Long Term Ride Dynamics of Large Order Vehicle Models With Nonlinear Suspension

2005 ◽  
Author(s):  
P. Metallidis ◽  
I. Stavrakis ◽  
G. Verros ◽  
S. Natsiavas
Keyword(s):  
Nonlinear Models ◽  
Equations Of Motion ◽  
Original System ◽  
Response Spectra ◽  
Computationally Efficient ◽  
Large Order ◽  
Composite Models ◽  
Road Excitation ◽  
Set Up

This work presents a systematic methodology for investigating long term ride dynamics of large order vehicle models in a computationally efficient way. First, the equations of motion for each of the main structural components of the vehicle are set up by applying finite element techniques. The resulting composite models possess strongly nonlinear characteristics and as their order increases the existing numerical methodologies for a systematic determination of their dynamics become inefficient to apply. Therefore, the first step of the present methodology is to reduce the dimensions of the original system by applying a suitable component mode synthesis approach. Subsequently, this allows the application of appropriate numerical methodologies for predicting response spectra of the nonlinear models to periodic road excitation. Results obtained by direct integration of the equations of motion are also presented. The accuracy and validity of the applied methodology is verified by comparison with results obtained for the original models. The frequency ranges examined are useful for studies referring to both ride and acoustics response of the vehicle.

Ride Dynamics of Nonlinear Vehicle Models Using Component Mode Synthesis

2002 ◽  
Vol 124 (3) ◽  
pp. 427-434 ◽  
Author(s):  
G. Verros ◽  
S. Natsiavas
Keyword(s):  
Nonlinear Models ◽  
Equations Of Motion ◽  
Original System ◽  
Response Spectra ◽  
Component Mode Synthesis ◽  
Computationally Efficient ◽  
Strongly Nonlinear ◽  
Shock Absorbers ◽  
Road Excitation ◽  
Set Up

A general methodology is presented for investigating ride dynamics of large order vehicle models in a systematic and computationally efficient way. First, the equations of motion of representative vehicle models are set up by applying classical finite element techniques. In the simplest version of these models, the important system parameters are assumed to be constant, leading to linear formulations. Then, more accurate and involved models are examined by including typical nonlinearities in the tires and the shock absorbers of the vehicle suspension. Also, emphasis is placed on taking into account the possibility of temporary separation of a wheel from the ground. These models are strongly nonlinear and as their order increases the existing numerical methodologies for a systematic determination of their dynamics become inefficient to apply. Therefore, the first step of the present methodology is to reduce the dimensions of the original system by applying a component mode synthesis approach. Subsequently, this allows the application of appropriate numerical methodologies for predicting response spectra of the nonlinear models to periodic road excitations. Finally, results obtained by direct integration of the equations of motion are also presented for transient road excitation. In all cases, the accuracy and validity of the applied methodology is verified by comparison with results obtained for the original models.

Periodic Steady State Response of Complex Vehicle Models Using Multi-Level Substructuring

2007 ◽  
Author(s):  
I. Stavrakis ◽  
C. Theodosiou ◽  
S. Natsiavas
Keyword(s):  
Nonlinear Models ◽  
Equations Of Motion ◽  
Response Spectra ◽  
Computationally Efficient ◽  
Sparsity Pattern ◽  
Strongly Nonlinear ◽  
Road Excitation ◽  
Multi Level ◽  
Set Up ◽  
Coordinate Reduction

A systematic methodology is presented for investigating long term ride dynamics of large order vehicle models in a computationally efficient way. First, the equations of motion for each of the main structural components of the vehicle are set up by applying the finite element method. As a consequence of the geometric complexity of these components, the number of the resulting equations is so high that the classical coordinate reduction methodologies become numerically ineffective to apply. In addition, the composite model possesses strongly nonlinear characteristics. However, the method applied overcomes some of these difficulties by imposing a multi-level substructuring procedure, based on the sparsity pattern of the stiffness matrix. In this way, the number of the equations of motion of the complete system is substantially reduced. Subsequently, this allows the application of appropriate numerical methodologies for predicting response spectra of the nonlinear models to periodic road excitation. Results obtained by direct integration of the equations of motion are also presented. Where possible, the accuracy and validity of the applied methodology is verified by comparison with results obtained for the original models.

