Power flow through multidimensional compliant joints using mobility and modal approaches

Cairo was recorded the second noisiest city in 2018. Noise pollution can affect badly on human health and daily activities. However, Egypt suffered from limitation of controlling noise’s research. Planners and designers should be considering how controlling noise propagation at urban planning through determine the relation between urban morphology and noise paths. Here comes the role of this research, it aims to investigate the effect of some urban morphology parameters on noise propagations at selected case study. It was in Maadi, Cairo. The research workflow contained four stages. Firstly, defining urban morphology and its relation with noise propagations. Secondly, researchers visited the site to collate data and observe the traffic flow on weekdays and weekends during rush hour. Then simulate the selected case study on Predictor - LimA software to predict noise levels and create noise maps. Third, analysis noise maps to determine noise propagations characteries. Finally, link urban morphology parameters as buildings factors, road networks, landuses managements and human behaviours with noise separations. The results pointed out the most essential parameters affecting noise propagation and elaborated the direct relation between noise propagations and urban morphology to determine role of planners, governments, and vehicles owners to mitigate noise propagations.

Marine shafting system is the indispensable component of a ship power plant. As the "heart" of the ship, marine power plant provides propulsion and secondary energy for normal navigation, operations, combats, and other needs of the ship it. Compared with the classical vibration analysis and the oil analysis theory, the method based on power flow is easier to explain the energy distribution and transmission mechanism. Proposed a computing method for shaft system energy distribution of large ship propulsion shafting under torsional vibration, axial vibration, and whirling vibration and coupled vibration based on the theory of the power flow in the paper. According to the theory of power flow, the dynamic equation, constitutive equation, the relationship between displacement and strain, the relationship between displacement and velocity, and boundary conditions of a typical bar under the action of tension and compression, torsion and bending is provided. Combining with the bond graph theory, the bond graph model of the 8530 TEU container ship propulsion shafting is established. Based on the theories above, the power flow calculation formula of the shafting under longitudinal vibration, torsional vibration, whirling vibration and coupled vibration of different boundary conditions is deduced.

The fluctuations of the global parameters of an ultrafast frequency comb are analyzed using a novel measurement scheme and a modal representation. The propagation of excess noise added to the pump is also investigated.

In Brazil, the demand for the acquisition and installation of photovoltaic systems has grown exponentially and, with that, the importance of studies considering their effects on the distribution grids power flow also grows. Due to the intermittent nature of photovoltaic generation, it is important to approach the analysis in a discrete way, taking into account the changes in the power injections during the studied period. Thus, this article presents the daily analysis of the effects of photovoltaic generation on the distribution system through the computational implementation of a discretized power flow routine. The implemented routine can also analyze the effects of other distributed generations on distribution grids, whether those grids are radial or not. The study results show positive impacts on the voltage quality obtained by the photovoltaic systems insertion, for a well-known distribution test system.

High density high switching frequency power converter conducted EMC had been analysed, modelling the noise source and noise path, while providing accurate conducted EMC noise limits comparable to accredited noise measurements up to 100 MHz. The military specified DC-DC converters are applicable, spanning from 100 W handheld power managers up to 2 kW DC-DC battery chargers. The Step-Down converter, Step-Up converter and their multi-phase derivatives were analysed and modelled. Some techniques to reduce conducted EMI, such as phase dithering, were also analysed. Circuit layout high frequency effects as well as high frequency impedances of the power components were characterised. At first, a trapezoidal noise source and lumped element noise path model was adopted, showing the high frequency limitations of this technique. A mathematical model was also presented. Thereafter, a high frequency lumped element model including switching elements, was created by using equivalent impedance circuits obtained by measurement from an impedance analyser performed on individual components and traces. A time domain transient model circuit analysis was investigated to represent noncompliance circuit noise as measured with a LISN. Various affordable software packages were evaluated to be considered as a high frequency conducted EMC tool, noting accuracy and ease of use. The accuracy of these modelling tools was compared to accredited measurements. A compact LISN was manufactured and a measurement bench was set up and calibrated against an accredited LAB to perform these practical verification tests. Noise signals were recorded in a simultaneous digital manner so as to be able to perform a detailed post analysis as well as diagnostic calculations, such as common mode and differential mode separation, calibrated with an EMC ETS-Lindgren current probe. Good and workable model accuracies were achieved with the basic Step-Up and Step-Down circuits over the conducted emission frequency band and beyond. Prominent noise effects occur up to this frequency when high density and high switching speed converters are analysed.

