-phase regime (sub-cooled or saturated nucleate flow boiling) are investigated experimentally and theoretically, in quasi-steady state conditions. Forced oscillations are applied to water via a frequency controlled dc motor and a piston-cylinder device. Heat transfer is from the stationary concentric tubular electric heating element outer surface to the reciprocating flow. The heat transfer in an oscillating vertical annular fluid column flowing in the single phase or in the bubbly flow regime is altered by using stainless steel wool porous medium. For the single phase region of flow, it is understood that, the effective heat transfer mechanism is enhanced and it is due to the hydrodynamic boundary layer which can not follow the core flow. Bubbly (nucleate) flow boiling in oscillating flow is also investigated experimentally and theoretically using a simplified thermodynamic analysis. The onset of boiling temperature is distinctly dropped compared to the pool and flow boiling experiments on polished surfaces due the finned surface effect of the steel porous domain, due to the enhanced mixing of the boundary layer flow and core flow; due to the improvement of apparent surface roughness and due to the alteration of ebullition cycle (bubbles are limited by the cell volume here). The developed correlation predicted cycle-space averaged Nusselt number is shown to be in good agreement with the experimental data. The present investigation has possible applications in moderate sized wicked heat pipes, boilers, compact heat exchangers and steam generators. [ABSTRACT FROM AUTHOR]

The field lightning impulse withstand voltage test is an important step to ensure the safe operation of the gas insulated switchgear (GIS). The oscillating lightning impulse voltage is recommended in field test by IEC standard due to its high generating efficiency and lower impulse ratio. The insulation condition of GIS can be evaluated overall by detecting the partial discharge (PD) when conducting the field impulse withstand voltage test. In this paper, the protrusion defect was set in a 330 kV real GIS to study the PD characteristics under lightning impulse voltages, including SLI (standard lightning impulse) voltage and OLI (oscillating lightning impulse) voltages with different oscillating frequencies. The PD under impulse voltages was effectively detected by using the internal UHF sensor. The 50% probability PD inception voltage (PDIV50), maximum discharge amplitude, and discharge number were analyzed based on the measurement results. It was concluded that the PD number is significantly larger and the PDIV50 of OLI voltage is lower when the oscillating frequency is low by comparing the results of oscillating and standard impulse voltage. The PDIV50 increases and discharge number decreases with the increasing of oscillating frequency of the OLI voltage. [ABSTRACT FROM AUTHOR]

Objective/Background: To discuss a unique clinical entity where inappropriate activity of inhibitory and stimulatory thyroid antibodies resulted in alternating hypothyroidism and hyperthyroidism. Methods: We report the clinical history, laboratory data, and results of imaging studies, along with the pathophysiological mechanism and the subsequent treatment in a patient with fluctuating thyroid functional status. Results: A 52-year-old female was treated for hypothyroidism for more than two decades. She started having symptoms of hyperthyroidism along with a suppressed thyroid-stimulating hormone (TSH). She continued to have persistent symptoms despite stopping her levothyroxine. Her free T3 and T4 were elevated along with an increased radioactive uptake scan. She was diagnosed with Graves’ disease and started on methimazole, which relieved her symptoms for a few months. Subsequently, her TSH began to rise beyond expected level, her hypothyroid symptoms reappeared, and methimazole was discontinued. Following this, she again developed symptoms of hyperthyroidism and thyroid values revealed an undetectable TSH. She had at least two such documented cycles of hyperthyroidism alternating with hypothyroidism. She was eventually treated with radioactive iodine ablation followed by levothyroxine replacement. Swinging dominance of TSH-blocking autoantibodies (TBAb) and thyroid-stimulating autoantibodies (TSAb) triggered by methimazole and levothyroxine, respectively, is likely the underlying mechanism. Conclusions: Physicians should be vigilant to the phenomenon of spontaneous conversion of hypothyroidism to hyperthyroidism, or vice versa, in a subset of patients with autoimmune thyroid disease. Repeated assessment of thyroid function along with measurement of TBAb and TSAb are invaluable in identifying this rare clinical entity.

