Potential of Hyacinth Activated in Lowering Levels of Lead Heavy Metals by Method of Atomic Absorption Spectrophotometry

The Barito River as the largest and longest river in South Kalimantan has been convicted as the most polluted river on an international level. Where one of the most commonly found compounds is the heavy metal lead (Pb) with a high enough levels that alternatives are needed to reduce the levels of the metal. One way to reduce the levels of such heavy metals is to use activated carbon hyacinth. So the activated carbon from hyacinth is made in accordance with SII No.0258-79 and knows the effect of variations in the administration of activated carbon hyacinth at a time of 15 minutes, 30 minutes and 45 minutes in lowering the levels of lead heavy metals (Pb). The research method used to determine the effect of variations in the administration of activated carbon hyacinth is by quantitative testing using the Atomic Absorption Spectrophotometry tool. The results showed that activated carbon hyacinth has met SII No.0258-79 with a randemen test result of 15%, water content of 3%, and absorption of iodine of 241.16 mg / gram. Significant value produced 0.742 with regression value (r) 0.999 and resulted in decreased lead metal levels in the variation of 15 minutes activated carbon administration of -0.030 mg / l with an absorption of 120%, 30 minutes of 0.073 mg / l with an absorption of 48% and 45 minutes of -0.097 mg / l with an absorption of 167%. Hyacinth activated carbon can be used to lower the levels of lead heavy metals (Pb) with a maximum contact time of 45 minutes by 167%.

Modelling of contact and tribotechnical parameters of metal–polymer gears taking into account wear and correction of teeth

The estimation and the analysis of the arising contact pressures and tribotechnical parameters, that is, wear and durability, of metal-polymer spur gears using the author's computational method are presented in this study. Gears with a steel gear and pinion made of polyamide PA6 modified with dispersed carbon fibers (CF) or glass fibers (GF) whose content was 30%, PA6 + 30CF and PA6 + 30GF correspondingly, are studied. This took into account the parity of engagement, the effect of composite pinion teeth wear and gear correction. Quantitative and qualitative regularities of change of the specified parameters depending on composite type and gear correction type are established. It is found that the teeth wear of composite toothed wheels has a significant effect on reducing the values of the initial maximum contact pressures in the engagement. The distribution of linear wear along the teeth working profile and the localization of its maximum values, depending on the correction of engagement, are determined. The minimum durability of metal–polymer gears is calculated by simplified and improved methods. The optimal values of the correction coefficients at which the minimum durability is highest for both combination types of metal–polymer gears with height and angular teeth correction are established. The durability of metal–polymer gears with a driving pinion made of PA6 + 30CF composite calculated with the improved method is about seven times higher than the pinion made of PA6 + 30GF composite. In contrast to the methods of calculation of metal gears known from publications, the method presented in this study takes into account such practically significant factors as change of radii of tooth profile curvature owing to wear, their correction and number of teeth pairs at the engagement. In metal–polymer gears, there are no analytical calculation methods for modelling wear and tribological durability compared with that of the author's method.

An Adhesive Wear Model Based on a Complete Contact Model for a Fractal Surface

An adhesive wear model based on a complete contact model for a fractal surface is presented in this work. A contact model which contains effect of adhesion is firstly presented based on ME model. A complete contact model is then proposed. Finally, an adhesive wear model based on this model is given. The results suggest that the maximum contact area increases firstly and then decreases as fractal dimension increases. The percentage of plastic contact area increases with increase of the fractal dimension. And the experimental results for wear volume have shown a good consistency with the results calculated by the wear model.

