Search

This paper introduces a density penalty-based topology optimization method for designing shell–infill structures. During the optimization, the shell is identified by simultaneously penalizing density variables of both the solid and the void phases. Two-phase density filtering and Boolean operations are further applied to model the shell–infill structure. In the optimization of shell–infill structures, the shell thickness is controlled through density filtering and the density penalty. For explicit control of the shell thickness, its analytical relationship with the filter radius and the penalty parameter is derived. Both 2D and 3D numerical examples are investigated to showcase the effectiveness of the shell–infill optimization approach. The effects of mass constraints, filter radius, penalty parameter, mesh resolution, and material properties are thoroughly studied. The results demonstrate that the density penalty-based method can efficiently identify interfaces for different settings in shell–infill optimization. The presented formulations can be directly integrated into the optimization process, offering a new perspective for the design of shell–infill structures. [ABSTRACT FROM AUTHOR]

This paper proposes a topology optimization formulation for additive manufacturing, in which the part, supports and their machining directions are simultaneously optimized. The part and supports are represented by two groups of density fields. The support structures are optimized for heat dissipation efficiency by solving a pseudo heat conduction problem under heat flux boundary loading and constraining the maximum temperature. The temperature constraint allows us to obtain self-supporting overhangs or non-self-supporting overhangs with support structures underneath. During the optimization, the support structures are further filtered by the solution fields from the advection-diffusion equations to ensure their accessibility to the machining tools. Based on the developed formulation, the optimized support structures would be distributed in the machinable regions of the part to enhance heat transfer in the manufacturing process. The unmachinable regions of the part, including enclosed voids, are self-supported for additive manufacturing. The sensitivity of the manufacturing constraint with respect to the design variables of the part, supports and the machining directions is derived through the adjoint method. We validate the effectiveness of the proposed formulation through several examples in 2D and 3D cases. [ABSTRACT FROM AUTHOR]

This paper presents an efficient integrated multidisciplinary design optimization method for shaping a high-pressure cooling turbine blade in aero engines. This approach utilizes a novel regression/interpolation combination surrogate model (R/ICSM), facilitating comprehensive design optimization through collaborative coupling feature parameterization modeling and numerical simulation analysis across various disciplines. The optimized blade adjusts the load distribution on its surface, effectively eliminating flow separation at the tip and trailing edge. Notably, the optimized blade achieves a 0.69% increase in isentropic efficiency while satisfying aerodynamic, strength, and structural constraints. This highlights the effectiveness and progressiveness of the multidisciplinary design optimization method for a cooling turbine blade based on the R/ICSM in enhancing overall performance. It offers a novel and feasible approach for turbine blade design optimization and provides valuable insights for future research and applications. [ABSTRACT FROM AUTHOR]

The alternating active-phase algorithm (AAPA) is widely recognized as being efficient for multi-material topology optimization. It has the advantages of easy implementation and broad applicability, but faces shortcomings, such as a uniform punishment intensity for all elements, excessive gray elements, and slow optimization convergence. To overcome these shortcomings, proposed here is an enhanced AAPA (EAAPA), the core ideas of which are as follows. (1) A new equal-scale Heaviside projection function (EHPF) is proposed, with the scale factor introduced to adjust the physical density adaptively to overcome the challenges of the invariance of the density sum and the uniqueness of projecting faced by the traditional Heaviside projection function. This adaptation reduces the number of gray elements and accelerates the convergence. (2) An innovative solid isotropic material with exponential sigmoid function (SIMESF) is constructed, with a penalty threshold and a steepness factor introduced to divide different penalty intensity regions and control their transition steepness. This improves the applicability and flexibility of the interpolation model, addressing the issue of a single punishment intensity in the solid isotropic material with penalization. The parameter values of the SIMESF model are explored via the design of a bridge, and the performances of AAPA and EAAPA are evaluated via the designs of simply supported and cantilever beams. The results show clearly that EAAPA has significant advantages in terms of optimization effectiveness and convergence speed. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to present a multi-axis actuating approach to attenuate the bending and torsional vibration of the solar array through the reaction wheel (RW) actuators. Design/methodology/approach: The motion equation of the solar array with the RW actuators is derived in modal coordinates for controller design. The reaction torques, induced by the speed change of the RW actuators, are controlled for vibration attenuation through the constraints on the actuators' rotating speed. The proposed control approach is firstly verified with numerical simulation on the finite element model of a full-scale solar array. Experimental study of a simplified elastic plate model is subsequently performed for feasibility and validity investigation. Findings: Both the numerical and experimental studies demonstrated the success of adopting RW as the actuator. Results from numerical simulation reveal that the vibration response peak can be reduced by 80% with 2% of mass increase by using the RW actuators. Practical implications: It is demonstrated that the multi-axis actuating method using RW actuators has a great potential in vibration attenuation of the multi-panel deployable solar array. Originality/value: An approach to reduce bending and torsional vibration of solar array based on RW actuators is investigated. Theoretical analysis, numerical simulation and experimental study are conducted to demonstrate the validity of the proposed vibration attenuation approach and its potential application in the spacecraft design. [ABSTRACT FROM AUTHOR]

