•Propose a new FE-analytical slice model for load distribution analysis of PGT.•Reveal the load distribution behavior with coupling effects of elasticity and errors.•Optimize the load distribution by ...tooth modification and in-phase eccentricity arrangement.•Conduct the load distribution simulation and test of PGT to verify the proposed model.
Load distribution behavior of planetary gear train (PGT) is crucial for the contact and bending fatigue failure of wind turbine transmission system. With the increasing power of wind turbines, the load and failure rate of wind turbine become larger, which leads to the demand of accurate and efficient modeling, analysis and optimization for load distribution of PGT. In this paper, a new efficient and accurate FE-analytical slice model for load distribution analysis and optimization of PGT in wind turbine is proposed, which is explicitly formulated by the geometry slice model of external/internal gear contact, original FE-analytical slice model for local contact deformation, and efficient finite element (FE) model for global structural deformation. In the FE-analytical slice model, geometry errors are effectively descripted by discretizing gears into a series of slices, while gear tooth contact elasticity and structural elasticity are addressed by the FE-analytical method accurately and efficiently. Upon the proposed model, the load distribution behaviors of PGT with coupling effects of elasticity and errors are revealed and optimized by tooth modification and in-phase eccentricity arrangement strategy. The load distribution tests of PGT in wind turbine are conducted, verifying the proposed FE-analytical slice model which is significant to improve the load-bearing capacity and avoid the fatigue failure of wind turbine transmission system.
•An original FE-analytical slice model for accurate tooth local contact deformation.•Considered displacement datum and elastic interaction of tooth slices in the model.•Established a new mesh ...stiffness calculation method for gears by the original model.•Validated the accuracy and efficiency of the new method against the existing methods.
This paper proposes a new effective mesh stiffness calculation method for spur and helical gear pairs, which is explicitly formulated by an original FE-analytical slice model for tooth local contact deformation, efficient FE model for gear global deformation and mathematical programming approach for gear contact. The original FE-analytical slice model comprehensively integrates the advantages of FE method, Hertz contact theory and slice approach, which can address the displacement datum and elastic interaction of tooth slices effectively, so that tooth contact deformation is determined accurately. The geometry modeling of tooth slices is established and the pressure configuration in the contact region of each slice is prescribed by Hertz distribution. A specified FE programming is developed to derive the tooth contact flexibility matrix accurately. Thus, the mesh stiffness can be effectively calculated by using the proposed method with the FE-analytical slice model. The local contact deformation of gear tooth and mesh stiffness of gear pairs under ideal and error conditions are simulated. The accuracy and efficiency of the proposed method are validated against the ANSYS benchmark and common existing methods.
Endogenous anticonvulsant mechanisms represent a reliable and currently underdeveloped strategy against recurrent seizures and may recall novel original therapeutics. Here, we investigated whether ...the intensification of the astroglial Glu-GABA exchange mechanism by application of the GABA precursor putrescine (PUT) may be effective against convulsive and non-convulsive seizures. We explored the potential of PUT to inhibit spontaneous spike-and-wave discharges (SWDs) in WAG/Rij rats, a genetic model of absence epilepsy. Significant shortening of SWDs in response to intraperitoneally applied PUT has been observed, which could be antagonized by blocking GAT-2/3-mediated astrocytic GABA release with the specific inhibitor SNAP-5114. Direct application of exogenous GABA also reduced SWD duration, suggesting that PUT-triggered astroglial GABA release through GAT-2/3 may be a critical step in limiting seizure duration. PUT application also dose-dependently shortened seizure-like events (SLEs) in the low-Mg
in vitro model of temporal lobe epilepsy. SNAP-5114 reversed the antiepileptic effect of PUT in the in vitro model as well, further confirming that PUT reduces seizure duration by triggering glial GABA release. In accordance, we observed that PUT specifically reduces the frequency of excitatory synaptic potentials, suggesting that it specifically acts at excitatory synapses. We also identified that PUT specifically eliminated the tonic depolarization-induced desynchronization of SLEs. Since PUT is an important source of glial GABA and we previously showed significant GABA release, it is suggested that the astroglial Glu-GABA exchange mechanism plays a key role in limiting ictal discharges, potentially opening up novel pathways to control seizure propagation and generalization.