The effect of porosity in oscillating situations (to the authors' knowledge, for the first time) on a supercritical airfoil (SC0410) has been experimentally investigated. Tests have been carried out in an open circuit suction-type wind tunnel at a free stream Mach number of M = 0:80. Both static and dynamic (pitching) tests have been carried out on the mentioned airfoil. The oscillation frequency for the unsteady tests has been set to 3 and 6 Hz. The amplitude of frequency is ±1 deg. The effect of porosity has been surveyed on the magnitude of pressure fluctuations, phase shift, and lift coefficient loop. The investigations show that increasing porosity in the test section of transonic regime, contrary to the impression, does not necessarily improve results. [ABSTRACT FROM AUTHOR]

The vortex-induced vibration behind an isolated cylinder under the wake interference of an oscillating airfoil at different oscillating frequencies and amplitudes have been studied numerically. Our previous research [11] mainly focused on the two degree of freedom vibration problem, several types of the phase portraits of the displacement have been newly found, including the "half -8″ and "cone-net" types as reduced velocity increases. At present, we have continued the research to the single degree of freedom vibration, the corresponding results had been found that under the wake of the free steady flow, as the reduced velocity increases, the phase portraits displacements of the single degree of freedom vibrating cylinder will begin to rotate counterclockwise from the first and third quadrants to the second and fourth quadrants in a Cartesian coordinate system. Under the wake of the oscillating airfoil, the single bending curve and the single closed orbit (double “8-shape” like) of the displacements are newly found in the drag and thrust producing cases respectively. Except this, the two triplets of vortices have also been newly found in the pair and single plus pair wakes at each cycle. The vorticity dynamics behind the vibrating cylinder together with the corresponding force variations have also been obtained computationally and analyzed in details. [ABSTRACT FROM AUTHOR]

The vortex formation and shedding process behind an isolated cylinder under the wake interference of an oscillating airfoil at different oscillating frequencies and amplitudes have been studied numerically. The “2S” and “P+S” mode are found in the drag-producing von Kármán vortex wake and thrust-producing inverted von Kármán vortex wake, respectively. For the “2P” case, the pairs of vortices with different sizes are laterally parallel to each other. For the “2P+2S” case, the merged single vortices do not appear between the vortex pairs, but they only emerge after every two pairs of vortices. For the two-degree of freedom (2-DOF) VIV in the wake of the steady flow, seven types of the phase portraits of the displacement shapes are observed. In the range of small reduced velocity ( V r < 5 ), the body trajectories are mainly characterized by an “8-shape” with some differences in phase. At the peak amplitude, the body trajectories have changed into two shapes: i.e., the half “8-shape” (initial stage) and the crescent-shape (final stage). When V r = 6 , the body trajectories have also shown to have two shapes: i.e., the “8-shape” (initial stage) and the half “8-shape” (final stage). When V r arrives at the low branch ( V r > 7 ), the body trajectories will become irregularly shaped like a cone-net. [ABSTRACT FROM AUTHOR]

Wave energy is one of the most promising technologies for the future of renewable energy. Its steady, even if not dashing, development, both in theoretical and applied solutions, will bring the field, in the mid-term, to the point of being a viable, economical and sustainable technology, competitive when compared to more mature ones. This paper deals with the ISWEC (Inertial Sea Wave Energy Converter) power take off (PTO) technology and control strategies. In particular it focuses on the control strategy used for harnessing energy during its first deployment, and presents the development of a new controller designed using optimal control theory. The approach to the problem of this work is not to seek for the theoretical optimal control strategy. In fact, during the test period of the ISWEC into the sea, limitations of a model-optimized control strategy came out, due to well known shortcomings of hydrodynamics modeling theory for wave energy devices, and the idea of an easy-to-tune in the field controller arose. This work points out in the direction of developing a practical and effective strategy for industrial application, with the main objective of increasing the power production while simplifying the control law by which the device harnesses energy. [ABSTRACT FROM AUTHOR]

