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This paper presents a novel shear deformation theory for analyzing porous microbeams' bending, buckling, and free vibration resting on a foundation. The proposed shear function incorporating three kinetic variables satisfies zero-traction boundary conditions on the top and bottom surfaces of the beams and does not require a shear correction factor. The modified couple stress theory accounts for the size-dependent effects, and the governing equations are derived from Lagrange's equation using the proposed shear function. Legendre–Ritz functions are developed to analyze the porous microbeams' buckling, free vibration, and bending behaviors. The effects of material length scale parameter, porosity, span-to-height ratio, boundary condition, and foundation parameter on the mechanical responses of beams are investigated. Numerical results demonstrate the accuracy and efficiency of the proposed theory and can serve as benchmarks for future analysis of porous microbeams on elastic foundations. [ABSTRACT FROM AUTHOR]

This study aims to design and calculate a model for a wall-climbing robot to replace humans in performing dangerous tasks at great heights in construction sites. The research simultaneously addresses three main issues in the process of calculation, design, and simulation of the vertically climbing robot model. Firstly, the study conducts calculations and analyzes the dynamics of the model in various working states. Specifically, it calculates the suction force of the fan in non-contact conditions to ensure the suction capability of the model during practical operations. Secondly, the core content of this method involves utilizing the airflow generated by the engine through a specially designed suction mechanism to increase the airflow velocity significantly, thus creating a low-pressure area capable of adhering to the wall. This suction force calculation method and other forces acting on the robot model are based on numerical simulation software. The boundary conditions in the calculation process for the wall-climbing robot model are derived from the tasks that the robot performs during real operations, replacing humans. Thirdly, the study designs the wall-climbing robot using the non-contact suction force method through a 3D-printed fan model to enhance the model's durability and optimize the airflow under various conditions. In summary, through this research, the paper aims to construct a robot model using non-contact suction and complete it entirely with 3D printing technology. This model will generate cost-effective and highly efficient robot vehicles that can be widely applied in modern industrial environments. [ABSTRACT FROM AUTHOR]

The present study introduces a novel higher-order shear deformation theory for assessing buckling and free vibration characteristics in laminated composite and functionally graded porous beams. The proposed theoretical framework effectively considers three variables and eliminates the need for a shear correction factor. The governing equations are derived from the Lagrange principle, while Legendre-Ritz functions are utilised to solve the resulting problem. Various types of laminated composite beams with arbitrary lay-ups and functionally graded porous beams with symmetric or unsymmetric configurations are analysed. To validate the accuracy and efficiency of the proposed theory, several numerical examples are conducted and compared against the results of existing research endeavours. [ABSTRACT FROM AUTHOR]

This article proposes static, free vibration, and buckling analysis of thin-walled functionally graded (FG) sandwich and composite channel-section beams. It is based on the first-order shear deformable beam theory, which can recover to classical one by ignoring the shear effect. Ritz's approximation functions are developed to solve the characteristic problems. Both results from classical and the first-order shear deformable theories are given in a unified fashion. Ritz solutions are applied for thin-walled FG sandwich channel-section beams for the first time. Numerical examples are presented in relation to many important effects such as span-to-height ratio, material parameter, lay-ups, fiber orientation and boundary conditions on the beams' deflections, natural frequencies, and critical buckling loads. New results presented in this study can be of interests to the scientific and engineering community in the future. [ABSTRACT FROM AUTHOR]

Abstract The paper proposes a Ritz-type solution for free vibration and buckling analysis thin-walled composite and functionally graded sandwich I-beams. The variation of material through the thickness of functionally graded beams follows the power-law distribution. The displacement field is based on the first-order shear deformation theory, which can reduce to non-shear deformable one. The governing equations of motion are derived from Lagrange's equations. Ritz method is used to obtain the natural frequencies and critical buckling loads of thin-walled beams for both non-shear deformable and shear deformable theory. Numerical results are compared to those from previous works and investigate the effects of fiber angle, material distribution, span-to-height's ratio, and shear deformation on the critical buckling loads and natural frequencies of thin-walled I-beams for various boundary conditions. [ABSTRACT FROM AUTHOR]

In this paper, the Ritz-based solutions are developed for the bending, buckling and vibration behaviors of laminated composite beams with arbitrary lay-ups. A quasi-3D theory, which accounts for a higher-order variation of both the axial and transverse displacements, is used to capture the effects of both shear and normal deformations on the behaviors of composite beams. Numerical results for various boundary conditions are presented and compared with existing ones available in the literature. Besides, the effects of fiber angle, span-to-height ratio, material anisotropy and Poisson's ratio on the displacements, stresses, natural frequencies and buckling loads of the composite beams are investigated. [ABSTRACT FROM AUTHOR]

Breast cancer is a heterogeneous disease with different tumor subtypes. Identifying risk categories will help make better treatment decisions. Hence, this study aimed to predict the survival outcomes of invasive breast cancer in Vietnam, using St Gallen 2007 classification. This study was conducted on 501 patients with breast cancer who had surgical operations, but had not received neoadjuvant chemotherapy, from 2011 to 2013. The clinicopathological characteristics were recorded. Immunohistochemistry staining was performed on ER, PR, HER2/neu, and Ki67 markers. For HER2/neu(2+), fluorescence in situ hybridization was used as the test. All patients with breast cancer were stratified according to 2007 St Gallen categories. Kaplan-Meier and log-rank models were used to analyze survival rates. There were 3.8% cases classified as low risk (LR), 72.1% as intermediate risk (IR1: 60.1% and IR2: 12.0%), and 24.1% as high risk (HR1: 11.8% and HR2: 12.3%). Patients who were LR had the best prognosis, with a 5-year overall survival (OS) rate of 100%. Intermediate-risk patients were at 92.3%. High-risk patients had the worst prognosis, with a 5-year OS proportion of 69.3% ( P < .05). For disease-free survival (DFS), risk categories were categorized as LR: 100%, IR: 90.3%, and HR: 69.3% ( P < .05). Three main risk categories of breast cancer had a distinct OS and DFS. These findings suggest that the 2007 St Gallen risk category could be used to stratify patients with breast cancer into different risk groups in Vietnam.