Changes in hip Joint Contact Stress During a Gait Cycle based on the Individualized Modeling Framework of"Gait-Musculoskeletal System-Finite Element"

Objective: To construct a comprehensive simulation framework of "gait-musculoskeletal system(MS)-finite element(FE)" for analysis of hip joint dynamics characteristics and the changes in the contact stress in the hip throughout a gait cycle.Methods:Two healthy volunteers (male and female) were recruited. The 3D gait trajectories during normal walking and the CT images including the hip and femur of the volunteers were obtained. CT Imaging data in the DICOM were extracted for subjected 3D hip joint reconstruction. The reconstructed 3D model files were used to realize the subject-specific registration of the pelvis and thigh segment of general musculoskeletal model. The captured marker trajectory data were used to drive subject-specific musculoskeletal model to complete inverse dynamic analysis. Results of inverse dynamic analysis were exported and appliedas boundary and load settings of the hip joint finite element in ABAQUS. Finally, the finite element analysis(FEA) was performed to analyze contact stress of hip joint during a gait cycle of left foot.Results: In the inverse dynamic analysis, the dynamic changes of the main hip-femoral muscle force with respect to each phase of a single gait cycle were plotted. The hip joint reaction force reached a maximum value of 2.9%BW（Body weight）and appeared at the end of the terminal stance phase. Twin peaks appeared at the initial contact phase and the end of the terminal stance phase respectively. FEA showed the temporal changes in contact stress in the acetabulum. In the visual stress cloud chart, the acetabular contact stress was mainly distributed in the dome of the acetabulum and in the anterolateral area at the top of the femoral head during a single gait cycle. The acetabular contact area was 293.8-998.4 mm2 and the maximum contact area appear at the mid-stance phase or the loading response phase of gait. The maximum contact stress of the acetabulum reached 6.91 Mpa (Model 1) / 6.92 Mpa(Model 2) at the terminal stance phase. Conclusions:The "Gait-MS-FE" technology is integrated to construct a comprehensive simulation framework. Based on human gait trajectories and their CT images, individualized simulation modeling can be achieved. Subject-specific gait in combination with an inverse dynamic analysis of the MS provides pre-processing parameters for FE simulation for more accurate biomechanical analysis of hip joint.

Fretting Fatigue Experiment and Finite Element Analysis for Dovetail Specimen at High Temperature

The dovetail attachment between the turbine blade and disk for an aero-engine operates under varying centrifugal load and vibration at elevated temperatures. The fretting fatigue is prone to occur at the contact surface of the dovetail attachment. This paper investigated the fretting fatigue behavior of the dovetail specimen at 630 °C through experiment and numerical simulation, in which the blade-like dovetail specimen is nickel-based single crystal superalloy DD10 while two fretting pads in contact with the dovetail specimen simulating the mortise of the disk are made of powder metallurgy FGH99. It is revealed from all the tests that the fracture induced by the fretting wear occurs at the upper edge area of the contact surface. The contact surface near the upper edge is more severely worn; hence, the phenomenon of partition on the worn contact surface can be observed, which is consistent with the fretting fatigue mechanism. Moreover, the calculated area of maximum contact pressure gradient through finite element method is in good agreement with the experimental position of the initial fretting fatigue cracks.

A new incremental calculated approach to predict maximum contact stress of compressed packer in large deformation

Compressed packer rubber is large deformation material, which endures biaxial contact friction between oil-pipe and casing-pipe in sitting and sealing process. Large-deformation theory analysis of rubber brings huge difficulties to solve, this is due to the material, geometry and contact non-linearity should be considered. In this article, the deformation of compressed packer rubber tube (CPRT) is divided into free deformation, unidirectional and bidirectional constrained deformations. Based on the theory of thick-wall-cylinder and the linear constitutive of rubber material segment, the CPRT mathematical model in different deformation processes is established and the influences of axial load, axial height of CPRT and contact friction coefficient of casing inner wall etc are considered. Based on incremental calculated approach, the mathematical model is solved. By comparing the results of the theoretical model with the results of finite element method and experimental results, it is found that the theoretical maximum contact stress is more conservative than the FEM and experimental solutions, so the sealing reliability of packer effectively predicted under the premise of allowable contact stress and the theoretical results can provide a lower limit reference value for the contact stress of the packer in the actual seal process. Meanwhile, the deviation of contact stress in FEM and theoretical value at z150 height of CPRT is among 1.13%∼4.90%, which can predict the contact stress in the compressed area near the stress concentration upper end-face of CPRT under the low friction factor, the results provide a reference for the compressed packer design.

