The 10 most-cited articles in Applied Mechanics and Materials, 2020

This paper proposes a method of using the B-spline mathematical model to plan high smoothness curve trajectories with heading condition through given waypoints for autonomous underwater vehicles (AUVs) in particular and ships with rudder systems in general. In addition, this paper examines some of the physical limitations of this vehicle, which lead to some binding conditions of the trajectory. Besides, the paper applies B-spline approximation method to reduce the curvature of the trajectory, when waypoints are too close and we do not need to go through exactly these waypoints in the 2D plane. Finally, this paper also proposes the genetic algorithm application with some modifications to solve the optimization of B-spline path length with constraint in turning radius of the vehicle.

The impact resistance of micro-steel fiber-reinforced and hybrid fiber-reinforced reactive powder concrete is investigated in this study. Six groups of specimens were prepared with 2.5% volumetric contents of different combinations of fibers. For this purpose, micro-steel fibers with 6 and 15 mm length in addition to polypropylene fibers were used. Each group includes 12 identical specimens. The impact tests were conducted using the repeated drop-weight impact test of ACI 544-2R. However, higher drop-height (700 mm) and drop-weight (10 kg) were adopted to accelerate the failure and reduce the effort required to crack the specimens. The test results showed that the use of only 15 mm micro-steel fiber led to much higher impact resistance than other micro-steel fiber combinations. The recorded number of blows for the group with SF15 was 247, while those of SF6 and combined SF6 and SF15 were 127 and 112, respectively. The replacement of 0.5% of micro-steel fiber by 0.5% of PP fiber was found to reduce the impact resistance regardless of the type or combination of the used micro-steel…

Nowadays, radioactive materials are being applied in medical imaging. Because humans cannot observe radiation, radiation detection materials are very important to humans. A scintillator is a material that can change gamma photons to visible photons. Good scintillators should have the following properties: high scintillation light yield, good energy resolution, and high density. In this work, the scintillation light yield property of CWO crystals was studied due to its interesting properties, such as high stopping power and low hygroscopicity. CWO crystals were compared with BGO crystals. From the results, it was found that the BGO crystals showed higher scintillation light yield value at 662 keV energy from 137Cs radioactive source than the CWO crystals, resulting in better energy resolution value. The intrinsic light yield and loss parameters for both crystals are also presented in this work.

Construction project costs are often related to the availability of construction materials and proximity to the work site. So this paper studied the effect of transportation of materials on the cost of construction projects in the desert and identified the increment percentages of materials cost in comparison with main cities and re-accounted the BOQ items prices in the desert cities. The results showed that the cost of some works may be doubled in the desert areas due to lack of construction materials and high transport costs.

The dynamic process of an underwater explosion (UNDEX) is a complex phenomenon that involves several facets. After detonation, the shockwave radially propagates at a high speed and strikes nearby structures. Subsequently, bubble oscillation may substantially damage the structures because of the whipping effect, water jet impact, and bubble pulse. This paper presents an application of explicit finite element analyses to simulate the process of an UNDEX bubble in the vicinity of rigid wall, in which the coupled Eulerian-Lagrangian (CEL) approach was developed to overcome the difficulties regarding the classical finite element method (FEM), large deformations, and flow simulation of fluid and gas. The results demonstrate that the method is well suited to manage the UNDEX bubble problem and can be used to model the major features of the bubble dynamics. Furthermore, the behavior of an UNDEX bubble near a rigid wall was also examined in the present study, which showed that the migration of the bubble and the development of the water jet are influenced strongly by the standoff distance…

Lung cancer is the most common cancer globally with over 2 million new cases diagnosed every year. Fortunately, if caught early, the likelihood of survival is greatly improved. If diagnosed in Stage I, survival rates are >75% over 5 years, vs. just 1% if diagnosed in Stage IV. Early diagnosis requires finding and sampling (biopsy) small, peripheral nodules that are located in the parenchima of the lung and predominately outside small airways. Currently, for early diagnosis a bronchoscope is inserted into the lung airway but due to large size it cannot reach the small airways. Therefore, the doctor has to advance a sharp biopsy needle blindly from the tip of the bronchoscope and into the lung tissue in the approximate direction of the nodule. This blind procedure has low accuracy and carries a high risk of misdiagnosis. Currently, to improve the accuracy, real time x-ray (fluoroscopy) is use which causes exposure of the patient and physician to harmful radiation. Computer and image assisted surgery and medical robotics present viable solutions but are not optimal at present. The…

