Influence of mobility completeness and source behavior on the robust-ness of Transfer Path Analysis and Source Characterization methods: A numerical study.

Structure borne noise is considered a major contribution to the noise generated inside aircrafts. In order to analyze it, engineering methods have been developed such as Transfer Path Analysis (TPA) and Source Characterisation (SC). These methods are based on active and passive properties of the source and the receiving structure being coupled or decoupled. The theoretical formulation requires mobility according to all Degrees Of Freedom (DOFs) and rotational DOFs represent a challenge for experimental application. To fulfill the mobility matrix, indirect method have been developed and specific sensors have been proposed, resulting in a more complex experimental set-up and an increase in measurement uncertainties. The necessity of assessing the full matrix completeness is thus still questionable. The robustness of these methods with respect to the matrix completeness and the source behavior is investigated numerically in this work. A numerical model has been developed to simulate vibrating sources with simple or complex vibratory behavior and to assess the mobility matrices for any completenesses. Velocity on the receiving structure is used as a target indicator. The influence of source behavior and completeness are discussed and the results show that the required mobility completeness depends on the source behavior.

Assessing the impact of case mobility: issues and recommendations from Greece

This paper is concerned with the assessment of future applications of CASE (Co-operative, Autonomous, Shared, and Electric) mobility—a term that is also taken to include the more traditionally known applications of ITS (Intelligent Transport Systems). It sets the objective of making such assessments more holistic and horizontal in nature because future CASE mobility applications will include many technologies and service concepts as an integrated whole serving specific mobility objective. Traditional evaluation methodologies will therefore have to be modified to account for this situation, and to this end, the paper focuses on assessing and adapting such “traditional” methodologies. It draws from the experience gained in Greece in the last decade when a substantial number of ITS applications were implemented and assessed, especially in the second largest urban area of the country, the city of Thessaloniki (part of the EU’s European Network of Living Labs). Four basic methodologies are selected: the use of KPIs (Key Performance Indicators), focused interviews, the CMME (CASE Mobility Matrix Evaluation), and the use of safety audits before and after the CASE mobility application. For the first three, the paper suggests specific indicators and/or content. It also gives an example of the use of CMME based on a use case from Thessaloniki. The contents and recommendations of this paper provide a better understanding of the emerging situation as regards CASE mobility applications and point to the need for establishing a timely and comprehensive CASE mobility evaluation framework at both national and European levels, for future implementations.

Algorithm for computing the connectivity in planar kinematic chains and its application

The number of synthesized kinematic chains usually is too large to evaluate individual characteristics of each chain. The concept of connectivity is useful to classify the kinematic chains. In this paper, an algorithm is developed to automatically compute the connectivity matrix in planar kinematic chains. The main work is to compute two intermediate parameters, namely the minimum mobility matrix and the minimum distance matrix. The algorithm is capable of dealing with both simple-jointed and multiple-jointed kinematic chains. The present work can be used to automatically determine kinematic chains satisfying the required connectivity constraint, and is helpful for the creative design of mechanisms. The practical application is illustrated by taking the face-shovel hydraulic excavator for instance.

Mathematical Model of COVID-19 Transmission Dynamics in South Korea: The Impacts of Travel Restrictions, Social Distancing, and Early Detection

The novel coronavirus disease (COVID-19) poses a severe threat to public health officials all around the world. The early COVID-19 outbreak in South Korea displayed significant spatial heterogeneity. The number of confirmed cases increased rapidly in the Daegu and Gyeongbuk (epicenter), whereas the spread was much slower in the rest of Korea. A two-patch mathematical model with a mobility matrix is developed to capture this significant spatial heterogeneity of COVID-19 outbreaks from 18 February to 24 March 2020. The mobility matrix is taken from the movement data provided by the Korea Transport Institute (KOTI). Some of the essential patch-specific parameters are estimated through cumulative confirmed cases, including the transmission rates and the basic reproduction numbers (local and global). Our simulations show that travel restrictions between the epicenter and the rest of Korea effectively prevented massive outbreaks in the rest of Korea. Furthermore, we explore the effectiveness of several additional strategies for the mitigation and suppression of Covid-19 spread in Korea, such as implementing social distancing and early diagnostic interventions.