•Porosity and temperature-dependent material properties considered.•Slice model proposed for discretization.•Iteration algorithm developed for heat transfer analysis.•Exact 2-D thermoelasticity ...theory applied.•Effects of some key factors on the thermoelastic behaviors comprehensively studied.
Porosity usually occurs in functionally graded materials (FGMs) during the fabrication process. Its effects on the thermomechanical behaviors of FGM structures are worth studying. In this work, heat transfer and thermoelastic behaviors of porous FGM sandwich beams with temperature-dependent material properties are examined. The effective material properties are approximately estimated by the modified Voigt mixture rule. Because of the continuously varied material properties across the thickness direction, it is impractical to seek exact solutions for the beam. By proposing a slice model in which the face and core layers are divided into numerous thin slices, the material properties of each slice can be treated as uniform. Based on the model, the through-thickness temperature distribution is first obtained by using an iteration algorithm. Then the two-dimensional (2-D) thermoelasticity equations are analytically solved by using the state space method and Fourier series expansion method. The correctness of the proposed model is checked through comparison with results reported in previous works. The effects of some key factors such as the temperature dependence of material properties, volume fraction, and porosity on the thermomechanical behaviors of the beam are comprehensively studied. It is shown that with the increase of porosity, the thermal resistance capacity of the beam is enhanced yet the bending stiffness is weakened.
This study combines theoretical models with experiments to analyze the impurity migration mechanism and obtain the key factors of separation optimization for the design of layer melt crystallization. ...The fractal slice model was used to explore pore structure formation and calculate the heat properties of the crystal layer. It was found that the fractal characteristics approached the features of Euclidean geometry with increasing porosity, and the thermal conductivity showed a linear decrease with the porosity. Three kinetic models were established based on the temperature difference to reveal quantitative correlations with the degree of supercooling (or superheating). The effects of the pore structure, kinetic behavior, and sweating intensity on the separation process are highlighted. Finally, this work analyzed the important roles of kinetic factors and impurity migration distribution, where a qualitative analysis revealed that the kinetic effect was important in impurity migration in the sweating process.
Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer. PDAC has a dismal prognosis and an inherent resistance to cytostatic drugs. The lack of reliable experimental ...models is a severe limitation for drug development targeting PDAC. We have employed a whole tissue
ex vivo
culture model to explore the effect of redox-modulation by sodium selenite on the viability and growth of PDAC. Drug-resistant tumors are more vulnerable to redox-active selenium compounds because of high metabolic activity and redox imbalance. Sodium selenite efficiently and specifically reduced PDAC cell viability (p <0.02) (n=8) and decreased viable
de novo
tumor cell outgrowth (p<0.05) while preserving non-neoplastic tissues. Major cellular responses (damaged tumor cells > 90%, tumor regression grades III-IV according to Evans) were observed for sodium selenite concentrations between 15-30 µM. Moreover, selenium levels used in this study were significantly below the previously reported maximum tolerated dose for humans. Transcriptome data analysis revealed decreased expression of genes known to drive PDAC growth and metastatic potential (CEMIP, DDR2, PLOD2, P4HA1) while the cell death-inducing genes (ATF3, ACHE) were significantly upregulated (p<0.0001). In conclusion, we report that sodium selenite has an extraordinary efficacy and specificity against drug-resistant pancreatic cancer in an organotypic slice culture model. Our
ex vivo
organotypic tissue slice culture model can be used to test a variety of drug candidates for swift and reliable drug responses to individual PDAC cases.
The paper presents an extension of vortex particle methods (VPM) in the context of pseudo-three-dimensional (pseudo-3D) multi-slice coupled numerical model for complex aeroelastic interactions of ...thin-walled structures. The flow around immersed bodies is analysed using pseudo-3D VPM with boundary element discretisation. The existing coupled model performs the aeroelastic interactions of line-like flexible structures using rigid cross-sections; the deformation of the system is analysed using the natural vibration modes of beam elements. The novelty of the presented coupled model is the inclusion of 3D shell vibration modes for structural analysis within the existing framework. The structural equations are formulated at the mid-surface of the thin shell elements and solved in the modal coordinate system. The slice-wise pressures on surface panels are projected to the corresponding structural nodes. New positions and velocity of surface panels are calculated to satisfy the velocity boundary conditions for solving new surface vortex streets. The coupled method has been validated by identifying the critical flutter wind speed of a T-shaped cantilever system. Benchmarks aeroelastic flapping of different flexible plates are studied further. The vortex-induced vibration of a circular pipe and the ovalling oscillations in circular shells are simulated to show the applicability of the method. Finally, the aeroelastic response of a cantilever roof system is analysed under different incoming wind speeds.