The paper presents a formulation for simultaneous optimization of part and support in additive manufacturing. A pseudo heat conduction problem is solved to simulate heat transfer between the part and support. In the pseudo problem, a surface slope-dependent heat flux is applied on the part/support interfaces. The input heat is then transferred through the part and support to the build plate, which is treated as the heat sink. Since the density-based topology optimization does not involve explicit surface representation, the heat flux is implicitly imposed through a domain integration of a Heaviside projected density gradient. The proposed formulation has the inherent ability to control surface slope, which allows us to obtain self-supported enclosed voids and put removable external supports only on the open surfaces. Self-supporting supports can also be obtained by controlling the anisotropic thermal conductivity of the supports. Three different objective functions related to heat dissipation efficiency of the support are investigated. Both 2D and 3D numerical examples are presented to demonstrate the validity and efficiency of the proposed approach. [ABSTRACT FROM AUTHOR]

Background: Neurofilament proteins as biomarkers of axonal degeneration have the potential to improve our capacity to predict and monitor neurological outcome in experimental autoimmune encephalitis (EAE), a model of multiple sclerosis (MS). We urgently need more accurate early predictive markers to direct the clinician when to provide neuroprotective therapy.Aims: To highlight the possible roles of neurofilament proteins in physiological and pathophysiological processes in the MS.Materials and Methods: Fifty female Wistar rats with MOG35-55 peptide induced EAE were randomly divided into two parts: control group and EAE group. All of them were along with expanded disability status scale (EDSS). The mice were sacrificed on day 0, 1, 3, 7, 14, and 28 after the first immunization. Supernatant and pellet were separated at the same time. The degradation rates of NF in the brain nerve and spinal cord of each rat were measured by Western Blotting.Statistical Analysis: The data were expressed as mean ± SD. Statistical analysis was performed with one-way analysis of variance (ANOVA), followed by LSD's post-hoc tests, which was provided by SPSS 23.0 statistical software.Results and Conclusions: Neurofilament light protein may be more useful as a measure of ongoing neurodegenerative activity in EAE, which would make this protein a potential candidate for use as a surrogate marker for assessment of treatments aimed at reducing axonal injury. Future studies are warranted to support or refute the value neurofilament in clinical practice. [ABSTRACT FROM AUTHOR]

One way to solve topology optimization of continuum structures under design-dependent pressure loads is to recover the loading surface at each step of the minimization process. During the topology evolution, the intermediate topologies obtained by using the SIMP (Solid Isotropic Material with Penalization) method actually can be regarded as gray scale images, for which the paper proposes a new material boundary identification scheme based on image segmentation technique. The Distance Regularized Level Set Evolution (DRLSE) method proposed by Li et al., IEEE Trans Image Process 19(12):3243-3254 (2010) is utilized to detect the image edge. Then the pressure boundary is represented as the zero level contour of a level set function (LSF). Inheriting the merits of the level set method, the current scheme can handle the topological change of the pressure boundary efficiently and be easily extended to the three-dimensional problems. In addition, the scheme is more stable compared with the conventional loading surface searching methods since it works well for the intermediate topologies with local scattered densities. A new optimization framework is also proposed to avoid the load sensitivity analysis. Four numerical examples are presented to show the validity and advantages of the proposed scheme. [ABSTRACT FROM AUTHOR]

