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Mini Review: Is fluoroquinolone drug or poison?
Get PDFQuinolones are a class of broad-spectrum antibiotics with valuable pharmacological properties due to their improved pharmacokinetic properties, particular mechanism of action and broad and potent activity; being one of the fastest growing class antibacterial growths in terms of therapeutic use and overall benefit. Because of their effectiveness, spectrum of activity, and generally good safety profile, fluoroquinolones were used widely for multiple clinical indications throughout the world. Although still clinically valuable, fluoroquinolone use has become limited in some clinical situations, as bacterial resistance has emerged over time. In the sections that follow we review the range of molecular mechanisms that motivate quinolone resistance
DEM simulation and experimental study on the screening process of elliptical vibration mechanical systems
Get PDFFor an elliptical vibration system, the vibration parameters seriously affect conveying speed and sieving efficiency of the materials. In addition, considering the lack of studies about the elliptical vibration machine, we applied the discrete element method to simulate and analyze the elliptical vibration screening process in this paper. A vibration screening model is particularly based on the purpose of our research to fundamentally demonstrate the novel relationships among the conveying speed, sieving efficiency and vibration parameters of the materials. And the sieving experiment of typical materials is additionally carried out on the same simulation system. This paper analyzes the influence rule of vibration parameters on conveying speed and sieving efficiency of the materials during the elliptical vibration screening process by virtue of comprehensively comparing the results of experimental study coupled with simulation research. Consequently, we can throw up the optimal vibration screening parameters to guarantee high sieving efficiency and large throughput of the screening machine at the same time. The screening test carried out in this paper lays the experimental foundation for the study of the mechanism of elliptical vibration screening machine and the study of materials screening characteristics by combining the conclusions of DEM simulation analysis of lots of materials. It provides not only a basis for selecting the vibration parameters of the actual working process of the screening machine, but also data support based on the experiment and simulation for the study of the sieving mechanism of elliptical vibration systems. For screening mechanism, this is a significant progress which will affect future design and manufacture of elliptical vibration machines. Furthermore, the conclusions drawn from this research can help us study and explain better the screening process of other vibration machinery
Optimization of the longitudinal-torsional ultrasonic step-like horn design for milling tool applications via the tool load account
Get PDFUltrasonic horns are used in the ultrasonic-assisted milling and cutting tools. However, the interaction with tool end vibrations deteriorates the horn performance. In this study, the amplification coefficients and vibration node locations of an ultrasonic horn were determined via the 1D wave theory and optimized by the tool load effect account. By arranging spiral grooves at the straight part of the ultrasonic horn, a longitudinal-torsional modal converter was introduced. This made it possible to convert longitudinal vibrations into longitudinal-torsional coupled ones by the superposition of incident and reflected longitudinal waves with reflected transverse ones at grooves. Orthogonal L9 (33) tests with parameters of spiral grooves as variables were designed and conducted, and longitudinal-torsional ratios (LTR) of the milling tool end under different conditions were assessed using the commercial ANSYS software package. The in-depth analysis of simulation results implies that the LTR values are controlled by the following influence factors in the decreasing order: helical angle, number of grooves, and groove width. Single-factor tests indicate that LTR exhibits an initial drop and a further rise with the helical angle, attaining its minimal value at 30°; it drops with the number of grooves n, and remains practically unchanged with the groove width variation. Finally, the vibration tests of the proposed horn with the optimized parameters corroborated its feasibility and demonstrated its excellent performance in the ultrasonic-assisted milling tool application
Selection of ground motion prediction equations for probabilistic seismic hazard analysis based on an improved fuzzy logic
Get PDFThe fuzzy logic method has been used widely in civil and earthquake engineering, but there is no comprehensive point of view for utilizing fuzzy approach in order to obtain ground motion prediction equations (GMPEs) for probabilistic seismic hazard analysis (PSHA). Hence, fuzzy magnitude–distance method as a new approach for choosing GMPEs in the process of PSHA, is developed in this research through the selection of the ruling peak ground acceleration (PGA) of each common cell (the combined cell of earthquake intensity and site to source distance). The presented method reduces the need for engineering judgments in seismic analysis based on a newly developed benchmark. It enables designers to not only determine the range of acceptable fuzzy results but also introduces a concept which ensures the selection of initial well-suited GMPEs for the analysis
Modelling and simulation on behaviours of mild steel
Get PDFThe objective of the paper is to simulate the behaviours of mild steel at different strain rates (1-1500s-1) under tension and compression by using finite element analysis code in ANSYS. Numerical simulation are done using Cowper-Symonds (C-S) and Johnson-Cook (J-C) material models to represent the flow stresses of mild steel. The simulated results have good agreement with the predicted results of the above material models