•An extension of pseudo-3D vortex particle methods for FSI of thin-walled structures.•The boundary element method is used for the discretisation of deforming geometry.•Structural equations are solved at mid-surface of shell elements in modal coordinate.•Validation of the method is performed on aeroelastic flapping of thin flexible plates.•The method is proposed for aeroelastic interactions of towers, chimneys, and roofs.
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•Detailed hourly energy targeting considers all details in energy demands.•Maximum heat recovery from gray water in the test building via heat pumping.•Heat exchangers + TES network ...proposed for full heat recovery in buildings.•Transient 1D energy equation, TES stratification performance.
In this study, dynamic streams including space heating, domestic hot water, renewable solar thermal energy and waste heat such as gray water are extracted from a typical multi-family building under extreme winter conditions for one day or 24 h. The maximum heat recovery (MHR) is targeted through an adapted time slice model (TSM) of pinch analysis. Time slices are selected such that all changes in dynamic heat capacity flow rates can be included in the pinch analysis. Moreover, charging and discharging streams of the thermal energy storage (TES) is calculated based on the adapted TSM graphical approach. The integration of a heat pumping system, gray water and solar thermal collectors through mixed direct/indirect heat recovery (i.e. via TES) can reduce hot utility usage in the studied case by as much as 72 percent. An appropriate heat exchanger (HE) and TES network is proposed for the test building to benefit from this underutilized resource. Additionally, the dynamic thermal behavior of the proposed stratified TES is numerically investigated. The results reveals that combined heat loss and thermocline thickness can reduce the heat recovery from TES tank by 10 percent, which is 2 percent of MHR in the test building.
•A rolling simulation is performed based on a meshless numerical method.•A strong form formulation is used together with ideal plastic material law.•Local radial basis function collocation method is ...for the first time used for solution of rolling.•Direct iteration is used for solving highly non-linear material behavior.•Deformation, stress, strain and temperature fields are calculated.
This paper describes the development of a computational model for the hot rolling of steel in a continuous rolling mill. The solution procedure consists of slices aligned in the rolling direction. The deformation and heat flow are assumed to be only in the direction perpendicular to the rolling and the assumed behavior of the material is ideal plastic. The strongly coupled thermal and mechanical models are solved by a novel meshless, local radial basis function collocation method, based on subdomains with 5 nodes for the thermal, and 7 nodes for the mechanical model. Multiquadrics radial basis functions with first-order monomials are used for the shape functions. The rearrangement of the collocation nodes in this large deformation problem is based on elliptical node generation. The non-linear relations are coped with a direct iteration, where the material properties are linearized during each of the iterations. Verification is based on comparison with an analytical solution and results from the finite-element method. A complete rolling simulation with 5 rolling stands is presented. The results encompass the roll speed, the separating force and the torque. The displacement and temperature fields of the rolling from the square to the round profile are displayed.
Melissa officinalis
L. is used in traditional European and Iranian folk medicines to treat a plethora of neurological diseases including epilepsy. We utilized the
in vitro
and
in vivo
models of ...epilepsy to probe the anticonvulsant potentials of essential oil from
M. officinalis
(MO) to gain insight into the scientific basis for its applications in traditional medicine for the management of convulsive disorders. MO was evaluated for effects on maximal electroshock (MES) and pentylenetetrazole (PTZ) -induced seizures in mice, on 4–aminopyridine (4-AP)-brain slice model of epilepsy and sustained repetitive firing of current clamped neurons; and its ameliorative effects were examined on seizure severity, anxiety, depression, cognitive dysfunction, oxidative stress and neuronal cell loss in PTZ-kindled rats. MO reversibly blocked spontaneous ictal-like discharges in the 4-AP-brain slice model of epilepsy and secondary spikes from sustained repetitive firing, suggesting anticonvulsant effects and voltage-gated sodium channel blockade. MO protected mice from PTZ– and MES–induced seizures and mortality, and ameliorated seizure severity, fear-avoidance, depressive-like behavior, cognitive deficits, oxidative stress and neuronal cell loss in PTZ–kindled rats. The findings warrant further study for the potential use of MO and/or its constituent(s) as adjunctive therapy for epileptic patients.
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