Background/Aims: Alzheimer's disease (AD) is one of the most common dementias among aged people, and is clinically characterized by progressive memory loss, behavioral and learning dysfunction and cognitive deficits. So far, this is no cure for AD. A therapeutic effect of transplantation of mesenchymal stem cells (MSCs) into murine model of AD has been reported, but remains to be further improved. Brn-4 is a transcription factor that plays a critical role in neuronal development, whereas the effects of Brn-4 overexpression in transplanted MSCs on AD are unknown. Methods: MSCs were isolated from mouse bone marrow and induced to overexpress antisense of miRNA-937 (as-miR-937) through adeno-associated virus (AAV)-mediated transduction, and purified by flow cytometry based on expression of a GFP co-transgene in the cells. The Brn-4 levels in mouse MSCs were examined in miR-937-modified MSCs by RT-qPCR and by Western blot. These miR-937-modified MSCs were then transplanted into an APP/PS1 transgenic AD model in mice. The effects of saline control, MSCs and asmiR-937 MSCs on AD mice were examined by deposition of amyloid-beta peptide aggregates (Aβ), social recognition test (SR), Plus-Maze Discriminative Avoidance Task (PM-DAT) and the levels of Brain-derived neurotrophic factor (BDNF) in the mouse brain. Results: MSCs expressed high levels of Brn-4 transcripts but low levels of Brn-4 protein. Poor protein vs mRNA levels of Brn-4 in MSCs appeared to result from the presence of high levels of miR-937 in MSCs. miR-937 inhibited translation of Brn-4 mRNA through binding to the 3'-UTR of the Brn-4 mRNA in MSCs. Expression of as-miR-937 significantly increased Brn-4 protein levels in MSCs. Transplantation of as-miR-937-expressing MSCs significantly reduced the deposition of Aβ, increased the levels of BDNF, and significantly improved the appearance in SR and PM-DAT in AD mice. Conclusion: Overexpression of as-miR-937 in MSCs may substantially improve the therapeutic effects of MSCs on AD, possibly through augmenting Brn-4 levels in MSCs. © 2015 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background: Multiple sclerosis (MS) is a chronic autoimmune demyelination disorder of the central nervous system (CNS) and its etiology remains unknown. The inflammatory environment in demyelinating lesions leads to the generation of oxygen- and nitrogen-free radicals as well as proinflammatory cytokines, which contribute to the development and progression of multiple sclerosis. Inflammation can lead to oxidative stress and vice versa. Thus, oxidative stress is involved in the inflammation leading demyelination and neurodegeneration in the pathogenesis of multiple sclerosis. Summary: The present study aims to determine two biochemical markers of oxidative stress: TAC and MDA and to show their correlations whether oxidative stress reaction occurs in the demyelination through analyzing samples including peripheral blood and cerebrospinal fluid (CSF) from patients with relapsing-remitting MS (RR-MS). Totally, there were 20 patients in the control groups made from individuals with normal pressure hydrocephalus. Thirty MS patients diagnosed with McDonald diagnostic criteria (2010) treated with methylprednisolone were included in this study. Data were stratified by the degree of severity in order to clarify the role of oxidative stress in the mechanisms of MS and to assess its potential as a biomarker. Thirty clinically definite RRMS patients were enrolled in this study. Levels of MDA, GSH, total antioxidant capacity TAC, GSH-Px and ROS, were determined in serum of the control group and RRMS patients in 7 days before MP (methylprednisolone) treatment and one month after MP treatment. Statistical analysis was performed with one-way analysis of variance (ANOVA), followed by LSD's post hoc tests. Key Messages: Oxidative stress precedes the inflammatory response in the multiple sclerosis patients. And methylprednisolone treatment can decrease brain antioxidant enzymes to reduce the neuroinflammatory attack. © 2014 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]