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Investigation of the load’s variation rate effect on the efforts and moment intensity factors values in a cylindrical shell with a longitudinal crack
Get PDFThe limit equilibrium of a cylindrical shell with a longitudinal crack under the action of a time-varying load is considered. Dynamic coefficients of intensity of forces and moments near the tips of cracks in shells made of steel, copper, and cast iron are calculated. The influence of the mechanical characteristics of the shell material and the rate of load variation on their behavior is analyzed
Research on the launch dynamics characteristics of Gatling guns
Get PDFThe advantages of the Gatling gun, such as high firing rate, large interception range, and wide range of use, have made it an indispensable weapon system in the defense field. At present, the analysis of shooting vibration of the Gatling gun is a challenging key point in related research. In response to the lack of research on the shooting vibration characteristics of Gatling gun weapon systems, this paper carries out a numerical simulation study of the launch dynamic characteristics of the Gatling gun based on the nonlinear launch dynamics theory of artillery. The results of muzzle disturbance under continuous shooting conditions are obtained, and the shooting density of Gatling guns under different situations is analyzed and compared based on the method of shooting density calculation. This research fills the gap in the study of launch dynamics of Gatling weapons, providing design references and theoretical support for the overall design and performance verification of Gatling guns
Feedback force and velocity control of an arm exoskeleton to assist user motion
Get PDFThe paper proposes a feedback force and velocity control of an arm exoskeleton to assist user motion. The original published control so-called feedback hybrid force and position control was based on the force and position control and was designed to assist user motion. This original control was successful at providing assist for the user’s arm. This article presents an improved control scheme called the feedback force and velocity control. The proposed control is designed to regulate the velocities of joints of the exoskeleton and the feedback forces on links to assist user motion. The design and optimization of the feedback force and velocity control are realized by the Balancing Composite Motion Optimization (BCMO). The numerical method is realized in the paper to show that the proposed control is better than the original control in terms of less oscillation and fast response
An assembled hot wire anemometer design
Get PDFThe hot wire anemometer is a widely utilized device in laboratory settings for measuring air speed. This paper investigates the relationship between air speed and hot wire temperature across various air speed ranges, employing the theory of thermal equilibrium. We designed a measurement circuit and hot wire shape based on the hot wire anemometer principle, and validated the linear relationship between current and temperature at different air speeds within an adjustable air speed field. The measured current serves as a representative of air speed. Experimental validation of the designed hot wire anemometer demonstrates accurate measurement results that align with theoretical values across different air speed ranges. Finally, we determined the sensitivity of the anemometer in various measurement ranges, considering the instrument's uncertainty and measurement formula
Editor’s Letter. Malocclusion treatment tools evolution – mechanical vibration synergism. What is the current status of knowledge? Part II
Get PDFDeterminated area (DA) treatment goal when treating malocclusions with jaw functional orthopedics (JFO): Contribution to scientific evidence
Get PDFOne of the goals of malocclusion treatment with Jaw Functional Orthopedics (JFO) is to obtain touch of the inferior incisors against the superior incisors in Determinate Area (DA). It is postulated that this touch would bring better stimuli and consequently faster results. Surface electromyographic study of the muscles was performed in Masseter, Temporal and suprahyoid muscles bilaterally from 159 patients undergoing malocclusion treatment with functional orthopedic appliances (FOA). To record muscle electric activity were used a conditioning signal module from Lynx Electronics Ltda with 8 channels, model EMG1000; software AqDAnalysis 4,18 from Lynx Electronics Ltda.; Software Lynx BioInspector 1,8r; passive surface electrodes (Ag/AgCl) from Noraxon Dual Electrodes (USA); dischargeable reference electrodes Kendall Meditrace (Ag/AgCl) – Canada. Frequency calibration was 2000 Hz, with 2048 sample by channel and time 1,024 seconds, and filters regulation was 20 Hz and 1000 Hz. The results found prove that there is a better electromyographic activity (bilaterally balanced) of the studied muscles when there is touch on DA. Conclusion. Touch in DA improves the neuromuscular response of patients treated with JFO. sEMG is a trustable tool to analyze masticatory muscles function for Diagnosis, Treatment and evaluation post treatment/gained objective
Two-stroke engine with constant crank angular velocity
