Long-term and season-specific changes in the body concentrations of iron, copper, zinc, and selenium by means of quantitative analyses of beard samples collected every day — a case study

A total of 4269 beard samples were collected from the same person every day over a 12-year period and analyzed by PIXE using a standard-free method. It was found that the concentrations of copper and zinc showed certain short-term changes but did not show a noticeable long-term trend over the study period, with only iron showing a slightly decreasing tendency with age. All of these elements showed clear yearly variations with a cycle of a few years possibly due to periodic metabolic changes in the subject’s body or long-term changes in eating habits. In contrast, however, selenium showed clear seasonal variations. Its concentration significantly increased in the summer and decreased in the winter, just as was observed with arsenic and mercury. This suggests that most of the subject’s selenium intake was from marine products, whose supply and consumption were increased in the summer. These findings confirmed that beard analyses are useful not only for evaluating essential-element intake but also for estimating the relationship between the body-element concentrations and ingestion of certain foods.

Simulations of hot forming processes of variable thicknesses workpieces

Methodology of production process analysis – by means of hot forming – using workpieces of variable thickness, was presented. Finite element simulations were performed using specialized software for the typical car body element – the longitudinal longeron. The simulation results were presented and discussed as well as conclusions and recommendations were formulated.

Finite Element Method of Composite Steel-Concrete Beams Considering Interface Slip and Uplift

Introduction: In order to analyze the displacement and internal force of composite steel-concrete beams under the vertical load, The finite element solution of composite steel-concrete beams under concentrated loads considering the existence of interface slip and vertical uplift based on the basic idea of elastic mechanics was derived in this paper. Method: A new kind of stiffness equation of bar system was got and its correctness was demonstrated with experimental value, the problem of composite beams considering the existence of interface slip and vertical uplift was solved, avoiding to produce large amount of calculation with the body element method. Results and Conclusion: It can be seamlessly integrated into the current engineering design software, which provides effective help to practical engineering problems.

A New Dynamic Model of Ball-Bearing Rotor Systems Based on Rigid Body Element

Ball-bearing rotor systems are key components of rotating machinery. In this work, a new dynamic modeling method for ball-bearing rotor systems is proposed based on rigid body element (RBE). First, the concept of RBE is given, and then the rotor is divided into several discrete RBEs. Every two adjacent RBEs are connected by imaginary springs, whose stiffness is calculated according to properties of the RBEs. Second, all the parts of rolling ball bearings (i.e., outer ring, inner ring, ball, and cage) are considered as RBEs, and Gupta's model is employed to model bearings which include radial clearance, waviness, pedestal effect, etc. Finally, the rotor and all the rolling ball bearings are coupled to develop a dynamic model of the ball-bearing rotor system. The vibration responses of the ball-bearing rotor system can be calculated by solving dynamic equations of each RBE. The proposed method is verified with both simulation and experiment. The RBE model of the rotor is compared with its finite element (FE) model first, and numerical simulation shows the validity of the RBE model. Then, experiments are conducted on a rotor test rig which is supported with two rolling ball bearings as well. Good agreements between measurement and simulation show the ability of the model to predict the dynamic behavior of ball-bearing rotor systems.

New Simulation Method of Reinforcement Simulation in FEA

During the research of local stress distribution of polyline pretensioned beams by 3-D nonlinear finite element method, a problem of curve prestressed reinforcement simulation is discovered. If the line of prestressed reinforcement is curve, the calculated result of local stress distribution is greatly affected by element size, because of the tectonic stress concentration by the coupling between the linear element and body element. Then, the validity and applicability of the model couldn't be judged. To eliminate the harmful effect, the curve prestressed reinforcement is determined to simulate by body element. The result shows that it will solve the problem thoroughly, and the calculated result is truthful and reliable. This research presents a new thought and method about the local stress analysis of the prestressed concrete structure.

Discussion on Curve Prestressed Reinforcement Simulation in FEA

Considering the slender property, the reinforcement is always simulated by linear element in conventional FEA of concrete structures. But to the curve prestressed reinforcement, it will lead to the problem that the calculated result of local stress distribution is greatly affected by element size, because of the tectonic stress concentration by the coupling between the linear element and body element. To eliminate the harmful effect, the curve prestressed reinforcement can be simulated by body element. The result shows that it will solve the problem thoroughly, and the calculated result is truthful and reliable. Certainly, as a kind of slender component, there are some key point must be recognized when the curve prestressed reinforcement is simulated by body element. To reflect the mechanical properties of prestressed reinforcement and solve the key challenges of modeling, some key techniques of modeling and some special notices about element property settings are discussed detailedly in this paper.

Calculation for Equivalent Nodal Force of Prestress in 20 Nodes Isoparametric Element

When establishing the prestressed bridge model with the entity unit, the simulation of prestress bar has very big limitation. The paper takes 20 nodes isoparametric element as an example and puts forward a kind of numerical method combined with the Newton iterative algorithm and Gauss integral algorithm to calculate equivalent loads of prestress in body element. This method can be used to calculate the equivalent loads of prestress in the various complex steel in bundle shapes and suits the computer programming. Through the final regular inspection, this method has been proved to have very high precision.