Dynamics of Semi-Actively Controlled Vehicles Involving Wheel Hop

2001 ◽  
Author(s):  
G. Verros ◽  
S. Natsiavas
Keyword(s):  
Control Strategy ◽  
Nonlinear Models ◽  
Control Strategies ◽  
Damping Ratio ◽  
Equations Of Motion ◽  
Response Spectra ◽  
Shock Absorbers ◽  
Road Excitation ◽  
Active Control Strategy ◽  
Synthesis Approach

Abstract The present study investigates dynamic response of vehicle models, subjected to road excitation. In these models, a semi-active control strategy is applied on the suspension dampers, which is based on a switch of their damping coefficient between different values, so that the resulting system approximates the performance of a vehicle involving sky-hook damping. An alternative control strategy is also applied, which is passive and is based on selecting a different damping ratio when the wheel velocity relative to the car body is positive or negative. Both of these control strategies lead to oscillator models with parameter discontinuities. Similar terms are also introduced into the equations of motion by considering wheel hop phenomena, where a vehicle wheel leaves the ground temporarily. First, simple quarter-car models are examined but the analysis is also applied to more complicated models. For these models, their dimensions are reduced substantially by applying a component mode synthesis approach. Subsequently, this allows the efficient application of appropriate methodologies for predicting response spectra of the nonlinear models to periodic road excitation. Finally, results obtained by direct integration of the equations of motion are also presented for transient road excitation. In all cases, the results are compared to those obtained for vehicles with suspensions including passive shock absorbers. Moreover, special consideration is given to cases where wheel hop is possible to occur.

scholarly journals Effects of disk tillage on soil condition, crop yield and weed infestation

2011 ◽  
Vol 48 (No. 1) ◽  
pp. 20-26
Author(s):  
M. Birkás ◽  
T. Szalai ◽  
C. Gyuricza ◽  
M. Gecse ◽  
K. Bordás
Keyword(s):  
Winter Wheat ◽  
Crop Yield ◽  
Field Experiments ◽  
Soil Layer ◽  
Soil Condition ◽  
Perennial Weeds ◽  
Weed Infestation ◽  
Set Up ◽  
Different Levels

This research was instigated by the fact that during the last decade annually repeated shallow disk tillage on the same field became frequent practice in Hungary. In order to study the changes of soil condition associated with disk tillage and to assess it is consequences, long-term tillage field experiments with different levels of nutrients were set up in 1991 (A) and in 1994 (B) on Chromic Luvisol at Gödöllö. The effects of disk tillage (D) and disk tillage combined with loosening (LD) on soil condition, on yield of maize and winter wheat, and on weed infestation were examined. The evaluation of soil condition measured by cone index and bulk density indicated that use of disking annually resulted in a dense soil layer below the disking depth (diskpan-compaction). It was found, that soil condition deteriorated by diskpan-compaction decreased the yield of maize significantly by 20 and 42% (w/w), and that of wheat by 13 and 15% (w/w) when compared to soils with no diskpan-compaction. Averaged over seven years, and three fertilizer levels, the cover % of the total, grass and perennial weeds on loosened soils were 73, 69 and 65% of soils contained diskpan-compaction.

scholarly journals Spectrum Based Power Management for Congested IoT Networks

Sensors ◽  
2021 ◽  
Vol 21 (8) ◽  
pp. 2681
Author(s):  
Kedir Mamo Besher ◽  
Juan Ivan Nieto-Hipolito ◽  
Raymundo Buenrostro-Mariscal ◽  
Mohammed Zamshed Ali
Keyword(s):  
Power Management ◽  
Network Performance ◽  
Channel Allocation ◽  
Battery Life ◽  
Packet Routing ◽  
Data Packets ◽  
Increasing Demand ◽  
Iot Devices ◽  
Set Up

With constantly increasing demand in connected society Internet of Things (IoT) network is frequently becoming congested. IoT sensor devices lose more power while transmitting data through congested IoT networks. Currently, in most scenarios, the distributed IoT devices in use have no effective spectrum based power management, and have no guarantee of a long term battery life while transmitting data through congested IoT networks. This puts user information at risk, which could lead to loss of important information in communication. In this paper, we studied the extra power consumed due to retransmission of IoT data packet and bad communication channel management in a congested IoT network. We propose a spectrum based power management solution that scans channel conditions when needed and utilizes the lowest congested channel for IoT packet routing. It also effectively measured power consumed in idle, connected, paging and synchronization status of a standard IoT device in a congested IoT network. In our proposed solution, a Freescale Freedom Development Board (FREDEVPLA) is used for managing channel related parameters. While supervising the congestion level and coordinating channel allocation at the FREDEVPLA level, our system configures MAC and Physical layer of IoT devices such that it provides the outstanding power utilization based on the operating network in connected mode compared to the basic IoT standard. A model has been set up and tested using freescale launchpads. Test data show that battery life of IoT devices using proposed spectrum based power management increases by at least 30% more than non-spectrum based power management methods embedded within IoT devices itself. Finally, we compared our results with the basic IoT standard, IEEE802.15.4. Furthermore, the proposed system saves lot of memory for IoT devices, improves overall IoT network performance, and above all, decrease the risk of losing data packets in communication. The detail analysis in this paper also opens up multiple avenues for further research in future use of channel scanning by FREDEVPLA board.

