Partial Dissipation Research Articles

Stability for the 2D magnetic Bénard system with partial dissipation and thermal damping near an equilibrium

In this paper, we focus on the Boussinesq equations with magnetohydrodynamics convection, in which the temperature obeys degenerate damped wave equations. Under the influence of an equilibrium, we prove that the 2D magnetic Bénard system remains stable in the whole space . In particular, we obtain the decay rate and large‐time behavior. Without the coupling, the 2D MHD system with only vertical dissipation is not known to be stable. It is revealed that both the thermal damping and the horizontal background magnetic field are indispensable.

PH‐Tunable 3D Interconnected Network of Multiwalled Carbon Nanotubes /Polyacrylic Acid Hydrogel with Excellent Electromagnetic Radiation Shielding Capability

AbstractThe fabrication of durable and high anticorrosion hydrogel composite materials composed of multi‐walled carbon nanotubes (MCNTs) and crosslinked polyacrylic acid (PAA) for EMI shielding application is reported. The MCNTs contribute to the generation of 3D porous structures and enhance the mechanical properties of composite hydrogel. The 3D porous structure and high electrical conductivity inherited from ultrahigh electrically conductive MCNTs enable excellent EMI shielding properties with a total shielding efficiency EMI SE (SET) value of 32.8 dB (>99.9%) at only 3 wt% filler content of MCNTs. The MCNTs/PAA hydrogels also display superior EMI shielding performance under a strong acidic environment with SET > 99.99% while the 3D porous structure remained intact. The combination of electron–ion system in pH solution enriches the charge transfer and accumulation, enabling dipole orientation and polarization that are favorable for enhancing EMI attenuation. Moreover, the porous structure of MCNTs/PAA also contributes to partial trapping and dissipation of EM radiation energy via multiple scattering phenomena. This work thus paves the way toward applications of 3D hierarchical network materials for EMI shielding applications in both land and aqueous environments.

Global convergence rates from relaxed Euler equations to Navier–Stokes equations with Oldroyd-type constitutive laws

In a previous work (Peng and Zhao 2022 J. Math. Fluid Mech. 24 29), it is proved that the 1D full compressible Navier–Stokes equations for a Newtonian fluid can be approximated globally-in-time by a relaxed Euler-type system with Oldroyd’s derivatives and a revised Cattaneo’s constitutive law. These two relaxations turn the whole system into a first-order quasilinear hyperbolic one with partial dissipation. In this paper, we establish the global convergence rates between the smooth solutions to the relaxed Euler-type system and the Navier–Stokes equations over periodic domains. For this purpose, we use stream function techniques together with energy estimates for error systems. These techniques may be applicable to more complicated systems.

MANUFACTURING AND TESTING HIGH VOLTAGE FILTER CAPACITORS

This paper presents the manufacturing and testing methods of 30kV and 33nF high voltage filter capacitors. One of the biggest advantages of small companies is that they are able to produce a high diversity of capacitors in small quantities. One of the prices of this flexibility is a higher level of manual manufacturing process in production. But this higher level of manual manufacturing does not mean lower quality in the final product. For high quality products in the high voltage industry, it is necessary to do routine tests in all of the products. For high voltage capacitors the following three tests must be done to ensure quality: voltage strength test, partial discharge test, capacitance and dissipation factor test. The capacitance and dissipation factor test have to be done at different voltage levels. The voltage strength test has to be done at least 20% higher than the rated voltage. This kind of test gives us information not only about the quality of the product itself, but about distribution of the capacitance for example, or about the strength of the production process, and about the quality management system of the company.

Stability for the magnetic Bénard system with partial dissipation

We prove the stability of the magnetic Bénard system with partial dissipation on perturbations near a background magnetic field in T2. Neglecting the effect of the temperature, the stability result provides a significant example for the stabilizing effects of the magnetic field on electrically conducting fluids. In addition, we obtain an explicit large-time decay rate of the solutions.