Predictive Estimation of Sliding Bearing Load-Carrying Capacity and Tribological Durability

A computational method is presented as a method for solving a plane contact problem of the theory of elasticity to determine the contact strength and tribological durability of sliding bearings. The effect of load and radial clearance on the initial contact pressures and their reduction due to wear is studied. The durability of the bearing is estimated. Qualitative and quantitative regularities of changes in contact parameters and durability from the factors under study are established. In particular, it has been shown that both contact angles and maximum contact pressures are approximately linearly dependent on the load, and the durability decreases nonlinearly with increasing load.

Towards Rapid Fabrication of Superhydrophobic Surfaces by Multi-Beam Nanostructuring with 40,401 Beams

Superhydrophobic surfaces attract a lot of attention due to many potential applications including anti-icing, anti-corrosion, self-cleaning or drag-reduction surfaces. Despite a list of attractive applications of superhydrophobic surfaces and demonstrated capability of lasers to produce them, the speed of laser micro and nanostructuring is still low with respect to many industry standards. Up-to-now, most promising multi-beam solutions can improve processing speed a hundred to a thousand times. However, productive and efficient utilization of a new generation of kW-class ultrashort pulsed lasers for precise nanostructuring requires a much higher number of beams. In this work, we introduce a unique combination of high-energy pulsed ultrashort laser system delivering up to 20 mJ at 1030 nm in 1.7 ps and novel Diffractive Laser-Induced Texturing element (DLITe) capable of producing 201 × 201 sub-beams of 5 µm in diameter on a square area of 1 mm2. Simultaneous nanostructuring with 40,401 sub-beams resulted in a matrix of microcraters covered by nanogratings and ripples with periodicity below 470 nm and 720 nm, respectively. The processed area demonstrated hydrophobic to superhydrophobic properties with a maximum contact angle of 153°.

Assessment of Contact Pressures between a Mandibular Overdenture and the Prosthodontic Area

In this paper, we assess the pressure between the overdenture located in the mandible and supported by a bar retained on two implants and the prosthodontic area. For testing, a model of an edentulous mandible was created using a mold by FRASACO with two implants and a “rider” bar inserted. A complete mandibular denture with polypropylene matrices was made. Three types of matrices of various stiffness were applied. The mandible and overdenture geometry was mapped using a digital image obtained with a Steinbichler Comet L3D 3D scanner. Finite element method calculations were performed in the Abaqus FEA software. The results demonstrate that the maximum contact pressure is observed when the loads are associated with canines. A critical case for the lower posterior is chewing performed by the molars. The pressure zone is the largest for POM-1 with Young’s modulus of 1.5 GPa and is reduced by 5.0% and 7.8% for POM-2 (E = 2.5 GPa) and POM-3 (E = 3.5 GPa), respectively. The stress distribution under the prosthesis mostly depends on the region loaded onto it. The applied load produces a slight contact pressure between the denture and the prosthodontic area in the anterior zone. A change in polypropylene matrix stiffness does not affect contact pressures.

Theoretical modeling and numerical simulation of dynamic contact characteristics of a spherical pump with variable friction coefficient

In this paper, the dynamic contact characteristics between a piston system and a cylinder block in a spherical pump are studied theoretically and numerically. The theoretical contact model between a piston and a cylinder is established based on its structural and operational properties, to obtain the maximum contact force quantitatively. The effects of different structural parameters and working pressures on the contact force are analyzed and discussed. The relationship between friction coefficient and rotation speed is presented. The contact pairs are modeled numerically using the finite-element method and augmented Lagrange algorithm to obtain both the tangential and normal contact characteristics. Both static and dynamic contact characteristics of the piston are analyzed and discussed. These proposed studies can provide practical suggestions on improving the wear resistance performance and durability of the spherical pump.