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Repairing cracked aerial structures using patches is a common way to restore mechanical properties, strength and extend fatigue life. The performance of such patches can be obtained by comparing the maximum amount of force tolerated by the repaired piece with the unrepaired piece. The shape and dimensions of the patch used to repair the crack and the way the patch is bonded affect the repair quality which are of great importance. Therefore, in this paper, we investigate the factors affecting the diffusion bonding between the patch and the piece. The impact of the shape of the aluminum patch attached on a 10 mm central crack piece and perpendicular to the loading direction (mode I) is studied experimentally and numerically. The optimum conditions for the diffusion connection including the pressure, time and temperature of the connection were obtained experimentally using a composite rotatable centered design and in the connection made under these conditions, the patch shape and aspect ratio was considered as variables of design, and the results were obtained for square, rectangular, circular and elliptical patches. At the end, it was found that the best connection under the pressure conditions of 570 °C, 70 bar and 100 min was formed and the rectangular patch efficiency was greater whereas its extent is more in line with crack than the other modes. At a fixed area, the different patch geometries investigated in this study were able to influence up to 80% of the maximum force tolerated by the repaired parts. In addition, there is an acceptable convergence between experimental and numerical results. [ABSTRACT FROM AUTHOR]

This work presents a simple technique to identify elastic properties of composite materials. The identification is based on the adjustment of coefficients in an optimization process in which the objective function is defined by the difference between the analytical natural frequencies and the experimental measured ones. Such analytical natural frequencies are obtained by the Rayleigh-Ritz technique while the experimental ones are determined by ordinary modal tests. The proposed approach used Genetic Algorithm (GA) to solve the optimization problem. This paper describes an indirect (non-destructive) prediction method by using GA and the analytical Rayleigh-Ritz technique. A few examples are presented to identify the material properties of orthotropic rectangular plates with unidirectional fiber plies and completely free boundary conditions (FF-FF) for this research. [ABSTRACT FROM AUTHOR]

This article focuses on the experimental and theoretical investigation of the axial crushing behaviour of thick-walled tubes with a number of wide grooves, cut from their outer surface, under both static and dynamic loading. While this structure is subjected to axial loading, plastic deformation occurs within the space of each wide groove, and thick portions (grooveless areas) control and stabilize the collapsing of grooved thick-walled tubes. Therefore, the kinetic energy is dissipated by the plastic collapsing of the structure between grooves. In the present study, quasi-static compression tests of specimens with various geometric parameters are performed. Dynamic tests of some specimens using a drop hammer apparatus are also carried out to study the dynamic effects on the collapsing and energy absorption behaviour of the shock absorber. Numerical simulations of axial crushing of the shock absorber under both quasi-static and impact loading, using LS-DYNA finite-element explicit code, are also carried out in this article, and their results are verified with experimental findings. Based on experimental studies, an analysis with consideration of strain hardening effects to predict mean crushing load and energy absorption of the structure under axial compression is developed. Through the performed experimental, numerical, and analytical studies, major parameters in the design of the shock absorber are characterized and possible collapse modes of deformation during axial crushing of the structure are identified. In the present study, experimental and theoretical studies show that the introduced structure can be considered as an efficient energy-dissipating device since it provides favourable crash worthiness characteristics. [ABSTRACT FROM AUTHOR]

The coefficient of friction for steel-aluminium contact surfaces has been determined. The test was conducted by using a testing machine active on the basis of the twist-compression test. A fiat plate of aluminium was placed under pressure between two steel dies. One of the dies (the upper one) was capable of rotating while the other (the lower one) was stationary and attached to a load cell that was used for measuring the torque and force on the fiat plate. By using a strain bridge data logger, the coefficient of friction can be found within 0.75-second intervals. The results show that the friction coefficient for steel-aluminium interfaces started at an initial value of 0.2. increased to almost 0.8 in the elastic region, and then decreased to the value of 0.6 in the plastic region. [ABSTRACT FROM AUTHOR]