Global well-posedness of three-dimensional magneto-micropolar fluid equations with partial dissipation

In this paper, the three-dimensional magneto-micropolar fluid equations with partial dissipation is studied on R 3 . The main purpose of this paper is to establish global solutions with a small initial value. More specifically, we demonstrate the global stability of the perturbation solutions near the background magnetic field. The proof is mainly based on the energy estimate, the tricky interpolation techniques and bootstrapping argument.

Low temperature effect on cyclic behavior of shape memory alloy U-shaped dampers

Although Nickel-Titanium (NiTi) shape memory alloys (SMAs) have been widely studied as seismic response mitigation devices in civil structures, their temperature sensitivity due to the coupled thermo-mechanical behavior prevents their practical implementation in cold temperature environments. This paper investigated the effects of varying ambient temperatures (particularly low ambient temperature) on the hysteretic behavior and self-centering (SC) ability of shape memory alloy U-shaped dampers (SMAUDs) that were made of NiTi showing superelasticity (SE) at room temperature. Thermo-mechanical properties of SMAUDs were identified through differential scanning calorimetry (DSC) tests. Cyclic loading experiments on SMAUDs were conducted at a wide ambient temperature range from −40 °C to 20 °C. The variations in the hysteretic characteristics of the SMAUDs, including partial superelasticity (SE), strength, stiffness, SC, and energy dissipation capabilities, at different ambient temperatures were investigated. In general, the decreasing ambient temperature leads to the degradation of the SC ability. At ambient temperatures below the phase transformation temperature, the SMAUDs lose the SE but still maintain certain levels of strength and energy dissipation, which is different from common axial-type SMA elements. Meanwhile, the SMAUDs can restore their SC ability and strength after the recovery from low temperatures to room temperature, making them suitable for use in a cold environment.

The two-and-a-half-dimensional incompressible Hall-MHD system with partial dissipation

In this paper, we investigate the Cauchy problem for the two-and-a-half-dimensional incompressible Hall-magnetohydrodynamic equations with partial dissipation. We prove the global regularity of a certain system of equations with horizontal or vertical dissipation and magnetic hyper-diffusion for large initial data.

Optimal seismic design for self-centering concrete wall structures equipped with U-shaped flexural plate dissipaters

In self-centering wall (SCW) structural system, additional energy dissipation devices are crucial members that are expected to provide both partial lateral force resistance and energy dissipation capacity aiming at mitigating structural response. This research aims to develop a seismic design framework based on particle swarm optimization algorithm for SCW structures equipped with U-Shaped Flexural Plates (UFPs), which can be used to seek out the optimal configuration of UFPs of each floor to reduce seismic response, while maintaining a constant total lateral force resistance provided by all UFPs. For validation, a 10-story SCW structure is chosen as the design case. Specifically, two configurations are considered: a 10-story SCW structure equipped with identical UFPs following conventional design (SCF10-Original) and one equipped with UFPs from optimized configuration (SCF10-Optimized). Their drift and acceleration response are calculated and compared under different seismic intensities through nonlinear time history analysis (NATH). The results demonstrate that the optimized configuration of UFPs can significantly mitigate the drift response in SCW structure. For instance, the maximum inter-story drift ratios of SCF10-Optimized are 0.2 % smaller than those of SCF10-Original under maximum considered earthquake, while the maximum residual inter-story drift ratios of SCF10-Optimized are only half those of SCF10-Original under Extremely Rare Earthquake. Furthermore, the optimized UFPs can effectively reduce the maximum floor acceleration response under various seismic intensities. Therefore, the optimized configuration of UFPs is more effective in reducing both structural and non-structural damage for SCW structural systems compared to conventional configuration. It is also found that greater energy dissipation levels in SCW structure equipped with UFPs may not always result in smaller seismic response, while the configuration of UFPs may play a major influencing factor due to different inter-story lateral force resistance and inter-story energy dissipation demands of SCW structure.