Analysis of improved Nernst–Planck–Poisson models of compressible isothermal electrolytes

We consider an improved Nernst–Planck–Poisson model first proposed by Dreyer et al. in 2013 for compressible isothermal electrolytes in non-equilibrium. The elastic deformation of the medium, that induces an inherent coupling of mass and momentum transport, is taken into account. The model consists of convection–diffusion–reaction equations for the constituents of the mixture, of the Navier–Stokes equation for the barycentric velocity and of the Poisson equation for the electrical potential. Due to the principle of mass conservation, cross-diffusion phenomena must occur, and the mobility matrix (Onsager matrix) has a non-trivial kernel. In this paper, we establish the existence of a global-in-time weak solution, allowing for a general structure of the mobility tensor and for chemical reactions with fast nonlinear rates in the bulk and on the active boundary. We characterise the singular states of the system, showing that the chemical species can vanish only globally in space, and that this phenomenon must be concentrated in a compact set of measure zero in time.

Between Geography and Demography: Key Interdependencies and Exit Mechanisms for Covid-19

We develop a minimal compartmental model to analyze policies on mobility restriction in Italy during the Covid-19 outbreak. Our findings show that a premature lockdown barely shifts the epidemic in time: moreover, beyond a critical value of the lockdown strength, an epidemic that seems to be quelled fully recovers after lifting the restrictions. We investigate the effects on lockdown scenarios and exit strategies by introducing heterogeneities in the model. In particular, we consider Italian regions as separate administrative entities in which social interactions through different age classes occur. We find that, due to the sparsity of the mobility matrix, epidemics develop independently in different regions once the outbreak starts. Moreover, after the epidemics ha started, the influence of contacts with other regions becomes soon irrelevant. Sparsity might be responsible for the observed delays among different regions. Analogous arguments apply to the world/countries scenario. We also find that disregarding the structure of social contacts could lead to severe underestimation of the post-lockdown effects. Nevertheless, age class based strategies can help to mitigate rebound effects with milder strategies. Finally, we point out that these results can be generalized beyond this particular model by providing a description of the effects of key parameters on non-medical epidemic mitigation strategies.

3D closed-loop swimming at low Reynolds numbers

In this paper, the mobility matrix of helical microswimmers is investigated to compute the magnetic torque as a function of the angular velocities of the helical robot to achieve a 3D path following in closed-loop. Thus, the helical swimmer kinematics are expressed in the Serret–Frenet frame considering the weight of the robot and lateral disturbances using the compensation inclination and direction angles, respectively. A new chained formulation is used to design a stable controller. The approach is simple and quite general and can be used for different non-holonomic autonomous systems. The 3D path following is validated by presenting experimental results using a scaled-up helical microswimmer actuated magnetically. Different trajectories were tested: a spatial straight line, a helix trajectory, and an inclined sinusoidal trajectory. Several conditions have been tested experimentally, namely: different velocity profiles, compensation inclination angles, liquid viscosities, control gains and boundary effects, and their impact on the performance of the path following. To illustrate the robustness and accuracy of the visual servo control to disturbances presenting in the environment such as the magnetic field gradient and boundary effects, it is compared with the open-loop control. The results show the robustness of the controller and a submillimetric accuracy during the path following.

Model of mobility state of parts: The automation of feasibility test in disassembly sequence generation

Disassembly sequencing is a concurrent research subject in design for life-cycle. Many past and recent researches are made to give practical methods for disassembly sequencing. The problem of assembly information’s modeling is one of the important sub-problems of disassembly simulation. The problem includes connection determination, disassembly direction identification, and part mobility state definition. In the present paper, the authors propose a new representation model of disassembly directions, starting from geometric and assembly data of computer aid design models. This model is based on a mobility matrix definition for every part. This matrix is also called disassembly direction matrix. The model gives information about the mobility state of a part during disassembly sequencing by updating its mobility matrix. Mobility state data are used in a practical computing of disassembly sequence feasibility. In this paper, theoretical explication of this modeling is given and validated by computational results. In the validation section, the model is applied to a computer aid design mechanism using a selective disassembly.

Mobility Matrix of a Thin Circular Plate Carrying Concentrated Masses Based on Transverse Vibration Solution

When calculating the vibration or sound power of a vibration source, it is necessary to know the point mobility of the supporting structure. A new method is presented for the calculation of point mobility matrix of a thin circular plate with concentrated masses in this paper. Transverse vibration mode functions are worked out by utilizing the structural circumferential periodicity of the inertia excitation produced by the concentrated masses. The numerical vibratory results, taking the clamped case as an instance, are compared to the published ones to validate the method for ensuring the correctness of mobility solution. Point mobility matrix, including the driving and transfer point mobility, of the titled structure is computed based on the transverse vibration solution. After that, effect of the concentrated masses on the mechanical point mobility characteristics is analyzed.