Design and real time implementation of nonlinear sliding surface with the application of super-twisting algorithm in nonlinear sliding mode control for twin rotor MIMO system
Get PDFThis paper proposes the design of a nonlinear sliding surface based on the principle of variable damping concept for 2-degree of freedom Twin Rotor Multiple input Multiple output System (2-dof TRMS). The implementation of the designed nonlinear sliding surface in real time is demonstrated. Super-twisting algorithm is applied in nonlinear sliding mode control. The nonlinear sliding surface enables the system trajectory to be highly robust and with the application of super-twisting algorithm in nonlinear sliding mode controller (SMC), the designed controller has minimized the problem of chattering considerably. The system is modeled in such a way that it includes all nonlinearities and coupling effects. A decoupler is designed to nullify the coupling effect. This scheme is capable of reducing both the settling time and peak overshoot simultaneously for 2-dof TRMS. The scheme also reduces the chattering. The proposed method is compared with the design using PID controller. The applicability of the designed nonlinear sliding surface and nonlinear SMC with super-twisting algorithm have been tested both in simulation and in real time. This research paper is mainly dealing with the modeling of Twin rotor MIMO system by including all nonlinearities and coupling effects, the decoupler design for 2-dof TRMS, the design of nonlinear sliding surface for 2-dof TRMS and application of super-twisting algorithm in nonlinear sliding mode control for 2-dof TRMS
Movable short-circuit technique to extract the relative permittivity of materials from a coaxial cell
Get PDFIn recent years, industrial applications have been based on the use of intrinsic material properties that improve designs, processes, qualities and product controls. To get to those intrinsic parameters, various appropriate techniques are required. In this paper, a new technique has been developed and presented. It essentially puts the emphasis on the dielectric relative permittivity extraction from the principle of a movable short-circuit through the coaxial transmission-line cell. This technique is aimed at drastically reducing the discontinuity impacts at the interface feed line (connector) and ideal line, solving the phase constant frequency limit, stopping the constraints bound to the higher mode propagations and improving the accuracy level when the frequency range has increased. The technique is based on the use of the sum of two different lengths of the cell by removing the first value of the phase constant in the frequency range of interest when it is negative. This new technique can be easily implemented; its focus is not on iterative principles, but on the use of the constant propagation of a Quasi-TEM mode of the transmission-line. The bio-food industry (semolina), environmental field (palm tree) and building trade (aquarium sand) were used to test the validity of the technique in 2-20 GHz
Study on applicability of end corrections of extended inlet and outlet of expansion chamber hydraulic noise suppressor
Get PDFAt present, a study on the end corrections of extended inlets and outlets of expansion chamber gas mufflers is relatively mature. However, such a research for an expansion chamber hydraulic suppressor has not been made yet. A coaxial and a non-coaxial expansion chamber configurations were introduced into hydraulic systems in this paper, and one-dimensional (1D) analytical approach was used to construct mathematical models of these structures and to verify it by experiments. After that, combined with the finite element method (FEM), researches on whether end corrections of the structures are applicable or not were studied
Numerical simulation and experimental analysis of magneto-mechanical behavior of anti-seismic active sandwich structure
Get PDFThis work focuses on the quasi-static behavior study for simply supported sandwich beams with aluminum faces and magnetorheological elastomer core subjected to three points bending subjected to a magneto-mechanical loading by numerical and experimental investigations. The mechanical properties of the magnetorheological elastomer core are measured experimentally and the mechanical behavior of the MRE was identified by the generalized Maxwell rheological model. Depending upon the adjustable properties of the beam, energy dissipation is by core shear. A systematic series of experiments and finite elements simulations have been performed in order to assess the static behavior of the beam. The results obtained show a significant influence of the magnetic field intensity on the flexural displacement of the beam
Damage identification research on beam structures by integrating multiple modal parameters
Get PDFA new damage identification method with a fusion index to locate the damage position and identify the damage extent of beam structures is presented by integrating the modal strain energy and natural frequency sensitivity. The modal strain energy, which is with the limitation on obtaining the damage extent, is adopted to locate the damage position with avoiding the interference of structure itself. The natural frequency sensitivity, which is with false detection and interference happening when solely used, is adopted for identifying the damage extent. In order to further improve the precision of the damage quantification, additional masses are added on the beam structure to obtain more information about the natural frequency sensitivity. Then, the fusion index for damage identification is established through combining the modal strain energy and the natural frequency sensitivity before and after adding masses on beam structures. The results obtained by finite element analysis and experimental tests show that the presented method can locate and quantify damages on beam structures in an accurate and convenient way