A wideband end‐fire stepped slot antenna with gain enhancement and filtering capability

AbstractA wideband end‐fire stepped slot antenna with gain enhancement and filtering capability is proposed. On one hand, a parasitic dipole serving as a director is introduced in the stepped slot to improve the radiation gain of the slot antenna without increasing its physical size. It is found that a gain enhancement of about 2 dB can be achieved after adopting such approach. On the other hand, an absorptive branch possessing a nearly complementary frequency response with regard to the one of the slot antenna is in‐parallel loaded at the microstrip feedline. It allows the partial dissipation of the out‐of‐band/non‐radiated RF‐signal power of the antenna to attain both an RF‐quasi‐absorptive behaviour and filtering capability. It is found that after loading the dissipative branch, the out‐of‐band radiation efficiency of the slot antenna is reduced to less than 20%. The measured results of a fabricated proof‐of‐concept antenna prototype show a reasonable agreement with the simulated ones and verify the RF performance merits of the proposed stepped slot antenna, such as wide RF operating band covering the 3.39−4.73‐GHz range, end‐fire radiation with a front‐to‐back ratio (FBR) above 10 dB, flat radiation gain, and co‐integrated filtering functionality with RF‐quasi‐absorptive capability.

The stability of Boussinesq equations with partial dissipation around the hydrostatic balance

The stability of Boussinesq equations with partial dissipation around the hydrostatic balance

Stability for a system of the 2D incompressible magneto-micropolar fluid equations with partial mixed dissipation

This paper focuses on the 2D incompressible anisotropic magneto-micropolar fluid equations with vertical dissipation, horizontal magnetic diffusion, and horizontal vortex viscosity. The goal is to investigate the stability of perturbations near a background magnetic field in the 2D magneto-micropolar fluid equations. Two main results are obtained. The first result is based on the linear system. Global existence for any large initial data and asymptotic linear stability are established. The second result explores stability for the nonlinear system. It is proven that if the initial data are sufficiently small, then the solution for some perturbations near a background magnetic field remains small. Additionally, the long-time behaviour of the solution is presented. The most challenging terms in the proof are the linear terms in the velocity equation and the micro-rotation equation that will grow with respect to time t. We are able to find some background fields to control the growth of the linear terms. Our results reveal that some background fields can stabilise electrically conducting fluids.

Stability for the 2D Micropolar equations with partial dissipation near Couette flow

Stability for the 2D Micropolar equations with partial dissipation near Couette flow

Global solution of 3D MHD-Boussinesq system with mixed partial dissipation and thermal damping

Global solution of 3D MHD-Boussinesq system with mixed partial dissipation and thermal damping

Global regularity criteria for the 2D Magneto-micropolar Equations with Partial Dissipation

The magneto-micropolar equations model the motion of electrically conducting micropolar fluids in the presence of a magnetic field.These equations have been the focus of numerous analytical, experimental, and numerical investigations.One fundamental problem concerning these equations is whether their classical solutions are globally regular for all time or if they develop finite time singularities.The global regularity problem can be particularly challenging when there is only partial dissipation. In this paper, we study the 2D incompressible magneto-micropolar equations with partial dissipation prove two new regularity results. The first result addresses a weak solution, and the second result establishes global regularity criteria. As a consequence, we can single out one special partial dissipation case and establish the global regularity if (∂y u1, ∂y u2) ∈ L∞ [0, T ], R2. The proofs of our main results rely on anisotropic Sobolev-type inequalities and the appropriate combination and cancellation of terms.

Ergodicity for two class stochastic partial differential equations with anisotropic viscosity

We prove the ergodicity on anisotropic space H˜0,1 for two class stochastic PDEs with anisotropic viscosity: the Navier–Stokes equations, the primitive equations. The Maslowski-Seidler theory and an asymptotic coupling argument are invoked to overcome several aspects challenges causing by the fact that systems only have partial dissipation and the strong nonlinearity construction.