Cyclooxygenases (COX) play a pivotal role in inflammation and are responsible for the production of prostaglandins (PGs). Two types of COXs have been identified as key biological targets for drug design: Constitutive COX-1 and inducible COX-2. Nonsteroidal anti-inflammatory drugs (NSAIDs) target COX-1, while selective COX-2 inhibitors are designed for COX-2. These COX isoforms are involved in multiple physiological and pathological pathways throughout the body. Overproduction of tumor necrosis factor-alpha (TNF-α) plays a role in COX-2's inflammatory activity. Tumor necrosis factor-alpha can contribute to cardiac fibrosis, heart failure, and various cancers by upregulating the COX-2/PGE2 axis. Therefore, suppressing COX activity has emerged as a potentially effective treatment for chronic inflammatory disorders and cancer. This review explores the mechanisms of TNF-α-induced COX-2/PGE2 expression, a significant pathophysiological feature of cancer development. Furthermore, we summarize chemical compounds with dual COX-2/TNF-α inhibitory actions, providing an overview of their structure-activity relationship. These insights may contribute to the development of new generations of dual-acting COX-2/TNF-α inhibitors with enhanced efficacy., Competing Interests: The authors reported no conflict of interests., (Copyright © 2024, Tajdari et al.)

Objective: We investigated the impact of low-tempo, repetitive hand movements on vibrotactile sensitivity by employing various temporal and spatial patterns in the hand and wrist area., Background: The investigation of a human's ability to perceive vibrotactile stimuli during dynamic hand movements remains understudied, despite the prevalence of slow to mild hand motions in applications such as hand navigation or gesture control using haptic gloves in Virtual Reality (VR) and Augmented Reality (AR)., Method: We investigated vibrotactile sensitivity, analyzing the impact of various factors, including Motion (static and low-tempo repetitive hand movements), Temporal Patterns (Single or Double vibrations with varying onset times), Tactor Placements (hand and wrist), Spatial Patterns, and Biological Sex ., Results: Our study revealed that Motion significantly influences vibrotactile sensitivity in the hand and wrist areas, leading to reduced accuracy rates during dynamic conditions. Additionally, as the stimulus onset approached in Double vibrations, accuracy rates markedly decreased. Notably, Hand Placement resulted in significantly higher accuracy rates compared to the Wrist Placement ., Conclusion: Our findings underscore the impact of motion in reducing vibrotactile sensitivity on the back of the hand and around the wrist., Application: This research has wide-ranging practical applications, particularly in the field of VR/AR experiences, rehabilitation programs, and accessibility solutions through the use of haptic gloves. Insights from our study can be harnessed to enhance the efficacy of haptic gloves in conveying vibrotactile cues within these contexts., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Scoliosis is a 3D deformation of the spinal column, characterized by a lateral deviation of the spine, accompanied by axial rotation of the vertebrae. Adolescent Idiopathic Scoliosis (AIS), is the most common type, affecting children between ages 8 to 18 when bone growth is at its maximum rate. The selection of the most appropriate treatment options is based on the surgeon's experience. So, developing a clinically validated patient-specific model of the spine would aid surgeons in understanding AIS in early stages and propose an efficient method of treatment for the individual patient. This project steps include: Developing a clinically validated patient-specific Reduced Order Finite Element Model (ROFEM) of the spine, predicting AIS progression using data mining and proposing a method of treatment. First we implement FE synergistically with bio-mechanical information, image processing and data science techniques to improve predictive ability. Initial geometry of the spine will be extracted from the x-ray images from different planes and imported to FEM software to generate the spine model and perform analysis. A RO model is developed based on the detailed spinal FEM. Next, a neural network is used to predict the spinal curvature. The ability to predict the severity of AIS will have an immense impact on the treatment of AIS-affected children. Access to a predictive and patient-specific model will enable the physicians to have a better understanding of spinal curvature progression. Consequently, the physicians will be able to educate families, choose the most appropriate treatment option and asses for surgical intervention.