Balancing accuracy and computational cost in modeling and analyzing engineering problems has always been a crucial concern in the field. The same principle applies to the modeling of WAVE propagation in structures and deriving dispersion curves, which are crucial in structural health monitoring and material property identification. The importance of maintaining this balance appears especially in cases where there is a need for repetition in modeling. In this study, we aimed to improve the accuracy and computational cost of the semi-analytical finite element method by incorporating hierarchical shape functions. The results indicate that using appropriate shape functions can enhance the performance of the semi-analytical finite element method for modeling WAVE propagation in structures. The study also investigated the impact of the number of degrees of freedom on the calculation of the cutoff frequency, the accuracy of the dispersion curves and the increase in modelling error as a result of this point.

2Background and Aims: GUIDED endodontics is a new technique that is now evolving. It is used in many treatments, especially in access cavity preparation and locating root canals in teeth with pulp canal obliteration (PCO), microsurgical endodontics, and fiber post removal in retreatments. In addition, this technique is independent of operator experience, requires less treatment time for the patient, and is more precise and safer than conventional endodontics. This technique involves the use of cone beam computed tomography imaging (CBCT), tooth surface scanning, and special software to provide guidance for performing endodontic treatment in a fast, safe, and minimally invasive manner. This review article aims to introduce GUIDED endodontics and to describe its technique, advantages, and limitations.

Introduction & Objective: This study was performed to compare the visual and refractive outcomes of photorefractive keratectomy (PRK) in eyes with medium-high astigmatism by WF-GUIDED method using Visx system and cross-cylinder method using Nidek EC-5000 excimer laser system. Although there are many studies about efficacy and safety of WAVE front GUIDED and Cross Cylinder Photorefractive Keratectomy, there are few studies on moderate to high astigmatism.Materials & Methods: In a descriptive comparative study, WF-PRK was performed on 50 eyes of 25 patients with compound myopic astigmatism. Each patient underwent PRK by WF-GUIDED approach. Then the results were compared with the cross-cylinder PRK previously performed on 48 eyes of 24 patients.Results: After 6 months, 100% of the eyes in the WF group had uncorrected visual acuity of 20/25 or better compared to 79.2% in the cross-cylinder group. Mean refractive astigmatism had decreased by 1.57±0.53 in the WF group and 1.67±0.52 in the cross-cylinder group (P=0.75). Mean postoperative absolute change in total root-mean-square higher order aberrations in the WF group and cross-cylinder group were 0.05±0.22mm and 0.17±0.20 mm, respectively (P<0.001).Conclusion: Both methods of PRK using the Nidek EC-5000 and visx excimer laser systems are effective for correcting medium-high astigmatism. WF approach is more successful in improving the refractive results.

The aim of the present work is to use the spectral method to plot the dispersion curves of ultrasonic GUIDED WAVEs in anisotropic pipelines. We begin by describing the mathematical formulation of the problem, followed by the application of the spectral method algorithm to plot these curves, covering different levels of anisotropy to test the robustness of the method to various mechanical behaviors. Particular attention is paid to complex modes, poorly studied in the pipeline literature. Results are compared with analytical solutions, and computation time and coding effort are also compared with those of previous analytical methods. These studies demonstrate the significant advantage of the spectral method in terms of accuracy efficiency and computational time savings for plotting the dispersion curves of complex modes in anisotropic pipelines.

Polyethylene pipeline is an essential infrastructure of gas distribution network, and there are some problems such as complex damage assessment and tedious assessment process. How to choose an effective damage assessment method for polyethylene pipelines is the focus of the implementation of the gas distribution network at present. In this paper, a nonlinear directional WAVE method is proposed to detect the damage of polyethylene pipeline by an acoustic WAVE, and the damage results of polyethylene pipeline are searched. The rationality of this method is verified by calculating the aerodynamic equation.The results show that the nonlinear fixed WAVE method can accurately determine the damage and crack propagation degree of the pipeline and simplify the damage assessment process, and the results are superior to the linear directional WAVE method. Therefore, the nonlinear directional WAVE can be used to assess the damage to ethylene pipelines in gas distribution networks, which has strong rationality and practicality and provides support for the actual pipeline damage assessment.

Using surface GUIDED WAVE is one of the most reliable methods of structural health monitoring. Mostly the bulk WAVE is preferred for identification of internal defects, which is inefficient in localizing the surface cracks. In this research the procedure of ultrasonic surface WAVE tomography for crack detection in an aluminum plate is investigated and applied for three cracks with the length of 4, 7 and 10 millimeters. Analytical equations and numerical simulations are used to extract dispersion curves as a means for selection of plate thickness and piezoelectric characteristics. The Layout selection for transducers and providing numerical and experimental models are the next steps of inspection procedure. All the piezoelectric discs are actuated respectively. Meanwhile, other piezoelectric elements are used as sensors and their received signal is stored in both healthy and defected structures for both numerical and experimental models. Definition of signal difference criteria, signal reconstruction and tomogram generation are the last steps of the procedure presented in this paper.