scholarly journals Wavelet deconvolution technique for impact force reconstruction: mutual deconvolution approach

2021 ◽  
Vol 3 (SI2) ◽  
pp. first
Author(s):  
Hai Tran ◽  
Tat-Hien Le
Keyword(s):  
Indirect Method ◽  
Impact Force ◽  
Impulse Response Function ◽  
Reconstruction Process ◽  
Deconvolution Technique ◽  
Force Reconstruction ◽  
History Of ◽  
Ill Posed ◽  
And Shifts ◽  
Large Magnification

In the field of impact engineering, one of the most concerned issues is how to exactly know the history of impact force which often difficult or impossible to be measured directly. In reality, information of impact force apply to structure can be identified by means of indirect method from using information of corresponding output responses measured on structure. Namely, by using the output responses (caused by the unknown impact force) such as acceleration, displacement, or strain, etc. in cooperation with the impulse response function, the profile of unknown impact force can be rebuilt. A such indirect method is well known as impact force reconstruction or impact force deconvolution technique. Unfortunately, a simple deconvolution technique for reconstructing impact force has often encountered difficulty due to the ill-posed nature of inversion. Deconvolution technique thus often results in unexpected reconstruction of impact force with the influences of unavoidable errors which is often magnified to a large value in reconstructed result. This large magnification of errors dominates profile of desired impact force. Although there have been some regularization methods in order to improve this ill-posed problem so far, most of these regularizations are considered in the whole-time domain, and this may make the reconstruction inefficient and inaccurate because impact force is normally limited to some portions of impact duration. This work is concerned with the development of deconvolution technique using wavelets transform. Based on the advantages of wavelets (i.e., localized in time and the possibility to be analyzed at different scales and shifts), the mutual reconstruction process is proposed and formulated by considering different scales of wavelets. The experiment is conducted to verify the proposed technique. Results demonstrated the robustness of the present technique when reconstructing impact force with more stability and higher accuracy.

scholarly journals IMPACT FORCE RECONSTRUCTION USING WAVELET DECONVOLUTION TECHNIQUE

2018 ◽  
Vol 8 (1) ◽  
pp. 53-66
Author(s):  
Hai Tran ◽  
Hirotsugu Inoue
Keyword(s):  
Finite Element ◽  
Structural Model ◽  
Impact Force ◽  
Haar Wavelet ◽  
Reconstruction Process ◽  
Impact Forces ◽  
Deconvolution Technique ◽  
Force Reconstruction ◽  
The Impact ◽  
Wavelet Technique

Reconstruction or deconvolution of impact force history from corresponding impact responses such as strain, acceleration, and displacement has been considered as a useful indirect method for measuring the impact force. However, due to the ill-posed nature of deconvolution problem, impact force is often inaccurately and unstably reconstructed. This paper introduces and applies the deconvolution technique using wavelets as a robust method for reconstructing impact force with the advantageous properties of wavelets. First, an analytical process of impact force reconstruction by using the wavelet technique in terms of scaling and translating the Haar wavelet is formulated. The unknown impact force is represented by the expanded coefficients at different scales and shifts of Haar wavelet which is compactly supported in the time domain (finite in time). Then, based on the governing equation of impact force deconvolution, the reconstruction process of these expanded coefficients is formulated. Second, a structural model is built by finite element method to obtain impulse response function numerically. After that, the wavelet technique is applied to reconstruct the impact forces acting on the structure to verify its effectiveness. The comparisons between reconstructed forces and finite element analysis results demonstrate the success of the present technique in accurately reconstructing the numerical impact forces acting on the thin-walled column. These achievements show remarkable ability of the wavelet technique for reconstructing accurately any input forces.

scholarly journals Transient Response of an Impacted Beam and Indirect Impact Force Identification Using Strain Measurements

1994 ◽  
Vol 1 (3) ◽  
pp. 267-278 ◽  
Author(s):  
Hyungsoon Park ◽  
Youn-sik Park
Keyword(s):  
Impulse Response ◽  
Impact Force ◽  
Impulse Response Function ◽  
Time History ◽  
Impulse Response Functions ◽  
Transverse Impact ◽  
History Of ◽  
Convolution Approach ◽  
The Time Domain ◽  
The Impact

The impulse response functions (force-strain relations) for Euler–Bernoulli and Timoshenko beams are considered. The response of a beam to a transverse impact force, including reflection at the boundary, is obtained with the convolution approach using the impulse response function obtained by a Laplace transform and a numerical scheme. Using this relation, the impact force history is determined in the time domain and results are compared with those of Hertz's contact law. In the case of an arbitrary impact, the location of the impact force and the time history of the impact force can be found. In order to verify the proposed algorithm, measurements were taken using an impact hammer and a drop test of a steel ball. These results are compared with simulated ones.

