Modelling Parametric Vibration of Gear-Pair Systems as a Tool for Aiding Gear Fault Diagnosis

The main components in gear vibration spectra are the tooth-meshing frequency and its harmonics, together with sideband structures due to modulation effects. Sideband structures can be used as an important diagnostic symptom for gear fault detection. The main objective of the present paper is to unravel amplitude modulation effects which are responsible for generating such sidebands. The parametrically excited vibration of a gear-pair system in mesh was investigated. A comparison between the model result and actual experimental data from a test rig was also presented. Some analytical expressions are derived to provide a logical explanation for ob-served phenomena. The modelling result can be used to predict sideband amplitude in presence of the distributed gear faults such as non-uniform tooth wear, pittings. It may serve as a tool for aiding the gear fault diagnosis

Dynamic force analysis of a six-link planar mechanism under consideration of friction at the joints

The dynamic analysis of mechanisms with joints friction is complex since the frictional force depends nonlinearly on the resultant reactive force between the two mating surfaces of the joint. In this paper a non-iterative approximate method is used for determining the joint reaction forces and the driving torque of mechanisms is considered. By using the computing program MATLAB the dynamic forces of a six-link planar mechanism are calculated with this method

On the compression softening effect of prestressed beams

The main objective of the present paper is to study the transverse vibration of the prestressed beams. The differential equation of the transverse vibration of the Euler-Bernoulli beam is developed, in which the initial axial strain in every cross section of the beam is taken into account, so that the initial normal stress is not equal to zero. We have proposed some formulae to determine the natural frequencies of the prestressed beam. The forced transverse vibration of the beam with a moving external force has been considered. From this it follows compression softening effect of prestressed beams. A detailed comparison between the calculating results for the prestressed and the non-prestressed beam is also presented

Complete shaking force and shaking moment balancing of spatial multibody systems with open kinematic chains

This paper deals with a solution for the problem of full shaking force and shaking moment balancing of spatial multi body systems with open kinematic chains. Firstly, the general conditions for complete dynamic balancing of spatial multibody systems are formulated. These include formulae for complete elimination of the resultant inertia force and inertia couple caused by all moving bodies. In the following example, the equations of complete shaking force and shaking moment balancing of a nine-bar direct drive manipulator are given

Impact of Frequency Shift on Nonlinear Compensation Using Optical Phase Conjugation for M-QAM Signals

Nonlinear compensation using optical phase conjugation (OPC) have been considered a promising technique to increase the reach of high-speed fiber-optic transmission systems. OPC-based nonlinear compensation employs an optical phase conjugation located at a middle of the fiber link to generate a complexed conjugated signal with respect the signal in the first half of the link for propagation in the second half. OPC technique assumes a symmetry for signal propagating in the first and second half to obtain a perfect nonlinear and chromatic dispersion. However, as most of practical OPC schemes are realized by nonlinear effects such as four-wave mixing or a combination of second-harmonic generation and difference frequency generation, the frequency shift induced by OPC affects the signal symmetrical requirement for nonlinear compensation because the chromatic dispersion is different for the first and second half transmissions. In this paper, we investigate the impact of frequency shift on the nonlinear compensation using OPC for high symbol rate, high level modulation format signals. This will be important to understand the tolerance of the OPC techniques against such a practical condition for actual system implementations

An efficient numerical procedure for calculating periodic vibrations of elastic mechanisms

This paper proposes a numerical procedure based on the well-known Newmark integration method to determine initial conditions for the periodic solution of a system of linear differential equations with time-periodic coefficients. Based on this, steady-state periodic vibrations of mechanisms with elastic elements governed by linearized differential equations with time-periodic coefficients can be conveniently calculated. The proposed procedure is demonstrated by a dynamic model of a planar four-bar mechanism with the flexible coupler

Economic Performance of offshore Fisheries - the Case of Trawling and Purse Seining in Ben Tre Province, Vietnam

Ben Tre, located on the Tien Delta Triangle--with a coastline of 65 km and the 20,000 km2 Exclusive Economic Zone--is one of the Mekong Delta’s 13 provinces. Given both its vast access to coastline and the EEZ, fisheries is one of the Ben Tre’s key economic sectors. This study specifies some factors affecting revenues of trawling and light purse seining vessels by using a multivariate regression model. Data was collected through direct and intensive interviews with vessel owners and fishermen. The results seem to demonstrate that single boat trawlers achieved the highest return on investment, followed by pairtrawlers and light purse seiners, respectively. Factors including the vessel length, engine capacity, captain’s experience, fishing gears, and vessel age have considerable effects on revenues of single-boat trawlers and lighted purse seiners. Based on these findings, this study provides some recommendations to offshore fisheries in Ben Tre province, Vietnam

Inverse kinematic and dynamic analysis of redundant measuring manipulator BKHN-MCX-04

This paper deals with the problem of inverse kinematics and dynamics of a measuring manipulator with kinematic redundancy which was designed and manufactured at Hanoi University of Technology for measuring the geometric tolerance of surfaces of machining components. A comparison between the calculation result and the experimental measurement is also presented

From complement to complosome in non‐alcoholic fatty liver disease: when location matters

Non‐alcoholic fatty liver disease (NAFLD) is a growing public health threat and becoming the leading cause of liver transplantation. Nevertheless, no approved specific treatment is currently available for NAFLD. The pathogenesis of NAFLD is multifaceted and not yet fully understood. Accumulating evidence suggests a significant role of the complement system in the development and progression of NAFLD. Here, we provide an overview of the complement system, incorporating the novel concept of complosome, and summarise the up‐to‐date evidence elucidating the association between complement dysregulation and the pathogenesis of NAFLD. In this process, the extracellular complement system is activated through various pathways, thereby directly contributing to, or working together with other immune cells in the disease development and progression. We also introduce the complosome and assess the evidence that implicates its potential influence in NAFLD through its direct impact on hepatocytes or non‐parenchymal liver cells. Additionally, we expound upon how complement system and the complosome may exert their effects in relation with hepatic zonation in NAFLD. Furthermore, we discuss the potential therapeutic implications of targeting the complement system, extracellularly and intracellularly, for NAFLD treatment. Finally, we present future perspectives towards a better understanding of the complement system's contribution to NAFLD