Background: Non-coaxial rotation has wide applications in engineering devices, e.g. in food processing such as mixer machines and stirrers with a two-axis kneader, in cooling turbine blades, jet engines, pumps and vacuum cleaners, in designing thermal syphon tubes, and in geophysical flows. Therefore, this study aims to investigate unsteady free convection flow of viscous fluid due to non-coaxial rotation and fluid at infinity over an oscillating vertical plate with constant wall temperature. Methods: The governing equations are modelled by a sudden coincidence of the axes of a disk and the fluid at infinity rotating with uniform angular velocity, together with initial and boundary conditions. Some suitable non-dimensional variables are introduced. The Laplace transform method is used to obtain the exact solutions of the corresponding non-dimensional momentum and energy equations with conditions. Solutions of the velocity for cosine and sine oscillations as well as for temperature fields are obtained and displayed graphically for different values of time ( t ), the Grashof number ( Gr), the Prandtl number ( $$\Pr $$ ), and the phase angle ( $$\omega t$$ ). Skin friction and the Nusselt number are also evaluated. Results: The exact solutions are obtained and in limiting cases, the present solutions are found to be identical to the published results. Further, the obtained exact solutions also validated by comparing with results obtained by using Gaver-Stehfest algorithm. Conclusion: The interested physical property such as velocity, temperature, skin friction and Nusselt number are affected by the embedded parameters time ( t), the Grashof number ( Gr), the Prandtl number ( $$\Pr $$ ), and the phase angle ( $$\omega t$$ ). [ABSTRACT FROM AUTHOR]

In this work, a numerical study of two dimensional laminar incompressible flow around the flexible oscillating NACA0012 airfoil is performed using the open source code OpenFOAM. Oscillatory motion types including pitching and flapping is considered. Reynolds number for these motions is assumed fixed at 12000. One of the important issues that must be considered in designing air structures, in particular the aircraft wing, is the interaction between the air and the elastic aircraft wings that is known as the Aeroelastic phenomenon. For this purpose, the effect of airfoil flexibility and flow induced vibration in these motion types is investigated and compared with the case of rigid airfoil. It is observed that the flexibility in both types of motions causes improvement of the thrust which is boosted with increasing the frequency. Contrary to thrust, the significant improvement of lift is only achievable in high frequencies. It was also found that the effect of flexibility on the flapping motion is higher than the pitching motion. For flow control on the airfoil, Dielectric Barrier Discharge plasma actuator is used in the trailing edge of a flexible airfoil, and its effect on the flexible airfoil is also investigated. [ABSTRACT FROM AUTHOR]

The early low-cost, wood burning Thermo-Acoustic Engine (TAE) known as Demo2.0-build-1 was developed by SCORE™ at the UK Centre and was capable of achieving 22.7 Watts of electricity. This prototype was limited to an operating temperature of about 300oC and due to excessive leaks could not operate continuously above ambient pressure. To absorb a thermal heat input of 4.4 kW from the burning wood so as to fulfil the required acoustic power, the Hot Heat Exchanger (HHX) requires heating to the highest possible temperature. Therefore, a corrugated stainless steel plate HHX design that maximises heating surface area was adopted to the current Demo2 TAE design. In addition, the system is often pressurised to achieve higher acoustic intensity. Rigorous sealing of the system at high temperature is also required. A Demo2.1 TAE design based on the Demo2 TAE design and its prototype which is developed recently by the SCORE™ Centre in Malaysia was successfully constructed and well integrated with the stove. During the early construction and assembly process, fabrication difficulties and serious leak problems around the HHX’s edges were found when the apparatus operated at high temperatures. This is because the uneven geometrical HHX (convolution profile) makes it difficult and relatively costly to be sealed. The Demo2.1 TAE is focused on the sealing efficiency and effective manufacturing cost by meantime to allow further modification variation. The design was made to adopt the local manufacturing technologies and materials available or easy to access in Malaysia. It also aims to minimise the parasitic heat losses to lower the system onset temperature. By removing the Linear Alternator and Tuning Volume from the system, preliminary measurements shown that the apparatus was oscillating at the frequency of 70 Hz. A much lower onset temperature was observed at around 144oC for the new configuration when the apparatus was oscillating at approximately 200 Pa. This paper describes the main design features of the Demo2.1 TAE including easy fabrication and assembly methodology, together with apparatus construction and rig test assessment.

A free convective flow of a viscous incompressible flow past an infinite vertical oscillating plate with variable temperature and uniform mass diffusion is presented here, taking into account the homogeneous chemical reaction of the first-order. The plate temperature is raised linearly with respect to time, and the concentration level near the plate is raised to Cw′ . An exact solution to the dimensionless governing equations has been obtained by the Laplace transform method, when the plate is oscillating harmonically in its own plane. The effects of velocity and concentration are studied for different parameters like phase angle, chemical reaction parameter, Schmidt number and time. It is observed that the velocity increases with the decrease of the phase angle ωt or a chemical reaction parameter.