Sparse deconvolution for the large-scale ill-posed inverse problem of impact force reconstruction

2017 ◽  
Vol 83 ◽  
pp. 93-115 ◽  
Author(s):  
Baijie Qiao ◽  
Xingwu Zhang ◽  
Jiawei Gao ◽  
Ruonan Liu ◽  
Xuefeng Chen
Keyword(s):  
Inverse Problem ◽  
Large Scale ◽  
Impact Force ◽  
Force Reconstruction ◽  
Ill Posed

The Subaltern Critique of Dominant Historiography and a Case for Retrieving a Historiography of Dalit Literary Traditions in India

2021 ◽  
Vol 7 (1) ◽  
pp. 7-15
Author(s):  
Vandana
Keyword(s):  
Literary History ◽  
Historical Analysis ◽  
History Writing ◽  
Literary Traditions ◽  
Literary Historiography ◽  
History Of ◽  
Longue Duree ◽  
Longue Durée ◽  
And Shifts ◽  
The Third World

In order to retrieve literary history in India, teleology operates on three levels: ancient, medieval and modern. As per the longue duree approach to the study of history, history is not an event or an object, but like the concept of time, is a configuration and a process. The history of the longue duree gives priority to long-term monumental historic patterns, moments and shifts in society, that is, the slow-paced structural processes which tend to have strong historical consequences. Similarly, languages and literatures, too, marked by historical catastrophes, undergo a process of sedimentation. For this reason, instead of a single literary history of South Asia, Sheldon Pollock proposes the concept of ‘literary cultures’ which allows room for ‘historical individuation’ of each culture rather than homogenising them merely for the sake of historical analysis. The basic questions that I have tried to look into through this study include: Why is it problematic to retrieve literary history in India? Why is it essential to have an alternative literary historiography of Dalit literature? How does Dalit subalternity differ from colonial subalternity? How the Dalit voice is disintegrated from within because of the prevalence of graded inequality? What constitutes the politics of history writing and canon formation in the third world countries like India where retrieving subaltern literary trends remain a problematic discourse?

scholarly journals A Study about the Temporal Constraints on the Martian Yardangs’ Development in Medusae Fossae Formation

2021 ◽  
Vol 13 (7) ◽  
pp. 1316
Author(s):  
Jia Liu ◽  
Zongyu Yue ◽  
Kaichang Di ◽  
Sheng Gou ◽  
Shengli Niu
Keyword(s):  
Size Distribution ◽  
Indirect Method ◽  
Common Method ◽  
Planetary Surface ◽  
Temporal Constraints ◽  
History Of Development ◽  
Long Duration ◽  
History Of ◽  
Dating Method

The age of Mars yardangs is significant in studying their development and the evolution of paleoclimate conditions. For planetary surface or landforms, a common method for dating is based on the frequency and size distribution of all the superposed craters after they are formed. However, there is usually a long duration for the yardangs’ formation, and they will alter the superposed craters, making it impossible to give a reliable dating result with the method. An indirect method by analyzing the ages of the superposed layered ejecta was devised in the research. First, the layered ejecta that are superposed on and not altered by the yardangs are identified and mapped. Then, the ages of the layered ejecta are derived according to the crater frequency and size distribution on them. These ages indicate that the yardangs ceased development by these times, and the ages are valuable for studying the evolution of the yardangs. This indirect dating method was applied to the areas of Martian yardangs in the Medusae Fossae Formation (MFF). The ages of the selected six layered ejecta range from ~0.50 Ga to ~1.5 Ga, indicating that the evolution of the corresponding yardangs had been ceased before these times. Analysis of more layered ejecta craters and superposed yardangs implies that yardangs in the MFF have a long history of development and some yardangs are still in active development.

scholarly journals Impact force reconstruction and localization using nonconvex overlapping group sparsity

2022 ◽  
Vol 162 ◽  
pp. 107983
Author(s):  
Junjiang Liu ◽  
Baijie Qiao ◽  
Yuanchang Chen ◽  
Yuda Zhu ◽  
Weifeng He ◽  
...  
Keyword(s):  
Impact Force ◽  
Group Sparsity ◽  
Overlapping Group Sparsity ◽  
Force Reconstruction

Transitional Justice without Transition

2020 ◽  
pp. 397-446
Author(s):  
Beth Van Schaack
Keyword(s):  
Transitional Justice ◽  
Institutional Reform ◽  
International Community ◽  
Political Transition ◽  
Truth Commissions ◽  
Truth Telling ◽  
Historical Case ◽  
Reconstruction Process ◽  
History Of ◽  
Justice Process

The penultimate chapter offers a discussion of the prospects for a genuine transitional justice process in Syria. Chapter 10 begins with a short history of the development of the archetypal tools within the transitional justice toolkit—criminal accountability, truth commissions, reparations, amnesties, lustration, institutional reform, and guarantees of nonrecurrence—and the way in which transitional justice efforts have become increasingly internationalized. This enhanced involvement of the international community in promoting transitional justice reflects the belief—premised on historical case studies and emerging empirical research—that societies in transition must address the crimes of the past in some capacity or risk their repetition. The chapter surveys the most recent research testing these claims, which has benefited from the creation of a number of new databases gleaned from states in transition. The chapter then describes ways in which the international community has tried to prepare for a future transitional justice process in Syria even in the absence of a political transition, including by training Syrian advocates, surveying Syrian communities to understand their knowledge of transitional justice and preferences for Syria, promoting psychosocial rehabilitation and solidarity among victims, and preparing for truth-telling exercises and institutional reform measures. The conclusion suggests ways in which the international community could still promote some form of transitional justice as part of the reconstruction process, even if Assad remains in power, which seems increasingly likely.

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