Get PDFThe work is devoted to the dynamics of a two-stroke engine. The engine used in sea vessels is considered. A new scheme of the crank mechanism of a two-stroke engine is proposed. An elastic hinge with a given angular characteristic (dependence of the restoring moment on the angle of rotation of the crank) is supposed to be installed between the strut and the crank. The work shows that with certain parameters of the hinge it is possible to obtain a constant angular velocity of the crank for any angle of rotation of the crank. Currently, flywheel inertia can account for up to 80 percent of all moving parts in an engine. Since the mass of engines is large, eliminating the flywheel from the engine design or reducing its mass may be a promising direction in the production of two-stroke engines. The proposed hinge is a structure in which an elastic element (spring or air spring) moves between circular guides of a calculated shape, resulting in a given hinge characteristic. In this work, an air spring was chosen as the elastic element of the hinge, since in this case it becomes possible to change the characteristics of the hinge by changing the pressure in the air spring. The shape of the guides is such that when adding the characteristic of an elastic hinge to the existing characteristic of the engine, an “ideal” characteristic of the considered engine with an elastic hinge is obtained, at which the angular velocity of the crank will be constant. When the angular velocity of the crank changes, a different characteristic of the hinge is required. In progress it is supposed to change the characteristics of the elastic hinge by changing the pressure in the air spring, which is the elastic element of the hinge. It turned out that by changing the initial excess pressure in the air spring it is possible to compensate for the change in the characteristics of the hinge required for the angular velocity of the crank to remain constant at any angle of rotation when its value changes. The results of these studies can be used both in the production of two-stroke engines and for any two-stroke engines
Investigation of the propagation characteristics of train-induced vibration at Guangzhou Baiyun railway station
Get PDFIn densely populated cities, the increasing popularity of railways and urban rail transit interchange hubs has led to the extensive use of land resources and raised concerns about the environment, especially the inevitable noise and vibration impact. This study aims to identify the propagation patterns of roof structure vibrations in railway complexes through experimental research, with the premise of maintaining normal train operation and safety, in order to lay a foundation for developing vibration mitigation strategies and optimizing functional layout. The results found that the train-induced vibrations are strongest at track level, but decrease as they move vertically and horizontally. Vibrations from passing trains are most noticeable within a single floor slab and beams, with minimal transmission at the base of columns
Determination of kinematic and dynamic characteristics of a reversible vibratory conveyor with an electromagnetic drive
Get PDFThe paper considers the design parameters that must be provided during the practical implementation of small-sized reversible vibratory conveyors with an electromagnetic drive. The proposed conveyor is developed on the basis of a classical two-mass oscillatory system. Two oscillating masses are connected by symmetrically assembled round-shaped rods. In order to avoid angular (torsional) oscillations of the vibratory conveyor, the geometrical centers of mass and stiffness of the spring system are aligned at the same point. The analysis of kinematic characteristics is performed by means of numerical solving of the system of nonlinear Lagrange-Maxwell differential equations. The influence of the phase shift angle between the electromagnetic excitation of horizontal and vertical oscillations on the trajectories of the mass center of the conveying member is analyzed. The first two frequencies and forms of natural oscillations of the vibratory conveyor are determined for estimating its dynamic characteristics. The novelty of this study lies in the development of a new design of a vibratory conveyor with a controllable independent electromagnetic drive that provides the conveying reversibility and efficiency
Secure metric dimension of new classes of graphs
Get PDFThe metric representation of a vertex v of a graph G is a finite vector representing distances of v with respect to vertices of some ordered subset S⊆V (G). If no suitable subset of S provides separate representations for each vertex of V(G), then the set S is referred to as a minimal resolving set. The metric dimension of G is the cardinality of the smallest (with respect to its cardinality) minimal resolving set. A resolving set S is secure if for any v∈V–S, there exists x∈S such that (S–{x})∪{v} is a resolving set. For various classes of graphs, the value of the secure resolving number is determined and defined. The secure metric dimension of the graph classes is being studied in this work. The results show that different graph families have different metric dimensions