scholarly journals "Communist" dispossession meets "reactionary" resistance

Focaal ◽  
2009 ◽  
Vol 2009 (54) ◽  
pp. 89-96 ◽  
Author(s):  
Projit Bihari Mukharji
Keyword(s):  
Communist Party ◽  
West Bengal ◽  
Present Situation ◽  
The State ◽  
Political Subjectivity ◽  
Self Reflection ◽  
Term Change ◽  
Communist Government ◽  
Set Up

The reflections in this article were instigated by the repeated and brutal clashes since 2007 between peasants and the state government’s militias—both official and unofficial—over the issue of industrialization. A communist government engaging peasants violently in order to acquire and transfer their lands to big business houses to set up capitalist enterprises seemed dramatically ironic. De- spite the presence of many immediate causes for the conflict, subtle long-term change to the nature of communist politics in the state was also responsible for the present situation. This article identifies two trends that, though significant, are by themselves not enough to explain what is happening in West Bengal today. First, the growth of a culture of governance where the Communist Party actively seeks to manage rather than politicize social conflicts; second, the recasting of radical political subjectivity as a matter of identity rather than an instigation for critical self-reflection and self-transformation.

scholarly journals Long-term field fertilization experiment with energy willow (Salix sp.) − Elemental composition and chlorophyll fluorescence in the leaves

2018 ◽  
Vol 67 (1) ◽  
pp. 91-103
Author(s):  
László Simon ◽  
Marianna Makádi ◽  
György Vincze ◽  
Zsuzsanna Uri ◽  
Katalin Irinyiné Oláh ◽  
...  
Keyword(s):  
Chlorophyll Fluorescence ◽  
Energy Crop ◽  
Municipal Sewage ◽  
Municipal Sewage Sludge ◽  
Fertilization Experiment ◽  
Nitrogen Concentrations ◽  
Set Up ◽  
Leaf Chlorophyll Fluorescence ◽  
Term Field

A small-plot long-term field fertilization experiment was set up in 2011 with willow (Salix triandra x Salix viminalis ’Inger’) grown as an energy crop in Nyíregyháza, Hungary. The brown forest soil was treated three times (in June 2011, May 2013, May 2016) with municipal biocompost (MBC), municipal sewage sludge compost (MSSC) or willow ash (WA), and twice (June 2011, May 2013) with rhyolite tuff (RT). In late May – early June 2016 urea (U) and sulphuric urea (SU) fertilizers were also applied to the soil as top-dressing (TD). These fertilizers and amendments were also applied to the soil in 2016 in the combinations; MBC+SU, RT+SU, WA+SU and MSSC+WA. All the treatments were repeated four times. In July 2016 the highest nitrogen concentrations in willow leaves were measured in the U (3.47 m/m%) and SU (3.01 m/m%) treatments, and these values were significantly higher than the control (2.46 m/m%). An excess of nitrogen considerably reduced the Zn uptake of the leaves, with values of 39.5 μg g-1 in the U treatment, 53.4 μg g-1 in the SU treatment, and 63.5 μg g-1 in the control. All other amendments or TDs, except for WA, enhanced the specific potassium concentrations in willow leaves compared to the control. No significant quantities of toxic elements (As, Ba, Cd, Pb) were transported from soil amendments or TDs to the willow leaves. In July 2016 the most intensive leaf chlorophyll fluorescence was observed in the MSSC and MSSC+WA treatments.

scholarly journals 162 An Examination of Scar Modelling and Assessment Methods for the Evaluation of Scar Treatments

