scholarly journals A Time-Series Data Analyzing System Using a New Time-Frequency Transform

Author(s):  
Yih-Nen Jeng ◽  
You-Chi Cheng
2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tuan D. Pham

AbstractAutomated analysis of physiological time series is utilized for many clinical applications in medicine and life sciences. Long short-term memory (LSTM) is a deep recurrent neural network architecture used for classification of time-series data. Here time–frequency and time–space properties of time series are introduced as a robust tool for LSTM processing of long sequential data in physiology. Based on classification results obtained from two databases of sensor-induced physiological signals, the proposed approach has the potential for (1) achieving very high classification accuracy, (2) saving tremendous time for data learning, and (3) being cost-effective and user-comfortable for clinical trials by reducing multiple wearable sensors for data recording.


Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 1908
Author(s):  
Chao Ma ◽  
Xiaochuan Shi ◽  
Wei Li ◽  
Weiping Zhu

In the past decade, time series data have been generated from various fields at a rapid speed, which offers a huge opportunity for mining valuable knowledge. As a typical task of time series mining, Time Series Classification (TSC) has attracted lots of attention from both researchers and domain experts due to its broad applications ranging from human activity recognition to smart city governance. Specifically, there is an increasing requirement for performing classification tasks on diverse types of time series data in a timely manner without costly hand-crafting feature engineering. Therefore, in this paper, we propose a framework named Edge4TSC that allows time series to be processed in the edge environment, so that the classification results can be instantly returned to the end-users. Meanwhile, to get rid of the costly hand-crafting feature engineering process, deep learning techniques are applied for automatic feature extraction, which shows competitive or even superior performance compared to state-of-the-art TSC solutions. However, because time series presents complex patterns, even deep learning models are not capable of achieving satisfactory classification accuracy, which motivated us to explore new time series representation methods to help classifiers further improve the classification accuracy. In the proposed framework Edge4TSC, by building the binary distribution tree, a new time series representation method was designed for addressing the classification accuracy concern in TSC tasks. By conducting comprehensive experiments on six challenging time series datasets in the edge environment, the potential of the proposed framework for its generalization ability and classification accuracy improvement is firmly validated with a number of helpful insights.


2018 ◽  
Vol 29 (11) ◽  
pp. 1850109 ◽  
Author(s):  
Emrah Oral ◽  
Gazanfer Unal

This leading primary study is about modeling multifractal wavelet scale time series data using multiple wavelet coherence (MWC), continuous wavelet transform (CWT) and multifractal detrended fluctuation analysis (MFDFA) and forecasting with vector autoregressive fractionally integrated moving average (VARFIMA) model. The data is acquired from Yahoo Finances!, which is composed of 1671 daily stock market of eastern (NIKKEI, TAIEX, KOPSI) and western (SP500, FTSE, DAX) markets. Once the co-movement dependencies on time-frequency space are determined with MWC, the coherent data is extracted out of raw data at a certain scale by using CWT. The multifractal behavior of the extracted series is verified by MFDFA and its local Hurst exponents have been calculated obtaining root mean square of residuals at each scale. This inter-calculated fluctuation function time series has been re-scaled and used to estimate the process with VARFIMA model and forecasted accordingly. The results have shown that the direction of price change is determined without difficulty and the efficiency of forecasting has been substantially increased using highly correlated multifractal wavelet scale time series data.


Author(s):  
Greg M. Heaslip ◽  
Jeff M. Punch

There is considerable reported evidence that a large percentage of portable electronics product failure is due to impact or shock during use. Failures of the external housing, internal electronic components, package-to-board interconnects, and liquid crystal display panels may occur as the result of dropping. For many orientations of drop, the Printed Wire Board (PWB) will flex significantly during the impact event and subsequent clattering. Reducing the curvature and acceleration of the PWB during impact is an integral part of the design strategy for such products. This paper investigates the response of a PWB subjected to drop and shock tests through a combination of an analytical model, explicit dynamic Finite Element Analysis (FEA), and experimentation. A test vehicle consisting of a double-sided copper clad laminate PWB, mounted as a double cantilever, is used as a basis for the investigation. A free fall drop-test system is used to represent the drop scenario, and a vibration/shock system is used to impart shocks to the test vehicle. Measurements from strain gages and accelerometers are recorded using a high-speed data acquisition system. Results from experimentation show the strain/time series data from which maximum strain, natural frequencies, and damping coefficient are extracted. These measurements are compared with theoretical calculations and FEA output for the various shock and impact profiles. The investigation illustrates the response of a PWB to various shock and impact scenarios through theory, numerical simulation, and experimentation. Wavelet techniques are used to analyse the time series data, and from the resultant time/frequency space, component frequencies are extracted. It is shown that wavelet techniques are a useful tool in the analysis of shock and impact response data.


1978 ◽  
Vol 17 (4) ◽  
pp. 511-516
Author(s):  
Ole David Koht Norbye

In a comment [4] I discussed the methods used in two articles by A.R. Kemal [1, 2] which aimed at presenting new time series for the develop¬ment of Pakistan's large scale manufacturing industries during the period 1959-1960 to 1969-1970. I found the methods questionable, and concluded that the new series probably were more misleading than the existing official statistics. To illustrate the weakness of the methodology I gave some numerical examples from Kemal's own material, and I also compared his figures with some data from other sources. In a reply to my comments [3] Kemal finds my observations either marginal or not well founded or even ■directly wrong. Since Kemal's reply in part builds on a misrepresentation of some of my comments and since his rejection of my objections on some points is not substantiated, I find it necessary to come back to this subject once more with some few remarks.


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