China
Africa
Explore chapters and articles related to this topic
Trends, Seasonality, and Filtering
Published in Tucker S. McElroy, Dimitris N. Politis, Time Series, 2019
Tucker S. McElroy, Dimitris N. Politis
where the approximation is valid when Xt is close to Xt−1, i.e., if Xt∕Xt−1≈1, by a Taylor series argument. Multiplying the right-hand side of (3.3.1) by 100 yields the relative change in terms of a percentage. For example, if Xt=204 whereas Xt−1=200, then there is a 2% change going from time t − 1 to time t.
Solution of nonlinear programming problem by Bellman method while optimizing the two-level mining of benches in deep open pits
Published in Genadiy Pivnyak, Volodymyr Bondarenko, Iryna Kovalevska, Theoretical and Practical Solutions of Mineral Resources Mining, 2015
Now we will change the width of ore body M. Suppose that M = 650. In this case, the value of average overburden ratio significantly decreases and becomes equal to ksr = 0.351232. When M = 600, this ratio is equal to ksr = 0.370709. The absolute change is Δ = 0.019477, and the relative change is δ=0.0194770.370709⋅100=5.25%. The relative change of ore body width is δ=50600⋅100=8.3%.
Modeling three-dimensional forest structures to drive canopy radiative transfer simulations of bidirectional reflectance factor
Published in International Journal of Digital Earth, 2018
Wei Yang, Hideki Kobayashi, Xuehong Chen, Kenlo Nishida Nasahara, Rikie Suzuki, Akihiko Kondoh
Simulation experiments were conducted to test the sensitivity of BRF variations to TH and TD by changing one factor at a time. That is, in each simulation experiment, only one factor (either TH or TD in this study) was changed, while the other parameters were kept as their baseline values. For example, in the sensitivity experiment of TH, only the TH values of individual trees were changed, but the other parameters, like LAI, TD, and optical properties, were kept as the field measured constants. Specifically, the TD values were changed from 357 to 643 ha−1 and from 564 to 1003 ha−1 for the PFRR and Järvselja sites, respectively; the average TH values were changed from 2.42 to 5.02 m and from 8.97 to 14.31 m for the PFRR and Järvselja sites, respectively. The variation of input and output parameters was quantified by relative change, which is defined as the percentage ratio of absolute change to baseline value.
Effect of prolonged continuous smartphone gaming on upper body postures and fatigue of the neck muscles in school students aged between 10-18 years
Published in Cogent Engineering, 2021
Panida Hanphitakphong, Nuanlaor Thawinchai, Somruthai Poomsalood
A wireless surface electromyography (EMG) system (Plux wireless biosignals S.A., Arruda dos Vinhos, Portugal) was used to collect neck muscle electromyographic activity and process the trimmed EMG signals. Skin preparation was well performed before the data collection. Disposable self-adhesive Ag/AgCl snap electrodes were used for the signal collection. The bipolar electrodes were pre-gelled with 1 cm in diameter and an inter-electrode distance of 2 cm. The surface EMG electrodes were applied to the target muscles according to SENIAM recommendations (Hermens et al., 2000). The target muscles including both sides of the CES and UT muscles. The reference electrode was attached to olecranon process of the participant’s left elbow. To avoid interrater error, placing electrodes for all participants were performed by only one researcher. The CES electrodes were placed parallel to the spine, approximately 2 cm lateral to the C4 spinous process, over the CE muscle belly. The CES electrodes were attached 2 cm lateral to the midpoint between the acromion process and C7 spinous process, over the UT muscle belly (Hermens et al., 2000). In the current study, EMG signals were collected while using a smartphone at different time points (0, 10 and 20 minutes). The duration of the EMG signal collected at each time point is 1 minute. The frequency of EMG data acquisition was set at 2,000 Hz and the bandwidth for the EMG signal noise rejection was set at 20–450 Hz (S. Y. Kim & Koo, 2016). After that, the power spectral frequency analysis was used to investigate muscle fatigue due to the shift of median power frequency (MDF) which is widely used. A downshift of MDF of the EMG signal can indicate muscle fatigue since the process of electrical repolarization of muscle cells is delayed when muscle fatigue takes place (Jang & Ahram, 2014). The power spectrum was analyzed by Fourier Transform method (FFT). Then, the relative changes in the MDF were then used for comparison within group. At each time point, the relative change was used to express the absolute change as a percentage of the value of the indicator from the baseline period. In demonstrating the time effect, the MDF at 10 and 20 minutes was normalized to that at 0 minute (Bobet & Norman, 1984). For the interpretation, the muscle response was considered as higher level of muscle fatigue, if there was a shift of MDF of the EMG signal to the low end (De Luca, 1984).