Measuring gas discharge in contact electrification

Contact electrification in a gas medium is usually followed by partial surface charge dissipation caused by dielectric breakdown of the gas triggered during separation of the surfaces. It is widely assumed that such discharge obeys the classical Paschen’s law, which describes the general dependence of the breakdown voltage on the product of gas pressure and gap distance. However, quantification of this relationship in contact electrification involving insulators is impeded by challenges in nondestructive in situ measurement of the gap voltage. The present work implements an electrode-free strategy for capturing discrete discharge events by monitoring the gap voltage via Coulomb force, providing experimental evidence of Paschen curves governing nitrogen breakdown in silicone-acrylic and copper-nylon contact electrification. It offers an alternative approach for characterizing either the ionization energies of gases or the secondary-electron-emission properties of surfaces without the requirement of a power supply, which can potentially benefit applications ranging from the design of insulative materials to the development of triboelectric sensors and generators.

Large Time Behavior and Stability for Two-Dimensional Magneto-Micropolar Equations with Partial Dissipation

This paper is devoted to the stability and decay estimates of solutions to the two-dimensional magneto-micropolar fluid equations with partial dissipation. Firstly, focus on the 2D magneto-micropolar equation with only velocity dissipation and partial magnetic diffusion, we obtain the global existence of solutions with small initial in H^s({mathbb {R}}^2)(s>1), and by fully exploiting the special structure of the system and using the Fourier splitting methods, we establish the large time decay rates of solutions. Secondly, when the magnetic field has partial dissipation, we show the global existence of solutions with small initial data in dot{B}^0_{2,1}({mathbb {R}}^2). In addition, we explore the decay rates of these global solutions are correspondingly established in dot{B}^m_{2,1}({mathbb {R}}^2) with 0 le m le s, when the initial data belongs to the negative Sobolev space dot{H}^{-l}({mathbb {R}}^2) (for each 0 le l <1).

Development of a new T-bar for the geotechnical centrifuge at TU Delft

An accurate estimation of undrained shear strength of clay seabed is important for interpreting lateral pile-soil interaction response. The cylindrical T-bar is a widely used site investigation tool for profiling the undrained strength (su) of soft soils. As such, a new miniature T-bar penetrometer is designed and fabricated at TU Delft for characterization of the undrained shear strength profile of clay layer in centrifuge models, and OCR profile can be then derived from undrained shear strength profile with known pre-consolidation stress level. The miniature T-bar penetrometer head is a cylinder of 5 mm in diameter and 20 mm in length and the miniature T-bar penetrometer head is connected with a rigid shaft (Figure 1(a)). The T-bar penetration resistance along the depth of clay sample can be obtained and further interpreted into the undrained shear strength profile.&#x0D; Rate of penetration is one of the key parameters that govern the drainage behaviour of soil response around the T-bar and the resulting penetration resistance. A very low rate of penetration leads to partial pore water dissipation and thus partial drainage condition. When a very large rate of penetration is applied, the fully undrained condition is achieved. However, the effect of T-bar penetration rate has not previously been fully examined for normally consolidated and over consolicated clay in the centrifuge. In this paper, the tip resistance profile of T-bar penetration tests under different rates of penetration is analyzed to obtain undrained shear strength profile of clay soils.&#x0D; A series of T-bar tests are conducted in both normally consolidated and slightly over consolidated clay samples at 100 g. The sample drainage state is tested by varying the rate of penetration from 0.01 mm/s to 5 mm/s. The results are interpreted by two methods: (i) the conventional method by converting the measured penetration resistance to soil strength using a single bearing factor, indicating a full-flow mechanism at failure [1]; and (ii) an approach considering soil buoyancy and a reduced bearing factor arising from the shallow failure mechanism, indicating the shallow correction procedure has a significant influence on the soil strength profile inferred from a T-bar penetrometer test [2]. The interpreted undrained shear strength profile provides soil property and OCR information for further monopile tests in the centrifuge, allowing a comprehensive study of the soil-structure interaction on soft soils.

Stabilization Effects of Magnetic Field on a 2D Anisotropic MHD System with Partial Dissipation

Stabilization Effects of Magnetic Field on a 2D Anisotropic MHD System with Partial Dissipation