A hybrid analytical/numerical conducted an electromagnetic interference (EMI) modeling approach, which adopts both numerical method and analytical method, is proposed in this paper. In this model, the noise source is calculated directly with the original data from oscilloscopes. The noise path at different operating status is extracted from the original converter topology and its analytical expression is then derived. Also, according to the EMI receiver detector mode, the algorithm of the EMI receiver is proposed in this paper. Peak (PK), average (AV), and quasipeak (QP) values of the EMI can then be calculated to analyze the impact of each relevant component. The analytical method is provided to carry out PK, AV, and QP simulations accurately and fast. The simulation and experimental results for common mode leakage currents validate this EMI model. Furthermore, two analysis examples are given to illustrate how this model is applied for engineers.

Applications of GIFTS III to structural engineering problems

A method based on an energetic approach has been developed to optimize vibration isolation at low frequencies. The aim is to minimize the dynamic response of a main structure (car body, rocket core…) subjected to interface forces generated by connected substructures (engine, booster…). At first, using a direct approach, an eigenvalue problem is formulated by minimizing the average dissipated power flow resulting from external load work. In order to keep a strong mechanical meaning, a modal approach has been developed to obtain an analytical expression of these eigensolutions. Then, the energy introduced in the structure at a given frequency is characterized by projecting the junction forces on the previously calculated basis. Both approaches have been numerically studied on an academic discrete system. The method has then been applied to a simple multimode coupled structure.KeywordsPower FlowOptimal Power FlowInterface ForceModal Assurance CriterionVibration TransmissionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Helicopter gearbox support struts are structural members designed to take large compressive and tensile mechanical loads. They also act as vibration transmission paths connecting the major noise and vibration generators of the main rotor and gearbox to the fuselage and cabin. In this paper the mechanisms of vibration transmission through these struts are examined. The differences between the low frequency behavior that is important in the transmission of the rotor vibrations, and the high frequency behavior that is important in the transmission of gear noise are discussed. A flexible element is introduced in series with the strut, and the limitations of this simple passive measure in attenuating longitudinal and flexural vibrations are highlighted. The analysis shows that there is a difference in the mechanisms of vibration transmission between low and high frequencies, and that there are difficulties in applying effective passive vibration isolation measures to this system.

Power analysis of two-dof epicyclic gear transmission and experimental validation

ENERGY DENSITY EQUATIONS AND POWER FLOW IN STRUCTURES

Overview of Noise Source and Transmission Mechanisms by Type of Compressor

Development of a rating procedure for impact noise transmission through walls

The IT industry developed in the United States and was then transmitted to Japan and further to Taiwan, South Korea, and China. Adopting the ‘Flying Geese development’ model as its analytical framework, this paper examines the development of the IT industry and the changes in the exports and imports of the five economies. This paper estimated comparable time series data on the production, export, and import of IT goods and IT services separately for the five economies. It found that the US has already reached the reverse import stage for IT goods while East Asian economies are at the export stage. Furthermore, only the US exports IT services to the other four. It also provides an econometric analysis of the mechanism of international transmission of the IT industry. This paper also takes into account foreign direct investment, OEM, and mobility of IT specialists into the analysis and refers to the possibility of leapfrogging.

Compliant joints are widely used in the structural design of 3D-printed continuum robots as their monolithic structure can greatly simplify the assembly process. However, some highly flexible compliant joints, such as the leaf-spring joints, still suffer from unstable rotation centers when interfered by external forces, which greatly reduces the motion stability of the constructed continuum robots. To cope with this problem, we propose a topology-optimization-based method in this paper to achieve efficient structural design of the complaint joints in continuum robots. With our method, the rotation stability of compliant joints can be improved without causing stress concentration problems. Experiments were also carried out to evaluate the bending performance of the 3D-printed continuum robots equipped with optimized compliant joints. Results demonstrated that, compared to continuum robots with the conventional leaf-spring joints, the optimized robots showed much less twisting deformation caused by out-of-plane loads, which exhibited the high rotation stability of the optimized joints. In future work, the proposed method can be further developed to achieve optimization of other mechanical properties of the compliant joints in continuum robots.