2021 ◽  
Vol 108 (Supplement_2) ◽  
Author(s):  
R Mistry
Keyword(s):  
Assessment Tools ◽  
Randomised Control Trial ◽  
Silicone Gel ◽  
Scar Assessment ◽  
Significant Difference ◽  
Gel Treatment ◽  
Current Assessment ◽  
Set Up ◽  
Silicone Gel Sheeting

Abstract Introduction Scarring is the final common pathway for healing within the skin. Scars can be itchy, painful, tight, and disfiguring. Despite advances in surgery there is currently no reliably effective treatment for reducing or preventing scarring. The primary aim of this research is to assess the currently available models for scarring and evaluate/further develop the utility of current assessment tools, in an effort to design a pilot randomised control trial (RCT) for silicone gel treatment of scars. Method A systematic review of scar models in humans and animals. Examination of currently used subjective and objective scar assessment tools in a plastic surgery scar clinic. A retrospective cohort study assessing long-term scar outcomes in paediatric burn patients. Results Limitations and drawbacks of many existing methods to assess scar treatments were found. No statistically significant difference in long-term scarring outcomes was found between paediatric burns patients treated surgically versus conservatively. A RCT for silicone gel sheeting in the treatment of scars was set up and successful in recruitment. Conclusions Here, we have demonstrated difficulties in establishing a scientific scar treatment model; and created a pilot study that will help to provide high-quality evidence for the efficacy of silicone gel sheeting as a treatment for scars.

scholarly journals Acceptance of a Symptom-Based Approach for COVID-19 rtRT-PCR Testing to Conserve Resources in a Lower Middle-Income Setting

2021 ◽  
Vol 12 ◽  
pp. 215013272098771
Author(s):  
S. M. Rashed Ul Islam ◽  
Tahmina Akther ◽  
Md. Abdullah Omar Nasif ◽  
Sharmin Sultana ◽  
Saif Ullah Munshi
Keyword(s):  
Primary Method ◽  
Chain Reaction ◽  
Middle Income ◽  
Clinical Recovery ◽  
Clinical Presentations ◽  
Long Time ◽  
Nasopharyngeal Secretion ◽  
Polymerase Chain ◽  
Set Up

SARS-CoV-2 initially emerged in Wuhan, China in late 2019. It has since been recognized as a pandemic and has led to great social and economic disruption globally. The Reverse Transcriptase Real-Time Polymerase Chain Reaction (rtRT-PCR) has become the primary method for COVID-19 testing worldwide. The method requires a specialized laboratory set up. Long-term persistence of SARS-CoV-2 RNA in nasopharyngeal secretion after full clinical recovery of the patient is regularly observed nowadays. This forces the patients to spend a longer period in isolation and test repeatedly to obtain evidence of viral clearance. Repeated COVID-19 testing in asymptomatic or mildly symptomatic cases often leads to extra workload for laboratories that are already struggling with a high specimen turnover. Here, we present 5 purposively selected cases with different patterns of clinical presentations in which nasopharyngeal shedding of SARS-CoV-2 RNA was observed in patients for a long time. From these case studies, we emphasized the adoption of a symptom-based approach for discontinuing transmission-based precautions over a test-based strategy to reduce the time spent by asymptomatic and mildly symptomatic COVID-19 patients in isolation. A symptom-based approach will also help reduce laboratory burden for COVID-19 testing as well as conserve valuable resources and supplies utilized for rtRT-PCR testing in an emerging lower-middle-income setting. Most importantly, it will also make room for critically ill COVID-19 patients to visit or avail COVID-19 testing at their convenience.

A Very Simple Method to Calculate the (Positive) Largest Lyapunov Exponent Using Interval Extensions

2016 ◽  
Vol 26 (13) ◽  
pp. 1650226 ◽  
Author(s):  
Eduardo M. A. M. Mendes ◽  
Erivelton G. Nepomuceno
Keyword(s):  
Lyapunov Exponent ◽  
Lower Bound ◽  
Equations Of Motion ◽  
Original System ◽  
Glass System ◽  
Largest Lyapunov Exponent ◽  
Simple Method ◽  
Interval Extensions

In this letter, a very simple method to calculate the positive Largest Lyapunov Exponent (LLE) based on the concept of interval extensions and using the original equations of motion is presented. The exponent is estimated from the slope of the line derived from the lower bound error when considering two interval extensions of the original system. It is shown that the algorithm is robust, fast and easy to implement and can be considered as alternative to other algorithms available in the literature. The method has been successfully tested in five well-known systems: Logistic, Hénon, Lorenz and Rössler equations and the Mackey–Glass system.

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