Dental wear has accompanied human evolution, being strictly related to its way of life. Dental wear is a lesion of dental hard tissue commonly found in dental practice. Starting from the virtual skull model, the virtual models of the two upper premolars on the left hemisphere were generated, then the finite element method evaluated the stresses, displacements and strains generated by the resistance forces from the dental tissues of the two premolars during mandibular movements with occlusal contact. It is found that the value of these results increases as dental wear increases. This phenomenon is more visible in the teeth where the value almost doubles. Two explanations could be given for this situation: mechanically, these stresses are inversely proportional to the volume of the dental structures and, as they reduce, through dental wear, increase the stress, also, the sharp edges resulting from dental wear are mechanical stress concentrators.

This paper focuses on the characterized of the mechanical properties and hyper elastic behavior of lab made skin. Bovine Serum Albumin (BSA) combined with gelatin as a base. BSA is a plasma lead concentrations or heparin plasma which is separated from blood sample and it is not associated with significant changes in iron or hemoglobin concentrations. In general, the gelatin is widely used as the best material for skin substitution since it exhibits the characteristic of human skin. However, the lab made skin layer was made of non-halal type gelatin (Type B). The methodology process started by adding the BSA and using the type A gelatin to carry out the mechanical properties and hy-per elastic behavior of halal lab made skin layer. A uniaxial tensile test standard that being used in this study is ASTM D412. The raw data (Load-Extension) from computational was plotted on graph stress-strain. The numerical approach such as Mooney-Rivlin model and Yeoh’s model were selected to analyze a stress-stretch of composition gelatin and BSA. From the results Mooney-Rivlin model, the con-stant,…

The daily waste tonnage at Piyungan landfill is 600 tons consisting of organic and combustible waste which can be used as an energy source. The aim of this study is to determine the potential energy of waste in the Piyungan landfill by its characteristics based on technology options including landfill gas, anaerobic digestion, gasification, and incineration. The Piyungan landfill mostly contain organic waste, up to 62.1% and combustible waste (RDF) at 26.8%. Moisture content of Piyungan’s RDF is higher than international standards for RDF as raw material in several countries. The various result for Nett Calorific Value is about 7.27 MJ/kg for fresh waste, 12.78 MJ/kg for RDF, 1.74 MJ/kg for market waste and 4.14 MJ/kg for mining waste. Landfill gas can generate energy up to 1.2 MW at the beginning and reaches 2 MW during peak periods. The potential energy by using anaerobic digestion and gasification technology are 1.54 MW and 3.12 MW. By incinerate fresh waste, the potential energy can be generated up to 9 MW and 4.39 MW when incinerate RDF waste only. Calculation of potential…

An experimental program was directed in this study to evaluate the abrasion resistance of reactive powder concrete (RPC) under direct normal impact of water jet. Abrasion and compressive strength specimens were cast from six RPC mixtures using different single and hybrid distributions of 6 mm-length and 15 mm-length micros-steel fibers and 18 mm-length polypropylene fiber. Fixed mix proportions were used for the six RPC mixtures and with fixed total volumetric fiber content of 2.5%. In addition to the RPC mixtures, a normal concrete mixture was prepared for comparison purposes. All specimens were cured in the same conditions and tested at an age of 28 days. The test results showed that abrasion weight losses increase with time at rates that are independent of fiber type and fiber distribution. The results also showed that all RPC mixtures exhibited significantly lower abrasion losses than normal concrete. The lowest percentage abrasion weight losses were recorded for the mixture with pure 15 mm micro-steel, where after 12 testing hours, it was 0.41% of the total weight before…